JPH03213510A - Polyvinyl alcohol-based fiber and its production - Google Patents

Abstract

PURPOSE:To obtain the subject fiber, excellent in tensile strength and initial elastic modulus, having high hot water resistance and useful as reinforcing fiber in fishing nets, ropes, building materials, etc., and for reinforcing tires, etc., by applying a catalyst for accelerating dehydrating reaction to PVA fiber of a high polymerization degree and then heat-treating the resultant fiber at a high temperature. CONSTITUTION:The objective fiber, obtained by applying a catalyst for accelerating dehydrating reaction (preferably hydrochloric or p-toluenesulfonic acid) to PVA fiber having 1500-7000 polymerization degree, then heat-treating the resultant fiber at >=150 deg.C, preferably at 180-260 deg.C for 3-20sec and having >=10g/de tensile strength, >=200g/de initial elastic modulus and >=140 deg.C hot water resistance.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention is a polyvinyl alcohol (hereinafter referred to as "polyvinyl alcohol") which has high strength, high initial modulus, and excellent hot water resistance.

It is abbreviated as PVA. ) type polymer, and
This invention relates to conductive polyvinyl alcohol fibers with excellent tensile strength and methods for producing them.

(Conventional technology) PVA fiber has the highest strength among general purpose fibers.

Has a high initial modulus of elasticity, rubber hoses, conveyor belts, cement reinforcement fibers, sewing threads for materials 9 tatami threads, fishing nets, land nets 1
It is widely used as a fiber for industrial materials such as heavy fabrics and ropes.

However, PVA fibers have low resistance to hot water, which prevents them from being applied to industrial materials that require durability against hot water.

In particular, after it became clear that asbestos was carcinogenic, asbestos was used as a reinforcing fiber. The use of PVA fibers as a substitute for asbestos in building materials such as so-called asbestos slate boards and calcium silicate boards is being considered.

PVA fibers have the following problems because they have low resistance to hot water.

In other words, although PVA fibers are compatible with cement and have high strength, these building materials are mass-produced by autoclave curing, so conventional PV
Due to the following reasons, the fiber A deteriorates significantly during autoclave curing, and the strength of the resulting building material decreases, making it unsuitable for practical use.

Autoclave curing is a process in which molded bodies of hydraulic inorganic substances such as cement, quartzite, fly ash, and gypsum are heated in an autoclave with high-temperature, high-pressure saturated steam to harden the hydraulic inorganic substances through a hydrothermal reaction. Yes 1 Usually,
The curing temperature is in the range of 130 to 160°C, and the curing time is in the range of 4 to 24 hours. Therefore, conventional PVA fibers have poor hot water resistance.

It cannot withstand autoclave curing under the above conditions, and the strength of the resulting building material decreases.

For PVA fibers, the higher the degree of polymerization of the raw material PVA.

It is known that the resulting fibers have high hot water resistance. Therefore, it is obvious that PVA fibers with excellent hot water resistance can be obtained by using PVA with a high degree of monopolymerization.
140, which can be widely applied to industrial material applications.
In order to obtain high hot water resistance of ℃ or higher, the degree of polymerization is 100.
PVA with an ultra-high polymerization degree of 0.00 or higher had to be used. However, such ultra-high polymerization degree PVA is not only difficult to obtain commercially, but also has poor solubility in solvents, making it difficult to spin, making it difficult to obtain high-strength fibers.

For this reason, JP-A-61-108713 discloses a dimethyl sulfoxide (hereinafter abbreviated as DMS○) solution of PVA rich in syndiotactic structure prepared using vinyl trifluoroacetate as a raw material.

Alternatively, a method for obtaining PVA fibers with excellent hot water resistance by dry/wet spinning or gel spinning a glycerin solution is disclosed.

However, although this method does yield PVA fibers with excellent hot water resistance, strength, and initial elastic modulus, the hot water resistance is only 120°C at most, and PVA made from vinyl trifluoroacetate is extremely expensive. Moreover, it has the disadvantage that it is difficult to obtain commercially and difficult to implement on an industrial scale.

On the other hand, as an attempt to improve the hot water resistance using commercially available PVA, Japanese Patent Application Laid-Open No. 63120107 discloses that the degree of acetalization of drawn yarn is 5% under a stretch rate of -10% to 7%. A method is disclosed in which the acetalization treatment is performed so that the amount is mol % or more and 15 mol % or less.

However, as a result of detailed trials by the present inventors, we found that the hot water resistance of the fiber obtained using this method was only about 120°C, and that aldehydes such as formalin were introduced into the drawn yarn during the acetalization process. Since this method involves a reaction, it is clear that a long treatment time is required to obtain the desired degree of acetalization, and like the above-mentioned method, it is difficult to implement on an industrial scale.

Furthermore, in JP-A-1-104815, PVA fibers with high hot water resistance are produced by hot-stretching gel-like undrawn single-stretched fibers to 7 times or more, treating them with a boric acid aqueous solution, and then hot-stretching them. A method of manufacturing is described. However, the hot water resistance of the fiber obtained even with this method is at most 12
The temperature was only 5°C, and it could not withstand autoclave curing for cement reinforcement.

Furthermore, JP-A-1-156517 discloses a method of producing PVA fibers with high hot water resistance by attaching a crosslinking agent to yarns that have been stretched three times or more, and then dry-heat stretching them three times or more. Are listed. however.

The fibers obtained by this method also did not have enough hot water resistance to withstand autoclave curing for cement reinforcement. Moreover, the organic peroxide used as the crosslinking agent used in this method is very expensive, which not only increases the cost.

Since oxygen in the air acts as a terminator for the crosslinking reaction caused by the above-mentioned chemicals, there is a drawback that the crosslinking efficiency is poor.

On the other hand, it has been conventionally known that a method of mixing a small amount of conductive fibers is effective in eliminating static electricity problems in textile products. Generally, as such fibers having conductivity, conductive fibers made of a polymer containing conductive carbon black particles are used. However, conventional conductive fibers are composite fibers formed from thermoplastic polymers (e.g., polyamide, polyester, fluorocarbon, etc.) and thermoplastic polymers in which these polymers are mixed with conductive carbon black particles. Therefore, its tensile strength was only 4 g/d at most.

Further, carbon fiber is known as a conductive fiber having high tensile strength, and its tensile strength reaches 20 g/d or more. However, carbon fiber has a complicated manufacturing process and requires special oxidation, carbonization, etc. processes, making it extremely expensive, and the fact is that it is not used as a general-purpose conductive fiber.

As mentioned above, PVA fiber has the highest strength and highest initial elastic modulus among general-purpose fibers.

It is clear that if conductivity could be imparted to PVA fibers, they would be extremely useful as fibers for industrial materials.

However, conductive fibers made of PVA that do not contain conductive particles have not been known at all.

There are no documents that suggest this possibility.

(Problems to be Solved by the Invention) As mentioned above, various attempts have been made to improve the hot water resistance, which is an essential drawback of PVA fibers, and to provide them with high strength and high initial elastic modulus. All of them have the disadvantage that their hot water resistance is not sufficiently improved, and PVA fibers that have extremely high hot water resistance that can withstand autoclave curing for cement reinforcement have not been known.

Further, conventional general-purpose conductive fibers have a problem of low tensile strength, and carbon fibers with high tensile strength are extremely expensive, making it difficult to widely use them as fibers for industrial materials.

Therefore, the first object of the present invention is to provide a PVA-based fiber that has high strength and high initial modulus of elasticity, and also has hot water resistance to the extent that it can withstand autoclave curing for use in reinforcing cement.

A second object of the present invention is high strength.

Another object of the present invention is to provide a PVA-based fiber having conductivity.

Furthermore, a third object of the present invention is to provide a method for producing the above hot water-resistant PVA fibers and conductive PVA fibers with high productivity from commercially available PVA fibers with a degree of polymerization. .

(Means for Solving the Problems) As a result of intensive studies to solve the above problems, the present inventors have found that by heat-treating PVA fibers in the presence of a catalyst for promoting the dehydration reaction, the fibers can be amorphous. The present invention was achieved based on the finding that causing a dehydration reaction on the hydroxyl groups present in the amorphous part to substantially reduce the hydroxyl groups in the amorphous part is effective in improving hot water resistance and imparting conductivity.

That is, one aspect of the present invention has the following configuration.

(1) A hot water-resistant polyvinyl alcohol made of a polyvinyl alcohol polymer, having a tensile strength of 10 g/d or more, an initial elastic modulus of 200 g/d or more, and a hot water resistance of 140°C or more. type fiber.

(2) Made of polyvinyl alcohol polymer, has a tensile strength of 7 g/d or more and an electrical resistance of 1.0 x 108 Ω/
1. A conductive polyvinyl alcohol fiber characterized by having a thickness of less than cm.

(3) A method for producing polyvinyl alcohol fibers, which comprises applying a catalyst for promoting a dehydration reaction to fibers made of polyvinyl alcohol having a degree of polymerization of 1,500 or more and 7,000 or less, and then heat-treating the fibers at a temperature of 150° C. or more.

The present invention will be explained in more detail below.

The hot water resistant PVA fiber of the present invention which has high strength and high initial elastic modulus and is particularly excellent in hot water resistance.

Precursor for conductive PVA fiber with excellent tensile strength
The PVA fiber used is not particularly limited, but 1
For example, patent application No. 1-12203 proposed by the present inventors
It can be produced under optimal conditions according to the dry/wet (gel) spinning method described in 0.

That is, a spinning stock solution prepared by dissolving PVA with a degree of polymerization of 1,500 or more in a solvent containing DMSO as a main component is subjected to dry/wet spinning, and the resulting undrawn yarn is stretched to form PVA.
When producing fibers, the fibers can be produced by dry/wet spinning using a spinneret having a discharge hole protruding from the spinning dope exit side.

It can also be produced by a conventional spinning method (wet spinning method), for example, using a PVA aqueous solution containing boric acid or a borate as a spinning stock solution and a coagulating bath of alkali hydroxide, sodium sulfate, etc. It is possible to do so.

As described above, the PVA fibers that serve as precursors for the hot water-resistant PVA fibers and conductive PVA fibers of the present invention can be produced by various methods, but the PVA fibers used can be
The degree of polymerization of VA needs to be 1500 or more. When the degree of polymerization is less than 1500.

This is unsuitable because the tensile strength of the final product will be lower than the desired value. Also, what is the upper limit of the degree of polymerization?

7,000 or less in terms of polymer cost.

In the present invention, it is extremely important to reduce the hydroxyl groups in the amorphous portion by applying a catalyst for promoting the dehydration reaction to the PVA fiber and then subjecting it to hot stretching or heat treatment.

That is, the dissolution of PVA fibers by moist heat progresses as water molecules bond with hydroxyl groups in the amorphous portions of the fibers. Therefore, in order to improve the hot water resistance, it is necessary to reduce the fraction of the amorphous part or to reduce the hydroxyl groups in the amorphous part. However, no matter how highly oriented the polymer is using a polymer with a high degree of polymerization, it is not possible to obtain a perfectly crystalline body free of amorphous parts, and there is a limit to the improvement of hot water resistance.

On the other hand, the method of reducing the hydroxyl groups in the amorphous part is advantageous because it does not require the use of polymers with a high degree of polymerization, and is also effective because it selectively modifies the amorphous part, which has poor hot water resistance. It is.

When PVA fibers are heat-treated in the presence of a catalyst, an intramolecular dehydration reaction, an intermolecular dehydration reaction, or both dehydration reactions occur due to the hydroxyl groups of PVA as shown in the following formula. The PVA modified product produced by the dehydration reaction of the hydroxyl group in the molecule has a polyvinylene structure consisting of conjugated double bonds.
The product produced by the dehydration reaction of intermolecular hydroxyl groups has an intermolecular crosslinked structure.

1 H Furthermore, it is generally known that polymers having a molecular structure having a conjugated double bond exhibit conductivity because their pi electrons can move freely within the molecule. The PVA fiber obtained by heat treatment as described above has a conjugated double bond generated by dehydration of the hydroxyl group in one molecule, so it exhibits good electrical conductivity and is used to promote the dehydration reaction used in the present invention. Various catalysts can be used, such as inorganic acids such as phosphoric acid and hydrochloric acid, organic acid halides such as phthalic acid chloride and adipic acid chloride, and organic acids such as p-toluenesulfonic acid and terephthalic acid. However, hydrochloric acid and p-)luenesulfonic acid are particularly preferably used.

Solvents for these acids include water and alcohol.

Although ketones can be used, lt water is preferably used in the case of hydrochloric acid, and methanol is preferably used in the case of p-toluenesulfonic acid.

Since the present invention applies the dehydration reaction using hydroxyl groups as described above, boric acid, borax, organic peroxides, etc. that do not promote the dehydration reaction cannot be used as catalysts.

The acid concentration of the catalyst used in the present invention is set in conjunction with the heat treatment conditions in the subsequent process, but when the purpose is to produce hot water-resistant PVA fibers, it is preferably 0.01 to 5N, more preferably 0. .1 to 3 regulations. Acid concentration is 0.01
If it is thinner than the specified value, a long heat treatment will be required to sufficiently advance the dehydration reaction or crosslinking reaction, which is not preferable. On the other hand, if it is higher than 5 normal, the tensile strength tends to decrease, which is not preferable.

Moreover, when the purpose is a PVA-based conductive fiber, 14 is preferably 3 to 10 normal, more preferably 5 to 7 normal. If the acid concentration is lower than 3N, the dehydration reaction will not proceed sufficiently, making it difficult to achieve the desired conductivity. If the acid concentration is higher than 10N, the tensile strength will drop significantly. Hard to get.

In the present invention, the above-mentioned catalyst is applied to the PVA fibers prior to heat treatment, but the method of applying the catalyst to the fibers is not particularly limited, but there is a method of immersing the fibers in a catalyst solution, a method of applying the catalyst with a so-called oiling roller. , a method of spraying a catalyst solution, etc. can be used. Among these methods, the method of running fibers through a solution of the catalyst mentioned above is based on the concentration of the catalyst,
It is convenient because the amount of catalyst applied can be adjusted by adjusting the running time in the catalyst solution depending on the shape of the fibers, running speed, etc.

Further, the timing of applying the catalyst is preferably after the fibers have a certain degree of hot water resistance, and specifically, it is preferable to apply the catalyst after hot stretching.

The first invention of the present invention is a PVA-based fiber that has high strength and high initial elastic modulus and has excellent hot water resistance.

Furthermore, in order to obtain the conductive PVA fiber according to the second invention, it is necessary to heat-treat the PVA fiber to which the catalyst has been applied as described above.

Heat treatment methods include a method in which a yarn (preferably a drawn yarn) to which a catalyst has been applied is continuously run through a heat treatment machine such as a hot air heating furnace, or a method in which the yarn is wound once and then batchwise run in a heat treatment machine. Examples include a method of processing.

The heat treatment is carried out at a temperature range of 150°C or higher and lower than the melting point of the fiber, preferably 180°C to 260°C, with tension applied to the yarn for 1 to 60 seconds, preferably 3 to 20 seconds. The heat treatment temperature is lower than 150°C.

If the treatment time is shorter than 1 second, the dehydration reaction or crosslinking reaction will be insufficient, and the desired high hot water resistance and electrical conductivity will not be obtained. Furthermore, it is not preferable if the heat treatment temperature is higher than 260° C. and the heat treatment time is longer than 60 seconds, or if the heat treatment is performed without applying tension to the yarn, the strength of the yarn will significantly decrease. The tension of the yarn during heat treatment is not particularly limited, but in the case of continuous heat treatment.

The roller speed ratio before and after the heat treatment machine has a stretch rate of 0 to 10.
It is preferable to set it to %.

According to the present invention, the commercially available degree of polymerization is 1500.
As described above, it is possible to easily produce PVA-based fibers having high strength, high initial elastic modulus, and high hot water resistance, and conductive PVA-based fibers with good productivity using PVA having a molecular weight of 7000 or less.

Moreover, the hot water resistant PVA of the present invention obtained in this way
The fibers have a tensile strength of 10 g/d or more and a tensile strength of 200 g/d.
Has an initial elastic modulus of d or more, and has hot water resistance of 140℃
It has the above-mentioned characteristics that were completely unknown until now.
It can be used not only for fishing nets and robes, which are typical uses of PVA fibers, but also for reinforcing cement and concrete building materials produced by autoclave curing.

Furthermore, the conductive PVA fiber of the present invention has a tensile strength of 7.
g/d or more, preferably 8 g/d or more, electrical resistance value 1
．． It has a previously unknown property of 0x10 8 Ω/cm or less, and is suitable as a fiber for eliminating static electricity problems in floor coverings such as paper stacks, carpets, and automobile seats.

(Function) In the present invention, PVA fibers having high hot water resistance of 140° C. or higher and conductive PVA fibers can be obtained by using PVA fibers in the presence of a catalyst such as hydrochloric acid or p-)luenesulfonic acid. When heat treated.

This is believed to be because the hydroxyl groups of PVA undergo a dehydration reaction within or between molecules, resulting in a polyvinylene structure consisting of conjugated double bonds or an intermolecular crosslinked structure.

In addition, in the present invention, since the catalyst is applied from the outside, the polyvinylene structure and intermolecular crosslinked structure grow from the outside to the inside of the fiber, which makes the fiber surface strong, which particularly requires hot water resistance and electrical conductivity. It is suitable because it has hot water resistance and conductivity.

9 The tensile strength and initial elastic modulus in the present invention are based on JIS
-L-1013, the measurement is carried out at a gripping interval of 25 cm and a pulling speed of 30 cm/min, and the hot water resistance is measured by the following method.

8 Equipment: PerkinElmer DSC-2C differential scanning calorimeter Temperature increase rate: 10°C/min Sample cell: High pressure (50 atm) cell Sample preparation method: 5 m fiber sample cut to approximately 5 mm length
g is sealed in a sample cell with 10 mg of water.

Hot water resistance: The peak temperature of the melting curve obtained by the above method is defined as hot water resistance.

In addition, the electrical resistance value indicates the highest value among the resistance values measured when 10 cm long threads are randomly sampled 30 times from a 1000 m long sample and a DC voltage of lkv is applied to each sample. It is something that

(Example) Next, one embodiment of the present invention will be specifically explained using examples.

Example 1 PVA with a degree of polymerization of 5100 (degree of saponification 99.9 mol%)
Prepare a 12% by weight DMSO solution and use this spinning stock solution.

Using a spinneret in which 210 stainless steel cylindrical tubes with an inner diameter of 0.7 mm were embedded so as to protrude 3 mm from the spinning dope exit side, the linear discharge speed was 4 m/min, and the spinning draft was 4.0.
Dry/wet spinning was performed in a methanol coagulation bath through an air gap of 10 mm, DMSO was extracted with methanol, and then dried to obtain an undrawn yarn.

Next, this undrawn yarn was drawn by one person in a hot air bath set at a temperature of 180°C and an outlet temperature of 255°C, and the drawn yarn was continuously passed through 1N hydrochloric acid for about 5 seconds to remove the catalyst. Hydrochloric acid was added. Furthermore, this yarn has an internal temperature of 210℃.
Heat treated by running for 5 seconds at a constant length (stretch rate 0%) in a heat treatment machine set to 1490d/
21Of fibers were obtained.

The manufacturing conditions and the physical properties of the obtained hot water resistant fiber are shown in Table 1, and the hot water resistance of this fiber was 153° C., indicating extremely excellent hot water resistance.

Examples 2 and 3. Comparative Example 1 As shown in Table 1, 1 polymerization degree 1700.7000 and 1
A DMSO solution of 300% PVA was prepared, and using this spinning stock solution, dry/wet spinning and drawing were performed in the same manner as in Example 1 to obtain a drawn yarn. In addition, in Example 2.3 and Comparative Example 1, the inner diameter of the stainless steel cylindrical tube was 0.6 mm.
, 0.8 mm, and 0.5 mm were used.

Hydrochloric acid was applied to the obtained drawn yarn in the same manner as in Example 1.

Heat treatment was performed. The performance of the obtained heat-resistant water-resistant fibers was evaluated first.
Shown in the table.

Comparative Example 2 1510 was prepared in the same manner as in Example 1 except that hydrochloric acid was not added.
A fiber of d/21Of was produced.

The obtained fiber had a low hot water resistance of 115°C.

Example 4 Using PVA with a degree of polymerization of 5100, an aqueous solution prepared by adding 2.1% by weight of boric acid to adjust the pH to 4.2 was used as a spinning stock solution, and a spinning draft was passed through a spinneret with 500 holes. After performing wet spinning in a coagulation bath containing 350 g/1 of sodium sulfate and 40 g/l of caustic soda at a concentration of 4.5 The first stage stretching (spinning stretching) was carried out, and the film was further washed with water and then dried.

1 The obtained dry fibers were drawn 4 times with dry heat at 245°C.

Subsequently, after applying hydrochloric acid by passing it through 1N hydrochloric acid for about 5 seconds, heat treatment was performed in the same manner as in Example 1.
A fiber of 0f was obtained.

Table 1 shows the physical properties of the obtained hot water-resistant fiber.

Example 5 The undrawn yarn obtained in Example 1 was heated to an inlet temperature of 180 t.

The drawn yarn was drawn in a hot air bath set at an outlet temperature of 255°C, and the drawn yarn was continuously treated with 0.5 N p-)luenesulfonic acid (P).
-TSA) in a methanol solution for about 5 seconds, and then the yarn was heat-treated by running it for about 5 seconds in a heat treatment machine whose internal temperature was set to 210°C.

Table 1 shows the physical properties of the obtained hot water-resistant fiber.

=22 28 - Example 6 The undrawn yarn obtained in Example 1 was drawn in a hot air bath set at an inlet temperature of 180°C and an outlet temperature of 255°C, and the drawn yarn was continuously treated with 5N P-TSA methanol. The solution was allowed to flow through the solution for about 10 seconds, and P-TSA, which acts as a dehydration reaction catalyst, was applied.

Further, this yarn was heat-treated by running it for 5 seconds at a stretch rate of 1% in a heat treatment machine whose internal temperature was set to 250°C to obtain a conductive fiber of 1530d/21Of.

The physical properties of the obtained fiber are shown in Table 2, and the electrical resistance value of this yarn is 8. OX 10'Ω/cm, and had extremely excellent conductivity.

Examples 7 and 8. Comparative example 3 Examples 2 and 3. To the drawn yarn obtained in Comparative Example 1.

The same P-TSA application and heat treatment as in Example 6 were performed.

The performance of the obtained conductive fibers is shown in Table 2.

Comparative Example 4 The same operation as in Example 6 was performed except that the concentration of the P-TSA acid solution was 11N, and the obtained fiber 24- had electrical conductivity with an electrical resistance value of 3.0 x 107 Ω/cm. However, the tensile strength was only 6.1 g/d.

Comparative Example 5 The same operation as in Example 6 was performed except that the heat treatment temperature was 140°C, and the electrical resistance value of the obtained fiber was 5. Q
xlQIOΩ/cm, and the conductivity was poor.

Example 9 The dry fiber obtained in Example 4 was stretched 4 times with dry heat at 245°C, and then stretched about 1 times in a 5N P-TSA methanol solution.
P-TSA, which acts as a catalyst, was applied at a constant rate of 2 seconds. Further, this yarn was heat-treated in the same manner as in Example 6 to obtain 1510d
A conductive fiber of 1500 f was obtained.

The physical properties of the obtained fibers are shown in Table 2.

Example 10 The undrawn yarn obtained in Example 6 was heated at an inlet temperature of 180 t.

After drawing in a hot air bath set at an outlet temperature of 255°C, the drawn thread was continuously run through 5N hydrochloric acid for about 1 second, and then
The heat treatment was carried out by running the sample through the heat treatment machine 5 whose internal temperature was set to 250° C. for about 3 seconds.

Table 2 shows the physical properties of the conductive fibers obtained.

26- (Effect of the invention) The hot water resistant PVA fiber of the present invention not only has excellent tensile strength and initial elastic modulus, but also has extremely high hot water resistance of 140°C or higher, which is unprecedented.
Not only fishing nets and ropes, which are typical uses of fibers, but also
It is now possible to use fibers for reinforcing building materials such as slate boards and calcium silicate boards, which are mass-produced by autoclave curing, which was difficult to apply in the past, and the range of use is significantly expanded. Furthermore, the hot water-resistant PVA fiber of the present invention can be used as a rubber reinforcing material for tires, timing belts, belts, etc., or as a reinforcing material for plastics, and its usefulness is extremely large.

In addition, the conductive PVA fiber of the present invention not only has excellent conductivity, but also has an extremely high tensile strength of 7 g/d or more, which is not found in conventional general-purpose conductive fibers. Static electricity problems can be eliminated by mixing it with floor covers such as carpets, curtains, outer clothing, especially work clothes in clean rooms, or outer fabrics such as car seats 8 and chairs.

Furthermore, according to the manufacturing method of the present invention, tensile strength can be obtained from PVA having a commercially available degree of polymerization.

It is possible to easily produce PVA-based fibers and conductive PVA-based fibers with excellent initial elastic modulus and hot water resistance with good productivity.

Claims (3)

[Claims] (1) A hot water-resistant polyvinyl alcohol system consisting of a polyvinyl alcohol polymer, having a tensile strength of 10 g/d or more, an initial elastic modulus of 200 g/d or more, and a hot water resistance of 140°C or more. fiber. (2) Made of polyvinyl alcohol polymer, has a tensile strength of 7 g/d or more and an electrical resistance of 1.0 x 10^8 Ω.
/cm or less. (3) A method for producing polyvinyl alcohol fibers, which comprises applying a catalyst for promoting a dehydration reaction to fibers made of polyvinyl alcohol having a degree of polymerization of 1,500 or more and 7,000 or less, and then heat-treating the fibers at a temperature of 150° C. or more.