JPH0586504A - Method for producing polyvinyl alcoholic yarn - Google Patents

Abstract

PURPOSE:To obtain the subject yarn having high strength and high initial modulus of elasticity by blending two kinds of PVAs having different degrees of polymerization in a specific ratio to give a spinning dope, subjecting the dope to dry wet spinning in a coagulating bath having >=a specified temperature and thermally drawing. CONSTITUTION:A PVA having 3,000-5,000 degree of polymerization is blended with one having 300-2,000 degree of polymerization in a ratio of 99:1 to 80:20 by weight to give a spinning dope, which is subjected to dry wet spinning in a coagulating bath of >=25 deg.C to give undrawn yarn. The undrawn yarn in wound once, successively thermally drawn to give the objective yarn. In the cases when these PVAs are dissolved in a solvent to prepare the spinning dopes, DMSO is preferable as the solvent. The degree of saponification of both the PVAs is preferably >=99%.

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 fiber having a high strength and a high initial elastic modulus, which is made of a polyvinyl alcohol (hereinafter abbreviated as PVA) polymer.

[0002]

2. Description of the Related Art PVA fibers have the highest strength and the highest initial elastic modulus among general purpose fibers, and are rubber hoses, conveyor belts, fibers for cement reinforcement, sewing threads for materials, tatami threads, fishing nets, land nets, and heavy cloth. Widely used as a fiber for industrial materials such as ropes.

In recent years, PV has been responding to the demands of the increasingly sophisticated market.
Various attempts have been made to increase the strength and initial elastic modulus of the A-based fibers to the level of aramid fibers. For example, JP-A-59-130314 discloses a glycerin solution of PVA having a weight average molecular weight of 500,000 or more in a cooling bath. A method is disclosed in which gel spinning is performed, glycerin in the solidified yarn is removed, and then hot drawing is performed. Further, JP-A-60-126312 discloses that P having a polymerization degree of 1800 or more.
It discloses a method in which a VA solution of VA in dimethylsulfoxide (DMSO) is subjected to dry and wet spinning in a methanol bath, and the resulting undrawn yarn is hot-drawn.

In these methods, a low-concentration solution of highly polymerized PVA is subjected to gel spinning or dry / wet spinning to reduce the entanglement of molecular chains in the undrawn yarn, thereby improving the drawability, It is intended to obtain a high-strength fiber by drawing a stretched chain structure by drawing at a high ratio in the hot drawing step. Therefore, in order to obtain high-strength fibers of 17 g / d or more by these methods, it is difficult to obtain them commercially, and it is necessary to use expensive high-polymerization degree PVA. It is disadvantageous in terms of raw material cost and manufacturing cost, such as the need to lower the PVA concentration of, and industrial implementation was difficult.

Further, in JP-A 1-221512, a PVA-based polymer having an average degree of polymerization of 5000 or more and a PVA-based polymer having an average degree of polymerization of 1500 to 10000, which has a lower average degree of polymerization, have excellent fatigue resistance. A method for producing PVA-based fibers is disclosed.

Generally, PVA is industrially produced by saponifying polyvinyl acetate obtained by polymerizing vinyl acetate, but in order to obtain PVA having a degree of polymerization of 5000 or more, polymerization of vinyl acetate is required. Since it is necessary to take measures such as lowering the yield or polymerizing at low temperature, the average degree of polymerization is 5000
The above method using the above PVA-based polymer is disadvantageous because of the high cost.

[0007]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
Various attempts have been made to increase the strength and the initial elastic modulus of the A-based fiber, but all of them are disadvantageous in terms of cost and industrially difficult to implement. It is a technical object of the present invention to solve the above problems and provide a method for producing PVA-based fibers having high strength and high initial elastic modulus with high productivity from commercially available PVA. is there.

[0008]

Means for Solving the Problems As a result of intensive studies for solving the above problems, the present inventors have surprisingly found that PVA obtained by mixing two types of PVA having different polymerization degrees at a specific ratio. When the spinning dope is dried and wet-spun, the low degree of polymerization PVA falls off from the undrawn yarn, so that the entanglement of molecular chains is reduced, and an undrawn yarn with high drawability is obtained without lowering the PVA concentration. The present invention has been accomplished by finding that a high-strength / high initial elastic modulus PVA-based fiber of 17 g / d or more can be obtained by hot-drawing an undrawn yarn.

That is, according to the present invention, an unstretched yarn is formed by dry and wet spinning a spinning stock solution prepared by dissolving PVA in a solvent, and after winding the unstretched yarn once or continuously. When producing a PVA-based fiber by hot drawing, PVA (A) having a degree of polymerization of 3000 or more and less than 5000 and PVA (B) having a degree of polymerization of 300 or more and 2000 or less are used in a weight ratio of 99: 1 to 80:20. A method for producing a PVA-based fiber is characterized in that dry spinning and wet spinning are performed in a coagulation bath at a temperature of 25 ° C. or higher using a spinning stock solution mixed so as to achieve the following.

The present invention will be described in detail below.

High degree of polymerization PVA (A) used in the present invention
Has a degree of polymerization of 3000 or more, preferably 35
00 or more. When the degree of polymerization is lower than 3000, the strength of the obtained fiber is lower than 17 g / d and the object of the present invention cannot be achieved. The upper limit of the degree of polymerization of PVA (A) is 5000 from the viewpoint of polymer cost. On the other hand, the degree of polymerization of PVA (B) having a low degree of polymerization needs to be 300 or more and 2000 or less. PV
When the degree of polymerization of A (B) exceeds 2000 or PVA (B)
When the degree of polymerization is less than 300, the unstretched yarn obtained does not have high drawability, and high-strength fibers cannot be obtained. The degree of saponification of these PVA (A) and (B) is
It is preferably 99% or more.

The degree of polymerization referred to in the present invention is JIS-K6726.
It is calculated by the following formula from the intrinsic viscosity [η] of the PVA aqueous solution measured by the PVA test method described in 1. log P _A = 1.613 × log ([η] × 10 ⁴ /8.19)

In the present invention, PVA having a high degree of polymerization is used.
Although (A) and PVA (B) having a low degree of polymerization are mixed, it is important that the mixing ratio is 99: 1 to 80:20 (weight ratio). That is, PVA in the spinning dope has a high degree of polymerization of P
VA (A) and PVA (B) having a low degree of polymerization are dissolved together as a single body, and these PVA molecular chains form a certain number (N ₀ ) of entanglement. By dry-wet spinning the spinning dope, the spinning dope extruded into the coagulation bath immediately precipitates and solidifies while maintaining the (N ₀ ) entanglement due to the coagulation action and cooling action of the coagulation bath. However, PVA (B) having a low degree of polymerization is easily dropped from the solidified yarn and precipitates in the coagulation bath, so that a molecular chain of PVA (B) having a low degree of polymerization was formed (N ₁ ). Entanglement disappears, and the number of entanglements remaining in the undrawn yarn is (N ₀ −N
₁ ), which is an undrawn yarn having a structure with less entanglement and high drawability.

The present inventors have made a detailed study on the mixing ratio of PVA (A) and (B), and as a result, PV with a high degree of polymerization has been obtained.
It has been found that it is important that the mixing ratio of A (A) and PVA (B) having a low degree of polymerization is 99: 1 to 80:20 by weight. When the mixing ratio of PVA (A) is larger than the above range, the effect of mixing becomes too small and the stretchability does not increase,
On the other hand, if it becomes smaller, even if the stretchability increases, it will not be reflected in the strength, initial elastic modulus, etc., and the fiber will have poor physical properties, and the object of the present invention cannot be achieved.

In the present invention, these PVA are dissolved in a solvent to prepare a spinning dope, and the solvent is DM.
SO, glycerin, ethylene glycol, 1,3-dimethyl-2-imidazolidinone, water, a mixed solvent thereof or the like can be used, and DMSO is particularly preferably used.

As a method of mixing two types of PVA,
A method of mixing each PVA in a solid state before dissolving it in a solvent, a method of individually dissolving each PVA in a solvent and then mixing in a solution state, and the like, but a method of mixing in a solid state Is simple and preferred.

In the present invention, the concentration of PVA in the spinning dope is not particularly limited, but PVA (A),
Both (B) are preferably 5 to 35% by weight, and more preferably 10 to 35% by weight. Further, when dissolving, a graded dissolver as described in Japanese Patent Application No. 2-74632 is used, and when dissolved at 80 to 120 ° C. in a nitrogen atmosphere, decomposition and deterioration of the polymer are prevented, It is preferable because it can be uniformly dissolved. Furthermore, if desired, a crosslinking agent or a heat-resistant agent may be added to the spinning solution within a range that does not reduce the drawability of the undrawn yarn.
A pigment or the like may be mixed.

In the present invention, the spinning dope prepared as described above is subjected to dry / wet spinning in a coagulation bath. At that time, it is an object of the present invention to set the temperature of the coagulation bath to 25 ° C. or higher. Is important to achieve.

That is, in the present invention, PVA having a different degree of polymerization is used.
The use of the spinning dope mixed with is to remove the low polymerization degree PVA from the solidified yarn as described above to reduce the entanglement of the PVA molecular chain and improve the drawability, This is because the higher the bath temperature, the lower the degree of polymerization PVA is likely to fall from the solidified yarn. If the coagulation bath temperature is lower than 25 ° C., the PVA having a low degree of polymerization remains too much in the solidified yarn and the drawability is not improved.

Methanol is preferably used as the coagulation bath, and in order to keep the coagulation bath temperature at 25 ° C. or higher, the coagulation liquid may be passed through a heat exchanger having heating and cooling functions. Moreover, since the low-polymerization degree PVA that has fallen off floats in the coagulation bath, a filter may be installed in the above-mentioned flow path.

In the present invention, the solvent (for example, DMSO) in the solidified yarn obtained by dry and wet spinning is removed with a solvent such as methanol, and then an oil agent is applied and dried.
At this time, an oil agent to which a dehydration reaction catalyst such as phosphoric acid or paratoluenesulfonic acid is added may be used.

The unstretched yarn thus obtained is once wound or continuously supplied to the stretching step and hot-stretched. The thermal draw ratio is not particularly limited, but is preferably 17 times or more, more preferably 20 times or more. The stretching speed is preferably 10 m / min or more. Such hot stretching can be performed by various methods, for example, a method of stretching while contacting an unstretched yarn with a heating body such as a heat plate, a method of stretching in a heating medium,
Examples of the method include a method of stretching in a hot air heating bath and a method of stretching by a dielectric heating method, and a hot air heating bath is preferably used.

The temperature during hot stretching is not particularly limited, but for example, when stretching in a hot air heating bath,
It is preferable that the inlet temperature is 200 ° C or higher and the outlet temperature is 270 ° C or lower.

According to the present invention, PVA having a high strength and a high initial elastic modulus is prepared by using PVA having a polymerization degree which is commercially available.
It is possible to manufacture VA-based fibers at low cost with high productivity.

[0025]

In the present invention, the PVA fiber having high strength and high initial elastic modulus is obtained by mixing the high-polymerization degree PVA and the low-polymerization degree PVA to prepare a spinning dope. When dry / wet spinning is performed in a coagulation bath at a temperature of ℃ or higher, the low degree of polymerization PVA drops off from the undrawn yarn and remains high degree of polymerization PVA.
It is recognized that since the number of entanglement of the molecular chains of 1 decreases, it becomes possible to stretch at a high magnification.

[0026]

EXAMPLES Next, the present invention will be specifically described by way of examples.

Examples 1 and 2 and Comparative Examples 1 and 2 As shown in Table 1, PVA having a degree of polymerization of 3900 and PVA having a degree of polymerization of 1200 have a weight mixing ratio of 100: 0 (only PVA having a degree of polymerization of 3900), PVA mixed at 98: 2, 90:10, and 70:30 was added at 90 ° C. to a D concentration of 16% by weight.
A stock solution for spinning was prepared by dissolving in MSO.

The spinning stock solution was filled with 232 stainless steel cylindrical capillaries having an inner diameter of 0.45 mm so as to project 3 mm toward the spinning stock solution outlet side.
After dry and wet spinning in a methanol coagulation bath with a liquid temperature of 30 ° C through a 30 mm air gap to remove DMSO with methanol, add 1.1% by weight of an oil agent containing polyoxyethylene sorbitan trioleate as a main component. Further, it was dried at 85 ° C. to obtain an undrawn yarn.

Next, these undrawn yarns were heated at an inlet temperature of 2
Using a hot air heating bath having a length of 5 m and a temperature of 10 ° C. and an outlet temperature of 255 ° C., it was drawn at a draw ratio of 90% of the maximum draw ratio at a draw speed of 30 m / min.

The production conditions and the performance of the fibers obtained are shown in Table 1. The fibers obtained in Examples 1 and 2 had excellent performances in both tensile strength and initial elastic modulus.

On the other hand, Comparative Examples 1 and 2 are examples in which the mixing ratio of the low degree of polymerization PVA is outside the range of the present invention, and in Comparative Example 1, only a fiber having a low draw ratio and a low strength can be obtained. In Comparative Example 2, although the draw ratio was high, high-strength fiber was not obtained.

Example 3 and Comparative Example 3 As shown in Table 1, PVA having a polymerization degree of 2300 and 3300 was mixed with PVA having a polymerization degree of 700 at a mixing ratio of 90:10 to obtain a PVA concentration of 21. A stock solution for spinning was prepared by dissolving it in DMSO so that the concentration was 17% by weight and 17% by weight.

This spinning dope has an inner diameter of 0.8 mm.
Using a spinneret in which 300 0.7 mm stainless steel cylindrical capillaries were embedded, dry and wet spinning was performed through a 20 mm air gap in a methanol coagulation bath at a discharge linear velocity of 6.6 m / min, after removing DMSO with methanol, 0.8% by weight of a catalyst solution obtained by mixing phosphoric acid in an oil agent containing polyoxyethylene oleyl ether as a main component so that the concentration becomes 0.5 N.
It was applied and further dried at 85 ° C. to obtain an undrawn yarn.

Then, these undrawn yarns were hot-drawn in the same manner as in Example 1 to obtain drawn yarns. The production conditions and the performance of the obtained fiber are shown in Table 1. The fiber obtained from PVA having a polymerization degree of 2300 had a low tensile strength.

[0035]

[Table 1]

Comparative Example 4 A PVA fiber was produced in the same manner as in Example 1 except that the temperature of the coagulation bath was changed to 20 ° C. However, it could only be stretched 14.5 times, and the strength of the obtained fiber was 13.7 g / d. It was nothing more than

[0037]

INDUSTRIAL APPLICABILITY According to the present invention, PVAs having a high strength and a high initial elastic modulus are selected from commercially available PVA having a polymerization degree.
It is possible to manufacture the A-based fiber at low cost with high productivity.

Front Page Continuation (72) Inventor Shinya Takagi, 23 Uji Kozakura, Uji City, Kyoto Prefecture Unitika Central Corporation, Central Research Laboratory (72) Inventor Masatsugu Mochizuki, Uji City, Kyoto Prefecture 23, Uji Kozakura Unitika Stock Company Central Laboratory

Claims (1)

[Claims] 1. A spinning stock solution prepared by dissolving polyvinyl alcohol in a solvent is dry-wet spun in a coagulation bath to form an unstretched yarn, and the unstretched yarn is once wound or continuously heated. When producing a polyvinyl alcohol fiber by stretching, polyvinyl alcohol (A) having a degree of polymerization of 3000 or more and less than 5000 and polyvinyl alcohol (B) having a degree of polymerization of 300 or more and 2000 or less are used in a weight ratio of 99: 1 to 80:20. Using the spinning dope mixed to achieve the following, dry in a coagulation bath at a temperature of 25 ° C or higher.
A process for producing a polyvinyl alcohol fiber, which comprises wet spinning.