JP3048421B2 - Manufacturing method of injection molded products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an injection-molded article, in which a sheet is pasted in a cavity of a female mold in advance when injection molding is performed, and then the mold is closed and molded. Injection molded products in fields that require surface decoration, such as motorcycles and other vehicle bodies, OA equipment and home appliances, housings and stationery, and other fields that require surface decoration, improvements in surface hardness, weather resistance, and soft touch. And a method for producing the same.

[0002]

2. Description of the Related Art In recent years, as a way to increase the added value of plastics molded articles such as daily necessities and automobile interiors, a method of transferring a pattern printed on a sheet simultaneously with injection molding,
A method of attaching a thermoplastic sheet or the like has been performed. For example, in JP-A-59-202830, a continuous sheet on which a pattern is printed is sandwiched between a heating member having a vent and a frame member, and then supplied to an injection molding die, and the sheet is subjected to injection molding. Then, the portion of the sheet held opposite to the female mold is heated between the heating member and the female mold, and the sheet is closely adhered to the mold surface by vacuum / pressure molding. An apparatus for performing injection molding by performing (preliminary molding) has been proposed.

[0003]

According to the method disclosed in JP-A-59-202830, it is possible to transfer a pattern printed on a sheet to the surface of a deep-drawing molded article or to attach a thermoplastic sheet. Is possible. However, when the sheet is preformed into a female mold, the sheet is greatly stretched at the corners of the mold, etc., and the film thickness of the sheet is partially very thin, and the appearance of the obtained molded product is deteriorated. In some cases, or a problem in durability.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. It is an object of the present invention to increase the thickness of a sheet at the time of molding and to reduce a portion where the sheet becomes thin, such as a corner portion of a deep drawn molded product. It is an object of the present invention to provide a method for producing an injection-molded article, which is improved and enables a deep drawn product to be covered with a sheet.

[0005]

According to the present invention, there is provided a method of manufacturing an injection-molded article, comprising: a cavity having an opening on one side; a concave step provided on an opening edge of the cavity; and a gas provided in the concave step. A step of heating the sheet while holding the sheet between a female mold having an air outlet and a heating plate having an air vent, and blowing out gas from the air vent of the heating plate, and from the female air outlet. Deforming the sheet by blowing gas to dispose the sheet in the cavity, lowering the pressure in the cavity surrounded by the sheet relative to the outside air pressure to bring the sheet into close contact with the cavity, and Including a step of injecting a resin into the cavity, thereby achieving the above object.

Hereinafter, the present invention will be described with reference to the drawings.

FIGS. 1 (a) to 1 (f) show an example of an injection molding apparatus used in the manufacturing method of the present invention. This apparatus comprises a female member provided with a cavity 4 opening on one side. A mold 3, a male mold 5 having a convex portion 5a, a heating platen 1, and an injection molding machine 8 for supplying resin into the cavity 4 are provided.

The heating platen 1 is provided with a suction port 1a having an opening on its surface so as to be able to suck the sheet 2 (the surface temperature of the heating platen 1 is preferably uniform).

A concave step 10 is provided on the entire periphery or a part of the periphery of the opening of the cavity 4 of the female mold 3. Therefore, the cavity 4 has a wide mouth 4a formed inside the concave step 10 and a resin injection part 4b having a smaller opening area than the wide mouth 4a formed at the bottom. The concave step 10 is provided with an air outlet 3b for pushing up and removing the sheet 2, and the female mold 3 is provided with a vent 3a opening at the bottom of the cavity 4. On the outer surface of the frame of the female mold 3, a sealing material 3
c (O-ring) is provided.

As shown in FIG. 1 (f), the convex portion 5a of the male die 5 has a convex step portion 5b which is opposed to the concave step portion 10 with a small interval when fitted with the female die 3. A convex portion 5c that protrudes into the resin injection portion 4b is formed. A gate 6 is provided on the convex portion 5c of the male mold 5.

In order to manufacture an injection-molded article using such an apparatus, first, as shown in FIG. 1B, a sheet 2 is pressed against a heating surface of a heating plate 1 and the sheet 2 is sucked from a suction port 1a. The sheet 2 is heated in close contact with the heating surface. Next, as shown in FIG. 1 (c), the heating plate 1 and the sheet 2 are transferred to the side surface of the cavity 4 of the female die 3, and brought into contact with the end surface of the sealing material 3c.

Next, as shown in FIG.
Compressed air (gas) of about ² to 10 kg / cm ² is blown out from the ventilation port 1a provided at the same time, and the same amount of compressed air is blown out from the compressed air blowout port 3b of the female mold 3 at the same time. The sheet 2 corresponding to the concave step portion 10 is extended while pushing the portion into the cavity 4. At about the same time, after a few seconds, suction is started from the vent 3a of the female mold 3, and the air outlet 3b is switched from the gas blowing state to the suction state, so that the sheet 2 as shown in FIG.
Is formed along the concave step portion 10 of the female mold 3 and the resin injection portion 4b. Then, the heating platen 1 is moved upward, and FIG.
As shown in (f), the male mold 5 is fitted into the female mold 3 and the convex step 5b of the male mold 5 is arranged in the wide mouth 4a of the cavity 4.
The resin 7 is injected into the resin injection section 4b from the injection molding machine 8 to manufacture a molded product. If the concave step portion 10 and the convex step portion 5b have a bite-cut structure, release and finishing after molding are easy.

According to the present invention, a concave step 10 which is larger than the opening of the resin injection portion 4b is provided on the entire periphery or a part of the periphery of the opening of the cavity 4 of the female mold 3, and air is blown into the concave step 10. It is characterized in that the female mold 3 provided with the mouth 3b is used. If the concave step 10 is formed in multiple steps or the depth from the opening of the cavity 4 is increased, the area of the sheet 2 inserted into the cavity 4 becomes larger. Can reduce local stretching.

The shape of the cavity 4 of the female mold 3 used in the method of the present invention can be changed according to the shape of the injection molded product to be manufactured.

The cavity generally refers to a space corresponding to a molded product in a molding die, but in the present invention, for convenience, a cavity corresponding to the molded product and a space extending into the space. The whole of the recess is referred to.

The heating platen 1, the female mold 3 and the male mold 5 can be placed vertically or horizontally. Examples of uses of the injection-molded article manufactured by the method of the present invention include various bodies such as vehicle bodies and interior members such as automobiles and motorcycles, housings and stationery of OA equipment and home electric appliances and the like.

The vents and suction ports provided in the apparatus used in the present method are preferably provided in inconspicuous parts and sizes of the finished molded product.

The sheet 2 used in the present invention is preferably formed of a sheet (film) having ductility at least under heating. According to the method of the present invention, a relatively thin sheet which is easily broken at the time of spreading or an uncured or semi-cured sheet can be used. The material and shape of the sheet are selected depending on the purpose of using the sheet, for example, surface decoration, improvement of surface strength, improvement of weather resistance, or application of soft touch. For example, the following sheets are used.

Thermoplastic sheet: polystyrene, acrylic polymer, polycarbonate, polyvinyl chloride, polyethylene, polypropylene, ABS (acrylonitrile-butadiene-styrene copolymer), modified polyphenylene oxide, polyphenylene sulfide, polyetherimide, polyether A sheet mainly composed of ether ketone, ionomer, etc. (the surface is sometimes printed).

Thermosetting sheet: an uncured or semi-cured sheet mainly composed of a reactive acrylic resin such as acrylic polyol and a blocked isocyanate, a reactive vinyl monomer and / or an oligomer and a thermoplastic polymer and / or Alternatively, an uncured or semi-cured sheet mainly containing a polymer having a vinyl group and a peroxide.

Photocurable sheet: an uncured or semi-cured sheet mainly composed of a thermoplastic polymer, a reactive vinyl monomer and a photoinitiator.

A sheet having functions such as soft touch, antifouling, and antifungal.

A sheet obtained by laminating the above sheets.

[0024]

When the heated sheet is brought into close contact with the female mold, the peripheral portion of the sheet is extended by blowing gas from an air outlet provided in the concave step portion, and a wide portion including a portion corresponding to the concave step portion is provided. A sheet of surface area is deformed and disposed within the female cavity. For this reason, the film thickness of the sheet formed in the resin-injected portion can be made thicker than in the case where the concave step is not provided, and the sheet thickness of the corner portion or the like does not become too thin.

[0025]

EXAMPLES (A) Sheet used ABS sheet (A205, manufactured by Sanbo Resin Co., Ltd.)
(Film thickness 500 μm).

2. ABS sheet (Sanbo Plastics Co., Ltd.)
A106, film thickness 250 μm).

3. Photocurable sheet (300 parts ethyl acetate, Parapet beads 100 manufactured by Kyowa Gas Chemical Industry Co., Ltd.)
Department, Nippon Kayaku Co., Ltd. KAYARAD DPCA-2050 part, 2,4,6-
A curable resin composition obtained by mixing 4 parts of trimethylbenzoyl diphenylphosphine oxide, 2 parts of N-methyldiethanolamine, and 100 parts of rutile-type titanium oxide is applied to the release surface of a PET film, and dried at 80 ° C. for 5 minutes. An uncured light-curable sheet obtained by peeling off the PET film after the curing. Thickness 100
μm).

4. Photocurable sheet (the curable resin composition of Example 3 was replaced with an ABS sheet A similar to that of Example 1)
205 is a photocurable sheet obtained by coating on 205 and drying at 80 ° C. for 30 minutes. ABS resin layer 500 μm + photo-curable resin layer 100 μm).

5. A suede-like sheet (Nipporan 5120 (solid content: 30%) manufactured by Nippon Polyurethane Industry Co., Ltd., 100 parts by solid content, and 100 parts of elastic beads EBS100 manufactured by Nippon Shokubai Chemical Industry Co., Ltd.) were mixed. Similar AB
Suede-like sheet obtained by coating on S-sheet A106 and drying at 80 ° C for 30 minutes. ABS resin layer 500μm
+ Suede tone resin layer 100 μm).

(B) Molding test Molding was performed as follows. FIG. 2A shows the outline of the cavity of the female mold used, and FIG. 2B shows a plan view of the entire female mold. The heating plate (the surface of which has been treated with fluorine and the surface has about 10 holes / cm ^{2 of} about 0.5 mm open on the surface) and the female mold overlap each other when the heating plate is outside the cavity of the female mold. The protrusions should be uniformly protruded outside by 30 mm from the outside diameter. The dimensions (mm) of each part shown in FIG. 2 are as follows.

L ₁ = 150, L ₂ = 90, L ₃ = 30, L ₄
= 180, L ₅ = 120, L ₆ = 30, L ₇ = 90, L ₈ =
60, L ₉ = 30, L ₁₀ = 150, L ₁₁ = 90, L ₁₂ =
30, L ₁₃ = 60, L ₁₄ = 30, L ₂₀ = 15, L ₂₁ = 1
5.

The molding order is as follows.

The sheet is sucked into a heating plate and heated.

The sheet and the heating plate are moved to the position before the cavity of the female mold for injection molding.

The heating plate is moved in the female mold direction, and the suction of the heating plate is stopped.

The ventilation port provided on the heating plate is pressurized (discharges compressed air) and the ventilation port of the female concave step is pressurized.
After 0.5 seconds, the sheet is formed by evacuating the female mold cavity vent and further evacuating the female concave step vent.

The ventilation port of the heating plate is set to normal pressure, and the heating plate is separated from the female mold and moved upward.

A male mold is fitted and injection molding (ABS resin (ABS-ME, manufactured by Denki Kagaku Kogyo KK) is injected at 230 ° C.) to produce a molded product.

Table 1 shows the heating temperature of the sheet and the film thickness of each part of the formed sheet (measured at the time of the procedure. The part is shown in FIG. 1 (f)).

The appearance of the finished product was evaluated. Table 1 shows the results.

[0041]

[Table 1]

(Comparative Example) (A) Sheet used The same sheet as that used in the examples was used.

(B) Molding test Molding was carried out using a female mold having no concave step.

The molding order is as follows.

The sheet is heated while sucking the heating plate.

Remove the flat pressing plate from the sheet.

The sheet and the heating plate are moved to the position before the cavity of the female mold for injection molding.

The heating plate is moved in the female mold direction, and the suction of the heating plate is stopped.

The ventilation holes provided in the heating plate are pressurized (pressurized air is discharged) and the female ventilation holes are evacuated to form a sheet.

The ventilation port of the heating panel is set to normal pressure, and the heating panel is moved upward from the female mold.

A male mold is fitted and injection molded (ABS resin (ABS-ME, manufactured by Denki Kagaku Kogyo KK) is injected at 230 ° C.) to produce a molded product.

Table 2 shows the heating temperature of the sheet and the film thickness of each part (same as in the example) of the formed sheet.

The appearance of the finished product was evaluated. Table 2 shows the results.

[0054]

[Table 2]

[0055]

According to the present invention, the decrease in the thickness of the sheet formed in the cavity of the female mold is reduced, and the sheet such as the corner portion does not become too thin even in the deep drawn product. Therefore, it is possible to obtain a molded article having a relatively uniform surface performance and a desired pattern.

[Brief description of the drawings]

FIG. 1 is a manufacturing process diagram showing a method for manufacturing an injection-molded article of the present invention.

FIG. 2A is a diagram showing a contour of a cavity used in an embodiment of the present invention. (B) is a top view showing the shape of a female type.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heating board 1a Vent 2 Sheet 3 Female type 3a Vent 3b Air outlet 3c Sealing material 4 Cavity 4b Cavity resin injection part 5 Male mold 5a Convex part 6 Gate 7 Resin 8 Injection molding machine 10 Concave step

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B29C 45/00-45/84 B29C 33/00-33/76

Claims (1)

(57) [Claims] 1. A heating plate having a cavity having an opening on one side, a concave portion provided on the periphery of the opening of the cavity, a gas outlet provided on the concave portion, and a vent. Heating the sheet while holding the sheet in between, blowing out the gas from the ventilation port of the heating plate, and blowing the gas from the female gas blowing port to deform the sheet and dispose it in the cavity Injection molding, comprising the steps of: adhering the sheet into the cavity by lowering the pressure in the cavity surrounded by the sheet compared to the outside air pressure; and injecting resin into the cavity. Manufacturing method.