JPH06210782A - Porous molded product of fiber-reinforced thermally plastic resin and its production - Google Patents

Abstract

PURPOSE:To improve the mechanical nature of a fiber-reinforced porous molded product by thermally expanding a fiber-reinforced thermoplastic resin sheet molding material, then allowing a heated inorganic filler-containing thermoplastic resin layer to be present between these sheet molding material pieces and molding the pieces in a cooled condition under pressure, using a preparation method. CONSTITUTION:A compound sheet molding material 4 is composed of a fiber- reinforced thermoplastic resin sheet molding material 1, a fiber-reinforced thermoplastic resin layer 2 and an inorganic filler-containing thermoplastic resin layer 3. That is, thermoplastic resin containing 3 to 30vol.% of inorganic filler is present between fiber-reinforced thermoplastic resin layers 2 which is molded using a sheet molding material by a preparation method and has 10vol.% min of reinforcing fiber content and 0.2 to 1.0g/cm<3> of apparent density. Further, said resin layers 2 become bonded together by permeation of the thermoplastic resin into the continuous foam of the resin 2. Thus the mechanical nature of the porous molded product is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fiber-reinforced thermoplastic resin porous molded article and a molding method thereof. The porous molded article according to the present invention can be widely used for industrial materials such as automobile parts, construction, and civil engineering, for which wood has been conventionally used.

[0002]

2. Description of the Related Art In recent years, due to global environmental problems, the cutting of South Sea timber has been regarded as a problem. Conventionally, Nanyo wood has been processed into plywood, and has been used in large quantities for vehicle materials such as buses and trucks, industrial materials such as construction and civil engineering, and development of alternative materials is desired. As a substitute for wood, fiber-reinforced thermoplastic resin molded products composed of relatively long reinforcing fibers and thermoplastic resin have attracted attention because of their lightness and relatively high strength and rigidity. ing.

Since most of the wood substitutes are used as a plate, their mechanical properties such as bending strength and bending rigidity and weight reduction are important. In terms of material mechanics, the bending strength is 2 of the plate thickness.
The power and bending rigidity are proportional to the cube of the plate thickness. A method for producing a porous molded article using a sheet-shaped molding material by a papermaking method (Japanese Patent Publication No. 52-12283 and Japanese Patent Publication No. 55-9119) is used as a method of utilizing the merit of improving mechanical properties and weight saving. JP-A-60-179234 and JP-A-62.
No. 161529) has been proposed.

This sheet-shaped molding material is produced by applying a papermaking technique to uniformly disperse reinforcing fibers having a diameter of 3 to 30 μm and a length of 3 to 50 mm and a thermoplastic resin powder to produce a non-woven material,
It is manufactured by using this non-woven material as a raw material, heating, pressurizing, and further cooling. The porous molded article is molded by utilizing the sheet expansion that occurs when the sheet-shaped molding material is heated to the softening point or the melting point or higher of the matrix thermoplastic resin before molding.

The non-woven material produced by the paper-making method has the property of being very bulky because the reinforcing fibers are dispersed in the form of monofilaments (single fibers). The thickness of the non-woven material varies depending on the content of reinforcing fibers, its shape, and papermaking conditions, but is about 10 times as thick as that of a sheet from which voids are generally used as a sheet-shaped forming material. The heating of the sheet-shaped molding material weakens the binding force of the thermoplastic resin to the reinforcing fibers, so that the residual stress of the reinforcing fibers is released, and the sheet-shaped molding material expands due to the springback to return to the original state.

This expanded sheet-shaped forming material is inserted into a forming die, and a clearance is set within the expanded sheet thickness and within a range in which an enclosing void is left, and pressure is applied under the condition that a desired expansion ratio is obtained. Then, a porous molded product is manufactured by cooling and molding. The porous molded article has a reduced strength per unit area and elastic modulus due to expansion, but the bending strength and flexural rigidity of the article are improved due to an increase in plate thickness.

However, according to this method, when the thickness of the sheet-shaped molding material is large, the intended improvement in mechanical properties could not be obtained as described below. An example of a conventional method for molding a porous molded article is shown in FIG. Sheet-shaped molding material 1
Is generally heated in the far-infrared heating furnace 5 to a temperature above the softening point or melting point of the thermoplastic resin. The expansion of the sheet-shaped molding material starts from the surface of the sheet that is first heated, and gradually expands as the heat reaches the center of the plate thickness.
However, due to the expansion, a heat insulating air layer is formed inside the sheet, so that the thermal conductivity is reduced. Since the sheet is heated in a state where heat is not sufficiently transmitted to the inside, thermal deterioration of the thermoplastic resin occurs due to local heating on the surface of the expanded sheet. As a result, in the case of heating a sheet-shaped forming material having a large plate thickness, it is necessary to avoid local heating of the surface, so that a layer (9) which is expanded in the vicinity of the surface is formed and a layer (10) which is hardly expanded inside is formed. To form. This heated sheet-shaped forming material is inserted into the cooling press platen 7, the clearance is set to be equal to or less than the thickness of the expanded sheet, and pressurization and cooling-molding are performed under the condition of obtaining a target expansion ratio to obtain a porous sheet. The quality molded product 11 is manufactured. For this reason, when the porous molded article is bent, the surface portion to which a tensile load and a compressive load are applied has a mechanically weak structure, and the mechanical properties deteriorate.

[0008]

DISCLOSURE OF THE INVENTION The present invention provides a fiber-reinforced thermoplastic resin porous molded article and a method for molding the same for the purpose of improving such mechanical properties.

[0009]

The gist of the present invention is as follows. (1) A thermoplastic resin containing 3 to 30% by volume of an inorganic filler is formed from a sheet-shaped molding material by a papermaking method, has a reinforcing fiber content of 10% by volume or more, and an apparent density of 0.2 to 1. The fiber-reinforced thermoplastic resin layer is present between 0 g / cm ³ of the fiber-reinforced thermoplastic resin layer and penetrates into the continuous cells of the fiber-reinforced thermoplastic resin layer to bond the fiber-reinforced thermoplastic resin layers to each other. Plastic resin porous molded product.

(2) Reinforcing fiber content by the papermaking method is 10
3% or more of the fiber-reinforced thermoplastic resin sheet-shaped forming material was heated and expanded by utilizing the springback of the reinforcing fiber, and then heated between these sheet-like forming materials.
Fiber-reinforced thermoplastic resin porous molding according to the above (1), characterized in that the thermoplastic resin layer containing 30% by volume of an inorganic filler is pressed, cooled and molded to integrate the whole. Molding method.

(3) Reinforcing fiber content by the papermaking method is 10
A fiber-reinforced thermoplastic resin sheet-shaped molding material having a volume% or more, a fiber-reinforced thermoplastic resin layer having a reinforcing fiber content of 10 volume% or more by a papermaking method, and a thermoplastic resin layer containing 3 to 30 volume% of an inorganic filler. The composite sheet-shaped molding material consisting of is heated and expanded by utilizing the springback of the reinforcing fiber, and then the sheet-shaped molding material is pressurized and cooled while the thermoplastic resin layer is interposed between them. The method for molding a fiber-reinforced thermoplastic resin porous molded article according to (1) above, which comprises molding and integrating the whole.

An example of the method for molding the fiber-reinforced thermoplastic resin porous molded article of the present invention is shown in FIG. As the sheet-shaped molding material, a composite sheet-shaped molding material 4 including a fiber-reinforced thermoplastic resin sheet-shaped molding material 1, a fiber-reinforced thermoplastic resin layer 2 and an inorganic filler-containing thermoplastic resin layer 3 is used. The sheet-shaped molding material 1 is manufactured by heating, pressurizing, and cooling-molding a non-woven material made of a reinforcing fiber and a thermoplastic resin manufactured by a papermaking method. The composite sheet-shaped molding material 4 is manufactured by laminating an inorganic filler-containing thermoplastic resin film on one surface of a non-woven material composed of reinforcing fibers and a thermoplastic resin manufactured by a paper-making method, and heating, pressurizing, and cooling molding. It These sheet-shaped molding materials are heated in the far-infrared heating furnace 5 to the softening point or melting point of the thermoplastic resin or higher. The heating of the sheet-shaped molding material weakens the binding force of the thermoplastic resin to the reinforcing fibers, so that the residual stress of the reinforcing fibers is released, and the sheet-shaped molding material expands due to the springback to return to the original state. This expansion starts from the surface of the sheet to be heated first and gradually expands as the heat reaches the center of the plate thickness. On the surface of the heated sheet-shaped molding material 1 and the surface of the composite sheet-shaped molding material 4 where the inorganic filler-containing thermoplastic resin film is not laminated, the reinforcing fibers are exposed by springback, and the thermoplastic resin is exposed inside the expansion sheet. The amount of resin decreases due to absorption. On the surface of the composite sheet-shaped molding material 4 on which the inorganic filler-containing thermoplastic resin film is laminated in advance, the resin-rich layer 6 in which the reinforcing fibers are covered with the inorganic filler-containing thermoplastic resin is formed. The sheet-shaped molding material 1 and the composite sheet-shaped molding material 4 are laminated so that the resin-rich layer is interposed therebetween, and are inserted into the cooling press board 7 and the clearance is expanded to the thickness of the sheet-shaped molding material or less. Then, the porous molded article 8 of the present invention is molded by setting it in a range where the voids to be included therein are left, and pressurizing and cooling molding under the condition of obtaining a desired expansion ratio.

Also in the sheet-shaped molding material used in the present invention, its thermal conductivity is lowered by thermal expansion, as in the conventional method. The adverse effect of this decrease in thermal conductivity was solved by reducing the initial thickness of the sheet-shaped molding material used, and a uniform expansion of the heated sheet-shaped molding material was realized. The thickness of the sheet-shaped molding material used in the present invention is preferably 3.5 mm or less.

The expanded sheet-shaped molding material has a structure in which the intersections of the reinforcing fibers are three-dimensionally fused with a thermoplastic resin, and most of the internal voids are open cells penetrating the surface. In addition, the resin-rich layer of the composite sheet-shaped molding material is formed because the addition of the inorganic filler increases the melt viscosity of the thermoplastic resin and suppresses the absorption into the inside of the sheet-shaped molding material that has been heated and expanded. In the present invention, when the sheet-shaped molding material is laminated, a resin-rich layer of the composite sheet-shaped molding material is interposed between the two, and by pressurizing and cooling molding, the expanded foam of the sheet-shaped molding material is formed into continuous cells. The resin penetrates and solidifies by cooling to improve the interlayer strength by the anchor effect. The porous molded article of the present invention exhibits good mechanical properties due to the uniform expansion of the fiber-reinforced thermoplastic resin layer and the improvement of the interlaminar strength between the two layers.

The apparent density of the porous molded article according to the present invention is determined by the clearance setting during molding according to the expansion of the sheet-shaped molding material. Therefore, the range of apparent density is 0.2 to 1.0 g / cm ^3, which is the range of sheet expansion due to the springback of the reinforcing fibers. The apparent density is
It is represented by a value obtained by dividing the weight of the porous molded article by its volume.

The reinforcing fibers used as the raw material for the non-woven material include:
In addition to glass fiber, carbon fiber and metal fiber, inorganic fiber and organic fiber are used. The shape of the reinforcing fiber is preferably 3 μm or more in diameter from the viewpoint of easy handling and economical, and 30 μm or less in order to express sufficient strength, and the fiber length is 3 mm or more from the viewpoint of strength development and is uniform. It is desirable to set the thickness to 50 mm or less, which allows various dispersion. The reinforcing fiber is a water-soluble polymer for improving hydrophilicity for the purpose of good dispersion in water, a wetting agent, and a silane coupling agent for improving adhesiveness with the thermoplastic resin for expressing strength. For example, it is desirable to perform surface treatment.

The thermoplastic resin includes polyethylene, polypropylene, polystyrene, styrene-butadiene-acrylonitrile copolymer, styrene-acrylonitrile copolymer, holamide, polycarbonate, polyacetal, polyethylene terephthalate, polybutylene terephthalate, polyphenylene oxide, polysulfone, polyphenylene sulfide. Such as a plasticizer, a heat stabilizer, a light stabilizer, a filler, and the like, which also include a mixture of two or more of these resins.
It is also possible to add dyes and pigments, impact resistance agents, extenders, nucleating agents, processing aids and the like. The shape of the thermoplastic resin is appropriately selected from pellets, powders, flakes, and fibrous shapes.

The content of the reinforcing fiber is 10% by volume or more at which stable expansion due to springback occurs, and the reinforcing fiber and the thermoplastic resin can be adhered to each other to sufficiently exhibit the mechanical properties as a porous molded article. It is desirable to set the volume% or less.

Since the matrix resin of the thermoplastic resin film containing an inorganic filler to be laminated on the non-woven material needs to be fused with the fiber-reinforced thermoplastic resin layer to form a porous molded article, the thermoplastic resin of the non-woven material is It is common to use the same as the resin, but in the case of improving the adhesive strength for the purpose of improving the interlayer strength, a thermoplastic resin according to the purpose, a modified resin such as maleic anhydride modified, or a hot melt type resin is used. Adhesive resins may be used as well as mixtures with those resins.

As the inorganic filler, calcium carbonate,
Fine particle fillers such as talc, flake fillers such as mica, fibrous fillers such as chopped glass fibers and rock wool fibers are used. The inorganic filler is preferably surface-treated with a silane coupling agent or the like in order to improve the adhesiveness with the thermoplastic resin. The amount of the inorganic filler added is 3% by volume or more for the purpose of increasing the melt viscosity of the thermoplastic resin, and 30% by volume or less that allows stable film formation. The thickness of the thermoplastic resin film is appropriately selected from the range of 0.1 to 2 mm depending on the expansion ratio of the fiber reinforced thermoplastic resin layer.

In FIG. 1, a method for forming a porous molded product by laminating two sheet-shaped molding materials so that a resin-rich layer is interposed between them has been described. It is appropriately selected according to the purpose of the molded product, particularly the thickness of the molded product. That is, when the thickness of the porous molded product is large, it is desirable to stack three or more sheet-shaped molding materials in order to make the expanded state of the fiber-reinforced thermoplastic resin layer that affects the mechanical properties thereof uniform. .

In the present invention, when a thermoplastic resin film to which an inorganic filler is not added is used, it is necessary to increase the film thickness in order to form a stable resin rich layer on the surface of the composite sheet-shaped molding material. Therefore, it is not effective because it increases the weight of the product.

In the porous molded article of the present invention, a sheet-shaped molding material that has been uniformly expanded is laminated, and the two are firmly bonded by the anchor effect of the thermoplastic resin containing an inorganic filler. Mechanical properties are obtained.
Furthermore, the allowable range of thickness is expanded compared to the conventional method,
Beneficial results can be obtained as a fiber-reinforced thermoplastic resin porous molded product that takes advantage of the weight saving advantage.

[0024]

The present invention will be described in detail with reference to the following examples. Example 1 A glass fiber having a diameter of 10 μm and a length of 13 mm as a reinforcing fiber and a spherical pellet having a diameter of 3 mm as a thermoplastic resin were mechanically crushed, and the crushed product was sieved to from 70 mesh (opening diameter 0.212 mm) to 10 mesh (opening diameter). Using polypropylene resin powder classified to 1.7 mm), a glass fiber content of 45% by weight (22.3% by volume) and a polypropylene resin 55% by weight (77.7% by volume) were used for the basis weight by a papermaking method. A quantity of 2000 g / m ² of nonwoven material was produced.

The non-woven material is cut into 600 × 600 mm and 2
The sheets are stacked, stainless steel end plates are stacked on both sides, and inserted into a heating press platen whose temperature is set to 210 ° C. The temperature of the central part of the non-woven material is 190 ° C under the pressure of ² Kgf / cm ^2. Preheating was performed for about 5 minutes until the temperature was raised to the above. Next, pressurize at a pressure of 5 Kgf / cm ² for 1 minute, insert into a cooling press machine, pressurize at a pressure of 5 Kgf / cm ² for about 5 minutes,
After cooling and forming, the end plate was removed to form a sheet-shaped forming material having a plate thickness of 3.2 mm.

On the other hand, a non-woven material was cut into 600 × 600 mm pieces, and two pieces were superposed on each other, and 40% by weight of talc, which is a fine-particle inorganic filler having a diameter of 2 μm, was added to one surface of the polypropylene resin film (thickness: 0. 35 mm), and stainless steel end plates were superposed on both sides thereof, and a composite sheet-shaped molding material having a plate thickness of 3.6 mm was molded by the same method as the molding of the sheet-shaped molding material.

A porous molded article was molded by the method of the present invention shown in FIG. 1 using one sheet-shaped molding material and one composite sheet-shaped molding material. The sheet-shaped molding material and the composite molding material have a surface temperature of 220 by a far infrared heating furnace.
It heated for about 7 minutes until it heated up to ℃. Both of them expanded due to the springback of the glass fiber, and the expanded thickness was about 14 mm each. It was confirmed that the amount of resin on the surface of the heated sheet was reduced because the glass fiber was exposed by spring back and the polypropylene resin was absorbed inside the expanded sheet. However, it was confirmed that, on the surface of the composite sheet-shaped molding material on which the talc-containing polypropylene resin film was laminated, the exposure of the glass fiber was suppressed and a resin-rich layer was formed. Heated sheet-shaped molding material and composite sheet-shaped molding material are laminated so that this resin-rich layer is interposed between them, and inserted into a cooling press machine, and the clearance of the press machine is set by a spacer. A porous molded product having a plate thickness of 12 mm was molded by pressurizing and cooling at a pressure of 5 Kgf / cm ² for 5 minutes.

By optical microscope and scanning electron microscope observation,
The intersections of the glass fibers inside the porous molded product are efficiently adhered with polypropylene resin to achieve uniform expansion, and the talc-containing polypropylene resin is impregnated and solidified inside the open cells of the porous molded product between layers. Was confirmed. A test piece having a width of 70 mm and a length of 200 mm was sampled from the porous molded article and subjected to a three-point bending test with a span of 150 mm. The results are shown in Table 1.

Reference Example 1 A glass fiber content of 45% by weight (22.3) was obtained by a papermaking method using the glass fiber of Example 1 and polypropylene resin powder.
Volume%) and 55% by weight of polypropylene resin (77.7% by volume), and a non-woven material having a basis weight of 2100 g / m ² was produced. This non-woven material was cut into 600 × 600 mm pieces, four sheets were superposed, and stainless steel end plates were superposed on both sides thereof to form a sheet-shaped forming material having a plate thickness of 6.8 mm in the same manner as in Example 1. On the surface of the sheet-shaped molding material, the glass fibers were not exposed, and the resin-rich surface had a good appearance. In addition, by observation with an optical microscope and a scanning electron microscope,
It was confirmed that the glass fibers inside the sheet-shaped molding material were uniformly dispersed, and the thermoplastic resin was sufficiently impregnated between them. A test piece with a width of 70 mm and a length of 200 mm was sampled from this sheet-shaped molding material, and a three-point bending test with a span of 150 mm was performed. The results are shown in Table 1.

Comparative Example 1 The sheet-shaped molding material molded in Reference Example 1 was used as shown in FIG.
A porous molded article was molded by the conventional method shown in. The sheet-shaped molding material of Reference Example 1 was heated in a far infrared heating furnace for about 7 minutes until the surface temperature was raised to 220 ° C. At this time, the molding material is greatly expanded near the surface and the inside is not sufficiently heated, and the thickness after expansion is about 16 mm.
Met. It was also confirmed that the amount of resin on the surface was reduced because the glass fiber was exposed and the polypropylene resin was absorbed inside the expanded sheet. Insert the heated molding material into the cooling press machine, set the clearance of the press machine with the spacer, and press the pressure of 5 Kgf / cm ² for 5 minutes.
By pressurizing and cooling, a porous molded product having a plate thickness of 12 mm was molded.

By observation with an optical microscope and a scanning electron microscope,
It was confirmed that the expanded state of the inside of the porous molded product was extremely expanded near the surface and almost not expanded in the central part as well as in the molding material. This center layer was about 50% of the initial thickness of the molding material and had a thickness of 3.2 mm.
A test piece having a width of 70 mm and a length of 200 mm was sampled from the porous molded article and subjected to a three-point bending test with a span of 150 mm. The results are shown in Table 1.

In the porous molded article of Example 1, in the uniform expansion of the fiber-reinforced thermoplastic resin layer, the intersections of the glass fibers were efficiently adhered with the polypropylene resin, and the talc-containing polypropylene resin was provided inside the open cells between the laminated layers. Impregnation,
Good mechanical properties were obtained because it solidified and adhered firmly due to the anchor effect. The strength and elastic modulus per area are lower than those of the sheet-shaped molding material of Reference Example 1, but the bending strength (bending load) and bending rigidity (elastic gradient) of the product
Has been improved. The bending gradient is a load when the amount of deflection of the plate-shaped test piece is 2.5 mm in the three-point bending test and serves as an index of rigidity of the plate. Example 1 and Reference Example 1
Although the weight per unit area is the same, the plate thickness of Example 1 is about twice as thick as that of Reference Example 1 by expansion molding. This result is because the bending strength is proportional to the square of the product plate thickness, and the bending rigidity is proportional to the cube of the plate thickness, and it was confirmed that the rigidity is remarkably improved.

It was confirmed that the mechanical properties of Comparative Example 1 were lower than those of Example 1 and Reference Example 1. Comparative Example 1
In the porous molded product of, the expansion near the surface is very large,
The central part showed a structure with almost no expansion. Therefore, when the product is bent, the surface portion to which a tensile or compressive load is applied has a mechanically weak structure and mechanical properties are deteriorated.

[0034]

[Table 1]

[0035]

INDUSTRIAL APPLICABILITY As described above, the present invention provides a fiber-reinforced thermoplastic resin porous molded article and a molding method thereof as a method of utilizing the merit of improving the mechanical properties and weight saving of the fiber-reinforced thermoplastic resin. However, according to the present invention, the mechanical properties of the porous molded article are improved, and the allowable range of the thickness of the molded article is widened as compared with the conventional method, so that it has a beneficial result in applications such as wood substitutes.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of a method for molding a fiber-reinforced thermoplastic resin porous molded article of the present invention.

FIG. 2 is a schematic view showing an example of a conventional method for molding a fiber-reinforced thermoplastic resin porous molded article.

[Explanation of symbols]

 1 Fiber Reinforced Thermoplastic Resin Sheet Forming Material 2 Fiber Reinforced Thermoplastic Resin Layer 3 Inorganic Filler-Containing Thermoplastic Resin Layer 4 Composite Sheet Forming Material 5 Far Infrared Heating Furnace 6 Resin Rich Layer 7 Cooling Press Board 8 Porous of the Present Invention Molded product 9 Expanded layer 10 Almost unexpanded layer 11 Conventional porous molded product.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location B32B 27/12 8413-4F 27/20 I 8413-4F // B29K 105: 04 105: 08 B29L 9 : 00 4F (72) Inventor Takao Kimura 1 Toho-cho, Yokkaichi-shi, Mie Mitsubishi Petrochemical Co., Ltd. Yokkaichi Research Institute

Claims (3)

[Claims] 1. A thermoplastic resin containing 3 to 30% by volume of an inorganic filler, which is formed from a sheet-shaped molding material by a papermaking method, has a reinforcing fiber content of 10% by volume or more and an apparent density of 0.2 to Fibers present between 1.0 g / cm ³ of the fiber-reinforced thermoplastic resin layer, which penetrate into the continuous cells of the fiber-reinforced thermoplastic resin layer to bond the fiber-reinforced thermoplastic resin layers to each other. Reinforced thermoplastic resin porous molded product. 2. A fiber-reinforced thermoplastic resin sheet-shaped molding material having a reinforcing fiber content of 10% by volume or more produced by a paper-making method is heated and expanded by utilizing springback of the reinforcing fiber, and then these sheet-shaped moldings are formed. 3 to 3 heated between materials
The fiber-reinforced thermoplastic resin porous molded article according to claim 1, characterized in that the thermoplastic resin layer containing 0% by volume of an inorganic filler is intervened under pressure and cooling to integrate the whole. Molding method. 3. A fiber-reinforced thermoplastic resin sheet-shaped molding material having a reinforced fiber content of 10% by volume or more by a papermaking method, and a fiber-reinforced thermoplastic resin layer having a reinforced fiber content of 10% by volume or more by a papermaking method. After heating a composite sheet-shaped molding material composed of a thermoplastic resin layer containing 30% by volume of an inorganic filler and expanding it by utilizing the springback of reinforcing fibers, the heat treatment is performed between these sheet-shaped molding materials. The method for molding a fiber-reinforced thermoplastic resin porous molded article according to claim 1, wherein the molding is carried out by pressurizing, cooling and molding with the plastic resin layer interposed therebetween to integrate the whole.