JP2000327823A - Polyethylene resin expanded body and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an expanded body of a polyethylene resin that has flame retardancy and a good appearance, generates a reduced amount of smoke when burnt, and does not cause apparatuses to be corroded. SOLUTION: The polyethylene resin expanded body is made of (A) 100 pts.wt. of a resin component composed of 30 to 90 wt.% of a low density polyethylene resin having a density of 0.91 to 0.93 g/cm3 and a melt index of 1 to 10 g/10 minutes when measured according to ASTM D1238, and (B) 5 to 200 pts.wt. of a flame retardant composition composed of ammonium polyphosphate, tris(2- hydroxyethyl)isocyanurate and an inorganic oxide wherein when measured at 1,000 deg.C by use of a thermogravimetric analyzer, the resultant residue is not less than 10 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Resin foams have excellent heat insulation properties,
It is used for transportation equipment such as automobiles, packaging materials, household commodities, and a wide range of other uses.

[0003] Among them, olefin-based resin foams are rich in chemical stability, and have properties such as heat insulation, electric insulation, and light weight. In particular, cross-linked foams of low-density polyethylene are known as foams having uniform and fine closed cells, and having excellent mechanical strength and heat insulation properties, and are used for various purposes. Mechanical strength such as flexibility, tensile strength, elongation, and peel strength was not sufficient for use as a protective material or the like.

[0004] In order to improve these mechanical strengths, a method of reinforcing a skin layer by laminating a polyethylene film or the like,
Although a method of adjusting the degree of cross-linking of the surface skin layer has been used, there have been problems that sufficient strength cannot be obtained and the steps become complicated.

On the other hand, in order to use a foam obtained by foaming an olefin resin which is inherently flammable as the peripheral protective material for electric equipment, the performance as a flame retardant material is required.

As a method of making an olefin resin flame-retardant, a method of adding a halogen-containing compound is generally used. These do give a high degree of flame retardancy and relatively little decrease in molding processability and mechanical strength of molded products. There is a strong demand for a flame-retardant material that does not use a halogen-containing compound from the viewpoints of resistance and prevention of equipment corrosion.

Under these circumstances, aluminum hydroxide,
Magnesium hydroxide, it began to study the resin flame retardant is performed actively by the addition of hydrated metal oxides such as salt group magnesium carbonate. However, in order to impart sufficient flame retardancy to a polyolefin resin using only these thermally decomposable metal compounds, it is necessary to add a large amount of hydrated metal oxides. And it was difficult to obtain a foam having a fine closed cell structure.

Japanese Patent Application Laid-Open No. 63-61055 discloses that an olefin resin is made of ammonium polyphosphate and tris (2-hydroxyethyl) isocyanurate.
Although a component-mixed flame retardant system is used, sufficient flame retardancy cannot be obtained with a combination of these two components alone, so a large amount of addition is required to impart effective flame retardancy and mechanical properties In practice, it has been impossible to use it because it causes a great decrease in

In Japanese Patent Application Laid-Open No. Hei 7-196842, a group II, III or III of the periodic table is used for a thermoplastic resin.
Flame retardancy is achieved by a combination of an oxygen-containing solid compound containing an element belonging to Group IV, a nitrogen-containing organic compound, and powdered ammonium polyphosphate.However, when an olefin-based resin is used as a thermoplastic resin, a high level of difficulty is required. Increasing the amount of the oxygen-containing solid compound in order to obtain flammability may cause problems such as surface roughness during foaming.

[0010]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems, and provides a polyethylene-based resin foam which is excellent in flame retardancy and appearance, generates a small amount of smoke when burning, and does not corrode equipment. It is an object of the present invention to provide a manufacturing method thereof.

[0011]

The polyethylene resin foam of the invention according to claim 1 (hereinafter referred to as the "foam of the present invention") has (A) a density of 0.91 to 0.93 g / cm ³ ,
30 to 90% by weight of a low-density polyethylene resin having a melt index of 1 to 10 g / 10 minutes measured according to ASTM D1238 and a density of 0.915 to 0.94 g /
cm ³ , the melt index is 0.2 to 20 g / 10
10 to 70% by weight of linear low density polyethylene resin
And (B) ammonium polyphosphate, tris (2-hydroxyethyl) isocyanurate, and an inorganic oxide, and the residue at 1000 ° C. when measured with a thermogravimetric analyzer is 100 parts by weight. 1
It comprises 5 to 200 parts by weight of the flame retardant composition which is 0% by weight or more.

The resin component (A) used in the foam of the present invention comprises 30 to 90% by weight of a low density polyethylene resin.
And 10 to 70% by weight of a linear low density polyethylene resin
Consists of If the amount of the low-density polyethylene resin is too small, the foaming property of the resin component is reduced, so that a foam having a desired expansion ratio is not obtained. If the amount is too large, the tensile strength is reduced.

The above-mentioned low-density polyethylene resin is usually produced by a radical polymerization reaction under high pressure, and conventionally used low-density polyethylene (density 0.91 to 0.91).
0.93 g / cm ³ ). If the MI of the low-density polyethylene resin is too low, the moldability is reduced, and the appearance of the foam is liable to deteriorate. If the MI is too high, the heat resistance is reduced, so that the MI is limited to 1 to 10 g / 10 minutes. .

The above-mentioned linear low-density polyethylene refers to propylene, 1-butene, 1-pentene, 1-hexene, 1-hexene,
By copolymerizing a small amount (1 to 10 mol%) of an α-olefin such as octene and 4-methyl-1-pentene,
A resin in which an appropriate number of short-chain branches are introduced into a linear stem polymer, thereby reducing the density.If the density is too low, the heat resistance is reduced, and if the density is too high, the foaming property of the resin component is reduced. order but decrease, since not a foam having a desired expansion ratio, is limited to 0.915~0.94g / cm ^3, preferably 0.92~0.935g / cm ^3.

[0015] The MI of the above linear low density polyethylene is
If it is too low, the moldability is reduced, and the appearance of the foam is liable to deteriorate. If it is too high, the heat resistance is reduced.
It is limited to 0 g / 10 min, and preferably 1 g to 10 g / 10 min.

The flame retardant composition (B) used in the foam of the present invention comprises ammonium polyphosphate, tris (2-hydroxyethyl) isocyanurate, and an inorganic oxide.

As the above-mentioned ammonium polyphosphate, those commonly used conventionally can be used, and the degree of polymerization is generally 2%.
00 to 1000. The above-mentioned ammonium polyphosphate has a powdery surface whose surface is coated with a melamine-formaldehyde copolymer resin or the like, and has excellent fluidity in the resin,
Further, it is preferable because it is hardly soluble in water.

The above tris (2-hydroxyethyl) isocyanurate has a structure represented by the following formula.

Embedded image

Examples of the inorganic oxide include magnesium oxide, aluminum oxide, titanium oxide, cobalt oxide, vanadium oxide, chromium oxide, manganese oxide, iron oxide, nickel oxide, zinc oxide, antimony trioxide, and silicon oxide. No. Among them, titanium dioxide is excellent in flame retardancy, and exhibits excellent flame retardancy even in a small amount. Therefore, titanium dioxide is preferably used, and preferably at least 20% by weight of the inorganic oxide is titanium dioxide.

The composition ratio of the flame retardant composition (B) is preferably from 40 to 94.9% by weight, since the flame retardancy is lowered if the amount of ammonium polyphosphate is too small or too large. Also, tris (2-hydroxyethyl) isocyanurate has a low flame retardancy if it is too little or too much.
~ 40% by weight is preferred. Further, if the amount of the inorganic oxide is too small or too large, the flame retardancy is reduced.
Zero weight is preferred.

In the flame retardant composition (B) used in the present invention, if the residue at 1000 ° C. as measured by a thermogravimetric analyzer in an air atmosphere is too small, a sufficient nonflammable film is formed during combustion. Without this, sufficient flame retardancy cannot be imparted to the resin component (A), so that the content is limited to 10% by weight or more in the flame retardant composition (B), preferably 20%.
More than weight.

If the amount of the flame retardant composition (B) is too small, sufficient flame retardancy cannot be imparted. If the amount is too large, the mechanical properties are greatly reduced and the resin composition (A) cannot be used. It is limited to 5-200 parts by weight, preferably 7-100 parts by weight, per 100 parts by weight.

In the foam of the present invention, if necessary, a flame retardant aid, a crosslinking aid, an antioxidant, a stabilizer, a pigment, a metal damage inhibitor, and the like can be used.

As the above flame retardant aid, in addition to the three-component mixed flame retardant system, a flame retardant aid such as red phosphorus may be added as long as foaming of the resin is not hindered. However, as a flame retardant aid,
It is not preferable to use hydrated metal oxides such as aluminum hydroxide and basic magnesium carbonate. This is because the addition of these hydrated metal oxides may impair the flame-retardant performance of the flame-retardant coating generated during combustion and may not effectively exhibit a synergistic effect.

The above-mentioned red phosphorus may be a commercially available one, 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 amount of the main flame retardant to be blended. If the amount is too large, flame retardancy can be obtained, but the foaming property is impaired. On the other hand, 100 parts by weight or less is preferable.

The crosslinking assistant is not particularly limited as long as it is a polyfunctional monomer and causes a crosslinking reaction with an electron beam. One or more vinyl groups or allyl groups may be present in one molecule. Aromatic or aliphatic compounds; and compounds containing one or more acryloyloxy or methacryloyloxy groups.

Specifically, for example, divinylbenzene,
Diallylbenzene, divinylnaphthalene, trimethylolpropane trimethacrylate, ethylvinylbenzene, 1,9-nonanediol dimethacrylate, 1-nonanemonomethacrylate, 1,6-hexanediol methacrylate, 2,2-bis [4- (acryloxy Diethoxy) phenyl] propane, 1,2,4-benzenetricarboxylic acid diallyl ester, 1,2-benzenedicarboxylic acid diallyl ester, 1,3-benzenedicarboxylic acid diallyl ester, 1,4-benzenedicarboxylic acid diallyl ester and These closely related homologs and the like can be mentioned. These may be used alone or as a mixture of two or more.

If the amount of the crosslinking aid is too small, the crosslinking is insufficient and a homogeneous foam cannot be obtained, or the material strength at high temperature becomes insufficient. If the amount is too large, the crosslinking density increases. The amount is preferably 0.05 to 10 parts by weight, more preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the resin component (A).

Examples of the antioxidant include, for example, 2,6-di
cresol derivatives such as -t-butyl-p-cresol; sulfur compounds such as dilaurylthiopropionate; The antioxidant is preferably used in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of the resin component.

As the above-mentioned stabilizer, any of phenol-based, phosphorus-based, sulfur-based and amine-based stabilizers can be used.

As a method for producing a foam of the present invention, for example, a foaming agent is added to the resin component (A) and the flame retardant composition (B), and a single-screw extruder, a twin-screw extruder, a Banbury mixer, A method in which the mixture is supplied to a kneading device such as a kneader mixer or a roll, kneaded, formed into a sheet shape, irradiated with an electron beam, crosslinked, and heated and foamed in a hot blast stove.
The irradiation and the heating and foaming may be performed continuously or in a batch system.

The foaming agent (C) may be one that generates a decomposed gas upon heating (pyrolytic foaming agent),
Upon heating with the resin component (A), a material (physical foaming agent) that generates bubbles in the polymer formed body by heating and decompression may be used.

The thermal decomposition type foaming agent is not particularly limited as long as it generates a decomposition gas upon heating. Azodicarbonamide, benzenesulfonylhydrazide, dinitrosopentamethylenetetramine, toluenesulfonylhydrazide, 4,4- A thermally decomposable organic blowing agent such as oxybis (benzenesulfonyl hydrazide) is preferably used.

When a pyrolysis type organic foaming agent is used as the foaming agent (C), if the amount is too small, a predetermined expansion ratio cannot be obtained, and if it is too large, large bubbles may be partially formed. Since a uniform foam cannot be obtained, the amount is preferably 1 to 40 parts by weight based on 100 parts by weight of the resin component (A).

If the irradiation amount of the electron beam is too low, a foam having a desired expansion ratio cannot be obtained, and if it is too high, the mechanical properties of the obtained foam deteriorate. And more preferably 0.1 to 2 Mrad.

[0037]

The present invention will be described in more detail with reference to the following examples, which are merely for explanation and do not limit the present invention.

(Examples 1 to 4, Comparative Examples 1 to 7) Tables 1 and 2
A predetermined amount of low-density polyethylene having a density and MI described in (1) and a linear low-density polyethylene having 1-octene as a copolymerization component (referred to as “LLDPE” in the table). To 100 parts by weight of the resin component (A) consisting of: a predetermined amount of ammonium polyphosphate; tris (2-hydroxyethyl) isocyanurate (described as “TEHIC” in the table); and anatase-type titanium dioxide as an inorganic oxide ("Titanium dioxide" in the table
), Silicon dioxide, zinc oxide, diantimony trioxide (Comparative Example 5); a flame retardant composition (B) composed of decabromodiphenyl oxide (Comparative Example 5, described as “DBDPO” in the table); Azodicarbonamide 6 as C)
Parts by weight, 0.3 parts by weight of 2,6-di-t-butyl-p-cresol as an antioxidant, 0.3 parts of dilauryl thiopropionate
Parts by weight and 0.5 parts by weight of methylbenzotriazole as a metal damage inhibitor were supplied to a twin-screw extruder and melt-kneaded and extruded at 190 ° C. to obtain a continuous sheet having a thickness of 0.3 mm.

An electron beam is applied to the obtained continuous sheet at 1,000 k.
A predetermined amount is irradiated at an accelerating voltage of V to cause crosslinking, and further, the continuous sheet is continuously foamed in a vertical hot-air foaming furnace (maintained at 250 ° C. by hot air and an infrared heater),
A foam was obtained.

The residues of the flame retardant composition (B) at 1000 ° C. measured by a thermogravimetric analyzer are shown in Tables 1 and 2.
The obtained foams were subjected to the following tests, and the results are shown in Tables 1 and 2.

Evaluation thickness of foam : The thickness of the obtained foam was measured with a caliper. Expansion ratio: The density of the obtained foam was measured with an electronic hydrometer (manufactured by Mirage Co., model “ED120T”).
The reciprocal is noted. Flammability and fuming: The flammability classification and the fuming classification were evaluated in accordance with JIS D1201. Appearance: Observed visually, the presence or absence of appearance defects such as uneven foaming was observed, and evaluated as follows. ：: no poor appearance was observed ×: poor appearance was observed

[0042]

[Table 1]

[0043]

[Table 2]

[0044]

Since the polyethylene resin foam of the present invention has the above-described structure, it has self-extinguishing properties, excellent flame retardancy, a small amount of smoke generated during combustion, corrosion of equipment, etc. Does not occur and is excellent in safety. In addition, since primary foaming or the like does not occur in the extruder during the manufacturing process, bubbles are uniform and the appearance is good.

Therefore, the polyethylene resin foam of the present invention is suitably used for applications requiring flame retardancy, particularly as interior materials for automobile members, aircraft, trains and the like.

Since the method for producing a foam of the present invention has the above-described structure, a foam having the above-mentioned effects can be easily obtained.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 23/04 C08L 23/04 F-term (Reference) 4F071 AA18 AA82 AA88 AB17 AB18 AB23 AC19 AE07 AH03 AH04 AH07 BA01 BC01 4F073 AA05 BA07 BA48 BA51 BA52 BB01 CA42 HA11 4F074 AA20 AA21 AB00 AB05 AC17 AC21 AC31 AD13 BA13 BB25 CA29 CC04Y CC06X CC24X CC32Y CC46 CC49 DA02 DA18 DA23 DA32 DA33 DA35 DA45 4J002 BB03W BB03 DE0DE0 BB03 DE078 EQ029 ES009 EU197 EV289 FB266 FD030 FD070 FD130 FD140 FD329 GC00 GG02 GL00 GM00

Claims (4)

[Claims] (A) a density of 0.91 to 0.93 g / cm
³ , 30 to 90% by weight of a low density polyethylene resin having a melt index of 1 to 10 g / 10 minutes measured according to ASTM D1238, and a density of 0.915 to 0.94
g / cm ³ , the melt index is 0.2 to 20 g /
100 parts by weight of a resin component consisting of 10 to 70% by weight of a linear low-density polyethylene resin for 10 minutes, and (B) ammonium polyphosphate and tris (2-hydroxyethyl)
A polyethylene-based flame-retardant composition comprising 5 to 200 parts by weight of an isocyanurate and an inorganic oxide, wherein the residue at 1000 ° C. as measured by a thermogravimetric analyzer is 10% by weight or more. Resin foam. 2. The flame retardant composition (B) comprises 40 to 94.9% by weight of ammonium polyphosphate, 5 to 40% by weight of tris (2-hydroxyethyl) isocyanurate, and 0.1 to 20% of an inorganic oxide. 2. The polyethylene resin foam according to claim 1, wherein the foam comprises polyethylene. 3. The polyethylene resin foam according to claim 1, wherein the inorganic oxide contains titanium dioxide. 4. (A) Density 0.91 to 0.93 g / cm
³ , 30 to 90% by weight of a low density polyethylene resin having a melt index of 1 to 10 g / 10 minutes measured according to ASTM D1238, and a density of 0.915 to 0.94
g / cm ³ , the melt index is 0.2 to 20 g /
100 parts by weight of a resin component comprising 10 to 70% by weight of a linear low-density polyethylene resin for 10 minutes, (B) ammonium polyphosphate, tris (2-hydroxyethyl) isocyanurate, and an inorganic oxide. Of the residue at 1000 ° C. as measured by a thermogravimetric analyzer.
5 to 200 parts by weight of the flame retardant composition, which is 0% by weight or more, and 1 to 40 parts by weight of the foaming agent (C) are kneaded, formed into a sheet, and irradiated with an electron beam of 0.1 to 5 Mrad. The method for producing a polyethylene resin foam according to any one of claims 1 to 3, wherein the foam is foamed.