CA1334606C - Use of ester group containing polyols in a rim process - Google Patents

Abstract

The present invention is directed to a process for the production of polyurethane moldings by reacting a reaction mixture comprising a) a polyisocyanate, b) an isocyanate-reactive material having a molecular weight of from about 840 to about 5,000, and c) a chain extender, said reaction mixture being processed as a one-shot system by the RIM process at an isocyanate index of from about 70 to about 130, the improvement wherein component b) comprises a polyester polyol selected from the group consisting of i) a polyester polyol having the idealized structure:

ii) a polyester polyol having the idealized structure:

Description

Mo-2984 USE OF ESTER GROUP CONTAINING
POLYOLS IN A RIM PROCESS
BACKGROUND OF THE INVENTION
Polyester polyols produced from dicarboxylic acid anhydrides, polyols and polyepoxides are known. In U.S. Patent 4,403,093, such polyester polyols are produced by first reacting a 1,2-dicarboxylic acid anhydride with a polyol under conditions sufficient to form a half-ester with substantially no polyester-ification product. The resultant half-ester is then reacted with a polyepoxide under conditions sufficient to form an ungelled polyester oligomer. The resultant polyester oligomers are described as being useful as resinous binders in high solid containing compositions.
Polyester polyols produced from aromatic acids and polyoxyethylene glycols are also known and are described as being useful in the production of rigid polyurethane foams (see, e.g., U.S. Patent 4,039,487 and German Auslegeschrift 1,155,908).
Finally, in the known polyurethane/urea reaction injection molding (RIM) process, a wide variety of different polyols have been suggested (see e.g., U.S.
Patents 3,726,952, 4,218,543, 4,288,564, 4,442,235, 4,519,965, 4,581,396 and British Patent 1,534,258, and Canadian Application Serial No. 557,202, filed January 22, 1988. Similarly, polyester polyols of various types have been suggested for use in the RIM process (see, e.g., U.S. Patents 4,481,309, 4,590,219 and 4,595,705).
DESCRIPTION OF THE INVENTION
30 The present invention is directed to the discovery that when certain polyester polyols are used in the RIM process, the resultant part exhibits unexpectedly improved flame properties. More particularly, the present invention is directed to an Mo-2984 r l A ~

improved process for the production of polyurethane moldings by reacting a reaction mixture comprising a) a polyisocyanate, b) an isocyanate-reactive material having a molecular weight of from about 840 to about 5,000 and c) a chain extender and/or cross-linker, said reaction mixture being processed as a one-shot system by the RIM process at an isocyanate index of from about 70 to about 130, the improvement wherein component b) comprises a polyester polyol selected from the group consisting of (i) polyester polyol having the idealized structure O
~I 11 R-~ O-C-R'-C-O-X t OH)n]m (ii) a polyester polyol having the idealized structure O O
H- O-X'-O-C-R"-C -p O-X'-OH , and (iii) mixtures thereof, wherein R represents the residue of a polyepoxide after ring opening with a carboxylic acid group, R' represents the residue of a cyclic anhydride, 25 R" represents the residue of an aromatic anhydride or aromatic dicarboxylic acid, X and X' independently represent the organic residue of a polyol, m represents the number of epoxy groups of the polyepoxide ring opened with carboxylic acid groups, n is an integer of from 1 to 7, and p is a number of from 1 to 15.

M~-2984 -2-~ ,, In the preferred embodiments X-~OH)n represents the structure R"' --tCH2-CH-o ~ H

and X' represents the structure R"' R"' t CH2-1H-o )y 1 CH2-1H-where R"' represents hydrogen (-H) or methyl (-CH3), and y is a number of from 4 to 25. In the most preferred embodiments, m is 2 or 3 and most preferably 2, and p is from 1 to 7.
The polyesters of the formula (i) are made in a manner similar to that described in U.S. Patent 4,403,093. In the first step, a cyclic dicarboxylic acid anhydride is reacted with a polyol (preferably a polyoxyethylene or polyoxypropylene glycol having a 15 molecular weight of from about 200 to about 1500) under conditions sufficient to form a half-ester with substantially no polyesterification product. The resultant half-ester is then reacted with a polyepoxide under conditions to form the resultant polyester.
In preparing the formula (i) polyesters, a cyclic l,2-dicarboxylic acid anhydride is reacted with a polyol under conditions sufficient to ring open the anhydride, forming the half-ester with substantially no polyesterification occurring (i.e., both carboxyl groups 25 f the anhydride esterified by polyol in a recurring manner).
In bringing an anhydride and a polyol together under suitable reaction conditions, reaction can occur in at least two ways. The desired reaction mode involves 30 opening the anhydride ring with hydroxyl, i.e., Mb-2984 -3-!:
-- C --C I ~!
\ - C - C - OR
O + HOR > ¦C - C - C - C - OH
O l O

Alternately, carboxyl groups formed by opening of the anhydride ring can react with hydroxyl groups to give off water. The latter reaction is not desired since it can lead to polycondensation reactions resulting in products with broad molecular weight distributions.
To achieve reaction, the anhydride and polyol are contacted together, usually by mixing the two ingredients together in a reaction vessel. Preferably, the reaction is conducted in the presence of an inert atmosphere such as nitrogen.
For the desired ring-opening and half-ester formation reaction, a cyclic 1,2-dicarboxylic acid anhydride is used. Reaction of a polyol with a carboxylic acid instead of an anhydride would require esterification by condensation to eliminate water which would have to be removed by distillation which, under these conditions, would promote undesired polyester-ification.
The reaction temperature is preferably low,that is, no greater than 160C and usually within the range of 60C to 160C, and preferably from 100C to 140C. Temperatures greater than 160C are undesirable because they promote polyesterification, whereas temperatures less than 60C are undesirable because of sluggish reaction.
The time of the reaction can ~Jary depending upon the temperature of reaction. Usually, the reaction Mo-2984 - 4 -time will be from as low as 10 minutes to as high as 24 hours.
The molar ratio of anhydride to polyol is usually from about 0.5 to 1.5:1, and is preferably about 5 1:1 to obtain a maximum conversion with maximum purity.
Ratios less than 0.5:1 are undesirable because they result in unreacted polyol. Ratios greater than 1.5:1 are not preferred because of increased formation of high molecular weight polyesters.
Among the cyclic anhydrides which can be used in the practice of the invention are those which, exclusive of carbon atoms in the anhydride moiety, contain from about 2 to 30 carbon atoms. Substituted cyclic anhydrides can also be used provided the 15 substituents do not adversely affect the reactivity of the anhydride or the properties of the resultant polyester. Examples of substituents would be chloro and alkoxy. Examples of anhydrides include maleic anhydride, succinic anhydride, glutaric anhydride, 20 phthalic anhydride, tetrahydrophthalic anhydride, methyltetrahydroph~halic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, tetrachlorophthalic anhydride, endomethylene tetrahydrophthalic anhydride, and chlorendic anhydride.
The polyols used to prepare the half-ester are preferably polyoxyethylene or polypropylene glycols having molecular weight of from about 200 to about 1500, and preferably from about 200 to about 1000. However, substantially any polyol may be used. Among the polyols 30 which can be used are those which contain from about 2 to 20 carbon atoms. Preferred are aliphatic polyols, particularly aliphatic diols or triols, most preferably those containing from 2 to 10 carbon atoms. Examples include ethylene glycol, 1,2-propanediol, 35 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, glycerol, 1,2,3-butanetriol, 1,6-hexanediol, neopentyl Mo-2984 - 5 -glycol, diethylene glycol, dipropylene glycol, trimethylolpropane, 2,2,4-trimethylpentane-1,3-diol, 2,2-dimethyl-3-hydroxypropyl 2,2-dimethyl-3-hydroxy-propionate, and 1,4-cyclohexanedimethanol. Preferred are those aliphatic diols or triols selected from the class consisting of neopentyl glycol, 2,2,4-trimethylpentane-1,3-diol, 2,2-dimethyl-3-hydroxypropyl 2,2-dimethyl-3-hydroxypropionate, diethylene glycol, dipropylene glycol, 1,6-hexanediol and trimethylolpropane. Higher functionality polyols such as tetrols can be used but they are not preferred. An example would be 1,2,3,4-butanetetrol. Alkoxylated products of such polyols can also be used. In general, it is preferred that the molecular weight of the polyol range from 62 to 2000, and preferably from about 200 to about 1000.
After the anhydride and polyol are reacted together, the resultant half-ester is further reacted with a polyepoxide to chain extend the half-ester to form a liquid polyester oligomer. Chain extension occurs through reaction of the carboxylic acid groups of the half-ester with the epoxy groups of the polyepoxide.
Although the structure of the final product is not known with certainty, the major product (i.e. greater than 50 percent by weight based on total weight) is believed to be of the structure:

R -[0 -IC- R'-ICl O ~xtH)n]m O O

where R, R', X, n and m are as defined earlier.
The half-ester and the polyepoxide are reacted together by contacting under conditions sufficient to form the polyester. Preferably, the half-ester and the Mb-2984 -6-.

polyepoxide are reacted in the presence of an inert atmosphere such as nitrogen.
The half-ester and polyepoxide can be contacted together by simply mixing the two togeth~r. It is preferred to add the polyepoxide to the half-ester incrementally so as to better control the reaction and to obtain higher yields of the desired liquid polyester oligomer. The proportions of the half-ester and the polyepoxide are such that the equivalent ratio of epoxy to carboxylic acid is from about 1:1 to 2.5:1. To obtain maximum conversion to the desired polyester, the equivalent ratio of epoxy to carboxylic acid is chosen so that the acid number is reduced to acceptable low value (e.g., less than 2.0). A preferred ratio is from 1:1 to 1.10:1, and is most preferably about 1.05:1. Ratios less than 1:1 result in less than the optimum amount of product, whereas ratios greater than 1.1:1 may result in unreacted epoxy, which is undesirable.
The temperature of reaction should be less than 220C and usually within the range of about 60C to 220C, and preferably 140C or less. Temperatures higher than 140C are generally undesirable because of competition between the hydroxyl groups and epoxy groups for reaction with carboxyl groups and between hydroxyl groups and carboxyl groups for reaction with epoxy groups, resulting in undesirable polyesterification reactions. Reaction temperatures less than 60 C are undesirable because of sluggish reaction.
Further a catalyst (such as organophosphine) is preferably used. Examples of suitable catalyst of this include triarylphosphines such as triphenylphosphine.
Examples of other catalysts include amines such as triethylamine and inorganic bases such as potassium hydroxide. When catalyst is used, it is used in amounts of about 0.1 to 2 percent by weight, based on total Mo-2984 - 7 -weight of the reactants. The presently preferred catalyst is one sold as Cordova Accelerator A~C-2, available from Cordova Chemical Company and belie~Jed to be a chromium octoate.
The time of reaction depends on how tne reactants are contacted, the temperature of reaction and the presence or absence of catalyst. In general, reaction times will vary from about 30 minutes to 24 hours.
The polyepoxides which are used are those having 1,2-epoxy equivalency greater than 1, preferably 2 and up to about 3Ø Higher functionality polyepoxides, i.e., greater than 3, are not preferred because of considerable chain branching and gelation 15 problems. The preferred polyepoxides are polyglycidyl ethers of polyhydric phenols such as bisphenol A. These polyepoxides can be produced by etherification of a polyhydric phenol with an epichlorohydrin such as epichlorohydrin in the presence of an alkali. Examples 20 of polyphenols other than bisphenol A are halogenated bisphenol A; 1,1-bis-(4-hydroxyphenyl)ethane;
2-methyl-1,1-bis-(4-hydroxyphenyl)propane;
2,2-bis-(4-hydroxy-3-tertiarybutylphenyl)propane;
bis-(2-hydroxynaphthyl)methane; 1,5-dihydroxy-25 naphthalene; and the like. While polyhydric phenols arepreferred, other cyclic polyols can be used.
Cycloaliphatic polyols such as 1,2-cyclohexanediol, 1,4-cyclohexanediol, 1,2-bis-(hydroxymethyl)-cyclo-hexane, and hydrogenated bisphenol A, can be used.
Polyglycidyl ethers of polyhydric alcohols such as ethylene glycol, diethylene glycol, 1,2-propylene glycol, and 1,4-butylene glycol can also be used.
Polyglycidyl esters of polycarboxylic acids which are produced by the reaction of epichlorohydrin or 35 a similar epoxy compound with an aliphatic or aromatic polycarboxylic acid can also be used. Examples of Mo-2984 - 8 -1 334~05 polycarboxylic acids are dicarboxylic acids such as adipic acid, succinic acid, glutaric acid, terephthalic acid, dimerized linoleic acid and the like.
Also useful as the polyester polyol are those having the idealized structure O Q
Il 11 H--O-X ' -O-C-R"-C p O--X ' -OH

where R" represents the residue of an aromatic anhydride or aromatic dicarboxylic acid and X' represents the organic residue of a polyol, and p is a number of from from 1 to 15. Such polyester polyols are prepared by reacting an aromatic anhydride or acid with a dihydroxy material. Suitable diols are those of the type mentioned relative to preparation of the formula (i) polyesters.
Similarly, the anhydrides usable are those aromatic anhydrides described or useful in the preparation of the formula (i) polyesters. Acids such as isophthalic and terephthalic acids, as well as dimethyl esters of these acids produced via transesterification, are also useful.
The polyesters of formula (ii) are produced by art recognized techniques.
The polyesters of the present invention are liquid and are eminently suitable for use in a reaction injection molding process (RIM) to produce parts having excellent flame properties. As is known, the RIM process is a filling technique in which the highly active, liquid components are rapidly injected into a closed mold.
Substantially any of the isocyanates, chain extenders, and cross-linkers known in the art can be used in addition to the polyesters described herein.
The invention is further illustrated but is not intended to be limited by the following examples, in which all parts and percentages are by weight unless otherwise specified.
M~-2984 ~9~

EXA~LES 1 334606 Example 1 4850 parts of a polyoxyethylene glycol of about 400 molecular weight were added to a 12 liter flask.
5 1796 parts of phthalic anhydride were added over a period of about 15 minutes. The flask was heated to 130C and held at that temperature for 1 1/2 hours.
About 81 parts of AMC-2 (an accelerator available from Cordova Chemical Company and believed to be a chromium 10 octoate) were then added. 2377 parts of Epon 828 (a liquid bisphenol-A e'poxy resin available from Shell Chemical Company, having a maximum Gardner Color of 4, a viscosity at 25C of 100-160 poises and a weight per epoxide of 185-192) were then added and the reaction 15 mixture was held at'130C for 1 1/2 hours. The resultant product had an OH number of 149 and an acid number of 0.1.
Example 2 4950 parts of CarbowaX 600 (a polyoxyethylene 20 glycol of about,600 molecular weight) were added to a flask. Over a period of about one hour, about 1222 parts of phthalic anhydride were added, during which time the temperature gradually rose to 110C. After another ten minutes, the temperature had risen to 130C.
25 The temperature was held at 130C for 2 1/2 hours. 62 parts of- AMC-2-were then added. About 1540 parts of Epo~ 828 were then added over a period of about 15 minutes. The temperature was held at about 125C for about one hour. An additional 57 parts of Epon*828 were 30 then added and the temperature was held at 125C for 2 1/2 hours. Heating was stopped and the product, having an OH number of 118 and an acid number of 0.1, was stored at room temperature.
Example 3 2800 parts of Carbowax 200 (a polyethylene glycol of 200 molecular weight) were weighed into a Mo-2984 - 10 -* trade-mark B

- flask and heated to 80C. Over a period of about 20 minutes, 2074 parts of phthalic anhydride were added.
The temperature gradually rose during the addition, and after a total time of about 50 minutes, reached a 5 temperature of 145C. The temperature was then maintained at 130C for about 5 hours. 49 parts of AMC-2 were then added. About 2437 parts of Epon 828 were added over a period of about 55 minutes, after which time, the temperature had reached 165C. The 10 temperature was then adjusted to 130C. After about 8 hours, 203 parts of Epon 828 were added, and the temperature was kept at 130C for another 5 hours. 107 parts of Epon*828 were then added and the temperature was kept at 130C for another 5 hours, after which time 15 the product was cooled to room temperature. The product had an OH number of 187 and an acid number of 2.2.
Example 4 A 12 liter, 3 neck flask was charged with 4506 parts of Carbowa~ 400 (a polyoxyethylene glycol of 400 20 molecular weight) and heated to 100C with stirring.
2028 parts of resin 565 (the diether of propylene glycol and bisphenol-A) and 4.8 parts of Fascat 4102 (butyltin tricarboxylate available from M~T) were then added.
Phthalic anhydride (1668 parts) was then added over a 25 period of about 10 minutes. The ~emperature was then raised to 210C and held at that temperature for about 9 1/2 hours with removal of water. The resultant product had an OH number of 77 and an acid number of 0.3.
30 Example 5 A 12 liter, 3 neck flask was charged with 5600 parts of Carbowax*200 and heated to 100C with stirring.
2962 parts of phthalic anhydride and 5 parts of Fascat*
4102 were then added and the temperature was raised to 35 210C. The temperature was maintained at 210C for about 7 hours with removal of water. The resultant Mo-2984 - 11 -* trade-mark F ~ `

product had an OH number of 100 and an acid number of 0.2.
Example 6 A 12 liter! 3 neck flask was charged with 5195 S parts of Carbowax 200 and heated to 120C. 3193 parts of phthalic anhydride and 2.1 parts of Fascat ~102 were then added. The temperature was raised to 210C, ~nd held at that temperature for about 14 hours with removal of water. The resultant product had an O~. number of 60 - 10 and an acid number of 1.0 Examples 7 through 18 In these examples various parts were made via the RIM process. The components used were as follows:
POLYOL A - a glycerine-initiated polypropylene oxide 15 product having an OH number of about 1050.
POLYOL B - a glycerine initiated polypropylene oxide product having an OH number of about 28, and having ethylene oxide tips.
EG - Ethylene Glycol 20 ADDITIVE A - a quaternary ammonium salt of tall oil and the amide prepared from tall oil and N,N-dimethyl-1,3-propane diamine.
~C 193 - a silicone surfactant commercially available ~from Dow Corning.
25 PC 8 - Polycat--8 - N,N-dimethylcyclohexylamine, available-from Air Products.
T-12 - dibutyl tin dilaurate.
AB 19 - Antiblaze l9, a cvclic phosphate ester flame retardant available from Albri~ht & Wilson Americas Inc.
30 Iso - a 50/50 blend of Mondur*PF and Mondur MR*(two commercially available isocyanates from Miles Inc.) -~ having an isocyanate group content of about 27~.
The components and the amounts thereof were as 35 indicated in Table I.

~o-2984 - 12 -* trade-mark r 1~

RIM plaques were prepared using a laboratory piston metering unit and clamping unit. The metering unit was a two component instrument having a maximum metering capacity of 0.6 liters. A rectangular mold, 5 300 mm x 200 mm x 8 mm, was used to mold the samples under the following conditions:
Component A Temp 32C
Component B Temp 40C
Isocyanate Index 110 10 A/B Weight Rates (125-140)/100 Mold temperature 60C
Impingement Pressure 2646 psi External Mold Release Agent Silicone spray designated MR 515, available from Chemtrend Demold time 2 minutes No post cure.
Various physical properties and flame 20 properties were tested, with the results as set forth in Table I. Example 7 was a comparative test.

Mo-2984 - 13 -o o ,, f O 1 O ~1 O
O

O ~1 O

O ~1 O

O C~
O I I I u~ ~i 0 ,~

O
C`~ r--o CQ ~ t g ~ ~ O O O O O O
P~ O O O O O O O O ., o o c~ o o ~o o po~ o ~

Mo-2984 - 14 -,f~';~L

g C~
o '~ o~ ' .J r-- O H E~
~ co ,~ ~ z c~
c~i o r~ C~l ~ ^ ~ o o~
co ~ ~; ~ o ~ o c~
~D r1 C~ CO r1 r~ :~
o ~ g ~ C~
o ,~cr~ ^ o cq rl ~ . CJ~ O U~ O
CCOj CiO O O C~r~
~_ O
O
v cr coco ^co O
C`~o ~ O
C~ ~o C~l ~ I` r~ ~ o H O
g~ a~
U~ CS` ^ o U~
Cl~ o r~ ~J C~l O
J cr ,~
o o u~ c) c~ c~l 1~ c~l O
or~ o ~D ~
rl .,~
,~ o. v ~q r H r V ~ ~ ~C `~.
~ ~ r -`
C ~ ~-- G
:~ n o c~
r~ C~
~ C~ p~,C
C i~ ~ O
v U~
C~l O CO C~l CO CO
~: a c~
Mo-2984 - 15 -TABLE I (Cont'd) ASTM Test Example 13 14 15 16 17 18 D 792 Density, pcf 70~0 68.8 70.0 67.5 71.4 69.4 D256 Charpy Impact ft-lb/in2 13.49 5.05 17.58 18.88 19.27 13.60 D 790 Flex. Mod. @ RT, psi 395,000 410,000 390,000 3Y5,000 405,000 394,000 Heat Distortion D 648 C (60 psi~ 93.9 74 88 66.1 96.5 70.5 Radiant Panel Test E 162 (Flame Spread Index) 110 119 103 133 215 124 D 638 Tensi]e, psi lQ200 3100 9125 9550 10200 8950 ~, D 638 Elongation, /O 5 2 2 4 8 5 a~ ~1 I Flammability 30 sec 30 sec 32 sec 28 sec 23 sec 38 sec UL 94 V-0 V-0 V-0 V-0 V-O V-0 ~
o 1 334hO6 Although the invention has been described in detail in the foregoing for the purpose of illustration, it is to be understood that such detail is solely for that purpose and that variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention except as it may be limited by the claims.

Mo-2q84 - 17 -

Claims (5)

1. In a process for the production of polyurethane moldings by reacting a reaction mixture comprising a) a polyisocyanate, b) an isocyanate-reactive material having a molecular weight of from about 840 to about 5,000 and c) a chain extender and/or cross-linker, said reaction mixture being processed as a one-shot system by the RIM process at an isocyanate index of from about 70 to about 130, the improvement wherein component b) comprises a polyester polyol selected from the group consisting of (i) polyester polyol having the structure (ii) a polyester polyol having the structure , and (iii) mixtures thereof, wherein R represents the residue of a polyepoxide after ring opening with a carboxylic acid group, R' represents the residue of a cyclic anhydride, R" represents the residue of an aromatic anhydride or aromatic dicarboxylic acid, X and X' independently represent the organic residue of a polyol, m represents the number of epoxy groups of the polyepoxide ring opened with carboxylic acid groups, n is an integer of from 1 to 7, and p is a number of from 1 to 15.

2. The process of Claim 1 wherein X ? OH)n represents where R"' represents hydrogen or methyl, and y is a number of from 4 to 25.

3. The process of Claim 1 wherein X' represents where R"' represents hydrogen or methyl, and y is a number of from 4 to 25.

4. The process of Claim 3 wherein p is from 1 to 7.

5. The process of Claim 2 or 3 wherein m is 2 or 3.