JPH02283428A - Mold for in-mold foam-molding and manufacture thereof - Google Patents

Abstract

PURPOSE:To manufacture foam-molded products with a beautiful appearance by a method wherein a continuous pattern is formed of rugged patterns provided on the inner surfaces of the main bodies of molds and rugged patterns provided to core vents. CONSTITUTION:Rugged patterns provided on the inner surfaces of the main bodies of molds 1, 2 and rugged patterns provided to core vents 6 form a continuous pattern at the parts over the boundary between the inner surfaces of the mold main bodies and the core vents 6. Polyolefinic resin foaming particles 4 are packed by a packing machine 3 into the mold recess formed by both molds 1, 2, and molding is performed by feeding steam into both molds 1, 2 through steam pores of the core vents 6, starting molding under heating and completing molding while gradually relieving pressure. By this method, the patterns on the granular structure of the polyolefinic resin foaming particles 4 are covered up, and furthermore, the marks of the steam pores of the core vents becomes inconspicuous on the surface of foam-molded products.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a mold for polyolefin resin foam molding and a method for producing the same, and more specifically, to a mold for foam molding with a good appearance in which the grain boundary pattern of foamed particles is hidden. The present invention relates to a polyolefin resin foam molding mold capable of manufacturing a body and a method for manufacturing the same.

[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 foamed bottom shapes to lose their high-quality appearance, and their use is limited to popular or disposable products. was there. 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. That is, the geometric pattern is provided on the inner surface of the molding die, and the reflection from the uneven surface stripes 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 to be uniformly and beautifully finished so that it cannot be distinguished from the molded product made of foamed resin particle material.
Publication No. 8).

[Problems to be Solved by the Invention] However, in such in-mold foam molding, in order to send steam for heating into the mold cavity,
It is practiced to embed core vents with a diameter of 5 to 12 mm with many slits of mm or small holes of 0.5 to 1 m+n in diameter. As a result, the molded product was left with traces of steam holes from the core vent all over the place, which combined with the imperfection of the effect of erasing the grain boundary pattern of the expanded particles to reduce the aesthetic appearance of the molded product. The problem of damaging the data remains unresolved.

The present invention was made in view of the above points, and its purpose is to not only hide the grain boundary pattern of expanded particles, but also to enable in-mold foam molding without leaving any traces of core vent steam holes on the surface of the molded product. An object of the present invention is to provide a mold for polyolefin resin foam molding and a method for manufacturing the same.

[Failure to solve the problem]

According to the present invention, synthetic resin foam particles are filled into a mold cavity formed by a core mold in which a core vent having steam holes such as Surin 1- is embedded and a cavity mold to produce a foamed molded product. In the mold, the uneven pattern imparted to the inner surface of the mold body and the uneven pattern imparted to the core vent form a continuous pattern in a portion crossing the boundary between the inner surface of the mold body and the core vent. A mold for in-mold foam molding is provided.

The expanded polyolefin resin particles used in the present invention include polyethylene, polypropylene, copolymers thereof, copolymers with other monomers copolymerizable with these,
Expanded particles obtained from mixtures of these and the like are included. Polyolefin resin foam particles have an average particle diameter of 2 mm to 6 m.
m is preferred. If it is less than 2 mm, it is too small and the foaming ability is low and the aperture ratio required for steam heating cannot be increased.
If it exceeds this amount, the surface of the molded product will bulge in the shape of foamed particles, resulting in poor appearance, which is not preferable.

The mold of the present invention is composed of a core mold and a cavity mold, and a core vent having a diameter of 5 mm to 12 mm is embedded in these molds. Width 0.1 to 0 for core vent
．． A large number of 3 mm slits and small holes with a diameter of 0.5 to 1 mm are provided.

The inner surface of the mold and the surface of the core vent are provided with an uneven pattern. The uneven pattern provided on the inner surface of the mold and the uneven pattern provided on the surface of the core vent are continuous in a portion crossing the boundary between the inner surface of the mold and the core vent.

As a method for manufacturing such a mold, there is a method for manufacturing an in-mold foam molding mold comprising a core mold and a cavity mold, and a core vent having a steam hole such as a slit embedded therein. After sealing the steam holes in the core vent, a photosensitive resin layer is formed on the surface of the mold and the core vent, and then exposed to light through a patterned mask to harden the resin, and the uncured parts are dissolved and removed. Provided is a method for producing a mold for in-mold foam molding, which is characterized in that a resist is formed by etching, the resist film is removed after etching, and then the filler for the steam holes in the core vent is removed.

In order to embed the core vent in the mold, a through hole may be bored in the mold as in the conventional method, and the core vent may be driven into the through hole.

Next, the steam holes such as the slits in the core vents 1 to 1 of the mold are sealed by, for example, press-fitting a resin (filling resin) into the steam holes before or after placing the core vent. This filler resin is not soluble in the liquid used to dissolve the uncured portion of the photosensitive resin or in the etching liquid, but is soluble in certain solvents other than these.

The material of the core vent is preferably the same or similar metal material as the mold. In the present invention, it is preferable that the mold and the core vent are made of aluminum or an aluminum-based alloy from the viewpoints of workability, lightness, heat conductivity, and the like.

A photosensitive resin layer is formed on the inner surface of the mold in which the steam holes of the core vent have been sealed as described above. Formation of the photosensitive resin layer is performed by pasting a photosensitive resin sheet or coating a photosensitive resin.

Next, the resin is exposed to light through a mask having a predetermined pattern of bumps drawn on the photosensitive resin layer, and the resin is cured, and the uncured portions are dissolved and removed with a solvent to form a resist.

Next, with the resist attached, it is brought into contact with an etching solution for etching treatment. As the etching solution, ferric chloride, hydrochloric acid, nitric acid, etc. are used.

Since the etching depth varies depending on the type of etching solution, the contact time with the etching solution, and the number of times of processing, it is necessary to select and adjust it appropriately.

As described above, with the steam holes of the core vent sealed, resist is formed and etched on the surfaces of the mold body and core vent at the same time, so the uneven pattern on the inner surface of the mold body and the unevenness on the core vent are formed. The pattern becomes a continuous pattern in the part that straddles the boundary between the inner surface of the mold body and the core hen 1.

After etching, the resist film is removed by immersing it in a stripping solution, and then the sealing resin for the steam holes of the core vent is dissolved and removed using a solvent, and then dried to obtain the desired mold.

The mold described above is incorporated into the foam molding apparatus shown in FIG. 1 and used for in-mold foam molding.

In the first round, the mold consists of a cavity mold 1 and a core mold 2, and a filling machine 3 fills the mold cavity formed by both molds.
The foamed polyolefin resin particles 4 are filled by the following steps.

Molding is carried out by feeding steam into both molds from the steam holes of the core vent 6, starting hot molding, and completing the molding while gradually releasing the pressure.

This type of in-mold foam molding usually produces 0.3 to 2.0 kg/
This can be done by heating for 20 to 100 seconds using saturated steam of CRA G.

Heating is performed by reverse one-sided heating, forward one-sided heating, double-sided heating, etc. In reverse one-sided heating, steam is supplied to the core mold 2 from the core-side steam valve 8, and is further discharged from the cavity-side drain valve 9 through the core-side steam hole.

In the positive heating, steam is supplied from the cavity side steam valve 5, passes from the cavity mold 1 through the core mold 2 through the steam hole of the core vent, and is discharged from the core side drain valve 7.

In double-sided heating, heating is performed simultaneously from both the cavity mold 1 and the core mold 2 with the cavity side drain valve 9 and the core side drain valve 7 closed.

[For production]

As described above, since the mold of the present invention has an uneven pattern on the inner surface of the mold body and the core vent, the grain boundary pattern of the expanded polyolefin resin particles is formed. Furthermore, since the uneven pattern is a continuous pattern in the portion that crosses the boundary between the inner surface of the mold body and the core vent, traces of the steam holes of the core vent are not noticeable on the surface of the foam molded product.

〔Example〕

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

EXAMPLE A core mold and a cavity mold were made by aluminum die-casting so that a molded body in the shape of an auto-high saddle could be obtained. Drill a number of through holes in this mold and insert a core vent (width 0.2 m) with a diameter of 1 mm.
Five rows of sulins 1 to 1 are provided, and the material is aluminum, and styrene resin is press-fitted into the slits.

) was typed.

A photosensitive resin sheet with a thickness of about 0.2 mm is pasted on the inner surface of both molds, and is pasted through a mask with a leather grain pattern.
The photosensitive resin was cured by exposure to ultraviolet light. Next, after dissolving and removing the uncured portions with a solvent, a ferric chloride solution was applied to perform an etching treatment on the surface of the mold. After etching, the resist film was removed by immersing it in a stripping solution, and then the sealing resin for the slits of the core vent was immersed in toluene to dissolve and remove it, followed by drying to obtain the desired mold for foam molding.

The mold obtained as described above was installed in a foam molding apparatus as shown in FIG. 1, and foam molding was carried out under the following conditions.

Raw material double-foamed polyethylene particles (expansion ratio 20 times, average particle diameter 4 mm) Air impregnation internal pressure:
0.8kg/c+fiG Steam heating conditions: Forward heating 0.1 kg/ci G 3 seconds Reverse heating 0.3 kg
/ afl G 5 seconds double-sided heating 1.1 kg/c1
11G The molded product obtained as above for 3 seconds has a surface covered with a grain pattern, the grain boundary pattern of the expanded polyethylene particles is hidden in the grain pattern, and the traces of steam holes in the core vent are also visible. It had a beautiful and luxurious appearance.

〔Effect of the invention〕

According to the mold of the present invention, not only the grain boundary pattern of one expanded particle is hidden, but also in-mold foam molding can be performed without leaving any traces of the steam holes of the core vent on the surface of the molded product. Furthermore, according to the manufacturing method of the present invention, the mold described in item 1 can be easily manufactured.

[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 foam particles, 5-Cavity side steam valve, 6-Core vent, 7-Core side drain valve, 8-Core side steam Valve, 9-cavity side drain valve

Claims (2)

[Claims] (1) In a mold for manufacturing a foamed product by filling synthetic resin foam particles into a mold cavity formed by a core mold in which a core vent having a steam hole such as a slit is embedded and a cavity mold, The uneven pattern imparted to the inner surface of the mold body and the uneven pattern imparted to the core vent form a continuous pattern in a portion crossing the boundary between the inner surface of the mold body and the core vent. In-mold foam mold (2) In a method for manufacturing an in-mold foam molding mold comprising a core mold and a cavity mold and embedding a core vent having steam holes such as slits, the steam holes in the core vent are sealed. After that, a photosensitive resin layer is formed on the surface of the mold and core vent, and exposed through a patterned mask to harden the resin. The uncured portion is dissolved and removed to form a resist, and then etched. A method for producing a mold for in-mold foam molding, which comprises removing the resist film after treatment and then removing the filler for the steam holes in the core vent.