JPH02210014A - Production of polyvinyl alcohol multifilament yarn - Google Patents

Abstract

PURPOSE:To improve the strength, etc., of a multifilament PVA yarn produced by wet-spinning process by quenching a spinning dope at the orifice part of a spinneret, extruding the dope from the spinneret to form a yarn, extracting the solvent and hot drawing the yarn. CONSTITUTION:A polyvinyl alcohol having a polymerization degree of >=1,500 (preferably 4,500-7,000) is dissolved in a solvent (e.g. glycerol) and extruded through a spinneret to form a yarn while being quenched at the orifice part of the spinneret. The solvent is extracted with methanol, etc., and the yarn is hot-drawn (preferably at a total draw ratio of >=15) to obtain a polyvinyl alcohol multifilament yarn having high strength and initial modulus and suitable for fishing net, tire cord, etc., in high productivity and stability.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for producing polyvinyl alcohol (hereinafter abbreviated as PVA) multifilament yarn, and more specifically to a method for producing polyvinyl alcohol (PVA) multifilament yarn, which has high strength and high initial elastic modulus. The present invention relates to a method for manufacturing multifilament yarn with high productivity.

(Prior art) Recently, polyvalent phenylene terephthalamide (hereinafter referred to as P
It is abbreviated as PTA. ), 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,
It has become possible to obtain high strength/high initial elastic modulus fibers having a strength of 20 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 have the disadvantage that they are much more expensive 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.

In terms of initial elastic modulus as well, although fibers have been obtained that have performance quite close to the limit, 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 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 studied. For example, JP-A-59-13031
No. 4 or JP-A No. 61-289112 discloses that PVA having a molecular weight of 500,000 or more or 1,000,000 or more is obtained by dry/wet spinning using ultra-high polymerization degree PVA. A high strength, high initial modulus PVA fiber and a method for producing the same are described.

On the other hand, various methods have been proposed for obtaining PVA fibers with high strength and high initial elastic modulus by using PVA with a degree of polymerization of 9 or more than 1500 without using PVA with such a super high degree of polymerization. For example, JP-A-60-126312 and JP-A-62-16
No. 2010 discloses that a spinning stock solution is prepared by dissolving PVA with a degree of polymerization of 1500 or more in a solvent containing dimethyl sulfoxide (hereinafter abbreviated as DMSO) as a main component, and this spinning stock solution is subjected to dry/wet spinning. A method of forming a gel-like undrawn yarn and then drawing it is disclosed.

Also, JP-A-61-108711 and JP-A-61-108711
No. 108712 describes PVA with a degree of double polymerization of 1500 or more.
A method has been proposed in which a spinning stock solution prepared by dissolving ethylene glycol or glycerin in a nonvolatile solvent such as ethylene glycol or glycerin is wet-spun or dry-wet-spun into a solvent 1 that is immiscible with the solvent, such as decalin or trichlorethylene. has been done.

However, in all of these methods, the spinning tension becomes unstable due to the low spinning draft, resulting in uneven fineness and yarn quality in the longitudinal direction of the yarn.
There is a problem that A fiber cannot be obtained stably.

The present inventors aimed to solve the above problems.

In Japanese Patent Application No. 63-146144, the degree of polymerization is 1500.
The distance from the spinneret to the coagulation bath surface, the so-called air gap, of the spinning stock solution prepared by dissolving the above PVA in a solvent containing DMSO as the main component, was set to 15a+a+ or more.

In addition, a method for obtaining an undrawn yarn by performing dry/wet spinning under conditions where the spinning trough I-(Dr) satisfies 2≦Dr≦10 was proposed. According to this method, the spinning tension can be stabilized and the drawability is significantly improved.

It is now possible to produce undrawn yarn with no unevenness in fineness or yarn quality in the longitudinal direction of the yarn, making it possible to produce PVA with high strength and high initial elastic modulus.
It has become possible to produce fibers industrially and stably.

・However, as a result of intensive studies in order to more stably produce PVA fibers with high strength and high initial elastic modulus, the inventors found that by increasing the air gap, slight yarn sway within the air gap can be reduced. However, the area around the spinneret should be kept very close to avoid turbulence in the airflow around the spinneret and to prevent the surface of the coagulation bath from undulating. It was found that precise control was required and there was a limit to increasing the air gap.

(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, but
In the method of spinning using ultra-high polymerization degree PVA as in Publication No. 314, such polymers are difficult to obtain commercially, and such ultra-high polymerization degree PVA has low solubility in the WI medium. is low.

Moreover, it has a high solution viscosity when dissolved.

Due to poor spinnability, the polymer concentration had to be lowered,
This is disadvantageous in terms of both raw material cost and manufacturing cost.

Furthermore, in the method disclosed in JP-A-61-108711, etc., it is difficult to industrially and stably produce undrawn yarn with uniform fineness and quality due to the low spinning draft.

On the other hand, the two inventors previously proposed patent application No. 63-1461.
The above problem can be solved to some extent by setting the air gap to 15 mm or more and the spinning draft to a range of 2≦Dr≦10 according to the method of No. Therefore, there were certain limits.

The present invention overcomes the above-mentioned drawbacks and uses commercially available PVA with a degree of polymerization and has high strength and high initial elastic modulus, with a dual strength of at least 17 g/d and an initial elastic modulus of at least 400 g/d. PVA with virtually no sticking between single threads
The technical objective is to provide a method for stably manufacturing multifilament yarn with high productivity.

(Means for Solving the Problems) As a result of intensive studies to solve the above problems, the present inventors found that it is sufficient to rapidly cool the spinning dope in the orifice of the spinneret and then discharge it from the spinneret. The present invention was thus achieved.

In other words, when performing dry/wet spinning of a spinning stock solution prepared by heating and dissolving PVA with a polymerization degree of 1500 or more in a solvent, the spinning stock solution is rapidly cooled at the orifice of the spinneret and extruded from the spinneret to form a yarn. Form 1
The gist of the present invention is a method for producing a PVA multifilament yarn, which is characterized in that the solvent in the yarn is extracted to obtain an undrawn yarn, which is then hot-stretched.

The following two inventions will be explained in more detail.

The degree of polymerization of PVA used in the present invention needs to be 1500 or more in view of the physical properties of the fibers obtained, preferably 300 or more.
It is 0 or more, more preferably in the range of 4,500 to 7,000.

In addition, the degree of polymerization here is the apparent viscosity average degree of polymerization PA calculated from the following experimental formula.

[ηko ``5.08X10-''X PA'''''Here,
[η] (d!/g) is 2
Intrinsic viscosity measured at 0°C.

Moreover, the degree of saponification of PVA is preferably 99% or more.

A spinning stock solution is prepared by heating and dissolving such PVA in a solvent. Solvents for dissolving PVA include saturated aliphatic polyhydric alcohols such as glycerin, ethylene glycol, and propylene glycol, or DMSO, water, etc. Although the solvent may be selected from a mixture of these, DMSO or a mixed solvent of DMSO and water is preferably used.

In addition, in the present invention, a heat resisting agent for PVA, a pigment, a crosslinking agent, and other additives may be appropriately mixed into the above solvent.

The concentration of PVA in the spinning dope is 2 when the temperature of the spinning dope immediately after being discharged from the spinneret is approximately 40°C to 170°C.
It is preferable to adjust the content to a range of 35% by weight. concentration is 2
If it is less than 3% by weight, the spinnability of the spinning dope decreases and
When it exceeds 5% by weight, the viscosity is high and the uniformity of the spinning dope is reduced.

The drawability of the undrawn yarn also tends to decrease, which is not preferable.

In the present invention, a spinning stock solution prepared by heating and dissolving PVA in the above-mentioned solvent is extruded from a spinneret to form yarn.

It is extremely important to extrude the spinning solution while rapidly cooling it at the orifice of the spinneret.

Generally, when a polymer is dissolved in a solvent, one molecular chain of one polymer forms entanglements between one molecule within the molecule.

It is known that if there are too many entanglements, the drawability of the resulting undrawn yarn will be inhibited. As a method for disentangling this entanglement and improving drawability, the present invention focuses on the shearing force that PVA molecular chains are subjected to at the orifice of a spinneret. This is based on the knowledge that the stronger the force, the more effective the disentanglement.

If the spinning solution is extruded without quenching at the orifice of the spinneret, the viscosity of the spinning dope is too low, so the shearing force applied to the PVA molecular chains becomes weak, and the effect of disentangling the yarn is not sufficiently effective, resulting in difficulty in drawing the resulting undrawn yarn. This is not desirable because it lowers the performance.

On the other hand, if the spinning dope is cooled in advance before it reaches the spinneret and then extruded.

Although the viscosity of the spinning dope becomes high, it is undesirable because discharge unevenness tends to occur and the variation in fineness between the single fibers constituting the multifilament yarn and in the longitudinal direction of the fibers becomes large.

In the present invention, the quenching rate is not particularly limited, but the viscosity of the spinning dope immediately after discharge is at least twice, preferably at least three times, the viscosity immediately before the orifice of the spinneret, and the spinning dope is It is best to cool the mixture quickly enough to prevent it from gelling.

Further, as a method for rapidly cooling the spinning dope in the orifice portion of the spinneret, for example, a spinneret having a structure that allows cooling water to flow through the orifice portion may be used.

According to the present invention, there is no need to make the air gap thick (it does not need to be large, and the length may be about 2 to 12++ ua, so stable spinning is possible without sticking between single yarns, and the resulting undrawn yarn has a high It can withstand stretching at multiple ratios, and by stretching, it can be made into a highly oriented PVA multifilament yarn with high strength and high initial modulus.

Further, the draft during dry/wet spinning is not particularly limited, but in order to stably obtain an undrawn yarn that can be drawn at a high magnification, it is necessary to have a draft of 1 to 10. Particularly preferred is a range of 2 to 10.

The coagulation bath and extraction liquid bath into which the spinning solution extruded from the spinneret is introduced include alcohols such as methanol, ethanol, propatool, and butanol that are miscible with the solvent for dissolving PVA, or acetone, methyl ethyl ketone, and diethyl ketone. or a mixed solvent of these and a PVA solvent are used. In addition, as the cooling bath, decalin, paraffin, etc. which are immiscible with the solvent are used, and only cooling and gelation are performed in this cooling bath, and then the solvent may be extracted in the above-mentioned extraction liquid bath. .

In the present invention, the undrawn yarn thus formed is once wound up or continuously supplied to a drawing step and drawn.

In the present invention, drying, oil treatment, etc. are carried out during the step of forming undrawn yarn or before supplying it to the drawing step.

If necessary, other processing steps may be introduced as appropriate.

There are various stretching methods that can be applied in the present invention.5For example, a method in which the PVA yarn is stretched while it is in contact with a heating body such as a heat plate, a method in which the PVA yarn is stretched in a hot air bath such as a heating tube, and a method in which the PVA yarn is stretched in a heating medium. Method.

One example is a method of stretching using a dielectric heating method.

In the present invention, multi-stage stretching of one or two or more stages is performed using these methods, and multi-stage stretching is preferred. In addition, in multi-stage stretching, at least one stage of stretching is
The final stretching is preferably carried out at a temperature of 200°C or higher, more preferably a temperature of 200°C or higher.

In addition, in the multistage stretching, moisture application, oil application, etc. may be performed between the nth 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
A. To obtain multifilament yarn.

The total stretching ratio is preferably 10 times or more, more preferably 15 times or more.

According to the present invention, the commercially available degree of polymerization is 1500.
or more, preferably using PVA of 3000 or more.

It is possible to manufacture PVA multifilament yarn having high strength and high initial elastic modulus at low cost and with high productivity.

(Function) In the present invention, although it is not clear why the undrawn PVA yarn before drawing has high drawability, the spinning dope prepared by heating and dissolving PVA in a solvent is passed through the orifice of the spinneret into the gas. When the spinning dope is rapidly cooled and extruded through the orifice of the spinneret, shearing force acts on the PVA molecular chains in the spinning dope, disentangling the two molecular chains and forming threads. It is presumed that this is because of this.

(Example) The present invention will be specifically explained below using examples.

In addition, 1 strength and initial elastic modulus in the example are sample length 20c.
m, the value obtained when a tensile test was conducted at a tensile rate of 20 CO1/min. (20° C., 65% RH) Example 1 PVA with a degree of polymerization of 4800 was dissolved in DMSO at 120° C. to prepare a spinning stock solution with a concentration of 12% by weight. This spinning dope is rapidly cooled and extruded using a spinneret with 30 holes (1, the orifice part of which is cooled by water at a temperature of 4°C), and then placed in a dry/wet coagulation bath containing MSOIO %. spun. Further, the formed yarn was introduced into an extraction bath consisting of methanol to sufficiently extract the DMSO in the yarn.

It was dried and wound up to obtain an undrawn yarn. In addition, the air gap during the above dry/wet spinning was 5 mm, and the spinning draft was 4.0.
It was set to Also, what is the temperature of the spinning dope?

The temperature at the inlet of the spinneret was 90°C, but it dropped to 60°C immediately after discharge, and during this time the viscosity of the spinning dope increased 2.6 times.

The undrawn yarn wound above was wound at an internal temperature of 150°C and 24°C.
With two heating tubes at 0℃, the maximum stretching ratio of 95
Two-stage dry heat stretching was performed at a stretching ratio of 18.4 times, which corresponds to %. As a result, the obtained drawn yarn had a strength of 21.2 g/d.
, the initial elastic modulus was 504 g/d, no adhesion between single yarns was observed, and the fiber had excellent physical properties.

Comparative Example 1 Dry/wet spinning and hot stretching were performed in the same manner as in Example 1 except that the orifice of the spinneret was not cooled. The obtained drawn yarn had a dual strength of 15.2 g/d and an initial elastic modulus of 343 g/d.
d, and the physical properties were significantly inferior to those of Example 1. The temperature of the spinning dope is 90°C at the inlet of the spinneret.
The temperature immediately after discharge was 89°C, and there was almost no difference between the two.

Comparative Example 2 A spinning dope prepared in the same manner as in Example 1 was cooled to 60°C in a dissolution tank, and then subjected to dry/wet processing in the same manner as in Example 1, except that cooling at the orifice of the spinneret was not performed. spun. The resulting undrawn yarn had large unevenness in fineness in the longitudinal direction of the fibers, making it difficult to draw it stably, making it impossible to measure the physical properties of the drawn yarn.

Comparative Example 3 Dry/wet spinning and hot stretching were performed in the same manner as in Example 1 except that the orifice of the spinneret was not cooled and the air gap was changed to 150 mm except for the dot plate.

The obtained drawn yarn has a strength of 20.1 g/d and an initial elastic modulus of 4.
52 g/d, which was a relatively good value in terms of physical properties, but there was agglutination between the single yarns, and a yarn with stable quality could not be obtained.

(Effect of the invention) According to the present invention, the commercially available degree of double polymerization is 150.
By using PVA with a molecular weight of 0 or more, preferably 3000 or more, it is possible to produce a PVA multifilament yarn having high strength and high initial elastic modulus at low cost and with good productivity. Further two PVA multifilament yarns obtained by the method of the present invention are:

Because it has excellent heat resistance and hot water resistance, it can be used not only to expand the typical uses of PVA fibers, such as nets and ropes, but also as a reinforcing material for cement plastics, etc., as well as tire cords.

■It is also possible to expand its use as a rubber reinforcing material for belt timing belts, etc.

Claims (1)

[Claims] (1) When performing dry/wet spinning of a spinning stock solution prepared by heating and dissolving polyvinyl alcohol with a degree of polymerization of 1500 or more in a solvent, the spinning stock solution is rapidly cooled in the orifice of the spinneret and extruded from the spinneret to form yarns. After forming and then extracting the solvent in the yarn to obtain an undrawn yarn,
A method for producing polyvinyl alcohol multifilament yarn, which is characterized by hot drawing.