JPH0718052B2 - Manufacturing method of high strength acrylic fiber - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a high-strength acrylic fiber, and particularly to a degree of polymerization of a polymer constituting the fiber and a machine of the fiber as compared with a conventional commercial acrylic fiber. TECHNICAL FIELD The present invention relates to a novel method for producing an acrylonitrile fiber characterized by extremely high fiber surface smoothness and a dense fiber structure.

(Prior Art) Conventionally, acrylic fibers (hereinafter abbreviated as AN fibers) have been produced and sold in large quantities for clothing, but mechanical strength is not sufficient for industrial or industrial use. It is currently rarely used.

Many attempts to improve or improve the mechanical strength of AN fibers have been proposed so far.

For example, JP-B-45-19414 and JP-B-46-29891 disclose that an acrylonitrile-based polymer (hereinafter referred to as AN-based polymer) solution is introduced into a coagulation bath solution through an inert gas medium. A spinning method for coagulation, that is, a method for forming a coagulated filament by a dry-wet spinning method, washing, hot water drawing, oil treatment, drying, secondary drawing, and further heat treatment while allowing shrinkage, particularly the above two-stage drawing A method for obtaining a high-strength industrial AN-based fiber by selecting the conditions and the conditions of a high winding speed has been proposed.

Further, in JP-A-57-51810, fibers obtained by a wet or dry spinning method are wet-stretched, dried under tension, and subsequently contact-stretched to obtain an effective total draw ratio of 9 times or more.
A method of making the amount 25 times or less is proposed, and it is described that an AN fiber having a high elastic modulus can be obtained by this method.

Further, JP-A-57-161117 discloses that the relative viscosity is 2.5.
It has been proposed to dry- or wet-spin an AN polymer of up to 6.0, wash or wet-stretch after washing, dry on a heating roll under tension, stretch under dry heat, and heat-treat under dry heat. It is described that a high-strength AN fiber is obtained by this.

However, the strength of the AN-based fibers obtained by these known techniques is, for example, a tensile strength of about less than about 10 g / d at the maximum, and the improvement of the tensile strength is caused by other mechanical properties such as tensile modulus and knots. In many cases, the strength is lowered, and it does not comprehensively improve or improve not only tensile strength but also other mechanical properties such as elastic modulus and knot strength.

The inventors of the present invention have found the present invention by earnestly examining an ultra-high-strength AN fiber having improved and improved mechanical properties such as strength and elastic modulus of the AN fiber.

(Problems to be Solved by the Invention) That is, an object of the present invention is to provide a novel AN-based fiber whose mechanical strength is remarkably improved and improved as compared with the conventional AN-based fiber. Another purpose is to
It is to provide an industrial manufacturing method of AN fiber.

(Means for Solving Problems) In order to solve such problems, the method for producing a high-strength acrylic fiber of the present invention has the following constitution. That is, an acrylonitrile polymer solution having an intrinsic viscosity of more than 2.5 and not more than 3.3 and having a polymer concentration of 10 to 20% by weight and a solution viscosity at 45 ° C of not less than 1500 poise and not more than 10,000 poise is spinneret. After discharging once into air or an inert gas through the holes, the distance between the spinneret surface and the coagulating bath liquid surface is 1 to 20 mm, and the spinning draft is 0.1 to
It is introduced into a coagulation bath to be coagulated so as to be 1.5, and the coagulated fiber yarn obtained is washed with water, drawn, and dried, and then the total draw ratio is 10 to 20 under heating air of 160 to 250 ° C. X-ray crystal orientation is 94.0% or more and 96.4% or less, tensile strength is 10 g / d or more, tensile elastic modulus is 200 g / d or more, knot strength is 2.2 g / It is a method for producing a high-strength acrylic fiber having a smooth surface with d or more and surface smoothness expressed by relative glossiness of 18.2% or more and 23.1% or less.

Here, the X-ray crystal orientation degree is a scale showing the degree of orientation of the AN polymer molecular chain constituting the fiber in the fiber axis direction, and is a value obtained by the following measuring method.

"Measurement method of X-ray crystal orientation degree" It is a value calculated by the following formula from the half-value width H of the intensity distribution of the diffraction point on the equator line of the AN fiber by the X-ray diffraction method.

Orientation (%) = {(180-H) / 180} × 100 Wide-angle X-ray diffraction (counter method) (1) X-ray generator Rigaku Denki Co., Ltd. 4036A2 X-ray source: CuKα (using Ni filter) Output : 35KV 15mA (2) Goniometer manufactured by Rigaku Denki Co., Ltd. 2155D1 Slit system: 2MM 1 ° × 1 ° Detector: Scintillation counter Also, the glossiness of the fiber surface is the value determined by the following measurement method. It reflects the fineness of the fiber structure as well as the smoothness of the surface.

"Measurement method of surface gloss" Align the fiber bundles in parallel. At this time, the number of threads with crimp is 90
Straighten the yarn by removing the crimp in hot water at ~ 100 ° C. A light ray is applied to this sample surface from one direction to separate the reflected light into a specular reflection component (a) and a diffuse reflection component (b), and the ratio of the two is taken as the contrast glossiness.

Contrast gloss = (1-b / a) × 100 The feature of the present invention is that the polymer is relatively polymerized in comparison with the AN polymer which is a commercially available AN fiber as well as the known AN polymer. AN polymer having a remarkably large degree, that is, having a value of more than 2.5 and 3.3 or less when expressed as an intrinsic viscosity.Because the fiber is composed of such a relatively high degree of polymerization polymer, about 10 g / Not only does it have a tensile strength exceeding d, but it also exhibits extremely large values in other mechanical properties.
Incidentally, when the intrinsic viscosity is 2.5 or less, it becomes difficult to achieve fiber properties of strength 10 g / d or more, elastic modulus 200 g / d or more, knot strength 2.2 g / d or more, while the intrinsic viscosity is 3.3. If the viscosity exceeds the above value, the viscosity of the stock solution for spinning will be remarkably increased, and it will be difficult to obtain the target fiber physical properties due to a decrease in spinning and drawability, and the productivity during polymer production will be significantly reduced. The problem arises.

And, importantly, the AN obtained by the present invention, despite being composed of such a high degree of polymerization polymer,
The type fibers are highly distributed fibers having an X-ray crystal orientation degree of 94.0% or more and 96.4% or less, and it is only because the fibers are composed of this high orientation degree and the above-mentioned relatively high polymerized polymer As a result, it exhibits ultrahigh-strength physical properties that have never been considered. If the X-ray crystal orientation degree is less than 94.0%, the strength and elastic modulus of the fiber will decrease, while
If it exceeds 96.4%, the strength and elastic modulus will be improved, but the contrast glossiness will be decreased and the denseness of the fiber will be decreased, so the knot strength, which is an important physical property as an industrial fiber, will not reach 2.2 g / d. .

The tensile strength of the fiber obtained by the present invention is 10 g / d or more. If the tensile strength is less than 10 g / d, it is not sufficient for industrial and industrial purposes aimed at by the present invention. Incidentally, in order to obtain a tensile strength of more than 20 g / d with an acrylic fiber, industrial production is generally difficult because the degree of polymerization is remarkably increased, and drawing is required to exceed 20 times.

Further, the tensile elastic modulus of the fiber obtained by the present invention is 200 g / d
That is all. When the tensile elastic modulus is less than 200 g / d, it is difficult to use it for industrial purposes and industrial purposes aimed at by the present invention. It is generally difficult to obtain a tensile elastic modulus of more than 300 g / d with acrylic fibers. The knot strength of the fiber obtained by the present invention is 2.2 g / d or more. When the knot strength is less than 2.2 g / d, the flexibility and durability are insufficient, and it is difficult to use it for industrial purposes and industrial purposes which are the objectives of the present invention. It is generally difficult for the high-strength acrylic fiber obtained by the present invention to have a knot strength exceeding 4 g / d.

Furthermore, the AN-based fiber obtained by the present invention has a smooth fiber surface, and specifically, the contrast glossiness of the surface is 18.2 to
It is characterized by having a smooth surface with a value of 23.1%. If the contrast gloss is less than 18.2%, the fibers are highly oriented and the strength and elastic modulus are improved, but the knot strength is 2.2 g.
It becomes difficult to achieve fiber properties of / d or more. on the other hand,
If the contrast glossiness exceeds 23.1%, the degree of fiber orientation is insufficient and it becomes difficult to reach a strength of 10 g / d.

That is, instead of melt-spinning the polymer as it is, like AN-based fibers and polyamides and polyester-based fibers of other general-purpose synthetic fibers, a polymer is usually dissolved in various solvents, and a solution obtained by dissolving the polymer in the solvent is used. Is used as a spinning dope and is made into fibers by adopting means such as wet, dry or dry-wet spinning. When such means is used, the solvent contained in the fibers must be removed (desorption). Solvent) is required. This desolvation is usually performed using water, but voids are generated because the volumetric shrinkage of the fiber cannot follow the desolvation. Dry densification is performed to eliminate the voids, but as shown in the Textile Society of Japan Vol.29, No.8 (1973), when the polymer concentration becomes low, coagulated yarn with many voids is obtained, so the drying process Even after passing through, the voids are hard to disappear, and the strength-elongation property is also low.

On the other hand, if the degree of polymerization is increased, the viscosity of the stock solution when the polymer is dissolved in the solvent is increased, and the polymer concentration must be lowered from the viewpoint of the stability of the stock solution and the spinnability. Therefore, in the case of a polymer having a high degree of polymerization, it becomes difficult to densify it because of the adverse effect of a decrease in the polymer concentration, and a high strength yarn cannot always be obtained.

That is, the AN fiber obtained by the present invention is composed of a relatively high degree of polymerization polymer having an intrinsic viscosity of more than 2.5 and not more than 3.3, and such a relatively high degree of polymerization polymer has an X-ray crystallographic orientation in the fiber axis direction. The basic characteristic is that it is highly oriented with a high value of 93% or more and 97% or less when expressed in degrees, and its mechanical strength, such as tensile strength, is
10 g / d, preferably 12 g / d or more, tensile elastic modulus of 200 g
/ d or more, and the knot strength is 2.2 g / d or more, showing excellent physical properties.

In addition, the fiber obtained by the present invention has a high contrast glossiness in the range of 15 to 30% in terms of glossiness, so that there are few surface defects and in addition to the denseness of the fiber. Because it is excellent, a fiber having high strength and high elastic modulus and also strong against bending and friction can be obtained. Excellent physical properties as described above,
As a method for producing the fiber of the present invention having performance, as described above, the degree of polymerization of the polymer constituting the fiber is extremely high, and since the polymer needs to be highly oriented in the axial direction of the fiber, the AN system is used. It is difficult to manufacture by the wet or dry spinning method which is most widely adopted industrially as a method for producing fibers, and the dry-wet spinning method described in detail below,
That is, a spinning solution obtained by dissolving an AN polymer in the solvent is once discharged through a spinneret hole into air or an inert gas, preferably air, and the discharged yarn is coagulated through a minute space of gas. It is possible to obtain such high-strength AN fiber only by adopting a method of introducing it into a liquid bath and solidifying it, and further adopting a specific manufacturing process and its conditions.

Hereinafter, the method for producing the high-strength AN fiber of the present invention will be described in detail.

First, the AN polymer used in the present invention is preferably AN
Is 90 mol% or more, more preferably 95 to 100 mol%,
A vinyl compound having copolymerizability with respect to is preferably 0
It is an AN homopolymer or AN-based copolymer (hereinafter referred to as AN copolymer) composed of about 5 mol%. At this time, if the copolymerization ratio of the vinyl compound exceeds 5 mol%, the heat resistance and the denseness of the obtained fiber may deteriorate, which is not preferable.

The vinyl compound may be any known compound having copolymerizability with various ANs, and is not particularly limited, but preferable copolymerization components include acrylic acid, itaconic acid, methyl acrylate, methyl methacrylate, Examples thereof include vinyl acetate, sodium allyl sulfonate, sodium methallyl sulfonate, sodium p-styrene sulfonate, and the like.

Such AN-based polymers are used in the solvent such as dimethyl sulfoxide (DMSO), dimethylformamide (DM
A), dimethylacetamide (DMAc), ethylene carbonate, butyl lactone, etc., organic solvent, zinc chloride, calcium chloride, lithium bromide, sodium thiocyanate, etc. It is used as a spinning dope, that is, as a spinning dope.

The polymer concentration of this spinning dope is in the range of 10 to 20% by weight, preferably 12 to 18% by weight, and if the polymer concentration is lower than 10% by weight, the denseness of the fiber will deteriorate and It is not preferable because the elongation property is deteriorated and the manufacturing cost is also disadvantageous. When the polymer concentration exceeds 20% by weight, the viscosity of the stock solution becomes too high and the stability and spinnability of the stock solution deteriorate. Not preferable.

The solution viscosity at 45 ° C. is 1500 poises or more and 10,000 poises or less, preferably 2000 poises or more and 9000 poises or less, and more preferably 3000 to 8,000 poises. 45 ° C
If the solution viscosity is less than 1500 poise, the coagulated structure is deteriorated and drip is likely to occur on the spinneret surface, making it difficult to obtain a coagulated yarn for obtaining sufficient physical properties. On the other hand, if the solution viscosity at 45 ° C exceeds 10,000 poise,
Melt fracture occurs in the discharged yarn and the drawability decreases, so that only fibers having low strength can be obtained.

And the polymer concentration and solution viscosity of this spinning dope are extremely important in the dry-wet spinning method adopted in the present invention, and only when the polymer concentration and solution viscosity of the spinning dope are within the above range, the dry-wet process is performed. It is possible to obtain a fiber having high strength and high elastic modulus, which can be stably spun without causing problems such as drip and yarn breakage due to spinning.

When the temperature of the spinning dope is lower than 0 ° C, the concentration of the dosing solution becomes high, and there is a drawback that it tends to gel and spinning becomes difficult. When the temperature is higher than 130 ° C, the stability of the solvent and the undiluted solution becomes poor. However, it is generally preferable to keep the temperature within the range of 30 to 100 ° C.

The spinning dope thus prepared is dry-wet spun,
In this case, the distance between the spinneret surface and the coagulating bath liquid surface is 1 to
It is set to 20 mm, preferably in the range of 2 to 10 mm. When it is smaller than 1 mm, problems such as contact of the die surface with the liquid surface are likely to occur. It is not preferable because yarn breakage and adhesion between single yarns easily occur.

In such dry-wet spinning, the spinning draft determined by the discharge amount of the spinning dope and the take-up speed of the discharged yarn is 0.1 to 1.5,
It is preferably within the range of 0.2 to 0.8. If the spinning draft is less than 0.1, fusion between single fibers and unevenness of yarn will be caused, while if the spinning draft exceeds 1.5, yarn breakage will easily occur.

Further, as the coagulation bath, water used for the known wet or dry-wet spinning of AN-based fibers or an aqueous solution of a solvent of the AN-based polymer described above, for example, a concentration of 10 to 80 wt% and a temperature of 0 to 35 ° C A solvent aqueous solution is used.

The coagulated yarn thus obtained is subjected to conventionally known post-treatments, such as washing with water, drawing and drying. In the production method of the present invention, after coagulation, while sufficiently advancing the densification of fibers by stretching, from the viewpoint of preventing adhesion during drying and preventing yarn breakage during stretching, it is preferably about 2 to 10 times. ,
More preferably, primary stretching is performed 4 to 8 times.

In the present invention, it is necessary to subject the fibers after being dried and densified to the dry heat drawing which will be described in detail below. Is composed of a polymer having a relatively high degree of polymerization of 2.5 to 3.3 and having a high degree of X-ray crystal orientation of 93% or more and 97% or less. Is possible.

That is, in the dry heat drawing in the present invention, it is necessary to carry out dry heat secondary drawing so that the total draw ratio based on the original length of the coagulated fiber yarn becomes 10 to 20 under heated air of 160 to 250 ° C. Is. If the total draw ratio is less than 10, the fiber orientation and crystallization will be insufficient, and it will be difficult to obtain the target fiber physical properties. On the other hand, if the total draw ratio exceeds 20, yarn breakage frequently occurs during secondary drawing.

In addition, this dry heat secondary stretching is 1 g / d or more, further 1.5 to
It is preferable that the stretching tension is 2.0 g / d.

Here, the dry heat drawing is an important means for highly orienting the polymer chains made of the above-mentioned high degree of polymerization polymer in the fiber axis direction in the present invention, and in the case of other drawing means, the draw ratio is increased. Then, stretching is accompanied by breakage, which is not preferable.

Further, if the temperature range of the dry heat drawing is lower than 160 ° C, a sufficient draw ratio cannot be obtained, while if it exceeds 250 ° C, the drawability is deteriorated due to insufficient heat resistance of the fiber.

As a specific dry heat stretching means, various stretching means such as a hot plate, a heat drum, and a heat tube can be adopted, and although not particularly limited, preferably a heat drum or heated air is supplied, It is preferable to use a tube-shaped heating cylinder that can be discharged, and use a means or a combination thereof that stretches while allowing the yarn to pass through the heating cylinder kept at a predetermined temperature.

The draw ratio in this dry heat drawing depends on the history of the drawing of the yarn to be subjected to the dry heat drawing, and is set within a range in which the total draw ratio of the finally obtained drawn yarn is 10 to 20 times. . For example, in the case of a yarn that has been dry-wet spun, washed with water, and then subjected to primary stretching 4 to 8 times under moist heat, dry stretching of 1.5 to 4 times is performed. In the case of a yarn which has not been applied, the total draw ratio is preferably 10 to 20 times, preferably 13 by performing dry heat drawing in one step or in multiple steps.
Stretched to ~ 20 times.

(Examples) Hereinafter, the effects of the present invention will be described more specifically with reference to Examples. In addition, the intrinsic viscosity of polymers in the following Examples and Comparative Examples is a value measured by the following measuring method.

75 mg of dried polymer (sample) is placed in a 25 ml flask and dimethylformamide containing 0.1N sodium thiocyanate is added to the flask and dissolved. The specific viscosity of the obtained solution was measured at 25 ° C. using an Ostwald viscometer, and the intrinsic viscosity was calculated from the value by the following formula.

[Examples 1 to 3 and Comparative Examples 1 to 9] 100% AN was solution polymerized in DMSO to obtain intrinsic viscosity
Six kinds of AN-based polymers of 1.3, 1.9, 2.6, 3.0, 3.3 and 3.8 were prepared.

The viscosity η (45 ° C) of each of these 6 types of polymers is about
The spinning dope was prepared by adjusting it to 3,000 poise. Spinning was carried out by two methods, wet and dry-wet spinning, using the obtained 6 kinds of spinning dope. In both spinning methods, a 55% DMSO aqueous solution at 20 ° C. was used as the coagulation bath, and the spinning draft was 0.5.

In the case of dry-wet spinning, the distance between the spinneret surface and the coagulation bath liquid surface is
The distance from the coagulation bath surface to the focusing guide is 4 mm.
I set it to 00 mm.

The obtained unstretched yarn was washed with water, stretched 5 times in hot water to give an oily agent, and then dried and densified at 130 ° C. Then 1
The fiber was stretched in a dry heat tube in a temperature atmosphere of 60 to 230 ° C., a stretched yarn having a stretch ratio of 90% of the maximum stretch ratio was sampled, and the physical properties of the fiber were measured. The results are shown in Table 1.

The X-ray crystal orientation of Example 1 was 94.5%, and the relative glossiness was 23.1%.
The value was higher than that of 91.7% and relative gloss of 5.3%.

[Example 4, Comparative Examples 10 to 14] Solution polymerization in DMSO was performed at a composition ratio of AN 99.7 mol% and 2-acrylamido-2-methylpropanesulfonic acid 0.3 mol%, and the intrinsic viscosities were 3.3, 1.7 and 1.2. Polymers of

The polymer concentration was adjusted so that η (45 ° C.) was about 4,000 poise, and a spinning dope was prepared. This stock solution is heated to 70 ℃, using a spinneret with a hole diameter of 0.12 mmφ,
The length of the dry part was 3 mm, the distance from the surface of the coagulation bath to the focusing guide was 500 mm, and the mixture was discharged into a 30% DMSO aqueous solution at 15 ° C to obtain a coagulated yarn at a take-up speed of 10 m / min. The spinning draft at this time was 0.3.

The obtained coagulated yarn was washed with water at 50 ° C., stretched 5 times in hot water, added with an oil agent, and dried at 120 ° C.

The obtained fibers were subjected to secondary stretching in pressurized steam or dry hot air, respectively, and stretched at 95% of the maximum stretching ratio, and the results of physical property evaluation are shown in Table 2.

The fiber yarn of Example 4 had a high tension of 1.8 g / d at the time of secondary drawing at 190 ° C. in dry heat, and had an X-ray crystal orientation of 94.8.
%, And the relative glossiness was 21.2%. On the other hand, in the steam drawing of Comparative Examples 10 to 14, the drawing tension was as low as 0.8 g / d or less, and the strength and elastic modulus were also low.

[Examples 5 to 6, Comparative Examples 15 to 17] Solution polymerization in DMSO was carried out at a composition ratio of 99.5 mol% AN and 0.5 mol% 2-acrylamido-2-methylpropanesulfonic acid, and the intrinsic viscosity was 3.2. Got united.

This polymer was dissolved in DMSO and the polymer concentration was 4, 8, 12,
A spinning dope of 18 and 21% by weight was prepared. 50 of these stock solutions
The mixture was heated to ℃, the length of the dry part was adjusted to 10 mm, and dry-wet spinning was performed in a 30% DMSO aqueous solution at 15 ℃ to obtain a coagulated yarn. The spinning draft at this time was 0.4.

The stock solution having a polymer concentration of 4% by weight had a poor threading property, and the thread was frequently broken due to the occurrence of drip, and a satisfactory coagulated thread could not be obtained. In addition, the stock solution with a polymer concentration of 21% had a high viscosity, and melt fracture occurred during ejection.

The obtained coagulated yarn is stretched 5 times in hot water, washed with water, and then 110
Tension dried at ℃. 190 ° C using a dry heat tube
The drawn yarn having a draw ratio of 90% of the maximum draw ratio was sampled. Table 3 shows the results of evaluation of physical properties of the obtained fibers.

[Examples 7 to 11 and Comparative Examples 18 to 20] 100% AN was dissolved in DMSO and solution polymerization was performed to prepare polymers having an intrinsic viscosity of 2.8. The polymer concentration of the obtained polymer solution was adjusted to 16% by weight, and the solution viscosity at 45 ° C was 31%.
A spinning dope of 00 poise was prepared, heated to 70 ° C., the dry section length was 5 mm, and dry-wet spinning was performed in a coagulation bath of a 50% DMSO aqueous solution at 15 ° C. When obtaining the coagulated yarn, the pore diameter was changed to adjust the spinning draft.

The obtained coagulated yarn was washed in water at 30 ° C., drawn 4 times in boiling water, and then tension-dried at 130 ° C. Then, using a dry heat tube, carry out secondary stretching, and at 180 ° C the maximum stretch ratio of 9
A drawn yarn having a draw ratio of 0% was sampled. Table 4 shows the results of evaluation of the physical properties of the obtained fiber.

Note) In the case of Comparative Example 18, coagulated yarn cannot be collected due to slack in the coagulated yarn.

[Examples 12 to 13 and Comparative Examples 21 to 23] The coagulated yarn obtained in Example 8 was drawn twice in water at 30 ° C while being washed with water, then doubled in hot water at 85 ° C and 2.0 in boiling water. Stretched twice, and then model stretched slowly in ethylene glycol at 130 ℃ and 160 ℃.
Double, 19 times, 24 times and 28 times drawn yarns were obtained (the maximum draw ratio was 31 times). The drawn yarn thus obtained was washed with warm water of 60 ° C. and tension-dried at a temperature of 120 ° C. Table 5 shows the physical properties of the obtained fibers.

From Table 5, by increasing the total draw ratio, the strength, elastic modulus, and X-ray crystal orientation degree are improved, but the knot strength and the relative gloss are decreased, and the performance is unbalanced as an industrial fiber. I can understand.

[Examples 14 to 17 and Comparative Examples 24 to 25] The coagulated yarn obtained in Example 2 was washed with water, drawn 4 times in boiling water, and tension-dried at 120 ° C. The dry yarn thus obtained was subjected to secondary stretching with a dry heat tube whose temperature was changed to 140, 160, 180, 200, 230 and 260 ° C., and sampling was performed at a stretch ratio of 90% of the maximum stretch ratio. The results are shown in Table 6.

It can be seen from Table 6 that sufficient fiber performance cannot be obtained if the secondary drawing temperature is not appropriate. Using a spinneret with a diameter of 0.12 mm and a number of holes of 200, dry and wet spinning was performed in a coagulation bath of a 50% DMSO aqueous solution at 15 ° C. The spinning draft at this time was 0.5. The distance from the liquid surface of the coagulation bath to the focusing guide was 500 mm. Table 7 shows the results of observing the spinning state by changing the length of the dry section.

As shown in Table 7, the distance between the spinneret and the surface of the coagulation bath is
If it is 0.5 mm, the spinneret of the coagulation bath will wet the spinneret surface, making dry-wet spinning difficult.On the other hand, if it exceeds 25 mm, the filaments will adhere to each other before entering the coagulation bath. Was likely to occur, and a normal fiber yarn could not be obtained. That is, the distance between the spinneret surface and the liquid surface of the coagulation bath is 1 to 20 mm.
It can be seen that stable dry-wet spinning is possible by setting the ratio within the range.

(Effects of the Invention) The AN-based fiber obtained by the present invention is a multifilament having a single fiber fineness of 3 denier (d) or less, preferably 2d or less, and as described above, the X-ray crystal orientation degree is 93% or more.
It has a high orientation of 97% or less, and has outstanding strength in mechanical properties such as tensile strength. Moreover, the fiber structure is extremely dense, the surface of the fiber is also smooth,
Since it has the advantage of having few surface defects, it can be used in many fields for industrial or industrial use, fiber reinforcement, specifically canvas, asbestos substitute, sewing thread, hose, heavy cloth, etc. , Especially useful as a substitute fiber for asbestos.

Front Page Continuation (56) References JP-A-55-112310 (JP, A) JP-A-59-199809 (JP, A) JP-A-55-90616 (JP, A) JP-B-45-39494 (JP , B1) JP-B-49-14852 (JP, B1) JP-B-51-46856 (JP, B2) JP-B-52-48204 (JP, B2)

Claims (3)

[Claims] 1. An acrylonitrile polymer having an intrinsic viscosity of more than 2.5 and not more than 3.3 and a polymer concentration of 10 to 20% by weight,
A solution of acrylonitrile-based polymer having a solution viscosity at 45 ° C of not less than 1500 poise and not more than 10,000 poise is once discharged into air or an inert gas through the spinneret hole, and then the distance between the spinneret surface and the coagulating bath liquid surface is 1 It is introduced into a coagulation bath so that the spinning draft is 0.1 to 1.5 and coagulated, and the obtained coagulated fiber yarn is washed with water, stretched and dried, and then heated with air of 160 to 250 ° C. Below the total draw ratio
X, which is subjected to secondary stretching so as to be 10 to 20
Wire crystal orientation is 94.0% to 96.4%, tensile strength is 10g /
d or more, tensile elastic modulus of 200 g / d or more, knot strength of 2.2 g / d or more, and surface smoothness of 18.2% or more in terms of contrast gloss.
A method for producing high-strength acrylic fibers with a smooth surface of 23.1% or less. 2. The coagulated yarn according to claim 1, wherein the coagulated yarn is primarily stretched to 2 to 10 times, dried and then subjected to dry heat stretching of 1.5 to 10 times, and the total draw ratio is 13 to 20 times. High strength acrylic fiber manufacturing method. 3. The method for producing a high-strength acrylic fiber according to claim 1 or 2, wherein the dried yarn is stretched by dry heat while passing the dried yarn through a tube containing heated air.