JP3512041B2 - Vulcanizable rubber composition - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vulcanizable rubber composition containing, as a rubber component, an ethylenically unsaturated nitrile-conjugated diene copolymer rubber. The present invention also relates to a vulcanizable rubber composition having improved mold releasability at the time of vulcanization molding and exhibiting high strength characteristics stably irrespective of production conditions. 2. Description of the Related Art A vulcanized rubber having improved physical properties can be obtained by mixing a rubber with zinc dimethacrylate or basic zinc methacrylate and vulcanizing with an organic peroxide. , Are well known. These zinc salts of methacrylic acid can be obtained by reacting a zinc compound such as zinc oxide, zinc carbonate or zinc hydroxide with methacrylic acid. The zinc salt of methacrylic acid may be prepared in advance and mixed with the rubber. However, the adhesion of the zinc salt powder to a mixer or a roll surface is remarkable, so that it is difficult to obtain a uniform rubber composition. is there. As another mixing method, there is a method in which methacrylic acid and a zinc compound are added to rubber and reacted in the rubber to prepare a zinc salt of methacrylic acid. According to this method, the problem of the tackiness of the zinc salt of methacrylic acid is reduced, and a uniform rubber composition can be easily obtained. For example, JP-A-1-306441 discloses that
It is disclosed that a vulcanizable rubber composition in which methacrylic acid, a zinc compound, and an organic peroxide are mixed with an ethylenically unsaturated nitrile-conjugated diene copolymer rubber exhibits high tensile strength. JP-A-1-306443 describes that
Vulcanizable rubber obtained by mixing methacrylic acid, a zinc compound, and an organic peroxide with an ethylenically unsaturated nitrile-conjugated diene-based highly saturated rubber having a conjugated diene unit content of 30% by weight or less in a polymer chain. It is disclosed that the composition exhibits extremely high tensile strength as compared with conventional rubber. However, according to the research results of the present inventors, a vulcanizable rubber composition obtained by mixing methacrylic acid, a zinc compound and an organic peroxide with an ethylenically unsaturated nitrile-conjugated diene copolymer rubber. Has a problem that strength characteristics such as tensile strength vary depending on manufacturing conditions such as kneading temperature. On the other hand, a zinc salt of methacrylic acid is used as a co-crosslinking agent for a rubber for a core of a golf ball. The zinc salt of methacrylic acid contains 2 moles per mole of zinc compound.
2 moles of zinc dimethacrylate (hereinafter referred to as a normal salt) reacted with 1 mol of methacrylic acid and basic zinc methacrylate (hereinafter referred to as a basic salt) reacted with 1 mol of methacrylic acid per 1 mol of a zinc compound. There are types. When a zinc compound is reacted with methacrylic acid in a rubber (hereinafter, referred to as a direct mixing method), a normal salt and a basic salt are usually mixed and formed. However, normal salt is suitable for use in golf balls that require high resilience. Therefore, in the direct mixing method, various methods for efficiently producing a normal salt have been proposed. For example, JP-A-57-37459 discloses that
When reacting methacrylic acid with zinc oxide in a mixture of polybutadiene rubber and a small amount of natural rubber or polyisoprene rubber, add a dehydrating agent such as calcium oxide or activated aluminum oxide to adsorb and dehydrate the reaction water A method is disclosed, and according to this method, a vulcanized rubber having high resilience and suitable for a golf ball can be obtained. Japanese Patent Application Laid-Open No. 58-19344 discloses that, when polymethadiene rubber is reacted with methacrylic acid and zinc oxide, calcium hydroxide is present to suppress the formation of basic zinc methacrylate. It is disclosed that a rubber having: JP-A-58-87140 discloses that when methacrylic acid and zinc powder instead of zinc oxide are kneaded in a polybutadiene rubber at 60 to 130 ° C., only zinc dimethacrylate is formed. Have been. JP-A-58-101131 discloses that when methacrylic acid and zinc oxide are reacted in a polybutadiene rubber, zinc dimethacrylate is formed by the presence of a calcium salt of methacrylic acid. It is disclosed that a vulcanized rubber having resilience can be obtained. However, these prior arts all relate to golf balls, and the target rubber is mainly polybutadiene rubber. The methods disclosed in these prior art documents are for imparting a high coefficient of restitution to a golf ball, and the recognition regarding high strength and the recognition regarding ethylenically unsaturated nitrile-conjugated diene copolymer rubber are not disclosed. Absent. The present inventors have developed a vulcanizable rubber composition which exhibits high strength characteristics stably without being affected by the manufacturing conditions, and have already filed an application for this (Japanese Patent Application No. 5-9).
No. 7158). However, such a rubber composition needs to be further improved in terms of mold releasability during vulcanization molding. As a technique for improving the mold releasability, it is known to incorporate a higher fatty acid such as stearic acid (Japanese Patent Application Laid-Open No. 4-298546). There are problems such as lowering. SUMMARY OF THE INVENTION An object of the present invention is to improve mold releasability during vulcanization molding, and to obtain a stable and high strength property without being affected by manufacturing conditions such as kneading temperature. An object of the present invention is to provide a vulcanizable rubber composition exhibiting strength characteristics. The present inventors have conducted intensive studies and found that a zinc compound uniformly dispersed in an ethylenically unsaturated nitrile-conjugated diene copolymer rubber and an α, β-ethylenically unsaturated carboxylic acid were reacted in a kneader. By adding calcium oxide and / or calcium hydroxide to the composition and further adding a specific compounding compound for rubber, excellent mold releasability is obtained, and the production condition such as kneading temperature is affected. not,
The inventors have found that a vulcanizable rubber composition having excellent strength properties can be obtained stably, and based on these findings, have completed the present invention. Thus, according to the present invention, (a) a zinc compound and (b) α, β-ethylene are added to an ethylenically unsaturated nitrile-conjugated diene copolymer rubber. At least one compound selected from the group consisting of an unsaturated carboxylic acid, (c) a compound of a Group 2A metal of the periodic table, (d) a quinone-based compound, a tyrium-based compound, a thiazole-based compound, and a nitrosamine-based compound; e) A vulcanizable rubber composition characterized by comprising an organic peroxide is provided. Hereinafter, the present invention will be described in detail. Examples of the ethylenically unsaturated nitrile-conjugated diene copolymer rubber used in the present invention include acrylonitrile, methacrylonitrile, ethylenically unsaturated nitriles such as α-chloroacrylonitrile, and 1,3-butadiene, isoprene, and 1,3-butadiene.
Copolymer rubbers with conjugated dienes such as 3-pentadiene and 2,3-dimethyl-1,3-butadiene; hydrogenated copolymer rubbers obtained by hydrogenating conjugated diene units of these copolymer rubbers;
Two kinds of monomers, ethylenically unsaturated nitrile and conjugated diene, and monomers copolymerizable therewith, for example, vinyl aromatic compound, ethylenically unsaturated carboxylic acid alkyl ester, ethylenically unsaturated carboxylic acid alkoxy Multi-component copolymer rubbers with at least one kind of alkyl ester, ethylenically unsaturated carboxylic acid fluoroalkyl ester, (meth) acrylate cyano-substituted alkyl ester; hydrogenated copolymer obtained by hydrogenating conjugated diene units of these multi-component copolymer rubbers Polymerized rubber; and the like. Specific examples include acrylonitrile-butadiene copolymer rubber (NBR), acrylonitrile-butadiene-isoprene copolymer rubber (NBIR), acrylonitrile-isoprene copolymer rubber (NIR), acrylonitrile-butadiene-acrylate copolymer rubber, acrylonitrile Hydrogenated copolymer rubbers such as -butadiene-acrylic acid copolymer rubber, acrylonitrile-butadiene-acrylate-methacrylic acid copolymer rubber, and hydride of acrylonitrile-butadiene copolymer rubber (HNBR). Can be These copolymer rubbers can be used alone or in combination of two or more. These copolymer rubbers usually contain an ethylenically unsaturated nitrile unit in a polymer chain in a proportion of 10 to 60% by weight, preferably 20 to 50% by weight. If the content of the ethylenically unsaturated nitrile unit is less than 10% by weight, the oil resistance is not sufficient, and if it exceeds 60% by weight, the elasticity decreases, which is not preferable. Of these, highly saturated rubber obtained by hydrogenating acrylonitrile-butadiene copolymer rubber is preferred. In this case, the amount of bound acrylonitrile is 10 to 60% by weight, the iodine value is 80 or less, and the Mooney viscosity is 50 to 150. Examples of the zinc compound include zinc oxide,
Zinc carbonate, zinc hydroxide and the like can be mentioned. The α, β-ethylenically unsaturated carboxylic acids include unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, crotonic acid and 3-butenoic acid; unsaturated dicarboxylic acids such as maleic acid, fumaric acid and itaconic acid. Acids; monoesters of unsaturated dicarboxylic acids such as monomethyl maleate, monomethyl fumarate, monomethyl itaconate; unsaturated polycarboxylic acids other than those described above; unsaturated polycarboxylic acids leaving at least a monovalent free carboxyl group And the like. Among these, methacrylic acid is particularly preferred from the viewpoint of physical properties and availability. The zinc salt of an α, β-ethylenically unsaturated carboxylic acid is prepared by adding a zinc compound and an α, β-ethylenically unsaturated carboxylic acid to an ethylenically unsaturated nitrile-conjugated diene copolymer rubber. It is produced by reacting in situ in a copolymer rubber. In this case, as a zinc compound, coarse particles having a particle size of 20 μm or more are removed in advance by classification, and a content of the coarse particles of 5% by weight or less is used. Is preferred in improving the strength characteristics of the steel. The mixing ratio of the zinc compound is 10 to 60 parts by weight based on 100 parts by weight of the ethylenically unsaturated nitrile-conjugated diene copolymer rubber. The mixing ratio of the α, β-ethylenically unsaturated carboxylic acid is 20 to 60 parts by weight based on 100 parts by weight of the ethylenically unsaturated nitrile-conjugated diene copolymer rubber. The molar ratio of the α, β-ethylenically unsaturated carboxylic acid to the zinc compound calculated on the basis of the molecular weight of the α, β-ethylenically unsaturated carboxylic acid and the formula weight of the zinc compound is usually 1: 0. 5-1: 3.2,
Preferably it is in the range of 1: 0.5 to 1: 2.5. In the present invention, a vulcanizable rubber composition capable of providing a vulcanized rubber having significantly improved tensile stress can be obtained by blending a compound of a Group 2A metal of the periodic table. Further, by compounding the compound of Group 2A metal of the periodic table, a vulcanizable rubber composition capable of providing a vulcanized rubber having a high strength stably and appropriately without changing the strength characteristics depending on manufacturing conditions such as a kneading temperature. You can get things. The compounds of Group 2A metals of the periodic table used in the present invention include beryllium, magnesium, calcium,
Oxides, hydroxides, peroxides, carbonates, carbonates, carbonates, sulfates, nitrates, acetates, oxalates, phosphinates of Group 2A metals such as strontium and barium; Phosphonates, phosphates, hydrogen phosphates, ammonium salts and the like can be mentioned. Specific examples of the above compounds include beryllium compounds, such as beryllium oxide, beryllium carbonate, and beryllium nitrate;
Magnesium oxide, magnesium hydroxide, magnesium peroxide, magnesium carbonate, magnesium carbonate hydroxide,
Magnesium sulfate, magnesium nitrate, magnesium acetate, magnesium oxalate, magnesium phosphinate, magnesium phosphonate, magnesium phosphate, magnesium hydride phosphate, ammonium magnesium phosphate and the like; calcium compounds include calcium oxide,
Calcium hydroxide, calcium peroxide, calcium carbonate, calcium sulfate, calcium nitrate, calcium acetate, calcium oxalate, calcium phosphonate, calcium phosphate, etc .; as the strontium compound, strontium oxide, strontium hydroxide, strontium peroxide, strontium carbonate, Strontium sulfate,
Strontium nitrate, strontium acetate, strontium oxalate, strontium phosphate, etc .; barium compounds include barium oxide, barium hydroxide, barium peroxide, barium carbonate, barium sulfate, barium nitrate, barium acetate, barium oxalate, phosphinic acid Barium, barium phosphonate, barium phosphate and the like can be mentioned. A mixture of two or more of these can be mentioned. Among these metal compounds, oxides and hydroxides of magnesium and alkaline earth metals are preferred. In particular, when magnesium oxide and magnesium hydroxide are used, a vulcanized rubber having significantly improved tensile stress can be obtained. When using calcium oxide and calcium hydroxide, strength properties such as tensile strength,
A high-strength vulcanized rubber can be stably obtained without being changed by production conditions such as kneading. Therefore, it is preferable to select these metal compounds or use a combination of two or more of them according to the purpose of use and the desired physical properties of the vulcanized rubber. The compound of Group 2A metal of the periodic table is usually 0.5 to 30 parts by weight, preferably 0.1 to 30 parts by weight, based on 100 parts by weight of the ethylenically unsaturated nitrile-conjugated diene copolymer rubber.
It is 5 to 20 parts by weight, more preferably 1 to 10 parts by weight. If the compounding ratio is too small, the effect of improving the tensile stress is small, and if it is too large, the strength characteristics tend to decrease. When alkaline earth metal compounds such as calcium oxide and calcium hydroxide are used, it is preferable to add 2 parts by weight or more in order to stably obtain a high-strength vulcanized rubber. The vulcanizable rubber composition of the present invention dramatically improves the mold releasability during vulcanization molding by blending a specific compound among those known as rubber compounding chemicals. Is done. Compounds to be used include quinone compounds, tyrium compounds, thiazole compounds, and nitrosamine compounds. Each of these alone,
Alternatively, two or more kinds can be used in combination. Specific examples of the compound are as follows. Examples of the quinone-based compound include those in which the hydrogen atoms at positions 2, 3, 5, and 6 of p-benzoquinone are each independently substituted with a halogen, a phenyl group or an alkyl group. Specific examples include p-benzoquinone; 2,5-diphenyl-p-benzoquinone,
Dichloro-p-benzoquinone, 2,5-dibromo-p-
Benzoquinone, 2,5-difluoro-p-benzoquinone, 2,3,5,6-tetraphenyl-p-benzoquinone, 2,3,5,6-tetrachloro-p-benzoquinone, 2,3,5,6- Tetrabromo-p-benzoquinone, 2,3,5,6-tetrafluoro-p-benzoquinone; methyl-p-benzoquinone, 2,5-dimethyl-p
-Benzoquinone, 2,5-dibutyl-p-benzoquinone and the like. Examples of the tyrium-based compound include compounds having an alkyl group having 1 to 5 carbon atoms in the molecule. Specific examples include tetramethyl thiuram disulfide, tetraethyl thiuram disulfide, tetrabutyl thiuranium disulfide, and the like. As the thiazole compound, for example,
2,2'-dithiobis (benzothiazole), 2-mercaptobenzothiazole, zinc salt of 2-mercaptobenzothiazole, cyclohexylamine salt of 2-mercaptobenzothiazole, 2- (2 ', 4'-dinitrophenylthio) benzothiazole , 2- (N, N-diethylthiocarbamoylthio) benzothiazole, 2- (4'-
Morpholinodithio) benzothiazole and the like. Examples of the nitrosamine-based compound include N-nitrosodiphenylamine and N-nitrosodimethylamine. One or more of these compounds are used, and usually 0.05 to 5 parts by weight, preferably 0.1 to 5 parts by weight, per 100 parts by weight of the ethylenically unsaturated nitrile-conjugated diene copolymer rubber. It is used at a ratio of 1 to 3 parts by weight, and an optimum amount can be appropriately selected. The organic peroxide used in the present invention includes:
For example, dicumyl peroxide, di-t-butyl peroxide, t-butylcumyl peroxide, benzoyl peroxide, 2,5-dimethyl-2,5- (t
-Butylperoxy) hexyne-3,2,5-dimethyl-2,5-di (benzoylperoxy) hexane,
5-dimethyl-2,5-mono (t-butylperoxy)
Hexane, α, α'-bis (t-butylperoxy-m
-Isopropyl) benzene and the like. These organic peroxides are used alone or in combination of two or more, and are usually used in an amount of 0.2 to 10 parts by weight based on 100 parts by weight of the ethylenically unsaturated nitrile-conjugated diene copolymer rubber.
It is used in an amount of 0.5 parts by weight, preferably 0.5 to 8 parts by weight, and an optimum amount can be appropriately selected depending on required physical properties. In order to mix each component, usually, an ethylenically unsaturated nitrile-conjugated diene copolymer rubber, a zinc compound, an α, β-ethylenically unsaturated carboxylic acid, a periodic table 2A
Group metal compound and quinone compound, etc., kneaded by a roll, Banbury, kneader, twin screw extruder, etc.,
At a temperature at which the organic peroxide does not decompose, the organic peroxide is added and kneaded. The obtained vulcanized rubber composition is molded into a desired shape and then vulcanized by heating. Zinc compounds and α, β-
It is considered that the ethylenically unsaturated carboxylic acid reacts at the stage of preparing the vulcanizable rubber composition to form a zinc salt of an α, β-ethylenically unsaturated carboxylic acid. The vulcanizable rubber composition of the present invention may optionally contain reinforcing agents such as carbon black and silica, fillers such as calcium carbonate and talc, triallyl isocyanurate, trimethylolpropane triacrylate, and m-phenylene. Various additives commonly used in the rubber industry, such as a crosslinking aid such as bismaleimide, a plasticizer, a stabilizer, a vulcanization aid, and a coloring agent can be blended. EXAMPLES Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to only these Examples. Parts and% in Examples and Comparative Examples are based on weight unless otherwise specified. Examples 1 to 21 and Comparative Examples 1 to 14 Rubber compositions having the formulation shown in Tables 1 to 3 except for the organic peroxide were prepared by a kneader. The organic peroxides shown in Tables 1 to 3 were added thereto at a temperature at which the organic peroxides did not decompose, and further, quinone compounds and the like were added to prepare vulcanizable rubber compositions. Next, the obtained vulcanizable rubber composition was press-vulcanized under vulcanization conditions of 170 ° C. for 20 minutes,
A 1 mm thick vulcanized sheet was obtained. Using this sheet,
The vulcanization properties (JIS K-6301) such as tensile strength (T _B ), elongation (E _B ), and 100% modulus (M ₁₀₀ ) were measured, and the mold releasability was further evaluated. Table 1 shows the results.
~ Shown in Table 3. [Table 1] [Table 2] [Table 3] The method for evaluating the mold releasability is as follows. A test piece having a length of about 150 mm, a width of about 80 mm, and a thickness of about 2 mm is prepared from the unvulcanized rubber composition. This one
It is sandwiched between 50 × 80 × 2 mm sheet molds. After press vulcanization at 180 ° C. under a pressure of 100 kg / cm ³ for 10 minutes, the vulcanized rubber is pulled and its maximum peeling force is read. This operation is performed five times, and the average value is defined as the peel strength. The stain on the surface of the mold after repeated 5 times (the state of mold contamination by the adhered rubber and the rubber compounding agent) is visually determined. ◎: No dirt ○: Almost no dirt △: Dirt x: Dirt is severe [0045] The polymers in Tables 1 to 3 are as follows. HNBR: hydrogenated NBR; Zetpo manufactured by Zeon Corporation
l 2020 Bound acrylonitrile amount 36%, hydrogenation rate 90%, iodine value 28 MAA: Mitsubishi Rayon Co., Ltd. ZnO methacrylate: Shodo Chemical Co., Ltd. No. 1 zinc white (content of coarse particles having a particle diameter of 20 μm or more is 5 wt. % Peroxide: Peroximon F-40 manufactured by NOF Corporation; α,
α'-bis (t-butylperoxy-m-isopropyl) benzene (40% product) From Tables 1 to 3, the rubber composition of the present invention may contain various additives such as quinone compounds. By
It can be seen that the mold releasability is greatly improved. That is, when a calcium compound, a quinone-based compound, and the like are blended (Examples 1 to 13), over a wide range of composition,
A high-strength vulcanized rubber can be obtained, the peel strength is greatly reduced, and the mold fouling property is good. Similarly, when a magnesium compound and a quinone-based compound are blended (Examples 14 to 21), a vulcanized rubber having a particularly wide range of compositions and particularly high stress is obtained, and the peel strength is greatly reduced. Good mold contamination. On the other hand, when a conventionally used release agent such as a higher fatty acid metal salt such as sodium stearate or silicone is blended (Comparative Examples 1 to 4, 7, and 8).
Can reduce the peel strength, but does not improve the mold stainability. In addition, when the release agent was not used (Comparative Examples 5 to 7), it was found that the peel strength was extremely high and the mold stain was poor. The specific embodiments of the present invention are as follows. (Claim 1) A zinc compound (a) with respect to an ethylenically unsaturated nitrile-conjugated diene copolymer rubber,
Selected from the group consisting of (b) α, β-ethylenically unsaturated carboxylic acids, (c) compounds of Group 2A metals of the Periodic Table, (d) quinone compounds, tyrium compounds, thiazole compounds, and nitrosamine compounds. A vulcanizable rubber composition comprising at least one compound and (e) an organic peroxide. (1) With respect to 100 parts by weight of ethylenically unsaturated nitrile-conjugated diene copolymer rubber, (a) zinc compound 5 to 80
Parts by weight, (b) α, β-ethylenically unsaturated carboxylic acid 5
To 100 parts by weight, (c) a compound of a metal of Group 2A of the periodic table.
5 to 30 parts by weight, (d) at least one compound selected from the group consisting of quinone-based compounds, tyrium-based compounds, thiazole-based compounds, and nitrosamine-based compounds.
2. The vulcanizable rubber composition according to claim 1, wherein said vulcanizable rubber composition comprises from 0.5 to 5 parts by weight and (e) 0.2 to 10 parts by weight of an organic peroxide. (2) With respect to 100 parts by weight of the ethylenically unsaturated nitrile-conjugated diene copolymer rubber, (a) zinc compound 10 to 6
0 parts by weight, (b) 20 to 60 parts by weight of an α, β-ethylenically unsaturated carboxylic acid, (c) 0.5 to 20 parts by weight of a compound of Group 2A metal of the periodic table, (d) quinone-based compound, tyrium-based At least one compound selected from the group consisting of a compound, a thiazole compound and a nitrosamine compound, in an amount of 0.1 to 3 parts by weight, and (e) 0.2 to 10 parts by weight of an organic peroxide. The vulcanizable rubber composition according to claim 1. (3) The compound of Group 2A metal of the periodic table is an oxide, hydroxide, peroxide, carbonate, carbonate,
Carbonate hydroxide, sulfate, nitrate, acetate, oxalate,
The vulcanizable rubber composition according to claim 1, which is a phosphinate, a phosphonate, a phosphate, a hydrogen phosphate or an ammonium salt. (4) The vulcanizable rubber composition according to claim 1, wherein the compound of the Group 2A metal of the periodic table is at least one magnesium compound selected from the group consisting of magnesium oxide and magnesium hydroxide. (5) The vulcanizable rubber composition according to claim 1, wherein the compound of Group 2A metal of the periodic table is at least one calcium compound selected from the group consisting of calcium oxide and calcium hydroxide. (6) The vulcanizable rubber composition according to claim 1, which is a rubber material for sealing. According to the present invention, an ethylenically unsaturated nitrile-conjugated diene copolymer rubber is used as a rubber material, the mold releasability is good, and the strength depends on the production conditions such as the kneading temperature. There is provided a vulcanizable rubber composition which exhibits stable high-strength properties without being affected by the properties. The vulcanized rubber composition of the present invention is not limited to sealing materials such as packing, gaskets, O-rings and the like, which are required to have strength properties and mold releasability, and are further suitable for rolls, belts, hoses and the like. Useful as a rubber material.

──────────────────────────────────────────────────続 き Continued on front page (51) Int.Cl. ⁷ Identification code FI C08K 5/32 C08K 5/32 5/47 5/47

Claims (1)

(57) [Claims] 1. An ethylenically unsaturated nitrile-conjugated diene copolymer rubber, (a) a zinc compound, (b) α,
at least one selected from the group consisting of β-ethylenically unsaturated carboxylic acids, (c) compounds of Group 2A metals of the periodic table, (d) quinone compounds, tyrium compounds, thiazole compounds, and nitrosamine compounds. A compound of
(E) A vulcanizable rubber composition comprising an organic peroxide.