JPH0578910A - Polyvinyl alcohol fiber and its production - Google Patents

Abstract

PURPOSE:To obtain the subject fiber having high strength, high modulus and excellent hot-water resistance and thermal aging resistance and useful as a rubber-reinforcing material, etc., by dissolving a specific polymer in a solvent, adding an organic antioxidant, etc., to the dope during the spinning and drawing process and subjecting to dry-hot drawing under specific condition. CONSTITUTION:A PVA polymer having a viscosity-average polymerization degree of >=1,500 and a syndiotacticity of >=58% is dissolved in a solvent and subjected to spinning and dry-hot drawing. In the above process, one or more kinds of decomposition-suppressing agents composed of an organic antioxidant, an inorganic metal salt or a nitrogen-containing surfactant are added and/or applied in an amount of preferably 0.003-3.0wt.% to the fiber within a stage from the dissolution of the polymer to immediately before the dry-hot drawing and the fiber is subjected to dry-hot drawing at >=245 deg.C at a total draw ratio of >=18 to obtain the objective fiber having a single fiber strength of >=18g/d, a single fiber modulus of >=450g/d and a strength retention of >=60% after the dry-heat treatment at 160 deg.C for 24hr.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high syndiopolyvinyl alcohol (hereinafter abbreviated as PVA) fiber having excellent hot water resistance and heat aging resistance, high strength and high elastic modulus, and a method for producing the same. .. The fiber of the present invention is used for a long time at high temperature such as tires, hoses, rubber materials such as conveyor belts, reinforcing materials such as cement and plastics that are also required to have wet heat resistance, and ropes, canvas, tents that require water resistance. A high-strength, high-modulus PVA-based fiber suitable for industrial materials such as.

[0002]

2. Description of the Related Art Conventionally, PVA-based fibers are superior to polyamide, polyester and polyacrylonitrile-based fibers in strength, elastic modulus, weather resistance, chemical resistance, adhesiveness, etc. Has pioneered its own uses. Recently, it has been attracting attention as a fiber for cement reinforcement (alternative to asbestos fiber) that takes advantage of its alkali resistance. If PVA-based fibers with high hot water resistance and high heat aging resistance are developed in combination with even higher strength and higher elastic modulus,
It can be used in rubber or plastic reinforcements, ropes, fishing nets, tents, etc. even under severe conditions of water and heat, and is expected to have excellent safety, durability, and lightweight properties.

According to the tacticity evaluation method of the present invention (details will be described later), the three-dimensional structure of the PVA-based polymer, which is a raw material for PVA-based fibers currently on the market, has a syndiotacticity of 53 to 54 according to the diad display. % Atactic body. The fibers obtained from the PVA-based polymer have insufficient water resistance and resistance to moist heat, and cannot be said to have sufficiently high strength and elastic modulus.

A method of dissolving PVA rich in syndiotacticity having good water resistance in a solvent and performing wet spinning is described in Japanese Patent Nos. 539683, 581737 and 548856.
No. 615659 and the like. However, these methods have improved water resistance and wet heat resistance as compared with conventional atactic PVA, but have insufficient heat aging resistance and low strength of 9 to 11 g / d.

Recently, in order to improve strength and elastic modulus in addition to water resistance, it has been proposed to make a PVA-based polymer rich in syndiotacticity into fibers. That is, JP-A-61
According to -108713, PVA with 58% syndiotacticity and an average degree of polymerization of 6000 in diads
Of a dimethylsulfoxide (hereinafter referred to as D
A fiber having a maximum single yarn strength of 15 g / d and an elastic modulus of about 380 g / d is obtained by dissolving it in MSO) or glycerin and performing dry-wet spinning. However, these values are not particularly high, and the hot water resistance and heat aging resistance are not sufficient as in the above-mentioned Japanese patent.

On the other hand, by using PVA having a high degree of polymerization, high strength,
A method for obtaining a high elastic modulus fiber is disclosed in JP-A-59-130314.
No. 61-289112, 62-850.
No. 13, etc., and a fiber having a strength of 19 to 29 g / d and an elastic modulus of 550 to 650 g / d is obtained. However, these fibers are not sufficient in terms of hot water resistance and heat aging resistance.

The method of crosslinking in order to improve hot water resistance is described in JP-A-63-120107 and JP-A-64-15.
No. 6517, Japanese Patent Application Laid-Open No. 1-207435, etc., but there is a problem that fiber strength, elastic modulus, and heat aging resistance decrease with crosslinking.

Further, the present inventors have previously found that high syndio PVA
I have applied for fiber (Japanese Patent Application No. 2-22584)
9). In this application, by adding a decomposition inhibitor to the high syndio PVA fiber within a certain range, PVA during dry heat drawing can be obtained.
When decomposition is suppressed and the same degree of polymerization is compared, the strength of the present application is always 0.5 to 1 g / d or more and the elastic modulus is 30 g / d or more higher than that of the previous application. Further, the drawn yarn obtained in the present application is excellent in heat aging resistance, and the tenacity retention rate at 24 hours at 160 ° C. is 50% or less in the case of the previous application, whereas it is 60% or more in the present application, which is high performance. This indicates that industrial materials with high commercial value can be obtained.

[0009]

[Problems to be Solved by the Invention] Based on the above background,
An object of the present invention is to provide a PVA-based fiber having excellent hot water resistance and heat aging resistance, high strength and high elastic modulus. The present inventors have studied the structure of the fiber satisfying the above properties at the same time with the following points in mind. (1) Strong intermolecular hydrogen bond due to a more complete crystal ...
Uses high syndio PVA fiber. (2) A strong tie molecule that connects the crystal and the amorphous ... Uses PVA with high syndio and high polymerization degree. (3) Highly crystalline or amorphous orientation: Suppresses thermal decomposition during high-temperature high-magnification stretching. (4) Suppress thermal decomposition during and after stretching ... Addition of decomposition inhibitor.

The higher syndiolysis and the higher the degree of polymerization, the lower the draw ratio due to the crystallinity and the entanglement of the molecular chains.
In order to stretch it at a high temperature at a high temperature and with a small amount of decomposition of PVA, how to do it was pursued.

[0011]

Means for Solving the Problems The present invention provides a method for stretching a high syndio and high degree of polymerization PVA fiber at a high temperature and a high draw ratio.
By suppressing the oxygen decomposition and radical decomposition of A, the strength, elastic modulus and hot water resistance are further improved, and even if the obtained drawn yarn is exposed to high temperature for a long time, the strength does not decrease so much. It is an excellent fiber.

That is, according to the present invention, "(1) the viscosity average degree of polymerization is 1500 or more and the syndiotacticity is 58% or more,
0.0 or more of one or more decomposition inhibitors composed of an organic antioxidant, an inorganic metal salt or a nitrogen-containing surfactant.
It is composed of a polyvinyl alcohol-based polymer containing 03 to 3.0% by weight, has a single fiber strength of 18 g / d or more, a single fiber elastic modulus of 450 g / d or more, and is strong after dry heat treatment at 160 ° C. for 24 hours. A polyvinyl alcohol fiber having a retention rate of 60% or more. And ((2) a polyvinyl alcohol polymer having a viscosity average polymer of 1500 or more and syndiotacticity of 58% or more is dissolved in a solvent and spun by a conventional method to obtain a spun raw yarn, which is dried. During hot drawing, one or more kinds of decomposition inhibitors of organic antioxidants, inorganic metal salts or nitrogen-containing surfactants are added to the fiber from the time of dissolution to immediately before dry heat drawing. Or /
And the total stretching ratio is 1 at a temperature of 245 ° C or higher.
It is a method for producing polyvinyl alcohol fibers, which is characterized in that dry heat drawing is performed so as to be 8 times or more. "

The contents of the present invention will be described in more detail below. The PVA-based degree of polymerization referred to in the present invention means a viscosity average degree of polymerization determined by a measuring method described later.

The PVA polymer of the present invention has a degree of polymerization of 1
It is necessary to use 500 or more. Degree of polymerization is 150
When it is less than 0, it is difficult to obtain the hot water resistant or high strength and high elasticity fiber referred to in the present invention. The more preferable degree of polymerization is 6000 or more, and more preferably 10,000 or more.

In the present invention, the PVA-based polymer satisfying the above-mentioned degree of polymerization has a syndiotacticity of 58% or more as indicated by a diad. PVA having a syndiotacticity of less than 58% does not achieve more complete crystallization, and it is difficult to obtain the high-performance fiber according to the present invention.
Syndiotacticity is preferably 60% or more, but 70
If it exceeds%, the crystallization tends to be high and the solubility in a solvent or the draw ratio tends to be lowered.

In the present invention, the tacticity indicated by the diad is the deuterated dimethyl sulfoxide (d ↓).
Proton N of PVA polymer dissolved in 6-DMSO)
Syndiotacticity (T. Moritani et al., By triad display obtained by MR measurement)
Macromolecules, 5, 577 (19
72)) and syndiotacticity (S), heterotacticity (H), and isotacticity (I).
Is a value calculated from the following equation. s = S + H / 2 (Syndiotacticity by dyad display) i = I + H / 2 (Isotacticity by dyad display)

If necessary, 3% by weight or less of a pigment, an antioxidant, an ultraviolet absorber, a crystallization inhibitor, a crosslinking agent, and a surfactant may be added to the PVA polymer.

Solvents for PVA type polymers include glycerin, ethylene glycol, diethylene glycol, triethylene glycol, 3-methylpentane-1,3,5.
-Polyhydric alcohols such as triol, dimethyl sulfoxide (DMSO), dimethylformamide, dimethylacetamide, N-methylpyrrolidone, 1,3 dimethyl 2
-Imidazolidinone, ethylenediamine, diethylenetriamine, water and the like are used alone or in combination. Further, it is also possible to use an aqueous solution of an inorganic salt such as zinc chloride, magnesium chloride, calcium rhodanide or lithium bromide, which dissolves the polymer. A polyhydric alcohol that gels on cooling, a mixed solvent of them and water, dimethyl sulfoxide, dimethylformamide, a mixed solvent of them and water, and the like are preferable because spinning stability tends to occur.

As the spinning method, any generally used method such as a wet method, a dry method and a dry-wet method can be used without any problem. Among them, a dry-wet method is used to discharge a solution of a PVA-based polymer from a spinning nozzle and immediately immerse it in a low temperature alcohol such as methanol or ethanol or a mixed solution of them and the solvent, or an aqueous solution containing an inorganic salt or an alkali. It is preferable that the method is followed by rapid cooling to obtain a homogeneous transparent gel fiber.

The high syndio-PVA polymer used in the present invention is more likely to be crystallized than atactic PVA. Therefore, at the time of solidification, the temperature is kept at 20 ° C. or lower to suppress crystallization.
In addition, slow solvent extraction to obtain a homogeneous gel fiber leads to subsequent high-strength drawing and tends to be a highly functional fiber.

In addition, it prevents cross-sectional deformation and sticking of the gel fiber,
In addition, in order to destroy the microcrystals during spinning and improve the draw ratio, it is preferable to wet-draw at least 2 times, preferably at least 4 times while containing the solvent.

Then, almost all of the solvent is removed with an extractant such as alcohols such as methanol and ethanol, acetone and water, and then the extractant is evaporated by drying.

After that, dry heat drawing is further performed. In the present invention, a decomposition inhibitor is added or / and attached between the stock solution for spinning and immediately before dry heat drawing to decompose PVA during drawing and dry heat aging after drawing. Is to hold down.

The term "decomposition inhibitor" as used in the present invention means an organic antioxidant such as phenol, phosphite, thioester, benzotriazole, hindered amine or Cu, Mn, Ti, Sn, Pb, Zn, Cr. Examples thereof include inorganic metal salts of sulfates, nitrates, and halides, and further nitrogen-containing surfactants classified into the following three types, and one or more types thereof can be used. (1) An ammonium compound having an amide bond or a urea bond in the molecule, for example, a cationic surfactant represented by the structural formula of the following chemical formula 1.

[0025]

[Chemical 1] (2) A sulfonate compound having an amide bond or a urea bond in the molecule, for example, an anionic surfactant represented by the following chemical formula 2.

[0026]

[Chemical 2] (3) An amine compound of sulfonate, for example, an anion activator represented by the following chemical formula 3.

[0027]

[Chemical 3]

These decomposition inhibitors may be added to a compounded oil containing a smoothing agent or an emulsifier to be attached to the fiber, but if there are adhesion spots, drop from spinning to drawing, or hindering of drawability. Not preferable.

The content of the decomposition inhibitor is 0.003 to 3.0% by weight based on the fiber after stretching. Although the content of the decomposition inhibitor varies depending on the type, it is preferably 0.2 to 2% by weight for the organic antioxidant and 0.0 for the inorganic metal salt.
05 to 0.5% by weight is preferable, and 0.1 to 1% by weight is preferable for the nitrogen-containing surfactant. It should be noted that some of the decomposition inhibitors may promote the decomposition if they are too much. If the content of the decomposition inhibitor is less than 0.003% by weight, the decomposition suppressing effect is small, and if it exceeds 3% by weight, yarn breakage during spinning, a reduction in the draw ratio, or conversely, decomposition may be promoted, which is not preferable. The content when two or more kinds of decomposition inhibitors are used means the total amount.

Then, the obtained spun raw yarn is dry-heat drawn,
In this case, it is necessary to increase the total draw ratio to 18 times or more.
It is preferably 0 times or more. If it is less than 18 times, the orientation of the PVA molecular chain is insufficient, and it is difficult to obtain higher strength and elastic modulus. The total draw ratio is represented by the product of the wet draw ratio and the dry heat draw ratio.

Further, the stretching ratio and the crystallinity are increased, and the strength,
In order to produce a high syndio PVA fiber excellent in elastic modulus and hot water resistance, the stretching temperature needs to be 245 ° C or higher, preferably 250 ° C or higher. In particular, high syndio PVA fibers are easy to crystallize, so to draw at a high ratio, the PV should be raised to a high temperature.
It is necessary to increase the mobility of the A molecular chain. Further, the higher the degree of polymerization, the more the number of tie molecules that connect the molecular chains and the number of tie molecules that connect the microcrystals to each other, so that the draw ratio tends to decrease, and high-temperature drawing is necessary to cover it. However, the higher the conventional temperature, the more PV
The coloration and decomposition of A was severe, resulting in a decrease in stretching tension, a decrease in strength and elastic modulus, and a deterioration in heat aging resistance.

In the present invention, by adding or / and adhering a decomposition inhibitor, PVA decomposition is suppressed even at a higher drawing temperature, and high-magnification drawing becomes possible.

Stretching temperature is high polymerization degree, high syndio PVA
Although it can be made as high as possible, if it is too high, the flow of molecular chains occurs, the stretching tension is lowered, the performance is lowered, and color decomposition is easily induced, which is not preferable.

Air, an inert gas such as nitrogen, water vapor, an oil bath, etc. are generally considered as the stretching atmosphere, but heated air is suitable in view of operability and cost. Further, there are a contact type using a hot plate and a heat roller and a non-contact type using a hot stove, both of which are possible.

The feature of the present invention is that high syndio and high degree of polymerization PV
A is used to stretch at high temperature and high magnification while suppressing thermal decomposition with a decomposition inhibitor. Due to this, highly syndio-pVA drawn yarn with less coloration and lowering of the degree of polymerization can be obtained, and due to the high orientation and high crystallization, the hot water disconnection temperature is 140 ° C or higher, and the polymerization degree is 10,000 ° C or higher and 160 ° C or higher. Increased to
Furthermore, the single fiber strength is 18 g / d or more, and the single fiber elastic modulus is 4
With a polymerization degree of 50 g / d or higher, a polymerization degree of 23 g / d or higher and 550 g / d or higher are obtained. Also, due to the effect of the decomposition inhibitor, it has extremely high heat aging resistance when used in various applications, and it is a high-performance PVA fiber that has not been seen in the past for reinforcing materials such as rubber, cement and plastics, and general industrial materials. .. Further, the melting point also shows a value higher by 10 ° C. or more than PVA fiber made of ordinary atactic PVA, which is also advantageous for applications requiring heat resistance.

[0036]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the examples. Various physical property value parameters in the examples were measured by the following methods.

1) Viscosity average degree of polymerization and degree of decrease of degree of polymerization of PVA The specific viscosity η ↓ sp of a PVA diluted acetone solution of vinyl acetate obtained by acetylating a PVA polymer at 30 ° C. was measured at 5 points, and The intrinsic viscosity [η] was calculated by the mathematical formula 1, and the viscosity average degree of polymerization was further calculated by the mathematical formula 2. In addition, the degree of decrease in the degree of polymerization was obtained by determining the viscosity average degree of polymerization of the drawn yarn in the same manner as described above and from the rate of decrease with respect to the viscosity average degree of polymerization of the original PVA polymer.

[0038]

[Equation 1]

[0039]

[Equation 2]

2) Adhesion amount of antioxidant and surfactant: The undrawn yarn after drying was dissolved in hot water at 100 to 130 ° C., and the antioxidant and the surface activity against the CH ↓ 2 peak of PVA were measured by NMR. The peak ratio of the agent was calculated, and the adhesion amount was obtained from the calibration curve prepared in advance.

3) Content of Inorganic Metal Salt The undrawn yarn after drying was dissolved in hot water at 100 to 130 ° C., the peak of the specific element was measured by fluorescent X-ray, and the content was determined from the calibration curve.

4) Hot water disconnection temperature (WTb) A load of 200 mg per denier was applied to 25 monofilaments and suspended in the middle of a glass-made cylindrical sealed container filled with water, and the water was heated to 1 to 2 ° C. from the surroundings. The temperature at which the fibers melted was measured by heating and raising the temperature at a rate of / min.

5) Melting point A differential calorimetric analyzer (model DSC, manufactured by Perkin Elmer Co., Ltd.
-2C), 10 mg of a fiber having a cut length of about 1 mm was sampled, and the melting point (endothermic peak temperature) at a temperature rise of 10 ° C./min in a nitrogen stream was measured.

6) Tensile strength / elongation of single yarn and elastic modulus In accordance with JIS L-1013, single filaments whose humidity has been adjusted in advance are attached to a mount so as to have a test length of 10 cm and left at 25 ° C. × 60% for 12 hours or more. Then Instron 1122 2kg
Chuck, initial load 1/20 g / d, pulling speed 5
The breaking strength and elongation and the initial elastic modulus were determined at 0% / min, and n ≧ 20 average value was adopted. Denier is 1 / 10g
It was cut to 30 cm under / d load and determined by gravimetric method.
The single fiber after denier measurement was used to measure the strength / elongation and elastic modulus, and each fiber was made to correspond to denier.

7) Heat aging resistance (strength retention rate after dry heat treatment): The yarn is put in a hot air oven in a free state, 160 ° C. × 24
The tenacity of the yarn after dry heat treatment for 160 hours or 160 ° C. for 48 hours was measured, and the tenacity retention ratio (%) to the yarn strength before dry heat treatment was calculated.

Example 1: (PVA production method) A reaction vessel equipped with a stirrer was charged with 600 parts of vinyl pivalate monomer and 200 parts of methanol, and the system was replaced with nitrogen by bubbling nitrogen gas. Separately, a solution prepared by dissolving 0.0712 parts of 2,2′-azobisisobutyronitrile as an initiator in 26 parts of methanol was prepared, and the atmosphere was replaced with nitrogen by bubbling with nitrogen gas. The temperature of the reaction vessel was raised, and when the internal temperature reached 60 ° C., a methanol solution containing an initiator was injected to initiate polymerization. 19
After 0 minutes, when the rate of polymerization reached 50%, the polymerization was stopped by cooling, and unreacted vinyl pivalate monomer was removed under reduced pressure while adding t-butanol from time to time to obtain t-butanol of vinyl polypivalate. It was a solution. Then, t-butanol was removed under reduced pressure to obtain a tetrahydrofuran solution of 15 wt% vinyl polypivalate. Next, 70 parts of this solution was weighed in a reactor equipped with a stirrer and a reflux condenser, heated to 60 ° C., nitrogen gas was flowed to replace nitrogen, and the temperature was maintained at 60 ° C., then separately adjusted and replaced with nitrogen 25 % Of potassium hydroxide in methanol was added and stirred thoroughly. The system gelled in about 20 minutes, but after holding at 60 ° C. for 100 minutes, 6.8 parts of acetic acid was added to methanol 20 times.
Potassium hydroxide was added to neutralize the potassium hydroxide. Subsequently, the gel was crushed and then subjected to Soxhlet washing with methanol to obtain a polyvinyl alcohol polymer. The obtained polyvinyl alcohol-based polymer was dissolved in d ↓ 6-DMSO and measured by NMR. Saponification degree was 99.5 mol%, syndiotacticity-61.2%, vinyl pivalate content was 0.5 mol. %, Melting point 241 ° C. After adding 10 parts of acetic anhydride and 2 parts of pyridine to 0.5 part of the obtained polyvinyl alcohol polymer and sealing the tube, 120
It was acetylated by heating at ℃ for 8 hours. The obtained polyvinyl acetate was precipitated in n-hexane and re-precipitated twice with an acetone-n-hexane system for purification. The viscosity average degree of polymerization of this polyvinyl acetate determined from [η] in acetone at 30 ° C. was 1850.

(Production of PVA Fiber) The high syndio PVA obtained above was added to DMSO to a concentration of 16% by weight.
Dissolved in. Next, at 90 ° C., the number of holes is 80 and the hole diameter is 0.
It was discharged from a 12 mm nozzle and dropped by a dry-wet method into a coagulation bath 20 mm below. Coagulation composition is methanol / DMS
It was set to 5 ° C. at O = 7/3. The obtained transparent gel fiber is 3
The solvent was extracted in a methanol extraction bath after being double-stretched by wet stretching.
nCl ↓ 2 was added and the fiber was allowed to dwell for 4 minutes to adhere to the interior and surface of the methanol containing fiber. Then, a cationic surfactant of stearylamidopropyldimethyl-β-hydroxyethylammonium nitrate is attached,
It was dried at 80 ° C. MnCl of the obtained spinning yarn ↓ 2
The content was 0.025% by weight, and the attached amount of the cationic surfactant was 0.93% by weight. Then, the first hot air stove 17
After stretching to 0 ° C and stretching 2.5 times, the second hot air stove is moved to 255 ° C.
Then, two stages of dry heat drawing were carried out so that the total draw ratio was 22.8 times. The obtained drawn yarn was not colored and had a low polymerization degree reduction rate of 8%, a WTb of 146 ° C. and a single fiber strength of 20.
9 g / d, the elastic modulus was 520 g / d, and the melting point was 259 ° C., which were all high values. In addition, the drawn yarn was
After the dry heat treatment for 48 hours and 48 hours, the tenacity retentions were measured to be 81% and 68%, respectively, which was excellent in heat aging resistance. Furthermore, when wet with water and at 100 ° C
High-performance and high syndio P suitable for rubber or plastic reinforcements or general industrial materials with little decrease in elastic modulus at high temperatures
It was found to be VA fiber.

Comparative Example 1: The case where the decomposition inhibitor was not attached was carried out in Example 1, but the coloring was severe at the stretching of 255 ° C. and the total stretching ratio was as high as 21.7 times, but the stretching tension was low and the polymerization was performed. The rate of decrease was increased to 27%. WTb is 1
Although the value was as high as 40 ° C, the single fiber strength was 18.6 g /
d, the elastic modulus was as low as 450 g / d. Also,
After dry heat treatment at 160 ° C. for 24 hours, the strength retention was measured and found to be 38%. The stretching temperature is 2
When the temperature was lowered from 55 ° C to 240 ° C, coloring during stretching was almost eliminated, but the total stretching ratio was reduced to 19.5 times.
The single fiber strength was as low as 19.9 g / d and the elastic modulus was as low as 425 g / d. Moreover, the heat retention after heat treatment at 160 ° C. for 24 hours was 50%, which was inferior in heat aging resistance.

Example 2: According to the method for producing PVA from vinyl pivalate produced in Example 1, the viscosity average polymerization degree is 7500, the saponification degree is 99.9 mol%, and the syndiotacticity is 61.8. % PVA was obtained. 180% of this PVA with ethylene glycol to a concentration of 9% by weight
The mixture was stirred and dissolved in a nitrogen gas atmosphere at 6 ° C. for 6 hours. The obtained solution was discharged at 190 ° C. from a nozzle having 150 holes and a hole diameter of 0.18 mm and dropped into a coagulation bath 15 mm below by a dry-wet method. The coagulation bath composition was methanol / ethylene glycol = 7/3, and the temperature was kept at 0 ° C. The yarn in this coagulation bath stage became a transparent gel fiber which was almost circular. Subsequently, this fiber was wet-drawn 4 times in methanol at 40 ° C., and then the solvent was almost completely extracted in a methanol bath. At this time, 4'4-thiobis- (6-tbutyl-3-methylphenol), which is a phenolic antioxidant, was added to the final methanol extraction bath at a concentration of 0.5% by weight / bath to form a uniform solution. The fibers were then allowed to dwell for 3 minutes to adhere to the interior and surface of the methanol containing fibers. Then, it was dried with hot air at 90 ° C. with shrinkage of 3% to obtain a spun raw yarn. The content of the phenolic antioxidant in the raw yarn was 0.82% by weight. Subsequently, a laurylamidopropyltrimethylammonium which is a decomposition inhibitor, a cationic surfactant of methyl sulfonate and a glycerin trioleate which is a smoothing sizing agent are attached to the yarn by a roller touch method, and a radiation furnace at 170 ° C. and 260 ° C. is attached. Total draw ratio of 2
0.4 times dry heat drawing was performed. The drawn yarn obtained was not colored, and the amount of the cationic surfactant attached was 0.59% by weight. The drawn yarn had a high WTb of 159 ° C., a single fiber strength of 24.7 g / d, and an elastic modulus of 630 g / d, which was a high-performance fiber. The strength retention after dry heat treatment at 160 ° C. for 24 hours was 78%, and the wet elastic modulus after immersion in water for 1 day and the elastic modulus under 100 ° C. were 60 to 60 ° C.
Retained 70%. It has been found that it can be used as a high-value-added PVA fiber which has not been found in conventional rubber reinforcing materials such as tires, hoses and belts, or reinforcing materials such as plastics and cement, ropes, fishing nets and tents.

COMPARATIVE EXAMPLE 2 The procedure of Example 2 was repeated except that the atactic PVA having a viscosity average degree of polymerization of 8000, a saponification degree of 99.9 mol% and a syndiotacticity of 53.5% was used. When the drawing temperature was 260 ° C., the fibers were melted and colored, and the drawing was impossible. Stretching temperature is 250
The temperature was lowered to ℃ and the film could be stretched 18.5 times, but WTb was 135
℃, single fiber strength 20.4g / d, elastic modulus 505g /
d and lower than the fiber of Example 2 using high syndio PVA.

Example 3: According to the method for producing PVA of Example 1, the viscosity average polymerization degree is 15,000 and the saponification degree is 99.
PVA of 2 mol% and syndiotacticity 62.2% was obtained. This PVA was dissolved by stirring with glycerin at 190 ° C. for 10 hours in a nitrogen gas atmosphere so that the concentration was 4.5% by weight. At that time, 1.0 wt% of the phenolic antioxidant used in Example 2 was added and mixed. Next, the obtained solution was discharged from a nozzle having 100 holes and a hole diameter of 0.19 mm, and dropped by a dry-wet method into a coagulation bath 15 mm below. The coagulation bath composition was methanol / glycerin = 7/3, and the temperature was kept at -5 ° C. The obtained true transparent gel fiber was wet-stretched 3 times in methanol at 40 ° C., and the solvent was extracted almost completely in a methanol bath, and then glycerin monooleate (nonionic surface active agent) was used as a smooth focusing oil agent. 2% methanol solution of the agent) was attached by a gear pump system and dried with hot air at 100 ° C. The content of the phenolic antioxidant in the obtained spun yarn was 0.85% by weight, and the amount of the nonionic surfactant attached was 0.62% by weight. Then, using a radiation furnace at 170 ° C and 266 ° C, the total draw ratio is 1
9.1 times dry heat drawing was performed. The drawn fiber thus obtained had a single fiber strength of 28.4 g / d, an elastic modulus of 675 g / d, and a WTb of 177 ° C., which was a very high performance. The tenacity retention rate after dry heat treatment at 160 ° C for 24 hours was 75%, and the melting point was as high as 265 ° C. Furthermore, the wet elastic modulus is 450 g / d, and the elastic modulus at 100 ° C. is 5
The value was 10 g / d, and it was a high value-added PVA fiber suitable for industrial materials that could not be obtained with conventional PVA fibers.

Continuation of front page (51) Int.Cl. ⁵ Identification number Office reference number FI Technical indication location D02J 1/22 J 7199-3B H 7199-3B (72) Inventor Tomoyuki Sano 1621 Sakata, Kurashiki-shi, Okayama Co., Ltd. Inside the Kuraray

Claims (2)

[Claims] 1. A decomposition inhibitor which has a viscosity average degree of polymerization of 1500 or more and a syndiotacticity of 58% or more, and which comprises an organic antioxidant, an inorganic metal salt, or a nitrogen-containing surfactant, or It is made of a polyvinyl alcohol polymer containing 0.003 to 3.0% by weight of two or more kinds, and has a single fiber strength of 18 g / d or more and a single fiber elastic modulus of 45.
A polyvinyl alcohol fiber having a strength retention of 60% or more after dry heat treatment at 160 ° C. for 24 hours. 2. A polyvinyl alcohol polymer having a viscosity average degree of polymerization of 1500 or more and syndiotacticity of 58% or more is dissolved in a solvent and spun by a conventional method to obtain a spun yarn, which is dry-heat stretched. At the time of melting, one or two of decomposition inhibitors consisting of an organic antioxidant, an inorganic metal salt or a nitrogen-containing surfactant during the period from dissolution to immediately before hot drawing.
At least 245 ° C by adding or / and adhering one or more seeds to the fiber
A method for producing a polyvinyl alcohol fiber, which comprises drawing at a temperature of the above temperature so that the total draw ratio becomes 18 times or more.