Abstract:
A rubbery polymer composition comprises a crosslinked copolymer comprising the following components. 
     Type I 
     15 to 40 wt. parts of a vinyl carboxylate having the formula (I); 
     60 to 85 wt. parts of an alkoxyalkyl acrylate having the formula (II); 
     0 to 15 wt. parts of ethylene; (100 wt. parts of a total of said three components); 
     0 to 5 wt. parts of the components having the formula (III), (IV) or (V): 
     Type II 
     15 to 55 wt. parts of a vinyl carboxylate having the formula (I); 
     5 to 20 wt. parts of ethylene; an alkyl acrylate having the formula (II&#39;); 
     an alkoxyalkyl acrylate having the formula (II) (100 wt. parts of a total of said four components and more than 0.8 of a ratio of the alkoxyalkyl acrylate (II) to the alkyl acrylate (II&#39;) by weight); 
     0 to 5 wt. parts of the components having the formula (III), (IV) or (V): 
     
       RCOO--CH═CH.sub.2                                      (I) 
     
      wherein R represents a C 1-4  alkyl group. 
     
       CH.sub.2 ═CHCOO--R.sub.1 --O--R.sub.2                  (II) 
     
      wherein R 1  represents a C 1-4  alkylene group; and 
      R 2  represents a C 1-4  alkyl or alkoxyalkyl group. 
     
       CH.sub.2 ═CHCOO--R.sub.6                               (II&#39;) 
     
      wherein R 6  represents a C 3-8  alkyl group. ##STR1##  wherein R 3  represents hydrogen atom or methyl group. ##STR2##  wherein R 4  represents vinyl, allyl or methallyl group. 
     
       CH.sub.2 ═CH--O--R.sub.5                               (V) 
     
      wherein R 5  represents CH 2  Cl--CH 2  --or CH 2  Cl--CO--group.

Description:
This application is a continuation of application Ser. No. 06/274,537 filed June 17, 1981, now abandoned, which in turn is a divisional of application Ser. No. 06/094,951 filed Nov. 16, 1979, now U.S. Pat. No. 4,303,560. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a rubbery polymer composition having excellent mechanical characteristics and durabilities such as heat resistance, oil resistance and weathering property, which is obtained by crosslinking a copolymer of a vinyl carboxylate and an alkoxyalkyl acrylate as main components. 
     2. Description of the Prior Arts 
     High mechanical properties such as tensile strength and elongation and high durabilities such as heat resistance, oil resistance and weathering property have been required for rubber parts such as parts for cars and other machines. Recently, the demand for durabilities has been increased. 
     Heretofore, chloroprene rubber or nitrile rubber has been usually used for rubber parts which should have oil resistance. However, the demand for heat resistance and weathering property (ozone resistance) has been further increased. Thus, acryl rubber or epichlorohydrin rubber which has said properties, has been used. The acryl rubber has disadvantages that it is highly swellable in a fuel oil and accordingly, it can not be used as parts which should have high fuel oil resistance. On the other hand, epichlorohydrin rubber has disadvantages that it has low fluxural resistance and it is softened by heating. A rubber having excellent mechanical properties and durabilities has not been found. 
     The inventors have studied on various kinds of rubber having balanced mechanical properties and durabilities. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a rubbery polymer composition which has excellent durabilities such as heat resistance, oil resistance (fuel oil resistance) and weathering property as well as excellent mechanical properties. 
     The foregoing and other objects of the present invention have been attained by providing a rubbery polymer composition which is obtained by crosslinking a copolymer comprising the following components. 
     Type I 
     15 to 40 wt.parts of a vinyl carboxylate having the formula (I); 
     60 to 85 wt.parts of an alkoxyalkyl acrylate having the formula (II); 
     0 to 15 wt.parts of ethylene; (100 wt.parts of a total of said three components); 
     0 to 5 wt.parts of the components having the formula (III), (IV) or (V): 
     Type II 
     15 to 55 wt.parts of a vinyl carboxylate having the formula (I); 
     5 to 20 wt.parts of ethylene; an alkyl acrylate having the formula (II&#39;); 
     an alkoxyalkyl acrylate having the formula (II) (100 wt.parts of a total of said four components and more than 0.8 of a ratio of the alkoxyalkyl acrylate (II) to the alkyl acrylate (II&#39;) by weight); 
     0 to 5 wt.parts of the components having the formula (III), (IV) or (V): 
     
         RCOO--CH═CH.sub.2                                      (I) 
    
     wherein R represents a C 1-4  alkyl group. 
     
         CH.sub.2 ═CHCOO--R.sub.1 --O--R.sub.2                  (II) 
    
     wherein R 1  represents a C 1-4  alkylene group; and R 2  represents a C 1-4  alkyl or alkoxyalkyl group. 
     
         CH.sub.2 ═CHCOO--R.sub.6                               (II&#39;) 
    
     wherein R 6  represents a C 3-8  alkyl group. ##STR3## wherein R 3  represents hydrogen atom or methyl group. ##STR4## wherein R 4  represents vinyl, allyl or methallyl group. 
     
         CH.sub.2 ═CH--O--R.sub.5                               (V) 
    
     wherein R 5  represents CH 2  Cl--CH 2  -- or CH 2  Cl--CO-- group. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The vinyl carboxylates have the formula 
     
         R--COOCH═CH.sub.2                                      (I) 
    
     wherein R represents a C 1-4  alkyl group. 
     Suitable vinyl carboxylates include vinyl acetate, vinyl propionate and vinyl butyrate. When vinyl caproate (R is a C 5  alkyl group) is used, the satisfactory oil resistance can not be given. 
     The alkoxyalkyl acrylates have the formula 
     
         CH.sub.2 ═CHCOOR.sub.1 --O--R.sub.2                    (II) 
    
     wherein R 1  represents a C 1-4  alkylene group and R 2  represents C 1-4  alkyl or alkoxy group. 
     Suitable alkoxyalkyl acrylates include methoxyethyl acrylate, methoxymethyl acrylate, ethoxyethyl acrylate, butoxyethyl acrylate, methoxyethoxyethyl acrylate and ethoxyethoxyethyl acrylate. 
     The alkyl acrylates have the formula 
     
         CH.sub.2 ═CHCOO--R.sub.6                               (II&#39;) 
    
     wherein R 6  represents a C 3-8  alkyl group. 
     Suitable alkyl acrylates include n-butyl acrylate, n-hexyl acrylate, n-octyl acrylate and 2-ethylhexyl acrylate. 
     In Type I, the copolymer comprises the components of 15 to 40 wt.parts of a vinyl carboxylate (I), 60 to 85 wt.parts of an alkoxyalkyl acrylate (II) and 0 to 15 wt.parts of ethylene as 100 wt.parts of a total of said three components. 
     When the content of the vinyl carboxylate is less than 15 wt.parts, the mechanical properties of the composition are inferior and unsatisfactory whereas when it is more than 40 wt.parts, the cold resistance of the composition is unsatisfactory. 
     In the specification, the cold resistance means a low temperature property. 
     When the content of the alkoxyalkyl acrylate is less than 60 wt.parts, the oil resistance of the composition is unsatisfactory, whereas when it is more than 85 wt.parts, the mechanical properties of the composition are inferior and unsatisfactory. 
     Ethylene is not always incorporated. In order to improve the cold resistance of the composition, ethylene can be incorporated at a ratio of less than 15 wt.parts. When the content of ethylene is more than 15 wt.parts, the fuel oil resistance of the composition is unsatisfactory. The content ethylene is preferably less than 10 wt.parts. 
     In Type II, the copolymer comprises the components of 15 to 55 wt.parts of a vinyl carboxylate (I) 5 to 20 wt.parts of ethylene and an alkyl acrylate (II&#39;) and an alkoxyalkyl acrylate (II) as 100 wt.parts of a total of said four components and more than 0.8 of a ratio of the alkoxyalkyl acrylate (II) to the alkyl acrylate (II&#39;) by weight. 
     When the content of the vinyl carboxylate (I) is less than 15 wt.parts, the mechanical properties of the composition are inferior and unsatisfactory whereas when it is more than 55 wt.parts, the cold resistance of the composition is unsatisfactory. 
     When the content of ethylene is less than 5 wt.parts, the cold resistance of the composition is unsatisfactory whereas when it is more than 20 wt.parts, the oil resistance of the composition is unsatisfactory. The content of ethylene is preferably in a range of 5 to 15 wt.parts. 
     The ratio of the alkoxyalkyl acrylate (II) to the alkyl acrylate (II&#39;) by weight is more than 0.8. When it is less than 0.8, the oil resistance is unsatisfactory. 
     The alkyl acrylate (II&#39;) is incorporated in the copolymer in order to give superior cold resistance of the composition in comparison with that of the incorporation of only alkoxyalkyl acrylate, at a ratio for giving satisfactory oil resistance of the composition. The content of the alkyl acrylate (II&#39;) is preferably in a range of 10 to 35 wt.parts especially 15 to 35 wt.parts. 
     The alkoxyalkyl acrylate is incorporated in the copolymer in order to give superior oil resistance. The content of the alkoxyalkyl acrylate is usually in said range and preferably in a range of 15 to 65 wt.parts. 
     In both of Type I and Type II, 0 to 5 wt.parts of the components having the formula (III), (IV) or (V) are incorporated. 
     Suitable compounds having the formula (III) include glycidyl acrylate and glycidyl methacrylate. 
     Suitable compounds having the formula (IV) include vinylglycidyl ether, allylglycidyl ether and methallylglycidyl ether. 
     Suitable compounds having the formula (V) include vinyl chloroacetate and 2-chloroethyl vinyl ether. 
     The compounds (III), (IV), (V) provide crosslinking points in the composition of the present invention so that the crosslinking of the composition can be performed with a polyfunctional compound such as polyamine beside peroxides. The crosslinking can be performed in hot air. However, when the content of the compounds (III), (IV), (V) is excess, the crosslinked degree is too high to attain satisfactory mechanical strength. Thus, the content of the compounds (III), (IV), (V) is usually in a range of 0 to 5 wt.parts preferably 0.3 to 3 wt.parts. When it is more than 5 wt.parts, the crosslinked degree is too high to attain satisfactory mechanical strength. 
     The copolymer used in the present invention can be produced by a copolymerization of the monomers at substantially same ratios for the components in the compositions by an emulsion polymerization, a bulk polymerization, a solution polymerization, etc. It is preferable to produce it by the emulsion polymerization. 
     In order to produce the copolymer having ethylene component, the polymerization can be carried out in an atmosphere of ethylene under a pressure. The polymerization is usually carried out by a method similar to the conventional copolymerization of ethylene-vinyl acetate. The detail description of the method of the polymerization is eliminated. 
     The copolymer has 35 to 50 of Mooney viscosity (ML 1+4 ) at 100° C. measured by Mooney viscometer (manufactured by Toyo Seiki K.K.). 
     The crosslinking is carried out by incorporating 0.3 to 10 wt.% preferably 0.5 to 5 wt.% of a crosslinking agent based on the copolymer, into the copolymer. When the content of the crosslinking agent is less than 0.3 wt.%, the crosslinking is not satisfactory whereas when it is more than 10 wt.%, excess of crosslinking is caused or scorch is caused. 
     Suitable crosslinking agents include peroxides such as benzoylperoxide, 2,4-dichlorobenzoylperoxide, 1,1-di-(t-butylperoxy)-3,3,5-trimethylcyclohexane, n-butyl-4,4-bis(t-butylperoxy)valerate, dicumylperoxide, di-t-butylperoxy-diisopropylbenzene 2,5-dimethyl-2,5-di-(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di-(t-butylperoxy)hexine-3, etc. 
     An epoxide ring cleavage agent can be used as a crosslinking agent for a copolymer having any component derived from the compound (III), (IV), (V). 
     Suitable epoxide ring cleavage agents include polyamines such as tetraethylenepentamine, hexaethylenetetramine, hexamethylenediaminecarbamate, N,N&#39;-dicinnamylidene-1,6-hexanediamine and thermally decomposable ammonium salts such as ammonium benzoate, ammonium citrate ammonium tartarate. The crosslinking agent can be combined with a dithiocarbamate (metal salts), a thiuram or sulfur etc. 
     In order to impart practically advantageous properties as rubber products, it is preferable to incorporate a reinforcing agent such as carbon black, silicic acid anhydride, silicic acid hydrate, hard clay, surface treated calcium carbonate and micro talc at a ratio of 10 to 200 wt.parts especially 30 to 100 wt.parts per 100 wt.parts of the copolymer together with the crosslinking agent in the rubbery polymer composition. 
     In order to modify processability and other properties, it is possible to incorporate a lubricant such as stearic acid and its metal salt; a filler such as soft clay, precipitated calcium carbonate, crushed calcium carbonate and talc; a petroleum type softener; a plasticizer such as synthetic polyester, polyoxyethylene ester or ether type plasticizer; and an antioxidant. 
     When the copolymerization is carried out by forming crosslinking points with the compound (V), a stearic acid salt imparts a function as a crosslinking agent. Thus, the combination should be carefully considered. 
     The antioxidant can be most of antioxidants used for stabilizing polymers. 
     Suitable antioxidants include amine type antioxidants such as N-phenyl-N&#39;-isopropyl-p-phenylenediamine, phenyl-α-naphthylamine, acrylic acid esters having aromatic amine component, (NOCRAC G-1 manufactured by Ouchi Shinko Kagaku K.K.) trimethyldihydroquinoline polycondensed product; phenol type antioxidants such as 3,5-di-t-butyl-4-hydroxytoluene, 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 4,4&#39;-thiobis(6-t-butyl-3-methylphenol); dithioic acid type antioxidants such as nickel dibutyldithiocarbamate and dilauryldithiopropionate; phosphoric acid ester type antioxidants such as tris(nonylphenyl)phosphite etc. 
     One or more of the antioxidant can be incorporated. 
     In order to incorporate various additives into the composition of the copolymer, the conventional kneading methods used in the rubber industry can be used. It is possible, if necessary, to use a wet master batch method wherein carbon black and other additives are incorporated into a slurry of the copolymer obtained by the polymerization for producing the copolymer, and the mixture is dried. 
     The rubbery polymer composition of the present invention can be obtained by crosslinking the mixture obtained by kneading the copolymer, the additives and the crosslinking agent by a desired conventional vulcanization used in the rubber industry. 
     The condition of crosslinking i.e. vulcanization is depending upon a kind and amount of the crosslinking agnet and the crosslinking is usually performed at 120° to 200° C. for about 2 to 200 minutes. 
     The copolymer can be crosslinked at various crosslinking velocity depending upon the kind of the crosslinking agent. It is possible to incorporate sulfur together with the crosslinking agent. 
     Thus, in order to prepare the rubbery polymer composition of the present invention by the crosslinking, it is possible to blend the copolymer to the other rubbery polymer such as EPDM, NBR, chloroprene rubber, natural rubber, styrene-butadiene rubber, butadiene rubber, butyl rubber and isoprene rubber, whereby the oil resistance and the weathering property of the composition can be improved while the mechanical properties of the rubbery polymer are maintained in suitable levels. 
     The resulting rubbery polymer compositions of the present invention is molded before or during the crosslinking by a desired rubber molding method to obtain rubber parts suitable for usages requiring high oil resistance, heat resistance and weathering property together with the mechanical properties such as rubber parts for car especially rubber parts requiring high fuel oil resistance such as a fuel oil horse and industrial parts used in contacting with a hot lubricant oil. 
     The present invention will be further illustrated by certain examples and references which are provided for purposes of illustration only and are not intended to be limiting the present invention. 
     In the examples and references, the structures of the copolymer were measured by the following analysis of the components. 
     A solution of a copolymer is prepared and an aqueous solution of sodium hydroxide is added to the solution whereby a hydrolysis of the copolymer is carried out. After the hydrolysis, the content of --COONa in the solution is measured by a potentiometric titration. The free carboxylic acid the alcohol and the alkoxyalcohol in the solution are completely separated from the hydrolyzed copolymer. The free carboxylic acid is measured by a titration. The alcohol is measured by a gas chromatography. The contents of the vinyl carboxylate, the alkyl acrylate and the alkoxyalkyl acrylate are calculated. When the component of the compound (III), (IV), (V) is included, the compounds (III), (IV) are measured by a quantitative analysis of epoxy group, and the compound (V) is measured by a quantitative analysis of chlorine atom. The content of ethylene component is calculated by subtracting the contents of these components from the total weight of the copolymer. 
    
    
     EXAMPLE 1 
     In a 40 liter autoclave, 16.2 kg. of an aqueous solution containing 530 g. of polyvinyl alcohol (hereinafter referring to as PVA) and 21.6 g. of sodium acetate was charged and then, 2.16 kg. of vinyl acetate and 8.64 kg. of 2-methoxyethyl acrylate were added with stirring to emulsify the mixture. The autoclave was purged with nitrogen gas and ethylene monomer was fed from the top under a pressure. The partial pressure of ethylene was adjusted to 55 kg./cm 2  at a polymerization temperature of 65° C. 
     Then, 1% aqueous solution of ammonium persulfate was added for several times to stop the polymerization for about 10 hours. The residual monomer was removed, and the resulting emulsion of copolymer was coagulated with 3% aqueous solution of borax and the product was separated, dehydrated and dried on rolls to obtain the copolymer. The yield of the copolymer was 10.4 kg. and the copolymer had a structure comprising 18 wt.parts of vinyl acetate component, 76 wt.parts of 2-methoxyethyl acrylate component and 6 wt.parts of ethylene component. 
     The copolymer was admixed with the following additives and the mixture was kneaded by 8 inch rolls at 40° C. and then, press-vulcanized at 160° C. for 30 minutes to prepare a vulcanized sheet having 15 cm×15 cm and a thickness of 2 mm. Physical properties of the sample were measured. The results are shown in Table 1. 
     
         ______________________________________Copolymer             100    wt. partsAntioxidant (NOCRAC 224:                 1      wt. partsOuchishinko Kagaku)Stearic acid          1      wt. partsCarbon SRF-LM         60     wt. partsDicumyl peroxide      1.5    wt. partsTriallylcyanurate     2      wt. parts______________________________________ 
    
     Reference 1 
     In accordance with the process of Example 1 except using epichlorohydrin rubber (Hydrin 200 manufactured by Goodrich Co. Ltd.) the following components were mixed, kneaded and vulcanized and physical properties of the sample were measured. The results are shown in Table 1. 
     
         ______________________________________Epichlorohydrin rubber                 100    wt. partsAntioxidant (NOCRAC 224)                 1      wt. partsStearic acid          1      wt. partsCarbon SRF-LS         60     wt. partsRed lead              5      wt. partsVulcanization accelerator                 1.5    wt. parts(NOCCELER-22manufactured by SanshinKagaku Co. Ltd.)______________________________________ 
    
     Reference 2 
     In accordance with the process of Example 1 except using acryl rubber (AR-31 manufactured by Nippon Zeon Co., Ltd.), the following components were mixed, kneaded and vulcanized and physical properties of the sample were measured. The results are shown in Table 1. 
     
         ______________________________________Acryl rubber         100    wt. partsAntioxidant          1      wt. parts(NOCRAC 224)Stearic acid         1      wt. partsCarbon SRF-LM        60     wt. partsAmmonium benzoate    1      wt. parts______________________________________ 
    
     
                       TABLE 1______________________________________     Example  Reference Reference     1        1         2______________________________________Physical property*.sup. 1T.sub.B (kg./cm.sup.2)       107        145       118E.sub.B (%) 230        300       250Hs           56        67        62Heat resistance-1*.sup. 2A.sub.R (T.sub.B) (%)       108        87        93A.sub.R (E.sub.B) (%)        67        67        66ΔHs   +6         -2        +7Heat resistance-2*.sup. 3A.sub.R (T.sub.B) (%)       102        40        95A.sub.R (E.sub.B) (%)        68        87        64ΔHs   +7         -18       +7Oil resistance *.sup.4        41        39        77ΔV, (%)______________________________________ Note: *.sup.1 Japanese Industrial Standard K 6301 T.sub.B : tensile strength E.sub.B : elongation Hs: hardness measured by spring type hardness tester (Japanese Industrial Standard) *.sup.2 Japanese Industrial Standard K 6301 6.3: (measured after heatageing at 150°  C. for 96 hours) A.sub.R (T.sub.B): residual percent of T.sub.B after heatageing to T.sub. before heatageing (%) A.sub.R (E.sub.B): residual percent of E.sub.B after heatageing to E.sub. before heatageing (%) ΔH.sub.B : difference between Hs before heatageing and Hs after heatageing *.sup.3 Japanese Industrial Standard K 6301 6.3: (measured after ageing a 150° C. for 192 hours) The definitions of A.sub.R (T.sub.B), A.sub.R (E.sub.B) and ΔHs are defined above. *.sup.4 Japanese Industrial Standard K 6301 ΔV: volume increase percent after dipping into a fuel oilC at 20° C. for 48 hours (%) These definitions are also applied for the data in the following tables. 
    
     EXAMPLES 2 TO 4 
     Reference 3 
     In a 40 liter autoclave, 16.2 kg. of each aqueous solution containing 530 g. of PVA, 21.6 g. of sodium acetate, 34.2 g. of Rongalit, 1.08 g. of ethylenediaminetetraacetic acid and 0.54 g. of ferrous sulfate was charged and 2.16 kg. of each vinyl carboxylate was added to it with stirring to emulsify the mixture. The autoclave was purged with nitrogen gas and heated at 45° C. and a mixture of 8.64 kg. of 2-methoxyethyl acrylate and 162 g. of glycidyl methacrylate and 1% aqueous solution of ammonium persulfate were respectively fed dropwise from different inlets, during 8 to 16 hours and the polymerization was performed. After the polymerization, the residual monomer was removed and the resulting emulsion of copolymer was coagulated with an aqueous solution of borax and the product was separated, dehydrated and dried on rolls to obtain the copolymer. The structures and yields of the copolymers are shown in Table 2. 
     Each copolymer was admixed with the following additives and the mixture was kneaded by 8 inch rolls at 50° C. and then, press-vulcanized at 160° C. for 30 minutes to prepare a vulcanized sheet having 15 cm×15 cm and a thickness of 2 mm. Physical properties of each sample were measured. The results are shown in Table 2. 
     
         ______________________________________Copolymer            100    wt. partsAntioxidant          1      wt. parts(NOCRAC 224)Stearic acid         1      wt. partsCarbon HAF           40     wt. partsTetraethylenepentamine                1      wt. parts______________________________________ 
    
     
                       TABLE 2______________________________________                  Exp. 3         Exp. 2   vinyl   Exp. 4 Ref. 3         vinyl    propi-  vinyl  vinylVinyl carboxylate         acetate  onate   butyrate                                 caproate______________________________________Structure (wt. parts)vinyl caroxylate comp.         19       21      17     222-methoxyethyl acrylate         81       79      83     78comp.glycidyl methacrylate          1.0      0.9     1.1    1.0comp.Yield (kg.)   10.5     10.6    10.1   10.2Physical propertyT.sub.B (kg/cm.sup.2)         145      111     83     85E.sub.B (%)   170      170     190    130Hs            66       64      57     58Heat resistance-1A.sub.R (T.sub.B) (%)         104      100     121    100A.sub.R (E.sub.B) (%)         71       77      69     81ΔHs     +9       +7      +12    +7Oil resistance         30       35      43     66ΔV (%)Cold resistance*.sup. 5         -23      -33     -36    -39T.sub.b (°C.)Ozone resistance*.sup. 6         no crack no      no crack                                 no crack                  crack______________________________________  Note: *.sup.5 Japanese Industrial Standard K 6301 14 T.sub.b : brittle point temperature *.sup.6 A formation of cracking of a sample is observed after storing a sample treated by stretching 20% in an atmosphere containing 100 ppm of ozone at 40° C. These definitions are also applied for the data in the following table. 
    
     EXAMPLES 5 TO 8 
     References 4 to 6 
     In a 40 liter autoclave, 16.2 kg. of each aqueous solution containing 530 g. of PVA, 21.6 g. of sodium acetate, 32.4 g. of Rongalit, 1.08 g. of ethylenediaminetetraacetic acid and 0.54 g. of ferrous sulfate was charged and each vinyl acetate was added to it with stirring to emulsify the mixture. The autoclave was purged with nitrogen gas and ethylene monomer was fed from the top under a pressure in the case of a copolymerization of ethylene. In the examples, the partial pressure of ethylene was varied in a range of 20 to 150 kg/cm 2  at a polymerization temperature of 45° C. Then, a mixture of 2-methoxyethyl acrylate and 162 g. of glycidyl methacrylate and 1% aqueous solution of ammonium persulfate were respectively fed dropwise from different inlets during 8 to 16 hours and the polymerization was performed. A total amount of 2-methoxyethylacrylate and vinyl acetate was 10.8 kg. After the polymerization, a monomer was removed and the resulting emulsion of copolymer was coagulated with an aqueous solution of borax and the product was separated, dehydrated and dried on rolls to obtain the copolymer. The structures and yields of the copolymers are shown in Table 3. 
     Each copolymer was admixed with the following additives and the mixture was kneaded by 8 inch rolls at 50° C. and then, press-vulcanized to prepare a vulcanized sheet having 15 cm×15 cm and a thickness of 2 mm. Physical properties of each sample were measured. The results are shown in Table 3. 
     
         ______________________________________Copolymer            100    wt. partsAntioxidant          1      wt. parts(NOCRAC 224)Stearic acid         1      wt. partsCarbon HAF           40     wt. partsTetraethylenepentamine                1      wt. parts______________________________________ 
    
     
                                           TABLE 3__________________________________________________________________________       Exp. 5            Exp. 6                 Exp. 7                      Ref. 4                           Ref. 5                                Ref. 6__________________________________________________________________________Structure (wt. part)vinyl acetate comp.       36   24   18   47   24   52-methoxyethyl       64   65   78   53   57   92acrylate comp.ethylene comp.       0    11   4    0    19   3glycidyl methacrylate       1.0  1.0  1.1  1.0  0.9  1.1comp.Yield (kg.) 9.9  10.3 10.1 9.8  10.3 9.5Physical propertyT.sub.B (kg/cm.sup.2)       115  121  125  123  117  97E.sub.B (%) 240  250  220  240  260  70Hs          58   56   56   61   53   50Heat resistanceA.sub.R (T.sub.B) (%)       101  108  105  106  109  117A.sub.R (E.sub.B) (%)       63   67   61   68   65   55ΔHs   +8   +7   +8   +6   +8   +13Oil resistance       35   47   38   28   90   41ΔV (%)Cold resistance       -15  -31  -30  -5   -36  -35T.sub.b (°C.)Ozone resistance       no   no   no   no   no    no       crack            crack                 crack                      crack                           crack                                crack__________________________________________________________________________ 
    
     EXAMPLES 8 TO 11 
     Reference 7 
     In a 40 liter autoclave, 16.2 kg. of an aqueous solution containing 530 g. of PVA, 21.6 g. of sodium acetate, 32.4 g. of Rongalit, 1.08 g. of ethylenediaminetetraacetic acid and 0.54 g. of ferrous sulfate was charged and 2.7 kg. of vinyl acetate was added to it with stirring to emulsify the mixture. The autoclave was purged with nitrogen gas and ethylene monomer was fed from the top under a pressure. The partial pressure of ethylene was adjusted to 50 kg/cm 2  at a polymerization temperature of 55° C. Then, a mixture of 8.1 kg. of 2-methoxyethyl acrylate and glycidyl methacrylate (an amount varied in a range of 60 to 900 g.) and 1% aqueous solution of ammonium persulfate were respectively fed dropwise from different inlets during 8 to 10 hours and the polymerization was performed. After the polymerization, a residual monomer was removed and the resulting emulsion of copolymer was coagulated with an aqueous solution of borax and the product was separated, dehydrated and dried on rolls to obtain the copolymer. The structures and yields of the copolymers were shown in Table 4. Each copolymer was admixed with the following additives and the mixture was kneaded by 8 inch rolls at 50° C. and then, press-vulcanized at 160° C. for 31 minutes and post-vulcanized at 150° C. for 15 hours in Geer&#39;s oven to prepare a vulcanized sheet having an area of 15 cm 2  and a thickness of 2 mm. Physical properties of each sample were measured. The results are shown in Table 4. 
     
         ______________________________________Copolymer            100    wt. partsAntioxidant          1      wt. parts(NOCRAC NBC)Stearic acid         1      wt. partsCarbon SRF-LM        60     wt. partsTetraethylenepentamine                1.5    wt. parts______________________________________ 
    
     
                       TABLE 4______________________________________                    Exp.      Exp. 8            Exp. 9  10     Exp. 11                                  Ref. 7______________________________________Structure: (wt. parts)vinyl acetate comp.        23      21      22   21     202-methoxyethyl        70      73      70   72     74arcrylate comp.ethylene comp.         7       6       8    7      6glycidyl methacry-         0.4     0.7     1.6  4.2    6.1late comp.Yield (kg.)  10.1    10.3    10.4 10.2   10.5Physical propertyT.sub.B (kg/cm.sup.2)        108     117     125  121    87E.sub.B (%)  330     260     210  120    60Hs           52      59      62   68     79______________________________________ 
    
     EXAMPLE 12 
     In a 40 liter autoclave, 16.2 kg. of an aqueous solution containing 530 g. of PVA, 21.6 g. of sodium acetate, 32.4 g. of Rongalit, 1.08 g. of ethylenediaminetetraacetic acid and 0.54 g. of ferrous sulfate was charged and 2.7 kg. of vinyl acetate was added to it with stirring to emulsify the mixture. The autoclave was purged with nitrogen gas and ethylene monomer was fed from the top under a pressure. The partial pressure of ethylene was adjusted to 55 kg/cm 2  at a polymerization temperature of 55° C. Then, a mixture of 8.1 kg. of 2-methoxyethyl acrylate and 2l6 g. of vinyl chloroacetate and 1% aqueous solution of ammonium persulfate were respectively fed dropwise from different inlets, during 10 hours and the polymerization was performed. After the polymerization, the residual monomer was removed and the resulting emulsion of copolymer was coagulated with an aqueous solution of borax and the product was separated, dehydrated and dried on rolls to obtain 10.2 kg. of the copolymer. The composition of the copolymer comprises 20 wt. parts of vinylacetate component, 73 wt. parts of 2-methoxyethyl acrylate, 7 wt. parts of ethylene and 1.3 wt. parts of vinyl chloroacetate. 
     Each copolymer was admixed with the following additives and the mixture was kneaded by 8 inch rolls at 50° C. and then, press-vulcanized at 170° C. for 30 minutes to prepare a vulcanized sheet having 15 cm×15 cm and a thickness of 2 mm. Physical properties of the sample were measured. The results are shown in Table 5. 
     
         ______________________________________Copolymer          100 wt. partsAntioxidant (NOCRAC 224)              1 wt. partStearic Acid       1 wt. partCarbon SRF-LM      60 wt. partsTetraethylenepentamine              1 wt. part______________________________________ 
    
     
                       TABLE 5______________________________________         Example 12______________________________________Physical propertyT.sub.B (kg/cm.sup.2)           109E.sub.B (%)     230Hs              58Heat resistanceA.sub.R (T.sub.B) (%)           110A.sub.R (E.sub.B) (%)           56ΔHs       +8Oil resistance  41ΔV (%)Cold resistance -24T.sub.b (°C.)______________________________________ 
    
     EXAMPLES 13 TO 18 
     The copolymer obtained in Example 9 was admixed with the following additives and the mixture was kneaded by 8 inch rolls at 40° C. and vulcanized in the condition shown in Table 6 to prepare each vulcanized sheet having 15 cm×15 cm and a thickness of 2 mm. Physical properties of each sample were measured. The results are shown in Table 7. 
     
                       TABLE 7______________________________________        Exp. Exp.   Exp.   Exp. Exp. Exp.        13   14     15     16   17   18______________________________________Composition: (wt. part)Copolymer      100    100    100  100  100  100Antioxidant                  0.5  1(NOCRAC TNP)Antioxidant    1      1      1         1    1(NOCRAC 224)Stearic acid   1      1      1    1    1    1Carbon ISAF    40                           40Carbon FEF            80Carbon FT                         60Calcium carbonate                      80Hard clay                    80Plasticizer                                 10Ammonium benzoate                 1Hexamethylene         1diamine carbamateTriethylenetetramine          1             1         1    1Diethyleneglycol             2Vulcanization condition:Press-vulcanization:Temperature (°C.)          160    160    160  170  160  160Time (min.)    30     30     30   30   30   30Post-vulcanization:Temperature (°C.)          150    150    150  150  150  150Time (min.)    8      8      15   8    15   15Physical propertyT.sub.B (kg/cm.sup.2)          153    162    121  102  100  139E.sub.B (%)    210    120    150  270  450  230Hs             67     85     60   52   54   64Heat resistanceA.sub.R (T.sub.B) (%)          97     95     103  110  102  100A.sub.R (E.sub.B) (%)          80     77     71   63   67   78ΔHs      +4     +3     +5   +6   +8   +2Oil resistanceΔV (%)   43     38     44   40   46   35Cold resistance          -25    -13    -22  -23  -21  -33T.sub.b (°C.)______________________________________ 
    
     EXAMPLE 19 
     In a 40 liter autoclave, 16.2 kg. of an aqueous solution containing 530 g. of PVA, 21.6 g. of sodium acetate, 32.4 g. of Rongalit, 1.08 g. of ethylenediaminetetraacetic acid and 0.54 g. of ferrous sulfate was charged and 5.4 kg. of vinyl acetate was added to it with stirring to emulsify the mixture. The autoclave was purged with nitrogen gas and ethylene monomer was fed from the top under a pressure. The partial pressure of ethylene was adjusted to 50 kg/cm 2  at a polymerization temperature of 55° C. Then, a mixture of 2.7 kg. of n-butyl acrylate, 2.7 kg. of 2-methoxyethyl acrylate and 1% aqueous solution of ammonium persulfate were respectively fed dropwise from different inlets during 8 to 10 hours and the polymerization was performed. After the polymerization, a residual monomer was removed and the resulting emulsion of copolymer was coagulated with 3% of aqueous solution of borax and the product was separated, dehydrated and dried on two rolls at 120° to 130° C. to obtain the polymer. The structures and yields of the copolymers are shown in Table 8. 
     The copolymer was admixed with the following additives and the mixture was kneaded by 8 inch rolls at 40° C. and press-vulcanized at 160° C. for 30 minutes to prepare a vulcanized sheet having 15 cm×15 cm and a thickness of 2 mm. Physical properties of each sample were measured. The results are shown in Table 8. 
     
         ______________________________________Copolymer           100    wt. partsAntioxidant         1      wt. part(NOCRAC 224)Stearic acid        1      wt. partCarbon SRF-LM       60     wt. partsDicumyl peroxide    1.5    wt. partsTriallyl cyanurate  2.0    wt. parts______________________________________ 
    
     EXAMPLES 20, 21 
     References 8 to 11 
     In accordance with the process of Example 19, except varying ratio of monomers (10.8 kg. of total amount of vinylacetate, n-butyl acrylate, and 2-methoxyethyl acrylate) and varying the partial pressure of ethylene in a range of 30 to 70 kg/cm 2 , the preparation and the measurement were repeated. The results are shown in Table 8. 
     
                       TABLE 8______________________________________     Exp. Exp.   Exp.   Ref. Ref. Ref. Ref.     19   20     21     8    9    10   11______________________________________ Structure: (wt.part)vinyl acetate comp.       51     32     19   62   7    75   45n-butyl acrylate       19     28     37   15   41   8    43comp.2-methoxyethyl       23     31     38   17   44   0    0acrylate comp.ethylene comp.       7      9      6    6    8    17   12Yield (kg.) 10.4   10.6   10.3 10.8 9.9  10.9 10.3Physical property*.sup. 1T.sub.B (kg/cm.sup.2)       120    113    103  118  50   132  101E.sub.B (%) 220    240    250  230  310  210  320Hs          60     58     52   65   51   87   68Heat resistance*.sup.2A.sub.R (T.sub.B) (%)       107    102    111  109  115  98   104A.sub.R (E.sub.B) (%)       60     62     61   67   47   65   72ΔHs   +9     +7     +9   +7   +15  +6   +10Oil resistance*.sup.3       23     24     26   18   29   25   47ΔV (%)Cold resistance.sup.*4       -11    -25    -35  +1   -40  0    -20T.sub.b (°C.)______________________________________ 
    
     EXAMPLES 22 TO 24 
     Reference 12 
     In a 40 liter autoclave, 16.2 kg. of an aqueous solution containing 530 g. of sodium dodecylbenzenesulfonate, 21.6 g. of sodium acetate, 32.4 g. of Rongalit, 1.08 g. of ethylenediaminetetraacetic acid and 0.54 g. of ferrous sulfate was charged and vinyl acetate was added to it with stirring to emulsify the mixture. The autoclave was purged with nitrogen gas and ethylene monomer was fed from the top under a pressure. The partial pressure of ethylene was varied in a range of 60 to 150 kg/cm 2  at a polymerization temperature of 45° C. in the examples. Then, a mixture of n-butyl acrylate, 2-methoxyethyl acrylate and 162 g. of glycidyl methacrylate and 1% aqueous solution of ammonium persulfate were respectively fed dropwise from different inlets, during 8 to 12 hours and the polymerization was performed. A total of vinyl acetate, n-butyl acrylate and 2-methoxyethyl acrylate was 10.8 kg. but the ratios of the monomers were varied in the examples. In accordance with the process of Example 2 the physical properties of the vulcanized sheet obtained by using the resulting copolymer were measured. The results are shown in Table 9. 
     
                       TABLE 9______________________________________       Exp. 22              Exp. 23  Exp. 24  Ref. 12______________________________________Structure: (wt. part)vinyl acetate comp.         41       37       23     22n-butyl acrylate comp.          8       17       32     362-methoxyethyl acrylate         35       28       28     24comp.ethylene comp.         16       18       17     18glycidyl methacrylate          1.0      1.1      1.0    0.9 -comp.Yield (kg.)   10.8     10.6     10.4   10.3Physical propertyT.sub.B (kg/cm.sup.2)         123      131      113    115E.sub.B (%)   200      230      250    240Hs            66       67       67     68Heat resistanceA.sub.R (T.sub.B) (%)         115      110      121    114A.sub.R (E.sub.B) (%)         58       62       61     55ΔHs     +8       +9       +9     +7Oil resistance         20       26       30     41ΔV (%)Cold resistance         -26      -27      -37    -39T.sub.b (°C.)______________________________________ 
    
     EXAMPLES 25, 26 
     Reference 13, 14 
     In a 40 liter autoclave, 16.2 kg. of an aqueous solution containing 530 g. of PVA, 21.6 g. of sodium acetate, 32.4 g. of Rongalit, 1.08 g. of ethylenediaminetetraacetic acid and 0.54 g. of ferrous sulfate was charged and vinyl acetate was added to it with stirring to emulsify the mixture. The autoclave was purged with nitrogen gas and ethylene monomer was fed from the top under a pressure. The partial pressure of ethylene was varied in a range of 30 to 150 kg/cm 2  at a polymerization temperature of 45° C. in the examples. Then, a mixture of n-butyl acrylate, 2-methoxyethyl acrylate and 162 g. of glycidyl methacrylate and 1% aqueous solution of ammonium persulfate were respectively fed dropwise from different inlets, during 8 to 12 hours and in the polymerization was performed. A total of vinyl acetate, n-butyl acrylate and 2-methoxyethyl acrylate was 10.8 kg. but the ratios of the monomers were varied in the examples. 
     After the polymerization, a residual monomer was removed and the resulting emulsion of copolymer was coagulated with an aqueous solution of borax and the product was separated, dehydrated and dried on rolls to obtain the copolymer. The structures and yields of the copolymers are shown in Table 10. Each copolymer was admixed with the following additives and the mixture was kneaded by 8 inch rolls at 40° C. and then, press-vulcanized at 170° C. for 30 minutes and post-vulcanized at 150° C. for 8 hours in Geer&#39;s oven to prepare a vulcanized sheet having 15 cm×15 cm and a thickness of 2 mm. Physical properties of each sample were measured. The results are shown in Table 10. 
     
         ______________________________________Copolymer        100 wt. partsAntioxidant      1 wt. parts(NOCRAC TNP)Stearic acid     1 wt. partsCarbon FEF       1 wt. partsAmmonium benzoate            1 wt. parts______________________________________ 
    
     
                       TABLE 10______________________________________        Exp. 25               Exp. 26  Ref. 13 Ref. 14______________________________________Structure: (wt. part)vinyl acetate comp.          53       21       53    32n-butyl acrylate comp.          20       30       19    232-methoxyethyl acrylate          17       32       26    19comp.ethylene comp. 10       17        2    26glycidyl methacrylate           0.9      0.9      1.1   1.0comp.Yield (kg.)    10.5     11.1     10.0  11.3Physical propertyT.sub.B (kg/cm.sup.2)          129      115      124   108E.sub.B (%)    190      200      180   210Hs             68       61       75    58Heat resistanceA.sub.R (T.sub.B) (%)          103      100      100   111A.sub.R (E.sub.B) (%)          87       83       90    85ΔHs      +2       +2       +2    +4Oil resistance 21       28       13    43ΔV (%)Cold resistance          -11      -39            -38T.sub.b (°C.)______________________________________ 
    
     EXAMPLES 27, 28 
     Reference 15 
     In accordance with the process of Example 25 except feeding ethylene under a partial pressure of 50 kg/cm 2  at a polymerization temperature of 55° C. and varying the ratios of vinyl acetate, n-butyl acrylate, 2-methoxyethyl acrylate, ethylene and glycidyl methacrylate, each copolymer was produced, and each vulcanized sheet was prepared by admixing the copolymer with the following additives and physical properties were measured. The results are shown in Table 11. 
     
         ______________________________________Copolymer          100 wt. partsAntioxidant        1 wt. parts(NOCRAC NS-6)Stearic acid       1 wt. parts -Carbon SRF-LM 60 wt. partsPlasticizer        7 wt. parts(Emulgen 109 Pmanufactured by Kao Soap)Hexamethylene diamine-              1 wt. paartscarbamate______________________________________ 
    
     
                       TABLE 11______________________________________         Exp. 27  Exp. 28  Ref. 15______________________________________Structure: (wt. part)vinyl acetate comp.           45         49       44n-butyl acrylate comp.           22         17       212-methoxyethyl acrylate           24         21       25comp.ethylene comp.   9         13       10glycidyl methacrylate comp.            0.7        4.1      5.7Yield (kg.)     10.7       10.6     10.9Physical propertyT.sub.B (kg/cm.sup.2)           102        113      130E.sub.B (%)     260        160      75Hs              57         72       79Oil resistance  20         21       19ΔV (%)Cold resistance -17        -16      -18T.sub.b (°C.)______________________________________ 
    
     EXAMPLES 29 TO 31 
     Reference 16 
     In a 40 liter autoclave, 16.2 kg. of each aqueous solution containing 530 g. of PVA, 21.6 g. of sodium acetate, 34.2 g. of Rongalit, 1.08 g. of ethylenediaminetetraacetic acid and 0.54 g. of ferrous sulfate was charged and 5.4 kg. of each vinyl carboxylate was added to it with stirring to emulsify the mixture. The autoclave was purged with nitrogen gas and ethylene monomer was fed from the top under the pressure. The pressure of ethylene was adjusted to 50 kg/cm 2  at 45° C. Then, a mixture of 2.7 kg. of n-butyl acrylate, 2.7 kg. of 2-methoxyethyl acrylate and 162 g. of glycidylmethacrylate and 1% aqueous solution of ammonium persulfate were respectively fed dropwise from different inlets during 8 to 10 hours and the polymerization was performed. After the polymerization, the residual monomer was removed and the resulting emulsion of copolymer was coagulated with an aqueous solution of borax and the product was separated, dehydrated and dried on rolls to obtain the copolymer. The structure and yields of the copolymers are shown in Table 2. 
     Each copolymer was admixed with the following additives and the mixture was kneaded by 8 inch rolls at 50° C. and then, press-vulcanized at 160° C. for 30 minutes to prepare a vulcanized sheet having 15 cm×15 cm and a thickness of 2 mm. Physical properties of each sample were measured. The results are shown in Table 12. 
     
         ______________________________________Copolymer            100    wt. parts.Antioxidant          1      wt. parts.(NOCRAC 224)Stearic acid         1      wt. parts.Carbon HAF           40     wt. parts.Tetraethylene pentamine                1      wt. parts.______________________________________ 
    
     
                       TABLE 12______________________________________                  Exp.          Exp.    30          29      vinyl   Exp. 31                                 Ref. 16          vinyl   propi-  vinyl  vinylType of vinyl carboxylate          acetate onate   acetate                                 caproate______________________________________Structure: (wt. part)vinyl carboxylate comp.          30      30      29     27n-butyl acrylate comp.          28      27      28     272-methoxyethyl 33      34      35     38acrylate comp.ethylene comp.  9       7       8      8glycidyl methacrylate           0.9    0.9      1.0   0.9comp.Yield (kg.)    10.5    9.9     10.1   9.7Physical propertyT.sub.B (kg/cm.sup.2)          132     115     98     72E.sub.B (%)    190     210     250    300Hs             62      59      53     47Heat resistanceA.sub.R (T.sub.B) (%)          105     107     112    119A.sub.R (E.sub.B) (%)          63      60      59     53ΔHs      +7      +8      +11    +14Oil resistance 25      27      30     42ΔV (%)Cold resistance          -26     -38     -42    -49T.sub.b  (°C.)______________________________________ 
    
     EXAMPLE 32 
     In a 40 liter autoclave, 16.2 kg. of an aqueous solution containing 530 g. of PVA, 21.6 g. of sodium acetate, 32.4 g. of Rongalit, 1.08 g. of ethylenediaminetetraacetic acid and 0.54 g. of ferrous sulfate was charged and then, 5.4 kg. of vinyl acetate was added with stirring to emulsify the mixture. The autoclave was purged with nitrogen gas and ethylene monomer was fed from the top under a pressure. The partial pressure of ethylene was adjusted to 50 kg./cm 2  at a polymerization temperature of 45° C. Then, a mixture of 2.7 kg of 2-ethylhexyl acrylate and 2.7 kg. of 2-methoxyethyl acrylate and 216 g. of vinyl chloroacetate, and 1% aqueous solution of ammonium persulfate were respectively fed dropwise from different inlets during 8 to 10 hours and the polymerization was performed. After the polymerization, a residual monomer was removed and the resulting emulsion of copolymer was coagulated with 3% aqueous solution of borax and the product was separated, dehydrated and dried on rolls to obtain the copolymer. The structure of the copolymer is shown in Table 13. The yield was 10.7 kg. 
     The copolymer was admixed with the following additives and the mixture was kneaded by 8 inch rolls at 50° C. and then, press-vulcanized at 160° C. for 30 minutes to prepare a vulcanized sheet having 15 cm×15 cm and a thickness of 2 mm. Physical properties of the sample were measured. The results are shown in Table 13. 
     
                       TABLE 13______________________________________             Example 32______________________________________Structure: (wt. part)vinyl acetate comp. 432-ethylhexyl acrylate comp.               212-methoxyethyl acrylate comp.               24ethylene comp.      12vinyl chloroacetate comp.               1.4Additive: (wt. part)Copolymer           100Antioxidant          1(NOCRAC 224)Stearic acid         1Carbon FEF          20Calcium carbonate   60Triethylenetetraamine                1Physical propertyT.sub.B (kg./cm.sup.2)               111E.sub.B (%)         420Hs                  57Heat resistanceA.sub.R (T.sub.B) (%)               98A.sub.R (E.sub.B) (%)               83ΔHs           +3Oil resistance      30ΔV (%)Cold resistance     -20T.sub.b (°C.)______________________________________