BR9917722B1 - process of applying seal to an article and cured article. - Google Patents

Description

"PROCESS OF APPLICATION OF SEALING TO ARTICLE AND CURED ARTICLE"

Divided from P1 9917444-8, filed July 15, 1999

Field of the Invention

The present invention relates to elastomeric compositions which are curable by exposure to ultraviolet (UV) radiation. Further, the present invention relates to a fast curing process of elastomeric seals, wherein the seals are formed by applying an uncured polymeric composition directly onto a sealing member or a surface to be sealed.

Background of the Invention

Elastomeric compositions require a vulcanization, i.e. curing, step in order to develop the lattice lattice structure that confers ideal elastic properties to such compositions. Typically, curing processes are based on compression molding or transfer molding techniques in which an elastomer, fully mixed with a curing agent and other additives, is introduced into a mold which is then heated under pressure. The high temperatures used during the molding process cause chemical reaction of the elastomer and bandage to generate a crosslinked product.

The specific raw (i.e. uncured) elastomer used for the manufacture of a synthetic rubber article will be selected with reference to the specific environmental end use application upon which the finished article is to function. For example, different elastomers will be selected from alkylene ethylene acrylate copolymer rubbers, ethylene alpha olefin copolymer elastomers, fluoroelastomers and chlorinated elastomers, depending on whether or not the finished article is exposed to oils, water, fuels, acids or bases. It will also consider the temperature range to which the article will be subjected and special needs such as flame resistance. In addition, consideration will be given to the curing characteristics of the polymer and the ease with which defect-free parts can be produced.

Most commercial scale elastomeric seals are crosslinked under high temperature in molding processes. Generally, elastomeric gaskets and seals thus produced are manually fitted to an article to be sealed. Alternatively, adhesives are sometimes used to connect the cured sealing member to an article. These connection techniques are not completely satisfactory in all cases. In particular, manual methods are time consuming and adhesives can affect the physical properties of the seal.

Elastomeric joints are often used as sealing members for grooved parts, such as rocker caps and air inlet conductors, which are used in automotive engines. These joints must be resistant to the effects of heat and oil. Traditionally, oil-cured and elastomeric compositions such as alkyl and ethylene acrylate copolymer rubbers have been manually introduced into the groove of a metal part. Various automotive components are now formed from high performance thermoplastic materials other than metal. Manually fitting elastomeric seals onto these components is time consuming, but curing the seal in place is impractical because the cure temperature or, in some cases, the temperature after cure, is usually high enough to cause the thermoplastic to deform. Still, if the cure temperature is reduced, the cure rate is too low to be practical. Oil or fuel resistant elastomeric compositions which can easily be applied to an article or groove in its uncured state and which are adapted to low temperature curing techniques would therefore be especially useful in the manufacture of thermoplastic articles having connected sealing members. for industrial or automotive uses.

Low temperature curing processes that are initiated by high energy radiation, such as electron beam or gamma radiation, are known for use with almost all elastomers, including ethylene acrylate copolymer elastomers. For example, electron beam crosslinking of cable and wire insulation compositions, including elastomeric compositions, is described in E. Brandt and A. Berejka, Electron Beam Crosslinking of Wire and Cable Insulation, Rubber World, 49, November 1978. Eldred, U.S. Patent No. 3,950,238, describes the use of electron beam radiation for curing butadiene and acrylonitrile polymers, and Clarke, U.S. Patent No. 4,275,180, describes the use of radiation curing. of an electron beam of a mixture of an ethylene acrylate copolymer rubber and a thermoplastic polymer, for example for cable coating. Electron beam healing has the disadvantage that it requires very complex and expensive equipment for the generation of high energy particles. It would therefore be advantageous to have a low temperature curing process available that would not depend on the use of electron beam radiation. Low temperature ultraviolet (UV) curing of a number of polymers, including ethylene acrylate polymers, are described in U.S. Patent No. 4,863,536. However, the described process involves dissolving the specific polymer in an acrylate monomer and is not suitable for the preparation of general rubber products such as gaskets and seals.

In addition to the availability of an effective low temperature curing process for ethylene acrylate copolymer elastomers, the availability of similar curing techniques for use with other elastomers would also be advantageous. As with ethylene acrylate copolymers, typical curing processes for fluoroelastomers are based on transfer molding or high temperature compression molding techniques. Products manufactured using these processes include seals, gaskets, piping and other rubber products in general. In addition, fluoroelastomer coated textile compositions are commercially available and are generally subjected to a cooking process during manufacture, as described, for example, in U.S. Patent 4,770,927 to Effenberger et al.

Low temperature radiation curing processes for fluoroelastomers are known in the prior art. A stain-resistant protective floor fluoroelastomer coating composition that is curable using ultraviolet (UV) radiation is described, for example, in European Patent Application No. 570254. Ultraviolet (UV) curing of fluorinated copolymers containing Epoxy is described in Japanese Kokai Patent Application No. 5-302058. In addition, ultraviolet (UV) or electron beam cures of certain fluoroelastomer compositions which are normally cured with a polyamine or polyol crosslinking agent are described in German Patent No. 19642029 and Japanese Kokai Patent Application No. 61-031411. Mixtures of fluoroplastics and ethylene vinyl acetate copolymers or ethylene acrylic acid ester copolymers that are cured with ultraviolet (UV) radiation are described in Japanese Kokai Patent Application No. 5-078539.

These prior art compositions have interesting properties, but do not provide compositions that exhibit the tensile strength, modulus, and compression fit required in many commercial applications, such as joints for air inlet conductors. Therefore, there remains a need in the art for fluoroelastomer compositions which can be cured at low temperature by low energy radiation processes and which, when cured, exhibit excellent tensile strength, modulus and compression adjustment.

Similarly, chlorinated elastomers, such as chlorinated polyethylene, chlorosulfonated polyethylene and epichlorohydrin rubber, are traditionally thermally crosslinked, either through compression or free radical cure systems in compression molds. Prolonged exposure to high temperatures of curable compositions containing such polymers can be problematic due to the tendency for these polymers to "dehydrate". Due to the high cure temperatures required, these elastomers have little utility in applications involving the formation of elastomeric / thermoplastic compositions that are cured on site. As with alkyl and ethylene acrylate elastomers, the manufacture of chlorinated thermoplastic / elastomeric composite articles requires an elastomer that can be cured at a sufficiently low temperature to prevent thermoplastic deformation. Low temperature ultraviolet (UV) cures of chlorinated polyolefin coating compositions are known. U.S. Patent No. 4,880,849 describes an ultraviolet (UV) curable chlorinated polyolefin coating that has excellent adhesion to plastic substrates. Kokai Japanese Patent Application No. 63-26751517 describes ultraviolet (UV) curing of chlorosulfonated polyethylene rubber and epichlorohydrin hose which is first passed through an ultraviolet (UV) irradiation apparatus and vulcanized in followed at elevated temperature for 30 to 60 minutes. However, chlorinated elastomeric compositions that could easily be applied to a non-cured groove or article and which are adapted to low temperature curing techniques are not known in the prior art.

There is therefore a need for a method whereby an elastomeric sealing composition can be efficiently and adhesive-free applied to a substrate and cured under low temperature to produce a cured seal having excellent stress resistance equilibrium, module and compression adjustment.

Brief Description of the Invention

The present invention relates to curable elastomeric compositions which are capable of crosslinking at low temperatures. Particularly, the present invention relates to a curable and thermally stable elastomeric composition comprising:

A) 70 to 99% by weight of a fluoroelastomer containing at least one curing site selected from the group consisting of: 1) copolymerized brominated olefins, chlorinated olefins and iodinated olefins; 2) brominated and copolymerized unsaturated ethers, chlorinated unsaturated ethers and iodinated unsaturated ethers; 3) copolymerized unconjugated dienes and trienes; and 4) iodine atoms, bromine atoms and mixtures thereof which are present at terminal positions of the fluoroelastomer chain;

B) 0.5 to 20% by weight of a multifunctional crosslinking agent selected from the group consisting of multifunctional acrylic crosslinking agents, multifunctional methacrylic crosslinking agents, multifunctional cyanurate crosslinking agents and multifunctional isocyanurate crosslinking agents; and

C) 0.1 to 10% by weight of an ultraviolet (UV) primer;

wherein the weight percentages of each of components A), B) and C) are based on the combined weight of components A), B) and C).

The present invention further relates to an article sealing process comprising the steps of: A) mixing at a temperature of 25 ° C to 250 ° C of: 1) 70 to 99% by weight of a fluoroelastomer; 2) 0.5 to 20% by weight of a multifunctional crosslinking agent selected from the group consisting of multifunctional acrylic crosslinking agents, multifunctional methacrylic crosslinking agents, multifunctional cyanurate crosslinking agents and multifunctional isocyanurate crosslinking agents; and

3) 0.1 to 10% by weight of an ultraviolet (UV) primer;

wherein the weight percentages of each of components 1), 2) and 3) are based on the combined weight of components 1), 2) and 3) to form an extrusable, curable and thermally stable mixture; B) depositing said extrudable mixture on said article in

desired shape and thickness to form an uncured seal; and

C) irradiating said uncured seal with ultraviolet (UV) radiation long enough to cure said seal.

The present invention also relates to curable chlorinated elastomeric compositions which are capable of crosslinking at low temperatures. Particularly, the present invention relates to a curable and thermally stable elastomeric composition consisting essentially of:

A) 80 to 97% by weight of a chlorinated elastomer selected from the group consisting of chlorinated polyolefin elastomers and

epichlorohydrin elastomers;

B) 2 to 19.5% by weight of a multifunctional crosslinking agent selected from the group consisting of multifunctional acrylic crosslinking agents, multifunctional methacrylic crosslinking agents,

multifunctional cyanurate crosslinkers and multifunctional isocyanurate crosslinkers; and

C) 0.2 to 5.0% by weight of an ultraviolet (UV) primer;

wherein the weight percentages of each of components A), Β) and C) are based on the combined weight of components A), B) and C).

In one embodiment, the chlorinated olefin polymer is a chlorosulfonated olefin polymer.

The present invention additionally relates to an article sealing process comprising the steps of:

A) mixing at a temperature of 25 ° C to 250 ° C of:

1) 80 to 97% by weight of a chlorinated elastomer selected from the group consisting of chlorinated polyolefin elastomers and epichlorohydrin elastomers;

2) 2 to 19.5% by weight of a multifunctional crosslinking agent selected from the group consisting of multifunctional acrylic crosslinking agents, multifunctional methacrylic crosslinking agents, multifunctional cyanurate crosslinking agents and multifunctional isocyanurate crosslinking agents; and

3) 0.2 to 5.0% by weight of an ultraviolet (UV) primer; wherein the weight percentages of each of components 1), 2) and 3) are based on the combined weight of components 1), 2) and 3) to form an extrusable, curable and thermally stable mixture;

B) depositing said extrudable mixture onto said article in the desired shape and thickness to form an uncured seal; and

C) irradiating said uncured seal with ultraviolet (UV) radiation long enough to cure said seal.

Further, the present invention relates to a method of applying an article seal, comprising the steps of:

A) mixing at a temperature between 25 ° C and 250 ° C of:

1) 80 to 98% by weight of an alpha-olefin and ethylene copolymer comprising ethylene and a C3-C20 alpha-olefin;

2) 1 to 19.5% by weight of a multifunctional crosslinking agent selected from the group consisting of multifunctional acrylic crosslinking agents and multifunctional methacrylic crosslinking agents; and 3) 0.2 to 5% by weight of an ultraviolet (UV) primer;

wherein the weight percentages of each of components 1), 2) and 3) are based on the combined weight of components 1), 2) and 3) to form an extrusable, curable and thermally stable mixture;

B) depositing said extrudable mixture onto said article in the desired shape and thickness to form an uncured seal; and

C) irradiating said uncured seal with ultraviolet (UV) radiation long enough to cure said seal.

The present invention also relates to cured articles produced by these processes.

Detailed Description of the Invention

The curable and thermally stable compositions of the present invention comprise an elastomer, a multifunctional crosslinking agent, generally an acrylic or methacrylic crosslinking agent and an ultraviolet (UV) initiator. Such curable compositions are used as raw materials in the process of applying seal to an article which is a further embodiment of the present invention. In preferred embodiments of the process of the present invention, the elastomer, multifunctional crosslinking agent and ultraviolet (UV) initiator are present as three separate components. However, the ultraviolet (UV) primer may be present as a component chemically combined with the elastomer. That is, the ultraviolet (UV) initiator may be chemically incorporated into the elastomeric component in the form of polymer-bound photoinitiator. Such polymer-bound photoinitiators are described, for example, in U.S. Patent No. 5,128,386, wherein a photoinitiator which is copolymerized with an acrylate copolymer is described. The compositions are curable through the action of ultraviolet (UV) radiation. They are thermally stable at the temperatures used for processing uncured elastomeric formulations, such as in blending or extrusion operations. These temperatures generally range from 25 ° C to 250 ° C. By "thermally stable" is meant that the compositions do not spontaneously form a lattice lattice, that is, they do not cure or burn prematurely. This means that the viscosity of the compositions remains constant, within about 50% of the initial value when heated to the processing temperature, as indicated by the lack of substantial increase in torque (ie less than 1 dNm increase) when subjected to temperature. 30 minutes on a Moving Mold Rheometer. The appropriate processing temperature will depend upon the decomposition temperature of the specific ultraviolet (UV) initiator and the multifunctional crosslinking agent employed. However, the processing temperature must be high enough for the curable elastomeric composition to flow to the degree necessary for the production process. This temperature will generally be from 25 ° C to 250 ° C, preferably from 90 ° C to 170 ° C. The compositions, when heated or subjected to mechanical work, such as screw extruder, gear pump or piston pump, are capable of viscoelastic flow and can be measured and formed into molded articles such as seals. These articles can then be cured by exposure to ultraviolet (UV) radiation.

The elastomeric component of the thermally stable compositions of the present invention may be any of the members of the following classes of crude (i.e. uncured) elastomeric polymers: fluoroelastomers containing copolymerized units of brominated or chlorinated iodine curing site monomers, fluoroelastomers containing copolymerized units of unconjugated dienes, fluoroelastomers containing bromine or iodine atoms in terminal positions of the fluoroelastomer, chlorinated olefin elastomers, chlorosulfonated olefin elastomers and epichlorohydrin elastomers.

Fluoroelastomers suitable for use as an elastomeric component of the compositions of the present invention include fluoroelastomers comprising copolymerized units of one or more fluorine-containing monomers, such as vinylidene fluoride, hexafluoropropylene, 1-hydropentafluoropropylene, 2-hydropentafluoropropylene, tetrafluoroethylene, and perfluoro (alkyl vinyl) ether, as well as other non-fluorine-containing monomers, such as ethylene and propylene. Elastomers of this type are described in Logothetis, Chemistry of Fluorocarbon Elastomers, Prog. Polym Sci., Vol. 14, 251-296 (1989). The polymers may be prepared by polymerizing the appropriate monomer mixtures with the aid of a free radical generating initiator, either by mass, inert solvent solution, aqueous emulsion or aqueous suspension. The polymerizations may be conducted in continuous, batch or semi-batch processes. General preparative processes are described in Logothetis's article and U.S. Patent Nos. 4,281,092, 3,682,872, 4,035,565, 5,824,755, 5,789,509, 3,051,677 and 2,968,649.

Specific examples of such fluoroelastomers include vinylidene fluoride and hexafluoropropylene copolymers and optionally tetrafluoroethylene; vinylidene and chlorotrifluoroethylene fluoride copolymers; vinylidene fluoride copolymers; hexafluoropropylene, tetrafluoroethylene and chlorotrifluoroethylene; tetrafluoroethylene and propylene copolymers; and tetrafluoroethylene and perfluoro (alkyl vinyl) ether copolymers, preferably perfluoro (methyl vinyl) ether. Each of the fluoroelastomers of the composition of the present invention also comprises at least one halogenated curing site or a reactive double bond resulting from the presence of a copolymerized unit of an unconjugated diene. Halogenated curing sites may be copolymerized curing site monomers or halogen atoms that are present at the terminal positions of the fluoroelastomeric polymer chain. Curing site monomers, reactive double bonds, or halogenated terminal groups are capable of reacting to form crosslinks. Curing site monomers are selected from the group consisting of brominated, chlorinated and iodinated olefins, unconjugated dienes and unsaturated brominated, chlorinated and iodinated ethers.

Brominated curing site monomers may contain other halogens, preferably fluorine. Examples are bromotrifluoroethylene, 4-bromo-3,3,4,4-tetrafluorobutene-1 and others, such as vinyl bromide, 1-bromo-2,2-difluoroethylene, perfluoroalyl bromide, 4-bromo-1,1,2 -trifluorobutene, 4-bromo-1,1,3,3,4,4-hexafluorobutene, 4-bromo-3-chloro-1,1,3,4,4-pentafluorobutene, 6-bromo-5,5,6 , 6-Tetrafluorohexene, A-bromoperfluorobutene-1 and 3,3-difluoroalyl bromide. Brominated unsaturated ether curing site monomers useful in the present invention include ethers such as 2-bromo-perfluoroethyl perfluorovinyl ether and fluorinated compounds of the CF2Br-Rf-O-CF = CF2 class, such as CF2BrCF2O-CF = CF2, and ethers fluorovinyl of the ROCF = CFBr or ROCBr = CF2 class, where R is a lower alkyl group or fluoroalkyl group, such as CH3OCF = CFBr or CF3CH2OCF = CFBr.

Iodinated olefins may also be used as curing site monomers. Suitable iodinated monomers include iodinated olefins of the formula: CHR = CH-Z-CH 2 CHR-I, wherein R is -H- or -CH 3; Z is a straight or branched C1 -C8 (per) fluoroalkylene radical, optionally containing one or more oxygen ether atoms, or a (per) fluoropolyoxyalkylene radical, as described in U.S. Patent No. 5,674,959. Other examples of useful iodinated cure site monomers are unsaturated ethers of the formula: I (CH2CF2CF2) nOCF = CF2 and ICH2CF20 [CF (CF3) CF20] nCF = CF2 and the like, where η = 1 to 3, as described in the Patent U.S. Patent No. 5,717,036. In addition, suitable iodinated curing site monomers including iodoethylene, 4-iodo-3,3,4,4-tetrafluorobutene-1; 3-chloro-4-iodo-3,4,4-trifluorobutene, 2-iodo-1,1,2,2-tetrafluoro-1- (vinyloxy) ethane; 2-iodo-1- (perfluorovinyloxy) -1,1,2,2-tetrafluoroethylene; 1,1,2,3,3,3-hexafluoro-2-iodo-1- (perfluorovinyloxy) propane; 2-iodoethyl vinyl ether; 3,3,4,5,5,5-hexafluoro-4-iodopentene; and iodotrifluoroethylene are described in U.S. Patent No. 4,694,045.

Examples of unconjugated diene curing site monomers include 1,4-pentadiene, 1,5-hexadiene, 1,7-octadiene and others such as those described in Canadian Patent No. 2,067,891. A suitable triene is 8-methyl-4-ethylidene-1,7-octadiene.

Among the cure site monomers listed above, preferred compounds include 4-bromo-3,3,4,4-tetrafluorobutene-1; 4-iodo-3,3,4,4-tetrafluorobutene-1; and bromotrifluoroethylene.

Additionally or alternatively, iodine, bromine or mixtures thereof may be present at the ends of fluoroelastomer chains as a result of the use of molecular weight regulators or chain transfer agents during the preparation of fluoroelastomers. Such agents include iodine containing compounds that result in iodine bonded at one or both ends of the polymer molecules. Methylene iodide; 1,4-diiodoperfluoro-n-butane; and 1,6-diiodo-3,3,4,4, tetrafluorohexane are representative of such agents. Other iodinated chain transfer agents include 1,3-diiodoperfluoropropane; 1,4-diiodoperfluorobutane; 1,6-diiodoperfluorohexane; 1,3-diiodo-2-chloroperfluoropropane; 1,2-di (iododifluoromethyl) perfluorocyclobutane; monoiodoperfluoroethane;

monoiodoperfluorobutane; 2-iodo-1-hydroperfluoroethane; etc. Particularly preferred are diiodide chain transfer agents. Examples of brominated chain transfer agents include 1-bromo-2-iodoperfluoroethane; 1-bromo-3-iodoperfluoropropane; 1-Iodo-2-bromo-1,1-difluoroethane and others, such as those described in U.S. Patent No. 5,151,492.

Copolymers of ethylene, tetrafluoroethylene, perfluoro (alkyl vinyl) ether and a bromine-containing curing site monomer such as those described by Moore in U.S. Patent No. 4,694,045 are suitable for use in the present invention. Tetrafluoroethylene and perfluoro (alkyl vinyl) ether copolymers commonly containing fluorinated nitrile curing sites, such as perfluoro (8-cyano-5-methyl-3,6-dioxa-1-octene) and others described in US Patent No. 4,983,697, may also be used. Other useful fluoroelastomers containing brominated or iodinated olefin cure site monomers are described in U.S. Patent Nos. 4,035,565, 4,564,662, 4,745,165, 4,694,045, 4,948,852 and 4,973,633.

Each of these classes of copolymers includes higher order dipolymers or copolymers containing copolymerized units of other comonomers.

Crude fluoroelastomers having Mooney viscosities in the range of 5 to 150, ML 1 + 4 (121 ° C), preferably 10 to 70, ML 1 + 4 (121 ° C) have been found to be particularly useful in the compositions of the present invention. . Compositions in which the fluoroelastomer has Mooney viscosity within the preferred range exhibit an ideal balance of tensile properties and processability.

It has also been found that compositions containing fluoroelastomers with copolymerized curing site monomer unit levels in the range of 0.05 to 10.0 wt% exhibit better curing status.

Chlorinated olefin polymers are also suitable for use as an elastomeric component of the compositions of the present invention. Chlorinated olefin polymers also specifically include chlorosulfonated olefin polymers. "Olefin polymers" means C2 -C6 homopolymers and copolymers of alpha monoolefins, including graft copolymers. The copolymers may be higher order dipolymers or copolymers, such as terpolymers or tetrapolymers. The olefin polymers may be branched or unbranched and may be prepared by free radical processes, Ziegler-Natta catalysis or catalysis with metallocene catalyst systems such as those described in U.S. Patent Nos. 5,272,236 and 5,278,272. . Particularly useful examples of olefin polymers include C2 -C3 alpha monoolefin homopolymers, ethylene and carbon monoxide copolymers and ethylene copolymers and at least one ethylenically unsaturated monomer selected from the group consisting of C3-C20 alpha monoolefins, C1 esters -C12 alkyl and unsaturated C3 -C20 monocarboxylic acids, unsaturated C3 -C20 mono or dicarboxylic acids, unsaturated C4 -C8 dicarboxylic acid anhydrides and vinyl esters of saturated C2 -C18 carboxylic acids. Specific examples of such polymers include ethylene vinyl acetate copolymers, polypropylene, polyethylene, ethylene acrylic acid copolymers, methacrylic acid and ethylene copolymers, methylene ethyl acrylate copolymers, methyl methacrylate copolymers, methacrylate copolymers of ethylene n-butyl, glycidyl ethylene methacrylate copolymers, maleic anhydride graft copolymers and ethylene, maleic anhydride graft copolymers and propylene and ethylene copolymers with propylene, butene, 3-methyl-1-pentene, hexene or octeno. Preferred olefin polymers are polyethylene, propylene and ethylene copolymers, butene and ethylene copolymers, ethylene and octene copolymers, ethylene and acrylic acid copolymers, ethylene and methacrylic acid copolymers and ethylene and vinyl acetate copolymers. Olefin polymers have average numerical molecular weights in the range of 1,000 to 300,000, preferably from 50,000 to 300,000. Chlorinated and chlorosulfonated olefin polymers contain chlorine contents from about 15 wt% to about 70 wt%. Chlorosulfonated olefin polymers contain sulfur contents of 0.5 to 10 wt%, preferably 1 to 3 wt%.

Chlorinated or chlorosulfonated olefin polymers can be prepared from olefin polymers by free radical initiated chlorination and chlorosulfonation. Chlorination of olefin polymers can take place at temperatures of 50 ° C to 150 ° C and at pressures of 1 to 10 atmospheres using chlorine gas as the chlorinating agent. In chlorination of solutions, the reaction medium is an inert solvent such as carbon tetrachloride, chlorinated benzene, chloroform or fluorobenzene. Alternatively, aqueous or organic slurry chlorination may be used. Fluidized bed processes are also known as well as fusion processes. Chlorosulfonation of olefin polymer starting materials may be carried out in solution under similar conditions using chlorine gas and sulfur dioxide, sulfuryl chloride or a combination of chlorine, sulfur dioxide and sulfuryl chloride. Commercially available chlorinated and chlorosulfonated olefin polymers include Tyrin® chlorinated polyethylene, Hypalon® chlorosulfonated polyethylene and Acsium® chlorosulfonated polyethylene, all available from DuPont Dow Elastomers L. L. C.

Epichlorohydrin elastomers which are suitable for use as an elastomeric component of the compositions of the present invention include polypichlorohydrin copolymers and homopolymers comprising copolymerized units of epichlorohydrin and ethylene oxide. Terpolymers containing curing site monomers, such as allyl glycidyl ether, may also be used. Such compositions generally contain about 20 to 45% by weight of chlorine. Commercially available examples include Epichlomer® rubber manufactured by Daiso Epichlo Rubber Co. Ltd., Japan, and Epichlorohydrin Hydrin® rubber manufactured by Nippon Zeon Co. Ltd., Japan.

The elastomeric component of the compositions of the present invention may be a mixture of elastomers as well as an isolated elastomer. The mixtures may be mixtures of polymers of the same class, such as a brominated fluoroelastomer and an iodinated fluoroelastomer, or may be mixtures of more than one type of elastomer, such as a chlorinated polyolefin rubber and an ethylene copolymer rubber. Mixtures in which only one elastomer is capable of curing by exposure to ultraviolet (UV) radiation are also contemplated by the present invention. Mixing compositions will be particularly useful for balancing physical properties. It would be desirable, for example, to balance curable state with fuel resistance by mixing fluoroelastomers with epichlorohydrin rubbers. In other circumstances, mixtures of expensive polymers with less expensive polymers often generate a combination of properties suitable for less demanding applications. In this context, mixtures of fluoroelastomers and nitrile rubber or fluoroelastomers and copolymer ethylene acrylate elastomers would be suitable for use as an elastomeric component of the compositions of the present invention. The Mooney viscosities of the mixtures will preferably be in the range of 1 to 150 ° C, within which range the mixtures will be suitable for use in the process of the present invention for the production of general rubber articles such as seals.

In addition to an elastomeric component, the curable compositions of the present invention also include at least one multifunctional crosslinking agent. Preferably, the multifunctional crosslinking agent will be an acrylic or methacrylic crosslinking agent. In addition, it may be a multifunctional cyanurate or multifunctional isocyanurate, such as triallyl isocyanurate or triallyl cyanurate. By "multifunctional acrylic or methacrylic crosslinking agent" is meant an ester which is a reaction product of a polyhydroxyl compound, generally a polyhydroxyl alcohol, and acrylic acid or methacrylic acid, wherein the crosslinking agent has at least two carbon-carbon double bonds. Such compositions are commonly referred to in the art as multifunctional acrylates or multifunctional methacrylates. Typical multifunctional acrylates and methacrylates have molecular weights of 150 to 1,000 and contain at least two polymerizable unsaturated groups per molecule.

Representative multifunctional acrylic crosslinking agents include acrylates and methacrylates, such as ethylene glycol diacrylate; ethylene glycol dimethacrylate; 1,6-hexanediol diacrylate; 1,6-hexanediol dimethacrylate; 1,4-butanediol diacrylate; pentaerythritol triacrylate; pentaerythritol tetraacrylate; dipentaerythritol pentaacrylate; methoxy-1,6-hexanediolpentaerythritol triacrylate; trimethylolpropane triacrylate; tetraethylene glycol diacrylate; polymethacrylate urethanes; epoxy acrylates; polyester acrylate oligomers and monomers; trimethylolpropane triacrylate propoxylate; poly-n-butylene glycol oxide diacrylates; and bisphenol A alkylene oxide adduction diacrylates. Trimethylolpropane triacrylate and trimethylolpropane trimethacrylate are preferred crosslinking agents as these compounds are readily available. In addition, compression adjustment and crosslinking density are increased in compositions containing such crosslinking agents as compared to compositions containing difunctional acrylates such as diethylene glycol dimethacrylate.

Multifunctional acrylic and methacrylic crosslinking agents are capable of homopolymerization when irradiated. Thus, when curable compositions of the present invention containing multifunctional acrylates or methacrylates are exposed to ultraviolet (UV) radiation 1 two reactions occur simultaneously. The multifunctional crosslinking agent reacts with the elastomeric polymer component to form interchain and intrachain crosslinks, resulting in a rubber matrix. In addition, excess multifunctional crosslinking agent will homopolymerize (homopolymerize) and form an interpenetrating lattice that acts to reinforce the rubber matrix, much like that in which charges reinforce elastomers. It is therefore possible to control the hardness of the final cured product by adjusting the proportion of multifunctional crosslinker present in the curable composition. Generally, difunctional acrylates and methacrylates are less efficient crosslinking agents compared to their analogs which have greater functionality. Accordingly, crosslinking agents of the class having greater functionality are preferred for the purposes of the present invention.

Elastomeric materials combined and cured according to methods commonly used in rubber processing technology generally contain carbon black or mineral fillers as reinforcing agents. Reinforcement is reflected in properties such as hardness, modulus and tensile strength. Generally, reinforced elastomers are characterized by nonlinear pressure / stress dependence. On the other hand, non-reinforced elastomeric compositions are characterized by the accumulation of initial stress under low strain, which does not substantially increase at higher strain. In addition, unreinforced elastomeric compositions tend to break at relatively low end tensile strength.

The use of fillers in ultraviolet (UV) initiated reactions would normally be expected to interfere with the ultraviolet (UV) curing process. The present process allows, however, the cure of translucent compositions. Thus, the compositions of the present invention may contain limited amounts of fillers, generally not more than 15 parts by weight per hundred parts of polymer. Reinforcement is carried out simultaneously with crosslinking through the formation of an interpenetrating network. The resulting product exhibits stress / pressure behavior that is more linear than traditional elastomers, which contain fillers that are not chemically bonded to the elastomeric matrix.

The amount of multifunctional crosslinking agent present in the compositions of the present invention will depend on the specific elastomer used. Generally, the amount ranges from 0.5 to 25% by weight based on the combined weight of polymer, multifunctional crosslinking agent and ultraviolet (UV) initiator.

The third component of the curable compositions of the present invention is an ultraviolet (UV) initiator. This can be selected from the organic chemical compounds conventionally employed to promote ultraviolet (UV) initiated formation of radicals, either by cleavage of the intramolecular homolytic union or by intermolecular hydrogen abstraction. These agents include organic compounds containing aryl carbonyl or tertiary amino groups. Suitable compounds for use include benzophenone; acetophenone; benzyl; benzaldehyde; ortho-chlorobenzaldehyde; xanthone; thioxanthone; 9,10-anthraquinone; 1-hydroxycyclohexyl phenyl ketone; 2,2-diethoxyacetophenone; dimethoxyphenyl acetophenone; methyl diethanolamine; dimethylaminobenzoate; 2-hydroxy-2-methyl-1-phenylpropane-1-one; 2,2-di-sec-butoxyacetophenone; 2,2-dimethoxy-1,2-diphenylethan-1-one; benzyl dimethoxy ketal; benzoin methyl ether; and phenyl gloxal. Upon exposure to ultraviolet (UV) radiation, a series of photochemical transformations can occur, with the ultraviolet (UV) initiator forming, for example, reactive free radical fragments that react with acrylate or methacrylic crosslinking terminal groups multifunctional. This initiates polymer cross-linking as well as homopolymerization of the acrylic or methacrylic crosslinking agent. A preferred ultraviolet (UV) primer is 1-hydroxycyclohexyl phenyl ketone because of the rapidity with which it generates free radicals when exposed to ultraviolet (UV) radiation. Mixtures of ultraviolet (UV) primers may also be used. This is often desirable because it provides more efficient radical production in certain cases.

Generally, the ultraviolet (UV) initiator will be present in an amount from 0.1 to 10.0% by weight based on the total weight of polymer, multifunctional crosslinking agent and ultraviolet (UV) initiator. It is preferable, however, to use from 0.5 to 2.5 wt% ultraviolet (UV) initiator, more preferably 0.5 to 1.0 wt% ultraviolet (UV) initiator, based on weight. total polymer, crosslinker and ultraviolet (UV) initiator, as high levels of photoinitiator tend to interfere with penetration and do not substantially contribute to the overall crosslink density. Within the ranges described herein, there is an optimal level of photoinitiator for each specific combination of uncured gum elastomer and crosslinker. These ideal levels can easily be determined by those skilled in the art. Hydrogenated nitrile rubber, for example, will generally require a higher level of photoinitiator than a copolymer of ethylene, methyl acrylate and ethyl hydrogen maleate. Higher levels of photoinitiator increase the crosslinking density on the surface of the cured composition. Low levels of photoinitiators may result in better (ie lower) compression adjustments for samples that are several millimeters thick.

In addition, for the purposes of the present invention, the processing temperature should not exceed the temperature at which thermal degradation of the ultraviolet (UV) initiator occurs. In some cases, such degradation would result in singed compositions due to free radical formation. This is because thermally induced initiator fragmentation in processing equipment results in premature elastomer crosslinking. In other cases, slow curing compositions would result due to deactivation of the initiator. Degradation temperatures will differ for each specific ultraviolet (UV) primer. Depending on the type of rubber and the amount of additives, the processing temperature will range from 25 ° C to 250 ° C. It is an object of the present invention to provide stable elastomeric compositions which can be applied to a substrate at temperatures up to 250 ° C. An additional practical limitation of the processing temperature is that the temperature should not exceed the softening point of the substrate to which it is applied.

The elastomeric component, multifunctional crosslinking agent component and ultraviolet (UV) initiator component are present in the compositions of the present invention for specific relative reasons. Where the elastomeric component of the composition is a fluoroelastomer, the elastomer will be present in an amount of 70 to 99% by weight based on the total weight of elastomer, crosslinker and ultraviolet (UV) initiator. The multifunctional crosslinking agent is present in an amount of 0.5 to 20% by weight based on the total weight of elastomer, crosslinking agent and ultraviolet initiator (UV). Finally, the ultraviolet (UV) initiator is present in an amount from 0.1 to 10% by weight based on the total weight of elastomer, crosslinker and ultraviolet (UV) initiator. Preferably, the elastomeric component will be present in an amount of from 75 to 95% by weight based on the total weight of elastomer, crosslinker and ultraviolet (UV) initiator. The crosslinker level determines the compressive strength and hardness of the curable composition of the present invention. Preferably, the multifunctional crosslinker is present in an amount of from 4 to 15% by weight based on the weight of ultraviolet (UV) elastomer, crosslinker and initiator. If less than about 4% by weight of crosslinker is present, a composition having reasonably low hardness and relatively high compressive strength is formed. More than about 15% by weight of crosslinker results in high modulus cured composition, low breaking elongation and poor compressibility of the cured composition. Such compositions are less desirable for sealing use, especially joint applications. The specific range of components selected will therefore depend on the specific end use contemplated.

When chlorinated olefin polymers, chlorosulfonated olefin polymers or epichlorohydrin rubbers are used as the elastomeric component of the composition, the elastomer will be present in an amount of 80 to 97% by weight based on the total weight of elastomer, crosslinker and initiator. ultraviolet (UV). The multifunctional crosslinking agent is present in an amount of 2 to 19.5% by weight based on the total weight of elastomer, crosslinking agent and ultraviolet initiator (UV). The ultraviolet (UV) initiator is present in an amount of 0.2 to 5.0 wt.%, Based on the total weight of elastomer, crosslinking agent and ultraviolet (UV) initiator. Preferably, the elastomeric component will be present in an amount of from 85 to 95% by weight, based on the total weight of the ultraviolet (UV) elastomer, crosslinker and initiator. Preferably, the crosslinker will be present in an amount of 3 to 15% by weight based on the total weight of elastomer, crosslinker and ultraviolet (UV) initiator. If less than 3% by weight of crosslinker is present, generally a cured composition having relatively high compression adjustment results. More than 15% by weight of crosslinker results in a high level of homopolymerized acrylic or methacrylic crosslinker, producing a highly crosslinked highly hardened elastomeric matrix, low compressibility and low elongation at break. As with the other compositions of the present invention, the specific range of components selected will therefore depend upon the specific end use contemplated. Various additives commonly used in the rubber composition may be incorporated into the compositions of the present invention to modify, stabilize and reinforce them. Preferably, such additives will be used in amounts that do not substantially interfere with the crosslinking reaction of the uncured polymeric component. If large amounts of fillers that are opaque to ultraviolet (UV) radiation are used, for example, the loaded compositions will not cure regularly or only the surface of the composition will be cured. Normally, fillers in amounts of up to about 15 parts per 100 parts of elastomer may be employed. Typical examples include non-black fillers such as minerals or glass fibers. High efficiency reinforcing polymeric fillers such as aramid fibers and polytetrafluoroethylene can also be used, usually at low levels. It is preferable that the presence of additives does not raise the viscosity of the curable composition used in the process of the present invention to more than ML 1 + 4 (100 ° C) of 150 nor reduce it to less than ML 1 + 4 (100 ° C). Compositions outside this range are not suitable for the jointing process of the present invention.

Where the polymeric component is a fluoroelastomer, the preferred curable compositions of the present invention will include 0.01 to 2.0 parts by weight per hundred parts by weight of fluoroelastomer of an organotin hydride. Compositions in which this additive is present exhibit excellent cure profiles. This means that the healing speed increases rapidly after initiation and the healing state remains high throughout the healing process. Preferably, 0.1 to 1 parts by weight of organotin hydride per one hundred parts by weight of fluoroelastomer will be used. Tri-n-butyltin hydride is preferred. Small amounts of inhibitors may also be present in the compositions of the present invention as a result of the presence of these additives in commercial samples of acrylic or methacrylic crosslinking agents. Inhibitors are generally present in small amounts, for example below 1500 ppm (parts per million based on crosslinker weight). They act to prevent thermally induced polymerization of crosslinking agents during storage and shipping.

The compositions of the present invention are particularly suitable for manufacturing elastomeric joints and seals in situ using a technique which we refer to in the present on-site jointing. According to this technique, a curable elastomeric composition is heated to a temperature of 25 ° C to 250 ° C, preferably 90 ° C to 170 ° C. The heated composition is then measured on a substrate to form an uncured seal of desired thickness which is then cured. Thus, the seal is formed on site, directly over the object to be sealed, and not in a separate molding step. Typically, uncured seals are formed in thicknesses from 1 to 15 mm, preferably in thicknesses from 2 to 8 mm.

Robotic hot melt equipment may be used to apply joints on site. In one embodiment of the process of the present invention, a curable composition comprising a low viscosity elastomeric component, multifunctional crosslinking agent and ultraviolet (UV) initiator is introduced into a drum containing a heated plate and a piston. The composition, when heated, becomes soft and extrusable. It is forced out of the drum by the action of the piston, usually under relatively low pressures, typically less than 5.0 bars (ie 0.5 MPa). The composition is then fed by gear or piston pumping through heated tubing to an application gun fitted to a multidimensional industrial robot capable of quick and accurate measurement. In this way, the composition can be introduced into a one-part slot such as a thermoplastic article that has just been produced, for example by molding. The uncured elastomer ball in the groove rapidly solidifies as it cools and forms an uncured sealing member. The groove may be of a part also made of other materials, including but not limited to metals. Alternatively, the composition may be deposited on the outside of an object to form a seal. This hot melt application method is preferred for low viscosity elastomers, generally with Mooney viscosity from 1 to 20 ML 1 + 4 (100 ° C). The method allows extrusion of a drum using relatively low pressures. Metering and continuous feed pumps are capable of handling compositions of the present invention having viscosities of up to 1000 Pa.s. High melt equipment may be used for compositions having slightly higher viscosities, such as ML 1 + 4 (100 ° C) of 70, by employing an extruder to introduce the composition into the heated tubing. Its viscosity is low, which allows seals to form from the higher viscosity compositions.

In another embodiment of the process of the present invention, relatively high viscosity compositions or relatively low heat resistance compositions may be molded as uncured seals by joining technique in place. Instead of using hot melt equipment, only screw extruders are used to provide the elastomeric composition to the article to be sealed. This technique is particularly useful when using Mooney 10-90 viscosity chlorinated elastomers and chlorinated elastomers (ML 1 + 10 (1210C)) as the elastomeric component of the present invention. An extruder that is used in combination with a flexible arm to apply an uncured elastomer ball to a groove is particularly preferred for such in-place washer processes. It differs from conventional extruder technology in that the extruder is not used to form the finished part. Instead, it pumps the uncured elastomeric composition to a robotic application head that measures the composition and deposits it at the location to be sealed. The use of screw extruders results in relatively high energy input to the polymer compared to processes using hot melt equipment. In order to minimize degradation of the elastomer in the extruder, the extrusion process should not cause the compound temperature to rise above 250 ° C. This usually requires slow extrusion speeds. Consequently, extrusion processes are generally slower methods of manufacturing. In addition, this equipment requires high investment costs. Those skilled in the art will recognize that the appropriate extrusion temperature will depend upon the viscosity of the uncured elastomer, the molecular weight of the uncured elastomer, the crosslinking agent level, the photoinitiator decomposition temperature, and the crosslinking agent volatilization temperature. a value in the range of 25 ° C to 250 ° C that is ideal for the specific circumstances.

The gasketing process of the present invention may be employed for the manufacture of seals and gaskets using the compositions of the present invention or other curable elastomer compositions. Generally, the elastomeric component will be present in an amount of 70 to 99 parts by weight, the multifunctional crosslinker will be present in an amount of 0.5 to 29 parts by weight and the ultraviolet (UV) initiator will be present in an amount of 0.1 to 99 parts. 10 parts by weight, all based on combined weight of elastomer, crosslinker and ultraviolet (UV) initiator. The processes may be used, for example, to form joints from fluoroelastomer compositions comprising a fluoroelastomer, multifunctional crosslinker and ultraviolet (UV) initiator, wherein the fluoroelastomer component of the composition does not contain a curing site monomer. brominated, iodinated, chlorinated or unconjugated copolymerized diene, or iodinated or brominated polymeric end groups. Such copolymers are commercially available and include hexafluoropropylene vinylidene fluoride dispolymers; vinylidene fluoride, hexafluoropropylene and tetrafluoroethylene terpolymers; and tetrafluoroethylene and propylene copolymers. In addition, alpha olefin and ethylene elastomers, such as elastomeric copolymers and ethylene interpolymers with one or more comonomers selected from propylene, 1-butene, 1-hexene, 1-octene, 4-methyl-1-pentene and other C3-C20 alpha olefins are suitable elastomeric components in the ultraviolet (UV) curable composition. Elastomeric ethylene copolymers, a C3 -C8 olefin and a diene may also be used in the process of the present invention. These copolymers may be higher order copolymer terpolymers, tetrapolymers or elastomers of the ethylene / C3 -C8 alpha-olefin / diene type. These elastomers are ethylene copolymers, a C3 -C8 alpha-olefin and at least one unconjugated diene. They may additionally contain a small amount, usually up to 10% by weight, of at least one (different) diene or triene containing copolymerizable double bonds. Preferred C3 -C8 alpha olefins are propylene and butene. Unconjugated dienes of the first type include 1,4-hexadiene; 2-methyl-1,5-hexadiene; norbornene vinyl; 8-methyl-4-ethylidene-1,7-octadiene; 1,9-octadecadiene; dicyclopentadiene; tricyclopentadiene; 5-ethylidene-2-norbornene; or 5-methylene-2-norbornene. Preferred dienes containing a reactive double bond are 1,4-hexadiene, dicyclopentadiene and ethylidene norbornene. Unconjugated dienes of the second type include norbornadiene; 1,4-pentadiene; 1,5-hexadiene; 1,7-octadiene; 1,2-henicosadiene; or 5- (5-hexenyl) -2-norobornene, preferably norbornadiene. These polymers are generally produced by polymerization in the presence of Ziegler-Natta catalysts or by polymerization in the presence of metallocene catalysts. Preparative techniques for alpha-olefin and ethylene elastomers prepared in the presence of metallocene catalysts can be found in U.S. Patent Nos. 5,278,272 and 5,272,236. Typical alpha-olefin and ethylene copolymers and EPDM elastomers are commercially available as Engage® polyolefin elastomers and Nordel® hydrocarbon rubbers via DuPont Dow Elastomers LLC The ratio of elastomer, multifunctional crosslinker and ultraviolet (UV) initiator will generally be in the weight range of 70-99: 0.5-19.5: 0.1-10, respectively, when the elastomer is a fluoroelastomer, and 80-98: 1-20: 0.2-5.0 respectively, when the elastomer is an alpha-olefin and ethylene elastomer or an EPDM elastomer.

In order to optimize the elastomeric properties of seals manufactured by the process described above, they may be cross-linked, i.e. cured. It would be impractical to use a heat-activated curing system to perform rapid crosslinking reaction in these processes. It would be risky to convert the curable composition used to form the seals into an intractable crosslinked material during the measurement step. Specifically, as the curable composition was heated or subjected to temperature rise caused by mechanical work, the crosslinking reaction would be initiated. It would be difficult to control premature gel formation (ie burn) during measurement. As crosslinked compositions do not flow easily, processes that result in singed products are undesirable. Consequently, heterolytic curing systems, which depend on thermally induced crosslinking reactions, are not suitable for the present process. In addition, the most common homolytic curing processes, ie free radicals, which depend on thermal decomposition of peroxides, are also unsuitable for use in the present process. It has been found, however, that curable compositions utilizing the process of the present invention can be effectively cured by ultraviolet (UV) induced free radical processes.

Ultraviolet (UV) curing of elastomeric compositions by using the process of the present invention may be achieved at room temperature or at higher temperatures. In certain circumstances where the elastomeric composition is to be used as a sealant, for example, it may be desirable to photocure immediately upon application of the uncured composition to the object to be sealed. At that time, the temperature of the composition may be up to 250 ° C. Heating of the curable composition, however, is neither necessary nor particularly desirable for effective photocure. In addition, when the compositions are used to form seals by the technique of placing joints in place on thermoplastic articles, low temperature curing minimizes any possibility of thermal degradation or distortion of the thermoplastic. In addition, ultraviolet (UV) irradiation in an inert atmosphere is not required. The cure reaction may be conducted under atmospheric conditions without deleterious effects. In addition, it has also been found that in some cases, particularly when curing chlorinated or chlorosulfonated polyolefins, curing the composition under water is preferable to minimize heat buildup. This minimizes the tendency of dehydrochloride hydration of these polymers, a process that causes polymer degradation and discoloration and inhibits ultraviolet (UV) curing.

For purposes of the process of the present invention, the spectrum of radiation wavelengths used to effect the curing reaction typically corresponds to the maximum absorption of the ultraviolet (UV) primer. This typically ranges from about 200 to 400 nanometers. Suitable sources of ultraviolet (UV) radiation include medium pressure mercury vapor lamps, electrode-free lamps, pulsed xenon lamps, and hybrid mercury and xenon vapor lamps. A preferred arrangement comprises one or more lamps together with a reflector, which diffuses radiation evenly along the surface to be irradiated. The radiation dosage should be sufficient to cure the polymeric compositions, i.e. to produce a cured composition having a compression setting of 90 or less, preferably 50 or less, and breaking elongation of at least 100%. Dosage of at least about 10 Joules per square centimeter and preferably 20 Joules is usually sufficient for optimal cure. The dosage is a function of the time of exposure to ultraviolet radiation (UV), distance from the source of ultraviolet radiation (UV) and the power level of the radiation source. The required radiation dose can be readily determined by curing small samples of the curable composition and measuring physical properties such as tensile strength, compression fit and post-cure elongation. In most cases, an acceptable degree of cure can be achieved by exposures of 30 to 300 seconds using a lamp of about 80 W / cm. Appropriate adjustments can be made depending on the lamp power, output distribution over the ultraviolet (UV) range and sample thickness as well as the polymeric component, level of crosslinker present and level of charge present. Charge-containing ethylene acrylate copolymer rubber, for example, would require longer cure time than the same uncharged composition.

Foaming agents may be incorporated into the curable compositions of the present invention. In such circumstances, a cellular structure will be formed by exposing the curable composition to ultraviolet (UV) radiation as a result of the simultaneous heating induced thermal decomposition of the foaming agent that occurs during exposure to ultraviolet (UV) light. This heating phenomenon can be magnified and controlled by the additional external application of heat. Typical foaming agents which may be employed include ρ, ρ'-oxybenzenzenesulfonyl hydrazine, azodicarbonamides, p-toluenesulfonyl semicarbazides and dinitrosopentamethylene tetramine. Alternatively, the ultraviolet (UV) curing reaction may also be performed by cooling so that curing and foaming occurs in sequence rather than simultaneously. This means that the curable composition is exposed to ultraviolet (UV) radiation upon cooling and the cured composition is then passed through a hot air tunnel to cause foaming. Closed cell structures of low specific gravity can be prepared by these processes. For example, structures with specific gravities of 0.25 to 6.0 g / cm3 can be obtained.

Low viscosity compositions of the present invention may be used as coating compositions for solvent free systems or systems having low levels, i.e. up to about 2 wt% solvent, based on total elastomer weight, multifunctional crosslinker and ultraviolet (UV) primer. It is therefore not necessary to shape films from polymeric solutions. In contrast, the low viscosity curable composition flows to the substrate through the application of heat. The ideal ratio of elastomer, multifunctional crosslinking agent and ultraviolet (UV) initiator for coating compositions will be different from that of compositions useful in the manufacture of seals and joints. A relatively thin coating, for example, will cure faster and allow the use of relatively high levels of ultraviolet (UV) primer, as opacity will not be a problem. In addition, higher levels of multifunctional crosslinking agents can be used to reduce viscosity and allow easier processing, as coating compositions can tolerate greater hardness than jointing materials. In addition, the coating compositions do not require the compressive strength that is required for seals and joints.

The curable elastomeric compositions of the present invention are useful in the manufacture of general rubber products, coating compositions, foams and wire coating. They are most advantageously used, however, in the preparation of seals and gaskets for thermoplastic articles, particularly those employed in automotive applications.

The present invention is illustrated by the following specific embodiments, wherein all parts are by weight unless otherwise indicated.

Examples

Example 1

A curable elastomeric composition of the present invention, Sample 1A, was prepared by mixing the following components in a rubber mill: 94 parts of a vinylidene fluoride (VF2) 1 perfluoromethylvinyl ether (PMVE), tetrafluoroethylene (TFE) copolymer and 4-bromo-3,3,4,4-tetrafluorobutene-1 (BTFB) (weight ratio VF2-TFEPMVEIBTFB 54: 10: 35: 1,2), 6.0 parts trimethylolpropane triacrylate and 0.5 parts Irgacure 1800® photoinitiator. The milled composition was molded into 2mm thick uncured thick slices by molding into a Teflon® fluoropolymer resin coated mold. An uncured thick slice was exposed for one minute to ultraviolet (UV) radiation from a medium pressure mercury lamp that emitted radiation of about 250 to 400 nm at 80 watts / cm. The distance between the samples and the lamp was 10 cm. The cured samples exhibited the properties described in Table I. Two additional samples, 1B and 1C, were prepared in substantially the same manner except that Sample 1B contained 8 parts of trimethylolpropane triacrylate and Sample 16C contained 0.5 parts of tri-n-butyl tin hydride in addition to the six parts trimethylolpropane triacrylate. Samples 16B and 16C were cured in substantially the same manner as Sample 16A. The physical properties of cured thick slices are shown in Table I.

Table I

<table> table see original document page 35 </column> </row> <table>

Example 2

A curable elastomeric composition of the present invention, Sample 2A, was prepared by mixing the following components in a rubber mill: 94 parts of a VF2, PMVE1 TFE and BTFB iodinated copolymer (VF2: TFE: PMVE: BTFB weight ratio 54: 10: 35: 0.6, prepared in the presence of an iodinated chain transfer agent containing iodine content of 0.18), 6.0 parts trimethylolpropane triacrylate and one part Irgacure 1800® photoinitiator. The milled composition was molded into 2mm thick uncured thick slices by molding into a Teflon® fluoropolymer resin coated mold. An uncured thick slice was exposed for one minute to ultraviolet (UV) radiation from a medium pressure mercury lamp that emitted radiation of about 250 to 400 nm at 80 watts / cm. The distance between the samples and the lamp was 10 cm. The cured samples exhibited the properties described in Table II. Three additional samples, 2B, 2C and 2D, were prepared in substantially the same manner, except that each contained 0.5 parts of Irgacure 1800, Sample 17B contained 94 parts of a VF2 iodine-free copolymer, PMVE. , TFE and BTFB which has a monomer ratio of 54: 10: 35: 1,2; Sample 17C contained 94 parts of a VF2, PMVE, TFE and BTFB iodine free copolymer having a monomer ratio of 52.9: 10.2: 34.9: 2.2; and Sample 17D contained 94 parts of a VF2, PMVE, TFE and BTFB iodine free copolymer having a monomer ratio of 53.5: 10: 34.4: 2.2. Samples 2B to 2D were cured in substantially the same manner as Sample 2A. The physical properties of cured thick slices are shown in Table II.

Table II

<table> table see original document page 36 </column> </row> <table> Example 3

A curable elastomeric composition of the present invention, Sample 3A, was prepared by mixing the following components in a rubber mill: 92 parts of a VF2, PMVE1 TFE and BTFB copolymer (VF2: TFE: PMVE: BTFB 52 weight ratio , 9: 10.2: 34.9: 2.0), 8.0 parts trimethylolpropane triacrylate and 0.5 parts Irgacure 1800® photoinitiator. The milled composition was molded into 2mm thick uncured thick slices by molding into a Teflon® fluoropolymer resin coated mold. An uncured thick slice was exposed for one minute to ultraviolet (UV) radiation from a medium pressure mercury lamp that emitted radiation of about 250 to 400 nm at 80 watts / cm. The distance between the samples and the lamp was 10 cm. The cured samples exhibited the properties described in Table III. An additional sample, 3B, was prepared in substantially the same manner. However, Sample 3B contained 100 parts polymer and additionally contained 0.5 parts tri-n-butyltin hydride. Sample 3B was cured in substantially the same manner as Sample 3A. The physical properties of the cured slices are shown in Table III.

Table III

<table> table see original document page 37 </column> </row> <table> <table> table see original document page 38 </column> </row> <table>

Example 4

A curable elastomeric composition of the present invention, Sample 4A, was prepared by mixing the following components in a rubber mill: 92 parts of a VF2, PMVE, TFE and BTFB copolymer (VF2: TFE: PMVE: BTFB weight ratio 53.5: 10: 34.4: 2.2), 8.0 parts trimethylolpropane triacrylate and 0.5 parts Irgacure 1800® photoinitiator. The milled composition was molded into 2mm thick uncured thick slices by molding into a Teflon® fluoropolymer resin coated mold. An uncured thick slice was exposed for one minute to ultraviolet (UV) radiation from a medium pressure mercury lamp that emitted radiation of about 250 to 400 nm at 80 watts / cm. The distance between the samples and the lamp was 10 cm. The cured samples exhibited the properties described in Table IV. An additional sample, 4B, was prepared in substantially the same manner. However, Sample 4B contained 100 parts polymer, 1 part Irgacure 1800® photoinitiator and additionally 1 part tri-n-butyltin hydride. Sample 4B was cured in substantially the same manner as Sample 4A. The physical properties of cured thick slices are shown in Table IV. Table IV

<table> table see original document page 39 </column> </row> <table>

Example 5

A curable elastomeric composition of the present invention, Sample 5, was prepared by mixing the following components in a rubber mill: 90 parts of a chlorosulfonated polyethylene elastomer [chlorine content 29% by weight, sulfur content 1, 4% by weight and Mooney ML 1 + 4 (100 ° C) viscosity of 22], 10.0 parts trimethylolpropane triacrylate and 0.5 parts Irgacure 1800® photoinitiator (1-hydroxycyclohexyl phenyl ketone, available from Ciba Geigy , Inc.). The milled composition was shaped into 2 mm thick uncured thick slices for the preparation of stress test samples and 6 mm thickness for cutting compression adjustment discs. The slices were molded by molding into a Teflon® fluoropolymer resin coated mold. The uncured slices were exposed to ultraviolet (UV) radiation from a medium pressure mercury lamp that emitted radiation of wavelengths from about 250 to 400 nm at 80 watts / cm. The 2 mm slices were exposed for four minutes and the 6 mm thick slices were exposed for six minutes. Exposure was performed under water to limit heat buildup in the elastomeric composition, which could cause excessive dehydration and polymer degradation. The distance between the samples and the lamp was 10 cm. The cured samples exhibited the properties described in Table V.

Table V

<table> table see original document page 40 </column> </row> <table>

1 6 mm thick slices in water.

Example 6

A curable elastomeric composition of the present invention, Sample 6, was prepared by mixing the following components in a rubber mill: 85 parts of a chlorinated polyethylene elastomer (36% by weight chlorine content and Mooney ML 1 + 4 viscosity) (121 ° C) from 36), 15 parts trimethylolpropane triacrylate, 1 part Irgacure 1800® photoinitiator and 0.5 parts Naugard® 445 (4,4, -bis- (α, dimethylbenzyl) diphenylamine) antioxidant . The milled composition was shaped into 2 mm thick uncured thick slices for the preparation of stress test samples and 6 mm thickness for cutting compression adjustment discs. The thick slices were molded by molding into a Teflon® fluoropolymer resin coated mold. A thick uncured slice was exposed for four minutes under water to limit heat buildup in elastomeric compositions to the ultraviolet (UV) radiation of a medium pressure mercury lamp that emitted wavelength radiation of about 250 to 400 nm at 80 watts / cm. The distance between the samples and the lamp was 10 cm. The cured samples exhibited the properties described in Table VI.

Table VI

<table> table see original document page 41 </column> </row> <table> 1 6 mm thick slices in water.

Example 7

A curable elastomeric composition of the present invention, Sample 7, was prepared by mixing the following components in a rubber mill: 90 parts Hydrin®C 2000L epichlorohydrin elastomer (an ethylene oxide / epichlorohydrin copolymer, 26% by weight chlorine content, Mooney viscosity 65 available from Nippon Zeon1 Inc.), 10.0 parts trimethylolpropane triacrylate and 0.75 parts Irgacure 184® photoinitiator (1-hydroxycyclohexyl phenyl ketone available from Ciba Geigyl Inc.). The milled composition was shaped into 2 mm thick uncured thick slices for the preparation of stress test samples and 6 mm thickness for cutting compression adjustment discs. The slices were molded by molding into a Teflon® fluoropolymer resin coated mold. A thick uncured slice was exposed for four minutes in water to ultraviolet (UV) radiation from a medium pressure mercury lamp that emitted radiation of about 250 to 400 nm at 80 watts / cm. The distance between the samples and the lamp was 10 cm. The cured samples exhibited the properties described in Table VII.

Table VII

<table> table see original document page 42 </column> </row> <table> <table> table see original document page 43 </column> </row> <table>

1 6 mm slices in water.

Claims (3)

1. PROCESS OF APPLICATION OF Sealing TO AN ARTICLE, characterized in that it comprises the steps of: A) mixing at a temperature between 25 ° C and 250 ° C of: -1) 80 to 98% by weight of an alpha copolymer -olefin and ethylene comprising ethylene and a C3 -C20 alpha-olefin; -2) 1 to 19.5% by weight of a multifunctional crosslinking agent selected from the group consisting of multifunctional acrylic crosslinking agents and multifunctional methacrylic crosslinking agents; and -3) 0.2 to 5% by weight of an ultraviolet (UV) primer; wherein the weight percentages of each of components 1), -2) and 3) are based on the combined weight of components 1), 2) and 3) to form an extrusable, curable and thermally stable mixture; B) depositing said extrudable mixture onto said article in the desired shape and thickness to form an uncured seal; and C) irradiating said uncured seal with ultraviolet (UV) radiation long enough to cure said seal. Process according to Claim 1, characterized in that ethylene is an elastomeric ethylene copolymer, a C3-C8 alpha-olefin and at least one unconjugated diene. CURED ARTICLE, characterized in that it is produced by the process as defined in claim 1.