JPH06313066A - Process for preventing premature vulcanization of rubber - Google Patents

Abstract

PURPOSE:To suppress premature vulcanization of a rubber in the crosslinking of the rubber with an organic peroxide without deteriorating the physical properties of the vulcanized rubber. CONSTITUTION:Premature vulcanization in the crosslinking of a rubber with an organic peroxide is suppressed by carrying out the crosslinking in the presence of a sulfidized phenolic resin and/or sulfidized alkylphenolic resin. The amount of the sulfidized phenolic resin and/or sulfidized alkylphenolic resin is 0.1-5.0 pts.wt. (preferably 0.5-2.0 pts.wt.) based on 100 pts.wt. of the rubber.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for suppressing early vulcanization in rubber organic rubber crosslinking. The method of crosslinking a rubber with an organic peroxide has been used for a long time because a vulcanized rubber having heat resistance and low compression set can be obtained.
Since the cross-linking structure by the organic peroxide is a carbon-carbon cross-link, it is said that the tensile strength and tear strength are low and the dynamic properties are inferior as compared with sulfur cross-linking which is a general rubber vulcanization method. ing. Therefore, practically, a co-crosslinking agent is often used in combination for the purpose of improving the physical properties of the crosslinked product by the organic peroxide.

Examples of co-crosslinking agents include sulfur, polyfunctional monomers, metal salts of methacrylic acid or acrylic acid, and dioximes. When co-crosslinking agents other than sulfur are used in combination, vulcanization starts. Faster and premature vulcanization of rubber is often a problem. Further, even in the absence of the co-crosslinking agent, early vulcanization remains a problem. Suppressing early vulcanization of rubber is an important problem because it prevents material loss due to burning (scorch) in the processing step and reduces product defects.

[0003]

2. Description of the Related Art 2,2'-Methylenebis (4
It is generally known to add a small amount of an antioxidant such as -methyl-6-tert-butylphenol). However, although this method has an effect of suppressing early vulcanization,
Undesirable and useful anti-scorch agents have not yet been developed because they significantly reduce the degree of crosslinking and also adversely affect compression set.

[0004]

DISCLOSURE OF THE INVENTION It is an object of the present invention to provide a method for suppressing premature vulcanization when the rubber is crosslinked with an organic peroxide, without impairing the physical properties of the vulcanized rubber. To aim.

[0005]

The present invention is a method for inhibiting early vulcanization of a rubber in which a sulfurized phenol resin and / or a sulfurized alkylphenol resin is allowed to coexist when the rubber is crosslinked with an organic peroxide. By adding this resin, early vulcanization can be prevented without impairing the physical properties of the vulcanized rubber.

The sulfurized phenol resin and sulfurized alkylphenol resin are synthesized by the reaction of phenol or alkylphenol and sulfur. Examples of sulfurized alkylphenol resins include sulfurized-p-tert-butylphenol resins. The addition amount of the sulfurized phenol resin and / or the sulfurized alkylphenol resin according to the present invention is 0.1 to 5.0 parts by weight, preferably 0.5 to 2.0 parts by weight, relative to 100 parts by weight of rubber. Is.

Sulfurized phenolic resin according to the present invention and /
Or, as a crosslinking agent for an organic peroxide applicable when using a sulfurized alkylphenol resin, for example, dicumyl peroxide, 1,1-di-tert-butylperoxy-3,3,5-trimethylcyclohexane, di- ( tert
-Butylperoxyisopropyl) benzene, 2,5-
Examples include dimethyl-2,5-di (tert-butylperoxy) hexane and benzoyl peroxide.

In this compounding system, as a co-crosslinking agent, for example, a polyfunctional monomer such as trimethylolpropane trimethacrylate or ethylene dimethacrylate, a metal salt of methacrylic acid or acrylic acid, or a functional group of 1,2-polybutadiene is used. It is possible to blend a polyfunctional polymer, a sulfur-containing compound, etc.

In addition to this compounding system, compounding agents known in the ordinary rubber industry, such as fillers such as metal oxides such as zinc oxide and magnesium oxide, calcium carbonate, silica and carbon black, or Reinforcing agents, paraffin-based, naphthene-based or aromatic processing oils and other softeners,
Various higher fatty acids such as stearic acid, colorants and pigments, antiaging agents, various compounding agents such as UV absorbers and the like can be blended as necessary.

The compounding of various compounding agents according to the present invention with rubber is prepared by mixing them with a conventionally used mixer such as an open roll for rubber kneading, a Banbury mixer, or a pressure kneader.

[0011]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto.

Example 1 According to the formulation shown in Table 1, they were mixed by a conventional method,
A rubber composition was obtained. The compounded rubber was subjected to the Mooney scorch test according to JIS K6300, and the vulcanization behavior was measured using a rheometer. A vulcanized sample of the compounded rubber composition was subjected to a tensile test, a heat aging test, a compression set test, and a tear test according to JIS K6301. Among the results, Examples are shown in Table 3 and Comparative Examples are shown in Table 2.

In Table 1, Mitsui EPT3045 is a product name of EPDM manufactured by Mitsui Petrochemical Co., Ltd., Park Mill D.
-40 is the trade name of dicumyl peroxide manufactured by NOF CORPORATION, Sunester TMP is the trade name of trimethylolpropane trimethacrylate manufactured by Sanshin Chemical Industry Co., Ltd., and Sunester SK-30 is methacryl manufactured by Sanshin Chemical Industry Co., Ltd. Zandate 2246, a trade name of zinc oxide, is 2,2'-methylenebis (4-methyl-6) manufactured by Sanshin Chemical Industry Co., Ltd.
-Tert-butylphenol).

[0014]

[Table 1]

[0015]

[Table 2]

[0016]

[Table 3]

Example 2 According to the compounding recipes shown in Tables 4 and 5, mixing was carried out by an ordinary method to obtain a rubber composition. The vulcanization behavior of the compounded rubber was measured using a rheometer, and the results are shown in Tables 4 and 5. In Table 4, Zetpol 2020 is the product name of H-NBR manufactured by Nippon Zeon Co., Ltd., and in Table 5, Skyprene B-
30 is the trade name of non-sulfur-modified chloroprene rubber manufactured by Tosoh Corporation.

[0018]

[Table 4]

[0019]

[Table 5]

[0020]

According to the method of the present invention, when the rubber is cross-linked with the organic peroxide, the early vulcanization can be suppressed without deteriorating the physical properties of the vulcanized rubber.

Claims (1)

[Claims] 1. A method for inhibiting early vulcanization of a rubber, wherein a sulfurized phenol resin and / or a sulfurized alkylphenol resin is allowed to coexist when the rubber is crosslinked with an organic peroxide.