JPS61207614A - Hollow fiber for heat-exchanger - Google Patents

Abstract

PURPOSE:To obtain a hollow fiber having remarkably improved adhesivity to a potting resin and suitable for the heat-exchanger of artificial lung, etc., by boring minute pores to the wall of a hollow fiber made of a non-polar organic polymer such as PE. CONSTITUTION:The objective hollow fiber is made of a non-polar organic polymer, having continuous or separated minute pores of <=500Angstrom diameter on the tube wall, and having a wall thickness of 2-500mu and an inner diameter of 50-2,000mu. The fiber can be produced, e.g. by melting PE having a density of preferably >=0.94 or PP having a density of preferable >=0.86, extruding through a ring-shaped nozzle and taken up under cooling. The obtained fiber is annealed preferably at a temperature between the melting point and a temperature lower than the melting point by 100 deg.C, drawn by 5-25% preferably at a temperature lower than the melting point by 80 deg.C to develop minute pores to the tube wall and set preferably at a temperature between melting point and a temperature lower than the melting point by 60 deg.C.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a hollow fiber made of a non-polar organic polymer suitable for a heat exchanger, and particularly to a hollow fiber that can be usefully used as a heat exchanger for an oxygenator. .

Conventional technology> Artificial lungs are used as heart-lung auxiliary devices for surgical procedures, or as replacement devices for lungs whose function has deteriorated. It is essential to use a heat exchanger as a means for this purpose, and the details thereof are described in, for example, Japanese Patent Publication No. 55-2982 and Japanese Patent Application Laid-Open No. 57-3J854 as prior art.

<Problems to be solved by the invention> Conventionally, the material for the pipes of the heat exchanger used as an accessory device for oxygenators is often made of stainless steel, which has good thermal conductivity and good heat resistance. However, when assembling it into a heat exchanger, there are problems such as how to seal the end faces, the destruction of particles in the blood due to the edges of the end faces, and the reactivity of blood components with complex compositions with metals.

The use of hollow fibers made of organic polymers as heat exchangers is sufficient to solve the problems of conventional materials as described above, and these hollow fibers are sufficient as pipes for heat exchangers. When incorporating these pipes into a heat exchanger, it is generally necessary to arrange the pipes and partition them so that the materials on both the heat supply side and the heat absorption side do not mix, and botting technology using organic resin is used as a means for this purpose. However, hollow fibers made of non-polar substances such as polyethylene and polypropylene do not have sufficient adhesion to organic resins, and it is desired to improve this adhesion.

Therefore, the inventors of the present invention conducted extensive studies to solve the above-mentioned problems of hollow fibers for heat exchangers made of organic polymers, and found that by providing micropores in the tube wall of the hollow fibers,
The present invention was completed by discovering that the adhesiveness with organic resins used for botting was dramatically improved.

Means for Solving the Problems> That is, the gist of the present invention is to provide a tube wall that is made of a non-polar organic polymer, that has continuous or independent micropores with a size of 500λ or less in the tube wall portion, and that the tube wall thickness is 2 to 500 units, inner diameter 50 to 200
0/jff+.

That is, by utilizing the fact that polyethylene and polypropylene are essentially water-resistant, the tube wall portion of hollow fibers for heat exchangers made of organic polymers is used to absorb water when the heat exchanger is used. By creating micropores that do not allow water to pass through under pressure, we utilize not only the adhesive force at the interface with the organic resin, but also the mechanical bonding force that results from the organic resin penetrating into the micropores and solidifying. , which improves adhesiveness even more.

The present invention will be explained in more detail below.

The size of the micropores in the hollow fiber for a heat exchanger of the present invention may be any size that does not allow water to pass through under the pressure when the heat exchanger is used, but from the viewpoint of safety. from 10
Water will not leak even if the pressure exceeds V4/lyn"5
It is desirable that the current is 00A or less.

The hollow fiber for a heat exchanger of the present invention may have any form as long as it improves heat exchange efficiency and provides sufficient mechanical strength, but the tube wall thickness is 2 to 500 μm, the inner diameter is 5
Particularly preferred is about 0 to 2000 μm.

The hollow fibers for heat exchangers of the present invention are made by extruding an organic polymer t-IJ melted at a temperature above the melting point through a song-shaped nozzle, winding it up while cooling to obtain a hollow fiber, and annealing it at a temperature below the melting point. It is obtained by cold stretching at a low magnification at a relatively low temperature to develop micropores in the tube wall, and then heat setting at a relatively high temperature.

The melting temperature of the organic polymer may be any temperature as long as it can be extruded from the nozzle of the organic polymer ring.
If the melting temperature is too high, the melt viscosity will be too low, making it difficult to perform stable spinning.
Preferably, the temperature range is between 0.degree.

If the spinning draft is 50 or less, the orientation of the hollow fibers will deteriorate and the strength in the fiber axis direction will be insufficient, so it is desirable that the spinning draft is 30 or more.

Any temperature may be used as long as it stabilizes the internal crystal structure at the annealing temperature, but the melting point and the temperature 100°C lower than the melting point can be used to stabilize the crystal structure more quickly without completely forming the structure. It is preferable that it is between.

Cold stretching is a process that develops micropores in the tube wall of the hollow fiber after heat treatment. In order to develop micropores, the crystal itself must be stretched at a temperature that does not deform and the crystal interfaces peel off. There is a need. For this purpose, it is preferable to stretch the film by 5 to 25% at a relatively low temperature of 80° C. or lower than the melting point.

Heat setting is a process of expanding and stabilizing the fine pores developed by cold stretching, as the case may be, and it is necessary to heat set at a temperature that causes little deformation of the structure itself and stabilizes the fine pore structure. For this purpose, the heat set temperature is preferably between the melting point and 60°C below the melting point.

The structure of the raw organic polymer can be formed by the process described above, and any polymer can be used as long as it is essentially non-wettable by water, but polyethylene with a density of α94 or higher and polypropylene with a density of cL86 or higher are particularly suitable. preferable.

Since the hollow fiber obtained by the present invention has micropores in the tube wall portion, it not only has adhesive strength at the entire interface with the organic resin used in the potting process performed when assembling into a heat exchanger, but also the organic resin has micropores. By penetrating into the interior and solidifying, the mechanical bonding force can be dramatically improved, making it possible to increase the reliability of the heat exchanger.

Further, since the hollow fibers obtained by the present invention are shaped by the above-described drawing method, it is possible to obtain a pipe for a heat exchanger that has good orientation and excellent mechanical strength.

〔Example〕

The present invention will be explained in more detail with reference to Examples below. The diameter of the micropores in the tube wall was determined from an electron micrograph of the surface.

Example 1 Polyethylene with density [1968, melt index S, 5 (manufactured by Mitsui Petrochemicals Co., Ltd.] Izex 220
0J) was melted at 160°C and extruded from a ring-shaped nozzle to obtain a 9-volume and 9-middle nitrogen yarn at a draft ratio of 5900. The hollow fibers were annealed at 115°C for 140 seconds, cold stretched 10% at 30°C, and subsequently heat set at 115°C.

The thickness of the tube wall of the obtained hollow fiber was 22 μm, and the inner diameter was 550 μm.
μm, and there were many micropores of about 400 A in the tube wall. The hollow fibers were subjected to a botting process using a urethane adhesive (C-4403/N-4221 manufactured by Nippon Polyurethane Co., Ltd.), and after curing at room temperature for one week, the bottling portion was cut. As a result of visually observing the cut surface using an optical microscope, no hollow fibers were found to have peeled off from the urethane resin.

Comparative Example 1 The annealed hollow fiber of Example 1 was subjected to botting with a urethane adhesive in the same manner as in Example 1, and after curing for one week, the botting portion was cut. Visual observation of the cut surface using an optical microscope revealed that most of the hollow fibers had peeled off from the urethane resin.

Example 2 Polypropylene with density [191, melt index 15 (Ube Industries, Ltd. σBln Boligro, T-115)
G) was melted at 200° C. and extruded from a ring-shaped nozzle to obtain a volume and 9 hollow fibers at a draft ratio of 7000. The hollow fibers were annealed at 140°C for 140 seconds, and then annealed at 60°C for 140 seconds.
0% cold stretching followed by heat setting at 145°C.

The thickness of the tube wall of the obtained hollow fiber was 20 μm5, and the inner diameter was 500 μm.
μm, and there are many micropores with an average pore size of about 25 OA in the stomach wall. The hollow fibers were bonded with urethane adhesive (C!-44037N-422 manufactured by Nippon Polycretan Co., Ltd.).
After botting in step 1 and curing at room temperature for one week,
The botting part was cut off. As a result of visually observing the cut surface using an optical microscope, no hollow fibers were found to have peeled off from the urethane resin.

W Kujira 12 The annealed hollow fiber of Example 2 was subjected to a botting process using a urethane adhesive in the same manner as in Example 2, and after curing for one week, the botting portion was cut. Visual observation of the cut surface using an optical microscope revealed that most of the hollow fibers had peeled off from the urethane resin.

Claims (1)

[Claims] 1. Made of a non-polar organic polymer, with a size of 5 on the tube wall portion.
A hollow fiber for a heat exchanger, characterized in that it has continuous or independent micropores of 00 Å or less, a tube wall thickness of 2 to 500 μm, and an inner diameter of 50 to 2000 μm. 2. The hollow fiber according to claim 1, wherein the nonpolar organic polymer is polyethylene or polypropylene. 3. The hollow fiber for a heat exchanger according to claim 2, wherein the polyethylene has a density of 0.94 or more. 4. The hollow fiber for a heat exchanger according to claim 2, wherein the polypropylene has a density of 0.86 or more.