JP5500765B2 - Composite hollow fiber membrane for deaeration and method for producing the same - Google Patents

Description

  The present invention relates to a composite hollow fiber membrane for degassing a dissolved gas in an aqueous solution or an organic solvent, and a method for producing the same.

  In the liquid crystal or plasma display manufacturing process, if bubbles are mixed in the supplied chemical solution, problems such as processing spots occur. In particular, with the recent increase in the screen size of liquid crystals and plasma displays, defoaming by conventional spin coating can no longer be performed, and pattern defects may be caused by performing the lithography process while bubbles are still mixed.

  It is thought that the cause of mixing of bubbles is that the chemical liquid is pumped to the discharge nozzle by nitrogen gas. That is, since the pressure applied to the chemical liquid returns to the atmospheric pressure when the chemical liquid is discharged from the discharge nozzle, the dissolved gas in the chemical liquid becomes supersaturated, and the supersaturated portion becomes bubbles. Therefore, there is a demand for a technique for reducing the amount of dissolved gas by a membrane-type degassing method and suppressing the generation of bubbles in the chemical solution pressure feeding process.

As a hollow fiber membrane used for degassing a dissolved gas in a solvent, for example, Patent Document 1 discloses a three-layer hollow fiber made of a gas selective permeable homogeneous membrane coated on both sides with a hydrophobic porous membrane. A membrane is disclosed. A silicon-polycarbonate copolymer, a silicon-urethane copolymer, or the like is used as the material for the homogeneous membrane of such a three-layer hollow fiber membrane. Patent Document 2 exemplifies linear low density polyethylene as a material for the homogeneous film. Patent Document 3 discloses a hollow fiber membrane having a non-porous layer from the outer surface made of poly-4-methylpentene-1 to a depth of about 1 μm.
Japanese Patent Laid-Open No. 5-185067 Japanese Patent Laid-Open No. 11-47565 JP-A-6-335623

  However, since the silicon-polycarbonate copolymer and the silicon-urethane copolymer have poor solvent resistance, depending on the type of solvent used, swelling and strength reduction are caused.

  Moreover, it is difficult to reduce the thickness of linear low density polyethylene. Furthermore, since the oxygen permeability coefficient is low, in order to obtain a practically effective dissolved gas permeation flow rate, it is necessary to form a very thin film of 0.3 μm or less. When such a thin homogeneous film is formed, the mechanical strength is lowered, and pinholes are easily generated.

  Poly-4-methylpentene-1 is vulnerable to oxidation. Therefore, it is necessary to increase the amount of the antioxidant used, and this may be eluted, and the eluted antioxidant may react with the components of the resist solution to cause discoloration.

  The present invention has been made to solve the above-described problems of the prior art. That is, the object of the present invention is that no chemical solution leaks during degassing, excellent solvent resistance and low elution, a large permeation flow rate of gas such as oxygen and nitrogen, and a compact device can be formed. An object of the present invention is to provide a degassing composite hollow fiber membrane and a method for producing the same.

The present invention relates to a degassing composite hollow fiber membrane having a homogeneous membrane having gas permeability and a porous support layer made of a polyolefin resin that supports the homogeneous membrane, wherein the homogeneous membrane has a weight average molecular weight and a number. Copolymer of ethylene and α-olefin polymerized with a metallocene catalyst having an average molecular weight ratio (Mw / Mn) of 3 or less and a melt flow rate (MFR) of 0.1 to 2 g / 10 min · 190 ° C. A composite hollow fiber membrane for degassing, comprising a polyolefin resin.

  Furthermore, the present invention is a method for producing the above composite hollow fiber membrane, comprising a stretching step for making the support layer porous, and the stretching temperature in the stretching step is the melting point of the polymer constituting the homogeneous membrane. (Tm) −20 ° C. or more and (Tm + 40 ° C.) or less and a Vicat softening point or less of the support layer.

  Furthermore, the present invention is a method for producing the above composite hollow fiber membrane, comprising a stretching step for making the support layer porous, wherein the relaxation temperature in the stretching step is the melting point of the polymer constituting the homogeneous membrane. A method for producing a degassing composite hollow fiber membrane, wherein the temperature is (Tm) ° C. or more and (Tm + 60 ° C.) or less and the Vicat softening point or less of the support layer.

  According to the present invention, there is no leakage of chemicals at the time of deaeration, excellent solvent resistance and low elution, a large permeation flow rate of gas such as oxygen and nitrogen, and a desorption capable of forming a compact device. A care-use composite hollow fiber membrane and a production method thereof can be provided.

In the present invention, the melt flow rate (MFR) of the polyolefin resin constituting the homogeneous membrane of the hollow fiber membrane is 0.1 to 2 g / 10 min · 190 ° C., more preferably 0.3 to 2 g / 10 min · 190. ° C. The upper limit of each range of MFR is sufficient to prevent the fluidity of the polymer and the uniformity of the thickness of the homogeneous membrane due to the flow of the resin for the homogeneous membrane to the support layer. Significant in terms of maintenance. The lower limit is significant in terms of extrusion moldability. MFR is a value measured at a test temperature of 190 ° C. and a test load of 2.16 kgf in accordance with ASTM E1238 E condition.

  The ratio of the weight average molecular weight to the number average molecular weight (Mw / Mn) (polydispersity) of the polyolefin resin constituting the homogeneous film is 3 or less. This increases the crazing resistance while maintaining the formability of the homogeneous film. In addition, when a polyolefin resin having a relatively narrow molecular weight distribution is used, the proportion of low molecular weight components is reduced, and high solvent resistance, engine oil resistance, solvent extraction resistance, tallow resistance, and the like are improved.

Polyolefin resin constituting a homogeneous film, Ru polymer der obtained using a metallocene catalyst. When using a metallocene catalyst, the molecular weight distribution is basically narrow compared to the case of using other catalysts (such as Ziegler-Natta catalyst), although it is the same type of polyolefin resin, low molecular weight components and A polyolefin resin having a low crystalline component and a low melting point can be obtained.

Polyolefin resin constituting a homogeneous film, Ru ethylene · alpha-olefin copolymer der.

As the polyolefin resin constituting the homogeneous film, in particular a density (measured by JISK-7112 = ASTM D1505) is 0.910 g / cm ³ or less, 0.85 g / cm ³ or more polyolefin resin (especially polyethylenes) is preferred . If the density is within this range, the oxygen permeability of the homogeneous membrane can be further increased, and a practically suitable melting point or softening point is obtained. Specific examples of the polyethylene include (co) polymers mainly composed of ethylene obtained by using the above-mentioned HDPE, LDPE, LLDPE, VLDPE, and metallocene catalyst.

  Such polyethylenes are characterized by a low softening temperature and a narrow molecular weight distribution. From the correlation with the density, the melting point (Tm) of the polyethylene is preferably 40 to 100 ° C. or less. Tm is a value measured with a differential scanning calorimeter (DSC).

In the present invention, in particular, as valid as a gas permeable member in the metallocene catalyst based polyolefin resin, Ru with ethylene · alpha-olefin copolymer. A typical example is an ethylene / α-olefin copolymer obtained by using an insight (single site) catalyst developed by Dow Chemical Company, a constrained geometric catalyst which is a kind of so-called metallocene catalyst.

  The ethylene / α-olefin copolymer is preferably an ethylene / C3-C20 α-olefin copolymer. The ethylene / C3-C20 α-olefin copolymer is a copolymer of ethylene and at least one type of α-olefin having 3 to 20 carbon atoms. Specific examples of the C3-C20 α-olefin include propylene, isobutylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene and 1-octene. Furthermore, a C4 to C20 α-olefin is preferable, a C6 to C8 α-olefin is more preferable, and 1-hexene or 1-octene is particularly preferable. As the ethylene / α-olefin copolymer, a copolymer obtained by copolymerization using a C3 to C20 α-olefin at a ratio of about 10 mol% or more (particularly preferably about 20 to about 40 mol%) is preferable.

  Examples of commercially available ethylene / C8α-olefin copolymers include AFFINITY (trademark) manufactured by Dow Chemical Company. Examples of commercially available ethylene / C6α-olefin copolymers include Evolue (trademark) manufactured by Prime Polymer Co., Ltd.

  Additives such as antioxidants, UV absorbers, lubricants, anti-blocking agents, colorants, flame retardants, etc., to the polyolefin resin constituting the homogeneous film, do not impair the purpose of the present invention. Can be added in a range.

  The composite membrane constituting the hollow fiber membrane may be a two-layer composite membrane of a homogeneous membrane and a porous support layer, or a three-layer composite membrane in which a homogeneous membrane is sandwiched between porous support layers. .

  The thickness of the homogeneous film is preferably 0.5 to 10 μm. When this is 0.5 μm or more, pressure resistance during use is improved, and when it is 10 μm or less, gas permeability is improved.

Regarding the thickness of the porous support layer, the thickness of one layer in the case of the two-layer composite membrane and the thickness of one layer of the inner layer or the outer layer of the three-layer composite membrane are preferably 10 to 200 μm. If this is 10 μm or more, the mechanical strength is improved, and if it is 200 μm or less, the outer diameter of the hollow fiber membrane is reduced, and the volumetric efficiency of the membrane when incorporated in the membrane module is improved. Porous support layer in the present invention, ing a polyolefin resin.

  The thickness of the hollow fiber membrane is not particularly limited. Usually, the outer diameter is preferably about 100 to 2000 μm. When the outer diameter is 100 μm or more, the gap between the hollow fiber membranes is relatively wide and the potting material can easily enter. If it is 2000 μm or less, the overall size of the module having a large number of hollow fiber membranes will be reduced, and the volume of the potting part will be reduced accordingly. Can be suppressed.

  The porosity and pore size of the porous support layer are not particularly limited. Usually, the porosity is preferably 30 to 80 vol%. When the porosity is 30 vol% or more, gas permeability is improved, and when it is 80 vol% or less, mechanical strength such as pressure resistance is improved.

  The composite hollow fiber membrane is manufactured through, for example, a multilayer composite spinning process and a stretched porous process. The specific example of the manufacturing method is as follows. First, a molten polymer (high-density polyolefin, etc.) for the support layer precursor (unstretched layer) is supplied to the outermost layer nozzle portion and innermost layer nozzle portion of the concentric composite nozzle nozzle, and the homogeneous layer is melted to the intermediate layer nozzle portion. Supply polymer (polyolefin resin). Then, a molten polymer is extruded from a concentric die and cooled and solidified in a drafted state to obtain unstretched hollow fibers. Next, this unstretched hollow fiber is stretched to make the inner layer and the outer layer sandwiching the homogeneous membrane of the intermediate layer porous. Thereby, a three-layer composite hollow fiber membrane having a homogeneous membrane and a porous support layer (inner layer and outer layer) that supports the homogeneous membrane is obtained.

  In the stretching step for making the support layer porous, the stretching ratio may be determined according to the type of polymer used. Usually, the draw ratio is preferably 2 to 5 times that of undrawn fibers. If the draw ratio is 2 times or more, the porosity of the porous support layer is increased, and the gas permeability is improved. Moreover, if it makes it 5 times or less, the breaking elongation of a composite hollow fiber membrane will improve.

  In the stretching process for making the support layer porous, the stretching temperature is not lower than the melting point (Tm) of the polymer constituting the homogeneous film, not lower than 20 ° C. and not higher than (Tm + 40 ° C.), and lower than the Vicat softening point of the supporting layer. It is preferable. Furthermore, about a lower limit, (Tm-10 degreeC) or more is especially preferable. The upper limits of the above ranges are significant in that defects due to disorder of the polyolefin resin molecules are less likely to occur. In addition, it is significant in that the support layer polymer is sufficiently porous and has sufficient performance as a degassing membrane.

  A method for producing the composite hollow fiber membrane, comprising a stretching step for making the support layer porous, and a relaxation temperature in the stretching step is equal to or higher than a melting point (Tm) ° C. of a polymer constituting the homogeneous membrane , (Tm + 60 ° C.) or less is significant in that defects due to disorder of the polyolefin resin molecules are less likely to occur.

  Further, when the relaxation ratio for suppressing the shrinkage rate due to heat is 0.2 to 0.5 times, and further 0.3 to 0.45 times, the heat shrinkage after 75 ° C. × 8 hours Since the rate can be reduced to 5% or less, it is more preferable in terms of module molding stability.

  Using the composite hollow fiber membrane described above, the chemical solution can be degassed satisfactorily. Usually, a composite hollow fiber membrane configured as a hollow fiber membrane module is used for deaeration. The hollow fiber membrane module, for example, bundles several hundreds of hollow fiber membranes and inserts them into a cylindrical housing, and allows the sealing material to penetrate between the outer porous pores of the composite hollow fiber membranes so that adjacent hollow fiber membranes are inserted. It can be manufactured by filling with a sealing material.

  Hereinafter, the present invention will be described in more detail based on examples. Each physical property was measured by the following method.

[Melting point (Tm)]
A differential scanning calorimeter (DSC) manufactured by Seiko Denshi Kogyo was used for the measurement of the melting point (Tm). Specifically, about 5 mg of sample was melted at 200 ° C. for 5 minutes, crystallized by cooling to 40 ° C. at a rate of 10 ° C./min, and then further heated to 200 ° C. at 10 ° C./min to melt. The melting point was determined from the melting peak temperature at the time and the melting end temperature.

[Ratio of weight average molecular weight to number average molecular weight (Mw / Mn)]
It measured by the following conditions by gel permeation chromatography (GPC).
GPC measuring device: WATERS 150-GPC (manufactured by WATERS)
Temperature: 140 ° C
Solvent: 1,2,4-trichlorobenzene concentration: 0.05% (injection amount: 500 microliters)
Column: One Shodex GPC AT-807 / S, two Tosoh TSK-GEL GMH6-HT Dissolution conditions: 160 ° C., 2.5 hours Calibration curve: A polystyrene standard sample was measured, and a polyethylene conversion constant (0.48) ) And calculated in the third order.

[Melt flow rate (MFR)]
The melt flow rate (MFR 2.16) (g / 10 min) was determined by measuring the mass of the resin extruded in a strand shape for 10 minutes under a load of 2.16 kg at 190 ° C. according to ASTM D1238 E condition.

[density]
In accordance with JIS K7112, a sample obtained by heat-treating a strand obtained at the time of MFR measurement at 190 ° C. under a 2.16 kg load at 100 ° C. for 1 hour and gradually cooling to room temperature over 1 hour was measured using a density gradient tube. .

<Example 1>
High-density polyethylene (trade name Suntech B161, manufactured by using Ziegler-Natta catalyst) in the inner layer and the outer layer using a hollow fiber manufacturing nozzle having discharge ports arranged concentrically to form a three-layer structure Asahi Kasei Chemicals Co., Ltd., melting point 130 ° C., MFR 1.1 g / 10 min, density 0.964 g / cm ³ , Vicat softening point 120 ° C.), ethylene-octene copolymer produced with a metallocene catalyst in the middle layer (Trade name Affinity PL1880G, manufactured by Dow Chemical Co., Ltd., MFR 1.0 g / 10 min, density 0.9020 g / cm ³ , melting point 99 ° C., Mw / Mn = 2.2, octene content 30%) Then, spinning was performed at a discharge temperature of 180 ° C. and a winding speed of 100 m / min to obtain an unstretched hollow fiber. The inner diameter of the unstretched hollow fiber was 230 μm, and the three layers were arranged concentrically.

  This unstretched hollow fiber was annealed at 108 ° C. for 8 hours. Next, the film is stretched 1.25 times at 23 ± 2 ° C., and subsequently heat-stretched in a heating furnace at 100 ° C. until the total stretching amount becomes 4.4 times to make the inner layer and the outer layer porous. A relaxation step of 0.4 times was provided in the furnace, and finally a composite hollow fiber membrane was obtained by molding so that the total draw ratio was 4 times. This multilayer composite hollow fiber membrane had a three-layer structure in which a homogeneous membrane (non-porous thin film) was sandwiched between two porous layers.

When the air permeation rate of this composite intermediate yarn membrane was measured, the oxygen permeation rate (Q _O2 ) at room temperature (23 ± 2 ° C.) was 0.14 m / hr · Mpa, and the nitrogen permeation rate (Q _N2 ) was 0.000048 m / hr · Mpa, and the separation factor (Q _O2 / Q _N2 ) was 2.9. Moreover, since the separation factor 2.9 of the polymer used for the homogeneous membrane was maintained, no leakage occurred even when a solvent (isopropyl alcohol) was passed.

<Example 2>
In the intermediate layer, an ethylene-octene copolymer produced by a metallocene catalyst (trade name Affinity EG8100G, manufactured by Dow Chemical Co., Ltd., MFR 1.0 g / 10 min, density 0.870 g / cm ³ , melting point 55 ° C., Spinning was performed in the same manner as in Example 1 except that Mw / Mn = 2.0, octene content 35%) and the winding speed was changed to 90 m / min to obtain an unstretched hollow fiber. The inner diameter of the unstretched hollow fiber was 200 μm, and the three layers were arranged concentrically.

  This unstretched hollow fiber was annealed in the same manner as in Example 1. Next, the film was stretched 1.25 times at 23 ± 2 ° C., subsequently stretched 4.4 times in a heating furnace at 70 ° C., and then subjected to a relaxation process of 0.4 times in a heating furnace at 100 ° C. It was provided and finally molded so that the total draw ratio was 4 times, and heat-stretched until the total draw amount was 4 times to obtain a composite hollow fiber membrane. This multilayer composite hollow fiber membrane had a three-layer structure in which a homogeneous membrane (non-porous thin film) was sandwiched between two porous layers.

When the air permeation rate of this composite intermediate yarn membrane was measured, the oxygen permeation rate (Q _O2 ) at room temperature (23 ± 2 ° C.) was 0.33 m / hr · Mpa, and the nitrogen permeation rate (Q _N2 ) was 0.11 m / hr · Mpa, and the separation factor (Q _O2 / Q _N2 ) was 2.9. Further, since the separation factor 2.8 of the polymer used for the homogeneous membrane was maintained, no leakage occurred even when a solvent (isopropyl alcohol) was passed.

<Comparative Example 1>
An ethylene-octene copolymer (trade name ENGAGE 8400, manufactured by Dow Chemical Co., Ltd., MFR ³⁰ g / 10 min, density 0.870 g / cm ³ ) produced using a metallocene catalyst having a different MFR from that of Example 2 is used in the intermediate layer. , Melting point 55 ° C., Mw / Mn = 2.0, octene content 35%) and spinning in the same manner as in Example 1 except that the winding speed was changed to 90 m / min. Got. The unstretched hollow fiber had an inner diameter of 200 μm, and three layers were arranged concentrically.

  This unstretched hollow fiber was annealed in the same manner as in Example 1. Next, the film was stretched 1.25 times at 23 ± 2 ° C., and subsequently heat-stretched in a heating furnace at 70 ° C. until the total stretching amount became 4.4 times to make the inner layer and the outer layer porous. A relaxation step of 0.4 times was provided in the heating furnace, and finally, the composite hollow fiber membrane was obtained by molding so that the total draw ratio was 4 times. This multilayer composite hollow fiber membrane had a three-layer structure in which a homogeneous membrane (non-porous thin film) was sandwiched between two porous layers.

When the air permeation rate of this composite intermediate yarn membrane was measured, the oxygen permeation rate (Q _O2 ) at room temperature (23 ± 2 ° C.) was 0.90 m / hr · Mpa, and the nitrogen permeation rate (Q _N2 ) was 0.88 m / hr · Mpa, and the separation factor (Q _O2 / Q _N2 ) was 1.01. Since the separation factor 3.0 of the polymer used for the homogeneous membrane was not maintained, leakage occurred when a solvent (isopropyl alcohol) was passed through.

<Comparative example 2>
In the intermediate layer, polyethylene produced by a Ziegler-Natta catalyst having a Mw / Mn ratio different from that in Example 2 (trade name: FLEXMORE DFDB-1085NT, manufactured by Dow Chemical Co., Ltd., MFR 1.0 g / 10 min, density 0.884 g / Spinning was performed in the same manner as in Example 1 except that cm ³ , melting point 118 ° C., Mw / Mn = 7) was used, and the winding speed was changed to 90 m / min to obtain an unstretched hollow fiber. The unstretched hollow fiber had an inner diameter of 200 μm, and three layers were arranged concentrically.

  This unstretched hollow fiber was annealed in the same manner as in Example 1. Next, the film was stretched 1.25 times at 23 ± 2 ° C., and then continuously stretched in a 110 ° C. heating furnace until the total stretching amount became 4.4 times. A relaxation process of 4 times was provided, and finally, the composite hollow fiber membrane was obtained by molding so that the total draw ratio was 4 times.

Multilayer composite hollow fiber membrane of this is, homogeneous film (nonporous thin film) was a three-layer structure sandwiched between two porous layers.

When the air permeation rate of this composite intermediate yarn membrane was measured, the oxygen permeation rate (Q _O2 ) at room temperature (23 ± 2 ° C.) was 0.12 m / hr · Mpa, and the nitrogen permeation rate (Q _N2 ) was 0.048 m / hr · Mpa, and the separation factor (Q _O2 / Q _N2 ) was 2.5. Since the separation factor 3.2 of the polymer used in the homogeneous membrane was not maintained, leakage occurred when a solvent (isopropyl alcohol) was passed through.

  The degassing composite hollow fiber membrane of the present invention reduces the amount of dissolved gas in aqueous solutions, organic solvents, and resist solutions in, for example, semiconductor production lines, liquid crystal color filter production lines, and ink jet printer ink production. Useful for deaeration applications. In particular, it is very useful for deaeration of a photoresist solution and a developer used for lithography in a semiconductor production line.

Claims (5)

In the degassing composite hollow fiber membrane having a homogeneous membrane having gas permeability and a porous support layer made of a polyolefin resin that supports the homogeneous membrane, the homogeneous membrane is a ratio of the weight average molecular weight to the number average molecular weight. From copolymer polyolefin resin of ethylene and α-olefin polymerized with metallocene catalyst having (Mw / Mn) of 3 or less and melt flow rate (MFR) of 0.1 to 2 g / 10 min · 190 ° C. A composite hollow fiber membrane for deaeration characterized by comprising: Density of the polyolefin resin constituting the equalizing Shitsumaku A composite hollow fiber membrane of claim 1 wherein the 0.850~0.910g / cm ^3. The polyolefin resin constituting the equalizing Shitsumaku melting point (Tm) is, 40 ° C. or more and 100 ° C. or less claim 1 or 2 composite hollow fiber membrane as claimed.   A method for producing the composite hollow fiber membrane according to any one of claims 1 to 3, comprising a stretching step for making the support layer porous, and the stretching temperature in the stretching step is a homogeneous membrane. The melting point (Tm) of the polymer constituting the composition is -20 ° C. or more and (Tm + 40 ° C.) or less, and the Vicat softening point or less of the support layer is produced.   A method for producing the composite hollow fiber membrane according to any one of claims 1 to 3, further comprising a stretching step for making the support layer porous, wherein the relaxation temperature in the stretching step is a homogeneous membrane. A method for producing a degassing composite hollow fiber membrane, wherein the melting point (Tm) ° C. is not lower than (Tm + 60 ° C.) and lower than the Vicat softening point of the support layer.