JP2020151689A - Pore diffusion membrane separation module using nonwoven fabric - Google Patents

Abstract

To provide a pore diffusion membrane module implementing prediction performance in a pore diffusion membrane separation technique where structure characteristics to be equipped by nonwoven fabric is shown when the nonwoven fabric is used as a porous flat membrane loaded in the module.SOLUTION: In a pore diffusion module,: primary side flow passage is designed (a cloth-like material showing the role of a valve in a flow passage flowing a liquid from a laminar flow preparation region to a pore diffusion region is added and so on) so that dynamic pressure loaded on a porous membrane constituting the wall part of the primary side flow passage of a pore diffusion membrane module becomes zero; and nonwoven fabric constituted with cellulose nanofibers is adopted as a porous flat membrane in the module connected in series with the laminar flow preparation region and the pore diffusion region from the lower part of the flow passage.SELECTED DRAWING: Figure 1

Description

The module of the present invention and the membrane separation device of the present invention to which the module is applied separates and separates fine particle components including polymer substances and microorganisms dissolved or dispersed in an aqueous solution by maximizing the flow separation effect. Related to membrane modules for drawing, removing, and concentrating. More specifically, the present invention relates to a flat membrane loaded in the membrane module.

Flow separation means that when an aqueous solution is flowed in a laminar flow along a smooth membrane surface, the particle components present in the aqueous solution are distributed toward the center of the flow depending on the size, and as a result, It means that the larger the particle size, the more localized it is in the center of the flow. This phenomenon is caused by (a) the resistance from the film due to collision with the film surface (see Non-Patent Document 1, where it is expressed as a lamellar factor due to collision with the film wall) and (b) the rotation of particles in the fluid. The axial concentration effect toward the center of the particle flow inside the laminar flow resulting from the action of the accompanying lift and the effect of uniformizing the particle density distribution due to the diffusion of the particles (Non-Patent Document 1 summarizes these effects). It is explained by (expressed as a fluid separation factor).

The pore-diffuse flat membrane separation module is a membrane separation module having a fluid flow circuit that satisfies the following requirements for causing pore-diffuse membrane separation, and the flat membrane to be loaded is a hollow fiber membrane or a tubular. It means a porous flat membrane having a planar shape that is not a shaped membrane. The porous flat membrane means a membrane having an average pore diameter of 10 nm or more, a porosity of 30% or more, a bubble point in ethanol of 0.1 atm or more, and the presence of pores can be confirmed by a transmission electron microscope. The average pore size means the evaluation value by the water filtration rate method. The requirements for the shape of the flow path on the primary side for the module to realize hole diffusion are as follows. As the shape of the primary side flow path in the module, the wall surface forming the flow path is smooth so that the flow of the liquid in the primary side flow path (hereinafter abbreviated as the primary side liquid) is layered, and a part of the wall surface is covered. The unevenness of the film surface of the flat film formed is 10 μm or less. The streamline drawn by the flow path is a smooth straight line or a gentle curve. The primary flow path is connected to the liquid inlet, then the laminar flow preparation area and the pore diffusion area. The length (L) of the laminar flow preparation region and the pore diffusion region is 50 mm or more and 1500 mm or less, and the thickness (D) of the flow path is 4 mm or less and 1 mm or more.

It has been clarified that the following requirements must be satisfied for the flat membrane that can be loaded into the pore diffusion flat membrane separation module. That is, the smoothness value of the membrane surface of the flat membrane (the membrane surface forming the primary side flow path is defined as the membrane surface) is 10 μm or less, and there are no pinholes having a diameter of 10 μm or more in the flat membrane in the module. That is. The requirement for smoothness of the membrane surface is to ensure that the flow of the primary liquid flowing on the membrane surface on the membrane surface is laminar. The denial of the existence of pinholes is to prevent the collision angle of the particle components that collide with the film surface from being disturbed. In addition, the requirement for bubble points in ethanol ensures that the pore structure of the flat membrane is not destroyed even at the maximum value of 0.1 atm of the intermembrane differential pressure applied during the pore diffusion membrane separation treatment. In the present specification, the smoothness value is defined as follows. That is, when the plane is enlarged, fine irregularities are observed reflecting the characteristics of the substances constituting the plane. The average value of the amplitude of this unevenness per square centimeter is defined as the smoothness value. The above-mentioned amplitude is defined as the maximum value of the amplitude of unevenness when measured with a Dektak stylus type surface shape measuring instrument at any three points in one square centimeter with a measuring distance of 1 cm.

In the membrane separation device to which the pore-diffusion flat membrane module is applied, it is necessary that the environment of the module allows the following operating conditions. That is, the intermembrane differential pressure over the entire flat membrane in the module is always within 0.2 atm during operation. This condition must be satisfied at the start or stop of operation. In normal operation, the differential pressure between the membranes is 0.1 atm or less, the strain rate of the primary liquid on the membrane surface is 10 / sec or more, and at the same time, laminar flow occurs. Furthermore, in order to confirm that these operating conditions satisfy the necessary conditions at the same time, the ratio of the speed of the primary liquid passing through the flat membrane to the flow speed of the primary liquid must be 0.2 or less. Is also needed. That is, it is necessary that the flat membrane loaded in the module also corresponds to these module environments.

In the membrane separation module and the membrane separation device, the intermembrane differential pressure as a low hydrostatic pressure (positional head difference) of 0.1 atm or less is applied almost evenly to the entire surface of the membrane, and the liquid to be treated (primary side). (Consists of liquid) flows on the membrane surface in a lamellar flow. The lift force generated by the rotational motion of the particles caused by this flow has a particle size dependence on the rotational motion and the viscosity. Therefore, the particles are localized at the distance from the film surface corresponding to the size by the balance between the flow separation effect, which is a reflection of the lift depending on the particle size toward the center of the flow, and the diffusion based on the Brownian motion of the particles. Let me. If the localized particles can be sequentially recovered by paying attention to this localization and using the membrane, the particle fractionation by the membrane becomes possible.

The current state of membrane-based material separation and purification technology is the separation of substances according to their size by a sieving mechanism that uses the pores inside the membrane when transporting the material through the membrane using the differential pressure between the membranes as the driving force. That is, membrane filtration is the majority, and therefore the pore characteristics of the membrane loaded into the membrane filtration module are of particular importance. Membrane filtration is suitable for solid-liquid separation, which separates and purifies substances that are unstable to heat and chemicals and are easily denatured. On the other hand, the membrane filtration method is not suitable for the technique of continuously fractionating three or more kinds of component substances. This is because, in fractional fractionation, it is impossible to continuously fractionate this substance by a mechanism that captures only a part of the constituent substances in the pores of the membrane. The membrane filtration method is based on a mechanism for capturing the substance to be removed in the pores. Therefore, the membrane filtration method is not suitable for continuous fractionation. In addition to the membrane filtration method, there are centrifugal separation method, various chromatography, adsorption method, dialysis method, precipitation / dissolution method, and asymmetric field flow fractionation method as methods for separating and purifying physiologically active substances such as proteins and glycoproteins. For the purpose of analysis, it is sufficient to collect a small amount of sample, and these techniques achieve the purpose. However, when a large amount of fractionation / preparative treatment is required, it cannot be dealt with other than the precipitation / dissolution method. The membrane separation module of the present invention does not utilize the sieving mechanism of the membrane, but utilizes the spatial dimensional effect (Steric factor) that covers it in a broad concept. This effect is theoretically predicted in Non-Patent Document 1. The theory assumes that the particles are spherical particles and the pores are cylindrical pores. The spatial dimensional effect is explained by the movement of particles by considering them as flying objects and riding on them and colliding with the pores of the membrane or the surface of the membrane. The main contents of the difference between the spatial dimensional effect and the sieving effect are summarized in the following two points according to the theory of Non-Patent Document 1.
1. 1. The diameter of the particles that can penetrate into the pores of the membrane is the same as the pore diameter in the sieving effect, whereas it is 1/5 to 1/10 of the pore diameter in the dimensional effect.
2. 2. As for the particle removal performance by the film, the effect of pinholes is very large in the sieving effect, but it is hardly recognized in the dimensional effect.
If the above two points can be confirmed, it is possible to determine whether the membrane module and the membrane separation device in question are pore diffusion or membrane filtration of the present invention.

A problem with the membrane filtration method is the phenomenon of pore clogging. This phenomenon inevitably occurs as long as the sieving mechanism is used as the separation mechanism by the membrane. The dialysis method has been conventionally adopted as a membrane separation method for preventing clogging. In the dialysis method, only dissolution of the permeable substance in the membrane and subsequent diffusion in the substance of the membrane (this diffusion is abbreviated as a dissolution / diffusion mechanism) are used. In the dissolution / diffusion mechanism, the diffusion coefficient inside the membrane is extremely small, so it is not used for continuous mass processing. Pore diffusion Membrane separation is performed by membrane permeation using a diffusion mechanism in a solvent (usually water in an aqueous solution) in the pores inside the membrane. Therefore, in the pore diffusion membrane separation method, the membrane permeation rate of a low molecular weight substance is about 10,000 times that in the case of the dissolution / diffusion mechanism (Non-Patent Document 2 and Patent Document 1). The present invention has been developed as a membrane separation technique that eliminates the above-mentioned drawbacks of the membrane filtration method and the dialysis method (Patent Document 1 shows pores under conditions where the flow separation effect does not occur and when the intermembrane differential pressure is set to zero. The diffusion method is now called the stationary pore diffusion method).

The pore diffusion method introduced in Patent Document 1 and Non-Patent Document 2 is a stationary pore diffusion method. This method has the characteristic that both the solution medium (usually water) and the solute move in the pores by a diffusion mechanism, completely eliminating the problem of pore clogging caused by size-based solute molecules. To. Since the separation rate between substances based on the difference in diffusion coefficient is about 10,000 times that of the dissolution / diffusion mechanism, the problem of low separation rate is solved. However, the component molecules cannot be concentrated by the stationary pore diffusion method. In steady-state pore diffusion, the differential pressure between membranes is virtually zero, so in a stationary-pore diffusion module, the liquid feed pump for flowing the fluid on the primary side is the flow velocity between the inlet and outlet of the primary fluid in the module. By aligning the above, the condition that membrane filtration does not occur is forcibly given. Both flat membranes and hollow fiber membranes can be used for stationary pore diffusion. When the membrane used is a hollow fiber membrane, the pressure on the inlet side is always higher than the pressure on the outlet side in order to allow the liquid on the primary side to flow inside the hollow fiber, and the hollow has a constant pore diffusion length of 30 cm or more. It is difficult to carry out with a filament membrane. For example, in the case of a hollow fiber membrane, when the inner diameter is 0.5 mm, if the hollow fiber length is not 7 cm or less, the transport by filtration by pressure for flowing the liquid on the primary side (transport by viscous flow) is 10 of the transport amount of all components. If it exceeds%, clogging progresses and the particle removability is extremely lowered.

Of particular importance in the pore-diffusion flat membrane separation module using flow fractionation is the design of the primary flow path. The definition of the language related to the flow path is shown below.
Primary side; side in contact with the front surface of the flat membrane, secondary side; side in contact with the back surface of the flat membrane.
Primary liquid; a liquid that fills the primary flow path,
Primary side flow path; A path in a module through which the liquid to be treated flows along a circuit (primary side circuit) having the surface of the flat membrane as the wall surface of the flow path.
Primary side circuit: A continuum of spaces that determines the flow of primary side liquid, and is a circuit that directly connects to the primary side flow path of the module in the flow of liquid that connects various operation units that make up the membrane separation device.
Secondary side liquid, secondary side flow path, secondary side circuit; the contents defined on the primary side are defined on the side in contact with the back surface of the flat membrane.

A flow-separated type pore diffusion method has begun to be studied as a pore diffusion method for the purpose of removing fine particles in a liquid to be treated or concentrating fine particles by solving the problems of the stationary pore diffusion membrane separation technique (see Patent Document 2). ). In this technology, while the liquid on the primary side flows in parallel along the membrane surface, a slight intermembrane differential pressure (differential pressure as a hydrostatic pressure difference) is applied, and the intermembrane differential pressure causes the intermembrane differential pressure to pass through the membrane. The liquid solvent is allowed to flow out to the back surface side of the membrane. The outflowing liquid solvent (there is no particle component dispersed in the liquid and is substantially composed only of the solvent in the solution. It is defined as the recovered secondary liquid) is used as the particle removing liquid. The primary liquid after treatment is used as a particle concentrate liquid. The feature of this technique is that the differential pressure between the membranes is indirectly controlled to be 0.1 atm or less by controlling the flow velocities of the liquids on the primary side and the secondary side. The effectiveness of this control method is theoretically that in Non-Patent Document 1, the distance y from the film surface of the primary liquid that can flow into the pores and the collision angle α of the particles with the film surface are the primary liquid. It was clarified by the ratio of the flow velocity (equal to the membrane permeation velocity) and the membrane permeation velocity of the liquid on the secondary side. The advantage of this technology is that the intermembrane differential pressure is indirectly controlled by controlling the flow velocity of the secondary liquid, instead of controlling it by the pump pressure of the flow velocity pump of the primary liquid. I'm in control. Since the flow speed of the secondary fluid can be easily controlled by a cock or the like, the control by this method is suitable when the amount of the liquid to be treated is large. On the other hand, it is a necessary condition for this method to function that the secondary side flow path forms a closed system (the volume in the secondary side flow path is constant). Therefore, there is a time delay between the operation with the cock or the like and the response of the differential pressure between the membranes. In addition to the differential pressure between membranes, common requirements are given to the modules of the flow fractionation type pore diffusion method. That is, laminar flow of the primary liquid and securing of the flow velocity of the secondary liquid. For laminar flow, a unique design for laminar flow of the primary side flow path and a unique continuous space on the back surface of the flat membrane must be secured to secure the flow rate of the secondary side liquid. It doesn't become.

Japanese Unexamined Patent Publication No. 2006-055780 JP-A-2017-922

K.Kamide, S.Manabe, “Mechanism of Permselectivity of Porous Polymeric Membranes in Ultrafiltration Process, Polymer J., 13 (No.5), pp459-479 (1981) Rumiko Fujioka, Masako Yoshida, Chizu Yoshimura, Tomoko Yamamura, Seiichi Manabe, Bulletin of Faculty of Human Environment, Fukuoka Women's University, Vol. 29, pp. 13-20, 1998.

The following items are theoretically predicted in the pore diffusion membrane separation module in which the flow fractionation effect is fully utilized (disclosed in Non-Patent Document 1).
(1) Particles having a diameter of 1/5 (in the case of a strain rate of 10 / sec) to 1/10 (in the case of a strain rate of 100 / sec) or more of the average pore size of the flat film have pores in the film due to the flow fractionation effect. Cannot pass through. In the display of the particle logarithm removal coefficient LRV, the LRV is 2 to 3 when the strain rate of the primary liquid on the film surface is 10 / sec, and the LRV is 3 to 4 when the strain rate is 100 / sec.
(2) The collision angle α of the particles on the membrane surface is the ratio of the average flow velocity of the primary liquid to the average flow velocity from the primary side to the secondary side through the membrane (so-called membrane permeation velocity) and the sky of the membrane. It has the character of an average value (an average value that does not depend on the shape of the pore size distribution) that is almost uniquely determined by the pore ratio. When α is increased (for example, 70 degrees or more), the particles cannot pass through the pores even if the particle diameter is 1/2 or more of the pore diameter.

One of two types of regenerated cellulose porous membranes (two types with average pore diameters of 500 nm and 80 nm) was loaded into a pore-diffusing membrane module having an effective membrane area of 0.2 square meters and 0.0057 square meters, and the differential pressure between the membranes was set to 0. The following experimental results were obtained when the strain rate of the primary liquid on the film surface was 10 / sec at 05 atm. The solution to be treated was a culture solution containing a retrovirus.
(A) Bacterial removal performance (expressed as logarithmic removal performance LRV) was 0.0057 square meters, although LRV ≥ 6 for a module with a film area of 0.2 square meters (abbreviated as large module) for a film with an average pore size of 500 nm. There was also a module with LRV <5 in the module (small module) of. That is, the removal performance of bacteria is close to the above theoretical prediction.
(B) Virus removal performance (retrovirus as a virus type, diameter 70 to 80 nm), LRV is 2.0 (large module) to 0.5 (small module) when a flat membrane with an average pore size of 500 nm is loaded. ), The flat film having an average pore diameter of 80 nm was 4 or more (large module) to 2.5 (small module).
The experimental results of (a) and (b) were qualitatively consistent with the theoretical predictions (1) and (2). However, quantitatively, the deviation from the theory is large, and the practical application of the pore-diffuse membrane separation technology (for practical use, the reproducibility of this technology and the validity of the particle separation mechanism can be confirmed theoretically and empirically. The following specific issues remain in (assuming that they are).

As the problem of the flat membrane to be solved by the present invention, the cylindrical porous membrane can be arranged as follows from the above examination. That is, (a) as shown in (a) and (b) above, the cause of the deviation from the measured value is clarified, and a method for eliminating the deviation is shown. (B) Clarify the basics of designing the primary side flow path that realizes the expected function as a pore diffusion film module, (c) Make an appropriate design for the structure on the back side of the flat membrane, (d) ) Show the basic requirements for the structure of the secondary side flow path, and (e) if the pore structure of the flat membrane is significantly different from the cylindrical pore, further (f) to (e) below. Challenges are added.

If a non-woven fabric can be used as a flat film, a film for pore diffusion can be obtained by a method completely different from the method for producing a porous film, and a unique structure can also be used in the structure of the film. However, the following issues must be resolved. That is,
(F) In a non-woven fabric composed of fibers, the surface of the non-woven fabric (that is, the surface of the film) is composed of an aggregate of fine fibrous substances. Such filters are classified as depth filters in the conventional classification. It is uncertain whether a dimensional effect can be expected with a depth filter. It is unclear whether the theoretically predicted removal performance of the cylindrical holes will appear even when the non-woven fabric is used as a film.
(G) Does the flow separation effect appear if the surface is smooth?
(H) Is it possible to have a closed circuit as the primary flow path in the module?
(I) After mounting the dried flat membrane on the module, can the flatness of the membrane be maintained even if the membrane comes into contact with the aqueous solution?
(N) Does the pore size on the membrane surface change due to mechanical deformation of the membrane?
(L) Is it possible to secure a continuous space for the secondary side flow path on the back surface side of the membrane (whether the liquid that has passed through the membrane can flow out to the recovery side)?
(W) Is it possible to prepare an integrity test as a membrane module?

The present invention provides a flat membrane suitable for providing a membrane separation module which is a practical example of a pore-diffusion membrane separation technique which is a membrane separation technique emphasizing a flow separation effect which is an action effect that cannot be imagined by a conventional membrane filtration technique. To do.

The greatest feature of the membrane module of the present invention is that it employs a module that embodies the pore diffusion membrane separation technology. Embodying this technique means that the contribution of the membrane permeation phenomenon due to filtration is minimized in the design of the primary side flow path of the module. Flat membranes with the same pore characteristics were loaded into two types of membrane modules with different effective membrane areas, and the particle removal performance was examined. As a result, a phenomenon opposite to the removal performance of the membrane filtration module, in which the module having a large membrane area has a higher particle removal performance than the small module, occurs. It was clarified that the reason why the opposite phenomenon occurs is due to the dynamic pressure among the pressures applied to the flat membrane. That is, there are two types of pressure applied to the flat membrane, hydrostatic pressure and dynamic pressure, and a phenomenon has been found in which the particle removal performance decreases as the contribution of the dynamic pressure increases, and the present invention has been reached. The primary flow path is designed so that the dynamic pressure is substantially zero (that is, calculated to be zero) at all points of the flat membrane that constitutes about half of the primary side flow path. It is the greatest feature of the present invention. In one aspect, the membrane area of the portion where dynamic pressure is generated on the membrane surface is 1 / 10,000 or less of the membrane area of the membrane surface on which pore diffusion membrane separation is performed.

In one aspect, the streamlines of the primary liquid must be parallel along the flat membrane surface in order for the dynamic pressure applied to the flat membrane surface to be zero. In particular, the direction of the liquid inlet to the module needs to be set as parallel as possible to the membrane plane. It is premised that the flow of the primary liquid is a laminar flow, and if the direction of the streamline of the laminar flow is parallel to the membrane surface, the dynamic pressure is inevitably zero. When the dynamic pressure becomes zero at all points on the surface of the flat membrane, the fine particle removal performance (indicated by LRV) becomes close to the LRV in the case of membrane filtration with particles having a particle diameter ten times that of the fine particles. As one of the concrete measures to make the dynamic pressure substantially zero at any part of the film surface, there is a method of colliding the fluid perpendicularly with the film-like object to reduce its kinetic energy. For example, if there is a place where the direction of the streamline of the primary liquid changes on the film surface, the velocity in the flow direction is increased by collision with a flexible film-like material such as a film having a porosity of almost zero at that place. Set to zero (Fig. 1 illustrates a non-woven fabric close to a film (9 in the figure)).

The second feature of the present invention is that a non-woven fabric containing cellulose fibers is used as a flat film. The non-woven fabric has a two-layer structure, one layer (first layer) of which is a highly smooth film surface (10 μm or less in smoothness value expressing smoothness by its unevenness), and another layer (second layer). The layer) is a layer constituting the back surface of the film, and the smoothness value is 10 times or more that of the surface surface of the film. More preferably, the layer (first layer) is a film surface having high smoothness, and the smoothness value expressing the smoothness by the unevenness is 5 μm or less, and more preferably the smoothness value is 1 μm or less. .. When the smoothness value is 10 μm or less, when the liquid is flowed, the laminar flow state of the liquid is maintained even on the film surface, and the function of pore diffusion is exhibited. When the smoothness value is 5 μm or less, the laminar flow state of the liquid can be more maintained, and when the smoothness value is 1 μm or less, the laminar flow state of the liquid can be further maintained, which is preferable for exhibiting the pore diffusion function. In one aspect, the membrane surface is in contact with the primary flow path. The flow path on the primary side in the membrane module is directly connected in series with the laminar flow preparation area and subsequently the pore diffusion area along the flow path. A part of the flow path on the primary side is composed of the surface of a non-woven fabric flat film. The flat membrane surface exists only in the pore diffusion region, and the film permeation of the substance does not occur in the laminar flow preparation region. The laminar flow preparation area plays an important role only by guiding the primary liquid flowing into the membrane module to the pore diffusion region in a laminar flow state. That is, the cross-sectional shape of the liquid flow is usually circular or elliptical at the inlet of the laminar flow preparation area, but the cross-sectional shape is band-shaped at the pore diffusion region of the module of the present invention, which is the exit of the preparation area. .. The laminar flow preparation area has a role of changing the cross-sectional shape. If the module is installed so that the laminar flow preparation area has the same liquid level level as the inlet of the module or lower, the change in the cross-sectional shape of the primary liquid flow is the same due to the influence of gravity. It is possible to do it at the liquid level. Further, the volume of the laminar flow preparation area is desirable because it provides a space unrelated to the separation of the module.

The chemical structure of the cellulose fiber is natural cellulose or regenerated cellulose, and the mixture as a cellulose derivative is 10% by weight or less. This chemical structure property results in a decrease in the adsorptivity of protein molecules from the aqueous solution and an increase in crystallinity. Both of them show the suitability of proteins for aqueous solutions as the substance separation characteristics of the non-woven fabric in the present invention.

A third feature of the present invention is that, in a specific embodiment, the cellulose fibers constituting the surface of the flat membrane, which is a two-layered non-woven fabric sheet, contain cellulose fine fibers, and the number average fiber diameter of the cellulose fine fibers is large. It is 0.01 μm or more and less than 2 μm, preferably 0.02 μm or more and 1 μm or less, and more preferably 0.02 μm or more and 0.6 μm or less. Cellulose fibers are short fibers having an average length of 0.001 mm or more and less than 2 mm. The fibers constituting the back surface of the flat membrane are fibers having a number average fiber diameter of 2 μm or more and less than 50 μm and an average length of 1 mm or more.

The two-layered non-woven fabric sheet used in the present invention is optically isotropic in the plane direction of the film surface of the non-woven fabric and has anisotropy in the cross-sectional direction of the non-woven fabric on the film surface. That is, the direction of the maximum refractive index is parallel to the film surface, and the direction of the minimum refractive index is perpendicular to the film surface. Due to this anisotropy, when the non-woven fabric absorbs moisture, it swells in the film thickness direction, and the dimensional change in the film plane direction is small. The maximum refractive index and the minimum refractive index can be discriminated by observation with a transmission-type orthogonal Nicol using a polarizing microscope. When the polarizing plate is rotated at 0 °, 45 °, and 90 ° with respect to the film surface and the film cross section of the sample, no change in the visual field is observed on the film surface. On the other hand, in the cross section of the film, changes appear in the field of view due to the rotation of the polarizing plate. Further, when light can be confirmed in the field of view, it can be estimated from the property that when the stage of the polarizing microscope is lowered, the light moves to a higher refractive index, and when the stage is raised, the light moves to a lower refractive index.

By using the module and the apparatus of the present invention, it is possible to remove infectious microorganisms such as viruses and bacteria in an aqueous solution and recover a polymer substance in a state where the physiological activity is maintained. Microorganisms to be removed include viruses, mycoplasma, bacteria and the like. It is also possible to remove cells and aggregates of multiple cells. By determining the average pore size of the non-woven fabric to be loaded into the module according to the removal target, it is possible to remove only specific infectious microorganisms. In one embodiment, the average pore size upon removal is set to about 5 times the size of the microorganism of interest. This removal of microorganisms is different from the case of the membrane filtration method, and is not a mechanism for capturing microorganisms by the pores of the membrane (this mechanism is applicable to the case of the membrane filtration method). In the pore diffusion method, the particles to be removed are removed without clogging the pores of the membrane. That is, it is a separation technique for removing particles without clogging the membrane. The particles to be removed are also particles to be concentrated. The method of the present invention provides a literal membrane separation method different from the membrane filtration method, and embodies the principle features of the pore diffusion method. Since there is no clogging of the pores of the membrane, the processing capacity is more than doubled in one aspect as compared with the membrane filtration method.

By using the membrane separation module of the present invention, it is possible not only to remove infectious microorganisms in an aqueous solution but also to separate / concentrate and fractionate various components in the solution. Pharmaceutical raw materials and cosmetics in a raw state in which only infectious microorganisms are removed from biological raw materials (for example, body fluids such as blood and lymph, intracellular fluid, extracellular fluid, placenta, etc.) containing many kinds of physiologically active substances as the solution to be separated. Raw materials, food raw materials, etc. can be produced.

This module will be applied in the future for the removal of infectious microorganisms as a basic technology for safety measures in the manufacture of products such as regenerative medicine. It can be used for cell separation / purification and exosome purification / concentration / removal, and the separation target covers a wide range of particle sizes. The pressure required for separation is 0.1 atm or less, and separation is performed under energy saving. Therefore, it can be said that it can be replaced with the conventional separation technology based on affinity such as extraction separation, adsorption separation, and chromatography. For example, as an example of incorporating separation based on affinity, pore diffusion separation using the affinity between the membrane material and the particles or by adding a substance having a large affinity with the separation target substance to increase the size of the target substance to make the pore diffusion film larger. It is possible to use the particles to be separated by the separation method. For example, the arsenic compound can be made larger by adding ferric hydroxide colloidal particles to the arsenic compound dissolved in the aqueous solution. These particles can be removed by the pore diffusion membrane separation method.

Cross-sectional view of the bottom of the pore-diffusing membrane module loaded with two non-woven fabrics: shows the location of the laminar flow preparation area and the pore-diffusing area. Examples of devices that take advantage of the characteristics of the pore-diffusing film module: A; a device that controls the strain rate of the primary liquid on the flat membrane surface with a liquid feed pump, B; a device that controls the strain rate by the hydrostatic pressure difference. ..

Hereinafter, a form of a non-woven fabric for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described in detail. The present invention is not limited to the following embodiments and examples, and can be variously modified and implemented within the scope of the gist thereof.
The flat membrane loaded in the module of the present invention is a non-woven fabric sheet having a two-layer structure, and in one aspect, a layer containing cellulose fine fibers on the membrane surface (also referred to as “cellulose fine fiber layer” in the present disclosure) and It is a sheet composed of two layers with a porous support layer (also referred to as "support" in the present disclosure) under the porous support layer.

In one aspect, the cellulose fibers include cellulose fine fibers. If desired, the cellulose fine fiber layer may contain fine fiber components made of organic polymers other than cellulose. In the best form, the membrane surface is composed of fine cellulose fibers. The chemical structure of cellulose is natural cellulose or regenerated cellulose, and the mixture of cellulose derivatives is 10% by weight or less. The mixing ratio of the cellulose derivative is confirmed by the OH and CO expansion and contraction vibration peak ratios derived from the IR measurement of the cellulose fine fiber layer. This chemical structure property results in a decrease in the adsorptivity of protein molecules from the aqueous solution and an increase in crystallinity. Both of them show the suitability of proteins for aqueous solutions as the substance separation characteristics of the non-woven fabric in the present invention.

As natural cellulose, in a wide-angle X-ray diffraction pattern using x-rays monochromaticized with graphite and CuKα rays (wavelength λ = 0.15418 nm), an X-ray diffraction pattern in which the range of the diffraction angle 2θ is 0 ° to 30 °. However, it has two peaks at 10 ° ≤ 2θ <19 ° and 19 ° ≤ 2θ ≤ 26 °, and wood pulp, refined linter or various plant species (bamboo, hemp) obtained from hardwood or coniferous tree. Refined pulp from fiber, bagasse, kenaf, linter, etc.), so-called wood pulp and non-wood pulp such as coniferous pulp and hardwood pulp can also be used. As the non-wood pulp, cotton-derived pulp including cotton linter pulp, hemp-derived pulp, bagasse-derived pulp, kenaf-derived pulp, bamboo-derived pulp, straw-derived pulp and the like can also be used. Cotton-derived pulp, hemp-derived pulp, bagasse-derived pulp, kenaf-derived pulp, bamboo-derived pulp, and straw-derived pulp are cotton lint, cotton linter, and hemp-based abaca (for example, many from Ecuador or the Philippines), respectively. It means refined pulp obtained by refining or bleaching raw materials such as bagasse, bagasse, kenaf, bamboo, and straw by delignin by cooking. In addition, purified products of seaweed-derived cellulose and sea squirt cellulose can also be used. Further, an aggregate of fine fibers such as bacterial cellulose (BC) produced by a cellulose-producing bacterium (bacteria) can be mentioned.

Regenerated cellulose is a substance obtained by dissolving or crystallizing (mercerizing) natural cellulose and regenerating it, and is a wide angle using x-ray CuKα rays (λ = 0.15418 nm) monochromatic with graphite. In the X-ray diffraction pattern, the X-ray diffraction pattern in which the range of 2θ is 0 ° to 30 ° has one peak at 10 ° ≦ 2θ <19 ° and two peaks at 19 ° ≦ 2θ ≦ 30 °. .. For example, it means regenerated cellulose fibers such as rayon, cupra, and tencel. Among these, from the viewpoint of ease of miniaturization, it is preferable to use finely divided fibers using cupra or tencel, which has high molecular orientation in the fiber axis direction, as a raw material. Further, cut yarns of regenerated cellulose fibers and cut yarns of cellulose derivative fibers can also be used.

In one aspect, among the two-layered non-woven fabric sheets, the fibers constituting the surface of the flat film contain cellulose fine fibers, and the number average fiber diameter of the cellulose fine fibers is preferably 0.01 μm or more and less than 2 μm. Is 0.02 μm or more and 1 μm or less, more preferably 0.02 μmm or more and 0.6 μm or less. In one embodiment, the cellulose fibers are short fibers having an average length of 0.001 mm or more and less than 2 mm. In one aspect, the fibers constituting the back surface of the flat membrane are composed of fibers having a number average fiber diameter of 2 μm or more and less than 50 μm and an average fiber length of 1 mm or more to form a sheet.

Here, the number average fiber diameter will be described. The number average fiber diameter is a value measured by observing the surface of the porous sheet at three random points with a scanning electron microscope (SEM) at a magnification equivalent to 10,000 times. Specifically, with respect to the obtained SEM image, one line is drawn in each of the vertical direction and the horizontal direction orthogonal to the line, and the fiber diameter and the number of fibers intersecting the line are actually measured. Then, the number average fiber diameter is calculated using the measurement results of two vertical and horizontal series for one image. Further, the number average fiber diameter is calculated for the other two extracted SEM images in the same manner, and the results for a total of three images are averaged to obtain the number average fiber diameter of the target sheet. However, when the obtained number average fiber diameter is less than 100 nm, three random observations are performed at a magnification of 50,000 times, and a more accurate number average fiber diameter is calculated using the same method as described above. Adopt this value.

The reason why the number average fiber diameter of the cellulose fine fibers is preferably 0.01 μm or more and less than 2 μm is that the average through-hole diameter in the thickness direction and the surface unevenness formed by the cellulose fine fibers become uniform, and the cellulose fine fiber layer By increasing the specific surface area of the fiber, the number of paths for the medium to permeate through the membrane is increased, the accuracy of pore size control as the membrane is improved, and the amount of passage of the medium is expected to be improved.
Further, in the cellulose fine fiber layer, if the unevenness of the surface of the flat film is 10 μm or less, cellulose fibers having a fiber diameter larger than 1.5 μm and 15 μm or less may be intentionally mixed, and the cellulose raw material may be mixed. Cellulose fibers having a maximum fiber diameter of more than 1.5 μm and 15 μm or less may remain in the cellulose fine fibers that have been made finer by applying mechanical energy to the fibers. The content of cellulose fibers having a fiber diameter larger than 1.5 μm and 15 μm or less is preferably 0% or more and 40% or less, and more preferably 20% or less.
By containing cellulose fibers having a fiber diameter larger than 1.5 μm and 15 μm or less, the cellulose fibers and the cellulose fine fibers having a number average fiber diameter of 0.01 μm or more and less than 2.0 μm are entangled with each other, so that the cellulose fine fibers are entangled on the support. It is preferable because the yield can be increased as compared with the case where the cellulose fine fiber layer is formed by the fiber alone, and the tensile strength as the cellulose fine fiber layer can be increased.
The method for reducing the maximum fiber diameter is not limited, but a means for increasing the processing time and the number of times of the fibrillation treatment or the miniaturization treatment described later can be taken.

The area ratio calculated by the following procedures (1) to (5) is used as the content of the cellulose fibers having a fiber diameter larger than 1.5 μm and 15 μm or less present in the cellulose fine fibers.
(1) A fiber sheet having a basis weight of 10 g / m ² and 20 cm is subjected to calendar processing (model: H2TEM300, manufactured by Yuri Roll Co., Ltd.) at 3 t / 30 cm and a speed of 2 m / min.
(2) Optical microscope observation: An optical microscope observation is performed at 100 times for any 9 points in the fiber sheet.
(3) Thick fiber amount evaluation: A 2 mm square frame line is drawn in actual size on each of the images obtained by observing 9 points with a 100x optical microscope.
(4) The area of the cellulose fiber having a fiber diameter larger than 1.5 μm and 15 μm or less confirmed in the frame line is calculated using image analysis software (imageJ).
(5) Calculate the area / 4 mm ² .

The content of the cellulose fine fibers in the cellulose fine fiber layer is not particularly limited, but is 50% by weight or more, preferably 60% by weight, and more preferably 70% by weight or more. By containing 50% by weight or more of the cellulose fine fibers, the number of entangled points between the cellulose fine fibers is increased, and the control accuracy of the through average pore diameter in the thickness direction and the tensile strength as the cellulose fine fiber layer are increased, which is preferable. In addition, since cellulose fine fibers have innumerable hydroxyl groups on their high specific surface area, surface modification and functionalization by a chemical modification reaction are easier than with other organic resin materials.

In one aspect, the non-woven fabric having a two-layer structure can be obtained by processing cellulose fine fibers into a sheet on a support. The basis weight of the cellulose fine fiber layer is preferably 1.0 g / m ² or more and 20 g / m ² or less, and more preferably 4 g / m ² or more and 15 g / m ² or less. Here, a method for calculating the basis weight will be described. A 10.0 cm × 10.0 cm square piece is cut from a thin film cellulose fine fiber laminated sheet and allowed to stand for 24 hours in an environment of 23 ° C. and 50% RH, and its weight W (g) is measured. Next, using a surface contact type film thickness meter, for example, a film thickness meter manufactured by Mitutoyo (Model ID-C112XB), nine points were measured at various positions, and the average value of the measured values was defined as the film thickness T (μm). To do. Based on this, the following formula:
W0 = 100 × W
Can be used to calculate the basis weight W0 (g / m ² ) of the film.

In addition to the cellulose fine fiber component, the cellulose fine fiber layer may contain a fine fiber component made of an organic polymer other than cellulose. By containing an organic polymer other than cellulose, when a sheet is formed by a papermaking method or a coating method using a cellulose fine fiber slurry, shrinkage of the fiber sheet is suppressed during drying, and pores and pore diameters in the fiber sheet are reduced. It becomes possible to hold.

The content of the fine fiber component composed of an organic polymer other than cellulose contained in the cellulose fine fiber layer is preferably less than 50% by weight, more preferably less than 40% by weight, and further preferably less than 30% by weight. The organic polymer may be any organic polymer capable of producing fine fibers, for example, aromatic or aliphatic polyester, nylon, polyacrylonitrile, cellulose acetate, polyurethane, polyethylene, polypropylene, polyketone, aromatic polyamide, etc. Examples thereof include natural organic polymers other than cellulose such as polyimide, silk, and wool. Fine fibers made of organic polymers include fine fibers that are highly fibrillated or finely divided by beating organic fibers and finely processed with a high-pressure homogenizer, fine fibers obtained by electrospinning using various polymers as raw materials, and various polymers. Examples of the raw material include fine fibers obtained by the melt blown method, but the raw material is not limited thereto. Among these, aramid fine fibers obtained by micronizing polyacrylonitrile fine fibers and aramid fibers which are all aromatic polyamides by a high-pressure homogenizer are particularly preferable because they are easy to be finely divided and have high heat resistance and high chemical stability. The maximum fiber diameter of these organic polymers is preferably 15 μm or less. When the maximum fiber diameter is 15 μm or less, the thickness of the cellulose fine fiber layer can be reduced, and the uniformity of the pore diameter and the like can be easily ensured, which is preferable.

The Frazier air permeability of the two-layered non-woven fabric is preferably 10 cc / cm ² · s or less. When the Frazier air permeability becomes larger than 10 cc / cm ² · s, the amount of cellulose fine fibers on the support is insufficient, the cellulose fine fiber layer cannot be formed, or innumerable defects and pinholes occur. It is not preferable because it suggests the state of the fiber.

The air permeation resistance of the two-layered non-woven fabric is preferably 0.3 s / 100 ml or more with a Garley type air permeation resistance meter. The fact that the air permeation resistance of the Garley type air permeation resistance meter is 0.3 s / 100 ml or more means that a cellulose fine fiber laminate is formed on a support having a high porosity, which will be described later, and further, cellulose fine particles. It is preferable because it means that the fiber layer has no defects or pinholes. When the air permeation resistance is less than 0.3 s / 100 ml in the Garley type air permeation resistance meter, the amount of cellulose fine fibers on the support is insufficient and the cellulose fine fiber layer cannot be formed, or defects or pins. This is not preferable because it suggests a state in which innumerable holes have been generated.

The thickness of the cellulose fine fiber layer of the non-woven fabric having a two-layer structure is preferably 1 μm or more and 100 μm or less, more preferably 3 μm or more and 70 μm or less, and further preferably 3 μm or more and 50 μm or less. By reducing the thickness of the cellulose fine fiber layer to 100 μm or less, a unique flow path (that is, a secondary side flow path) is secured on the back surface side. The space for the secondary side flow path is provided by the unevenness if the back surface of the flat film has an unevenness. Since the hydrostatic pressure on the back surface side of the flat membrane fluctuates the differential pressure between the membranes, the design of the secondary side flow path is usually simplified by setting the atmospheric pressure. By setting the hydrostatic pressure on the back surface of the flat membrane to atmospheric pressure, pore diffusion is performed only by controlling the pressure in the primary side flow path. The pressure in the flow path on the primary side is set only to generate the hydrostatic pressure on the primary side to prevent the generation of dynamic pressure, and the pressure is controlled only by the hydrostatic pressure on the primary side.

The support for forming the two-layered non-woven fabric is mainly used for maintaining the structure of the cellulose fine fiber layer. For example, a woven fabric made of organic polymer fibers, a knitted fabric, a mesh material, a long-fiber non-woven fabric, a short-fiber non-woven fabric, Examples include paper and functional paper. In order to form the cellulose fine fiber layer, the surface of the support is preferably smooth, so that it is more preferably porous paper or functional paper.

Further, the support is preferably hydrophilic in order to improve the papermaking property and the adhesiveness with the cellulose fine fiber layer, and in order to make it hydrophilic, the surface of the sheet surface is modified by corona discharge treatment or plasma treatment. It may be of good quality.

The support forming the non-woven fabric having a two-layer structure is not particularly limited as a material constituting the support. However, for example, a fluororesin such as polyethylene, polypropylene, ethylene-propylene copolymer, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, ethylene-vinyl acetate copolymer, polyvinyl alcohol, polyacetal, polyvinylidene fluoride, polyethylene terephthalate. , Polybutylene terephthalate, polyethylene naphthalate, polystyrene, polyacrylonitrile, styrene-acrylonitrile copolymer, ABS resin, polyphenylene ether (PPE) resin, polyimide, polyamideimide, polymethacrylic acid, polyacrylic acids, polycarbonate, polyphenylene sulfide, polysulfone , Polyether sulfone, polyether nitrile, polyether ketone, thermoplastic, liquid crystal polymer, silicone resin, ionomer, cellulose (natural cellulose fibers such as wood pulp and cotton, recycled cellulose such as biscous rayon, copper ammonia rayon and tencel), Cellulous derivatives, cellulose acetate, nitrocellulose, styrene-butadiene or styrene-isoprene block copolymers, styrene-based thermoplastic elastomers, olefin-based thermoplastic elastomers, vinyl chloride-based thermoplastic elastomers, polyester-based thermoplastic elastomers, polyurethane-based thermoplastics Elastomer, polyamide-based thermoplastic elastomer, epoxy resin, polyimide resin, phenol resin, unsaturated polyester resin, diallyl phthalate resin, silicone resin, polyurethane resin, polyimide silicone resin, heat-curable polyphenylene ether resin, modified PPE resin, natural rubber, Butadiene rubber, isoprene rubber, styrene-butadiene copolymer rubber, nitrile rubber, chloroprene rubber, ethylene-propylene rubber, chlorinated polyethylene, chlorosulfonated polyethylene, butyl rubber and halogenated butyl rubber, fluororubber, urethane rubber, silicone rubber, etc. These can be used alone or in combination of two or more.

Further, one or more kinds of fibers made of the above-mentioned organic polymer may be fixed with a binder. The binder is preferably hydrophilic in order to improve papermaking and adhesion to the cellulose fine fiber layer, and the surface of the sheet is modified by corona discharge treatment or plasma treatment in order to make it hydrophilic. May be good.

The support forming the non-woven fabric having a two-layer structure is preferably porous, and its porosity is 30% or more and 95% or less, and preferably 50% or more and 90% or less. When the porosity is in the range of 30% or more and 95% or less, the cellulose fine fibers can be filtered and produced by the papermaking method.

The basis weight of the support forming the two-layered non-woven fabric is 8.0 g / m ² or more. Since the basis weight of the support is in the range of 8.0 g / m ² or more, the strength as a sheet can be maintained, and curl generation due to drying shrinkage after impregnation with a solvent such as water and drying can be suppressed. preferable.

In one aspect, a cross-linking agent is added to the non-woven fabric having a two-layer structure in order to reinforce the strength of the cellulose fine fiber layer, maintain the structure in a wet environment, and further improve the adhesion between the cellulose fine fiber layer and the support. Then, the cellulose fine fibers and the cellulose fine fiber layer and the support are chemically crosslinked.

The (reactive) cross-linking agent contained in the thin-film cellulose fine fiber laminated sheet is not limited as long as it chemically cross-links between the cellulose fine fibers, but contains polyisocyanate having two or more isocyanate groups and active hydrogen. It is preferable to use a resin produced by the addition reaction of the compound. Examples of the polyisocyanate having two or more isocyanate groups include aromatic polyisocyanates, alicyclic polyisocyanates, and aliphatic polyisocyanates. Examples of the active hydrogen-containing compound include polyester polyols, 1- to 6-valent hydroxyl group-containing compounds including polyether polyols, amino group-containing compounds, thiol group-containing compounds, and carboxyl group-containing compounds. It also includes water, carbon dioxide, etc. existing in the air or in the reaction field.

The amount of the cross-linking agent added to the non-woven fabric having a two-layer structure is 100% by weight or less, more preferably 10% by weight or less, based on the weight of the cellulose fine fibers. By controlling the weight of the cellulose fine fiber in a range of 100% by weight or less, the strength of the cellulose fine fiber layer can be reinforced, the structure can be maintained in a wet environment, and the adhesion between the cellulose fine fiber layer and the support can be maintained. It is preferable because the sheet can be formed without the cross-linking agent filling the microporous structure of the cellulose fine fiber layer while improving the quality.

The adhesiveness between the cellulose fine fiber layer and the support in the two-layered non-woven fabric may be such that the tape peeling strength between the cellulose fine fiber layer and the support is 2.0 gf / 18 mm or more. For the tape peeling strength, a test piece with a width of 18 mm was collected from each multilayer structure, and a mending tape (MP-24 manufactured by 3M) was attached to each of the cellulose fine fiber layer and the support layer to attach the fine fibers at the end of the sample. After peeling the layer and the support layer, each layer is fixed to the upper and lower chucks of a tensile tester manufactured by ORIENTEC, and then a tensile test is performed for a displacement of 100 mm from a distance between the chucks of 180 mm. The average tensile strength between the displacements of 20 to 60 mm after the measured value of this tensile test is corrected for the load derived from the apparatus is defined as the tape peel strength (gf / 18 mm). When the tape peeling strength is in the range of 2.0 gf / 18 mm or more, the cellulose fine fibers in the cellulose fine fiber layer are chemically bonded to each other, and the structure is maintained even when immersed in a solvent such as water. It is preferable because it can be used. Further, even when the thin film cellulose fine fiber laminated sheet is bent or handled in a roll state in a manufacturing process, the cellulose fine fiber layer and the support are not peeled off and can be handled in an adhered state, which is preferable.

The non-woven fabric having a two-layer structure can be newly given a function by chemically modifying the surface hydroxyl groups of the cellulose fine fiber layer and introducing an additive or a resin into the porous space.

Hereinafter, an example of a method for producing a non-woven fabric having a two-layer structure according to the present embodiment will be described.
The method for producing the two-layer structure nonwoven fabric of the present embodiment can be produced by a papermaking method or a coating method. In the case of the papermaking method
(1) Cellulose fine fiber production step by refining cellulose fiber (2) Preparation step of papermaking slurry of the cellulose fine fiber (3) Papermaking step of forming a wet paper by filtering the papermaking slurry on a porous support (4) The wet paper is dried to obtain a drying sheet.
Further, (A) a smoothing step of heat-pressing the dried sheet in order to homogenize the sheet and reduce the thickness of the dried sheet (B) to form a chemical bond with a fiber sheet cross-linking agent by heat treatment. Either one or both of the heat treatment steps to be accelerated may be carried out.

Further, in the case of the coating method, the coating slurry prepared by the same steps as in (1) and (2) above is applied onto the support and dried to form a film. Further, (A) smoothing step and (B) heat treatment step may be performed. In the case of the coating method, various coating methods such as spray coating, gravure coating, and dip coating can be selected.

The non-woven fabric having a two-layer structure preferably undergoes a pretreatment step, a beating treatment step, and a miniaturization step using the above-mentioned cellulose fibers. In the pretreatment step of the natural cellulose fiber, the raw material pulp is kept in a state where it can be easily refined in the subsequent steps by autoclaving treatment under water impregnation at a temperature of 100 to 150 ° C., enzyme treatment, or a combination thereof. That is valid. In the pretreatment step, an autoclave treatment may be performed by adding an inorganic acid (hydrochloric acid, sulfuric acid, phosphoric acid, boric acid, etc.) or an organic acid (acetic acid, citric acid, etc.) having a concentration of 1% by weight or less. It is valid in some cases. These pretreatments not only reduce the load of the miniaturization treatment, but also discharge the impurity components such as lignin and hemicellulose existing on the surface and gaps of the microfibrils constituting the cellulose fibers to the aqueous phase, resulting in fineness. Since it also has the effect of increasing the α-cellulose purity of the converted fibers, it may be very effective in improving the heat resistance of the cellulose fine fiber non-woven fabric. Further, in the case of regenerated cellulose fiber, water washing using a surfactant can be carried out in the pretreatment step in order to remove the oil agent.

In the beating process, the solid content of the raw material pulp is 0.5% by weight or more and 4% by weight or less, preferably 0.8% by weight or more and 3% by weight or less, and more preferably 1.0% by weight or more and 2.5% by weight or less. Disperse in water to a concentration and thoroughly promote fibrillation with a beating device such as a beater or a disc refiner (double disc refiner). When a disc refiner is used, if the clearance between the discs is set as narrow as possible (for example, 0.1 mm or less) and the processing is performed, extremely high beating (fibrillation) proceeds. Therefore, the conditions of the miniaturization treatment by a high-pressure homogenizer or the like described later can be relaxed, which may be effective.
The degree of beating process is defined as follows. In the study by the inventors of the present application, the CSF value (indicating the degree of beating of cellulose, evaluated by the Canadian standard freeness test method for pulp defined in JIS P 8121) decreased with time as the beating treatment was performed. It was confirmed that once it became close to zero, it tended to increase again when the beating process was continued. In the production of cellulose fine fibers in the present invention, the CSF value in the beating treatment is preferably at least zero, and more preferably 30 ml or more of CSF. Such a slurry with a degree of beating has an advantage in terms of production efficiency, in which the uniformity is increased and clogging in the subsequent miniaturization treatment by a high-pressure homogenizer or the like can be reduced.

It is preferable that the non-woven fabric having a two-layer structure is subjected to a miniaturization treatment using a high-pressure homogenizer, an ultra-high-pressure homogenizer, a grinder, or the like, following the beating step described above. At this time, the solid content concentration in the slurry is 0.5% by weight or more and 4% by weight or less, preferably 0.8% by weight or more and 3% by weight or less, more preferably 1.0% by weight, according to the beating treatment described above. It is 2.5% by weight or less. When the solid content concentration is in this range, clogging does not occur and efficient miniaturization processing can be achieved.

Examples of the high-pressure homogenizer to be used include NS type high-pressure homogenizer of Niro Soabi Co., Ltd. (Italy), Lanier type (R model) pressure type homogenizer of SMT Co., Ltd., and high-pressure homogenizer of Sanwa Machinery Co., Ltd. Any device other than these may be used as long as it is a device capable of performing miniaturization by a mechanism substantially similar to these devices. Examples of the ultra-high pressure homogenizer include high-pressure collision type miniaturization machines such as a microfluidizer of Mizuho Kogyo Co., Ltd., a nanomizer of Yoshida Kikai Kogyo Co., Ltd., and an ultimateizer of Sugino Machine Co., Ltd. Any device other than these may be used as long as it is a device that performs miniaturization by a mechanism substantially similar to that of the device. Examples of the grinder type miniaturization device include a pure fine mill manufactured by Kurita Kikai Seisakusho Co., Ltd. and a stone mill type grinding type represented by Super Mascoroider manufactured by Masuyuki Sangyo Co., Ltd., which are almost the same as these devices. Any device other than these may be used as long as the device is miniaturized by the mechanism of.

The fiber diameter of the cellulose fine fibers is determined by the conditions of the micronization treatment by a high-pressure homogenizer or the like (selection of equipment, operating pressure and number of passes) or the pretreatment conditions before the miniaturization treatment (for example, autoclave treatment, enzyme treatment, beating treatment). Etc.) can be controlled.

Furthermore, as natural cellulose fine fibers, cellulose-based fine fibers that have undergone surface chemical treatment, and cellulose-based fibers in which the hydroxyl group at the 6-position is oxidized by a TEMPO oxidation catalyst to become a carboxyl group (including acid type and salt type). Fine fibers of the above can also be used. In the former case, by performing various surface chemical treatments according to the purpose, for example, some or most of the hydroxyl groups existing on the surface of the cellulose fine fibers are esterified containing an acetate, a nitrate ester, and a sulfate ester. , An alkyl ether typified by methyl ether, a carboxy ether typified by carboxymethyl ether, and an esterified product containing cyanoethyl ether can be appropriately prepared and used. In particular, it may be preferable to use cellulose chemically modified with a hydrophobic substituent as a sheet raw material because it is easy to control the high porosity.

Further, in the latter, that is, in the preparation of cellulose fine fibers in which the hydroxyl group at the 6-position is oxidized by a TEMPO oxidation catalyst, it is not always necessary to use a finer device that requires high energy such as a high-pressure homogenizer, and the cellulose fine fibers Dispersions can be obtained. For example, as described in the literature (A. Isogai et al., Biomacromolecules, 7, 1687-1691 (2006)), 2,2,6,6-tetramethylpiperidinooxy in an aqueous dispersion of natural cellulose. A catalyst called TEMPO such as radical and an alkyl halide coexist, an oxidizing agent such as hypochlorous acid is added thereto, and the reaction is allowed to proceed for a certain period of time. After purification treatment such as washing with water, a normal mixer is used. By applying the treatment, a dispersion of cellulose fine fibers can be obtained very easily.

It is preferable that the aramid fiber is also miniaturized through the same pretreatment step, beating treatment step and micronization step as the cellulose fine fiber. In the pretreatment step, washing with a surfactant is carried out to remove the oil. In the beating treatment step, the fibers after washing with water are 0.5% by weight or more and 4% by weight or less, preferably 0.8% by weight or more and 3% by weight or less, and more preferably 1.0% by weight or more and 2.5% by weight or less. Disperse in water to a solid content concentration, and thoroughly promote fibrillation with a beating device such as a beater or a disc refiner (double disc refiner). When using a disc refiner, if the clearance between discs is set as narrow as possible (for example, 0.1 mm or less) and processing is performed, extremely high beating (fibrillation) will proceed, so fineness using a high-pressure homogenizer or the like will proceed. The conditions of the conversion process can be relaxed and may be effective. As the degree of beating treatment, the CSF value used in the production of the cellulose fine fiber can be used.

In the production of aramid fine fibers, it is preferable to carry out a micronization treatment with a high-pressure homogenizer, an ultra-high-pressure homogenizer, a grinder, or the like, following the beating step described above. The solid content concentration in the aqueous dispersion at this time is 0.5% by weight or more and 4% by weight or less, preferably 0.8% by weight or more and 3% by weight or less, more preferably 1.0, according to the beating treatment described above. By weight% or more and 2.5% by weight or less. When the solid content concentration is in this range, clogging does not occur and efficient miniaturization processing can be achieved. The high-pressure homogenizer used is not limited to, but at least the devices described in Cellulose Fine Fiber Production can be used.
The fiber diameter of the aramid fine fibers shall be controlled by the conditions of the micronization treatment by a high-pressure homogenizer or the like (selection of equipment, operating pressure and number of passes) or the pretreatment conditions before the miniaturization treatment (for example, beating treatment). Can be done.

In the present embodiment, two or more types of cellulose fine fibers having different raw materials, cellulose fine fibers having different degrees of fibrillation, cellulose fine fibers whose surface has been chemically treated, or organic polymer fine fibers such as aramid fine fibers are used. It is also possible to produce a sheet composed of two or more types of cellulose fine fibers or cellulose fine fibers and aramid fine fibers by performing a paper making / drying treatment described later using a slurry mixed at an arbitrary ratio.

In the thin film cellulose fine fiber laminated sheet composed of two or more kinds of fine fibers, it is preferable that the fine fibers are not aggregated and are uniformly dispersed in the sheet. In a dispersed state in which each fine fiber is unevenly distributed in the slurry, the film quality uniformity of the obtained thin film cellulose fine fiber laminated sheet is not good. Therefore, it is necessary that an appropriately uniform dispersion is achieved in the slurry. As a method for dispersing a slurry containing fine fibers of two or more components, a high-speed disperser equipped with a dispar type blade (for example, TK homomixer of Primix Corporation) or a disc refiner (including a double disc refiner), Examples thereof include a high-pressure homogenizer, an ultra-high-pressure homogenizer, and a grinder.
In the process of producing cellulose fine fibers, by mixing the raw materials of aramid fine fibers, cellulose and aramid can be finely divided at the same time and high dispersibility can be achieved at the same time, which may be effective.

Various additives (oil-based compound, water-dispersible blocked isocyanate, functionalizing agent, etc.) may be further added to the above-mentioned slurry of cellulose fine fibers to prepare a papermaking slurry. The papermaking slurry preferably has a cellulose fine fiber concentration of 0.01% by weight or more and 0.5% by weight or less. More preferably, it is 0.03% by weight or more and 0.35% by weight or less, so that stable papermaking can be carried out. If the concentration of cellulose fine fibers in the slurry is lower than 0.01% by weight, the drainage time becomes very long and the productivity becomes remarkably low, and at the same time, the film quality uniformity becomes remarkably poor, which is not preferable. Further, if the concentration of the cellulose fine fibers is higher than 0.5% by weight, the viscosity of the dispersion liquid becomes too high, which makes it difficult to form a uniform film, which is not preferable.

In producing a porous two-layered non-woven fabric, the papermaking slurry may contain an emulsified oily compound described in JP-A-2012-46843.
Specifically, an oily compound having a boiling point range of 50 ° C. or higher and 200 ° C. or lower under atmospheric pressure is dispersed in a papermaking slurry in the form of an emulsion at a concentration of 0.15% by weight or more and 10% by weight or less. Is preferable. The concentration of the oily compound in the papermaking slurry is preferably 0.15% by weight or more and 10% by weight or less, more preferably 0.3% by weight or more and 5% by weight or less, and further preferably 0.5% by weight or more and 3% by weight. % Or less. Although the cellulose fine fiber porous sheet of the present invention can be obtained even if the concentration of the oily compound exceeds 10% by weight, the amount of the oily compound used in the manufacturing process increases, and safety measures are required accordingly. It is not preferable because it causes restrictions on properties and cost. Further, if the concentration of the oily compound is smaller than 0.15% by weight, only a sheet having an air permeation resistance higher than a predetermined air permeation resistance range can be obtained, which is also not preferable.

It is desirable that the oily compound be removed during drying. Therefore, the oily compound contained as an emulsion in the papermaking slurry is preferably in a certain boiling point range. Specifically, when the boiling point under atmospheric pressure is preferably 50 ° C. or higher and 200 ° C. or lower, more preferably 60 ° C. or higher and 190 ° C. or lower, the papermaking slurry can be easily operated as an industrial production process, and the papermaking slurry is easy to operate. , It becomes possible to heat and remove relatively efficiently. If the boiling point of the oily compound under atmospheric pressure is less than 50 ° C., it is necessary to handle the papermaking slurry under low temperature control in order to handle it stably, which is not preferable in terms of efficiency. Further, if the boiling point of the oil-based compound under atmospheric pressure exceeds 200 ° C., a large amount of energy is required to heat-remove the oil-based compound in the drying step, which is also not preferable.

Further, the solubility of the oily compound in water at 25 ° C. is preferably 5% by weight or less, more preferably 2% by weight or less, and further, from the viewpoint of efficiently contributing to the formation of the required structure of the oily compound. It is preferably 1% by weight or less.

Examples of the oily compound include hydrocarbons in the range of 6 to 14 carbon atoms, chain saturated hydrocarbons, cyclic hydrocarbons, chain or cyclic unsaturated hydrocarbons, aromatic hydrocarbons, and carbon atoms. Examples thereof include monovalent and first-class alcohols in the range of 5 to 9 carbon atoms. In particular, when at least one compound selected from 1-pentanol, 1-hexanol, and 1-heptanol is used, the cellulose fine fiber porous sheet of the present embodiment can be produced particularly preferably. This is considered to be suitable for producing a non-woven fabric having a high porosity and a fine porous structure because the oil droplet size of the emulsion is extremely small (1 μm or less under normal emulsification conditions).
These oily compounds may be blended as a single substance or a plurality of mixtures may be blended. Furthermore, the water-soluble compound may be dissolved in the papermaking slurry in order to control the emulsion properties to an appropriate state.

The water-soluble compound specifically contains one or more water-soluble compounds selected from the group consisting of sugars, water-soluble polysaccharides, water-soluble polysaccharide derivatives, polyhydric alcohols, alcohol derivatives, and water-soluble polymers. May be. Here, the water-soluble polysaccharide means a water-soluble polysaccharide, and various compounds exist as natural products. For example, starch, solubilized starch, amylose and the like. Further, the water-soluble polysaccharide derivative includes the above-mentioned water-soluble polysaccharide derivative, for example, an alkylated product, a hydroxyalkylated product, and an acetylated product, which are water-soluble. Alternatively, even if the polysaccharide before derivatization is insoluble in water such as cellulose and starch, those that have been made water-soluble by derivatization, for example, hydroxyalkylation, alkylation, carboxyalkylation, etc. Included in water-soluble polysaccharide derivatives. Also included are water-soluble polysaccharide derivatives derivatized with two or more functional groups. However, the water-soluble compounds that can be used are not limited to the compounds described above.

The mixing amount of the above water-soluble compound is preferably 25% by weight or less with respect to the oil-based compound. If the amount added is larger than this, the ability to form an emulsion of the oily compound is lowered, which is not preferable. Further, in the papermaking slurry, it is preferable that the water-soluble compound is dissolved in the aqueous phase. The concentration of the water-soluble compound is 0.003% by weight or more and 0.3% by weight or less, more preferably 0.005% by weight or more and 0.08% by weight or less, and further preferably 0.006% by weight or more and 0.07% by weight. The amount is as follows, and within this range, a porous thin film cellulose fine fiber laminated sheet can be easily obtained, and at the same time, the state of the papermaking slurry is often stabilized.

For the purpose of stabilizing the emulsion, the papermaking slurry may contain a total amount of a surfactant in addition to the above-mentioned water-soluble compound in the above-mentioned concentration range with the above-mentioned specific water-soluble polymer.
Examples of the surfactant include anionic surfactants such as alkyl sulfates, polyoxyethylene alkyl sulfates, alkylbenzene sulfonates and α-olefin sulfonates, alkyltrimethylammonium chloride, dialkyldimethylammonium chloride and benzalco chloride. Cationic surfactants such as nium, amphoteric surfactants such as alkyldimethylaminoacetate betaine and alkylamide dimethylaminoacetic acid betaine, and nonionic surfactants such as alkylpolyoxyethylene ether and fatty acid glycerol ester can be mentioned. It is not limited to these.

In addition, various additives may be added to the papermaking slurry depending on the purpose. For example, inorganic particulate compounds such as water-dispersible block polyisocyanate, water-soluble polymer, thermoplastic resin, thermosetting resin, photocurable resin, silica particles, alumina particles, titanium oxide particles, calcium carbonate particles, resin. Fine particles, various salts, an organic solvent that does not impair the stability of the papermaking slurry, a defoaming agent, and the like can be added within a range that does not adversely affect the production of the sheet structure (selection of type and composition).

The water-dispersible block polyisocyanate is a compound that can be used as a cross-linking agent for the above-mentioned two-layer structure non-woven fabric by heating. Specifically, (1) a polyisocyanate compound such as a polyisocyanate and a polyisocyanate derivative is basically used. As a skeleton, (2) the isocyanate group is blocked by the blocking agent, (3) it does not react with the functional group having active hydrogen at room temperature, and (4) the blocking group is heat-treated above the dissociation temperature to form the blocking group. It is characterized in that (5) it is dispersed in water in the form of an emulsion in which a desorbed and active isocyanate group is regenerated and reacts with a functional group having active hydrogen to form a bond.

The above-mentioned water-dispersible blocked polyisocyanate is considered to exhibit the following behavior in the production of a two-layered non-woven fabric.
(1) Adsorbed to cellulose fine fibers in the papermaking slurry (2) Wet paper containing the water-dispersible block polyisocyanate is formed (3) As the wet paper dries, the water-dispersible block polyisocyanate is dried and cellulose is fine. Formation of Block Polyisocyanate Coating on Fibers (4) Progression of Block Group Dissociation and Cross-linking Reaction by Thermal Cure The above-mentioned water-dispersible block polyisocyanate is a compound obtained by directly binding a hydrophilic compound to the block polyisocyanate and emulsifying it. Either (self-emulsifying type) or a compound forcibly emulsified with a surfactant or the like (forced emulsifying type) may be used.

The average particle size of the aqueous dispersion may be 1 to 1000 nm, preferably 10 to 500 nm, and more preferably 10 to 200 nm. If it is 1000 nm or more, it is too large for the diameter of the cellulose fine fibers, so that uniform adsorption becomes difficult. Therefore, the number of cellulose fine fibers that are not cross-linked by the cross-linking agent increases, which is not preferable from the viewpoint of enhancing the sheet strength.

Any of anionic, nonionic, and cationic hydrophilic groups is exposed on the surface of these emulsions, but cationic hydrophilic groups are more preferable. The reason is that the water-dispersible blocked polyisocyanate (0.0001 to 0.5% by weight) is effective in the dilute cellulose fine fiber slurry (0.01 to 0.5% by weight) at the stage of producing the papermaking slurry. This is because it is effective to utilize electrostatic interaction in adhering to cellulose fine fibers. It is known that the surface of general cellulose fibers is anionic (zeta potential in distilled water-30 to -20 mV) (Non-Patent Document 1 J. Brandrup (editor) and EHImmergut (editor) "Polymer Handbook 3rd edition". "V-153 to V-155). Therefore, since the surface of the aqueous dispersion is cationic, it can be easily adsorbed in the form of fine cellulose fibers. However, even if it is nonionic, it can be sufficiently adsorbed on cellulose fine fibers depending on the polymer chain length and rigidity of the hydrophilic group of the emulsion. Furthermore, even when adsorption is more difficult due to electrostatic repulsion such as anionic, it can be adsorbed on cellulose fine fibers by using a generally well-known cationic adsorption aid or cationic polymer. it can.

The water-dispersible blocked polyisocyanate is not particularly limited as long as it is a polyisocyanate or a polyisocyanate derivative containing at least two or more isocyanate groups. Examples of the polyisocyanate include aromatic polyisocyanates, alicyclic polyisocyanates, and aliphatic polyisocyanates.

Examples of the polyisocyanate derivative include one or more types of active hydrogen-containing compounds in addition to the above-mentioned polyisocyanate multimers (for example, dimer, trimer, pentamer, heptalite, etc.). Examples thereof include compounds obtained by reaction. The compound is an allophanate modified product (for example, an allophanate modified product produced by the reaction of polyisocyanate with alcohols), a polyol modified product (for example, a polyol modified product produced by the reaction of polyisocyanate with alcohols (alcohol addition)). Body), etc.), biuret modified products (for example, biuret modified products produced by the reaction of polyisocyanate with water or amines, etc.), urea modified products (for example, urea modified products produced by the reaction of polyisocyanate with diamine). Etc.), oxadiazine trione modified product (for example, oxadiazine trione produced by the reaction of polyisocyanate with carbonic acid gas, etc.), carbodiimide modified product (carbodiimide modified product produced by decarbonate condensation reaction of polyisocyanate, etc.), Examples include uretdione denatured products and uretonimine denatured products.

Examples of the active hydrogen-containing compound include polyester polyols, 1- to 6-valent hydroxyl group-containing compounds including polyether polyols, amino group-containing compounds, thiol group-containing compounds, and carboxyl group-containing compounds. It also includes water, carbon dioxide and the like present in the air or in the reaction field.

The blocking agent is added to the isocyanate group of the polyisocyanate compound to block it. This blocking group is stable at room temperature, but when heated to a heat treatment temperature (usually about 100 ° C. to about 200 ° C.), the blocking agent is desorbed and the free isocyanate group can be regenerated.

Blocking agents that satisfy such requirements include alcohol compounds, alkylphenol compounds, phenol compounds, active methylene compounds, mercaptan compounds, acid amide compounds, acid imide compounds, imidazole compounds, and urea compounds. Examples thereof include oxime compounds and amine compounds, and these blocking agents can be used alone or in combination of two or more.

The self-emulsifying type blocked polyisocyanate is obtained by binding an active hydrogen group-containing compound having an anionic, nonionic or cationic group to a blocked polyisocyanate skeleton.

The active hydrogen group-containing compound having an anionic group is not particularly limited, and examples thereof include a compound having one anionic group and having two or more active hydrogen groups. Examples of the anionic group include a carboxyl group, a sulfonic acid group, and a phosphoric acid group.

The active hydrogen group-containing compound having a nonionic group is not particularly limited, and for example, a polyalkylene ether polyol containing an ordinary alkoxy group as a nonionic group is used.

The active hydrogen group-containing compound having a cationic group is not particularly limited, but an aliphatic compound having an active hydrogen-containing group such as a hydroxyl group or a primary amino group and a tertiary amino group, among others. A polyhydroxy compound having a tertiary amino group and containing two or more active hydrogens reactive with an isocyanate group is preferable.

The cationic group can be easily dispersed in water in the form of a salt by being neutralized with a compound having an anionic group. Examples of the anionic group include a carboxyl group, a sulfonic acid group, and a phosphoric acid group. Further, the introduced tertiary amino group can be quaternized with dimethyl sulfate, diethyl sulfate or the like.

Forced emulsification type block polyisocyanate is known as block polyisocyanate. General anionic surfactants, nonionic surfactants, cationic surfactants, amphoteric surfactants, polymer surfactants, reactive surfactants. It is a compound emulsified and dispersed by the above.

The water-dispersible blocked polyisocyanate may contain 20% by weight of a solvent other than water in both the self-emulsifying type and the forced emulsifying type. The solvent is not particularly limited, and examples thereof include ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, ethylene glycol, diethylene glycol, and triethylene glycol. These solvents may be used alone or in combination of two or more.

The water-soluble polymer may be cationic, anionic, amphoteric or nonionic.

The cationic polymer is a polymer having a primary amino group, a secondary amino group, a tertiary amino group, a quaternary ammonium base, pyridinium, imidazolium, and a quaternized pyrrolidone. For example, cationized starch. , Cationic polyacrylamide, polyvinylamine, polydiallyldimethylammonium chloride, polyamideamine epichlorohydrin, polyethyleneimine, water-soluble cationic polymers such as chitosan and the like.

The anionic polymer is a polymer having an anionic group such as a carboxyl group, a sulfo group, or a phosphoric acid group, and examples thereof include carboxymethyl cellulose, polyacrylic acid, anionic polyacrylamide, urea phosphorylated starch, and succinic acid-modified starch. Examples thereof include sodium polystyrene sulfonate.

Examples of the amphoteric polymer include an amphoteric water-soluble polymer in which both an anionic monomer unit and a cationic monomer unit are contained in the molecular chain skeleton. For example, diallylamine hydrochloride / maleic acid copolymer, amphoteric polyacrylamide and the like can be mentioned.

Examples of the nonionic polymer include polyethylene glycol, hydroxypropyl methylcellulose, polyvinyl alcohol and the like.

Examples of the thermoplastic resin that can be added to the slurry include styrene resin, acrylic resin, aromatic polycarbonate resin, aliphatic polycarbonate resin, aromatic polyester resin, aliphatic polyester resin, and aliphatic polyolefin resin. , Cyclic olefin resin, polyamide resin, polyphenylene ether resin, thermoplastic polyimide resin, polyacetal resin, polysulfone resin, amorphous fluorine resin and the like. The number average molecular weight of these thermoplastic resins is generally preferably 1000 or more, more preferably 50 or more and 5 million or less, and further preferably 10,000 or more and 1 million or less. These thermoplastic resins may be contained alone or in combination of two or more. When two or more kinds of thermoplastic resins are contained, the refractive index of the resin can be adjusted by the content ratio, which is preferable. For example, when polymethyl methacrylate (refractive index about 1.49) and acrylonitrile styrene (acrylonitrile content about 21%, refractive index about 1.57) are contained at 50:50, a resin having a refractive index of about 1.53 can be obtained. ..

The thermosetting resin that can be added to the slurry is not particularly limited, and specific examples thereof include an epoxy resin, a thermosetting modified polyphenylene ether resin, a thermosetting polyimide resin, and a urea resin. Acrylic resin, silicon resin, benzoxazine resin, phenol resin, unsaturated polyester resin, bismaleimide triazine resin, alkyd resin, furan resin, melamine resin, polyurethane resin, aniline resin, and other industrially used resins and these. Examples thereof include a resin obtained by mixing two or more resins. Among them, epoxy resin, acrylic resin, unsaturated polyester resin, vinyl ester resin, thermosetting polyimide resin and the like have transparency and are therefore suitable for use as an optical material.

Examples of the photocurable resin that can be added to the slurry include an epoxy resin containing a latent photocationic polymerization initiator. These thermosetting resins or photocurable resins may be contained alone or in combination of two or more.

The thermosetting resin and photocurable resin mean substances having a relatively low molecular weight, which are liquid, semi-solid, solid, etc. at room temperature and exhibit fluidity at room temperature or under heating. These can be insoluble and insoluble resins formed by forming a network-like three-dimensional structure while causing a curing reaction or a cross-linking reaction by the action of a curing agent, a catalyst, heat or light to increase the molecular weight. Further, the cured resin product means a resin obtained by curing the thermosetting resin or the photocurable resin.

The curing agent and curing catalyst that can be added to the slurry are not particularly limited as long as they are used for curing a thermosetting resin or a photocurable resin. Specific examples of the curing agent include polyfunctional amines, polyamides, acid anhydrides, and phenolic resins, and specific examples of the curing catalyst include imidazole and the like, which are contained alone or as a mixture of two or more kinds. May be.

The thermoplastic resin, thermosetting resin, and photocurable resin that can be added to the above slurry are often hydrophobic, and even if they are added to the papermaking slurry, it is difficult to uniformly disperse them in the slurry. .. Therefore, the emulsion form is preferred. The emulsion is obtained by stirring a hydrophobic compound, which is a fine polymer particle having a particle size of about 0.001 to 10 μm, and an emulsifier in water. Further, for thermosetting resins and photocurable resins, by including a curing agent and a curing catalyst in the emulsion, the thin film cellulose fine fiber laminated sheet containing the emulsion is subjected to heat and light irradiation to be inside the thin film cellulose fine fiber laminated sheet. Can be cured with.

Well-known general anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants are used as emulsifiers for emulsions of thermoplastic resins, thermocurable resins, and photocurable resins that can be added to the slurry. A surfactant, a polymer-based surfactant, a reactive surfactant, or the like may be used.

Emulsions of thermoplastic resins, thermosetting resins, and photocurable resins that can be added to the slurry should have a large particle size in consideration of yield and dehydration, and if they are too large, the sheet uniformity or optical properties 0.001 to 10 μm, which is an appropriate size suitable for the purpose, is preferable. The surface charge of the emulsion may be in any of cationic, nonionic, and anionic states, but considering the mixing of the cellulose fine fiber slurry and the emulsion of the resin compound, the dispersion stability is that it is cationic. Or it is advantageous in terms of yield. However, even if it is nonionic, it can be sufficiently adsorbed on cellulose fine fibers depending on the polymer chain length and rigidity of the hydrophilic group of the emulsion. Furthermore, even when adsorption is more difficult due to electrostatic repulsion such as anionic, it can be adsorbed on cellulose fine fibers by using a generally well-known cationic adsorption aid or cationic polymer. it can.

As a method for preparing a paper-making or coating slurry, for example, (1) a cellulose fine fiber slurry is mixed with a compound containing an additive prepared in advance and dispersed to obtain a paper-making slurry, and (2) a cellulose fine fiber slurry is stirred. However, there are methods such as adding various additives individually one by one. In the case of adding a plurality of kinds of additives, in a system in which the additives aggregate with each other (for example, in a system in which a cationic polymer and an anionic polymer form an ion complex), papermaking may be performed in the order of addition. The dispersion state of the slurry and the zeta potential may change. However, the order and amount of addition are not particularly limited, and it is preferable to add them by a method that can obtain a desired dispersed state of papermaking slurry and sheet physical properties.

Examples of the stirring device for uniformly mixing and dispersing the above additives include an agitator, a homomixer, a pipeline mixer, a disperser of a type that rotates blades having a cutting function at high speed, a high-pressure homogenizer, and the like. , Not limited to these. In stirring, the dispersion average diameter of the slurry is preferably 1 μm or more and 300 μm or less. However, excessive stirring may cause excessive shear stress to be applied to an emulsion-based additive such as water-dispersible blocked polyisocyanate, and the emulsion structure may be broken. Therefore, depending on the slurry composition, it may not be preferable to use a high-pressure homogenizer, a grinder-type miniaturization device, a millstone-type grinding device, or the like.

Next, a papermaking process of forming a wet paper by filtering the papermaking slurry on a porous substrate will be described.

This papermaking process is basically any device that dehydrates water from the papermaking slurry and uses a filter or filter cloth (also called a wire in the technical field of papermaking) that retains cellulose fine fibers. You may use it.

As the paper machine, a sheet-like fiber sheet having few defects can be preferably obtained by using an apparatus such as an inclined wire type paper machine, a long net type paper machine, or a circular net type paper machine. Whether the paper machine is a continuous type or a batch type, it may be used properly according to the purpose. In order to improve the uniformity of the film quality, use one or more machines (for example, use an inclined wire type paper machine for the base layer paper machine, a round net paper machine for the upper layer paper machine, etc.) and use a multi-stage paper machine. It is also effective in some cases. The multi-stage papermaking means, for example, that the first stage is made with a grain of 1 g / m ² and the wet paper obtained there is used to make a second stage of 2 g / m ² with a total grain of 3 g / m. ^This is a technique for obtaining a non-woven fabric having a two-layer structure having two cellulose fine fiber layers. In the case of multi-stage papermaking, when the upper and lower layers are formed from the same dispersion, it becomes a single-layer non-woven fabric, but in the first stage as the lower layer, for example, fine-grained wet paper using fibrillated fibers. It is also possible to form a layer, perform papermaking with the dispersion described above in the second stage from above, and make the wet paper, which is the lower layer, function as a filter described later.

In the papermaking process, the size of the mesh of the wire or filter cloth is important because soft aggregates such as cellulose fine fibers dispersed in the papermaking slurry are filtered. In the present embodiment, the yield ratio of the water-insoluble component containing cellulose fine fibers and the like contained in the papermaking slurry is 70% by weight or more, preferably 95% by weight or more, and more preferably 99% by weight or more. Any wire or filter cloth can be used.

However, even if the yield ratio is 70% by weight or more, if the drainage is not high, the papermaking takes time and the production efficiency is significantly deteriorated. Therefore, the water permeation amount of the wire or filter cloth at 25 ° C. under atmospheric pressure is preferably 0.005 ml / (cm ² · sec) or more, more preferably 0.01 ml / (cm ² · sec) or more. Is preferable from the viewpoint of productivity. On the other hand, when the yield ratio is lower than 70% by weight, not only the productivity is significantly reduced, but also water-insoluble components such as cellulose fine fibers are clogged in the wire and filter cloth used, so that the two-layer structure after film formation The peelability of the non-woven fabric is significantly deteriorated.

The amount of water permeation of the wire or filter cloth under atmospheric pressure is evaluated as follows.
In a batch paper machine (for example, an automatic square sheet machine manufactured by Kumagai Riki Kogyo Co., Ltd.), a wire or filter cloth is installed on a metal mesh of 80 to 120 mesh (one having almost no drainage resistance). Next, a sufficient amount (y (ml)) of water is injected into a paper machine having a papermaking area of x (cm ² ), and the drainage time is measured under atmospheric pressure. The amount of water permeated when the drainage time is z (sec) is defined as y / (x · z) (ml / (cm ² · s)).

Examples of wires or filter cloths that can be used in this embodiment are TETEXMONODLW07-8435-SK010 (PET) manufactured by SEFAR (Switzerland), NT20 (PET / nylon blend) manufactured by Shikishima Kambas, and plastic wire manufactured by Nippon Filcon. Examples thereof include, but are not limited to, LTT-9FE and the multilayer wire described in Japanese Patent Application Laid-Open No. 2011-42903.

Dehydration by the papermaking process gives wet paper with advanced solidification. By further pressing the wet paper, a dispersion medium such as water can be removed with higher efficiency, and the solid content in the obtained wet film can be increased. The solid content of the wet paper can be controlled by the suction pressure (wet suction or dry suction) of the papermaking and the pressing conditions, and the solid content concentration is preferably 6% by weight or more and 30% by weight or less, more preferably the solid content concentration is 8% by weight. Adjust to the range of 25% by weight or less. If the solid content of the wet paper is lower than 6% by weight, the strength of the wet paper is low, so that the wet paper is not self-supporting and problems in the process are likely to occur. Further, when the wet paper is dehydrated to a concentration in which the solid content ratio exceeds 30% by weight, the uniformity such as the thickness of the sheet is lost.

For a non-woven fabric having a two-layer structure, a multilayer sheet can be manufactured by setting the support on a wire or a filter cloth and making paper. In order to produce a multi-layered sheet having three or more layers, a support having a multi-layered structure of two or more layers may be used. Further, a multi-stage papermaking of a non-woven fabric having a two-layer structure having two or more layers may be performed on the support to form a multi-layer sheet having three or more layers. At this time, it is sufficient to select a material that can satisfy the requirements related to the yield ratio and the amount of water permeation by combining the wire or filter cloth of the paper machine with the support. The support may be made hydrophilic by corona discharge treatment or plasma treatment before papermaking in order to improve the wettability at the time of papermaking and the adhesiveness with the cellulose fine fiber laminate.

For the purpose of making the two-layered non-woven fabric porous, papermaking is performed on a filter cloth, and the water in the obtained wet paper is replaced with an organic solvent in the step of replacing it with an organic solvent and dried. May be good. Details of this method can be followed in WO 2006/004012. Specifically, when an organic solvent having a certain degree of solubility in water is used when the non-woven fabric is replaced with an organic solvent or the like and then dried, a non-woven fabric having a high porosity can be obtained by one-step substitution. Examples of such a solvent include, but are not limited to, methyl ethyl ketone, isopropyl alcohol, tert-butyl alcohol, and isobutyl alcohol. The more hydrophobic solvent is used, the easier it is to produce a non-woven fabric having a higher porosity. When substituting with an organic solvent that is insoluble in water such as cyclohexane or toluene, the substitution is first performed with an organic solvent that is soluble in water such as acetone, methyl ethyl ketone, isopropyl alcohol, or isobutyl alcohol, and then the cyclohexane or toluene. A two-step substitution method of substituting with a water-insoluble solvent such as that is also effective. The solvent used at this time may be a mixed solvent with water or a mixed solvent between organic solvents. By passing the sheet after the organic solvent substitution through the drying step described later, a sheet having a porosity of 60% to 90% can be obtained.

Next, the drying process will be described. The wet paper obtained in the above-mentioned papermaking process becomes a non-woven fabric having a two-layer structure by evaporating a part of water in the drying process by heating. From the viewpoint of uniform heat treatment and suppression of sheet shrinkage due to heating, a fixed-length drying type dryer such as a drum dryer or a pin tenter is preferable. The drying temperature may be appropriately selected depending on the conditions, but preferably in the range of 45 ° C. or higher and 180 ° C. or lower, more preferably 60 ° C. or higher and 150 ° C. or lower, a uniform fiber sheet can be produced. If the drying temperature is less than 45 ° C., the evaporation rate of water is slow in many cases, and productivity cannot be ensured, which is not preferable. On the other hand, if the drying temperature is higher than 180 ° C., the drying speed in the sheet becomes uneven, wrinkles are generated in the sheet, and energy efficiency is poor, which is not preferable. In addition, multi-stage drying of low temperature drying of 100 ° C. or lower and subsequent high temperature drying of 100 ° C. or higher is effective for obtaining a highly uniform two-layered non-woven fabric.

In the above film forming process, the filter cloth or plastic wire for paper making used is an endless specification, and the entire process is performed with one wire, or the endless filter or endless felt cloth of the next process is used in the middle. It may be picked up and handed over, transferred and handed over, or all or part of the continuous film forming step may be a roll-to-roll step using a filter cloth. However, the method for producing a non-woven fabric having a two-layer structure according to the present embodiment is not limited to this.

Next, the smoothing step will be described. The non-woven fabric having a two-layer structure obtained in the above-mentioned drying step may be provided with a smoothing step of smoothing by a calendar device. By going through the smoothing step, the surface of the non-woven fabric having a two-layer structure can be smoothed and thinned. In addition, the air permeability and strength can be adjusted accordingly. For example, a non-woven fabric having a two-layer structure having a film thickness of 20 μm or less (the lower limit is about 1 μm) can be easily produced under a basis weight setting of 3 g / m ² . As the calendar device, in addition to a normal calendar device using a single press roll, a super calendar device having a structure in which these are installed in a multi-stage system may be used. By selecting these devices and the materials (material hardness) and linear pressure on both sides of the roll during calendar processing according to the purpose, a non-woven fabric having a two-layer structure having various physical property balances can be obtained.

Next, the heat curing process will be described.
By heat-treating the sheet obtained in the above-mentioned drying step or smoothing step, a chemical bond between the blocked polyisocyanate contained in the sheet and the cellulose fine fibers is formed. At the same time, cross-linking of the organic polymer sheet and the cellulose fine fibers in the laminated structure and immobilization of other additives to the non-woven fabric having a two-layer structure are also progressing.
In the heat curing step, a fixed-length drying type heat treatment machine such as a drum dryer or a pin tenter that heats in a fixed-length state is preferable from the viewpoint of uniform heat treatment and suppression of sheet shrinkage due to heating.

As described above, the blocked polyisocyanate is stable at room temperature, but when the heat treatment is performed above the dissociation temperature of the blocking agent, the blocking group is dissociated and the isocyanate group is regenerated, which is chemically combined with the functional group having active hydrogen. Bonds can be formed. The heating temperature varies depending on the blocking agent used, but is preferably 80 ° C. or higher and 220 ° C. or lower, more preferably 100 ° C. or higher and 180 ° C. or lower, and the temperature is higher than the dissociation temperature of the blocking group. When the temperature is lower than the dissociation temperature of the block group, the isocyanate group is not regenerated and cross-linking does not occur. On the other hand, heating at 220 ° C. or higher is not preferable because the cellulose fine fibers and the cross-linking agent are thermally deteriorated and may be colored.

The heating time is preferably 15 seconds or more and 10 minutes or less, and more preferably 30 seconds or more and 2 minutes or less. If the heating temperature is sufficiently higher than the dissociation temperature of the block group, the heating time can be shortened. Further, when the heating temperature is 130 ° C. or higher, if heating for 2 minutes or longer is performed, the moisture in the sheet is extremely reduced, so that the sheet immediately after heating becomes brittle and handling may become difficult, which is not preferable. ..
The heat curing step may be performed at the same time as the smoothing treatment described above.

The pore-diffusing membrane module of the present invention preferably has the following configuration. First, the non-woven fabric containing cellulose fibers shows a two-layer structure. One layer is a cellulose fine fiber that forms a surface layer as a film and forms a film surface having high smoothness (that is, a small smoothness value). The average fiber diameter of the cellulose fine fibers is 0.6 μm or less. The average length of the cellulose fibers is less than 2 mm. The smoothness value on the back surface side of the film, which is the other layer of the non-woven fabric, is 1/40 or less of the surface surface of the film, and the average fiber diameter of the cellulose fibers constituting the back surface is about 30 μm. The average length of the cellulose fibers is about 40 mm. The adhesion between the front surface and the back surface of the non-woven fabric is enhanced by a cross-linking agent having an isocyanate group as a cross-linking group. The non-woven fabric is mounted parallel to the support of the membrane module as shown in the flat membrane 1 in FIG. The surface of the non-woven fabric (shown by the solid line of the film-like material in FIG. 1) is attached so as to contact the circuit in the flow direction 4 of the primary fluid.

FIG. 1 illustrates a pore diffusion module composed of three plate-shaped supports and two non-woven fabric sheets. The non-woven fabric sheet having a two-layer structure is formed between two plate-shaped supports (support plates 2 (support plates 2a and 2b) and support plates 7 in the drawing) as shown by the flat film 1 in FIG. A 0-ring-shaped packing material (packing 11 in the figure) adheres to the support. Two types of support plates (two grooves for the 0-ring and a groove for the primary side flow path or a groove for the secondary side flow path and the flow path or the secondary of the laminar flow preparation area in the plane of each support The space between the two types of support plates (which have outlets leading from the side flow path to the circuit to the recovery tank) and the flat membrane 1 becomes the liquid flow path (secondary side flow path 3 and primary side flow path 6). .. The primary side liquid flows in the flow direction 4 and the secondary side liquid flows in the flow direction 5 in the flow path. The wall surface of the space portion (primary side flow path 6) is smooth in order to allow the flow of the primary side liquid in the flow direction 4 to flow as a laminar flow. The direction of flow of the primary fluid is indicated by a solid arrow, and the direction of flow of the secondary fluid is indicated by a dashed arrow. The membrane surface of the flat membrane 1 is defined as the surface in contact with the primary liquid.

FIG. 1 illustrates two types of polypropylene plate-shaped supports (support plates 2a and 2b), an end portion and an intermediate portion of the support plate 7. As shown in the support plate 7 in the figure, one of them has a primary side flow path having a circular cross section that serves as a laminar flow preparation area 8, and pushes up a cloth-like object 9 that acts as a valve from the laminar flow preparation area 8. Leads the primary liquid to the primary flow path 6. The flow path (laminar flow preparation area 8) is connected to the inlet of the primary side flow path of the module. As the material of the support, polypropylene, polycarbonate, or acrylic resin is preferable. Grooves with a depth of 1 to 2 mm are carved on the support so that the surface of the support becomes a smooth flat surface so as to be a primary side flow path or a secondary side flow path. The flow path provided by the support plates 2a and 2b is the secondary side flow path 3. A cloth-like material 9 that acts as a valve is fused to the support. A non-woven fabric such as nylon or polyester is suitable as the cloth-like material. These non-woven fabrics are fused to the location of the fluid outflow port on the support. The two types of supports are manufactured by cutting from a plastic plate or by an injection molding method using a mold.

FIG. 2 shows an example of an apparatus for exerting the function of the pore diffusion film module of the present invention. Two methods are adopted: a method in which the strain rate of the primary liquid on the flat membrane surface is controlled by a liquid feed pump (Fig. A) and a method in which the strain rate is controlled by a hydrostatic pressure difference (Fig. B). When the module of FIG. 1 is used in the intermembrane differential pressure applied to the membrane surface, the dynamic pressure becomes zero. Operate at a hydrostatic pressure difference of 0.05 atm or less. The strain rate is operated under a constant condition of 10 to 100 / sec. In Fig. A, what is open to the atmosphere is the receiving tank (connected to the filter F3 for opening), the secondary flow path (F2) of the pore diffusion membrane module M, and the liquid level L (via the F1 filter). Open). In this method, stable operation in the liquid transport section is important. On the other hand, in the method shown in FIG. B, the intermembrane differential pressure and the strain rate can be stably controlled by setting the liquid level L.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples and the like.

<Measurement and evaluation method>
The non-woven fabric sheet having a two-layer structure obtained in Examples and the like was evaluated using the following measurement method or evaluation method. Before the measurement, samples of various sizes were cut out, and the humidity was adjusted for 24 hours in a constant temperature and humidity chamber controlled at 23 ° C. and 50% RH, and then the measurement was carried out.

(1) A square piece of 10.0 cm × 10.0 cm was cut out from a non-woven fabric sheet having a two-layer structure with a basis weight, and its weight W (g) was measured. Based on this, the following formula:
W0 = 100 × W
The basis weight W0 (g / m ² ) of the film was calculated using.

(2) Number average / maximum fiber diameter of cellulose fine fibers Three random observations with a scanning electron microscope (SEM) on the cellulose fine fiber surface of the thin cell cellulose fine fiber laminated sheet are used to determine the fiber diameter of the fine fibers. Therefore, the magnification was increased to 10,000 to 100,000 times. For the obtained SEM image, lines were drawn in the horizontal and vertical directions with respect to the screen, the fiber diameters of the fibers intersecting the lines were measured from the enlarged image, and the number of intersecting fibers and the fiber diameter of each fiber were counted. .. In this way, the number average fiber diameter was calculated using the measurement results of two vertical and horizontal series for one image. Further, the number average fiber diameter was calculated in the same manner for the other two extracted SEM images, and the results for a total of three images were averaged to obtain the average fiber diameter of the target sample. Among the fiber diameters obtained by this method, the largest one was defined as the maximum fiber diameter.

(3) Thickness of non-woven sheet with two-layer structure After measuring the weight W (g) of a 10.0 cm x 10.0 cm square piece from the thin film cellulose fine fiber laminated sheet used for measuring the grain size, a surface contact type film thickness meter With a film thickness meter (Model ID-C112XB) manufactured by Mitutoyo, the in-plane thickness was measured at each center of the sheet divided into 9 equal areas, and the average value was measured for the thin film cellulose fine fiber laminated sheet. The average thickness (μm) was used.

(4) Garley-type air permeation resistance A 20 cm square multi-layer structure is divided into five equal areas, and a Garley-type densometer (manufactured by Toyo Seiki Seisakusho Co., Ltd., model GB2C) is used for each of the five central points. , The air permeation resistance was measured, and the average value of 5 points was taken to obtain the air permeation resistance (sec / 100 ml) of the sample.

(5) Porosity of Cellulose Fine Fiber Layer The density of the cellulose fine fiber was assumed to be 1.5 g / cm ³ and calculated from the following formula.
Porosity (%) = 100-([Metsuke (g / m ² ) / {Fiber layer thickness (μm) x 1.5 (g / cm ³ )}] x 100)

<Slurry production example>
[Slurry Production Example 1]
Tencel cut yarn (3 mm long), which is a regenerated cellulose fiber obtained from Sojitz Corporation, is placed in a washing net, a surfactant is added, and the oil on the fiber surface is removed by washing with water many times in a washing machine. did. The obtained swollen pulp was dispersed in water so as to have a solid content of 1.5% by weight (400 L), and an SDR14 type lab refiner (pressurized DISK type) manufactured by Aikawa Iron Works Co., Ltd. was used as a disc refiner device. The aqueous dispersion having a clearance of 1 mm and 400 L was beaten for 20 minutes. Following that, the beating process was continued under the condition that the clearance was reduced to a level close to almost zero. Sampling was performed over time, and the CSF value of the Canadian standard freshness test method (hereinafter referred to as CSF method) for pulp defined in JIS P 8121 was evaluated for the sampled slurry. As a result, the CSF value decreased over time. After that, once it became close to zero, it was confirmed that it tended to increase when the beating process was continued. The beating treatment was continued under the above conditions for 10 minutes after the clearance was set to near zero, and a beating water dispersion having a CSF value of 100 ml or more was obtained. The obtained beating water dispersion was directly subjected to a micronization treatment 5 times under an operating pressure of 100 MPa using a high-pressure homogenizer (NS015H manufactured by Niro Soabi (Italy)), and a slurry of cellulose fine fibers (solid content concentration) was carried out. : 1.5% by weight) was obtained. The CSF value was 650 ml or more.

<Sheet manufacturing example>
[Sheet Production Example 1] The slurry of Slurry Production Example 1 was diluted to a solid content concentration of 0.05% by weight and stirred with a household mixer for 4 minutes to prepare a 400 g papermaking slurry. While stirring 375 g of papermaking slurry with a three-one motor, 0.59 g of nonionic block polyisocyanate (trade name "Meikanate CX", manufactured by Meisei Chemical Works, Ltd., diluted to a solid content concentration of 1.0% by weight) was added dropwise to 3 Stirring was carried out for 1 minute to obtain a papermaking slurry (375.6 g in total). The weight ratio of the added nonionic block polyisocyanate was 3% by weight with respect to the weight of the solid content of the cellulose fine fibers. Plain fabric made of PET / nylon blend {NT20 manufactured by Shikishima Kambas Co., Ltd., water permeation at 25 ° C in the air: 0.03 ml / (cm ² · s), 99% of cellulose fine fibers filtered at 25 ° C under atmospheric pressure Batch type paper machine (Kumaya Riki Kogyo Co., Ltd.) set with the above-mentioned ability to filter} and functional paper of cellulose / PET / acrylic mixed paper {carboxymethyl cellulose treatment, manufactured by Nippon Paper Papilia, with a mesh size of 11 g / m ² } as a support. The above-adjusted papermaking slurry is added to an automatic square sheet machine (25 cm x 25 cm, 80 mesh) with a cellulose sheet with a grain size of 10 g / m ² as a guide, and then the papermaking (dehydration) is performed with the decompression degree to atmospheric pressure set to 50 KPa. Was carried out.

The wet paper consisting of the concentrated composition in a wet state on the obtained filter cloth was peeled off from the wire and pressed at a pressure of 1 kg / cm ² for 1 minute. The wet paper surface is brought into contact with the drum surface, and the wet paper is brought into contact with the drum surface in a drum dryer whose surface temperature is set to 130 ° C. in a state of three layers of support / wet paper / filter cloth. It was dried for 120 seconds. Of the obtained dried three-layered body, the filter cloth was peeled off from the cellulose sheet-like multilayer structure, and heat-treated in an oven heated to 180 ° C. for 5 minutes to obtain a white two-layered non-woven fabric sheet S1 ( A 25 cm × 25 cm, cellulose fine fiber layer with a texture of 10.3 g / m ² ) was obtained.

As a result of evaluation of the non-woven fabric sheet S1 having a two-layer structure, the sheet grain size is 21.4 g / m ² , the average fiber diameter is 0.39 μm, the sheet thickness is 70 μm, the Garley type air permeability resistance is 9 sec / 100 ml, and the porosity of the cellulose fine fiber layer. It was 85%.

[Example 1]
A pore-diffusing membrane module loaded with a flat membrane (S1) having a cellulose nanofiber layer having an average pore diameter of 360 nm obtained in Sheet Production Example 1 was assembled. The effective film area was 140 cm ² , and a film module was prepared so as to sandwich two non-woven fabrics between three plate-shaped supports as in FIG. The film surface of the non-woven fabric is attached to the primary side flow path, and the cross-sectional shape of the flow path is a band shape with a thickness of 3 mm. The back surface of the non-woven fabric was attached to the secondary flow path. The device of FIG. 2B was assembled using the module. A commercially available product of expanded polystyrene was pulverized with a mixer under water at 20 ° C. to prepare a dispersion aqueous solution having various areas in the form of flakes (thickness of about 10 μm). An aqueous solution in which ferric hydroxide colloidal particles having a particle diameter of 50 nm were dispersed (pH = 2.7, particle concentration 1000 ppm) was mixed with this aqueous solution to prepare an aqueous solution having a pH of 4. This aqueous solution was used as a model test solution for an aqueous solution in which a mixture of virus / bacteria / cells was dispersed. This test solution was subjected to pore diffusion treatment with the apparatus shown in Fig. B under the following conditions.
Average intermembrane differential pressure; 0.05 atm, strain rate on the membrane surface; 50 / sec treatment rate is 2.0 LMH (liters / square meter / hour), polystyrene flakes and ferric hydroxide in the recovered solution The concentrations of the colloidal particles were all below the detection limit (that is, 1 ppm or less). The treatment rate decreased slightly over time, but was approximately constant for 24 hours.

It can be applied in a wide range of fields as a technology for separating, removing, concentrating, and fractionating molecules and particles without heating. It can be typically used for safety measures during the manufacture of biopharmacy (for example, for virus removal / inactivation process validation) and for safety measures during the manufacture of products such as regenerative medicine, for the removal of infectious particles. .. It is used for manufacturing other health foods and cosmetics as a safety measure. The environmental industry (eg, water recycling as an example of the recycling industry) is one of the fields to be considered for future application in the field of safety measures.

The feature of the pore diffusion membrane separation technology is that the components are separated using the membrane. There is a principle difference from the membrane filtration method that utilizes the sieving effect that captures large-sized components such as particles inside the membrane. Therefore, the technique of the present invention can be used in fields that cannot be applied by the conventional membrane filtration technique. For example, it can be applied in a fraction recovery step of a component having physiological activity rather than a biological resource, such as a plasma fractionation step or a fraction recovery step of a body fluid component. It is also applied in fields such as concentration and recovery of fresh ingredients in agriculture, concentration of ingredients in liquid fertilizers, and long-term storage. It can be applied to the removal of microorganisms as an alternative to heat sterilization in the fermentation industry and can be used for the production of new raw products (eg, production of raw placenta).

1 Flat membrane composed of non-woven fabric 2 Support plate constituting the skeleton of the module 3 Secondary side flow path in the module 4 Flow direction of the liquid to be treated flowing in the laminar flow state in the primary side flow path 5 Secondary side flow path Flow direction of flowing membrane permeation liquid 6 Primary side flow path in the module 7 Support plate with built-in laminar flow preparation area 8 Laminar flow preparation area existing inside the support plate 9 Valve for reducing dynamic pressure to zero Cloth-like material that plays a role 10 Liquid inlet toward the outlet of the membrane permeable liquid module 11 O-ring-shaped packing for adhering the non-woven fabric to the support M Pore diffusion membrane module of the present invention T Receiving tank part L Liquid level Level control unit R Recovery tank P Liquid transport pump G Pressure gauge F1, F2, F3 Air inlet / outlet for opening to the atmosphere, sterilization or virus eradication filter installed at the inlet / outlet

Claims (3)

In a membrane module embodying the pore-diffusion membrane separation technology, the dynamic pressure of the pressure applied to the membrane is substantially zero, and the flat membrane filled in the module contains cellulose fibers having the following characteristics. A pore-diffusing membrane module characterized by using a non-woven fabric.
(A) The non-woven fabric has a two-layer structure, the first layer has a flat membrane surface which is a highly smooth membrane surface having a smoothness value of 10 μm or less, and the second layer has a flat membrane surface more than the flat membrane surface. It has the back surface of a flat film, which is a film surface having low smoothness, and the smoothness value of the front surface of the flat film is 1/10 or less of the smoothness value of the back surface of the flat film.
(B) Cellulose fibers have only a crystal structure of natural cellulose or regenerated cellulose, and do not have a chemical structure or a crystal structure as a cellulose derivative. The first layer having the surface of the flat film is composed of cellulose fibers containing cellulose fine fibers, and the number average fiber diameter of the cellulose fine fibers is 0.01 μm or more and less than 2 μm, and the cellulose fibers have an average length. The second layer is a short fiber having a diameter of 0.001 mm or more and less than 2 mm, and the second layer is a fiber having a number average fiber diameter of 2 μm or more and less than 50 μm and an average length of 1 mm or more. The pore diffusion module according to claim 1, which is a support that is. It is optically isotropic in the direction in the plane of the non-woven fabric, and has anisotropy in which the direction of the maximum refractive index is parallel to the film surface and the direction of the minimum refractive index is perpendicular to the film surface in the direction in the cross section. The pore diffusion module according to claim 1 or 2, characterized in that.

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