JPH11279314A - Olefinic resin crosslinked foamed body and preparation thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a foamed body having excellent flame retardancy and vacuum formability, no abnormal cell, and good external appearance, by comprising an olefinic resin consisting of a certain ratio of a polypropylenic resin and an ethylenic resin, a bromine-contg. compd. and Sb2 O3 each of a specific amt. and by giving a specific degree of crosslinking and swelling ratio. SOLUTION: The foamed body is made by blending 100 pts.wt. (pts.wt., hereinafter abbreviated pts.) of an olefinic resin consisting of 40-80 wt.% of a polypropylenic resin and 20-60 wt.% of an ethylenic resin, 1/30 pts. of a bromine- contg. compd., 0.3-20 pts. of Sb2 O3 , and pref. adding 1-50 pts. of a heat decomposition type foaming agent and 2-4 pts. of a (meth)acrylic multifunctional monomer, melt kneading at a temp. where the heat decomposition type foaming agent does not decompose substantially and extruding a sheet, irradiating to the sheet an ionizing radiation of 5-10 Mrad to crosslink, thereafter by heating up to the decomposition temp. or above of the heat decomposition type foaming agent to foam, with the foam having a degree of crosslinking of 30-60% and a swelling ratio of 20-100.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a crosslinked olefin resin foam and a method for producing the same.

[0002]

2. Description of the Related Art Crosslinked olefin resin foams have excellent heat insulating properties and cushioning properties. Therefore, they have been used for building materials, interior materials of transportation equipment such as automobiles, and sound and vibration proof materials.
It is widely used in various fields, such as heat insulation materials for electrical appliances, packaging materials, and daily necessities.

[0003] In particular, as automotive interior materials, for example, they are widely used for ceiling materials, doors, instrument panels, console boxes, rear wheel house covers, luggage house covers, trunk rooms, and the like. After laminating the skin material on one side, it is processed into a predetermined shape by vacuum forming and commercialized.

However, in recent years, the irregularities of the shape have become larger, and particularly in the case of doors having large irregularities, armrest portions of instrument panels and the like, and wood-grained portions, etc., between the crosslinked foam and the skin material during vacuum forming. There have been problems such as so-called blistering, which occurs due to accumulation of air, and molding defects, such as the so-called avatar phenomenon, in which the surface of the crosslinked foam is roughened during vacuum forming due to insufficient heat resistance.

[0005] As a method for solving the above-mentioned blister phenomenon,
A method of increasing the peel strength between the crosslinked foam and the skin material at a high temperature (especially 100 ° C. or higher), increasing the high temperature elongation of the crosslinked foam, or decreasing the degree of crosslinking of the crosslinked foam, thereby increasing the high temperature elastic modulus. However, this method has a problem that the above-mentioned avatar phenomenon is likely to occur because the heat resistance is reduced.

[0006] Further, in order to improve the flame retardancy of the crosslinked foam, it has been practiced to add a halogen-containing compound and antimony trioxide. However, antimony trioxide increases the decomposition rate of the blowing agent more than necessary. As it promotes, it is easy for abnormal bubbles to be generated and foam unevenness in which the bubble diameter and the thickness of the bubble wall become uneven, resulting in uneven heat resistance and high temperature elongation of the crosslinked foam. And the vacuum formability is reduced, and the blistering phenomenon and the avatar phenomenon as described above are likely to occur.

Further, JP-A-6-80811 discloses a method of adding a bromine-containing compound, antimony trioxide and an inorganic filler as a method for obtaining a crosslinked foam having excellent flame retardancy and heat resistance. However, the crosslinked foam obtained by the method is not applicable to vacuum forming due to low moldability,
There is a problem that it is not suitable for interior materials of automobiles.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a crosslinked olefin resin foam having excellent flame retardancy and vacuum moldability, free from abnormal cells and the like, and having a good appearance. It is in.

[0009]

The crosslinked olefin resin foam of the present invention comprises 100 parts by weight of an olefin resin comprising 40 to 80% by weight of a propylene resin and 20 to 60% by weight of an ethylene resin, and a bromine-containing compound 1. -30 parts by weight and 0.3-20 parts by weight of antimony trioxide, and has a degree of crosslinking of 30-60% and a swelling ratio of 20-10.
It is characterized by being 0.

The olefin resin used in the present invention comprises:
Consisting of propylene-based resin and ethylene-based resin, the blending amount of the propylene-based resin decreases heat resistance and decreases,
When the amount increases, the melt viscosity increases, and the appearance of the obtained crosslinked foam deteriorates. Therefore, the amount is limited to 40 to 80% by weight, and the amount of the ethylene-based resin is limited to 20 to 60% by weight.

As the propylene-based resin, any of those conventionally used for foams can be used. For example, polypropylene, α-olefins other than propylene containing propylene as a main component and preferably containing not less than 80% by weight of propylene And a terpolymer of ethylene-propylene-butene containing propylene as a main component. These may be used alone or in combination of two or more. As α-olefins other than propylene,
For example, ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1
-Octene and the like.

When the melt index (hereinafter referred to as "MI") of the propylene-based resin is small, extrusion molding becomes difficult, the appearance of the obtained crosslinked foam becomes poor, and when it is large, the heat resistance decreases. 0.3 to 30 g
/ 10 minutes, preferably 0.4 to 20 g / 10 minutes,
More preferably, it is 0.4 to 8 g / 10 minutes.

The MI in the present invention is JIS K7
It is a value measured according to No. 210.

As the ethylene-based resin, any of those conventionally used for foams can be used, such as linear low-density polyethylene, ultra-low-density polyethylene, low-density polyethylene, medium-density polyethylene, and high-density polyethylene. These may be used alone or in combination of two or more. Among them, linear low-density polyethylene,
It is preferable because it has excellent heat resistance and high temperature elongation. The linear low-density polyethylene is a copolymer with an α-olefin other than ethylene containing ethylene as a main component. Examples of the α-olefin other than ethylene include propylene, 1-butene, 1-pentene, -Methyl-1-pentene, 1-hexene, 1-heptene, 1-octene and the like.

When the MI of the ethylene-based resin is small, extrusion molding becomes difficult, the appearance of the obtained crosslinked foam deteriorates, and when the MI is large, the heat resistance decreases.
3 to 30 g / 10 min, preferably 0.5 to 10 g
/ 10 minutes, more preferably 0.5 to 5 g / 10 minutes.

The bromine-containing compound used in the present invention preferably contains 40% by weight or more of bromine atoms, since the flame retardancy decreases when the bromine content decreases.
Tetrabromobenzene (about 81% by weight), pentabromobenzene (about 85% by weight), hexabromobenzene (about 87% by weight), hexabromobiphenyl ether (about 7% by weight)
4% by weight), tribromophenol (about 72% by weight),
Tetrabromophthalic anhydride (about 69% by weight), hexabromocyclododecane (about 75% by weight), decabromodiphenyl oxide (about 83% by weight), tetrabromophenoxybenzene (about 66% by weight), ethylenebistetrabromophthalimide ( About 67% by weight), 1,2-bistetrabromophenylethane (about 79% by weight), 1,2-
Bispentabromophenylethane (about 82% by weight), tetrabromobisphenol A (about 59% by weight) and the like can be mentioned, and these may be used alone or in combination of two or more. The content in parentheses is the content of each bromine atom.

When the amount of the bromine-containing compound is small, the flame retardancy is reduced, and when the amount is large, various physical properties such as foaming properties are reduced. Therefore, the amount is limited to 1 to 30 parts by weight, preferably 3 to 20 parts by weight, based on 100 parts by weight of the olefin resin.

The antimony trioxide used in the present invention is:
When used in combination with the above bromine-containing compound, the flame retardancy of the obtained crosslinked foam is improved. The average particle size is 1 μm
Or less, more preferably 0.5 μm or less.

When the amount of antimony trioxide is reduced, the effect of improving the flame retardancy is reduced, and when the amount is increased, antimony trioxide promotes the decomposition of the pyrolytic foaming agent described later more than necessary, so Abnormal bubbles are easily generated, and the appearance of the obtained cross-linked foam deteriorates. Therefore, the amount is limited to 0.3 to 20 parts by weight, preferably 1 to 15 parts by weight, based on 100 parts by weight of the olefin resin. .

The ratio of the amount of the bromine-containing compound and the amount of antimony trioxide to be added is as follows: (the amount of the bromine-containing compound) :( the amount of the antimony trioxide).
The ratio is preferably 5 to 1: 1 because the effect of improving the flame retardancy is great.

The crosslinked olefin-based resin foam of the present invention comprises:
It is composed of the olefin resin, a bromine-containing compound and antimony trioxide.

The degree of crosslinking of the crosslinked olefin resin foam is as follows:
As the size decreases, the heat resistance decreases, and as the size increases, the elongation at high temperatures deteriorates.
It is limited to ~ 60%, preferably 35 ~ 50%.

The swelling ratio of the crosslinked olefin resin foam is as follows:
When the size is small, the elongation at high temperature is poor, and when the size is large, various properties of the crosslinked foam are not uniform, and the vacuum formability is reduced.
0 to 80.

The degree of crosslinking and the swelling ratio in the present invention are values measured by the following methods. About 50 mg (dry weight) of the crosslinked foam is precisely weighed in the thickness direction, and the dry weight of the olefin-based resin in the weighed crosslinked foam is calculated from the compounding ratio. Next, the cells of the crosslinked foam were crushed, immersed in 50 ml of xylene at a temperature of 120 ° C. for 24 hours, and then filtered through a 200-mesh stainless steel wire mesh. The weight of the residue is determined. Thereafter, the residue was dried at 80 ° C. under reduced pressure for 5 hours,
Measure the dry weight of the residue.

From the above, the degree of crosslinking and the swelling ratio are calculated from the dry weight of the olefin resin in the crosslinked foam, the weight of the residue in the xylene swelling state, and the dry weight of the residue in the weighed crosslinked foam according to the following equations. Degree of crosslinking (%) = {dry weight of residue (mg) / dry weight of olefin resin (mg)} × 100 Swelling ratio = weight of residue in xylene swelling state (mg) / dry weight of residue (mg)

In the above measurement, components other than the olefin resin in the crosslinked foam were mixed together with xylene by 200%.
Since the residue passes through the mesh wire mesh, the residue is substantially composed of only the olefin resin.

The expansion ratio of the crosslinked olefin resin foam is not particularly limited, and may be appropriately determined depending on the use.

The crosslinked olefin resin foam of the present invention comprises:
For example, a thermal decomposition type foaming agent and a crosslinking agent are added to the olefin resin, the bromine-containing compound and antimony trioxide, and any conventionally known kneading apparatus such as a twin-screw extruder, a Banbury mixer, a kneader mixer, and a mixing roll is used. In, melt-kneading at a temperature at which the pyrolyzable foaming agent does not substantially decompose, usually extruded into a sheet, subjected to crosslinking by irradiating the sheet with ionizing radiation, and then exposed to hot air, infrared rays, etc. It can be obtained by heating and foaming at a temperature not lower than the decomposition temperature of the thermal decomposition type foaming agent by any conventionally known method such as immersion in an oil bath, metal bath, salt bath or the like.

The thermal decomposition type foaming agent generates a decomposition gas by heating, and examples thereof include azodicarbonamide, benzenesulfonylhydrazide, dinitrosopentamethylenetetramine, and toluenesulfonylhydrazide. They may be used alone or in combination of two or more.

The amount of the pyrolytic foaming agent to be added may be appropriately adjusted depending on the desired expansion ratio, but is generally 1 to 50 parts by weight based on 100 parts by weight of the olefin resin.
Preferably it is 4 to 25 parts by weight.

The crosslinking agent is added to promote crosslinking by ionizing radiation, and (meth) acrylic polyfunctional monomers and other polyfunctional monomers are used.

Examples of the (meth) acrylic polyfunctional monomer include trimethylolpropane tri (meth) acrylate, 1,8-octanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, Examples thereof include 1,10-decanediol di (meth) acrylate, and these may be used alone or in combination of two or more.

The amount of the (meth) acrylic polyfunctional monomer to be added is 2 to 100 parts by weight of the olefin resin in order to keep the degree of crosslinking and the swelling ratio of the obtained crosslinked foam within the above-mentioned ranges. 4 parts by weight are preferred.

Examples of the polyfunctional monomer other than the (meth) acrylic polyfunctional monomer include divinylbenzene, trivinylbenzene, divinylcyclohexane, trivinylcyclohexane, diallyl isocyanurate,
Triallyl isocyanurate and the like may be mentioned, and these may be used alone or in combination of two or more.

The amount of the polyfunctional monomer other than the (meth) acrylic polyfunctional monomer to be added is such that the degree of cross-linking and the swelling ratio of the obtained cross-linked foam are within the above-mentioned ranges. 4 to 7 parts by weight per part by weight is preferred.

Examples of the ionizing radiation include an electron beam, α-ray, β-ray, and γ-ray.

The irradiation amount of the ionizing radiation is appropriately adjusted depending on the desired degree of crosslinking, but is generally 1 to 20 Mrad. When a (meth) acrylic polyfunctional monomer is used as a crosslinking agent, When the polyfunctional monomer other than the (meth) acrylic polyfunctional monomer is used as a cross-linking agent, the cross-linking degree and swelling of the obtained cross-linked foam are set to 5 to 10 Mrad. This is preferable because the ratio is likely to be within the above range.

The crosslinked olefin-based resin foam of the present invention may have 2,6-
Phenols such as di-t-butyl-p-cresol,
Various additives such as sulfur-based, phosphorus-based, amine-based antioxidants such as dilaurylthiopropionate, metal damage inhibitors such as methylbenzotriazole, heat stabilizers, and pigments may be added.

[0039]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

[0040]

EXAMPLES (Examples 1 to 6, Comparative Examples 1 to 6) A predetermined amount of an ethylene-propylene random copolymer shown in Table 1 (ethylene content = 3.5% by weight, MI = 7 g / 10 min, Density = 0.89 g / cm ³ ), linear low density polyethylene copolymerized with 1-octene (1-octene content = about 5% by weight, MI = 3.4 g / 10 min, density = 0.915)
g / cm ³ ), decabromodiphenyl oxide, ethylenebistetrabromophthalimide, 1,2-bistetrabromophenylethane, antimony trioxide (average particle size = 0.5 μm), azodicarbonamide, trimethylolpropane trimethacrylate and After divinylbenzene is melt-kneaded at about 180 ° C. with a twin-screw extruder, the thickness is 1.
Extruded into a 2 mm continuous sheet. After irradiating a predetermined amount of an electron beam having an accelerating voltage of 700 kv as shown in Table 1 from one side of the continuous sheet, it was heated to about 250 ° C. with hot air and an infrared heater.
Was heated and foamed in a vertical hot-air foaming furnace maintained at a temperature of 40 ° C. to obtain a crosslinked foam.

The crosslinking degree, swelling ratio and expansion ratio of the obtained crosslinked foam were as shown in Table 1. The expansion ratio was measured using an electronic hydrometer (trade name “ED120” manufactured by Mirage Co., Ltd.).
T ") is the reciprocal of the density (g / cc) of the crosslinked foam measured by the method.

The obtained crosslinked foam was evaluated for vacuum moldability, flame retardancy, and appearance by the following methods.

(Vacuum moldability) Both sides of the crosslinked foam were 180
When heated to 100 ° C and vacuum molded in a mold having a cylindrical concave shape with a diameter of 100 mm with the depth of the concave shape changed arbitrarily, a good molded product is obtained without breaking the crosslinked foam. Drawing ratio (concave depth (mm) / concave diameter (m
Table 1 shows the maximum values of m)).

(Flame Retardancy) A combustion test was performed in accordance with JIS D 1201, and the flammability classification is shown in Table 1.

(Appearance) The surface of the crosslinked foam was visually observed and evaluated as follows. The results are shown in Table 1. ：: There was no uneven foaming such as abnormal air bubbles, and the appearance was good. X: Foaming unevenness was observed.

[0046]

[Table 1]

[0047]

As described above, the crosslinked olefin resin foam of the present invention has the above-mentioned structure, and therefore, is excellent in flame retardancy, and has little decrease in various physical properties due to the addition of a bromine-containing compound or antimony trioxide. Excellent vacuum formability. Also,
Even when a propylene-based resin is used, there is no uneven foaming such as abnormal bubbles, and the appearance is good. Therefore, it can be suitably used for automobile interior materials.

Claims (4)

[Claims] 1. 100 parts by weight of an olefin resin comprising 40 to 80% by weight of a propylene resin and 20 to 60% by weight of an ethylene resin, 1 to 30 parts by weight of a bromine-containing compound, and 0.3 to 20 parts by weight of antimony trioxide. Composed of
A crosslinked olefin-based resin foam having a degree of crosslinking of 30 to 60% and a swelling ratio of 20 to 100. 2. The crosslinked olefin resin foam according to claim 1, wherein the average particle size of antimony trioxide is 1 μm or less. 3. 100 parts by weight of an olefin resin comprising 40 to 80% by weight of a propylene resin and 20 to 60% by weight of an ethylene resin, 1 to 30 parts by weight of a bromine-containing compound, and 0.3 to 20 parts by weight of antimony trioxide. , Pyrolytic foaming agent 1
To 50 parts by weight and 2 to 4 parts by weight of the (meth) acrylic polyfunctional monomer are melt-kneaded at a temperature at which the thermal decomposition type foaming agent does not substantially decompose and extruded into a sheet. After cross-linking by irradiating 〜１０10 Mrad,
The method for producing a crosslinked olefin-based resin foam according to claim 1 or 2, wherein the foaming is performed by heating to a temperature equal to or higher than the decomposition temperature of the thermal decomposition type foaming agent. 4. 100 parts by weight of an olefin resin composed of 40 to 80% by weight of a propylene resin and 20 to 60% by weight of an ethylene resin, 1 to 30 parts by weight of a bromine-containing compound, and 0.3 to 20 parts by weight of antimony trioxide. , Pyrolytic foaming agent 1
５０50 parts by weight and 4 to 7 parts by weight of a polyfunctional monomer other than the (meth) acrylic polyfunctional monomer are melt-kneaded at a temperature at which the pyrolytic foaming agent does not substantially decompose and extruded into a sheet. The olefin-based resin cross-linking foam according to claim 1 or 2, wherein the foam is subjected to cross-linking by irradiating ionizing radiation with 2 to 5 Mrad, and then heated to a decomposition temperature of the pyrolytic foaming agent or higher to foam. How to make the body.