JPH05125613A - Drawing of polyvinyl alcohol-based fiber - Google Patents

Abstract

PURPOSE:To obtain the title inexpensive fiber of good whiteness with little degradative deterioration by putting a polyvinyl alcohol spinning dope to multistage drawing under specified conditions. CONSTITUTION:A spinning dope prepared by dissolving polyvinyl alcohol in a solvent is put to wet or wet-dry spinning in a coagulating bath of organic solvent or aqueous base having coagulating or gelling effect on the polyvinyl alcohol, followed by wet drawing and then drying. The resultant raw yarn is then put to dry heat drawing. In this case, (A) the raw yarn is put to wet drawing by a factor of 2.5-6; (B) for the raw yarn, fiber/fiber coefficient static friction is <=0.270; (C) the raw yarn is heated using a thermally conductive type heating means; and (D) the raw yarn is put to the first stage dry heat drawing at 130-220 deg.C by a factor of 1.2-4.00 followed by the second stage dry heat drawing at 220-265 deg.C by a factor of 1.2-4.

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 an inexpensive PVA fiber by drawing polyvinyl alcohol (hereinafter referred to as PVA) fiber in which polymer degradation and deterioration are small by a compact drawing equipment.

[0002]

2. Description of the Related Art PVA fibers have a higher strength and elastic modulus than general-purpose synthetic fibers such as polyamide fibers and polyester fibers, and as a main use fiber for industrial materials, of course, recently, cement reinforcing materials and rubbers that replace asbestos are used. It is being used as a reinforcing material or a plastic reinforcing material.

[0003] The final drawing method for polyester fibers uses a hot-conducting drawing machine, which has the greatest heat conductivity, such as hot water drawing, hot pins, hot plates, and hot rollers, as a method of applying heat to the fibers. Necking drawing is performed. Therefore, the drawing equipment is compact even though the yarn speed is extremely high at 500 m / min or more.

On the other hand, in the final drawing method of PVA fiber, hot oil, wood metal, heating tube, hot air stove, etc. have been tried, but industrially the hot air oven is mainly used and a part of the heating tube is used. ing.

In recent years, many proposals have been made to apply the concept of gel-spun super-drawing of high molecular weight polyethylene to a method for producing high-strength PVA fibers. For example, JP-A-59-10071
In No. 0, high molecular weight PVA having a molecular weight of 500,000 or more was dissolved in glycerin, glycerin in the yarn was extracted with methanol after cooling and gelling, and the methanol was dried. Hold the tube in the heat tube for at least 1 minute or more and subject it to dry heat drawing to obtain a strength of 17
High-strength PVA fibers of g / d or more are obtained. However, when the residence time in the hot tube is 40 seconds or less, even if the high molecular weight PVA is used, only 15 g / d or less is obtained. According to JP-A-61-252313, a dimethyl sulfoxide (hereinafter abbreviated as DMSO) -based spinning stock solution is dry-wet spun into methanol, and the final stretching method is 220 ° C. in an air (or preferably nitrogen) atmosphere. By using the above heating tube, a PVA-based fiber having a fiber structure having no birefringence difference between the inner and outer layers of the fiber or having a larger refractive index in the central portion of the fiber than in the surface layer of the fiber is obtained, and Fibers that are difficult to melt are obtained, but as described in the comparative example of the specification, only a low tensile strength and a low knot strength are obtained by the drawing method using a hot plate (hot plate). ..

As described above, the final drawing of the conventional PVA fiber is carried out by using a heat radiation type heating tube or a heat tube or a heat convection type hot air oven, which does not have good heat conductivity. In particular, when trying to obtain a high-strength PVA fiber by spinning a spinning dope obtained by dissolving PVA having a polymerization degree higher than about 2000, which has been generally used conventionally, in an organic solvent into a coagulating organic solvent. Since heating tubes and heat pipes that have particularly poor heat transfer properties are used, it is necessary to lengthen the heating residence time because of poor heat transfer properties when attempting to carry out on an industrial scale, which makes the stretching equipment long and therefore expensive. .. Furthermore P
There is a problem that VA is decomposed and is easily colored to cause fiber deterioration.

In view of the above circumstances, some of the inventors of the present invention have found that the preliminary draw ratio of the drawn raw yarn, the temperatures and draw ratios of the first and second stage draws, the total residence time and the total draw. Regarding multi-stage drawing using a heat conduction type heating means with limited magnification,
I applied for it earlier, but in this application, the winding speed is at most 70m.
Up to / min. After further studying to further increase the speed, it was found that when the winding speed exceeded 80 m / min, the drawability was poor and fuzz was likely to occur.

[0008]

Therefore, the present invention is
Regarding the final dry heat drawing method of VA fiber, it has good heat conductivity, no fluff occurs even when the winding speed is 80 m / min or more, and the residence time is short, so that the drawing equipment can be made compact and PVA decomposition This is to pursue how to apply the heat transfer type dry heat drawing capable of producing fibers with little deterioration.

[0009]

Means for Solving the Problems In pursuit of the above-mentioned problems, the present inventors have carried out wet or dry-wet spinning and then wet drawing to form a flexible filament bundle without sticking, and further have a fiber-to-fiber static friction coefficient (hereinafter F / Fμs) (abbreviated as F / Fμs) is used to improve the slippage of the fibers during drawing,
Moreover, the present invention has been found to be achieved by the two-stage drawing under specific conditions, even if the winding speed (hereinafter abbreviated as TU) is 80 m / min or more, the film can be drawn without generating fluff. That is, the present invention provides "wet or dry-wet spinning of a spinning dope obtained by dissolving polyvinyl alcohol in a solvent into an organic solvent-based or water-based solidifying bath having a coagulating action or a gelling action on polyvinyl alcohol, and wet stretching. When the raw yarn obtained by drying is subjected to dry heat drawing, (1) the raw yarn is subjected to a wet drawing of 2.5 to 6 times, (2) the raw yarn is a fiber-to-fiber static friction Coefficient is 0.27
0 or less, (3) heating the raw yarn using a heat conduction type heating means, (4) temperature 130 to 220 ° C.
Polyvinyl alcohol system characterized in that the first stage dry heat drawing of 1.2 to 4.00 times is carried out, and then the second stage dry heat drawing of 1.2 to 4 times is carried out at a temperature of 220 to 265 ° C. Fiber drawing method. It is.

The degree of polymerization of the PVA used in the present invention is not particularly limited, but it is preferable that the average degree of polymerization determined by the viscosity method in an aqueous solution at 30 ° C. is 1500 or more because the strength of the obtained fiber increases. It is more preferable that the average degree of polymerization is 3500 or more, and if it is 7,000 or more, the number of molecular chain ends that are likely to become defective portions is small and the number of tie molecules that connect the crystals is large, so that high strength is likely to occur, and it is most preferable. The higher the degree of polymerization, the easier the decomposition of the polymer (decrease in the degree of polymerization) during dry heat drawing, and the greater the effect of the present invention. There is no particular limitation on the saponification degree of the PVA used in the present invention, but 98 mol% or more is preferable, 99 mol% or more is more preferable, and 99.8 mol% or more is particularly excellent in hot water resistance. preferable. The degree of branching of the PVA used in the present invention is not particularly limited, but linear ones having a low degree of branching are preferred because they are more likely to crystallize and have higher strength. The PVA used in the present invention is composed of another monomer having a vinyl group, such as ethylene, propylene, butylene, itaconic acid, vinylpyrrolidone or the like.
There may be a PVA-based polymer copolymerized at a ratio of 0 mol% or less. In addition, a small amount (10% or less) of another polymer having miscibility with the PVA-based polymer, such as polyvinylpyrrolidone or polyacrylic acid, may be blended.

The spinning method for obtaining the drawn raw yarn of the present invention is as follows:
Method of wet or dry-wet spinning a stock solution of PVA dissolved in a solvent consisting mainly of water into a solidifying bath such as an aqueous solution of alkali and / or dehydrating salts having a coagulating action or a gelling action, DMSO, dimethylformamide, dimethylacetamide, Dimethylimidazolidinone, glycerin,
PV in an organic solvent such as ethylene glycol or a mixture of these organic solvents or a mixed solvent of these organic solvents and water.
There is a method in which a stock solution in which A is dissolved is wet- or dry-wet spun in a solidifying bath of an organic solvent such as methanol, ethanol, or acetone having a coagulating action or a gel action, or a mixed solvent of a stock solution solvent and a coagulating organic solvent. Either method can be adopted. However, a fiber obtained by wet- or dry-wet spinning an organic solvent-based stock solution into a mixed solvent system containing a stock solution solvent and a coagulating organic solvent tends to cause decomposition of PVA during heating, as compared with other spinning methods. It is a more preferable embodiment because the effect is large when a drawing method having a short residence time during hot drawing is applied. Also, as the fiber in the heat conduction type drawing machine, the flexibility required for the drawing filament bundle is important, and it is necessary that the filament bundle in the hot-air stove is not unbalanced. Is.

In order to obtain a filament bundle that is free from sticking and is flexible, after wet or dry-wet spinning, a wet drawing of 2.5 to 6 times is performed in a state of containing a solvent or a solidifying bath solvent. If the wet drawing is less than 2.5 times, it tends to stick when dried, and a flexible filament bundle cannot be obtained.
If it exceeds 6 times, fluff tends to appear. Wet draw ratio is 3.0-
It is more preferably 5.5 times, further preferably 3.5 to 5 times.

The point of the present invention is to reduce the friction coefficient of the thus-obtained original yarn for drawing. In the present invention, a heat conduction type drawing having a high heat transfer property is adopted, and specifically, drawing is performed with a hot plate, a hot pin, a hot roller or the like, so that the fiber receives frictional resistance on the plate or the roller. Therefore, it is preferable that the coefficient of friction is small. In particular, the higher the yarn speed, the more important it becomes. Initially, it was important that the coefficient of dynamic friction between the fiber and the metal such as the plate was small, and the coefficient of static friction between the fiber and the metal and the coefficient of dynamic friction between the fiber and the fiber and the coefficient of static friction were not important, but as a result of various studies,
It has been found that it is extremely important that the coefficient of static friction between fibers is smaller than the coefficient of dynamic friction between fibers and metal, that is, F / Fμs is 0.270 or less. Why F / F
The reason why μs is important is unknown, but when the multifilaments rub against each other during drawing and the relative speed of the single filaments is small, it is considered that the static friction is close to the static state. It is estimated that a small coefficient is important. The F / F μs is more preferably 0.250 or less, further preferably 0.220 or less.

There is no particular limitation on the method for reducing the μs of the drawing raw yarn, but in general, a surfactant effective for reducing the μs is added to the stock solution or added in the spinning step. Can be achieved. Examples of the surfactant include amine neutralized products of long-chain alkyl phosphoric acid, glycerin ester of long-chain carboxylic acid, dimethyl silicone, amino-modified silicone and the like. The amount of the surfactant added or added varies depending on the kind of the surfactant, but is 0.005 to 2% with respect to the polymer. When applying the surfactant in the spinning process, there are dip-nip method, touch roller method, gear pump method, etc., but there is no particular limitation. It has excellent controllability of the amount of coating on the yarn.

In the present invention, the drawn raw yarn obtained as described above is subjected to dry heat drawing using a heat conduction type drawing machine. The heat conduction type stretching machine referred to in the present invention has a heating means such as a hot plate, a hot pin, and a hot roller that directly contacts the fibers to raise the temperature of the fibers by heat conduction, and the speed of the entrance roller and the speed of the exit roller. It is equipment for stretching according to the ratio. Heat conduction type compared to the radiation type that heats the fiber by radiation while passing through the gas in the heating tube or heat tube and the convection type that actively circulates hot air and blows hot air to the fiber to raise the temperature by convection Has the characteristic that the heat transfer property is remarkably large.

In the present invention, dry heat drawing is performed at least 2.
If not done in steps, it is not possible to obtain high-strength fibers free of sticking and fluff. In the first stage dry heat drawing, the temperature of the heating element (hot plate, hot roller, hot pin) is set to 1
30 ~ 220 ℃, the first stage dry heat draw ratio 1.2 ~
It must be 4.0 times. 1st stage drawing temperature is 1
If the temperature is lower than 30 ° C., the stretchability is low, the oriented crystallization effect is small even if stretching is possible, and the fusion cannot be prevented when the temperature becomes high in the second stage dry heat stretching. If the first stage drawing temperature is higher than 220 ° C., the orientation and crystallization of the raw yarn is not sufficient, resulting in sticking. More preferably, the first stage dry heat drawing temperature is 160 to 210 ° C. The draw ratio of the first stage varies depending on the wet draw ratio in the raw yarn stage, but the draw ratio of the first stage is 1.
If it is less than 2 times, the oriented crystallization is not sufficient and the structure cannot withstand the subsequent second-stage stretching. If the stretching exceeds 4.0 times, the stretching becomes excessive and the second stage stretching cannot be performed smoothly. In many cases, it is preferable to divide the first stage drawing itself into multiple stages. For example, set the plate temperature to 1
By setting the temperature to 60 ° C. and 190 ° C., it is preferable to perform the first stage stretching in two stages. As described above, the first stage drawing is carried out at a high temperature in order to achieve more complete oriented crystallization.
It has been found that this is a preliminary stretching step for smoothly performing the stepwise dry heat stretching and is essential for the heat conduction type stretching of PVA.

After the first-stage stretching, the second-stage stretching is performed.
In the second stage stretching, the temperature of a heating body such as a hot plate or hot roller is set to 220 to 265 ° C., and the stretching ratio is 1.
2 to 4 times. If the temperature is lower than 220 ° C., the oriented crystallization required for the final stretching is not sufficient, and the strength and water resistance cannot be excellent. If the temperature is higher than 265 ° C, the crystals will melt and the fibers will stick. Further, PVA is decomposed and deteriorated. The more preferable second stage drawing temperature is 230 to 255 ° C. although it depends on the degree of polymerization of PVA. The higher the degree of polymerization, the higher the temperature should be set. If the second stage draw ratio is lower than 1.2 times, the orientation crystallization of the obtained fiber is not sufficient and the strength / hot water resistance is poor. If the second stage draw ratio is higher than 4 times, fluff appears. The second stage stretching itself can be divided into multiple stages.
For example, it may be preferable to perform the second stage stretching in two stages by setting the plate temperature to 230 ° C. and 235 ° C. In the case of plate stretching, a driving roller may be provided between the first stage stretching and the second stage stretching to control the first stage stretching ratio and the second stage stretching ratio to their respective predetermined values. On the other hand, no driving roller is provided in the middle, only the entrance roller and the exit roller are used, the region lower than 220 ° C is the first stage stretching part, and the region higher than 220 ° C is the second stage stretching part. There is also a mode in which the film is continuously stretched by controlling the contact length. In the latter case, the stretching ratio is set so that the tension is the same in each region. The draw ratio in each region can be obtained by actually measuring the yarn speed or by measuring the thinning curve of the fiber denier. It is better to use an intermediate roller in that it is easy to set the draw ratio of each region to a predetermined value, but it is better to use no intermediate roller in that it is not cooled by the intermediate roller and there is no possibility of winding around the intermediate roller. Are better. In the case of multi-stage plate stretching,
Free guide rollers can be provided between the plates to ensure full fiber contact with each plate.

The total draw ratio (hereinafter abbreviated as TD) obtained by multiplying all of the wet draw ratio, the first-stage draw ratio and the second-stage draw ratio at the raw yarn stage has a great influence on the performance. In many cases, it is preferable to use at least 12 times. T
When D is less than 12 times, the oriented crystallization as the final drawn yarn is insufficient, and the strength and hot water resistance are insufficient. TD
Is more preferably 15 times or more, and most preferably 18 times or more.

In the present invention, the total residence time of the first stage stretching and the second stage stretching is 10 seconds or less, and in most cases 5
Another feature is that it can be done in seconds or less. This is a remarkable difference from the conventional heating tube, hot tube, and hot-air stove, which requires a residence time of at least 30 seconds or more, and further increases the performance to achieve higher performance.

The heating elements such as hot pins, hot plates, and hot rollers used in the present invention are not limited as long as they do not damage even when they come into contact with fibers and the contact surface can be controlled to a predetermined temperature, but they have high heat conductivity. It is preferably made of metal. The surface shape of the heating element is not particularly limited, but a mirror finish or satin finish is preferable. The heating element in the first-stage stretching region is preferably a hot pin, hot plate or hot roller. Second
A hot plate or hot roller is preferably used as the heating element in the step drawing region. In the case of a hot plate, it is also possible to form the first-stage and second-stage heating bodies with one plate by providing an appropriate temperature gradient. The size of this heating element (contact length with the fiber) varies depending on the stretching conditions, but is 0.5
It is about 10 m. After stretching, heat setting or heat shrinking may be performed as necessary. In the polyester fiber that is commonly used for heat-conducting stretching, necking stretching occurs at a certain point, it is not necessary to further stretch after necking stretching, and it is difficult to stretch even if it is attempted to stretch at a high temperature. It was found that multi-stage drawing is possible with PVA fiber depending on the temperature, and multi-stage drawing is indispensable, and it was recognized that the drawing behavior greatly differs depending on the type of polymer.

As described above, according to the present invention, when a PVA fiber is drawn by using a heat conduction type drawing machine, a wet drawing with a predetermined ratio is performed to form a flexible filament bundle without sticking, and a fiber-to-fiber By using a stretchable raw yarn with a static friction coefficient of not more than a predetermined value and drawing in two stages under specific conditions, there is no fluff even at a high speed of TU 80 m / min or more, there is no thermal deterioration, and there is no difference in hot air drawing. It is possible to manufacture high-strength fibers with a residence time significantly shorter than hot-air drawing.

The fiber-to-fiber static friction coefficient referred to in the present invention is J
It is measured according to IS L-1015. That is, in the friction coefficient measuring method of JIS L-1015 (chemical fiber staple test method), instead of a cylindrical sliver in which staples are hand-carded and wound around a cylinder,
A drum-shaped filament in which a sample filament was wound in parallel in a drum shape as shown in FIG. 2 was used on a bobbin with both brim needles as shown in FIG.

[0023]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

Example 1 PVA having a viscosity average degree of polymerization of 3300 and a saponification degree of 99.9 mol% was added to DMSO so as to be 12% by weight, and dissolved at 80 ° C. in a nitrogen atmosphere. The spinning solution obtained was passed through a nozzle with 50 holes,
Wet spinning was carried out in a solidifying bath consisting of methanol / DMSO = 7/3 (weight ratio) at 3 ° C., and methanol / DMSO at 40 ° C.
= 4.5 / 6 wet drawing was carried out with a wet drawing bath of 94/6, DMSO was completely extracted with a methanol bath, the attached methanol was blown off with air, and a 1% hexane solution of dimethyl silicon was contacted by a roller touch method. After 90
It was dried with hot air at ℃. The obtained drawn raw yarn had a yarn denier of 750 denier, was free from sticking and was flexible, and had an F / F μs of 0.240.

This drawn raw yarn was preheated and dried with a hot roller at 130 ° C., and then dry-heated and drawn by contact running on a hot plate at 150 ° C., 190 ° C. and 235 ° C. Enter speed is 2
3m / min, TU is 100m / min, TD is 1
It was 9.5 times. From the actual measurement of denier immediately after passing through the plate at 190 ° C., the total first stage dry heat stretching ratio at 150 ° C. and 190 ° C. plates was 2.41 times, 235 ° C.
The dry heat draw ratio of the plate was 1.8 times. The total residence time was 4 seconds. The stretched condition is good, there is almost no fluff, and the single fiber strength of the obtained fiber is 18.3 g / d.
And PVA with a degree of polymerization of 2400 has high strength, and T
The performance was the same as that of hot air drawing with U15 m / min and residence time of 40 seconds.

Comparative Example 1: A drawn raw yarn was obtained in the same manner as in Example 1 except that the hexane solution of dimethyl silicon was not contacted. The F / Fμs of the obtained drawn raw yarn was 0.29. This drawn raw yarn was drawn under the same conditions as in Example 1, but with TD19.5 times, many fluffs were generated and normal drawing could not be performed.

When TU is set to 40 m / min, TD1
9.5 times draw is possible and single yarn strength is 18.2 g /
d, which was the same as in Example 1.

Comparative Example 2: Spinning, extraction, application of an oil agent and drying were carried out in the same manner as in Example 1 except that the wet draw ratio was 2.4 times. The drawn drawn yarn was sticky and hard. When this was subjected to three-stage plate stretching in the same manner as in Example 1, T
Even when D was 16 times, fluffs frequently occurred and normal stretching could not be performed.

Example 2: A viscosity average degree of polymerization of 1700,
PVA with a saponification degree of 99.9 mol% is adjusted to 17% D
It was added to MSO and dissolved at 80 ° C. under a nitrogen atmosphere.
The spinning solution obtained was passed through a nozzle having 40 holes to obtain 10
mm air / mmSO at 5 ° C. =
Dry-wet spinning was carried out in a solidification bath consisting of 6/4, and wet stretching was performed 4.0 times in a wet stretching bath of methanol / DMSO = 94/6 at 40 ° C., and DMSO was completely extracted in a methanol bath to remove adhered methanol. It was removed by a squeezing roller, a 0.2% hexane solution of amino-modified silicon was brought into contact with the roller touch method, and then dried with hot air at 90 ° C. The drawn raw yarn thus obtained had a yarn denier of 600 dr, was flexible without sticking, and had a low F / Fμs of 0.191.

This drawn raw yarn was heated at 150 ° C., 180 ° C., 20 ° C.
The heat conduction type dry heat drawing was carried out by contacting with a hot plate at 0 ° C and 235 ° C. The entry speed was 24 m / min, the TU was 120 m / min, and the TD was 20 times. 150
C., 180.degree. C., 200.degree. C., the total first stage plate draw ratio by the three plates was 1.9 times, the second stage draw ratio by the 237.degree. C. plate was 2.6 times, and the total residence time was It was about 2 seconds. The stretched condition was good, there was almost no fluff, and the strength of the obtained single fiber was 15.6 g / d.
The maximum single fiber strength obtained by hot air drawing at 15 m / min and residence time of 25 seconds was almost the same as 15.8 g / d.

Comparative Example 3: The same raw yarn as in Example 2 was used to contact only the hot plate at 237 ° C., and the imprinting speed was 24.
Attempts were made to guide the yarn at m / min, but the yarn was melted on the hot plate and the yarn could not be introduced.

Comparative Example 4 Using the same yarn as in Example 2,
Plate stretching was performed in the same manner as in Example 2 except that the temperature of the final plate was set to 218 ° C. The yarn was broken at TD 20 times. The single fiber strength 14 times TD was as low as 10 g / d.

Comparative Example 5: An intermediate drive roller was provided between the third plate and the fourth plate, and the roller speed was set to 2
It was tried to stretch in the same manner as in Example 2 except that the stretching speed was 8 m / min, and the first stage stretching of the first to third plates was 1.17 times, but it was fused on the fourth plate.

Example 3: Using the same yarn as in Example 2, a hot plate at 160 ° C., 190 ° C., 205 ° C. and 238 ° C. was brought into contact with the yarn, and dry heat drawing was performed at TU 180 m / min. TD1 by reducing the speed to 37 m / min
Even at 9.5 times, there was almost no fluff and it could be smoothly drawn. The yarn speed after the third plate was measured, and the draw ratio between the first to third plates was 2.1 and the draw ratio on the fourth plate was 2.3.
It was double. Further, the total residence time was on the order of 1 second, and the single fiber strength of the obtained drawn yarn was 15.1 g / d.

Example 4 PVA having a viscosity average degree of polymerization of 8500 and a saponification degree of 99.8 mol% was adjusted to 6 wt% D.
It was added to MSO and dissolved at 90 ° C. under a nitrogen atmosphere.
The spinning solution thus obtained is heated at 2 ° C. from a nozzle having 100 holes.
Wet spinning at 40 ° C. methanol / DMSO = 92/8
The wet drawing was performed 4.2 times in the above bath, DMSO was completely extracted in the methanol bath, and a 0.1% hexane solution of aminosilicon was contacted by a roller touch method, and then 90 ° C.
Dried with hot air. The obtained drawn raw yarn had a yarn denier of 1130 dr and was flexible without sticking and F / Fμs.
Was 0.15.

This drawn raw yarn was dried at 170 ° C, 210 ° C, 23 ° C.
Dry hot drawing was carried out by traveling in contact with a hot plate at 8 ° C and 249 ° C. The entry speed was 19.9 m / min, the TU was 90 m / min, and the TD was 19.0 times. 210 ° C
The measured denier immediately after passing the plate was 170 ° C and 21
The total dry heat draw ratio on the 0 ° C. plate was 2.32 times. The second stage dry heat drawing using a 238 ° C. and 249 ° C. hot plate was 1.95 times, and the total residence time was 4 seconds. The drawing condition was good and there was no fluff, and the single fiber strength of the obtained fiber was 22.1 g / d, which was comparable to the hot air drawing method.

[0037]

As described above, according to the present invention, when the wet or dry-wet spun PVA fiber is drawn using the heat conduction type drawing machine, the wet draw ratio is set to a predetermined range and the static friction coefficient of the fiber to the fiber is set to a predetermined range. By using a stretched raw yarn having a slipperiness of not more than a value and performing two-stage stretching under specific conditions,
High speed of TU 80m / min or more (for example, 150m / mi
Even in n), it is possible to produce a PVA fiber having a strength comparable to that in hot air drawing without fluff and with a residence time significantly shorter than that in hot air drawing. As a result, it became possible to perform drawing at high speed using a compact heat-conduction drawing machine with a low equipment cost. Compared with the conventional hot air drawing method, the obtained fiber has less heat deterioration, has a good white color, and can be manufactured at low cost, so it is used in fields such as rubber materials such as automobile tires and brake hoses, and cement reinforcement materials as a substitute for asbestos. Useful for.

[Brief description of drawings]

FIG. 1 is an explanatory view of a side surface and a cross section of a bobbin having needles 1 on both side brim portions used for measuring a friction coefficient of a raw yarn in the present invention.

FIG. 2 is an external view of a drum-shaped filament obtained by winding a measurement sample 2 around the bobbin shown in FIG.

[Explanation of symbols]

 1 ... Needle 2 ... Sample filament

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsushi Ejiri 1621 Sakata, Kurashiki, Okayama Prefecture, Kuraray Co., Ltd. (72) Takanori Kitamura 1621 Sakata, Kurashiki, Okayama, Kuraray Co., Ltd.

Claims (1)

[Claims] 1. A spinning stock solution obtained by dissolving polyvinyl alcohol in a solvent is wet- or dry-wet spun in an organic solvent-based or water-based solidifying bath having a coagulating action or a gelling action for polyvinyl alcohol, and wet stretching. When dry-drawing the raw yarn obtained by drying, (1) the raw yarn has been subjected to wet stretching of 2.5 to 6 times, (2)
The raw yarn has a fiber-to-fiber static friction coefficient of 0.270 or less, (3) the raw yarn is heated using a heat-conduction type heating means, and (4) the temperature is 130 to 220 ° C. and 1.2 to.
The first stage dry heat drawing of 4.00 times was performed, and then the temperature was set to 22.
A second-stage dry heat drawing of 1.2 to 4 times at 0 to 265 ° C. is carried out, and a drawing method of a polyvinyl alcohol fiber.