JP2001261854A - Fire retardant sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fire retardant sheet, particularly a fire retardant sheet for a facility treating radioactive substances, which does not contain poisonous materials such as halogen, phosphorous, etc., does not generate halogenic gas when burning and is less in 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 polyvinyl alcohol; and (C) a metal hydroxide, 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 halogen and phosphorus, does not generate halogen-based gas during combustion, and has a low ash content when incinerated. It relates to a flame retardant sheet.

[0002]

2. Description of the Related Art Conventionally, vinyl chloride sheets, halogen-containing flame retardant-containing sheets, phosphorus-containing flame retardant-containing sheets, and highly filled metal hydroxide sheets have been used as fire-retardant sheets for facilities handling radioactive substances. . However, these sheets are subject to environmental pollution such as generation of halogen-based gas during combustion, water pollution by phosphorus, and radioactive contamination due to the adsorption of radioactive substances by the ash after burning a large amount of metal hydroxide. There was a problem. In order to solve such a problem, a flame-retardant sheet that is non-halogen or non-phosphorus 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 JP-B-58-42218, but it is not satisfactory because sufficient flexibility cannot be 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). In these inventions, the composition ratio 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, polymerized fatty acid-based polyamide, It is described that the composition ratio of the saponified ethylene-ethyl acrylate copolymer (JP-A-11-116801) has no effect on flame retardancy. 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.

[0004]

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

[0005]

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 comprising at least one of polyvinyl alcohol and (C) a metal hydroxide. % Or more.

[0006]

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-based elastomer, a polyamide-based 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 such as 4,4'-diphenylmethane diisocyanate and 2,4 '& 2,6-toluene diisocyanate and short-chain polyols such as 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.

(Metal hydroxide) The metal hydroxide used in the present invention includes aluminum hydroxide, magnesium hydroxide, calcium hydroxide and the like. Magnesium hydroxide is preferred in view of flame retardancy and processability. preferable. Further, it may be a synthesized product, a natural product or a crushed product thereof. Further, some of them may be surface-treated with a higher fatty acid, a higher fatty acid metal salt, a higher fatty acid ester, or a silane coupling agent such as aminosilane or epoxysilane.

The average particle size of the metal hydroxide is 0.1
It is preferably from 10 to 10 μm, more preferably from 0.1 to 10 μm.
2 to 5 μm. If the average particle size is less than 0.1 μm, the metal hydroxide will agglomerate and the sheet appearance will be poor. In addition, the viscosity of the resin composition increases, and sheet extrudability deteriorates. When the average particle diameter exceeds 10 μm, there arises a problem that the flame retardancy is deteriorated and the film becomes white when bent.

(Shrinkage Ratio) The fact that the shrinkage ratio of the flame-retardant sheet after heating is 40% or more in terms of 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 preferably includes a method of subjecting a sheet to stretching. 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 the component (A) to the 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 drip burning. 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 preferably 100: 0 to 80:20, more preferably 97: 3 to 85:15.
Most preferably, it is 95: 5 to 90:10. If the weight fraction of the component (C) exceeds 20%, the shrinkage of the sheet decreases, and the ash content after combustion increases, which makes it easier to adsorb radioactive substances, which is not preferable.

[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 were stretched by adjusting the take-off speed in molding with a T-die to produce a 100 μm sheet. Comparative Example 5 of Table 2
In No. 7, the pellet was press-molded to prepare a 100 μm sheet.

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.) Magnesium hydroxide 1: average particle diameter 0.8 μm, no surface treatment, Kisuma 5 (manufactured by Kyowa Chemical Co., Ltd.) Magnesium hydroxide 2: average particle diameter 0.8 μm, fatty acid surface treatment, Kisuma 5B (Kyowa 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 (5)

[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 metal hydroxide; A flame-retardant sheet having a ratio of 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 80:20.
Or the flame-retardant sheet according to 2. 4. The method according to claim 1, wherein the metal hydroxide has an average particle size of 0.1.
The flame-retardant sheet according to any one of claims 1 to 3, which has a thickness of 1 to 10 µm. 5. The flame-retardant sheet according to claim 1, wherein (C) the metal hydroxide is magnesium hydroxide.