JPH0925351A - Foamable polyolefin resin composition, foamable polypropylene resin composition, and production of foam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a foamable polyolefin resin compsn. excellent in strain recovery and fabricability by compounding a specific polyolefin resin, a polypropylene resin, a cross-linking aid, and a thermally decomposable blowing agent. SOLUTION: A foamable polyolefin resin compsn. is prepd. by compounding 100 pts.wt. resin component comprising 10-50wt.% olefin resin which has a wt. average mol.wt. of 80,000-500,000 and exhibits, when subjected to fractionation under temp. rise by cross fractionation, an amt. of eluted resin of 30-70wt.% (based on the total amt. of olefin resins) at 0-10 deg.C, that of 0-30wt.% at higher than 10 deg.C but not higher than 60 deg.C, and that of 15-65wt.% at higher than 60 deg.C but not higher than 130 deg.C and 90-50wt.% polypropylene resin which has α-olefin units as comonomer units and a melt index of 0.2-10g/min with 0.5-10 pts.wt. crosslinking aid and 1-50 pts.wt. thermally decomposable blowing agent.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a foamable polyolefin resin composition, a foamable polypropylene resin composition, and a method for producing a foam.

[0002]

2. Description of the Related Art Polyolefin resin foams are generally excellent in flexibility and heat insulation and have been conventionally used as interior materials for vehicles such as ceilings, doors and instrument panels. These interior materials are mainly polyolefin-based resin foams, laminated with a vinyl chloride resin sheet, a thermoplastic elastomer sheet, a cloth-like material, and a skin material such as leather to form a laminated composite. It is obtained by secondary processing such as vacuum forming or compression forming.

As a problem in secondary processing of such a laminated composite material, in a portion to which a strong force is applied, the skin material peels off from the foam and swells, or the foam constituting the laminated composite material is destroyed by bubbles. As a result, the unevenness is generated on the surface of the skin material. For such a problem,
Studies have been conducted to improve the adhesiveness between a foam and a skin material. For example, in JP-A-2-255740, surface treatment of a polyolefin resin foam with a nitrate or a nitrite is carried out to improve the adhesiveness. How to do it, special fair 4
Japanese Patent Publication No. 17784 discloses a method in which an adhesive layer is provided in advance on the surface of a foam and heat-bonded to a skin material to enhance the adhesiveness.

However, even if any of the methods is effective in reducing the blistering phenomenon caused by the peeling of the skin material from the foam, it is difficult to prevent the foam from breaking.

Flexible polyolefin resin foams are currently used in a wide variety of applications. Examples of such applications include poultice materials, anti-inflammatory analgesic plasters, and medical tapes such as surgical tapes applied to wounds. Substrate: An industrial tape substrate used for an adhesive tape for a side molding of an automobile and the like.

In order to obtain a flexible foam for such use, for example, in JP-B-61-57334, a resin composition comprising low density polyethylene and linear low density polyethylene is used. A method is disclosed. Further, for example, Japanese Patent Publication No. 2-33387 proposes a crosslinked foamed sheet made of a blend of an ethylene-vinyl acetate copolymer and a linear low density polyethylene.

However, in these foam sheets, when the composition ratio of low density polyethylene or ethylene-vinyl acetate copolymer is increased in order to obtain a flexible foam sheet, the heat resistance and mechanical strength of the foam sheet are increased. However, there was a problem that In general, the foam used for the tape base material is required to have flexibility, elongation, mechanical strength and heat resistance, but no one satisfying all of these performances at the same time has been obtained.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object thereof is
It is an object of the present invention to provide a polyolefin-based resin composition suitable for producing a resin foam that maintains good strain recovery even when subjected to stress and has excellent secondary processability. Another object of the present invention is to provide a polypropylene resin composition suitable for producing a resin foam having flexibility and having excellent mechanical strength and heat resistance.

[0009]

The expandable polyolefin resin composition of the invention according to claim 1 (hereinafter referred to as the first invention) is a polyolefin resin (a) or polypropylene resin (b) having specific properties. , Crosslinking aid (d)
And a thermal decomposition type foaming agent (e).

The present invention will be described in detail below. The resin component (c) used in the first invention comprises a polyolefin resin (a) and a polypropylene resin (b) having specific properties.

The above-mentioned polyolefin resin (a) is characterized in that it exhibits the following characteristics (1) to (4) when temperature rising elution fractionation is carried out by the cross fractionation method. The amount of resin eluted at 0 ° C. or higher and 10 ° C. or lower is 30 to 70% by weight of the total amount of olefin resin, and preferably 35 to 6
0% by weight. When the resin elution amount is less than 30% by weight, the flexibility of the obtained resin foam is insufficient and the strain recovery property is deteriorated to impair the original properties of the foam, and when it exceeds 70% by weight, the heat resistance of the resin foam is increased. And the surface smoothness after secondary processing deteriorates due to bubble destruction.

The amount of resin eluted above 10 ° C. and below 60 ° C. is 0 to 30% by weight, preferably 0 to 20% by weight, based on the total amount of olefin resin. If the resin elution amount exceeds 30% by weight, the elution component at 0 ° C. or higher and 10 ° C. or lower and the elution component at 60 ° C. or higher and 130 ° C. or lower, which will be described later, become insufficient, resulting in flexibility and heat resistance of the resin foam obtained. It becomes difficult to achieve both at the same time.

The amount of resin eluted above 60 ° C. and below 130 ° C. is 15 to 65% by weight of the total amount of olefin resin,
It is preferably 20 to 55% by weight. Resin elution amount is 1
If it is less than 5% by weight, the heat resistance of the obtained resin foam will be insufficient, and if it exceeds 65% by weight, the flexibility will be insufficient.

When the molecular weight is small, the elongation and heat resistance of the resulting foam will be insufficient, and when it is large, the productivity of the resin foam, that is, the extrusion moldability will be reduced, so the weight average molecular weight is limited to 80,000 to 500,000. It

The above cross fractionation method is performed by the following method. First, the above-mentioned polyolefin resin (a)
It is dissolved in o-dichlorobenzene at 0 ° C or a temperature at which the polyolefin resin is completely dissolved, and this solution is cooled at a constant rate, and a thin polymer layer is formed on the surface of an inert carrier prepared in advance in order of high crystallinity and molecular weight. Are generated in descending order of. Next, the temperature is raised continuously or stepwise,
The concentration of the eluted components is detected and the composition distribution (crystallinity distribution) is measured. The temperature rising elution fractionation (TREF =
Temperature RisingElution
Fractionation).

Along with the temperature rising elution fractionation, the molecular weight and the molecular weight distribution of the above-mentioned sequentially eluted components are measured by high temperature GPC. In the present invention, the temperature rising elution fractionation part and the high temperature GPC (SEC = Size Exclusio) are used.
n Chromatograph) part as a system, a cross fractionation chromatograph device (for example, CFC-T150A type: manufactured by Mitsubishi Petrochemical Co., Ltd.) is used to measure the above data.

The polyolefin resin (a) is prepared by first polymerizing propylene in the presence of a titanium compound and an aluminum compound to form a titanium-containing polypropylene resin. Then, in the second and subsequent polymerizations, in the presence of the titanium compound and the aluminum compound, the first
Propylene-ethylene copolymer or propylene-α characterized by copolymerizing propylene and α-olefin with the titanium-containing polypropylene resin produced in the step
-Olefin copolymer. Furthermore, the titanium-containing polyolefin produced in the first step is a propylene homopolymer, a propylene-ethylene copolymer or a propylene-α.
-It is an olefin copolymer.

The polypropylene resin (b) contains α-olefin as a copolymerization component. If the proportion of α-olefin is low, flexibility and elongation of the obtained resin foam will be insufficient, and if it is high, the appearance will be deteriorated when the resin foam is formed into a sheet, so 1 to 8% by weight is preferable,
It is more preferably 2 to 5% by weight.

When the melt index (hereinafter referred to as "MI") of the polypropylene resin (b) becomes small, the moldability of the resin composition deteriorates, so that the surface smoothness of the obtained resin foam becomes poor and becomes large. The heat resistance of the obtained resin foam is impaired, and bubbles are destroyed during the secondary processing, so that it is limited to 0.2 to 10 (g / 10 minutes).
The MI is a load of 2. in accordance with JIS K7210.
It is a value measured at 16 kgf and 130 ° C.

Examples of the polypropylene resin (b) include a random copolymer of propylene and an α-olefin other than propylene, a block copolymer, or a random block copolymer obtained by multistage polymerization.
Examples of the α-olefin include ethylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene and the like.

The resin component (c) is blended in a proportion of 10 to 50% by weight of the polyolefin resin (a) and 90 to 50% by weight of the polypropylene resin (b). By blending in this proportion, it is possible to obtain a crosslinked foam having good physical properties, moldability and appearance of the resin foam at high temperature. If the proportion of the polypropylene-based resin (b) is low, the heat resistance of the resulting resin foam will be insufficient, and if it is high, flexibility and strain recovery will be poor.
It is limited to 0 to 50% by weight, preferably 85 to 55% by weight.

As the cross-linking aid (d) used in the first invention, any of commonly used monofunctional monomers and polyfunctional monomers can be used. For example, divinylbenzene and trimethylol. Propane trimethacrylate, 1,9-nonanediol dimethacrylate,
1,10-decanediol dimethacrylate, trimellitic acid triallyl ester, triallyl isocyanurate, ethyl vinyl benzene and the like can be mentioned, and these may be used alone or in combination of two or more kinds.

In the resin composition of the first invention, if the amount of the above-mentioned crosslinking aid (d) used is small, the crosslinking will be insufficient, so that a homogeneous resin foam cannot be obtained, and if the amount is large, the crosslinking density will be high. If the amount of the resin component (c) [= (a) + (b)] is 100 parts by weight, the amount is limited to 0.5 to 10 parts by weight, and preferably 0.8 to 6 because the moldability is lowered.
Parts by weight.

The organic thermal decomposition type foaming agent (e) used in the first invention is a compound which generates a decomposition gas by heating, and specifically, azodicarbonamide, benzenesulfonyl hydrazide, dinitrosopentamethylene. Examples include tetramine, toluenesulfonyl hydrazide, 4,4-oxybis (benzenesulfonyl hydrazide),
These may be used alone or in combination of two or more.

The amount of the thermal decomposition type foaming agent (e) used is in the range of 1 to 50 parts by weight based on 100 parts by weight of the resin component (c) [= (a) + (b)]. It can be appropriately used depending on the desired expansion ratio, and is preferably 4 to 25 parts by weight.

The composition of the polyolefin-based resin composition in the first invention is as described above, but within the range that does not impair the physical properties of the resin foam obtained, phenol-based, phosphorus-based,
Additives such as amine-based and sulfur-based antioxidants, metal damage inhibitors, flame retardants, fillers, antistatic agents, stabilizers and pigments may be added. These additives may be used alone or in combination of two or more.

As the above-mentioned antioxidant, for example, 2,6
-Di-t-butyl-p-cresol, dilauryl thiopropionate and the like can be mentioned, and examples of the metal damage inhibitor include methylbenzotriazole and the like.

A foam is obtained by crosslinking the resin composition of the first invention by any known method and then heat-foaming. Specifically, for example, using a general-purpose kneading device such as a single-screw extruder, a twin-screw extruder, a Banbury mixer, a roll, the resin composition is melt-kneaded at a temperature lower than the decomposition temperature of the foaming agent, It is molded into a resin sheet in the shape of.
Then, the resin sheet is irradiated with ionizing radiation to be crosslinked, and then the resin sheet is heated to a temperature equal to or higher than the decomposition temperature of the foaming agent to be foamed to obtain a foam. As the ionizing radiation, α
Rays, β rays, γ rays, electron rays, etc. are used, and when the irradiation dose is low, the heat resistance of the obtained foam is insufficient, and when the irradiation dose is high, the foam becomes harder than necessary, so it is usually 1 to 20 Mrad is preferable.

The foam thus obtained has a good appearance, a uniform cell structure, excellent heat resistance, flexibility, strain recovery and toughness, and is processed at high temperature. Occasionally, there is no bubble destruction and no unevenness occurs on the surface, and it is possible to carry out secondary processing into a deep shaped molded body.

Next, the invention according to claim 2 (hereinafter referred to as the second invention) will be described. The expandable polypropylene-based resin composition of the second invention comprises a polypropylene-based resin (f) having specific properties and an organic heat-decomposable foaming agent (e).

The polypropylene resin (f) is the first
When the temperature rising elution fractionation is carried out by the cross fractionation method similar to that of the invention, it is characterized in that it exhibits the following characteristics. The resin elution amount at 0 ° C. or higher and 10 ° C. or lower is 30 to 70% by weight of the total polypropylene resin amount, and preferably 35.
６０60% by weight. When the resin elution amount is less than 30% by weight, the flexibility of the obtained resin foam is insufficient and the strain recovery property is insufficient, and when it exceeds 70% by weight, the heat resistance of the resin foam is insufficient.

The resin elution amount above 10 ° C. and below 60 ° C. is 0 to 30% by weight of the total polypropylene resin amount,
It is preferably 0 to 20% by weight. Resin elution amount is 30
When the content exceeds 0% by weight, the elution components at 0 ° C or higher and 10 ° C or lower and the elution components at 60 ° C or higher and 130 ° C or lower described below are insufficient,
It becomes difficult to achieve both flexibility and heat resistance of the obtained resin foam.

The resin elution amount above 60 ° C. and below 130 ° C. is 15 to 65% by weight of the total olefin resin amount,
It is preferably 20 to 55% by weight. Resin elution amount is 1
If it is less than 5% by weight, the heat resistance of the obtained resin foam will be insufficient, and if it exceeds 65% by weight, the flexibility will be insufficient.

When the molecular weight is low, the elongation and heat resistance of the resulting foam will be insufficient, and when it is high, the productivity of the resin foam, that is, the extrusion moldability will be reduced, so the weight average molecular weight is limited to 80,000 to 500,000. It

The polypropylene resin (f) is prepared by first polymerizing propylene in the presence of a titanium compound and an aluminum compound to form a titanium-containing polypropylene resin. Then, in the second and subsequent polymerizations, in the presence of the titanium compound and the aluminum compound, the first
It is a propylene-ethylene copolymer or propylene-α-olefin copolymer characterized by copolymerizing propylene and ethylene or α-olefin with the titanium-containing polypropylene resin produced in the step. Further, the titanium-containing polypropylene produced in the first stage is characterized by being a propylene homopolymer, a propylene-ethylene copolymer or a propylene-α-olefin copolymer.

As the thermal decomposition type foaming agent (e) used in the resin composition of the second invention, the same compounds as the thermal decomposition type foaming agent used in the resin composition of the first invention are used. The thermal decomposition type foaming agent (e) is used in an amount of 1 to 50 parts by weight based on 100 parts by weight of the polypropylene resin (f), and can be appropriately used according to a desired expansion ratio. .

In the resin composition of the second invention, if necessary, a thermoplastic resin other than the polypropylene resin (f), a crosslinking aid, an antioxidant, a metal damage inhibitor, a flame retardant, a filler, Antistatic agents, pigments and the like may be added.

Examples of the thermoplastic resin include low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, polypropylene resins not included in the above claims, ethylene-propylene rubber, polyvinyl acetate, polybutene. Etc. The addition amount of the thermoplastic resin is the same as the polypropylene resin (f) 1
It is preferably 40 parts by weight or less with respect to 00 parts by weight.

As the above-mentioned crosslinking aid, the same crosslinking aid (d) as that used in the first invention is preferably used.
In the resin composition of the second invention, when the amount of the above-mentioned crosslinking aid added is too small, the crosslinking becomes insufficient and a homogeneous resin foam cannot be obtained. When the amount is too large, the crosslinking density becomes too high and the moldability deteriorates. , The polypropylene resin (f) 1
The amount is preferably 0.5 to 10 parts by weight, more preferably 0.8 to 6 parts by weight with respect to 00 parts by weight.

As the flame retardant, antioxidant and metal damage inhibitor, the same components as those used in the first invention are preferably used.

A foam can be obtained by crosslinking the resin composition of the second invention by a conventionally known method and then heat-foaming. As a specific method, for example, the resin composition of the second invention is supplied to an extruder, melt-kneaded to obtain a resin sheet by extrusion molding, and then the obtained resin sheet is irradiated with ionizing radiation. Method of cross-linking and then supplying the cross-linked resin sheet to a foaming furnace for heat-foaming; Method of supplying the resin composition to an extruder and foaming with a heating roll simultaneously with extrusion molding; Supplying the resin composition to a mold Then, a method of heating and then foaming in a batch method can be mentioned.

As the ionizing radiation, α rays,
β rays, γ rays, electron rays, etc. are used. When the irradiation dose is low, the heat resistance of the resulting foam will be insufficient, and when the irradiation dose is too high, the foam will be harder than necessary.

When the apparent density of the foam obtained by the above-mentioned production method becomes small, the mechanical strength of the foam decreases, and when the pressure is applied, the cells are broken, so that the strain recovery property becomes poor, and when the apparent density becomes large, the foam Since the flexibility decreases, 0.
02~0.2 (g / cm ^3), and more preferably from 0.03~0.1 (g / cm ^3).

[0044]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited thereto. Note that “parts” means “parts by weight”.

(Example 1) The polyolefin resin (a) whose analysis results by cross fractionation chromatography are shown in Table 1 and 3.2% by weight of an ethylene component as a copolymerization component contained MI = 2 (g / g). Polypropylene resin (b) (ethylene-propylene random copolymer) which is 10 minutes) was mixed with 1,9 as a crosslinking aid with respect to 100 parts of the resin component (c) mixed in the ratio shown in Table 1. 2 parts nonanediol dimethacrylate and 1 part trimethylolpropane trimethacrylate, 10 parts azodicarbonamide as blowing agent, 2,6-di-t as antioxidant
-Butyl-p-cresol 0.3 parts and dilauryl thiopropionate 0.3 parts and methylbenzotriazole 0.5 part as a metal damage inhibitor were added and melt-kneaded at 190 ° C using a twin-screw extruder. Then, a resin sheet having a thickness of 1 mm was obtained. Next, this resin sheet was irradiated with an electron beam at an acceleration voltage of 700 kV so that the irradiation amount was 3 Mrad and crosslinked. Further, the crosslinked resin sheet was continuously heated to foam to obtain a foam. The foaming was performed in a foaming furnace while maintaining the temperature at 250 ° C. with hot air and an infrared heater.

Example 2 The results of analysis by cross fractionation chromatography are shown in Table 1. The polyolefin resin contains 3.2% by weight of ethylene component as a copolymerization component, and MI = 2 (g / 10 min). And a polypropylene resin (ethylene-propylene random copolymer) which is
To 100 parts of the resin component mixed in the ratio shown in Table 1, 2.5 parts of divinylbenzene and 1, as a crosslinking aid
6 parts of 6-hexanediol dimethacrylate, 10 parts of azodicarbonamide as a foaming agent, 0.3 part of 2,6-di-t-butyl-p-cresol as an antioxidant and 0.3 part of dilaurylthiopropionate A foam was obtained in the same manner as in Example 1 except that a resin sheet containing 0.5 part of methylbenzotriazole as a metal damage inhibitor was produced by an extruder.

(Example 3) The results of analysis by cross fractionation chromatography are shown in Table 1. The polyolefin resin contains 3.3% by weight of ethylene component as a copolymerization component, and MI = 0.5 (g / 10). Polypropylene resin (ethylene-propylene random copolymer), which is 1), is mixed with trially 1,2,4-benzenetricarboxylic acid triallyl as a crosslinking aid with respect to 100 parts of the resin component mixed in the ratio shown in Table 1. 3 parts and 1 part of trimethylolpropane trimethacrylate, 10 parts of azodicarbonamide as a foaming agent, 2,6-di-t-butyl-p as an antioxidant
Same as Example 1, except that a resin sheet containing 0.3 part of cresol and 0.3 part of dilaurylthiopropionate and 0.5 part of methylbenzotriazole as a metal damage inhibitor was produced by an extruder. To obtain a foam.

Example 4 The analysis results by cross fractionation chromatography are as shown in Table 1. The polyolefin resin contains 3.3% by weight of ethylene component as a copolymerization component, and MI = 0.5 (g / 10). 2) 1,9-nonanediol dimethacrylate as a cross-linking aid based on 100 parts of the resin component mixed with the polypropylene-based resin (ethylene-propylene random copolymer) that is And 1 part of trimethylolpropane trimethacrylate, azodicarbonamide 10 as a foaming agent
Parts, 2,6-di-t-butyl-p-cresol 0.3 part as an antioxidant and 0.3 parts dilaurylthiopropionate 0.3 parts, and methylbenzotriazole 0.5 part as a metal damage inhibitor. A foam was obtained in the same manner as in Example 1 except that the resin sheet was produced by an extruder.

Comparative Example 1 A foam was obtained in the same manner as in Example 2 except that the mixing ratio of the polyolefin resin and the polypropylene resin in the resin component was changed as shown in Table 2. .

(Comparative Example 2) The mixing ratio of the polyolefin resin and the polypropylene resin in the resin component was changed as shown in Table 2, and 100 parts of the resin component was added with 1, 2, and A foam was obtained in the same manner as in Example 1 except that 3 parts of triallyl 4-benzenetricarboxylate and 1 part of trimethylolpropane trimethacrylate were used.

(Comparative Example 3) As a polyolefin resin, a linear low density polyethylene (comonomer:
1-octene, MI = 2.5, density: 0.920) was used, and the mixing ratio of the polyolefin resin and the polypropylene resin in the resin component was changed as shown in Table 2. A foam was obtained in the same manner as in Example 4.

(Comparative Example 4) The results of analysis by cross fractionation chromatography are shown in Table 2. The polyolefin resin contains 3.3% by weight of ethylene component as a copolymerization component, and MI = 0.5 (g / 10). With a polypropylene resin (ethylene-propylene random copolymer), which is a mixture of 100 parts of resin components mixed in the proportions shown in Table 2, and 2.5 parts of divinylbenzene and 1,6 as a crosslinking assistant. -Hexanediol dimethacrylate 2 parts, azodicarbonamide 10 parts as a foaming agent, 2,6-di-t-butyl-p-cresol 0.3 parts and dilauryl thiopropionate 0.3 parts as an antioxidant and Except that a resin sheet containing 0.5 part of methylbenzotriazole as a metal damage inhibitor was produced by an extruder,
A foam was obtained in the same manner as in Example 1.

The following performance evaluations were performed on the foams obtained above, and the results are shown in Tables 1 and 2. (1) Density The density was measured using "Electron specific gravity meter ED120T" manufactured by Mirage.

(2) Strain recovery property The composition is compressed at room temperature for 5 minutes until the thickness of the foam becomes 25% of the thickness before compression. When the thickness 10 minutes after the compression was released was 90% or more of the thickness before the compression, the result was ◯, and when it was less than 90%, the result was x.

(3) Formability of Laminated Composite The surface of the foamed body was subjected to corona discharge treatment, and a two-component curing type polyester adhesive (polyester: "Hybon" manufactured by Hitachi Chemical Polymer Co., Ltd., isocyanate: manufactured by Sumitomo Bayer Urethane Co., Ltd.) Desmnodur R ") to a thickness of 0.
A 65 mm resin sheet made of a mixture of a vinyl chloride resin and an acrylonitrile-butadiene-styrene copolymer was attached to the foam to obtain a laminated composite.

The surface temperature of the foam of the laminated composite is 1
Heated to 50 to 160 ° C., diameter 100 mm,
Using a cylindrical female mold having a depth of 90 mm, the foam and the mold were arranged so as to be in contact with each other, and vacuum molding was carried out. When the foam could be molded without breaking, the result was ○, and the molding was not possible. The case was judged as x. Regarding the appearance of the obtained vacuum-formed product, it was determined by visual observation that no swelling, dents, surface roughness, etc. were observed, and that even one spot was observed, x.

[0057]

[Table 1]

[0058]

[Table 2]

The following components were used in the table. [Polypropylene Resin] A: Ethylene-Propylene Random Copolymer (Ethylene Content = 3.2% by Weight, MI = 2.0 g / 10 min) B: Ethylene-Propylene Random Copolymer (Ethylene Content = 3. 3% by weight, MI = 0.5 g / 10 minutes) [Crosslinking aid] (1): 1,9-nonanediol dimethacrylate 2 parts + trimethylolpropane trimethacrylate 1 part (2): divinylbenzene 2.5 parts + 1,6-hexanediol dimethacrylate 2 parts (3): 1,2,4-benzenetricarboxylic acid triallyl 3 parts + trimethylolpropane trimethacrylate 1
Department

Example 5 100 parts of polypropylene resin (f) (“Cataloy” manufactured by Highmont Co., Ltd.) whose analysis results by cross fractionation chromatography are as shown in Table 3 were used as a crosslinking aid with 1,9- 2 parts of nonanediol dimethacrylate and 1 part of trimethylolpropane trimethacrylate, azodicarbonamide 1 as a foaming agent
0 part, 2,6-di-t-butyl-p-as an antioxidant
Cresol (0.3 parts), dilaurylthiopropionate (0.3 parts) and methylbenzotriazole (0.5 parts) as a metal damage inhibitor were added to 170 parts by using a double roll.
After melt-kneading at 0 ° C., hot pressing was performed to obtain a resin sheet having a thickness of 1 mm. Next, this resin sheet was irradiated with an electron beam at an accelerating voltage of 750 kV so that the irradiation amount was 2 Mrad to obtain a crosslinked resin sheet having a crosslinking degree of 40% by weight. The crosslinked resin sheet was hung in an oven at 260 ° C. and foamed to obtain a foam.

Example 6 With respect to 100 parts of polypropylene resin (f) (“Cataloy” manufactured by Highmont Co., Ltd.) whose analysis results by cross fractionation chromatography are as shown in Table 3, divinylbenzene as a cross-linking aid 4. A resin sheet was obtained in the same manner as in Example 5 except that 5 parts were used, and then crosslinked and foamed in the same manner as in Example 5 to obtain a foam.

Example 7 100 parts of a polypropylene-based resin (f) (“Cataloy” manufactured by Highmont Co., Ltd.) whose analysis results by cross fractionation chromatography are as shown in Table 3 were used as a crosslinking assistant 1, 2, A resin sheet was obtained in the same manner as in Example 5 except that 3 parts of triallyl 4-benzenetricarboxylate was used, and then crosslinked and foamed in the same manner as in Example 5 to obtain a foam.

Comparative Example 5 100 parts of a polypropylene resin (f) (“Cataloy” manufactured by Highmont Co., Ltd.) whose analysis results by cross fractionation chromatography are as shown in Table 4 were used as a crosslinking aid with 1,9- A resin sheet was obtained in the same manner as in Example 5 except that 2 parts of nonanediol dimethacrylate and 1 part of trimethylolpropane trimethacrylate were used, and then crosslinked and foamed in the same manner as in Example 5 to obtain a foam. It was

(Comparative Example 6) A linear low density polyethylene resin whose analysis results by cross fractionation chromatography are as shown in Table 4 ("Amotech" manufactured by Idemitsu Kasei Co., Ltd., "L" in the table)
LDPE ") and 30 parts of ethylene-vinyl acetate copolymer (Sumitomo Seika Co., Ltd.," EVA "in the table) of 70 parts, to 100 parts of a resin component, 1,9- as a crosslinking aid. Nonanediol dimethacrylate 2 parts and trimethylolpropane trimethacrylate 1 part, azodicarbonamide 10 parts as a foaming agent, zinc stearate 2 parts as a foaming aid, 2,6-di-t-as an antioxidant.
After adding 0.3 part of butyl-p-cresol and 0.3 part of dilaurylthiopropionate and 0.5 part of methylbenzotriazole as a metal damage inhibitor, and melt-kneading at 170 ° C. using a two-roll mill Heat pressed, thickness 1m
m after obtaining the resin sheet, cross-linking in the same manner as in Example 5,
It was foamed to obtain a foam.

The following performance evaluations were performed on the foams obtained above, and the results are shown in Tables 3 and 4. (1) Density The density was measured using "Electron specific gravity meter ED120T" manufactured by Mirage.

(2) Surface hardness JIS A hardness was measured using a Shimadzu JIS hardness meter in accordance with JIS K6301.

(3) Tensile Strength According to JIS K6767, No. 1 dumbbell was punched out from the foam, and tensile elongation and breaking strength were measured at room temperature.

(4) Melting point Differential scanning calorimeter (“SSC520” manufactured by Seiko Instruments Inc.)
0 ”) was used to obtain a DSC melting curve at a temperature rising rate of 10 ° C./min, and the melting point was determined from the peak top temperature thereof.

[0069]

[Table 3]

[0070]

[Table 4]

[0071]

EFFECT OF THE INVENTION The polyolefin resin composition of the present invention comprises a polyolefin resin having specific properties, a polypropylene resin, a cross-linking aid, and a thermal decomposition type foaming agent, so that the strain recovery property and the secondary Provided is a polyolefin resin foam excellent in processability. The polypropylene-based resin composition of the present invention is composed of a polypropylene-based resin having a specific property and an organic heat-decomposable foaming agent, so that the polypropylene-based resin has excellent flexibility, mechanical strength and heat resistance. Provide a foam.

Claims (3)

[Claims] 1. A melt index containing 10 to 50% by weight of an olefin resin (a) exhibiting the following characteristics (a) and α-olefin as a copolymerization component when the temperature rising elution fractionation is carried out by the cross fractionation method: Is 0.2-10
(G / 10 min) polypropylene resin (b) 90
Resin component (c) [= (a) +
(B)] 100 parts by weight, a crosslinking aid (d) 0.5 to 10 parts by weight, and a thermal decomposition type foaming agent (e) 1 to 50 parts by weight, a foamable polyolefin resin composition. The resin elution amount from 0 ° C to 10 ° C is 30 to 70% by weight of the total olefin resin amount, and the resin elution amount from 10 ° C to 60 ° C is 0 to 30% by weight of the total olefin resin amount. The resin elution amount at a temperature higher than 60 ° C. and lower than 130 ° C. is 15 to 65% by weight of the total olefin resin amount, and the weight average molecular weight is 80,000 to 500,000. 2. A foamable polypropylene comprising 1 to 50 parts by weight of a polypropylene-based resin (f) and a thermal decomposition type foaming agent (e) which exhibit the following characteristics when subjected to temperature rising elution fractionation by a cross fractionation method. -Based resin composition. The resin elution amount from 0 ° C to 10 ° C is 30 to 70% by weight of the total polypropylene resin amount, and the resin elution amount from 10 ° C to 60 ° C is 0 to 30% by weight of the total polypropylene resin amount. The resin elution amount at a temperature above 60 ° C. and below 130 ° C. is 15 to 65% by weight of the total polypropylene resin amount, and the weight average molecular weight is 80,000 to 500,000. 3. A method for producing a foam, which comprises cross-linking the expandable polyolefin-based resin composition according to claim 1 or the expandable polypropylene-based resin composition according to claim 2 and then foaming by heating.