JPH0919928A - Heat insulating layer clad mold and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a molded article having an excellent surface by a method wherein a heat insulating layer having a substantially uniform thickness ranging to the end of a mold wall surface is formed by applying a heat-resistant polymer solution, a heat-resistant polymer precursor solution or a heat-resistant polymeric monomer on the mold wall surface. SOLUTION: In order to make a heat insulating layer clad mold, firstly an auxiliary 7 is pasted to the edge face of a mold insert 1. The auxiliary 7 is made, for example, of an epoxy resin and, after being mixed with a hardener, applied to the edge face of the mold insert 1 and then machined to be flush with the surface of the mold insert 1. Next, by applying a heat-resistant polymer solution, a heat-resistant polymer precursor solution or a heat-resistant polymeric monomer and hardening, a heat insulating layer 3 is formed. Thus, a thin walled portion 9 and a thick walled portion 10 are formed on the surface portion of the auxiliary 7. Then, by heating up to the temperature, which is higher than the glass transition temperature of an epoxy resin of the auxiliary 7 and lower than the glass transition temperature of the heat insulating layer 3, the auxiliary 7 is removed. After that, through machining and polishing, the heat insulating layer 3, which is uniform in thickness to the end part 11, is finished.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a mold for molding synthetic resin. More specifically, the present invention relates to a method for producing a heat-insulating layer-coated mold used for injection molding, blow molding, vacuum molding, compression molding, and the like of a synthetic resin.

[0002]

2. Description of the Related Art When a thermoplastic resin is injected into a mold cavity for molding, it is necessary to improve reproducibility in imparting a shape state of a mold surface to a molded product and to improve the appearance of the molded product.
Generally, it can be achieved to some extent by selecting molding conditions such as increasing the resin temperature and the mold temperature, and 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 for cooling and solidifying the plasticized resin is prolonged and the molding efficiency is reduced, so that the reproducibility of the mold surface is improved without increasing the mold temperature, and There is a demand for a method in which the required cooling time is not prolonged even when the mold temperature is increased. There is also a method in which heating and cooling holes are attached to the mold, and heating medium and cooling medium are alternately flowed to heat and cool the mold.
This method also consumes a lot of heat and prolongs the cooling time.

A mold in which the mold wall forming the mold cavity is coated with a substance having a small thermal conductivity, that is, a heat insulating layer is disclosed in WO 93/06980, and a polyimide precursor solution is used as a heat insulating material. It has been shown to be applied to the mold wall and then imidized to form a thermal insulation layer.

[0005]

In recent years, there has been an increasing demand for omitting post-processing such as painting on injection molded products and blow molded products of synthetic resins. There is an extremely strong desire to eliminate painting in order to reduce manufacturing costs, reduce environmental destruction due to solvent evaporation during painting, and facilitate the recycling of molded products. There is a strong demand for omitting post-processing of synthetic resin housings for electrical equipment, electronic equipment, office equipment, etc. As a method for molding a molded product having good productivity and good mold surface reproducibility, a method of molding using a heat insulating layer-coated mold is the best method. There are various methods for coating the heat insulating layer on the surface of the mold, but the method of applying a heat insulating material to the surface of the mold is a good method.

However, it is extremely difficult to uniformly apply the heat insulating material solution or the like to the surface of the mold. For example, when the fixed side of the main mold is composed of one or more mold nests,
A method is employed in which each mold insert is separately coated with a heat insulating material to form a heat insulating layer and then assembled into a mold. In that case, between the mold inserts, or between the mold insert and the fixed-side main mold, there is a step in the mating portion, and if injection molding is performed with the mold, a good molded product cannot be obtained. There's a problem. That is, the end portion of each mold insert is not covered with the heat insulating layer to a uniform thickness due to the effect of the surface tension of the heat insulating material coating, and the thickness of the heat insulating layer at the end portion becomes thin. It is required to solve this problem. .

This problem will be described with reference to FIGS. 1 and 2. FIG. 1 shows a heat-insulating-layer-covered mold in which the mold surface 2 of the mold insert 1 is uniformly covered with a heat-insulating layer 3, which is the object of the present invention. FIG. 2 shows that when a heat insulating material is applied to the surface 2 of the mold insert 1 and heated to form the heat insulating layer 3, a thin heat insulating layer 5 is generated at the end 4 of the mold insert, and in some cases, a little from the end. A thick heat insulating layer 6 is generated at a position inside (2-1). When this heat insulating layer is polished to be smooth, the heat insulating layer 5 at the end portion becomes a thin heat insulating layer (2-2), and the heat insulating layer-covering mold shown in FIG. 1 cannot be obtained. When this heat insulation layer-covered mold insert is used for injection molding, the surface of the molded product at the end of the heat insulation layer 5 has a swollen shape. If the heat insulating layer is formed by applying a heat insulating material by an ordinary method, this defect occurs. Therefore, a solution is required.

[0008]

In order to solve these problems, the present inventors have conducted a study on a method for producing a mold covered with a heat insulating layer, and arrived at the present invention. That is, the present invention is as follows. 1. A mold wall forming a mold cavity of a mold made of metal is a mold in which a heat-insulating layer of a predetermined size made of a heat-resistant polymer is coated, a heat-resistant polymer solution, a heat-resistant polymer precursor solution, or A heat-insulating layer-coated mold having a heat-insulating layer formed by applying a heat-resistant polymer monomer to a mold wall surface and having a substantially uniform thickness up to the end of the mold wall surface. 2. An auxiliary tool is attached to the end surface of the mold wall surface, and a heat-resistant polymer solution, a heat-resistant polymer precursor solution, or a heat-resistant polymer monomer is applied to the mold wall surface and the auxiliary tool surface at the same time, followed by heat curing. A method for producing a heat-insulating layer-coated mold, which comprises forming a heat-insulating layer made of a heat-resistant polymer, then removing the auxiliary tool, cutting and polishing the applied heat-insulating layer, and finishing the heat-insulating layer to a predetermined size. 3. After a heat-resistant resin film having almost the same thermal conductivity as that of the heat insulating layer is attached to the end of the mold wall, a heat-resistant polymer solution, heat-resistant polymer precursor solution, or heat-resistant polymer monomer is applied to the mold wall. Is applied and heat-cured to form a heat-insulating layer made of a heat-resistant polymer, and then the applied heat-insulating layer is cut and polished to obtain a heat-insulating layer-coated mold for finishing into a heat-insulating layer having a predetermined size. 4. A protrusion of the main mold is provided at the end of the mold wall surface, the protrusion has substantially the same height as the heat insulating layer to be formed, and the width of the upper surface of the protrusion is substantially 0. A polymer solution, a heat-resistant polymer precursor solution, or a heat-resistant polymer monomer is applied, heat-cured to form a heat-insulating layer made of the heat-resistant polymer, and then the applied heat-insulating layer is cut and polished. ,
A method for manufacturing a heat insulation layer-covering mold that finishes a heat insulation layer of a specified size. 5. A heat-resistant polymer solution, heat-resistant polymer precursor solution, or heat-resistant polymer monomer is applied to a mold material slightly larger than the mold to be manufactured, and heat-cured to form a heat-insulating layer made of the heat-resistant polymer. Then, a method for producing a heat-insulating layer-covered mold, in which a mold material coated with a heat-insulating layer is cut to a mold size and polished to a predetermined size.

The present invention will be described in detail below. Synthetic resin molded using the mold of the present invention is a thermoplastic resin that can be used for general injection molding and blow molding, and polyethylene, polyolefin such as polypropylene, polystyrene, styrene-acrylonitrile copolymer, rubber-reinforced polystyrene, Styrene resins such as ABS resin, polyamide, polyester, polycarbonate, methacrylic resin, vinyl chloride resin and the like. 1-6 for synthetic resin
It is preferable to contain 0% of resin reinforcement. The resin-reinforced material includes various fibers such as various rubbers, glass fibers, and carbon fibers, and inorganic powders such as talc, calcium carbonate, and kaolin. Particularly preferred are rubber-reinforced synthetic resins, and among them, rubber-reinforced styrene-based resins are more preferably used.

Good molded products molded by the mold of the present invention are generally used synthetic resin injection molded products such as housings for light electric appliances, electronic devices, office equipment, various automobile parts, various daily necessities and various industrial parts. Is. Particularly preferred are housings of electronic equipment, electric equipment, office equipment, etc., which have many weld lines. Further, good molded products molded by the mold of the present invention are various blow molded products that are required to have an appearance.

The metal mold described in the present invention is generally composed of iron or a steel material containing iron as a main component, aluminum, an alloy containing aluminum as a main component, a zinc alloy such as ZAS, or a beryllium-copper alloy. Includes metal molds used to mold resins. Particularly, a mold made of a steel material can be used favorably. The mold surface of the mold cavity made of these metals is preferably plated with hard chromium, nickel or the like.

The heat resistant polymer used in the heat insulating layer in the present invention is a polymer having a softening temperature higher than the molding temperature of the synthetic resin to be molded, and preferably has a glass transition temperature of 1 or less.
It is a heat resistant polymer having a temperature of 40 ° C. or higher, preferably 160 ° C. or higher, more preferably 200 ° C. or higher, and / or a melting point of 200 ° C. or higher, more preferably 250 ° C. or higher. The heat conductivity of the heat resistant polymer is generally 0.0001 to 0.002 ca.
1 / cm · sec · ° C, which is significantly smaller than metal.
Further, a tough polymer having a breaking elongation of 5% or more, preferably 10% or more is preferable for the heat resistant polymer. The elongation at break is measured according to ASTM D638, and the tensile speed at the time of measurement is 5 mm / min.

The heat-resistant polymer which can be favorably used as the heat insulating layer in the present invention is a heat-resistant polymer having an aromatic ring in its main chain, and for example, various amorphous heat-resistant polymers and various polyimides which are soluble in an organic solvent. Etc. can be used satisfactorily. Examples of the non-crystalline heat resistant polymer include polysulfone, polyether sulfone and polyether imide. These amorphous heat-resistant polymers can be used as the heat-insulating layer of the present invention by lowering the coefficient of thermal expansion by adding a filler such as carbon fiber. There are various types of polyimides, and linear high molecular weight polyimides, polyamideimides, and partially crosslinked polyimides can be used favorably. In general, straight-chain high molecular weight polyimides have large breaking elongation, are tough, have excellent durability, and can be used particularly favorably.

Further, in the present invention, an epoxy resin having a small coefficient of thermal expansion, that is, an epoxy resin cured product obtained by combining an epoxy resin having a small coefficient of thermal expansion and a curing agent, or an epoxy resin containing an appropriate amount of various fillers can be used. . In the present invention, the cured epoxy resin is also referred to as epoxy resin. Further, a compounded epoxy resin having toughness obtained by adding toughness thermoplastic resin such as nylon, and various compounds such as rubber to provide toughness to the epoxy resin or filler-containing epoxy resin can be preferably used. In particular, a polymer alloy cured by mixing polyethersulfone or polyetherimide with an epoxy resin has a large elongation at break, has excellent toughness, and can be used favorably.

The heat-insulating layer-coated mold of the present invention has a mold wall surface coated with a heat-insulating layer, and the surface thereof is 1 / th of the thickness of the heat-insulating layer.
It is preferable to coat and use a thin metal layer of 5 or less, preferably 1/7 or less. In injection molding, blow molding and the like, a mold surface that comes into contact with a heated resin to be molded is subjected to a severe cooling / heating cycle for each molding. Further, in the prior art, the metal layer formed on the surface of the heat insulating layer by plating or the like generally has a smaller coefficient of thermal expansion than the heat insulating layer made of a polymer, and the coefficient of thermal expansion of the heat insulating layer and that of the metal layer are largely different. Stress is repeatedly generated and peeling occurs at the interface. By reducing the difference between the coefficient of thermal expansion of the mold and / or the metal layer in contact with the heat insulating layer and the coefficient of thermal expansion of the heat insulating layer, the stress that causes peeling can be reduced. In the present invention, the difference between the coefficient of thermal expansion of the mold and / or the metal layer in contact with the heat insulating layer and the coefficient of thermal expansion of the heat insulating layer is preferably less than 4 × 10 ⁻⁵ / ° C., and more preferably 3 × 10 ^−. It is less than ⁵ / ° C. In general, metals have a lower coefficient of thermal expansion than polymers, and it is therefore preferable to select a heat-resistant polymer having a smaller coefficient of thermal expansion.

The coefficient of thermal expansion described here is a coefficient of linear expansion. The thermal expansion coefficient of the heat insulating layer is a linear expansion coefficient in the surface direction of the heat insulating layer, and is measured by the method shown in JIS K7197-1991, and is the average value between the temperatures of 50 ° C. and 250 ° C., or the glass transition temperature of the heat insulating layer. If the temperature is below 250 ℃,
It is shown as an average value between 50 ° C. and the glass transition temperature. That is, a heat insulating layer is formed on a smooth flat metal, and then the heat insulating layer is peeled off, and the heat insulating layer is heated between 50 ° C. and 250 ° C.
Alternatively, the average coefficient of thermal expansion between 50 ° C and the glass transition temperature is measured.

In the present invention, a mold comprising two or more heat insulating layers can be favorably used. In this case, it is preferable that at least the difference between the coefficient of thermal expansion of the mold and / or the metal layer in contact with the heat insulating layer and the coefficient of thermal expansion of the heat insulating layer is small, which is 4 × 10.
It is preferably less than ^-5 / ° C, more preferably 3x.
10 ⁻⁵ / ° C. The most severe stress is generated at the interface between the metal layer and the heat insulating layer when the mold is coated with the heat insulating layer and the metal, or when injection molding or the like is performed. The stress generated can be reduced by selecting and using a material having a thermal expansion coefficient close to both layers forming the interface.

The cause of peeling between the heat insulating layer and the mold or between the heat insulating layer and the metal layer is not only the difference in the coefficient of thermal expansion. However, the difference in the coefficient of thermal expansion is an extremely large factor. If the heat insulating layer has a large adhesion between the mold and / or metal layer, the heat insulating layer has a small tensile elastic modulus, and the breaking elongation is large, a so-called rubbery soft material heat insulating layer has a difference in thermal expansion coefficient. Does not occur even if is slightly larger. However, a material suitable for the heat insulating layer, that is, a heat insulating material having high heat resistance, high hardness, and easily becoming a mirror surface by polishing is generally a heat resistant hard synthetic resin having an aromatic ring in the main chain with a large elastic modulus. Therefore, in order to bring the heat-resistant synthetic resin layer into close contact with the mold and / or the metal layer so as not to cause peeling, it is preferable that the difference in the coefficient of thermal expansion is small.

When the wall surface of the mold is covered with a heat insulating layer, the heat insulating layer is required to have various performances. In addition to adhesion to the main mold, toughness, surface hardness, glossiness when the surface is polished, and the like are required. In addition to having a small coefficient of thermal expansion, it may be difficult to obtain a polymer satisfying all of these properties. In this case, it is preferable to use two or more heat insulating layers.

Table 1 shows the thermal expansion coefficients of the metal of the mold which can be favorably used in the present invention, the metal of the metal layer coated on the outermost surface, the heat resistant polymer of the heat insulating layer, and general synthetic resins.

[0021]

[Table 1]

If the coefficient of thermal expansion of the mold and / or the metal layer is increased, the heat insulating layer having a relatively large coefficient of thermal expansion can be used. Steel is most often used as a mold material, but recently aluminum alloys and zinc alloys have also been used. Table 2 shows the structure and glass transition temperature (Tg) of the heat-resistant polymer which can be favorably used in the present invention.

[0023]

[Table 2]

Injection molding has an economic value in that a molded product having a complicated shape can be obtained by a single molding. In order to coat the complex mold surface with a heat-resistant polymer and make it adhere tightly, a heat-resistant polymer solution and / or a heat-resistant polymer precursor solution is applied, and then heated to heat-resistant polymer. It is most preferable to form a united heat insulating layer. Therefore, the heat resistant polymer of the present invention or the precursor of the heat resistant polymer needs to be soluble in a solvent. A method in which a solution of a polyamic acid, which is a precursor of polyimide, is applied to a mold wall surface and then cured by heating to form polyimide on the mold wall surface can be used favorably. Formula 1 shows a formula for forming a polyimide from a polyamic acid.

[0025]

Embedded image

It is necessary that the heat-insulating layer and the mold of the present invention and / or the heat-insulating layer and the metal layer have a high adhesion, and the width at room temperature is preferably 0.5 kg / 10 mm or more, more preferably 0.8 kg. / 10 mm width or more, most preferably 1 kg
/ 10 mm width or more. This is the peeling force when the metal layer or the heat-insulating layer or the metal layer in contact with each other is cut to a width of 10 mm and pulled at a speed of 20 mm / min in a direction perpendicular to the bonding surface. This peeling force varies considerably depending on the measurement location and the number of measurements, but it is important that the minimum value is large.
A stable and large peeling force is preferable. The adhesion described in the present invention is the minimum value of the adhesion of the main part of the mold.
In order to improve the adhesion, it is possible to appropriately form the surface of the mold into fine irregularities, perform various kinds of plating, and perform a primer treatment. As a preferable example of the primer treatment, a polyimide containing a large amount of CO ₂ group or SO ₂ group easily adheres to the surface of the metal mold, and a thin layer of polyimide having excellent adhesion is used as a primer layer. Can be favorably used.

Injection molding has the greatest merit that a mold having a complicated shape can be formed by one molding, and therefore, the mold cavity generally has a complicated shape. However, it is extremely difficult to apply a coating substance to the surface of this complex-shaped mold cavity in a mirror-like manner.Therefore, the applied coating layer is polished later, and the coating layer is numerically controlled by a numerical control milling machine. The best method is to grind the surface after polishing with a control machine tool and finish it to a mirror surface.

In the present invention, the total thickness of the heat insulating layer is 0.1 mm.
It is preferable to select an appropriate value within a narrow range of 1 mm. More preferably, it is 0.1 mm to 0.3 mm in injection molding and 0.3 mm to 0.6 mm in blow molding. For thin insulation layers less than 0.1 mm,
There is little effect of improving the appearance of molded products. If the thickness of the heat insulating layer exceeds 1 mm, the cooling time in the mold becomes long, which is not preferable from an economic viewpoint.

In molding a thermoplastic resin, the mold temperature and the molding cycle time are closely related. That is, the relationship between the mold temperature (Td) and the required cooling time (θ) in the mold during molding is theoretically expressed by the following equation. θ = − (D ² / 2πα) · ln [(π / 4) {(Tx−
Td) / (Tc−Td)｝] θ: Cooling time (sec) D: Maximum thickness of molded article (cm) Tc: Cylinder temperature (° C) Tx: Softening temperature of molded article (° C) α: Heat of resin Diffusivity Td: Mold temperature (° C) Cooling time (θ) is proportional to the square of the molded product thickness (D),
It is a function of the (Tx-Td) value. That is, it is a function of the value obtained by subtracting the mold temperature from the softening temperature of the synthetic resin. When this value is small, a change in this value causes a large change in the cooling time. However, when this value is large, a change in the cooling time becomes small.

Covering the mold with a heat-insulating layer has the same function as increasing the thickness of the molded product and lengthening the cooling time, while decreasing the mold temperature shortens the cooling time. Work in the direction. It is preferable from the viewpoint of the molding cycle time that the thickness of the heat insulating layer is thin and the appearance can be improved. When the surface of a metal mold is covered with a heat insulating layer, and the heated resin injected into contact with the surface of the mold, the mold surface receives the heat of the resin and rises in temperature. The lower the thermal conductivity of the heat insulating layer and the thicker the heat insulating layer, the higher the mold surface temperature.

The heat-insulating layer-coated mold of the present invention can be manufactured by various methods. That is, it is a method for producing a heat-insulating layer-covering mold formed by applying a heat-insulating material, and is a method using any of the following. (1) An auxiliary tool is attached to an end face of a mold wall surface, a heat insulating material is applied to the mold wall surface and the auxiliary tool surface at the same time, and heat-cured to form a heat insulating layer made of a heat-resistant polymer, and then the auxiliary tool. Is removed, and the applied heat insulation layer is cut and polished to obtain a heat insulation layer of a specified size. (2) After a heat-resistant resin film having substantially the same thermal conductivity as that of the heat insulating layer is attached to the end of the mold wall, a heat insulating material is applied to the mold wall and heat-cured to form a heat-insulating layer made of a heat-resistant polymer. And then cutting and polishing the applied heat-insulating layer to finish it into a heat-insulating layer having a predetermined size. (3) A protrusion of the main mold is provided on the end of the mold wall surface, the protrusion is almost at the same height as the heat insulating layer to be covered, and the width of the upper surface of the protrusion is substantially 0. A method of applying a material, heat-curing it to form a heat-insulating layer made of a heat-resistant polymer, and then cutting and polishing the applied heat-insulating layer to finish it into a heat-insulating layer having a predetermined size. (4) A heat insulating material is applied to a main mold material that is slightly larger than the mold to be manufactured, heat-cured to form a heat insulating layer made of a heat resistant polymer, and then the mold size for manufacturing the main mold and the heat insulating layer is set. The auxiliary tool described in the method (1) of cutting and polishing to finish to a predetermined size is an object to be attached to the end of the mold insert or the fixed-side mold for performing the heat insulating layer coating,
It is an object that extends the mold insert and the stationary mold slightly to the end face side. This auxiliary tool may be adhered to the end of the mold insert or the fixed side mold by using metal or heat resistant resin, or epoxy resin or other various adhesives may be applied and used as the auxiliary tool. . Epoxy resins can be successfully used in the aids of the present invention. It is necessary that these adhesives and adhesives can be easily removed later. The epoxy resin can be easily peeled off by heating the glass transition temperature of the epoxy resin or higher. By selecting an epoxy resin having an appropriate glass transition temperature, the epoxy resin can be favorably used as an auxiliary tool or an adhesive for the auxiliary tool. That is, when a heat-resistant resin such as polyimide is used for the heat insulating material, the epoxy resin loses its adhesive force and can be easily peeled off by heating at a temperature higher than the glass transition temperature of the epoxy resin and lower than the glass transition temperature of the polyimide.

The end surface of the mold wall surface described here is an end surface that constitutes an end portion that covers the heat insulating layer up to the end portion of the mold and / or the mold nest, and the heat insulating layer has an acute angle at the end surface portion. Bent or the insulation is over. Stated here,
To apply the heat insulating material to the mold wall surface and the auxiliary tool surface at the same time means to simultaneously apply the auxiliary tool attached to the end surface of the mold wall surface and the mold wall surface simultaneously.

The finishing of the heat insulating layer having a predetermined size described here is to cut the applied heat insulating layer to a predetermined size by cutting, polishing or the like. Cutting is performed by using a machine tool such as a milling machine. The heat-resistant resin film having substantially the same heat conductivity described in (2) means a heat-resistant resin film having a heat conductivity of 1/2 to 2 times that of the heat insulating layer. Further, the heat resistant resin film is a material that can be well adhered to the heat insulating layer formed by coating, and is preferably made of the same resin as the heat insulating material. For example, when the heat insulating material is polyimide, the heat resistant resin film is preferably a polyimide film of the same quality. The width of the heat resistant resin film to be stuck is about 1 to 20 mm and is appropriately selected according to the shape of the mold. The film is adhered with a heat resistant adhesive.
In the case of a polyimide film, a polyimide heat resistant adhesive is preferable.

As described in (3), when the width of the upper surface is substantially 0, when the synthetic resin is molded using the mold, when the molded product is viewed with the naked eye, the mark of the protrusion is the surface of the molded product. In general, the width is preferably 0.5 mm or less, and more preferably 0.3 mm or less. Moreover, the height substantially equal to that of the heat insulating layer formed means that the gap between the protrusion and the heat insulating layer formed is ± 20 μm or less.

The main mold described in (4), which is slightly larger than the mold to be manufactured, is a mold in which the main mold is projected so that the mold surface is extended to the mold end face of the main mold. Is 1
It is about 20 mm. It is preferable that a thin metal layer having a thickness of ⅕ or less of the thickness of the heat insulating layer is provided on the surface of the heat insulating layer manufactured by these methods and finished to a predetermined size, if necessary. The metal layer can be coated in various ways, but is better coated by plating. The plating described here is chemical plating and electrolytic plating. Generally, plating is performed through some of the following steps. That is, first, chemical plating is performed in contact with the heat insulating layer.

Pretreatment (deburring, degreasing) → chemical corrosion (chemical etching with acid or alkali: making the surface have appropriate irregularities) → neutralization → sensitization treatment (adsorption of a reducing metal salt on the synthetic resin surface) To activate the effect) → Activation treatment (applying precious metal such as palladium with catalytic action on the resin surface) → Chemical plating (chemical nickel plating, chemical copper plating, etc.) → Electrolytic plating (electrolytic nickel plating, electrolysis) (Copper plating, electrolytic chrome plating, etc.) (For details, refer to "Plastic plating" written by Tatsumu Romo, 1974, published by Nikkan Kogyo Shimbun, etc.).

The present invention will be described with reference to the drawings. 3, 4, 5, 6, and 7 show the mold manufacturing method of the present invention. In FIG. 3, an auxiliary tool 7 is attached to the end surface of the mold insert 1. The mold insert 1 is made of metal, and the auxiliary tool 7 is made of heat resistant resin, epoxy resin or the like. In the case of an epoxy resin, the epoxy resin is coated with a curing agent on the end face of the mold insert to be cured, and the epoxy resin is cut until the surface of the mold insert 1 is flush with the surface. In this state, a heat insulating material made of a heat resistant resin such as polyimide is simultaneously applied to the surface of the mold insert 1 and the surface of the auxiliary tool 7 and cured to form the heat insulating layer 3. The heat insulating layer 3 has a thin portion 9 and a thick portion 10 on the surface of the auxiliary tool 7 (3-1). The thick portion 10 and / or the thin portion 9 are always generated due to the surface tension of the applied heat insulating material. Then, the auxiliary tool 7 is removed by heating it to a temperature higher than the glass transition temperature of the epoxy resin of the auxiliary tool 7 and lower than the glass transition temperature of the heat resistant resin of the heat insulating layer 3 (3-2). Next, the heat insulating layer 3 is cut and polished to complete the heat insulating layer 3 having a predetermined size. The heat insulating layer 3 becomes a heat insulating layer having a uniform thickness up to the heat insulating layer end portion 11 required by the present invention (3-3).

FIG. 4 shows a case where an auxiliary tool 12 made of a solid object is attached as an auxiliary tool so as to rise above the mold surface. In this state, a heat insulating material made of a heat resistant resin such as polyimide is simultaneously applied and cured on the surface of the mold insert 1 and the surface of the auxiliary tool 12 to form the heat insulating layer 3 (4-
1). Then, similarly, the auxiliary tool 12 is removed. The formed heat insulating layer 3 has a raised portion at the end (4-
2). Next, the heat insulating layer 3 is cut and polished to complete the heat insulating layer 3 having a predetermined size. The heat insulating layer 3 becomes a heat insulating layer having a uniform thickness up to the heat insulating layer end portion 11 required by the present invention (4-3).

In FIG. 5, a heat-resistant resin film 13 having substantially the same thermal conductivity as that of the heat insulating layer is attached to the end of the mold surface of the mold insert 1 (5-1). A heat insulating material made of a heat resistant resin such as polyimide is applied to the surface and cured to form the heat insulating layer 3 (5-2). Then, the heat insulating layer 3 is cut and polished to finish the heat insulating layer 3 up to the end 11 of the heat insulating layer to obtain the heat insulating layer-coated mold of the present invention (5-3).

FIG. 6 shows that at the end of the mold wall surface of the mold insert 1,
The protrusion 14 is provided, and the height 16 of the protrusion 14 is made substantially the same as that of the heat insulating layer, and the width 15 of the upper surface of the protrusion is substantially 0 (6-1). A heat insulating material is applied to the mold wall surface to form the heat insulating layer 3 (6-2), and then the heat insulating layer 3 is cut or polished to a substantially constant thickness up to the end of the mold wall surface. Is formed to obtain the heat-insulating layer-covering mold of the present invention (6-3). The width 15 of the upper surface being substantially 0 means that the protrusion 14 is formed on the surface of a molded product molded using this mold.
The width is such that the traces of can be invisible to the naked eye.
Is preferably 0.5 mm or less, more preferably 0.3 m
m or less.

In FIG. 7, a protruding portion 17 protruding from the mold insert 1 to be produced is provided on the end face of the mold, a heat insulating material is applied to the mold surface and the protruding portion 17, and heat-cured to form a heat insulating layer 3 (7). -1). Next, the heat insulating layer 13 and the overhanging portion 17 are cut and polished to the desired size of the mold, and the heat insulating layer 3 having a uniform thickness is obtained up to the heat insulating layer end 11 to obtain the heat insulating layer-coated mold of the present invention. (7-2).

By using the mold of the present invention, the conspicuous weld lines of the synthetic resin molded product can be reduced, the reproducibility of the mold surface can be improved, and post-processing such as painting performed after molding can be omitted.

[0043]

EXAMPLE The following mold, heat insulating layer and metal layer are used. Main mold and mold nest: A steel (S55C) mold for injection molding. The coefficient of thermal expansion of the mold is 1.1 × 10 ^-5
/ ° C. The portion forming the mold cavity of the main mold 18 used in FIG. 8 is composed of the two mold inserts 19 and 2 shown in FIG.
Consists of zero. The two mold nests 19 and 20 are the mating section 2
1 is in contact. Three sets of these mold inserts are prepared. Hard chrome plating is performed on the surface constituting the mold cavity of each nest. Insulation layer: Prime the inner mold surface of the main mold. As a primer, a polyimide precursor solution containing a large amount of CO ₂ groups is applied to a thin layer and heated to form a polyimide thin layer, which is used as a primer. A polyimide varnish (Treney # 3000 trade name manufactured by Toray Industries, Inc.) is applied thereon, and heated at 160 ° C., and then this application and heating are repeated until a predetermined thickness is obtained, and then the polyimide layer is heated at 290 ° C. To form. The coefficient of thermal expansion of the polyimide is 3.3.
× 10 ⁻⁵ / ° C.

[0044]

Example 1 A heat insulating layer-coated mold of the present invention is manufactured by the process shown in FIG. In FIG. 3, an epoxy resin (ARALDITE manufactured by Asahi Chiba Co., Ltd.) is attached to the end surface of the mold insert 1.
AER 260) is applied and cured, and the epoxy resin is cut until the surface of the mold insert 1 is flush with the surface of the mold insert 1 to form the auxiliary tool 7. In this state, the heat insulating layer 3 is simultaneously formed on the surface of the mold insert 1 and the surface of the auxiliary tool 7. The heat insulating layer 3 has a thin portion 9 and a thick portion 10 on the surface of the auxiliary tool 7 (3-1). Next, the auxiliary tool 7 is removed by heating to 250 ° C. higher than the glass transition temperature of the epoxy resin of the auxiliary tool 7 and lower than the glass transition temperature of the heat insulating layer 3 (3-2).
Next, the heat insulating layer 3 is cut and polished to complete the heat insulating layer 3 having a predetermined size. The heat insulating layer 3 is cut and polished until the heat insulating layer end 11 has a uniform thickness (3-3).

[0045]

[Embodiment 2] A mold coated with a heat insulating layer, which is the object of the present invention, is manufactured by the method shown in FIG. In FIG. 4, an auxiliary tool 12 made of a solid object is attached to the end face of the mold insert 1 so as to rise above the mold surface. In this state, a heat insulating material is simultaneously applied to the surface of the mold insert 1 and the surface of the auxiliary tool 12 and heat-cured to form the heat insulating layer 3 (4-1). Then, the auxiliary tool 12 is removed. The heat insulating layer 3 thus formed has a raised portion at the end (4-2). Next, the heat insulating layer 3 is cut and polished to complete the heat insulating layer 3 having a predetermined size. The heat insulating layer 3 has a uniform thickness up to the heat insulating layer end portion 11 required by the present invention (4-3).

[0046]

Comparative Example 1 A heat insulating layer-covering mold is manufactured by the method shown in FIG. In FIG. 2, a heat insulating material is applied to the surface of the mold insert 1 and heat-cured to form a heat insulating layer 3. The heat insulating layer 3 is cut and polished to form the heat insulating layer 3 having a predetermined thickness.
The heat insulating layer 5 at the end portion is a thin heat insulating layer, and the heat insulating layer-covering mold of the present invention cannot be obtained.

[0047]

EFFECT OF THE INVENTION It is possible to provide a mold in which a plurality of mold materials are combined, in which a heat insulating layer is uniformly formed on the mold surface. A molded product molded using this mold has an excellent surface.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an end portion of a mold wall surface of a heat insulating layer-covered mold which is an object of the present invention.

FIG. 2 is a cross-sectional explanatory view showing the steps of the conventional method for producing a heat-insulating layer-coated mold.

FIG. 3 is an explanatory view showing steps of a method for producing a heat-insulating layer-coated mold according to the present invention.

FIG. 4 is an explanatory view showing steps of a method for producing a heat-insulating layer-coated mold according to the present invention.

FIG. 5 is an explanatory view showing steps of a method for producing a heat insulating layer-coated mold of the present invention.

FIG. 6 is an explanatory view showing steps of a method for producing a heat-insulating-layer-coated mold according to the present invention.

FIG. 7 is an explanatory view showing the steps of the method for producing a heat insulating layer-coated mold of the present invention.

FIG. 8 is a cross-sectional view showing a part of a mold using a nest.

[Explanation of Codes] 1 Mold Nesting 2 Surface 3 Heat insulation layer 4 Thick part of heat insulation layer 5 Thin heat insulation layer 6 Thick heat insulation layer 7 Auxiliary equipment 8 Mold surface 9 Thin part 10 Thick part 11 End of heat insulation Part 12 Auxiliary tool 13 Heat-resistant resin film 14 Protrusion 15 Width of the upper surface of the protrusion 16 Height of the protrusion 17 Overhanging part 18 Main mold 19 Mold insert 20 Mold insert 21 Mold insert mating part

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hiro Kataoka 1-3-1 Yokou, Kawasaki-ku, Kawasaki-shi, Kanagawa Asahi Kasei Corporation

Claims (5)

[Claims] 1. A mold in which a mold wall forming a mold cavity made of a metal is coated with a heat insulating layer made of a heat resistant polymer and having a predetermined size. A solution of the heat resistant polymer, a heat resistant polymer A heat-insulating layer-coated mold having a heat-insulating layer formed by applying a precursor solution or a heat-resistant polymer monomer to a mold wall surface and having a substantially uniform thickness up to the end of the mold wall surface. 2. An auxiliary tool is attached to an end surface of a mold wall surface, and a heat resistant polymer solution, a heat resistant polymer precursor solution, or a heat resistant polymer monomer is applied to the mold wall surface and the auxiliary tool surface at the same time. A method for producing a heat-insulating layer-coated mold for forming a heat-insulating layer made of a heat-resistant polymer by heating and curing, then removing the auxiliary tool, cutting and polishing the applied heat-insulating layer, and finishing the heat-insulating layer to a predetermined size. . 3. A heat-resistant polymer solution, a heat-resistant polymer precursor solution, or a solution of a heat-resistant polymer on the mold wall, after a heat-resistant resin film having substantially the same thermal conductivity as that of the heat insulating layer is attached to the end of the mold wall. A heat-insulating layer-coated mold that coats a heat-resistant polymer monomer, heat-cures it to form a heat-insulating layer made of a heat-resistant polymer, and then cuts and polishes the applied heat-insulating layer to form a heat-insulating layer of a predetermined size. Manufacturing method. 4. A mold projection is provided at the end of the mold wall surface, the projection having substantially the same height as the heat insulating layer to be formed, and the width of the upper surface of the projection being substantially zero. A solution of a heat-resistant polymer, a heat-resistant polymer precursor solution, or a heat-resistant polymer monomer is applied to form a heat-insulating layer made of a heat-resistant polymer by heat curing, and then cutting the applied heat-insulating layer, A method of manufacturing a heat-insulating layer-covering mold that polishes and finishes a heat-insulating layer of a specified size. 5. A heat-resistant polymer solution, a heat-resistant polymer precursor solution, or a heat-resistant polymer monomer is applied to a mold material slightly larger than the mold to be manufactured, and is heat-cured to form a heat-resistant polymer. A method for producing a heat-insulating layer-coated mold, which comprises forming a heat-insulating layer, and then cutting and polishing the mold material to produce a mold material coated with the heat-insulating layer, and finishing it to a predetermined size.