Carboxyl group-containing acrylic rubber composition and crosslinked product thereof

Abstract

To provide, regarding a carboxyl group-containing acrylic rubber composition and a crosslinked product thereof, a crosslinked product having excellent handling property during processing, excellent scorch stability during crosslinking, no generation of harmful substances during crosslinking, and excellent heat resistance and compression set properties after crosslinking.MEANS FOR SOLVING THE PROBLEM: It was discovered that the handling property during processing is excellent, the scorch stability during crosslinking is excellent, no harmful substances are generated during crosslinking, and the heat resistance and compression set properties after crosslinking are excellent when 100 pts.mass of (A) a carboxyl group-containing acrylic rubber, 0.15 to 4 pts.mass of (B) an ammonium salt of an aromatic carboxylic acid or an ammonium salt of a C3-10 aliphatic carboxylic acid and / or (C) an amine salt of mercaptobenzothiazole, 0.1 to 10 pts.mass of (D) a tertiary amine and / or a guanidine compound, and 0.01-10 pts.mass of (E) an aliphatic diamine compound and / or an aromatic diamine compound are contained.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a carboxyl group-containing acrylic rubber composition and a crosslinked product thereof. More specifically, the present invention relates to a crosslinked product thereof that has excellent handleability during processing, excellent scorch stability during crosslinking, does not generate harmful substances during crosslinking, and has excellent heat resistance and compression set after crosslinking. [Background technology]

[0002] Compositions in which an aliphatic diamine compound is used as a crosslinking agent for carboxyl group-containing acrylic rubber give crosslinked products that are superior in heat resistance and compression set compared to conventional acrylic rubbers. However, because the crosslinking rate is fast, scorching is likely to occur during molding of the rubber composition, resulting in poor appearance of the rubber product. However, there is a problem in that it is difficult to control the processability of the uncrosslinked rubber composition because there are only a limited number of effective retarders.

[0003] In response to this situation, Patent Document 1 describes adding a benzothiazolyl sulfenamide compound as a retarder for carboxyl group-containing acrylic rubber, but the retardation effect is low and is not suitable for practical use.

[0004] Furthermore, Patent Document 2 describes adding a monoprimary amine compound as a retarder, which has a high retarding effect, but the compounds that can be used in practice are waxy, which makes handling difficult, such as measuring.

[0005] Furthermore, Patent Document 3 lists thiuram compounds as retarders, and the examples show the retardation effect of tetramethylthiuram disulfide (TMTD). TMTD has a sufficient retardation effect on carboxyl group-containing acrylic rubber, but thiuram compounds generate carcinogenic nitrosamines. Therefore, in Japan, thiuram compounds were restricted under the Water Pollution Control Act in 1994, and in Europe, they are listed as one of the sources of carcinogenic nitrosamines, so their use is restricted. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 3663859 [Patent Document 2] Patent No. 4273671 [Patent Document 3] Patent No. 3937172 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a crosslinked product which has excellent handleability during processing, excellent scorch stability during crosslinking, does not generate harmful substances during crosslinking, and has excellent heat resistance and compression set after crosslinking. [Means for solving the problem]

[0008] As a result of extensive research to achieve the above object, the present inventors have found that the above object can be achieved by incorporating (A) 100 parts by mass of a carboxyl group-containing acrylic rubber, (B) 0.15 to 4 parts by mass of an ammonium salt of an aromatic carboxylic acid or an ammonium salt of an aliphatic carboxylic acid having 3 to 10 carbon atoms, and / or (C) 0.15 to 4 parts by mass of an amine salt of mercaptobenzothiazole, (D) 0.1 to 10 parts by mass of a tertiary amine and / or a guanidine compound, and (E) 0.01 to 10 parts by mass of an aliphatic diamine compound and / or an aromatic diamine compound. The present invention was completed based on these findings. The above cross-linked product may also be referred to as an "acrylic rubber cross-linked product."

[0009] That is, the present invention provides a carboxyl group-containing acrylic rubber composition containing (A) 100 parts by mass of a carboxyl group-containing acrylic rubber, (B) 0.15 to 4 parts by mass of an ammonium salt of an aromatic carboxylic acid or an ammonium salt of an aliphatic carboxylic acid having 3 to 10 carbon atoms, and / or (C) 0.15 to 4 parts by mass of an amine salt of mercaptobenzothiazole, (D) 0.1 to 10 parts by mass of a tertiary amine and / or a guanidine compound, and (E) 0.01 to 10 parts by mass of an aliphatic diamine compound and / or an aromatic diamine compound.

[0010] The (B) ammonium salt of an aromatic carboxylic acid or an ammonium salt of an aliphatic carboxylic acid having 3 to 10 carbon atoms is preferably at least one selected from the group consisting of ammonium benzoate, ammonium citrate, and ammonium adipate.

[0011] The (C) amine salt of mercaptobenzothiazole is preferably at least one selected from the group consisting of cyclohexylamine salt of 2-mercaptobenzothiazole, tert-butylamine salt of 2-mercaptobenzothiazole, and methylamine salt of 2-mercaptobenzothiazole.

[0012] The present invention also provides a crosslinked product obtained by crosslinking the above carboxyl group-containing acrylic rubber composition.

[0013] The present invention also provides a rubber hose and a sealing part made of the above crosslinked product. [Effects of the Invention]

[0014] The cross-linked acrylic rubber produced from the carboxyl group-containing acrylic rubber composition of the present invention has excellent handleability during processing, excellent scorch stability during cross-linking, does not generate harmful substances during cross-linking, and is excellent in heat resistance and compression set after cross-linking. BEST MODE FOR CARRYING OUT THE INVENTION

[0015] The carboxyl group-containing acrylic rubber composition of the present invention contains at least (A) a carboxyl group-containing acrylic rubber, (B) an ammonium salt of an aromatic carboxylic acid or an ammonium salt of an aliphatic carboxylic acid having 3 to 10 carbon atoms, and / or (C) an amine salt of mercaptobenzothiazole, (D) a tertiary amine and / or a guanidine compound, and (E) an aliphatic diamine compound and / or an aromatic diamine compound.

[0016] The (A) carboxyl group-containing acrylic rubber used in the present invention includes an acrylic rubber containing (A-1) 10 to 98.9 mass% of structural units derived from a (meth)acrylic acid ester having an alkyl group with 1 to 3 carbon atoms or an alkoxyalkyl group with 2 to 3 carbon atoms, (A-2) 0 to 88.9 mass% of structural units derived from a (meth)acrylic acid ester having an alkyl group with 4 to 8 carbon atoms or an alkoxyalkyl group with 4 to 8 carbon atoms, and (A-3) 0.1 to 5 mass% of structural units derived from an ethylenically unsaturated carboxylic acid. The (A) carboxyl group-containing acrylic rubber may be used alone or in combination with two or more types. The term "(meth)acrylic acid ester" means "acrylic acid ester or methacrylic acid ester," and the same applies to similar expressions in the present application.

[0017] Specific examples of (A-1) (meth)acrylic acid esters having an alkyl group having 1 to 3 carbon atoms or an alkoxyalkyl group having 2 to 3 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, methoxymethyl (meth)acrylate, methoxyethyl (meth)acrylate, and ethoxymethyl (meth)acrylate. These can be used alone or in combination of two or more. Among these, ethyl (meth)acrylate and methoxyethyl (meth)acrylate are particularly preferred.

[0018] The content of the structural unit (A-1) in the carboxyl group-containing acrylic rubber (A) is 10 to 98.9 mass% of all structural units, preferably 15 to 98 mass%, and more preferably 20 to 97.5 mass%. If the content of the structural unit (A-1) is too low, the acrylic rubber will have increased tackiness, particularly when made into a crosslinkable rubber composition, resulting in reduced roll processability. On the other hand, if the content is too high, the cold resistance will be reduced.

[0019] Specific examples of (A-2) (meth)acrylic acid esters having an alkyl group having 4 to 8 carbon atoms or an alkoxyalkyl group having 4 to 8 carbon atoms include n-butyl (meth)acrylate, isobutyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, n-heptyl acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl (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, 4-ethoxybutyl (meth)acrylate, etc. These may be used alone or in combination of two or more. Among these, n-butyl (meth)acrylate and 2-ethoxyethyl (meth)acrylate are particularly preferred.

[0020] The content of the structural unit (A-2) in the carboxyl group-containing acrylic rubber (A) is 0 to 88.9% by mass, preferably 0 to 75% by mass, and more preferably 0 to 65% by mass, of all structural units. If the content of the structural unit (A-2) is too high, roll processability will decrease.

[0021] Examples of (A-3) ethylenically unsaturated carboxylic acids include ethylenically unsaturated monocarboxylic acids having 3 to 12 carbon atoms, ethylenically unsaturated dicarboxylic acids having 4 to 12 carbon atoms, and monoalkyl esters of ethylenically unsaturated dicarboxylic acids having 4 to 12 carbon atoms with alkanols having 1 to 8 carbon atoms (sometimes referred to as ethylenically unsaturated dicarboxylic acid monoesters).

[0022] Specific examples of the ethylenically unsaturated monocarboxylic acid having 3 to 12 carbon atoms include acrylic acid, methacrylic acid, α-ethylacrylic acid, crotonic acid, and cinnamic acid.

[0023] Specific examples of the ethylenically unsaturated dicarboxylic acid having 4 to 12 carbon atoms include fumaric acid, maleic acid, citraconic acid, mesaconic acid, itaconic acid, 2-pentenedioic acid, acetylenedicarboxylic acid, and anhydrides thereof.

[0024] Specific examples of the ethylenically unsaturated dicarboxylic acid monoester having 4 to 12 carbon atoms include monomethyl fumarate, monoethyl fumarate, monopropyl fumarate, mono-n-butyl fumarate, monoisobutyl fumarate, monocyclohexyl fumarate, monomethyl maleate, monoethyl maleate, monopropyl maleate, mono-n-butyl maleate, monomethyl citraconic acid, monoethyl citraconic acid, monopropyl citraconic acid, mono-n-butyl citraconic acid, monomethyl mesaconic acid, monoethyl mesaconic acid, and monomethyl ... monopropyl ester, mono-n-butyl mesaconic acid, monomethyl itaconate, monoethyl itaconate, mono-n-butyl itaconate, monocyclohexyl itaconate, monomethyl 2-pentenedioate, monoethyl 2-pentenedioate, monopropyl 2-pentenedioate, mono-n-butyl 2-pentenedioate, monomethyl acetylenedicarboxylate, monoethyl acetylenedicarboxylate, monopropyl acetylenedicarboxylate, mono-n-butyl acetylenedicarboxylate, and monocyclohexyl acetylenedicarboxylate.

[0025] These (A-3) ethylenically unsaturated carboxylic acids can be used alone or in combination of two or more. Among these, monoethyl fumarate, monopropyl fumarate, mono-n-butyl fumarate, monoisobutyl fumarate, monomethyl itaconate, and mono-n-butyl itaconate are preferred.

[0026] The content of the structural unit (A-3) in the carboxyl group-containing acrylic rubber (A) is 0.1 to 5 mass% of all structural units, preferably 0.2 to 4 mass%, and more preferably 0.5 to 3 mass%. If the content of the structural unit (A-3) is too low, the effectiveness of the structural unit (A-3) may not be fully obtained, the cross-linking density of the obtained cross-linked rubber product may not be sufficient, and good cross-linking properties may not be obtained. On the other hand, if the content is too high, the elongation of the obtained cross-linked rubber product may decrease.

[0027] As long as the properties of acrylic rubber are maintained, the (A) carboxyl group-containing acrylic rubber may have structural units derived from other copolymerizable monomers in addition to the structural units (A-1) to (A-3) derived from the (meth)acrylic acid ester or ethylenically unsaturated carboxylic acid described above.

[0028] The copolymerizable other monomer is not particularly limited, but examples thereof include aromatic vinyl monomers, ethylenically unsaturated nitrile monomers, conjugated diene monomers, olefin monomers, and vinyl ether compounds.

[0029] Specific examples of aromatic vinyl monomers 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 a salt thereof, α-vinylnaphthalene, 1-vinylnaphthalene-4-sulfonic acid or a salt thereof, 2-vinylfluorene, 2-vinylpyridine, 4-vinylpyridine, divinylbenzene, diisopropenylbenzene, and vinylbenzyl chloride.

[0030] Specific examples of the ethylenically unsaturated nitrile monomer include acrylonitrile, methacrylonitrile, α-methoxyacrylonitrile, and vinylidene cyanide.

[0031] Specific examples of conjugated diene monomers include 1,3-butadiene, 2-methyl-1,3-butadiene, 2-chloro-1,3-butadiene (chloroprene), 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 (piperylene), and 1,3-hexadiene.

[0032] Specific examples of olefin-based monomers include ethylene, propylene, vinyl chloride, vinylidene chloride, 1,2-dichloroethylene, vinyl acetate, vinyl fluoride, vinylidene fluoride, 1,2-difluoroethylene, vinyl bromide, vinylidene bromide, and 1,2-dibromoethylene.

[0033] Specific examples of the vinyl ether compound include ethyl vinyl ether, dimethylaminoethyl vinyl ether, and n-butyl vinyl ether.

[0034] Other examples include non-conjugated dienes such as 1,4-pentadiene, 1,4-hexadiene, ethylidenenorbornene, norbornadiene, and dicyclopentadiene; and esters such as dicyclopentadienyl acrylate, dicyclopentadienyl methacrylate, dicyclopentadienylethyl acrylate, dicyclopentadienylethyl methacrylate, and vinyl acetate.

[0035] The copolymerizable other monomers may be used alone or in combination of two or more. The content of structural units derived from copolymerizable other monomers in the (A) carboxyl group-containing acrylic rubber is 0 to 45% by mass, and preferably 0 to 20% by mass, of all structural units.

[0036] The carboxyl group-containing acrylic rubber (A) used in the present invention can be obtained by copolymerizing the above-mentioned monomers. The polymerization reaction can be carried out by any of emulsion polymerization, suspension polymerization, bulk polymerization, and solution polymerization, but from the viewpoint of ease of control of the polymerization reaction, emulsion polymerization under normal pressure, which is commonly used as a conventional method for producing acrylic rubber, is preferred.

[0037] The emulsion polymerization method may be any of a batch method, a semi-batch method, and a continuous method. The polymerization temperature is usually 0 to 70°C, and preferably 5 to 50°C.

[0038] The Mooney viscosity (ML) of the carboxyl group-containing acrylic rubber (A) used in the present invention thus produced is 1+4 , 100°C) (polymer Mooney) is preferably 10 to 80, more preferably 20 to 70, and even more preferably 25 to 60. In this specification, the Mooney viscosity (ML 1+4 , 100°C) is determined according to JIS K6300.

[0039] The carboxyl group-containing acrylic rubber composition of the present invention contains at least (A) a carboxyl group-containing acrylic rubber, (B) an ammonium salt of an aromatic carboxylic acid or an ammonium salt of an aliphatic carboxylic acid having 3 to 10 carbon atoms, and / or (C) an amine salt of mercaptobenzothiazole, (D) a tertiary amine and / or a guanidine compound, and (E) an aliphatic diamine compound and / or an aromatic diamine compound.

[0040] (B) the ammonium salt of an aromatic carboxylic acid or the ammonium salt of an aliphatic carboxylic acid having 3 to 10 carbon atoms, and / or (C) the amine salt of mercaptobenzothiazole are components that act as retarders for the carboxyl group-containing acrylic rubber composition. The reason for the improved retardation effect is not entirely clear, but it is presumed that the heat generated when crosslinking the carboxyl group-containing acrylic rubber composition of the present invention decomposes (B) the ammonium salt of an aromatic carboxylic acid or the ammonium salt of an aliphatic carboxylic acid having 3 to 10 carbon atoms, and / or (C) the amine salt of mercaptobenzothiazole, and the amine thus produced acts on the crosslinking groups to form amides, thereby reducing the crosslinking group concentration, thereby improving the retardation effect.

[0041] The ammonium salt of aromatic carboxylic acid (B) used in the present invention can be an ammonium salt of a carboxylic acid having a carboxyl group directly bonded to the aromatic ring, or an ammonium salt of a carboxylic acid having a carboxyl group in a side chain. The aromatic hydrocarbon group in the ammonium salt of aromatic carboxylic acid may be either a monocyclic or a polycyclic condensed ring, and examples thereof include benzene, naphthalene, anthracene, phenanthrene, indene, fluorene, and biphenyl. The ammonium salt of aromatic carboxylic acid can be an ammonium salt of a monocarboxylic acid, an ammonium salt of a dicarboxylic acid, or an ammonium salt of another polycarboxylic acid. Specific examples of the ammonium salt of aromatic carboxylic acid include ammonium benzoate, ammonium phthalate, ammonium phenylacetate, ammonium mandelate, and derivatives thereof. Among the ammonium salts of aromatic carboxylic acids, ammonium benzoate is preferred because it is easily available and inexpensive.

[0042] The ammonium salt of (B) aliphatic carboxylic acid having 3 to 10 carbon atoms used in the present invention is not particularly limited and can be appropriately selected depending on the purpose. Ammonium salts of monocarboxylic acids, ammonium salts of dicarboxylic acids, and ammonium salts of other polycarboxylic acids can be used. Among these, ammonium salts of polycarboxylic acids are preferred because they can impart a delay effect with a relatively small amount added, as long as the physical properties of the rubber in the carboxyl group-containing acrylic rubber composition are not affected. Specific examples of ammonium salts of aliphatic carboxylic acids having 3 to 10 carbon atoms include ammonium acetate, ammonium oxalate, ammonium bioxalate, ammonium citrate, ammonium adipate, and ammonium succinate. Among these, ammonium citrate and ammonium adipate are particularly preferred from the viewpoint of excellent compatibility with the carboxyl group-containing acrylic rubber composition.

[0043] The amine salt of mercaptobenzothiazole (C) used in the present invention is not particularly limited and can be appropriately selected depending on the purpose, and a primary amine salt of 2-mercaptobenzothiazole can be used. Secondary amine salts and tertiary amine salts of 2-mercaptobenzothiazole, and benzothiazolylsulfenamide compounds having similar partial structures, are not preferred because they have low reactivity with crosslinking groups due to steric hindrance, resulting in low retardation effect.

[0044] In the primary amine salt of 2-mercaptobenzothiazole (C) used in the present invention, examples of the amine include methylamine, cyclohexylamine, isopropylamine, tert-butylamine, and nonylamine.

[0045] Specific examples of the primary amine salt of 2-mercaptobenzothiazole (C) used in the present invention include cyclohexylamine salt of 2-mercaptobenzothiazole, tert-butylamine salt of 2-mercaptobenzothiazole, methylamine salt of 2-mercaptobenzothiazole, etc. Among these, cyclohexylamine salt of 2-mercaptobenzothiazole and tert-butylamine salt of 2-mercaptobenzothiazole are particularly preferred because they are easily available and inexpensive.

[0046] In the present invention, (B) an ammonium salt of an aromatic carboxylic acid or an ammonium salt of an aliphatic carboxylic acid having 3 to 10 carbon atoms, and / or (C) an amine salt of mercaptobenzothiazole, which also corresponds to (D) a tertiary amine and / or guanidine compound, and (E) an aliphatic diamine compound and / or aromatic diamine compound, which will be described later, are treated as component (B) or component (C).

[0047] The (B) ammonium salt of an aromatic carboxylic acid or the ammonium salt of an aliphatic carboxylic acid having 3 to 10 carbon atoms, and / or the (C) amine salt of a mercaptobenzothiazole may be used alone or in combination of two or more. In particular, the use of two or more types of (B) and (C) in combination provides a crosslinked product with excellent handleability during processing, excellent scorch stability during crosslinking, and a well-balanced compression set. The content of the (B) ammonium salt of an aromatic carboxylic acid or the ammonium salt of an aliphatic carboxylic acid having 3 to 10 carbon atoms, and / or the (C) amine salt of a mercaptobenzothiazole is preferably 0.15 to 4 parts by mass, more preferably 0.5 to 3 parts by mass, and even more preferably 1 to 2.5 parts by mass, per 100 parts by mass of the (A) carboxyl group-containing acrylic rubber. If the content of the (B) ammonium salt of an aromatic carboxylic acid or the ammonium salt of an aliphatic carboxylic acid having 3 to 10 carbon atoms, and / or the (C) amine salt of a mercaptobenzothiazole is too low, the effect may be insufficient, and good scorch stability may not be achieved. On the other hand, if the content is too high, poor dispersion and crosslinking inhibition tend to occur during roll processing, and the crosslinking accelerator may bloom from the obtained crosslinked rubber product, adversely affecting the appearance. Here, when a plurality of components (B) or (C) are contained, the above content refers to the total content. The same applies to the contents of other components.

[0048] (D) The tertiary amine and / or guanidine compound is a component that acts as a crosslinking accelerator for (A) the carboxyl group-containing acrylic rubber in the carboxyl group-containing acrylic rubber composition of the present invention.

[0049] Specific examples of the (D) tertiary amine include aliphatic tertiary amines, dithiocarbamates, diazabicycloalkene compounds, etc. Among these, diazabicycloalkene compounds are preferred from the viewpoints of normal physical properties and heat resistance.

[0050] Specific examples of (D) aliphatic tertiary amines include trimethylamine, triethylamine, tripropylamine, triallylamine, triisopropylamine, tri-n-butylamine, tri-t-butylamine, tri-sec-butylamine, trihexylamine, triheptylamine, trioctylamine, trinonylamine, tridecylamine, triundecylamine, and tridodecylamine.

[0051] Specific examples of (D) dithiocarbamate salts include zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, zinc dipentyldithiocarbamate, zinc dihexyldithiocarbamate, zinc N-pentamethylenedithiocarbamate, zinc N-ethyl-N-phenyldithiocarbamate, zinc dibenzyldithiocarbamate, copper dipropyldithiocarbamate, copper diisopropyldithiocarbamate, copper dibutyldithiocarbamate, sodium diethyldithiocarbamate, sodium diisopropyldithiocarbamate, sodium dibutyldithiocarbamate, ferric dimethyldithiocarbamate, and ferric diethyldithiocarbamate.

[0052] Specific examples of the (D) diazabicycloalkene compound include 1,8-diazabicyclo(5.4.0)undecene-7 (DBU), 1,5-diazabicyclo(4.3.0)nonene-5, 1,4-diazabicyclo(2.2.2)octane, and their p-toluenesulfonate salts, phenol salts, phenol resin salts, orthophthalate salts, formate salts, octylate salts, naphthoate salts, etc. Among these, from the viewpoints of normal state physical properties and heat resistance, 1,8-diazabicyclo(5.4.0)undecene-7 and naphthoate salts of 1,8-diazabicyclo(5.4.0)undecene-7 are preferred.

[0053] Specific examples of the (D) guanidine compound include 1,3-diphenylguanidine, 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, di-o-tolylguanidine salt of dicatechol borate, 1,3-di-o-cumenylguanidine, 1,3-di-o-biphenylguanidine, 1,3-di-o-cumenyl-2-propionylguanidine, etc. Among these, 1,3-di-o-tolylguanidine is preferred from the viewpoints of normal state physical properties, heat resistance, and compression set.

[0054] Among these compounds, from the viewpoint of improving crosslink density, at least one selected from the group consisting of 1,8-diazabicyclo(5.4.0)undecene-7, its salts, and 1,3-di-o-tolylguanidine is preferred, and 1,8-diazabicyclo(5.4.0)undecene-7 is more preferred. Furthermore, among the salts of 1,8-diazabicyclo(5.4.0)undecene-7, naphthoate is preferred.

[0055] In the present invention, (D) a tertiary amine and / or guanidine compound that also corresponds to (E) an aliphatic diamine compound and / or aromatic diamine compound described below is treated as component (D).

[0056] The (D) tertiary amine and / or guanidine compound may be used alone or in combination of two or more. The content of the (D) tertiary amine and / or guanidine compound is preferably 0.1 to 10 parts by mass, more preferably 0.15 to 8 parts by mass, and even more preferably 0.2 to 7 parts by mass, per 100 parts by mass of the (A) carboxyl group-containing acrylic rubber.

[0057] Since the (E) aliphatic diamine compound and / or aromatic diamine compound can easily form a crosslinked structure with the carboxyl group, it is a component that acts as a crosslinking agent for the (A) carboxyl group-containing acrylic rubber in the carboxyl group-containing acrylic rubber composition of the present invention. As (E), an aliphatic diamine compound is preferred.

[0058] Specific examples of the (E) aliphatic diamine compound include hexamethylenediamine, hexamethylenediamine carbamate, ethylenediamine, ethylenediamine carbamate, 3,3′-diaminopropylamine, diamino-modified siloxane, etc. Among these, hexamethylenediamine carbamate is preferred from the viewpoints of normal physical properties and heat resistance.

[0059] Specific examples of the aromatic diamine compound (E) include 4,4'-methylenedianiline, m-phenylenediamine, p-phenylenediamine, p,p'-ethylenedianiline, 4,4'-methylenebis(o-chloroaniline), 4,4'-(m-phenylenediisopropylidene)dianiline, 4,4'-(p-phenylenediisopropylidene)dianiline, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, bis[4-(4-aminophenoxy)phenyl]ether, 2,2'-bis[4-(4-aminophenoxy)phenyl]propane ...propane, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, bis[4-(4-aminophenoxy)phenyl]propane, 3,4'-diaminodiphenyl ether, bis[4-(4-aminophenoxy)phenyl]propane, 3,4'-diaminodiphenyl ether, bis[4-(4-aminophenoxy)phenyl]propane, 3,4'-diaminodiphenyl ether, bis[4-(4-aminophenoxy)phenyl]propane, 3,4'-diaminodiphenyl ether, bis[4-(4-aminophenoxy)phenyl]propane, 3,4'- Examples of such an additive include aminobenzanilide, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)biphenyl, m-xylylenediamine, p-xylylenediamine, 4,4'-diaminodiphenyl sulfone, bis[4-(4-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)phenyl]sulfone, hexamethylenediamine-cinnamaldehyde adduct, hexamethylenediamine-dibenzoate salt, and N,N'-dicinnamylidene-1,6-hexanediamine. Among these, 2,2-bis[4-(4-aminophenoxy)phenyl]propane is preferred from the viewpoints of normal physical properties and heat resistance.

[0060] As the (E) aliphatic diamine compound and / or aromatic diamine compound, hexamethylenediamine carbamate and / or 2,2'-bis[4-(4-aminophenoxy)phenyl]propane are preferred, and hexamethylenediamine carbamate is more preferred. The (E) aliphatic diamine compound and / or aromatic diamine compound may be used alone or in combination of two or more. The content of the (E) aliphatic diamine compound and / or aromatic diamine compound is preferably 0.01 to 10 parts by mass, more preferably 0.15 to 5 parts by mass, and even more preferably 0.2 to 4 parts by mass, relative to 100 parts by mass of the (A) carboxyl group-containing acrylic rubber.

[0061] Furthermore, the carboxyl group-containing acrylic rubber composition of the present invention can be blended with various additives, such as fillers, lubricants (processing aids), plasticizers, acid acceptors, softeners, antioxidants, colorants, stabilizers, adhesion aids, release agents, electrical conductivity imparting agents, thermal conductivity imparting agents, surface anti-tack agents, tackifiers, flexibility imparting agents, heat resistance improvers, flame retardants, ultraviolet absorbers, oil resistance improvers, foaming agents, scorch inhibitors, lubricants, etc., as long as the effects of the present invention are not impaired. These may be used alone or in combination of two or more.

[0062] As the filler, known fillers can be used, and specific examples include calcium carbonate, talc, silica, clay, carbon fiber, glass fiber, carbon black, titanium oxide, magnesium oxide, hydrotalcite, magnesium hydroxide, antimony oxide, zinc oxide, etc. Among these, carbon black and silica are preferred, and carbon black is more preferred. When carbon black is contained, its nitrogen adsorption specific surface area (N2SA) is 15 to 90 m from the viewpoint of reinforcement. 2 / g is preferred, and 30 to 85m 2 When a filler is contained, the content thereof is preferably 1 to 150 parts by mass, more preferably 10 to 100 parts by mass, per 100 parts by mass of (A) the carboxyl group-containing acrylic rubber. In this specification, the nitrogen adsorption specific surface area of ​​carbon black is determined in accordance with JIS K6217-2:2001.

[0063] Examples of lubricants (processing aids) include higher fatty acids such as stearic acid, oleic acid, palmitic acid, and lauric acid; higher fatty acid salts such as sodium stearate and zinc stearate; higher fatty acid amides such as stearic acid amide and oleic acid amide; higher fatty acid esters such as ethyl oleate; higher aliphatic amines such as stearylamine and oleylamine; petroleum waxes such as carnauba wax and ceresin wax; polyglycols such as ethylene glycol, glycerin, and diethylene glycol; aliphatic hydrocarbons such as petrolatum and paraffin; silicone oils, silicone polymers, low-molecular-weight polyethylene, phthalates, phosphates, rosin, (halogenated) dialkylamines, (halogenated) dialkylsulfones, surfactants, etc. When a lubricant (processing aid) is included, its content is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 5 parts by mass, per 100 parts by mass of (A) the carboxyl group-containing acrylic rubber.

[0064] Examples of the plasticizer include phthalic acid derivatives such as dioctyl phthalate (bis(2-ethylhexyl) phthalate) and diallyl phthalate ester, adipic acid derivatives such as dibutyl diglycol adipate and di(butoxyethoxy)ethyl adipate, sebacic acid derivatives such as dioctyl sebacate, and trimellitic acid derivatives such as trioctyl trimellitate, and these may be used alone or in combination of two or more.

[0065] Examples of the antioxidant include amines, phosphates, quinolines, cresols, phenols, and dithiocarbamate metal salts, and preferred are amines such as diphenylamine derivatives such as 4,4'-bis(α,α-dimethylbenzyl)diphenylamine and phenylenediamine derivatives. When an antioxidant is contained, the content thereof is preferably 0.3 to 10 parts by mass, and more preferably 0.5 to 5 parts by mass, per 100 parts by mass of the (A) carboxyl group-containing acrylic rubber.

[0066] The carboxyl group-containing acrylic rubber composition of the present invention can be compounded using any means conventionally used in the field of polymer processing, such as an open roll, a Banbury mixer, or various kneaders.

[0067] The compounding procedure can be a normal procedure used in the field of polymer processing, for example, by first kneading only the polymer, then adding compounding ingredients other than the crosslinking agent and crosslinking accelerator to prepare kneaded compound A, and then kneading compound B to add the crosslinking agent and crosslinking accelerator.

[0068] The carboxyl group-containing acrylic rubber composition of the present invention obtained in this manner exhibits excellent roll processability during processing. When the carboxyl group-containing acrylic rubber composition of the present invention is formed into a sheet (uncrosslinked sheet) with a thickness of approximately 2 to 2.5 mm, the scorch time t5 (JIS K6300) at a temperature of 125°C is 60 minutes or less, preferably 5 minutes to 60 minutes, more preferably 5.5 minutes to 60 minutes, and even more preferably 6 minutes to 55 minutes. If the scorch time t5 is too long, the crosslinking rate will be slow, and complete crosslinking will take a long time, which may prevent good crosslinked physical properties and adhesiveness from being obtained. The scorch time t5 can be adjusted to a desired value by adjusting the type and content of the crosslinking agent and crosslinking accelerator.

[0069] The carboxyl group-containing acrylic rubber composition of the present invention can be made into a carboxyl group-containing acrylic rubber cross-linked product by heating it usually at 100 to 250° C. The cross-linking time varies depending on the temperature, but is usually carried out for 0.5 to 300 minutes.

[0070] A general crosslinking molding method may be any of a method of integrally carrying out crosslinking and molding, a method of heating a previously molded crosslinkable acrylic rubber composition again to form a crosslinked product, and a method of processing an acrylic rubber crosslinked product that has been previously heated for molding. Specific methods for crosslinking molding include compression molding using a mold, injection molding, heating using a steam can, an air bath, infrared rays, or microwaves, and any other method can be used.

[0071] The carboxyl group-containing acrylic rubber cross-linked product thus obtained is obtained using the carboxyl group-containing acrylic rubber composition of the present invention, and therefore has excellent roll processability during processing, and when cross-linked, has excellent normal physical properties, heat resistance and oil resistance.

[0072] The carboxyl group-containing acrylic rubber cross-linked product of the present invention is suitably used for fuel piping or air piping products such as tubes and hoses.

[0073] The present invention will be described in more detail below with reference to examples, but the following examples are not intended to limit the scope of the invention. Tests and evaluations of physical properties and characteristics were carried out as follows. [Example]

[0074] (Scorch Time t5) The carboxyl group-containing acrylic rubber composition was kneaded using a kneader and an open roll to prepare an uncrosslinked rubber sheet having a thickness of 2 to 2.5 mm. The scorch time t5 (the time from the start of measurement until the Mooney viscosity increases by 5 points compared to the minimum Mooney viscosity value) was measured at 125°C using a Mooney Viscometer AM-3 manufactured by Toyo Seiki Co., Ltd. in accordance with JIS K6300. If the scorch time t5 is 5 minutes or longer, good processing stability and fluidity during molding are obtained. On the other hand, if the scorch time t5 is shorter than 5 minutes, curing due to crosslinking begins during processing, which may result in poor fluidity during molding and may prevent the production of a crosslinked product with good appearance.

[0075] (Compression set) The carboxyl group-containing acrylic rubber composition was pressed in a mold for preparing a test piece at 180°C for 10 minutes, and then heated in an air oven at 180°C for 3 hours to obtain a cylindrical cross-linked acrylic rubber product with a diameter of approximately 29 mm and a height of approximately 12.5 mm. Using the obtained cross-linked acrylic rubber product, testing was carried out in accordance with the method described in JIS K6262 under conditions of 150°C and 72 hours. A compression set value of 15% or less was considered to have good compression set properties.

[0076] (Raw materials used) Carboxyl group-containing acrylic rubber Lacrestar CH (Osaka Soda Co., Ltd.) carbon black SEAT SO (ASTM D1765 classification: N550, manufactured by Tokai Carbon Co., Ltd.) Lubricant Stearic acid (NOF Corporation) Anti-aging agents Nocrac CD (4,4'-bis(α,α-dimethylbenzyl)diphenylamine, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) Crosslinking agent Sanfel 6-MC (hexamethylenediamine carbamate, manufactured by Sanshin Chemical Industry Co., Ltd.) BAPP (2,2-bis[4-(4-aminophenoxy)phenyl]propane, manufactured by Wakayama Seika Kogyo Co., Ltd.) Crosslinking accelerator Noccela DT (1,3-di-o-tolylguanidine, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) Rhenogran XLA-60 (DBU content: 60% by mass, manufactured by Rhein Chemie) Vulcofac ACT-55 (DBU content: 70% by mass, manufactured by Safic-Alcan) retarder Valnoc AB-S (ammonium benzoate, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) Sancerer HM (cyclohexylamine salt of 2-mercaptobenzothiazole (primary amine salt of mercaptobenzothiazole), manufactured by Sanshin Chemical Industry Co., Ltd.) Noccela CZ (N-cyclohexyl-2-benzothiazolyl sulfenamide, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) Noccela TRA (dipentamethylene thiuram tetrasulfide, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) Sancerer MA (dicyclohexylamine salt of 2-mercaptobenzothiazole (secondary amine salt of mercaptobenzothiazole)), manufactured by Sanshin Chemical Industry Co., Ltd.

[0077] Example 1 100 parts by mass of carboxyl group-containing acrylic rubber (Lacrestar CH, manufactured by Osaka Soda Co., Ltd.), 60 parts by mass of carbon black N550, 2 parts by mass of stearic acid, and 2 parts by mass of 4,4'-bis(α,α-dimethylbenzyl)diphenylamine (Nocrac CD, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) were kneaded using a kneader at 100°C. Furthermore, 0.53 parts by mass of ammonium benzoate (Balnoc AB-S, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.), 2 parts by mass of 1,3-di-o-tolylguanidine (Noccela DT, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.), and 0.6 parts by mass of hexamethylenediamine carbamate (Sunfel 6-MC, manufactured by Sanshin Chemical Industry Co., Ltd.) were kneaded using an open roll at room temperature to prepare a carboxyl group-containing acrylic rubber cross-linked product.

[0078] The obtained carboxyl group-containing acrylic rubber cross-linked product was tested and evaluated for scorch time t5 and compression set by the above-mentioned methods. The results are shown in Tables 1 and 2.

[0079] Examples 2 to 11, Comparative Examples 1 to 10 A carboxyl group-containing acrylic rubber cross-linked product was prepared in the same manner as in Example 1, except that the formulation was changed as shown in Tables 1 and 2, and the same tests and evaluations were carried out as in Example 1. The results are shown in Tables 1 and 2.

[0080] [Table 1]

[0081] [Table 2]

[0082] The results in Tables 1 and 2 show that the acrylic rubber cross-linked products (Examples 1 to 11) obtained from the carboxyl group-containing acrylic rubber composition of the present invention had longer scorch times (t5) and exhibited a stronger retardation effect than those in Comparative Examples 1 to 5 and Comparative Example 9. Comparative Example 10, in which a secondary amine salt of 2-mercaptobenzothiazole was used as a retarder, was even unmoldable. The amounts of ingredients other than the retarder and the amount of retarder blended were the same in Example 5 compared to Comparative Example 6, and in Example 7 compared to Comparative Example 7, but both the compression set and scorch time (t5) of Comparative Examples 6 and 7 were worse than those of Examples 5 and 7, indicating a poorer retardation effect. Comparative Example 8, in which a thiuram compound was used as a retarder, did not show an increase in scorch time (t5) and exhibited a poorer retardation effect. From the above, it has become clear that by blending an appropriate amount of a suitable retarder, it is possible to obtain a crosslinked product that has excellent handleability during processing, excellent scorch stability during crosslinking, and a well-balanced compression set. [Industrial Applicability]

[0083] The carboxyl group-containing cross-linked acrylic rubber of the present invention is suitably used for various gaskets such as O-rings, packings, diaphragms, oil seals, shaft seals, bearing seals, mechanical seals, wellhead seals, seals for electric and electronic equipment, seals for pneumatic equipment, cylinder head gaskets attached to the joint between a cylinder block and a cylinder head, rocker cover gaskets attached to the joint between a rocker cover and a cylinder head, oil pan gaskets attached to the joint between an oil pan and a cylinder block or a transmission case, gaskets for fuel cell separators attached between a pair of housings sandwiching a unit cell comprising a positive electrode, an electrolyte plate and a negative electrode, and gaskets for the top cover of a hard disk drive, as well as extrusion molded products and mold cross-linked products used in automobiles, such as fuel oil hoses around fuel tanks such as fuel hoses, filler neck hoses, vent hoses, vapor hoses and oil hoses, air hoses such as turbo air hoses and emission control hoses, and various hoses such as radiator hoses, heater hoses, brake hoses and air conditioner hoses.

[0084] Variations of the invention according to the present disclosure are described below. [Appendix 1] A carboxyl group-containing acrylic rubber composition comprising: (A) 100 parts by mass of a carboxyl group-containing acrylic rubber; (B) 0.15 to 4 parts by mass of an ammonium salt of an aromatic carboxylic acid or an ammonium salt of an aliphatic carboxylic acid having 3 to 10 carbon atoms, and / or (C) 0.15 to 4 parts by mass of an amine salt of mercaptobenzothiazole; (D) 0.1 to 10 parts by mass of a tertiary amine and / or a guanidine compound; and (E) 0.01 to 10 parts by mass of an aliphatic diamine compound and / or an aromatic diamine compound. [Appendix 2] (B) A carboxyl group-containing acrylic rubber composition according to Appendix 1, wherein the ammonium salt of an aromatic carboxylic acid or the ammonium salt of an aliphatic carboxylic acid having 3 to 10 carbon atoms is at least one selected from the group consisting of ammonium benzoate, ammonium citrate, and ammonium adipate. [Appendix 3] The carboxyl group-containing acrylic rubber composition according to Appendix 1 or 2, wherein the amine salt of (C) mercaptobenzothiazole is at least one selected from the group consisting of cyclohexylamine salt of 2-mercaptobenzothiazole, tert-butylamine salt of 2-mercaptobenzothiazole, and methylamine salt of 2-mercaptobenzothiazole. [Appendix 4] A crosslinked product obtained by crosslinking the acrylic rubber composition according to any one of Appendices 1 to 3. [Appendix 5] A rubber hose or a sealing part made of the cross-linked product according to any one of Appendices 1 to 4.

Claims

1. A carboxyl group-containing acrylic rubber composition comprising: (A) 100 parts by mass of a carboxyl group-containing acrylic rubber; (B) 0.15 to 4 parts by mass of an ammonium salt of an aromatic carboxylic acid or an ammonium salt of an aliphatic carboxylic acid having 3 to 10 carbon atoms, and / or (C) an amine salt of mercaptobenzothiazole; (D) 0.1 to 10 parts by mass of a tertiary amine and / or a guanidine compound; and (E) 0.01 to 10 parts by mass of an aliphatic diamine compound and / or an aromatic diamine compound.

2. The carboxyl group-containing acrylic rubber composition according to claim 1, wherein (B) the ammonium salt of an aromatic carboxylic acid or the ammonium salt of an aliphatic carboxylic acid having 3 to 10 carbon atoms is at least one selected from the group consisting of ammonium benzoate, ammonium citrate, and ammonium adipate.

3. 3. The carboxyl group-containing acrylic rubber composition according to claim 1 or 2, wherein the amine salt of mercaptobenzothiazole (C) is at least one selected from the group consisting of a cyclohexylamine salt of 2-mercaptobenzothiazole, a tert-butylamine salt of 2-mercaptobenzothiazole, and a methylamine salt of 2-mercaptobenzothiazole.

4. A crosslinked product obtained by crosslinking the acrylic rubber composition according to claim 1 or 2.

5. A rubber hose and a sealing part made of the cross-linked product according to claim 4.

Images