JP2501708B2 - Rubber mold - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to ethylene, propylene,
Ethylene / propylene / diene / methylene rubber (hereinafter referred to as EPDM) produced by copolymerization of dienes,
The present invention relates to a rubber molding die which is excellent in corrosion resistance and releasability of rubber such as isobutylene isoprene copolymer rubber (hereinafter referred to as IIR), polyisoprene rubber, and natural rubber.

[0002]

2. Description of the Related Art Rubbers are widely used in fields such as hoses for automobiles, weather strips, sealing materials, vehicle parts such as bellows, general belts, tires and tubes.

Molds for molding parts for these various uses are made of iron, stainless steel or the like, and the inner surface is usually plated with industrial chrome.

The above-mentioned industrial chrome plating is applied to improve the wear resistance, corrosion resistance, heat resistance, releasability, etc. of the surface of iron, stainless steel or the like.

[0005]

However, when molding rubber, the durability is insufficient only by applying the industrial chrome plating to the inner surface of the mold. Particularly when EPDM is molded, sufficient performance cannot be obtained in terms of corrosion resistance, releasability and the like.

[0006] If the corrosion resistance is low, rust and scum are generated due to corrosion, and contamination due to deposition of compounding chemicals, non-rubber components in the polymer, and the like is unsatisfactory in terms of releasability. Since these are factors that directly affect the quality of products and productivity, their solutions are strongly desired.

[0007] As a conventional solution to mold contamination, there is a method in which a deposit attached to the inner surface of the mold, such as a drug or a non-rubber component in a polymer, is washed with a solvent or mechanically every fixed number of moldings. It is dealt with by a complicated method such as removal.

[0008] The mold releasability has been dealt with by using a mold release agent. However, there have been problems such as a decrease in productivity due to labor and cooling of the mold and generation of defective products.

The inventors of the present invention have found that the rubber molding die has a corrosion resistance of the die in view of a decrease in productivity, an increase in defective rate, and the like.
I think that there are points that must be improved in terms of releasability,
As a result of diligent research, it was found that the formation of the NiPW film was extremely excellent in terms of corrosion resistance to rubber and releasability.

The present invention has been made based on the above findings, and has as its object to provide a rubber molding die having excellent corrosion resistance, releasability and the like.

[0011]

In order to achieve the above object, in a rubber molding die according to the present invention, a Ni film is formed on the first layer, a NiP film is formed on the second layer, at a portion in contact with the rubber.
The formation of NiPW films as the third layer was used as a means for solving the problem.

[0012]

Since the present invention has the above-mentioned constitution, the nickel film as a whole maintains the adhesiveness with the base material by the Ni plating, and the NiP film covering the nickel film strengthens the adhesiveness with the Ni film. It is used in the third layer and has an action of releasing stress that causes cracking due to the hardness of NiPW that exhibits corrosion resistance and releasability with respect to rubber.

[0013]

[Example] Conventionally, iron, stainless steel, etc. have been used as the base material of a rubber mold, but an oxide film is formed on the surface of these metals, and the oxide film is removed by washing with hydrochloric acid or the like. It After removing the oxide film, normal electric Ni
A Ni film is formed by plating.

The Ni plating is used so that the film formed by the subsequent surface treatment maintains the adhesion to the base material. The thickness of this Ni plating is preferably 1 to 10 μm, particularly preferably 1 to 5 μm. When the thickness of the Ni plating exceeds 10 μm, a film having an uneven thickness is formed and unevenness is formed on the surface, which is not preferable.

A NiP film is formed on the second layer by electroless plating. This NiP layer is the Ni used for the third layer.
It is formed in order to release the stress caused by the hardness of the PW coating and to help improve the corrosion resistance. This NiP layer is 1
It is preferably at least μm, particularly preferably at least 5 μm. If the thickness is less than 1 μm, stress cannot be released.

Next, as a third layer, a NiPW film excellent in corrosion resistance and releasability is formed by electroless plating. Ni
The thickness of the PW film is preferably 1 to 20 μm, especially 1 to 10 μm
Is preferred. If the thickness exceeds 20 μm, the problem of cracking due to hardness occurs.

The hardness of the film formed by the above surface treatment is 700 to 800 in HV, and it is not always sufficient in terms of releasability as it is. Therefore, vacuum treatment is performed subsequent to the surface treatment.

The degree of vacuum in the above vacuum treatment is 1 mmHg or less,
The temperature is 300 to 600 ° C., especially 350 to 500 ° C.
Heat treatment is performed for 2 hours. At this point the hardness is 1000 HV
~ 1200 rises. By the above treatment, a rubber molding die having excellent corrosion resistance and mold releasability can be obtained.

Examples 1 to 3 and Comparative Examples 1 to 3 For evaluation of releasability, EPDM without addition of a release agent, IIR,
A weather strip was molded using natural rubber, and the number of continuous moldings until the adhesion of dross was recognized was measured. The measurement was performed on 5 samples, and the average value of 5 samples is shown in Table 1.

[0020]

[Table 1]

Example 4 Using a weather-strip molding die, the first layer: a Ni film having a thickness of 1 μm, and the second layer: a thickness of 1 at a portion in contact with rubber.
0 μm NiP coating, 3rd layer: 10 μm thick NiPW
It was 60 days when the operating time which can produce a favorable molded product was measured using EPDM using the metal mold | die which laminated | stacked the film. Comparative Example 4 The operating time during which a good molded product could be molded was measured in the same manner as in Example 4 except that a metal mold plated with industrial chrome was used, and it was 7 days.

[0022]

As described above, the rubber molding die according to the present invention has significantly improved corrosion resistance and releasability as compared with the conventional die, and not only the productivity but also the defective rate is improved. The workability of rubber molding is improved, which greatly contributes to the rubber molding field.

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Claims (1)

(57) [Claims] 1. A Ni film as a first layer, a NiP film as a second layer, and a NiPW as a third layer at a portion of a rubber molding die which comes into contact with rubber.
A rubber molding die, characterized in that films are formed in layers.