KR20130064812A - Porous polyethylene hollow-fiber membrane, cartridge for water purifier, and hollow-fiber membrane module - Google Patents

Abstract

A polyethylene porous hollow fiber membrane using a resin composition having excellent fluidity including polyethylene, having excellent membrane quality and rigidity, and having a high water permeability and excellent filtration characteristics, and a cartridge and a hollow fiber membrane module for water purifier provided with the polyethylene porous hollow fiber membrane For the purpose of providing The average pore diameter of the hollow fiber membrane is 0.1 to 0.5 µm, the pore diameter distribution is 70% or more of the total pore diameter distribution in the region of ± 0.05 m from the average pore diameter, and JIS K 7210. Melt flow rate measured in accordance with code D of 0.1 to 0.9 g / 10 minutes, melt flow rate measured in accordance with code G is 50 to 100 g / 10 minutes, the ratio FRR (G / D) is 50 to Polyethylene porous hollow fiber formed with the resin composition excellent in the fluidity | liquidity containing 100 and a density of 0.962-0.68 g / cm <3>. Moreover, the water filter cartridge and hollow fiber membrane module provided with the said polyethylene porous hollow fiber membrane.

Description

Polyethylene porous hollow fiber membrane, cartridge for water purifier and hollow fiber membrane module {POROUS POLYETHYLENE HOLLOW-FIBER MEMBRANE, CARTRIDGE FOR WATER PURIFIER, AND HOLLOW-FIBER MEMBRANE MODULE}

The present invention relates to a polyethylene porous hollow fiber membrane and a cartridge for a water purifier and a hollow fiber membrane module including the polyethylene porous hollow fiber membrane.

This application claims priority in September 29, 2010 based on Japanese Patent Application No. 2010-218043 for which it applied to Japan, and uses the content for it here.

Polyethylene porous hollow fiber is widely used as the separation, selective permeation, and isolation of various materials. As a manufacturing method of a polyethylene porous hollow fiber, the method of obtaining a porous hollow fiber membrane by making it porous by heat-processing and extending | stretching, for example, after spinning, dense polyethylene with a suitable draft is known (patent documents 1-3). ).

Moreover, after obtaining the yarn excellent in the orientation property of a liquid crystal by spinning with appropriate draft using the high density polyethylene whose melt flow rate (MFRD) measured according to the code D of JISK7210 is 0.1-1 g / 10min as polyethylene, And the method of heat-processing and extending | stretching are known (patent document 4). That is, after the polyethylene is molded under specific spinning conditions, annealing is performed to form lamellar laminated crystals (stacked lamellar) in the film wall of the excipient. Subsequently, by stretching the excipient, a porous hollow fiber membrane obtained by peeling stacked lamellar livers and growing fibrils connecting lamellar laminated crystals is obtained. Since the hollow fiber membrane has a specific porous structure as described above, it is excellent in mechanical strength. Moreover, it is excellent in not using a solvent in the manufacturing process.

In the porous hollow fiber having a homogeneous structure as described above, in order to increase the amount of permeation, it is conceivable to make the thickness of the porous hollow fiber membrane thinner. However, when the film thickness is made thin, the mechanical strength of the porous hollow fiber membrane is insufficient, and especially when the porosity is increased, sufficient pressure resistance cannot be maintained. On the contrary, when the film thickness is increased, the mechanical strength of the porous hollow fiber membrane increases, but the water permeation amount decreases.

In order to obtain a porous hollow fiber membrane having high mechanical strength and high water permeability, it is conceivable to improve the material strength and rigidity of polyethylene, which is a membrane material. However, when the ratio of the high molecular weight component of polyethylene is increased to improve rigidity, the MFRD is lowered, so that the moldability is lowered, such as the spinning speed at the time of melt spinning is lowered. On the other hand, when the ratio of the low molecular weight component is increased in order to obtain excellent moldability, in order to maintain the pressure resistance in particular, it is necessary to increase the film thickness, and sufficient filtration characteristics cannot be maintained.

Japanese Laid-Open Patent Publication No. 52-137026 Japanese Laid-Open Patent Publication No. 57-66114 Japanese Patent Publication No. 63-42006 Japanese Patent Laid-Open No. 6-277475

The present invention relates to a polyethylene porous hollow fiber membrane formed of a resin composition having excellent moldability, maintaining excellent rigidity, having a large water permeability, and having excellent filtration characteristics, and a cartridge for a water purifier and a hollow fiber membrane module including the polyethylene porous hollow fiber membrane. It is for the purpose of providing.

MEANS TO SOLVE THE PROBLEM This invention employ | adopted the following structures in order to solve the said subject.

[1] A polyethylene porous hollow fiber, wherein the average pore diameter is 0.1 to 0.5 µm, and the pore diameter distribution is 70% or more of the total pore diameter distribution in the pore diameter distribution in the region of ± 0.05 m from the average pore diameter.

[2] The polyethylene porous hollow fiber according to [1], which is formed of a resin composition containing polyethylene that meets the requirements of the following (a) to (d).

(a) Melt flow rate (MFRD) measured based on code D of JISK7110 is 0.1-0.9 g / 10min.

(b) Melt flow rate (MFRG) measured based on code G of JISK7110 is 50-100 g / 10min.

(c) The ratio FRR (G / D) (= MFRG / MFRD) of the MFRD and the MFRG is 50 to 100.

(d) Density is from 0.962 to 0.968 g / cm 3.

[3] The polyethylene porous hollow fiber according to [1] or [2], wherein the ratio Mw / Mn of the mass average molecular weight (Mw) and the number average molecular weight (Mn) in the polyethylene is 8.0 to 12.0.

[4] The polyethylene porous hollow fiber according to any one of [1] to [3], wherein the environmental stress cracking resistance measured in accordance with JIS K 6760 of the polyethylene is 10 to 50 hours.

[5] The polyethylene porous according to any one of the above [1] to [3], wherein an amount of the component having a molecular weight of 1,000 or less in the polyethylene is 2.0% by mass or less, and a component amount of 1 million or more in the molecular weight is 1.5 to 3.0% by mass. Hollow fiber membrane.

[6] The polyethylene porous hollow fiber according to any one of [1] to [5], wherein the inner surface and the outer surface of the hollow fiber membrane are hydrophilized with a hydrophilic copolymer.

[7] The polyethylene porous hollow fiber according to [6], wherein the hydrophilic copolymer is an ethylene-vinyl alcohol copolymer.

[8] A water purifier cartridge, comprising the polyethylene porous hollow fiber according to any one of [1] to [7].

[9] A hollow fiber membrane module, comprising the polyethylene porous hollow fiber according to any one of [1] to [7].

[10] The polyethylene porous hollow fiber according to any one of [1] to [7], wherein the mean flow pore diameter is 0.1 to 0.5 µm and the pore diameter variation is 100% or less.

The polyethylene porous hollow fiber of this invention is formed of the resin composition which is excellent in moldability, maintains excellent rigidity, and has a large amount of permeability, and is excellent in filtration characteristics.

Moreover, this invention provides the water filter cartridge and hollow fiber membrane module provided with the said polyethylene porous hollow fiber membrane.

1 is a pore diameter distribution of a polyethylene porous hollow fiber of the present invention.

<Polyethylene porous hollow fiber membrane>

The polyethylene porous hollow fiber of this invention (henceforth "this hollow fiber membrane") is a resin composition containing polyethylene which satisfies the requirements of the following (a)-(d) (henceforth "this resin composition") It is a porous hollow fiber formed by.

(a) Melt flow rate (henceforth "MFRD") measured based on code D (measurement temperature: 190 degreeC, load: 2.16 kg) of JISK7110 is 0.1-0.9 g / 10min.

(b) Melt flow rate (henceforth "MFRG") measured based on code G (measurement temperature: 190 degreeC, load: 21.6 kg) of JISK7210 is 50-100 g / 10min.

(c) The ratio FRR (G / D) (= MFRG / MFRD) of the MFRD and the MFRG is 50 to 100.

(d) Density is from 0.962 to 0.968 g / cm 3.

If the MFRD of polyethylene is 0.1 g / 10 min or more, the melt viscosity is not too large, and the molding range in which the orientation of the crystal can be improved becomes large. The present invention can also be applied to a field requiring miniaturization such as a water purifier. When MFRD of polyethylene is 0.9 g / 10min or less, melt viscosity is not too small, and the orientation of a crystal | crystallization improves by raising a draft ratio. Therefore, this hollow fiber membrane which fully made porous by extending | stretching at the time of manufacture is obtained. In addition, the rigidity is improved, thinning and high porosity can be improved to improve the transmission performance.

If the MFRG of polyethylene is 50 g / 10 min or more, excellent high formability is obtained. If MFRG of polyethylene is 100 g / 10min or less, favorable environmental stress crack resistance (henceforth "ESCR") will be obtained. Here, the high-speed moldability is evaluated by judging whether the load of the extruder can be lowered and the discharge speed can be increased and the molding temperature can be lowered to the same extent under the same conditions. It is characteristic to do.

As for MFRG of polyethylene, 60-90 g / 10min is preferable.

The ratio FRR (G / D) of MFRG and MFRD of polyethylene generally correlates with the molecular weight distribution, and it tends to increase as the molecular weight distribution becomes wider.

If the FRR (G / D) of polyethylene is 50 or more, the load of the extruder at the time of shaping | molding will not become high too much and it is excellent in high speed moldability. Moreover, excellent stress crack resistance is also obtained. When the FRR (G / D) of polyethylene is 100 or less, this hollow fiber membrane with high impact strength is obtained. As for FRR (G / D) of polyethylene, 60-80 are preferable.

When forming a hollow fiber membrane by the melt-stretching method, since a crystal orientation is raised, spinning is often performed at low temperature than normal extrusion molding. Since this condition is a condition that a load is easily applied to the extruder, it is necessary to improve the fluidity of the molecules. If FRR (G / D) is in the said range, the orientation of a crystal | crystallization can be made favorable, improving the flow of a molecule. Therefore, not only the uniformity of the membrane pore diameter is increased, but also the porosity is increased.

If the density of polyethylene is 0.962 g / cm <2> or more, the quantity of the low crystalline component is small, the porosity becomes high, and sufficient permeability is obtained. If the density of polyethylene is 0.968 g / cm 3 or less, ESCR for 20 hours or more is maintained.

 Density is measured by the method based on JISK7112 (ASTM D 1505).

As for the ratio Mw / Mn of the mass mean molecular weight of a polyethylene (henceforth "Mw"), and a number average molecular weight (henceforth "Mn"), 8.0-12.0 are preferable. When Mw / Mn is 8.0 or more, ESCR improves because the quantity of a high molecular weight component increases. When Mw / Mn is 12.0 or less, low molecular weight components, such as wax, become small, and it is easy to suppress that the said low molecular weight component elutes in water in drinking water applications, such as a water purifier and water supply. Moreover, narrowing of molecular weight distribution improves the rigidity of this hollow fiber membrane.

The ratio Mw / Mn of polyethylene is computed from the measurement by high temperature gel permeation chromatography (henceforth "high temperature GPC"). High temperature GPC means GPC which measures in the state which heated and dissolved the sample. The ratio Mw / Mn is computed using the analytical curve created using polystyrene as a standard sample in the measurement by high temperature GPC.

As a measuring apparatus, brand names "150-GPC", "Alliance GPCV 2000" (above, Waters Corporation make), etc. are mentioned.

0.1-2.0 mass% is preferable with respect to 100 mass% of all the copolymers which comprise polyethylene, and, as for the component amount (henceforth "FL") of molecular weight 1000 or less in polyethylene, 0.2-1.0 are more preferable, 0.3-0.7 are especially preferable. FL is what is called a low molecular weight component among the components of polyethylene. If it is 0.1 mass% or more, it contributes to the improvement of flexibility, and if it is 2.0 mass% or less, a bad smell does not become a problem and it is suitable also for application to food use etc.

1.5-3.0 mass% is preferable with respect to 100 mass% of all the copolymers which comprise polyethylene, and, as for the component amount (henceforth "FH") of a molecular weight of 1 million or more in polyethylene, 2.0-3.0 are more preferable, 2.5-3.0 are especially preferable. When FH is 1.5 mass% or more, since the quantity of a high molecular weight component increases, long-term characteristics, such as stress crack resistance and ESCR, are improved. When FH is 3 mass% or less, since sufficient fluidity | liquidity is easy to be obtained at the time of shaping | molding, an unmelted gel will not generate | occur | produce easily and a non-porous part contrary to intention at the time of extending | stretching will not generate | occur | produce.

FL and FH are calculated | required from the high temperature GPC same as the ratio Mw / Mn mentioned above. That is, in the chart of the molecular weight distribution obtained by the measurement by high temperature GPC, FL is calculated | required from the ratio of the area of the part of molecular weight 1000 or less with respect to the area of the whole molecular weight distribution. Similarly, FH is calculated | required from the ratio of the area of the part with a molecular weight of 1 million or more with respect to the area of the whole molecular weight distribution.

10-50 hours are preferable, as for ESCR (environmental stress cracking resistance) of polyethylene, 15-40 hours are more preferable, and 15-30 hours are especially preferable. When ESCR is 10 hours or more, this hollow fiber membrane which does not crack easily even if a stress is applied is obtained. In addition, when performing porousization (stretching) by making a crack generate | occur | produce between crystal components at the time of manufacture, the fracture of this hollow fiber membrane does not occur easily. When ESCR is 50 hours or less, since density improves and crystallinity also improves, porosity improves and favorable pore is formed.

ESCR of polyethylene is measured by the positive strain environmental stress cracking test based on JISK6760. ESCR is the time when the probability of a crack generate | occur | producing by environmental stress becomes 50%.

As polyethylene contained in this resin composition, polyethylene with few short branched chains is especially preferable from a viewpoint of porosity. MFRD, MFRG, and molecular weight of polyethylene can be adjusted by, for example, using a molecular weight modifier such as hydrogen in the production of polyethylene.

As a commercial item of polyethylene, brand names "H6670B" and "H6430BM" (above, SCG Chemical company make) are mentioned, for example.

As for this resin composition, the composition which has polyethylene as a main component is preferable. The composition containing polyethylene as a main component is a composition whose content of polyethylene is 50 mass% or more. 80 mass% or more is preferable with respect to 100 mass% of this resin composition, as for content of polyethylene in the composition which has polyethylene as a main component, 90 mass% or more is more preferable, 100 mass% is especially preferable.

As another polymer component other than polyethylene contained in this resin composition, other olefin monomers, such as a polypropylene, etc. are mentioned, for example.

When this resin composition contains polymer components other than polyethylene, MFRD, MFRG, FRR (G / D), density, Mw / Mn, ESCR, FL, and FH in all the polymers containing them are in the above ranges. It is desirable to be mine.

Moreover, a small amount of additives, fillers, etc. may be added to this resin composition in the range which does not impair the effect of this invention.

As an additive, antioxidant, a lubricating agent, the nucleating agent which raises a crystallization rate and improves moldability, etc. are mentioned.

As antioxidant, hindered phenol type antioxidants, such as brand names "IRGANOX 1076" and "IRGANOX 1010" (above, Chiba Specialty Chemicals make), etc. are mentioned, for example.

As a lubricating agent, calcium stearate and magnesium stearate are mentioned, for example. 800 ppm or less is preferable, 600 ppm or less is more preferable, and, as for the addition amount of a lubricant, 300 ppm or less is further more preferable.

Examples of the nucleating agent include pigments such as titanium oxide.

Moreover, as an additive, an antistatic agent, a light stabilizer, an ultraviolet absorber, an antifog agent, an organic peroxide, etc. are mentioned.

Examples of the filler include talc, silica, carbon, mica, calcium carbonate, magnesium carbonate, wood flour, and the like. Moreover, you may add a titanium oxide and an organic pigment in a masterbatch as needed.

This hollow fiber membrane may be a hollow fiber membrane formed of a single membrane, or may be a composite hollow fiber membrane formed of a composite membrane in which a plurality of membranes are stacked.

Although the thickness of this hollow fiber membrane is not specifically limited, It is preferable that a hollow fiber membrane outer diameter is 100-2000 micrometers. When the hollow fiber membrane outer diameter is 100 µm or more, the gap between the hollow fiber membranes is easily taken at the time of manufacturing the hollow fiber membrane module or the like, and the resin for potting easily enters between the hollow fiber membranes. If a hollow fiber membrane outer diameter is 2000 micrometers or less, even when the hollow fiber membrane module etc. which used many hollow fiber membranes were manufactured, the size of the whole module can be made small. Thereby, since the volume of a potting process part becomes small, it is easy to suppress the fall of the dimensional precision by shrinkage of the resin for potting at the time of a potting process.

As for the porosity of this hollow fiber membrane, 30-80 volume% is preferable with respect to 100 volume% of whole this hollow fiber membranes. If the porosity is 30% by volume or more, the amount of permeability tends to increase, and excellent filtration characteristics are likely to be obtained. When the porosity is 80% by volume or less, mechanical strength such as pressure resistance is improved.

The size of the pores of the hollow fiber membrane is not particularly limited and may be a size that satisfies sufficient filtration characteristics and mechanical strength.

It is preferable that the membrane surface (inner surface and outer surface) of this hollow fiber membrane is hydrophilized by a hydrophilic polymer.

The said hydrophilic copolymer is a copolymer obtained by copolymerizing the monomer mixture containing 20 mol% or more of ethylene and 10 mol% or more of a hydrophilic monomer. The said hydrophilic copolymer may be any type of copolymer, such as a random copolymer, a block copolymer, and a graft copolymer.

When the content of ethylene in the hydrophilic copolymer is 20 mol% or more, the affinity of the hydrophilic copolymer with respect to the present hollow fiber membrane is increased, and the hydrophilic copolymer can be sufficiently covered. Therefore, the film surface of this hollow fiber membrane can be fully hydrophilized.

As a hydrophilic monomer, vinyl compounds, such as vinyl alcohol, (meth) acrylic acid and its salt, hydroxyethyl (meth) acrylate, polyethyleneglycol (meth) acrylic acid ester, vinylpyrrolidone, acrylamide, are mentioned, for example. Can be. Especially, vinyl alcohol is especially preferable.

Only 1 type may be used for a hydrophilic monomer and it may use 2 or more types together.

The hydrophilic copolymer may contain third components other than ethylene and a hydrophilic monomer.

As a 3rd component, vinyl acetate, (meth) acrylic acid ester, a vinyl alcohol fatty acid ester, the foamed compound of a vinyl alcohol, butyral compound, etc. are mentioned, for example.

3-30 mass% is preferable with respect to 100 mass% of this hollow fiber membrane, and, as for the coating amount of a hydrophilic copolymer, 7-15 mass% is more preferable. When the coating amount of the hydrophilic copolymer is 3% by mass or more, the affinity with water of the present hollow fiber membrane is improved, and the water permeation amount is improved. When the coating amount of the hydrophilic copolymer is 30% by mass or less, it is easy to suppress the blocking of pores of the present hollow fiber membrane by the hydrophilic copolymer and the water permeation rate is improved.

In the pore diameter distribution of the hollow fiber membranes, a narrow distribution is preferable. Specifically, when the average pore diameter ± 0.05 μm is in the range of 70% or more, the fractionation performance is not only sharp, but also the effect of lowering the filtration resistance of the entire membrane is reduced because the presence ratio of extremely small pore diameters that do not contribute to the permeability is lowered. As a result, the pitcher performance is improved.

Moreover, since the ratio of the average pore diameter ± 0.05 micrometer is less than 70% of the whole pore diameter distribution, that is, the ratio of the extremely small pore diameter becomes 15% or more of the whole, the permeability falls because the filtration resistance of the whole membrane increases. .

(Manufacturing method)

This hollow fiber membrane can be manufactured by the method which has the following spinning process, an extending process, and an inverted hydrophilization process, for example.

Spinning step: A step of spinning the resin composition to obtain an unstretched hollow fiber membrane precursor.

Stretching process: The process of extending | stretching a hollow fiber membrane precursor, making it porous, and obtaining a porous hollow fiber membrane.

Port hydrophilization process: A process of imparting port hydrophilicity to the membrane surface of a porous hollow fiber membrane.

Spinning process:

For example, by using the composite nozzle mold in which a plurality of annular discharge ports are arranged concentrically, the resin composition is extruded from the nozzle mold and cooled and solidified in an unstretched state while appropriately adjusting the extrusion speed and the winding speed. . Thereby, an unstretched hollow fiber membrane precursor is obtained.

It is preferable that the discharge temperature of this resin composition is more than melting | fusing point of polymers, such as polyethylene, and 10-100 degreeC higher than the said melting point. It is preferable to take out discharged material at the pulling speed of 0.1-3 m / sec in 10-40 degreeC atmosphere.

Drawing process:

The unstretched hollow fiber membrane precursor obtained by melt spinning is subjected to a moderate heat treatment (anneal treatment) at or below the melting point before stretching.

The suit heat treatment is preferably performed at 105 to 120 ° C. for 8 to 16 hours. If temperature is 105 degreeC or more, this hollow fiber membrane with favorable quality will be easy to be obtained. When temperature is 120 degrees C or less, sufficient elongation will be easy to be obtained, the stability at the time of extending | stretching will improve, and extending | stretching in high magnification will become easy. Moreover, when processing time is 8 hours or more, this hollow fiber membrane with favorable quality will be easy to be obtained.

As for extending | stretching, the two stage extending | stretching which carries out hot drawing following cold drawing, or the multistage extending | stretching which divides and implements hot drawing into 2 or more multistage multistage | strand is preferable after cold drawing. Moreover, in order to obtain the dimensional stability of the porous hollow fiber obtained by the said extending | stretching, heat setting is performed in the state which suited the porous hollow fiber membrane or relaxed slightly in 40% or less of range.

The stretching is preferably slow stretching.

Cold drawing is a process that causes structural breakdown of the film under relatively low temperatures and causes micro cracking. The temperature of cold drawing is performed at a relatively low temperature within the range from 0 degreeC to the temperature 50 degreeC or more lower than melting | fusing point of the polymer to be used (for example, 0-80 degreeC when the polymer in this resin composition is polyethylene only). It is desirable to. If cold stretching is performed at a temperature exceeding the above range, the occurrence of microcracks is reduced, and there is a fear that the pores are reduced.

Hot stretching is a process of enlarging the micro cracking which generate | occur | produced in cold drawing, and forming a pore. Although it is preferable to perform heat drawing under comparatively high temperature, it carries out at the temperature which does not exceed melting | fusing point of the polymer to be used.

What is necessary is just to select suitably according to the hole diameter made into the objective as a thermal draw ratio, and it is preferable to set it as 3-7 times with respect to the length of the hollow fiber membrane precursor before extending | stretching from a process stability viewpoint.

It is preferable to make hot drawing into multistage drawing of 2 or more steps. By using multistage stretching, it becomes easy to form pores while preventing the yarn diameter from becoming too thin at the time of stretching.

Moreover, it is preferable to perform hot drawing at low speed. In the case of low-speed stretching, it is easy to form pores while preventing the yarn diameter from becoming too thin at the time of stretching.

In order to implement a heat set effectively, it is preferable that a heat set temperature is more than extending | stretching temperature and below melting | fusing point temperature.

Port hydrophilization process:

As a method of coating a hydrophilic copolymer, the method of drying this hollow fiber membrane after immersing this hollow fiber membrane in the solution (henceforth a "copolymer solution") which melt | dissolved the said hydrophilic copolymer in a solvent is mentioned, for example. have. As a method of immersing this hollow fiber membrane in a copolymer solution, the method of immersing twice or more in the copolymer solution of the same density may be sufficient, and the method of performing immersion 2 or more times using the solution from which concentration differs may be sufficient. .

As a solvent, a water miscible organic solvent is preferable.

As a water miscible organic solvent, alcohol, such as methanol, ethanol, N-propanol, isopropyl alcohol, dimethyl sulfoxide, dimethylformamide, etc. are mentioned, for example. These solvents may use only 1 type, and may use 2 or more types together. Moreover, since these solvents improve the solubility of a hydrophilic copolymer, it is preferable to set it as the liquid mixture with water.

When drying the hollow fiber membrane coated with a hydrophilic copolymer, alcohols having a boiling point of less than 100 ° C in terms of easily forming a vapor-containing atmosphere of the solvent, ie, low vapor pressure of the solvent and low toxicity to the human body (eg For example, it is particularly preferable to use a mixed solvent of methanol, ethanol, isopropyl alcohol, etc.) and water.

The mixing ratio of the water-miscible organic solvent and water may be in a range in which the water solubility of the hydrophilic copolymer is not excessively reduced without decreasing the water permeation amount of the present hollow fiber membrane. Although it changes also with the kind of hydrophilic copolymer specifically, when using ethanol as an organic solvent, the ratio of ethanol / water is preferable 90/10-30/70 (vol%).

0.1-10 mass% is preferable with respect to a total of 100 mass% of a solvent and a hydrophilic copolymer, and, as for content of the hydrophilic copolymer in a copolymer solution, 0.5-5 mass% is more preferable. When content of a hydrophilic copolymer is 0.1 mass% or more, it becomes easy to coat | cover a hydrophilic copolymer uniformly to this hollow fiber membrane. When content of a hydrophilic copolymer is 10 mass% or less, it becomes easy to suppress that the viscosity of a copolymer solution becomes too large and to suppress that the pore of this hollow fiber membrane is blocked by a hydrophilic copolymer.

The viscosity of the copolymer solution at the time of performing the immersion treatment is preferable because the viscosity thereof decreases, and the permeability of the solution to the hollow fiber membrane is improved. Moreover, since the immersion process can be performed stably, it is preferable that it is below the boiling point of a copolymer solution.

Although immersion processing time changes with film thickness, pore diameter, and porosity of this hollow fiber membrane to be immersed, it is preferable to set it as the range of several seconds-several minutes.

After immersing in the copolymer solution and before drying the hollow fiber membrane, the hollow fiber membrane is at least 30 in an atmosphere in which 3% by volume or more of the vapor of the organic solvent is contained and the temperature is in the range of room temperature or lower than the boiling point of the solvent. The setting process which stays for more than a second is performed.

 The purpose of the above treatment is to (1) prevent the blockage of pores by forming a film of a hydrophilic copolymer on the surface of the nodules of the microfibrils and stacked lamellas constituting the hollow fiber membrane, and (2) the microfibrils The slit-like pores are largely hardened to form elliptic pores, the permeability is increased, and the affinity with the treated water is increased.

As a drying process of this hollow fiber membrane after a setting process, well-known drying methods, such as vacuum drying and hot air drying, are mentioned.

The drying temperature should just be a temperature range in which this hollow fiber membrane does not deform | transform by heat. For example, in the case of this hollow fiber membrane which consists of polyethylene, 120 degreeC or less is preferable and, as for a drying temperature, 40-70 degreeC is especially preferable.

In addition, the manufacturing method of this hollow fiber membrane is not limited to the method mentioned above. For example, the method which does not implement a port hydrophilization process may be sufficient.

<Water purifier cartridge>

The water purifier cartridge of the present invention is a module provided with the present hollow fiber membrane described above. As the cartridge for water purifier of the present invention, except for using the hollow fiber membrane, the same form as that of a known cartridge for water purifier is used.

For example, a faucet direct type water purifier cartridge, a feature type water purifier cartridge, a stationary water purifier cartridge installed and used on a sink, and an undersink type water purifier cartridge provided in a storage space under the sink.

<Hollow fiber membrane module>

The hollow fiber membrane module of this invention is a module provided with this hollow fiber membrane mentioned above. The hollow fiber membrane module of the present invention uses the same form as the known hollow fiber membrane module except for using the hollow fiber membrane.

For example, the hollow fiber membrane module of the well-known form which bundled hundreds of this hollow fiber membrane, inserted it in the normal housing | casing, and enclosed this composite hollow fiber membrane with the sealing material (resin for potting) is mentioned.

Example

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples. However, this invention is not limited by the following description.

(Melt flow rate (MFR))

About MFR of polyethylene, MFRD (unit: g / 10min) was measured based on code D (measurement temperature: 190 degreeC, load: 2.16 kg) of JIS K 7210, and also code G (measurement temperature of JIS K 7210). : MFRG (unit: g / 10min) was measured based on 190 degreeC and a load of 21.6 kg.

Moreover, FRR (G / D) (= MFRG / MFRD) was calculated | required from these measurement results.

(density)

The density (unit: kg / m <3>) of polyethylene was measured based on JISK7112.

(Ratio Mw / Mn)

The ratio Mw / Mn of polyethylene calculated | required Mw and Mn from the calibration curve obtained by the measurement by GPC (high temperature GPC) of the following conditions, respectively, and computed it. The calibration curve measured the standard sample of polystyrene, and computed it in 3rd order using the polyethylene conversion constant (0.48). The column used the following three columns connected in series.

Measuring conditions :

Measuring device: `` 150-GPC '' (manufactured by Waters)

Column: `` Shodex GPC AT-807 / S '' (Showa Denko) (1), `` Tosoh TSK-GEL GMH6-HT '' (Tosoh Corporation) (2)

Solvent: 1,2,4-trichlorobenzene

Column temperature: 140 ℃

Sample concentration: 0.05 mass% (injection amount: 500 μl)

Flow rate: 1.0 ml / min

Sample dissolution temperature: 160 ℃

Sample dissolution time: 2.5 hours

Moreover, about polyethylene, when a shoulder peak is observed in the chart of the molecular weight distribution measured by the said high temperature GPC, Mw and Mn of each component, such as a low molecular weight component and a high molecular weight component, are approximated by a Gaussian distribution, and those The blending ratio of the components was calculated.

(FL, FH)

The molecular weight (FL) (unit: mass%) of the molecular weight 1000 or less of polyethylene, and the component amount (FH) (unit: mass%) of 1 million or more of molecular weights measured and calculated molecular weight distribution by the high temperature GPC of the following conditions. That is, in the chart of the molecular weight distribution obtained by the measurement by the high temperature GPC of the following conditions, the ratio of the area of the part of molecular weight 1000 or less with respect to the area of the whole molecular weight distribution, or the ratio of the area of the part of molecular weight 1 million or more is calculated | required, and FL And FH were calculated. The column used the following three columns connected in series.

Measuring conditions :

Measuring device: 「Alliance GPCV 2000」 (made by Waters)

Column: `` AT-807S '' (Showa Denko) (1), `` GMHHR-H (S) HT '' (2)

Solvent: 1,2,4-trichlorobenzene

Column temperature: 140 ℃

Sample concentration: 20 mg / 10 ml solvent

Flow rate: 1.0 ml / min

Sample dissolution temperature: 140 ℃

Sample dissolution time: 1 hour

(ESCR)

ESCR (environmental stress cracking resistance, unit: time) of polyethylene was measured by the static strain environmental stress cracking test based on JISK6760. As a test liquid, the 10 mass% aqueous solution of brand name "Igeparu CO-630" (made by Rhodia Corporation) was used. The time at which the probability of cracking due to environmental stress was 50% was measured, and the value of ESCR was set.

(Coating amount of hydrophilic copolymer)

The coating amount W (unit: mass%) of the hydrophilic copolymer was calculated by the following formula.

W = (X-Y) / Y × 100

In the formula, X is the dry film mass (unit: g) after the hydrophilization treatment, and Y is the dry mass (unit: g) of the hollow fiber membrane before the treatment.

(Permeability)

The water permeation amount (unit: m 3 / m 2 · hour · MPa) of the obtained hollow fiber membrane was made by tying the hollow fiber membrane in a U shape to fix the end of the hollow fiber membrane with urethane resin to produce a hollow fiber membrane module having an effective membrane area of 70 to 90 cm 2. Then, ion-exchanged water was filtered at a differential pressure of 0.1 MPa, and the water permeability at that time was measured.

(Bubble point, porosity, hole diameter distribution)

The obtained hollow fiber membrane was bundled in a U-shape to fix an end portion of the hollow fiber membrane with a urethane resin, a hollow fiber membrane module having an effective membrane area of about 50 m 2 was produced, and the hollow fiber membrane module was made to have a concentration of 95 so as to completely lock the hollow fiber membrane module. It was immersed in ethanol or more than%. After sucking 100 mL or more of ethanol from the inside of a hollow fiber membrane so that the porous inside of a hollow fiber membrane might be fully wetted with ethanol, nitrogen was sent in the inside of a hollow fiber membrane as it was immersed, and the air pressure was boosted at 1 kPa every 10 seconds. The bubble was generated from almost the entire surface of the hollow fiber membrane, and the nitrogen pressure when the gap between the bubble generation points was within 1 mm was defined as the bubble point (B. P.). In addition, the relationship between bubble point P (pressure) and an average hole diameter is as showing by the following formula.

P = 2σcosθ / r

Where σ is the surface tension of ethanol, θ is the contact angle between ethanol and the hollow fiber membrane, and r is the average pore radius.

In addition, the porosity (unit: volume%) was measured using the mercury porosimeter type 221 (made by Carlo Elbas company).

The pore diameter distribution and the average pore diameter of the hollow fiber membrane are PMI's palm poshimeter based on the bubble point method (ASTM F316-86) PMI's palm porosimetry CFP-1200AE (porous material automatic pore diameter distribution measuring system) It measured using the fluorine-type surfactant fluorine nut FC-72 (made by 3M Corporation) as a measurement solvent.

The ratio (%) which occupies in the pore diameter (micrometer) and pore diameter distribution of a polyethylene porous hollow fiber membrane is shown in FIG. Moreover, the range of the average hole diameter +/- 0.05 micrometer which influences the flow volume most from the measured pore diameter distribution was computed by integration.

(Average flow hole diameter)

The average flow rate hole diameter was measured by PMI's palm porimeter CFP-1200AE (porous material automatic pore diameter distribution measuring system) according to ASTM F316-86.

(Opening diameter deviation)

The pore diameter deviation was measured in accordance with ASTM F316-86, PMI Co., Ltd. palm porometer CFP-1200AE (porous material automatic pore diameter distribution measurement system), and the flow rate when the cumulative flow rate was 100% was 5%. The hole diameter used as% is made into the minimum hole diameter when it is the maximum hole diameter and 95%, and it calculated and calculated | required by the following formula | equation.

Opening Diameter Deviation (%) = [(5% Maximum Hole Diameter-95% Minimum Hole Diameter) / Average Flow Hole Diameter] × 100

Example 1

High density polyethylene (trade name "H6670B", manufactured by SCG Chemical, density 0.966 g / cm 3, MFRD: 0.7 g / 10 min, MFRG: 54 g / 10 minutes, FRR (G / D) = 77, FL: 0.38 mass%, FH: 2.64 mass%, Mw / Mn = 8.8, ESCR: 20 hours).

Moreover, about the said high density polyethylene, the three components which approximated the chart of the molecular weight distribution measured by high temperature GPC by Gaussian distribution were as follows. The said chart had the shoulder peak of 1 point each in molecular weight 1 million vicinity and molecular weight 5000 vicinity.

1) Mn: 1.99 × 10 ⁴ Mw: 1.09 × 10 ⁵ Compounding rate: 88%

2) Mn: 2.76 × 10 ³ Mw: 5.25 × 10 ³ Compounding rate: 6%

3) Mn: 7.52 × 10 ⁵ Mw: 9.74 × 10 ⁵ Compounding rate: 6%

Spinning process:

Using the said resin composition, melt spinning was performed at the discharge temperature of 170 degreeC, and the winding speed of 70 m / min using the nozzle for hollow fiber manufactures in which the circular-shaped discharge port was arranged concentrically. Further, the yarn was wound around the yarn discharged from the nozzle while uniformly flowing the cooling wind at a temperature of 20 ° C. and a wind speed of 0.5 m / sec to obtain an unstretched composite hollow fiber membrane precursor.

Drawing process:

The obtained unstretched composite hollow fiber membrane precursor was wound around bobbin and subjected to annealing for 16 hours in 115 ° C air. The composite hollow fiber membrane precursor after the annealing treatment was cold drawn 1.5 times between the rollers maintained at 30 ° C., and then hot drawn between the rollers so as to have a maximum draw amount of 6.0 times in a heating furnace heated at 117 ° C., and further to 118 ° C. By carrying out 20% relaxation in the heated furnace, the polyethylene porous hollow fiber membrane was obtained by making the total draw ratio at the time of winding (magnification with respect to the unstretched composite hollow fiber membrane precursor) 5 times.

Port hydrophilization process:

Next, 1.5 mass% of ethylene-vinyl alcohol copolymers (brand name "Soanol DC3203", the Nippon Synthetic Chemical Co., Ltd. make) of ethylene content of 32 mol% were added to a 70 degreeC ethanol / water = 40/60 (vol%) mixed solution. It melt | dissolved and the copolymer solution was prepared. After the said hollow fiber membrane was immersed in the said copolymer solution for 30 second, the hollow fiber membrane was pulled up, and the guide part squeezed and dropped some of the copolymer solution adhering to the surface of the hollow fiber membrane. Subsequently, in the atmosphere of 40 volume% of ethanol vapor concentration and 60 degreeC, the hollow fiber membrane was made to stand at 90 degrees of standing angles, and it stayed for 80 second, and the hydrophilic polymer was made to adhere uniformly to the surface inside the pore of a hollow fiber membrane. Then, it dried with hot air of 70 degreeC, and removed the solvent. The adhesion rate of the ethylene-vinyl alcohol copolymer after drying was 10.5 mass% with respect to 100 mass% of hollow fiber membranes.

As a result of observing the obtained polyethylene porous hollow fiber membrane with a scanning electron microscope, the inner and outer surfaces of the polyethylene porous hollow fiber membrane and the microporous surface were uniformly covered with a thin film of ethylene-vinyl alcohol copolymer.

Moreover, the bubble point which shows the pore diameter of a membrane was 122 kPa. The public rate was 73.5% by volume.

When the measurement was carried out using PMI Co., Ltd. palm porosimeter using fluorine-based surfactant fluorine nut FC-72 (manufactured by 3M Corporation) as the measurement solvent, the average pore diameter was 0.3123 µm and the average pore diameter ± 0.05 µm. It was a film with a sharp pore diameter distribution in which the proportion of the total pore diameter distribution was 85.5%.

[Example 2]

High-density polyethylene (trade name "H6430BM", manufactured by SCG Chemical, Inc., density: 0.966 g / cm 3, MFRD: 0.4 g / 10 min, MFRG: 30 g, manufactured by a three-stage continuous polymerization method using a Ziegler type catalyst as the resin composition. / 10 min, FRR (G / D) = 75, FL: 0.66 mass%, FH: 3.00 mass%, Mw / Mn = 12, ESCR: 25 hours).

Moreover, about the said high density polyethylene, the three components which approximated the chart of the molecular weight distribution measured by high temperature GPC by Gaussian distribution were as follows. The said chart had the shoulder peak of 1 point each in molecular weight 1 million vicinity and molecular weight 5000 vicinity.

1) Mn: 2.81 × 10 ³ Mw: 6.57 × 10 ³ Compounding rate: 9%

2) Mn: 2.24 × 10 ⁴ Mw: 1.15 × 10 ⁵ Compounding rate: 84%

3) Mn: 4.68 × 10 ⁵ Mw: 9.40 × 10 ⁵ Compounding rate: 7%

Using the said resin composition, the polyethylene porous hollow fiber membrane hollow fiber membrane was obtained like Example 1 except having set the winding speed in melt spinning to 40 m / min. Moreover, the port hydrophilization process similar to Example 1 was implemented. The adhesion rate of the ethylene-vinyl alcohol copolymer was 10.5 mass% with respect to 100 mass% of hollow fiber membranes.

As a result of observing the obtained polyethylene porous hollow fiber membrane with a scanning electron microscope, the inner and outer surfaces of the polyethylene porous hollow fiber membrane and the microporous surface were uniformly covered with a thin film of ethylene-vinyl alcohol copolymer.

Moreover, the bubble point which shows the pore diameter of a membrane was 127 kPa. The public rate was 73.8% by volume.

When the measurement was carried out using PMI Co., Ltd. palm porosimeter using fluorine-based surfactant fluorine nut FC-72 (manufactured by 3M Corporation) as the measurement solvent, the average pore diameter was 0.3155 µm and the average pore diameter ± 0.05 µm. It was a film with a sharp hole diameter distribution in which the ratio which occupies for the whole hole diameter distribution shows 87.3%.

Comparative Example 1

High-density polyethylene (trade name "HY540", manufactured by Nippon Polyethylene, Density 0.960 g / cm 3, MFRD: 1.0 g / 10 min, MFRG: 45 g / 10 min, manufactured by slurry polymerization method using a Ziegler catalyst as a resin composition, FRR (G / D) = 45, FL: 0.37 mass%, FH: 1.07 mass%, Mn: 1.8 x 10 ⁴ , Mw: 1.18 x 10 ⁵ , Mw / Mn = 6.6, ESCR: 100 hours).

With respect to the high-density polyethylene, no shoulder peak or the like was observed in the molecular weight distribution measured at high temperature GPC around 1 million molecular weight.

Spinning process:

Except having made discharge temperature 180 degreeC using the said resin composition, it melt-spun similarly to Example 1 and obtained the unstretched composite hollow fiber membrane precursor.

Drawing process:

The obtained unstretched composite hollow fiber membrane precursor was wound around bobbin and annealed for 16 hours in 115 ° C air. The hollow fiber membrane after the annealing treatment was cold drawn 1.5 times between the rollers held at 30 ° C., and then hot drawn between the rollers so as to have a maximum draw amount of 6.0 times in the heating furnace heated at 117 ° C., and further heated to 118 ° C. The polyethylene porous hollow fiber membrane hollow fiber membrane was obtained by carrying out formal relaxation in a heating furnace and making 6 times the total draw ratio (magnification with respect to an unstretched composite hollow fiber membrane precursor) at the time of winding.

Port hydrophilization process:

Port hydrophilization was performed in the same manner as in Example 1.

As a result of observing the obtained polyethylene porous hollow fiber membrane with a scanning electron microscope, the inner and outer surfaces of the polyethylene porous hollow fiber membrane and the microporous inner surface were uniformly covered with a thin film of ethylene-vinyl alcohol copolymer.

The bubble point indicating the pore diameter of the membrane was 132 mm 3. The public rate was 71.3% by volume.

When measured using a fluorine-based surfactant fluorine nut FC-72 (manufactured by 3M Corporation) as a measurement solvent using a palm porosimeter manufactured by PMI, the average pore diameter was 0.3813 µm and the average pore diameter ± 0.05 µm. As the ratio of the total pore diameter distribution represented 58%, the pore diameter distribution had a wider film than the example.

Table 1 shows the results of evaluating the water permeability of the polyethylene porous hollow fiber obtained in each example.

As shown in Table 1, in Examples 1 and 2 which are the polyethylene porous hollow fiber membranes of this invention, there were many water permeability and was excellent in filtration characteristics. Moreover, the used resin composition had sufficient fluidity | liquidity and was also excellent in moldability. Moreover, since the quantity of the low molecular weight component is not increased in order to improve moldability, the outstanding rigidity is also maintained.

In addition, the polyethylene porous hollow fiber of Example 2 had a higher porosity than the polyethylene porous hollow fiber of Example 1, had a large water permeability, and was excellent in filtration characteristics.

On the other hand, the polyethylene porous hollow fiber of Comparative Example 1 using polyethylene having an extremely low density had a significantly low permeability and poor filtration characteristics.

In Example 1 which is the polyethylene porous hollow fiber of this invention, the average pore diameter was 0.3123 and the ratio which occupies for the whole pore diameter distribution of the pore diameter range of the said average pore diameter ± 0.05 micrometer was 85.5%, and showed a high result. Moreover, in Example 2 which is the polyethylene porous hollow fiber of this invention, the average pore diameter was 0.3155 and the ratio which occupies for the whole pore diameter distribution of the pore diameter range of the said average pore diameter ± 0.05micrometer was 87.3%, and showed a high result.

On the other hand, in Comparative Example 1 using polyethylene having a too low density, although the average pore diameter of the polyethylene porous hollow fiber membrane was 0.3813, the proportion of the total pore diameter distribution in the pore diameter range of the average pore diameter ± 0.05 μm was 58.0%. Low.

Industrial availability

Since the polyethylene porous hollow fiber of this invention is excellent in filtration characteristics and membrane strength, it can be used suitably for the filtration of various types of various to-be-processed liquids.

Claims (10)

Polyethylene porous hollow fiber having an average pore diameter of 0.1 to 0.5 µm and a pore diameter distribution of at least 70% of the total pore diameter distribution of the pore diameter distribution in a region of ± 0.05 m from the average pore diameter. ). The method of claim 1,
Polyethylene porous hollow fiber formed by resin composition containing polyethylene which satisfy | fills requirements of following (a)-(d):
(a) Melt flow rate (MFRD) measured based on code D of JISK7110 is 0.1-0.9 g / 10min;
(b) the melt flow rate (MFRG) measured according to code G of JIS K 7210 is 50 to 100 g / 10 minutes;
(c) the ratio FRR (G / D) (= MFRG / MFRD) of the MFRD and the MFRG is 50 to 100;
(d) Density is between 0.962 and 0.968 g / cm 3. 3. The method according to claim 1 or 2,
The polyethylene porous hollow fiber of the ratio Mw / Mn of the mass mean molecular weight (Mw) and the number average molecular weight (Mn) in the said polyethylene is 8.0-12.0. The method according to any one of claims 1 to 3,
Polyethylene porous hollow fiber having an environmental stress crack resistance of 10 to 50 hours, measured according to JIS K 6760 of the polyethylene. The method according to any one of claims 1 to 3,
Polyethylene porous hollow fiber membrane whose component amount of the molecular weight 1000 or less in the said polyethylene is 2.0 mass% or less, and is 1.5-3.0 mass% of component amounts of 1 million or more of molecular weight. 6. The method according to any one of claims 1 to 5,
A polyethylene porous hollow fiber in which the inner surface and the outer surface of the hollow fiber membrane are hydrophilized with a hydrophilic copolymer. The method according to claim 6,
The polyethylene porous hollow fiber as said hydrophilic copolymer is an ethylene-vinyl alcohol copolymer. The water purifier cartridge provided with the polyethylene porous hollow fiber of any one of Claims 1-7. The hollow fiber membrane module provided with the polyethylene porous hollow fiber of any one of Claims 1-7. The method according to any one of claims 1 to 7,
Polyethylene porous hollow fiber with an average flow volume hole diameter of 0.1-0.5 micrometer, and a pore diameter variation of 100% or less.

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