JPS61135714A - Molding of copolymer of tetrafluoroethylene and molding mold therefor - Google Patents

Abstract

PURPOSE:To prevent the adhesion of copolymer of tetrafluoroethylene to the mold as well as the foaming of molded product by a method wherein the copolymer of tetrafluoroethylene and one or two kinds of comonomer, shown by the formula I, is heated to melt it, thereafter, the copolymer is cooled and solidified in the metallic mold, coated by polyallylenesulfide (PAS). CONSTITUTION:The dispersion coating medium or powder coating medium of PAS is coated on the metallic mold by the conventional technique such as spraying, dipping, brushing, roller coating, fludization dip coating or the like and, subsequently, is baked at the temperature of 300-450 deg.C. Heating and melting are effected outside of the metallic mold or in a barrel in case of injection molding while they are effected in a pot in case of transfer molding. Successively, the molten copolymer is poured into the metallic mold coated by PAS. On the other hand, the copolymer is heated and molten in the metallic mold, coated by PAS, in case of compression molding, rotary molding or the like and, successively, is cooled and solidified in the metallic mold.

Description

Detailed Description of the Invention (Field of Industrial Application) This invention provides a method for molding a tetrafluoroethylene copolymer that has good peelability in molded products and does not generate bubbles in molded products, and a method for molding tetrafluoroethylene copolymers that can be used in this molding. Regarding molds.

(Prior art) Tetrofluoroethylene copolymer resin has excellent heat resistance, chemical resistance, electrical properties, non-stick properties, low friction properties, and other properties unique to fluororesins, and it melts at high temperatures and becomes plastic. Therefore, it is known as a resin that can be used to produce molded products using molding methods such as injection, transfer, compression, rotation, and casting.

(Problems to be Solved by the Invention) The first problem in molding such a tetrafluoroethylene copolymer is that the resin sticks to the mold.

The above-mentioned polyolefin ethylene copolymer is a non-adhesive polymer, and in its non-molten state (solid state), it is hardly wetted by fluids and viscous substances such as adhesives. However, when the tetrafluoroethylene copolymer resin melts into a liquid state, the surface tension decreases and it becomes possible to wet many solid materials. Sticks to surfaces. Therefore, a phenomenon of sticking to the mold occurs.

The second problem is foaming of the molded product.

When molding tetrafluoroethylene copolymer under high pressure such as injection molding or extrusion molding, even if the molten resin contains gaseous substances such as resin decomposition gas and air, degassing is compared. This is not a problem because it is easy to carry out, but when there is no pressure and the temperature of the mold is high, as in rotational molding, a large amount of decomposed gas is generated, and it is difficult to remove the gas. This causes bubbles to form in the molded product.

The first problem, that is, the release of the molded product from the mold, can be fixed by polishing the mold surface or applying a mold release agent such as a silicone mold release agent to the mold surface. Although the problem has been solved, surface polishing requires a lot of time and effort, has a short service life, and does not have sufficient mold releasability. In addition, the method of using a mold release agent is such that even silicone mold release agents cannot withstand the molding temperature of fluororesin, and furthermore, the mold release agent adheres to the surface of the molded product, worsening the surface condition of the molded product. However, there are disadvantages in that the mold release effect is short-lived.

In addition, to solve the second problem, that is, the problem of air bubbles occurring in molded products, it has been proposed to add stabilizers such as zinc and tin to the resin, but the addition of these metals has a high acid and alkali resistance. This is undesirable because it impairs the properties of fluororesin, such as a decrease in electrical insulation, a decrease in electrical insulation, and the absence of impurities.

(Means for Solving the Problems) In order to solve the above problems, the first invention of the present application provides tetrafluoroethylene and the following formula (where R7t is H or a fluoroalkyl group having 1 to 5 carbon atoms, R /, is carbon number 1-5
A copolymer of one or more comonomers of fluoroalkyl group, Xl, X, and This paper proposes a method for molding a tetrafluoroethylene copolymer by cooling and solidifying it in a mold.

The second invention of the present application proposes a mold for molding a tetrafluoroethylene copolymer coated with PAS.

Examples of the PAS used in this invention include polyphenylene sulfide (hereinafter referred to as PPS).

It should be noted that PAR is preferably one that is as pure as possible and has high purity; for example, excessive addition of pigments and fillers such as fermented titanium, for example, PAR containing 50 or more of these fillers, often reduces mold releasability. There is.

It is also preferable that the PAR coating surface be smooth and smooth.
If the surface condition of the coating film is poor, the mold releasability may be insufficient.

In addition, if the surface condition of the coating film is poor and the mold releasability is insufficient, the mold releasability can be improved by polishing the surface and performing re-baking.

The mold is coated with PAR according to a conventional method.

For example, a dispersion paint or powder paint of PP8 is applied to the mold by spraying, dipping, brushing, rolling, fluid dipping, or other conventional methods, and then
Baking is carried out at a temperature of °C.

On the other hand, examples of the tetrafluoroethylene copolymer suitable for the molding method of the present invention include Teflon PF^, Teflon FEP, Teflon EPE [San Jl De (registered trademark) Epon 70 Rochemical Co., Ltd. product], and Tekzel. ETE
Examples include thermofluid fluororesins known under trade names such as E (DuPont product).

When using Tekzeku ETFE, the temperature is approximately 300-400℃
In the case of Teflon PFA, Teflon FEP, and f'' flon EPE, it is heated and melted at a temperature of 330 to 450°C.

This heating, melt expansion injection molding, transfer molding, etc. are performed outside the mold. That is, in the case of injection molding, it is carried out in a barrel, and in the case of transfer molding, it is carried out in a pot, and then it is injected into a mold coated with PAS.

On the other hand, in the case of compression molding, rotational molding, etc., a method is adopted in which the material is heated and melted in a mold coated with PAS, and then cooled and solidified in the mold.

(Effects of the Invention) The above molding method, that is, the molding method of the first invention of the present application, simultaneously solves the problems of sticking of the tetrafluoroethrene copolymer to the mold and foaming of the molded product, which have different causes. This will solve the problem.

On the other hand, in the second invention of the present application, the PAS coating can only reduce the thermal decomposition of the tetrafluoroethylene copolymer and prevent the corrosive pyrolysis gas from coming into direct contact with the metal mold surface. Therefore, it is possible to manufacture molds using inexpensive carbon steel instead of using conventional corrosion-resistant alloys such as Hastelloy and stainless steel as materials for molds for molding tetrafluoroethylene copolymer. .

Furthermore, since PA8 is baked into gold, it does not wear out like normal mold release agents, and its surface hardness is high, so it can maintain its mold release effect for a long time.

(Example) Embodiment 1 of the present invention will be described below.

Example 1 A 5QXIQQ x 2.5m iron plate (material 8841) was degreased with solvent and air-baked, and half of its surface was coated with pps (
Approximately 20 pmlk of water-based dispersion paint (Sasteel C-400: Hodogaya Chemical Industry Product) was applied on a cloth and dried at 590°C.
Baking was performed for 50 minutes.

This iron plate was used as the bottom mold of a mold for hot compression molding, and a 1 gm thick Teflon PFA sheet (manufactured by Mitsui DuPont Chemical Co., Ltd.) was placed on top of it, heated in a furnace at 340 to 350°C, and the PFA sheet was melted.

Next, this was taken out of the furnace and compressed at a molding pressure of 50 degrees.
Cooling was performed.

After cooling, the iron plate (bottom mold) was taken out from the outer cylinder of the mold, and PFA was not adhered to the PPS-covered part (peel strength 0(j)).

On the other hand, PFA was strongly adhered to the part not coated with PPS, and its peel strength was 5.9 q/cs.

Example 2 PPS aqueous dispersion V-1 in a hemispherical fund shape with a diameter of 200 m
(Odugaya Chemical Industry product) was applied and baked at 330°C for 50 minutes. The PPS coated surface was then polished with waterproof abrasive paper (CC-600) and rebaked at 560°C for 60 minutes.

In this mold, Teflon PFA powder with a particle size of 200μ (Mitsui)
DuPont fluorochemical product) 270f was added, and the temperature was 5.
υ diameter 200■ by two-wheel rotation method in a 70℃ oven for 2 hours,
A 2-thick hollow sphere was molded.

No foaming was observed in the molded product, and the molded product did not adhere to the mold.

Patent Applicant: Limited Partnership Company Kichihi Nis.K.T. Procedural Amendment (Reference 6, January 17, 1985)

Claims (2)

[Claims] (1) Tetrafluoroethylene and the following formulas ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ and ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (In the formula, Rf_1 is H or a fluoroalkyl group with 1 to 5 carbon atoms, Rf_2 is Heating a copolymer with one or more comonomers of a fluoroalkyl group having 1 to 5 carbon atoms,
A method for molding a tetrafluoroethylene copolymer, which is characterized by melting, cooling and solidifying in a mold coated with polyarylene sulfide, and molding. (2) A mold for molding a tetrafluoroethylene copolymer, characterized in that it is coated with polyarylene sulfide.