JPS6155208A - Drying of porous regenerated cellulose hollow fiber - Google Patents

Abstract

PURPOSE:To carry out the drying of a wet porous hollow fiber of regenerated cellulose, without deteriorating the fiber, by substituting the water in the hollow fiber with a specific organic solvent, and drying the fiber under tension while applying pressure of gas to the hollow part. CONSTITUTION:The water in a cellulosic hollow fiber is substituted with an organic solvent having a boiling point of <=70 deg.C, solubility of >=10wt% in water, and free from hydroxyl group, and the fiber is dried under a tension higher than 0.1g/d and lower than the tensile breakage strength of the fiber, while applying pressure to the hollow part with a gas having a relative humidity of <=70%. The pressure is >=100mm.Hg and lower than the burst strength of the fiber. USE:Artificial kidney, artificial liver, artificial pancreas, ultrafiltration membrane, etc. of filtration/dialysis-type or of filtration-type.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for drying porous hollow fibers in a wet state. More specifically, in the manufacturing process of porous regenerated cellulose hollow fibers obtained from a cellulose cupric ammonia solution, when drying the hollow fibers in a wet state, the boiling point is 70°C or less and the solubility in water is 10% by weight. With the above steps, water in the hollow fibers is replaced with an organic solvent that does not have a hydroxyl group,
Next, the hollow part of the hollow fiber is pressurized with a gas having a relative humidity of 70 or less at a pressure of 100 ttrmHg or more and less than bursting strength, and then 0. I This invention relates to a method for drying porous regenerated cellulose hollow fibers, which is characterized by drying under a tension of not less than II/d and not more than tensile υ breaking strength. In addition, "porous hollow fiber" in the present invention means that when the wall thickness part is observed with an electron microscope, there are 10 pores of 0.02 μm or more on the surface of the wall thickness part.
Hollow fibers with a length of 967 cm or more are defined as "non-porous hollow fibers".

(b) Among conventional technology for separation and purification of substances, research is actively conducted on membrane separation technology as a means of separating micron-order substances such as ions, low-molecular substances, and suspended solids and fine particles in the liquid phase. It is. The biggest problem preventing commercialization of this type of technology on an economic scale is the low rate of material separation.

Since the rate of substance separation depends on the membrane area, as the amount of substances to be treated increases, the membrane area must be increased, and with the normally used flat membrane, the apparatus inevitably becomes dusty. This problem can be solved by separating substances using extremely thin hollow fibers and using the fiber wall surrounding the hollow part as a separation membrane, and by bundling a large number of these hollow fibers to form a substance separation part. This can be solved by increasing the effective area of the device and downsizing the device. Fields where membrane separation systems may become the main focus in the future include: ■ Fields that require concentration, purification, and recovery at low temperatures (food and biochemical industries); ■ Fields that require sterility and dust-free operation (pharmaceuticals) Concentration and recovery of trace amounts of expensive substances (nuclear power, heavy metals fields), ■Special small quantity separation field (pharmaceutical field), ■Energy-intensive separation field (alternative to distillation), etc. As membranes used in these fields, there is an increasing need for hydrophilic membranes with large pore sizes and easy handling.

Regenerated cellulose is a highly hydrophilic material. Regenerated cellulose has excellent organic solvent resistance and mechanical properties,
Also, unlike synthetic polymers, it is less toxic to living organisms. Therefore, the appearance of hollow fibers composed of regenerated cellulose and having a large average pore diameter was expected.

The present inventors first extruded the cellulose copper ammonia solution through the annular spinning spout, and in the process of coagulating, regenerating, and washing with water, the spinning dope (outer annular spinning spout) was The liquid is discharged from the central spinning port,
In addition, by causing microphase separation before coagulation, we succeeded in producing porous regenerated cellulose hollow fibers having hollow portions that continuously penetrated through the entire fiber.

However, since porous regenerated cellulose hollow fibers have pores with an average pore size of 0.02 μm to 10 Am in the wall thickness (inner and outer walls), conventional drying methods for non-porous regenerated cellulose, such as wet This porous method describes a method in which the hollow fibers are lifted up by an unwinding roller, fed through a feed roller and a take-up roller into a high-temperature dryer, and then passed through continuously to heat and evaporate the moisture in the hollow fibers. If applied directly to regenerated cellulose hollow fibers, problems such as collapse of the hollow portion of the hollow fibers and collapse of pores in the thick wall portion will occur. As a result of intensive research to overcome the above problems, the present invention has been achieved.

(c) Problems to be Solved by the Invention The purpose of the present invention is to solve the problems of the prior art as described above (such as the collapse of the hollow part of the hollow fiber and the collapse of the holes in the thick wall part), and to To provide a method for advantageously drying porous regenerated cellulose hollow fibers without any damage.

B) Means for Solving the Problems The method for drying porous regenerated cellulose hollow fibers according to the present invention is characterized in that, in the manufacturing process of porous regenerated cellulose hollow fibers, when drying the hollow fibers in a wet state, the boiling point is 70°C or less, the water solubility in water is 10 times higher, and the water in the hollow fibers is replaced with an organic solvent that does not have a hydroxyl group, and then
The hollow part of the hollow fiber is io
- It is characterized by drying under a tension of 0 or 1 F/d or more and less than the tensile breaking strength while applying pressure at a pressure of at least one hour and less than the tablet breaking strength.

The main feature of the present invention is to remove moisture in the porous regenerated cellulose hollow fibers in a wet state using an organic solvent with a boiling point of 70°C or less, a solubility in water of 10% by weight or more, and no hydroxyl group. Then, the hollow portion of the hollow fiber is dried while being pressurized with a gas having a relative humidity of 70 degrees or less. The method of replacing water with an organic solvent and drying is a common method, but as in the present invention, an organic solvent with a boiling point of 70°C or less, a solubility in water of 10% by weight or more, and no hydroxyl group is used. When the water in the hollow fibers is replaced with , hollow fibers with almost the same performance as in the wet state can be obtained. When water is replaced using an organic solvent other than the organic solvent (for example, methanol or ethanol), the average pore diameter of the porous regenerated cellulose hollow fibers becomes extremely small during drying, and K becomes 0.02 am or less. Furthermore, it is common for the hollow fibers to become thick and brittle after drying. Therefore, it is essential to replace the water in the hollow fibers with an organic solvent that has a boiling point of 70°C or less, a solubility in water of 10% by weight or more, and does not have hydroxyl groups. A hollow system can be obtained that can fully exhibit the performance as a hollow fiber used in such applications, and at the same time, a hollow fiber with high flexibility and stiffness can be obtained. Here, the term "hollow fibers" after drying refers to fibers with a moisture content of 10 cm or less. A preferred organic solvent is acetone. When water is replaced with acetone, the reason is currently unknown, but compared to conventional non-porous hollow fibers + hollow fibers that have been replaced with a solvent other than the organic solvent and dried, it becomes more flexible and has a finer structure. They also have low crystallinity, and their intermolecular and intramolecular hydrogen bonds are not sufficiently developed.

Preferably, the porous regenerated cellulose hollow fibers in a wet state are pressurized with a gas having a relative humidity of 70 degrees or less over a 50-volt electric plate at a pressure below the bursting strength. Then, the organic solvent is used to replace the moisture in the hollow fibers, and the hollow portions of the hollow fibers are further dried while being pressurized with the gas. This method (which can quickly replace organic solvents,
In addition, it is possible to prevent defects such as pinhole A- in the thick wall portion of the hollow fibers from being detected in the product.

11001 as the pressure of gas added to the hollow part of the hollow fiber
131LH or more and bursting strength or less is required. If the pressure is less than 110011 sH, drying may be insufficient or the drying time may be extremely long, and the hollow portion may often be deformed during the drying process. Moreover, if the bursting strength is exceeded, problems such as bursting of the thick wall portion may occur. When simultaneously checking for pinholes in the wall thickness of hollow fibers, the pressure is 100 ar.
It is preferable that the temperature is equal to or higher than xHg and equal to or lower than the pre-predicted Paplevoice/t. Further, the relative humidity of the gas added to the hollow portion of the hollow fiber is 70% or less, preferably 50° or less. If the relative humidity is greater than 70 yen, the hollow fibers will adsorb moisture in the gas, making drying difficult. Therefore, the lower the relative humidity of the gas, the better. Furthermore, after replacing the organic solvent, if the atmospheric humidity in which the organic solvent is evaporated is high, drying becomes difficult.
By controlling as follows, porous regenerated cellulose hollow fibers in a dry state with good reproducibility and stability can be obtained. It is also important to apply a tension of 0.1 Ivd or more to prevent shrinkage during drying. When drying under no tension without applying any tension, shrinkage occurs, resulting in changes in the outer diameter and inner diameter of the hollow fibers, and a decrease in the average pore diameter.

The porous regenerated cellulose hollow fibers obtained by the method of the present invention can be used for separation and removal of target components in liquid or gas mixtures containing water, such as filtration/dialysis type or filtration type artificial kidneys, artificial Examples include hollow fibers for the liver or artificial pancreas. This porous regenerated cellulose hollow fiber, which is hydrophilic and has excellent mechanical properties, is suitable for use in bio-related fields (medicine, biochemical industry) and food fermentation fields. .

Prior to the examples, methods for measuring various physical property values used in the detailed explanation of the invention are shown below.

Average molecular weight> By substituting the intrinsic viscosity number (Da) (m/Jl) measured in a cupric ammonia solution (20°C) into the following formula (1), the average molecular weight (viscosity average molecular weight) My can be calculated. calculate.

My= (η) X 3.2 X 10 (1
) Average pore radius, pore density> Pore radius of porous membrane 1cIIL2 is r − r + dr
If the number of holes existing in lc is expressed as N(r)dr, then (N(
r) is a pore size distribution function), the average pore radius F3s and the pore density N are given by the following equations (3) and (4).

N=/''' gr) d r (4) Electron micrographs of the inner and outer wall surfaces and the intermediate surface of the wall thickness of the hollow fiber obtained by replacing the moisture inside the wet hollow fiber with acetone and then air drying. Images are taken using a scanning electron microscope. Sampling of the thick wall part is performed using an ultramicrotome (LKB (Sweden) Ultratome III 8800 m after embedding the hollow fiber in epoxy resin).
, ) Using a glass knife equipped with K, cut an approximately 1 μm thick piece parallel to the fiber axis direction of the central yarn at a position of 1/1.8 to 1/2.2 of the wall thickness as measured from the outer wall surface. The sample was cut out. From the photograph, the pore size distribution function N(r) is determined by a known method.
is calculated and substituted into equation (3). That is, a scanning electron micrograph of the part where the pore size distribution is to be determined is enlarged and printed to an appropriate size, for example, 20 ci x 20 α)K, and 20 test lines (straight lines) are drawn at equal intervals on the obtained photograph. Each straight line crosses a number of holes. Measure the length of the straight line that exists within the hole when it crosses the hole, and find this frequency distribution function. Using this frequency distribution function, we can use, for example, Stereolono
N(r) is determined by the method of Iwanami Shoten). Note that the average pore diameter is 2i3.

<Bubble point and bursting strength> A needle connected to a syringe is inserted into the hollow part of one end of the hollow fiber in a wet state, and this part is fixed. Seal the other end of the hollow fiber with adhesive or the like.

After that, the hollow fiber was immersed in water at 25°C, and the upper part of the syringe was pressurized using nitrogen as a pressure source. Read and set it as a bubble point. Further increasing the nitrogen pressure causes the hollow fibers to burst. The pressure at this time is the bursting strength.

Tensile fracture strength> Hollow fibers with a length of 10α were tested at 20°C using a Tensilon UTM-n20 type tensile strength testing machine manufactured by Toyo YN- and Ludwin Co., Ltd.

Tensile speed 50 wJ't+ under the condition of 60 S RH
Measure with.

(e) Examples Hereinafter, the present invention will be specifically explained with reference to Examples.

<Examples 1 to 5> Cellulose linter (viscosity average molecular weight 2.3 x 105)
Anthonia concentration 6.8% by weight prepared by a known method,
6 F% in copper ammonia solution with a copper concentration of 3.1 F/-11
The mixture was dissolved in water, filtered and defoamed to obtain a spinning stock solution. The spinning stock solution is passed through the outer spinning outlet (outside @ 2 rarx) of the annular spinning outlet.
dr) is υ2.0 gin, so on the other hand, the ratio of acetone to water is 67.3% by weight, and the ratio of ammonia to water is 0.
A 9% by weight mixed solution was added to the central spinning spout (outside (40,4 rtr
凰φ), directly discharged at 92.5 at/min into a mixed solution with acetone and water ratio of 67.3 weight tS and ammonia and water ratio of 0.9% by weight, and 5 m/min. It was wound at a speed of 1 minute. Immediately after being discharged, the transparent blue fibrous material gradually turned white, coagulated while causing microphase separation, and maintained its shape as a fiber (hollow fiber). Thereafter, it was regenerated with a 2% by weight aqueous sulfuric acid solution at 25°C, and then washed with water at 25°C. Insert a needle connected to a syringe into the hollow part of one end of the hollow fiber in a moist state,
This part has been fixed. The other end of the hollow fiber was sealed with adhesive. After that, while immersing the hollow fiber in acetone,
The moisture in the hollow fibers was replaced with air having the relative humidity shown in Table x1 for 2 minutes while applying a pressure of 300*1. Thereafter, the hollow fiber was taken out in an atmosphere with a relative humidity of 40%, and one end of the hollow fiber sealed with adhesive was applied with a force of 0.0% to that end.
A tension of 5 N/d was applied, and the hollow part was pressurized with air at a relative humidity of 5 (l), and then the acetone was evaporated to obtain a dry hollow fiber.Drying conditions and the outer wall surface of the obtained hollow fiber were The average pore diameter is shown in Table 1.

As shown in Table 1, the lower the relative humidity of pressurized air during one displacement, the faster the drying time is and the more efficient it is.

<Comparative Example 1> A syringe needle connected to a syringe was inserted into a hollow portion at one end of the wet hollow fiber obtained in Example 1, and this portion was fixed. The other end of the hollow fiber was side chained with adhesive. Thereafter, while the hollow fibers were immersed in acetone, the moisture in the hollow fibers was replaced with air at a relative temperature of 80% for 2 minutes while applying a pressure of 300 wXmHg.

After that, the hollow fiber was taken out in an atmosphere with a relative humidity of 40 parts.
One end of the hollow fiber sealed with adhesive was cut, a tension of 0.51/d was applied to the end, and the hollow part was pressurized with air at a relative humidity of 50 cm to evaporate the acetone and dry. Even if it was carried out for a minute, shrinkage occurred when the moisture content was increased, and the hollow fibers were also significantly deformed.

<Example 6> A syringe needle connected to a syringe was inserted into a hollow portion at one end of the wet hollow fiber obtained in Example 1, and this portion was fixed. The other end of the hollow fiber was sealed with adhesive. Thereafter, while the hollow fibers were immersed in propylamine, the relative humidity was adjusted to 40°C.
Water in the hollow fibers was replaced with air for 2 minutes while applying a pressure of 300 imHg. After that, the hollow fiber was taken out in an atmosphere with a relative humidity of 40 °C, one end of the hollow fiber sealed with adhesive was cut, and a tension of 0.5, F/d was applied to the end, and the hollow fiber was placed in an atmosphere with a relative humidity of 40 °C. The propylamine was evaporated while pressurizing the hollow part to obtain a dry hollow fiber.

The average pore diameter of the outer wall surface of the obtained hollow fiber was 2.4 μm.

<Comparative Example 2> A syringe needle connected to a syringe was inserted into a hollow portion at one end of the wet hollow fiber obtained in Example 1, and this portion was fixed. The other end of the hollow fiber was sealed with adhesive. after that,
While the hollow fiber is immersed in methanol, the relative humidity is 50%.
The moisture in the hollow fibers was replaced with air for 2 minutes while applying a pressure of 300 mm. After that, the hollow fiber was taken out in an atmosphere with a relative humidity of 40%, one end of the hollow fiber sealed with adhesive was cut, and a tension of 0.5, F/d was applied to the end, and the air with a relative humidity of 40% was placed. The methanol was evaporated while pressurizing the hollow part to obtain a dry hollow fiber, but the hollow fiber was transparent and no pores could be observed with an electron microscope.

Comparative Example 3 A syringe needle connected to a syringe was inserted into the hollow part of one end of the wet hollow fiber obtained in Example 1, and this part was fixed. The other end of the hollow fiber was sealed with adhesive. Then, while immersed in acetone,
- Moisture in the hollow fibers was replaced for 2 minutes while applying constant pressure. Thereafter, the hollow fibers were taken out in an atmosphere with a relative humidity of 40 °C, one end of the hollow fibers sealed with adhesive was cut, and the fibers were left in the atmosphere. After 10 minutes, the moisture content of the hollow fiber was less than 10%, but the hollow fiber had shrunk and the hollow part of the hollow fiber had collapsed, making it unusable.

Claims (1)

[Claims] 1. In the manufacturing process of porous regenerated cellulose hollow fibers obtained from a cellulose cupric ammonia solution, when drying the hollow fibers in a wet state, the boiling point is 70°C or less and the solubility in water is The water in the hollow fibers is replaced with an organic solvent that has a content of 10% by weight or more and does not have hydroxyl groups, and then the relative humidity is 70%.
% or less of gas, the hollow part of the hollow fiber is
0.1g while pressurizing at a pressure of Hg or more and less than bursting strength.
A method for drying porous regenerated cellulose hollow fibers, characterized by drying under a tension of /d or more and tensile breaking strength or less. 2. When drying porous regenerated cellulose hollow fibers,
The hollow part of the hollow fiber is heated for 50 m with gas having a relative humidity of 70% or less.
The drying method according to claim 1, wherein water in the hollow fibers is replaced with the organic solvent while pressurizing at a pressure of mHg or more and less than bursting strength. 3. The drying method according to claim 1 or 2, wherein the hollow portion is pressurized at a pressure of 100 mmHg or more and not more than the bubble point of the hollow fiber. 4. Claim 1, wherein the organic solvent is acetone;
The drying method according to item 2 or 3.