JP2001162648A - Method for molding skin integrated lightweight molded article and molded article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a molding method for obtaining a skin integrated lightweight resin molded article excellent in strength, dimensional stability and uniformity even if a heat insulating skin material such as a foamed sheet or the like is used. SOLUTION: In a molding method wherein a molten thermoplastic resin containing fibers and having expansion properties is injected in a mold cavity in which a skin material is arranged or injected in this mold cavity to be compressed to fill the cavity and the cavity is subsequently expanded, a mold of which the molding surface opposed to the molding surface on which the skin material is mounted has a heat insulating structure is used or the temperature of a mold in which the skin material is not arranged is made higher than that of the mold in which the skin material is arranged by 20 deg.C or higher.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding method and a molded article of a skin-integrated lightweight resin molded article. The present invention relates to a molding method for obtaining a skin-integrated lightweight resin molded product in which a molten thermoplastic resin having the following formula is injected or injection-compressed and filled, and then a mold cavity is expanded and expanded.

[0002]

2. Description of the Related Art Conventionally, thermoplastic resins and fiber-reinforced thermoplastic resins have been widely used as automobile parts, home appliances, OA fields, members for construction and civil engineering, and the like. These molded products are mainly formed by injection molding or injection compression molding in view of productivity and the like. The feature of these molded products is that they are lighter in weight than other materials, but the industry demands further weight reduction from the viewpoint of resource saving and effective use of resin. This reduction in weight of the resin molded product is a desirable use form from the viewpoint of high strength and rigidity per unit mass and effective utilization of resources. On the other hand, molded articles are provided with functions such as eliminating appearance defects such as sink marks, surface decoration by integral molding with a skin material, and softness.

[0003] In injection molding (including injection compression molding; the same applies hereinafter), as a method for reducing the weight of a resin molded product, there are a method using a foaming agent-containing resin, a method of injecting a gas, and a method of containing a fiber to expand the resin. There is known a method of utilizing a molten thermoplastic resin having a swelling property, that is, an expansion property which is a restoring force of entanglement of fibers.

[0004] Among them, the usual injection molding using a foaming agent-containing resin, that is, a method of injecting a smaller amount of resin than the volume of a cavity to foam the resin cannot uniformly mold the end portion of the molded product. Also, there is a problem that a molded article having an excellent appearance cannot be obtained, for example, silver is generated on the surface of the molded article by a foaming agent. As a method for solving this problem, a counter pressure method for suppressing foaming at the time of injection has been proposed, but there is a problem in economy, and a problem in which molding of a thin end portion is difficult is not solved. Furthermore, the expansion ratio is also limited, and there is a problem in that the weight and weight are limited, and the strength and rigidity are rapidly reduced with the weight reduction.

On the other hand, in a gas injection (including gasification by liquid injection) molding method, similarly, after injecting a smaller amount of molten resin than the volume of a mold cavity, a gas is injected to form a hollow in a molded article. There is a molding method for forming a part. However, this method has a problem that a large hollow portion is formed in the molded product, and the strength and rigidity are rapidly reduced as the weight is reduced.

[0006] In the above-mentioned molding method for the purpose of reducing the weight of a resin molded product in the injection molding, a molded product that is less reduced in strength and rigidity in terms of weight reduction, strength, rigidity, and surface properties even though the weight is reduced. Has been attracting attention as an expansion molding method that utilizes fibers and expandability caused by entanglement of fibers with a molten thermoplastic resin, which is a very excellent method.

[0007] The lightweight resin molded product obtained by this expansion molding method has excellent bending strength and impact strength due to reinforcement with fibers such as glass fibers and formation of continuous voids in the skin layer and intermediate layer formed on the surface. It is a lightweight resin molded product with high quality, unprecedented properties such as strength, heat insulation and sound absorption.

[0008] Even with such lightweight resin molded articles having excellent features, depending on the application, decoration of the molded article surface, impartation of luxury, feel such as softness, further improvement of heat insulation, surface Improvements in hardness, surface slipperiness, etc. may be desired. In improving the surface properties, a lamination molding method in which a skin material is integrated is disclosed in Japanese Patent Application Laid-Open No. 11-1067.
No. 3 discloses this.

[0009]

However, in the case of the integral skin molding method, although it depends on the type of the skin material, there are generally many skin materials containing bubbles, such as foamed sheets and fiber materials. When the skin material is used, there is a problem that heat conduction between the molten resin and the mold becomes poor, and the molding cycle becomes long. Further, it has been found that there are new problems such as strength and warpage of the obtained molded product, depending on the thickness of the lightweight resin molded product. The present invention has excellent strength and dimensional stability even for a heat insulating skin material such as a foam sheet.
It is an object of the present invention to provide a molding method capable of obtaining a lightweight resin molded product having excellent uniformity.

[0010]

Means for Solving the Problems The present inventors diligently studied the above-mentioned problems with respect to the cooling conditions of the molded article during molding and the characteristics of the molded article. As a result, it was found that by approximating the cooling of the resin surface on the back side of the skin material and the cooling of the resin surface on the side having no skin material, a lightweight resin molded product having good quality can be obtained. Is completed.

That is, the present invention provides: (1) A molten thermoplastic resin containing fibers and having expandability is filled by injection or injection compression into a molding die cavity equipped with a skin material, and then the cavity is expanded. A molding method for a skin-integrated lightweight resin molded product, wherein a molding surface having a heat insulating structure is used for a molding surface facing a molding surface on which a skin is mounted. (2) The method for molding a skin-integrated lightweight resin molded product according to (1), wherein the heat insulating structure has a layer made of a heat-resistant resin and / or a ceramic. (3) The skin integral lightweight according to (1) or (2), wherein the heat insulating structure is formed of a heat insulating layer having a thickness of 0.1 to 5 mm and a metal layer having a thickness of 0.01 to 0.5 mm on the heat insulating layer. Molding method for resin molded products. (4) Raw material in which the molten thermoplastic resin containing fibers and having expandability contains fibers having a length of 3 to 100 mm, and at least partially contains fiber reinforced resin pellets having a length substantially equal to the fiber length. The method for molding a skin-integrated lightweight resin molded article according to any one of (1) to (3), wherein the molded article is a molten resin. (5) In a molding method in which a thermoplastic resin containing fibers and having expandability is injected or injection-compressed into a molding die cavity in which a skin material is mounted, and the cavity is expanded, a metal without a skin material is used. A method for molding a skin-integrated lightweight resin molded product, wherein the temperature of a mold is set to be 20 ° C. or more higher than the temperature of a mold on which a skin material is mounted. (6) A raw material in which the molten thermoplastic resin containing fibers and having expandability contains fibers having a length of 3 to 100 mm, and at least partially contains fiber-reinforced resin pellets having substantially the same length as the fiber length. Wherein the fiber content is from 10 to 80% by mass. (7) The present invention relates to a skin-integrated lightweight resin molded product having an area density of 0.2 to 2.5 g / cm ² of a resin portion containing fibers excluding a skin material.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. In the method for molding a skin-integrated lightweight resin molded product according to the first invention of the present application, a molten thermoplastic resin containing fibers and having expandability is injected or injected and compressed into a molding die cavity equipped with a skin material. Thereafter, in a molding method for expanding a cavity, a mold having a heat insulating structure on a mold surface facing a mold surface on which a skin is mounted is used.

[0013] That is, this is different from the conventional molding method in that the mold surface on which the skin material is not mounted is a mold having a heat insulating structure. The use of heat-insulating dies in injection molding is already known. However, the use of the conventional heat-insulating mold prevents rapid cooling by the mold during injection of the molten resin, suppresses rapid cooling of the molten resin flowing on the mold surface, improves mold transferability, and generates flow marks. It aims at prevention and reduction of flow distortion. Therefore, generally, the heat insulating structure in the mold is provided for the above purpose.

Therefore, the first invention of the present application suppresses the cooling of the mold surface on which the skin material is not mounted, and makes the cooling of the resin surface in contact with the mold surface equal to the cooling of the resin side surface having the skin material. By doing so, a sufficient skin layer is formed on the resin surface layer just below the back surface of the skin material and the resin surface at the mold contact surface, and the idea is completely different from the conventional heat-insulating mold. It is to be. However, the mold having the heat insulation structure in the first invention of the present application can also employ the molds having various heat insulation structures that have already been proposed in terms of having the heat insulation structure. The heat insulation structure is not limited to the one having the heat insulation layer on the mold surface, but is constituted by a multilayer such as a metal layer on the surface above the heat insulation layer or a thin heat resistant resin layer having a small heat insulation effect. Can also be exemplified.

The reason why the metal layer is provided on the heat insulating layer is that when the molten resin is injected, the surface is made to be the same as that of a conventional metal mold as a metal layer. This is because the effect of heat insulation is minimized and the heat insulating effect appears after the start of cooling after resin filling. That is, the purpose of forming the heat insulating structure at a specific position is to make the cooling speed of the molten resin in the specific portion slower than that of other general portions.

The molding die is generally made of a metal material such as general steel, nickel, aluminum, copper, zinc or an alloy thereof. General metallic materials have high thermal conductivity and good thermal conductivity, and the injected molten resin is rapidly cooled, and the surface of the molded product is solidified.

The material for forming the heat insulating structure (layer) in the present invention is not particularly limited. For example, heat-resistant materials such as polyimide, polysulfone, polyethersulfone, polyarylate, polyallylsulfone, polyphenylene ether, epoxy resin, etc. A resin can be exemplified. Among these resins, the glass transition temperature is 140
° C or higher, preferably 170 ° C or higher, or a melting point of 22
A resin having a heat resistance of 0 ° C. or higher, preferably 240 ° C. or higher can be used.

Other materials for forming the heat insulating structure (layer) include metal compounds such as glass, alumina, zirconia, silica, magnesium oxide and titanium nitride, and heat-resistant materials such as ceramics. The materials used to form these heat-insulating structures (layers) include melt spray coating, solution or paste coating, curing or sintering, chemical vapor deposition, physical vapor deposition, and film-like simple substance. Are formed in advance and bonded, and a heat insulating structure can be formed by combining a plurality of these, including forming a metal layer.

The thickness of the heat insulating layer in the heat insulating structure is as follows:
It is not particularly limited, and can be appropriately set in consideration of the type of the resin to be molded, the filling thickness of the molten resin, other molding conditions, and the like. For example, the heat insulating layer portion is 0.1 to 5 mm, preferably 0.2 to 2 mm, and the surface metal layer is 0.01 to 0.2 mm.
5 mm, preferably 0.02 to 0.3 mm. Here, if the thickness of the surface metal layer is 0.01 mm or less, the strength of the metal layer may be insufficient, and the protection effect of the heat insulating layer may be inferior. If it is 0.5 mm or more, the heat insulating effect may be reduced.

It is to be noted that a surface layer can be further formed on the surface metal layer. The effect of the surface layer in this case is to improve the releasability, and examples thereof include fluororesin, silicone resin, and fluororesin-dispersed metal plating. Due to this layer, even if the cooling is delayed more than other general parts, the molding cycle is shortened without hindering the overall cooling after the cooling, and the molded product is easily released from the mold.

Next, the molding method of the present invention will be described with reference to the drawings. FIG. 1 and FIG. 2 are conceptual diagrams showing a mold portion and a mold operation during molding according to an embodiment of the present invention. FIG.
Shows a state in which a thermoplastic resin containing fibers and having melt-expandability is injected into the molding die cavity in which the skin material is mounted. FIG. 2 shows a state after the mold cavity is expanded and a thermoplastic resin containing fibers and having expandability is expanded.

In FIG. 1, 1 is a fixed mold, 2 is a movable mold, 3 is a movable mold, 4 is a sprue, 5 is a gas injection pipe, 6
Is a gas exhaust pipe, 7 is a heat insulating structure, 8 is a mold cavity, 9
Denotes a skin material, 10 denotes a molten resin, and 11 denotes a molded product.

With reference to the drawings, a method for molding a skin-integrated lightweight resin molded product using a thermoplastic resin containing fibers and having expandability will be described. Moving mold 2 with respect to fixed mold 1
Are clamped, and the clearance of the mold cavity 8 can be expanded and contracted by moving the movable mold 3 forward and backward. The fixed mold 1 has a heat insulating structure 7 on its cavity surface. In the mold cavity shown in FIG. 1, the skin material thickness + (clearance: D1) as a resin foam sheet is usually set.

A molten thermoplastic resin containing an amount of fiber corresponding to the clearance D2 and having expandability is melt-plasticized and kneaded by a plasticizer (not shown) and injected into the cavity in this state. Resin 10 is obtained. Usually, at the same time as or slightly after the start of injection of the molten resin, the movable mold 3 is moved forward to compress the molten resin 10 together with the skin material 9 and completely fill the mold cavity with the molten resin (D
2).

By this resin compression and filling, the molten resin is cooled from the mold surface. Here, cooling of the molten resin on the skin material insertion side is delayed due to the heat insulating property of the skin material. Also, even in a fixed mold that is on the anti-skin material side without the skin material,
Due to the heat insulation structure, cooling is delayed.
Thereby, both surfaces of the molten resin are cooled substantially simultaneously, and skin layers are formed on both sides of the molten resin. Here, even if the foamed resin sheet is used for the skin material,
Since the foamed sheet is compressed together with the molten resin and becomes dense, it does not exhibit extreme heat insulating properties, and thus has little effect on the molding cycle.

Next, the movable mold 3 is retracted to the position where the clearance of D3 is secured as the molten resin containing the fiber, and the molten thermoplastic resin containing the fiber expands, thereby obtaining a molded resin product with an integral skin. . In this case, a part of the skin material may be able to be further integrated as the molten resin enters. Next, the molded product is taken out by retracting the movable mold.

As the molding die used in the first invention of the present application, preferably, a surface other than the movable die surface having the skin material can have a heat insulating structure. That is, it can be provided on the sliding surface between the movable mold 2 and the movable mold 3 and on the movable mold surface when the skin material is partial. Although a flow path for gas injection is shown in the drawings, it may be provided if necessary. In addition, although the sprue and the gas injection pipe are provided in the fixed mold, a means of the side gate and the side injection from the moving mold side may be employed in some cases.

Next, the second invention of the present application is characterized in that the molding is performed with a difference in the mold temperature, instead of the cooling control using the heat insulating structure of the molding die of the first invention. That is, the temperature of the mold without the skin material is higher than the temperature of the mold with the skin material by 20 ° C. or more, preferably 30 ° C. or more. Here, the mold temperature is controlled by independently controlling the temperature of the fixed mold and the movable mold.

Here, as the control of the mold temperature, a circulation system of the heat medium oil is generally used. In this case, it is possible to adopt a method in which the temperature of the heat medium oil circulating between the fixed mold and the movable mold is set to a temperature difference corresponding to each, or a method of setting a difference in the circulation amount.

According to the invention of the molding method of the present invention, the degree of heat insulation and the temperature difference in the heat insulation structure of the mold and the temperature difference are determined by the material and type of the skin material, the type of the molten resin, the molding temperature,
It can be appropriately determined in consideration of the melt fluidity, the fiber content, the initial filling thickness of the molten resin, and the like.

The thermoplastic resin used in the present invention is not particularly limited. For example, polypropylene, propylene-ethylene block copolymer, propylene-ethylene random copolymer, polyolefin resin such as polyethylene, and polystyrene resin Resin, ABS resin, polyvinyl chloride resin, polyamide resin, polyester resin, polyacetal resin, polycarbonate resin,
A polyaromatic ether or thioether resin, a polyaromatic ester resin, a polysulfone resin, an acrylate resin, or the like can be used.

Here, the above-mentioned thermoplastic resins can be used alone or in combination of two or more. Among such thermoplastic resins, polypropylene, block copolymers of propylene and other olefins, random copolymers, or polypropylene-based resins such as mixtures thereof, high-density polyethylene, polyamide-based resins, polycarbonate-based resins And a thermoplastic resin containing an acid-modified polyolefin resin modified with an unsaturated carboxylic acid or a derivative thereof, a polyolefin resin, and particularly a polypropylene resin.

An acid-modified polyolefin resin modified with an unsaturated carboxylic acid or a derivative thereof improves the interfacial adhesive strength between a resin such as glass fiber or a filler such as talc and the resin, and consequently the physical properties of the molded article are improved. This is preferable because it contributes to improvement of long-term stability and promotes resin impregnation into the fiber bundle.

The unsaturated carboxylic acids used for the modification include, for example, acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, crotonic acid, citraconic acid, sorbic acid, mesaconic acid, angelic acid and the like. And derivatives thereof include acid anhydrides, esters,
Examples include amides, imides, metal salts, and the like. For example, maleic anhydride, itaconic anhydride, citraconic anhydride, methyl acrylate, methyl methacrylate, ethyl acrylate, butyl acrylate, monoethyl maleate, acrylamide, monoamide maleate , Maleimide, N-butylmaleimide, sodium acrylate, sodium methacrylate and the like.

Of these, unsaturated dicarboxylic acids and derivatives thereof are preferred, and maleic anhydride and fumaric acid are particularly preferred. As the acid-modified polyolefin-based resin, the unsaturated carboxylic acid and the derivative thereof are added in an amount of 0.
The content is preferably in the range of 01 to 20% by mass, and more preferably 0.02 to 10% by mass, and particularly preferably maleic anhydride- or fumaric acid-modified polypropylene-based resin.

The fibers used in the expanded thermoplastic resin containing fibers in the method for molding a skin-integrated lightweight resin molded article of the present invention include glass fibers, carbon fibers, copper fibers, brass fibers, and steel. Fiber, stainless steel fiber, aluminum fiber, aluminum alloy fiber, titanium alloy fiber, boron fiber, inorganic fiber such as silicon carbide fiber, alumina fiber, silicon nitride fiber, zirconia fiber, aramid fiber, polyamide imide fiber, polyester fiber, polyamide fiber And organic fibers such as polyarylate fibers and ultrahigh molecular weight polyethylene fibers. Of these, continuous fibers such as glass fiber, carbon fiber, and metal fiber are preferable, and glass fiber is particularly preferably used. In addition, a plurality of these fibers can be used as necessary.

Here, as the glass fiber, glass fibers such as E-glass and S-glass having an average fiber diameter of 25 μm or less, particularly in the range of 3 to 20 μm can be preferably used. When the diameter of the glass fiber is less than 3 μm, the glass fiber does not conform to the resin during the production of the fiber-reinforced pellet, and it becomes difficult to impregnate the resin.
If it exceeds 0 μm, cutting and chipping are likely to occur during melt-kneading.

For the molding method of the skin-integrated lightweight resin molded article of the present invention, for example, a fiber-reinforced pellet produced by a drawing method using a thermoplastic resin and continuous fibers can be used as a molding material. A preferred example of the molding raw material pellet is a fiber-reinforced pellet containing fibers having a length of 3 to 100 mm and having substantially the same length as the fiber length.

That is, fibers having a length equal to the total length of the pellets are arranged in parallel with each other and become 20 to 8 fibers.
The fiber is 10 to 80% by mass, preferably 15 to 70% by mass of the fiber reinforced pellet alone containing 0% by mass or a mixture of the fiber reinforced pellet and another resin pellet.
It is a molding raw material in mass%. The use of pellets in which the fibers are arranged in parallel to each other and contained 20 to 80% by mass of the total makes it difficult for the fibers to break even when plasticizing and kneading with the screw of the injection device, and to disperse the fibers. The property is also good. Thereby, the length of the fiber present in the injection molten resin can be kept relatively long, and the expansion property of the molten resin can be easily improved. In addition, the physical properties and surface appearance of the molded product are improved.

In the case where the pellets are produced by a pultrusion method or the like when the fibers are glass fibers, the glass fibers are surface-treated with a coupling agent, and then treated with a sizing agent.
100 to 10000, preferably 150 to 5000
It is desirable to bundle them in the range of the book. The coupling agent can be appropriately selected from so-called silane coupling agents and titanium coupling agents that have been conventionally used. For example, γ-aminopropyltriethoxysilane, N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxy Amino silane such as silane or epoxy silane can be employed. In particular, it is preferable to employ the amino silane compound.

A glass fiber reinforced resin pellet is manufactured by attaching and impregnating a thermoplastic resin to the glass fiber converged by the above-mentioned converging agent. As a method of attaching and impregnating a thermoplastic resin to glass fibers, for example, a method of passing a fiber bundle through a molten resin and impregnating the resin with the fiber, a method of impregnating the fiber bundle through a coating die, or a method using a die A method in which the molten resin adhering around the fibers is spread and impregnated into the fiber bundle can be adopted.

Here, in order to make the fiber bundle and the resin well blended, that is, to improve the wettability, the fiber bundle is pulled out through the tensioned fiber bundle into the inside of the die provided with the uneven portion on the inner periphery. After the fiber bundle is impregnated with the molten resin, a pultrusion method in which a step of pressing the fiber bundle with a pressure roller is further incorporated may be employed. In addition, if the glass fiber and the molten resin are compatible with each other, if the wettability is good, the molten resin is easily impregnated into the glass fiber,
Since the production of pellets is facilitated, the step of converging the fibers with the above-mentioned converging agent may be omitted in some cases.

Here, as a method of making the resin compatible with each other, a method of imparting polarity to the resin or grafting a functional group which reacts with the coupling agent on the surface of the glass fiber is effective. Furthermore, after treating the glass fiber bundle with a liquid material such as liquid paraffin having a boiling point equal to or higher than the melting temperature of the molten resin at the time of impregnation, a plurality of fiber bundles are introduced in a separated state into the resin impregnation section, and the A method of integrating the bundle is also preferable. By this method, the impregnation of the resin is improved,
High speed pultrusion molding becomes possible.

By cutting the resin-impregnated strand or the like along the longitudinal direction of the fiber by the method described above, a fiber-reinforced resin pellet containing a long fiber having the same length as the entire length of the pellet can be obtained. Can be. At this time, the pellets are not limited to those obtained by cutting the resin-containing long fiber bundle in which the fiber bundle is made into a strand and the cross-sectional shape of which is substantially circular.
By arranging the fibers flat, a sheet-shaped, tape-shaped or band-shaped resin-containing long fiber bundle may be cut into a predetermined length.

In the method for molding a skin-integrated lightweight resin molded product of the present invention, foaming can be used together if necessary. The amount of the foaming agent is merely to assist expansion, and the amount of the foaming agent is, for example, about 0.05 to 5% by mass, and preferably about 0.1 to 1% by mass. here,
The type of the foaming agent is not limited as long as it decomposes by heat to generate gas. For example, oxalic acid derivatives, azo compounds, hydrazine derivatives, semicarbazides, azide compounds, nitroso compounds, triazoles, ureas and related compounds, nitrites, hydrides, carbonates, bicarbonates and the like can be employed. More specifically, azodicarbonamide (ADCA), benzenesulfohydrazide, N, N-dinitropentamethylenetetramine,
Terephthalazide can be used.

Further, in order to form the skin-integrated lightweight resin molded product of the present invention, an antioxidant, an ultraviolet absorber, an antistatic agent, a weathering agent, a light stabilizer, and a colorant may be added to the raw material resin, if necessary. And fillers such as short glass fiber and talc.

Next, the skin material used in the present invention is not particularly limited, and can be arbitrarily selected depending on the use and function of the molded article. For example, resin foam sheet, surface embossed pattern / printed pattern sheet, film, woven fabric, nonwoven fabric, elastomer sheet, film, ordinary sheet,
Examples include films, trees, particle boards, and the like, or a multilayer material composed of a plurality of these materials.

Next, when a gas injection molding method is used as a molding method of the skin-integrated lightweight resin molded article of the present invention, nitrogen or the like is injected from an injection nozzle, a runner, or a gas injection pin provided on the cavity wall. Is injected into the molten resin in the cavity. Gas injection is generally
This is performed after the retreat of the movable mold starts. In the present invention, the gas injection is performed while the movable mold is retracted, unlike the general gas injection molding method. Therefore, the pressure in the cavity is relatively low, and the pressure of the injected gas is generally 5
A low gas pressure of less than or equal to MPa, especially less than or equal to 2 Mpa, is sufficient.

The molding method of the skin-integrated lightweight resin molded product of the present invention is characterized in that the molten resin is injected into the mold cavity in which the skin material is mounted, or the injection molding is performed to fill the mold cavity with the molten resin and then move. This is a molding method of a skin-integrated lightweight resin molded product in which a mold is retracted to expand a molten resin. That is, when expanding the cavity volume by retreating the movable mold, the thermoplastic resin portion containing the fiber on the skin material side also includes
This is to form an apparent high-density layer corresponding to the skin layer on the general surface.

In the case of injecting a gas, the injected gas must be circulated while exhausting the gas to the outside while maintaining a certain pressure (ensure shapeability) during the cooling step of the molded article. Is preferred. Accordingly, the molded product is uniformly cooled by the flowing gas even though it is a skin-integrated lightweight resin molded product, and the cooling efficiency and the molding cycle can be improved.

Next, the skin-integrated lightweight resin molded article of the present invention
Is, the surface density of the resin part containing fibers excluding the skin material,
0.2-2.5 g / cm^Two, Preferably 0.3 to 2 g /
cm ^TwoIt is a skin-integrated lightweight resin molded product. Also,
In the molded article of, preferably the skin material has a foam layer
It is a molded product. That is, the conventionally proposed molding method
In this way, good molded products with low areal density
Shapes could not always be obtained. That is,
If the cavity expansion after filling is faster,
It becomes difficult to form the skin layer equivalent part, and the skin layer equivalent part
If the priority is given to the formation of the
However, skin layers should be formed on both sides of the molten resin part.
There was a difficulty in satisfying both swelling and expansion properties.

According to the method for molding a skin-integrated lightweight resin molded article of the present invention, a wide range of skin-integrated lightweight resin molded articles, including the specific skin-integrated lightweight resin molded article of the present invention, can be manufactured. The lightweight resin molded article of the present invention is excellent in strength, rigidity, heat insulation, sound absorbing properties, etc., while being lightweight, and has surface properties of the skin material, so that it can be used for automobile parts, home appliances, 0A equipment, furniture, construction, It is possible to expand the application fields as various molded articles in the civil engineering field and the like. In particular, application to molded articles having a high degree of weight reduction per molded article area, which has been difficult in the past, is expected.

[0053]

Next, the effects of the present invention will be described based on specific examples, but the present invention is not limited to these examples.

Example 1 Glass fiber-reinforced polypropylene pellets in which glass fibers (fiber diameter: 13 μm) are arranged in parallel and whose content is 60% by mass and length is 16 mm (containing 3% by mass of maleic anhydride-modified polypropylene) ) 60% by mass and melt index [MI: 230 ° C, 21.2 N (2.16 kg)
f)] is 500 g / 10 min polypropylene pellet 4
0% by mass was dry blended to obtain a raw material for molding.

The injection molding machine is provided with a screw having a mold clamping force of 450 t and a compression ratio of 1.8 (to prevent glass fiber breakage as much as possible). A molding device equipped with an Idemitsu IPM unit for moving the mold forward and backward was used. The molding die is 6
The heat-insulating mold was made of a 1 mm thick epoxy resin layer on the cavity surface of the fixed mold and a 0.5 mm nickel layer on the cavity surface of the fixed mold. Further, a gas injection pin for injecting a low-pressure gas was provided on the fixed mold side.

The mold is opened, and the thickness of the movable mold is 3 mm.
Then, a skin material consisting of a surface layer (textured surface PVC) / polyurethane foam layer was attached, and the mold was closed so that the mold cavity thickness became 3 mm (thickness excluding the skin material). A molten resin obtained by melt-kneading and plasticizing and measuring the amount of resin corresponding to the thickness of the mold cavity and 1 mm was injected into the mold cavity. After the start of injection, the movable mold was advanced and compressed, and the molten resin was completely filled. Two seconds after the completion of the compression, the movable mold was retracted so that the mold cavity thickness became 2.5 mm (thickness excluding the skin material). Two seconds after the start of the retreat of the movable mold, a nitrogen gas of 2 MPa was injected into the inside of the molded product. Other molding conditions are as follows: resin temperature = 250 ° C., mold body temperature = 6
0 ° C. After cooling, the mold was opened to obtain a molded product. Table 1 shows the evaluation results of the molded articles.

Example 2 In Example 1, an ordinary mold was used in place of the heat-insulating mold as the fixed mold, and the molding mold temperature was set to 50 ° C. for the movable mold (skin-mounted side). A molded product was obtained in the same manner as in Example 1 except that the fixed mold was set to 90 ° C. Table 1 shows the evaluation results of the molded articles.

Comparative Example 1 A molded product was obtained in the same manner as in Example 2 except that the temperature of the molding die was set at 50 ° C. and the fixed die was set at 50 ° C. Was. Table 1 shows the evaluation results of the molded articles.

Comparative Example 2 A molded product was obtained in the same manner as in Example 1 except that the movable mold was not retracted and gas was not injected. Table 1 shows the evaluation results of the molded articles.

Example 3 Glass fiber reinforced polypropylene pellets in which glass fibers (fiber diameter: 13 μm) are arranged in parallel with a content of 60% by weight and a length of 12 mm (containing 3% by weight of maleic anhydride-modified polypropylene) ) Polypropylene pellets 40 having 60% by mass and a melt index of 60 g / 10 min.
With respect to 100 parts by mass of a pellet composed of 100% by mass, a foaming agent master batch pellet [Polyslen EE (foaming agent 10
1.5 mass parts was dry-blended to obtain a raw material for molding.

Using the same injection molding apparatus as in Example 1, the mold was opened, and a 2 mm-thick skin material composed of a surface layer (textured surface PVC) / polyurethane foam layer was mounted on the movable mold surface. The mold was closed so that the mold cavity thickness was 3 mm (thickness excluding the skin material). A molten resin obtained by melt-kneading and plasticizing and measuring a resin amount corresponding to a mold cavity thickness of 1.5 mm was injected into the mold cavity.
After the start of the injection, the movable mold was advanced and compressed, and the molten resin was completely filled. Two seconds after the completion of the compression, the movable mold was retracted so that the mold cavity thickness became 3.0 mm (the thickness excluding the skin material). Two seconds after the start of the retreat of the movable mold, a nitrogen gas of 2 MPa was injected into the inside of the molded product. Other molding conditions are as follows: resin temperature = 250 ° C., mold body temperature = 70
° C. After cooling, the mold was opened to obtain a molded product. Table 1 shows the evaluation results of the molded articles.

Comparative Example 3 A molded product was obtained in the same manner as in Example 3 except that a pellet consisting of 40% by mass of a polypropylene pellet having a melt index of 60 g / 10 min was used instead of the glass fiber reinforced pellet. Was. Table 1 shows the evaluation results of the molded articles.

[0063]

[Table 1]

[0064]

According to the present invention, the back surface of the skin material, that is, the skin material and the fiber, particularly in the case of a skin material having heat insulating properties such as a foam layer and a fiber layer, in the molding of the skin material-integrated lightweight resin molded product. Can be increased in the density of the adhesive interface portion with the resin containing. It is possible to obtain a skin-integrated lightweight molded product in which the density of both sides of the fiber-reinforced lightweight resin portion is high and the strength and the like correspond to the case without the skin. In particular, the thickness of the cavity at the time of injection of the molten thermoplastic resin containing fibers and having expandability,
As in the case of 2 mm or less, that is, the areal density of the resin portion containing the fibers excluding the skin material is 0.1 to 2.5 g / c.
A lightweight resin molded product of m ² can be suitably obtained.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing a mold portion and a mold operation at the time of molding according to an embodiment of the present invention, in which a molding cavity in which a skin material is mounted contains fibers and has a thermal expansion property. This shows a state where a plastic resin is injected.

FIG. 2 shows a state after expanding a mold cavity and expanding a thermoplastic resin containing fibers and having expandability.

[Explanation of symbols]

 1: fixed mold 2: movable mold 3: movable mold 4: sprue 5: gas injection pipe 6: gas discharge pipe 7: heat insulating structure 8: mold cavity 9: skin material 10: molten resin 11: molded product

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // B29K 101: 12 B29K 101: 12 105: 12 105: 12 B29L 9:00 B29L 9:00 F term ( 4F202 AA11 AB25 AC01 AD05 AD08 AD16 AG03 AH17 AH39 AH48 AH51 AJ03 AJ06 AJ09 CA11 CB01 CB13 CK19 CK90 CQ01 4F206 AA11 AB25 AC01 AD05 AD08 AD16 AJ03 AJ06 AJ09 JA03 JA07 JB13 JL81 JN81

Claims (7)

[Claims] 1. A molding method for injecting or injecting and compressing a molten thermoplastic resin having fibers and having expandability into a molding die cavity in which a skin material is mounted, and then expanding the cavity, wherein the skin is mounted. A method of molding a skin-integrated lightweight resin molded product, characterized in that a mold surface having a heat insulating structure is used for a mold surface facing the mold surface. 2. The molding method of a skin-integrated lightweight resin molded article according to claim 1, wherein the heat insulating structure has a layer made of a heat-resistant resin and / or a ceramic. 3. The integral skin according to claim 1, wherein the heat insulating structure is formed of a heat insulating layer having a thickness of 0.1 to 5 mm and a metal layer having a thickness of 0.01 to 0.5 mm on the heat insulating layer. Molding method for lightweight resin molded products. 4. The molten thermoplastic resin containing fibers and having expandability contains fibers having a length of 3 to 100 mm, and at least a part of a fiber-reinforced resin pellet having a length substantially the same as the fiber length. The method for molding a skin-integrated lightweight resin molded product according to any one of claims 1 to 3, wherein the raw material containing the resin is melted and the fiber content is 10 to 80% by mass. 5. A molding method for injecting or injecting and compressing a thermoplastic resin containing fibers and having expandability into a molding die cavity in which a skin material is mounted, and then expanding the cavity, wherein the skin material is mounted. A method for molding a skin-integrated lightweight resin molded product, wherein the temperature of a mold not to be heated is 20 ° C. or more higher than the temperature of a mold equipped with a skin material. 6. The molten thermoplastic resin containing fibers and having expandability contains fibers having a length of 3 to 100 mm, and at least a part of fiber-reinforced resin pellets having substantially the same length as the fiber length. The method for molding a skin-integrated lightweight resin molded product according to claim 5, wherein the raw material containing the resin is melted and the fiber content is 10 to 80% by mass. 7. A lightweight resin molded article with integral skin, wherein the surface density of the resin portion containing fibers excluding the skin material is 0.2 to 2.5 g / cm ² .