JPH05222607A - Production of polyvinyl alcohol-based fiber excellent in properties - Google Patents

Abstract

PURPOSE:To produce the subject polyvinyl alcohol-based fiber excellent in over all characteristics such as strength, Young's modulus, hot water resistance and durability by using low-cost water as the main solvent of the stock spinning solution of polyvinyl alcohol. CONSTITUTION:In wet spinning or dry wet spinning a spinning solution prepared by dissolving a polyvinyl alcohol-based polymer in water, the above-mentioned spinning is carried out by using a coagulation bath composed of an organic solvent such as methanol as a typical example while controlling the residual solution ratio in the resultant coagulated yarn at the first godet roller unit or at the first guide unit to 60 to 110wt.%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wet or dry-wet spinning method used for producing a polyvinyl alcohol (hereinafter abbreviated as PVA) fiber having excellent performance, and further using an aqueous solvent. The present invention relates to a method for spinning a spinning dope.

[0002]

2. Description of the Related Art PVA fibers have higher strength and elastic modulus than polyamide, polyester and polyacrylonitrile fibers, and play an important role not only as fibers for industrial materials but also as various reinforcing fibers such as rubber, cement and plastics. At the end, with the rise of high-tech in the world,
There is a demand for higher performance PVA fibers.

In order to meet such requirements, high performance P
As a method for producing a VA fiber, a method has been proposed in which the concept of gel spinning-ultradrawing of ultrahigh molecular weight polyethylene is applied to a PVA system (for example, JP-A-59-130314). Also, instead of gel spinning, high degree of polymerization PV
It is also possible to perform coagulation spinning by wet or dry-wet spinning using A and an organic solvent in JP-A-59-100170, JP-A-60-126313 and JP-A-63-9.
It is known from Japanese Patent No. 9315. Further, it is also known from Japanese Patent Laid-Open No. 1-266212 that a spinning solution prepared by adding boric acid to an aqueous solvent is wet-spun in a hot aqueous solution of an alkaline dehydrating salt.

However, when water, which is a solvent having industrially important properties of low price and safety, is mainly used as a stock solution of PVA, strength, hot water resistance, and durability are combined. It is difficult to obtain PVA fibers with excellent performance. Therefore, the inventors of the present invention have sought to find out why a high-performance PVA fiber cannot be obtained by spinning mainly using a conventionally known aqueous solvent, and one of the prominent causes thereof is the solidification extraction process of the spinning dope. I found that.

That is, as a result of detailed analysis of the solidification extraction process when the PVA-based spinning stock solution is subjected to wet or dry-wet spinning, when the conventionally known stock solution solvent is water-based and the solidification bath is also water-based, the stock solution solvent is discharged from the nozzle. It has been found that the fibers are not extracted in a circular shape in the fiber cross section because they are rapidly extracted later and between the first godet rollers and cause solidification unevenness in the fiber radial direction.

[0006]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a wet or dry-wet spinning method using a cheap and safe water-based solvent as a stock solution solvent to eliminate solidification spots on the fiber surface and the fiber center. Thus, the pursuit of obtaining a high-performance PVA fiber.

[0007]

Means for Solving the Problems That is, the present invention is to dissolve a PVA-based polymer having a viscosity average degree of polymerization of 1500 or more in a solvent mainly composed of water, and to prepare the obtained spinning dope in a solidification bath in a wet or dry condition. In the case of the spinning process, a solidifying bath mainly composed of an organic solvent is used as the solidifying bath, and the solidification of the first godet roller part or the first guide part (hereinafter, both are representatively referred to as the first godet roller part) A method for producing a PVA-based fiber having excellent performance, which is characterized in that the residual liquid content of the yarn is 60 to 110%.

The PVA used in the present invention cannot obtain a high-performance PVA-based fiber which is the object of the present invention unless the average degree of polymerization determined by a viscosity method in an aqueous solution at 30 ° C. is 1500 or more. Particularly, the viscosity average degree of polymerization is preferably 3000 or more, and the use of PVA of 8000 or more is preferable because the effect of the present invention becomes more remarkable.

The degree of saponification of PVA used is not particularly limited, but 97 mol% or more is preferable from the viewpoint of performance and process passability, and 98.5 mol or more is more preferable, and 9 or more is preferable.
It is more preferably 9.5 mol% or more. The PVA used may also be a monomer having another vinyl group, such as ethylene, itaconic acid or vinylpyrrolidone.
It may be a PVA-based polymer copolymerized at a ratio of 0 mol% or less, preferably 2 mol% or less.

In the present invention, water is mainly used as a solvent for spinning dope which dissolves PVA. Water is cheaper than other organic solvents and has high safety (health and flammability), and water is the most preferable solvent from an industrial viewpoint.

The solubility of water alone is not necessarily the best, and phase separation during solidification is easy. Therefore, in order to improve the solubility of PVA, rhodanate salts (sodium rhodanate, potassium rhodanate, etc.) and metal halide salts (chloride) are used. When adding solubilizers such as zinc, calcium chloride, lithium chloride, lithium bromide), inorganic acids (sulfuric acid, hydrochloric acid, nitric acid, etc.), organic solvents (dimethyl sulfoxide, dimethylformamide, glycerin, ethylene glycol, etc.) to water It may be preferable. The preferred amount of addition greatly varies depending on the type of solubilizing agent, but it is not preferable to add more than water since it is expensive. The amount of water added is preferably 80% or less, more preferably 60% or less.

The concentration of PVA in the spinning dope is determined by the degree of polymerization of PVA,
It depends on the type of the solubilizing agent, the discharge temperature of the undiluted solution during spinning, etc., but is usually 2 to 40% by weight, preferably 3 to 25% by weight
And In particular, the present invention aims to obtain a high-performance PVA fiber, and for this purpose, the PVA concentration is lowered within a range in which process passability such as single yarn breakage, yarn unevenness, and single-yarn hardening is allowed during spinning. Or increase the temperature of the stock solution during spinning,
In many cases, it is preferable to discharge from the nozzle in a state where the stock solution viscosity is low.

In addition to PVA, water and a dissolution aid, various additives may be added to the spinning dope depending on the purpose.
For example, an antioxidant, an ultraviolet absorber, a surfactant, a cross-linking agent, a coloring agent, an antifreezing agent, etc. may be added. In particular, in the present invention, as described below, it is preferable to lower the temperature of the solidification bath (synonymous with the conventional coagulation bath) than that of the conventional water-based spinning. If the dissolution aid is not added to the undiluted solution, the undiluted solution may freeze. It is preferable to add an inhibitor. Further, it is preferable to add an anionic surfactant such as a sulfate ester or a sulfonate to the stock solution because the spinnability of the spinning solution may be improved.

As the spinning method of the present invention, a wet spinning method or a dry wet spinning method is used. In the dry spinning method, a yarn without sticking cannot be stably produced unless the PVA concentration is extremely high, for example, 50%. If the concentration of PVA is high, a high-performance (particularly high-strength) fiber cannot be obtained because the PVA molecular chain is entangled severely and the drawability is poor.
In wet or dry-wet spinning, since it is solidified in a solidifying bath, fibers free from sticking can be obtained even at a lower concentration than dry spinning. The wet spinning referred to in the present invention is a spinning method in which the nozzle holes are in contact with the solidifying bath, and has the advantage that the equipment can be made compact because the nozzle hole pitch can be made small.
On the other hand, the dry-wet spinning referred to in the present invention is a spinning method in which an inert gas layer such as air is interposed between the nozzle hole and the solidifying bath, and the so-called gel spinning method in most cases involves air. In the dry-wet spinning method. Since air is present between the nozzle and the solidifying bath in the dry-wet spinning method, there is an advantage that when the temperature difference between the undiluted solution and the solidifying bath is large, it is less likely to be affected by the mutual temperature. Wet and dry should be used according to the purpose.

As the solidifying bath used in the present invention, an organic solvent having solidifying ability for PVA is mainly used. When a dehydrating salt aqueous solution such as a sodium sulfate aqueous solution which is a conventionally known solidifying bath when an aqueous solution is used as the stock solution solvent is used as the solidifying bath,
With the state of the art, the residual liquid content of the solidified yarn, which will be described later, becomes too small to be within the range of the present invention. The organic solvent having a solidifying ability is not particularly limited as long as it is soluble in water and has a solidifying ability in PVA, such as alcohols such as methanol and ethanol, ketones such as acetone and methyl ethyl ketone. Methanol is preferable in terms of cost. Further, the solidifying bath may contain water as a stock solution solvent, a dissolution aid, and the like. Rather, it is preferable to include water or a dissolution aid in the solidification bath in order to control the solidification ability and reduce the cost of collecting the stock solution solvent.

In the present invention, solidification is so-called "gelation" in which the solid solution is solidified only by cooling without changing the composition.
Also, the term "solidification" is used to include both so-called "coagulation" in which the solid solution does not solidify only by cooling, but the solidifying bath solution permeates the stock solution and solidifies when the composition changes.

In the present invention, the solidifying bath temperature is the first temperature described below.
This is an important factor in controlling the residual liquid content of the solidified yarn in the godet roller portion, and the residual liquid content must be set within a predetermined range. It is usually 15 ° C. or lower, preferably 5 ° C. or lower, and more preferably −20 to 0 ° C.

Next, one of the most important points of the present invention is to set the residual liquid content of the solidified yarn in the first godet roller portion to 60 to 110%. The basic idea of the present invention is to suppress the extraction of the stock solution solvent in the solidification bath as much as possible within the range in which the solidified yarn can pass through the subsequent step.
The structure of the solidified yarn is made as uniform as possible, and as an index thereof, attention is paid to the residual liquid content of the solidified yarn in the first godet roller portion. The first term referred to in the present invention
The residual liquid content of the solidified yarn in the godet roller part was determined as follows. First, the solidified yarn at the first godet roller portion is sampled, the solidifying liquid adhering to the surface is wiped off, and the solidified yarn weight Ag is obtained. Next, the pure amount Bg of PVA in the solidified yarn is determined by Soxhlet extraction. P in the spinning dope
The weight ratio C of the solvent (including the dissolution aid) to VA is determined. From these, the residual liquid content of the solidified yarn in the first godet roller portion can be determined by 100 × (AB) / B × C (%).

The residual liquid content of the solidified yarn is determined by the composition of the stock solution including the solubilizing agent, the temperature of the stock solution, the composition of the solidifying bath, the temperature of the solidifying bath, and the residence time of the solidifying bath (solidifying bath length and first godet roller speed). However, in the present invention, the above factors must be controlled so that they fall within the range of 60 to 110%. If the residual liquid content is less than 60%, it means that the amount of the stock solution solvent was rapidly extracted in the solidification bath up to the first godet roller, causing solidification unevenness, and the cross section of the obtained fiber is likely to be flat. , High-performance fiber cannot be obtained. When dimethyl sulfoxide is used as the stock solution solvent,
In contrast to similar solidifying bath conditions, high performance fibers can be obtained even with a residual liquid content of 50%. It is speculated that this is related to the fact that the aqueous solvent is inferior in solubility of PVA as compared with dimethylsulfoxide. In the present invention, if the residual liquid content of the solidified yarn exceeds 110%, solidification tends to be insufficient because of insufficient solidification and should be avoided. As a result of a basic analysis of the solidification behavior, in the liquid yarn immediately after the nozzle discharge, the stock solution solvent does not interdiffuse into the solidification bath, but the solidification bath does not interdiffuse into the liquid yarn. It was found that the liquid thread was solidified and then the stock solution solvent was diffused and extracted into the solidification bath. Therefore, the residual liquid content of the solidified yarn is temporarily 10
It was recognized that it is possible to exceed 0% and reach 130%. The residual liquid content of the solidified yarn is increased by increasing the stock solution solvent content of the solidifying bath, lowering the solidifying bath temperature, or shortening the solidifying bath residence time, but at the same time, it is likely to result in poor solidification,
Easy to wear. However, lowering the solidification bath temperature is effective as a method for increasing the residual liquid content of the solidified yarn without causing poor solidification.

The solidified yarn taken up by the first godet roller is made into fibers according to the following steps. That is, by dipping it in a bath having almost the same composition and temperature as the solidifying bath to reinforce the solidified state, and then dipping it in an organic solvent bath having stronger desolvent extraction ability, the undiluted solvent (dissolution aid) (Including the agent) and the like are extracted, washed and dried. It is preferable to carry out wet stretching in one step or more preferably in multiple steps in the air or in the liquid in each step from immediately after the first godet roller to before drying, because sticking during drying can be prevented. Usually, the total wet stretch ratio is 2 to 6 times, hard adhesion, performance,
In terms of fluff, it is more preferably 3 to 5 times. The drying temperature is preferably 40 to 150 ° C. in terms of drying efficiency and performance. Further, multi-stage drying in which the drying temperature is gradually increased from low temperature to high temperature is preferable.

After drying, the obtained raw yarn is subjected to hot drawing at a high temperature to orient and crystallize the PVA chains to obtain a high performance PVA fiber. The hot stretching temperature is 140 to 260 ° C. Preferably, a multi-stage drawing at 150 to 200 ° C. and then 210 to 265 ° C. is preferable. The final stretching temperature is more preferably 225 to 255 ° C. It is preferable to stretch at a high temperature as the degree of polymerization of PVA increases. The total draw ratio including the wet draw ratio is 12 times or more. In the conventional water-based spinning method utilizing boric acid crosslinking, a high-strength fiber can be obtained only by high-drawing at a draw ratio of 22 times or more, but in the spinning method of the present invention, the total draw ratio is 22 times or less. Even if stretched at a low ratio, the PVA chains are sufficiently oriented and crystallized, and high-performance PVA fibers can be obtained. This is presumed to be because the conventional method has a part where the molecular chain is slippery and effective drawing was not performed, whereas in the method of the present invention, the entire fiber is uniform and slippage is unlikely to occur, and effective drawing is effective. ing.

The reason why the sundling portion of the solidified yarn for measuring the residual liquid content in the present invention is the godet roller portion is as follows. The yarn discharged from the nozzle has a bath draft of less than 1, that is, an inverse draft in the solidifying bath up to the first godet roller, as described above, and the stock solution solvent is extracted under low tension, so that the yarn is easily extracted. On the other hand, after the first godet roller, constant length or wet stretching is performed, and the solvent extraction is several times higher than that before the godet roller.
The solvent is extracted with a tension of several tens of times. It is presumed that this difference in tension has a great influence on the structure formation, that solvent extraction in a low tension state is suppressed as compared with the conventional method, and that uniform solidified yarns are important for the subsequent fiber structure formation. It is presumed that when the solvent extraction in the low tension state is suppressed to form a uniform solidified yarn, the molecular chain slip during the hot drawing is suppressed, and sufficient performance can be obtained even at a low draw ratio.

As described above, by controlling the liquid-containing residual ratio of the solidified yarn in the first godet roller part in the spinning stock solution of the aqueous solvent within a specific range, a uniform raw fiber can be obtained, and the total draw ratio is obtained. It was possible to realize high-performance PVA fibers even when the ratio was 22 times or less. The first godet roller or the first guide referred to in the present invention is a roller or guide with which the spun raw yarn discharged from the nozzle first comes into substantial contact.

[0024]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Example 1 P having a viscosity average degree of polymerization of 3900 and a saponification degree of 99.9 mol%
VA and water were added, and the mixture was mixed and dissolved at 100 ° C. with stirring to prepare a spinning dope having a PVA concentration of 13%. This spinning dope was placed with a hole diameter of 0.18 mm and a space of 8 mm from a nozzle having 100 holes, and the weight ratio of methanol to water at −15 ° C. was 80.
/ 20 was extruded into a solidifying bath to perform dry-wet spinning. The depth of the solidification bath was 50 cm, and the speed of the first godet roller was 4.0 m / min. At this time, the residual liquid content of the solidified yarn in the first godet roller portion was 95%.

The obtained solidified yarn was dipped in the same solidifying bath for a fixed length of 1 minute and then dipped in a methanol bath at 15 ° C. for 30 seconds to obtain 4
Wet stretching was carried out four times in a 0 ° C. methanol bath, and it was immersed in a 20 ° C. methanol bath for 5 minutes to extract the solvent, followed by hot air drying at 70 ° C. and winding. Then, the dried raw yarn is passed through the first furnace 190.
In a hot air oven at 240 ° C. in a second oven at 240 ° C., so that the total draw ratio was 17 times. The obtained yarn strength is 17 g / d.
The hot water cutoff temperature was excellent at 125 ° C.

The stock solution solvent was dimethyl sulfoxide, which is more expensive and dangerous than water, and had a polymer concentration of 11%, and the solidification bath was methanol / dimethyl sulfoxide at 70 ° C. = 70.
Stretching was performed in the same manner as above except that the solidifying bath was / 30.

Stock solution 25 times / 10 cm in two 1500 denier yarns where the solvent is water and dimethyl sulfoxide.
Twisted 25 times / 10 times with 10 cm top twist 1500 /
A 1 × 3 tire cord was used and embedded in rubber to obtain a belt. This belt was subjected to bending fatigue at 25 ° C and 100 ° C, and the tire cord was taken out from the belt after the bending fatigue,
The strength of the tire cord after fatigue was measured, and the strength retention ratio to the strength of the cord before fatigue was determined. It was found that both of the two types of yarns showed similar tenacity retention rates at 25 ° C. and 100 ° C., and that water having a low stock solution solvent exhibited fatigue properties similar to expensive dimethyl sulfoxide.

Comparative Example 1 The same spinning stock solution and nozzle as in Example 1 were used, the air gap length was the same, and the mixture was extruded into a solidifying bath consisting of an aqueous solution of 420 g / l of Glauber's salt at 45 ° C. to carry out dry-wet spinning. At this time, the residual liquid content of the solidified yarn in the first godet roller portion was 25.
%Met.

The obtained solidified yarn is dipped in the same solidifying bath for 1 minute, stretched by a wet heat of 4 times in a saturated aqueous solution of Glauber's salt at 90 ° C., further dipped in the same bath for 15 seconds and subjected to wet heat treatment, and then at 10 ° C.
It was washed with running water and dried in a hot air dryer having a temperature gradient of 50 to 100 ° C. Then, the obtained dry raw yarn was drawn in the same manner as in Example 1. The total draw ratio was only 12 times. The obtained yarn strength was 10 g / d, which was lower than that of Example 1.

Comparative Example 2 Spin-drawing was carried out in the same manner as in Example 1 except that the solidifying bath was a 100% solution of methanol at 20 ° C. At this time, the residual liquid content of the solidified yarn in the first godet roller portion was 50%. Although the solidified yarn in the solidifying bath was almost transparent in Example 1, it was cloudy and whitish. The strength of the obtained yarn was 11 g / d, which was lower than that of Example 1.

Comparative Example 3 Spinning was attempted in the same manner as in Example 1 except that the solidification bath was methanol / water = 60/40 at -15 ° C. At this time, the transparency of the solidified yarn was very good and was close to that of the dimethylsulfoxide system, but it was difficult to spin the solidified yarn around the first godet roller, and normal spinning was difficult. The liquid content was as high as 130%.

Example 2 PVA having a viscosity average degree of polymerization of 8700 and a saponification degree of 99.7 mol%, water and sodium lauryl sulfate (hereinafter abbreviated as SLS) were added and mixed at 100 ° C. with stirring to dissolve, and the PVA concentration was 75. %, SLS was 0.05% to prepare a spinning dope. This stock solution was subjected to dry-wet spinning in the same manner as in Example 1 in a solidifying bath consisting of methanol / water = 89/11 at -12 ° C.
It was confirmed that the addition of SLS increased the length of the yarn from the nozzle as compared with Example 1 and improved the spinnability. At this time, the residual liquid content of the solidified yarn in the first godet roller portion was 90.
%Met. The obtained solidified yarn was subjected to first stage methanol extraction, wet drawing, second stage methanol extraction and drying in the same manner as in Example 1. The obtained dry raw yarn is put in the first furnace at 200 ° C. and the second furnace
It was drawn in a hot air oven at 245 ° C. so that the total draw ratio was 18 times.

The yarn strength of the obtained drawn yarn is 19 g / d.
The hot water cutoff temperature was excellent at 135 ° C. The belt bending fatigue resistance was superior to that of the yarn of Example 1.

Example 3 P having a viscosity average polymerization degree of 4500 and a saponification degree of 99.8 mol%
VA was dissolved in a mixed aqueous solution of sodium thiocyanate / water = 1/2 at 80 ° C. with stirring. This spinning solution was added with a pore size of 0.1
Wet spinning was carried out by extruding from a nozzle having a diameter of 8 mm and a number of holes of 100 into a solidifying bath consisting of 100% methanol at -25 ° C. The depth of the solidification bath was 80 cm, and the speed of the first godet roller was 3.0 m / min. At this time, the residual liquid content of the solidified yarn in the first godet roller portion was 105%.

The obtained solidified yarn was dipped in the same solidifying bath for a fixed length of 2 minutes and then dipped in a methanol bath at 10 ° C. for 1 minute to obtain 40
Wet stretching was carried out 4 times in a methanol bath at ℃, immersed in a methanol bath at 20 ℃ for 8 minutes to extract the solvent, dried with hot air at 70 ℃ and wound up. Then, the dried raw yarn is passed through the first furnace 190.
C., in a hot air oven at 245.degree. C. in the second furnace so that the total draw ratio was 18 times. The obtained yarn has a yarn strength of 18 g.
/ D. The hot water cutoff temperature and belt bending fatigue resistance were also excellent.

[0037]

EFFECTS OF THE INVENTION When a spinning dope containing PVA dissolved in a water-based solvent is wet- or dry-wet, the conventional spinning method does not properly extract the solvent in the solidifying bath. It became a solidified yarn having a highly dense and dense structure such as phase separation and had large irregularities, and a fiber excellent in overall performance such as strength, hot water resistance and durability could not be obtained. Further, since the amount of solvent extraction is too small, problems such as winding on a roller and hard adhesion during drying tend to occur, and it was unavoidable to use extremely mild drying conditions. On the other hand, in the present invention,
By controlling the composition of the undiluted solution, the composition of the solidifying bath, the temperature of the solidifying bath, and the residence time in the solidifying bath from the nozzle to the first godet roller, the residual liquid content of the solidified yarn is set within a predetermined range,
By extracting, wet drawing, drying and dry heat drawing the obtained uniformly solidified yarn, it is possible to produce fibers having excellent overall performance. Therefore, according to the present invention, PVA fibers having excellent overall performance can be obtained at low cost, so that the cost performance is superior to other high-strength fibers such as para-amide fibers and conventional PVA fibers, and tires for automobiles and high-performance hoses. It can be widely and effectively used in the field of rubber materials such as, and the field of reinforcement such as FRC and FRP.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoru Kobayashi 1621 Sakata, Kurashiki City, Okayama Prefecture Kuraray Co., Ltd.

Claims (1)

[Claims] 1. A polyvinyl alcohol-based polymer having a viscosity average degree of polymerization of 1500 or more is dissolved in a solvent containing water as a main component, and the obtained spinning dope is wet- or dry-wet spun in a solidifying bath. A polyvinyl alcohol fiber excellent in performance, characterized by using a solidifying bath mainly composed of a solvent and having a residual liquid content of the solidified yarn of the first godet roller part or the first guide part of 60 to 110%. Manufacturing method.