JP2001329461A - Flame-retardant polysaccharide based fiber and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a flame-retardant fiber such as a flame-retardant cellulosic fiber without a halogen-based flame retardant and without lowering the strength of the fiber. SOLUTION: This method for producing the flame-retardant polysaccharide- based fiber, characterized by treating a polysaccharide-based fiber, such as a cellulosic fiber, uniformly containing a phosphoryl group-having compound such as condensed phosphoric acid in the fiber with the aqueous solution of an aluminum compound and, if necessary, further treating the fiber with the aqueous solution of silicic acid, boric acid or the like. Thereby, the flame- retardant polysaccharide-based fiber is obtained in which uniformly contains the phosphoryl group-containing compound and on whose surface the layer of a hydrated compound containing aluminum as an essential component is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flame retardant polysaccharide fiber such as rayon and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, techniques for flame retarding materials used for houses, clothes, and the like have been gaining importance from the viewpoint of safety.

[0003] Conventionally, the flame retardation of organic polymer materials has been (1)
Halogen-based flame retardants (including combined use of antimony trioxide),
(2) phosphorus-based flame retardants (red phosphorus, reactive phosphorus compounds, etc.),
(3) Using hydrated metal-based flame retardants (aluminum hydroxide particles, magnesium hydroxide, etc.), etc., these are appropriately introduced into an organic polymer material by a method such as copolymerization, kneading, internal addition, and post-treatment. It is done by that.

[0004] Regarding the performance of the above flame retardant, generally, the use of the halogen-based flame retardant (1) can provide the highest flame retardancy, and if the flame retardancy is reduced in the order of (2) and (3), It is said.

The halogen-based flame retardant (1) generates radicals during combustion, suppresses the thermal decomposition of the organic material in an organic material, acts as a radical trap in a combustion gas, and further generates nonflammable chloride generated by the combustion. By covering the organic material with hydrogen gas or the like, the supply of oxygen necessary for combustion is shut off, thereby preventing the expansion of combustion. Halogen-based flame retardants exhibit excellent flame retardancy even when used in small amounts, and are currently widely used in fibers, films, bulks, and the like made of plastics and the like.

However, it is pointed out that there is a problem in safety because toxic gas and black smoke are generated during combustion. Furthermore,
In recent years, there has been a problem of dioxin generated at the time of waste incineration, and it has been considered that the burden on the environment is great.

The phosphorus-based flame retardant (2) is a flame retardant effective for flame retarding an organic polymer material composed of carbon C such as cellulose, hydrogen H, and oxygen O. For example, a flame retardant containing a reactive phosphorus compound as a main component has a dehydration and carbonization decomposition effect of extracting oxygen and hydrogen from a cellulose material or the like at the time of flame contact, and further generates polyphosphoric acid to coat the material surface, making it difficult. Flammable to impart flame retardancy to the material. Usually, it is said that flame retardancy is imparted to cellulose at an addition amount of about 15% by mass.

Reactive phosphorus compounds have long been used as flame retardants in post-treatment flame-retarding techniques such as cotton. However, it has been pointed out that the flame-retarding method involves the use of a special reactive phosphoric acid compound and the necessity of complicated post-treatments such as putting and curing, resulting in high costs.

The hydrated metal flame retardant (3) itself is a nonflammable material. It is also known that dehydration occurs from a hydrated metal at the time of flame contact, thereby imparting flame retardancy by cooling an organic polymer material or the like.

Heretofore, it has been widely practiced to add internally aluminum hydroxide and magnesium hydroxide particles having a particle size of 0.5 to several μm to pulp fibers to make the pulp fibers flame-retardant.
However, the target flame retardancy cannot be obtained unless a large amount of hydrated metal as much as 100 to 500% by mass of the pulp fiber is internally added, and this method is excellent in terms of environmental protection. In practice, it is actually used only for flame retarding applications such as paper and plastic bulk, or as a flame retardant aid.

Particularly, in the field of general-purpose fibers, there are few examples of using a flame retardant mainly composed of a hydrated metal. There is an example in which Finnish company Chemila manufactures flame-retardant fiber by using a method of synthesizing a zeolite composition in a fiber by adding a large amount of hydrated metal of about 50% by mass to the fiber. Hei-506629).

[0012] However, in the case of the flame retarding method of Chemila, there are problems such as a remarkable decrease in the performance and hand of the obtained fiber, and a decrease in the yield in production. I have.

[0013]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above circumstances, and can maintain various physical properties and the like of polysaccharide-based fibers such as cellulose to the maximum, and impart flame retardancy reliably by a simple operation. It is an object of the present invention to provide an environment-friendly flame-retardant polysaccharide-based fiber which can be produced and minimizes generation of harmful gas upon flame contact, and a method for producing the same.

[0014]

The present invention to achieve the above object is as described below.

[1] A method for producing a flame-retardant polysaccharide fiber, comprising treating a polysaccharide fiber containing a phosphoryl group-containing compound uniformly inside the fiber with an aqueous aluminum compound solution.

[2] A polysaccharide fiber containing a compound having a phosphoryl group uniformly inside the fiber is treated with an aqueous solution of an aluminum compound, and then silicic acid, boric acid, or a salt or calcium salt or magnesium salt thereof. A method for producing flame-retarded polysaccharide-based fibers, characterized by treating with an aqueous solution.

[3] A polysaccharide fiber containing a compound having a phosphoryl group uniformly inside the fiber is treated with an aqueous solution of silicic acid, boric acid or a salt thereof, or a calcium salt or a magnesium salt, and then an aluminum compound A method for producing flame-retarded polysaccharide-based fibers, characterized by treating with an aqueous solution.

[4] The method for producing flame-retarded polysaccharide fibers according to any one of [1] to [3], wherein the polysaccharide fibers are regenerated cellulose fibers or starch fibers.

[5] The compound having a phosphoryl group is
The method for producing a flame-retarded polysaccharide-based fiber according to any one of the above [1] to [4], which is a condensed phosphate compound or a urea phosphate esterified starch.

[6] The content of the compound having a phosphoryl group in the polysaccharide fiber is 0.01 to 10 as a phosphorus element.
The method for producing flame-retarded polysaccharide-based fibers according to any one of the above [1] to [5], which is a mass%.

[7] A flame-retardant polysaccharide-based fiber comprising a compound containing a phosphoryl group uniformly in the fiber and a hydrated compound layer containing aluminum as an essential component on the fiber surface.

[8] The content of the compound having a phosphoryl group in the flame-retardant polysaccharide fiber is 0.01 as phosphorus element.
The flame-retarded polysaccharide-based fiber according to the above [7], which is 10 to 10% by mass.

[0023]

[9] The method according to the above [7] or [8], wherein the amount of the hydrated compound layer containing aluminum as an essential component formed on the fiber surface is 1 to 30% by mass of the total mass of the flame-retardant polysaccharide-based fiber. Flame retardant polysaccharide fiber.

[10] The above-mentioned [8] or [8], wherein the hydrate layer contains silicon, boron, calcium or magnesium in an amount of 50 to 300 mol% based on aluminum.

The flame-retardant polysaccharide fiber according to [9].

[0025]

In the flame-retarded polysaccharide fiber of the present invention, a compound having a phosphoryl group is distributed uniformly throughout the fiber, and the fiber surface is further coated with a hydrated metal compound layer containing aluminum as an essential component. Has a fiber structure.

The present inventors believe that the phosphoryl group of the compound having a phosphoryl group uniformly distributed throughout the fiber is strongly ion-bonded to the metal atom of the hydrated metal compound layer on the fiber surface. Due to this ionic bond, the hydrated metal compound layer is firmly bonded to the fiber surface, and as a result, the fiber of the present invention is presumed to have excellent weather resistance.

The flame-retardant polysaccharide fiber of the present invention is provided with flame retardancy by a hydrated metal compound layer containing aluminum as a main component formed on the fiber surface. Since the compound having a phosphoryl group uniformly distributed throughout the fiber has a smaller amount than the conventional phosphorus-based flame retardant addition amount, the compound having the phosphoryl group contributes to imparting flame retardancy. The proportion is much smaller.

The hydrated metal mainly composed of aluminum unevenly distributed on the surface of the fiber selectively cools the fiber surface where a combustion reaction is likely to proceed at the time of flame contact, and coats the fiber surface to protect it from flame. Since the structure is such that the hydrated metal mainly composed of aluminum necessary for flame retardation is unevenly distributed on the fiber surface, flame retardancy can be efficiently imparted with an extremely small amount of hydrated metal.

Furthermore, since the hydrated metal does not exist inside the fiber, the deterioration of the physical properties of the fiber is kept to a minimum.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a polysaccharide-based fiber is a fiber containing a saccharide in a polymer main chain, and specific examples thereof include a polymer fiber containing cellulose or starch as a main component.

Preferred examples of the cellulosic fibers include regenerated cellulose fibers such as viscose rayon, cupra, and polynosic, and starch fibers.

A phosphoryl group uniformly contained in the fiber;

[0033]

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Compounds having the following are water-soluble phosphoric acid,
Examples thereof include condensed phosphoric acid, metal salts, ammonium salts and amine salts thereof, and organic phosphoric acid compounds. Compounds having a phosphoryl group bind advantageously to aluminum ions and preferably form precipitates.

Examples of the condensed phosphoric acid include orthophosphoric acid, polyphosphoric acid, hexametaphosphoric acid and ultraphosphoric acid.

Examples of the metal salt of phosphoric acid or condensed phosphoric acid include metal salts of Na, K, Ca, Ma and the like.

As the amine salt of phosphoric acid or condensed phosphoric acid, lower amine salts such as monomethylamine, dimethylamine, trimethylamine, methylethylamine and triethanolamine are preferred.

As the organic phosphoric acid compound, a phosphoric acid ester, a natural polymer compound derivative and the like are preferable.

Examples of the phosphoric acid ester include alkyl phosphoric acid, polyoxyethylene alkyl ether phosphoric acid, and polyoxyethylene alkyl phenyl ether phosphoric acid.

Examples of natural polymer compound derivatives include urea phosphorylated starch, phosphorylated starch, phosphorylated guar gum and the like.

In the present invention, the compound having a phosphoryl group is uniformly contained in the polysaccharide-based fiber.

Although any method can be adopted as a method for incorporating the compound having a phosphoryl group into the fiber, a particularly preferable method is to prepare a spinning solution in which the fiber and the compound having the phosphoryl group are dissolved, and to prepare a spinning solution. This is a method in which a compound having a phosphoryl group is uniformly contained inside the polysaccharide-based fiber by spinning.

For example, when the polysaccharide-based fiber is rayon, a compound having a phosphoryl group is dissolved in viscose in a predetermined amount, and this is spun to uniformly disperse the compound having a phosphoryl group inside the polysaccharide-based fiber. Viscose rayon in which it is contained can be obtained. The spinning method and the like are known to those skilled in the art.

The content of the compound having a phosphoryl group in the polysaccharide fiber is preferably 0.01 to 10% by mass in terms of phosphorus element based on the mass of the flame-retarded polysaccharide fiber as the final product. And particularly preferably 0.03 to 8% by mass.
The content of the compound having a phosphoryl group is 0.01% by mass.
If it is less than 3, the formation of a hydrated compound layer containing aluminum as an essential component, which will be described later, will be insufficient, and the flame retarding effect will be insufficient, and the weather resistance of the hydrated compound layer will be insufficient. The content of the compound having a phosphoryl group is 10% by mass.
When the amount exceeds, the flame-retardant performance does not improve in proportion to the content, and there is no point in containing a larger amount.

Then, the hydrated compound layer containing aluminum as an essential component is formed on the outer surface of the polysaccharide-based fiber by treating the polysaccharide-based fiber produced as described above with an aqueous solution of an aluminum compound. The present invention provides a flame-retardant polysaccharide-based fiber of the present invention.

As the aluminum compound, various water-soluble aluminum compounds can be used. Specifically, sodium aluminate, potassium aluminate, aluminum chloride, basic polyaluminum chloride (PAC), aluminum sulfate, basic aluminum sulfate, aluminum ammonium sulfate, potassium aluminum sulfate and the like are preferable.

The concentration of the aluminum compound in the aqueous aluminum compound solution is usually preferably 0.5 to 5% by mass. The pH of the aluminum compound aqueous solution is preferably from 3 to 13.

The processing time is preferably 0.5 to 10 minutes.
The processing temperature is preferably 5 to 50C.

The hydrated compound layer is formed on the fiber surface by treating the polysaccharide-based fiber with the above-mentioned aqueous solution of the aluminum compound. Aluminum ions on the inner surface of the hydrated compound layer and phosphoryl groups on the fiber surface are formed. Reacts to form a strong bond, so that the hydrated compound layer is firmly fixed on the fiber surface and has high weather resistance.

The flame-retardant polysaccharide fiber produced in this manner is further post-treated with an aqueous solution of silicic acid, boric acid, or a salt thereof, or a calcium salt or a magnesium salt, to further improve the weather resistance and the flame resistance. Flammability can be improved.

By performing the post-treatment, a hydrated aluminosilicate compound, hydrated aluminum borate, hydrated calcium aluminate, hydrated magnesium aluminate and the like are formed in the hydrated compound layer.

The concentration of silicic acid or the like in the aqueous solution for the post-treatment is preferably 0.5 to 10% by mass. The post-treatment time is preferably 0.5 to 10 minutes. Post-treatment temperature is 5-50 ° C
Is preferred.

In the method for producing the flame-retardant polysaccharide-based fiber, after the hydrated compound layer was formed, post-treatment was optionally performed with an aqueous solution of silicic acid or the like. After treating a polysaccharide-based fiber containing a compound having a phosphoryl group uniformly in the fiber with an aqueous solution of silicic acid or the like, a hydrated compound layer containing aluminum as an essential component is formed by treating with an aqueous solution of an aluminum compound. You may. The processing conditions are the same as described above.

Hereinafter, the present invention will be described more specifically with reference to examples.

[0055]

Example 1 Bisco-rayon fiber kneaded with urea phosphate esterified starch (brand name Niel Gum A-85, phosphorus content: 0.6% by mass, manufactured by AVEBE) was prepared by the following procedure. did.

Cellulose concentration of 9.0 produced according to a conventional method.
20 parts by weight of an aqueous solution of urea-phosphorylated starch (9.0% by mass of urea-phosphorylated starch, 0.5% by mass of sodium hydroxide) in 80 parts by mass of biscoice having an alkali concentration of 5.7% by mass. Was added, mixed well with a stirring bath, and dispersed and dissolved. Thereafter, spinning is carried out through a normal spinning process to 3.0.
Denier, 51 mm cut length fiber.

The fiber was desulfurized, washed with water, bleached and washed with water through a refining machine, and the fiber was diluted 5 times with a basic polyaluminum chloride solution (JIS K 1475-96 for water supply, content 10% in terms of aluminum oxide). For 2 minutes at room temperature. Thereafter, the mixture was neutralized and washed with a 0.1% sodium hydroxide solution, washed with water, treated with an oil agent, and dried.

The hydrated compound layer of the obtained fiber was 1.5% by mass of the total weight of the fiber.

When the obtained fiber was analyzed by fluorescent X-ray,
The phosphorus element content is 0.06% by mass. The aluminum content was 0.15% by mass. 2.2 g fiber dry strength
/ D, the nodule strength was 1.3 g / d.

After the fibers were formed into a web by a carding machine for testing, the fibers were entangled in a needle punch non-woven fabric facility. A nonwoven fabric having a basis weight of 1000 g / m ² was processed and a flammability test was performed. The LOI value was 30.5, indicating self-extinguishing. After washing this non-woven cloth (wash under running water 1
5 times) LOI value of 30.0, L after dyeing (direct dyeing)
The OI value was 26.0, and it was found that the self-extinguishing level was maintained after dyeing and washing.

Example 2 A urea phosphate esterified starch was kneaded in the same manner as in Example 1, treated with a basic polyaluminum chloride solution, and then treated with an aqueous solution of sodium silicate No. 3 (content in terms of silicon dioxide: 28% by mass). ) With a 10-fold diluted solution for 2 minutes,
Treated at room temperature. After being sufficiently washed and treated with an oil agent, it was dried.

The hydrated compound layer of the obtained fiber was 5% by mass of the total weight of the fiber.

When the obtained fiber was subjected to fluorescent X-ray analysis,
The phosphorus element content is 0.06% by mass. The aluminum content was 0.13% by mass and the silicon content was 0.35% by mass. The fiber has a dry strength of 2.2 g / d and a knot strength of 1.
It was 2 g / d.

After the fibers were formed into a web by a carding machine for testing, the fibers were entangled in a needle punch non-woven fabric facility. A nonwoven fabric having a basis weight of 100 g / m ² was processed and a flammability test was performed. The LOI value was 30.0, indicating self-extinguishing. After washing this non-woven cloth with water (wash under running water 15
LOI value of 30.0), LO after dyeing (direct dyeing)
The I value was 29.0.

Example 3 In the same manner as in Example 1, urea phosphate esterified starch was kneaded into a viscos. Then, after spinning in a usual spinning process, the mixture was desulfurized, washed with water, bleached, and washed with water through a scouring machine. The fibers were then treated with a 20 g / l aqueous sodium aluminate solution at 20 ° C. for 1 minute. Then, it was treated with a 3% by mass aqueous solution of boric acid at 20 ° C. for 1 minute, then washed with water, treated with an oil agent, and dried.

The hydrated compound layer of the obtained fiber was 3% by mass of the total weight of the fiber.

When the obtained fiber was subjected to fluorescent X-ray analysis,
The phosphorus element content was 0.06% by mass, and the aluminum content was 0.18% by mass. 2.5 g fiber dry strength
/ D, the nodule strength was 1.3 g / d.

After the fibers were formed into a web with a test carding machine, the fibers were entangled in a needle punch non-woven fabric facility. A nonwoven fabric having a basis weight of 100 g / m ² was processed and a flammability test was performed. The LOI value was 30.0, indicating self-extinguishing. After washing this non-woven cloth with water (wash under running water 15
LOI value of 30.0), LO after dyeing (direct dyeing)
The I value was 29.5.

[0069] Visco was kneaded Example 4 sodium hexametaphosphate (P ₂ 0 ₅ content of 68%) - thread - four fibers were created by the following procedure.

Cellulose concentration of 9.0 produced according to a conventional method.
20 parts by weight of an aqueous solution (30% by weight) of sodium hexametaphosphate was added to 80 parts by weight of biscoe having an alkali concentration of 5.7% by mass and mixed and dispersed sufficiently in a stirring bath. Thereafter, spinning is performed through a normal spinning step, and 3.0 denier is obtained.
And a fiber having a cut length of 51 mm. The fibers were desulfurized, washed with water, bleached and washed with water through a scouring machine, and then treated with a solution obtained by diluting an aqueous solution of No. 3 sodium silicate by 10 times. Then, it was treated with a solution obtained by diluting a basic polyaluminum chloride solution (JIS K 1475-96 aluminum oxide content for water supply: 10 mass% in terms of aluminum oxide) five-fold. Thereafter, the mixture was neutralized and washed with a 0.1% by mass sodium hydroxide solution, washed with water, treated with an oil agent, and dried.

The hydrated compound layer of the obtained fiber was 15% by mass of the total weight of the fiber.

When the obtained fiber was subjected to fluorescent X-ray analysis,
The phosphorus element content was 8.5% by mass, the aluminum content was 1.5% by mass, and the silicon content was 1.3% by mass. The fiber has a dry strength of 1.9 g / d and a knot strength of 0.9 g.
/ D. After forming the web with a carding machine for testing, the fiber was entangled in a needle punch non-woven fabric apparatus. A nonwoven fabric having a basis weight of 100 g / m ² was processed and a flammability test was performed. The LOI value was 31.5, indicating self-extinguishing. After washing this non-woven cloth (wash under running water 1
5) LOI value 31.5, L after dyeing (direct dyeing)
The OI value was 31.0.

Comparative Example 1 In the same manner as in Example 1, urea-phosphorylated starch was
Kneaded into the steel. Thereafter, after spinning in a usual spinning process, the mixture was desulfurized, washed with water, bleached, washed with water through a refining machine, and then treated with an aqueous aluminum (III) solution to give an oil agent and dried. When the obtained fiber was subjected to fluorescent X-ray analysis, the phosphorus element content was 0.06% by mass. The content of aluminum was 0.001% by mass or less. Fiber dry strength is 2.4
g / d and knot strength were 1.5 g / d.

After the fibers were formed into a web using a test carding machine, the fibers were entangled using a needle punch nonwoven fabric facility. Processing into a non-woven fabric with a basis weight of 100 g / m ² , and a combustion test method for polymer materials by oxygen index method (J
A flammability test was performed according to IS-K7201). The LOI value of this fiber was 17.5, the level of a flammable material.

Comparative Example 2 In the same manner as in Example 4, sodium hexametaphosphate was kneaded into a viscos. After spinning in the normal spinning process,
After desulfurization, washing with water, bleaching, and washing with water through a scouring machine, an oil agent was applied without being treated with an aqueous aluminum (III) solution and dried. When the obtained fiber was subjected to fluorescent X-ray analysis, the phosphorus element content was 8.5% by mass. The content of aluminum was 0.001% by mass or less. Fiber dry strength is 2.0
g / d and knot strength were 1.8 g / d.

This fiber had a basis weight of 1 as in Comparative Example 1.
It was processed into a needle punch non-woven fabric of 00 g / m ² , and a combustion test method of a polymer material by an oxygen index method (JIS-K720)
A flammability test was performed according to 1). LOI value is 18.0
At the level of flammable materials.

The results of Examples 1 to 4 and Comparative Examples 1 and 2 are summarized in Table 1.

[0078]

[Table 1]

Comparative Example 3 Hydrous aluminosilicate compound particles having a diameter of 1 to 3 μm (natural zeolite, trade name: Shilton, manufactured by Mizuno Chemical Industry Co., Ltd.) 20
The mass% was kneaded into viscose rayon using the viscose used in Example 1. The dry strength of the obtained fiber was 1.5 g / d, and the knot strength was 0.5 g / d. Since the fibers kneaded the particles, the physical properties were deteriorated. It was processed into a nonwoven fabric in the same manner as in the comparative example, and the LOI value was measured. The result was 19.0, which was at the level of a flammable material.

[0080]

According to the flame retardant polysaccharide fiber of the present invention, a hydrated compound layer containing aluminum as a flame retardant as an essential component is formed only on the fiber surface, which is a flame contact point, so that a small amount of hydration can be obtained. Flame retardancy can be efficiently achieved with compounds. Further, since the aluminum atom of the hydrated compound layer is bonded to the phosphoryl group contained in the fiber, the hydrated compound layer is strongly bonded to the fiber surface, and thus has excellent weather resistance. Furthermore, since it does not contain a halogen compound as a flame retardant,
It produces little black smoke or harmful gas when in contact with flames, and is friendly to the human body and the natural environment. Further, since the solid fine particles are not kneaded into the fiber as a flame retardant, a decrease in fiber strength is small.

The method for producing a flame-retarded polysaccharide fiber of the present invention comprises uniformly blending a compound having a phosphoryl group into the fiber, followed by treatment with an aqueous solution of an aluminum compound. Can produce flammable fibers.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) D06M 101: 06 F term (reference) 4L031 AA02 AA12 AB01 BA07 BA09 BA19 DA16 4L035 BB03 DD19 EE14 4L041 AA02 BA02 BC11 CA57 CB19

Claims (10)

[Claims] 1. A method for producing a flame-retardant polysaccharide fiber, comprising treating a polysaccharide fiber containing a compound having a phosphoryl group uniformly inside the fiber with an aqueous solution of an aluminum compound. 2. A polysaccharide-based fiber containing a compound having a phosphoryl group uniformly inside the fiber is treated with an aqueous solution of an aluminum compound, and then an aqueous solution of silicic acid, boric acid or a salt or calcium salt or magnesium salt thereof. A method for producing flame-retarded polysaccharide-based fibers, characterized in that the treatment is carried out by using 3. A polysaccharide fiber containing a compound having a phosphoryl group uniformly inside the fiber, treated with an aqueous solution of silicic acid, boric acid or a salt thereof, or a calcium salt or a magnesium salt, and then an aqueous solution of an aluminum compound A method for producing flame-retarded polysaccharide-based fibers, characterized in that the treatment is carried out by using 4. The method for producing a flame-retardant polysaccharide fiber according to claim 1, wherein the polysaccharide fiber is a regenerated cellulose fiber or a starch fiber. 5. The method for producing a flame-retarded polysaccharide fiber according to claim 1, wherein the compound having a phosphoryl group is a condensed phosphoric acid compound or a urea phosphorylated starch. 6. The content of the compound having a phosphoryl group in the polysaccharide fiber is 0.01 to 10% by mass as a phosphorus element.
The method for producing a flame-retarded polysaccharide-based fiber according to any one of claims 1 to 5. 7. A flame-retardant polysaccharide-based fiber comprising a compound containing a phosphoryl group uniformly in the fiber and a hydrated compound layer containing aluminum as an essential component on the surface of the fiber. 8. The content of the compound having a phosphoryl group in the flame-retardant polysaccharide fiber is 0.01 to 10 as a phosphorus element.
The flame-retarded polysaccharide-based fiber according to claim 7, which is mass%. 9. The method according to claim 7, wherein the amount of the hydrated compound layer containing aluminum as an essential component formed on the fiber surface is 1 to 30% by mass of the total mass of the flame-retardant polysaccharide-based fiber. Combustible polysaccharide fiber. 10. The flame-retarded polysaccharide-based fiber according to claim 8, wherein the hydrate layer contains silicon, boron, calcium, or magnesium in an amount of 50 to 300 mol% based on aluminum.