JPH0625910A - Production of acrylic yarn for high-performance cf - Google Patents

Abstract

PURPOSE:To draw yarn in high ratio without damaging the surface of yarn and to obtain the subject dense yarn having high orientation by drawing wet yarn spun by dry wet type spinning method under a specific condition. CONSTITUTION:Wet yarn spun by dry wet type spinning method is sent through a feed side guide to a hot water bath and drawn in the water bath. An ultrasonic vibration is applied at least to the feed side guide and the yarn is drawn while being vibrated with ultrasonic wave and to utterly eliminate bonding between yarns in the drawing process. The drawn yarn is heated, dried and the structure is more densified by evaporation of water.

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 acrylic fiber for high performance CF spun by a dry-wet spinning method, and particularly in a step of drawing a moistened yarn at a high ratio and at a high temperature. The present invention relates to a method for producing an acrylic fiber for high performance CF, which can be stretched without adhering to each other and without causing scratches on the surface of the single yarn, and thus does not generate fluff due to single yarn breakage in the firing step.

[0002]

2. Description of the Related Art Conventionally, acrylic fibers have been widely used as precursor fibers for producing CF (carbon fibers) (hereinafter referred to as precursors). Since carbon fibers obtained by firing acrylic fibers have high physical properties (high strength and high elastic modulus), they have been utilized in many fields as reinforcing fibers for composite materials.

In recent years, further improvement in the performance of the carbon fiber has been desired more than ever before. In general, the physical properties of carbon fiber are generally determined by the physical properties of the starting material precursor, and therefore the improvement of the precursor is still active. Particularly regarding the enhancement of the strength of carbon fiber, since it is an essentially brittle material, its strength is also affected by minute scratches on the surface of the carbon fiber. Of course, high-quality products with no quality are required. In addition to this, in order to develop high-strength performance, it is possible to obtain wet yarn obtained by washing and removing the spinning solvent during the process of producing the precursor. It is indispensable to carry out stretching as long as possible to obtain a highly oriented and highly dense precursor.

Generally, there are a wet spinning method, a dry spinning method, and a dry-wet spinning method as a spinning method of acrylic fiber. As a result of the research on the precursor,
The precursor obtained by spinning by the dry-wet spinning method is likely to have a highly dense structure, but on the other hand, since the surface of the single yarn is smooth, adhesion between the single yarns easily occurs, and the adhesion between the single yarns. It has been found that the scratches are likely to occur on the fiber surface due to. In addition, a plicar that imparts a particularly high stretching ratio
In the manufacturing process of the ser, high tension is applied to the yarns, so that the adhesion between the single yarns is more likely to occur.

Therefore, as a method for reducing the adhesion between single yarns, for example, as in the method disclosed in Japanese Patent Laid-Open No. 63-35821, multi-step drawing with an increased number of drawing rollers and stepwise drawing. In addition, a combination with a multi-step temperature for increasing the temperature of the drawing bath solution is proposed. However, although this method has some effect in reducing the adhesion between single yarns, it is extremely difficult to eliminate the adhesion between single yarns. For example, each draw ratio in multi-stage drawing is considerably reduced. Therefore, an increase in the number of drawing stages is unavoidable, and as a result, the number of drawing rollers is increased,
The number of fibers in contact with the roller surface increases, which damages the surface of the single yarn. At the same time, the stretching roll
There is also a problem that the entire precursor manufacturing facility becomes large-scaled or complicated due to an increase in the number of la and an increase in the drawing bath length.

Further, Japanese Patent Laid-Open No. 61-108715,
In Japanese Patent Laid-Open No. 2-74608, the washing of the yarn is performed in water under ultrasonic irradiation or in a water bath having a guide that vibrates at a low frequency, thereby obtaining an acrylic fiber with a small amount of residual solvent. A method is disclosed. In this method, the efficiency of desolvation is improved, and the fusion of the yarn due to the residual solvent in the so-called firing step of flameproofing and carbonizing the precursor can be prevented, but the precursor used in the firing step. In the production of the above, specifically, it is not possible to eliminate the adhesion between the single yarns in the drawing step of the wet yarn in hot water, and consequently the precursor without the adhesion between the single yarns. Couldn't get

[0007]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention An object of the present invention is to achieve adhesion between single yarns when a wet yarn obtained by spinning by a dry-wet spinning method is drawn in a hot water bath. The purpose is to draw with a high draw ratio in the state of nothing and without damaging the fiber surface.

[0008]

The object of the present invention is to bring a wet yarn obtained by spinning by a dry-wet spinning method into contact with a guide to which ultrasonic vibration is applied in a hot water bath. It can be achieved by a method for producing a high-performance CF acrylic fiber, which is characterized by stretching while being stretched. Hereinafter, the present invention will be described in detail.

The acrylic polymer used in the practice of the present invention may be an acrylonitrile copolymer containing 90 mol% or more of acrylonitrile, but is preferably oxidized, crosslinked or nitrile group ring in the flameproofing treatment. Comonomer copolymers containing functional groups capable of accelerating the chemical reaction are preferred. Examples of such comonomers include carboxyl group-containing monomers such as acrylic acid, itaconic acid and methacrylic acid, and ester group-containing monomers such as methyl acrylate and methyl methacrylate.
And so on. One or more comonomers may be used, and any polymer may be used as long as it is a polymer which can be spun in a so-called solvent to be spun and coagulated in a coagulation bath to form a wet yarn.

The polymerization method of the present invention is not particularly limited, and known methods can be used. Solvents used for spinning are organic ones such as dimethylsulfoxide, dimethylformamide and dimethylacetamide, inorganic ones such as nitric acid, sulfuric acid, zinc chloride and rodan soda, alone or mixed with other solvents. Can be used. Further, as the coagulation bath liquid, water, alcohols such as methanol, acetones, aromatic hydrocarbons such as toluene, or a solution containing one or more of them can be used. The solvent of the spinning dope used in the present invention may be contained in the solution.

At the time of spinning, the spinning stock solution consisting of the above-mentioned acrylic polymer and solvent is spun into air from the spinneret once, and it is introduced into a coagulating bath for coagulation to be solidified by a dry-wet spinning method. To get The obtained yarn is suitable for producing a high-strength yarn because its surface is smooth and high elongation is easily obtained. In the present invention, the wet yarn to be stretched refers to a yarn in a wet state obtained by removing a solvent from a yarn obtained by a dry-wet spinning method with a water washing tank or the like, and usually dry-wet spinning It is obtained by directly guiding the swollen yarn obtained by the method to a washing tank and washing and removing the solvent present in the yarn.The spinning bath for carrying out the dry and wet spinning method and the washing for carrying out washing with water A bath containing a solvent is provided between the yarn and the bath, and the yarn is drawn at a temperature of 1 times or more at a temperature above the spinning bath, and then the solvent in the yarn is washed in a washing bath. It may be obtained by removing. When this method is used, a higher draw ratio is imparted to the yarn, which is more preferable for improving the performance of the precursor.

The wet yarn obtained by the above method is
Then, it is introduced into a heated water bath and stretched. At this time, the feature of the present invention lies in that the stretching is carried out while the ultrasonic vibration is directly transmitted to the yarn. The stretching method may be any method, but generally, a method utilizing the speed ratio of the supply roller and the take-up roller (take-off speed / supply speed) is adopted. The term "stretching" as used herein means that the speed ratio is substantially 1.1 or more, and the number of times of stretching in the bath liquid may be once or more.

The most characteristic method of the present invention is that, when a yarn in a wet state (wet yarn) is drawn in a hot water bath, ultrasonic waves are applied to a feed side guide in the hot water bath. The oscillating rod is brought into contact to vibrate the guide, and then the yarn is passed through the guide to be brought into contact with the guide so that vibration is propagated to the yarn and stretched. In order to obtain a further effect, it is preferable to apply ultrasonic vibration to the take-up side guide as well to vibrate the yarn and stretch it.

The ultrasonic device used in the present invention is not particularly limited, and the ultrasonic frequency emitted by the device is in the range of 10 to 90 KHZ and the vibration width is 100 to 40.
It is applied at 0 μm, and it is particularly preferable to set the vibration width to 200 to 300 μm. The control of the amplitude is different depending on the device, but it is usually determined by the wattage and the current control. If the vibration width is too small, the effect of preventing adhesion will be insufficient. On the other hand, if the vibration width is too large, the effect of preventing adhesion will be obtained, but ultrasonic vibration will damage the yarn surface, which is not preferable. Furthermore, when ultrasonic vibration is applied to the yarn in a non-contact manner, the action and effect are not so great. The guide is not particularly limited, but a stainless rod having a smooth surface, or a hard chromium-plated surface, a glass rod, a ceramic rod, or the like having excellent wear resistance. Is preferred. Of course, scratches on the surface will cause scratches on the yarn.Although the coefficient of friction is low like Teflon, if it is inferior in wear resistance, the surface will wear over time and groove-like scratches will occur. As a result, the yarn may be damaged, which is not preferable.

The drawn yarn obtained is dried at 125 ° C. after adhering a silicon-based oil agent. By this drying, the drawn yarn loses the water content in the yarn, and at the same time, the structure becomes more compact when water evaporates during drying. A yarn obtained by drying this drawn yarn is called a precursor, and is used in the firing process as a precursor for the subsequent carbon fiber.

[0016]

EXAMPLES The present invention will be described in more detail with reference to the following examples. The adhesion evaluation, crystal orientation, and surface observation of the single yarns of the fibers described in the examples were measured by the following methods. Adhesion evaluation of single filaments of wet fiber: Score roll 400 (manufactured by Kao Corporation) 0.1% aqueous solution 100 cc
3000 fibers cut into a length of 5 mm were put therein, stirred for 30 seconds, and when the fibers were suspended in the aqueous solution, the dispersion state of the dispersed fibers was judged as follows.

A: The number of bonded single yarns is 0. B: The number of bonded single yarns is 1 to 2. C: 3 to 5 single yarns are bonded together. D: The number of single yarns bonded together is 6 to 10. E: The number of bonded single yarns is 10 or more, which is extremely large.

Crystal orientation: Using a fiber bundle mounted on a fiber sample stand, an X-ray diffractometer manufactured by Rigaku Denki Co., Ltd., using Cu, kα rays as X-ray sources, the scattering angle 2θ = 17 ° of the fiber in the equatorial direction. An azimuth angle diffraction profile was obtained for reflection in the vicinity, a base line was drawn on the graph, and the peak half width H1 / 2 was obtained.
It was calculated by the following formula from (degree).

[0019]

[Equation 1] Surface observation with a scanning electron microscope (SEM): Gold is coated on the fiber surface and manufactured by Topcon (alpha 25) S
Using EM, observation was performed at an acceleration voltage of 15 KV at a magnification of 100 to 10000 times, and an average surface shape was observed at a magnification of 5000 times.

[0020]

Example 1 Acrylonitrile / methacrylic acid = 98 /
2 (weight ratio) of an acrylonitrile-based polymer was dissolved in dimethyl sulfoxide so as to be 20% by weight to prepare a spinning dope. Dimethyl sulfoxide / water = 3 for coagulation bath
Using a solution in which a 0/70 (weight ratio) solution was kept at -3 ° C,
Dimethyl sulfoxide / water was kept at a bath temperature of 30 ° C after the nozzle surface and the coagulation bath liquid surface distance were kept at 3 mm through a spinneret with a diameter of 0.12 mm and a hole number of 3,000, and was once discharged into the air and spun. = 30/70 (weight ratio), drawn twice, taken out of the bath, and then desolvated in a washing bath to obtain a wet yarn.

The wet filaments obtained were subsequently subjected to a three-stage drawing in a heated water bath with the temperature of the final water bath being 97 ° C. and the temperature being raised stepwise. Stretching was carried out by applying ultrasonic vibration with a vibration width of 300 μm at 20 KHZ to the guides on the yarn supply side of each heated water bath, directly contacting the yarns with the guides, and stretching 4 times to give a total of 8 times the drawn yarns. Obtained. The drawn yarn thus obtained had an extremely good result in the adhesion evaluation (A) that there was no adhesion between single yarns.

After that, a silicone-based oil agent is applied to the layer and the
It was dried at 5 ° C and wound on a winder. As a result of re-adhesion judgment of the precursor wound on the winder, the evaluation was the same (A). The results are shown in Table 1 as Example 1. As a result of observing the surface of this precursor, almost no scratch was confirmed on the surface. The result is shown in FIG. Also, the measurement result of the degree of crystal orientation,
The crystal orientation degree was 93%.

Using this precursor, flame resistance and carbonization were carried out in accordance with a conventional method with stretching, and no fluff was generated and stable operation could be realized. Further, the physical properties of the obtained carbon fiber strand are 600 kg / strength.
The elastic modulus was mm ² and the elastic modulus was 30 ton / mm ² .

[0024]

[Example 2] Spinning was carried out in the same manner as in Example 1 to obtain a moistened thread in the same manner as the drawing method, and 5 times drawing was carried out in a heated water bath while contacting a guide to which ultrasonic vibration was applied. A total of 10 times the drawn yarn was obtained and dried to obtain a precursor.
The evaluation results of the adhesion of the drawn yarn and the precursor obtained were each (A), which was an extremely good result when the number of single yarns adhered was 0. The results are shown in Table 1 as Example 2.

[0025]

Comparative Example 1 Spinning was carried out in the same manner as in Example 1 to obtain a yarn in a wet state, and then three-stage drawing was carried out in a similarly heated water bath at a final water bath temperature of 97 ° C. In the drawing, the yarn was brought into contact with a stationary guide in each heated hot water bath which was not subjected to ultrasonic vibration and was drawn 4 times to obtain a drawn yarn of 8 times in total. The adhesive evaluation of the obtained drawn yarn was (E).

After that, in the adhesion evaluation after the precursor formation by the same method, the result was (E), and a stick-like sticky state was partially formed. When the surface of the precursor was observed by SEM, many scratches were observed on the surface of the precursor. The result of the SEM observation is shown in FIG. Furthermore, this precursor was subjected to firing in the same manner as in Example 1, but the yarn became stick-shaped due to adhesion and was cut during the carbonization process, and no further operation was possible.

[0027]

Example 3 Acrylonitrile / Itaconic Acid = 99 /
1 (weight ratio) of an acrylonitrile-based polymer was dissolved in dimethyl sulfoxide so as to be 20% by weight to prepare a spinning dope. Dimethyl sulfoxide / water = 3 for coagulation bath
Using a solution in which a 0/70 (weight ratio) solution was kept at -3 ° C,
Through a spinneret having a diameter of 0.12 mm and a number of holes of 3000, the distance between the nozzle surface and the liquid surface of the coagulating bath was kept at 3 mm, and the product was once discharged into the air and spun. The obtained swollen filament was directly washed with water in a washing bath to remove the solvent, and a wet filament was obtained.
This is then heated in a heated water bath to a final warm water temperature of 97 ° C.
As a result, a total of 6 stages were stretched by the method of gradually increasing the temperature. Stretching was performed in the same manner as in Example 1 while applying ultrasonic vibration to obtain a stretched yarn with a draw ratio of 8 times, and then 12
It was dried at 5 ° C. and made into a precursor.

The evaluation of the adhesion between the obtained drawn yarn and the precursor was (A). The surface of this precursor was observed by SEM, and as a result, almost no scratch was confirmed on the surface. Also, the measurement result of the crystal orientation degree,
The degree of orientation was 90%. Further, when this precursor was subjected to calcination, generation of fluff was hardly observed in each step of flame resistance and carbonization, and stable operation could be realized.

[0029]

[Comparative Example 2] An eight-fold stretched yarn and a precursor obtained in exactly the same manner as in Example 3 except that ultrasonic vibration was not applied when the wet filament was stretched eight times. The evaluation of adhesion was (C) in all cases, and it was not possible to completely eliminate the adhesion. In addition, the surface of the precursor is SEM
As a result, it was observed that many scratches were observed on the surface of the precursor. This scratch is considered to be a scratch due to peeling of the adhesive due to the bonding of the single yarns. This pre-cursor
When subjected to a firing step in the same manner as in Example 3, flame resistance,
In each step of carbonization, fluff, which is considered to be caused by single yarn breakage, frequently occurred, and the yarn was wound around the roller or the like during the firing step, and stable operation could not be realized.

[0030]

[Table 1]

[0031]

According to the method of the present invention, when a yarn in a wet state is drawn in a hot water bath, the contact pressure applied to the contact surface between the single yarns in the yarn is changed by the vibration from ultrasonic waves. Since each single yarn is dispersed, it seems that it is possible to eliminate the adhesion between the single yarns. Further, troubles in the process such as single yarn breakage are reduced, and good operability is brought about. Furthermore, since it is possible to increase the draw ratio or the temperature in the bath liquid, there is no adhesion between the single yarns, moreover, it is possible to obtain a more precise and highly dense precursor, which is excellent in mechanical properties. CF can be obtained.

[Brief description of drawings]

FIG. 1 (a) is an 8-fold stretched precursor obtained in Example 1.
Is a SEM photograph of the surface state, and (b) is a SEM photograph showing the surface state of the 8-fold stretched precursor obtained in Comparative Example 1.

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Claims (1)

[Claims] 1. A high-performance acrylic fiber for CF, characterized in that a wet filament obtained by spinning by a dry-wet spinning method is stretched in a hot water bath while being brought into contact with a guide to which ultrasonic vibration is applied. Manufacturing method.