JP2656332B2 - Polyvinyl alcohol fiber drawing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a drawing method for industrially advantageously producing a polyvinyl alcohol (abbreviated as PVA) fiber having high strength and high elastic modulus. .

(Prior art) Conventional PVA fibers have higher strength and elastic modulus than polyamide, polyester, and polyacrylonitrile fibers, and are used mainly for industrial materials, which are their main applications, and recently as substitutes for asbestos, such as cement reinforcing materials. It has also been used.

As a method for obtaining a PVA-based fiber having a high strength and a high elastic modulus, JP-A-59-100710 applying the concept of gel spinning and ultra-drawing of high molecular weight polyethylene (for example, JP-A-60-194109) is applied.
Japanese Patent Application Laid-Open Nos. Sho 59-130314 and 61-108711 are known. In each of these methods, the solvent is extracted and stretched using methanol having a high solvent extraction rate, but satisfactory strength has not yet been obtained.

On the other hand, as disclosed in JP-A-62-149909 and JP-A-62-149910, a method of coagulating a PVA aqueous solution containing boric acid with an alkaline aqueous solution by dry-wet spinning is also known, but gelling does not occur only by cooling. Therefore, it is difficult to obtain a uniform gel, and it is difficult to obtain a high-strength fiber due to swelling between single yarns due to water swelling.

In order to obtain a PVA-based fiber having a high strength and a high elastic modulus, it must be drawn at a high magnification to have a structure of a highly oriented crystal. For this purpose, it is necessary to draw near the melting point of PVA. However, the melting point and the decomposition temperature of PVA are almost the same, so that the PVA is decomposed in the stretching process, and the strength tends to be reduced. The present inventors focused on the suppression of PVA decomposition during stretching and made various studies on the stretching deformation degree Draw Rate. For PVA fibers, the stretching deformation rate D
There is no description about raw rate so far.

(Problems to be Solved by the Invention) In view of the above background, the present inventors intend to provide a technique capable of suppressing the decomposition of PVA and performing dry heat drawing at a high magnification.

(Means for Solving the Problems) That is, the present invention provides a method for producing a spinning yarn obtained from a solution containing a PVA-based polymer having an average degree of polymerization of 1500 or more by a conventional method, using a method having a non-contact hollow heater between rollers. When stretching, 20
Using the heater in air at 0 ° C. or more and stretching at one or more stages at a stretching deformation rate (DR) satisfying the following formula,
A method for drawing PVA-based fibers, wherein the total drawing ratio is at least 16 times.

DRn = (HDn−1) × Vn / Ln (0.1 ≦ DRn ≦ 5) (1) 0.028 (Tn−180) −1.3 ≦ DRn ≦ 0.028 (Tn−180) +1.3 (200 ≦ Tn ≦ 280) (2) ) It is about.

 Hereinafter, the contents of the present invention will be described in more detail.

In general, in order to increase the fiber strength, it is necessary to increase the orientation and crystallization of the molecular weight, and therefore, high draw ratio is required.

The PVA-based polymer referred to in the present invention is a linear polymer having an average degree of polymerization of 1500 or more as determined by a viscosity method in a 30 ° C. aqueous solution, a degree of saponification of 99 mol% or more, and a low degree of branching. . Higher strength and higher modulus fibers are easier to obtain as the average degree of polymerization of PVA is higher, preferably 4,000 or more, more preferably 1,000.
0 or more. The higher the degree of polymerization, the smaller the number of molecular chain ends that are liable to become defective, and the more tie molecules that connect the crystals, the more likely it is to become a high-strength modulus fiber.

The saponification degree of PVA is 99% or more, and if it is less than 99%, the disorder of the molecular chain is too large, crystallization does not proceed, the melting point is lowered, the heat resistance is lowered, and a high-strength high-modulus fiber cannot be obtained. The PVA may contain 5% by weight or less of additives such as boric acid, a pigment, an ultraviolet absorber, and a surfactant.

Examples of the solvent for the PVA-based polymer include polyhydric alcohols such as ethylene glycol, trimethylene glycol, diethylene glycol, and glycerin, and a mixed solvent thereof with water or dimethyl sulfoxide, dimethylformamide, diethylene triamine, and a mixed solvent thereof with water. Either solvent may be used, but a solvent which gels upon cooling is preferable. In this case, since rapid cooling gelation is possible, it is convenient to easily form a uniform gel such as amorphization, entanglement fixation, and delay in solvent extraction rate.

Any spinning method may be used, and any of a wet method, a dry method, and a dry-wet method may be used, and a dry-wet gel spinning method is preferred.

The coagulation bath may be of any type, for example, alcohols such as methanol and ethanol, acetone and ether, alkali aqueous solution, sodium sulfate aqueous solution and a mixture thereof.

Although wet stretching may or may not be performed, it is preferable that stretching is performed three times or more during the steps up to drying. The reason for the draw ratio of 3 times or more is that the degree of crystallinity is reduced, the intermolecular hydrogen bonds are weakened, and the molecular chains are easily moved so that the dry heat drawing in the final step can be performed at a high draw ratio. It is to reduce sticking.

The extraction of the solvent of the PVA-based polymer may be performed with alcohol, acetone, water or the like, but is preferably performed with lower alcohol such as ethanol or ethanol.

After that it has to be dried, but its temperature is 130
70 ° C. or more, preferably 70 to 100 ° C. When the temperature exceeds 130 ° C., crystallization increases, and it is difficult to increase the magnification in subsequent stretching.

In the present invention, the film must be finally stretched at a high temperature at a high magnification. In the case of a contact type heater, a non-contact type heater is preferred because the fibers are easily melted or damaged. The maximum measured temperature of the heater is
Must be in the range 200-280 ° C. If the temperature is lower than 200 ° C., a fiber having a high strength and a high elastic modulus is difficult to obtain because the draw ratio is lowered and the orientation crystallization does not proceed. On the other hand, if the temperature is higher than 300 ° C., the fibers are undesirably melted or decomposed by oxidation. Preferably 220
In the range of ~ 260 ° C.

Next, the drawing deformation rate draw rate (DR) will be described. When the DR at the time of the n-th stretching, that is, DRn is theoretically obtained, the following expression is finally satisfied.

DRn = (Vn _{+ 1} −Vn) / Lr = (Vn _{+ 1} / Vn−1) × Vn / Ln = (HDn−1) × Vn / Ln (0.1 ≦ DRn ≦ 5) (1) Experimentally high When the stretching conditions of magnification stretching and low resolution were determined, it was found that the formula (2) was established between DRn and the nth heater temperature Tn.

0.028 (Tn-180) -1.3 ≤ DRn ≤ 0.028 (Tn-180) + 1.3 (200 ≤ Tn ≤ 280) (2) If DR is less than 0.1min- ¹ , the feed speed is slower than the heater length and stays in the heater. As the time increases, the decomposition of the polymer proceeds. If the DR exceeds 5 min ^-1 , the feed rate is too high with respect to the heater length, so that the total draw ratio is low, and it is difficult to produce a high-strength high-modulus fiber. When the heater temperature is as high as 250 ° C. or higher, the larger the DR, the smaller the decomposition. The preferred range of DR in this case is 0.2 to 2 min ^-1 . First
The relationship of the equation (2) is shown in FIG. In the present invention, stretching must be performed in the range of the hatched portion, which is a condition necessary for suppressing decomposition of PVA and stretching at a high tension and a high magnification to obtain a final high strength and high elasticity fiber.

The stretching tension is comparable to the strength at high temperature, and the higher the tension, the higher the strength. When the stretching temperature is high, the stretching ratio increases, but the tension tends to be 1.5 g / d or less, resulting in a decrease in strength. On the other hand, the total stretching ratio is 16 times or more, preferably 20 times or more. Here, the total draw ratio means a value obtained by multiplying a wet draw ratio at the time of spinning and a hot draw ratio of less than 200 ° C., and further multiplying the result by a hot draw ratio at 200 ° C. or more. If it is less than 16 times, the orientation of the molecules is insufficient and it is difficult to obtain high strength.

Therefore, the feature of the present invention is that the stretching deformation rate is such that a relatively high degree of polymerization of PVA-based fibers can be reduced in decomposition, high in tension and high in magnification.
The stretching is performed at the DR and the heater temperature T, whereby a fiber having a yarn strength of 17 g / d or more and a yarn elasticity of 450 g / d or more can be easily obtained.

Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to Examples.

Example 1 and Comparative Example 1 5 dry PVAs having an average polymerization degree of 17,000 and a saponification degree of 99.4 mol%
It was dissolved in glycerin at 180 ° C. so as to become a weight% solution.

Then, the solution was discharged at 190 ° C. from a nozzle having a hole diameter of 0.2 mm and 20 holes and dropped into a coagulation bath 25 mm below. The coagulation bath composition was methanol / glycerin = 8/2 weight ratio and the temperature was 0 ° C. After the gel fiber was obtained by cooling in a coagulation bath, it was wet-drawn four times in methanol at 40 ° C., glycerin was almost completely extracted with methanol, dried with hot air at 100 ° C., and wound around a bobbin.

When the obtained spun yarn is stretched in one step, a 3 m non-contact radiant heater is used, a feed speed is 1.2 m / min, a stretching ratio is 5.0 times at a heater maximum temperature of 260 ° C. (total stretching ratio is 20.0 mm).
Times) and stretched. The DR at this time was 1.60, and the stretching tension was as high as 3.2 g / d. The obtained stretched multifilament had a strength of 22.4 g / d and an elasticity modulus of 590 g / d, and had characteristics not found in the past. The obtained drawn yarn is 140 ° C
The polymer was dissolved in hot water and the degree of polymerization was determined by measuring the viscosity.

As Comparative Example 1, the same stretching was performed at a feed speed of 0.4 m / min and a maximum heater temperature of 260 ° C., but the total stretching ratio was 17.6 times, the DR was 0.45, the fiber was colored yellow, and the polymerization degree was 37.
%, And the strength was as low as 16.8 g / d.

Example 2 and Comparative Example 2 PVA having an average degree of polymerization of 7000 and a degree of saponification of 99.9 mol% was dissolved in dimethyl sulfoxide at 100 ° C. so as to form a 10% by weight solution.

Next, the solution was heated to 85 ° C. and discharged from a nozzle having 40 holes. The coagulation bath composition was methanol / dimethyl sulfoxide = 6/4 weight ratio, and the temperature was 10 ° C. The film was stretched 5 times in methanol at 40 ° C, extracted with a solvent, dried with hot air at 100 ° C, and wound around a bobbin.

When the obtained spun yarn was stretched in one step, it was stretched using a radiant heater of 3 m, at a feed speed of 2.0 m / min, at a maximum heater temperature of 250 ° C., and at a draw ratio of 3.9 times (total draw ratio of 19.5 times). . DR at this time is 1.93 min ^-1 and the stretching tension is
It was 2.8 g / d. The obtained drawn fiber showed a high value of 19.7 g / d in strength and 505 g / d in elastic modulus.

As Comparative Example 2, the feed speed in Example 2 was 6 m
/ min and stretch ratio 3.5 times (total stretch ratio 17.5 times)
The DR is 3.75 min ^-1 and the obtained fiber strength is 16.2 g
/ d, the modulus decreased to 410 g / d.

Example 3 13 dry PVAs having an average polymerization degree of 3300 and a saponification degree of 99.5 mol%
It was dissolved in water to give a weight%. At that time, 3.5 against PVA
Boric acid was added to give a weight percent.

Then, the solution was heated to 110 ° C. and discharged from a nozzle having 1000 holes into a coagulation bath maintained at 70 ° C. with a composition of NaOH 10 g / and Na ₂ SO ₄ 300 g /, and wet spinning was performed. Next, water washing was performed after neutralization with a dilute H ₂ SO ₄ aqueous solution, and during this time, the film was stretched at a total wet stretching ratio of 5.0 times. In stretching the raw yarn dried by hot air at 120 ° C and wound on a bobbin in one stage, the feed rate was 18m / min in a 25m hot air furnace, and the draw ratio was 4.9 at the furnace maximum temperature of 244 ° C.
(Total stretching ratio 24.5 times) and stretched. DR at this time is 2.
It was 81min ^-1 . The obtained drawn fiber had a strength of 18.4 g / d and an elastic modulus of 470 g / d.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the heater temperature Tn under the stretching conditions in the present invention.
And the drawing deformation speed DRn, wherein a hatched area indicates a preferable condition range.

Claims (1)

(57) [Claims] When a spinning yarn obtained by a conventional method from a solution containing a polyvinyl alcohol-based polymer having an average degree of polymerization of 1500 or more is drawn by a method having a non-contact hollow heater between rollers, it is heated to 200 ° C. or more. Using the heater in air and at a stretch deformation rate (DR) that satisfies the following equation:
A method for drawing polyvinyl alcohol-based fibers, wherein the drawing is carried out in two or more steps and the total drawing ratio is at least 16 times. DRn = (HDn−1) × Vn / Ln (0.1 ≦ DRn ≦ 5) (1) 0.028 (Tn−180) −1.3 ≦ DRn ≦ 0.028 (Tn−180) +1.3 (200 ≦ Tn ≦ 280)
(2)