JP3320556B2 - Flame retardant polyolefin resin foam - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flame-retardant polyolefin resin foam.

[0002]

2. Description of the Related Art Resin foams have excellent heat insulation properties,
It is widely used in transportation equipment such as automobiles, packaging materials, household goods, and the like. Among them, polyolefin-based foams have properties such as chemical stability, heat insulating properties, electric insulating properties, and light weight, and are required to have a performance as a flame-retardant material with the expansion of use. However, since polyolefin resins are inherently flammable, flame retarding treatment has been conventionally performed by various methods.

As a method of making a polyolefin resin flame-retardant, a method of adding a halogen-containing compound is generally used. However, although flame retardancy can be imparted by this method, a large amount of gas is generated at the time of processing or burning, which causes corrosiveness to equipment and toxicity to the human body. The demand for non-halogen flame retardant materials is increasing.

Under these circumstances, aluminum hydroxide, magnesium hydroxide, basic magnesium carbonate, etc.
Research on flame retardancy of resins by adding hydrated metal oxides that do not generate toxic gas during combustion has been actively conducted.
However, in order to impart sufficient flame retardancy to the flammable polyolefin resin, it is necessary to add a large amount of hydrated metal oxide, and as a result, the physical properties are reduced, and the foamability is also adversely affected. It is difficult to obtain a foam having a closed cell structure.

[0005] On the other hand, it is known that a condensed polyphosphate compound is used as a flame retardant, but sufficient flame retardancy cannot be obtained by itself. Therefore, Japanese Patent Publication No. 5-50536 discloses the use of a condensed phosphoric acid compound and a triazine-based nitrogen compound as a flame retardant in combination with a nitrogen-based compound. There is no suggestion about obtaining

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a polyolefin resin foam having excellent flame retardancy and good appearance. is there.

[0006]

The flame-retardant polyolefin resin foam of the present invention is obtained by crosslinking a resin composition comprising a polyolefin resin, a nitrogen-containing compound, a condensed polyphosphate ester compound and a pyrolytic organic foaming agent. , Foamed.

The polyolefin resin is not particularly limited, but is preferably, for example, a polypropylene resin or a polyethylene resin. These may be used alone or in combination of two or more. When the polypropylene resin and the polyethylene resin are used in combination, the content of the polyethylene resin in the polyolefin resin is 15% by weight or more because the flexibility as a foam is lost when the proportion of the polypropylene resin increases. It is preferable.

The polypropylene resin is not particularly limited, and examples thereof include a propylene homopolymer, a copolymer containing propylene as a main component, and a mixture thereof. The copolymer contains, for example, 85% by weight or more of a propylene part (propylene-
α-olefin) copolymer, and examples of the α-olefin include ethylene, 1-hexene, and 4-methyl-
Examples thereof include 1-pentene, 1-octene, 1-butene, 1-pentene and the like.

[0009] The polypropylene resin is ASTM D1
If the melt index (hereinafter referred to as “MI”) according to the 238 standard is small, it becomes difficult to form a sheet, and if it is large, the heat resistance is deteriorated.

The polyethylene resin is not particularly limited, and examples thereof include an ethylene homopolymer, a copolymer containing ethylene as a main component, and a mixture thereof. Examples of the copolymer include ethylene containing at least 80% by weight of an ethylene part, propylene,
Copolymers with α-olefin, vinyl acetate, ethyl acrylate and the like can be mentioned. Examples of the α-olefin include ethylene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-butene, 1-pentene, and the like.

When the MI of the polyethylene resin is small, a problem such as melt fracture occurs when formed into a sheet, and when the MI is large, the strength is reduced.
40 is preferred.

The nitrogen-containing compound has the following general formula I or
It is at least one kind represented by II.

Embedded image

Embedded image (Formula R ₁ to R ₃ in the I, the functional group having a terminal double bond are included at least one. The other R ₁ ~
R ₃ represents hydrogen, a hydroxyl group, an alkyl group, an alkoxyl group, an aryl group, or an aryloxyl group, which may be different or the same. ) (General formula R ₄ to R ₆ in the II, the functional group having a terminal double bond are included at least one. The other R ₄ ~
R ₆ represents hydrogen, a hydroxyl group, an alkyl group, an alkoxyl group, an aryl group, or an aryloxyl group, which may be different or the same. )

Examples of the functional group having a terminal double bond in the above general formulas I and II include an allyl group, a homoallyl group, a vinyl group, a methacryloyl group and an acryloyl group.

Examples of the nitrogen-containing compound include triallyl isocyanuric acid ester and isocyanuric acid (N
-Propyl) diallyl ester, isocyanuric acid (N-
Ethyl) diallyl ester, isocyanuric acid (N-ethyl) allyl vinyl ester, isocyanuric acid (tri) homoallyl ester, cyanuric acid triallyl ester, cyanuric acid triacryloyl ester, cyanuric acid diallyl monopropyl ester, cyanuric acid (tri) homo Examples include allyl esters and acrylic acid esters of tris (2-hydroxyethyl) isocyanurate.

When the content of the nitrogen-containing compound is too small, the degree of crosslinking becomes insufficient, and the polyolefin resin foam obtained by gas release or the like becomes unsatisfactory. Since the nitrogen-containing compound bleeds out from the surface of the resin composition, the content is limited to 0.5 to 30 parts by weight based on 100 parts by weight of the polyolefin resin.

The condensed polyphosphate compound is
It is represented by the following general formula III.

Embedded image (N in the general formula III is an integer of 20 or more. R _{7 to} R
₉ represents H, NH ₄ or CONH ₂ , which may be different or the same. However, it is assumed that R ₇ , R ₈ and R ₉ are not H or CONH ₂ at the same time. ) The value of n in the general formula III is limited to an integer of 20 or more because the condensed polyphosphate compound becomes soluble in water as the value decreases.

Examples of the above-mentioned condensed polyphosphate compound include ammonium polyphosphate and polyphosphoramide. When the content of the condensed polyphosphate ester compound is too small, sufficient flame retardancy cannot be obtained, and when it is too large, the mechanical strength is reduced and foaming is hindered. Therefore, 3 to 100 parts by weight based on 100 parts by weight of the polyolefin resin. Department.

The mixing ratio of the nitrogen-containing compound and the condensed polyphosphate compound is not particularly limited, but from the viewpoint of flame retardancy, the nitrogen-containing compound: condensed polyphosphate compound = 9: 1 to 1: It is preferable to use in the range of 9.

Further, in addition to the above two-component mixed flame retardant system, a flame retardant auxiliary such as hydrated metal oxide and red phosphorus may be added as long as foaming of the resin is not hindered. Examples of the hydrated metal oxide include aluminum hydroxide, magnesium hydroxide,
And basic magnesium carbonate. Commercially available red phosphorus can be used, but it is preferable to use red phosphorus particles whose surfaces are coated with a resin from the viewpoint of moisture resistance and safety (spontaneous ignition during kneading).

The amount of the flame retardant aid varies depending on the type of the main flame retardant to be blended. If the amount is large, high flame retardancy can be obtained, but the foaming property is impaired. 100 parts by weight or less.

As the above-mentioned pyrolytic organic foaming agent, any known one can be used as long as it decomposes upon heating to generate gas and generates air bubbles in the polymer molded article. For example, azodicarbonamide, Examples thereof include benzenesulfonylhydrazide, dinitrosopentamethylenetetraamine, toluenesulfonylhydrazide, and 4,4-oxybis (benzenesulfonylhydrazide). Of these, azodicarbonamide and dinitrosopentamethylenetetraamine are preferable.

If the content of the thermal decomposition type organic foaming agent is too small, the required expansion ratio cannot be obtained, and if it is too large, a uniform foam cannot be obtained, for example, partially large bubbles are formed. 1 to 40 parts by weight per part by weight is preferred.

The polyolefin resin composition used in the present invention has a viscosity that can withstand foaming during foaming.
Crosslinking is further performed to improve the heat resistance of the finally obtained foam. Examples of the crosslinking method include a method of crosslinking with a peroxide in the presence of a polyfunctional monomer as a crosslinking agent, and a method of crosslinking with ionizing radiation. And the like.
Examples of the polyfunctional monomer include the nitrogen-containing compounds described above. These compounds have both functions as a flame retardant and a polyfunctional monomer, and thus need not be newly added. Examples of the peroxide include benzoyl peroxide, octanoyl peroxide, acetyl peroxide, tertiary butyl peroxyisobutyrate,
Cumene hydroperoxide and the like. Examples of the ionizing radiation include an electron beam, a γ-ray, an X-ray, and a neutron beam, and among them, the electron beam is most preferable. The irradiation dose is not particularly limited, but is generally 1 to 10 Mrad.

The polyolefin-based resin composition is foamed after being crosslinked. Examples of the foaming method include a method of heating the above-mentioned polyolefin-based resin composition and foaming it by decomposing the above-mentioned pyrolytic organic foaming agent. Is mentioned.

Further, as shown in the present invention 2, it is preferable to add a decomposition inhibitor to the polyolefin resin composition in order to prevent the initial decomposition due to kneading of the above-mentioned thermal decomposition type organic foaming agent. Examples of the decomposition inhibitor include those containing an acid hydrazide and an organic acid, and may be used alone or in combination of two or more. Examples of the acid hydrazide include oxalic hydrazide, maleic hydrazide and the like. Examples of the organic acid include itaconic acid, maleic acid, malic acid, fumaric acid, citric acid, adipic acid, trimellitic acid, trimellitic anhydride, oxalic acid, barbituric acid, 1,2-phthalic acid, Examples include 2,6-dihydroxybenzoic acid, anthranilic acid, and isosebacic acid.

When the amount of the decomposition inhibitor is small, the effect is not sufficient, and when the amount is large, foaming is hindered and a good foam cannot be obtained.
It is limited to 0.5 to 40 parts by weight based on parts by weight.

The polyolefin resin composition used in the present invention may contain an antioxidant, a stabilizer, a pigment,
A metal harm inhibitor may be added. The antioxidant,
For 100 parts by weight of the polyolefin resin composition,
It is preferable to add 0.1 to 5 parts by weight. As the stabilizer, any of known phenol-based, phosphorus-based, sulfur-based, and amine-based stabilizers can be used.

The polyolefin resin foam of the present invention comprises:
For example, a single-screw extruder, a twin-screw extruder, a Banbury mixer, a kneader mixer, a resin composition is prepared using a kneading device such as a roll, and then the above components are formed into a sheet, and then ionizing radiation is applied. It is obtained by irradiating and crosslinking, and heating and foaming in a hot air oven. These irradiation and foaming steps may be performed continuously or in a batch system.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments. (Examples and Comparative Examples) Each component was melt-kneaded using a Labo Plastomill at each molding temperature in the table at a rotation speed of 60 rpm for 5 minutes to obtain a resin composition in accordance with the number of parts shown in Tables 1 and 2. Was. This resin composition was pressed at the same temperature as that at the time of melting to form a sheet having a thickness of 1.0 mm, and the sheet was absorbed with an electron beam accelerator at an absorption dose of 3.0 Mrad.
After irradiation with a dose corresponding to the above, the foam was heated and foamed in an oven adjusted to 240 ° C. to obtain a foamed sheet. The resulting sheet was evaluated for flammability, appearance, and expansion ratio as described below, and the results are shown in Table 3.

[Evaluation of flammability] The flammability classification was evaluated according to JIS D1201. [Evaluation of Appearance] The appearance of the foam was visually observed and evaluated according to the following criteria. ：: good without uneven foaming etc. ×: poor with uneven foaming etc. [Measurement of expansion ratio] For a sample of 5 cm × 8 cm,
The specific gravity was measured using an automatic hydrometer, and the reciprocal thereof was calculated as the expansion ratio.

The components used in the examples and comparative examples are as follows. -Resin PP: polypropylene, MI = 1.5 LLDPE: linear low density polyethylene, density = 0.9
2, MI = 7.0 LDPE: low density polyethylene, density = 0.92, MI
= 3.4 EVA: ethylene-vinyl acetate copolymer, vinyl acetate content = 19% by weight, density = 0.92, MI = 3.4. Nitrogen-containing compound A: Cyanuric acid triallyl ester (manufactured by Nippon Kasei Co., Ltd.) B: Triallyl isocyanurate (Nippon Kasei) C: Acrylate of tris (2-hydroxyethyl) isocyanurate (Hitachi Chemical)

Condensed polyphosphate compound (indicated by "phosphate compound" in the table) A: Hostaflam AP422 (manufactured by Hoechst) B: Sumisafe PM (manufactured by Sumitomo Chemical) Aluminum hydroxide: B703S (Japan・ Red phosphorus: Nova Red 120 (manufactured by Rin Kagaku Kogyo) ・ Blowing agent: azodicarbonamide (manufactured by Otsuka Chemical) ・ Decomposition inhibitor A: Trimellitic acid (manufactured by Wako Pure Chemical Industries) B: Itaconic acid (Wako Pure Chemical Industries, Ltd.)

[0033]

[Table 1]

[0034]

[Table 2]

[0035]

[Table 3]

[0036]

The polyolefin resin foam of the present invention is as described above, and contains a nitrogen-containing compound and a condensed polyphosphate ester compound, and self-digests without containing a halogen compound which is a toxic gas generating source. Has the property. Furthermore, without impairing the foamability as a foam,
Since it has excellent flame retardancy and good appearance, it is suitable for use in foams requiring flame retardancy, particularly as a member for automobiles.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C08J 9/06 C08L 23/00-23/26

Claims (2)

(57) [Claims] 1. A polyolefin resin 100 parts by weight, at least one kind of nitrogen-containing compound represented by the general formula I or II 0.5 to 30 parts by weight, a condensed polyphosphate compound 3 to 3 represented by the general formula III A flame-retardant polyolefin-based resin foam obtained by crosslinking and foaming a resin composition comprising 100 parts by weight and a pyrolytic organic foaming agent. Embedded image Embedded image Embedded image (Formula R ₁ to R ₃ in the I, the functional group having a terminal double bond are included at least one. The other R ₁ ~
R ₃ represents hydrogen, a hydroxyl group, an alkyl group, an alkoxyl group, an aryl group, or an aryloxyl group, which may be different or the same. ) (General formula R ₄ to R ₆ in the II, the functional group having a terminal double bond are included at least one. The other R ₄ ~
R ₆ represents hydrogen, a hydroxyl group, an alkyl group, an alkoxyl group, an aryl group, or an aryloxyl group, which may be different or the same. ) (N in the general formula III which is more than 20 integer .R ₇ to R
₉ represents H, NH ₄ and CONH ₂ , which may be different or the same. However, it is assumed that R ₇ , R ₈ and R ₉ are not H or CONH ₂ at the same time. ) 2. The resin composition according to claim 1, further comprising 0.5 to 40 parts by weight of a decomposition inhibitor comprising an acid hydrazide or an organic acid based on 100 parts by weight of the polyolefin resin. A flame-retardant polyolefin resin foam, characterized in that a product is crosslinked and foamed.