CA1069638A - Low smoke density fire-retardant unsaturated aliphatic polyester resins containing alumina hydrate - Google Patents
Low smoke density fire-retardant unsaturated aliphatic polyester resins containing alumina hydrateInfo
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- CA1069638A CA1069638A CA257,044A CA257044A CA1069638A CA 1069638 A CA1069638 A CA 1069638A CA 257044 A CA257044 A CA 257044A CA 1069638 A CA1069638 A CA 1069638A
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- polyester
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
- C08G63/02—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds
- C08G63/12—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds derived from polycarboxylic acids and polyhydroxy compounds
- C08G63/52—Polycarboxylic acids or polyhydroxy compounds in which at least one of the two components contains aliphatic unsaturation
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
- C08K3/20—Oxides; Hydroxides
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
- C08K3/20—Oxides; Hydroxides
- C08K3/22—Oxides; Hydroxides of metals
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- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Macromonomer-Based Addition Polymer (AREA)
- Compositions Of Macromolecular Compounds (AREA)
- Polyesters Or Polycarbonates (AREA)
Abstract
Abstract of the Disclosure Curable polyester resin compositions formed from unsaturated polycarboxylic acids and polyols and a crosslinking aliphatic vinyl monomer component being essentially free of aromaticity are disclosed.
The degree of unsaturation in the polyesters is carefully controlled so that the resin can be cured to produce strong thermoset products.
Resins of this nature can be filled with high levels of aluminum hydrate to give compositions that have high oxygen indices and very low smoke densities as measured by the National Bureau of Standards Smoke Chamber.
Also, when burned, the compositions of the invention emit non-toxic gases.
Preferably, both the polyester and the vinyl monomer component are aliphatic, although a controlled amount of aromaticity can be present in the polyester portion.
The degree of unsaturation in the polyesters is carefully controlled so that the resin can be cured to produce strong thermoset products.
Resins of this nature can be filled with high levels of aluminum hydrate to give compositions that have high oxygen indices and very low smoke densities as measured by the National Bureau of Standards Smoke Chamber.
Also, when burned, the compositions of the invention emit non-toxic gases.
Preferably, both the polyester and the vinyl monomer component are aliphatic, although a controlled amount of aromaticity can be present in the polyester portion.
Description
~069638 Back~round of t!le Invention Field of the Invention: This invention is in the field of unsaturated polyesters curable with an unsaturated monomer, and more particularly, is in the field of low smoke density polyesters.
Brief Description of the Prior Art: Traditionally, fire~retardant polyesters have been made with chlorinated or brominated materials, or, in :: :
some cases, phosphorus-containing materials. These materials may be merely . , .
, , , ~ - ~ ,: , , ' - :
~06g~38 additives to the polyester or they may be actual reactants. Although polyesters prepared with such materials are fire-retardant in the sense that they have low flame spreads and are self-extinguishing, they unfortunately emit a thick, dense smoke when exposed to an open flame. The high smoke levels are, of course, undesirable and often are more serious than the fire itself.
We have found that high smoke levels are due not only to the presence of halogen-containing or phosphorus-containing materials in the polyester, but are also due to aromatic components in the cured polyester.
An example of an aromatic crosslinking monomer is styrene which is by far the most widely used crosslinking monomer.
We have found that polyester resins made from unsaturated aliphatic polyesters and from polyesters containing some aromaticity when cured with aliphatic vinyl crosslinking monomers such as methyl methacrylate produce very little smoke when cured thermosets are exposed to an open flame.
Unfortunately, many of these cured polyesters are weak, ha~ing low flexural strength and flexural modulus.
The weakness of polyesters cured with aliphatic monomers such as methyl methacrylate is well known in the art. It is believed that the unsaturated polyesters and methyl methacrylate do not copolymerize readily and, therefore, give a composition in which some of the polyester remains unreacted in a mixture of polymethyl methacrylate and some loosely formed polyester-methyl methacrylate copolymer. See, for example, "Factors Affecting Durability of Glass-Reinforced Polyester Resins" by A. C. Smith and J. R. Lowry, Plastics Technology, June 1959, pages 42-56.
This lack of strength and related properties due to poor copolymerization or curing has been a principal reason why methyl methacrylate has not been more vlde1y used for the curi-g of uns~CuraCed polyescers.
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Summary of the Invention We have found that unsaturated polyesters can be fully cured or copolymerized with aliphatic crosslinking nonomers such as methyl methacrylate to produce strong thermoset articles.
The key to achieving complete curing is to use an unsaturated polyester having a high degree of ethulenic unsaturation. When these highly unsaturated polyesters are cured with an aliphatic vinyl crosslinking monomer such as methyl methacrylate, strong thermoset articles results. The cured resins produce little smoke when burned and when filled with aluminum hydrate have low flame spreads and have surprisingly high oxygen indices.
Thus, according to the present invention, there is provided a curable aliphatic polyester resin being essentially free of aromatic constituents comprising a mixture of:
(A) an unsaturated aliphatic polyester derived from polycondensing:
(1) organic polyols having a functionality of at least 2,
Brief Description of the Prior Art: Traditionally, fire~retardant polyesters have been made with chlorinated or brominated materials, or, in :: :
some cases, phosphorus-containing materials. These materials may be merely . , .
, , , ~ - ~ ,: , , ' - :
~06g~38 additives to the polyester or they may be actual reactants. Although polyesters prepared with such materials are fire-retardant in the sense that they have low flame spreads and are self-extinguishing, they unfortunately emit a thick, dense smoke when exposed to an open flame. The high smoke levels are, of course, undesirable and often are more serious than the fire itself.
We have found that high smoke levels are due not only to the presence of halogen-containing or phosphorus-containing materials in the polyester, but are also due to aromatic components in the cured polyester.
An example of an aromatic crosslinking monomer is styrene which is by far the most widely used crosslinking monomer.
We have found that polyester resins made from unsaturated aliphatic polyesters and from polyesters containing some aromaticity when cured with aliphatic vinyl crosslinking monomers such as methyl methacrylate produce very little smoke when cured thermosets are exposed to an open flame.
Unfortunately, many of these cured polyesters are weak, ha~ing low flexural strength and flexural modulus.
The weakness of polyesters cured with aliphatic monomers such as methyl methacrylate is well known in the art. It is believed that the unsaturated polyesters and methyl methacrylate do not copolymerize readily and, therefore, give a composition in which some of the polyester remains unreacted in a mixture of polymethyl methacrylate and some loosely formed polyester-methyl methacrylate copolymer. See, for example, "Factors Affecting Durability of Glass-Reinforced Polyester Resins" by A. C. Smith and J. R. Lowry, Plastics Technology, June 1959, pages 42-56.
This lack of strength and related properties due to poor copolymerization or curing has been a principal reason why methyl methacrylate has not been more vlde1y used for the curi-g of uns~CuraCed polyescers.
, :
Summary of the Invention We have found that unsaturated polyesters can be fully cured or copolymerized with aliphatic crosslinking nonomers such as methyl methacrylate to produce strong thermoset articles.
The key to achieving complete curing is to use an unsaturated polyester having a high degree of ethulenic unsaturation. When these highly unsaturated polyesters are cured with an aliphatic vinyl crosslinking monomer such as methyl methacrylate, strong thermoset articles results. The cured resins produce little smoke when burned and when filled with aluminum hydrate have low flame spreads and have surprisingly high oxygen indices.
Thus, according to the present invention, there is provided a curable aliphatic polyester resin being essentially free of aromatic constituents comprising a mixture of:
(A) an unsaturated aliphatic polyester derived from polycondensing:
(1) organic polyols having a functionality of at least 2,
(2) organic polycarboxylic acids having a functionality of at least 2 in which the un-saturated component of the unsaturated polyester is an alpha, beta-ethylenically unsaturated polycarboxylic acid and the equivalent ratio of alpha, beta-ethylenically unsaturated poly-carboxylic acid to all other polycarboxylic acid components in the polyester is at least 1 to 1;
and (B) an aliphatic vinyl monomer copolymerizable with said polyester, ; (c) at least 50 percent by weight hydrated alumina, the percentage by weight being based on total weight of (A), ; (B) and (C), 1069~38 ~,, ~
said composition capable of being ombined with glass gibers and completely cured to producc strony thcrmosct articles wllich arc difficult to burn and which when exposed to an open flame produce little smoke.
The resins of the present invention can be cured at elevated temperatures, that is, 82C. and above, and can be made room temperature curable.
Besides resinous mixtures, cured thermoset articles are also included within the scope of the present invention.
Particularly strong thermoset articles, useful as articles of construction, can be prepared by reinforcing the cured resinous products of the invention with fiber glass.
Brief Description of the Drawings-FIG. 1 is a graph showing the effect of hydrated alumina loadings on oxygen index of two polyester resins;
FIG. 2 is a graph showing the effect of the degree of unsaturation in the polyester on flexural strength;
FIG. 3 is a graph showing the effect of the degree of unsatura ion in the polyester on flexural modulus; and ' .
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and (B) an aliphatic vinyl monomer copolymerizable with said polyester, ; (c) at least 50 percent by weight hydrated alumina, the percentage by weight being based on total weight of (A), ; (B) and (C), 1069~38 ~,, ~
said composition capable of being ombined with glass gibers and completely cured to producc strony thcrmosct articles wllich arc difficult to burn and which when exposed to an open flame produce little smoke.
The resins of the present invention can be cured at elevated temperatures, that is, 82C. and above, and can be made room temperature curable.
Besides resinous mixtures, cured thermoset articles are also included within the scope of the present invention.
Particularly strong thermoset articles, useful as articles of construction, can be prepared by reinforcing the cured resinous products of the invention with fiber glass.
Brief Description of the Drawings-FIG. 1 is a graph showing the effect of hydrated alumina loadings on oxygen index of two polyester resins;
FIG. 2 is a graph showing the effect of the degree of unsaturation in the polyester on flexural strength;
FIG. 3 is a graph showing the effect of the degree of unsatura ion in the polyester on flexural modulus; and ' .
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3 _ ~
1069~3~3 FIG. 4 is a graph showing the effect of the degree of unsaturation in the polyester on Barcol Hardness.
Detailed Description The present invention relates to a curable polyester resin and to cured resinous products prepared therefrom. The resin comprises a mixture of an unsaturated polyester and an aliphatic vinyl monomer component copolymerizable with the polyester. Preferably, the unsaturated polyester is aliphatic. The term "aliphatic" as it relates to the preferred composition of aliphatic polyester and aliphatic vinyl monomer means the polyester resin of the present invention is essentially free of aromatic constituents, although a minor amount, for example, less than 2 percent by weight based on resin weight, of aromatic materials may be present. Also, for low smoke generation, the unsaturated polyester resin should be substantially free of chlorine, bromine and phosphorus-containing materials.
The unsaturated polyesters are derived from condensing organic polycarboxylic acids having a functionality of at least 2 with organic polyols having a functionality of at least 2. The unsaturated component in the polyester is an alpha, beta-ethylenically unsaturated organic poly-carboxylic acid and the equivalent ratio of alpha, beta-ethylenically unsaturated polycarboxylic acids to all other polycarboxylic acid com-ponents in the polyester is at least 1 to 1, and preferably at least about 2.5 to 1, and in certain cases~ all the organic polycarboxylic acid components may be alpha, beta-ethylenically unsaturated.
The polyesters of the present invention when cured with an alphatic vinyl crosslinking monomer component produce strong thermoset articleswhich,when subjected to an open flame, produce little smoke.
The amoant of smoke generated by burning a cured resinous sample of the invention can be determined by measuring the smoke density according to .
ASTM D-2843. Briefly, the testing procedure involves inserting a specimen of accurate, predetermined dimensions inside a smoke chamber. The chamber is substantially air-tight and contains a photocell in the ceiling and a standardi~ed light source in the floor which cooperate with one another to measure the optical transmittance through the height of the cham~er.
The specimen is then exposed to an open flame and burned, or, in another aspect of the test, the specimen can be subjected to a source of radiant heat and permitted to smolder. In both aspects of the test, the samples are subjected to combustion and the smoke that is generated is collected in the chamber. During the course of the test, which usually lasts about 20 minutes, the optical transmission is constantly recorded, and the minimum value is taken as a measure of the smoke density.
The smoke density is a logrithmic function of the optical transmission as is shown by the following table:
Smoke Densit~Y-(Dm) Conversion of Percent Transmittance to Smoke Density Percent Transmittance 17.5 lO0 3.0 201 0.52 301 0.090 401 0.016 501 0.0028 601 `' : . - ' :
Cured polyesters of the present invention when burned as described in ASTM D-2843 have smoke densities of about 200 or less, preferably lO0 or less (flaming modification). Smoke densities of about lO0 are equivalent to optical transmissions of about 18 percent. At this level of transmission, one could at least see a lighted exit sign in case of a fire. As a point of comparison, highly aromatic systems such as styrene cured polyesters have smoke densities of 300 and above and often 500 and above. Aromatic, chlorinated and brominated self-extinguishing polyester resin systems have smoke density values of about 800 and above and further, emit toxic vapors of chlorine and bromine or related compounds. The polyester resins of the present invention are not likely to emit effluents of such toxicity, and, in fact, have been found to emit essentially non-toxic effluents such as carbon monoxide when burned.
Besides generating little smoke when burned, the cured polyester resins of the present invention are difficult to burn as evidenced by their high oxygen indices and their low flame spreads when filled with about 50 percent by weight or more hydrated alumina.
The oxygen index is determined according to ASTM D-2863. In general terms, the oxygen index of a material is percentage by volume of oxygen in the atmosphere necessary to support combustion of the material. For example, air contains 21 percent by volume oxygen. If a material burned in air, it would have an oxygen index of 21 or lower.
The higher the oxygen index of the material, the harder it is to get the sample to burn. Thus, the oxygen index is a measure of the fire retardance of the sample. Cured resinous materials of the invention containing hydrated alumina have oxygen indices of at least 35 and preferably at least 50 which is easily obtainable when the resin contains from about 50 to 75 percent by weight hydrated alumina filler. Hydrated - ''' alumina is a particularly desirable filler because, although it raises the oxygen index, it does not appreciably affect the smoke density.
Besides oxygen index~ flame spread is another indication of fire retardance. The flame spread characteristics of the polyesters of the present invention can be determined according to the Underwriters' Tunnel Test (ASTM ~-184).
According to the ASTM manual, the Underwriters' Tunnel Test is for evaluating the burning characteristics of building materials and is applicable to any type of building material. The purpose of the test is to determine the comparative burning characteristics of the material under test by evaluating the flame spread over its surface.
The test chamber is a horizontal duct, 17-1/2 inches wide, 12-1/2 inches high and 25 feet long. Red oak i5 tlle calibration standard and is arbitrarily assigned a value of 100. A value of O is assigned to asbestos. Other materials are reported proportionately.
It has been suggested that the following classifications be assigned to the various flame-spread ratings:
Flame Spread Classification 0-25 Class A, non-combustible 25-75 Class B, fire-retardant 75 and up Class C, combustible The Underwriters' Tunnel Test is a good measure of flame spread, however, the test is expensive to set~up and to conduct.
There is a laboratory scale test which gives an indication of flame spread. The laboratory scale test is referred to as the Monsanto Tunnel Test and is described in J. of Paint Technolo~y, 39, (511), 494 (August 1967). In the Monsanto Tunnel Test, a sample 2 feet by 3-3/4 inches is slanted at an angle of about 45 from the horizontal. A
specified heat source is burned at the bottom of the sample and the sample is then burned for four minutes. The flame spread or how far the flame spreads up the sample is reported.
It has been found that cured polyester resins of the invention have flame-spread ratings less than 50 as determined by the Monsanto Tunnel Test.
The polyesters of the present invention can be cured to form a strong, hard5 thermoset article with an aliphatic vinyl crosslinking monomer such as methyl methacrylate. As has been mentioned above, this is surprising since methyl methacrylate usually only gives partial cures with unsaturated polyesters resulting in weak thermosets of low hardness.
Complete cures with aliphatic crosslinking monomers can be insured if the polyester contains a high degree of ethylenic unsaturation such as that specified above. Such resins completely cure with methyl methacrylate to produce strong thermoset articles of high hardness. The effect of unsaturation on strength and hardness can be seen in FIGS. 2, 3 and 4 which are plots of flexural strength (FIG. 2), flexural modulus tFIG. 3) and Barcol Hardness (FIG. 4) versus percent maleic unsaturation.
The polyester resins evaluated for the data depicted in FIGS. 2, 3 and 4 are described in Working Examples 35-41 infra. Briefly, the polyesters were ethylene, propylene, adipate, maleate polyesters in which the maleic anhydride to adipic acid mole ratio was varied over the range of 10-4 to 0-6. Fifty (50) parts by weight of the various polyesters were cured with 50 parts by weight of methyl methacrylate and 7 parts by weight of N-vinyl pyrrolidone. FIGS. 2, 3 and 4 show that stronger, llarder resins are obtained with higher levels of unsaturation indicating 1069631~3 more complete curing at the higher levels of unsaturation. This trend with alipllatic curing agents such as methyl methacrylate is opposite to that observed with aromatic curing agents such as styrene. At high levels of unsaturation, styrene cured systems become increasingly embrittled and lose strength.
In view of the excellent strength and fire-retardant properties reported above, the cured polyester resins of the present invention are particularly desirable for use as materials of construction, that is, they can be used as molding resins or laminating resins, although, of course, they could be used as coating compositions. However, the resins have been particularly formulated for use as materials of construction such as automobile and truck body components, liners for truck walls, aircraft parts, boat hulls, plumbing fixtures, piping, duct work and the like.
The polycarboxylic acids used in the practice of the invention are preferably aliphatic and preferably dibasic and have a high content of alpha, beta-ethylenic unsaturation, that is, the equivalent ratio of alpha, beta-ethylenically unsaturated polycarboxylic acid in the polyester to all other polycarboxylic acids is at least 1 to 1 and preferably at least 2.5 to 1. Of course, the entire polycarboxylic acid component can be alpha, beta-ethylenically unsaturated, and the present claims are intended to cover this embodiment.
Examples of alpha, beta-ethylenically unsaturated polycarboxylic acids are maleic acid, fumaric acid, aconitic acid, mesaconic acid, citraconic acid, itaconic acid and alkyl derivatives of such acids. The anhydrides of these acids where anhydrides exist are embraced within the term "acid" since the reaction products produced there~rom, that is, the polyesters, are tlle same. Maleic acid and fumaric acid are preferred acids.
_ g _ 106963~3 Cther polycarboxylic acids and anhydrides can, of course, be used.
Examples would be acyclic polycarboxylic acids and anhydrides, preferably dibasic acids and anhydrides. Among the acyclic saturated dicarboxylic acids can be mentioned those which are saturated and which contain from about 2 to 10 carbon atoms such as succinic acid, adipic acid, suberic acid, and the like.
Although aromatic dicarboxylic acids are not preferred, they can be present in controlled amounts, that is, 50 mole percent or less based on total moles of dicarboxylic acids or anhydrides. Examples include isophthalic or phthalic acids.
Polyesters prepared from symmetrical glycols such as ethylene glycol, neopentyl glycol and the like have a tendency to crystalli~e and to be only moderately soluble in crosslinking monomer. The incorporation of an acyclic saturated or aromatic polycarboxylic acid in the polyester formulation reduces the tendency of the polyester to crystallize, makes the resin more soluble in crosslinking monomer and lowers the viscosity of the resultant resin.
The tendency of the polyester to crystallize can be minimized by incorporating a branched glycol into the formulation. However, alkyl branch-ing had an adverse effect on oxygen index.
The effect of branching in the polyester chain on oxygen index can be seen in FIG. 1 which is a plot of oxygen index versus percent hydrated alumina content. The two plots in the figure represent different polyesters.
Plot A represents an ethylene, propylene, maleate, adipate polyester prepared in the mole ratio of 9/2/8/2. Plot B represents a propylene-fumarate poly-ester prepared in a molar ratio of 11.5/10. Fifty (50) parts by weight of the polyesters were combined with 50 parts by weight of methyl methacrylate, filled wlth hydrated alumina in the various percentages shown ln FIG. 1 and cured as generally described in Examples 28-34 infra. The data in FIG. 1 slows that regardless of the hydrated alumina loading, the polyester resin A with less alkyl branching has a higher oxygen index than resin B.
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The organic polyol component used to prepare the polyester is also preferably aliphatic and preferably is difunctional. The polyol can be an alkylene glycol or an alkylene oxide glycol containing fro~ 2 to 10 carbon atoms such as ethylene glycol, propylene glycol, butylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, neopentyl glycol or the like. ~ixtures of polyols can obviously be used.
Also, in certain preferred embodiments, alcohols and polyols containing allyl or acrylic substitution can be included in the polyol component of the polyester. Examples include the monoallyl or diallyl ether of trimethylol propane, the monoallyl or diallyl ether of glycerol, the diallyl or triallyl ether of pentaerythritol. These components have been found to speed the cure of the polyesters cured with aliphatic monomers. In the embodiments where these allyl substituted alcohols and polyols are used, they should be used in amounts of up to 25 percent by weight based on total weight of the resin.
A minor amount of the polycarboxylic acid or polyol component, that is, less than about 15 percent by weight, may have a functionality greater than 2. This may be in the polyol component and can be glycerine, pentaerythritol, hexanetriol or trimethylol propane. Polyfunctional material may also be in the acid component and can be, for example, citric acid.
; In producing polyesters from the organic polycarboxylic acids and polyols, the equivalent ratio of polyol components to acid components is generally from about 1 to 1.3:1. A slight excess of polyol is normally used because some is usually volatilized or decomposed during the eslerificatlon.
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, . , . .. ' ' , : . ' . ' . ~ . :
~o696~8 The aliphatic vinyl monomer component copolymerizable with the polyester is an aliphatic material containing at least one CH2 = C
group, and preferably in the terminal position. The aliphatic vinyl monomer component is essentially free of aromaticity. This means the vinyl monomer component contains less than 2 percent aromaticity based on total weight of unsaturated polyester and crosslinking monomer.
Preferably, the aliphatic vinyl monomer component is free of aromaticity.
Examples of aliphatic vinyl monomers include esters of organic and inorganic acids, such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl valerate, vinyl caproate, vinyl enanthate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, amyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, decyl methacrylate; methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, isobutyl acrylate, amyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, heptyl acrylate, octyl acrylate, 3,5,5-trimethylhexyl acrylate, decyl acrylate, and dodecyl acrylate; allyl formate, allyl acetate, allyl propionate, allyl butyrate, allyl valerate, allyl caproate, allyl-3,5,5-trimethyl hexoate, allyl acrylate, allyl crotonate, allyl lactate, allyl aceto-acetate, as well as methallyl esters corresponding to the above allyl esters, as well as esters from such alkenyl alcohols as beta-ethyl allyl alcohol and beta-propyl allyl alcohols. ~lso, esters such as dimethyl maleate, diethyl maleate, diallyl maleate, dimethyl fumarate, diethyl fumarate, dimethallyl fumarate and diethyl glutaconate can be employed. Also, 1o69638 aliphatic nitriles such as acrylonitrile and methacrylonitrile can be employed. Obviously, mixtures of monomers can be used.
A preferred, rapid room temperature curing system employs up to 20 percent, and preferably from about 5 to 20 percent N-vinyl pyrrolidone in the vinyl monomer component; the percentage by weight being based on total weight of the vinyl crosslinking monomer. By room temperature curing is meant the curing is accomplished without the addition of external heat such as would occur at normal room temperatures, that is, from about 20 to 27~C.
With regard to the ratio of polyester to crosslinking monomer, about 40 to 70 percent by weight polyester and about 30 to 60 percent by weight aliphatic crosslinking monomer should be employed, the percentages by weight being based on total weight of the polyester and crosslinking monomer. The amount of polyester and crosslinking monomer should be varied with one another in amounts sufficient to provide liquid, flowable, interpolymeri~able mixtures which cure to form strong thermoset products. If the amount of polyester is too high or the amount of cross-linking monomer too low, resins of extremely high viscosity which produce insufficiently cured products will result. On the other hand, if the amount of crosslinking monomer is too high and the amount of polyester too low, cured products with unsatisfactory properties will result.
As has been described above, the polyester and crosslinking monomer are the principal components of the resinous systems of the present invention. However, another important component is hydrated alumina filler. The hydrated alumina increases the oxygen index and decreases the flame spread of the cured resinous products of the invention.
The effect of hydrated alumina on the oxygen index of cured polyester .
. ~ . . . .
- ~069638 resins can be seen in FIG. 1 which, as described above, is a plot of percent hydrated alumina versus oxygen index. The graph shows that for two different polyester resins, the oxygen index goes up as the hydrated alumina content of the polyester resin goes up.
The hydrated alumina content of the polyester resin should be about 25 to 75 percent, and preferably from about 50 to 70 percent by weight, based on total weight of the polyester resin and the hydrated alumina. Amounts less than 25 percent by weight, although contributing desirable properties, do not provide the optimum fire-retardant properties desired in the products of the invention. Higher hydrated alumina contents, that is, lligher than 75 percent, are undesirable because of resulting high resin viscosities.
Besides hydrated alumina, other fillers or pigments may be included in the resin formulation, although the total filler content should not exceed 80 percent by weight, based on total weight of filler and resin because of viscasity considerations. Examples of other fillers include calcium carbonate, diatomaceous earth and clay. Examples of pigments are TiO2, transparent iron oxide and phthalocyanine pigments.
Polyester resins of the present invention are cured through addition polymerization of the unsaturated monomer with the unsaturation sites in the polyester molecule. This polymerization is free radical initiated. Suitable free radical addition polymerization catalysts include benzoyl peroxide, tertiary butyl perbenzoate, tertiary butyl hydroperoxide, cumine hydroperoxide, azo bis(isobutylronitrile), methyl ethyl ketone peroxide and the like. The catalyst is generally used in amounts of up to 0.1 to 2 percent by weight based on total weight of resin (polyester plus monomer); the amounts varying wlth the activlty and amount of any accelerator and inhibitor used in the resinous system.
Accelerators are used in room temperature curing systems where it is desirable to initiate the polymerization without the application of e~ternal heat. Suitable accelerators include cobalt salts such as cobalt octoate or cobalt naphthenate. The amount of accelerator used can vary widely, but is usually within the range of 0.1 to 1 percent based on total weight of polyester resin.
To prevent any tendency for premature gelation, a gelation inhibitor may be incorporated into the polyester resin system. Suitable inhibitors are selected from the quinone and phenolic compounds and include ben~oquinone, hydroquinone and 4-tert-butyl catechol. The amount ~ -of inhibitor required in the mixture is susceptible to wide variation but preferably is in the range of 0.001 to about 0.1 percent by weight based upon weight of the polyester component.
When the polyester resins of the present invention are used as materials of construction, such as laminating and molding resins, they can be reinforced with glass fibers or other common reiaforcements such as steel wire, boron fibers, wood and vegetable fibers. However, because of strength and cost considerations, fiber glass reinforcement is preferred.
Fiber glass for reinforcement of polyester resin systems is well known in the art and a detailed description of the various types of glass fibers is not considered as a necessary part of the detailed description of the present ~nvention. If such a detailed description is desired, reference is made to Reinforced Plastics, Theory and Procedure by M. W. Gaylord, copyrighted 1969 by Koppers Co., Inc., pages 47-72.
In general, where the resins of the present invention are re-inforced with glass, about 10 to 70 percent by weight glass fibers based on total weight of the polyester resin (polyester plus crosslinking monomer plus filler) should be used.
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Besides the ingredients mentioned above, other materials may be added to the resinous mixture. Examples include mold release agents such as zinc stearate or ultraviolet light stabilizers sucn as o-hydroxy-phenylketones, and 2-(2-hydroxyphenyl)benzotriazoles. The amounts of these other additionai components are quite small and do not generally in combination exceed about 3 percent by weight of the total weight of the resinous system.
Polyester resins of the present inventlon are prepared by techniques well known in the art. For example~ the organic unsaturated polycarboxylic acid can be mixed with the organic polyol materials and the mixture heated gradually to about 150 to about 230C. An esterification reaction catalyst can be employed such as dibutyltin oxide. Tl-e reaction mixture is maintained within this temperature range until esterlfication i8 completed, with accompanying evolution of and evaporation of water. A solvent may be used, such as xylene or toluene, to distill azeotropically with the water of the reaction.
The polyesterification reaction can also be conducted without azeotroping agents as, for example, by means of a fusion process in which a non-reactive gas is blown through a reaction mixture in order to remove the water. Such a process is described in U. S. Patents 3,109,831, 3,109,832 and 3,109,834.
106~638 Examples 1 - 10 A series of unsaturated polyesters cured with various unsaturated monomers, and in some cases, filled with hydrated alumina and reinforced with fiber glass were prepared. The catalyst system, time and temperatures of cure, amount and type of filler, amount of fiber glass reinforcement, as well as certain physical properties of cured resin castings are reported in Table I below.
In all cases, the polyester was an ethylene-propylene-maleate-adipate. The method of preparation was as follows:
To a suitable reaction vessel equipped with a condenser, stirrer, thermometer and a source of nitrogen purging (to assist in removal of water formed in the condensation) was charged ethylene glycol, propylene glycol, maleic anhydride and adipic acid in a molar ratio of 9/2/8/2.
The charge was heated to about 100C. to melt the maleic anhydride, after which time the reaction mixture exothermed, the bighest temperature being 140C. The reaction was continued at a temperature of 210C. with a moderate nitrogen sparging and heat being applied to drive off water formed in the condensation. Samples were taken off periodically until the polyester attained a reduced Gardner-Holdt Viscosity of G-H, as a 60 percent solution in ethyl CELLOSOLVE. At this viscosity, the polyester had an acid number of 27-28.
At the completion of the reaction, the polyester at a temperature of about 210C. was kept under a nitrogen atmosphere and cooled to 155C., at which time inhibitors and modifiers were added. At about 90C., the crosslinking agent is added to form the resin solution which is then cooled to room temperature and filtered to remove any gel particles.
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The percentages of polyester, methyl methacrylate and comonomer are percentages by weight based on total weight of polyester, methyl methacrylate and comonomer.
With regard to the comonomers, the abbreviations in Table I
stand for: _ STY = styrene EA = ethyl acrylate NPGDA = neopentyl glycol diacrylate VP = N-vinyl pyrrolidone The resin/filler ratio is by weight.
The viscosity is measured in a Brookfield Viscometer at 25C.
using a No. 2 spindle at 20 rpm.
The type of fiber glass used for reinforcement was 2 ounce chopped strand mat and the percentage by weight is based on total weight of resin tinCluding filler) and fiber glass.
BP0 represents benzoyl peroxide.
TBP represents tertiary butyl perbenzoate.
VD-l represents cobalt octoate.
P-40 represents PERCADOX ~ 40 (Noury Chem.) described as a pentanedio~e peroxide.
Unless otherwise indicated, 1 percent by weight catalyst is used.
DMA is dimethyl aniline.
~ n oven cure is generally at about 120C. for about 15 minutes.
RT means room temperature cure.
Barcol is a measure of hardness determined by a 934 Barcol Impressor. It is a comparable measure of hardness using a scale of values of 0 to 100, and the higher the number,~the harder the material.
OI is oxygen index, determined according to ASTM D 2863. D
represents smoke density. F represents a flaming sample and S represents a smoldering sample. Smoke density is determined according to ASTM D-2843.
~06963~3 In the Modified Monsanto Tunnel Test, a sample 23~3/4 inches by 3-3/4 inches is slanted at an angle of about 45 from the horizontal.
A specified heat source is burned at the bottom of the sample and the sample then burned for four minutes. The flame spread, a function of distance and time, is then compared with a sample of redwood and a flame spread rating is reported. The test is similar to ASTM E-286, part 14 (1974).
Flame spreads for the front (F) and back (B) surfaces are reported.
The flexural strength and modulus is determined according to ASTM D-790.
The heat distortion temperature is determined according to ASTM D-648.
Some significant observations from the examples presented in Table I above are as follows.
By comparing Examples 1 and 2 at similar filler loading, the oxygen index of the cured resin increases as the level of methyl methacrylate is increased and polyester decreased. Although the polyester in Example 3 is kept at the same level as in Example 2, one-half of the methacrylate was substituted with styrene. This produced rather substantial changes since the oxygen index decreased unexpectedly while the smoke density increased very sharply. In a totally styrene thinned experiment (Example 4), the filled resin had a very high viscosity in comparison to Example 1 due to the poor solubility of this type of polyester in styrene compared to methyl methacrylate, while the cured resin again showed a very low oxygen index and a very high smoke density.
The use of comonomers with methyl methacrylate can be carried out without greatly affecting the oxygen index of the system. Thus, ethyl acrylate and vinyl pyrrolitone can be used to give faster reactivity with -. - . . .
- ~i9638 the polyester and better overall cure without contributing greatly to the oxygen index or smoke density (Examples 6 and 10). Where a difunctional monomer is used, such as in Example 7, the increase in the crosslinking density renders more thermal stability to the system as exemplified by a higher heat distortion temperature and a lower flame spread than in Example 5. The oxygen index remained almost unchanged although the smoke density increased. Even at this level, this system has a lower smoke density than styrene based systems and a higher oxygen index.
In Examples 8 and 9, other fire-retardant additives such as antimony oxide and zinc borate can be incorporated and yet maintain a low smoke density system. Their use, however, does not really reflect any dramatic improvements in the oxygen index or ~he flame spread rating.
Examples 11 - 20 A second series of unsaturated polyesters cured for the most part with methyl m~thacrylate were prepared. The principal variant in this series of polyesters was the formulation of the polyester itself.
The polyester formulation, the catalyst systems, time and temperature of cure, amount and type of filler, amount of fiber glass reinforcement, as well as certain physical properties are reported in Table II above.
In the examples, the abbreviations for the polyesters are as follows:
EG = ethylene glycol PG = propylene glycol TMPDAE = trimethylol propane diallyl ether F = fumaric acid MA = maleic anhydride AD = adipic acid .
' ' ': ' ' : " . ', . ' ' ~069~i38 The polyesters were prepared in a manner generally described above in Examples l-lO, that is, all the ingredients were charged to a suitable reaction vessel equipped with a condenser, stirrer and a source of nitrogen purging. The reactants were heated to initiate an exotherm and the reaction continued with heating and nitrogen sparging to drive of f water.
At the completion of the polyesterification, the polyester is cooled to about 155C. under a nitrogen atmosphere at which time catalyst promoters and inhibitors, if used, are usually added. At about 90C., a crosslinking agent is added to form the resin solution which is then cooled to room temperature and filtered to remove any gel particles.
The abbreviations used in Table II have the same significance as described above in connection with Table I.
Some significant observations from the data presented in Table II
above are as follows.
The resins of Examples 16-20 are formed from highly unsaturated polyesters giving the potential for more complete and room temperature cures. However, with highly unsaturated polyesters such as propylene-fumarate resins, the oxygen indices are relatively low. See Example 16 in which a propylene-fumarate resin at a 1:1 filler ratio has an oxygen index of 36.
This oxygen index should be compared with the one obtained with an ethylene-propylene-maleate-adipate polyester such as is shown in Example 5 in which the oxygen index is 43.8. The oxygen index of the propylene-fumarate resin can be improved if the hydrated alumina level is increased.
See Examples 16 and 17; however, note also that the viscosity increases.
The effects of benzoyl peroxide on smoke density can be seen by comparing Example 17 with Example 18. Example 17 contains benzoyl ., . , ~......... . . . . . .. . .
peroxide and Example 18 employs a catalyst system of pentanedione peroxide and cobalt octoate promoter. Benzoyl peroxide, being aromatic, appears to contribute significantly to the smoke density, whereas the aliphatic catalyst system of Example 18 appears to have minimal effect on the smoke density. Also, the benzoyl peroxide of Example 17 is applied as a slurry in tricresyl phosphate which also is aromatic and contains phosphate groups which are believed to contribute significantly to smoke density.
Examples 21 - 27 The following examples show the dramatic effect of N-vinyl pyrrolidone on accelerating curing so as to be able to achieve room temperature cures.
Example 21 An ethylene propylene-maleate-adipate polyester was prepared as generally described in Examples 1-10. The polyester was blended with methyl methacrylate to form a 1:1 weight ratio of polyester to methyl methacrylate. The resin was filled with aluminum hydrate in a 1:1 weight ratio and cured at room temperature with a catalyst system consisting of one percent by weight pentanedione peroxide and 0.2 percent by weight cobalt octoate promoter; the percentages by weight being based on resin weight. The resin gelled in 19.75 minutes and reached a peak exotherm of 119C. when 100 gram quantity was placed in a 150 milliliter glass beaker and placed in a 66C. bath with mild agitation.
- 1069~38 Example 22 Example 21 was repeated with the exception that 0.2 percent by weight dimethyl para-toluidiene wa.s used in the catalyst system. ThP
gel time was reduced to 5.5 minutes but the peak exotherm was only 100C.
indlcating an incomplete cure.
Example 23 A resin system similar to Example 21 was prepared from the following charge:
Component Percent ~y Wei~ht Polyester + Methyl Methacrylate (50/50) 47.5 N-vinyl pyrrolidone 2.5 TiO2 2.0 Hydrated alumina S0.0 As in Example 21, the catalyst system was one percent pentanedione peroxide and 0.2 percent cobalt octoate. The gel test results are shown in Table III below.
Examples 24 - 27 Resin systems similar to Example 23 were prepared from the following charges:
. .
~0~9638 Example No. 24 25 26 27 polyester + methyl methacrylate 47.5 46.5 46.5 46.5 N-vinyl pyrrolidone - 2.5 3.5 3.5 3.5 TiO2 2.0 2.0 2.0 2.0 hydrated alumina 50 50 50 50 cobalt octoate 0~1 0.1 0.05 0.2 pentanedione peroxidel 1.0 1.0 1.0 1.0 DMPTl 0. 01 Percent by weight based on resin weight.
Table III
Example No. 23 24 25 26 27 gel time, minutes at 66C. 0.78 2.00 1.45 7.90 0.75 total time 1.30 3.42 2.42 11.60 1.25 peak temperature, F. 282 264 269 221 282 .
Examples 28 - 34 Hydrated alumina has a pronounced effect on oxygen index.
Higher hydrated alumina loadings result in higher oxygen indices.
This is seen in FIG. 1 which is a plot of oxygen index versus percent hydrated alumina content of two different polyester resins.
Plot A represents an ethylene-propylene-maleate-adipate polyester prepared as generally described in Examples 1-10 in a molar ratio of 9/2/8/2.
Plot B represents a propylene-fumarate polyester prepared as generally described in Examples 16 through 20 in a molar ratio of 11.5/10.
The polyesters were combined with 50 percent by weight of methyl methacrylate; the percentages by weight being based on total weight of polyester and methyl methacrylate, and filled with aluminum hydrate in the various percentages shown in FIG. l; the percentages by weight being based on total weight of polyester resin and hydrated alumina.
The filled resins were laminated with two layers of 2 ounce chopped strand mat and cured at 82~C. for 30 minutes using 1 percent benzoyl peroxide as the catalyst. After curing, the laminates were evaluated for oxygen index according to ASTM D-2863.
~ 069638 Examples 35 - 41 In order to develop adequate strength, the aliphatic polyesters of the present invention cured with aliphatic monomer, must be highly unsaturated. Strength as a function of the percentage unsaturation is shown in FIGS. 2, 3 and 4. The resins evaluated for the data shown in FIGS. 2, 3 and 4 were prepared by blending 50 parts by weight polyester with 50 parts by weight methyl methacrylate, 7 parts by weight N-vinyl pyrrolidone and 0.5 parts by weight cobalt octoate and 1.0 part by weight pentanedione peroxide.
The polyesters used in preparing the various resins were prepared from the following charges:
Component Mole Ratios maleic anhydride 10 9 8 7 6 5 4 adipic acid 1 2 3 4 5 6 ethylene glycol 9 9 9 9 9 9 9 propylene 2 2 2 2 2 2 2 The polyesters and resultant resins were prepared as generally described in Examples 1-10.
The resultant resins were cast in a 12 inch by 12 inch by 1/8 inch closed cell and allowed to gel at room temperature followed by a one-half hour post cure at 82C, After curing, the resin castings were released from the cell and evaluated for flexural strength and modulus according to ASTM D-790 and for Barcol hardness using a 934 Barcol Impressor.
.''~ . .
- - ~06963~3 Examples 42 - 52 To show the effect that aromaticity has on the oxygen index and smoke density of unsaturated polyester resins, the following experiments were conducted:
A series (Examples 42-46) of unsaturated polyester resins were prepared as generally described in Examples 1-10 from condensing maleic and phthalic anhydrides with ethylene glycol. Five unsaturated polyesters were prepared in which the mole ratio of maleic anhydride to phthalic anhydride varied from 9/1 to 5/5. The unsaturated polyesters were thinned with methyl methacrylate crosslinking monomer in a 1:1 ~ -weight ratio, filled with alumina hydrate in a weight ratio of 150 parts by weight of filler to 100 parts by weight of resin, and 75 parts by weight of the filled resin were then combined witII 25 parts by weight continuous glass filament which is commercially available from Owens-Corning as continuous filament strand M8620. The resin-filler-glass composites were then molded for three minutes at 255~. (124C.) in the presence of one percent by weight based on weight of resin plus alumina I hydrate of a diperoctoate-type peroxide catalyst commercially available from Witco Chemical as USP-245 peroxide. The composition of the unsaturated poIyesters is shown ln Table IV beIow.
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~069638 Table IV
Composition of Unsaturated Polyesters with Varying Amounts of Aromaticit~__n Polyesterl _ Mole Ratio ExampleMaleic - Phthalic Ethylene Propylene Acid NoAnhydride Anhydride Glycol Glycol Number Viscosity_ 42 9 1 11.3 0 53.6 G
43 8 2 11.3 0 46.8 G
44 7 3 11.3 0 40.5 J
6 4 11.3 0 41.4 G
46 5 5 11.3 0 35.8 G
0.02% methyl hydroquinone cooked with polyester.
Reduced Gardner-Holdt viscosity, 60% solution in ethyl CELLOSOLVE.
A second series (Examples 47-52) of unsaturated polyester resins was prepared in which the aromaticity was introduced into the crosslinking monomer portion. Six unsaturated polyesters were prepared from condensing maleic anhydride, ethylene glycol, and propylene glycol in a mole ratio of 10/813.3 in the manner generally described in Examples 1-10. The unsaturated polyester resin was cooked to an acid number of 53.1 and had a reduced Gardner-~oldt viscosity of about H- as a 60 percent solids solution in ethyl CELLOSOLVE. The unsaturated polyester was then thinned with mixtures of methyl methacrylate and styrene in the weight ratios shown in Table V below.
1069~;3~3 Table V
Weight Ratios of Ethylene Propylene Maleate Polyesters with Methyl Methacrylate and Styrene _ Example _ Wei~ht Ratio No. Polyester ~ Styrene The unsaturated polyester resins (polyester plus crosslinking monomer) shown in Examples 47 through 52 above were then filled with alumina hydrate filler in a weight ratio of 150 parts by weight of alumina hydrate to 100 parts by weight of resin, and 75 parts by weight of the filled resin was then combined with 25 parts by weight of continuous glass filament commercially available from Owens-Corning as continuous filament strand M8620. The resin-filler-glass composites-were then molded for 3 minutes at 255F. (124C.) in the presence of one percent by weight based on weight of resin and alumina hydrate of a diperoctoate-type peroxide catalyst commercially available from Witco Chemical as USP-245.
The cured thermoset articles in Examples 42 through 46 above were then evaluated for oxygen index according to ASTM D-2863 and smoke density in both the smoldering and flaming modification according to ~STM D-2343. Table VI below shows the results of the testing.
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. .
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Table VI
Oxygen Index and Smoke Density Results Weigllt Weight Example Percentage Percentlage Oxygen Dm No. Phthalicl Styrene Index Flaming SmolderinR
42 4.8 0 material is crystalline, could not be evaluated 43 9.2 0 47.1 78 121 44 13.5 ~ 46.5 78 161 17.4 0 46.1 58 155 46 21.1 0 43.5 58 98 47 0 20 37.1 191.0 234 48 0 15 40.5 150 193 49 0 10 42.5 124 149 0 5 47.3 108 188 51 0 2 51.7 105 194 52 ~ 0 52.4 88 164 Percentages by weight based on resin weight.
The data in Table VI above shows that as aromaticity is introduced into the resin, the oxygen index becomes lower. However, the data indicates that how the aromaticity is introduced is also a factor.
From a comparison of the oxygen index values in Examples 42 through 46 with those of Examples 47 through 52, it appears that aromaticity introduced into the resin through the crosslinking monomer has more of an effect in lowering the oxygen index than introducing aromaticity through the unsaturated polyester.
. '' : : .
.
, -. . . . . .
The data with regard to smoke density, flaming modification, shows that introduction of aromaticity into the resin through the crosslinking monomer greatly increases the amount of smoke generated.
Examples 47 through 52 show that increasing the styrene content from O to a high of 20 percent by weight results in over 100 percent increase in smoke density. However, somewhat surprisingly, introducing aromaticity into the resin through the unsaturated polyester does not seem to increase the smoke density. In fact, the data in Examples 52 and 42 through 46 indicate that introducing aromaticity in the unsaturated polyester actually decreases smoke density for the flaming modification. ~ -With regard to smoke density measurements for the smoldering variation, the data shown in 1able VI is not conclusive. ~lowever, the data does seem to indicate that introducing aromaticity into the resin through the crosslinking monomer has more of an effect in raising the smoke density than introducing aromaticity through the unsaturated polyester portion.
Example 53 The following experiment was conducted to determine the toxicity of gases evolved from burning unsaturated polyester resins of the present invention.
An ethylene propylene maleate adipate polyester as described in Examples 1-10 with O.OI percent by weight methyl hydroquinone was prepared in the method as generally described in Examples 1-10. The unsaturated polyester was cooked at 210C. until it attained the reduced Gardner-Holdt viscosity of G-H as a 60 percent solution in ethyl CELLOSOLVE.
At tbis viscosity, the poly=er had an tcid n~mber of ZO-30.
, .,, ., . . . . . , . . ~ . . ..
The unsaturated polyester was cooled from 210C. to 155C.
at which time 0.0625 parts by weight of sodium acetate (as a 25 percent by weight water solution) and 0.005 percent by weight methyl hydroquinone were added. The polyester (53.76 parts by weight) was further cooled to 90C. and 46.24 parts by weight of methyl methacrylate added to form a 50 percent solids solution which had a Brookfield viscosity at 77F.
(25C.) of 70 + S cps.
The above-described resinous composition forms one package of a two-package system. In the second package was 0.05 parts by weight of cobalt octoate and 7.0 parts by weight of N-vinyl pyrrolidone.
The two packages were mixed together (47.4 parts by weight) and mixed Witll 49.3 parts by weight of alumina hydrate and 2.8 parts by weight of titanium dioxide and 1.0 parts by weight of 2,4-pentanedione peroxide free radical catalyst. The filled resin was poured onto chopped strand fiber glass mat (two plies of 2 oz. (5.67 kg) A~) so as to form a composite with 20 percent by weight fiber glass.
The composite was then molded under heat and pressure to form the laminate which was then subjected to smoke density measurements in a flaming modification. The gases evolved were collected in a cold trap at -80C. and the condensate analyzed by gas chromatography and found to contain the following constituents:
Consti_uents Percent by Weight methyl methacrylate 0.37 methanol 0.27 acetone 0.07 acetaldehyde 0.04 unidentified about 0.07 water 99.18 .
Other laminates as described above were subjected to smoke density measurements in a flaming and a smoldering mode. Gaseous samples were taken of both modes and passed through 100 milliliters of a .1 normal sodium hydroxide aqueous solution for a cyanide determination. The gases collected from the flaming modification of the smoke density showed 2Y0 parts per billion of cyanide and the gases collected from the smoldering modlfication showed 12 to 17 parts per billion cyanide.
Gaseous samples were also analyzed by mass spectroscopy. For this analysis, the evolved gases were collected when the highest smoke density was recorded in 250 ml. glass tubes which were subsequently sealed. The collected gases were then analyzed by mass spectroscopy and found to contain:
Flaming ~odification Smoldering Modification IngredielltParts by Weight IngredientParts by Weight carbon dioxide 1.79 carbon dioxide 0.22 nitrogen 78.42 nitrogen 77.86 argon 0.92 argon 0.90 oxygen 18.88 oxygen 21.01 - ,.
The results presented above show that the gases evolved are relatively non-toxic. It is interesting to note that no carbon monoxide -was detected by mass spectroscopy.
`
1069~3~3 FIG. 4 is a graph showing the effect of the degree of unsaturation in the polyester on Barcol Hardness.
Detailed Description The present invention relates to a curable polyester resin and to cured resinous products prepared therefrom. The resin comprises a mixture of an unsaturated polyester and an aliphatic vinyl monomer component copolymerizable with the polyester. Preferably, the unsaturated polyester is aliphatic. The term "aliphatic" as it relates to the preferred composition of aliphatic polyester and aliphatic vinyl monomer means the polyester resin of the present invention is essentially free of aromatic constituents, although a minor amount, for example, less than 2 percent by weight based on resin weight, of aromatic materials may be present. Also, for low smoke generation, the unsaturated polyester resin should be substantially free of chlorine, bromine and phosphorus-containing materials.
The unsaturated polyesters are derived from condensing organic polycarboxylic acids having a functionality of at least 2 with organic polyols having a functionality of at least 2. The unsaturated component in the polyester is an alpha, beta-ethylenically unsaturated organic poly-carboxylic acid and the equivalent ratio of alpha, beta-ethylenically unsaturated polycarboxylic acids to all other polycarboxylic acid com-ponents in the polyester is at least 1 to 1, and preferably at least about 2.5 to 1, and in certain cases~ all the organic polycarboxylic acid components may be alpha, beta-ethylenically unsaturated.
The polyesters of the present invention when cured with an alphatic vinyl crosslinking monomer component produce strong thermoset articleswhich,when subjected to an open flame, produce little smoke.
The amoant of smoke generated by burning a cured resinous sample of the invention can be determined by measuring the smoke density according to .
ASTM D-2843. Briefly, the testing procedure involves inserting a specimen of accurate, predetermined dimensions inside a smoke chamber. The chamber is substantially air-tight and contains a photocell in the ceiling and a standardi~ed light source in the floor which cooperate with one another to measure the optical transmittance through the height of the cham~er.
The specimen is then exposed to an open flame and burned, or, in another aspect of the test, the specimen can be subjected to a source of radiant heat and permitted to smolder. In both aspects of the test, the samples are subjected to combustion and the smoke that is generated is collected in the chamber. During the course of the test, which usually lasts about 20 minutes, the optical transmission is constantly recorded, and the minimum value is taken as a measure of the smoke density.
The smoke density is a logrithmic function of the optical transmission as is shown by the following table:
Smoke Densit~Y-(Dm) Conversion of Percent Transmittance to Smoke Density Percent Transmittance 17.5 lO0 3.0 201 0.52 301 0.090 401 0.016 501 0.0028 601 `' : . - ' :
Cured polyesters of the present invention when burned as described in ASTM D-2843 have smoke densities of about 200 or less, preferably lO0 or less (flaming modification). Smoke densities of about lO0 are equivalent to optical transmissions of about 18 percent. At this level of transmission, one could at least see a lighted exit sign in case of a fire. As a point of comparison, highly aromatic systems such as styrene cured polyesters have smoke densities of 300 and above and often 500 and above. Aromatic, chlorinated and brominated self-extinguishing polyester resin systems have smoke density values of about 800 and above and further, emit toxic vapors of chlorine and bromine or related compounds. The polyester resins of the present invention are not likely to emit effluents of such toxicity, and, in fact, have been found to emit essentially non-toxic effluents such as carbon monoxide when burned.
Besides generating little smoke when burned, the cured polyester resins of the present invention are difficult to burn as evidenced by their high oxygen indices and their low flame spreads when filled with about 50 percent by weight or more hydrated alumina.
The oxygen index is determined according to ASTM D-2863. In general terms, the oxygen index of a material is percentage by volume of oxygen in the atmosphere necessary to support combustion of the material. For example, air contains 21 percent by volume oxygen. If a material burned in air, it would have an oxygen index of 21 or lower.
The higher the oxygen index of the material, the harder it is to get the sample to burn. Thus, the oxygen index is a measure of the fire retardance of the sample. Cured resinous materials of the invention containing hydrated alumina have oxygen indices of at least 35 and preferably at least 50 which is easily obtainable when the resin contains from about 50 to 75 percent by weight hydrated alumina filler. Hydrated - ''' alumina is a particularly desirable filler because, although it raises the oxygen index, it does not appreciably affect the smoke density.
Besides oxygen index~ flame spread is another indication of fire retardance. The flame spread characteristics of the polyesters of the present invention can be determined according to the Underwriters' Tunnel Test (ASTM ~-184).
According to the ASTM manual, the Underwriters' Tunnel Test is for evaluating the burning characteristics of building materials and is applicable to any type of building material. The purpose of the test is to determine the comparative burning characteristics of the material under test by evaluating the flame spread over its surface.
The test chamber is a horizontal duct, 17-1/2 inches wide, 12-1/2 inches high and 25 feet long. Red oak i5 tlle calibration standard and is arbitrarily assigned a value of 100. A value of O is assigned to asbestos. Other materials are reported proportionately.
It has been suggested that the following classifications be assigned to the various flame-spread ratings:
Flame Spread Classification 0-25 Class A, non-combustible 25-75 Class B, fire-retardant 75 and up Class C, combustible The Underwriters' Tunnel Test is a good measure of flame spread, however, the test is expensive to set~up and to conduct.
There is a laboratory scale test which gives an indication of flame spread. The laboratory scale test is referred to as the Monsanto Tunnel Test and is described in J. of Paint Technolo~y, 39, (511), 494 (August 1967). In the Monsanto Tunnel Test, a sample 2 feet by 3-3/4 inches is slanted at an angle of about 45 from the horizontal. A
specified heat source is burned at the bottom of the sample and the sample is then burned for four minutes. The flame spread or how far the flame spreads up the sample is reported.
It has been found that cured polyester resins of the invention have flame-spread ratings less than 50 as determined by the Monsanto Tunnel Test.
The polyesters of the present invention can be cured to form a strong, hard5 thermoset article with an aliphatic vinyl crosslinking monomer such as methyl methacrylate. As has been mentioned above, this is surprising since methyl methacrylate usually only gives partial cures with unsaturated polyesters resulting in weak thermosets of low hardness.
Complete cures with aliphatic crosslinking monomers can be insured if the polyester contains a high degree of ethylenic unsaturation such as that specified above. Such resins completely cure with methyl methacrylate to produce strong thermoset articles of high hardness. The effect of unsaturation on strength and hardness can be seen in FIGS. 2, 3 and 4 which are plots of flexural strength (FIG. 2), flexural modulus tFIG. 3) and Barcol Hardness (FIG. 4) versus percent maleic unsaturation.
The polyester resins evaluated for the data depicted in FIGS. 2, 3 and 4 are described in Working Examples 35-41 infra. Briefly, the polyesters were ethylene, propylene, adipate, maleate polyesters in which the maleic anhydride to adipic acid mole ratio was varied over the range of 10-4 to 0-6. Fifty (50) parts by weight of the various polyesters were cured with 50 parts by weight of methyl methacrylate and 7 parts by weight of N-vinyl pyrrolidone. FIGS. 2, 3 and 4 show that stronger, llarder resins are obtained with higher levels of unsaturation indicating 1069631~3 more complete curing at the higher levels of unsaturation. This trend with alipllatic curing agents such as methyl methacrylate is opposite to that observed with aromatic curing agents such as styrene. At high levels of unsaturation, styrene cured systems become increasingly embrittled and lose strength.
In view of the excellent strength and fire-retardant properties reported above, the cured polyester resins of the present invention are particularly desirable for use as materials of construction, that is, they can be used as molding resins or laminating resins, although, of course, they could be used as coating compositions. However, the resins have been particularly formulated for use as materials of construction such as automobile and truck body components, liners for truck walls, aircraft parts, boat hulls, plumbing fixtures, piping, duct work and the like.
The polycarboxylic acids used in the practice of the invention are preferably aliphatic and preferably dibasic and have a high content of alpha, beta-ethylenic unsaturation, that is, the equivalent ratio of alpha, beta-ethylenically unsaturated polycarboxylic acid in the polyester to all other polycarboxylic acids is at least 1 to 1 and preferably at least 2.5 to 1. Of course, the entire polycarboxylic acid component can be alpha, beta-ethylenically unsaturated, and the present claims are intended to cover this embodiment.
Examples of alpha, beta-ethylenically unsaturated polycarboxylic acids are maleic acid, fumaric acid, aconitic acid, mesaconic acid, citraconic acid, itaconic acid and alkyl derivatives of such acids. The anhydrides of these acids where anhydrides exist are embraced within the term "acid" since the reaction products produced there~rom, that is, the polyesters, are tlle same. Maleic acid and fumaric acid are preferred acids.
_ g _ 106963~3 Cther polycarboxylic acids and anhydrides can, of course, be used.
Examples would be acyclic polycarboxylic acids and anhydrides, preferably dibasic acids and anhydrides. Among the acyclic saturated dicarboxylic acids can be mentioned those which are saturated and which contain from about 2 to 10 carbon atoms such as succinic acid, adipic acid, suberic acid, and the like.
Although aromatic dicarboxylic acids are not preferred, they can be present in controlled amounts, that is, 50 mole percent or less based on total moles of dicarboxylic acids or anhydrides. Examples include isophthalic or phthalic acids.
Polyesters prepared from symmetrical glycols such as ethylene glycol, neopentyl glycol and the like have a tendency to crystalli~e and to be only moderately soluble in crosslinking monomer. The incorporation of an acyclic saturated or aromatic polycarboxylic acid in the polyester formulation reduces the tendency of the polyester to crystallize, makes the resin more soluble in crosslinking monomer and lowers the viscosity of the resultant resin.
The tendency of the polyester to crystallize can be minimized by incorporating a branched glycol into the formulation. However, alkyl branch-ing had an adverse effect on oxygen index.
The effect of branching in the polyester chain on oxygen index can be seen in FIG. 1 which is a plot of oxygen index versus percent hydrated alumina content. The two plots in the figure represent different polyesters.
Plot A represents an ethylene, propylene, maleate, adipate polyester prepared in the mole ratio of 9/2/8/2. Plot B represents a propylene-fumarate poly-ester prepared in a molar ratio of 11.5/10. Fifty (50) parts by weight of the polyesters were combined with 50 parts by weight of methyl methacrylate, filled wlth hydrated alumina in the various percentages shown ln FIG. 1 and cured as generally described in Examples 28-34 infra. The data in FIG. 1 slows that regardless of the hydrated alumina loading, the polyester resin A with less alkyl branching has a higher oxygen index than resin B.
.
The organic polyol component used to prepare the polyester is also preferably aliphatic and preferably is difunctional. The polyol can be an alkylene glycol or an alkylene oxide glycol containing fro~ 2 to 10 carbon atoms such as ethylene glycol, propylene glycol, butylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, neopentyl glycol or the like. ~ixtures of polyols can obviously be used.
Also, in certain preferred embodiments, alcohols and polyols containing allyl or acrylic substitution can be included in the polyol component of the polyester. Examples include the monoallyl or diallyl ether of trimethylol propane, the monoallyl or diallyl ether of glycerol, the diallyl or triallyl ether of pentaerythritol. These components have been found to speed the cure of the polyesters cured with aliphatic monomers. In the embodiments where these allyl substituted alcohols and polyols are used, they should be used in amounts of up to 25 percent by weight based on total weight of the resin.
A minor amount of the polycarboxylic acid or polyol component, that is, less than about 15 percent by weight, may have a functionality greater than 2. This may be in the polyol component and can be glycerine, pentaerythritol, hexanetriol or trimethylol propane. Polyfunctional material may also be in the acid component and can be, for example, citric acid.
; In producing polyesters from the organic polycarboxylic acids and polyols, the equivalent ratio of polyol components to acid components is generally from about 1 to 1.3:1. A slight excess of polyol is normally used because some is usually volatilized or decomposed during the eslerificatlon.
.
.
.
, . , . .. ' ' , : . ' . ' . ~ . :
~o696~8 The aliphatic vinyl monomer component copolymerizable with the polyester is an aliphatic material containing at least one CH2 = C
group, and preferably in the terminal position. The aliphatic vinyl monomer component is essentially free of aromaticity. This means the vinyl monomer component contains less than 2 percent aromaticity based on total weight of unsaturated polyester and crosslinking monomer.
Preferably, the aliphatic vinyl monomer component is free of aromaticity.
Examples of aliphatic vinyl monomers include esters of organic and inorganic acids, such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl valerate, vinyl caproate, vinyl enanthate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, amyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, decyl methacrylate; methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, isobutyl acrylate, amyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, heptyl acrylate, octyl acrylate, 3,5,5-trimethylhexyl acrylate, decyl acrylate, and dodecyl acrylate; allyl formate, allyl acetate, allyl propionate, allyl butyrate, allyl valerate, allyl caproate, allyl-3,5,5-trimethyl hexoate, allyl acrylate, allyl crotonate, allyl lactate, allyl aceto-acetate, as well as methallyl esters corresponding to the above allyl esters, as well as esters from such alkenyl alcohols as beta-ethyl allyl alcohol and beta-propyl allyl alcohols. ~lso, esters such as dimethyl maleate, diethyl maleate, diallyl maleate, dimethyl fumarate, diethyl fumarate, dimethallyl fumarate and diethyl glutaconate can be employed. Also, 1o69638 aliphatic nitriles such as acrylonitrile and methacrylonitrile can be employed. Obviously, mixtures of monomers can be used.
A preferred, rapid room temperature curing system employs up to 20 percent, and preferably from about 5 to 20 percent N-vinyl pyrrolidone in the vinyl monomer component; the percentage by weight being based on total weight of the vinyl crosslinking monomer. By room temperature curing is meant the curing is accomplished without the addition of external heat such as would occur at normal room temperatures, that is, from about 20 to 27~C.
With regard to the ratio of polyester to crosslinking monomer, about 40 to 70 percent by weight polyester and about 30 to 60 percent by weight aliphatic crosslinking monomer should be employed, the percentages by weight being based on total weight of the polyester and crosslinking monomer. The amount of polyester and crosslinking monomer should be varied with one another in amounts sufficient to provide liquid, flowable, interpolymeri~able mixtures which cure to form strong thermoset products. If the amount of polyester is too high or the amount of cross-linking monomer too low, resins of extremely high viscosity which produce insufficiently cured products will result. On the other hand, if the amount of crosslinking monomer is too high and the amount of polyester too low, cured products with unsatisfactory properties will result.
As has been described above, the polyester and crosslinking monomer are the principal components of the resinous systems of the present invention. However, another important component is hydrated alumina filler. The hydrated alumina increases the oxygen index and decreases the flame spread of the cured resinous products of the invention.
The effect of hydrated alumina on the oxygen index of cured polyester .
. ~ . . . .
- ~069638 resins can be seen in FIG. 1 which, as described above, is a plot of percent hydrated alumina versus oxygen index. The graph shows that for two different polyester resins, the oxygen index goes up as the hydrated alumina content of the polyester resin goes up.
The hydrated alumina content of the polyester resin should be about 25 to 75 percent, and preferably from about 50 to 70 percent by weight, based on total weight of the polyester resin and the hydrated alumina. Amounts less than 25 percent by weight, although contributing desirable properties, do not provide the optimum fire-retardant properties desired in the products of the invention. Higher hydrated alumina contents, that is, lligher than 75 percent, are undesirable because of resulting high resin viscosities.
Besides hydrated alumina, other fillers or pigments may be included in the resin formulation, although the total filler content should not exceed 80 percent by weight, based on total weight of filler and resin because of viscasity considerations. Examples of other fillers include calcium carbonate, diatomaceous earth and clay. Examples of pigments are TiO2, transparent iron oxide and phthalocyanine pigments.
Polyester resins of the present invention are cured through addition polymerization of the unsaturated monomer with the unsaturation sites in the polyester molecule. This polymerization is free radical initiated. Suitable free radical addition polymerization catalysts include benzoyl peroxide, tertiary butyl perbenzoate, tertiary butyl hydroperoxide, cumine hydroperoxide, azo bis(isobutylronitrile), methyl ethyl ketone peroxide and the like. The catalyst is generally used in amounts of up to 0.1 to 2 percent by weight based on total weight of resin (polyester plus monomer); the amounts varying wlth the activlty and amount of any accelerator and inhibitor used in the resinous system.
Accelerators are used in room temperature curing systems where it is desirable to initiate the polymerization without the application of e~ternal heat. Suitable accelerators include cobalt salts such as cobalt octoate or cobalt naphthenate. The amount of accelerator used can vary widely, but is usually within the range of 0.1 to 1 percent based on total weight of polyester resin.
To prevent any tendency for premature gelation, a gelation inhibitor may be incorporated into the polyester resin system. Suitable inhibitors are selected from the quinone and phenolic compounds and include ben~oquinone, hydroquinone and 4-tert-butyl catechol. The amount ~ -of inhibitor required in the mixture is susceptible to wide variation but preferably is in the range of 0.001 to about 0.1 percent by weight based upon weight of the polyester component.
When the polyester resins of the present invention are used as materials of construction, such as laminating and molding resins, they can be reinforced with glass fibers or other common reiaforcements such as steel wire, boron fibers, wood and vegetable fibers. However, because of strength and cost considerations, fiber glass reinforcement is preferred.
Fiber glass for reinforcement of polyester resin systems is well known in the art and a detailed description of the various types of glass fibers is not considered as a necessary part of the detailed description of the present ~nvention. If such a detailed description is desired, reference is made to Reinforced Plastics, Theory and Procedure by M. W. Gaylord, copyrighted 1969 by Koppers Co., Inc., pages 47-72.
In general, where the resins of the present invention are re-inforced with glass, about 10 to 70 percent by weight glass fibers based on total weight of the polyester resin (polyester plus crosslinking monomer plus filler) should be used.
'~
~ . . .. .... .
Besides the ingredients mentioned above, other materials may be added to the resinous mixture. Examples include mold release agents such as zinc stearate or ultraviolet light stabilizers sucn as o-hydroxy-phenylketones, and 2-(2-hydroxyphenyl)benzotriazoles. The amounts of these other additionai components are quite small and do not generally in combination exceed about 3 percent by weight of the total weight of the resinous system.
Polyester resins of the present inventlon are prepared by techniques well known in the art. For example~ the organic unsaturated polycarboxylic acid can be mixed with the organic polyol materials and the mixture heated gradually to about 150 to about 230C. An esterification reaction catalyst can be employed such as dibutyltin oxide. Tl-e reaction mixture is maintained within this temperature range until esterlfication i8 completed, with accompanying evolution of and evaporation of water. A solvent may be used, such as xylene or toluene, to distill azeotropically with the water of the reaction.
The polyesterification reaction can also be conducted without azeotroping agents as, for example, by means of a fusion process in which a non-reactive gas is blown through a reaction mixture in order to remove the water. Such a process is described in U. S. Patents 3,109,831, 3,109,832 and 3,109,834.
106~638 Examples 1 - 10 A series of unsaturated polyesters cured with various unsaturated monomers, and in some cases, filled with hydrated alumina and reinforced with fiber glass were prepared. The catalyst system, time and temperatures of cure, amount and type of filler, amount of fiber glass reinforcement, as well as certain physical properties of cured resin castings are reported in Table I below.
In all cases, the polyester was an ethylene-propylene-maleate-adipate. The method of preparation was as follows:
To a suitable reaction vessel equipped with a condenser, stirrer, thermometer and a source of nitrogen purging (to assist in removal of water formed in the condensation) was charged ethylene glycol, propylene glycol, maleic anhydride and adipic acid in a molar ratio of 9/2/8/2.
The charge was heated to about 100C. to melt the maleic anhydride, after which time the reaction mixture exothermed, the bighest temperature being 140C. The reaction was continued at a temperature of 210C. with a moderate nitrogen sparging and heat being applied to drive off water formed in the condensation. Samples were taken off periodically until the polyester attained a reduced Gardner-Holdt Viscosity of G-H, as a 60 percent solution in ethyl CELLOSOLVE. At this viscosity, the polyester had an acid number of 27-28.
At the completion of the reaction, the polyester at a temperature of about 210C. was kept under a nitrogen atmosphere and cooled to 155C., at which time inhibitors and modifiers were added. At about 90C., the crosslinking agent is added to form the resin solution which is then cooled to room temperature and filtered to remove any gel particles.
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106963~
The percentages of polyester, methyl methacrylate and comonomer are percentages by weight based on total weight of polyester, methyl methacrylate and comonomer.
With regard to the comonomers, the abbreviations in Table I
stand for: _ STY = styrene EA = ethyl acrylate NPGDA = neopentyl glycol diacrylate VP = N-vinyl pyrrolidone The resin/filler ratio is by weight.
The viscosity is measured in a Brookfield Viscometer at 25C.
using a No. 2 spindle at 20 rpm.
The type of fiber glass used for reinforcement was 2 ounce chopped strand mat and the percentage by weight is based on total weight of resin tinCluding filler) and fiber glass.
BP0 represents benzoyl peroxide.
TBP represents tertiary butyl perbenzoate.
VD-l represents cobalt octoate.
P-40 represents PERCADOX ~ 40 (Noury Chem.) described as a pentanedio~e peroxide.
Unless otherwise indicated, 1 percent by weight catalyst is used.
DMA is dimethyl aniline.
~ n oven cure is generally at about 120C. for about 15 minutes.
RT means room temperature cure.
Barcol is a measure of hardness determined by a 934 Barcol Impressor. It is a comparable measure of hardness using a scale of values of 0 to 100, and the higher the number,~the harder the material.
OI is oxygen index, determined according to ASTM D 2863. D
represents smoke density. F represents a flaming sample and S represents a smoldering sample. Smoke density is determined according to ASTM D-2843.
~06963~3 In the Modified Monsanto Tunnel Test, a sample 23~3/4 inches by 3-3/4 inches is slanted at an angle of about 45 from the horizontal.
A specified heat source is burned at the bottom of the sample and the sample then burned for four minutes. The flame spread, a function of distance and time, is then compared with a sample of redwood and a flame spread rating is reported. The test is similar to ASTM E-286, part 14 (1974).
Flame spreads for the front (F) and back (B) surfaces are reported.
The flexural strength and modulus is determined according to ASTM D-790.
The heat distortion temperature is determined according to ASTM D-648.
Some significant observations from the examples presented in Table I above are as follows.
By comparing Examples 1 and 2 at similar filler loading, the oxygen index of the cured resin increases as the level of methyl methacrylate is increased and polyester decreased. Although the polyester in Example 3 is kept at the same level as in Example 2, one-half of the methacrylate was substituted with styrene. This produced rather substantial changes since the oxygen index decreased unexpectedly while the smoke density increased very sharply. In a totally styrene thinned experiment (Example 4), the filled resin had a very high viscosity in comparison to Example 1 due to the poor solubility of this type of polyester in styrene compared to methyl methacrylate, while the cured resin again showed a very low oxygen index and a very high smoke density.
The use of comonomers with methyl methacrylate can be carried out without greatly affecting the oxygen index of the system. Thus, ethyl acrylate and vinyl pyrrolitone can be used to give faster reactivity with -. - . . .
- ~i9638 the polyester and better overall cure without contributing greatly to the oxygen index or smoke density (Examples 6 and 10). Where a difunctional monomer is used, such as in Example 7, the increase in the crosslinking density renders more thermal stability to the system as exemplified by a higher heat distortion temperature and a lower flame spread than in Example 5. The oxygen index remained almost unchanged although the smoke density increased. Even at this level, this system has a lower smoke density than styrene based systems and a higher oxygen index.
In Examples 8 and 9, other fire-retardant additives such as antimony oxide and zinc borate can be incorporated and yet maintain a low smoke density system. Their use, however, does not really reflect any dramatic improvements in the oxygen index or ~he flame spread rating.
Examples 11 - 20 A second series of unsaturated polyesters cured for the most part with methyl m~thacrylate were prepared. The principal variant in this series of polyesters was the formulation of the polyester itself.
The polyester formulation, the catalyst systems, time and temperature of cure, amount and type of filler, amount of fiber glass reinforcement, as well as certain physical properties are reported in Table II above.
In the examples, the abbreviations for the polyesters are as follows:
EG = ethylene glycol PG = propylene glycol TMPDAE = trimethylol propane diallyl ether F = fumaric acid MA = maleic anhydride AD = adipic acid .
' ' ': ' ' : " . ', . ' ' ~069~i38 The polyesters were prepared in a manner generally described above in Examples l-lO, that is, all the ingredients were charged to a suitable reaction vessel equipped with a condenser, stirrer and a source of nitrogen purging. The reactants were heated to initiate an exotherm and the reaction continued with heating and nitrogen sparging to drive of f water.
At the completion of the polyesterification, the polyester is cooled to about 155C. under a nitrogen atmosphere at which time catalyst promoters and inhibitors, if used, are usually added. At about 90C., a crosslinking agent is added to form the resin solution which is then cooled to room temperature and filtered to remove any gel particles.
The abbreviations used in Table II have the same significance as described above in connection with Table I.
Some significant observations from the data presented in Table II
above are as follows.
The resins of Examples 16-20 are formed from highly unsaturated polyesters giving the potential for more complete and room temperature cures. However, with highly unsaturated polyesters such as propylene-fumarate resins, the oxygen indices are relatively low. See Example 16 in which a propylene-fumarate resin at a 1:1 filler ratio has an oxygen index of 36.
This oxygen index should be compared with the one obtained with an ethylene-propylene-maleate-adipate polyester such as is shown in Example 5 in which the oxygen index is 43.8. The oxygen index of the propylene-fumarate resin can be improved if the hydrated alumina level is increased.
See Examples 16 and 17; however, note also that the viscosity increases.
The effects of benzoyl peroxide on smoke density can be seen by comparing Example 17 with Example 18. Example 17 contains benzoyl ., . , ~......... . . . . . .. . .
peroxide and Example 18 employs a catalyst system of pentanedione peroxide and cobalt octoate promoter. Benzoyl peroxide, being aromatic, appears to contribute significantly to the smoke density, whereas the aliphatic catalyst system of Example 18 appears to have minimal effect on the smoke density. Also, the benzoyl peroxide of Example 17 is applied as a slurry in tricresyl phosphate which also is aromatic and contains phosphate groups which are believed to contribute significantly to smoke density.
Examples 21 - 27 The following examples show the dramatic effect of N-vinyl pyrrolidone on accelerating curing so as to be able to achieve room temperature cures.
Example 21 An ethylene propylene-maleate-adipate polyester was prepared as generally described in Examples 1-10. The polyester was blended with methyl methacrylate to form a 1:1 weight ratio of polyester to methyl methacrylate. The resin was filled with aluminum hydrate in a 1:1 weight ratio and cured at room temperature with a catalyst system consisting of one percent by weight pentanedione peroxide and 0.2 percent by weight cobalt octoate promoter; the percentages by weight being based on resin weight. The resin gelled in 19.75 minutes and reached a peak exotherm of 119C. when 100 gram quantity was placed in a 150 milliliter glass beaker and placed in a 66C. bath with mild agitation.
- 1069~38 Example 22 Example 21 was repeated with the exception that 0.2 percent by weight dimethyl para-toluidiene wa.s used in the catalyst system. ThP
gel time was reduced to 5.5 minutes but the peak exotherm was only 100C.
indlcating an incomplete cure.
Example 23 A resin system similar to Example 21 was prepared from the following charge:
Component Percent ~y Wei~ht Polyester + Methyl Methacrylate (50/50) 47.5 N-vinyl pyrrolidone 2.5 TiO2 2.0 Hydrated alumina S0.0 As in Example 21, the catalyst system was one percent pentanedione peroxide and 0.2 percent cobalt octoate. The gel test results are shown in Table III below.
Examples 24 - 27 Resin systems similar to Example 23 were prepared from the following charges:
. .
~0~9638 Example No. 24 25 26 27 polyester + methyl methacrylate 47.5 46.5 46.5 46.5 N-vinyl pyrrolidone - 2.5 3.5 3.5 3.5 TiO2 2.0 2.0 2.0 2.0 hydrated alumina 50 50 50 50 cobalt octoate 0~1 0.1 0.05 0.2 pentanedione peroxidel 1.0 1.0 1.0 1.0 DMPTl 0. 01 Percent by weight based on resin weight.
Table III
Example No. 23 24 25 26 27 gel time, minutes at 66C. 0.78 2.00 1.45 7.90 0.75 total time 1.30 3.42 2.42 11.60 1.25 peak temperature, F. 282 264 269 221 282 .
Examples 28 - 34 Hydrated alumina has a pronounced effect on oxygen index.
Higher hydrated alumina loadings result in higher oxygen indices.
This is seen in FIG. 1 which is a plot of oxygen index versus percent hydrated alumina content of two different polyester resins.
Plot A represents an ethylene-propylene-maleate-adipate polyester prepared as generally described in Examples 1-10 in a molar ratio of 9/2/8/2.
Plot B represents a propylene-fumarate polyester prepared as generally described in Examples 16 through 20 in a molar ratio of 11.5/10.
The polyesters were combined with 50 percent by weight of methyl methacrylate; the percentages by weight being based on total weight of polyester and methyl methacrylate, and filled with aluminum hydrate in the various percentages shown in FIG. l; the percentages by weight being based on total weight of polyester resin and hydrated alumina.
The filled resins were laminated with two layers of 2 ounce chopped strand mat and cured at 82~C. for 30 minutes using 1 percent benzoyl peroxide as the catalyst. After curing, the laminates were evaluated for oxygen index according to ASTM D-2863.
~ 069638 Examples 35 - 41 In order to develop adequate strength, the aliphatic polyesters of the present invention cured with aliphatic monomer, must be highly unsaturated. Strength as a function of the percentage unsaturation is shown in FIGS. 2, 3 and 4. The resins evaluated for the data shown in FIGS. 2, 3 and 4 were prepared by blending 50 parts by weight polyester with 50 parts by weight methyl methacrylate, 7 parts by weight N-vinyl pyrrolidone and 0.5 parts by weight cobalt octoate and 1.0 part by weight pentanedione peroxide.
The polyesters used in preparing the various resins were prepared from the following charges:
Component Mole Ratios maleic anhydride 10 9 8 7 6 5 4 adipic acid 1 2 3 4 5 6 ethylene glycol 9 9 9 9 9 9 9 propylene 2 2 2 2 2 2 2 The polyesters and resultant resins were prepared as generally described in Examples 1-10.
The resultant resins were cast in a 12 inch by 12 inch by 1/8 inch closed cell and allowed to gel at room temperature followed by a one-half hour post cure at 82C, After curing, the resin castings were released from the cell and evaluated for flexural strength and modulus according to ASTM D-790 and for Barcol hardness using a 934 Barcol Impressor.
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- - ~06963~3 Examples 42 - 52 To show the effect that aromaticity has on the oxygen index and smoke density of unsaturated polyester resins, the following experiments were conducted:
A series (Examples 42-46) of unsaturated polyester resins were prepared as generally described in Examples 1-10 from condensing maleic and phthalic anhydrides with ethylene glycol. Five unsaturated polyesters were prepared in which the mole ratio of maleic anhydride to phthalic anhydride varied from 9/1 to 5/5. The unsaturated polyesters were thinned with methyl methacrylate crosslinking monomer in a 1:1 ~ -weight ratio, filled with alumina hydrate in a weight ratio of 150 parts by weight of filler to 100 parts by weight of resin, and 75 parts by weight of the filled resin were then combined witII 25 parts by weight continuous glass filament which is commercially available from Owens-Corning as continuous filament strand M8620. The resin-filler-glass composites were then molded for three minutes at 255~. (124C.) in the presence of one percent by weight based on weight of resin plus alumina I hydrate of a diperoctoate-type peroxide catalyst commercially available from Witco Chemical as USP-245 peroxide. The composition of the unsaturated poIyesters is shown ln Table IV beIow.
~' ' ,.
.
-' ' . ' , ' '. - ' . ':
~069638 Table IV
Composition of Unsaturated Polyesters with Varying Amounts of Aromaticit~__n Polyesterl _ Mole Ratio ExampleMaleic - Phthalic Ethylene Propylene Acid NoAnhydride Anhydride Glycol Glycol Number Viscosity_ 42 9 1 11.3 0 53.6 G
43 8 2 11.3 0 46.8 G
44 7 3 11.3 0 40.5 J
6 4 11.3 0 41.4 G
46 5 5 11.3 0 35.8 G
0.02% methyl hydroquinone cooked with polyester.
Reduced Gardner-Holdt viscosity, 60% solution in ethyl CELLOSOLVE.
A second series (Examples 47-52) of unsaturated polyester resins was prepared in which the aromaticity was introduced into the crosslinking monomer portion. Six unsaturated polyesters were prepared from condensing maleic anhydride, ethylene glycol, and propylene glycol in a mole ratio of 10/813.3 in the manner generally described in Examples 1-10. The unsaturated polyester resin was cooked to an acid number of 53.1 and had a reduced Gardner-~oldt viscosity of about H- as a 60 percent solids solution in ethyl CELLOSOLVE. The unsaturated polyester was then thinned with mixtures of methyl methacrylate and styrene in the weight ratios shown in Table V below.
1069~;3~3 Table V
Weight Ratios of Ethylene Propylene Maleate Polyesters with Methyl Methacrylate and Styrene _ Example _ Wei~ht Ratio No. Polyester ~ Styrene The unsaturated polyester resins (polyester plus crosslinking monomer) shown in Examples 47 through 52 above were then filled with alumina hydrate filler in a weight ratio of 150 parts by weight of alumina hydrate to 100 parts by weight of resin, and 75 parts by weight of the filled resin was then combined with 25 parts by weight of continuous glass filament commercially available from Owens-Corning as continuous filament strand M8620. The resin-filler-glass composites-were then molded for 3 minutes at 255F. (124C.) in the presence of one percent by weight based on weight of resin and alumina hydrate of a diperoctoate-type peroxide catalyst commercially available from Witco Chemical as USP-245.
The cured thermoset articles in Examples 42 through 46 above were then evaluated for oxygen index according to ASTM D-2863 and smoke density in both the smoldering and flaming modification according to ~STM D-2343. Table VI below shows the results of the testing.
' .~
".
. .
, . . . ~ . .
Table VI
Oxygen Index and Smoke Density Results Weigllt Weight Example Percentage Percentlage Oxygen Dm No. Phthalicl Styrene Index Flaming SmolderinR
42 4.8 0 material is crystalline, could not be evaluated 43 9.2 0 47.1 78 121 44 13.5 ~ 46.5 78 161 17.4 0 46.1 58 155 46 21.1 0 43.5 58 98 47 0 20 37.1 191.0 234 48 0 15 40.5 150 193 49 0 10 42.5 124 149 0 5 47.3 108 188 51 0 2 51.7 105 194 52 ~ 0 52.4 88 164 Percentages by weight based on resin weight.
The data in Table VI above shows that as aromaticity is introduced into the resin, the oxygen index becomes lower. However, the data indicates that how the aromaticity is introduced is also a factor.
From a comparison of the oxygen index values in Examples 42 through 46 with those of Examples 47 through 52, it appears that aromaticity introduced into the resin through the crosslinking monomer has more of an effect in lowering the oxygen index than introducing aromaticity through the unsaturated polyester.
. '' : : .
.
, -. . . . . .
The data with regard to smoke density, flaming modification, shows that introduction of aromaticity into the resin through the crosslinking monomer greatly increases the amount of smoke generated.
Examples 47 through 52 show that increasing the styrene content from O to a high of 20 percent by weight results in over 100 percent increase in smoke density. However, somewhat surprisingly, introducing aromaticity into the resin through the unsaturated polyester does not seem to increase the smoke density. In fact, the data in Examples 52 and 42 through 46 indicate that introducing aromaticity in the unsaturated polyester actually decreases smoke density for the flaming modification. ~ -With regard to smoke density measurements for the smoldering variation, the data shown in 1able VI is not conclusive. ~lowever, the data does seem to indicate that introducing aromaticity into the resin through the crosslinking monomer has more of an effect in raising the smoke density than introducing aromaticity through the unsaturated polyester portion.
Example 53 The following experiment was conducted to determine the toxicity of gases evolved from burning unsaturated polyester resins of the present invention.
An ethylene propylene maleate adipate polyester as described in Examples 1-10 with O.OI percent by weight methyl hydroquinone was prepared in the method as generally described in Examples 1-10. The unsaturated polyester was cooked at 210C. until it attained the reduced Gardner-Holdt viscosity of G-H as a 60 percent solution in ethyl CELLOSOLVE.
At tbis viscosity, the poly=er had an tcid n~mber of ZO-30.
, .,, ., . . . . . , . . ~ . . ..
The unsaturated polyester was cooled from 210C. to 155C.
at which time 0.0625 parts by weight of sodium acetate (as a 25 percent by weight water solution) and 0.005 percent by weight methyl hydroquinone were added. The polyester (53.76 parts by weight) was further cooled to 90C. and 46.24 parts by weight of methyl methacrylate added to form a 50 percent solids solution which had a Brookfield viscosity at 77F.
(25C.) of 70 + S cps.
The above-described resinous composition forms one package of a two-package system. In the second package was 0.05 parts by weight of cobalt octoate and 7.0 parts by weight of N-vinyl pyrrolidone.
The two packages were mixed together (47.4 parts by weight) and mixed Witll 49.3 parts by weight of alumina hydrate and 2.8 parts by weight of titanium dioxide and 1.0 parts by weight of 2,4-pentanedione peroxide free radical catalyst. The filled resin was poured onto chopped strand fiber glass mat (two plies of 2 oz. (5.67 kg) A~) so as to form a composite with 20 percent by weight fiber glass.
The composite was then molded under heat and pressure to form the laminate which was then subjected to smoke density measurements in a flaming modification. The gases evolved were collected in a cold trap at -80C. and the condensate analyzed by gas chromatography and found to contain the following constituents:
Consti_uents Percent by Weight methyl methacrylate 0.37 methanol 0.27 acetone 0.07 acetaldehyde 0.04 unidentified about 0.07 water 99.18 .
Other laminates as described above were subjected to smoke density measurements in a flaming and a smoldering mode. Gaseous samples were taken of both modes and passed through 100 milliliters of a .1 normal sodium hydroxide aqueous solution for a cyanide determination. The gases collected from the flaming modification of the smoke density showed 2Y0 parts per billion of cyanide and the gases collected from the smoldering modlfication showed 12 to 17 parts per billion cyanide.
Gaseous samples were also analyzed by mass spectroscopy. For this analysis, the evolved gases were collected when the highest smoke density was recorded in 250 ml. glass tubes which were subsequently sealed. The collected gases were then analyzed by mass spectroscopy and found to contain:
Flaming ~odification Smoldering Modification IngredielltParts by Weight IngredientParts by Weight carbon dioxide 1.79 carbon dioxide 0.22 nitrogen 78.42 nitrogen 77.86 argon 0.92 argon 0.90 oxygen 18.88 oxygen 21.01 - ,.
The results presented above show that the gases evolved are relatively non-toxic. It is interesting to note that no carbon monoxide -was detected by mass spectroscopy.
`
Claims (16)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A curable aliphatic polyester resin being essentially free of aromatic constituents comprising a mixture of:
(A) an unsaturated aliphatic polyester derived from polycondensing:
(1) organic polyols having a functionality of at least 2, (2) organic polycarboxylic acids having a functionality of at least 2 in which the unsaturated component of the unsaturated polyester is an alpha, beta-ethylenically unsaturated polycarboxylic acid and the equivalent ratio of alpha, beta-ethylenically unsaturated polycarboxylic acid to all other polycarboxylic acid components in the polyester is at least 1 to 1; and (B) an aliphatic vinyl monomer copolymerizable with said polyester, (C) at least 50 percent by weight hydrated alumina, the percentage by weight being based on total weight of (A), (B) and (C), said composition capable of being combined with glass fibers and completely cured to produce strong thermoset articles which are difficult to burn and which when exposed to an open flame produce little smoke.
(A) an unsaturated aliphatic polyester derived from polycondensing:
(1) organic polyols having a functionality of at least 2, (2) organic polycarboxylic acids having a functionality of at least 2 in which the unsaturated component of the unsaturated polyester is an alpha, beta-ethylenically unsaturated polycarboxylic acid and the equivalent ratio of alpha, beta-ethylenically unsaturated polycarboxylic acid to all other polycarboxylic acid components in the polyester is at least 1 to 1; and (B) an aliphatic vinyl monomer copolymerizable with said polyester, (C) at least 50 percent by weight hydrated alumina, the percentage by weight being based on total weight of (A), (B) and (C), said composition capable of being combined with glass fibers and completely cured to produce strong thermoset articles which are difficult to burn and which when exposed to an open flame produce little smoke.
2. The composition of Claim 1 which contains:
(A) from 40 to 70 percent unsaturated polyester, and (B) from 30 to 60 percent vinyl monomer, the percent by weight being based on total weight of unsaturated polyester and vinyl monomer.
(A) from 40 to 70 percent unsaturated polyester, and (B) from 30 to 60 percent vinyl monomer, the percent by weight being based on total weight of unsaturated polyester and vinyl monomer.
3. The composition of Claim 1 in which the alpha, beta-ethylenically unsaturated polycarboxylic acid is maleic acid or its anhydride, or fumaric acid.
4. The composition of Claim 1 in which the organic poly-carboxylic acid component contains an acyclic saturated poly-carboxylic acid or anhydride containing from 2 to 10 carbon atoms.
5. The composition of Claim 4 which contains:
(A) from 0 to 50 equivalent percent of an acyclic saturated polycarboxylic acid or anhydride containing from 2 to 10 carbon atoms, and (B) from 50 to 100 equivalent percent of an alpha, beta-ethylenically unsaturated polycarboxylic acid or its anhydride.
(A) from 0 to 50 equivalent percent of an acyclic saturated polycarboxylic acid or anhydride containing from 2 to 10 carbon atoms, and (B) from 50 to 100 equivalent percent of an alpha, beta-ethylenically unsaturated polycarboxylic acid or its anhydride.
6. The composition of Claim 1 in which the polyol compon-ent includes alcohols or polyols containing allylic or acrylic unsaturation.
7. The composition of Claim 6 which includes trimethylol propane diallyl ether.
8. The composition of Claim 1 in which the polyol compon-ent is an alkylene glycol or an alkylene oxide glycol contain-ing from 2 to 10 carbon atoms.
9. The composition of Claim 1 in which the polyol component contains in part a polyol having a functionality greater than 2.
10. The composition of Claim 1 in which the aliphatic monomer is selected from lower alkyl esters containing 1 to 4 carbon atoms of methacrylic or acrylic acid.
11. The composition of Claim 1 in which the aliphatic vinyl monomer contains up to 20% N-vinyl pyrrolidone based on the total weight of aliphatic vinyl monomer.
12. The composition of Claim 1 in which the aliphatic vinyl monomer includes 5 to 20% N-vinyl pyrrolidone based on the total weight of aliphatic vinyl monomer.
13. The composition of Claim 1 which further includes antimony oxide.
14. The composition of Claim 1 which further includes about 10 to 70 percent by weight glass fibers; the percentage by weight being based on total weight of aliphatic polyester resin, hydrated alumina and fiber glass.
15. The composition of Claim 1 in a cured, cross-linked state.
16. The composition of Claim 4 in a cured, crosslinked state.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US68635076A | 1976-05-14 | 1976-05-14 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1069638A true CA1069638A (en) | 1980-01-08 |
Family
ID=24755951
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA257,044A Expired CA1069638A (en) | 1976-05-14 | 1976-07-15 | Low smoke density fire-retardant unsaturated aliphatic polyester resins containing alumina hydrate |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPS52139188A (en) |
| CA (1) | CA1069638A (en) |
| DE (1) | DE2714039C2 (en) |
| FR (1) | FR2351154A1 (en) |
| IT (1) | IT1068743B (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| IE47608B1 (en) * | 1977-12-22 | 1984-05-02 | Ici Ltd | Antiviral tetracyclononane derivatives,processes for their manufacture and pharmaceutical compositions containing them |
| EP2210911A1 (en) * | 2009-01-23 | 2010-07-28 | Advansa Sasa Polyester Sanay A.S. | Production of polymers |
Family Cites Families (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5035226B2 (en) * | 1971-11-30 | 1975-11-14 | ||
| BE792508A (en) * | 1971-12-09 | 1973-06-08 | Dart Ind Inc | TRANSVERSALLY CROSS-LINKABLE THERMOPLASTIC COMPOSITION AND PROCESS FOR ITS PRODUCTION |
| JPS5615412B2 (en) * | 1972-01-03 | 1981-04-10 | ||
| JPS513760B2 (en) * | 1973-02-01 | 1976-02-05 | ||
| JPS5242083B2 (en) * | 1974-02-20 | 1977-10-22 | ||
| JPS5242084B2 (en) * | 1974-06-06 | 1977-10-22 | ||
| CA1052928A (en) * | 1974-07-22 | 1979-04-17 | Hooker Chemicals And Plastics Corp. | Unsaturated polyester resins having improved fire retardance |
| JPS5113511A (en) * | 1974-07-23 | 1976-02-03 | Nippon Electric Co | CHUKEISETSUZOKUSHIKENNIOKERU SHIKENYOAITEKYOKUSOCHI |
| FR2279815A1 (en) * | 1974-07-26 | 1976-02-20 | Asahi Chemical Ind | Unsaturated polyester moulding compsns - contg methyl methacrylate copolymer inorg additives |
-
1976
- 1976-07-15 CA CA257,044A patent/CA1069638A/en not_active Expired
- 1976-07-16 JP JP8648176A patent/JPS52139188A/en active Pending
- 1976-08-20 FR FR7625421A patent/FR2351154A1/en active Granted
- 1976-09-29 IT IT69329/76A patent/IT1068743B/en active
-
1977
- 1977-03-30 DE DE2714039A patent/DE2714039C2/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| FR2351154B1 (en) | 1980-09-19 |
| DE2714039A1 (en) | 1977-11-17 |
| JPS52139188A (en) | 1977-11-19 |
| IT1068743B (en) | 1985-03-21 |
| DE2714039C2 (en) | 1982-10-14 |
| FR2351154A1 (en) | 1977-12-09 |
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