JPH06184330A - Flame-retardant sheet - Google Patents

Abstract

PURPOSE:To provide a flame-retardant sheet which is useful for covering a building, an instrument, etc., of the site where radiative material is handled, is excellent in self-extiguishability, and does not generate a halogen gas during combustion by selecting a flame-retardant sheet made from a specific resin compsn. and having specified thickness and limiting oxygen index. CONSTITUTION:A flame-retardant sheet is selected which is made from a resin compsn. comprising 100 pts.wt. ethylene-vinyl acetate copolymer resin having a melt index of 0.5-20g/10min and a vinyl acetate content of 5-28wt.% 5-25 pts.wt. melamine cyanurate, and 0.5-5 pts.wt. red phosphorus compd. (e.g. a masterbatch comprising red phosphorus and EEA) and which has a thickness of 30-1.000mum and a limiting oxygen index of 26 or higher.

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 for a radioactive material handling place. More specifically, the present invention does not generate a halogen-based gas at the time of combustion, has no ash residue, and has excellent handleability. Floors, wall surfaces, devices, desks, buildings and materials of radioactive material handling sites. The present invention relates to a flame-retardant sheet used for covering places, shelves, etc.

[0002]

2. Description of the Related Art Conventionally, nuclear power plants, chemical plants, hospitals,
Since laboratories, etc. handle radioactive materials, in order to prevent contamination with radioactive materials as much as possible, the floor surface, wall surface, equipment, desks, etc. of the workplace handling radioactive materials should be covered with radioactive material adhesive sheets, or , In order to avoid damage from wind and rain, theft, etc. of the building under construction, material storage, shelves, etc.
Protective sheets have been used from an aesthetic point of view. However, since the olefin resin sheet has been used for the radioactive substance adhesive sheet as well, there is no protection against the flame of the burner during construction, and there is a trouble such as a fire, so there is a need for a flame-retardant sheet. Is increasing. In response to this, vinyl chloride sheets, halogen-based flame retardant-containing polyolefin sheets, etc. were proposed, but halogen-containing compounds are generated in the event of a fire or incineration, which causes environmental pollution problems and is not desirable. It has not been proposed, and a polyolefin-based sheet containing a large amount of halogen-free inorganic flame retardant (aluminum hydroxide, magnesium hydroxide, etc.) was also proposed, but the sheet becomes thick and heavy, and the handling and strength become weak. Moreover, when it is incinerated, a large amount of ash that adsorbs a trace amount of radioactive material is generated, and it takes a lot of money to store it for a long period of time.
It's a problem.

In order to solve such a problem, there has been proposed a flame-retardant sheet which does not generate a halogen-containing compound even when incinerated and generates little ash. For example, a thermoplastic polymer having a polyvalent lower fatty acid and / or an ammonium salt thereof (JP-A-4-46963), oxalic acid, ammonium oxalate or a derivative thereof (JP-A-4-46964),
_{H 2 N-C (= X} ) -NHCH compound represented by ₂ COOH (JP 4-46965), guanidino compound (JP-A-4-46966), urea (JP-A-3-155
No. 39) is proposed. However, these flame retardants are polar compounds and are difficult to mix with non-polar polyolefin resins, and the thermal decomposition temperature is lower than the processing temperature of the polyolefin resin, resulting in thermal decomposition and large amounts. Gas is generated and continuous production is not possible. Therefore, these flame retardants are mixed with the powder of ethylene-vinyl acetate copolymer, sprayed on the surface of the polyester film at a rate of 200 g / m ² , and passed through a hot air oven at 130 ° C. to obtain ethylene-acetic acid. Melt the vinyl copolymer,
Immediately, a low-density polyethylene film having a thickness of 25 μm was pressure-bonded to the upper surface of the film using a pressing roll to obtain a three-layer film (Example 1 of JP-A-4-46963), which required a film cost due to a special production method. It is not economical, and in another example, a large amount of a softening agent and urea are blended to form a middle layer, and both outer layers are film layers containing no flame retardant (JP-A 3-1).
5539), if such a three-layer film is produced by the air-cooled inflation method, it is not economical because it can only make a film with a small diameter, and since both outer layers do not contain a flame retardant, it is inferior in flame retardancy and is a self-extinguishing sheet. Is insufficient.

[0004]

In view of such a situation, in the present invention, the most economical method for producing a sheet is single-layer inflation or single-layer T-die casting, which has the most processability as a film resin component. Adopting good polyethylene resin, excellent self-extinguishing property, LOI of 26 or more, light and easy to handle, excellent mechanical strength, easy to adsorb radioactive material dust, non-slip property and safe, when incinerated An object of the present invention is to provide a flame-retardant sheet that does not generate a halogen-containing compound, does not generate a large amount of ash, and is suitable for use in a radioactive material handling office that burns completely at high temperatures to become a gas.

[0005]

Means for Solving the Problems The inventors of the present invention blended a large number of organic compounds and inorganic compounds into a polyethylene resin and tested the production of a large number of single-layer sheets by an air-cooled inflation method or a T-die casting method. As a result, when a single-layer film was made of a resin composition consisting of a specific organic compound and an inorganic compound and a specific polyethylene resin, it was difficult to satisfy many of the above-mentioned requirements used in radioactive material handling offices. The present invention has been completed by finding that a fuel sheet can be provided.

That is, the present invention has a melt index of 0.5.
~ 20g / 10min, vinyl acetate content 5 ~ 28wt%
Of a resin composition comprising 100 parts by weight of ethylene-vinyl acetate copolymer resin, 5 to 25 parts by weight of melamine cyanurate, and 0.5 to 5 parts by weight of a red phosphorus compound.
A flame-retardant sheet for preventing radioactive material contamination, having a self-extinguishing property and a limiting oxygen index of 26 or more.

In the present invention, as the matrix of the sheet, many ethylene-vinyl acetate copolymer resins (hereinafter referred to as EVA) having a melt index of 0.5 to 20 g / 10 min and a vinyl acetate content of 5 to 28% by weight are used. Selected from among the polyethylene-based resins of. The reason is that when a sheet is laid on the floor, it is dangerous if a person walking on it slips, EVA is non-slip, and very small amounts of radioactive substance dust and general dust are adsorbed very well. Among them, EVA has the best flame retardancy among polyethylene resins, EVA has very rubber-like elasticity and is easy to handle, and even if a large amount of flame retardant is added, the physical properties of the sheet do not deteriorate. Prove things in an experiment,
This is because they have found that they meet the requirements for flame retardant sheets for nuclear power plants. EVA melt index is 0.5
If it is less than g / 10 min, it becomes difficult to form the sheet, and if it is more than 20 g / 10 min, the sheet strength becomes weak and it is too tacky, which is undesirable because of blocking. Further, if the vinyl acetate content of EVA is less than 5% by weight, the sheet loses its tackiness and slips, which is dangerous, and the adsorptivity of dust deteriorates.
The flame retardancy also deteriorates, the rubber elasticity also disappears, the handleability also deteriorates, and when a large amount of a flame retardant is added, the mechanical strength of the sheet decreases, which is not desirable. Vinyl acetate content is 28
If it is more than 5% by weight, the film will be blocked, the handleability will be poor, the tackiness of the sheet will be too strong, the feel will be poor when walking on it, and the molding of the sheet will be difficult, such being undesirable.

In the present invention, as the flame retardant, melamine cyanurate is used in an amount of 5 to 25 parts by weight based on 100 parts by weight of EVA. This melamine cyanurate is a reaction product of melamine and cyanuric acid. Two tautomeric forms of cyanuric acid are considered, and chemically, the enol form is usually called cyanuric acid and the keto form is isocyanuric acid. The cyanuric acid used in the present invention includes both enol form and keto form. Means

The melamine cyanurate used in the present invention can be obtained, for example, by mixing an aqueous solution of melamine and an aqueous solution of cyanuric acid, reacting them, and filtering the formed precipitate, but the production method is not particularly limited. Not a thing. Also, it is acceptable to contain a small amount of unreacted melamine and cyanuric acid, but if a large amount remains, it should be avoided as it will deteriorate the environment of the sheet processing workplace and cause the foaming phenomenon on the surface of the sheet. Is good. This melamine cyanurate, which is preferably surface-treated with an organic or inorganic compound, is desirable because it is well dispersed in a resin. Such melamine cyanurate is commercially available from Nissan Chemical Industries under the trade name of MC-610. Its chemical structural formula is as follows.

[Chemical 1]

The reason why melamine cyanurate is used as a flame retardant in the present invention is that it has good compatibility with EVA,
Even if a large amount is added to EVA, the workability of the sheet does not decrease, the thermal decomposition temperature is 300 ° C. or higher, and it does not decompose at the EVA processing temperature of 160 to 220 ° C. Therefore, the surface of the EVA sheet Without causing the foaming phenomenon,
A good quality sheet can be obtained, and the EVA-only sheet is sticky and causes blocking, or melamine cyanurate is a fine powder with a high melting point and therefore exists in a particle state on the surface of the EVA sheet to prevent blocking. The effect is given, the handleability of the sheet is improved, and the flame retardant effect is also EVA.
This is because it is possible to clear the flame-retardant requirement standard as a sheet for a radioactive handling site by a synergistic action with a red phosphorus compound. When the blending amount of melamine cyanurate to EVA is 5 parts by weight or less, the flame retarding effect and the blocking preventing effect are not exhibited, and when it is 25 parts by weight or more, the film forming property, mechanical strength, handleability, etc. of the sheet are poor. It is also not desirable because it is not economical. However, even if melamine cyanurate has a flame-retardant effect, a sheet of only EVA and melamine cyanurate cannot clear the above criteria.

Therefore, in the present invention, it is preferable to use EVA, melamine cyanurate and a red phosphorus compound in combination.
It is an essential component of the invention. In the present invention, the red phosphorus compound is a flame retardant aid containing red phosphorus as a main component, and since red phosphorus is a relatively unstable compound, it easily ignites,
Particularly, it is preferable that the surface of red phosphorus particles is coated with a stabilizer such as a thermosetting resin because it is easy to cause dust explosion and economically easily generate phosphine or an oxidation product to deteriorate EVA. . Red phosphorus has very little smoke generation and gas generation, and when added in a small amount, it gives an extremely high flame retardant effect through the synergistic action of EVA and melamine cyanurate. You can clear the criteria. In the present invention, EVA
0.5 to 5 parts by weight of a red phosphorus compound is mixed with 100 parts by weight. When the amount is 0.5 parts by weight or less, the predetermined flame retardancy standard cannot be cleared, and when the amount is 5 parts by weight or more, the flame retardancy effect becomes uncertain, the moldability of the sheet is poor, and the mechanical properties of the formed sheet are poor. It is not desirable because it deteriorates the strength, gives the sheet a red color, increases the cost, and produces ash when the sheet is incinerated.

In the present invention, it has been found that when EVA, melamine cyanurate and a red phosphorus compound are used in combination, a flame retardant synergistic effect is produced, but the reason is not clear, but E
Since the combustion starting temperature of VA and the decomposition temperature of melamine cyanurate are close to each other, it is assumed that melamine cyanurate takes away the combustion heat of EVA and that ammonia and carbon dioxide generated by thermal decomposition act for self-extinguishing. On the other hand, since red phosphorus compounds are also close to the combustion start temperature of EVA, they start burning rapidly, but soon they become oxygen-deficient and carbonization begins immediately, which becomes a bulky state and prevents spread of fire. It is thought that the effects of the above will be combined to rapidly extinguish the flame.

The resin composition for producing the flame-retardant sheet of the present invention may contain various auxiliary agents. For example, E
LDPE, LLDPE, within the range that does not impair the physical properties of VA
VLDPE, HDPE, EEA, ionomer, PP,
Stabilizer, antioxidant, neutralizer, UV absorber, pigment, carbon black, cross-linking agent, lubricant, etc.
A processability improving agent, a coupling agent, an antistatic agent, an antifungal agent, an anti-tracking agent and the like may be added.

The resin composition for producing the flame-retardant sheet of the present invention comprises EVA, melamine cyanurate, red phosphorus compound and other above-mentioned compounding agents, Banbury mixer, pressure kneader, twin-screw extruder, Using a Busco kneader, Henschel mixer, roll kneader, etc., 130-230 ° C
The mixture can be heated and kneaded in the range of 1 to prepare a mixture, which can be directly or once pelletized, and then a sheet can be prepared by an inflation method, a T die casting method or the like.

The flame-retardant sheet of the present invention has a thickness of 30 to 1,
000 μm. If it is less than 30 μm, the mechanical strength is poor and the handleability is poor, which is undesirable.
If it is more than μm, the self-extinguishing property is lost and the economical efficiency is also lost, which is not desirable. Generally, a flame-retardant sheet having a thickness of 200 μm is used because it has a good balance of strength, handleability, moldability, flame retardancy, economical efficiency and the like.

The flame-retardant sheet of the present invention has a good film-forming property of the resin composition as a raw material, and therefore, compared with the flame-retardant sheet for a nuclear power plant, a single-layer wide sheet is formed and the sheet has a low temperature. Since it has good heat-sealing properties, there is an advantage that wide sheets can be joined together by heat-sealing and a large-area sheet can be easily produced.

The present invention is described in detail below with reference to examples, but the present invention is not limited to these examples.

Example 1 Preparation of Raw Material Resin Composition Ethylene-vinyl acetate copolymer (EV manufactured by Nippon Unicar Co., Ltd.
A, melt index 2, vinyl acetate content 18% by weight) 100 parts by weight, melamine cyanurate (manufactured by Nissan Kagaku, MC-610) 22 parts by weight, master batch of red phosphorus compound (WN-221 manufactured by Nippon Unicar. Is a red phosphorus masterbatch made by Nippon Unicar, which comprises 80 wt% EEA and 20 wt% red phosphorus.) 6.5 parts by weight,
0.5 parts by weight of phenolic antioxidant (Ciba Geigy, Irganox 1010) in a Banbury mixer
After kneading at 60 ° C for 10 minutes, pellets were obtained with a granulator.

Method for producing blown film An blown film having a thickness of 200 μm was produced by the air cooling method under the following apparatus and processing conditions, and a slit width of 500 mm
And the sheet. (1) Extruder: Placo L-40, φ40 mm
Inflation film processing device, screw type: full flight L / D: 24/1 Screen: 40/60/40 mesh (2) Dye: Modern Machinery Co., Ltd., φ75mm die cap: 0.8mm (3) Cooling Equipment: Single lip straight and with conical color (4) Resin temperature: 160-170 ℃ (5) Expansion ratio: 2.2 (6) Winding speed: 5.0m / min

Sheet evaluation (1) Tensile strength: JIS z-1702 Vertical 250 kg / cm ² Horizontal 190 kg / cm ² (2) Stretch: JIS z-1702 Vertical 680% Horizontal 700% (3) Tear strength: JIS P -8116 Vertical> 100kg / cm Horizontal> 100kg / cm JIS K-6781 Vertical 1.7kg / 500mm Horizontal 1.9kg / 500mm (4) Limiting oxygen index: K-7201 28 (5) Vicat softening temperature: K-7206 69 ℃ (6) Density: 1.02g
/ Ml (7) Ash content: 800 ℃, 30 minutes 0.4wt% (8) Embrittlement temperature: K-6301 F ₅₀ -60 ℃ (9) Water content: 120ppm (10) Self-extinguishing property: Vertical sheet The flame was fired for 10 seconds with the prescribed combustion flame, but it did not ignite. (11) Non-slip property: Even if a person walks on the seat, the seat does not move from the floor surface and the person does not slip on the seat, which is safe. (12) Handleability: The flexibility of the seat and the balance of the waist are well balanced, and workability is good when the seat is opened or covered. (13) Blocking property: The sheets can be easily pulled out from the original roll without sticking to each other. (14) Dust adsorption property: Once dust in the air was adsorbed to the sheet, it did not separate. (15) Heat-sealing property: When the sheets were overlapped and heat-sealed at 130 ° C, they were easily adhered and the sealing strength was 0.75 kg / 15 mm, and they did not peel off when used in a nuclear power plant. .

Example 2 Preparation of Raw Material Resin Composition Ethylene-vinyl acetate copolymer (EV manufactured by Nippon Unicar Co., Ltd.
A, melt index 5, vinyl acetate content 28% by weight) 100 parts by weight, melamine cyanurate (manufactured by Nissan Kagaku, MC-610) 6 parts by weight, master batch of red phosphorus compound (WN-221 manufactured by Nippon Unicar. Is a red phosphorus masterbatch consisting of 80 wt% EEA and 20 wt% red phosphorus made by Nippon Unicar.) 20 parts by weight, 0.5 parts by weight of a phenolic antioxidant (made by Ciba Geigy, Irganox 1010) is Banbury mixer. At 160
After kneading at 10 ° C. for 10 minutes, pellets were obtained with a granulator.

Method for producing blown film An blown film having a thickness of 35 μm was produced by the air cooling method under the following apparatus and processing conditions, and the slit width was 1800 mm.
And the sheet. (1) Extruder: Placo K-50, φ50 mm
Inflation film processing device Screw type: Full flight L / D: 28/1 Screen: 40/60/40 mesh (2) Dye: Modern Masimery Co., Ltd., φ300m
m Die cap: 1.0mm (3) Cooling device: Single lip straight and with conical color (4) Resin temperature: 160-170 ° C (5) Expansion ratio: 2.2 (6) Winding speed: 15.0m / min

Sheet Evaluation (1) Tensile Strength: JIS z-1702 Vertical 190 kg / cm ² Horizontal 180 kg / cm ² (2) Elongation: JIS z-1702 Vertical 690% Horizontal 700% (3) Tear strength: JIS P -8116 Vertical> 100kg / cm Horizontal> 100kg / cm JIS K-6781 Vertical 1.6kg / 500mm Horizontal 1.8kg / 500mm (4) Limiting oxygen index: K-7201 27 (5) Vicat softening temperature: K-7206 45 ℃ (6) Density: 1.01g
/ Ml (7) Ash content: 800 ℃, 30 minutes 0.3wt% (8) Embrittlement temperature: K-6301 F ₅₀ -63 ℃ (9) Water content: 123ppm (10) Self-extinguishing property: Sheet vertically The flame was fired for 10 seconds with the prescribed combustion flame, but it did not ignite. (11) Non-slip property: Even if a person walks on the seat, the seat does not move from the floor surface and the person does not slip on the seat, which is safe. (12) Handleability: The flexibility of the seat and the balance of the waist are well balanced, and workability is good when the seat is opened or covered. (13) Blocking property: The sheets can be easily pulled out from the original roll without sticking to each other. (14) Dust adsorption property: Once dust in the air was adsorbed to the sheet, it did not separate. (15) Heat-sealing property: When the sheets were overlapped and heat-sealed at 130 ° C., they were easily adhered and the sealing strength was 0.78 kg / 15 mm, and did not peel off when used in a nuclear power plant. .

Comparative Example 1 The ethylene-vinyl acetate copolymer of Example 1 was replaced with high-pressure low-density polyethylene (manufactured by Nippon Unicar, melt index 5, density 0.922 g / ml).
When the same experiment as in Example 1 was conducted, the limiting oxygen index was 25, the self-extinguishing property was poor, and the non-slip property, handleability, dust adsorbing property, heat sealing property, etc. were poor.

Comparative Example 2 Except that no red phosphorus compound was used in Example 1,
When the same experiment as in Example 1 was conducted, the limiting oxygen index was 22, and the self-extinguishing property and flame retardancy were insufficient.

Comparative Example 3 The same experiment as in Example 1 was carried out except that 6 parts by weight of the red phosphorus compound was used in Example 1. As a result, the limiting oxygen index was 29.5, and the self-extinguishing property and flame retardancy were high. Although the flammability was sufficient, the tensile strength (longitudinal) was 218 kg / cm ² , the sheet was colored red, and the ash content was 4 wt%, which was not good.

Comparative Example 4 An experiment similar to that of Example 1 was carried out except that the amount of melamine cyanurate used in Example 1 was changed to 3 parts by weight. The flammability was insufficient.

Comparative Example 5 The amount of melamine cyanurate used in Example 1 was 30
An experiment similar to that of Example 1 was carried out except that the parts by weight were changed. As a result, the limiting oxygen index was 31, and the self-extinguishing property and flame retardancy were sufficient, but the film-forming property of the sheet was poor and the productivity was low. Fell, and the mechanical strength and handleability deteriorated.

Comparative Example 6 In Example 1, the expansion ratio was 1.5 and the winding speed was 3.
The same experiment as in Example 1 was carried out except that the die cap was 5 m / min and the die cap was 1.3 mm, and a sheet having a thickness of 1200 μm was produced. The limiting oxygen index was 25, and the self-extinguishing property and flame retardancy were It was insufficient.

Comparative Example 7 In Example 1, the expansion ratio was 3.5 and the winding speed was 8.
The same experiment as in Example 1 was carried out except that the thickness was 3 m / min and the die cap was 0.5 mm, and a sheet with a thickness of 20 μm was produced. The sheet had insufficient mechanical strength and puncture resistance, was easily torn, and was too thin. When you wind or stretch the sheet,
It was difficult to handle and took a long time to work.

Comparative Example 8 In Example 1, an EV having a vinyl acetate content of 4% by weight was used.
The same experiment as in Example 1 was carried out except that A was replaced, but the dust adsorption and non-slip properties were deteriorated.

Comparative Example 9 In Example 1, the vinyl acetate content was 30% by weight of E
An experiment similar to that of Example 1 was conducted except that the sheet was placed on the floor and walked on it, except that the VA was replaced. Moreover, when the rolled sheet was unrolled, it was blocked and the workability of spreading was poor.

[0033]

INDUSTRIAL APPLICABILITY According to the present invention, since a sheet for radioactive material handling offices is made of a resin composition in which an ethylene-vinyl acetate copolymer, melamine cyanurate and a red phosphorus compound are used in combination, it is used in a nuclear power plant or the like. Self-extinguishing property, flame retardancy, mechanical strength, low temperature embrittlement resistance, heat sealability, dust adsorption, handleability, blocking resistance, low incineration residue (ash content) required for various sheets It does not generate harmful substances when incinerated, the aesthetics of the sheet, the odorlessness of the sheet, the weather resistance, the water resistance, the non-toxicity, etc. are clear, and the film formation and productivity of the sheet are good and it is a single layer. ,
Economical efficiency is also sufficient.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Susumu Suda 2-17-7 Matsuba-cho, Higashimatsuyama City, Saitama Prefecture (72) Inventor Hachiro Vineyard 4-2-18 Teraodai, Ayase City, Kanagawa Prefecture (72) Inventor Shoji Hayashi 726-35 Shimbashi-cho, Izumi-ku, Yokohama-shi, Kanagawa Prefecture (72) Inventor Katsuhiro Hotta 5-25-17 Takeshi, Yokosuka City, Kanagawa Prefecture

Claims (1)

[Claims] 1. A melt index of 0.5 to 20 g / 1
0 min, ethylene with vinyl acetate content of 5-28% by weight
A thickness of 30 to 1000 μm made of a resin composition comprising 100 parts by weight of vinyl acetate copolymer resin, 5 to 25 parts by weight of melamine cyanurate and 0.5 to 5 parts by weight of a red phosphorus compound.
m, self-extinguishing, flame-retardant sheet for radioactive material handling offices with a limiting oxygen index of 26 or more.