JPH0734296A - Composite film and its production and molding die therefor - Google Patents

Abstract

PURPOSE:To improve the corrosion resistance and the releasing property of a composite film by preparing an eutectoid of a specified water-soluble fluorine- containing org. polymer in the NiSn alloy film which is used at the part of a metal mold in contact with rubber. CONSTITUTION:One or more kinds of water-insoluble fluorine-contained org. polymer selected from among polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-ethylene copolymer, chlorotrifluoroethylene-alkylene copolymer, vinylidene fluoride-pentafluoropropylene copolymer is made into eutectoid in the NiSn alloy film. This composite film is subjected to a vacuum heat treatment at about 270-370 deg.C. The average grain size of the fluorine-containing org. polymer is preferably 2-8mum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to 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 composite film having excellent corrosion resistance and mold releasability used for molding rubber such as chloroprene rubber (CR) and nitrile rubber (NBR), a method for producing the same, and a molding die.

[0002]

Rubbers are widely used mainly in the fields of automobiles such as hoses, 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 surface treatment is usually performed by industrial chrome plating. This 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.

[0004]

However, when molding rubber, the durability is insufficient only by applying the industrial chrome plating to the inner surface of the mold. In particular, when molding EPDM, sufficient performance cannot be obtained in terms of corrosion resistance and releasability. If the corrosion resistance is low, rust and dross will be generated due to corrosion, and contamination due to the deposition of compounded chemicals, non-rubber components in the polymer, etc. will cause unsatisfactory release properties.
Since these are factors that directly affect the quality of rubber products and productivity, their solution is strongly desired.

As a conventional solution to mold contamination, a fixed amount of molding is performed by solvent cleaning or mechanical removal of chemicals adhering to the inner surface of the mold and non-rubber components in the polymer. You are dealing with it in a complicated way. Further, the mold releasability is dealt with by using a mold release agent, but there have been problems that it takes time and labor, productivity is lowered, mold cooling and defective products occur.

The inventors of the present invention have found that the mold for molding rubber has a corrosion resistance of the mold in view of a decrease in productivity and an increase in defective products.
Considering that there is a point that must be improved in terms of releasability, as a result of intensive studies, a composite coating of a NiSn alloy with a water-insoluble fluorine-based organic polymer compound was found to have corrosion resistance to rubber, It was found that it is extremely excellent in terms of moldability. The present invention is based on the above findings,
An object of the present invention is to provide a composite film having excellent corrosion resistance, releasability, etc., a method for producing the same, and a molding die.

[0007]

The composite coating according to claim 1 is a NiSn alloy coating containing polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, a tetrafluoroethylene-hexafluoropropylene copolymer, Co-deposit one or more water-insoluble fluorine-based organic polymers selected from tetrafluoroethylene-ethylene copolymer, chlorotrifluoroethylene-alkylene copolymer, vinylidene fluoride-pentafluoropropylene copolymer It is characterized by

A method for producing a composite coating according to claim 2 is characterized in that the composite coating according to claim 1 is subjected to vacuum heat treatment at a temperature of 270 to 370 ° C. A molding die according to claim 3 is characterized in that the composite coating film according to claim 1 is used in at least a portion of the molding die which comes into contact with rubber.

A detailed description will be given below. A composite plating solution is used for manufacturing the NiSn alloy. This composite plating solution is a NiSn alloy plating solution to which a fluorine-based organic polymer is added. As this NiSn alloy plating solution,
A pyrophosphoric acid solution, a fluoride solution or the like can be used. Regardless of which of these pyrophosphoric acid solutions and fluoride solutions is used, by adding a fluorine-based organic polymer to these solutions, it is possible to obtain a composite plating solution with excellent releasability. it can. If necessary, additives such as a brightener and a buffer may be added to these plating solutions.

The average particle size of the fluorine-based organic polymer is 2 to
It is desirable to set it to 8 μm. When the average particle diameter of the fluorinated organic polymer is 2 μm or less, the releasability is deteriorated, the hardness of the composite coating is lowered, and the life of the composite coating is shortened. When the average particle size of the fluorine-based organic polymer is 8 μm or more, the eutectoid of the fluorine-based organic polymer becomes non-uniform under the influence of gravity and the circulating flow of the plating solution.

As the fluorine-based organic polymer, polytetrafluoroethylene (PTFE) co-deposited composite plating exhibits good release properties. Here, the amount of eutectoid in the composite coating is preferably 0.3 to 10% by weight, particularly 1 to 7%. Therefore, the amount of the fluorine-based organic polymer added to the composite plating solution is 50 to 400 g / l, particularly 100 to 3
00 g / l is preferred. That is, when the addition amount of the fluorine-based organic polymer is increased, the releasability is good, the contact angle of water is large, and it is difficult to wet, but the hardness is small and the surface brightness is low. On the other hand, when the amount of the fluorine-based organic polymer added is small, the hardness is high and the surface brightness is high, but the releasability is poor, the contact angle of water becomes small, and the surface becomes wet easily.

In order to prepare the composite plating solution, a surfactant is added when the dispersant (water-insoluble fluorine-based organic polymer) is dispersed in the plating solution. As this surfactant, an increase in the amount of eutectoid fluorine-based polymer as a dispersant,
From the viewpoint of the smoothness of the plating film, a cationic surfactant is used among the four types of nonionic, cationic, anionic and amphoteric. It is preferable to use a surfactant other than a cationic one, because it has a harmful effect such as a decrease in the amount of eutectoid and the occurrence of nodules (bundle-like crystals) on the surface of the plating film, increasing the surface roughness. Absent.

Here, the cationic surfactant is classified into a fluorine type and a hydrocarbon type depending on the structure of the hydrophobic group, and any of the surfactants increases the co-deposition amount of the dispersant to increase the plating surface. Can be smoothed. Examples of this surfactant include Coatamine 24 (manufactured by Kao Corporation), Florard 1
35 (Sumitomo 3M Co., Ltd.), FT-300 (Neos Co., Ltd.), S-121 (Asahi Glass Co., Ltd.) and the like.

The amount of the cationic surfactant added is 1.5 to 3.
It is preferably 5 g / l. Since the surfactant is mostly adsorbed on the surface of the water-insoluble fluorine-based organic polymer which is the dispersed particles, it is desirable to add the surfactant in proportion to the surface area of the dispersed particles. When the amount of the surfactant added is insufficient, the dispersant in the composite plating solution aggregates, the eutectoid amount decreases, and a non-uniform eutectoid state occurs. Further, when the amount of the surfactant added is excessive, nodules are generated on the surface of the composite coating, and the composite coating becomes brittle.

The conditions for forming the composite film using the composite plating solution may be the usual conditions for the plating solution, but the current density is such that the plating is carried out at a current density below a certain value. For example, the current density of the pyrophosphoric acid solution is 3.0 A / dm ² or less,
The current density of the fluoride solution is preferably 4.0 A / dm ² or less. The current density is set to such a value, because of the fluorine-based organic polymer adsorbed on the plating surface, the actual current density becomes higher than the apparent current density, and the current efficiency decreases due to the generation of hydrogen, This is to prevent deterioration of the smoothness of the plating surface and the like.

The composite coating produced from the composite plating solution is vacuum heat treated. By performing this vacuum heat treatment at a temperature of 200 to 400 ° C., which is different from the Sn content of the composite coating,
The composite film undergoes transformation. This is because NiSn, which is a metastable layer of the NiSn alloy film, transforms into a mixed layer of Ni ₃ Sn ₂ and Ni ₃ Sn ₄ which is an equilibrium layer. Further, although the fluorine-based organic polymer varies depending on the type and the average molecular weight, for example, PTFE reaches the melting point at about 320 ° C. and deforms at a temperature higher than that. From these results, as a result of diligent examination of the conditions of the vacuum heat treatment of the composite coating, the mold release property of the composite coating was set by setting the vacuum degree to 1 Torr or less, the heat treatment temperature to 270 to 370 ° C., and the heat treatment time to 2 hours or more. It was found that the wear resistance was improved.

When the above-described composite coating is applied to a molding die, the pretreatment may be ordinary degreasing or pickling to improve the adhesion to the base material, the smoothness, and the uniform film thickness. In order to reduce the size of the rubber and the peeling of rubber and the like, it is preferable to configure as follows. It is also possible to form a three-layered film in a layer where rubber or the like contacts, a Ni film as the first layer, a NiP film as the second layer, and a composite film as the third layer. With such a three-layer structure, the entire Ni film maintains high adhesion to the base matrix by the Ni film, and the NiP film that covers the Ni film strengthens the adhesion to the Ni film, and at the same time, forms a third layer. It has the function of assisting the hardness of the composite film that is used and exhibits corrosion resistance to rubber and release properties. Here, the film thickness of each layer is about 1 μm for the Ni film.
m, NiP film 3 to 30 μm, composite film 5 to 50 μm
Is preferably formed. Although the composite film is formed on the portion of the molding die that contacts the rubber or the like, the composite film may be formed on the entire molding die.

By thus forming a composite film on at least a portion of the molding die which is in contact with rubber or the like, conventional chromium plating, Teflon coating, electroless Teflon composite plating (NiP) regardless of the presence or absence of vacuum heat treatment. /
It is possible to improve releasability, life, and corrosion resistance with respect to a film such as PTFE.

According to such a composite coating, polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, a tetrafluoroethylene-hexafluoropropylene copolymer and a tetrafluoroethylene-ethylene copolymer are contained in the NiSn alloy coating. Since one or more water-insoluble fluorine-based organic polymers selected from polymers, chlorotrifluoroethylene-alkylene copolymers and vinylidene fluoride-pentafluoropropylene copolymers are co-deposited, a composite film It is possible to greatly improve the corrosion resistance and the releasability.

Since the composite coating is subjected to vacuum heat treatment at a temperature of 270 to 370 ° C., the corrosion resistance and releasability of the composite coating can be further improved. Furthermore, by using such a composite film at least in a portion where the rubber of the molding die comes into contact, the corrosion resistance of the molding die and the releasability are significantly improved as compared with the conventional die, The productivity of rubber molded products can be improved, the defective rate of rubber molded products can be reduced, and the workability of rubber molding can be improved. In addition, the amount of release agent used can be greatly reduced.

[0021]

EXAMPLE An example of the composite coating of the present invention, a method for producing the same, and a molding die will be described below. Here, as the base material of the composite coating, a JIS standard general steel material (S
Using S41), this steel material was formed into a plate shape having a vertical length of 3 cm and a horizontal length of 5 cm and used as a test piece.
The surface of this test piece was polished with # 400 abrasive paper to form a composite film on the surface of this test piece. The test piece formed with this composite film and the test piece subjected to the conventional surface treatment were compared with each other for the releasability with respect to various rubbers, the hardness which is an index of life, and the dye (ΔE) which is an index of corrosion resistance.

As a method for evaluating the releasability, as shown in FIG. 1, a rubber S is sandwiched between a pair of surface-treated test pieces T1 and T2 for vulcanization. The vulcanization conditions vary depending on the type of rubber, but for example, the temperature is 150 to 200 ° C,
The holding time is set to 5 to 15 minutes. After vulcanization, the rubber S is cooled at room temperature for 2 minutes, the test piece T1 is fixed to a workbench, and the other test piece T2 is pulled up by the spring 1 only. At this time, the pulling force (kgf) when the rubber S peels off is measured, and the value obtained by dividing the measurement result of this pulling force by the adhesion area (cm ³ ) of the rubber S is the rubber releasing force. Although rubber was used for the method of evaluating releasability, resin may be used.

On the other hand, as a color difference evaluation method, before vulcanization,
The color of the test piece T2 after 10 vulcanization operations is measured by a color meter, and the degree of discoloration before and after vulcanization is calculated by the following color difference formula. Here, ΔE ^* is color difference, L ^* is lightness index, a ^* and b ^* are chromatic index,
X, Y, and Z are tristimulus values, and Xn, Yn, and Zn are tristimulus values in a double visual field under standard light. 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 a hardness measuring method, a micro Vickers hardness meter was used, and a test piece having a composite coating formed thereon was measured under a load of 50 g and a holding time of 30 seconds.

Examples 1 and 2 and Comparative Examples 1 and 2 Example 1 is a composite coating, and Example 2 is a composite coating obtained by vacuum heat treating the composite coating of Example 1.
Is a bright Cr plating, and Comparative Example 2 is an electroless composite plating. Table 1 shows the components of these raw materials, and Table 2 shows the film forming conditions.

[0026]

[Table 1]

[0027]

[Table 2]

Examples 1 and 2 As shown in Table 1, in Examples 1 and 2, NiSn pyrophosphate solution was used as the basic solution. Each component (g / l) of this NiSn pyrophosphate solution contained 28 tin chloride and 3 nickel chloride.
0, potassium pyrophosphate is 200, glycine is 20, ammonia is 0.005, and brightener is 0.001. PTFE as a dispersant added to the basic liquids of Examples 1 and 2
The average particle size of the dispersant is 4 μm, and the concentration of the dispersant added is 100 g / l. Coatamine 24P (manufactured by Kao Corporation) was used as a surfactant added to the basic liquids of Examples 1 and 2, and the addition concentration of this coatamine 24P was 4 g / l.

As the film forming conditions, as shown in Table 2, in Examples 1 and 2, the temperature was 55 ° C. and the film growth rate was 30 μm /
At this time, stirring was performed by pump circulation to form a film thickness of 10 μm. As the vacuum heat treatment, only Example 2 was performed. In this Example 2, after forming a composite film having a film thickness of 10 μm,
The composite coating was heated at 330 ° C. for 2 hours in vacuum. In Example 1, the vacuum heat treatment was not performed.

Comparative Examples 1 and 2 In Comparative Example 1, the Sargent solution was used as the basic solution, and Comparative Example 2 was used.
Then, the electroless NiP liquid is used as the basic liquid. In each component (g / l) of the Sargent liquid, chromic acid is 250, chromium sulfate is 100, and sulfuric acid is 2. In each component (g / l) of the electroless NiP liquid, nickel chloride is 30, sodium hypophosphite is 10, sodium citrate is 50, and lead sulfate is 0.003. As a dispersant added to the basic liquid,
In Comparative Example 1, no dispersant was used, in Comparative Example 2, PTFE was used as the dispersant, and the average particle size of this dispersant was 0.25 μm.
m, and the added concentration of the dispersant is 5 g / l. In Comparative Example 1, no surfactant was used, and in Comparative Example 2, Emulgen 930 (manufactured by Kao Corporation) and F-135 were used as surfactants.
(Sumitomo 3M Co., Ltd.), the addition concentration of this surfactant is 0.5 g / l for Emulgen 930 and 1 g / l for F-135.

As a film forming condition, in Comparative Example 1, the temperature was 5
At 0 ° C., the film growth rate was 16 μm / hour, stirring was carried out by pump circulation to form a film thickness of 10 μm. In Comparative Example 2,
The temperature was 90 ° C., the film growth rate was 12 μm / hour, and stirring was performed by pump circulation to form a film thickness of 10 μm. In Comparative Examples 1 and 2, the vacuum heat treatment was not performed.

For the evaluation of hardness, Examples 1 and 2 and Comparative Examples 1 and 2 were measured with a micro Vickers hardness meter,
The results are shown in Table 2. From the results shown in Table 2, Example 1
In Example 2, the hardness was higher. Further, from the results of Example 1 and Comparative Examples 1 and 2, it is considered that the composition of the coating film affects the hardness.

EPDM was used as an evaluation of releasability and corrosion resistance.
Rubber, elastrene rubber, natural rubber, SBR rubber, epichlorohydrin rubber, and butyl rubber were used in Examples 1 and 2 and Comparative Examples 1 and 2, and the releasing force and color difference were measured, and the measurement results are shown in Table 3. Shown in.

[0034]

[Table 3]

As shown in Table 3, when comparing the releasing force of each rubber, the releasing forces of Examples 1 and 2 were lower than those of Comparative Examples 1 and 2. Therefore, it is understood that Examples 1 and 2 have higher releasability than Comparative Examples 1 and 2. On the other hand, comparing the color differences of the rubbers, the values of Comparative Example 1 are large for all the rubbers, and
Compared with Comparative Examples 1 and 2, EPDM rubber, SBR rubber,
In the case of butyl rubber, there was a small color difference. Therefore, it is understood that Examples 1 and 2 have high corrosion resistance in the case of EPDM rubber or the like. Further, it can be seen that Example 2 has lower releasing force and color difference than Example 1, and has high releasability and high corrosion resistance.

[0036]

As described above, according to the composite film, the method for producing the same, and the molding die of the present invention, the following effects can be obtained. The composite coating of the present invention is made of NiSn.
In the alloy film, polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-ethylene copolymer, chlorotrifluoroethylene-alkylene copolymer, Since one or more kinds of water-insoluble fluorine-based organic polymers selected from vinylidene fluoride-pentafluoropropylene copolymer are co-deposited, corrosion resistance and releasability can be significantly improved.

On the other hand, according to the method of the present invention, since the composite coating according to claim 1 is vacuum heat-treated at a temperature of 270 to 370 ° C., the corrosion resistance and releasability of the composite coating can be further improved. it can. Further, according to the molding die of the present invention, since the composite coating film according to claim 1 is used at least in a portion of the molding die which comes into contact with the rubber, the corrosion resistance and the releasability are the same as those of the conventional mold. Compared with the above, the productivity of rubber molded products can be improved, the defective rate of rubber molded products can be reduced, and the workability of rubber molding can be improved. In addition, the amount of release agent used can be greatly reduced. Therefore, it can greatly contribute to the field of rubber molding.

[Brief description of drawings]

FIG. 1 is a front view showing an instrument for evaluating releasability.

Claims (3)

[Claims] 1. A NiSn alloy film containing polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-
A co-deposition of one or more water-insoluble fluorine-based organic polymers selected from ethylene copolymers, chlorotrifluoroethylene-alkylene copolymers, vinylidene fluoride-pentafluoropropylene copolymers. Characteristic composite film. 2. The composite coating according to claim 1,
A method for producing a composite coating, which comprises performing a vacuum heat treatment at a temperature of 70 ° C. 3. A molding die, wherein the composite film according to claim 1 is used at least in a portion of a molding die which comes into contact with rubber.