Copolymer rubber, rubber composition, and crosslinked rubber product

Abstract

Provided is a copolymer rubber obtained by copolymerizing a butenedioic acid diester structure-containing monomer represented by general formula (1) and a radically polymerizable monomer. (In general formula (1), R1 represents an alkyl group having 1-4 carbon atoms; r2 represents a group represented by R7 or OR8; r7 represents an optionally substituted alkyl group having 1 to 8 carbon atoms; r8 represents an optionally substituted alkyl group having 1 to 8 carbon atoms or an optionally substituted polyalkylene glycol group; r3, R4 and R6 are each independently a hydrogen atom or an alkyl group having 1-4 carbon atoms; r5 represents a hydrogen atom, a group represented by R7 or OR8; when R3 is a hydrogen atom, R2 is a group represented by OR8; r1 and R2 can be bonded to each other to form a ring; r4 and R5 can be bonded to each other to form a ring. > # imgabs0 #

Description

Technical Field

[0001] The present invention relates to a copolymer rubber, a rubber composition, and a rubber crosslinked product. Background Art

[0002] As a method for crosslinking a copolymer rubber typified by an acrylic rubber, the following method is generally adopted: after heating at about 150°C to 190°C for several minutes to several tens of minutes for primary crosslinking, heating is carried out for several hours in a heated air environment at 140°C to 200°C for secondary crosslinking (Patent Document 1).

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2009-084514. Summary of the Invention

[0006] Problems to be Solved by the Invention

[0007] From the viewpoints of the productivity of the rubber crosslinked product, energy saving, and carbon neutrality, it is desired to provide a rubber composition that can produce a rubber crosslinked product having good physical properties only by primary crosslinking without secondary crosslinking.

[0008] The present invention has been completed in view of such actual circumstances, and an object thereof is to provide a copolymer rubber that can have good scorch stability and can form a rubber crosslinked product having sufficient mechanical properties without secondary crosslinking.

[0009] Means for Solving the Problems

[0010] The present inventors conducted in-depth research and found that the above object can be achieved by a copolymer rubber obtained by copolymerizing a specified monomer having a maleic acid diester structure with a radically polymerizable monomer, and thus completed the present invention.

[0011] That is, according to the present invention, the following copolymer rubber, rubber composition, and rubber crosslinked product can be provided.

[0012] [1] A copolymer rubber obtained by copolymerizing a monomer having a maleic acid diester structure represented by the following general formula (1) with a radically polymerizable monomer.

[0013] [Chemical Formula 1]

[0014]

[0015] (In the general formula (1), R 1 is an alkyl group having 1 to 4 carbon atoms; R 2 is R 7 or OR8 The group represented; R 7 is an alkyl group having 1 to 8 carbon atoms which may have substituents; R 8 is an alkyl group having 1 to 8 carbon atoms which may have substituents or a polyalkylene glycol group which may have substituents; R 3 , R 4 and R 6 are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; R 5 is a hydrogen atom, R 7 or the group represented by OR 8 ; when R 3 is a hydrogen atom, R 2 is the group represented by OR 8 ; R 1 and R 2 can bond to each other to form a ring; R 4 and R 5 can bond to each other to form a ring.)

[0016] [2] The copolymer rubber according to [1], wherein the content ratio of the unit of the maleic acid diester structure monomer represented by the above general formula (1) is 0.1 to 10% by weight.

[0017] [3] The copolymer rubber according to [1] or [2], wherein the copolymer rubber contains at least one selected from (meth)acrylate monomers, (meth)acrylonitrile monomers, aromatic vinyl monomers, conjugated diene monomers, (meth)acrylamide monomers, vinyl acetate monomers, and ethylene monomers as the radical polymerizable monomer.

[0018] [4] The copolymer rubber according to any one of [1] to [3], wherein the glass transition temperature of the copolymer rubber is 0 °C or lower.

[0019] [5] The copolymer rubber according to any one of [1] to [4], wherein the copolymer rubber contains (meth)acrylate as the radical polymerizable monomer.

[0020] [6] The copolymer rubber according to any one of [1] to [5], wherein the Mooney viscosity (ML1+4, 100 °C) of the copolymer rubber is 10 to 150.

[0021] [7] The copolymer rubber according to any one of [1] to [6], wherein the maleic acid diester structure monomer represented by the above general formula (1) is a maleic acid diester structure monomer represented by the following general formula (2) or general formula (3).

[0022] [Chemical formula 2]

[0023]

[0024] (In General Formulas (2) and (3), R 1 , R 3 , R 4 , R 6 , and R 8 are each independently the same as the group in General Formula (1) above; R 9 is an alkyl group having 1 to 17 carbon atoms that can have substituents; R 10 is an alkyl group having 1 to 8 carbon atoms that can have substituents or a polyalkylene glycol group that can have substituents; R 1 and R 8 can bond to each other to form a ring; R 4 and R 10 can bond to each other to form a ring.)

[0025] [8] A rubber composition containing the copolymer rubber according to any one of [1] to [7] and a crosslinking agent.

[0026] [9] The rubber composition according to [8], wherein the rubber composition further contains a crosslinking accelerator.

[0027]

[10] The rubber composition according to [8] or [9], wherein the rubber composition further contains a filler.

[0028]

[11] A rubber crosslink obtained by crosslinking the rubber composition according to any one of [8] to

[10] .

[0029]

[12] The rubber crosslink according to

[11] , wherein the rubber crosslink is a hose material, a sealing material, a pipe material, a belt material, or a protective cover material.

[0030] Advantages of the Invention

[0031] According to the present invention, a copolymer rubber can be provided that can have good scorch stability and can form a rubber crosslink having sufficient mechanical properties without secondary crosslinking. Detailed Embodiments

[0032] The copolymer rubber of the present invention is obtained by copolymerizing a maleic acid diester structure monomer represented by General Formula (1) described later with a radically polymerizable monomer.

[0033] The copolymer rubber of the present invention can have good scorch stability by containing a unit of a monomer having a maleic acid diester structure represented by the general formula (1), and can form a rubber crosslink having sufficient mechanical properties (specifically, sufficient tensile properties, moderate hardness, and sufficient compression set resistance, and the change in tensile properties due to aging is sufficiently suppressed) without secondary crosslinking.

[0034] <Maleic acid diester structure monomer>

[0035] The maleic acid diester structure monomer used in the present invention is represented by the following general formula (1).

[0036] [Chemical formula 3]

[0037]

[0038] (In the general formula (1), R 1 is an alkyl group having 1 to 4 carbon atoms; R 2 is a group represented by R 7 or OR 8 ; R 7 is an alkyl group having 1 to 8 carbon atoms which may have a substituent; R 8 is an alkyl group having 1 to 8 carbon atoms which may have a substituent or a polyalkylene glycol group which may have a substituent; R 3 , R 4 and R 6 are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; R 5 is a hydrogen atom, a group represented by R 7 or OR 8 ; when R 3 is a hydrogen atom, R 2 is a group represented by OR 8 ; R 1 and R 2 can be bonded to each other to form a ring; R 4 and R 5 can be bonded to each other to form a ring.)

[0039] The unit derived from the maleic acid diester structure monomer represented by the general formula (1) functions as a crosslinkable monomer unit in the copolymer rubber of the present invention. The mechanism by which it functions as a crosslinkable monomer unit is not yet clear, but it is speculated that during crosslinking, a carboxyl group is generated in the unit derived from the maleic acid diester structure monomer represented by the general formula (1), and this functions as a crosslinking point. In addition, as long as heating for crosslinking is not carried out, the generation of carboxyl groups in the unit derived from the maleic acid diester structure monomer represented by the general formula (1) is greatly suppressed. Therefore, for the copolymer rubber of the present invention, an increase in Mooney viscosity caused by unwanted crosslinking is effectively suppressed. By containing the unit derived from the maleic acid diester structure monomer represented by the general formula (1) as a crosslinkable monomer unit, the copolymer rubber of the present invention can have good scorch stability and can form a rubber crosslinked product having sufficient mechanical properties without secondary crosslinking.

[0040] In the general formula (1), the bonding form of the group represented by -COO-C(-R 1 )(-R 2 )(-R 3 ) with the carbon atom can be a cis-bonding or a trans-bonding, and preferably a trans-bonding. That is, the maleic acid diester structure monomer represented by the general formula (1) has a fumaric acid diester structure (trans-bonding type) or a maleic acid diester structure (cis-bonding type), and preferably has a fumaric acid diester structure (trans-bonding type).

[0041] In the general formula (1), R 1 ~R 6 can be linear, branched, or can have a cyclic structure.

[0042] In the general formula (1), R 1 as long as it is an alkyl group having 1 to 4 carbon atoms, there is no particular limitation. From the viewpoint of being able to balance scorch stability and crosslinking speed at a higher level, it is preferably methyl or ethyl, and more preferably methyl. In addition, when R 1 and R 2 are bonded to each other to form a ring, R 1 is preferably methylene.

[0043] In the general formula (1), R 2 is a group represented by R 7 or OR 8 . Here, R 7 is an alkyl group having 1 to 8 carbon atoms which can have a substituent, and R 8 is an alkyl group having 1 to 8 carbon atoms which can have a substituent or a polyalkylene glycol group which can have a substituent.

[0044] Examples of the polyalkylene glycol group include a polyethylene glycol group, a polypropylene glycol group, and a group composed of a copolymer chain of ethylene glycol and propylene glycol. As for R 8 In one embodiment of the polyalkylene glycol group, the number of repetitions of the alkylene glycol unit is preferably from 1 to 3.

[0045] Examples of the substituent include: halogen atoms such as a fluorine atom, a chlorine atom, and a bromine atom; alkoxy groups having 1 to 10 carbon atoms such as a methoxy group, an ethoxy group, and an isopropoxy group; a nitro group; a cyano group; an aryl group having 6 to 10 carbon atoms such as a phenyl group, a 4-methylphenyl group, a 2-chlorophenyl group, a 1-naphthyl group, and a 2-naphthyl group.

[0046] As for R 2 , a group represented by OR 8 is preferred. In the group represented by OR 2 as one embodiment of R 8 , from the viewpoint of achieving a higher level of balance between scorch stability and crosslinking rate, R 8 is preferably a linear alkyl group having 1 to 8 carbon atoms, a branched alkyl group having 3 to 8 carbon atoms, or a linear polyalkylene glycol group having 2 to 8 carbon atoms, more preferably a linear alkyl group having 1 to 8 carbon atoms or a branched alkyl group having 3 to 8 carbon atoms, still more preferably a linear alkyl group having 2 to 6 carbon atoms or a branched alkyl group having 4 to 8 carbon atoms, and particularly preferably an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group, or a 2-ethylhexyl group.

[0047] In addition, when R 1 and R 2 are bonded to each other to form a ring, the ring (a ring formed by bonding the two ends of the chain represented by -R 1 -C ＊ -R 2 -, where C ＊ is a carbon atom bonded to R 1 , R 2 , R 3 and an oxygen atom) is preferably a five-membered ring or a six-membered ring capable of having an oxygen atom, and more preferably a five-membered ring or a six-membered ring having an oxygen atom. Specific examples of the five-membered ring include a five-membered ring formed by bonding the two ends of the chain represented by -(CH2)2-C ＊ -O-CH2- or -(CH2)2-C ＊ -(CH2)2-, and a five-membered ring in which one or more hydrogen atoms in these chains are substituted with a substituent such as an alkyl group. Specific examples of the six-membered ring include a six-membered ring formed by bonding the two ends of the chain represented by -(CH2)3-C ＊ -O-CH2- or -(CH2)3-C ＊A six-membered ring formed by bonding the two ends of a chain represented by -(CH2)2-, and a six-membered ring in which one or more hydrogen atoms in these chains are substituted with substituents such as alkyl groups. Particularly preferred is -(CH2)2-C ＊ -O-CH2- or -(CH2)3-C ＊ A ring formed by bonding the two ends of a chain represented by -O-CH2-.

[0048] In the general formula (1), R 3 As long as it is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, there is no particular limitation. From the viewpoint of being able to balance scorch stability and crosslinking speed at a higher level, it is preferably a hydrogen atom or a methyl group, and more preferably a hydrogen atom. In addition, in the general formula (1), when R 3 is a hydrogen atom, R 2 is a group represented by OR 8 .

[0049] In the general formula (1), R 4 As long as it is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, there is no particular limitation. From the viewpoint of being able to balance scorch stability and crosslinking speed at a higher level, it is preferably a hydrogen atom or a methyl group, and more preferably a hydrogen atom. In addition, when R 4 and R 5 are bonded to each other to form a ring, R 4 is preferably a methylene group.

[0050] In the general formula (1), R 5 is a hydrogen atom, R 7 or a group represented by OR 8 . Here, R 7 and OR 8 are the same as R 2 which is R 7 and OR 8 .

[0051] From the viewpoint of being able to balance scorch stability and crosslinking speed at a higher level, R 5 is preferably a group represented by R 7 , more preferably a straight-chain alkyl group having 1 to 8 carbon atoms, still more preferably a straight-chain alkyl group having 1 to 4 carbon atoms, and particularly preferably a methyl group or a n-propyl group.

[0052] In addition, when R 4 and R 5 are bonded to each other to form a ring, this ring (is a ring formed by bonding the two ends of a chain represented by -R 4 -C ＊ -R 5 -, where C ＊ is the same as R4 , R 5 , R 6 and the carbon atom bonded to an oxygen atom) is preferably a five - or six - membered ring capable of having an oxygen atom, more preferably a five - or six - membered ring without an oxygen atom. As a specific example of this ring, there can be mentioned the ring formed by the mutual bonding of R 1 and R 2 as described above, and particularly preferably a ring formed by the mutual bonding of the two ends of a chain represented by -(CH2)2 - C ＊ -(CH2)2 - or -(CH2)3 - C ＊ -(CH2)2 -.

[0053] In the general formula (1), R 6 is not particularly limited as long as it is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. From the viewpoint of being able to balance scorch stability and crosslinking speed at a higher level, it is preferably a hydrogen atom or a methyl group, and more preferably a hydrogen atom.

[0054] From the viewpoint of being able to balance scorch stability and crosslinking speed at a higher level, the maleic acid diester - containing structural monomer represented by the general formula (1) is preferably the maleic acid diester - containing structural monomer represented by the following general formula (2) or general formula (3).

[0055] [Chemical formula 4]

[0056]

[0057] (In the general formula (2) and the general formula (3), R 1 , R 3 , R 4 , R 6 and R 8 are each independently the same as the group in the above - mentioned general formula (1); R 9 is an alkyl group having 1 to 17 carbon atoms capable of having a substituent; R 10 is an alkyl group having 1 to 8 carbon atoms capable of having a substituent or a polyalkylene glycol group capable of having a substituent; R 1 and R 8 can bond to each other to form a ring; R 4 and R 10 can bond to each other to form a ring.)

[0058] In the general formula (2) and the general formula (3), -COO - C(-R 1 )(-OR 8 )(-R 3) The bonding form of the group represented by the carbon atom can be cis-bonding or trans-bonding, and trans-bonding is preferred. That is, the monomer containing a dimaleate structure represented by the general formula (1) has a fumarate diester structure (trans-bonding type) or a maleate diester structure (cis-bonding type), and preferably has a fumarate diester structure (trans-bonding type).

[0059] In the general formulas (2) and (3), R 1 , R 3 , R 4 , R 6 and R 8 ~R 10 can be linear, branched, or can have a cyclic structure.

[0060] In the general formulas (2) and (3), R 1 , R 3 , R 4 , R 6 and R 8 are each independently the same as the group in the above general formula (1), and the preferred groups are also the same.

[0061] In the general formula (2), R 9 is an alkyl group having 1 to 17 carbon atoms that can have a substituent, preferably an alkyl group having 1 to 16 carbon atoms that can have a substituent. As the substituent, the above-mentioned substituents can be cited. R 9 in the general formula (2) corresponds to the group represented by -C(-R 4 )(-R 5 )(-R 6 ) in the general formula (1).

[0062] From the viewpoint of being able to balance scorch stability and crosslinking speed at a higher level, R 9 is preferably a linear alkyl group having 1 to 8 carbon atoms or a cycloalkyl group having 3 to 8 carbon atoms, more preferably a linear alkyl group having 2 to 6 carbon atoms or a cycloalkyl group having 4 to 8 carbon atoms, further preferably a linear alkyl group having 2 to 4 carbon atoms or a cycloalkyl group having 5 to 7 carbon atoms, and particularly preferably ethyl, n-butyl, or cyclohexyl.

[0063] In the general formula (3), R 10 is an alkyl group having 1 to 8 carbon atoms that can have a substituent or a polyalkylene glycol group that can have a substituent. As the substituent, the above-mentioned groups can be cited. R 10 in the general formula (3) is the same as R 8 in the general formula (3).

[0064] From the viewpoint of being able to balance scorch stability and crosslinking speed at a higher level, R 10Preferably a straight-chain alkyl group having 1 to 8 carbon atoms, a branched-chain alkyl group having 3 to 8 carbon atoms, or a straight-chain polyalkylene glycol group having 2 to 8 carbon atoms, more preferably a straight-chain alkyl group having 1 to 8 carbon atoms or a branched-chain alkyl group having 3 to 8 carbon atoms, further preferably a straight-chain alkyl group having 2 to 6 carbon atoms or a branched-chain alkyl group having 4 to 8 carbon atoms, and particularly preferably ethyl, n-propyl, isopropyl, n-butyl or 2-ethylhexyl. In addition, when R 4 and R 10 are bonded to each other to form a ring, the ring (formed by bonding the two ends of the chain represented by -R 4 -C ＊ -OR 10 -) is a ring formed by bonding the two ends of the chain, where C ＊ is a carbon atom bonded to R 4 , OR 10 , R 6 and an oxygen atom) is preferably a five-membered or six-membered ring capable of having an oxygen atom, preferably a five-membered or six-membered ring having an oxygen atom. As a specific example of the ring, the above-mentioned ring as a ring formed by bonding R 1 and R 2 to each other is particularly preferably a ring formed by bonding the two ends of the chain represented by -(CH2)2-C ＊ -O-CH2- or -(CH2)3-C ＊ -O-CH2- to each other.

[0065] In addition, the method for producing the maleic acid diester structure-containing monomer represented by the general formula (1) is not particularly limited, and conventionally known methods can be appropriately combined and used. For example, the maleic acid diester structure-containing monomer represented by the general formula (1) can be produced by reacting a maleic acid monoester represented by R 4 R 5 R 6 COOCHC=CHCOOH with an unsaturated compound represented by R 1’ =CR 2 R 3 (wherein R 1’ is a group that becomes R 1 after the reaction).

[0066] The content ratio of the unit of the maleic acid diester structure-containing monomer represented by the general formula (1) in the copolymer rubber of the present invention is preferably 0.1 to 10% by weight, more preferably 0.5 to 7% by weight, and further preferably 1 to 5% by weight. By making the content ratio of the unit of the maleic acid diester structure-containing monomer represented by the general formula (1) within the above range, scorch stability and crosslinking speed can be balanced at a higher level.

[0067] <Free-radical polymerizable monomer>

[0068] As the radically polymerizable monomer, any monomer having radical polymerizability and capable of copolymerizing with the maleic acid diester structure monomer represented by the above general formula (1) may be used, and there is no particular limitation. Examples thereof include (meth)acrylate monomers [meaning acrylate monomers and / or methacrylate monomers. Hereinafter, the same applies to (meth)acrylic acid methyl ester, etc.], (meth)acrylonitrile monomers, aromatic vinyl monomers, conjugated diene monomers, (meth)acrylamide monomers, vinyl acetate monomers, ethylene monomers, etc.

[0069] The radically polymerizable monomer preferably contains at least one selected from (meth)acrylate monomers, (meth)acrylonitrile monomers, aromatic vinyl monomers, conjugated diene monomers, (meth)acrylamide monomers, vinyl acetate monomers, and ethylene monomers, and more preferably contains (meth)acrylate monomers.

[0070] In addition, the copolymer rubber of the present invention may be, for example: acrylic rubber containing (meth)acrylate monomer units; nitrile rubber containing (meth)acrylonitrile monomer units; styrene-butadiene rubber containing styrene units as aromatic vinyl monomer units and butadiene units as conjugated diene monomer units; conjugated diene rubber containing conjugated diene monomer units, etc. Among them, the copolymer rubber of the present invention is preferably acrylic rubber containing (meth)acrylate monomer units.

[0071] When the copolymer rubber of the present invention is acrylic rubber containing (meth)acrylate monomer units, the (meth)acrylate monomer forming the (meth)acrylate monomer units is not particularly limited, and examples thereof include (meth)acrylic acid alkyl ester monomers and (meth)acrylic acid alkoxyalkyl ester monomers.

[0072] As the (meth)acrylic acid alkyl ester monomer, there is no particular limitation, and esters of alkanols having 1 to 8 carbon atoms and (meth)acrylic acid are preferred. Specifically, examples thereof include (meth)acrylic acid methyl ester, (meth)acrylic acid ethyl ester, (meth)acrylic acid n-propyl ester, (meth)acrylic acid isopropyl ester, (meth)acrylic acid n-butyl ester, (meth)acrylic acid isobutyl ester, (meth)acrylic acid n-hexyl ester, 2-ethylhexyl (meth)acrylate, and cyclohexyl (meth)acrylate. Among these, (meth)acrylic acid methyl ester, (meth)acrylic acid ethyl ester, and (meth)acrylic acid n-butyl ester are preferred, and acrylic acid ethyl ester and acrylic acid n-butyl ester are particularly preferred. These can be used alone or in combination of two or more.

[0073] In one embodiment, the copolymer rubber of the present invention may contain both ethyl acrylate units and n-butyl acrylate units as (meth)acrylate monomer units. The weight ratio of the content ratios of the two monomer units in this case [content ratio of ethyl acrylate units: content ratio of n-butyl acrylate units] is preferably 1:99 to 99:1, more preferably 5:95 to 90:10, and still more preferably 10:90 to 80:20.

[0074] The (meth)acryloyloxyalkyl ester monomer is not particularly limited, and an ester of an alkoxyalkyl alcohol having 2 to 12 carbon atoms and (meth)acrylic acid is more preferred, and an ester of an alkoxyalkyl alcohol having 2 to 8 carbon atoms and (meth)acrylic acid is more preferred. Specifically, examples include methoxymethyl (meth)acrylate, ethoxymethyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-propoxyethyl (meth)acrylate, 2-butoxyethyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, and 4-methoxybutyl (meth)acrylate. Among these, 2-ethoxyethyl (meth)acrylate and 2-methoxyethyl (meth)acrylate are preferred, and 2-ethoxyethyl acrylate and 2-methoxyethyl acrylate are particularly preferred. These can be used alone or in combination of two or more.

[0075] When the copolymer rubber of the present invention is an acrylic rubber, the content ratio of the (meth)acrylate monomer units in all the monomer units is preferably 50 to 99.9% by weight, more preferably 70 to 99.5% by weight, still more preferably 90 to 99.5% by weight, particularly preferably 93 to 99.5% by weight, and most preferably 95 to 99% by weight. By making the content ratio of the (meth)acrylate monomer units within the above range, the mechanical properties of the obtained rubber crosslink can be further improved.

[0076] In addition, when the copolymer rubber of the present invention is an acrylic rubber, the weight ratio of the content ratio of the (meth)acrylic acid alkyl ester monomer units to the content ratio of the (meth)acrylic acid alkoxyalkyl ester monomer units [(content ratio of the (meth)acrylic acid alkyl ester monomer units: content ratio of the (meth)acrylic acid alkoxyalkyl ester monomer units)] is preferably 10:90 to 100:0, and more preferably 20:80 to 100:0.

[0077] When the copolymer rubber of the present invention is acrylic rubber, the copolymer rubber of the present invention may be a copolymer rubber obtained by copolymerizing, in addition to the maleic acid diester structure monomer and (meth)acrylate monomer represented by the general formula (1), other monomers capable of copolymerizing with them. Examples of other monomers capable of copolymerizing include ester monomers other than the maleic acid diester structure monomer represented by the general formula (1), conjugated diene monomers, non-conjugated diene monomers, aromatic vinyl monomers, α,β-ethylenically unsaturated nitrile monomers such as (meth)acrylonitrile monomers, acrylamide-based monomers such as (meth)acrylamide monomers, and other olefin-based monomers.

[0078] Examples of ester monomers other than the maleic acid diester structure monomer represented by the general formula (1) include α,β-ethylenically unsaturated monocarboxylic acid esters and α,β-ethylenically unsaturated dicarboxylic acid diesters other than the maleic acid diester structure monomer represented by the general formula (1). In addition, ester monomers other than the maleic acid diester structure monomer represented by the general formula (1) are usually non-crosslinkable monomers.

[0079] Examples of conjugated diene monomers include 1,3-butadiene, isoprene, and piperylene. Examples of non-conjugated diene monomers include ethylidene norbornene, dicyclopentadiene, (meth)acrylic acid dicyclopentadienyl ester, and 2-dicyclopentadienyl ethyl (meth)acrylate.

[0080] Examples of aromatic vinyl monomers include styrene, α-methylstyrene, and divinylbenzene.

[0081] Examples of α,β-ethylenically unsaturated nitrile monomers include acrylonitrile and methacrylonitrile.

[0082] Examples of acrylamide-based monomers include acrylamide and methacrylamide.

[0083] Examples of other olefin-based monomers include ethylene, propylene, vinyl chloride, vinylidene chloride, vinyl acetate, ethyl vinyl ether, and butyl vinyl ether.

[0084] Other monomers capable of copolymerizing can be used alone or in combination of two or more. The content ratio of the units of other monomers capable of copolymerizing in the monomer units constituting the copolymer rubber of the present invention is preferably 0 to 30% by weight, more preferably 0 to 20% by weight, and further preferably 0 to 10% by weight.

[0085] In addition, examples of other monomers capable of copolymerizing include carboxyl group-containing monomers. Examples of carboxyl group-containing monomers include α,β-ethylenically unsaturated dicarboxylic acid monoester monomers, α,β-ethylenically unsaturated monocarboxylic acids, and α,β-ethylenically unsaturated dicarboxylic acids.

[0086] The content ratio of carboxyl group-containing monomer units in all monomer units constituting the copolymer rubber of the present invention is preferably 0 to 1% by weight, more preferably 0 to 0.5% by weight, still more preferably 0 to 0.2% by weight, and particularly preferably 0 to 0.1% by weight. By making the content ratio of carboxyl group-containing monomer units within the above range, scorch stability and crosslinking speed can be balanced at a higher level.

[0087] The weight-average molecular weight (Mw) of the copolymer rubber of the present invention is not particularly limited, and is preferably 50,000 to 5,000,000, more preferably 100,000 to 4,000,000, and still more preferably 150,000 to 3,500,000. The weight-average molecular weight of the acrylic rubber can be measured as a value in terms of polystyrene by, for example, gel permeation chromatography.

[0088] The polymer Mooney viscosity (ML1+4, 100 °C) of the copolymer rubber of the present invention is preferably 10 to 150, more preferably 15 to 80, and still more preferably 20 to 70.

[0089] The glass transition temperature of the copolymer rubber of the present invention is preferably 0 °C or lower, more preferably -70 to -5 °C, and still more preferably -50 to -15 °C.

[0090] <Manufacturing method of copolymer rubber>

[0091] The copolymer rubber of the present invention can be obtained by polymerizing the above-mentioned respective monomers. As the polymerization reaction method, any of emulsion polymerization method, suspension polymerization method, bulk polymerization method, and solution polymerization method can be used. From the viewpoint of controlling the ease of polymerization reaction, etc., the emulsion polymerization method is preferably used. That is, as the manufacturing method of the copolymer rubber of the present invention, a method of emulsion-polymerizing a monomer component containing a maleic acid diester structure monomer represented by the general formula (1) and a radically polymerizable monomer component in the presence of a polymerization catalyst is preferred.

[0092] As the monomer components used in emulsion polymerization, the above-mentioned respective monomers can be mentioned, and the preferred monomers are also as described above. In addition, the amounts of the respective monomers can be appropriately selected as long as they are within the above-mentioned composition ranges.

[0093] The emulsifier is not particularly limited, and examples thereof include nonionic emulsifiers, anionic emulsifiers, cationic emulsifiers, etc.

[0094] As the nonionic emulsifier, there is no particular limitation, and examples thereof include: polyoxyalkylene fatty acid esters such as polyoxyethylene stearate and polyoxyethylene sorbitan alkyl esters; polyoxyalkylene alkyl ethers such as polyoxyethylene dodecyl ether; polyoxyalkylene alkyl phenyl ethers such as polyoxyethylene nonyl phenyl ether, etc. Among these, polyoxyalkylene alkyl ethers and polyoxyalkylene alkyl phenyl ethers are preferred, and polyoxyethylene alkyl ethers and polyoxyethylene alkyl phenyl ethers are more preferred. The weight-average molecular weight of the nonionic emulsifier (weight-average molecular weight in terms of polystyrene conversion measured by gel permeation chromatography (GPC)) is not particularly limited, and is usually in the range of 300 to 50,000, preferably 500 to 30,000, and more preferably 1,000 to 15,000. These nonionic emulsifiers can be used alone or in combination of two or more.

[0095] As the anionic emulsifier, there is no particular limitation, and examples thereof include: salts of fatty acids such as myristic acid, palmitic acid, oleic acid, and linolenic acid; alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate; higher alcohol sulfates such as sodium lauryl sulfate, and phosphate esters such as sodium alkyl phosphate. Preferred examples include: higher alcohol phosphate esters such as sodium phosphate esters of alcohols having 6 or more carbon atoms in the hydrophobic group; alkyl sulfosuccinates, etc. Among these anionic emulsifiers, phosphate esters and higher alcohol sulfates are preferred, higher alcohol phosphate esters and higher alcohol sulfates are more preferred, and higher alcohol phosphate esters are further preferred. These anionic emulsifiers can be used alone or in combination of two or more.

[0096] As the cationic emulsifier, examples include alkyltrimethylammonium chloride, dialkylammonium chloride, benzylammonium chloride, etc.

[0097] These emulsifiers can be used alone or in combination of two or more. Particularly preferred are nonionic emulsifiers and anionic emulsifiers, and more preferred is anionic emulsifier.

[0098] The amount of the emulsifier, based on the total amount of the emulsifier used relative to 100 parts by weight of the monomer component for polymerization, is usually in the range of 0.01 to 10 parts by weight, preferably 0.1 to 5 parts by weight, and more preferably 1 to 3 parts by weight.

[0099] As a method for emulsifying a monomer component for polymerization containing a maleic acid diester structure monomer represented by the general formula (1) and a radically polymerizable monomer using water and an emulsifier, there is no particular limitation. A method of mixing the monomer component, water, and an emulsifier is preferred, and a method of stirring the monomer component, water, and an emulsifier using a stirrer such as a homogenizer or a disc turbine is more preferred. In addition, polymerization auxiliary materials such as a particle size regulator, a chelating agent, and a deoxidizing agent may be contained in the monomer emulsion as needed.

[0100] As the polymerization initiator, there is no particular limitation, and the polymerization initiators commonly used in emulsion polymerization can be used without limitation. As the polymerization initiator, it is preferably, for example, a peroxide, an azo compound, or a redox polymerization initiator composed of a peroxide and a reducing agent.

[0101] As the peroxide, either an inorganic peroxide or an organic peroxide can be used.

[0102] Examples of the inorganic peroxide include, for example, sodium persulfate, potassium persulfate, hydrogen peroxide, ammonium persulfate, etc. Among these, potassium persulfate, hydrogen peroxide, and ammonium persulfate are preferred, and potassium persulfate is particularly preferred.

[0103] Examples of the organic peroxide include, for example, 2,2-bis(4,4-di-(tert-butylperoxy)cyclohexyl)propane, 1-di-(tert-hexylperoxy)cyclohexane, 1,1-di-(tert-butylperoxy)cyclohexane, n-butyl 4,4-di-(tert-butylperoxy)valerate, 2,2-di-(tert-butylperoxy)butane, tert-butyl hydroperoxide, cumene hydroperoxide, diisopropylbenzene peroxide, terpinane hydroperoxide, benzoyl peroxide, 1,1,3,3-tetraethylbutyl hydroperoxide, cumyl tert-butyl peroxide, di-tert-butyl peroxide, di-tert-hexyl peroxide, di(2-tert-butylperoxyisopropyl)benzene, dicumyl peroxide, diisobutyryl peroxide, bis(3,5,5-trimethylhexanoyl)peroxide, dilauroyl peroxide, di-succinic peroxide, dibenzoyl peroxide, bis(3-methylbenzoyl)peroxide, benzoyl(3-methylbenzoyl)peroxide, diisobutyl peroxydicarbonate, di-n-propyl peroxydicarbonate, bis(2-ethylhexyl) peroxydicarbonate, di-sec-butyl peroxydicarbonate, 1,1,3,3-tetramethylbutyl peroxypivalate, tert-hexyl peroxypivalate, tert-butyl peroxypivalate, tert-hexyl peroxypivalate, tert-butyl peroxypivalate, 2,5-dimethyl-2,5-bis(2-ethylhexanoylperoxy)hexane, 1,1,3,3-tetramethylbutyl 2-ethylhexanoate peroxide, tert-hexyl 2-ethylhexanoate peroxide, tert-butyl 3,5,5-trimethylhexanoate peroxide, tert-hexyl isopropylmonoperoxycarbonate, tert-butyl isopropylmonoperoxycarbonate, tert-butyl 2-ethylhexylmonoperoxycarbonate, 2,5-dimethyl-2,5-bis(benzoylperoxy)hexane, tert-butyl peroxyacetate, tert-hexyl peroxybenzoate, tert-butyl peroxybenzoate, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, etc. Among these, diisopropylbenzene peroxide, cumene hydroperoxide, terpinane hydroperoxide, benzoyl peroxide, etc. are preferred.

[0104] Examples of the azo compound include azobisisobutyronitrile, 4,4'-azobis(4-cyanovaleric acid), 2,2'-azobis[2-(2-imidazolin-2-yl)propane], 2,2'-azobis(propane-2-carboxamidine), 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamide], 2,2'-azobis{2-[1-(2-hydroxyethyl)-2-imidazolin-2-yl]propane}, 2,2'-azobis(1-imino-1-pyrrolidin-2-yl-2-methylpropane), 2,2'-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propionamide}, and the like.

[0105] These peroxides and azo compounds can be used alone or in combination of two or more. The amount of the peroxide and azo compound in the initial polymerization step is preferably 0.001 to 0.5 parts by weight, more preferably 0.002 to 0.4 parts by weight, and further preferably 0.003 to 0.3 parts by weight, based on 100 parts by weight of the monomer component for polymerization.

[0106] As the reducing agent used in combination with the peroxide, any reducing agent that can be used as a redox catalyst for emulsion polymerization can be used without limitation. As the reducing agent, it is preferred to use at least two reducing agents, and particularly preferred is a combination of a metal ion compound in a reduced state and a reducing agent other than that.

[0107] The metal ion compound in a reduced state is not particularly limited, and examples thereof include ferrous sulfate, sodium iron(III) hexamethylenediaminetetraacetate, and copper naphthenate. Among these, ferrous sulfate is preferred.

[0108] The metal ion compound in a reduced state can be used alone or in combination of two or more. The amount of the metal ion compound in a reduced state in the initial polymerization step is preferably 0.0005 to 0.0030 parts by weight, more preferably 0.0007 to 0.0025 parts by weight, and further preferably 0.0010 to 0.0020 parts by weight, based on 100 parts by weight of the monomer component for polymerization.

[0109] The reducing agent other than the metal ion compound in the reduced state is not particularly limited, and examples thereof include: ascorbic acid such as ascorbic acid, sodium ascorbate, and potassium ascorbate, or salts thereof; isoascorbic acid such as isoascorbic acid, sodium isoascorbate, and potassium isoascorbate, or salts thereof; sulfite salts such as sodium formaldehyde sulfoxylate; sulfites such as sodium sulfite, potassium sulfite, sodium bisulfite, aldehyde sodium bisulfite, and potassium bisulfite; pyrosulfites such as sodium pyrosulfite, potassium pyrosulfite, sodium pyrosulfate, and potassium pyrosulfate; thiosulfates such as sodium thiosulfate and potassium thiosulfate; phosphorous acid or salts thereof such as phosphorous acid, sodium phosphite, potassium phosphite, sodium hydrogen phosphite, and potassium hydrogen phosphite; pyrophosphorous acid or salts thereof such as pyrophosphorous acid, sodium pyrophosphite, potassium pyrophosphite, sodium hydrogen pyrophosphate, and potassium hydrogen pyrophosphate. Among these, ascorbic acid or its salts and sodium formaldehyde sulfoxylate are preferred.

[0110] The reducing agent other than the metal ion compound in the reduced state can be used alone or in combination of two or more. The amount of the reducing agent other than the metal ion compound in the reduced state in the initial polymerization step is preferably 0.005 to 0.080 parts by weight, more preferably 0.010 to 0.060 parts by weight, and further preferably 0.020 to 0.040 parts by weight relative to 100 parts by weight of the monomer component for polymerization.

[0111] As a preferred combination of the metal ion compound in the reduced state and the reducing agent other than the metal ion compound in the reduced state, a combination of ferrous sulfate and ascorbic acid or its salts and / or sodium formaldehyde sulfoxylate can be cited, more preferably a combination of ferrous sulfate and ascorbate salts and / or sodium formaldehyde sulfoxylate, and particularly preferably a combination of ferrous sulfate and sodium formaldehyde sulfoxylate.

[0112] The amount of water used in the emulsion polymerization is preferably 5 to 500 parts by weight, more preferably 10 to 300 parts by weight, and further preferably 20 to 200 parts by weight relative to 100 parts by weight of the monomer component for polymerization.

[0113] In addition, during the emulsion polymerization, polymerization auxiliary materials such as a molecular weight regulator, a particle size regulator, a chelating agent, and an oxygen supplement can be used as needed.

[0114] The emulsion polymerization can be carried out by any one of batch, semi-batch, and continuous methods, and the semi-batch method is preferred.

[0115] The polymerization temperature and polymerization time are not particularly limited and can be appropriately selected according to the type of polymerization catalyst used, etc. The polymerization temperature is preferably 0 to 100°C, more preferably 5 to 80°C, and further preferably 10 to 50°C. In addition, the polymerization time is preferably 0.5 to 100 hours, more preferably 1 to 10 hours. In addition, the polymerization conversion rate is not particularly limited and is preferably 80% by weight or more, more preferably 90% by weight or more, and further preferably 95% by weight or more.

[0116] In addition, when terminating the polymerization reaction, a polymerization terminator can be used. Examples of the polymerization terminator include hydroxylamine, hydroxylamine sulfate, diethylhydroxylamine, hydroxylamine sulfonic acid and its alkali metal salts, sodium dimethyldithiocarbamate, hydroquinone, etc. The amount of the polymerization terminator is not particularly limited and is preferably 0.1 to 2 parts by weight relative to 100 parts by weight of the monomer component used for polymerization.

[0117] Next, by bringing a coagulant into contact with the obtained emulsion polymerization liquid, coagulation is carried out to generate water-containing agglomerates.

[0118] The coagulant is not particularly limited, and examples thereof include metal salts of 1 to 3 valences. The metal salt of 1 to 3 valences is a salt of a metal that becomes a metal ion of 1 to 3 valences when dissolved in water, and is not particularly limited. Examples thereof include inorganic acids such as hydrochloric acid, nitric acid, and sulfuric acid, organic acids such as acetic acid, and salts of metals selected from sodium, potassium, lithium, magnesium, calcium, zinc, titanium, manganese, iron, cobalt, nickel, aluminum, and tin. In addition, hydroxides of these metals can also be used.

[0119] Specific examples of the metal salt of 1 to 3 valences include: metal chlorides such as sodium chloride, potassium chloride, lithium chloride, magnesium chloride, calcium chloride, zinc chloride, titanium chloride, manganese chloride, iron chloride, cobalt chloride, nickel chloride, aluminum chloride, and tin chloride; nitrates such as sodium nitrate, potassium nitrate, lithium nitrate, magnesium nitrate, calcium nitrate, zinc nitrate, titanium nitrate, manganese nitrate, iron nitrate, cobalt nitrate, nickel nitrate, aluminum nitrate, and tin nitrate; sulfates such as sodium sulfate, potassium sulfate, lithium sulfate, magnesium sulfate, calcium sulfate, zinc sulfate, titanium sulfate, manganese sulfate, iron sulfate, cobalt sulfate, nickel sulfate, aluminum sulfate, and tin sulfate, etc. Among these, calcium chloride, sodium chloride, aluminum sulfate, magnesium chloride, magnesium sulfate, zinc chloride, zinc sulfate, and sodium sulfate are preferred. Particularly preferred are metal salts of 1 valence or 2 valences, more preferably metal salts of 2 valences, further preferably magnesium salts, still further preferably inorganic magnesium salts, and particularly preferably magnesium sulfate. In addition, these can be used alone or in combination of multiple kinds.

[0120] The amount of the coagulant is preferably 0.01 to 100 parts by weight, more preferably 0.1 to 50 parts by weight, and still more preferably 1 to 30 parts by weight, relative to 100 parts by weight of the monomer components for polymerization. By setting the amount of the coagulant within the above range, the coagulation of the copolymer rubber can be made sufficient, and the resulting copolymer rubber can have excellent water resistance.

[0121] In addition, the method of bringing the emulsion polymerization liquid into contact with the coagulant is not particularly limited, and examples thereof include: a method of adding the emulsion polymerization liquid to the aqueous solution containing the coagulant being stirred while stirring the aqueous solution containing the coagulant; a method of adding the aqueous solution containing the coagulant to the emulsion polymerization liquid being stirred while stirring the emulsion polymerization liquid. Alternatively, a method of adding only the emulsion polymerization liquid to the aqueous solution containing the coagulant without stirring; a method of adding the aqueous solution containing the coagulant to the emulsion polymerization liquid can also be employed. Among these, a method of adding the emulsion polymerization liquid to the aqueous solution containing the coagulant being stirred while stirring the aqueous solution containing the coagulant is preferred. By performing the coagulation operation in such a manner, the particle diameter of the water-containing agglomerates formed by coagulation can be controlled within a relatively uniform range, and thus, the cleaning efficiency of the generated water-containing agglomerates can be improved.

[0122] The concentration of the magnesium salt in the aqueous solution containing the coagulant is not particularly limited, and from the viewpoint of more appropriately controlling the particle diameter of the water-containing agglomerates formed by coagulation, it is preferably 0.1 to 20% by weight, more preferably 0.5 to 10% by weight, and still more preferably 1 to 5% by weight.

[0123] The temperature of the aqueous solution containing the coagulant (i.e., the coagulation temperature) is not particularly limited, and from the viewpoint of more appropriately controlling the particle diameter of the water-containing agglomerates formed by coagulation, it is preferably 40°C or higher, more preferably 40 to 90°C, and still more preferably 50 to 85°C.

[0124] In addition, the stirring method when stirring the aqueous solution containing the coagulant is not particularly limited, and examples thereof include a method using a stirring device that stirs with stirring blades. In this case, a method is preferably adopted in which the aqueous solution containing the coagulant is contained in a stirring tank, and the emulsion polymerization liquid is added while stirring the aqueous solution containing the coagulant in the stirring tank with the stirring blades.

[0125] Furthermore, the solid content concentration of the emulsion polymerization liquid for coagulation is not particularly limited, and it can be used directly in the state obtained by emulsion polymerization. From the viewpoint of more appropriately controlling the particle diameter of the water-containing agglomerates formed by coagulation, it is preferably adjusted to the range of 5 to 50% by weight, more preferably adjusted to the range of 10 to 45% by weight, and particularly preferably adjusted to the range of 20 to 40% by weight.

[0126] Next, it is preferable to wash the water-containing agglomerates obtained by the solidification operation. The washing method is not particularly limited, and examples thereof include a method of washing the water-containing agglomerates obtained by the solidification operation with water, and a method of mixing the water-containing agglomerates obtained by the solidification operation with water, etc. The temperature during the water washing is not particularly limited, and it is preferably 5 to 60°C, more preferably 10 to 50°C. The mixing time is 1 to 60 minutes, more preferably 2 to 30 minutes.

[0127] In addition, when performing water washing, the amount of water mixed with the water-containing agglomerates is not particularly limited. From the viewpoint of further improving the water washing efficiency, relative to 100 parts by weight of the monomer components used for polymerization, it is preferably set to an amount of 50 parts by weight or more, more preferably set to an amount of 50 to 15000 parts by weight, further preferably set to an amount of 100 to 10000 parts by weight, and particularly preferably set to an amount of 500 to 5000 parts by weight.

[0128] The water washing time is not particularly limited, and it is preferably 1 to 120 minutes, more preferably 2 to 60 minutes, and further preferably 3 to 30 minutes.

[0129] In addition, the number of water washing times is not particularly limited, and it is preferably 1 to 10 times, more preferably 1 to 5 times, and further preferably 1 to 3 times. In the present invention, the number of water washing times refers to the number of times in the case where the operation of adding water to the water-containing agglomerates, then mixing for a specified time, and then separating the water-containing agglomerates from the water used for water washing is regarded as one water washing. That is, for example, the number of water washing times of 2 times means performing the operation of adding water to the water-containing agglomerates, then mixing for a specified time, and then separating the water-containing agglomerates from the water used for water washing, and then further performing the operation of adding water to the water-containing agglomerates, then mixing for a specified time, and then separating the water-containing agglomerates from the water used for water washing. In addition, when the number of water washing times is set to 2 times or more, the temperature of the water used for water washing, the amount of water, and the water washing time can be the same or different.

[0130] In addition, in the present invention, after performing water washing, acid washing using an acid as a cleaning liquid can be further performed. It is preferable to further perform water washing after acid washing. As the conditions for water washing, as long as they are the same as the above conditions.

[0131] In addition, the water-containing agglomerates after washing can be dried. The drying method of the water-containing agglomerates is not particularly limited, and it can be carried out according to a conventional method. Examples thereof include a method of drying using a hot air dryer, a vacuum dryer, an expansion dryer, a kneading type dryer, a screw type extruder, etc.

[0132] In addition, the drying temperature of the water-containing agglomerates is not particularly limited, preferably 80 to 250 °C, more preferably 100 to 200 °C, and further preferably 110 to 180 °C.

[0133] The copolymer rubber of the present invention can be produced, for example, as described above. In the present invention, the copolymer rubber can be obtained in the form of agglomerates or as a rubber encapsulated rubber, that is, a rubber package (a copolymer rubber formed into a block of a specified shape).

[0134] <Rubber composition>

[0135] The rubber composition of the present invention contains the above-described copolymer rubber of the present invention and a crosslinking agent.

[0136] The crosslinking agent is not particularly limited, and examples thereof that can be used include polyamine compounds such as diamine compounds and their carbonates; sulfur; sulfur donors; triazine mercaptan compounds; polyepoxy compounds; ammonium salts of organic carboxylic acids; organic peroxides; metal salts of dithiocarbamic acid; polycarboxylic acids; quaternary ammonium salts; imidazole compounds; isocyanuric acid compounds and other conventionally known crosslinking agents. These crosslinking agents can be used alone or in combination of two or more.

[0137] The polyamine compound and its carbonate are not particularly limited, and a polyamine compound having 4 to 30 carbon atoms and its carbonate are preferred. Examples of such polyamine compounds and their carbonates include aliphatic polyamine compounds and their carbonates, and aromatic polyamine compounds.

[0138] The aliphatic polyamine compound and its carbonate are not particularly limited, and examples thereof include hexamethylenediamine, hexamethylenediamine carbamate, and N,N'-bis(cinnamaldehyde)-1,6-hexanediamine.

[0139] The aromatic polyamine compound is not particularly limited, and examples thereof include 4,4'-methylenedianiline, p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-(m-phenylene diisopropylidene)diphenylamine, 4,4'-(p-phenylene diisopropylidene)diphenylamine, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 4,4'-diaminobenzanilide, 4,4'-bis(4-aminophenoxy)biphenyl, m-xylylenediamine, p-xylylenediamine, and 1,3,5-benzenetriamine. Among these, 2,2'-bis[4-(4-aminophenoxy)phenyl]propane is preferred.

[0140] As a crosslinking agent, among these, from the viewpoint of being able to achieve a higher level of balance between scorch stability and crosslinking speed and being able to further improve the mechanical properties of the obtained rubber crosslinked product, polyamine compounds and their carbonates are preferred, aliphatic polyamine compounds and their carbonates are more preferred, and hexamethylenediamine carbamate is further preferred.

[0141] The content of the crosslinking agent in the rubber composition of the present invention is preferably 0.1 to 10 parts by weight, more preferably 0.2 to 5 parts by weight, based on 100 parts by weight of the copolymer rubber of the present invention. By making the content of the crosslinking agent within the above range, it is possible to achieve a higher level of balance between scorch stability and crosslinking speed and to further improve the mechanical properties of the obtained rubber crosslinked product.

[0142] The rubber composition of the present invention may also contain a rubber other than the above-mentioned copolymer rubber of the present invention. The rubber other than the copolymer rubber of the present invention is not particularly limited, and examples thereof include rubbers that do not contain units of the maleic acid diester structure monomer represented by the general formula (1) (acrylic rubber, natural rubber, polybutadiene rubber, polyisoprene rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, silicone rubber, fluororubber, olefin-based elastomer, styrene-based elastomer, vinyl chloride-based elastomer, polyester-based elastomer, polyamide-based elastomer, polyurethane-based elastomer, polysiloxane-based elastomer, etc.). These can be used alone or in combination of two or more.

[0143] The content of the copolymer rubber of the present invention in the rubber composition of the present invention can be appropriately selected according to the use purpose. In 100 parts by weight of the rubber components in the rubber composition of the present invention, it is preferably 70 parts by weight or more, more preferably 90 parts by weight or more, further preferably 95 parts by weight or more, and particularly preferably 100 parts by weight (that is, the rubber components of the rubber composition of the present invention are substantially composed only of the copolymer rubber of the present invention).

[0144] The rubber composition of the present invention preferably further contains a crosslinking accelerator. The crosslinking accelerator is not particularly limited. When the crosslinking agent is a polyamine compound or its carbonate, guanidine compounds, diazabicycloolefin compounds, imidazole compounds, quaternary ammonium salts, tertiary phosphine compounds, aliphatic primary secondary amine compounds, and aliphatic primary tertiary amine compounds can be used. Among these, guanidine compounds, diazabicycloolefin compounds, and aliphatic primary secondary amine compounds are preferred, and guanidine compounds and diazabicycloolefin compounds are particularly preferred. These crosslinking accelerators can be used alone or in combination of two or more.

[0145] Specific examples of the guanidine compound include 1,3-ditolylguanidine, 1,3-diphenylguanidine, etc. Specific examples of the diazabicycloolefin compound include 1,8-diazabicyclo[5.4.0]undec-7-ene, 1,5-diazabicyclo[4.3.0]non-5-ene, etc. Specific examples of the imidazole compound include 2-methylimidazole, 2-phenylimidazole, etc. Specific examples of the quaternary ammonium salt include tetra-n-butylammonium bromide, octadecyltri-n-butylammonium bromide, etc. Specific examples of the tertiary phosphine compound include triphenylphosphine, tri-p-tolylphosphine, etc.

[0146] The aliphatic primary secondary amine compound is a compound obtained by substituting two hydrogen atoms of ammonia with aliphatic hydrocarbon groups. The aliphatic hydrocarbon group substituting the hydrogen atom preferably has 1 to 30 carbon atoms. Specific examples of the aliphatic primary secondary amine compound include dimethylamine, diethylamine, dipropylamine, diallylamine, diisopropylamine, di-n-butylamine, di-t-butylamine, di-sec-butylamine, dihexylamine, diheptylamine, dioctylamine, dinonylamine, didecylamine, bis(undecyl)amine, bis(dodecyl)amine, bis(tridecyl)amine, bis(tetradecyl)amine, bis(pentadecyl)amine, bis(hexadecyl)amine, di-2-ethylhexylamine, and bis(octadecyl)amine, etc.

[0147] The aliphatic primary tertiary amine compound is a compound obtained by substituting all three hydrogen atoms of ammonia with aliphatic hydrocarbon groups. The aliphatic hydrocarbon group substituting the hydrogen atom preferably has 1 to 30 carbon atoms. Specific examples of the aliphatic primary tertiary amine compound include trimethylamine, triethylamine, tripropylamine, triallylamine, triisopropylamine, tri-n-butylamine, tri-t-butylamine, tri-sec-butylamine, trihexylamine, triheptylamine, trioctylamine, trinonylamine, tridecylamine, tris(undecyl)amine, and tris(dodecyl)amine, etc.

[0148] The content of the crosslinking accelerator in the rubber composition of the present invention is preferably 0.1 to 10 parts by weight, more preferably 0.5 to 7.5 parts by weight, and particularly preferably 1 to 5 parts by weight with respect to 100 parts by weight of the copolymer rubber of the present invention. By making the content of the crosslinking accelerator within the above range, the scorch stability and the crosslinking speed can be balanced at a higher level, and the mechanical properties of the obtained rubber crosslinked product can be further improved.

[0149] The rubber composition of the present invention preferably contains fillers such as reinforcing fillers and non-reinforcing fillers.

[0150] Examples of the reinforcing filler include carbon blacks such as furnace black, acetylene black, thermal cracking carbon black, channel black, and graphite; and silicas such as wet silica, dry silica, and colloidal silica. In addition, examples of the non-reinforcing filler include clay such as quartz powder and diatomaceous earth, zinc white, basic magnesium carbonate, activated calcium carbonate, magnesium silicate, aluminum silicate, titanium dioxide, talc, aluminum sulfate, calcium sulfate, and barium sulfate. The filler can be used alone or in combination of two or more kinds.

[0151] The content of the filler in the rubber composition of the present invention is not particularly limited, and is preferably 1 to 200 parts by weight, more preferably 10 to 150 parts by weight, and still more preferably 20 to 100 parts by weight, based on 100 parts by weight of the rubber component containing the copolymer rubber of the present invention.

[0152] The rubber composition of the present invention may contain an antioxidant as needed. The antioxidant is not particularly limited, and examples thereof include phenolic antioxidants such as bis hindered phenol antioxidants, semi hindered phenol antioxidants, low hindered phenol antioxidants, and phenol antioxidants without a hindered group; phosphite antioxidants; thioester antioxidants; secondary amine antioxidants such as phenyl-α-naphthylamine, phenyl-β-naphthylamine, p-(p-toluenesulfonamide)-diphenylamine, 4,4'-bis(α,α-dimethylbenzyl)diphenylamine, N,N-diphenyl-p-phenylenediamine, N-isopropyl-N'-phenyl-p-phenylenediamine, and butyraldehyde-aniline condensate; imidazole antioxidants; quinoline antioxidants; and hydroquinone antioxidants. The antioxidant can be used alone or in combination of two or more kinds.

[0153] The content of the antioxidant in the rubber composition of the present invention is not particularly limited, and is preferably 0.01 to 15 parts by weight, more preferably 0.05 to 10 parts by weight, and still more preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the rubber component containing the copolymer rubber of the present invention.

[0154] In addition, the rubber composition of the present invention can be further compounded with compounding agents commonly used in the rubber processing field in addition to the above components. Examples of such compounding agents include light stabilizers; anti-coking agents; plasticizers; processing aids; adhesives; slip agents; lubricants; flame retardants; mildew-proof agents; antistatic agents; colorants; and delayed crosslinking agents. The compounding amount of these compounding agents is not particularly limited as long as it does not hinder the object and effect of the present invention, and an appropriate amount corresponding to the compounding purpose can be compounded.

[0155] The rubber composition of the present invention is prepared by the following method: a crosslinking agent and other various compounding agents used as needed are compounded in the above rubber component containing the copolymer rubber of the present invention, and are mixed and kneaded by an open roll, a Banbury mixer, various kneaders, etc., and then further kneaded by a kneading roll.

[0156] The mixing order of each component is not particularly limited. It is preferable to fully mix the components that are not easily reactive or decomposable upon heating, and then mix crosslinking agents and the like, which are components that are easily reactive or decomposable upon heating, at a temperature at which no reaction or decomposition occurs, in a short time.

[0157] <Rubber crosslinked product>

[0158] The rubber crosslinked product of the present invention is obtained by crosslinking the above-described rubber composition of the present invention.

[0159] The rubber crosslinked product of the present invention can be produced as follows: Using the rubber composition of the present invention, it is molded by a molding machine corresponding to a desired shape, such as an extruder, an injection molding machine, a compressor, and a roll, and then heated to carry out a crosslinking reaction, thereby fixing the shape as the rubber crosslinked product. In this case, crosslinking can be carried out after pre-molding, or crosslinking can be carried out simultaneously with molding. In addition, the molding temperature is usually 10 to 140 °C, preferably 25 to 120 °C.

[0160] The crosslinking temperature is usually 150 to 190 °C, preferably 160 to 180 °C, and the crosslinking time is usually 2 to 60 minutes, preferably 3 to 40 minutes. As the heating method, methods for crosslinking rubber, such as press heating, steam heating, oven heating, and hot air heating, can be appropriately selected.

[0161] In the production method of the rubber crosslinked product of the present invention, secondary crosslinking is not necessarily required, but secondary crosslinking can also be carried out. Secondary crosslinking is usually carried out in a heated air environment of 130 to 220 °C for 1 to 48 hours.

[0162] From the viewpoints of productivity, energy saving, and carbon neutrality, the rubber crosslinked product of the present invention is preferably a primary crosslinked product of the rubber composition of the present invention. For example, the rubber crosslinked product of the present invention is preferably a primary crosslinked product obtained by heating and crosslinking the rubber composition of the present invention at a temperature of 150 °C to 190 °C for 2 to 60 minutes.

[0163] The rubber crosslinked product of the present invention can be preferably used as: sealing materials such as O-rings, packings, diaphragms, oil seals, shaft seals, bearing seals, mechanical seals, wellhead seals, seals for electrical and electronic equipment, and seals for air compression equipment; various gaskets such as a cylinder head gasket installed at the connection part between the cylinder block and the cylinder head, a rocker cover gasket installed at the connection part between the rocker cover and the cylinder head, an oil pan gasket installed at the connection part between the oil pan and the cylinder head or the transmission case, a gasket for a fuel cell spacer installed between a pair of outer casings sandwiching a unit cell having a positive electrode, an electrolyte plate, and a negative electrode, and a gasket for the top cover of a hard disk drive; cushioning materials, shockproof materials; wire coating materials; industrial belts; pipe and hose materials; strip materials; protective cover materials; sheet materials, etc.

[0164] In addition, the rubber crosslinked product of the present invention, as an extruded molded product and a crosslinked product used in automotive applications, is preferably used for various hose materials such as fuel hoses, filler neck hoses, exhaust hoses, steam hoses, oil hoses, etc. for fuel oil systems of fuel tanks, turbo air hoses, transmission control hoses, etc. for air systems, radiator hoses, heater hoses, brake hoses, air conditioning hoses, etc.

[0165] Examples

[0166] Hereinafter, the present invention will be described in detail by way of examples, but the present invention is not limited to these examples. In addition, unless otherwise specified, "parts" hereinafter are based on weight. In addition, various physical properties are measured as follows.

[0167] <Monomer composition of copolymer rubber>

[0168] The monomer composition of the copolymer rubber is calculated based on the amounts of the respective monomers used in the polymerization reaction and the polymerization conversion rate. Specifically, in the emulsion polymerization reactions of the respective examples and comparative examples, no unreacted monomers were confirmed, and the polymerization conversion rate was approximately 100%. Therefore, the amounts of the respective monomers used in the polymerization reaction were set to be the same as the content ratios of the respective monomer units constituting the copolymer rubber.

[0169] <Glass transition temperature>

[0170] For the copolymer rubber, a differential scanning calorimeter (DSC) was used to measure from -80°C to 30°C at a heating rate of 10°C / minute, and the glass transition temperature was determined based on the peak of the differential curve.

[0171] <Polymer Mooney viscosity>

[0172] For the copolymer rubber, the polymer Mooney viscosity (ML1+4, 100°C) was measured in accordance with JIS K6300-1:2013.

[0173] <Scorch stability test>

[0174] For the rubber composition, the Mooney scorch was measured in accordance with JIS K6300 under the measurement conditions of 125°C, and the minimum value (Vmin) of the Mooney viscosity was measured. In addition, the time when the Mooney viscosity increased by 5 percentage points from the minimum value (Vmin) of the Mooney viscosity was determined as the Mooney scorch time (t5). The larger the Mooney scorch time (t5), the better the scorch stability can be judged.

[0175] <Crosslinkability test>

[0176] For the rubber composition, a crosslinkability test was carried out using a rubber vulcanization testing machine (trade name “Moving Die Rheometer”, manufactured by Alpha Technology Co., Ltd.) under the conditions of 170 °C for 20 minutes in accordance with JIS K6300-2. Based on the results of the crosslinkability test, the minimum torque (ML) (unit: dN·m), the maximum torque (MH) (unit: dN·m), and T90 (unit: minute) were determined. In addition, T90 refers to the time required for the torque to rise by 90% from the minimum torque ML when “maximum torque MH - minimum torque ML” is set to 100%. The smaller the value of T90, the faster the crosslinking speed can be judged.

[0177] <Normal physical properties of the rubber crosslink (primary crosslink)>

[0178] According to JIS K6251, test pieces were cut from the sheet-shaped rubber crosslink (primary crosslink), and the tensile strength, elongation at break, and stress at 100% elongation of the obtained test pieces were measured. In addition, in accordance with JIS K6253-3, the hardness of the sheet-shaped rubber crosslink (primary crosslink) was measured using a Shore hardness tester (type A).

[0179] <Air heating aging test of the rubber crosslink (primary crosslink)>

[0180] For the sheet-shaped acrylic rubber crosslink (primary crosslink), an air heating aging test was carried out at 175 °C for 72 hours in accordance with JIS K6257. Then, test pieces were cut from the acrylic rubber crosslink after the air heating aging test in accordance with JIS K6251, and the tensile strength, elongation at break, and stress at 100% elongation of the obtained test pieces were measured. Subsequently, the increase ratio (%) of each measured value after the air heating aging test was calculated with respect to the case where each measured value before the air heating aging test was taken as the reference value (100%).

[0181] <Compression set of the rubber crosslink (primary crosslink)>

[0182] Using the cylindrical rubber crosslink (primary crosslink), the compression set under the compression conditions of a 25% compression ratio, 175 °C, and 72 hours was determined in accordance with JIS K6262.

[0183] <Maleic acid diester structure monomer-containing>

[0184] In the examples, maleic acid diester structure monomers (a) to (e) represented by the following formulas (a) to (e) were used. The maleic acid diester structure monomers (a) to (e) were manufactured according to the following production examples.

[0185] [Chemical formula 5]

[0186]

[0187] <Manufacturing Example 1>

[0188] (Manufacture of monomer (a) containing a maleic acid diester structure)

[0189] Under a nitrogen atmosphere, 61 mL of acetone (product of Fujifilm Wako Pure Chemical Corporation), 69 g (400 mmol) of monobutyl fumarate (product of Fujifilm Wako Pure Chemical Corporation), and 66 mL (600 mmol) of isopropyl vinyl ether (product of Fujifilm Wako Pure Chemical Corporation) were added to a 500 mL three-necked flask. Then, 0.45 mL (1.6 mmol) of 2-ethylhexyl phosphate (product of Tokyo Chemical Industry Co., Ltd.) was added, and the mixture was stirred at 50 °C for 6 hours and then cooled to room temperature. Subsequently, extraction with 250 mL of 1 M aqueous potassium hydroxide solution (product of Fujifilm Wako Pure Chemical Corporation) was carried out 3 times, followed by washing with water. The organic phase was separated, anhydrous magnesium sulfate (product of Fujifilm Wako Pure Chemical Corporation) was added, the residual water was dried, and the solvent was removed under reduced pressure, thereby obtaining 91 g of a colorless transparent liquid containing monomer (a) with a maleic acid diester structure.

[0190] <Manufacturing Example 2>

[0191] (Manufacture of monomer (b) containing a maleic acid diester structure)

[0192] Under a nitrogen atmosphere, 61 mL of acetone (product of Fujifilm Wako Pure Chemical Corporation), 69 g (400 mmol) of monobutyl fumarate (product of Fujifilm Wako Pure Chemical Corporation), and 77 mL (600 mmol) of n-butyl vinyl ether (product of Fujifilm Wako Pure Chemical Corporation) were added to a 500 mL three-necked flask. Then, 0.45 mL (1.6 mmol) of 2-ethylhexyl phosphate (product of Tokyo Chemical Industry Co., Ltd.) was added, and the mixture was stirred at 50 °C for 6 hours and then cooled to room temperature. Subsequently, extraction with 250 mL of 1 M aqueous potassium hydroxide solution (product of Fujifilm Wako Pure Chemical Corporation) was carried out 3 times, followed by washing with water. The organic phase was separated, anhydrous magnesium sulfate (product of Fujifilm Wako Pure Chemical Corporation) was added, the residual water was dried, and the solvent was removed under reduced pressure, thereby obtaining 105 g of a colorless transparent liquid containing monomer (b) with a maleic acid diester structure.

[0193] <Manufacturing Example 3>

[0194] (Manufacture of monomer (c) containing a maleic acid diester structure)

[0195] Under a nitrogen atmosphere, 61 mL of acetone (product of FUJIFILM Wako Pure Chemical Corporation), 69 g (400 mmol) of mono-n-ethyl fumarate (product of FUJIFILM Wako Pure Chemical Corporation), and 58 mL (600 mmol) of ethyl vinyl ether (product of FUJIFILM Wako Pure Chemical Corporation) were added to a 500 mL three-necked flask. Then, 0.45 mL (1.6 mmol) of 2-ethylhexyl phosphate (product of Tokyo Chemical Industry Co., Ltd.) was added, and the mixture was stirred at 50 °C for 6 hours and then cooled to room temperature. Subsequently, extraction with 250 mL of 1 M aqueous potassium hydroxide solution (product of FUJIFILM Wako Pure Chemical Corporation) three times and washing with water were carried out. The organic phase was separated, anhydrous magnesium sulfate (product of FUJIFILM Wako Pure Chemical Corporation) was added, the remaining water was dried, and the solvent was removed under reduced pressure, thereby obtaining 87 g of a colorless transparent liquid containing the maleic acid diester structure monomer (c).

[0196] <Manufacturing Example 4>

[0197] (Manufacture of the maleic acid diester structure monomer (d))

[0198] Under a nitrogen atmosphere, 41 mL of acetone (product of FUJIFILM Wako Pure Chemical Corporation), 46 g (270 mmol) of mono-n-butyl fumarate (product of FUJIFILM Wako Pure Chemical Corporation), and 43 mL (227 mmol) of 2-ethylhexyl vinyl ether (product of FUJIFILM Wako Pure Chemical Corporation) were added to a 500 mL three-necked flask. Then, 0.45 mL (1.6 mmol) of 2-ethylhexyl phosphate (product of Tokyo Chemical Industry Co., Ltd.) was added, and the mixture was stirred at 50 °C for 6 hours and then cooled to room temperature. Subsequently, extraction with 250 mL of 1 M aqueous potassium hydroxide solution (product of FUJIFILM Wako Pure Chemical Corporation) three times and washing with water were carried out. The organic phase was separated, anhydrous magnesium sulfate (product of FUJIFILM Wako Pure Chemical Corporation) was added, the remaining water was dried, and the solvent was removed under reduced pressure, thereby obtaining 64 g of a colorless transparent liquid containing the maleic acid diester structure monomer (d).

[0199] <Manufacturing Example 5>

[0200] (Manufacture of the maleic acid diester structure monomer (e))

[0201] Under a nitrogen atmosphere, 61 mL of acetone (product of FUJIFILM Wako Pure Chemical Corporation), 79 g (400 mmol) of cyclohexyl fumarate (product of ChemBridge Corporation), and 55 mL (600 mmol) of 3,4-dihydro-2H-pyran (product of FUJIFILM Wako Pure Chemical Corporation) were added to a 500 mL three-necked flask. Then, 0.45 mL (1.6 mmol) of 2-ethylhexyl phosphate (product of Tokyo Chemical Industry Co., Ltd.) was added, and the mixture was stirred at 50 °C for 6 hours and then cooled to room temperature. Subsequently, extraction was performed three times with 250 mL of 1 M aqueous potassium hydroxide solution (product of FUJIFILM Wako Pure Chemical Corporation), and washing was performed with water. The organic phase was separated, anhydrous magnesium sulfate (product of FUJIFILM Wako Pure Chemical Corporation) was added to dry the remaining water, and the solvent was removed under reduced pressure, thereby obtaining 75 g of a colorless transparent liquid containing the monomer (e) having a maleate diester structure.

[0202] <Example 1>

[0203] (Manufacture of copolymer rubber (A-1))

[0204] 46.294 parts of ion-exchanged water, 60.0 parts of ethyl acrylate as a monomer, 38.1 parts of n-butyl acrylate, 1.9 parts of the monomer (a) having a maleate diester structure represented by the above formula (a), and 1.8 parts of sodium tridecoxyhexa(oxyethylene) phosphate as an anionic emulsifier were added to a mixing container equipped with a homogenizer and stirred to obtain a monomer emulsion.

[0205] Subsequently, 170.853 parts of pure water and 2.962 parts of the monomer emulsion obtained above were introduced into a polymerization reaction tank equipped with a thermometer and a stirring device, and cooled to 12 °C under a nitrogen stream. Then, 145.132 parts of the monomer emulsion obtained above, 0.00033 parts of ferrous sulfate (reducing agent), 0.264 parts of sodium ascorbate (reducing agent), and 7.72 parts (the amount of potassium persulfate is 0.22 parts) of a 2.85 wt% aqueous potassium persulfate solution (polymerization initiator) were continuously added dropwise to the polymerization reaction tank over 3 hours while maintaining the temperature at 12 °C. Thereafter, the reaction was continued for 1 hour while maintaining the temperature in the polymerization reaction tank at 23 °C. After confirming that the polymerization conversion rate reached approximately 100%, hydroquinone as a polymerization terminator was added to terminate the polymerization reaction, thereby obtaining an emulsion polymerization solution.

[0206] Next, 60 parts of a 30 wt% aqueous magnesium sulfate solution adjusted to 85°C were introduced into a coagulation tank equipped with a thermometer and a stirring device, and stirred with a stirring blade in a state of being heated to 85°C. Then, with stirring, 100 parts of the emulsion polymerization liquid prepared above were continuously added to the aqueous magnesium sulfate solution, whereby the polymer was coagulated and subjected to filtration separation to obtain water-containing agglomerates.

[0207] Next, 388 parts of industrial water were added to 100 parts of the solid content of the water-containing agglomerates obtained above, and stirred at room temperature in the coagulation tank for 5 minutes. Then, the water was drained from the coagulation tank, whereby the water-containing agglomerates were washed. Then, the washed water-containing agglomerates were dried with a hot air dryer at 110°C for 1 hour to obtain a copolymer rubber (A-1) in solid form with a 100% recovery rate. The glass transition temperature and polymer Mooney viscosity of the obtained copolymer rubber (A-1) were measured according to the above method. The results are shown in Table 2.

[0208] (Preparation of rubber composition)

[0209] Using a kneader, 60 parts of carbon black (trade name "Seast SO", manufactured by Tokai Carbon Co., Ltd.), 2 parts of stearic acid, 1 part of an ester wax (trade name "Greg G-8205", manufactured by DIC Corporation), and 2 parts of 4,4'-bis(α,α-dimethylbenzyl)diphenylamine (trade name "Nocrac CD", manufactured by Ouchi Shinko Chemical Industry Co., Ltd., antioxidant) were added to 100 parts of the copolymer rubber (A-1) and mixed at 50°C for 7 minutes. The obtained mixture was transferred to a roll at 50°C, and 0.5 part of hexamethylenediamine carbamate (trade name "Diak No.1", manufactured by DuPont Dow Elastomers, crosslinking agent) and 2 parts of 1,3-ditolylguanidine (trade name "NOCCELER DT", manufactured by Ouchi Shinko Chemical Industry Co., Ltd., crosslinking accelerator) were added, and kneaded with the roll to obtain a rubber composition. Then, using the obtained rubber composition, the scorch stability test and crosslinkability test were carried out according to the above method. The results are shown in Table 2.

[0210] (Manufacture of rubber crosslink)

[0211] The rubber composition was molded and crosslinked by pressing at 10 MPa at 170 °C for 20 minutes to obtain a sheet-like acrylic rubber crosslinked product (primary crosslinked product) of 15 cm × 15 cm × 2 mm. Using the obtained sheet-like rubber crosslinked product (primary crosslinked product), the normal physical properties were measured according to the above method, and an air heating aging test was carried out. The results are shown in Table 2. In addition, the rubber composition was molded and crosslinked by pressing at 10 MPa at 170 °C for 20 minutes to produce a cylindrical rubber crosslinked product (primary crosslinked product) with a diameter of 29 mm and a thickness of 12.5 mm, and the compression set was measured. The results are shown in Table 2.

[0212] <Examples 2 to 7, Comparative Examples 1 to 2>

[0213] (Manufacture of copolymer rubber (A-1))

[0214] The types and amounts of the respective monomers were changed as described in Table 1, and otherwise, the same procedure as in Example 1 was carried out to obtain copolymer rubbers (A-2) to (A-9). Using the obtained copolymer rubbers (A-2) to (A-9), otherwise, the same procedure as in Example 1 was carried out to obtain a rubber composition and a rubber crosslinked product, and the evaluation was carried out in the same manner as in Example 1. The results are shown in Table 2.

[0215] Table 1

[0216] Table 1

[0217]

[0218] Table 2

[0219] Table 2

[0220]

[0221] As shown in Table 1, the copolymer rubber obtained by copolymerizing the maleic acid diester structure monomer represented by the general formula (1) and the radically polymerizable monomer has a long scorch time (t5), has good scorch stability, and can form a rubber crosslinked product having sufficient mechanical properties without secondary crosslinking (Examples 1 to 7).

[0222] On the other hand, the copolymer rubber not containing the unit derived from the maleic acid diester structure monomer represented by the general formula (1) has a short scorch time (t5) and poor scorch stability (Comparative Examples 1 to 2).

Claims

1. A copolymer rubber is obtained by copolymerizing a monomer having a maleic acid diester structure represented by the following general formula (1) with a radically polymerizable monomer. In the general formula (1), R 1 is an alkyl group having 1 to 4 carbon atoms; R 2 is a group represented by R 7 or OR 8 ; R 7 is an alkyl group having 1 to 8 carbon atoms which may have a substituent; R 8 is an alkyl group having 1 to 8 carbon atoms which may have a substituent or a polyalkylene glycol group which may have a substituent; R 3 , R 4 and R 6 are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; R 5 is a hydrogen atom, a group represented by R 7 or OR 8 ; when R 3 is a hydrogen atom, R 2 is a group represented by OR 8 ; R 1 and R 2 can bond to each other to form a ring; R 4 and R 5 can bond to each other to form a ring.

2. The copolymer rubber according to claim 1, wherein, The content ratio of the unit of the monomer having a maleic acid diester structure represented by the general formula (1) is 0.1 to 10% by weight.

3. The copolymer rubber according to claim 1 or 2, wherein, The copolymer rubber contains at least one selected from (meth)acrylate monomers, (meth)acrylonitrile monomers, aromatic vinyl monomers, conjugated diene monomers, (meth)acrylamide monomers, vinyl acetate monomers, and ethylene monomers as the radically polymerizable monomer.

4. The copolymer rubber according to any one of claims 1 to 3, wherein, The glass transition temperature of the copolymer rubber is 0 °C or lower.

5. The copolymer rubber according to any one of claims 1 to 4, wherein, The copolymer rubber contains a (meth)acrylate monomer as the radically polymerizable monomer.

6. The copolymer rubber according to any one of claims 1 to 5, wherein, The Mooney viscosity (ML1+4, 100 °C) of the copolymer rubber is 10 to 150.

7. The copolymer rubber according to any one of claims 1 to 6, wherein, The monomer having a maleic acid diester structure represented by the general formula (1) is a monomer having a maleic acid diester structure represented by the following general formula (2) or general formula (3). In General Formulas (2) and (3), R 1 , R 3 , R 4 , R 6 , and R 8 are each independently the same as the group in General Formula (1); R 9 is an alkyl group having 1 to 17 carbon atoms that can have substituents; R 10 is an alkyl group having 1 to 8 carbon atoms that can have substituents or a polyalkylene glycol group that can have substituents; R 1 and R 8 can bond to each other to form a ring; R 4 and R 10 can bond to each other to form a ring.

8. A rubber composition contains a crosslinking agent and the copolymer rubber according to any one of claims 1 to 7.

9. The rubber composition according to claim 8, wherein, The rubber composition further contains a crosslinking accelerator.

10. The rubber composition according to claim 8 or 9, wherein, The rubber composition further contains a filler.

11. A rubber crosslinked product is obtained by crosslinking the rubber composition according to any one of claims 8 to 10.

12. The rubber crosslinked product according to claim 11, wherein, The rubber crosslinked product is a hose material, a sealing material, a pipe, a strip, or a protective cover material.

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