JP2019011535A - Porous sheet and porous laminated sheet - Google Patents

Abstract

To provide a porous sheet and a porous laminated sheet containing a fine cellulose fiber satisfying following conditions simultaneously: 1) porous structure is uniform and 2) air permeation resistivity does not change even when wetting and drying operation is repeated.SOLUTION: The porous sheet satisfies all of the following requirements (1)-(6): (1) the sheet is composed of a fine cellulose fiber having an average fiber diameter of 2-1000 nm, (2) its air permeation resistivity per a basis weight 10 g/mis 7000 sec/100 ml or under, (3) its basis weight is 0.5-40 g/m, (4) its thickness is 1-100 μm, (5) its rate of change of air permeation resistivity after wetting and drying is 100% or under, and (6) its average maximum major axis of pores at the sheet center part is 10 μm or under.SELECTED DRAWING: Figure 2

Description

  The present embodiment relates to a porous sheet and a porous laminated sheet containing fine cellulose fibers.

  In recent years, fine cellulose fibers obtained by beating and crushing cellulosic fibers at a high level and refining them to a fiber diameter of 1 μm or less (fibrillation) have attracted attention. Since the specific surface area increases due to the fiber diameter becoming nano-order, for example, when a composite sheet in which a resin is impregnated with a fine cellulose fiber sheet is produced, the thermal expansion coefficient is greatly reduced compared to a resin single film, and elasticity is increased. The rate increases. Further, since the fiber diameter is reduced, it is possible to produce a thin film sheet having a thickness of 10 μm or less. In recent years, performances such as a low coefficient of thermal expansion and thin film properties are required for substrates and interlayer insulating materials in electronic components. However, a fine cellulose fiber sheet can be an excellent core material for that purpose. Further, by utilizing the high specific surface area and the thin film property, it is expected to be developed as a filter with high collection efficiency and low pressure loss. Furthermore, the development as a diaphragm for a total heat exchanger having high moisture permeability is expected by utilizing the high hydrophilicity and thin film property of cellulose.

  In consideration of uses such as a resin composite film and a filter, the sheet is preferably a porous body, but it is not easy to make the fine cellulose fiber sheet porous. The fibrillation of the cellulosic fibers is basically performed in a state containing a large amount of water, and finally obtained in the form of a slurry in which fine cellulose fibers are dispersed in water. A fine cellulose fiber sheet can be produced by dehydrating and drying this slurry. However, 1) the fiber has a high specific surface area, 2) the fiber surface is hydrophilic, and 3) the water is a solvent having a high surface tension, so that a significant shrinkage occurs upon drying and a dense film without air permeability is formed. (Keratinization phenomenon). Therefore, making the fine cellulose fiber sheet porous is an important issue in the field, and various methods have been tried so far.

  Patent Document 1 discloses a method in which a fine cellulose fiber sheet in a state containing water is prepared and then replaced with an organic solvent having a low surface tension and dried. Patent Document 2 discloses a method in which a fine cellulose fiber slurry obtained by adding an emulsion containing an organic solvent having a boiling point higher than that of water is added to fine cellulose fibers and then dried including the organic solvent.

  On the other hand, Patent Document 3 discloses a method of making a fine cellulose fiber slurry having an average fiber diameter of 430 nm and drying it. Patent Document 4 discloses a method of making a fine cellulose fiber having a fiber surface hydrophobized by adding a hydrophobizing agent when producing fine cellulose fiber from pulp, and papermaking and drying.

JP 2006-193858 A JP 2010-53461 A International Publication No. 2016/047764 Japanese Patent Laid-Open No. 2006-160554

  For example, when the sheet described in Patent Documents 1 and 2 is used for a diaphragm for a total heat exchanger, it can exhibit a desired moisture permeability in the initial stage of use in an appropriate porous state. Further, there is a problem that the moisture permeation performance is deteriorated due to gradual densification due to condensation and drying. Further, when used as a liquid filter (for example, a filter for water treatment), there is a problem that when it is dried, the assumed fractionation performance is not exhibited due to a significant decrease in pore diameter or an increase in filtration pressure. Further, in the production of a composite film with a water-soluble resin, such as polyvinyl alcohol, there is a problem that strict process control for controlling the dimensions is required because of the large drying shrinkage of the film accompanying the volatilization of water. That is, even if the porous sheet obtained by the methods described in Patent Documents 1 and 2 is porous immediately after production, drying shrinkage occurs when the sheet is dried after being wet with water during use, and becomes densified. . Therefore, there is a demand for a sheet that does not change the porous structure even after the wet drying operation, specifically, the air resistance resistance does not change.

  These methods are expensive because they use a large amount of organic solvent, and are also disadvantageous in terms of industrial production and environmental problems because exhaust gas treatment is essential. Therefore, from the viewpoint of the manufacturing process, it is desired to make the porous body completely porous so that exhaust gas treatment is unnecessary.

  On the other hand, the methods described in Patent Documents 3 and 4 are a method of making a fine cellulose fiber sheet porous in an aqueous system, and the obtained sheet is less likely to change its air resistance even after being subjected to a wet drying operation. However, when these sheets are used for, for example, a total heat exchanger diaphragm, a moisture-permeable agent (such as calcium chloride) that improves moisture-permeable performance flows out during long-term use, and the moisture-permeable performance decreases. . Further, when used as a liquid filter (for example, a water treatment filter), there is a problem in that the supplement rate is reduced. In addition, when a resin composite film is produced, there is a problem that the thermal expansion coefficient increases and the elastic modulus decreases compared to the theoretical value. When the present inventors examined the porous structure of the sheet | seat manufactured by the water system by the cross-sectional SEM image, the non-uniform | heterogenous porosity which has a large pore whose major axis exceeds 10 micrometers and a major axis has a small pore of several hundred nm order. A quality structure was seen. In the total heat exchange membrane, the moisture permeable agent flows out through the large pores, the liquid filter captures the large pores and the target passes through, and in the resin composite film, the large pores are areas of resin only that do not contain fine cellulose fibers. Therefore, the effect on the thermal expansion coefficient and elastic modulus of the fine cellulose fiber is limited. Therefore, it has been desired that the porous structure in the sheet is uniform.

  The problem to be solved by the present invention is a fine cellulose fiber that can simultaneously satisfy the following characteristics: 1) the porous structure is uniform, and 2) the air resistance does not change even after repeated wet and dry operations. It is providing the porous sheet and porous laminated sheet containing this.

  As a result of intensive studies and experiments to solve the above problems, the present inventors have found that the above problems can be solved according to the configuration of the present disclosure, and have completed the present invention. . That is, the present invention includes the following embodiments.

[1] The following requirements (1) to (6):
(1) The average fiber diameter is composed of fine cellulose fibers of 2 nm to 1000 nm,
(2) The air resistance per 10 g / m ² per unit weight is 7000 sec / 100 ml or less,
(3) The basis weight is 0.5 g / m ² or more and 40 g / m ² or less,
(4) The thickness is 1 μm or more and 100 μm or less,
(5) The rate of change in air resistance before and after wet drying is 100% or less,
(6) The average maximum major axis of the pores at the center of the sheet is 10 μm or less,
A porous sheet that meets all requirements.
[2] The porous sheet according to aspect 1, wherein the water-based wet strength per unit weight of 10 g / m ² is 0.3 kg / 15 mm or more.
[3] The porous sheet according to the above aspect 1 or 2, wherein the non-aqueous wet strength per unit weight of 10 g / m ² is 0.3 kg / 15 mm or more.
[4] A porous laminated sheet comprising one or more base sheet layers and one or more fine cellulose fiber layers, wherein the fine cellulose fiber layers are the following requirements (1) to (3):
(1) The average fiber diameter is composed of fine cellulose fibers of 2 nm to 1000 nm,
(2) The layer thickness is 1 μm or more and 100 μm or less,
(3) The average maximum major axis of the pores at the center of the layer is 10 μm or less,
The porous laminate sheet satisfies the following requirements (4) to (7):
(4) The air resistance is 20000 sec / 100 ml or less,
(5) The rate of change in air resistance before and after wet drying is 100% or less,
(6) The basis weight is 2 g / m ² or more and 1000 g / m ² or less,
(7) The thickness is 2 μm or more and 1000 μm or less,
A porous laminate sheet that meets all requirements.
[5] A porous laminate sheet of 5 cm × 5 cm is immersed in 200 ml of ion-exchanged water, shaken at 23 ° C. and 200 rpm for 10 minutes using a shaker, and then the fine cellulose fiber layer is peeled off from the base sheet layer The porous laminated sheet according to the above aspect 4, wherein
[6] The porous laminated sheet according to the above aspect 4 or 5, wherein the aqueous wet strength is 0.5 kg / 15 mm or more.
[7] The porous laminated sheet according to any one of the above aspects 4 to 6, wherein the non-aqueous wet strength is 0.7 kg / 15 mm or more.
[8] A preparation step of preparing a slurry containing a porosifying agent, fine cellulose fibers, and water, a film forming step of forming a wet paper by dehydrating the slurry by a papermaking method, and the wet paper The manufacturing method of the porous sheet in any one of the said aspect 1-3 including the porous sheet formation process of obtaining a porous sheet by making it dry at least.
[9] The method for producing a porous sheet according to the aspect 8, wherein the slurry further contains a block polyisocyanate, and the porous sheet forming step includes a thermal curing treatment performed after the wet paper is dried.
[10] The method for producing a porous sheet according to the aspect 8 or 9, wherein the porous sheet forming step includes a calendar process performed after the humidity is dried.
[11] The porous sheet, basis weight 10 g / m ² per aqueous wet strength 0.3 kg / 15 mm or more, and / or basis weight has a higher non-aqueous wet strength 0.3 kg / 15 mm per 10 g / m ^2, The porous sheet forming step includes a thermal curing process and a calendar process performed after drying the wet paper, and the calendar process is performed before the thermal curing process, simultaneously with the thermal curing process, or the thermal curing process. The manufacturing method of the porous sheet of the said aspect 9 performed after a process.
[12] A preparation step of preparing a slurry containing a porosifying agent, fine cellulose fibers, and water, and a film forming step of forming a multilayer wet paper by dehydrating the slurry on a base sheet by a papermaking method And a porous laminated sheet forming step of obtaining a porous laminated sheet by at least drying the multilayer wet paper, and producing the porous laminated sheet according to any one of the above aspects 4 to 7.
[13] The porous laminated sheet according to the above aspect 12, wherein the slurry further contains a block polyisocyanate, and the porous laminated sheet forming step includes a thermal curing treatment performed after drying the multilayer wet paper. Production method.
[14] The method for producing a porous laminated sheet according to the above aspect 12 or 13, wherein the porous laminated sheet forming step includes a calendar process performed after the multilayer wet paper is dried.
[15] The porous laminated sheet forming step includes a thermal curing process and a calendar process performed after the multilayer wet paper is dried, and the calendar process is performed before the thermal curing process and simultaneously with the thermal curing process. Or the manufacturing method of the porous laminated sheet of the said aspect 13 performed after the said heat curing process.

  For example, when the porous sheet of this embodiment is used for a resin composite film, it can realize a low thermal expansion coefficient and a high elastic modulus by a uniform porous structure. For example, when the resin composite film is used as an interlayer insulating film in a wiring board, it can contribute to higher integration and higher density of semiconductors and the like. Moreover, when the porous sheet of this embodiment is used for a liquid filter, for example, the liquid can be filtered with a high capture rate due to the uniform porous structure. Furthermore, when the porous sheet of the present embodiment is used for a diaphragm for a total heat exchanger, for example, even if it is used for a long time in a high-temperature and high-humidity region, the change in the air resistance is suppressed and the moisture permeability performance is improved. Can be maintained.

It is a figure explaining the calculation method of the average largest long diameter of a porous sheet. 6 is a view showing a cross-sectional SEM image of a porous sheet obtained in Example 12. FIG. 6 is a view showing a cross-sectional SEM image of a sheet obtained in Comparative Example 5. FIG. 10 is a view showing a cross-sectional SEM image of a sheet obtained in Comparative Example 16. FIG.

  Hereinafter, exemplary embodiments for carrying out the present invention (hereinafter referred to as “present embodiments”) will be described in detail. In addition, this embodiment is not limited to the following embodiment, It can implement in various deformation | transformation within the range of the summary.

The porous sheet of this embodiment is composed of fine cellulose fibers. In the present disclosure, “fine cellulose fiber” means a cellulose fiber having a number average fiber diameter of 2 to 1000 nm.
The fine cellulose fiber of this embodiment preferably has a crystal structure of cellulose type I and / or type II. The crystal structure can be identified from a diffraction profile obtained by wide-angle X-ray diffraction using CuKα (λ = 0.15418 nm) monochromatized with graphite. Cellulose type I has peaks at two positions near 2θ = 14 to 17 ° and 2θ = 22 to 23 °. Cellulose type II has one peak at 2θ = 10 ° to 19 ° and two peaks at 2θ = 19 ° to 25 °. When cellulose type I and cellulose type II are mixed, a maximum of 6 peaks are observed in the range of 2θ = 10 ° to 25 °.

  The fine cellulose fiber of the present embodiment preferably has a crystallinity of 20% or more. The degree of crystallinity is determined by X-ray diffraction method or solid state NMR method. The degree of crystallinity is preferably 30% or more, more preferably 40% or more, and further preferably 50% or more. When the degree of crystallinity is in the above range, particularly excellent performance can be expected in terms of heat resistance and low linear expansion.

The fine cellulose fiber of this embodiment preferably has a degree of polymerization (DP) of 100 or more and 12000 or less. The degree of polymerization is the number of repeating anhydroglucose units forming the cellulose molecular chain. When the degree of polymerization of the cellulose fiber is 100 or more, the tensile strength and elastic modulus of the fiber itself are improved. As a result, by improving the strength of the sheet and remarkably improving the handleability of the sheet, for example, tearing of the water treatment filter during pleating or rupture of the filter in the filtration step is suppressed. Further, the degree of polymerization being 100 or more is advantageous in that a resin composite film having a low thermal expansion coefficient or a high elastic modulus can be obtained. Although there is no particular upper limit to the degree of polymerization of the fine cellulose fibers, cellulose having a degree of polymerization exceeding 12000 is substantially difficult to obtain and tends to be difficult to industrially use. The degree of polymerization of the cellulose fiber is preferably 150 to 8000 from the viewpoints of handleability and industrial implementation. First, after determining the intrinsic viscosity (JIS P 8215: 1998) of a dilute cellulose solution using a copper ethylenediamine solution, the degree of polymerization is determined by the relationship between the intrinsic viscosity of cellulose and the degree of polymerization DP of the following formula (1). Utilized, it is determined as the degree of polymerization DP.
Intrinsic viscosity [η] = K × DPa (1)
Here, K and a are constants determined by the type of polymer. In the case of cellulose, K is 5.7 × 10 ⁻³ and a is 1.

  The fine cellulose fiber of this embodiment may be chemically modified. For example, some or most of the hydroxyl groups present on the surface of fine cellulose fibers are esterified with acetate ester, nitrate ester, sulfate ester, phosphate ester, alkyl ether represented by methyl ether, carboxymethyl ether The 6-position hydroxyl group is oxidized by a TEMPO (2,2,6,6-tetramethylpiperidinooxy radical) oxidation catalyst to form a carboxyl group (acid). Type and salt type). It is preferable that the chemical modification occurs particularly on the surface of the cellulose fiber.

  The fine cellulose fibers are preferably short fibers (staples). In a preferred embodiment, the fine cellulose fibers are substantially free of endless long fibers (filaments). The number average fiber length of the fibers is not particularly limited, but is preferably 200 nm or more, more preferably 1000 nm or more, and preferably 100 times or more, more preferably 500 times or more of the number average fiber diameter, Preferably it is 1000 times or more. When the number average fiber length is 100 times or more the number average fiber diameter, the fine cellulose fibers are highly entangled and the sheet strength is good, which is preferable.

  The fine cellulose fiber of the present embodiment has a number average fiber diameter of 2 nm to 1000 nm, preferably 2 nm to 500 nm, more preferably 2 nm to 300 nm. This range is advantageous in maintaining the strength and dimensional stability of the sheet and forming fine and uniform pore diameters. When the number average fiber diameter is less than 2 nm, the cellulose fiber may be dissolved in water particularly when the cellulose fiber is chemically modified. In such a case, the physical properties (mechanical strength such as rigidity and dimensional stability) as fine fibers are not expressed, and cannot be used as fine cellulose fibers for sheet production. On the other hand, when the average fiber diameter of the fine cellulose fibers is more than 1000 nm, the entanglement points of the fibers are decreased, and the sheet strength per unit basis weight is decreased, so that thinning may be difficult.

  The number average fiber diameter is a value measured by conducting observation with a scanning electron microscope (SEM) at a magnification equivalent to 10,000 times at three locations on the porous sheet surface. Specifically, one line is drawn in the longitudinal direction and the transverse direction orthogonal to the obtained SEM image, and the fiber diameter and the number of fibers crossing the line are 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 in the same manner for the other two extracted SEM images, 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 points are randomly observed at a magnification of 50000 times, and a more accurate number average fiber diameter is calculated using the same method as described above. Is adopted.

The porous sheet of this embodiment has a sheet weight W of 0.5 g / m ^{2 to} 40 g / m ² , preferably 1 g / m ^{2 to} 30 g / m ² , more preferably 1 g / m ^{2 to} 20 g / m ^2. It is as follows. If it is less than 0.5 g / m ^2, it is difficult to obtain good film quality uniformity, which is not preferable. On the other hand, if it exceeds 40 g / m ² , it is not preferred because it takes time for drainage and drying at the time of paper making and it becomes difficult to improve the film quality uniformity. The basis weight was evaluated by cutting a sample stored for 24 hours in an environment controlled at room temperature 23 ° C. and humidity 50% RH into 20 cm × 20 cm (area 0.04 m ² ), measuring the weight W1 (g), Calculate from (2).
Weight per unit area W (g / m ² ) = W1 / 0.04 Formula (2)

The porous sheet of this embodiment has a thickness of 1 μm to 100 μm, preferably 1 μm to 90 μm, more preferably 1 μm to 80 μm. If it is thinner than 1 μm, it becomes difficult to form a porous sheet uniformly without pinholes. On the other hand, if the thickness exceeds 100 μm, the resin impregnation time becomes long during the production of the resin composite film, which is not preferable for continuous production.
As a method of measuring the thickness, a sample for cross-sectional SEM observation of a porous sheet is prepared, and SEM observation is performed in three views at a magnification of 1000 times. Subsequently, in each obtained cross-sectional SEM image, three points are arbitrarily selected from the surface on one side of the sheet. After each point is taken as a starting point, a perpendicular line is drawn to obtain three intersections with the lower surface of the sheet, and then the distance between the starting point and the intersection is measured. And the average value of the distance of a total of 9 points | pieces is made into a film thickness (micrometer).

The porous sheet of this embodiment has an average air resistance per unit weight of 10 g / m ^{2 of} 7000 sec / 100 ml or less, preferably 6000 sec / 100 ml or less, more preferably 5000 sec / 100 ml or less. When the air resistance exceeds 7000 sec / 100 ml, the porosity is low, the original function of the filter is poor, the resin impregnation into the sheet becomes difficult, and a resin composite film cannot be produced. In addition, although the air resistance is preferably low because of the nature of the sheet, the air resistance is less than 1 sec / 100 ml because of the fineness of the network, so the average air resistance per 10 g / m ^{2 is} 10 The degree is preferably 1 sec / 100 ml or more.

The air resistance is the time required for 100 ml of air to pass through the sheet. For the measurement, an Oken type air permeability resistance tester (for example, model EG01 manufactured by Asahi Seiko Co., Ltd.) is used. 10 points are measured at different positions on one sheet sample (20 cm × 20 cm) at room temperature, and the average value is defined as the average air permeability resistance (AR). At this time, using the basis weight W of the base paper measured in advance, the value per 10 g / m ² basis weight is calculated from the following formula (3).
Permeation resistance per unit weight 10 g / m ² = AR / W × 10 Formula (3)

The porous sheet of this embodiment is excellent in the porous retainability before and after the wet and dry operation. Specifically, the change rate of the air resistance before and after the wet drying operation is 100% or less, preferably 80% or less, more preferably 70% or less. Since the total heat exchanger is used in a humid environment, condensation and drying are repeated. At this time, if the porous retainability of the porous sheet to be used is poor (specifically, the rate of change is over 100%), the air resistance is likely to change (typically increase) due to condensation and drying. This is not preferable because it leads to a decrease in On the other hand, there is no lower limit value for the rate of change, and the smaller the rate of change, the better.
The wet drying operation refers to an operation in which water is uniformly applied to a stationary porous sheet so that the moisture content of the sheet becomes 300% by weight or more and 400% by weight or less and then dried in an oven. The air resistance of the sheet is measured before and after this operation, and the change is defined as the rate of increase of the air resistance. The sheet moisture content is calculated from the following formula (4) using the initial sheet weight W2 and the wet sheet weight W3.
Sheet moisture content = (W3-W2) / W2 × 100 Formula (4)
A specific measurement method is to cut a porous sheet (20 cm × 20 cm) that is allowed to stand for one day in an environment of 23 ° C. and 50% RH into 5 cm × 5 cm, and select five sheets therefrom. The air resistance is measured for each of the five samples, and the measurement location is marked. This air permeability resistance is the initial air resistance R1 and the average value of the five sheets is AR1. Subsequently, the sample is placed on a metal plate, sprayed with water uniformly with a spray, and wiped off water droplets adhering to the periphery of the sample. The sheet weight before and after the wetting operation is measured, and the sheet moisture content is measured according to the equation (4). After confirming that the moisture content at this time was not less than 300% by weight and not more than 400% by weight, it was dried in an oven at 80 ° C. for 1 hour, and the air resistance at the marked place was measured again. This air resistance is defined as the post-operation air resistance R2, and the average value of the five samples is AR2. Finally, the rate of increase in air resistance (%) is calculated from the following equation (5).
Permeability increase rate (%) = (AR2-AR1) / AR1 × 100 Formula (5)

The porous sheet of this embodiment has a uniform porous structure. Specifically, a sample for cross-sectional SEM observation of a porous sheet is prepared, and 10 views of SEM observation are performed at a magnification of 5000 times. From the obtained 10 cross-sectional SEM images, the largest major axis is measured among the pores at the center of the porous sheet, and then the average value (average maximum major axis) of the ten sheets is calculated. It can be considered that the porous structure is more uniform as the average maximum major axis is smaller. The porous sheet central portion refers to a portion excluding the surface layer portions 1 and 2 when the porous sheet cross section is equally divided into four in the thickness direction (surface layer portion 1 -center portion 1 -center portion 2 -surface layer portion 2). . Dividing into four equal parts is done by marking the left and right edges of the sheet into four equal parts, connecting and dividing each other (see FIG. 1). For example, when the thickness of the porous sheet is 20 μm, 10 μm excluding the surface layer portions of 5 μm on both sides is set as the central portion of the porous sheet.
The porous sheet of the present embodiment has an average maximum major axis of 10 μm or less, preferably 8 μm or less, more preferably 6 μm or less, and further preferably 4 μm or less. If the average maximum major axis exceeds 10 μm, the area of the resin that does not contain fine cellulose fibers increases during the production of the resin composite film, so the effects such as low thermal expansion and high elastic modulus obtained by the fine cellulose fiber composite become limited. It is not preferable.

The porous sheet of this embodiment preferably has a dry strength per unit weight of 10 g / m ² of 0.4 kg / 15 mm or more, more preferably 0.5 kg / 15 mm or more, and even more preferably 0.6 kg / 15 mm or more. In the case of 0.4 kg / 15 mm or more, handling at the time of sheet preparation is easy, and it is preferable that breakage does not easily occur in the sheet drying / winding process particularly in continuous production. On the other hand, the upper limit of the dry strength of the porous sheet of the present embodiment is not particularly limited, but is 10.0 kg / 15 mm or less per unit weight of 10 g / m ² from the viewpoint of feasibility.
As a method for measuring the dry strength, first, the basis weight (W) of a sample (20 cm × 20 cm) stored for 24 hours in an environment controlled at a room temperature of 23 ° C. and a humidity of 50% RH is measured by the above method. Next, it is cut into a width of 15 mm, and a tensile strength of 10 points is set at a distance between chucks of 100 mm and a tensile speed of 10 mm / min using a desktop horizontal tensile tester (for example, No. 2000 manufactured by Kumagai Riki Kogyo Co., Ltd.). The average value is measured as the dry strength (DS). At this time, using a basis weight (W) of the base paper measured in advance, a value per 10 g / m ² basis weight (kgf / 15 mm) is calculated from the following formula (6).
Drying strength per 10 g / m ² basis weight (kgf / 15 mm) = DS / W × 10 Formula (6)

The porous sheet of the present embodiment preferably has an aqueous wet strength per unit weight of 10 g / m ^{2 of} 0.3 kg / 15 mm or more, more preferably 0.4 kg / 15 mm or more, and further 0.5 kg / 15 mm or more. preferable. In the case of 0.3 kg / 15 mm or more, a porous sheet can be favorably used as a water treatment filter, a cell culture substrate, or a diaphragm for a total heat exchanger, which is a use environment in contact with water. On the other hand, there is no particular upper limit value for the water-based wet strength of the porous sheet of the present embodiment, but from the viewpoint of feasibility, it is, for example, 6.0 kg / 15 mm or less per 10 g / m ² basis weight.
As a method for measuring the water-based wet strength, the basis weight (W) of a sample (20 cm × 20 cm) stored for 24 hours in an environment controlled at a room temperature of 23 ° C. and a humidity of 50% RH is first measured by the method described above. Next, it is cut into a width of 15 mm, and the center of the 15 mm width test piece is immersed in water for 10 seconds. Subsequently, using a desktop horizontal tensile tester (for example, No. 2000 manufactured by Kumagai Riki Kogyo Co., Ltd.), the distance between chucks is 100 mm (placed so that the wet 50 mm is in the center), and the tensile speed is 10 mm / min. Ten points of tensile strength are measured in a wet state, and the average value is defined as aqueous wet strength (WS). At this time, using the basis weight (W) of the base paper measured in advance, the value per 10 g / m ² basis weight (kgf / 15 mm) is calculated from the following formula (7).
10 g / m ² basis weight per aqueous wet strength (kgf / 15mm) = WS / W × 10 Equation (7)

The porous sheet of this embodiment preferably has a nonaqueous wet strength per unit weight of 10 g / m ^{2 of} 0.3 kg / 15 mm or more, more preferably 0.4 kg / 15 mm or more, and 0.5 kg / 15 mm or more. Further preferred. In the case of 0.3 kg / 15 mm or more, sheet breakage is less likely to occur in the resin impregnation step for producing a filtration filter or a resin composite film, which is a use environment in contact with a non-aqueous liquid, and is easy to use and manufacture. On the other hand, the upper limit value of the non-aqueous wet strength of the porous sheet of the present embodiment is not particularly limited, but is 8.0 kg / 15 mm or less per 10 g / m ² basis weight from the viewpoint of feasibility. The non-aqueous liquid referred to here is methyl cellosolve.
As the method for measuring the non-aqueous wet strength, the same method is used except that the solvent of the aqueous wet strength measuring method is changed to methyl cellosolve. The average value of 10 points of tensile strength is defined as non-aqueous wet strength (NWS), and the non-aqueous wet strength (kgf / 15 mm) per unit weight of 10 g / m ² is expressed by the following formula using the basis weight (W) of the base paper measured in advance. Calculate from (8).
Non-aqueous wet strength per 10 g / m ² basis weight (kgf / 15 mm) = NWS / W × 10 Formula (8)

The porosity of the porous sheet of the present embodiment is preferably 20% or more and 90% or less. When the porosity is 20% or more, the pores are not too small and function well as a porous sheet, and can be suitably used as a core material for filters and resin composite films. On the other hand, when the porosity is 90% or less, the strength as a sheet is maintained well, and it can be suitably used as a core material for a filter or a resin composite film.
The porosity means the volume ratio of voids in the porous sheet. The porosity can be determined by the following formula (9) from the area, thickness and mass of the porous sheet.
Porosity (volume%) = {(1-B / (M × A × t)} × 100 Formula (9)
Here, A is the porous sheet area (cm ² ), t is the thickness (cm), B is the porous sheet mass (g), and M is the density of cellulose (1.5 g / cm ³ in this embodiment). .

The specific surface area of the porous sheet of the present embodiment is preferably 1 m ² / g or more 1000 m ² / g or less, more preferably 3m ² / g or more 500 meters ² / g or less, more preferably 5 m ² / g or more 100 m ² / g or less. The specific surface area means a BET specific surface area measured by a nitrogen gas adsorption method. If the specific surface area of the porous sheet is 1 m ² / g or more, it can be regarded as porous and can be used favorably for resin-impregnated films, liquid filtration filters, and the like. On the other hand, if it is 1000 m < ² > / g or less, manufacture of a porous sheet will be easy.

  In the porous sheet of the present embodiment, the content of the volatile organic solvent (the boiling point under atmospheric pressure is less than 250 ° C.) with respect to the weight of the porous sheet is 100 ppm or less, more preferably 50 ppm or less, and even more preferably 10 ppm or less. . When a porous sheet having a volatile organic solvent content of 100 ppm or less is used for the diaphragm for a total heat exchanger, it can be avoided that the volatile organic solvent is released into the room as a bad odor, which is preferable. On the other hand, there is no lower limit of the content rate, and the smaller the content rate, the better. As an example of a volatile organic solvent, 1-hexanol etc. which are added on a manufacturing method in order to manufacture the porous fine cellulose fiber sheet described in Unexamined-Japanese-Patent No. 2010-053461 can be mentioned.

  The porous laminated sheet of this embodiment includes one or more base sheet layers and one or more fine cellulose fiber layers, and is typically composed of these. For example, a porous laminated sheet in which a fine cellulose fiber layer is disposed on a base sheet, a porous laminated sheet composed of three or more layers in which a fine cellulose fiber layer is sandwiched between base sheets, and fine cellulose on both sides of the base sheet Examples thereof include a porous laminated sheet in which a fiber layer is disposed. According to the porous laminated sheet, even if the basis weight of the porous sheet is small, the tensile strength and the like are strengthened by the base sheet, and it becomes strong and the handleability is improved. Further, when the porous laminated sheet contains two or more base sheet layers or two or more fine cellulose fiber layers, two or more kinds of base sheet layers or two or more kinds of fine layers are used. You may be comprised with the cellulose fiber layer.

  The form of the base material sheet of this embodiment should just be a sheet form, and forms, such as a textile fabric, a knitted fabric, a long fiber nonwoven fabric, a short fiber nonwoven fabric, a microporous film, are mentioned. The thickness of the base sheet is preferably 1 μm or more and 1000 μm or less. As a method for measuring the thickness, a sample for cross-sectional SEM observation of a porous laminated sheet is prepared, and SEM observation is performed in three views at a magnification of 250 times. Subsequently, in the obtained base sheet of each cross-sectional SEM image, three points are arbitrarily selected from the base sheet surface (interface with fine cellulose fibers). A perpendicular line is drawn with each point as a starting point, and after obtaining three intersections with the lower surface of the base sheet, the distance between the starting point and the intersection is measured. And let the average value of the distance of a total of 9 points | pieces be the film thickness (micrometer) of a base material sheet.

  Although it does not specifically limit as a constituent fiber of the woven fabric, knitted fabric, long fiber nonwoven fabric, or short fiber nonwoven fabric constituting the base sheet, for example, natural cellulose fiber, regenerated cellulose fiber, cellulose derivative fiber, nylon fiber, polyester Examples thereof include fibers, polyolefin fibers, carbon fibers, glass fibers, aramid fibers, and blended yarns of these fibers. These fibers may be used alone or in combination. The number average fiber diameter of these fibers is preferably 0.1 μm or more and 30 μm or less, more preferably 0.5 μm or more and 25 μm or less, and further preferably 1.0 μm or more and 20 μm or less. The number average fiber diameter is a porous laminate. It is preferable for improving the strength of the sheet, maintaining flexibility, and uniformity of film quality. As the measurement of the number average fiber diameter, arbitrary 10 fibers are selected from the electron micrograph (1000 times magnification) of the base sheet, the diameter of the selected fibers is measured, and the number average is obtained.

  Although it does not specifically limit as a microporous film, Polyolefin-type resin, such as regenerated cellulose, polyethylene, a polypropylene, polysulfone, polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, polycarbonate, 6-nylon, 6, 6 -Nylon resins such as nylon, acrylic resins such as polymethyl methacrylate, polyketones, polyether ether ketones and the like.

The porous laminated sheet of this embodiment has an air permeability resistance of 20000 sec / 100 ml or less, preferably 10,000 sec / 100 ml or less, more preferably 7000 sec / 100 ml or less. When the air resistance exceeds 20000 sec / 100 ml, the porosity is low and the original function of the filter is poor, which is not preferable. From the viewpoint of sheet use, the air resistance is basically preferably low, but the air resistance is 1 sec / 100 ml or more because of the fineness of the network, so the preferable lower limit is 1 sec. / 100 ml.
The method for measuring the air resistance of the porous laminated sheet is the same as the method for measuring the air resistance of the porous sheet.

The porous laminated sheet of this embodiment is excellent in the porous retainability before and after the wet drying operation. Specifically, the change rate of the air resistance before and after the wet drying operation is 100% or less, preferably 80% or less, more preferably 70% or less. Since the total heat exchanger is used in a humid environment, the resistance to air permeability may change (typically increase) due to condensation and drying. Therefore, when the rate of change exceeds 100%, it is not preferable because the heat exchange efficiency is lowered when used as a diaphragm for a total heat exchanger. On the other hand, there is no lower limit value for the rate of change, and the smaller the rate of change, the better.
The wet drying operation is an operation in which water is evenly applied to the porous laminate sheet that has been allowed to stand so that the moisture content of the fine cellulose fiber layer is not less than 300% by weight and not more than 400% by weight, followed by drying in an oven. I mean. The air resistance of the porous laminated sheet is measured before and after this operation, and the change is defined as the rate of change of the air resistance. The sheet moisture content is calculated from the following formula (10) using the initial porous laminated sheet weight W4, the wet porous laminated sheet weight W5, and the estimated initial weight W6 of the fine cellulose fiber layer.
Sheet moisture content = (W5-W4) / W6 × 100 Formula (10)
W6 is calculated from the following formula (11) using the fact that the fine cellulose fiber layer thickness (D1, μm) calculated from cross-sectional SEM observation described later is approximately proportional to the fine cellulose fiber basis weight.
Estimated initial weight W6 (g) of fine cellulose fiber layer =
Fine cellulose fiber layer thickness D1 (μm) × 1 (g / μm / m ² ) Formula (11)
The measuring method of the air permeability resistance change rate is in accordance with the measuring method using the porous sheet.

The porous laminated sheet of the present embodiment has a sheet weight of 2 g / m ² or more and 1000 g / m ² or less, preferably 2 g / m ² or more and 900 g / m ² or less, more preferably 2 g / m ² or more and 800 g / m ² or less. is there. If it is less than 2 g / m ² , the sheet strength is weak and it is difficult to obtain good film quality uniformity, which is not preferable. Moreover, since the ratio of the porous sheet with respect to a porous laminated sheet will be too small when it exceeds 1000 g / m < ² >, the characteristic (for example, high adsorption performance by the height of a specific surface area) cannot be exhibited, and it is unpreferable.
The measurement method is in accordance with the measurement method for the basis weight of the porous sheet.

The porous laminated sheet of this embodiment has a thickness of 2 μm to 1000 μm, preferably 2 μm to 900 μm, more preferably 2 μm to 800 μm, and even more preferably 2 μm to 700 μm. If it is thinner than 2 μm, it becomes difficult to form a porous laminated sheet uniformly without pinholes. On the other hand, if it exceeds 1000 μm, it takes a long time to impregnate the base sheet layer with the resin during the production of the resin composite film, which is disadvantageous for continuous production, and drying unevenness tends to occur, which is not preferable.
As a method for measuring the thickness, a sample for cross-sectional SEM observation of a porous laminated sheet is prepared, and SEM observation is performed in three views at a magnification of 250 times. Subsequently, in the obtained cross-sectional SEM images, three points are arbitrarily selected from the surface of the fine cellulose fiber layer. A perpendicular line is drawn with each point as a starting point, and after obtaining three intersections with the lower surface of the base sheet, the distance between the starting point and the intersection is measured. And let the average value of the distance of a total of nine points be the film thickness (micrometer) of a base material sheet.

  The fine cellulose fiber layer in the porous laminated sheet of this embodiment is comprised with the above-mentioned fine cellulose fiber.

The fine cellulose fiber layer in the porous laminated sheet of this embodiment has a thickness of 1 μm to 100 μm, more preferably 90 μm or less, and still more preferably 80 μm or less. If it is thinner than 1 μm, it becomes difficult to form a fine cellulose fiber layer uniformly without pinholes. On the other hand, if the thickness exceeds 100 μm, the resin impregnation time becomes long during the production of the resin composite film, which is not preferable for continuous production.
As a method for measuring the thickness, a sample for cross-sectional SEM observation of a porous laminated sheet is prepared, and SEM observation is performed in three views at a magnification of 1000 times. Subsequently, in the obtained fine cellulose fiber layer of each cross-sectional SEM image, three points are arbitrarily selected from the layer surface. After each point is taken as a starting point, a perpendicular line is drawn to obtain three intersections with the lower layer surface (interface with the base material sheet), and then the distance between the starting point and the intersection is measured. And let the average value of the distance of a total of 9 points | pieces be the film thickness (micrometer) of a fine cellulose fiber layer.

  The fine cellulose fiber layer in the porous laminated sheet of this embodiment has a uniform porous structure. Specifically, a cross-sectional SEM observation sample of the porous laminated sheet is prepared, and SEM observation of the fine cellulose fiber layer is performed for 10 fields at a magnification of 5000 times. From the obtained 10 cross-sectional SEM images, the largest major axis is measured among the pores at the center of the fine cellulose fiber layer, and then the average value (average maximum major axis) of the ten sheets is calculated. It can be considered that the porous structure is more uniform as the average maximum major axis is smaller. The fine cellulose fiber layer central portion is a portion excluding the outer layer portions 1 and 2 when the cross section of the fine cellulose fiber layer is equally divided into four in the thickness direction (outer layer portion 1-central portion 1-central portion 2-outer layer portion 2). Point to. Dividing into four equal parts is performed by marking the left and right ends of the fine cellulose fiber layer into four equal parts, connecting and dividing each other. For example, when the thickness of the fine cellulose fiber layer is 20 μm, 10 μm excluding the outer layer portions 5 μm on both sides is set as the central portion of the fine cellulose fiber layer. The fine cellulose fiber layer of the porous laminated sheet of this embodiment has an average maximum major axis of 10 μm or less, preferably 8 μm or less, more preferably 6 μm or less, and further preferably 4 μm or less. When the average maximum major axis exceeds 10 μm, it is not preferable because it leads to permeation of coarse particles when used in a filtration filter and the fractionation performance decreases.

The weight ratio of the fine cellulose fibers in the porous laminated sheet of the present embodiment is preferably from 0.1% by weight to 50% by weight, more preferably from 0.5% by weight to 50% by weight, and more preferably from 1% by weight to 50% by weight. More preferably, it is% or less. When the amount is 50% by weight or less, the overall strength of the sheet including the porous fine cellulose fiber layer is effectively improved by reinforcement with the base sheet. On the other hand, when it is 0.1% by weight or more, the characteristics of the porous laminated sheet (for example, high adsorption performance due to the high specific surface area) are maintained well.
As a method for measuring the weight ratio, the basis weight (W) of a sample (20 cm × 20 cm) stored for 24 hours in an environment controlled at a room temperature of 23 ° C. and a humidity of 50% RH is first measured by the above method. Subsequently, the fine cellulose fiber estimated basis weight W6 (g / m ² ) is calculated using the fine cellulose fiber layer thickness (D1, μm) obtained from the cross-sectional SEM image described above. And the weight ratio (%) of the fine cellulose fiber in a porous lamination sheet is computed from a following formula (12).
Weight ratio (%) of fine cellulose fiber in porous laminated sheet = W6 / W × 100 Formula (12)

  In the porous laminated sheet of this embodiment, the base sheet and the fine cellulose fiber layer preferably have adhesiveness in water. Here, having adhesiveness in water means that a 5 cm × 5 cm porous laminate sheet is immersed in a bottle containing 200 ml of ion-exchanged water and shaken at 23 ° C. and 200 rpm for 10 minutes. It means that the fine cellulose fiber layer is not peeled off from the base sheet by visual observation even after shaking. If peeling does not occur after this operation, a porous laminated sheet is applied to a water filter, a cell culture sheet, or a membrane for a total heat exchanger that requires high dimensional stability under high humidity, etc. This is preferable because it can be used.

The porous laminated sheet of this embodiment preferably has an aqueous wet strength of 0.5 kg / 15 mm or more, more preferably 0.7 kg / 15 mm or more, and further preferably 1.0 kg / 15 mm or more. In the case of 0.5 kg / 15 mm or more, a porous laminated sheet can be favorably used as a water treatment filter, a cell culture substrate, or a diaphragm for a total heat exchanger, which is a use environment in contact with water. On the other hand, the upper limit of the water-based wet strength of the porous laminated sheet of the present embodiment is not particularly limited, but is 8.0 kg / 15 mm or less, for example, from the viewpoint of feasibility.
As a method for measuring the water-based wet strength, a portion having a center of 50 mm in the length direction of a test piece having a width of 15 mm and a length of 200 mm is immersed in water for 10 seconds. Subsequently, using a desktop horizontal tensile tester (for example, No. 2000 manufactured by Kumagai Riki Kogyo Co., Ltd.), the distance between chucks is 100 mm (disposed so that the wet 50 mm is in the center), and the tensile speed is 10 mm / min. Ten points of tensile strength are measured in a wet state, and the average value is defined as water-based wet strength. Even if the porous laminated sheet does not break, it is regarded as a sample fracture when the fine cellulose fiber layer breaks or peels off from the base sheet, and the value is taken as the water-based wet strength of the porous laminated sheet.

The porous laminated sheet of the present embodiment preferably has a non-aqueous wet strength of 0.7 kg / 15 mm or more, more preferably 0.9 kg / 15 mm or more, and further preferably 1.0 kg / 15 mm or more. In the case of 0.7 kg / 15 mm or more, sheet breakage is less likely to occur in the resin impregnation process for producing a filtration filter or a resin composite film, which is a use environment in contact with a non-aqueous liquid, so that it is easy to use and manufacture. On the other hand, the upper limit value of the non-aqueous wet strength of the porous laminated sheet of the present embodiment is not particularly limited, but is 10.0 kg / 15 mm or less from the viewpoint of feasibility. In addition, the non-aqueous liquid here means methyl cellosolve.
As the method for measuring the non-aqueous wet strength, the same method is used except that the solvent of the aqueous wet strength measuring method is changed to methyl cellosolve. Even if the porous laminated sheet does not break, it is regarded as a sample break when the fine cellulose fiber layer breaks or peels off from the base sheet, and the value is taken as the non-aqueous wet strength of the porous laminated sheet.

  In the porous laminated sheet of the present embodiment, the content of the volatile organic solvent (the boiling point under atmospheric pressure is less than 250 ° C.) with respect to the weight of the porous laminated sheet is 100 ppm or less, more preferably 50 ppm or less, and even more preferably 10 ppm or less. It is. When a porous laminated sheet having a volatile organic solvent content of 100 ppm or less is used for the diaphragm for a total heat exchanger, it is preferable because the volatile organic solvent can be prevented from being released indoors as a bad odor. On the other hand, there is no lower limit of the content rate, and the smaller the content rate, the better. As an example of a volatile organic solvent, 1-hexanol etc. which are added on a manufacturing method in order to manufacture the porous fine cellulose fiber sheet described in Unexamined-Japanese-Patent No. 2010-053461 can be mentioned.

Hereinafter, although the example of the manufacturing method of the porous sheet and porous laminated sheet of this embodiment is demonstrated, it does not specifically limit to this method.
The porous sheet and porous laminated sheet of this embodiment may contain a porosifying agent in the sheet. The porous agent contained in the sheet is preferably 0.1% by weight to 100% by weight, more preferably 0.1% by weight to 50% by weight, and more preferably 0.1% by weight to 30% by weight of the fine cellulose fiber weight. % Or less is more preferable.

  Usually, when a fine cellulose fiber slurry consisting only of water and fine cellulose fibers is made and dried, a dense film is formed. On the other hand, when a slurry containing a porosifying agent is made and dried, a porous sheet is obtained. Further, since the porosifying agent remains in the sheet even after drying, an increase in the air resistance can be suppressed even if a wet drying operation is performed. When the amount of the porous agent is 0.1% by weight or more, the amount of the porous agent is sufficient, and the desired air resistance can be achieved satisfactorily. In the case of 100% by weight or less, it is possible to avoid an increase in the air resistance due to the pores being filled with the porous agent, and the liquid porous agent does not ooze out from the sheet, which is preferable in continuous production.

  As the porosifying agent, various compounds capable of making the fine cellulose fiber sheet porous can be used. Specifically, 1) the boiling point under atmospheric pressure is 250 ° C. or higher, preferably 280 ° C. or higher, more preferably 300. A compound having a temperature of not lower than ° C. and 2) insoluble in water is preferable. The temperature of the drying process of sheet production is usually less than 250 ° C., and if the boiling point of the porosifying agent is 250 ° C. or higher under atmospheric pressure, it is difficult to vaporize in the drying process, so there is no need to introduce exhaust equipment, The load in continuous production can be reduced. On the other hand, the upper limit of the boiling point is not particularly limited, but may be, for example, 400 ° C. or less from the viewpoint of feasibility.

  Here, “does not dissolve in water” means that the aqueous dispersion of the porosifying agent having a solid content of 1% by weight is cloudy at 23 ° C. or is separated into an aqueous layer and an oil layer. Specifically, after adding 99 g of ion-exchanged water and 1 g of a porosifying agent (solid content: 100% by weight) to a 100 ml glass vial, the mixture was stirred at 750 rpm for 1 hour while adjusting the temperature to 50 ° C., and then 23 ° C. Judging from the turbidity and appearance in a state where the temperature is lowered to agitation and stirring is stopped. First, it is visually confirmed whether or not the two layers are separated, and if the two layers are separated, it is determined that “it does not dissolve in water”. Moreover, when it is not isolate | separating into two layers, turbidity is measured using a turbidimeter, and the case where turbidity is 1 NTU or more is judged as "it does not melt | dissolve in water." Turbidity is preferably 1 NTU or more, more preferably 3 NTU or more, further preferably 5 NTU or more, and extremely preferably 10 NTU or more. As a method for measuring turbidity, a turbidimeter (for example, TN100 (manufactured by Eutech)) is used, and measurement is performed by adding 10 ml so that bubbles do not enter the measurement vial. When the solid content of the porous agent is less than 100% by weight, the amount of ion-exchanged water added is adjusted so that the final aqueous dispersion becomes 1% by weight.

  In the fine cellulose fiber slurry, the porosifying agent does not dissolve in the slurry, and therefore exists as oil droplets, and it seems that fine cellulose fibers cover the oil droplets. Then, it is considered that some or all of the oil droplets remain on the sheet during paper making and become porous. Therefore, it is desired as a porosifying agent that it can exist as droplets in water, that is, does not dissolve in water. These droplets can be used in such a form that they self-assemble in water such as phospholipid to form a vesicle structure and become cloudy. Further, even when the phase completely separates when left standing, it can be used because it can exist as droplets by vigorous stirring with a mixer or the like. Furthermore, a hydrophobic compound that does not dissolve in water can be forcibly emulsified with a surfactant or the like, and can be used even if it is a stable droplet in water. On the other hand, when the porous agent is completely dissolved in water, most of the porous agent flows out as filtrate during paper making, so the porous agent does not stay in the fine cellulose fibers and functions well as a porous agent. do not do.

  As the porosifying agent, various compounds having the above-mentioned characteristics can be used, but one or more of three types of hydrocarbon group, perfluoroalkyl group or organosiloxane structure are included in the skeleton of the compound. In particular, a compound containing a hydrocarbon group is more preferable because of its excellent affinity with a resin in producing a resin composite. Only one of the above three types may be included in the compound, or two or more types may be included at the same time. The compound may be a low molecular compound or a high molecular compound.

  As said hydrocarbon group, a C2-C40 group is preferable from a viewpoint that the solubility with respect to water is low and it is excellent in affinity with resin. The hydrocarbon group may be a saturated or unsaturated aliphatic group (linear, branched or alicyclic), an aromatic group, or a combination thereof.

The perfluoroalkyl group has 1 to 10 carbon atoms, such as 1 to 8, particularly 1 to 6, particularly 4 or 4 in terms of low solubility in water and excellent affinity with the resin. 6 is preferable, for example, —CF ₃ , —CF ₂ CF ₃ , —CF ₂ CF ₂ CF ₃ , —CF (CF ₃ ) ₂ , —CF ₂ CF ₂ CF ₂ CF ₃ , —CF ₂ CF ( _{CF 3) 2, -C (CF} 3) 3, - (CF 2) 4 CF 3, - (CF 2) 2 CF (CF 3) 2, -CF 2 C (CF 3) 3, -CF (CF 3 ) CF ₂ CF ₂ CF ₃ , — (CF ₂ ) ₅ CF ₃ , — (CF ₂ ) ₃ CF (CF ₃ ) ₂ , — (CF ₂ ) ₄ CF (CF ₃ ) ₂ , — (CF ₂ ) ₇ CF _{3, - (CF 2) 5} CF (CF 3) 2, - (CF 2) 6 CF (CF 3) 2, - (CF 2) 9 CF 3 , and the like.

As said organosiloxane structure, an average composition is general formula (1) from a viewpoint that the solubility with respect to water is low and it is excellent in affinity with resin.
R ¹ _a SiO _{(4-a) / 2} (1)
[In the formula, R ¹ may be the same or different in the molecule, and includes a hydrogen atom, a hydroxyl group, a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, and a substitution having 1 to 20 carbon atoms. Or, it is selected from an unsubstituted alkoxy group, and a is a natural number of 1.0 to 3.0. ]
The structure represented by these is preferable.

R ^{1 in the} general formula (1) is preferably an unsubstituted monovalent hydrocarbon group from the viewpoint of low solubility in water and excellent affinity with a resin. Is an alkyl group such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, dodecyl, tetradecyl, hexadecyl, octadecyl, etc .; vinyl group Cycloalkyl groups such as allyl group, cyclopentyl group and cyclohexyl group; aryl groups such as phenyl group; and aralkyl groups such as 2-phenylethyl and 2-phenylpropyl.

Examples of the hydrocarbon substituent when R ¹ is a substituted monovalent hydrocarbon group include an amino group, an aminoalkyl group, a halogen atom, a nitrile group, and a polyoxyalkylene group. As an alkoxy group, a C1-C3 methoxy group, an ethoxy group, and a propyl group can be mentioned.

A in the general formula (1) represents an average number of R ¹ bonded to the silicon atom of the polysiloxane, and is 1.0 to 3.0. The organosiloxane molecular structure having an average composition represented by the general formula (1) may have a branched structure as well as a straight chain, but preferably has a linear structure. Preferred specific examples when the porosifying agent is an organosiloxane include trimethylsiloxy-terminated dimethylsilicone, hydroxy-terminated dimethylsilicone, and methylhydrogensiloxane, with trimethylsiloxy-terminated dimethylsilicone and hydroxy-terminated dimethylsilicone being preferred. .

  The porosifying agent of this embodiment is composed of a vinyl monomer, a (meth) acrylate monomer, a (meth) acrylamide monomer, and a styrene monomer containing the hydrocarbon group, perfluoroalkyl group, and / or organosiloxane structure. A polymer compound containing at least one monomer unit selected from the group may be used, and two or more types of monomer units may be simultaneously contained in the polymer compound skeleton.

  Although it does not specifically limit as a monomer containing a hydrocarbon group, For example, methyl (meth) acrylate, butyl (meth) acrylate, t-butyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (Meth) acrylate, tetradecyl (meth) acrylate, octadecyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, trimethylcyclohexyl (meth) acrylate, cyclodecyl (meth) acrylate, cyclodecylmethyl (meth) acrylate, Alkyl such as tricyclodecyl (meth) acrylate, benzyl (meth) acrylate, and allyl (meth) acrylate, alkenyl, cycloalkyl, (meth) acrylate having an aromatic ring Relate and the like.

Although it does not specifically limit as a monomer containing a perfluoroalkyl group and a monomer containing an organosiloxane structure, For example, the following can be illustrated.
CH ₂ = CR′COOCH ₂ CH ₂ Rf,
_{CH 2 = CR'COOCH 2 CH 2 N} (CH 2 CH 2 CH 3) CORf,
CH ₂ = CR′COOCH (CH ₃ ) CH ₂ Rf,
_{CH 2 = CR'COOCH 2 CH 2 N} (CH 3) SO 2 Rf,
_{CH 2 = CR'COOCH 2 CH 2 N} (CH 3) CORf,
_{CH 2 = CR'COOCH 2 CH 2 N} (CH 2 CH 3) SO 2 Rf,
_{CH 2 = CR'COOCH 2 CH 2 N} (CH 2 CH 3) CORf,
_{CH 2 = CR'COOCH 2 CH 2 N} (CH 2 CH 2 CH 3) SO 2 Rf,
_{CH 2 = CR'COOCH (CH 2 Cl} ) CH 2 OCH 2 CH 2 N (CH 3) SO 2 Rf.
[In the above formula, R ′ represents a hydrogen atom, a methyl group, a fluorine atom, or a trifluoromethyl group, and Rf represents the perfluoroalkyl group or the organosiloxane structure. ]

  The porosifying agent of the present embodiment may be an amphiphilic compound containing one or more of the aforementioned hydrocarbon group, perfluoroalkyl group, and / or organosiloxane structure in the compound. An amphiphilic compound refers to a compound containing a hydrophobic block and a hydrophilic block simultaneously in the molecular skeleton. Examples of the portion corresponding to the hydrophobic block include the above-described hydrocarbon group, perfluoroalkyl group, organosiloxane structure, and a polymer structure containing these. Examples of the portion corresponding to the hydrophilic block include a structure containing a hydrophilic functional group and a hydrophilic polymer structure.

  In the case where the amphiphilic compound is a polymer, the polymerization form is not particularly limited, but for example, a block copolymer, a gradient copolymer, a graft copolymer, a random copolymer, a tapered copolymer, A periodic copolymer is mentioned. Among these, block copolymers and graft copolymers are preferable because they are self-emulsified in water and easily become cloudy.

Examples of the hydrophilic functional group is not particularly limited, a hydroxyl group, a thiol group, a carboxyl group, a sulfonic acid group, sulfuric ester group, phosphoric acid group, or a sulfate _{group, -OM, -COOM, -SO 3 M} , - A group represented by OSO ₃ M, —HMPO ₄ , or —M ₂ PO ₄ (M represents an alkali metal or an alkaline earth metal), a primary to tertiary amine, and a quaternary ammonium salt (a hydroxide as a counter anion). Ion, fluoride ion, chloride ion, bromide ion, halide ion such as iodide ion, nitrate ion, formate ion, acetate ion, trifluoroacetate ion, p-toluenesulfonate ion, hexafluorophosphate, tetrafluoro Borate etc.). The porous agent of this embodiment may contain one or more of these hydrophilic groups in the molecular skeleton, and may contain two or more different hydrophilic groups at the same time.

  The hydrophilic polymer structure is not particularly limited, but polyvinyl alcohol, polyvinylpyrrolidone, sodium polyacrylate, carboxyvinyl polymer, polyglutamic acid, polylysine, polyvinylpyridine, cellulose, dextran, polyalkylene oxide, poly (methylene ether) And polymer structures such as polymers of poly (methacrylic acid) and poly (acrylamide) (meth) acrylate monomers. The porosifying agent of the present embodiment may contain one or more of these hydrophilic polymer structures in the molecular skeleton, and may contain two or more different hydrophilic polymers at the same time.

  Although it does not specifically limit as a (meth) acrylate type monomer, For example, hydroxyl-containing (meth) acrylates, such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, Poly (alkylene glycol mono (meth) acrylate, polyprolene glycol mono (meth) acrylate and other polyalkylene glycol mono (meth) acrylate; (poly) ethylene glycol monomethyl ether (meth) acrylate, (poly) ethylene glycol monoethyl ether (meta ) Acrylates, glycol ether type (meth) acrylates such as (poly) propylene glycol monomethyl ether (meth) acrylate, glycidyl (meth) acrylate, 3,4-ester Glycidyl group-containing (meth) acrylates such as xylcyclohexyl (meth) acrylate, (meth) acryloyloxyethyl glycidyl ether, (meth) acryloyloxyethoxyethyl glycidyl ether; (meth) acryloyloxyethyl isocyanate, 2- (2 -Isocyanatoethoxy) ethyl (meth) acrylate, and isocyanate group-containing (meth) acrylates such as isocyanate-blocked monomers such as ε-caprolactone, methyl ethyl ketoxime, and pyrazole of the isocyanate; oxetanylmethyl (meth) acrylate, etc. Oxygen atom-containing cyclic (meth) acrylate; dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, t-butylaminoethyl (meth) acrylate Examples thereof include amino group-containing (meth) acrylates such as rate and quaternary ammonium type thereof. “Poly” and “(poly)” in the above mean n = 2 or more.

  In the amphiphilic compound containing a hydrocarbon group in the present embodiment, the hydrophilic group is roughly classified into two types, an ionic group (anionic, cationic and amphoteric) and a nonionic group.

Although it does not specifically limit as an amphiphilic compound which has an anionic group and a hydrocarbon group, For example, the following compounds are mentioned.
(1) Linear or branched alkylbenzene sulfonate.
(2) Linear or branched alkane sulfonate.
(3) α-olefin sulfonate.
(4) A linear or branched alkyl sulfate or alkenyl sulfate.
(5) Alkyl ether sulfate having a linear or branched alkyl group or an alkenyl ether sulfate having a linear or branched alkenyl group to which 0.5 to 10 moles of alkylene oxide is added on average However, the alkylene oxide is preferably any one of alkylene oxides having 2 to 4 carbon atoms or a mixture of ethylene oxide (EO) and propylene oxide (PO) (EO / PO = 0.0.0 in molar ratio). 1 / 9.9 to 9.9 / 0.1).
(6) Alkyl phenyl ether sulfate having a linear or branched alkyl group or an alkenyl phenyl ether sulfate having a linear or branched alkenyl group to which 3 to 30 moles of alkylene oxide is added on average However, the alkylene oxide is preferably any one of alkylene oxides having 2 to 4 carbon atoms or a mixture of EO and PO (EO / PO = 0.1 / 9.9 to 9 in molar ratio). .9 / 0.1).
(7) Alkyl ether carboxylate having a linear or branched alkyl group or an alkenyl ether carboxyl having a linear or branched alkenyl group to which an average of 0.5 to 10 moles of alkylene oxide is added However, the alkylene oxide is preferably any of alkylene oxides having 2 to 4 carbon atoms or a mixture of EO and PO (EO / PO = 0.1 / 9.9 in molar ratio). ~ 9.9 / 0.1).

(8) Alkyl polyhydric alcohol ether sulfates such as linear or branched alkyl glyceryl ether sulfonates.
(9) Saturated or unsaturated α-sulfo fatty acid salt or methyl, ethyl or propyl ester salt thereof.
(10) Long chain monoalkyl phosphate, long chain dialkyl phosphate or long chain sesquialkyl phosphate.
(11) Polyoxyethylene monoalkyl phosphate, polyoxyethylene dialkyl phosphate or polyoxyethylene sesquialkyl phosphate.
(12) A long-chain monoalkyl sulfonate, a long-chain dialkyl sulfonate, or a long-chain sesquialkyl sulfonate.
(13) Fatty acids and salts having a linear or branched alkyl group.
(14) Polyvalent carboxylic acids and salts having a linear or branched alkyl group.
The counter cation can be used as alkali metal salts such as sodium salt and potassium salt; amine salt and ammonium salt. Of these, alkali metal salts such as sodium salt and potassium salt are preferred.

Although it does not specifically limit as an amphiphilic compound which has a cationic group and a hydrocarbon group, For example, the following compounds are mentioned.
(1) Dilong chain alkyl dishort chain alkyl type quaternary ammonium salt.
(2) Mono long chain alkyl tri short chain alkyl type quaternary ammonium salt.
(3) Tri long chain alkyl mono short chain alkyl type quaternary ammonium salt.
However, the above “long-chain alkyl” represents an alkyl group having 5 to 26 carbon atoms, preferably 8 to 18 carbon atoms.
“Short chain alkyl” includes a phenyl group, a benzyl group, a hydroxy group, a hydroxyalkyl group and the like in addition to an alkyl group having 1 to 4 carbon atoms. Moreover, you may have an ether bond between carbon atoms. Specifically, an alkyl group having 1 to 4 carbon atoms, preferably 1 to 2 carbon atoms; a benzyl group; a hydroxyalkyl group having 2 to 4 carbon atoms, preferably 2 to 3 carbon atoms; 2 to 4 carbon atoms, preferably 2 to 3 carbon atoms. The polyoxyalkylene group is preferable.

  Although it does not specifically limit as an amphiphilic compound which has an amphoteric group and a hydrocarbon group, For example, an imidazoline type and an amide betaine type compound are mentioned. Specifically, 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine and amidopropyl betaine laurate are preferable.

Although it does not specifically limit as an amphiphilic compound which has a nonionic group and a hydrocarbon group, For example, what is shown below is mentioned.
(1) A polyoxyalkylene alkyl obtained by adding an average of 1 to 30 moles, preferably 5 to 20 moles of an alkylene oxide having 2 to 4 carbon atoms to an aliphatic alcohol having 6 to 22 carbon atoms, preferably 8 to 18 carbon atoms Ether or polyoxyalkylene alkenyl ether. Among these, preferable examples include polyoxyethylene alkyl ether, polyoxyethylene alkenyl ether, polyoxyethylene polyoxypropylene alkyl ether, and polyoxyethylene polyoxypropylene alkenyl ether.
Examples of the aliphatic alcohol used here include primary alcohols and secondary alcohols, and primary alcohols are preferred. Moreover, the alkyl group or alkenyl group may be linear or branched.
(2) Polyoxyethylene alkyl phenyl ether or polyoxyethylene alkenyl phenyl ether.
(3) A fatty acid alkyl ester alkoxylate represented by, for example, the following general formula (2) in which an alkylene oxide is added between ester bonds of a long-chain fatty acid alkyl ester.
R ¹ CO (OA) _q OR ² (2)
[Wherein R ¹ CO represents a fatty acid residue having 6 to 22 carbon atoms, preferably 8 to 18 carbon atoms; OA represents an alkylene oxide having 2 to 4 carbon atoms, preferably 2 to 3 carbon atoms (for example, ethylene oxide, propylene Q represents the average number of moles of alkylene oxide added, and is generally 3-30, preferably 5-20. R ² represents a lower alkyl group having 1 to 4 carbon atoms which may have a substituent having 1 to 3 carbon atoms. ]
(4) Polyoxyethylene sorbitan fatty acid ester.
(5) Polyoxyethylene sorbite fatty acid ester.
(6) Polyoxyethylene fatty acid ester.
(7) Polyoxyethylene hydrogenated castor oil.
(8) Glycerin fatty acid ester.
(9) the following general formula (3) Polyoxyethylene alkyl amine represented by polyoxyethylene alkylamide R ³ a-A - [(R ³ bO) _p -R ³ c] _q (3)
[Wherein R ³ a represents an alkyl group or alkenyl group having 6 to 18 carbon atoms, preferably 8 to 16 carbon atoms, and R ³ b represents an alkylene group having 2 or 3 carbon atoms, preferably ethylene. R ³ c represents an alkyl group having 1 to 3 carbon atoms or a hydrogen atom, and p is an average added mole number of an alkyleneoxy group, preferably 2 to 100, more preferably 5 or more 80 or less, more preferably 5 or more and 60 or less, even more preferably 10 or more and 60 or less, A represents —CONH—, —NH—, —CON <, or —N <, and A represents —CONH—. Or, q is 1 when -NH-, and q is 2 when A is -CON <or -N <. ]
(10) Monohydric alcohol or polyhydric alcohol having one or more hydroxyl groups

  About the amphiphilic compound which has a nonionic group and a hydrocarbon group, the solubility to water will fall that HLB is less than 12, and it is suitable as a porous agent. The above-mentioned “HLB” is a value determined by the Griffin method (Yoshida, Shindo, Ogaki, Yamanaka, edited by “New Edition Surfactant Handbook”, Kogyoshosho, 1991, p. 234) reference).

Although it does not specifically limit as an amphiphilic compound containing a perfluoroalkyl group, For example, a hydrophilic group has an anionic or nonionic compound.
Examples of the amphiphilic compound containing an anionic hydrophilic group and a perfluoroalkyl group include perfluoroalkyl carboxylates, perfluoroalkyl phosphates, and perfluoroalkyl sulfonates.

  Examples of amphiphilic compounds containing a nonionic hydrophilic group and a perfluoroalkyl group include perfluoroalkyl ethylene oxide adducts, perfluoroalkyl amine oxides, perfluoroalkyl polyoxyethylene ethanol, and perfluoroalkyl alkoxylates. it can.

  As specific examples, LE-604, LE-605, LIN-151-EPA (manufactured by Kyoeisha Chemical Co., Ltd.), MegaFac (registered trademark) F171, 172, 173, F444, F477 (manufactured by DIC), Fluorard (registered trademark) FC430, FC431 (manufactured by Sumitomo 3M), Asahi Guard AG (registered trademark) 710, Surflon (registered trademark) S-382, SC-101, 102, 103, 104, 105 (manufactured by Asahi Glass Co., Ltd.) .

  Although it does not specifically limit as an amphiphilic compound containing an organosiloxane structure, The thing which introduce | transduced the hydrophilic group into the terminal or molecular chain of organosiloxane is mentioned. Examples thereof include organosiloxanes modified with a hydrophilic group such as polyoxyethylene-modified organosiloxane, polyoxyethylene / polyoxypropylene-modified organosiloxane, polyoxyethylene sorbitan-modified organosiloxane, and polyoxyethylene glyceryl-modified organosiloxane.

  As specific examples, DBE-712, DBE-821 (manufactured by Amax Co.), KF-6011, KF-6012, KF-6013, KF-6014, KF-6015, KF-6016, KF-6100 (manufactured by Shin-Etsu Chemical Co., Ltd.) ), ABIL-EM97 (manufactured by Goldschmidt), polyflow KL-100, polyflow KL-401, polyflow KL-402, polyflow KL-700 (manufactured by Kyoeisha Chemical) and the like.

  As the porosifying agent in the present embodiment, the above-described bulking agent for paper having 1) a boiling point of 250 ° C. or higher under atmospheric pressure and 2) insoluble in water can also be used. For example, an alkylene oxide adduct of a higher alcohol (described in International Publication No. WO 98/03730), a polyhydric alcohol type nonionic surfactant in which the polyhydric alcohol is an oil, sugar alcohol, sugar or the like (Japanese Patent Laid-Open No. 11-200283) Described in Japanese Laid-Open Patent Publication No. 11-269799), fatty acid alkylene oxide adducts (described in Japanese Patent Laid-Open No. 11-200284), cationic compounds, amines, and acid salts of amines (Japanese Laid-Open Patent Publication Nos. 11-269799 and 2001-355197). Description), amphoteric compounds (described in JP-A-11-269799), polyhydric alcohol fatty acid esters (described in Japanese Patent No. 2971447, JP-A-11-350380), (A) organosiloxane, (B) glyceryl ether , (C) amide, (D) amine, (E) amine acid salt, (F) quaternary ammonium A salt, (G) imidazole, (H) an ester of a polyhydric alcohol and a fatty acid, and (I) an ester of a polyhydric alcohol and a fatty acid (Japanese Patent No. 3283248, JP-A-2003-105568, etc.), an aliphatic carboxylic acid, An amide compound obtained by reacting with a polyamine is crosslinked with urea, and then obtained by reacting an alkylating agent, or an alkylating agent is reacted with the amide compound, and then obtained by crosslinking with urea. Compounds (described in JP-A-2005-60891) and the like.

  The porosifying agent in this embodiment may be used alone or in combination of two or more. Furthermore, it may be emulsified and dispersed by a known general anionic surfactant, nonionic surfactant, cationic surfactant, amphoteric surfactant, polymer surfactant, reactive surfactant, and the like.

  The melting point of the porosifying agent in the present embodiment is not particularly limited, but if it is 50 ° C. or less, preferably 40 ° C. or less, more preferably 30 ° C. or less, and even more preferably 20 ° C. or less, mild addition is performed during slurry addition. Since it can be treated as a liquid at a high temperature, it is suitable for production. The melting point is a value measured by a melting point measurement method described in JIS K 0064-1992 “Method for measuring melting point and melting range of chemical product”.

  The porous sheet and the porous laminated sheet contain a porosifying agent, more specifically, a hydrocarbon group, a perfluoroalkyl group, and / or an organosiloxane structure. It can be confirmed by a direct analysis method using a spectroscopic method such as -IR or mass spectrometry such as pyrolysis GC-MS or TOF-SIMS. In addition, the porous sheet and the porous laminated sheet are washed with a solvent such as acetone, dimethylacetamide, dimethylformamide, etc., and the porous agent eluted in the washing solution is subjected to solution NMR, FT-IR, LC-MS, GC-MS, etc. Can also be analyzed.

  The fine cellulose fiber layer of the porous sheet and porous laminated sheet of this embodiment may contain a binder in addition to the fine cellulose fiber. Polyurethane is preferred because it is excellent in the effect as a binder.

  Polyurethane is a resin having a polyisocyanate compound as a main component and a compound having an active hydrogen such as a polyol compound (active hydrogen compound) as a curing agent.

  The polyisocyanate compound is not particularly limited as long as it contains at least two isocyanate groups. Examples of the basic skeleton of polyisocyanate include aromatic polyisocyanates, alicyclic polyisocyanates, aliphatic polyisocyanates, polyisocyanate derivatives, and the like. Among these, alicyclic polyisocyanates and aliphatic polyisocyanates are more preferable from the viewpoint of low yellowing.

  Examples of the raw material of the aromatic polyisocyanate include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate and a mixture thereof (TDI), diphenylmethane-4,4′-diisocyanate (MDI), and naphthalene-1,5. -Aromatic diisocyanates such as diisocyanate, 3,3-dimethyl-4,4-biphenylene diisocyanate, crude TDI, polymethylene polyphenyl diisocyanate, crude MDI, phenylene diisocyanate and xylylene diisocyanate.

  Examples of the raw material for the alicyclic polyisocyanate include alicyclic diisocyanates such as 1,3-cyclopentane diisocyanate, 1,3-cyclopentene diisocyanate, and cyclohexane diisocyanate.

  Examples of the aliphatic polyisocyanate include aliphatic diisocyanates such as trimethylene diisocyanate, 1,2-propylene diisocyanate, butylene diisocyanate, pentamethylene diisocyanate, and hexamethylene diisocyanate.

  As the polyisocyanate derivative, for example, in addition to the above polyisocyanate multimer (for example, dimer, trimer, pentamer, heptamer, etc.), polyisocyanate is one kind of active hydrogen-containing compound or The compound obtained by making it react with 2 or more types is mentioned. The compounds include allophanate-modified products (for example, allophanate-modified products produced from the reaction of polyisocyanates and alcohols), polyol-modified products (for example, polyol-modified products produced from the reaction of polyisocyanates and alcohols (addition of alcohols). Etc.), biuret-modified products (for example, biuret-modified products produced by reaction of polyisocyanate with water or amines), urea-modified products (eg, urea-modified products produced by reaction of polyisocyanate and diamine) Etc.), oxadiazine trione modified products (for example, oxadiazine trione produced by reaction of polyisocyanate and carbon dioxide gas), carbodiimide modified products (carbodiimide modified product produced by decarboxylation condensation reaction of polyisocyanate, etc.), Modified uretdione Uretonimine modified products and the like.

Although it does not specifically limit as an active hydrogen containing compound, For example, the polyester polyol, the 1-6 valent hydroxyl group containing compound containing a polyether polyol, an amino group containing compound, a thiol group containing compound, a carboxyl group containing compound etc. are mentioned. Further, water, carbon dioxide, etc. existing in the air or in the reaction field are also included.
Examples of the 1-6 valent alcohol (polyol) include a non-polymerized polyol and a polymerized polyol. The non-polymerized polyol is a polyol that does not undergo polymerization history, and the polymerized polyol is a polyol obtained by polymerizing monomers.

  Non-polymerized polyols include monoalcohols, diols, triols, tetraols and the like. Examples of monoalcohols include methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, s-butanol, n-pentanol, n-hexanol, n-octanol, n-nonanol, 2 -Ethylbutanol, 2,2-dimethylhexanol, 2-ethylhexanol, cyclohexanol, methylcyclohexanol, ethylcyclohexanol and the like. Examples of diols include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1, 3-butanediol, 1,4-butanediol, 2,3-butanediol, 2-methyl-1,2-propanediol, 1,5-pentanediol, 2-methyl-2,3-butanediol, 1, 6-hexanediol, 1,2-hexanediol, 2,5-hexanediol, 2-methyl-2,4-pentanediol, 2,3-dimethyl-2,3-butanediol, 2-ethyl-hexanediol, 1,2-octanediol, 1,2-decanediol, 2,2,4-to Methylpentanediol, 2-butyl-2-ethyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, phloroglucin, pyrogallol, catechol, hydroquinone, bisphenol A, bisphenol F, bisphenol S, etc. Can be mentioned. Examples of triols include glycerin and trimethylolpropane. Examples of tetraols include pentaerythritol, 1,3,6,8-tetrahydroxynaphthalene, 1,4,5,8-tetrahydroxyanthracene and the like.

  Although it does not specifically limit as a polymerization polyol, For example, polyester polyol, polyether polyol, acrylic polyol, polyolefin polyol etc. are mentioned.

  As the polyester polyol, for example, succinic acid, adipic acid, sebacic acid, dimer acid, maleic anhydride, phthalic anhydride, isophthalic acid, terephthalic acid or the like alone or a mixture thereof, ethylene glycol, propylene glycol, diethylene glycol, Polyester polyols obtained by condensation reaction of polyhydric alcohols such as neopentyl glycol, trimethylolpropane and glycerin alone or in mixtures, and polycaprolactones obtained by ring-opening polymerization of ε-caprolactone using polyhydric alcohols And the like.

  Examples of polyether polyols include hydroxides such as lithium, sodium and potassium, strong basic catalysts such as alcoholates and alkylamines, complex metal cyanide complexes such as metal porphyrins and hexacyanocobaltate zinc complexes, and the like. Polyether polyols obtained by random or block addition of alkylene oxides such as ethylene oxide, propylene oxide, butylene oxide, cyclohexene oxide, and styrene oxide, alone or in mixture, to polyvalent hydroxy compounds alone or in mixtures, and ethylenediamines And polyether polyols obtained by reacting an alkylene oxide with a polyamine compound such as the above. Examples include so-called polymer polyols obtained by polymerizing acrylamide or the like using these polyethers as a medium.

As the polyhydric alcohol compound,
1) For example, diglycerin, ditrimethylolpropane, pentaerythritol, dipentaerythritol, etc.
2) Sugar alcohol compounds such as erythritol, D-threitol, L-arabinitol, ribitol, xylitol, sorbitol, mannitol, galactitol, rhamnitol,
3) Monosaccharides such as arabinose, ribose, xylose, glucose, mannose, galactose, fructose, sorbose, rhamnose, fucose, ribodesource,
4) Disaccharides such as trehalose, sucrose, maltose, cellobiose, gentiobiose, lactose, melibiose,
5) Trisaccharides such as raffinose, gentianose, meletitose,
6) Tetrasaccharides such as stachyose,
Etc.

  Examples of the acrylic polyol include acrylic acid monoester or methacrylic acid such as acrylic acid ester having active hydrogen such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and 2-hydroxybutyl acrylate. Monoester, trimethylolpropane acrylic acid monoester or methacrylic acid monoester, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 3-hydroxypropyl methacrylate, A single component or a mixture selected from the group of methacrylic acid esters having active hydrogen such as 4-hydroxybutyl methacrylate is an essential component, methyl acrylate, ethyl acrylate, isopropyl acrylate, acrylic acid Acrylic acid esters such as n-butyl and 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, -n-butyl methacrylate, isobutyl methacrylate, n-hexyl methacrylate, lauryl methacrylate, etc. Methacrylic acid esters, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, itaconic acid, unsaturated amides such as acrylamide, N-methylol acrylamide, diacetone acrylamide, and glycidyl methacrylate, styrene, vinyl toluene, acetic acid Others such as vinyl monomers having hydrolyzable silyl groups such as vinyl, acrylonitrile, dibutyl fumarate, vinyltrimethoxysilane, vinylmethyldimethoxysilane, and γ-methacryloxypropylmethoxysilane And an acrylic polyol obtained by polymerization in the presence or absence of a single or a mixture selected from the group of polymerizable monomers.

  Examples of the polyolefin polyol include polybutadiene having two or more hydroxyl groups, hydrogenated polybutadiene, polyisoprene, and hydrogenated polyisoprene. Furthermore, isobutanol, n-butanol, 2-ethylhexanol and the like, which are monoalcohol compounds having 50 or less carbon atoms, can be used in combination.

  Examples of the amino group-containing compound include monohydrocarbylamines having 1 to 20 carbon atoms [alkylamine (butylamine and the like), benzylamine and aniline and the like], aliphatic polyamines having 2 to 20 carbon atoms (ethylenediamine, hexamethylenediamine and the like). Diethylenetriamine, etc.), C6-C20 alicyclic polyamines (diaminocyclohexane, dicyclohexylmethanediamine, isophoronediamine, etc.), C2-C20 aromatic polyamines (phenylenediamine, tolylenediamine, diphenylmethanediamine, etc.), carbon Heterocyclic polyamines of 2 to 20 (such as piperazine and N-aminoethylpiperazine), alkanolamines (such as monoethanolamine, diethanolamine and triethanolamine), dicarboxylic acid and excess poly Polyamide polyamine, polyether polyamine, hydrazine (such as hydrazine and monoalkyl hydrazine), dihydrazide (such as succinic acid dihydrazide and terephthalic acid dihydrazide), guanidine (such as butyl guanidine and 1-cyanoguanidine) and dicyandiamide obtained by condensation with amine Is mentioned.

  Examples of the thiol group-containing compound include monovalent thiol compounds having 1 to 20 carbon atoms (alkyl thiol such as ethyl thiol, phenyl thiol and benzyl thiol) and polyvalent thiol compounds (ethylene dithiol and 1,6-hexanedithiol). Etc.).

  Examples of the carboxyl group-containing compound include monovalent carboxylic acid compounds (alkyl carboxylic acids such as acetic acid, aromatic carboxylic acids such as benzoic acid) and polyvalent carboxylic acid compounds (alkyl dicarboxylic acids such as oxalic acid and malonic acid). And aromatic dicarboxylic acids such as terephthalic acid).

  In the porous sheet and the porous laminated sheet of the present embodiment, the polyurethane solid content weight ratio is preferably 0.5 wt% or more and 100 wt% or less, more preferably 1 with respect to 100 wt% of the fine cellulose fibers. % By weight to 70% by weight, more preferably 1% by weight to 50% by weight, and still more preferably 1% by weight to 30% by weight. Since the fine cellulose fiber has a large specific surface area, if the weight ratio is less than 0.5% by weight, it is not easy to cover the entire fiber surface with polyurethane, and the aqueous wet strength or non-aqueous wet strength tends to be low. On the other hand, if it is 100% by weight or less, it is possible to prevent the surroundings of the fine cellulose fibers from being excessively coated with polyurethane, and to maintain well the properties inherent to cellulose such as high heat resistance and decorating properties.

In the porous sheet and porous laminated sheet of the present embodiment, it is preferable that the fine cellulose fibers and polyurethane in the sheet are chemically bonded. The chemical bond includes a covalent bond, a coordination bond, an ionic bond, a hydrogen bond, and the like, and is not particularly limited, but a covalent bond is preferable. For example, a urethane bond by reaction with a large number of hydroxyl groups present on the surface of fine cellulose fibers, an amidourea bond by reaction with a small amount of carboxyl groups, and the like can be mentioned. Further, the chemically modified cellulose fiber can also form a covalent bond if a functional group having active hydrogen is present on the fiber surface. Examples of the functional group having active hydrogen include a hydroxyl group, an amino group, a thiol group, and a carboxyl group. The chemical bond is formed in three dimensions with respect to the fine cellulose fiber, so that the dry strength, aqueous wet strength and non-aqueous wet strength of the sheet are improved.
The formation of chemical bonds can be directly confirmed by spectroscopy such as solid state NMR, FT-IR, and X-ray photoelectron spectroscopy, and mass spectrometry such as TOF-SIMS. In addition, the porous sheet is washed with a solvent such as acetone, dimethylacetamide, dimethylformamide, etc., and it can be indirectly assumed that a chemical bond is formed because polyurethane does not elute in the washing solution. . As an analysis method by elution of polyurethane, a combustion ion chromatography method, solution NMR, ICP, liquid chromatography, gas chromatography, mass spectrometry, FT-IR, CHN analysis or the like may be selected.

  When the porous sheet and the porous laminated sheet of the present embodiment contain polyurethane, the distribution state of the polyurethane is not particularly limited, but the polyurethane is uniformly distributed in the porous sheet or the fine cellulose fiber layer of the porous laminated sheet. It is preferable. Since the polyurethane is uniformly distributed, the water-based wet strength and non-water-based wet strength of the sheet become uniform, so that the number of sheet breaks can be reduced when continuously producing composite films by resin impregnation. In the porous sheet and the fine cellulose fiber layer, the uniform distribution of polyurethane means that the polyurethane is uniformly distributed in both the plane direction and the thickness direction in the sheet.

  Specifically, the uniformity of the polyurethane distribution in the sheet plane direction is the ratio of the polyurethane amount (P1) and the cellulose amount (C1) at an arbitrary point of the fine cellulose fiber layer of the porous sheet and the porous laminated sheet. This means that (P1 / C1) is constant. Here, “constant” means that the variation of P1 / C1 at an arbitrary four places on a 20 cm × 20 cm sheet is a variation coefficient of 50% or less.

  The uniformity of the polyurethane distribution in the sheet thickness direction is the ratio of the amount of polyurethane in the upper, middle and lower parts and the amount of cellulose when the fine cellulose fiber layers of the porous sheet and porous laminated sheet are equally divided into three in the thickness direction. Are the same. Here, the same means that when calculating the average of P1 / C1 at the upper part, the average of P1 / C1 at the middle part, and the average of P1 / C1 at the lower part at any four locations in a 20 cm × 20 cm sheet, these 3 The variation between two average values is a coefficient of variation of 50% or less.

In the polyurethane distribution in the sheet plane direction and the sheet thickness direction, the coefficient of variation is preferably 50% or less. When the coefficient of variation exceeds 50%, the water-based wet strength and the non-aqueous wet strength tend to be lower than those of a sheet uniformly containing the same amount of polyurethane. The coefficient of variation is a value representing relative variation and can be calculated from the following equation (13).
Coefficient of variation (CV) = (standard deviation / arithmetic mean) × 100 (13)

  The ratio of the amount of polyurethane and the amount of cellulose can be determined from, for example, three-dimensional composition analysis by TOF-SIMS with sputter etching described in International Publication No. WO2015 / 008868.

  The polyurethane in the porous sheet and porous laminated sheet of the present embodiment may use block polyisocyanate as a raw material. The block polyisocyanate is (1) based on a polyisocyanate compound such as polyisocyanate and polyisocyanate derivatives, (2) an isocyanate group is blocked by a blocking agent, and (3) a functional group having active hydrogen at room temperature. (4) A heat treatment at a temperature equal to or higher than the dissociation temperature removes the blocking group and regenerates an active isocyanate group, which reacts with a functional group having active hydrogen to form a bond.

  A normal isocyanate compound having no blocking group reacts easily with water and cannot be added to the papermaking slurry. However, since the block polyisocyanate does not react with water in the papermaking slurry, it can be added to the papermaking slurry. Furthermore, the reaction of the isocyanate compound with water in the wet paper can be prevented by drying the wet paper below the dissociation temperature of the blocking agent. And the block polyisocyanate has active hydrogen present on the surface of the base sheet of the fine cellulose fiber and the porous laminated sheet together with its own curing by heat-treating the finally dried sheet above the dissociation temperature of the blocking agent. It effectively forms a covalent bond with a functional group (hydroxyl group, amino group, carboxyl group, thiol group, etc.).

  A blocking agent adds and blocks to the isocyanate group of a polyisocyanate compound. This blocking group is stable at normal temperature, but when heated to a heat treatment temperature (usually about 100 to about 250 ° C.), the blocking agent can be eliminated to regenerate the free isocyanate group.

The following can be illustrated as a blocking agent satisfying such requirements.
(1) Alcohols such as methanol, ethanol, 2-propanol, n-butanol, sec-butanol, 2-ethyl-1-hexanol, 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol,
(2) Alkylphenol type: mono- and dialkylphenols having an alkyl group having 4 or more carbon atoms as a substituent, such as n-propylphenol, isopropylphenol, n-butylphenol, sec-butylphenol, t-butylphenol, n -Monoalkylphenols such as hexylphenol, 2-ethylhexylphenol, n-octylphenol, n-nonylphenol, di-n-propylphenol, diisopropylphenol, isopropylcresol, di-n-butylphenol, di-t-butylphenol, di-sec -Dialkylphenols such as butylphenol, di-n-octylphenol, di-2-ethylhexylphenol, di-n-nonylphenol,
(3) Phenol: phenol, cresol, ethylphenol, styrenated phenol, hydroxybenzoate, etc.
(4) Active methylene series: dimethyl malonate, diethyl malonate, methyl acetoacetate, ethyl acetoacetate, acetylacetone, etc.
(5) Mercaptans: butyl mercaptan, dodecyl mercaptan, etc.
(6) Acid amide system: acetanilide, acetic acid amide, ε-caprolactam, δ-valerolactam, γ-butyrolactam, etc.
(7) Acid imide type: succinimide, maleic imide, etc.
(8) Imidazole: imidazole, 2-methylimidazole, 3,5-dimethylpyrazole, 3-methylpyrazole, etc.
(9) Urea system: urea, thiourea, ethylene urea, etc.
(10) Oxime series: formaldoxime, acetaldoxime, acetoxime, methyl ethyl ketoxime, cyclohexanone oxime, etc.
(11) Amine series: diphenylamine, aniline, carbazole, di-n-propylamine, diisopropylamine, isopropylethylamine, etc.
These blocking agents can be used alone or in combination of two or more.

  Since the block polyisocyanate of this embodiment is uniformly mixed and used in the fine cellulose fiber slurry, the block polyisocyanate itself is a stable form as an aqueous dispersion, and is stable when mixed with fine cellulose fibers and the like. Preferably it is. The block polyisocyanate aqueous dispersion is a compound (forced emulsification type) that is forcibly emulsified with a surfactant or the like, even if it is a compound (self-emulsification type) in which a hydrophilic compound is directly bonded to the block polyisocyanate and emulsified. May be. Each of the emulsions obtained by each method has an anionic, nonionic, or cationic hydrophilic group exposed on the surface.

  The self-emulsifying block polyisocyanate is obtained by binding an active hydrogen group-containing compound having an anionic group, a nonionic group or a cationic group to a block 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. More specifically, examples of the active hydrogen group-containing compound having a carboxyl group include dihydroxyl carboxylic acids such as 2,2-dimethylolacetic acid and 2,2-dimethylollactic acid, such as 1-carboxy-1,5-pentyl. Examples thereof include diaminocarboxylic acids such as range amine and dihydroxybenzoic acid, and half ester compounds of polyoxypropylene triol with maleic anhydride and / or phthalic anhydride.

Examples of the active hydrogen group-containing compound having a sulfonic acid group include N, N-bis (2-hydroxyethyl) -2-aminoethanesulfonic acid, 1,3-phenylenediamine-4,6-disulfonic acid, and the like. Can be mentioned.
Examples of the active hydrogen group-containing compound having a phosphate group include 2,3-dihydroxypropylphenyl phosphate.
Examples of the active hydrogen group-containing compound having a betaine structure-containing group include a sulfobetaine group-containing compound obtained by a reaction between a tertiary amine such as N-methyldiethanolamine and 1,3-propane sultone. .
These active hydrogen group-containing compounds having an anionic group may be modified as an alkylene oxide by adding an alkylene oxide such as ethylene oxide or propylene oxide.
Moreover, the active hydrogen group containing compound which has these anionic groups can be used individually or in combination of 2 or more types.

Although it does not restrict | limit especially as an active hydrogen group containing compound which has a nonionic group, For example, the polyalkylene ether polyol etc. which contain the normal alkoxy group as a nonionic group are used. Ordinary nonionic group-containing polyester polyols and polycarbonate polyols are also used.
As the polymer polyol, those having a number average molecular weight of 500 to 10,000, particularly 500 to 5,000 are preferably 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, such as N , N-dimethylethanolamine, N-methyldiethanolamine, N, N-dimethylethylenediamine and the like. Further, N, N, N-trimethylolamine and N, N, N-triethanolamine having a tertiary amine can also be used. Of these, polyhydroxy compounds having a tertiary amino group and containing two or more active hydrogens reactive with isocyanate groups are preferred.
These active hydrogen group-containing compounds having a cationic group may be modified as an alkylene oxide by adding an alkylene oxide such as ethylene oxide or propylene oxide. Moreover, the active hydrogen group containing compound which has these cationic groups can be used individually or in combination of 2 or more types.

  The cationic group can be easily dispersed in water in the form of a salt by neutralizing 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. Examples of the compound having a carboxyl group include formic acid, acetic acid, propionic acid, butyric acid, and lactic acid. Examples of the compound having a sulfone group include ethanesulfonic acid and the like. An acid, an acidic adjacent acid ester, etc. are mentioned. A compound having a carboxyl group is preferred, and acetic acid, propionic acid, and butyric acid are more preferred. In the case of neutralization, the equivalent ratio of cationic group: anionic group introduced into the blocked polyisocyanate is 1: 0.5 to 1: 3, preferably 1: 1 to 1: 1.5. The introduced tertiary amino group can be quaternized with dimethyl sulfate, diethyl sulfate or the like.

  In this embodiment, the ratio of reacting the block polyisocyanate with the active hydrogen group-containing compound for the purpose of introducing the hydrophilic group is preferably an isocyanate group / active hydrogen group equivalent ratio of 1.05 to 1,000, more preferably. Is in the range of 2 to 200, more preferably 4 to 100. When the equivalent ratio is 1.05 or more, the isocyanate group content in the hydrophilic polyisocyanate is not too low, so that the curing rate of the block polyisocyanate is good and the cured product is less likely to be weakened. The cross-linking points with the fine cellulose fibers are not reduced too much, and the aqueous wet strength and non-aqueous wet strength of the porous sheet and porous laminated sheet are good. When the equivalent ratio is 1000 or less, the effect of lowering the interfacial tension is great, and hydrophilicity is favorably expressed. In addition, as a method of reacting a polyisocyanate compound having two or more isocyanate groups in one molecule and an active hydrogen group-containing compound in this embodiment, a method in which both are mixed and a normal urethanization reaction is performed is exemplified. it can.

  Forced emulsification type block polyisocyanate is a block polysiloxane with known general anionic surfactants, nonionic surfactants, cationic surfactants, amphoteric surfactants, polymeric surfactants, reactive surfactants, etc. A compound in which isocyanate is emulsified and dispersed. Among these, anionic surfactants, nonionic surfactants and cationic surfactants are preferable because they are low in cost and can provide good emulsification.

Examples of the anionic surfactant include alkyl carboxylate compounds, alkyl sulfate compounds, and alkyl phosphates.
Nonionic surfactants include ethylene oxide and / or propylene oxide adducts of alcohols having 1 to 18 carbon atoms, ethylene oxide and / or propylene oxide adducts of alkylphenols, ethylene oxide and / or propylene oxide of alkylene glycols and / or alkylene diamines. Examples include adducts.

  Examples of the cationic surfactant include quaternary ammonium salts such as primary to tertiary amines, pyridinium salts, alkylpyridinium salts, and alkyl quaternary ammonium salts.

  When using these emulsifiers, the amount used is not particularly limited, and any amount can be used. However, when the mass ratio of the block polyisocyanate is 1, it is 0.01 or more. In the case where good dispersibility is obtained and it is 0.3 or less, the physical properties such as water resistance and functional agent fixing property can be maintained well, so 0.01 to 0.3 is preferable, 0.05 to 0 .2 is more preferred.

  The block polyisocyanate aqueous dispersion may contain up to 20% by weight of a solvent other than water in both the self-emulsifying type and the forced emulsifying type. The solvent in this case 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. From the viewpoint of dispersibility in water, the solvent preferably has a solubility in water at 23 ° C. of 5% by weight or more, and specifically, dipropylene glycol dimethyl ether and dipropylene glycol monomethyl ether are preferable.

  The average dispersed particle size of the block polyisocyanate aqueous dispersion is preferably 1 to 1000 nm, more preferably 10 to 500 nm, and still more preferably 10 to 200 nm.

  The surface of the block polyisocyanate aqueous dispersion may be anionic, nonionic, or cationic, but more preferably is cationic. The reason for this is that in the stage of producing the papermaking slurry, the block polyisocyanate aqueous dispersion (solid content concentration 0.0001-0.0.0%) in dilute fine cellulose fiber slurry (solid concentration 0.01-0.5 wt%). This is because it is effective to use electrostatic interaction for effectively adsorbing 5 wt%) to fine cellulose fibers. It is known that the surface of a general cellulose fiber is anionic (zeta potential −30 to −20 mV in distilled water) (Non-Patent Document 1 J. Brandrup (editor) and EH Immergut (editor) “Polymer”. Handbook 3rd edition "see V-153 to V-155). Therefore, the surface of the block polyisocyanate aqueous dispersion is more preferably cationic. However, even if it is nonionic, it can be sufficiently adsorbed on fine cellulose fibers depending on the polymer chain length and rigidity of the hydrophilic group of the emulsion. Furthermore, even if adsorption is more difficult due to electrostatic repulsion such as anionic property, it can be adsorbed on fine cellulose fibers by using a generally known cationic adsorption aid. Cationic adsorption aids include polymers having primary amino groups, secondary amino groups, tertiary amino groups, quaternary ammonium bases, pyridinium, imidazolium, and quaternized pyrrolidone, specifically Examples include water-soluble cationic polymers such as cationized starch, cationic polyacrylamide, polyvinylamine, polydiallyldimethylammonium chloride, polyamidoamine epichlorohydrin, polyethyleneimine, and chitosan.

  When the fine cellulose fiber layer of the porous sheet and porous laminated sheet of the present embodiment contains polyurethane, the aqueous wet strength and non-aqueous wet strength are enhanced, and the use of the sheet in water and in an organic solvent becomes easier. . Furthermore, when the porosifying agent and polyurethane are used in combination in the present embodiment, the porosity is satisfactorily maintained even when a wet drying operation is performed. When polyurethane is used alone, water-based wet strength and non-water-based wet strength are strengthened, but there is a tendency that it is difficult to maintain the porosity in the wet-drying operation. It becomes easy.

  The fine cellulose fiber layers of the porous sheet and the porous laminated sheet of the present embodiment may each include one or more filler materials selected from the group consisting of inorganic particles, polymer particles, inorganic fibers, and polymer fibers. good.

  Although it does not specifically limit as an inorganic particle, For example, chemically stable metal particles, such as gold | metal | money, silver, copper, iron, zinc, tin, nickel, titanium, various alloys (for example, stainless steel), alumina, titanium oxide, zinc oxide, Metal oxide particles such as iron oxide, tin oxide, copper oxide, silver oxide and zirconium oxide, composite metal oxide particles such as barium titanate, metal nitride particles such as aluminum nitride, fumed silica, colloidal silica, zeolite, Examples thereof include silica-based particles such as mica and smectite, and carbon-based particles such as activated carbon, graphite, and carbon nanotube.

  The polymer particles are not particularly limited. For example, in addition to various latexes such as styrene-butadiene (SB) latex, acrylic latex, various rubber latexes, polyvinylidene chloride latex, urethane latex, polyolefin-based particles. Examples thereof include particles, polymethyl methacrylate particles, polyamide particles, polyester particles, wholly aromatic polyamide particles, polyimide particles, polycarbonate particles, cellulose particles such as crystalline cellulose, and polyacetal particles.

  Examples of inorganic fibers include, but are not limited to, for example, fibers that do not dissolve in the dispersion medium described later, and include carbon-based fibers such as carbon nanotubes obtained by firing and carbonizing glass fibers, metal fibers, and polymer fibers. it can.

  The polymer fiber is not particularly limited, but various synthetic fibers (polyester, nylon, polyacrylonitrile, cellulose acetate, polyurethane, polyethylene, polypropylene, polyketone, wholly aromatic polyamide, polyimide, etc.), natural fibers (cotton, silk, wool, etc.) ), Or fine fibers that have been highly fibrillated by beating regenerated cellulose fibers or by refining with a high-pressure homogenizer, etc., fine fibers obtained by electrospinning using various polymers as raw materials, and melt blown methods using various polymers as raw materials Although the fine fiber etc. which are obtained can be mentioned, it is not limited to these. Among these, a microfibrous aramid obtained by refining an aramid fiber, which is a wholly aromatic polyamide, with a high-pressure homogenizer, Tiara (registered trademark) (manufactured by Daicel Chemical Industries) has an average fiber diameter of 0.2 to 0.00. The fiber length is 3 μm and the average fiber length is 500 to 600 μm, and it can be suitably used as a fibrous filler due to the high heat resistance and high chemical stability of aramid fibers.

  The filler material contained in the porous sheet of the present embodiment is preferably 1% by weight to 50% by weight, more preferably 1% by weight to 30% by weight, and more preferably 1% by weight to 10% by weight of the weight of the porous sheet. Is more preferable.

  The filler material contained in the porous laminated sheet of the present embodiment is preferably 0.1% by weight or more and 50% by weight or less, more preferably 0.1% by weight or more and 30% by weight or less of the weight of the porous laminated sheet. 1% by weight or more and 10% by weight or less is more preferable.

  The filler material contained in the fine cellulose fiber layer in the porous laminated sheet is preferably 1% by volume or more and 100% by volume or less, and preferably 1% by volume or more and 50% by volume or less with respect to 100% by volume of the fine cellulose fiber. More preferably, it is more preferably 1 volume% or more and 20 volume% or less.

The fine cellulose fiber and the filler material can be distinguished from each other by contrast due to the difference in electron density in the cross-sectional SEM observation. Specifically, using this, a sample for cross-sectional SEM observation of the porous laminated sheet is prepared, and SEM observation of the fine cellulose fiber layer is performed for 3 fields at a magnification of 5000 times. By image analysis of the obtained cross-sectional SEM image, the respective areas (A1, A2, μm ² ) of the fine cellulose fibers and the filler material are obtained, and the volume ratio of the filler material to the fine cellulose fibers is calculated from the following formula (14). The average of 3 fields of view is adopted.
Volume ratio (%) of filler material to fine cellulose fiber = A2 / A1 × 100 (14)

  The porous sheet and porous laminated sheet of this embodiment are a filler, a paper strength enhancer, a sizing agent, a yield improver, a drainage improver, a sulfuric acid band, a wet paper strength enhancer, a coloring dye, a coloring pigment, and a fluorescent enhancement. Known papermaking materials such as whitening agents, fluorescent decoloring agents, pitch control agents, and the like can be appropriately used as long as the intended effects of the present embodiment are not impaired.

  As a manufacturing method of the porous sheet and porous laminated sheet of this embodiment, a papermaking method and a coating method are preferable. The papermaking method typically includes (1) a process for producing fine cellulose fibers by refining cellulose fibers, (2) a process for preparing a papermaking slurry containing the fine cellulose fibers, and (3) filtering (ie, dehydrating) the papermaking slurry. ) To form a wet paper, and (4) a drying step of drying the wet paper to obtain a dry sheet. The coating method typically includes a step of preparing a coating slurry by the same steps as in the above (1) and (2), and (3) a coating film obtained by coating the coating slurry on a support. And (4) a drying step of drying the coated film. The coating method is also useful for producing the porous laminated sheet of the present embodiment. In this case, a base sheet may be used as the support. Below, the preparation method of the papermaking slurry or coating slurry containing the fine cellulose fiber of this embodiment, and the formation method of the porous sheet and porous laminated sheet by a papermaking method are demonstrated.

The present embodiment is a method for producing a porous sheet according to the present disclosure, a preparation step for preparing a slurry containing a porosifying agent, fine cellulose fibers, and water, and by dehydrating the slurry by a papermaking method. There is provided a method comprising a film forming step for forming a wet paper and a porous sheet forming step for obtaining a porous sheet by at least drying the wet paper.
The present embodiment is also a method for producing a porous laminated sheet of the present disclosure, a preparation step for preparing a slurry containing a porosifying agent, fine cellulose fibers, and water. And a porous laminated sheet forming step of obtaining a porous laminated sheet by at least drying the multilayer wet paper. .

  The fine cellulose fibers constituting the porous sheet and the porous laminated sheet of the present embodiment are 1) fine cellulose fibers produced by bacteria, 2) fine cellulose fibers of regenerated cellulose or cellulose derivatives obtained by electrospinning. 3) Microfibrillated cellulose obtained by refining natural cellulose fiber, regenerated cellulose fiber or cellulose derivative fiber, which is a bundle of cellulose microfibrils, can be used. From the viewpoint of cost and quality control, microfibrillated cellulose is preferred.

  Examples of the raw material for microfibrillated cellulose include animal-derived cellulose fibers (eg, squirt cellulose), higher plant-derived cellulose fibers, regenerated cellulose fibers, and chemically synthesized cellulose derivative fibers.

  Examples of cellulose fibers derived from higher plants include, for example, wood fibers (wood pulp such as conifers and hardwoods), bamboo fibers, sugarcane fibers, seed hair fibers (cotton linters, Bombax cotton, kapok, etc.), gin leather fibers (for example, Hemp, kenaf, kouzo, mitsumata, etc.), leaf fibers (eg, Manila hemp, New Zealand hemp, abaca hemp, etc.). These raw materials are provided as refined pulp through a refining process such as delignification by digestion and a bleaching process, and the amount of residual lignin and hemicellulose in the pulp can be changed according to the purpose.

  Examples of the regenerated cellulose fiber include rayon, cupra, lyocell, and tencel.

Examples of cellulose derivative fibers include organic acid esters such as cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, and cellulose acetate butyrate; inorganic acid esters such as cellulose nitrate, cellulose sulfate, and cellulose phosphate; Examples thereof include mixed acid esters such as cellulose nitrate acetate; hydroxyalkyl celluloses such as hydroxyethyl cellulose and hydroxypropyl cellulose; carboxyalkyl celluloses such as carboxymethyl cellulose and carboxyethyl cellulose; alkyl celluloses such as methyl cellulose and ethyl cellulose.
These fibers can be used alone or in combination of two or more.

  The microfibrillated cellulose of this embodiment preferably undergoes a cellulose fiber raw material pretreatment step, a beating treatment step, and a refinement step. In the pretreatment step, the object is to make the cellulose fiber raw material easy to be refined by autoclave treatment under water impregnation at a temperature of 100 to 150 ° C., chemical treatment, enzyme treatment, etc., or a combination thereof. To do.

  Chemical treatment is a technique for introducing an anionic group or a cationic group into microfibrils. Due to the presence of these functional groups, electrostatic repulsion and osmotic pressure effects are manifested, and fine cellulose fibers can be obtained with less energy without using a refining device that requires high energy such as a high-pressure homogenizer.

Examples of the anionizing agent include a carboxylic acid having a plurality of carboxyl groups or an anhydride thereof, or a salt thereof, an oxo acid containing a phosphorus atom or a salt thereof, ozone, 2,2,6,6-tetramethylpiperidinooxy A radical etc. are mentioned.
Examples of the cationizing agent include glycidyltrialkylammonium halides or halohydrin type compounds thereof.

  The enzyme treatment is a treatment for mainly decomposing cellulose in the amorphous part by cellulase or the like.

  These pretreatments not only reduce the load of the micronization process, but also discharge impurity components such as lignin and hemicellulose present on the surface and gaps of the microfibrils that make up the cellulose fibers to the aqueous phase, resulting in a finer process. Since there is also an effect of increasing the α-cellulose purity of the formed fiber, it is effective for improving the heat resistance of the porous sheet and the porous laminated sheet.

  In the beating treatment step, the raw material pulp is preferably 0.5 wt% or more and 4 wt% or less, more preferably 0.8 wt% or more and 3 wt% or less, further preferably 1.0 wt% or more and 2.5 wt%. Disperse in water to the following solid content concentration, and highly promote fibrillation with a beating device such as a beater or 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 processing is performed, extremely advanced beating (fibrillation) proceeds, so a high-pressure homogenizer or the like is used. The conditions for the miniaturization treatment can be relaxed and may be effective.

  In the production of the fine cellulose fiber, it is preferable to carry out a refining treatment with a high-pressure homogenizer, an ultra-high pressure homogenizer, a grinder or the like following the above-described beating step. In this case, the solid content concentration in the aqueous dispersion is preferably 0.5% by weight or more and 4% by weight or less, more preferably 0.8% by weight or more and 3% by weight or less, more preferably, in accordance with the beating treatment described above. 1.0 wt% or more and 2.5 wt% or less. In the case of a solid content concentration in this range, clogging does not occur and an efficient miniaturization process can be achieved.

  Examples of the high-pressure homogenizer used include NS type high-pressure homogenizer manufactured by Niro Soabi (Italy), SMT Co., Ltd., Lanier type (R model) pressure-type homogenizer, and Sanwa Kikai Co., Ltd. high-pressure type homogenizer. be able to. Examples of the ultra-high pressure homogenizer include a high-pressure collision type miniaturization machine such as a microfluidizer from Mizuho Kogyo Co., Ltd., a nanomizer from Yoshida Kikai Kogyo Co., Ltd., and an optimizer from Sugino Machine Co., Ltd. Examples of the grinder type miniaturization device include a pure fine mill manufactured by Kurita Machinery Co., Ltd. and a stone mill type milled type represented by a super mass colloid manufactured by Masuko Sangyo Co., Ltd. It should be noted that devices other than these devices may be used as long as they are miniaturized by a substantially similar mechanism.

The fiber diameter of the fine cellulose fiber is determined according to the conditions for refinement using a high-pressure homogenizer (selection of equipment and operating pressure and number of passes) or pre-treatment conditions (for example, autoclave treatment, chemical treatment, enzyme treatment). , Beating process, etc.).
In the present embodiment, two or more kinds of fine cellulose fibers having different raw materials, fine cellulose fibers having different degrees of fineness, and chemically treated surfaces may be mixed and used at an arbitrary ratio. .

  In the papermaking slurry preparation step of the present embodiment, the fine cellulose fibers contained in the slurry are preferably 0.01 wt% or more and 0.5 wt% or less of the papermaking slurry weight, and 0.01 wt% or more and 0.35 wt% or less. More preferred. When the content is 0.01% by weight or more, the drainage time does not become too long, the productivity is good, and at the same time, the film quality uniformity is good, which is preferable. On the other hand, when the content is 0.5% by weight or less, the viscosity of the dispersion liquid does not increase excessively, and it is easy and uniform to form a film.

  In the coating slurry adjusting step, the composition of water is preferably 80% by weight or more and 99.8% by weight or less, more preferably 85% by weight or more and 99.5% by weight or less, and 90% by weight or more and 99% by weight or less. Further preferred.

  In the papermaking slurry adjusting step, the porous agent to be added is preferably 0.0001% by weight or more and 0.5% by weight or less, more preferably 0.0001% by weight or more and 0.3% by weight or less of the slurry weight. In the case of 0.0001% by weight or more, although the porosifying agent can have a good solubility in general depending on the kind thereof, the effect of making it porous is great. When the amount is 0.5% by weight or less, the slurry viscosity does not increase excessively, the generation of bubbles by stirring is suppressed, and uniform film formation becomes easy.

  In the coating slurry preparation step, the amount of the porosifying agent to be added is preferably 0.001% to 0.5% by weight of the slurry weight, more preferably 0.001% to 0.3% by weight. preferable.

  Examples of the mixing device for uniformly dispersing the porosifying agent in the slurry include an agitator, a homomixer, a pipeline mixer, a disperser of a type that rotates blades having a cutting function such as a blender, and a high-pressure homogenizer. It is done. The stirrer is not particularly limited as long as the fine cellulose fibers and the porous agent are uniformly dispersed without generating bubbles. In particular, when the porosifying agent is self-emulsified in water or already emulsified, a low-shear stirring device such as an agitator may be used. On the other hand, when the porosifying agent is phase-separated in water and not emulsified, a strong shearing mixing method such as a homomixer or a high-pressure homogenizer is more preferable.

A water-dispersible block polyisocyanate may be added to the papermaking slurry or coating slurry for the purpose of improving the aqueous wet strength and non-aqueous wet strength of the sheet. Furthermore, in addition to the porosifying agent and the blocked polyisocyanate, the known papermaking material can be appropriately used within a range not impairing the intended effect of the present embodiment, and 0.0001 weight in the papermaking slurry. % Or more and 0.5% by weight or less.
In addition, the order of addition of other additives such as a porosifying agent and block polyisocyanate is not particularly limited as long as the intended effect of the present embodiment is not impaired.

In the papermaking process of this embodiment, wet paper is formed by filtering papermaking slurry on a water-based substrate.
In this papermaking process, any apparatus may be used as long as the operation uses a filter or filter cloth (also called a wire in the technical field of papermaking) that dehydrates water from the papermaking slurry and retains fine cellulose fibers. .
As the paper machine, if a device such as an inclined wire type paper machine, a long net type paper machine, or a circular net type paper machine is used, a porous sheet with few defects can be suitably obtained. Whether the paper machine is a continuous type or a batch type, it may be properly used according to the purpose.

  In the coating process of this embodiment, spray coater, air doctor coater, blade coater, knife coater, rod coater, squeeze coater, impregnation coater, gravure coater, kiss roll coater, die coater, reverse roll coater, transfer roll coater, etc. The prepared coating slurry may be applied to a water-based substrate or a nonporous film. In the case of using a water-permeable substrate, dehydration and subsequent drying described later are performed, and in the case of a nonporous film, direct heat drying is performed.

  Since the papermaking process is a process of filtering soft aggregates such as fine cellulose fibers dispersed in the papermaking slurry using a wire or a filter cloth, the size of the wire or the filter cloth is important. In this embodiment, the yield ratio of the water-insoluble component containing fine cellulose fibers and the like contained in the papermaking slurry is, for example, 70% by weight or more, preferably 80% by weight or more, more preferably 90% by weight, More preferably, any wire or filter cloth that can make paper at 95% by weight or more, particularly preferably 99% by weight can be used.

However, even if the yield ratio of fine cellulose fibers and the like is 70% by weight or more, if the drainage is not high, it takes time to make paper and the production efficiency is remarkably deteriorated. When the water permeation amount is preferably 0.005 ml / (cm ² · sec) or more, more preferably 0.01 ml / (cm ² · sec) or more, it is possible to make a suitable paper from the viewpoint of productivity. . When the yield ratio of the water-insoluble component is 70% by weight or more, the productivity is good, and a phenomenon in which water-insoluble components such as fine cellulose fibers are clogged in the wire or filter cloth used, or the porosity after film formation The deterioration of the peelability of the quality sheet can be avoided.

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

  As an example of the wire or filter cloth of this embodiment, mention may be made of TETEXMONODW07-8435-SK010 (PET) manufactured by SEFAR (Switzerland), NT20 (PET / nylon blend), TT30 (PET) manufactured by Shikishima Canvas. However, it is not limited to these.

  In the dehydration by the papermaking process of this embodiment, high solid differentiation proceeds, and a wet paper having a concentrated composition higher than the fine cellulose fiber concentration of the papermaking slurry is obtained. The solid content ratio of the wet paper is controlled by the degree of dehydration by the suction pressure (wet suction or dry suction) of the papermaking or the pressing step, preferably the solid content concentration is 6 wt% or more and 25 wt% or less, more preferably the solid content. The concentration is adjusted in the range of 8 wt% to 20 wt%. When the solid content of the wet paper is 6% by weight or more, the self-supporting property of the wet paper is good, and problems in the process hardly occur. In addition, when dewatering to a concentration at which the solid content of the wet paper is 25% by weight or less, remarkable penetration of fine cellulose fibers into the wire or filter cloth does not occur, and irregularities are transferred to the sheet, or the wire or filter cloth. It is possible to avoid problems such as clogging.

In the production of the porous laminated sheet of the present embodiment, paper making is performed by placing a nonwoven fabric such as cellulose, nylon, polyester, polypropylene, etc. as a support on a wire or filter cloth as a base material. By this method, a porous laminated sheet composed of a multilayer structure having at least two layers can be produced. In order to produce a multilayer sheet having three or more layers, a base sheet having a multilayer structure having two or more layers may be used. Moreover, it is good also as a laminated sheet of 3 or more layers by performing the multistage papermaking of the fine cellulose fiber layer of this embodiment of 2 or more layers on a base material sheet.
The base sheet preferably has an air permeability resistance of 100 sec / 100 ml or less and a thickness of 1 μm or more and 1000 μm or less. The method for measuring the air resistance is in accordance with the method for measuring the air resistance in the porous sheet. Thickness is measured at 23 ° C and 50% RH in a porous laminate sheet (20cm x 20cm) left standing for one day, using a table-top offline contact film thickness meter (eg, TOF-5R01 manufactured by Yamabun Denki). The length of 150 mm is measured once at a pitch of 0.1 mm, and the number average value is defined as the film thickness (μm).

The substrate sheet surface of the present embodiment is preferably hydrophilic. It is preferable that the surface of the base sheet is hydrophilic because the porous laminated sheet is excellent in adhesiveness and the drainage when producing the porous laminated sheet by a papermaking method is improved. No particular limitation is imposed on the hydrophilic functional group, a hydroxyl group, a thiol group, a carboxyl group, a sulfonic acid group, sulfuric ester group, phosphoric acid group, or a sulfate _{group, -OM, -COOM, -SO 3 M} , -OSO 3 M , —HMPO ₄ or —M ₂ PO ₄ (M represents an alkali metal or alkaline earth metal), a primary to tertiary amine, and a quaternary ammonium salt.

  In addition, a functional group having active hydrogen may be introduced on the surface of the base sheet. It is preferable that the functional group on the surface of the base sheet is a functional group having active hydrogen because a chemical bond by polyurethane can be formed and the base sheet and the porous sheet are firmly bonded via the polyurethane. The functional group having active hydrogen here refers to, for example, a hydroxyl group, an amino group, a thiol group, a carboxyl group, and the like. In the case of a hydroxyl group, a urethane bond is formed, and in the case of a carboxyl group, an amidourea bond is formed.

  As a base sheet having a hydrophilic surface or having an active hydrogen group, a base sheet having the original properties such as cellulose or nylon can be selected, or corona discharge treatment or plasma before paper making. It is also possible to use a base sheet obtained by performing the treatment to form a hydrophilic surface on the sheet surface or to form a functional group having active hydrogen.

  In the drying process of this embodiment, a porous sheet or a porous laminated sheet can be obtained by evaporating water by heating the wet paper obtained in the paper making process (film forming process) described above. The drying method is not particularly limited, but when using a constant-length drying type dryer that can dry water with a constant width such as a drum dryer or pin tenter, the air resistance is This is preferable because a porous sheet or a porous laminated sheet having a low thickness can be obtained stably. The drying temperature may be appropriately selected according to the conditions, but is preferably 45 ° C. or higher and 250 ° C. or lower, more preferably 60 ° C. or higher and 200 ° C. or lower, and further preferably 80 ° C. or higher and 200 ° C. or lower. When the drying temperature is 45 ° C. or higher, the evaporation rate of water is relatively fast in many cases, so that good productivity can be secured, and when the drying temperature is 250 ° C. or lower, the porous agent is thermally denatured. Can be avoided, and the energy efficiency is good and the cost is low. It is also effective to obtain a highly homogeneous porous sheet or porous laminated sheet by preparing a composition by low-temperature drying at 100 ° C. or lower and performing multi-stage drying in which drying is performed at a temperature of 100 ° C. or higher in the next stage. .

  In a preferred embodiment, the slurry further contains a block polyisocyanate, and the porous sheet forming step or the porous laminated sheet forming step includes a thermal curing process performed after drying the wet paper or the multilayer wet paper. That is, when a block polyisocyanate is used, a dry sheet obtained by drying a wet paper or a multilayer wet paper is heat-cured (heat-treated), thereby dissociating the block groups of the block polyisocyanate contained in the sheet, A chemical bond with the subsequent fine cellulose fibers is formed. Moreover, in a porous laminated sheet, bridge | crosslinking with a base sheet and a fine cellulose fiber also advances simultaneously with this block polyisocyanate.

  A known method using convection heat transfer, conduction heat transfer, radiant heat transfer, or the like can be used for the heat curing treatment, and heating by hot air, infrared rays, or heat contact can be used. From the viewpoint of uniform heat treatment in a short time, contact heating to the heating roller is preferable. The amount of thermal energy that ignites the sheet can be adjusted by the roll temperature, roll diameter, feed rate, and the like.

  Although the block polyisocyanate is stable at normal temperature, the heat treatment at a temperature higher than the dissociation temperature of the blocking agent dissociates the blocking group, regenerates the isocyanate group, and can form a chemical bond with the functional group having active hydrogen. The heating temperature varies depending on the blocking agent to be used, but it is heated to the dissociation temperature of the blocking group in the range of 80 ° C. or more and 300 ° C. or less, preferably 100 ° C. or more and 280 ° C. or less, more preferably 120 ° C. or more and 250 ° C. or less. When the temperature is lower than the dissociation temperature of the blocking group, crosslinking is not caused because the isocyanate group is not regenerated. Heating at a temperature of 300 ° C. or lower is preferable because it can avoid thermal deterioration of fine cellulose fibers and block polyisocyanate and coloration caused thereby.

  The lower limit of the heating time is 1 second or more, and the upper limit is 5 minutes or less, preferably 3 minutes or less, more preferably 1 minute or less. When the heating temperature is sufficiently higher than the dissociation temperature of the blocking group, the heating time can be shortened. In addition, when the heating temperature is 200 ° C. or higher, if the heating is performed for more than 5 minutes, the moisture in the sheet is extremely reduced, so that heating within 5 minutes avoids embrittlement of the sheet immediately after heating. This is preferable in terms of easy handling.

In a preferred embodiment, the porous sheet forming step or the porous laminated sheet forming step includes a calendar process performed after drying the wet paper or the multilayer wet paper. That is, you may perform a calendar process (smoothing process) with the calendar apparatus to the dry sheet obtained by drying. A porous sheet or a porous laminated sheet having a smooth surface and a thin film can also be obtained through a calendar process. That is, the dry sheet can be further thinned by subjecting the dry sheet to a smoothing process using a calendar device, and the porous sheet or porous laminate of this embodiment having a wide range of film thickness / air resistance / strength combinations. Sheets can be provided. For example, it is possible to easily manufacture a porous sheet and a porous laminated sheet having a film thickness of 20 μm or less under a setting with a basis weight of 10 g / m ² or less. 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 multistage manner may be used. What is necessary is just to select these apparatuses and the material (material hardness) and linear pressure of each side of a roll at the time of a calendar process according to the objective.

When heat curing treatment is performed in the production of a porous sheet or porous laminated sheet containing a block polyisocyanate, the calendar treatment may be performed between drying and heat curing treatment, or after drying and heat curing treatment. The thermal curing process and the calendar process (smoothing process) may be performed simultaneously by the thermal calendar process. In a preferred embodiment, in the porous laminated sheet forming step, the multilayer wet paper is dried, heat-cured, and calendared in this order. To produce the porous sheet by a method comprising a combination of thermal curing process, and calendering, the basis weight aqueous wet strength per 10 g / m ² 0.3 kg / 15 mm or more, and / or basis weight nonaqueous per 10 g / m ² This is particularly advantageous in the production of a porous sheet having a wet strength of 0.3 kg / 15 mm or more.

  Hereinafter, the present embodiment will be specifically described with reference to examples. The main measured values of physical properties were measured by the following methods.

(1) Number average fiber diameter of fine cellulose fibers The sample surface was randomly observed at three places with a scanning electron microscope (SEM) at a magnification equivalent to 10,000 times. From the obtained SEM image, one line was drawn in each of the vertical direction and the horizontal direction, and the fiber diameter and the number of fibers crossing the line were measured. And the number average fiber diameter was computed using the measurement result of two length and width series about one image. Furthermore, 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 number average fiber diameter of the target sheet. In addition, when the obtained number average fiber diameter is less than 100 nm, three points are randomly observed at a magnification of 50000 times, and a more accurate number average fiber diameter is calculated using the same method as described above. It was adopted.

(2) A sample stored for 24 hours in an environment controlled at a room temperature of 23 ° C. and a humidity of 50% RH is cut into 20 cm × 20 cm (area 0.04 m ² ), and the weight W1 (g) is measured. Calculated from
Weight per unit area W (g / m ² ) = W1 / 0.04 Formula (15)

(3) Thickness The thickness of the porous sheet and the porous laminated sheet was measured by cross-sectional SEM observation. In preparing a sample for cross-sectional SEM measurement, a cross-section of the sheet was obtained by processing using a Broad-Ion-Beam BIB apparatus (manufactured by JEOL Ltd., SM-09010, acceleration voltage 3.5 kV). Subsequently, as a conductive treatment, about 1 nm of osmium was coated to prepare a speculum sample. Then, cross-sectional SEM observation was performed at three magnifications at 1000 magnifications (manufactured by Hitachi High-Tech, S-4800, acceleration voltage 1.0 kV, downward detector). In each of the obtained cross-sectional SEM images, three points were arbitrarily selected from the surface on one side of the sheet. Each point was used as a starting point, a perpendicular line was drawn to obtain three intersections with the lower surface of the sheet, and the distance between the starting point and the intersection was measured. And the average value of the distance of a total of nine points was made into the film thickness (micrometer).

(4) Air permeation resistance per unit weight of 10 g / m ² After measuring the basis weight (W) for a sample (20 cm × 20 cm) left standing for one day in an environment of 23 ° C. and 50% RH, Oken type air permeation Ten points were measured using a resistance tester (Asahi Seiko Co., Ltd., Model EG01), and the average value was defined as the average air permeability resistance AR (sec / 100 ml). At this time, the value per 10 g / m ² basis weight was calculated according to the following formula. The upper limit of the air resistance that can be measured by this apparatus is 1,000,000 sec / 100 ml, and the value exceeding the upper limit was calculated as 1,000,000 sec / 100 ml.
Permeation resistance per unit weight 10 g / m ² (sec / 100 ml) = AR / W × 10 Formula (16)

(5) Porous agent water-soluble After adding 99 g of ion-exchange water and 1 g of porosifying agent (solid content: 100% by weight) to a 100 ml glass vial, the mixture is stirred at 750 rpm for 1 hour while adjusting the temperature to 50 ° C. After that, it was judged from the appearance and turbidity when the temperature was lowered to 23 ° C. and stirring was stopped. First, the case where it was visually separated into two layers was marked with x. Next, when it was not separated into two layers, turbidity was measured using a turbidimeter. The case where the turbidity was 1 NTU or more was evaluated as x, and the case where the turbidity was less than 1 NTU was evaluated as ◯. In addition, when the solid content of the porous agent was less than 100% by weight, the addition amount of the porous agent was adjusted so that the final aqueous dispersion would be 1% by weight.

(6) Porous agent content rate After measuring the weight W1 (g) of a sample (20 cm × 20 cm) which was allowed to stand for 1 day in an environment of 23 ° C. and 50% RH, it was cut into 2 cm square and 200 ml of acetone contained. The sample was placed in a beaker and irradiated with ultrasonic waves for 10 minutes, followed by filtration. The filtrate was extracted twice more with acetone in the same manner. A total of 600 ml of the filtrate was dried with an evaporator, and the weight W7 (g) of the solid content was measured. From the following formula, the porosifying agent content relative to the fine cellulose fiber weight was calculated.
Porous agent content (%) = W7 / (W1-W7) × 100 Formula (17)

(7) Porous retention property A sample (20 cm × 20 cm) which was allowed to stand for 1 day in an environment of 23 ° C. and 50% RH was cut into 5 cm × 5 cm, and 5 pieces were selected therefrom. Each of the five samples was measured for air resistance by one point, and the measurement location was marked. This air permeability resistance was the initial air resistance R1, and the average value of the five sheets was AR1. Subsequently, the sample was placed on a metal plate, sprayed with water uniformly with a spray, and water droplets adhering to the periphery of the sample were wiped off. The sheet weight before and after the wetting operation was measured to determine the sheet moisture content. After confirming that the moisture content of the sheet at this time was not less than 300 wt% and not more than 400 wt%, the sheet was dried in an oven at 80 ° C. for 1 hour, and the air resistance at the marked place was measured again. The air resistance was post-operation air resistance R2, and the average value of the five samples was AR2 (sec / 100 ml). Finally, the rate of increase in air permeability resistance (%) was calculated from the following formula 18. When the rate of increase in air permeability resistance was 100% or more, it was rated as x, and when it was less than 100%, it was marked as ◯.
Permeability increase rate (%) = (AR2-AR1) / AR1 × 100 Formula (18)
In the case of a porous sheet, the sheet moisture content was calculated from the initial porous sheet weight W2 (g) and the wet porous sheet weight W3 (g) using Equation 19.
Sheet moisture content = (W3-W2) / W2 × 100 Formula (19)
In the case of a porous laminated sheet, the weight was calculated from the initial porous laminated sheet weight W4 (g), the wet laminated porous sheet weight W5 (g), and the fine cellulose fiber layer estimated initial weight W6 (g) using Equation 20. In addition, W6 was calculated from the following formula 21 using the fact that the fine cellulose fiber layer thickness D1 (μm) calculated from the cross-sectional SEM observation was approximately proportional to the fine cellulose fiber basis weight.
Sheet moisture content = (W5-W4) / W6 × 100 Formula (20)
Estimated initial weight W6 (g) of fine cellulose fiber layer =
Fine cellulose fiber layer thickness D1 (μm) × 1 (g / μm / m ² ) Formula (21)
In preparing a sample for cross-sectional SEM measurement, a cross-section of the sheet was obtained by processing using a Broad-Ion-Beam BIB apparatus (manufactured by JEOL Ltd., SM-09010, acceleration voltage 3.5 kV). Subsequently, as a conductive treatment, about 1 nm of Os was coated to prepare a spectroscopic sample. SEM observation was performed at three magnifications at 1000 magnifications, and the thicknesses of three arbitrary points were measured with each of the obtained SEM images. The average thickness of nine points in total was defined as the thickness D1 (μm) of the fine cellulose fiber layer of the porous laminate sheet (manufactured by Hitachi High-Tech, S-4800, acceleration voltage 1.0 kV, downward detector).

(8) Dry strength per 10 g / m ² The basis weight W (g / m ² ) of a sample (20 cm × 20 cm) stored for 24 hours in an environment controlled at room temperature 23 ° C. and humidity 50% RH was measured. A 15 mm wide test piece was prepared, and the tensile strength at 10 points was measured at a chuck distance of 100 mm and a tensile speed of 10 mm / min using a tabletop horizontal tensile tester (No. 2000) of Kumagai Riki Kogyo Co., Ltd. The average value was defined as the dry strength (DS). At this time, the weight per unit weight of 10 g / m ² was calculated using the basis weight W of the base paper measured in advance.
Drying strength per 10 g / m ² basis weight (kgf / 15 mm) = DS / W × 10 Formula (22)

(9) Aqueous wet strength per 10 g / m ² Aqueous wet strength per 10 g / m ² A basis weight W (g / m ² ) of a sample (20 cm × 20 cm) stored for 24 hours in an environment controlled at room temperature 23 ° C. and humidity 50% RH It was measured. Next, it cut | judged to 15 mm width, and 50 mm center of 15 mm width test piece was immersed in water for 10 second. Subsequently, using a tabletop horizontal tensile tester (No. 2000) of Kumagai Riki Kogyo Co., Ltd., the tensile strength at 10 points was measured in a wet state at a distance between chucks of 100 mm and a tensile speed of 10 mm / min. The average value was defined as aqueous wet strength WS (kgf / 15 mm). At this time, the porous sheet sample was calculated as a value per 10 g / m ² basis weight (kgf / 15 mm) from the following formula (22) using the basis weight W of the base paper measured in advance. On the other hand, for the porous laminated sheet, only WS was measured in the MD direction of the base sheet. The strength at the time when the fine cellulose fiber layer was broken or peeled off from the substrate sheet was adopted as the breaking strength.
Water-based wet strength per unit weight of 10 g / m ² (kgf / 15 mm) = WS / W × 10 Formula (23)

(10) non-aqueous wet strength, non except that the liquid to 10 g / m ² per nonaqueous wet strength used was changed to methyl cellosolve in the same manner as the measuring method of the water-based wet strength and 10 g / m ² per nonaqueous wet strength The aqueous wet strength NWS (kgf / 15 mm) was calculated, and the non-aqueous wet strength (kgf / 15 mm) per 10 g / m ² basis weight was calculated from the following formula (24).
Non-aqueous wet strength (kgf / 15 mm) per 10 g / m ² basis weight = NWS / W × 10 formula (24)

(11) Uniformity of porous structure In preparation of a sample for cross-sectional SEM measurement, a cross-section of the sheet is obtained by processing using a Broad-Ion-Beam BIB apparatus (manufactured by JEOL Ltd., SM-09010, acceleration voltage 3.5 kV). It was. Subsequently, as a conductive treatment, about 1 nm of osmium was coated to prepare a speculum sample. Then, a cross-sectional SEM observation was performed at 10 magnifications at a magnification of 5000 (manufactured by Hitachi High-Tech, S-4800, acceleration voltage 1.0 kV, downward detector). From the obtained 10 cross-sectional SEM images, the largest major axis was measured among the pores at the center of the porous sheet, and the average value (average maximum major axis) of the ten sheets was calculated. The central portion of the porous sheet is a portion excluding the surface layer portions 1 and 2 when the cross section of the porous sheet is equally divided into four in the thickness direction (surface layer portion 1-central portion 1-central portion 2-surface layer portion 2). Point to. For example, when the thickness of the porous sheet is 20 μm, 10 μm excluding the surface layer portions of 5 μm on both sides is set as the central portion of the porous sheet. In the case of a porous laminated sheet, the fine cellulose fiber layer was similarly divided into four equal parts in the thickness direction, and the average maximum major axis was calculated. When the average maximum major axis is 10 μm or more, ×, when it is less than 10 μm, it is evaluated as ◯.

(12) Adhesiveness of porous laminated sheet The porous laminated sheet was cut out at 5 cm × 5 cm, immersed in a plastic bottle containing 100 ml of ion-exchanged water, and 10 minutes at 200 rpm using a shaker in an environment of 23 ° C. Shake. It was visually observed whether or not the fine cellulose fiber layer was peeled off from the substrate sheet after shaking. The case where it peeled was evaluated as x, and the case where it did not peel was evaluated as ○.

Production Example 1
Five types of fine cellulose fiber slurries were produced by the following method.

[Production Example 1-1]
Cotton linter pulp obtained from Nippon Paper Pulp Shoji Co., Ltd. was immersed in water so as to be 10% by weight, and heat-treated at 130 ° C. for 4 hours in an autoclave. The obtained swollen pulp was washed with water to obtain purified pulp containing water. Subsequently, the refined pulp is dispersed in water so as to have a solid content of 1.5% by weight (400 L), and a disk refiner apparatus using SDR14 type laboratory refiner (pressurized DISK type) manufactured by Aikawa Tekko Co., Ltd. is used. The clearance was 1 mm and 400 L of the aqueous dispersion was beaten for 20 minutes. Subsequently, thorough beating was performed under conditions where the clearance was reduced to almost zero, and a beating water dispersion (solid content concentration: 1.5% by weight) was obtained. The obtained beating water dispersion was subjected to refinement treatment 10 times under an operating pressure of 100 MPa using a high-pressure homogenizer (NSO Soabi (I) NSO15H) as it was, and a fine cellulose fiber slurry A-1 (solid) Minor concentration: 1.5% by weight).

[Production Example 1-2]
The high-pressure homogenizer treatment in Production Example 1-1 was performed only once to obtain a fine cellulose fiber slurry A-2 (solid content concentration: 1.5% by weight for both).

[Production Example 1-3]
Fine cellulose fiber slurry A-3 (solid content concentration: 1.5% by weight) was obtained in the same manner as in Production Example 1-1 using abaca pulp obtained from Nippon Paper Pulp Shoji Co., Ltd. as a cellulose raw material.

[Production Example 1-4]
Fine cellulose fiber slurry A1 / A3 = 50/50 (g / g) was mixed to obtain fine cellulose fiber slurry A-4 (solid content concentration: 1.5% by weight).

[Production Example 1-5]
Put the tencel cut yarn (3mm length), a regenerated cellulose fiber obtained from Sojitz Corporation, into the washing net, add a surfactant, and wash it with water in the washing machine many times to remove the oil on the fiber surface. did. The obtained refined tencel fiber (cut yarn) was refined by the same method as in Production Example 1 to obtain a fine cellulose fiber slurry A-5 (solid content concentration: 1.5% by weight).

Production Example 2
Five types of papermaking slurries were produced by the following method. The composition of the papermaking slurry is shown in Tables 1 and 2.

[Production Example 2-1]
A slurry Cg obtained by diluting the fine cellulose fiber slurry A to a solid content concentration of B% by weight was dropped with Eg of the following porous agent (D, 1% aqueous solution) while stirring with a three-one motor, and the paper was made by stirring for 3 minutes. A slurry was obtained (M1-26). Since the porosifying agent does not dissolve in water, it was collected after shaking vigorously by hand immediately before addition. The added porous agent solid content weight with respect to the fine cellulose fiber weight was defined as F%.
D1: KF-6013, polyether-modified methylpolysiloxane, Shin-Etsu Chemical Co., Ltd. D2: KF-6100, polyglycerin-modified organopolysiloxane, Shin-Etsu Chemical Co., Ltd. D3: Perex TR, sodium dialkylsulfosuccinate, Kao Corporation D4: Mega Fuck F-444, perfluoroalkyl group-containing polyoxyethylene, DICD D5: Eleganol NZ-800, cationic polymer emulsion (paper bulking agent), Meisei Chemical Industries D6: Emulgen 103, polyoxyethylene lauryl Ether, HLB8.1, Kao D7: Emulgen 106, polyoxyethylene lauryl ether, HLB10.5, Kao D8: Emulgen 408, oleyl polyoxyethylene, HLB10.0 Kao D9: Amiate 102, Polyoxyethylene Down alkyl amines, HLB6.3, manufactured by Kao Corporation D10: Rheodol SP-L10, sorbitan monolaurate, HLB8.6, manufactured by Kao Corporation

[Production Example 2-2]
After adding the following porous agent (D, 1% aqueous solution) to the slurry Cg obtained by diluting the fine cellulose fiber slurry A to a solid content concentration of B wt%, the slurry is made with a household mixer for 10 minutes, and the papermaking slurry (M26-29). Since the porosifying agent does not dissolve in water, it was collected after shaking vigorously by hand immediately before addition. The added porous agent solid content weight with respect to the fine cellulose fiber weight was defined as F%.
D11: Emulgen 102KG, polyoxyethylene lauryl ether, HLB6.3, Kao D12: LUNAC O-V, oleic acid, Kao D13: Octadecane, Wako Pure Chemical Industries, Ltd.

[Production Example 2-3]
While stirring the papermaking slurry containing the porosifying agent produced by the method of Production Example 2-1 or 2-2 with a three-one motor, the following block polyisocyanate (G, diluted to a solid content concentration of 1.0% by weight) Hg The papermaking slurry was obtained by dripping and stirring for 3 minutes (M30-38, M40-42, M48-50). The added block polyisocyanate solid content weight with respect to the fine cellulose fiber weight was defined as I%.
G1: Meikanate CX, Cationic, Meisei Chemical Co., Ltd. G2: Meikanate WEB, Cationic, Meisei Chemical Industry Co., Ltd. G3: Meikanate TP-10, Nonionic, Meisei Chemical Co., Ltd. G4: MF-25K, Nonionic, Daiichi Kogyo Seiyaku G5: E-37, anionic, Daiichi Kogyo Seiyaku

[Production Example 2-4]
While stirring the papermaking slurry containing the porosifying agent and block polyisocyanate produced by the method described in Production Example 2-3 with a three-one motor, the following polycation (J, diluted to a solid content concentration of 1.0% by weight) Kg was dropped and a papermaking slurry was obtained by stirring for 3 minutes (M39, 51). The added polycation solid content weight with respect to the fine cellulose fiber weight was L%.
J1: PAS-H-10L, diallyldimethylammonium chloride polymer, manufactured by Nitto Bo Medical Co., Ltd.

[Production Example 2-5]
The fine cellulose fiber slurry A was diluted to a solid content concentration of B% by weight to obtain a papermaking slurry Cg containing only fine cellulose fibers (L43-47).

[Production Example 2-6]
While stirring the slurry Cg obtained by diluting the fine cellulose fiber slurry A to a solid content concentration of B wt% with a three-one motor, Hg was added dropwise to the block polyisocyanate (G, diluted to a solid content concentration of 1.0 wt%) for 3 minutes. The papermaking slurry was obtained by stirring (M30-38, M40-42, M48-50). The added block polyisocyanate solid content weight with respect to the fine cellulose fiber weight was defined as I%.

[Production Example 2-7]
A slurry Cg obtained by diluting the fine cellulose fiber slurry A to a solid content concentration of B% by weight was dropped with Eg of the following porous agent (D, 1% aqueous solution) while stirring with a three-one motor, and the paper was made by stirring for 3 minutes. A slurry was obtained (M1-20, 24-29). Since the porosifying agent does not dissolve in water, it was collected after shaking vigorously by hand immediately before addition. The added porous agent solid content weight with respect to the fine cellulose fiber weight was defined as F%.
D14: Emulgen 108, polyoxyethylene lauryl ether, HLB12.1, Kao D15: Emulgen 220, polyoxyethylene cetyl ether, HLB14.2, Kao D16: KF-6011, polyether-modified methylpolysiloxane, Shin-Etsu Chemical D17: Cotamine 60W, cetyltrimethylammonium chloride, Kao

[Production Example 2-8]
1-hexanol and hydroxypropylmethylcellulose (HPMC, trade name “60SH-4000”, manufactured by Shin-Etsu Chemical Co., Ltd.) are each added to 1.2 wt% (3) 0.9g) and 0.012% by weight (0.039g) were added, and the mixture was emulsified and dispersed for 4 minutes with a home mixer to obtain a papermaking slurry (M56).

[Production Example 2-9]
While stirring the papermaking slurry obtained in Production Example 2-8 with a three-one motor, Hg was added dropwise to the block polyisocyanate (G, diluted to a solid content concentration of 1.0% by weight), and stirring was performed for 3 minutes. ) The added block polyisocyanate solid content weight with respect to the fine cellulose fiber weight was defined as I%.

[Example 1-29]
Plain fabric made of PET / nylon blend (Shikishima Canvas Co., Ltd., NT20: water permeation amount at 25 ° C. in air: 0.03 ml / (cm ² · s), filtration of fine cellulose fibers at 25 ° C. under atmospheric pressure With a batch type paper machine (made by Kumagai Riki Kogyo Co., Ltd., automatic square sheet machine 25 cm x 25 cm, 80 mesh) set to a porous sheet with a basis weight of 10 g / m ² Then, a papermaking slurry (M1 to 29) was added, and then papermaking (dehydration) was performed with a degree of vacuum with respect to atmospheric pressure being 4 KPa to obtain a wet paper.
The obtained wet paper was covered with a plain fabric made of the same PET / nylon blend as a covering cloth, and then the entire filter cloth was peeled off from the paper machine. Next, after pressing for 1 minute at a pressure of 1 kg / cm ² sandwiched between cardboards, it is dried for about 120 seconds with a drum dryer whose surface temperature is set to 130 ° C. so that the cloth surface is in contact with the drum surface. It was. By removing the covering cloth and the filter cloth from the obtained covering cloth / sheet / filter cloth trilayer, a porous sheet (25 cm × 25 cm) composed of fine cellulose fibers was obtained. The results are shown in Table 3.
As a representative example, as shown by a cross-sectional SEM image (FIG. 2) of the sheet of Example 12, the porous structure was uniform, and the porous structure was retained after wet drying.

[Examples 30-39]
A porous sheet containing a block polyisocyanate formed by the same method as in Example 1 for the papermaking slurry (L30 to 39) is sandwiched between two SUS metal frames (25 cm × 25 cm), fixed with clips, and 170 in an oven. A heat treatment was performed at 3 ° C. for 3 minutes to obtain a porous sheet crosslinked with urethane. The results are shown in Table 4.
The porous structure of the sheet was uniform, and the porosity was retained after wet drying. Further, 10 g / m ² per aqueous wet strength, 10 g / m ² per nonaqueous wet strength is improved by polyurethane crosslinking.

[Examples 40-46]
A base sheet L (27 cm × 27 cm) shown below is placed on a plain fabric made of PET / nylon blend, and the papermaking slurry (M4, 33, 37, 38, 40 to 42) is prepared in the same manner as in Example 1. Paper making and drying were performed to obtain a porous laminated sheet. For Examples 41-46, heat curing was performed in the same manner as in Example 30 to obtain polyurethane-crosslinked porous laminated sheets. The porous structure of the sheet was uniform, and the porosity was retained after wet drying. The results are shown in Table 5.
About Example 40, the adhesiveness of the porous laminated sheet was weak, and peeling was confirmed. In Examples 41 to 46, the water-based wet strength and the non-water-based wet strength were improved by polyurethane crosslinking, and the adhesiveness was also improved.
L1: Benlyse SA14G, cupra long fiber nonwoven fabric, basis weight 14 g / m ² , thickness 70 μm, manufactured by Asahi Kasei Corporation L2: Benlyse SE103, cupra long fiber nonwoven fabric, basis weight 100 g / m ² , thickness 540 μm, Asahi Kasei Corporation L3: Eltus NO1020, nylon Spunbond nonwoven fabric, basis weight 20 g / m ² , thickness 150 μm, Asahi Kasei Corporation L4: Eltus EO1020, polyester spunbond nonwoven fabric, basis weight 20 g / m ² , thickness 140 μm, manufactured by Asahi Kasei Co., Ltd. Corona discharge treatment before use L5: Eltus PO3020, polypropylene spunbond nonwoven fabric, basis weight 20 g / m ² , thickness 190 μm, manufactured by Asahi Kasei Co., Ltd., subjected to corona discharge treatment before use L6: Eltas Aqua PA3020, water-permeable polypropylene spunbond nonwoven fabric, basis weight 20 g / m ² , thickness 190 μm, Asahi Company made

[Examples 47-48]
The sheets produced in Example 4 and Example 32 were cut into 20 cm × 20 cm, and the distance between the metal mirror roll (upper roll) and the resin roll (hardness D85, lower roll) was 23 ° C. and the linear pressure was 1.0 ton. Calendar processing was performed at a traveling speed of 2 m / min. The results are shown in Table 6.
Both sheets had a uniform porous structure, and the porous structure was maintained even after wet drying. On the other hand, the thickness was thinner than the sheets of Examples 4 and 32. Furthermore, for Examples 48, 10 g / m ² per aqueous wet strength, 10 g / m ² per nonaqueous wet strength is improved by polyurethane crosslinking.

[Comparative Example 1-5]
The papermaking slurries M43 to M47 were formed by the same method as in Example 1 to obtain fine cellulose fiber sheets. The results are shown in Table 7.
Comparative Example 1-4 was not porous. Although Comparative Example 5 was porous as shown in FIG. 3, the maximum pore size was remarkably large and not uniform.

[Comparative Example 6-9]
About the papermaking slurry M48-51, it formed into a film by the same method as Example 30, and obtained the fine cellulose fiber sheet. The results are shown in Table 7.
Aqueous wet strength per 10 g / m ² by also polyurethane crosslinking either sheet was improved 10 g / m ² per nonaqueous wet strength, but not in the porous structure.

[Comparative Example 10-13]
About the papermaking slurry M52-55, it formed into a film by the same method as Example 1, and obtained the fine cellulose fiber sheet. The results are shown in Table 7.
Since the added porosifying agent was water-soluble, none of the sheets had a porous structure. It did not contribute to porosity.

[Comparative Example 14]
The wet paper before drying obtained in Comparative Example 1 was dipped in acetone together with the filter cloth and subjected to substitution treatment for about 10 minutes. Thereafter, it was immersed in a mixed solvent of toluene / acetone = 50/50 (g / g) and similarly subjected to substitution treatment for 10 minutes. Thereafter, the filter cloth was attached to a metal container with the filter cloth down, and dried at 50 ° C. for 60 minutes to obtain a porous sheet. The results are shown in Table 7.
Although the porous structure of the sheet was uniform, significant shrinkage occurred after wet drying, and the porous structure was not retained.

[Comparative Example 15]
The sheet of Comparative Example 14 was dipped in tetrahydrofuran in which 2% by weight of 1,6′-hexamethylene diisocyanate was dissolved, pressed between cardboards at a pressure of 1 kg / cm ² for 1 minute, and then air-dried. Thereafter, the dried sheet was sandwiched between two SUS metal frames (25 cm × 25 cm), fixed with clips, and heat treated at 170 ° C. for 3 minutes in an oven to obtain a urethane-crosslinked porous sheet. The results are shown in Table 7.
The porous structure of the sheet was uniform, and the aqueous wet strength per 10 g / m ² was improved by non-aqueous wet strength per 10 g / m ² by polyurethane crosslinking. However, although the shrinkage after wet drying was suppressed, the porous structure was not retained.

[Comparative Example 16]
About the papermaking slurry M56, it formed into a film by the same method as Example 1, and obtained the fine cellulose fiber sheet. The results are shown in Table 7.
As shown in FIG. 4, it had pores with a major axis exceeding 10 μm, and the porous structure was non-uniform. In addition, significant shrinkage occurred after wet drying, and the porous structure was not retained.

[Comparative Example 17]
The papermaking slurry M57 was formed into a film by the same method as in Example 30 to obtain a polyurethane crosslinked fine cellulose fiber sheet. The results are shown in Table 7.
It had pores with a major axis exceeding 10 μm, and the porous structure was non-uniform. Compared with Comparative Example 14, a non-aqueous wet strength per 10 g / m ² per aqueous wet strength, 10 g / m ² of polyurethane crosslinking is improved, but also suppressed contraction after wet drying, porous structures lead to the holding There wasn't.

[Comparative Example 18]
About the papermaking slurry M47, it formed into a film on the base material sheet L1 by the same method as Example 40, and the fine cellulose fiber laminated sheet was obtained. Although the sheet was porous, the maximum pore size was extremely large and was not uniform. The results are shown in Table 8.

[Comparative Example 19]
The papermaking slurry M43 was made on the base sheet L1 in the same manner as in Example 40, and the wet paper before drying was dipped in acetone together with the filter cloth and subjected to a substitution treatment for about 10 minutes. Then, it was immersed in a mixed solvent of toluene / acetone = 50/50 (g / g) and similarly subjected to substitution treatment for 10 minutes. Thereafter, the filter cloth was attached to a metal container with the filter cloth facing down and dried at 50 ° C. for 60 minutes to obtain a fine cellulose fiber laminated fiber sheet. The results are shown in Table 8.
Although the porous structure of the sheet was uniform, significant shrinkage occurred after wet drying, and the porous structure was not retained.

[Comparative Example 20]
About the papermaking slurry M56, it formed into a film on the base material sheet L1 by the same method as Example 40, and the fine cellulose fiber laminated sheet was obtained. The results are shown in Table 8.
Although the sheet was porous, it had pores with a major axis exceeding 10 μm, and the porous structure was uneven. In addition, significant shrinkage occurred after wet drying, and the porous structure was not retained.

[Comparative Example 21]
The papermaking slurry M57 was formed into a film by the same method as in Example 41 to obtain a polyurethane crosslinked fine cellulose fiber sheet. The results are shown in Table 8.
Although the sheet was porous, it had pores with a major axis exceeding 10 μm, and the porous structure was uneven. Compared with Comparative Example 20, a non-aqueous wet strength per 10 g / m ² per aqueous wet strength, 10 g / m ² of polyurethane crosslinking is improved, but also suppressed contraction after wet drying, porous structures lead to the holding There wasn't.

  The porous sheet and porous laminated sheet of this embodiment are a filter, a cell culture substrate, a total heat exchanger element, various functional papers, absorbent materials, a support for medical materials, and a fiber reinforced plastic support. As applicable. In particular, thermosetting compounds, photo-curable compounds, resins obtained by thermosetting or photo-curing these compounds, and resin composite films produced by impregnating thermoplastic resins are used in printed circuit boards, insulating films, for example, in the field of electronic materials. It can be suitably used for the core material. Further, it can be suitably used as an alternative to steel plates, carbon fiber reinforced plastics, and glass fiber reinforced plastics. Specifically, industrial machine parts (for example, electromagnetic equipment housings, roll materials, transfer arms, medical equipment members, etc.), general machine parts, automobile / railway / vehicle parts (for example, outer plates, chassis, aerodynamic members, Seats, etc.), ship components (eg hulls, seats, etc.), aviation-related parts (eg fuselage, main wing, tail wing, moving wings, fairings, cowls, doors, seats, interior materials, etc.), spacecraft, satellite components ( Motor cases, main wings, structures, antennas, etc.), electronic / electrical parts (eg personal computer housings, mobile phone housings, OA equipment, AV equipment, telephones, facsimiles, home appliances, toy supplies, etc.), construction / civil engineering materials ( For example, rebar replacement materials, truss structures, cables for suspension bridges, etc., daily necessities, sports / leisure products (eg golf club shafts, fishing rods, tennis and batmin) ), Wind power generation casing members, containers and packaging members, for example, materials for high pressure containers filled with hydrogen gas used in fuel cells, transparent materials (for example, automobiles and Glass for buildings, cover glass for displays of OA equipment and AV equipment, etc.).

Claims (15)

The following requirements (1) to (6):
(1) The average fiber diameter is composed of fine cellulose fibers of 2 nm to 1000 nm,
(2) The air resistance per 10 g / m ² per unit weight is 7000 sec / 100 ml or less,
(3) The basis weight is 0.5 g / m ² or more and 40 g / m ² or less,
(4) The thickness is 1 μm or more and 100 μm or less,
(5) The rate of change in air resistance before and after wet drying is 100% or less,
(6) The average maximum major axis of the pores at the center of the sheet is 10 μm or less,
A porous sheet that meets all requirements. The porous sheet according to claim 1, wherein the water-based wet strength per unit weight of 10 g / m ² is 0.3 kg / 15 mm or more. The porous sheet according to claim 1 or 2, wherein the non-aqueous wet strength per unit weight of 10 g / m ² is 0.3 kg / 15 mm or more. A porous laminated sheet comprising one or more base sheet layers and one or more fine cellulose fiber layers, wherein the fine cellulose fiber layers are the following requirements (1) to (3):
(1) The average fiber diameter is composed of fine cellulose fibers of 2 nm to 1000 nm,
(2) The layer thickness is 1 μm or more and 100 μm or less,
(3) The average maximum major axis of the pores at the center of the layer is 10 μm or less,
The porous laminate sheet satisfies the following requirements (4) to (7):
(4) The air resistance is 20000 sec / 100 ml or less,
(5) The rate of change in air resistance before and after wet drying is 100% or less,
(6) The basis weight is 2 g / m ² or more and 1000 g / m ² or less,
(7) The thickness is 2 μm or more and 1000 μm or less,
A porous laminate sheet that meets all requirements.   A 5 cm x 5 cm porous laminate sheet is immersed in 200 ml of ion exchange water, and after shaking for 10 minutes at 23 ° C and 200 rpm using a shaker, the fine cellulose fiber layer does not peel from the base sheet layer. Item 5. The porous laminated sheet according to Item 4.   The porous laminated sheet according to claim 4 or 5, wherein the aqueous wet strength is 0.5 kg / 15 mm or more.   The porous laminate sheet according to any one of claims 4 to 6, wherein the non-aqueous wet strength is 0.7 kg / 15 mm or more. A preparation step for preparing a slurry containing a porosifying agent, fine cellulose fibers, and water;
A film forming step of forming wet paper by dehydrating the slurry by a papermaking method; and
The manufacturing method of the porous sheet as described in any one of Claims 1-3 including the porous sheet formation process of obtaining a porous sheet by drying this wet paper at least. The slurry further comprises a blocked polyisocyanate;
The method for producing a porous sheet according to claim 8, wherein the porous sheet forming step includes a thermal curing process performed after the wet paper is dried.   The manufacturing method of the porous sheet of Claim 8 or 9 in which the said porous sheet formation process includes the calendar process performed after drying the said humidity. The porous sheet, basis weight 10 g / m ² per aqueous wet strength 0.3 kg / 15 mm or more, and / or basis weight has over 10 g / m ² per nonaqueous wet strength 0.3 kg / 15 mm,
The porous sheet forming step includes a thermal curing process and a calendar process performed after drying the wet paper, and the calendar process is performed before the thermal curing process, simultaneously with the thermal curing process, or the thermal curing process. The manufacturing method of the porous sheet of Claim 9 performed after a process. A preparation step for preparing a slurry containing a porosifying agent, fine cellulose fibers, and water;
The slurry is dehydrated on a base sheet by a papermaking method to form a multilayer wet paper, and
A porous laminated sheet forming step of obtaining a porous laminated sheet by at least drying the multilayer wet paper;
The manufacturing method of the porous laminated sheet as described in any one of Claims 4-7 containing this. The slurry further comprises a blocked polyisocyanate;
The manufacturing method of the porous laminated sheet of Claim 12 with which the said porous laminated sheet formation process includes the heat curing process performed after drying the said multilayer wet paper.   The manufacturing method of the porous laminated sheet of Claim 12 or 13 in which the said porous laminated sheet formation process includes the calendar process performed after drying the said multilayer wet paper.   The porous laminated sheet forming step includes a thermal curing process and a calendering process performed after drying the multilayer wet paper, and the calendering process is performed before the thermal curing process, simultaneously with the thermal curing process, or The manufacturing method of the porous laminated sheet of Claim 13 performed after a heat curing process.