JPH08218221A - Polyvinyl alcohol-based fiber excellent in durability and dimensional stability and its production - Google Patents

Abstract

PURPOSE: To obtain a fiber, excellent in durability and dimensional stability and useful for rubber reinforcing materials or usual industrial materials by thermally shrinking a fiber drawn at a high temperature and a high draw ratio, coating the resultant fiber with a polyamide-based or a polyurethane-based resin and applying an oil agent having a low friction coefficient thereto. CONSTITUTION: A fiber drawn at a high temperature and a high draw ratio is thermally shrunk to provide a highly crystalline fiber having a high elongation. A polyamide-based or a polyurethane-based resin in an amount of 0.5-8wt.% is then applied to the fiber surface and an oil agent having <=0.28 F/F static friction coefficient is subsequently applied to afford a PVA-based fiber having >=6% yarn elongation and <=2% dry heat shrinkage factor at 180 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber reinforcing material such as a tire, an oil brake hose, a radiator hose, a fire hose, a conveyor belt, a timing belt, a V-belt, a fishing net, and a rope which are repeatedly bent or rubbed at high temperature for a long time. The present invention relates to a polyvinyl alcohol (hereinafter abbreviated as PVA) fiber having excellent durability and dimensional stability, which is suitable for general industrial materials such as a net, a tent, a canvas, and a civil engineering sheet warp, and a method for producing the same.

[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., and are mainly used in the field of industrial materials. Has pioneered its own unique uses. Recently, attention has been focused on cement-reinforcing fibers (substitute for asbestos) and alkaline battery separators that take advantage of alkali resistance. However, when it is repeatedly used for a long time, there is a problem that the fibers are worn out or a kink is generated due to bending, resulting in a decrease in strength. In addition, there was a case in which the fiber contracted due to heat generated during use and lacked dimensional stability. If the durability and dimensional stability when used at high temperature for a long time is improved, fibers with high added value can be expected as a rubber reinforcing material or a general industrial material. Although methods for obtaining PVA-based fibers having high strength and high elastic modulus are known, the fibers obtained by these methods have insufficient fatigue resistance and abrasion resistance, and lack dimensional stability. Further, there is a method in which the stretched PVA fiber is subjected to heat shrinkage to enhance fatigue resistance.
Although disclosed in Japanese Patent Laid-Open No. 192813 and Japanese Patent Laid-Open No. 169709/1990, none of them have sufficiently satisfactory performance against bending wear for a long time at high temperature.
On the other hand, there is a method of impregnating fibers or twisted cords with epoxy resin or liquid rubber to improve the adhesiveness and fatigue resistance.
No. 146876, JP-A-63-66382, JP-A-63-196778 and the like are known, but unlike the present invention, since a fiber having a high elongation and an oil agent having a low friction coefficient are not used, the durability is improved. It was hard to say that the stability and dimensional stability were sufficient.

[0003]

Based on the above background, the present inventors have earnestly studied how to obtain a PVA-based fiber having excellent fatigue resistance, abrasion resistance and dimensional stability. After heat-shrinking the fiber stretched at high temperature and high magnification to obtain the fiber with high elongation and high crystallinity, the fiber surface is further coated with heat-resistant polyamide-based or polyurethane-based resin having relatively high film strength. Then, it was found that a means for applying an oil agent having a low friction coefficient was effective.

[0004]

According to the present invention, a polyamide-based or polyurethane-based resin is attached to the fiber surface in an amount of 0.5 to 8% by weight, and an oil agent having an F / F static friction coefficient of 0.28 or less is used. Adhered, yarn elongation of 6% or more, 18
PV characterized by 0 ° C dry heat shrinkage of 2% or less
A fiber, and as a method for producing such a PVA-based fiber, a spinning raw yarn obtained by spinning a solution of a PVA-based polymer is subjected to the following steps, and a total draw ratio of at least 220 ° C. is 16 times or more. So as to achieve the following: a step of subjecting it to a heat shrinkage of 1 to 15%; a step of applying 0.5 to 8% by weight of a polyamide-based or polyurethane-based resin on the fiber surface; and a F / F static friction coefficient of 0. The steps of applying an oil agent of 28 or less are sequentially performed to produce PVA-based fibers.

That is, in the present invention, a PVA-based spun raw yarn is dry-heat drawn at a high temperature of 220 ° C. or more so that the total draw ratio is 16 times or more, and further heat-shrinked by 1 to 10%, and then the After heat-resistant polyamide-based or polyurethane-based resin was attached to the fiber surface in an amount of 0.5 to 8% by weight and heat-treated under a relatively weak tension, the F / F friction coefficient was 0.28.
The following oil agents are added to give a yarn elongation of 6% or more, 180
The present invention provides a PVA-based fiber having a dry heat shrinkage rate of 1.5% or less and excellent in durability and dimensional stability.

The contents of the present invention will be described in more detail below. The PVA referred to in the present invention has a viscosity average degree of polymerization of 1,500.
The above is preferable, and the linear one having a saponification degree of 98 mol% or more and a low branching degree is preferable. The higher the degree of polymerization of PVA, the greater the number of tie molecules penetrating many crystals in the network structure, and it is easy to obtain a tie molecule with high strength and high elastic modulus that can withstand abrasion and bending fatigue, and preferably 3,000.
Or more, more preferably 6,000 or more. PVA
If necessary, 5% by weight or less of a pigment, an antioxidant, an ultraviolet absorber, a crystallization inhibitor, a crosslinking agent, a surfactant, etc. may be added to the system polymer. It also includes those obtained by copolymerizing 5 mol% or less of a modifier.

Solvents for PVA type polymers include glycerin, ethylene glycol, diethylene glycol, triethylene glycol, 3-methylpentane-1,3,5.
-A polyhydric alcohol such as triol, dimethyl sulfoxide (DMSO), dimethylformamide, dimethylacetamide, N-methylpyrrolidone, 1,3-dimethyl-2-imidazolidinone, ethylenediamine, diethylenetriamine and water are used alone or in combination. To be done. Further, it is also possible to use a solution that dissolves the polymer, such as an aqueous solution of an inorganic salt such as zinc chloride, magnesium chloride, calcium rhodanide or lithium bromide. A polyhydric alcohol that gels upon 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 wet method or a dry-wet method is used to discharge a solution of a PVA-based polymer from a spinning nozzle and immediately contain alcohols such as low-temperature methanol or ethanol or a mixed solution thereof with the solvent, and further an inorganic salt or an alkali. A method of obtaining a homogeneous and transparent gel fiber by immersing in an aqueous solution and rapidly cooling is preferable.
Further, in order to prevent the cross-sectional deformation and sticking of the gel fiber and to break the fine crystals during spinning to improve the draw ratio, it is preferable to wet-draw at least 2 times, preferably at least 4 times while containing the solvent. Then, after removing almost all of the solvent with an extracting agent such as alcohols such as methanol and ethanol and acetone and water, the extracting agent is evaporated by drying.

The obtained spun raw yarn is subjected to dry heat drawing at a high temperature of 220 ° C. or more and a total draw ratio of 16 times or more by an ordinary method. The total draw ratio is represented by the product of the wet draw ratio and the dry heat draw ratio, but if it is less than 16 times, the orientation of the PVA molecular chain is insufficient and it is difficult to obtain a high-strength, high-modulus fiber. If the temperature is lower than 220 ° C, the magnification is lowered and the crystallization is insufficient, so that the dimensional stability is likely to decrease. It should be noted that there is no problem even if an oil agent, an antioxidant or the like is attached before the stretching in order to prevent the PVA from being colored at the time of stretching at a high temperature, coloring of the PVA during stretching and subsequent heat treatment, and decomposition.

Next, in the present invention, a heat shrinkage treatment of 1 to 15% is applied in order to improve fatigue resistance, wear resistance and dimensional stability. The purpose of this is to disturb the orientation of the amorphous part to relax the external force during wear and bending, and to further promote crystallization to reduce the heat shrinkage rate during subsequent use and to improve dimensional stability. is there. Therefore, heat shrinkage of less than 1% is not preferable because the above-mentioned object is not sufficiently achieved. Again 1
When it exceeds 5%, the strength and elastic modulus of the fiber are seriously deteriorated, and a preferable shrinkage is 2 to 10%.
On the other hand, the temperature during the shrinking treatment is 180 ° C. or higher, preferably 20
When the temperature is 0 ° C or higher and the temperature is lower than 180 ° C, it becomes difficult to produce a highly shrinkable material or a highly crystalline material, and it is difficult to obtain a yarn elongation of 6% or more and a 180 ° C dry heat shrinkage ratio of 2% or less according to the present invention. . However, if the temperature is too high, color decomposition and melting of the PVA molecular chain occur, which is not preferable. Therefore, the shrinkage treatment temperature is
200-2 depending on the degree of PVA polymerization and the draw ratio
60 ° C is desirable. Further, in order to improve resistance to moist heat and oil brake fluid, a crosslinking agent generally used such as phosphoric acid, sulfuric acid, chromium chloride, or copper chloride may be attached before the shrinking treatment and subjected to heat treatment for crosslinking.

Thereafter, in the present invention, the PVA fiber obtained in order to further improve fatigue resistance and wear resistance is added with 0.5 to 0.5%.
It is necessary to coat 8% by weight of resin. The resin is a polyamide-based or polyurethane-based resin that is relatively heat resistant and has good compatibility with PVA. For example, the melting point is 80 to 200
Examples thereof include a copolyamide-based resin obtained by copolymerizing nylon 6,66,12, etc. at 0 ° C., and an ether-based or ester-based polyurethane resin having many hard segments and a Vicat softening temperature of 80 to 180 ° C. A resin having a low melting point or a low softening temperature is likely to lose its effect due to a decrease in coating strength due to repeated bending or heat generation during friction, and a resin which is too high hardens the fiber and is subject to concentration of external force and is highly fatigued and worn, which is preferable. A polyamide resin having a melting point of 100 to 170 ° C. or a polyurethane resin having a Vicat softening temperature of 110 to 160 ° C. is preferable. On the other hand, the amount of resin attached is preferably 1 to 6% by weight,
If it is less than 0.5% by weight, fatigue resistance and wear resistance cannot be sufficiently satisfied, and if it exceeds 8% by weight, strength is reduced or the fiber becomes hard and easily broken, and conversely, a kink band is formed by bending. It is not desirable because it induces and proliferates intensively. The resin is dissolved or emulsified in water or an organic solvent and coated on the fiber surface by a roller touch type dip nip system, a gear pump oiling system or the like.

Next, after the resin is attached, heat treatment including drying is performed to react the resin with the fibers or form a resin film. In that case, it is preferable to treat the resin at an elongation rate of 1% or less.
When the elongation ratio exceeds 1%, it is difficult to maintain the yarn elongation of 6% or more, preferably 7 to 10%, which is referred to in the present invention, and high tension tends to cause single yarn breakage and resin film breakage. Not preferable.

In the present invention, the coefficient of static friction between fibers measured by the method described below after resin adhesion-heat treatment is 0.28.
Apply the following oil agent. The purpose of this is to improve the process passability after that, and to increase the strength utilization ratio (ratio of the cord strength to the yarn strength) when manufacturing twisted cords such as tire cords, ropes, fishing nets, etc. to suppress strength reduction. Especially. Therefore, the above effect cannot be expected when only the resin is used and there is no oil agent, or when an oil agent having a static friction coefficient exceeding 0.28 is attached. Examples of the low friction oil include mineral oils, copolymers of polypropylene oxide and polyethylene oxide (PO / EO), fatty acid ester of polyhydric alcohol, silicone, and fluorine. The adhesion amount is preferably 0.1 to 1% by weight. According to the present invention, a resin-coated PVA fiber having a yarn strength of 10 g / d or more, a relatively high strength, a high elongation of 6% or more, and a low 180 ° C. dry heat shrinkage of 2% or less. Thus, it has excellent durability and dimensional stability suitable for rubber reinforcing materials such as tires, hoses and belts and general industrial materials such as fishing nets, ropes, nets, tents and civil engineering sheets.

[0014]

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 properties in the examples were measured by the following methods. (1) Viscosity average degree of polymerization (PA) of PVA-based polymer According to JIS K-6726, the PVA-based polymer is dissolved in hot water to prepare a dilute aqueous solution, and the specific viscosity at 30 ° C is measured at 3 points. Obtain the intrinsic viscosity [η] from these values,
The viscosity average degree of polymerization was determined by PA = ([η] × 10 ⁴ /8.29) ^1.63 . (2) Fiber-to-fiber static friction coefficient (F / Fμs) Using a fiber to which an oil agent is applied in an amount of 1.0% by weight in solid content, J
Measured in accordance with IS L-1015. However, instead of the cylindrical slass bar by staple, a bobbin with both brim needles and filaments wound in parallel in a drum shape was used.

(3) Adhesion amount of resin About 5 g of a sample was precisely weighed, and only the fiber was dissolved in hot water to calculate the residual weight, or only the resin was dissolved to determine the weight reduction of the sample. (4) Yarn Tensile Strength, Initial Elastic Modulus According to JIS-L1013, the yarn is pre-twisted 80 times / m and left at 20 ° C. and 65% RH for 24 hours.
Using a Grip for Instron TN-M type pneumatic cord at a test length of 20 cm, a pulling speed of 10 cm / min, and an initial load of 1/20 g / d in a standard condition of 20 ° C. and 65% RH, the cutting strength and elongation are increased. The degree was measured. Further 80 times / m
Making a 90 m long skein winding of twisted yarn under 1/20 g / d tension, and calculating the yarn denier by weight measurement,
The breaking strength was divided by denier to obtain the strength (g / dr). Also, 100% elongation from the initial gradient of the strength-elongation curve
The tenacity corresponding to was calculated | required, it was divided by this denier, and the initial elastic modulus was calculated | required. In each case, the average value of n = 10 was adopted. The high temperature performance was measured in a hot air oven at 100 ° C or 150 ° C in the same manner as at 20 ° C.

(5) Heat Shrinkage (DSr) According to JISL-1013, an initial load of 1/30 g / d is applied to a sample and two marks are accurately placed at a length of 1 m.
Next, the initial load was removed, the sample was allowed to stand in a dryer for 180 × 30 minutes, cooled to room temperature, and then the initial load was applied to measure the sample length (two-point distance) l, which was calculated by the following formula. Dry heat shrinkage = 100 x (1000-l) / 1000
(%) (L = distance between 2 points mm) (6) Rubber fatigue resistance 10 to 50 t / t for resin-adhered PVA yarn of 1500 dr
After twisting in the 10 cm Z direction, the two cords are combined and twisted in the S direction with the same number of twists as the lower twist to prepare a raw cord. Then R
FL (resorcin, formalin, rubber emulsion) is attached to prepare a dip code. Next, two cord layers are formed by arranging 20 cords on the compression side and the extension side, and a rubber layer is arranged in the middle and outside of the cord layer, and a sandwich-shaped width of 25.4 mm × length of 420 mm × thickness of about 8 mm. After making a rubber sheet, 150 ℃ x 45 minutes 90kg / cm ²
And vulcanize to make a belt. Use a belt with a pulley diameter of 2
After being bent 200,000 times at room temperature with a belt bending tester of 5 mm, the cord on the compression side was taken out from the belt, and the retention rate was obtained from the cord strength before and after bending to evaluate the rubber fatigue resistance. (7) Wear resistance (twisting wear) 1500 dr of resin-adhered PVA yarn is twisted in the direction of 80 t / mZ to form a ring, and then S is repeated three times at the center of the ring.
Twisted in the same direction, the upper and lower yarns were worn at room temperature, and the number of times of cutting was read.

Examples 1 and 2 and Comparative Example 1 PVA having a viscosity average degree of polymerization of 2000 (Example 1) and 4000 (Example 2) and a saponification degree of 99.4 mol%.
Dimethylsulfoxide (hereinafter abbreviated as DMSO) at 100 ° C. so that the concentration becomes 14% by weight and 10% by weight, respectively.
The resulting solution was discharged from a nozzle having 500 holes and methanol / DMSO = 7/3 weight ratio, 10
Wet spinning was carried out in a coagulation bath at 0 ° C. Further, the film was wet-stretched 4 times in a 40 ° C. methanol bath, and then almost all the solvent was removed with methanol. Finally, 0.2% of phosphoric acid and 0.5% of ester oil were attached and dried at 120 ° C.

The spun yarn obtained in Example 1 was 170 ° C.,
Dry hot drawing was performed in a hot air oven consisting of three sections at 200 ° C. and 235 ° C. so that the total draw ratio was 18.0. Example 2 has a total draw ratio of 1 at 170 ° C, 200 ° C and 240 ° C.
It was stretched 7.5 times. All drawn yarns are colored purple, and the hot water cutoff temperature is about 20 ° C compared to the case without phosphoric acid.
It was found to be high, and the heat resistance was improved by crosslinking. Next, the drawn yarn obtained in Example 1 was shrunk by 5% at 230 ° C, and the drawn yarn of Example 2 was shrunk by 10% at 240 ° C. Then, 3 fibers of nylon 6, nylon 66, and nylon 12 were copolymerized on both fibers by a roller touch method, and a 2% methanol solution of Grilltex 1P (made by EMS Japan) having a melting point of 110 ° C. was adhered to the fiber, and the tension was applied. 0.5 g /
At d, heat treatment was performed at 210 ° C. for 30 seconds. The amount of resin adhered was 3.8% by weight in Example 1 and 3.2% by weight in Example 2. Then, subsequently, 0.6% by weight of a silicon-based oil having a friction coefficient of 0.21 was attached and dried at 120 ° C.

The resin-adhered yarn obtained in Example 1 was 1200.
Strength is 11.5 g / d at d / 500f, elongation is 7.8%,
180 ° C. dry heat shrinkage (DSr) shows 1.6%, and in Example 2, 1200 d / 500 f, strength 13.7 g / d,
Elongation was 9.2% and 180 ° C DSr was 0.8%, both of which were fibers with high elongation and low shrinkage. Also, to evaluate rubber fatigue resistance, 1200d / 1 × 2 20 × 20t / 10c
The raw code of m was RFL processed to create a dip code. The strength retention after bending the belt at 100 ° C. and 25φ × 30,000 times was 88% in Example 1 and 95% in Example 2, and the bending fatigue resistance was excellent. The number of cuts due to twisting wear was 4810 times in Example 1 and 5146 times in Example 2, showing good wear resistance. Furthermore, when used as a reinforcing material for oil brake hoses, it is excellent in steam vulcanization at 130 ° C due to cross-linking and resin adhesion and has excellent resistance to brake oil liquids, and has little dimensional change, fatigue, wear, oil resistance, and steam resistance. It was a high value-added PVA fiber that has never been seen before as a reinforcing material for oil brake hoses such as dimensional stability.

Comparative Example 1 was carried out in Example 2 without shrinkage treatment, but the yarn after resin adhesion was 1320 d /
Strength of 17.8 g / d at 500f, elongation of 5.1%, 180
The DSC at 2.4 ° C. was 2.4%, which was a high-strength and low-elongation type with high shrinkage. Further, the belt bending fatigue resistance was observed as in Example 2, but the strength retention decreased to 83%, and the twisting abrasion was cut at 3155 times, which was inferior to Example 2 in durability and dimensional stability. It was

Example 3 and Comparative Example 2 Viscosity average degree of polymerization 8000, saponification degree 99.8 mol%
Of PVA was dissolved in DMSO at 110 ° C. to a concentration of 7% by weight, and the resulting solution was discharged from a nozzle of 400 holes, methanol / DMSO = 7/3, 7 ° C.
Wet spinning was performed in the coagulation bath. Further, the film was wet-stretched 4 times in a 40 ° C. methanol bath, and then almost all of the solvent was removed with methanol. The obtained spun raw yarn was heated at 170 ° C. and 250 ° C.
After performing dry heat drawing using one radiation furnace so as to have a total draw ratio of 18.3 times, subsequently, shrinkage treatment of 3% was performed at 245 ° C. and winding was performed. Further, 3% of the fiber is made of polyether polyurethane (made by Kuramiron 9196 Kuraray) having a Vicat softening temperature of 125 ° C. by a dip nip method.
DMF solution is attached and 100 ° C under tension of 0.3g / d.
Dry-160 degreeC heat processing was given. The amount of the urethane resin attached was 2.4% by weight. Subsequently, 0.7% by weight of a mineral oil-based oil having a friction coefficient of 0.25 was adhered and dried at 110 ° C. The obtained resin-adhered yarn is 1500d / 400f
Strength is 17.9 g / d, elongation is 6.6%, 180 ° C D
Sr was 1.3%.

Using the resin-adhered yarn, 1500 d / 1
After forming a raw cord of × 250 × 50t / 10 cm, a dip code was obtained by RFL treatment. 100 ° C 2
The strength retention after bending the belt 5φ × 500,000 times was as high as 96%, and the number of cuts due to twisting abrasion was 6211 times. This fiber was used as a carcass reinforcing material for automobile tires and had high value added with excellent durability and dimensional stability. As Comparative Example 2, a case in which no resin was attached was performed in Example 3.
The strength and elongation and the DSC at 180 ° C. were not so different from those in Example 3, but it was found that the strength retention after belt bending was 84% and the number of abrasion cuts was 4770, which deteriorated the durability.

Example 4 PVA having a viscosity average polymerization degree of 17,000 and a saponification degree of 99.8 mol% was dissolved in glycerin at 180 ° C. to a concentration of 6% by weight, and the resulting solution was obtained. Is discharged from a 200-hole nozzle, and methanol / glycerin = 7
Dry-wet spinning was carried out in a coagulation bath at a weight ratio of / 3. 4 more
Almost all of the solvent was removed with methanol after 4 times wet drawing in a 0 ° C. methanol bath. 1 spun yarn obtained
Dry hot stretching was performed in a hot air oven at 90 ° C to 260 ° C so that the total stretching ratio was 19.2 times, and then 2% shrinkage treatment was performed at 250 ° C, and the film was wound. Then, the fiber was heat-treated at 210 ° C. for 30 seconds at a tension of 0.9 g / d by applying a 3% aqueous emulsion of the same copolymer nylon as in Example 1 by a roller touch method. The amount of the nylon resin attached was 4.8% by weight. Subsequently, the same silicon-based oil agent as in Example 1 was attached, and 750
A d / 200f yarn was obtained. The resin-bonded yarn has a strength of 21.4 g / d, an elongation of 6.2%, and a DSr of 180 ° C.
Was 0.6%. Furthermore, combine the two yarns 15
After a raw cord of 00d / 1 × 2 31.5 × 31.5t / 10 cm was prepared, a dip cord was obtained by RFL treatment. 100 ° C, 20φ x 13 times and 100 ° C, 8
The belt flexural strength retention ratio of 0φ × 100,000 times was 89% and 94%, respectively, and it was proved that the rubber fatigue resistance was excellent.
Moreover, the number of times of abrasion cutting was as high as 7910 times, and it was found that the material exhibited extremely excellent performance as a reinforcing material for automobile tire belt parts, conveyor belt duck parts, etc. or general industrial materials.

[0024]

EFFECTS OF THE INVENTION According to the present invention, it has high elongation and low shrinkage, and its surface is coated with a specific resin, so that it is excellent in fatigue resistance, wear resistance and dimensional stability. A PVA fiber is obtained. The PVA fiber of the present invention is
Due to these features, it is extremely suitable as a reinforcing material for rubber and plastics, and for general industrial materials such as ropes, fishing nets, nets, sailcloth, and civil engineering sheets.

Front page continued (72) Inventor Satoru Kobayashi 1621 Sakata, Kurashiki City, Okayama Prefecture Kuraray Co., Ltd.

Claims (2)

[Claims] 1. A polyamide-based or polyurethane-based resin is adhered to the fiber surface in an amount of 0.5 to 8% by weight, and further F
/ F has an oil agent with a static friction coefficient of 0.28 or less,
A polyvinyl alcohol fiber having a yarn elongation of 6% or more and a 180 ° C. dry heat shrinkage of 2% or less. 2. A method for producing a polyvinyl alcohol fiber by spinning a solution of a polyvinyl alcohol polymer, comprising the steps of: stretching at 220 ° C. or higher so that the total stretching ratio is 16 times or higher; A step of applying a heat shrinkage of 15% to 15%, a step of applying 0.5 to 8% by weight of a polyamide-based or polyurethane-based resin to the fiber surface, and a step of applying an oil agent having an F / F static friction coefficient of 0.28 or less. A method for producing a polyvinyl alcohol fiber, which is characterized by carrying out.