JPH0515747A - Conjugate hollow fiber and production thereof - Google Patents

Abstract

PURPOSE:To separate a specific substance and to enhance permeability by bonding two layers composed of polyolefin A and a blend polymer consisting of polyolefin A and polyolefin B having an m.p. lower than that of polyolefin A and having pores having different sizes. CONSTITUTION:In conjugate hollow fiber formed by bonding two layers one of which is composed of polyolefin A and the other one of which is composed of a blend polymer consisting of polyolefin A and polyolefin A containing polyolefin B being the same kind as polyolefin A but having an m.p. lower than that of polyolefin A in an amount of 3-40% by wt. of polyolefin A, two layers have pores having different sizes and communicating with each other within and between the layers so as to be connected from one surface of the fiber to the other surface thereof. The layer having larger pores of the conjugate hollow fiber is thicker than the layer having smaller pores.

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 by polypropylene in the range of 200 to 2000 liters. According to this, the gas permeability is 1.4 to 6.7 × 10 ⁻⁶ (cc · cm / cm ² · sec ·
cmHg).

US Pat. No. 4,401,567 discloses a polyethylene porous hollow fiber. 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 · 7).
60 mmHg), the water transmittance is 1900 to 3200 (m
1 / m ² · hr · mmHg), albumin permeability is 1
It is described to be 00%.

Further, US Pat. No. 3,423,491 discloses a polyethylene hollow fiber membrane having permeable fine pores, which shows a salt rejection of 75% or more, and US Pat. No. 4,020,23.
No. 0 shows that porous polyethylene each having an effective maximum micropore radius of about 50 Å or less capable of blocking the 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 all uniform in the distribution of micropore diameters. The hollow fibers disclosed in these prior arts have a function of separating substances, and mechanically, a specific substance may 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 point of view, 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 the above 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 are easily varied. It tends to be a hollow fiber with large spots. Further, since the crystal orientation and the maximum draw ratio are different between the inner layer and the outer layer, yarn breakage frequently occurs during the process of stretched and porous, and stable production is difficult.

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 stably manufactured, and a manufacturing method thereof. To provide.

[0010]

Means and Actions for Solving the Problems In order to achieve such an object, the present inventors have arrived at the present invention as a result of intensive studies on the above-mentioned problems.

In the composite hollow fiber of the present invention, one layer is composed of polyolefin A, and the other layer is the same kind as polyolefin A and has a melting point lower than that of polyolefin A. Polyolefin C consisting of a blended polymer with A or polyolefin A, the other layer being the same kind as polyolefin A and having a lower MI value than polyolefin A
On the other hand, it is a composite hollow fiber in which two layers made of a blend polymer of polyolefin C containing 3 to 40% by weight of polyolefin B are joined, and each is composed of two layers having micropores of different sizes. The micropores in and between the layers are in communication with each other to form micropores connected from one surface to the other surface, and the thickness of the layer of the composite hollow fiber having larger micropores. Is a composite hollow fiber that is thicker than the thickness of the layer with smaller microvoids.

[0012] Preferably, the composite hollow fiber has an inner diameter of 50 to 10
00μ, the total thickness of each layer is 5 to 3
00μ, the water permeation rate from the inside to the outside of the hollow fiber is 0.01
It is at least ml / m ² · min · mmHg. This composite hollow fiber uses a hollow fiber manufacturing nozzle having two circular tubular discharge ports arranged concentrically, and uses polyolefin A for one discharge port and polyolefin A for the other discharge port, Blend polymer with polyolefin A containing 3 to 40% by weight of polyolefin B having a low melting point relative to polyolefin A, or polyolefin A
And a blended polymer of polyolefin C containing 3 to 40 wt% of polyolefin B to polyolefin C having the same MI value as that of polyolefin A but having a lower MI value than polyolefin A, melt-spun, and a composite having two different layers. It is produced by obtaining a hollow fiber, annealing the composite hollow fiber, and then stretching and heat setting.

Examples of the polyolefin A constituting one layer of the hollow fiber of the present invention include polyethylene, polypropylene, poly-3-methyl-butene-1, poly-4-methylpentene-1, and copolymers thereof. be able to. The polyolefin constituting the other layer comprises 3 to 40% by weight, and more preferably 10 to 30% by weight, of polyolefin B, which is the same kind as polyolefin A and has a low melting point. When the content of polyolefin B, which is the same kind as polyolefin A and has a low melting point, 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. Further, if the content of the polyolefin B, which is the same kind as the polyolefin A and has a low melting point, exceeds 40% by weight with respect to the polyolefin A, micropores do not occur.

Polyolefin A used in the present invention
The MI value of the polyolefin C is preferably in the range of 0.1 to 50, more preferably 0.5 to 10. The MI value is a value measured by ASTM D-1238. 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. The blend ratio of polyolefin B is 3
If it is less than%, the difference in hole diameter between the larger micropores and the smaller micropores is small, and the target performance cannot be obtained. If the blending ratio of polyolefin B exceeds 40%, it becomes impossible to form pores.

In the present invention, such a polyolefin is melt-spun by using a nozzle for producing a hollow fiber, and is a hollow fiber composed of two layers having fine pores of different sizes, which are minute in and between each layer. A composite hollow fiber is produced in which the pores are in communication with one another from one surface to the other and the layer with larger microvoids is thicker than the layer with smaller micropores. The nozzle preferably has two circular tubular discharge ports arranged concentrically.

The undrawn yarn is annealed 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 in which structural cracking occurs 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 polymer melting point (for example, 0 to 80 ° C. for polyethylene). The hot drawing is a step of expanding microcracking generated by cold drawing to form micropores, and it is preferable to carry out at a relatively high temperature, but it is better to carry out at a temperature not exceeding the melting point of the polyolefin.

Further, 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 by the thinner layer of the composite hollow fiber layer is such that the blend ratio of polyolefin B, which is of the same type as polyolefin A and has a low melting point, to polyolefin A, and the MI value of polyolefin A and polyolefin C. It is determined by appropriately selecting the combination of the differences.

[0020]

EXAMPLES The present invention will be specifically described below based on examples. In addition, the measurement of the trapped particle size using the latex standard particles is performed by the following method. "After a container filled with a hollow fiber membrane having a membrane area of about 50 cm ² was immersed in ethanol, the ethanol was replaced with water to make it hydrophilic and further
1 wt% of surfactant (polyethylene glycol-p-
Isooctyl phenyl ether) aqueous solution,
Polystyrene latex particles having a monodisperse particle size of 0.1% are filtered at a pressure of 0.7 kg / cm ² , and the concentration of latex particles in the filtrate is measured by a Hitachi spectrophotometer (U-3400) to measure the absorbance at a wavelength of 320 nm. Then, the capture rate was obtained. (Example 1) Using a hollow fiber manufacturing nozzle having two concentrically arranged circular tubular ejection ports, the density was 0.968 g / cm ³ , the MI value was 5.5, and the melting point was 13 from the outer ejection port.
High density polyethylene (Hizex 2200J, 4 ° C)
Mitsui Petrochemical Co., Ltd.) and a density of 0.920 g / cm ³ ,
15% by weight of low-density polyethylene (Ultzex 20100J, manufactured by Mitsui Petrochemical Co., Ltd.) having an MI value of 8.0 and a melting point of 120 ° C. was blended with the high-density polyethylene in an amount of 15% by weight. Polyethylene discharge rate 7.5g / min, discharge temperature 155 ℃,
The high density polyethylene and the low density polyethylene blend polymer were discharged at a discharge rate of 0.75 g / min and a discharge temperature of 155 ° C., respectively, and were wound at a winding speed of 100 m / min.

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

The inside diameter of the obtained composite hollow fiber was 271 μm, the total thickness of the inner layer and the outer layer was 54 μm, and the pore size of the micropores of the inner layer was smaller than that of the outer layer by observation with a scanning electron microscope. The size of the trapped particles is 0.088μ, which can prevent 99.5% or more of the latex standard particles.
Met. The water flux of this composite hollow fiber is 3.4 ml /
It was m ² · hr · mmHg (at 25 ° C).

(Example 2) The same procedure as in Example 1 except that the polymer used was changed so that the density from the inner discharge port to 0.
968 g / cm ^3, MI value 5.5, high density polyethylene having a melting point of 134 ℃ (Hizex 2200J, manufactured by Mitsui Petrochemical Co.), the density from the outside of the discharge port 0.920 g / cm ^3, M
Low density polyethylene (Ultzex 20100J, manufactured by Mitsui Petrochemical Co., Ltd.) having an I value of 8.0 and a melting point of 120 ° C. has a density of 0.968 g / cm ³ , an MI value of 0.7 and a melting point of 134 ° C.
High density polyethylene (Mitsubishi Polyethylene BU007U,
A composite hollow fiber was obtained in the same manner as in Example 1 by using polyethylene blended with Mitsubishi Kasei Co., Ltd. at 15% by weight.

The inner diameter of the obtained composite hollow fiber was 275 μ, the total thickness of the inner layer and the outer layer was 53 μ, and the pore size of the micropores of the inner layer was smaller than that of the micropore of the outer layer by observation with a scanning electron microscope. The size was large, and the trapped particle size capable of blocking the latex standard particles by 99.5% or more was 0.03 μ. The water flux of this composite hollow fiber is 2.8 ml / m.
^{It was 2} · hr · mmHg (at 25 ° C.).

(Comparative Example 1) A hollow fiber producing nozzle having a single tubular discharge port was used to obtain a density of 0.968 g / c.
High-density polyethylene (Hizex 2200J, manufactured by Mitsui Petrochemical Co., Ltd.) with m ³ , MI value of 5.5 and melting point of 134 ° C. was discharged at a discharge rate of 8.25 g / min and a discharge temperature of 155 ° C., and wound at 100 m / min. Winded at speed.

The obtained undrawn yarn was annealed in air at 95 ° C. for 12 hours while being wound on a bobbin. Furthermore,
This annealed yarn is 80% cold drawn between rollers kept at 30 ° C. or lower, and then hot drawn between rollers so that the total drawn amount is 400% in a heating box heated to 109 ° C. 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 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 were almost the same in the inner layer and the outer layer, and were the same as the micropores in the outer layer of the composite hollow fiber obtained in Example 1, and the latex was 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 /
It was m ² · min · mmHg (at 25 ° C.).

[0028]

As is clear from the above description, the present invention has two layers having micropores of different sizes,
A composite hollow fiber capable of separating a specific substance, excellent in permeability, and stably manufactured, and a manufacturing method thereof are realized.

Claims (6)

[Claims] 1. One layer comprises polyolefin A, the other layer is of the same type as polyolefin A and is polyolefin A.
Polyolefin B, which has a lower melting point, is
Is a composite hollow fiber in which two layers composed of a blended polymer with polyolefin A, which is contained in an amount of 3 to 40% by weight, are bonded to each other, and the two layers have micropores of different sizes,
The micropores in each layer and between the layers communicate with each other to form micropores connected from one surface to the other surface of the layer having larger micropores of the composite hollow fiber. A composite hollow fiber, characterized in that the thickness is greater than the thickness of the layer having smaller microvoids. 2. One layer comprises polyolefin A, the other layer is of the same type as polyolefin A and is polyolefin A.
A composite hollow fiber in which two layers made of a blend polymer of a polyolefin C containing 3 to 40% by weight of the polyolefin B with respect to a polyolefin C having a lower MI value are joined, and the two layers have different sizes. Micropores in each layer and the micropores between layers are in communication with each other to form micropores connected from one surface to the other surface. The composite hollow fiber according to claim 1, wherein the layer having large micropores is thicker than the layer having smaller micropores. 3. Polyolefin A and polyolefin C
Is a high density polyethylene having a density of 0.960 g / cm ³ or more, and the composite hollow fiber according to claim 1 or 2. 4. The composite hollow fiber has an inner diameter of 50 to 1000 μm,
The total layer thickness of each layer is 5 to 300 μ,
The particle size of trapping particles that can prevent latex standard particles by 99.5% or more is 0.001 to 0.5, and the water permeation rate from the inside to the outside is 0.01 ml / m ² · min · mmHg or more. Or the composite hollow fiber according to 2. 5. A hollow fiber producing nozzle having two concentrically arranged circular tubular ejection ports, wherein each of the ejection ports has a polyolefin A and a polyolefin of the same kind as polyolefin A and a melting point lower than that of polyolefin A. A composite hollow fiber having two layers composed of the polyolefin A and the blend polymer of the polyolefin A and the polyolefin B is separately supplied by melt-spinning by separately supplying the blend polymer with the polyolefin A containing 3 to 40% by weight of B. After the composite hollow fiber is annealed, it is drawn to form a large number of micropores in each layer so that larger micropores are formed in a thicker layer and smaller micropores are formed in a thinner layer. The method for producing a composite hollow fiber according to claim 1, characterized in that it is caused to occur and then heat-set. 6. In place of the blend polymer of the polyolefin A and the polyolefin B, the polyolefin B is 3 to 4 with respect to the polyolefin C which is the same kind as the polyolefin A and has a lower MI value than the polyolefin A.
The method for producing a composite hollow fiber according to claim 5, wherein a blended polymer with 0% by weight of polyolefin C is used.