JP2899426B2 - Manufacturing method of high strength vinyl alcohol polymer fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for inexpensively and stably obtaining a vinyl alcohol polymer (hereinafter abbreviated as PVA) fiber having excellent strength.

[0002]

2. Description of the Related Art Conventionally, PVA-based fibers have higher strength and elastic modulus than polyamide, polyester, and polyacrylonitrile-based fibers. It is being used as a rubber reinforcing material or a plastic reinforcing material.

[0003] As a method of obtaining a high-strength PVA-based fiber,
JP-A-59-130314, which applies the idea of gel-spinning and super-stretching a thin solution of high molecular weight polyethylene,
Japanese Patent Application Laid-Open No. 59-100 where dry and wet spinning is performed using an organic solvent
No. 710, Japanese Unexamined Patent Publication No. 61-108711, and the like are known.

However, the dry-wet spinning employed in these inventions is a system in which a PVA solution is extruded from a nozzle and discharged into a coagulating liquid through an air layer. PV for maintaining spinnability in the layer
The A concentration cannot be reduced unnecessarily.

On the other hand, when the PVA concentration is lowered, the polymer liquid sticks on the nozzle surface, and stable spinning cannot be performed. Furthermore, if the pitch between the holes of the nozzle is small, the polymer streams are likely to come into contact with each other, and in the air layer immediately after the discharge, the discharged yarns are stuck together, so that stable spinning cannot be performed. Even if the spinning is completed, it becomes an agglomerated yarn, and this agglomerated yarn breaks a single yarn during stretching, which means that the draw ratio cannot be increased, so that it is difficult to obtain a high-strength fiber. Therefore, in order to solve this problem, the pitch between holes must be increased,
This method prevents a large number of holes and raises a large problem in terms of cost increase if industrial production is carried out. Even if a maximal nozzle having a large number of holes is manufactured, the size of the nozzle is disadvantageous in various points in terms of handling, maintenance and maintenance, and also causes a problem that discharge spots are easily generated between discharge holes. As described above, the dry-wet spinning method has various problems when considering industrial production.

On the other hand, as disclosed in Japanese Patent Publication No. 43-16675, a wet spinning method is also known. In this case, although the above-mentioned problems in the dry-wet spinning method do not occur, fibers having high strength and high elastic modulus are produced. Not obtained. The present inventors studied why the high-strength fiber could not be obtained for the wet spinning method and the like,
We found a prominent factor.

In the conventional wet spinning method, since the nozzle and the stock solution pipe leading to the nozzle are immersed in the coagulation bath, the coagulation bath temperature affects the stock solution temperature, and the stock solution temperature affects the coagulation bath temperature. If the temperature difference in the coagulation bath is large, unevenness in the temperature of the solution and the center and periphery of the nozzle and unevenness of the solution will occur, making it impossible to achieve a uniform discharge in a normal manner. This is one of the factors that hinders the production of high-strength PVA fibers. Has become,
In particular, it has been found that this problem is remarkable when the coagulation bath temperature is as low as 20 ° C. or less.

[0008]

SUMMARY OF THE INVENTION Accordingly, the present invention seeks to find out how to achieve normal and uniform discharge and to produce high-strength PVA fiber stably and inexpensively in a wet spinning method that is easy to make porous. It was done.

[0009]

In other words, the present invention provides a method for dissolving PVA having a viscosity average degree of polymerization of 1500 or more in a solvent,
When the obtained spinning stock solution is wet-spun from the nozzle into a coagulation bath at a bath temperature of 20 ° C. or lower, the nozzle is brought into a state in which the stock solution discharge surface is substantially in contact with the coagulation bath, that is, the stock solution discharge surface of the nozzle is in the coagulation bath. A method for producing a high-strength PVA fiber, wherein the spinning is performed in a state where the immersion length is 30 mm or less. ".

The PVA used in the present invention must have an average degree of polymerization of 1500 or more in a 30 ° C. aqueous solution by a viscosity method. If it is lower than 1500, high strength P
VA fiber cannot be obtained. When the viscosity average degree of polymerization is 3,000 or more, preferably 4,000 or more, a high-strength PVA fiber is easily obtained. When the degree of polymerization is 7000 or more, the number of molecular ends that are liable to become defects is further reduced, and a high-strength fiber is easily obtained.

The saponification degree of the PVA used is not particularly limited, but is preferably 98.5 mol% or more, and 99.9 mol%.
It is more preferable if the amount is more than the above because the hot water resistance is particularly excellent. The PVA used may be a polyvinyl alcohol-based polymer obtained by copolymerizing a monomer having another vinyl group, for example, a monomer such as ethylene, itaconic acid, or vinylpyrrolidone at a ratio of 10 mol or less, preferably 2 mol% or less. .

The solvent used in the present invention is not particularly limited as long as it dissolves PVA, and includes dimethyl sulfoxide (hereinafter abbreviated as DMSO), dimethylformamide, dimethylimidazolidinone, water, glycerin, ethylene glycol, and rhodanate. And mixtures of two or more of these solvents, such as DMS
O and water, dimethylformamide and ethylene glycol,
Ethylene glycol or glycerin and water, and water and n-
And propanol and isopropanol. However, in order to obtain the fiber of the present invention, wet spinning in a relatively low-temperature coagulation bath is effective in obtaining a high-strength and novel surface structure as described below. It is preferable to select a solvent composition that gives a gelation temperature of 50 ° C. or lower. In that sense, glycerin alone or ethylene glycol alone is not preferred because of its high gelation temperature. D
MSO is a particularly preferred solvent that can be dissolved at a temperature of 80 ° C. or less and has a small decrease in the degree of polymerization.

The PVA concentration of the spinning dope varies depending on the degree of polymerization of PVA 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 at obtaining a high-strength fiber. For this purpose, it is preferable to lower the PVA concentration within a range where single yarn breakage, yarn spots, inter-single yarn sticking, etc. do not occur at the time of spinning. This is preferable because stretching can be performed at a high magnification with a small amount.

In addition to the PVA and the solvent, various additives other than PVA and a solvent, such as a coloring agent such as a pigment,
PH of antioxidants, UV absorbers, surfactants, acids, etc.
A necessary amount of a regulator, a gelling accelerator such as boric acid, and the like may be added. Furthermore, if a solvent having a relatively high freezing temperature, such as DMSO, is added within a range in which PVA does not coagulate even if it has a coagulating action such as methanol, the spinning stock solution is frozen even when the coagulation bath is kept at a temperature lower than the freezing temperature of the solvent. May not be preferred.

As the coagulation bath, methanol, ethanol,
A coagulation bath mainly containing an organic solvent having a coagulation effect on PVA such as acetone is used. Needless to say, a mixed solution of these and a solution with a stock solution can also be used as a coagulation bath.

The coagulation bath temperature must be below 20 ° C. If the temperature exceeds 20 ° C., the coagulated yarn has many voids and becomes opaque, and is not homogeneous, and high-strength fibers cannot be obtained. The coagulation bath temperature is more preferably 15 ° C. or lower, and further preferably 10 ° C. or lower in terms of obtaining a uniformly coagulated yarn. However, if the coagulation bath temperature is too low, the spinning solution discharged from the nozzle may freeze and become unable to discharge, so this point should be considered.

Next, in the present invention, the nozzle is not disposed in a state of being completely immersed in a coagulation bath as in the case of the conventional wet spinning method (see FIG. 6). A major feature is that the device is arranged in contact with a coagulation bath having a bath temperature of 20 ° C. or lower. In the specification of the present application, the term "nozzle" is used in a broad sense including parts such as a nozzle case for fixing the nozzle and a filter rectifying plate.

Substantially in contact with the coagulation bath at the undiluted solution discharge surface of the nozzle means that the nozzle is directly in contact with the coagulation bath with the undiluted solution discharge surface of the nozzle as the tip in FIGS. Immersed in the coagulation bath at the tip of the nozzle at a maximum of 30 mm or less, preferably 20 mm or less, more preferably 10 m
m or less. As shown in FIG. 3, when the side surface of the nozzle is partially covered with a heat insulating material or a heating member, the immersion length L is the length of a range from a position not covered by the heat insulating material or the heating member to the undiluted liquid discharge surface. Means.

The most preferred embodiment of the present invention is, as shown in FIG. 4, where only the stock solution discharge surface of the nozzle comes into contact with the coagulation bath due to the surface tension of the coagulation solution. Also in FIG.
The case where the entire side surface of the nozzle is covered with a heat insulating material or a heating material, and only the undiluted solution discharge surface of the nozzle is configured to be in contact with the coagulation bath (that is, L = 0) and spinning is performed by the flow-up method, Similarly, a highly preferred embodiment.

Conventionally, the dry-wet spinning method is frequently used in the production of high-strength PVA fibers because the stock solution for spinning and the coagulation bath are not in contact at all, the heat conduction is independent, and the temperature difference between the two is large. This seems to be one of the reasons. On the other hand, the conventional wet spinning method for obtaining a high-strength PVA fiber can reduce the PVA concentration of the spinning dope compared to the dry-wet spinning method, that is, because a spinning dope with a small molecular chain can be used. Despite the possibility of obtaining higher strength fibers, as described above, if the temperature difference between the spinning dope and the coagulation bath is increased, the ejection from the nozzle holes will not be uniform, and coagulation spots and denier spots will occur. Large and high strength PV
A fiber could not be obtained. In particular, when an organic solvent was used as the solvent, the tendency was large.

According to the present invention, the nozzle is arranged so that the stock solution discharge surface thereof is substantially in contact with the coagulation bath and spinning is performed, so that the temperature difference between the stock solution and the coagulation bath is unexpectedly large even in the wet spinning method. It was also found that coagulation spots and denier spots were remarkably smaller than those of conventional wet spinning, and that high strength fibers were obtained.

When the immersion length exceeds 30 mm, heat transfer by heat conduction between the spinning solution in the nozzle and the coagulation bath becomes large, the local temperature unevenness of the stock solution and the coagulation bath increases, and the coagulation unevenness and denier unevenness increase. Become. The immersion length is preferably 20 mm or less, more preferably 10 mm or less.

The most preferred embodiment of the present invention is the case where the nozzle is in contact with the coagulation bath only at the discharge surface of the nozzle. Such a state is, as shown in FIG. It can be easily realized by using tension. When the coagulation bath comes into contact only with the undiluted solution discharge surface of the nozzle in FIG. 4, there was a fear that the coagulation bath would separate from the nozzle discharge surface and no wet spinning would be possible even if the coagulation bath liquid surface was slightly wavy. It was experimentally confirmed that the coagulation bath did not separate from the nozzle discharge surface even if the coagulation liquid surface was slightly wavy, and it was found that the coagulation bath could be stably maintained for a long time.
It is estimated that the contribution of surface tension is large.

The present invention can be applied not only to the flow-down system as shown in FIGS. 1 and 4, but also to the flow-through system as shown in FIGS. The same effect can be obtained in the case of a contact state.

As described above, the nozzle is in direct contact with the coagulation bath so as not to be directly affected by the temperature of the coagulation bath, that is, in order to suppress a decrease in the temperature of the stock solution discharge portion of the nozzle, and to control the temperature of the stock solution. In order not to affect the coagulation bath temperature, it is also possible to attach a jig made of highly heat-insulating plastic, preferably foamed plastic, etc. to the nozzle. It is preferable that a heating member for heating the discharge section and a heat insulating material are combined and attached to prevent heat transfer between the undiluted liquid discharge section of the nozzle and the coagulation bath.

Bath draft (ratio of first godet roller speed to discharge linear speed when stock solution passes through nozzle)
Is preferably 0.1 to 0.5.

The coagulated yarn taken by the first roller in the coagulation bath or on the coagulation bath is converted into a fiber according to the following steps. That is, the undiluted solvent in the yarn is extracted, washed, removed, and dried with an extract such as methanol or water. It is preferable to perform wet stretching in a single stage or more preferably in multiple stages before drying, so that sticking during drying can be prevented. A more preferable wet stretching ratio is 2.5 to 5.5.
It is twice. If the wet stretching ratio exceeds 6 times, the single yarn breakage or cross-sectional deformation is liable to occur, so that it should be avoided. Drying temperature is 30 ° C ~
150 ° C. is preferred in terms of drying efficiency and performance.

Next, the film is hot-drawn at a high temperature and a high magnification to orient and crystallize the molecule to obtain a high-strength fiber. Hot stretching is preferably 2
The operation is carried out at 10 ° C or more, more preferably 220 to 250 ° C, so that the total stretching ratio becomes 16 times or more, more preferably 18 times or more, and further preferably 20 times or more. In the production method of the present invention, a uniform raw yarn free of coagulation spots and denier spots can be spun, so that a high draw ratio can be achieved, and a high-strength fiber can be realized. The hot stretching may be dry, wet heat in a heat medium bath such as silicon, or high-temperature steam. The stretching may be performed in one step or two or more steps. Further, heat treatment and heat shrinkage may be applied as necessary.

As described above, the immersion length of the nozzle in the coagulation bath is shortened so that the temperature of the stock solution discharged from the nozzle is not affected as much as possible by the temperature of the coagulation bath. It is important that the solidification rate of the discharged polymer is increased and the extraction is performed slowly. This makes it possible to produce a uniform yarn without coagulation spots or denier spots. Then, a high-strength, high-modulus PVA fiber can be stably and inexpensively produced by performing high-magnification stretching of the uniform yarn at a total stretching ratio of 16 times or more.

[0030]

According to the conventional wet spinning method for high-strength PVA fibers, the temperature of the spinning solution is greatly affected by the temperature of the coagulation bath, and it is difficult to increase the temperature difference between the stock solution and the coagulation bath or to spin at a low temperature in the coagulation bath. On the other hand, in the present invention, the immersion length of the nozzle in the coagulation bath is made as short as possible, thereby overcoming the disadvantages of the conventional wet spinning method and the low concentration spinning which is an advantage of the wet spinning method. In addition, the multi-hole nozzle spinning can be utilized as it is, thereby making it possible to provide high-strength PVA fiber at low cost. Therefore, the high-strength PVA fiber obtained by the present invention is superior in cost performance to other high-strength fibers such as para-aramid fibers and conventional high-strength PVA fibers, and is used for rubbers such as automobile tires and hoses. Material field, FRC and FRP
Can be widely and effectively used in the field of reinforcing materials.

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

[0032]

Example 1 Viscosity average degree of polymerization: 4100, degree of saponification: 9
9.8 mol% of PVA was added to 9 wt% of DMSO
And dissolved at 80 ° C. under a nitrogen atmosphere. The obtained spinning stock solution was heated to 65 ° C., the pore size was 0.12 mm, and the number of pores was 4
0, methanol of 0 ° C /
In a coagulation bath composed of DMSO = 7/3, wet spinning was performed in a state where the nozzle was in contact with only the nozzle discharge surface due to the surface strength of the coagulation bath as shown in FIG.

The obtained coagulated yarn is immersed in a methanol bath,
The DMSO was extracted, and wet stretching was performed four times in total in two stages, and dried with hot air at 90 ° C. Then 170-1
The film was stretched in a hot blast stove having a temperature gradient of 90 ° C. to 235 ° C. so that the total stretching ratio became 22 times.

Throughout the entire process, there was no trouble such as winding of the roller, and the process was stable, and the cross section was circular and uniform. The obtained yarn had a strength of 20.8 g / d, an elastic modulus of 475 g / d, and a fluctuation rate of the single yarn dr of 8%.

[0035]

Comparative Example 1 In the case of using the same spinning solution and nozzle as in Example 1 and performing dry-wet spinning as shown in FIG. 5, if a nozzle having a hole pitch of 2 mm is used, the discharged yarns are stuck and normal spinning is performed. I can't do it. Therefore, the hole pitch is 5m
m using a nozzle with a hole diameter of 0.12 mm and 40 holes,
Dry-wet spinning was performed in a coagulation bath through a 5 mm air layer.

However, in the PVA stock solution used in Example 1,
Since the concentration of the stock solution was low and the viscosity of the stock solution was low, thread breakage occurred partially and roller winding occurred, so that normal spinning could not be continued.

[0037]

COMPARATIVE EXAMPLE 2 The nozzle was set in the coagulation bath by the flow-down method shown in FIG.
The spinning was carried out in the same manner as in Example 1 except for immersion in mm. However, normal ejection was not performed from the nozzle, and when the spun yarn was observed, unevenness was large and the variation rate of single yarn denier was as large as 19%.

This spun yarn was drawn in the same manner as in Example 1, but the number of single yarns was large, the total draw ratio was reduced to 17 times, and the yarn strength was as low as 16.5 g / d.

[0039]

Comparative Example 3 The same procedure as in Example 1 was conducted except that the PVA concentration of the spinning stock solution was set to 12% by weight, a nozzle having a hole pitch of 5 mm was used, and a 5 mm air layer was provided between the nozzle and the coagulation bath. did. Spinning went smoothly,
The total draw ratio is only 18 times and the yarn strength is 17.6 g.
/ D, which is lower than Example 1.

[0040]

Comparative Example 4 The same stock solution as in Example 1 was used with a pore size of 0.11 m.
A nozzle having a length of 80 mm, a number of holes of 300, and a hole pitch of 0.8 mm was immersed in a coagulation bath of methanol / DMSO = 85/15 at 5 ° C. with an immersion length of 80 mm as shown in FIG. When the cross section of the obtained yarn was observed, the spots were large, and the variation rate of the denier was as large as 34%.

[0041]

Example 2 Viscosity average degree of polymerization: 4900, saponification degree: 9
9.9 mol% of PVA was added to DMSO to 8 wt% and dissolved at 80 ° C. under a nitrogen atmosphere. The obtained spinning dope was adjusted to 60 ° C., the pore diameter was 0.11 mm, and the number of holes was 30.
Wet spinning was carried out from a nozzle having a hole pitch of 1.8 mm into a coagulation bath of methanol / DMSO = 6/4 at 2 ° C. by a flow-down method as shown in FIG. In this case, the immersion length of the nozzle was 4 mm.

The obtained coagulated yarn is immersed in a methanol bath,
The DMSO was extracted, and a total of 3.5 times wet stretching was performed in three stages, followed by drying with 90 ° C. hot air. Then 180
The film was stretched in a hot air oven having a temperature gradient of -200 to 240 ° C so that the total stretching ratio became 21 times.

There was no trouble such as winding during the entire process, and the denier variation rate of the obtained single yarn was 5%.
And the yarn strength was excellent at 21.5 g / d.

[0044]

COMPARATIVE EXAMPLE 5 The same procedure as in Example 2 was carried out except that the coagulation bath temperature was set at 25 ° C., but the coagulated yarn was whitened and had many voids, so the strength of the drawn yarn was reduced to 18.7 g / d.

[0045]

EXAMPLE 3 PVA having a viscosity average degree of polymerization of 8,000 and a saponification degree of 99.5 mol% was used, and DMSO was used as a solvent.
Using a mixed solvent of / water = 8/2, a solution having a PVA concentration of 6% by weight was prepared. The solution at 90 ° C. was then cooled to a pore size of 0.18.
Wet spinning was performed by bringing only the nozzle discharge surface into contact with a coagulation bath by a flow-down method as shown in FIG. 4 from a nozzle having a hole diameter of 1,000 mm and a hole pitch of 1.8 mm. The coagulation bath had a composition of ethanol / water = 95/5 and a temperature of −2 ° C.

The coagulated yarn was wet-drawn in two steps in an ethanol bath, three times in total, and dried with hot air at 100 ° C. to obtain a spun yarn with little water and ethanol. Subsequently, this raw yarn was drawn by a radiant hollow heater at 170 ° C. to 250 ° C. so that the total draw ratio became 20.4 times. The strength of the obtained yarn was as high as 21.8 g / d.

[Brief description of the drawings]

FIG.

FIG. 2

FIG. 3 is a model diagram for explaining the spinning method of the present invention.

FIG. 4 is a model diagram of a preferred embodiment of the spinning method of the present invention;
The case where the coagulation bath is in contact with only the nozzle discharge surface due to surface tension is shown.

FIG. 5 is a model diagram of a known dry-wet spinning method.

FIG. 6 is a model diagram of a known wet spinning method.

[Explanation of symbols]

 L Indicates the immersion length in the present invention.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Akio Omori 1621 Sazu, Kurashiki-shi, Okayama Pref. Kuraray Co., Ltd. Examiner Tadahiro Manada (56) References JP-A-1-272809 (JP, A) JP 46 −12098 (JP, B1) (58) Fields investigated (Int. Cl. ⁶ , DB name) D01F 6/14 D01D 5/06

Claims (8)

(57) [Claims] 1. A method for dissolving a vinyl alcohol-based polymer having a viscosity average degree of polymerization of 1500 or more in a solvent and discharging the resulting spinning solution from a nozzle into a coagulation bath at a bath temperature of 20 ° C. or lower by wet spinning. A method for producing a high-strength vinyl alcohol-based polymer fiber, characterized in that the surface is dipped in a coagulation bath and the spinning length is 30 mm or less. 2. The method according to claim 1, wherein the viscosity average polymerization degree of the vinyl alcohol polymer is 3000 or more.
Of high-strength vinyl alcohol-based polymer fibers. 3. The method for producing a high-strength vinyl alcohol-based polymer fiber according to claim 1, wherein the coagulation bath temperature is 15 ° C. or lower. 4. The method for producing a high-strength vinyl alcohol-based polymer fiber according to claim 1, wherein the immersion length of the undiluted solution discharge surface of the nozzle in the coagulation bath is 20 mm or less. 5. The method according to claim 1, wherein the nozzle is separated from the coagulation bath, and only the undiluted solution discharge surface of the nozzle is placed in contact with the coagulation bath surface by utilizing the surface tension of the coagulation bath, and spinning is performed by a flow-down method. 1. A method for producing a high-strength vinyl alcohol-based polymer fiber. 6. The nozzle is covered with a heat insulating material or a heating material on all side surfaces of a portion submerged in a coagulation bath, and is arranged and arranged so that only the undiluted solution discharge surface of the nozzle is in contact with the coagulation liquid. The method for producing a high-strength vinyl alcohol-based polymer fiber according to claim 1, wherein the fiber is spun. 7. One or more stages of the yarn before drying,
2. The method for producing a high-strength vinyl alcohol-based polymer fiber according to claim 1, wherein the wet drawing is performed 2 to 6 times in total. 8. A single or multi-staged yarn after drying.
The method for producing a high-strength vinyl alcohol-based polymer fiber according to claim 1, wherein the dry heat drawing is performed at a temperature of 210 ° C or higher so that the total draw ratio including the wet draw ratio is 16 times or more.