JPS61227804A - Production of finely pored hollow yarn - Google Patents

Abstract

PURPOSE:To reduce only the diameter of a pore while keeping the porosity of a membrane by treating a melt-spun crystalline org. high molecular hollow yarn with corona discharge and then stretching the yarn by >=1.5 times at a temp. higher than the glass transition temp. and lower than the m.p. CONSTITUTION:A melt-formable crystalline org. polymer is melt-spun by using a spinneret for producing hollow yarn to obtain unstretched hollow yarn having substantially no through-pores leading from the outer wall to the inner wall. The hollow yarn is treated with corona discharge at 1-50W/m<2>. The yarn is then stretched by 1.5-4 times at temps. ranging from the glass transition temp. of the org. polymer to the m.p. at >=2/sec deformation speed with use of >=2 rolls.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method of drawing and making an undrawn inner wall yarn made of a crystalline organic polymer porous. More specifically, the present invention relates to a method for manufacturing microporous hollow fibers suitable for hemodialysis or blood filtration.

[Conventional technology]

Hemodialysis for patients with renal impairment has already been widely implemented, and conventional separation membranes for hemodialysis include the cuprammonium method, regenerated cellulose, acetylcellulose,
A semipermeable membrane made of polyacrylonitrile and ethylene-vinyl alcohol co-merged '4' is provided.

However, in recent years, a phenomenon called complement activation, that is, a series of symptoms such as a temporary decrease in the number of white blood cells and a temporary decrease in blood pressure, has become a problem during hemodialysis. This t'1.
This is caused by a reaction between some components in plasma and the polymers that make up the entire membrane, and we are eagerly awaiting the emergence of a membrane in which such a reaction does not occur.

On the other hand, recently, medium-molecular-weight toxic components in the blood have been attracting attention, and the number of artificial kidneys using a blood e-proper method that is effective in removing these components is increasing. In such blood filtration, ultraviolet filtration membranes are used as separation membranes, and porous membranes such as acetylcellulose and polysulfone are used, but these porous membranes have only one function. The water permeability, which is one of the key factors, is far from satisfactory, and improvements in this point are strongly recommended.

The present inventors have developed a membrane made of a crystalline organic polymer that can be melt-formed using a known method of fully stretching 9 filaments during unstretching to make it porous. It was found that the invention has high safety and excellent water permeability.However, the problem that the invention aims to solve is that the molecular weight cut-off is high, making it difficult to use for hemodialysis or blood filtration. It has been found that it is necessary to suitably reduce the pore diameter, but within the known technical range, a complete reduction in the pore diameter inevitably results in a decrease in porosity. It was not possible to reduce only the pore diameter without maintaining the full porosity.

[Means for solving all the problems] The present inventors looked at the situation VC@, and as a result of conducting various tests on the stretching method to make the porous material ='t'(]l-), it was found that It is possible to reduce the pore diameter while maintaining the full porosity by cold-stretching at a certain ratio. It was discovered that such slippage could be completely prevented by subjecting the entire drawn yarn to corona discharge treatment, and the present invention was completed.

The gist of the present invention is to melt-spun a melt-formable crystalline organic polymer using a spinneret for producing an inner-walled yarn, and to obtain a hollow undrawn yarn in which all through-holes communicating from the outer wall to the inner wall are substantially free from M. After corona discharge treatment, the deformation rate expressed by the following formula is from 2 to 100/sec within the temperature range from the glass transition temperature to the melting point of the organic polymer, and the stretching ratio is 1.5 times or more. The method for producing microporous hollow fibers is characterized in that the fibers are stretched between two or more rolls so that the fibers are drawn.

Examples of crystalline organic polymers that can be melt-formed include polyethylene, polypropylene, poly4-methylpentene-1, poly3-methylbutene-1, and polyoxymethylene.

The previously developed porous mid-wall fibers are made by cold-drawing nine undrawn fibers at high speed within a short drawing section, and then hot-drawing them. The pores are large and have a microscopic pore size! It is extremely difficult to make porous medium nitrogen yarn using this technology. Based on the studies conducted by the present inventors, it was found that when a specific undrawn yarn is cold-stretched at a deformation rate expressed by the formula shown above from 2 to 100/sec and at a stretching ratio of 1.5 times or more, the porosity increases. It was discovered that the porous hollow fiber had a completely reduced pore diameter while maintaining the same large value as the porous hollow fiber produced by the conventional drawing method.

In other words, when the deformation rate is low, the stress due to cold drawing acts to expand the microcrazes generated by crystal interfacial exfoliation, whereas when the deformation rate is high, it acts to increase the frequency of crystal interfacial exfoliation. It is necessary that the stretching ratio is 1.5 times or more, and preferably up to 4 times. The stretching temperature is preferably within a temperature range at which the molecular arrangement of the organic polymers constituting the entire undrawn yarn is possible and the crystal structure does not change, that is, the range from the glass transition temperature to the melting point of the organic polymers.

Further, it is preferable that the deformation speed is 27 seconds, that is, more than double the length per second; if the deformation speed is less than this, the desired effect will not be obtained. On the other hand, if the deformation rate is 100/sec, that is, the length is 100 times longer per second, if the undrawn yarn is drawn at a rate higher than 100/sec, the undrawn yarn will undergo so-called stretch breakage.
It cannot be stretched to a length of five times or more, and it is virtually impossible to form a porous hollow fiber having through holes that communicate from the outer wall to the inner wall.

The stretching ratio is expressed, for example, as the ratio of the speed of the winding-side roller to the speed of the yarn-feeding roller of the undrawn yarn.

Although various aspects of the stretching method can be considered, the most practical method is to use rolls and perform the stretching between the rolls because the stretching section is as short as possible and continuous stretching is possible. . In this case, it may be stretched in one stage using two rolls, or it may be stretched in multiple stages using three or more rolls.

Another important point of the present invention is that the undrawn yarn is subjected to corona discharge treatment prior to cold drawing. In other words, when drawing between rollers at high deformation speeds as mentioned above, not only does the undrawn yarn tend to slip on the rollers, causing uneven drawing, but the desired effect is not obtained at all. be. As a result of studies to prevent this slipping, we found that applying corona discharge treatment to all undrawn yarns causes unevenness to occur on the surface of the undrawn yarns, making the surface rough and rough, and that the undrawn yarns become electrically charged and the roll surface The electrostatic attraction has two effects, effectively preventing slippage.

For corona discharge treatment, conditions of 1 to 50 w/m" are appropriate; under conditions of 1 w/m2, it is difficult to achieve slip prevention effects; on the other hand, under conditions of 50 W/m2 or more, undrawn yarn may deteriorate and be damaged. Therefore, it is undesirable.

What kind of pores the drawn porous hollow fiber obtained under these conditions has can be evaluated as follows.◎ The speed of gas passing through the porous wall surface of the porous hollow fiber is The flow type is classified into Boiszeuille flow or Knudsen flow depending on the size of the pores, but in any case, when the average pore diameter is r, the film thickness is set to r, the porosity is φ, and the gas flow rate is tJ, the following I don't know how to show this in a relationship like this.

Among these, the film thickness can be easily measured using an optical microscope or the like, and the porosity can be easily measured by mercury porosimetry. In addition, the gas permeation rate was determined by fixing one end of the porous hollow fiber bundle with an adhesive, etc., and sealing the other end by melting, etc., and fully pressurized the inside of the middle 9 fibers. It is possible to measure the flow velocity of the air that permeates to the outside.

This allows for relative evaluation of pore size.

It is shown that the porous hollow fiber according to the present invention has a high porosity and a small pore diameter.

〔Example〕

The present invention will be fully explained below with reference to Examples.

Example 1 High-density polyethylene (Mitsui Petrochemical Co., Ltd. Hi-Zex 2)
200J)il was melted at 60°C and spun using a spinning trough (5500J) using a hollow fiber production spinneret to obtain an undrawn fiber.

After corona discharge treatment under the condition of the undrawn yarn'z 10 w/m2, the undrawn yarn was heated at 30°C between two rolls with a diameter of 7α at a roll speed of 120 m/min on the feeding side and a roll speed on the winding 9 side. The porous hollow fiber (A) is drawn so that the Obtained. The deformation speed is 45/sec. obtained n7'
All measurement results of the porous hollow fibers are shown in Table 1 together with the results of the hollow fibers of Comparative Example 1.2.

Comparative Example 1 An undrawn yarn obtained in the same manner as in Example 1 was produced at 30°C between two rolls with a diameter of 7α, with a roll speed of 3 m/min on the undrawn yarn feeding side and a roll speed of 15 m/min on the winding side. A porous hollow fiber CB) was obtained by drawing as shown in FIG. The deformation speed is 1.12/
Seconds.

Comparative Example 2 Corona discharge treatment of undrawn yarn in Example 1? Porous hollow fibers (0) were prepared in the same manner as in Example 1 except that no treatment was performed.
? Obtained.

Table 1 Example 2 Isotactic polypropylene (J1 manufactured by Ube Industries, Ltd.)
15G) The undrawn yarn was melted at a total temperature of 190°C, spun at a spinning trough using a spinneret for hollow fiber production at a temperature of 8,000°C, and the undrawn yarn was subjected to corona discharge treatment under the conditions of 30 w/m''. , at 30°C between two rolls with a diameter of 7 cm at a roll speed of 120 m/min on the undrawn yarn feeding side and a roll speed of 400 m/min on the winding side to obtain porous inner wall yarn C.
D) Got k. The deformation speed is 61. Obtained nfC porous inner wall measurement results? The contents of Comparative Example 6.4 are shown in Table 2 along with the yarn profile◇ Comparative Example 3 Undrawn yarn obtained in Example 2? Similarly! Diameter 7cm at Iθ℃
The undrawn yarn was drawn between two rolls at a feeding speed of 3 m/min and a winding side roll speed of 10 m/min to obtain a porous inner wall yarn (K)Tr.

The deformation speed is 1.5/sec.

Comparative Example 4 A porous inner wall yarn (F) was produced in the same manner as in Example 2, except that the undrawn yarn was not subjected to the corona discharge treatment in Example 2.
I met you.

Effects of the invention] As is clear from the above, the hollow fiber manufacturing method of the present invention has nine advantages.
This is an extremely elegant method that can completely reduce the pore diameter without reducing the pore size.

Claims (1)

[Scope of Claims] 1. A hollow undrawn fiber obtained by melt-spinning a crystalline organic polymer using a die for producing hollow fibers and having substantially no through holes communicating from the outer wall to the inner wall is subjected to corona discharge treatment. Afterwards, two or more fibers are applied so that the deformation rate expressed by the following formula is 2 to 100/sec within the temperature range of the organic polymer above the glass transition temperature and below the melting point, and the stretching ratio is 1.5 or more. A method for producing a microporous hollow fiber, which comprises stretching between the above rolls. Deformation speed = stretching ratio / [length of stretching section (cm) / feeding speed (cm/sec)] 2, corona discharge treatment conditions are 1 to 5
1. The method for producing a microporous hollow fiber according to claim 1, which is 0 w/m^2. 3. The crystalline organic polymer is polyethylene, polypropylene, poly4-methyl-1-pentene, poly3-methyl-1
- The method for producing a microporous hollow fiber according to claim 1 or 2, characterized in that the microporous hollow fiber is selected from -butene and polyoxymethylene.