JPH0623758A - Manufacture of synthetic resin hollow body - Google Patents

Abstract

PURPOSE:To constitute the title manufacture so that water is not leaked through a gap of a mold, by a method wherein the water filled into an inner shell and frozen is thickened by high-water-absorbing resin. CONSTITUTION:Members 11 injection-molded by spliting into two is made into a hollow body by adhesion or welding or mechanical holding or an inner shell 1 is made by making use of a hollow body 12 by blow forming, one side owing part is covered by making use of a cap 14, the inside is filled with a core material 3 obtained by mixing high-water-absorbing resin powder 32 with water 31 and the other opening part also is closed and covered. In other words, the inner shell 1 filled with the frozen core material is inserted into the mold, the mold is clamped, melt is injection-mold and overmolded. Then though the core part can be discharged by thawing the core part by heating or leaving as it is under the normal temperature, discharging by compressed air 5 also is performed effectively when necessity arises. With this construction, a condition can be held sufficiently until completion of injection of short-time over molding.

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 hollow molded article made of a synthetic resin material and having a complicated shape and high strength.

[0002]

2. Description of the Related Art Conventionally, a blow molding method has been generally used as a method for manufacturing a hollow body made of synthetic resin. However, this method has a large thickness, high strength, and a smooth inner surface. so,
There are many drawbacks such as inability to produce products with high dimensional accuracy and uneven wall thickness. In particular, it is impossible to manufacture products having a large number of branches, for example, an intecumanifold.

Next, in order to solve the drawbacks of the blow molding method, for example, as a lost core method, a core material is made of a low melting point alloy, mainly tin / bismuth alloy, and is inserted into a mold, and the
It is possible to accurately mold a complex shape by performing a method of forming a hollow molded product by melting and molding the core material and heating and melting the core material. Not only there are many steps such as elution, cleaning, and drying of the core, but there are drawbacks such as expensive capital investment for casting and elution of the core alloy.

There is also a method in which a water-soluble plastic is molded and used as a core, that is, Solble Core (Belland Co.), but the core material is expensive, and it is difficult to collect and recycle it. The strength is low, there is a risk of lack of accuracy, and the melting point is low, so there is a risk of melt-out near the injection gate.

In addition, an inner shell having a split shape is formed and joined to form a hollow body, and the hollow body is inserted into a mold to perform an over molding method (for example, Dual process of Hetlinga Co.). ), The inner shell is easily damaged and it is difficult to use unless it is a thick product with a special shape. There is also a method (two-shell method) in which the entire hollow molded product is divided into two parts and is post-process welded by vibration welding or the like, but the strength of the joint is unstable, and especially the strength of the material containing the reinforcing material is significantly reduced. However, there was a major drawback in that burrs were generated inside and outside the joint, and the functions and appearance were restricted.

[0006]

Conventionally, many methods for producing a hollow molded article having a complicated shape have been proposed or implemented as described above. However, in view of strength of the core and other performances, the shape is improved. There was a big problem in terms of cost and equipment cost. The present invention uses a thin-walled molded product (blow molded product or divided molded product joined to the inner shell), and when performing overmolding, the inner shell is controlled by temperature and pressure.
It has been completed as a result of various studies in order to prevent deformation of the shell and to easily obtain a desired accurate molded product at low cost.

[0007]

Means for Solving the Problem and Its Action The present invention is
A hollow thin blow molded product or a hollow body that is a combination of two or more divided molded parts is used as an inner shell, and one end of the hollow body is closed with a cap, etc. Water mixed with resin powder (for example, Aquamate manufactured by Sekisui Plastics Co., Ltd.) was injected, frozen, frozen in a freezer, taken out, immediately inserted into the mold, and the mold was closed. Then, the molten resin is injected to carry out the over mode. After that, the core ice is thawed by leaving it at room temperature or by heating it, and if necessary, use compressed air or the like to discharge the thawed and thickened water to complete the molding.
In addition, the discharged thickened water can be repeatedly used as a core material.

A method for manufacturing a hollow body according to the present invention will be described below.
A specific description will be given based on the drawings showing an example of the embodiment. FIG. 1 shows a manufacturing process of an inner shell 1 filled with a core material 3. A member 11 which is split and injection-molded into two cracks is made into a hollow body by bonding, welding, mechanical tying or the like, or is blow-molded. A core material 3 in which a hollow body 12 according to the above is used and an inner shell 1 whose cross-sectional view is shown at 13 is formed, one opening is covered with a cap 14, and a highly water-absorbent resin powder 32 is mixed with water 31 inside. And seal the other openings.

At this time, the mixing ratio of the highly water-absorbent resin powder 32 and the water 31 must be such that the thickened mixture does not leak out from the gap such as the cap. Next, the inner shell 1 in which the core material 3 is injected and filled is cooled and frozen in a cooling device such as a freezer, and is directly overheated.
It will be used as a core for the field. When the core is frozen, the inner
Condensation may occur on the surface of the shell 1. In this case, by covering the surface with a super-absorbent resin powder impregnated sheet in advance, moisture on the surface is absorbed and dew condensation is completely prevented. You can

FIG. 2 shows a process for manufacturing a hollow molded body by overmolding. An inner shell 1 filled with a frozen core material 33 is inserted into a mold 4 and the mold is removed. close,
The melt is injection molded and overmolded 2. After that, the core portion can be heated or thawed by leaving it at room temperature and discharged, but discharging by compressed air 5 is also effective if necessary. In addition, the discharged core material 3
Can be reused and used repeatedly.

The resin material for the inner shell 1 and the overmold 2 used in the method for producing the hollow synthetic resin product of the present invention may be any material which is welded at the time of overmolding. For example, various resin materials can be used, glass fiber,
Materials with various fillers such as carbon fiber reinforcements can also be used.

[0012]

As described above, according to the feature of the present invention, since the water packed in the inner shell and frozen is thickened by the super absorbent resin, it may leak from the gap of the mold or the like. Absent. In addition, since frozen ice has a high elastic modulus and does not change easily, the inner shell itself becomes a core that is extremely difficult to deform, and it can withstand the pressure of the overmold sufficiently and that of the frozen body. The surface is plastic inner
Since it is covered with the shell, the state can be sufficiently maintained until the completion of the injection of the over mold in a short time.

Further, there is an advantage that it can be thawed and discharged in a liquid state by leaving it in a normal greenhouse after demolding. Conventionally, when making a hollow molded product of this kind, a lost core method using a low melting point alloy has been used, but the present invention does not use an expensive metal for a core and requires a large amount of capital investment.
It is a novel invention with many advantages, such as no complicated process is required, the water-absorbent resin mixed water can be used repeatedly, there is little loss, and no pollution problem due to discharge of cleaning liquid occurs.

[0014]

EXAMPLES The method for producing a synthetic resin hollow body according to the present invention will be described below with reference to examples. (1) Manufacture of Inner Shell and Core Material Polyamide resin (PA 66) (glass fiber 30% reinforced product) Toray Industries, Inc. (CM 3006 G 30) is used to perform two molding processes with an injection molding machine. (Thickness 2.5 mm, resin temperature 295 ℃, mold temperature 80
C.) Next, as shown in FIG. 1, a hollow inner shell is assembled by snap fitting, and the lid is covered with a super absorbent polymer powder (Aquamate AQ-10 manufactured by Sekisui Plastics Co., Ltd.).
Gel water was added and mixed with 0.5% (weight) of 0) and frozen in a freezer at -70 ° C to obtain a core material.

(2) Overmolding Immediately inserting the frozen core material into a mold and closing the mold, a polyamide resin (AP 66) Amylan (GM 3007) manufactured by Toray Industries, Inc. was used. After molding at a thickness of 2.0 mm, a resin temperature of 290 ° C., a mold temperature of 80 ° C., and an injection time of 1.5 seconds, the core material was allowed to melt and discharge for 3 hours at room temperature to obtain a molded product. Molded products were manufactured with the desired shape and strength.

[Brief description of drawings]

FIG. 1 is a manufacturing process diagram of an inner shell filled with a core material.

FIG. 2 is a manufacturing process drawing of a hollow molded body by overmolding.

[Explanation of symbols]

 1 Inner Shell 11 Split Molded Inner Shell Member 12 Blow Molded Inner Shell Member 13 Inner Shell Cross Section 14 Cap 15 Snap Fit Protrusion 16 Snap Fit Claw 2 Over Mold Part 3 Core Material 31 Water 32 Super absorbent resin powder 33 Core material in frozen state 4 Mold 41 Lower mold 42 Upper mold 43 Injection hole 5 Compressed air

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Claims (1)

[Claims] 1. A hollow body inner shell is formed by combining a plurality of inner shell divided molded products or a blower.
In a method of molding a hollow body, in which a molded product is used as an inner shell, and a molten resin of the same or another material is injected to the outer side of the molded product to form an overmold and to be integrated with the inner shell, Water-thickening material such as super-absorbent resin is thickened to the extent that water does not flow out from the gap, and then poured into the mold. A method for producing a synthetic resin hollow body, comprising: inserting into an inner shell, forming an integrally molded product with the inner shell, and melting and removing the core material.