JP2001261855A - Fire retardant sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fire retardant sheet, particularly a retardant sheet for a facility treating radioactive substances, which does not contain poisonous material such as halogen, etc., does not generate halogenic gas when burning and is less ash left when incinerated. SOLUTION: The fire retardant sheet is obtained by processing a resin composition constituted of at least: (A) a thermoplastic elastomer composed of at least one of a polyamide elastomer, a polyurethane elastomer and a polyester elastomer: (B) a thermoplastic elastomer composed of at least one of an ethylene-vinyl acetate copolymer, an ethylene-ethyl acrylate copolymer, an ethylene-butyl acrylate copolymer, an ethylene-methyl acrylate copolymer, an ethylene-methyl methacrylate copolymer, an ethylene-vinyl alcohol copolymer and poly vinyl alcohol; and (C) a phosphorus compound, and the contraction rate of the sheet after heating is not less than 40% in an area ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flame-retardant sheet which does not contain harmful substances such as halogens, does not generate halogen-based gas during combustion, and has a low ash content during incineration. Related to the adhesive sheet.

[0002]

2. Description of the Related Art Conventionally, vinyl chloride sheets, halogen-containing flame retardant-containing sheets, and highly filled sheets of metal hydroxide have been used as flame-retardant sheets for facilities handling radioactive substances. However, these sheets have problems such as generation of halogen-based gas at the time of combustion, and radioactive contamination due to adsorption of radioactive substances by a large amount of ash after burning of metal hydroxide. In order to solve such problems, a flame-retardant sheet which is non-halogen and has less residual ash is required. A method of adding melamine cyanurate to a nylon 66/6 copolymer to make it flame-retardant is disclosed in
Although disclosed in Japanese Patent Application Laid-Open No. 8-42218, it was not satisfactory because sufficient flexibility was not obtained.

Further, a composition comprising at least one kind of a polyamide elastomer, a polymerized fatty acid type polyamide and an ethylene-vinyl acetate-vinyl alcohol copolymer, and at least one kind of a nitrogen-containing compound and a phosphorus-containing compound, and a molded product thereof (Japanese Unexamined Patent Publication No. 10-101928), at least one of polyamide-based elastomer and polymerized fatty acid-based polyamide,
There has been proposed a composition comprising a saponified ethylene-ethyl acrylate copolymer, at least one of a nitrogen-containing compound and a phosphorus-containing compound, and a molded product thereof (JP-A-11-116801).

[0004] In these inventions, the composition ratios of polyamide-based elastomer, polymerized fatty acid-based polyamide and ethylene-vinyl acetate-vinyl alcohol copolymer (Japanese Patent Laid-Open No. 10-101928), polyamide-based elastomer and polymerized fatty acid-based It is described that the composition ratio of a polyamide and a saponified ethylene-ethyl acrylate copolymer (JP-A-11-116801) does not affect the flame retardancy at all. However, it has been found that dripping is severely generated and burns depending on the composition ratio, and flame retardancy has not been sufficiently exhibited.

[0005]

SUMMARY OF THE INVENTION The present invention aims at achieving flame retardancy by utilizing the shrinkage of a sheet.
The present invention provides a flame-retardant sheet which does not generate harmful gases such as halogens when burning, does not contain halogen, and has a small residual ash content when incinerated, particularly a flame-retardant sheet suitable for use in a facility handling radioactive substances. Aim.

[0006]

That is, the present invention provides:
(A) a thermoplastic elastomer comprising at least one of a polyamide elastomer, a polyurethane elastomer and a polyester elastomer, (B) ethylene-
Vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-butyl acrylate copolymer, ethylene-methyl acrylate copolymer, ethylene-methyl methacrylate copolymer, ethylene-vinyl alcohol copolymer, And a thermoplastic resin composed of at least one of polyvinyl alcohol and (C) a phosphorus-based compound, and a sheet obtained by processing the resin composition, wherein the shrinkage in area is 40%. A flame-retardant sheet characterized by the above.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The flame-retardant sheet referred to in the present invention is
The thickness is 50 μm to 3 mm. (Thermoplastic Elastomer) The thermoplastic elastomer (A) used in the present invention refers to a Vicat softening point (ASTM).
D1525) is preferably 70 ° C. or higher. If the Vicat softening point is 70 ° C. or less, the material may drip and burn when igniting the flame-retardant sheet when the fire approaches. The thermoplastic elastomer comprises at least one of a polyamide-based elastomer, a polyurethane-based elastomer, and a polyester-based elastomer, and is preferably a polyamide-based elastomer.

As the polyamide elastomer, a polyamide elastomer comprising a polyamide skeleton and a polyether and / or polyester skeleton is preferable.
Specifically, the constituent components of the hard segment having a polyamide skeleton include, for example, polycaprolactam, polyhexamethylene adipamide, polyhexamethylene sebacamide,
Polyundecanamid, polylaurolactam and the like can be used. The constituent components of the soft segment having a polyether and / or polyester skeleton include, for example, poly (oxytetramethylene) glycol, poly (oxypropylene) glycol, and poly (ethylene adipate).
Glycol, poly (butylene-1,4 adipate) glycol and the like can be used.

As the polyurethane elastomer, diisocyanates having a bulky molecule as a hard segment, for example, 4,4'-diphenylmethane diisocyanate or 2,4 '& 2,6-toluene diisocyanate and a short-chain polyol, for example, ethylene glycol,
Polyurethane obtained by the reaction of 1,3-propylene glycol, bisphenol A or the like, and a polyether diol such as poly (oxytetramethylene) glycol, poly (oxypropylene) glycol or polyester diol such as polycaprolactone glycol as a soft segment Polyurethane obtained by the reaction of poly (ethylene 1,4 adipate) glycol, poly (butylene 1,4 adipate) glycol, poly (diethylene glycol adipate) glycol, poly (hexanediol-1,6 carbonate) glycol with diisocyanate Polyurethane-based elastomers, which are linear multi-block copolymers of these hard segments and soft segments, can be used.

As the polyester-based elastomer, a multi-block copolymer of a hard segment and a soft segment having an aromatic crystalline polyester skeleton as a hard segment and a polyether skeleton or a polyester skeleton as a soft segment is preferable. Specifically, as a component of the hard segment having an aromatic crystalline polyester skeleton, for example, polybutylene terephthalate, polyethylene terephthalate, polybutylene naphthalate, or the like can be used. As a component of the soft segment, for example, polytetramethylene ether glycol, poly (1,2 propylene oxide) glycol, poly (ethylene oxide) glycol, or the like can be used.

(Thermoplastic resin) The thermoplastic resin (B)
Ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-butyl acrylate copolymer, ethylene-methyl acrylate copolymer, ethylene-
One or more of methyl methacrylate copolymer, ethylene-vinyl alcohol copolymer, and polyvinyl alcohol can be used. Preferably, it is at least one of an ethylene-vinyl acetate copolymer and an ethylene-vinyl alcohol copolymer. More preferably, the ethylene vinyl acetate copolymer and the ethylene vinyl alcohol copolymer are mixed at a ratio of 80:20 to 20:80.

When an ethylene-vinyl acetate copolymer is used, even if the ethylene-vinyl acetate copolymer having a vinyl acetate (VA) content of 10 to 50% by weight is used alone,
A mixture of a high-content ethylene-vinyl acetate copolymer and a low-VA ethylene-vinyl acetate copolymer or polyethylene to adjust the VA content to 10 to 50% by weight may be used. . When the VA content of the ethylene-vinyl acetate copolymer is less than 10% by weight,
In many cases, the flame retardancy of the flame retardant sheet becomes insufficient,
If the content is more than 10% by weight, the tackiness may become severe or the thermal deformation may increase. When an ethylene-vinyl alcohol copolymer is used, the ethylene content is preferably less than 50 mol%. When the ethylene content is 50 mol% or more, the flame retardancy of the flame retardant film and sheet becomes insufficient.

(Phosphorus Compound) Examples of the phosphorus compound used in the present invention include phosphine, phosphine oxide, biphosphine, phosphonium salt, phosphinate, phosphate, phosphite and the like.
More specifically, triphenyl phosphate, methyl neopentyl phosphate, pentaerythritol diethyl diphosphite, methyl neopentyl phosphate, phenyl neopentyl phosphate, pentaerythritol diphenyl diphosphate, dicyclopentyl hypophosphate, dicyclopentyl phosphate Neopentyl hypophosphite, phenyl pyrocatechol phosphite, ethyl pyrocatechol phosphate, dipyrocatechol hypopositive phosphate and the like can be mentioned.

Further, as the phosphorus compound, a phosphoric acid ester is preferable, and a hydroxyl group-containing aromatic phosphoric acid ester is more preferable. These phosphate esters may be used in combination with the above-mentioned phosphorus compound not containing a hydroxyl group. The hydroxyl group-containing aromatic phosphate is a phosphate containing one or two or more phenolic hydroxyl groups in tricresyl phosphate, triphenyl phosphate, a condensed phosphate thereof, or the like.

(Shrinkage Ratio) The fact that the shrinkage ratio of the flame-retardant sheet after heating is 40% or more in area ratio is defined by the following equation. Shrinkage = (Area of sheet surface before heating−Area of sheet surface after heating) ÷ Area of sheet surface before heating The method for measuring the shrinkage is the Vicat softening point of the thermoplastic elastomer (A) component + 10 ° C. Vicat softening point +10
In the range of 0 ° C, the maximum value among the shrinkage rates measured at 10 levels at 10 ° C intervals is adopted as the shrinkage rate.

The method of shrinking the area by 40% or more is preferably a method of stretching a sheet. Such stretching may be performed at the same time as the sheet is formed, such as by increasing the take-up speed in inflation molding or T-die molding, or the material once formed into a sheet may be processed by an existing stretching method such as biaxial stretching. good. The shrinkage after heating is preferably at least 40% in area ratio, more preferably at least 60%. Most preferably, it is at least 80%. If the shrinkage is less than 40%, the shrinkage of the film or sheet is insufficient, and the material may ignite and burn.

(Others) The weight ratio of component (A) to component (B) is preferably from 90:10 to 10:90, more preferably from 70:30 to 30:70.
When the weight fraction of the component (A) exceeds 90%, the flame retardancy of the flame retardant sheet becomes insufficient, and the shrinkage when approaching a fire is high, but the material is ignited and burns while dripping. May be. On the other hand, when the weight fraction of the component (B) exceeds 90%, the shrinkability of the flame-retardant sheet may be insufficient, and sufficient flame retardancy may not be exhibited. The weight ratio of the total amount of the components (A) and (B) to the component (C) is 100: 0 to 100:
The ratio is preferably 50:50, more preferably 9:50.
5: 5-65: 35, most preferably 90: 10-7
0:30. When the weight fraction of the component (C) exceeds 50%, the sheet shrinkage becomes insufficient, and sufficient flame retardancy is not exhibited.

[0018]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not limited to these examples. After dry-blending with the composition shown in Tables 1 and 2, the mixture was melt-kneaded with a twin-screw extruder and then pelletized. Table 1
Examples 1 to 10 and Comparative Examples 1 to 4 in Table 2 were stretched by adjusting the take-up speed in molding with a T-die to produce a 100 μm sheet. In Comparative Examples 5 to 7 in Table 2, pellets were press-molded to produce 100 μm sheets.

Various evaluations were performed based on the following. (1) Shrinkage: The shrinkage rate (%) of a sheet having a size of 3 cm × 3 cm and a thickness of 100 μm was measured and evaluated. The contraction rate was derived according to the following equation. Shrinkage = (Area of sheet surface before heating−Area of sheet surface after heating) ÷ Area of sheet surface before heating (2) Flame retardancy: Thickness of 100 measured by UL94 vertical combustion test
Performed on μm film. (3) Ash content: About 1 g of the pellet was kept at 600 ° C. for 30 minutes, and the residual substance was evaluated in terms of% by weight.

(Description of Abbreviations in Table) TPA: Vicat softening point (ASTM D1525) 156 ° C., specific gravity 1.0
1. Polyamide-based thermoplastic elastomer having a melt index of 8 (at 235 ° C., 1 kg) TPU: Softening point (JIS K7206) 130 ° C., polyurethane-based thermoplastic elastomer having a specific gravity of 1.18 TPEE: Vicat softening point (ASTM D1525) 8
9 ° C, specific gravity 1.07, melt index 10 (AST
MD1238) thermoplastic polyester elastomer

EVA1: VA content 41% by weight, Evaflex EV40LX (manufactured by Mitsui DuPont Chemical Co., Ltd.) EVA2: VA content 25% by weight, Evaflex P25
05C (manufactured by Mitsui Dupont Chemical Co., Ltd.) EVOH: ethylene content 47 mol%, EVAL EPG
156 (manufactured by Kuraray Co., Ltd.) Phosphate ester: aromatic-containing condensed phosphate ester, C
R-733S (manufactured by Daihachi Chemical Co., Ltd.)

[0022]

[Table 1]

[0023]

[Table 2]

[0024]

As described above, the flame retardant sheet according to the present invention is
Achieved high flame retardancy by utilizing the shrinkage of the sheet, and is useful as a flame retardant sheet suitable for use in facilities handling radioactive materials, such as floor-covered sheets such as floors, walls, and ceilings. It is.

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Claims (4)

[Claims] 1. A thermoplastic elastomer comprising at least one of a polyamide elastomer, a polyurethane elastomer and a polyester elastomer,
(B) Ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-butyl acrylate copolymer, ethylene-methyl acrylate copolymer, ethylene-methyl methacrylate copolymer, ethylene-vinyl A sheet obtained by processing a resin composition comprising at least a thermoplastic resin comprising at least one of an alcohol copolymer and polyvinyl alcohol, and (C) a phosphorus-based compound; Is 40% or more. 2. The weight ratio of component (A) to component (B) is 9
The flame retardant sheet according to claim 1, wherein the ratio is from 0:10 to 10:90. 3. The total amount of the components (A) and (B) and (C)
The weight ratio of the components is from 100: 0 to 50:50.
Or the flame-retardant sheet according to 2. 4. The flame-retardant sheet according to claim 1, wherein the phosphorus compound (C) is a phosphoric acid ester.