JPH0763505B2 - Method for producing porous hollow fiber for artificial lung - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a porous hollow fiber, particularly a porous hollow fiber for artificial lung suitable as a gas exchange membrane for use in artificial lung.

[Prior Art] A porous thermoplastic resin hollow fiber having a structure in which a large number of fine pores are formed in a hollow fiber made of a polymer material is used, for example, in filtration membranes or separation membranes used for water treatment and artificial membranes. It is used in various fields as a gas exchange membrane or a separation membrane for use in lung or plasma separation.

As a method for producing a porous thermoplastic resin hollow fiber, for example, a polymer material in which an easily soluble substance is mixed and dispersed is molded into a hollow fiber, and then the easily soluble substance is dissolved and removed by a solvent to form a hollow fiber. A method of forming a large number of fine through holes is known.

In recent years, a method of forming a porous body by using a method in which a thermoplastic crystalline polymer material is molded as a hollow fiber, heat-treated, and then stretched to generate pores in the hollow fiber It is also common.

A porous thermoplastic resin hollow fiber using a polymer material and a method for producing the same are described, for example, in JP-B-56-52123, JP-A-55-107507, JP-A-57-66117, and JP-A-57-66117. Five
It is disclosed in Japanese Patent Publication No. 7-5914. Most of the porous thermoplastic resin hollow fibers and the method for producing the same disclosed in the above-mentioned publications are such that after the formed thermoplastic resin hollow fibers are first heat-treated, they are near room temperature or the secondary transition of the thermoplastic resin used. At a temperature higher than the temperature (for example, -100 ° C or higher when using polyethylene), pores are generated by forming a porous body, and the formed pores are then heat treated again by heat treatment. The method is the essence.

The porous hollow fiber obtained as described above and used as a gas exchange membrane for an artificial lung passes through the fine pores as a volume flow because its fine pores are significantly larger than the gas molecules to be permeated. For example, various artificial lungs using a porous hollow fiber such as a macroporous polypropylene membrane have been proposed.

A homogeneous membrane is also known as a gas exchange membrane for artificial lungs, and gas molecules are transmitted by dissolving and diffusing permeating gas molecules in the membrane. A typical example of this is polydimethylsiloxane rubber, which is commercialized as a coloboe membrane lung.

[Problems to be Solved by the Invention] However, since the above-mentioned porous hollow fibers that have been conventionally proposed for artificial lungs have high water vapor permeability, not only performance deteriorates due to dew condensation water but also long-term When circulating and using blood, there was a drawback that plasma leaked out.

Further, the above-mentioned homogeneous membrane is the only known silicone that can be used at present in terms of gas permeability,
The silicone film cannot have a film thickness of 100 μm or less in strength. Therefore, there is a limit to gas permeation, and there is a drawback that carbon dioxide gas permeation is particularly poor.

[Means for Solving Problems] The present inventor takes advantage of the chemical stability of a silicone film, the lack of toxicity to living organisms, the good permeability of oxygen gas, and the like, and is a drawback of the silicone film. As a result of intensive research to obtain a porous hollow fiber for an artificial lung that compensates for the low mechanical strength, the present invention has been achieved.

That is, the present invention provides a method for producing a porous hollow fiber for artificial lung, which comprises a step of forming a large number of fine pores in a hollow fiber by stretching a hollow fiber prepared by dispersing and mixing a silicone resin in a thermoplastic resin. In the stretching step, nitrogen, oxygen,
In a medium selected from the group consisting of argon, carbon monoxide, methane and ethane, and the stretching temperature is -100 ° C.
A method for producing a porous hollow fiber for artificial lung, which is carried out at a temperature below 50 ° C. higher than the boiling point of the medium from the freezing point of the medium. is there.

In the present invention, a non-stretched hollow fiber is stretched as a hollow fiber formed by dispersing and mixing a silicone resin in a thermoplastic resin to produce a porous hollow fiber that can be effectively used as a gas exchange membrane in an artificial lung. The present invention has been completed by focusing on the finding that it can be done.

The porous hollow fiber obtained by the production method of the present invention generally has an outer diameter of 10 to 1000 μm and a peripheral wall portion thickness of 10 to 500 μm.
m, the through hole diameter is 0.01 to 5 μm, and the porosity is 20 to 75%.
The structure is such that the silicone resin is inserted into the through holes formed in the peripheral wall of the thermoplastic resin hollow fiber at a constant rate.

Further, in the present invention, the unstretched hollow fiber is stretched in a specific medium at a temperature of −100 ° C. or lower and a temperature in the range of 50 ° C. or higher from the freezing point of the medium to the boiling point of the medium or higher. It is necessary to.

Examples of the thermoplastic resin used in the present invention include polyolefins (polypropylene, high-density polyethylene, etc.),
Examples thereof include poly (4-methyl-pentene-1), polyvinylidene fluoride, and ethylene tetrafluoroethylene copolymer, and these can be used alone or in combination.

In addition, the melt viscosity of the thermoplastic resin used [melt flow index (MFI) or melt index (MFI
I)] is not particularly limited as long as the hollow fiber can be spun, but, for example, when polyethylene is used, considering the efficiency or productivity of hollow fiber spinning, the MI It is preferable to use one having 0.5 to 40 g / 10 minutes.

The silicone resin used in the present invention is a broad concept including silicone oil and silicone rubber, and specifically, silicone resin such as dimethylpolysiloxane, methylphenylpolysiloxane, methylhydrogenpolysiloxane, dimethylsilicone oil, Silicone oil such as methylphenyl silicone oil, and silicone rubber obtained by increasing the molecular weight of the above polysiloxane to have a polymerization degree of 2000 or more are preferably used.

In addition, additives such as a plasticizer, a colorant, a flame retardant, and a filler can be used by being included in the thermoplastic resin or the silicone resin.

As a method for dispersing and mixing the silicone resin in the thermoplastic resin, a conventionally known mixing method can be used. For example, a known mixing device such as a kneader, a single-screw extruder or a twin-screw extruder can be used in a molten state. It can be performed by kneading.

The mixing ratio of the silicone resin to the thermoplastic resin is usually 1
-30% by weight, preferably 2-10% by weight.

In the present invention, first, a thermoplastic resin as described above in which a silicone resin is dispersed and mixed is spun according to a known hollow fiber spinning method to obtain an unstretched hollow fiber. Such spinning conditions can be appropriately selected from known techniques. For example, the spinning temperature may be a temperature above the temperature at which the thermoplastic resin used can be discharged, and below the thermal decomposition temperature of the resin. For example, when polypropylene is used as the thermoplastic resin, it is usually 160 to 280 ° C, preferably 180 to 280 ° C, and when high density polyethylene is used, it is usually 150 to 300 ° C, preferably 160 to 280 ° C. 270 ° C, poly (4-methyl-pentene-1)
If used, usually 260 ~ 330 ℃, preferably
270 ~ 300 ℃, when using an ethylene tetrafluoroethylene copolymer, usually 290 ~ 350 ℃, preferably
190 to 280 ° C, when using polyvinylidene fluoride, it is usually 190 to 300 ° C, preferably 190 to 280 ° C.

The unstretched hollow fiber may be heat-treated before being subjected to the stretching step. By performing the heat treatment before the stretching, the crystallinity of the unstretched hollow fiber can be increased, so that the characteristics of the porous hollow fiber obtained by the stretching are further improved.

The above heat treatment is carried out by a method of heating the unstretched hollow fiber for 3 seconds or more in the air heated to a temperature 30 to 5 ° C. lower than the melting temperature of the thermoplastic resin which is the base material of the hollow fiber.

In the stretching step in the present invention, in a medium selected from the group consisting of nitrogen, oxygen, argon, carbon monoxide, methane and ethane, the stretching temperature is -100 ° C. or lower, and the stretching point is from the freezing point of the medium. It is necessary to carry out at a temperature not higher than 50 ° C higher than the boiling point of the medium.

In the stretching step in the present invention, the above-mentioned media can be used alone or in combination.

An example of a preferred stretching temperature when using the above medium, when using nitrogen, the range of -209 ℃ ~ -146 ℃,
When oxygen is used, the range is −218 ° C. to −132 ° C., when argon is used, the range is −189 ° C. to −140 ° C., when carbon monoxide is used, −205 ° C. The range is -141 ° C, the range is -182 ° C to -111 ° C when methane is used, and the range is -183 ° C to -100 ° C when ethane is used. When the stretching temperature is out of the above range, the rate of formation of effective through holes is lowered by the stretching.

The draw ratio in the above-mentioned low temperature drawing step is generally a value in the range of 1 to 200% with respect to the undrawn hollow fiber. However,
The preferred draw ratio is a value in the range of 10 to 150%. With a draw ratio within these ranges, the number of through holes tends to increase as the draw ratio increases, and the average through hole diameter and porosity of the porous hollow fiber obtained by utilizing this tendency are adjusted according to the purpose. It is also possible.

The stretching step described above can be repeated twice or more until the desired average pore diameter and porosity are obtained.

Under the specific medium of the present invention, the hollowing of the hollow fiber using the drawing step under cooling at low temperature is different from the conventional drawing step at around room temperature, in which the through holes are uniform and the porosity is high. It is possible to obtain an excellent porous hollow fiber having a high level.

It is preferable that the hollow fiber, which has been made porous through the drawing step in the above-mentioned specific medium, is then subjected to a heat setting treatment. The main purpose of this heat setting treatment is heat setting for holding the formed fine through holes. This heat-set hollow fiber was heated to 70 to 5% from the melting temperature of the thermoplastic resin used.
It is carried out by a method of heating for 3 seconds or more in air heated to a temperature lower by ℃. The specific heating temperature is usually 100 to 160 when polypropylene is used.
℃, preferably 110 ~ 155 ℃, when using high density polyethylene, usually 70 ~ 125 ℃, preferably 80 ~ 120
℃, when using poly (4-methyl-pentene-1), usually 150 ~ 210 ℃, preferably 160 ~ 200 ℃, when using ethylene tetrafluoroethylene copolymer, usually 180 ~ 240 ℃, preferably 200 ~ 230 ℃, when using polyvinylidene fluoride, usually 100 ~ 1
The temperature is 65 ° C, preferably 110 to 160 ° C. If the heating temperature is significantly higher than the stated upper limit, the formed micropores may be closed, and if the temperature is significantly lower than the lower limit, or if the heating time is shorter than 3 seconds, heat fixation will occur. Is likely to be insufficient, the through holes formed later may be closed, and thermal contraction is likely to occur due to temperature changes during use. The low temperature stretching and heat setting treatment described above
It can be repeatedly performed until the desired average through-hole diameter and porosity are obtained. That is, the temperature of the hollow fiber can be returned to room temperature and subjected to a process including repeated low temperature drawing (and heat setting treatment). It is possible to increase the number of through holes formed by repeating the low temperature drawing and to increase the average through hole diameter.

The porous hollow fiber prepared as described above has good average properties of the formed large pore diameter and high porosity, and further exhibits good characteristics. Its properties are improved.

The hot drawing step of the hollow fiber which has been made porous through the drawing step at least once is carried out as follows. This hot drawing step is performed mainly for the purpose of expanding the diameter of the fine through holes formed at a low temperature. This hot drawing step is carried out by drawing in air heated to a temperature 70 to 5 ° C. lower than the melting temperature of the thermoplastic resin using the hollow fiber made porous. For example, when polypropylene is used, it is usually 100 to 160 ° C,
Preferably 110-155 ℃, when using high-density polyethylene, usually 70-125 ℃, preferably 80-120 ℃,
When using poly (4-methyl-pentene-1), usually 150 ~ 210 ℃, preferably 160 ~ 200 ℃, when using ethylene tetrafluoroethylene copolymer, usually 180 ~ 240 ℃, preferably 200 ~ 230 ℃, when using polyvinylidene fluoride, usually 100 ~ 1
The temperature is set to 65 ° C, preferably 110 to 160 ° C. In addition,
When the heating temperature is higher than the upper limit of the above temperature, the formed fine pores may be closed, and when the temperature is lower than the lower limit, the expansion of the through hole diameter by stretching may be insufficient. is there.

The draw ratio in this hot drawing step is usually 10 with respect to the length (initial length) of the hollow fiber before being subjected to the low temperature drawing step.
% -700%, preferably 50% -550%. If the draw ratio is lower than 10%, the expansion of the through holes may be insufficient, and if it is higher than 700%, the hollow fiber may be cut.

The hot stretching step is performed alternately with the low temperature stretching step described above, or is performed after at least one low temperature stretching step is completed.

The hollow fiber made porous by this stretching treatment is preferably subjected to heat setting treatment between stretching steps. The main purpose of this heat setting treatment is to heat set the through holes formed through the heat drawing step.

This heat-setting treatment is usually performed by heating the porous thermoplastic resin hollow fiber in the air for 3 seconds or more while keeping the stretched state, and heating it to a temperature 20 to 5 ° C lower depending on the melting temperature of the thermoplastic resin used. It is carried out by. The specific heating temperature is usually 10 when polypropylene is used.
0-160 ℃, preferably 110-155 ℃, when using high-density polyethylene usually 70-125 ℃, preferably 80-120
℃, when using poly (4-methyl-pentane-1), usually 150 ~ 210 ℃, preferably 160 ~ 200 ℃, when using ethylene tetrafluoroethylene copolymer usually 180 ~ 240 ℃ It is usually 200 to 230 ° C., and when using polyvinylidene fluoride, it is usually 100 to 165 ° C., preferably 110 to 160 ° C.

It is desirable that the heat setting treatment be similarly performed on the hollow fibers that have undergone the drawing process.

When the heating temperature is higher than the above upper limit temperature, the formed pores may be closed, and when the temperature is lower than the above lower limit temperature or the heating time is shorter than 3 seconds, heat fixation tends to be insufficient. The through holes are closed, and thermal contraction easily occurs due to temperature change during use.

The porous hollow fiber obtained as described above is effectively used as a gas exchange membrane used in an artificial lung.

[Examples] Hereinafter, the present invention will be further described based on Examples.

(Example 1) Polypropylene (UBE-PP-J109G, trade name: Ube Industries, Ltd., MFI = 9 g / 10 min) and dimethylpolysiloxane 3
Using a hollow fiber manufacturing nozzle equipped with a gas supply pipe with a diameter of 8 mm and an inner diameter of 7 mm, the mixture of the weight% dispersed and mixed was used at the spinning temperature.
Spinning was performed under the conditions of 200 ° C. and a take-up speed of 122 m / min. The obtained hollow fiber was heat-treated in a heated air bath at 145 ° C for 30 minutes, and then stretched in liquid nitrogen (-195 ° C) by 20% with respect to the initial length, and the stretched state was maintained at 145 ° C. Heat treatment was performed for 15 minutes in the heated air tank.

This hollow fiber was hot-stretched at 400% in an air atmosphere at 145 ° C, and then was heated in a heated air tank at 145 ° C for 1 hour while maintaining the stretched state.
Heat treatment was performed for 5 minutes to produce a porous hollow fiber.

The average pore diameter of the obtained porous hollow fiber was measured using a mercury porosimetry method [Measurement was performed using POROSIMETRO SERIES 1500 manufactured by CARLOERBA (Italy). The same applies below], 0.4
μm, and the porosity was 65%.

The gas exchange performance of this porous hollow fiber for use in an artificial lung was evaluated. Evaluation is oxygenation capacity and SERUM LEAKAGE (bleeding of plasma)
About.

First, regarding the oxygen addition ability, it was 250 ml / min / m ² when the plasma velocity was 3 / min / m ² .

For the seam leakage, plasma oozes out after 100 hours at a temperature of 37 to 38 ° C.

(Example 2) Poly (4-methyl-pentene-1) (TPX RT18 trade name: manufactured by Mitsui Petrochemical Co., Ltd.) in which 4% by weight of methylphenylpolysiloxane was dispersed and mixed, had a diameter of 8 mm and an inner diameter of 7
Using a hollow fiber manufacturing nozzle equipped with mm gas supply pipe,
Spinning was performed under the conditions of a spinning temperature of 280 ° C., a take-up speed of 200 m / min, and a draft ratio of 726. The obtained hollow fiber was heat-treated in a heating air tank at 180 ° C for 30 minutes, and then stretched in liquid nitrogen (-195 ° C) by 20% with respect to the initial length while keeping the stretched state.
Heat treatment was performed for 15 minutes in a heated air bath at 180 ° C.

This hollow fiber was subjected to 80% hot drawing in an air atmosphere at 180 ° C, and then it was heated in a heated air tank at 180 ° C for 1 hour while maintaining the drawn state.
Heat treatment was performed for 5 minutes to produce a porous hollow fiber.

The average pore diameter of the obtained porous hollow fiber was measured using a mercury porosimetry method [Measurement was performed using POROSIMETRO SERIES 1500 manufactured by CARLOERBA (Italy). The same applies below], 0.1
μm, and the porosity was 40%.

The gas exchange performance of this porous hollow fiber for use in an artificial lung was evaluated under the same conditions as in Example 1, and it was found that the oxygen addition capacity was 260 when the plasma velocity was 3 / min / m ^2.
ml / min / m ^{2 and} 90 for searum leakage
Plasma oozing occurred at time.

[Effects of the Invention] As described above, according to the method for producing a porous hollow fiber for artificial lung of the present invention, although gas permeability is high, moisture such as water vapor does not permeate and blood is circulated for a long time. It is possible to obtain a porous hollow fiber which can be used as a gas exchange membrane for an artificial lung, in which plasma does not leak even when used and whose strength is large.

Claims (2)

[Claims] 1. A method for producing a porous hollow fiber for artificial lung, comprising the step of forming a large number of fine pores in the hollow fiber by drawing a hollow fiber obtained by dispersing and mixing a silicone resin in a thermoplastic resin. The stretching step is carried out in a medium selected from the group consisting of nitrogen, oxygen, argon, carbon monoxide, methane and ethane, and the stretching temperature is −100 ° C. or lower. 50 from the boiling point of the medium from the freezing point of
A method for producing a porous hollow fiber for artificial lung, which is carried out at a temperature not higher than ℃. 2. The method according to claim 1, wherein the thermoplastic resin is polypropylene, high density polyethylene, poly (4-methyl-pentene-1), polyvinylidene fluoride or ethylene tetrafluoroethylene copolymer. .