JPS60250920A - Preparation of thick molded piece - Google Patents

Abstract

PURPOSE:To obtain a molded piece free from mold cavities and rich in thickness at low compression by a method wherein thermoplastic resin is defoamed under repeated change of compression between the highest softening temperature and the lowest melting temperature, then, heated to the highest melting temperature or higher to make compression molding. CONSTITUTION:In the compression molding of thermoplastic resin material, variation of compression is repeated keeping the highest softening temperature in the minimum and the lowest melting temperature in the maximum to defoam the material. Then, the defoamed material is heated to the highest melting temperature in the minimum to be compression-molded into the desired thick molded piece. Additionally, thermoplastic resin material is molded in a mold using several laminated sheets or films or pellets or equivalents. In this manner, it becomes possible to manufacture a thick molded piece free from mold cavities at low compression.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a method for manufacturing a thick-walled molded product, and more specifically, a method for manufacturing a molded product such as a container or a plate having a wall thickness of 10 mm or more. The present invention relates to a compression molding method that can produce good thick molded products without forming cavities.

(Prior art) Conventionally, extrusion molding or compression molding is generally used to produce thick-walled molded products. However, extrusion molding can successfully mold sheets with a thickness of 2 to 3 mm. However, when molding a very thick plate with a wall thickness of about 10 mm, for example, the molten sheet coming out of the goose will sag under its own weight, making stable molding impossible, and the resulting molded product will have large uneven thickness and deformation. On the other hand, although it is possible to manufacture thick-walled molded products using compression molding, it requires a large amount of pellets and powder as raw materials, resulting in a large mold volume. There is a problem in that the air existing between the particles cannot be defoamed and only molded products with cavities can be obtained.Therefore, as a method for obtaining such thick molded products, for example, Japanese Patent Publication No. 44-25480 discloses As described, a technology has been proposed in which a block-shaped product is produced by extruding molten resin into a sheet from an extruder and folding the resin while it is still in a molten state to continuously stack the sheets.However, this technology In addition, the equipment becomes complicated and large, and it is difficult to obtain molded products with complex shapes.In addition, Japanese Patent Publication No. 58-40018 discloses that two or more thermoplastic resin sheets of the same or different types can be heated to maximum thermal deformation. The technology involves uniformly preheating the entire product at a temperature that is 30°C or more and below the lowest melting point, and then compressing and deforming the preheated sheets in a stacked state at a pressure of 400kg/cm+ or less to produce thick-walled molded products. According to this technology, it is possible to miniaturize the mold and produce molded products with no comparative results, but even with soft resins such as ethylene-vinyl acetate copolymer, in most cases the weight is 100 kg/c+a or more. Unless a high compressive force is applied to the sheet, it will not be integrated properly.Furthermore, if this method is used in a normal compression molding method using pellets or powder, there is still the problem that only a thickly molded product with voids can be obtained.

[Purpose of the invention]

The inventors of the present invention have conducted repeated studies on a compression molding method that can produce thick-walled molded products with low compressive force and no cavities, regardless of the shape of the thermoplastic resin material. discovered that the objective could be achieved by pre-treating the thermoplastic resin material in a process suitable for defoaming gases such as air present in the material, and then performing normal compression molding.

[Structure and outline of the invention]

That is, the present invention provides a method for compression molding a thermoplastic resin material, in which the thermoplastic resin constituting the material is maintained at a temperature range from the maximum softening temperature to the minimum melting temperature, while reducing the pressure and molding the material.
This is a method for forming a thick-walled molded product, which is characterized by comprising the steps of repeatedly applying pressure to defoam gas existing between the materials, and heating to a temperature higher than the maximum melting temperature and compression molding.

The thermoplastic resin material used in the method of the present invention may be in any shape such as a sheet, film, pellet, flake, or powder made of thermoplastic resin, and the thermoplastic resin may also be low-density polyethylene. , high-density polyethylene, ultra-high molecular weight polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene or ethylene, propylene, 1
- Polyolefins such as random or block copolymers of α-olefins such as butene and 4-methyl-1-pentene, ethylene/acrylic acid copolymers, ethylene/acrylic acid copolymers, etc.
Ethylene/vinyl compound copolymers such as vinyl acetate copolymer, ethylene/vinyl alcohol copolymer, ethylene/vinyl chloride copolymer, polystyrene, acrylonitrile/styrene copolymer, ABS, methyl meccrylate/styrene copolymer , styrenic resins such as α-methylstyrene/styrene copolymer, polyvinyl chloride, polyvinylidene chloride, vinyl chloride/vinylidene chloride copolymer, polymethyl acrylate, polyvinyl compounds such as methyl methacrylate, nylon 6 , polyamides such as nylon 6-10, nylon 11, and nylon 12, thermoplastic polyesters such as polyethylene terephthalate and polybutylene terephthalate, polycarbonate, polyphenylene oxide, etc., or mixtures thereof.

In the compression molding method of the present invention, thick-walled molded products are manufactured using materials of various shapes made of the various thermoplastic resins mentioned above. The plastic resin material is pressurized with a mold while being maintained within the temperature range of the highest softening temperature or higher and lower than the lowest melting temperature of the resin constituting the material, and then the pressure is reduced, and by repeating this pressurization and depressurization multiple times, the gap between the materials is reduced. Defoaming gases such as air present in the air. Here, the heating temperature is within the above-mentioned temperature range, but a temperature range of (minimum melting temperature -10)°C to (minimum melting temperature -30)°C is particularly suitable for defoaming at low pressure and in a short time. If the temperature range is below the maximum softening point, defoaming does not occur completely, and the thick-walled molded product obtained by the compression molding process described below will contain cavities. If the temperature is higher than the minimum melting temperature, a portion becomes molten, and degassing in this portion becomes insufficient, resulting in only a molded product containing voids. Pressure conditions for pressurization and depressurization vary depending on the size and thickness of the molded product, but the upper limit is generally 100 kg/
cf or less, mostly 50kg/cJ or less, lower limit is Okg
/af1 or more. Especially when depressurizing, there is no pressurizing force.
g/ctA (atmospheric pressure) conditions are preferred. There are no particular restrictions on the cycle of pressurization and depressurization, and for example, as in the examples described later, pressurization for 3 seconds and depressurization for 2 seconds may be repeated 15 to 20 times, but the cycle is not limited to this in any way. .

There are no particular restrictions on the method for bringing the thermoplastic resin material into the above-mentioned temperature range; for example, heating the mold after filling it into a compression mold to heat the material inside the mold, or heating the material inside the mold before filling it into the mold. An example is a method of preheating with a heating machine.

The material from which the gas present in the material has been defoamed by the above defoaming process is then heated to a temperature higher than the highest melting temperature of the thermoplastic resin constituting the material and compression molded. At this time, it is preferable to heat to a temperature higher than the highest melting temperature or higher than 10° C. if possible. Moreover, the pressure for compression molding is higher than the pressure applied in the defoaming process.

In this way, the compression molding method of the present invention degasses by expelling the gas existing between the materials by applying pressure fluctuations while all the thermoplastic resin is softened but not melted. After that, pressure is applied while the metal resin is melted to completely melt and add it together to obtain a thick-walled molded product with no cavities.

A preferred example of the present invention is a technique for manufacturing a thick plate or block-like object using a plurality of sheets or films of thermoplastic resin. That is, it is heated to the highest softening temperature and lower than the lowest melting temperature of the thermoplastic resins constituting the sheet or film made of the same or different thermoplastic resins. As for the heating method, a plurality of sheets may be heated in advance in a heater in parallel or in series, or may be carried out by heating the mold while stacking the sheets in a mold. Once heated to within the target temperature range, the sheets or films are placed in a stacked state into a heated mold, and then pressurized by the mold while maintaining the temperature by continuing to heat the mold. and depressurization are repeated multiple times.

Next, under pressure, the mold temperature is raised to a temperature higher than the maximum melting temperature, and compression molding is performed. After that, the mold is slowly cooled, the mold is opened, and the molded product is taken out. The boundaries between each sheet or film of the molded product thus obtained are completely integrated by fusion, especially sheets or films of the same type of resin. If only the film is used, the boundary will not be visible and will be completely integrated.In addition, when using this sheet, if you use a sheet with a thickness of 2 to 6 mm, you can thicken it in a short time. There are no restrictions on the number of sheets, and the number of sheets can range from a few sheets to several tens of sheets.The dimensions of each sheet can also be different, and the shapes can be round sheets, round sheets, etc.
It may be of any shape such as a square sheet or a polygonal sheet. Furthermore, if necessary, a wire mesh, metal rod, porous ceramic membrane, etc. may be interposed between each sheet.

〔Effect of the invention〕

The features of the compression molding method of the present invention are as follows: (1) A thick-walled molded product without cavities can be produced.

■Applicable to any shape of thermoplastic resin material.

■Can be molded with low compression force.

■The strength of the molded product is high.

etc. can be mentioned.

〔Example〕

Preferred examples of the present invention are shown below as Examples, but the present invention can take any form as long as the purpose is not impaired and is not limited to these Examples.

Example 1 Poly4-methyl-1-pentene (TPX[F]MX00
4. Mitsui Petrochemical Industries, Ltd., melting point 240°C, Vicat softening point 160°C) pellets were filled into a mold set in a press at 220°C and preheated at a resin pressure of 100 kg/c+ll for 30 minutes. Next, after repeating pressure reduction and pressure application of Okg/cJ 20 times, the temperature of the press was increased to 270℃.
was reset and compression molded at a resin pressure of 100 kg/cnT. After 15 minutes, the mold was transferred to a water-cooled press and cooled for 15 minutes at a resin pressure of 100 kg/c-.

After cooling, a disk-shaped molded product with a thickness of 20 mm and a diameter of 180 mm was taken out. When the molded product was cut, the pellets were completely adhered and integrated, and no nests were formed.

Comparative Example 1 The same poly-4-methyl-1-pentene pellet as in Example 1 was filled into a mold set in a press at 270°C.
Preheating was performed for 30 minutes at a resin pressure of 100 kg/cn+. Next, after repeating the depressurization and pressurization of Okg/c+fl and 100kg/c+Il 20 times, the pressure was reduced to 100kg/cII.
Compression molded with + resin pressure. After 15 minutes, the mold was transferred to a water-cooled press and pressed at a resin pressure of 100 kg/c♂.
Cooled for 5 minutes.

After cooling, a disc-shaped molded product with a thickness of 20 mm and a diameter of 180 mm was taken out. A nest had developed inside the molded product.

Example 2 7.8 of the same poly-4-methyl-1-pentene as in Example 1
Two sheets with a thickness of mm were prepared, filled into a mold set in a press at 220° C., and preheated at a resin pressure of 30 kg/c♂ for 30 minutes. Then Okg/cn! and 30
After repeating the depressurization and pressurization of kg/c+a 20 times, the press temperature was reset to 240℃, and the pressure was reduced to 30kg/cnt.
Compression molded with resin pressure of After 15 minutes, the mold was transferred to a water-cooled press and cooled for 30 minutes at a resin pressure of 30 kg/cJ.

After cooling, a disc-shaped molded product with a thickness of 14 mm and a diameter of 330 mm was taken out. When the molded product was cut, it was found that even though it was made of two sheets, they were completely adhered to each other and were integrated into one piece, and there were no cavities.

Comparative Example 2 7.8 of the same poly-4-methyl-1-pentene as in Example 1
Two sheets with a thickness of mm were prepared, filled into a mold set in a press at 220° C., and preheated for 30 minutes at a resin pressure of 30 kg/cJ. Next, the temperature of the press was set to 240℃.
was reset and compression molded at a resin pressure of 30 kg/cJ. After 15 minutes, transfer the mold to a water-cooled press and
It was cooled for 30 minutes at a resin pressure of 0 kg/cJ.

After cooling, a disc-shaped molded product with a thickness of 14 mm and a diameter of 330 mm was taken out. A nest had developed inside the molded product.

Example 3 7.8 of the same poly-4-methyl-1-pentene as in Example 1
Two sheets with a thickness of mm, one sheet with a thickness of 5 mm,
A total of three sheets were prepared, filled into a mold set in a press at 220°C, and preheated at a resin pressure of 20 kg/ci for 1 hour. Next, after repeating the depressurization and pressurization of Okg/cJ and 20kg/ci 20 times, the temperature of the press was increased to 240
The temperature was reset to 0.degree. C., and compression molding was performed at a resin pressure of 20 kg/cJ. After 1 hour, water was flowed through the press while maintaining the resin pressure at 20 kg/cn+, and the press was cooled for about 1 hour. After cooling, a disc-shaped molded product with a thickness of 17 mm and a diameter of 700 mm was taken out. When the molded product was cut, it was found that even though it was made of three sheets, they were completely adhered to each other and were integrated into one piece, and there were no cavities.

Applicant Mitsui Petrochemical Industries Co., Ltd. Agent Wate Yamaguchi Amendment (spontaneous) August 9, 1980 Commissioner of the Japan Patent Office Gakudono Shiga1, Indication of the case 1982 Patent Application No. 1066352, Invention Name of molding method for thick-walled molded products 3, Relationship with the case of the person making the amendment Patent applicant (58B) Mitsui Petrochemical Industries, Ltd. 4, Agent 3-2 Kasumigaseki, Chiyoda-ku, Tokyo 100 @ No. 5 No. 7 Amendment Contents (1) On page 9, line 7 of the specification, the phrase ``Repeated multiple times.'' is corrected to ``Repeated multiple times.''

(2) In the specification, page 9, lines 9-10, the phrase "then slowly cooled down" should be corrected to "then cooled down."

(5) On page 11 of the specification, line 4, ``Then, Qkq/cm'' should be changed to [Then, CJk'j/C1N,! = 100
k(1/Cttt2)J d correction.

(4) On page 14 of the specification, line 1 “240°C” should be replaced with “25°C”.
Correct to 0°C.

that's all

Claims (5)

[Claims] (1) In a method of compression molding a thermoplastic resin material,
The process of defoaming the gas in the material by repeating depressurization and pressurization while maintaining the temperature within the maximum softening temperature or higher and lower than the minimum melting temperature of the thermoplastic resin that makes up the material, and compression molding by heating the material to a temperature higher than the maximum melting temperature. A method for forming a thick-walled molded product, comprising the steps of: (2) The molding method according to claim 1, wherein the thermoplastic resin material is formed by laminating a plurality of sheets and/or films. (3) The molding method according to claim 1, wherein the thermoplastic resin material is in the form of pellets. (4) The molding method according to claim 1, wherein the thermoplastic resin material is in powder form. (5) Claim 1 using the same type of thermoplastic resin
The molding method according to any one of Items 1 to 4.