JP3021944B2 - Manufacturing method of polyvinyl alcohol fiber with excellent strength - Google Patents

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 polyvinyl alcohol (hereinafter abbreviated as PVA) fibers 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, and thus are used not only for industrial materials such as fishing nets and ropes, but also for cement, It is also used for reinforcing materials such as plastic. On the other hand, with the advancement of society, demands for higher strength of PVA-based fibers are increasing.

In order to meet such a demand, as a method for producing a PVA-based fiber having higher strength, Japanese Patent Application Laid-Open No. Sho 59-130314 in which the concept of gel spinning and ultra-drawing of ultra-high molecular weight polyethylene is applied to PVA. And coagulation and spinning using a PVA having a high degree of polymerization and an organic solvent by a wet or dry-wet method.
Japanese Patent Application Laid-Open Nos. -100710, 60-12312 and 63-99315. In the present invention, gel spinning refers to a case where a spinning dope is solidified only by cooling without a change in composition, and coagulation spinning does not solidify a spinning dope only by cooling, and a solidification bath penetrates the spinning dope. It refers to the case where the composition changes and solidifies.

[0004] However, gel spinning is extremely easy to adhere when spinning in multiple holes for industrial implementation, and coagulation spinning is advantageous for industrial implementation, but has been employed in conventional known techniques. In the case of coagulation spinning, when a high degree of polymerization PVA is used, PVA fibers as high as gel spinning cannot always be obtained. In pursuit of this cause in various ways,
The present inventors have found that one prominent factor lies in the solidification and extraction process of the spinning stock solution, and as a means for solving this problem, the present inventors have previously proposed Japanese Patent Application No. 3-267203. That is, it has been found that it is important to increase the solvent remaining ratio of the solidified yarn in the first godet roller section to 25 to 80% of the stock solution amount.

On the other hand, gel spinning and coagulation spinning are classified into solution spinning from the viewpoint of the solidification mechanism as described above. However, from the viewpoint of spinning mode, 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 a solidification bath.The wet spinning method includes a flowing wet spinning method in which a stock solution is discharged vertically above the nozzle surface, and a stock solution in the nozzle surface. There are a falling wet spinning method that discharges more vertically downward and a horizontal wet spinning method that discharges an undiluted solution horizontally from the nozzle surface, etc., but the operation that has been commercialized with PVA fibers and the most proven spinning form is the flowing wet spinning method. . Thus, when the spinning method proposed in Japanese Patent Application Laid-Open No. 3-267203 was applied to wet-floating spinning, it was found that, especially when the speed of the first godet roller was high, the processability and fiber performance became unstable. .

[0006]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a PVA in which both the stock solution and the coagulation bath use an organic solvent system.
In the case where the coagulation spinning of a system fiber is carried out at a high speed by a flowing wet spinning method, it has been sought to find out how to stably produce a high strength PVA fiber comparable to the gel spinning method even at a high degree of polymerization.

[0007]

That is, the present invention relates to a spinning dope obtained by dissolving a PVA-based polymer having a viscosity-average degree of polymerization of 1500 or more in an organic solvent in a solidification bath of an organic solvent-based solidifying bath. In the wet-wet spinning, in which the solidified yarn is extruded in a state of less than draft 1 and the formed 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 solidification bath is T ↓ B, T ↓ A is the air retention time before contacting the first godet roller from above
When 0.5T ↓ B ≦ T ↓ A ≦ 10T ↓ B is satisfied, and the solvent remaining rate of the solidified yarn in the first godet roller portion is set to 25 to 80% with respect to the undiluted solvent amount. This is a method for producing a characteristic PVA-based 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 of
00 or more. If the average degree of polymerization is less than 1500, a 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, and even more preferably 7000 or more. In particular, when the average degree of polymerization is 1500 or more, the effect of the spinning method of the present invention becomes more remarkable.

The degree of saponification of the PVA polymer used is not particularly limited, but is preferably 98.5 mol% or more, more preferably 99.7 mol% or more. Further, the PVA-based polymer used may contain another monomer having a vinyl group, for example, a monomer such as ethylene, itaconic acid, or vinylpyrrolidone at 10 mol% or less, preferably 2 mol%.
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 P is introduced by infiltration of an organic solvent having a solidifying ability such as methanol.
There is no particular limitation as long as it is an organic solvent that can solidify the solution of the VA-based polymer, and dimethyl sulfoxide (DMS
O), dimethylformamide, dimethylimidazolidinone and the like. Also, a mixture of these solvents and the like can be used. Among many solvents, DMSO can be dissolved at a low temperature of 80 ° C. or less.
A decrease in the degree of polymerization of the VA-based polymer can be reduced,
Preferred solvents.

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.
% 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 PVA-based polymer concentration within a range that does not cause breakage of single yarn, yarn spots, and firm adhesion between single yarns during spinning. preferable.

In addition to the PVA-based polymer and the solvent, various additives such as a coloring agent such as a pigment, an antioxidant, an ultraviolet absorber, a cross-linking agent, a surfactant, an acid and the like may be added to the spinning dope in accordance with the purpose. May be added in required amounts. Further, when a solvent having a relatively high freezing temperature such as DMSO is added in a range such that a PVA-based polymer does not solidify even if a solvent such as water or a solvent showing a coagulating action such as methanol is added, the solidification bath is heated to a freezing temperature of the solvent. The following may be preferable because the spinning solution does not freeze.

[0013] A PVA-based polymer, a solvent and additives are charged into a dissolver. For example, when DMSO is used as a solvent, the temperature is raised to 50 to 120 ° C while stirring the mixture.
Stirring is continued for 4 to 16 hours to dissolve the PVA-based polymer in the solvent, and then defoam to obtain a spinning dope. At this time, inert gas such as nitrogen is pressurized and injected into the dissolver after charging and before raising the temperature, and the reduced pressure is repeatedly replaced with the inert gas. It is preferable from the viewpoint of suppressing the decomposition of the PVA-based polymer that the pressure is applied so that the PVA-based polymer solution is not brought into contact with oxygen as much as possible. As the degree of polymerization increases, the temperature for dissolving and defoaming must be increased, and in this case, it is particularly important not to contact oxygen by replacement with an inert gas or the like.

Unless the bath draft (defined by the ratio of the first godet roller speed to the discharge linear speed when the stock solution is discharged from the nozzle) is less than 1.0, the stretchability in the subsequent process is insufficient. And it becomes difficult to obtain high-strength fibers. The range of the bath draft is more preferably 0.1 to 0.5, and further preferably 0.15 to 0.3. It is important to select the nozzle diameter so that the bath draft is suitable.

The spinning mode used in the present invention is a wet-floating spinning method. In the dry-wet spinning method in which an inert gas is interposed between the nozzle surface and the solidification bath, the hardening between the single yarns in the inert gas layer easily occurs, and the hole pitch of the nozzle must be increased, making compactification difficult. . In the wet spinning method, in which the nozzle surface is in direct contact with the solidification bath, the solidification bath penetrates immediately after the nozzle is discharged and solidifies immediately, so that the hole pitch of the nozzle can be reduced, and therefore, the multihole can be made compact. Among the wet spinning methods, the upstream wet spinning method is the most commonly used in the production of PVA-based fibers, has a large accumulation of technology, and is the spinning method most industrially easy to carry out.

As the solidification bath, an organic solvent capable of coagulating the PVA-based polymer is used. When an aqueous solution of a dehydrating salt such as sodium sulfate is used for the solidification bath, the surface of the solidified yarn is preferentially dehydrated, 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 properties deteriorate, and high-strength PVA-based fibers cannot be obtained. Examples of the organic solvent having a coagulation ability with respect to the PVA-based polymer include alcohols such as methanol and ethanol, ketones such as acetone and methyl ethyl ketone, and are not particularly limited. Methanol is preferred in this respect.

In the present invention, the undiluted solvent is added to the solidification bath in an amount of 5%.
Preferably, it is contained in an amount of up to 70%. The content of the undiluted solvent varies depending on the type of the organic solvent used as the solidification bath, the temperature of the solidification bath, and the like, but if it is less than 5%, the solidification occurs too rapidly immediately after being discharged from the nozzle, and tends to be an uneven solidified yarn. . On the other hand, if it exceeds 70%, the solidification rate is too slow, and it is easy to harden. The content of the undiluted solvent in the solidification bath is 10 to
The content is more preferably 50% by weight, and further preferably 15 to 45%.

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

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 make the residual ratio of the solvent contained in the solidified yarn in the first godet roller section 25 to 80%. The first godet roller according to the present invention is a solid in which an undiluted solution is discharged from a nozzle and becomes a solidified yarn in a solidifying bath, and the solidified yarn contacts for the first time,
Used as a drive roller rotating at a predetermined speed, an ary roller rotating by friction with the solidified yarn, and further used to change the yarn path direction of the solidified yarn, and it does not move itself, but a rod-shaped, T-shaped, or snake-shaped And other guides.
However, a so-called 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 ratio of the solvent contained in the solidified yarn in the first godet roller portion to 25 to 80% is not possible in the first godet roller.
By suppressing extraction of the undiluted solvent up to the godet roller portion within a range where the solidified yarn is formed, the structure of the solidified yarn is made as uniform as possible. It focuses on the residual ratio of the solvent contained in the solidified yarn in the section. Solvent residual rate is
It can be controlled by the content of the undiluted solvent in the solidification bath, the temperature and the residence time. That is, to increase the residual solvent ratio,
Increasing the concentration of the undiluted solvent in the solidification bath, lowering the temperature of the solidification bath, or shortening the solidification bath length or increasing the speed of the first godet roller to shorten the residence time in the solidification bath. I just need. If the solvent residual ratio exceeds 80%, the solidification becomes insufficient, and the obtained solidified yarn hardens,
In extreme cases, for example, when the stock solution content of the solidification bath is 75%, normal spinning becomes difficult. When the residual ratio of the solvent is less than 25%, the solvent extraction in the solidification bath is too large and the PVA has excellent strength.
The system fiber cannot be obtained. Solvent residual rate is 30-60
%, It is easy to obtain high-strength fibers.

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

Next, in the present invention, the retention time of the solidified yarn in the solidification bath is T ↓ B, and the residence time of the air on the solidification bath from the solidification bath to the air until it contacts the first godet roller is T ↓. A
In this case, it is important that the fiber is spun so as to satisfy 0.5T ↓ B ≦ T ↓ A ≦ 10T ↓ B. When the first godet roller speed is relatively low, by controlling the solvent remaining ratio of the solidified yarn to a range of 25 to 80%,
Although high-strength fibers can be obtained almost stably, when the first godet roller speed becomes as large as 10 m / min or more, even if the residual solvent ratio is controlled in the range of 25 to 80%, the process passability becomes high at one step. It was difficult to stably obtain the strength fibers. Therefore, as a result of various studies on this point, if the residence time in the air from the solidification bath to the contact with the first godet roller after leaving the solidification bath is set to be half to 10 times the residence time in the solidification bath, the first godet It has been found that even when the roller is operated at a high speed, both the process passability and the strength are stabilized.
If the residence time in the air on the solidification bath is shorter than half the residence time on the solidification bath, the processability and strength will be unstable. If the solidification bath residence time is longer than 10 times, the volatilization amount of a volatile solidification bath such as methanol is undesirably increased.

It is unclear why the residence time of the air on the solidification bath is important when the speed is high, but when the speed is high, the extraction of the undiluted solvent in the solidification bath is easy to vary between single yarns, and therefore, the process passability is high. And the performance becomes unstable, while the solidified yarn is not immersed in the solidifying bath during the air retention between the solidifying bath and the first godet roller, so the extraction of the solidified yarn as a whole hardly occurs. It is presumed that the solvent content between the solidified single yarns was made uniform through the solidifying bath attached thereto. It is presumed that the homogenizing action of the single-filament solvent extraction during the residence in the air on the solidification bath is effective when the first godet roller operates at high speed.

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

Next, the film is subjected to hot stretching 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.
Particularly important final stage stretching is preferably performed at 225 to 255 ° C. At this time, the total draw ratio including the wet draw ratio is usually 16 times or more, and more preferably 18 times or more in the conventional method, but the feature of the method of the present invention is that a relatively low draw ratio of 12 to 18 times is sufficient. High strength can be obtained. In the hot drawing, the temperature of the fiber may be raised using a gas as a heat medium, such as hot air or a radiant furnace, or the temperature of the fiber may be raised using a liquid such as silicon or wood metal as a heat medium. And the fiber may be heated by heat conduction. Further, the heat stretching may be performed in multiple stages. Further, heat treatment and heat shrinkage may be performed as necessary.

It is unknown why the solvent remaining rate of the solidified yarn in the first godet roller section has a great influence on the fiber performance, but it is presumed that the tension at the time when the solvent is extracted is an important factor. . That is, as described above, up to the first godet roller portion, the bus draft is less than 1.0, which is 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 a junction point due to microcrystals.After solidification, solvent extraction is performed. At this time, generation, growth and phase separation of microcrystals proceed simultaneously and in parallel. If the tension of the yarn is low, phase separation proceeds preferentially, and it is likely to become an opaque solidified yarn. Therefore, it is considered that the solvent extraction should be suppressed after solidification in order to control the phase separation up to the low tension first godet roller portion. On the other hand, the steps after the first godet roller are at least fixed length or stretched, and the tension applied to the yarn is dramatically increased. Under high tension, phase separation is remarkably suppressed, so that phase separation does not progress even when subjected to solvent extraction, and the uniform structure formed at the time of solidification, that is, the junction points are uniform and many, so the total stretching ratio is It is presumed that effective stretching is effective even if the ratio is low, and the molecular chain of the PVA-based polymer becomes highly oriented, leading to high strength.

As described above, by setting the air residence time on the solidification bath to a specific range and controlling the solvent remaining rate of the solidified yarn in the first godet roller section to a specific range, the first godet roller speed is increased. However, even if the total draw ratio is relatively low, a PVA having excellent strength can be obtained.
Thus, stable production of a system fiber with good reproducibility was realized.

[0029]

EXAMPLES The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1 P having a viscosity average degree of polymerization of 4200 and a saponification degree of 99.9 mol%
VA was added to DMSO to 9% by weight, methanol was further added as a deicing agent at 2%, and the mixture was dissolved at 80 ° C. in a nitrogen atmosphere for 8 hours, and the pore size was 0.17 mm and the number of pores was 40.
Methanol / DMSO at 1 ° C from nozzle 0 = 75/2
In a solidification bath made of No. 5, spinning was performed with a spinning cylinder length of 1.0 m, a first godet roller speed of 12 m / min, and a bath draft of 0.2. At this time, the first godet roller is set to 1.5 times of the spinning cylinder.
m, that is, the distance between the nozzle face and the first godet roller was 2.5 m, and the air retention time T ↓ A on the spinning cylinder was 1.5 times the spinning cylinder residence time T ↓ B. At this time, the residual ratio of the solidified yarn in the first godet roller was 40%.

The solidified yarn obtained is immersed in a methanol bath,
The DMSO was extracted and subjected to a 4.2-fold wet stretching, followed by drying with hot air at 100 ° C. Next, the first furnace at 170 ° C.
The second furnace was hot-drawn in a hot-air oven at 240 ° C. so that the total draw ratio became 15.5 times, to obtain 2 kg of drawn yarn. There was no breakage during spinning and stretching, there was almost no roller winding, and the process stability was good. The yarn strength of the obtained fiber was excellent at 19.7 g / d. There was almost no fluff.

Comparative Example 1 The spinning stock solution used in Example 1 was spun 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. At this time, the residual ratio of the solvent was 18%. Since the distance between the nozzle surface and the first godet roller was set to 2.5 m as in Example 1, T ↓ A
/T↓B=0.25 times. Thereafter, the same operation as in Example 1 was carried out, and a total stretching ratio of 25 times was possible, but the yarn strength was 18.5 g / d. It was lower than 1. In addition, roller winding during stretching was occasionally observed, and process stability was insufficient.

Comparative Example 2 Spinning and stretching were performed in the same manner as in Example 1 except that the distance between the nozzle face and the first godet roller was 1.2 m.
At this time, T ↓ A / T ↓ B = 0.2 times. The residual ratio of the solidified yarn in the first godet roller was 42%. The strength of the obtained yarn was 19.5 g / d, which was Example 1.
Although not inferior to the above, the yarn was broken twice per 2 kg of the drawn yarn at the time of drawing, and roller winding was sometimes seen, and thus the drawn yarn had fluff on the wound.

Example 2 P having a viscosity average degree of polymerization of 9000 and a saponification degree of 99.8 mol%
VA was added to DMSO to 6%, water was further added to 1.5%, and dissolved at 90 ° C. for 12 hours in a nitrogen atmosphere, and −1 ° C. from a nozzle having a hole diameter of 0.17 mm and 600 holes.
In a solidification bath consisting of methanol DMSO = 83/17, spinning cylinder length 1.2 m, first godet roller speed 15 m /
The spinning was performed with a bath draft of 0.2. At this time, the distance between the nozzle face and the first godet roller was set to 3.6 m, and T ↓
A / T ↓ B = 2.0 times. The solvent remaining rate of the solidified yarn in the first godet roller was 50%. The obtained solidified yarn was immersed in a methanol bath to extract DMSO, perform 3.8 times wet stretching, and dry with 100 ° C. hot air. Next, the film was stretched in a hot furnace at 180 ° C. in the first furnace and 248 ° C. in the second furnace so that the total stretching ratio became 15.8 times. The obtained yarn strength was as high as 21.7 g / d. Also, there was no yarn breakage during stretching, there was almost no roller winding or fluff, and the process passability was good.

[0035]

According to the conventional method for producing high-strength PVA fiber by coagulation spinning, rapid solidification in a solidification bath and slow solvent extraction have been considered effective. Therefore, the residence time in the solidification bath is long, and the low tension is low. High-strength PV
It was difficult to produce the A fiber. In addition, when the speed of the first godet roller is increased, the stability of stretching is deteriorated,
Winding and fluffing were observed. On the other hand, in the present invention, the spinning cylinder length, the first godet roller speed, the solidification bath composition,
By controlling the temperature of the solidification bath, the solvent remaining rate of the solidified yarn at the first godet roller section is set higher, and the solidified yarn rising from the spinning cylinder is retained in the air to some extent, thereby increasing the solvent remaining rate of the single yarn. By reducing the variation between them, high-strength PVA fibers can be stably produced even at high speed. Therefore, the PVA fiber having excellent strength obtained by the present invention is more excellent in cost performance than other high-strength fiber such as para-aramid fiber and conventional PVA fiber, and is used in the field of rubber materials such as automobile tires and hoses. And it can be effectively used widely in the field of reinforcing materials such as FRC and FRP.

Continued on the front page (56) References Patent 2833887 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) D01F 6/14 D01D 5/06

Claims (1)

(57) [Claims] 1. A spinning solution obtained by dissolving a polyvinyl alcohol-based polymer having a viscosity-average degree of polymerization of 1500 or more in an organic solvent is extruded into an organic solvent-based solidifying bath having a coagulation ability in a state of less than 1 bath draft to form a spinning solution. In the up-flow 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 solidification bath is T ↓ B, and the first godet roller is contacted from the solidification bath. 0.5T ↓ B, where T ↓ A is the air residence time before
≦ T ↓ A ≦ 10T ↓ B, and the residual solvent ratio of the solidified yarn at the first godet roller is 25 to 25% with respect to the undiluted solvent amount.
A method for producing a polyvinyl alcohol-based fiber, which is 80%.