JPH0424211A - Production of superfine fiber - Google Patents

Abstract

PURPOSE:To obtain superfine fibers suitable for high performance filters, etc., by treating conjugate fibers prepared from an acrylonitrile solution and a hydroxyalkyl cellulose solution in a specific ratio with water. CONSTITUTION:A polymer solution containing >=85wt.% of acrylonitrile and a hydroxyalkyl cellulose solution are extruded from a spinneret so as to give an extrusion area ratio of 1/500-1/1 in the cross section vertical to the extrusion directions. The fibers are coagulated and drawn three times or more. The prepared conjugate fibers are treated with water to dissolve and remove only the hydroxyalkyl cellulose for providing the objective superfine fibers.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a novel method for producing ultrafine fibers suitable for high-performance filters and the like.

[Prior art and problems to be solved by the invention] With the development of industry and changes in lifestyles, the demand for clean air has increased in recent years, and various air filters have been proposed.

Particularly in the electronics industry, there is a demand for the removal of so-called submicron-order fine particles, and filters made of ultra-fine glass fibers have been developed that have high filtration rates and low filtration resistance. However, due to the brittle nature of glass fibers, they tend to break easily, creating a new source of pollutants, and there are several problems that have been pointed out, such as the fact that the volume of used filters cannot be reduced by incineration. There are n. Under these circumstances, filters made of organic fibers are strongly desired.

It is important that filters withstand the environment in which they are used, and must have resistance to acids and alkalis, as well as light resistance to ultraviolet rays, etc., but organic fibers such as Volip-A-Pyrene-M, fibers, and polyester fibers are sufficient. This requirement is not met. On the other hand, fibers made of polymers containing acrylonitrile as a main component have excellent deterioration resistance, and from this point of view, it can be said that they have very excellent performance as filters.

By the way, in order to completely capture and remove particulates, the distance between the fibers of the button must be sufficiently small, but on the other hand, reducing the distance between the fibers decreases the void area per unit filtration area, leading to an increase in filtration resistance. . Therefore, in order to efficiently capture and remove fine particles, it is necessary to construct the filter with fibers as thin as possible. When filtering particles of 1 micron or less, electrostatic effects are added in addition to inertial collision effects, so the inventors' research has shown that the required distance between surface fibers does not actually need to be less than the diameter of the particles. It is clear from the results that the fiber diameter should be 2 microns or less, preferably 1 micron or less.

Conventionally, such ultra-fine I was made from acrylonitrile fiber.
It has been considered extremely difficult to produce IL fibers. The reason for this is that, unlike other fibers, acrylonitrile fibers are manufactured using a wet method or a dry-wet method. It is cited that it is very difficult to adopt a method for producing fibers.

Ultra-fine # made of polyester or polypropylene mentioned above
? Fibers have been produced by composite melt spinning of incompatible multi-component polymers while maintaining sufficient spinning draft, and later by dividing or removing only one component. On the other hand, Aku+7 ronitrile polymer fibers are generally produced by wet spinning or dry-wet spinning, but in this case, although there is a technology for composite melt spinning of incompatible multicomponent polymers, a large spinning draft can be achieved. It has been difficult to produce ultrafine fibers.

Another method for producing acrylonitrile polymer concentration is the dry spinning method, which uses a dilute spinning dope and can theoretically produce fibers with a fine diameter. The organic solvent used for this process generally has a high boiling point, making spinning extremely difficult.

In view of this situation, the inventors of the present invention have arrived at the present invention as a result of intensive studies on a method for producing acrylic*M having a diameter of 2 microns or less, preferably 1 micron or less, which can be used for high-performance filters and the like.

[Means to solve the problem]

That is, the gist of the present invention is that a solution (B) in which a polymer containing 854 or more acrylonitrile is dissolved in a solvent and a solution (B) in which a hydroxyalkyl cellulose is dissolved in a solvent are fed from a spinneret in a direction perpendicular to the discharge direction. Solution in cross section - and melt ff! (The ratio of the discharge area of Bl is 11500
Composite spinning is performed so that the ratio is ~1/1, and the resulting coagulated yarn is
It is possible to produce ultra-fine fibers by treating the conjugate fibers produced by stretching the fibers with water to dissolve and remove only the hydroxyalkyl cellulose.

Acrylonitrile-based polymers contain 8% acrylonitrile.
It is desirable to contain 54 or more from the viewpoint of chemical resistance and light resistance of the fiber. Further, it is desirable that the molecular weight of the polymer is as high as possible. The reason for this is that it is desirable that the part made of acrylonitrile polymer be as thin as possible from the beginning, so it is desirable that the polymer concentration in solution (A) be as low as possible within the range that allows spinning, and the viscosity required for spinning is ensured at a low concentration. Therefore, the higher the K value of the polymer molecules, the better. However, if the concentration of solution (AJ) is too low, voids are likely to occur during the solidification process, so the polymer concentration is 5
4 or more and 304 or less, preferably 10 or more and 254 or less, and in order to ensure an appropriate viscosity within this range, the molecular weight should be 1 million to 2 million, expressed as a weight average molecular weight determined from the viscosity of a dilute solution. Preferably Fil is 50,000 to 1,000,000.

On the other hand, hydroxyalkylcellulose is used to ensure the thickness of the thinned fibers until the final solvent treatment step, and hydroxyalkylcellulose yarn polymers are not compatible with acrylonitrile-based polymers, so acrylonitrile-based polymers are used. It has a characteristic that the interface between it and the polymer component is smooth.

Examples include hydroxyalkylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, and hydroxyethylgalactomannan. These molecular weights are not particularly limited.

Melt II! The concentration of the polymer (B) is not limited to 1%, but it is better to have as few irregularities as possible on the interface between the acrylonitrile-based polymer component and the hydroxyalkyl cellulose component, and to ensure stable spinning. It is desirable that the viscosity is approximately the same as that of (A).

The solvents of solution (A) and solution (B) may be different and may be Kameoka-based. For example, NN dimethylformamide, NN
Dimethylacetamide, dimethylsulfoxide and the like can be mentioned.

The ratio of the discharge amounts of both solutions is very important because it determines the handleability of the composite fiber and the thickness of the obtained ultrafine fiber. If the nucleation is too large, the final fiber will not be thin enough, while if it is too small, the coagulation in the coagulation bath will be incomplete. The ratio of the discharge area of the solution (5) and the solution F&(B) in a cross section perpendicular to the discharge direction is preferably 11500 to 1/1. ld 1 /
It is best to set K to 100 to 1/10. Both of the discharged solutions are wet-spun, wet-dry spun, or dry spun in a conventional manner. In the wet or wet-dry spinning method, the coagulation bath is a mixture of hydroxyalkyl cellulose and Acrylic IJ cr
Any polymer that coagulates both unitrile polymers in the same way may be used. For example, methyl alcohol, ethyl alcohol,
Inglovir alcohol, ethylene glycol, glycerin, etc. can be mentioned. At this time, in order to make the coagulation uniform, it is preferable to mix the solvents used in solution (A) and solution (B).

The coagulated yarn needs to be stretched 3 times or more, more preferably 5 times or more, and most preferably 10 times or more in order to obtain fiber properties.

The manufactured composite fibers may be finally treated with water to dissolve and remove only the hydroxyalkyl cellulose. It goes without saying that the water temperature at this time is preferably higher than l<, for example, 70°C or higher, preferably 85°C or higher.

〔Example〕

The present invention will be specifically explained below using Examples.

"Excellent" indicates "excellent weight.""Fiberdiameter" was measured with a scanning electron microscope.

Example 1 Consisting of 974 acrylonitriles and 3 methacrylic acids,
An Ac IJ ronitrile polymer having a weight average molecular weight of 80,000 to 1,500,000 as determined from the viscosity of a dilute solution was dissolved in dimethylacetamide. The polymer concentration at this time was such that the solution viscosity at 50'C was approximately 500 voids (solution (A)).

On the other hand, the concentration of hydroxyethyl cellulose was determined so that the solution viscosity at 50'C was approximately SOO voids,
Dimethylacetamide was dissolved (solution (B)).

Next, the instep of the 400 micron diameter outlet (1) has a diameter of 30 microns.
Of the composite spinneret in which 10 micron discharge ports (2) are arranged, from the discharge port (1) to the solution (B), the discharge port (2)
solution (A) at 1occ/min, α6cC/
It was discharged at a speed of 10 minutes, coagulated in a mixed solution of dimethylacetamide/methanol (weight ratio 70/30), and then stretched in three stages: in air at room temperature, in hot water at 70"C, and in boiling water.
Finally, it was continuously dried with a roller at 150°C to obtain a composite *M.

The composite fiber was soaked in 100 times the amount of water at 90'C for 30 minutes.
The hydroxyethyl cellulose polymer was completely removed to obtain ultrafine acrylonitrile fibers as shown in Table 1.

Claims (1)

[Claims] 1. Solution (A) in which a polymer containing 85% or more of acrylonitrile is dissolved in a solvent and a solution (B) in which hydroxyalkyl cellulose is dissolved in a solvent are taken from a spinneret in a cross section perpendicular to the discharge direction (A) Composite spinning is performed so that the ratio of discharge area of solution (B) and solution (B) is 1/500 to 1/1, and the resulting coagulated fiber is stretched three times or more, and the composite fiber is produced by water treatment. A method for producing ultra-fine fibers characterized by dissolving and removing only hydroxyalkyl cellulose.