Age Resistors and Age Resistant Polymeric Compositions

This invention relates to age resistors, age resistant polymeric compositions and processes for preparing said age resistors and age resistant compositions. More particularly, the invention relates to polymeric compositions that possess a high degree of resistance to the deleterious effects of oxidative aging over a prolonged period of time even after said compositions have been subjected to solvents which would extract a significant portion of many conventional age resistors when used to stabilize polymeric compositions.

Essentially all types of rubber, both natural and synthetic, and particularly rubbers formed from dienes, are known to be susceptible to deterioration resulting from prolonged exposure to oxidative aging. A great deal of effort has been expended by those engaged in the field of polymer technology to develop various stabilizers that will effectively inhibit the adverse effects of aging of polymeric compositions. Unfortunately, many of the commercially accepted stabilizers may be volatilized when the polymeric products are exposed to elevated temperatures and/or high vacuum over prolonged periods of time. Furthermore, they are rather quickly extracted from polymeric compositions by repeated washings with aqueous detergent solutions or organic solvents. These severe conditions are routinely encountered by garments containing latex treated fabric when they are subjected to frequent laundering or dry-cleaning.

It is therefore an object of this invention to provide polymeric compositions that are resistant to oxidative aging. It is another object of this invention to provide a process for preparing age resistant polymeric compositions. A further object of this invention is to provide polymeric compositions that are highly resistant to oxidative aging at elevated temperatures even after repeated exposure to aqueous detergent solutions or dry-cleaning fluids. It is a still further object of this invention to provide polymers possessing antioxidants chemically bound thereto.

In accordance with the present invention age resistant polymeric compositions are prepared by polymerizing certain nitrogen-containing compounds by themselves or with one or more comonomers. The nitrogen-containing compounds which can be so used are selected from the group consisting of (A) amides having the following structural formula: ##STR1## wherein R and R.sup.1 are tertiary alkyl radicals having from 4 to 8 carbon atoms, wherein R.sup.2 is selected from the group consisting of hydrogen; alkyl radicals having from 1 to 4 carbon atoms, i.e, methyl, ethyl, propyl and butyl radicals; carboxymethyl radical and carbalkoxymethyl radicals and wherein R.sup.3 is selected from the group consisting of hydrogen; alkyl radicals having from 1 to 4 carbon atoms, i.e, methyl, ethyl, propyl and butyl radicals; phenyl and substituted phenyl, e.g., a phenyl group having located in the para position, an alkyl radical having 1 to 4 carbon atoms such as methyl, or an alkoxy radical having 1 or 2 carbon atoms, e.g., methoxy; carboxyl radical and carbalkoxy radicals, and (B) imides selected from the group consisting of (1) compounds having the following structural formula: ##STR2## wherein R and R.sup.1 are as previously defined herein under structural formula (I) and wherein R.sup.4 and R.sup.5 are selected from the group consisting of hydrogen and alkyl radicals having from 1 to 4 carbon atoms and (2) compounds having the following structural formula: ##STR3## wherein R and R.sup.1 are as previously defined herein under structural formula (I) and wherein R.sup.6, R.sup.7, R.sup.8 and R.sup.9 are selected from the group consisting of hydrogen and alkyl radicals having from 1 to 4 carbon atoms.

Under structural formula (I) the carbalkoxymethyl radicals preferably have the following structural formula: ##STR4## wherein R.sup.10 is an alkyl radical having from 1 to 4 carbon atoms. The carbalkoxy radicals preferably have the following structural formula: ##STR5## wherein R.sup.11 is an alkyl radical having from 1 to 4 carbon atoms.

In structural formulae (I), (II), and (III) R and R.sup.1 are preferably tert.butyl, tert.amyl or tert.hexyl radicals, most preferably a tert.butyl radical. In structural formula (I) preferably R.sup.2 is hydrogen or methyl. Preferably R.sup.3 is hydrogen. In structural formula (II) preferably R.sup.4 and R.sup.5 are hydrogen. In structural formula (III) preferably R.sup.6, R.sup.7, R.sup.8 and R.sup.9 are hydrogen. In structural formula (IV) R.sup.10 is preferably methyl or ethyl. In structural formula (V) R.sup.11 is preferably methyl or ethyl.

Representative amides which can be used in the present invention are as follows:

N-(3,5-di tert.butyl-4-hydroxyphenyl)acrylamide

N-(3,5-di tert.butyl-4-hydroxyphenyl)methacrylamide

N(3,5-di tert.butyl-4-hydroxyphenyl)cinnamamide

N-(3,5-di tert.butyl-4-hydroxyphenyl)crotonamide

N-(3,5-di tert.amyl- 4-hydroxyphenyl)acrylamide

N-(3,5-di tert.amyl-4-hydroxyphenyl)methacrylamide

N-(3,5-di tert.amyl-4-hydroxyphenyl)cinnamamide

N-(3,5-di tert.amyl-4-hydroxyphenyl)crotonamide

N-(3,5-di tert.butyl-4-hydroxyphenyl)maleamic acid

N-(3,5-di tert.butyl-4-hydroxyphenyl)itaconamic acid

Ethyl N-(3,5-di tert.butyl-4-hydroxyphenyl)maleamate

N-[3,5-bis(1,1-dimethylbutyl)-4-hydroxyphenyl]acrylamide

N-[3,5-bis(1,1-dimethylbutyl)-4-hydroxyphenyl]methacrylamide

N-[3,5-bis(1,1-dimethylbutyl)-4-hydroxyphenyl]cinnamamide

N-[3,5-bis(1,1-dimethylbutyl)-4-hydroxyphenyl]crotonamide

N-[3,5-bis(1,1-dimethylbutyl)-4-hydroxyphenyl]maleamic acid

N-[3,5-bis(1,1,2-trimethylpropyl)-4-hydroxyphenyl]acrylamide

N-[3,5-bis(1,1,2-trimethylpropyl)-4-hydroxyphenyl]methacrylamide

N-(3-tert.butyl-5-tert.amyl-4-hydroxyphenyl)acrylamide

N-(3-tert.butyl-5-tert.amyl-4-hydroxyphenyl)methacrylamide

N-[3-tert.butyl-5-(1,1-dimethylbutyl)-4-hydroxyphenyl]acrylamide

N-[3-tert.butyl-5-(1,1-dimethylbutyl)-4-hydroxyphenyl]methacrylamide

N-[3-tert.amyl-5-(1,1-dimethylbutyl)-4-hydroxyphenyl]methacrylamide

N-[3,5-bis(1,1,3,3-tetramethylbutyl)-4-hydroxyphenyl]acrylamide

N-[3,5-bis(1,1,3,3-tetramethylbutyl)-4-hydroxyphenyl]methacrylamide

N-[3,5-bis(1,1-dimethylpentyl)-4-hydroxyphenyl]acrylamide

N-[3,5-bis(1,1-dimethylpentyl)-4-hydroxyphenyl]methacrylamide

N-[3-tert.butyl-5-(1,1,3,3-tetramethylbutyl)-4-hydroxyphenyl]methacrylamide

N-[3-tert.butyl-5-(1,1,-dimethylpentyl)-4-hydroxyphenyl]methacrylamide

N-[3-(1,1-dimethylbutyl)5-(1,1,3,3-tetramethylbutyl)-4-hydroxyphenyl]methac rylamide

Representative imides which can be used in the present invention are as follows:

N-(3,5-di tert.butyl-4-hydroxyphenyl)itaconimide

N-(3,5-di tert.butyl-4-hydroxyphenyl)citraconimide

N-(3,5-di tert.amyl-4-hydroxyphenyl)itaconimide

N-(3,5-di tert.amyl-4-hydroxyphenyl)maleimide

N-[3,5-bis(1,1-dimethylbutyl)-4-hydroxyphenyl]maleimide

N-[3,5-bis(1,1-dimethylbutyl)-4-hydroxyphenyl]itaconimide

N-[3,5-bis(1,1-dimethylbutyl)-4-hydroxyphenyl]citraconimide

N-[3,5-bis(1,1,3-trimethylpropyl)-4-hydroxyphenyl]maleimide

N-[3,5-bis(1,1,3-trimethylpropyl)-4-hydroxyphenyl]itaconimide

N-(3-tert.butyl-5-tert.amyl-4-hydroxyphenyl)maleimide

N-(3-tert.butyl-5-tert.amyl-4-hydroxyphenyl)itaconimide

N-[3-tert.butyl-5-(1,1-dimethylbutyl)-4-hydroxyphenyl]maleimide

N-[3,5-bis(1,1,3,3-tetramethylbutyl)-4-hydroxyphenyl]maleimide

N-[3-tert.amyl-5-(1,1-dimethylbutyl)-4-hydroxyphenyl]maleimide

N-[3,5-bis(1,1-dimethylpentyl)-4-hydroxyphenyl]maleimide

N-[3-tert.butyl-5-(1,1,3,3-tetramethylbutyl)-4-hydroxyphenyl]maleimide

N-[3-tert.butyl-5-(1,1-dimethylpentyl)-4-hydroxyphenyl]maleimide

N-[3-(1,1-dimethylbutyl)-5-(1,1,3,3-tetramethylbutyl)-4-hydroxyphenyl]malei mide

N-(3,5-di tert.butyl-4-hydroxyphenyl)-2,3-dimethyl-maleimide

N-(3,5-di tert.butyl-4-hydroxyphenyl)-.alpha.-methylitaconimide

The method of preparing the monomeric age resistors is not critical to the performance of these compounds in the practice of the present invention.

The amides can be prepared by reacting, normally in substantially equal molar amounts, an amine of the structure ##STR6## with an acid halide of the structure: ##STR7## wherein R, R.sup.1, R.sup.2 and R.sup.3 are as defined earlier herein and wherein X is selected from the group consisting of chloride and bromide radicals, in the presence of an acid absorbing agent which may be an inorganic salt, e.g. sodium carbonate, or an organic tertiary amine, e.g. triethylamine. The reaction is usually carried out by dropwise addition of a solution of the acid halide in an aprotic solvent to a solution of the amine which contains in solution or in suspension a compound capable of reacting with the hydrogen halide formed during the reaction. A slight excess of acid halide may be used. The reaction is usually exothermic so the temperature during reaction is held to a maximum of 50.degree. C. by means of an ice water bath. The reaction mixture is stirred for an hour or more after the addition of acid halide has been completed. The product usually precipitates during the course of the reaction. It is then filtered off, dried, and purified as necessary.

The imides are prepared by reacting, normally in substantially equal molar amounts, an amine of the structure described above in the preparation of amides with a cyclic acid anhydride selected from the group consisting of compounds having the following structural formulae: ##STR8## wherein R.sup.4, R.sup.5, R.sup.6, R.sup.7, R.sup.8 and R.sup.9 are as defined earlier herein, separating the amic acid which forms, and dehydrating this compound with a dehydrating agent such as acetic anhydride in a subsequent reaction. The first reaction is carried out by mixing a solution of the anhydride in an inert solvent with a solution of the amine, likewise in an inert solvent. The reaction can be carried out at room temperature. The reaction mixture is stirred for several minutes and the product which has precipitated is filtered off, washed with solvent, and dried. The second step is carried out by heating a mixture of the intermediate amic acid with sodium acetate and a large excess of acetic anhydride at 60.degree. C. to 80.degree. C. for a brief period of time and then pouring the reaction mixture into water. The product which precipitates is filtered off, dried, and purified if desired.

Examples of amines which can be used in preparing the amides and imides are as follows:

2,6-di tert.butyl-4-aminophenol

2,6-di tert.amyl-4-aminophenol

2,6-bis(1,1-dimethylbutyl)-4-aminophenol

2,6-bis(1,1,2-trimethylpropyl)-4-aminophenol

2,6-bis(1,1-dimethylpenthyl)-4-aminophenol

2,6-bis(1,1,3,3-tetramethylbutyl)-4-aminophenol

2-tert.butyl-6-tert.amyl-4-aminophenol

2-tert.butyl-6-(1,1-dimethylbutyl)-4-aminophenol

2-tert.amyl-6-(1,1-dimethylbutyl)-4-aminophenol

2-tert.butyl-6-(1,1-dimethylpentyl)-4-aminophenol

2-tert.butyl-6-(1,1,3,3-tetramethylbutyl)-4-aminophenol

2-(1,1-dimethylbutyl)-6-(1,1,3,3-tetramethylbutyl)-4-aminophenol

Examples of acid halides which can be used in preparing the amides are as follows:

acryloyl chloride

methacryloyl chloride

crotonyl chloride

cinnamoyl chloride

acryloyl bromide

Examples of cyclic acidic anhydrides which can be used in preparing imides are maleic anhydride, itaconic anhydride, and citraconic anhydride.

Examples of dehydrating agents which can be used in preparing imides are acetic anhydride and propionic anhydride.

The aforementioned monomeric age resistors may be polymerized by well known free radical emulsion polymerization techniques with one or more comonomers that are known to polymerize in free radical initiated polymerization systems. Some adjustments in the polymerization recipe and/or conditions may be necessary to obtain a satisfactory rate of polymer formation, depending on the amount of monomeric age resistor included and the other monomers involved. Adjustments which may be necessary in the polymerization conditions to improve polymerization rates include increasing the temperature of polymerization and/or increasing the initiator level and/or increasing the level of activator ingredients. Solvents may also be required to obtain adequate solubility of the monomers with each other as well as to solubilize other ingredients where required. Some solvents, such as methyl ethyl ketone or isopropyl alcohol, can be used to advantage with the emulsion polymerization system. These adjustments, where necessary, are to counteract the inhibitory effect of the monomeric age resistor and to insure its solubility in the system.

Examples of free radical initiators that are useful in the practice of this invention are those known as "Redox" initiators, such as appropriate combinations of chelated iron salts, sodium formaldehyde sulfoxylate and organic hydroperoxides such as cumene and paramenthane hydroperoxides. Other initiators such as azoisobutyronitrile, benzoyl peroxide, hydrogen peroxide and potassium persulfate may also be used, depending on the particular polymerization recipe.

The monomeric age resistors used in the practice of this invention have certain chemical characteristics which preclude their use in polymerization processes other than those initiated by free radicals. By "free radical initiated systems" is meant systems wherein free radicals are generated by any of various processes such as thermal decomposition of various persulfate, perborate, peroxide, azo or azonitrile compounds; induced (catalytic or "redox" promoted) decomposition of various persulfate, peroxide or hydroperoxide compounds and generation of free radicals by exposure of the system to high energy radiation such as radiation from a radioactive source of ultraviolet light. Such systems are very well known in the art and are widely used commercially, e.g., in the preparation of SBR, styrene/butadiene copolymers.

The most widely used system for preparation of elastomeric polymers, i.e., polymers prepared from a monomer charge made up of at least 40 weight percent diene, preferably at least 60 weight percent diene, by free radical initiation is the emulsion system. Polymers ranging all the way from liquid, low molecular weight (molecular weights of about 2,000 to 10,000 to polymers of intermediate molecular weight (60,000 to 70,000 and higher), to oil extendable, at least 50% soluble, rubbery solid, high molecular weight (100,000 to 500,000 or more) and even highly gelled, less than 50% soluble, may be prepared by emulsion polymerization. The monomeric age resistors of the present invention can be used in such emulsion polymerization systems to produce polymers of the aforementioned type.

The principles of emulsion polymerization are discussed in references such as "Synthetic Rubber" by G. S. Whitby, Editor-in-Chief, John Wiley and Sons, 1954, particularly Chapter 8, and "Emulsion Polymerization" by F. A. Bovey et al, Vol. IX of "High Polymers", Interscience Publishers Inc. 1955. Some specialized applications of these principles are indicated in U.S. Pat. Nos. such as 3,080,334; 3,222,334; 3,223,663; 3,468,833 and 3,099,650.

Some apparently have assumed that antioxidants such as sterically hindered phenols would react rapidly with free radicals of the type useful for initiating polymerization. Various techniques have been developed to obtain the desired end products by round-about routes. U.S. Pat. No. 3,457,328 teaches the preparation of polymeric acid chlorides from carboxylated polymers, which, in turn, are reacted with various chemicals possessing chemical functions, including hindered phenols, which contribute desirable properties to the polymers to which they are attached. G. Manerke et al [Makromolekulare Chemie 99 175-185 (1966)]prepared polymers using phenolic derivatives where the phenolic group was blocked by esterification or some other appropriate reaction. Then, after the polymerization step was completed, the free phenolic group was regenerated by a chemical process such as hydrolysis. The invention described herein provides a much simpler and straightforward system for building antioxidant systems into polymers.

Very effective as free radical polymerization initiators used within the practice of the present invention when used under appropriate conditions, are compounds such as t-butyl hydroperoxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide and paramenthane hydroperoxides, and even hydrogen peroxide. These compounds perform very effectively when used in polymerization recipes containing appropriate levels of supporting ingredients. By "supporting ingredients" is meant those materials often referred to as activators in emulsion, or other systems, where required. U.S. Pat. No. 3,080,334 describes some of these materials at column 5, lines 20-26. Such materials can also be referred to as catalyst activators. The term "Redox Polymerization" is often used where the complete initiation system includes a Redox system, i.e., reducing agents and oxidizing agents in a proportion that yields polymerization initiating species. All of these initiator systems are well known in the art.

Emulsion polymerizations are normally accomplished in the range of 5.degree. to 90.degree. C. Though the activated or "Redox" initiated systems are preferred for low temperature polymerizations, they are very effective at high temperatures also, normally requiring appreciably lower quantities of the various ingredients to obtain a desirable polymerization rate

The free radical sources used in the initiator systems are those customarily used in free radical polymerizations, for example, organic initiators such as azo-nitriles, azo-derivatives, peroxides, and hydroperoxides and inorganic initiators such as inorganic peroxy compounds. Radiation, e.g., of the ultra-violet and gamma ray type can also be used as a free radical source. Various organic initiators are described by J. Brandrup and E.H. Immergut, Polymer Handbook(John Wiley & Sons), Wiley & Sons), 1965, pages II-3 to II-51. Peroxide initiators include the aralkyl, aliphatic, aliphatic acyl, aromatic acyl, ketone, aldehyde and perester types. Hydroperoxide compounds include aralkyl and aliphatic hydroperoxides. Inorganic peroxy compounds include persulfates, perborates, perphosphates and hydrogen peroxide.

Aralkyl peroxides are represented by dicumyl peroxide; aliphatic peroxides by di tert.butyl peroxide; aliphatic acyl peroxides by acetyl peroxide, decanoyl peroxide and lauroyl peroxide; aromatic acyl peroxides by benzoyl peroxide, and 2,4-dichlorobenzoyl peroxide; ketone peroxides by methylethyl ketone peroxide and cyclohexanone peroxide; aldehyde peroxides by heptaldehyde peroxide; and perester peroxides by tert-butyl peracetate, tert.butyl perpivalate and tert.butyl perbenzoate. Aralkyl hydroperoxides are represented by cumene hydroperoxide and diisopropylbenzene hydroperoxide and aliphatic hydroperoxides by tert.butyl hydroperoxide and paramenthane hydroperoxide. Persulfate, perborate and perphosphate compounds are represented by the sodium, potassium and ammonium persulfates, perborates and perphosphates; azo-nitriles and azo-derivatives by 2,2'-azo-bis-isobutyronitrile, 2,2'-azo-bis-2-methylpropionitrile and azo-bis-diphenylmethane.

Supporting ingredients, i.e., activators capable of activating certain initiators to produce free radicals include iron compounds such as ferrous sulfate or cobalt compounds, complexed with compounds such as sodium salts of ethylene diamine tetra acetic acid or sodium or potassium pyrophosphate. Reducing agents used in Redox systems include sodium formaldehyde sulfoxylate, various sugars and hydrosulfites.

Various initiator system components are described at column 4, lines 14 to 32 in U.S. Pat. No. 3,080,334.

Examples of comonomers that are useful in the practice of this invention are polymerizable unsaturated hydrocarbons, both substituted and unsubstituted, including conjugated diene monomers, such as butadiene-1,3; 2-chlorobutadiene-1,3; isoprene; 2-ethyl-butadiene-1,3; 2,3-dimethyl butadiene-1,3; piperylene; and hexadienes and copolymerizable monoolefins including vinyl and vinylidene monomers such as styrene, alpha-methylstyrene, divinyl benzene, vinyl chloride, vinyl acetate, vinylidene chloride, methylmethacrylate, ethylacrylate, the vinylpyridines including 2-vinyl pyridene, 5-methyl-2-vinyl pyridine, 4-vinyl pyridine and 2-vinyl-5-ethyl pyridine, acrylonitrile, methacrylonitrile, methacrylic acid and acrylic acid. Mixtures of the monomeric age resistors and mixtures of the comonomers may be used. The monomer charge weight ratio is normally from about 0.10/99.9 to about 10/90 or even 20/80 monomeric age resistor/comomomer. The ratio may even be as high as 30/70, or 60/40. A charge ratio of about 0.5/99.5 to about 5.0/95 is preferred. Ratios will vary depending on the amount of age resistor desired to be bound and on the reactivity ratios of the monomers in the particular polymerization system used. In all cases the monomer system will always contain at least 40 parts by weight of a diene monomer. However, the ratio may be even higher and the monomeric age resistor may even constitute all of the monomer charged, i.e., the ratio can be 100/0.

Preferably the monomer system contains at least 50 parts by weight per 100 parts by weight of total monomer of at least one diene, preferably a conjugated diene, such as 1,3butadiene or isoprene.

One embodiment of the present invention involves the use of a monomer system comprised of from about 50 to about 99.9 parts of at least one diene monomer, preferably a conjugated diene, 0 to about 49.9 parts of at least one monomer selected from the group consisting of vinyl monomers and vinylidene monomers and from about 0.10 to about 5.0 parts by weight of at least one monomeric age resistor, all parts being parts by weight per 100 parts by weight of total monomer. Preferably at least 0.5 part of monomeric age resistor is used. When at least 0.5 part of the monomeric age resistor is used, the upper limit on the diene monomer range is 99.5 parts and the upper limit of the vinyl monomer and/or vinylidene monomer range is 49.5 parts. The upper limit of the monomeric age resistor range may be even higher than 5.0, i.e., 10, 20, 30 and even 50.

the polymers resulting from the free radical polymerizations of monomeric systems containing the monomeric age resistors of the present invention contain segmeric units having the following structures. Where the monomeric age resistor has a structural formula according to (I) the segmeric unit has the following structural formula: ##STR9## wherein R, R.sup.1, R.sup.2 and R.sup.3 are as defined in structural formula (I).

Where the monomeric age resistor has a structural formula according to (II), the segmeric unit has the following structural formula: ##STR10## wherein R, R.sup.1, R.sup.4 and R.sup.5 are as defined earlier herein in structural formulae I and II.

Where the monomeric age resistor has a structural formula according to (III), the segmeric unit has the following structural formula: ##STR11## wherein R, R.sup.1, R.sup.6, R.sup.7, R.sup.8 and R.sup.9 are as defined in structural formulae (I) and (III). Preferably the comonomers are selected to produce and elastomeric copolymer.

These polymers, whether liquid or solid, have a special advantage in that the age resistant portion is not extractable, and therefore the polymeric compositions are highly resistant to oxidative aging even after repeated exposure to aqueous detergent solutions or dry-cleaning fluids. This feature is especially significant where polymers are used in foam backings for rugs and where polymers are used in solution or latex form to treat fabrics, since such products are often exposed to aqueous detergent solutions or dry-cleaning fluids. This feature is also significant where factors such as contact with lubricating oils or exposure to high vacuum conditions are a consideration.

One of the advantages of the present process is that it permits the preparation of polymers prepared from monomer systems containing diene monomers and containing bult-in stabilizers, without the formation of appreciable gel, that is, polymers can be made which are essentially gel-free. Gel formation is generally undersirable in a polymer since it can cause processing difficulties and directly and/or indirectly can affect the physical properties of the polymer in its vulcanized form. Normally a marco gel content of less than 50 percent is desirable. Preferably a gel content of less than 10 percent is desirable. Most preferably a gel content below 5 percent is desirable. Gel is the amount of polymer that is insoluble in an organic solvent such as benzene. One way to measure gel content is to place about 0.20 to about 0.30 grams of the polymer in 100 milliliters of benzene an permit the mixture to stand for 48 hours. The mixture is then filtered through a 100 mesh stainless steel wire cloth having a wire diameter of 0.045 inch. A solids is then run on the filtrate to determine the amount of soluble polymer. The amount of gel is the difference between the amount of polymer placed in the benzene originally and the amount of soluble polymer. The percent gel is one hundred times the gel weight divided by the original polymer weight.

To afford adequate protection against degradation the polymers should contain from about 0.10 part to about 10.0 parts by weight of the segmeric form of the monomeric age resistor per 100 parts by weight of the polymer, although from about 0.50 part to about 5.0 parts is normally satisfactory, from about 0.50 part to about 3.0 parts being preferred. As much as 20 parts. 30 parts, 50 parts and more of the polymer may consist of the age resistor segmeric unit while the lower limit may be 0.50 part to 0.10 part and lower. However, as the amount of bound age resistor increases the physical characteristics of the polymer are altered accordingly. Where it is desired to produce a polymer which is self-stabilizing and which substantially retains the physical properties of the comonomer or comonomers, normally the polymer should contain no more than about 10.0 parts by weight of the age resistor segmeric unit. Such polymers preferably are elastomeric solids, although they may be liquid. Where it is desired that the polymer act as a polymeric age resistor which may be blended with unstabilized polymers, the polymer should normally contain greater amounts of the monomeric age resistor. The remainder of the polymer is comprised preferably of the segmeric form of at least one conjugated diene monomer and/or the segmeric form of at least one vinyl monomer. Preferably the polymers contain at least 50 percent by weight of the segmeric form of a diene, preferably a conjugated diene such as butadiene-1,3 or isoprene. Most preferred as polymers containing from about 50 to about 99.9 parts by weight of the segmeric form of at least one diene, preferably a conjugated diene, 0 to about 49.9 parts by weight of the segmeric form of at least one monomer selected from the group consisting of vinyl monomers and vinylidene monomers and 0.10 to 5.0 parts by weight of the segmeric form of at least one monomeric age resistor, all parts being by weight per 100 parts by weight of polymer. Preferably the polymer contains at least 0.5 part of the segmeric form of the monomeric age resistor. When the polymer contains at least 0.5 part of the segmeric form of the monomeric age resistor, the upper limit of diene segmer range is 99.5 parts and the upper limit of the vinyl segmer and/or vinylidene segmer range is 49.5 parts. The upper limit of the segmeric form of the monomeric age resistor range may be even higher than 5.0, i.e., 10, 20, 30 and even 50. In all instances the polymers must contain at least 40 parts by weight of the segmeric form of a diene monomer, preferably a conjugated diene. In polymers generally prepared by free radical, particularly emulsion techniques, the trans 1,4 content is generally greater than the cis-1.4 or 1,2 content.

All of the monomeric age resistors described herein are capable of stabilizing polymers by simple incorporation into the polymers by conventional techniques such as by addition to polymer latices or by addition to the solid polymer on a mill or in a Banbury. When blending a self-stabilizing polymer with other polymers, especially when the self-stabilizing polymer contains large amounts of the segmeric form of the monomeric age resistor, one must consider the solubility problems involved in blending dissimilar polymers.

Polymers subject to deterioration by oxidation that can be conveniently protected by the age resistors described herein include substituted and unsubstituted, saturated and unsaturated, natural and synthetic polymers. The oxidizable natural polymers of interest include natural rubber in its various forms, e.g., pale crepe and smoked sheet, and balata and gutta percha. The oxidizable synthetic polymers are prepared from a single monomer (homopolymer) or a mixture of two or more copolymerizable monomers (copolymers) wherein the monomers are combined in a random distribution or block form. The monomers may be substituted or unsubstituted and may possess one or more double bonds, for example, diene monomers, both conjugated and nonconjugated, and monoolefins including cyclic and acyclic monoolefins, especially vinyl and vinylidene monomers. Examples of conjugated dienes are 1,3-butadiene, isoprene, chloroprene, 2-ethyl-1,3butadiene, 2,3-dimethyl-1,3-butadiene and piperylene. Examples of nonconjugated dienes are 1,4-pentadiene, 1,4-hexadiene, 1,5-hexadiene, dicyclopentadiene, 1,5-cyclooctadiene and ethylidene norbornene. Examples of acyclic monoolefins are ethylene, propylene, 1-butene, isobutylene, 1-pentene and 1-hexene. Examples of cyclic monoolefins are cyclopentene, cyclohexene, cycloheptene, cyclooctene and 4-methylcyclooctene. Examples of vinyl monomers are styrene, acrylonitrile, acrylic acid, ethylacrylate, butylacrylate, methyl vinyl ether, vinyl acetate and vinyl pyridine. Examples of vinylidene monomers are .alpha.-methylstyrene, methacrylic acid, methyl methacrylate, ethylmethacrylate, glycidylmethacrylate and vinylidene chloride. Representative examples of the synthetic polymers used in the practice of this invention are polychloroprene; homopolymers of a conjugated 1,3-diene such as isoprene and butadiene, and in particular, polyisoprenes and polybutadienes having essentially all of their repeat units combined in a cis-1,4 structure; copolymers of a conjugated 1,3-diene such as isoprene and butadiene with up to 50 percent by weight of at least one copolymerizable monomer including ethylenically unsaturated monomers such as styrene of acrylonitrile; butyl rubber, which is a polymerization product of a major proportion of a monoolefin and a minor proportion of a multiolefin such as butadiene or isoprene; polyurethanes containing carbon to carbon double bonds; and polymers and copolymers of monoolefins containing little or no unsaturation, such as polyethylene, polypropylene, ethylene propylene copolymers and terpolymers of ethylene, propylene and a nonconjugated diene such as dicyclopentadiene, 1,4-hexadiene, ethylidene norbornene and methylene norbornene.

When added in free form normally 0.001 to 10.0 percent of the age resistor by weight, i.e., parts by weight based on the weight of the polymer, i.e., 100 parts by weight of the polymer can be used, although the precise amount of the age resistors which is to be employed will depend somewhat on the nature of the polymer and the severity of the deteriorating conditions to which the polymer is to be exposed. In unsaturated polymers such as those made from conjugated dienes, the amount of age resistor necessary is greater than that required by a saturated polymer such as polyethylene. It has been found that an effective antioxidant amount of the disclosed stabilizers in rubbery unsaturated polymers will generally range from 0.05 to 5.0 percent by weight, i.e., parts by weight based on the weight of the polymer, although it is commonly preferred to use from 0.5 to 3.0 percent by weight, i.e., parts by weight based on the weight of the polymer. Mixtures of the age resisters may be used.

The following examples illustrate the practice of the present invention. Unless otherwise indicated, all parts are parts by weight.

Examples 1 to 5 illustrate the preparation of age resistors which can be used to stabilize polymers by physically combining the polymers therewith or which can be used in free radical polymerization systems as monomers to produce selfstabilizing polymers.

N-(3,5-di tert.butyl-4-hydroxyphenyl)acrylamide was prepared by adding a solution of 10 grams of acryloyl chloride in 50 milliliters of benzene to a mixture of 22.1 grams of 2,6-di tert.butyl-4-aminophenol, 6 grams of sodium carbonate, and 100 milliliters of benzene. The addition was accomplished in 25 minutes at 19.degree. C. to 38.degree. C. The mixture was stirred for 21/2 hours and the precipitate which had formed was filtered off, washed thoroughly with water, and dried. The yield was 12.5 grams and the product melted at 204.degree. C. to 206.degree. C.

2,6-di tert.butyl-4-aminophenol was prepared by hydrogenating a mixture of 23.5 grams of 2,6-di tert.butyl-4-nitrosophenol, 2 grams of 5% Palladium on carbon, and 200 milliliters of absolute ethanol in a Parr Pressure Reaction Apparatus. The reduction was accomplished in 1 hour at a maximum hydrogen pressure of 50 psi and a maximum temperature of 50.degree. C. The resulting solution of 2,6-di tert.butyl-4-aminophenol was removed from the Pressure Apparatus and filtered to remove the catalyst.

N-(3,5-di tert.butyl-4-hydroxyphenyl)methacrylamide was prepared by adding a solution of 11.5 grams of methacryloyl chloride in 50 milliliters of benzene to the solution of 2,6-di tert.butyl-4-aminophenol to which had been added 6 grams of sodium carbonate. The addition was accomplished in 30 minutes at 24.degree. C. to 37.degree. C. The mixture was stirred for 1 hour and the solid product was filtered off, washed thoroughly with 2% hydrochloric acid and dried. The yield was 10.0 grams of product which melted at 222.degree. C. to 225.degree. C.

N-(3,5-di tert.butyl-4-hydroxyphenyl)crotonamide was prepared by adding a solution of 11.5 grams to crotonyl chloride in 50 milliliters of benzene to a solution of 2,6-di tert.butyl-4-aminophenol prepared as described in Example 2 to which had been added 6 grams of sodium carbonate. The addition was accomplished in 30 minutes at 25.degree. C. to 38.degree. C. The mixture was stirred for 11/4 hours and the solid product was filtered, washed thoroughly with 2% hydrochloric acid, and dried. The yield was 12.8 grams of product which melted at 211.degree. C. to 214.degree. C.

N-(3,5-di tert.butyl-4-hydroxyphenyl)cinnamamide was prepared by adding a solution of 18.2 grams of cinnamoyl chloride in 50 milliliters of benzene to a solution of 2,6-di tert.butyl-4 -aminophenol prepared as described in Example 2 to which had been added 6 grams of sodium carbonate. The addition was accomplished in 30 minutes at 24.degree. C. to 37.degree. C. The mixture was stirred for 1 hour. The solid product was filtered, washed thoroughly with 2% hydrochloric acid, and dried. The yield was 17 grams of product which melted at 211.degree. C. to 214.degree. C.

2,6-di tert.butyl-4-aminophenol was prepared by adding in a nitrogen atmosphere, a solution of 70 grams of sodium dithionate in 300 milliliters of water to a mixture of 23.5 grams of 2,6-di tert.butyl-4-nitrosophenol, 80 milliliters of 5 N sodium hydroxide solution and 160 milliliters of water. The addition was accomplished in 45 minutes at 24.degree. C. to 41.degree. C. After stirring for 21/4 hours, 100 milliliters of benzene was added to dissolve the solid product, and the layers were separated.

N-(3,5-di tert.butyl-4-hydroxyphenyl)maleamic acid was prepared by adding to the benzene solution of 2,6-di tert.butyl-4-aminophenol in 15 minutes at 15.degree. C. to 31.degree. C. a solution of 9.8 grams of maleic anhydride in 50 milliliters of benzene. The mixture was stirred for 2 hours and the solid product was filtered off and dried. The yield was 19.5 grams and the product melted at 206.degree. C. to 207.degree. C. (with decomposition).

The following examples illustrate the preparation of polymers containing monomeric age resistors as part of the polymeric chain. They also illustrate the age resistance possessed by said polymers as well as by polymers having the monomeric age resistors physically combined therewith. Unless otherwise indicated all parts are parts by weight.

A copolymer of butadiene, styrene and N-(3,5-ditertiary butyl-4-hydroxyphenyl) acrylamide was prepared by polymerizations in 4-ounce bottles using the following proportions of ingredients.

The groups of ingredients were added to the 4-ounce bottles in the order indicated above. The paramenthane hydroperoxide was dissolved in a small portion of the styrene, about 4.5 parts, while group 4 was added as an aqueous solution in a small portion of the water, about 10 parts. Polymerization was accomplished at 5.degree. C. A conversion of 37.0% was reached after 18 hours. The polymer was coagulated in acidified 2-propanol and washed in methanol, then vacuum dried at 60.degree. C.

Polymerizing in a process similar to that of Example 6 a copolymer of butadiene, styrene and N-(3,5-ditertiary butyl-4-hydroxyphenyl) methacrylamide was produced. Two and five-tenths (2.5) parts of the antioxidant monomer were charged. The proportion of FeSO.sub.4 .7H.sub.2 O was reduced to 0.00075 part and the paramenthane hydroperoxide level was adjusted to 0.18 part. Polymerization was accomplished at 25.degree. C. to 28.degree. C. The redox ingredients were charged a second time after 5 hours. Polymerization continued for an additional 16hours after which the polymer was coagulated and washed with methanol and vacuum dried at 80.degree. C.

Acrylonitrile, butadiene and N-(3,5-ditertiary butyl-4-hydroxyphenyl) methacrylamide were polymerized in 4-ounce bottles at 50.degree. C. Thirty-three (33) parts of acrylonitrile, 67 parts of butadiene and 1.25 parts of antioxidant monomer were charged. The antioxidant monomer was dissolved in a mixture of 20 parts methylethylketone and 20 parts methanol before charging. The recipe was similar to that of Example 6 with the exception that 0.5 part paramenthane hydroperoxide was used. Conversion after 18 hours was found to be 80%.

A high solids latex was produced using the following proportions of ingredients and polymerizing in 4-ounce bottles tumbled in a water bath at 25.degree. C.

The soap was charged first in about 91 parts of water along with the sodium salt of the sulfonic acids and the Na.sub.2 SO.sub.4. The mercaptan was then charged, being dissolved in about 20 parts of acrylonitrile. The butadiene was charged next, followed by the addition of the crotonamide in approximately 6.7 parts of acrylonitrile. The activator system, i.e. the chelating agent, the FeSO.sub.4 .7H.sub.2 O, the sulfoxylate and Na.sub.2 S.sub.2 O.sub.4 were added in about 2.6 parts of water. Finally the hydroperoxide was added in about 6.7 parts of acrylonitrile, A latex of about 50% solids was produced. A portion of the polymer was coagulated in 2-propanol, washed in methanol and vacuum dried at 80.degree. C.

Example 9 was repeated substituting N-(3,5-ditertiary butyl-4-hydroxyphenyl) cinnamamide for the N-(3,5-ditertiary butyl-4-hydroxyphenyl) crotonamide. The polymer was alcohol coagulated, washed and vacuum dried at 80.degree. C.

A copolymer of acrylonitrile, butadiene and antioxidant monomer was made in 4-ounce narrow-mouth screw-capped bottles using a recipe similar to that of Example 9. One and one-fourth (1.25) parts of N-(3,5-ditertiary butyl-4-hydroxyphenyl) acrylamide was used as the antioxidant monomer instead of the crotonamide. The acrylamide was dissolved in 7.5 parts of methylethylketone to facilitate charging. Polymerization was accomplished at 25.degree. C. The polymer was coagulated using 2-propanol and was washed with methanol before vacuum drying at 80.degree. C.

Table I contains oxygen absorption data for polymers prepared by emulsion polymerization techniques from monomer systems containing monomeric age resisters of the present invention. The polymerizations were similar if not identical to those described in Examples 6 to 11. Table II contains oxygen absorption data for SBR-1006 (butadiene/styrene elastomer) containing monomeric age resisters physically incorporated therein.

Before oxygen absorption tests were run on the polymers described in Table I, the dry polymers were extracted for 48 hours with methanol in a Soxhlet type apparatus to remove any of the free monomeric age resister, dried again, and then dissolved in benzene. The benzene solutions were poured into aluminum trays and the solvent was allowed to evaporate. The resulting films were placed in an oxygen absorption apparatus. The amount of oxygen absorbed in a particular interval of time was determined and is listed in the following Table I. The testing procedure is described in further detail in INDUSTRIAL AND ENGINEERING CHEMISTRY, Vol. 43, page 456 (1951) and INDUSTRIAL AND ENGINEERING CHEMISTRY, Vol. 45, page 392 (1953).

The SBR polymer (1006) in Table II was dissolved in benzene and benzene solutions of the age resistors were added to portions of the SBR solutions to provide 1.00 part of the age resisters per 100 parts of rubbery polymer. The benzene solutions were used to form films and tested in oxygen absorption apparatus as described above.

The above data demonstrate that the monomeric age resistors described herein are capable of providing age resistant polymeric compositions by either polymerizing the monomeric age resistor in an emulsion-free radical polymerization system along with comonomers or by incorporating the monomeric age resistors by conventional techniques into the polymers. That is, the age resistors provide protection whether in a free or bound condition. Any of the monomeric age resisters, comonomers, initiator systems or polymers described earlier herein can be substituted for their counterparts in the above working examples to provide age resistant polymeric compositions. Naturally certain changes in variables such as the emulsification system to be used may be necessary as a result of the use of different monomers. However, such changes would be routine to those skilled in the art.

For example, in Examples 6 to 11 isoprene could have been substituted for the butadiene. Likewise, vinylidene chloride or 2-vinyl chloride could have been substituted for the styrene or acrylonitrile used in said examples. N-[3,5-bis(1,1-dimethylbutyl)-4-hydroxyphenyl]acrylamide; N-(3,5-ditertiary butyl-4-hydroxyphenyl)itaconimide or N-(3,5-ditertiary butyl-4-hydroxy-phenyl)-.alpha.-methylitaconimide could have been substituted for any of the monomeric age resisters described in any of said examples. Also for example, tertiary butyl hydroperoxide could have been substituted for para-menthane hydroperoxide in Example 6 at a level of, for example, 0.03 to 0.04 parts.

All of the polymers prepared in Examples 6 to 11 were solid elastomers.

Naturally polymerization rates and amounts of bound monomer can vary, as well as the type of emulsifier to be used, depending upon the monomers used. Also, reactor size and degree of agitation can affect polymerization rates. However, optimum conditions and systems can be determined based upon the above revelations by routine experimentation by one possessing ordinary skill in the art.

All polymer molecular weights referred to herein, unless otherwise indicated, are number average molecular weights.

The age resistant polymeric compositions prepared by chemically binding the age resistors or by physically incorporating them into polymers, are age resistant, whether in vulcanized or unvulcanized form. They may be used, depending on the particular polymer involved, in products such as tires, industrial rubber products, such as transmission belts and hose, and molded goods. Where the polymeric composition contains the age resistor as an integral part of the polymer chain, it is especially useful in applications where a product is frequently exposed to aqueous detergent solutions or dry-cleaning fluids, for example, in foam backings for rugs and in polymer treated fabrics.

Polymerization rates can oten be improved by using a purified monomeric age resistor and/or by raising the polymerization temperature, using more potent initiator systems, increasing the initiator level or by any of the conventional means of improving polymerization rates.

While certain representative embodiments and details have been shown for the purpose of illustrating the invention, it will be apparent to those skilled in this art that various changes and modifications may be made therein without departing from the spirit or scope of the invention.