JP2733400B2 - Synthetic resin molding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold for molding a synthetic resin and a molding method such as an injection molding method or an extrusion blow molding method using the mold.

[0002]

2. Description of the Related Art In order to improve the reproducibility of imparting a shape state of a mold surface to a molded article by injecting a thermoplastic resin into a mold cavity and mold the molded article, and to improve the gloss of the molded article, it is usually necessary to set a resin temperature. It can be achieved to some extent by selecting molding conditions such as increasing the injection pressure or increasing the injection pressure.

[0003] Among these factors, the mold temperature has the greatest effect, and it is preferable to increase the mold temperature.
However, when the mold temperature is increased, the cooling time required to cool and solidify the plasticized resin is increased, and the molding efficiency is reduced. There is a need for a method that improves the reproducibility of the mold surface without increasing the mold temperature and that does not increase the required cooling time even if the mold temperature is increased.

A heating hole and a cooling hole are attached to a mold, and a heating medium and a coolant are alternately flowed to heat the mold.
Although cooling is repeated, this method consumes a large amount of heat, and the cooling time is also reduced by using a mold in which the mold wall surface forming the mold cavity is coated with a thin tetrafluoroethylene or the like. It is introduced that injection molding improves the reproducibility of the mold surface, but tetrafluoroethylene has low hardness and it is difficult to make the mold surface mirror-finished,
Furthermore, there is also a problem with the durability of the thin tetrafluoroethylene layer, and this method has heretofore been generally difficult.

On the other hand, a method has been proposed in which only the mold wall surface of an iron mold cavity is rapidly heated by high-frequency induction heating, and injection molding is immediately performed while only the mold surface is heated (Japanese Patent Publication No. 58-40504). No. 57-4748, etc.). However, in this method, the high-frequency induction heating device is very expensive and is not common.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems. The present invention improves the reproducibility of imparting mold surface properties to a molded article when molding a thermoplastic resin by injection molding, compression molding, hollow molding, or another method, and particularly with a smooth mirror surface. If such is the case, a method for making the surface of the molded article a mirror surface as close as possible is provided.

[0007] In particular, when the synthetic resin contains a reinforcing material such as rubber, glass fiber, asbestos, a foaming agent or a filler, the surface of the mold is rough and a smooth surface cannot be obtained. The present invention also addresses these problems.

[0008]

Means for Solving the Problems The present inventors have proposed a mold surface.
The following conditions are required as preferable conditions for coating
Was found. (1) Low thermal conductivity (2) Excellent heat resistance (3) High tensile strength, resistant to thermal cycles (4) High surface hardness (5) Excellent wear resistance (6) To mold body coating is better able (7) adhesion to the mold body is good and the like. The smaller the thermal conductivity of the coating material, the better,
0.002 cal / cm · sec · ° C or less at room temperature, preferably
Or less than 0.001 cal / cm · sec · ° C
You. Heated and plasticized molten resin is injected into the mold cavity.
Since it is ejected and molded, the high temperature of the synthetic resin and the mold
Exposed to severe thermal cycling between body temperature
Therefore, the coating material has high strength, heat resistance,
It must be a material that can withstand cycling. Also, the mold body
Good adhesion to the film, and no peeling in the heat cycle
is required. Materials meeting these conditions include poly
Ether sulfone, polysulfone, polyphenylene a
The inventors have found that tellurium is preferred, and arrived at the present invention. sand
That is, according to the present invention, the thermal conductivity of the material of the main mold at room temperature is 0.05 cal / cm · sec · ° C. or more, and the unit shown in the following formula 2 is formed on the wall of the mold forming the mold cavity. To
At least one of the heat-resistant aromatic polymers as the repeating unit
A solution mainly composed of two components is applied and cured, and the cured coating film has a thickness of (a) 0.01 to 0.5 mm, and (b) an adhesion force to a mold of 200 g / 10 mm width (peeling speed 20 mm / Min) or more, (c) coating thickness (cm) / thermal conductivity (cal / cm · s)
(ec · ° C.) is a synthetic resin molding method of injecting and molding a heat-plasticized synthetic resin into a mold having a temperature of 1 to 100 .

Embedded image Further, the present invention provides a method for molding a synthetic resin, which is an injection molding method.
The synthetic resin molding method described above. Further, the present invention relates to a synthetic resin
The above synthetic resin molding, wherein the molding method is an extrusion blow molding method
Is the law.

Hereinafter, the present invention will be described in detail. The synthetic resin used in the present invention is a thermoplastic resin generally usable for injection molding, blow molding and the like. For example, styrene polymers and their copolymers, polyethylene, polypropylene and other olefin polymers and their copolymers, vinyl chloride polymers and copolymers, polyamides, polyesters and other thermoplastic resins can be used, especially for injection molded articles. Resin with poor appearance can be used favorably.

Various fillers can be blended with these resins.
For example, rubber that improves impact strength, glass fiber, asbestos, calcium carbonate, talc, calcium sulfate,
One or more of a foaming agent, wood flour and the like. The thermal conductivity at room temperature described in the present invention is 0.05 cal / cm · s
The main mold material of ec · ° C or higher is a metal mold material generally used widely for injection molding, extrusion blow molding, and the like.
Alloys mainly composed of steel and iron, aluminum and its alloys, zinc alloys and the like.

The heat-resistant polymer solution mainly composed of an aromatic polymer described in the present invention is a solution containing a polymer having an aromatic ring in the main chain as a main component, dissolved in a solvent and modified as necessary. The cured film has a heat resistance of 150 ° C at the continuous use temperature.
Above and / or a tough glass transition temperature of 200 ° C. or more. Further, in the present invention, there is also included a substance which is a precursor of a heat-resistant polymer in a solution state, and which becomes a tough aromatic polymer having excellent heat resistance by heating and curing after coating.

[0012] As the aromatic-based polymer are preferably used in the present invention, Ru poly <br/> sulfone, polyether sulfone, polyphenylene ether der in units repeated unit represented by the following formula 3.

[0013]

Embedded image

[0014]

[0015]

The adhesion of the polymer covering the mold surface to the mold is preferably as high as possible, but it is necessary that the polymer does not peel off at the time of injection molding of the synthetic resin.
The peel strength when the coating film is pulled at a speed of 200 mm / min is 200
Adhesion force of at least g / 10 mm width is required, and preferably at least 400 g / 10 mm width. The expression "mainly composed of the heat-resistant aromatic polymer described in the present invention" means that at least 40% by weight of the coating composition after curing is an aromatic polymer.
Preferably 50% by weight or more, more preferably 60% by weight
That is all.

In order to improve the adhesion of these aromatic polymers to the mold wall, it is possible to use an epoxy resin or the like having good adhesion in the solution. Polyphenylene ether and polyether sulfone are well compatible with epoxy resins and can be used particularly well in the present invention.

[0018]

[0019]

[0020]

The epoxy compound described herein has an average of two or more epoxy groups per molecule.

[0022]

Embedded image

It has a bond. These compounds are saturated or unsaturated aliphatic, aromatic or heterocyclic compounds, which may have a substituent such as halogen, hydroxy, ether and the like. Particularly preferred epoxy compounds include (1) glycidyl ether of polyphenol,
(2) glycidyl ether of polyphenyl ether,
(3) Aromatic glycidyl compound, (4) polynuclear aromatic glycidyl ether or (5) glycidyl ether glycidylbenzene.

The glycidyl ether of polyphenol is obtained by reacting epichlorohydrin with polyphenol in the presence of an alkali. Good polyphenols include 2,2-bis (4-hydroxyphenyl) propane,
1,1 ′, 2,2′-tetrakis (4-hydroxyphenyl) ethane, α, α, α ′, α ′, α ″, α ″ -hexakis (4-hydroxyphenyl) -1,3,5-tri Ethylbenzene 1,3,5-trihydroxybenzene or 1,1,5,5-tetrakis- (hydroxyphenyl) pentane or other glycidyl ether of novolak obtained by reaction of polyhydroxyphenol with formalin and novolak obtained by reaction of epichlorohydrin Etc.

Preferred examples of the glycidyl ether of polyphenyl ether include glycidyl ether of dihydroxydiphenyl ether. Bisphenol A
And an epoxy resin prepolymer synthesized from epichlorohydrin has the following structural formula.

[0026]

Embedded image

The epoxy resin may contain a curing agent for the epoxy compound having an epoxy ring as required. As the curing agent, primary and secondary amines and their compounds, acid anhydrides, polyamides, tertiary amines, amine salts, boron trifluoride, dicyandiamide and the like can be used. Dicyandiamide, diaminodiphenylsulfone, benzyldimethylamine and the like can be favorably used.

The epoxy ring of the epoxy resin has reactivity with the terminal hydroxyl group of the polyphenylene ether, and has adhesiveness with a mold. Epoxy resins containing from 2 to 10 epoxy rings in one molecule are highly preferred, as they bind to both polyphenylene ether and the mold under moderate reaction conditions. Polyethersulfone also has good compatibility with epoxy resins and can be used well.

The heat resistance of the coating film applied to the mold wall surface is preferably as high as possible, but a continuous use temperature of 150 ° C. or more and / or a glass transition temperature of 190 ° C. or more is required. Since the resin injected into the mold cavity is generally injected at a temperature exceeding 20 ° C., heat resistance close to the resin temperature is preferable. However, since the injected resin is rapidly cooled in contact with the cooled mold wall surface, heat resistance at a temperature slightly lower than the resin temperature at the time of injection may be sufficient, and generally a continuous use temperature of 150 ° C. or more and / or a glass transition temperature of 190 ° C. Can be used at ℃ or higher.

[0030]

An aromatic polymer having an aromatic ring in the main chain, generally called super engineering plastic, has excellent heat resistance,
Those which are tough and easily form a solution in these super engineering plastics and / or are easily compatible with an adhesive such as an epoxy resin are suitably used for the purpose of the present invention. Among super engineering plastics having an aromatic ring in the main chain, the non-crystalline polymer has good solubility in a solvent, and has good compatibility with an adhesive such as an epoxy resin, and can be used particularly preferably in the present invention. .

Crystalline aromatic polymers whose molecular weight has been reduced or whose solubility has been improved by adding a copolymer component are also:
It can be used in the present invention. The solvent described here is a solvent that forms a solution suitable for application to a mold, and includes concentrated sulfuric acid,
Solvents such as concentrated nitric acid and concentrated alkali cannot be used and are not included in the present invention. In the present invention, the thickness of the aromatic polymer coated on the mold surface is 0.01 to 0.5 mm. This thickness is determined by the thermal conductivity of the aromatic polymer, the mold temperature, the temperature at the time of injection of the synthetic resin to be injection-molded, the softening temperature of the resin, and the like.

If the thickness of the aromatic polymer is too large, the time required for cooling the injected synthetic resin in the mold becomes long, causing problems such as difficulty in mirror-like coating. The thickness of the aromatic polymer is thinner as the thermal conductivity is smaller, and thicker as the thermal conductivity is larger. Thickness (cm) / thermal conductivity (cal / c
m · sec · ° C) value is preferably 1 to 100, more preferably 2 to 100.
50 can be used particularly well. If it is smaller than this range,
If the mold surface reproducibility deteriorates and it exceeds this range,
This tends to increase the cooling time in the mold.

In injection molding, it is required to reduce one cycle for obtaining a molded product, and it is required to shorten the in-mold cooling time. The gloss of the molded product and the molding cycle are greatly affected by the mold temperature. Regarding the mold temperature during molding, if the mold temperature is high, the cooling time inside the mold may be undesirably long, and if it is too low, condensation may occur on the mold surface, and the injected synthetic Heat deformation temperature of resin (AST
Molding is preferably performed at a mold temperature between less than MD648 (18.6 kg / cm ² ) and room temperature. Generally, a mold at about room temperature or slightly higher temperature is often used. However, a heat-resistant resin having a high softening temperature is molded at a high mold temperature.

The temperature at the time of injection of the synthetic resin is determined by the thermal stability temperature-viscosity relationship of the synthetic resin and the like, and there is generally no wide selection range. The present invention covers the mold cavity surface of a metal mold that is a good heat conductor in a thin layer with an aromatic polymer that is a low heat conductor, and heats the mold surface with the heat of the injected heating resin itself, The purpose is to improve the mold surface reproducibility of molded products. The thermal conductivity of an aromatic polymer is generally half that of iron.
The thermal conductivity is sufficiently low for the purpose of the present invention. Therefore, when a low thermal conductive material is selected, it is selected in terms of hardness, heat resistance, abrasion resistance, coating adhesion and the like.

[0036]

【Example】

[0037]

Example 1 An experiment was conducted using the following. Main mold: made of steel (S55C) and having a 2 mm thick flat mold cavity. The thermal conductivity of the steel is 0.
12 cal / cm · sec · ° C. Polyphenylene ether: poly (2,6-dimethylphenylene-1,4-ether), number average molecular weight is 1500
0 epoxy resin: an epoxy equivalent produced using bisphenol A and epichlorohydrin as main raw materials having an epoxy equivalent of 180 to 19
Epoxy resin 70 parts by weight of polyphenylene ether, epoxy resin 30
Parts by weight and 0.1 parts by weight of triethyleneammonium chloride were mixed and stirred at 230 ° C. for 6 hours to react polyphenylene ether with the epoxy resin. A solution was prepared by mixing 10 parts by weight of the above reactant and 89.6 parts by weight of diaminodiphenylmethane 0.4% trichloroethylene, and the solution was applied to the mold cavity wall of the main mold, dried at room temperature, and then cured at 200 ° C. for 1 hour. To cover the mold wall.

Next, the coated surface was polished to obtain a mirror-shaped mold having a coating film thickness of 0.04 mm. The thermal conductivity of the coating film was 0.0004 cal / cm · sec · ° C., and the adhesion to the mold was 700 g / 10 mm width. Using a mold coated with epoxy resin modified port polyphenylene ether described above, the mold having a steel mold surface of the main mold, rubber reinforced polystyrene, Asahi Chemical Industry Co., Ltd., with Styron 495 exit as a synthetic resin After molding, the gloss of the molded product was measured and the results are shown in Table 1.

[0039]

[Table 1]

[0040]

Example 2 An experiment was conducted in the same manner as in Example 1 using polyether sulfone, and almost the same results were obtained.

[0041]

According to the present invention, a molded article having excellent mold surface reproducibility can be economically obtained.

Claims (3)

(57) [Claims] The thermal conductivity of a material of a main mold at room temperature is at least 0.05 cal / cm · sec · ° C., and a unit represented by the following formula 1 is formed on a wall surface of a mold forming a mold cavity.
At least one of the heat-resistant aromatic polymers as the repeating unit
A solution mainly composed of two components is applied and cured, and the cured coating film has a thickness of (a) 0.01 to 0.5 mm, and (b) an adhesion force to a mold of 200 g / 10 mm width (peeling speed (C) coating thickness (cm) / thermal conductivity (cal / cm · s)
(ec · ° C.) is a synthetic resin molding method in which a synthetic resin that has been plasticized by heating is injected into a mold having a temperature of 1 to 100 and molded. Embedded image 2. The method according to claim 1, wherein the synthetic resin molding method is an injection molding method.
Item 4. The synthetic resin molding method according to Item 1. 3. The synthetic resin molding method is an extrusion blow molding method.
The method for molding a synthetic resin according to claim 1 .