JPS61108712A - Production of polyvinyl alcohol fiber of high strength and high elastic modulus - Google Patents

Abstract

PURPOSE:A PVA polymer of a specific polymerization degree is dissolved in a solvent which dissolved the PVA at a lower temperature than the melting point of the polymer, extruded through a spinneret, converted into gel in an immiscible cooling bath, drawn and subjected to desolvation to give the titled fibers of high openability and flexibility in high productivity. CONSTITUTION:A polyvinyl alcohol with a polymerization degree of at least 1,500 is dissolved in such a solvent as the polymer is dissolved in a temperature range from 80 deg.C to the melting point of the polymer such as glycerol and the solution is extruded through a spinneret. The extruded yarn is led into a cooling bath which is kept at a temperature lower than the gelling point of the polymer solution and contains a solvent immiscible to the solvent for the spinning dope to effect gelation of the yarn. The gel yarn is subjected to drawing and desolvation or desolvation and drawing at a draw ratio of at least 13 to give the objective fibers.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides high strength, high modulus polyvinyl alcohol (
The present invention relates to a method for producing PVA (hereinafter abbreviated as "PVA") fiber, particularly an industrial or commercial method for producing the same.

[Prior Art] Conventionally, a semi-diluted solution of an ultra-high molecular weight polyolefin polymer is spun, and the resulting discharged yarn is cooled and gelled.
It is known that if the solvent is extracted from this gelled yarn and then ultra-stretched, fibers with extremely high strength and elastic modulus can be obtained (JP-A-56-15408; JP-A-58
-5228M publications and Journal of
MaterialS S C1ence Vol.
, 15.505-514, 1980 and 258.
4-2590, 1980).

As a method for producing ultra-high strength and high elastic modulus fibers using ultra-high polymerization degree PVA and applying the above-mentioned gel spinning, JP-A-59
Publication No. 130314 discloses that first, strictly rectified vinyl acetate monomer, which is a raw material for PVA, is polymerized by irradiating it with ultraviolet rays for a long time of about 100 hours at a low temperature of -40°C or less. We created ultra-high d-degree PVA with a polymerization degree of over 6000, and used this ultra-high polymerization degree PVA to cool and gel the yarn obtained by the gel spinning method, that is, by discharging the spinning dope from a spinneret. discloses a method for producing high-strength, high-modulus fibers by producing fibers from this gelled yarn.

However, in such a gel spinning method,
Apart from monofilaments, when manufacturing a commonly produced multifilament yarn consisting of a large number of single fibers, the single fibers that make up the multifilament yarn are easily fused to each other. Fibers have problems such as poor flexibility, low strength of the fiber as a whole, strength reduced by high-order processing such as twisting, and low strength utilization.

In addition, high polymerization degree PVA with a polymerization degree exceeding 6000
It is difficult to create a highly concentrated polymer solution with good uniformity, and a spinning stock solution with a high polymer concentration has a significantly high viscosity and deteriorates spinnability. Although it is necessary to use a low-temperature solution,
A spinning stock solution with a low polymer concentration has a problem in that productivity in fiber production is low and industrial production methods cannot be used.

In the above-mentioned gel spinning method, when water is used as a cooling bath for gelling the discharged yarn, the gelled yarn in a wet state is likely to fuse, and the solubility of the PVA-based polymer, handling, etc. The disadvantage is that water, which is advantageous in terms of safety, cannot be used.

Furthermore, the special method for producing PVA as described in JP-A-59-130314 can hardly be called an industrial method for producing polymers, and can be said to be one of the reasons for restricting its industrialization.

[Problems to be Solved by the Invention] The present inventors have developed a method for producing high-strength, high-modulus PVA-based fibers that is comparable to the ultra-high-strength PVA-based fibers described in JP-A-59-130314. P has high physical properties that
The present invention was discovered after extensive research into a method for manufacturing VA fibers that is industrially and economically advantageous.

That is, an object of the present invention is to provide a highly productive and technically advantageous method for producing PVA fibers exhibiting excellent physical properties in terms of strength and elastic modulus.

Still another object is to provide a PVA-based fiber that is free from fusion, has excellent openability and flexibility, and is excellent in high-order processability.

Hereinafter, the present invention will be explained in more detail and specifically.

[Means for Solving the Problems] The object of the present invention is to achieve a polymerization degree of at least 1500.
Using a PVA-based polymer, this polymer is dissolved in a solvent that dissolves in a temperature range of below its melting point and above 80°C,
The resulting polymer solution is discharged from a spinneret as a spinning dope, and the discharged thread is introduced into a liquid cooling bath that is immiscible with the polymer solvent and maintained at a temperature sufficient to gel. This is achieved by gelling the resulting gelled yarn and stretching the resulting gelled yarn after removing the solvent, or by removing the solvent after stretching to obtain a drawn yarn with a total stretching ratio of at least 13 times.

The PVA-based polymer used in the present invention includes conventionally known PVA and derivatives thereof, and is not particularly limited. Polymerization components such as those copolymerized with a small amount of olefin monomers such as ethylene, propylene, butylene, PVA that has been partially saponified without being completely saponified in the PVA manufacturing process, or PVA polymers that have been chemically post-treated. Also, examples include blends with other types of polymers that are miscible with a small amount of PVA, such as 10% by weight or less.

However, these PVA-based polymers have a degree of polymerization of at least 1500. Preferably, it is within the range of 1,500 to 6,000. If the degree of polymerization is less than 1,500, it will not be possible to obtain a fiber that satisfies the ultra-high strength physical properties that are the object of the present invention.
If it exceeds 00, the manufacturing cost of the PVA-based polymer itself is high and it is difficult to obtain it commercially, and it is also difficult to create a solution with a concentration and viscosity that can be used as a spinning dope with good productivity. This is not preferable because it makes industrial production difficult in terms of spinning and spinning of the fibers.

The PVA-based polymer of the present invention having a degree of polymerization within this range is dissolved so that the polymer concentration is within the range of 5 to 25% by weight to prepare a spinning dope.

Here, if the polymer concentration is lower than 5%, productivity will be poor and the cost burden of solvent recovery will increase, and on the other hand,
When it is higher than 25%, the viscosity of the spinning dope is too high, resulting in a large pressure loss in the polymer flow path and a drawback that stable flow becomes difficult.

As a solvent for the PVA-based polymer used for making the above-mentioned spinning stock solution, the melting point of the PVA-based polymer is below its melting point, 80°C.
Things that are dissolved within the above temperature range and the resulting solution turns into a gel when cooled, are generally non-volatile at room temperature, such as ethylene glycol, glycerin, diethylene glycol, trimethylolpropane, benzenesphonamide, and caprolactam. Glycerin and ethylene glycol, which are miscible with solvents, preferably water, are preferred. The spinning stock solution is prepared by dissolving the PVA-based polymer in the above-mentioned solvent heated to a temperature range below the melting point of the polymer (approximately 250°C) and above 80°C.

If it is dissolved in a solvent with a temperature higher than the melting point of the polymer, the polymer will decompose, which is not preferable, and if it is lower than 80°C, for example, it will be difficult to gel in the range of room temperature to 0°C, making it difficult to obtain a stable gel thread.

The spinning dope thus obtained is discharged from the spinneret hole, but the spinning dope may be discharged directly into a cooling bath, or once discharged into air or an inert gas such as nitrogen, helium, argon, etc. It may then be introduced into a cooling bath. When discharging into air or inert gas, the temperature of the air or inert gas should be 0 to 80°C, and the distance between the spinneret surface and the cooling bath should be about 3 to 50 degrees. .

Here, the cooling bath liquid used is a hydrophobic liquid that is neither compatible nor miscible with the solvent of the PVA-based polymer, such as decalin, trichlorethylene, carbon tetrachloride, paraffin oil, and kerosene. By using a cooling liquid, the polymer concentration of the gelled yarn in the cooling liquid is kept substantially the same as the polymer concentration of the spinning dope, and it is only through such gelled yarn that the polymer concentration is kept substantially the same as that of the spinning dope. This makes it possible to produce the high strength, high modulus PVA fiber of the invention.

That is, if the cooling liquid has compatibility and miscibility with the polymer solvent, interdiffusion occurs between the polymer solvent in the discharged yarn and the cooling liquid in the cooling liquid, for example, the skin , core, etc. are formed, making it difficult to obtain a gel yarn or a desolventized undrawn yarn that is dense and has excellent drawability.

Here, the temperature of the cooling liquid is determined by the gelling temperature of the spinning dope, and is preferably within the range of 0 to 60°C. In other words, when the temperature rises above 60°C, the cooling efficiency of the discharged yarn is insufficient, resulting in: - subsequent desolvation;
It becomes difficult to run the yarn stably in processes such as drawing, and when the temperature is lower than 0°C, special cooling equipment is required, which is not preferable.

For example, 151i of PVA with a degree of polymerization of 3000
% glycerin solution, its gelation temperature is approximately 103
In order to discharge this solution from a spinneret nozzle and cool the resulting discharged yarn, the temperature of the cooling bath is preferably 40 °C or less.

In addition, the depth and length of the cooling bath are not particularly limited, but when discharging as a multifilament, the single fibers that make up the multifilament are sufficiently cooled in the cooling bath before being bundled. The temperature, depth, and length of the cooling bath should be set appropriately so that gelation is completed.

The gelled yarn thus obtained has the characteristic that the concentration of the polymer constituting the gelled yarn is substantially the same as the polymer concentration in the spinning stock solution, and this characteristic is due to the polymerization method of the present invention. This is extremely important in forming high-strength, high-modulus fibers from PVA-based polymers in the 50% range.

That is, having such characteristics means that the obtained gelled yarn is subjected to solvent removal treatment and then stretched or stretched and then desolubilized l55I! X-processing is an essential requirement for stretching at a high magnification of at least 13 times, preferably 16 times or more.

The solvent removal treatment is performed using a liquid that is miscible with the solvent contained in the gelled yarn and is a non-solvent for the PVA polymer, such as methanol, ethanol, acetone, etc. This is particularly preferably carried out by treating the gelled yarn using condensate obtained by hot drawing the gelled yarn.

After the solvent removal treatment, the yarn is heated and dried to remove the chemical contained in the yarn used in the solvent removal treatment.

The undrawn yarn thus obtained is then drawn, and the drawing is carried out in either a single step or in multiple steps, with the drawing temperature being in the range of 160 to 250°C, which is a temperature below the melting point of the PVA polymer. It's okay.

On the other hand, when the gelled yarn is immediately stretched before the solvent removal treatment, the stretching temperature is preferably set to a temperature equal to or lower than the melting point of the PVA-based polymer gel. If this gelled yarn in a wet state before the solvent removal treatment is heated and stretched and then subjected to the solvent removal treatment, even if water is used for the solvent removal treatment, the fusion between the single fibers during the solvent removal treatment and the subsequent drying process will increase. High strength and high elastic modulus P that can substantially prevent drying and is flexible and spreadable.
VA-based multifilament yarn can be advantageously produced industrially. However, the stretching temperature of the above-mentioned gel-like yarn varies depending on the gelation temperature of the spinning dope;
For example, when the gelling temperature of the spinning dope is around 110 to 120°C, stretching at room temperature will not only result in poor stretching properties, but will only be able to stretch at most twice as much, and will not be heat-set after stretching, resulting in shrinkage.

Therefore, in this case, in order to obtain a fiber yarn in which the polymer chains constituting the fiber are sufficiently oriented and have a crystallized fiber structure and sufficient water resistance, the stretching temperature is in the range of 60 to 110'C. It is better.

Further, the stretching device may be any means such as a heating tube, a hot plate, a heating roller, a heating pin, a heated liquid temperature, or a fluidized bed, and is not particularly limited.

The desolvation treatment of the yarn drawn in the wet gel state can use water as a solvent and is industrially advantageous as described above, but the conditions for the desolvation treatment in this case are as follows:
Although it varies depending on the degree of polymerization and toughness of the PVA polymer constituting the fiber, the conditions are such that fusion between single filaments of the drawn yarn does not occur and that the solvent is removed efficiently, preferably at a temperature of usually 10 to 50°C. It is sufficient to process within the temperature range.

The drawn and desolventized yarn thus obtained is dried, but
In this case, in order to alleviate the fusion between single yarns, reduce the frictional resistance with the metal in the subsequent post-treatment process, and suppress the spreading of single yarns due to static electricity, they are treated with various oils and dried. Good too. As the drying means, a known heating drum, heating tube, hot air, etc. can be employed.

The dried drawn yarn is heated using the heating tube, heating plate, heating roll, heating bottle, heating liquid, fluidized bed, etc.
One or more stages of secondary stretching is performed at a temperature of 100 to 250 degrees Celsius, and the total stretching ratio of the resulting yarn is at least 1.
It is stretched by 3 times, preferably 18 to 30 times. This total stretching ratio is an important requirement for highly oriented the polymer chains constituting the PVA fiber yarn of the present invention in the fiber axis direction and highly increasing its strength and elastic modulus. This makes it possible to obtain an outstanding IIN with a tensile strength of 18 g/76 or more and a tensile modulus of 3500/d or more.

[Operations and Effects of the Invention] According to the present invention, the polymerization degree of commercially available PVA-based polymers is at least 1500, preferably 1500-6.
PV with extremely excellent mechanical strength using 0oO polymer
A-type fibers can be produced.

We succeeded in obtaining fibers with excellent physical properties such as a tensile strength of at least 18 g/d and an elastic modulus of 350 a/d or more from a PVA polymer with the above degree of polymerization. , a PVA-based polymer solution with a concentration range with good solution stability and spinnability was discovered, and gelled yarn polymer 8! obtained from this spinning stock solution! It has been found that by making the polymer concentration substantially the same as the polymer concentration of the spinning dope, the drawability of the resulting gelled yarn or desolvation yarn is highly improved, and by combining these in one piece, the present invention can be applied. The purpose has been achieved.

In the present invention, when the wet gelled yarn is drawn and then subjected to solvent removal treatment, water can be used as the solvent for the solvent removal treatment, and conventional flammable and toxic solvents such as methanol are used. The present invention has the advantage of not having to use water, and not only because the water is cheap, but also because it has established an industrial manufacturing method for the ultra-high strength PVA fiber of the present invention.

Further, according to the present invention, it is possible to easily produce a variety of multifilament fibers having a total fineness of about 100 to 10,000 d from monofilaments.

Hereinafter, the present invention will be specifically explained with reference to Examples.

In addition, in the examples, the physical properties of the fibers are values measured under the following conditions. .

Measurement sample: Single yarn measurement length: 100111 m Tensile speed during measurement: 100 m/min Measurement atmosphere: 20°C, 65% relative humidity Example 1 Polymerization degree 2100. PVA with a saponification degree of 99.5% was dissolved at 170°C using glycerin as a solvent, and the polymer concentration was 17.
．． A 5% by weight spinning dope was prepared.

This spinning dope was maintained at 170°C, discharged into the air from a spinning nozzle with a hole diameter of o, osmm, and 10 holes, and cooled by guiding it into a bath containing decalin at 15°C below the nozzle surface as a cooling liquid. . The total discharge rate of the spinning dope from the nozzle was 0.970 G/min, and the cooled rubbery gelled yarn was taken off at 5+a/min.

The obtained gelled yarn has a length of 80 CIIl and an internal air temperature of 1
It was stretched 4.0 times in a heated tube at 00°C and wound up on a plastic bobbin. The wound thread together with the bobbin was repeatedly immersed in warm water at 40°C to extract the glycerin in the thread. The yarn was then dried to remove moisture, and was stretched 3.8 times and 4.5 times using a hot plate with a surface temperature of 230°C. Table 1 shows the physical properties of the obtained drawn yarns with total stretching ratios of 16 times and 18 times, respectively.

In addition, these drawn yarns showed no fusion between single fibers, and were excellent in flexibility and spreadability.

Comparative Example 1 In the hot plate stretching after the solvent removal treatment in Example 1, the stretching ratios were 1 (no further stretching), 2°0 and 2.7.
A drawn yarn was produced in the same manner as in Example 1 except for the following changes. The physical properties of the obtained fiber threads are shown in Table 1.

As can be seen from the table, when the total stretching ratio is lower than 13 times, the physical properties of the resulting fiber yarns are also significantly lowered.

Example 2 Polymerization [3900, degree of nylation 99.6% (F) PVAe
When dissolved at 170°C using glycerin as a solvent, the concentration was 11.
A 0% by weight spinning stock solution was prepared.

This spinning stock solution was maintained at 170°C and discharged into the air from a spinning nozzle with a hole diameter of 0.06mm and 20 holes, and placed in a cooling bath with decalin at 15°C as a cooling liquid, which was placed 1oIIl below the nozzle surface. to gel the discharged thread. The total discharge rate of the spinning dope from the nozzle was 0.97 cc/min, and the cooled rubbery gelled yarn was drawn off at 2 m/min.

The obtained gelled yarn was heated to a length of 80 cm and an internal temperature of 100°C.
The film was stretched 4.0 times in a heating tube and wound up on a plastic bobbin. 40 pieces of wound yarn per bobbin
The yarn was repeatedly immersed in warm water at ℃ to extract the solvent in the yarn. The yarn is then dried to remove water and have a surface density of 230.
It was roughly stretched to 5.5 times using a hot plate at ℃.

The obtained fiber yarn with a total drawing ratio of 22 times is a multifilament yarn with a single fiber fineness of 1.54 d without inter-filament fusion, and a strength of 20. I+/d.

It exhibited excellent physical properties with an elongation of 4.9% and an elastic modulus of 4300/d.

Comparative Example 2 In Example 2, the gelled yarn obtained by discharging the spinning stock solution from the nozzle and cooling it was immediately immersed repeatedly in 40°C warm water to extract the solvent without stretching it with a heating tube. When dried, a yarn with significant inter-filament fusion was formed, and as a result of stretching this yarn using a hot plate at 230°C, the maximum stretching ratio was 15 times as a total stretching ratio. Stretching was difficult. In addition, the obtained yarn was extremely fused, brittle, and lacked rjaIIA properties, and when its physical properties were measured as a multifilament yarn, the fiber physical properties were low, with a strength of 13.8 o/d and an elastic modulus of 3270/d. showed that.

Example 3 In Example 1, using ethylene glycol as the polymer solvent and spinning under the same conditions as above, the total draw ratio was at most 16 times, the strength was 18.3 a / d , and the elastic modulus was 3.
A yarn of 84 g/d with good spreadability and no inter-filament fusion was obtained.

Comparative Example 3 The degree of polymerization of the polymer was 1300. PV with saponification degree of 99.5%
A was dissolved in glycerin at 160°C to prepare a spinning stock solution with a concentration of 20% by weight. The obtained spinning stock solution was subjected to spinning, gelling, stretching (however, the stretching ratio was 4 times), solvent removal treatment, drying, and secondary stretching (however, using a hot plate at 230° C.) in the same manner as in Example 2. (stretched 8 times).

The total draw ratio of the obtained yarn was 19.2 times, and the fiber physical properties were strength 13.5 o/d, elongation 6.1%, and elastic modulus 354 o/d.

Claims (2)

[Claims] (1) A polyvinyl alcohol-based polymer having a degree of polymerization of at least 1500 is dissolved in a solvent that dissolves at a temperature below the melting point of the polymer and above 80°C, and this solution is discharged from the spinneret hole as a spinning stock solution, After forming a gelled yarn by introducing the discharged yarn into a cooling bath that is immiscible with the solvent of the spinning dope and maintained at a temperature below its gelling temperature, the resulting gelled yarn is A method for producing a high-strength, high-modulus polyvinyl alcohol fiber, which comprises removing the solvent after stretching or stretching after removing the solvent to obtain a drawn yarn with a total stretching ratio of at least 13 times. (2) In claim 1, the solvent of the spinning dope is a solvent that is miscible with water, and after gelling in a cooling bath and hot drawing the yarn, the solvent is removed using water. A method for producing high-strength, high-modulus polyvinyl alcohol-based fibers, which comprises processing, drying, and secondary stretching.