JPS62238812A - Production of polyvinyl alcohol fiber having high strength and elastic modulus - Google Patents

Abstract

PURPOSE:To easily produce the titled fiber having mechanical strength and elastic modulus comparable to those of Kevlar, by dissolving a polyvinyl alcohol polymer having ultra-high polymerization degree in a glycol-type solvent and carrying out dry-wet spinning of the obtained spinning dope under specific condition. CONSTITUTION:A polyvinyl alcohol polymer having a polymerization degree of >=5,000, preferably >=7,000 is dissolved in a glycol-type solvent to obtain a spinning dope. The dope is maintained at 150-240 deg.C and subjected to dry-wet spinning into a coagulation bath composed of a solvent miscible with the above glycol-type solvent under a spinning draft of 0.05-1.0, preferably 0.07-0.75 to obtain an undrawn yarn. The objective fiber is produced by drawing the undrawn yarn e.g. with a roller so as to attain a strength of >=18g/d and an elastic modulus of >=350g/d and winding with a winder, etc.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing high-strength, high-modulus polyvinyl alcohol fibers, particularly high-strength, high-modulus polyvinyl alcohol fibers using ultra-high polymerization degree polyvinyl alcohol-based polymers. The method for manufacturing fibers is discussed.

[Prior art] In recent years, a semi-dilute solution of ultra-high molecular weight polyethylene is spun into a cooling bath to form a -H crystal gel, and after the resulting gel-like thread is desolvated, it is highly stretched to form Kevlar. Since the discovery of a technique for obtaining high-strength, high-modulus polyethylene fibers with superior mechanical performance, studies have been widely conducted to apply this manufacturing technique to ultra-high degree of polymerization flexible polymers other than polyethylene.

Among these, polyvinyl alcohol (hereinafter referred to as PVA)
) has a zigzag polymer crystal structure, so its theoretical strength and theoretical modulus are expected to be extremely high compared to other flexible polymers [T, 0HTA Poly
+ner Engineering and 5cie
ncevo1.23 No, L3 p, 697 (19
83), Masatoshi Iguchi, Journal of the Organic Synthesis Society, vol. 42
No. 11 p. 1050 (1984).The melting point is also 230 to 240°C or higher, and it has extremely high utility value in the field of industrial textiles where high mechanical performance is required.

Regarding the manufacturing method of such high-strength, high-modulus PVA-based fibers, Japanese Patent Application Laid-open No. 1530314/1983 describes
A method is disclosed in which a glycerin solution of 00 or higher PVA is spun into a paraffin oil bath, cooled and gelled, and the resulting gel-like thread is removed from the solvent, dried, and then stretched three times or more. However, this method tends to cause fusion during cooling gelling or drying, and has low drawability, making it difficult to industrially produce multifilaments with a fineness of 10 deniers or less.

Zara Lko JP-A No. 60-126312 discloses that a dimethyl sulfoxide solution of PVA with a degree of polymerization of 3000 or more is wet-dry spun in a methanol coagulation bath and highly stretched and oriented to produce high-strength, high-modulus PVA fibers. A method of manufacturing is disclosed. However, when dimethyl sulfoxide is used as a spinning solvent, the solvent is strongly basic (pH ≧ 12), so if spinning is carried out at 100°C or higher, the degree of polymerization of PvA with a degree of polymerization of 5000 or more will decrease significantly due to alkaline decomposition. [Naito et al., Polymer Chemistry Vol. 16]
Vol. 168, p. 217 (1959)], there were problems such as the fibers being colored brown.

The inventors of the present invention have discovered the present invention as a result of intensive studies on an industrial method for producing high-strength, high-modulus PVA-based fibers using ultra-high polymerization degree PVA-based polymers.

[Problems to be solved by the invention, that is, the object of the present invention is to
The object of the present invention is to provide an industrially advantageous method for producing high-strength, high-modulus PVA-based fibers having mechanical strength and elastic modulus comparable to those of Kevlar (2).

Means for Solving Problems] The above-described objects of the present invention can be achieved by the invention described in the claims.

One of the features of the present invention is that an ultra-high polymerization degree polymer having a polymerization degree of 5000 or more, preferably 7000 or more, and more preferably 8000 or more is used as the PVA-based polymer. By using such a polymer with an extremely high degree of polymerization, the strength can be increased to 18 g/d or more, preferably 20 g/d or more.
It is possible to produce high-strength, high-modulus PVA-based fibers with a g/c of 1 or more, more preferably 22 g/d or more, and an elastic modulus of 350 g/d or more, preferably 400 g/d or more, and even more preferably 450 g/d or more. It can be done.

According to studies conducted by the present inventors, such ultra-high polymerization degree PVA-based polymers have extremely low solubility in solvents and have extremely high solution viscosity, so wet spinning, which is known as a general method for producing PVA-based fibers, It is difficult to spin with 15
Industrially productive and stable spinning can only be achieved by a dry-wet spinning method that uses a specific solvent as a spinning solvent that can dissolve ultra-high polymerization degree PVA without thermally decomposing it at high temperatures of 0°C or higher. I found out that it can be done.

In other words, the PVA polymer used in the present invention is a fully saponified or partially saponified PVA polymer having a polymerization degree of at least 5000, preferably 7000, more preferably 8000 or more, and a copolymerized PVA polymer in the main chain. As a component, for example, a PVA-based polymer copolymerized with a small amount of olefinic monomers such as ethylene, propylene, and styrene can be mentioned, but preferably a completely saponified polymer with a degree of saponification of 99 mol% or more and a degree of polymerization of 8,000 or more. PVA is good.

In the present invention, it is essential to use a glycol-based solvent that is ionically neutral and has good solubility in PVA as the spinning solvent. Not only can it be dissolved without thermal decomposition even at high temperatures of 150°C or higher, but the viscosity of the solution can also be lowered. Specific examples of such glycol-based solvents include glycerin, ethylene glycol, propylene gelylcol, tetramethylene glycol, diethylene glycol, and triethylene glycol, singly or in combination, but preferably glycerin, Ethylene glycol is good.

In the present invention, the PVA-based polymer purity of the spinning solution is 3.
% by weight or more and 20% by weight or less, preferably 5% by weight or more1
It is 5% by weight or less. At this time, the polymer concentration was 3% by weight.
If it is less than this, the solution viscosity becomes extremely low, making spinning difficult, and the resulting coagulated yarn has a rough structure, which tends to deteriorate the fiber properties. Also, the polymer concentration is 20
If it exceeds % by weight, the solution viscosity becomes significantly high and PVA
Problems such as difficulty in dissolving the polymer and difficulty in spinning tend to occur.

In the present invention, the spinning solution must be maintained at a temperature of 150°C or higher and 240°C or lower, preferably 170°C or higher and 230°C or lower. At temperatures below 150°C, the PVA polymer will precipitate and phase separate, causing the solution to gel and become impossible to spin.
At temperatures above 240°C, PVA-based polymers begin to undergo thermal decomposition.

Such a high-temperature ultra-high polymerization degree PVA-based polymer solution cannot be spun by a normal wet spinning method, and the dry-wet spinning method used in the present invention, that is, the spinning solution is directly discharged from a spinneret into a coagulation bath. Rather, the spinning solution is once discharged from a spinneret into an inert atmosphere such as air, nitrogen, helium, argon, etc., and then this discharged yarn is placed in a coagulation bath consisting of a solvent that is miscible with the spinning solvent. Spinning can only be achieved by introducing the material into a solvent, removing the solvent, and coagulating it. In addition, by employing such a dry-wet spinning method, the coagulation tension applied to the coagulated yarn during desolvation and coagulation is absorbed and relaxed by the discharged yarn in a solution state in an inert atmosphere, resulting in a dense coagulated yarn. Not only does it become possible to draw to a high degree, but because the cooling and desolvation of the high-temperature ultra-high polymerization degree PVA solution proceed simultaneously, there is no adhesion between single filaments, and the fibers can be stretched to 10 deniers or less, preferably 6 deniers or less. This makes it possible to industrially produce multifilaments.

In the present invention, in order to improve the density and stretchability of the coagulated yarn, the spinning draft shown by the following formula (1) is set to 0.
．． It is necessary to set the sail value to 05 or more and 1.0 or less, preferably sail 07 or more and sail 75 or less.

Take-up speed of coagulated yarn (m/min) Spinning draft = □ Linear speed of spinning solution discharge (m/min) ・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・ (1) Spinning If the draft is less than 0.05, the take-up speed of the coagulated yarn will be too slow compared to the linear velocity of the spinning solution discharged from the spinneret hole, and the yarn will become slack in the coagulation bath.
The variation in fineness between single yarns becomes large, making stable spinning impossible. Furthermore, if the spinning draft exceeds 1.0, the resulting coagulated yarn will have lower density and drawability, making it impossible to obtain high-strength fibers.

In the present invention, the solvent used as the coagulation bath may be any solvent as long as it is miscible with the glycol-based solvent, but preferably methanol, ethanol, or acetone has a precipitation effect on the PVA-based polymer. or a mixed solvent of one selected from methanol, ethanol, and acetone and a glycol solvent.

The temperature of the coagulation bath is preferably 30° C. or lower, preferably 20° C. or lower, in order to increase the density of the coagulated yarn and to prevent fusion.

- The obtained coagulated yarn is dried and subsequently stretched using various means such as a heating tube, a heating medium bath, and a hot plate. In this case, the stretching ratio must be such that the total stretching ratio is at least 12 times, preferably 15 times or more, relative to the undrawn yarn. By drawing the coagulated yarn of highly dense ultra-high polymerization degree PVA-based polymer obtained by dry-wet spinning to such a high magnification, the strength is 183/d, preferably 20 g/d, more preferably 22 g. /d or more, elastic modulus is 350 g/d or more, preferably 400 g/d
As described above, it is possible to obtain a high-strength, high-modulus PVA-based fiber that has excellent fiber performance compared to conventionally known PVA-based fibers, preferably 450 g/d or more.

[Operations and Effects of the Invention] As described above, the present invention uses a glycol solvent, which is extremely advantageous in terms of thermal stability and solution viscosity, as a spinning solvent for ultra-high polymerization degree PVA having a polymerization degree of 5000 or more, and By performing wet-dry spinning under the spinning conditions, conventionally known PV
The present invention not only provides a means for industrially stably producing a high-strength, high-modulus PVA-based multifilament that has excellent fiber performance exceeding Kevlar 3, which is completely different from A-based fibers, but also In addition to its excellent mechanical performance, PVA-based fibers are extremely useful, as they can be widely used in general industrial materials by taking advantage of the good weather resistance inherent to PVA-based polymers. big.

Hereinafter, the present invention will be explained in more detail based on Examples.

In the following examples, the degree of polymerization of PVA and the mechanical properties of fibers are values measured by the measurement method described below.

(2) Δ゛'l'' Based on JIS K6726, the degree of polymerization (Pn) was calculated from the limiting viscosity ([η) of the aqueous solution at 30°C using the following formula.

log(Pn) = 1.613 X log([7t
] X 104/8.29) However, [ηko: (
ml/g) The Toyosumi Sako two-plate fiber was conditioned in advance at 20°C and 65% relative humidity for 24 hours, and then stretched at a sample length of 2 On+ m and a pulling speed of 100+n+n/min. Single yarn strength and initial elastic modulus were measured using a testing machine.

Example 1 Bulk ultraviolet polymerization of vinyl acetate was carried out at -40°C using dimethylphosphinate pivalate (PDME) as an initiator, and the resulting polyvinyl acetate was completely saponified with sodium methylate to produce PVA with a polymerization degree of 11,000. (polymerization rate 13%).

The obtained PVA was heated and dissolved in glycerin at a temperature of 2000C to prepare a spinning solution having a PVA concentration of 8% by weight.

The resulting spinning solution was kept at a temperature of 190°C and the pore size was adjusted to 0.1.
A discharge amount of 7.3 ccZ was discharged into the air through a nozzle with 2 mm diameter and 20 holes, and in the air of approximately I Q m n+ (
After running the distance (distance between the mouthpiece surface and the coagulation bath liquid level),
It was introduced into a methanol coagulation bath containing 5 % of glycerin and coagulated, and taken off at a take-up speed of 10 m/7 min (spinning trough l-: 0.31).

The resulting undrawn yarn was washed with methanol, stretched three times with double rollers, and dried with heated rollers at 80°C. The dried yarn was passed through a heating tube with a nitrogen stream at 255°C, stretched 5.5 times, and wound up on a winder. The total drawing ratio of the obtained drawn yarn was 16.5 times, and the single yarn fineness was 2. Od, single yarn strength is 23.8 g/d,
The initial elastic modulus was 550 g/d and the elongation was 4.7%.

Examples 2 and 3, Comparative Example 1 Under the polymerization conditions shown in Table 1, three completely saponified PVAs having different degrees of polymerization were produced.

Table 1 ADVN...Azobisdimethylvaleroni, tolyl AI
BN...Azobisisobutyronitrile Obtained PVA
PVA with a polymer concentration of 3500 is 12-polyffi
%, degree of polymerization 6300 (7) PVA is 10%,
PVA having a degree of polymerization of 9500 was dissolved in glycerin by heating to a concentration of 8% by weight, and dry-wet spinning was performed in the same manner as in Example 1. The obtained undrawn yarn was washed with methanol to remove glycerin, and then hot-stretched in a heating cylinder at 250°C. The strength and elastic modulus of the fibers drawn at each maximum draw ratio were measured, and the results are summarized in Table 2.

(Hereinafter, blank spaces) Table 2 Example 4, Comparative Example 2 The PVA used in Example 1 was dissolved in ethylene glycol at 180°C to create a spinning solution with a polymer concentration of 9% by weight. As a comparison, the same PVA was dissolved in dimethyl sulfoxide at 130° C. to create a solution with a polymer concentration of 6% by weight. The dimethyl sulfoxide solution was colored reddish brown and had extremely high viscosity even though it was purged with nitrogen.

Each solution was spun and drawn in the same manner as in Example 1 to obtain a yarn with a total draw ratio of 16 times. When the physical properties of the obtained yarn were measured, the yarn using ethylene glycol as a solvent had a fineness of 2.3 d and a strength of 23.4 g/
d, the elastic modulus was 510 g/d, but when dimethyl sulfoxide was used as a solvent, the yarn became brown, the fineness was 2.2 d, the strength was 17.13/d, and the elastic modulus was 470 g/d.
There was lJ. In addition, when we dried each coagulated thread before drawing and measured the polymerization degree, the polymerization degree of the coagulated thread from ethylene glycol solvent was 10,300, but that of the coagulated thread from dimethyl sulfoxide solvent was 5,800, which was significantly higher. was decreasing.

Example 5, Comparative Example 3 Using the spinning solution prepared in Example 1, spinning was carried out in the same manner as in Example 1, except that the hole diameter of the spinneret used was changed to 0.15 u + mφ, 0.30 n field φ. Ta. Table 3 shows the maximum stretching ratio of the obtained coagulated yarn and the physical properties of the drawn yarn.

Table 3

Claims (6)

[Claims] (1) A spinning solution obtained by dissolving a polyvinyl alcohol polymer having a degree of polymerization of at least 5000 in a glycol solvent is kept at a temperature of 150°C or more and 240°C or less, and is miscible with the glycol solvent. Wet-dry spinning is performed in a coagulation bath containing a solvent so that the spinning draft is 0.05 or more and 1.0 or less, and the resulting undrawn yarn has a strength of 18 g/
A method for producing high-strength, high-modulus polyvinyl alcohol fibers, which comprises stretching the fibers so that the elastic modulus is 350 g/d or more and the elastic modulus is 350 g/d or more. (2) A method for producing a high-strength, high-modulus polyvinyl alcohol fiber according to claim (1), wherein the polyvinyl alcohol polymer has a degree of polymerization of 7,000 or more. (3) A method for producing a high-strength, high-modulus polyvinyl alcohol fiber according to claim (1), wherein the polymer concentration of the spinning solution is 3% by weight or more and 20% by weight or less. (4) In claim (1), the glycol solvent is selected from glycerin, ethylene glycol, propylene glycol, tetramethylene glycol, diethylene glycol, and triethylene glycol;
Or a method for producing high-strength, high-modulus polyvinyl alcohol fibers using a mixed solvent. (5) In claim (1), the solvent compatible with the glycol solvent is at least one selected from methanol, ethanol, and acetone, or at least one selected from methanol, ethanol, and acetone and glycol A method for producing high-strength, high-modulus polyvinyl alcohol-based fibers using a mixed solvent with a polyvinyl alcohol-based solvent. (6) A method for producing a high-strength, high-modulus polyvinyl alcohol fiber according to claim (1), wherein the stretching is performed at a stretching ratio of 12 times or more.