JPH0351309A - Production of acrylic fiber - Google Patents

Abstract

PURPOSE:To obtain the title fiber having a few end breakage in spinning bath, small degree of variability of fineness, excellent drawing properties and operation stability free from micro voids by spinning a dope of an acrylonitrile-based polymer from nozzle holes under a specific condition. CONSTITUTION:An acrylonitrile-based polymer containing at least 90wt.% acrylonitrile is dissolved in an organic solvent to give spinning dope, which is spun from nozzle holes in a coagulating bath having a composition to make 0.6-0.9 VF/VD correlation between spinning dope delivery linear velocity (VD) and free delivery linear velocity (VF) and 1-5 Vt/VD correlation between take-off velocity (Vt) and VD and fiber is traveled through a guide to give the objective fiber.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing acrylic fibers, and more specifically, the present invention relates to a method for producing acrylic fibers, and more specifically, wet spinning using an organic solvent reduces yarn breakage in the spinning bath and fineness fluctuation rate. The present invention relates to a method for producing acrylic fibers that have small microvoids and essentially have no macrovoids.

[Conventional technology]

Conventionally, acrylonitrile fibers have been widely used in interior fields such as curtains and carpets, bedding fields such as blankets, and clothing fields such as knits and jerseys, taking advantage of their excellent light resistance and dyeability.

In addition, in recent years, acrylic fibers have been used as precursor fibers for carbon fibers.
A (precursor) is converted into carbon fiber through subsequent flame resistance and carbonization reactions, and the carbon fiber is widely used as a reinforcing fiber for composite materials due to its excellent physical properties.

In addition, with the recent diversification of needs, the demand for industrially stable production of acrylic fibers has become stronger year by year.

Stable production here means minimizing yarn breakage in the coagulation bath or drawing bath, and at the same time making it possible to efficiently produce fibers.

On the other hand, when wet-spinning acrylonitrile-based polymers using organic solvents, etc., in consideration of spinnability and operational stability, conditions are set so that the spinning stock solution in the coagulation bath quickly coagulates into fibers. Generally, the coagulation bath composition is set so as to achieve the desired result, and the spinning draft is set correspondingly low.

However, when obtaining fibers under such spinning conditions, although the coagulation force is strong, it is easy to form macro voids.If the drawability in the coagulation bath or drawing bath is poor and the spinning draft or drawing ratio is increased. , thread breakage occurs.

Problems such as this are likely to occur. Regarding ■, it is thought to be the main factor causing the devitrification phenomenon of acrylic fibers, hindering the diffusion of dyes during dyeing, or inhibiting the increase in strength of carbon fibers. This is not desirable when considering stable productivity improvement of fibers.

[Problem to be solved by the invention]

The present invention is directed to a manufacturing method for stably obtaining acrylic fibers, and more specifically, to produce acrylic fibers with less yarn breakage in a coagulation bath and with a small rate of fineness fluctuation in wet spinning using an organic solvent. The purpose is to provide a manufacturing method for manufacturing.

[Means for Solving Section F1] The present invention provides a spinning solution prepared by dissolving an acrylonitrile polymer containing at least 90 to 1 acrylonitrile units in an organic solvent at a linear velocity (v
D) and free ejection linear velocity (VF) is vF/vD=
Q, take-up speed (
The method for producing acrylic fibers is characterized in that the relationship between V.

In the method of the present invention, an acrylonitrile polymer containing at least a qoM amount of acrylonitrile is dissolved in an organic solvent.

A suitable spinning stock solution contains 1
It contains 0 to 40 weight percent of acrylonitrile polymer, preferably 15 to 25 weight percent.

Next, this spinning stock solution is wet-spun into a coagulation solution consisting of water and an organic solvent to form fibers.

The spinning dope is spun in a coagulation bath atmosphere consisting of water and an organic solvent such that the spinning dope discharge linear velocity (vD) and free discharge linear velocity (vF) are VD/Vy = α6 to α9.

Note that the free discharge linear velocity here refers to the raw solution discharge linear velocity in a state where no spinning draft is applied, and is determined by the pulling speed just before the yarn wobbles during coagulation or the shape becomes sagging.

If the linear velocity VD of spinning dope discharged from the nozzle hole and the linear velocity Vp of free discharge are vF/vD>α9, solidification takes a long time, which is not preferable in terms of industrial productivity. Further, in the case of VF/VD <α6, although the coagulation force is strong, thread breakage is likely to occur in the coagulation bath, and the stretchability in the drawing bath is also reduced. Considering the above, vF/vD=cL6 to α9 is preferably selected. That is,
In order to densify the fiber structure and prevent yarn breakage in the coagulation bath, slow coagulation that does not apply stress to the yarn is desired.

On the other hand, in such slow solidification, when the take-off speed is increased, for example when the spinning draft exceeds 6, tensile unevenness occurs in the take-off direction and the fineness variation rate increases. In order to prevent such an increase in the fineness variation rate, it is essential not to apply excessive spinning draft during coagulation. Note that the spinning draft is defined by the following formula (%). If the draft is small, yarn wobbling occurs, causing problems such as increased adhesion between fibers and increased fineness fluctuation rate. Therefore, in the present invention, an optimum spinning draft of 1 to 5 is indispensable, and in order to prevent adhesion due to yarn wobbling, the yarn running shape in the bath is adjusted to a guide such as a ring guide. It is necessary to regulate it.

In the absence of a guide, adhesion between fibers occurs frequently due to yarn wobbling, and the rate of variation in fineness increases.

The shape of the guide is not limited to any shape as long as it provides the same effect as a ring guide.
A combination of multiple guides may be provided.

The fineness variation rate of the fiber obtained in the present invention was determined by measuring the diameter of each yarn from an optical micrograph of the cross section of the yarn after passing through the drawing bath, and using the following formula.

The presence or absence of macrovoids was determined by directly observing the fractured surface of the freeze-dried coagulated thread using an electron microscope.

That is, using a scanning electron microscope EA manufactured by JEOL Ltd., the fracture surface was observed at an accelerating voltage of 5 to 15 Kv and a magnification of 10,000 times, and the presence or absence of macrovoids was determined.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 A copolymer consisting of acrylonitrile (93 kg) and vinyl acetate (5 kg) was dissolved in dimethylacetamide to prepare a spinning dope having a weight of 21 kg (21 kg).

Next, this stock solution was heated to 60°C and the pore size (1076 m, 40
Using a nozzle of 0, it was extruded into the coagulation bath at a discharge linear speed of 5.92 m/min, passed through two ring guides with different diameters, and taken out from the coagulation bath at a winding speed of 6 m/min. Ta. In addition, the coagulation bath at this time has a free discharge linear velocity, that is, a take-up speed %++=+4.7 m/min just before the shape of the coagulated thread sag during yarn wobbling, and a coagulation bath composition of 81% dimethylacetamide by weight. It was composed of an aqueous solution and the temperature was 35°C. As shown in Table 1, the maximum spinning draft of the fiber obtained under this coagulation bath composition is extremely high at 10, and the subsequent total stretching in air or at bath temperature is also as high as 12 times. The fiber had good stretchability.

In this case, there is almost no yarn breakage in the spinning bath, and
When the filamentation unevenness was measured from a cross-sectional photograph of the obtained drawn yarn, it was found to be 5 or less, which was very good.

On the other hand, when only a guide was used, the fineness variation rate was high, 8%. Also, when the Vt/Vp ratio was set to 7, the fineness fluctuation rate was high, 84. In addition, the presence of macrovoids was not observed in the observation of the stone fracture surface using a scanning electron microscope of the yarn spun within the scope of the present invention, that is, VF/'VD 瓢α6 to [L9.

Comparative Example 1 The spinning stock solution obtained in Example 1 was
, using a nozzle with 400 holes, 5.92 m/min
It was extruded into the coagulation bath at a discharge linear velocity of 4.67 m/
It was taken out from the coagulation bath at a winding speed of min. In this case, the coagulation bath is VF=2.47F! /min, that is, the coagulation bath composition is 71 times a day! The temperature was 35°C.

In this case, as shown in Table 1, the maximum spinning draft is very low at 1, and the subsequent total stretching in air or bath temperature is up to 75 times, iyl/VD-α6~
Compared to fibers obtained within the range of 19, the drawability of the fibers was lower than that of fibers obtained within the range of 19.

In this case, yarn breakage was likely to occur in the coagulation bath, and the fineness fluctuation rate of the obtained yarn was as high as 9 mm even in the presence of a guide.

Further, when the fracture surface was observed using a scanning electron microscope, the occurrence of macrovoids with a diameter of several thousand amps was observed.

Table 1 *The entire yarn tends to shrink in the discharge direction, and the measurement of 77 is solid. Arukomi is an acrylic fiber with essentially no adhesive threads, and has an extremely low variation in fineness of less than 5. In addition, it has improved drawability, resulting in high operational stability and high productivity. Manufacture is possible.

Claims (1)

[Claims] When performing wet spinning using a spinning stock solution containing an acrylonitrile polymer containing at least 90% by weight of acrylonitrile dissolved in an organic solvent, the linear velocity (v_D) of the spinning stock solution discharged from the nozzle hole and the free discharge linear velocity (v_F) are determined. In a coagulation bath with a composition where the relationship is v_F/v_D = 0.6 to 0.9, the relationship between take-up speed (v_t) and v_D is v_t.
A method for producing acrylic fibers, which comprises spinning the fibers with /v_D=1 to 5, and running the yarns in a bath through a guide.