JP2652732B2 - Blow molding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blow molding method capable of efficiently molding a molded article having a foamed resin layer therein.

[0002]

2. Description of the Related Art Conventionally, various plastic products having a resin filled therein are commercially available. In these conventional products, for example, a urethane resin is injected into a hollow resin body molded by a blow molding method. However, the urethane resin is expensive, and the urethane resin injection machine is also expensive, so that there is a disadvantage that the product itself is expensive.

An object of the present invention is to provide a blow molding method which solves the above-mentioned disadvantages.

[0004]

The gist of the present invention will be described with reference to the accompanying drawings.

[0005] Mold 3 having desired unevenness on the inner surface
A cylindrical body 2 made of a heated thermoplastic resin is provided therein, and air is introduced into the cylindrical body 2 to swell the cylindrical body 2 so that the outer surface of the cylindrical body 2 is formed in the molding die. 3. Then, the foamed resin granules 10 which are slightly foamed are introduced into the cylindrical body 2 and the foamed resin granules 10 are further foamed in the cylindrical body 2 so that the foamed resin granules 10 are further foamed. According to a blow molding method, a cylindrical molded article 17 having a desired outer shape provided with a foamed resin layer 4 is molded.

[0006]

The foamed resin layer 4 formed in the product is formed during the product molding process.

[0007]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows the case where the present invention is applied to an extrusion blow method.

[0008] In the first step shown in FIG.
The cylindrical body 2 made of a thermoplastic resin, for example, made of polyethylene and heated to 170 ° C. to 180 ° C. is disposed in the molds 3. The molding die 3 is provided with an introduction pipe 5 having an air outlet 18 for introducing air and heated steam, and an introduction gun 6 for introducing the foamed resin granules 10. A compressed air supply unit (not shown) is connected to the introduction gun 6. An air supply pipe 8 and a heating steam supply pipe 16 are connected to a base end of the introduction pipe 5 for introducing air and heating steam, and an exhaust pipe 14 is connected to the air supply pipe 8. Reference numerals 7, 13, and 15 are valves. The introduction gun 6 for introducing the foamed resin granules 10 is connected via a hose 12 to the foamed resin granules 10.
A hopper 11 for filling is provided in series.

Next, in the second step shown in FIG. 2, the molds 3 are closed, the valve 7 of the air supply pipe 8 is opened, and air is introduced from the introduction pipe 5 at a pressure of 1 kg / cm ² for 10 seconds into the cylinder. 2, the outer surface of the cylindrical body 2 is pressed against the inner surfaces of the molds 3 to form the hollow cylindrical body 9 into a hollow molded body 9.

Subsequently, in a third step shown in FIG. 3, a granular polystyrene foam resin having a diameter of about 1 mm slightly foamed from the introduction gun 6 is filled by air pressure. At this time, extra air introduced into the hollow molded body 9 is supplied to the valve 13.
Is opened and exhausted to the outside via the introduction pipe 5 and the exhaust pipe 14. Next, open the valve 15 and open the heating steam air pipe.
16, 0.8 kg / cm ² , about 105 ° C. through the introduction pipe 5 (the foaming temperature of the polystyrene foamed resin is about 105 ° C.)
Is introduced into the hollow molded body 9 for about 20 seconds, and the slightly foamed granular polystyrene foam resin is further foamed and fused.

Subsequently, in a fourth step shown in FIG. 4, the introduction pipe 5 is removed, the molds 3 are opened by opening the molds 3, and the mold is released, and a foamed resin layer 4 is provided inside. A cylindrical molded product 17 is obtained.

The constituent resin of the cylinder 2 is not limited to polyethylene, but may be any resin such as polypropylene.

If a polystyrene foamed resin that does not foam at all is used, the particles tend to be located below the cylinder 2 due to its own weight, so that the density of the foamed resin layer 4 on the upper side and the lower side of the cylinder 2 is low. There is a possibility that it will be uniform, on the other hand, if using a polystyrene foam resin that has been sufficiently expanded, that is, large diameter particles,
If the diameter is larger, the larger the diameter, the larger the gap between the particles when filled in the cylindrical body 2, and there is a possibility that a dense portion is formed in the foamed resin layer 4 as described above. Therefore, the granular polystyrene foam resin used is one slightly foamed by steam heating. That is, a granular foamed polystyrene foam resin is used in order to make the foamed resin layer 4 uniform without being sparse and dense. Note that the degree of foaming to be slightly foamed is appropriately selected in consideration of the volume of the cylindrical body 2.

It is possible to introduce the polystyrene foam resin while the cylinder 2 is being expanded without introducing the polystyrene foam resin after the expansion of the cylinder 2 is completed. Time until The cylinder 2 heated to 170 to 180 ° C. without using heating steam.
Wait until the temperature reaches about 105 ° C.
At this point, it is possible to introduce a polystyrene foam resin containing a larger amount of water than usual by introducing a large amount of steam into the cylinder 2 when the foam is slightly foamed.

In this embodiment, since the foamed resin layer 4 is formed during the product molding process, the production is simplified as compared with the conventional method in which a urethane resin is introduced after the completion of a hollow resin product. Costs can be reduced. That is, in the conventional method of filling the finished product with the urethane resin, the finished product is put into a mold that can keep the foaming pressure of the urethane resin, and then the urethane resin is injected. Since the polystyrene foam resin is introduced into the mold, the molds 3 play the role of the mold, and therefore, the production efficiency is significantly improved as compared with the conventional method.

Further, since it is not necessary to use an expensive urethane resin, the production cost can be reduced even in that case, and the filling of the polystyrene foam resin with the introduction gun 6 is also possible.
, The workability is good, the equipment is inexpensive, and the manufacturing cost is reduced in this respect as well.

Further, the product molded by the method according to the present embodiment is not a low-strength product, which is a weak point of the blow-molded product, because the foamed resin layer 4 is formed therein. The application of the product will be expanded. For example, a member for keeping cold, such as an ice box, an intermediate cushion material, such as a chair, various heat insulating / soundproof panels, various molded products for buoyancy, and the like.

Further, since the foamed polystyrene resin slightly foamed is used, the foamed resin layer 4 in the cylindrical molded product 17 becomes an extremely uniform foamed resin layer 4.

The present invention can of course be applied to various blow molding methods such as an injection blow method and an injection blow method.

[0020]

As described above, the present invention provides a blow molding method capable of efficiently manufacturing a molded product having a foamed resin layer formed therein at low cost.

[Brief description of the drawings]

FIG. 1 is a process explanatory view of the present invention.

FIG. 2 is a process explanatory view of the present invention.

FIG. 3 is an explanatory view of a process of the present invention.

FIG. 4 is a process explanatory view of the present invention.

[Explanation of symbols]

 2 Cylindrical body 3 Mold 4 Foam resin layer 10 Foam resin granule 17 Cylindrical molded product

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location B29L 23:00

Claims (1)

(57) [Claims] 1. A heated thermoplastic resin cylinder is disposed in a mold having desired irregularities formed on an inner surface thereof, and air is introduced into the cylinder to expand the cylinder. The outer surface of the cylindrical body is pressed against the inner surface of the molding die, and then a slightly expanded foamed resin granule is introduced into the cylindrical body, and the foamed resin granule is further foamed in the cylindrical body to thereby form an inner portion. A blow molding method characterized by molding a cylindrical molded product having a desired outer shape provided with a foamed resin layer on the surface thereof.