JPH08120526A - Production of polyvinyl alcohol fiber having high strength and high hot-water resistance - Google Patents

Abstract

PURPOSE: To provide a process for producing a PVA fiber having high strength and high hot-water resistance and free from fray when cut in the direction of the fiber axis of a rubber conjugate material-obtained by using the PVA fiber as reinforcing material. CONSTITUTION: A spinning stock solution is prepared by dissolving PVA in an organic solvent. A coagulated fiber yarn is obtained by spinning the stock solution into a coagulation bath by wet and dry-type spinning. The coagulated fiber yarn is provided with a spinning oil mainly containing a composition consisting of the two components of A and B shown below and being mixed with dehydration reaction-stimulating catalysts, and further provided with a finishing oil shown below after heat drawing. The spinning oil consists of (A) 5-40wt.% of an ester of an aliphatic alcohol with an aliphatic carboxylic acid and (B) 95-60wt.% of an ethylene oxide and/or propylene oxide adduct to an aliphatic alcohol. The finishing oil consists of an oil containing >=40wt.% of an ethylene oxide and/or a propylene oxide adduct to an aliphatic amine compound.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing high-strength, highly heat-resistant water-soluble polyvinyl alcohol (hereinafter abbreviated as PVA) fiber suitable for industrial materials, especially for belts.

[0002]

2. Description of the Related Art PVA-based fibers have higher strength and elastic modulus, better dimensional stability against heat, and better adhesiveness than general-purpose fiber materials such as nylon fibers and polyester fibers. It has extremely excellent characteristics. In addition, recently, various attempts have been made to further increase the strength and elastic modulus, and as a result, it is regarded as a representative of high-strength and high-modulus fibers, although it is not as good as polyethylene fibers by the so-called gel spinning method. Fibers with strength and elastic modulus comparable to that of polyparaphenylene terephthalamide fibers have been obtained.

However, nylon fibers and polyester fibers are insoluble in hot water, whereas PVA-based fibers are soluble in hot water, so that their application fields have been limited. In order to overcome this drawback, a method of acetalizing with formalin has been proposed in the past, and recently, as shown in, for example, Japanese Patent Laid-Open No. 2-133605, an acrylic acid polymer is blend-spun. Method and JP-A-4-126829
As described in Japanese Patent Publication No.
There has been proposed a method of improving hot water resistance by performing heat treatment and dehydration reaction.

On the other hand, rib V belts, timing belts, etc. typified by transmission belts are PVA-based fiber reinforced rubber composites which have been preliminarily molded into a tubular shape and vulcanized in order to simplify the manufacturing process and reduce the cost. It is commercialized by cutting the body into slices. However, a single yarn may fray from the PVA-based fiber exposed on the side surface of the belt cut in the fiber axis direction, and may protrude in a fluff shape. In that case, not only the quality of the product will deteriorate, but if the product is set in the pulley and operated as it is, the frayed part of this single yarn will be rubbed by the pulley and the frayed single yarn will scatter, and this fraying will cause the belt to break. However, there is a problem that the durability is reduced.

As a method for solving this problem, after twisting the PVA-based fiber into a cord, the cord is impregnated with an epoxy adhesive and / or an isocyanate adhesive and heat-treated to give a PVA-based fiber. There is a method of bonding between the single yarns. However, a conventional spinning oil agent, for example, an oil agent containing an aliphatic ester compound as a main ingredient and a so-called straight oil agent having a mineral oil as a diluent has a poor compatibility between the oil agent and the adhesive agent, and is not compatible with the oil agent. A sufficient effect cannot be obtained because the adhesive separates and the adhesive does not penetrate into the fiber. On the other hand, when a spinning oil agent which does not have such a problem such as an aliphatic amide compound, an aliphatic amine compound, an ethylene oxide and / or a propylene oxide adduct of an aliphatic alcohol or an aliphatic carboxylic acid is used, a process for producing a PVA-based fiber At
There is a problem that single yarn breakage occurs frequently because the yarns on the supply roller and the drawing roller do not have a bundling property. Further, as in Japanese Patent Application No. 6-189508 proposed by the present inventors, an ester of an aliphatic alcohol and an aliphatic carboxylic acid or an ethylene oxide and / or propylene oxide adduct thereof, an ethylene oxide of an aliphatic alcohol and / or In the method of using an oil agent in which a propylene oxide adduct, an ethylene oxide of an aliphatic amine and / or a propylene oxide adduct are mixed at a specific ratio, the oil agent modified product is deposited on the hot stretching roller or the heat treatment roller in the manufacturing process of the PVA fiber. However, there is a problem that it is often necessary to stop the operation and perform cleaning.

[0006]

DISCLOSURE OF THE INVENTION The present invention has a high strength, a high elastic modulus, and excellent hot water resistance, and is treated with an epoxy adhesive and / or an isocyanate adhesive as a cord to obtain a normal resorcin / formalin rubber. Latex (hereinafter RFL
Abbreviated. ) Adhesion with rubber is improved only by treatment, and when a PVA fiber reinforced rubber composite is prepared using this cord and cut in the fiber axis direction, the PVA fiber exposed on the cut surface is It is a technical object to provide a method for producing a PVA-based fiber with good operability, which does not cause fray of a single yarn or fray from the cut surface.

[0007]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventors dry-wet-spin a stock solution prepared by dissolving PVA in an organic solvent in a coagulation bath. The coagulated yarn is obtained by applying a spinning oil mixed with a catalyst for promoting the dehydration reaction to the coagulated yarn, and then dry heat drawing to produce a high-strength, high heat-resistant PVA-based fiber.
When a fiber-reinforced rubber composite is made using a series of fibers and cut in the fiber axis direction, it prevents fraying of the single yarn of PVA-based fibers exposed on the cut surface and fraying of the fray from the cut surface. The present inventors have found that this object can be achieved by using two kinds of oil agents as an oil agent to be used, and by adding one kind of oil agent by mixing with a spinning oil agent having a specific composition that improves spinnability.

That is, according to the present invention, a spinning stock solution prepared by dissolving PVA in an organic solvent is subjected to dry-wet spinning in a coagulation bath to obtain a coagulated filament, and the coagulated filament is mixed with a catalyst for promoting a dehydration reaction. When a PVA-based fiber is produced by dry drawing after applying the above spinning oil agent, the following A as the spinning oil agent,
Applying an oil agent whose main component is a composition consisting of B2 component,
The gist of the present invention is a method for producing a high-strength, highly heat-resistant water-based PVA-based fiber, which comprises applying the following finishing oil agent after hot drawing and immediately before winding. (1) Spinning oil agent; A: Ester of aliphatic alcohol and aliphatic carboxylic acid ... 5 to 40% by weight B: Ethylene oxide and / or propylene oxide adduct of aliphatic alcohol ... 95 to 60% by weight (2) Finishing oil agent An oil agent containing 40% by weight or more of an ethylene oxide and / or propylene oxide adduct of an aliphatic amine compound

The present invention will be described in detail below.

The degree of polymerization and the degree of saponification of PVA used in the present invention are not particularly limited, but the degree of polymerization is 1500 or more,
It is preferably 7,000 or less, and the saponification degree is 99 mol% or more. Examples of the organic solvent that dissolves PVA include dimethyl sulfoxide (hereinafter abbreviated as DMSO), glycerin, ethylene glycol, and the like, and DMSO is preferable. The concentration of PVA in the spinning dope may be appropriately adjusted depending on the degree of polymerization, but when the degree of polymerization is 1500 to 7000, it is preferably adjusted to 5 to 24% by weight. In the present invention, the spinning solution may be appropriately mixed with a crosslinking agent, a pigment, a heat-resistant agent and the like.

In the present invention, this spinning solution is dry-wet spun in a coagulation bath to form an undrawn yarn. The air gap during dry-wet spinning is preferably 20 mm or more and 100 mm or less. As the coagulation bath liquid, methanol, ethanol, acetone or the like can be used, and methanol is particularly preferable. In the present invention, the coagulating bath solution may be mixed with a solvent for PVA.

The spinneret used for dry-wet spinning is not particularly limited, but the discharge linear velocity v (cm / sec), the hole diameter d (cm) of the spinneret, and the viscosity of the spinning dope μ (g / cm · sec). ) And the density ρ (g / cm ³ ) and the ray noise number (Re) defined by the following formula is preferably 0.05 to 200 and the hole diameter and the ejection linear velocity are preferably selected. Re = (dvvρ) / μ

In the present invention, the coagulated yarn thus formed is further washed with a solvent and then dried to obtain an undrawn yarn. The solvent used for washing is preferably the same as that used as the coagulation bath solution. The washing method is preferably carried out by causing the solvent to flow in the direction opposite to the advancing direction of the coagulated yarn and contacting it. During this washing, the coagulated yarn may be so-called wet-stretched. The magnification is preferably less than 8 times.

Next, an oil agent mixed with a catalyst is applied to the yarn after washing, in which case the liquid content of the yarn (the ratio of the weight of the washing solvent in the yarn to the weight of the entire yarn). 5
It is preferable to add the oil agent in an amount of not less than 30% by weight, especially 7 to 25% by weight. If the liquid content of the yarn is less than 5% by weight, or conversely 30% by weight or more, the penetration of the catalyst into the yarn becomes insufficient and it becomes difficult to obtain high hot water resistance. The reason for this is not clear, but the yarn shrinks as it dries, so if the liquid content goes below 5% by weight, the yarn will shrink too much and the catalyst will not penetrate sufficiently. it is conceivable that. On the contrary, when the liquid content is 30% by weight or more,
Since the solvent occupies the space where the catalyst must penetrate,
It is recognized that the catalyst becomes difficult to penetrate.

In order to set the liquid content of the yarn in this range,
Drying is preferably performed between washing with a solvent and applying a catalyst, but the method is not particularly limited as long as the liquid content can be within the above range, and for example, in a heated gas. The yarn can be passed through or dried by contacting the yarn with a drum whose surface is heated.

Examples of the catalyst that can be used in the present invention include inorganic acids such as phosphoric acid and hydrochloric acid, and organic acids such as paratoluenesulfonic acid and terephthalic acid. Particularly, phosphoric acid and paratoluenesulfonic acid are preferably used. To be

Further, the catalyst is used together with the spinning oil agent, that is,
A catalyst is mixed with the oil-spinning agent and applied to the yarn. If the catalyst and the spinning oil agent are separately provided, the process becomes complicated, which is not preferable. The amount of the catalyst mixed with the spinning oil agent depends on the acid concentration.
It is preferable to mix the catalyst with the oil agent so that the amount is 0.005 to 0.5 N.

The spinning oil to which the catalyst is mixed is the above-mentioned A,
An oil agent containing the composition consisting of the component B2 as a main component and preferably containing 80% by weight or more of the above composition is applied. In the following description of the oil component, EO means ethylene oxide, PO means propylene oxide, POE means polyoxyethylenation, and the value in parentheses means the number of moles added.

First, the component A is an ester of an aliphatic alcohol and an aliphatic carboxylic acid, which has the function of improving the yarn bundle converging property in the yarn making process. As the aliphatic alcohol and the aliphatic carboxylic acid, those having 6 to 22 carbon atoms are preferable, and those having a sulfur atom, a phosphorus atom, or the like introduced therein may be used for improving heat resistance. Specific examples of the component A include dioleyl adipate, oleyl oleate, lauryl oleate, isostearyl oleate,
Examples include isotridecyl palmitate, diglycerin dioleate, dioleyl thiodipropionate. The amount of component A is 5-40% by weight, especially 10-35% by weight
Is preferred. If this amount is less than 5% by weight, the spinnability is reduced, and if it is more than 40% by weight, the effect of preventing fraying is reduced.

Component B is an EO of an aliphatic alcohol and / or
Alternatively, it is a PO adduct, and has a function of permeating the adhesive to a deep portion when the cord is treated with the adhesive. The aliphatic alcohol preferably has 4 to 22 carbon atoms, and the added mole number of EO and / or PO is 4 to 20.
Is preferred. Specific examples of the component B include POE (6) stearyl ether, POE (6) oleyl ether, POE (10) oleyl ether, POE (10) cetyl ether, POE (8) lauryl ether, PO (5) / EO ( 5) Monobutyl ether, POE (20)
Examples thereof include glycerin ether. The component B does not easily cause roller contamination even if it is applied in front of the heat treatment roller. By applying the component B as a spinning oil agent, the oil agent for permeating the adhesive into the fiber penetrates deep into the fiber. Can be made. The amount of component B is 60 to 95% by weight,
Particularly, 65 to 90% by weight is preferable. If it is out of this range, the effect of preventing fraying is reduced.

The spinning oil used in the present invention is A or B.
The total content of the components should be 100% by weight, this composition should preferably be 80% by weight or more, and emulsifier, antistatic agent, heat-resistant agent, etc. should be blended in the range of 20% by weight or less before use. To be The spinning oil agent is usually used in the form of a straight oil agent (non-water oil agent) diluted with a low-viscosity mineral oil, methanol, ethanol or the like, but may be an aqueous emulsion oil agent. It should be noted that if EO and / or PO adducts of aliphatic amine compounds, which are essential components of finishing oils, are added to the spinning oil agent, roller stains tend to occur, so it is desirable not to add this to the spinning oil agent.

The spinning oil agent is applied to the yarn by a usual roller lubrication method or nozzle lubrication method. The amount of the spinning oil agent applied is 0.05 to 1.0% by weight, particularly 0.1 to 0.5% by weight. % Is preferred.

The yarn to which the spinning oil is added is subjected to a dehydration reaction at the same time as being once wound or continuously hot-stretched without being wound, and at the same time, the dry-heat stretching ratio is 15 It is preferable that the number is twice or more. Dry heat draw ratio
When it is less than 15 times, it becomes difficult to obtain the high-strength PVA fiber which is another object of the present invention.

As a heating method of the yarn in the hot drawing, a method using a hot air heating furnace, a method using a contact type heater, a method using a radiant heat heater, a method using a heating roller, etc. can be adopted. A combination of some of these may be used. The temperature during dry heat drawing is not particularly limited, but for example, when drawing in a hot-air heating furnace, it is preferable that the inlet temperature of the yarn is 150 ° C or higher and the outlet temperature is 270 ° C or lower.

When a yarn mixed with a catalyst and provided with a spinning oil agent is subjected to dry heat drawing, hot drawing and dehydration reaction simultaneously proceed. However, in order to sufficiently proceed the dehydration reaction, further heat treatment is performed after dry heat drawing. Good. The heat treatment is preferably performed at a temperature 5 to 10 ° C. higher than the maximum temperature of hot stretching and at a constant length (relaxation rate 0%) or a relaxation rate of 10% or less.

In the present invention, the undrawn yarn to which the spinning oil agent has been applied as described above is dry-heat drawn, and then the finishing oil agent is applied immediately before winding. The finishing oil agent is an aliphatic amine compound E
It has an O and / or PO adduct as a main component, and has a function of penetrating the adhesive to a deep portion and curing the adhesive when the cord is treated with the adhesive. As the aliphatic amine compound, those having 4 to 22 carbon atoms are preferable, and the number of added moles of EO and / or PO is 4
~ 20 is preferred. Specific examples of EO and / or PO adducts of aliphatic amine compounds include POE (20) lauryl amino ether, POE (15) lauryl amino ether, POE (10)
Lauryl amino ether, POE (10) Stearyl amino ether, POE (15) Lauryl ethanolamine, POE (15)
Examples thereof include lauryl diethanolamine. EO and / or PO of aliphatic amine compound in finishing oil
The content of the adduct is preferably 40% by weight or more, particularly preferably 50% by weight or more. If it is out of this range, the effect of preventing fraying is reduced. Other components to be added to the finishing oil agent include A,
In addition to the B component, natural oils such as coconut oil, rapeseed oil and sperm oil can be mentioned. Furthermore, if necessary, an emulsifier, a dispersant, an antistatic agent, a heat-resistant agent, etc. may be mixed and used.

The finish oil agent is usually used in the form of an aqueous emulsion, but it may be used as a straight oil agent diluted with a low-viscosity mineral oil, methanol, ethanol or the like.

This finishing oil agent is applied to the yarn by using a roller type oil supply method, a nozzle type oil supply method or the like, and the amount of the finish oil application is 0.1 to 2.0% by weight, particularly 0.2 to 0.2% by weight. 0.8% by weight
Is preferred.

[0029]

According to the present invention, when the PVA fiber is used as a cord and treated with an adhesive, two types of oil agents are used as an oil agent containing a component for permeating the adhesive to a deep portion or hardening the adhesive. EO of aliphatic alcohol and / or
Alternatively, the PO adduct-based oil agent is mixed with the spinning oil agent and applied to the fiber before hot drawing, and the EO of the aliphatic amine compound is added.
Since the oil agent containing 40% by weight or more of PO adduct is applied as a finishing oil agent after hot drawing, the spinnability is improved, and the cord using the PVA fiber obtained is treated with usual epoxy adhesive agent. And / or the adhesion to rubber becomes good only by performing the isocyanate adhesive treatment and then the RFL treatment. Also, using this code, P
When a VA-based fiber-reinforced rubber composite is formed and the composite is cut in the fiber axis direction, the PVA-based fiber single yarn exposed on the cut surface is frayed, and this fray is projected like fluff from the cut surface. Can be prevented. Furthermore, 40% by weight of EO and / or PO adducts of aliphatic amine compounds
The above-mentioned finishing oil agent may deteriorate the operability when it is applied in front of the heat treatment roller, resulting in roller contamination, but this problem can be solved by applying it immediately after winding after dry heat drawing. .

[0030]

EXAMPLES Next, the present invention will be specifically described by way of examples. In addition, "part" means a part by weight, and the measuring method is as follows. (a) Cord strength and elongation were measured according to JIS-L-1017 using an autograph. (b) Spinnability The number of single yarn breaks caused by roller stains on the drawing roller and heat treatment roller in the spinning process was evaluated in the following three grades. ○: 0 to 3 times / 1 day △: 4 to 10 times / 1 day ×: 11 times or more / 1 day (c) Fraying resistance Treated cords are arranged in parallel between two 3 mm thick rubber sheets. Sandwich and vulcanize at 150 ° C for 30 minutes under a pressure of 20 kg / cm ² to obtain a rubber sheet. This sheet is cut with a cutter knife at a slight angle from the fiber axis direction of the cords arranged in rubber so that the end faces of the cords are exposed on the cut surface. Then, while observing the protruding state of the single yarn of PVA fiber from the end face with the naked eye, the end face was rubbed with sandpaper (# AA-120) 10 times to observe the frayed state of the single yarn. The grade was evaluated. ◯: Neither the single yarn jumping out nor the single yarn fraying is observed. Δ: Single yarn does not pop out, but single yarn is unraveled. X: Single yarn jumping out and single yarn fraying are recognized. (e) Adhesiveness Natural rubber (RSS # 4) 40.0% by weight, butadiene-styrene rubber (# 1502) 28.5% by weight, HAF carbon black 26.0% by weight, zinc white 2.8% by weight, stearic acid 0.7% by weight, sulfur 1.5% by weight %, And 0.5% by weight of a vulcanization accelerator, a rubber compound was used and measured according to the method A of JIS-L-1017.

Examples 1 to 3, Comparative Examples 1 to 4 [Preparation of Spinning Oil Agents 1 to 2] 75 parts of 90% ethyl alcohol
The mixture was heated to 30 ° C., the components were mixed in the proportions (parts) shown in Table 1, and 25 parts of the oil agent composition heated to 40 ° C. was slowly added and stirred, and then cooled to room temperature. Furthermore, 0.03 parts of 98 wt% phosphoric acid was slowly added and stirred.

[0032]

[Table 1]

[Preparation of Finishing Oil Solution] 80 parts of water was heated to 40 ° C., each component was mixed in a ratio (part) shown in Table 2, and 20 parts of the oil agent composition heated to 40 ° C. was slowly added. While stirring, the mixture was cooled to room temperature.

[0034]

[Table 2]

[Preparation of Isocyanate Adhesive] Tris (p-isocyanatephenyl) thiophosphate with a solid concentration of 27% was added to 75 parts of toluene;
25 parts of "E" (Sumitomo Bayer Urethane Co., Ltd.) was slowly added and dissolved by stirring.

[Preparation of RFL solution] To 125 parts of water, 19 parts of 10% sodium hydroxide aqueous solution was added, then 17 parts of resorcinol was added, stirred and dissolved, and then 30 parts of 37% formaldehyde aqueous solution was added and stirred. Then, the mixture was reacted at 25 ° C for 30 minutes. The obtained reaction liquid was VP latex having a solid content of 41%; "Pilatex J-1904" (trade name of Sumitomo Dow) 190 parts and SBR latex having a solid content of 40%; "JSR-2108" (Japan Synthetic Rubber) Company brand name) Add to 190 parts of the mixed solution with stirring,
Further, 431 parts of water was added with stirring, the mixture was stirred for 10 minutes, mixed, and then aged at 25 ° C. for 24 hours.

[Production of PVA Fiber] 15 parts of PVA having a polymerization degree of 4000 and a saponification degree of 99.9 mol% was dissolved in 85 parts of DMSO to prepare a spinning dope. This spinning dope is passed through a 30 mm air gap from a spinneret with a hole diameter of 0.3 mm and 300 holes,
Coagulated yarn was obtained by dry and wet spinning in a methanol coagulation bath containing 15% by weight of DMSO. The discharge conditions were selected so that the number of Reynolds was 2. The coagulated yarn was washed with methanol and dried using a heating drum to reduce the liquid content of the yarn to 10
Then, the spinning oil agent shown in Table 3 was applied to the yarn in an amount of 0.3% by weight based on the roller type oiling method, and further dried at 80 ° C. to obtain an undrawn yarn. Then, this undrawn yarn was put on a supply roller having a surface temperature of 80 ° C and a surface speed of 10 m / min, and passed through a hot air heating furnace having a length of 3 m and an inlet temperature of 160 ° C and an outlet temperature of 220 ° C. Surface temperature 1
The yarn that was drawn 9 times with the first drawing roller at a surface speed of 90 m / min at 60 ° C and then exited the first drawing roller was set to have an inlet temperature of 210 ° C and an outlet temperature of 240 ° C. After passing through a hot air heating furnace with a length of 5 m, the surface temperature was 180 ° C and the surface speed was 190.
It was stretched 2.11 times with a second stretching roller of m / min. In addition, the yarn exiting the second drawing roller is
℃, outlet temperature is set to 250 ℃, while passing through a hot air heating furnace with a surface temperature of 50 ℃, surface speed of 185 m / min relaxation heat treatment 0.97 times with a heat treatment roller, then by the nozzle oiling method Apply the finishing oil agent shown in Table 3 prepared by the above method to the yarn at 0.4% by weight and wind it up.
1500 d / 300 f of PVA fiber was obtained.

[Treatment of Cord] While twisting two obtained PVA-based fibers, a twist of 115 times / m is applied to obtain a twisted cord, and then three twisted cords are twisted together to twist the yarn. A twisted cord with a twist number of 115 turns / m in the opposite direction,
It was dipped in the isocyanate-based adhesive solution prepared by the above method (solid content: 3.5 to 4.5% by weight), dried with hot air at 120 ° C, and then heat-treated at 180 ° C for 100 seconds. Then, after soaking in the RFL bath prepared by the above method (solid content amount 4.5 to 5.5% by weight) and drying at 120 ° C. for 60 seconds,
Heat treatment was performed at 180 ° C for 100 seconds.

Table 3 shows the strength and elongation of the thus treated cord, the resistance to fraying, the adhesiveness, and the spinnability in the raw yarn manufacturing process.

[0040]

[Table 3]

As is clear from Table 3, Example 1 of the present invention
In the case of, the spinnability, the fray resistance, and the adhesiveness were all good. Further, in Examples 2 to 3, although there were some problems in the spinnability, they were good in all of the fray resistance and the adhesiveness. On the other hand, in Comparative Examples 1 to 3, although the spinnability was good, there was a problem in the fraying resistance of the single yarn, and in Comparative Example 4, all of the spinnability, the fraying resistance, and the adhesiveness were satisfied. It wasn't possible.

[0042]

EFFECTS OF THE INVENTION According to the present invention, the adhesion to rubber is remarkably good only by treating the cords with an epoxy adhesive and / or an isocyanate adhesive in a conventional manner and performing a usual RFL treatment. Moreover, when a fiber-reinforced rubber composite is formed by using this cord and the composite is cut in the fiber axis direction, the single yarn of the fiber exposed on the cut surface does not fray or protrude in a fluff shape. It is possible to produce strong, highly heat-resistant water-based PVA fibers. Moreover, during the production of the PVA-based fiber, the stretching roller is not contaminated with the modified oil, and can be stably operated for a long period of time. The effect of the present invention is not limited to the improvement of the PVA fiber itself, but is directly related to the quality improvement of the rubber product to be reinforced, and has an extremely large practical effect.

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Claims (1)

[Claims] 1. A spinning oil solution in which a spinning dope prepared by dissolving polyvinyl alcohol in an organic solvent is dry-wet spun in a coagulation bath to obtain coagulated filaments, and a dehydration reaction promoting catalyst is mixed with the coagulated filaments. When a polyvinyl alcohol fiber is produced by dry-stretching after applying, an oil agent containing a composition consisting of the following A and B2 components as a main component is applied as the spinning oil agent, and after hot drawing, immediately before winding. A method for producing a high-strength, highly heat-resistant water-soluble polyvinyl alcohol fiber, which comprises adding the following finishing oil to (1) Spinning oil agent; A: Ester of aliphatic alcohol and aliphatic carboxylic acid ... 5 to 40% by weight B: Ethylene oxide and / or propylene oxide adduct of aliphatic alcohol ... 95 to 60% by weight (2) Finishing oil agent An oil agent containing 40% by weight or more of an ethylene oxide and / or propylene oxide adduct of an aliphatic amine compound