JPH0411091B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for manufacturing a molded article having a highly foamed layer. More specifically, a composite highly foamed sheet obtained by directly laminating a polyolefin resin onto a highly foamed sheet is set or temporarily placed on the inner surface of a mold so that the polyolefin laminate layer side of the highly foamed sheet becomes the inner surface of the mold. The present invention relates to a method for manufacturing a polyolefin molded product having a highly foamed layer, which comprises pasting the polyolefin resin onto a polyolefin resin and then injection molding the polyolefin resin thereon.

Currently, various polyolefin resins including polypropylene are used in various fields of synthetic resin molded products, and injection molded products in particular can be manufactured in a single process even with fairly complex three-dimensional shapes. Because of this, it is widely used in the fields of automobile parts, electrical products, household goods, and miscellaneous goods. Furthermore, in recent years, there has been a demand for molded products having a highly foamed layer on the surface of the molded product due to demands for heat insulation, sound absorption, sound deadening, appearance, feel, and the like.

(Conventional technology and its problems) However, it is difficult to produce a polyolefin molded product with a highly foamed layer only on the surface. Attempts have been made to attach the adhesive using adhesives, and to combine it with in-mold foam molding using polyurethane or other materials.

However, each method has its own problems, and the reality is that no satisfactory molded product has yet been obtained. In other words, the method of attaching a foam sheet to the surface of a molded product using an adhesive increases manufacturing steps and costs, and there is no good adhesive for polyolefin, so the resulting molded product with a highly foamed layer There is a problem with the adhesion between the surface of the molded product body and the highly foamed sheet. In addition, when combined with in-mold foam molding of polyurethane, etc., the shape of the molded product obtained is limited, and in-mold foam molding itself takes a long time to form, and requires specialized equipment. This inevitably increases manufacturing costs.

The present inventors have conducted extensive research in order to solve the above-mentioned problems of polyolefin molded products having a highly foamed layer on the surface. As a result, a composite highly foamed sheet obtained by directly laminating a polyolefin resin onto a highly foamed sheet was set or pasted in a mold so that the polyolefin laminate layer side of the highly foamed sheet became the inner surface of the mold. Next, they discovered that by injection molding a polyolefin resin, a molded product with a highly foamed layer on the surface of the molded product and a high adhesive strength between the surface of the molded product and the highly foamed layer was obtained. As a result, the present invention was completed.

As is clear from the above description, the object of the present invention is to provide a polyolefin molded product having a highly foamed layer only on the surface thereof, and which has a highly foamed layer with excellent adhesion between the surface of the molded product and the highly foamed layer. An object of the present invention is to provide a manufacturing method.

(Means for solving problems) The present invention has the following configuration.

A composite highly foamed sheet obtained by directly laminating a polyolefin resin onto a highly foamed sheet is set or temporarily attached to the inner surface of a mold in advance so that the polyolefin laminate layer side of the highly foamed sheet becomes the inner surface of the mold. 1. A method for producing a polyolefin molded product having a highly foamed layer, the method comprising: forming a polyolefin molded product, and then injection molding a polyolefin resin thereon.

The highly foamed sheet used in the present invention has a foaming ratio of 20
~60 times larger, and is made by processing foam into a sheet with a thickness of 2 mm to 30 mm by slicing, etc., and is a highly foamed material with a structure in which cell walls due to foaming are exposed on both sides or one side of the sheet. be. An example of such a highly foamed sheet is a polyurethane foamed sheet. Further, the composite highly foamed sheet used in the present invention is a composite highly foamed sheet obtained by directly laminating a polyolefin resin on the surface where the cell walls of a highly foamed sheet having cell walls on both sides or one side are exposed.

In general, composite sheets made of a combination of different materials are generally made of three-layer sheets with an intermediate layer that is compatible with both materials, since the solubility of each material is an issue. Conventionally, a two-layer composite sheet has not been obtained because the compatibility between the polyolefin and polyurethane is poor.

The composite highly foamed sheet used in the present invention is made by directly laminating a polyolefin resin onto a highly foamed sheet, so that the molten polyolefin resin that comes into contact with the foamed sheet wraps around the exposed cell walls of the foamed sheet and solidifies, making it mechanically strong. combined,
This is a composite sheet that is firmly bonded by the so-called anchor effect, and is a composite highly foamed sheet that solves the problem of compatibility between the materials of polyolefin resin and the highly foamed sheet. The advantage of using such a composite highly foamed sheet is that the composite highly foamed sheet is set or temporarily attached to the inner surface of a mold so that the polyolefin laminate layer side of the highly foamed sheet becomes the inner surface of the mold, and then the polyolefin resin is injected. When molded, the polyolefin laminate layer is subjected to the high pressure during injection molding and the frictional stress caused by the flow of molten resin in the mold. Therefore, the highly foamed sheet layer is not affected by the injection pressure and frictional stress. As a result, the highly foamed layer used is not destroyed and a molded product can be obtained that is neatly bonded to the surface of the molded product.In addition, the material of the highly foamed sheet has somewhat inferior mechanical strength and heat resistance. Even if it is a product, it can be subjected to injection molding. In addition, as shown in Figure 4, the method for directly laminating a polyolefin resin onto a highly foamed sheet is to melt and extrude the polyolefin resin for lamination after extruding it while feeding the highly foamed sheet to the pinch roll section immediately after the die of the extruder. Lamination is performed by adjusting the pinch roll spacing and pressing pressure.

The composite highly foamed sheet used in the present invention is not only a flat sheet, but also a composite sheet that has been formed three-dimensionally into a molded product shape using a vacuum forming method or a pressure forming method, or a flat sheet. It can also be used by bending a shape that matches the inner shape of the mold.

Next, the manufacturing method of the present invention will be explained based on the drawings. The above-described composite highly foamed sheet is first set at a predetermined position on the inner surface of a mold so that the polyolefin laminate layer of the composite highly foamed sheet is on the inside, that is, the surface that contacts the injected molten resin (FIG. 1). If foam layers are required on both the inner and outer surfaces of the molded product depending on the purpose of the product, the composite highly foamed sheet can be set on the mold surfaces of both the cavity side mold and the core side mold as described above. . However, it is desirable to avoid the gate portion so as not to interfere with the injection injection of molten resin during injection molding. In addition, in order to set the composite highly foamed sheet in a mold, depending on the shape of the molded product, that is, the shape of the mold, it is possible to simply fit it into the mold, but it is also possible to set the composite highly foamed sheet in the mold. If it is difficult to fix, use a weak adhesive, pressure-sensitive adhesive, or double-sided adhesive tape to place the composite highly foamed sheet in the mold so that the polyolefin laminate layer side of the highly foamed sheet becomes the inner surface of the mold. Just stick it inside and fix it. Furthermore, when using a rigid injection molding machine, it is sufficient to simply place the composite highly foamed sheet on the lower mold.

After the composite highly foamed sheet is set in the mold in this way, the mold is closed and the rest is injection molded with polyolefin resin in the same way as the normal injection molding method.
An injection molded product having a highly foamed layer on the surface is obtained (FIGS. 3 and 4).

The cross-sectional structure of the molded article obtained in the present invention has a three-layer structure consisting of a highly foamed layer, a polyolefin laminate layer, and a polyolefin injection molded product layer.

The polyolefin resin used in the present invention is a propylene homopolymer, mainly composed of propylene, propylene, ethylene, butene-1, hexene-1, etc.
1, octene-1 or two or more of these α-
Crystalline propylene copolymer with olefin, ethylene homopolymer, ethylene and propylene with ethylene as the main component, butene-1, hexene-1,
Examples include high-density ethylene copolymers with octene-1 or two or more of these α-olefins, particularly propylene homopolymers, crystalline propylene-ethylene block copolymers, and crystalline propylene-ethylene random copolymers. Copolymer, crystalline propylene-butene-1 block copolymer, crystalline propylene-butene-1 random copolymer, crystalline propylene-hexene-1 block copolymer, crystalline propylene-hexene-1 random copolymer coalescence, crystalline propylene-octene-1 copolymer, crystalline propylene-ethylene-butene-1
Ternary copolymer, crystalline propylene-ethylene-hexene-1 Ternary copolymer, crystalline propylene-
Ethylene-octene-1 ternary copolymers, propylene-based polymers that are mixtures of two or more of these, ethylene homopolymers, high-density ethylene-propylene copolymers whose main component is ethylene, high-density ethylene-butene- Preferred are ethylene polymers such as 1 copolymer, high-density ethylene-hexene-1 copolymer, linear polyethylene, or a mixture of two or more of these.

Further, for laminating the composite highly foamed sheet, the above-mentioned laminating grade of polyolefin resin is used, and for injection molding, the above-mentioned injection molding grade of polyolefin resin is used. At this time, it is not necessarily necessary to use the same type of polyolefin resin for the polyolefin resin for laminate and the polyolefin resin for injection molding, but in order to strengthen the adhesion between the laminate layer and the injection molded body layer, it is necessary to use propylene resins with each other. Alternatively, it is preferable to use polyolefin resins of the same type, such as ethylene resins.

In addition, the polyolefin resin used in the present invention includes various synthetic rubbers (e.g., ethylene-propylene copolymer rubber, ethylene-propylene-nonconjugated diene copolymer rubber, polybutadiene, polyisoprene, chlorinated polyethylene, chlorinated polypropylene, styrene). -butadiene rubber, styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, styrene-ethylene-butylene-styrene block copolymer, styrene-propylene-butylene-styrene block copolymer, etc.) or thermoplastic resins (e.g. polybutene, poly4-methylpentene,
Polystyrene, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene copolymer, polyamide, polyethylene terephthalate, polybutylene terephthalate, polyvinyl chloride, etc.) can also be mixed within a range that does not impair the effects of the present invention. The polyolefin resin used in the present invention also contains various additives that are normally added to polyolefin resins, such as thioether-based and phosphorus-based antioxidants, light stabilizers, clarifying agents, nucleating agents, lubricants, and pigments. , heavy metal deactivators (copper inhibitors), dispersants or neutralizing agents for metal soaps, inorganic fillers (e.g. talc, mica, clay, wollastonite, zeolite, asbestos, calcium carbonate, aluminum hydroxide) , magnesium hydroxide, barium sulfate, calcium silicate, glass fiber, carbon fiber, and mixtures of two or more of these), and organic fillers (such as wood flour, pulp, waste paper, synthetic fibers, natural fibers, etc.) according to the present invention. It can be added and used within a range that does not impair the effect.

(Effects) In the manufacturing method of the present invention, a molded product having a clean highly foamed layer can be obtained in one step, and the molded product has a highly foamed layer and the molded product body that are firmly bonded via a laminate layer. Suitable for use in various molded products fields that require good insulation, sound absorption, sound deadening, appearance, and feel without fear of peeling, such as automobile parts, home appliance parts, OA equipment parts, etc. I can do it.

(Example) Hereinafter, the present invention will be specifically described using Examples and Comparative Examples.

Examples 1-2, Comparative Examples 1-2 As polyolefin resin for lamination, melt flow rate (discharge amount of molten resin in 10 minutes when temperature is 230°C and load of 2.16 kg is applied) 0.5 g/10
Propylene homopolymer resin (Chitsuso Polypropylene)
F3020) was melt-extruded using a single-screw extruder with a diameter of 60 mm at a melt-kneading temperature of 230°C, and an open-cell polyurethane foam sheet (width 300 mm, thickness 6 mm ) was supplied and directly laminated with a pinch roll interval of 1 mm and pressure adjusted to a pressing pressure that overcomes the rebound force of the foam to obtain a composite highly foamed polyurethane sheet with a width of 300 mm. The obtained composite highly foamed sheet is cut so as to cover the inner surface of the cavity side of the box mold, and using double-sided adhesive tape, it is attached to the mold with the laminate layer facing inside, and a holding pressure is applied as the injection pressure. 10Kg/cm ² G, primary pressure
Example 1 had a melt flow rate of 45 as a polyolefin resin for injection molding under injection molding conditions of 20Kg/cm ² G, injection speed 40mm/sec, metering rate 100mm, screw rotation speed 100rpm, resin temperature 210℃, and mold temperature 50℃.
g/10 min, a propylene-ethylene block copolymer resin (Titsopolypro K7750) with an ethylene content of 12% by weight, and a melt flow rate of 6 in Example 2.
g/10 minutes, injection molded using propylene polymer resin (Chitsuso Polyprooleforum TA) with a talc content of 40% by weight, and the appearance of the box is 4 to 5 mm.
Box-formed product covered with a highly foamed layer (112 mm wide, horizontal
235mm, depth 115mm).

In addition, Comparative Example 1 is the same as Example 1 except that a polyurethane foam single layer sheet is used instead of the composite highly foamed polyurethane sheet in Comparative Examples 1 and 2.
Comparative Example 2 was injection molded in accordance with Example 2 to obtain a box-shaped product.

The molded products obtained in each example were molded products having a highly foamed layer uniformly on the surface, and the highly foamed layer was not destroyed by the pressure and molten resin during injection molding, and remained the same as the original foamed sheet. It kept its shape.

In addition, the molded product is composed of three layers: a highly foamed layer, a polyolefin laminate layer, and an injection molded polyolefin layer.Although the highly foamed layer and the polyolefin laminate layer are made of different materials as described above, they have an anchoring effect. The polyolefin laminate layer and the injection molded polyolefin layer are also strongly mechanically bonded by mutual fusion of the same resins. Due to such a strong bond, when a peel test was performed, the high foam layer was destroyed before the high foam layer and the molded product body were separated, making it impossible to measure the peel strength.

Peeling tests were also carried out on products subjected to thermal history of -40℃ for 1 hour and 80℃ for 1 hour, but the bond between the highly foamed layer and the molded product body remained strong despite the thermal shock caused by temperature changes. was not affected in any way and remained strongly bonded, and the highly foamed layer was destroyed before the highly foamed layer and the molded product body were separated, making it impossible to measure the peel strength.

On the other hand, in the molded products obtained in each comparative example, the highly foamed sheet was destroyed by the molten resin during injection molding and adhered to the surface of the molded product in scattered places.
A good molded product having a uniform foam layer on the surface of the molded product could not be obtained.

[Brief explanation of drawings]

FIGS. 1 to 3 schematically show the method of the present invention, and each is a vertical sectional view of a mold. 1... Mold (cavity side), 2... Mold (core side), 3... Gate, 4... Composite highly foamed sheet layer, 5... Injection molded polyolefin resin layer. FIG. 4 shows an outline of the method for manufacturing the composite highly foamed sheet used in the present invention.

Claims (1)

[Claims] 1. A composite highly foamed sheet obtained by directly laminating a polyolefin resin onto a highly foamed sheet is placed on the inner surface of a mold in advance so that the polyolefin laminate layer side of the highly foamed sheet becomes the inner surface of the mold. 1. A method for producing a polyolefin molded product having a highly foamed layer, which comprises setting or temporarily pasting the polyolefin resin on the foam layer and then injection molding the polyolefin resin thereon. 2. A method for producing a polyolefin molded article having a highly foamed layer according to claim 1, using a composite highly foamed sheet that is obtained by directly laminating a polyolefin resin onto highly foamed polyurethane. 3 As the polyolefin resin, propylene homopolymer, crystalline propylene-ethylene copolymer containing propylene as a main component, crystalline propylene-butene-1 copolymer, crystalline propylene-hexene-
1 copolymer, crystalline propylene-ethylene-butene-1 ternary copolymer, crystalline propylene-ethylene-hexene-1 ternary copolymer, ethylene homopolymer, high-density ethylene whose main component is ethylene. Propylene copolymer, high density ethylene-butene-1 copolymer, high density ethylene-hexene-1
A method for producing a polyolefin molded article having a highly foamed layer according to claim 1 or 2, using a copolymer, linear polyethylene, or a mixture of two or more thereof.