JPH059387A - Silicone rubber composition - Google Patents

Abstract

PURPOSE:To obtain a silicone rubber composition having improved mold- releasability without deteriorating the rubber characteristics and productivity by adding an internal release agent to a silicone rubber compound. CONSTITUTION:A composition produced by kneading a silicone rubber, a pigment, an organic peroxide and a polyoxyethylene nonylphenol ether (having HLB of 13.0) is formed and vulcanized. The mold-releasability can be remarkably improved without deteriorating the dry strength and permanent compression set.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a silicone rubber composition. More specifically, it relates to a silicone rubber composition having excellent releasability.

[0002]

2. Description of the Related Art Since a vulcanized molded product of silicone rubber has a weak mechanical strength, when the mold is released from the mold during vulcanization molding, if the mold release resistance is high, the molded product is liable to be cracked and complicated. In the case of a molded product having a shape, in addition to the problem of cracking of the molded product, there is a problem that it takes time to release the mold and workability is poor.

In order to solve these problems, an external mold release agent is applied to the mold, or an internal mold release agent is added to the silicone rubber compound. However, each of them has the following problems. is doing.

First, in the method of applying an external release agent to a mold, the external release agent has a small surface energy of -Si-O.
-Silicone-based ones having a bond are often used, but this is structurally similar to the siloxane bond of the silicone rubber, and therefore has poor releasability from the silicone rubber and requires a long coating time. Also, there are variations in coating, which reduces productivity.

In addition, in the method of adding an internal release agent to a silicone rubber compound, a fatty acid (salt) having a low compatibility with silicone rubber, a silicone modified ether, a higher alcohol, etc. are generally used as the internal release agent. However, in the case of silicone rubber, the siloxane bond is hydrolyzed and deteriorated by the action of the -COOH group or -OH group of the internal release agent, resulting in a decrease in hardness, deterioration of compression set, etc. As a result, it becomes difficult to maintain the rubber property and the releasability at the same time.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to improve the releasability of a silicone rubber compound by adding an internal release agent to the silicone rubber compound without deteriorating the rubber properties and productivity. Another object is to provide a silicone rubber composition.

[0007]

The object of the present invention is as follows.
As an internal release agent, a polyoxyethylene alkylphenol ether-based surfactant represented by the following formula,
It is achieved by using values of 8-18.

In this nonionic surfactant, n
The hydrophilicity changes depending on the number of, and there is an HLB value as the one showing the hydrophilicity, but in the present invention, those having a value of 8 to 18 are preferably used from the viewpoint of compatibility with silicone rubber. Be done. The addition ratio is 0.1 to 3 parts by weight, preferably about 0.1 to 100 parts by weight of the silicone rubber compound.
1 part by weight.

As the silicone rubber compound, solid silicone rubber such as polydimethylsiloxane, vinyl silicone rubber, phenyl silicone rubber, fluorosilicone rubber and the like, organic peroxide as a vulcanizing agent thereof, pigment as an optional component, filling A suitable mixture of agents and the like is used. Each of these compounding ingredients is an open roll or a closed kneader (kneader, Banbury mixer).
The composition formed by the kneading and the like is generally about 170 to 180 ° C., about 4 to 10 minutes of primary vulcanization and about 200 to 230 ° C., about 2 to 5 hours of secondary vulcanization. It is vulcanized and molded by vulcanization.

[0010]

By adding a polyoxyethylene alkylphenol ether type surfactant to the silicone rubber compound, the releasability can be greatly improved without lowering the rubber characteristics and the productivity.

[0011]

EXAMPLES The present invention will now be described with reference to examples.

Examples 1-2 Silicone rubber (TSE220-7u, a product of Toshiba Silicone) 100 parts
(Weight, same below), 2 parts brown pigment (resino color product Resino Brown K100), 2 parts organic peroxide (Shin-Etsu Chemical product C-8; Perhexa 25B-40) and polyoxyethylene nonylphenol ether (Lion product Liponox) NC-95 ； HL
B value 13.0) 0.3 part [Example 1] or 1 part [Example 2] was kneaded with a kneader, and the composition obtained was 180
Primary vulcanization was performed at 4 ° C for 4 minutes and secondary vulcanization at 200 ° C for 5 hours.

For the vulcanized product, the normal value and compression set (150 ° C., 70 hours) were measured according to JIS K-6301. Further, an O-ring having a diameter of 3.1 mm was vulcanized and molded, and the releasability rank at that time was evaluated as follows. A: The vulcanized molded product floats when the mold is opened. B: The vulcanized molded product can be released from the mold by hand. C: The mold cannot be released without applying air. D: The vulcanized molded product adheres to the mold.

Comparative Example 1 In Examples 1 and 2, polyoxyethylene nonylphenol ether was not used.

Comparative Examples 2 to 4 In Example 1, instead of polyoxyethylene nonylphenol ether (Liponox NC-95), the same amount of polyoxyethylene nonylphenol ether was used.
(Lion product Liponox NC-10; HLB value 3.3) [Comparative Example 2], stearic acid internal release agent (Tore Dow Silicone Product MR-3) [Comparative Example 3] or higher fatty acid alcohol internal release agent ( Kawaken Fine Chemicals VLTN-2000) [Comparative Example 4] was used.

Measurement results in each of the above Examples and Comparative Examples
Are shown in the following table.Example Comparative example  Measurement item 1 Two 1 Two Three Four  Hardness (JIS A) 69 67 70 68 69 68 Tensile strength (kgf / cm²) 71 68 73 67 70 64 Elongation (%) 150 170 140 170 160 160 Compression set (%) 12 16 12 14 24 20 Releasability rank B A C C to B B C to B

Claims (1)

Claims: 1. A silicone rubber composition having excellent releasability, which is obtained by adding a polyoxyethylene alkylphenol ether-based surfactant having an HLB value of 8 to 18 to a silicone rubber compound.