JPH0885153A - Manufacture of composite material - Google Patents

Abstract

PURPOSE: To inexpensively manufacture a product which has a light weight, excellent mechanical characteristics and heat insulation by covering a core material having an air gap with a melted thermoplastic resin, and then pressurizing the material and the melted resin. CONSTITUTION: A core material 1 having an air gap is mounted by a core material fixing stay 4 in a mold 3 which can be pressurized, a melted thermoplastic resin 2 is extruded from a hollow molding machine die 5 to set to the state that the material 1 is covered with the resin. The mold 3 is closed, the material 1 and the melted resin 2 are pressurized and press bonded, the mold 3 is then cooled with water, and then the mold 3 is opened to remove a product. In this case, as the material 1, a foamed material having gas which has low thermal conductivity such as chloro fluorocarbon gas, etc., is used to obtain a product which has remarkably excellent heat insulation. When the material 1 is a synthetic resin foam, the reduction ratio of the thickness of the material 1 having the air gap is so compressed and pressurized as to be 2-70%, preferably 5-40%, with respect to the original thickness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a composite comprising a core material having voids and a thermoplastic resin, and to a method for producing a product which is lightweight and has excellent mechanical properties and heat insulating properties. Is.

[0002]

2. Description of the Related Art Conventionally, there are many composites composed of a core material having voids and a thermoplastic resin, and there are products having a foam structure inside, for example, products such as cooler boxes. Conventionally, as a method of molding a product having a foam structure inside, polypropylene or polyethylene is injection-molded or hollow-molded into a hollow body, and a resin solution or urethane containing a foaming agent is injected into the hollow body to foam. Method (JP-A-4-71692), method in which hollow beads are filled with expandable beads or slightly expanded beads and then foaming and fusion are performed (JP-A-4-165283, JP-A-5-13).
8722) and the like. There is also a method of merely inserting a preformed foam into the hollow body.

[0003]

In the method of injecting urethane into the hollow body, since the cooling time at the time of molding is long,
In order to improve the molding efficiency, a facility for picking up a large number of pieces is required, which results in an increase in cost. It is difficult to obtain a product having a uniform foam structure by a method in which the hollow beads are filled with expandable beads or slightly expanded beads and then expanded.
Further, when the beads that have been slightly foamed are further foamed, steam heating of the beads in the hollow body is performed, so that there is a disadvantage that steam water remains in the hollow body. The product in which the foam is simply inserted into the hollow body has poor bonding strength between the hollow body and the foam and thus has poor mechanical properties. The present invention solves these drawbacks and provides a method capable of inexpensively manufacturing a product which is lightweight and has excellent mechanical properties and heat insulating properties.

[0004]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that a core material having voids is covered with a molten thermoplastic resin and then melted with the core material. It has been found that by pressurizing the above-mentioned thermoplastic resin, it is possible to inexpensively manufacture a product which is lightweight and has excellent mechanical properties and heat insulating properties.

The present invention will be specifically described below.
In the present invention, the core material having voids is a material having a partial gap, for example, a material having independent or open cells, a material having a honeycomb structure, a material having a structure in which straws are bundled, and fibers are deposited. Or a material which is entangled with each other, more specifically, a synthetic resin foam,
Inorganic foam, wood, cardboard, paper, etc. may be mentioned.
Of these, synthetic resin foams are preferable because they are lightweight and easy to mold.

Examples of the synthetic resin of the synthetic resin foam include polyolefin, polystyrene, polyvinyl chloride, acrylic resin, polyamide, polyester and polyurethane. Further, specific examples of the polyolefin include propylene homopolymer, propylene-α-olefin random copolymer, propylene-α-olefin block copolymer, high density polyethylene, medium density polyethylene, low density polyethylene (for example, linear low Density polyethylene, branched low density polyethylene, etc.), ethylene and α-olefins (eg propylene, butene-1, pentene-
1, hexene-1, etc.) or another comonomer (for example, vinyl acetate, maleic anhydride, etc.) and one or more kinds thereof are copolymerized. The synthetic resins may be used alone or in combination of two or more. Moreover, you may mix ethylene-propylene copolymer elastomer, ethylene-propylene-diene copolymer elastomer, etc. as needed. In addition, various additives such as inorganic substances, crystal nucleating agents, stabilizers, flame retardants, processability improvers, lubricants, antistatic agents, antioxidants, UV absorbers, colorants, pigments, etc. are required for these resins. You may add according to.

As the synthetic resin foam, those molded by various methods can be used. For example, (1) a product obtained by heating and foaming a kneaded product of a resin and a foaming agent, and (2) a resin containing a foaming agent. After impregnation, foaming is performed to form beads, which is heat-fused and molded, and (3) First, slightly foamed beads are prepared and then further heated to be foamed. The foaming ratio of the synthetic resin foam can be appropriately selected depending on the application of the product, and a foaming ratio of up to about 100 times is particularly preferably applicable. Synthetic resin foam,
It is obtained by heating the synthetic resin by various heating methods. Examples of the heating method include hot air heating, steam heating, microwave heating and the like.

In the present invention, the thermoplastic resin that covers the core material having voids is a usual so-called thermoplastic resin, and examples thereof include polyolefin, polystyrene, polyvinyl chloride, acrylic resin, polyamide, polyester, polyurethane and the like. . Further, specific examples of the polyolefin include propylene homopolymer and propylene-α-
Olefin random copolymer, propylene-α-olefin block copolymer, high density polyethylene, medium density polyethylene, low density polyethylene (eg linear low density polyethylene, branched low density polyethylene etc.), ethylene and α-olefin (eg Propylene, butene-1, pentene-1, hexene-1, etc.) or a copolymer of at least one other comonomer (for example, vinyl acetate, maleic anhydride, etc.). The synthetic resins may be used alone or in combination of two or more. Also,
You may mix ethylene-propylene copolymer elastomer, ethylene-propylene-diene copolymer elastomer, etc. as needed. In addition to these resins, for example, inorganic substances, crystal nucleating agents, stabilizers, flame retardants, processability improvers, lubricants, antistatic agents, antioxidants, ultraviolet absorbers, colorants,
You may add various additives, such as a pigment, as needed.

In the present invention, the core material having voids and the thermoplastic resin covering it may be of different types, but the same material ensures that the bonding force between the core material and the thermoplastic resin is the same. Improved, the mechanical properties of the product become better,
Moreover, it is preferable because it can be easily recycled. In addition, two or more kinds of resins that cover the core material may be used so as to form a multilayer structure having a layered structure. further,
An adhesive or the like may be used between the core material and the resin covering it.

In the present invention, the composite body comprising the core material having voids and the thermoplastic resin is obtained by covering the core material with the molten thermoplastic resin and then pressing the core material and the thermoplastic resin. Obtained by When the core material is covered with the thermoplastic resin, the core material may be entirely covered or a part of the core material may be covered. Various methods can be adopted to pressurize the core material and the thermoplastic resin, and for example, it can be molded by a molding machine having a function capable of substantially pressurizing such as a blow molding machine, a sheet blow molding machine, and a stamping molding machine. . The pressure at which the pressure is applied is not particularly limited and is appropriately determined depending on the type of the core material and the thermoplastic resin covering the core material.

In the present invention, the core material having voids preferably has elasticity. When the core material has elasticity, when the core material and the thermoplastic resin are pressed and then the pressure is released, the core material restores to its original shape and the surface smoothness is good. It is preferable because a product having an excellent appearance can be obtained.

When pressurizing the core material having voids and the molten thermoplastic resin, the pressurizing pressure can be appropriately set depending on the types of the core material and the thermoplastic resin. The core material is a synthetic resin foam. In the case of, the reduction rate of the thickness of the core material having voids is 2 to 70% of the original thickness, preferably 5
It is preferable to compress and press so that it is -40%. Two
If it is less than%, the bonding force between the core material and the thermoplastic resin is weak and the core material and the resin are separated from each other, resulting in deterioration of mechanical properties. 70
If it exceeds%, unevenness occurs on the surface of the product when it is restored after the pressure is released, and the appearance deteriorates.

The method of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of a state in which a core material according to the present invention is covered with a molten thermoplastic resin. In FIG. 1, a core material 1 having voids is mounted in a mold 3 that can be pressurized by a core material fixing stay 4. Then, the molten thermoplastic resin 2 is extruded from the hollow molding machine die 5 so that the core material 1 is covered. Next, as shown in FIG. 2, the mold 3 is closed, and the core material 1 and the molten thermoplastic resin 2 are pressed and pressure-bonded. At this time, the mold may be cooled by water cooling. After cooling under pressure, open the mold and take out the product. A cross-sectional view of an example of a product molded by the method of the present invention is shown in FIG. The above-mentioned molding can be performed by an ordinary blow molding machine. Also,
Since the molding cycle can be performed at the same level as that of ordinary blow molding, the molding efficiency is better than the method in which the hollow body is filled with urethane or the beads are foamed.

In the method of the present invention, when the cornerability of the product is poorly shaped, a product having a good appearance can be obtained by providing an air vent hole on the mold cavity surface, particularly on the corner part. Further, by forcibly depressurizing the inside of the mold through the air vent hole, a product having a good appearance can be obtained more efficiently. Further, in order to improve the air bleeding property, sandblasting, graining, etc. of the mold cavity surface may be performed.

By the method of the present invention, products having various shapes such as a flat plate shape, a spherical shape, an egg shape and a box shape can be obtained. By using a foam having a gas having a small thermal conductivity such as CFC gas as the core material having voids, it is possible to obtain a product having a remarkably excellent heat insulating property.

[0016]

EXAMPLES Next, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. (A) Core material having voids (A-1) 15-fold expanded propylene-ethylene random copolymer having an ethylene content of 3% by weight (A-2) 45-fold expanded ethylene content of 3% by weight Propylene-ethylene random copolymer (A-3) which is 15 times foamed has a density of 0.925 g / cm
Polyethylene (A-4) which is ³ is polystyrene containing 6% by weight of styrene-butadiene rubber expanded 15 times (A-5) Propylene homopolymer expanded 15 times (A-6) Lauan plate

(B) Thermoplastic resin covering the core material (B-1) Propylene-having a melt flow rate of 0.3 g / 10 minutes at a temperature of 230 ° C. and a load of 2.16 kg and an ethylene content of 10% by weight. Ethylene block copolymer (B-2) High-density polyethylene having a melt flow rate of 0.03 g / 10 minutes at a temperature of 190 ° C. and a load of 2.16 kg and a density of 0.945 g / cm ^3.

(C) Product shape (C-1) Flat plate outer dimension: 550 × 350 × 40 mm (C-2) Flat plate having recesses (FIGS. 4 and 5) External dimension: 550 × 350 × 40 mm (longitudinal direction) Vertical 455 mm, horizontal 25 mm, depth 3 on one side
A flat plate having two 8 mm recesses)

(D) Molding machine A hollow molding machine having an extruder screw of 90 mm and a mold clamping function of 40 T was used.

(E) Evaluation Method of Product Judgment of product appearance is ○ (roughness and good moldability), △ (roughness and slightly good moldability), ×
A three-level evaluation of (unevenness and poor moldability) was performed. The maximum bending strength of the product was measured as follows.
As shown in FIG. 6 and FIG. 7, two support bases 9 (70 × 7
The product 7 was placed so that the pressing jig 10 (20 × 50 × 360 mm) hits the product 0 (0 × 360 mm) in the direction perpendicular to the longitudinal direction of the product 7. In the case where the product shape was (C-2), the product was placed so that the surface having the recess was the lower surface. The distance between the support bases 9 (distance between fulcrums) was 300 mm. 2 pressure jigs
The maximum bending strength was determined by pressing down at a speed of 0 mm / min, measuring the load and the amount of deflection until the product broke. The flexural modulus of the product was evaluated by the amount of deformation at a bending strength of 150 kg in the above-mentioned bending test, and was evaluated as ○ (deformation amount of 5 m
less than m), Δ (deformation amount of 5 mm or more and less than 10 mm), ×
A three-level evaluation (deformation amount of 10 mm or more) was performed. The evaluation of the adhesiveness between the core material and the thermoplastic resin of the product is judged by the peeling state between the core material and the thermoplastic resin when deformed in the above bending test, and ○ (no peeling), △ (some peeling) ) And x (with considerable peeling).

Example 1 A mold having (A-1) and a product shape (C-1) was used as a core material having a void, and the core material was placed in the mold by a core material fixing stay. I put it on. Thermoplastic resin melted from the die of the blow molding machine (B
-1) (Parison) was extruded to cover the core material. The parison at this time was extruded at 200 ° C. and had a thickness of 2 mm. The mold at a temperature of 20 ° C. was closed and the core material and the parison were compressed and cooled. At this time, the reduction rate of the core material is 5%
It was pressurized so that. After cooling for 1 minute with the mold closed, the mold was opened and the product was taken out. The appearance of the product taken out was checked and the mechanical properties were evaluated. The results of this example are shown in Table 1.

(Comparative Example 1) The same procedure as in Example 1 was carried out except that the rate of decrease in the thickness of the core material during pressurization was 0%, and the results are shown in Table 1.

(Comparative Example 2) Using the same mold as in Example 1, the thermoplastic resin (B) melted from the die of the blow molding machine was used.
-1) (Parison) was extruded, the mold was closed, and then hollow molding was performed to mold the hollow body of (B-1). The hollow body is taken out, a part of it is opened, and a core material (A-
After 1) was inserted therein, the open part was welded and closed to obtain a product. The same evaluations as in Example 1 were performed, and the results are shown in Table 1.

(Comparative Example 3) After hollow molding was carried out in the same manner as in Comparative Example 2, urethane was injected into the hollow body and foamed while the mold was closed. The mold was opened, the product was taken out, the same evaluation as in Example 1 was performed, and the results are shown in Table 1.

(Comparative Example 4) The procedure of Comparative Example 3 was repeated except that polypropylene beads were used instead of urethane.
The results are shown in Table 1.

(Examples 2 to 6) (A-2) was used as the core material having voids, and the reduction rate of the thickness of the core material under pressure was set to 2, 5, 20, 40 and 70%, respectively. The procedure was the same as in Example 1 except for the above, and the results are shown in Table 2.

(Comparative Examples 5 to 6) With Example 1 except that (A-2) was used as the core material having voids and the reduction ratio of the thickness of the core material at the time of pressurization was 1 and 80%, respectively. The same procedure was performed and the results are shown in Table 2.

(Examples 7 to 11) (A-3) was used as the core material having voids, and (B-2) was used as the molten thermoplastic resin, and the ratio of the decrease in the thickness of the core material under pressure was used. Example 1 except that the respective contents were 2, 5, 20, 40 and 70%, respectively.
The results are shown in Table 3.

(Comparative Examples 7 to 8) (A-3) was used as the core material having voids, and (B) was used as the molten thermoplastic resin.
-2) was used, and the reduction rate of the thickness of the core material under pressure was set to 1 and 80%, respectively, and the same results as in Example 1 were obtained.

(Examples 12 to 16) A mold in which (A-4) was used as a core material having voids, and holes having a diameter of 0.1 mm were uniformly provided at intervals of 5 cm in the flat surface and corners of the mold. And the reduction rate of the thickness of the core material at the time of pressurization is 2,
The same procedure as in Example 1 was carried out except that the amounts were 5, 20, 40, and 70%, and the results are shown in Table 4.

(Comparative Examples 9 to 10) A mold in which (A-4) was used as the core material having voids, and holes having a diameter of 0.1 mm were evenly provided at intervals of 5 cm in the flat surface and corners of the mold. And the reduction ratio of the thickness of the core material under pressure is 1 and 80, respectively.
The same procedure as in Example 1 was carried out except that the percentage was changed, and the results are shown in Table 4.

(Examples 17 to 21) As a core material having voids, a mold having (A-5) and a product shape (C-2) was used, and the ratio of the decrease in the thickness of the core material under pressure was 2, each
The same procedure as in Example 1 was carried out except that the amounts were 5, 20, 40, and 70%, and the results are shown in Table 5.

(Comparative Examples 11 to 12) As a core material having voids, a mold having (A-5) and a product shape (C-2) was used, and the reduction rate of the thickness of the core material under pressure was 1 and 8 respectively
The same procedure was performed as in Example 1 except that the content was 0%, and the results are shown in Table 5.

(Examples 22 to 23) Example 1 was repeated except that (A-6) was used as the core material having voids, and the rate of decrease of the thickness of the core material during pressurization was respectively 1 and 2%. The results are shown in Table 6.

(Comparative Examples 13 to 15) Examples except that (A-6) was used as the core material having voids, and the reduction ratio of the thickness of the core material under pressure was 0, 4, and 75%, respectively. The same procedure as in Example 1 was performed, and the results are shown in Table 6.

[0036]

[Table 1]

[0037]

[Table 2]

[0038]

[Table 3]

[0039]

[Table 4]

[0040]

[Table 5]

[0041]

[Table 6]

[0042]

According to the method of the present invention, it is possible to inexpensively obtain a product that is lightweight, has high rigidity, is excellent in heat insulation, and has voids inside. Since the core material and the resin that covers it are compression molded, they are extremely tightly bonded, so they have excellent mechanical strength, and are used for applications requiring durability such as pallets and automobile seat backs. be able to.
Further, it can also be used for heat insulation / cold insulation boxes, various cold insulation containers, etc. by utilizing its heat insulating property.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a state in which a core material according to the present invention is covered with a molten thermoplastic resin.

FIG. 2 is a sectional view showing a state in which a core material according to the present invention and a molten thermoplastic resin are pressurized.

FIG. 3 is a cross-sectional view of a product molded by the method of the present invention.

FIG. 4 is a perspective view of a product according to an embodiment of the present invention.

FIG. 5 is a cross-sectional view taken along the line AA of the product according to the embodiment of the present invention.

FIG. 6 is a perspective view of a product during a bending test in the example of the present invention.

FIG. 7B of the product at the time of bending test in the example of the present invention
It is a -B sectional view.

[Explanation of symbols]

 1 Core Material Having Voids 2 Melted Thermoplastic Resin 3 Mold 4 Stay for Fixing Core Material 5 Hollow Molding Machine Die 6 Thermoplastic Resin 7 Product 8 Receiving Stand 9 Supporting Stand 10 Pressing Jig

Claims (4)

[Claims] 1. A method for producing a composite body, which comprises covering a core material having voids with a molten thermoplastic resin and then pressing the core material and the molten thermoplastic resin. 2. The method for producing a composite body according to claim 1, wherein the core material having voids is a synthetic resin foam. 3. The method for producing a composite according to claim 1, wherein the core material having voids has elasticity. 4. The method for producing a composite according to claim 1, wherein the core material having voids and the melted thermoplastic resin are the same material.