JP2003155621A - Method for producing acrylic fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain in high productivity acrylic fibers useful as a precursor for high-grade carbon fibers with slight fluffs by reducing fiber breakages during the steam drawing step in a steam drawing unit with a labyrinth seal section to improve operability. SOLUTION: The acrylic fibers are produced by steam drawing of a plurality of acrylic filaments arranged in parallel to each other in the steam drawing unit with the labyrinth seal section; wherein 5-50 wt.% water is applied to the respective filaments just before being introduced into the labyrinth seal section.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing an acrylic fiber useful as a carbon fiber precursor.

[0002]

2. Description of the Related Art Acrylic fibers are widely used as carbon fiber precursors, and in the production process as carbon fiber precursors, a method is generally used in which steam drawing is carried out while running acrylic fiber yarns in a steam drawing device. ing.

In the steam drawing, the yarn is drawn in pressurized steam. As a steam drawing device, a stable drawing atmosphere is maintained and a yarn having no unevenness in the yarn quality is obtained. It is necessary to reduce the leakage of steam from the inlet and outlet of the mold or box type pressurized steam drawing unit as much as possible.A labyrinth seal is installed at the inlet and outlet of the pressure steam drawing unit to reduce steam leakage. JP-A-6-55772 and JP-A-2001-
According to such a technique, it is possible not only to reduce the energy loss but also to make the pressurized steam drawing chamber compact.

However, as the number of labyrinth nozzles in the labyrinth seal portion is increased, the seal is further strengthened and the steam leakage reducing effect is improved, but the frequency of running yarns coming into contact with the seal portion increases, and the rubbing with the seal portion increases. As a result, there is a new problem that yarn breakage and fluffing occur and the quality of the carbon fiber precursor is degraded.

[0005]

DISCLOSURE OF THE INVENTION The present invention is directed to running yarns and seals, if water is added to the yarns to improve the focusing property during steam drawing in a steam drawing device having a labyrinth seal portion. It is based on the technical idea that it is possible to reduce the frequency of contact with the section, and reduce damage due to rubbing with the seal section, and an object of the present invention is to provide a steam drawing apparatus having a labyrinth seal section in steam drawing. It is intended to reduce the yarn breakage and improve the operability and to obtain the acrylic fiber useful as a high-quality carbon fiber precursor with less fluff with high productivity.

[0006]

According to the present invention, when a plurality of acrylic fiber yarns arranged in parallel are steam-drawn by a steam drawing device having a labyrinth seal portion to produce an acrylic fiber, a steam drawing device is used. 5 to 50% by weight of water is applied to each yarn immediately before being introduced into the labyrinth seal part.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The acrylic fiber yarn used in the present invention contains 90 mol% of acrylonitrile.
It is composed of the acrylonitrile-based polymer contained above, and the acrylonitrile-based polymer may contain other vinyl monomer copolymerizable with acrylonitrile as long as it is less than 10 mol%. Other copolymerizable vinyl monomers are not particularly limited, for example, acrylic acid,
Methacrylic acid, itaconic acid or their alkyl esters, allyl sulfonic acid, methallyl sulfonic acid, styrene sulfonic acid or their alkali metal salts may, for example, be mentioned.

In the present invention, such an acrylonitrile polymer is dissolved in a solvent such as dimethylacetamide, dimethylformamide, dimethylsulfoxide, etc. to prepare a spinning dope, which is spun by a wet, dry-wet or dry spinning method, followed by desolvation and bathing. An acrylic fiber yarn obtained by medium stretching, application of an oil agent, and drying and densification is used, and the method itself for producing the acrylic fiber yarn to be steam-stretched is not particularly limited.

The steam drawing apparatus having a labyrinth seal section used for steam drawing in the present invention is a drawing apparatus having labyrinth seal sections at the yarn inlet and the yarn outlet of the pressure steam drawing unit. The labyrinth seal portion is provided so that the labyrinth nozzles are perpendicular to the running yarns and face each other with a slit-like gap in which the yarns can run, with the labyrinth nozzles facing each other in the running direction of the yarns. It is distributed. The number of stages of the labyrinth nozzle is not particularly limited, but is 10 stages or more, preferably 80 stages or more.

The steam drawing apparatus may have a mold structure capable of running a plurality of acrylic fiber yarns in parallel and collectively performing steam drawing. The pressure steam drawing section and the labyrinth seal section are operated. It is preferable to be a box type from the standpoint of property and installation of facilities.

In the present invention, when a plurality of acrylic fiber yarns are steam-drawn by the steam drawing device, 5-50 wt% water is added to each yarn immediately before being introduced into the labyrinth seal section of the steam drawing device. Is required to be given.

The means for applying water may be a spray method, a dip method, or a touch roll method, but it is not in contact with the running yarns and water can be applied to the surface layer of the yarns. In terms of equipment installation, the spray method is preferable. In the spraying means with water, water is applied to the running yarn by spraying water from a spray nozzle. The spray nozzle may be installed for each running path of each running yarn, or one or more spray nozzles may be installed so that water is sprayed for all or some groups of running yarns in parallel. Good.

The steam drawing step in the present invention will be explained with reference to FIG. 1. After spraying water whose water amount has been adjusted by the water amount adjusting valve 2 from the water spray nozzle 1 on the acrylic fiber yarn that has passed through the drying roll 6, The acrylic fiber yarn provided with is introduced into the labyrinth seal section 3a of the steam drawing apparatus, and the steam is drawn in the pressure steam drawing section 4 under the pressurized steam atmosphere supplied from the steam supply port 5, and the labyrinth seal section is provided. It is taken out from 3b and taken by a take-up roll (not shown).

Although FIG. 1 shows an example in which steam drawing is continuously carried out from the step of drying and densifying with a drying roll, after drying and densifying with a drying roll, the acrylic fiber yarn is once wound up. Of course, steam stretching may be performed.

The amount of water added to the yarn is 5 to 50 wt%,
The content is preferably 10 to 30% by weight, and by applying such water, the yarn converging property is improved, the frequency of contact between a part of the running yarn and the seal part is reduced, and damage caused by rubbing with the seal part is reduced. Further, it is possible to avoid contact between yarns that run adjacent to each other. If the amount of water added is less than 5 wt%, it is insufficient to give the yarn a bundle,
If it exceeds t%, the yarn weight increases and conversely the frequency of contact with the seal portion increases, which is not preferable.

The water to be applied to the yarn is not particularly limited as long as it wets the yarn to provide a bundle property and a lubricating effect, but the acrylic fiber according to the present invention is used as a carbon fiber precursor. Considering that it is calcined, ion-exchanged water containing no chlorine, iron, etc. is preferable. The temperature of water to be applied is not particularly limited, and depends on the amount of water applied, but it is 20 to 40 ° C. so as not to disturb the drawing in the steam drawing subsequent to the application of water and to make the water application complicated. desirable.

[0017]

EXAMPLES The present invention will be specifically described below with reference to examples. In the examples, the yarn moisture content, the number of yarn breakages, and the number of fluffs were based on the following methods.

Moisture content of yarn: From the yarn weight (B) after the yarn was sampled immediately before being introduced into the steam drawing apparatus and dried at 110 ° C. for 2 hours and the yarn weight before drying (A). The yarn moisture content (%) was determined by the following formula. Moisture content of yarn (%) = [(AB) / B] × 100

Number of yarn breakage: The yarn breakage is visually judged,
The number of times of thread breakage was converted into the number of times per winding length of the wound product to obtain the number of times of thread breakage.

Number of fluff: The appearance of the wound bobbin was visually observed to measure the number of fluff, which was converted into the number of fluff per wound length of the product to obtain the number of fluff.

Example 1 An acrylonitrile polymer consisting of 96 mol% of acrylonitrile, 2 mol% of methyl acrylate and 2 mol% of methacrylic acid was dissolved in dimethylacetamide in an amount of 20 wt% to prepare a spinning stock solution from a spinneret having a hole number of 12000. Discharge into an aqueous solution with a dimethylacetamide concentration of 70 wt% and a liquid temperature of 35 ° C., draw this coagulated yarn 3 times in a hot water bath, apply an oil agent by an oil agent treatment, then dry and densify at 135 ° C. A fiber yarn was obtained.

The obtained yarns are separated from each other by a distance of 30m.
The water spray nozzles (fan nozzles manufactured by Ikeuchi Co., Ltd., 1 / 4MVP11505S), spraying water in an amount of 0.5 liter / min per water spray nozzle onto the yarn, and then providing a labyrinth seal portion at the yarn inlet and yarn outlet of the pressure steam drawing unit. Introduced into the steam drawing device from the labyrinth seal part side of the yarn inlet side of the pressure steam drawing part, the steam pressure in the pressure steam drawing part is drawn under the conditions of 0.25 MPa in steam gauge pressure and 3 times the draw ratio. I went. The evaluation results of the obtained drawn yarn are shown in Table 1.

Comparative Example 1 A drawn yarn was obtained by steam drawing under the same conditions as in Example 1 except that the step of spraying water from the spray nozzle was omitted. The evaluation results of the obtained drawn yarn are shown in Table 1.

[0024]

[Table 1]

[0025]

EFFECTS OF THE INVENTION According to the present invention, yarn breakage in a steam drawing apparatus having a labyrinth seal portion when steam-drawing an acrylic fiber yarn is reduced to improve operability, and at the same time, the number of fluffs is reduced. An acrylic fiber useful as a high-quality carbon fiber precursor can be obtained with high productivity.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of an example of a steam stretching device according to the present invention.

[Explanation of symbols]

1 water spray nozzle 2 Water quantity control valve 3a Labyrinth seal part 3b Labyrinth seal part 4 Pressurized steam drawing section 5 Steam supply port 5 drying rolls

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masashi Okamoto             20-1 Miyuki-cho, Otake-shi, Hiroshima Mitsubishi Rayo             Otake Office F-term (reference) 4L031 AA17 AB01 BA08 CA07 DA00                 4L035 BB03 BB06 BB11 BB15 BB17                       BB72 BB80 BB82 BB85 BB91                       MB03 MB06 MB19

Claims (2)

[Claims] 1. When producing an acrylic fiber by steam-drawing a plurality of juxtaposed acrylic fiber yarns with a steam drawing device having a labyrinth seal part, immediately before being introduced into the labyrinth seal part of the steam drawing device. 5. A method for producing an acrylic fiber, which comprises applying 5 to 50 wt% of water to each yarn. 2. The method for producing an acrylic fiber according to claim 1, wherein water is applied by spraying.