JPH04325215A - Manufacture of injection molding - Google Patents

Abstract

PURPOSE:To give smooth printed patterns even in manufacturing draw-moldings and cover a thermoplastic sheet with smooth film thickness and thereby provide a manufacture of injection moldings improved in its appearance and ability by reducing the difference of film thickness of the sheet during the period of preliminary molding. CONSTITUTION:At the time of molding a sheet 1, the sheet 1 is expanded by spouting air toward the sheet 1 from the place except the internal angle part 9 of a female mold 4, after that, the sheet is brought into close contact with the inner surface of a cavity 5 and then resin 7 is injected thereto.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an injection molded article, in which a sheet is attached to the surface of the molded article or printing ink from the sheet is transferred to the surface of the molded article at the same time as injection molding.

0002

[Prior Art] Conventionally, vehicle bodies such as automobiles and motorcycles,
When applying surface decoration to injection molded products such as housings for office automation equipment, home appliances, stationery, etc., improving surface hardness and weather resistance, or adding soft touch, coatings such as painting are applied in the post-process. It was done.

In recent years, in order to increase the added value of plastic molded products such as daily necessities and automobile interior parts, methods of transferring patterns printed on sheets onto the surface of molded products at the same time as injection molding, and thermoplastic sheets have been developed. A method of pasting it onto the surface of a molded product is being used.

For example, Japanese Patent Application Laid-Open No. 59-202830 proposes a method of preforming a continuously unrolled decorative sheet in a female mold and then injecting resin as a method of performing painting at the same time as injection molding. has been done. This method is shown in Figures 7 to 9.
As shown in FIG. 2, the sheet 1 is attached to the heating section by suction through the vent 2a of the heating platen 2 to give it ductility, and at the same time, the continuous sheet 1 is fed out to the front of the female die 13 while being held by a frame member (not shown). (Fig. 7), attach the heating plate 2 to the frame of the female mold 13, stop the suction of the heating plate 2 (Fig. 8), apply vacuum from the suction port 13a provided in the female mold 13, and then The sheet 1 is molded into the female mold 13 by compressed air from the vent 2a provided in the
After the resin is brought into close contact with the inner surface of the cavity 5 (FIG. 9) and the mold is clamped, resin is injected into the cavity 5 (FIG. 10).

[0005]

[Problem to be solved by the invention] According to the method disclosed in the above publication, it is not possible to transfer a pattern printed on a sheet or to attach a thermoplastic sheet to the surface of a deep-drawn molded product. be. However, when the sheet is preformed into a female mold, the sheet is stretched significantly at the corners of the mold, resulting in a thin film thickness. As a result, the film thickness of the preformed sheet may become uneven depending on the area, which may deteriorate the appearance of the obtained molded product or cause problems with durability, especially if the sheet is thin or uncured. If this method is used, the sheet on the obtained molded product may be torn or the like.

The present invention has solved the above-mentioned problems, and its purpose is to achieve uniform printing even in the production of deep-drawn molded products by reducing the difference in sheet thickness during preforming. It is an object of the present invention to provide a method for producing an injection molded product that can be patterned or coated with a thermoplastic sheet to improve its appearance and performance.

[0007]

[Means for Solving the Problems] In the method of manufacturing an injection molded product of the present invention, a sheet is brought into close contact with the inner surface of a cavity having a corner provided in a female mold, and after the mold is clamped, a resin is injected into the cavity. In a method of manufacturing an injection molded product in which the sheet is injected, the peripheral edge of the sheet is fixed around a female mold cavity, and the air pressure inside the cavity surrounded by the sheet is lowered compared to the outside air pressure. When the sheet is brought into close contact with the inner surface of the cavity, the sheet is spread by blowing gas toward the sheet from a location other than the corner of the female mold, and after the sheet is spread, the sheet is spread on the inner surface of the cavity. The method is characterized by including a step of bringing them into close contact with each other, thereby achieving the above object.

The present invention will be explained below based on the drawings.

FIGS. 1 to 5 show an example of the main parts of an injection molding apparatus used in the manufacturing method of the present invention. Figure 1
- As shown in FIG. 5, this device includes a female mold 4 having a cavity 5, a male mold 10 having a convex portion 11, and a sheet 1.
It is equipped with a heating plate 2 for heating. A vent hole 2a is provided on the lower surface side of the heating plate 2 so that the sheet 1 can be sucked. As shown in FIG. 3, a vent hole 4b is provided on the inner surface of the cavity 5 of the female mold 4 at a portion (near the center of the female mold 4) that contacts a relatively difficult-to-extend portion of the sheet. Contact part (entering corner 9 of female mold 4)
) are respectively provided with suction ports 4a. A sealing material (O-ring) 6 is provided on the upper surface of the frame 8 of the female mold 4. A gate 12 is provided on the convex portion 11 of the male die 10.

To manufacture an injection molded product using such an apparatus, as shown in FIG. 1, the sheet 1 is brought into close contact with the lower surface of the heating plate 2 by suction from the vent 2a of the heating plate 2. In this state, by moving the heating plate 2 onto the female mold 4, the sheet 1 is placed above the cavity 5 of the female mold 4. During this time, the sheet 1 is heated by the heating plate 2 to give it malleability. Next, as shown in FIG. 3, the heating plate 2 is lowered and placed on the female mold 4, the peripheral edge of the sheet 1 is fixed between the frame 8 of the female mold and the heating plate 2, and the ventilation holes are closed. Stop suction from 2a.

Next, as shown in FIG. 3, relatively high pressure gas (such as air) is ejected into the cavity 5 from the vents 2a and 4b of the heating plate 2, and is then sucked from the suction port 4a. This allows the sheet 1 to be stretched relatively uniformly. At this time, the ventilation port 2a of the heating plate 2 and the ventilation port 4b of the female mold 4
The pressure of the gas ejected from is preferably about 3 kg/cm2, which is a pressure that does not significantly deform the sheet 1. Further, the pressure of the gas ejected from the vent 2a of the heating plate 2 and the vent 4a of the female mold 4 may be approximately the same.

Next, as shown in FIG. 4, by stopping the pressurized air from the vent 4b of the female mold 4, the pressure is reduced in the area surrounded by the sheet 1 and the inner surface of the female mold 4, and the sheet 1 is brought into close contact with the inner surface of the female mold 4 to complete the preforming.

Thereafter, as shown in FIG. 5, the heating plate 2 is removed from the female mold 4 and the female mold 4 and the male mold 10 are combined, and a gate is inserted into the cavity 5 formed by both the molds 4 and 10. 1
The molten resin 7 is injected from 2. The resin used for injection is not particularly limited, but for example, polyolefins such as ABS resin, polyethylene, and polypropylene, and vinyl chloride resin are preferably used. In this way, an injection molded product whose surface is coated with the sheet 1 is obtained. In addition, in the apparatus used in the method of the present invention, the ventilation ports 2a, 4b and the suction port 4a are
It is preferable to provide it at a position corresponding to an inconspicuous part of the finished molded product. Further, these vent holes and suction ports are preferably formed in crystalline metal or the like.

[0014] The shape of the female mold 4 used in the method of the present invention,
Alternatively, the arrangement of the female mold 4, heating plate 2, and male mold 10 can be changed depending on the shape of the injection molded product to be manufactured. Applications of injection molded products manufactured by the method of the present invention include:
Vehicle bodies and interior parts for automobiles, motorcycles, etc., OA equipment,
Examples include housings for home appliances, stationery, etc.

The sheet 1 used in the present invention is preferably formed of a sheet (film) that is malleable at least under heating. In particular, according to the method of the present invention, even relatively thin sheets and uncured or semi-cured sheets that are easily broken during spreading can be used. The material and shape of the sheet are selected depending on the purpose of using the sheet, such as surface decoration, improvement of surface strength, improvement of weather resistance, or imparting a soft touch. For example, the following sheets are used.

■Thermoplastic sheet: polystyrene, acrylic polymer, polycarbonate, polyvinyl chloride, polyethylene, polypropylene, ABS resin (acrylonitrile-butadiene-styrene copolymer), modified polyphenylene oxide, polyphenylene sulfide,
Sheets whose main ingredients are polyetherimide, polyetheretherketone, polyethylene sulfide, etc.

■ Thermosetting sheet: An uncured or semi-cured sheet containing a reactive acrylic resin such as acrylic polyol and a blocked isocyanate as main components; a reactive vinyl monomer and/or oligomer, a thermoplastic polymer and/or Or an uncured or semi-cured sheet containing a vinyl group-containing polymer and peroxide as the main components.

[0018] Photocurable sheet: An uncured or semi-cured sheet containing a thermoplastic polymer, a reactive vinyl monomer, and a photoinitiator as main components.

■A sheet obtained by laminating the sheet ■■ on the sheet ■■ above.

[0020]

[Function] When the sheet is brought into close contact with the cavity of the female mold, the central part of the sheet, which is difficult to stretch, can be expanded by blowing gas toward the sheet from a location other than the corner of the female mold. can. Therefore, in normal sheet molding, it is possible to stretch areas that are difficult to stretch because it immediately adheres to the mold, and this reduces the decrease in film thickness in areas where the film thickness normally tends to decrease, such as the corners of the mold. can do.

[0021] Therefore, even in deep drawing molding, it is possible to obtain a molded product with a uniform printed pattern or a molded product with a thermoplastic resin sheet of uniform thickness attached.

[0022]

EXAMPLES The present invention will be specifically explained below based on examples.

Example (A) Sheet 1. ABS sheet (manufactured by Sanpo Jushi Kogyo Co., Ltd., A205,
Film thickness: 500 μm) 2. ABS sheet (manufactured by Sanpo Jushi Kogyo Co., Ltd., A404,
Film thickness: 250 μm) 3. Photocurable sheet This sheet is made by adding 300 parts by weight of ethyl acetate, 100 parts by weight of Parapet beads (manufactured by Kyowa Gas Chemical Industry Co., Ltd.), and K.
AYARAD DPCA-20 (manufactured by Nippon Kayaku Co., Ltd.)
50 parts by weight, 2,4,6-trimethyl benzoyl
4 parts by weight of diphenylphosphine oxide, 2 parts by weight of N-methyldiethanolamine, 1 part by weight of rutile titanium oxide
A photocurable resin composition obtained by mixing 00 parts by weight is applied to the release surface of a polyethylene terephthalate film (hereinafter referred to as PET film), and after drying at 80°C for 5 minutes, the PET film is peeled off. This is an uncured photocurable sheet obtained by this method. Film thickness is 100
It was μm.

4. Photocurable sheet This sheet was obtained by coating the photocurable resin composition used in Example 3 above on the same ABS sheet A205 as in Example 1 and drying it at 80°C for 30 minutes. It is a photocurable sheet. The film thickness of the sheet is ABS resin layer 500μ
m+photocurable resin layer was 100 μm.

5. Suede-like sheet This sheet is made by mixing 100 parts by weight of Nipporan 5120 (manufactured by Nippon Polyurethane Industries Co., Ltd., solid content 30%) and 100 parts by weight of elastic beads EBS100 (manufactured by Nippon Shokubai Chemical Co., Ltd.). , ABS similar to Example 2 above
This is a suede-like sheet obtained by coating on sheet A106/ and drying at 80° C. for 30 minutes. The film thickness of the sheet is A
The BS resin layer was 250 μm+the suede-like resin layer was 100 μm.

(B) Molding test Molding was carried out as follows. The shape of the cavity 5 of the female mold 4 used is shown in FIGS. 6(a) and 6(b). In the figure,
The dimensions L1 of each part of the cavity 5 are 200 mm, L2 is 200 mm, L3 is 100 mm, and the radius of curvature R is 10 mm.
And so.

(2) The sheet 1 was heated while being suctioned by the heating plate 2, and was conveyed to a position above the cavity 5 of the female mold 4 for injection molding (FIG. 1).

■ Place the heating plate 2 on the female mold 4, and place the heating plate 2 on the female mold 4.
suction was stopped (Figure 2).

■As shown in FIG. 3, the vent 2 of the heating plate 2
The sheet 1 was stretched relatively uniformly by compressed air from the air outlet 4b, air pressure from the vent hole 4b of the female mold 4, and suction from the suction port 4a of the female mold 4.

(2) Pressurized air from the vent 4b of the female mold 4 was stopped, and the sheet 1 was brought into close contact with the inner surface of the cavity 5 of the female mold 4 (FIG. 4).

Table 1 shows the heating temperature of the sheet 1 at this time and the film thickness of each part of the formed sheet 1 (the parts are indicated by A, B, and C in FIG. 6).

■ After the mold is clamped, ABS resin (manufactured by Denki Kagaku Kogyo Co., Ltd., ABS-ME) is poured into the cavity 5 at 230°C.
It was injected (Fig. 5).

The appearance of the finished product was evaluated. The results are shown in Table 1.

[0034] Comparison example (A) Sheet used The same sheets as Sheets 1 to 5 used in Examples were used.

(B) Molding Test Molding was carried out as follows using the apparatus shown in FIGS. 7 to 10. The shape of the cavity 5 of the female die 13 used is the same as in the above embodiment.

(2) The sheet 1 was heated while being suctioned by the heating plate 2 and conveyed to a position above the cavity 5 of the female mold 13 for injection molding (FIG. 7).

(2) The heating plate 2 was placed on the female mold 13, and the suction of the heating plate 2 was stopped (FIG. 8).

■Vacuum is drawn from the suction port 13a provided on the female mold 13, and the ventilation port 2a provided on the heating plate 2
The sheet 1 was brought into close contact with the inner surface of the cavity 5 of the female mold 13 by compressed air (FIG. 9).

Table 2 shows the heating temperature of the sheet 1 at this time and the film thickness of each part of the formed sheet (the parts are shown in FIG. 6).

[0040] After the mold is clamped, place ABS inside the cavity 5.
230 resin (manufactured by Denki Kagaku Kogyo Co., Ltd., ABS-ME)
(Figure 10).

The appearance of the injection molded product obtained was evaluated. The results are shown in Table 2.

[0042]

[Table 1]

[0043]

[Table 2]

[0044]

[Effects of the Invention] According to the present invention, by reducing the difference in film thickness of sheets during preforming, it is possible to produce thermoplastic sheets with uniform printing patterns and uniform film thickness even in the production of deep-drawn molded products. can be coated. Therefore, there is an advantage that injection molded products with excellent appearance and performance can be obtained, and since sheets having poor rolling strength can also be used, injection molded products for various uses can be manufactured.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a main part of an apparatus suitable for use in explaining an example of the method for manufacturing an injection molded article of the present invention.

FIG. 2 is a sectional view of a main part of an apparatus suitable for use in explaining an example of the method for manufacturing an injection molded article of the present invention.

FIG. 3 is a sectional view of a main part of an apparatus suitable for use in explaining an example of the method for producing an injection molded article of the present invention.

FIG. 4 is a sectional view of a main part of an apparatus suitable for use in explaining an example of the method for producing an injection molded article of the present invention.

FIG. 5 is a sectional view of a main part of an apparatus suitable for use in explaining an example of the method for producing an injection molded article of the present invention.

FIG. 6(a) is a plan view of a female mold used in an embodiment of the present invention. (b) is a sectional view of the female mold.

FIG. 7 is a sectional view showing an example of an apparatus for explaining a conventional method of manufacturing an injection molded product.

FIG. 8 is a cross-sectional view showing an example of an apparatus for explaining a conventional injection molded product manufacturing method.

FIG. 9 is a cross-sectional view showing an example of an apparatus for explaining a conventional injection molded product manufacturing method.

FIG. 10 is a cross-sectional view showing an example of an apparatus for explaining a conventional injection molded product manufacturing method.

[Explanation of symbols]

1 Sheet 2 Heating plate 2a Vent 4 Female type 4a Suction port 4b Vent 5 Cavity 6 Seal material 7 Molten resin 8 Female frame 9 Entry corner 10 Male type 11 Male convex part 12 Gate

Claims (1)

[Claims] Claim 1. A method for producing an injection molded product, in which a sheet is brought into close contact with the inner surface of a cavity having a corner provided in a female mold, and after the mold is clamped, a resin is injected into the cavity, the peripheral edge of the sheet being injected into the cavity. When the seat is fixed around the cavity of the female mold and the sheet is brought into close contact with the inner surface of the cavity by lowering the air pressure inside the cavity surrounded by the sheet compared to the outside air pressure, the inner corner of the female mold is fixed. A method for producing an injection molded product, which includes the steps of spreading the sheet by jetting gas toward the sheet from a location other than the molding part, and after spreading the sheet, bringing the sheet into close contact with the inner surface of a cavity.