JPH0912765A - Cross-linked olefinic resin foam - Google Patents

Abstract

PURPOSE: To obtain the subject foam, having a specific energy of fusion, excellent in heat resistance, flexibility and secondary processability of complicated shapes and useful as interior vehicular trim materials, etc., such as a ceiling, a door or an instrument panel. CONSTITUTION: This cross-linked olefinic resin foam has 30-60mJ/mg energy of fusion at 120 deg.C in that obtained from a fusion peak area of a differential scanning caloric distribution based on 1g. For example, the subject foam is obtained by exposing a molding prepared from a resin composition comprising an olefinic resin comprising 40-90wt.% propylene-based resin and 60-10wt.% ethylenic resin and an organic thermal decomposition type foaming agent to ionizing radiations, cross-linking the molding and expanding the irradiated molding in a high-temperature atmosphere sufficient to decompose the foaming agent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crosslinked olefin resin foam, and more particularly to a crosslinked olefin resin foam which is excellent in heat resistance and excellent in secondary processing of complicated shapes.

[0002]

2. Description of the Related Art Foams of olefin resins are generally excellent in flexibility and heat insulation, and have been conventionally used in ceilings, doors,
It has been used as a vehicle interior material such as an instrument panel. These interior materials are mainly formed by laminating a vinyl chloride resin sheet, a thermoplastic elastomer sheet, a cloth-like material, or a skin material such as leather on an olefin resin foam, and molding it by secondary processing such as vacuum molding or compression molding. To be done.

During the secondary processing, there is a blistering phenomenon in which the foam and the skin material are separated from each other at a portion to which a strong force is applied, or the foam in the laminate is destroyed to cause irregularities on the surface of the skin material. With respect to the problem of blisters, studies have been conducted to improve the adhesion between the foam and the skin material. Japanese Patent Laid-Open No. 2-25
Japanese Patent No. 5740 discloses a method in which an olefin resin foam is subjected to a surface treatment with a nitrate or a nitrite to enhance the adhesiveness with a skin material. In addition, Japanese Patent Publication 4-17
Japanese Patent No. 784 discloses a method in which an adhesive layer is provided in advance on the surface of the foam and the skin material is heat-bonded.

However, in both cases, the blistering phenomenon due to peeling of the skin material due to poor adhesion between the foam and the skin material is reduced, but the occurrence of surface irregularities due to bubble breakage inside the foam cannot be suppressed.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a crosslinked olefin resin foam which is excellent in heat resistance and flexibility and is excellent in secondary processability in a complicated shape.

[0006]

The crosslinked olefin resin foam of the present invention has a value obtained by dividing the calorific value obtained from the melting peak area of differential scanning calorimetry by the sample weight, that is, 120 of the melting energy per gram. The melting energy at a temperature of 0 ° C. or higher is 30 mJ / mg to 60 mJ / mg.

The melting energy in the present invention is determined by JIS
Measured in accordance with K7122-1987, DS
A straight line connecting the value at the melting start temperature and the value at the melting end temperature of the C melting curve (hereinafter referred to as "base line").
And the area surrounded by the DSC melting curve (hereinafter referred to as “ΔH _T ”)

The melting energy above 120 ° C. (hereinafter referred to as “ΔH ₁₂₀ ”) is included in the above ΔH _T.
The melting energy is 0 ° C. or higher.

The crosslinked olefin resin foam of the present invention is 1
If the melting energy at 20 ° C. or higher is low, the heat resistance of the foam is insufficient, and the foam breaks during secondary processing, resulting in irregularities on the surface of the skin material and peeling of the foam. When the amount is large, the crystal component is large and the flexibility of the foam is insufficient, so 30 mJ / mg to 60 m
J / mg, preferably 35 mJ / mg to 55 mJ
/ Mg.

The olefin resin used in the present invention is
It consists of a propylene resin and an ethylene resin.

Examples of the propylene-based resin include propylene homopolymers or propylene and α other than propylene.
-Copolymers with olefins.

Examples of the α-olefin other than propylene include ethylene, 1-butene, 1-pentene,
1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene and the like can be mentioned.

If the melt index of the propylene-based resin (hereinafter referred to as "MI") is small, the moldability of the resulting foam is low, and if it is high, the heat resistance of the foam is low. It is preferably 1 to 12 g / 10 minutes, more preferably 0.3 to 10 g / 10 minutes.

When the content of the propylene-based resin is low, the heat resistance of the crosslinked olefin-based foam is lowered, and when the content of the propylene-based resin is high, the moldability and flexibility of the crosslinked olefin-based foam are lowered. 90 wt% is preferable, and 45 to 85 wt% is more preferable.

Examples of the ethylene-based resin include ethylene homopolymers and ethylene / α-olefin copolymers. Examples of the α-olefin include
Propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene and the like can be mentioned.

Examples of the ethylene homopolymer include low density polyethylene, linear low density polyethylene,
Examples include medium density polyethylene and high density polyethylene.

When the content of the ethylene resin is low, the moldability of the crosslinked olefin resin foam is lowered, and when it is high, the heat resistance of the crosslinked olefin resin foam is lowered. % Is preferable, and more preferably 55 to 15% by weight.

The crosslinked olefin resin foam of the present invention is
Melting energy of 120 ° C. or higher is 30 mJ / mg-60
In order to obtain mJ / mg, the method of adjusting the composition ratio of the propylene resin and the ethylene resin as described above is effective.

The cross-linked olefin resin used in the present invention includes, in addition to the above-mentioned propylene resin and ethylene resin, other thermoplastic resins such as ethylene-propylene rubber,
Polyvinyl acetate, polybutene, thermoplastic olefin, etc. may be added to form a crosslinked olefin resin foam.

The crosslinked olefin resin foam of the present invention is
A crosslinking aid is added to the crosslinked olefin resin to obtain a foam.
As the above-mentioned cross-linking aid, any one may be used as long as it is a polyfunctional monomer and a monofunctional monomer which are generally used for foams. For example, divinylbenzene,
Trimethylolpropane trimethacrylate, 1,9-
Nonanediol dimethacrylate, 1,10-decanediol dimethacrylate, trimellitic acid triallyl ester, triallyl isocyanurate, ethyl vinylbenzene and the like are exemplified, and these crosslinking aids may be used alone or in combination.
You may use it in combination of 2 or more types.

If the amount of the above-mentioned cross-linking aid is too small, the cross-linking will be insufficient, and a uniform foam will not be obtained. If the amount is too large, the cross-linking density will be too high, resulting in difficulty in moldability.
It is preferable to add 0.5 to 10.0 parts by weight, and more preferably 0.8 to 6 parts by weight, based on 100 parts by weight of the total of the propylene resin and the ethylene resin.

The foam of the present invention is obtained by foaming the above olefin resin. As a method of foaming, for example, a predetermined amount of an olefin resin, a thermoplastic resin, a crosslinking aid, a pyrolytic foaming agent or the like is supplied to an extruder, melt-kneaded and extruded to obtain a resin sheet, which was obtained. The resin sheet is irradiated with a predetermined amount of ionizing radiation to be crosslinked, and the obtained crosslinked sheet is supplied to a foaming furnace to be heated and foamed. Examples include conventionally known methods such as a method of foaming and a method of supplying a predetermined amount of the above material to a mold and heating it to perform foaming in a batch system.

The ionizing radiation is, for example, α
Ray, β ray, γ ray, electron beam and the like.

The above-mentioned olefin-based resin includes phenol-based, phosphorus-based, amine-based, sulfur-based antioxidants, metal-damage-preventing agents, etc. within a range that does not impair the properties of the resulting foam.
Phosphorus-based, nitrogen-based, halogen-based, antimony-based, and mixed flame retardants, fillers, antistatic agents, pigments and the like may be added.

In order to obtain a crosslinked olefin resin foam having a melting energy of 120 ° C. or higher of the present invention of 30 mJ / mg to 60 mJ / mg, the composition ratio of the propylene resin and the ethylene resin is adjusted and extrusion is carried out. It is effective to suppress foaming in the crosslinking and foaming steps.

The thermal decomposition type foaming agent is preferably an organic type thermal decomposition type foaming agent, and examples thereof include azodicarbonamide, benzenesulfonylhydrazide, dinitrosopentamethylenetetramine, toluenesulfonylhydrazide, and the like.
4,4-oxybis (benzenesulfonyl hydrazide)
And the like. These may be used alone,
You may use together.

When the amount of the thermal decomposition type foaming agent added is small, the foamability of the resulting foam is low, and when it is high, the strength of the foam is low, so that the total amount of the olefin resin is 100 parts by weight. 1 to 50 parts by weight is preferable.

If the apparent density of the crosslinked olefin resin foam of the present invention becomes smaller, the strength of the foam becomes lower, so that when pressure is applied, cell breakage or the like occurs and strain does not recover, and if it becomes large. Since the flexibility of the foam decreases, it is preferably 0.02 to 0.20 g / cm ³ , and more preferably 0.03 to 0.10 g / cm ³ .

The crosslinked olefin resin foam of the present invention is
It may be used as a laminate by laminating with an epidermis material using an adhesive, the epidermis material used in that case can be a conventionally known epidermis material, for example, a vinyl chloride resin sheet, Vinyl chloride resin and ABS resin mixed sheet,
Thermoplastic polyolefin sheet, urethane resin sheet,
Other thermoplastic elastomer sheet, cloth, leather,
Examples of the adhesive include polyester-based and polyurethane-based adhesives, as well as polar acrylic resins, water-based emulsion adhesives composed of urethane resin and aziridine, and urethanes. A water-based emulsion adhesive composed of a resin and an epoxy compound can be used. Further, they are simply laminated by heat without using an adhesive.

When the above laminate is used for the interior of automobiles, etc., the skin side is usually used as the side that can be seen.

In the second aspect of the present invention, the olefin resin is 40 to 90% by weight of the propylene resin and 60 to 60% of the ethylene resin.
The crosslinked olefin resin foam according to claim 1, which comprises 10% by weight.

The same propylene-based resin and ethylene-based resin as those used in the present invention can be used. When the amount of the propylene-based resin added is small, the heat resistance of the crosslinked olefin-based foam decreases, and when the amount is large, the crosslinked olefin-based resin is increased. Since the moldability and flexibility of the foam deteriorate,
Is preferably 90 to 90% by weight, more preferably 45 to 85% by weight.

In the second aspect of the present invention, a crosslinked olefin resin foam is produced using the above olefin resin in the same manner as in the present invention.

The crosslinked olefin resin foam of 2 of the present invention is a value obtained by dividing the calorific value obtained from the DSC melting curve of the differential scanning calorimetry by the sample weight, that is, the melting energy per gram of 120 ° C. or more. Energy
It is 30 mJ / mg to 60 mJ / mg.

The third aspect of the present invention is propylene resin 40-9.
A molding obtained from a resin composition composed of an olefin resin consisting of 0% by weight and 60 to 10% by weight of an ethylene resin and an organic thermal decomposition type foaming agent is crosslinked by irradiating with ionizing radiation. 2. The crosslinked olefin resin foam according to claim 1, which is foamed in a high temperature atmosphere sufficient to decompose.

As the propylene resin, ethylene resin, organic thermal decomposition type foaming agent and ionizing radiation used in 3 of the present invention, the same ones as used in the present invention can be used.

When the amount of the above-mentioned propylene-based resin added is small, the heat resistance of the crosslinked olefin-based foam is lowered, and when it is too large, the moldability and flexibility of the crosslinked olefin-based foam are lowered. 90 wt% is preferable, and 45 to 85 wt% is more preferable.

When the addition amount of the above-mentioned organic thermal decomposition type foaming agent is small, the foaming property of the obtained foam is deteriorated, and when the addition amount is large, the strength of the foamed product is deteriorated. Therefore, the total amount of the olefin resin is 100 parts by weight. 1 to 50 parts by weight is preferable.

The crosslinked olefin resin foam of 3 of the present invention is obtained by molding a resin composition comprising the above olefin resin and an organic thermal decomposition type foaming agent, and then irradiating the resulting molded body with ionizing radiation. It is obtained by cross-linking and foaming in a high temperature atmosphere sufficient to decompose the foaming agent.

As the above-mentioned ionizing radiation, the same ones as mentioned in 1 of the present invention can be used.

The cross-linked olefin resin foam of 3 of the present invention is a value obtained by dividing the calorific value obtained from the melting peak area of the differential scanning calorimetry by the sample weight, that is, the melting energy per gram of 120 ° C. or more. Energy
It is 30 mJ / mg to 60 mJ / mg.

Next, embodiments of the present invention will be described. Hereinafter, "parts" means "parts by weight".

Example 1 (Production of Foam) 50 parts of ethylene-propylene random copolymer (ethylene content 3.2% by weight, MI: 1.0 g / 10 minutes) as propylene resin, ethylene resin Linear low-density polyethylene (density 0.920 g /
cm ³ , MI: 2.0 g / 10 minutes) 50 parts, 1,9-nonanediol dimethacrylate 4.0 as a crosslinking aid
Parts, 10 parts of azodicarbonamide as an organic thermal decomposition type foaming agent, and 2,6-di-t-butyl-p as an antioxidant.
Supplying 0.3 parts of cresol and 0.3 part of dilauryl thiodipropionate and 0.5 part of methylbenzotriazole as a metal damage inhibitor to a twin-screw extruder (manufactured by Ikegai Tekko KK, type: PCM87), temperature It was melt-kneaded at 190 ° C. and extruded to obtain a sheet having a thickness of 1.3 mm. The obtained resin sheet is irradiated with an electron beam of 6.0 Mrad at an accelerating voltage of 600 kV to be crosslinked, and the obtained crosslinked sheet is put in an oven and allowed to freely foam at a temperature of 250 ° C. for 5 minutes to give a crosslinked olefin resin foam. Got

(Measurement of Melting Energy of Foam at 120 ° C. or More) The melting energy is JIS K7122-198.
It measured based on 7. First, using a SSC5200 differential scanning calorimeter manufactured by Seiko Instruments Inc., a temperature rising rate of 10 ° C.
The DSC melting curve was obtained in / min. Next, using an analysis job program, the melting energy was calculated from the DSC melting curve and the area surrounded by the base lines.

ΔH of the crosslinked olefin resin foam
_{For 120} , copy the DSC melting curve obtained by the above measurement onto a high-quality paper and measure the enclosed area (unit: “mJ / mg”)
Corresponding to the melting energy “ΔH _T ” of. ) Is cut out and its weight is measured. Next, the area (Δ
Corresponds to H ₁₂₀ . ) Was measured and the melting energy ΔH _{120 at} 120 ° C. or higher was calculated from the weight ratio. Table 1 shows the results.

(Measurement of Degree of Crosslinking) Regarding the above foam,
The degree of crosslinking (% by weight) as well as the apparent density of the foam were measured. The degree of cross-linking was 0.1 g of the foam, the bubbles were crushed, the mixture was kept in 50 ml of xylene at a temperature of 120 ° C. for 24 hours, and then the dry weight (g) of the residue permeated through a 200-mesh wire net was measured. Was measured and calculated by the following formula, and the results are shown in Table 1. Crosslinking degree (% by weight) = (dry weight of residue / 0.1) × 1
00

(Measurement of Density) The density of the foam was measured by using an electronic pycnometer ED120T manufactured by Mirage Co., Ltd., and the results are shown in Table 1.

(Evaluation of Heat Resistance of Foam) In order to measure the heat resistance of the above-mentioned foam during secondary processing, the stretch ratio of the foam generated by unevenness was measured. The unevenness occurrence stretch ratio of the foam was determined by the following method. The obtained foam was used as a test piece having a size of 3 cm × 16 cm, a chuck distance was 10 cm, and a pulling speed was 5
00 mm / min. Then, an autograph (“DCS-5000” manufactured by Shimadzu Corporation) was arbitrarily stretched at a temperature of 20 ° C. and then placed in an oven at 160 ° C. for 5 minutes to check whether the surface of the foam had irregularities. The minimum stretching rate at which unevenness was observed was taken as the unevenness-occurring stretching rate. Table 2 shows the results.

(Production of Laminated Body) The surface of the foamed product is subjected to corona discharge treatment, and a two-component curing type polyester adhesive (polyester: manufactured by Hitachi Chemical Co., Ltd., trade name: Hibon;
Isocyanate: Sumitomo Bayer Urethane Co., Ltd. product name:
Desmodur (R) was used to adhere to a 0.65 mm thick vinyl chloride resin and a mixed resin sheet of acrylonitrile-butadiene-styrene copolymer resin to obtain a laminate.

(Evaluation of Formability of Laminate) The above laminate was subjected to vacuum forming, and whether or not vacuum forming was possible and the appearance of the obtained molded product were evaluated. The vacuum molding was performed using a far-infrared heater to heat the laminate to a surface temperature of 150 ° C. to 160 ° C. and using a cylindrical female die having a diameter of 100 mm and a depth of 90 mm. Those that could be molded without breaking the laminate were rated as ◯, and those that could not be molded were rated as x. The appearance was rated as ◯ when blisters, dents, surface roughness, etc. were not visually observed, and x when even one spot was observed. Table 2 shows the evaluation results.

(Examples 2, 3 and Comparative Examples 1, 2) Crosslinked olefin resin foams having the compositions shown in Table 1 were prepared,
The same evaluation as in Example 1 was performed. The results are shown in Table 1.
The resin composition of Comparative Example 2 had a high viscosity and the extruded sheet had low surface smoothness, and the obtained foam had low surface smoothness and flexibility.

[0051]

[Table 1]

[0052]

EFFECTS OF THE INVENTION The crosslinked olefin resin foam of the present invention, which has the above-mentioned constitution, has excellent heat resistance and flexibility, and can be formed into a molded article having an excellent appearance by secondary processing of a complicated shape. .

Claims (3)

[Claims] 1. The melting energy at 120 ° C. or higher of the melting energy per gram obtained from the melting peak area of differential scanning calorimetry is 30 mJ / mg to 60 mJ / mg.
The crosslinked olefin resin foam is characterized by: 2. The olefin resin is a propylene resin 4
The crosslinked olefin resin foam according to claim 1, comprising 0 to 90% by weight and 60 to 10% by weight of an ethylene resin. 3. A molded article obtained from a resin composition comprising an olefin resin comprising 40 to 90% by weight of a propylene resin and 60 to 10% by weight of an ethylene resin and an organic pyrolysis type foaming agent is ionizable. The crosslinked olefin-based resin foam according to claim 1, wherein the foamed agent is foamed in a high temperature atmosphere sufficient to decompose the foaming agent by irradiating with radiation.