JPH05125614A - Drawing of polyvinyl alcohol-based fiber - Google Patents

Abstract

PURPOSE:To obtain the title inexpensive fiber good in whiteness with little degradative deterioration by multistage dry heat drawing under specified conditions of polyvinyl alcohol raw yarn low in fiber/fiber coefficient of static friction. CONSTITUTION:A spinning dope prepared by dissolving polyvinyl alcohol in a solvent is put to such dry spinning as to extrude the dope through a nozzle into a hot air to evaporate and expel the solvent, and the resultant raw yarn is then put to dry heat drawing. In this case, (A) for the raw yarn, fiber/fiber coefficient of static friction is <=0.270; (B) the raw yarn is heated using a thermally conductive type heating means; and (C) the raw yarn is put to the first stage dry heat drawing at 130-220 deg.C by a factor of 2.5-6.0 followed by the second stage dry heat drawing at 220-250 deg.C by a factor of 1.3-3.0.

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 purpose, they are fibers for industrial materials, and recently, cement reinforcements that replace asbestos, It is being used as a rubber reinforcing material or a plastic reinforcing material.

The final stretching method for polyester fibers utilizes a heat-conducting type stretching machine, which has the largest heat transfer property, such as hot water stretching, pot pins, hot plates, and hot rollers, as a method of applying heat to the fibers. The necking stretching is being 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. It is only about.

In recent years, many proposals have been made in which the concept of gel-spun super-drawing of high-molecular-weight polyethylene is applied to a method for producing a high-strength PVA fiber. For example, JP-A-59-1007
In No. 10, a 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, and the obtained xerofiber was heated in a nitrogen atmosphere at 252 to 261 ° C in a hot tube. It is retained for at least 1 minute or more and subjected 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 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 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 in which there is no difference in birefringence between the inner and outer layers of the fiber and the refractive index of the central portion of the fiber is larger than that of 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, the stretching method using a hot plate (hot plate) only gives low tensile strength and knot strength.

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. Therefore, when it is carried out on an industrial scale, a long heating residence time is required, which makes the stretching equipment long and therefore expensive. Further, there is a problem that PVA is decomposed and 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. We have previously filed an application to carry out multistage drawing using a heat conduction type heating means with a limited magnification, but in this application, the winding speed is at most 70.
It was up to m / min. After further studying to further increase the speed, it was found that when the winding speed exceeded 80 m / min, the draw ratio was poor and fuzz was likely to occur.

[0008]

Therefore, the present invention relates to a final dry heat drawing method of PVA fibers obtained by a dry spinning method, which has good heat conductivity and does not generate fluff even when the winding speed is 80 m / min. The goal is to find out how to apply the heat conduction type dry heat drawing, which allows the residence time to be short and therefore the drawing equipment to be made compact, and also allows the production of fibers with less decomposition and deterioration of PVA. is there.

[0009]

Means for Solving the Problems In order to solve the above-mentioned problems, the inventors of the present invention used a raw yarn having a small fiber-to-fiber static friction coefficient (hereinafter abbreviated as F / Fμs) to prevent slippage between fibers during drawing. By improving and performing a two-stage stretching under specific conditions,
The present invention has been accomplished by finding that even when the winding speed (hereinafter abbreviated as TU) is 80 m / min or more, the film can be drawn without generating fluff.

That is, according to the present invention, "a spinning stock solution obtained by dissolving PVA in a solvent is extruded through a nozzle into heated air to carry out dry spinning to evaporate and remove the solvent, and dry-stretching the obtained raw thread. , (1) the fiber has a fiber-to-fiber static friction coefficient of 0.270 or less, (2) the fiber is heated using a heat conduction type heating means, (3) the temperature 13
PVA characterized by performing a first stage stretching of 2.5 to 6.0 times at 0 to 220 ° C, and then performing a second stage stretching of 1.3 to 3.0 times at a temperature of 220 to 250 ° C. Method for stretching base fiber. 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. More preferably, the average degree of polymerization is 2200 or more. The degree of saponification of PVA used in the present invention is not particularly limited, but it is preferably 98 mol% or more,
It is more preferably 9 mol% or more, and 99.8 mol%
It is most preferable because it is excellent in hot water resistance. 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. PVA used in the present invention
Is a PV obtained by copolymerizing another vinyl group-containing monomer, for example, a monomer such as ethylene, propylene, butylene, itaconic acid or vinylpyrrolidone at a ratio of 10 mol% or less.
It may be an A-based polymer. In addition, a small amount (10% or less) of another type of polymer that is miscible with the PVA-based polymer, such as polyvinylpyrrolidone or polyacrylic acid.
It may be blended.

The spinning method of the present invention is dry spinning in which a spinning dope obtained by dissolving PVA in a solvent is extruded into heated air through a nozzle to evaporate and remove the solvent. For example, when water is used as the solvent, the PVA concentration can be significantly increased to 40 to 70% as compared with 10 to 20% for wet or dry-wet, and it is not necessary to use a solidifying bath. It is advantageous over dry-wet spinning. In the case of conducting the heat conduction type drawing, since the raw yarn used for the drawing needs to be a flexible filament bundle, the wet drawing or the wet drawing of 2.5 times or more is essential in the wet or dry-wet spinning. In dry spinning, this is not necessary, and thus a raw yarn can be obtained without wet drawing. In an extreme case, the point is to add a sizing agent to secure the Shino molding so that the filament bundle does not come apart in the hot air drawing, whereas in the heat conduction drawing the flexibility is the point. There is a clear difference in the tendency depending on the stretching method.

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, the drawing is performed by a hot plate, a hot pin, a hot roller or the like, so that the fiber receives frictional resistance on these. Therefore, it is easy to think that a smaller friction coefficient is preferable. In particular, the higher the yarn speed, the more important it becomes. Initially, I thought that the dynamic friction coefficient of fiber-to-metal (abbreviated as F / Mμd) was important and F / Fμs was not important, but as a result of various studies, surprisingly, F / Mμd
d is not important and F / Fμs is small, that is, F
It has been found that it is extremely important that / Fμs is 0.270 or less. The reason why F / Fμs is important is unknown, but since multifilaments rub against each other during drawing, the relative velocity between single fibers is small and it is close to a static state, so it is important that F / Fμs is small. Is estimated to be 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 type of the surfactant, but is 0.005 to 2% with respect to the polymer. When a surfactant is applied in the spinning process, there are dip-nip method, touch roller method, gear pump method, etc., but there is no particular limitation, but the dip-nip method has less adhesion unevenness between single yarns, and the gear pump method uses filaments. 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 pot plate, a hot pin, and a hot roller for directly contacting the fibers and raising 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 to 220 ° C., and the first stage draw ratio is 2.5 to 6.0.
It must be doubled. If the first stage stretching temperature is lower than 130 ° C., the stretchability is low, the oriented crystallization effect is small even if stretching is possible, and fusion cannot be prevented when the second stage stretching temperature becomes high. 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. First
It is more preferable that the stage drawing temperature is 160 to 210 ° C. If the first stage draw ratio is less than 2.5 times, the oriented crystallization in the first stage is not sufficient, and the structure cannot withstand the next high temperature second stage stretch. First stage draw ratio is 6.0
If it exceeds twice, it will be over-stretched and the second stage stretching cannot be carried out smoothly. More preferably, the first stage draw ratio is 3.0 to 5.0 times. In many cases, it is preferable that the first-stage stretching itself is divided into multiple stages. For example, the first stage stretching is divided into two stages to perform stretching by setting a temperature gradient between the plate temperature of 160 ° C. and 190 ° C., which are 220 ° C. or less. As described above, the first stage stretching can be understood as a preliminary stretching step for smoothly performing the second stage stretching performed at a high temperature near the melting point of the crystal for the purpose of more complete oriented crystallization.
It has been found that it is an essential requirement for the heat conduction type stretching of VA.

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 250 ° C. and the stretching ratio is set to 1.3.
~ 3.0 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. When the temperature is higher than 250 ° C, the crystals melt and the fibers stick. Further, PVA is decomposed and deteriorated. A more preferable second stage drawing temperature is 230 to 245 ° 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 less than 1.3 times, the orientation crystallization of the obtained fiber is insufficient and the strength / hot water resistance is poor. If the second stage draw ratio is higher than 3.0 times, fuzz appears. The second stage stretching itself can be divided into multiple stages for stretching. 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 proposed 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 desired 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 drawing, a free guide roller can be provided between the plates in order to bring the fibers into complete contact with each plate.

The total draw ratio (hereinafter abbreviated as TD) obtained by multiplying all of the first-stage draw ratio and the second-stage draw ratio has a great influence on the performance, and it is often preferable to set it to at least 8 times. .. If the TD is lower than 8 times, the orientation and crystallization as the final drawn yarn will be insufficient, and the strength and hot water resistance will be insufficient. More preferably, the TD is 10 times or more.

A major feature of the present invention is that the total residence time of the first-stage stretching and the second-stage stretching can be 10 seconds or less, and in most cases, 5 seconds or less. This is a residence time of at least 3 for conventional heating tubes, hot tubes and hot blast stoves.
It requires 0 seconds or more, and the higher the length, the higher the performance becomes.

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 to
It is about 10 m. After stretching, heat setting or heat shrinking may be performed as necessary. In polyester fibers that are commonly used for heat conduction type stretching, necking stretching occurs at a certain point, it is not necessary to further stretch after the necking stretching, and it is difficult to stretch even when trying 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 the dry-spun PVA fiber is drawn by using the heat conduction type drawing machine,
By setting F / Fμs to a predetermined value or less to obtain a slippery raw yarn, and drawing two stages under specific conditions, TU80m /
It was possible to produce a fiber having no fluff even at a high speed of min or more, no thermal deterioration, and having high strength comparable to hot air drawing with a residence time significantly shorter than that of hot air drawing.

Fiber-to-fiber static friction coefficient (F /
F μs) is measured according to JIS 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 bobbin with double brim needles as shown in FIG. Thus, a drum-shaped filament in which the sample filaments were wound in parallel in a drum shape was used. Others were based on JIS L-1015.

[0023]

EXAMPLES The present invention will be specifically described with reference to the following examples, but the present invention is not limited to these examples.

Example 1: Viscosity average degree of polymerization is 1700,
PVA having a saponification degree of 99.9 mol% was added to water so as to be 40%, and kneaded and dissolved in a nitrogen atmosphere to obtain a concentrated aqueous solution of PVA. The obtained spinning dope was extruded into heated air through a nozzle having a hole number of 36, water was evaporated, dried and wound up. The obtained yarn denier yarn 2000dr was contacted with a 0.1% hexane solution of dimethyl silicone in a touch roller system and dried with a hot roller at 120 ° C, and then dried on a plate at 150 ° C, 200 ° C, 233 ° C. Dry running was carried out by running in contact. F / Fμs after drying with a hot roller was 0.221, and the speed of entry was 9.0 m / m.
The in and TU were 90 m / min, and the TD was 10 times.
By measuring the yarn speed immediately after passing through the 200 ° C plate, 15
The total first stage draw ratio on the 0 ° C and 190 ° C plates was 3.7 times, and the second stage draw ratio on the 233 ° C plate was 2.3 times. The total residence time was about 4 seconds. The stretching condition was good, almost no fluff was observed, and the single fiber strength of the obtained stretched system was 10.5 g / d.
The performance was the same as that of hot air drawing at 15 m / min and residence time of 30 seconds.

Comparative Example 1: Using the same yarn as in Example 1,
Multi-stage plate stretching was performed in the same manner as in Example 1 except that dimethyl silicon was not applied, but many fluffs were generated and normal stretching could not be performed. Enter speed 11.3m /
When it was raised to min and TD was lowered to 8 times, the generation of fluff disappeared, but the strength was as low as 8 g / d and only low strength was obtained. The F / Fμs of the raw yarn was as large as 0.301.

Example 2: Using the same yarn as in Example 1,
Dimethyl silicon was added in the same manner as in Example 1, and the temperature was 120 ° C.
After drying with a hot roller, 160 ℃, 190 ℃, 210 ℃, 2
Dry heat drawing was carried out by traveling while contacting on a plate at 36 ° C. Entry speed is 12.5 m / min, TU is 120 m / mi
n and TD were 9.6 times. By measuring the yarn speed after passing the 210 ℃ plate, 160 ℃, 190 ℃, 210 ℃
The total first stage draw ratio by the plate was 3.5 times, and the second stage draw ratio by the 236 ° C. plate was 2.7 times. The total residence time was as short as about 3 seconds. The stretched condition was good, fluff was hardly seen, and the single fiber strength of the obtained stretched yarn was 10.1 g / d.

Comparative Example 2: All plate temperatures were 236 ° C.
Stretching was performed in the same manner as in Example 2 except that However, under these conditions, the fibers were fused on the plate and the yarn could not be introduced. T
Even if U was lowered, it was also melted and the yarn could not be guided.

Comparative Example 3: Final plate temperature of 218 ° C.
Stretching was performed in the same manner as in Example 2 except that However, under this condition, 10 times the TD was broken. When the speed was increased and the TD was decreased, only those with low strength were obtained.

Comparative Example 4: An intermediate drive roller was provided between the third plate and the fourth plate, and the speed of entry was 12 m / min.
Example 2 except that the intermediate drive roller is 28 m / min
An attempt was made to perform stretching in the same manner as in. However, TU120m /
The thread was broken at min. Therefore, it was attempted to find a point where the fluff and the strength were compatible by changing the TU, but it was not possible to obtain a drawn yarn having a single fiber strength of 9 g / d or more without the fluff.

Example 3: Using the same yarn as in Example 1,
Amino silicon was applied by the same method as in Example 1 14
After drying with a hot roller at 0 ° C, 170 ° C, 190 ° C, 21
Dry heat drawing was performed by making the plate run in contact with the plate at 0 ° C and 238 ° C. Entry speed is 19m / min, TU is 180m / m
in and TD were 9.5 times. The F / F μs after drying with a heat roller was 0.16, and by measuring the yarn speed after passing the plate at 210 ° C., 160 ° C., 190 ° C., 210 ° C.
The total first stage draw ratio by the plate of No. 2 was 3.4 times, and the second stage draw ratio by the 238 ° C. plate was 2.8 times. The total residence time was as short as about 2 seconds. The stretched condition was good, there was almost no fluff, and the single fiber strength of the obtained stretched yarn was 9.9 g / d.

[0031]

INDUSTRIAL APPLICABILITY As described above, according to the present invention, when the dry-spun PVA fiber is stretched by using the heat conduction type stretching machine, F / Fμs is a slippery raw yarn having a predetermined value or less, and specific conditions are satisfied. TU8 by stretching two stages below
It is possible to produce a PVA fiber having a strength comparable to that in hot air drawing without fluff even at a high speed of 0 m / min or more and with a residence time significantly shorter than that in hot air drawing. As a result, it is possible to make the equipment compact and, therefore, to reduce the equipment cost. Further, the obtained fiber has less heat deterioration as compared with the conventional hot air drawing method, has good whiteness and can be manufactured at low cost, and thus is useful in the fields of rubber materials such as automobile tires and brake hoses, ropes, etc. ..

[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 front page (51) Int.Cl. ⁵ Identification number In-house reference number FI Technical indication location D02J 1/22 J (72) Inventor Isao Sakuragi 1-2-1 Kaigandori, Okayama-shi Kuraray Co., Ltd. ( 72) Inventor Yuichiro Yoshida 1-2-1, Kaigan-dori, Okayama-shi Kuraray Co., Ltd.

Claims (1)

[Claims] 1. A dry spinning process in which a spinning dope obtained by dissolving polyvinyl alcohol in a solvent is extruded through a nozzle into heated air to evaporate and remove the solvent, and the obtained spinning yarn is subjected to dry heat drawing (1). ) The fiber has a fiber-to-fiber static friction coefficient of 0.270 or less, (2) the fiber is heated using a heat conduction type heating means, and (3) a temperature of 130 to 2
Polyvinyl alcohol characterized by performing a first stage stretching of 2.5 to 6.0 times at 20 ° C. and then performing a second stage stretching of 1.3 to 3.0 times at a temperature of 220 to 250 ° C. Method for stretching base fiber.