JP2019047779A - Method for producing soy sauce using porous film - Google Patents

Abstract

To provide a method for producing a soy sauce including a filtration step using a porous film and a cleaning step, which is a filtration method that is excellent in resistance to a cleaning liquid (medicine liquid) (medicine liquid resistance), is excellent in filtration performance, has a long lifetime, and dispenses with cleaning dye to a surface active agent-containing cleaning agent.SOLUTION: A method for producing a soy sauce includes the following steps of a filtration step of passing soy sauce through a porous film formed of a resin having a three-dimensional network structure to separate a filtrate from a dregs component; and a cleaning step of passing or immersing a cleaning liquid through/in the porous film to clean inside of the porous film, where the total of the area of a resin part having an area of 1 μmor less is 70% or more based on the total area of the resin part, and the cleaning liquid is hot water at 50°C or higher and 90°C or lower as primary cleaning water, 0.05 wt.% or more and 0.5 wt.% or less of sodium hypochlorite as secondary cleaning water, and 0.4 wt.% or more and 4 wt.% or less of an aqueous solution at 15°C or higher and 35°C or lower containing sodium hydroxide.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing soy sauce comprising a filtration step using a porous membrane and a washing step. More specifically, the present invention relates to a method for producing soy sauce which includes a filtration step using a porous membrane and a washing step, and is a method excellent in the resistance to a washing solution (chemical solution) and the washing recovery.

  Water treatment to obtain drinking water and industrial water from natural water sources such as suspended water, river water, lake water, groundwater, etc., treatment of domestic wastewater such as sewage to produce reclaimed water, clear water that can be released In order to treat sewage for the purpose of removal and removal of the sediment component in the method of producing soy sauce, a solid-liquid separation operation (cloud removal operation) for separating and removing the suspension is required. In this turbidity removal operation, suspended matter (clay, colloid, bacteria, etc.) derived from natural water source water which is suspended water is removed for the treatment of fresh water, and for sewage treatment, suspended matter in the lower water, activated sludge, etc. Suspensions (sludge etc.) in treated water subjected to biological treatment (secondary treatment) are removed, and in the method of producing soy sauce, sedimented components such as aggregated proteins and polysaccharides are removed.

Heretofore, these turbidity removal operations have mainly been carried out by the pressure flotation method, sedimentation method, sand filtration method, coagulation sedimentation sand filtration method, centrifugation, filter press, sieving, etc. Instead of the method, the membrane filtration method is spreading. Among the advantages of the membrane filtration method are: (1) high turbidity removal level of the obtained water quality and stability (high safety of the obtained water) (2) the installation space of the filtration device is small And (3) ease of automatic operation. For example, in the pretreatment of seawater desalination reverse osmosis filtration, as an alternative means of the pressurized flotation method, or as a subsequent stage of the pressurized flotation method, a membrane filtration method to further improve the water quality of the treated water subjected to pressurized flotation treatment Is used. A flat or hollow fiber porous ultrafiltration membrane or a microfiltration membrane having an average pore diameter in the range of several nm to several hundreds nm is used for the turbidity removal operation by the membrane filtration.
Thus, since the turbidity removal operation by the membrane filtration method has many advantages which the above-mentioned conventional pressurized flotation method, sand filtration method and the like do not have, there is a desalination pretreatment for seawater as an alternative or complementary means of the conventional method. Dissemination to, etc. is progressing, and an organic film composed of a resin as described in Patent Document 1 below is widely used as a porous film.

  Conventionally, in the method of producing soy sauce, after the membrane filtration step for separating and removing the sediment components such as proteins and polysaccharides, the used porous membrane is washed with water and then hypochlorous acid as a washing solution. The sodium hypochlorite and / or sodium hydroxide aqueous solution can not be removed if it is washed with an aqueous solution of sodium and / or sodium hydroxide and the amount of water after such washing does not exceed 70% of the water permeability of the new product. It was judged that it still adhered to the porous membrane, and further washing with a surfactant-containing washing solution was carried out.

JP, 2011-168741, A

As described above, although an organic membrane composed of a resin is often used as a porous membrane, when producing a porous filtration membrane using a resin material, if the film forming method is different, the microstructure of the material constituting the membrane is used. A difference appears. Usually, when the filtration operation is continued, the membrane is clogged, so the operation of the filtration method using the porous filtration membrane involves the washing step. On the other hand, the use of agents in the washing process induces membrane strength degradation. At this time, if there is a difference in the microstructure of the material constituting the porous filtration membrane, the degree of damage to the porous filtration membrane by the cleaning liquid (chemical solution) used in the repeated washing step is different, resulting in the filtration performance and the life. There is a problem of influence.
Further, in the method for producing soy sauce, after the membrane filtration step for separating and removing sediment components such as proteins and polysaccharides, the used porous membrane is washed with water, and then sodium hypochlorite as a washing solution and Washing with an aqueous solution of sodium hydroxide and carrying out further washing with a detergent containing detergent, in addition to the cost of the water and detergents used in the washing step, a large amount of waste water is generated which is further treated There is a problem of having to
In view of this problem, the problem to be solved by the present invention is a method of producing soy sauce including a filtration step using a porous filtration membrane and a washing step using a washing solution (chemical solution), which is excellent in chemical resistance and filtration performance, It is an object of the present invention to provide a method which has a long service life and does not require cleaning with a surfactant-containing detergent.

  The inventor of the present invention has conducted intensive studies and repeated experiments to solve the above-mentioned problems, and as a result, communication of pores from the inside of the membrane on the treated side of the porous filtration membrane to the outside of the membrane on the filtrate side By using a film having good conductivity, as a washing solution (chemical solution) used in the washing step, hot water of 50 ° C. or more and 90 ° C. or less as primary washing water, and 0.05 wt% or more as secondary washing water Using an aqueous solution at 15 ° C. or more and 35 ° C. or less containing 0.5% by weight or less of sodium hypochlorite and 0.4% by weight or more and 4% by weight or less of sodium hydroxide, and then further containing surfactant Even when the cleaning agent is not used, it has been unexpectedly found that the deterioration of the membrane can be minimized and the water permeability of the porous membrane can be recovered, and the present invention has been completed. is there.

That is, the present invention is as follows.
[1] The following steps:
A filtration step of passing a soy sauce containing a sediment component through a porous membrane composed of a resin having a three-dimensional network structure to separate a filtrate from the sediment component; and passing or immersing a cleaning solution in the porous membrane Washing the inside of the porous membrane;
A method of producing soy sauce containing
A field of view including the inner surface, a field of view including the outer surface of the film, and an equal distance between the fields of the SEM image of the cross section in the film thickness direction orthogonal to the inner surface of the porous membrane 2 The total area of the resin part having an area of 1 μm ² or less is 70% or more with respect to the total area of the resin part in each area of a total of four visual fields.
The cleaning solution comprises hot water of 50 ° C. to 90 ° C. as primary washing water, and 0.05 wt% to 0.5 wt% of sodium hypochlorite and 0.4 wt% as secondary washing water It is an aqueous solution of 15 ° C. or more and 35 ° C. or less containing sodium hydroxide of 4% by weight or less, and after washing with hot water as the primary washing water in the washing step, an aqueous solution as the secondary washing water To wash,
The manufacturing method of the said soy sauce characterized by the above-mentioned.
[2] the following steps:
A filtration step of passing a soy sauce containing a sediment component through a porous membrane composed of a resin having a three-dimensional network structure to separate a filtrate from the sediment component; and passing or immersing a cleaning solution in the porous membrane Washing the inside of the porous membrane;
A method of producing soy sauce containing
A field of view including the inner surface, a field of view including the outer surface of the film, and an equal distance between the fields of the SEM image of the cross section in the film thickness direction orthogonal to the inner surface of the porous membrane 2 The total area of the resin part having an area of 10 μm ² or more is 15% or less of the total area of the resin part in each area of a total of four visual fields of visual field, and
The cleaning solution comprises hot water of 50 ° C. to 90 ° C. as primary washing water, and 0.05 wt% to 0.5 wt% of sodium hypochlorite and 0.4 wt% as secondary washing water It is an aqueous solution of 15 ° C. or more and 35 ° C. or less containing sodium hydroxide of 4% by weight or less, and after washing with hot water as the primary washing water in the washing step, an aqueous solution as the secondary washing water To wash,
The manufacturing method of the said soy sauce characterized by the above-mentioned.
[3] The following steps:
A filtration step of passing a soy sauce containing a sediment component through a porous membrane composed of a resin having a three-dimensional network structure to separate a filtrate from the sediment component; and passing or immersing a cleaning solution in the porous membrane Washing the inside of the porous membrane;
A method of producing soy sauce containing
A field of view including the inner surface, a field of view including the outer surface of the film, and an equal distance between the fields of the SEM image of the cross section in the film thickness direction orthogonal to the inner surface of the porous membrane 2 The total area of the resin part having an area of 1 μm ² or less is 70% or more with respect to the total area of the resin part in each area of a total of four visual fields, and a resin having an area of 10 μm ² or more The total area of the part is 15% or less of the total area of the resin part, and
The cleaning solution comprises hot water of 50 ° C. to 90 ° C. as primary washing water, and 0.05 wt% to 0.5 wt% of sodium hypochlorite and 0.4 wt% as secondary washing water It is an aqueous solution of 15 ° C. or more and 35 ° C. or less containing sodium hydroxide of 4% by weight or less, and after washing with hot water as the primary washing water in the washing step, an aqueous solution as the secondary washing water To wash,
The manufacturing method of the said soy sauce characterized by the above-mentioned.
[4] The porous film is a SEM image of a film cross section in a film thickness direction orthogonal to the inner surface of the porous film, a field of view including the inner surface, a field of view including the outer surface of the film, and these fields of view in 2 field each region a total of four field of between was taken at regular intervals of, 1 [mu] m ² total area of the resin portion having an area of less than super 10 [mu] m ² is at most 15% of the total area of the resin portion The method according to any one of the above [1] to [3].
[5] The method according to any one of the above [1] to [4], wherein the surface open area ratio of the porous membrane is 25 to 60%.
[6] The relationship between the tensile breaking elongation E0 of the porous membrane before the washing step and the tensile breaking elongation E1 of the porous membrane after the washing step is E1 / E0 × 100 ≧ 80% , The method in any one of said [1]-[5].
[7] Tensile elongation at break E0 of the porous membrane before the washing step, and the porous membrane after repeating the washing step X times (here, X is an integer of 2 to 100) The method according to any one of the above [1] to [5], wherein the relationship with the tensile elongation at break EX is EX / E0 × 100 ≧ 70%.
[8] The above-mentioned [1], wherein the relationship between the flux L0 of the porous membrane before the filtration step and the flux L1 of the porous membrane after the cleaning step is L1 / L0 × 100 ≧ 95%. The method according to any one of [7].
[9] The flux L0 of the porous membrane before the filtration step, and the flux LX of the porous membrane after repeating the cleaning step X times (here, X is an integer of 2 to 100) The method according to any one of the above [1] to [7], wherein the relationship of is LX / L0 × 100 ≧ 90%.
[10] The method according to any one of the above [1] to [9], wherein the porous membrane is a hollow fiber membrane.
[11] The method according to any one of the above [1] to [10], wherein the resin constituting the porous membrane is a thermoplastic resin.
[12] The method according to [11] above, wherein the thermoplastic resin is a fluorine resin.
[13] The fluorine resin is vinylidene fluoride resin (PVDF), chlorotrifluoroethylene resin, tetrafluoroethylene resin, ethylene-tetrafluoroethylene copolymer (ETFE), ethylene-monochlorotrifluoroethylene copolymer (ECTFE) The method according to [12] above, which is selected from the group consisting of hexafluoropropylene resins, and mixtures of these resins.
[14] The washing step includes any of the washing steps for washing with the washing liquid and the rinsing steps for rinsing with rinse water for removing the remaining washing liquid components thereafter. How to describe.
[15] The method according to [14], wherein the amount of rinse water used in the rinse step is 100 L / m ² or less per unit area of the porous membrane.
[16] The above [14] or [14], wherein the chlorine concentration in the filtrate after resuming the filtration step after the rinsing step is 0.1 ppm or less and the pH of the filtrate is 8.6 or less 15].

  The filtration step in the method for producing soy sauce according to the present invention uses a membrane having good communication of pores extending from the inside of the membrane on the liquid side to the outside of the membrane on the filtrate side of the porous filtration membrane Therefore, as the cleaning solution (chemical solution) used in the cleaning step, the hot water of 50 ° C. or more and 90 ° C. or less as the primary cleaning water, and the next of 0.05% by weight or more and 0.5% by weight or less as the secondary cleaning water When using an aqueous solution of 15 ° C. or more and 35 ° C. or less containing sodium chlorite and 0.4% by weight or more and 4% by weight or less of sodium hydroxide, the deterioration of the membrane can be minimized. In a method of producing soy sauce comprising a filtration step using a porous filtration membrane and a washing step using a chemical solution, it is excellent in chemical solution resistance and filtration performance, has a long life, and further omits cleaning with a surfactant-containing cleaning solution Recovery of Permeability of Porous Membranes It is that way.

It is an example of the SEM image of the cross section of the porous membrane used for the filtration process in the manufacturing method of the soy sauce of this embodiment (a black part shows resin and a white part shows a pore (open hole)). A field of view including the inner surface, a field of view including the outer surface of the film, and the like between the fields of view in a SEM image of a film cross section in a film thickness direction orthogonal to the inner surface of the porous film used in Example 1. It is a histogram which shows the ratio (%) of the total of the area of the resin part which has a predetermined area with respect to the total area of the resin part in each area | region (circle 1-circle 4) of a total of four visual fields of 2 visual fields image | photographed by space | interval. A field of view including the inner surface, a field of view including the outer surface of the film, and the like between the fields of view in a SEM image of a film cross section in a film thickness direction orthogonal to the inner surface of the porous film used in Example 2. It is a histogram which shows the ratio (%) of the total of the area of the resin part which has a predetermined area with respect to the total area of the resin part in each area | region (circle 1-circle 4) of a total of four visual fields of 2 visual fields image | photographed by space | interval. A field of view including the inner surface, a field of view including the outer surface of the film, and the like between the fields of view in a SEM image of a film cross section in a film thickness direction orthogonal to the inner surface of the porous film used in Example 3. It is a histogram which shows the ratio (%) of the total of the area of the resin part which has a predetermined area with respect to the total area of the resin part in each area | region (circle 1-circle 4) of a total of four visual fields of 2 visual fields image | photographed by space | interval. In the SEM image of the film cross section in the film thickness direction orthogonal to the inner surface of the porous film used in Comparative Example 2, a field of view including the inner surface, a field of view including the outer surface of the film, and It is a histogram which shows the ratio (%) of the total of the area of the resin part which has a predetermined area to the total area of the resin part in each field (circle 1-circle 4) of a total of four views of 2 views photographed at equal intervals .

  Hereinafter, an embodiment of the present invention (hereinafter, also referred to as the present embodiment) will be described in detail. The present invention is not limited to the present embodiment.

<Filtration process>
In the method for producing soy sauce of this embodiment, a filtration step of separating the filtrate from the sediment component by passing the soy sauce containing the sediment component through a porous membrane composed of a resin of a three-dimensional network structure; A washing step of washing the inside of the porous membrane by passing or immersing the washing liquid in the porous membrane;
A method for producing soy sauce comprising: a hot water of 50 ° C. or more and 90 ° C. or less as primary washing water; and a next of 0.05 wt. It is an aqueous solution of 15 ° C. or more and 35 ° C. or less containing sodium chlorite and 0.4 wt% or more and 4 wt% or less of sodium hydroxide, and after washing with hot water as the primary washing water in the washing step. Washing with an aqueous solution as the secondary washing water,
It is characterized by
The shape of the porous membrane is not particularly limited, and may be a flat membrane, a tubular membrane, or a hollow fiber membrane, but from the viewpoint of space saving of the filtration device, that is, the membrane area per unit volume of membrane module is large. Hollow fiber membranes are preferred because they can be

As a filtration step in the method for producing soy sauce according to the present embodiment, for example, soy sauce (liquid to be treated) containing a sediment component is supplied to the hollow portion (inner surface) of the porous hollow fiber membrane. It may be a so-called internal pressure type filtration step which passes the membrane thickness (thickness) portion and takes out the liquid exuded from the outer surface of the porous hollow fiber membrane as a filtrate, or the outer side of the porous hollow fiber membrane It may be a so-called external pressure type filtration step in which the liquid to be treated is supplied from the surface and the filtrate which has exuded from the inner surface of the porous hollow fiber membrane is taken out through the hollow portion.
As used herein, the term "inside of the porous membrane" refers to a portion of a film thickness (thickness) in which a large number of pores are formed.

<Washing process>
The washing step in the method for producing soy sauce according to the present embodiment is a porous membrane with a hot water of 50 ° C. to 90 ° C. as primary washing water (hereinafter also referred to as hot water) as a primary washing water and a secondary washing water. An aqueous solution of 15 ° C. to 35 ° C. containing 0.05% by weight or more and 0.5% by weight or less of sodium hypochlorite and 0.4% by weight or more and 4% by weight or less of sodium hydroxide B) passing or immersing in this order to wash the inside of the porous membrane. That is, in the washing step, after washing with hot water as the primary washing water, it is washed with an aqueous solution as the secondary washing water. The washing step may include a washing step of washing with the washing solution and a rinsing step of rinsing with rinse water to remove the remaining washing component. The temperature of the primary washing water can be preferably 55 ° C. or more and 85 ° C. or less, more preferably 60 ° C. or more and 80 ° C. or less. The temperature of the secondary washing water can be preferably 20 ° C. or more and 35 ° C. or less. The concentration of sodium hydroxide in the secondary washing water is more preferably 0.7% by weight or more and 4% by weight or less, and still more preferably 1% by weight or more and 4% by weight or less. The concentration of sodium hypochlorite in the secondary washing water is more preferably 0.1 wt% or more and 0.5 wt% or less, and still more preferably 0.2 wt% or more and 0.5 wt% or less. As the washing step, for example, the washing solution is allowed to pass from the filtrate side to the soy sauce side in the opposite direction to the flow direction of soy sauce in the filtration step, ie, from the filtration side (soy sauce side surface) of the porous membrane. Examples of the method include reverse pressure water washing to separate and remove a deposit (insoluble component), and air scrubbing to shake the porous film with air to shake off the insoluble component attached to the porous film. The amount of rinsing water used in the rinsing step, it is preferable that the porous film per unit area 100L / m ² or less of, and more preferably at 50L / m ² or less. Moreover, it is preferable that chlorine concentration in the filtrate after restarting the said filtration process after the said rinse process is 0.1 ppm or less, and pH of this filtrate is 8.6 or less.
As described below, since the porous membrane used in the filtration step in the method for producing soy sauce of this embodiment has high porosity communication, it is possible that sediment component aggregates and the like adhere or remain on the surface or inside of the porous membrane. The residual rate of the substance to be removed is low, and in the washing step, the residual substance is easily removed by washing with hot water first, and then the amount of water permeation is sufficient by washing with a chemical solution. As a result, the conventional cleaning with surfactant-containing aqueous solution is not necessary.
The structure, raw material (material) and manufacturing method of the porous membrane used for the filtration process in the manufacturing method of soy sauce of this embodiment are explained in full detail below.

<Porous membrane>
The porous membrane is a field of view including the inner surface, a field of view including the outer surface of the membrane, and the like between the fields of view in the SEM image of the membrane cross section in the film thickness direction orthogonal to the inner surface of the porous membrane The total area of the resin part having an area of 1 μm ² or less is 70% or more with respect to the total area of the resin part in each area of a total of four visual fields of two visual fields photographed at a distance; The total area of the resin part having an area of 10 μm ² or more is 15% or less with respect to the total area of the resin part; the total area of the resin part having an area of 1 μm ² or less in each region But the total area of the resin part having an area of 70 μm or more and 10 μm ² or more with respect to the total area of the resin part is 15% or less with respect to the total area of the resin part; It is either. Preferred porous membranes in the respective regions, the total area of the resin portion having an area of 1 [mu] m ² or less, is 70% or more of the total area of the resin portion, an area of less than 1 [mu] m ² Ultra 10 [mu] m ² The total area of the resin part is 15% or less of the total area of the resin part, and the total area of the resin part having an area of 10 μm ² or more is the total area of the resin part It is 15% or less.

FIG. 1 is an example of a SEM image of a cross section of a porous membrane used in the filtration method of the present embodiment. Such an SEM image is a SEM image of a cross section of the membrane in the film thickness direction orthogonal to the inner surface of the hollow fiber porous membrane, a field of view including the inner surface, a field of view including the outer surface of the membrane, and a field of view Among the areas of the total of four visual fields of two visual fields photographed at equal intervals, among the areas closest to the inner side, the SEM image obtained by photographing the predetermined visual field in the area closest to the inner side is a binarized image is there.
In each of the regions, the difference in the presence distribution of the resin portion, ie, the pores, between the cross section in the thickness direction orthogonal to the inner surface of the hollow fiber porous membrane and the cross section parallel to the inner surface. The communication anisotropy of can be virtually ignored. In the present specification, the term "resin part" is a dendritic skeleton part of a three-dimensional network structure composed of a resin, which forms a large number of pores in a porous membrane. The portions shown in black in FIG. 1 are resin portions, and the white portions are holes.
Inside the porous membrane, there are formed communicating holes which are communicated while being bent from the inside to the outside of the membrane, and the inside of the SEM image of the membrane cross section in the film thickness direction orthogonal to the inside surface of the porous membrane The total area of the resin part having an area of 1 μm ² or less in each field of a total of four fields of view including the surface, the field of view including the outer surface of the film, and two fields captured at equal intervals between these fields However, if the total area of the resin portion is 70% or more, the communication of the holes is high (that is, the existence ratio of the communication holes in the membrane is high), and the flux of the liquid to be treated (water permeability, Permeability), retention of water permeability after cleaning is high, and damage to the membrane after chemical solution cleaning indicated by tensile breaking elongation is also alleviated. However, when the ratio of the total area of the resin part having an area of 1 μm ² or less to the total area of the resin part is too high, a tree of a three-dimensional network structure made of resin forms many pores in the porous membrane. to become as Jo skeletal portion is too thin, the total area of the resin portion having an area of 1 [mu] m ² or less, while maintaining 70% or more relative to the total area of the resin portion, 1 [mu] m ² greater than The total area of the resin part having an area is preferably 2% to 30% of the total area of the resin part, and the total area of the resin part having an area of 10 μm ² or more is the resin The total area of the resin part having an area of more than 1 μm ^{2 and} less than 10 μm ² is more preferably 15% or less with respect to the total area of the resin part. , and, 10μm ² or more Total area of the resin portion having a product is, those present at less than 15% 2% relative to the total area of the resin portion are more preferable. If the total area of the resin part having an area of more than 1 μm ² is present at 2% or more and 30% or less with respect to the total area of the resin part, the dendritic skeleton part having a three-dimensional network structure composed of resin Since it is not too thin, the strength and tensile elongation at break of the porous membrane can be maintained properly.

  2 to 5 respectively show SEM images of the cross section of the membrane in the thickness direction orthogonal to the inner surface of the porous membrane used in Example 1, Example 2, Example 3 and Comparative Example 2. In each of the four fields of view (circles 1 to 4) of 2 fields of view including 2 fields of view including the field of view including the outer surface of the film and the fields of view including the outer surface of the film It is a histogram which shows the ratio (%) of the sum total of the area of the resin part which has an area. In FIG. 1, the resin part appears in a granular form. 2 to 5 measure the area of each of the granular resin parts, and for each of the areas of the granular resin parts, the ratio of the area to the total area of all the resin parts in the field of a predetermined size in each region is a histogram It shows. The circle 1 in FIGS. 2 to 5 is a field of view including the inner surface, a field of view including the outer surface of the film, and a field of view in the SEM image of the film cross section in the film thickness direction orthogonal to the inner surface of the porous film. Of the total of four visual field areas of two visual fields photographed at regular intervals, it is the number of the area closest to the inner side, and the circle 4 is the number of the area closest to the inner side. For example, Example 1 circle 1 is a histogram when a visual field of a predetermined size in the innermost region of the porous hollow fiber membrane of Example 1 is photographed. The measuring method of the area distribution of the resin part in each area | region of a porous hollow fiber membrane is mentioned later.

  The surface open area ratio of the porous membrane is preferably 25 to 60%, more preferably 25 to 50%, and still more preferably 25 to 45%. If the surface opening ratio on the side to be in contact with the liquid to be treated is 25% or more, the clogging and the deterioration of the water permeability due to abrasion of the membrane surface are reduced, so that the filtration stability can be enhanced. On the other hand, if the surface open area ratio is high and the pore diameter is too large, the required separation performance may not be exhibited. Therefore, it is preferable that it is 10-700 nm, and, as for the average pore diameter of a porous membrane, 20-600 nm is more preferable. When the average pore size is 30 to 400 nm, the separation performance is sufficient, and the connectivity of the pores can be ensured. The method of measuring the surface aperture ratio and the average pore diameter will be described later, respectively.

  The thickness of the porous membrane is preferably 80 to 1,000 μm, more preferably 100 to 300 μm. If the film thickness is 80 μm or more, the strength of the film can be secured, and if it is 1000 μm or less, the pressure loss due to the film resistance will be small.

  The shape of the porous hollow fiber membrane may be an annular single layer membrane, but it may be a multilayer membrane having different pore sizes in the separation layer and the support layer supporting the separation layer. In addition, the inner and outer surfaces of the membrane may have an irregular cross-sectional structure such as having projections.

(Material of porous membrane (material))
The resin constituting the porous membrane is preferably a thermoplastic resin, and more preferably a fluorine resin. As a fluorine resin, vinylidene fluoride resin (PVDF), chlorotrifluoroethylene resin, tetrafluoroethylene resin, ethylene-tetrafluoroethylene copolymer (ETFE), ethylene-monochlorotrifluoroethylene copolymer (ECTFE), hexameric resin Those selected from the group consisting of fluoropropylene resins, and mixtures of these resins.
Thermoplastic resins include polyolefins, copolymers of olefins and halogenated olefins, halogenated polyolefins, and mixtures thereof. As a thermoplastic resin, for example, polyethylene, polypropylene, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride (which may contain a hexafluoropropylene domain), a mixture thereof It can be mentioned. These resins are excellent as a membrane material because they are thermoplastic and have excellent handleability and toughness. Among these, vinylidene fluoride resin, tetrafluoroethylene resin, hexafluoropropylene resin or mixtures thereof, ethylene, tetrafluoroethylene, homopolymers or copolymers of chlorotrifluoroethylene, or mixtures of homopolymers and copolymers are mechanical. It is preferable because it has excellent strength and chemical strength (chemical resistance) and good moldability. More specifically, fluorine resin such as polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, ethylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer and the like can be mentioned.

  The porous membrane can contain components (impurity and the like) other than the thermoplastic resin up to about 5% by mass. For example, the solvent used at the time of porous membrane manufacture is included. As described later, it contains the first solvent (hereinafter also referred to as non-solvent), the second solvent (hereinafter also referred to as good solvent or poor solvent), or both used as the solvent at the time of production of the porous membrane. . These solvents can be detected by pyrolysis GC-MS (gas chromatography mass spectrometry).

The first solvent is sebacic acid ester, citric acid ester, acetyl citric acid ester, adipic acid ester, trimellitic acid ester, oleic acid ester, palmitic acid ester, stearic acid ester, phosphoric acid ester, having 6 to 30 carbon atoms And at least one selected from the group consisting of epoxidized vegetable oils.
In addition, the second solvent is different from the first solvent in sebacic acid ester, citric acid ester, acetyl citric acid ester, adipic acid ester, trimellitic acid ester, oleic acid ester, palmitic acid ester, stearic acid ester, phosphorus It may be at least one selected from the group consisting of an acid ester, a fatty acid having 6 to 30 carbon atoms, and an epoxidized vegetable oil. Examples of fatty acids having 6 to 30 carbon atoms include capric acid, lauric acid and oleic acid. Moreover, as epoxidized vegetable oil, epoxy soybean oil, epoxidized linseed oil and the like can be mentioned.
The first solvent is thermoplastic even if the temperature of the first mixed solution is raised to the boiling point of the first solvent in the first mixed solution in which the ratio of the thermoplastic resin to the first solvent is 20:80. It is preferable that the resin be a non-solvent which does not dissolve uniformly in the first solvent.
The second solvent is a second mixture having a ratio of the thermoplastic resin to the second solvent of 20:80, and the temperature of the second mixture is higher than 25 ° C. and not more than the boiling point of the second solvent. It is preferable that the thermoplastic resin is a good solvent which is uniformly dissolved in the second solvent at a certain temperature.
The second solvent is a second mixed solution in which the ratio of the thermoplastic resin and the second solvent is 20:80, and the temperature of the second mixed solution is 25 ° C., and the thermoplastic resin is uniformly mixed in the second solvent. The thermoplastic resin is a poor solvent which is uniformly dissolved in the second solvent at any temperature which is higher than 100.degree. C. and not higher than the boiling point of the second solvent. preferable.

In the filtration step of the method for producing soy sauce of this embodiment, a porous hollow fiber membrane using polyvinylidene fluoride (PVDF) as a thermoplastic resin, which contains a first solvent (non-solvent) It can be used.
In this case, the first solvent is sebacic acid ester, citric acid ester, acetyl citric acid ester, adipic acid ester, trimellitic acid ester, oleic acid ester, palmitic acid ester, stearic acid ester, phosphoric acid ester, carbon number 6 At least one selected from the group consisting of fatty acids of 30 or less and epoxidized vegetable oil, wherein the ratio of polyvinylidene fluoride to the first solvent is 20:80 in the first mixed solution; The polyvinylidene fluoride can be a non-solvent which does not dissolve uniformly in the first solvent even if the temperature of the liquid is raised to the boiling point of the first solvent. As a non-solvent, bis 2-ethylhexyl adipate (DOA) is preferred.
Also, the porous hollow fiber membrane may contain a second solvent different from the first solvent. In this case, the second solvent is sebacic acid ester, citric acid ester, acetyl citric acid ester, adipic acid ester, trimellitic acid ester, oleic acid ester, palmitic acid ester, stearic acid ester, phosphoric acid ester, carbon number 6 At least one selected from the group consisting of fatty acids of 30 or less and epoxidized vegetable oil, wherein the ratio of polyvinylidene fluoride to the second solvent is 20:80; It is preferable that polyvinylidene fluoride be a good solvent which is uniformly dissolved in the second solvent at any temperature which is higher than 25 ° C. and not higher than the boiling point of the second solvent. In the second solvent, polyvinylidene fluoride is not uniformly dissolved in the second solvent when the temperature of the second mixed solution is 25 ° C., and the temperature of the second mixed solution is higher than 100 ° C. It is more preferable that polyvinylidene fluoride is a poor solvent which is uniformly dissolved in the second solvent at any temperature below the boiling point of the above. As a poor solvent, tributyl acetyl citrate (ATBC) is preferred.

(Physical properties of porous membrane)
In the porous membrane, the relationship between the tensile breaking elongation E0 of the porous membrane before the washing step and the tensile breaking elongation E1 of the porous membrane after the washing step is E1 / E0 × 100 ≧ 80%. Some are preferred. In addition, the tensile breaking elongation E0 of the porous membrane before the washing step and the tensile breaking of the porous membrane after repeating the washing step X times (here, X is an integer of 2 to 100). It is preferable that the relationship with the elongation EX is EX / E0 × 100 ≧ 70%.
The initial value of the tensile elongation at break is preferably 60% or more, more preferably 80% or more, still more preferably 100% or more, and particularly preferably 120% or more. The measuring method of tensile elongation at break will be described later.
The resistance to a chemical (resistance to damage to a film) can be indicated by the retention of tensile elongation at break before and after immersion in a chemical (the retention of elongation after immersion in a chemical), specifically, 0.5 weight Tensile elongation at break after immersing in an aqueous solution containing 10% sodium hypochlorite and 4% by weight sodium hydroxide (corresponding to the tensile elongation at break E1 of the porous hollow fiber membrane after the washing step) Is preferably kept at 80% or more, more preferably 85% or more, still more preferably 90% or more with respect to the initial value (corresponding to the tensile elongation at break E0 of the membrane before the washing step). is there.
Further, the relationship between the initial value E0 and the tensile elongation at break EX of the film after repeating the cleaning process such as the chemical cleaning process X times (X is an integer of 2 to 100) is: EX / E00 The ratio is preferably 70%, more preferably EX / E0 / 75%, and still more preferably EX / E0 ≧ 80%.

  Moreover, from a practical viewpoint, the compressive strength of the porous membrane is preferably 0.2 MPa or more, more preferably 0.3 to 1.0 MPa, and still more preferably 0.4 to 1.0 MPa.

(Permeability of porous membrane)
As the porous membrane, one having a relationship between the flux L0 of the porous membrane before the filtration step and the flux L1 of the porous membrane after the washing step is preferably L1 / L0 × 100 ≧ 95%.
In addition, as the porous membrane, the flux L0 of the porous membrane before the filtration step and the porous membrane after repeating the cleaning step X times (here, X is an integer of 2 to 100) It is preferable that the relationship between the flux and the flux LX be such that LX / L0 × 100 ≧ 90%.

<Method of producing porous membrane>
Hereinafter, the manufacturing method of a porous hollow fiber membrane is demonstrated. However, the method for producing a porous hollow fiber membrane used in the filtration step in the method for producing soy sauce of the present embodiment is not limited to the following production method.
The method for producing a porous hollow fiber membrane comprises the steps of (a) preparing a melt-kneaded product, and (b) supplying the melt-kneaded product to a spinning nozzle having a multiple structure, and extruding the melt-kneaded product from the spinning nozzle. The method may include the steps of obtaining a membrane and (c) extracting the plasticizer from the hollow fiber membrane. When the melt-kneaded product contains an additive, the method may further include the step (d) of extracting the additive from the hollow fiber membrane after the step (c).

The concentration of the thermoplastic resin of the melt-kneaded product is preferably 20 to 60% by mass, more preferably 25 to 45% by mass, and still more preferably 30 to 45% by mass. If this value is 20 mass% or more, mechanical strength can be increased, and if it is 60 mass% or less, water permeability can be increased. The melt-kneaded product may contain an additive.
The melt-kneaded product may be composed of two components of a thermoplastic resin and a solvent, or may be composed of three components of a thermoplastic resin, an additive and a solvent. The solvent contains at least a non-solvent as described later.
As the extractant used in step (c), it is preferable to use a liquid such as methylene chloride or various alcohols which does not dissolve the thermoplastic resin but which has a high affinity for the plasticizer.
When a melt-kneaded product containing no additive is used, the hollow fiber membrane obtained through the step (c) may be used as a porous hollow fiber membrane. When a porous hollow fiber membrane is produced using a melt-kneaded product containing additives, after step (c), the additive (d) is extracted and removed from the hollow fiber membrane to obtain a porous hollow fiber membrane It is preferable to go through the process further. As the extractant in the step (d), it is preferable to use a liquid which can dissolve the used additives such as hot water or an acid or an alkali but not the thermoplastic resin.

An inorganic substance may be used as an additive. The inorganic substance is preferably an inorganic fine powder. The primary particle diameter of the inorganic fine powder contained in the melt-kneaded product is preferably 50 nm or less, and more preferably 5 nm or more and less than 30 nm. Specific examples of the inorganic fine powder include silica (including fine powder silica), titanium oxide, lithium chloride, calcium chloride, organic clay and the like, and among these, fine powder silica is preferable from the viewpoint of cost. The above-mentioned "primary particle size of inorganic fine powder" means a value determined from analysis of an electron micrograph. That is, first, a group of inorganic fine powders is pretreated by the method of ASTM D3849. Thereafter, the particle diameters of 3000 to 5000 particles photographed in the transmission electron micrograph are measured, and the primary particle diameter of the inorganic fine powder can be calculated by arithmetically averaging these values.
About the inorganic fine powder inside a porous hollow fiber membrane, the raw material (material) of the inorganic fine powder which exists can be identified by identifying the element which exists by a fluorescent X ray etc.
When an organic substance is used as the additive, the hollow fiber membrane can be rendered hydrophilic by using a hydrophilic polymer such as polyvinyl pyrrolidone or polyethylene glycol. In addition, the viscosity of the melt-kneaded product can be controlled by using an additive having high viscosity such as glycerin and ethylene glycol.

Next, the step of preparing (a) the melt-kneaded product in the method for producing a porous hollow fiber membrane of the present embodiment will be described in detail.
In the method of manufacturing the porous hollow fiber membrane of the present embodiment, the non-solvent of the thermoplastic resin is mixed with the good solvent or the poor solvent. The mixed solvent after mixing becomes a non-solvent of the thermoplastic resin to be used. Thus, when a non-solvent is used as a raw material of the membrane, a porous hollow fiber membrane having a three-dimensional network structure can be obtained. The mechanism of action is not necessarily clear, but it is thought that crystallization of the polymer is appropriately inhibited and a three-dimensional network structure is more likely to be obtained if a solvent having a lower solubility is used by mixing a non-solvent. . For example, non-solvent and poor solvent or good solvent are phthalic acid ester, sebacic acid ester, citric acid ester, acetyl citric acid ester, adipic acid ester, trimellitic acid ester, oleic acid ester, palmitic acid ester, stearic acid ester It is selected from the group consisting of phosphate esters, fatty acids having 6 to 30 carbon atoms, and various esters such as epoxidized vegetable oil.
The solvent which can dissolve the thermoplastic resin at normal temperature is a good solvent. The solvent which can not dissolve at normal temperature but can be dissolved at high temperature can be a poor solvent of the thermoplastic resin. The solvent which can not dissolve even at high temperature. Although called non-solvent, good solvent, poor solvent, and non-solvent can be determined as follows.
Add about 2 g of thermoplastic resin and about 8 g of solvent in a test tube, heat to the boiling point of the solvent in 10 ° C increments with a test tube block heater, mix the inside of the test tube with a spatula, etc. What dissolves is a good solvent or a poor solvent, and what does not dissolve is a non-solvent. Those which are soluble at relatively low temperatures of 100 ° C. or less are judged as good solvents, and those which do not dissolve unless they are heated to a temperature of 100 ° C. or more and boiling points or less are judged as poor solvents.
For example, using polyvinylidene fluoride (PVDF) as a thermoplastic resin and tributyl acetyl citrate (ATBC), dibutyl sebacate or dibutyl adipate as a solvent, PVDF is uniformly mixed with these solvents at about 200 ° C. Dissolve. On the other hand, using bis (2-ethylhexyl) adipate (DOA), diisononyl adipate, or bis (2-ethylhexyl) sebacate as the solvent, PVDF does not dissolve in these solvents even if the temperature is raised to 250 ° C.
When ethylene-tetrafluoroethylene copolymer (ETFE) is used as the thermoplastic resin and diethyl adipate is used as the solvent, ETFE is uniformly mixed and dissolved at about 200 ° C. On the other hand, it does not dissolve when bis 2-ethylhexyl adipate (DIBA) is used as a solvent.
Also, when ethylene-monochlorotrifluoroethylene copolymer (ECTFE) is used as a thermoplastic resin and triethyl citrate is used as a solvent, it dissolves uniformly at about 200 ° C. When triphenylphosphorous acid (TPP) is used, it dissolves do not do.

  EXAMPLES Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto. Each physical property value in an Example and a comparative example was calculated by the following methods, respectively.

(1) Outer diameter and inner diameter of porous hollow fiber membrane The porous hollow fiber membrane was thinly sliced using a razor in a cross section orthogonal to the length direction, and the outer diameter and inner diameter were measured with a 100-fold magnifying glass. . For one sample, measurement was performed on 60 cross sections at intervals of 30 mm in the length method, and the average value was taken as the outer diameter and the inner diameter of the hollow fiber membrane.

(2) Electron Microscopy The porous hollow fiber membrane was cut in an annular shape in a cross section orthogonal to the length direction, 10% phosphotungstic acid + osmium tetraoxide staining was performed, and embedded in an epoxy resin. Then, after trimming, the sample cross section was subjected to BIB processing to produce a smooth cross section, and a conductive processing was performed to produce a speculum sample. Using the electron microscope SU8000 series manufactured by HITACHI, the produced microscope sample is an electron microscope (SEM) image of a cross section of the film at an acceleration voltage of 1 kV at 5,000 to 30,000 times a thickness (thick portion) cross section Within each of the four fields of view (circles 1 to 4 in FIGS. 2 to 5), the field of view including the inner surface of the field of view, the field of view including the outer surface of the film, and two fields of view taken at equal intervals between these fields of view. Taken with a given field of view. Depending on the average pore size, the magnification can be changed, and specifically, when the average pore size is 0.1 μm or more, 5000 times, and when the average pore size is 0.05 μm or more and less than 0.1 μm. And 10,000 times, and when the average pore diameter is less than 0.05 μm, 30,000 times. The size of the field of view was 2560 × 1920 pixels.
For image processing, ImageJ was used, and threshold processing (Image-Adjust-Treshold: Otsu method (select Otsu)) was performed on the photographed SEM image to binarize the hole portion and the resin portion. .
Surface aperture ratio: The surface aperture ratio was measured by calculating the ratio of the resin part and the hole part of the binarized image.
Area distribution of resin part: The size of the binarized granular resin part included in the photographed SEM image was measured using the "Analyze Particle" command (Analyse Particle: Size 0.10-Infinity) of ImageJ. . Assuming that the total area of all the resin parts contained in the SEM image is ΣS and the area of the resin part of 1 μm ² or less is ΣS (<1 μm ² ), 1 μm is calculated by calculating ΣS (<1 μm ² ) / ΣS. The area ratio of the resin part having an area of ² or less was calculated. Similarly, the area ratio of the resin part having an area in a predetermined range was calculated.
In addition, about the noise removal at the time of performing a binarization process, the resin part of the area less than 0.1 micrometer ² was removed as a noise, and the resin part of the area 0.1 micrometer ² or more was made into analysis object. Also, noise removal was performed by applying median filtering (Process-Filters-Median: Radius: 3.0 pixels).
In addition, the granular resin portion cut at the end of the SEM image was also measured. In addition, "Incude Holes" was not processed. In addition, no process was performed to correct the shape of the "snowman" type into a "flat" type or the like.
Average pore size: Measured using ImageJ's "Plugins-Bone J-Thickness" command. In addition, space size was defined as the largest circle size which enters an air gap.

(3) Flux (water permeability, initial pure water flux)
After immersing the porous hollow fiber membrane in ethanol, the pure water immersion is repeated several times, and then one end of the wet hollow fiber membrane of about 10 cm length is sealed, and the injection needle is inserted into the hollow portion at the other end, 25 Pure water of 25 ° C. is injected from the injection needle at a pressure of 0.1 MPa in an environment of 0 ° C., and the amount of pure water transmitted from the outer surface of the membrane is measured, and the following formula:
Initial pure water flux [L / m ² / h] = 60 × (permeate flow rate [L]) / {π × (outer membrane diameter [m]) × (effective membrane length [m]) × (measurement time [min] )}
The pure water flux was determined by the following equation to evaluate the water permeability.
The "membrane effective length" refers to the net length of the membrane excluding the portion where the injection needle is inserted.

(4) Permeability retention rate at the time of real liquid (soybean oil) filtration As a real liquid, a fresh soy sauce stock solution was used.
Permeability retention rate at the time of filtration of a real liquid is an index for judging the degree of permeability degradation due to clogging (fouling). After immersing in ethanol, the wet hollow fiber membrane, in which immersion in pure water was repeated several times, was filtered by an internal pressure method with an effective membrane length of 11 cm. First, pure water was filtered at a filtration pressure of 10 m ³ per day per 1 m ^{2 of} surface area of the membrane, and permeated water was collected for 1 minute to obtain an initial pure water water permeability.
The measurement procedure of permeability retention rate at the time of real liquid filtration is
(I) Measurement of water permeability with pure water, (ii) real liquid filtration, (iii) washing with pure water, (iv) hot water washing, (v) chemical solution washing. When the water permeability was less than 70% of the initial water permeability in (v), it was decided to carry out (vi) surfactant washing.
First, (i) pure water was introduced into the circulation tank, circulation filtration was performed so that the pressure difference between the membranes was 0.05 MPa, and permeated water was collected for 1 minute to obtain an initial water permeability.
Next, (ii) after draining the water in the piping, the fresh soy sauce stock solution was charged into the circulation tank, and circulation filtration was performed so as to obtain a transmembrane pressure difference of 0.15 MPa until 90% recovery was made on the filtration side.
Next, after (iii) draining the uncooked soy sauce stock solution in the piping, add pure water to the circulation tank, wash it with water, carry out circulation filtration so that the pressure difference between membranes is 0.05 MPa, and permeate for 1 minute Collected water permeability was compared with the initial water permeability.
Next, (iv) after draining the water in the piping, warm water at 60 ° C. was charged into the circulation tank, circulation filtration was performed for 30 minutes, and hot water washing was performed. After warm water washing, circulation filtration was carried out so that the transmembrane pressure difference would be 0.05 MPa, the permeated water was collected for 1 minute, and the water permeation amount was compared with the initial water permeation amount.
Next, after (v) hot water in the pipe was removed, the prepared chemical solution was charged into the circulation tank, and membrane circulation filtration was performed to perform chemical solution cleaning for 30 minutes. As a chemical solution, an aqueous solution in which 0.3% sodium hypochlorite and 2% caustic soda were mixed was used. After chemical solution cleaning, after removing the chemical solution in the piping, pure water is put into the circulation tank, circulation filtration is performed so that the pressure difference between the membranes = 0.05 MPa, and the permeated water coming out is 10 L / m ² The sampling was repeated repeatedly, and when the chlorine concentration of the permeate water was 0.1 ppm or less and the pH was 8.6 or less, the water washing was ended, and the amount of water in the rinse was recorded. In addition, circulation filtration was performed with the same transmembrane differential pressure to collect the permeated water for 1 minute, and the water permeability was determined and compared with the initial water permeability.
If the water permeability is less than 70% of the initial water permeability in (v), then (vi) drain the water in the piping, then charge the chemical solution into the circulation tank and perform membrane circulation filtration for 30 minutes. Chemical cleaning was performed. For the drug solution, Ultra Zeal 11 aqueous solution made by 0.5% Ecolab was used. After chemical solution cleaning, after removing the chemical solution in the pipe, pure water is put into the circulation tank, and water washing is performed by circulation filtration so that the pressure difference between membranes is 0.05 MPa, and then the same pressure difference between membranes is continued. Circulating filtration was performed to collect permeated water for 1 minute, and the amount of water permeation was regarded as the amount of water permeation, and was compared with the initial amount of water permeation.
Permeability retention rate during real liquid filtration, the following formula:
Permeability retention ratio during actual liquid filtration [%] = 100 × (water permeability after each step [g]) / (initial pure water water permeability [g])
Determined by
Each parameter was calculated by the following equation:
Transmembrane differential pressure filtration pressure = {(input pressure) + (output pressure)} / 2
Transmembrane surface area [m ² ] = π × (Hollow fiber membrane outer diameter [m]) × (Hollow fiber membrane effective length [m])
Membrane surface linear velocity [m / s] = 4 × (circulating water volume [m ³ / s]) / π × (inner diameter of membrane [m]) 2 Moreover, all the operations were performed at 25 ° C. and a film surface linear velocity of 1.0 m / sec.

Example 1
40% by mass of PVDF resin (Kureha KF-W # 1000) as a thermoplastic resin, 23% by mass of finely powdered silica (primary particle diameter: 16 nm), and bis 2-ethylhexyl adipate (DOA) as a non-solvent. A melt-kneaded product was prepared using 9% by mass and tributyl acetyl citrate (ATBC, boiling point 343 ° C.) 4.1% by mass as a poor solvent. The temperature of the obtained molten mixture was 240.degree. The resulting melt-blended material is passed through a free running distance of 120 mm using a double tube structure spinning nozzle, and then solidified in water at 30 ° C., and a porous structure is obtained by heat induced phase separation method. Developed. The resulting hollow fiber extrudates were pulled at a speed of 5 m / min and wound on a skein. The wound hollow fiber extrudate is immersed in isopropyl alcohol to extract and remove DOA and ATBC, and then immersed in water for 30 minutes to replace the hollow fiber membrane with water, and then to 70% in a 20 mass% aqueous NaOH solution. C. for 1 hour, and then repeated washing with water to extract and remove finely divided silica, thereby producing a porous hollow fiber membrane.
Table 1 below shows the composition and manufacturing conditions of the obtained porous membrane and various physical properties. The obtained porous hollow fiber membrane had a three-dimensional network structure. In addition, the flux (water permeability) was high, the permeability retention during filtration was 75%, and the membrane had high communication.
In addition, the tensile rupture elongation retention after chemical immersion was 80%, and the tensile rupture elongation retention after chemical cycle cleaning repeatedly for 10 cycles was as high as 70%. Furthermore, the retention of water permeability after immersion in chemical solution is 99%, the retention of water permeability after repeated chemical cycle cleaning is 95%, the water permeability can be maintained, and the large pore diameter of the membrane due to chemical solution deterioration is also seen It was not done.
After filtering 27 L (90% recovery) of 30 L of deep-opening raw soy sauce with a viscosity of 3.6 mPa · s, turbidity 21.8 NTU, and Brix 35.1% over about 14 hours, hollow fiber under the washing conditions shown in Table 1 below The permeability retention when the membrane was washed with hot water at a temperature of about 60 ° C. was 66%. Then, when it wash | cleaned in 30 degreeC aqueous solution containing 0.3 weight% sodium hypochlorite and 2 weight% sodium hydroxide for 30 minutes, the water permeation retention showed a high washing | cleaning recovery property as 87%.

Example 2
40% by mass of ETFE resin (manufactured by Asahi Glass Co., Ltd., TL-081) as a thermoplastic resin, 23% by mass of finely powdered silica (primary particle diameter: 16 nm), 32.9% by mass of bis-2-ethylhexyl adipate (DOA) as a non-solvent A melt-kneaded product was prepared using% and 4.1% by mass of diisobutyl adipate (DIBA) as a poor solvent. The temperature of the obtained molten mixture was 240.degree. The resulting melt-blended material is passed through a free running distance of 120 mm using a double tube structure spinning nozzle, and then solidified in water at 30 ° C., and a porous structure is obtained by heat induced phase separation method. Developed. The resulting hollow fiber extrudates were pulled at a speed of 5 m / min and wound on a skein. The wound hollow fiber extrudate is immersed in isopropyl alcohol to extract and remove DOA and DIBA, and then immersed in water for 30 minutes to replace the hollow fiber membrane with water, and then to 70% in a 20 mass% aqueous NaOH solution. C. for 1 hour, and then repeated washing with water to extract and remove finely divided silica, thereby producing a porous hollow fiber membrane.
Table 1 below shows the composition and manufacturing conditions of the obtained porous membrane and various physical properties. The obtained porous hollow fiber membrane had a three-dimensional network structure. In addition, the flux (water permeability) was high, the permeability retention during filtration was 70%, and the membrane had high communication.
In addition, the tensile rupture elongation retention after chemical immersion was 98%, and the tensile rupture elongation retention after chemical cycle cleaning repeated 10 cycles was as high as 90%. Furthermore, the retention of water permeability after immersion in chemical solution is 100%, the retention of water permeability after chemical cycle cleaning is 96% after repeated chemical solution cleaning, and the water permeability can be maintained, and the large pore diameter of the film due to chemical solution deterioration is also seen It was not done.
After filtering 27 L (90% recovery) of 30 L of deep-opening raw soy sauce with a viscosity of 3.6 mPa · s, turbidity 21.8 NTU, and Brix 35.1% over about 14 hours, hollow fiber under the washing conditions shown in Table 1 below The permeability retention when the membrane was washed with hot water at a temperature of about 60 ° C. was 57%. Then, when it wash | cleaned in 30 degreeC aqueous solution containing 0.3 weight% sodium hypochlorite and 2 weight% sodium hydroxide for 30 minutes, the water permeation retention showed a high washing | cleaning recovery property as 87%.

[Example 3]
40% by mass of ECTFE resin (manufactured by Solvay Specialty Polymers, Halar 901) as thermoplastic resin and 23% by mass of finely divided silica (primary particle diameter: 16 nm) and triphenylphosphorous acid (TPP) 32 as non-solvent A melt-kneaded product was prepared using 9% by mass and bis-2-ethylhexyl adipate (DOA) 4.1% by mass as a poor solvent. The temperature of the obtained molten mixture was 240.degree. The resulting melt-blended material is passed through a free running distance of 120 mm using a double tube structure spinning nozzle, and then solidified in water at 30 ° C., and a porous structure is obtained by heat induced phase separation method. Developed. The resulting hollow fiber extrudates were pulled at a speed of 5 m / min and wound on a skein. The wound hollow fiber extrudate is immersed in isopropyl alcohol to extract and remove TPP and DOA, and then immersed in water for 30 minutes to replace the hollow fiber membrane with water, and then to 70% in 20% by weight aqueous NaOH solution. C. for 1 hour, and then repeated washing with water to extract and remove finely divided silica, thereby producing a porous hollow fiber membrane.
Table 1 below shows the composition and manufacturing conditions of the obtained porous membrane and various physical properties. The obtained porous hollow fiber membrane had a three-dimensional network structure. In addition, the flux (water permeability) was high, the permeability retention during filtration was 80%, and the membrane had high communication.
Moreover, the tensile rupture elongation retention after chemical immersion was 97%, and the tensile rupture elongation retention after chemical cycle cleaning repeated 10 cycles was as high as 95%. Further, the retention of water permeability after immersion in a chemical solution was 98%, the retention of water permeability after repeated chemical cycle cleaning for 10 cycles was 95%, and no chemical degradation was observed.
After filtering 27 L (90% recovery) of 30 L of deep-opening raw soy sauce with a viscosity of 3.6 mPa · s, turbidity 21.8 NTU, and Brix 35.1% over about 14 hours, hollow fiber under the washing conditions shown in Table 1 below The permeability retention when the membrane was washed with hot water at a temperature of about 60 ° C. was 60%. Thereafter, the plate was washed with an aqueous solution at 30 ° C. containing 0.3% by weight sodium hypochlorite and 2% by weight sodium hydroxide for 30 minutes, and the water retention rate showed a high washing recovery property of 86%.

Comparative Example 1
A hollow fiber membrane of Comparative Example 1 was obtained in the same manner as in Example 1 except that the solvent was changed to ATBC only. Table 1 below shows the composition and manufacturing conditions of the obtained porous membrane and various physical properties. The obtained porous hollow fiber membrane had a spherulite structure. In addition, the film had a low flux and low communication, and the retention of elongation at break after immersion in a chemical solution was also low at 30%.
After filtering 27 L (90% recovery) of 30 L of deep-opening raw soy sauce with a viscosity of 3.6 mPa · s, turbidity 21.8 NTU, and Brix 35.1% over about 14 hours, hollow fiber under the washing conditions shown in Table 1 below When the membrane was washed with hot water at a temperature of about 60 ° C., the water permeability retention rate was as low as 3%. Thereafter, the plate was washed with an aqueous solution of 0.3% by weight sodium hypochlorite and 2% by weight sodium hydroxide at 30 ° C. for 30 minutes, but the retention of water permeability was as low as 23%.

Comparative Example 2
A hollow fiber membrane of Comparative Example 2 was obtained in the same manner as in Example 1 except that the amount of finely divided silica was 0% and the solvent was only γ-butyrolactone. Table 1 below shows the composition and manufacturing conditions of the obtained porous membrane and various physical properties. The obtained porous hollow fiber membrane had a spherulite structure. In addition, the flux was low and the membrane was low in communication, and the retention of elongation at break after immersion in a chemical solution was as low as 30%.
The hollow fiber membrane was washed with hot water at a temperature of about 60 ° C. after filtering 27 liters (recovery rate 90%) of 30 liters of concentrated fresh raw soy sauce having a viscosity of 3.6 mPa · s, turbidity 21.8 NTU, and Brix 35.1% over about 14 hours. Permeability retention rate was as low as 5%. Thereafter, the plate was washed with an aqueous solution of 0.3% by weight sodium hypochlorite and 2% by weight sodium hydroxide at 30 ° C. for 30 minutes, but the water retention was as low as 35% and showed a washing recovery property.

Comparative Example 3
A hollow fiber membrane of Comparative Example 3 was obtained in the same manner as in Example 3, except that the solvent was only DOA. Table 1 below shows the composition and manufacturing conditions of the obtained porous membrane and various physical properties. The obtained porous hollow fiber membrane had a spherulite structure. In addition, the flux was low and the membrane was low in communication, and the retention of elongation at break after immersion in a chemical solution was as low as 30%.
The hollow fiber membrane was washed with hot water at a temperature of about 60 ° C. after filtering 27 liters (recovery rate 90%) of 30 liters of concentrated fresh raw soy sauce having a viscosity of 3.6 mPa · s, turbidity 21.8 NTU, and Brix 35.1% over about 14 hours. Permeability retention rate was as low as 5%. Thereafter, the plate was washed with an aqueous solution of 0.3% by weight sodium hypochlorite and 2% by weight sodium hydroxide at 30 ° C. for 30 minutes, but the retention of water permeability was as low as 41%.

Comparative Example 4
It carried out like Example 1 except having changed washing | cleaning conditions after soy sauce filtration. The water permeability retention after washing with water at 25 ° C. as the primary washing liquid was 27%, and the water permeability retention after washing with an aqueous solution containing 3000 ppm sodium hypochlorite and 2% sodium hydroxide was 60%. Further washing with a surfactant-containing aqueous solution was carried out, but the water permeability after washing with the surfactant-containing aqueous solution remained at 84%.

  From the above results, it was found that the membrane having good communication was excellent in resistance to a chemical solution, filtration performance, and had a long life.

  The filtration step in the method for producing soy sauce according to the present invention uses a membrane having good communication of pores extending from the inside of the membrane on the liquid side to the outside of the membrane on the filtrate side of the porous filtration membrane Therefore, as the cleaning solution (chemical solution) used in the cleaning step, the hot water of 50 ° C. or more and 90 ° C. or less as the primary cleaning water, and the next of 0.05% by weight or more and 0.5% by weight or less as the secondary cleaning water When using an aqueous solution of 15 ° C. or more and 35 ° C. or less containing sodium chlorite and 0.4 wt% or more and 4 wt% or less of sodium hydroxide, deterioration of the film can be minimized and chemical resistance It is excellent in filtration performance and has a long life, and furthermore, the surfactant-containing detergent can eliminate the need for cleaning.

Claims (16)

The following steps:
A filtration step of passing a soy sauce containing a sediment component through a porous membrane composed of a resin having a three-dimensional network structure to separate a filtrate from the sediment component; and passing or immersing a cleaning solution in the porous membrane Washing the inside of the porous membrane;
A method of producing soy sauce containing
A field of view including the inner surface, a field of view including the outer surface of the film, and an equal distance between the fields of the SEM image of the cross section in the film thickness direction orthogonal to the inner surface of the porous membrane 2 The total area of the resin part having an area of 1 μm ² or less is 70% or more with respect to the total area of the resin part in each area of a total of four visual fields.
The cleaning solution comprises hot water of 50 ° C. to 90 ° C. as primary washing water, and 0.05 wt% to 0.5 wt% of sodium hypochlorite and 0.4 wt% as secondary washing water It is an aqueous solution of 15 ° C. or more and 35 ° C. or less containing sodium hydroxide of 4% by weight or less, and after washing with hot water as the primary washing water in the washing step, an aqueous solution as the secondary washing water To wash,
The manufacturing method of the said soy sauce characterized by the above-mentioned. The following steps:
A filtration step of passing a soy sauce containing a sediment component through a porous membrane composed of a resin having a three-dimensional network structure to separate a filtrate from the sediment component; and passing or immersing a cleaning solution in the porous membrane Washing the inside of the porous membrane;
A method of producing soy sauce containing
A field of view including the inner surface, a field of view including the outer surface of the film, and an equal distance between the fields of the SEM image of the cross section in the film thickness direction orthogonal to the inner surface of the porous membrane 2 The total area of the resin part having an area of 10 μm ² or more is 15% or less of the total area of the resin part in each area of a total of four visual fields of visual field, and
The cleaning solution comprises hot water of 50 ° C. to 90 ° C. as primary washing water, and 0.05 wt% to 0.5 wt% of sodium hypochlorite and 0.4 wt% as secondary washing water It is an aqueous solution of 15 ° C. or more and 35 ° C. or less containing sodium hydroxide of 4% by weight or less, and after washing with hot water as the primary washing water in the washing step, an aqueous solution as the secondary washing water To wash,
The manufacturing method of the said soy sauce characterized by the above-mentioned. The following steps:
A filtration step of passing a soy sauce containing a sediment component through a porous membrane composed of a resin having a three-dimensional network structure to separate a filtrate from the sediment component; and passing or immersing a cleaning solution in the porous membrane Washing the inside of the porous membrane;
A method of producing soy sauce containing
A field of view including the inner surface, a field of view including the outer surface of the film, and an equal distance between the fields of the SEM image of the cross section in the film thickness direction orthogonal to the inner surface of the porous membrane 2 The total area of the resin part having an area of 1 μm ² or less is 70% or more with respect to the total area of the resin part in each area of a total of four visual fields, and a resin having an area of 10 μm ² or more The total area of the part is 15% or less of the total area of the resin part, and
The cleaning solution comprises hot water of 50 ° C. to 90 ° C. as primary washing water, and 0.05 wt% to 0.5 wt% of sodium hypochlorite and 0.4 wt% as secondary washing water It is an aqueous solution of 15 ° C. or more and 35 ° C. or less containing sodium hydroxide of 4% by weight or less, and after washing with hot water as the primary washing water in the washing step, an aqueous solution as the secondary washing water To wash,
The manufacturing method of the said soy sauce characterized by the above-mentioned. The porous membrane is a field of view including the inner surface, a field of view including the outer surface of the membrane, and a field of view in the SEM image of the cross section of the membrane in the thickness direction orthogonal to the inner surface of the porous membrane. in each area of a total of four field of 2 field taken at regular intervals, the total area of the resin portion having an area of less than 1 [mu] m ² ultra 10 [mu] m ² is 15% or less relative to the total area of the resin portion, wherein The method according to any one of Items 1 to 3.   The method according to any one of claims 1 to 4, wherein the surface open area ratio of the porous membrane is 25 to 60%.   The relationship between the tensile breaking elongation E0 of the porous membrane before the washing step and the tensile breaking elongation E1 of the porous membrane after the washing step is E1 / E0 × 100 ≧ 80%. The method according to any one of 1 to 5.   Tensile breaking elongation E0 of the porous membrane before the washing step, and tensile breaking elongation of the porous membrane after repeating the washing step X times (where X is an integer of 2 to 100) The method according to any one of claims 1 to 5, wherein the relationship with the degree EX is EX / E0 x 100 70 70%.   The relationship between the flux L0 of the porous membrane before the filtration step and the flux L1 of the porous membrane after the washing step is L1 / L0 × 100 ≧ 95%. Method according to paragraph 1.   The relationship between the flux L0 of the porous membrane before the filtration step and the flux LX of the porous membrane after repeating the cleaning step X times (where X is an integer of 2 to 100) is The method according to any one of claims 1 to 7, wherein LX / L0 x 100 90 90%.   The method according to any one of claims 1 to 9, wherein the porous membrane is a hollow fiber membrane.   The method according to any one of claims 1 to 10, wherein the resin constituting the porous membrane is a thermoplastic resin.   The method according to claim 11, wherein the thermoplastic resin is a fluorocarbon resin.   The fluorine resin is vinylidene fluoride resin (PVDF), chlorotrifluoroethylene resin, tetrafluoroethylene resin, ethylene-tetrafluoroethylene copolymer (ETFE), ethylene-monochlorotrifluoroethylene copolymer (ECTFE), hexamer The method according to claim 12, selected from the group consisting of fluoropropylene resins, and mixtures of these resins.   14. The method according to claim 1, wherein the washing step includes a washing step of washing with the washing solution and a rinsing step of rinsing with rinse water to remove the remaining washing liquid component. the method of. The method according to claim 14, wherein the amount of rinse water used in the rinse step is 100 L / m ² or less per unit area of the porous membrane.   The method according to claim 14 or 15, wherein the chlorine concentration in the filtrate after resuming the filtration step after the rinse step is 0.1 ppm or less, and the pH of the filtrate is 8.6 or less. .