MXPA98009895A - Stabilizing formula for polymers termoplasti - Google Patents

Abstract

A process for stabilizing polymers during the melting process, said process comprises the step of incorporating within a polymer a stabilizing formula comprising a hindered amine, at least one hydrolytically resistant phosphite, and a hydroxyl amine, said stabilizing formula inhibits the formation of Smoke during the processing of melted and increases the thermal stability of the polyme

Description

FORMULA STABILIZER ^. FOR THERMOPLASTIC POLYMERS Field of the Invention The present invention relates generally to a stabilizing formula for thermoplastic polymers that improves the properties of the polymers during the melting process. More particularly, the present invention is directed to incorporating into a polymer, such as polypropylene, a combination of stabilizers that provides the polymer with process stability, low yellowing, an increase in thermal aging stability, and a generation of Low smoke during the melting process, without adversely affecting other properties of the polymer.

Background of the Invention Many woven fabrics and non-woven fabrics and fabrics are formed of thermoplastic polymers, such as polypropylene and polyethylene. For example, knitted fabrics, which are used to make diapers, disposable garments, personal care articles, and the like, are made by spinning a polymeric resin into filaments and then thermally bonding the filaments together. More particularly, the polymer resin is typically first heated to at least its softening temperature and then extruded through a spinner to form filaments, which may subsequently be fed through a fiber pulling unit. From the fiber pull unit, the filaments are spread to a perforated surface where they are formed into a fabric of material.

In addition to spunbond fabrics, other fabrics made of polymers include meltblown fabrics. The meltblown fabrics are made by extruding a melted polymeric material through a matrix to form filaments. As the filaments exit the matrix, a high-pressure fluid, such as a vapor or heated air, attenuates and breaks the filaments into discontinuous fibers of small diameter. The fibers are randomly deposited on a perforated surface to form a fabric.

During the formation of many polymeric products, such as spin-bonded fabrics and melt-blown fabrics, the polymers used to make the products are exposed to various harsh conditions which adversely affect the properties of the polymers. For example, during extrusion, a polymer is not only subjected to various external forces but also heated to high temperatures. Because of these conditions, polymers can decrease in strength and elasticity, they can become brittle, they can yellow or otherwise degrade in color, or they can produce an article with a short product life.

Another problem typically encountered when heating and processing the polymers as described above is that the polymers generate smoke. Smoke production can possibly decompose the equipment, which reduces efficiency and can discolor the polymer.

In the past, several attempts have been made to improve the performance of polymer resins that are processed with melt to form various articles and products. As used herein, melt processing refers to any processes, such as spinning processes or a meltblowing process, wherein a polymer is heated and formed into a particular shape. In the past, in order to improve the performance of polymer resins, additives such as stabilizers had been added to the polymers. For example, several stabilizers are commercially available that are designed either to prevent degradation of the polymer when exposed to light, to prevent the polymer from fading or yellowing, to prevent the polymer from becoming brittle or otherwise Keep the properties of the polymer during use.

Unfortunately, typically when a particular stabilizer is added to the polymer to improve a particular property of the polymer, other polymer properties may be adversely affected. As an example, the phenols are typically added to the polymers in order to increase the thermal stability and process stability of the polymers. Phenols, however, can make the polymers yellow and have a shorter product life.

Other problems have also been experienced when trying to combine different stabilizers in a polymer to improve the properties of the polymer. In particular, many stabilizing products are incompatible. For example, when combined together, the stabilizers may become ineffective to each other or instead of improving the performance characteristics of the polymer, they may adversely affect the polymer. In fact, since many stabilizers are relatively complex chemical compounds, the results and effects that will occur when different stabilizers are combined are very unpredictable.

A particular problem experienced in the past has been the ability to add a stabilizer to a polymer that will increase the thermal aging stability of the polymer without compromising other properties of the polymer. The stability of thermal aging of a polymer refers to the ability of the polymer to resist degradation when exposed to high temperatures for an extended period of time. When exposed to high temperatures, most polymers become brittle and eventually lose most of their strength and elasticity.

For polymeric products that are exposed to high temperatures during use, it is important that said polymers have a substantial amount of stability to thermal aging. For example, woven and non-woven polymeric fabrics used in the health care industry are typically sterilized before being used by being placed in a steam oven for a fixed period of time. For these products, it is important that the polymers do not degrade essentially during the sterilization process.

As stated above, however, in the past, it has been found that it is very difficult to increase the stability of the thermal aging of a polymer without adversely affecting other properties of the polymer. For example, when stabilizers have been added to polymers to increase the stability of thermal aging, problems have been experienced with yellowing, with the production of polymer smoke during the melting process, and with the ability to maintain the rate of Melt flow of the polymer within pre-established limits. Significant problems have been experienced in achieving the combination of a stabilizer that improves the stability of thermal aging of the polymer with other stabilizers. Stabilizers used in the past to increase the thermal aging stability of a polymer have been found to be incompatible with many other additives and stabilizers.

In view of the prior deficiencies of the prior art, there is a need at present for a stabilizer or a combination of stabilizers that significantly improve more than one property of a polymer without any adverse side effects. In particular, it would be highly desirable if a stabilizing formula could be created which provides stability to the polymer during the melt processing, which prevents the formation of smoke during the melt processing, and which makes the polymer more thermally stable when exposed to the high temperatures for an extended period of time.

Synthesis of the Invention The present invention recognizes and refers to the above and other disadvantages of the constructions and methods of the prior art.

Therefore, it is an object of the present invention to provide an improved stabilizing form for improving the various properties of the polymers during melt processing.

Another object of the present invention is to provide a stabilizing formula which, when a polymer is added, inhibits the formation of smoke during the melting process.

It is another object of the present invention to provide a stabilizing formula which, when a polymer is added, improves the thermal aging stability of the polymer.

Still another object of the present invention is to provide a stabilizing formula that increases the stability of the polymer process.

Another object of the present invention to provide a combination of stabilizers for adding to the polymeric materials that inhibit the generation of smoke during the melt processing, improve the thermal aging stability of the polymer, and improve the melt flow stability of the polymer during the melting process without significantly adversely affecting other properties of the polymer.

It is a further object of the present invention to provide a stabilizing formula containing a hindered amine, a mixture of phosphites, a hydroxyl amine and, if desired, an acid purifier.

These and other objects of the present invention are achieved by providing a process for stabilizing the polymers during melt processing. The process includes the step of incorporating a stabilizing formula into a polymer. The stabilizing formula includes a hindered amine, at least one hydrolytically resistant phosphite and a hydroxyl amine. The stabilizing formula inhibits the formation of smoke during the melting process and increases the stability of thermal aging of the polymer. Of a particular advantage, the aforementioned properties of the polymer are improved without adversely affecting any other properties of the polymer.

In one embodiment, the stabilizing formula also includes a second hydrolytically resistant phosphite which inhibits the melt flow rate of the polymer to increase during the melting process. If desired, the formula can further include an acid scavenger to prevent the acids contained within the polymer or that were produced during the melting process from damaging the polymer. For example, the acid scavenger may be calcium lactate, carbonate hydrate, basic magnesium aluminum hydroxide or mixtures of both.

The hindered amine present in the formula of the present invention may, in one embodiment, be an amine containing a triazine ring. Examples of hindered amines for use in the present invention include 1,3,5-Triazine-2,4,6-triamine, N, N '' '- [1,2-ethanediylbis [[[.6- bis [butyl (1,2,2,6,6-pentamethyl -4- piperidinyl) amino] -1,3,5-triazine-2- yl] imino] -3,1-propanediyl]] -bis [N ', N "- dibutyl-N' -N" -bis (1,2,2,6,6, -pentamethyl-4-piperidinyl) -, Poly [[6- [(1, 1, 3, 3, tetramethyl butyl) amino] -s-triazine-2,4-diyl] [[2,2,6,6-t (emethyl-4-piperidyl) imino] ] hexamethylene [(2,2,6,6, -tetramethyl-4-piperidyl) imino]], and mixtures thereof. The hindered amine may be present within the polymer in an amount of up to about 0.1 percent by weight and particularly from about 0.04 percent to about 0.075 percent by weight.

The hydroxyl amine included in the formula of the present invention can, in one embodiment, have the following chemical formula: CH3 (CH2) i7 \ N-OH / CH3 (CH2) i7 and may be present in a polymer in an amount of up to about 0.075 percent by weight.

In addition to the hindered amine and the hydroxyl amine as indicated above, the formula may also include one or more hydrolytically resistant phosphites. Preferably, the phosphites are organophosphites. For example, a phosphite that can be incorporated into the polymer to reduce the production of smoke during the melting process includes: 2- [[2,4,8,10-Tetrakis (1, 1-dimethylethyl) dibenzo [d, f] [1,3,2] dioxaphosphopin-6-yl] oxy] -N, N-bis [ 2- [[2,4,8,10-tetrakis (1,1-dimethylethyl) dibenzo [d, f] [1,3,2] dioxaphosphepin-6-yl] oxy] -ethyl] ethanamine A second phosphite that can to be incorporated into the formula of the present invention is tris (2,4-di-tert-butylphenyl) phosphite. Said Tris (2,4-di-tert-butylphenyl) phosphite provides the polymer with process stability by inhibiting the melt flow rating of the polymer by preventing it from increasing during the melt processing.

Each of the phosphites may be present within the polymer in an amount of up to about 0.075 percent by weight, and particularly from about 0.03 percent to about 0.06 percent by weight.

Other objects, features and aspects of the present invention will be discussed in more detail below.

Detailed Description of Preferred Additions It is understood by one of ordinary skill in the art that the present discussion is a description of example embodiments only, and no attempt is made to limit the broader aspects of the present invention, the broader aspects of which are included in the construction of the invention. example.

In general, the present invention is directed to a stabilizing formula for improving the properties of a polymeric material. In particular, the stabilizing formula is well suited for use with thermoplastic polymers that are used in melt processing operations. For example, the stabilizing formula of the present invention is particularly well suited for incorporation into thermoplastic polymers used to produce woven and non-woven fabrics.

When added to a polymer, the stabilizing formula of the present invention inhibits the polymer from generating smoke during the melting process and substantially increasing the thermal aging stability (also known as aging stability in the furnace) of the polymer. The stabilizing formula also improves the stability of the polymer process by decreasing the amount of melt flow rate of the polymer by preventing it from increasing during the melt processing. In addition, the formula may include an acid scavenger to prevent the acid formed during the melting process from damaging the polymer. Of particular advantage, the stabilizing formula improves the aforementioned properties of the polymer without significantly adversely affecting any of the other properties of the polymer.

In the past, as described above, it has been found to be very difficult to improve more than one property of a polymer through the use of stabilizers without adversely affecting other properties of the polymer. Also, other difficulties have been experienced when combining different stabilizers, due to the effect that different stabilizers may have on one another and due to the effect that a mixture of stabilizers can have on the polymer. For example, until the present invention, the prior art was deficient in providing a combination of stabilizers for a polymer that would provide process stability, a low yellowing, a longer thermal aging stability, and a low smoke generation during processing. .

In general, the stabilizing formula of the present invention contains in combination a hindered amine, at least one hydrolytically resistant phosphite and a hydroxyl amine. When added to a polymer together, it has been found that the hindered amine, the phosphite and the hydroxyl amine inhibit the polymer from making smoke during the melting process and significantly increase the thermal aging stability of the polymer. Optionally, the formula of the present invention may further include a second hydrolytically resistant phosphite to stabilize the melt flow rate of the polymer during processing and an acid scavenger to prevent any acid from forming during the melt processing degrades the polymer.

Each individual ingredient added to the stabilizing formula of the present invention will now be discussed in detail with reference to a particular embodiment of the present invention.

The first ingredient present in the formula is a hindered amine. In the past, hindered amines had been added to the polymers as a light stabilizer. With respect to the present invention, the hindered amine is currently within the formula primarily in order to essentially improve the thermal aging properties of the polymer. More particularly, when combined with a polymer, the hindered amine improves the ability of the polymer to withstand higher temperatures for longer periods of time. Of particular advantage the hindered amine increases the thermal aging stability of the polymer without having a yellowing effect on the polymer, as may occur when other stabilizers, such as phenols, are used.

In a particular embodiment of the present invention, the hindered amine present within the stabilizing formula contains a triazine ring. During the development of the present invention, it was found that hindered amines containing a triazine ring remained effective even when combined with other stabilizing ingredients. In fact, the present inventors discovered that other amines not containing a triazine ring but which improve the thermal aging stability of the polymers will become ineffective when combined with other stabilizers contained in the formula of the present invention.

Two examples of commercially available hindered amines can be used in the stabilizing formula of the present invention are CHIMASSORB 119 and CHIMASSORB 944 which are available from Ciba Specialty Chemicals Corporation, additive division located in Tarryto n, New York. The CHIMASSORB 119 amine and the amine CHIMASSORB 944 both contain triazine rings. In addition to providing the stability of thermal aging, CHIMASSORB 119 and CHIMASSORB 944 also provide the polymer with protection against ultraviolet degradation.

Specifically CHIMASORB 119 is a monomeric hindered amine which has the following chemical name: 1, 3, 5-Triazine-2,4,6-triamine, N, N '' '- [1,2-ethanediylbis [[[4.6- bis [butyl (1,2,2,6,6-pentamethyl- 4- piperidinyl) amino] -1,3,5-triazine-2 yl] imino] -3,1-propanediyl]] -bis [N ', N "-dibutyl-N' -N" -bis ( 1,2,2,6,6, -pentamethyl-4-piperidinyl) -, and the following chemical structure: the CHIMASSORB 944 on the other hand has the following chemical name: Poly [[6- [(1, 1, 3,3, tetramethylbutyl) amino] -s-triazine-2,4-diyl] [[2,2,6,6-t (emethyl-4-piperidyl) imino] ] hexamethylene [(2,2,6,6, -tetramethyl-4-piperidyl) imino]], and the following chemical structure: CHIMASSORB 119 and CHIMASSORB 944 may be incorporated in a stabilizing formula of the present invention either alone or in combination.

In the past, in order to provide the stability of thermal aging, the phenols were typically combined with polymer resins. Unfortunately, however, phenols can cause the polymers to yellow. The stabilizing formula of the present invention does not require the presence of phenols to increase the stability of thermal aging of the polymer. However, if desired, a phenol can additionally be added to the formula. For example, an example of a phenol that can be added to the formula is IRGANOX 1076, which is commercially available from Ciba Specialty Chemicals Corporation, additives division. The IRGANOX 1076 has the following chemical name: Octadecyl 3- (3 ', 5' -di-tert-butyl-4'-hydroxyphenyl) propanoate When present in the formula of the present invention, the phenol can be added to the polymer in a concentration of up to about 1,000 parts per million and particularly from about 5,000 parts per million to about 1,000 parts per million.

In general, the amount of hindered amine added to a polymer according to the present invention will generally depend on the particular polymer being treated and the particular application. For most applications, hindered amine can be added to a polymer in an amount of up to about 0.1 percent by weight, particularly from about 0.04 percent to about 0.075 percent by weight, and in a preferred embodiment in an amount of about 0.05 percent by weight.

In addition to a hindered amine, the stabilizing formula of the present invention further includes a hydrolytically resistant first phosphite and a hydroxylamine. Phosphite and hydroxylamine both contribute to inhibiting a polymer so that it does not generate smoke during the melting process. Of a particular advantage it was discovered by the present inventors that phosphite and hydroxylamine inhibit the formation of smoke without adversely interfering with the ability of the hindered amine to increase the stability of thermal aging of the polymer.

In fact, it was unexpectedly discovered that a synergistic effect occurs when the hydroxylamine is combined with the hindered amine in the stabilizing formula. For example, it has been discovered that hydroxylamine, in addition to decreasing the amount of smoke produced by a polymer during the melting process, also tends to stabilize the melt flow rate of the polymer when present with the hindered amine. Although not known, it is believed that the hindered amine prevents the free radicals contained in the stabilizing formula and the polymer from reacting with the hydroxylamine, thereby allowing the hydroxylamine to serve as a process stabilizer.

As indicated above, the hydroxylamine and the first hydrolytically resistant phosphite are primarily added to the formula of the present invention in order to reduce the smoke generated by a polymer during processing. In particular, the formula of the present invention is capable of reducing smoke production by at least 80 percent. During the development of the present invention it was found that neither hydroxylamine nor hydrolytically resistant phosphite only reduce smoke by 80 percent. However, it was found that when both stabilizers are combined, smoke production can be reduced by 80 percent and even more if desired.

The hydroxyl amines that can be used in the stabilizing formula of the present invention generally have the following chemical structure: Ri I HO - N I R2 wherein Rt and R2 are, for example, hydrocarbon chains. A commercially available hydroxylamine very suitable for use in the present invention is FS-042 amine sold by Ciba Specialty Chemicals Corporation, additive division. The amine FS-042 has the following chemical structure: CH3 (CH2) 17 I HO - N CH3 (CH2) 17 In general, the hydroxylamine stabilizer may be present within the polymer in an amount generally similar to the amount of the hindered amine present in the polymer. For most applications, hydroxylamine can be incorporated into the polymer in an amount of up to about 0.075 percent by weight, and particularly in an amount of from about 0.01 percent to about 0.06 percent by weight. In a preferred embodiment, the hydroxylamine is added in an amount of about 0.04 percent by weight, particularly when the hindered amine is present in the polymer in an amount of about 0.05 percent by weight.

As described above, hydroxylamine works in conjunction with a phosphite in order to lower the smoke generation levels of a polymer during the melt processing. The phosphite added to the stabilizing formula must be hydrolytically resistant, meaning that the phosphite does not hydrolyze immediately when exposed to moisture. If the phosphite were not hydrolytically resistant, the phosphite could interfere adversely with the effectiveness of the hindered amine present in the stabilizing formula.

Hydrolytically resistant phosphites that can be used in the formulation of the present invention include organophosphites, even though it was discovered that not all commercially available organophosphites will produce the desired results. A commercially available particular phosphite that can be used in the formula of the present invention, for example, is IRGAFOS 12 available from Ciba Specialty Chemicals Corporation, additive division. IRGAFOS 12 is a phosphite organ that has been used in the past as an antioxidant to protect polymers from thermal breakage and discoloration. The phosphite IRGAFOS 12 has the following chemical name: 2- [[2,4,8,10-Tetrakis (1,1-dimethylethyl) dibenzo [d, f] [1,3,2] dioxaphosphine-6-yl ] oxy] -N, N-bis [2- [[2,4,8,10-tetrakis (1, 1-dimethylethyl) dibenzo [d, f] [1,3,2] dioxaphosphepin-6-yl] oxy ] - ethyl] ethanamine and the following chemical structure: The hydrolytically resistant phosphite used in the present invention to lower the production of smoke during the melt processing can be added to the polymer generally in amounts similar to the amount of the hydroxylamine present in the polymer. For example, the phosphite can be added to the polymer in an amount of up to about 0.075 percent by weight, particularly from about 0.03 percent by weight to about 0.06 percent by weight, and more particularly in an amount around of 0.04 percent by weight.

Of particular importance, it has been found that the phosphite present in the stabilizing formula for inhibiting the production of smoke should not be present in the polymer in an amount that is substantially greater than the amount of the hindered amine present. When present in larger amounts, the phosphite may have an adverse impact on the ability of the hindered amine to increase the stability in the thermal aging of the polymer. In particular, it has been found that the phosphite mentioned above begins to have an adverse impact on the damaged amine when it is present in an amount twice as large as the hindered amine. In this regard, for most applications, the phosphite must be present in the formulation in an amount essentially equal to or less than the amount of the hindered amine present.

Further containing a phosphite to prevent smoke formation, the stabilizing formula of the present invention may also contain a second phosphite to provide process stability for a polymer. In particular, it has been discovered that a second phosphite can be added to the formula in order to stabilize the melt flow rating of the polymer during the melt processing.

For example, during melt processing operations, such as when the polymer resins are extruded, the melt flow rating of the polymer can be significantly increased. The melt flow rate of a polymer refers to a measure of a viscosity of the polymer and is expressed as the weight of the material flowing from a capillary of known dimensions under a load or cut rate specified for a predetermined period of time and it is measured in g / 10 min according to, for example, the ASTM 1238 test. During most melt processing applications, it is desirable to maintain the melt flow rate of the polymer below a particular level. For example, in many spinning processes, the melt flow rate of the polymer is typically around 35 mfr initially and can increase to levels greater than 50 or 60 mfr after extrusion. For most applications, it is desirable to maintain the melt flow rate of the polymer below 50 mfr. In case the melt flow rate of a polymer increases beyond the desired levels, the polymer may begin to lose many of its strength and bonding properties.

According to the present invention by the incorporation of a second phosphite in the stabilizing formula, the melt flow rate of a polymer containing the formulation can be kept below desired levels. In particular, the phosphite can be added to the polymer in an amount sufficient to maintain the melt flow rate of the polymer within the predetermined levels.

The second phosphite added to the formulation must be hydrolytically resistant so that the phosphite does not interfere adversely with the hindered amine as described above. A particular example of the hydrolytically resistant phosphite that can be used in the present invention is the IRGAFOS 168 which is commercially available from Ciba Specialty Chemicals Corporation, additives division. It has been found that IRGAFOS 168 not only provides a polymer with process stability, but does not interfere adversely with the other stabilizing ingredients contained in the formula of the present invention. The chemical name of IRGAFOS 168 is Tris (2,4-di-tert-butylphenyl) phosphite, which has the following chemical structure: When contained in the stabilizing formula and added to a polymer according to the present invention, the phosphite described above can be added to a polymer generally in an amount of up to about 0.075 percent by weight, particularly from about 0.03. percent by weight to about 0.06 percent by weight, and more particularly in an amount of about 0.04 percent by weight.

If desired, the stabilizing formula of the present invention may also contain an acid scavenger. An acid scavenger chemically reacts with any acids present within the polymer or produced during the melting process to prevent acids from degrading the polymer. For example, acid catalysts, such as Ziegler-Natta catalysts are frequently used to produce polymers. Unfortunately, the residual amounts of the acidic substances can remain in the polymers. Acid scrubbers can reduce or eliminate the corrosivity associated with the presence of acids.

Examples of the acid scavengers that can be used in the present invention include calcium lactate which is commercially available as PATIONIC 1240 from Pateo Polymer Additives Division, American Ingredients Company, Kansas City, Missouri, and the basic magnesium aluminum hydroxide carbonate hydrate which is commercially available as DHT-4A from Kyo to Chemical Industry Company, Limited, located in Osaka, Japan. The amount of the acid scavenger added to the polymer will generally depend on the amount of acid contained within the polymer. For most applications, the acid scavenger can be added to the polymer in an amount of up to about 0.1 percent by weight, particularly from about 0.01 percent to about 0.05 percent by weight, and in one mode at an amount of about 0.025 percent by weight.

As described above, the stabilizing formula of the present invention is particularly suitable for use with the thermoplastic polymers that are subject to melt processing. For example, the stabilizing formula can be added to the polyolefins, such as polypropylene, polyethylene and random copolymers of polyethylene and polypropylene. In one example, the formula is added to the PLTD 713 experimental polypropylene resin available from Exxon Corporation, which can be used to form the non-woven fabrics. The PLTD 713 polypropylene is a controlled rheology polymer. In addition to polypropylene, it is believed that the formula can also be added to an ethylene vinyl acetate, polycarbonates and polyamides.

The stabilizing formula can be added to a pure polymeric resin or it can be added to a polymeric material containing other substances. For example, the polymer that is being stabilized by the formulation may contain fillers, such as clay or calcium carbonate, or may contain other polymers including polyamides such as nylon or polyesters, or liquid crystal polymers.

In addition to fillers and other polymers, the polymeric material that is being stabilized by the formula of the present invention may also contain organic softeners. Such softeners may include, for example, polyethylene wax, polypropylene wax, silicones, etc.

When added to a polymer, the stabilizing formula can be mixed with melted with the polymeric resin. In particular, the formula can be premixed with the resin or can be mixed with the polymer resin during the melting process, such as before being fed or while being fed to an extruder.

In a preferred embodiment of the present invention, the stabilizing formula, when combined with a polypropylene polymer, contains the following ingredients in the following amounts: a b l a The present invention can be better understood with reference to the following examples.

EXAMPLE The following example was made in order to demonstrate the superiority of a stabilizing formula made in accordance with the present invention compared to stabilizing formulas containing a phenol.

The following stabilizer formulas were prepared and mixed with the Exxon PLTD-713 polypropylene resin: With respect to the Table given above, IRGANOX 1076 is a phenol, DHT4A is an acid scavenger and contains a basic magnesium aluminum hydroxide carbonate hydrate, IRGAFOS 12 is a phosphite, FS042 is a hydroxyl amine, PATIONIC 1240 is an acid scavenger containing calcium lactate, CHIMASSORB 119 is a hindered amine, and IRGAFOS 168 is a phosphite. Sample number 3 represents a stabilizing formula made in accordance with the present invention while sample numbers 1 and 2 represent more conventional formulas containing a phenol. In the past, the phenols were added to the polymers in order to improve the stability of thermal aging and the stability of the polymer process.

Once each of the stabilizing formulas mentioned above was added to the polypropylene, said polypropylene was tested for the stability of thermal aging, the melt flow stability and the whiteness.

The stability of thermal aging was tested by first extruding the polypropylene into a spunbonded fabric. A sample of the fabric was then placed in an air forced oven set at a temperature of 140 degrees centigrade. The samples were placed flat on a plate PYREX and were tested periodically until the failure occurred.

The point of failure for the test was when the fabric became so brittle that the fabric disintegrated when a small force was exerted on the fabric in the direction transverse to the machine.

Once the cloth was formed, the melt flow rate in the polymer was also determined. In particular, a sample of the fabric was heated to a temperature of 245 degrees centigrade and the melt flow rate was determined according to ASTM procedure D1238. Three repetitions were made for each sample and the results were averaged. The initial melt flow rate of the polypropylene polymer before being formed in the fabric was approximately 35 mfr.

After the fabric was formed, the polymer was also tested for whiteness and yellowing. The yellowing tests were carried out by exposing the samples to nitrogen oxides in an atmospheric smoke chamber of the United States Testing Company (model number 8727) according to the AATCC test method 23-1972. The samples were exposed to three cycles.

The whiteness of the samples was determined by the method ASTM E313-73. The color values were measured on a Hunter Color model D27-9 with a standard C CIÉ lighting source.

The following results were obtained: Table 1 As shown above, the stabilizing formula made according to the present invention produced much better results when combined with the polypropylene compared to the other stabilizing formulas. In particular, the stability and thermal aging of the polymer increased about four times without significantly adversely affecting the whiteness or melt flow rate of the polymer. In fact, the polymer containing sample No. 3 was much more resistant to yellowing than when the polymer contained the other samples. In the past, it was very difficult to increase the stability to the thermal aging of a polymer without adversely affecting other properties of the polymer.

EXAMPLE No. 2 The following tests were carried out in order to compare the differences between a stabilizing formula containing a phenol and the stabilizing formulas made according to the present invention.

In this example, the following stabilizer formulas were tested. The formulas were added to the Exxon-713 polypropylene in the indicated quantities.

With respect to the formulas given above, samples numbers 3 and 4 were made according to the present invention while samples numbers 1 and 2 represent formulas containing a phenol instead of a hindered amine.

Similar to example number 1 after being combined with each of the formulas given above, the polymer was formed into a yarn-bonded fabric and tested for thermal aging stability and yellowing. The melt flow rate of the polymer was also tested before being formed in the fabric. The following results were obtained : Table In addition to the results given above, sample number 1 containing a phenol was also compared to sample number 4 with respect to smoke generation during extrusion. It was noted that the polymer containing sample number 4 of the stabilizer formula produced a dramatically lower amount of smoke than the polymer containing sample number 1.

As indicated above, the polymers containing a stabilizing formula made according to the present invention had significantly improved properties compared to the polymers containing the formulas including a phenol. Stabilizing formulas made according to the present invention provided better process stability, lower amounts of yellowing, longer aging and lower smoke generation than those of the other samples tested.

These and other modifications and variations to the present invention may be practiced by those of ordinary skill in the art without departing from the spirit and scope of the present invention which is more particularly set forth in the appended claims. In addition, it should be understood that these aspects of the various embodiments may be exchanged in whole or in part.

In addition, those of ordinary skill in the art will appreciate that the foregoing description is given by way of example only, and that it is not intended to limit the invention thus described in such appended claims.

Claims (25)

R E I V I N D I C A C I O N S

1. A process for stabilizing polymers during melt processing, said process comprises the step of incorporating within a polymer a stabilizing formula, said stabilizing formula comprising a hindered amine, at least one hydrolytically resistant phosphite, and a hydroxyl amine, said stabilizing formula inhibits the formation of smoke during the melt processing and increases the stability of thermal aging of the polymer.

2. A process as claimed in clause 1 characterized in that said stabilizing formula includes a first hydrolytically resistant phosphite which works in conjunction with said hydroxyl amine to inhibit the formation of smoke during the melt processing, and a second hydrolytically resistant phosphite which inhibits the melt flow rate of said polymer increase during the melt processing.

3. A process as claimed in clause 1 characterized in that said hindered amine comprises an amine containing a triazine ring.

4. A process as claimed in clause 1 characterized in that said hindered amine comprises an amine selected from the group consisting of: 1,3,5-Triazine-2,4,6-triamine, N, N '' '- [1, 2-ethanediylbis [[[4.6-bis [butyl] (1,2,2,6,6-pentamethyl- 4- piperidinyl) amino] -1,3,5-triazine-2 yl] imino] -3,1-propanediyl]] -bis [N ', N "-dibutyl-N' -N" -bis ( 1,2,2, 6, 6, -pentamethyl-4-piperidinyl) -, Poly [[6- [(1,1,3,3, tetramethyl butyl) amino] -s-triazine-2,4-diyl] [[2,2,6,6-t (emethyl-4-piperidyl) imino] ] hexamethylene [(2,2,6,6, -tetramethyl-4-piperidyl) imino]]; and mixtures thereof.

5. A process as claimed in clause 2 characterized in that said first hydrolytically resistant phosphite and said second hydrolytically resistant phosphite comprise phosphites organ.

6. A process as claimed in clause 5 characterized in that said hydrolytically resistant phosphite comprises: 2- [[2,4,8,10-Tetrakis (1, 1-dimethylethyl) dibenzo [d, f] [1, 3, 2] dioxaphosphine-6-yl] oxy] -N, N-bis [2- [[2,4,8,10-tetrakis (1,1-dimethylethyl) dibenzo [d, f] [1,3, 2] dioxaphosphepin-6-yl] oxy] -ethyl] ethanamine and said second hydrolytically resistant phosphite comprises Tris (2,4-di-tert-butylphenyl) phosphite.

7. A process as claimed in clause 1 characterized in that said stabilizing formula further comprises an acid scavenger.

8. A process as claimed in clause 7 characterized in that said acid scavenger comprises calcium lactate, basic magnesium aluminum hydroxide carbonate hydrate or mixtures thereof.

. A process as claimed in clause 1 characterized in that said hydroxyl amine comprises: CH3 (CH2) 17 \ N-OH / CH3 (CH2) 17

10. A process as claimed in clause 1 characterized in that said stabilizing formula does not contain any phenolics.

11. A process as claimed in clause 2 characterized in that said polymer comprises polypropylene and wherein said hindered amine is present within said polymer in an amount of up to about 0.1 percent by weight, and said first hydrolytically resistant phosphite, said second hydrolytically resistant phosphite, and said hydroxyl amine are present in said polymer in an amount of up to about 0.75 percent by weight.

12. A process for stabilizing polymers during melt processing, said process comprises the step of incorporating a stabilizing formula into a thermoplastic polymer, said stabilizing formula comprising: a) a hindered amine added to said thermoplastic polymer in an amount sufficient to increase the thermal aging stability of said polymer, said hindered amine comprises an amine containing a triazine ring; b) a first hydrolytically resistant phosphite and a hydroxyl amine present in said thermoplastic polymer in an amount sufficient to inhibit the formation of smoke during the melt processing, said first hydrolytically resistant phosphite being added to said polymer in an amount insufficient to affect significantly adverse to the hindered amine; Y c) a second hydrolytically resistant phosphite being present within the thermoplastic polymer in an amount sufficient to inhibit the melt flow rate of said polymer to increase during the melt processing.

13. A process as claimed in clause 12 characterized in that said hindered amine is present within said polymer in an amount of up to about 0.1 percent by weight, and said first hydrolytically resistant phosphite, said hydroxyl amine and said second hydrolytically phosphite resistant are each present within said polymer in the amount of up to about 0.075 percent by weight.

14. A process as claimed in clause 12 characterized in that said hindered amine is present within said thermoplastic polymer in an amount of from about 0.4 percent to about 0.075 percent by weight, and said first hydrolytically resistant phosphite, said hydroxyl amine and said second hydrolytically resistant phosphite are each present within said polymer in an amount of from about 0.03 weight percent to about 0.06 weight percent.

15. A process as claimed in clause 12 characterized in that said stabilizing formula further comprises an acid scavenger, said acid scavenger comprises calcium lactate, a magnesium basic hydroxide carbonate hydrate or mixtures thereof.

16. A process as claimed in clause 12 characterized in that said hindered amine comprises an amine selected from the group consisting of: 1, 3, 5-Triazine-2,4,6-triamine, N, N '' '- [1,2-ethanediylbis [[[4.6- bis [butyl (1,2,2,6,6-pentamethyl- 4- piperidinyl) amino] -1,3,5-triazine-2 yl] imino] -3,1-propanediyl]] -bis [N ', N "-dibutyl-N' -N" -bis ( 1,2,2,6,6, -pentamethyl-4-piperidinyl) -, Poly [[6- [(1,1,3,3, tetramethyl butyl) amino] -s-triazine-2,4-diyl] [[2,2,6,6-t (emethyl-4-piperidyl) imino] ] hexamethylene [(2,2,6,6, -tetramethyl-4-piperidyl) imino]]; and mixtures thereof.

17. A process as claimed in clause 16 characterized in that said first hydrolytically resistant phosphite comprises: 2- [[2,4,8,10-Tetrakis (1,1-dimethylethyl) dibenzo [d, f] [1,3,2] dioxaphosphopin-6-yl] oxy] -N, N-bis [ 2- [[2,4,8,10-tetrakis (1,1-dimethylethyl) dibenzo [d, f] [1,3,2] dioxaphosphepin-6-yl] oxy] -ethyl] ethanamine and said second hydrolytically resistant phosphite comprises Tris (2,4-di-tert-butylphenyl) phosphite.

18. A process as claimed in clause 17 characterized in that said thermoplastic polymer comprises polypropylene.

19. A thermoplastic polymer composition adapted to be formed by melt processing into fibers and filaments, said thermoplastic polymer comprises: a polymer mixed with a stabilizing formula, said polymer comprises polypropylene, polyethylene or copolymers thereof, said stabilizing formula comprises a hindered amine, at least one hydrolytically resistant phosphite, and a hydroxyl amine, said stabilizing formula inhibits the formation of smoke during the processing of melted and increases the stability of thermal aging of said polymer.

20. A polymer composition as claimed in clause 19 characterized in that said hindered amine is present in said composition in an amount of up to about 0.1 percent by weight, and said at least one hydrolytically resistant phosphite and said hydroxyl amine are present. each present within said composition in an amount of up to about 0.075 percent by weight.

21. A polymer composition as claimed in clause 20 further characterized in that it comprises a second hydrolytically resistant phosphite, said second hydrolytically resistant phosphite inhibthe melt flow rate of said polymer from increasing during the melt processing, said second hydrolytically phosphite resistant being added to said composition in an amount of up to about 0.75 percent by weight.

22. A polymer composition as claimed in clause 21 further characterized in that it comprises an acid scavenger.

23. A polymer composition as claimed in clause 22 characterized in that said acid scavenger comprises calcium lactate.

24. A polymer composition as claimed in clause 21 characterized in that said hindered amine comprises an amine selected from the group consisting of: 1,3,5-Triazine-2,4,6-triamine, N, N '' '- [1,2-ethanediylbis [[[4.6- bis [butyl (1,2,2,6,6-pentamethyl- 4- piperidinyl) amino] -1,3,5-triazine-2 yl] imino] -3,1-propanediyl]] -bis [N ', N "-dibutyl-N' -N" -bis ( 1,2,2,6,6, -pentamethyl-4-piperidinyl) -, Poly [[6- [(1, 1, 3, 3, tetramethyl butyl) amino] -s-triazine-2,4-diyl] [[2,2,6,6-t (emethyl-4-piperidyl) imino] ] hexamethylene [(2,2,6,6, -tetramethyl-4-piperidyl) imino]]; and mixtures thereof, and wherein said first hydrolytically resistant phosphite comprises: 2- [[2,4,8,10-Tetrakis (1,1-dimethylethyl) dibenzo [d, f] [1,3,2] dioxaphosphopin-6-yl] oxy] -N, N-bis [ 2- [[2,4,8,10-tetrakis (1,1-dimethylethyl) dibenzo [d, f] [1,3,2] dioxaphosphepin-6-yl] oxy] -ethyl] ethanamine and said second hydrolytically resistant phosphite comprises Tris (2,4-di-tert-butylphenyl) phosphite.

25. A polymer composition as claimed in clause 24 characterized in that said hindered amine is present within said composition in an amount of from about 0.4 percent to about 0.05 percent by weight, and wherein said first hydrolytically phosphite resistant, said hydroxyl amine and said second hydrolytically resistant phosphite are present within said polymer composition in an amount of from about 0.03 weight percent to about 0.05 weight percent. SUMMARY A stabilizing formula particularly well suited to improve the properties of polymers 5 thermoplastics is described. The stabilizing formula contains a combination of stabilizers that improves the process stability of a polymer, prevents the polymer from yellowing, increases the thermal aging stability of the polymer and inhibthe polymer from generating smoke during the melt processing. Of particular advantage, the stabilizing formula improves the stability of a polymer without adversely affecting any other polymer properties adversely. In one embodiment, the stabilizing formula includes a hindered amine, a hydroxyl amine, and one or more hydrolytically resistant phosphites. In one embodiment, the formula may also contain an acid scavenger to prevent an acid contained within the polymer or produced during processing from damaging the polymer.