JPH03199410A - Method for wet-spinning and storing acrylic fiber - Google Patents

Abstract

PURPOSE:To prepare an acrylic fiber having improved bundling property and increased operation stability and useful for preparing a carbon fiber by treating a fiber of water-swollen state after spun with an aminosilicone surfactant- containing aqueous solution having an adjusted pH, during and re-drawing the treated fiber. CONSTITUTION:(A) A fiber of water-swollen state after spun is treated with (B) an aqueous solution or aqueous dispersion containing an amino-silicone surfactant [e.g. a compound of the formula (m, n are 1-100000 wherein m+n is >=10; R<1>, R<2> are 1-10C alkyl or aryl)] capable of being converted into a resin when thermally treated at 250 deg.C for 30min in air and adjusted to a pH of <=4, preferably 2-3.5, with an acid such as hydrochloric acid, sulfuric acid, phosphoric acid, acetic acid or formic acid in an adhesion amount of the amino silicone surfactant of 0.03-2.0wt.% based on the weight of the dry fiber, followed by drying and re-drawing the fiber to prepare the objective acrylic fiber. The acrylic fiber is received in a case preferably in a water content of 30-50wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION [Production: Field of Application] The present invention relates to a wet spinning method for acrylic fibers (acrylic precursor) for producing carbon fibers and a method for storing the acrylic fibers.

In particular, the present invention relates to an acrylic fiber manufacturing method that improves the cohesiveness of acrylic fiber bundles, thereby increasing operational stability in the carbon fiber manufacturing process.

[Prior art and problems]

When manufacturing carbon fiber from acrylic fiber (precursor), it is generally done in an oxidizing atmosphere at 200 to 300°C.
It is necessary to carry out so-called flameproofing treatment, and then to carry out carbonization treatment or graphitization treatment in an inert gas atmosphere at 350° C. or higher.

In particular, it is important to prevent the single fibers that make up the fiber bundle from sticking to each other during flameproofing treatment at 200 to 300°C, and for this reason, methods of applying various silicone oils have been proposed. (JP-A-51-116225, No. 52-24136, No. 52-34025, No. 5
No. 3-10175, No. 5B-49022, No. 60-9
(Refer to publications such as No. 9011).

However, although these silicone-based oils are effective in preventing sticking during flame-retardation, when these oils are applied to water-swollen yarn after spinning in the acrylic fiber manufacturing process, Static electricity was generated in the fibers, resulting in problems such as disordered fiber bundles, wrapping around rollers and guides, and generation of fuzz. In order to improve these problems, the use of aminosilicon to form a film has been proposed (see Japanese Patent Application Laid-Open No. 11-174424).

However, when the amino silicone was used, an oil coating (scum) adhered to rollers and guides due to heat treatment such as drying, which impaired the operational stability of the acrylic fiber manufacturing process.

[Purpose of the invention]

The storage method of the present invention improves the convergence of fiber bundles during the manufacturing process of acrylic fibers (precursor), and reduces fuzziness.
The purpose is to use acrylic fibers that prevent roll-up and have improved process passability.

Another purpose of the Mokko Ming spinning method is to provide an acrylic fiber that can be used to produce excellent carbon fibers with high strength and no fluff or sticking.

The storage method of the present invention aims to store items in a stable high moisture content state without moisture uneven distribution.

[Structure of the invention]

The present invention consists of the following configuration.

(1) When producing acrylic fibers for carbon fiber production by the wet spinning method, first, the threads in a water-swollen state after spinning are treated with an aqueous solution or dispersion containing an aminosilicon surfactant whose pH is adjusted to below 4. The aminosilicon-based surfactant at this time is an aminosilicon-based surfactant that has been made into a resin by heat treatment in air at 250°C for 30 minutes, and has a residual amount of 80% by weight or more. A wet spinning method for acrylic fibers for producing carbon fibers, which is then dried and re-stretched.

(2) The wet spinning method for acrylic fibers for producing carbon fibers according to claim (1), wherein the pH adjustment is carried out using hydrochloric acid, sulfuric acid, phosphoric acid, acetic acid, or formic acid.

(3) The wet spinning method for acrylic fibers for producing carbon fibers according to claim (1), wherein the amino silicone surfactant-containing aqueous solution or aqueous dispersion has a pH of 2 to 3.5.

(4) The wet spinning method for acrylic fibers for producing carbon fibers according to claim (1), wherein the amino silicone surfactant is a compound represented by the following general formula.

General formula % Formula % (man): Number 10 or more RI R2: Alkyl group or aryl group having 1 to 10 carbon atoms] (5) The amount of amino silicone surfactant attached is 0.03 to 2.0% per dry fiber weight. The wet spinning method for acrylic fibers for producing carbon fibers according to claim 1, wherein the amount is 0% by weight.

(6) An acrylic fiber for producing carbon fiber, characterized in that the acrylic fiber for producing carbon fiber produced by the wet spinning method according to claim (1) is stored in a can at a moisture content of 30 to 50% by weight. Wide storage.

According to the wet spinnability of the present invention, the hydrophilicity of the aminosilicon surfactant is increased, so that it becomes possible to uniformly apply the aminosilicon surfactant to the water-swollen fibers after spinning.

For this reason, scum (oil scum) in the drying and densification process
There is no occurrence of problems such as fuzzing, curling of fiber bundles, and disturbance of convergence due to static electricity, and process passability is improved.

In the present invention, carbon fiber has a broad meaning including graphite fiber.

In the present invention, acrylic fibers refer to fibers of polymers containing at least 90% by weight, preferably 95% by weight or more of acrylonitrile.

The comonomer copolymerized with acrylonitrile is usually
It is the same as that used as a comonomer for acrylonitrile. Examples of comonomers include alkyl acrylates (such as methyl acrylate, ethyl acrylate, butyl acrylate, etc.), alkyl methacrylates, vinyl acetate, acrylamide, N-
These include methylol acrylamide, acrylic acid, methacrylic acid, vinyl sulfonic acid, arylsulfonic acid and their salts, vinyl acetate, vinyl imidazole, vinyl pyridine and their derivatives.

As the spinning solvent for the acrylonitrile polymer or copolymer, organic solvents [e.g. dimethylformamide (DMF)]
, dimethyl sulfoxide (DMSO), dimethyl acetamide (DMAA)], and inorganic solvents (eg, zinc chloride, rhodan salt, nitric acid). In particular, a zinc chloride-based aqueous solution is preferred as the spinning material i& for acrylic fibers. The zinc chloride-based aqueous solution is an aqueous solution containing zinc chloride as a main component and having a la degree sufficient to dissolve the acrylonitrile polymer or copolymer as described above,
It is a concentrated aqueous solution of zinc chloride alone or a mixed salt containing an inorganic salt such as sodium chloride, calcium chloride, magnesium chloride, or ammonium chloride. The zinc chloride content in the mixed salt is preferably about 65% by weight or more.

The spinning dope can be prepared by known methods such as solubility or solution polymerization. When a zinc chloride-based aqueous solution is used as a solvent, a polymer concentration of 1 to 25% by weight, preferably 3 to 5% by weight, more preferably 4 to 12% by weight is used.

For wet spinning, a commonly known method, ie, a method in which the material is directly discharged into a low concentration spinning solvent, or a method in which the material is discharged into star air and then introduced into a low concentration spinning solvent and the solvent is removed, etc. is adopted. I can do it.

Solvent removal is carried out by washing with water until the residual amount of solvent becomes 0 to 0.3% by weight or less.

For example, when zinc chloride-based water-soluble 't(l) is used as a solvent, a spinneret as described in JP-A-58-13714 is used, and a coagulation bath with a relatively low concentration, for example, lO to 40% by weight, is used. Spinning is carried out using this method.

Coagulation bath temperature -20~25°C1 preferably 0~t5°C
1 more preferably 6~i0°C1 discharge linear velocity 5~50m
1m1n, preferably 10-30m/min,
The film is taken at a draft rate of 02 to 10 times, then washed with water to remove the solvent, and stretched 2 to 4 times during this period.

Spun fibers are usually 400% by weight immediately after spinning.
Although it contains the above amount of water, the film swells as the molecular orientation progresses, and after washing with water, the water content is 100 to 200% by weight. The amino silicone surfactant is applied to the water-swellable fibers in this state.

Stretching is carried out both before and after drying, and is usually carried out at full stretch, 5 to 20 times, preferably 8 to 16 times.

In the stretching before drying, water is used as the stretching medium and 1
2 to 6 times, preferably 2 to 6 times under conditions of 5 to 90°C
A four-fold stretch is applied.

In the stretching (re-stretching) after drying, saturated steam is used as the stretching medium, and the stretching is carried out by 2 to 10 times, preferably 2 to 8 times, under the conditions of 0.4 to 1.2 kg/cm' (G). administered.

Drying is generally carried out by a heated roller contact method, a suction drum method, etc., and a hot air drying method using a suction drum is particularly preferred. During drying, the fibers are held under tension to a constant length or under conditions that provide no more than 15% shrinkage.

The water-swollen fiber is a fiber that has been subjected to water washing, desolvation, and stretching after spinning, and has a moisture content of L00 to 200% by weight before drying. The amine silicone surfactant is applied to the water-swollen fibers in this state.

A dipping method, a spray method, a roller transfer method, a lip method, etc. can be used to apply the aminosilicon surfactant to the fibers in a water-swollen state, but the dipping method is preferable from the viewpoint of uniform application inside the fiber bundle. .

The amino silicone surfactant is preferably applied to the water-swollen fibers in an amount of 0.03 to 2.0% by weight based on the weight of the fibers. If the applied amount is less than 0.03% by weight, the anti-sticking effect will not be sufficient. Moreover, if it exceeds 2.0% by weight, the strength of the carbon fiber after firing will decrease. The aminosilicon surfactant is preferably a compound represented by the following general formula (A), and may also be a compound represented by the following general formula (B). These amino silicone surfactants are known as fiber treatment agents (water repellents, fabric softeners, hand improvers).

(A) General formula % Formula % (B) General formula [m, n, p: number of l to 100000 (
man): 10 or more number RI R2, carbon number 1~(0 alkyl group or aryl group) The heat resistance of the aminosilicon surfactant is 250°C, 3
It is necessary that when heat treated in air for 0 minutes, a film is formed by resinization, and the residual rate is 80% by weight or more. This is necessary to improve the cohesiveness of the fiber bundle in the flameproofing process and to obtain high strength carbon fibers.

Here, the residual rate (heat-resistant residual rate) and resinization are determined as follows.

Approximately 1 g of the sample was accurately weighed into a stainless steel flat-bottomed dish with a diameter of 100 m + n and a height of 10 mm, treated in a hot air circulation dryer heated to 250°C for 30 minutes, cooled, weighed accurately, and determined to be resistant to sweetfish using the following formula. Find the survival rate.

Resistance, 42 residual rate - (weight after addition treatment/weight before heating)
xl, 00 (wt%) Regarding resin formation, the sample remaining in (1) after heat treatment is visually observed to determine whether it is resin-like or wavy.

The aminosilicon surfactant is used in the form of an aqueous solution or dispersion, and its concentration is suitably 1 to 30 g/R.

Aqueous solution & or water dispersion of amine silicone surfactant
Fibers to which the pH is 4 or less, usually 1 or more, and a water-soluble i(l) or aqueous dispersion of a surfactant is applied, do not fluff due to static electricity during drying and densification, and have good cohesiveness of fiber bundles. be.

Usually, water-swollen fibers to which an aminosilicon surfactant has been applied are subjected to drying and densification, re-stretching, shrinkage treatment, and the like.

Re-stretching is performed in saturated steam of 0.4 to L2 kg/cm' (G). At this time, when an aminosilicon surfactant is applied under high PR conditions by the conventional method, the fibers become hydrophobic in the drying and densification step, causing fluff due to static electricity, and the re-stretchability is also significantly reduced. Also, in the conventional case,
Even after re-stretching, the fibers are highly water-repellent, making it difficult to add moisture and making it impossible to improve cohesiveness.

By setting the pH of the aminosilicon surfactant to 4 or less, the fiber after drying and densification has hydrophilicity.
There is no generation of static electricity, and the stretchability is also good.

The fibers that have gone through each process in this way have a moisture content of 30 to 50.
The weight is adjusted to % and stored in a can.

If the moisture content after re-stretching is lower than 30% by weight, spray method, dipping/J! 1?1. Water can be applied by roller transfer method, lip method, etc. to adjust the moisture content. If the moisture content is higher than 50% by weight, it can be easily adjusted by the squeezing pressure of the nip roller.

〔Example〕

Hereinafter, the present invention will be specifically described with reference to Examples.

The number of stuck carbon fibers and the number of fluffs were measured by the following method.

(Method for measuring the number of sticks) Cut the strand into 31 lengths, put it in acetone, perform ultrasonic cleaning to dissolve and remove the sizing agent, and then measure the thick stick threads under 6.3 magnification using a microscope. count.

(Number of fluff is fixed) The strand is immersed in acetone to dissolve and remove the sizing agent, then air-dried, and the end of the strand is placed under tension of about 30 g and looped around a hard glass rod with a diameter of 10 mmφ. , and the number of fluffs protruding from the tip of the loop is measured using a microscope under 63 magnification over a distance of 1 m.

Example 1 Using 600 weight of aqueous zinc chloride as a solvent, a polymer base containing 97% by weight of acrylonitrile, methyl acrylate triple Q00, molecule Q80,000, and a concentration of 7% by weight as a spinning raw material, with a number of pores of 12,000 and a pore diameter of 12,000. Using a nozzle with a diameter of 0.065 mm, the mixture was discharged into a 25% by weight zinc chloride aqueous solution at 10° C. and solidified.

The obtained coagulated thread was washed in hot water at 15 to 95°C and subjected to multi-stage stretching by a total of 3.2 times to obtain a water-swollen acrylic fiber with a water content of 160% by weight.

Next, the water-swollen fibers were mixed with an aqueous dispersion of amino silicone (10 g
#2), it was dried and densified using a suction drum dryer at 70 to 150°C until the moisture content became 1% by weight or less. Then, after passing through a hot water tower at 80°C, 0.7
It was re-stretched 5 times in saturated steam of kg/cm' (G) and transferred into a can to obtain 12,000 strands of 0°9 denier.

The thus obtained strand was an acrylic fiber (precursor) having a water content of 34% by weight, an amount of aminosilicon attached of 0.25%, no fuzz, and excellent cohesiveness.

Using this precursor, 240 to 270
Flame retardant treatment was carried out continuously for 40 minutes in a flame retardant furnace with a temperature gradient in the range of 300 to 130 °C in a nitrogen stream.
It was treated for 5 minutes in a carbonization furnace with a temperature gradient of 0°C to obtain carbon fibers.

The obtained carbon fiber has a tensile strength of 550 kgf/mm'
It had a tensile property of 24.3 t/mm2. The number of stuck carbon fibers was 7 and the number of fuzz was as low as 36/m.

From the above results, it was confirmed that the physical properties of the carbon fiber obtained by the method of the present invention are excellent.

CHI Ch CHs CH3 Example 1
Precursors were produced under the same spinning conditions as above, but by changing the pH of the aminosilicon water-dispersed acid, and the process conditions at this time were observed, and the results shown in Table 1 were obtained.

Table 1 Clh CH3C3HGCH3 H C2H,.

H2 (m:350) (n near) Example 2 Note: Experiment number 1.2 is a comparative example.

Next, these precursors were carbonized under the same conditions as in Example 1, and the process conditions and performance of the carbon fibers were evaluated in the second example.
Shown in the table.

Table 2 Table 3 Note: Experiment numbers 1 and 2 are comparative examples.

From the results in Tables 1 and 2, it is clear that when the pH of the aminosilicon dispersion is 4 or less, the process passability in the precursor and carbon fiber manufacturing process is improved, and the strength of the obtained carbon fibers is 0. Recognize.

Example 3 A precursor was produced under the same spinning conditions as in Example 1, using amino recon with different copper compatibility. When the process status at this time was observed, the results shown in Table 743 were obtained.

Note: Experiment numbers 7 to 9 are comparative examples.

Next, these precursors were carbonized under the same conditions as in Example 1, and the process conditions and performance of the carbon fibers were evaluated in the fourth example.
Shown in the table.

Table 4 Table 5 For surfactants that have a residual amount of 80% by weight or more and can be converted into a resin by heating at 250°C for 30 minutes, process passability and carbon It can be seen that the fiber has excellent performance.

Example 4 A precursor was molded by changing the concentration of amino recon under the same spinning conditions as in Example 1, and this precursor was used in Example 1.
Carbonization was performed under the same carbonization conditions. Table 5 shows the performance of the carbon fibers obtained.

Note: Experiment number 13.19 is a comparative example.

From the results in Table 5, the amount of attached oil and fat is 0.03 to 2.0% by weight.
It can be seen that when - layer, excellent performance is obtained.

〔Effect of the invention〕

(1) By adjusting the amino silicon surfactant to a low pH condition, the fiber after drying becomes hydrophilic,
The convergence of the fiber bundle can be improved.

(2) Generation of scum after drying is suppressed.

(3) Aminosilicon surfactant imparts low pH
Since the process is carried out under such conditions, the fiber bundle after drying and densification becomes hydrophilic. As a result, the re-stretching was 0°4~1.2kg/cm'
(G) When carried out in saturated steam, the moisture content of the fiber is 2
0 to 50% by weight, no static electricity is generated, the convergence is improved, and process troubles are eliminated.

(4) Cans can be stored in a stable state with a moisture content of 30 to 50% by weight, making it possible to form large packages with good unraveling properties.

(5) By using an aminosilicon surfactant with high heat resistance, there is no sticking during the flame-retardant process, and high-quality carbon fibers can be obtained.

Claims (6)

[Claims] (1) When producing acrylic fibers for carbon fiber production by the wet spinning method, first, the threads in a water-swollen state after spinning are treated with an aqueous solution or dispersion containing an aminosilicon surfactant whose pH is adjusted to below 4. The aminosilicon-based surfactant at this time is an aminosilicon-based surfactant that has been made into a resin by heat treatment in air at 250°C for 30 minutes, and has a residual amount of 80% by weight or more. A wet spinning method for acrylic fibers for producing carbon fibers, which is then dried and re-stretched. (2) The wet spinning method for acrylic fibers for producing carbon fibers according to claim (1), wherein the pH adjustment is carried out using hydrochloric acid, sulfuric acid, phosphoric acid, acetic acid, or formic acid. (3) The wet spinning method for acrylic fibers for producing carbon fibers according to claim (1), wherein the amino silicone surfactant-containing aqueous solution or aqueous dispersion has a pH of 2 to 3.5. (4) The wet spinning method for acrylic fibers for producing carbon fibers according to claim (1), wherein the amino silicone surfactant is a compound represented by the following general formula. General formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ [m, n: number of 1 to 100,000 (m+n): number of 10 or more R^1, R^2: alkyl group or aryl group having 1 to 10 carbon atoms] (5) The wet spinning method of acrylic fiber for producing carbon fibers according to claim (1), wherein the amount of the amino silicone surfactant attached is 0.03 to 2.0% by weight based on the weight of the dry fiber. (6) An acrylic fiber for producing carbon fiber, characterized in that the acrylic fiber for producing carbon fiber produced by the wet spinning method according to claim (1) is stored in a can at a moisture content of 30 to 50% by weight. Storage method.