JP2000154422A - Polyvinyl alcohol flame-retarded fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyvinyl alcohol flame-retarded fiber useful for clothes and industrial and house hold materials, producible at low cost, and excellent in spinning stability and dimensional stability in hot water. SOLUTION: This fiber is obtained by dissolving a vinyl alcohol-based polymer and halogenated vinyl-based polymer in dimethyl sulfoxide to form a spinning solution with droplets (1 to 50 μm in diameter) of the halogenated vinyl- based polymer solution dispersed in the vinyl alcohol-based polymer solution; and spinning the spinning solution into a low-temperature solidification bath containing a solidification solvent (e.g. methanol) and dimethyl sulfoxide; the raw fiber thus produced being treated by extraction, drying, drawing under dry heating, and, as required, thermal shrinkage and further acetalization. The fiber thus produced is composed of the sea phase of the vinyl alcohol-based polymer having a degree of crystallinity of 65 to 85% and island phase of the halogenated vinyl polymer of 0.1 to 3 μm in diameter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vinyl alcohol polymer (hereinafter abbreviated as PVA) flame retardant fiber which can be industrially manufactured at low cost and has excellent spinning stability. The present invention relates to a fiber which can be suitably used for living materials such as curtains and carpets, and industrial materials such as car seats.

[0002]

2. Description of the Related Art As flame-retardant fibers, acrylic and polyester fibers copolymerized with a flame-retardant monomer, rayon fibers into which a flame-retardant agent has been kneaded or reacted, and thermosetting in which the polymer itself is flame-retardant Synthetic fibers, aramid fibers, and cotton and wool post-processed with a flame retardant are known. Acrylic fiber generates cyan gas when burned, polyester fiber melt drip, thermosetting fiber has low fiber strength, aramid fiber is expensive, cotton and wool have post-processing hardening and washing durability etc. There is a problem,
Each is being considered for improvement.

On the other hand, PVA-based flame retardant fibers are also disclosed in, for example, JP-B-37-12920 and JP-B-49-10823.
And used in the field of clothing such as firefighting clothes and work clothes, the field of living such as carpets, and the field of industrial materials such as car seats. In some cases, it is difficult to expand quantitatively due to the problem of high cost.

A conventional PVA-based flame-retardant fiber is obtained by adding a vinyl chloride-based polymer (hereinafter abbreviated as PVC) aqueous emulsion to an aqueous PVA solution and spinning the undiluted spinning solution. PVC is dissolved in water. Therefore, it is difficult to use inexpensive commercially available PVC powdered PVC by a conventional method using water as a solvent for the spinning stock solution.
It uses a PVC emulsion that is several times more expensive than VC. In order to make the PVA fiber flame-retardant, this expensive P
VC must be used for several tens of percent of PVA.
The production cost of the A-based flame retardant fiber has been increased. Also PVA
Aqueous solution of PVC and PVC emulsion at 7
It is not stable at 0 to 100 ° C., and its mechanical stability, particularly when passing through a gear pump, is insufficient, and it is necessary to add a surfactant or the like for stabilization, which further increases the cost.

In a conventional PVA-based flame retardant fiber, an aqueous emulsion of polyvinyl chloride having an emulsion particle size of 0.01 to 0.08 μm and an aqueous PVA solution are mixed, and if necessary, a tin compound or an antimony compound is used as a flame retardant. The solution to which the aqueous dispersion was added was used as a spinning stock solution, wet-spun into a solidification bath composed of an aqueous sodium sulfate solution, dried, dry-heat stretched, heat-treated, and, if necessary, acetalized with formalin to improve hot water resistance. Manufactured. Further, in order to obtain high-strength fibers, a spinning solution obtained by adding boric acid to a mixed aqueous solution of PVA and a PVC emulsion is discharged to a solidification bath composed of a mixed aqueous solution of caustic soda and sodium sulfate to perform boric acid cross-linking spinning. However, in all of the methods, glaze salt, which is a dehydrated salt, is used as a solidification bath, so that a dense skin layer is formed on the fiber surface immediately after solidification, the cross section becomes an uneven skin-core structure, and the core part is oriented and crystallized. Tends to be insufficient. In fact, the PVA crystallinity of this fiber is 5
It is as small as 0 to 60%, and therefore, there is room for improvement in dimensional stability, especially dimensional stability in dry and wet conditions, even if a treatment for improving hot water resistance such as formalization is performed.

[0006]

As described above, the conventional P
Although VA-based flame-retardant fibers are superior to other flame-retardant fibers, their applications have been limited due to high production costs and insufficient dimensional stability. An object of the present invention is to provide a PVA-based flame-retardant fiber that can be industrially manufactured at low cost and has excellent spinning stability.
Furthermore, the conventional PVA-based flame-retardant fiber has a drawback of being inferior in dimensional stability in hot water, and the present invention is to solve this drawback.

[0007]

SUMMARY OF THE INVENTION In view of the above situation, the present inventors have developed an inexpensive PV powder using inexpensive commercial PVC powder.
The present inventors have intensively studied the use of A-based flame-retardant fibers, and have reached the present invention. That is, the present invention comprises PVA (1) having a degree of polymerization of at least 1,000 and a degree of saponification of at least 98 mol%, and a halogen-containing vinyl polymer (hereinafter abbreviated as PVX) (2), wherein (1) is a sea component, and (2) Is a sea-island fiber of an island component, and the size of the island of (2) in the fiber cross section is 0.1 to 3 μm;
Further, the PVA-based flame-retardant fiber is characterized in that the crystallinity of (1) is 65 to 85%. Preferably, the fiber contains 0.1 to 10% by weight of PVA (3) having a saponification degree of 50 to 90 mol% with respect to (2).
Further, PVX is a fiber in which PVC is PVC, a fiber in which the mixing weight ratio of (1) and (2) is 95: 5 to 55:45, and at least one selected from the group consisting of a tin compound and an antimony compound. Fibers containing from 0.1 to 15% by weight of the compound, based on the total weight of the polymer.

In the present invention, the above-mentioned (1) and (2) are dissolved in a common solvent, and the obtained spinning dope is solidified by mixing a solidifying solvent having a solidifying ability with (1) and a stock solution solvent. After wet or dry-wet spinning in a bath and wet-drawing, the solvent of the stock solution contained in the fiber is extracted and removed, dried, and further subjected to dry-heat drawing, and if necessary, heat-treated or acetalized to obtain a PVA-based fiber. In producing the flame-retardant fiber, the spinning dope has a sea-island structure in which the solution of (2) exists in an island state in the solution of (1), and the island diameter of the solution of (2) is 1 to 1. 5
A method for producing a PVA-based flame-retardant fiber, which is characterized by having a thickness of 0 μm. Preferably, when the island diameter change rate of the solution of (2) in the spinning dope is 1 μm / hr or more, the above-mentioned production method wherein the spinning dope is continuously stirred during the period from when the spinning dope is formed to when spinning is performed. The spinning solution is (1), (2) and
(3) is obtained by dissolving (3) in a common solvent of (1), (2) and (3) so that (3) is 0.1 to 10% by weight with respect to (2). The above-mentioned production method, wherein at least a part of (2) and (3) is obtained by adding 0.1 to 3% by weight of (3) to the halogen-containing vinyl monomer at the time of polymerization of the monomer ( 3) The above production method using the content (2), which is obtained by adding 0.1 to 3% by weight of (3) to the halogen-containing vinyl monomer during polymerization of the monomer as a part of (3). (3) Using the content (2), the remainder of (3) is added at the time of preparing the spinning dope, and the amount of (3) in the spinning dope is 0.1 to 8 with respect to the total weight of the polymer in the spinning dope. It is the above-mentioned production method in which the weight% is used. Further, at least one compound selected from the group consisting of tin compounds and antimony compounds is contained in the spinning dope in an amount of 0.1 to 15% based on the total weight of the polymer.
It is the above-mentioned production method in which the weight% is mixed.

Hereinafter, the flame-retardant fiber of the present invention will be described in detail. The sea component, ie, the matrix component, of the fiber of the present invention is a PV having a degree of polymerization of 1000 or more and a saponification degree of 98 mol% or more.
Must be A. PVA is the only general-purpose polymer that has a common solvent with PVX that imparts flame retardancy, and that can form strong intermolecular hydrogen bonds with hydroxyl groups that enable high strength sea-island fibers.

In the present invention, PVA (1) means a polymer having a vinyl alcohol unit in an amount of 70 mol% or more of all the constituent units. Therefore, ethylene, itaconic acid, vinylamine, acrylamide, maleic anhydride, sulfonic acid 30 monomers such as vinyl compounds
It may be copolymerized in a proportion of less than mol%. The degree of saponification must be 98 mol% or more, preferably 99 mol% or more, more preferably 99.8 mol% or more in order to obtain a high-strength fiber. The upper limit is of course 100 mol%. Therefore, in PVA (1), a saponifiable vinyl unit, for example, a vinyl acetate unit or a vinyl pivalate unit, is used in a proportion of 0 to 2 mol% based on the total amount of the vinyl alcohol unit and the saponifiable vinyl unit. It may be polymerized. Regarding the degree of polymerization of PVA, the degree of polymerization must be 1000 or more for the same reason, and preferably 1500 or more. However, polymerization degree 2
It is difficult to produce PVA of 0000 or more industrially. In order to improve water resistance, PVA may be acetalized in the molecule and / or between molecules of PVA by post-reaction after fibrillation, such as formaldehyde, glutaraldehyde, and nonaldehyde, or monoaldehydes or dialdehydes or derivatives thereof. Further, the inside and / or between the molecules may be cross-linked by a cross-linking agent other than these.

The island component of the fiber of the present invention must be PVX. Only when PVX is used as the island component can the fiber of the present invention be a flame-retardant fiber. PVX referred to in the present invention is a halogen element, ie, fluorine, chlorine, bromine,
It is a vinyl polymer having a vinyl unit containing any of iodine in an amount of 50 to 100 mol% of the total vinyl unit. For example, vinyl chloride polymer (PVC), vinylidene chloride polymer, vinyl bromide polymer, vinylidene bromide polymer, chlorinated polyolefin, brominated polyolefin and the like are included. Among them, PVC is preferred in terms of flame retardancy, heat decomposition resistance, cost balance and the like. In the present invention, a monomer other than a vinyl unit may be copolymerized in the PVX as long as the flame retardancy is not significantly impaired. PVX has low crystallinity and does not have fiber forming ability or has low strength even if it is formed into fibers. In particular, PVX fibers are produced by wet spinning, which is a production method excellent in cost performance of staple fibers. Not. The fiber of the present invention contains PVX as an island component, generates a hydrogen halide gas when the fiber is exposed to high temperature and burns, and captures radicals generated during burning to suppress combustion. Play a role.

Further, the fiber of the present invention has a saponification degree of 50-9.
0 mol% of PVA (3) is 0.1% to PVX (2).
Preferably, the content is 10 to 10% by weight. The undiluted solution of the solution of (1) and the solution of (2) causes agglomeration of the islands composed of the solution of (2) with time, resulting in poor spinnability and difficulty in spinning. Due to the presence of 3), the aggregation of the islands composed of the solution of (2) hardly occurs even when the stock solution is left. PVX and PVA are inherently poorly compatible,
(3) has a high surface activity due to a large amount of acetic acid groups, and therefore has a high affinity with (2). Accordingly, (3) having such a high surface activity acts as a compatibilizing agent which mediates between (1) and (2), and as a result, the dispersion stability of the island composed of the solution of (2) is improved. is there.

PVA acting as such a compatibilizer
As such, those having high surface activity are preferable, and for that purpose, PVA having a low saponification degree is preferable. The lower the degree of saponification, the higher the dispersion stability of the island component composed of the PVX solution. However, if it is too low, the lower the saponification, the worse the dispersion stability. Therefore
The saponification degree of (3) is preferably 50 to 90 mol%, more preferably 60 to 88 mol%, and most preferably 70 to 90 mol%.
80 mol%. PVA used as a compatibilizer
The degree of polymerization of (3) is not particularly limited and can be used if the degree of polymerization is 500 or more, but it is more preferable if the degree of polymerization is 1700 or more. However, PVA whose degree of polymerization exceeds 20,000
Is difficult to manufacture industrially. Further, the PVA having a saponification degree of 50 to 90 mol% as used herein means a polymer having 50 to 90 mol% of a vinyl alcohol unit based on the total amount of the saponifiable units before saponification. It has 10 to 50 mol% of vinyl acetate and vinyl pivalate units which are functionalizable units.
Surprisingly, monomers such as ethylene, itaconic acid, vinylamine, acrylamide, maleic anhydride, and a sulfonic acid-containing vinyl compound may be copolymerized at a ratio of 10 to 30 mol%.

Degree of polymerization: 1000 or more, degree of saponification: 98 mol%
In order for the PVA (1) to be a sea component and the PVX (2) to be an island component, it is preferable that (1) is 55% by weight or more based on the total amount of (1) and (2). If (1) is less than 55% by weight, a part of (2) may become a sea component, and the strength may decrease, or (2) may be eluted in the extraction bath, and the process may pass through the process. It is not preferable in terms of sex. on the other hand,
If the amount of (1) exceeds 95% by weight, the amount of halogen in the fiber is small, and the flame retardancy becomes insufficient. Therefore, the mixed weight ratio of (1) / (2) is 95
The range of / 5 to 55/45 is adopted, and 90/10 to 55/45 is preferable from the balance of flame retardancy, strength and the like.
More preferably, it is 0/20 to 60/40. In the present invention, the PV is set within a range that does not impair the object of the present invention.
A polymer other than A and PVX may be added. Further, various stabilizers and coloring agents may be added.

The size of PVX islands in the fiber is 0.1
3 μm. The size of the islands of PVX in the present invention, after the insolubilized PVA treated formalized fiber sample in a constant length state, the epoxy resin treatment, to prepare an ultrathin section (thickness about 800 nm), Ru0 ₄
After performing steam staining, the obtained ultrathin section of the cross section of the fiber was observed at a magnification of 20,000 times with a transmission electron microscope (hereinafter abbreviated as TEM), and PVX was arbitrarily selected from the obtained electron micrograph. Is an average value when at least 50 island diameters are actually measured.

FIG. 1 shows an example of a 20,000 × TEM photograph of the cross section of the fiber of the present invention. For reference, FIG. 2 shows an electron micrograph of a cross section of a water-based PVA-based flame-retardant fiber mixed with a conventional PVC emulsion. In FIGS. 1 and 2, the gray dispersion component is PVC, the dispersion medium component that looks whitish is PVA, and the black substance is metastannic acid, and the black substance is metastannic acid. Was confirmed by EDX analysis.
Note that 2 cm in these drawings corresponds to an actual 1 μm.

While the conventional PVA-based flame-retardant fiber has a PVC island diameter of less than 0.1 μm and almost no 0.2 μm or more, the PVA-based flame-retardant fiber of the present invention has a PVX island diameter of 0 μm. 0.2 to 1.5 μm. The conventional PVA-based flame-retardant fiber uses a PVC emulsion having a particle diameter of 0.01 to 0.08 μm as a raw material PVC, and is stretched at a high temperature during the production process and further reduced in diameter. The size of the middle PVC island does not exceed 0.08 μm, and is generally 0.05 μm or less. On the other hand, in the present invention, as a result of diligently examining and changing the conventional idea to use inexpensive commercial PVX powder as a component of the PVA-based flame-retardant fiber, the common solvent of PVA and PVX powder was used as the solvent of the spinning solution. Inexpensive PVX powder by using a sea-island phase separation solution containing PVA as a sea component and PVX as an island component as a spinning solution, spinning in a solidification bath, and performing extraction, drying, dry heat drawing and, if necessary, heat treatment. Was obtained as one component. In the present invention, since (2) forms an island by polymer phase separation of (1) and (2), when the size of the island of the PVX solution in the spinning stock solution is 1 to 50 μm, after the dry heat drawing, The PVX island diameter of the fiber is 0.1 to 3 μm. Conventional PVA
In the case of 0.01 to 0.08 μm, which is the particle size of the PVC emulsion used for the flame-retardant fiber, the island diameter of PVX of the spinning dope used for the fiber of the present invention is too small, and the spinning dope becomes unstable and stable spinning is performed. Have difficulty.

Further, in the fiber of the present invention, the polymerization degree is 100
The crystallization degree of the sea component PVA (1) having a degree of saponification of 0 or more and 98 mol% is 65 to 85%. This is one of the important features in the production of the fiber of the present invention. As described above, the conventional PVA-based flame-retardant fiber formed by dewatering and coagulation has a crystallinity of 50 to 60 because its cross section has a skin core structure.
%, And there was a problem in the dimensional stability of wet and dry. On the other hand, the formation of the fiber of the present invention is uniform solidification by cooling gelation. Is greatly improved as compared with the prior art.

Further, in the PVA-based flame-retardant fiber of the present invention,
When at least one compound selected from the group consisting of tin compounds and antimony compounds is contained in an amount of 0.1 to 15% by weight based on the total weight of the polymer, the flame retardancy is further improved, which is preferable. The tin compound referred to in the present invention is not particularly limited as long as it is a compound containing a tin element.
In terms of cost performance, inorganic oxides such as tin oxide and metastannic acid are preferred. The antimony compound is not particularly limited as long as it is a compound containing an antimony element, but is preferably an oxide such as antimony trioxide or antimony pentoxide, like the tin compound. These compounds react with the hydrogen halide gas generated when the fiber is exposed to high temperature and PVX is decomposed to produce tin halide and antimony halide, which trap the radicals during combustion and suppress the oxidation reaction. It is presumed that the combustion reaction is suppressed by promoting the dehydration and carbonization reaction of PVA, and the flame retardancy is improved. The content of the tin compound or antimony compound is 0.5 to
When the content is 10% by weight, flame retardancy and process passability are more preferable, and when it is 1 to 7% by weight, it is more preferable. There is no particular limitation on the method of dispersing the mixture in the spinning dope, and when PVA and PVX are charged and dissolved in a common solvent, a tin compound or an antimony compound may be charged at the same time.

Next, a method for producing the fiber of the present invention will be described. First, PVA and PVX are dissolved in a common solvent to prepare a spinning solution. Examples of the common solvent include polar organic solvents such as dimethylsulfoxide (hereinafter abbreviated as DMSO), dimethylacetamide, and dimethylformamide. Particularly, DMSO is preferred from the viewpoint of low-temperature solubility, low polymer decomposability and the like. The concentration of the polymer in the stock solution is preferably in the range of 10 to 30% by weight.

It is important that the spinning dope has a phase structure in which a PVA solution has 1 to 50 μm particle-based islands composed of a PVX solution. By spinning such a stock solution, the size of the PVX island is 0.1 to 3 μm.
Can be obtained. The phase structure of the spinning solution referred to in the present invention means that the spinning solution is placed on a slide glass for about 200 hours.
It is a value measured by dropping a liquid to a thickness of μm, taking a photograph using a differential interference microscope (BX-60) manufactured by Olympus Optical Co., Ltd. The particle size as referred to in the present invention means that particles that can be discriminated when observed with a differential interference microscope are at least 50 particles.
It is the average value when the actual measurement was performed. When the majority of the PVX solution has an island diameter of more than 50 μm, it is not preferable in terms of processability, and spinning cannot be performed stably for a long period of time. If the majority is less than 1 μm, PVA cannot form a clear sea phase. Preferably 1-4
A phase structure having a particle size of 0 μm;
m is more preferable.

When the spinning stock solution is allowed to stand at 80 ° C. and the PVX island diameter change rate is 1 μm / hr or more, the spinning stock solution is continuously agitated from the formation of the spinning stock solution to spinning. Is preferred. This is because PVA and PVX have essentially poor compatibility, and depending on the PVX, aggregation of PVX islands occurs over time, resulting in poor spinnability and difficulty in spinning. The island diameter change rate is a value obtained by dividing the difference between the average PVC island diameters immediately after the dissolution of the undiluted solution and after standing for 15 hours by the standing time, and means the ease of aggregation of PVC islands. Therefore, it is important to improve the dispersion stability of the PVX island, and it is the PVA (3) having a saponification degree of 50 to 90 mol% as described above that enables defoaming on standing.

PVA (3) having a saponification degree of 50 to 90 mol%
Is greatly contributed to the island dispersion stability of PVX (2) in the spinning dope, and therefore, its introduction method is also important. As a method of introduction, there are a method of adding at the time of suspension polymerization of (2) and a method of adding at the time of dissolving a spinning stock solution. In the former method, (3) is combined with (2) at the time of polymerization, so that even a small amount of addition can efficiently contribute to the stabilization of island dispersion of (2). However, when the amount of addition is large, there arises a problem that foaming during washing after polymerization becomes large. Therefore, the amount of addition is preferably in the range of 0.1 to 3% by weight based on the halogen-containing vinyl monomer. On the other hand, in the latter method, since (3) cannot be selectively introduced into the interface between the matrix PVA (1) and (2), the required amount of (3) tends to be larger than the former method. However, since there is no foaming problem, the amount of addition can be increased. However, an excessively large amount is not preferable because the water resistance of the obtained fiber is reduced. The addition amount is preferably from 0.1 to 10% by weight, particularly preferably from 2 to 10% by weight, based on (2). It is also possible to use both the former and the latter simultaneously. This method is preferable because the problems of each method, that is, foaming and reduction in water resistance during polymerization can be reduced. In this case, the amount of (3) is preferable because the total amount can be reduced to 0.1 to 8% by weight based on (2).

The temperature of the stock solution is preferably 100 ° C. or less.
When the temperature exceeds 100 ° C., the solubility of PVC is improved, but the decomposition rate is remarkably increased, coloring is remarkable, and the degree of polymerization is reduced. Therefore, the lower the temperature, the better. However, if the temperature is too low, the solubility of PVC and PVA in the polar organic solvent deteriorates. Therefore, a stock solution temperature of 40 ° C. or more and 90 ° C. or less is preferable. More preferably, it is 50 ° C or higher and 80 ° C or lower. The viscosity of the spinning solution is 1 when wet spinning.
0 to 400 poise, 50 to 20 for dry-wet spinning
A range of 00 poise is preferred.

The method for dissolving the polymer is not particularly limited, but a method in which one polymer is dissolved in a solution in which the other polymer is dissolved, a method in which each polymer is dissolved simultaneously, and a method in which each polymer is dissolved alone in a stock solution solvent. Any of the above methods can be employed.
In addition, the spinning solution may be used in combination with an acid or an antioxidant as a polymer stabilizer.

The spinning solution 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 causing the fibers to stick 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. In the present invention, which of the wet spinning method and the dry-wet spinning method is used can be appropriately selected depending on the purpose and application.

The solidification bath used in the present invention is a mixed solution comprising a solidification solvent and a stock solution solvent. Examples of the solidifying solvent include PVA such as alcohols such as methanol and ethanol, and ketones such as acetone and methyl ethyl ketone.
Is preferable, and the composition weight ratio of the solidification solvent / stock solution solvent in the solidification bath is 25/75.
８５85/15. The temperature of the solidification bath is preferably 30 ° C. or lower, and is preferably 20 ° C. or lower, more preferably 15 ° C. or lower for uniform cooling and gelation. However, if the temperature is lower than −20 ° C., it is difficult to perform the subsequent wet drawing of the fiber, so that the temperature is −20 ° C.
C. or higher is preferred. Since the fiber of the present invention contains PVX, it is liable to be colored when exposed to high temperatures.However, since solidification is uniform in the cross-sectional direction, PVA tends to be oriented and crystallized only by drawing under dry heat. A fiber in which PVA is sufficiently oriented and crystallized can be obtained without performing a heat treatment at a higher temperature after the dry heat drawing as employed.
Therefore, there is little opportunity to be exposed to a high temperature, so that coloring can be suppressed. However, in the present invention, it is a matter of course that the dry heat treatment or the formalization treatment is not prevented in order to further improve the water resistance.

In the present invention, in order to properly maintain the solidification level, the composition ratio between the organic solvent-based solidifying solvent and the stock solution solvent in the solidification bath is important, and in the present invention, the weight ratio is 25/75.
A range of ~ 85/15 is employed. If the concentration of the undiluted solvent in the solidification bath is less than 15% by weight, the coagulation ability is too high, the nozzle breaks, the spinning condition becomes poor, and the performance of the obtained fiber such as strength and Young's modulus tends to decrease. On the other hand, if the concentration of the undiluted solvent in the solidification bath is more than 75% by weight, sufficient solidification cannot be performed, and the spinning process is poor in passage.
Fibers having satisfactory performance in terms of strength and the like cannot be obtained. A more preferable concentration of the undiluted solvent in the solidification bath is 20 to
70% by weight, most preferably 25-65% by weight.
In the present invention, as described above, the solidification bath is a mixture of the solidification solvent and the undiluted solvent. However, if the amount is small, other liquids and solids may be dissolved therein. In the present invention, the most preferable combination of the solidifying solvent and the stock solution is a combination of methanol and DMSO.

The yarn formed in the solidifying bath is sent to a dry heat drawing step after wet drawing, extraction of a stock solution solvent, and drying. In the method of the present invention, the wet stretching ratio is preferably in the range of 1.5 to 5 times. Then, the wet-drawn fiber is immersed in a bath of methanol, ketone or the like to extract and remove the stock solution solvent contained in the fiber. Then dry. Of course, an oil agent or the like may be applied to the fiber before drying. And it is necessary to perform dry heat stretching so that the total stretching ratio becomes 6 times or more. Dry heat stretching is usually performed under a temperature condition of 180 to 250 ° C. The total draw ratio in the present invention is a ratio represented by a product of a wet draw ratio and a dry heat draw ratio, and when the total draw ratio is less than 6, a fiber having excellent strength and Young's modulus is used. I can't get it. However, it is industrially difficult to perform the stretching so that the total stretching ratio exceeds 30 times. Usually, a total draw ratio of 10 to 20 times is used.

[0030]

Next, the present invention will be further described with reference to Examples.
The present invention is not limited to these examples. The strength and elongation of the fibers in the examples are JIS L-1013,
The flame retardancy index (LOI value) was measured according to JIS K-7201. The boiling water shrinkage ratio (hereinafter abbreviated as WSr) in the present invention is 2 mg / d to the sample fiber.
The load of r is suspended, and a predetermined length L ₀ (for example, 1.00 m)
Is accurately collected, boiled at 100 ° C. for 30 minutes in a free state, then air-dried, and the sample after air-drying is again 2 mg / d.
Measure the yarn length exactly as with hanging the load of r (L ₁ )
Then, WSr is calculated by the following equation. WSr = [(L ₀ −L ₁ ) / L ₀ ] × 100 (%) In the examples,% and ratio are values based on weight unless otherwise specified.

Example 1 PVA having a polymerization degree of 1750 and a saponification degree of 99.8 mol%, PVC powder having a polymerization degree of 400, and metastannic acid were stirred and dissolved in DMSO under a nitrogen stream at 80 ° C. for 5 hours. 65
/ 35, a polymer concentration of (PVA + PVC) 18%, and a spinning dope having a composition of metastannic acid 5% / polymer were obtained.
Observation of the spinning dope immediately after dissolution with a differential interference microscope revealed that the PVC solution had a phase structure in which the PVA solution formed an island phase having an island diameter of about 25 μm in average particle diameter. However, the PVC island diameter change rate of this stock solution was as large as 2.4 μm / hr, and when left to defoam at 80 ° C. for 15 hours, the spinnability was considerably poor and spinning was impossible. Therefore, spinning was possible by continuously stirring from the start of melting to the end of spinning. The obtained spinning dope was used with a pore size of 0.08 m.
m, through a nozzle having 2,000 holes, and wet spinning into a 5 ° C. solidification bath having a weight ratio of methanol / DMSO of 70/30. Next, while DMSO is being extracted with methanol, the film is wet-stretched 3.5 times, the methanol is dried with hot air at 100 ° C., dry-heat-stretched at 228 ° C. 4.0 times, and the single fiber thickness is 1.8 denier. Fiber was obtained. Production of this fiber
When (spinning) was performed continuously for 24 hours, it was possible to spin very stably without any trouble. FIG. 1 shows a 20,000-times TEM photograph of the cross section of the obtained fiber. From this photograph, it was found that PVC was a sea-island fiber forming an island having a size of about 0.9 μm. LOI value of this fiber is 3
9 and high flame-retardant fiber. The sea component P of the fiber
The crystallinity of VA is as high as 71%, so that the strength is 8.3.
g / d, and the WSr was as low as 2.4%, and was excellent in dimensional stability against humidity even after dry heat drawing. Although the hue was slightly yellow-pink, the conventional PV
It was lighter than the coloring of the A-based flame-retardant fiber.

Comparative Example 1 PVC emulsion having a particle size of 0.06 μm, degree of polymerization 175
0, 98.5 mol% of saponification degree PVA, metastannic acid and boric acid were stirred and dissolved in water at 90 ° C for 5 hours, and PVA / PVC was dissolved.
= 65/35, polymer concentration 20 of (PVA + PVC)
%, 5% metastannic acid / polymer, 2.5% boric acid / PVA, to obtain a spinning dope. This spinning dope was used in Example 1
Observation was performed with a differential interference microscope in the same manner as described above, but the PVC particles could not be observed to be too small. The obtained spinning dope was wet-spun through a nozzle having a hole diameter of 0.08 μm and a number of 2,000 holes into a solidification bath comprising a 45 ° C. aqueous solution containing 20 g / l of caustic soda and 350 g / l of sodium sulfate. Then, the roller was stretched 1.5 times, neutralized in a neutralization bath consisting of an aqueous solution of sulfuric acid and sodium sulfate, wet stretched 2.3 times in a saturated aqueous solution of sodium sulfate at 95 ° C., and washed with boric acid in a 30 ° C. washing bath.
Replace with Glauber's salt with 0 g / l aqueous solution of Glauber's salt, dry at 100 ° C, 2
The film was stretched 4.0 times at 28 ° C. by dry heat, and subjected to 5% dry heat shrinkage at 230 ° C. to obtain a PVA-based flame-retardant fiber by a water-based spinning method. FIG. 2 shows a 20,000-fold TEM photograph of the cross section of the obtained fiber. The diameter of PVC observed from this photograph is about 0.
It was 05 μm. The LOI value of this fiber was 39 and Example 1 was used.
Was equivalent to On the other hand, the crystallinity of the sea component PVA of this fiber is as low as 56%, and therefore the strength is as low as 5.9 g / d.
Further, WSr was as high as 11.5%, and the dimensional stability against moisture was insufficient. This fiber was further subjected to a formalization reaction at 70 ° C. for 30 minutes with a solution containing 10% formaldehyde and 10% sulfuric acid. Although the WSr of the obtained fiber was improved to 3.5%, the LOI value was 36, which was lower than that of Example 1.
The strength was 5.9 g / d.

Example 2 PVA having a polymerization degree of 1750 and a saponification degree of 99.8 mol%,
A PVC having a polymerization degree of 400 obtained by adding 0.6% by weight of PVA having a polymerization degree of 2400 and a saponification degree of 80 mol% per vinyl chloride monomer was added to DMSO together with metastannic acid, and a nitrogen stream was applied at 80 ° C. for 5 hours. Dissolve with stirring under PVA /
A mixed spinning dope having a PVC weight ratio of 67/33, a polymer concentration of 18% by weight, and metastannic acid of 1% by weight was obtained. When the PVC used here was analyzed by NMR, the degree of polymerization was 24.
PVA having a degree of saponification of 80 mol% and a pH of 0.000 per PVC.
It was confirmed that the content was 3% by weight. When the undiluted solution was observed with a differential interference microscope, it was found that the PVC solution had a phase structure in which the PVC solution was present as an island component having an island diameter of about 11 μm in the PVA solution. Also P
VC island diameter change rate is as small as 0.3 μm / hr, 80 ° C.
The spinnability after defoaming for 15 hours is the same as immediately after dissolution,
The spinning condition was very good. The obtained spinning dope at 80 ° C. was passed through a spinneret having 2,000 holes and a hole diameter of 0.08 mm, and the methanol / DMSO weight ratio was 70%.
/ 30, wet spinning in a solidification bath at a temperature of 0 ° C. Then, while extracting DMSO with methanol, it was subjected to 3.5 times wet stretching and dried with hot air at 100 ° C.
The film was stretched 4.0 times at 100 ° C. Production of this fiber (spinning)
Was carried out continuously for 24 hours. As a result, it was possible to spin very stably without any trouble. From the TEM photograph of the cross section, the obtained fiber was found to be a sea-island fiber in which PVC formed an island having a size of about 0.4 μm. L of this fiber
The OI value was 39. Further, the crystallinity of the sea component PVA of the present fiber is as high as 70%, so that the strength is 8.6 g / d,
WSr was as excellent as 2.6%. The hue was similar to that of Example 1.

Example 3 PVA having a degree of polymerization of 1750 and a degree of saponification of 99.8 mol%,
The weight ratio of PVC having a polymerization degree of 400 obtained by polymerization without adding PVA is 67/33, and the polymerization degree is 2400 and the saponification degree is 80.
The stock solution was dissolved, spun and stretched in the same manner as in Example 2, except that mol% of PVA was added at 0.6% by weight per PVC.
When the obtained spinning solution was observed with a differential interference microscope,
It was found that the PVC solution had a phase structure in which the PVC solution was present as island components having island diameters with an average particle size of about 18 μm. The rate of change in PVC island diameter is 0.5μ.
At m / hr, although the island diameter change rate was higher than in Example 2, the spinnability was almost the same as immediately after dissolution even after defoaming at 80 ° C. for 15 hours, and the spinning condition was extremely good as in Example 2. Met. From the TEM photograph of the cross section, the obtained fiber was found to be a sea-island fiber in which PVC formed an island having a size of about 0.5 μm. The LOI value of this fiber was 38. The crystallinity of the sea component PVA of the present fiber was as high as 71%, so that the strength was 8.3 g / d and the WSr was excellent at 2.5%. The hue was similar to that of Example 1.

Example 4 PVA having a degree of polymerization of 1750 and a degree of saponification of 99.8 mol%,
A weight ratio of vinyl acetate of 5% by weight, hydroxypropyl acrylate of 2.5% by weight, and a polymerization degree of 400 obtained by copolymerization without adding PVA, is 67/33,
Further, PVA having a degree of polymerization of 2400 and a saponification degree of 80 mol% is converted to P
The stock solution was dissolved, spun and stretched in the same manner as in Example 2 except that 0.5% by weight of VC was added. Observation of the obtained spinning dope with a differential interference microscope revealed that PVA was contained in the PVA solution.
It was found that the C solution had a phase structure in which an island component having an average diameter of about 10 μm was present as an island component. The PVC island diameter change rate of this stock solution was as small as 0.3 μm / hr, and the spinning property was the same as that immediately after dissolution even after defoaming at 80 ° C. for 15 hours, and the spinning condition was extremely good as in Example 2. there were. The obtained fiber is PVC from the cross-sectional TEM photograph.
Was found to be sea-island fibers forming islands of about 0.4 μm in size. The crystallinity of the sea component PVA of this fiber is 7
Although the strength was as high as 0%, the strength was excellent at 8.4 g / d and the WSr was 2.7%, but the LOI value was slightly lower at 37 because PVC was a copolymer. On the other hand, the hue was better than that of Example 1.

Example 5 A DMSO dispersion of metastannic acid and antimony trioxide was added with PVA having a polymerization degree of 1750 and a saponification degree of 99.8 mol% to give 8
Stir and dissolve at 80 ° C for 5 hours in a nitrogen stream at 0 ° C for 5 hours.
A solution of 20% VA, 6% metastannic acid / PVA, 1.5% antimony trioxide / PVA was obtained. Degree of polymerization 4
PVA having a degree of polymerization of 2400 and a saponification degree of 80 mol% was added to the PVC powder of No. 00 by 0.5% by weight per PVC, and this was stirred and dissolved in DMSO under a nitrogen stream at 70 ° C. for 5 hours.
A solution of 20% C was obtained. The obtained PVA solution and PVC solution were mixed while being measured with a gear pump, respectively, and T.K. K. The mixture was stirred and mixed at 3000 revolutions per minute in the middle of the pipe by a pipeline homomixer. The mixture is P
VA / PVC ratio 67/33, total polymer concentration 20
%, Metastannic acid 4% / polymer, antimony trioxide 1
% / Polymer, and when observed with a differential interference microscope, PV
It was found that in the solution A, the PVC solution had a phase structure forming an island phase having an island diameter of about 37 μm in average particle size. This mixed stock solution was spun, wet drawn, and treated in the same manner as in Example 1.
Extraction, drying, hot stretching and further 23
A 5% dry heat shrink treatment was performed at 0 ° C. From the TEM photograph of the cross section, the obtained fiber was found to be a sea-island fiber forming an island having a PVC of about 1.4 μm. This fiber was superior in hue to the fiber of Example 1. The LOI value of this fiber was 37. The sea component PVA of the present fiber had a crystallinity of 70%, a strength of 7.6 g / d and a WSr of 2.0%. When the method of this example was continuously performed for 24 hours, fibers could be produced with good spinning stability.

Comparative Example 2 In Example 5, the degree of polymerization was 2400
, A PVA-based flame-retardant fiber was produced in the same manner as in Example 5 except that PVA having a saponification degree of 80 mol% was not added to PVC. Observation of the spinning dope with a differential interference microscope revealed that the PVC solution formed an island phase having an average diameter of about 70 μm in the PVA solution. Continuous spinning was carried out in the same manner as in Example 5, but there was no problem up to 3 hours, but the spinnability deteriorated after 3 hours, and the spinning had to be stopped after 6 hours. .

[0038]

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 aims to further improve the cost performance of the fiber. The conventional PVA-based flame-retardant fiber uses a special and expensive PVC emulsion aqueous solution as PVX for obtaining flame retardancy, and spins a spinning stock solution mixed with a PVA aqueous solution into an aqueous solution containing sodium sulfate, drawing, heat treatment, and formal. The fiber of the present invention uses commercially available inexpensive PVX powder as PVC, and is dissolved in a common solvent of PVX and PVA to form an island phase of a specific size in the PVA solution in the PVA solution. A mixed solution having a phase structure is used as a spinning stock solution, which is subjected to cooling gel spinning in a solidification bath containing low-temperature methanol and the like, stretched, heat-treated as necessary, and acetalized. The degree of crystallinity of the fiber thus obtained is different from the conventional PVA-based flame-retardant fiber in that the PVA-based flame-retardant fiber is as high as 65-85% compared with the conventional PVA-based flame-retardant fiber as low as 50-60%. Also, the spinning stability is extremely excellent. Therefore, PVX powder which is several times cheaper than PVC emulsion can be used for PVX which must be used in a large amount of several tens of percent, and the PVA phase can be highly oriented and crystallized, so that a PVA-based flame retardant excellent in cost performance can be obtained. It can be a 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,
It can be effectively used in the field of living materials such as blankets, futon side sheets, sheet covers, and cotton filling.

[Brief description of the drawings]

FIG. 1 is a transmission electron micrograph showing an example of a cross-sectional shape of a fiber of the present invention.

FIG. 2 is a transmission electron micrograph showing an example of a cross-sectional shape of a conventional flame-retardant fiber.

Continued on the front page (72) Inventor Akio Omori 1621 Sakurazu, Kurashiki-shi, Okayama Prefecture Kuraray Co., Ltd. (72) Inventor Isao Tokunaga 1621 Sakurazu, Kurashiki-shi, Okayama Prefecture Kuraray Co., Ltd. 2045, Sakurazu, Kurashiki Prefecture, Japan Kuraray Co., Ltd. (72) Inventor Shoichi Nishiyama 1-2-1, Kaigan-dori, Okayama-shi Kuraray Co., Ltd. No.1 F-term in Kuraray Co., Ltd. (Reference) 4L035 AA04 AA07 BB03 BB04 BB85 CC20 DD01 EE01 EE08 EE20 FF01 FF04 JJ04

Claims (9)

[Claims] 1. A polymerization degree of 1,000 or more and a saponification degree of 98 mol%.
It comprises the above vinyl alcohol polymer (1) and a halogen-containing vinyl polymer (2), wherein (1) is a sea component,
(2) is a sea-island fiber which is an island component, and the size of the island of (2) in the fiber cross section is 0.1 to 3 μm, and the crystallinity of (1) is 65 to 85%. A polyvinyl alcohol-based flame-retardant fiber. 2. The fiber contains a vinyl alcohol-based polymer (3) having a saponification degree of 50 to 90 mol% in an amount of 0.1 to 0.1% based on (2).
The fiber according to claim 1, which is contained in an amount of 10% by weight. 3. The fiber according to claim 1, wherein the fiber contains at least one compound selected from the group consisting of a tin compound and an antimony compound in an amount of 0.1 to 15% based on the total weight of the polymer. 4. A polymerization degree of at least 1,000 and a saponification degree of 98 mol%.
The above vinyl alcohol polymer (1) and the halogen-containing vinyl polymer (2) were dissolved in a common solvent, and the obtained spinning dope was mixed with a solidifying solvent having a solidifying ability with respect to (1) and a stock solvent. Wet or dry-wet spinning in a solidification bath,
After wet drawing, the solvent in the fiber is extracted and dried,
In order to produce polyvinyl alcohol-based flame-retardant fibers by further performing dry heat drawing, and further performing heat treatment or acetalization as necessary, the spinning stock solution contains the solution (2) in the solution (1) in an island state. A method for producing a polyvinyl alcohol-based flame-retardant fiber, characterized in that the solution has a sea-island structure and the island diameter of the solution of (2) is 1 to 50 μm. 5. In the spinning dope, when the island diameter change rate of the solution (2) is 1 μm / hr or more, the spinning dope is continuously stirred from the formation of the spinning dope to spinning. The production method described in 1. 6. The spinning dope comprises (1), (2) and a saponification degree of 5.
0 to 90 mol% of a vinyl alcohol polymer (3)
(3) should be 0.1 to 10% by weight based on (2).
The production method according to claim 4, which is obtained by dissolving in a common solvent of (1), (2) and (3). 7. The method according to claim 1, wherein at least a part of (2) and (3) is used for polymerization of the halogen-containing vinyl monomer during polymerization.
(3) containing (2) obtained by adding 0.1 to 3% by weight of (3)
The production method according to claim 4, wherein 8. The content of (3) according to claim 7, as a part of (3).
Using (2), the remainder of (3) is added at the time of preparing the spinning dope so that the amount of (3) in the spinning dope is 0.1 to 8% by weight based on the total weight of the polymer in the spinning dope. The method according to claim 4. 9. The spinning dope contains at least one compound selected from the group consisting of tin compounds and antimony compounds,
The method according to any one of claims 4 to 8, wherein the content is 0.1 to 15% by weight based on the total weight of the polymer.