JPH03130411A - Ultrafine fiber and its production - Google Patents

Abstract

PURPOSE:To obtain the objective ultrafine fiber suitable for artificial leather, etc., by mixing a polymer solution containing a specific amount of acrylonitrile with a polymer solution containing a specific amount of methyl methacrylate, spinning and drawing the mixed solution and removing the methyl methacrylate polymer from the fiber. CONSTITUTION:The objective ultrafine fiber composed of a polymer containing >=85% of acrylonitrile and having a diameter of <=2mu and an aspect ratio of >=1,000 can be produced by mixing (A) 1 pt.wt. of a solution having a viscosity of 100-2,000 poise at 50 deg.C and produced by dissolving a polymer containing >=85% of acrylonitrile in a solvent (e.g. dimethylformamide) and (B) 1-100 pts.wt. of a solution having a viscosity of 100-2,000 poise at 50 deg.C and produced by dissolving a polymer containing >=90% of methyl methacrylate in a solvent (e.g. acetone), spinning and drawing the obtained mixed solution containing the component A dispersed in the component B in the form of fine particles having a diameter of 1-100mu and dissolving and removing the methyl methacrylate polymer from the obtained drawn fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ultrafine fiber suitable for so-called wiping cloths, artificial leather, etc., and a method for producing the same.

[Conventional technology]

In recent years, with the development of industry, the demand for clean air used in the manufacture of glass products and electronic components has increased, and to meet this demand, there is a demand for high-performance wiping cloths! It has increased by 1. On the other hand, as people's lifestyles become more upscale, the demand for leather products is increasing, but there are various problems with the supply of natural leather, so expectations for artificial leather are increasing.

In the production of such wiping cloths and artificial leather, the most important thing is ultrafine fibers with a diameter of 1 to 2 microns, and today, with increasingly sophisticated requirements, fibers with even smaller diameters are desired. . Moreover, it is preferable that the fiber length be as long as possible, since this increases the degree of freedom in product production.

It is important for wiping cloths used especially in the industrial field to withstand the environments in which they are used, such as acids,
Durability against alkali, light resistance against ultraviolet rays, etc. are required, but organic fibers such as polypropylene #j fiber and polyester fiber do not fully satisfy these requirements.

On the other hand, fibers made of polymers containing acrylonitrile as a main component are excellent materials for wiping cloths because of their excellent durability.

[Problems to be Solved by the Invention] Conventionally, it has been extremely difficult to produce ultrafine fibers using acrylonitrile fibers.

The reason for this is that unlike other fibers, acrylonitrile fibers are manufactured using a wet or wet-dry method, making it difficult to manufacture composite fibers that can be applied to the splitting and elution methods established in melt spinning. It can be said that it is extremely difficult.

In view of this situation, the present inventors have completed the present invention as a result of extensive studies regarding ultrafine fibers having sufficient length.

[Means to solve the problem]

That is, the gist of the present invention is that the polymer is made of a polymer having acrylonitrile of 85 or more, and has a diameter of 2 microns or less, preferably 1 micron or less, more preferably (L5 microns or less, even more preferably IIL 1 micron). and the aspect ratio is 1000 or more, preferably 10,000 or more,
More preferably, it provides a superpolarity mM, m of 1° or more.

The reason why ultra-fine fibers such as those of the present invention could not be produced by conventional wet or dry-wet spinning methods is that 1. The reason why ultra-fine fibers such as those of the present invention could not be produced by conventional wet or dry-wet spinning methods is that 1.
This is due to the inability to highly control multicomponent polymers.

The polymer for fibers of the present invention contains 85% acrylonitrile.
It is desirable to contain t6 or more from the viewpoint of chemical resistance and light resistance of the fiber! Yes.

When manufacturing wiping cloths, artificial leather, etc.
It goes without saying that fibers need a certain length, and from the point of view of processability, it is preferable to use fibers that are at least 1000 times the diameter! If the ratio is 10,000 times or more, more preferably 100,000 times or more, but less than 1m01,000 times, it is very difficult to form a structure by, for example, a paper making method or a spun bonding method. On the other hand, if the fiber length is too long, it is no problem at all because it can be cut to an appropriate length.

As a result of various studies regarding the method for manufacturing the ultra-fine fibers of the present invention, it was found that acrylonitrile-based polymers and methyl methacrylate-based polymers are not compatible, and that solutions in which both are dissolved individually are mixed or they are dissolved at the same time. In this case, a solution containing an acrylonitrile polymer is dispersed using a solution containing a methyl methacrylate polymer as a continuous phase, and what is truly surprising is that when this mixed solution is wet-spun, fibers made of a methyl methacrylate polymer are formed. The acrylonitrile-based polymer is distributed in the form of extremely thin bNl fibers, and the length of the acrylonitrile-based polymer is much longer than estimated from the size of the dispersed state of the acrylonitrile-based polymer solution mentioned above. It was found that the larger the molecular weight of the polymer, the more pronounced the appearance of the polymer, which led to the completion of the present invention. The method of the present invention is not only unique in that it makes use of a phenomenon that has not been recognized in the past, but also requires the use of complex composite materials that have not previously been used to produce such ultra-fine fibers. Whereas a spinning nozzle was required, the method of the present invention is industrially, technically, and economically significant in that it can be easily carried out using a conventional spinning nozzle.

To carry out the method of the invention, acrylonitrile is
1 part by weight of a solution having a viscosity of 100 to 2000 poise at 50°C obtained by dissolving a polymer containing 4 or more in a solvent that can dissolve the polymer, and a polymer containing 904 or more methyl methacrylate; IQQ/1 to 1 of a binary copolymer consisting of acrylonitrile and methyl methacrylate or a ternary block copolymer consisting of acrylonitrile, methyl methacrylate, and another third monomer as necessary
The viscosity at 50°C obtained by dissolving a 0000/1 polymer mixture in a solvent is 100 to 2000.
Poise solution B1 to 100 parts by weight are mixed, and solution A is dispersed in the form of fine particles with a diameter of 1 to 100 microns in a continuous phase consisting of solution B. Wet process from a spinneret with an effective diameter calculated from the diameter of a circle of 100 microns or less, preferably 50 microns or less, more preferably 30 microns or less! Alternatively, a methyl methacrylate-based polymer is produced from a composite coagulated yarn obtained by spinning a composite coagulated yarn by a dry-wet method and stretched by a conventional method by a factor of 2 times or more, preferably 4 times or more, and more preferably 6 times or more. Ultrafine fibers are obtained by dissolving and removing the fibers.

In the method of the present invention, the larger the molecular weight of the acrylonitrile polymer, the larger the diameter of the fibers obtained, which is much longer than estimated from the size of the dispersed particles in the solution state. For example, if the size of the dispersed particles of a solution containing 10 tlj of acrylonitrile polymer is 5 microns, and the diameter of the yttm obtained by spinning this fiber is α3 microns, one N1 fiber is obtained from one dispersed particle. ! is formed, its length is at most [
It will only be 12m. However, it has been found that according to the method of the present invention, the length of the fiber obtained is one or more, and even extends to several lengths.

This was not known at all in 1, and the detailed mechanism is unknown, but it is presumed that the long chain length of the acrylonitrile polymer caused a change in the dispersion state of the solution during spinning. Ru.

Further, it is desirable that the molecular weight of the polymer be as high as possible for the following reasons. One! In order to obtain thin fibers, it is desirable that the polymer concentration in solution A be as low as possible while spinning is possible, and in order to ensure the viscosity necessary for spinning at a low concentration, the molecular weight of the polymer should be high. When the molecular weight is lower than, for example, 150,000, the resulting ultrafine fibers lack so-called flexibility and, in extreme cases, become brittle.

This is because voids are likely to occur during the coagulation process if the concentration of the solution is too low, so the polymer concentration should be between 5 and 30, preferably between 10 and 25, within this range. In order to secure an appropriate viscosity of 100 poise to 2000 poise as described later, the molecular weight must be 1.
It needs to be between 50,000 and 1,500,000, preferably between 300,000 and 1,000,000.

The solvents of solutions A and B may be different or the same. For example, the solvent for solution A is an organic solvent such as dimethylformamide, dimethylacetamide, dimethylsulfoxide, gamma-butyrolactone, or an aqueous solution of thiocyanate, various inorganic acids such as nitric acid, and the like.

In addition to those exemplified above, solvents for solution B include acetone, chloroform, dichloromethane, tetrahydrofuran, and the like.

The polymer mainly composed of methyl methacrylate is used to ensure the thickness of the thinned fibers in the process of treating the drawn yarn with a solvent, and the methyl methacrylate polymer used in the case is compatible with the acrylonitrile polymer. Because of the absence of acrylonitrile-based polymers, the interface with the acrylonitrile-based polymer component is smooth.

The methyl methacrylate-based polymer may be one that satisfies such requirements, and the content of methyl methacrylate may be 80 or more.

Although the molecular weight is not particularly limited, there is a problem that if the molecular weight is too low, spinnability will be insufficient, and if it is too high, elution and removal in the subsequent process of treating the drawn yarn with a solvent will be insufficient.

Therefore, a button weight of around 20,000 to 100,000 is appropriate.

Solution A is dispersed in solution B, which is a continuous phase, as fine particles with a diameter of 1 to 100 microns, but depending on conditions such as composition and viscosity, the dispersion state may easily collapse, and as soon as the dispersion state is created, spinning is performed. It is preferable to take such measures or use a dispersion stabilizer. The dispersion stabilizer is a binary copolymer of acrylonitrile and methyl methacrylate or a quintuple copolymer of acrylonitrile, methyl methacrylate, and a third monomer, particularly a polymer of 10 to 50 acrylonitrile polymer portions, methyl methacrylate, and vinyl acetate. Copolymer portion 50-9
A ternary block copolymer consisting of 0 or more is very effective.

The viscosity of the polyacrylonitrile-based polymer, polymethyl methacrylate-based polymer, and compatibilizer is important for ensuring stringiness, but for example, the viscosity at 50°C is 1.
00 to 2000 poise is sufficient, especially for solution and B.
There is no need to worry about the viscosity difference.

The dispersion can be produced by using an apparatus capable of applying a high shear, and then extruding the liquid through a nozzle with a hole diameter as small as possible. For example, the material is discharged from a spinneret whose pore cross-sectional area has an effective diameter calculated from the diameter of an equivalent circle of 100 microns or less, preferably 50 microns or less, and more preferably 30 microns or less. The discharged liquid should be brought into contact with a coagulating liquid that can coagulate each polymer at the same time. Examples of the coagulating liquid include water, methanol, ethanol, isofuropanol, glycerin, etc.
These may be mixed with the solvents of solutions A and B.

The obtained coagulated thread is drawn by a conventional method to obtain a composite drawn thread by stretching it by at least 2 times, preferably at least 4 times, and even more preferably at least 6 times. For stretching, cold stretching, drought stretching, and hot stretching may be appropriately combined.

If this drawn yarn is dissolved in a solvent that does not dissolve polyacrylonitrile 4-based polymer but can dissolve polymethyl methacrylate-based polymer, examples of such solvents include acetone, dichloromethane, chloroform, and tetrahydrofuran. can. The purpose can be achieved by immersing it in these solvents. Heating at this time is effective in accelerating the process.

The characteristics of the fiber thus obtained can be easily determined, for example, the fiber diameter and length using a scanning electron microscope or the like.

〔Example〕

The present invention will be specifically described below with reference to Examples. The "molecular weight" of a polymer is the weight average molecular weight determined by the dilute solution viscosity method. "Excellent" indicates heavy f# width.

Examples 1-5. Comparative Examples 1-2 Rust liquid A) in which polyacrylonitrile having a molecular weight of 80,000 to 1,500,000 is dissolved in dimethylacetamide. At this time, the polymer concentration is such that the solution viscosity at 50°C is approximately 500°C.
Made it become a poise.

On the other hand, 10071 of a block copolymer (hereinafter abbreviated as compatibilizer a) consisting of a polymethyl methacrylate homopolymer having a molecular weight of 300,000 and an acrylonitrile polymer part 304 and a copolymer part of methyl methacrylate and vinyl acetate 70 scratches. The mixture was dissolved in dimethylacetamide to give a solution with a concentration of 12% (solution B).

When solution A and solution Btl were mixed, it was confirmed by observation using an optical microscope that the solution was dispersed in the form of fine particles with a diameter of 1 to 100 microns in the continuous phase consisting of solution B. The mixed solution is discharged from a spinneret having a discharge hole of 30 microns in diameter into a coagulating liquid made from a mixed solution of water/dimethylacetamide (1/1),
Stretched 15 times in a warm room at 60°C, and finally stretched 150 times.
It was continuously dried with roller C to obtain a drawn yarn. The drawn yarn was immersed in acetone 10 times its weight for 2 hours to remove polymethyl methacrylate and obtain ultrafine fibers.

When these ultrafine fibers were observed using a scanning electron microscope, the results shown in Table 1 were obtained.

Table Examples 6 to B, Comparative Example 6.4 Example 3)b) The same procedure as Example 3 was carried out except that the compatibilizer was changed to 1150 to 1/20 Q OO relative to polymethyl methacrylate.

When these ultrafine fibers were observed using a scanning electron microscope, the results were as shown in Table 2.

Table 2

Claims (1)

[Claims] 1. Made of a polymer containing 85% or more of acrylonitrile, having a diameter of 2 microns or less and an aspect ratio of 1000.
Ultra-fine fibers. 2. 1 part by weight of a solution A having a viscosity of 100 to 2000 poise at 50°C obtained by dissolving a polymer containing 85% or more acrylonitrile in a solvent, a polymer containing 90% or more methyl methacrylate, and acrylonitrile as necessary. and methyl methacrylate or a tertiary copolymer consisting of acrylonitrile, methyl methacrylate, and another third monomer at 50°C.
Solution B having a viscosity of 100 to 2000 poise at
1 to 100 parts by weight are mixed to form a state in which solution A is dispersed in the form of fine particles with a diameter of 1 to 100 microns in a continuous phase consisting of solution B, and then the mixed solution is passed through a spinneret using a wet or wet-dry method. 2. The method for producing ultrafine fibers according to claim 1, wherein the methyl methacrylate polymer is dissolved and removed from a composite drawn yarn obtained by stretching a composite coagulated yarn obtained by spinning a composite coagulated yarn twice or more. 3, the ternary copolymer has an acrylonitrile polymer portion of 10
3. The method according to claim 2, wherein the block copolymer is a block copolymer consisting of 50% to 90% copolymer portion of methyl methacrylate and vinyl acetate.