JPH05287608A - Production of high-tenancity polyvinyl alcohol-based fiber - Google Patents

Abstract

PURPOSE:To provide the subject polyvinyl alcohol-based fiber excellent in heat resistance, fatigue resistance and abrasion resistance and suitable for a reinforcing material such as rubber, plastic or cement and an industrial material such as a rope, a fish net and a sheet for construction. CONSTITUTION:The objective polyvinyl alcohol-based fiber is obtained by dissolving a polyvinyl alcohol-based polymer having >=6000 viscosity-average polymerization degree in a dimethyl sulfoxidebased solvent and dry and wet spinning it while keeping the temperature of the coagulation bath to <=15 deg.C, keeping the temperature of the discharged polyvinyl alcohol solution to a temperature 90 to 150 deg.C higher than that of the coagulation bath and controlling the spinning draft to 0.1 to 1.0 so as to form a uniform and crystallite-network structured gel yarn and subsequently carrying out wet drawing and dry heat stretching.

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 a high-strength polyvinyl alcohol (hereinafter abbreviated as PVA) fiber. The fiber obtained in the present invention is a reinforcing material for rubber materials such as tires, automobile hoses, fire hoses, conveyor belts, V-belts or the like used for a long time at high temperature, or a reinforcing material for plastics or cement, as well as ropes, tents, canvas, fishing nets. It is a high-strength PVA fiber suitable for general industrial materials such as tension members, civil engineering and construction.

[0002]

2. Description of the Related Art Conventionally, PVA-based fibers are
It is superior to polyamide, polyester, and polyacrylonitrile-based fibers in terms of weather resistance, chemical resistance, adhesiveness, etc., and has pioneered unique applications mainly in the field of industrial materials. If PVA-based fibers with improved performance such as strength, resistance to moist heat, and resistance to rubber fatigue are developed, they will be used as reinforcement materials for rubber and plastics or general industrial materials.
Expecting products that satisfy safety, durability, and lightness under harsh conditions.

Methods for obtaining high strength and high modulus fibers using a high degree of polymerization PVA are disclosed in JP-A-59-130314, JP-A-61-289112 and JP-A-62-8501.
A fiber having a strength of 19 to 29 g / d and an elastic modulus of 550 to 650 g / d, which is disclosed in Japanese Patent No. 3 or the like, is obtained. The higher the degree of polymerization of PVA, the higher these physical properties become, but the idea is that the molecular chain is long due to the high degree of polymerization, and the number of entanglements increases, but by reducing it in a dilute solution and stretching at a high ratio. It was intended to be highly powerful. However, when spinning a dilute solution, fiber physical properties such as adhesion to nozzles and rollers or defective parts due to poor spinnability or single yarn breakage, and further decrease in durability due to decrease in the number of tie molecules connecting crystals are not observed. I was not completely satisfied.

On the other hand, the method of spinning using a dimethyl sulfoxide solvent is disclosed in Japanese Examined Patent Publication No. 43-16675 and Japanese Unexamined Patent Publication No.
0-126311, JP-A-60-126312, JP-A-62-162010 and the like. However, in these methods, the degree of polymerization was 5000 or less, or the solution temperature was 80 ° C. or less. When the degree of polymerization was 5000 or less, there were few tie molecules penetrating between the crystals, and the strength and durability were poor. Further, when the polymerization temperature is high and the solution temperature is 80 ° C. or lower, the PVA concentration cannot be increased due to the spinning viscosity, and there is a drawback in the above dilute solution.

With polyhydric alcohols such as glycerin and ethylene glycol, since the gelling temperature is high, a solution temperature of, for example, 170 ° C. or higher is used. However, increasing the PVA concentration in order to suppress the drawbacks of a dilute solution increases the viscosity and thus the viscosity. There is a problem that the solution temperature rises and the degree of polymerization is lowered due to thermal decomposition or the like.

[0006]

SUMMARY OF THE INVENTION Based on the above background, the object of the present invention is to obtain high homogeneity by using PVA having a high degree of polymerization and selecting a solvent and spinning conditions in an appropriate range to produce a more homogeneous amorphous gel structure. It is to provide a PVA-based fiber having excellent durability such as fatigue resistance and hot water resistance. The inventors of the present invention have found out how to use a high degree of polymerization PVA-based polymer to form a homogeneous gel structure while suppressing thermal decomposition, and to connect molecules in a network with fine crystals, and then to extend and cut chains by dry heat drawing. The inventors have made extensive studies on whether the structure should have a high orientation and a high crystal structure close to the above, or a structure with many tie molecules in the vertical and horizontal directions connecting the crystals. As a result, a dimethylsulfoxide (hereinafter abbreviated as DMSO) solvent that dissolves PVA with a high degree of polymerization at a relatively low temperature is used, and the PVA concentration is increased at a slightly higher spinning temperature while rapidly cooling in a reverse draft state. By doing so, it was found that a gel thread having a network structure that is homogeneous and rich in fine crystals can be obtained, and the present invention has been completed.

[0007]

Means for Solving the Problems That is, according to the present invention, a solution in which a ponivinyl alcohol-based polymer having a viscosity average degree of polymerization of 6000 or more is dissolved in a solvent containing 60% by weight or more of dimethyl sulfoxide is introduced into a gas from a nozzle. In the dry-wet spinning method of discharging and subsequently solidifying in a coagulation bath, the coagulation bath temperature is set to 15 ° C. or lower, and the temperature of the discharge solution is set to 90 to 150 ° C. higher than the coagulation bath temperature, and further spinning draft 0.1. The present invention relates to a method for producing a high-strength ponivinyl alcohol fiber, which is characterized in that spinning is performed at 1.0 to 1.0.

The contents of the present invention will be described in more detail below. The PVA polymer referred to in the present invention is a linear polymer having a viscosity average polymerization degree of 6,000 or more, preferably a saponification degree of 99 mol% or more and a low branching degree. P
The higher the average degree of polymerization of VA, the greater the number of molecules (tie molecules) penetrating many fine crystals in the network structure, and the higher the strength, the higher the elastic modulus, the higher the durability, the easier it is to obtain.
000 or more, more preferably 10,000 or more. If necessary, 3% by weight or less of a pigment, an antioxidant, an ultraviolet absorber, a crystallization inhibitor, a cross-linking agent, and a surfactant may be added to the PVA-based polymer. Moreover, what copolymerized the modifier of 2 mol% or less is also contained in PVA.

The solvent for the PVA-based polymer contains at least 60% by weight of DMSO. If it is less than 60% by weight, the solubility of the high degree of polymerization PVA is reduced, and the PVA is dissolved at a higher temperature, so that the PVA is colored or decomposed, and the fiber performance is likely to be deteriorated. Therefore, the solvent of the present invention,
DMSO 100%, of course, other solvents less than 40% by weight, such as water and polyhydric alcohols such as glycerin, ethylene glycol, diethylene glycol, triethylene glycol, and amine compounds such as dimethylformamide, dimethylacetamide, ethylenediamine, diethylenetriamine. There is no problem even if one or more of these are mixed. However, if the dissolution temperature and spinning temperature of the PVA-based polymer exceed 165 ° C., decomposition is likely to occur, so it is necessary to select a solvent and a mixing ratio at which the temperature is lower than that and a uniform solution is formed.

The concentration of the PVA-based polymer varies depending on the degree of polymerization and the solvent, but in the present invention, the spinning temperature is raised to be higher than the concentration of PVA usually used. For example, in a solvent having a degree of polymerization of 8,000 and DMSO 100%, the spinning temperature is usually 60 to 80 ° C. and the PVA concentration is 5.5 to 7.5% by weight, whereas the spinning temperature is 90 to 165 in the present invention.
A PVA concentration of 8-11 wt.% At C is used. P at high temperature
When the VA concentration is lowered, the spinnability is deteriorated, the tackiness is increased, and the spinning cannot be stabilized. By increasing the PVA concentration slightly, the number of tie molecules between crystals can be increased and a highly durable fiber can be produced.

Further, it is important to quench rapidly in order to suppress the growth of crystals and form a fine crystal structure. In the present invention, the spinning temperature is 90 to 150 ° C. while the solidification temperature is 15 ° C. or lower.
It's high. When the coagulation temperature exceeds 15 ° C., crystals easily grow and a devitrified gel yarn is obtained, and high strength and high durability cannot be sufficiently satisfied due to the non-uniform structure due to the difference in PVA density and the deviation of tie molecules. The coagulation temperature is preferably below 10 ° C, but must be above the temperature at which DMSO in the solvent freezes. When DMSO freezes, DMSO
A difference in PVA density is likely to occur in the crystals of, and a uniform gel structure cannot be obtained.

If the spinning temperature is lower than 90 ° C. with respect to the solidification temperature, rapid cooling cannot be performed, and the microcrystalline network structure is difficult. At a temperature difference of 150 ° C. or more, decomposition of PVA is likely to occur, and when the PVA concentration is increased for spinning stability, entanglement of molecular chains increases and high-magnification stretching cannot be performed.
It is difficult to obtain highly oriented, high strength fibers. The preferred spinning temperature is 100 to 150 ° C.

As a spinning method, a dry-wet spinning method is used in order to obtain a homogeneous and transparent gel fiber by discharging a high temperature solution of a PVA polymer from a spinning nozzle and then rapidly cooling it in a low temperature coagulation bath. The dry-wet spinning method is a spinning method in which a gas layer is present between the nozzle and the coagulation bath so that the nozzle does not directly exist in the coagulation bath, and therefore the discharged spinning stock solution passes through the gas layer. You will enter the coagulation bath. An air layer is usually used as the gas layer.

As a coagulant in the coagulation bath, methanol,
Although any coagulant such as alcohols such as ethanol, acetone, an aqueous alkali solution, an aqueous alkali metal salt solution can be used, an alcohol / solvent mixed system is preferable for slowly extracting the solvent and forming a uniform gel.

On the other hand, in order to suppress the crystal growth of PVA and the phase separation between PVA and the solvent to form a microcrystalline network structure, a spinning draft is also involved. The spinning draft is P
The ratio of the take-up speed to the speed at which the VA solution is ejected from the nozzle (that is, the ratio of the first godet roller speed to the discharge linear velocity when the stock solution is discharged from the nozzle: the first godet roller in the present invention is , A stock solution is discharged from a nozzle and solidified in a coagulation bath, and the solidified yarn is a solid that is substantially in contact for the first time, and a driving roller that rotates at a predetermined speed, or an alley roller that rotates by friction with the solidified yarn, Furthermore, guides such as rod-shaped, T-shaped, snake-shaped, etc., which are used to change the yarn path direction of the solidified yarn and do not move by themselves, are included. It does not include a solid that is slight, and is represented by the following formula.

Df = πD ↑ 2 × H × Tu / 4Q where D: nozzle diameter mm H: nozzle hole number Tu: take-up speed m / min Q: discharge rate cc / min

A spinning draft of more than 1.0 is not preferable because the orientation of the molecular chains and the growth of crystals due to the approach of the molecular chains are likely to occur by pulling the yarn discharged from the nozzle. If the spinning draft is less than 0.1, the injection speed of the solution will be too high and the ballooning (bulging in the direction perpendicular to shear) phenomenon will increase under the nozzle, and spinning will become unstable due to problems such as sticking and yarn wobbling at the nozzle. .. Preferably 0.2-0.
It is 6.

Further, in order to prevent the cross-section deformation and sticking of the gel fiber and to break the fine crystals at the time of spinning to improve the draw ratio, wet drawing is carried out at least 2 times, preferably at least 4 times while containing the solvent. Is good. Subsequently, almost all 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, the film is dry-heat stretched at a temperature of 200 ° C. or more, and the total draw ratio represented by the product of the wet draw ratio and the dry heat draw ratio is 16 times or more, preferably 18 times or more. Since the spun raw yarn obtained in the present invention suppresses crystal growth by quenching and low spinning draft, the total draw ratio is higher than usual. High-performance PV with higher orientation and higher crystallization at higher temperatures
A fiber is easily obtained. However, it is necessary to prevent the decomposition phenomenon of PVA and the flow phenomenon of the molecular chain (the phenomenon of crystal melting, which causes the molecular chain to come out by stretching) at too high temperature. Further, in order to suppress the decomposition and to make the drawing smooth, it is no problem to add a decomposition inhibitor or an oil agent to the fiber between the spinning stock solution and immediately before the dry heat drawing.

The fiber obtained by the present invention has high strength and high elastic modulus, is excellent in durability such as rubber fatigue resistance, hot water resistance and heat aging resistance, and is a high performance PV suitable for industrial materials.
It was an A-based fiber.

[0021]

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. The various physical properties in the examples were measured by the following methods.

1) Viscosity average degree of polymerization (P) and degree of decrease in degree of polymerization of PVA The specific viscosity ηsp of a PVA diluted acetone solution of vinyl acetate obtained by acetylating a PVA polymer at 30 ° C. was measured at 5 points, η] = lim c → o ηsp / C to obtain [η], and further P = ([η] × 100 / 7.94) ↑ 1/0.
The viscosity average degree of polymerization was determined from 64. Also, the degree of decrease in the degree of polymerization is
The P of the drawn yarn was determined in the same manner as above, and the P of the PVA polymer was determined.
It was calculated from the rate of decrease.

2) Hot water disconnection temperature (WTb) A load of 200 mg per denier was applied to 25 monofilaments and hung 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.

3) Single-filament Tensile Strength and Elongation, Elastic Modulus According to JIS L-1013, pre-conditioned humidity-adjusted single fibers are attached to a mount so that the test length is 10 cm, and 25 ° C. × 60%.
Leave it for 12 hours or more. Then at Instron 1122 2
Using a kg chuck, the breaking strength and elongation and the initial elastic modulus were determined at an initial load of 1/20 g / d and a tensile speed of 50% / min, and an average value of n ≧ 20 was adopted. Denier is 1/1
It was cut to 30 cm under a load of 0 g / d and determined by a 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.

4) Rubber fatigue resistance About 5,000 denier ply-twisted cord is subjected to RFL treatment, 20 cords are arranged on the raw rubber, and the raw rubber is put on the cord. Two layers of cord are made on the sandwich and vulcanized to form a rectangular belt. Then, the belt was subjected to compression fatigue at 100 ° C. 30,000 times with a belt bending tester having a pulley diameter of 25φ, the cord of the compression portion was taken out of the rubber, and the retention rate was calculated from the cord strength before and after fatigue.

Example 1 PVA having a viscosity average degree of polymerization of 17,000 and a degree of saponification of 99.8 mol% was added to DMSO100 so as to have a concentration of 5.3%.
% Solvent and dissolved at 100 ° C. The obtained solution was heated to 140 ° C. and discharged from a nozzle having 300 holes and a hole diameter of 0.18φ, and dry-wet spinning was performed in a coagulation bath at a methanol / DMSO = 7/3 weight ratio of 5 ° C. The discharge rate at that time was 120 cc / min, and the take-up roller speed in the coagulation bath was 4 m /
The spinning draft was 0.25. The gel yarn obtained was transparent and had a perfect circular cross section. Next, the film was wet-stretched 4 times in a methanol bath at 40 ° C., and then almost all the solvent was removed with methanol. The obtained spun raw yarn was heated at 180 ° C. and 2
Stretching was performed in a hot-air stove consisting of three sections at 10 ° C. and 250 ° C. so that the total stretching ratio was 19.5 times.

The drawn yarn had no coloring or sticking, and the reduction rate of the degree of polymerization of the drawn yarn with respect to the degree of polymerization of the polymer was as low as 13%. The single yarn strength of the drawn yarn was 26.7 g / d, and the elastic modulus was 540 g / d, and it was a high-strength, high-modulus PVA fiber which was not found in the past. It also has a hot water cutoff temperature (WTb) of 158 ° C and a melting point of about 260 ° C. It has excellent heat and water resistance and heat resistance, as well as general industrial materials such as ropes, fishing nets, civil engineering sheets and canvas, and reinforcement materials such as plastics and cement. However, the value added was high. Also, about 500
A belt bending test was carried out using a twisted cord of 0 denier, and it was found that the strength retention at 100 ° C x 30,000 cycles was as high as 81% and the rubber fatigue resistance of tires and belts was also excellent.

Comparative Example 1 In Example 1, the PVA concentration was set to 4.5% and the temperature was changed to 85 ° C.
The solution of is discharged from the nozzle and methanol / DMSO =
Dry-wet spinning was performed in a coagulation bath at a weight ratio of 7/3 and 5 ° C. The obtained spun raw yarn was drawn at the same temperature as in Example 1, but the total draw ratio was 17.8 times. The single yarn strength of the drawn yarn is 22.6.
The g / d and elastic modulus were 490 g / d, which were lower than those of the fiber of Example 1. WTb is 149 ° C., melting point is 2
The temperature was as low as 52 ° C, and the strength retention of belt bending at 100 ° C x 30,000 cycles was also reduced to 62%. If the PVA concentration is low and the difference between the solution temperature and the solidification temperature is small, the crystals become slightly large, and the number of tie molecules between the crystals is small.
It was found to be inferior in durability.

Example 2 PVA having a viscosity average degree of polymerization of 8,000 and a degree of saponification of 99.5 mol% was adjusted to a concentration of 9% by weight in DMSO / H ↓.
It was added to a solvent of 2O = 8/2 and dissolved at 95 ° C. The obtained solution was heated to 120 ° C. and discharged from a nozzle having 80 holes and a hole diameter of 0.15φ, and dry-wet spinning was performed in a coagulation bath at a methanol / DMSO = 6/4 weight ratio of 2 ° C. The spinning draft at this time was 0.31. The gel thread obtained is transparent,
It had a circular cross section. Next, the film was wet-stretched 4 times in a methanol bath at 40 ° C., and then almost all the solvent was removed with methanol. The obtained raw yarn was drawn in a radiation furnace consisting of two sections at 170 ° C. and 248 ° C. so that the total draw ratio was 20.1 times. The single yarn strength of the drawn yarn is 23.1 g / d,
Elastic modulus is 520g / d, high strength, high elastic modulus PVA
It was a fiber. WTb is also high at 146 ° C, 100 ° C
The strength retention after belt bending fatigue of 30,000 times was as high as 75%.

Comparative Example 2 When the coagulation temperature was set to 25 ° C. in Example 2, a cloudy gel yarn was obtained. When stretched in the same manner as in Example 2, the total stretching ratio was as high as 21.0 times, but the stretching tension was low and the strength and elastic modulus of the single fiber were 20.4 g / each.
d, 480 g / d, which was inferior to Example 2. The reason for this is not clear, but it is considered that the solidification temperature is high, the extraction rate of the solvent is high, and a non-uniform structure is likely to be formed due to the difference in PVA density. As a result, it is considered that a large crystal was generated, a white turbidity phenomenon due to the density and a deviation of the tie molecules occurred, and the film was easily stretched, but a structure having low stretching tension and strength was formed.

Example 3 PVA having a viscosity average degree of polymerization of 23,000 and a degree of saponification of 99.9 mol% was added to a solvent of DMSO / ethylene glycol = 7/3 so that the concentration was 5% by weight, and 100 It melted at ℃. The obtained solution was heated to 145 ° C. and the pore number was 15
The mixture was discharged from a nozzle having a pore size of 0.2 and a pore diameter of 0.22φ, and was dry / wet spun in a coagulation bath at a temperature of −2 ° C., consisting of ethanol / DMSO / ethylene glycol = 8/14/6 weight ratio. The spinning draft at this time was 0.27. The obtained transparent gel yarn was wet-stretched 3 times with methanol at 40 ° C., then almost all the solvent was removed with ethanol, a cation activator of a quaternary ammonium salt was further attached, and dried at 120 ° C. The obtained raw yarn was drawn at a total draw ratio of 18.9 times in a hot air oven consisting of two sections at 180 ° C and 253 ° C. At that time, the drawing exit tension was 4.1 g / d, which was very high, but the single yarn strength of the drawn yarn was 28.8 g / d and the elastic modulus was 6
It was a high-performance PVA fiber with an unprecedented value of 05 g / d and WTb of 162 ° C. Furthermore, it has excellent belt bending fatigue, dry heat aging resistance, and wear resistance, making it a high-value-added fiber suitable for industrial materials.

Claims (1)

[Claims] 1. A polyvinyl alcohol-based polymer having a viscosity average degree of polymerization of 6000 or more contains dimethyl sulfoxide of 60.
In a dry-wet spinning method in which a solution dissolved in a solvent containing not less than wt% is discharged into a gas from a nozzle and then solidified in a coagulation bath, the coagulation bath temperature is set to 15 ° C. or lower, and the temperature of the discharged solution is 90 to 150 ℃ higher than the coagulation bath temperature,
Further, a method for producing a high-strength polyvinyl alcohol fiber, which comprises spinning with a spinning draft of 0.1 to 1.0.