JPH0733456B2 - Vulcanizable rubber compound with excellent storage stability - Google Patents

Description

TECHNICAL FIELD The present invention relates to a vulcanizable rubber compound having excellent storage stability. More specifically, the present invention relates to a vulcanizable rubber composition having improved storage stability of a crosslinkable group-containing elastomer containing a vulcanization accelerator.

[Prior Art] and [Problems to be Solved by the Invention] Elastomer containing a carboxyl group as a crosslinkable group, glycidyl group-containing polyepoxy compound vulcanizing agent and water in the range of 10 ⁻¹² to 10 ³ at 25 ° C. Dissociation constant (Kb)
And a vulcanizable rubber composition containing a vulcanization accelerator which is a base or a conjugated base that does not cause cross-linking by a reaction with the cross-linkable group of the elastomer, and is described in JP-B-60-8007. ing. This vulcanizable rubber compound gives an excellent vulcanized product in terms of vulcanized physical properties, heat aging resistance and compression set, but it is preserved in the state of a compounded compound containing a vulcanizing agent and a vulcanization accelerator. Improved stability is desired.

Therefore, as a result of various investigations aimed at improving this point, the present inventors have found that triazine thiols mainly used as a cross-linking agent for halogen-containing polymer substances (elastomer and resin) (JP-A-58-58). 180539,
No. 54-23651, No. 51-23553, U.S. Pat.
It has been previously found that such problems can be effectively solved by using (for example, JP 804,450) as a stabilizer (JP-A-63-172748). It has been found that such a solution can be applied not only to an elastomer containing a carboxyl group as a crosslinkable group but also to an elastomer containing a carboxyl group and an epoxy group as a crosslinkable group.

[Means for solving problems]

Therefore, the present invention provides a vulcanizable rubber composition having excellent storage stability, which comprises (1) an elastomer containing an epoxy group as a crosslinkable group, (2) water at 25 ° C. within a range of 10 ⁻¹² to 10 ³ . Vulcanization accelerator and (3) triazine thiol stabilizer which are bases or conjugated bases having a base dissociation constant (Kb) of 3 and not causing cross-linking by the reaction with the cross-linkable group of the elastomer. .

As the elastomer containing a carboxyl group and an epoxy group, a copolymer obtained by copolymerizing a small amount (about 0.1 to 10% by weight) of a carboxyl group-containing monomer and an epoxy group-containing monomer is used.

As the carboxyl group-containing monomer, for example, acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, monoalkyl maleate and the like are used. As the epoxy group-containing monomer, for example, glycidyl (meth) acrylate, vinyl glycidyl ether, allyl glycidyl ether, methacryl glycidyl ether, etc. are used.

Each of these crosslinkable group-containing monomers includes vinyl chloride, vinylidene chloride, (meth) acrylonitrile, styrene, divinylbenzene, vinyl acetate, alkyl vinyl ether,
It is copolymerized with at least one of various monomers such as alkyl acrylate, alkyl methacrylate, alkoxyalkyl acrylate, (poly) ethylene glycol diacrylate, hydroxyalkyl acrylate, acrylamide, α-olefin, and conjugated diene.

Since these copolymers contain a carboxyl group and an epoxy group in the molecule, they are vulcanized by self-crosslinking by the reaction of these crosslinkable groups without using a vulcanizing agent.

The base or conjugated base used as a vulcanization accelerator has a base dissociation constant (Kb) in the range of 10 ^-12 to 10 ³ at 25 ° C in water and is crosslinked by a reaction with the crosslinkable group of the above elastomer. That does not give rise to quaternary ammonium salts, specifically quaternary ammonium salts, quaternary phosphonium salts, alkali metal salts of organic weak acids, guanidines and their weak acid salts, 2-, 3- or 4-substituted urea derivatives, aminopyridines and At least one of the weak acid salt, amine imides, cyclic amidines and the weak acid salt or nitrone is generally used in a ratio of about 0.1 to 10 parts by weight per 100 parts by weight of the elastomer.

A more detailed description of base and conjugated base vulcanization accelerators is given in Japanese Examined Patent Publication No. 60-8007.

Examples of the triazine thiols used as a stabilizer in the vulcanizable rubber composition according to the present invention include triazine trithiol, triazine dithiol, triazine monothiol and partial thioesters thereof, partial epoxy reaction products, and the like, and the elastomer 100 is generally used. It is used in an amount of about 0.01 to 1 part by weight, preferably about 0.05 to 0.5 part by weight. When used in a proportion higher than this, the compression set of the obtained vulcanized rubber will increase,
On the other hand, if the usage ratio is less than this, the object of the present invention cannot be achieved.

The vulcanizable rubber compound is prepared by the above-mentioned essential components and other additives such as a reinforcing agent, a filler, an antiaging agent optionally added, another stabilizer, a plasticizer, a lubricant, and a processing agent. The auxiliaries and the like are mixed by a commonly used mixing method, for example, roll mixing, Banbury mixing, solution mixing, or the like, and the mixture is heated to a heating temperature according to the type of elastomer used. Is vulcanized by.

〔The invention's effect〕

The value of t ₅ which is a physical property value showing the storage stability of the elastomer is measured as Mooney scorch t ₅ within 1 to 24 hours after kneading the rubber, and the storage stability of 6 to 35 minutes is good. In the vulcanizable rubber composition according to the present invention, the scorch time does not change with time when the triazine thiols are not added to the vulcanizable rubber composition according to the present invention. While the triazinethiols are used, the change in scorch time with time is small and the desirable physical properties of the elastomer are not substantially impaired. The present invention has an effect of obtaining a sulfide.

〔Example〕

 Next, the present invention will be described with reference to examples.

Example 1 A copolymer obtained by emulsion polymerization of 97 parts of ethyl acrylate (weight, the same applies hereinafter), 2.5 parts of allyl glycidyl ether and 0.5 part of methacrylic acid in the presence of a redox polymerization initiator (Moonie viscosity ML _{1 +4} , 100 ° C: 46.5) 100
Parts, 50 parts of FEF carbon black, 0.6 parts of urea, 2 parts of cetyltrimethylammonium bromide and 0.15 part of triazine trithiol (2,4,6-trimercapto- _S -triazine) were kneaded with an 8-inch open roll.

The Mooney scorch time (t _S ) of the obtained compound was measured (measured at 121 ° C. using SMV-200 manufactured by Shimadzu Corporation).
The Mooney scorch time was measured after leaving it in a thermo-hygrostat at 50 ° C and 50% RH for 8 days.

The compound was press-vulcanized at 170 ° C. for 10 minutes, and then post-vulcanized in a gear oven at 175 ° C. for 4 hours. With respect to the obtained vulcanized product, various vulcanized properties and compression set (150 ° C., 70 hours) were measured according to JIS K-6301. Further, this vulcanized product was subjected to a heat aging test under conditions of 175 ° C. and 70 hours, and changes in various vulcanized physical properties were measured.

Example 2 In Example 1, the amount of triazine trithiol used was
Changed to 0.3.

Example 3 In Example 1, instead of triazine trithiol,
0.2 part of Triazine DB (6-dibutylamino-1,3,5-triazine-2,4-dithiol) was used.

Comparative Example In Example 1, no triazine trithiol was used.

The measurement results in each of the above Examples and Comparative Examples are shown in the following table.

Claims (1)

[Claims] (1) 100 parts by weight of an elastomer containing a carboxyl group and an epoxy group as a crosslinkable group,
(2) A base or conjugated base which has a base dissociation constant (Kb) in the range of 10 ^-12 to 10 ³ at 25 ° C. in water and does not cause cross-linking by reaction with the cross-linkable group of the elastomer. Quaternary ammonium salt, quaternary phosphonium salt, alkali metal salt of weak organic acid, guanidines and weak acid salts thereof,
0.1-10 parts by weight of a vulcanization accelerator comprising at least one of 2-, 3- or 4-substituted urea derivatives, aminopyridines and weak acid salts thereof, amineimides, cyclic amidines and weak acid salts thereof, or nitrone, and (3) A vulcanizable rubber compound containing 0.01 to 1 part by weight of a triazine thiol stabilizer and having excellent storage stability.