JP2011092875A - Method for manufacturing nanofiltration membrane - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a ceramic membrane, with a segment molecular weight of 400 to 800 g/mol, which is best suited for effectively separating a photoresist from a photoresist-containing waste liquor. <P>SOLUTION: The method for manufacturing a nanofiltration membrane is to form a nanofiltration membrane by laminating a nanofiltration membrane layer on a ceramic filter with an ultrafiltration membrane layer. The nanofiltration membrane formed by the lamination process comprises a first nanofiltration membrane forming process consisting of a membrane making process nanofiltration by a dip membrane manufacturing method, a drying process and a calcining process, and a second membrane forming process made up of a membrane making process by gravity-flowing down membrane manufacturing method, a drying process and a calcining process. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing a nanofiltration membrane.

  To manufacture electronic parts, etc., a photoresist film is formed on a substrate, light is irradiated through a pattern mask, unnecessary photoresist is then dissolved and developed with a developer, and further processing such as etching is performed. After that, the insoluble photoresist film on the substrate is peeled off. Further, resist is applied to the end (edge) of the substrate to the end, and the resist at the end is peeled off in the cassette and the apparatus to become dust, and therefore the end resist is removed by edge rinse.

  For removal of the photoresist film, for example, a stripping solution composed of DMSO (dimethyl sulfoxide), MEA (monoethanolamine) or the like is used, and for edge rinse, for example, PGMEA (propylene glycol monomethyl ether acetate), PGME (propylene) A thinner solution composed of glycol monomethyl ether) or the like is used.

  There is a demand for removing the photoresist from the stripping solution or thinner solution after being used for the processing of the photoresist film and reusing it as a stripping solution or a thinner solution, respectively. Various techniques for this purpose have been studied (for example, Patent Document 1).

  As a method for regenerating a photoresist-containing waste liquid, as a technique that has been practically used in the past, there has been a method of introducing the photoresist-containing treatment liquid into a distillation column and separating the waste liquid by distillation. However, the distillation method has problems such as resist sticking in the distillation column and an increase in the installation area of the distillation column. In addition, the distillation method involves a phase change (liquid → gas → liquid) in the distillation process, which increases the energy cost.

  In order to solve various problems associated with the distillation method, there is a demand for a technique using a separation membrane. However, the organic film uses an adhesive in the film forming process, and the adhesive component is decomposed by DMSO or MEA that constitutes the stripping solution for the photoresist film, so the organic film cannot be used. was there.

  Further, in order to separate and remove the photoresist from the photoresist-containing waste liquid, it is preferable that the separation performance of the membrane is 800 or less in terms of a molecular weight cutoff using polyethylene glycol (PEG) as a molecular weight standard substance. Among the inorganic membranes used, even the UF membrane with the highest separation performance has a lower limit of the molecular weight cut off of about 4000 g / mol, and sufficient separation performance for separating and removing the photoresist can be obtained. There was no problem.

JP 2007-213074 A

  The object of the present invention is to solve the above problems and to provide a method for producing a nanofiltration membrane having a molecular weight cut-off of 400 to 800 g / mol, which is suitable for effectively separating a photoresist from a photoresist-containing waste liquid. is there.

  The method for producing a nanofiltration membrane of the present invention made to solve the above problems is a method for producing a nanofiltration membrane in which a nanofiltration membrane layer is further laminated on a ceramic filter having an ultrafiltration membrane layer. The nanofiltration membrane formed by laminating is formed by a first film forming step comprising a film forming step by a dip method, a drying step and a baking step, and a film forming step by a natural flow forming method, a drying step and a baking. It consists of the 2nd film formation process which consists of a process, It is characterized by the above-mentioned. Here, the dip method is a method in which a substrate is placed in a film formation chamber, a coating solution is poured from the lower part of the chamber, and when the coating solution reaches the upper part of the substrate, the coating solution is stopped from being poured. It refers to a film forming method characterized in that a coating layer is coated on the surface of a substrate by discharging the liquid from the lower part of the chamber while controlling the discharge amount. In addition, the spontaneously falling film forming method refers to a film forming method characterized in that the coating liquid is flowed from the upper part of the base material to the lower part so as to spread all the cells, and then the surface of the base material is coated.

  The invention according to claim 2 is the method for producing a nanofiltration membrane according to claim 1, wherein the ceramic filter penetrates between both end faces of the columnar shape in the axial direction inside the ceramic filter having the columnar shape. It is a ceramic filter which has an ultrafiltration membrane layer in each inner wall of the provided several flow path.

  According to the method for producing a nanofiltration membrane according to the present invention, in the method for producing a nanofiltration membrane in which a nanofiltration membrane layer is further laminated on a ceramic filter having an ultrafiltration membrane layer, the layer is formed by laminating. The first membrane formation process consisting of a film formation process by a dip method, a drying process, and a firing process, and the second film formation comprising a film formation process, a drying process, and a firing process by a natural flow film formation method The structure formed from the process makes it possible to provide a separation membrane having a molecular weight cut-off (400 to 800 g / mol) suitable for effectively separating the photoresist from the photoresist-containing waste liquid.

It is explanatory drawing of the dipping apparatus used for dip film forming. It is explanatory drawing of the state which accommodated the element in the dipping apparatus. It is explanatory drawing of the film forming process by the natural falling film forming method. It is explanatory drawing of the nano drying process by the natural falling film forming method. It is a fraction curve obtained by measuring the blocking rate of each molecular weight standard substance.

  Preferred embodiments of the present invention are shown below.

  In this embodiment, dip film formation is performed for the purpose of forming an NF film having a fractional molecular weight of 600 to 800 on a UF film (pore diameter 5 to 10 nm) formed inside a columnar ceramic filter. Repeatedly.

  The UF film is formed on the MF film. The MF membrane is formed on the inner wall surface of each flow path of the monolithic porous substrate. In addition, all the film formation processes are based on a film formation process for attaching a coating liquid having a predetermined particle size, a drying process after film formation, and a baking process after drying. The coating liquid is a liquid used at the time of film formation, and the UF film and NF film are prepared in two stages using a sol liquid as a raw material. For the MF film, the sol solution is not used as a raw material, and alumina particles are prepared to directly form a coating solution. Hereinafter, the process for forming the NF film used in the present invention will be described. As the MF membrane and the UF membrane, those prepared by a cross flow circulation method according to a conventional method are used.

<Dipping device>
FIG. 1 shows a dipping apparatus used for dip film formation. As shown in FIG. 1, the dipping apparatus includes a film formation chamber 12 that houses the element 11e, a flange connection pipe 21a connected to a bottom flange 123b on the upstream side of the film formation chamber 12, and a flange connection pipe 21a. A connected T branch 22, a drain pipe 21 d and a supply pipe 21 b connected to the flange connection pipe 21 a via the T branch 22, a drain valve (drainage valve) 13 connected to the drain pipe 21 d, A supply pump 14 connected to the supply pipe 21b, a tank pipe 21c connected to the supply pump 14, and a supply tank 15 connected to the tank pipe 21c are provided. The supply tank 15 is a tank for storing a ceramic coating liquid (hereinafter also simply referred to as “coating liquid”) for forming an NF film. The coating liquid stored in the supply tank 15 by the supply pump 14 is sent to the film forming chamber 12 through the tank pipe 21c, the supply pipe 21b, and the lung connection pipe 21a. As shown in FIG. 2, the film forming chamber 12 has a structure in which the inside can be seen with a transparent material such as an acrylic resin. When excessive sol liquid comes out from the upper part of 11e, liquid supply by the supply pump 14 is stopped, the drain valve (drain valve) 13 is opened, and the coating liquid in the film forming chamber 12 can be discharged.

  The film forming chamber 12 is a cylindrical storage case for storing the element 11e. A cylindrical upper element holding ring 122a is provided above the film forming chamber 12, and a cylindrical lower element is held below the film forming chamber 12. A ring 122b is provided. The glaze part 112a of the element 11e is fixed by the upper element holding ring 122a by the O-ring 121a, and the glaze part 112b of the element 11e is fixed to the lower element holding ring 122b by the O-ring 121b.

<Nanofiltration membrane formation method by dip membrane method>
Hereinafter, a method for forming a titania film will be described as an example of a method for forming an NF film by a dip film forming method.

(A) First, an element 11e having a lotus shape (outer diameter 30 mm, cell inner diameter 3 mm × 37 cells, length 65 to 1000 mm) having a UF membrane formed on the surface layer is prepared. Then, the outer periphery of the element 11e is sealed with a film tape 118 having a thickness of 1 to 10 μm. In order to prevent the coating liquid from permeating through the UF membrane from the outer periphery of the element 11e, the film tape 118 is wound around the glaze portions 112a and 112b on both sides with a width of about 2 to 3 mm.

(B) The coating liquid used for forming the nanofiltration membrane by the dip film forming method is obtained by first diluting a ceramic sol stock solution (hereinafter also simply referred to as “sol stock solution”) with isopropyl alcohol (IPA) or an aqueous solution thereof. The stock solution of sol was added with nitric acid, hydrochloric acid or sulfuric acid while maintaining a mixed liquid of metal alkoxide (for example, titanium tetraisopropoxide) and IPA at 2 to 10 ° C., and further the holding temperature was set at 2 to 10 ° C. It is obtained by mixing with water previously mixed with nitric acid, hydrochloric acid or sulfuric acid. The sol stock solution is a sol solution containing 0.10% by mass to 1.2% by mass, preferably 0.2% by mass to 0.5% by mass of titania (TiO ₂ ).

(C) Then, the obtained sol stock solution is diluted with IPA and adjusted so that the IPA concentration in the diluted coating solution is 70% by mass or more, preferably 75% by mass or more, to obtain a coating solution. Specifically, the sol stock solution is added little by little while stirring IPA to obtain a coating solution. In order to obtain a coating solution, the mixture is stirred for about 5 minutes. The titania concentration after dilution is particularly preferably 0.02 to 0.2% by mass. If the concentration is 0.02% by mass or less, the film becomes too thin, the number of film formations to obtain the desired film thickness increases, and the productivity is deteriorated. Defects such as cracks are likely to occur. When the concentration is 0.2% by mass or more, the film thickness obtained by a single film formation becomes large and cracks are likely to occur. Furthermore, since IPA has a higher drying speed and lower surface tension than water, it is very effective in obtaining a dense film with few defects. Here, titania is used as a component of the ceramic sol. However, a sol of silica or zirconia can be used instead of titania. A binder such as PVA (polyvinyl alcohol) is not used for the coating liquid. The method for preparing the coating liquid in the present invention is a two-stage process in which a ceramic sol stock solution is first prepared and diluted with IPA. Thus, the sol stock solution is prepared and then diluted with IPA to obtain a coating solution. Thus, an NF film having a small pore diameter can be produced. On the other hand, in a one-stage process in which IPA is mixed in advance as a diluent solvent when preparing a ceramic sol stock solution to obtain a coating solution having a desired concentration, agglomerated sol particles increase and the number of coarse pores increases. Absent. After the stirring, the coating solution prepared by the two-stage process is filtered through a filter cloth made of nylon and having a pore diameter of 10 to 100 μm, for example. The filter cloth is washed with distilled water immediately before.

(D) Next, in order to adhere the coating solution prepared by the two-stage process onto the inner wall surface of the flow path (cell) of the element 11e by the dipping method, the element 11e is deposited in the film forming chamber 12 of the dipping apparatus shown in FIG. Install in an upright position. Next, the coating liquid is supplied from the lower part of the element 11e by the supply pump 14 at a liquid supply speed of 500 mL / min. When an excessive sol liquid comes out from the upper part of the element 11e, the liquid supply is stopped, and the drain valve (drain valve) 13 Was opened, and the coating solution within the diameter was discharged. The coating liquid is discharged at a rate of 5 to 10 minutes. If the discharge is performed for 10 minutes or more, the film thickness becomes too thick, and cracks are likely to occur during drying and firing. The discharge time is within 10 minutes regardless of the length of the ceramic film and the film area. Thereafter, the element 11e is taken out from the film forming chamber 12, and the element 11e is moved so as to be shaken by hand, so that excess sol solution is removed.

(E) After coating of the coating liquid, wipe off the coating liquid remaining in the element 11e, and as a first drying process, for example, the air is brought into contact with the flow path (cell) along the film surface by a blower or the like. Send while drying. The temperature of the wind is preferably about 10 to 40 ° C, more preferably 20 to 30 ° C. The humidity is preferably 70% or less. When air having a temperature lower than 10 ° C. is passed, drying of the titania sol adhering to the flow path (cell) surface does not progress, so that a dense film cannot be obtained and the film has a large pore diameter. Moreover, if warm air is passed at a temperature higher than 40 ° C., cracks are likely to occur on the film surface, which is not preferable. The speed at which the wind for drying passes through the flow path (cell) is 1 to 300 m / second, more preferably 50 to 200 m / second. If the speed of the wind passing through the flow path (cell) is 1 m / second or less, a dense film cannot be obtained and the pore diameter increases, and the speed of the wind passing through the flow path (cell) is 300 m / second. If it is above, cracks are likely to occur on the film surface, which is not preferable. Blow drying may be performed for about 6 to 20 hours, preferably for about 12 to 18 hours. Under the conditions as described above, the solvent evaporates from the inside of the channel (cell), that is, from the surface side of the membrane, by sending the air into the channel (cell) while being in contact with the membrane surface. When dried by performing such blowing, the NF film can be densely formed on the UF film. In addition, blow drying is very effective for a lotus root shape which is difficult to dry uniformly. Since it is thought that drying of the solvent from the film surface is important for the densification of the film, masking the outer peripheral surface prevents the solvent containing titania sol from evaporating from the outer peripheral surface, and forms a better film. can do.

(F) After the 1st drying process by ventilation, the 2nd drying process using a dryer (constant temperature bath) is implemented. The second drying treatment is performed for 4 to 12 hours in a dryer controlled at 28 to 75 ° C. and humidity (no humidity control).

(G) After completion of the second drying treatment, the film tape 118 wound around the outer periphery is removed, and 1 to 50 ° C./h, preferably 8 to 30 ° C./h, for example, 400 to 500 ° C. at a rate of 25 ° C./h. The temperature is raised to the firing temperature, and the firing temperature is maintained for 1 hour, and then cooled at 1 to 50 ° C./h, preferably 8 to 30 ° C./h, for example, 25 ° C./h to obtain an NF film.

  The NF membrane obtained in the steps (2) to (g) has a separation performance of a molecular weight cutoff of 1000 to 1500 g / mol. Here, the fractional molecular weight represents a pore membrane size capable of blocking a substance having a specific molecular weight by 90% or more. For example, a membrane having a fractional molecular weight of 1000 to 1500 g / mol is a molecular weight of 1000 to 1000 A membrane having a pore membrane size capable of blocking 90% or more of 1500 g / mol polyethylene glycol (PEG).

<Nanofiltration membrane formation method by natural flow membrane formation>
In the present embodiment, the surface of an NF membrane having a fractional molecular weight of 1000 to 1500 g / mol (hereinafter referred to as a first NF membrane) is further subjected to film formation treatment under natural flow, whereby a fractional molecular weight of 1000 to 1500 g / mol. The NF membrane (hereinafter referred to as the second NF membrane) is formed to improve the membrane separation performance. Hereinafter, a method for forming a titania film will be described as an example of a method for forming a second NF film by a natural flow film forming method.

(A ') First, an element 11e having a lotus shape (outer diameter 30 mm, cell inner diameter 3 mm × 37 cell, length 65 to 1000 mm) formed by forming the NF film obtained in the steps (2) to (g) on the surface layer. Prepare. Then, the outer periphery of the element 11e is sealed with a film tape 118 having a thickness of 1 to 10 μm. In order to prevent the coating liquid from permeating through the membrane from the outer periphery of the element 11e, the film tape 118 is wound around the glaze portions 112a and 112b on both sides with a width of about 2 to 3 mm.

(B) A coating solution used for forming a nanofiltration membrane by a natural flow membrane formation method is obtained by first diluting a ceramic sol stock solution (hereinafter also simply referred to as “sol stock solution”) with isopropyl alcohol (IPA). The stock solution of sol was added with nitric acid, hydrochloric acid or sulfuric acid while maintaining a mixed liquid of metal alkoxide (for example, titanium tetraisopropoxide) and IPA at 2 to 10 ° C., and further the holding temperature was set to 2 to 10 ° C. It is obtained by mixing with IPA previously mixed with nitric acid. The sol stock solution is a sol solution containing 0.10% by mass to 1.2% by mass, preferably 0.2% by mass to 0.5% by mass of titania (TiO ₂ ).

(C ') Then, the obtained sol stock solution is diluted with IPA, and adjusted so that the IPA concentration in the diluted coating solution is 70% by mass or more, preferably 75% by mass or more, to obtain a coating solution. Specifically, the sol stock solution is added little by little while stirring IPA to obtain a coating solution. In order to obtain a coating solution, the mixture is stirred for about 5 minutes. The titania concentration after dilution is particularly preferably 0.02 to 0.2% by mass. If the concentration is 0.02% by mass or less, the film becomes too thin, the number of film formations to obtain the desired film thickness increases, and the productivity is deteriorated. Defects such as cracks are likely to occur. When the concentration is 0.2% by mass or more, the film thickness obtained by a single film formation becomes large and cracks are likely to occur. Furthermore, since IPA has a higher drying speed and lower surface tension than water, it is very effective in obtaining a dense film with few defects. Here, titania is used as a component of the ceramic sol. However, a sol of silica or zirconia can be used instead of titania. A binder such as PVA (polyvinyl alcohol) is not used for the coating liquid. The method for preparing the coating liquid in the present invention is a two-stage process in which a ceramic sol stock solution is first prepared and diluted with IPA. Thus, the sol stock solution is prepared and then diluted with IPA to obtain a coating solution. Thus, an NF film having a small pore diameter can be produced. On the other hand, in a one-stage process in which IPA is mixed in advance as a diluent solvent when preparing a ceramic sol stock solution to obtain a coating solution having a desired concentration, agglomerated sol particles increase and the number of coarse pores increases. Absent. After the stirring, the coating solution prepared by the two-stage process is filtered through a filter cloth made of nylon and having a pore diameter of 10 to 100 μm, for example. The filter cloth is washed with distilled water immediately before.

(D ') Next, in order to adhere the coating liquid prepared by the two-stage process onto the inner wall surface of the flow path (cell) of the element 11e by the natural flow film forming method, the element 11e is set up as shown in FIG. Install. Next, the coating liquid is poured from the upper part of the element 11e and allowed to flow down naturally. After pouring is completed, the element 11e is moved by hand to remove the excess sol solution.

(E ') After coating of the coating liquid, the coating liquid remaining in the element 11e is wiped off, and as a first drying process, for example, as shown in FIG. Send it in contact with the top and dry it. The temperature of the wind is preferably about 10 to 40 ° C, more preferably 20 to 30 ° C. When air having a temperature lower than 10 ° C. is passed, drying of the titania sol adhering to the flow path (cell) surface does not progress, so that a dense film cannot be obtained and the film has a large pore diameter. Moreover, if warm air is passed at a temperature higher than 40 ° C., cracks are likely to occur on the film surface, which is not preferable. The speed at which the wind for drying passes through the flow path (cell) is 1 to 300 m / second, more preferably 50 to 200 m / second. If the speed of the wind passing through the flow path (cell) is 1 m / second or less, a dense film cannot be obtained and the pore diameter increases, and the speed of the wind passing through the flow path (cell) is 300 m / second. If it is above, cracks are likely to occur on the film surface, which is not preferable. Blow drying may be performed for about 10 to 60 minutes, preferably for about 10 to 20 minutes. Under the conditions as described above, the solvent evaporates from the inside of the channel (cell), that is, from the surface side of the membrane, by sending the air into the channel (cell) while being in contact with the membrane surface. When dried by performing such blowing, a structure in which the first NF film is densely formed can be obtained. In addition, blow drying is very effective for a lotus root shape which is difficult to dry uniformly. Since it is thought that drying of the solvent from the film surface is important for the densification of the film, masking the outer peripheral surface prevents the solvent containing titania sol from evaporating from the outer peripheral surface, and forms a better film. can do.

(F ') After the 1st drying process by ventilation, the 2nd drying process using a drier (constant temperature bath) is carried out. The second drying treatment is performed for 4 to 12 hours in a dryer controlled at 28 to 75 ° C. and humidity (no humidity control).

(G ') After the completion of the second drying treatment, the film tape 118 wound around the outer periphery is removed, and 1-50 ° C./h, preferably 8-30 ° C./h, for example, 450 ° C. at a rate of 25 ° C./h. After raising the temperature to the firing temperature and maintaining the firing temperature for 1 hour, cooling is performed at 1 to 50 ° C./h, preferably 8 to 30 ° C./h, for example, 25 ° C./h to obtain an NF film.

  The NF membrane obtained in the steps (2 ′) to (g ′) has a separation performance of a molecular weight cut off of 600 to 800 g / mol.

  FIG. 4 shows fraction curves obtained by measuring the blocking rate of each molecular weight standard substance for four types of membranes. (PEG200, PEG1000, PEG4000, and PEG6000 are used as molecular weight standard substances. The average molecular weights are 200, 1000, 4000, and 6000, respectively) As shown in FIG. The molecular weight is about 4000 g / mol. A first NF film was formed on the substrate by a dip film forming method, and the molecular weight cut off of the film formed by baking at 450 ° C. is 1000 g / mol. When the NF film formation by the dip film forming method is repeated twice, the molecular weight cutoff of the film is 900 g / mol. On the other hand, after the first NF film is formed, the second NF film is formed by the natural flow casting method, and the molecular weight cut off of the film formed at 450 ° C. is increased to 800 g / mol. be able to. According to the inventor's guess, according to the natural falling film forming method, the film thickness is too thick and cracks are likely to occur in the dip film forming twice. On the other hand, with the natural flow film formation method alone, the film thickness is too thin and the base material that is the base is exposed. Therefore, after the dip film forming, which is an intermediate manufacturing method, the film is naturally flowed on the dip film to prevent damage such as cracks on the base. In addition, since the dip film formation has already been performed on the base, a sufficiently small pore diameter has been obtained, so even if the natural flow film formation is performed thereon and the base is exposed, the effect is small. . As a result, the above effect can be obtained.

11e ... Element 12 ... Deposition chamber 14 ... Supply pump 15 ... Supply tank 21a ... Flange connection piping 21a ... Lung connection piping 21b ... Supply piping 21c ... Tank piping 21d ... Drain piping 22 ... T branch 112a, 112b ... Glaze part 118 ... Film tape 121a ... Ring 121b ... Ring 122a ... Upper element holding ring 122b ... Lower element holding ring 123b ... Bottom flange

Claims (2)

A method for producing a nanofiltration membrane, which is formed by further laminating a nanofiltration membrane layer on a ceramic filter having an ultrafiltration membrane layer,
The nanofiltration membrane formed by laminating is composed of a first nanofiltration membrane formation step comprising a film formation step by a dip film formation method, a drying step and a firing step, and a film formation step and a drying step by a natural flow film formation method. And a second nanofiltration membrane forming step comprising a firing step. The ceramic filter has an ultrafiltration membrane layer on each inner wall of a plurality of flow paths provided so as to penetrate between both end faces of the columnar shape in the axial direction inside the columnar ceramic filter. 2. The method for producing a nanofiltration membrane according to claim 1, wherein the nanofiltration membrane is a filter.