Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/04—Oxygen-containing compounds
  • C08K5/14—Peroxides
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/0008—Organic ingredients according to more than one of the "one dot" groups of C08K5/01 - C08K5/59
  • C08K5/0025—Crosslinking or vulcanising agents; including accelerators
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
  • C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
  • C08L23/04—Homopolymers or copolymers of ethene
  • C08L23/08—Copolymers of ethene
  • C08L23/0807—Copolymers of ethene with unsaturated hydrocarbons only containing more than three carbon atoms
  • C08L23/0815—Copolymers of ethene with aliphatic 1-olefins
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L2312/00—Crosslinking

Definitions

• Crosslinking of ethylene- ⁇ -olefin copolymer rubbers is carried out using not sulfur, but organic peroxides, because the copolymers have no double bond in their main chains.
• the rubbers have been used for automotive parts, industrial packing, electrical wires and electrical wire connecting parts, but these parts are desired to be produced at a low cost.
• it is included to decrease an amount of an organic peroxide crosslinking agent. In these methods, however, the crosslinking is insufficiently performed, resulting in problems of low modulus and poor resistance to permanent set.
• ethylene-propylene copolymer rubbers or ethylene-propylene-diene copolymer rubbers formed by a diene such as ethylidene norbornene, cyclopentadiene or 1,4-hexadiene have excellent mechanical and electrical properties. Moreover, they shows high thermal aging resistance and weathering resistance because they have no double bond in their main chains. Therefore, these rubbers have been widely used for automotive parts, industrial rubber parts, electrical parts and civil engineering and building materials, as described above.
• the ethylene-propylene copolymer rubbers and the ethylene-propylene-diene copolymer rubbers have been recently desired to have much higher thermal aging resistance and fluidity (molding processability).
• an ethylene copolymer rubber composition which is imparted with good processability (fluidity) by blending an ethylene- ⁇ -olefin-polyene copolymer rubber having a different molecular weight is proposed in Japanese Patent Publication No. 14497/1984.
• this rubber composition does not show such high thermal aging resistance as desired.
• An anti-aging agent is added to the ethylene-propylene copolymer rubber or the ethylene-propylene-diene copolymer rubber.
• Japanese Patent Laid-Open Publication No. 23433/1985 proposes a rubber composition for sulfur vulcanization which is prepared by blending 100 parts by weight of an ethylene- ⁇ -olefin-diene copolymer rubber having an iodine value of 5 to 12, 1 to 10 parts by weight of a phenol compound and 1 to 4 parts by weight of an imidazole compound.
• compositions proposed in the publication are improved in the thermal aging resistance, but the level thereof is not satisfactory in the uses for automotive parts and electrical parts, so that the thermal aging resistance should be much more improved.
• a heat-resistant rubber composition comprising an ethylene- ⁇ -olefin copolymer rubber, polyorganosiloxane and a silica type filler treated with a silane compound is disclosed as a heat-resistant rubber composition of high thermal aging resistance.
• the rubber composition disclosed in the publications are obviously improved in the thermal aging resistance, but the level thereof is not satisfactory in the uses for automotive parts and electrical parts, so that the thermal aging resistance should be much more improved. Moreover, these compositions do not show such high fluidity (molding processability) as desired.
• a vulcanizable heat-resistant rubber composition capable of providing a vulcanized rubber molded product of prominently high thermal aging resistance without losing excellent mechanical and electrical properties inherent in the ethylene-propylene copolymer rubber or the ethylene-propylene-diene copolymer rubber has been also desired.
• the present invention is intended to solve such problems associated with the prior art as described above, and it is an object of the invention to provide a heat-resistant rubber composition being vulcanizable and having high crosslinking efficiency and capable of providing a vulcanized rubber molded product of high thermal aging resistance.
• a heat-resistant rubber composition according to the invention is a vulcanizable composition comprising:
• an ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A) composed of ethylene, an ⁇ -olefin of 3 to 20 carbon atoms and a nonconjugated polyene, and
• said ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A) having the following properties:
• a molar ratio of ethylene to the ⁇ -olefin of 3 to 20 carbon atoms is in the range of 40/60 to 95/5 (ethylene/ ⁇ -olefin),
• the nonconjugated polyene is 5-vinyl-2-norbornene, 5-isopropenyl-2-norbornene or 5-isobutenyl-2-norbornene,
• the other heat-resistant rubber composition according to the invention is a vulcanizable composition comprising:
• an amine type anti-aging agent (C) composed of diphenylamines and/or phenylenediamines, in an amount of 0.2 to 5 parts by weight, and/or a hindered phenol type anti-aging agent (D) in an amount of 0.2 to 5 parts by weight,
• said ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A) having the following properties:
• a molar ratio of ethylene to the ⁇ -olefin of 3 to 20 carbon atoms is in the range of 40/60 to 95/5 (ethylene/ ⁇ -olefin),
• the nonconjugated polyene is 5-vinyl-2-norbornene, 5-isopropenyl-2-norbornene or 5-isobutenyl-2-norbornene,
• the nonconjugated polyene content is in the range of 0.5 to 50 g/100 g in terms of an iodine value
• the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A) may be an ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber having been graft-modified with an unsaturated carboxylic acid or its derivative.
• the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A) may be a blend of:
• the total amount of said components (A1) and (A2) being 100 parts by weight.
• the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A1) has the following properties:
• said copolymer rubber is a copolymer rubber composed of ethylene, an ⁇ -olefin of 3 to 20 carbon atoms and a nonconjugated polyene;
• a molar ratio of ethylene to the ⁇ -olefin of 3 to 20 carbon atoms is in the range of 40/60 to 95/5 (ethylene/ ⁇ -olefin);
• the nonconjugated polyene is 5-vinyl-2-norbornene
• the nonconjugated polyene content is in the range of 0.5 to 50 g/100 g in terms of an iodine value.
• the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A2) has the following properties:
• said copolymer rubber is a copolymer rubber composed of ethylene, an ⁇ -olefin of 3 to 20 carbon atoms and a nonconjugated polyene;
• a molar ratio of ethylene to the ⁇ -olefin of 3 to 20 carbon atoms is in the range of 40/60 to 95/5 (ethylene/ ⁇ -olefin);
• the nonconjugated polyene is 5-vinyl-2-norbornene, 5-isopropenyl-2-norbornene or 5-isobutenyl-2-norbornene;
• the nonconjugated polyene content is in the range of 0.5 to 50 g/100 g in terms of an iodine value.
• the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A) which is a blend of the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A1) and the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A2) has:
• the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A1) and/or the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A2) may be an ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber having been graft-modified with an unsaturated carboxylic acid or its derivative.
• ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A) which is a blend of the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A1) and the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A2) is used, a vulcanizable heat-resistant rubber composition having extremely good fluidity and capable of forming a vulcanized rubber molded product showing not only excellent mechanical and electrical properties but also prominently high thermal aging resistance and high crosslinking efficiency can be obtained.
• a heat-resistant rubber composition according to the invention is described in detail hereinafter.
• a heat-resistant rubber composition according to the invention is a vulcanizable rubber composition comprising:
• the other heat resistant rubber composition of the invention according to the invention is a vulcanizable rubber composition comprising:
• the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A) is a rubber prepared by copolymerizing ethylene, an ⁇ -olefin of 3 to 20 carbon atoms and a nonconjugated polyene.
• the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A) may be a blend of ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubbers (A1) and (A2) each of which is by copolymerizing ethylene, an ⁇ -olefin of 3 to 20 carbon atoms and a nonconjugated polyene.
• Examples of the ⁇ -olefins of 3 to 20 carbon atoms include propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-nonadecene, 1-eicosene, 9-methyl-1-decene, 11-methyl-1-dodecene and 12-ethyl-1-tetradecene.
• These ⁇ -olefins are used singly or in combination of two or more kinds.
• ⁇ -olefins preferred are propylene, 1-butene, 1-hexene, 1-octene and 1-decene.
• a molar ratio of ethylene to the ⁇ -olefin of 3 to 20 carbon atoms is in the range of 40/60 to 95/5 (ethylene/ ⁇ -olefin), preferably 50/50 to 90/10, more preferably 55/45 to 85/15, particularly preferably 55/45 to 80/20.
• the nonconjugated polyene of the ethylene- ⁇ - olefin - nonconjugated polyene copolymer rubber ( A ) is a vinyl end group—containing norbornene compound which includes 5 - vinyl - 2 - norbornene, 5 - isopropenyl - 2 - norbornene, and 5 - isobutenyl - 2 - norbornene, or 5 - methylene - 2 - norbornene.
• the nonconjugated polyene of the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A1) is 5-vinyl-2-norbornene
• the nonconjugated polyene of the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A2) is 5-vinyl-2-norbornene, 5-isopropyenyl-2-norbornene or 5-isobutenyl-2-norbornene.
• Any of the nonconjugated polyene is a vinyl end group-containing norbornene compound. used in combination with the following nonconjugated polyene compounds:
• chain nonconjugated diene compounds such as 1,4-hexadiene, 3-methyl-1,4-hexadiene, 4-methyl-1,4-hexadiene, 5-methyl-1,4-hexadiene, 4,5-dimethyl-1,4-hexadiene and 7-methyl-1,6-octadiene;
• cyclic nonconjugated diene compounds such as methyltetrahydroindene, 5-ethylidene-2-norbornene, 5-methylene-2-norbornene, 5-isopropylidene-2-norbornene, 5-vinylidene-2-norbornene and 6-chloromethyl-5-isopropenyl-2-norbornene; and
• triene compounds 2,3-diisopropylidene-5-norbornene, 2-ethylidene-3-isopropylidene-5-norbornene and 2-propenyl-2,2-norbornadiene.
• the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A) used in the invention has a nonconjugated polyene content of 0.5 to 50, preferably 1 to 40 in terms of an iodine value.
• the nonconjugated polyene content is less than 0.5 in terms of an iodine value, the crosslinking efficiency is lowered.
• the nonconjugated polyene content exceeds 50, the resulting rubber composition has poor resistance to environmental deterioration.
• the nonconjugated polyene content is an indication of a vulcanizing rate in the vulcanization process. Together with other properties such as an intrinsic viscosity and an ethylene content, the nonconjugated polyene content contributes to the preparation of a copolymer rubber having good fluidity (molding processability) and high strength.
• the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A) used in the invention has an intrinsic viscosity [ ⁇ ], as measured in decalin at 135° C., of 0.1 to 10 dl/g, preferably 0.5.to 7 dl/g, more preferably 0.9 to 5 dl/g.
• the intrinsic viscosity [ ⁇ ] is an indication of a molecular weight of the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A). Together with other properties such as the nonconjugated polyene content, the intrinsic viscosity contributes to the preparation of a copolymer rubber having excellent fluidity (molding processability), strength, heat resistance and weathering resistance.
• each of the copolymer rubbers (A1) and (A2) has a nonconjugated polyene content of 0.5 to 50, preferably 1 to 40 in terms of an iodine value.
• the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A1) has an intrinsic viscosity [ ⁇ ], as measured in decalin at 135° C., of 1 to 10 dl/g, preferably 2 to 6 dl/g, more preferably 3 to 5 dl/g.
• the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A2) has an intrinsic viscosity [ ⁇ ], as measured in decalin at 135° C. of 0 1 to 5 dl/g, preferably 0.2 to 2 dl/g, more preferably 0.3 to 1 dl/g.
• ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A2) having an intrinsic viscosity within the above range and the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A1) By blending the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A2) having an intrinsic viscosity within the above range and the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A1), a rubber composition showing good fluidity (molding processability) and capable of providing a vulcanized rubber of excellent properties can be obtained.
• the blend of the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubbers (A1) and (A2) has a Mooney viscosity [ML 1+4 (100° C.)] of 5 to 180, a molar ratio of ethylene to the ⁇ -olefin of 40/60 to 95/5 (ethylene/ ⁇ -olefin), and a polyene content of 0.5 to 50 in terms of an iodine value.
• the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubbers (A), (A1) and (A2) can be prepared by processes described in, for example, Japanese Patent Publication No. 14497/1984. That is, the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubbers (A), (A1) and (A2) can be obtained by copolymerizing ethylene, the ⁇ -olefin of 3 to 20 carbon atoms and the nonconjugated polyene in the presence of Ziegler catalyst using hydrogen as a molecular weight modifier.
• the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubbers (A), (A1) and (A2) may be graft-modified products obtained by graft-modifying the above-described ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubbers with unsaturated carboxylic acids or their derivatives (acid anhydrides, esters).
• unsaturated carboxylic acids examples include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, tetrahydrophthalic acid and bicyclo(2,2,1)hepto-2-ene-5,6-dicarboxylic acid.
• unsaturated carboxylic anhydrides examples include maleic anhydride, itaconic anhydride, citraconic anhydride, tetrahydrophthalic anhydride and bicyclo(2,2,1)hepto-2-ene-5,6-dicarboxylic anhydride.
• maleic acid is maleic acid.
• unsaturated carboxylic esters examples include methyl acrylate, methyl methacrylate, dimethyl maleate, monomethyl maleate, dimethyl fumarate, dimethyl itaconate, diethyl citraconate, dimethyl tetrahydrophthalate and dimethyl bi(cyclo(2,2,1)hepto-2-ene-5,6-dicarboxylate. Of these, preferred are methyl acrylate and ethyl acrylate.
• the graft modifiers such as the unsaturated carboxylic acids are used singly or in combination of two or more kinds.
• the graft quantity is preferably not more than 0.1 mol based on 100 g of the aforementioned unmodified ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber.
• the graft-modified ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber can be obtained by causing the unmodified ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber to react with the unsaturated carboxylic acid or its derivative in the presence of a radical initiator.
• This graft reaction can be carried out in a solution state or a molten state.
• the graft reaction is performed in the molten state, it is most efficient and preferred to continuously perform the reaction in an extruder.
• radical initiators used for the graft reaction include:
• dialkyl peroxides such as dicumyl peroxide, di-t-butyl peroxide, di-t-butylperoxy-3,3,5-trimethylcyclohexane, t-butylcumyl peroxide, di-t-amyl peroxide, t-butyl hydroperoxide, 2,5-dimethyl-2,5-di(t-butylperoxyne)hexyne-3,2,5-dimethyl-2,5-di(benzoylperoxy)hexane, 2,5-dimethyl-2,5-mono(t-butylperoxy)hexane and ⁇ , ⁇ ′-bis(t-butylperoxy-m-isopropyl)benzene;
• peroxy esters such as t-butyl peroxyacetate, t-butyl peroxyisobutyrate, t-butyl peroxypivalate, t-butyl peroxymaleate, t-butyl peroxyneodecanoate, t-butyl peroxybenzoate and di-t-butyl peroxyphthalate;
• ketone peroxides such as dicylohexanone peroxide
• organic peroxides having a temperature, at which the half-life period thereof corresponds to one minute, of 130° to 200° C.
• organic peroxides having a temperature, at which the half-life period thereof corresponds to one minute, of 130° to 200° C.
• dicumyl peroxide di-t-butyl peroxide, di-t-butylperoxy-3,3,5-trimethylcyclohexane, t-butylcumyl peroxide, di-t-amyl peroxide and t-butyl hydroperoxide.
• the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubbers (A), (A1) and (A2) having a Mooney viscosity [ML 1+4 (100° C.)] of 5 to 180, particularly 10 to 120, are preferably used from the viewpoints of mechanical properties and fluidity molding processability).
• the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A1) is used in an amount of 30 to 95 parts by weight, preferably 35 to 80 parts by weight, more preferably 40 to 70 parts by weight, based on 100 parts by weight of the total amount of the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A1) and the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A2); and the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A2) is used
• the organic peroxide used in the invention is an organic peroxide which is conventionally used for rubbers.
• organic peroxides examples include:
• dialkyl peroxides such as dicumyl peroxide, di-t-butyl peroxide, di-t-butylperoxy-3,3,5-trimethylcyclohexane, t-butylcumyl peroxide, di-t-amyl peroxide, t-butyl hydroperoxide, 2,5-dimethyl-2,5-di(t-butylperoxyne)hexyne-3, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, 2,5-dimethyl-2,5-mono(t-butylperoxy)hexane and 5, ⁇ , ⁇ ′-bis(t-butylperoxy-m-isopropyl)benzene;
• peroxy esters such as t-butyl peroxyacetate, t-butyl peroxyisobutyrate, t-butyl peroxypivalate, t-butylperoxymaleic acid, t-butyl peroxyneodecanoate, t-butyl peroxybenzoate and di-t-butyl peroxyphthalate;
• ketone peroxides such as dicyclohexanone peroxide
• organic peroxides having a temperature, at which the half-life period thereof corresponds to one minute, of 130° to 200° C.
• organic peroxides having a temperature, at which the half-life period thereof corresponds to one minute, of 130° to 200° C.
• particularly preferred are dicumyl peroxide, di-t-butyl peroxide, di-t-butylperoxy-3,3,5-trimethylcyclohexane, t-butylcumyl peroxide, di-t-amyl peroxide and t-butyl hydroperoxide.
• the organic peroxide is used in an amount of 0.0003 to 0.05 mol, preferably 0.001 to 0.03 mol, based on 100 g of the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A), but it is desired that the optimum amount is properly determined according the required property values.
• a vulcanization aid is preferably used in combination.
• the vulcanization aids include sulfur; quinonedioxime compounds, such as p-quinonedioxime; methacrylate compounds, such as polyethylene glycol dimethacrylate; allyl compounds, such as diallyl phthalate and triallyl cyanurate; maleimide compounds; and divinyl benzene.
• the vulcanization aid is used in an amount of 0.5 to 2 mol based on 1 mol of the organic peroxide, preferably in an equimolar amount.
• diphenylamines and/or phenylenediamines are used as the amine type anti-aging agent (C).
• phenylenediamines examples include p-phenylenediamines, such as N,N′-diphenyl-p-phenylenediamine, n-isopropyl-N′-phenyl-p-phenylenediamine, N,N′-di-2-naphthyl-p-phenylenediamine, N-cyclohexyl-N′-phenyl-p-phenylenediamine, N-phenyl-N′-(3-methacryloyloxy-2-hydroxypropyl)-p-phenylenediamine, N,N′-bis(1-methylheptyl)-p-phenylenediamine, N,N′-bis(1,4-dimethylpentyl)-p-phenylenediamine, N,N′-bis(1-ethyl-3-methylpentyl)-p-phenylenediamine, N-bis(1,3-dimethylbutyl)-
• the amine type anti-aging agent (C) is used in an amount of 0.2 to 5 parts by weight, preferably 0.5 to 4 parts by weight, more preferably 1 to 3 parts by weight, based on 100 parts by weight of the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A).
• the thermal aging resistance can be highly improved, and crosslinking of the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A) is not inhibited.
• Examples of the hindered phenol type anti-aging agents (D) include:
• the hindered phenol type anti-aging agent (D) is used in an amount of 0.2 to 5 parts by weight, preferably 0.5 to 4 parts by weight, more preferably 1 to 3 parts by weight, based on 100 parts by weight of the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A).
• the hindered phenol type anti-aging agent (D) is used in the above-mentioned amount, the thermal aging resistance can be highly improved, and crosslinking of the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A) is not inhibited.
• the sulfur type anti-aging agent (E) used in the invention is a sulfur type anti-aging agent which is conventionally used for rubbers.
• sulfur type anti-aging agents (E) include those of imidazole type, such as 2-mercaptobenzimidazole, zinc salt of 2-mercaptobenzimidazole, 2-mercaptomethylbenzimidazole and zinc salt of 2-mercaptomethylbenzimidazole; and those of aliphatic thioether type, such as dimyristyl thiodipropionate, dilauryl thiodipropionate, distearyl thiodipropionate and ditridecyl thiodipropionate, pentaerythritol-tetrakis-( ⁇ -lauryl-thiopropionate).
• imidazole type such as 2-mercaptobenzimidazole, zinc salt of 2-mercaptobenzimidazole, 2-mercaptomethylbenzimidazole and zinc salt of 2-mercaptomethylbenzimidazole
• aliphatic thioether type such as dimyristyl thiodipropionate,
• the heat-resistant rubber composition according to the invention can be used in an unvulcanized state, but when it is used in the form of a vulcanized product such as a vulcanized rubber molded product or a vulcanized rubber foamed product, its properties are most conspicuously exhibited.
• known additives such as rubber reinforcement, softener, vulcanization aid, processing aid, foaming agent, foaming aid, colorant, dispersant and flame retardant can be added according to the use of the aimed vulcanized product, in addition to the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A), the organic peroxide (B), if necessary, the amine type anti-aging agent (C) and/or the hindered phenol type anti-aging agent (E), and the sulfur type anti-aging agent (E).
• A ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber
• B organic peroxide
• C amine type anti-aging agent
• E hindered phenol type anti-aging agent
• sulfur type anti-aging agent E
• the total amount of the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A), the amine type anti-aging agent (C), the hindered phenol type anti-aging agent (D) and the sulfur type anti-aging agent (E) in the rubber composition is usually not less than 25% by weight, preferably not less than 40% by weight, though it varies depending on the uses.
• the rubber reinforcement serves to enhance mechanical properties such as tensile strength, tear strength and abrasion resistance of the vulcanized rubber.
• the rubber reinforcements include carbon black such as SRF, GPF, FEF, MAF, HAF, ISAF, SAF, FT and MT, carbon black thereof which are surface-treated with, for example, silane coupling agents, silica, activated calcium carbonate, powdery talc and powdery silicic acid.
• the amount of the rubber reinforcement can be selected according to the use of the vulcanized rubber, the amount thereof is usually not more than 200 parts by weight, particularly not more than 100 parts by weight, based on 100 parts by weight of the total amount of the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A), the amine type anti-aging agent (C), the hindered phenol type anti-aging agent (D) and the sulfur type anti-aging agent (E).
• softeners those conventionally used for rubbers are employable, and examples thereof include:
• petroleum type softening agents such as process oil, lubricating oil, paraffin, liquid paraffin, petroleum asphalt and vaseline;
• coal tar type softeners such as coal tar and coal tar pitch
• fatty oil type softeners such as castor oil, linseed oil, rapeseed oil and coconut oil;
• waxes such as beeswax, carnauba wax and lanolin
• fatty acids and fatty acid salts such as ricinolic acid, palmitic acid, barium stearate, calcium stearate and zinc laurate; and
• synthetic polymer materials such as petroleum resin, atactic polypropylene and coumarone-indene resin.
• petroleum type softeners and among them, particularly preferred is process oil.
• the amount of the softener can be selected according to the use of the vulcanized rubber, but the amount thereof is usually not more than 200 parts by weight, particularly not more than 100 parts by weight, based on 100 parts by weight of the total amount of the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A), the amine type anti-aging agent (C), the hindered phenol type anti-aging agent (D) and the sulfur type anti-aging agent (E).
• the unvulcanized compounded rubber is irradiated with the electron rays having energy of 0.1 to 10 MeV (megaelectron volt), preferably 0.3 to 2 MeV, in such a manner that the absorbed dose becomes 0.5 to 35 Mrad (megarad), preferably 0.5 to 10 Mrad.
• the electron rays having energy of 0.1 to 10 MeV (megaelectron volt), preferably 0.3 to 2 MeV, in such a manner that the absorbed dose becomes 0.5 to 35 Mrad (megarad), preferably 0.5 to 10 Mrad.
• the vulcanization aid that is used in combination with the organic peroxide (vulcanizing agent), may be used.
• the vulcanization aid is used in an amount of 0.0001 to 0.1 mol, preferably 0.001 to 0.03 mol, based on 100 g of the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A).
• those conventionally used for rubbers are employable, and examples thereof include higher fatty acids, such as ricinolic acid, stearic acid, palmitic acid and lauric acid; salts of higher fatty acids, such as barium stearate, zinc stearate and calcium stearate; and esters of higher fatty acids, such as recinolic acid ester, stearic acid ester, palmitic acid ester and lauric acid ester.
• higher fatty acids such as ricinolic acid, stearic acid, palmitic acid and lauric acid
• salts of higher fatty acids such as barium stearate, zinc stearate and calcium stearate
• esters of higher fatty acids such as recinolic acid ester, stearic acid ester, palmitic acid ester and lauric acid ester.
• the processing aid is used in an amount of not more than 10 parts by weight, preferably not more than 5 parts by weight, based on 100 parts by weight of the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A), but it is desired that the optimum amount is properly determined according the required property values.
• foaming agents examples include:
• inorganic foaming agents such as sodium bicarbonate, sodium carbonate, ammonium bicarbonate, ammonium carbonate and ammonium nitrite;
• nitroso compounds such as N,N′-dimethyl-N,N′-dinitrosoterephthalamide and N,N′-dinitrosopentamethylenetetramine;
• azo compounds such as azodicarbonamide, azobisisobutyronitrile, azocyclohexylnitrile, azodiaminobenzene and barium azodicarboxylate;
• sulfonylhydrazide compounds such as benzenesulfonylhydrazide, toluenesulfonylhydrazide, p,p′-oxybis(benzenesulfonylhydrazide) and diphenylsulfone-3,3′-disulfonylhydrazide; and
• azide compounds such as calcium azide, 4,4-diphenyldisulfonylazide and p-toluenesulfonylazide.
• the foaming agent is used in an amount of 0.5 to 30 parts by weight, preferably 1 to 20 parts by weight, based on 100 parts by weight of the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A).
• A ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber
• a foaming aid may be used in combination with the foaming agent, if desired.
• the foaming aid has functions of lowering a decomposition temperature of the foaming agent, acceleration of decomposition and production of uniform foam.
• foaming aids examples include organic acids, such as salicylic acid, phthalic acid, stearic acid and oxalic acid, urea and its derivative.
• the foaming aid is used in an amount of 0.01 to 10 parts by weight, preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A), but it is desired that the optimum amount is properly determined according the required property values.
• the heat-resistant rubber composition of the invention can be used in the unvulcanized state, but when it is used in the form of a vulcanized product such as a vulcanized rubber molded product or a vulcanized rubber foamed product, its properties are most conspicuously exhibited.
• an unvulcanized compounded rubber is first prepared, then the compounded rubber is molded into a product of desired shape, and the product is vulcanized, similarly to a method of vulcanizing conventional rubbers.
• any of a heating method using a vulcanizing agent and an electron ray-irradiation method may be adopted.
• the heat-resistant rubber composition of the invention can be prepared by, for example, the following process.
• the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A), and if necessary, additives such as filler and softener are kneaded at 80° to 170° C. for 3 to 10 minutes using internal mixers (closed type mixers) such as Banbury mixer, kneader and intermixer; then the organic peroxide (vulcanizing agent), and if necessary, the vulcanization aid and the foaming agent are added; and the resulting mixture is kneaded at a roll temperature of 40° to 80° C. for 5 to 30 minutes using rolls (e.g., open rolls) or kneaders, followed by rolling.
• internal mixers closed type mixers
• vulcanizing agent organic peroxide
• vulcanization aid and the foaming agent are added
• the resulting mixture is kneaded at a roll temperature of 40° to 80° C. for 5 to 30 minutes using rolls (e.g., open rolls) or k
• the heat-resistant rubber composition of the invention comprising the anti-aging agent can be prepared by kneading the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A), the amine type anti-aging agent (C), the hindered phenol type anti-aging agent (D), the sulfur type anti-aging agent (E), and if necessary, additives such as filler and softener at 80° to 170° C.
• the anti-aging agents (C), (D) and (E), the vulcanizing agent, and other additives such as colorant, dispersant, flame retardant and foaming agent may be kneaded together with the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A) and additives such as filler and softener.
• the vulcanizable heat-resistant rubber composition of the invention obtained as above is molded into a desired shape using various means such as an extrusion molding machine, a calender roll, a press, an injection molding machine or a transfer molding machine, and simultaneously or thereafter the molded product is heated at a temperature of 120° to 270° C. for 1 to 30 minutes in a vulcanizing bath to perform vulcanization.
• the vulcanized product can be obtained by irradiation to it with electron rays in the aforesaid manner.
• a mold may be used or may not be used. When a mold is not used, the vulcanization is generally carried out continuously.
• the heating in the vulcanizing bath can be performed by the use of heating means such as hot air, glass bead fluidized bed, UHF (ultrahigh frequency electromagnetic wave), steam or LCM (molten salt bath).
• heating means such as hot air, glass bead fluidized bed, UHF (ultrahigh frequency electromagnetic wave), steam or LCM (molten salt bath).
• UHF ultrahigh frequency electromagnetic wave
• steam or LCM (molten salt bath).
• a compounded rubber containing no vulcanizing agent is used in the vulcanization using irradiation with electron rays.
• a heat-resistant rubber composition of the invention comprises the specific ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A) and the organic peroxide (B). Therefore, the composition has high crosslinking efficiency and a high modulus, and can provide a vulcanized rubber molded product having excellent resistance to environmental deterioration such as thermal aging resistance.
• the other heat-resistant rubber composition of the invention comprises the specific ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A), the amine type anti-aging agent (C) and/or the hindered phenol type anti-aging agent (E), the sulfur type anti-aging agent (E) and the organic peroxide (B). Therefore, the composition can provide a vulcanized rubber molded product showing not only excellent mechanical and electrical properties but also prominently high thermal aging resistance.
• a composition comprising ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubber (A) containing a blend of specific amounts of the ethylene- ⁇ -olefin-nonconjugated polyene copolymer rubbers (A1) and (A2) having different intrinsic viscosities (i.e., having different molecular weights) particularly has extremely good fluidity (molding processability) and can provide a vulcanized rubber molded product showing not only excellent mechanical and electrical properties but also prominently high thermal aging resistance.
• the heat-resistant rubber composition which exerts such effects as mentioned above can be favorably used for automotive parts such as weatherstrip, door glass run channel, window frame, radiator hose, brake parts and wiper blade; industrial rubber parts such as rubber roll, belt, packing and hose; electrical insulating materials such as anode cap and grommet; and building materials such as building gasket.
• EPT rubber (A component) *1 100 Zinc white *2 5 Stearic acid *3 1 HAF carbon black *4 50 Softener *5 10 Activator *6 1 Hindered phenol anti-aging agent *7 2 Sulfur anti-aging agent *8 4 *1 Ethylene-propylene-5-vinyl-2-norbornene copolymer rubber (1) having a molar ratio of ethylene to propylene (ethylene/propylene by mol): 68/32; an intrinsic viscosity [ ⁇ ], as measured in decalin at 135° C.: 2.2 dl/g; and an iodine value: 3. *2: available from Sakai Chemical Industry Co., Ltd.
• a rubber composition containing the resulting blend (HA1) was wound around 8 inch open rolls (a product of NIHON ROLL K.K.).
• the ingredients shown in Table 2 were added in accordance with the formulation as shown in Table 2 and kneaded for 3 minutes, followed by sheeting to prepare a sheet of a blend (HA2) having a thickness of 3 mm.
• the surface temperature of the front roll was 50° C. and that of the back roll was 60° C.
• the resulting blend was heated at a molding temperature 170° C. for 20 minutes by means of a press molding apparatus (a product of KOHTAKI SEIKI K.K.) to prepare a vulcanized rubber sheet having a thickness of 2 mm.
• the resulting sheet was evaluated in modulus, tensile properties, cross-linking density and aging properties.
• Tensile test in accordance with JIS K 6301 was carried out at a measuring temperature of 25° C. at a pulling rate of 500 mm/min. and the modulus M200 at 200% elongation was measured.
• Tensile test in accordance with JIS K 6301 was carried out at a measuring temperature of 25° C. at a pulling rate of 500 mm/min., and elongation (E B ) and strength (T B ) at rupture of the vulcanized sheet were measured.
• the vulcanized sheet was immersed in toluene at 37° C. and the effective network chain density was calculated by the following formula.
• ⁇ (cc ⁇ 1 ) ( ⁇ R +ln(1 ⁇ R )+ ⁇ R 2 )/( ⁇ V 0 ( ⁇ R 1 ⁇ 3 ⁇ R /2)
• ⁇ R Volume ratio of a pure rubber to the volume of the swelled pure rubber in the swelled vulcanized rubber (i.e., to the volume of pure rubber+absorbed solvent).
• the vulcanized sheet was allowed to age in an oven at 175° C. for 168 hours. Then, the sheet was subjected to the tensile test at a measuring temperature of 25° C. at a pulling rate of 500 m/min. to measure elongation (E B ) and strength (T B ) at rupture of the vulcanized sheet. From the measurements, a tensile strength retention ratio A R (T B ) and an elongation retention ratio A R (E B ) were calculated.
• Example 1 was repeated except that Kayacumyl AD-40 (trade name) available from KAYAKUAKZO Co. was used as the organic peroxide (B).
• Example 1 was repeated except that the ethylene-propylene-5-vinyl-2-norbornene copolymer rubber (2) described below was used in place of the ethylene-propylene-5-vinyl-2-norbornene copolymer rubber (1) in Example 1.
• Example 1 was repeated except that the ethylene-propylene-5-vinyl-2-norbornene copolymer rubber (3) described below was used in place of the ethylene-propylene-5-vinyl-2-norbornene copolymer rubber (1) in Example 1.
• Example 1 was repeated except that the ethylene-propylene-5-vinyl-2-norbornene copolymer rubber (4) described below was used in place of the ethylene-propylene-5-vinyl-2-norbornene copolymer rubber (1) in Example 1.
• Example 1 was repeated except that the ethylene-propylene-5-vinyl-2-norbornene copolymer rubber (5) described below was used in place of the ethylene-propylene-5-vinyl-2-norbornene copolymer rubber (1) in Example 1.
• Example 1 was repeated except that the ethylene-1-butene-5-vinyl-2-norbornene copolymer rubber (6) described below was used in place of the ethylene-propylene-5-vinyl-2-norbornene copolymer rubber (1) in Example 1.
• Example 6 was repeated except that 1.5 phr of sulfer, and 0.5 phr of Nocceller M (trade name, available from Ouchi-Shinko Chemical industry Co., Ltd.) and 1.0 phr of Nocceller TT (trade name, available from Ouchi-Shinko Chemical Industry Co., Ltd.) as the vulcanizing accelerators were used in place of the organic peroxide and the crosslinking assistant in Example 6.
• Nocceller M trade name, available from Ouchi-Shinko Chemical industry Co., Ltd.
• Nocceller TT trade name, available from Ouchi-Shinko Chemical Industry Co., Ltd.
• Example 1 was repeated except that the ethylene-propylene-5-ethylidene-2-norbornene copolymer rubber (9) described below was used in place of the ethylene-propylene-5-vinyl-2-norbornene copolymer rubber (1) in Example 1.
• Example 1 was repeated except that the ethylene-propylene-5-ethylidene-2-norbornene copolymer rubber (10) described below was used in place of the ethylene-propylene-5-vinylidene-2-norbornene copolymer rubber (1) in Example 1.
• Example 1 was repeated except that the ethylene-propylene-5-ethylidene-2-norbornene copolymer rubber (11) described below was used in place of the ethylene-propylene-5-vinyl-2-norbornene copolymer rubber (1) in Example 1.
• Example 1 was repeated except that the ethylene-propylene-dicyclopentadiene copolymer rubber (12) described below was used in place of the ethylene-propylene-5-vinyl-2-norbornene copolymer rubber (1) in Example 1.
• Example 1 was repeated except that the ethylene-propylene-dicyclopentadiene copolymer rubber (13) described below was used in place of the ethylene-propylene-5-vinyl-2-norbornene copolymer rubber (1) in Example 1.
• Example 1 was repeated except that the ethylene-propylene-1,4-hexadiene copolymer rubber (14) described below was used in place of the ethylene-propylene-5-vinyl-2-norbornene copolymer rubber (1) in Example 1.
• Example 1 was repeated except that the ethylene-propylene-1,4-hexadiene copolymer rubber (15) described below was used in place of the ethylene-propylene-5-vinyl-2-norbornene copolymer rubber (1) in Example 1.
• Ethylene-propylene-1,4-hexadiene copolymer rubber (15):
• Example 1 2 3 4 5 Composition [parts by weight] Copolymer rubber Ethylene-propylene-VNB c.r. (1) 100 100 — — — Ethylene-propylene-VNB c.r. (2) — — 100 — — Ethylene-propylene-VNB c.r. (3) — — — 100 — Ethylene-propylene-VNB c.r. (4) — — — — 100 Ethylene-propylene-VNB c.r. (5) — — — — — Ethylene-propylene-VNB c.r.
• Example 6 7 1 2 3 Composition [parts by weight] Copolymer rubber Ethylene-propylene-VNB c.r. (1) — — — — — Ethylene-propylene-VNB c.r. (2) — — — — Ethylene-propylene-VNB c.r. (3) — — — — Ethylene-propylene-VNB c.r.
• (A-1) Ethylene-propylene-5-vinyl-2-norbornene copolymer rubber
• (A-2) Ethylene-propylene-5-vinyl-2-norbornene copolymer rubber
• (A-4) Ethylene-propylene-dicyclopentadiene copolymer rubber
• the tensile test and the aging test were carried out in accordance with JIS K 6301. That is, tensile strength (T B ) and elongation (E B ) were measured in the tensile test.
• Rubber compounding ingredients common to Examples 8 to 14 and Comparative Examples 10 to 20 and the amounts thereof are set forth in Table 4.
• Amine anti-aging agent N,N′-di-2-naphthyl-p- 1 1 1 2 1 1 phenylenediamine (C-1) N,N′-diphenyl-p-phenylene- — — — — — — diamine (C-2) Hindered phenol anti-aging — 1 1 2 — — agent (D) 3,9-bis [2- ⁇ 3-(3-t- butyl-4-hydroxy-5-methyl- phenyl) propinonyloxy ⁇ -1,1-dimethyl- ethyl]-2,4-8,10-tetraoxaspiro [5,5]undecane (D-1) Sulfur anti-aging agent (E) 4 4 4 — 4 4 4 Pentaerythritol-tetrakis-( ⁇ - lauryl-thiopropionate) (E-1) Vulcanized rubber Original state tensile strength
• (A-7) — — — — — Amine anti-aging agent (C) N,N′-di-2-naphthyl-p- 1 — — phenylenediamine (C-1) N,N′-diphenyl-p-phenylenediamine — 1 — (C-2 4,4′-( ⁇ , ⁇ -dimethylbenzyl) — — 1 diphenylamine (C-3) Hindered phenol anti-aging agent (D) 1 1 1 3,9-bis [2- ⁇ 3-(3-t-butyl-4- hydroxy-5-methylphenyl) propinonyloxy ⁇ -1,1-dimethylethyl]- 2,4-8,10-tetraoxaspiro [5,5]undecane (D-1) Sulfur anti-aging agent (E) 4 4 4 4 Pentaerythritol-tetrakis-( ⁇ - lauryl-thiopropionate) (E-1) Phosphin
• Rubber compounding ingredients common to Examples 15 to 18 and Comparative Examples 21 to 25 and the amounts thereof are set forth in Table 6.
• the ingredients other than the organic peroxide were kneaded at 140° to 150° C. for 5 minutes using a 1.7 liter Banbury mixer. Then, the resulting kneadate and the organic peroxide were kneaded at 50° to 60° C. for 5 minutes using an 8 inch open roll.
• the resulting kneadate was subjected to press vulcanization at 170° C. for 10 minutes to prepare a vulcanized rubber sheet having a thickness of 2 mm, from which specimens for the above tests were prepared.
• Copolymer rubber A-1) (A1-1) — — 50 50 (A1-6) 50 — — — (A1-7) — 100 — — Copolymer rubber (A2) (A2-1) — — 50 50 (A2-6) 50 — — — Amine anti-aging agent (C) 1 1 1 1 (C-1) Hindered phenol anti-aging agent (D) 1 1 1 1 (D-1) Sulphur anti-aging agent (E) 4 4 — 4 (E-1) Phosphite anti-aging agent — — 4 — 4,4′-butylidenbis(3-methy- 6-t-butyl-di-tridecylphosphite) (F-1) Vulcanized rubber Original state Tensile strength 104 125 103 138 T B (kgf/cm 2 ) Elogation E B (%) 670 680 480 550 Thermal aging resistance 190° C.
• Example 18 In Example 18, 1 part by weight of Sanceler AP (Trademark, available from Sanshin Kagaku Kogyo K.K.) was added as vulcanization aid in addition to the above components.
• Sanceler AP Trademark, available from Sanshin Kagaku Kogyo K.K.

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