JPH07108534A - Mold - Google Patents

Abstract

PURPOSE:To enable a mirror surface with fine appearances, or a hollow resin molding with excellent texture surfaces to be produced at a simple process by making use of a low molding pressure of a specific value or less. CONSTITUTION:The mold is featured such that molten thermoplastic resin is put into close contact with the molding surfaces 1a, 1b of a mold in the pressure of 100kg/cm<2> or lower to then be cured. It includes heating means 5a for heating, before close contact, the molding surfaces 1a, 1b to a vicat softening temperature (T) deg.C of thermoplastic resin (preferably of a vicat softening temperature (T)+5 deg.C) or higher, and cooling means for cooling, after the completion of close contact, the molding surfaces 1a, 1b to a vicat softening temperature (T)-10 deg.C or lower. The molding surfaces 1a, 1b are heat-insulated from the mold main bodies 3a, 3b by a heat insulators 2a, 2b to be reduced in its heat capacitance, and between the opposite surface side of the molding surfaces 1a, 1b and the mold main bodies 3a, 3b, there is provided spaces 4a, 4b for supplying a heating air or cooling liquid.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a mold for molding a thermoplastic resin. More specifically, the present invention relates to a molding die that can satisfactorily transfer the molding surface of the mold to a molded product even when molding at low pressure.

[0002]

2. Description of the Related Art Injection molding methods and blow molding methods are used as methods for obtaining resin molded products. The injection molding method uses high pressure (200-1000 kg) in a mold in which molten resin is sealed.
/ Cm ² ) and the molding surface of the mold is transferred to the resin. Since the pressure is high, the molding surface is accurately transferred. Therefore, it is suitable for obtaining a molded product having a mirror surface or a grain surface. However, since a mold capable of withstanding high pressure is required, the structure of the mold becomes complicated and the cost becomes high, which is not suitable for high-mix low-volume production. In addition, a special process is required to mold the hollow product, which complicates the production process. Blow
The molding method is to supply the parison (hollow cylindrical resin in a molten and softened state) between the molds, then clamp the mold and press the fluid into the hollow part to press the outer surface of the parison against the molding surface of the mold. It is a method of transferring. Since it is pressed by the pressure of the fluid, the pressure is relatively low (4 to 10 kg / cm ² ), and therefore the molding surface is not transferred cleanly, which is unsuitable for obtaining a molded product having a mirror surface or a grain surface. However, it is widely used because it is suitable for mass production of hollow products.

Japanese Unexamined Patent Publication (Kokai) No. 58-102734 discloses a hollow molding die including a thin molding inner die and a cooling outer die which can contact / separate from the molding inner die. In this mold, the inner mold for heating is heated before the parison is supplied in order to improve the surface gloss of the hollow molded product.
After the parison is brought into contact with the molding surface of the molding inner die, the inner surface of the cooling outer die is brought into contact with the outer surface of the molding inner die to rapidly cool the molding inner die to obtain a molded product. ing.

In Japanese Patent Laid-Open No. 4-77231, when the parison is brought into contact with the molding surface of the molding die to be molded, the temperature of the molding die is changed from a temperature near the maximum crystallization rate of the parison to the melting point. By holding it between the die line and weld line to prevent it from remaining on the surface of the molded product, and by circulating the refrigerant in the hollow part of the parison during molding, the molding cycle time can be extended. A blow molding method is disclosed which is adapted to prevent this.

[0005]

There is a demand to obtain a resin molded product having a mirror surface or a grain surface with a relatively low molding pressure, using a mold having a relatively simple structure. There is also a demand for producing a hollow resin molded product having a mirror surface or a grain surface (eg, an automobile air spoiler) in a simple process.

In the hollow molding die disclosed in JP-A-58-102734, the molding surface is beautifully transferred by heating the molding inner die, but the molding inner die is used as the cooling outer die. On the other hand, since the resin is cooled by being relatively displaced and brought into contact with each other, the structure of the mold may be complicated and weakened, and the cooling time may be prolonged. Further, there is no mention of the optimum heating temperature or cooling temperature range for cleaning the surface of the resin molded product and shortening the total molding cycle time.

The blower disclosed in the above-mentioned JP-A-4-77231.
In the molding method, the molding surface is cleaned by heating and holding the temperature of the molding die to the above temperature, but the heating time is kept at this temperature even during cooling, so the effect of shortening the cooling time is not very large. . Further, since the parison is cooled from the inside by circulating the refrigerant, the temperature control for heating and maintaining the temperature of the molding die at the above temperature becomes complicated.

An object of the present invention is to produce a resin molded product having a good mirror surface and grain surface with a relatively low molding pressure. Another object of the present invention is to produce a hollow resin molded product having a good mirror surface or grain surface in a simple process.

[0009]

The invention according to claim 1 is a mold for solidifying a molten thermoplastic resin by bringing it into close contact with a molding surface of the mold at a pressure of 100 kg / cm ² or less. Heating means for heating the molding surface to a Vicat softening temperature (T) ° C. or higher of the thermoplastic resin before, and the Vicat softening temperature (T) -1 for the molding surface after completion of the adhesion.
And a cooling means for cooling to 0 ° C. or lower. That is, the molding method does not matter as long as the molding pressure is 100 kg / cm ² or less. If the heating temperature by the heating means is Vicat softening temperature (T) + 5 ° C. or higher, more preferable results can be obtained.

According to a second aspect of the present invention, the heat capacity is reduced by insulating the metal body on which the molding surface is formed from the mold body from the mold body to a Vicat softening temperature (T) ° C. or higher. The heating and the cooling to the Vicat softening temperature (T) of -10 ° C or less can be rapidly performed. As in the first aspect, more preferable results are obtained when the heating temperature is Vicat softening temperature (T) + 5 ° C. or higher. In the invention of claim 3, a preferred example is given as the heating means in claim 2, and in claim 4
In the invention of (1), a suitable example is given as the cooling means in claim 2. Further, in the invention of claim 5, a preferable example is given as the heating means in claim 1.

The mold of the present invention can be used for molding various thermoplastic resins. Examples of the thermoplastic resin include AS resin, polystyrene, high-impact polystyrene, acrylonitrile-butadiene rubber-styrene graft copolymer (ABS resin), acrylonitrile-butadiene rubber-styrene-α-methylstyrene graft copolymer. From a polymer (heat resistant ABS resin), acrylonitrile-ethylene-propylene rubber-styrene and / or methyl methacrylate graft copolymer (AES resin), acrylonitrile-hydrogenated diene rubber-styrene and / or methyl methacrylate Graft copolymer, polyethylene, polypropylene, polycarbonate, polyphenylene ether, polyoxymethylene, nylon, methyl methacrylate polymer, polyethylene sulfone, polyarylate, etc., and And these composites, resins obtained by adding filler thereof.

[0012]

Function: Before the molten thermoplastic resin is brought into close contact with the molding surface of the mold, the molding surface is heated to the Vicat softening temperature (T) ° C. or higher of the thermoplastic resin, resulting in good adhesion. As a result, the molding surface is accurately transferred to the surface of the resin. Further, since the molding surface is cooled to the Vicat softening temperature (T) -10 ° C. or less after the completion of adhesion, the resin transferred onto the molding surface is rapidly solidified.

[0013]

EXAMPLES Examples of the present invention and comparative examples will be described below.
In the following examples and comparative examples, ABS resin (JSR / AB
S / 45A) is blow-molded to obtain a box-shaped molded product. That is, in each example and each comparative example,
As shown in FIG. 11, the extruder 81 melts the ABS resin and sends it to the accumulator die 82, and the accumulator die 82 forms a hollow cylindrical parison 90 and sends it downward to the parison 90. Blow molding is carried out by any one of 3 (each mold of Examples A to C and Comparative Examples a to e).

Here, the screw diameter of the extruder 81 is 5
5 mm, maximum extrusion capacity is 2000 cc. The diameter of the parison 90 delivered from the accumulator die 82 is 100 mm, the temperature is 200 ° C., and the delivery time to each die 3 is 2 sec. Also, each mold
The width of 3 is 250 mm, the height is 600 mm, and the thickness is 50 m.
m, and the maximum mold clamping force is 15 TON. Further, the molding surface of each mold 3 is a mirror surface.

At the start of blow molding, the outer surface of the parison 90 is maintained by maintaining a vacuum degree of 30 mmHg between the parison 90 and the molding surface of the mold 3 for 10 seconds in any mold. Is sucked into the molding surface of the mold 3, and air is continuously fed into the parison 90 at a pressure of 7 kg / cm ² until the end of the blow molding. It is in close contact with the molding surface of mold 3. That is, the molding pressure is 7 kg / cm ² . The mold clamping force of mold 3 is 15TO.
N.

Next, conditions and the like which differ depending on each mold will be described.

Example A In this mold, heating is performed by the method of FIG. 4 and cooling is performed by the method of FIG. That is, the outer surface of the parison 90 is covered with the metal bodies 1a, 1b.
Before making close contact with the molding surface of
Each space between the back side of the metal body 1a, 1b and the mold body 3a, 3b
Heating elements (electric heating heater) 50 provided inside 4a and 4b, respectively
By making a, 50b generate heat respectively, and pushing the heating elements 50a, 50b forward through the rods 50a2, 50b2 by the action of the hydraulic cylinders 50a1, 50b1 and abutting the back surface of the metal bodies 1a, 1b, Each of the molding surfaces on the surface side of the metal bodies 1a and 1b is 1
It is heated to 20 ° C. In addition, each heating element 50a, 50b
Are retracted to their original positions by the action of the hydraulic cylinders 50a1 and 50b1 during cooling. In addition, in FIG. 4, 2a and 2b are heat insulators.

Further, the outer surface of the parison 90 is provided with metal bodies 1a, 1b.
After it is brought into close contact with the molding surface of, the cooling water (pressurized water) is passed through the liquid supply pipes 61a and 61b to the spaces 4a and 4b as shown in FIG.
Is jetted. The flow rate is 100 cc / sec. Further, the injection direction is the direction toward the back surface of the metal body 1a, 1b, whereby heat exchange is performed on the back surface, the cooling water is evaporated, and the metal body 1a, 1b is cooled. It The cooling time is 30 seconds. Further, the vapor is sucked and discharged through the exhaust pipes 61a1 and 61b1 by the vacuum pumps 61a2 and 61b2. That is, the pressure in the spaces 4a and 4b is reduced, and the evaporation is promoted.

After cooling, the molded product was degassed, the mold was opened and the molded product was taken out. The transfer on the mirror surface was good, and there was no warp in the molded product. The required time to take out is 60 seconds, and the total cycle time is 70 seconds.
It was ec. The same result was obtained when the molding was performed in the same manner using a mold having a textured surface.

Example B In this mold, heating is performed by the method of FIG. 5 and cooling is performed by the method of FIG. That is, before the outer surface of the parison 90 is brought into close contact with the molding surfaces of the metal bodies 1a and 1b as described above, as shown in FIG. 5, line condensing type heaters provided in the spaces 4a and 4b are provided. The molding surfaces on the front surface side are heated to 120 ° C. by radiating heat to the back surface side of the metal bodies 1a, 1b by the heaters 51a, 51b. It should be noted that this heating was stopped 2 seconds after the start of feeding the air into the parison 90.

After the heating by the line condensing type heaters 51a, 51b is stopped, as shown in FIG.
50b of air at -10 ° C into b through the air supply pipes 6a and 6b.
Send in at a flow rate of / min. This feed is a metal body 1
It is performed through a diffusion nozzle so that air is jetted toward the back surface of a, 1b, whereby heat exchange is performed on the back surface and the metal bodies 1a, 1b are cooled from the back surface side. . The air sent into each of the spaces 4a, 4b is
After heat exchange, it is discharged through the exhaust pipes 6a1 and 6b1.

After cooling, the molded product was degassed, the mold was opened, and the molded product was taken out. The transfer on the mirror surface was good, and there was no warp in the molded product. The required time to take out is 110 seconds, and the total cycle time is 130
It was sec. The same result was obtained when the molding was performed in the same manner using a mold having a textured surface.

Example C In this mold, heating is performed by the method of FIG. 3 and cooling is performed by the method of FIG. That is, the outer surface of the parison 90 is covered with the metal bodies 1a, 1b.
Before making close contact with the molding surface of
The heated steam at 150 ° C. is injected into the spaces 4a and 4b through the air supply pipes 5a and 5b toward the back surface of the metal bodies 1a and 1b.
As a result, heat exchange was performed on the back surface to condense the heated steam into droplets, and the front surface side (molding surface side) of the metal bodies 1a and 1b was heated to 120 ° C. The droplets are discharged from the drain pipes 5a1 and 5b1 via the pressure control valves 5a2 and 5b2.

After the above heating by the heating steam of 150 ° C. is stopped, the metal bodies 1a, 1b are manufactured by the method shown in FIG.
Was cooled to below 80 ° C.

After cooling, the molded product was degassed, the mold was opened and the molded product was taken out. The transfer on the mirror surface was good, and there was no warp in the molded product. The time required for removal is 65 seconds, and the total cycle time is 75 seconds.
Met. The same result was obtained when the molding was performed in the same manner using a mold having a textured surface.

Comparative Example Each of the molds of Comparative Examples a to e has a structure in which the molding surface is integral with the mold body, and therefore does not have a heat insulator. For this reason, when the mold is heated in order to cleanly transfer the molding surface, it takes a long time to cool the mold.

The molding temperature of each mold is 50 in Comparative Example a.
C., Comparative Example b is 120.degree. C., Comparative Example c is 170.degree. C., Comparative Example d is 30.degree. C., and Comparative Example e is 150.degree. That is, Comparative Example a and Comparative Example d have low temperatures, and Comparative Example b, Comparative Example c, and Comparative Example e.
Has been hot. For this reason, the mirror surface state of the molded article is normally in Comparative Example a at a medium temperature, good in Comparative Example b at a high temperature, Comparative Example c and Comparative Example e, and impossible at Comparative Example d at a low temperature. However, the time required until the molded product is taken out and the total cycle time of molding are 60 s for Comparative Example a at a medium temperature.
ec and 70 sec, and Comparative Example b of high temperature is 150 sec and 1
70 sec, high temperature comparative example c is 290 sec and 310 s
ec, the comparative example d at low temperature is 45 sec and 55 sec, and the comparative example e at high temperature is 250 sec and 280 sec. That is, the higher the temperature, the longer the time required to take it out and the cycle time, and the result was opposite to the state of the mirror surface. As described above, in the mold of the comparative example, it is possible to satisfactorily transfer the mirror surface to the molded product by increasing the temperature at the time of molding, but the time required to take it out and the total cycle time of molding are long. There is a problem. Similar results were obtained with the transfer in the case of the grain surface.

Other Embodiments In the above embodiments A to C, FIGS. 3, 4, 5, 9, and 1 are used.
Although the method of 0 has been described, heating in the method of FIGS. 6 to 8 is also possible. In FIG. 6, heating gas is supplied through the air supply pipes 52a and 52b to heat the gas, and the gas after heat exchange is discharged to the exhaust pipe 52a.
It is a method of exhausting from 1,52b1, and FIG.
In this method, the line condensing heaters 51a and 51b are made to temporarily enter the molding surface side of and heated. In addition, FIG. 8 shows a metal body.
This is a method in which the air supply pipes 53a, 53b are temporarily inserted into the molding surface side of 1a, 1b to heat them.

Further, FIG. 1 shows that the heat capacity of the metal bodies 1a, 1b is reduced by insulating the metal bodies 1a, 1b having the mold bodies 3a, 3b and the molding surface with the heat insulators 2a, 2b. FIG. 2 shows that the spaces 4a and 4b are provided between the back side of the metal bodies 1a and 1b and the mold bodies 3a and 3b.
4a and 4b show a state in which a heating medium and a cooling medium can be supplied.

In addition to the heating method described above, a method of heating with a high frequency or a method of heating with a far infrared heater can be adopted. Further, as a method for obtaining heating steam, for example, a dielectric heating method can be adopted.

[0031]

According to the first aspect of the present invention, since the molten thermoplastic resin is adhered to the molding surface of the mold heated to the Vicat softening temperature (T) ° C. or higher, for example, blow molding is performed. Even at a low molding pressure of 100 kg / cm ² or less, the molding surface having a mirror surface or a grain surface can be accurately transferred to the surface of the resin. The resin transferred to the molding surface is rapidly solidified by the molding surface cooled to the Vicat softening temperature (T) -10 ° C or lower. Therefore, a hollow resin molded product having a mirror surface or a grain surface can be produced in a relatively simple process.

According to the second aspect of the present invention, since the metal body on which the molding surface is formed is insulated from the mold body to reduce the heat capacity, heating up to the Vicat softening temperature (T) ° C. or higher, or Vicat Cooling to a softening temperature (T) of -10 ° C or lower is promptly performed. Therefore, the total cycle time of molding is shortened.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a state in which a metal body on which a molding surface of a mold is formed is thermally insulated from a mold body.

FIG. 2 is a schematic cross-sectional view showing a mold corresponding to claim 2.

FIG. 3 is a schematic sectional view showing a mold corresponding to (A) of claim 3.

FIG. 4 is a schematic cross-sectional view showing a mold corresponding to claim 3 (B).

FIG. 5 is a schematic cross-sectional view showing a mold corresponding to (C) of claim 3.

FIG. 6 is a schematic cross-sectional view showing how a metal body having a molding surface is heated from the space side by the mold of FIG.

FIG. 7 is a schematic sectional view showing a mold corresponding to (D) of claim 5.

FIG. 8 is a schematic sectional view showing a mold corresponding to (E) of claim 5.

FIG. 9 is a schematic cross-sectional view showing how a metal body having a molding surface formed therein is cooled from the space side by the mold of FIG.

FIG. 10 is a schematic cross-sectional view showing a mold corresponding to claim 4.

FIG. 11 is a schematic diagram showing the overall configuration of blow molding.

[Explanation of symbols]

 1a, 1b Metal body 2a, 2b Insulating body 3 Mold 3a, 3b Mold body 4a, 4b Space 5a, 5a1, 5a2 Heating means 6a, 6a1 Cooling means 81 Extruder 82 Accumulator die 90 Parison

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Yasuo Takahashi 2-11-24 Tsukiji, Chuo-ku, Tokyo Japan Synthetic Rubber Co., Ltd.

Claims (5)

[Claims] 1. A molten thermoplastic resin of 100 kg /
A molding die which is brought into close contact with a molding surface of a mold by a pressure of cm ² or less to be solidified, and the molding surface is heated to a temperature of Vicat softening temperature (T) ° C. or higher of the thermoplastic resin before the adhesion. And a cooling unit that cools the molding surface to a temperature of the Vicat softening temperature (T) -10 ° C. or lower after completion of the adhesion. 2. The molding surface according to claim 1, wherein the molding surface is formed on a surface of a metal body supported in a heat insulating state by the mold body, and the mold body is provided on the opposite side of the molding surface. Mold for forming a space between. 3. The molding die according to claim 2, wherein the heating means is a means selected from the following (A) to (C). (A) A means for supplying a heated gas to the space and injecting it toward the opposite surface when the molding surface is heated, and discharging the liquid condensed by heat radiation in the space. (B) A heating element provided in the space so as to face the opposite surface, and a drive mechanism for bringing the heating element into contact with / separated from the opposite surface, and generate heat when the molding surface is heated. A means for causing a body to generate heat so as to come into contact with the opposite surface, and to separate the heating element from the opposite surface when the molding surface is cooled. (C) A means that is provided in the space so as to face the opposite surface and radiates heat toward the opposite surface when the molding surface is heated. 4. The cooling means according to claim 2, wherein the cooling means supplies a liquid having a Vicat softening temperature (T) of −10 ° C. or less to the space and directs it to the opposite surface when cooling the molding surface. A mold for molding, which is a means for depressurizing the space while ejecting the gas and sucking and discharging the gas evaporated by the heat absorption in the space. 5. The molding die according to claim 1, wherein the heating means is a means selected from the following (D) to (E). (D) Before supplying the thermoplastic resin to the molding surface, immediately before starting the supply of the thermoplastic resin to the molding surface, a radiator is introduced into a position facing the molding surface to radiate heat toward the molding surface. Means for retracting the radiator from the facing position. (E) Before supplying the thermoplastic resin to the molding surface, a fluid supply pipe is introduced into a position facing the molding surface to jet a heated fluid toward the molding surface, and heat the molding surface. Means for retracting the fluid supply pipe from the facing position immediately before starting the supply of the plastic resin.