JPH08109277A - Cross-linked polyolefin resin foam - Google Patents

Abstract

PURPOSE: To obtain a cross-linked polyolefin resin foam which is excellent in heat resistance, high-temp. elongation, and modability and is homogeneous in appearance. CONSTITUTION: In producing a polyolefin resin foam by cross-linking and foaming a polyolefin resin compsn. at least contg. a cross-linker. a cross-linking aid, and a thermally decomposable foaming agent, the polyolefin resin used is a mixture comprising 60-10wt.% polyethylene resin and 40-90wt.% reactor- olefin thermoplastic elastomer (P.E.R) which is obtd. by the direct polymn. of 5-35wt.% polypropylene component and 95-65wt.% ethylene-propylene rubber component and has a melt flow rate of 0.5-20g/10min, a density of 0.87-0.90g/cm<3> , and an m.p. of 140-155 deg.C. The foam is produced by mixing and kneading all the materials, molding the mixture with a molding machine into a sheet, and thermally foaming the sheet.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is directed to the polypropylene without substantially impairing the mechanical strength and heat resistance peculiar to polypropylene.
The present invention relates to a cross-linked polyolefin resin foam having uniform cells and excellent in heat resistance and molding processability.

[0002]

2. Description of the Related Art Polyolefin foams are excellent in mechanical strength, flexibility, texture, heat resistance and the like, and are widely used as automobile interior materials, heat insulating materials, cushioning materials and the like. Among them, polypropylene foam is excellent in mechanical strength such as tensile strength and bending strength and heat resistance, and is therefore being used more widely in these applications. As a polyolefin resin having such properties, thermoplastic elastomers obtained by melt-kneading and cross-linking compounds of polypropylene and ethylene-propylene rubber with an extruder have been used. On the other hand, in the production of a cross-linked foamed product of polypropylene, a method mainly using a cross-linking agent such as an organic peroxide, a method of irradiating an ionizing radiation such as an electron beam to cross-link, and the like are performed. In these methods, the main chain of the polymer is cleaved by radicals, and therefore, it is usually performed by using a crosslinking aid together to promote crosslinking and foam. (JP-A-57-212236, JP-A-64-
87641, JP-A-4-248847, etc.)

[0003]

However, a crosslinked polypropylene resin produced by using a conventional olefinic thermoplastic elastomer (TPO) obtained by melt-kneading and cross-linking each compound of polypropylene and ethylene propylene rubber in an extruder. The foam has insufficient toughness, heat resistance, etc., the elongation rate in the high temperature region around 140 ° C. rapidly decreases, and the shape retention becomes poor when molded at high temperature.
In particular, it was difficult to process a molded product having a complicated and deep shape, and the foamed product was sometimes broken. In addition, since polypropylene has a higher melting point than polyethylene, it is necessary to set the molding resin temperature at the time of molding into a sheet shape high.Especially in sheet molding by an extruder, premature crosslinking in the extruder and partial decomposition of the foaming agent are necessary. And the like, and as a result, a defective appearance of the foamed raw material is likely to occur.

[0004]

In order to provide a polyolefin resin crosslinked foam which is excellent in heat resistance, toughness, molding processability and is uniform in appearance, the present invention provides at least a crosslinking agent, a crosslinking aid, and In a polyolefin resin foam obtained by crosslinking and foaming a polyolefin resin composition containing a pyrolyzable foaming agent, the polyolefin resin composition is a polypropylene component of 5 to 35% by weight and an ethylene propylene rubber component of 95 to 65% by weight. Obtained by polymerization,
Density 0.87-0.90 g / cm ³ , melting point 140-1
It is a mixture of 40 to 90% by weight of a reactor olefinic thermoplastic elastomer (P.E.R.) and 60 to 10% by weight of a polyethylene resin at 55 ° C, and after kneading all the materials in advance, it is formed into a sheet, It is characterized by heating and foaming.

The present invention will be described in detail below. The P. E. FIG. R. Is the melt flow rate (230
C., 2.16 kg load) is 0.5 to 20 g / 10 minutes, preferably 4 to 10 g / 10 minutes. When the melt flow rate is less than 0.5, the fluidity is low and the extrusion moldability is lowered,
If it exceeds 20, molding is difficult and heat resistance becomes insufficient. Further, the density is 0.87 to 0.90 g / cm ³ , the melting point is 140 to 155 ° C., preferably 142 to 150 ° C., and the ethylene content is 10 to 40% by weight, preferably 15 to 3
5% by weight. In addition, P. E. FIG. R. The polypropylene to obtain is not particularly limited, and may be either homopropylene or random propylene.

In the present invention, when a foam having a smooth appearance and fine cells is desired, low density polyethylene or linear low density polyethylene is further used, and when rigidity is required, medium density polyethylene or high density polyethylene. Is compounded.

For example, P. E. FIG. R. The mixing ratio of low density polyethylene to P. E. FIG. R. Is 40 to 90 parts by weight, preferably 60 to 80 parts by weight, and the low-density polyethylene occupies 60 to 10 parts by weight, preferably 40 to 20 parts by weight. When the blending ratio is within the above range, mechanical properties and heat resistance can be maintained, more uniform bubbles can be obtained, the high temperature elongation rate is improved, and molding processability is excellent. The polyethylene resin used as described above can be used alone, or after a plurality of polyethylenes are kneaded in advance, the P. E. FIG. R. It can also be used as a mixture with.

A polyolefin resin cross-linked foam can be obtained by adding a thermal decomposition type foaming agent, a cross-linking agent, a cross-linking aid, and various additives to the above polyolefin-based resin component and heating.

The thermal decomposition type foaming agent used in the present invention is a compound which decomposes to generate a gas when heated, and examples thereof include azodicarbonamide, benzenesulfonyl hydrazide, dinitrosopentamethylene tetramine and toluene sulfonyl hydrazide. To use. The addition ratio of the thermal decomposition type foaming agent can be appropriately determined according to the desired expansion ratio, but is 2 to 5 relative to 100 parts by weight of the total amount of the resin components.
It is used in an amount of 0 parts by weight, preferably 5 to 30 parts by weight.

Examples of the cross-linking agent include t-butylcumyl peroxide, 2,5 dimethyl-2,5 di (t-butylperoxy) hexane and 2,5 dimethyl-2,5 di (t-butylperoxy). ) Hexin-3 or the like can be used, and the addition ratio is preferably in the range of 0.5 to 5 parts by weight with respect to 100 parts by weight of the total amount of the resin components. If this ratio is less than 0.5 parts by weight, cross-linking is insufficient and a homogeneous foam cannot be obtained. On the contrary, if it exceeds 5 parts by weight, the cross-linking density becomes too high, and the foam may have edge cracks and coarse cells. Occurs and a good foam cannot be obtained.

Examples of the crosslinking aid include trimethylolpropane trimethacrylate, trimethylolpropane triacrylate and ethylene glycol dimethacrylate. The addition ratio of these cross-linking aids can be appropriately determined according to the desired degree of cross-linking, but is usually preferably in the range of 0.2 to 5 parts by weight with respect to the total amount of the resin components.

Further, various additives such as antioxidants, foam stabilizers, lubricants, ultraviolet absorbers, polymerization regulators and pigments can be added, if necessary.

As a procedure of kneading and forming into a sheet, first, P. E. FIG. R. It is preferable to knead all the materials such as various polyethylene resins, heat-decomposable foaming agents, crosslinking agents, crosslinking aids and desired additives before molding them into a sheet. This is because by kneading all the materials, the dispersibility and kneading property of the materials are increased, and the smoothness of the appearance when formed into a sheet is improved. A Banbury mixer, a single-screw extruder, a twin-screw extruder, a roll or the like is used for kneading.
During kneading, the temperature of the material is set below the decomposition temperature of the crosslinking agent and the thermal decomposition type foaming agent. Further, a single-screw extruder, a twin-screw extruder, a calendar, a press or the like can be used as a molding machine for molding into a sheet.

The foamable resin composition molded into a sheet is
A crosslinked foamed product can be obtained by heating above the decomposition temperature of the organic peroxide and the thermal decomposition type foaming agent to foam.

When the foamable composition is crosslinked by irradiation with ionizing radiation, the ionizing radiation may be α,
β and γ rays are preferable, but X rays and ultraviolet rays may be used. These radiation doses vary depending on the type of the crosslinking accelerator, the target crosslinking ratio, etc., but are usually 0.5 to 2
It is 0 Mrad, preferably 3 to 10 Mrad.

The cross-linking degree is usually used as a measure for evaluating the appearance and properties of the cross-linked foam. The method for measuring the cross-linked foam is to use a boiling xylene solvent in a predetermined amount (about 0.3).
g) It was dipped and calculated by calculating the insoluble content at 135 ° C. for 16 hours. The degree of crosslinking of the obtained crosslinked foam is 40.
It is desirable to adjust the addition amount of the cross-linking agent, the cross-linking aid and the like so as to be -80%, preferably 50-60%. If the degree of cross-linking is too small, it becomes impossible to obtain heat resistance due to stickiness during foaming, and if it is too large, the elongation decreases and the appearance of the cross-linked foam becomes cracked or blistered. This is also not preferable.

[0017]

Examples 1 to 6 The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to these examples.

As shown in Table 1, polyethylene resin and polypropylene resin were mixed with a total number of materials such as a thermal decomposition type foaming agent, a cross-linking agent, a cross-linking aid, and other additives in a predetermined ratio, and 8 inches A masterbatch was prepared by kneading with a roll at 150 ° C. and 20 rpm for about 7 minutes. Supply the master patch to a φ40mm single screw extruder (full flight type screw: L / D = 26),
A sheet-shaped foam raw fabric having a thickness of 2 mm and a width of 150 mm was obtained through a sheet die. [Extrusion Conditions] Cylinder No. 1 temperature: 140 ° C. Cylinder No. 2 Temperature: 143 ° C. Cylinder No. 3 Temperature: 145 ° C Adapter temperature: 150 ° C Die temperature: 150 ° C Screw rotation speed: 50 rpm

Next, the prepared sheet-shaped foam original fabric is
It was cut into 0 mm square and placed in an oven at 230 ° C. for about 6 minutes to obtain a crosslinked foam. The appearance, cross-linking degree, expansion ratio, heat resistance, elongation, vacuum formability, and appearance of the foamed raw fabric of the obtained cross-linked foam are also shown in Tables 1 and 2.

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

According to the present invention, the reactor olefin thermoplastic elastomer (PER) obtained by the direct polymerization of polypropylene and ethylene propylene rubber and the polyethylene resin are mixed and molded into a sheet. As a result, a polyolefin resin crosslinked foam having an improved smoothness of the appearance of the foamed raw material, having a good appearance when heated and foamed, and having remarkably improved heat resistance at high temperature, elongation and vacuum moldability are provided. can do.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koji Shimoyama 1150 Gogomiya, Shimodate City, Ibaraki Prefecture Hitachi Chemical Co., Ltd. Inside the Yuki Plant

Claims (1)

[Claims] 1. A polyolefin resin foam obtained by crosslinking and foaming a polyolefin resin composition containing at least a cross-linking agent, a cross-linking aid, and a thermal decomposition type foaming agent.
5% by weight, obtained by direct polymerization of ethylene-propylene rubber component 95-65% by weight, melt flow rate of 0.5
To 20 g / 10 min, density of 0.87~0.90g / cm ^3,
It is a mixture of 40 to 90% by weight of a reactor olefin-based thermoplastic elastomer (PER) having a melting point of 140 to 155 ° C. and 60 to 10% by weight of a polyethylene resin. A polyolefin resin crosslinked foam formed by molding, heating and foaming.