JPH10182895A - Flame-retardant plastic sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a sheet excellent in flame retardance by compounding an ethylene-vinyl acetate copolymer having a specified vinyl acetate content with specified amts. of red phosphorus and melamine sulfate and further with a metal hydroxide, an antioxidant, and an ultraviolet absorber. SOLUTION: 100 pts.wt. ethylene-vinyl acetate copolymer having a vinyl acetate content of 8-20wt.% is compounded with 3-10 pts.wt. red phosphorus and 7-25 pts.wt. melamine sulfate as flame retardants and, in order to enhance the flame retardance, is further compounded with 30-120 pts.wt. metal hydroxide (e.g. magnesium hydroxide and/or aluminum hydroxide), an antioxidant, an ultraviolet absorber, and if necessary a plasticizer, a stabilizer, a lubricant, etc. The resultant compsn. is formed by a T-die method, etc., into a plastic sheet with a thickness of 0.05-1.0mm, pref. 0.15-0.5mm, which does not generate a noxious as when incinerated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for extending a building to a construction site or for covering equipment to protect equipment for periodic repairs in a place where radioactive materials are handled, such as a nuclear power plant. The present invention relates to a flame-retardant plastic sheet which is flammable, emits no toxic gas even when burned, has little residual ash, and can be easily disposed of. More specifically, the present invention relates to a flame-retardant plastic sheet formed using a composition comprising an ethylene-vinyl acetate copolymer as a base material and red phosphorus, melamine sulfate, and optionally a metal hydroxide.

[0002]

2. Description of the Related Art Conventionally, halogen-containing compounds and heavy metals have been used as flame retardants in order to make plastic sheets used in construction sites and the like flame-retardant. There is a problem that toxic gas is generated or a large amount of ash is generated.In addition, in the case of a polyolefin resin sheet that has not been subjected to a flame retardant treatment, when sparks of welding are scattered, it may cause a fire and is not desirable. . For this reason, a polyolefin-based resin sheet has been proposed in which a large amount of a metal hydroxide such as aluminum hydroxide or magnesium hydroxide is blended with a polyolefin-based resin to impart flame retardancy. The ash content is not preferable because enormous expense is required for long-term storage management of the ash. Especially when used in a place where radioactive materials are handled, it is difficult to treat ash remaining radioactive.

[0003] In order to solve such problems, there have been proposed flame-retardant films and resin compositions which do not generate a halogen-based gas at the time of incineration and generate little residual ash. For example, urea (Japanese Unexamined Patent Publication No.
-7767), poly (lower) fatty acids and their ammonium salts (JP-A-4-46963), oxalic acid, ammonium oxalate or derivatives thereof (JP-A-4-4696).
4) a flame-retardant composition comprising a compound represented by H2NC (= X) -NHCH2COOH (JP-A-4-46965) and a carbonate of a guadinino compound (JP-A-4-46966) as a flame retardant; (Japanese Patent Application Laid-Open No. 4-332640) has been proposed. However, these flame retardants are polar substances, and have very poor compatibility with polyolefin resins which are nonpolar substances, and the thermal decomposition temperature of the substance to be blended as a flame retardant is lower than the processing temperature of the polyolefin resin. For this reason, stable processing is difficult. For this reason, a large amount of a softening agent is blended into the resin, and the molding temperature of the resin is adjusted to be equal to or lower than the decomposition temperature of the flame retardant (Japanese Unexamined Patent Publication No. 3-7767). A special manufacturing method is used in which the mixture is sprayed on a polyester film, heated, and then immediately pressed against a polyethylene film to form a film (Japanese Patent Laid-Open No. 3-15539). In such a production method, there were problems that the film did not have sufficient strength and the production cost was extremely high.

In addition, a method has been proposed in which a specific number of red phosphorus and melamine cyanurate are used as a flame retardant in an ethylene-vinyl acetate copolymer (JP-A-6-184330). Due to poor compatibility with vinyl acetate copolymer resin, it may plate out on the sheet surface during processing, or the melamine cyanurate that has plated out may stick to heated metal rolls etc., making it impossible to produce sheets stably. There was a problem. Melamine cyanurate is especially suitable for greases and pastes, water-based lubricants, lubricating dry films with various binders, forging, drawing, pressing, etc. A 6-membered melamine molecule and a cyanuric acid molecule are strongly bonded by hydrogen bonding and arranged in a plane, and the planes overlap with each other with a weak bonding force to form a cleaving property such as MoS ₂ or graphite. It is estimated that it has.
In addition, when hitting eyelets for hanging the sheet as a protective sheet for equipment, both of the proposed sheets have a single sheet structure, so the eyelets may fall out due to the weight of the sheet,
Moreover, there is a possibility that the form cannot be maintained, and the building construction sheet or the like does not satisfy the use standard.

[0005]

DISCLOSURE OF THE INVENTION The present invention has excellent flame retardancy and does not generate toxic gas or a large amount of ash during incineration disposal.
When fixed, it can be fixed properly with fixing tools such as eyelets,
Provided is a plastic sheet capable of maintaining a posture when suspended.

[0006]

According to the present invention, there is provided a composition comprising: "1. 100 parts by weight of an ethylene-vinyl acetate copolymer having a vinyl acetate content of 8 to 28% by weight;
A flame-retardant plastic sheet formed from a composition comprising a mixture of parts by weight of red phosphorus and 7 to 25 parts by weight of melamine sulfate. 2. 2. The flame-retardant plastic sheet according to item 1, wherein a composition containing 30 to 120 parts by weight of a metal hydroxide is used. 3. 3. The flame-retardant plastic sheet according to item 2, wherein the metal hydroxide is magnesium hydroxide and / or aluminum hydroxide. 4. 4. The flame-retardant plastic sheet according to any one of items 1 to 3, wherein the composition comprises a composition containing an antioxidant and an ultraviolet absorber. About.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the use of an ethylene-vinyl acetate copolymer having a vinyl acetate content of 8 to 28% by weight as a synthetic resin for a base material has been carried out in consideration of various physical properties such as flexibility. Because it is similar to the soft vinyl chloride resin used for the flame retardant sheet for construction made of soft vinyl chloride used in places, etc., it can be used in the same way as the conventional product, so it is easy to use. There is an advantage that there is no need to dispose an apparatus, and that processing can be easily performed with existing facilities for processing soft vinyl chloride resin. If the vinyl acetate content is 8% by weight or less, the flexibility of the film is impaired and the handling property is deteriorated. If the content is 28% by weight or more, the conventional processing equipment sticks to a heated metal roll and the workability is remarkably reduced, which is not preferable.

In the present invention, the use of red phosphorus and a melamine derivative as flame retardants is such that when a flame is brought close to a plastic containing red phosphorus, the plastic on the surface and the red phosphorus first burn,
Plastic combines with oxygen in the air to form carbon dioxide, water and carbon. In this case, the red phosphorus promotes carbonization of the ethylene-vinyl acetate copolymer. Red phosphorus, on the other hand, combines with oxygen to form oxides and water to form condensed phosphoric acid, and the film of the mixture of carbon and condensed phosphoric acid formed on the surface of the plastic becomes a layer that does not allow oxygen to pass through the surface of the plastic, thereby burning the plastic. Suppress and flame retardant. Red phosphorus must be present in an amount of 3 to 10 parts by weight. If the amount is less than 3 parts by weight, the flame retardant effect is not exhibited. If the amount is more than 10 parts by weight, the flame retardant effect is not improved and the mechanical strength of the film is reduced. This is because a chalk mark is easily formed and the handling property is deteriorated.

In this case, if melamine sulfate is present, the melamine sulfate is thermally decomposed during combustion to generate a nitrogen-containing gas. This generated gas blocks oxygen, and the melamine condenses while generating a nitrogen-containing gas. It becomes an insoluble insoluble material, and forms a layer of an insoluble infusible material mixed with a film of a mixture of carbon and condensed phosphoric acid to block oxygen, thereby improving the flame retardant effect. In the present invention, the addition of 25 parts by weight of melamine sulfate from 7 parts by weight is less than 7 parts by weight, the flame-retardant effect is reduced, and if it exceeds 25 parts by weight, the mechanical strength of the sheet is reduced or the chalk mark is reduced. This is because the handleability deteriorates, for example, it is easy to stick. The melamine sulfate used in the present invention has excellent compatibility with the ethylene-vinyl acetate copolymer resin, the thermal decomposition temperature is 350 ° C., and the processing temperature of the ethylene-vinyl acetate copolymer resin is between 120 ° C. and 200 ° C. When melamine sulfate is mixed with an ethylene-vinyl acetate copolymer resin and processed with a heated metal roll, problems such as adhesion of the melamine sulfate to the surface of the heated metal roll do not occur. Therefore, even if melamine sulfate is blended as a flame retardant, a high-quality sheet can be easily and stably produced. Since red phosphorus is a relatively unstable substance, it is easily ignited by itself, and phosphine and oxidation products may be purified to deteriorate the ethylene-vinyl acetate copolymer resin. What encapsulated red phosphorus with a thermosetting resin is preferable.

It is preferable to further add a metal hydroxide because the flame retardant effect is improved. As the metal hydroxide, magnesium hydroxide and aluminum hydroxide are preferable, and the blending amount is 30.
If it is less than 30 parts by weight, the flame-retardant effect is not improved, and if it is more than 120 parts by weight, the ash content when incinerated is increased, which is not preferable. When an antioxidant and an ultraviolet absorber are blended, aging when a sheet is stretched at a building construction site is prevented, and durability is improved. In the present invention, an auxiliary agent such as a plasticizer, a stabilizer, a lubricant, and a coloring agent can be blended as needed as long as the flame retardant effect is not impaired, and the characteristics of the ethylene-vinyl acetate copolymer resin are not impaired. A halogen-free polyolefin-based resin such as a polyethylene resin, a polypropylene resin, a polystyrene resin, and an ethylene-methyl methacrylate copolymer resin can be added as a resin component within the range.

The sheet can be produced by using a conventional apparatus for producing a soft vinyl chloride resin sheet. For example, a calendering method, a T-die method, an inflation method and the like are used. The thickness of the sheet can be adjusted depending on the use and scale in which it is used, but generally the thickness of the sheet is preferably about 0.05 mm to 1.0 mm, and about 0.1 mm.
Particularly preferred is 5 mm to 0.5 mm. If the thickness of the sheet is less than 0.05 m, the mechanical strength becomes small, and it becomes difficult to obtain a sheet having excellent durability and handleability. On the other hand, if the thickness of the sheet exceeds 1.0 mm, the productivity of the sheet deteriorates, and the handleability deteriorates because the sheet is heavy and the flexibility is impaired.

[0012]

【Example】

Examples 1 to 6 Ethylene-vinyl acetate copolymer resin (trade name: Tosoh Ultracene 631, manufactured by Tosoh Corporation, vinyl acetate content: 20)
%) 100 parts by weight of stearic acid phosphate 0.3 parts by weight as a lubricant, red phosphorus (Nova Red 120, manufactured by Rin Kagaku Kogyo KK) and melamine sulfate (Apinone 901, manufactured by Sanwa Chemical Co., Ltd.) as a flame retardant The components blended in the proportions shown in Fig. 1 were kneaded with a heating roll at 150 ° C to 160 ° C for 5 minutes. A sheet having a thickness of 1 mm was prepared from this kneaded material by a hot press at 160 ° C., and the limiting oxygen index was measured by a combustion test method for a high-grade pre-material by the oxygen index method of JIS K 7201. As shown in Table 1, each combination showed a self-extinguishing property with a limiting oxygen index of 23. In addition, in any of the combinations, the mixture was successfully kneaded and sheeted without sticking to the hot metal roll during the kneading of the rolls.

[0013]

[Table 1]

Example 7 Ethylene-vinyl acetate copolymer resin (trade name: Tosoh Ultracene 620F, manufactured by Tosoh Corporation, vinyl acetate content: 8)
%) 100 parts by weight of a lubricant, 0.3 parts by weight of stearic acid phosphate as a lubricant, 5 parts by weight of red phosphorus (Nova Red 120, manufactured by Rin Kagaku Kogyo KK) as a flame retardant, melamine sulfate (Apinone 901; manufactured by Sanwa Chemical Co., Ltd.) ) Were blended in an amount of 10 parts by weight, and kneaded with a heated roll at 150 ° C to 160 ° C for 5 minutes. This kneaded product is heated to a thickness of 1
mm sheet was prepared. When the limiting oxygen index was measured, a value of 23 indicated autodigestibility. In addition, the compound does not stick to the hot metal roll during roll kneading,
The seat is ready.

Example 8 The resin was an ethylene-vinyl acetate copolymer (trade name: Tosoh Ultracene 751, manufactured by Tosoh Corporation, vinyl acetate content: 28)
%), Except that the sheet was prepared in the same manner as in Example 2, and the sheet was evaluated in the same manner. In addition, the mixture did not stick to the hot metal roll during the kneading of the rolls, and the kneading and sheeting were successfully performed.

Comparative Examples 1-4 Ethylene-vinyl acetate copolymer resin (trade name: Tosoh Ultracene 631, manufactured by Tosoh Corporation, vinyl acetate content: 20)
%) 100 parts by weight of a mixture of 0.3 part by weight of stearic acid phosphate as a lubricant and melamine sulfate (Apinone 901; manufactured by Sanwa Chemical Co.) as a flame retardant at a ratio shown in Table 2 from 150 ° C. to 160 ° C. 5 with heating roll
Kneaded for a minute. A sheet having a thickness of 1 mm was prepared from the kneaded material by a hot press at 160 ° C., and the limiting oxygen index was measured. As shown in Table 2, the limiting oxygen index was 2 for all the formulations.
At 0, no self-extinguishing property was exhibited.

[0017]

[Table 2]

Comparative Examples 5 to 10 Ethylene-vinyl acetate copolymer resin (trade name: Tosoh Ultracene 631, manufactured by Tosoh Corporation, vinyl acetate content: 20)
%) 100 parts by weight of a lubricant, 0.3 parts by weight of stearic acid phosphate as a lubricant, 0.5 parts by weight of melamine sulfate (Apinone 901; manufactured by Sanwa Chemical Co., Ltd.) as a flame retardant, red phosphorus (Nova Red 120, phosphorus chemistry) (Manufactured by Kogyo Co., Ltd.) at the ratio shown in Table 4 and kneaded with a heating roll at 150 ° C. to 160 ° C. for 5 minutes. A sheet having a thickness of 1 mm was prepared from the kneaded material by a hot press at 160 ° C., and the limiting oxygen index was measured. As shown in Table 3, none of the formulations showed a self-extinguishing property with a limiting oxygen index of less than 23 '.

[0019]

[Table 3]

Comparative Examples 11 to 19 Ethylene-vinyl acetate copolymer resin (trade name: Tosoh Ultracene 631, manufactured by Tosoh Corporation, vinyl acetate content: 20)
%) 100 parts by weight of a lubricant, 0.3 parts by weight of stearic acid phosphate as a lubricant, and melamine cyanurate (MCA, manufactured by Mitsubishi Chemical Corporation) and red phosphorus (Nova Red 1) as flame retardants
20, manufactured by Rin Kagaku Kogyo Co., Ltd.) and kneaded with a heating roll at 150 ° C. to 160 ° C. for 5 minutes. Melamine cyanurate adhered to the hot metal roll and kneaded stably. Could not take out the sheet.

[0021]

[Table 4]

[0022]

Industrial Applicability The present invention has excellent flame resistance for uses such as protective covers for equipment and the like at the time of periodic repairs at nuclear power plants and the like, and does not generate harmful halogen-based gases when incinerated. In addition, an excellent effect with little residual ash is exhibited. Also, when used in building construction sites, it has good flame resistance and is easy to dispose.

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Claims (4)

[Claims] 1. An amount of 3 to 100 parts by weight of an ethylene-vinyl acetate copolymer having a vinyl acetate content of 8 to 28% by weight.
A flame-retardant plastic sheet formed of a composition containing 10 to 10 parts by weight of red phosphorus and 7 to 25 parts by weight of melamine sulfate. 2. The flame-retardant plastic sheet according to claim 1, wherein a composition containing 30 to 120 parts by weight of a metal hydroxide is used. 3. The flame-retardant plastic sheet according to claim 2, wherein the metal hydroxide is magnesium hydroxide and / or aluminum hydroxide. 4. The flame-retardant plastic sheet according to claim 1, wherein a composition comprising an antioxidant and an ultraviolet absorber is used.