JPH02307908A - High-gloss, high-strength polyvinyl alcohol-based yarn and production thereof - Google Patents

Abstract

PURPOSE:To obtain the title polyvinyl alcohol-based yarn suitable for rope, etc., having specific tensile strength, knot strength, gloss, fatigue resistance and impact resistance free from whitening comprising PVA-based yarn having >=specific average polymerization degree. CONSTITUTION:A PVA-based polymer having >=3,000 average polymerization degree is dissolved in a solvent containing at least 20wt.% polyhydric alcohol- based solvent, spun in a coagulating bath containing >=50wt.% ethanol, quenched to <=30 deg.C, retardingly coagulated, drawn in a wet state, extracted, dried, the solvent is dried and then the yarn is drawn at >=220 deg.C so as to make >=17 times total draw ratio to give the aimed polyvinyl alcohol-based yarn having no lateral strip in the perpendicular direction to fiber axis on the surface of fiber or <=10 lateral stripes based on 100mu length, >=18g/d tensile strength of single yarn and >=3.5g/d knot strength of single yarn.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a glossy, high-strength polyvinyl alcohol (hereinafter abbreviated as PVA) fiber and a method for producing the same, and is particularly applicable to industrial materials and composite materials. The aim is to obtain PVA-based fibers suitable for reinforcement.

(Conventional technology) Conventional PVA fibers have higher strength and elastic modulus than polyamide, polyester, and polyacrylonitrile fibers, and are used not only as fibers for industrial materials and reinforcing composite materials, but also as asbestos substitute fibers. It is also used as cement reinforcing material.

A method for obtaining PVA fibers with high strength and high elastic modulus is gel spinning of high molecular weight polyethylene - Organic solvent applying the concept of ultra-stretching - JP-A-59-100710 on dry-wet spinning.
Publication No. 1987-108711, Japanese Patent Application Laid-open No. 1987-108711
-252313, or Japanese Patent Application Laid-Open No. 83-99315 for organic solvent wet spinning. These dimensions are determined by cooling the solution discharged from the nozzle, turning it into a gel, extracting the solvent with methanol, etc., and then stretching it to a high sound rate.
Fibers with a weight of 5 g/d or more are obtained, but the fast solvent extraction tends to result in non-uniform gels (and the high stretching ratio causes voids and defects due to horizontal stripes (whitening), and the orientation of molecular chains. was too high, and it was not possible to obtain sufficiently satisfactory values for bending fatigue resistance and impact.

On the other hand, JP-A-82-149909, JP-A-62-1
P■A containing boric acid as seen in Publication No. 49910
A method is known in which an aqueous solution is coagulated with an alkaline aqueous solution by dry-wet spinning, but since it does not gel by cooling alone, it is difficult to obtain a uniform gel and it is difficult to obtain fibers with excellent fatigue resistance and impact resistance.

In order to obtain PVA-based fibers with high strength and high elastic modulus, it is necessary to draw them at a high magnification to create a highly oriented crystal structure. , friction, impact, etc.? I couldn't bear it anymore.

(Problems to be Solved by the Invention) Therefore, the present invention aims at producing a glossy, high-strength, high-modulus P with almost no horizontal stripes by obtaining a uniformly transparent gel through delayed solidification.
The purpose is to obtain VA fibers.

(Means for Solving the Problems) That is, the present invention provides: (1) In PVA fibers having an average degree of polymerization of 3000 or more, the fiber surface has no horizontal stripes in the direction perpendicular to the fiber axis, or has an average of 10 stripes per 100 μm length. or less, and single l&fiber tensile strength is 113 g/d or more, single fiber knot strength is 3
．． High-strength PVA fiber with a strength of 5 g/d or more.

(2) PVA-based polymer with an average degree of polymerization of 3000 or more,
When dissolved in a solvent containing at least 20% by weight of a polyhydric alcohol solvent and coagulated by dry-wet or wet spinning, 50% by weight or more of the coagulation bath is ethanol, and the temperature is quenched at 20°C or less and delayed. After coagulation, wet stretching, extraction, drying, etc. are carried out by conventional methods, and after removing most of the solvent, stretching is carried out at a temperature exceeding 220°C to a total stretching ratio of 17 times or more. A method for producing strong PVA-based fibers. ”.

The requirements of the present invention are as follows.

(1) Dissolve in a solvent containing at least 20% by weight of a polyhydric alcohol solvent.

(2) When coagulating by dry-wet spinning or wet spinning, 50% by weight or more of the coagulation bath is ethanol, and the coagulation bath is rapidly cooled to 30° C. or lower to perform delayed coagulation.

(3) Perform wet stretching, extraction, drying, etc. in a conventional manner to remove most of the solvent, and then dry heat stretch to a high magnification at a high temperature.

That is, the present invention performs delayed coagulation in a coagulation bath containing ethanol, promotes uniform transparent gelation of PVA fibers with few voids and defects, and fixes them in a state with less entanglement of molecular chains, thereby preventing whitening during stretching. Furthermore, the fibers obtained have high strength, high knot strength, and improved fatigue resistance and impact resistance, making them suitable for industrial materials such as rubber materials, composite materials, and robes. Become.

The contents of the present invention will be explained in more detail below.

The PVA-based polymer referred to in the present invention is one with an average degree of polymerization of 3000 or more as determined by the viscosity method in an aqueous solution at 30°C, a linear polymer with a saponification degree of 99.5 mol% or more, and a low degree of branching. It is something. The higher the average degree of polymerization of PVA, the easier it is to obtain high-strength fibers, preferably 6000 or more, more preferably toaoo or more. The higher the degree of polymerization, the fewer the molecular chain ends that tend to become defective parts (and the more tie molecules that connect crystals), the easier it is to become a high-strength fiber.If the saponification degree of the drawn yarn is less than 99.5 mol%, the molecular If the chain disorder is too large, crystallization does not proceed and the melting point decreases, which tends to cause problems such as decreased heat resistance.Also, there is no problem with adding boric acid, antioxidants, pigments, oils, etc., but the amount added is preferably suppressed to an extent that does not cause performance deterioration.

The solvent for the PVA polymer must contain 20% by weight or more of a polyhydric alcohol solvent. Polyhydric alcohol solvents include glycerin, ethylene glycol, diethylene glycol, triethylene glycol, trimethylene glycol, propylene glycol, butanediol,
Examples include 3-methylpentane-1,3,5-triol. If the polyhydric alcohol solvent that causes gelation due to rapid cooling is less than 20% by weight, it is difficult to obtain uniform gel fibers and high strength and knot strength cannot be obtained. Preferably 5
It is 0% by weight or more, more preferably 70% by weight or more. When adding other solvents, such as water,
Possible examples include dimethyl sulfoxide, dimethylformamide, and dimethylformamide.

The spinning method may be a wet-dry or wet-spinning method, but the wet-dry method is preferable in order to obtain dog-gel fibers by rapid cooling.

The coagulation bath must contain ethanol at least 50% by weight. If the ethanol content is less than 50% by weight, the coagulation rate will be too high and uniform gelation will not occur, whitening will occur during stretching, horizontal stripes will appear, and knot strength and fatigue resistance will decrease.

Further, in order to cause delayed coagulation and to enable uniform gelation, it is preferable that the coagulation bath contains 10% by weight or more of the solvent. Further, the solidification temperature is 30°C or lower, preferably 20°C or lower. If the temperature exceeds 30°C, the solidification rate will increase, which is undesirable because the same phenomenon as described above will occur.

Uniform gel fibers can be obtained under the above conditions.

When delayed coagulation is performed, the amount of solvent remaining in the gel fiber increases,
If wet stretching is performed in this state, the cross section will be crushed and easily deformed, and the knot strength will be low and fatigue resistance will deteriorate. Therefore, it is preferable to extract the solvent before wet stretching to reduce the amount of remaining solvent. Wet stretching is performed 2 to 5 times before the drying process. The purpose of performing wet stretching is to reduce distortion between fibers and break microcrystals to make them amorphous.

Next, the solvent is removed by washing with water and then dried. In order to suppress crystallization and prevent sticking, drying is carried out at 130° C. or lower to remove almost all of the solvent.

Thereafter, stretching is carried out at 220°C or higher, preferably 230-260°C. Stretching can be done by any method, one step, two or more steps,
Any of dry heat, oil bath, and nitrogen gas zone stretching may be used. If the stretching temperature is lower than 220° C., oriented crystallization will not proceed and the stretching ratio will be low, making it impossible to obtain a high strength product. Moreover, at temperatures above 260° C., PVA decomposes rapidly and molecular chains flow, making it impossible to obtain high strength. Stretching is performed so that the total stretching ratio is 17 times or more. If it is less than 17 times, the orientation of the molecular chains will be insufficient and only low strength will be obtained. The drawn yarn obtained by the present invention is uniform and has a circular cross section, has no macrovoids, and has almost no horizontal stripes, so it is glossy and has a high level of knot strength. By the way, the single fiber tensile strength is 18g.
/d or more, and the single fiber knot strength is 3.5 g/d or more.

(Examples) The present invention will be specifically described below with reference to Examples, but the present invention is not limited to the Examples.

In addition, various physical property values in the examples described below were measured by the following methods.

1) Number of horizontal stripes was observed by microscopic observation, and the average value of 10 or more points was adopted.

2) Single fiber tensile strength According to JIS LOL 3, pre-moistened fibers were tested to length 2.
The breaking strength was determined at 0c++, an initial load of 0.25 g/d, and a tensile speed of 50%/min, and the average value of 10 or more points was adopted. Denier was measured gravimetrically.

3) Single fiber knot strength Almost the same as single fiber tensile strength, 100% at sample length 10 cm
The breaking strength was determined at a tensile rate of /min, and the average value of 10 points or more was adopted.

4) Belt bending fatigue test HID denier yarn 27.8 turns/'l [1cm twist, two more 27.8 turns/loc+
Create a cord by applying ply twist of e. Then RFL (
Make dip cords of resorcinol (formalin latex) and attach 20 of the cords to a 25mm wide rubber belt.
Arrange and vulcanize. Continue to apply a load of 42 to the 25φ pulley.
The strength after bending the cord 100,000 times at a reciprocating speed of 179 times/min was measured, and the strength retention rate (average value of 10 times) was calculated from the strength of the dip cord of the bending hall.

Example 1 and Comparative Example 1 PV with average polymerization degree of 1700G and saponification degree of 99.6 mol%
A was dissolved in glycerin at 180°C to a concentration of 6% by weight. The melting machine was a closed system, and after the pressure was reduced, h gas was flowed into the system to suppress color decomposition of PVA. The solution was then heated to 190°C.
The material was discharged from a nozzle with a hole diameter of 0.15 mm and 80 holes at a discharge rate of 36 cc/min, and dropped into a coagulation bath 25 mm below to perform wet-dry spinning. The coagulation bath composition is ethanol/methanol/glycerin = 70/10/
20, and the temperature was 0°C. Next, the solvent was extracted in a bath of ethanol/methanol = 87/13 kept at 40°C, and wet stretching was carried out at a roller speed of 3.5 m/min to a factor of 4. Subsequently, it was washed with water and dried with 3% shrinkage using hot air at gO<0>C. Finally, stretching was carried out at a temperature of 254° C. so that the total stretching ratio was 19.0 times.

The resulting drawn yarn was glossy, had as few horizontal stripes as an average of 5 per 100μ, and had a single yarn tensile strength of 21.88/d.
The single yarn knot strength was 5.8 g/d, resulting in high strength fiber. Furthermore, in the belt bending fatigue test, the strength retention rate after being bent 100,000 times was as high as 75%.

Comparative Example [Example 1 was carried out in which the coagulation bath composition was methanol/glycerin = 8/2 and the coagulation temperature was 0°C. Solidification occurs rapidly and the total stretch ratio is 18 at a temperature of 254°C.
．． When stretched to 5 times the size, whitening occurred and the horizontal stripes were 1
The number increased to 46 lines per 00μ.

Single yarn tensile strength is 21.2 g/d, single yarn knot strength is 5.1
g/d, but in the belt bending fatigue test, the strength retention rate after being bent 100,000 times was as low as 58%.

Example 2 Average degree of polymerization 7700. PVA with saponification degree of 99.8 mol%
140 in ethylene glycol to make 10% by weight.
Dissolved at ℃. Then, the solution was heated to 110°C and the composition was changed to ethanol/methanol/ethylene glycol-60/
Wet-dry spinning was carried out by dropping the mixture into a coagulation bath kept at -5°C. The subsequent operations were the same as in Example 1. The final dry heat treatment was performed at 250°C and the total stretching sound modulus was 19.
, 5 times. The drawn yarn was glossy and had very few horizontal stripes, an average of 2 lines per 100μ, and had a high tensile strength of 20.2 g/d and knot strength of 4.9 g/d. . Furthermore, in the belt bending fatigue test, the strength retention rate after being bent 100,000 times was at a high level of 67%.

Example 3 Average degree of polymerization 12flQO, degree of saponification 9g, 7 mol% P
Ethylene glycol/water = VA to 8% by weight
515% by weight of the solvent, and at the same time, 0.5% by weight of boric acid/PVA was added and dissolved at 100°C.

Then, the solution was heated to 80°C and the composition was changed to ethanol/methanol/ethylene glycol/water = 80/10/5.
15 and discharged into a coagulation bath maintained at 20°C, wet spinning was performed. The subsequent operations were the same as in Example 1. The resulting drawn yarn was glossy, had as few horizontal stripes as 3 per 100 μm, had a single yarn tensile strength of 19.8 g/d, and had a high single yarn knot strength of 4.5 g/d.

Claims (2)

[Claims] (1) PVA-based fibers with an average degree of polymerization of 3000 or more have no horizontal stripes on the fiber surface in the direction perpendicular to the fiber axis, or have an average of 10 or less stripes per 100μ length, and have a single fiber tensile strength of 18 g/d or more , single fiber knot strength 3.5g
High-strength polyvinyl alcohol fiber having a polyvinyl alcohol content of /d or more. (2) PVA-based polymer with an average degree of polymerization of 3000 or more,
When dissolved in a solvent containing at least 20% by weight of a polyhydric alcohol solvent and coagulated by dry-wet or wet spinning, 50% by weight or more of the coagulation bath is ethanol, and the temperature is kept at 30°C or less and rapidly cooled to delay the process. After coagulation, wet stretching, extraction, drying, etc. are carried out by conventional methods, and after removing most of the solvent, stretching is carried out at a temperature exceeding 220°C to a total stretching ratio of 17 times or more. A method for producing strong polyvinyl alcohol fibers.