JPS63119802A - Polyolefin-based porous hollow yarn membrane partially imparted with hydrophilicity - Google Patents

Abstract

PURPOSE:To obtain the title membrane having excellent permeability to air bubbles and capable of easily filtering water contg. air bubbles by using polyolefin-based porous hollow yarn having a hydrophilic part and a hydrophobic part in the axial direction of the yarn and having a specified value for water flux/(air flux)<2>. CONSTITUTION:A polyethylene porous hollow yarn membrane, etc., are brought into contact with the outer peripheral part of a notched roller 5 and traveled, and a hydrophilicity imparting agent 2 difficultly soluble in water such as the melt of propylene glycol monostearate is deposited on the porous hollow yarn membrane. Since the hydrophilicity imparting agent is not deposited on the porous membrane corresponding to the notches 6 of the roller 5, a hollow yarn membrane having a hydrophobic part 11 and a hydrophilic part 12 in the axial direction of the yarn is obtained. The polyolefin-based porous hollow yarn membrane partially deposited with the hydrophilicity imparting agent has water permeability over the whole surface and air permeability while being wetted with water.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a partially hydrophilized polyolefin porous hollow fiber membrane, and more specifically, the present invention relates to a partially hydrophilized polyolefin porous hollow fiber membrane. The present invention relates to a polyolefin porous hollow fiber membrane in which a hydrophobic portion and a hydrophobic portion coexist. Such hollow fiber membranes are suitable, for example, as separation membranes for various water treatments in the food industry, medicine, drinking water, and the like.

(Conventional technology) Polyolefin porous hollow fiber membranes have superior water resistance, chemical resistance, and bacterial resistance compared to those made of base materials such as cellulose acetate, and they also have excellent water resistance, chemical resistance, and bacterial resistance. Compared to hollow fiber membranes made by other methods such as solution spinning and extraction, membranes made porous by this method do not contain impurities such as additives such as solvents and extraction residues, and have superior strength and elongation properties and are easier to handle. Water purifier for drinking water because it has the characteristics,
It is widely used as a separation membrane for various main treatments such as sterile wood production equipment for hospitals.

However, polyolefin hollow fiber membranes are originally hydrophobic and cannot allow water to pass through them as they are under normal pressure, and must be made hydrophilic by some means before being used for water filtration. The hydrophilization method that is currently commonly used is to fill the microporous part of a polyolefin porous hollow fiber membrane with a water-soluble liquid with low surface tension, such as ethyl alcohol, and then replace this liquid with water. It's a method. In the case of this method, once the water filled inside the micropores leaves, its wood-philicity disappears, and it becomes necessary to perform the hydrophilic treatment as described above again. Therefore, there was a problem that it was difficult to handle the porous hollow fiber membrane after the hydrophilic treatment.The present inventors proposed propylene glycol monostearate in Japanese Patent Application No. 59-23484 as a solution to this problem. We proposed a permanent wood parenting method in which a polyolefin porous hollow fiber membrane is immersed in an ethyl alcohol solution, the ethyl alcohol is removed by evaporation, and the membrane is heat treated.

(Problems to be Solved by the Invention) The membrane treated by this method has propylene glycol that is poorly soluble in water and has excellent water wettability, so it is permanently made hydrophilic and has excellent water permeability. When air bubbles get mixed into the water being treated during water treatment, it is difficult for air to permeate through such membranes, and the air bubbles accumulate on the upstream side of the membrane, reducing the actual membrane area for water source applications by the amount of air bubbles accumulated. A problem arises. In order to avoid such a phenomenon, an air venting mechanism must be provided, which requires mechanically complicated measures.

Furthermore, even if an air bleed mechanism is provided, air bubbles that reach the vicinity of the air bleed mechanism, which is usually installed above, are removed from the system, but air that adheres to the membrane surface as minute bubbles is not removed, and the actual membrane remains. This leads to a decrease in area.

Under these circumstances, the inventors of the present invention have conducted intensive studies to develop a membrane that does not have the above-mentioned problems and can easily filter water mixed with air bubbles, and as a result has arrived at the present invention.

(Means for solving the problem) That is, the gist of the present invention is that a hydrophilic part and a hydrophobic part coexist in the yarn axis direction, and water flux/(air flux)2 is o, 5xto- 8 or more, 2.0X1
0-' or less.

The present invention will be explained below using the drawings. FIG. 1 is a schematic diagram showing an example of the distribution of the hydrophilic portion and hydrophobic portion of the hollow fiber membrane of the present invention, and FIG. 2 is a schematic diagram showing an example of the processing equipment for obtaining the hollow fiber membrane of the present invention. FIG.

As the material for the porous hollow fiber membrane used in the present invention, polyolefins such as polyethylene and polypropylene are used from the viewpoint of water resistance and chemical resistance, and hollow fiber membranes made porous by melt spinning and stretching are preferably used. It will be done.

The porous hollow fiber membrane of the present invention must have a woody part (12) and a hydrophobic part (11) coexisting in the fiber axis direction, and the hydrophilic part is defined by the hydrophilic treatment. , means a portion that has become hydrophilic, and those that are substantially permanently hydrophilic are preferred. Such hydrophilic treatment can be obtained by attaching a hydrophilic compound that is sparingly soluble in water, such as propylene glycol monostearate or propylene glycol monobehenate, to the surface of the micropores of the membrane. The coexistence of hydrophilic portions and hydrophobic portions in the direction of the yarn axis means that, for example, when a certain length is taken in the direction of the yarn axis, there are hydrophilic portions and hydrophobic portions in any portion. The length of the hollow fiber depends on the shape of the filter constructed using the hollow fiber, and although it cannot be determined generally, it is usually about 2 cm in the fiber axis direction.
More preferably, a hydrophilic portion and a hydrophobic portion are present in every portion of the length of 1 cm. In such a distribution state, the hydrophilic portion and the hydrophobic portion are substantially evenly distributed over the entire hollow fiber, so that the problems in the prior art described above are solved.

The porous hollow fiber membrane of the present invention is measured in a dry state, and the relationship between the air flux value and the water flux is water flux/(air flux)2≧0.6X10-
' must be. This relational expression shows that the water permeability of a polyolefin membrane depends not only on the degree of hydrophilization but also on the size of the membrane's micropores, porosity, etc.
This is because it is difficult to objectively grasp the state of 0% hydrophilicity, and in polyolefin porous membranes, water permeability, that is, water flux, even though it is temporarily made hydrophilic with alcohol etc. This was derived from the empirical finding that there is a good correlation with the square of air flux, and satisfying the above relational expression is necessary for it to be an excellent water purification membrane. be. If this value is less than 0.6 x 10-8, the membrane is not made sufficiently hydrophilic, resulting in insufficient water permeation, which is not preferable.

This value must be 2.0×10 −′ or less; if this upper limit is exceeded, the hydrophobic portion becomes insufficient and air bubbles cannot be removed sufficiently.

Here, air flux and water flux can be measured by the following method.

Air flux-dried hollow fiber membranes are bundled in a U-shape, and the ends of the hollow fiber membranes are airtightly fixed in a U-shaped module (effective membrane length along the 0-shaped part: 10 cm, fixed length: 5 cm, hollow fibers in the hollow fiber bundle) Number 16
0.5kg/crr from the hollow opening of the book)? 2 at the pressure of
The value obtained by dividing the flow rate of air passing through the porous membrane section by the membrane area based on the inner diameter of the hollow fiber when air at 0°C is introduced is calculated as follows: Air flux.

U-shaped module in which hollow fiber membranes are bundled in a U-shape and the ends of the hollow fiber membranes are liquid-tightly fixed (membrane effective length 18c along the 0-1 part)
m, fixed length 1cm, hollow fiber outer diameter display effective membrane area 0.6
When water at 20°C is introduced from the outer surface of the hollow fiber at a pressure of 0.1 kg/crn' and filtered, the flow rate of water passing through the porous membrane is calculated based on the outer diameter of the hollow fiber. Value divided by membrane area (unit: JZ/hr, +m'.

0.5kg/crr? ) is the water flux.

The porous hollow fiber membrane of the present invention can be obtained by treating a polyolefin porous hollow fiber membrane that has not been subjected to wood-carrying treatment using, for example, an apparatus as shown in FIG.

A melt (2) of a poorly water-soluble hydrophilic agent such as propylene glycol monostearate or propylene glycol monobehenate is passed through the rotating roller (3) and the notched roller (5) to the outer periphery of the notched roller (5). It adheres to the polyolefin porous hollow fiber membrane that runs while contacting the notch roller.
6), the hydrophilic agent does not adhere to the porous hollow fiber membrane corresponding to this part, so the hydrophobic part (11) and hydrophilic part (12) as shown in Figure 1 are Hollow fiber membranes that coexist in the fiber axis direction are obtained. In Fig. 2, only four notches are shown for the sake of simplicity, but
The number of notches is determined based on the desired pitch of the wood-friendly portions, the pitch of the hydrophobic portions, and the diameter of the notch roller.

The amount of the above-mentioned wood-loving agent attached to the porous hollow fiber membrane is 5 to 3
It is preferably 0% by weight, more preferably 15 to 25% by weight. This amount of adhesion can be adjusted using a roller (
3) by means of a squeezing roller (4) in contact with.

The polyolefin porous hollow fiber membrane to which the hydrophilic agent is partially attached in this way has water permeability over its entire surface and air permeability when wet with water.
In order to obtain a partially lignophilized hollow fiber membrane with a better balance between lignophilicity and hydrophobicity and excellent water permeability, the hollow fiber membrane to which the lignophilic agent has been attached is made lignophilic as described above. Melting point of the agent (melting point of propylene glycol monostearate: 43-4
8℃, melting point of propylene glycol monobehenate: 5
1 to 4 at a temperature of 5 to 63℃) or higher, e.g. 60 to 70t
It is preferable to perform a heat treatment for a period of time.

(Example) The present invention will be further explained below using Examples.

Example 1 Polyethylene pores made porous by a stretching method with an inner diameter of 270 μm, a film thickness of 55 μm, a porosity of 70%, and an inner diameter of 270 μm, a film thickness of 55 μm, and a porosity of 65%, which can substantially inhibit bacteria in water. Each quality hollow fiber membrane is cut out with a roller (
5) Propylene glycol monostearate heated and melted at 70° C. was applied using the processing equipment shown in FIG.
Heat treatment was performed at 0°C for 4 hours (A'), (B).

When some of these hollow fibers were taken and the adhesion amount of the hydrophilic agent was measured by the Soxhlet extraction method using ethyl alcohol as a solvent, it was found that A was 18.0% by weight and B was 16.5% by weight. The adhesion amount was % by weight. Also,
Separately, these hollow fiber membranes were immersed in a 0.5% aqueous solution of the dye Rhodamine B for about 5 minutes at room temperature, stirred, and then air-dried. Only the parts to which propylene glycol monostearate had adhered were colored, but the direction of the fiber axis was On the other hand, it was found that a porous hollow fiber membrane as shown in FIG. 1 was obtained in which the length of the woody part was about 411 I111 and the length of the hydrophobic part was about 11.

When the air flux and water flux of these hollow fiber membranes were measured, the values were as shown in Table 1.

Table 1 Air flux (Fl) Water flux (F2) F2
/ (Fl) 'A 26X10'
670 0.99X10-8B 1
7xlO' 350 1.21xl
O=effective membrane area 0.6rr using these hollow fiber membranes?
I created a water purifier using a U-shaped module with the hollow fiber end fixed part facing up, which filters from the outer surface of the hollow fiber membrane toward the hollow fiber hollow part, and connected it to a water faucet to filter tap water.
Both of the hollow fiber membranes (A) and (B) above are effective at removing air bubbles from the water being treated, and even if the water purifier is not equipped with an air vent, air will not accumulate in the container. There wasn't. Furthermore, no living bacteria were observed in any of these filtered waters. Also, when suspended water containing 0.001% of 0.1 μm standard particles was filtered instead of tap water,
The removal rate of standard particles was higher in (B) than in (A).

Example 2 Using the same hollow fiber as that used to obtain the partially hydrophilized hollow fiber A of Example 1, and using two sets of hydrophilic agent adhering devices similar to those used in Example 1, a hollow fiber membrane circle was prepared. Partially hydrophilized hollow fibers were obtained in the same manner as in Example 1, except that the notch rollers were brought into contact with the hollow fibers at positions 180° different from each other in the circumferential direction. The amount of the hydrophilic agent attached to this hollow fiber was 25%, and the lengths of the hydrophilic portion and the hydrophobic portion in the fiber axis direction were about 4 square inches and about 11 inches, respectively.

The air flux (Fl) of this hollow fiber membrane is 25X10'
, water flux (F,) is too.

Tear, F2 / (Fl)' (D value + t1.6X
It was 10-'. A water purifier similar to Example 1 was made using this hollow fiber membrane, and when it was connected to a tap and filtered tap water, air bubbles in the water to be treated were removed well, and air was removed from the water purifier. Even without the opening, air did not accumulate inside the container.

Comparative Example 1 A polyethylene porous hollow fiber membrane similar to that used to obtain A in Example 1 was used, and a notched roller having a circumferential convex width of 1 mm and a concave width of 4 m111 was used as the notched roller. 7 in the same manner as in Example 1 except for
Propylene glycol monostearate heated and melted at 0°C was attached, and then heat-treated at 70°C for 4 hours.

When this hollow fiber was also dyed in the same manner as in Example 1, it was found that a woody part and a hydrophobic part coexisted over the entire hollow fiber membrane, and the length of the hydrophilic part was about l in the fiber axis direction.
ll1ffl, the length of the hydrophobic part was confirmed to be approximately 411+, but the air flux (Fl) was 28X1
0', water flux (F2) is 100, F2/(
The value of Fl)2 was 0.13xto''a. Also, when examined by Soxhlet extraction method, the amount of propylene glycol monostearate attached to the hollow fiber membrane was 5.2%.

A water purifier similar to that made in Example 1 was made using this hollow fiber membrane, and when it was connected to a tap and filtered tap water, the air bubbles in the water to be treated were removed well. Although there was no accumulation of water, a sufficient amount of filtered water per unit time could not be obtained.

Comparative Example 2 A polyethylene porous hollow fiber membrane similar to that used to obtain A in Example 1 was immersed in an ethanol solution of 5% Pro and rangelicol monostearate for 5 minutes, taken out, and subjected to dry heat treatment at 60°C for 8 hours. A hollow fiber membrane made hydrophilic was obtained. When this hollow fiber was subjected to the same dyeing treatment as in Example 1, it was found that the hollow fiber membrane was uniformly dyed and the entire membrane was made hydrophilic. The amount of hydrophilic agent attached to this hollow fiber was 35.2%, the air flux (Fl) was 22X10', and the water flux (F2) was 1
100, and the value of F2/(Fl)2 is 2.20X10
A water purifier similar to Example 1 was created using this hollow fiber, and tap water was filtered in the same way. Although the amount of water was large at the beginning of water flow, air bubbles did not come out from the hollow fiber membrane. The amount of water accumulated in the water purifier decreased, and the amount of filtrated water was not satisfactory.

(Effects of the Invention) As described above, the partially hydrophilized polyolefin porous hollow fiber membrane of the present invention has the water resistance of polyolefin.
Although it uses a material with excellent chemical resistance, it has excellent water permeability, and is particularly effective at removing air bubbles during water filtration, so there is no air trapped inside the water purifier, and the entire hollow fiber membrane surface is almost uniformly hydrophobic. The hydrophilic part and the hydrophilic part coexist, and the value of F2/(Fl)2 is 0.6X10-8 or more, 2.
Since it is adjusted to 0XIO-' or less, water permeability and air bubble removal are well balanced, making it an excellent membrane for water purifiers and highly useful.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of the distribution of the hydrophilic portion and hydrophobic portion of the hollow fiber membrane of the present invention, and FIG. 2 is a schematic diagram showing an example of the processing equipment for obtaining the hollow fiber membrane of the present invention. FIG. In the figure, 1: Polyolefin porous hollow fiber membrane, 11: Hydrophobic part, 12: Hydrophilic part, 2: Hydrophilic agent melt, 3: Roller, 4: Squeezing roller, 5: Notch roller, 6: The cutout is shown.

Claims (1)

[Claims] 1) A hydrophilic portion and a hydrophobic portion coexist in the fiber axis direction, and water flux/(air flux)^2 is 0.
．． 6×10^-^8 or more, and 2.0×10^
A polyolefin porous hollow fiber membrane having a molecular weight of -^8 or less. 2) The polyolefin porous hollow fiber membrane according to claim 1, wherein the hydrophilic portion is made hydrophilic with propylene glycol monostearate. 3) The polyolefin porous hollow fiber membrane according to claim 1, wherein the hydrophilic portion is made hydrophilic with propylene glycol monobehenate.