SOFT POLYMER GEL

Abstract: A polymeric gel composition includes a polymer having anhydride and alkenyl units, a crosslinking agent, a maleated polyalkylene, an extender, and an organic fatty acid. This composition has superior high-temperature stability, mechanical strength, and moldability.

Description: SOFT POLYMER GEL BACKGROUND OF THE INVENTION The present invention relates to a high damping polymer gel composition with superior high-temperature stability, mechanical strength and moldability. The polymerization of isobutylene with maleic anhydride, styrene with maleic anhydride, and alkyl vinyl ethers with maleic anhydride are known. These polymerizations are carried out by free radical initiation. Further, imidization between a maleic anhydride and a primary arnine group is a commonly known chemical reaction. Two or more polymers may be blended together to form a wide variety of random or structured morphologies to obtain products that potentially offer desirable combinations of characteristics. However, it may be difficult or even impossible in practice to achieve many potential combinations through simple blending. Frequently, the polymers are thermodynamically immiscible, which precludes generating a truly homogeneous product. While immiscibility may not be a problem since it may be desirable to have a two-phase structure, the situation at the interface between these two phases very often does lead to problems. The typical case is one of high interfacial tension and poor adhesion between the two phases. This interfacial tension contributes, along with high viscosities, to the inherent difficulty of imparting the desired degree of dispersion to random mixtures and to their subsequent lack of stability, giving rise to gross separation or stratification during later processing or use. Poor adhesion can lead, in part, to the very weak and brittle mechanical behavior often observed in dispersed blends and may render some highly structured morphologies impossible. SUMMARY OF THE INVENTION The present invention provides a polymeric gel composition that includes a polymer including anhydride and alkenyl units; a crosslinking agent; a maleated polyalkylene; an extender; and an organic fatty acid. The centipede polymer composition exhibits improved properties such as tensile strength, maximum elongation, tear strength, damping properties, high temperature compression set, and the like, with emphasis on high temperature compression set. More particularly, the combination of a grafted poly(alkenyl-co-maleimide) copolymers combine with organic fatty acids improves the tensile strength, tear strength, damping properties, and high-temperature compression set of the polymer. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS A representative polymer gel composition of the present invention contains 0.5-200 parts by weight of a poly(alkenyl-co-malei ide) having at least one maleated polyalkylene segment grafted thereto through at least one functional linkage formed by a cross-linking reaction with a grafting agent; and greater than 0 to about 100 parts by weight of an organic fatty acid. The poly(alkenyl-co-maleimide) is a centipede polymer formed by imidizing a poly(alkenyl-co-maleic anhydride) with a primary arnine. The centipede polymer has a high molecular weight spine and many relatively short side chains formed from the addition of the primary amines. The main chain usually is longer than the entanglement length, which is herein defined theoretically as an order of magnitude of 100 repeating units, while the side chains are less than the entanglement length. Preferred alkenyl monomer units of the poly(alkenylbenzene-co- maleimide) include one or combination of styrene, α-methyl styrene, 1- vinylnaphthalene, 2- vinylnaphthalene, 1 -α-methyl- vinylnaphthalene, 2-α-methyl vinylnaphthalene, as well as alkyl, cycloalkyl, aryl, alkaryl, and aralkyl derivatives thereof, in which the total number of carbon atoms in the combined hydrocarbon is generally not greater than 12, as well as any di- or tri- vinyl aromatic hydrocarbons. Preferred vinyl aromatic hydrocarbons include styrene and α-methylstyrene. The terms "alkenyl benzene" and "vinyl aromatic" are interchangeable as used herein. Preferred R 1 R 2 ethylene contributed monomer units of the poly(R 1 R 2 ethylene-co-maleimide) include alkenes such as ethylene, propylene, butylene, isobutylene, pentene, hexene, heptene, and the like, as well as any di- or tri- alkene, with preference given to isobutylene. Preferred alkyl vinyl ether contributed monomer units of the poly(alkylvinyl ether-co-maleimide) include alkylvinyl ethers such as methylvinyl ether, ethylvinyl ether, propylvinyl ether, butylvinyl ether, and any other alkyl vinyl ether wherein the number of carbons in the alkyl substituent is not greater than about 12. The poly(alkenyl-co-maleimides) are graft-reacted through a difunctional linking or grafting agent to a maleated polyalkylene to yield a maleated polymer having at least one polyalkylene segment grafted thereto through at least one functional linkage thus formed. The alkylene moiety of the polyalkylene is ethylene and/or propylene. A preferred polyalkylene is polypropylene. The maleated polypropylene may be any of the conventionally known polypropylene compounds that are subsequently maleated by methods known in the art. The polypropylene grafted segment(s) have weight molecular weights (M w ) of about 10,000 up to about 10,000,000 or higher, preferably about 20,000 to about 300,000. The crystallinity, or tacticity, of the polypropylene may vary from being substantially amorphous to being completely crystalline, that is from about 10- 100% crystallinity. Most typically, because of the extensive commercial use of isotactic polypropylene, the grafted polypropylene will be substantially crystalline, e.g., greater than about 90%. Generally, the polypropylene is substantially free of ethylene. However, under certain circumstances small amounts of ethylene, on the order of less than about 10% by weight, may be incorporated. Furthermore, in certain instances the polypropylene contains small amounts of ethylene in copolymers known as reactor copolymers. Thus, the grafted polypropylenes can contain minor amounts of ethylene, both as part of the ethylene-propylene segments and as polyethylene segments. The maleated polypropylene contains from about 0.01 wt.% incorporated maleic anhydride, based upon the weight of the maleated polypropylene, up to about 5 wt.%. Preferably the maleic anhydride content is from about 0.01 to about 2 wt.%, most preferably about 0.03 to about 0.2 wt.%. Unreacted polypropylene will be present in the reaction mix as will minor amounts of reaction by-products, such as decomposed free-radical initiator compounds and low molecular weight free-radical products. These by-products are substantially removed, by methods known in the art, e.g., sparging withN or washing with water. Maleic anhydride cannot be left in substantial amounts in the polymer without detrimental effects on the subsequent reaction of the poly(alkenyl-co-maleimide) with the maleated polyalkylene. The poly(alkenyl-co-maleimide) is formed by reacting a poly(alkenyl-co- maleic anhydride) with a mono-primary amine at temperatures from about 100° to about 300°C and at a pressure from about slightly above vacuum to about 20 atmospheres, under substantially dry conditions. The reactants are preferably dry mixed in the absence of solvents in a suitable mixing apparatus such as a Brabender mixer. Preferably, the mixer is purged with N 2 prior to charging the reactants. The primary amine may be added in a singular charge, or in sequential partial charges into the reactor containing poly(alkenyl-co-maleic anhydride). Preferably, the primary amine is charged in a ratio of between 0.8 to 1.0 moles of amine per monomer contributed units of maleic anhydride in the poly(alkenyl-cø- maleic anhydride). Suitable primary amines include, but are not limitied to alkyl amines; alkyl benzyl amines; alkyl phenyl amines; alkoxybenzyl amines; allyl aminobenzoates; alkoxy aniline; and other linear primary amines containing from 1 to 50 carbon atoms, preferably 6 to 30 carbon atoms in the alkyl and alkoxy substituents in these primary amines. It is understood that the alkyl and alkoxy substituents on the above discussed primary amines can be linear or branched, preferably linear, and saturated or unsaturated, preferably saturated. Exemplary, but not exclusive of such amines are hexylamine, octylamine, dodecylamine, and the like. The poly(alkenyl-co-maleimide), prior to grafting with maleated polyalkylene, preferably has M w of between about 10,000 and 500,000, and even more typically between about 150,000 and 450,000. The alkylene/maleimide copolymer may be prepared by any means for combining such ingredients, such as blending, milling, or internal batch mixing. A rapid and convenient method of preparation involves heating a mixture of components to a temperature of about 50° to about 290°C. The polymers of this invention preferably are manufactured by mixing and dynamically heat-treating the components described above, namely, by melt- mixing. As for the mixing equipment, any conventional equipment such as an open-type mixing roll, closed-type Banbury mixer, closed-type Brabender mixer, extruding machine, kneader, continuous mixer, or the like is acceptable. The closed-type Brabender mixer is preferable, and mixing in an inactive gas environment, such as N 2 or Ar, is also preferable. Grafting of the maleated polyalkylene to the poly(alkenyl-co-maleimide) can be performed by addition of a grafting agent. The preferred grafting agent is a low molecular weight organic compound with at least 2 functional groups capable of crosslking the polymer. Exemplary functional groups include primary amine, secondary amine, carboxyl, formyl, and hydroxyl. A preferred grafting involves adding a polyamine, preferably an organic diamine, to a blend of maleated polyalkylene and poly(alkenyl-co-maleimide) to partially cross-link the polyalkylene to the poly(alkenyl-co-maleimide) through the maleate functional groups. Suitable organic diamines or diamine mixtures containing two aliphatically or cycloaliphatically bound primary amino groups are used as grafting agents for the process according to the present invention. Such diamines include, for example, aliphatic or cycloaliphatic diamines corresponding to the following formula R 3 (NH 2 ) 2 wherein R 3 represents an aliphatic hydrocarbon group having from 2 to 20 carbon atoms, a cycloaliphatic hydrocarbon group having from 4 to 20 carbon atoms, or an aromatic hydrocarbon group having from 6 to 20 carbon atoms or an N-heterocyclic ring having from 4 to 20 carbon atoms, e.g., ethylenediamine; 1,2- and 1,3-propylene diamine; 1,4-diaminobutane; 2,2- dimethyl-l,3-diaminopropane; 1,6-diaminohexane; 2,5-dimethyl-2,5- diaminohexane; l,6-diammo-2,2,4-trimethyldiaminohexane; 1,8-diaminooctane; 1,10-diaminodecane; 1,11-diaminoundecane; 1,12-diaminododecane; l-methyl-4- (ammoisopropyl)-cyclo-hexylamme; 3-aminomethyl-3,5,5-trimethyl- cyclohexylamine; l,2-bis-(amino-methyl)-cyclobutane; l,2-diamino-3,6- dimethylbenzene; 1,2- and 1,4-diaminocyclo-hexane; 1,2-, 1,4-, 1,5-, and 1,8- diaminodecalin; l-methyl-4-anmoisopropyl-cyclo-hexylamine; 4,4'-diamino- dicyclohexyl; 4,4'-diamino-dicyclohexyl methane; 2,2'-(bis-4-amino-cyclohexyl)- propane; 3,3'-dimethyl-4,4'-diaminodicyclohexyl methane; l,2-bis-(4- ammocyclohexyl)-ethane; 3,3^5,5'-te1ramethyl-bis-(4-anιinocyclohexyl)-methane and -propane; l,4-bis-(2-aminoethyl)-benzene; benzidine; 4,4'-thiodianiline; 3,3'- dimeth-oxybenzidine; 2,4-diaminotoluene, diaminoditolylsulfone; 2,6- diaminopyridine; 4-methoxy-6-methyl- -phenylenediamine; diaminodiphenyl ether; 4,4'-bis( -toluidine); o-phenylenediamine; o-phenylenediamine, methylenebis(o-chloroaniline) ; bis(3 ,4-diaminophenyl)sulfone; diaminodiphenylsulfone; 4-c oro-o-phenyIenediarnine; m-anamobenzylamine; m- phenylenediamine; 4,4'-C 1 -C6-dianiline; 4,4'-methylene-dianiline; aniline- formaldehyde resin; trimethylene glycol di-p-aminobenzoate; bis-(2-aminoethyι)- amine, bis-(3-ammopropyl-amine, bis-(4-anιinobutyl)-amine; bis-(6-aminohexyι)- amine, and isomeric mixtures of dipropylene triamine and dibutylene triarnine. Mixtures of these diamines may also be used. Other suitable polyamines for use as grafting agents include bis- (aminoalkyl)-amines, preferably those having a total of from 4 to 12 carbon atoms, such as bis-(2-aminoethyl) amine, bis-(3-aminopropyl) amine, bis-(4-aminobutyl) amine, and isomeric mixtures of dipropylene triamine and dibutylene triamine. Hexamethyl diamine, tetramethylene diamine, and especially 1,12- diaminododecane are preferred. The centipede polymers may be glassy and therefore, addition of an extender during final processing can be desired. Suitable extenders include extender oils and low molecular weight compounds or components, such as naphthenic, aromatic, paraffinic, phthalic, and silicone oils. A preferred extender is a phthahc oil. The preferred phthalic oil is di(tridecyl)pthalate. This oil can be added in the final stages of preparation of the centipede polymer. The final centipede polymer can contain between 25 and 40% extender and therefore be a thermoreversible elastomer. After the centipede polymer is formed, a fatty acid is added. The fatty acid can be saturated (such as butyric acid, caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, or stearic acid) or unsaturated (such as palmitoleic acid, oleic acid, linoleic acid, or linolenic acid). Saturated acids are preferred. The fatty acids used may also be monofunctional or difunctional. Suitable monofunctional acids include butyric acid, caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, palmitoleic acid, oleic acid, linoleic acid, linolenic acid, or mixtures thereof. Suitable difunctional acids include sabaric acid, hexadecanedioc acid, dodecanedioc acid, 5-(octadecyloxy) isophthalic acid, and any other difunctional organic acids with up to 50 carbons. Polyacids are also acceptable. Preferred polyacids have a M w between about 500 to about 500,000. Suitable polyacids include poly(ethylene-co-acrylic acid), poly(propylene-co-acrylic acid), poly(acrylic acid), and other polyacids containing acrylic acid, acrylonitrile, and acrylamide monomer units, and mixtures thereof. Generally, these polyacids may have an acrylic acid weight percent between about 0.2% to about 100%. In general, the preferred organic fatty acids in the present invention are both mono and di functional, also preferred are low M w polyacids. The preferred acrylic acid content of the polyacids is less than about 25%. Generally, about 5 to 65 parts by weight of organic fatty acid can be mixed with about 35 to 100 parts by weight of centipede polymer. The resulting gel has a high temperature compression set at 100°C of less than about 40%, and at 130° of less than about 50%. The Shore A hardness for the centipede polymer mixed with fatty acid is between about 10 and 55, and the tan δ at temperatures greater than 20°C is greater than about 0.25. In summary, the molded polymers produced from the blend of the present centipede polymer and fatty acid retain elastomeric characterstics and are useful in high damping applications. Other additives known in the art can be added to the compositions of the present application. Stabilizers, antioxidants, conventional fillers, reinforcing agents, reinforcing resins, pigments, fragrances, and the like are examples of some such additives. Specific examples of useful antioxidants and stabilizers include 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, nickel di-butyl-di-thiocarbamate, zinc di-butyl-di-thiocarbamate, tris(nonylphenyl) phosphite, 2,6-di-t-butyl-4- methylphenol, and the like. Exemplary conventional fillers and pigments include silica, carbon black, TiO , iron oxide, and the like. These compounding ingredients are incorporated in suitable amounts depending upon the contemplated use of the product, preferably in the range of 1-350 parts of additives or compounding ingredients per 100 parts of the polymer composition. A reinforcement is a material added to a polymer matrix to improve the strength of the polymer. Most reinforcing materials are inorganic or organic products of high molecular weight. Various examples include glass fibers, asbestos, boron fibers, carbon and graphite fibers, whiskers, quartz and silica fibers, ceramic fibers, metal fibers, natural organic fibers, and synthetic organic fibers. Other elastomers and resins are also useful to enhance specific properties like damping properties, adhesion, and processability. Examples of other elastomers and resins include adhesive-like products including Reostomer™ (produced by Riken- Vinyl, Inc.), hydrogenated polystyrene-(medium or high 3,4)- polyisoprene-polystyrene block copolymers such as Hybler™ (produced by Kurare, Inc.), polynorbornenes such as Norsorex™ (produced by Nippon Zeon, Inc.), and the like. Damping is the absorption of mechanical energy by a material in contact with the source of that energy. It is desirable to damp or mitigate the transmission of mechanical energy from, for example, a motor, engine, or power source to its surroundings. Elastomeric materials are often used for this purpose. Such materials can be highly effective in converting this mechanical energy into heat rather than transmitting it to the surroundings. This damping or conversion preferably is effective over a wide range of temperatures and frequencies commonly found near motors, automobiles, trucks, trains, planes, and the like. The compositions of the present invention are favorably used in the manufacturing of any product in which the following properties are advantageous: a degree of softness, heat resistance, decent mechanical properties, elasticity, good adhesion, and/or high damping. The compositions of the present invention can be used in all industry fields, in particular, in the fabrication of automotive parts, tire tread rubbers, household electrical appliances, industrial machinery, precision instruments, transport machinery, constructions, engineering, medical instruments, and tire rubber formulations. Representative examples of the composition of the present invention are in the fabrication of damping materials and vibration restraining materials. These uses involve connecting materials such as sealing materials, packing, gaskets, and grommets; supporting materials, such as mounts, holders, and insulators; and cushion materials such as stoppers, cushions, and bumpers. These materials are also used in equipment producing vibration or noise and household electrical appliances, such as in air conditioners, laundry machines, refrigerators, electric fans, vacuums, dryers, printers, and ventilator fans. These materials are also suitable for impact absorbing materials in audio equipment and electronic or electrical equipment, sporting goods, and shoes. The present invention will also be useful in any application where a superior high temperature compression set is desirable. With a compression set of less than 50% at 130°C, this composition can be used in a variety of high temperature apphcations. One example of this would be as coatings, especially for windows and car windshields which retain heat and cause polymers with lower service temperatures to melt. EXAMPLES Example 1 To a 6L kneader-extruder (MXE-6, Jaygo Inc.) equipped with sigma blades was added 1.25 kg Isoban™ 10 poly(maleic anhydride-α t-isobutlyene) (Kuraray Ltd.), and 0.99 kg octylamine (BASF, 99% purity) at 54°C. Mixing was started with a blade speed of 25 rpm and a screw speed of 40 rpm for 5 minutes, then the temperature of the mixer was adjusted to rise to 190°C at a rate of about 3°C per minute. Mixing was continued for 2 more hours isothermally at 190°C. Then, 0.56 kg PO1015 maleated polypropylene (Exxon) was added to the mixer. Mixing was continued for another 30 minutes. Then, to the mixer was added 23 g dodecane diamine (Aldrich, 98% purity). After an additional 15 minutes, 1.4 kg di(tridecyl)phtalate oil, (C.P. Hall Co.) was added to the mixer and the temperature adjusted to 160°C. After another 2 hours, the final product was then extruded through a 6.35 mm die. The final product contained 33% DTDP oil and was a thermoreversible elastomer. Example 2 A charge of 25 g of the product from Example 1 was added to a Brabender mixer (~55g capacity) equipped with a roller blade and N 2 purging. The mixer was initially set to 160°C and 60 rpm. After 3 minutes, 10 g stearic acid was added to the mixer. The material was further mixed at those conditions for 17 minutes. Then, agitation was stopped and the mixture was removed from the mixer. Examples 3-6 In Example 3, to a Brabender mixer (~55 g capacity) equipped with a roller blade and N 2 purging, 45 g of the product from Example 1 was added. The mixer was initially set to 160°C and 60 rpm. After 3 minutes, 5 g stearic acid was added to the mixer. The material was further mixed at those conditions for 17 minutes. Then, the agitation was stopped and the mixture was removed from the mixer. For Example 4, the procedure of example 3 was repeated except that the mixer was charged with 40 g of the product of Example 1 and 10 g stearic acid. For Example 5, the procedure of example 3 was repeated except that the mixer was charged with 35 g of the product of Example 1 and 15 g stearic acid. For Example 6, the procedure of example 3 was repeated except that the mixer was charged with 30 g of the product of Example 1 and 20 g stearic acid. Examples 7-8 To the same Brabender mixer used in Example 1, 36 g of the product from Example 1 was added. The mixer was initially set to 160°C and 60 rpm. After 3 minutes, 4 g stearic acid was added to the mixer. After an additional 7 minutes, a total 10 g of DTDP oil was added slowly (~2 g/rnin.) to the mixer. The material was further mixed at those conditions for 5 minutes. Finally, agitation was turned off and the mixture was removed from the mixer. The procedure of the preceding paragraph was repeated except that the mixer was charged with 21 g of the product of Example 1, 9 g stearic acid, and 20 g DTDP oil. The products of Examples 1-8 were molded into sheets and cylinder buttons at ~160 °C. Ring samples were cut from these sheets for tensile measurements. The details of the physical properties are shown in Table 1. As can be seen, the products were soft and thermoreversible gels. Those materials with fatty acids in their compositions (examples 2 through 8) exhibited better thermostabilities. Moreover, examples 2 to 8 may have a service temperature up to 130°C. Finally, all materials shown in the table are thermally recyclable at 160°C. Table 1

Claims: We claim: 1. A polymeric gel composition comprising: a. a polymer comprising an anhydride unit and an alkenyl unit, b. a crosslinking agent, c. a maleated polyalkylene, d. an extender, and e. an organic fatty acid. 2. The composition of claim 1 wherein said anhydride unit is derived from maleic anhydride. 3. The composition of any of claims 1 to 2 wherein said alkenyl unit is chosen from vinyl aromatic hydrocarbons, R R 2 ethylenes, and alkylvinyl ethers. 4. The composition of claim 3 wherein at least one of the following is true: said vinyl aromatic hydrocarbons comprise styrene or α-methylstyrene, said R 1 R 2 ethylene unit is isobutylene, and said alkylvinyl ether is methylvinyl ether. 5. The composition of any of claim 1 to 4 wherein said crosslinking agent comprises a low molecular weight organic compound having 1 or more functional groups chosen from primary amine, secondary amine, carboxyl, formyl, and hydroxyl. 6. The composition of any of claims 1 to 5 wherein said maleated polyalkylene is grafted to said polymer. 7. The composition of any of claims 1 to 6 wherein the monomer from which the alkylene moiety of said maleated polyalkylene is formed is at least one of ethylene and propylene. 8. The composition of any of claims 1 to 7 wherein said organic fatty acid is mono- or di-functional or wherein said organic fatty acid is a polyacid. 9. The composition of any of claims 1 to 8 wherein said composition has compression set values, at 100°C, of less than about 40% and, at 130°C of less than about 50%. 10. A method of forming a soft polymer gel compound comprising reacting a poly(alkenyl-cø-maleic anhydride) with a primary amine, followed by grafting thereto a maleated polyalkylene via a di-functional grafting agent, and mixing the resulting product with an organic fatty acid.

Inventors: FOLTZ VICTOR, HALL JAMES, WANG XIAORONG, FOLTZ, VICTOR, HALL, JAMES, WANG, XIAORONG
Applicants: BRIDGESTONE CORP, FOLTZ VICTOR, HALL JAMES, WANG XIAORONG, BRIDGESTONE CORPORATION, FOLTZ, VICTOR, HALL, JAMES, WANG, XIAORONG
Application year: 2001
Main classification: C08L35
IPC codes: C08F8, C08K5, C08L23, C08L35, C09K3