EPOXY CONTAINING IMPACT MODIFIERS FOR THERMOPLASTIC RESINS

Abstract: An epoxy functionalized EPM and/or EPDM rubber prepared in a bulk reaction for use as a modifier for improv­ ing the impact and knitline strengths of thermo plastic resins.

Description: This invention relates to modifiers for thermoplastic resins. More particularly, this invention relates to epoxy-functionalized elastomeric materials for use as modifiers for thermoplastic resins. Common thermoplastic resins, i.e., polycarbonates, polyesters, polyphenylene ethers and polyamides have excellent combinations of properties making them suitable for use as molded articles. Such resins, in general, show good elongation, good tensile strength and good impact, among other properties. However, it is widely recognized that such resins are notch sensitive and subject to brittle failure upon impact due to poor resistance to crack propagation and weakness at the knitline. These flaws in an otherwise excellent spectrum of physical properties greatly restrict the usefulness of articles molded from such resins. Improving the notch sensitivity, knitline strength and preventing brittle failure upon impact of thermoplastic resins has been the subject matter of considerable research and development. Generally, the problem is addressed by the addition or admixture of additives to the thermoplastic resin which improve notch sensitivity without substantially effecting other properties. The most common type of such additives are rubber-like or elastomeric materials, such as ethylene-propylene copolymers (EPM), or ethylene-propylene-polyene terpolymers (EPDM), which form discrete particles dispersed throughout the thermoplastic resin. However, the desired level of improvement has not been achieved with the addition of such rubber-like or elastomeric materials by reason of the relative incompatibility between such rubber-like or elastomeric materials and many thermoplastic resins. Attempts have been made to overcome this problem and to increase the compatibility between the rubber-like or elastomeric materials and thermoplastic resins by modification of the rubber-like or elastomeric materials to provide such with sites that adhere to the thermoplastic resin and thus increase compatibility. U.S. Patent No. 3,435,093 describes blends of polyethylene terephthalate and ionic hydrocarbon copolymers of alpha-olefins of the formula R-CH=CH₂ in which R is hydrogen (ethylene) or alkyl of 1-3 carbon atoms (propylene-pentene) with the copolymer modified wit an alpha-beta ethylenically unsaturated carboxylic acid of 3-5 carbon atoms. The patent does not teach or suggest the components of the additive employed in the practice of the present invention. The problem was faced directly in U.S. Patent No. 4,172,859. The patent is somewhat confusing in that it seeks to cover the waterfront by listing an almost endless number of materials and combinations thereof for use as additives to improve the toughness and impact strength of polyester and polycarbonate resins. In the patent, stress is placed on the particle size and tensile modulus of the copolymer additive. While it contemplates the use of ethylene-propylene copolymers and ethylene-propylene-polyene terpolymers from amongst the large number of other varieties of materials and the use of alpha-beta ethylenically unsaturated carboxylic and dicarboxylic acids and anhydrides as modifying agents to provide sites which adhere to the matrix resin, the patent does not recognize the concepts of the present invention. The invention described in U.S. Patent No. 4,948,842 is based on the thought that an ethylene C₃-C₁₆ mono-olefin polyene, and preferably an ethylene propylene diene rubbery interpolymer would make a good impact modifier for thermoplastic polyester, if the two could be made compatible. The two are relatively incompatible because the rubber is a hydrocarbon while the polyester is a much more polar substance. Thus, the objective of the invention was addressed to the modification of the ethylene, mono-olefin, polyene interpolymer rubber greatly to improve its compatibility with polyester to provide an improved impact modifier for the thermoplastic polyester resin. Briefly described, the features of the invention of that patent are embodied in a composition comprising 60-90 percent by weight of a matrix resin in the form of a polyester blended with 10-40 percent by weight of an unsaturated rubber formed by copolymerization of ethylene - one or more mono-olefins and one or more polyenes in which the backbone unsaturated rubber component has been modified with an ester of an α,β-unsaturated acid having an epoxide functionality on the alkoxy portion, such as the ester derived from methacrylic acid and an epoxy alcohol and which attaches to the backbone rubber chiefly by way of a grafting reaction with little if any cross-linking reaction. U.S.Patent No. 4,956,501 describes an improvement over the invention described and claimed in U.S.Patent No. 4,948,842 in that controlled cross-linking of the rubber backbone phase (EPDM) of the grafted modifier provides a significant improvement in the knitline strength of the final blend with the matrix (polyester or polyamide) resin, when the cross-linking reaction is carried out after proper dispersion of the grafted rubber phase in the plastic matrix resin and when the cross-linking is concentrated between the rubber phase of the grafted rubber. For this purpose, use is made of a cross-linking agent in the form of a compound having functionalities capable of reaction with the grafted rubber, such a diacids or corresponding dianhydrides and/or diamines such as hexamethylene diamine (HDA), melamine, benzophenone tetracarboxylic dianhydride, adipic acid, maleic acid and maleic anhydride. Reference is also made to U.S. Patent No. 3,886,227 and U.S. Patent No. 4,026,967. Those patents seek to avoid the type of cross-linking of the modifier of this invention and they are further deficient from the standpoint of the characteristics of the modifier described and claimed herein from the standpoint of gel content, epoxide functionality and degree of graft. Though less pertinent, the following patents may be mentioned, namely: U.S. Patents No. 3,884,882, No. 3,274,289, No. 3,484,403, No. 3,882,194, No. 4,017,557, No. 4,147,740, No. 4,346,194, No. 3,376,182 and Japanese patent No. 45-30943. Briefly described, the concepts of this invention are embodied in a modifier for improving the impact and knitline strength of a thermoplastic matrix resin in which the modifier is blended for dispersion in the matrix resin. In accordance with the invention, the modifier comprises an EPM or EPDM-type backbone rubber which has been subjected to graft polymerization with an alpha-beta ethylenically unsaturated hydrocarbon having epoxide functionality wherein the graft polymerization is carried out at elevated temperature in bulk in the presence of a peroxide catalyst. The graft polymerization product is characterized by a gel content of greater than 5 percent and preferably 7-65 percent, an epoxy functionality of more than 2.5 per 1000 carbon atoms up to 13 per 1000 carbon atoms and a degree of graft of at least 2.5 % and preferably within the range of 2.5-8 percent. When the graft polymerization is carried out in bulk, at elevated temperature, in the presence of a peroxide catalyst, a modifier having the described characteristics can be produced with a backbone formed by copolymerization of ethylene and one or more C₃-C₁₆ mono-olefins, preferably propylene (EPM) or preferably a terpolymer rubber formed by interpolymerization of ethylene, one or more mono-olefin, having from 3-16 carbon atoms, preferably propylene (EPDM), and one or more polyenes. In the practice of this invention, the EPDM-type component can be substituted in whole or in part by an EPM-type rubber. As the EPM-type rubber, use can be made of an ethylene-C₃-C₁₆ mono-olefin and preferably an ethylene-propylene copolymer rubber formed by copolymerization in solution, in the presence of a Ziegler-type catalyst, of ethylene and one or more mono-olefins, preferably propylene, but which may include 1-butene, 1-pentene or other mono-olefins having 3-12 carbon atoms. The ratio of ethylene to propylene or other C₃-C₁₂ mono-olefin may range from 10-95 moles of ethylene to 90-5 moles of propylene or other mono-olefins. The preferred range of ethylene to propylene or other mono-olefin is 45-75 moles of ethylene to 55-25 moles of propylene or other mono-olefin. In the preparation of the EPDM-type rubber, the polyene monomer containing a plurality of carbon-to-carbon double bonds may be selected from those described in the prior art for use as third monomers in the preparation of ethylene-mono-olefin-polyene terpolymers, including open chain polyunsaturated hydrocarbons containing 4-20 carbon atoms, such as 1,4-hexadiene, monocyclic polyenes and polycyclic polyenes. The polyunsaturated bridged ring hydrocarbons or halogenated bridged ring hydrocarbons are preferred. Examples of such bridged ring hydrocarbons include the polyunsaturated derivatives of bicyclo (2,2,1) heptane wherein at least one double bond is present in one of the bridged rings, such as dicyclo-pentadiene, bicyclo(2,2,1)hepta-2,5-diene, the alkylidene norbornenes, and especially the 5-alkylidene-2-norbornenes wherein the alkylidene group contains 1-20 carbon atoms and preferably 1-8 carbon atoms, the alkenyl norbornenes, and especially the 5-alkenyl-2-norbornenes wherein the alkenyl group contains 3-20 carbon atoms and preferably 3-10 carbon atoms. Other bridged ring hydrocarbons include polyunsaturated derivatives of bicyclo(2,2,2) octane as represented by bicyclo(3,2,1) octane, polyunsaturated derivatives of bicyclo(3,3,1) nonane, and polyunsaturated derivatives of bicyclo(3,2,2) nonane. Specific examples of preferred bridged ring compounds are 5-methylene-2-norbornene, 5-ethylidene-2-norbornene, 5-n-propylidene-2-norbornene, 5-isobutylidene-2-norbornene, 5-n-butylidene-2-norbornene, 5-isobutylidene-2-norbornene, dicyclopentadienes; the methyl butenyl norbornenes such as 5-(2-methyl-2-butenyl)-2-norbornene or 5-(3-methyl-2-butenyl)-norbornene, and 5-(3,5-dimethyl-4-hexenyl)-2-norbornene. The elastomer prepared from 5-ethylidene-2-norbornene is much preferred as it has outstanding properties and produces many unusual and unexpected results. The EPDM-type backbone rubber may contain chemically bound therein molar ratios of ethylene to propylene or other C₃-C₁₆ mono-olefin varying from 95:5 to 10:90 and preferably from 70:30 to 55:45. The polyene or substituted polyene may be chemically bound therein in an amount of 0.1 to 10 mol percent, and preferably 0.3 to 1 mol percent. The level of unsaturation in the backbone rubber may range from 2 to 20 double bonds per 1,000 carbon atoms in the polymer chain. The polyermization for preparation of the EPM and EPDM is carried out in the presence of a catalyst in a solvent. The polymerization solvent may be any suitable inert organic solvent that is liquid under reaction conditions. Examples of satisfactory hydrocarbon solvents include straight chain paraffins having from 5-8 carbon atoms, with best results often being secured by the use of hexane; aromatic hydrocarbons and preferably an aromatic hydrocarbon having a single benzene nucleus, such as benzene or toluene; and saturated cyclic hydrocarbons having boiling ranges approximating those of the straight chain paraffin hydrocarbons and aromatic hydrocarbons described above, and preferably saturated cyclic hydrocarbons having 5-6 carbon atoms in the ring. The solvent selected may be a mixture of one or more of the foregoing hydrocarbons and is preferably a mixture of aliphatic and naphthenic hydrocarbons having approximately the same boiling range as normal hexane. It is desirable that the solvent is dry and free of substances that will interfere with the Ziegler-type catalyst used in the polymerization reaction. The interpolymerization is carried out in the presence of a Ziegler catalyst of the type well known to the prior art. Such Ziegler-type catalysts are described in a large number of patents, such as U.S. Patents No. 2,933,480, No. 3,093,620, No. 3,093,621, No. 3,211,709 and No. 3,113,115. Examples of Ziegler catalysts include metal organic coordination catalysts prepared by contacting a compound of a heavy metal of the group IV-a, V-a, VI-a and VII-a of the Mendeleeff periodic system of elements, such as titanium, vanadium and chromium halides with an organo-metallic compound of a metal of groups I, II or II of the Mendeleeff periodic system which contains at least one carbon-metal bond, such as trialkyl aluminum, and allyl aluminum halides in which the alkyl groups contain from 1-20 and preferably 1-4 carbon atoms. The preferred Ziegler catalyst is prepared from a vanadium compound and an alkyl aluminum halide. Examples of suitable vanadium compounds include vanadium trichloride, vanadium tetrachloride, vanadium oxychloride and vanadium acetyl acetonate. Activators which are especially preferred include alkyl aluminum chlorides of U.S. Patent No. 3,113,115, having the general formula R₁AlCl₂ and R₂AlCl and the corresponding sesquichlorides of the general formula R₃Al₂Cl₃, in which R is methyl, ethyl, propyl, butyl or isobutyl. In the catalyst system, the aluminum to vanadium mol ratio of the aluminum and vanadium compounds may be within the range of 5/1 to 200/1 and preferably within the range of 15/1 to 60/1, with best results being secured in the ratio of 40 aluminum to 1 vanadium. These same ratios apply with respect to corresponding compounds of others of the heavy metals substituted for the vanadium compound and the organo-metallic compounds of groups I, II and III for the aluminum compounds. A catalyst prepared from alkyl aluminum sesquichloride, such as the methyl or ethyl aluminum sesquichloride and vanadium oxychloride is preferred in the ratio of 1 mole vanadium oxychloride per 5-300 moles of aluminum and more preferably 15-60 moles of aluminum, with 40 moles of aluminum per mole of vanadium yielding the best results. The polymerization is preferably carried out on a continuous basis in a reaction vessel closed to the outside atmosphere, which is provided with an agitator, cooling means and conduit means for continuously supplying the ingredients of the reaction including monomer, catalyst and accelerators and conduit means for continuously withdrawing solution containing elastomer, and the catalyst is killed by the addition of a catalyst deactivator. The preparation of EPM- and EPDM-type polymers is well known and is fully described in such patents as U.S. Patents No. 2,933,480, No. 3,093,621, No. 3,211,709, No. 3,646,168, No. 3,790,519, No. 3,884,993, No. 3,894,999 and No. 4,059,654. The epoxy functionality may be described as a monovalent group of the general formula: wherein R³ is hydrogen or methyl; R² is hydrogen or alkyl of from one to six carbon atoms; and R¹ is alkylene having one to ten carbon atoms. Preferably, R¹ is methylene, R² is hydrogen and R³ is hydrogen, i.e., glycidyl. The above epoxy functionality of formula I may be joined to the alpha-beta ethylenically unsaturated portion of the monomer through any number of organic groups including a carbon-to-carbon bond, through an amide group, through an ether linkage, or through an ester linkage. Suitable epoxy functional graft monomers are glycidyl ethers of unsaturated alcohols, i.e., allyl-glycidyl ether, methallyl-glycidyl ether; glycidyl esters of unsaturated carboxylic acids, i.e, glycidyl-2-ethyl acrylate, glycidyl-2-propyl acrylate, glycidyl acrylate; glycidyl ethers of alkenylphenols, i.e., isopropenylphenyl-glycidyl ethers; vinyl and allyl esters of epoxy carboxylic acids, vinyl esters of epoxidized oleic acid. Preferred as the graft monomer is glycidyl methacrylate (GMA). Of course, the chain formed by the interpolymerization need not be a homopolymer or even be of entirely epoxy functional graft monomers. For example, combinations of the above epoxy functional graft monomers may be used as well as combinations of such with other alpha-beta ethylenically unsaturated hydrocarbons. Other such alpha-beta ethylenically unsaturated hydrocarbons suitable for use as comonomers are the alk-l-enes, including allyl compounds, acrylates and alkyl acrylates, methacrylates and alkyl methacrylates, acrylonitrile, methacrylonitrile, styrenes, and vinyl halides. Particularly useful comonomers are glycidyl acrylate and methyl methacrylate. It is critical to the invention that the gel content of the elastomeric material is controlled either during polymerization or in subsequent processing to achieve a value of greater than 5 percent by weight and preferably greater than 10 percent by weight. Gel content may range up to 100 percent by weight. Gel content, according to ASTM D-3616, is measured by the weight percent of remaining elastomeric material after extraction in hexane or toluene. Gel content is an indication of the degree of cross-linking in the elastomeric material. Persons skilled in the art are familiar with a variety of ways to control the degree of cross-linking and thus the gel content. The cross-link reaction may be a direct rubber backbone to rubber backbone joining, an epoxy functionality to epoxy functionality or rubber backbone joining, or a graft chain free radical addition to a second chain or to a rubber backbone. Further, cross-linking may be achieved by the addition of a cross-linking agent to effectively achieve any of the above reactions. Thus, any of several steps to control gel content may be taken. Thermal aging will increase gel content. Increasing the amount of epoxy functional monomer will increase gel content. Increasing the amount of polyene monomer in the rubber backbone will increase gel content. The addition of a cross-linking agent will increase gel content. The use of monomers with greater tendency to cross-link will increase gel content, for example, a homopolymer graft of glycidyl acrylate will cross-link more readily than a homopolymer of glycidyl methacrylate or a copolymer of glycidyl acrylate and methyl methacrylate. As stated above, gel content of the elastomeric material may range up to 100 percent by weight. However, persons skilled in the art will readily understand that cross-linking can be carried on well past the 100 percent by weight gel content level. However, such high levels of cross-linking will destroy the rubbery characteristic of the elastomeric material and lead to a brittle network polymer. Also, high levels of localized cross-linking will create brittle areas within the elastomeric material which will decrease rubbery character. It is apparent that cross-linking should be kept to the minimum reguired to achieve a given gel content. Further, such cross-linking should be uniformly dispersed through the elastomeric material. The reaction is carried out in accordance with the preferred practice of this invention in a single step bulk process wherein the separate ingredients forming the modifier are combined for reaction in melt processing equipment, such as an injection machine or banbury heat processing equipment at a temperature of 175-290 o C (350-550 o F) and preferably 200-235 o C (400-450 o F). This permits a different reaction between the ingredients whereby a more desirable and uniform system is obtained which functions more effectively in the final combination with the matrix resin to yield products molded therefrom, having improved properties. The reaction is carried out in the presence of a peroxide catalyst such as a dialkyl peroxide, dicumyl peroxide, t-butyl hydroperoxide, benzoyl peroxide, t-butylperoctanoate, di-t-butylperoxide, t-butylhydroperoxide, cumene hydroperoxide, t-butylperbenzoate, 2,5-dimethyl-2,5-di(t-butylperoxy) hexane, or other free radical source capable of hydrogen abstraction, as represented by alkyl peroxy esters, alkyl peroxides, alkyl hydroperoxides and diacylperoxides, which is added with the EPM, reactive agent and polyamide, in bulk, to the reaction. Such catalyst component is employed in an amount of 0.1-3 parts by weight per 100 parts by weight of the backbone rubber forming the modifier. The modifier, produced in accordance with this invention, enjoys improved compatability with the matrix resin subsequently blended therewith to provide a more uniform product. In use, the modifier of this invention is physically dispersed in a thermoplastic polymer melt to form discrete particles of modifier in a continuous phase of a thermoplastic matrix resin or blend. At least an impact strength improving amount of modifier is dispersed in the matrix resin. Generally, this requires that the modifier constitutes at least 2 parts by weight per 100 weight parts total thermoplastic content, including the modifier material. The matrix resin may contain elastomeric material up to the point of phase inversion, that is, where the elastomeric material becomes the continuous phase. However, where a rigid article is to be molded from a molding composition containing modifier, the molding composition should contain no more than 40 parts by weight modifier per 100 weight parts total thermoplastic content. The dispersion is simply carried out by standard techniques, for example, by simple melt blending or dry mixing and melt extruding at an appropriate elevated temperature for any given thermoplastic matrix. The resultant admixture is then molded into a thermoplastic piece of specific dimensions or further extruded into a film or sheet product. With the modifier of this invention, it has been found advantageous to preblend the modifier with less than the full increment of matrix resin to form a masterbatch. The masterbatch or concentrate may be simply formed by coextruding the modifier material and the concentrate resin. The molding product may subsequently be formed by blending masterbatch with the remaining resin during an extruder reaction as described above. Suitable thermoplastics for use as the masterbatch or matrix resin herein are epoxy resins, polyolefins, polyimides, polyaryl ethers, polyphenylene sulfides, polysulfones, polycarbonates, polyesters, polyphenylene ethers and polyamides, including blends thereof. There may be present in an elastomeric material/thermoplastic resin blend the adhesion reaction product of the epoxy functionality of the elastomeric material and a hydroxy, carboxy, or amine functionality (including reactive derivatives thereof, i.e., ester, salt, ether) of the matrix resin or concentrate resin. It is preferred that the matrix resin and especially the masterbatch has terminal or mid-chain hydroxy, carboxy, or amine functionalities, including reactive hydroxy or carboxy derivatives, to permit adhesion. Thus, preferred matrix resins and especially preferred concentrate resins are polyamides; polyesters; polycarbonates, polyphenylene ethers, and polyimides containing phthalic acid or phthalic anhydride terminal groups. It is immediately apparent that a concentrate resin having hydroxy or carboxy functionality could be employed to increase compatibility of the elastomeric material to a second matrix resin where such concentrate is more compatible with the matrix resin than is the elastomeric material. The polyesters suitable for use herein may be any of the linear or branched saturated polyesters known to those skilled in this art. Generally, the polyesters will comprise linear saturated polyesters derived from C₁-C₁₀ alkylene glycols such as ethylene glycol, propylene glycol and 1,4-butanediol, including cycloaliphatic glycols, such as 1,4-cyclohexane-dimethanol, and mixtures of any of these glycols with one or more aromatic dicarboxylic acids. Preferably, the polyesters will comprise poly(C₁-C₆ alkylene terephthalates) prepared by known techniques, such as the transesterification of esters of terephthalic acid alone or mixtures of esters of terephthalic acid and isophthalic acid, with the glycol or mixture of glycols and subsequent polymerization, by heating the glycols with the free acids or with halide derivatives thereof, and similar processes. These methods are described in U.S. Patents No. 2,465,319 and No. 3,047,539. In addition, blends of one or more of these polyesters or copolyesters may be employed. A suitable poly(1,4-butylene terephthalate) resin is commercially available from General Electric Company under the Trade Mark VALOX® 315; and poly(ethylene terephthalate) resins are also extremely well known and are abundantly available commercially. Suitable polycarbonate resin for use herein may be prepared by reacting a dihydric phenol with a carbonate precursor, such as phosgene, haloformate or a carbonate ester. Typically, such polycarbonate will have recurring structural units of the formula: wherein A is a divalent aromatic radical of the dihydric phenol employed in the polymer producing reaction. Preferably, the aromatic carbonate polymers have an intrinsic viscosity ranging from 0.30 to 1.0 dl./g. (measured in methylene chloride at 25 o C). By dihydric phenols is meant mononuclear or polynuclear aromatic compounds containing two hydroxy radicals, each of which is attached to a carbon atom of an aromatic nucleus. Typical dihydric phenols are bisphenols joined by an alkylene radical, an ether link, or a sulfur link. Preferred bisphenols include 2,2-bis-(4-hydroxyphenyl)propane; 2,2-bis-(3,5-dimethyl-4-hydroxyphenyl)propane; 4,4'-dihydroxy-diphenyl ether; bis(2-hydroxyphenyl)methane; and mixtures thereof. The preferred aromatic carbonate polymer for use herein is a homopolymer derived from 2,2-bis(4-hydroxyphenyl)propane, i.e., bisphenol-A. Polycarbonates suitable for use herein, including methods of polymerization, and further monomer constituents, are described in U.S. Patents No. 2,999,835, No. 3,028,365, No. 3,334,154, No. 4,131,575, No. 4,018,750, and No. 4,123,436. Included within the polycarbonate resins herein are the poly(ester-carbonates). In addition to the dihydric phenol and carbonate precursor as described above, poly(ester-carbonate) is polymerized from an aromatic dicarboxylic acid, such as, for example, iso- or terephthalic acid. The preparation of the poly(ester-carbonates) is described in U.S. Patents No. 3,030,331, No. 3,169,121, No. 3,207,814, No 4,194,038, and No. 4,156,069. Also suitable for use herein are the polyphenylene ether compounds. Such compounds are generally produced by the oxidative coupling of phenol compounds by oxygen or oxygen-containing gas in the presence of a catalyst to produce homopolymers and copolymers of, for example, poly(2,6-diphenyl-1,4-phenyl)ether; and poly(2,6-dichloro-1,4-phenylene)ether. An especially preferred family of polyphenylene ethers include homopolymers and copolymers of those having a C₁ to C₄ alkyl substitution in the two positions ortho to the oxygen ether atom. Illustrative members of this class are poly(2,6-dimethyl-1,4-phenylene)ether; poly(2,6-diethyl-1,4-phenylene)ether; poly(2,6-dipropyl-1,4-phenylene)ether; and poly(2-ethyl-6-propyl-1,4-phenylene)ether. The most preferred polyphenylene ether is poly(2,6-dimethyl-1,4-phenylene)ether. Polyphenylene ethers are well known in the art and may be prepared by any number of catalytic and non-catalytic processes from corresponding phenols or reactive derivatives thereof. Examples of polyphenylene ethers and methods for their production are described in U.S. Patents No. 3,306,874, No. 3,306,875, No. 3,257,357, No. 3,257,358, No. 3,337,501 and No. 3,787,361. Polyimides suitable for use herein are the reaction products of a dianhydride and a diamine. Preferred dianhydrides are the bis(aromatic anhydrides), particularly the bis(aromatic ether anhydrides). Preferred diamines are aromatic diamines and bis(aromatic amine). Suitable polyimides and means for their production are shown in U.S. Patent No. 4,024,101. Marked improvement in impact and knitline strength is experienced by blends of the impact modifiers of this invention with polyamide resins. As used herein, the term "polyamide resin" includes all polymers having recurring carbonamide groups in the main chain, and having molecular weights greater than 2000. "Molecular weight", as used herein, refers to number average molecular weight for polyamides (see Flory "Principals of Polymer Chemistry", page 273, published 1953 by Cornell University Press). The polyamide resin is ordinarily produced by condensation of equimolar amount of dicarboxylic acid or acid derivative containing from two to twenty carbon atoms with a diamine, containing from two to fifteen carbon atoms, or by lactam polymerization according to well known techniques. Preferred polyamides are those based on lactams and those based on aliphatic diamines condensed with aliphatic or aromatic diacids. Included in this group are polyhexamethylene adipamide (nylon 6,6), polycaprolactam (nylon 6), poly(undecaneamide) (Nylon 11), polyhexamethylene sebacamide (nylon 6,10), polyhexamethylene isophthalamide, polyhexamethylene tereco-isophthalamide, and mixtures or copolymers thereof. Similar polyamides have been marketed by Allied Corporation under the trade name Capron® 8202C and under the designations LSM and BAT and by Firestone Rubber Company under the trade name 228-001 (low viscosity) and with the suffix HS, which means heat stabilized. The blends described may be used alone as molding pellets or mixed with other polymers, and may contain fillers such as glass fibers and mica, as well as pigments, dyes, stabilizers and plasticizers. The ingredients forming the modifiers described in U.S. Patents 4,948,842 and 4,956,501 are combined by first reacting the olefinic components in the presence of a Ziegler-type catalyst to form a backbone rubber which is subsequently grafted with the component containing the epoxide functionality by a grafting reaction carried out in solvent solution. An important feature of this invention resides in the discovery that considerable improvement in the characteristics of the modifier is achieved when the ingredients making up the modifier are combined in a single step bulk reaction. This not only provides a less expensive and simpler route for producing a modifier, but unexpectedly it provides the opportunity to achieve a desired degree of epoxide functionality as well as a desired gel level which are outside the domain of the solution polymerization. The result is a matrix resin blend having improved knitline strength, an important property in products molded thereof. The present invention is further distinguished over the art previously described in the use of a peroxide catalyst in the bulk process, especially in the presence of unsaturated groupings in the reaction components whereby an improved level of desirable cross-linking is obtained, an instrumental factor in the improvement in knitline strength that is achieved in the moldings formed of the blends. The prior art has sought to minimize cross-linking since such cross-linked modifiers were thought to be undesirable. The invention will now be described by way of the following Examples. Examples 9 to 13 and 19 to 26 are provided for comparative purposes only. Products of various of the examples were subjected to one or more of the following test procedures: Degree of Graft: (DOG) was determined by IR using a calibrated curve of values obtained by IR versus those obtained by filtration. The calibrated curve was generated on the basis of the data on solution polymers. Gel Determination: One gram of finely divided polymer was shaken with 100 ml. toluene for 4 hours at room temperature. Undissolved polymer was filtered out through glass wool. Percent solids in filtrate was determined and gel (% insolubles) was determined by difference. ASTM D3616. Notched Izod impact strength was measured according to ASTM D256. Knitline Izod impact strength was measured on unnotched double-gated samples. Except for this variation, the procedure was similar to ASTM D256. Tensile strength was measured according to ASTM D256. RSV: Reduced solution viscosity - measured in a 0.1% solution of decalin at 135 o C. Mooney Viscosity: ASTM D1646, ML+4 (125 o C). Unnotched Double Gate Izod Impact - is a variation of ASTM D256 wherein the test piece is double-gate injection molded from opposite ends under conditions which center the tack line between the ends of the test piece. Procedure : Blends containing 20 percent by weight modifier and 80 percent Valox® 315 (a poly(1,4-butylene terephthalate) manufactured by the General Electric Company under the Trade Mark Valox® 315) were prepared using three extrusions through a 25 mm (1 inch) single screw extruder (Killion) having an L/D ratio of 20/1. Temperatures used for extrusion were: Zone 1 -235 o C (450 o F), Zone 2 - 235 o C (450 o F), Die - 220 o C (425 o F). The extruded strands were air-cooled and chopped into pellets. The pellets were molded into test specimens for tensile and notched Izod impact strengths, using a plunger injection molder with a cavity temperature of 275-285 o C (530-540 o F) and a mold temperature of 93 o C (200 o F). The knitline impact strength samples were molded, using a double-gated mold on a screw injection molder. The molded test specimens were stored in moisture proof polyethylene bags for at least 16 hours prior to testing. Example 1 A 2.2 RSV, 66/34 (molar ratio) ethylene/propylene, 8 weight percent ethylidene norbornene EPDM polymer (EPsyn® 55, Copolymer Rubber and Chemical Corporation) containing 9 carbon-to-carbon double bonds (C=C) per 1000 carbon atoms was fed with a screw feeder (K-tron Corporation) into a co-rotating twin-screw extruder (Werner & Pfleiderer Corporation's ZSK-30, 12 barrels) at a rate of 2 kg/hr (4.6 lbs/hr). Screw # 2 shown in Figure 1 was used in the extruder. The temperature set points on the extruder were: Zone 1: 70 o C, all other Zones: 200 o C. A 10/1 (wt/wt) mixture of glycidyl methacrylate/2,5-dimenthyl-2,5 di(t-butylperoxy) hexane was fed at the rate of 170g/hr (0.385 lbs/hr), in the third barrel of the extruder. The extrudate was cooled in a water bath and pelletized. The pellets were dried for 4 hours at 70 o C. The dry pellets had a degree of graft of 5.86 and toluene gel of 17%. Example 2 Same as Example 1, except the rubber feed rate was 2.75 kg/hr (6.3 lbs/hr) and the monomer/initiator feed rate was 130 g/hr (0.3 lbs/hr). The dry pellets had a degree of graft of 4.03 and toluene gel of 14%. Example 3 Same as Example 1, except the rubber feed rate was 2.6 kg/hr (6 lbs/hr) and the monomer/initiator feed rate was 93 g/hr (0.214 lbs/hr). The dry pellets had a degree of graft of 2.5 and toluene gel of 12%. Example 4 Same as Example 1, with the following exceptions: (a) The rubber was a 2.5 RSV 66/34 (molar ratio) ethylene/propylene, 4.5 weight percent ethylidene norbornene EPDM (EPsyn® 70A, Copolymer Rubber and Chemical Corporation). (b) The rubber feed rate was 2.5 kg/hr (5.7 lbs/hr). (c) The monomer/initiator feed rate was 220 g/hr (0.5 lbs/hr). The dry pellets had a degree of graft of 4.8 and toluene gel of 65%. Example 5 Same as Example 1, with the following exceptions: (a) The rubber was a 2.2 RSV 83/17 (molar ratio) ethylene/propylene, 4.5 weight percent ethylidene norbornene EPDM (EPsyn® E-901, Copolymer Rubber and Chemical Corporation). (b) The rubber feed rate was 2.6 kg/hr (6 lbs/hr). (c) The monomer/initiator feed rate was 200 g/hr (0.45 lbs/hr). The dry pellets had a degree of graft of 4.2 and toluene gel of 11%. Example 6 The following composition was mixed in a Brabender Plasticorder for 5 minutes at 200 o C using cam blades at 40 RPM: 60 gms of a 2.2 RSV, 66/34 (molar ratio) ethylene/propylene, 8 weight percent ethylidene norbornene EPDM (EPsyn® 55, Copolymer Rubber and Chemical Corporation) plus 4.2 gms of glycidyl methacrylate plus 0.42 gms of 2,5-dimethyl-2,5di(t-butylperoxy) hexane. The resultant product was ground in a blender. The degree of graft was 4.5. Example 7 Same as Example 6, except the rubber used was a 1.9 RSV, 60/40 (molar ratio) ethylene/propylene, 0.5 weight percent vinyl norbornene (EPsyn® 4106, Copolymer Rubber and Chemical Corporation). The degree of graft was 4.5. Example 8 Same as Example 6, except the rubber used was a 2.75 RSV, 60/40 (molar ratio) ethylene/propylene EPM (EPsyn® 7006, Copolymer Rubber and Chemical Corporation). The degree of graft was 0.62. Example 9 Same as Example 8, except 4.8 gms of glycidyl acrylate was used instead of 4.2 gms of glycidyl methacrylate and 0.48 gms (instead of 0.42 gms) of 2,5-dimethyl-2,5di(t-butylperoxy) hexane was used. Example 10 Same as Example 8, except 3.6 gms of glycidyl acrylate was used instead of 4.2 gms of glycidyl methacrylate and 0.36 gms (instead of 0.42 gms) of 2,5-dimethyl-2,5di(t-butylperoxy) hexane was used. Example 11 Same as Example 7, except allyl glycidyl ether was used instead of glycidyl methacrylate. Example 12 Same as Example 11, except a 2.2 RSV, 66/34 (molar ratio) ethylene/propylene, 8 weight percent ethylidene norbornene EPDM (EPsyn 55, Copolymer Rubber and Chemical Corporation) was used instead of the rubber stated in Example 11. Example 13 Same as Example 9, except 4.2 gms (instead of 4.8 gms) of glycidyl acrylate and 0.21 gms (instead of 0.48 gms) of 2,5-dimethyl-2,5 di(t-butylperoxy) hexane were used. Examples 14 through 26 Products of Examples 1 through 13 were blended (20%) with polybutylene terephthalate - Valox 315 (General Electric Company) (80%) and the blends were injection molded into test specimens for tensile and impact strengths, as heretofore described. Control I Control I is unmodified Valox 315. Control II Control II is an 80/20 blend of Valox 315 and the starting rubber of Example 1. Control III Control III is the same as Example 5 except the modifier was prepared by grafting in solution. Table I summarizes the data on Examples 1 through 26 and Controls I, II and III. The foregoing examples are believed to demonstrate the improved utility of the bulk polymerization for preparing EPM (ethylene-mono-olefin) (a ethylene-propylene) or EPDM (ethylene-mono,olefin-polyene) based impact modifiers for blending by dispersion in thermoplastic matrix resins, such as the polyester or polyamide resins. It will be apparent that the bulk polymerization process of this invention results in degrees of graft (DOG) and gel values outside the domain of the solution polymerization processes of the copending applications: Process DOG % Gel % Solution less 2.8 less 5 Bulk up to 8 5-100 and preferably 7-65 Glycidyl methacrylate grafted EPDM and glycidyl acrylate EPM give comparable properties in polyester blends if the graft polymers are prepared by the bulk polymerization process of this invention. If instead the modifier was prepared by solution polymerization, glycidyl acrylate grafted polymers result in much inferior properties. Polyester matrix resin blended with a modifier having a low degree of graft, such as below 2.5%, has inferior notched Izod impact strength. 2.5% gel appears to be the lower limit for degree of graft in the modifier (Example 16). The amount of initiator used in the preparation of glycidyl grafted EPM polymers has a noticeable effect on the impact strength of polyester blends (see Examples 22 and 26). Unlike the blends formed with modifiers prepared by solution polymerization, the blends prepared from modifiers prepared by bulk polymerization give good knitline impact strength such as values greater than 14 compared to values of less than 4. Example 27 EPsyn® 55 was fed into a twin screw extruder (Werner & Pfleiderer's ZSK-30, 12 barrels) at the rate of 2 kg/hr (4.6 lbs/hr). A 10/1 mixture of glycidyl methacrylate/2,5-dimethyl 1-2,5 di(t-butylperoxy) hexane was fed at the rate of 170 g/hr (0.385 lbs/hr) in barrel 3 of the extruder. The extrudate was cooled in a water bath and pelletized. The properties of the pellets were as follows: D.O.G. 5.86, graft efficiency 82%, gel 17%. The pellets (20%) were blended with polybutylene terephthalate (Valox® 315, 80%), extruded and injection molded into test specimens for physical properties. The physical properties were: tensile strength 30.7 · 10³ kPa (4390 psi), elongation 43%, flexural modulus 1.47 · 10⁶ kPa) (210,130 psi), Rockwell hardness R96, notched Izod impact strengths 15.4 and 4.6 ft. lbs/inch at 25 o C and -20 o C respectively, unnotched knitline impact strength 13.0 ft. lbs/inch. Example 28 Same as Example 1, except the feed rates of rubber and monomer/initiator were 6.0 and 0.214 lbs/hr (2.6 kg/hr and 93 g/hr) respectively. The properties of pellets were as follows: D.O.G. 2.5, graft efficiency 79%, gel 12%. The physical properties of the blend with Valox® 315 were as follows: tensile strength 28.21 · 10³ kPa (4030 psi), elongation 50%, flexural modulus 1.36 · 10⁶ kPa (194,600 psi), notched Izod impact strength 3.8 ft. lbs/inch at 25 o C. It will be seen from the above that (a) the graft efficiency remains relatively unchanged regardless of the amount of glycidyl methacrylate charge level, and (b) a substantial drop in impact strength (from 15.4 to 3.8) at the lower D.O.G. and gel level.

Claims: A modifier for improving the impact and knitline strengths of thermoplastic resins in which it is dispersed, the modifier comprising the product of graft polymerization in bulk at elevated temperature in the presence of a peroxide catalyst, of an elastomeric backbone polymer selected from (a) copolymer rubbers formed by the copolymerization of ethylene and one or more C₃-C₁₆ mono-olefins, and (b) interpolymer rubbers formed by interpolymerization of ethylene, one or more C₃-C₁₆ mono-olefins and a polyene, and a graft monomer in the form of alpha-beta ethylenically unsaturated hydrocarbon having an epoxy functionality, the bulk reaction product having a gel content greater than 5%, an epoxy functionality of 2.5 to 13.0 per 1000 carbon atoms and a degree of graft of at least 2.5%. A modifier according to claim 1, in which the interpolymer rubber is an EPDM rubber of ethylene, propylene and 5-ethylidene-2-norbornene. A modifier according to claim 1, in which the copolymer rubber is an EPM rubber of ethylene and propylene. A modifier according to claim 3, in which the EPM rubber contains 10 to 95 mole % ethylene units and 90 to 5 mole % propylene units. A modifier according to any one of claims 1 to 4, in which the graft polymerization is carried out in the presence of 0.1 to 3.0 parts by weight peroxide catalyst per 100 parts by weight of backbone rubber. A modifier according to any one of claims 1 to 5, in which the backbone rubber contains 2 to 20 carbon-carbon double bonds per 1000 carbon atoms. A modifier according to any one of claims 1 to 6, in which the epoxy functional graft monomer contains a group of the general formula in which R³ is hydrogen or methyl, R² is hydrogen or C₁-C₆ alkyl and R¹ is C₁-C₁₀ alkylene. A modifier according to claim 1, in which the graft monomer is glycidyl acrylate or glycidyl methacrylate. A modifier according to any one of claims 1 to 8, in which the product has a gel content of 7 to 65%. A modifier according to any one of claims 1 to 9, in which the product has a degree of graft of 2.5 to 8%. A method for producing a modifier for improving the impact and knitline strengths of a thermoplastic resin upon admixture therewith, the method comprising bulk polymerizing at elevated temperature in the presence of a peroxide catalyst an elastomeric backbone polymer selected from (a) copolymer rubbers formed by copolymerization of ethylene and one or more C₃-C₁₆ mono-olefins and (b) interpolymer rubbers formed by interpolymerization of ethylene, one or more C₃-C₁₆ mono-olefins and a polyene, and a graft monomer in the form of alpha-beta ethylenically unsaturated hydrocarbon having an epoxy functionality, the bulk reaction product having a gel content greater than 5%, an epoxy functionally 2.5 to 13.0 per 1000 carbon atoms and a degree of graft of at least 2.5%. A method according to claim 11, in which the bulk polymerization is carried out in a single step in melt processing equipment. A method according to claim 11 or claim 12, in which the bulk reaction is carried out at a temperature of 175-290°C (350-550°F). A method according to any one of claims 11 to 13, in which the backbone rubber contains 2 to 20 carbon-carbon double bonds per 1000 carbon atoms. A method according to any one of claims 11 to 14, in which polymerization is carried out in the presence of 0.1 to 3.0 parts by weight peroxide catalyst per 100 parts by weight of backbone rubber. A method according to any one of claims 11 to 15, in which the gel content of the reaction product is 7 to 65%. A method according to any one of claims 11 to 16, in which the degree of graft of the reaction product is 2.5 to 8%.

Inventors: PHADKE,SHRIKANT VASUDEO
Applicants: COPOLYMER RUBBER & CHEMICAL CORPORATION
Application year: 1988
Main classification: C08F255
IPC codes: C08F255, C08L101