JPH11314232A - Production of synthetic resin molded product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a soft synthetic resin molded product such as an artificial bait or the like in low cost with good productivity. SOLUTION: A plastisol high in a plasticizer ratio is heated until it again becomes a sol state through a gel state and the heated sol is injected into a mold 1 to be cooled to produce a soft synthetic resin molded product. Therefore, since the plastisol brought to a sol state by heating is cooled by the mold and heating is not required at a time of molding, a molding cycle is shortened and molding is possible by a simple mold.

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 synthetic resin molded article, particularly a soft product such as artificial bait or other miscellaneous goods at low cost.

[0002]

2. Description of the Related Art Conventionally, injection molding and casting molding have been adopted as a molding method of a pseudo bait using a plastisol.

[0003]

In the injection molding, the production cost of the mold is high, the production equipment is large because the material (plastisol) is injected under high pressure. However, there is a problem that the molding cycle is prolonged since the material tends to remain and it is necessary to heat and melt the material for each shot at the time of injection. Also, in casting molding, one side of the product can be three-dimensionally molded because the material is poured into a dish-shaped mold and heated.
The opposite surface must be flat, and a three-dimensional molded product cannot be obtained. Moreover, since no pressure is applied during the injection of the material, the molding accuracy is poor. In addition, there is a problem in that the molding cycle is lengthened because heating is performed after material injection.

[0004]

According to the present invention, a plastisol having a high plasticizer ratio is heated through a gel state until it becomes a sol state again, then injected into a mold and cooled to produce a synthetic resin molded article. Things. When the mold is made of silicon, the mold has good releasability (claim 2). The mold is a split mold that is divided into upper and lower parts. Each split mold has a plurality of molding recesses, and is directed toward each molding recess from a sol injection port provided in the center of the upper mold or the lower mold. When a mold having a sol flow path is used and the mold is rotated while the sol is being injected from the injection port, the molding accuracy is improved (claim 3).

[0005]

The plastisol having a high plasticizer ratio is in a sol state at room temperature, solidifies into a gel state when heated, and returns to a sol state when heating is further continued. Then, when the material that has gone into the sol state beyond the gel state is cooled, it gels and maintains its shape even at room temperature. Therefore, according to the method of the present invention, a desired molded article can be obtained by injecting a material that has been converted into a sol beyond the gel state into a mold and cooling it. No special equipment is required for cooling, and the material is cooled and gelled by touching the mold.

If a silicon mold is used,
The molded plastisol molded article has good releasability and improves productivity. Also, if a split mold is used, three-dimensional molding can be performed on both sides of the molded product, and when the sol is injected into the mold while rotating the mold, the sol is pressurized by centrifugal force,
Molding accuracy is improved.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION A plastisol (for example, 7 ×
-123, RA-200 to 600, trade name of Kobayashi Co., Ltd.) is heated with stirring. The plastisol is in a sol state at room temperature, but becomes a solid gel state when heated to about 160 ° C. and melts when further heated (about 200 ° C.). The melted plastisol in a sol state is poured into a mold and molded. When the plastisol is injected into the mold, if the inside of the mold is depressurized (preferably in a vacuum state), the transferability is improved and a molded product with high molding accuracy is obtained.

FIGS. 1 and 2 show a mold used for this molding. The molding die 1 has a split mold shape in which an upper die 2 and a lower die 3 are combined, and a plurality of molding recesses 4 are provided in the upper and lower dies, respectively. A sol injection port 5 is provided at the center of the upper mold, and a sol flow path 6 is formed radially from the injection port 5 to each molding recess 4 in the upper and lower molds. A hole 7 for venting air is provided above each molding recess 4. The mold 1 is made of silicon.

The molding die 1 constructed as described above is mounted on a rotating device, and while the molding die 1 is rotated, the sol injection port 5 is rotated.
Inject sol from. The injected sol flows into the molding recess 4 from the injection port 1 via the flow path 6, but since the molding die 1 is rotating, centrifugal force acts on the sol, and the sol quickly flows into the molding recess 4 and , Surely flows into the details of the molding recess. Since each molding recess 4 is provided with an air vent hole 7, no air remains in the molding recess 4. Therefore, a molded article with high accuracy can be obtained.

The sol that has flowed into the molding die is rapidly cooled by the heat of the molding die 1 itself, and gelates into a solid. Then, the mold is opened and the molded product is taken out. Since the mold is made of silicon, it is easy to release the molded product.

[0011] The material of the plastisol used in the present invention is not limited as long as it has a property of being mixed with a plasticizer, gelled by heating, and then turned into a sol by further heating. The amount of the plasticizer is usually about twice as large as that of the vinyl chloride paste resin, and the above characteristics can be obtained. If the above characteristics are obtained, the amount can be appropriately selected.

In the above embodiment, since a plurality of molding recesses 4 are formed in the molding die 1, it is suitable for mass production. However, only one molding depression may be used. May be.

[0013]

According to the present invention, the plastisol that has been heated from the gel state to the sol state again is injected into the molding die. There is no need to heat after injection into a mold as in casting molding. If a large amount of the plastisol to be used is heated and melted in advance, then molding can be performed only by sequentially injecting it into a mold. Therefore, the working efficiency is good, and a molded product of plastisol can be manufactured at low cost.

If silicon is used for the mold, mold release is easy and the mold is easy to manufacture. And
If the mold is provided with a plurality of molding recesses and the sol is injected while rotating, the sol spreads over the details of the molding die by the action of centrifugal force without the need to pressurize during injection. Further, since it is not necessary to apply pressure at the time of injection, a sol having a low viscosity can be used, and burrs hardly remain. Therefore, there is an effect that a high-precision molded product can be obtained at low cost.

[Brief description of the drawings]

FIG. 1 is a perspective view of a lower mold used in an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the same molding die.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mold 2 Upper mold 3 Lower mold 4 Mold recess 5 Inlet 6 Flow path 7 Air vent hole

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Kenichi Kushida 3-15-14 Higashi Tateishi, Katsushika-ku, Tokyo Inside the Kobayashi Katsushika Plant

Claims (3)

[Claims] 1. A method for producing a synthetic resin molded article, comprising heating a plastisol having a high plasticizer ratio through a gel state to a sol state again, and then pouring it into a mold and cooling. 2. The method for producing a synthetic resin molded product according to claim 1, wherein the molding die is made of silicon. 3. The mold is a split mold that is divided into upper and lower parts. Each split mold has a plurality of molding recesses, and each mold is formed from a sol injection port provided in the center of an upper mold or a lower mold. The method for producing a synthetic resin molded product according to claim 1, wherein a sol flow path is formed toward the concave portion, and the mold is rotated while injecting the sol from the injection port.