MXPA95002846A - Cover for constant improved speed joints and method for the manufacture of the mi - Google Patents

Abstract

The present invention relates to: A plastic substrate such as an elastomeric material is provided. A coating layer is used to coat the plastic substrate. In a highly preferred aspect, the plastic substrate is a constant velocity joint cover made of a chloroprene or a polyester elastomer. The coating layer is made of a mixture that includes a prepolymer, a monomer, a curing agent, a catalyst and a graft polymerization initiator, which is grafted to the chloroprene or polystyrene elastomer.

Description

"COVER FOR CONSTANT IMPROVED SPEED JOINTS AND METHOD FOR MANUFACTURING THE SAME" INVENTORS: GARY D. GRABAUM. THEODORE H. COLLINS. G YNNE WILLIAMS MOHAN L. SANDUJA CARL HOROWITZ BORIS SHVARTSMAN PAUL THOTTATHIL NATIONALITY: CITIZEN NORTH AMERICAN CITIZEN NORTH AMERICAN CITIZEN ENGLISH NORTH AMERICAN CITIZEN NORTH AMERICAN CITIZEN SOVIET INDIAN CITIZEN.

RESIDENCE: 4835 PCKFORD DRIVE, TROY, MI 480 568 PINEHURST, ROCHESTER HILLS, 48309 E.U.A. 1986 BERRY'S CHAPEL RD, TN FRANK 37064 E.U.A 144-90 41ST. AVENUE, APT. 508 FLUSHING, N Y 11355 E.U.A. 5607 FILLMORE AVENUE, BROOKLYN, ET # C4, L0NG ISLAN 11106 E.U.A. E, NEW HYDE PARK, E.U.A.

OWNER: GKN AUTOMOTIVE, INC.

NATIONALITY: NORTH AMERICAN SOCIETY.

RESIDENCE: 3300 UNIVERSITY DRIVE, AUBURN H MI 48326 E.U.A.

BACKGROUND OF THE INVENTION Technical Field The present invention relates to a multilayer article and more particularly relates to a multilayer article for use in constant speed joint covers, where a first layer is an elastomer upon which a second layer is polymerized by grafting of a side chain. Discussion of Related Art ~ 10 Constant velocity joints ("CV") are common components in automotive vehicles. Typically a cover is used to cover the CV joint, and by this means protect it from the elements found during its use and service. 15 CV joint covers are made of a plastic or polymeric material. The covers are desirably flexible to allow for elastic deformation in response to the dynamics of the CV joint beneath it. Materials commonly found to make covers for CV joints include elastomeric materials such as coloprene or elastomers of the polyester type. In service, covers made with these materials generally protect the CV joint from dust, road salts, water, oils, gasoline and the like. While these materials generally provide a desirable half-life of the cover, there is a perceived need to further extend the life of the cover by providing a cover that has improved wear characteristics, improved high temperature resistance (such as that can be found in the service of the joints CV), and improved physical properties. There is also a need to extend the service life as well as the storage life of the covers which are not in service, but are stored in a warehouse or in some other way in advance of their service, by improving the service life. Capability of the roof to resist corrosion and degradation. SUMMARY OF THE INVENTION According to the method and article of the present According to the invention, an improved multilayer article (including an elastomeric substrate layer and another layer) is produced which is capable of being used advantageously, without limitation, _A as a cover for constant speed joints. The resulting article, by comparison with substrates monolayer plastics, exhibit improved wear characteristics. The resulting article also exhibits improved physical properties (e.g., impact resistance), and an improved ability to resist corrosive media compared to a monolayer plastic substrate.

BRIEF DESCRIPTION OF THE ILLUSTRATIONS Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates based on the subsequent detailed description of the preferred embodiments and the accompanying clauses, taken in conjunction with the illustrations. accompanying it: Figure 1 is a cross section of a conventional CV joint cover. Figure 2 is a cross section of a conventional CV joint cover being bent, as can be found during service. Figure 3 is a cross section of a cover for multilayer CV joint according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED MODALITY _ = Referring to Figure 1 a cover for conventional CV joint is shown. As discussed in more detail herein, the cover is a monolayer article made of a plastic material such as an elastomer, a polyester or a mixture thereof. The cover 10 has a wall 12 having an inner surface 14 and an outer surface 16. The inner and outer surfaces 14 and 16 of the cover are not coated. The cover 10 has a longitudinal axis and is folded - generally in the same manner as an accordion about the longitudinal axis and has a bellows-like configuration that includes a plurality of circumferential folds 18 spaced substantially along the length of its axis longitudinal. Figure 2 exemplifies the cover 10 of Fig. 1 in a flexed position as can be found in service (the CV joint is not shown). As can be seen, two or more folds 18 can come into contact with one another. After prolonged use, material wear in areas near the folds can occur due to contact. Figure 3 illustrates a cover 20 according to the teachings of the present invention. The cover has a wall 22 having an inner surface 24 and an outer surface 26. The wall 22 has one or more predetermined thicknesses which vary depending on the intended use and the material of the cover. "Default weights" is defined for the purposes of the present invention as the distance between the inner and outer surfaces through a section taken through the wall 22 perpendicular to the "surfaces 24 and 26 of the wall. cover for a CV joint made of an elastomer of the chloroprene type can have a wall thickness ranging from about 1.5 to about 3.5 mm, and preferably about 2.5 mm A covering layer 28 includes an interior surface 30 which preferably rests on at least part of the outer surface 26 of the cover 20. The cover layer also includes an outer surface 32 which is generally exposed.In other embodiment (not shown), a coating layer also rests on at least part of the interior surface 24 of the cover.The cover layer 28 also has one or more predetermined thicknesses (ie, the r. 0 defined distance from the outer surface of the coating layer to the outer surface 26 of the cover 20 through a section taken through the wall 22 perpendicular to the outer coating layer), which may vary depending on a number of things such as . material of the cover, the desired properties in the coated cover, and the like. An example of the thickness of a surface for the coating layer varies from about 34 microns to about 45 microns, and more preferably about 37 microns to about 40 microns. micrometers Under a preferred embodiment the ratio of the wall thickness to the thickness of the coating layer varies from about 80: 1 to about 40: 1, and more preferably is about 60: 1. The method of the present invention includes steps (1) contacting a polymeric substrate surface with a mixture that includes a prepolymer, a monomer, a curing agent, a catalyst, and a graft polymerization initiator; and (2) curing the mixture to polymerize by grafting the mixture with said polymeric substrate. In a preferred embodiment the polymeric substrate is a cover for CV hinge, such as the cover 20 and the mixture is cured to form a coating layer such as a coating layer 28. The polymeric substrate that is useful in the method of the present invention invention can be any suitable material capable of being graft polymerized according to the present method. In a preferred embodiment the substrate is a flexible bondable polymer, preferably an elastomer. More preferably an elastomer is a chloroprene (such as and without limitation - neoprene), a polyester or a mixture thereof. The polymer to be used in the present method and articles preferably has physical properties that fall within the ranges of Table I. Table I Hytrel Neoprene (TPE) Specific Gravity at 25 ° C 1.2-1.3 1.1-1.3 Hardness 55-65 Margin A 40-55 D margin Tensile force, psi 1450-2400 4000-6000 - Elongation,% 280-400 340-600 Psi flexural modulus (RT) N / A 15,000-23,000 The polymer also generally has a good resistance to most the corrosive or degradation chemicals found in ordinary service in automobiles (eg, road salts, water, oils, gasoline, etc.) Preferably, the polymer is also able to withstand temperatures in excess of 100 ° C without deterioration or degra¬ # ^ 10 substantial donation. The skilled artisan will appreciate that chloroprenes are well known synthetic elastomers available in solid form, such as latex, or as foam, such as flexible foam. Preferably, according to the present method chloroprene is provided in a solid form. Examples of alternative elastomers that can be used in place of, or in combination with, chloroprenes, and particularly # with wetsuits include those, available under the brand names Santoprene, Pelpreno, Arnital and Lomod. Substrates of natural rubber can also be employed. Preferably the rubber or the elastomer is a diene-containing material which has one or more active labile hydrogen atoms which are activated to generate a free radical. An example of a particularly preferred material is commercially available under the brand name HYTREL, supplied by DuPont. Hytrel is a polyester-based elastomer used more commonly as a thermoplastic rubber. In a preferred embodiment the polymer substrate is provided in the form of the desired end article, which is still more preferably a cover for a CV joint such as the type shown as the cover 10 in FIGS. 1 and 2 or the cover 20 of Fig. 3. The substrate is preferably molded into its desired shape using any ¬ ^ Any suitable method such as blow molding or injection molding. The substrate can also be provided in a suitable configuration as an extruded material. As used herein, "mixture of resultant coating layers" refers to the mixture which is polymerized by grafting with the elastomeric substrate as it exists prior to graft polymerization. The prepolymer of the present invention is preferably based on an epoxy system. Even more preferably there is a selection of an epoxy prepolymer selected from among the aliphatic, cycloaliphatic, aromatic systems or "mixtures of them." The epoxy prepolymer can be prepared using any suitable method.Preferably, the epoxy prepolymer is derived from systems employing Bisphenol A, epichlorohydrin or mixtures thereof. Other phenols or alcohols, in any manner, can be employed as, without limitation, epoxy polyfunctional novolak resins having either phenol bases or cresol bases, or mixtures thereof. The skilled artisan will be aware of other alternatives. Examples of specific systems for the epoxy prepolymer include but are not limited to aliphatic epoxy resin - 1,4-diglycidyl diol butane, epoxy cycloaliphatic resin - 3,4-epoxycyclohexylmethyl-3,4-epoxy; cyclohexane carboxylate and bis (3,4-epoxy-6-methylcyclohexylmethyl) ^ c adipate; diglycidyl ether of epoxy polyphenol resins such as bisphenol A and epoxy resin resorcinol diglycidyl resins; polyglycidyl novolak phenol-formaldehyde, or mixtures thereof. In a preferred embodiment the epoxy prepolymer is¬ is present in an amount which varies in the range of a percentage weight from about 1 to about 4 of the mixture for the resulting coating layer, and more preferably at least a percentage weight of about 3 to about 4. The monomers to be used in the method and article Those of the present invention are preferably acrylic-based monomers, such as those containing hydroxyl, carboxyl or allyl functional groups (e.g. glycidyl). The monomer can be derived from a corresponding salt, amide ester or nitrile. Examples of preferred monomers Ridos include, without limitation, hydroxyethyl. methacrylate, hydroxypropyl methacrylate, dimethyl amino ethyl acrylate, dimethyl amino ethyl acrylate, dimethyl amino ethyl methacrylate, dimethyl amino ethyl methacrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, glycidyl methacrylate or mixtures thereof. In a preferred embodiment, the selected monomer is used by itself or in combinations of two or three monomers. An example of commercially available monomers is hydroxy ethyl methacrylate, distributed by Rohm & Haas Co. from Philadelphia, ^ 10 Pennsylvania. The coating layer mixture resulting from the prepolymer and the monomer can be varied depending on how far the reaction is carried out. The monomer and the prepolymer are used in sufficient quantities to result in the mixture having the desired viscosity. While any of a number of different catalysts can be employed, a catalyst with free radicals is preferred. A peroxide type catalyst is even more preferred. Examples of suitable catalysts include benzoyl peroxide, methyl ethyl ketone peroxide, tertiary butyl hydroperoxide, di-tertiary butyl peroxide, tertiary butyl perbenzoate, peracetic acid or mixtures thereof. An example of a commercially available catalyst is benzoyl peroxide. Preferably the catalyst is em¬ poured in an amount ranging from about a percentage weight of 0.5 to about 1.0 of the mixture for the resulting coating layers. A variety of suitable curing agents are available to carry out the curing, binding or hardening of the mixture for coating layers of the present invention. Some examples include materials selected from polyesters, polyamides, polysulfides, polyurethanes, carboxylic acids, acid anhydrides or mixtures thereof. Preferred curing agents include a material selected from primary-secondary aliphatic amines, hydroxyaliphatic amines, aromatic amines or the like. Alternatively, preferred curing agents may include selected amino or polyamines of the alkyl, aryl, alkyloxy or mixtures thereof type. An example of a commercially available curing agent is a polyamide available under the brand name Versamid 140 distributed by Henkel Corporation of Gulph Mills, Pennsylvania. The curing agent is preferably used in an amount ranging from about 5 percent to about 12 percent of the mixture for the resulting coating layers, and more preferably a percentage weight from about 6 to about 10 percent. hundred. Additionally, the curing agent is preferably used in a ratio of about 0.5 to about 10 parts of curing agent to about 1.0 to 4.0 parts of epoxy prepolymer. The graft polymerization initiator employed in the coating layer mixture of the present invention is preferably an ion initiator which, when in the presence of the substrate of the present invention, will graft the substrate polymer into the mixture. In a highly preferred embodiment the graft polymerization initiator contains a silver ion preferably derived from a salt with a silver content. Examples of preferred silver-containing salts from which such an ion can be derived include silver nitrate, silver perchlorate, silver acetate or mixtures thereof. In some cases it may be desirable to dissolve the salt with silver content in a. organic solvent. In such cases, the salt with silver content is preferably soluble in organic solvents (e.g. methyl ethyl ketone). An example of such a salt is silver perchlorate. Examples of alternative ion initiators other than those containing silver include salts of iron, cobalt and copper. Examples of commercially available common graft polymerization initiators include silver nitrates and silver perchlorates. The amount of silver salt used is very small e.g. a percentage weight of 0.001 to 1.0% of the monomer solution and preferably about 0.05 to 0.10% by weight. "Other additives can optionally be incorporated into the mixture to adjust the resulting characteristics, for example, suitable fillers can be used in an amount as high as between about 20-30% by weight of the mixture for coating layers. Resulting examples of suitable fillers include tungsten sulfide, molybdenum sulphide, titanium dioxide, aluminum oxide and mica, among others. Viscosity modifiers can also be employed in adequate quantities. For example, an organic solvent can be employed such as the ketone (e.g., without limitation, methyl ethyl ketone, methyl isobutyl ketone or the like), or an organic aromatic (e.g., without limitation, toluene or the like). Suitable conventional flexibility modifiers, thickening agents or thixotropic agents can also be used. Conventional dyes and reinforcers can be used in a similar way. The mixture for coating layers resulting from the present invention is preferably prepared by mixing a first and a second sub-mixtures. The The first sub-mix preferably contains the epoxy prepolymer, a monomer, one or more fillers and other ingredients. Preferably, the components of the first sub-mix are placed in a suitable container such as a mixing vessel and are scrambled or ground. using a rotary ball grinding machine. The mixing of the submix is typically carried out at ambient temperature for a period of time ranging from 24 to 48 hours, or until a substantially homogeneous mixture is obtained. The skilled artisan, of course, will appreciate that mixing periods (as with all mixing steps herein) will vary with such conditions, without limitation, with temperatures, mixing speed and the amounts of each of the ingredients. By grinding the submix preferably the particle size or any filler or large particles contained in the formula will be reduced to more than 7 or less based on the Hegeman scale. The second sub-mix preferably includes the curing agent or bond, a catalyst, a graft polymerization initiator and optional materials such as fillers. These ingredients are placed together in a suitable container such as a mixing vessel, in the raw state. Then, they are mixed under a suitable atmosphere (e.g., ambient air) using a suitable mixing apparatus for a time and at a temperature sufficient to achieve a substantially homogeneous single-phase solution. Generally, mixing is carried out at room temperature for a time ranging from 3 to 6 minutes, and more preferably from about 4 to 5 minutes.

The first and second submixes are then mixed together. At this stage the ratio of the first to the second submix can be selected to achieve the resulting properties of the material when cured. In a preferred embodiment the ratio (expressed in parts by weight) of the first to the second submixes, namely Part A to Part B, is about 14: 3 for Hytrel and varies from 3: 2 to 12: 1 for the Nene in the sample mixture. As with the individual submixes, the mixture of F < S1LrO. First and second submixes together are mixed under a suitable atmosphere (e.g., ambient air) using any apparatus for mixing for a time and at a temperature sufficient to achieve a substantially homogeneous single phase solution. For example, if it is carried out When mixed at room temperature, the mixing is usually carried out for a period of time ranging from about 3 to 6 minutes, and more preferably from 4 to 5 minutes. The mixture for the resulting coating layers can to be stored or can be applied immediately to the polymeric substrate. It should be appreciated that the mixture can be prepared in a concentrated form in the same way. Therefore, the quantities of components previously sketched can be higher or lower to adjust to the concentration ¬ do. If used as a concentrate, prior to the application to the polymeric substrate the mixture is preferably dissolved in a suitable solvent to achieve the desired resulting concentrations. In a preferred embodiment, the mixture for resultant coating layers is brought into contact with part or all of the polymeric substrate by means of conventional spray coating techniques. One or more application techniques may also be employed including but not limited to brush-applied coating, dipping, foaming, roller coating or the like. Preferably the resulting mixture is applied to a sufficient thickness to achieve the desired properties in the resulting coated article. For example, for a joint cover which has a thickness of walls of the polymer substrate of about 1. Omm, the thickness of the coating preferably varies in the range of about 0.5 to about 2. Omm, more preferably 0.8mm to about 1.6, and even more preferably about 1.2mm. Once coated with the mixture for layers of recu¬ After the resulting bridging, the coated polymeric substrate is heated to achieve the graft polymerization reaction and the curing of the resulting mixture. The heating is done in any suitable environment (e.g., ambient air), in a suitable heating furnace (e.g. circulating air oven), and at a suitable pressure (eg g. atmospheric pressure) . Preferably heating is done at a temperature ranging from about 200 ° F which may be preferable for Hytrel and 265 ° F which may be preferable for wetsuits. More preferably the heating is done at a temperature ranging in the range from about 220 ° F for Hytrel to about 250 ° F for the neoprene. The time for heating should be selected to carry out the curing through the resulting mixture layer, and sufficient graft polymerization of a side chain between the resulting mixture and the polymeric substrate and the resulting cured mixture layer. For example, using the above reaction conditions to make a material with a mixture layer thickness resulting in about 1. Omm, a time from about 20 to about 30 minutes is necessary, and more particularly about 25 minutes is required. The skilled artisan will appreciate that the times specified for the steps in the present may be. higher or lower depending on a number of factors such as the temperature used during each step, the amount of material involved in the step, and the like. Without intending to be limited by theory, it is believed that the chemical grafting mechanism according to the present invention occurs substantially as follows. The elastomer substrate includes a plurality of branch points for receiving monomer chains otherwise known in the field of polymer chemistry as a side chain or graft. In accordance with the present invention the graft generally involves the activation of the substrate by suitable means such as and without heat limitation, ultraviolet radiation and more commonly through the use of chain transfer agents. Once the substrate has been activated, chains of monomers linked by means of carbon-carbon bonds are bonded to the substrate, thus unceasing the substrate without substantially affecting the existing characteristics of the materials involved. Many materials, both naturally occuring and synthetic, are believed to possess active hydrogens which are typically more reactive under graft polymerization systems than in "block hydrogens" (e.g., tertiary hydrogen in polypropylene). It is believed that the graft polymerization initiators of the present invention have the ability to remove these active hydrogens and initiate concomitantly the growth of polymer chains at the site (i.e. branch points) from which the active hydrogen was removed. Polymerization according to the mechanisms of free radicals, anions or cations is advantageously possible according to the present invention, depending on whether one electron or electron, no electrons or two electrons, respectively, are removed by the initiator. In many cases a mixture of monomers can be employed and often more than one property can be altered in one processing step. These polymer chains, whose length can be controlled by several techniques such as "grafting from" methods, which generate initiation sites selectively for the growth of chains of ingestion and radical termination, among others., are permanently fixed to the substrate. The bond between the graft polymer and the substrate is covalent in nature, therefore, it is believed that the graft polymer should not be susceptible to be. extracted from the substrate. With this background, the mechanisms with respect to neoprene for coating and polyester elastomer substrates are explored. B. Chemical Grafting Applied to Neoprene: Rubber parts usually describe parts made of synthetic elastomers or natural rubber (neoprene is an example of a synthetic elastomer) containing diene units such as butadiene, isoprene, pentadiene and chloroprene. These units generally have active labile hydrogen atoms which can be activated in the presence of a graft polymerization initiator ("Gl"), resulting in the appearance of free radicals ("X"). Free radicals must be able to initiate graft polymerization. An example of a series of reaction steps involved in graft polymerization are as follows: R H R In the presence of vinyl monomers, it is believed that the elastomeric radical produced in this process initiates graft polymerization. »10 R R 'CUrOC-CHr- + CH? CHX -CH2 -C = C-CH2 -CHX vinyl monomers CH2 I initiation of the graft 15 -CHX) to -CH 2 -CHX H2 CH2 20 propagation of the graft R in the above formula can be alkyl or aryl groups with a variable number of carbon chains, and n can be any suitable whole number starting at 2.

It is believed that the graft polymerization initiating ion starts the reaction and therefore the process as a whole * tends to behave as an autocatalytic. A relatively small amount of the graft initiator ion (e.g., 10-100 ppm silver ion) should therefore be sufficient to carry out the graft polymerization process. It is believed that the presence of peroxide in the injecting initiator not only aids the regeneration of the initiator ion of ingestion but also in producing rubber hydroperoxides which subsequently decompose to result in rubber radicals which aid in curing. Ri in the following formula is generally an alkyl or aryl group, n again is any suitable whole number that begins with 2 and m is also any suitable whole number beginning with 2. 15 CH- + 02 > - CH -OC-CH H OOH CH2 -OC-CH- + GI -CH2-C = CH-CH- +1/2 02 + GI + + OH H OOH The process can be terminated by the combination of radicals: R R, CH2-OC- (CH2-CHX), - CH2-CHX + - CH2C = CH-CH2 CH2 C- (CH2-CHX) "- CH2-CH-CH-CH = C-CH2 I R R? CH2-OC- (CH2-CHX) n-CH2-CHX + XCH-CH2 - (CHX-CH2) m-OC-CH2 1 1 # CH2 CH2 ? C. Chemical grafting as applied to polyester elastomer covers. As in the case of HYTREL covers ("PE" polyester) or any other rubber material, it is believed that the chemical grafting will be carried out by abstraction of the hydrogen atom with the desired monomer / prepolymer to form a polymeric film, which can then be chemically bonded to the HYTREL deck surface. The sequence of the reaction steps that is created is invoked used in the graft polymerization of a HYTREL roofing substrate that is given as follows: O O 15 PE-C-OH + GI + -v PE-C-0 + H + + GI Polyester substrates Radical Formation * O O 20 PE-C-0 + CH2 = CH PE-C-0 + CH2 - CH X X initiation monomers 25 PE-C-0 - CH2- CH + n (CH2 = CH) > PE-C-0 - (CH2-CH) n-CH2-CH X X X X spread GI + ROOH? RO + OH - GG peroxide Again, the process can be terminated by the combination of radicals: O PE-C-0 - (CH2- CH) n-CH2 - CH + RO + OR PE-C-0 - (CH2- CH) n-CH2-CHOR X X O * O PE-C-0 (CH2-CH) n-CH2-CH + CH-CH2 - (CH-CH ^ -O-C-PE? X X X X o o PE-C-0 - (CI- - CH) m + n -0- PE * 10 X For the above reaction mechanisms, the value of m is any suitable whole number beginning with .2, the value of n is any proper whole number that also starts with 2 and R. can be any alkyl or aryl group with the desired chain length. The following are examples of suitable compositions that are used to coat a polymeric substrate. The compositions are described in their state as they exist before of mixing the first and second submixes. The scope of this invention is not limited to the details specified in the examples. For Examples I-IV, the underlying plastic substrate is a polyester elastomer, preferably HYTREL. For Examples V-VII, the substrate plas underlying is neoprene.

EXAMPLE 1 PART A PART BY WEIGHT Epoxy prepolymer (Araldite 488N40) 100.00 F5A polypulverized fluropolymer 10.00 Polyfluor 200 fluropolymer 5.00 Molybdenum sulphide 6.00 Tungsten disulfide 2.00 Methyl ethyl ketone 50.00 Silane monomer A 187 1.00 trimethylol propane triacrylate 1.00 * PART B Urethane prepolymer (Desmodur N-75) 37.50 Benzoyl peroxide solution 1.0% MEK * 0.20 Silver Perchlorate solution 0.1% MEK * 0.10 * methyl ethyl ketone EXAMPLE II PART A PART BY WEIGHT Epoxy prepolymer (Epotuf 38525) 100.00 Polypropylene Fluropolymer F5A 10.00 Polyfluoro Fluropolymer 200 5.00 Molybdenum Sulphide 5.00 Tungsten Disulfide 3.00 Methyl Ethyl Ketone 5 * 0.00 S100 Monomer Al100 1.00 Trimethyl Propane Triacrylate 1.00 PART B PARTS BY WEIGHT Urethane Prepolymer (Desmodur N-75) 37.50 Benzoyl Peroxide Solution 1.0% MEK * 0.20 Silver Perchlorate Solution 0.1% MEK * 0.10 * Methyl Ethyl Ketone EXAMPLE III PART A PART BY WEIGHT Epoxy Prepolymer DER 684 EK40 100.00 F5A Polypropylene Fluropolymer 10.00 Polyfluo Fluropolymer 200 5.00 Molybdenum Sulphide 4.00 Tungsten Disulfide 4.00 Methyl Ethyl Ketone 30.00 Methyl isobutyl ketone 20.00 Al87 silane monomer 1.00 Trimethylol propane triacrylate 1.00 PART B Prepolymer urethane (Desmodur N-75) 37.50 Benzoyl peroxide solution 1.0% MEK * 0.20 Silver Perchlorate Solution 0.1% MEK * 0.10 * methyl ethyl ketone EXAMPLE IV PART A PART BY WEIGHT Epoxy prepolymer (Araldite R88N40) 50.00 F5A polypropylene fluropolymer 8.00 DER epoxide prepolymer? 684 EK40 25.00 Polyurethane Fluropolymer 200 3.00 Molybdenum sulfide 4.00 Tungsten sulfide 2.00 Methyl ethyl ketone 40.00 Al74 silane monomer 1.00 Trimethylol propane triacrylate 1.00 * Dow epoxy resin PART B Urethane prepolymer (Desmodur N-75) 28.00 * Benzoyl peroxide solution 1.0% MEK * 0.15 Silver Perchlorate solution 0.1% MEK * 0.10 NEOPRENE EXAMPLE V PART A PART BY WEIGHT Araldite epoxy prepolymer 6010 13.00 Methyl isobutyl ketone 14.00 Flouropolymer aquabead 916 2.00 Molybdenum sulfide 4.00 Tungsten Disulfide 2.00 Fluoropolymer F5A 2.00 polipulverizado Carbon black 0.40 Grind the above for 2 days and then add: Polysulfide RLP 2078A 25.00 Monomer alkyl glycidyl ether 0.50 Monomer alkyl methacrylate 0.50 Trimethylol propane triacrylate 0.50 Dow Corning DCI 9770 0.30 Additive Functional monomer of allylic ureide 0.50 PART B Versamid 140 6.00 Benzoyl peroxide 10% in MEK * 0.20 Silver Perchlorate 0.1% in MEK * 0.10 Liquid Polysulfide RLP 2078B 4.50 Toluene 30.00 * methyl ethyl ketone EXAMPLE VI PART A PART BY WEIGHT Epoxy prepolymer (Epon 828) 66.00 Methyl isobutyl ketone 72.00 Flouropolymer aquabead 916 10.00 Molybdenum sulphide 20.00 * Tungsten disulfide 9.00 F5A polypropylene fluropolymer 10.00 Black Tintayd EP30-35 2.00 Monomer silane Al87 2.00 Hycar ATBN 1312-32B2 20.00 PART B Polyamide 830 2.50 Polyamide 850 2.00 Benzoyl peroxide solution 10% MEK * 0.20 Silver perchlorate solution 0.1% 0.10 * methyl ethyl ketone EXAMPLE VII PART A PART BY WEIGHT Epoxy prepolymer (Araldite G010) 13.00 Methyl ethyl ketone 14.00 Polyfluor 200 Fluropolymer 2.00 Molybdenum sulphide 3.50 Tungsten sulphide 2.50 F5A polypropylene fluropolymer 2.00 Black Tintayd EP 30-35 1.50 LP ^ 3 polysulfide 6.00 Al87 silane monomer 0.50 allyl methacrylate 0.50 Dow Corning DCI 9770 0.20 Trimethyl propane triacrylate 0.50 PART B Polyamide 830 2.50 Polyamide 850. 2.00 Benzoyl peroxide solution 10% in MEK * 0.20 Silver perchlorate solution 0.1% 0.10 * methyl ethyl ketone EXAMPLE VIII PART A BY WEIGHT Epoxy prepolymer (Epon 828) 6.00 Methyl ethyl ketone 30.00 Flouropolymer aquabead 916 4.00 Molybdenum sulphide 8.00 Disulfide tungsten 4.00 Polymerized Fluropolymer F5A 4.50 Black Tintayd EP30-35 2.00 Polysulphide LP-3 12.00 Allan silane monomer Al87 '1.00 allyl methacrylate 1.00 Trimethylol propane triacrylate 0.50 PART B Polyamide 830 6.00 Polyamide 880 2.00 Methyl ethyl ketone peroxide 0.30 Silver perchlorate solution 0.1 % in MEK * 0.15 * Methyl ethyl ketone For the examples listed above, several products with commercially available brand names have been used. The following is a summary of many of these products. Araldite GOlO is an epoxy prepolymer available from Ciba Geigy, Inc., a division of Ciba Geigy, Ltd. located in Basel, Switzerland. The polysulfide RLP2078A is a polysulfide available from Thiokol Corp., located in Shreveport, Louisiana. Versamid 140 is an amide curing agent available from Henkel Corp, located in Gulph Mills, Pennsylvania. Epon 828 is an epoxy prepolymer available from Shell Chemical Co. , located in Houston, Texas. Hycar ATBN 1312 32b2 is an amino-terminated butadine resin available from B.F. Goodrich, located in Akron, Ohio. Polyamide 830 and Polyamide 850 are amide curing agents available from Ciba Geigy, Inc., a division of Ciba Geigy, Ltd., located in Basel, Switzerland. Polysulfide LP3 is a polysulfide available from Thiokol Corp., of Shreveport, Louisiana. The following Table II and Graphs I and II summarize the improvement in wear resistance offered by coating the constant speed joint cover according to the teachings of the present invention. Table II shows the results of wear tests carried out on multiple tire runs of Hytrel constant velocity joint and neoprene coated and uncoated. For Hytrel constant speed tires covered and uncoated, the covers were placed in a test device designed to simulate a constant speed joint in an automotive vehicle. The simulated joint was suspended at 40 ° and then rotated at 200 rpm in an atmosphere maintained at 55 ° Celsius. This test procedure was continued for both the coated cover and the uncoated cover until a hole was detected in each of the covers used for the various runs. The holes that occurred resulted from the folded sections rubbing together during the rotation of the cover. How can % 10 see in Table II uncoated Hytrel covers failed between '0.6 and 9.3 hours. In any case, the Hytrel covers coated with the product described in Example I did not fail. The test was discontinued after 118 hours of rotation. 15 Similarly, the constant speed covers of coated and uncoated neoprene were subjected to wear tests. Again the covers were placed¬ • P in a test device suspended at an angle of 41 ° relative to the supporting substrate. Simulation articulation The day was then rotated at 400 rpm at an ambient temperature of about 68 ° F. While the failure of the uncoated neoprene covers occurred between 2.3 and 10.8 hours, the covers that had a coating made with the product described in example 5 failed at time intervals between 3.6 and 23.9 hours.

As can be seen with reference to Table II and the graphs below, the Hytrel covers coated with the product of Example I showed an average increase in durability of more than two hundred percent compared to the uncoated Hytrel cover. In addition, the neoprene cover coated with the product of Example V showed an average increase in durability of more than one hundred and eighty percent. Table II Neoprene Neoprene Hytrel Hytrel uncoated Example 5 s / coating Example Run 1 2.3 3.6 0.6 118.1 * Corrida 2 3.3 4.0 2.2 118.1 * Corrida 3 4.1 10.2 7.9 118.1 * Run 4 5.0 20.0 9.3 118.1 * Corrida 5 7.8 21.8 - - Corrida 6 10.7 22.1 - - Corrida 7 10.8 23.9 - - # MINIMUM 2.3 3.6 0.6 118.1 MXIMO 10.8 23.9 9.3 118.1 AVERAGE 6.3 15.1 5.0 118.1 * The test was discontinued after one hundred and eighteen hours without significant signs of wear.

GRAPH I GRAPH II PRODUCTION VS COVERED INJURED WITH POLYMER ÜCUDIEK..A DE I EOPRtl.? WITHOUT COVERING NEOPRENE COUBLED WITH THE PRODUCT OF EXAMPLE V.

NEOPRENE Although the invention has been described with particular reference to certain preferred embodiments thereof, variations and modifications may be made within the spirit and scope of the following clauses. The article of the present invention has been illustrated in connection with a cover for constant speed articulation. While such an intended use of the resulting materials of the present invention is preferred, the skilled artisan will appreciate that numerous alternative uses may also be contemplated, including but not limited to those applications where it is desired to improve the characteristics of a plastic substrate. Examples include an elastomeric seal that includes, but is not limited to those used in articulated force transmission devices.

Claims (15)

1. *
2. NOVELTY OF THE INVENTION Having described the invention, it is considered as a novelty, and therefore the provisions of the following are stated: CLAUSES 1. A method for coating a plastic substrate comprising the steps of: 10 (a) entering into contact a plastic substrate with a mixture that includes: (i) an epoxy prepolymer; (ii) an acrylic monomer; (iii) an agent for curing; 15 (iv) a catalyst; (v) an initiator for graft polymerization; and Jjfe (b) curing said mixture for graft polymerizing said mixture to said plastic substrate. 2. The method of Clause 1 further comprising the step of applying the mixture to the plastic substrate.
3. 3. The method of Clause 1 wherein said epoxy prepolymer is selected from the group consisting of polyfunctional epoxy novolak resins, aliphatic epoxy resins, cycloaliphatic epoxy resins, diglycidyl ether 25 of epoxy polyphenol resins, and mixtures thereof.
4. 4. The method of Clause 1 wherein said acrylic monomer includes hydroxyl, carboxyl or alkyl functional groups.
5. 5. The method of Clause 4 wherein said acrylic monomer is selected from the group consisting of hydroxyethyl methacrylate, hydroxypropyl methacrylate, dimethyl amino ethyl acrylate, dimethyl amino ethyl acrylate, dimethyl amino ethyl methacrylate, dimethyl amino ethyl methacrylate , methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, 10 ethyl methacrylate, butyl methacrylate, glycidyl methacrylate or mixtures thereof.
6. 6. The method of Clause 1 wherein said curing agent is selected from the group consisting of polyamines, polysulfides, polyurethanes, carboxylic acids, anhydride 15 acid dridos or mixtures of them.
7. 7. The method of Clause 1 in which the graft polymerization initiator is selected from the group that ^ - consists of salts of silver, iron, cobalt and copper.
8. 8. The method of Clause 1 in which said mixture 20 includes fillers. A method for protecting a surface of an elastomeric constant velocity joint cover, comprising the steps of: (a) mixing: (i) a first submix, including an epoxy prepolymer and an acrylic monomer; and (ii) a second sub-mix including a curing agent, a free radical polymerization catalyst, wherein said graft polymerization initiator is an ion derived from a salt selected from the group consisting of silver, iron, cobalt or copper. (b) contacting a surface of an elastomeric constant velocity joint cover made of a chloroprene, a polyester or a mixture of 10, with said mixture for coating layer; and curing said mixture for coating layer to achieve graft polymerization between said cover and said coating layer mixture. 10. The method of Clause 9 which also includes 15 the step of applying the mixture to the plastic substrate. 11. The method of Clause 9 wherein said epoxy prepolymer is selected from the group consisting of ^ _ ^ epoxy polyfunctional novolak resins, aliphatic epoxy resins, cycloaliphatic epoxy resins, diglycidyl ether 20 of polyferol epoxy resins, and mixtures thereof. 12. The method of Clause 9 wherein said acrylic monomer includes hydroxyl, carboxyl or functional alkyl groups. 13. The method of Clause 12 in which said mo¬ 25 acrylic number is selected from the group consisting of / '" hydroxyethyl methacrylate, hydroxypropyl methacrylate, dimethyl amino ethyl acrylate, dimethyl amino ethyl acrylate, dimethyl amino ethyl methacrylate, dimethyl amino ethyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, glycidyl methacrylate or mixtures of them. 14. The method of Clause 9 wherein said curing agent is selected from the group consisting of polyamines, polyamides, polysulfides, polyurethanes, carboxylic acids, * 10 xylic acids, acid anhydrides or mixtures of them. 15. The method of Clause 9 in which said mixture includes fillers. IN WITNESS WHEREOVER, I have signed the above description and claims of novelty of the invention, as attorney of GKN AUTOMOTIVE 15 INC., In Mexico City, Republic of Mexico on June 29, 1995. 25