JP2830275B2 - Method for producing high strength polyvinyl alcohol fiber excellent in hot water resistance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing a polyvinyl alcohol (hereinafter referred to as PVA) fiber having excellent hot water resistance, particularly a rubber reinforcing material,
The present invention relates to a method for producing a high-strength PVA-based fiber, which is useful for ropes, seat belts, fishing nets, and the like.

[Prior art] Conventionally, mixed spinning of a PVA-based polymer and a cross-linking agent (for example, boric acid), in particular, after previously mixing the PVA-based polymer and the cross-linking agent, dissolves in a solvent to obtain a spinning dope. The mixed spinning method is known, for example, from JP-B-46-11457.

[Problem to be Solved by the Invention] However, the first problem in the mixed spinning is that the cross-linking agent is already contained in the dissolving step of the spinning dope, and thus the spinning dope is discharged from the spinneret. The cross-linking reaction proceeds during the process, causing a problem of clogging of the stock solution piping line, the filter and the base during the process due to the thickening or gelling of the stock solution for spinning.

In response to this problem of cross-linking of the spinning dope, attempts have been made to lower the temperature of the spinning dope or to shorten the residence time in the spinning process, but the former causes an increase in viscosity of the spinning dope. The latter is limited by the dissolving tank, storage tank, filtration filter section, and the like, and as a result, is not a sufficient solution.

The second problem is that when the stock solution is changed during the spinning, a large amount of stock solution loss occurs in order to completely eliminate the spinning stock solution during the process, and the spinning machine requires a long time for switching. It is not desirable from the viewpoint of productivity, such as the need to stop.

That is, the object of the present invention is to solve the above-mentioned problems of the prior art in the production of crosslinked PVA-based fibers, and to minimize the problems of thickening and gelation due to crosslinking of the spinning dope in the spinning process. An object of the present invention is to solve the problem of clogging of a stock solution piping line, a filter, a base, and the like therein, and to stably produce the fiber or to further improve the productivity.

[Means for Solving the Problems] An object of the present invention is to mix a crosslinkable agent immediately before a metering pump or immediately before a spinneret with a spinning solution in which a polyvinyl alcohol polymer is dissolved in a solvent, and then spin. The method can be solved by a method for producing a polyvinyl alcohol fiber excellent in hot water resistance, characterized by the following.

In other words, the PVA-based polymer in the present invention has a degree of polymerization of 1500 to obtain a high-strength PVA-based fiber having excellent water resistance.
Or more, preferably 2500 or more. This PVA-based polymer is dissolved in a solvent to form a spinning dope, and examples of the solvent include dimethyl sulfoxide (hereinafter, referred to as DMSO), ethylene glycol, glycerin, and water.

The polymer concentration of the spinning dope is preferably 2 to 30% by weight, more preferably 5 to 25% by weight.

On the other hand, examples of the crosslinking agent in the present invention include polyacrylic acid, sodium polyacrylate, potassium polyacrylate, and boric acid. Among these, a particularly preferred crosslinking agent is polyacrylic acid. In addition, this crosslinking agent is generally used by dissolving it in, for example, DMSO or water.

The mixing of the crosslinkable agent with the spinning solution is performed immediately before the spinneret. As a result, the residence time of the crosslinkable drug in the liquid sending line can be reduced, and the crosslinking reaction in the liquid sending process can be prevented.

The mixing means at this time is preferably a static mixer, and is a "static mixer" (Noritake Co., Ltd.)
), "High Mixer" (manufactured by Toray Industries, Inc.) and "Skeya Mixer" (manufactured by Sakura Seisakusho Co., Ltd.).

When the number of stages of the static mixer is too small, the crosslinking agent is not sufficiently dispersed in the spinning solution, and is preferably 10 to 30 stages, more preferably 20 to 30 stages. On the other hand, if it is too large, the residence time becomes long, which is not desirable.

The spinning solution containing the cross-linking agent that has exited the mixer is spun and drawn. In order to obtain a high-strength PVA-based fiber, it is desirable that the spun yarn be drawn at a high magnification. As a spinning method for this purpose, a dry / wet spinning method, a gel spinning method and the like are preferable.

As an example of such a dry / wet spinning method or gel spinning method, a spinning dope containing a crosslinkable agent blended by the above method is preferably 2 to 200 mm, more preferably 3 to 2 mm, from the surface of a coagulation bath or cooling bath. Discharge into a coagulation bath or a cooling bath through a spinneret installed 20 mm above. The yarn after spinning is washed with an extractant such as methanol or acetone to remove the solvent, and then stretched in methanol preferably 2 to 10 times, more preferably 3 to 6 times, and dried. Furthermore, by stretching and winding so that the total draw ratio is preferably 12 times or more, more preferably 15 times or more in an air or nitrogen atmosphere at 200 to 260 ° C., a high-strength PVA fiber excellent in hot water resistance. Is obtained.

EXAMPLES Hereinafter, the present invention will be described more specifically based on examples.

In this example, the hot water index of the PVA fiber was measured according to the following measuring method. In addition, other characteristics were the same as those of the ordinary method.

Using a yarn with a hot water index of 1500D, a twin-twisted cord with a twist of 33T / 10cm, and spraying steam at 120 ° C for 10 minutes under a load of 500g. Then, after standing at 20 ° C. and 65% RH for 24 hours, the tensile strength was measured using a UTM-III L-type “Tensilon” tensile tester at a test length of 25 cm and a tensile speed of 300 mm / min. The chuck used was an air jaw for cord.

On the other hand, for cords not subjected to steam treatment (twisted twist), the tensile strength is determined in the same manner as described above, and the hot water resistance index (%) is calculated by the following equation.

Example 1 A 15% solution of a completely saponified PVA polymer having a degree of polymerization of 3500 dissolved in DMSO was prepared and used as a stock solution for spinning. On the other hand, a 25% by weight aqueous solution of polyacrylic acid having a degree of polymerization of 400 was added as a crosslinking agent to the polymer in the PVA-based spinning stock solution at 2% by weight immediately before the metering pump, and a static mixer (30 elements) was used.
After blending using a spinneret, the mixture was discharged from a spinneret and dried and wet-spun. The spun yarn is washed with DMSO in a methanol bath, further stretched 5 times in a room temperature methanol bath, and dried.
The yarn was further stretched 3.6 times in an air bath at 252 ° C.

At this time, the thickening state of the spinning dope was examined. In addition, the spinnability and hot water index of the drawn fiber were measured. The results are shown in Table 1.

Example 2 Using the same spinning solution and cross-linking agent as in Example 1, adding the cross-linking agent immediately before the spinneret and blending using a static mixer (30 stages of element stages). Spinning and stretching were performed under the same conditions.

Table 1 shows the spinnability and hot water-resistant resin of the obtained drawn fiber.
No difference from Example 1 as shown in FIG.

Comparative Example 1 Completely saponified PVA polymer having a polymerization degree of 3500 and 25 having a polymerization degree of 400
% Polyacrylic acid aqueous solution was previously mixed to give a polymer polymerization ratio of 98/2, and dispersed and dissolved in DMSO to give a total polymer concentration of 15%.
By weight, a spinning stock solution was prepared. This spinning stock solution was spun and drawn by the method shown in Example 1.

At this time, the thickening state of the spinning dope was examined. In addition, the spinnability and hot water index of the drawn fiber were measured. The results are shown in Table 1.

In this method, the temperature of the spinning dope line was lowered to about 120 ° C. in order to reduce the thickening (gelation) of the spinning dope. However, if the spinning was performed for a long time, the spinning became unstable, for example, a dripping occurred at the spinneret outlet, which is considered to be caused by the thickening of the stock solution.

[Effects of the Invention] According to the method of the present invention as described above, in a mixed spinning of a PVA-based polymer and a crosslinkable agent, a feed line or a filtration filter for a spinning stock solution based on thickening or gelling of the stock solution. The problem of clogging of the base, etc., and problems such as loss of stock solution that occurs in large quantities when switching stock solutions and reduction in productivity caused by stopping the spinning machine for a long time are eliminated at once. For example, the tensile strength is 15g /
This has a remarkable effect that high-strength PVA fibers of d or more can be stably produced.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-1-156517 (JP, A) JP-A-1-298205 (JP, A) JP-A-1-192814 (JP, A) 11457 (JP, B1) JP-B 53-10168 (JP, B1) JP-B 48-32773 (JP, B1) JP-B 47-42058 (JP, B1) (58) Fields surveyed (Int. Cl. ⁶ , DB name) D01F 6/14 D01F 6/50 D01D 1/02

Claims (2)

(57) [Claims] 1. A polyvinyl alcohol having excellent hot water resistance, comprising mixing a crosslinkable agent immediately before a metering pump or immediately before a spinneret with a spinning solution in which a polyvinyl alcohol polymer is dissolved in a solvent, and then spinning. Method for producing base fiber. 2. The method according to claim 1, wherein the mixing means for mixing the spinning solution of the polyvinyl alcohol polymer and the crosslinking agent is a static mixer.