JPH02283429A - Mold for polyolefinic resin foam-molding - Google Patents

Abstract

PURPOSE:To manufacture foam-molded products with a beautiful appearance by forming multiple steam pores of a small diameter in molds and providing embossed patterns on the inner surfaces of the molds. CONSTITUTION:Multiple steam pores 6 of a small diameter are formed in molds 1,2, the diameter of the steam pores 6 being 0.5 to 1.2mm, the pitch thereof being 5 to 20mm and the forming rate thereof to the surfaces of the molds being 0.5 to 4%, and embossed patterns are provided on the inner surfaces of the molds. As the steam pores 6 are formed in such a state, the marks of the steam pores on the surface of foam-molded products become indistinguishable, and further, the patterns on the granular structure of foaming particles, which appear on the surface of the foam-molded products, are covered up while the marks of the steam pores 6 become more invisible due to the embossed patterns. Thus, the foam-molded products with a high-grade impression and a beautiful appearance can be obtained.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a mold for polyolefin resin foam molding, and more specifically, to manufacturing a foam molded product with a good appearance in which grain boundary patterns of foamed particles are hidden. The present invention relates to a mold for polyolefin resin foam molding.

[Conventional technology]

Polyolefin resin foam particles are filled into a mold cavity formed by a core mold and a cavity mold, and then heated and molded to obtain various polyolefin resin foam molded products such as box-shaped containers and cushioning materials. The method is widely used.

However, when observing the surface of these in-mold foamed products,
There is a grain boundary pattern that occurs when foamed particles expand and fuse together, and this pattern causes these in-mold foam molded products to lose their high-quality appearance, and their use is limited to popular or disposable products. there were. The phenomenon in which such a grain boundary pattern occurs is inevitably caused by the low foam expansion properties of polyolefin resins and poor mold reproducibility.

To solve this problem, a geometric pattern consisting of uneven stripes with a pitch equal to or narrower than the unit diameter of the grain boundary pattern on the surface of the material is applied in advance to the visible surface of the molded container. By providing the geometric pattern on the inner surface of the mold, the reflection from the uneven surface of the molded product is visually highlighted, and the grain boundary pattern of the expanded particles is mixed and buried in the shadow. , a technique has been disclosed in which the surface of a resin molded product appears uniformly and beautifully finished so that it cannot be distinguished from the molded product made of foamed resin particle material (Utility Model Application Publication No. 63-10872).
Publication No. 8).

(Problem to be Solved by the Invention) However, in such in-mold foam molding, a slit with a diameter of 0.1 to 0.3 mm is provided as a steam hole for sending heating steam into the mold cavity. A core vent of 5 to 10 mm is embedded in the mold, and in the mold of the above-mentioned Japanese Utility Model Publication No. 63-108728, no treatment was taken for this core vent, and the molded product was left with traces of steam holes here and there. The problem that the grain boundary pattern of the original expanded particles becomes noticeable depending on the viewing angle and the problem that the appearance of the molded product is spoiled has not yet been solved.

The present invention has been made in view of the above points, and its purpose is to:
To provide a mold for polyolefin resin foam molding which not only hides the grain boundary pattern of expanded particles but also allows in-mold foam molding without leaving any traces of steam holes on the surface of the molded product.

[Failure to solve the problem]

According to the present invention, in a mold for manufacturing a foam molded article by filling a mold cavity formed by a core mold and a cavity mold with polyolefin resin foam particles having an average particle diameter of 2n+m to 6 mm, The mold has a large number of small-diameter steam holes, the diameter of the steam holes is 0.5 mm to 1.2 mm, the pitch of the steam holes is 5 mm to 20 mm, and the porosity of the i-pores to the mold surface is 0. .5% to 4%, and a mold for polyolefin resin foam molding is provided, which is characterized in that the inner surface of the mold is provided with a textured pattern.

The expanded polyolefin resin particles used in the present invention include polyethylene, polypropylene, copolymers thereof, and copolymers with other monomers copolymerizable with these.
Expanded particles obtained from mixtures of these and the like are included. The polyolefin resin foam particles have an average particle diameter of 2 mm to 6
mm is used. If it is less than 2 mm, it is too small and the foaming ability is low, depressions are formed between the foamed particles, the fusion properties between the foamed particles become poor, and the appearance is also unfavorable.

Moreover, if it exceeds 6M, the surface of the molded product will bulge in the shape of resin particles, which will deteriorate the appearance, which is not preferable.

The mold of the present invention is composed of a core mold and a cavity mold, and these molds are provided with a large number of small-diameter steam holes. The diameter of this steam hole is 0.5 mm to 1.2 mm.
It is mm. If it is less than 0.5 mm, it will be difficult to supply heating steam, and if it exceeds 1.2 mm, the marks of the steam holes will be noticeable, which is not preferable.

The pitch between steam holes is 5+++ m to 20 mm. If the diameter is less than 5 mm, the number of holes to be drilled in the mold will be large, requiring a great deal of labor and expense to manufacture the mold, and if the diameter exceeds 20 mm, the number of steam holes will be small, making steam heating difficult.

In addition, the porosity of the steam hole relative to the mold surface is 0.5% to 4%.
It is. If it is less than 0.5%, the amount of steam necessary for foaming and fusing the expanded polyolefin resin particles cannot be secured, and even if the porosity exceeds 4%, it will not have the effect of increasing the porosity, making it economical. There is no profit.

As the material constituting the mold of the present invention, aluminum-based metal is preferable in terms of workability, lightness, heat conductivity, and the like.

The inner surface of the mold of the present invention has a grain pattern.

As the grain pattern, an uneven pattern such as a round shape, a lattice shape, a leather grain shape, a diamond cut shape, etc. is preferable. For the purpose of the present invention, a leather grain pattern is particularly preferred.

Such a textured pattern can be applied to a mold by etching the mold, by pasting punched metal with a textured pattern on the surface of the mold, or the like.

In the etching method, for example, a photosensitive resin layer is formed on the mold surface by pasting a photosensitive resin sheet or coating the photosensitive resin, and then a mask with a pattern is attached and exposed. Then, the uncured portion is dissolved and removed. Next, a chemical solution is applied through the cured resin layer to etch the mold surface. After etching, peel off the cured resin film,
Clean and dry the mold surface.

Here, the above-mentioned etching may be performed either before or after forming the steam holes in the mold. When etching is performed after drilling the steam hole, the hole may be sealed to prevent chemical liquid from entering the hole.

In addition, when pasting punching metal, you can create a steam hole by pasting the punching metal and then drilling a hole that passes through the punching metal and the mold body, or you can create a hole in the mold and punching metal separately. You may also attach it so that the holes are aligned.

[Function] In the mold of the present invention, steam holes having a diameter of 0.5 mm to 1.2 mm are provided at a pitch of 5 mm to 20 mm, and the porosity of the steam holes with respect to the mold surface is 0.5% to 4%. Therefore, the traces of steam holes on the surface of the foamed molded product are difficult to distinguish, and furthermore, since the inner surface of the mold has a grain pattern, the pattern of the particle interface of the foamed particles can be seen on the surface of the foamed molded product. In addition to being hidden, the marks of the steam holes become even more difficult to see due to the grain pattern. Therefore, it becomes possible to obtain a foamed molded product having a beautiful appearance with a high-class feel.

〔Example〕

Next, the present invention will be explained with reference to Examples.

Incidentally, the porosity (%) was determined by the following method.

Example 1 A core mold and a cavity mold were made by aluminum die-casting so that a molded product in the shape of a motorcycle saddle could be obtained. The inner surface of both molds has a thickness of approximately 0.2
The photosensitive resin sheet with a diameter of 1.5 mm is pasted by exposing it to ultraviolet light through a mask with a leather grain pattern drawn on it.
The photosensitive resin was cured. Next, in step 1, after removing the uncured portion by dissolving it with a solvent, a ferric chloride solution was applied to process and etch the surface of the mold. After etching, it was thoroughly washed and dried, and then the following steam holes were opened with a drill to obtain a mold for foam molding.

Diameter (mm): 0.8 Pitch (mm): 5 Porosity (%): 2.2 The mold obtained as above was assembled into a foam molding machine as shown in Figure 1, and the following conditions were applied. Foam molding was performed.

Raw material: Foamed polyethylene particles (expansion ratio 20 times, average particle diameter 4mm) Molding impregnation internal pressure:
0.8 kg/cJG steam heating conditions: Positive one side heating 0
．． 1 kg/c+ilG 3 seconds reverse heating 0.3 kg
/ ci G 5 seconds double-sided heating 1.1 kg/c+fl
G The molded product obtained in the above manner for 3 seconds or more has a surface covered with a grain pattern, the grain boundary pattern of the foamed polyethylene particles is hidden in the grain pattern, and is beautiful with no visible traces of steam holes. It had a luxurious appearance.

Example 2 A polyethylene foam particle molded product in the shape of a motorcycle saddle was obtained in the same manner as in Example 1, except that the steam holes had a diameter of 1 mm or 2 mm, a pitch of 15 mm, and a porosity of 0.6%.

As in Example 1, the grain boundary pattern of the expanded particles was hidden by the leather grain pattern, and the molded product had a beautiful and luxurious appearance with no visible traces of steam holes, and also had good fusion bonding. Ta.

[Effects of the Invention] According to the mold of the present invention, not only the grain boundary pattern of the expanded particles is hidden, but also in-mold foam molding can be performed without leaving any traces of steam holes on the surface of the molded product.

[Brief explanation of drawings]

FIG. 1 is a schematic explanatory diagram showing an example of a foam molding apparatus equipped with a mold according to the present invention. 1-cavity mold, 2-core mold, 3-filling machine, 4
-Polyolefin resin beads, -Cavity side steam valve, 6-Steam hole, 7-Core side drain valve, 8-Core side steam valve, 9-Cavity side drain valve Patent applicant Asahi Kasei Corporation

Claims (1)

[Claims] In a mold for producing a foamed molded product by filling foamed polyolefin resin particles with an average particle size of 2 mm to 6 mm into a mold cavity formed by a core mold and a cavity mold,
The mold has a large number of small diameter steam holes, the diameter of the steam holes is 0.5 mm to 1.2 mm, and the pitch of the steam holes is 5 mm.
~20mm, the open area ratio of the steam hole to the mold surface is 0.5%
-4%, and a mold for polyolefin resin foam molding, characterized in that the inner surface of the mold is provided with a textured pattern.