JP2002210783A - Mold for injection-molding synthetic resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of cracks in a part directly on the outside of a window in a mold for injection-molding a resin in which a cavity surface is heated and cooled alternately and which has push-cutting structure for making a product having a window-like hole. SOLUTION: A push-cutting part 5 for making the product having the hole is formed in the partition surface of the mold, and a void 6 is formed in the push-cutting part 5. In this way, the contact area of the push-cutting part is reduced, and the press force and thermal distortion caused by temperatures on the cavity side and the core side of the push-cutting part are reduced so that the generation of cracks can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synthetic resin injection mold in which a cavity surface is alternately heated and cooled.

[0002]

2. Description of the Related Art In injection molding of a thermoplastic resin, if the temperature of the cavity surface is set high when filling the cavity with a molten resin, the quality of the cavity surface is improved such that the transfer of the cavity surface is good and the weld line is inconspicuous. Therefore, a heat cycle method of heating the cavity surface while filling the cavity with the molten resin has been put to practical use.

As means for heating and cooling the cavity surface in a short time, for example, a heating method using hot air is disclosed in
Japanese Unexamined Patent Publication No. 220220 discloses a combination of a heating method using an electric heater and water cooling, and Japanese Unexamined Patent Publication No. 55-109639 discloses a high-frequency induction heating method. JP-A-57-
Japanese Patent Application Laid-Open No. 165229/1989 discloses a method of sandwiching a hot plate between a cavity and a core, and Japanese Patent Application Laid-Open No. 64-42217 discloses a method of heating with a halogen bulb. Japanese Patent Laid-Open No. 4-2
65720.

[0004]

The present inventors have applied a heat cycle molding method for heating and cooling a cavity surface in a short time by a combination of steam and water as disclosed in Japanese Patent Application No. 11-375069. In order to manufacture a product having a perforated portion such as a window in a mold, a press-cut portion 5a is provided on a dividing surface of the cavity 1 of the mold on the cavity side or the core side as shown in FIGS. Was.

In the above-mentioned mold, when at least one of the cavity surfaces 2 and 3 on the mold side and the core side is repeatedly heated and cooled, a crack 9 is generated in a portion just outside the window, and a medium flow path provided near the cavity surface is provided. 4 caused a problem that the medium flows out through the crack 9 to the outside.

The present invention relates to a mold for resin injection molding, which is a mold whose cavity surface is alternately heated and cooled, and which has a push-cut structure for producing a product having a perforated portion such as a window. The purpose of the present invention is to prevent the occurrence of cracks in the portion just outside the cradle.

[0007]

SUMMARY OF THE INVENTION A synthetic resin injection mold according to the present invention, in which the cavity surface is alternately heated and cooled, is provided with a push-off portion for producing a product having a perforated portion on a divided surface of the mold. In addition, a void is provided inside the push-off portion to reduce the contact area. Accordingly, the contact area of the pushed-out portion is reduced, and the crimping force of the pushed-out portion and the thermal distortion due to the temperatures on the cab side and the core side are reduced, and the occurrence of cracks can be prevented. In addition, it is preferable that a gas vent hole communicates with the gap.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described based on embodiments with reference to the drawings.

FIG. 1 is a sectional view showing a push-off structure of a synthetic resin injection molding die according to one embodiment of the present invention, and FIG. 2 is a view taken along the line AA of FIG.

As shown in FIGS. 1 and 2, a cavity 1 is formed on the mold side of the mold, and a heating medium and a cooling medium are alternately repeated near the cavity surfaces 2 and 3 on the mold side and the core side. A medium flow path 4 for inflow is provided. In the above embodiment, the medium flow path 4 is provided on each of the mold side and the core side, but may be provided only on one side.

As the heating medium, saturated steam, superheated steam, pressurized water, hot water or the like is used, and as the cooling medium, cooling water is used.

A push-cut portion 5 for forming a product having a perforated portion such as a window is provided on the divided surface on the mold side or the core side.
Is provided. A void 6 is provided inside the pushed-out portion 5, and only the vicinity of the outer periphery of the pushed-out portion 5 is a dividing surface with the core side. A gas vent hole 7 communicates with the space 6.

Next, the operation of the mold will be described.

When the mold on the mold side or the core side is moved and the mold is clamped, the division surface of the cut-off portion 5 on the mold side or the core side is also pressed against the division surface on the core side. While filling the cavity 1 with the molten resin, a heating medium is supplied to the medium flow path 4 to heat the cavity surfaces 2, 3. Thereafter, a cooling medium is supplied to the medium flow path 4, and the molten resin is solidified and the product 8. Becomes

The portion outside the push-off portion 5 expands and contracts freely with the heating / cooling of the cavity surface, whereas no space is provided in the push-off portion 5 as shown in FIGS. In this case, the window portion is constrained by the push-off portion 5, and the portion just outside the push-off portion 5 is distorted to cause cracks. The force constraining the window portion of the pushed-out portion 5 is attributable to the press-fitting force of the pushed-off portion 5 and the thermal strain due to the temperature difference between the mold side and the core side caused by the pushed-off portion 5. Conceivable.

Therefore, in the present invention, as shown in FIG. 1 and FIG. Thereby, the thermal distortion due to the pressing force of the push-off portion 5 and the temperature difference between the mold side and the core side is reduced, and the occurrence of cracks can be prevented. In addition, gas generated from the molten resin is discharged to the outside through a gas vent hole provided in the gap 6 of the push-off portion 5.

The raw material resin applied to the synthetic resin injection mold according to the present invention includes vinyl chloride resin (resin composition including hard and soft, the same applies hereinafter), acrylate resin (acrylic acid as an acid, Such as methacrylic acid, alkyl groups such as methyl group and ethyl group, styrene resins (general, high impact, etc.), acrylonitrile-styrene resins, acrylonitrile-styrene-butadiene resins, modified polyphenylene oxide, polycarbonate, polysulfone, poly Amorphous resins such as arylate, polyetherimide, polyethersulfone, etc., polyethylene resins (low density, linear low density, medium density, high density, etc.), polypropylene resins (homopolymer, random polymer, block polymer, etc.) ), Polybutene-
1, polymethylpentene-1, fluorine resin (polyvinylidene fluoride etc.), polyoxymethylene, polyamide resin (6, 66 etc.), terephthalate resin (polyethylene terephthalate, polybutylene terephthalate etc.), polyphenylene sal Crystalline resins such as phyto, polyetheretherketone, polyetherketone, and polyimide; liquid crystal polymers (such as aromatic polyesters and aromatic polyesteramides); epoxy resins, melamine resins, phenolic resins, urea resins, and unsaturated polyester resins And thermosetting resins such as urethane-based resins, silicone resins and alkyd resins, and alloys and fillers thereof (granular fillers such as talc and fibrous materials such as glass fibers).

In the above embodiment, the case of heating or cooling with a heat medium is shown, but the invention is not limited to this. For example, the heat medium may be oil, or may be of a different type such as an electric heater instead of the heat medium.

As the molding method to which the synthetic resin injection molding die according to the present invention is applied, in addition to a usual injection molding method, an injection compression method, a local vibration / pressing method, a gas press method,
Gas assist method, hollow molding method, sandwich molding method, 2
Color molding method, in-mold molding method, push-pull molding method,
Including high-speed injection molding.

[0020]

According to the present invention, as described above, the crimping force of the push-off portion and the thermal distortion due to the temperature difference between the mold side and the core side are reduced, and the occurrence of cracks can be prevented. .

[Brief description of the drawings]

FIG. 1 is a front sectional view showing a structure for pushing and cutting a cavity of a synthetic resin injection molding die according to one embodiment of the present invention.

FIG. 2 is a view taken along the line AA of FIG. 1;

FIG. 3 is a front cross-sectional view showing a push-cut structure of a cavity of a conventional synthetic resin injection mold.

FIG. 4 is a view as viewed in the direction of arrows BB in FIG. 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cavity 2, 3 Cavity surface 4 Medium flow path 5, 5a Push-off part 6 Void 7 Gas vent 8 Product 9 Crack

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Masahiko Yamaki 2-1 Tango-dori, Minami-ku, Nagoya City, Aichi Prefecture Inside of Mitsui Chemicals Co., Ltd. (72) Inventor Akihiko Imagawa 2-1 Tango-dori, Minami-ku, Nagoya City, Aichi Prefecture Mitsui (72) Inventor Mitsuharu Mikawa 2-1 Tangodori, Minami-ku, Nagoya-shi, Aichi F-term (reference) 4F202 AG28 CA11 CB01 CK83 CN01 CN05 CN15 CP01 CP04

Claims (2)

[Claims] 1. A synthetic resin injection mold in which a cavity surface is alternately heated and cooled, wherein a press-cut portion for forming a product having a perforated portion is provided on a divided surface of the mold,
A mold for synthetic resin injection molding, characterized in that a gap for reducing the contact area is provided inside the cut-off portion. 2. The synthetic resin injection molding die according to claim 1, wherein a gas vent hole communicates with said space.