JPH02154008A - Drawing of polyvinyl alcohol-based fiber - Google Patents

Abstract

PURPOSE:To stably obtain the subject polyvinyl alcohol-based fiber having high strength and high elastic modules by drawing a raw spun yarn of polyvinyl alcohol under a specified condition. CONSTITUTION:A raw spun yarn produced from a solution containing a polyvinyl alcohol with >=1,500 average polymerization degree is drawn at one or two or more stages using a system having a non-contact hollow heater between rollers and utilizing the heater at >=210 deg.C in an atmosphere containing >=85% N2 and at 0.05-5/min. rate of draw deformation give by the formula [DRn is draw rate in drawing at the n-th stage; HDn is draw ratio in drawing at the n-th stage; Vn is feed ratio (m/min.) in drawing at the n-th stage; Ln is length(m) of heater in drawing at the n-th stage] to obtain the objective fiber with >=1.8g/d draw tension and >=16 times total draw ratio at the final stage.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention is a drawing method for industrially advantageously producing polyvinifre alcohol (hereinafter abbreviated as P■Δ) fibers having high strength and high modulus. It is about the method.

(Conventional technology) Conventional PVA fibers have higher strength and modulus of elasticity than polyamide, polyester, and polyacrylonitrile fibers, and have been used not only as fibers for industrial materials, which is their main use, but also as cement reinforcement materials as asbestos substitute fibers. It is also used in

As a method for obtaining PVA-based fibers with high strength and high modulus, the concept of gel spinning and super-stretching of high molecular weight polyethylene (for example, JP-A-60-194109) was applied.
9-100710, JP-A-59-130314, JP-A-61-108711, etc. are known. In all of these methods, the solvent is extracted using methanol, which has a high solvent extraction rate, and stretching is performed, but satisfactory strength has not yet been obtained.

On the other hand, JP-A-62-149909, JP-A-62-1
1'V containing boric acid as seen in Publication No. 49910
It is also known to coagulate an aqueous solution A with an alkaline aqueous solution by dry-wet spinning, but it is difficult to obtain a uniform gel because it does not gel with cooling alone, and it is difficult to obtain a high-strength fiber because it tends to cause agglutination between single filaments due to water swelling. is difficult.

In order to obtain PVA fibers with high strength and high elastic modulus, it is necessary to draw the fibers at a high magnification to form a highly oriented crystal structure, but for this purpose it is necessary to draw the fibers near the melting point of PVa. However, P.V.
A has the same melting point and decomposition temperature, and in the stretching process, PVa
decomposition occurs, which tends to lead to a decrease in strength.

(Problems to be Solved by the Invention) Therefore, the present invention aims to obtain a technology that suppresses the decomposition of PVA in the stretching process and allows stretching at a high magnification.

(Means for solving problems) That is, the present invention.

"When drawing a spun yarn obtained by a conventional method from a solution containing a polyvinyl alcohol-based polymer with an average degree of polymerization of 15 oo or higher using a method that has a non-contact hollow heater between rollers, N2-containing fibers are drawn at a temperature of 210°C or higher rate is 8
Using the heater in an atmosphere of 5% or more, the stretching deformation speed draw rate expressed by the following formula is 0.05 to 5 rn
1. A method for stretching polyvinyl alcohol-based fibers, which comprises stretching in one or more stages in ', with a final stage stretching tension of 1.8 g or more, and a total stretching ratio of at least 16 times.

1) Bn = (river) n-1) X Vn/Ln (m
1n-').

The feature of the present invention is that the draw rate (DB) is changed according to the stretching temperature and atmosphere (N2 content) to increase the stretching tension and total stretching ratio while suppressing the oxidative decomposition of PVA. It is possible to obtain PVA-based fibers with high elastic modulus.

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

Generally, in order to increase fiber strength, it is necessary to increase the orientation and crystallization of molecular chains, which requires high-magnification stretching.

The PVA thread polymer referred to in the present invention is a linear polymer with an average degree of polymerization of 1.500 or more determined by a viscosity method in an aqueous solution at 30°C, a saponification degree of 99 mol% or more, and a low degree of branching. It is. The higher the average degree of polymerization of PVA, the easier it is to obtain high-strength, high-modulus fibers, preferably 4,000 or more, more preferably 10,000 or more. The higher the degree of polymerization, the fewer molecular chain ends tend to become defects, and the more tie molecules connecting crystals, the more likely it is to become a high-strength, high-modulus fiber.

The degree of saponification of PVa is 99% or more, and if it is less than 99%, the disorder of the molecular chains is too large and crystallization does not proceed, the melting point decreases, the heat resistance decreases, and high strength and high modulus fibers cannot be obtained. Furthermore, P
Additives such as boric acid, pigments, ultraviolet absorbers, surfactants, etc. may be added to VA in an amount of 5% by weight or less.

P V A type ho! Any solvent can be used as a solvent for J-mer, but
Solvents that gel when cooled are preferred, such as polyhydric alcohols such as ethylene glycol, trimethylene glycol, diethylene glycol, and glycerin, mixed solvents of these with water, dimethyl sulfoxide, dimethyl formamide, diethylene triamine, and mixtures of these with water. There is a solvent. In these cases, rapid cooling gelation is possible, so it is advantageous to produce a homogeneous gel without crystallization, entanglement fixation, and retardation of solvent extraction rate.

The spinning method may be any method, and may be wet, dry, or wet-dry, but wet-dry gel spinning is preferred.

The coagulation bath can be any type of bath, such as Ci methanol,
Alcohols such as ethanol and acetone.

The ether solution may be any alkali aqueous solution, mirabilite aqueous solution, or a mixture thereof.

Although wet stretching may or may not be carried out, it is preferable to carry out stretching three times or more during the process up to drying. The reason for the draw ratio of 3 times or more is to lower the degree of crystallinity, weaken the intermolecular hydrogen bonds, and make the molecular chains more mobile, so that the dry heat drawing in the final step can be performed at a high draw ratio, and the The goal is to reduce stalemate.

The solvent extraction of the PVA-based polymer may be carried out using alcohol, acetone, water, etc., but preferably methanol,
It is better to use a lower alcohol such as ethanol.

After that, it must be dried at a temperature of 130°C.
℃ or less, preferably 70 to 100℃. When the temperature exceeds 130°C, crystallization increases and it is difficult to increase the stretching ratio in subsequent stretching.

In the present invention, it is necessary to finally stretch the film at a high temperature and at a high magnification. A contact type heater tends to melt or damage the fibers, so a non-contact type heater is preferable. Heater temperature must be 210°C or higher. If the temperature is lower than 210°C, the draw ratio decreases and oriented crystallization does not proceed, making it difficult to obtain fibers with high strength and high modulus. Heater temperature here means the highest temperature actually measured.
Preferably it is 230-260°C. The N2 content of the heated stretching atmosphere is preferably 8596 or more, preferably 90% or more.

If it is less than 85%, the polymer is likely to be decomposed by oxygen. In addition, the stretching deformation speed draw rate (Dki) is (1,
tl must be 5-5m1n-1. D)l
If it is less than 0.05 m1n-', the feed rate is slow relative to the length of the heater, the residence time in the heater becomes long, and the decomposition of the polymer progresses. When DB exceeds 5 m1n-', the feed rate is too high relative to the heater length, and it is difficult to obtain a high-strength, high-modulus fiber due to partial cleavage of molecular chains and a decrease in the degree of molecular orientation due to a decrease in the total draw ratio. When the heater temperature is as high as 250° C. or higher, it is preferable that the DH be large, since decomposition will be less. In this case, the preferred range of DB is 0.2 to 2.
m1n=.

On the other hand, in order to obtain high-strength fibers, it is preferable to draw at a high tension and a high magnification, and in the case of the present invention, the final drawing tension must be 1.8 y/d or more, preferably 2. sg7'a or higher. The stretching tension is comparable to the strength under high temperature, with a tension of 1.8 g.
If it is less than /d, it is difficult to obtain high strength fibers. If the stretching temperature is too high, the molecular chains will move easily and the stretching ratio will be high, but the molecular chains will flow and the stretching tension and strength will decrease. If the stretching temperature is too low, the molecular chains will have strong resistance to stretching.

Although the stretching tension shows a high value, the strength tends to be low because the stretching ratio is low and the molecular chains are insufficiently oriented. Therefore, high tenacity yarns are achieved when both the draw ratio and tension are high. Generally, when the degree of polymerization is high, the number of molecules penetrating between the crystals is large, and the stretching tension increases.

On the other hand, the total stretching ratio is 16 times or more, preferably 20 times or more. Here, the total draw ratio is approximately 21 times the wet draw ratio during spinning and the hot draw ratio below 210°C.
It means the value multiplied by the hot stretching ratio at 0°C or higher. 16
If it is less than twice as strong, the molecular orientation will be insufficient and it will be difficult to achieve high strength.

Therefore, the feature of the present invention is to draw PVA-based fibers with a relatively high degree of polymerization in an N2 atmosphere at a drawing deformation rate D)I that increases the tension and temperature ratio, thereby increasing the strength, for example, 18 g/ d or more 1 elastic modulus 4 s o g/a
It is easy to obtain fibers of the above.

EXAMPLES The present invention will be specifically explained below with reference to Examples, but the present invention is not limited only to the Examples.

Example 1 and Comparative Example J Average degree of polymerization: 17,000. Dry PVA with a saponification degree of 99.4 mol% was added to glycerin at 180% to make a 5% by weight solution.
It was dissolved at ℃. The melting machine was a closed system, and N2 gas was flowed into the system after reducing the pressure to suppress color decomposition of PVA.

Next, the solution was heated to 190° C. and discharged from a nozzle with a hole diameter of 0.2 (turn) and 20 holes, and dropped into a coagulation bath 25 mm below. The coagulation bath composition is methanol/glycerin.
The weight ratio was 8:2 and the temperature was 0°C.

After obtaining gel fibers by cooling in a coagulation bath, 40℃ mep/
The film was wet-stretched 4 times in -/l/, and the glycerin was almost completely extracted with methanol, then dried with hot air at 100°C and wound up on a bobbin.

When the obtained spun yarn was drawn in one stage, N2 was flowed through a 4 m non-contact radiant heater to bring the NZ content in the heater to 95%, and then the feed rate was set at 0.8-'min.
Stretching was carried out at a maximum heater temperature of 260° C. and a stretching ratio of 5.3 times (total stretching ratio of 21.2 times). The DI (DI) at this time was 0.86, and the drawing tension was as high as 3.6 Q/d.The obtained drawn fiber had a strength of 23.1 y/d and an elastic modulus of 620 Q/d, compared to the conventional The obtained drawn yarn was dissolved in hot water at 140°C, and the degree of polymerization was determined by viscosity measurement to determine the degree of decrease in degree of polymerization relative to the polymer, which was as low as 15%.

As Comparative Example 1, the same stretching as above was carried out in air without flowing N2 into the heater, but the total stretching ratio was 19.8 times, the stretching tension was reduced to 2.5 Q/d, and the fiber was colored yellow. However, the 2 degree of polymerization decreased by 38% and the 1 strength became as low as 17.6 y/d.

Example 2 and Comparative Example 2 1'V with average polymerization degree of 7000 and saponification degree of 99.9 mol%
A was dissolved in dimethyl sulfoxide at 100°C to make a 10% by weight solution.

Next, the solution was heated to 85° C. and discharged from a nozzle with 40 holes. The coagulation bath composition was methanol/dimethyl sulfoxide = 6/4 weight ratio, and the temperature was 10°C. 4
Wet stretching was carried out 5 times in methanol at 0°C, and after solvent extraction, it was dried with hot air at 100°C and wound up on a bobbin.

When drawing the obtained spun yarn in one stage, the N2 content in the heater was brought to 97% using a 4-person radiant heater, and then the feed rate was 201 m1n and the maximum heater temperature was 2.
Stretching ratio is 4.8 times at 53℃ (total stretching ratio 24.0 times)
It was then stretched. The DE at this time was 1.9 m1n7' and the stretching tension was 3.117/d. The obtained drawn fiber has a strength of 2 o, s g/d and an elastic modulus of 540 g/d.
showed a high value.

As Comparative Example 2, the feed rate in Example 2 was changed to 10
When m%nin was used, the stretching tension was 2.9 g/d, but the stretching ratio was 3.5 times (total stretching ratio 17.5 times).
The strength of the obtained fiber was 6.9 y/d, and the elasticity Rate 460 Q/
It decreased to d.

Example 3 and Comparative Example 3 Dry P with average polymerization degree of 3300 and saponification degree of 99.5 mol%
Va was dissolved in water to a concentration of 13% by weight.

At that time, boric acid was added in an amount of 3.5% by weight based on PVA.

Next, the solution was heated to 110°C and passed through a nozzle with 1000 holes to give a composition of NaOH10Q/II, Na80<3.
Wet spinning was performed by discharging the product into a coagulation bath maintained at 70°C at 00 g/A'. Next, the film was neutralized with a dilute R25u4 aqueous solution and washed with water, during which time stretching was carried out at a total wet stretching ratio of S and O times. When drawing the raw yarn that has been dried with hot air at 120°C and wound around a bobbin in one stage, the feed speed is 231m+ after the N2 content in the 25-hour hot air oven is set to 90%.
The film was stretched at a maximum heater temperature of 254° C. and a stretching ratio of 5.6 times (total stretching ratio of 28.0 times). D at this time
The drawn fiber had a strength of 18.9 Q/d.

It showed an elastic modulus of 4 s Og/d.

As Comparative Example 3, when the heater maximum temperature was 265°C and the same stretching was performed, the stretching ratio was 6.2 times (total stretching ratio 31
．． 0 times], but the stretching tension was 1.5 y/d L
Suddenly, a flow of molecular chains occurred. The strength of the drawn fibers obtained was as low as 15.7 g/d.

Claims (1)

[Scope of Claims] When a spun yarn obtained by a conventional method from a solution containing a polyvinyl alcohol polymer having an average degree of polymerization of 1,500 or more is drawn by a method having a non-contact hollow heater between rollers, N_2 content is 85 at temperatures above ℃
% or more in an atmosphere, and the stretching deformation speed draw rate expressed by the following formula is 0.05 to 5 min^
- A method for stretching polyvinyl alcohol fibers, characterized by stretching in one or two or more stages at ^1, with a final stage stretching tension of 1.8 g/d or more, and a total stretching ratio of at least 16 times. . DRn=(HDn-1)×Vn/Ln(min^-^1
) DRn: Draw rate during n-th drawing HDn: Stretching ratio (times) during n-th drawing Vn: Feed speed during n-th drawing (m/min) Ln: Heater length during n-th drawing ( m)