JP2001162146A - Carrier film for filtration - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carrier film for a filter which highly efficiently traps fine particles, filtration amount of which is voluminous, of which through holes have small pore diameters as 0.1 to 10 μm, and which has high affinity with water, excellent mechanical strength and therefore, excellent durability, and also which traps foreign matters contained in protein by the carrier even for a large flow amount in the filtration of protein. SOLUTION: The carrier film is a porous polyamide film having a porous structure with fine through-holes and having 15 to 85% porosity, 0.01 to 5 μm pore diameter and 10 to 50 μm thickness. In the cross section of the film, the film has a laminated structure of a layer consisting of a fine porous material and a layer having relatively large vacancies or openings, with the two layers connected with each other by the fine through-holes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filtration support membrane useful for microfiltration of proteins and the like in the bioindustry, fermentation industry, food industry and the like.

[0002]

2. Description of the Related Art Conventional microfiltration of proteins involves the use of a 0.1 micron filter to separate and purify proteins from a protein suspension.
It is necessary to capture protein aggregate particles of 1 to 10 μm, and various filters have been used in the fermentation industry.

[0003] Filtration of occlusions (supports) of protein aggregates involves molecular interactions other than covalent disulfide bonds, such as Van der Waals's forces, electrostatic forces, hydrophobic interactions, hydrogen bonding forces. (J. Memb. Sci. 130, (1997) 23-3
It is said that it may be due to the adsorption action such as 0).
It has long been said that diatomaceous earth and the like capture fine particles and, at the same time, form a dense layer on the surface of the cake, and serve to remove finer particles before they reach the filter.

JP-A-10-265462 discloses that a solution of a pyrimidine derivative is brought into contact with an acidic zeolite, the derivative is adsorbed at an appropriate pH value, and then the derivative is desorbed at another pH value. A method for separating and purifying a pyrimidine derivative, which is characterized by being recovered, is disclosed. It discloses the use of ceramic or organic membranes / porous surfaces having ultrafiltration properties or microfiltration properties on the order of micrometers or nanometers.

Japanese Patent Application Laid-Open No. 11-89590 discloses a method for recovering and purifying a protein having epidermal growth factor activity by specifically precipitating a contaminant protein, removing the contaminant protein, and then efficiently purifying the EGF activity. It is disclosed that a protein having the following can be separated and recovered from a culture. It discloses that if microfiltration is performed using a filtration membrane having a pore size of 0.45 μm, the precipitate can be concentrated on the membrane and removed.

[0006] Japanese Patent Application Laid-Open No. 9-110896 discloses that whey is concentrated and dialyzed using an ultrafiltration membrane in the purification of milk proteose peptone. It involves processing at high temperatures.

[0007] Japanese Patent Application Laid-Open No. 7-133290 discloses that nucleic acids in all existing states can be efficiently removed from a water-soluble solution containing a protein while maintaining a high recovery rate of the protein. It is disclosed that the filtration filter is a cellulose hollow hollow fiber membrane regenerated by a copper ammonia method.

Conventionally, in the beer filtration step, a method of filtering using diatomaceous earth has been adopted. However, this method requires a large amount of diatomaceous earth and has no possibility of regenerating diatomaceous earth. The problem of environmental destruction sometimes occurred. JP-A-5-301034 discloses a beer characterized by comprising a porous composite structure in which a water-insoluble water-soluble polymer is provided in a porous space of a polytetrafluoroethylene porous material instead of diatomaceous earth. A microfiltration membrane for food such as wine, sake, soy sauce, juice and the like is disclosed.

[0009] As shown in these examples, it is difficult to filter proteins, and various attempts have been made. That is, a high flow rate and high protein purification have been desired.
Further, when used as a liquid filter, the wettability with respect to the liquid may not always be good. For this reason, the function as a filter was restricted. Further, since the treatment is performed at a high temperature, a material that can withstand a high temperature of 80 to 120 ° C. is required.
Further, as the filtration membrane, the average pore size is usually 0.1 to 10μ
m was said to be preferred.

However, the characteristics required for a filtration membrane for food are that bacteria such as yeasts can be filtered reliably, and that the taste and quality of the food are not changed, and that good tensile strength and ductility are obtained. It is listed that it has mechanical properties of, disinfectant, sterilizing agent, for example, it is chemically stable to alkaline hypochlorite solution, and it is hard to cause clogging by filtration. You. Few filtration membranes and filtration means satisfying these conditions were found.

[0011]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a filter for a filter having a small pore size of 0.1 to 10 .mu.m and a through hole, so that the efficiency of collecting fine particles is high and the filtration amount is relatively large. The support membrane has good affinity for water and excellent mechanical strength, so it has excellent durability performance.It is suitable for the carrier to have a large flow rate in protein filtration and to collect impurities in the protein. Another object of the present invention is to provide a filtration supporting membrane.

[0012]

The present invention relates to a porous material having a porous structure having fine through holes, a porosity of 15 to 85%, a pore diameter of 0.01 to 5 μm, and a film thickness of 10 to 50 μm. A polyamide film, and in the cross-sectional direction of the film,
A porous polyamide film having a structure in which a layer made of microporous material and a layer having relatively large voids or openings are stacked, and wherein the two layers are connected to each other by through micropores. The present invention relates to a filtration supporting membrane comprising: Further, the present invention relates to a filtration support membrane made of a porous polyamide film, characterized in that a granular structure is generated on the layer side surface having relatively large voids, and the positions of the voids are not biased on the grain boundaries. is there.

[0013] The filtration support membrane comprising the porous polyamide film of the present invention is useful for microfiltration in the food industry, medicine and the like. In particular, it is useful as a membrane for filtration of protein aggregates. The present invention also relates to a single-layer or multi-layer filtration supporting membrane characterized by laminating one or more of the above-mentioned supporting membranes, or laminating the supporting membrane with a nonwoven fabric or another porous membrane. is there. The present invention also relates to a protein-supporting membrane and a yeast-supporting membrane.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The following describes the filtration support membrane of the present invention. The carrier film of the present invention has a porous structure having fine through holes, a porosity of 15 to 85%, a pore diameter of 0.01 to 5 μm, and a film thickness of 10 to 50 μm. The vicinity of the surface of the carrier film is made of relatively coarse pores having a pore diameter of 4 to 10 μm.

The through hole according to the present invention means that a through hole is formed from one surface to the other surface of the film. It does not have to be a straight hole. It may be winding. The performance as a filtration support membrane is exhibited by such a through-hole.

The filtration membrane of the present invention has a porosity of 1
It is 5 to 85%, preferably 15 to 70%. If the porosity is lower than 15%, the permeability coefficient of the filter will be low, and if the porosity exceeds 85%, the collection efficiency of fine particles tends to be low. It is not suitable because the mechanical strength of the membrane is also low.

Further, the filtration membrane of the present invention has a pore size of 0.1.
The pore size is from 0.01 to 5 μm, preferably from 0.5 to 5 μm.
When the pore size is smaller than 0.01 μm, when applied as a filtration support membrane, the processing amount is too small, and the filtration support membrane may not be able to exhibit the function of expecting a filtration rate. On the other hand, if the pore diameter exceeds 5 μm, the fine particles may similarly pass therethrough, and the function of the filter deteriorates.

The filtration membrane of the present invention has a thickness of 10
５０50 μm, preferably 10-35 μm.
If the thickness is less than 10 μm, the mechanical strength becomes weak. On the other hand, when the thickness exceeds 50 μm, the ratio of the continuous holes decreases, so that the passing amount through the filter decreases.

The filtration support membrane of the present invention has a structure in which a microporous layer and a layer having relatively large voids or openings are stacked in the cross-sectional direction of the membrane. They are connected to each other by through micro holes. With such a structure, fine particles are easily captured. In addition, it is possible to prevent the coarse particles from being trapped by the openings near the surface and the large voids, resulting in poor filtration efficiency.

Further, a grain structure is formed on the surface of the layer having relatively large voids, and the location of the voids is not biased on the grain boundaries. It can be said that the granular structure of this surface is excellent in mechanical strength and dimensional stability because the position of the void is not biased on the grain boundary.

The present invention also provides a single-layer or multi-layer structure characterized by laminating one or more of the above-mentioned filtration supporting membranes, or laminating the filtration supporting membrane with a nonwoven fabric or another porous membrane. It is a filtration support membrane. The supporting membrane for filtration is 1
By combining two or more sheets, a wider performance can be expected as a supporting film. The collection rate of the filtration supporting membrane is further increased. When combined with other materials, the mechanical strength of the filter and the ability to trap fine particles are further improved.

The filtration membrane of the present invention has an air permeability of 0.5
２０００2000 seconds / 100 CC. Air permeability is 0.5 seconds /
If it is higher than 100 CC, it is not suitable because it has inferior trapping ability as a filter supporting membrane. 2000 seconds / permeability
If it is lower than 100 CC, the passing amount as a filter becomes low.

The filtration support membrane may have a single-layer or multi-layer structure, and the total thickness of the filtration support membrane is 5 to 100 μm, preferably 0.5 to 2000 seconds. / 100 cc.

Further, it is a filtration support membrane having a single-layer or multi-layer structure in which other filter elements, non-woven fabrics and woven fabrics are laminated. As the nonwoven fabric and the woven fabric to be combined, a nonwoven fabric and a woven fabric such as a cellulosic fiber, a fluorine fiber, a glass fiber, a carbon fiber, a metal fiber, and an organic heat-resistant fiber are preferable. Also, other porous carbon plates, graphite powder, silicon nitride,
Sintered films of inorganic materials such as aluminum nitride and plate-like materials can also be suitably used as long as they are porous films.

Further, the present invention is preferably used for a carrier membrane for protein microfiltration. There are various proteins, and the pore size is 0.1 to 10 μm for removing the protein aggregate by filtration.
If m, then it can be applied. Preferably, bovine serum albumin, lysozyme, ovalbumin, casein and the like can be applied.

Further, the present invention is preferably a yeast-carrying membrane. When yeast is carried in a cake form, protein aggregates are adsorbed in a yeast cake form, which helps filtration efficiency. It is preferable because it becomes a so-called filter aid. East is also environmentally friendly. Further, structurally, this carrier film has relatively coarse pores on the film surface, and 2 to 10
μm, and the supporting membrane has a structure convenient for supporting yeast and the like.

Next, the method for producing the filtration support membrane of the present invention will be described below. The support membrane for filtration of the present invention is prepared by preparing a uniform solution comprising polyamide and an alcohol solvent having a boiling point of 80 ° C. or lower, casting the solution in a film on a substrate, and applying the obtained film to a film. It is manufactured by drying while causing a fluctuation in the polyamide concentration in the film in the in-plane direction.

The polyamide used in the present invention includes:
Various known ones can be mentioned. For example, oxalic acid, adipic acid, sebacic acid, terephthalic acid, isophthalic acid, dicarboxylic acids such as 1,4-cyclohexyldicarboxylic acid and ethylenediamine, hexamethylenediamine, 1,4-cyclohexyldiamine, m-xylylenediamine, pentamethylene Diamine, crystalline polyamide obtained by polycondensation of a diamine such as decamethylene diamine, ε-caprolactam, ε-aminocaproic acid, ω
-Crystalline polyamide obtained by polymerizing laurolactam, ω-aminododecanoic acid, ω-aminoundecanoic acid,
And crystalline polyamides composed of these copolymers. Specifically, polyamide 6, polyamide 6
6, polyamide 610, polyamide 12, polyamide 6
6 / 6T (T represents a terephthalic acid component) and the like.
It may be a mixture of the above polyamides.

The molecular weight of the polyamide resin is not particularly limited, as long as it can form a homogeneous solution with an alcoholic solvent having a boiling point of 80 ° C. or lower. Preferably,
The polyamide resin has a number average molecular weight of 9,000 to 100,0.
00. If the number average molecular weight is less than 9,000, the mechanical strength is insufficient, and the number average molecular weight becomes 10
If it is larger than 000, the solution viscosity becomes too high, so that it is difficult to form a uniform porous film.

The fluorinated alcohol solvent having a boiling point of 80 ° C. or lower used in the present invention is specifically a fluorinated alcohol such as hexafluoroisopropanol (HFIP) or trifluoroethanol, or the above fluorinated alcohol 40
It is a solvent in which at least mol% and at most 60 mol% of aliphatic alcohol are mixed. The aliphatic alcohol is, specifically,
These are methanol, ethanol and 1-butanol. Preferred are methanol and ethanol. When the proportion of the aliphatic alcohol mixed with the fluorinated alcohol is 60
If it exceeds mol%, the solubility of the polyamide resin in the solvent is greatly reduced, so the above ratio is preferable.

In the present invention, the polyamide and the alcohol-based solvent are 0.5 to 7% by weight, preferably 2 to 5% by weight of the polyamide and 99.5 to 9% by weight of the alcohol-based solvent.
The polyamide solution is prepared by dissolving at a ratio of 3% by weight, preferably 98 to 95% by weight. When the proportion of the polyamide is more than 7% by weight, the air permeability of the obtained porous membrane decreases, which is not appropriate. The above-mentioned ratio is preferable because the film is uniformly peeled and easily broken.

In the present invention, the polyamide solution may contain a filler such as fiber, powder, woven fabric and the like. For example, a carbon fiber, a glass fiber, a fibrous zonotolite, a silicon nitride fiber, a fiber reinforcing material of a metal fiber, activated carbon, graphite powder, a granular reinforcing material such as silicon oxide, silicon nitride, boron nitride, and quartz may be blended. . Further, additives such as a surfactant, a heat-resistant material, a flame retardant, a colorant, and an antioxidant may be added. These additives and reinforcing materials can be appropriately blended with the above-mentioned polyamide solution within a range that does not hinder the filtration supporting membrane of the present invention.

In the present invention, the polyamide solution is cast on a substrate in the form of a film, and the obtained film is dried while fluctuating the polyamide concentration in the film in the in-plane direction of the film. Thus, a polyamide porous membrane can be produced.

The substrate used in the present invention is a substrate which does not repel the polyamide solution when the solution is dropped onto the substrate. For example, a glass plate, a mica plate, a quartz plate, a cloth, or the like is suitable. The substrate is not limited to a flat plate, but may be a cylinder or a substrate having a complicated shape as necessary.

The method of forming the film of the polyamide solution on the substrate is not particularly limited, and the method of casting the polyamide solution on a plate or a movable belt serving as a substrate, A method such as a method of impregnating the substrate with the substrate can be used.

The thickness of the film of the polyamide solution formed on the substrate is adjusted in the range of 5 to 50 μm, preferably 10 to 35 μm, as the average thickness of the support film including voids after drying. This depends on the concentration of the polyamide solution and the thickness of the liquid film. When the average thickness is smaller than 5 μm, the film is likely to be densified or broken in the drying step, and when the average thickness is larger than 50 μm, the air permeability of the obtained support membrane is reduced.

The film of the polyamide solution formed on the substrate is dried under such conditions that the polyamide concentration fluctuates in the in-plane direction of the film during the drying process. The fluctuation of the polyamide concentration is about 1 mm between a part where the solution film during drying is slightly clouded and a transparent part.
It can be known by dividing at the following intervals. Conditions in which the fluctuation of the polyamide concentration occurs include conditions in which the drying is performed at a temperature of 40 ° C. or less for 1 minute or more, and preferably for a drying time of 2 minutes or more. For example, a crystalline polyamide having a number average molecular weight of about 10,000 When polyamide 6 is used, it is preferable to dry the solution film in an air atmosphere at about 30 ° C. or lower. It is not preferable that the film is dried under conditions that do not cause the concentration fluctuation, since the resulting film becomes dense. Then, the dried membrane is peeled from the substrate to obtain a filtration carrier membrane.

The obtained filtration support membrane has a microporous layer and a layer having relatively large voids or openings stacked in the cross-sectional direction of the membrane. Have a structure connected to each other.
Furthermore, a granular structure is generated on the layer side surface having relatively large voids, and the positions of the voids are not biased on the grain boundaries. Therefore, it is superior in mechanical strength and dimensional stability as compared with a polyamide porous membrane obtained by a conventional production method.

[0039]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not limited to these examples. Test / evaluation methods or criteria in Reference Examples, Examples and Comparative Examples are as follows.

(Evaluation of Polyamide Porous Carrier Film) The thickness and porosity of the polyamide porous carrier film were measured as follows.

(1) Porosity The thickness and weight of the porous film cut to a predetermined size were measured, and the porosity was determined from the basis weight by the following equation (1). In the formula (1), S represents the area of the porous film, d represents the film thickness, W represents the measured weight, and D represents the density of the polyamide. Porosity (%) = 100−100 × (W / D) / (S × d) (1)

(2) Tensile strength Measured according to JIS K 7127. Test speed 1 using Toyo Baldwin Tensilon universal testing machine
The tensile strength was measured at 0 mm / min.

(3) Piercing Strength A sample was fixed to a circular holder having a diameter of 11.28 mm and an area of 1 cm ² , and a needle having a tip shape of 0.5R and a diameter of 1 mm was lowered at a speed of 2 mm / sec to pierce and penetrate. The load was measured.

(4) Dry Heat Shrinkage Temperature 23 ° C., relative humidity 5 according to JIS K 7100
After marking the sample conditioned at 0% for a predetermined length, the sample was placed in an oven set at 160 ° C. in an unconstrained state.
After leaving still for a minute, the dimensions after removal were measured. The dry heat shrinkage ratio follows the following equation (2). L1 in the equation (2) means the film size after being removed from the oven, and L0 means the initial film size. Dry heat shrinkage (%) = [1− (L1 / L0)] × 100 (2)

Example 1 (Preparation of Polyamide Porous Film) Polyamide 6 having a number average molecular weight of 13,000 was used as a polyamide, and HFIP was used as an alcohol solvent having a boiling point of 80 ° C. or lower. H so that the polyamide has a concentration of 2% by weight.
The polyamide solution was obtained by dissolving in FIP at room temperature.

The obtained polyamide solution was cast on a glass plate so that the thickness of the solution was 300 μm. When the film of the polyamide solution was naturally dried at normal temperature and atmospheric pressure, the film fluctuated in the in-plane direction of the film, and then a dried film was obtained. Subsequently, the film was peeled from the glass plate to obtain a polyamide porous film. The thickness of the obtained porous film was 15 μm. When a liquid such as water, methanol, or acetone was dropped on the film surface, the liquid permeated. Observation with a scanning electron microscope revealed that the obtained porous film had a layer having a pore size of about 3 μm or less and a layer having a relatively large pore size of about 8 μm or more in the cross-sectional direction of the film. It had a stacked structure, and had a structure in which the two layers were connected to each other by through-holes having a diameter of about 1 μm or less.

The porosity obtained by using 1.13 g / cm ³ as the density of polyamide 6 in the obtained porous membrane is 51.
%, Tensile strength is 1.9 kgf / mm ² , piercing strength is 76
gf and dry heat shrinkage were 1.0%. This film is designated as PPA1.

Example 2 (Evaluation of Filtration Supporting Membrane) Two PPA1 films obtained in Example 1 were superposed and evaluated as a filtration carrying membrane. The operation was carried out without the support. Bovine serum albumin [BSA / bovine serum albumin, Cohn FR-V modified powder, heat-treated product, manufactured by Kanto Chemical Co., Ltd.] (1 g / l), lysodium [LY / hen egg, egg white, manufactured by Kanto Chemical Co., Ltd.] (1 g / l) ,
One liter of an equivalent protein mixture of oval albumin [OV / ovalbumin, manufactured by Kanto Chemical Co., Ltd.] (1 g / l) was charged onto the filtration membrane, and the time required to pass the whole amount was measured. The filtration membrane is a disk having a diameter of 2.5 cm and an initial pressure of 1.
6 kg / cm ^{2 was} applied. The amount of protein recovered from the filtrate and the protein aggregate on the filtration membrane were measured, and compared with the mother liquor composition before filtration. Table 1 shows the results.

Example 3 Two PPA1 films obtained in Example 1 were stacked,
Yeast (manufactured by Kanto Chemical) 0.74 g (dry thickness 0.1c
m), filtered under vacuum, washed, made into a cake, and the yeast was supported on the porous membrane. Thereafter, filtration was performed in the same manner as in Example 2. Table 1 shows the results.

Example 4 3.69 g of supported yeast (dry thickness 0.5 cm)
And filtration was performed in the same manner as in Example 3. Table 1 shows the results.

Comparative Example 1 Two porous polyolefin membranes (UPORE 2015, manufactured by Ube Industries, Ltd.) were used as a filtration membrane, and filtration was carried out in the same manner as in Example 2. The results are shown in Table 1.

Comparative Example 2 A porous polyolefin membrane (Upore UP2015 manufactured by Ube Industries, Ltd.) was used as a filtration membrane by stacking two sheets, and the yeast was supported and filtered in the same manner as in Example 3. The results are shown in Table 1. Show.

[0053]

[Table 1]

[0054]

The support membrane for filtration of the present invention is produced from a porous film having fine continuous pores, has excellent affinity for water, has excellent mechanical strength, is durable, and has a pore size of 0. A film-like filtration supporting membrane for collecting fine particles of 1 to 10 μm, which is suitable for filtration of a protein by a carrier so that the flow rate is large and impurities and aggregates in the protein are collected. The present invention relates to a carrier film for use. INDUSTRIAL APPLICABILITY The present invention can provide a filtration support membrane useful for microfiltration of the bioindustry such as protein, fermentation industry, and food industry.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C12N 11/08 C12N 11/08 H 4H045 // C07K 1/34 C07K 1/34 F term (reference) 4B028 AC06 4B033 NA01 NA14 NB02 NB13 NB34 NB63 NB68 NB70 NC04 ND03 ND08 ND11 4D006 GA07 KA32 MA03 MA06 MA22 MA24 MA25 MA31 MB16 MC54 MC55X MC88 NA05 NA10 NA64 PA01 PB12 PB52 PC11 PC12 4F074 AA71 AB01 DA23 CE22 DA23 CE DA54 4F100 AK46A AK46B AK46C BA02 BA03 BA07 BA10B BA10C DC11A DC11B DC11C DG15C GB90 JA20A JB05 JL00 JM02A JM02B JM02C YY00A 4H045 AA40 GA10

Claims (5)

[Claims] 1. A porous polyamide film having a fine pore, a porous structure, a porosity of 15 to 85%, a pore size of 0.01 to 5 μm, and a film thickness of 10 to 50 μm, and It has a structure in which a microporous layer and a layer having relatively large voids or openings are stacked in the cross-sectional direction of the membrane, and the two layers are connected to each other by through-holes. A filtration membrane comprising a porous polyamide film. 2. The filtration membrane according to claim 1, wherein a granular structure is formed on the surface of the layer having relatively large voids, and the positions of the voids are not biased on the grain boundaries. 3. A carrier for filtration having a single-layer or multi-layer structure, characterized in that one or more of the carrier membranes according to claim 1 or 2 are laminated, or a non-woven fabric or another porous membrane is laminated on the carrier membrane. film. 4. The supported membrane for filtration according to claim 1, which is used for protein filtration. 5. The filtration supporting membrane according to claim 1, which carries yeast.