JPH0910564A - Micro-filtration film and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a micro-filtration film which has high fungus- and particle- removing performance and long life by covering the inside of a pore and the surface of the film with a cross-linked polymer containing polyethylene glycol diacrylate. SOLUTION: A micro-filtration film is immersed in the solution of a polyethylene glycol diacrylate monomer. Thereafter, a cross-linked polymer is formed by thermal polymerization and the whole surface of a pore wall in the inside of the film is covered with the cross-linked polymer and dried after washing and extracting an unreacted monomer. A compound shown in the formula (wherein (n) is 2-20) is used for polyethylene glycol diacrylate. Liquid containing fermentation liquid, polymeric sugar such as fruit juice and protein or the like is filtrated through the micro-filtration film obtained such a way. The micro- filtration film has fungus- and, particle-removing performances for a long period.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a microfiltration filter used for microfiltration of a liquid. In particular, it relates to hydrophilization treatment of microfiltration membranes used for filtering water and aqueous solutions.

[0002]

2. Description of the Related Art Most of the materials used for microfiltration membranes are inherently hydrophobic materials, and most of the membranes formed are water repellent as they are, and there are many obstacles to filtration of water and aqueous solutions. In addition, in a fermented liquor containing a protein or an aqueous solution for food / medicine use, there is a drawback that the protein is likely to be adsorbed on the surface of the membrane and thus clogging is likely to occur. For this reason, attempts have been made to extend the filtration life by hydrophilizing the surface of conventional microfiltration membranes by various treatments. JP-A-7-5
In 1550, a porous membrane substrate formed of a first polymer having an average pore size of 0.001 to 10 microns is formed, and a second cross-linked polymer is coated over the entire surface of the substrate to form a porous membrane substrate. A composite porous membrane is described that has essentially the same porous structure as the porous substrate. However, in this method, the stability of the solution of the monomer of the second polymer, the crosslinking agent for the monomer, and the polymerization initiator for the monomer is poor, and a large amount of hydrophilic microfiltration membrane is industrially produced. It is not a suitable method.

[0003]

The object of the present invention is to filter fermentation liquors, fruit juices, foods, pharmaceuticals and the like, which contain high molecular weight sugars, proteins and / or agglomerated particles composed of these components, particularly sake and wine. Alcohol like beer and beer, food such as soy sauce and vinegar, amino acids, organic acids, nucleic acids,
Filtration of fermented liquid produced by microbial fermentation of various chemicals used for pharmaceuticals such as vitamins and proteins and general industrial applications, especially in the final stage sterilization filtration application, high sterilization and particle removal that has never been seen before It is an object of the present invention to provide a microfiltration membrane having characteristics of both performance and long life.

[0004]

The present invention has been accomplished by a microfiltration membrane characterized in that the inside of the pores and the surface of the membrane are covered with a cross-linked polymer containing polyethylene glycol diacrylate. That is, a microfiltration membrane is immersed in a solution of polyethylene glycol diacrylate monomer, and then a cross-linked polymer is formed by thermal polymerization over the entire surface of the pore walls inside the membrane to cover it, and the unreacted monomer is washed and extracted, and then dried. The above problems were solved by the obtained microfiltration membrane.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The polyethylene glycol diacrylate used in the present invention is represented by the general formula (1), and n in the formula is from 2 to 20. Chemical formula (1) CH ₂ = CH-COO (-CH ₂ CH ₂ O-) _n CH ₂ CH ₂ OOC-CH = CH _{2 When} the material of the microfiltration membrane to be treated is polysulfone, the number of n is 7 to 16 Those in the range are particularly preferable. As the monomer, in addition to polyethylene glycol diacrylate, a nonionic and hydrophilic monofunctional or polyfunctional monomer may be mixed and used. Examples of the nonionic and hydrophilic monomer include hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxyalkyl acrylate or methacrylate such as hydroxypropyl acrylate, acrylamide, methacrylamide, hydroxylethyl acrylamide or methacrylamide, polyoxyethylene acrylate or methacrylate, and polyoxyethylene acrylate. Examples thereof include acrylate or methacrylate of oxypropylene, and vinylpyrrolidone. Basic or acidic monomers cannot be used because they have almost no effect of increasing the filtration amount or conversely the filtration amount decreases. It is presumed that the cross-linked polymer formed by using a basic or acidic monomer has no affinity for increasing the filtration amount because it has an affinity for the basic or acidic portion of the protein and easily adsorbs the protein. Particularly effective monomers among the monomers to be mixed with polyethylene glycol acrylate are hydroxyethyl acrylate, hydroxyethyl methacrylate, and polyoxyethylene acrylate.

When the mixed monomer is used, the ratio of polyethylene glycol diacrylate to polyethylene glycol diacrylate is 20 with respect to the total amount of the monomers.
% Or more, preferably 30% or more is necessary, and polyethylene glycol diacrylate can be used alone. Within the experimental range, the monomer concentration in the solution was 0.
2% to 5% is preferable, and 0.5% to 2.0% is particularly preferable. The optimum monomer concentration varies depending on the type of monomer used, the polymerization temperature, the material of the microfiltration membrane, and the pore size. With a microfiltration membrane made of polysulfone with an average pore size of 0.65 micron, at a polymerization temperature of 120 ° C, for example, when polyethylene glycol diacrylate is used alone, 0.5
To 1.2% is most preferable, and in the case where 63 parts of polyethylene glycol diacrylate and 37 parts of hydroxyethyl methacrylate are used in combination, 1.0 to 1.5% is most preferable. If the monomer concentration is too high, the water permeability of the treated membrane will be significantly reduced, making it impractical. A radical initiator may be used for the polymerization, but thermal polymerization without a polymerization initiator is preferable. When a polymerization initiator is used, the polymerization reaction proceeds in the solution during storage and use of the solution, and the quality of the treated film is likely to deteriorate. Preferred solvents for the monomer solution include monoalcohols such as methanol, ethanol and propanol, polyhydric alcohols such as ethylene glycol, propylene glycol and diethylene glycol, and water. These can be used alone or as a mixed solvent. The original microfiltration membrane material to be treated with the crosslinked polymer can be applied to many membrane materials as described above without particular limitation, but when it is applied to the microfiltration membrane using polysulfone as a material, it shows a particularly remarkable effect. . Next, preferable pore characteristics of the original microfiltration membrane treated with the crosslinked polymer will be described. The average pore size of the original microfiltration membrane can be applied to a membrane having a value of 0.1 micron or more and 5 micron or less when measured by the method of ASTM F-316. Further, in the case of a membrane having a densest pore layer inside the membrane as disclosed in JP-A-2-151636 and having a relatively large pore size on the front and back sides of the membrane, water permeability associated with the formation of a crosslinked polymer. Is preferable because there is almost no decrease. After immersing the membrane in this solution, the excess solution is scraped off, and then immediately heated to polymerize. The polymerization temperature is 80 ° C or higher, preferably 100 ° C to 170 ° C, and most preferably 120 ° C to 140 ° C. The polymerization time is 1 to 30 minutes, but the lower the polymerization temperature, the longer the time is required. After completion of the polymerization, a washing treatment is performed to remove unreacted monomers and a solvent, and then the membrane is dried. A more detailed description will be given below with reference to examples.

[0007]

【Example】

Example 1 A film-forming solution having the following composition was prepared, the solution was cast on a polyester film, and precisely controlled humidity wind with a dew point of 14 ° C. and a wind speed of 3 m / s was applied for 8 seconds, and immediately a water bath at 25 ° C. 2 in
Soak for 0 seconds to form holes. After that, the film is peeled from the polyester film, further washed, and then dried. The resulting membrane had a thickness of 180 microns, a porosity of 71% and an average pore size of 0.7 micron. Solution composition Polysulfone resin 14 parts Polyvinylpyrrolidone 16 parts N-methyl-2-pyrrolidone 67 parts Lithium chloride 0.5 parts Water 2.5 parts

Example 2 Solutions 1 to 4 shown in Table 1 were prepared. PEGDA in Table 1 refers to polyethylene glycol diacrylate, and n value of 12 in the chemical formula (1) was used.
The polysulfone membrane formed in Example 1 was dipped in each solution,
After scraping off the excess solution adhering to the membrane surface, 120
It was placed in a C oven for 20 minutes, then washed in hot water of 80 C for 30 minutes and dried. Permeation flux of the formed membrane (m
/ h) at a differential pressure of 50 kPa and the increase in membrane weight (g
/ m ² ) was measured and is shown in Table 2.

[0009]

[Table 1]

[0010]

[Table 2]

Example 3 Solution 2 used in Example 2 and the membrane prepared in Example 1 were treated in the same manner as in Example 2 except that the heating time was 120 ° C, and the weight of the treated membrane was increased. Was measured. Table 3 shows the comparison between the measured amount of weight increase and the heating time. As can be seen from Table 3, the amount of crosslinked polymer formed increases with the heating time, but the amount of crosslinked polymer formed is almost saturated when the heating time is more than 10 minutes.

[0012]

[Table 3]

Example 4 A membrane prepared by the same method as in Example 1 was used as solution 5 shown in Table 4.
Was treated under the same conditions as in Example 2. The water permeation flux and the membrane weight increase of the resulting membrane were measured in the same manner as in Example 2 and are shown in Table 5. Further, comparison of filtration life was performed using commercially available beer, and the results are also shown in Table 5. The beer filtration was carried out at a flux of 5 ml / cm ² / min. For 60 minutes.
After beer filtration for 60 minutes, the membrane was washed by immersing it in water at 80 ° C. for 20 minutes. This beer filtration and membrane washing were repeated alternately, the cumulative filtration time until the filtration pressure difference reached 100 kPa was measured, and the cumulative filtration time ratio between the simultaneously measured membranes was calculated to compare the filtration lives. Basic monomer MAPA
The membrane treated with the solution containing H or acidic monomer AMPSH does not show the effect of increasing the filtration life as compared with the untreated membrane, but the membrane treated with the solutions 5, 6 and 7 using only the nonionic monomer An increase in filtration life was observed. H in Table 5
EMA refers to hydroxyethyl methacrylate, HE
A refers to hydroxyethyl acrylate. Also MAP
AH is a basic monomer represented by the chemical formula (2), and AMP
SH indicates an acidic monomer represented by the chemical formula (3).

[0014]

[Table 4]

Chemical formula (2) CH ₂ = CH-CONH-C ₃ H ₆ -N (-CH ₃ ) ₂ Chemical formula (3) CH ₂ = CH-CONH-C (-CH ₃ ) ₂ CH ₂ SO ₃ H

[0016]

[Table 5]

Example 5 A treatment liquid having the same composition as that of the solution 5 of Example 4 was prepared by changing the n value in the general formula (1) of polyethylene glycol diacrylate to 4, 8, and 12. The polysulfone membrane was treated under the same conditions. Only for those treated with a liquid having an n value of 4, the polysulfone membrane was dissolved and deformed during heating.

Example 6 A treatment liquid having the same composition as that of the solution 6 of Example 4 was prepared by changing the n value in the general formula (1) of polyethylene glycol diacrylate to 4, 8, and 12, and The polysulfone membrane was treated under the same conditions. All the solutions, including those treated with the solution having an n value of 4, could be treated without any problem. Polyethylene glycol diacrylate having an n value of 4 can be used without dissolving the polysulfone film if used in combination with another nonionic monomer.

[0019]

EFFECT OF THE INVENTION A microfiltration membrane made by immersing a microfiltration membrane in a solution of a polyethylene glycol diacrylate monomer, forming a crosslinked polymer by thermal polymerization, washing and extracting unreacted monomer, and then drying the microfiltration membrane. By using it, it is possible to increase the filtration life of a liquid containing a high-molecular sugar, a protein, and / or agglomerated particles composed of these components, such as a fermented liquid, fruit juice, foods and pharmaceuticals.

Claims (4)

[Claims] 1. A microfiltration membrane in which the inside of the pores and the surface of the membrane are covered with a cross-linked polymer containing polyethylene glycol diacrylate. 2. The microfiltration membrane according to claim 1, wherein the crosslinked polymer is obtained by polymerization. 3. The microfiltration membrane is dipped in a solution of a polyethylene glycol diacrylate monomer, and then a crosslinked polymer is formed by thermal polymerization over the entire surface of the pore walls inside the membrane to coat the microfiltration membrane. Manufacturing method of microfiltration membrane. 4. A microfiltration membrane is dipped in a solution of a polyethylene glycol diacrylate monomer, and then a cross-linked polymer is formed by thermal polymerization over the entire surface of the pore walls inside the membrane to coat it, the unreacted monomer is washed and extracted, and then dried. A method for producing a hydrophilic microfiltration membrane, which comprises: