Crosslinking agent master batch, rubber composition containing crosslinking agent master batch, and crosslinked product thereof

Abstract

Under the condition that aromatic polyamine is used as a cross-linking agent, the scorching stability is good. On the other hand, the aromatic polyamine has poor dispersibility, and because the aromatic polyamine is a powder, it is worried that the work environment is deteriorated due to scattering. The present invention addresses the problem of providing a method for using an aromatic polyamine in which the aromatic polyamine has excellent dispersibility and does not scatter. It was found that the above-mentioned problem can be solved by producing a master batch in which an aromatic polyamine and a lubricant are dispersed in a synthetic rubber in advance.

Description

Technical Field

[0001] The present invention relates to a crosslinking agent masterbatch, a rubber composition containing the crosslinking agent masterbatch and a crosslinked product thereof. Background Art

[0002] Examples of the rubber having a carboxyl group as a crosslinking group include acrylic rubber, ethylene-acrylate rubber, and carboxyl-containing nitrile rubber. A polyamine compound can be used as a crosslinking agent.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent No. 4087178

[0006] Patent Document 2: Japanese Patent No. 6879212 Summary of the invention

[0007] Problem that the invention aims to solve

[0008] However, when hexamethylenediamine or hexamethylenediamine carbamate, which is an aliphatic polyamine, is used as a crosslinking agent, there are problems in that the scorch time is short and processing is difficult.

[0009] It is reported that by using acrylic rubber and a part of aromatic polyamines such as 2,2-bis[4-(4-aminophenoxy)phenyl]propane, silica, aliphatic polyols, and guanidine compounds, scorching does not occur during kneading and injection molding, and sufficient mechanical properties are exhibited by only one vulcanization (Patent Document 1).

[0010] Here, as a general method for kneading synthetic rubber, there are two stages, first, a stage of kneading in a ratio not containing a crosslinking agent and a crosslinking accelerator (hereinafter referred to as A kneading), and then a stage of adding a crosslinking agent and a crosslinking accelerator when necessary, and kneading at a low temperature in a manner that does not cause scorching (hereinafter referred to as B kneading).

[0011] However, since the aromatic polyamine crosslinking agent 2,2-bis[4-(4-aminophenoxy)phenyl]propane has a high melting point of 128°C, when it is added in a B-roll or when it is kneaded only in an open roll as described in the above patent document, there is a concern that the dispersibility may be low.

[0012] Furthermore, since 2,2-bis[4-(4-aminophenoxy)phenyl]propane is a powder, there is a concern of scattering and inhalation or surrounding contamination during handling such as when measuring or adding to an open mixing mill, and thus there is room for improvement in terms of the working environment.

[0013] On the other hand, in a method for producing a crosslinkable rubber composition for obtaining a carboxyl-containing nitrile copolymer rubber, a step of mixing an acrylic rubber and an aromatic polyamine crosslinking agent at a temperature 10° C. or higher than the melting point to prepare a masterbatch has been reported. (Patent Document 2)

[0014] As an aromatic polyamine crosslinking agent, 2,2-bis[4-(4-aminophenoxy)phenyl]propane is used. However, in the embodiments, the proportion of the aromatic polyamine crosslinking agent is 30 to 50% by mass, and the effective ingredient is low, resulting in an increase in the amount of masterbatch used as a crosslinking agent. When added, a large amount of unnecessary ingredients such as adhesive rubber will be added. In addition, the transportation cost of the masterbatch will increase, etc., and many improvements are needed.

[0015] The object is to provide a method for improving the above-mentioned problems.

[0016] Solutions for solving problems

[0017] The present inventors have conducted various studies to achieve the above-mentioned object, and as a result, have found that the above-mentioned problems can be solved by preparing a masterbatch in which an aromatic polyamine and a lubricant are dispersed in advance in a synthetic rubber.

[0018] The embodiments of the present invention are as follows.

[0019] Item 1 A crosslinking agent masterbatch, which comprises at least (A) synthetic rubber, (B) aromatic polyamine and (C) lubricant, wherein the crosslinking agent masterbatch contains 17% to 55% by mass of (A) synthetic rubber, 40% to 78% by mass of (B) aromatic polyamine and 0.1% to 10% by mass of (C) lubricant.

[0020] Item 2: The crosslinking agent masterbatch according to Item 1, wherein the synthetic rubber (A) is at least one selected from the group consisting of acrylic rubber, ethylene-acrylate rubber, nitrile rubber and hydrogenated nitrile rubber.

[0021] Item 3: The crosslinking agent masterbatch according to Item 1 or 2, wherein the (B) aromatic polyamine is an aromatic polyamine having no benzidine structure.

[0022] Item 4: The crosslinking agent masterbatch according to any one of Items 1 to 3, wherein the (B) aromatic polyamine is a compound represented by the following general formula (1) or the following general formula (2).

[0023]

[0024] (In formula (1), R 1 ~R 5 are optionally the same or different, are monovalent groups, and R 1 ~R 5At least one of them is an amino group, and R 1 ~R 5 Optionally, a ring structure is formed by bonding via a carbon atom, an oxygen atom and / or a sulfur atom.)

[0025]

[0026] (In formula (2), m is an integer of 2 to 4. Rx is a divalent to tetravalent group. 6 ~R 10 are optionally the same or different, are monovalent groups, and R 6 ~R 10 At least one of them is an amino group, and in each unit, the substituents at the same position may be the same or different, and R which is not an amino group 6 ~R 10 Optionally, a ring structure is formed by bonding via a carbon atom, an oxygen atom and / or a sulfur atom.)

[0027] Item 5: A rubber composition comprising at least the crosslinking agent masterbatch according to any one of Items 1 to 4 and a polyamine crosslinkable rubber.

[0028] Item 6. The rubber composition according to Item 5, comprising 0.5 to 9.0 parts by mass of the crosslinking agent masterbatch according to any one of Items 1 to 4, based on 100 parts by mass of the polyamine crosslinkable rubber.

[0029] Item 7 A rubber composition according to Item 5 or 6, wherein the polyamine cross-linkable rubber is at least one selected from the group consisting of acrylic rubber having a carboxyl group, ethylene-acrylate rubber having a carboxyl group, nitrile rubber having a carboxyl group and hydrogenated nitrile rubber having a carboxyl group.

[0030] Item 8: A cross-linked rubber product produced using the rubber composition according to any one of Items 5 to 7.

[0031] Effects of the Invention

[0032] The present invention is a crosslinking agent masterbatch containing at least a synthetic rubber, an aromatic polyamine, and a lubricant, which can improve the processability when preparing the crosslinking agent masterbatch and increase the concentration of the aromatic polyamine. In addition, when preparing a rubber composition, the dispersibility of the aromatic polyamine as a crosslinking agent is improved, and further, by using the crosslinking agent masterbatch, the working environment can be improved by reducing the scattering of the crosslinking agent. DETAILED DESCRIPTION

[0033] <Crosslinking Agent Masterbatch>

[0034] The crosslinking agent masterbatch (hereinafter sometimes referred to as "masterbatch") of the present invention contains at least (A) a synthetic rubber, (B) an aromatic polyamine, and (C) a lubricant.

[0035] (A) Synthetic rubber

[0036] The synthetic rubber used in the crosslinking agent masterbatch of the present invention is not particularly limited, and examples thereof include acrylic rubber, ethylene-acrylate rubber, nitrile rubber, and hydrogenated nitrile rubber. They can be used alone or in combination of two or more. In addition, the synthetic rubber used in the crosslinking agent masterbatch and the polyamine crosslinkable rubber used in the rubber composition mixed with the crosslinking agent masterbatch may be the same or different, but in the present invention, the synthetic rubber used in the crosslinking agent masterbatch and the polyamine crosslinkable rubber are preferably substances of the same classification. Here, in this specification, substances of the same classification refer to that when the synthetic rubber used in the crosslinking agent masterbatch is acrylic rubber, the polyamine crosslinkable rubber is acrylic rubber, and the structural units of the two acrylic rubbers may also be different.

[0037] The synthetic rubber used in the crosslinking agent masterbatch of the present invention mainly functions as a component that improves the dispersibility of the (B) aromatic polyamine contained in the crosslinking agent masterbatch in the rubber composition. Therefore, the synthetic rubber used in the crosslinking agent masterbatch may have a structural unit derived from an unsaturated monomer having a crosslinking group, or may not have a structural unit derived from an unsaturated monomer having a crosslinking group.

[0038] The acrylic rubber used in the crosslinking agent masterbatch of the present invention is preferably a polymer containing 50% by mass or more of a structural unit derived from a (meth)acrylate as a main component. Examples of the acrylic rubber used in the masterbatch of the present invention include polymers containing 50% by mass to 100% by mass of a structural unit derived from a (meth)acrylate and 0% by mass to 20% by mass of a structural unit derived from an unsaturated monomer having a crosslinking group. It should be noted that "(meth)acrylate" means "acrylate or methacrylate", and similar expressions are also used in the present application.

[0039] Examples of the structural unit derived from (meth)acrylate include structural units derived from alkyl (meth)acrylate and structural units derived from alkoxyalkyl (meth)acrylate. The structural unit derived from alkyl (meth)acrylate is preferably a structural unit derived from an alkyl acrylate having an alkyl group with 1 to 8 carbon atoms, more preferably a structural unit derived from an alkyl acrylate having an alkyl group with 2 to 6 carbon atoms, and further preferably a structural unit derived from an alkyl acrylate having an alkyl group with 2 to 4 carbon atoms. In addition, the structural unit derived from an alkoxyalkyl (meth)acrylate is preferably a structural unit derived from an alkoxyalkyl acrylate having an alkoxyalkyl group with 2 to 8 carbon atoms, more preferably a structural unit derived from an alkoxyalkyl acrylate having an alkoxyalkyl group with 2 to 6 carbon atoms, and further preferably a structural unit derived from an alkoxyalkyl acrylate having an alkoxyalkyl group with 2 to 4 carbon atoms. The structural unit derived from (meth)acrylate may be a structural unit derived from one or more types of (meth)acrylate.

[0040] Specific examples of the alkyl (meth)acrylate include (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and cyclohexyl (meth)acrylate, and ethyl (meth)acrylate and n-butyl (meth)acrylate are preferred.

[0041] Specific examples of the alkoxyalkyl (meth)acrylate include (meth)acrylates such as methoxymethyl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxymethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-propoxyethyl (meth)acrylate, 2-butoxyethyl (meth)acrylate, 2-methoxypropyl (meth)acrylate, 2-ethoxypropyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, 3-ethoxypropyl (meth)acrylate, 4-methoxybutyl (meth)acrylate, and 4-ethoxybutyl (meth)acrylate, and 2-methoxyethyl (meth)acrylate is preferred.

[0042] The content of the structural unit derived from (meth)acrylate of the acrylic rubber used in the crosslinking agent masterbatch of the present invention relative to the total structural units is preferably 50% to 100% by mass, more preferably 50% to 99.9% by mass, further preferably 60% to 99.9% by mass, particularly preferably 70% to 99.9% by mass, further preferably 80% to 99.9% by mass. If the content of (meth)acrylate is too low, oil resistance and heat resistance may be reduced.

[0043] The acrylic rubber used in the crosslinking agent masterbatch of the present invention may contain a structural unit derived from an unsaturated monomer having a crosslinking group. Examples of the structural unit derived from an unsaturated monomer having a crosslinking group include a structural unit derived from an unsaturated monomer having a halogen group (e.g., a chlorine group, etc.), a structural unit derived from an unsaturated monomer having an epoxy group, a structural unit derived from an unsaturated monomer having a carboxyl group, and a structural unit derived from an unsaturated monomer of a conjugated diene monomer or a non-conjugated diene monomer. It is preferred that the structural unit derived from an unsaturated monomer having a carboxyl group be contained or that the structural unit derived from an unsaturated monomer having a crosslinking group be not contained.

[0044] Examples of the unsaturated monomer having a halogen group include vinyl monochloroacetate and allyl chloroacetate, and vinyl monochloroacetate is preferred.

[0045] Examples of the unsaturated monomer having an epoxy group include glycidyl (meth)acrylate and (meth)allyl glycidyl ether.

[0046] Examples of the unsaturated monomer having a carboxyl group include unsaturated monocarboxylic acids such as (meth)acrylic acid, crotonic acid, 2-pentenoic acid, and cinnamic acid; unsaturated dicarboxylic acids such as fumaric acid, maleic acid, and itaconic acid; carboxylic anhydrides such as maleic anhydride and citraconic anhydride; single-chain alkyl esters of butenedioic acid such as monomethyl fumarate, monoethyl fumarate, monon-butyl fumarate, monomethyl maleate, monoethyl maleate, mono-2-ethylhexyl maleate, and monon-butyl maleate; monocyclic alkyl esters of butenedioic acid such as monocyclopentyl fumarate, monocyclohexyl fumarate, monocyclopentyl maleate, and monocyclohexyl maleate; monoitaconic acid monoesters such as monomethyl itaconate, monoethyl itaconate, monon-butyl itaconate, and monocyclohexyl itaconate; and the like. Among them, unsaturated dicarboxylic acid monoesters such as monoethyl fumarate, monopropyl fumarate, monobutyl fumarate, monoethyl itaconate, monopropyl itaconate, and monobutyl itaconate are preferred.

[0047] Examples of the conjugated diene monomer include 1,3-butadiene, 2-methyl-1,3-butadiene, 2-chloro-1,3-butadiene, 1,2-dichloro-1,3-butadiene, 2,3-dichloro-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-neopentyl-1,3-butadiene, 2-bromo-1,3-butadiene, 2-cyano-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, chloroprene, piperylene, etc. These monomers may be used alone or in combination of two or more.

[0048] Examples of the non-conjugated diene monomer include 1,4-pentadiene, 1,4-hexadiene, ethylidene norbornene, norbornadiene, and dicyclopentadiene.

[0049] These unsaturated monomers having a crosslinking group may be used alone or in combination of two or more.

[0050] The content of structural units derived from unsaturated monomers having crosslinking groups in the acrylic rubber used in the crosslinking agent masterbatch is preferably 0 to 20% by mass, more preferably 0 to 15% by mass, particularly preferably 0.1 to 10% by mass, based on all structural units.

[0051] The ethylene-acrylate rubber used in the crosslinking agent masterbatch of the present invention may be a polymer containing as main components 50 to 99.9% by mass of structural units derived from (meth)acrylate, 0.1 to 50% by mass of structural units derived from ethylene, and 0 to 20% by mass of structural units derived from an unsaturated monomer having a crosslinking group.

[0052] The structural unit derived from a (meth)acrylic acid ester is not particularly limited, and examples thereof include the above-mentioned alkyl (meth)acrylate monomers and alkoxyalkyl (meth)acrylate monomers.

[0053] The content of the structural unit derived from (meth) acrylate of the ethylene-acrylate rubber used in the crosslinking agent masterbatch of the present invention relative to the total structural units is preferably 50% to 99.9% by mass, more preferably 60% to 99.5% by mass, further preferably 70% to 99% by mass, and particularly preferably 80% to 99% by mass. In addition, the content of the structural unit derived from ethylene is preferably 0.1% to 50% by mass, more preferably 0.5% to 40% by mass, further preferably 1% to 30% by mass, and particularly preferably 1% to 20% by mass.

[0054] In addition to the structural units from (meth) acrylate and the structural units from ethylene, the ethylene-acrylate rubber used in the crosslinking agent masterbatch of the present invention may also contain structural units from unsaturated monomers having crosslinking groups. It should be noted that as structural units from unsaturated monomers having crosslinking groups, the above-mentioned structural units can be cited. The content of structural units from unsaturated monomers having crosslinking groups in all structural units of ethylene-acrylate rubber is preferably 0% to 20% by mass, more preferably 0.1% to 15% by mass, and further preferably 0.1% to 10% by mass. If the content of crosslinkable monomer units is too much, the elongation of the obtained rubber crosslinked product may be reduced.

[0055] The nitrile rubber used in the crosslinking agent masterbatch of the present invention can be exemplified by a polymer containing as main components 10% to 70% by mass of a structural unit derived from an ethylenically unsaturated nitrile, 30% to 90% by mass of a structural unit derived from a conjugated diene, and 0% to 20% by mass of a structural unit derived from an unsaturated monomer having a crosslinking group.

[0056] The nitrile rubber used in the crosslinking agent masterbatch of the present invention contains a structural unit from an ethylenically unsaturated nitrile and a structural unit from a conjugated diene. As ethylenically unsaturated nitrile monomers, for example, acrylonitrile, methacrylonitrile, α-methoxyacrylonitrile, dicyanoethylene (vinylidene cyanide) etc. can be cited. As conjugated diene monomers, for example, 1,3-butadiene, 2-methyl-1,3-butadiene, 2-chloro-1,3-butadiene, 1,2-dichloro-1,3-butadiene, 2,3-dichloro-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-neopentyl-1,3-butadiene, 2-bromo-1,3-butadiene, 2-cyano-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, chloroprene, piperylene etc. can be cited. They can be used alone or in combination of two or more.

[0057] The structural unit derived from the ethylenically unsaturated nitrile is preferably 10% to 70% by mass, more preferably 15% to 60% by mass, and further preferably 20% to 50% by mass. In addition, the structural unit derived from the conjugated diene is preferably 30% to 90% by mass, more preferably 40% to 85% by mass, and further preferably 50% to 80% by mass.

[0058] In addition to the structural units from ethylenically unsaturated nitrile and the structural units from conjugated diene, the nitrile rubber used in the crosslinking agent masterbatch of the present invention may also include structural units from unsaturated monomers with crosslinking groups. It should be noted that as structural units from unsaturated monomers with crosslinking groups, the above structural units can be cited. The content of structural units from unsaturated monomers with crosslinking groups in all structural units of nitrile rubber is preferably 0% to 20% by mass, more preferably 0% to 15% by mass, and further preferably 0% to 10% by mass. If the content of crosslinkable monomer units is too much, the elongation of the obtained rubber crosslinked product may be reduced.

[0059] The hydrogenated nitrile rubber used in the crosslinking agent masterbatch of the present invention is obtained by hydrogenating a part or all of the carbon-carbon unsaturated bonds in the nitrile rubber composed of the structural units derived from the ethylenically unsaturated nitrile and the structural units derived from the conjugated diene.

[0060] Furthermore, the synthetic rubber used in the cross-linking agent masterbatch may contain a structural unit derived from a copolymerizable monomer other than the above-mentioned monomers, unless it deviates from the gist of the present invention.

[0061] Regarding acrylic rubber and ethylene-acrylate rubber, for example, ethylenically unsaturated nitrile monomers, (meth)acrylamide monomers, aromatic vinyl monomers, conjugated diene monomers, non-conjugated diene monomers, carboxylic acid vinyl ester monomers, other olefin monomers, etc. These can be used alone or in combination of two or more.

[0062] Examples of nitrile rubber and hydrogenated nitrile rubber include (meth)acrylate monomers, (meth)acrylamide monomers, aromatic vinyl monomers, carboxylic acid vinyl ester monomers, and other olefin monomers, etc. These monomers may be used alone or in combination of two or more.

[0063] Examples of the ethylenically unsaturated nitrile monomer include acrylonitrile, methacrylonitrile, α-methoxyacrylonitrile, and dicyanoethylene. These monomers may be used alone or in combination of two or more.

[0064] As for the (meth)acrylate monomer, for example, specific examples of the (meth)acrylate alkyl ester include (meth)acrylate methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate and the like. Specific examples of the (meth)acrylate alkyl ester include (meth)acrylate methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate and the like. (Meth)acrylates such as methoxymethyl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxymethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-propoxyethyl (meth)acrylate, 2-butoxyethyl (meth)acrylate, 2-methoxypropyl (meth)acrylate, 2-ethoxypropyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, 3-ethoxypropyl (meth)acrylate, 4-methoxybutyl (meth)acrylate, and 4-ethoxybutyl (meth)acrylate can be used alone or in combination of two or more.

[0065] Examples of the (meth)acrylamide monomers include acrylamide, methacrylamide, diacetone acrylamide, diacetone methacrylamide, N-butoxymethyl acrylamide, N-butoxymethyl methacrylamide, N-butoxyethyl acrylamide, N-butoxyethyl methacrylamide, N-methoxymethyl acrylamide, N-methoxymethyl methacrylamide, N-propoxymethyl acrylamide, N-propoxymethyl methacrylamide, N-methyl acrylamide, N-methyl methacrylamide, N,N-dimethyl acrylamide, N,N-dimethyl methacrylamide, N,N-diethyl acrylamide, N,N-diethyl methacrylamide, N-hydroxymethyl acrylamide, N-hydroxymethyl methacrylamide, ethyl acrylamide, crotonamide, cinnamamide, maleic acid diamide, itaconic acid diamide, methyl maleamide, methyl itaconamide, maleimide, itaconimide, etc. These monomers may be used alone or in combination of two or more thereof.

[0066] Examples of the aromatic vinyl monomer include styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, o-ethylstyrene, p-ethylstyrene, α-fluorostyrene, p-trifluoromethylstyrene, p-methoxystyrene, p-aminostyrene, p-dimethylaminostyrene, p-acetoxystyrene, styrenesulfonic acid or its salts, α-vinylnaphthalene, 1-vinylnaphthalene-4-sulfonic acid or its salts, 2-vinylfluorene, 2-vinylpyridine, 4-vinylpyridine, divinylbenzene, diisopropenylbenzene, vinylbenzyl chloride, etc. These monomers may be used alone or in combination of two or more thereof.

[0067] Examples of the carboxylic acid vinyl ester monomer include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl crotonate, vinyl cinnamate, vinyl pivalate, etc. These may be used alone or in combination of two or more.

[0068] As other olefin monomers, for example, esters such as dicyclopentadienyl acrylate, dicyclopentadienyl methacrylate, dicyclopentadienyl ethyl acrylate, and dicyclopentadienyl ethyl methacrylate, ethylene (which is an essential component in the case of ethylene-acrylate rubber, so it is excluded), propylene, vinyl chloride, vinylidene chloride, 1,2-dichloroethylene, vinyl fluoride, vinylidene fluoride, 1,2-difluoroethylene, vinyl bromide, vinylidene bromide, 1,2-dibromoethylene, ethyl vinyl ether, butyl vinyl ether, etc. These can be used alone or in combination of two or more.

[0069] The content of the structural units derived from other copolymerizable monomers in the synthetic rubber used in the crosslinking agent masterbatch is 30% by mass or less, preferably 20% by mass or less, and more preferably 10% by mass or less, based on the total structural units.

[0070] The content of the synthetic rubber in the crosslinking agent masterbatch of the present invention is preferably 17% to 55% by mass, more preferably 20% to 50% by mass, further preferably 20% to 45% by mass, and particularly preferably 20% to 40% by mass in 100% by mass of the crosslinking agent masterbatch. Within the above range, the mechanical strength of the obtained rubber cross-linked product tends to be better, and the preparation of the masterbatch itself tends to be easier.

[0071] (B) Aromatic polyamines

[0072] The aromatic polyamine used in the crosslinking agent masterbatch of the present invention can be used without restriction as long as it can be crosslinked with synthetic rubber and polyamine crosslinkable rubber. They can be used alone or in combination of two or more. Preferably, it is a substance other than an aromatic polyamine having a benzidine structure that is classified as a Class 1 specific chemical substance in the Specific Chemical Substance Obstacle Prevention Rules (i.e., an aromatic polyamine that does not have a benzidine structure), more preferably an aromatic polyamine having a substituent represented by the following general formula (1) or the following general formula (2), and further preferably an aromatic polyamine having a substituent represented by the following general formula (2).

[0073]

[0074] (In formula (1), R 1 ~R 5 are optionally the same or different, are monovalent groups, and R 1 ~R 5 At least one of them is an amino group, and R1 ~R 5 Optionally, a ring structure is formed by bonding via a carbon atom, an oxygen atom and / or a sulfur atom.)

[0075]

[0076] (In formula (2), m is an integer of 2 to 4. Rx is a divalent to tetravalent group. 6 ~R 10 are optionally the same or different, are monovalent groups, and R 6 ~R 10 At least one of them is an amino group, and in each unit, the substituents at the same position may be the same or different, and R which is not an amino group 6 ~R 10 Optionally, a ring structure is formed by bonding via a carbon atom, an oxygen atom and / or a sulfur atom.)

[0077] R 1 ~R 5 are optionally the same or different, are monovalent groups, and R 1 ~R 5 At least one of R is an amino group. 1 ~R 5 One of them is preferably an amino group. 1 ~R 5 , as long as it is a univalent group, there is no particular limitation, and for example, it can be an atom (carbon, oxygen, hydrogen, sulfur, etc.) or an atomic group composed of a plurality of atoms (carbon, oxygen, hydrogen, sulfur, etc.). 1 ~R 5 , hydrogen, alkyl, halogen, halogenated alkyl, hydroxy, carboxyl, sulfone, etc. can be mentioned. Among them, hydrogen and alkyl are preferred, and hydrogen is more preferred. 1 ~R 5 , preferably R 1 ~R 5 One of them is an amino group, and the rest are all hydrogen.

[0078] R not amino 1 ~R 5 A cyclic structure bonded via a carbon atom, an oxygen atom and / or a sulfur atom may be formed.

[0079] m is an integer of 2 to 4. m is preferably an integer of 2 to 3, more preferably 2.

[0080] Rx is not particularly limited as long as it is a 2- to 4-valent group. As Rx, nitrogen, oxygen, a straight-chain alkyl group or a branched alkyl group having 1 to 6 carbon atoms, an aromatic group, a benzene glycol group, a phenylene diisopropylidene group, an isopropylidene diphenylene group, a biphenyl diphenol group, a bisphenol group, a sulfone group, a carbonyl group, and an anilino group are preferred. Here, for example, an alkyl group is a univalent group, but the alkyl group described in this paragraph is also referred to as a 2- to 4-valent group corresponding to the alkyl group. The same applies to other groups.

[0081] As Rx, a divalent group is more preferred, and oxygen (ether group), benzene glycol group (group represented by the following formula (A-1)), phenylene diisopropylidene group, isopropylidene diphenylene group (group represented by the following formula (A-2)), biphenylene diphenol group (group represented by the following formula (A-3)) are further preferred. Oxygen (ether group), benzene glycol group (group represented by the following formula (A-1)), isopropylidene diphenylene group (group represented by the following formula (A-2)), biphenylene diphenol group (group represented by the following formula (A-3)) are particularly preferred. Oxygen (ether group), group represented by the following formula (B-1), group represented by the following formula (B-2), group represented by the following formula (B-3) are most preferred. It should be noted that in the O- in the formula, the structural unit represented by [] in the formula (2) is bonded.

[0082]

[0083]

[0084] R 6 ~R 10 are optionally the same or different, are monovalent groups, and R 6 ~R 10 Preferably, at least one of R 6 ~R 10 One of them is an amino group, and more preferably R 7 or R 8 is amino, and more preferably R 8 As R which is not an amino group 6 ~R 10 , as long as it is a univalent group, there is no particular limitation, and for example, it can be an atom (carbon, oxygen, hydrogen, sulfur, etc.) or an atomic group composed of a plurality of atoms (carbon, oxygen, hydrogen, sulfur, etc.). 6 ~R 10 , hydrogen, alkyl, halogen, halogenated alkyl, hydroxy, carboxyl, sulfone, etc. can be mentioned. Among them, hydrogen and alkyl are preferred, and hydrogen is more preferred. 6 ~R 10 , preferably R 6 ~R 10 One of them is an amino group, and the rest are all hydrogen.

[0085] In each unit, the substituents at the same position may be the same or different. Here, the substituents at the same position refer to the R 6 and R in other units 6 It should be noted that in the present specification, the unit refers to the structural unit represented by [ ] in formula (2).

[0086] R not amino 6 ~R 10 A cyclic structure bonded via a carbon atom, an oxygen atom and / or a sulfur atom may be formed.

[0087] Examples of the aromatic polyamine corresponding to the general formula (1) include o-phenylenediamine, p-phenylenediamine, m-phenylenediamine, 2,6-diamino-3,5-diethyltoluene and 1,3,5-phenyltriamine.

[0088] Examples of the aromatic polyamine corresponding to the general formula (2) include aromatic diamines such as 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 4,4'-methylenedianiline, 4,4'-ethylenedianiline, 1,3-bis(4-aminophenoxy)propane, 1,4-bis(4-aminophenoxy)butane, 1,5-bis(4-aminophenoxy)pentane, 1,6-bis(4-aminophenoxy)pentane, phenoxy)hexane, 3,3'-dichloro-4,4'-diaminodiphenylmethane, 4,4'-diamino-3,3'-dimethyldiphenylmethane, 4,4'-diamino-3,3'-diethyl-5,5'-dimethyldiphenylmethane, 5,5'-methylenebis(2-aminobenzoic acid), 4,4'-methylenebis(o-chloroaniline), 2,2'-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, bis(3-amino-4-hydroxyphenyl) sulfone, 3,7-diamino-2,8-dimethyldibenzothiophene sulfone, 1,3-bis(3-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)biphenyl, 4,4'-(p-phenylene diisopropyl)benzene Examples of the aromatic triamines include tris(4-aminophenyl)amine, 1,3,5-tris(4-aminophenyl)benzene, 4,4',4"-(m-phenylene diisopropylidene)diphenylamine, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, bis[4-(3-aminophenoxy)phenyl]sulfone, bis[4-(4-aminophenoxy)phenyl]sulfone, 4,4'-diaminobenzanilide, and 4-aminophenyl-4-aminobenzoate. Examples of the aromatic triamines include tris(4-aminophenyl)amine, 1,3,5-tris(4-aminophenyl)benzene, 4,4',4"-(methanetriyl)triphenylamine, and 2,4,6-tris(4-aminophenyl)-1,3,5-triazine. Examples of the aromatic tetraamines include tetrakis(4-aminophenyl)methane.

[0089] Among them, more preferred are aromatic polyamines having a substituent (preferably an ether group) different from the amino group at the para-position or meta-position (preferably the para-position) from the amino group undergoing the crosslinking reaction, for example, p-phenylenediamine, m-phenylenediamine, 4,4'-methylenedianiline, 1,3-bis(4-aminophenoxy)propane, 1,4-bis(4-aminophenoxy)butane, 1,5-bis(4-aminophenoxy)pentane, 1,6-bis(4-aminophenoxy)hexane, 4,4'-ethylenedianiline, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, 1,3 -bis(3-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 4,4'-(p-phenylene diisopropylidene)diphenylamine, 4,4'-(m-phenylene diisopropylidene)diphenylamine, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, bis[4-(3-aminophenoxy)phenyl]sulfone, bis[4-(4-aminophenoxy)phenyl]sulfone, 4,4'-bis(4-aminophenoxy)biphenyl, 4,4'-diaminobenzanilide, 4-aminophenyl-4-aminobenzoate. These may be used alone or in combination of two or more. Among them, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 1,3-bis(4-aminophenoxy)benzene, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, and 4,4'-bis(4-aminophenoxy)biphenyl are preferred. When there is a substituent other than a hydrogen atom at the ortho position relative to the amino group undergoing the crosslinking reaction, the crosslinking reaction does not proceed sufficiently due to steric hindrance, and the physical properties of the obtained crosslinked product may be impaired.

[0090] The melting point of the aromatic polyamine is preferably 50° C. or higher, more preferably 70° C. or higher, and further preferably 110° C. or higher as the lower limit. On the other hand, it is preferably 220° C. or lower, more preferably 150° C. or lower, and most preferably 135° C. or lower as the upper limit. As described above, when such an aromatic polyamine having a relatively high melting point is added in a B-roll or kneaded only in an open roll, there is a concern that the dispersibility is low. However, even when an aromatic polyamine having a relatively high melting point is used as the crosslinking agent masterbatch of the present invention, the dispersibility can be greatly improved.

[0091] In this specification, the melting point of the aromatic polyamine is measured in accordance with JIS K0064:1992.

[0092] The content of the aromatic polyamine in the crosslinking agent masterbatch of the present invention is preferably 40 to 78 mass %, more preferably 43 to 75 mass %, further preferably 45 to 75 mass %, particularly preferably 47 to 75 mass %, based on 100 mass % of the crosslinking agent masterbatch.

[0093] If the content of the aromatic polyamine in the masterbatch is too low, it is not preferred because a large amount of unnecessary components such as synthetic rubber as a binder polymer and additives described below will be added when the masterbatch is added as a crosslinking agent.

[0094] On the other hand, when the content ratio of the aromatic polyamine in the masterbatch is too high, there is a concern that the obtained masterbatch will become a hard masterbatch without rubber elasticity, and when used as a cross-linking agent masterbatch, the masterbatch itself is not fully dispersed in the rubber composition and becomes an aggregate, which may cause poor dispersion.

[0095] (C) Lubricant

[0096] As the lubricant used in the crosslinking agent masterbatch of the present invention, the lubricant commonly used in rubber processing can be used. They can be used alone or in combination of two or more. Usually, lubricant refers to a processing aid for improving the workability during processing such as adhesion or demoulding properties during mixing and / or molding of the rubber composition, but in the present invention, the embodiments show that it helps to improve the dispersibility of synthetic rubber and aromatic polyamines, and then helps to improve the concentration of aromatic polyamines.

[0097] Examples of lubricants include: fatty acid lubricants having 10 to 30 carbon atoms, such as stearic acid; higher alcohol lubricants having 10 to 30 carbon atoms; fatty acid ester lubricants, such as polyol fatty acid esters and higher fatty acid alkyl esters having 10 to 30 carbon atoms; metal soap lubricants, such as magnesium stearate, calcium stearate, and zinc stearate; aliphatic amine lubricants having 10 to 30 carbon atoms, such as octylamine, dodecylamine, and stearylamine; and carbonyl amine lubricants, such as stearamide, oleamide, erucamide, and ethylenebisstearamide. Fatty acid amide lubricants having 10 to 30 atoms; polyalkylene glycol lubricants such as polyoxyethylene glycol, polyoxyethylene glycol alkyl ether, polypropylene glycol, polypropylene glycol alkyl ether, polytetramethylene glycol, polytetramethylene glycol alkyl ether; hydrocarbon lubricants such as liquid paraffin, paraffin, synthetic polyethylene wax; phosphate lubricants such as polyoxyethylene lauryl ether phosphate, polyoxyethylene stearyl ether phosphate, polyoxyethylene oleyl ether phosphate, polyoxyethylene tridecyl ether phosphate, etc. Preferred are fatty acid lubricants, fatty acid ester lubricants, aliphatic amine lubricants, fatty acid amide lubricants, hydrocarbon lubricants, and phosphate ester lubricants. One or more of these lubricants may be used.

[0098] In the present specification, fatty acid-based lubricants refer to lubricants with fatty acids as the main component, higher alcohol-based lubricants refer to lubricants with higher alcohols as the main component, fatty acid ester-based lubricants refer to lubricants with fatty acid esters as the main component, metal soap-based lubricants refer to lubricants with fatty acid metal salts as the main component, aliphatic amine-based lubricants refer to lubricants with aliphatic amines as the main component, fatty acid amide-based lubricants refer to lubricants with fatty acid amides as the main component, polyalkylene glycol-based lubricants refer to lubricants with polyalkylene glycols as the main component, hydrocarbon-based lubricants refer to lubricants with hydrocarbons as the main component, and phosphate-based lubricants refer to lubricants with phosphate esters as the main component.

[0099] In addition, in this specification, a main component refers to a component whose content exceeds 50 mass % (preferably 80 mass % or more) in 100 mass % of the lubricant.

[0100] The content of the lubricant in the cross-linking agent masterbatch of the present invention is 0.1 to 10% by mass, preferably 0.3 to 9% by mass, and more preferably 0.5 to 8% by mass in 100% by mass of the cross-linking agent masterbatch.

[0101] In addition to (A) synthetic rubber, (B) aromatic polyamine and (C) lubricant, the crosslinking agent masterbatch of the present invention may further contain additives as required. Examples of additives include anti-aging agents, light stabilizers, fillers, reinforcing agents, plasticizers, pigments, colorants, crosslinking delay agents, crosslinking aids, antistatic agents, foaming agents, antiscorch agents, release agents, etc. These may be used alone or in combination of two or more.

[0102] The total content of (A) synthetic rubber, (B) aromatic polyamine and (C) lubricant in the crosslinking agent masterbatch of the present invention is preferably 80 mass% or more, more preferably 85 mass% or more, further preferably 88 mass% or more, particularly preferably 92 mass% or more, most preferably 95 mass% or more, in 100 mass% of the crosslinking agent masterbatch. It may also be 100 mass%.

[0103] As a kneading method for obtaining the crosslinking agent masterbatch of the present invention, any means conventionally used in the field of rubber processing can be used. The kneading device can be a batch type such as an open roll mill, a Banbury mixer, various kneading machines, or a continuous type such as a single screw extruder, a twin screw extruder, a feeder ruder, etc.

[0104] The crosslinking agent masterbatch of the present invention has no concern about powder scattering and the aromatic polyamine in the masterbatch has good dispersibility, so it can be used at any stage of the process of producing the rubber composition starting from kneading. In addition, the kneading temperature can be used without particular limitation as long as it is a temperature that allows kneading.

[0105] <Rubber Composition>

[0106] The rubber composition of the present invention is a composition comprising at least the cross-linking agent masterbatch of the present invention and a polyamine-cross-linkable rubber.

[0107] (Polyamine cross-linked rubber)

[0108] The polyamine crosslinkable rubber used in the rubber composition of the present invention is not particularly limited, as long as it can be crosslinked using aromatic polyamines. It is preferably a rubber containing a structural unit from an unsaturated monomer having a carboxyl group on the crosslinking group, more preferably an acrylic (type) rubber having a carboxyl group, an ethylene-acrylate rubber having a carboxyl group, a nitrile rubber having a carboxyl group, and a hydrogenated nitrile rubber having a carboxyl group, and further preferably an acrylic (type) rubber having a carboxyl group, an ethylene-acrylate rubber having a carboxyl group, and a hydrogenated nitrile rubber having a carboxyl group. One or more of these can be used.

[0109] In addition, the polyamine crosslinkable rubber used in the rubber composition of the present invention and the synthetic rubber used in the crosslinking agent masterbatch may be different. However, if the polyamine crosslinkable rubber and the synthetic rubber used in the crosslinking agent masterbatch are different, the synthetic rubber used in the crosslinking agent masterbatch is not originally added to the rubber composition, so it is preferred that the polyamine crosslinkable rubber and the synthetic rubber used in the crosslinking agent masterbatch are of the same classification. For example, when the polyamine crosslinkable rubber is an acrylic rubber, the synthetic rubber used in the crosslinking agent masterbatch is preferably an acrylic rubber.

[0110] In the rubber composition of the present invention, the content of the crosslinking agent masterbatch of the present invention is preferably 0.5 to 9.0 parts by mass, more preferably 1.0 to 7.0 parts by mass, and even more preferably 1.0 to 5.0 parts by mass, relative to 100 parts by mass of the polyamine crosslinkable rubber. If the content is too small, the crosslinking density of the obtained crosslinked product is reduced, and the expected mechanical strength cannot be obtained. On the other hand, if the content is too large, excessive crosslinking occurs, and it is considered that the obtained crosslinked product becomes too hard.

[0111] Additives may be added to the rubber composition of the present invention as required. Examples of additives include crosslinking agents, lubricants, anti-aging agents, light stabilizers, fillers, reinforcing agents, plasticizers, pigments, colorants, crosslinking delay agents, crosslinking aids, antistatic agents, foaming agents, scorch retarders, and mold release agents. These may be used alone or in combination of two or more.

[0112] <Rubber cross-linked product>

[0113] The cross-linked rubber of the present invention can be obtained by cross-linking the above-mentioned rubber composition.

[0114] The cross-linked rubber of the present invention can be made into a cross-linked rubber by heating the rubber composition to 100°C to 250°C. The cross-linking time varies depending on the temperature, but is usually carried out between 0.5 minutes and 300 minutes. The cross-linking molding can be any of the following: cross-linking and molding are performed integrally, the rubber composition that has been molded is reheated to form a cross-linked rubber, and the cross-linked rubber is first heated and then processed for molding. As a specific method of cross-linking molding, any method such as compression molding using a mold, injection molding, heating using a steam tank, an air bath, infrared rays or microwaves can be used.

[0115] The rubber composition of the present invention obtained in this way is excellent in dispersibility of the cross-linking agent, and the cross-linked rubber of the present invention is excellent in quality.

[0116] Example

[0117] The present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

[0118] (Raw materials used)

[0119] (A) Synthetic rubber

[0120] Acrylic rubber (cross-linking group: carboxyl, manufactured by Osaka Soda Co., Ltd.)

[0121] Ethylene-acrylate rubber (crosslinking group: carboxyl, manufactured by Celanese Corporation)

[0122] Nitrile rubber (nitrile rubber without crosslinking groups, manufactured by Arlanxeo)

[0123] Hydrogenated nitrile rubber (hydrogenated nitrile rubber without crosslinking groups, manufactured by Zeon Co., Ltd., Japan)

[0124] (B) Aromatic polyamines

[0125] 2,2-Bis[4-(4-aminophenoxy)phenyl]propane (trade name BAPP, manufactured by SEIKA Corporation, melting point 128°C)

[0126] 1,3-Bis(4-aminophenoxy)benzene (trade name TPE-R, manufactured by SEIKA Corporation, melting point 116°C)

[0127] 4,4'-Diaminodiphenyl ether (trade name DPE, manufactured by SEIKA Corporation, melting point 191°C)

[0128] 3,4'-Diaminodiphenyl ether (trade name 3,4'-DPE, manufactured by SEIKA Corporation, melting point 74°C)

[0129] 4,4'-Bis(4-aminophenoxy)biphenyl (trade name 4-APBP, manufactured by Japan Junryo Pharmaceutical Co., Ltd., melting point 199°C)

[0130] (C) Lubricant

[0131] Stearic acid (fatty acid lubricant, trade name STEARIC ACID CHERRY, manufactured by NOF Corporation)

[0132] Paraffin wax (hydrocarbon lubricant, trade name paraffin wax 135, manufactured by Nippon Seiro Co., Ltd.)

[0133] Fatty acid ester wax (fatty acid ester lubricant, trade name: Gleck G8205, manufactured by NI Chemitech Co., Ltd.)

[0134] Polyol fatty acid ester (fatty acid ester lubricant, trade name Struktol WB222, manufactured by Schill + Seilacher)

[0135] Higher fatty acid ester (fatty acid ester lubricant, trade name Struktol WB212, manufactured by Schill+Seilacher)

[0136] Stearylamine (aliphatic amine lubricant, trade name: LIPOMIN 18D, manufactured by Lion Corporation)

[0137] Ethylene bisstearamide (fatty acid amide lubricant, trade name KAO wax EB-P, manufactured by Kao Corporation)

[0138] Polyoxyethylene alkyl phosphate (phosphate ester lubricant, trade name PHOSPHANOL RL-210, manufactured by Toho Chemical Industry Co., Ltd.)

[0139] Phosphate ester of modified fatty alcohol (phosphate ester lubricant, trade name: Ofalub SEO, manufactured by Safic Alcan Co., Ltd.)

[0140] (D) Others

[0141] Carbon black (trade name: SEAST SO, manufactured by Tokai Carbon Co., Ltd.)

[0142] Silica gel (trade name: Nipsil ER, manufactured by Tosoh Silicone Chemical Co., Ltd.)

[0143] Talc (trade name: hi-filler #5000PJ, manufactured by Matsumura Industry Co., Ltd.)

[0144] 4,4'-Bis(α,α-dimethylbenzyl)diphenylamine (trade name: Nocrac CD, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.)

[0145] 2-Mercaptobenzimidazole (trade name: Nocrac MB, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.)

[0146] Zinc salt of 2-mercaptobenzimidazole (trade name: Nocrac MBZ, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.)

[0147] Adipic acid ether ester plasticizer (trade name ADK CIZER RS107, manufactured by ADEKA Corporation) Polyether ester plasticizer (trade name ADK CIZER RS735, manufactured by ADEKA Corporation)

[0148] Tri-n-alkyl (C8, C10) trimellitate (trade name TRIMEX N-08, manufactured by Kao Corporation)

[0149] Iron (III) oxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.)

[0150] <Example 1: Production of Masterbatch A>

[0151] As shown in Table 1, 46 parts by mass of acrylic rubber, 50 parts by mass of BAPP, 2 parts by mass of stearic acid, and 2 parts by mass of carbon black were added to Labo Plastomill (manufactured by Toyo Seiki Seisaku-sho, Ltd., capacity 60 ml) in this order, and kneaded for 12 minutes at a temperature of 110° C. to 135° C. to obtain a master batch A. The following evaluations were performed on the master batch A, and the results are shown in Table 1.

[0152] (Dump)

[0153] The ease of taking out the masterbatch from the Labo Plastomill (unloading property) was evaluated by visually observing the viscosity of the masterbatch in the mixing tank. The unloading property of the masterbatch was evaluated according to the following criteria.

[0154] ○: There was no sticking of the masterbatch in the mixing tank, and the masterbatch could be taken out without any problem.

[0155] ×: The masterbatch became sticky in the mixing tank and was difficult to remove.

[0156] The master batch A was kneaded 10 times using an 8-inch roll to obtain a sheet of the master batch A. The sheet of the master batch A was evaluated as follows. The results are shown in Table 1.

[0157] (Roller processability)

[0158] The roll processability was evaluated when the master batch was kneaded 10 times using an 8-inch roll. The roll processability was evaluated based on the following criteria.

[0159] ○: 10 passes of kneading were possible without interfering with the roll kneading operation.

[0160] ×: The masterbatch sticks to the rollers, and the rollers must be stopped when taking it out, which hinders the mixing operation.

[0161] (Softness)

[0162] The flexibility of the sheet obtained by roll kneading was evaluated by bending the sheet 180 degrees and visually observing the surface state. The flexibility was evaluated according to the following criteria.

[0163] ○: No cracks or fissures were generated and the product was flexible.

[0164] ×: Cracking and cracking occurred, and the product lacked flexibility.

[0165] <Examples 2 to 14, Comparative Examples 1 to 2: Production of Masterbatches B to P>

[0166] Various compounding agents shown in Table 1 were added to obtain master batches. The kneading temperature and kneading time were carried out within the temperature range and time shown in Table 1. The master batches obtained as described above were evaluated, and the evaluation results are shown in Table 1.

[0167] [Table 1]

[0168]

[0169] Unit: mass % According to the above results, by adding a lubricant to Examples 1 to 3, the dispersibility of the crosslinking agent is improved, and the concentration of the crosslinking agent (aromatic polyamine) contained in the synthetic rubber can be increased. In addition, the obtained crosslinking agent masterbatch has sufficient softness. Furthermore, the same results are obtained even when the type of synthetic rubber, the type of aromatic polyamine or the type of lubricant is changed in Examples 4 to 14. On the other hand, in the case of Comparative Example 1 where a lubricant is not used, the workability for obtaining the masterbatch, such as unloading property and roller processability, is significantly reduced. In addition, in Comparative Example 2, when the content of the crosslinking agent (aromatic polyamine) is too much, the roller processability during the manufacture of the masterbatch is deteriorated, and the softness of the obtained masterbatch is significantly reduced, so it is not suitable as a masterbatch.

[0170] The present invention has found that the lubricant not only improves the processability during masterbatch production, but also helps to increase the concentration of the aromatic polyamine. Although the essence of the part cannot be analyzed, it is believed that the effect is obtained by improving the dispersibility of the aromatic polyamine by the lubricant.

[0171] Next, the masterbatch prepared above, powdered 2,2-bis[4-(4-aminophenoxy)phenyl]propane and polyamine crosslinkable rubber were kneaded to prepare a rubber composition, and the dispersibility of the crosslinking agent, and the smoothness and hardness of the vulcanized sheet when the rubber crosslinked product was prepared were evaluated.

[0172] <Example 15>

[0173] As shown in Table 2, 100 parts by mass of acrylic rubber (crosslinking group: carboxyl, manufactured by Osaka Soda Co., Ltd.) as a polyamine crosslinkable rubber, 60 parts by mass of carbon black, 2 parts by mass of stearic acid, and 2 parts by mass of an antioxidant were mixed, and A-milling was performed for 7 minutes in a temperature range of 100 to 140° C. using a 0.5L kneader to obtain an A-milled mixture. To the obtained A-milled mixture, 2 parts by mass of the master batch B prepared in Example 2 (2,2-bis[4-(4-aminophenoxy)phenyl]propane content 1.2 parts by mass) and 2 parts by mass of an accelerator (RHENOGRAN XLA60, manufactured by LANXESS) were added, and B-milling was performed using an 8-inch roll to obtain an uncrosslinked sheet of the rubber composition. The dispersibility of the crosslinking agent was evaluated using the obtained uncrosslinked sheet as follows, and the results are shown in Table 2.

[0174] (Dispersibility of cross-linking agent)

[0175] The surface of the uncrosslinked sheet of the rubber composition obtained above and the cross section cut with scissors perpendicular to the separation direction of the uncrosslinked sheet were visually observed to evaluate the dispersion state of the crosslinking agent. The evaluation was performed based on the following criteria.

[0176] ○: The dispersion state of the crosslinking agent in the uncrosslinked sheet is good, and no aggregates are observed on the sheet surface and cross section.

[0177] ×: The dispersion state of the cross-linking agent in the uncross-linked sheet is poor, and white aggregates are observed on the sheet surface and cross section.

[0178] In addition, the uncrosslinked sheet of the rubber composition obtained above was press-treated at 180°C for 10 minutes to obtain a primary crosslinked product of 15 cm in length × 15 cm in width × 2 mm in height. This was then heated in an air oven at 180°C for 3 hours to obtain a secondary crosslinked product (rubber crosslinked product). The smoothness and hardness of the obtained rubber crosslinked product were evaluated as follows, and the results are shown in Table 2.

[0179] (Smoothness)

[0180] The surface of the rubber cross-linked product obtained above was visually observed and evaluated. The smoothness was evaluated based on the following criteria.

[0181] ○: The surface of the cross-linked rubber has no irregularities or almost no irregularities are observed, and the surface condition is good.

[0182] ×: The cross-linked rubber has many surface irregularities and a poor surface condition.

[0183] (hardness)

[0184] Using the obtained cross-linked rubber, measurement was performed at 11 arbitrary locations, and the maximum value, minimum value, difference therebetween, and standard deviation were calculated. The hardness test was performed according to the method described in JIS K6253:2012.

[0185] <Comparative Example 3>

[0186] The same operation as in Example 15 was performed except that the crosslinking agent masterbatch was not used and 2,2-bis[4-(4-aminophenoxy)phenyl]propane was used as the crosslinking agent to obtain an uncrosslinked sheet of the rubber composition.

[0187] The uncrosslinked sheet was crosslinked to obtain a cross-linked rubber.

[0188] [Table 2]

[0189]

[0190] Unit: mass parts

[0191] According to the above results, by using a masterbatch of 2,2-bis[4-(4-aminophenoxy)phenyl]propane as an aromatic polyamine crosslinking agent, the dispersibility of 2,2-bis[4-(4-aminophenoxy)phenyl]propane in the uncrosslinked sheet can be improved, and the quality of the rubber crosslinked product obtained by crosslinking the uncrosslinked sheet can be improved (the uniformity of hardness is improved). In addition, by making a masterbatch, the scattering of powder is eliminated, and the working environment in rubber processing can be improved.

[0192] Industrial Applicability

[0193] The masterbatch of the present invention has good processability during manufacture and can increase the concentration of aromatic polyamines. This is beneficial for reducing the amount of masterbatch used as a crosslinking agent, reducing unnecessary components such as adhesive rubber, and further reducing the transportation cost of the masterbatch. Furthermore, by using the masterbatch of the present invention to carry out the mixing operation, the dispersibility of the aromatic polyamines is improved, and the quality of the rubber crosslinked product finally obtained is improved. In addition, there is no need to worry about scattering during handling, so the working environment can be improved.

Claims

1. A crosslinking agent masterbatch comprising at least (A) a synthetic rubber, (B) an aromatic polyamine and (C) a lubricant, The crosslinking agent masterbatch contains (A) 17 to 55% by mass of a synthetic rubber, (B) 40 to 78% by mass of an aromatic polyamine, and (C) 0.1 to 10% by mass of a lubricant.

2. The crosslinking agent masterbatch according to claim 1, wherein The (A) synthetic rubber is at least one selected from the group consisting of acrylic rubber, ethylene acrylate rubber, nitrile rubber and hydrogenated nitrile rubber.

3. The crosslinking agent masterbatch according to claim 1, wherein The (B) aromatic polyamine is an aromatic polyamine without a benzidine structure.

4. The crosslinking agent masterbatch according to claim 1, wherein The (B) aromatic polyamine is a compound represented by the following general formula (1) or the following general formula (2), In formula (1), R 1 ~R 5 are optionally the same or different, are monovalent groups, and R 1 ~R 5 At least one of them is an amino group, and R 1 ~R 5 Optionally forming a ring structure bonded via a carbon atom, an oxygen atom and / or a sulfur atom; In formula (2), m is an integer of 2 to 4; Rx is a 2 to 4-valent group; R 6 ~R 10 are optionally the same or different, are monovalent groups, and R 6 ~R 10 At least one of them is an amino group, and in each unit, the substituents at the same position may be the same or different, and R which is not an amino group 6 ~R 10 A cyclic structure bonded via a carbon atom, an oxygen atom and / or a sulfur atom may be formed. 5 . A rubber composition comprising at least the cross-linking agent masterbatch according to claim 1 and a polyamine cross-linkable rubber.

6. The rubber composition according to claim 5, wherein The crosslinking agent masterbatch according to any one of claims 1 to 4 is contained in an amount of 0.5 to 9.0 parts by mass based on 100 parts by mass of the polyamine crosslinkable rubber.

7. The rubber composition according to claim 5, wherein The polyamine crosslinkable rubber is at least one selected from the group consisting of acrylic rubber having a carboxyl group, ethylene-acrylate rubber having a carboxyl group, nitrile rubber having a carboxyl group, and hydrogenated nitrile rubber having a carboxyl group.

8. A rubber cross-linked product produced using the rubber composition according to claim 5.

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