EPICHLOROHYDRIN ELASTOMER COMPOSITIONS

Abstract: Elastomeric articles, such as automotive fuel hoses and seals, containing one or more layers containing polyepichlorohydrin gum, polyphenol curing agent, acid acceptor, and certain organo-onium compounds; such articles also containing an optional layer or layers containing polyphenol curing agent, acid acceptor, said organo-onium compounds, and fluoropolymer gum or blends of polyepichlorohydrin and fluoropolymer gum; those articles with more than one layer being shaped and cured without the need for an adhesion-promoting coating between adjacent layers and having resistance to permeation by hydrocarbons and degradation due to hydroperoxides found in fuels; and those articles with a layer or layers containing polyepichlorohydrin gum having improved resistance to scorch and having, when cured, improved heat resistance and compression set.

Description: EPICHLOROHYDRIN ELASTOMER COMPOSITIONS Technical Field This invention relates to polyepichlorohydrin gum stock, curable compositions thereof, and to shaped articles of the cured elastomer products thereof. This invention also relates to gum stocks containing blends of polyepichlorohydrin gum and fluoroelastomer gum, curable compositions thereof, and to shaped articles of the cured elastomer products thereof. Background Art Linear homopolymers of epichlorohydrin and linear copolymers of epichlorohydrin with other cyclic ethers are commonly referred to as polyepichlorohydrin gums. These linear polymers are typically thermally cured (i.e. crosslinked or vulcanized, thereby undergoing conversion from a thermoplastic substance to a thermoset substance) into useful elastomeric products using imidazolines (e.g. 2-mercaρtoimidazoline) , diamines (e.g. hexamethylene diamine), internal salts of diamines (e.g. hexamethylene diamine carbamate), and thioureas (e.g. trimethylthiourea) as curing agents, in conjunction with acid acceptors such as red lead (Pb^O.) and dibasic lead phosphite (PbHP0 3 ). These conventionally compounded polymers or curable gum stocks tend to undergo premature, partial cure ("scorch") during compounding, milling or storage. If significant scorch occurs, the gum stock ' can ^ no longer be readily molded. In addition, conventionally cured epichlorohydrin elastomers have limited life at moderately elevated temperatures (for example, about 1 to 3 weeks at 150°C for epichlorohydrin homopoly er) , losing strength and resilience. Failure of the cured elastomer may be due to excessive cross-linking (whereby the rubber part becomes rigid or brittle) or reversion (whereby the rubber part becomes soft and weak). Sometimes failure of these cured elastomers is rapid and catastrophic, resulting in machine breakdown, inconvenience, expense and lost time. Also, most conventionally cured epichloro¬ hydrin elastomers undergo significant compression set in use, i.e., they lose their resilience after being subjected to long-term compressive stress, failing to return to their original dimensions when released. Compression set is aggravated at elevated temperatures. Rubber gaskets and O-rings are especially vulnerable to compression set - the increase in compression set and attendant loss of resiliency may result in fluid leakage, contamination, etc. A need exists for a cure system for curable polyepichlorohydrin gum stocks which would reduce the tendency of such curable gum stocks to undergo scorch, and improve the heat aging and compression set of cured articles thereof. The most generally useful cure system for epichlorohydrin polymer gums employs 2-mercaptoimidazoline and red lead (see Encyclopedia of Polymer Science and Technology, Vol. 6 (Interscience, New York, 1967) pp. 198-200). U.S. Patent No. 3,726,841 discloses a process for accelerating the cross-linking of epihalohydrin polymers with halide salts of aliphatic quaternary ammonium and tetraalkyl phosphonium compounds. The cross-linking agents employed are various polyamines and certain heterocyclic compounds combined with certain metal compounds. U.S. Patent No. 4,051,078 discloses a cure system for epichlorohydrin comprising a metal oxide with a valence state of two to five and certain polyhydroxy compounds with four or more -OH groups. in the past, polyepichlorohydrin gums have found wide use in the manufacture of automotive hoses and seals. However, vulcanized articles made from such gums exhibit undesirable permeability to automotive fuels, thereby representing a significant source of hydrocarbon emissions from modern automobiles. Also, vulcanized articles made from polyepichlorohydrin can undergo reversion to their unvulcanized state upon exposure to hydroperoxides such as are commonly found in lead-free gasoline in cars equipped with recirculating fuel systems, see "Effect of Sour Gasoline on Rubber Hose", A Nasasian, Rubber and Plastics News, 26 June 1978, pp. 14-16. In an effort to reduce hydrocarbon emissions and improve the resistance of automotive fuel system hoses and seals to degradation in the presence of hydroperoxides, automobile hose and seal manufacturers have begun to specify the use of fluoroelastomers for fuel system hoses and seals. Fluoroelastomers exhibit outstanding resistance to hydrocarbon permeation and excellent stability in the presence of lead-free fuels. Fluoroelastomers actually have much better performance than is required for auto- motive use with respect to resistance to hydrocarbon permeation and stability in the presence of lead-free gasoline or sour gasoline. However, fluoroelastomers generally have poorer low temperature properties than currently used polyepichlorohydrin elastomers, that is, if temperatures drop, then fluoroelastomers lose their resilience and become brittle sooner than currently used polyepichlorohydrin elastomers. This loss of resilience at low temperatures can lead to fracture, leakage, or other failure of a hose or seal made from a fluoro- elastomer when exposed to cold weather conditions commonly found in the continental United States and elsewhere. In addition, fluoroelastomers are generally much more expensive than commercially available polyepichorohydrin elastomers. Automobile seal and hose manufacturers have therefore sought to obtain a composition which combines the low hydrocarbon permeability and stability upon exposure to lead-free gasoline or sour gasoline that are characteristics of fluoroelastomers, with the good low temperature properties and low cost that are character¬ istics of polyepichlorohydrin elastomers. Current research has focused on combinations of various fluoroelastomers (of the polymethylene type having substituent fluoro groups on the polymer chain) with epichlorohydrin/ethylene oxide copoly er (hereinafter referred to by the ASTM designation "ECO"), in preference to combinations of fluoroelastomers with epichlorohydrin homopolymer (hereinafter referred to by the ASTM designation "CO"), since ECO has superior low temperature properties. Two commercial approaches have been investigated by such manufacturers - (1) attempting to manufacture laminated articles containing one or more layers of polyepichlorohydrin elastomer bonded to one or more layers of fluoroelasto er, and (2) attempting to manufacture articles containing a blend of polyepichloro¬ hydrin gum and fluoroelastomer gum. In practice, it has been difficult to laminate curable polyepichlorohydrin gum stock to a curable gum stock containing fluoropolymer gum, and cure the resulting laminated article. Such laminated articles have required the use of an adhesion-promoting coating (i.e., a primer or adhesive) between the polyepichlorohydrin layer and the fluoropolymer layer in order to achieve good bonding and prevent delamination of the hose assembly, adding to the cost of manufacture of such laminated articles. A need exists for a compatible cure system which will enable fabrication of laminated articles containing a layer of curable polyepichlorohydrin gum stock disposed adjacent a layer of curable fluoroelastomer gum stock, without the need for an adhesion-promoting coating or other surface ^ treatment between such layers. No cure system has been reported as meeting this need. An additional need exists for curing systems which will enable polyepichlorohydrin gums and fluoro¬ elastomer gums to be blended and cured, as such blends can be used to make automotive hoses and seals having good solvent resistance (compared to similar articles containing no fluoroelastomer) and low cost (compared to similar articles containing no polyepichlorohydrin). A * - few such systems have been reported. Peroxide cure systems for blends of an olefin-containing epichlorohydrin copolymer gum and a fluoropolymer gum are described in "Automotive Fuel Permeation Resistance - A Comparison of Elastomeric Materials", J. D. MacLachlan, presented to the Passenger Car Meeting, Society of Automotive Engineers, June, 1979 (Paper No. 79 0657). Also, a cure system for blends of a polyepichlorohydrin gum and fluoropolymer gum comprising an acid acceptor, certain tertiary amines, salts of those amines, or certain tertiary phosphines, and a fluorine-containing polyhydroxy compound have been described in U.K. Published Patent Specification No. 2,011,924 A. Disclosure of Invention The present invention provides a curable gum stock composition comprising polyepichlorohydrin gum, polyphenol curing agent, and acid acceptor, characterized in that the mixture contains (a) organoammonium, organoarsonium, or organophosphonium cocuring agent of the formula: (i) (R 1 ) 4 Q + l(X-πi) 1/m or ( ii) (R l )3Q R2 Q( Rl ) 3+2 ( χ- )2/m wherein Q is a nitrogen, arsenic or phosphorus atom; X is an anion of valence m, each R-*- is a monovalent organic radical containing 1 to 2-0 ~z~- carbon atoms, is the same as or different from any other R^, and can combine with another R^ to form a cyclic structure containing a Q atom; and R 2 is a divalent organic radical containing 2 to 12 carbon atoms; or (b) organosulfonium cocuring agent of the formula: ( i ) (R 3 )3S +l (x -m )l/m or ( ii) ( R3 )2 SR4s ( R3 )2 +2 ( χ-m )2/ιn wherein S is sulfur; X is an anion of valence m; each R is a monovalent organic radical containing 1 to 20 carbon atoms, is the same as or different from any other R , and can combine with another R3 to form a cyclic structure containing an S atom; R4 is a divalent organic radical containing 2 to 12 carbon atoms; and at least one R3 or R 4 group is aromatic, and shaped and cured articles thereof. The present invention also provides blended curable gum stock compositions containing the above ingredients and further characterized in that the blended curable gum stock also contains fluoropolymer gum. Shaped and cured articles containing such blended gum stocks are also provided in this invention. Detailed Description In the practice of this invention, the polyepi¬ chlorohydrin gum is a solid, predominantly amorphous, high molecular weight (i.e., greater than about 40,000 number average molecular weight) epichlorohydrin homopolymer gum, copolymer gum containing epichlorohydrin with other cyclic ethers (for example, ethylene oxide, propylene oxide, 2-butene oxide, ethyl glycidyl ether, and trimethylene oxide), or blends of the above polymer gums. Generally useful copolymer gums will contain about 50 mol % of epichlorohydrin gum. Representative polyepichlorohydrins useful in this invention are described in U.S. Patent Nos. 3,158,580, 3,158,581, and 3,726,841. Readily available commercial polymer gums include "Herclor H" epichloro¬ hydrin homopolymer (see Hercules Inc. Technical Bulletin ORH-1D), "Hydrin 100" epichlorohydrin homopolymer (see B. F. Goodrich Chemical Co. Product Information Bulletin 6702-SPM), "Herclor C" epichlorohydrin-ethylene oxide copolymer (see Hercules Inc. Technical Bulletin ORH-lD) and "Hydrin 200" epichlorohydrin-ethylene oxide copolymer (see B. F. Goodrich Chemical Co. Product Information Bulletin 6702-SPM) . The fluoropolymer gums which can be used in this invention comprise a copolymer of (1) terminally ethylenically unsaturated olefin which has 2 to 4 carbon atoms and can be homopolymerized by emulsion poly¬ merization in the presence of a water soluble free radical catalyst such as K2S2O8, and (2) at least one terminally ethylenically unsaturated fluoromonoolefin, each of the doubly bonded chain carbon atoms of said fluoromonoolefin being bonded to at least one fluorine atom substituent and any remaining valence of any chain carbon atoms of said fluoromonoolefin being satisfied by hydrogen, fluorine, chlorine or bromine, or a fluoroalkyl or fluoroalkoxy radical of 1 to 4 carbon atoms, with at least 10 percent of the chain carbon atoms of said copolymer being -CH2- units, at least 10 percent of the chain carbon atoms of said copolymer being bonded to alkyl or alkoxy radicals with the proviso that only one such radical is bonded to a given carbon atom, and with at least 50 percent of the total number of carbon-bonded moieties in said copolymer being fluorine atoms, but with no chain carbon atom of said copolymer being bonded to more than one chlorine or bromine atom. Representative olefins which can be copoly- merized with fluoromonoolefin to prepare such fluoro¬ polymer copolymer gums include ethylene, propylene, 1-butylene, isobutylene, 1 ,1-chlorofluoroethylene, butadiene, 2-chlorobutadiene, vinyl ethyl ether, vinyl chloride, vinyl acetate, and vinylidene fluoride. Vinylidene fluoride is a preferred olefin. Representative fluoromonoolefins which can be copolymerized with the above olefins include 1-chloro-l,2-difluoroethylene, chlorotrifluoroethylene, 1 ,2-dichloro-l,2-difluoro¬ ethylene, trifluoroethylene, tetrafluoroethylene. 1-hydroρerfluoropropene (CFH=CFCF3), hexafluoropropene, 2-chloroperfluoropropene, and fluorinated methylvinyl- ethers (such as CF3θCF=C 2). Said fluoropolymer gums and their preparation are known in the art and some of them are commercially available. Preferred fluoropolymer gums are those produced by copolymerizing 65 to 85 ol % vinylidene fluoride and 35 to 15 mol % hexafluoropropene as described in U.S. Patent Nos. 3,051,677 and 3,318,854 and fluoropolymer gums produced by copolymerizing vinylidene fluoride with 10 to 35 mol % hexafluoropropene, and 15 to 25 mol % tetrafluoroethylene as described in U.S. Patent No. 2,968,649. Fluoropolymer gums need not be included in the compositions of the present invention. The curable gum stock compositions of this invention which contain poly¬ epichlorohydrin gum but no fluoroelastomer gum have substantial utility by themselves. Such compositions have excellent resistance to scorch and good shelf life. These curable gum stocks can be vulcanized into elastomeric articles, such as gaskets, O-rings, hose, etc., having good physical properties, initially and after exposure to elevated temperatures, and having improved resistance to compression set when compared to conventionally cured polyepichlorohydrin gums. The curable polyepichlorohydrin gum stocks of this invention which contain no fluoro¬ polymer gum can also be laminated to one or more layers of curable fluoropolymer gum stock, or one or more layers of curable, blended polyepichlorohydrin/fluoropolymer gum stock, and the resulting layered assembly then cured to form a laminated article containing a layer of cured polyepichlorohydrin gum, together with one or more layers of cured fluoropoymer gum and/or cured, blended polyepichlorohydrin/fluoropolymer gum. The blended compositions of this invention which contain polyepichlorohydrin gum and fluoropolymer gum also have substantial utility. The amounts and types of polyepichlorohydrin gum and fluoropolymer gum can be adjusted to alter the properties of the final, cured article. For example, the type of polyepichlorohydrin gum used in such blended compositions affects the low temperature performance and high temperature resistance of cured articles made from such blends. Cured CO homo¬ polymer and cured fluoropolymers retain useful properties down to approximately the same low temperature. Cured ECO copolymer retains useful properties down to lower temperatures, but is not stable to as high a temperature range as are cured CO or cured fluoropolymers. For blended compositions of this invention containing both polyepichlorohydrin gum and fluoropolymer gum, which when cured will be used at low temperatures, a greater amount of ECO gum should be used relative to the amount of fluoropolymer gum or CO gum. The higher the projected use temperature of such blended compositions, the greater the amount of fluoropolymer gum or CO gum which should be used relative to the amount of ECO gum. The polyphenol curing agent can be any aromatic compound with two or more hydroxyl groups directly bonded to aromatic ring carbon atoms. Preferred compounds include polyhydroxy benzenes, naphthalenes, anthracenes, chromones, xanthones, anthraquinones, and polyphenols of the formula: wherein p is O or 1; the sum (q + r) is 2 to 4 or more; and A is a thio, oxy, sulfinyl, sulfonyl or carbonyl radical, or a divalent organic radical containing 1 to 13 carbon atoms. The polyphenol curing agent can optionally be substituted with moieties which do not interfere with the functioning of the compound as a curing agent in the practice of this invention. Unsubstituted polyphenol curing agents are preferred. Salts of the above polyphenols or other derivatives which decompose or rearrange into the above polyphenols can be used. Mixtures of more than one of the above polyphenols may be used in this invention. Representative polyphenols useful in this invention include hydroquinone, 2-methyl hydroquinone, 2,5-dimethyl hydroquinone, 2-t-butyl hydroquinone, resorcinol, 2-methyl resorcinol, 5-methyl resorcinol, 2,4-dibenzoylresorcinol, catechol, 2,4-dihydroxy- acetophenone, 1,5-dihydroxynaphthalene, 9,10-dihydroxy- anthracene, 1,4,9,10-tetrahydroxyanthracene, 3,6-dihydroxy- xanthone, 2,6-dihydroxyanthraquinone, 4,4'-dihydroxy- diphenylsulfoxide, 4,4'-dihydroxydiphenylsulfone (Bisphenol S), l,l-cyclohexylidene-bis(4-hydroxybenzene) , 2-chloro-l,4-cyclohexylene-bis(4-hydroxybenzene) , 2,2-isopropylidene-bis(4-hydroxybenzene) (Bisphenol A), hexafluoroisopropylidene-bis( -hydroxybenzene) (Bisphenol AF), 2,4'-dihydroxybenzophenone, 4,4'-dihydroxybenzo- phenone, 2,2' ,4,4'-tetrahydroxybenzophenone, and 2-fluoro-l,4-phenylene-bis(4-hydroxybenzene) . Bisphenol S is a preferred polyphenol but others may be chosen by those skilled in the art in order to provide selected curing characteristics for particular applications. The organo-onium cocuring agent is an organoammonium, organoarsonium or organophosphonium compound of the formula or (R 1 ) 3 QR 2 Q(R 1 ) 3 +2 (X "m ) 2/m II wherein Q is a nitrogen, arsenic, or phosphorus atom; X is an anion of valence m; each R is a monovalent organic radical which -is the same as or different from any other R , can combine with another R to form a cyclic structure containing a Q atom, can contain from 1 to about 20 carbon atoms, can have a carbon skeletal chain which is linear, branched or cyclic and is saturated, unsaturated or aromatic, which chain can contain hetero skeletal atoms other than carbon (e.g., oxygen or sulfur) and can be unsubstituted or substituted with moieties which do not interfere with the functioning of the compound as a cocuring agent; and R 2 i.s a divalent organic radical containing from 2 to 12 (preferably 2 to 8) carbon atoms. The organo-onium cocuring agent can also be an organosulfonium compound of the formula { R 3 ) 3 S +1 (X- m )l/m III or (R 3 ) 2 SR 4 S(R 3 ) 2 +2 (X- m ) 2/m IV wherein S is sulfur; X is an anion of valence m; each 3 R is a onovalent organic radical which is the same 3 as or different from any other R , can combine with another R 3 to form a cycli.c structure contai.ni.ng an S atom, can contain from 1 to about 20 carbon atoms, can have a carbon skeletal chain which is linear, branched, or cyclic and is saturated, unsaturated or aromatic, which chain can contain hetero skeletal atoms other than carbon (e.g., oxygen or sulfur) and can be unsubstituted or substituted with moieties which do not interfere with the functioning of the compound as a cocuring agent; R 4 i.s a divalent organic radical having from 2 to 12 (preferably 2 to 8) carbon atoms; and at least one R 3 or R4 group " is ~ aromatic. Mixtures of more than one of the above organo- onium cocuring agents can be used in this invention. In the above organo-onium cocuring agent formulas, suitable anions X include chloride, bromide, sulfate, bisulfate, nitrate, hydroxide, carbonate, per- chlorate, trifluoromethane sulfonate, acetate, benzene sulfonate, phenate, tetrafluoroborate, hexachloro- phosphate, hexafluorophosphate, hexachlorostannate, hexafluoroarsenate, and hexafluoroantimonate. In the above formulas, preferably R 1 and R3 are alkyl, alkenyl, cycloalkyl, phenyl, or combinations thereof, and R 2 and R4 are alkylene, phenylene or combinations thereof such as phenylenedialkylene with at least one of R 3 and R4 containing an aromatic nucleus with 6 ring-carbon atoms. The R 1, R2, R3, or R4 groups can contain substituents which do not interfere with the function of the compound as a cocuring agent, such as halo, alkoxy, alkylthio, phenylthio, carboalkoxy, acetoxy, and acetamido. Most preferably R 1, R2, R3 and R4 are unsubstituted. In general, organophosphonium compounds are preferred as cocuring agents due to their ready availability. Representative organo-onium cocuring agent compounds include: (CH 3 ) 4 N + OH~, (C 4 H 9 ) 4 N + Br~, (HOCH 2 CH 2 ) 3 N + CH 3 l " , HO " (C 4 H 9 ) 3 + CH 2 CH 2 + (C 4 H 9 ) 3 OH " , (C 2 H 5 ) 3 (C 6 H 5 ) + Br " , , (C 8 H 17 ) 3 (CH 2 =CHCH 2 )N + BF 4 " , (C^g) 3 (CF 3 CH 2 )N + (S0 4 ~ 2 ) χ/2 , (CH 3 ) 4 As + OH~, (C 6 H 5 ) 4 As + Cl~, (CH 3 ) 2 (C 2 H 5 ) 2 P + C1-, (C 2 H 5 ) 3 (C 18 H 37 )P + Br-, (C 3 H 7 ) 3 (c clo-C 6 H 1:L )P + OH~, (C^) 3 (CH 2 =CHCH 2 )P + C1~, (C 6 H 5 ) 3 (C 6 H 5 CH 2 ) + C1~, (C g H 5 ) 3 (C 6 H 5 COCH 2 )P + Br " , (CgH 17 ) 3 (CH 3 OCH 2 CH 2 )P + 0 3 " , Cl,-+(C £ .H r -) PCH„ +„-,- 6 5 3 2C c 6H4.CH2P(C c 6H5 c )3 Cl , , (C • 6.H n 5 ς ) ; 3,S° + Cl " ,' ( C V -6,R Q 5-, ) ; 3* i S° + ~ 2 )'1,/ .2.'. ' (C 6 H 5 ) 2 (CH 3 )S + BF 4 " , diphenylnaphthylsulfonium trifluoromethanesulfonate, tritolylsulfonium nitrate, anisyldiphenylsulfonium hexafluoroantimonate, 4-butoxyphenyldiphenylsulfonium tetrafluoroborate, 4-chlorophen ldiphenylsulfonium acetate, tris(4-phenoxyphenyl) sulfonium hydroxide, di(4-ethoxyphenyl)methylsulfonium hexafluoroarsenate, 4-acetoxy-phenyIdiphenylsulfonium carbonate, tris (4-thiomethoxyphenyl) sulfonium hexafluorophosphate, di(methoxysulfonyIphenyl)methylsulfonium chloride, di(methoxynaphthyl)methylsulfonium tetrafluoroborate, tris(carbomethoxyphenyl) sulfonium " hexafluorophosphate, and 4-acetamidophenyldiphenylsulfonium perchlorate. Synthetic routes to the above organo-onium compounds are well known and are described, for example, in "Concerning Amines", David Ginsburg, (Pergamon Press, New York, 1967) page 73; "Psuedohalo Metal Compounds XVIII", Beck et al, Chem Ber, 100, 2335-61 (1967) (arsenic), "Organic Phosphorus Compounds", G. M. Kosolapoff and L. Maier, (Wiley-Interscience, New York, 1972) Vol. 2, page 189; J. Org. Chem., G. H. iegand, et al, 33_, 2671-75(1968) (sulfur); J. Org. Chem., K. Ohkubo, et al, _36_, 3149-55(1971) (sulfur); "Topics in Sulfur Chemistry", J. P. Marino, (Georg Thieme, Stuttgart, 1976) page 32; and U.S. Patent 2,807,648. Prior to curing, an acid acceptor (preferably an inorganic base) is added to the gum stock to provide a curable gum stock or compound. Suitable acid acceptors include lead-based compounds, calcium hydroxide, and magnesium oxide. Mixtures of more than one acid acceptor can be used in this invention. Preferred acid acceptors are lead-based compounds such as dibasic lead phosphite, dibasic lead phthalate, tribasic lead maleate monohydrate, tribasic lead fumarate, and white lead (PbO). Other gum stock ingredients commonly used as compounding adjuvants for polyepichlorohydrin gums and for fluoropolymer gums can also be included in the gum stock prior to curing, such as one or more heat stabilizers (additives which improve retention of physical properties at elevated temperatures such as p enyl-beta-naphthyl- amine, N, '-di-beta-naphthyl-p-phenylenediamine, N-isooctyl-p-aminophenol, polymerized 2,2,4-t imethyl-l,2- dihydroquinoline, nickel dibutyldithiocarbamate and nickel di ethyldithiocarbamate) , processing aids, lubricants, plasticizers, and fillers (e.g., high surface carbon blacks and amorphous silicas). Organic primary monoamines and polysecondary (e.g., disecondary) amines are preferred heat stabilizers. Blended gum stock compositions of the present invention which contain ECO copolymer preferably contain at least one organic primary monoamine as a heat stabilizer. Suitable organic primary monoamines include octyl amine and octadecyl amine. In general, as the amount of CO or ECO is increased in a blended composition of the present invention, a greater amount of heat stabilizer is needed to maintain the elevated temperature stability of the final cured article. If a cured blended composition of the present invention has a proposed use at temperatures in excess of about 200°C, i.e., if it has a high concentration of fluoroelastomer, then the amount of "' heat stabilizer used should be held to a minimum consistent with good retention of physical properties after aging. If more than this amount of heat stabilizer is used in such compositions, then the final cured article will actually have decreased stability at elevated temperatures. The amounts of polyepichlorohydrin gum, optional fluoropolymer gum, polyhydroxy curing agent, acid acceptor, organo-onium cocuring agent, and any compounding adjuvants used, will depend upon the proposed application and desired cure characteristics. As mentioned above, use of ECO copolymer in a blended composition of the present invention is preferred where improved low temperature properties are of major concern in the final cured article. CO homopolymer should be used in a blended composition of the present invention where improved high temperature properties are more important in the final cured article. Also, as the amount of fluoropolymer gum is increased in a blended composition of the present invention, the stability of that composition at elevated temperatures is improved. In general, many of the properties of a cured blended composition of the present invention will be intermediate between the physical properties, when cured, of the individual gumstocks used to make the blend composition. Whether the composition of the invention contains polyepichlorohydrin gum and no fluoropolymer gum or contains a blend of polyepichlorohydrin gum and fluoropolymer gum, a lower concentration of polyphenol curing agent in the gum stock generally will produce a lower crosslink density and lower modulus in the cured compound, while a higher concentration of polyphenol curing agent generally will produce higher crosslink density and higher modulus. Low concentrations of organo-onium cocuring agent and acid acceptor will produce slower cures. Suitable concentration ranges for producing a useful cured product are shown below. The term "parts" refers to parts by weight of polyepichlorohydrin gum or fluoropolymer gum. The term "phr" refers to parts per hundred parts of the total weight of polyepichlorohydrin gum plus fluoropolymer gum. The term "mmhr" refers to millimoles per hundred grams of polyepichlorohydrin gum plus fluoropolymer gum. Gum S tock Component Amount polyepichlorohydrin gum 100 to 1 parts fluoropolymer gum 0 to 99 parts polyphenol curing agent 0.3 to 15 mmhr acid acceptor 0.5 to 40 phr organo-onium cocuring agent 0.2 to 7.5 mmhr Compounding adjuvants may be added in conventional quantities, e.g., heat stabilizers at 0.1 to 20 phr, and preferably at 0.5 to 10 phr. The addition of conventional amine curing agents (e.g., hexamethylene diamine) ordinarily should be avoided. The presence of such amines tends to slow down the cure rate and degrade the storage life, heat aging and compression set of the compositions of the present invention. Mixing of the above components and additives can be carried out in any order. For a composition of this invention which contains polyepichlorohydrin gum but no fluoropolymer gum, it may be convenient to mill polyphenol curing agent and organo-onium cocuring agent into polyepichlorohydrin gum, forming a gum stock. For a blended composition of the present invention containing polyepichlorohydrin gum and fluoropolymer gum, it may be convenient to mill polyepichlorohydrin gum and fluoro¬ polymer gum together and then mill into this mixture polyphenol curing agent and organo-onium cocuring agent, forming a gum stock. The above gum stocks will have an extended storage life at room temperature, e.g., one year or more. Prior to curing, the acid acceptor(s) are milled into either of the above gum stocks (forming a curable gum stock), after which the room temperature shelf life is more limited, e.g., to a few months. Additives can be milled into such gum stocks or such curable gum stocks at any time prior to curing. Variations on the above mixing schemes can be used, e.g., the polyphenol curing agent, organo-onium cocuring agent, and the acid acceptor can be admixed and later combined with polyepichlorohydrin gum or fluoropoly- mer gums. Masterbatch techniques can be used in preparing such curable gum stocks. For example, a masterbatch may be prepared by combining 100 parts (by weight) of polyepi¬ chlorohydrin gum or fluoropolymer gum or a blend of these gums (e.g., 1 to 99 parts polyepichlorohydrin gum with 99 to 1 parts fluoropolymer gum) with about 100 to 900 parts of curing agent, and with about 100 to 900 parts of cocuring agent, and the resulting masterbatch later combined with the requisite balance of polyepichlorohydrin gum or fluoropolymer gum or a blend of these gums to form a gum stock composition. Alternatively, the polyphenol curing agent can be mixed into a carrier (at a concentra¬ tion of about 100 to 900 parts of curing agent in 100 parts of carrier) to provide a first masterbatch and the organo-onium cocuring agent can be separately mixed into a carrier (at a concentration of about 100 to 900 parts of cocuring agent in 100 parts of carrier) to form a second masterbatch, and the first and second masterbatches later milled into the desired polymer gums in desired proportions to prepare a gum stock, to which acid acceptor is subsequently added to form a curable gum stock. This latter masterbatch technique allows convenient adjustment by the use of the amount of each component in the gum stock and helps ensure thorough dispersion of the components in the gum stock. In addition, mixing either the polyphenol curing agent or the organo-onium cocuring agent with a carrier reduces the likelihood that hazardous or environmentally deleterious substances will be released into the atmosphere during mixing, since some of these components are in the form of a dusty, powdered solid. Suitable carriers include polyepichlorohydrin gum, fluoro¬ polymer gum, neoprene, chlorosulfonated polyethylene, chlorinated polyethylene, and ethylene-propylene c:.:?ι -- V1PO copolymer. Said polyepichlorohydrin gum and fluoropolymer gum (e.g., said 65-85:35-15 mol % vinylidene fluoride:hexafluoropropylene copolymer) are the preferred carriers. Mixing of the gum stock components can be carried out using any of the usual rubber mixing devices, such as Banbury mixers, roll mills, or any other convenient mixing device. It has been found that a two-roll rubber mill equipped with heat exchange means, e.g., cored chambers for cooling, is particularly suitable since the heat generated by the high shearing forces in mixing can be dissipated and the temperature more accurately regulated with this device than with devices providing other means for temperature control. The temperature of the mixture on the mill generally should not be allowed to rise above about 120°C. The mixture should be milled sufficiently to distribute the cross- linking agents and other ingredients throughout the gum stock. About 5 to 20 minutes or longer is recommended for this process. The curable gum stock is shaped by molding or extruding, then thermally cured into a useful elastomeric product. By "elastomeric" is meant the ability of the cured vulcanizate, when slowly stretched at room tempera- ture to at least twice its original length and released, to return rapidly to essentially its orignal length. Forming a shaped article by molding typically comprises pressing the curable gum stock in a hot mold, releasing the shaped part from the mold, and (to develop optimum properties) subsequently post curing the part in an oven. The mold can first be coated with a release agent, such as a silicone oil. Molding can be carried out at a temperature between about 95°C and about 230°C, preferably between about 150°C and about 205°C, for a period of from about 1 minute to 15 hours, usually from 5 minutes to 30 minutes, and at a pressure of between about 0.7 MPa and about 20.6 MPa, preferably between about - \ r- i : : ' 3.4 MPa and about 6.8 MPa. The vulcanized molded article can be post cured at a temperature between about 120°C and about 230°C, usually at about 150°C to 200°C, for a period of from about 4 hours to 24 hours or more depending on the cross-sectional thickness of the sample. For thick sections, the temperature during the post cure usually is raised gradually from the lower limit of the range to the desired maximum temperature selected. For thinner sections, e.g., less than 5 mm, the section can be put into the oven at the desired maximum temperature. Alternatively, the curable gum stock can be shaped by extrusion rather than molding. Extrusion typically comprises heating the curable gum stock to a temperature of about 100°C and forcing it through a suitable die or orifice at a pressure of between about 330 MPa and about 400 MPa. The shaped extrudate can then be press cured as above, or, alternatively, steam autoclaved at a temperature of between about 135°C and about 160°C, for a period from about 30 minutes to 4 hours. The vulcanized extruded article can then be post cured in the same manner as a molded article. Shaped layered or laminated articles of this invention made of polyepichlorohydrin gum and fluoro¬ polymer gum are prepared as follows. Such gums, taken singly or blended together as described above, can be prepared as curable compositions and shaped as sheets or the like and the shaped parts laid up together, and the layup then subjected to heat and pressure to produce a laminated article without requiring the use of an adhesion-promoting coating between the layers. Laminating may be carried out at a pressure of about 0.3 to 20 MPa and preferably at about 0.5 to 10 MPa. In one aspect thereof, such an article can comprise a first layer in the form of a sheet, cylinder, or the like. In a first embodiment, said first layer can be a laminate of a first sublayer of curable gum stock (wherein the gum is said polyepichlorohydrin gum) disposed adjacent a second sublayer of curable gum stock (wherein the gum is said fluoropolymer gum). Alternatively, in a second embodiment, said first layer can be a curable gum stock containing the above-described blend of polyepichloro- hydrin gum and fluoropolymer gum. In each of said first and second embodiments, one or both sides of said first layer (e.g., one or both faces in the case of a sheet, and the inner and/or outer surfaces in the case of a cylinder) is disposed adjacent one or more second layers, each of which second layers is a curable gum stock wherein the gum is said polyepichlorohydrin gum or said fluoropolymer gum, or the gum in said second layer is said blend of polyepichlorohydrin gum and fluoropolymer gum, each second layer being the same as or different from said first layer and any other of said second layers (when present). The resulting layered article, when cured, has a strong layer-to-layer bond formed without the need for an adhesion-promoting coating at the interface between contiguous layers or sublayers. Thus, if said first layer in the resulting cured article is a laminate of said first sublayer of polyepi¬ chlorohydrin and said second sublayer of fluoroelastomer, then the cured article will have two sublayers (within a single first layer) and one or more of said second layers. And if said first layer in the resulting cured article is a blend of polyepichlorohydrin elastomer and fluoro¬ elastomer, then the cured article will have a blended first layer and one or more of said second layers. In an additional aspect of this invention, shaped layered articles are provided consisting essentially of a layer of curable polyepichlorohydrin gum stock disposed adjacent a layer of curable fluoropolymer gum stock, the resulting article, when cured, having a strong layer-to-layer bond formed without the need for an adhesion-promoting coating at the interface between the elastomeric layers. The resulting article has only two layers, neither of which is a blend. The curable gum stocks in layers and sublayers of the layered articles described above contain the gums recited above plus polyphenol curing agent, acid acceptor, organo-onium cocuring agent, and any optional compounding adjuvants. Layered articles are prepared by mixing a curable gum stock for each layer or sublayer, using mixing techniques as outlined above in the discussion of uni¬ formly blended articles of the present invention. The individual curable gumstocks are then placed into a mold or coextruded, using techniques well known in the art, and then cured as described above in the discussion of uniformly blended articles of the present invention. Upon curing, the contiguous layers adhere to one another, forming a strong layer-to-layer bond whose strength at the bond line equals or exceeds the strength of the individual layers themselves. The layers are thereby joined without the need for an additional adhesion promoting coating between them. For example, a layered fuel hose assembly may be prepared by extruding a thin-walled cylindrical inner liner of fluoropolymer gum stock, covering that liner with a thick-walled coaxial cylindrical sheath of CO gum stock, and covering that sheath with a thin-walled coaxial cylindrical cover made from a gum stock containing a blend of ECO and fluoropolymer gums. After cure, the resulting hose assembly would have low hydrocarbon permeation due to the inner fluoroelastomer liner layer, good oil and solvent resistance due to the outer ECO/fluoroelastomer elastomer blended cover layer, and moderate cost due to the thick intermediate CO elastomer layer. In cross-section, such a hose assembly would have a hollow core and five concentric annulli or rings of cured elastomer - the three principal elastomer layers mentioned above, plus the two interfaces between contiguous principal layers. Other laminated articles, such as gaskets, tank lining, and seals, can also be prepared in accordance with this invention. Shaped articles of the present invention may also be prepared by laminating a curable gum stock of thi invention to another elastomer (e.g., neoprene), for example by using a suitable primer or adhesive between th two elastomer layers. The following examples are offered to aid under standing of the present invention and are not to be construed as limiting the scope thereof. Curing characte istics are reported under the heading "Rheometer". Data were obtained in accordance with ASTM D 2084-75 using a Monsanto Oscillating Disk Rheometer Model MP-V, with a 20 second preheat, a 100 cpm oscillator frequency, and a 3° arc. Resistance to scorch is reported under the heading "Mooney Scorch". Data were obtained in accordanc with ASTM D 1646-74 using a Scott Testing Inc. Mooney Viscometer Model ST1, with a 1 minute preheat and a small rotor at 121°C. Physical properties of press cured and post cured samples are reported under the headings "Press cure" and "Post cure". Samples were in the form of 150 x 150 x 1.8 mm sheets and were pressed at about 5 MPa at the indicated conditions. After measurement of the indicated physical properties, portions of the samples were then post cured in an oven at the indicated conditions, and physical properties re-measured. Measurements were in accordance with ASTM D 412-75 using an Instron Tensile Tester, Method "A", using dumbell samples cut from 1.8 mm sheet with die "C π . Resistance to heat aging is reported under the heading "Accelerated aging of post cured sample". Data were obtained in accordance with ASTM D 412-75 (as above) and ASTM D 573-72. Low temperature properties are reported under the heading "Low temperature retraction". Data were obtained in accordance with ASTM D 1329-72, and are reported as the temperature at which a frozen sample retracted 10 percent from a specified elongation. Resistance to degradation upon exposure to solvents is reported under the heading "Volume swell". Data were obtained in accordance with ASTM D 1460-68, using ASTM #3 oil, as well as Reference Fuel "C" (a 50% aliphatic, 50% aromatic test fuel). Resistance to compression set is reported under the heading "Compression set, O-rings". Data were obtained in accordance with ASTM D 395-69 (reapproved 1975), Method B using type "1" O-rings with a 3.53 mm cross section, subjected to 25% compression at the indicated conditions. EXAMPLE 1 Epichlorohydrin (CO) homopolymer was milled on a two-roll mill with a polyphenol, a tetraorganophosphonium salt, an acid acceptor, a filler, and two conventional heat stabilizers to form a curable gum stock. The ingredients were milled by putting the gum on the mill, adding the curing and cocuring agents as a group, adding all other ingredients as a group, and cutting the mixture back and forth until all ingredients were well dispersed. The curable gum stock was then molded and cured as indicated. The cure characteristics of the curable gum stock and the mechanical properties of the cured elastomer were determined before and after accelerated aging. Compression set data were also obtained. The composition of the curable gum stock and the above mentioned mechanical properties are set forth in Table I (as "Example 1") together for purposes of comparison with corresponding data on the same polymer gum using a conventional curing system (as "Comparison Run".) A low tendency to scorch, more rapid cure, superior aging properties and improved compression set values are shown for the novel composition of Example 1. Table I Coπparison Ingredient Example 1 Run Polymer gum (parts) 100 100 Bisphenol S (mute 6.25 — 2-Mer captomidazoline c ( πirihr ) — 9.8 (n-C4Hg)3(CH 2 =CHCH2)P + Cl- (mmhr) 3.5 — PbHP0 3 d (phr) 12 5 Dibasic lead phthalate (phr) — 7 ASTM N-550 Carbon black f (phr) 30 30 Nickel dibutyldithiocarbamate 9 (phr) 1 1 Nickel dimethyldithiocarbamate (phr) 1 1 "Hydrin 100", epichlorohydrin homopolymer, commercially available from B. F. Goodrich Chemical Co. b 4,4'-dihydroxydiphenylsulfone c "NA-22", commercially available from E. I. duPont de Nemours & Co. d "Dyphos", commercially available from National Lead Co. e "Dythal", commercially available from National Lead Co. f "Philblack A", commercially available from Phillips Chemical Co. "Butyl Niclate", commercially available from R. T. Vanderbilt Co. "Methyl Niclate", commercially available from R. T. Vanderbilt Co. Table I ( cont . ) Comparison Rheometer , 160 °C : Example 1 Run M L (N*m) 0.40 0.40 M H (N -m) 8.9 6.1 Min . to M. 36 36 H 5.9 4.2 u sl t ' ( 90 ) 26 29 Rheometer, 177°C: M τ (N-m) 0.40 0.34 M„ 9.8 7.3 π. (N-m) Min to M 24 25 H 4.3 3.0 'si (90) 13.5 17 Mooney Scorch, 121°C: Minimum viscosity 10 1 11 Minutes to 10 point rise >25 1 22.5 Point rise in 25 min. 13 Press cure, 15 min., 177°C: Tensile (MPa) 15.16 15.16 100% Modulus (MPa) 3.79 2.20 Elongation at break (%) 405 700 Hardness (Shore A-2) 69 61 Post cure, 16 hr. , 149°C: Tensile (MPa) 17.22 17.91 100% Modulus (MPa) 4.82 5.34 Elongation at break (%) 00 260 Hardness (Shore A-2) 76 73 . No change after 8 weeks storage at room temperature, Accelerated aging of post cured sample tensile (MPa) 149°C 163°C Comparison Comparison Time Example 1 Run Example 1 Run 1 day 16.91 17.87 17.00 18.04 3 days 16.81 16.78 13.72 15.73 1 week 15.17 15.92 8.25 6.65 2 weeks 9.12 8.83 3.33 * 3 weeks 4.55 1.18 1.95 * 4 weeks 3.62 * 1.09 * 5 weeks 3.41 * 0.78 * 6 weeks 2.52 * * * Accelerated aging of post cured sample - 100% modulus (MPa): 149°C 163°C Comparison Comparison Time Example 1 Run Example 1 Run 1 day 6.02 6.13 6.42 6.75 3 days 6.78 6.80 6.50 5.97 1 week 6.62 7.74 3.62 2.69 2 weeks 3.79 3.51 1.87 * 3 weeks 2.43 0.87 1.32 * 4 weeks 2.00 * 0.83 * 5 weeks 1.50 * * * 6 weeks 1.10 * * * * too weak to test Table I (cont. ) Accelerated aging of post cured sample - elongation at break (%): 149°C 163°C Comparison Comparison Time Example 1 Run Example 1 Run 1 day 267 233 240 220 3 days 237 200 200 200 1 week 200 183 250 287 2 weeks 240 225 250 * 3 weeks 250 200 255 * 4 weeks 250 * 280 * 5 weeks 250 * * * 6 weeks 250 * * * Accelerated aging of post cured sample - hardness (Shore A-2) : 149°C 163°C Comparison Comparison Time Example 1 Run Example 1 Run 1 day 76 76 79 78 3 days 78 79 79 78 1 week 80 79 72 64 2 weeks 74 72 65 35 3 weeks 70 55 60 * 4 weeks 66 * 77 * 5 weeks 70 * 55 * 6 weeks 62 * * * too weak to test .∑ Table I (cont. ) Compression set, O-rings (%): Comparison Example 1 Run 72 hrs. at 121°C Press cured, 15 min. , 177°C 17 65 Post cured, 24 hrs., 149°C 13 25 72 hrs. at 135°C Press cured, 15 min., 177°C 33 78 Post cured, 24 hrs., 149°C 28 42 72 hrs. at 149°C Press cured, 15 min., 177°C 47 89 Post cured, 24 hrs., 149°C 44 77 EXAMPLES 2 through 11 In a series of 10 runs polyepichlorohyd in gum (as used in Example 1) was compounded with polyphenol curing agent, various cocuring agents, an acid acceptor, a filler, and two conventional heat stabilizers. The resulting curable gum stock compositions were mixed, cured, and evaluated as in Example 1. Curing characteristics of the several compositions are set forth in Table II. Table II Example Ingredient 2 3 4 5 6 7 8 Polymer gum (parts) 100 100 100 100 100 100 100 Bisphenol S (irenhr) 6.25 6.25 6.25 6.25 6.25 6.25 6.25 (n-C 4 H 9 ) 3 (CH 2 =CHCH 2 ) P + Cl " (παr r) 3.6 (C 6 H 5 ) 3 P + (C 2 H 5 ) r (mmhr) 3.6 (n-C 4 H 9 ) 4 P + c (mmhr) 3.6 (C 6 H 5 ) 3 (C g H 5 CH 2 )P + c (mπhr) 3.6 (CgH 5 ) 3 (CgH 5 COCH 2 ) P + Br " (mmhr) 3.6 (n-C 4 H g ) 4 N + OH " (mmhr) 3.6 (C g H 5 ) (C 6 H 5 CH 2 ) (CH 3 )S + Br " (mπhr ) 3.6 PbHP0 3 (phr) 12 12 12 12 12 12 12 ASIM N-550 Carbon black (phr) 30 30 30 30 30 30 30 Nickel dibutyldithio¬ carbamate (phr) 1 1 1 1 1 1 1 Nickel di ethyldithio- carbarnate (phr) 1 1 1 1 1 1 1 Rheometer, 177°C: M j ^ (N-m) 0.23 0.34 0.34 0.34 0.23 0.45 0.0 MJJ (N-m) 9.83 9.83 9.83 10.28 6.55 9.72 5.10 Min. to M^ 24 24 24 24 36 24 48 fc sl 6 5 6.2 5.8 7.5 4.5 23 t' (90) 13.3 10.2 12.7 14.0 30 13.5 43 Table II (cont. ) Exaπple Ingredient 10 11 Polymer gum (parts) 100 100 100 Bisphenol S (mmhr) 6. 25 6.25 6.2! (n-C 4 H 9 ) 4 N + Br~ (mmhr) 3. 6 (CH 3 C 6 H 4 ) 3 S + C1~ (mmhr) 3.6 (C g H 5 ) 4 As Cl (mmhr) 3.6 PbHP0 3 (phr) 12 12 12 AS1M N-550 Carbon black (phr) 30 30 30 Nickel dibutyldithio¬ carbamate (phr) 1 1 1 Nickel di ethyldithio- carbamate (phr) Rheometer, 177 °C: M^ (N-m) 0.23 0.11 0.11 1< (N-m) 8.70 8.48 9.60 Min. to Mg 24 24 24 sl 6.0 5.4 4.5 t' c (90) 11.5 20.0 10.2 Mooney Scorch, 121°C: Minimum viscosity 2 2 Minutes to 10 point rise 5 >25 Point rise in 25 min. 0 0 Compression set, O-rings (%): 72 hrs at 121°C Press cured, 11.5 min, 177°C 24.1 Press cured, 20 min, 177°C 25.7 Post cured, 24 hrs, 149°C 22.2 20.4 " VΛ " EXAMPLES 12 through 16 In a series of 5 runs polyepichlorohydrin gum (as used in Example 1) was compounded with various polyphenol curing agents, a tetraorganophosphonium cocuring agent, an acid acceptor, and a filler. The resulting curable gum stock compositions were mixed, cured, and evaluated as in Example 1. Curing characteristics of each formulation are set forth in Table III. All polyphenols were effective and gave good cures, although cure rates varied. Table III Example Ingredient 12 13 14 15 16 Polymer gum (parts) 100 100 100 100 100 Hydroquinone (mmhr) 6.25 Bisphenol A (mmhr) 6.25 4,4'-HOCgH 4 COC 6 H 4 OH (mmhr) 6.25 Bisphenol S (mmhr) 6.25 Bisphenol AF (mmhr) 6.25 (n-C 4 H 9 ) 3 (CH^CHO^)P + Cl " (mmhr) 3.6 3.6 3.6 3.6 3.6 PbHP0 3 (phr) 12 12 12 12 12 ASTM N-550 Carbon black (phr) 30 30 30 30 30 2,2-iscprcpylidene-bis(4-hydroxybenzene) 4,4'-HOC 6 H C(CF3)2C5H4OH Rheometer, 177°C: M j ^ (N-m) 0.45 0.23 0.23 0.23 0.23 Mg (N-m) 4.52 5.31 9.83 9.83 9.23 Min to L 24 24 24 24 24 fc sl 6.2 6.0 4.7 6.0 5.5 t 1 (90) c 16.5 18.5 9.5 13.3 12.5 EXAMPLE 17 Epichlorohydrin-ethylene oxide (ECO) copolymer was compounded with a polyphenol, a tetraorganophosphonium salt, an acid acceptor, a filler, a heat stabilizer, and a processing aid. The gum stock was mixed, cured, and evaluated as in Example 1. The composition of the curable gum stock and the indicated mechanical properties are set forth in Table IV (as "Example 17") together for purposes of comparison with corresponding data on the same polymer gum using a conventional curing system (as "Comparison Run") . Superior retention of properties was obtained for the elastomeric rubber employing the cure system of the present invention (Example 17). Table IV Comparison Ingredient Exanple 17 Run Polymer gum (parts) 100 100 Bisphenol S (mmhr) 6.25 — (CgH 5 ) 3 (CgH 5 CH 2 )P + Cl~ (mπhr) 3.6 — 2-Mercaρtoimidazoline (mmhr) — 9.8 PbHP0 3 (phr) 12 12 ASTM N-550 Carbon black (phr) 50 50 Polymerized 2,2,4- trimethy1-1,2-dihydroquinoline (phr) 2.5 2.5 Polymer processing additive 0 (phr) 1 1 "Hydrin 200", commercially available from B. F. Goodrich Chemical Co. "Agerite Resin D", commercially available from R. T. Vanderbilt Co. C C g F 17 S0 2 (CH 3 )CH 2 CH 2 Ce/CaC0 3 , 3/1 by wt. Table IV (cont. ) Coπparison Press cure, 20 min. 188°C: Example 17 Run Tfensile (MPa) 12.00 12.69 100% Modulus (MPa) 4.09 4.49 Elongation at break (%) 343 353 Hardness (Shore A-2) 73 75 Post cure, 24 hrs. , 149°C: Tensile (MPa) 13.05 14.65 100% Modulus (MPa) 6.10 6.76 Elongation at break (%) 217 207 Hardness (Shore A-2) 82 78 Accelerated aging of post cured sample - - tensile (MPa) : _ •_> Time at 149°C 1 week 10.44 9.42 3 weeks 7.88 3.28 5 weeks 6.86 1.71 Accelerated aging of post cured sample - 100% modulus (MPa) : Time at 149°C 1 week 6.04 8.1 3 weeks 6.25 — 5 weeks 6.15 — Accelerated aging of post cured saπple - elongation at break (%) Time at 149°C l week 170 130 3 weeks 150 70 5 weeks 120 30 Table IV (cont. ) Accelerated aging of post cured sample - hardness (Shore A-2) : Comparison Time at 149°C Exaπple 17 Run 1 week 84 85 3 weeks 87 84 5 weeks 87 77 EXAMPLES 18 through 20 In a series of three runs, epichlorohydrin homo¬ polymer was compounded with a polyphenol , a tetraorgano- ammonium salt, an acid acceptor, a filler and optionally with one of two heat stabilizers . The resulting gum stock compositions were mixed, cured, and evaluated as in Example 1 . The composition of the curable gum stocks and their indicated mechanical properties are set forth in Table V. The heat stabilizers (polymerized 2 , 2 , 4-trimethyl-l , 2-dihydroquinoline and N ,N ' -di-beta- naphthyl-p-phenylenediamine ) were useful in prolonging elastomeric properties. Table V Example Ingredient 18 19 20 Polymer gum (parts) 100 100 100 Hydroquinone (mmhr) 9 9 9 (n-C 4 H 9 ) 4 N + OH~ a (mmhr) 1.5 1.5 1.5 PbHP0 3 (phr) 18 18 18 ASTM N-990 Carbon blackb (phr) 30 30 30 Polymerized 2,2,4-trimethyl- 1-2-dihydroquinoline (phr) 2.5 N,N'-di-beta- naphthyl-p-phenylenediamine (phr) 5.9 In 25% CH3OH solution. "Thermax MT", commercially available from Thermatomic Carbon Co. 0 "Agerite White", commercially available from R. T. Vanderbilt Co. Properties after press cure (10 min. at 177°C) and post C ure (24 hrs. at 177°C): Tensile (MPa) 8.06 7.44 5.65 Elongation at break (%) 280 200 230 Hardness (Shore A-2) 62 78 64 Accelerated aging of post cured sample, 177°C - Tensile (MPa) : Time 3 days 0.55 4.24 5.37 7 days * 2.55 2.17 14 days * 3.72 2.07 Table V ( cont . ) Accelerated aging of post cured sample, 177°C - Elongation at break (%): Example Time 18 19 20 3 days 300 110 190 7 days * 100 130 14 days * 105 100 Accelerated aging of post cured sample, 177°C - Hardness (Shore A-2) : Time 3 days 52 70 68 7 days 54 75 66 14 days * 77 67 * too weak to test EXAMPLES 21 through 24 In a series of 4 runs, epichlorohydrin homopolymer was compounded with a polyphenol, a tetraorganophosphonium salt, two different acid acceptors (at two different concentrations), a filler, and two conventional heat stabilizers. The curable gum stocks were mixed, cured and evaluated as in Example 1. The composition of each gum stock and the indicated mechanical properties are set forth in Table VI. The acid acceptor white lead was more effective than the acid acceptor red lead. Higher levels gave more rapid cures. Table V3 Exaπple Ingredient 21 22 23 24 Polymer gum (parts) 100 100 100 100 Bisphenol S (mmhr) 6.25 6.25 6.25 6.25 (C g H 5 ) 3 (CgH 5 CH 2 )P + C1~ (mmhr) 3.6 3.6 3.6 3.6 PbO (phr) 5 10 — — 3 0 4 (phr) — — 5 10 ASTM N-550 Carbon Black (phr) 40 40 40 40 Nickel dibutyldithio¬ carbamate (phr) 1 1 1 1 Nickel di ethyldithio- carba ate (phr) 1 1 1 1 Rheαieter, 177°C: IL (N-) .11 .23 .23 .11 ^ (N-m) 10.85 11.07 8.81 11.3 Min to Mg 36 24 36 31 ^1 5.0 4.5 8.7 7.3 t' c (90) 22.2 13.8 30.5 26.7 - sTΪ - - /' A ^- ~ Example 25 In a series of four runs, fluoropolymer gum and epichlorohydrin homopolymer gum were combined with a polyphenol, a tetraorganophosphonium salt, an acid acceptor, a filler, and a heat stabilizer. The ingredients were milled by putting the gum stock on the mill, adding the curing and cocuring agents as a group, adding all other ingredients as a group, and cutting the mixture back and forth until all ingredients were well dispersed. The curable gum stock was then molded and cured as indicated. The mechanical properties of the cured elastomers were determined before and after accelerated aging. Low temperature retraction, volume swell, and compression set data were also obtained. The composition of the curable gum stocks and the above mentioned mechanical properties are set forth in Table VII. Comparative data are shown for the unblended gums (Runs 1 and 6) . Table VII Run No. Ingredient Fluoropolymer gum? (parts) 100 76 55 44 29 Polyepichlorohydrin guro (parts) 24 45 56 71 100 Bisphenol AF (mmhr) 6.25 6 6 6 6 6 (CgH 5 ) 3 (CgH 5 CH 2 )P + Cl " (mmhr) 1.3 1.6 1.9 2 2.2 2.6 MgOC (phr) 3 Ca(OH) 2 (phr) 6 Dibasic lead phthalate (phr) 6.2 12 15 15 Tribasic lead naleate monohydrate^ (phr) 18 ASTM N-990 carbon black (phr) 30 30 30 30 30 30 N,N'-di-beta-naphthyl- p-phenylenediamine (phr) 0.7 1.3 1.6 2.1 Polymerized 2,2,4-trimethyl- 1,2-dihydroquinoline (phr) 2.5 An 80/20 mol % copolymer of "Hydrin 100", epichlorohydrin homopolymer, commercially available from B. F. Goodrich Chemical Co. c "Maglite D", commercially available from C.P. Hall Co. d "Trimal", commercially available from National Lead Co. Table VII (cont. ) Run No. Properties after press cure (10 min. at 177°C unless indicated otherwise) and post cure (24 hrs. at 177°C unless indicated otherwise ) : Tensile (MPa) 13.44 3 7.31 6.48 7.00 8.10 b 12.76 100% Modulus (MPa) 6.20 a 3.93 4.93 4.41 3.41 b 2.62 Elongation at break (%) 119955 a " 270 140 180 280 b 190 Hardness (Shore A-2) 75 a 76 77 76 72* 67 Accelerated aging of post cured sample - tensile (MPa) : Time at 177°C 3 days 10.69 c 8.89 6.48 8.31 6.93 5.07 7 days * 7.83 5.96 7.52 4.17 4.79 14 days * 6.27 4.93 5.69 3.14 2.93 3 Post cured for 24 hrs . at 260°C Press cured for 20 min. at 177°C *- Aged at 276°C. ( Essentially no change in properties when aged at 177°C . ) * Not run Table VII (cont.) Run No. Accelerated aging of post cured sanple - elongation at break (%): Time at 177°C 3 days 190° 200 125 145 200 * 7 days * 210 125 145 100 90 14 days * 160 110 115 100 90 Accelerated aging of post cured sanple - hardness (Shore A-2): Time at 177°C 3 days 77° 79 80 80 76 72 7 days * 80 81 81 74 77 14 days * 80 82 82 75 74 Lew teπperature retraction - TR, Q (°C): -17 * * -17 -18 -21 Volume swell, 70 hr. immersion (%) : AS3M #3 oil at 175°C 3 2 4 10 17 19 Reference Fuel C at 25°C 2 17 24 27 35 45 Compression set, O-rings, 70 hrs. at 150°C (%) : 10 21 20 36 37 42 Aged at 276 °C . ( Essentially no change in properties when aged at 177°C. ) * Not run Example 26 In this example fluoropolymer gum and epichloro- hydrin/ethylene oxide copolymer gum were combined with a polyphenol , a tetraorganophosphonium salt, a bas ic lead compound , a f iller , and two heat stabilizers . The curable gum stocks were compounded, milled and evaluated as in Example 25 . The compositions of the curable gum stocks and mechanical properties are set forth in Table VIII . Comparative data are shown for the unblended gums (Runs 7 and 10 ) . Table VIII Run No. Ingredient 7 8 9 10 Fluoropolymer gum (parts) 100 44 44 Polyepichlorohydrin gum! 3 (parts) 56 56 100 Bisphenol AF (mmhr) 6.25 6 6 6 (CgH 5 ) 3 (CgH 5 CH 2 )P + Cl " (mmhr) 1.3 2 2 2.6 MgO (phr) 3 Ca(0H) 2 (phr) 6 PbHP0 3 (phr) 18 Dibasic lead phthalate (phr) 15 c Tribasic lead fumarate (phr) 12 ASTM N-990 carbon black (phr) 30 30 Polymerized 2,2,4-trimethyl- 1,2-dihydroquinoline (phr) 2.5 N,N*-di-beta-naphthyl- p-phenylenediamine (phr) 2.5 2.5 Octadecyl amine 1.65 1.65 a An 80/20 mol % copolymer of and CF-CF CF,. "Hydrin 200", a 50/50 mol % copolymer of epichlorohydrin and ethylene oxide, commercially available from B.F. Goodrich Chemical Co. "Lectro 78" , commercially available from National Lead Co. "Armeen 18D", commercially available from Armour Chemical Co. Table VIII (cont. ) Run No. 10 Properties after press cure (20 min. at 177°C unless indicated otherwise) and post cure (24 hrs at 177°C unless indicated otherwise) : Tensile (MPa) 13.44 a 5.17 2.76 3.08 100% Modulus (MPa) 6.20 2.34 1.10 0.63 Elongation at break (%) 195 a 190 300 370 Hardness (Shore A-2) 75 a 67 58 33 Accelerated aging of post cured sample - tensile (MPa) : Time at 177°C 3 days 10.69 ' b 3.90 1.38 1.83 7 days * 2.65 0.97 * 14 days * 2.65 1.62 * Accelerated aging of post cured sairple - elongation at break (%) : Time at 177°C 3 days 190°'" 110 180 187 7 days * 80 100 * 14 days * 60 90 * Accelerated aging of post cured sairple - hardness (Shore A-2) : Time at 177 °C 3 days 77*' b 72 59 32 7 days * 72 60 19 14 days * 81 65 * a Press cured for 10 min at 177 °C and post cured for 24 hrs at 260°C Aged at 276°C. ( Essentially no change in properties when aged at 177°C. ) * Not run Example 27 In a series of five runs, fluoropolymer gum, epichlorohydrin homopolymer gum, and epichlorohydrin/ ethylene oxide copolymer gum were combined with a polyphenol, a tetraorganophosphonium salt, a basic lead compound, a filler, and two heat stabilizers. The curable gum stocks were compounded, milled and evaluated as in Example 25. The compositions of the curable gum stock and mechanical properties are set forth below in Table IX. Table IX Run No. 11 12 13 14 15 Fluoropolymer gum (parts) 28 28 28 44 44 Polyepichlorohydrin gum (parts) 36 36 36 20 20 Polyepichlorohydrin gum c (parts) 36 36 36 36 36 Bisphenol AF (mmhr) 6 6 6 6 6 (CgH 5 ) 3 (CH 2 =CHCH 2 )P + Cl~(mmhr) 2 2 2 2.2 2.2 Dibasic lead phthalate (phr) 15 15 PbO (phr) 24 Tribasic lead fumarate (phr) 24 Tribasic lead aleate onohydrate (phr) 12 ASTM N-990 carbon black (phr) 30 30 30 30 30 N ,N ' -di-beta-naphthyl p-phenylenediamine (phr) 2.5 2.5 2.5 2.2 2.2 Octadecyl amine (phr) 0.7 0.7 0.72 0.55 0.55 a An 80/20 mol % copolymer of CF 2 =CH 2 and CF 3 CF=CF 2 . "Hydrin 100 " , epichlorohydrin homopolymer , commercially available from B . F . Goodrich Chemical Co . c "Hydrin 200 " , a 50/50 mol % copolymer of epichlorohydrin and ethylene oxide , commercially available from B . F . Goodrich Chemical Co . Table IX (cont.) Run No. 11 12 13 14 15 Prcperties after press cure (20 min at 177°C) and post cure (24 hrs at 177°C): Tensile (MPa) 6.17 3.79 3.52 6.55 3.48 100% Modulus (MPa) 1.90 1.34 1.34 2.86 1.34 Elongation at break (%) 290 390 350 240 320 Hardness (Shore A-2) 66 60 60 69 62 Accelerated aging of post cured sanple - tensile (MPa): Tine at 177°C 3 days 5.38 3.52 3.24 5.24 2.96 7 days 3.24 2.72 2.72 3.65 2.41 14 days 2.69 2.17 2.41 3.14 2.17 Accelerated aging of post cured sanple - elongation at break (%) Time at 177°C 3 days 140 200 140 150 300 7 days 100 100 100 115 160 14 days 60 80 60 100 100 Accelerated aging of post cured sanple - hardness (Shore A-2): Time at 177°C 3 days 74 66 67 74 66 7 days 74 70 73 73 66 14 days 79 73 77 75 71 / Example 28 A laminated article was prepared by preparing two curable gum stocks (one containing a blend of a fluoropolymer gum and epichlorohydrin copolymer gum, and the other containing epichlorohydrin copolymer gum) , extruding the two curable gum stocks into 0.5 cm sheets or layers, I and II, and pressing the sheets against one another in a heated platen press under a pressure of 8 MPa at 160°C for 30 minutes. The excellent bond strength of the laminated article was demonstrated by pulling the two elastomeric layers apart according to a T-peel test as described in ASTM D-1876, on an Instron tensile tester at 23°C. At a crosshead separation rate of 5 cm/minute the T-peel test value was 6.96 Kg per lineal cm, with failure taking place mainly within the elastomeric layers rather than at the bond surface between them. The compositions of the curable gum stocks used to form the two layers are set forth below in Table X. V- Table X Ingredient Layer I Layer I Fluoropolymer gum (parts) Polyepichlorohydrin gum (parts) 25 100 Bisphenol S (mmhr) 6 6 (CgH 5 ) 3 (CgH 5 CH 2 )P + Cl~ (mmhr) 2.6 2.6 PbHP0 3 (phr) 4.5 18 Ca(OH) 2 (phr) 4.5 MgO (phr) 2.25 ASTM N-990 carbon black (phr) 30 30 Nickel dibutyldithiocarbamate (phr) 1 1 Nickel dimethyldithiocarbamate (phr) 1 1 C 8 F 17 S0 2 (C 2 H 5 )C 2 H 4 0(C 2 H 4 0) 2 H C (phr) 1 a An 80/20 mol % copolymer of CF 2 =CH 2 and CF 3 C =CF 2 . b "Hydrin 200", a 50/50 mol % copolymer of epichlorohydrin and ethylene oxide, commercially available from B. F. Goodrich Chemical Co. c A processing aid. Example 29 A laminated article was prepared from two sheets of curable gum stock, as described in Example 28, one sheet being curable fluoropolymer gum stock (layer I) and the other sheet being curable epichlorohydrin copolymer gum stock (layer II). The bond strength of the resulting laminate was 4.3 kg per lineal cm as measured in the T-peel test described in Example 28. The compositions of the two layers are set forth in Table XI. In a comparative experiment, a sheet of curable fluoropolymer gum stock (layer I) and a sheet of conven¬ tional curable epichlorohydrin gum stock (layer III) were pressed together in a heated platen press under a pressure of 8 MPa at 177°C for 30 minutes. The resulting article had a very weak sheet-to-sheet bond whose strength was not measurable on the Instron tensile tester. Table XI Ingredient Layer I Layer II Layer III Fluoropolymer gum (parts) 100 Epichlorohydrin copolymer gum (parts) 100 100 Bisphenol S (mmhr) 6.4 Bisphenol AF (mmhr) 4.2 (CgH 5 ) 3 (CgH 5 CH 2 )P + Cl " (mmhr) 1.8 5.0 2-Mercaptoimidazoline (mmhr) 9.8 PbHP0 3 (phr) 12 12 MgO (phr) 9 ASTM N-990 carbon black (phr) 15 ASTM N-762 carbon black 0 (phr) 7 ASΪM N-326 carbon black" (phr) 5 ASTM N-550 carbon black (phr) 50 50 Polymerized 2,2,4-trimethyl-l,2-dihydroquinoline (phr) 2.5 Nickel dibutyldithiocarbamate (phr) 1 Nickel dimethyldithiocarbamate (phr) 1 CgF 17 S0 2 N(C 2 H 5 )C 2 H 4 0(C 2 H 4 0) 2 H (phr) 1 Polyethylene wax e (phr) 1 Table XI (cont. ) Ingredient Layer I Layer II Layer III Carnauba wax (phr) 0.5 4,4'-Dichlorodiphenylsulfone 1 a An 80/20 mol % copolymer of F 2 =CH 2 and CF 3 CF=CF . "Hydrin 200", a 50/50 mol % copolymer of epichlorohydrin and ethylene oxide, commercially available from B. F. Goodrich Chemical Co. "Continex N-762", ccxπmercially available frcm Continental Carbon Co. "Continex N-326", commercially available frcm Continental Carbon Co. "AC-Polyethylene 6A" processing aid, commercially available frcm Allied Chemical Co. A processing aid Various modifications and alterations of this invention will be apparent to those skilled in the art without departing from the scope and spirit of this invention and the latter should not be restricted to that set forth herein for illustrative purposes.

Claims: Claims : 1. A curable gum stock composition comprising polyepichlorohydrin gum, polyphenol curing agent, and acid acceptor, characterized in that said composition contains: (a) organoammonium, organoarsonium, or organophosphonium cocuring agent of the formula: (i ) (R 1 ) 4 Q+1 (X "m )l/ια or (ii) (Rl) 3 QR 2 Q(Rl)3 +2 (χ- m ) 2 / ra wherein Q is a nitrogen, arsenic or phosphorus atom; X is an anion of valence m; each R^ is a monovalent organic radical containing 1 to 20 carbon atoms, is the same as or different from any other R-*-, and can combine with another ~T- to form a cyclic structure containing a Q atom; and R 2 is a divalent organic radical containing 2 to 12 carbon atoms; or (b) organosulfonium cocuring agent of the formula: (i) (R3) 3 s+l(X-m) 1/m or (ii) (R3) 2 SR S(R3) 2 + (X- m )2/ m wherein S is sulfur; X is an anion of valence m; each 3 is a monovalent organic radical containing 1 to 20 carbon atoms, is the same as or different from any other R3, and can combine with another R to form a cyclic structure containing an S atom; R 4 is a divalent organic radical containing 2 to 12 carbon atoms; and at least one R3 or R4 group is aromatic. 2. A composition according to Claim 1, further characterized in that said curing agent is selected from the class consisting of: (i) polyhydroxy benzenes, naphthalenes, anthracenes, chromones, xanthones, and anthraquinones; and (ii) polyphenols of the formula wherein p is 0 or 1; the sum (q+r) is 2 or more; and A is a thio, oxy, sulfinyl, sulfonyl or carbonyl radical or a divalent organic radical containing 1 to 13 carbon atoms. 3. A composition according to Claim 2, further characterized in that said curing agent comprises Bisphenol S or AF and said cocuring agent comprises tetraorganophosphonium salt. 4. A composition according to Claim 3, further characterized in that said composition contains, per 100 grams of the total weight of said polyepichlorohydrin gum, from 2.3 to 15 millimoles of said curing agent, from 0.2 to 7.5 millimoles of said cocuring agent, from 0.5 to 40 grams of acid acceptor selected from the group consisting of lead-based compounds, calcium hydroxide, and magnesium oxide, and from 0.1 to 20 grams of organic primary monoamine and/or polysecondary amine as heat stabilizer. 5. The composition of Claim 4 which is cured into an article having one or more layers of cured elastomer. 6. A composition according to Claim 1, further characterized in that said composition contains fluoro¬ polymer gum comprising a copolymer of (1) terminally ethylenically unsaturated olefin which has 2 to 4 carbon atoms and can be homopolymerized by emulsion polymeriza¬ tion in the presence of a water soluble free radical catalyst such as K 2 S 2 0g, and (2) at least one terminally unsaturated fluoromonoolefin, each of the doubly bonded chain carbon atoms of said fluoromonoolefin being bonded to at least one fluorine atom substituent and any remaining valence of any chain carbon atom of said fluoromonoolefin being satisfied by hydrogen, fluorine, chlorine, bromine, or a fluoroalkyl or fluoroalkoxy radical of 1 to 4 carbon atoms, with at least 10 percent of the chain carbon atoms of said copolymer being -CH_- units, at least 10 percent of the chain carbon atoms of said copolymer being bonded to alkyl or alkoxy radicals with the proviso that only one such radical is bonded to a given carbon atom, and with at least 50 percent of the total number of carbon-bonded moieties in said copolymer being fluorine, but with no chain carbon atom of said copolymer being bonded to more than one chlorine or bromine atom. 7. A composition according to Claims 4 and 6, characterized in that said polyepichlorohydrin gum is a homopolymer of epichlorohydrin or copolymer of epichlorohydrin and ethylene oxide, and said fluoropolymer gum comprises a copolymer of vinylidene fluoride and hexafluoropropene. 8. A method for preparing a shaped article from a composition according to Claim 6, characterized in that: (a) said fluoropolymer gum, said polyepichlorohydrin gum, said polyphenol curing agent, and said organo- onium cocuring agent are blended with acid acceptor to form a curable gum stock; (b) said curable gum stock is shaped; and (c) said shaped gum stock is subjected to sufficient heat and pressure to form a vulcanized elastomeric article. 9. A masterbatch composition for making the gum stock composition of Claim 1, characterized in that said masterbatch comprises: (a) polyepichlorohydrin gum; and (b) polyphenol curing agent; said masterbatch containing 100 to 900 parts of said curing agent per 100 parts of said gum. 10. A masterbatch composition for making the gum stock composition of Claim 1, characterized in that said masterbatch comprises: (a) polyepichlorohydrin gum; and (b) organo-onium cocuring agent selected from compounds of the formulas (i) (Rl) 4 Q + l(X- m ) 1 m or (ii) (R 1 ) 3 QR Q(R 1 )3 +2 (X-m )2/in wherein Q is a nitrogen, arsenic or phosphorus atom; X is an anion of valence ~ m; each R! is a monovalent organic radical containing 1 to 20 carbon atoms, is the same as or different from any other R!, and can combine with another R 1 to form a cyclic structure containing a Q atom; and R 2 is a divalent organic radical containing 2 to 12 carbon atoms; (iii) (R3) 3 s+l(X-m) 1/in or (iv) (R3) 2 SR4S(R3) 2 + ( -*)2 ITI wherein S is sulfur; X is an anion of valence m; each R3 is a monovalent organic radical containing 1 to 20 carbon atoms, is the same as or different from any other R3, and can combine with another R to form a cyclic structure containing an S atom; R 4 is a divalent organic radical containing 2 to 12 carbon atoms; and at least one R or R 4 group is aromatic; said masterbatch containing 100 to 900 parts of said cocuring agent per 100 parts of said gum.

Inventors: STIVERS D, WORM A
Applicants: MINNESOTA MINING & MFG, MINNESOTA MINING & MFG CO
Application year: 1980
Main classification: C08L63
IPC codes: C08J3, C08K5, C08L27, C08L71, C08L87