JPH05311516A - Conjugate hollow yarn and its production - Google Patents

Abstract

PURPOSE:To provide a conjugate hollow polyolefin yarn capable of separating a specific substance, having excellent permeability and producible in high stability. CONSTITUTION:The objective conjugate hollow yarn is composed of an outer layer, an inner layer and an intermediate layer. The outer and inner layers are made of a polyolefin A and the intermediate layer is made of a blended polyolefin produced by (I) blending the polyolefin A with 3-40wt.% of a polyolefin B of the type same as the polyolefin A and having a melting point lower than that of the polyolefin A or (2) blending the polyolefin A with 3-40wt.% of the polyolefin B and 3-40wt.% of a polyolefin C having low MI value. The intermediate layer has micropores having diameters different from those of the outer and inner layers and the micropores of the layers are interconnected with each other. The thickness of the intermediate layer is <=1/4 of the thickness of the outer layer or the inner layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite hollow fiber made of polyolefin and a method for producing the same.

[0002]

2. Description of the Related Art It is already known that a polyolefin, which is a typical thermoplastic resin, is melt-spun and then stretched to obtain a porous hollow fiber.

For example, US Pat. No. 4,055,696 discloses a porous hollow fiber having fine pores distributed in a range of 200 to 2000 Å by polypropylene. According to this, the gas permeability is 1.4 to 6.7 × 10 ⁻⁶ (cc · cm / cm ² · s at a film thickness of 17.5 to 22.5 μm).
ec · cmHg).

US Pat. No. 4,401,567 discloses a porous hollow fiber made of polyethylene.
According to this, when the thickness of the membrane wall is 50 to 60 μm, the N ₂ gas permeability is 4.9 to 7.2 × 10 ⁵ (l / m ² · hr · 760 m
mHg), water permeability is 1900 to 3200 (ml / m
²・ hr ・ mmHg), albumin transmittance is 100%
Is described.

Further, in US Pat. No. 3,423,491, a polyethylene hollow fiber membrane having permeable fine pores showing a salt rejection of 75% or more is also disclosed in US Pat. No. 4,020,230.
In the specification, it is shown that porous polyethylene having an effective maximum micropore radius of about 50 Å or less, which can prevent permeation of albumin having a free rotation radius of about 30 Å by about 95% or more, is produced.

Further, a hollow fiber capable of separating a specific substance and having good permeability is disclosed in Japanese Patent Publication No. 62-44046.

[0007]

However, the above-mentioned U
The inventions disclosed in the respective specifications of SP are only those in which the distribution of micropore diameters is uniform. The hollow fibers disclosed in these prior arts have a function of separating substances, and mechanically, a specific substance can be permeated depending on the size of micropores and the geometrical shape of the substance to be separated. , It is something to stop. From an industrial standpoint, it is also important to increase the permeation rate of the permeable substance as much as possible. However, in the hollow fibers disclosed by these prior arts,
In order to separate a specific substance, it is necessary to limit the size of the micropores, which reduces the area of the flow path through which the substance moves, and reduces the permeation rate of the permeable substance.

On the other hand, in the method disclosed in Japanese Patent Publication No. 62-44046, since polymers having different melt viscosities are bonded and melt-spun at the same time, the thinning points are likely to vary and the inner diameter and the film thickness unevenness are easily varied. Tends to become a large hollow fiber.
Further, since the crystal orientation and the maximum draw ratio are different between the inner layer and the outer layer, yarn breakage frequently occurs in the process of stretched and porous, and it is difficult to stably manufacture. The present invention has been made in view of the above circumstances, and an object thereof is to provide a composite hollow fiber capable of separating a specific substance, excellent in permeability, and capable of stable production, and a method for producing the same. It is in.

[0009]

In order to achieve the above object, the inventor of the present invention has arrived at the present invention as a result of extensive studies on the above problems. The present invention is a composite hollow fiber comprising three layers, an outer layer, an inner layer and an intermediate layer, wherein the outer layer and the inner layer are made of polyolefin A, and the intermediate layer is (1) the same kind as the polyolefin A and the polyolefin A.
Polyolefin B, which has a lower melting point, is
3 to 40% by weight of the blended polymer or (2) polyolefin C and polyolefin B having the same MI value as polyolefin A and a lower MI value than polyolefin A, and 3 to 40% of polyolefin A, respectively.
A composite hollow fiber in which three layers composed of three kinds of blended polymers blended by weight% are joined, wherein an intermediate layer has micropores of different sizes from the outer and inner layers, and micropores in and between each layer. The pores communicate with each other to form minute pores connected from one surface to the other surface, and the thickness of the intermediate layer is 1/4 or less of the thickness of the outer layer or the inner layer. It is a composite hollow fiber.

The composite hollow fibers are arranged in concentric circles.
Using a hollow fiber manufacturing nozzle having one circular tubular discharge port, polyolefin A is used for the two discharge ports (1) The same kind as the polyolefin A and the polyolefin A
Polyolefin B, which has a lower melting point, is
3 to 40% by weight of the blended polymer or (2) polyolefin C and polyolefin B having the same MI value as polyolefin A and a lower MI value than polyolefin A, and 3 to 40% of polyolefin A, respectively.
Produced by separately supplying three kinds of blended polymers blended by weight% and performing melt spinning to obtain a composite hollow fiber having three layers having different layers, annealing the composite hollow fiber, and then stretching and heat setting. To be done.

Examples of the polyolefin A constituting one layer of the composite hollow fiber of the present invention include polyethylene, polypropylene, poly-3-methyl-butene-1, poly-4-methylpentene-1 and copolymers thereof. it can.

The polyolefin constituting the intermediate layer is a polyolefin obtained by blending 3 to 40% by weight, more preferably 10 to 30% by weight, of polyolefin A, which is the same kind as polyolefin A and has a low melting point. When the content of polyolefin B is less than 3% by weight with respect to polyolefin A, there is no difference in the size of the micropores in the two layers. Also polyolefin B
However, if it exceeds 40% by weight with respect to the polyolefin A, micropores do not occur.

The MI values of the polyolefin A and the polyolefin C used in the present invention are preferably in the range of 0.1 to 50, and more preferably 0.5 to 10. If the MI values of the polyolefin A and the polyolefin C are 0.1 or less, the melt viscosity is too high, and stable spinning is difficult to perform. If the MI value is 50 or more, the melt viscosity is too low, and stable spinning is also difficult.

The blend ratio of polyolefin B with polyolefin A or polyolefin C is preferably 3 to 40% by weight. If the blend ratio of the polyolefin B is less than 3%, the difference in pore size between the larger micropores and the smaller micropores is small, and the target performance cannot be obtained. When the blending ratio of polyolefin B exceeds 40%, it becomes impossible to form pores.

In the present invention, such a polyolefin is melt-spun using a nozzle for producing a hollow fiber and has micropores of different sizes, and the micropores in each layer and between layers communicate with each other, A composite hollow fiber is manufactured in which minute pores are formed from one surface to the other surface and the thickness of the intermediate layer is 1/4 or less of the thickness of the outer layer or the inner layer. It is preferable that the nozzle has three circular tubular discharge ports arranged concentrically.

The undrawn yarn is annealed at a temperature below its melting point and then drawn. The stretching is preferably a two-stage stretching in which cold stretching is followed by hot stretching or a multi-stage stretching in which hot stretching is further divided into multiple stages. Cold stretching is a process of causing structural destruction at a relatively low temperature to generate microcracking.
It is preferable to carry out at a relatively low temperature of 50 ° C. to 50 ° C. lower than the melting point of the polymer (for example, 0 to 80 ° C. for polyethylene). The hot stretching is a step of expanding microcracking generated by cold stretching to form fine pores, and it is preferable to perform the stretching at a relatively high temperature, but it is better to perform the stretching at a temperature not exceeding the melting point of the polyolefin.

Furthermore, in order to maintain the physical dimensional stability of the product, heat setting is performed in a fixed length or in a relaxed state.
In order to effectively perform heat setting, the heat setting temperature is preferably equal to or higher than the stretching temperature.

The size of the pores formed in the intermediate layer of the composite hollow fiber layer is determined by appropriately selecting the combination of the blend ratio of polyolefin B to polyolefin A and the difference in MI value between polyolefin A and polyolefin C. Be done.

[0019]

EXAMPLES The present invention will be specifically described below based on examples. "MI value" was measured by ASTM D-1238. The following method was used to measure the trapped particle size using latex standard particles. “After a container filled with a hollow fiber membrane having a membrane area of about 50 cm ² is immersed in ethanol, the ethanol is replaced with water to make it hydrophilic, and
After substituting with a wt% aqueous solution of a surfactant (polyethylene glycol-p-isooctylphenyl ether), 0.1% of polystyrene latex particles having a single dispersed particle diameter was filtered at a pressure of 0.7 kg / cm ² , and the filtrate was obtained. The latex particle concentration of 3 was determined by Hitachi spectrophotometer (U-3400).
The absorbance at a wavelength of 20 nm was measured to obtain the capture rate. "

Example 1 Using a hollow fiber manufacturing nozzle having three circular tubular discharge ports arranged concentrically, the density was 0.968 g / cm ³ and the MI value was 5.5 from the discharge port on the intermediate layer side. , A high density polyethylene (Hizex 2200J, manufactured by Mitsui Petrochemical Co., Ltd.) with a melting point of 134 ° C., a density of 0.920 g / cm ³ , an MI value of 18, and a low density polyethylene (Ultze of 120 ° C.).
x 20200J, Mitsui Petrochemical Co., Ltd.) blended with 15% by weight of polyethylene, and the discharge rate is 0.375 g /
The high-density polyethylene was discharged at a discharge rate of 7.5 g / min and a discharge temperature of 155 ° C. from the discharge ports on the outer and inner layers, respectively, and was wound at a winding speed of 100 m / min.

The undrawn yarn thus obtained was annealed in air at 110 ° C. for 12 hours while being wound on a bobbin. Further, this annealed yarn is cold-drawn by 80% between rollers kept at 30 ° C. or lower, and then hot-drawn between rollers in a heating box heated at 117 ° C. so that the total drawn amount becomes 400%. Further, heat setting was performed in a heating box heated to 120 ° C. in a state where the total stretched amount was relaxed by 25% to obtain a composite hollow fiber.

The inside diameter of the obtained composite hollow fiber was 271 μm,
The total film thickness of the outer, intermediate, and inner layers was 54 μm, and the film thickness of the intermediate layer was 2 μm by observation with a scanning electron microscope. The trapped particle size capable of blocking 99.5% of the latex standard particles was 0.088μ. The water flux of this composite hollow fiber is 6.5 ml / m ² · hr · mmHg (at 25
℃).

Example 2 The polymer used for the intermediate layer had a density of 0.968 g / cm ³ ,
High-density polyethylene with a MI value of 5.5 and a melting point of 134 ° C (H
izex 2200J, manufactured by Mitsui Petrochemical Co., Ltd.) and density 0.920 g / cm ³ , low density polyethylene with an MI value of 18, melting point 120 ° C. (Ultzex 20200J, manufactured by Mitsui Petrochemical Co., Ltd.) and density 0.968 g / cm 3. MI to ³
68 / of high-density polyethylene with a value of 0.4 and a melting point of 134 ° C
A composite hollow fiber was obtained in the same manner as in Example 1 except that the polymer blended was 15/17% by weight.

The inner diameter of the obtained composite hollow fiber was 275 μm,
The total thickness of the outer layer, the intermediate layer, and the inner layer was 53 μm, and the thickness of the intermediate layer was 2 μm when observed with a scanning electron microscope. The trapped particle size capable of blocking 99.5% of the latex standard particles was 0.038μ. The water flux of this composite hollow fiber is 4.5 ml / m ² · hr · mmHg (at 2
5 ° C.).

Comparative Example 1 A high-density polyethylene (Hizex 2200) having a density of 0.968 g / cm ³ , an MI value of 5.5 and a melting point of 134 ° C. was prepared by using a hollow fiber producing nozzle having one circular tubular outlet.
J, manufactured by Mitsui Petrochemical Co., Ltd.) discharge rate of 8.25 g / mi
It was discharged at a discharge temperature of 155 ° C. and was wound at a winding speed of 100 m / min.

The obtained undrawn yarn was annealed in air at 95 ° C. for 12 hours while being wound on a bobbin. Further, this annealed yarn is 80% cold-drawn between rollers kept at 30 ° C. or lower, and then hot-rolled between rollers in a heating box heated to 109 ° C. so that the total amount of drawing is 400%. Further, heat setting was performed in a heating box heated to 120 ° C. in a state where the total stretched amount was relaxed by 25% to obtain a composite hollow fiber.

The hollow fiber thus obtained had an inner diameter of 284 μm and the total thickness of the inner layer and the outer layer was 59 μm. The micropores of this hollow fiber observed with a scanning electron microscope had almost the same pore diameter in the inner layer and the outer layer, and the pore diameter of the micropores in the outer layer of the composite hollow fiber obtained in Example 1 were almost the same. Captured particle size of 0.15μ that can prevent standard particle size of 99.5% or more
Met. The water flux of this hollow fiber is 3.8 ml / m.
^{It was 2} · min · mmHg (at 25 ° C.).

Comparative Example 2 Using a hollow fiber manufacturing nozzle having two circular tubular discharge ports, the density was 0.968 g / cm ³ from the discharge port on the outer layer side.
High-density polyethylene with a MI value of 5.5 and a melting point of 134 ° C (H
izex 2200J, manufactured by Mitsui Petrochemical Co., Ltd., and low density polyethylene (Ultzex 20200J, manufactured by Mitsui Petrochemical Co., Ltd.) having a density of 0.920 g / cm ³ , MI value of 18, and a melting point of 120 ° C. with respect to the above high-density polyethylene. Polyethylene blended 15% by weight with a discharge rate of 0.3
75 g / min, discharge temperature 155 ° C., discharge amount of the high-density polyethylene from the discharge port on the inner layer side is 7.5 g / min,
Discharge at a discharge temperature of 155 ° C, 100 m / min
It was wound up at a winding speed of. The same annealing treatment and drawing as in Example 1 were carried out, but yarn breakage frequently occurred in the hot drawing process, and a composite hollow fiber could not be obtained.

[0029]

As is apparent from the above description, the present invention has the separation layer in the intermediate layer and can be made extremely thin, so that it can separate a specific substance, has excellent permeability and is stable. A composite hollow fiber that can be manufactured by the method and a method for manufacturing the same are realized.

Claims (6)

[Claims] 1. A composite hollow fiber comprising three layers, an outer layer, an inner layer and an intermediate layer, wherein the outer layer and the inner layer are made of polyolefin A, the intermediate layer is the same kind as polyolefin A and has a lower melting point than polyolefin A. B is composed of a blended polymer of 3 to 40% by weight with respect to polyolefin A, the intermediate layer has micropores of different sizes from the outer and inner layers, and the micropores in and between each layer communicate with each other. The composite hollow fiber is characterized in that minute pores are formed from one surface to the other surface and the thickness of the intermediate layer is 1/4 or less of the thickness of the outer layer or the inner layer. 2. A polyolefin C whose intermediate layer is of the same kind as polyolefin A and has a lower MI value than polyolefin A.
The composite hollow fiber according to claim 1, which comprises a blended polymer of 3 to 40% by weight of polyolefin B and 3 to 40% by weight of polyolefin B. 3. The composite hollow fiber according to claim 2, wherein the polyolefin A and the polyolefin C are high-density polyethylene having a density of 0.960 g / cm ³ or more. 4. A composite hollow fiber having an inner diameter of 50 to 1000 μ, a thickness of each layer of 10 to 300 μ, and latex standard particles of 9
Captured particle size that can prevent 9.5% or more is 0.0001 to
The composite hollow fiber according to claim 1, which has a size of 0.5 μm. 5. A hollow fiber manufacturing nozzle having three concentrically arranged circular tubular discharge ports is used, and polyolefin A and polyolefin B are separately supplied to each discharge port and melt-spun to form three fibers. A composite hollow fiber having a layer is obtained, and after the composite hollow fiber is annealed, it is stretched to form a large number of micropores in the outer and inner layers and small micropores in the intermediate layer. 2. The method for producing a composite hollow fiber according to claim 1, wherein the micropores are produced, and then heat setting is performed. 6. The production method according to claim 5, wherein a blend polymer of polyolefin A, polyolefin B and polyolefin C is supplied instead of polyolefin B.