JPS61223048A - Vulcanized rubber composition - Google Patents

Abstract

PURPOSE:The vulcanized rubber composition suitable especially as rubber parts for automobiles, having improved molding properties and high mechanical strength, obtained by blending ethylene propylene rubber with a specific reactive rubber compounding oil. CONSTITUTION:(A) 100pts.wt. paraffin process oil having preferably 0.86-0.92 (15/4 deg.C) specific density, 5-800cSt (40 deg.C) kinematic viscosity, and 70-145 deg.C aniline point, especially preferably secondary hydrogenated oil, is heated to 60-120 deg.C, blended with (B) 0.5-5pts.wt. peroxide, preferably dicumyl peroxide having 120-180 deg.C half-life temperature, cooled to room temperature, mixed with (C) 5-30pts.wt. acrylic acid alkyl ester and/or methacrylic acid alkyl ester, preferably (meth)acrylic acid methyl ester to give a reactive rubber compounding oil. 100pts.wt. ethylene propylene rubber is blended with 30-200pts. wt. of the reactive rubber compounding oil, kneaded, and mixed with sulfur and a vulcanization promoter by open rolls.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a vulcanized rubber composition, and more particularly to a vulcanized rubber composition that has excellent moldability and high mechanical strength.

[Technical background of the invention and its problems] A method of manufacturing a vulcanized rubber composition by blending a paraffinic, naphthenic or aromatic process oil with an ethylene propylene rubber elastomer is known (Tokuko Sho et al. 58-48217).

Also known is a copolymer obtained by graft polymerizing an acrylic monomer to the above elastomer (Japanese Patent Publication No. 80-3
No. 411, JP-A-52-42591.

(See Japanese Patent Application Laid-Open No. 128757/1983).

However, the vulcanized rubber composition obtained by the above method,
All are hardness, tensile modulus, and breaking strength.

Mechanical strength such as elongation at break does not have a sufficient value, and moldability when molded into a molded product is poor.

Therefore, these vulcanized rubber compositions can be used for everyday miscellaneous goods, materials,
Although it has some usefulness in various fields of use such as packaging materials and containers, it is not necessarily a useful material in fields where it is used under harsh conditions, such as rubber parts for automobiles.

[Object of the invention] The present invention solves the above-mentioned problems with conventional vulcanized rubber compositions, has excellent moldability, and above all, has high mechanical strength and can be used even under harsh conditions. The purpose of the present invention is to provide a vulcanized rubber composition capable of

[Summary of the Invention] In order to achieve the above object, the present inventors have conducted intensive research on the properties and compounding relationships of each component constituting a vulcanized rubber composition, and have found that the rubber compounding oil described below can be used as a process oil. Discovered the fact that a rubber composition with high mechanical strength can be obtained without deteriorating moldability when blended in a fixed amount,
The vulcanized rubber composition of the present invention has been developed.

That is, the vulcanized rubber composition of the present invention contains 1 part by weight of ethylene propylene rubber and 3 parts of reactive rubber compounding oil.
It is characterized by containing 0 to 200 parts by weight.

This reactive rubber compounding oil essentially contains three components: paraffinic process oil, peroxide, alkyl acrylate and/or alkyl methacrylate, and the blending amount of each is 100% of paraffinic process oil.
It is composed of 0.5 to 5 parts by weight of peroxide and 5 to 30 parts by weight of the above-mentioned ester.

Among these, paraffinic process oil is the base oil for the reactive rubber compounding oil according to the present invention.

Those having the physical properties shown in Table 1 are extremely suitable.

Table 1 Among these physical properties, specific gravity, kinematic viscosity, and 7-nilin point are important factors.For example, oils with specific gravity greater than the upper limit in Table 1 are highly aromatic oils with a CA value of 30% or more. (The kinematic viscosity at 40°C is 20 centimeters) - If the weather resistance is lower than the lower limit, the kinematic viscosity is 20 centimeters).
Oils larger than 0 cSt (40°C) have too high a viscosity, making it difficult to blend uniformly into ethylene propylene rubber, and oils smaller than 5 cSt (5°C) result in increased bleeding in the resulting vulcanized rubber composition. . Furthermore, oils with an aniline point higher than 145°C will have lower compatibility with ethylene propylene rubber and will also increase bleeding, while oils with an aniline point lower than 70°C will have a negative effect on the properties of the resulting vulcanized rubber composition, such as a decrease in weather resistance. I don't like inviting people.

Among these paraffinic process oils, secondary hydrogenated oils such as Diana Process Oil PIi 1380 (trade name, manufactured by Idemitsu Kosan Co., Ltd.) are particularly suitable.

Finally, peroxide is a polymerization initiator for graft polymerizing acrylic acid ester or methacrylic acid ester blended in this reactive rubber compounding oil onto rubber molecules. This results in crosslinking between rubber molecules via acid esters or methacrylic esters.

The peroxide is one that can react with other components during the heat treatment in the step of blending with the above-mentioned paraffin-based process oil or the step of blending the obtained rubber compounding oil with ethylene propylene rubber. Specifically, the time range temperature at IO.

Examples include those having a temperature of 120 to 180°C.

For example, dicumyl peroxide, t-butylcumyl peroxide, 1,3-bis(t-butylperoxy-
isopropyl)benzene, 2,5-dimethyl-2,5-
Dialkyl peroxides such as di(t-butylperoxy) hexanes, dibutyl peroxide, 2,5-dimethyl-2,5-(t-butylperoxy)hexyne-3; 1.4,4-trimethyl -pentyl-2-hydroperoxide, diisopropylbenzene hydroperoxide: cumene hydroperoxide, t-
Organic peroxides such as hydroperoxides such as butyl hydroperoxide, each alone or in combination.
More than one species may be used in an appropriate combination, and dicumyl peroxide is particularly suitable.

These peroxides are the paraffinic process oil 1.
0.5 to 5 parts by weight are added to 00 parts by weight. If this amount is more than 5 parts by weight, not only will the addition efficiency decrease, but also the heat aging properties will be adversely affected, such as excessive hardening of the rubber progressing with the thermal history, and if it is less than 0.5 parts by weight, The effect of peroxide combination is not demonstrated,
Preferably it is 0.1 to 1 part by weight.

The peroxide compounding may be carried out at room temperature, but at a temperature of 8ON.
It is preferable to blend it into paraffinic process oil and dissolve it therein at 120°C.

Acrylic acid alkyl esters and methacrylic acid alkyl esters reduce the viscosity of this rubber compounding oil and improve the operability of rubber processing processes such as mixing of rubber compounding agents and molding. Formation of a radical polymer consisting of acrylic ester and/or methacrylic ester, and formation of a graft to rubber molecules.

It is a component that contributes to improving properties such as hardness, mechanical strength, and heat aging properties of the vulcanized rubber composition by forming crosslinks between rubber molecules. The alkyl group in these esters preferably has 1 to 18 carbon atoms. Among these esters, preferable ones include acrylic acid methyl ester, methacrylic acid methyl ester, dodecyl methacrylate, and stearyl methacrylate. However, the first two are particularly preferred, and the amount to be added is as follows.

5 parts per 100ffi of paraffinic process oil
~30 parts by weight. If this amount is less than 5 parts by weight, the intended improvement in the physical properties of the vulcanized rubber composition will not be noticeable, and if it is more than 30 parts by weight, unreacted acrylic ester and/or methacrylic acid will remain in the rubber product. The ester monomer may remain, which may cause problems such as deterioration of rubber properties and odor and skin irritation due to leaching of 7-mer. Preferably it is 10 to 20 parts by weight.

This reactive rubber compounding oil is blended in an amount of 30 to 200 parts by weight per 100 parts by weight of the aforementioned ethylene propylene rubber. If the amount is less than 30 parts by weight, the mechanical strength of the resulting vulcanized rubber composition will not improve, and the kneading processability and moldability will deteriorate, and if it exceeds 200 parts by weight, rubber products will be It is unsuitable because problems such as oil bleed occur.

The vulcanized rubber composition of the present invention usually contains carbon black, zinc white, and stearic acid as reinforcing agents.

Vulcanizing agents and vulcanization accelerators such as moxibustion and peroxide are added, and predetermined amounts of known additives such as inorganic fillers such as titanium white, talc, and calcium carbonate, anti-aging agents and antistatic agents are added. There is no problem in doing so.

The vulcanized rubber composition of the present invention can be produced as follows. That is, predetermined amounts of the aforementioned ethylene propylene rubber, reactive rubber compounding oil, carbon black, zinc white, and stearic acid are sufficiently kneaded using, for example, a Banbury mixer, and then sulfur and a vulcanization accelerator are added using an open roll. .

The vulcanized rubber composition of the present invention is thus obtained.

By press-molding this composition, a desired rubber molded article can be obtained.

[Examples of the Invention] Examples 1 to 5 Diana process oil PW380 (trade name, manufactured by Idemitsu Kosan ■) having the following properties was prepared as a paraffinic process oil.

That is, specific gravity (15H'D): 0.87811; flash point COC: 30G°C; kinematic viscosity at 40°C and 100°C: 381.8cSt, 30:10cS
t; Viscosity coefficient: 100; Pour point knee ts, o°C: Refractive index (n20): 1.4808; Sulfur content: 8P pH Nianiline analysis: CA 0%, C127.0%, Cp 73.0%;
It is.

Dicumyl peroxide (trade name, Kayakumiluchi) was prepared as a peroxide.

First, Diana Process Oil PW380 10Ot
Part Ji was placed in a container and heated to 90°C, and then 1 part by weight of dicumyl peroxide was added thereto with stirring and completely dissolved. After cooling to room temperature, the indicated amounts (parts by weight) of each compound shown in Table 2 were added thereto, and the mixture was stirred and mixed until the whole was homogeneous to prepare various rubber compounding oils.

Next, ethylene propylene diene rubber EP 4095
(Product name, manufactured by Mitsui Petrochemical ■) 100 parts by weight.

Carbon black Asahi carbon 80H, MAF (product name,
Asahi Carbon ■) 140 parts by weight, zinc white (No. 3, JIS
Add the above rubber compounding oil in the amount shown in Table 2 to 5 parts by weight of stearic acid (specified in Item K 10-1962), 1 part by weight of stearic acid (manufactured by Wako Pure Chemical Industries, Ltd., special grade reagent), 248 parts by weight, and make the whole. were kneaded in a Banbury mixer at 120°C for 5 minutes, and then at 80°C on an open roll, 1 part by weight of 2-mercaptobenzothiazole, 1.5 parts by weight of tetramethylthiuram monosulfide, and 1.5 parts by weight of '+Ii@ was added and finally press-molded and vulcanized at 160° C. for 15 minutes to produce rubber specimens.

The hardness (Hs), tensile modulus at 100% strain, breaking strength, and breaking elongation of each specimen obtained were measured according to the following specifications, and the results are shown in Table 2.

Hardness (Hs): Based on JISK-13301,
Type A test elongation at break (%): Compliant with JISK-8301 [Effects of the invention] As is clear from the above explanation, the vulcanized rubber composition of the present invention can be easily molded by the conventional press molding method. is possible,
Since the mechanical strength of the molded product is greatly improved, it has great industrial value as a material for various rubber molded products, especially in the field of manufacturing rubber parts for automobiles.

Claims (1)

[Claims] A vulcanized rubber composition characterized in that 30 to 200 parts by weight of a reactive rubber compounding oil is blended with 100 parts by weight of ethylene propylene rubber.