JPH0357636A - Fire retardant sheet - Google Patents

Abstract

PURPOSE:To secure sufficient thremal insulation properties while holding a carbonized foaming layer without boring the base material described hereunder by combustion and melting thereof even when it is strongly heated by providing a fire retardant layer wherein the carbonized foaming layer is formed by heating at least on the single side of the base material made of a film constituting of polymeric material which incorporates many hydroxyl groups in the molecular chain and has decomposition temp. close to m.p. or lower than it. CONSTITUTION:PVA is optimum as polymeric material constituting a film forming base material. The following substance is properly utilized as a fire retardant. This substance incorporates a carbonized layer forming agent, a carbonization catalyst and a foaming agent as a main component and furthermore is blended with a carbonized layer reinforcing agent and a binder in accordance with necessity. As the carbonized layer forming agent, carbohydrate such as starch and saccharose or polyhydric alcohol such as pentaerythritol, dipentaerythritol and hexytol can be utilized. Phosphate e.g. such as ammonium phosphate is utilized as the carbonization catalyst. As the foaming agent, the fire retardant foaming agent which generates noncombustible gas by thermal decomposition is preferably utilized.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a flame retardant sheet for covering combustible materials to prevent the combustible materials from burning in the event of a fire. This relates to a flame-retardant sheet suitable for wrapping around cables such as cables and communication lines to prevent burnout of these cables. Conventional technology Conventional flame retardant treatment methods for combustible materials such as cables include applying a flame retardant paint to the surface of the combustible material, or forming a flame retardant layer on the surface of a sheet-like base material. Methods such as winding are used.

The flame retardant used here generally contains a halogen compound. Although this type of flame retardant has good flame retardant properties and is an excellent flame retardant, it generates harmful halogen gas when ripened and generates a large amount of smoke, making it difficult to perform its function in emergency situations such as fire. is not appropriate. On the other hand, in recent years, flame retardants that do not contain halogen and form a carbonized foam layer when ripened to provide flame retardancy have been developed and are now commercially available. This type of flame retardant usually consists of a carbon layer-forming agent such as a carbohydrate or polyhydric alcohol, a carbonization catalyst such as a phosphate, a phosphate ester, a sulfate, or a sulfamate, and a foaming agent that generates gas and foams when heated. The main component is a carbonized layer reinforcing agent, a binder, etc., and when heated, it decomposes and carbonizes without burning and foams, and the carbonized foam layer dissipates heat. This is to protect the combustible materials inside.

These flame retardants are usually supplied in the form of paints, but since it takes time and effort to apply and dry them, they are applied to a sheet-like base material and applied to cables, etc. It is possible to prevent combustion of the object by wrapping it around the object.

In view of the problems that the invention aims to solve, it is preferable to use a material that is itself non-flammable or flame-retardant as the base material for this type of flame-retardant sheet.
There are no suitable materials for wrapping cables, etc., because they lack mechanical strength or flexibility, or are expensive.

Therefore, ordinary woven fabrics made of natural, recycled or synthetic fibers and films made of composite resin are used, but the selection of the material is extremely difficult.

That is, the base material is woven fabric of natural, recycled or synthetic fibers,
If a flame retardant is coated on one side, when it is strongly ripened, the flame retardant will carbonize and foam on the side coated with the flame retardant, producing a flame retardant effect, but the threads that make up the woven fabric Because it is made of thin fibers, it has a large contact area with air, and when heated strongly, it easily ignites and burns on surfaces that are not coated with flame retardant. When the woven fabric catches fire and burns, the fiber molecules rapidly decompose and lose strength, causing it to fall apart under the slightest external force. The carbonized and foamed flame retardant itself does not have strength and can only hold its shape when it is supported on the base material, so if the woven fabric of the base material collapses, the carbonized foam layer of the flame retardant will no longer be able to maintain its shape. It is not possible to sufficiently prevent internal cables, etc. from burning, which may exist. In addition, woven fabric has a thick structure, so it has poor workability when wound around gables, etc., and the wound thickness becomes thick. On the other hand, if a synthetic resin film such as polyester, nylon, or polyolefin is used as the base material and a flame retardant is coated on the surface, the base material can be made sufficiently thin and the winding process will be easier. It has excellent elasticity, can be rolled thinly, and unlike woven fabric, it does not catch fire or burn. However, these synthetic resins are easily melted by heat. The carbonized foam layer produced from the flame retardant blocks heat from the outside, but its insulation effect is not complete, and some of the heat is transmitted to the inside, albeit gradually. As a result, when the base material is heated above its melting point, the heat melts it into a low-viscosity liquid, which flows down and creates holes. Moreover, the film surrounding the hole contracts due to the heat, causing the hole to expand rapidly. As mentioned above, the carbonized foam layer of the flame retardant cannot exist on its own, so it shrinks as the film shrinks, or when the film melts, it flows away with the melt. Therefore, when using a film like the one mentioned above, if it is heated strongly, holes will form in the base material, and internal cables will be directly exposed to heat through the holes, making it impossible to achieve a sufficient combustion prevention effect. Can not. The present invention has been developed in view of the above circumstances, and is thin and flexible, does not burn or melt holes in the base material even when strongly aged, and retains the carbonized foam layer sufficiently. The purpose of this is to provide a flame retardant sheet that can ensure a good ripening effect. As a means to solve the problem, the flame retardant sheet of the present invention is made of a base material made of a film of a polymeric material that contains a large number of hydroxyl groups in its molecular chains and whose decomposition temperature is close to or lower than the melting point. It is characterized by having a flame retardant layer formed on at least one side that forms a carbonized foam layer when heated. Polyvinyl alcohol is most suitable as the polymer material constituting the base film.

The flame retardant forming the flame retardant layer preferably contains a carbonized layer forming agent, a carbonization catalyst, and a blowing agent as main components.

As mentioned above, in the present invention, a flame retardant layer is formed on one or both sides of a base material. As the base material, a film of polymeric material is used, which contains a large number of hydroxyl groups in its molecular chains and whose decomposition temperature is close to or lower than the melting point. As such a film, a polyvinyl alcohol film is most preferred.

Cellulose-based films such as cellophane and cellulose diacetate films can also be used.
The appropriate thickness of the film is about 10 to 200 mm. The flame retardant in the present invention forms a carbonized foam layer when heated, and prevents ripening by the carbonized foam layer. As such flame retardants, as mentioned above, carbonized layer retardant,
It is suitable that the composition contains a carbonization catalyst and a blowing agent as main components, and further contains a carbonization layer reinforcing agent and a binder as necessary. As the carbonized layer forming agent, carbohydrates such as starch and sweet potato loin, or polyhydric alcohols such as bentaerythritol, diventaerythritol, hexitol, etc. can be used. These substances have a large amount of hydroxyl groups, and when ripened, a dehydration reaction occurs under the action of a carbonization catalyst, resulting in carbonization. The blending amount of this carbonized layered drug is 20 to 30 in dry weight ratio.
The weight percentage is appropriate. Examples of carbonization catalysts include phosphates such as ammonium phosphate, trimethyl phosphate, triethyl phosphate, tributyl phosphate, trioctyl phosphate, tributoxyethyl phosphate, triphenyl phosphate, cresyl diphenyl phosphate, octyl phosphate, etc. g4 acid esters such as diphenyl phosphate, V
Examples include fa acid salts such as Ah ammonium, and sulfamic acid salts such as ammonium sulfamate. In particular, ammonium polyphosphate is suitable. The appropriate amount of the carbonization catalyst is about 20 to 35% by weight on a dry weight basis.

Next, as the blowing agent, various substances that generate gas by thermal decomposition can be used, but flame-retardant blowing agents that generate nonflammable gas are particularly preferred. Specific examples of flame retardant foaming agents include dicyandiamide, melamine, urea, methylurea, butylurea, pentaerythritol, and ammonium phosphate. In particular, dicyandiamide has the effect of producing nonflammable gas and foaming, as well as promoting the polycondensation reaction of phosphoric acid as a carbonization catalyst, and has a synergistic effect of flame retardation. In addition, pentaerythritol and ammonium phosphate themselves generate nonflammable gas and foam, and also act as carbonization layer-forming agents and carbonization catalysts, respectively. Other foaming agents include azo foaming agents such as azodicarbonamide and azobisisobutyronitrile, and nitroso foaming agents such as dinitrosopentamethylenetetramine and N,N'-dinitroso-14.14'-dimethylterephthalamide. agent, p-toluenesulfonyl hydrazide, p
, p'-oxybis(benzenesulfonylhydrazide)
It is also possible to use organic blowing agents such as hydrazide blowing agents, such as hydrazide blowing agents, and inorganic blowing agents such as sodium bicarbonate. Generally more effective than inorganic blowing agents! I blowing agent is preferable because it has a higher decomposition temperature. Furthermore, even among substances that generate gas or foam through thermal decomposition, it is preferable that the decomposition product or gas is mainly composed of nonflammable gas. Even if the material generates gas through thermal decomposition, it is undesirable to use a substance that generates hydrogen gas, such as sodium borohydride. The amount of foaming agent blended is 20-3571 in dry weight ratio! amount%
The degree is appropriate. It is also possible to add a metal compound as a reinforcing agent for the carbonized layer. It is preferable to use a metal hydroxide as a reinforcing agent for the carbonized layer because it produces a flame retardant effect due to the absorption reaction (release of crystallized water) during heating and a foaming effect due to the released water. Examples of metal hydroxides that can be used as carbon layer reinforcement agents include aluminum hydroxide, magnesium hydroxide, dawsonite, calcium aluminoxide, gypsum dihydrate, calcium hydroxide, subborate borate, barium metaborate, and borax. , kaolin clay, calcium carbonate, etc. Further, other metal compounds such as titanium dioxide, zinc oxide, and calcium oxide can also be used.

The amount of carbonized layer reinforcing agent is 8 to 15% by weight on dry weight basis.
is appropriate.

It is also preferable to add a binder to bind the ingredients in the flame retardant. As a binder, synthetic resins such as acrylic, vinyl acetate, urethane, and silicone,
Natural rubber, SBR, NBR, urethane rubber, silicone rubber, etc. can be used.

Considering the flexibility of the flame retardant, it is preferable to use a rubber-based binder. However, those with a highly three-dimensional structure are not preferred because they hinder the foaming of the flame retardant. The appropriate amount of the binder is about 5 to 10% by weight on a dry weight basis.

In addition, other additives such as pigments, thickeners, and antioxidants may be added as appropriate. Function The polymer material used as the base material in the present invention has a melting point when ripened and a decomposition temperature that is close to each other or a decomposition temperature lower than the melting point, so the base material does not melt when heated. Decomposition occurs first, or melting and decomposition proceed simultaneously. Therefore, unlike films made of polyester or nylon, the film does not melt and flow or shrink and form holes, and the film decomposes under heat while retaining its shape.

In addition, since these polymer materials have a large number of hydroxyl groups, carbonization progresses through a dehydration reaction by the carbonization catalyst in the flame retardant during thermal decomposition reactions, and the released water has a foaming effect. The film then carbonizes while retaining its shape, and the carbonized film supports the carbonized flame retardant on its surface. Furthermore, even when melting occurs before decomposition, there is no clear melting point, and the melting temperature and decomposition temperature are close to each other. Therefore, when heated strongly, melting and decomposition proceed simultaneously, and the melt viscosity when melted is also relatively high. The decomposed and carbonized product becomes a skeleton, and the highly viscous molten material is stuck to it, and the molten material does not drip or flow like with polyester or nylon. Furthermore, the molten material acts as a binder and is firmly bound to the decomposition products, so that they do not easily collapse with a small force. In this state, carbonization of the melt further progresses, eventually forming a strong carbonized layer. In addition, the polymeric material used as the material for the film in the present invention decomposes at the same time as or before melting, so it cannot be manufactured by extrusion molding like polyester or nylon. It is not widely promoted. Therefore, even when heated, large thermal contraction does not occur.

Therefore, in the present invention, when the flame retardant sheet is strongly heated, carbonization occurs in the heated portion before the base material melts, or melting and carbonization proceed in parallel, so that the molten material There is no flow, no collapse of decomposition products, and no shrinkage of the surrounding base material. Therefore, even if the base material is heated and decomposed, the heated part will not melt and open, and it will continue to maintain its original shape and support the carbonized foam layer of the flame retardant layer on its surface. be.

Example: A flame retardant composition was prepared according to the formulation shown in the following table.

Flame retardant formulation (solid content 52.8%) The above-mentioned flame retardant formulation was applied to a 25 μm thick polyvinyl alcohol film (Example 1) and cellophane (Example 2).
It was applied to one side of the film to give a dry coverage of 70 to 729/ml. This was then dried to form a flame retardant layer to produce the flame retardant sheet of the example. For comparison, a polyethylene terephthalate film (Comparative Example 1), a nylon 6 film (Comparative Example 2), and a polypropylene film (Comparative Example 3) each having a thickness of 25 μm were prepared.
) and rayon soft woven fabric (warp count 30 density 60 pieces/25ll1, weft count 30 density 53 pieces/25nn,
A flame retardant sheet was manufactured by applying a flame retardant to a plain weave structure (240 μn thick) (Comparative Example 4) under the same conditions. The following tests were conducted on the flame retardant sheets of Examples and Comparative Examples. ■Oxygen index Compliant with JIS K 7201. (Test piece A-2)
■Insulating properties Fix a 501 mm square heat insulating sheet to a 401 lφ holder and support it horizontally with the flame retardant coated side facing upward.
Adjust the oxidizing flame of the Bunsen burner to 35 mm, and apply the tip of the reducing flame to the underside of the insulation sheet for 2 minutes. IIR
The maximum temperature on the top surface of the ripened sheet was measured using a radiation thermometer.

■Flame barrier property The heat insulating sheet was exposed to the flame of a burner for 20 minutes under the same conditions as the heat insulation test, and the time required for the flame to penetrate the heat insulating sheet was measured.

■Drip resistance A 180x10I sheet is hung vertically and its upper end is supported. Bunsen burner oxidizing flame of 35 liters
The tip of the reducing flame touched the bottom edge of the heat insulating sheet, and the combustion state of the sheet was clearly observed. ■Sheet thickness Compliant with JIS 1 1096.

The test results were as follows. The umbrella carbonized foam layer collapses and has no insulation properties, making it impossible to measure. Drip resistance ○: Does not drip and continues to maintain the shape of the insulation sheet.

×: The base material melts and drips. It cannot hold its shape. Δ: Melting and dripping No, but do not apply flame retardant The surface catches fire and burns.

Effects of the Invention Therefore, according to the present invention, even if the base material is carbonized when the flame retardant sheet is ripened, it retains its shape and continues to support the flame retardant layer. Therefore, the carbonized foam layer of the flame-retardant layer does not collapse, remains extremely effective for a long time, and can prevent internal cables from burning out. In addition, since the base material is a film, it does not easily ignite and burn even when heated strongly, unlike woven fabric, and the polymeric film that makes up the base material has sufficient strength and flexibility. Therefore, it can be easily wound around an object to be protected such as a cable.

Furthermore, the base material and flame retardant layer do not contain halogen compounds, and no toxic gas is generated when ripened.
It produces little smoke and has good flame retardant effects.

Claims (1)

[Scope of Claims] 1. A carbonized foam layer formed by heating on at least one side of a base material made of a film of a polymeric material that contains a large number of hydroxyl groups in its molecular chains and whose decomposition temperature is close to or lower than the melting point. 2. The flame retardant sheet 3 according to claim 1, wherein the polymeric material is polyvinyl alcohol. The flame retardant sheet according to claim 1 or 2, wherein the constituent flame retardant is mainly composed of a carbonized layer forming agent, a carbonization catalyst, and a foaming agent.