JPH05263312A - Production of polyvinyl alcoholic fiber excellent in strength - Google Patents

Abstract

PURPOSE:To provide a method for stably producing polyvinyl alcoholic fiber having high strength even at a high speed. CONSTITUTION:This method for producing polyvinyl alcoholic(PVA) fiber is to wet spin a PVA spinning solution under conditions of 0.5T B<=T A<=10 T B when the residence time in a solidifying bath is T B and the residence time in the air from the upper part of the solidifying bath to the first godet roller is T A and regulate the solvent residual ratio of solidified yarn in the first godet roller part to 25-80% in wet spinning an organic solvent-based spinning solution of the PVA having a high polymerization degree into the organic solvent-based solidifying bath at a high speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wet spinning method mainly used for producing a polyvinyl alcohol (hereinafter abbreviated as PVA) fiber having excellent strength.

[0002]

2. Description of the Related Art Among general-purpose fibers, PVA-based fibers have higher strength and elastic modulus than polyamide, polyester and polyacrylonitrile-based fibers, so that they are not only used for industrial materials such as fishing nets and ropes, but also for cement, It is also used for reinforcing materials such as plastics. On the other hand, with the advancement of society, there is an increasing demand for higher strength of PVA-based fibers.

In order to meet such demands, as a method for producing a higher strength PVA-based fiber, JP-A-59-130314, which applies the concept of gel spinning-ultra-drawing of ultra-high molecular weight polyethylene to PVA, etc. Japanese Patent Laid-Open No. Sho 59-59, in which PVA with a high degree of polymerization is used and coagulated spinning is performed by a wet or dry-wet method using an organic solvent.
-100710, JP-A-60-126312, JP-A-63-99315 and the like. In the present invention, gel spinning means a case where the spinning dope is solidified only by cooling without accompanying a composition change, and coagulating spinning is that the spinning dope does not solidify only by cooling, and the solidification bath permeates the spinning dope. It refers to the case where the composition changes and solidifies.

[0004] However, gel spinning is extremely easy to settle when it is spun in a large number of holes for industrial purposes, and coagulated spinning is advantageous for industrial purposes, but it has been adopted in conventional known techniques. In the case of coagulation spinning, when PVA having a high degree of polymerization is used, it is not always possible to obtain PVA fibers having a strength as high as gel spinning. We will investigate various causes of this,
One of the prominent causes was found to be the solidification extraction process of the spinning dope, and the inventors previously proposed Japanese Patent Application No. 3-267203 as a means for solving this. That is, it has been found that it is important to increase the solvent residual rate of the solidified yarn in the first godet roller portion to 25 to 80% of the amount of the stock solution solvent.

On the other hand, gel spinning and coagulation spinning are classified into solution spinning from the viewpoint of the solidification mechanism as described above, but from the viewpoint of the spinning form, an inert gas such as air is present between the nozzle surface and the solidification bath. There are a dry-wet spinning method in which a layer is interposed and a wet spinning method in which the nozzle surface is brought into direct contact with the solidifying bath. There are a falling wet spinning method that discharges more vertically downward, and a horizontal wet spinning method that discharges the stock solution horizontally from the nozzle surface. .. Therefore, when the spinning method proposed in JP-A-3-267203 was applied to the upstream wet spinning, it was found that the process passability and the fiber performance became unstable especially when the first godet roller speed was high. ..

[0006]

Accordingly, the present invention is a PVA in which both the stock solution solvent and the coagulation bath use an organic solvent system.
When the coagulating spinning of the system fibers is carried out at a high speed by the flow-up wet spinning method, how to stably produce PVA fibers having a high degree of polymerization and having a high strength comparable to the gel spinning method is pursued.

[0007]

[Means for Solving the Problems] That is, according to the present invention, a spinning stock solution obtained by dissolving a PVA-based polymer having a viscosity average degree of polymerization of 1500 or more in an organic solvent is placed in a bath in an organic solvent-based solidifying bath having coagulability. In the upstream wet spinning, which extruded in a state of less than draft 1 and took the formed solidified yarn at the first godet roller speed of 10 m / min or more, the residence time of the solidified yarn in the solidifying bath was T ↓ B, the solidifying bath The atmospheric residence time from the top to the contact with the first godet roller is T ↓ A
When 0.5T ↓ B ≦ T ↓ A ≦ 10T ↓ B is satisfied, and the solvent residual rate of the solidified yarn in the first godet roller portion is set to 25 to 80% with respect to the stock solution solvent amount. This is a method for producing a characteristic PVA fiber.

The PVA polymer used in the present invention is 30
The viscosity average degree of polymerization determined by the viscosity method in an aqueous solution at ℃ is 15
00 or more. If the average degree of polymerization is less than 1500, the high-strength PVA-based fiber, which is the object of the present invention, cannot be obtained. The average degree of polymerization is more preferably 3500 or more, further preferably 7,000 or more. Particularly when the average degree of polymerization is 1500 or more, the effect of the spinning method of the present invention becomes more remarkable.

The saponification degree of the PVA-based polymer used is not particularly limited, but is preferably 98.5 mol% or more, and more preferably 99.7 mol% or more. The PVA-based polymer used is 10 mol% or less, preferably 2 mol%, of another vinyl group-containing monomer such as ethylene, itaconic acid, or vinylpyrrolidone.
It may be copolymerized in the following ratio.

As a solvent for the PVA-based polymer used in the present invention, a PVA-based polymer can be dissolved and an organic solvent having a coagulating ability, such as methanol, permeates into the PVA-based polymer.
There is no particular limitation as long as it is an organic solvent that can solidify the solution of the VA polymer, and dimethyl sulfoxide (DMS
Abbreviated as O), dimethylformamide, dimethylimidazolidinone, and other polar solvents. Also, a mixture of these solvents may be used. Among many solvents, DMSO can be dissolved at a low temperature of 80 ° C or less,
It is possible to reduce the decrease in the degree of polymerization of the VA polymer,
It is the preferred solvent.

The concentration of the PVA-based polymer in the spinning dope varies depending on the degree of polymerization of the PVA-based polymer and the type of solvent, but is usually 2 to 30% by weight, preferably 3 to 20%.
% By weight. In particular, the present invention aims to obtain a high-strength PVA fiber, and for this purpose, it is better to lower the concentration of the PVA-based polymer within the range in which single yarn breakage, yarn unevenness, single yarn adhesion and the like do not occur during spinning. preferable.

In addition to the PVA-based polymer and the solvent, various additives such as colorants such as pigments, antioxidants, ultraviolet absorbers, crosslinking agents, surfactants, acids, etc. may be added to the spinning dope. You may add the required amount of the pH adjuster and the like. Furthermore, for a solvent having a relatively high freezing temperature such as DMSO, if a PVA-based polymer is added within a range that does not coagulate even a solvent such as water or a solvent that exhibits a coagulating action such as methanol, the solidifying bath freezes the solvent. The following may also be preferable because the spinning dope does not freeze.

When the PVA-based polymer, the solvent and the additives are charged into a dissolver and, for example, DMSO is used as the solvent, the temperature is raised to 50 to 120 ° C. while stirring the mixture.
Stirring is continued for 4 to 16 hours, the PVA polymer is dissolved in a solvent, and then defoamed to prepare a spinning dope. At this time, an inert gas such as nitrogen was injected under pressure into the dissolver after the charging and before the temperature was raised, and the inert gas was repeatedly discharged under reduced pressure to replace the inert gas with the reduced pressure or the inert gas during the temperature rising dissolution or the degassing. From the viewpoint of suppressing decomposition of the PVA-based polymer, it is preferable to apply pressure to prevent the solution of the PVA-based polymer from contacting with oxygen as much as possible. As the degree of polymerization becomes higher, it is necessary to raise the melting and defoaming temperature. In this case, it is particularly important not to contact with oxygen by replacement with an inert gas.

If the bath draft (defined by the ratio of the first godet roller speed to the discharge linear velocity when the stock solution is discharged from the nozzle) is not less than 1.0, the stretchability in the subsequent step is insufficient. Therefore, it becomes difficult to obtain high-strength fibers. The bath draft is more preferably in the range of 0.1 to 0.5, further preferably 0.15 to 0.3. It is important to select the nozzle hole size so that the bath draft is suitable.

The spinning form used in the present invention is an upstream wet spinning method. In the dry-wet spinning method in which an inert gas is interposed between the nozzle surface and the solidifying bath, single yarn yarn sticking is likely to occur in the inert gas layer, and it is difficult to make the nozzle compact because the hole pitch of the nozzle must be increased. .. In the wet spinning method in which the nozzle surface is in direct contact with the solidifying bath, the solidifying bath permeates immediately after discharge from the nozzle and solidifies immediately, so that the hole pitch of the nozzle can be made small, and therefore, it can be made compact even with many holes. Among the wet spinning methods, the upstream wet spinning method is most commonly used for the production of PVA-based fibers, has a large amount of accumulated technology, and is the most industrially easy spinning method.

As the solidifying bath, an organic solvent having a coagulating ability with respect to the PVA polymer is used. When an aqueous solution of dehydrating salt such as Glauber's salt is used for the solidifying bath, the surface of the solidified yarn is dehydrated preferentially, the dehydration inside the solidified yarn is inhibited, and a non-uniform structure in the cross-sectional direction, that is, a skin-core structure, is drawn. The property becomes poor and it is not possible to obtain a high-strength PVA-based fiber. Examples of the organic solvent having a coagulability with respect to the PVA-based polymer include alcohols such as methanol and ethanol, ketones such as acetone and methyl ethyl ketone, and there is no particular limitation. From the viewpoint, methanol is preferable.

In the present invention, the stock solution solvent is added to the solidification bath at 5%.
˜70% is preferable. The content of the stock solution solvent varies depending on the type of the organic solvent used as the solidification bath and the solidification bath temperature, but if it is less than 5%, solidification will occur too rapidly immediately after being discharged from the nozzle, and a nonuniform solidified yarn is likely to be formed. .. On the other hand, when it exceeds 70%, the solidification rate is too slow, and the material tends to be hardened. The content of the stock solution solvent in the solidification bath is 10
It is more preferably 50% by weight and even more preferably 15 to 45%.

When the temperature of the solidifying bath exceeds 20 ° C., the solidified yarn is in a state of advanced phase separation, has many voids, becomes opaque and has a non-uniform structure, and it becomes difficult to obtain high strength fibers. It is more preferable that the temperature of the solidifying bath is 10 ° C. or lower, and if the temperature is 5 ° C. or lower, a solidified yarn having a transparent uniform structure can be obtained, and it is further preferable. However, if the temperature of the solidification bath is too low, the spinning dope discharged from the nozzle may freeze, so it is necessary to consider adding an antifreezing agent to the dope.

In the present invention, the solidified yarn formed in the solidifying bath is taken up at a first godet roller speed of 10 m / min or more. If it is less than 10 m / min, the production speed is low and the cost is high for industrial production.

Next, one of the points of the present invention is to set the residual solvent ratio of the solidified yarn in the first godet roller portion to 25 to 80%. The first godet roller referred to in the present invention is a solid discharged from a nozzle to become a solidified yarn in a solidifying bath, and the solidified yarn is the first solid to come into contact with the solidified yarn.
It is used to change the direction of the driving path of the drive roller that rotates at a predetermined speed, the friction roller that rotates due to friction with the solidified yarn, and the solidified yarn, and the rod shape, T-shape, and snake shape that does not move by itself. Guides such as are included.
However, the so-called liquid draining guide used only for removing the solidified liquid adhering to the solidified yarn is not included in the first godet roller according to the present invention.

Increasing the residual solvent ratio of the solidified yarn in the first godet roller portion to 25 to 80% is
By suppressing the extraction of the stock solution solvent to the godet roller portion within the range where the solidified yarn is formed, the structure of the solidified yarn is made as uniform as possible, and the first godet roller is used as an index thereof. It is intended to pay attention to the residual ratio of the solvent contained in the solidified yarn in part. Solvent residual rate is
It can be controlled by the solvent content of the stock solution of the solidification bath, the temperature, the residence time, and the like. That is, to increase the solvent residual rate,
Increase the stock solution solvent content of the solidification bath, lower the temperature of the solidification bath, or shorten the solidification bath length to shorten the residence time in the solidification bath or increase the speed of the first godet roller. Good. If the solvent residual ratio exceeds 80%, the solidification becomes insufficient, and the obtained solidified yarn is hard-fixed,
In an extreme case, for example, if the concentration of the stock solution solvent in the solidification bath is 75%, normal spinning becomes difficult. If the residual solvent ratio is less than 25%, the solvent extraction in the solidification bath is too large and the strength is excellent.
No fiber can be obtained. Solvent residual rate is 30-60
%, It is easier to obtain high strength fibers.

The solvent residual ratio contained in the coagulated yarn in the first godet roller portion according to the present invention is measured as follows. First, the solidified yarn at the first godet roller portion is wiped off the surface-adhering liquid, and two samples are taken for the same time. One is to use Soxhlet extraction of the stock solution solvent, additives, and solidification bath, and dry it to dryness to obtain the weight of PVA-based polymer (A
g) is calculated. The other one is dissolved in water, and the weight (Bg) of the stock solution solvent is determined by gas chromatography analysis. From this, the undiluted solvent content of the solidified yarn B / A × 100 (% / PV
Calculate A). On the other hand, the weight% of the solvent to the PVA-based polymer in the stock solution was calculated from the composition of the stock solution to obtain C (% / PVA).
Then, the residual solvent ratio (%) contained in the solidified yarn in the first godet roller portion can be calculated as 100 B / AC.

Next, in the present invention, the residence time of the solidified yarn in the solidification bath is T ↓ B, and the atmospheric residence time on the solidification bath from the solidification bath to the atmosphere until it contacts the first godet roller is T ↓ B. A
In that case, it is an important point that spinning is performed so as to satisfy 0.5T ↓ B ≦ T ↓ A ≦ 10T ↓ B. When the first godet roller speed is relatively low, by controlling the solvent residual ratio of the solidified yarn in the range of 25 to 80%,
High-strength fiber can be obtained almost stably, but when the first godet roller speed is as high as 10 m / min or more, even if the solvent residual rate is controlled within the range of 25 to 80%, the process passability is still high. I faced a situation where it was difficult to obtain strong fibers stably. Therefore, as a result of various studies on this point, if the atmospheric residence time on the solidifying bath from the leaving of the solidifying bath to the contact with the first godet roller is set to be half to 10 times the residence time in the solidifying bath, the first godet It was found that the process passability and strength are stabilized even when the roller is operated at high speed.
If the atmospheric residence time on the solidifying bath is shorter than half the residence time on the solidifying bath, the process passability and strength become unstable. If it is longer than 10 times the residence time of the solidifying bath, the amount of volatilization of a volatile solidifying bath such as methanol increases, which is not preferable.

Although it is not clear why the atmospheric residence time on the solidifying bath is high at a high speed, the extraction of the stock solution solvent in the solidifying bath tends to vary among the single yarns at a high speed, and thus the process passability is high. And the performance becomes unstable, while the solidified yarn is hardly immersed in the solidifying bath during the air residence between the solidifying bath and the first godet roller, the solidified yarn is hardly extracted, but It is presumed that this is because the solvent content between the solidified single yarns is made uniform through the solidifying bath attached. It is presumed that the uniformizing action of the single yarn solvent extraction during the residence in the air on the solidifying bath effectively acts when the first godet roller becomes high speed.

The solidified yarn taken up by the first godet roller is made into fibers according to the following steps. That is, the undiluted solution solvent in the solidified yarn is extracted and washed with an extraction bath made of an organic solvent having a coagulating ability, and then dried. At this time, it is preferable to perform wet stretching in one step or more preferably in two steps or more in the steps from immediately after the first godet roller to before drying, because it is possible to prevent sticking during drying. Wet stretching includes roller stretching in which air is stretched between the rollers and air, and in-bath stretching in a wet stretching bath between the rollers, and both stretching methods are often used in combination. The preferable wet stretch ratio is 2.5 to 5.5 times, and more preferably 3 to 5 times. Drying temperature is 4
0 to 150 ° C. is preferable, and 70 to 130 ° C. is more preferable in terms of drying efficiency and performance. Further, it is preferable to raise the drying temperature in multiple stages.

Then, hot drawing is performed at a high temperature to orient and crystallize the PVA-based polymer to obtain a high-strength PVA-based fiber. The hot stretching temperature is 140 to 270 ° C. More preferably, the hot stretching temperature is controlled in multiple stages between 150 and 265 ° C.
The particularly important final stage stretching is preferably performed at 225 to 255 ° C. At this time, the total stretching ratio including the wet stretching ratio is usually 16 times or more in the conventional method, and more preferably 18 times or more, but the characteristic of the method of the present invention is that even a relatively low stretching ratio of 12 to 18 times is sufficient. It is possible to obtain various strengths. In the hot stretching, the temperature of the fiber may be raised by using a gas as a heat medium such as hot air or a radiant furnace, the temperature of the fiber may be raised by using a liquid such as silicon or wood metal as the heat medium, and the fiber may be further placed on a heat plate. May be brought into contact with each other to heat the fiber by heat conduction. Further, hot drawing may be performed in multiple stages. Further, heat treatment or heat shrinkage may be performed if necessary.

It is unclear why the solvent residual ratio of the solidified yarn in the first godet roller part has a great influence on the fiber performance, but it is presumed that the tension when the solvent is extracted is an important factor. .. That is, up to the first godet roller portion, the bus draft is less than 1.0, as described above, in a so-called back draft state, and the tension applied to the solidified yarn is extremely low. In the spinning method of the present invention, it is considered that solidification is caused by the formation of junction points due to the microcrystals, but it is extracted with a solvent after solidification. At this time, the formation and growth of the microcrystals and the phase separation proceed concurrently, but the solidification occurs. If the tension of the yarn is low, phase separation will proceed preferentially, and an opaque solidified yarn is likely to be formed. Therefore, since the phase separation is controlled up to the first godet roller portion having a low tension, it is considered that the solvent extraction should be suppressed after the solidification. On the other hand, the steps after the first godet roller are at least fixed length or stretched, so that the tension received by the yarn is significantly increased. Since the phase separation is significantly suppressed under high tension, the phase separation does not proceed even when subjected to solvent extraction, and the uniform structure formed at the time of solidification, that is, the number of junction points are even and many, so the total draw ratio It is presumed that effective stretching is effective even when the value is low, and the molecular chains of the PVA-based polymer are highly oriented, leading to higher strength.

As described above, the first godet roller speed is increased by controlling the residence time on the solidifying bath in the atmosphere to a specific range and further controlling the solvent residual ratio of the solidified yarn in the first godet roller part to a specific range. However, a uniform raw yarn can be obtained, and PVA with excellent strength even if the total draw ratio is relatively low.
It was possible to realize stable and reproducible production of system fibers.

[0029]

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 polymerization degree of 4200 and a saponification degree of 99.9 mol%
VA was added to DMSO so as to be 9% by weight, 2% of methanol was further added as an antifreezing agent, and the mixture was melted at 80 ° C. for 8 hours in a nitrogen atmosphere to have a pore diameter of 0.17 mm and a pore number of 40
Nozzle of 0 from 1 ℃ methanol / DMSO = 75/2
In a solidifying bath of No. 5, the spinning cylinder length was 1.0 m, the first godet roller speed was 12 m / min, and the up-spinning was performed at a bath draft of 0.2. At this time, set the first godet roller to 1.5 in the spinning cylinder.
m, that is, the distance between the nozzle surface and the first godet roller was 2.5 m, and the atmospheric residence time T ↓ A on the spinning cylinder was 1.5 times the residence time T ↓ B. At this time, the residual solvent ratio of the solidified yarn in the first godet roller portion was 40%.

The obtained solidified yarn is immersed in a methanol bath,
DMSO was extracted, wet stretched 4.2 times, and dried with hot air at 100 ° C. Then the first furnace 170 ℃,
In a hot air oven at 240 ° C. in a second furnace, hot drawing was performed so that the total draw ratio was 15.5 times, and 2 kg of drawn yarn was obtained. There was no yarn breakage during spinning and drawing, there was almost no roller winding, and the process stability was good. Further, the yarn strength of the obtained fiber was excellent at 19.7 g / d. Also, there was almost no fuzz.

Comparative Example 1 The spinning dope used in Example 1 was subjected to up-spinning in the same manner as in Example 1 with a spinning cylinder length of 2.0 m, a first godet roller speed of 3 m / min and a bath draft of 0.2. The residual solvent ratio at this time was 18%. The distance between the nozzle surface and the first godet roller was 2.5 m as in Example 1, so T ↓ A
/T↓B=0.25 times, the same operation as in Example 1 was performed thereafter, and the total draw ratio was 25 times, but the yarn strength was 18.5 g / d. It was lower than 1. In addition, roller winding was occasionally seen during stretching, and the process stability was insufficient.

Comparative Example 2 Spinning and drawing were carried out in the same manner as in Example 1 except that the distance between the nozzle surface and the first godet roller was 1.2 m.
At this time, T ↓ A / T ↓ B was 0.2 times. The solvent residual rate of the solidified yarn in the first godet roller part was 42%. The strength of the obtained yarn was 19.5 g / d, and Example 1 was used.
However, the yarn was broken twice per 2 kg of the drawn yarn at the time of drawing, and roller winding was occasionally observed. Therefore, fluff was observed in the drawn yarn on the winding top.

Example 2 P having a viscosity average polymerization degree of 9000 and a saponification degree of 99.8 mol%
VA was added to DMSO to be 6%, water was further added to 1.5%, and the mixture was dissolved at 90 ° C. for 12 hours in a nitrogen atmosphere.
Of methanol DMSO = 83/17 in a solidifying bath with a spinning cylinder length of 1.2 m and a first godet roller speed of 15 m /
Min, and spin-up spinning was performed with a bath draft of 0.2. At this time, the distance between the nozzle surface and the first godet roller is 3.6 m, and T ↓
A / T ↓ B = 2.0 times. The solvent residual rate of the solidified yarn in the first godet roller portion was 50%. The obtained solidified yarn was dipped in a methanol bath to extract DMSO, subjected to 3.8 times wet drawing, and dried with hot air at 100 ° C. Then, it was stretched in a hot air oven at 180 ° C. in the first furnace and 248 ° C. in the second furnace so that the total stretching ratio was 15.8 times. The obtained yarn strength was as high as 21.7 g / d. In addition, there was no yarn breakage during drawing, there was almost no roller winding or fluff, and the process passability was good.

[0035]

In the conventional method for producing high-strength PVA fibers by coagulation spinning, rapid solidification in the solidification bath and slow solvent extraction have been considered effective, so that the residence time in the solidification bath is long and the tension is low. Since the phase separation was performed in, high strength PV
It was difficult to produce the A fiber. When the speed of the first godet roller is increased, the stability of drawing is deteriorated,
There was winding and fluffing. On the other hand, in the present invention, the spinning cylinder length, the first godet roller speed, the solidifying bath composition,
By controlling the temperature of the solidifying bath, the solvent residual ratio of the solidified yarn in the first godet roller portion is set to be high, and the solidified yarn rising from the spinning cylinder is retained in the air to some extent, so that the single yarn having the solvent residual ratio is set. By reducing the variation between them, it is possible to stably produce high-strength PVA fibers even at high speed. Therefore, the PVA fiber having excellent strength obtained by the present invention is superior in cost performance to other high-strength fibers such as para-aramid fiber and the conventional PVA fiber, and is used for rubber materials such as automobile tires and hoses. It can be widely and effectively used in the field of reinforcing materials such as and 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 spinning stock solution obtained by dissolving a polyvinyl alcohol polymer having a viscosity average degree of polymerization of 1500 or more in an organic solvent is extruded into a solidification bath of an organic solvent system having a coagulating ability in a state of a bath draft of less than 1. In the run-up wet spinning in which the solidified yarn is drawn at a first godet roller speed of 10 m / min or more, the residence time of the solidified yarn in the solidifying bath is T ↓ B, and the first godet roller is contacted from above the solidifying bath. Assuming that the atmospheric residence time until T is T ↓ A, 0.5T ↓ B
≦ T ↓ A ≦ 10T ↓ B is satisfied, and the solvent residual ratio of the solidified yarn at the first godet roller portion is 25 to the stock solution solvent amount.
A method for producing a polyvinyl alcohol fiber, which comprises 80%.