JPH03190723A - Manufacture of foamed-in-place molded form - Google Patents

Abstract

PURPOSE:To prevent possibility, in which clogging is generated due to the clogging of a molten resin in a steam hole for supplying steam, etc., for heating, by using a mold in which the surface of at least the steam hole on the mold recessed surface side is coated with a gas-permeable porous sheet. CONSTITUTION:The inside of a mold recess 9 composed of a pair of molds 1, 2 with a plurality of steam holes 3 is filled with thermoplastic resin foaming particles, a heating medium is fed from the steam holes 8, the foaming particles are heated, and the particles are fused mutually, thus manufacturing a templated molded form. The molds 1, 2 in which the surfaces of at least the steam holes 8 on the mold recess 9 surface side are covered with a gas-permeable porous sheet 16 are used at that time.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for manufacturing an in-mold foam molded article.

[Conventional technology]

After filling thermoplastic resin foam particles into a mold cavity formed by a pair of molds having a large number of steam holes through which steam etc. can pass, a heating medium such as steam is supplied to fill the mold cavity. BACKGROUND ART There is a known method for producing a molded body according to a mold (so-called in-mold foam molded body) by heating foamed particles to fuse the particles to each other. In the mold used to manufacture the above-mentioned molded product, the steam vent is usually constructed by fitting a part called a core vent, which has multiple slits or small holes through which steam can pass, into a through hole provided in the mold. There is. The reason why a removable part such as a core vent is inserted into a through hole of a mold to form a steam hole is because the steam hole is easily clogged with resin during repeated molding, and the core vent is By constructing the steam vents with removable parts such as, even if the steam vents become clogged, you can simply remove the core vent from the mold and remove the resin clogging the steam vents, allowing the steam to flow directly into the mold. This is because the workability is better than when holes are formed.

[Problem that the invention attempts to solve]

However, usually 7000~io, ooo shots (
In industrial-scale production, the core vent must be removed from the mold every 20 to 30 days) and heated to 200 to 300°C to melt and remove the resin clogging the core vent's steam holes. During this period, molding operations were forced to stop, which was a major problem in terms of production efficiency.In addition, the core vents had multiple steam holes, and many of the core vents were scattered over the mold surface. As a result, many traces of core vent steam holes remain scattered on the surface of the obtained molded product, resulting in problems such as a decrease in commercial value.

The present invention has been made in view of the above points, and an object of the present invention is to provide a method for producing an in-mold foam molded article that solves the conventional drawbacks.

[Means to solve the problem]

That is, in the present invention, foamed thermoplastic resin particles are filled into a mold cavity formed by a pair of molds having a plurality of steam holes, and then a heating medium is supplied from the steam holes to heat the foamed particles to form particles. In-mold foaming in a method of manufacturing a molded body according to a mold by fusing them together, characterized by using a mold in which at least the steam hole surface on the mold cavity side is covered with an air-permeable porous sheet. The gist is a method for manufacturing a molded body.

〔Example〕· Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 shows a molding apparatus used for carrying out the method of the present invention, in which reference numeral 1.2 denotes a mold, and each of the molds 1.2 is fixed to a frame 3.4. The frame 3 is connected to a piston shaft 5 such as a cylinder so as to be slidable, and the mold is opened and closed by sliding the frame 3. Each mold 1.2 is provided with a large number of through holes 6, and a core vent 7 is fitted into each through hole 6. As shown in FIG. 2, the core vent 7 is provided with a plurality of steam holes 8, and the foamed particles filled into the mold cavity 9 are supplied from the steam holes 8 through the supply port 11 of the foamed particle feeder 10. Heated by a heating medium such as steam. In the figure, 12.13 is an inlet for a heating medium such as steam or cooling water, and 14.15 is an outlet for steam or cooling water.

In the present invention, the surface of the mold cavity side of the mold 1.2 is covered with an air-permeable porous sheet 16, and this porous sheet 16 has sufficient ventilation to allow heating medium such as steam and air to pass through. Any material may be used as long as it has the properties and is not easily attacked by the heat of the heating medium. However, in order to prevent the resin melted by the heating medium from penetrating and to allow steam and air to pass through, the porous sheet preferably has an average pore diameter of 10 to 100 nm, particularly 100 to 10 nm. As the heat-resistant base material used for the porous sheet 16, polytetrafluoroethylene,
Examples include polyamide, polyarylate, polysulfone, polyethersulfone, polyetherimide, polyamideimide, polyphenylene sulfide, polyetheretherketone, polyoxybenzoate, etc., and these can be used alone or in combination of two or more. Among these, polytetrafluoroethylene is particularly preferred since it has excellent mold releasability from molded products. The porous sheet 16 used in the method of the present invention can be prepared, for example, by the method described in JP-A-1-176549, or by adding 35% of an inorganic filler to the above-mentioned resin.
It is obtained by stretching a sheet containing at least 35% to 70% by weight, particularly 35 to 70% by weight. When forming a porous sheet by stretching a sheet containing an inorganic filler, the resin containing the inorganic filler may be formed into a sheet shape and then stretched by a conventional uniaxial or two-wheel stretching method. This stretching is not particularly limited, but generally the area stretching ratio is 1.5 times or more at a temperature below the softening point, preferably 2 to 2 times.
A method with a six-fold range is adopted. 35 inorganic fillers
When a sheet containing at least 50% of the inorganic filler is stretched, a gap is created between the resin portion of the sheet and the inorganic filler, and this gap becomes minute pores to obtain a porous sheet. The above-mentioned inorganic filler generally has an average particle size of 0.1 to 100μ,
Particularly preferred are metal oxides, hydroxides, salts, etc. having a particle size of about 0.5 to 20n. More specifically, the metal oxides include calcium oxide, alumina, silica, etc.
Hydroxides include aluminum hydroxide, calcium hydroxide, etc. Salts include calcium carbonate, magnesium chloride,
basic magnesium carbonate, calcium sulfate, magnesium sulfate, aluminum sulfate, etc. Furthermore, other than these, clays such as calcium silicates, cements, zeolites, and talc can also be used. A porous sheet using polytetrafluoroethylene as a base resin is sold by Nitto Electric Industry Co., Ltd. under the trade name Microtex NFT-5200. The thickness of the porous sheet 16 is preferably 5 to 100 nm.

As shown in FIG. 2(a), the porous sheet 16 covers the entire surface of the cavity side of the mold (however, only the portion where the foamed particle supply port 11 is provided has holes or is attached separately).
It may be provided to cover only the surface portion of the core vent 7 and the surrounding mold portion as shown in FIG. 2(C). Furthermore, although not specifically shown,
The entire inner surface of mold cavity 9 may be provided so as to be covered with porous sheet 16 (of course, even in this case, supply port 11 portion for foamed particles is not covered or is attached separately).

Since the porous sheet 16 is thin and a material is used, even if only a part of the inner surface of the mold is covered with the porous sheet 16 as shown in Fig. 16
Although it is unlikely that marks will remain due to the thickness of the
If the core vent 7 is fitted so as to be retracted by the thickness of the porous sheet 16 and the surface of the core vent is covered with the porous sheet 16 as shown in FIG. It is preferable that there is almost no

An adhesive is used to attach the porous sheet 16 to the cavity side surface of the mold 1.2, but it is preferable to use an adhesive with excellent heat resistance. For example, phenolic/vinyl,
Phenolic/nitrile, phenolic/neoprene, epoxy/phenolic, epoxy/polyamide, epoxy/polysulfide, epoxy/
Mixed adhesives such as silicone, nitrile rubber/epoxy, epoxy resin adhesive, phenoxy resin adhesive, polysulfone resin adhesive, polyallylsulfone resin adhesive, silicone resin adhesive, polyamide-imide adhesive,
Examples include polyimide adhesives.

The foamed thermoplastic resin particles used in the method of the present invention may be based on any resin as long as the foamed particles are made of a thermoplastic resin, such as polystyrene,
PolyP-methylstyrene, styrene-acrylonitrile copolymer, styrene-acrylic acid copolymer, styrene-
Styrenic resins such as maleic anhydride copolymers, polyethylene of various densities (high-density polyethylene, low-density polyethylene, linear low-density polyethylene, etc.), polypropylene, ethylene-propylene copolymers, ethylene-butene copolymers, propylene -Butene copolymers, propylene-ethylene-butene three-dimensional copolymers, and other olefinic resins, vinyl chloride, vinylidene chloride, various nylons, various polyesters, and the like can be used.

Steam is normally used as a heating medium for heating the foamed thermoplastic resin particles filled in the mold cavity 9. The pressure of the steam used for heating varies depending on the type of base resin of the foamed particles, the vapor permeability of the porous sheet 16, etc., but the porous sheet 16 has a thickness of 5 to 100 μm and a pore diameter of about 10 to 10,013 μm as described above. In general, foam particles based on styrene resin have a weight of 0 to 2 kg/c.
d(G) is approximately 0.5 to 5 kg/C1M(G) in the case of expanded particles using an olefin resin as the base resin.

In the above example, a steam hole was formed by fitting a core vent into a through hole provided in a mold, but in the method of the present invention, at least the surface of the steam hole is covered with a breathable porous sheet. Therefore, there is no risk that the steam holes will be clogged with molten resin, so a mold in which the steam holes are directly formed can also be used.

In addition, an eject bin may be used to release the molded body from the mold (in this case, make sure that only the eject bin part is equipped with a porous sheet,
Or it can be installed separately. ), it is also possible to install a device that can supply compressed air of 3 to 15 kg/cd (G) from the foam particle supply port without using an eject bin, and to release the mold by blowing the compressed air onto the molded product. In this case, the resulting molded product has even higher product value.

〔Effect of the invention〕

As explained above, according to the method of the present invention, there is no possibility that the steam holes for supplying heating steam etc. will be clogged with molten resin. There is no need to interrupt the molding operation to perform this, and the production efficiency of molded bodies is improved, and the work can be carried out efficiently without the hassle of removing clogging.

Furthermore, since the surface of the steam holes is covered with a porous sheet, there is no risk of leaving traces of the steam holes on the surface of the molded product, and the molded product has the advantage of being able to obtain a molded product with high commercial value.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is a longitudinal cross-sectional view showing an example of a molding apparatus used for carrying out the present invention, and FIG. 2(a)
-(C) are longitudinal cross-sectional views showing different states of attachment of the porous sheet. 1.2... Mold 8... Steam vent 9... Mold cavity 1
6... Porous sheet

Claims (1)

[Claims] Thermoplastic resin foam particles are filled into a mold cavity formed by a pair of molds having a plurality of steam holes, and then a heating medium is supplied from the steam holes to heat the foam particles and fuse the particles to each other. A method for manufacturing an in-mold foam molded product, the method comprising using a mold in which at least the surface of the steam holes on the side of the mold cavity is covered with an air-permeable porous sheet. .