JPH09151268A - Flame-retardant polyolefin resin foam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a flame-retardant polyolefin resin foam improved in flame retardance and appearance by compounding a resin component mainly comprising an ethylene-vinyl acetate copolymer with a hydrated metal compd., a specific phosphorus flame retardant, and a blowing agent and cross-linking and foaming the resultant compsn. SOLUTION: A hundred (100) pts.wt. component mainly comprising an ethylene-vinyl acetate copolymer having a vinyl acetate unit content of 5-20wt.% and a melt index of 1-15g/10min is compounded with 50-200 pts.wt. hydrated metal compd., five (5)-100 pts.wt. phosphorus flame retardant contg. at least two phosphorus compds. having thermal decomposition points different from each other by at least 5 deg.C, and 15-30 pts.wt. thermally decomposable blowing agent. The resultant resin compsn. is melt kneaded, formed into a sheet, cross linked by the exposure to an ionizing radiation of 1-10 Mrad, and foamed under heating at the decomposition point of the blowing agent or higher in a hot air oven.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a flame-retardant polyolefin resin foam.

[0002]

2. Description of the Related Art Conventionally, resin foams have generally been used for building materials, transportation equipment such as automobiles, packaging materials, household daily necessities,
It is used in a wide range of other applications. Among them, polyolefin resin foams have chemical stability, heat insulation,
Since it has properties such as electric insulation and lightness, it is preferably used in a wide range of fields. However, many polyolefin-based resin foams are inherently easy to burn, and in recent years the performance as a flame-retardant material has been required with the expansion of applications, and flame-retardant treatment is performed by various methods. There is.

As a method of making a polyolefin resin flame-retardant, a method of adding a halogen-containing compound is generally used. However, in such a method, although it is possible to impart a high degree of flame retardancy by relatively reducing the deterioration of the molding workability and the mechanical strength of the molded body, a large amount of smoke is generated during the molding processing and combustion. Occasionally, there is a risk of corroding the equipment, and therefore, an abatement facility was sometimes required. Therefore, recently, it has been strongly desired to impart flame retardancy by using a non-halogen-based substance that does not use a halogen-containing compound.

Under these circumstances, a method of using flame retardant without using a halogen-containing compound is a method of using aluminum hydroxide, magnesium hydroxide, basic magnesium carbonate, etc. It is disclosed in Japanese Patent No. 269029.

However, in order to impart sufficient flame retardancy to the polyolefin resin which is easily flammable by adding only these hydrated metal oxides, it is necessary to add a large amount of hydrated metal oxides. As a result, it is difficult to obtain a flexible foam having a fine closed cell structure, since the physical properties of the obtained molded article are deteriorated and the foamability is adversely affected.

Further, although it is a known method to use ammonium polyphosphate as a flame retardant for polyolefin resins, it has been difficult to impart sufficient flame retardancy with ammonium polyphosphate alone.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and to provide excellent flame retardance without using any halogen-containing compound, thereby producing smoke during combustion. It is intended to provide a flame-retardant polyolefin-based resin foam which is free from the occurrence of and has an excellent appearance.

[0008]

The flame-retardant polyolefin resin foam of the present invention comprises a resin component containing an ethylene-vinyl acetate copolymer as a main component, a hydrated metal compound, and phosphorus-containing compounds having different thermal decomposition temperatures. A resin composition comprising a phosphorus-based flame retardant containing at least two of the above and a foaming agent is crosslinked, and then heated to a temperature equal to or higher than the decomposition temperature of the foaming agent to foam.

The resin composition used in the present invention comprises a resin component containing an ethylene-vinyl acetate copolymer as a main component, a hydrated metal compound, a phosphorus-containing compound and a foaming agent.

The ethylene-vinyl acetate copolymer may be an ethylene-vinyl acetate copolymer or a mixture of an ethylene-vinyl acetate copolymer and another polyolefin resin.

Other polyolefin resins mixed with the above ethylene-vinyl acetate copolymer include, for example, α-olefins such as polyethylene, polypropylene and polybutene; ethylene-propylene copolymer and ethylene-propylene-diene ternary. Copolymers, ethylene-ethyl acrylate copolymers, ethylene-butene copolymers, ethylene-butene-diene terpolymers and the like ethylene-based copolymers such as terpolymers, may be used alone, Two or more kinds may be used in combination.

When the above ethylene-vinyl acetate copolymer is used alone, if the content of vinyl acetate decreases, it becomes difficult to mix the flame retardant (particularly the hydrated metal compound described below), and if it increases, the melt viscosity increases. The amount is preferably 5 to 20% by weight because the amount is increased to deteriorate the moldability, and further, acetic acid is liberated during melt-kneading to deteriorate the copolymer to lower the physical properties.

When the ethylene-vinyl acetate copolymer is used in a mixture with other polyolefin resin, the vinyl acetate content in the mixture is 5 to 20.
It is preferable to adjust the content to be in the range of% by weight.

When the melt index (the value measured according to ASTM D1238, hereinafter referred to as "MI") of the above ethylene-vinyl acetate copolymer is smaller, the melt viscosity becomes higher and the moldability becomes worse. Since the physical properties of the resin foam obtained when it becomes large are deteriorated, 1 to 1
5 g / 10 min is preferred.

Examples of the hydrated metal compound include aluminum hydroxide, magnesium hydroxide, basic magnesium carbonate, calcium hydroxide, barium hydroxide, etc. These may be used alone or in combination of two kinds. The above may be used in combination. Among these, especially by using aluminum hydroxide and magnesium hydroxide together,
Higher flame retardancy can be obtained.

In the resin composition used in the present invention,
If the amount of the hydrated metal compound used is too small, sufficient flame retardancy cannot be obtained, and if the amount is too large, the mechanical strength of the resulting resin foam is reduced. Therefore, an ethylene-vinyl acetate copolymer is used as a main component. 50 to 2 with respect to 100 parts by weight of the resin component
Limited to 100 parts by weight.

The above-mentioned phosphorus-based flame retardant contains at least two phosphorus-containing compounds having different thermal decomposition temperatures, and one of them is preferably ammonium polyphosphate. Further, the difference in the thermal decomposition temperature of the phosphorus-containing compounds having different thermal decomposition temperatures is preferably 5 ° C. or more. The ammonium polyphosphate preferably has a degree of polymerization of 200 to 1,000, and has a powdery surface coated with a melamine / formaldehyde resin or the like and has good fluidity and is hardly soluble in water. Is preferably used.

Examples of phosphorus-containing compounds other than the above ammonium polyphosphates include phosphoric acid esters such as triphenyl phosphate, octyldiphenyl phosphate, trioctyl phosphate, tricresyl phosphate, trixylyl phosphate; methylphosphonic acid,
Various phosphonic acids such as ethylphosphonic acid, isopropylphosphonic acid, n-butylphosphonic acid, t-butylphosphonic acid, phenylphosphonic acid; sodium phosphate, potassium phosphate, magnesium phosphate, zinc phosphate, aluminum phosphate, etc. Examples thereof include metal salts of phosphoric acid, which may be used alone or in combination of two or more kinds.

By using two or more phosphorus-containing compounds in combination as the phosphorus-based flame retardant, the temperature at which the flame-retardant coating formed by heating the phosphorus-containing compound is widened,
Excellent flame retardant effect is obtained over a wide temperature range.

In the above resin composition, when the amount of the phosphorus-based flame retardant used is small, it is not possible to impart sufficient flame retardancy to the foam, and when the amount is large, the melt viscosity of the resin composition increases and the high magnification ratio is increased. The foam is not obtained, so the amount is limited to 5 to 100 parts by weight with respect to 100 parts by weight of the resin component.

In the above resin composition, when ammonium polyphosphate is used in combination with another phosphorus-containing compound, the amount of ammonium polyphosphate used is small, the flame retardancy of the resulting foam is insufficient, and the amount is large. Since the mechanical strength of the body decreases, it is preferably 4 to 80 parts by weight with respect to 100 parts by weight of the resin component.

In the above resin composition, when the amount of the phosphorus-containing compound (B) other than ammonium polyphosphate (A) used is small, the flame retardancy of the foam is insufficient, and when it is too large, the melt viscosity of the resin composition is increased. Since it becomes difficult to obtain a foam having a high expansion ratio, the usage ratio of ammonium polyphosphate (A) and phosphorus-containing compound (B) is 100:
1 to 1:10 (weight ratio) is preferable.

The above-mentioned foaming agent is preferably a thermal decomposition type foaming agent, for example, azodicarbonamide, benzenesulfonyl hydrazide, N, N'-dinitrosopentamethylenetetramine, toluenesulfonyl hydrazide, 4,4'-.
Pyrolysis-type organic foaming agents such as oxybis (benzenesulfonyl hydrazide); Pyrolysis-type inorganic foaming agents such as sodium bicarbonate and ammonium carbonate.

In the above resin composition, when the amount of the pyrolyzable foaming agent used is small, a foam having a predetermined expansion ratio cannot be obtained, and when the amount is large, huge bubbles are partially formed.
Since a uniform foam cannot be obtained, the resin component 10
15 to 30 parts by weight is preferable with respect to 0 parts by weight.

A foaming aid may be added to the resin composition in order to obtain a good foam. Examples of the foaming aid include urea compounds, borax, ethanolamine, zinc oxide, and fatty acid metal salts, and the addition amount thereof is preferably 0.1 to 5 parts by weight with respect to 100 parts by weight of the resin component. .

The above-mentioned resin composition may further contain, if necessary, a phenol-based, phosphorus-based, sulfur-based, amine-based antioxidant or the like, and a metal damage as long as the foaming characteristics and physical properties of the resin composition are not impaired. Inhibitors, fillers, antistatic agents, stabilizers, crosslinking agents, lubricants, softeners, pigments and the like may be added.

In the present invention, the above resin composition is crosslinked. As the crosslinking method, a method of irradiating with ionizing radiation is preferable. Examples of the ionizing radiation include electron beams and γ
Rays, X-rays, neutron rays and the like can be mentioned. Among them, electron beams are most preferable, and the irradiation dose thereof is preferably 1 to 10 Mrad.

The above resin composition can be obtained, for example, by melt-kneading the respective components using a kneading device such as a single-screw extruder, a twin-screw extruder, a Banbury mixer, a kneader mixer or a roll. Then, this resin composition is an extruder,
A resin foam is obtained by molding into a sheet using a calender roll or the like, irradiating the obtained foamable sheet with ionizing radiation to crosslink, and then heat-foaming in a hot air oven. Irradiation of the above-mentioned ionizing radiation and heat foaming,
It may be carried out continuously or batchwise.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is described below by way of examples, but the present invention is not limited thereto. (Examples 1 to 5 and Comparative Examples 1 to 5) Resin components (ethylene-vinyl acetate copolymer, a predetermined amount of which are shown in Tables 1 and 2)
Low-density polyethylene, linear low-density polyethylene), a hydrated metal compound, a phosphorus-containing compound, an inorganic oxide, a lubricant, a crosslinking aid and a foaming agent are kneaded with a roll at 140 ° C. to obtain a resin composition, This resin composition was pressed at a molding temperature of 140 ° C. to mold a foamable sheet material having a thickness of 1 mm. Next, this foamable sheet material was irradiated with a dose corresponding to an absorbed dose of 3 Mrad using an electron beam accelerator to crosslink, and then the foamable sheet material was placed in an oven at 240 ° C. and heat-foamed. A resin foam was obtained.

The following performance evaluations were carried out on the resin foams obtained in the above Examples and Comparative Examples, and the results are shown in Tables 1-2.
It was shown to. (1) Expansion ratio The specific gravity of the resin foam was measured, and the reciprocal thereof was taken as the expansion ratio.

(2) Flammability test The oxygen index was measured in accordance with the JIS D1201 combustion test.

(3) Appearance Inspection By visual observation, those having no unevenness of foaming were evaluated as ◯, and those having unevenness of foaming were evaluated as x.

[0033]

[Table 1]

[0034]

[Table 2]

In Comparative Example 5, since it was very difficult to mix the flame retardant, a foamable sheet could not be produced.

The components used in Tables 1 and 2 are as follows. EVA: ethylene-vinyl acetate copolymer (vinyl acetate content 19% by weight, density = 0.94 g / cm ³ , MI =
2.5 g / 10 minutes) LDPE: Low density polyethylene (density = 0.92 g /
cm ³ , MI = 3.4 g / 10 min) LLDPE: Linear low-density polyethylene (density = 0.
94 g / cm ³ , MI = 7 g / 10 minutes)

Aluminum hydroxide: "B703S" manufactured by Nippon Light Metal Co., Ltd.-Magnesium hydroxide: "Kisuma 5A" manufactured by Kyowa Chemical Co., Ltd.-Ammonium polyphosphate: "AP42 manufactured by Hoechst"
2 "-Phenylphosphonic acid: Wako Pure Chemical Industries-n-Butylphosphonic acid: Aldrich-t-Butylphosphonic acid: Aldrich-Triphenylphosphate lAidrich-Tricresylphosphate lAidrich

TiO ₂ : rutile type "CR made by Ishihara Sangyo Co., Ltd.
80 "-MgO: Wako Pure Chemical Industries-Lubricant (1): Hoechst polyethylene wax-Lubricant (2): Hoechst montanic acid partially saponified ester wax-Foaming agent: Otsuka Chemical's azodicarbonamide-Foaming Auxiliary agent: Bayer active zinc oxide

[0039]

EFFECT OF THE INVENTION The flame-retardant polyolefin resin foam of the present invention is as described above, and is imparted with a high degree of flame retardance without using a halogen-based flame retardant, and produces smoke during combustion. And has an excellent appearance. Therefore, it can be suitably used as a heat insulating material in the field of building materials where high flame retardancy is required.

Claims (1)

[Claims] 1. A resin component comprising an ethylene-vinyl acetate copolymer as a main component, 100 parts by weight, and a hydrated metal compound 50 to 20.
0 parts by weight, 5 to 100 parts by weight of a phosphorus-based flame retardant containing at least two phosphorus-containing compounds having different thermal decomposition temperatures, and a resin composition comprising a foaming agent are crosslinked, and then heated to a temperature above the decomposition temperature of the foaming agent. A flame-retardant polyolefin-based resin foam characterized by being foamed.