JPH03115574A - Metal mold for molding - Google Patents

Abstract

PURPOSE:To produce a metal mold for molding having superior releasing property at the surface by coating the surface of a metal mold with boron nitride. CONSTITUTION:The surface of a metal mold used for molding thermoplastic resin, etc., is coated with boron nitride by using boron compounds and nitrogen- containing compounds by a plasma chemical vapor deposition method. The thickness of this boron nitride film is regulated to about 0.5-2.0mu in the case of a metal mold having smooth surface and to about 1.0-5.0mu in the case of a metal mold having highly rugged surface, and also the Vickers hardness (HV) of this film is regulated to >=350. By this method, superior releasing property can be provided to the surface of the metal mold, and further, the releasing effect can be maintained for a long period because boron nitride does not pass into a molded product at the time of molding.

Description

Detailed Description of the Invention (Field of Application in Industry A) The present invention relates to a mold for molding, particularly a mold used for molding thermoplastic resin, thermosetting resin, rubber, etc., whose surface is coated with boron nitride. The present invention relates to a molding die whose surface has excellent mold releasability.

(Prior art) For molds used for molding thermoplastic resins, thermosetting resins, or rubber, it is necessary to provide the mold with releasability in order to make it easier to remove the molded product from the mold after molding. For this purpose, a method generally used is to apply silicone oil, silicone grease, or fluorine oil to the surface of the mold by spraying or coating.

(The i!i! problem that the invention aims to solve) However, the method of applying silicone oil, grease, or fluorine-based oil to the mold surface is very effective in terms of imparting mold release properties to the mold. However, there is a problem with this process: Since the mold release agent applied to the mold transfers to the molded product after molding, contamination of the molded product may become a fatal defect depending on the material purchase and use of the molded product. , 2) The release agent remaining in the mold decreases with each molding due to the transfer of the release agent to the molded product, so in some cases it may be necessary to apply the mold release agent every time molding is completed.
) When the shape of the mold is complex, it is difficult to uniformly apply the mold release agent to the mold surface, so the mold release properties vary depending on the location.4) Mold material, molded object Depending on the type of molding, there is a problem in that the surface of the mold is worn out during molding, causing scratches on the surface of the molded product, and a solution to this problem is desired.

(Means for Solving the Problems) The present invention relates to a molding die that solves these problems, and is characterized in that its surface is coated with boron nitride.

That is, as a result of various studies aimed at developing a molding die that does not allow the release agent to migrate into the molded product and exhibits good mold release properties over a long period of time, the inventors of the present invention found that the surface of the molding die was coated with nitrided metal. This boron nitride exhibits good mold release properties when coated with a mold release agent, and since boron nitride does not transfer to the molded product, the surface of the molded product is not contaminated, and it is not necessary to use a conventional mold release agent. It was discovered that the disadvantages associated with migration can be eliminated, and that the mold release effect of boron nitride lasts for a long time. It is possible to uniformly coat a complex-shaped mold with boron nitride by using the method (abbreviated as "method"), and since this uncoated boron nitride has high hardness, it is possible to coat the mold with boron nitride uniformly. The present invention was completed after confirming that the surface protection function can be provided.

This will be explained in further detail below.

(Function) The molding die of the present invention is an ordinary die whose surface is coated with boron nitride to impart mold releasability.

There are no particular restrictions on the material or shape of the mold itself that constitutes this molding mold. Therefore, this mold can be made of carbon steel for machine structures, chromium-molybdenum steel, carbon tool steel, alloy tool steel, stainless steel, An appropriate material such as aluminum may be selected depending on the forming method and the hardness required for the formed body, and the shape and structure may be arbitrary, but the molding of the present invention The mold used for the mold is coated with boron nitride as described below.
Since it is performed by the VD method, it may have a complicated structure.

This mold was coated with boron nitride using a chemical vapor deposition method (
This C
Boron halides such as boron trichloride and boron hydrides such as diborane (BJs) are used as boron sources to coat the mold surface with boron nitride in the VD method. A nitrogen-containing compound such as ammonia or amines may be used as the solvent.

This CVD method is called the LP-CVD method, in which the pressure is 0.5 to 50 Torr and the temperature is 1,000°C or higher, and the pressure is 0.1 to 10 Torr, and the temperature is 2.
There is a method called plasma CVD method in which CVD is performed under plasma discharge at a temperature of 00 to 400°C.
Boron nitride obtained by CVD method is P-BN, plasma C
Boron nitride obtained by the VD method is classified as α-BN (amorphous BN), and either of these methods may be used to obtain the molding mold of the present invention. In the CVD method, the reaction temperature is 1,000℃
Due to the high temperature, there is a risk that the mold material may deform or melt depending on the material of the mold, and a special material is required for this reaction equipment, but since the reaction temperature is low in plasma CVD method, Since there is no need to worry about this, it is practically preferable to use the plasma CVD method.

Furthermore, when a mold is coated with boron nitride using this CVD method, the reactant is gaseous, so even if the mold has a complex shape, it can be coated with boron nitride homogeneously. However, if the surface of this mold is dirty, especially if oil or fat remains on the surface, the boron nitride film coated thereon may peel off. It is necessary to thoroughly clean the surface in advance, and it is desirable to completely remove oil and fat with an organic solvent or the like.

In addition, this CVD method is carried out using a boron compound and a nitrogen-containing compound as described above, but in this case, SIL is added to the boron compound and nitrogen-containing compound at a ratio that does not impair the mold release properties of boron nitride. , Si, H, etc., or C physical compounds such as CH4, C,)H6, C3N8, C2H, etc. may be mixed, and in the case of plasma CVD method, the purpose is to maintain stable plasma discharge. It is desirable to use argon, xenon, or the like as a carrier gas.

By this CVD method, a boron nitride coating is formed on the mold surface, but the thickness of this boron nitride coating may be as long as it can add practical mold release performance. For molds with smooth surfaces, a thickness of 0.5 to 2.0 μI is sufficient, while for molds with uneven surfaces, a thickness of 1.0 to 5.0 μI is sufficient. Since boron nitride has excellent mold releasability, molding molds whose surfaces are coated with boron nitride in this way can be used to manufacture molded products. This CVD method has the advantage of making it easier to take out the molded product after manufacturing, and since the boron nitride coating does not dissolve into the molded product, it exhibits excellent mold releasability over a long period of time. Boron nitride made by this method has high hardness, for example, a Vickers hardness (HV) of 350 or more, so
The surface of molds made of aluminum, chromium-molybdenum steel, and other alloys with a Vickers hardness (HV) of 350 or less is protected by this boron nitride film, preventing wear and gas generation. This effect is also added.

For molding using this mold, thermoplastic resin,
Examples include those in which thermosetting resins, various synthetic rubbers, etc. are molded by compression molding, injection molding, extrusion molding, etc., and the mold of the present invention is coated with boron nitride to provide mold releasability. Therefore, it is particularly useful for molding sticky resins and rubbers that have poor releasability from molds.

(Example) Next, examples of the present invention and comparative examples will be given.

Examples 1 to 2, Comparative Examples 1 to 6 (Manufacture of molds) Carbon tool steel was used, the width and length were 150 mm, the thickness was 5■■, and the surface had a width of 1.0++* and a depth of 1. .0m
A mold was manufactured in which ten +a-shaped grooves were provided in each of the vertical and horizontal directions.

(Formation of boron nitride coating on the mold surface) - Set the mold described above on the sample stand of a chamber that has a gas supply port at one end and is connected to an exhaust port at the other end, and 350℃
The pressure inside the chamber was reduced to 5 Torr.

Diborane diluted to 10% concentration with hydrogen gas from the gas supply port 200ml/min, 100% pure ammonia gas 1
20 m1/min and argon gas 100 m1/min were supplied into the chamber, a high frequency output of 150 watts was applied, a plasma flame was generated in the chamber, and the reaction was carried out for 20 minutes. Since the boron nitride film was uniformly coated with a thickness of 0.8μ, the hardness of this boron nitride film was determined according to JIS Z-2244.
The Vickers hardness (HV) was 53B when measured using a directrix method.

(Molding of silicone rubber by compression molding method) Silicone rubber composition E951U [Part name manufactured by Shin-Etsu Chemical Co., Ltd.] 100 parts organic peroxide curing catalyst C-8 [manufactured by Shin-Etsu Chemical Co., Ltd.] [Product name] 2 parts were added, kneaded with a two-wood roll, and then separated into a sheet with a thickness of 1 mm to make an unvulcanized silicone rubber sheet A. Addition reaction vulcanization type silicone rubber composition E1214^ , KE1214B
[All products are trade names manufactured by Shin-Etsu Chemical Co., Ltd.] 50 parts were thoroughly mixed in a kneader and dispensed into sheets with a thickness of 1 inch to prepare an unvulcanized silicone rubber sheet 8.

Next, a predetermined amount of this unvulcanized silicone rubber sheet ^, B was placed on the mold described above, and a Teflon plate with a width and length of 150 mm and a thickness of 1.0 + am was placed on top of the mold, and the unvulcanized silicone rubber sheet was placed on top of the mold. Temperature 17 for silicone rubber sheet eight
Compression molding was carried out for 15 minutes at 0°C and a pressure of toog/c, and for unvulcanized silicone rubber sheet B, the temperature was 12.
After compression molding for 10 minutes at 0°C and a pressure of 20 kg/c+*', the Teflon plate was peeled off, the vulcanized silicone rubber molded product obtained by this molding was taken out of the mold, and the peeling when taken out was peeled off. Speed 50cm/min, peel strength 18
The peeling force was measured using an autograph at 0°C, and the peeling force was measured using an autograph.
When we examined the fine moldability of the molded product by observing the striped molded part of the mold, we obtained the results shown in Table 1. This test was repeated 10 times to determine the mold releasability and fine moldability of this mold. When a moldability sustainability test was conducted, the results shown in Table 1 were obtained.

However, for comparison, this mold was not coated with boron nitride (Comparative Example 1.2). Instead of coating the mold with boron nitride, dimethyl silicone oil with a viscosity of 100 cS was used. 96 [part name manufactured by Shin-Etsu Chemical Co., Ltd.] (comparative example 3.4) and the mold were coated with fluorine-based mold release agent Daifree^441 [Daikin Industries, Ltd.
When compression molding was carried out in the same manner as above using the parts coated with [Comparative Examples 5 and 6], the peeling force and fine moldability were examined, and the results were as listed in Table 1. was gotten.

(Effects of the Invention) The present invention relates to a mold for molding, and is characterized in that the surface thereof is coated with boron nitride.
This product uses boron nitride, which has good mold release properties, and since boron nitride does not migrate into the molded product during molding, this product has the advantage of having a long connection time due to this mold release effect. Since this boron nitride coating is carried out by the CVD method using a boron compound and a nitrogen-containing compound, even if the mold has a complicated shape, it can be coated uniformly. Since this boron nitride itself has a high hardness, with a Vickers hardness of 350 or more, it is also advantageous in that it can protect the surface of a mold with low hardness.

Claims (4)

[Claims] 1. A molding die characterized by having a surface coated with boron nitride. 2. The molding die according to claim 1, wherein the boron nitride coating is performed by chemical vapor deposition. 3. The molding die according to claim 2, wherein the chemical vapor deposition method is a plasma enhanced chemical vapor deposition method. 4. The molding die according to claim 1, wherein the boron nitride coating has a Vickers hardness (HV) of 350 or more.