JPH04348919A - Manufacture of thermoplastic resin molded article - Google Patents

Abstract

PURPOSE:To prevent cold mark from developing by a method wherein molten resin is fed in a cavity through the molten resin feed opening for only non- product molding part when the clearance of the cavity is larger than the thickness of a molded article. CONSTITUTION:Molds 3 and 4, which have product molding part 5 and non- product molding part 6, are prepared. Next, when the clearance of a cavity, which is formed by the upper and lower molds 3 and 4, is larger than the thickness of a molded article, molten resin 7 is fed in the mold cavity through a molten resin path provided in the mold from a molten resin feed opening, which is provided only in the non-product molding part 6.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a method for manufacturing thermoplastic resin molded products, and more specifically, the present invention relates to a method for manufacturing thermoplastic resin molded products, and more specifically, to improve the appearance of molded products made only of thermoplastic resin and multilayer molded products made of thermoplastic core resin and skin material. It relates to a method for efficiently manufacturing without damaging.

0002

BACKGROUND OF THE INVENTION Various improvements have been proposed in the past regarding methods for producing thermoplastic resin molded articles in order to improve the quality of the molded articles and improve production efficiency. For example, JP-A-59
Japanese Patent No. 101322 proposes a method of supplying molten resin through a resin passage provided in a mold wall of a mold (lower mold) attached to a lower platen. Further, Japanese Patent Application Laid-Open No. 60-31929 proposes supplying molten resin through a resin passage provided in the wall of the lower mold, and performing a mold closing operation at a specific timing. However, none of these methods could completely prevent the occurrence of uneven gloss and fine wrinkles called cold marks around the resin passages opened on the inner surface of the mold. In order to suppress the occurrence of cold marks, it is possible to raise the resin temperature and mold temperature, but this increases the time required to cool the molded product to a temperature at which it can be taken out after molding, which ultimately lengthens the molding cycle. Productivity deteriorates.

On the other hand, in order to enhance the decorativeness and functionality of thermoplastic resin molded products, multilayer molded products in which a skin material is integrally molded on the surface of the molded product are being used in large quantities in many fields, including automobiles and home appliances. used in One method for manufacturing this multilayer molded product is disclosed in Japanese Patent Application Laid-Open No. 1-235613. In conventional manufacturing methods for multilayer molded products, including this method, high-temperature molten resin is continuously supplied from near a certain part of the skin material, so some parts of the skin material are exposed to high temperatures longer than other parts. This causes the skin material to denature and deform, causing defects such as crushing, unevenness, and tears in the skin material.

0004

SUMMARY OF THE INVENTION Therefore, there is a need for a method for manufacturing thermoplastic resin molded products without cold marks, and a method for manufacturing multilayer molded products that does not damage the skin material.

[0005]

[Means for solving the problem] While researching the manufacturing method of thermoplastic resin molded products and multilayer molded products, we divided the mold into a product molded part and a non-product molded part, and melted the non-product molded part. It has been found that if a resin supply port is provided to supply molten resin, no cold marks will occur in the product part, and no crushing, unevenness, or tearing of the skin material of the multilayer molded product will occur.

That is, the first gist of the present invention is to supply a thermoplastic resin in a molten state between upper and lower molds, press,
In a method for producing a thermoplastic resin molded product by cooling,
When a mold having a product part molding part and a non-product part molding part is used, and the clearance of the cavity formed by the upper and lower molds is larger than the thickness of the molded product, non-molten resin is A second gist of the present invention resides in a method for manufacturing a thermoplastic resin molded product characterized by supplying molten resin into a mold cavity from a molten resin supply port provided only in the molded part of the product, and the second gist of the present invention is to A method of manufacturing a multilayer molded product consisting of a core resin and a skin material by supplying the resin in the same state between the skin material placed between the upper and lower molds and one of the upper and lower molds, pressing and cooling the resin. In this method, a mold having a product part molding part and a non-product part molding part is used, and when the clearance of the cavity formed from the upper and lower molds is larger than the thickness of the molded product, the molten resin is The method of manufacturing a multilayer molded product is characterized in that a molten resin is supplied into a space formed by a mold and a skin material from a molten resin supply port provided only in a non-product molded part.

In the manufacturing method of the present invention, any thermoplastic resin conventionally used in press molding, injection molding, extrusion molding, etc. can be used as the thermoplastic resin. Examples include thermoplastic resins such as polypropylene, polyethylene, polystyrene, polymethyl methacrylate, polycarbonate, polyacrylimide, acrylonitrile-styrene-butadiene block copolymer, and nylon. In addition to thermoplastic resins, non-foaming or foamable resins such as thermoplastic elastomers such as ethylene-propylene block copolymers and styrene-butadiene block copolymers are used as core resins for multilayer molded products. be able to. Of course, such resins may contain the usual additives, such as fillers such as glass fibers, pigments, lubricants, antistatic agents, etc.

[0008] Conventionally known skin materials can also be used for the multilayer molded product, such as woven fabrics, nonwoven fabrics, metals, fibers, thermoplastic resin nets, paper, metal foils, thermoplastic resins, and thermoplastic elastomers. sheet or film. In addition, uneven patterns such as grains, printing,
Those decorated with dyeing or the like can also be used. In addition, the skin material may be made of thermoplastic resin such as polyolefin or polyvinyl chloride, thermosetting resin such as polyurethane, or foamed rubber such as cis-1,4-polybutadiene or ethylene-propylene copolymer. You can also use your body. Furthermore, it is also possible to use these materials alone or in a form in which two or more of them are laminated with an adhesive or the like. When using these skin materials, in order to adjust the tensile stress and elongation of the skin material, the entire surface or a portion of the skin material may be preheated prior to supply.

[0009] In the present invention, the product part refers to the part of the molded product that is used as a product, and the non-product part refers to the part of the molded product that is not useful as a product and is removed or removed during use. , refers to the part that is hidden behind the back.

The method for manufacturing a molded article according to the present invention will be explained below with reference to the drawings.

FIG. 1 is a plan view of a molded article manufactured by the manufacturing method of the present invention, and FIG. 2 is a perspective view thereof. The molded article consists of a product part 1 and a non-product part 2. The non-product part 2 may be cut out or bent to the back side of the product part 1.

In the molded product shown in FIG. 1, there is one non-product part, but the invention is not limited to this, and two or more non-product parts may be provided.

FIG. 3 shows a partial sectional view of a mold used for molding such a molded product, including a non-product molding portion. The mold consists of a lower mold 4 and an upper mold 3, both of which form a product part molding part 5 and a non-product part molding part 6. FIG. 3 shows a state in which the upper and lower molds 3 and 4 are completely closed after the molten resin 7 is supplied. In the present invention, it is preferable that the clearance W1 at the boundary between the product part molded part and the non-product part molded part in this state is 0.03 to 1.5 mm. If the width of this clearance is too large, the thickness of the boundary portion connecting the product part and the non-product part becomes large, making it difficult to cut out or bend the non-product part. On the other hand, if the width of the clearance is too small, the molten resin supplied to the non-product molded portion will not be sent to the product molded portion at a sufficient speed.

The clearance W2 between the two at the outermost periphery of the lower mold is normally 0.01 to 0.07 mm. If this clearance is too large, the supplied molten resin may leak out of the mold, which is not preferable.

[0015] Note that two or more molten resin supply ports may be provided in one non-product part molding portion.

The molten resin is normally supplied when the cavity clearance t of the product molding portion of the upper and lower molds is from (C+0.1) to 50 mm, as shown in FIG. Here, C means the cavity clearance upon completion of shaping. When supplying molten resin, set the mold closing speed to 0 to 3.
By setting the speed to 0 mm/sec, the relationship between the supply of molten resin and the cavity clearance is accurately controlled. In addition, when using a transparent resin such as polymethyl methacrylate or polycarbonate as the thermoplastic resin, the cavity clearance t when supplying the molten resin is (C+0.
1) to (C+7) mm is particularly preferable in order to obtain a molded product without cold marks.

[0017] Final mold clamping and shaping can be carried out during and/or after supplying the molten resin, and after pressurizing and cooling,
Take out the molded product.

Regarding the positional relationship between the product part and the non-product part, as shown in FIG. 1, the non-product part may be outside the product part.
As shown in FIG. 5, there may be a non-product part 2 inside the product part 1.

Next, a method for manufacturing a multilayer molded product consisting of a resin core material and a skin material will be explained.

[0020] The manufacturing method is the same as above for manufacturing the thermoplastic resin molded product, except that the skin material is supplied between the upper and lower molds in advance, and the molten resin is supplied between the skin material and one of the upper and lower molds. The method is basically the same.

The skin material 8 shown in FIG.
It can be fixed to the mold by the means described in JP-A-235613.

In the case of manufacturing a multilayer molded product, the clearance W1 at the boundary between the product part molded part and the non-product part molded part when the mold is completely closed as shown in FIG. 6 is determined by the thickness of the skin material ( mm)+(0.1 to 1.0) mm. Here, the "thickness of the skin material" in the present invention means the thickness when a compressive load of 60 kg/cm2 is applied to the skin material. FIG. 7 is a diagram corresponding to FIG. 4. In addition, when supplying molten resin in the case of manufacturing multilayer molded products, when the cavity clearance is (C+100) mm to (C+5) mm,
It is preferable to perform the mold clamping at a speed of 0 to 30 mm/sec.

[0023]

[Examples] Hereinafter, the present invention will be explained in more detail with reference to Examples.

[0024] In order to evaluate the "warpage" of a molded product, place the sample of the molded product from which the non-product parts have been removed as shown in Figure 2 on a flat plate, press the top of the corner The lower end of the corner is the highest and is displayed at the height above the flat plate. Moreover, the measurement conditions for the melt flow rate (MFR) of a thermoplastic resin are as follows.

MFR of polypropylene: JIS K67
58, the temperature is 230° C. and the load is 2.16 kg. MFR of polymethyl methacrylate: ASTM D12
38, the temperature is 230°C and the load is 3.8 kg. MFR of polycarbonate: Measured in accordance with ASTM D1238 at a temperature of 300° C. and a load of 1.2 kg.

Example 1 440mm (length) x 55mm (width) x 20mm (
A box-shaped molded product with dimensions (height) x 2.5 mm (wall thickness) as shown in Figure 1 was press-molded using a mold with a molten resin supply port in the non-product molding part of the lower mold. .

When polypropylene (Sumitomo Noblen AZ564, manufactured by Sumitomo Chemical Industries, Ltd.) is used as the resin, the resin temperature is 220°C, the mold temperature is 40°C, and the clearance (t) of the product part molding part of the upper and lower molds is 5 mm. Supply of the molten resin was started and stopped when the clearance was 3 mm. During this time, the upper mold was lowered to close the mold.

[0028] The molding cycle in this molding method was 30 seconds, and the appearance of the product part was good.

Comparative Example 1 Molding was carried out under the same conditions as in Example 1, except that a conventional mold having a molten resin supply port in the product molding part of the lower mold was used. Uneven gloss occurred on the surface of the molded product near the resin supply port.

Comparative Example 2 A conventional mold having a molten resin supply port in the product molding part of the lower mold was used, and the resin temperature was 265°C and the mold temperature was 90°C.
Molding was carried out under the same conditions as in Example 1 except that the temperature was 0°C. The appearance of the obtained molded product was good overall, with no uneven gloss on the surface near the resin supply port, but the molding cycle was 4.
5 seconds, which is 15 seconds longer than in Example 1.

Example 2 Using polymethyl methacrylate (Sumipex-B MHO, manufactured by Sumitomo Chemical Co., Ltd.) as the resin,
Molding was carried out under the same conditions as in Example 1 except that the resin temperature was 250°C and the mold temperature was 60°C. The molding cycle using this molding method was 35 seconds, and the appearance of the product part was good.

Comparative Example 3 A conventional mold having a molten resin supply port in the product molding part of the lower mold was used, the polymethyl methacrylate used in Example 2 was used as the resin, and the resin temperature was 280°C. Molding was carried out under the same conditions as in Example 1 except that the mold temperature was 60°C. Ring-shaped uneven gloss occurred on the surface of the molded product near the resin supply port. Moreover, the molding cycle was 45 seconds.

Example 3 A multilayer molded product with dimensions of 440 x 55 x 20 x 2.5 (mm) and a planar shape as shown in Fig. 1 with a skin material laminated on the surface was placed in the non-contact mold of the lower mold. Press molding was performed using a mold with a molten resin supply port in the molding part of the product.

[0034] Polypropylene (Sumitomo Noblen AZ564, manufactured by Sumitomo Chemical Co., Ltd.) was used as the resin, and a polypropylene foam layer (expansion ratio 25 times) was laminated to a polyvinyl chloride sheet as the skin material (the thickness of the skin material was 3 mm). was used, the resin temperature was 190°C, the mold temperature was 30°C, and the supply of molten resin was started when the clearance (t) of the product part molding part of the upper and lower molds was 20 mm, and the supply was stopped when the clearance was 5 mm. During this time, the upper mold was lowered to close the mold. The appearance of the product section was good.

Comparative Example 4 A multilayer molded product was manufactured under the same conditions as in Example 3, except that a conventional mold having a molten resin supply port in the product molding portion of the lower mold was used. The foam layer of the skin material near the resin supply port was melted by the heat of the resin, and unevenness occurred on the surface of the skin material.

Example 4 Figure 1 with dimensions of 440 x 55 x 20 x 3 (mm)
A box-shaped molded product as shown in is press-molded using a mold that has a molten resin supply port in the non-product molding part of the lower mold.

Polymethyl methacrylate (Sumipex-B MMO, melt flow rate 0.6
g/10 minutes, manufactured by Sumitomo Chemical Co., Ltd.), the resin temperature was 257°C, the female mold was 70°C, and the male mold was 60°C, and the clearance (t) of the product molding part of the upper and lower molds was 8
When the temperature reaches mm, the closure of the mold is temporarily stopped and molten resin is supplied. Immediately before completing the supply of molten resin, close the mold again, set the mold clamping force to 100 kg/cm2, and perform shaping.
Cool and take out the molded product. The product part of the obtained molded product had a good appearance and had very little warpage.

Examples 5 to 8 Molding was carried out in the same manner as in Example 4, except that the type of resin and the conditions for supplying the molten resin were as shown in Table 1. All of the molded products obtained had good external appearance and very little warpage.

Comparative Examples 5 to 6 Polymethyl methacrylate shown in Table 1 was used as the resin, and injection was performed at a resin temperature of 277°C, a female mold of 75°C, a male mold of 65°C, and a mold clamping force of 800 kg/cm2. Perform molding. The resulting molded product has a good appearance, but is very warped.

[0040]

[Table 1]

Examples 9 to 10 A molded article as shown in FIG. 8 was press-molded using a mold having a molten resin supply port in the non-product molding portion of the lower mold.

Polycarbonate (Caliber) is used as the resin.
300-22, MFR 22 g/10 minutes, manufactured by Sumitomo Naugatac Co., Ltd.), the molten resin is supplied under the conditions shown in Table 2, and the mold is clamped, shaped, and cooled to obtain a molded product. A molded article with good appearance is obtained.

[0043]

[Table 2]

Examples 11 to 14 Using the same mold as used in Example 9, press molding was performed with the type of resin and the conditions for supplying the molten resin as shown in Table 3. A molded article with good appearance is obtained.

Comparative Example 7 A molded article was obtained in the same manner as in Example 11, except that the conditions for supplying the molten resin were as shown in Table 3. The appearance of the product part of the molded product was poor, with ring marks and cold marks occurring.

Comparative Example 8 Using the polypropylene shown in Table 3 as the resin, injection molding was carried out at a resin temperature of 240°C, a female mold at 60°C, and a male mold at 55°C. The resulting molded product has a good appearance, but is very warped.

[0047]

[Table 3]

[0048]

Effects of the Invention: It is possible to efficiently produce thermoplastic resin molded products without cold marks and multilayer molded products that do not damage the skin material.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a molded product formed by the manufacturing method of the present invention.

FIG. 2 is a perspective view of a molded product formed by the manufacturing method of the present invention.

FIG. 3 is a partial cross-sectional view of a mold for explaining the method for manufacturing a thermoplastic resin molded article of the present invention.

FIG. 4 is a partial cross-sectional view of a mold for explaining the method for manufacturing a thermoplastic resin molded article of the present invention.

FIG. 5 is a plan view of a molded product formed by the manufacturing method of the present invention.

FIG. 6 is a partial cross-sectional view of a mold for explaining the method for manufacturing a multilayer molded product of the present invention.

FIG. 7 is a partial cross-sectional view of a mold for explaining the method for manufacturing a multilayer molded product of the present invention.

FIG. 8 is a perspective view of a molded product molded by the manufacturing method of the present invention.

FIG. 9 is a partial cross-sectional view of a mold for explaining the method for manufacturing a thermoplastic resin molded article of the present invention.

[Explanation of symbols]

1... Product department, 2... Non-product department, 3... Upper mold, 4... Lower mold,
5... Molded part of product part, 6... Molded part of non-product part, 7... Molten resin, 8... Skin material.

Claims (4)

[Claims] Claim 1: A method for manufacturing a thermoplastic resin molded article by supplying a molten thermoplastic resin between upper and lower molds, pressing and cooling, the method comprising a product part molding part and a non-product part molding part. When a mold is used and the clearance of the cavity formed by the upper and lower molds is larger than the thickness of the molded product, the molten resin is supplied from the molten resin supply port provided only in the non-product molded part through the molten resin passage provided in the mold. A method for producing a thermoplastic resin molded product, characterized by supplying molten resin into a mold cavity. 2. The manufacturing method according to claim 1, wherein when the upper and lower molds are closed, the upper and lower mold clearance at the boundary between the product part molding part and the non-product part molding part is 0.03 to 1.5 mm. Method. 3. A molten resin is supplied between a skin material placed between the upper and lower molds and one of the upper and lower molds, pressed and cooled to form a multi-layered resin consisting of a core resin and a skin material. In a method for manufacturing a molded product, a mold having a product part molding part and a non-product part molding part is used, and when the clearance of the cavity formed from the upper and lower molds is larger than the thickness of the molded product, a A method for manufacturing a multilayer molded product, characterized in that molten resin is supplied into a space formed by a mold and a skin material from a molten resin supply port provided only in a non-product molded part through a molten resin passage. . 4. When the upper and lower molds are closed, the upper and lower mold clearance at the boundary between the product part molding part and the non-product part molding part is [skin material thickness + (0.1 to 1.0)] ] mm. The manufacturing method according to claim 3.