JP2001329428A - Flame retardant polyvinyl alcohol fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flame retardant polyvinyl alcohol fiber having a high flame resistance and excellent in fiber properties and a fabric using the fiber. SOLUTION: This flame retardant polyvinyl alcohol fiber includes a phosphorus based flame retardant and a heat decomposition type foaming agent and/or a thermally expansive graphite.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyvinyl alcohol (hereinafter abbreviated as PVA) -based flame-retardant fiber which can be industrially produced at low cost, and a fabric using the fiber.

[0002]

2. Description of the Related Art Methods for imparting flame retardancy to various fibers such as acrylic fibers, polyester fibers, rayon fibers, and aramid fibers have been studied. Above all, PVA-based fibers have attracted attention as flame-retardant fibers because of their characteristics such as high mechanical performance, low cost, and low occurrence of melt drip.

For example, PVA fibers containing a halogen-containing resin such as polyvinyl chloride or a halogenated flame retardant,
PVA-based fibers using PVA copolymerized with vinyl chloride have been proposed (JP-B-37-12920, JP-B-37-19720).
No. 12920, Japanese Patent Publication No. 49-10823,
JP-B-51-19494). However, in recent years, the influence of various materials on the environment has been regarded as a problem. Particularly, since dioxin is generated during incineration, halogen-containing materials represented by polyvinyl chloride (halogen-containing resins, halogen-based resins). There is a strong demand for replacing non-halogen materials with fuels.

[0004] In view of the above, non-halogen PVA-based flame-retardant fibers containing substantially no halogen have been studied. For example, as a method using a phosphorus-based flame retardant, a method in which PVA-based fibers are immersed in an aqueous suspension of ammonium polyphosphate or the like and subjected to a surface coating treatment (JP-A-45-347).
62, JP-A-49-74768), a method in which a PVA-based fiber is immersed in a solution obtained by mixing a condensed phosphoric acid solution and a reaction accelerator, and then the fiber is heated to be phosphorylated. 48-28085), and a method of dry spinning an aqueous solution of PVA containing ammonium polyphosphate or polyphosphoramide (Japanese Patent Application Laid-Open Nos. 50-22050 and 50-22051). However, phosphorus-based flame retardants have low flame-retardant effect compared to halogen-based flame retardants, so that it is difficult to obtain sufficient flame-retardant effect. There is a problem that performance is impaired. JP-A-53-115794 discloses that a mixture of a phosphate-esterified PVA-based resin and a normal PVA-based resin is fiberized. However, it is still difficult to obtain sufficient flame retardancy. If the proportion of the phosphate ester is increased in order to enhance the flammability, the fiber performance is reduced.

On the other hand, there has been proposed a method for improving the hot water resistance of PVA fibers by forming a crosslinked structure with a phosphoric acid-containing compound (JP-A-2-249705, JP-A-4-228610, JP-A-4-228610). JP-A-2-84587, JP-A-4-228610, JP-A-3-287
812, JP-A-4-163309, JP-A-4-100912, JP-A-3-213510, JP-A-4-240207, JP-A-4-126
829, JP-A-4-163310, JP-A-4-126830, etc.). Certainly, although the hot water resistance of the fiber is improved when the crosslinked structure is formed, there is a problem that the flame retardancy of the fiber having the crosslinked structure is apt to be reduced. In addition, PVA undergoes intramolecular dehydration to form a conjugated double bond, which causes intense coloration. In addition, there is a problem that the flexibility of the fiber is deteriorated and the quality is impaired. It is unsuitable for the living field such as for example, and the industrial material field such as car seats. Further, when the purpose is to form such a crosslinked structure, the phosphorus-based compound to be incorporated into the fiber is at most 5% by mass / fiber (normally 1% by mass).
Below / fiber), a sufficient flame retardant effect is not exhibited.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a PVA-based flame-retardant fiber having high flame retardancy and excellent in various properties such as mechanical performance and quality, and a fabric using the fiber. is there.

[0007]

The present invention provides (1) a polyvinyl alcohol-based flame-retardant fiber containing a phosphorus-based flame retardant, a pyrolytic foaming agent and / or heat-expandable graphite, (2)
(3) The polyvinyl alcohol-based flame-retardant fiber according to (1), wherein the vinyl alcohol-based polymer constituting the polyvinyl alcohol-based flame-retardant fiber has a crystallinity of 65 to 85% and an orientation degree of 55 to 95%. The polyvinyl alcohol-based flame-retardant fiber according to (1) or (2), wherein at least a phosphoric acid-based compound is used as the flame retardant, (4) 280 ° C.
(1) to (3) in which the water generation rate is 70% or more.
Polyvinyl alcohol-based flame-retardant fiber according to any of
(5) A fabric using the polyvinyl alcohol-based flame-retardant fiber according to any one of (1) to (4).

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, it is necessary to contain at least a phosphorus-based flame retardant in order to impart sufficient flame retardancy to fibers. Phosphorus-based flame retardants have a higher flame-retardant effect than other non-halogen-based flame retardants, and are excellent in that they do not easily deteriorate the fiber performance. The flame retardant effect of the phosphorus-based flame retardant is exhibited by at least one of the following mechanisms, and it is considered that usually two or more mechanisms act synergistically. The phosphorus-based flame retardant condenses during combustion to form polyphosphoric acid, which coats the fiber surface layer to block external combustion heat and suppress the generation of combustible gas from inside the fiber. The phosphorus-based flame retardant accelerates the dehydration reaction of the vinyl alcohol-based polymer, accelerating the crosslinking and carbonization reactions. At this time, the PVA-derived carbide (called char) coats the fiber surface, and the heat of combustion from the outside To block the generation of combustible gas from inside the fiber. Phosphorus atoms in the flame retardant act as traps for active radicals generated during combustion. The fiber surface is cooled by heat of vaporization of water generated by a dehydration reaction of the vinyl alcohol-based polymer.

The present inventors have developed PVA with phosphorus-based flame retardants.
As a result of a detailed study on flame retardancy of the system fibers, it was found that among the above-mentioned manifestation mechanisms, the influence greatly affects the flame retardancy of the fibers. In order to sufficiently exhibit the above mechanism and mechanism, it is important that the dehydration reaction occurs before the decomposition reaction of the fiber greatly proceeds during combustion, and that the dehydration reaction rapidly proceeds at a certain temperature or higher. From the above, the moisture generation rate at 280 ° C. is preferably 70% or more, particularly preferably 75% or more, and further preferably 80% or more. In addition, the water generation rate referred to in the present invention is defined as “the amount of PVA-based fibers in nitrogen at 280 ° C. is 2 to the amount of water theoretically generated from the vinyl alcohol-based polymer constituting the fibers.
The percentage (percentage) of "amount of water generated when left for a while" is obtained by the method described in Examples. 280 ° C
The higher the moisture generation rate of the fibers, the more effectively the above-mentioned mechanism and the above-mentioned mechanism are exhibited, and an excellent flame retardant effect is exhibited.

From the viewpoint of efficiently exhibiting the above mechanism and mechanism, it is preferable to use a phosphorus-based flame retardant having sufficient acidity to promote the dehydration reaction of the vinyl alcohol-based polymer during combustion. Specifically, a phosphoric acid compound is preferably used. Considering industrial versatility, the effect of expressing flame retardancy, the ability to suppress coloring, etc., phosphoric acid, phosphorous acid,
Metaphosphoric acid and the like and derivatives thereof (phosphoric acid, phosphorous acid, metaphosphoric acid and the like, compounds in which an alkyl group or a phenyl group is directly bonded to a phosphorus atom, etc.), and further phosphoric acid, phosphorous acid, metaphosphoric acid and the like or derivatives And esters (alkyl esters, phenyl esters, etc.), ammonium salts, amidates and the like of the condensate can be suitably used as the phosphoric acid compound. Among these, phosphoric acid and phosphoric acid derivatives, or alkyl esters, phenyl esters, ammonium salts, and amidates of these condensates can be more preferably used for the same reason.

More specifically, methyl phosphate, dimethyl phosphate, trimethyl phosphate, ethyl phosphate, diethyl phosphate, triethyl phosphate, diethylhexyl phosphate, butyl phosphate, dibutyl phosphate, tributyl phosphate, tricresyl phosphate, trixylenyl phosphate, ethyl Diethyl phosphonoacetate, butyl pyrophosphate, butoxyethyl phosphate, 2-
Phosphate esters (alkyl esters, phenyl esters, etc.) such as ethylhexyl phosphate, di (2-ethylhexyl) phosphate, phenyl phosphate, diphenyl phosphate, triphenyl phosphate and cresyl diphenyl phosphate; triammonium phosphate, ammonium phosphite And phosphoric acid compound salts such as diammonium hydrogen phosphate and ammonium dihydrogen phosphate, as well as phosphate amine compounds, phosphoric amides, phenylphosphonic acid, dimethylphenylphosphonate, diethylphenylphosphonate and the like. In addition, methyl polyphosphate, ethyl polyphosphate, propyl polyphosphate,
Esters (alkyl esters, phenyl esters) of condensates of phosphoric acid or phosphoric acid derivatives such as butyl polyphosphate and phenyl polyphosphate can also be used preferably.

Further, a polymer of a phosphorus-containing monomer having a polymerizable double bond, a copolymer of the phosphorus-containing monomer and another polymerizable monomer, or a derivative of these polymers may be used as a phosphorus-based flame retardant. Absent. The phosphorus-containing monomer having a polymerizable double bond is not particularly limited. For example, a monomer having at least one group selected from an acrylamide group, a methacrylamide group, an acrylate group, a methacrylate group, a vinyl ester group, and a vinyl ether group is preferable. It is listed. The method of obtaining a polymer from these double bond-containing compounds is not particularly limited, and is generally used depending on the reactivity of the double bond, such as a radical polymerization method, an anion polymerization method, a cationic polymerization method, and a coordination polymerization method. It is appropriately selected from the polymerization methods used.

The components copolymerized with the phosphorus-containing monomer include α-olefins (ethylene, propylene, butene, pentene, hexene, heptene, octene, etc.), styrene, styrene derivatives, methacrylates, acrylates, acrylonitrile, vinyl esters And one or more components selected from polymerizable monomers such as vinyl ethers, butadiene, isoprene, isobutene, ethylene glycol, propylene glycol, ethylene oxide and propylene oxide.
Above all, methacrylates, acrylates,
Methacrylamides, acrylamides, and vinyl esters can be suitably used. The copolymer composed of these copolymerized monomers and the phosphorus-containing polymerizable monomer may be any of a random copolymer, a block polymer, a graft polymer, and the like. Further, derivatives obtained by post-modification of the copolymer are also suitable. Used.

More specifically, a vinyl ester obtained by copolymerizing a vinyl ester and a phosphorus-containing polymerizable monomer, and then saponifying some or all of the side chain ester groups to convert the ester group into a vinyl alcohol unit. After copolymerization of an alcohol / phosphorus-containing unit copolymer, acrylates or methacrylates, and a phosphorus-containing polymerizable monomer, some or all of the ester groups as side chains are hydrolyzed to be converted to acrylic acid or acrylate. Acrylic acid (or acrylate) -containing polymer / phosphorus-containing unit copolymer obtained by the above method.

Further, from the viewpoint of exhibiting the above and obtaining a high flame-retardant effect, a condensed phosphoric acid-based compound or a low molecular weight compound which easily condenses to form a polyphosphoric acid-type condensate when burned is used as a phosphorus-based flame retardant. It is preferable to use a condensed phosphoric acid-based compound, particularly from the viewpoint of affinity and compatibility with a vinyl alcohol-based polymer and further enhancing spinnability. Preferable examples include condensed phosphoric acid such as polyphosphoric acid, condensed phosphate such as ammonium polyphosphate, and polyphosphoramide, polyphosphoric esters (alkyl esters, phenyl esters, etc.).

Suitable polyphosphoric amides include a phosphoric acid source, a nitrogen source and, if necessary, a polymer compound containing an amide type nitrogen obtained by mixing a condensing agent, followed by calcination and condensation reaction. Can be Suitable phosphoric acid sources include one or more compounds selected from ammonium phosphate, urea phosphate, phosphoric anhydride, condensed phosphoric acid, phosphoric acid, and suitable nitrogen sources include melamine, dicyandiamide, guanidine, guanylurea and the like. Cyanamide derivatives, suitable condensing agents include urea and urea phosphate. Dehydration may occur partially depending on the calcination conditions, but a compound obtained by such a method, for example, a compound having a phosphorylamide or phosphorylimide bond in a part thereof, or a compound in which a urea bond partially remains in the compound is obtained. Etc. are also included in the polyphosphoramide.

From the viewpoints of flame retardancy, spinnability and fiber performance, it is preferable to use at least ammonium polyphosphate as a phosphoric acid-based compound, and the use of the flame retardant has a remarkable effect. Ammonium polyphosphates are generally phosphoric acid sources and ammonia generating sources, such as orthophosphoric acid and urea, phosphoric anhydride and ammonia, condensed phosphoric acid and urea, or ammonium orthophosphate and urea, phosphoric anhydride and ammonium, and the like. And, if necessary, one or more kinds of appropriate combined raw materials obtained by blending a condensing agent, followed by heat condensation. Of these _{H (n -m) +2 (NH} 4) m P n O 3n + 1 linear phosphates represented by can be suitably used. Note that n is an integer of 5 or more, and 0 <m ≦ n + 2. In particular, n is 10
It is preferably an integer greater than or equal to the above, and (nm) +2 is preferably substantially 0.

The phosphorus-based flame retardant referred to in the present invention is a compound containing phosphorus. From the viewpoint of flame retardancy and fiber performance, the mass ratio of phosphorus atoms in the phosphorus-containing compound is 10% by mass.
As described above, the content is particularly preferably 20 to 80% by mass. Two or more phosphorus-based flame retardants may be used in combination, and a flame retardant other than the phosphorus-based flame retardant may be further used as long as the effects of the present invention are not impaired. The total content of the phosphorus-based flame retardant in the PVA-based fiber may be changed depending on the type of the flame-retardant, etc., but from the viewpoint of the flame-retardant effect, the mechanical performance of the fiber, the suppression of coloring, etc. It is preferred to be 8 to 45% by mass / fiber, especially 10 to 30% by mass / fiber.

A further feature of the present invention is that a pyrolytic foaming agent and / or thermally expandable graphite are used together with a phosphorus-based flame retardant as a flame retardant for imparting flame retardancy to PVA-based fibers. One of the mechanisms by which the phosphorus-based flame retardant imparts flame retardancy is, as described above, that the phosphorus-based flame retardant condenses during combustion to form polyphosphoric acid, which forms a polyphosphoric acid surface, and that is coated from the outside by coating the fiber surface layer. It is considered that the heat of combustion is blocked or the generation of combustible gas from inside the fiber is suppressed. Here, by using the pyrolytic foaming agent and / or the heat-expandable graphite together with the phosphorus-based flame retardant, minute voids are generated in the polyphosphoric acid film. As a result, the fiber surface is covered with the foamed polyphosphoric acid coating layer, and it is possible to further enhance the effect of blocking combustion heat from the outside and suppressing generation of combustible gas from inside the fiber.

Further, the char generated by the thermal decomposition of the polyvinyl alcohol polymer during combustion also plays an important role in imparting flame retardancy. When a phosphorus flame retardant is added, the dehydration reaction of the vinyl alcohol polymer is accelerated. As described above, the cross-linking / carbonization reaction is accelerated and the formation of char is promoted, but minute voids are formed in the char by blending the pyrolytic blowing agent and / or the heat-expandable graphite. As a result, the effect of imparting flame retardancy by the char can be further enhanced. Such effects can be obtained only by combining a vinyl alcohol-based polymer with a phosphorus-based flame retardant, a pyrolytic foaming agent and / or a heat-expandable graphite, and when the phosphorus-based flame retardant is not blended. Since it is difficult to generate PVA-derived char, the effect is hardly obtained.

The pyrolytic foaming agent used in the present invention generates a gas such as a decomposition gas when the fiber is burned, and does not substantially foam during the fiber spinning step, but after forming the fiber. Those which foam by heating are more preferred. Specifically, those which foam at 200 ° C. or higher, preferably 230 ° C. or higher are preferable. For example, those conventionally used as foaming agents for producing foams can be used. Specific examples include azo-based blowing agents (eg, azodicarbonamide, azoisobutyronitrile, azodiaminobenzene, barium azodicarboxylate), hydrazine derivative-based blowing agents (eg, benzenesulfonyl hydrazide, p-toluenesulfonyl hydrazide, 4,4'-oxybisbenzenesulfonyl hydrazide, p, p'-oxybisbenzenesulfonyl hydrazide, hydrazodicarbonamide, a nitroso foaming agent (for example, N, N'-dinitrosopentamethylenetetramine, N, N'- Dinitroso
N, N'-dimethylterephthalamide), bicarbonate (for example, sodium bicarbonate), melamine-based blowing agent (melamine powder, melamine resin), urea, urea resin, isocyanuric acid, etc., which are used alone Or two or more of them may be used in combination. Among them, azo-based blowing agents, hydrazine derivative-based blowing agents, and nitroso-based foaming agents are preferable because they are not easily foamed in the spinning and drawing steps of PVA fibers, and are excellent in the amount of gas generated during foaming and the safety in handling. One or more selected from the systemic foaming agents are more preferably used. Among them, hydrazine derivative-based blowing agents are more preferable.

The thermally expandable graphite used in the present invention is graphite having a property of expanding between graphite layers when fibers are burned.
Graphite is composed of hexagonal crystals in which six-membered ring polymer layers are stacked, and generally has a layered structure in which layers of such hexagonal crystals are stacked. Since the bonding strength between the layers is small and a space is formed between the layers, acid,
An alkali metal or the like can be introduced into the interlayer gap.
Therefore, when such graphite is heated, gas is generated due to decomposition of the substance introduced into the interlayer gap,
The layers expand and the graphite expands. As a result, a large number of fine voids are formed inside the char or polyphosphoric acid film due to the gas generated from the substance introduced between the layers during the combustion and the layers, and the heat insulating effect and the effect of suppressing the generation of combustible gas from inside the fibers are reduced. It is possible to increase it further. If desired, a substance that generates a flame-retardant / extinguishing gas during combustion can be introduced between the graphite layers. From the viewpoint of the flame retardant effect, it is preferable that the fiber does not substantially expand (decompose) in the fiber spinning step but expands when the fiber is burned. Specifically, those which expand at a temperature of 200 ° C. or higher, particularly 230 ° C. or higher are preferable.

For example, heat-expandable graphite or a known material such as expanded graphite can be used. Graphites such as natural graphite, pyrolytic graphite, and quiche graphite are mixed with an inorganic acid (concentrated sulfuric acid, nitric acid, etc.) and a strong oxidizing agent (peroxide). Chloric acid, perchlorate, aqueous hydrogen peroxide, etc.). Further, those treated with an acid by adding ammonium persulfate or the like can also be used, and after the acid treatment, an aliphatic lower amine (such as monomethylamine), an alkali metal compound or an alkaline earth metal compound (potassium, sodium, calcium, barium, Hydroxides, oxides, carbonates such as magnesium,
Those which have been subjected to a neutralization treatment with a sulfate or the like can also be used. Specific examples include graphite acid sulfate, sodium graphite, potassium graphite, halogenated graphite, graphite oxide, aluminum chloride graphite, ferric chloride graphite, and the like. In the present invention, the pyrolytic foaming agent and the heat-expandable graphite may be used in combination, or any one of them may be used. The total content of the pyrolytic foaming agent (and the thermally expandable graphite is 0.1% by mass or more / fiber from the viewpoint of the flame retardant effect, particularly 0.5% by mass or more / fiber, and further 0.5% by mass. %
More preferably, the ratio is 30% by mass or less / fiber, particularly 10% by mass or less / fiber, and further preferably 5% by mass or less / fiber from the viewpoint of fiber performance and the like.

The vinyl alcohol polymer constituting the flame retardant fiber of the present invention is not particularly limited, and any vinyl alcohol polymer can be used. However, by using a fiber composed of a specific vinyl alcohol-based polymer, the flame retardancy of the fiber can be significantly improved. As shown in the above, PV with phosphorus-based flame retardant
The most important effect in the flame retardation of A is that the phosphorus-based flame retardant promotes the dehydration reaction of the PVA-based resin constituting the fiber, and the subsequent cross-linking and carbonization-induced carbonization (char) of the PVA-based resin generates the fiber. The present inventors have clarified that the purpose of the present invention is to coat the surface to block external combustion heat and to suppress generation of combustible gas from inside the fiber.

At this time, actually, the thermal decomposition reaction of PVA itself exists as a competitive reaction. When the thermal decomposition reaction of PVA occurs, not only does the amount of char generation decrease, but also the decomposition product becomes a combustible gas. Because it works, it greatly hinders the development of flame retardancy. Therefore, it is very important how to suppress the thermal decomposition reaction of the PVA-based resin constituting the fiber. Furthermore, the nature of the PVA-derived char generated during combustion is of course also important, and the point is how to efficiently generate a high heat-resistant char that can withstand combustion in high yield.

Then, as a result of a detailed study of the mechanism of char formation from PVA during combustion, a dehydration reaction of PVA was caused by the phosphorus-based flame retardant, and when the resulting polyene structure was cyclized by the Diels-Alder reaction, the same molecule was formed. Intramolecular cyclization, which cyclizes within (chain), and intermolecular cyclization, which cyclizes and crosslinks between different molecules (chains), can be broadly divided into two paths. It has been found that it is very effective for improving the yield and heat resistance of the finally obtained char, that is, for expressing the flame retardancy. That is,
How to promote intermolecular cyclization of polyene chains during combustion is very important for the development of flame retardancy.

The present inventors have found that when the PVA-based polymer constituting the fiber has a high crystallinity and a high degree of orientation, the flame retardancy of the fiber is further improved. From the viewpoint of the flame retardant effect, it is preferable that the crystallinity of the vinyl alcohol-based polymer constituting the PVA-based fiber is 65% or more. By adopting such a configuration, the thermal decomposition of the PVA-based resin during combustion is suppressed. That is, it is presumed that it is possible to increase the time required for char generation, thereby improving the char generation yield and enhancing the flame retardancy effect.

Further, by setting the degree of orientation of the vinyl alcohol polymer constituting the fiber to 55% or more, a more remarkable effect can be obtained. In other words, the more the molecular chains are arranged in the same direction with a high degree of orientation, the more likely the Diels-Alder reaction after dehydration occurs between molecular chains, and as a result,
It is thought that the yield, heat resistance, etc. of the char finally regenerated are improved, which greatly contributes to the development of flame retardancy. However, if the degree of crystallinity and orientation of the fiber is too high, the workability, wear resistance, flexibility, and the like will be reduced.
Hereinafter, the degree of orientation is preferably 95% or less.

The vinyl alcohol-based polymer constituting the PVA-based fiber of the present invention is not particularly limited, but the viscosity average degree of polymerization is preferably 1000 or more, particularly 1500 or more from the viewpoints of crystallinity, mechanical performance and flame retardancy of the polymer. Is preferably
It is preferably 5000 or less from the viewpoint of spinnability and cost. For the same reason, the saponification degree is preferably at least 98 mol%, more preferably at least 99 mol%, particularly preferably at least 99.5 mol%. Other monomers may be copolymerized in the vinyl alcohol-based polymer, and examples of the copolymerization component include ethylene, vinyl acetate, itaconic acid, vinylamine,
Acrylamide, vinyl pivalate, maleic anhydride,
And sulfonic acid-containing vinyl compounds. From the viewpoints of fiber performance, flame retardancy and the like, it is preferable to use a polymer having a vinyl alcohol unit of 70 mol% or more of all the constituent units. In addition, as long as the effects of the present invention are not impaired, the fiber may contain a polymer other than the vinyl alcohol-based polymer and other additives. From the viewpoint of fiber performance and the like, the content of the vinyl alcohol polymer is preferably 30% by mass or more / fiber, particularly preferably 50% by mass or more / fiber.

The method for producing the PVA-based flame-retardant fiber of the present invention is not particularly limited. For example, an aqueous solution of a vinyl alcohol-based polymer is used as a spinning solution, and this is discharged into a coagulation bath such as a saturated sodium sulfate bath to produce a PVA-based fiber. A method or the like may be adopted. However, according to such a method, a dehydration and coagulation reaction occurs rapidly in a coagulation bath, so that a skin core structure in which a dense skin layer is formed on the fiber surface layer is formed. In this case, even if the vinyl alcohol-based polymer generates moisture by a dehydration reaction, the fiber surface layer portion is covered with the dense skin layer and cannot be efficiently vaporized, so that the cooling effect on the fiber surface is reduced. Further, since the solidification reaction does not sufficiently proceed to the inside of the fiber, and the drawing cannot be performed at a higher degree, the crystallinity of the fiber obtained is at most 50 to 6.
0%. It is also known to employ a dry spinning method in which the stock solution is discharged into a gas.However, even if this method is employed, it is difficult to sufficiently solidify the inside of the fiber. At most, it is as small as 50 to 60% and the degree of orientation is as small as 40 to 50%.

Therefore, when it is desired to increase the crystallinity of the fiber and further improve the mechanical performance, dimensional stability and flame retardancy, a spinning solution obtained by dissolving a vinyl alcohol polymer in an organic solvent is used. It is preferable to spin under the following conditions. According to the method described below, since the solidification reaction takes place over time, the skin core structure is not formed and the fiber is sufficiently solidified to the inside of the fiber. ,as a result,
Not only the mechanical performance, the dimensional stability in wet and dry conditions, etc. are improved, but also an excellent flame retardant effect is achieved. Hereinafter, a preferred method for producing the PVA-based flame-retardant fiber of the present invention will be described in detail.

First, as a solvent for the vinyl alcohol-based polymer constituting the spinning dope, for example, polyhydric alcohols such as glycerin, ethylene glycol, diethylene glycol, triethylene glycol, butanediol, dimethyl sulfoxide (DMSO), dimethylformamide, diethylene triamine and the like are used. An organic solvent selected from
Alternatively, it is preferable to use a mixed solvent of two or more of these, and a mixed solvent of these organic solvents and water. However, when a phosphorus-based flame retardant is directly added to a spinning solution and spinning is performed, it is preferable to use a solvent that does not cause the flame retardant to coagulate or separate, and from the above points, dimethyl sulfoxide and / or glycerin, particularly Dimethyl sulfoxide is more preferred. From the viewpoint of spinnability and fiber performance, the concentration of the vinyl alcohol polymer in the spinning dope is 5 to 25% by mass.
The temperature is preferably about 80 to 230 ° C. Boric acid, a surfactant, a decomposition inhibitor, a dye, a pigment, and the like may be added to the spinning solution as long as the effects of the present invention are not impaired.

The spinning dope thus obtained is wet-spun or dry-wet spinning through a spinning nozzle into a solidification bath. The wet spinning method in which the solidification bath is brought into direct contact with the spinning nozzle is suitable for spinning using a multi-hole nozzle because the fibers can be spun without sticking together even if the nozzle hole pitch is narrowed. Dry-wet spinning with an air gap between them is suitable for high-speed spinning because the elongation at the air gap is large. It is preferable to appropriately select a spinning method according to the purpose and use.

As the solidifying solution for solidifying the raw spinning solution into fibers, an organic solvent having an ability to solidify PVA, such as alcohols such as methanol and ethanol, and ketones such as acetone and methyl ethyl ketone, is preferable.
At this time, it is important to slowly extract the solvent in the solidification to form a uniform gel structure from the viewpoint of obtaining a fiber having a high degree of crystallinity, and from this point, the solidified solution contains 10 mass% of the organic solvent constituting the spinning solution. % Or more is preferably mixed. Methanol as solidification solvent, D as spinning stock solution solvent
It is more effective to use MSO. From the viewpoint of spinnability, fiber performance, etc., the concentration of the spinning dope solvent in the solidification bath should be 20 to
70 mass%, more preferably 25 to 65 mass%, and the composition mass ratio of the solidifying solution / spinning solution solvent is 25/7.
It is preferably from 5 to 85/15. Other additives may be blended as long as the effects of the present invention are not impaired.

In order to further reduce the solidification reaction rate and form a sufficiently uniform gel structure inside the fiber, the temperature of the solidification bath is preferably 30 ° C. or less, particularly preferably 20 ° C. or less.
Further, the temperature is preferably set to 15 ° C. or lower. By employing such a method, a fiber having a high degree of crystallinity can be obtained even when the solidification is uniform in the cross-sectional direction and no heat treatment or the like is performed. From the viewpoint of reducing sticking between the fibers and facilitating the subsequent dry heat drawing, it is preferable to perform the 2-10-fold wet drawing of the shino which has been separated from the solidifying bath while containing an organic solvent. It is more preferable to perform the wet stretching in a temperature range of ６０60 ° C.

Next, the fibers may be immersed in an extraction bath to extract the solvent. As the extractant, alcohols such as methanol, ethanol and propanol, acetone, methyl ethyl ketone, ether and water can be used. Subsequently, an oil agent or the like may be applied and dried if necessary.
From the viewpoint of increasing the strength, heat resistance and wet heat resistance of the PVA-based fiber, it is preferable to perform dry heat stretching, and it is particularly preferable to perform dry heat stretching so that the total draw ratio is 6 times or more, preferably 8 times or more. preferable. The total draw ratio is represented by the product of the wet draw ratio and the dry heat draw ratio.

At this time, it is preferable to carry out drying and dry heat stretching under the condition that the dehydration reaction of the vinyl alcohol-based polymer does not proceed with the phosphorus-based flame retardant. When the phosphorus-based flame retardant causes the dehydration reaction of the vinyl alcohol-based polymer to proceed, severe coloration occurs due to the formation of a conjugated double bond in the molecule, thereby deteriorating the fiber quality and inhibiting the fiber orientation. As a result, it becomes difficult to produce a highly heat-resistant char, and a sufficient flame-retardant effect cannot be obtained due to moisture generated by a dehydration reaction during combustion.

Specifically, it is desirable that the temperature conditions for performing drying, dry heat stretching, heat treatment, and the like be lower than the dehydration start temperature of the phosphorus-based flame retardant. For example, phosphoric acid, polyphosphoric acid,
230 ° C. or less when using a strongly acidic phosphorus-based flame retardant such as orthophosphoric acid, and ammonium salts such as ammonium phosphate and ammonium polyphosphate, or when using a phosphorus-based flame retardant such as phosphoric amide and polyphosphoric amide. When using a phosphorus-based flame retardant such as a phosphoric ester such as trimethyl phosphate, triethyl phosphate and triphenyl phosphate at 250 ° C. or less, it is preferable to perform drying and dry heat stretching at a temperature condition of 260 ° C. or less. Even when the dehydration start temperature of the phosphorus-based flame retardant is high,
Since the decomposition of PVA occurs under the condition of 60 ° C. or higher,
It is preferable to perform drying and dry heat stretching under a temperature condition of 260 ° C. or less. When a phosphorus-based flame retardant is blended, an excellent effect is obtained because the dehydration reaction of the vinyl alcohol-based polymer is easier to control than other compounds.

The present invention is to produce a PVA-based fiber having an excellent feeling and color tone, and forms a cross-linked structure only upon burning by fire or the like (by causing a dehydration reaction).
A flame retarding mechanism is developed to obtain an excellent flame retarding effect. Until now, a method of forming a crosslinked structure by blending a phosphorus compound for the purpose of increasing the hot water resistance of PVA-based fibers has been studied. However, the fiber obtained by such a method has the above-described problems in terms of color tone and the like. Therefore, the effect of the present invention cannot be obtained.

However, from the viewpoint of the mechanical performance and crystallinity of the fiber, it is preferable to perform the dry heat drawing at a high temperature, so that the drawing temperature is preferably higher, and particularly the polymerization degree of the vinyl alcohol polymer is high. It is preferable to increase the stretching temperature as the stretching temperature increases. From the above, it is preferable to select a temperature at which coloring is the least (the PVA dehydration reaction does not proceed) and a temperature at which a high draw ratio can be achieved. When the dehydration start temperature of the phosphorus-based flame retardant is X, (X
-30) It is preferable to perform dry heat stretching at a temperature of not less than 30 ° C. Further, if desired, a heat treatment or a formalization treatment may be further performed, but in the case of performing such treatment, it is preferable to perform various treatments under conditions under which the dehydration reaction of the vinyl alcohol polymer does not substantially proceed.

The addition of the phosphorus-based flame retardant, the pyrolytic foaming agent and the heat-expandable graphite can be performed in such a manner that the fibers can be provided in a sufficient amount to exhibit the flame retardancy and the vinyl constituting the fibers finally obtained. As long as the method is such that the alcohol-based polymer can have sufficient crystallinity, it may be carried out in any step after the spinning dope and the dry heat drawing. For example, a method of adding it to a spinning dope, a method of passing swollen itoshino through an extraction bath containing a flame retardant and / or a compound containing the above substance,
Further, a method of applying a phosphorus-based flame retardant dissolved and / or dispersed in an appropriate liquid and / or a compound containing the above substance to a surface of a spun fiber may be used. However, it is preferable to adopt a method in which the substance is added to the spinning dope from the viewpoint of the process of producing the fiber and the fact that the substance is uniformly dispersed inside the fiber.
Other additives (such as a flame retardant) may be added as long as the effects of the present invention are not impaired. However, from an environmental point of view, the halogen content in the fiber is less than 5% by weight / fiber, especially less than 0.1% by weight / fiber, more preferably less than 0.1% / fiber, and further less than 0.1% by weight / It is preferable to use fibers, among which 0 to 0.001% by mass
/ Fiber is preferred. When the halogen content is high, environmental problems such as generation of dioxin occur. Generally, when the halogen content is low, it is difficult to obtain sufficient flame retardancy. However, according to the present invention, a PVA-based fiber having excellent flame retardancy can be obtained without substantially using halogen. In addition, the halogen content referred to in the present invention is the ratio of the mass of the halogen element to the mass of the fiber, and is determined by the method described in Examples.

The single fiber fineness of the fiber may be appropriately changed depending on the application and purpose. For example, when used for fabrics, a fiber having a fineness of about 0.01 to 20 dtex, particularly about 0.1 to 10 dtex can be widely applied. The fiber strength is preferably 3 cN / dtex or more, particularly preferably 5 cN / dtex or more. In the present invention, excellent flame retardancy can be imparted without significantly impairing the mechanical performance of the fiber. The LOI value is preferably 25 or more, particularly preferably 30 or more, and more preferably 32 or more. The flame-retardant fiber obtained by the present invention is excellent in various properties such as combustion gas toxicity, melt drip property, cost, and washing durability,
Moreover, it has not only high flame retardant effect but also excellent quality and mechanical performance, so that it can be used not only for industrial materials but also for various uses. Specifically, the field of protective clothing such as combat uniforms and firefighting clothing, industrial materials such as car seats and vehicle spring receiving materials and air filters, curtains, carpets, blankets, futon side lands, sheet covers, and cotton padding It can be used effectively in the material field.

The flame-retardant fiber can be used in any form. For example, it can be used in the form of filaments, cut fibers (such as crimped fibers), spun yarns, cords, ropes, fabrics (non-woven fabrics, woven or knitted fabrics), and other non-flame-retardant fibers and / or other flame-retardant fibers. A fiber structure may be formed in combination. Among them, the flame-retardant fiber of the present invention has an excellent feeling, so that a remarkable effect can be obtained when used as a fabric. A more excellent flame-retardant effect can be achieved by using a fabric containing the flame-retardant fiber of the present invention in an amount of 50% by mass or more, more preferably 80% by mass or more, particularly 90% by mass or more.

[0044]

Next, the present invention will be further described with reference to Examples.
The present invention is not limited to these examples. In Examples,% and ratio are values based on mass unless otherwise specified. [Fiber strength] Measured according to JIS L-1013.

[Moisture generation rate at 280 ° C. mass%]
The weighed fiber is placed in a cell of a Karl Fischer-type moisture measuring device which has been heated to 280 ° C. in advance, and left standing for 2 hours while flowing nitrogen to determine the total amount of moisture generated.
Next, the mass ratio (%) of the total water content to the theoretical water content generated from the polyvinyl alcohol-based polymer in the charged fiber sample is calculated. [Crystallinity%] Rigaku Electric "Differential Differential Thermal Balance TA
Using S-2000, about 2-3 mg of a precisely weighed fiber sample was heated from 25 ° C. to 300 ° C. in nitrogen at a heating rate of 8 ° C.
The heat of fusion (J) was determined from the endothermic peak area based on the crystal melting of the vinyl alcohol-based polymer when the temperature was raised at 0 ° C./min and the gas flow rate was 20 ml / min. Next, the heat of fusion (ΔH / g) per 1 g of the vinyl alcohol-based polymer excluding the flame retardant and the like was converted, and the crystallinity of this value was calculated as 100
% Of the heat of fusion (174.5 J / g) per 1 g of the vinyl alcohol-based polymer was determined as the crystallinity. [Orientation degree%] Using a pulse type direct-reading viscoelasticity meter DDV-5-B manufactured by Orientec Co., Ltd., measure the speed C of a 10 KHz sound wave along the fiber axis of the fiber sample, and measure the velocity C from the cast film of polyvinyl alcohol. The degree of orientation was calculated according to Mosley's formula (degree of orientation = 1-Cu ² / C ² ) in comparison with the sound velocity Cu (2.20 km / sec) of the obtained non-oriented sample.

[Flame Retardancy Index (LOI Value)] JIS K-7
The measurement was performed in accordance with No. 201. [Halogen content mass%] A sample (A1 mg) was thermally decomposed in an oxygen stream, and this gas was brought into contact with a platinum catalyst at 800 ° C to generate a simple halogen. And the mass increase (A2 mg) of silver after the reaction was measured, and A22 / A1 ×
Calculated by 100.

Example 1 Degree of polymerization 1750, degree of saponification 9
9.8 mol% of PVA, ammonium polyphosphate ("Sumisafe P" manufactured by Sumitomo Chemical Co., Ltd.), and barium azodicarboxylate (foaming start temperature 2
50 ° C. or higher), and these are added under a nitrogen stream in DMSO 8
Stir at 0 ° C. for 5 hours, PVA / ammonium polyphosphate / barium azodicarboxylate = 82/16/2,
A spinning dope having a PVA polymer concentration of 18% was obtained. The obtained spinning dope was used with a pore size of 0.08 mm and 10 pores.
The mixture was wet-spun through a 00-hole nozzle into a 5 ° C. solidification bath having a methanol / DMSO mass ratio of 70/30. Next, while extracting DMSO with methanol, the film was wet-stretched three times, and methanol was dried with hot air at 100 ° C.
It is stretched by 3.3 times dry heat at 0 ° C and has a single fiber fineness of 3.2 dtex.
(Fiber strength: 5.7 cN / dtex, PVA crystallinity: 6
7%, a degree of orientation of 61%, a moisture generation rate at 280 ° C. of 87%, and a halogen content of 0%) were obtained. The hue of the fiber was slightly light purple, but the conventional phosphoric acid-crosslinked P
It was much lighter than the coloring of the VA-based fiber, had a good feel and quality, and had a high LOI value of 35 and excellent flame retardancy. Since fine voids were formed in the polyphosphoric acid film and char in the fiber after burning, such a foam further enhanced the flame retardant effect. The fiber obtained according to Example 1 has excellent feeling and mechanical performance,
Moreover, it exhibits excellent flame retardancy during combustion.
It was possible to provide a fabric excellent in various performances.

Example 2 A fiber having a single fiber fineness of 3.2 dtex (fiber strength) was used in the same manner as in Example 1 except that hydrazodicarbonamide (foaming start temperature: 245 ° C. or more) was used instead of barium azodicarboxylate. 5.8cN / dte
x, PVA crystallinity 69%, orientation 62%, 280 ° C
Of 84% and a halogen content of 0%). Although the hue of the fiber was slightly light purple, it was much lighter than conventional PVA-based fiber cross-linked with phosphoric acid, and had a good feeling and quality.
5 and excellent flame retardancy. Since a large number of fine voids are formed in the polyphosphoric acid film and char in the fiber after burning, such a foam further enhances the flame retardant effect. The fiber obtained in Example 1 was excellent in feeling and mechanical performance, and exhibited excellent flame retardancy during combustion, and could provide a fabric excellent in various performances.

Example 3 Example 1 was repeated except that barium azodicarboxylate was replaced by heat-expandable graphite (“heat-expandable graphite 5099” manufactured by Sumikin Chemical Co., Ltd .: expansion start temperature of 300 ° C. or more). Similarly, single fiber fineness 3.3
Thus, a dtex fiber (having a fiber strength of 6.0 cN / dtex, a degree of crystallinity of PVA of 68%, a degree of orientation of 63%, a water generation rate at 280 ° C. of 82%, and a halogen content of 0%) was obtained. Although the hue of the fiber was slightly light purple, it was much lighter than the conventional phosphoric acid-crosslinked PVA-based fiber, and the feeling and quality were high, and the LOI value was as high as 34. It had excellent flame retardant performance. Since a large number of fine voids are formed in the polyphosphoric acid film and char in the fiber after burning, such a foam further enhances the flame retardant effect. The fiber obtained in Example 3 was excellent in feeling and mechanical performance, and exhibited excellent flame retardancy during combustion, and could provide a fabric excellent in various performances.

Comparative Example 1 Degree of polymerization 1750, degree of saponification 9
8.5 mol% of PVA and ammonium polyphosphate (Sumisafe PM manufactured by Sumitomo Chemical Co., Ltd.) were stirred in water at 90 ° C. for 5 hours, and PVA / ammonium polyphosphate = 100/10,
A spinning dope having a composition of PVA having a polymer concentration of 20% was obtained. The obtained spinning dope was used with a pore size of 0.08 μm,
The mixture was wet-spun through a 00-hole nozzle into a solidification bath comprising a 45 ° C. aqueous solution containing 20 g / l of caustic soda and 350 g / l of sodium sulfate. Next, roller stretching of 1.5 times, neutralization from an aqueous solution of sulfuric acid and sodium sulfate in a neutralizing bath, wet stretching of 2 times in a saturated aqueous solution of sodium sulfate at 95 ° C., washing with boric acid in a washing bath at 30 ° C., 300 g / l Glauber's salt solution replaced with sodium sulfate solution, 100
Drying at 230 ° C and stretching by 3.0 times at 230 ° C,
PVA-based flame-retardant fibers were obtained by a water-based spinning method. Fiber with a single fiber fineness of 3.4 dtex (fiber strength 6.3 cN / dtex, P
The degree of crystallinity of VA was 56%, the degree of orientation was 50%, the moisture generation rate at 280 ° C. was 87%, and the halogen content was 0%. Although the color of the fiber was slightly light purple, the color was much lighter than that of the conventional PVA-based fiber cross-linked with phosphoric acid, and the feeling and quality were high. However, the LOI value was 31 which was lower than the example.

[0051]

The fibers of the present invention are flame-retardant acrylic fibers, flame-retardant polyester fibers, thermosetting fibers, aramid fibers,
Compared to non-PVA flame retardant fiber materials such as flame retardant cotton and flame retardant wool, PVA flame retardants are superior in terms of combustion gas toxicity, melt drip properties, strength, cost, washing durability, hand feeling, etc. It is aimed at non-halogen flame retardant fiber. The fibers of the present invention are used in the field of protective clothing such as combat uniforms and firefighting suits, industrial materials such as car seats and vehicle spring receiving materials and air filters, curtains, carpets, blankets, futon side linings, sheet covers, and cotton fillings. It can be used effectively in the field of living materials.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) D01F 1/07 D01F 1/07 D03D 15/00 D03D 15/00 E 15/12 15/12 Z D04B 1 / 16 D04B 1/16 21/00 21/00 BF term (reference) 4J002 BE021 DA028 DH026 DH036 DH046 DH056 EQ017 ES007 EV287 EW046 FD136 FD208 FD327 GK01 4L002 AA05 AC00 EA04 FA01 FA06 4L035 BB03 BB20 A14 EB15 BB91 BB20 BB15 BB20 AA53 AA56 AC14 CA06 DA01 DA13 DA16 DA19 DA25

Claims (5)

[Claims] 1. A polyvinyl alcohol-based flame-retardant fiber containing a phosphorus-based flame retardant, a pyrolytic foaming agent and / or a heat-expandable graphite. 2. The crystallinity of the vinyl alcohol polymer constituting the polyvinyl alcohol flame retardant fiber is 65 to 8.
The polyvinyl alcohol-based flame-retardant fiber according to claim 1, wherein the polyvinyl alcohol-based flame-retardant fiber has a degree of orientation of 5% and an orientation degree of 55 to 95%. 3. The polyvinyl alcohol-based flame-retardant fiber according to claim 1, wherein at least a phosphoric acid-based compound is used as the phosphorus-based flame retardant. 4. The polyvinyl alcohol-based flame-retardant fiber according to claim 1, wherein a water generation rate at 280 ° C. is 70% or more. 5. A fabric comprising the polyvinyl alcohol-based flame-retardant fiber according to claim 1.