JPS6030330A - Manufacture of composite structure - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] The present invention relates to a method for manufacturing a lightweight and highly rigid composite structure.

In recent years, plastic materials have come to be used in many fields due to their high productivity.

Furthermore, by reinforcing it with glass fiber, etc., it has become comparable to metal materials, and has even come to replace aluminum die-cast products. Although reinforcing with fibers and inorganic fillers is widely practiced, on the other hand, the addition of such reinforcing materials increases the density, causing the resin to lose its inherent advantage of being lightweight. be. Particularly in fields where light weight is important, such as sporting goods and aircraft parts, there is a demand for materials that have dual strength, rigidity, and light weight.

Conventionally, the above-mentioned materials have been manufactured using methods such as one in which a polyurethane sponge is used as a core material and coated with glass fiber-reinforced unsaturated polyester resin, and a fiber-reinforced hollow body is formed by injection molding or blow molding, and then polyurethane is added to the hollow part. A method of injecting and foaming resin has been proposed. However, the former method takes time to mold, resulting in poor productivity, and the latter method has the disadvantage that the shape is severely restricted because it is molded into a hollow body.

As a method of obtaining a lightweight and highly rigid structure, a two-foam molded product is used as a core material, and the outer periphery of the core material is injection-coated with a reinforced thermoplastic resin. So-called insert molding can be considered.

The characteristics required for such a core material are that it is as light as possible, the expansion ratio is at least 3 times or more, the bubbles are uniform and there are no large bubbles especially near the surface, and the core material has good heat resistance, compressive strength, and compressive elastic modulus. is large. With a foam core material that does not have such characteristics, the core material deforms during insert molding, resulting in uneven thickness of the skin. It contracts or deforms significantly due to injection pressure and the heat of the molten resin. The bubble bursts and resin flows from that part.

Such problems occur and the intended structure cannot be obtained. For example, for polymers with relatively high heat resistance such as polypropylene, acrylonitrile/phtadiene/styrene copolymer, and polycarbonate, it is difficult to increase the expansion ratio to 2 times or more, so the expansion ratio should be increased to about 6 times.

The bubbles become very coarse and cannot be used as a core material for insert molding.

As a result of various studies, the inventors of the present invention found that two polyamide foams satisfy the characteristics required for the above-mentioned core material, and arrived at the present invention.

That is, the present invention is a method for manufacturing a composite structure, which is characterized in that a polyamide foam with a foaming ratio of 3 to 6 times is used as a core material, and the outer periphery of the polyamide foam is coated with a reinforcing thermoplastic resin by injection.

Since the composite structure obtained by the present invention is lightweight and highly rigid, it has a wide range of uses such as tennis racket frames and bicycle frames.

The raw material of the polyamide foam in the present invention includes nylon 6, nylon 66, nylon 610°, nylon 11
．． Nylon 12 is preferably used.

The expansion ratio of the polyamide foam is 3 to 6 times, preferably 4
~6 times. If the foaming ratio is smaller than the filtering ratio, the weight of the resulting composite structure will be large.2If the foaming ratio is greater than 6x, coarse air bubbles will easily form on the surface of the foam, and the strength of the foam itself will be too high. This is not desirable because it becomes smaller.

As the reinforcing thermoplastic resin injection-coated around the outer periphery of the polyamide foam, a thermoplastic resin containing 5 to 50% by weight of a known inorganic reinforcing material such as carbon fiber, glass fiber, talc, or wollastonite is used. Ru. Specific examples of the thermoplastic resin include nylon 6, nylon 66, nylon 610. Nylon 11. Examples include polyamides such as nylon 12, polypropylene, polycarbonate, high density polyethylene, acrylonitrile/phtadiene/styrene copolymers, and polyacetals. Among these, polyamide is preferably used because of its good adhesion to the polyamide foam core material. Even when using polymers that have poor affinity with the core polyamide foam, such as polypropylene, 7-trilonitrile/butadiene/styrene copolymers.

Since the surface of the core material is rich in fine irregularities unique to foam, this anchor effect provides sufficient adhesion.

A known insert molding method can be employed as a method for injection coating the outer periphery of the polyamide foam with the reinforced thermoplastic resin. The coating thickness of the reinforcing thermoplastic resin cannot be defined according to various rules depending on the physical properties required of the resulting composite structure, but it is usually 1 to 45 m1.

When the composite structure obtained by the present invention is subjected to a load, especially a bending load, the skin where the stress is maximum is a reinforced thermoplastic resin, and the center part where the stress level is low is a polyamide foam with relatively low strength. So.

Supports the load efficiently as a whole. Furthermore, since the skin and the core material are well bonded and the compressive strength of the polyamide foam core material is relatively high, buckling at load points is unlikely to occur.

Examples are shown below.

The bending rigidity of a composite structure is determined by a three-point bending test using the load (W).
From the deflection (δ) at the load point when applying .

It was calculated using the following formula.

Bending rigidity = Wt3/48δ (t: length between fulcrums =, 1,001rrIn) Example 1 A rectangular parallelepiped nylon 6 foam (expansion ratio: 4.2 times) with a cross-sectional shape of 13.5 m x 15-Om. The outer periphery is made of nylon 66 containing 30% by weight of carbon fiber.

This nylon 66 was injection coated so that the coating thickness was two layers to obtain a rectangular parallelepiped-shaped composite structure with a cross-sectional shape of 17.5 mm x 19.0 mm.

The bending rigidity of the obtained composite structure was 95300KLi・-
The weight per 9 unit length was 2.2197 cm.

Example 2 Example 1 except that nylon 66 containing 30% glass fiber by weight was used instead of nylon 66 containing carbon fiber.
repeated.

The bending rigidity of the obtained composite structure was 44,100 kg/shoulder,
The weight per unit length was 2°2qy/cm.

Example 1 Example 1 was repeated except that a nylon 12 foam with an expansion ratio of 5.1 was used in place of the nylon 6 foam.

The bending rigidity of the obtained composite structure was 947ooKq・shoulder,
The weight per unit length was 2.099/cm.

Example 4 Example 3 except that polypropylene containing 30% by weight of talc was used instead of carbon fiber-blended nylon 66.
repeated.

The bending rigidity of the obtained composite structure was 17,900 kg/shoulder,
The weight per unit length was 2.291/cm.

For reference, a structure having the same bending rigidity as the composite structure obtained in Example 1 is manufactured using only nylon 66 with a carbon fiber content of 30% by weight.

Similar cross-sectional dimensions and weight per unit length were calculated using the following formula.

1)=Kh V=ρbh h: Height of similar cross section (cm) b: Width of similar cross section (cm) K: Width to height ratio (1, o s b ) E: Elastic modulus of material (176oooKg/shoulder) )CEI: ]: Bending rigidity of structure (95300KL!・CIA) 7: Weight per unit length (f//cm) ρ: Specific gravity of material (1, 28) From the above formula, similar cross section 16.9 ran X 15.6
ffl+weight per unit length 6.67ff/cm. From this value and the results of Example 1, it can be seen that the weight per unit length that provides the same bending rigidity is about 34 times smaller for the composite structure of the present invention.

Patent applicant Ube Industries Co., Ltd. Mitsuno Co., Ltd.

Claims (1)

[Claims] A method for manufacturing a composite structure, characterized in that a polyamide foam with an expansion ratio of 3 to 6 times is used as a core material, and the outer periphery of the polyamide foam is coated with a reinforcing thermoplastic resin.