JP2000109040A - Injection molded article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To have a hard-to-adhere oligomer produced by the decomposition of polyester resin to a movable mold, and thus reduce the main-hour of cleaning the mold by forming minute unevennesses on the bottom wall inner surface of a cupped vessel in order to improve its releasing property from a mold. SOLUTION: The cupped, injection-molded beverage vessel 1 consists of polyester resin, and fine unevennesses are formed on the whole part of the inner surface of a bottom wall 2b. The fine unevennesses are made by giving blast work onto a mold surface for forming an inner surface of the bottom wall 2b in the movable mold of a mold for injection-molded articles. Besides, a roughness of the unevennesses is preferably made 20 μm or lower in order to maintain transparency of the bottom wall 2b. However, it is most suitable to produce vessels in the order of 5 μm for a sufficient releasing property.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cup-shaped injection molded product made of a polyester resin.

[0002]

2. Description of the Related Art Molded products of this type are lightweight, excellent in disposability, and low in odor, so that they are particularly suitable for containers of aromatic drinks such as sake, and their practical use has been demanded. The powder generated by the decomposition of the polyester resin during the injection molding adheres to the mold and must be removed on a regular basis.

That is, in this type of mold, a polyester resin injected through a gate provided in a fixed mold first contacts a mold surface forming an inner surface of a bottom wall of the molded article in a movable mold. However, the ester bond of the polyester resin is separated by the strong injection pressure and high resin temperature at this time,
Trimeric to pentameric low molecular oligomers are produced.

[0004] About 1 to several percent of oligomers are already contained in the state of the polyester resin pellets before molding, and this ratio is increased by injection molding. Oligomer formation can be suppressed by lowering the injection pressure and resin temperature as much as possible, but in practice, a somewhat higher injection pressure and resin temperature are required in consideration of moldability and production capacity. Generation cannot be completely suppressed.

[0005] The produced oligomer remains in a movable type when the mold is opened and in a fixed type when the product is ejected. That is, when the mold is opened or the product is protruded, the product that is strongly adhered to the mold is forcibly separated from the mold, so that the oligomer is unavoidably attached to the mold as well as the product, and the molding is repeated. The oligomer powder gradually accumulates on the mold. In addition, such adhesion of the powder was particularly likely to occur on the movable mold side having the mold surface forming the inner surface of the bottom wall.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a cup-shaped injection molded product made of a polyester resin, thereby reducing the time required for cleaning the mold. It is to provide something to do.

[0007]

In order to achieve the above object, an invention according to claim 1 is a cup-shaped injection molded product made of polyester resin, wherein the inner surface of a bottom wall has a releasability from a molding die. Characterized in that fine irregularities for improving the quality are formed.

[0008] The invention of claim 2 is the injection-molded article of claim 1, wherein the irregularities are formed on the outer surface of the bottom wall.

A third aspect of the present invention is the injection molded article according to the first or second aspect, wherein the irregularities are formed such that the surface roughness is 20 μm or less.

A fourth aspect of the present invention is the injection molded article according to any one of the first to third aspects, wherein the polyester resin is polyethylene terephthalate.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an exploded perspective view of a beverage container 1 using an injection molded product 2 according to one embodiment of the present invention, FIG. 2 is a bottom view of the beverage container 1, and FIG.
FIG. 4 is a partially cutaway side view of the beverage container 1, and FIG.

This beverage container 1 is for accommodating alcohol, and as shown in FIG. 1, a cup-shaped injection molded product 2 and a lid for closing an upper end opening 2a of the injection molded product 2. It consists of three.

The injection molded article 2 is made of polyethylene terephthalate, which has excellent transparency and is inexpensive, and as shown in FIG. 3, a bottom wall 2b and an upwardly extending portion from the periphery of the bottom wall 2b. An outer peripheral flange 2d is formed at the upper end of the peripheral wall 2c.

The lid 3 is made of paper or a flammable synthetic resin film,
Alternatively, it is formed of a composite material of these, and has a heat seal layer on the inner surface.

Exterior films 4 and 5 made of a biaxially stretched film are fixed on the outer surfaces of the bottom wall 2b and the peripheral wall 2c of the injection molded article 2, respectively. The exterior films 4 and 5 may be, for example, a heat-sealing layer laminated on one side of a 38 μm-thick PET film, or a 50 μm-thick OPP (biaxially-stretched polypropylene) film on one side of a 12 μm-thick PET film. It is constituted by a material in which seal layers are sequentially laminated.

The exterior film 5 is formed in a tubular shape so as to wind around the peripheral wall 2c, and its axial width is set so that the lower end of the exterior film 5 does not protrude from the lower end of the peripheral wall 2c.
It is slightly shorter than the axial width of the peripheral wall 2c. The exterior film 5 is transparent, and a printed layer such as a design or a precautionary note is provided on the inner surface.

On the other hand, the exterior film 4 is formed in a washer shape so as to cover a portion other than a molten resin injection portion (a portion facing a tip end opening of a mold gate) at a central portion of the bottom wall 2b. .

In this embodiment, as shown in FIG. 4, fine irregularities 6 for improving the releasability are formed on the entire inner surface of the bottom wall 2b. The irregularities 6 are formed by blasting a mold surface that forms the inner surface of the bottom wall 2b of the movable mold of the injection molded product 2. The surface roughness of the unevenness 6 is preferably 20 μm or less in order to maintain the transparency of the bottom wall 2 b, but is most preferably about 5 μm that provides sufficient releasability.

By forming such irregularities 6 on the inner surface of the bottom wall 2b, oligomers generated by the decomposition of polyethylene terephthalate are less likely to remain on the movable mold when the mold is opened, and the time required for cleaning the mold is reduced. Therefore, the production efficiency is improved.

It should be noted that the present invention is not limited to the above embodiment, and various changes can be made.

For example, in the above-described embodiment, since the oligomer does not adhere to the fixed mold, irregularities are provided only on the inner surface of the bottom wall of the injection molded product. Irregularities for improving the releasability may be provided on the entire outer wall surface.

Various changes can be made without departing from the spirit of the present invention.

[0023]

As described above, according to the injection-molded article of the first aspect, the polyester resin is decomposed by forming fine irregularities on the inner surface of the bottom wall to improve the releasability from the molding die. Since the oligomer produced by the above is less likely to adhere to the movable mold, the labor for cleaning the mold is reduced.

According to the second aspect of the present invention, the oligomer is less likely to adhere to the fixed mold by forming the unevenness on the outer surface of the bottom wall to improve the releasability. The labor is reduced.

According to the third aspect of the present invention, since the unevenness is formed so that the surface roughness is 20 μm or less, the transparency of the bottom wall is increased and the appearance is improved.

According to the injection molded product of the fourth aspect, since it is formed of polyethylene terephthalate, it can be manufactured with high transparency and at low cost.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a beverage container 1 using an injection molded product 2 according to an embodiment of the present invention.

FIG. 2 is a bottom view of the beverage container 1. FIG.

FIG. 3 is a partially cutaway side view of the beverage container 1.

FIG. 4 is a schematic sectional view of a bottom wall 2b of the injection molded product 2.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Beverage container 2 Injection molded article 2a Top opening 2b Bottom wall 2c Perimeter wall 3 Lid 6 Unevenness

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3E033 AA08 BA17 BA18 BB08 DA06 DA08 DD05 EA07 FA02 FA10 GA02 4F206 AA24 AG05 AG07 AG24 AJ11 JA07 JQ81

Claims (4)

[Claims] 1. A cup-shaped injection-molded product made of a polyester resin, characterized in that fine irregularities for improving releasability from a molding die are formed on an inner surface of a bottom wall. . 2. The injection-molded product according to claim 1, wherein the unevenness is formed on an outer surface of a bottom wall. 3. The injection-molded article according to claim 1, wherein the irregularities are formed so that the surface roughness is 20 μm or less. 4. The injection-molded article according to claim 1, wherein the polyester resin is polyethylene terephthalate.