JPS6399315A - Production of high-strength and high-initial elastic modulus polyvinyl alcohol fiber - Google Patents

Abstract

PURPOSE:To obtain the titled PVA fibers in a state without gluing of filaments together in spinning, by wet spinning a PVA solution under specific condition and drawing the resultant undrawn yarns at a high ratio. CONSTITUTION:PVA having >=1,500, preferably >=4,500 polymerization degree is dissolved in a mixed solvent of water and DMF (at 5:95-60:40 mixing weight ratio) to give a PVA solution, which is then wet spun into a mixture solution of DMSO and an alcohol (at 10:90-70:30 mixing weight ratio). The resultant undrawn yarns are once wound or continuously drawn at least >=15 times, preferably >=20 times draw ratio.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for producing polyvinyl alcohol (hereinafter abbreviated as PVA) fibers having high strength and high initial elastic modulus. P with high initial modulus
The present invention relates to a method for stably spinning and producing VA fibers without causing filaments to stick to each other during spinning.

(Prior art) Recently, polyvalent phenylene terephthalamide (hereinafter referred to as PP)
It is abbreviated as TA. ), a polymer with a rigid molecular chain is used, and the polymer is dissolved in a specific solvent such as sulfuric acid to a concentration such that the solution exhibits liquid crystallinity, and then spun. By performing so-called liquid crystal spinning, 2
It has become possible to obtain high strength and high initial elastic modulus fibers having a strength of 0 g/d or more and an initial elastic modulus of 500 g/d or more, and PPTA fibers have already entered the practical stage. However, such fibers are disadvantageous in that they are much more costly than ordinary yarns in terms of raw material costs and manufacturing costs.

On the other hand, a method for obtaining high-strength, high-initial-modulus fibers from flexible high-molecular-weight polymers has also been developed and is attracting attention. This is the so-called gel spinning method. Polyethylene fibers produced using the gel spinning method have a strength that is approximately twice or more than that of PPTA fibers.

Although fibers have been obtained that have performance that is quite close to the limit in initial elastic modulus, they have the drawback of lacking heat resistance due to their low melting points.

PVA fibers are superior to general-purpose fibers in terms of strength and initial elastic modulus, and are also superior to polyethylene fibers in heat resistance. Therefore, if PVA fibers having strength and initial elastic modulus comparable to those of PPTA IIIi fibers could be obtained, it would be very advantageous in terms of cost performance and the range of uses could be expanded.

Conventionally, various methods for improving the strength and initial elastic modulus of PVA fibers have been studied9.For example, Japanese Patent Publication No. 48-32623
Publication No. 48-32624, Special Publication No. 4B-
Various proposals have been made in Japanese Patent Publication No. 9210, Japanese Patent Publication No. 1368/1980, and the like. In the method proposed by these methods, a spinning stock solution is prepared by dissolving PVA in an aqueous boric acid solution, and wet spinning is performed in an alkaline aqueous solution containing dehydrating salts such as sodium sulfate to once form a gel-like undrawn yarn.

Next, the method involves removing boric acid from the undrawn yarn in an acidic aqueous solution, and then stretching the yarn, which essentially uses water as a solvent for PVA.

The strength of the obtained fibers is only 17 g/d at most.

In addition, dimethyl sulfoxide (hereinafter abbreviated as DMSO) was used as the solvent, and methanol was used as the coagulation liquid.

A wet spinning method for PVA using acetone, toluene, etc. is also known from Japanese Patent Publication No. 16675/1983.

However, in this method, although the initial elastic modulus is improved, the 2 strength is only 10 g/d, even though the PVA fiber is drawn by about 20 times.

On the other hand, methods for improving both the strength and initial elastic modulus of PVA fibers are disclosed in JP-A-59-130314 and JP-A-60-
This is proposed in Japanese Patent No. 126312. These methods use various organic solvents 1, for example, DMS as a solvent for PVA.
A spinning stock solution is prepared using O, glycerin, ethylene glycol, etc., water, or a mixed solvent thereof, and this spinning stock solution is passed through a layer of inert atmosphere such as air or nitrogen through a spinneret. PVA fibers with high strength and high initial elastic modulus are produced by extrusion into a coagulation bath (mainly methanol), that is, by dry/wet spinning.

(Problems to be Solved by the Invention) As described above, various methods for producing PVA fibers having high strength and high initial elastic modulus have been proposed. According to the law, 18g/
A pvA fiber having a strength of d or higher has not been obtained, and furthermore, since the filaments stick to each other after spinning, a heat treatment step is required.

Furthermore, it was not possible to obtain PVA11 fibers with high strength using a wet spinning method using DMSO as a PVA solvent.

Furthermore, the dry/wet spinning method, which can improve both strength and initial elastic modulus, is superior to the above two methods.

The problem is that there is an inert atmosphere layer between the cap and the coagulating liquid (cooling liquid). Namely.

When the spinning dope is extruded from the nozzle discharge hole, the shape is unstable directly below the first nozzle (in an inert atmosphere layer).

Moreover, thick gel-like filaments are formed.

When the spinning dope is extruded from multiple discharge holes, the interval between the discharge holes (the distance between one discharge hole and the discharge hole next to it)
If the diameter is narrow, the respective gel-like filaments tend to adhere to each other, which often causes the formation of adhesive threads.

Therefore, the present invention enables stable spinning without the filaments sticking to each other during spinning, and has high strength and
It is an object of the present invention to provide a method for producing PVA fibers having a high initial modulus at a lower cost than PPTA fibers.

(Means for Solving the Problems) In view of the current situation, the present inventors conducted intensive studies to achieve the above object using PVA, which has higher heat resistance than polyethylene, and as a result, they arrived at the present invention.

That is, 9 The present invention uses PVA with a degree of polymerization of 1500 or more in water and DM in a weight mixing ratio of 5:95 to 60:40.
A spinning stock solution is prepared by dissolving SO in a mixed solvent, and the spinning stock solution is passed through a spinneret by a wet spinning method.

DMS with a weight mixing ratio of 10:90 to 70:30
High strength and high initial elasticity characterized by extruding into a mixed solution of O and alcohol to form an undrawn yarn, and then winding up the undrawn yarn once or continuously stretching it at least 15 times or more. The gist of this paper is a method for producing polyurethane PVA fiber.

The present invention will be explained in more detail below.

The degree of polymerization of PVA used in the present invention is 1,500 or more, preferably 3,000 or more, and more preferably 4,500 or more in view of the physical properties of the resulting fiber. Also, PVA
The saponification degree of is preferably 99% or more.

A spinning stock solution is prepared by dissolving such PVA in a mixed solvent of water and U5MSO.
When the temperature is 120°C, it is preferable to adjust the concentration of PVA to a range of 2 to 35% by weight. If the concentration is less than 2% by weight, the stringability will decrease.

If it exceeds 35% by weight, the viscosity is high and the uniformity of the spinning dope tends to decrease, as well as the drawability of the undrawn yarn tends to decrease, which is not preferable.

Further, the weight mixing ratio of water and DMSO in the mixed solvent is in the range of 5:95 to 60:40. Outside this range, the effectiveness as a mixed solvent is reduced and a phenomenon in which filaments often stick together during spinning is undesirable. Moreover, the most preferable weight mixing ratio of water and DMSO is 20:80 to 45:55.
It is. In the present invention, a PVA heat resistant agent is added to this mixed solvent.

Pigments, crosslinking agents, etc. may be appropriately mixed in and used.

In the present invention, PV is added to the above water/DMSO mixed solvent.
A spinning solution prepared by dissolving A is then extruded into the solution through a spinneret by a wet spinning method to form an undrawn yarn. The liquid for extruding the spinning dope from the spinneret has a 1 part weight ratio of 10:90 to 70:30. Preferably from 10:90
A mixed solution of DMSO and alcohol in a ratio of 50:50 is used.

In the present invention, this mixed solution may contain a small amount of water. For example, in the present invention, water in the spinning stock solution may be brought into the solution, and as a result, the composition of the solution may become three components: water/DMSO/alcohol. The increase in concentration is small;
There is no particular problem.

Examples of alcohols used here include 9.

Aliphatic alcohols such as methanol, ethanol, propatool, isopropanol, butanol are preferred;
In particular, methanol is preferably used.

In the present invention, the undrawn yarn formed in the liquid is once wound up or continuously supplied to a drawing step and drawn. In the present invention, during this time, other steps such as drying, oil treatment, etc. may be appropriately introduced if necessary.

There are various stretching methods that can be applied in the present invention. For example, a method in which the PVA fiber is stretched while being in contact with a heating body such as a heat plate, a method in which the PVA fiber is stretched in a hot air bath such as a heat oven, and a method in which it is stretched in a heating medium. , a dielectric heating method for stretching.

In these methods, the stretching can be carried out in one stage or in multiple stages of two or more stages, but in the present invention, it is preferable to perform the stretching in multiple stages of two or more stages. Further, in the case of multi-stage stretching, moisture application, oil application, etc. may be performed between the n-th stage stretching and the (n+1)th stage stretching (n is an integer of 1 or more).

PV having high strength and high initial elastic modulus which is the object of the present invention
In order to obtain fiber A, the total draw ratio including spinning and drawing needs to be at least 15 times or more, preferably 20 times or more. The spinning drawing referred to here refers to the ejection linear velocity (Vo) when the spinning dope is extruded from the spinneret,
Stretching in the spinning draft and hot drawing steps, which is expressed as the ratio (V+/VO) of the speed (V+) of the roller at which the formed PvA undrawn yarn is first taken off, was excluded. This refers to all stretching performed in other processes, and stretching performed in drying processes, oil treatment processes, etc. is also included in spinning/drawing.

Therefore, the total draw ratio as used in the present invention is calculated from all drawings except for the above-mentioned spinning draft.

(Function) According to the present invention, the filaments can be stably spun without sticking to each other during spinning, and the obtained undrawn yarn can be stretched to a high ratio, resulting in a PVA with high strength and high initial elastic modulus.
It is possible to obtain fibers.

The reason why these filaments do not stick to each other is not fully understood at present, but using a water/DMSO mixed solvent as the solvent for the spinning stock solution and a DMSO/alcohol mixed solution as the liquid for extruding the spinning stock solution, There is a clear difference compared to the conventional method described above.

In addition, the reason why undrawn yarn with high drawability can be obtained is as follows.
After the spinning dope is extruded from the spinneret, the extraction of water and DMSO starts, but the time required for this extraction to almost complete is controlled so that it is longer than the extraction time of conventional wet spinning. It is presumed that this is due to the fact that

In other words, water and DMSO in the undrawn yarn are mixed with 10% alcohol.
It is presumed that such control was made possible by extracting with alcohol containing DMSO, which is one of the components of the spinning solution, instead of extracting with 0%. Therefore, in the process of extraction leading to coagulation, the mixed solvent of water and DMSO remains around the PVA molecules for a relatively long time, or one of the solvents, water or DMSO, is preferentially extracted.

The other solvent may remain for a relatively long time, so the movement of PVA molecules is relatively free, and P
It is presumed that the VA molecular chain becomes more likely to assume a folded structure.

On the other hand, in the method of wet spinning using a boric acid aqueous solution of PVA as a spinning stock solution in a coagulating solution containing dehydrating salts such as sodium sulfate, or the method of wet spinning in methanol using a DMSO solution of PVA as a spinning stock solution, Since the time required for the spinning dope to solidify after being extruded from the spinneret is short, undrawn yarn is formed with a relatively large amount of entanglement of PVA molecules, resulting in a high drawing ratio in the subsequent drawing process. It is presumed that it cannot be stretched.

In experiments conducted by the present inventors, when obtaining an undrawn yarn of 50 denier/10 filaments by setting the PVA depth of the spinning stock solution to 15 wt%, the time required to extract 90% or more of the solvent was 1. In contrast, it took more than 3 minutes in the case where DMSO and methanol were used as the solvent for the spinning solution and the coagulation liquid.

In both cases where an aqueous solution containing water and dehydrating salts was used, a result of less than 1 minute was obtained. About this.

This seems to suggest the above idea.

(Example) Hereinafter, the present invention will be explained in more detail with reference to Examples.

In addition, 1 strength and initial elastic modulus in one example are for a sample length of 20
cm, values obtained when a tensile test was conducted at a tensile speed of 20 cm/min (20° C., 65% RH).

Examples 1-3. Comparative Example 1 PVA with polymerization degree of 2300.3500 and 4800 (7) was added to a mixed solvent of water/DMSO at a weight ratio of 20:80 at 100°C.
Each was dissolved to prepare a spinning stock solution having a concentration of 15% by weight.

These spinning stock solutions were extruded from a spinneret at 70° C. into a DMSO7/methanol mixed solution with a weight mixing ratio of 10:90 to form an undrawn PVA yarn. Next, the water and DMS in the undrawn yarn were sufficiently removed. After extraction, the undrawn yarn was wound up. At this time, no adhesion between the filaments was observed. After drying the rolled-up undrawn yarn, it was hot-stretched in two stages at the ratio shown in Table 1 to 500 denier/1
A drawn yarn of 00 filament was obtained. However, the stretching ratio at this time was 90% of the maximum stretching ratio.

For comparison, a drawn yarn was obtained in the same manner as in Example 1 except that the total draw ratio was 14.6 times.

Table 1 shows the drawing conditions and the results of measuring the quality of the drawn yarn.

Water/DMSO weight mixing ratio and DMSO
When the weight mixing ratio of /methanol is 20:80 and 10:90, respectively, a high strength PVA fiber with a single strength of 15 g/d or more and a cavity initial elastic modulus can be obtained by setting the total stretching ratio to 15 times or more. .

Examples 4-6. Comparative Examples 2 to 4 As a solvent, the weight mixing ratio of water/DMSO was 10:90.
30nia 0, 50:50 or 70:30 mixed solvent, DMS0 100% (0:100) and water 100% (1
PVA having a degree of polymerization of 4800 was dissolved in these solvents to prepare spinning stock solutions each having a concentration of 12% by weight.

These spinning stock solutions were extruded from a spinneret at 80°C into a DMSO/methanol mixed solution with a weight mixing ratio of 15 = 85 (however, only when a 100% water solvent was used;
(extruded into an aqueous solution containing 350 g/l of sodium sulfate) to form an undrawn PVA yarn.Next, the solvent contained in the undrawn yarn was sufficiently extracted, and the yarn was once rolled up and dried.

These undrawn yarns were hot-stretched in two stages in a hot air oven at the ratio shown in Table 2 to obtain drawn yarns of 400 denier/100 filaments. However, the total stretching ratio at this time was 85% of the maximum stretching ratio.

Table 2 shows the drawing conditions and the yarn quality measurement results of the obtained drawn yarn.

Table 2 1,000 → Yoyo force Example 7 PVA with a degree of bipolymerization of 5500 was dissolved in a mixed solvent of water/DMSO at a weight mixing ratio of 15:85.

PVA? A spinning dope having a W degree of 8% was prepared. This spinning dope was added to a spinneret at 80°C at a mixing ratio of 20:8 by weight.
Extruded into 0 DMSO/ethanol mixed solution, PV
After forming an undrawn yarn A, the solvent in the undrawn yarn was sufficiently extracted, the PVA undrawn yarn was dried, and then continuously stretched. Stretching was performed in three stages in a dry heat oven, with a total stretching ratio of 25.2 times, to obtain a PVA drawn yarn of 250 denier/100 filaments. The strength of the obtained drawn yarn was 23.98/d, and the initial elastic modulus was 527.
It was a high value of g/d.

Examples 8-10. Comparative Example 5.6 PVA with a degree of polymerization of 4800 was dissolved in a water/DMSO mixed solvent with a weight mixing ratio of 20:80 L*: a1 degree 12
% spinning stock solution was prepared. This spinning stock solution was mixed from the spinneret at a weight mixing ratio of 0:100.20:80°40:60.60.
:40. Alternatively, each is extruded into a DMSO/methanol mixed solution of 80:20 to form an undrawn PVA yarn.Next, the water/DMSO in the undrawn yarn is sufficiently extracted, and the undrawn yarn is wound up. 3.
A drawn yarn of 00 denier/150 filament was obtained.

Table 3 shows the drawing conditions and the yarn quality measurement results of the obtained drawn yarn.

Table 3 Regarding Comparative Example 6, the proportion of DMSO in the coagulation solution was too high, and the HA solidification ability was extremely reduced.

An undrawn yarn that could be subjected to drawing could not be obtained.

Furthermore, in Example 10, the immersion time of the undrawn yarn in the coagulation bath was longer than in Examples 8 and 9 (about 10 minutes).

(Effects of the Invention) According to the present invention, stable spinning can be performed without filaments sticking to each other during spinning.

Moreover, it has high strength and high initial elastic modulus P comparable to PPTA fiber.
Since it is possible to produce VA fibers and has better heat resistance than polyethylene gel spun fibers, it is possible to expand the range of uses.

Moreover, since the filaments do not stick together,
The size of the nozzle can be smaller than that used for dry/wet spinning (gel spinning), or if the size is the same, the number of discharge holes can be increased, so the number of discharge rings between the discharge holes can be reduced. It is very advantageous because it can be made into filaments or made into multifilaments.

Another advantage of the present invention is that conventional wet spinning equipment can be used without significant modification.

Claims (7)

[Claims] (1) Prepare a spinning stock solution by dissolving polyvinyl alcohol with a degree of polymerization of 1500 or more in a mixed solvent of water and dimethyl sulfoxide at a weight mixing ratio of 5:95 to 60:40,
The spinning stock solution is extruded from a spinneret into a mixed solution of dimethyl sulfoxide and alcohol with a weight mixing ratio of 10:90 to 70:30 to form an undrawn yarn, and then the undrawn yarn is wound once. A method for producing high-strength, high-initial-modulus polyvinyl alcohol fibers, which comprises stretching at least 15 times or more continuously. (2) The manufacturing method according to claim 1, wherein the polyvinyl alcohol has a degree of polymerization of 3000 or more. (3) The polyvinyl alcohol concentration of the spinning stock solution is 2 to 35
% by weight. (4) The weight mixing ratio of water and dimethyl sulfoxide is 20:
The manufacturing method according to claim 1, wherein the ratio is 80 to 45:55. (5) The manufacturing method according to claim 1, wherein the weight mixing ratio of dimethyl sulfoxide and alcohol is 10:90 to 50:50. (6) The production method according to claim 1, wherein the alcohol is methanol. (7) The manufacturing method according to claim 1, which involves stretching at least 20 times or more.