JP2001334540A - Method for manufacturing skin material laminated foamed resin molded article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a skin material laminated foamed resin molded article wherein a foamed layer is certainly formed and the appearance of the surface on the side opposite to the skin material laminated surface of a core material is also excellent because the volatilization of a foaming agent, the so-called venting can be sufficiently prevented when a molten resin mixed with the foaming agent is injected in a mold. SOLUTION: The method for manufacturing the skin material laminated foamed thermoplastic resin molded article wherein a skin material and a thermoplastic resin foam layer are integrally laminated has a skin material supply process using molds wherein a cavity clearance (t) can be adjusted to supply the skin material to the gap between the molds, a resin injection process setting (t) to a resin injection clearance of <(C+5) mm to perform the injection of a molten polyolefinic resin containing the foaming agent, a pressure process contracting (t) to fully fill the mold cavity with the injected resin to shape the same, a foaming process expanding (t) to foam the resin to form a foamed thermoplastic resin molded object and a cooling and demolding process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a thermoplastic resin molded article, and more particularly to a panel-shaped thermoplastic resin foam molded article laminated with a lightweight and highly rigid skin material suitable for automobile interior members and the like. It relates to a manufacturing method.

[0002]

2. Description of the Related Art A skin layered thermoplastic resin molded article used for interior parts of automobile parts and the like, which is formed by molding a thermoplastic resin by a method such as injection molding and provided with a skin layer on the surface, has been conventionally used. However, since these molded products have a high density and are therefore heavy, they are required to be reduced in weight, particularly in the field of interior materials for automobiles, and to be further improved in quality. In particular, recently, there is a strong demand for improving the appearance quality of the back side of the synthetic material with a skin material.

A technique for reducing the weight of a foamed thermoplastic resin resin in which a skin material is laminated and an inner layer of the resin is formed as a foamed layer as an interior material of an automobile part is disclosed in Japanese Patent Application Laid-Open No. 6-34436.
No. 2, JP-A-4-148907.

The above publication discloses a mold stamping molding method. That is, a skin material is set between a pair of upper and lower molds, a mold interval is set to a specific value, and then a foaming agent-containing polypropylene resin composition is injected between the molds having the skin material, and simultaneously, the mold is closed and the resin is closed. A technique is disclosed in which a resin is molded into a predetermined shape and adhered to a skin material, and then the resin is foamed by opening the mold, and then cooled and solidified to perform molding.

[0005]

In the technique described in the above-mentioned publication, resin injection is performed with a large mold interval in order to reduce the resin injection pressure. Therefore, when the molten resin mixed with the foaming agent is injected into the mold, volatilization of the foaming agent, that is, so-called outgassing, cannot be sufficiently prevented. The appearance of the back surface of the core material to which the skin material was bonded was not sufficient.

SUMMARY OF THE INVENTION An object of the present invention is to sufficiently prevent volatilization of the foaming agent when the molten resin mixed with the foaming agent is injected into the mold, that is, so-called outgassing. An object of the present invention is to provide a method for producing a foamed thermoplastic resin molded article having an excellent appearance on the skin material bonding surface side, that is, on the side opposite to the skin material bonding surface of the core material in the molded product.

[0007]

Means for Solving the Problems The inventors of the present invention have studied a technology for preventing outgassing of a molten thermoplastic resin mixed with a foaming agent in stamping molding, and as a result, the conventional stamping molding has a characteristic of molten resin. In order to greatly reduce the injection pressure required for injection compared to general injection molding, it was considered essential to increase the resin injection clearance of the molding die. Thus, it has been found that outgassing can be effectively prevented by reducing the resin injection clearance more than it was thought that stamping molding could not be performed, and the present invention was completed.

That is, the present invention relates to a method for producing a foamed thermoplastic resin molded article in which a skin material and a thermoplastic resin foam are laminated and integrated, comprising a male mold and a female mold slidable with each other. And a molding die having an adjustable cavity clearance (t), and having the following steps (1) to (5).

(1) A skin material supplying step of supplying the skin material in a state where the male and female molds are opened. (2) The male mold and the female mold are brought close to each other and t is set to (C +
5) A resin injection clearance of less than mm (C is the thickness of the skin material before molding), and a gap between the skin material and the mold through a resin supply port formed in one of the male mold and the female mold. A resin injecting step of injecting a molten polyolefin-based resin containing a foaming agent (3) Filling the injected polyolefin-based resin to a mold cavity terminal by reducing t from the resin injection clearance by applying pressure, and shaping the resin. And pressurizing step of laminating and integrating the skin material and the polyolefin-based resin. (4) After completion of the shaping of the polyolefin-based resin injected in a molten state, the value of t is expanded to reduce the polyolefin-based resin. Foaming, forming a foamed layer to form a foamed thermoplastic resin molded body (5) cooling the foamed thermoplastic resin molded body in a mold,
Next, a cooling and demolding step of opening the mold and taking out the foamed thermoplastic resin molded article.

[0010] By the above-mentioned steps, the volatilization of the foaming agent, that is, the so-called outgassing, can be sufficiently prevented when the molten resin mixed with the foaming agent is injected into the mold. As a result, the foamed layer is reliably formed. It has become possible to produce a foamed thermoplastic resin molded article having an excellent appearance of the anti-skin material bonding surface.

In particular, (2) the resin injection clearance of the mold in the resin injection step is considered to be difficult due to the excessively high injection resin pressure in conventional stamping molding (C).
By setting it to less than +5) mm, outgassing is effectively prevented, and the time required for opening and closing the mold after the injection of the molten thermoplastic resin is reduced.

As the skin material used in the present invention, various kinds of skin materials having a single layer or a plurality of layers conventionally used can be used. When using a skin material in which a cushion layer is laminated as a multilayer skin material, it is preferable to use a skin material having a cushion layer having a compression elastic modulus of 0.3 MPa or less, and further serves as a protective layer for the cushion layer. It is necessary to provide a backing layer.

The foamed thermoplastic resin article of the present invention can be suitably used particularly for automobile interior parts, and specifically includes an instrument panel, a seat back, a partition board, a console box, a door trim and the like. Is done.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of manufacturing a panel having a convex portion in which a skin material layer is laminated on the surface of the present invention will be described with reference to FIGS. FIG. 5 is a diagram showing the mold cavity clearance t in each step shown in FIGS.

The method for manufacturing a panel according to the present invention comprises a female mold 23 and a male mold 25 fixed to a base 26, and the cavity is formed by the relative movement between the female mold 23 and the male mold 25. A set of molds whose clearance (t) can be set arbitrarily is used.

The skin material 30 is held by the end face of the female mold 23 and the clamper 28 (FIG. 1). At this time, the mold is widely opened for easy operation (FIG. 5A). The holding of the skin material 30 by the clamper 28 is performed to the extent that the skin material 30 is slidable when the skin material 30 is drawn into the mold concave part during molding (skin material supply step).

Next, at least one of the female mold 23 and the male mold 25 is moved to form a resin supply start clearance (FIG. 5 (2)). If the resin supply start clearance is too wide, foaming of the resin occurs rapidly, gas escape occurs, and the appearance of the anti-skin material bonding surface is impaired. Therefore, when the thickness of the skin material 30 before molding is C, C + 5) mm.

The step shown in FIG. 2 is a step of injecting a molten thermoplastic resin 33 containing a foaming agent through the resin supply passage 32 (resin injection step, FIG. 5 (3)).

The mold cavity clearance reduction speed is appropriately set in consideration of the size of the molded product, the characteristics of the material to be used, and the like. However, in practice, one mold, for example, a female mold is 1 to 50 mm / mm. It is preferred to move at a speed of seconds.

Although three branch passages 32B of the resin supply passage 32 are formed in the example shown in this figure, the present invention is not limited to this, and is arbitrarily set according to the shape and size of the molded product. You.

The step shown in FIG. 3 is a step of injecting a predetermined amount of a molten thermoplastic resin 33 containing a foaming agent and then compressing the mold so that the cavity clearance of the mold becomes equal to or less than a set thickness of the molded article. The resin surface layer is cooled in the pressurized state to form a resin skin layer. The skin material and the resin layer are adhered by the compression in this step. (Pressing process, FIG. 5
(4)).

The pressing time in the pressing step is appropriately set according to the thickness of the molded product, the thickness of the skin layer to be formed, the temperature of the mold, and the like. It is preferable to be about 1 second to 30 seconds.

The skin material and the resin layer 33 are laminated by the pressurization in the above pressurizing step. Next, the cavity clearance t of the mold is enlarged so as to become the set thickness of the molded article (FIG. 4), and the resin between the skin layers is foamed to form a foamed layer, thereby forming the skin material 30 and the skin material side. A panel-shaped thermoplastic resin foam molded product 34 as a final product having a core material composed of the skin layer 11, the foam layer 13, and the back side (anti-skin material bonding side) skin layer 15 is obtained (foaming process,
FIG. 4, FIG. 5 (5)).

By cooling the molded article formed in the foaming step (cooling step, FIG. 5 (6)), the production of the molded article is completed.

In the foaming step, after the mold is opened so as to be thicker than the set thickness of the molded product, the mold is closed so as to have the set thickness, t is slightly reduced, and after keeping the pressure at a predetermined pressure, cooling is performed. May be. In this case, “slightly” is not particularly limited, but is usually not more than a predetermined thickness of the molded product.

As the thermoplastic resin used in the present invention, resins conventionally used in automobile interior parts and the like can be used without limitation, and specifically, polyolefin resins such as polypropylene resins and polyethylene resins. And acrylic resins such as polystyrene resins and polymethyl methacrylate resins, polyamide resins such as ABS and nylon-6, polyester resins, polycarbonate resins, and polyphenylene ether resins.

The thermoplastic resin used in the method for producing a foamed thermoplastic resin molded article of the present invention is preferably a polyolefin-based resin, especially a polypropylene-based resin among the above-mentioned examples. Even if it is less than (C + 5) mm, a molten resin mixed with a foaming agent can be injected at the same low resin injection pressure as the conventional stamping molding, and it is a low-cost, high-strength, high-rigidity foamed thermoplastic resin molded product. Because you can get
preferable.

The above-mentioned polypropylene resin preferably has a melt flow rate (MFR) value of 15 or more, and more preferably a polypropylene resin having an MFR of 25 or more.

By using a polypropylene resin having a high MFR, outgassing is particularly effectively prevented, the formation of a foamed layer is surely performed, and it is possible to obtain a molded article which sufficiently satisfies the requirement of lightness. it can.

The blowing agent to be added to the above thermoplastic resin is
A known chemical foaming agent used in producing a thermoplastic resin foam can be used. In particular,
Sodium bicarbonate, ammonium bicarbonate as blowing agents
Inorganic blowing agents such as ammonium carbonate, nitroso compounds such as N, N'-dinitrosopentamethylenetetramine, azo compounds such as azodicarbonamide, azobisisobutyronitrile, benzenesulfonylhydrazide, toluenesulfonylhydrazide, diphenylsulfone- 3,3 '
Blowing agents such as sulfonyl hydrazides such as -disulfonyl hydrazide and p-toluenesulfonyl semicarbazide can be used. It is a preferred embodiment to add salicylic acid, urea and a foaming aid containing these as necessary.

The type of the chemical foaming agent is selected in consideration of the melting temperature of the thermoplastic resin used, the desired expansion ratio, and the like. The addition amount is adjusted in consideration of the strength, density and the like of the target molded product, but is generally 0.1 to 5 parts by weight based on 100 parts by weight of the resin.

In addition to the chemical foaming agent, liquid or gaseous carbon dioxide and / or nitrogen may be directly injected into the molten resin.

As the skin material of the thermoplastic resin foam molded article for a panel of the present invention, a known skin material can be used. As a specific skin material, a woven fabric, a nonwoven fabric, a knitted fabric, a film formed of a thermoplastic resin or a thermoplastic elastomer,
Sheets and the like are exemplified. Further, a composite skin material in which a non-foamed sheet of polyurethane, rubber, thermoplastic elastomer, or the like is laminated on these skin materials may be used.

In a preferred embodiment, the skin material is further provided with a cushion layer on the side of the lamination surface with the thermoplastic resin foam as the base material. Examples of the material constituting the cushion layer include polyurethane foam, EVA foam, polypropylene foam, polyethylene foam and the like. The compression set is small, and the compression elastic modulus provides a soft feeling suitable for the skin material layer. Most preferred is a material of 0.3 MPa or less.

When a cushion layer is provided on the skin material, it is necessary to provide a backing layer serving as a protective layer.
Examples of the backing layer include a woven fabric, a nonwoven fabric, a knitted fabric, a sheet or film of a thermoplastic resin or a thermoplastic elastomer, and the like. However, it is preferable to use a nonwoven fabric in terms of moldability, cost, and the like.

[0036]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment specifically illustrating the structure and effects of the present invention will be described below with reference to a press machine having a mold clamping force of 500 tons.
The following describes an example of molding performed by attaching a pair of male and female molds shown in FIG.

As the skin material, polyvinyl chloride sheet having a thickness of 0.5 mm was applied to a sheet having a thickness of 3 mm and a compression modulus of 0.2 MPa.
a having a nonwoven fabric having a thickness of 0.2 mm and a basis weight of 50 g / m ² as a backing material.
A layered skin material was used.

As the foamed thermoplastic resin as the core material, polypropylene (Sumitomo Noblen AZ564, manufactured by Sumitomo Chemical Co., Ltd .: melt flow rate 30 g / 10
3 parts by weight of an inorganic chemical foaming master batch (manufactured by Sankyo Kasei Co., Ltd., CellMike MB3072) was added to 100 parts by weight, and heated and melted at 200 ° C. for use.

The molding process is as follows. (I) The skin material (30) is arranged between the female mold (23) and the male mold (25) set at a temperature of 60 ° C., and the female mold (23) is moved to mold the mold. When the tea clearance (t) became 8 mm (skin material thickness C + 4.3 mm), the press was stopped, and the foamed thermoplastic resin heated and melted from the resin supply passage (32) provided in the male mold (25). The resin is supplied between the skin material (30) and the male mold (25), the mold is clamped at a compression speed of 10 mm / sec, and the skin material (30) and the molten foamed thermoplastic resin core material (33) are pressed. It was shaped, laminated and integrated, and a skin layer was formed on the surface of the core material. The pressing and shaping conditions at this time were pressing at a surface pressure of 5 MPa for 2 seconds, and the cavity clearance at the time of pressing was 2.5 mm.

(Ii) Immediately after the press forming, the female mold (23) is moved by 2 mm in the mold opening direction to foam the molten core material portion in which the cooling and solidification has not progressed. The state was cooled for 50 seconds.

After cooling, the molded product taken out has a cross section composed of fine foam cells without gas escape of the foam gas, and the surface on which the skin material is bonded and the core material surface on the back surface are also gas-free. It had a good appearance without any defects due to omission.

(Comparative Example) The mold cavity clearance (t) for supplying the heat-melted foamed thermoplastic resin in (i) of the above embodiment was set to 15 mm (skin material thickness C + 11.3 mm). Except for this, molding was performed in the same manner as in the example.

The obtained molded product had a cross section composed of very coarse cells due to outgassing of the foaming gas, and had a streak-like appearance defect due to outgassing on the core material surface opposite to the skin material bonding surface. Had occurred.

[Brief description of the drawings]

FIG. 1 is a diagram showing a skin material supply step in an example of a production method of the present invention.

FIG. 2 is a view showing a resin injection step in an example of the manufacturing method of the present invention.

FIG. 3 is a diagram showing a pressing step in an example of the manufacturing method of the present invention.

FIG. 4 is a diagram showing a foaming step in an example of the production method of the present invention.

FIG. 5 is a diagram showing a state of adjustment of a mold cavity clearance in each manufacturing process.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) B29L 31:30 B29L 31:30

Claims (5)

[Claims] 1. A method for producing a foamed thermoplastic resin molded article in which a skin material and a thermoplastic resin foam are laminated and integrated, comprising a male mold and a female mold slidable with each other, A method for producing a foamed thermoplastic resin molded article, comprising using a molding die having an adjustable tea clearance (t) and having the following steps (1) to (5). (1) A skin material supplying step of supplying the skin material in a state where the male and female molds are opened. (2) The male mold and the female mold are brought close to each other to set t to (C +
5) A resin injection clearance of less than mm (C is the thickness of the skin material before molding), and a gap between the skin material and the mold through a resin supply port formed in one of the male mold and the female mold. A resin injecting step of injecting a molten polyolefin-based resin containing a blowing agent (3) Filling the injected polyolefin-based resin to the mold cavity terminal by reducing t from the resin injection clearance by pressurization and shaping And pressurizing step of laminating and integrating the skin material and the polyolefin-based resin. (4) After completion of the shaping of the polyolefin-based resin injected in a molten state, the value of t is expanded to reduce the polyolefin-based resin. Foaming, forming a foamed layer to form a foamed thermoplastic resin molded body (5) cooling the foamed thermoplastic resin molded body in a mold,
Next, the mold is opened and the foaming thermoplastic resin molded product is taken out and the cooling and demolding process is performed. 2. The method according to claim 1, wherein the skin material has a compression modulus of 0.3 MPa.
The method for producing a foamed thermoplastic resin molded article according to claim 1, comprising the following cushion layer and backing layer. 3. The method for producing a foamed thermoplastic resin article according to claim 1, wherein the backing layer of the skin material is a nonwoven fabric. 4. After completion of the foaming step (4), the t
The method for producing a foamed thermoplastic resin molded article according to any one of claims 1 to 3, further comprising a step of slightly reducing the pressure and pressurizing. 5. The method for producing a foamed thermoplastic resin molded article according to claim 1, wherein said polyolefin resin is a polypropylene resin.