JP2000345429A - Production of acrylic fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an acrylic fiber capable of minimizing fluffs and yarn breakages and suitable as a carbon fiber precursor by stretching a yarn tow obtained by spinning the acrylic polymer in a bath, and then, stretching the stretched product in steam while controlling the degree of dryness of the steam. SOLUTION: This method for producing an acrylic fiber comprises spinning an acrylic polymer to form a yarn tow having 4,000-100,000 number of filaments, stretching it by 1.5-6 fold, preferably 2-4 fold in a bath at 35-98 deg.C, preferably 50-80 deg.C bath temperature, drying and then, performing a secondary stretching in steam, stretching the two in the steam by 10-20 fold, preferably 12-18 fold total stretching ratio while controlling 0.7-1 preferably 0.8-1 range of the degree of dryness by adjusting the amount of water supplied into a stretching machine through an atomizer in accordance with the degree of dryness obtained by monitoring the dryness of the steam to obtain the acrylic fiber.

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 acrylic fibers mainly used as precursor fibers for carbon fibers and the like. More particularly, the present invention relates to a method for producing fluff on the fiber surface and yarn breakage during production. The present invention relates to a method for producing an acrylic fiber capable of minimizing generation.

[0002]

2. Description of the Related Art Acrylic fibers such as precursor fibers for carbon fibers are prepared by dissolving an acrylic polymer in an organic or inorganic solvent into a coagulation bath to form a yarn, and then washing with water. It is often manufactured by stretching in a bath or stretching in a bath and then washing with water.

[0003] In such in-bath stretching, it is preferable to stretch in a high temperature environment as much as possible because the draw ratio can be increased and a fiber with high orientation and high strength can be obtained.
If water or an aqueous solution is used as the stretching bath solution, there is a limit to increasing the stretching temperature.

[0004] On the other hand, Japanese Patent Application Laid-Open No.
Japanese Patent Application Publication No. 2002-131, discloses a method in which after drawing in a bath and further drying and densifying, secondary drawing is performed by using a pressurized steam and adjusting the yarn tension to 0.3 to 0.7 g / d in a steam drawing machine having a small-diameter nozzle. Has been proposed. However, such a method has a problem that the fluff on the surface of the obtained acrylic fiber cannot be sufficiently reduced, and yarn breakage frequently occurs during production.

Japanese Patent Application Laid-Open No. 58-214521 discloses that a yarn immediately after steam drawing is controlled by controlling the wetness of steam when drawing using a pressurized steam after drawing in a bath and further drying and densifying. 7 moisture content
A method has been proposed in which the content is in the range of ２０20% by weight. However, in such a method, although the generation of fluff is suppressed to a certain extent, if the water content is excessive, yarn baking occurs during the subsequent baking treatment for forming carbon fibers, that is, the oxidation treatment and the carbonization treatment. In some cases, the strength of the carbon fiber may be reduced.

Further, Japanese Patent Application Laid-Open No. 10-292240 discloses that when a fiber is drawn using pressurized steam, the inside of a draw tank is maintained at a predetermined pressure, and a pressurized steam used for a drawing process is used. Suggest a temperature T ₁ (° C.) and then the temperature of the saturated steam pressurizing steam the same pressure when the T ₂ (℃), be temperature controlled to satisfy the _{T 2 <T 1 <T 2} +5 Have been. However, in such a method, it is assumed that the steam supplied to the drawing machine is partially heated, and in this case, in the drawing of the acrylic fiber, the water acts as a polymer plasticizer for forming the fiber. Effect is weakened, and the tension applied to each single yarn of the yarn is likely to be uneven, and as a result, a thin portion of the single fiber is cut and becomes fluff, or a yarn break occurs in a firing process of forming a carbon fiber. There was a case.

Further, as disclosed in the above publication,
In the method of monitoring the temperature of the steam line and supplying water according to the measured temperature, there is a problem that the temperature control cannot be performed at a temperature lower than the saturation temperature of the steam.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for stably producing a high-quality acrylic fiber which has few yarn breaks, has good processability, and has few fluffs. .

[0009]

The present invention has the following structure to solve the above-mentioned problems. That is, after spinning the acrylic polymer into a yarn, and further stretching in a bath,
A method for producing acrylic fiber in which secondary drawing is performed using steam, wherein the dryness of the steam is controlled in the range of 0.7 to 1.

The present invention has the following configuration in order to solve the above-mentioned problems. That is, a stretching machine for stretching a running yarn, a mechanism for monitoring the dryness of steam, a means for supplying moisture to the stretcher, and a supply for supplying steam to the stretcher so that the steam has a target dryness. And a mechanism for adjusting the amount of moisture to be produced.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail.

In the present invention, an acrylic polymer is spun, stretched in a bath, dried and densified in some cases, and then subjected to secondary stretching using steam to obtain an acrylic fiber.

The acrylic polymer includes a homopolymer of acrylonitrile or a copolymer of acrylonitrile obtained by copolymerizing a small amount of a comonomer, specifically, itaconic acid,
A copolymer obtained by copolymerizing methacrylic acid, acrylic acid, or the like at about 0.1 to 1% by weight can be used. The stock solution for spinning is prepared by dissolving such a copolymer in a conventionally known organic or inorganic solvent, or by directly polymerizing in a solvent.

Next, the yarn is spun by a wet spinning method in which the yarn is spun directly into a coagulation bath or a dry-wet spinning method in which the yarn once spun into the air is coagulated in the bath.

Next, the stretching in the bath may be performed immediately after the yarn is spun, or may be performed after the yarn is washed with water to remove the solvent. The stretching in the bath is 35 to 98.
In a stretching bath at a temperature of 50 ° C., preferably 50 to 80 ° C., the stretching ratio is 1.5 to 6 times, preferably 2 to 4 times. Further, in the case of drying and densification, the yarn after drawing in a bath is performed using a hot roll or the like, and the drying temperature and the drying time can be appropriately selected from conventionally known methods.

After that, using a steam having a pressure of 1 to 6 kg / cm ² G, preferably 3 to 6 kg / cm ² G and a dryness in a range described later, the stretching ratio is set to 2 to 6 kg.
2 times, preferably 3 to 5 times. It is preferable that the yarn before the second stretching has a moisture content of substantially 0% by weight, for example, after drying and densification.

In the present invention, means for supplying water such as an atomizer is used so that the steam has a dryness of 0.7 to 1, preferably 0.8 to 1, and more preferably 0.9 to 1. After use and control, the yarn is fed into a drawing machine for secondary drawing. If it is less than 0.7, the moisture imparted to the yarn becomes excessive, and in the subsequent flameproofing step,
Not only does the load of electric power increase to evaporate and remove water, but also the amount of steam supplied into the drawing machine fluctuates, and fuzz may occur due to unevenness in tension applied to the yarn in the drawing machine. On the other hand, if it exceeds 1, a dry steam state, that is, a so-called superheated state may occur, the water given to the yarn decreases, the plasticizing effect of the water contained in the fiber weakens, and the inside of the steam drawing machine is reduced. As a result, the tension applied to the yarn may become uneven, and the resulting fiber may be fluffed.

In the present invention, the total draw ratio of the yarn is 1
It is good to make it the range of 0-20 times, preferably 12-18 times. If the ratio is less than 10 times, the obtained carbon fiber may have insufficient mechanical strength such as tensile strength.
If it exceeds twice, fluff may be generated due to breakage of single yarn.

In the present invention, the number of filaments in the yarn is 4,000 to 100,000, preferably 6,
000 to 50,000, more preferably 8,000 to 1
The range is preferably 5,000. If the molecular weight is less than 4,000, the water supplied to the yarn becomes excessive, and the yarn may break due to temperature unevenness in the longitudinal direction of the yarn.
If it exceeds 000, the water supplied to the yarn becomes insufficient, and fluff may be generated. In the present invention, even in the case of a thick yarn, if the number of filaments is within such a range,
The generation of fluff due to the decrease in the amount of water that penetrates into the yarn bundle,
In the firing step of carbon fibers, that is, in the flameproofing step and the carbonizing step, damage to the yarn and breakage of the single yarn can be effectively suppressed.

In the present invention, since a part of the steam supplied from the steam boiler is in a superheated state, an appropriate heat medium such as water is used for the double pipe. Means for adjusting the dryness of steam can also be employed as an auxiliary.

The dryness of steam is affected by the pressure at the time of supply and the heat retention of the supply line.
It is preferable to monitor as much as possible just before being fed into the stretching machine and control the set value. The control method is
Conventionally known various control methods such as off control and PID control can be adopted, but from the viewpoint of further improving control stability,
It is preferable to employ ID control. In the control, it is preferable to set the control parameters so that the fluctuation range of the dryness of the steam falls within 0.05, preferably within 0.03. Further, the means for supplying water such as an atomizer is preferably installed as close as possible to the stretching machine from the viewpoint of stabilizing the dryness of steam in the stretching machine.

Further, steam, and pressure when supplied to the stretching machine, and minimize the pressure difference between the original pressure in the steam boiler unit, preferably not more than 10 kg / cm ² G, more preferably 7 kg / cm ² It is good to supply as G or less. If it exceeds 10 kg / cm ² G, a superheat state may occur, and it may be difficult to control the dryness of steam to a value in the above range.

FIGS. 1 and 2 are schematic system diagrams of the stretching machine and the steam supply line in the present invention. The high-pressure steam is once depressurized by the pressure reducing valve 1 and then passes through the filter 2.
Further, in order to make the pressure suitable for use in the stretching machine, the pressure is reduced by the pressure reducing valve 3, the drain is removed by the drain separator 5, and the pressure is supplied into the stretching machine 7.

Here, the dryness of the steam in the stretching machine (FIG. 1) or in the pipe (FIG. 2) is monitored by the dryness meter 6 and compared with the target dryness.
The water amount is adjusted by the water amount adjustment automatic valve 8 according to the value,
The adjusted water is supplied into the pipe in a mist state by the atomizer 4.

The embodiment of the present invention is not limited to these. For example, water may be added by a forced injection method in addition to the atomizer in order to supply the water. It is also preferable to provide a drain trap immediately after the atomizer. Furthermore, a mode in which water is directly supplied into the stretching machine by an atomizer may be adopted. Furthermore, in the present invention, it is also possible to employ means other than a dryness meter to monitor the dryness of steam.

[0026]

The present invention will be described below in detail with reference to examples.
You. In the examples, it occurs in the acrylic fiber.
Yarn breakage, fluff, specific gravity of oxidized yarn, tensile strength of carbon fiber,
The elastic modulus and specific gravity were measured as follows. Also charcoal
The single fiber diameter and elongation at break of the elementary fiber are calculated as follows.
Was. (Acrylic fiber breakage) Visual observation for 24 hours
Observed more. (Acryl fiber fluff) 5 minutes after running yarn
Observation was made visually, and the number of fluffs generated was counted. (Specific gravity of flame-resistant yarn) The flame-resistant yarn to be measured is placed in an oven,
After drying at 120 ° C. for 2 hours, its weight W ₁Measure
After further drying at 120 ° C. for 1.5 hours, the flame-resistant yarn was
D in ethanol with a weight d_TwoMeasure
It was determined by the following equation.

Specific gravity (−) = W ₁ × d / (W ₁ −W ₂ ) (tensile strength and elastic modulus of carbon fiber) 10 pieces of “Bakelite” ERL-4221 manufactured by Union Carbide Co., Ltd.
A carbon fiber to be measured is impregnated with a resin composition obtained by mixing 00 g (100 parts by weight), 30 g (3 parts by weight) of boron trifluoride monoethylamine and 40 g (4 parts by weight) of acetone to obtain a resin-impregnated strand. Was. 130 ° C,
The cured product was obtained by heating for 0.5 hour, and determined according to the resin impregnated strand test method (JIS R7601). Weighed W ₁ of the carbon fiber to be measured (specific gravity of the carbon fibers), further immersed in orthodichlorobenzene specific gravity d, measured in liquid weight W _2, it was determined by the following equation.

Specific Gravity (-) = W ₁ × d / (W ₁ -W ₂ ) (Single Fiber Diameter of Carbon Fiber) It was determined from the carbon fiber to be measured by the following equation.

Single fiber diameter (μm) = 2000 × (Y / (C
× d × 3.14)) ^0.5 Here, Y: weight of fiber (g / m), C: number of filaments, d: specific gravity. (Elongation at break of carbon fiber) It was determined from the carbon fiber to be measured by the following equation.

Elongation at break (%) = (strength / elastic modulus) × 100 In the following Examples and Comparative Examples, the conditions of secondary stretching and the state of yarn breakage and fluffing of acrylic fibers immediately after secondary stretching. Are summarized in Tables 1 to 3. (Examples 1 to 4) A stock solution of dimethyl sulfoxide (hereinafter abbreviated as DMSO) spinning solution composed of 99 mol% of acrylonitrile and 1 mol% of itaconic acid and containing 20% by weight of an acrylic copolymer was prepared.

Next, a discharge hole of 0.15 mmφ
DMSO: water = 35% by weight: 6 by dry-wet spinning method (air path length: 10 mm) from a die having 00 holes.
5% by weight is discharged into a coagulation bath at 10 ° C. to form a thread, washed with water, stretched three times by stretching in a bath at a temperature of 80 ° C., dried, densified, and then steamed. The yarn is secondarily drawn 5 times and the single fiber fineness is 1d, the number of filaments is 1
2,000 acrylic fibers were produced.

The dryness of the steam is determined in accordance with the embodiment shown in FIG. 2 by setting a predetermined dryness as a target value and adjusting the supply of water by an automatic water flow control valve while supplying water in a mist form by an atomizer. Controlled by feeding into.
At this time, the supplied steam has an original pressure of 15 kg / cm ² G
Was reduced to 8 kg / cm ² G, and then 4.4 kg / cm ² G
The pressure was reduced to cm ² G before use.

Here, an OSK 129 model from Ogawa Sampling Co., Ltd. was used as a dryness meter, and a part of steam from a steam supply line (steam pressure: 4.4 kg / cm ² G) was used. The dryness was supplied to the main body of the dryness meter via a throttle valve, and the temperature and pressure of steam in the main body were measured to determine the dryness. (Examples 5 to 9) After stretching by 3 times by stretching in a bath, drying and densification were performed, and the ratio of the secondary stretching was changed so that the total stretching ratio was 1
An acrylic fiber was produced in the same manner as in Example 1 except that the ratio was 6 times or 18 times. (Examples 10 to 16) Example 1 except that the number of holes in the die was changed and the number of filaments of the spun yarn was partially changed.
In the same manner as in the above, an acrylic fiber was produced. (Comparative Examples 1 to 4) Acrylic fibers were produced in the same manner as in Example 1 except that the target value of the dryness of steam was set to a higher value. (Comparative Example 5) An acrylic fiber was produced in the same manner as in Example 1 except that a steam stretching apparatus having no means for supplying moisture into the stretching machine was used and the dryness of steam was not controlled. (Comparative Example 6) An acrylic fiber was manufactured in the same manner as in Example 1 except that the dryness of steam was adjusted by cooling with water at a temperature of 25 ° C using a double tube. (Comparative Examples 7 to 13) Number of filaments in yarn (Comparative Example 10
To 12) and the secondary draw ratio of the yarn is changed (Comparative Examples 7 to 12).
9) Then, an acrylic fiber was produced in the same manner as in Example 1 except that the target value of the dryness of steam was set to a higher value. (Example 17) An acrylic copolymer consisting of 98 mol% of acrylonitrile and 2 mol% of methacrylic acid was polymerized by a solution polymerization method, and 22% by weight of the acrylic copolymer was DM.
The SO spinning stock solution was prepared. Here, the hydrophilicity of the spinning stock solution was improved by blowing ammonia gas until the pH of the spinning stock solution became 8.5, neutralizing methacrylic acid, and introducing an ammonium group into the polymer.

Next, a 0.15 mmφ discharge hole is formed in a 12
DMSO: Water = 35% by weight: 65 by dry / wet spinning method (air path length: 5 mm) from a die having 00 holes.
The mixture was discharged into a coagulation bath of 3% by weight and formed into a thread, and then washed with water and stretched three times by stretching in a bath at a temperature of 80 ° C.

Then, after applying the amino-modified silicone oil agent to the fiber, the yarn was dried and densified using a heating roller adjusted to 150 ° C.
Secondary drawing with steam in the same manner as in Step 4 and single fiber fineness 1
d. An acrylic fiber having 12,000 filaments was produced.

The obtained acrylic fiber was converted to 230-26
In air at 0 ° C., the film was heated at a draw ratio of 0.90 to convert it into oxidized fiber having a specific gravity of 1.30. /
Min, the temperature rising rate in the temperature range of 1,000 to 1,200 ° C. was 500 ° C./min, and the stretching ratio was 0.92.
The temperature was raised to 00 ° C. and calcination was performed.

Thereafter, in an aqueous solution of ammonium carbonate,
Anodizing treatment of 10 coulomb / g-CF was performed.

The obtained carbon fiber had a single fiber diameter of 7.0 μm.
m, strength: 5.2 GPa, elastic modulus: 230 GPa, elongation at break: 2.26%, specific gravity: 1.80, and high quality.

[0039]

[Table 1]

[0040]

[Table 2]

[0041]

[Table 3]

[0042]

According to the present invention, it is possible to appropriately control the dryness of steam supplied into a drawing machine, and to stabilize high-grade acrylic fibers having good process passability and little fluff. Can be manufactured.

According to the present invention, a sufficient amount of water can be supplied to the yarn during the secondary stretching, so that the water acts as a plasticizer in the yarn, thereby enabling high-magnification stretching. Also,
As a result, highly oriented precursor fibers can be obtained, and firing can be performed without impairing the quality of the fibers.

[Brief description of the drawings]

FIG. 1 is a view showing one embodiment of a steam stretching apparatus according to the present invention.

FIG. 2 is a view showing another embodiment of the steam stretching apparatus according to the present invention.

[Explanation of symbols]

 1: Pressure reducing valve 2: Filter 3: Pressure reducing valve 4: Atomizer 5: Drain pot 6: Dryness meter 7: Stretcher 8: Automatic water volume control valve

Continued on the front page F-term (reference) 4L035 BB04 BB06 BB11 BB15 BB17 BB60 BB69 BB72 BB80 BB82 BB85 BB89 BB94 FF01 GG04 MB03 MB04 4L036 AA01 MA04 PA03 PA19 PA26 UA21 4L037 AT02 CS03 FA03 FA06 PA08 PS08 PC03 PA03 PC PS17

Claims (9)

[Claims] An acrylic polymer is spun to form a yarn,
A method for producing acrylic fiber, wherein the acrylic fiber is subjected to secondary stretching using steam after being further stretched in a bath, wherein the dryness of the steam is controlled in the range of 0.7 to 1. 2. The method according to claim 1, wherein the dryness of the steam is controlled in a range of 0.8 to 1. 3. The dryness of the steam is controlled by monitoring the dryness of the steam and adjusting the amount of water supplied into the stretching machine according to the dryness.
The method for producing an acrylic fiber according to the above. 4. The method for producing acrylic fiber according to claim 3, wherein an atomizer is used for supplying water into the drawing machine. 5. The method for producing an acrylic fiber according to claim 1, wherein the total draw ratio of the yarn is 10 to 20 times. 6. The filament having a filament number of 4,000 to 4,000.
The method for producing an acrylic fiber according to any one of claims 1 to 5, which is 100,000. 7. The method for producing an acrylic fiber according to claim 1, wherein after the stretching in the bath, before the second stretching, the fiber is dried and densified. 8. A drawing machine for drawing a running yarn, a mechanism for monitoring the dryness of steam, a means for supplying water to the drawing machine, and a drawing machine so that the steam has a target dryness. A steam stretching apparatus for producing an acrylic fiber having a mechanism for adjusting the amount of water supplied into the machine. 9. The steam stretching apparatus for producing acrylic fibers according to claim 5, wherein the means for supplying water into the stretching machine is an atomizer.