JPS58120808A - Production of hollow fiber of regenerated cellulose - Google Patents

Abstract

PURPOSE:Specific thin-film hollow fibers of regenerated cellulose are impregnated with a specific amount of a plasticizer and dried to produce the titled hollow fibers that is suitable for use in artificial dialysis membranes, because of their high permeation selectivity, improved permeability and out of roundness. CONSTITUTION:A cellulose ester is extruded into hollow fibers and the hollow fibers are hydrolyzed with an alkali to give hollow fibers of regenerated cellulose with a ratio of an inner diameter to membrane thickness of less than 1/0.2 in a wet state. Then, the resultant fibers are impregnated with 50-150wt% of a water-soluble plasticizer such as polyethylene glycol of average molecular weight of 200-1,000 on the basis of the weight of the hollow fibers and dried so that the dimension in the fiber axis direction is kept at more than 95% and more than 90% in the fiber diameter direction in its wet state.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing permselective hollow fibers consisting essentially of cellulose.

Semipermeable hollow fibers of regenerated cellulose are used as various separation membranes 1. The method of using regenerated cellulose membranes for various separation membranes is already known. It is a matter of good separation.

To produce regenerated cellulose hollow fiber membranes, cellulose ester hollow fibers can be hydrolyzed to form regenerated cellulose hollow fiber membranes.

At this time, a hollow fiber membrane with improved dialysis performance can be obtained by immersing regenerated cellulose hollow fibers in a water-soluble plasticizer in a wet state during the hydrolysis process, and then drying the treated hollow fibers.

During the drying process, it is desirable to reduce the dimensional change of the hollow fibers and effectively maintain the porous structure of the membrane. It is necessary to add a plasticizer.

In recent years, artificial dialysis membranes have been required to have excellent ultrafiltration performance in order to improve dialysis performance.

Various methods have been studied to improve the dialysis performance of these hollow fibers, among which the dialysis performance can be efficiently improved by reducing the membrane thickness of the hollow fibers.

Conventionally, the thickness of the hollow fiber is generally in the range of 40 to 50 microns. If the film thickness is within this range, the mechanical strength of the film is high, there is no breakage during production, the operation is stable, and hollow fibers with good roundness can be easily produced.

On the other hand, in order to obtain a high degree of permeability, it is effective to reduce the thickness of the hollow fibers to 20 to 30 microns. When the film thickness is reduced, the buckling strength of the hollow wire t is reduced and the roundness is extremely reduced. In addition, as the film becomes thinner, defects such as local unevenness caused by polymer foreign matter and foreign structural parts generated during spinning become apparent, and pinholes in hollow fibers increase.

The production of hollow fibers with thin membranes requires technological sophistication, but the quality characteristics of hollow fibers include good dialysis performance, roundness of the hollow fibers, and no pinholes in the hollow fibers. 3- Becomes an essential quality requirement characteristic for use.

As described above, the technology for producing thin hollow fiber membranes has not yet been established (C), and as a result of intensive study of the intercondylar point in the thinning technology, the present inventor was able to obtain the following knowledge.

(b) The roundness of the hollow fibers is such that in the wet state, the ratio of the film thickness to the inner diameter is 0.06-i, which means that the hollow fibers can maintain perfect roundness even after a few seconds after drying. (・(
By holding the hollow fibers in the thin film, the circularity can be improved; (b) Hollow fiber kIf PI due to thinning
Regarding the occurrence of pinholes in A, it is said that the cause is deeply related to the densification of the microstructure due to the fiber tension and shrinkage stress applied during the drying process of the hollow fibers; however, even during the drying process, the hydroxyl groups of cellulose During the dehydration process of the hydration water bound to the hydration water, this hydroxyl group is substituted with a plasticizer and bonded to it, thereby suppressing changes in the volume of the film, reducing the generation of shrinkage stress, and densifying the microstructure. Things that can be avoided: 4- (c) Maintaining a slightly moist state even during the drying process has the effect of improving the dialysis performance of the membrane.

Based on such knowledge, we have succeeded in controlling the fragile portions of the membrane structure so that they do not appear during drying, and have arrived at the present invention.

That is, the present invention uses regenerated cellulose hollow fibers obtained by hydrolyzing cellulose ester hollow fibers, which have an inner diameter to membrane thickness ratio of 1:0.2N or less in a wet state, using a water-soluble plasticizer. and impregnating the regenerated cellulose hollow fibers with a plasticizer in a range of more than 50 weight φ and less than 150 itft% Jν based on the weight of the regenerated cellulose hollow fibers, and then drying the regenerated cellulose hollow fibers.
This is a method for producing selectively permeable regenerated cellulose hollow fibers with improved permeability and roundness.

The present invention involves spinning hollow fibers using cellulose esters such as cellulose triacetate and cellulose diacetate, and hydrolyzing the obtained hollow fibers using an alkali such as caustic potash or caustic soda. This method is applied to the regenerated cellulose hollow fibers obtained.

The present invention is not applicable to regenerated cellulose obtained by the cupro method or the viscose method.

In order to obtain a final storage membrane with excellent roundness and permeability, it is desirable that the dimensional ratio of the inner diameter and membrane thickness of the hollow fibers before treatment be within a predetermined range.

regenerated cellulose hollow fiber]7 in a water-swollen state,
The ratio of film thickness to inner diameter is 0.2 or less, preferably 0.0
It should be a hollow fiber with a membrane ranging from 6 to 0.2. If the membrane is extremely thin, it will not be able to maintain its roundness due to buckling, causing problems such as flattening and rupture of the membrane.

In the present invention, such thin regenerated cellulose hollow fibers that have undergone saponification treatment are impregnated with a predetermined amount of a water-soluble plasticizer, and the hollow fibers containing the plasticizer are dried to form desired hollow fibers. A fiber membrane is obtained.

6- As water-soluble plasticizer used in the method of the invention d
l Glycerin, sorbitol, ethylene glycol,
Examples include glycerin esters, tetraethylene glycol, and polyethylene glycol having an average molecular weight fFt2oo to ]000. However, polyethylene glycol is not ingenious because it has a small swelling effect for those with a molecular weight of 1,200 or more.

The swollen and dried hollow fibers to which more than 50% by weight but less than 150% by weight of a water-soluble plasticizer is attached based on 100 parts by weight of the regenerated cellulose hollow fibers have excellent roundness retention due to the swelling action of the water-soluble plasticizer. Therefore, even thin hollow fibers have sufficient shape retention. If the amount of adhesion falls within this range, the roundness of the regenerated cellulose thin film hollow fibers can be maintained extremely well.

Surprisingly, when such hollow fibers are embedded in separated cells with an adhesive and used in a wet state, the hollow fibers at the bonded portion are less deformed and good roundness can be maintained.

In order to prevent deterioration of roundness due to deformation during rewetting at the adhesive embedded part, the dimensions should be 95% when wet in the fiber axis direction and 90% when wet in the fiber radial direction. It is important to keep it dry.

Note that the dimensional retention rate can be expressed by the yarn length or yarn diameter of the wet hollow fiber using the following formula. Regarding permeation performance, the treatment with the water-soluble plasticizer of the present invention has the advantage of improving ultrafiltration performance.

If the amount of plasticizer attached is less than 50 inches, the swelling effect will not be sufficient in a thin film like the one of the present invention, and hollow #l! The hollow fibers have poor shape retention due to the large contraction of the fibers. In particular, when hollow delicates are re-wetted after being embedded in the adhesive of the separation cell,
The hollow fibers fixed to the adhesive undergo self-deformation due to swelling stress, resulting in a decrease in roundness. In extreme cases, the hollow fibers are completely crushed and the permeation performance is significantly reduced. Furthermore, the occurrence of pinholes in the hollow fibers during the drying process also increases.

On the other hand, if it exceeds 150% by weight, the swelling agent will adhere to the hollow fiber surface more than necessary, making it difficult to handle, and
The adhesion of Ji[j to the adhesive decreases.

Therefore, in order to maintain the roundness of high-performance hollow fibers and prevent pinholes in hollow fibers by forming a thin film of regenerated cellulose hollow fibers, a water-soluble plasticizer should be added in an amount of 50 to 150% by weight.
It is necessary to make it adhere.

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

Example 1 A regenerated cellulose hollow fiber with an inner diameter of 210 μm and a film thickness of 23 μm in a wet state was immersed in an aqueous solution of polyethylene glycol (concentration 20 to 6o%) having an average molecular weight of 200 at 40° C. for 10 minutes. Wipe off the aqueous solution on the fiber surface using F paper and dry at 100℃ for 30 minutes.
9- The fibers were dried by blowing dry air.

The treated hollow fibers were measured for dimensional retention and circularity of the hollow fibers. The results are shown in Table-1.

The roundness is indicated by 2 below.

Total number of hollow fibers It was found that when the amount of polyethylene glycol attached exceeds 50%, the dimensional retention of the fibers is high and the roundness of the hollow fibers is improved.

Table -1 10- Example 2 Inner diameter 210μ measured in wet state, film thickness 23μ and 30μ
The μ hollow fibers were immersed in an aqueous solution of polyethylene glycol (concentration 20-60) with an average molecular bone of 200 at 40°C for 15 minutes, and after removing excess aqueous solution with an air knife, the yarn length was maintained at a constant length when wet. Dry at 80℃ 3
The dried hollow fibers were placed in a separation cell and the pneumatic pressure was applied for 1.0 minutes. o K4/ca of air was introduced into the hollow fibers, and the number of leaks was measured by the bubbling method. The relationship between the amount of polyethylene glycol adhered and the hollow fiber leakage in this case is as shown in Table 2, and it was found that when the amount of adhered polyethylene glycol exceeds 50 inches, the occurrence of leakage from the hollow fiber membrane is small.

Incidentally, the amount of adhesion was measured by the following method.

W, -W.

Adhesion amount--X 100 W.

Table 2 Example 3 Hollow fibers having the same thread diameter as Example 1 were made of glycerin 6
After being immersed in a 0% aqueous solution at 60°C for 30 seconds and dried at 60°C for a day and night, 10,000 swollen and dried hollow fibers with a length of 20L:nl were bundled on the module tube plate surface, centrifugally molded with polyurethane, and bonded. . The cross section of the hollow fibers on the module tube plate surface is close to a perfect circle, and sufficiently swollen dried regenerated cellulose hollow fibers with an inner diameter of 203 μm and a film thickness of 21 μm are obtained.

The ultrafiltration performance of water is 2.7. /! /-・hr・torso I (g
Met. The amount of glycerin deposited was 87 parts by weight.

Comparative Example 1 An aqueous solution containing lo% glycerin was treated in the same manner as in Example 3, and adhered with polyurethane. The cross section of the hollow fibers on the module tube plate surface had an inner diameter of 155μ and was shrunken. Water ultrafiltration performance is t, s7! /-・hr-wqHg Example 3
It was found that there was a decrease compared to The amount of glycerin deposited was measured and found to be 35 parts by weight.

Comparative Example 2 When a 50% glycerin aqueous solution was treated in the same manner as in Example 3 and bonded with polyurethane, it was difficult to bond the hollow fibers to the polyurethane, and the hollow fibers separated from the urethane tube plate surface.

The amount of glycerin attached to the hollow fibers was measured and found to be 160 parts by weight. It was assumed that adhesion was inhibited because a large amount of glycerin was attached.

Procedural amendment January 1980? Mr. Commissioner of the Japan Patent Office 1, Indication of the case Patent application No. 1983-1590 2 Name of the invention Process for manufacturing regenerated cellulose hollow fibers 3 Person making the amendment Relationship to the case Patent applicant 1-11 Minamihonmachi, Higashi-ku, Osaka 300) Teijin Ltd. Representative Tomoo Tokusue 5 "Detailed explanation of the invention" column of the specification subject to amendment (1) Specification, page 5, line 1, "Small L<J is 'equal'" and correct it.

(2) Same, page 6, line 6, "processing film" is corrected to "processing film".

that's all 2- 39-

Claims (1)

[Claims] Regenerated cellulose hollow fibers obtained by hydrolyzing cellulose ester hollow fibers, which have a ratio of inner diameter to membrane thickness in a wet state of 1:0.2 or less, are treated with a water-soluble plasticizer to make them plastic. permeability and roundness by impregnating the regenerated cellulose hollow fibers with the plasticizer in an amount exceeding 50 tremors and not more than 150% by weight based on the weight of the regenerated cellulose hollow fibers, and then drying the regenerated cellulose hollow fibers. A method for producing improved permselective regenerated cellulose hollow fibers.