JP3272061B2 - Rubber mold - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an ethylene / propylene / diene / methylene rubber (hereinafter referred to as EPDM), isobutylene / isoprene rubber (hereinafter referred to as IIR), polyisobutylene rubber, natural rubber, styrene / butadiene rubber (SBR), The present invention relates to a rubber mold having excellent corrosion resistance and releasability used for molding rubber such as chloroprene rubber (CR) and nitrile rubber (NBR).

[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.

[0003] A mold for molding parts for these various uses is made of iron, stainless steel, or the like, and is usually subjected to industrial chrome plating for surface treatment. This industrial chrome plating is applied to improve the wear resistance, corrosion resistance, heat resistance, mold release property, etc. of the surface of iron, stainless steel, or the like.

[0004]

However, in the case of molding rubber, the durability is insufficient if only the inner surface of the mold is coated with industrial chrome. In particular, when molding EPDM, sufficient performance cannot be obtained in terms of corrosion resistance, releasability, and the like. If the corrosion resistance is low, rust or scum is generated due to corrosion, and contamination due to deposition of compounding chemicals, non-rubber components in the polymer, etc. is unsatisfactory in terms of releasability.
Since these are factors directly affecting the quality of rubber products and productivity, their solutions are strongly desired.

[0005] As a conventional solution to mold contamination, a method of cleaning or mechanically removing deposits such as chemicals and non-rubber components in a polymer adhered to the inner surface of the mold every predetermined number of moldings. To deal with in a complicated way. In addition, the mold releasability is dealt with by using a mold release agent. However, there are problems such as a decrease in productivity due to troublesome work, cooling of the mold and generation of defective products.

[0006] The present inventors have found that a rubber molding die has a high corrosion resistance, in view of a decrease in productivity and an increase in defective products.
Considering that there is a need to improve the releasability, the present inventors have conducted intensive studies and found that the formation of the NiSn alloy film is extremely excellent in terms of rubber corrosion resistance 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.

[0007]

According to the present invention, a rubber molding die according to the present invention comprises a Ni film as a first layer, a NiP film as a second layer, and a NiSn film as a third layer at a portion where the rubber of the rubber molding die contacts. The film is characterized by being formed by lamination.

[0008]

In the rubber molding die of the present invention, the Ni film as a whole keeps high adhesion with the base material by the Ni film, and the NiP film covering the Ni film strengthens the adhesion with the Ni film.
It is used as a third layer and has an effect of assisting the hardness of the NiSn film that exhibits corrosion resistance and release properties against rubber.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the rubber mold according to the present invention will be described below. Metals such as iron and stainless steel are used as a base material of the rubber mold. 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. A Ni film is formed on the surface of the metal from which the oxide film has been removed by ordinary electric Ni plating.

The above-mentioned Ni film is used for the film formed by the subsequent surface treatment to maintain the adhesion to the base material. The thickness of this Ni film is 1 to 10 μm,
In particular, 1 to 5 μm is preferable. Ni coating thickness is 10μm
Exceeding the limit results in the formation of a film having an uneven thickness, and the formation of irregularities on the surface of this film is not preferred.

A NiP film is formed on the second layer by electroless plating. This NiP layer is coated with a uniform thickness on a mold surface having a complicated shape due to the electroless plating method. Since the NiP film has excellent corrosion resistance and a hardness of 600 to 700 in Vickers hardness (hereinafter referred to as HV), the NiP film also has excellent wear resistance. This NiP layer is preferably at least 1 μm, particularly preferably at least 5 μm. A thickness of less than 1 μm does not help maintain hardness above 500 in HV.

Next, as a third layer, a NiSn film having excellent corrosion resistance and releasability is formed by electroplating. This N
The thickness of the iSn film is preferably 1 to 50 μm, particularly 10 to 50 μm.
30 μm is preferred. The hardness of the NiSn film is increased by performing a heat treatment at 100 to 500 ° C. for 1 to 2 hours after the electroplating process. The temperature for increasing the hardness of NiSn is desirably 400 to 500 ° C., but if the heat treatment temperature is not set below the tempering temperature of the material of the mold base material, the mold base material may be deformed. For this reason, it is appropriate to set the heat treatment temperature at about 200 ° C. in order to maintain the accuracy of the mold itself.

Examples 1 and 2 and Comparative Examples 1 to 6 For evaluation of releasability, an EPDM (two types, a sponge type and a solid type) was used, and a NiSn film, a chromium plating film (20 μm), and an electroless NiP film were used. Plating (20μ
m) and a Ti film (2 μm) by an ion plating method.
m) and the result of the rubber adhesion test with a sponge type E
The results of PDM are shown in Table 1 as Example 1, and the results of solid type EPDM are shown in Table 2 as Example 2.

[0014]

[Table 1]

[0015]

[Table 2]

FIG. 1 shows a rubber adhesion test method.
As shown in FIG. 2, a pair of test pieces T1 and T
2 is prepared for each film. These test pieces T
1, T2 is composed of an iron plate serving as a base material and the above-mentioned respective coatings formed on the surface of the iron plate. Then, the film of the test piece T1 faces upward,
Is placed on a workbench or the like. An unvulcanized rubber S containing a predetermined amount is placed on the upper surface of the coating of the test piece T1.
The test piece T2 is placed on the upper surface of the unvulcanized rubber S with the film of the test piece T2 facing downward. For this reason,
The unvulcanized rubber S is sandwiched between the coatings of the test pieces T1 and T2.

Thereafter, with the unvulcanized rubber S held between the test pieces T1 and T2, the unvulcanized rubber S is put into a drying furnace, and the unvulcanized rubber S is held at 200 ° C. for 30 minutes. And vulcanized. After the vulcanization, the rubber S is air-cooled for 2 minutes, one test piece T1 is fixed to a workbench or the like, and the other test piece T2 is pulled up by a spring 1. The tensile force (kgf) when the rubber S was peeled from the other test piece T2 was measured, and the value obtained by dividing the measurement result of the tensile force by the bonding area (cm ³ ) of the rubber S was shown in Tables 1 and 2. Adhesive force. This operation is repeated 10 times for each film, and the adhesive force of the rubber is calculated. Here, "impossible" means that the adhesive force of the rubber is strong (adhesive force is 0.7 or more) and the film on the test piece T1 is peeled off from the iron plate.

On the other hand, the color of the test piece T2 before vulcanization and after 10 vulcanization operations are measured with a color meter, and the degree of discoloration before and after vulcanization is calculated by the following color difference equation. here,
ΔE ^* is a color difference, L ^* is a lightness index, a ^* and b ^* are chromatics indices, X, Y, and Z are tristimulus values, and Xn, Yn, and Zn are those of a standard light. And the tristimulus value twice in the visual field. ΔE ^* = [(ΔL ^* ) ² + (Δa ^* ) ² + (Δb ^* ) ² ] ^1/2 L ^* = 116 (Y / Yn) ^1/3 −16 a ^* = 500 ｛(X / Xn) ^1/3 − (Y / Yn) ^1/3 {b ^* = 200} (Y / Yn) ^1/3 − (X / Xn) ^1/3 }

As shown in Tables 1 and 2, in Comparative Example 1 showing the results of test pieces having a chromium plating on the surface,
Although the adhesion of the rubber is small and the releasability is excellent, the adhesive force of the rubber increases as the number of times of molding the rubber increases, and the releasability of the rubber deteriorates. Therefore, the frequency of cleaning the surface of the mold increases.

In Comparative Example 2, which shows the results of a test piece having a NiP film formed thereon by electroless plating, the rubber is firmly adhered to the surface of the test piece only by molding the rubber several times. Then, nickel is attacked by sulfurization by a sulfur compound contained in the rubber vulcanizing agent and urea ammonia gas caused by a foaming agent and a foaming aid, so that the test pieces T1 and T2 turn black and undergo 10 times of vulcanization. After the sulfurizing operation, the color changes to black.

In Comparative Example 3, which shows the results of a test piece having TiN ion-plated on the surface, when the rubber is vulcanized several times, the releasability is preferable. Is attached to the test piece T1, and the rubber cannot be removed from the test piece T1. Then, the surface of the test piece T1 changes from gold to pure black due to sulfuration or thermal oxidation of rubber, and the surface of the test piece T1 is corroded. In addition, in ion plating, a thick film cannot be formed, and pitting is likely to occur on the test piece T1.

Example 3, Comparative Examples 7 to 9 To evaluate the releasability, chloroprene (neoprene) rubber was used to form the same films as in Examples 1 and 2, and a rubber adhesion test for each film was performed. Are shown in Table 3 as Example 3. Here, when chloroprene rubber is used, since the chloroprene rubber has a structure containing chlorine, the mold is easily corroded during vulcanization.

[0023]

[Table 3]

As shown in Table 3, the nickel-based alloy has excellent corrosion resistance to chloride ions, but the chromium-based alloy as shown in Comparative Example 7 has low acid resistance and shortens the life of the mold. For this reason, the NiSn film has good releasability and corrosion resistance even with respect to chloroprene rubber, so that the life of the mold can be extended.

Examples 4 to 6 and Comparative Examples 10 to 12 As the evaluation of the releasability, EPDM, IIR,
Using a natural rubber, a weatherstrip was molded and the number of continuous moldings until the adhesion of scum was measured. The measurement was performed on five samples, and the average value of the five samples is shown in Table 4.

[0026]

[Table 4]

As shown in Table 4, a mold having a NiSn film coated on the surface has a larger number of continuous formations in any rubber than a mold having a chromium plating on the surface. For this reason,
The work of cleaning the mold is reduced.

Example 7 A weatherstrip molding die was used. A die was formed by laminating a Ni film on the first layer, a NiP film on the second layer, and a NiSn film on the third layer, respectively, at the portion where the rubber contacts. , EPD
Using M, continuous molding was performed at a mold temperature setting of 175 ° C. and a vulcanization time of 3 minutes (about 120 shots a day). It was 35 days until rubber release and contamination (discoloration) occurred, maintaining good releasability, without replenishing just applying the release agent at first, and maintaining good release properties. Comparative Example 13 Example 4 was performed except that a mold plated with industrial chrome was used.
When molded in the same manner as described above, it was necessary to frequently apply a release agent to the mold as needed to restore the mold releasability. Rubber adhesion and contamination began to occur at about 10 shots, and the mold had to be cleaned daily.

[0029]

As described above, according to the rubber molding die of the present invention, the corrosion resistance and the releasability are greatly improved as compared with the conventional die, and the productivity of the rubber molded product is improved. Thus, the defective rate of a rubber molded product can be reduced, and the workability of rubber molding can be improved. Also, the amount of the release agent used can be significantly reduced. For this reason, the effect of greatly contributing to the rubber molding field can be obtained.

[Brief description of the drawings]

FIG. 1 is a front view showing a rubber adhesion test method.

Continuation of the front page (56) References JP-A-5-245846 (JP, A) JP-A-6-23756 (JP, A) JP-A-55-70452 (JP, A) JP-A-1-168407 (JP) JP-A-1-186309 (JP, A) JP-A-4-161308 (JP, A) JP-B-63-63288 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB Name) B29C 33/38 C23C 18/52

Claims (1)

(57) [Claims] 1. A portion of the rubber molding die where the rubber comes into contact is a Ni film as a first layer, a NiP film as a second layer, and a Ni layer as a third layer.
A rubber molding die, wherein Sn films are formed by lamination.