JP2888498B2 - Production method of high strength polyvinyl alcohol fiber with little coloring - 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 producing a high-strength polyvinyl alcohol (hereinafter abbreviated as PVA) fiber having little coloring.

[0002]

2. Description of the Related Art Conventionally, PVA-based fibers have higher strength and elastic modulus than polyamide, polyester and polyacrylonitrile-based fibers, and are widely used as fibers for industrial materials. In particular, recently, with the advancement of high-tech sports and leisure, articles and clothing used for the same are required to have higher and higher functions, and there is an increasing need for textiles that combine aesthetics with high strength and weather resistance.

[0003] Among high-strength fibers, aramid fibers such as Kevlar and polyacrylate fibers such as Vectran are colored, resulting in a limited hue and lack of color clarity. On the other hand, PVA-based fibers have the potential to combine strength close to that of aramid fibers, outstanding weather resistance, and basically sufficient whiteness.

As methods for producing high-strength PVA fibers, JP-A-59-130314 and JP-A-59-100710 are known.
And JP-A-61-108711 have been proposed. However, in the known methods of these conventional high-strength PVA fibers, the content of sodium acetate in the spinning solution of by-produced sodium acetate necessarily produced by the ordinary PVA production method is always considered. No mention is made of the whiteness of the PVA fibers obtained. When manufacturing PVA fiber 220
It is well known that when dry heat drawing is performed at a high temperature of from about 250C to about 250C, the fiber is colored when it contains sodium acetate. Therefore, in order to prevent this, generally, the raw material PVA is washed with water to wash and dry the sodium acetate. That is, it is general to use water-washed PVA and not to contain sodium acetate in the spinning dope. Therefore, the conventional method requires washing and drying steps of PVA, and also requires treatment of washing wastewater to avoid environmental problems.

On the other hand, JP-A-3-40807 discloses a sodium acetate-containing PVA solution obtained by dissolving dimethyl sulfoxide (hereinafter abbreviated as DMSO) at the stage of polyvinyl acetate, adding an alkali, and uniformly saponifying the solution. It has been proposed that the fiber be concentrated to a predetermined concentration and then spun as it is. In this case, a long extraction step in the spinning step is required to extract sodium acetate.

Japanese Patent Application Laid-Open No. 62-235348 proposes adjusting the pH by adding an acid to a spinning solution in which PVA is dissolved in DMSO.
When the solution is left at a high temperature, the purpose is to prevent PVA from being easily decomposed and deteriorated.

[0007]

Accordingly, the present invention relates to a PV
A: The PVA is dissolved in an organic solvent such as DMSO without washing water by-produced sodium acetate during the production of A, and a high-strength PVA fiber without coloring is obtained by using a spinning solution containing sodium acetate as a coloring-causing substance. It is a serious thing.

[0008]

In other words, the present invention provides an organic solvent-based spinning solution of a PVA-based polymer containing 0.2 to 2% of sodium acetate / polymer by using an organic solvent having a solidifying ability with respect to the polymer. When performing wet or dry-wet spinning in a coagulation bath of 20 ° C. or lower, which is mainly used, the coagulation bath and / or
Alternatively, a method for producing a high-strength PVA-based fiber, wherein the pH of the extraction bath is 4.0 to 6.0. ".

The degree of polymerization of the PVA used in the present invention is not particularly limited, but it is preferable that the average degree of polymerization determined by a viscosity method in a 30 ° C. aqueous solution is 1500 or more. Further, when the average degree of polymerization is 3,000 or more, preferably 7000 or more, a high-strength PVA fiber is easily obtained. On the other hand, it is necessary to raise the dry heat stretching temperature as the degree of polymerization increases, the coloring with residual sodium acetate tends to be larger, and the sodium acetate needs to be more strictly washed and removed. Will be noticeable.

The degree of saponification 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 is an organic solvent capable of dissolving PVA. Polar solvents such as DMSO, dimethylformamide, dimethylacetamide and dimethylimidazodinone, and polyhydric alcohols such as glycerin and ethylene glycol. And mixtures of these solvents and the like. Among them, DMSO is a preferable solvent because it dissolves PVA well even at a relatively low temperature.

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, it is 3 to 20% by weight. In particular, the present invention aims at obtaining high-strength fibers, and for this purpose, it is better to lower the PVA concentration within a range where single yarn breakage, yarn spots, inter-single yarn sticking, etc. do not occur during spinning. It is preferable because it is possible to perform high-magnification stretching with little entanglement.

In the present invention, sodium acetate is used in an amount of 0.2 to 2%.
% / Polymer stock solution is used. If sodium acetate is contained in an amount exceeding 2% / polymer, heat treatment coloring cannot be completely prevented even if an acid addition bath described later is used. When the content of sodium acetate is less than 0.2% / polymer, the effect of the present invention is not exhibited. When the sodium acetate content is 0.3 to 2% / polymer, the effect of the present invention becomes more remarkable.

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, ultraviolet 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. When the fiber of the present invention is colored with a dye, a pigment, or the like, the original color is white, so that the hue is clear and an aesthetically excellent one is obtained.

As the coagulation bath, an organic solvent having a coagulation ability for PVA is used. For example, alcohols such as methanol and ethanol, and ketones such as acetone and methyl ethyl ketone are not particularly limited, but among them, methanol is preferable in terms of balance of coagulation and cost. Further, it is preferable to control the coagulation property by adding a stock solution solvent to the coagulation bath. The content of the undiluted solvent varies depending on the conditions of the undiluted solution and the coagulation bath, but is preferably from 5 to 70%, more preferably from 15 to 45%.

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.

There is no particular limitation on the spinning method of the present invention. A wet spinning method in which the nozzle directly catalyzes the coagulation bath or a dry-wet spinning method in which an air layer is interposed between the nozzle and the coagulation bath may be used. In addition, as another classification method of the spinning method, there is a case where it is classified into gel spinning and coagulation spinning depending on the difference in solidification form, but in the present invention, even in gel spinning, when an air layer is interposed between the nozzle and the coagulation bath, a dry-wet method is used. It is referred to as spinning. Wet spinning has the feature that it solidifies immediately after nozzle ejection, so that even if the nozzle hole pitch is small, it is easy to make porous without hardening, while dry-wet spinning has an air layer that plays the role of a heat insulating layer. Since the temperature of the undiluted solution and the temperature of the coagulation bath can be controlled independently of each other, they are uniformly discharged, and have a feature that the spots on the fiber cross section are small. These can be appropriately selected according to the purpose.

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 hole diameter of the nozzle is selected so that the bath draft falls within this range. A more preferred bath draft is 0.15 to 0.3.

The coagulated Ishino taken by the first roller in the coagulation bath or on the coagulation bath is immersed in an extraction bath composed of an organic solvent having the same coagulation ability as the coagulation bath, and the undiluted solvent in the Ishino is extracted and washed. Remove. A single extraction bath may be used, but multiple extraction baths are more efficient. When the stock solution solvent is DMSO and the coagulation bath is methanol, the diffusion rate of DMSO from the yarn to the extraction bath is high, and the DMSO concentration in the yarn is DMS in the extraction bath.
The point of DMSO extraction is to keep the concentration of DMSO in the extraction bath low, because the concentration immediately becomes equilibrium with the O concentration.
For this purpose, a so-called countercurrent multistage extraction in which fresh methanol is corrected in the final extraction bath and the overflow of the final extraction bath is successively supplied to the previous extraction bath is preferable.

The point of the present invention is to add an acid to the coagulation bath and / or the extraction bath to control the pH to 4.0 to 6.0. The pH in the present invention is a value obtained by measuring a solution obtained by adding the same amount of distilled water to a coagulation bath or an extraction bath at 20 ° C. using a pH meter. There is no particular limitation on the type of acid to be added, and either an inorganic acid or an organic acid may be used, and non-volatile sulfuric acid or phosphoric acid or acetic acid present as sodium acetate in the yarn is preferable. Usually, a large part of the sodium acetate contained in the stock solution elutes into the coagulation bath during coagulation, and is extracted and removed together with the solvent when the stock solution is extracted in the extraction bath. Significantly affects coloring during hot stretching. Therefore, generally, sodium acetate contained in the spun yarn before drawing is 0.02%.
It is necessary to wash the PVA in advance with water or to wash and remove it by immersing it for a long time in the spinning process. On the other hand, the present invention has been found that when the pH of the coagulation bath and / or the extraction bath is adjusted to 4.0 to 6.0, a white PVA fiber having no color can be obtained even if washing with acetic acid is insufficient. It is unclear why the degree of coloring is improved, but it is presumed that the thread is slightly acidic, which makes PVA difficult to decompose. The acid may be added to the coagulation bath and / or the extraction bath, but may also be added to a wet stretching bath or an oil bath. The amount of acid added must be in the range of pH 4-6. If the pH is lower than 4, the acid becomes too strong and burns with acid, resulting in coloring. When the pH exceeds 6, the amount of acid is so small that the effect of adding acid is lost. More preferably, the pH is between 4.5 and 5.5.

Extract and remove the undiluted solvent from the coagulated shinoshi
After the adjustment, an appropriate oil agent is applied to improve the stretchability and the bunching property, etc., and dried. In any step from the first roller to the drying roller, it is preferable to perform wet stretching in a single stage or in multiple stages in a total of twice or more, because it is possible to prevent hard adhesion during drying and the like. More preferred wet stretch ratio is 2.5
~ 5.5 times. The drying temperature is preferably from 40 to 150 ° C. in terms of drying efficiency and fiber performance.

Next, hot stretching is performed at high temperature and high magnification,
A molecule is oriented and crystallized to obtain a high-strength fiber. The hot stretching is performed at 210 to 260 ° C. so that the total stretching ratio becomes 14 times or more. If the degree of polymerization is high, the melting point of the crystal is high, and it is necessary to perform hot stretching at a higher temperature. Accordingly, the higher the degree of polymerization, the easier the coloration, and the effect of adding the bath acid of the present invention becomes more remarkable. After the heat stretching, heat treatment or heat shrinkage may be performed as necessary.

As described above, the present invention provides an organic solvent-based spinning system which contains sodium acetate as a coloring causative substance.
By making the organic solvent-based coagulation bath such as methanol and / or the extraction bath slightly acidic, it is possible to produce a fiber which is difficult to be colored during hot drawing even if the residence time of the extraction bath is short.

[0024]

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 A number average polymerization degree was 8300, a saponification degree was 99.6 mol%, and sodium acetate was 1.2% / PVA.
The contained PVA was added to DMSO to 6%,
The mixture was stirred and dissolved under a nitrogen atmosphere at 0 ° C. for 8 hours to remove bubbles. The obtained spinning dope was adjusted to 80 ° C., wet-spun from a nozzle having a pore diameter of 0.14 mm into a coagulation bath having a weight ratio of methanol / DMSO = 70/30 at 4 ° C., and subjected to 4 times wet stretching. After that, it was immersed in an extraction bath made of methanol having a pH of 5.0 with sulfuric acid for 20 seconds, and dried with hot air at 100 ° C.
A spun yarn was obtained. Next, this spun yarn is used for 160-180-
In a hot blast stove with a temperature gradient of 240 ° C, the total draw ratio is 2
The film was hot-stretched so as to be 0 times. The resulting fiber was white with little coloration and good appearance. Strength is 21.5
g / d, and the strength retention after irradiation with a weather meter at 63 ° C. × 100 hours was as excellent as 95%.

Comparative Example 1 A PVA fiber was produced in the same manner as in Example 1 except that sulfuric acid was not added to the extraction bath. The fibers obtained were colored pale yellow. The strength was slightly low at 21.2 g / d. Example 1 Weather Meter
Similarly to the above, the strength retention after irradiation was slightly lower at 90%.

Example 2 A number average polymerization degree was 4100, a saponification degree was 99.8 mol%, and sodium acetate was 0.8% / PVA.
The contained PVA was added to DMSO to 8%
The mixture was stirred and dissolved at 11 ° C. under a nitrogen atmosphere for 11 hours to remove bubbles. The obtained spinning dope was adjusted to 75 ° C., and wet-spun from a nozzle having a pore diameter of 0.14 mm to a coagulation bath having a weight ratio of methanol / DMSO = 70/30 at 2 ° C. At this time, acetic acid was added to the stock solution so as to have a pH of 0.1% and the coagulation bath to have a pH of 5.5. The obtained gel shinoshi was subjected to a 4.5-fold wet stretching, then immersed for 30 seconds in an extraction bath composed of methanol having a pH of 5.5 with acetic acid, dried with hot air at 100 ° C., and then dried. The film was hot-stretched in a hot-air furnace having a temperature gradient of 180-200-235 ° C so that the total stretching ratio became 19.5 times. The fibers obtained were almost colorless white fibers. The strength was also excellent at 20.2 g / d.

[0028]

According to the conventional method for producing a high-strength PVA fiber of an organic solvent, in order to obtain a fiber without coloring, the raw material PVA is washed with water to remove sodium acetate, which is a coloring substance, and then used. In the case of a spinning dope containing, a long residence time of the extraction bath was required. On the other hand, in the present invention, the coagulation bath and / or the extraction bath of the organic solvent system is made slightly acidic, and the raw yarn before hot drawing is made slightly acidic,
Even when a spinning solution containing sodium acetate is used and the residence time in the extraction bath is short, a high-strength PVA fiber without coloring can be obtained at low cost. Therefore, the fiber of the present invention is excellent in whiteness and strength, and also excellent in weather resistance, which is a characteristic of PVA fiber, and is the latest article and clothing in the sports and leisure fields that require all of aesthetics, strength, and weather resistance. It can be used effectively as such.

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Hirofumi Sano 1621 Sazu, Kurashiki-shi, Okayama Pref. Kuraray Co., Ltd. Examiner Tadahiro Manada (56) References JP-A-62-289606 (JP, A) (58) Survey Field (Int.Cl. ⁶ , DB name) D01F 6/14 D01D 5/06

Claims (1)

(57) [Claims] An organic solvent-based spinning solution of a polyvinyl alcohol-based polymer containing 0.2% to 2% of sodium acetate / polymer in a coagulation bath of 20 ° C. or lower mainly containing an organic solvent capable of coagulating the polymer. PH of coagulation bath and / or extraction bath during wet or dry-wet spinning
And a high-strength polyvinyl alcohol-based fiber with little coloring, wherein the pH is 4.0 to 6.0.