JPH0742606B2 - High-strength and high-modulus PVA fiber and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a high-strength, high-modulus polyvinyl alcohol (abbreviated as PVA in the present specification and may be abbreviated hereinafter) fiber and its production. The present invention relates to a method, particularly to obtain a high-strength and high-modulus PVA fiber suitable for industrial materials having good handleability by suppressing swelling in water and adhesion between fibers.

<Prior Art> Conventional PVA fibers have higher strength modules than polyamide, polyester, and polyacrylonitrile fibers, and are used as reinforcing materials for industrial materials and cement.

However, the PVA fibers obtained so far do not have high strength and modulus like aromatic polyamide (aramid) fibers and ultra high molecular weight polyethylene fibers.

PVA fibers are usually produced by a method in which a PVA aqueous solution is used as a spinning stock solution, wet-spun in a coagulable inorganic salt aqueous solution, and subjected to stretching, drying, heat treatment, or an acetal-based treatment for improving water resistance. Various methods have been proposed to improve the strength and elastic modulus of PVA fibers.

For example, JP-B-43-16675 discloses a method of wet spinning a PVA dimethyl sulfoxide (hereinafter abbreviated as DMSO) solution in an organic solvent such as methanol, ethanol, benzene or chloroform as a spinning stock solution, and JP-A-56-128309. Japanese Patent Publication proposes a method in which a PVA fiber obtained by a wet or dry spinning method is drawn at least 10 times or more and then heat-treated.

Further, in Japanese Examined Patent Publication No. 37-14422 and Japanese Examined Patent Publication No. 47-32142, a PVA aqueous solution containing boric acid or borate is spun in an alkaline coagulation bath containing various salts to cross-link boric acid with PVA. After that, a method of removing boric acid or a crosslinked product thereof again is disclosed. However, the strength of PVA fiber obtained by these methods was less than 12 g / d and the modulus of PVA fiber was less than 400 g / d.

On the other hand, in JP-A-60-126312, the polymerization degree of PVA is about 4000.
The total draw ratio is about 30 by dry-wet spinning method using MDSO as a solvent.
Double, strength 20 g / dr, PVA fiber of module 450 g / dr is disclosed, JP-A-59-130314 discloses a gel fiber by cooling with glycerin or ethylene glycol as a solvent, and strength 19 g / dr by stretching, Module 500-600g / dr
However, it is difficult to easily break strength 20g / dr or more and modular 500g / dr or more as in the present invention, and suppress swelling in water and adhesion between fibers. Was difficult.

Further, JP-B-47-42057 discloses that polyvinyl chloride and PVA are mixed and subjected to emulsion spinning to enhance water resistance, and JP-B-47-42050 discloses an ethylene-vinyl acetate copolymer. Fibers obtained by PVA emulsion spinning are:
It has been shown that it is flexible and does not lower the tensile strength and is suitable for paper or non-woven fabric, but it is not described that a high degree of polymerization PVA is stretched to a high ratio as in the present invention to obtain a fiber having high strength and high modulus. .

A method of adding inorganic fine particles such as silica gel to prevent the fibers from sticking to each other is also known, but in this case, the inorganic fine particles may hinder the stretching, and thus high-stretching is difficult.

<Problems to be Solved by the Invention> Based on the above background, the present inventors have obtained a high-strength and high-modulus PVA fiber by highly orienting the fiber molecules by high-stretching and preventing orientation relaxation. I thought it necessary to crystallize.

In the process of stretching the PVA fiber at a high ratio, a large deformation occurs in which crystals generated during spinning are once destroyed and rearranged. As a method to facilitate this deformation, spinning is performed by adding a third component other than PVA and a solvent. Keeping in mind that disordering the crystal of the yarn and suppressing intermolecular hydrogen bonding, and using high degree of polymerization PVA (the phenomenon of defects at the end of the molecular chain and the reduction of molecular chain entanglement in a low concentration PVA solution) I put it in. In addition, it was considered desirable that the additive as the third component be one that softens or melts during stretching and does not interfere with the stretching of the PVA fiber.

On the other hand, when extracting and removing the solvent from the PVA spun yarn, an organic solvent such as methanol or acetone is generally used, but when inexpensive water is used, the PVA fiber easily swells and stretches easily. Is often deteriorated, and the fibers tend to stick together, resulting in poor operability and drawability. Further, even when the obtained drawn yarn is used in water, swelling and sticking easily occur, and a PVA fiber having good handleability has been desired.

As a result of diligent studies aimed at solving such a problem, the present inventors have found that a high-strength and high-modulus PVA fiber having good handleability can be easily obtained.

<Means for solving the problem> That is, the present invention, the average degree of polymerization is 1500 or more polyvinyl alcohol-based polymer fiber, ethylene copolymerization rate of 15-85 mol% ethylene-acetic acid as an additive The vinyl-based copolymer or saponified product thereof is contained in an amount of 0.5 to 10% by weight based on the polymer, and the tensile strength of single fiber is 15 g.
/ dr or more, the tensile modulus is a high-strength high-modulus PVA fiber having a modulus of 400 g / dr or more, and as a production method thereof, when the polyvinyl alcohol-based polymer having an average degree of polymerization of 1500 or more is dissolved in an organic solvent, Ethylene copolymerization rate is 15
~ 85 mol% of ethylene-vinyl acetate copolymer or saponified product thereof is added to the polyvinyl alcohol polymer in an amount of 0.5 to 10% by weight, and the two substances are dissolved and mixed by stirring, and then the liquid is spun. After removing most of the solvent, the obtained spun yarn with a solvent content of 20% by weight or less was
A method is used in which stretching is performed at ˜240 ° C. so that the stretching ratio is 5 times or more and the total stretching ratio is 15 times or more.

The contents of the present invention will be described in more detail below.

The PVA polymer referred to in the present invention is an average degree of polymerization determined by a viscosity method in an aqueous solution at 30 ° C. of 1500 or more, and a linear polyvinyl chloride having a saponification degree of 98 mol% or more and a low branching degree. It is alcohol. It should be noted that other vinyl compounds of 2 mol% or less (for example, R: C _{1 to} C ₆ alkyl group, M: sulfone group, alkyl ester group, carboxyl group, etc.) copolymerized, and further 3% by weight or less of pigment, antioxidant, ultraviolet absorber , Those containing other modifiers are also included.

The higher the average degree of polymerization of PVA, the higher the strength, the greater the possibility of obtaining a high modulus fiber, preferably 6000 or more, more preferably 10000 or more, the PVA concentration 15% by weight or less, preferably 10% by weight or less, It is preferable to reduce the entanglement of the molecular chain to 5% by weight or less.

As a solvent for dissolving PVA, polyhydric alcohols such as ethylene glycol, trimethylene glycol, diethylene glycol and glycerin, and dimethyl sulfoxide,
Any solvent such as dimethylformamide, diethylenetriamine, a mixed system of two or more kinds of these solvents, or a mixed solvent with alcohol may be used, but a solvent capable of dissolving the ethylene-vinyl acetate copolymer or a saponified product thereof is particularly preferable.

The ethylene-vinyl acetate copolymer or its saponified product, which is an additive, is preferably added in a dispersion state before PVA is dissolved in the solvent in order to uniformly dissolve it in the mixed solution of the solvent and PVA. Further, the additive needs to be dissolved in the PVA solution.

The feature of the present invention is that the additive disturbs the crystal of PVA, and increases the draw ratio without hindering the drawability by melting or softening during drawing, and suppressing the swelling property and sticking to water. is there. Therefore, as an additive satisfying the above points, the ethylene copolymerization rate is 15 to 85 mol%, preferably 30 to 50 mol%, and if it is less than 15 mol%, it is an obstacle to the suppression of crystallization of PVA and stretching. Inhibition of intermolecular hydrogen bonding cannot be sufficiently satisfied, and further, handling property in water is slightly improved.

PVA and P when ethylene copolymerization rate exceeds 85 mol%
Since the compatibility of VA with the solvent disappears and it is difficult to dissolve it, it is easy to induce yarn breakage and fluff during spinning and drawing.

As the ethylene-vinyl acetate copolymer or the saponified product thereof referred to in the present invention, those having a saponification degree of 0 to 100 mol% are used, but the saponification degree is 90 mol% or more in view of compatibility with PVA. Those are preferable. The ethylene may be either block copolymer or random copolymer, but the random copolymer is preferable for the purpose of disturbing the crystal of PVA and suppressing hydrogen bonding, which are the features of the present invention.

Further, the additive desirably melts during dry heat drawing at 200 ° C. or more, and preferably has a melting point of 200 ° C. or less, and further, changes in form or feel and stretchability when the PVA fiber of the present invention is used. Considering the above, those having a melting point of 80 to 180 ° C are particularly preferable. Average polymerization of the additives in terms of solubility in the PVA solution, bleed-out property of the additives during use (the property that the additives come out from the inside of the PVA fiber to the surface due to drying or washing with water), and dropout. 50-2000 is preferred).

The amount of the additive added is 0.5 to 10% by weight, preferably 1 to 6% by weight, based on the PVA polymer. If the addition amount is less than 0.5% by weight, the effect of the additive in the present invention is reduced and it becomes difficult to obtain a high-performance PVA fiber by high-stretch drawing. If the addition amount exceeds 10% by weight, the performance of the PVA fiber is impaired, heat resistance and morphological stability are deteriorated, and in addition, it may have an adverse effect on the stretchability, which is not preferable.

Regarding the preparation of the spinning dope, the PVA solvent and additives and other compounds such as antioxidants may be added if necessary, and the PVA dispersion may be made into a highly viscous solution under heating and stirring to obtain a uniform spinning dope. If possible, the dissolution method may be a batch method or a continuous method.

The spinning method may be a conventional wet spinning, dry spinning, dry wet spinning,
Although there is no problem with methods such as gel spinning that match the solvent,
Gel spinning, which gels upon cooling, is desirable in terms of fixing the entanglement of PVA molecular chains and facilitating high-magnification stretching. Although a solvent such as a polyhydric alcohol or a mixture of dimethyl sulfoxide and water is generally used for gel spinning, a good solvent such as dimethyl sulfoxide can also be used by the method of low temperature gelation.

The yarn discharged from the nozzle contains a large amount of solvent, and it is necessary to remove the solvent from the viewpoint of morphological stability of the spinning base yarn, prevention of sticking and stretchability. Solvent removal methods include extraction methods such as water, methanol, ethanol, acetone, and other extraction agents and coagulation / extraction agents of inorganic salt aqueous solutions, and evaporation removal methods by drying, but in terms of fiber cross-section and surface uniformity. The method of making and extracting is desirable. After the extraction, there is no problem even if a drying process is performed to remove the attached extractant. When removing the solvent by washing with water, PV
A fiber is swollen and easily stretched, and slightly dissolved, so that it is difficult to handle, but when the additive of the present invention is present, the above problems hardly occur, and the solvent and water remain. Less sticking problems that occur when
Remarkably improve process passability.

The solvent content is 100% by weight or less, preferably 20% by weight or less, and more preferably 5% by weight or less based on the PVA fiber. When the content of the solvent is high, a problem particularly occurs in terms of sticking or coloring during stretching.

Regarding the stretching, it may be stretched by wet heat or dry heat as needed in the spinning step, but in view of improvement of the draw ratio and molecular chain orientation and crystallinity of the obtained stretched yarn, dry heat stretching at at least high temperature Is good to do. The dry-heat drawing heater is preferably a non-contact type, and a high temperature of 200 to 240 ° C. is used in order to soften or melt the additive according to the present invention and not hinder the drawability. Further, in order to obtain a high-strength, high-modulus PVA-based fiber, high temperature dry heat drawing is performed at least 5 times or more, preferably 10 times or more.
It is necessary that the stretching is performed at least twice, and the total draw ratio including the draw ratio during spinning is at least 15 times, preferably at least 20 times.

The PVA fiber obtained according to the present invention has a tensile strength of a single fiber of 15 g / dr or more, a tensile module of 400 g / dr or more,
Especially, when the average degree of polymerization of PVA was 6000 or more, the tensile strength was 20 g / dr or more and the tensile modulus was 500 g / dr or more. Further, there is little morphological change due to swelling in water or sticking during long-term use, and according to the present invention, it is possible to obtain a high-strength and high-modulus PVA fiber for industrial materials with good handleability that has never been seen before.

The present invention will be specifically described below with reference to examples.

Examples 1 to 4 and Comparative Example 1 Completely saponified PVA having an average degree of polymerization of 1700, 3400, 7000, and 12000, ethylene glycol as a solvent, and polyvinyl copolymer having an ethylene copolymerization rate of 48 mol% and an saponification degree of 100 mol% as an additive. An alcohol compound (polymerization degree: 700, melting point: 157 ° C.) was mixed with 0.5% by weight of antioxidant / PVA at 165 ° C. for 3 hours with stirring to prepare a high-viscosity spinning dope. The PVA concentration depends on the degree of polymerization and is as shown in Table 1. In all cases, the additive was 3% by weight based on PVA.

After defoaming the dissolved stock solution, the denier of the spinning base yarn is 300d.
The undiluted solution was discharged from a single-hole nozzle with a gear pump to achieve r, and cooled and gelled in air. The spinning draft at this time was 1.2 to 1.6. Subsequently, the gel fiber was passed through water in the first bath and methanol in the second bath to remove most of the solvent, and then water and methanol were evaporated from the spinning raw yarn by hot air at 80 ° C. and wound on a bobbin.

The obtained spun raw yarn is drawn by a hollow heater at 235 ° C.
Although the results shown in the table were obtained, the results without the additive as Comparative Example 1 are also shown.

In Examples 1 to 4, all spinning stock solutions were uniform transparent solutions at 160 ° C, and the additives were completely dissolved. When ethylene glycol and the additive are stirred at 160 ° C for 10 minutes, the additive dissolves and becomes a transparent liquid.
When cooled to ℃, the whole became cloudy.

Gelation (solidification) during spinning is faster than without additives,
There was no fluff and no yarn breakage, and the spinning condition was good.

In any of Examples 1 to 4, there was almost no swelling and elongation of the fiber in the water of the first bath, and even if the elongation ratio between the first bath and the second bath was as low as 2 to 5%, the raw yarn was obtained. No slack was observed, and a yarn with a circular cross section was obtained. The solvent residual ratio of the spun raw yarn after winding was as low as 2 to 3 wt%, and no sticking of the raw yarn was observed. After dry heat drawing at 235 ℃, the total draw ratio is as high as 16 times or more, strength 17-22g / dr, modular 425-600g / dr
It was. The higher the degree of polymerization of PVA, the higher the draw ratio and fiber performance. Further, the drawn yarn obtained was immersed in water for 10 days, but there was almost no swelling, and no sticking was observed during the subsequent air-drying, which clearly improved the morphological stability and handleability as compared with Comparative Example 1 without additives. Was there.

According to the present invention, a high-strength and high-modulus PVA fiber having excellent handleability which has never been obtained can be obtained.

In Comparative Example 1, no additive was added, but the swelling elongation in the first bath during spinning was large, and the elongation ratio was 20% and the film was wound. Although the residual solvent ratio was as low as 3.7%, sticking of the yarn was observed, and the draw ratio and fiber performance were lower than with the additive.

Example 5 A completely saponified PVA having an average degree of polymerization of 7,000 was dispersed in dimethyl sulfoxide so that the concentration became 7 wt%, and at the same time, a polyvinyl acetate compound having an ethylene copolymerization rate of 31 mol% was added at 6 wt% /
PVA was added and dissolved by stirring at 70 ° C. The obtained stock solution was a uniform transparent solution, which was discharged into a coagulation bath of methanol / DMSO = 90/10 using a 6-hole nozzle, and the spun base thread was wound by wet spinning. The elongation during spinning did not occur. The solvent residual rate of the obtained yarn is as high as 89%, and in order to remove the solvent, the bobbin wound yarn is methanol / water = 1 /
After being immersed in 1 for 3 days, it was vacuum dried at 100 ° C. for 24 hours to make the residual solvent ratio 0.7%. There was almost no swelling of the yarn with methanol / water = 1/1, and no sticking was observed after vacuum drying.

The vacuum-dried raw yarn was drawn in two stages using two hollow heaters at 190 ° C to 210 ° C to obtain a drawn yarn having a total draw ratio of 20.5 times.
The strength of the drawn filament is 21.4g / dr, Modulus 532g / dr
Thus, it was possible to easily obtain a high-strength and high-modulus PVA fiber.

Example 6 As an additive, the ethylene copolymerization rate was 20 mol% and the saponification degree was 95.
A completely saponified PVA with an average degree of polymerization of 4000 using a mol% ethylene-vinyl acetate copolymer saponification product (degree of polymerization 900) and dimethylsulfoxide (DMSO) as the solvent.
And the additive were added to the solvent and stirred at 100 ° C. for 3 hours to prepare a uniformly dissolved spinning dope having a PVA concentration of 15% by weight and an additive concentration of 1.35% by weight. This spinning stock solution was wet-spun with methanol from a 12-hole nozzle.
Discharge into coagulation bath of / DMSO = 70/30 (weight ratio), then 40
The film was wet-stretched 4 times in methanol at 0 ° C, and most of DMSO was extracted and removed with methanol, dried at 100 ° C and wound up. The obtained spun raw yarn was drawn by a hollow heater at 170 ° C. and 235 ° C. so that the total draw ratio was 19.0 times. The obtained drawn yarn has a single fiber strength of 19.4 g / dr and a modulus of 520 g.
It was / dr.

Example 7 As an additive, the copolymerization ratio of ethylene was 70 mol% and the degree of saponification was 95.
Using a mol% ethylene-vinyl acetate copolymer saponification product (polymerization degree 650), using dimethyl sulfoxide (DMSO) as a solvent, the average polymerization degree is 8000 and the saponification degree is 99.3.
Mol% PVA and the additive were added to the solvent and stirred at 100 ° C. for 3 hours to prepare a spinning stock solution having a PVA concentration of 10% by weight and an additive concentration of 0.2% by weight. This spinning dope was made into methanol / D from a 12-hole nozzle by the wet spinning method.
Discharge into coagulation bath of MSO = 70/30 (weight ratio), then 40 ℃
Wet-stretched 4 times in methanol and then with methanol
After most of DMSO was removed by extraction, it was dried at 100 ° C. and wound up. The obtained spun raw yarn was drawn by a hollow heater at 170 ° C. and 235 ° C. so that the total draw ratio was 20.2 times. The obtained drawn yarn has a single fiber strength of 21.0 g / dr and a modulus of 525 g / d.
It was r.

Claims (6)

[Claims] 1. A fiber comprising a polyvinyl alcohol polymer having an average degree of polymerization of 1500 or more, wherein an ethylene-vinyl acetate copolymer having an ethylene copolymerization rate of 15 to 85 mol% or a saponified product thereof is used as an additive. Against 0.5
A high-strength, high-modulus PVA fiber containing ~ 10% by weight and having a tensile strength of single fiber of 15 g / dr or more and a tensile modulus of 400 g / dr or more. 2. A high-strength, high-modulus PVA fiber according to claim 1, wherein the average degree of polymerization is 6000 or more, the tensile strength of the single fiber is 20 g / d or more, and the tensile modulus is 500 g / d or more. 3. A saponified ethylene-vinyl acetate copolymer having a saponification degree of 90 mol% or more and a melting point of 200 ° C.
The high-strength, high-modulus PVA fiber according to claim 1 or 2, which has the following average polymerization degree of 50 to 2000. 4. When dissolving a polyvinyl alcohol polymer having an average degree of polymerization of 1500 or more in an organic solvent, an ethylene-vinyl acetate copolymer having an ethylene copolymerization ratio of 15 to 85 mol% or a saponified product thereof is used as the polyvinyl. After adding 0.5 to 10% by weight to the alcohol-based polymer, stirring and dissolving and mixing both substances, the solution was spun to remove most of the solvent, and the solvent content obtained was 20% by weight. % Or less of the spinning raw yarn is drawn at 200 to 240 ° C. so that the drawing ratio is 5 times or more and the total draw ratio is 15 times or more.
Manufacturing method of PVA fiber. 5. The method for producing a high-strength, high-modulus PVA-based fiber according to claim 4, wherein the polyvinyl alcohol-based polymer has an average degree of polymerization of 6000 or more. 6. A saponified ethylene-vinyl acetate copolymer having a saponification degree of 90 mol% or more and a melting point of 200.
The method for producing a high-strength and high-modulus PVA-based fiber according to claim 4 or 5, wherein the polymerization degree is 50 ° C or less and the average degree of polymerization is 50 to 2000.