JPH09174564A - Mold for plastic molding and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable molding with a good transfer property with the fluidity of a molten resin packed in a cavity maintained by coating the wall surface of a mold which forms the cavity with an electric resistance layer in which a conductive material is dispersed in glass. SOLUTION: A molten resin R is packed into a cavity 3 from the nozzle of an injection molding machine through a sprue, a runner 5, and a gate 6. The wall surface of the cavity 3 is coated with an electric resistance layer 7 through an insulating layer 8 to be reinforced by a backing material 9. The resistance layer 7 is composed of a mixture containing at least one kind of powder of glass selected from a group consisting of borosilicate glass, silicate glass, crystallized glass, and lead glass and at least one kind of particles of noble metal selected from a group consisting of Ag, Au, Pa, and Pt or alloy containing one kind of the above noble metals. The resistance layer 7 is connected to an external power source by an electric terminal part 12. When the layer 7 generates heat by energization, the fluidity of the molten resin is maintained to obtain a molding with a good transfer property.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic molding die and a method for manufacturing the same. When the plastic molding die is a thermoplastic resin, it is used for injection molding, blow molding, stamping molding and the like. In the case of a thermosetting resin, it can be used for injection molding, compression molding, transfer molding and the like.

[0002]

2. Description of the Related Art For example, in conventional injection molding of a thermoplastic resin, a molding die having a cavity having the same shape as a desired product shape is injection-filled with the molten resin, and then the molten resin is cooled and solidified. Since it is carried out in process, it looks simple as a molding process. However, at the injection molding site, product defects such as so-called "weld" and "sink" are likely to occur in the product appearance, so in order to reduce the product defects, resin melting temperature, injection pressure, injection speed, etc. However, it is extremely difficult to eliminate product defects in appearance.

As a measure to eradicate such product defects, an ion plating method or a sputtering method is applied to an appropriate portion of the surface of the cavity wall formed by a metal male mold and a metal female mold for injection molding. TiN,
There has been proposed a molding die in which an electrically conductive layer made of a metal nitride thin film such as TiCN is provided so that the temperature of the cavity wall surface can be adjusted (see, for example, JP-A-4-265720). .

A molding die has also been proposed in which a resistance heating layer made of a polyimide resin in which carbon black is dispersed is formed on the wall surface of the cavity.

Further, as a method for forming a thin film layer on the wall surface of the cavity, a master die having a shape substantially the same as the shape of the molded product is produced, and a thin metal layer is formed on the surface of the master die by electroforming or the like. A method has been proposed in which a layer made of an organic material such as an epoxy resin is formed thereon by spraying, coating, etc., and further, after being reinforced with an appropriate backup material, the master mold is removed (for example, See JP-A-55-55818).

[0006]

In the conventional plastic molding die, the cavity wall surface is heated by energizing the electrically conductive layer or the resistance heating layer formed on the cavity wall surface in contact with the molten resin. Therefore, it is effective in that the temperature of the molten resin is suppressed from being lowered, the fluidity of the molten resin is maintained, and the appearance and surface shape of the molded product can be satisfactorily transferred.

Further, since the electrically conductive layer or the resistance heating layer is formed only on the cavity wall surface, the heat capacity of the heating portion is small, and as a result, the temperature rise and temperature drop of the cavity wall are rapidly increased. It is also effective in that the extension of the molding cycle can be suppressed.

However, there are problems to be solved as described below. That is, in the case of a molding die provided with an electrically conductive layer made of a metal nitride thin film such as TiN or TiCN, the size of the die is large due to restrictions caused by the device for forming the metal nitride thin film. It is difficult to form an electrically conductive layer on the molding die, and the electrically conductive layer is a thin film and has low mechanical strength, and damage such as film breakage easily occurs. Then, when repairing the damage, since the joint strength between the electrically conductive layer and the cavity wall surface is large, it is not easy to peel off the electrically conductive layer for repair, and it is also difficult to repair only the damaged portion. There was a problem.

Further, in the case of a molding die in which a resistance heating layer made of a polyimide resin in which carbon black is dispersed is formed on the cavity wall surface, heat resistance, surface hardness of the polyimide resin and adhesion to the cavity wall surface. However, the surface of the resistance heating layer is liable to be damaged or peeled off due to long-term use, and in this case also, there is a problem that the repair cannot be performed easily.

Moreover, when the resistance heating layer made of a polyimide resin in which carbon black is dispersed is formed on the wall surface of the cavity, after the film is formed by a printing method, a dipping method or the like,
Since it is formed by baking and curing, there is also a problem that it is difficult to obtain dimensional accuracy of the cavity.

Further, when the thin film layer is formed on the cavity wall surface using the master mold, the master mold can be easily processed.
In many cases, the master die is made of a metal material in terms of easy finishing accuracy. However, when removing a master mold formed of a metal material, if a thin metal layer is present on the surface of the master mold, the metal layer is weak in chemical resistance, so the master mold needs to be removed by mechanical treatment. There is. Therefore, the surface of the master mold is subjected to a treatment that facilitates the mold release, so that the thin metal layer and the master mold are easily mechanically separated from each other. If the mold size is small,
Although it is possible to remove the master mold by mechanical peeling by performing such a process that facilitates mold release, if the size of the mold becomes large, the mechanical force for removing the master mold becomes When the size of the mold is large, the master mold is removed by this method because it also acts on the adhesion state between the metal layer and the layer of organic material formed on the surface of the metal layer, and they easily peel off. There was a problem that I could not do it.

[0012]

In order to solve the above-mentioned problems, in the present invention, at least a part of the wall surface of a mold for forming a cavity is covered with an electric resistance layer in which a conductive material is dispersed in glass. In the case of manufacturing, a master mold having a shape corresponding to a cavity is used, and after forming an electric resistance layer in which a conductive material is dispersed in glass on the surface thereof, the master mold is melted and removed. There is.

By doing so, the electric resistance layer covering the wall surface of the cavity is mainly composed of molten glass and the conductive material is dispersed therein, so that it is heat resistant and strong in strength. In addition, a certain degree of film thickness can be secured and damage is less likely to occur, and further, the adhesion to the cavity wall surface is good and the surface hardness is also excellent.

In addition, since the electric resistance layer has excellent acid resistance and alkali resistance, the master mold can be easily removed by chemically dissolving it, and the gold having the electric resistance layer formed on the cavity wall surface can be easily removed. The mold is easy to manufacture.

When the electric resistance layer is damaged due to film breakage or the like, a glaze resistance material is applied to the damaged portion, and then flame is blown to the applied portion to locally heat and melt it, thereby damaging the cavity wall surface. It can be easily repaired.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION In a plastic molding die of the present invention, at least a part of a wall surface of a die for forming a cavity is covered with an electric resistance layer in which a conductive material is dispersed in glass, for example, a so-called glaze resistance material layer. It was done.

As the conductive material, for example, Ag, A
at least one noble metal selected from the group of u, Pa, Pt, or Au-Pa, Ag-Pa, Au-Pa, A
u-Pd-Pt, Ag- Pa-RuO 2, Ag-PdO
As described above, an alloy containing at least one of the above noble metals can be used, and as the glass, at least one glass selected from the group consisting of borosilicate glass, silicate glass, crystallized glass, and lead glass can be used. .

When a metal mold is used and the cavity wall surface is covered with an electric resistance layer, it is necessary to cover it via an electric insulation layer, and the electric insulation layer is preferably a glass layer.

It is effective that the surface resistivity of the electric resistance layer covering the wall surface of the cavity is 0.05 to 1.00 Ω / □.

Further, the electric resistance layer covering the wall surface of the cavity is formed by forming an electric resistance layer in which a conductive material is dispersed in glass on the surface of a master mold having a shape corresponding to the cavity, and the heat resistance is provided outside the electric resistance layer. With high resistance, corrosion resistance, and mechanical strength, such as metals, alloys, fine ceramics,
It can be formed by providing a backing material made of a material such as an epoxy resin, and then melting and removing the master mold.

Further, a master mold having a shape corresponding to a cavity is made of metal, and an electric resistance layer in which a conductive material is dispersed in glass is formed on the surface of the master mold, and the molten glass of the above-mentioned molten glass is formed on the surface of the electric resistance layer. It can also be manufactured by forming an electric insulating layer having a softening temperature lower than the softening temperature, providing a backing material on the outer side of the electric insulating layer, and then melting and removing the metal master mold.

Further, a master mold having a shape corresponding to a cavity is formed of ceramics, for example, machinable ceramics, and an electric resistance layer in which a conductive material is dispersed in glass is formed on the surface of the master mold. On the surface of the molten glass, an electric insulating layer having a softening temperature lower than the softening temperature of the molten glass is formed, a metal backing material is provided on the outside of the electric insulating layer, and then the ceramic master mold is melted and removed. However, it can be produced.

Further, a master mold having a shape corresponding to the cavity is formed of gypsum, and the surface of the master mold is
An electric resistance layer in which a conductive material is dispersed in glass is formed, and on the surface of the electric resistance layer, an electric insulation layer having a softening temperature lower than the softening temperature of the molten glass is formed, and a metal made of metal is formed on the outside of the electric insulation layer. It can also be manufactured by providing a backing material and then melting and removing the plaster master mold.

Then, in order to dissolve and remove the master mold, it is possible to carry out a chemical dissolution treatment using, for example, an inorganic acid, an alkali or the like.

Further, the electric resistance layer is formed by, for example, adding a mixture of glass powder having excellent heat resistance, corrosion resistance, wear resistance and surface hardness to a powdery conductive material having heat resistance, corrosion resistance and stable conductivity, Using a binder such as ethyl cellulose and a solvent such as butyl carbitol acetate and terpene oil to make a paste-like electric resistance material, and applying this electric resistance material to the paste and firing it The conductive material can be formed in a uniformly dispersed state. The paste-like electric resistance material can be applied by spraying, knife coating, screen printing, dipping, transfer with release paper, and firing at a temperature of 450 to 1,000 ° C. It is preferably performed in the atmosphere, in vacuum, in a nitrogen gas atmosphere, in a reducing atmosphere, or the like.

In the plastic molding die configured as described above, the electric resistance layer formed on the wall surface of the cavity is mainly made of glass having excellent heat resistance, corrosion resistance and abrasion resistance. Since it contains a conductive material that has heat resistance, corrosion resistance, and chemical stability, it has excellent heat resistance and mechanical strength. In addition, the adhesion to the cavity wall surface is good and the surface hardness is excellent.

Moreover, since the electric resistance layer has excellent acid resistance and alkali resistance, the master mold can be easily removed by chemically dissolving it.
It becomes easy to manufacture a mold in which an electric resistance layer is formed on the wall surface of the cavity.

Further, since the electric resistance layer has excellent wear resistance, chemical resistance and surface hardness, the surface is less likely to be scratched even after long-term use, and film breakage is less likely to occur, resulting in durability. In addition to being excellent, it is possible to obtain a molded product having excellent dimensional accuracy, good transferability, and no defective appearance of the product.

Further, even if the electric resistance layer is damaged due to film breakage or the like, a glaze resistance material is applied to that portion,
Then, flame is sprayed on this coating portion and locally heated and melted, whereby the damage on the cavity wall surface can be easily repaired.

Next, the embodiment will be specifically described below in the case of a plastic injection molding die.

[0031]

Embodiments will be described in detail with reference to FIGS. 1 to 3.

(Embodiment 1) FIG. 1 is a schematic diagram of the construction of a plastic injection molding die, FIG. 2 is an explanatory view of a main part of the plastic injection molding die, and FIG. 3 is a manufacturing process of the plastic injection molding die. The process explanatory drawing is shown.

In FIG. 1, reference numeral 1 denotes a fixed type, which is a member 1a,
It is composed of the member 1b. 2 is a movable mold, 3 is a cavity formed when the fixed mold 1 and the movable mold 2 are closed, 4 is a spool, 5 is a runner, 6 is a gate, and the molten resin R is from a nozzle of an injection molding machine to a spool 4 and a runner. 5, the cavity 3 is filled through the gate 6. Reference numeral 7 is an electric resistance layer formed by coating the wall surface of the cavity 3 with an electric insulation layer 8 interposed therebetween, and 9 is a lining material for reinforcing the electric resistance layer 7.
It is attached to the fixed mold 1 by mechanical fastening means such as bolts. Reference numeral 10 is an ejector pin, and 11 is a support plate.

The electric resistance layer 7 is made of a so-called glaze resistance material, and a specific example of this glaze resistance material will be described later, but it is selected from the group consisting of borosilicate glass, silicate glass, crystallized glass and lead glass. At least one glass powder and at least one noble metal selected from the group of Ag, Au, Pa and Pt, or Au-Pa, A
g-Pa, Au-Pa, Au-Pd-Pt, Ag-Pa
-RuO _2, Ag-PdO at least the precious metal as a mixture of particles of one containing alloy, a binder and butyl carbitol acetate, such as ethyl cellulose, paste by adding a solvent such as terpene oil And then the glass powder is melted to form metal particles dispersed in the molten glass.

The electric resistance layer 7 is heat resistant and electrically stable, has excellent surface hardness, and is chemically stable.

The electric resistance layer 7 is connected to an external power source and can be energized by the electric terminal portion 12 having the structure shown in FIG. That is, a conductive plate 13 is brought into contact with the electric resistance layer 7, an electric terminal 16 is connected to the conductive plate 13, and the conductive plate 13 is fixed to the fixed mold 1 by a bolt 15 electrically insulated by an insulating washer 14. It is fixed.

When the electric resistance layer 7 generates heat when energized, the fluidity of the molten resin injected and filled into the cavity 3 whose wall surface is covered with the electric resistance layer 7 is maintained, and a molded article having good transferability is obtained. . Moreover, since the heat capacity of the electric resistance layer 7 is small, the temperature of the wall surface of the cavity 3 can be rapidly raised or lowered, and the extension of the molding cycle can be prevented.

Next, the electric resistance layer 7 is formed on the wall surface of the cavity 3.
A method of forming the will be described with reference to FIG.

First, a master die 17 having a predetermined shape is prepared (see FIG. 3 (a)). The master die 17 is preferably made of a metal material such as steel, brass, and aluminum in terms of dimensional accuracy and workability, but for example,
It can also be made of non-metallic materials such as ceramics and gypsum. In the case of using ceramics, machinable ceramics, in which boron nitride is uniformly dispersed in a matrix of aluminum nitride and which has excellent machinability, is effective.

A paste-like glaze resistance material is applied to the surface of the master mold 17 by spraying, brushing or the like to form the electric resistance layer 7 (see FIG. 3B). To form the electric resistance layer 7, a glaze resistance material is printed on the surface of a release-treated paper, a plastic film, or the like by a silk screen method or the like, and the printed glaze resistance material is printed on the surface of the master mold 17. It can also be formed by transfer.

On the electric resistance layer 7, the same glass powder as in the case of the glaze resistance material, to which a solvent is added, is applied to form an electric insulation layer 8 (see FIG. 3C). In this case, the film thickness of the electric insulating layer 8 is preferably 0.03 to 2.0 mm, and when the film thickness is 0.03 mm or less, the electric insulating property between the wall surface of the cavity 3 and the electric resistance layer 7 is stably maintained. This is because it is difficult, and when the film thickness is 2.0 mm or more, it becomes weak against thermal shock.

In this way, the master mold 17 is heated to 450 with the electric resistance layer 7 and the electric insulation layer 8 formed on the surface.
When baked at a temperature of up to 1,000 ° C., the glass powder of the glaze resistance material is melted and the metal powder is uniformly dispersed therein to form a film.

Alternatively, only the electric resistance layer 7 may be fired to form a film, and then the electric insulating layer 8 may be fired to form a film.
However, the firing temperature in this case is preferably the same as the firing temperature at the time of forming the electric resistance layer 7, or a temperature within a range lower by about 200 ° C. than that. If the temperature is higher than the firing temperature for forming the electric resistance layer 7, a sufficient film thickness cannot be maintained,
Further, when the temperature difference is 200 ° C. or more, the electric resistance layer 7 and the electric insulation layer 8 cannot be firmly joined. Further, as the electric insulating layer 8, an organic material such as an epoxy resin or a ceramic material can be used.

A backing material 9 is provided on the electric insulating layer 8 (see FIG. 3D). This backing material 9 is an electric resistance layer 7
And has a backup function to reinforce the lack of strength of the electric insulation layer 8, for example, by spraying a metal such as zinc, zinc alloy, nickel, nickel alloy, copper, copper alloy, aluminum, aluminum alloy, or lead, It is formed by using a low melting point metal such as a lead alloy in a mold or by spraying a ceramic material such as alumina, silicon carbide or zirconia.

The backing material 9 is shaped so that it can be joined to the fixed die 1 (see FIG. 3E), and then the member 1 of the fixed die 1 is formed.
It is fitted into a recess previously formed in a and fixed to the fixed mold 1 using a bolt (see FIG. 3 (f)).

Finally, the master die 17 is chemically dissolved and removed (see FIG. 3 (g)) to obtain a die member in which the wall surface of the cavity 3 is covered with the electric resistance layer 7.
The master mold 17 can be dissolved and removed by dissolving the master mold 17 with a chemical such as an inorganic acid or an alkali.

The surface of the electric resistance layer 7 may be covered with a protective film for the purpose of protecting the electric resistance layer 7 and facilitating the release of the molded product. This protective film is formed by baking a glass layer on the surface of the master mold 17, PVD method, CV
A thin film of SiO ₂ , Si ₃ N ₄ may be formed by the D method, sol-gel method or the like, and the electric resistance layer 7 may be formed on this thin film.

Next, when the molding die is used for molding the plastic and the electric resistance layer 7 covering the wall surface of the cavity 3 is damaged due to cracks, film breakage or the like and cannot be energized, glaze is performed. Apply resistance material to the damaged area,
Then, a flame can be sprayed onto this coated portion, and the coating portion can be locally heated and melted to be repaired.

When the electric resistance layer 7 formed as described above is energized to generate heat, its surface resistivity value r
Is effectively within the range given by Equation 1.

(Equation 1) Wr / (Ia / D) ² ≦ r ≦ (1 / Wr) × (Va / L) ² where Wr is the electric resistance layer 7 required due to the temperature rise of the wall surface of the cavity 3. Input power value per unit area, Ia is the maximum value of the current flowing through the electric terminal portion 12, and D is the electric resistance layer existing in the direction perpendicular to the line connecting the electric terminal portions 12 supplying the electric resistance layer 7 with current. 7, Va is the maximum value of the voltage applied to the electric resistance layer 7, and L is the length of the electric resistance layer 7 existing between the electric terminal portions 12.

When the electric resistance layer 7 is used to generate heat, the electric resistance layer 7 must have a sufficiently high temperature rising rate.
It is effective that the surface resistivity of 0.05 to 1.00 Ω / □.

When electric power of 25 V and 53 Ampere was applied to the electric resistance layer having the surface resistivity of 0.2 Ω / □ formed as described above, a temperature rising rate of 10 ° C. or more was observed per second. . In addition, an attempt was made to confirm the molding effect by actually performing injection molding of styrene resin using a mold in which this electric resistance layer was formed on the mold wall surface. At the site of injection molding, there is a visual defect called "weld", which means a defect that the resin merged marks remain on the surface of the molded product and it looks like a streak, but this is the judgment item of the molding effect. . As a result, when the mold wall temperature, which is a normal molding condition, is 100 ° C. or lower, the rate of occurrence of “weld” is 3 to 10 out of 10 molded products.
Although the number was 5, the product having the electric resistance layer of the present invention formed on the mold wall surface and molded at a mold wall temperature of 120 ° C. or higher has a "weld" occurrence rate of 0, which is a remarkable effect. confirmed.

(Embodiment 2) A steel material (S54C) is machined into a master die 17 having a predetermined shape. In addition, borosilicate glass powder (softening temperature 775 ° C) 30 wt%, 60w
t% Ag powder (average particle size 0.022 mm) and 40 wt
% Pa powder (average particle size 0.3 μm) was mixed, and ethyl cellulose as a binder was 3.6 wt% and ethyl carbitol acetate was 17.3 wt as a solvent.
% Of terpene oil is added to obtain a paste-like glaze resistance material. On the other hand, the above-mentioned glaze resistance material is printed on the surface of a Teflon-coated mount by a silk screen method and dried at 120 ° C. for 10 minutes to obtain a transfer paper having an electric resistance layer fixed to the mount.

Next, an adhesive that decomposes and disappears by baking at a high temperature is applied to the surface of the master mold 17 in a thin film form,
An electric resistance layer was transferred onto the surface of the master mold 17 using the above transfer paper, and then heated by an electric furnace at a temperature rising rate of 40 ° C./min.
Peak temperature 850 ° C, holding time 10 minutes, cooling rate 20 ° C
The electrical resistance layer 7 was formed by firing under the condition of / minute. The surface of the electric resistance layer 7 may be sandblasted, if necessary,
Alternatively, when the surface resistivity was adjusted to 0.5 Ω / □ by processing by the surface polishing method, the film thickness was 20 to 25 μm.

A lead-free glass paste [ZnO-SiO ₂ -B] having a softening temperature of 673 ° C. was formed on the surface of the electric resistance layer 7.
₂ O ₃ , trade name OC-780, Okuno Seiyaku Co., Ltd.] is applied with a brush so that the film thickness after firing is 80 to 200 μm, and then dried at 150 ° C. for 10 minutes and then at 760 ° C. for 1 minute.
It was fired for 0 minutes to form the electric insulating layer 8. A backing material 9 is provided on the surface of the electric insulation layer 8 by using a metal spray coating method using aluminum, and after that, the backing material 9 is shaped into a predetermined size and shape by machining and fitted and fixed to the fixed mold 1. After that, the master die 17 is removed by cutting to the vicinity of the electric resistance layer 7 by machining, and the remaining master die 17 is dissolved and removed by hydrochloric acid.

(Example 3) Machinable ceramics [Shapal M Soft (trade name) Tokuyama Soda Co., Ltd.], which is a composite sintered body of AlN and BN, is machined into a master mold 17 having a predetermined shape. . Next, 3.0 wt% of B ₂ O ₃ powder, 42.3 wt% of Ag powder, and 28.2 wt% of Pa powder were added and mixed to 1.5 wt% of borosilicate glass powder, and ethyl cellulose 3. 6
wt%, ethyl carbitol acetate as solvent 1
7.3 wt% and 4.1 wt% of terpene oil are added to make a paste-like grace resistance material. On the other hand, the above-mentioned glaze resistance material is printed on the surface of a Teflon-coated mount by a silk screen method and dried at 120 ° C. for 10 minutes to obtain a transfer paper having an electric resistance layer fixed to the mount.

Next, an adhesive that decomposes and disappears by baking at a high temperature is applied to the surface of the master mold 17 in a thin film form,
An electric resistance layer was transferred onto the surface of the master mold 17 using the above transfer paper, and then heated by an electric furnace at a temperature rising rate of 40 ° C./min.
Peak temperature 850 ° C, holding time 10 minutes, cooling rate 20 ° C
The electrical resistance layer 7 was formed by firing under the condition of / minute. The surface resistivity of this electric resistance layer 7 was 0.05 Ω / □, and its film thickness was 25 μm.

On the surface of this electric resistance layer 7, a zirconia layer having a function of both an electric insulating layer and a backing material is 4 mm.
Is formed by a thermal spraying method. Then, after shaping this zirconia layer, it is fixed to the fixed die 1 and the master die 17 is removed to the vicinity of the electric resistance layer 7 by machining, and then aluminum nitride in the master die 17 is dissolved and removed by caustic soda. The remaining brittle boron nitride portion is mechanically broken and removed.

Example 4 An electric resistance layer 7 was formed on the surface of a master mold 17 made of plaster having a predetermined shape by using the same glaze resistance material as in Example 2 and in the same procedure. On the surface of the electric resistance layer 7, a zirconia layer having a function of both an electric insulation layer and a backing material is formed by a thermal spraying method to have a film thickness of 2 mm, and after shaping the zirconia layer, a master mold 17 is formed. Dissolve and remove with hydrochloric acid.

(Embodiment 5) Steel material (PD of Daido Steel Co., Ltd.)
-555) is used to form a mold having the cavity 3, and the wall surface of the cavity 3 of the mold is mirror-polished,
By heating in air at a temperature of 510 ° C. for 60 minutes, a dense and strong oxide film is formed on the wall surface of the cavity 3.

On the other hand, 40 wt% of borosilicate glass powder and B
In a glass mixture (softening temperature 770 ° C.) with 40.0 wt% of i ₂ O ₃ powder, 3.0% of ethyl cellulose as a binder, 13.8% of butyl carbitol acetate as a solvent, and 3.2% of terpell oil, respectively. A paste-like ink added and dispersed is prepared, and the paste-like ink is printed on the surface of the release paper by the silk screen method to obtain a transfer paper.

Using this transfer paper, an electric insulating layer 8 having a film thickness after firing of 80 to 100 μm is transferred and formed on the wall surface of the cavity 3. The firing conditions in this case are 120 to 1.
Dry at 50 ° C for 10 minutes, heating rate 40 ° C / min, peak temperature (in air) 850 ° C, holding time 10 minutes, cooling rate 2
0 ° C./min.

Next, an electric resistance layer 7 was formed on the surface of the electric insulation layer 8 by using the same glaze resistance material as in Example 2 and in the same procedure. The firing conditions in this case are
In consideration of the existence of the electric insulation layer 8, 12
Dry for 10 minutes at a temperature of 0 to 150 ° C, heating rate 40 ° C
/ Min, peak temperature (in air) 800 ° C, holding time 10
Min, and the cooling rate was 20 ° C./min.

Example 6 A ceramic die having a cavity 3 was formed by using silicon nitride Si ₃ N ₄ (Mitsui Mining Material Co., Ltd.), and the wall surface of the cavity 3 of this die was roughened by sandblasting. And degrease it.

As the glaze resistance material used, 42.3 wt% of Ag powder and 28.2 wt% of Pa powder, a conductive material of borosilicate glass powder of 1.5 wt% and glass of Bi ₂ O ₃ powder of 3.0 wt% (softened) were used. Temperature 670 ° C.), 3.6% ethyl cellulose as a binder, 17.3% butyl carbitol acetate as a solvent,
4.1% terpel oil was added and dispersed to prepare a paste-like ink, and the paste-like ink was printed on the surface of the release paper by the silk screen method to obtain a transfer paper.

Using this transfer paper, the surface resistivity after firing was 0.05 Ω / □ and the film thickness was 25 on the wall surface of the cavity 3.
The electric resistance layer 7 having a thickness of μm is transferred and formed. The firing conditions in this case were drying at 120 to 150 ° C. for 10 minutes, a temperature rising rate of 40 ° C./minute, a peak temperature (in air) of 760 ° C., a holding time of 10 minutes, and a cooling rate of 20 ° C./minute.

Using the plastic molding dies obtained in Examples 1 to 6 described above, electric current is supplied from the electric terminal portions 12 to both ends of the electric resistance layer 7 to heat the electric resistance layer 7. In this state, the molded product formed by injection-filling the molten resin into the cavity 3 has excellent transferability,
It was confirmed that there was no abnormality in the surface shape.

[0068]

The present invention is embodied in the form described above and has the following effects.

Since the electric resistance layer made of glass and a conductive material having excellent heat resistance and abrasion resistance is formed on the wall surface of the cavity, the molten resin filled in the cavity is supplied by energizing the electric resistance layer. A mold for plastic molding that retains fluidity and can be molded with good transferability can be easily manufactured, and its repairability is also excellent. Moreover, the cavity wall of the mold has heat resistance and wear resistance. ， The surface hardness is large and the durability is excellent.

Further, since the electric resistance layer can be easily formed by coating, it is easy to form even if the mold size is large. Further, since the electric resistance layer has excellent chemical resistance, the master mold is used. When it is manufactured by using it, it can be easily removed by melting, and it has excellent manufacturability and correctability.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a configuration of a plastic molding die according to an embodiment of the present invention.

FIG. 2 is an explanatory view of a main part of the plastic molding die.

FIG. 3 is an explanatory view of a manufacturing process of the same plastic molding die.

[Explanation of symbols]

 1 Fixed type 2 Movable type 3 Cavity 7 Electric resistance layer 8 Electric insulation layer 17 Master type

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Chiaki Nakamura 1-3-7 Dainichicho, Moriguchi City, Osaka Prefecture Daiho Kogyo Co., Ltd. (72) Inventor Masahiko Funaki 1-3-3 Dainichicho, Moriguchi City, Osaka Prefecture No. 7 Daiho Industry Co., Ltd.

Claims (10)

[Claims] 1. A plastic molding mold in which at least a part of a wall surface of a mold forming a cavity is covered with an electric resistance layer in which a conductive material is dispersed in glass. 2. The conductive material is at least one metal selected from the group of gold (Au), silver (Ag), palladium (Pa) and platinum (Pt), or an alloy containing at least one of these metals. The plastic molding die according to claim 1. 3. The plastic molding die according to claim 1, wherein the glass is at least one glass selected from the group consisting of borosilicate glass, silicate glass, crystallized glass and lead glass. 4. The plastic molding mold according to claim 1, wherein the mold is made of metal, and the cavity wall surface of the mold is covered with an electric resistance layer through an electric insulating layer. 5. The plastic molding die according to claim 4, wherein the electrically insulating layer comprises a glass layer. 6. The surface resistivity of the electric resistance layer is from 0.05 to
It is 1.00 Ω / □, and the plastic molding die according to any one of claims 1 to 5. 7. An electric resistance layer in which a conductive material is dispersed in glass is formed on the surface of a master mold having a shape corresponding to a cavity, a lining material is provided outside the electric resistance layer, and then the master mold is dissolved and removed. A method for producing a plastic molding die. 8. A master mold having a shape corresponding to a cavity is made of a steel material, and an electric resistance layer having a conductive material dispersed in glass is formed on the surface of the master mold, and the molten glass is formed on the surface of the electric resistance layer. A method for producing a plastic molding die, in which an electric insulating layer having a softening temperature lower than the softening temperature is formed, a metal backing material is provided on the outer side of the electric insulating layer, and then the master mold is dissolved and removed. 9. The master mold having a shape corresponding to the cavity is made of ceramics or gypsum.
A method for producing the described plastic molding die. 10. The method for producing a plastic molding die according to claim 9, wherein the ceramic is a machinable ceramic.