WO2020145354A1 - Porous fine cellulose fiber complex sheet - Google Patents

Abstract

The present invention provides a complex sheet which comprises a porous fine cellulose fiber sheet and a thermoplastic resin, and which has low linear thermal expansion coefficient and reduced anisotropy. One embodiment of the present invention provides a porous fine cellulose fiber complex sheet which satisfies all of the requirements (1)-(4) described below. (1) One or more porous fine cellulose fiber sheets, each having an average fiber diameter of from 2 nm to 1,000 nm (inclusive), are contained. (2) Each porous fine cellulose fiber sheet is arranged so as to have a film thickness of from 25 μm to 2,000 μm (inclusive). (3) A thermoplastic resin is contained. (4) A porosity imparting agent is contained.

Description

Porous fine cellulose fiber composite sheet

The present invention relates to a porous fine cellulose fiber composite sheet containing fine cellulose fibers and a thermoplastic resin, which is optimal as a material for automobile parts.

In recent years, automobile parts have been required to be lightweight from the viewpoint of improving fuel efficiency and reducing CO ₂ emission, and studies have been made to adapt a resin material to an outer plate member and a structural member. However, since resin generally has a high coefficient of linear expansion, if the resin is used as it is for a conventionally used metal component, interference will occur at the interface with the adjacent metal component due to thermal expansion at high temperatures. was there. On the contrary, when a resin component designed according to the dimensions at high temperature is mounted, a large gap is generated at the boundary with the adjacent metal component at room temperature. Further, when the metal component and the resin are surface-bonded to each other, a large stress is generated due to a difference in linear expansion between the metal and the resin at a high temperature, causing a problem that the joint surface is peeled off.

On the other hand, in automobile parts, the resin used is required to have recyclability in order to reduce CO ₂ emission. That is, rather than a thermosetting resin that is difficult to recycle materials, a thermoplastic resin that can do this is preferably used. Since thermoplastic resins generally have a large linear expansion coefficient, studies have been made so far to suppress the linear expansion coefficient by blending a fibrous or plate-like inorganic filler. However, when injection molding is performed using a resin containing a fibrous inorganic filler, the linear expansion coefficient in the injection flow direction can be made small, but the linear expansion coefficient in the direction perpendicular to the flow cannot be made small. On the other hand, even when a resin containing a plate-like inorganic filler is used, it is difficult to reduce the linear expansion coefficient to the same level as a metal in both the flow direction and the direction perpendicular to the flow. That is, it has been difficult to reduce the linear thermal expansion to the same level as that of a metal in all directions with a thermoplastic resin reinforced with an inorganic filler.

In recent years, attention has been paid to fine cellulose fibers obtained by refining and pulverizing cellulosic fibers at a high level to make them finer (fibrillated) to a fiber diameter of 1 μm or less. Since the specific surface area increases as the fiber diameter becomes nano-order, for example, when a composite sheet in which a fine cellulose fiber sheet is impregnated with a resin is produced, the coefficient of thermal expansion decreases as compared with a resin-only film, and the elastic modulus is Increase. In particular, if a fine cellulose fiber sheet having a small anisotropy can be produced, the anisotropy also becomes small in the coefficient of linear thermal expansion of a sheet obtained by compounding this with a resin. The fine cellulose fiber sheet has the potential of becoming an excellent core material of a resin material for that purpose and is expected to be put into practical use, but there are many technical problems.

When considering the use of automobile parts, it is preferable that the fine cellulose fiber sheet is a porous body in order to impregnate the thermoplastic resin. However, when the conventional thermoplastic resin is impregnated into the porous body by hot pressing, the fine cellulose fiber sheet is used. The fiber sheet has a problem that it is easily broken. When the fine cellulose fiber sheet is destroyed, it becomes difficult to exhibit desired linear expansion coefficient and mechanical properties in the composite sheet of the fine cellulose fiber sheet and the resin.

Patent Document 1 discloses a first fiber having a number average fiber width of 2 nm or more and less than 1000 nm and a second fiber having a number average fiber width of 1000 nm or more and 100000 nm or less and a number average fiber length of 0.1 to 20 mm. A composite sheet in which a resin is contained in a nonwoven fabric containing is described.

Patent Document 2 describes a composite sheet containing at least fine fibers and a matrix resin, wherein the fine fibers are unevenly distributed on at least one surface of the composite sheet.

In Patent Document 3, when a fine cellulose fiber is produced from pulp, a hydrophobizing agent is added to produce a fine cellulose fiber having a hydrophobic surface, and a papermaking/dried fine cellulose fiber sheet is impregnated with a resin. A composite sheet is described.

JP-A-2015-25003 JP, 2005-17184, A International Publication No. 2016/047764

As a method for producing a porous fine cellulose fiber sheet described in Patent Documents 1 and 2, after producing a fine cellulose fiber sheet containing water to express high porosity, an organic material having a low surface tension is prepared. A method of partially substituting with a solvent and drying is shown. However, the sheet produced by the above-mentioned production method can exhibit a desired resin impregnation performance at the initial stage of use in a proper porous state, but when it is stored in the atmosphere for a long period of time, it gradually becomes dense due to humidity fluctuation or condensation-drying. However, there is a problem that the resin impregnation performance is deteriorated. That is, the porous fine cellulose fiber sheets obtained by the methods described in Patent Documents 1 and 2 are densified by drying shrinkage when dried in a hygroscopic state even if they are porous immediately after production. Generally, when a fine cellulose fiber and a thermoplastic resin are compounded by hot pressing, it is necessary to dry the fine cellulose fiber sheet before hot pressing in order to avoid irregularities on the surface of the molded product caused by evaporation of water in cellulose. However, at that time, the porous fine cellulose fiber sheet is densified. Therefore, there is a demand for a porous fine cellulose fiber sheet in which the porous structure does not change even after the wet-drying operation, specifically, the air permeation resistance does not change. The porous fine cellulose fiber sheet described in Patent Documents 1 and 2 is not sufficiently impregnated with resin when the porous fine cellulose fiber sheet is densified when it is combined with a thermoplastic resin after drying. The problem occurs. Further, although Patent Documents 1 and 2 describe examples in which a fine cellulose fiber sheet is impregnated with a thermosetting resin, technical difficulties in complexing the fine cellulose fiber sheet with a thermoplastic resin are described. There is no description about sex.

On the other hand, Patent Document 3 describes a method in which a resin is compounded with a fine cellulose fiber sheet whose air resistance does not easily change even after a wet drying operation. However, these sheets can be produced only as a thin sheet, and when used for automobile outer panel parts, when the prepreg containing the fine cellulose fiber sheet and the thermoplastic resin is hot pressed, the sheet in the prepreg is used. There was a problem that it was easy to tear. When the sheet is torn, the prepreg cannot exhibit the desired coefficient of linear expansion and mechanical properties. Therefore, there has been a demand for a fine cellulose fiber sheet that does not break even when it is hot pressed with a thermoplastic resin.

The problem to be solved by the present invention is to provide a composite sheet containing a porous fine cellulose fiber sheet and a thermoplastic resin, which has a low coefficient of linear thermal expansion and a small anisotropy.

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

[1] Requirements for (1) to (4) below:
(1) Containing one or more layers of porous fine cellulose fiber sheet having an average fiber diameter of 2 nm or more and 1000 nm or less,
(2) The porous fine cellulose fiber sheet is arranged with a film thickness of 25 μm or more (preferably 25 μm or more and 2000 μm or less),
(3) Including a thermoplastic resin,
(4) Including a porosifying agent,
A porous fine cellulose fiber composite sheet that satisfies all of the above.
[2] The following requirements (1) to (4):
(1) Containing one or more layers of porous fine cellulose fiber sheet having an average fiber diameter of 2 nm or more and 1000 nm or less (2) Porous fine cellulose fiber sheet having a thickness of 25 μm or more (preferably 25 μm or more and 4000 μm or less) To be
(3) Including a thermoplastic resin,
(4) The porous fine cellulose fiber sheet is impregnated with the thermoplastic resin,
A porous fine cellulose fiber composite sheet that satisfies all of the above.
[3] The porous fine cellulose fiber composite sheet according to the above aspect 2, wherein the sheet thickness of the porous fine cellulose fiber composite sheet is 50 μm or more and 4000 μm or less.
[4] The porous fine cellulose fiber composite sheet according to Aspect 2 or 3 above, which contains a porosifying agent.
[5] The porous fine cellulose fiber composite sheet according to the above aspect 1 or 4, which contains the porosifying agent in an amount of 0.1% by mass or more and 100% by mass or less based on 100% by mass of the fine cellulose fibers.
[6] The porous fine cellulose fiber composite sheet according to any one of the above aspects 1 to 5, wherein the porous fine cellulose fiber composite sheet has an air bubble ratio of 0.5% or less.
[7] The porous fine cellulose fiber composite sheet according to any one of the above aspects 1 to 6, which further comprises a blocked polyisocyanate or a crosslinked product thereof.
[8] The porous fine cellulose fiber composite sheet according to any one of the above aspects 1 to 7, wherein the porous fine cellulose fiber sheet does not have a broken portion having a length of 1 cm or more and a width of 1 mm or more.
[9] Any of Embodiments 1 to 8 above, wherein the porous fine cellulose fiber sheet contains fine cellulose fibers having a branched structure in which a thick trunk having a fiber diameter of 1 μm to 30 μm branches fine branches having a fiber diameter of 2 to 1000 nm. A porous fine cellulose fiber-composite sheet according to Crab.
[10] The porous fine cellulose fiber composite sheet according to any one of the above aspects 1 to 9, wherein the porous fine cellulose fiber sheet contains cellulose type I crystals.
[11] The porous fine cellulose fiber composite sheet according to any one of the above aspects 1 to 10, wherein the porous fine cellulose fiber sheet contains acetylated cellulose having an acetylation degree of 0.1 to 1.5.
[12] The porous fine cellulose fiber composite sheet according to any one of the above aspects 1 to 11, which comprises at least one base sheet layer.
[13] Any of Aspects 1 to 12 above, wherein the thermoplastic resin includes one or more selected from the group consisting of a polyolefin resin, a polyamide resin, a polyester resin, a polyacetal resin, a poly(meth)acrylate resin, and a polyphenylene ether resin. A porous fine cellulose fiber-composite sheet according to Crab.
[14] A molded article containing the porous fine cellulose fiber composite sheet according to any one of the above-mentioned Embodiments 1 to 13, wherein the molded article has a temperature of 0° C. to 60° C. in any two directions perpendicular to each other. A cellulose nanofiber-reinforced resin molded product having a coefficient of linear thermal expansion of 50 ppm/K or less.
[15] An outer panel part for an automobile, which includes the cellulose nanofiber-reinforced resin molded product according to the above-mentioned aspect 14.
[16] A slurry preparation step of preparing a slurry containing a porosifying agent, fine cellulose fibers, and water,
A film forming step of forming a wet paper web by dehydrating the slurry by a papermaking method,
Porous fine cellulose fiber sheet forming step of obtaining a porous fine cellulose fiber sheet by at least drying the wet paper, and porous fine cellulose fiber composite sheet by impregnating the porous fine cellulose fiber sheet with a thermoplastic resin A compounding process to obtain
A method for producing a porous fine cellulose fiber composite sheet, comprising:

According to the present invention, it is possible to provide a composite sheet including a porous fine cellulose fiber sheet and a thermoplastic resin, which has a low coefficient of linear thermal expansion and a small anisotropy. The porous fine cellulose fiber composite sheet according to an aspect of the present invention can achieve excellent thermal linear expansion coefficient and mechanical properties with little anisotropy when used for, for example, an automobile outer panel component. Further, the porous fine cellulose fiber composite sheet according to an aspect of the present invention can exhibit a thermal linear expansion coefficient close to that of a metal and less anisotropy when used for, for example, a fender. It can contribute to weight reduction of the automobile.

A cross-sectional SEM image of a porous fine cellulose fiber composite sheet. The photograph which observed from the upper surface the porous fine cellulose fiber composite sheet in which the porous fine cellulose fiber sheet has a fractured portion with a length of 1 cm or more and a width of 1 cm or more. The photograph which observed the porous fine cellulose fiber composite sheet which has no breakage part in the porous fine cellulose fiber sheet from the upper surface. SEM image of fine cellulose fibers with a branched structure.

Hereinafter, an exemplary embodiment for implementing the present invention (hereinafter referred to as “the present embodiment”) will be described in detail. The present invention is not limited to the following embodiments, and various modifications can be carried out within the scope of the gist.

One aspect of the present invention includes the following requirements (1) to (4):
(1) Containing one or more layers of porous fine cellulose fiber sheet having an average fiber diameter of 2 nm or more and 1000 nm or less,
(2) The porous fine cellulose fiber sheet is arranged with a film thickness of 25 μm or more (preferably 25 μm or more and 2000 μm or less),
(3) Including a thermoplastic resin,
(4) Including a porosifying agent,
There is provided a porous fine cellulose fiber composite sheet that satisfies all of the above.

Another aspect of the present invention provides the following requirements (1) to (4):
(1) Containing one or more layers of porous fine cellulose fiber sheet having an average fiber diameter of 2 nm or more and 1000 nm or less,
(2) The porous fine cellulose fiber sheet is arranged with a film thickness of 25 μm or more (preferably 25 μm or more and 4000 μm or less),
(3) Including a thermoplastic resin,
(4) The porous fine cellulose fiber sheet is impregnated with the thermoplastic resin,
There is provided a porous fine cellulose fiber composite sheet that satisfies all of the above.

In one aspect, the porous fine cellulose fiber composite sheet of the present disclosure includes a porosifying agent.
In one aspect, the porous fine cellulose fiber composite sheet of the present disclosure includes one or more base sheet layers.
In one aspect, the porous fine cellulose fiber composite sheet of the present disclosure contains a blocked polyisocyanate or a crosslinked product thereof.

Another aspect of the present invention provides the following requirements (1) to (6):
(1) Containing one or more layers of porous fine cellulose fiber sheet having an average fiber diameter of 2 nm or more and 1000 nm or less,
(2) At least one base sheet layer is included,
(3) The porous fine cellulose fiber sheet is arranged with a film thickness of 25 μm or more,
(4) Including a thermoplastic resin,
(5) Including a porosifying agent,
(6) Including a blocked polyisocyanate or a crosslinked product thereof,
There is provided a porous fine cellulose fiber composite sheet that satisfies all of the above.

The porous fine cellulose fiber sheet of this embodiment is composed of fine cellulose fibers. In the present disclosure, “fine cellulose fibers” means cellulose fibers having a number average fiber diameter of 2 to 1000 nm. In an exemplary embodiment, the finely divided cellulose fibers have a crystalline structure of cellulose type I and/or type II. Known crystal forms of cellulose include I type, II type, III type, IV type and the like. Type I and type II celluloses are commonly used, while type III and type IV celluloses have been obtained on a laboratory scale but not on an industrial scale. As the fine cellulose fibers, cellulose I-type crystals are more preferable because they are resistant to deterioration by heating when forming a composite sheet and have a high tensile elastic modulus.

The crystal structure can be identified from the diffraction profile obtained from wide-angle X-ray diffraction using CuKα (λ=0.15418 nm) monochromated 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 crystallinity of the fine cellulose fiber of this embodiment is preferably 50% or more. When the crystallinity is within this range, the mechanical properties (in particular, strength and dimensional stability) of the fine cellulose fibers themselves are enhanced, so that the strength and dimensional stability of the porous fine cellulose fiber sheet and the porous fine cellulose fiber composite sheet are improved. Tends to be higher. The crystallinity of the fine cellulose fiber of the present embodiment is more preferably 60% or more, further preferably 65%, and most preferably 70%. The higher the crystallinity of the fine cellulose fibers, the more preferable it is. Therefore, the upper limit is not particularly limited, but from the viewpoint of production, 99% is the preferable upper limit.

When the fine cellulose fibers are cellulose type I crystals (derived from natural cellulose), the crystallinity is determined by the Segal method from the diffraction pattern (2θ/deg. is 10 to 30) when the sample is measured by wide-angle X-ray diffraction. Is calculated by the following formula (1).

Crystallinity (%)=[I ₍₂₀₀₎ −I _(amorphous) ]/I ₍₂₀₀₎ ×100 Formula (1)
I ₍₂₀₀₎ : Diffraction peak intensity due to 200 plane (2θ=22.5°) in cellulose I type crystal I _(amorphous) : Halo peak intensity due to amorphous state in cellulose I type crystal, which is 4 from the diffraction angle of 200 plane. Peak intensity at 0.5° low angle side (2θ=18.0°)

Further, the crystallinity is 2θ=12.6 which is attributed to the (110) plane peak of the cellulose II type crystal in wide-angle X-ray diffraction when the fine cellulose fiber is a cellulose II type crystal (derived from regenerated cellulose). From the absolute peak intensity h0 at ° and the peak intensity h1 from the baseline at this plane interval, it is determined by the following equation (2).
Crystallinity (%)=h1/h0×100 Formula (2)

The degree of polymerization (DP) of the fine cellulose fibers is preferably 100 or more and 12000 or less. The degree of polymerization is the number of repeats of anhydroglucose units forming a cellulose molecular chain. Since the degree of polymerization of the fine cellulose fibers is 100 or more, the tensile breaking strength and elastic modulus of the fine cellulose fibers themselves are improved, and the high tensile breaking strength and thermal stability of the porous fine cellulose fiber composite sheet are expressed. preferable. There is no particular upper limit to the degree of polymerization of the fine cellulose fibers, but cellulose having a degree of polymerization of more than 12000 is practically difficult to obtain, and industrial utilization tends to be difficult. From the viewpoint of handleability and industrial implementation, the degree of polymerization of the fine cellulose fibers is preferably 150 to 8000. Regarding the degree of polymerization, first, the intrinsic viscosity (JIS P 8215:1998) of a dilute solution of cellulose using a copper ethylenediamine solution is determined, and then the intrinsic viscosity of cellulose and the degree of polymerization DP have the relationship of the following formula (3). Is used to obtain the degree of polymerization DP.
Intrinsic viscosity [η]=K×DPa Formula (3)
Here, K and a are constants determined by the type of polymer, and in the case of cellulose, K is 5.7×10 ⁻³ and a is 1.

The fine cellulose fibers of this embodiment may be chemically modified. For example, hydroxyl groups present on the surface of fine cellulose fibers are esterified to ester acetate, nitrate ester, sulfate ester, phosphate ester, etc. (esterified fine cellulose fibers), alkyl ethers represented by methyl ether, and carboxymethyl. Carboxy ether represented by ether, etherified to cyanoethyl ether, etc. (etherified fine cellulose fiber), silyl etherified by silane coupling agent (silylated fine cellulose fiber), TEMPO (2,2,2) 6,6-tetramethylpiperidinooxy radical) oxidation catalyst oxidizes the hydroxyl group at the 6-position to give a carboxyl group (including acid type and salt type) (carboxylated fine cellulose fiber). The chemical modification increases the affinity between the resin and the fine cellulose fibers, and improves the tensile breaking strength and thermal stability of the porous fine cellulose fiber composite sheet. The chemical modification is preferably esterification, more preferably acetylation, from the viewpoint of simplifying the reaction process and improving the heat resistance of the fine cellulose fibers themselves.

The degree of esterification (preferably the degree of acetylation) (DS) of the fine cellulose fibers is preferably 0.1 or more and 1.5 or less, more preferably 0.2 or more and 1.2 or less. When the DS is in the range of 0.1 or more and 1.5 or less, the heat resistance is high, the affinity with the resin is high, and the physical properties such as CTE of the porous fine cellulose fiber composite sheet are improved, which is preferable. The calculation of DS can be performed by infrared spectroscopic measurement of fine cellulose fibers.
Ratio of peak intensity of absorption band based on chemical modifying group (peak height of absorption band of C═O based on ester group) to peak intensity (height) of absorption band of C—O of cellulose skeleton The modification ratio (IR index 1030) defined by the peak height of the absorption band based on the above/the peak height of the absorption band of the cellulose skeleton C—O is preferably 0.02 or more and 0.37 or less.
The IR index can be converted into an average substitution degree (DS) by the following formula (4).
DS=4.13×IR index formula (4)

The chemical modification may occur on some (eg, both internal or surface) or all (eg, both internal and surface) of the fine cellulosic fibers, but the chemical modification only occurs on some of the fine cellulosic fibers. As a result, the cellulose skeleton can be left in the fine cellulose fibers. For example, only the surface of the fine cellulose fiber can be chemically modified to leave the cellulose skeleton in the center. High tensile breaking strength derived from cellulose when a part of the fine cellulose fiber is chemically modified and the fine cellulose fiber has a crystal structure (typically type I and/or type II, preferably type I) And, while maintaining the dimensional stability, the heat resistance is improved by chemical modification, the affinity between the resin and the fine cellulose fiber in the porous fine cellulose fiber composite sheet is improved, and the dimensional stability of the porous fine cellulose fiber composite sheet is improved. It is more preferable because the improvement can be realized.

The number average fiber diameter of the fine cellulose fibers of the present embodiment is 2 nm or more and 1000 nm or less, preferably 10 nm or more and 800 nm or less, more preferably 20 nm or more and 500 nm or less, further preferably 20 nm or more and 400 nm or less, particularly preferably 30 nm or more and 300 nm or less. This range is advantageous in maintaining the strength and dimensional stability of the sheet, and forming minute and uniform pore sizes. When the number average fiber diameter of the fine cellulose fibers is less than 2 nm, keratinization due to aggregation of the fine cellulose fibers is likely to occur in the drying step in the production of the porous fine cellulose fiber sheet, and the porous fine cellulose fibers having a desired porosity. I can't get a seat. On the other hand, when the number average fiber diameter of the fine cellulose fibers exceeds 1000 nm, the effect as a filler is small because the interface between the resin and the fine cellulose fibers is small, and the desired tensile breaking strength and thermal stability of the composite sheet (specifically, , Low linear thermal expansion coefficient, and elastic retention at high temperature) cannot be obtained.

As the fiber diameter of the fine cellulose fiber of the present embodiment, the specific surface area equivalent diameter calculated from the specific surface area is used. In the present disclosure, the specific surface area equivalent diameter is a diameter calculated from the specific surface area obtained by the BET method by nitrogen adsorption.

The specific surface area-equivalent diameter is measured using a BET method by nitrogen adsorption on a porous fine cellulose fiber sheet prepared by drying an aqueous dispersion of fine cellulose fibers with a solvent and then drying the solvent. It is calculated from the specific surface area thus obtained. The relationship between the specific surface area and the equivalent surface area of the specific surface area is i) an ideal state in which there is no aggregation between the fine cellulose fibers, and ii) the cellulose density is d (g/cm ³ ) and the diameter is D ( nm), it is represented by the following equation (5).
Specific surface area (m ² /g)=4000/(dD) Formula (5)
Then, when the cellulose density is 1.50 g/cm ³ , the specific surface area equivalent diameter is represented by the following formula (6).
D (nm)=2667/specific surface area (m ² /g) Formula (6)

The fine cellulose fibers of the present embodiment preferably include fibers having a structure in which a thick trunk having a fiber diameter of 1 μm to 30 μm branches fine branches having a fiber diameter of 2 nm to 1000 nm (see FIG. 4). In the production of a composite sheet by impregnation with a resin film, a porous fine cellulose fiber sheet is subjected to high heat and pressure by hot pressing. Therefore, the porous fine cellulose fiber sheet is required to have a certain strength or more, and the thick film is preferable.
However, originally, the production of a sheet using fine cellulose fibers is characterized by 1) longer draining time, 2) longer drying time, 3) distortion of the sheet due to drying shrinkage, compared to general pulp. However, this tendency becomes more remarkable as the sheet weight increases and the film thickness increases, and the productivity decreases. In order to solve such problems, it is required to increase the number average fiber diameter of the fine cellulose fibers in order to secure a certain productivity.
On the other hand, the fact that the porous fine cellulose fiber sheet has a high specific surface area is important for improving the tensile rupture strength and thermal stability of the fine cellulose fiber composite sheet.
Therefore, when the fine cellulose fibers having the branched structure are included, these problems can be solved.

The presence or absence of the fine cellulose fibers having the branched structure can be confirmed by the following method. That is, using a high-shear homogenizer (for example, trade name "Excel Auto Homogenizer ED-7" manufactured by Nippon Seiki Co., Ltd.) of fine cellulose fibers dispersed in water or a water-soluble organic solvent, processing conditions: rotation speed 15,000 rpm × A water dispersion dispersed for 5 minutes was diluted with pure water to 0.1 to 0.5% by mass, cast on a hydrophilized Si substrate, and air dried to obtain a measurement sample, which was a scanning type. Observe 10 visual fields with an electron microscope (SEM) at a magnification of 2000 times (the visual field size is 60 μm×60 μm). Of 10 fields of view, it is preferable that at least one field of fine cellulose fibers having the branched structure is confirmed, more preferably at least 2 fields of view, further preferably at least 3 fields of view.

The number average fiber length of the fine cellulose fibers is not particularly limited, but is preferably 200 nm or more, more preferably 500 nm or more, further preferably 1000 nm or more. The ratio (L/D) of the number average fiber length (L)/number average fiber diameter (D) of the fine cellulose fibers is preferably 30 or more, more preferably 100 or more, still more preferably 200 or more, still more preferably 300. As described above, it is most preferably 500 or more, preferably 5000 or less, more preferably 4000 or less, still more preferably 3000 or less. When the ratio L/D of the number average fiber length (L)/the number average fiber diameter (D) is 30 or more, the fine cellulose fibers are highly entangled with each other, and the obtained sheet has high self-sustaining property and is a porous fine cellulose fiber sheet. Can be easily obtained. On the other hand, when it is 5000 or less, when the porous fine cellulose fiber sheet is continuously produced, the remarkable orientation of the fine cellulose fiber in the porous fine cellulose fiber sheet does not occur, and the porous fine cellulose fiber composite sheet It has small anisotropy in tensile strength at break and coefficient of thermal expansion, and is preferable in applications such as automobile parts.

For the L/D of the fine cellulose fibers, an aqueous dispersion of the fine cellulose fibers was used with a high shear homogenizer (eg, Nihon Seiki Co., Ltd., trade name “Excel Auto Homogenizer ED-7”), and processing conditions: rotation speed 15, An aqueous dispersion dispersed at 000 rpm for 5 minutes was diluted with pure water to 0.1 to 0.5% by mass, cast on mica, and air-dried to obtain a measurement sample, which was used as a high-resolution scanning microscope (SEM). ) Or by measuring with an atomic force microscope (AFM). Specifically, the number average fiber length and the number average fiber diameter of 100 randomly selected fine cellulose fibers are selected in an observation visual field in which the magnification is adjusted so that at least 100 fine cellulose fibers are observed. measure. The L/D of each fine cellulose fiber was calculated from this value, and the average value was L/D.

The porous fine cellulose fiber sheet of the present embodiment preferably has a sheet areal weight W of 20 g/m ² or more and 1000 g/m ² or less, or 20 g/m ² or more and 500 g/m ² or less, or 20 g/m ² or more and 200 g. /M ² , or 40 g/m ² or more and 150 g/m ² or less, or 60 g/m ² or more and 120 g/m ² or less. When the basis weight is 20 g/m ² or more, the porous fine cellulose fiber sheet is less likely to break during hot pressing with a thermoplastic resin, which is preferable. When the basis weight is 1000 g/m ² or less, the resin easily impregnates the inside of the porous fine cellulose fiber sheet during hot pressing with the thermoplastic resin, which is preferable. The weight is evaluated by cutting a sample stored in an environment controlled at room temperature of 23° C. and a humidity of 50% RH for 24 hours into 20 cm×20 cm (area 0.04 m ² ) and measuring the weight W1 (g). Calculated from (7).
Basis weight W (g/m ² )=W1/0.04 formula (7)

The thickness of the porous fine cellulose fiber sheet of the present embodiment is, in one aspect, 25 μm or more, preferably 25 μm or more and 4000 μm or less, more preferably 25 μm or more and 2000 μm or less, more preferably 25 μm or more and 1000 μm or less, more preferably 25 μm or more and 500 μm or less. , More preferably 50 μm or more and 300 μm or less, still more preferably 75 μm or more and 200 μm or less. When the thickness is less than 25 μm, the porous fine cellulose fiber sheet is likely to be broken during hot pressing with the thermoplastic resin. A thickness of 4000 μm or less, particularly 2000 μm or less is preferable for continuous production without lengthening the resin impregnation time when producing a composite sheet with a thermoplastic resin. The porous fine cellulose fiber sheet in the porous fine cellulose fiber composite sheet may be present in one layer or two or more layers. In the case of two or more layers, the total thickness of the porous fine cellulose fiber sheet portion in the porous fine cellulose fiber composite sheet may be 50 μm or more and 4000 μm or less, or 100 μm or more and 3000 μm or less, or 200 μm or more and 2000 μm or less. The thickness is measured at 23° C. and 50% RH in an environment of porous fine cellulose fiber sheet (20 cm×20 cm) left standing for 1 day, whereas in the case of porous fine cellulose fiber sheet, arbitrary 10 points are set. It is measured by a contact type film thickness meter, and the number average value is taken as the thickness (μm). In the case of a porous fine cellulose composite sheet, the cross section of the composite sheet is cut out, and SEM observation or optical microscope observation of 10 cross sections is arbitrarily performed, and the thickness of the fine cellulose fiber sheet is measured at each place. The obtained measurement value×the number average value at the above 10 points is calculated to obtain the thickness (μm) of the fine cellulose fiber sheet.

The average air permeation resistance per unit weight of 10 g/m ² of the porous fine cellulose fiber sheet of the present embodiment is preferably 1 sec/100 ml or more and 7000 sec/100 ml or less, more preferably 1 sec/100 ml or more and 6000 sec/100 ml or less, and more preferably Is from 1 sec/100 ml to 5000 sec/100 ml, more preferably from 10 sec/100 ml to 4000 sec/100 ml, even more preferably from 100 sec/100 ml to 3000 sec/100 ml, and most preferably from 200 sec/100 ml to 2000 sec/100 ml. When the air resistance is 7,000 sec/100 ml or less, the porosity does not become too low, the resin can be easily impregnated into the sheet, and a porous fine cellulose fiber composite sheet can be easily produced, which is preferable. In addition, although it is preferable that the air permeability resistance is low due to the nature of the sheet, it is difficult to make air permeability resistance smaller than 1 sec/100 ml due to the fineness of the network, so the average air permeability resistance per unit weight of 10 g/m ² The degree is preferably 1 sec/100 ml or more.

The air permeation resistance is the time required for 100 ml of air to pass through the sheet, and the larger the value, the denser the air. An Oki type air resistance tester (for example, Model EG01 manufactured by Asahi Seiko Co., Ltd.) is used for the measurement. For one sheet sample (20 cm×20 cm), 10 points are measured at different positions at room temperature, and the average value is taken as the average air resistance (AR). At this time, the weight per unit area W of the base paper, which has been measured in advance, is used to calculate the value per unit weight per 10 g/m ² from the following formula (8).
Permeation resistance per unit weight of 10 g/m ² =AR/W×10 Formula (8)

The porous fine cellulose fiber sheet of the present embodiment has excellent porous retention before and after the wet and dry operation. Specifically, the rate of change in air permeation resistance before and after the wet-drying operation is 100% or less, preferably 80% or less, and more preferably 70% or less. When the rate of change is 100% or less, when the porous fine cellulose fiber composite sheet is produced by impregnating the water-soluble resin into the porous fine cellulose fiber composite sheet, shrinkage of the porous fine cellulose fiber composite sheet is small, It is preferable because it is easy to produce a porous fine cellulose fiber composite sheet having a uniform film thickness. On the other hand, there is no particular lower limit to 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 evenly applied to a stationary porous fine cellulose fiber sheet so that the sheet moisture content is 300% by mass or more and 400% by mass or less and then dried in an oven. .. The air permeation resistance of the sheet is measured before and after this operation, and the change is taken as the rate of increase in air permeation resistance. The sheet moisture content is calculated from the following formula (9) using the initial sheet W2 and the wet sheet weight W3.
Moisture content of sheet=(W3-W2)/W2×100 Formula (9)

As a specific measuring method, a porous fine cellulose fiber sheet (20 cm×20 cm), which has been allowed to stand for 1 day in an environment of 23° C. and 50% RH, is cut into 5 cm×5 cm, and 5 sheets are selected from there. The air permeation resistance of each of the five samples is measured, and the measurement place is marked. This air permeation resistance is defined as the initial air permeation resistance R1, and the average value of five sheets is defined as AR1. Subsequently, the sample is placed on a metal plate, water is sprayed evenly on the metal plate, and water drops adhering to the periphery of the sample are wiped off. The sheet weight before and after this wetting operation is measured, and the sheet moisture content is measured according to the equation (9). After confirming that the water content at this time was 300% by mass or more and 400% by mass or less, it was dried in an oven at 80° C. for 1 hour, and the air permeation resistance at the marked place was measured again. Let this air permeability resistance be the air permeability resistance R2 after the operation, and let AR2 be the average value of the five samples. Finally, the air permeation resistance increase rate (%) is calculated from the following formula (10).
Permeation resistance increase rate (%)=(AR2-AR1)/AR1×100 Formula (10)

The dry fineness of the porous fine cellulose fiber sheet of this embodiment is preferably 1.5 kg/15 mm or more, more preferably 2.0 kg/15 mm or more, and further preferably 3.0 kg/15 mm or more. When it is 1.5 kg/15 mm or more, the porous fine cellulose fiber sheet is less likely to be broken at the time of hot pressing when compounded with the thermoplastic resin, which is preferable. On the other hand, there is no particular upper limit to the Dry strength of the porous fine cellulose fiber sheet of the present embodiment, but from the viewpoint of feasibility, it is 100 kg/15 mm or less.

As a method of measuring Dry strength, first, the basis weight (W) of a sample (20 cm × 20 cm) stored for 24 hours in an environment controlled at room temperature of 23°C and humidity of 50% RH is measured by the above method. Next, it is cut into a width of 15 mm, and the tensile strength at 10 points is measured using a tensile tester at a chuck distance of 100 mm and a tensile speed of 10 mm/min, and the average value is defined as the Dry strength (DS).

In the porous fine cellulose fiber sheet of the present embodiment, the non-aqueous Wet strength per unit weight of 10 g/m ² is preferably 0.3 kg/15 mm or more, more preferably 0.4 kg/15 mm or more, and 0.5 kg/ 15 mm or more is more preferable. In the case of 0.3 kg/15 mm or more, the porous fine cellulose fiber sheet is less likely to break during the production of the porous fine cellulose fiber composite sheet in which the impregnated resin and the solvent are hydrophobic, so that the use and production are easy. On the other hand, there is no particular upper limit for the non-aqueous Wet strength of the porous fine cellulose fiber sheet of the present embodiment, but from the viewpoint of feasibility, it is, for example, 8.0 kg/15 mm or less per unit weight of 10 g/m ² . The non-aqueous liquid referred to here is methyl cellosolve.

As the non-aqueous Wet intensity measurement method, the same method is used except that the solvent used in the aqueous Wet intensity measurement method is changed to methyl cellosolve. The average value of the tensile strength at 10 points is defined as the non-aqueous Wet strength (NWS), and the non-aqueous Wet strength per 10 g/m ² basis weight (kgf/15 mm) is calculated using the basis weight (W) of the base paper that was measured in advance. It is calculated from (11).
Non-aqueous wet strength per unit weight of 10 g/m ² (kgf/15 mm)=NWS/W×10 Formula (11)

The porosity of the porous fine cellulose fiber sheet of the present embodiment is preferably 20% or more and 90% or less. When the porosity is 20% or more, it can be regarded as porous having good porosity, and the resin can be easily impregnated into the porous fine cellulose fiber sheet. On the other hand, when the porosity is 90% or less, the porous fine cellulose fiber sheet has flexibility and the porous fine cellulose fiber composite sheet can be easily manufactured.
The porosity means the volume ratio of voids in the porous fine cellulose fiber sheet. The porosity can be determined by the following formula (12) from the area, thickness and weight of the porous fine cellulose fiber sheet.
Porosity (volume %)={(1-B/(M×A×t)}×100 Formula (12)
Here, A is the area of the porous fine cellulose fiber sheet (cm ² ), t is the thickness (cm), B is the weight of the porous fine cellulose fiber sheet (g), and M is the density of cellulose (1.5 g in this embodiment). /Cm ³ ).

The specific surface area of the porous fine cellulose fiber sheet of the present embodiment is preferably 1 m ² /g or more and 500 m ² /g or less, more preferably 1 m ² /g or more and 300 m ² /g or less, further preferably 1 m ² /g or more. 200 m ² /g or less, more preferably 1 m ² /g or more and 100 m ² /g or less, particularly preferably 2 m ² /g or more and 90 m ² /g or less, most preferably 3 m ² /g or more and 80 m ² /g or less. .. The above-mentioned specific surface area means the BET specific surface area measured by the nitrogen gas adsorption method. When the specific surface area of the porous fine cellulose fiber sheet is 1 m ² /g or more, a porous fine cellulose fiber composite sheet having good porosity can be produced. On the other hand, when the specific surface area is 500 m ² /g or less, it is easy to produce a porous fine cellulose fiber sheet.

In one aspect, the porous fine cellulose fiber composite sheet can include one or more base material sheet layers. More specifically, the porous fine cellulose fiber sheet of the present embodiment has at least one fine cellulose fiber layer that is the porous fine cellulose fiber sheet, and a base sheet layer (hereinafter, also referred to as a base sheet). ) It may be provided in the form of a porous fine cellulose fiber laminated sheet containing one or more layers. For example, a porous fine cellulose fiber laminated sheet in which a fine cellulose fiber layer is arranged on a base material sheet, a porous fine cellulose fiber laminated sheet composed of three or more layers in which a fine cellulose fiber layer is sandwiched between base material sheets, a base material Examples include a porous fine cellulose fiber laminated sheet in which fine cellulose fiber layers are arranged on both sides of the sheet. Further, when the porous fine cellulose fiber laminated sheet contains two or more base material sheets, or two or more fine cellulose fiber layers, two or more kinds of base material sheets, or two or more kinds of base material sheets. It may be composed of a fine cellulose fiber layer.

The form of the base material sheet of the present embodiment may be a sheet form, and examples thereof include a woven fabric, a knitted fabric, a long fiber nonwoven fabric, a short fiber nonwoven fabric, and a microporous membrane.

The constituent fibers of the woven fabric, knitted fabric, long-fiber non-woven fabric, or short-fiber non-woven fabric constituting the base sheet are not particularly limited, and examples thereof include 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 spun yarns of these fibers. Also, these fibers may be used alone or in combination.

The microporous membrane is not particularly limited, but regenerated cellulose, polyolefin resin such as polyethylene and polypropylene, polysulfone, polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, polycarbonate, 6-nylon, 6,6 -Polyamide resins such as nylon, acrylic resins such as polymethylmethacrylate, polyketones, polyether ether ketones and the like.

Hereinafter, an example of a method for producing the porous fine cellulose fiber sheet and the porous fine cellulose fiber composite sheet of the present embodiment will be described, but the method is not particularly limited to this method.

The porous fine cellulose fiber sheet and the porous fine cellulose fiber composite sheet of the present embodiment preferably contain a porosifying agent in the sheet from the viewpoint of satisfactorily impregnating the thermoplastic resin inside the porous fine cellulose fiber sheet. .. The porosifying agent contained in each of the above sheets is preferably 0.1% by mass or more and 100% by mass or less, more preferably 0.1% by mass or more and 50% by mass or less, and 0.1% by mass or less of the weight of the fine cellulose fiber. It is more preferably 30% by mass or less.

Usually, a fine film is formed when a fine cellulose fiber slurry consisting of water and fine cellulose fibers is made into a sheet (for example, papermaking) and dried. On the other hand, when the slurry containing the porosifying agent is formed into a sheet and dried, a porous fine cellulose fiber sheet can be satisfactorily formed. Further, since the porosifying agent remains in the sheet even after drying, it is possible to suppress an increase in air permeation resistance even when performing a wet drying operation. When the amount of the porosifying agent is 0.1% by mass or more, the amount of the porosifying agent is large and the desired air permeation resistance can be satisfactorily achieved. When the content is 100% by mass or less, it is possible to avoid an increase in air permeation resistance due to the pores being filled with the porosity-imparting agent, and the liquid porosity-imparting agent is preferable for continuous production because it does not exude from the sheet.

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 less than 0° C. and not soluble in 2) water is preferable. The temperature of the drying step of the sheet production is usually less than 250° C., and if the boiling point of the porosifying agent is 250° C. or more under atmospheric pressure, it is difficult to vaporize in the drying step, so it is not necessary to introduce an exhaust facility, The load in continuous production can be reduced. On the other hand, there is no particular upper limit of the boiling point, but from the viewpoint of feasibility, it may be 400° C. or lower.

The phrase "not soluble in water" as used herein means that an aqueous dispersion of a porosifying agent having a solid content of 1% by mass becomes cloudy at 23°C, or separates into an aqueous layer and an oil layer. Specifically, 99 g of ion-exchanged water and 1 g of a porosifying agent (solid content 100% by mass) were added to a 100 ml glass vial, and the mixture was stirred at a magnetic stirrer of 750 rpm for 1 hour while controlling the temperature at 50° C., and then at 23° C. Judging from the turbidity and appearance when the temperature is lowered to 0 and stirring is stopped. First, it is visually confirmed whether or not the layer is separated into two layers, and if the layer is separated into two layers, it is determined that "it is not dissolved in water". In addition, when the turbidity is not separated into two layers, the turbidity is measured using a turbidimeter, and when the turbidity is 1 NTU or more, it is judged as “not dissolved in water”. The turbidity is preferably 1 NTU or higher, more preferably 3 NTU or higher, further preferably 5 NTU or higher, and most preferably 10 NTU or higher. As a method for measuring turbidity, a turbidimeter (for example, TN100 (manufactured by Eutech)) is used, and 10 ml is put in the measurement vial so that bubbles do not enter the measurement. When the solid content of the porosifying agent is less than 100% by mass, the amount of ion-exchanged water added is adjusted so that the final water dispersion becomes 1% by mass.

　In the fine cellulose fiber slurry, the porosifying agent does not dissolve in the slurry and therefore exists as oil droplets, and it is considered that the fine cellulose fibers surround the oil droplets. Then, it is considered that some or all of the oil droplets remain on the sheet and become porous when it is formed into a sheet (for example, papermaking). Therefore, it is desirable as a porosifying agent that it can exist as droplets in water, that is, it does not dissolve in water. The droplets can also be used in a form in which they self-assemble in water such as phospholipids to form a vesicle structure and become cloudy. Further, even when the phase is completely separated 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 is forcibly emulsified with a surfactant or the like, and even stable droplets in water can be used. On the other hand, when the porosifying agent is completely dissolved in water, most of the porosifying agent flows out as a filtrate at the time of forming into a sheet, so that the porosifying agent does not remain in the fine cellulose fibers and is excellent as a porosifying agent. It doesn't work.

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

As the above hydrocarbon group, a group having 2 to 40 carbon atoms is preferable from the viewpoint of low solubility in water and excellent 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 above-mentioned perfluoroalkyl group has a carbon number of 1 to 10, for example 1 to 8, particularly 1 to 6, especially 4 or 4 from the viewpoint of low solubility in water and excellent affinity with resins. A group of 6 is preferable, and examples thereof include —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.

The above-mentioned organosiloxane structure has an average composition represented by the general formula (1): from the viewpoint of low solubility in water and excellent affinity with a resin.
R ¹ _a SiO _(4-a)/2 (1)
[In the formula, R ^{1 s} may be the same or different in the molecule, and are a hydrogen atom, a hydroxyl group, a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, and a substituent having 1 to 20 carbon atoms. Alternatively, it is selected from unsubstituted alkoxy groups and a is a natural number of 1.0 to 3.0. ]
The structure represented by is preferred.

R ¹ of 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, but as a specific example in this case Is an alkyl group such as methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, dodecyl group, tetradecyl group, hexadecyl group, octadecyl group; vinyl group A cycloalkyl group such as an allyl group, a cyclopentyl group and a cyclohexyl group; an aryl group such as a phenyl group; and an aralkyl group such as 2-phenylethyl and 2-phenylpropyl.

When R ¹ is a substituted monovalent hydrocarbon group, examples of the hydrocarbon substituent include an amino group, an aminoalkyl group, a halogen atom, a nitrile group, a polyoxyalkylene group and the like. Examples of the alkoxy group include a methoxy group having 1 to 3 carbon atoms, an ethoxy group, and a propyl group.

A in the general formula (1) represents the average number of R ¹ bonded to the silicon atom of the polysiloxane, and is 1.0 to 3.0. The organosiloxane molecular structure whose average composition is represented by the general formula (1) may have not only a linear structure but a branched structure, but preferably has a linear structure. When the porosifying agent is an organosiloxane, preferred specific examples include trimethylsiloxy-terminated dimethyl silicone, hydroxy-terminated dimethylsilicone, and methylhydrogensiloxane, with trimethylsiloxy-terminated dimethylsilicone and hydroxy-terminated dimethylsilicone being preferred. ..

The porosifying agent of the present embodiment comprises a vinyl-based monomer, a (meth)acrylate-based monomer, a (meth)acrylamide-based monomer, and a styrene-based monomer containing the above-mentioned hydrocarbon group, perfluoroalkyl group, and/or organosiloxane structure. The polymer compound may include at least one kind of monomer unit selected from the group consisting of two or more kinds of monomer units at the same time in the polymer compound skeleton.

The hydrocarbon group-containing monomer is not particularly limited, and examples thereof include methyl (meth)acrylate, butyl (meth)acrylate, t-butyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and lauryl. (Meth)acrylate, tetradecyl (meth)acrylate, octadecyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, trimethylcyclohexyl (meth)acrylate, cyclodecyl (meth)acrylate, cyclodecylmethyl (meth)acrylate, Examples thereof include alkyl, alkenyl, cycloalkyl, such as tricyclodecyl (meth)acrylate, benzyl (meth)acrylate, and allyl (meth)acrylate, and (meth)acrylate having an aromatic ring.

The monomer containing a perfluoroalkyl group and the monomer containing an organosiloxane structure are not particularly limited, but examples thereof include the following.
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'is a hydrogen atom, a methyl group, a fluorine atom, or a trifluoromethyl group, and Rf is the perfluoroalkyl group or the organosiloxane structure. ]

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

Incidentally, when the amphipathic compound is a polymer, the polymerization form is not particularly limited, for example, a block copolymer, a gradient copolymer, a graft copolymer, a random copolymer, a tapered copolymer, Examples include periodic copolymers. Of these, block copolymers and graft copolymers are preferred because they are self-emulsifying in water and are easily clouded.

The hydrophilic functional group is not particularly limited, but it may be a hydroxyl group, a thiol group, a carboxyl group, a sulfonic acid group, a sulfuric acid ester group, a phosphoric acid group, a sulfuric acid group or —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 (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.) and the like. The porosifying agent of the present embodiment may include one or more of these hydrophilic groups in the molecular skeleton, and may include two or more different hydrophilic groups at the same time.

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

The (meth)acrylate-based monomer is not particularly limited, and examples thereof include a hydroxyl group-containing (meth)acrylate such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 3-hydroxypropyl (meth)acrylate. Polyalkylene glycol mono(meth)acrylates such as polyethylene glycol mono(meth)acrylate and polypropylene glycol mono(meth)acrylate; (poly)ethylene glycol monomethyl ether (meth)acrylate, (poly)ethylene glycol monoethyl ether (meth ) Acrylate, glycol ether type (meth)acrylate such as (poly)propylene glycol monomethyl ether (meth)acrylate, glycidyl (meth)acrylate, 3,4-epoxycyclohexyl (meth)acrylate, (meth)acryloyloxyethyl Glycidyl ether-containing (meth)acrylates such as glycidyl ether and (meth)acryloyloxyethoxyethyl glycidyl ether; (meth)acryloyloxyethyl isocyanate, 2-(2-isocyanatoethoxy)ethyl (meth)acrylate, and isocyanates thereof Isocyanate group-containing (meth)acrylates such as monomers whose isocyanates are blocked with ε-caprolactone, methylethylketoxime, and pyrazole; oxygen atom-containing cyclic (meth)acrylates such as oxetanylmethyl (meth)acrylate; dimethylaminoethyl (meth) ) Acrylate, diethylaminoethyl (meth)acrylate, t-butylaminoethyl (meth)acrylate, and other amino group-containing (meth)acrylates and quaternary ammonium type thereof. In addition, both "poly" and "(poly)" in the above mean n=2 or more.

In the amphipathic 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.

The amphipathic compound having an anionic group and a hydrocarbon group is not particularly limited, but examples thereof include the following compounds.
(1) A linear or branched alkylbenzene sulfonate.
(2) A 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 alkenyl ether sulfate having a linear or branched alkenyl group to which an average of 0.5 to 10 mol 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 ethylene oxide (EO) and propylene oxide (PO) (EO/PO=0. 1/9.9 to 9.9/0.1).
(6) Alkyl phenyl ether sulfate having a linear or branched alkyl group or alkenyl phenyl ether sulfate having a linear or branched alkenyl group to which an average of 3 to 30 mol 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 to 9 in molar ratio). .9/0.1).
(7) Alkyl ether carboxylate having a linear or branched alkyl group or alkenyl ether carboxyl having a linear or branched alkenyl group to which an average of 0.5 to 10 mol of alkylene oxide is added 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 in molar ratio). Up to 9.9/0.1).

(8) Alkyl polyhydric alcohol ether sulfate such as linear or branched alkyl glyceryl ether sulfonate.
(9) Saturated or unsaturated α-sulfo fatty acid salt or its methyl, ethyl or propyl ester salt.
(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) Long-chain monoalkyl sulfonate, long-chain dialkyl sulfonate or long-chain sesquialkyl sulfonate.
(13) A fatty acid and a salt 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 an alkali metal salt such as sodium salt or potassium salt; an amine salt or an ammonium salt. Of these, alkali metal salts such as sodium salt and potassium salt are preferable.

The amphipathic compound having a cationic group and a hydrocarbon group is not particularly limited, but examples thereof include the following compounds.
(1) Di long chain alkyl di short 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 quaternary ammonium salt.
However, the above-mentioned “long-chain alkyl” refers to an alkyl group having 5 to 26 carbon atoms, preferably 8 to 18 carbon atoms.
The “short chain alkyl” is intended to include 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 of is mentioned as a suitable thing.

The amphipathic compound having an amphoteric group and a hydrocarbon group is not particularly limited, but examples thereof include imidazoline compounds and amidobetaine compounds. Specifically, 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine and lauric acid amidopropyl betaine are preferable.

The amphipathic compound having a nonionic group and a hydrocarbon group is not particularly limited, but examples thereof include the compounds shown below.
(1) Polyoxyalkylene alkyl in which an alkylene oxide having 2 to 4 carbon atoms is added to an aliphatic alcohol having 6 to 22 carbon atoms, preferably 8 to 18 carbon atoms, on average 1 to 30 mol, preferably 5 to 20 mol. Ethers or polyoxyalkylene alkenyl ethers. Among these, polyoxyethylene alkyl ether, polyoxyethylene alkenyl ether, polyoxyethylene polyoxypropylene alkyl ether, and polyoxyethylene polyoxypropylene alkenyl ether are preferred.
Examples of the aliphatic alcohol used here include primary alcohols and secondary alcohols, with primary alcohols being preferred. 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 the following general formula (2), for example, 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 alkylene oxide having 2 to 4 carbon atoms, preferably 2 to 3 carbon atoms (eg, ethylene oxide, propylene) Oxide, etc.); q represents the average number of moles of alkylene oxide added, and is generally 3 to 30, preferably 5 to 20. R ² represents a lower alkyl group having 1 to 4 carbon atoms, which may have a substituent group having 1 to 3 carbon atoms. ]
(4) Polyoxyethylene sorbitan fatty acid ester.
(5) Polyoxyethylene sorbit fatty acid ester.
(6) Polyoxyethylene fatty acid ester.
(7) Polyoxyethylene hydrogenated castor oil.
(8) Glycerin fatty acid ester.
(9) Polyoxyethylene alkylamine represented by the following general formula (3), polyoxyethylene alkylamide R ³ a-A-[(R ³ bO) _p -R ³ c] _q (3)
[In the formula, R ³ a represents an alkyl group or an 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 represents the average number of moles of the alkyleneoxy group added, preferably 2 or more and 100 or less, 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— Alternatively, 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

With respect to the amphipathic compound having a nonionic group and a hydrocarbon group, when the HLB is less than 12, the solubility in water is lowered and it is suitable as a porosifying agent. The above "HLB" is a value obtained by the Griffin's method (edited by Yoshida, Shindo, Ogaki and Yamanaka, "New Surfactant Handbook", Kogyo Tosho KK, 1991, p. 234. reference).

The amphipathic compound containing a perfluoroalkyl group is not particularly limited, and examples thereof include compounds in which the hydrophilic group is anionic or nonionic.
Examples of the amphipathic compound containing an anionic hydrophilic group and a perfluoroalkyl group include perfluoroalkylcarboxylic acid salts, perfluoroalkylphosphoric acid esters and perfluoroalkylsulfonic acid salts.

Examples of the amphipathic compound containing a nonionic hydrophilic group and a perfluoroalkyl group include perfluoroalkylethylene oxide adducts, perfluoroalkylamine oxides, perfluoroalkyl polyoxyethylene ethanol, perfluoroalkyl alkoxylates and the like. it can.

Specific examples include LE-604, LE-605, LINC-151-EPA (manufactured by Kyoeisha Chemical Co., Ltd.), Megafac (registered trademark) F171, 172, 173, F444, F477 (manufactured by DIC Corporation), Florard (registered trademark). Examples thereof include FC430, FC431 (manufactured by Sumitomo 3M Ltd.), Asahi Guard AG (registered trademark) 710, Surflon (registered trademark) S-382, SC-101, 102, 103, 104, 105 (manufactured by Asahi Glass Co., Ltd.). ..

The amphipathic compound containing an organosiloxane structure is not particularly limited, and examples thereof include those in which a hydrophilic group is introduced at the terminal or molecular chain of organosiloxane. Examples thereof include organosiloxanes modified with a hydrophilic group such as polyoxyethylene-modified organosiloxane, polyoxyethylene/polyoxypropylene-modified organosiloxane, polyoxyethylenesorbitan-modified organosiloxane, and polyoxyethyleneglyceryl-modified organosiloxane.

As specific examples, DBE-712, DBE-821 (manufactured by Azumax), 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 Gold Schmidt), Polyflow KL-100, Polyflow KL-401, Polyflow KL-402, Polyflow KL-700 (manufactured by Kyoeisha Chemical Co., Ltd.) and the like.

As the porosifying agent in the present embodiment, the above-mentioned bulking agent for paper having the characteristics of 1) boiling point at atmospheric pressure of 250° C. or higher and 2) insoluble in water can be used. For example, alkylene oxide adducts of higher alcohols (described in International Publication No. WO98/03730), polyhydric alcohol-type nonionic surfactants in which polyhydric alcohols are fats, sugar alcohols, sugars, etc. (JP-A-11-200283). ), alkylene oxide adducts of fatty acids (described in JP-A No. 11-200284), cationic compounds, amines, acid salts of amines (described in JP-A No. 11-269799, 2001-355197). A), an amphoteric compound (described in JP-A No. 11-269799), a polyhydric alcohol fatty acid ester (described in Patent No. 2971447, JP-A No. 11-350380), (A) organosiloxane, (B) glyceryl ether. , (C) amide, (D) amine, (E) amine acid salt, (F) quaternary ammonium salt, (G) imidazole, (H) polyhydric alcohol ester of fatty acid, and (I) polyhydric alcohol An ester of a fatty acid (Japanese Patent No. 3283248, JP-A-2003-105685, etc.), an amide compound obtained by reacting an aliphatic carboxylic acid with a polyamine are crosslinked with urea, and then obtained by reacting with an alkylating agent. Examples thereof include compounds obtained by reacting the amide compound with an alkylating agent, and then crosslinking with urea (described in JP-A-2005-60891).

The porosifying agent in this embodiment may be used alone or in combination of two or more kinds. Further, it may be emulsified and dispersed by a well-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 lower, preferably 40° C. or lower, more preferably 30° C. or lower, further preferably 20° C. or lower, mild addition during slurry addition is performed. It is suitable for manufacturing because it can be handled as a liquid at a high temperature. The melting point is a value measured by a melting point measuring method described in JIS K 0064-1992 “Measuring point and melting range of chemical products”.

The porous fine cellulose fiber sheet and the porous fine cellulose fiber composite sheet contains a porosifying agent, more specifically, a hydrocarbon group, a perfluoroalkyl group, and/or an organosiloxane structure. The sheet itself is analyzed by solid-state NMR (nuclear magnetic resonance), FT-IR (Fourier transform infrared spectroscopy) or other spectroscopy, or thermal decomposition GC-MS (gas chromatograph mass spectrometry), TOF-SIMS (time-of-flight secondary ion mass). It can be confirmed by a method of direct analysis by mass spectrometry such as analysis). Further, the porous fine cellulose fiber sheet and the porous fine cellulose fiber composite sheet are washed with a solvent such as acetone, dimethylacetamide or dimethylformamide, and the porosifying agent eluted in the washing liquid is subjected to solution NMR, FT-IR, LC. It is also possible to analyze by -MS (liquid chromatograph mass spectrometry), GC-MS and the like.

The porous fine cellulose fiber sheet and the fine cellulose fiber layer inside the porous fine cellulose fiber composite sheet of the present embodiment may contain a binder in addition to the fine cellulose fibers, and the DRY strength and WET of the porous fine cellulose fiber sheet. It is preferable from the viewpoint of improving the strength and preventing the fine cellulose fiber layer inside the porous fine cellulose fiber composite sheet from breaking during hot pressing. Polyurethane is preferable because of its excellent effect as a binder.

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

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 polyisocyanate, alicyclic polyisocyanate, aliphatic polyisocyanate, polyisocyanate derivative and the like. Among them, alicyclic polyisocyanates and aliphatic polyisocyanates are more preferable from the viewpoint of less 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), 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 alicyclic polyisocyanate raw material include alicyclic diisocyanates such as 1,3-cyclopentane diisocyanate, 1,3-cyclopentene diisocyanate, and cyclohexane diisocyanate.

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

As the polyisocyanate derivative, for example, in addition to the above-described multimers of polyisocyanate (for example, dimer, trimer, pentamer, heptamer, etc.), polyisocyanate may be used as one type of active hydrogen-containing compound or The compound obtained by making it react with 2 or more types is mentioned. The compound is an allophanate modified product (for example, an allophanate modified product produced by the reaction of polyisocyanate and alcohols), a polyol modified product (for example, a polyol modified product produced by the reaction of polyisocyanate and alcohols (alcohol addition Body)), biuret modified product (for example, biuret modified product formed by reaction of polyisocyanate with water or amines), urea modified product (for example, urea modified product formed by reaction of polyisocyanate and diamine) Etc.), oxadiazinetrione modified product (for example, oxadiazinetrione produced by reaction of polyisocyanate and carbon dioxide gas), carbodiimide modified product (carbodiimide modified product produced by decarboxylation condensation reaction of polyisocyanate, etc.), Examples include modified uretdione and modified uretonimine.

The active hydrogen-containing compound is not particularly limited, and examples thereof include a monovalent to hexavalent hydroxyl group-containing compound including a polyester polyol and a polyether polyol, an amino group-containing compound, a thiol group-containing compound, and a carboxyl group-containing compound. It also includes water, carbon dioxide, etc. existing in the air or in the reaction field.
Examples of the monovalent to hexavalent alcohols (polyols) include non-polymerized polyols and polymerized polyols. The non-polymerized polyol is a polyol that does not undergo polymerization history, and the polymerized polyol is a polyol obtained by polymerizing a monomer.

Examples of non-polymerized polyols include monoalcohols, diols, triols and tetraols. 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 can be mentioned. Examples of the 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-trimethylpentanediol, 2-butyl-2-ethyl-1,3-propanediol, 2,2-diethyl-1,3-propane Examples thereof include diol, phloroglucin, pyrogallol, catechol, hydroquinone, bisphenol A, bisphenol F, bisphenol S and the like. Examples of triols include glycerin and trimethylolpropane. Further, examples of the tetraols include pentaerythritol, 1,3,6,8-tetrahydroxynaphthalene, 1,4,5,8-tetrahydroxyanthracene and the like.

The polymerized polyol is not particularly limited, but examples thereof include polyester polyol, polyether polyol, acrylic polyol, polyolefin polyol and the like.

Examples of the polyester polyol include, for example, succinic acid, adipic acid, sebacic acid, dimer acid, maleic anhydride, phthalic anhydride, isophthalic acid, dicarboxylic acids such as terephthalic acid, alone or in a mixture, 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 a mixture, and polycaprolactones obtained by ring-opening polymerization of ε-caprolactone using polyhydric alcohols. And the like.

As the polyether polyol, for example, hydroxides of lithium, sodium, potassium, etc., alcoholates, strong basic catalysts such as alkylamines, metal porphyrins, complex metal cyanide compound complexes such as zinc hexacyanocobaltate complex, etc. are used. Polyether polyols and ethylenediamines obtained by randomly or block-adding alkylene oxides such as ethylene oxide, propylene oxide, butylene oxide, cyclohexene oxide, and styrene oxide, alone or as a mixture, to a polyhydric hydroxy compound alone or as a mixture. Polyether polyols obtained by reacting a polyamine compound such as alkylene oxide. So-called polymer polyols and the like obtained by polymerizing acrylamide or the like using these polyethers as a medium are also included.

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 and rhamnitol,
3) For example, monosaccharides such as arabinose, ribose, xylose, glucose, mannose, galactose, fructose, sorbose, rhamnose, fucose and ribodeose,
4) Disaccharides such as trehalose, sucrose, maltose, cellobiose, gentiobiose, lactose and melibiose,
5) For example, trisaccharides such as raffinose, gentianose and melezitose,
6) Tetrasaccharides such as stachyose,
Etc.

Examples of the acrylic polyol include acrylic acid esters having active hydrogen such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and 2-hydroxybutyl acrylate, acrylic acid monoesters of glycerin, and methacrylic acid. Monoester, acrylic acid monoester or methacrylic acid monoester of trimethylolpropane, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 3-hydroxypropyl methacrylate, Methyl acrylate, ethyl acrylate, isopropyl acrylate, -n-butyl acrylate, which is used alone or as a mixture selected from the group of methacrylic acid esters having active hydrogen such as 4-hydroxybutyl methacrylate, is an essential component. Acrylic acid esters such as 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, methacrylate-n-butyl methacrylate, isobutyl methacrylate, methacrylate-n-hexyl, lauryl methacrylate, etc. Unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid and itaconic acid, unsaturated amides such as acrylamide, N-methylol acrylamide and diacetone acrylamide, and glycidyl methacrylate, styrene, vinyltoluene, vinyl acetate, acrylonitrile, Presence of a single or a mixture selected from the group of other polymerizable monomers such as vinyl monomers having a hydrolyzable silyl group such as dibutyl fumarate, vinyltrimethoxysilane, vinylmethyldimethoxysilane and γ-methacryloxypropylmethoxysilane. An acrylic polyol obtained by polymerizing under or in the absence thereof may be mentioned.

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

Examples of the amino group-containing compound include monohydrocarbylamines having 1 to 20 carbon atoms [alkylamine (butylamine etc.), benzylamine and aniline etc.], aliphatic polyamines having 2 to 20 carbon atoms (ethylenediamine, hexamethylenediamine and Diethylenetriamine, etc.), alicyclic polyamines having 6 to 20 carbon atoms (diaminocyclohexane, dicyclohexylmethanediamine, isophoronediamine, etc.), aromatic polyamines having 2 to 20 carbon atoms (phenylenediamine, tolylenediamine, diphenylmethanediamine, etc.), carbon Heterocyclic polyamines having a number of 2 to 20 (such as piperazine and N-aminoethylpiperazine), alkanolamines (such as monoethanolamine, diethanolamine and triethanolamine), polyamide polyamines obtained by condensation of dicarboxylic acid and excess polyamine, Examples thereof include polyether polyamine, hydrazine (hydrazine and monoalkylhydrazine, etc.), dihydrazide (succinic acid dihydrazide, terephthalic acid dihydrazide, etc.), guanidine (butylguanidine, 1-cyanoguanidine, etc.), and dicyandiamide.

Examples of the thiol group-containing compound include monovalent thiol compounds having 1 to 20 carbon atoms (alkylthiols such as ethylthiol, phenylthiol and benzylthiol) and polyvalent thiol compounds (ethylenedithiol and 1,6-hexanedithiol). Etc.) and the like.

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

In the porous fine cellulose fiber sheet and the porous fine cellulose fiber composite sheet of the present embodiment, the polyurethane solid content weight ratio is preferably 0.5% by mass or more and 100% by mass with respect to 100% by mass of the fine cellulose fiber. % Or less, more preferably 1% by mass or more and 70% by mass or less, more preferably 1% by mass or more and 50% by mass or less, and further preferably 1% by mass or more and 30% by mass or less. Since the fine cellulose fibers have a large specific surface area, if the weight ratio is less than 0.5% by mass, it is not easy to cover the entire fiber surface with polyurethane, and the water-based Wet strength or the non-water-based Wet strength tends to be low. On the other hand, when the content is 100% by mass or less, the surroundings of the fine cellulose fibers can be prevented from being excessively coated with polyurethane, and the inherent properties of cellulose such as high heat resistance and decorating property can be favorably maintained.

In the porous fine cellulose fiber sheet and the porous fine cellulose fiber composite sheet of the present embodiment, it is preferable that the fine cellulose fibers in the sheet and the polyurethane are chemically bonded. The chemical bond is a covalent bond, a coordinate bond, an ionic bond, a hydrogen bond or the like, and is not particularly limited, but a covalent bond is preferable. For example, a urethane bond due to reaction with a large number of hydroxyl groups present on the surface of fine cellulose fibers, an amidourea bond due to a reaction with a small amount of carboxyl groups, and the like can be mentioned. Furthermore, regarding the above-mentioned chemically modified cellulose fiber, a covalent bond can be formed 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. Since the chemical bond is formed three-dimensionally with respect to the fine cellulose fibers, the Dry strength, the water-based Wet strength and the non-water-based Wet strength of the sheet are improved.

The formation of chemical bonds can be directly confirmed by solid-state NMR, FT-IR, X-ray photoelectron spectroscopy and other spectroscopic methods, or TOF-SIMS and other mass spectrometric methods. In addition, the porous fine cellulose fiber sheet is washed with a solvent such as acetone, dimethylacetamide, or dimethylformamide, and it is indirectly considered that a chemical bond is formed because polyurethane is not eluted in the washing liquid. You can also As the analysis method by elution of polyurethane, combustion ion chromatography, solution NMR, ICP (inductively coupled plasma), liquid chromatography, gas chromatography, mass spectrometry, FT-IR, CHN analysis, or the like may be selected.

When the porous fine cellulose fiber sheet and the porous fine cellulose fiber composite sheet of the present embodiment contain polyurethane, the distribution state of the polyurethane is not particularly limited, but the polyurethane is in the porous fine cellulose fiber sheet or in the porous fine cellulose. It is preferably uniformly distributed in the fine cellulose fiber layer of the fiber laminated sheet. The uniform distribution of polyurethane makes the water-based Wet strength and the non-water-based Wet strength of the sheet uniform, so that the number of sheet breakages can be reduced during continuous production of resin-impregnated composite sheets. In addition, in the porous fine cellulose fiber sheet and the fine cellulose fiber layer, that the polyurethane is uniformly distributed means that the polyurethane is uniformly distributed in both the plane direction and the thickness direction within the sheet.

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

The uniformity of distribution of polyurethane in the thickness direction of the sheet is determined by dividing the amount of polyurethane in the upper, middle and lower parts of the fine cellulose fiber layer of the porous fine cellulose fiber sheet and the porous fine cellulose fiber laminated sheet into three equal parts in the thickness direction. And the amount of cellulose are the same. Here, the same means that when calculating the average of P1/C1 in the upper part, the average of P1/C1 in the middle part, and the average of P1/C1 in the lower part at any four points on a 20 cm×20 cm sheet, these 3 It means that the variation between the two average values has a coefficient of variation of 50% or less.

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

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

The polyurethane in the porous fine cellulose fiber sheet and the porous fine cellulose fiber composite sheet of the present embodiment is a crosslinked product of a block polyisocyanate (that is, a product formed by a crosslinking reaction after the block group of the block polyisocyanate is eliminated). It is more preferable that the Blocked polyisocyanate means (1) a polyisocyanate compound such as polyisocyanate and a polyisocyanate derivative as a basic skeleton, (2) an isocyanate group is blocked by a blocking agent, and (3) a functional group having active hydrogen at room temperature. By the heat treatment at (4) the dissociation temperature or higher, which does not react with the group, the blocking group is eliminated and the active isocyanate group is regenerated, which reacts with the functional group having active hydrogen to form a bond. In one embodiment, the porous fine cellulose fiber sheet or the porous fine cellulose fiber composite sheet contains a blocked polyisocyanate or a crosslinked product of the blocked polyisocyanate.

Ordinary isocyanate compounds that do not have a blocking group cannot be added to the slurry (eg papermaking slurry) because they react easily with water. However, the blocked polyisocyanate can be added to the slurry because it does not react with water in the slurry. Further, by drying the wet paper below the dissociation temperature of the blocking agent, the reaction of the isocyanate compound with water in the wet paper can be prevented. Then, by finally heat-treating the dried sheet at a dissociation temperature of the blocking agent or higher, the block polyisocyanate is hardened by itself and the activity present on the surface of the base sheet of the fine cellulose fiber or the porous fine cellulose fiber laminated sheet. Effectively forms a covalent bond with a functional group having hydrogen (hydroxyl group, amino group, carboxyl group, thiol group, etc.).

The blocking agent is to block by adding to the isocyanate group of the polyisocyanate compound. This blocking group is stable at room temperature, but when heated to a heat treatment temperature (usually about 100 to about 250° C.), the blocking agent can be eliminated to regenerate a free isocyanate group.

Examples of the blocking agent satisfying such requirements include the following.
(1) Alcohols such as methanol, ethanol, 2-propanol, n-butanol, sec-butanol, 2-ethyl-1-hexanol, 2-methoxyethanol, 2-ethoxyethanol and 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) Phenolic type: phenol, cresol, ethylphenol, styrenated phenol, hydroxybenzoic acid ester, etc.
(4) Active methylene type: dimethyl malonate, diethyl malonate, methyl acetoacetate, ethyl acetoacetate, acetylacetone, etc.
(5) Mercaptan type: butyl mercaptan, dodecyl mercaptan, etc.
(6) Acid amide type: acetanilide, acetic amide, ε-caprolactam, δ-valerolactam, γ-butyrolactam, etc.
(7) Acid imide type: succinimide, maleic imide, etc.,
(8) Imidazole type: imidazole, 2-methylimidazole, 3,5-dimethylpyrazole, 3-methylpyrazole, etc.
(9) Urea type: urea, thiourea, ethylene urea, etc.
(10) Oxime type: formaldoxime, acetaldoxime, acetoxime, methylethylketoxime, cyclohexanoneoxime, etc.
(11) Amine type: 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 the present embodiment is used by uniformly mixing it in the fine cellulose fiber slurry, the block polyisocyanate itself is in a stable form as an aqueous dispersion, and is stable even when mixed with fine cellulose fibers or the like. Is preferred. The block polyisocyanate aqueous dispersion is a compound in which a hydrophilic compound is directly bonded to a block polyisocyanate and emulsified (self-emulsifying type), but is a compound in which a surfactant or the like is forcibly emulsified (forced emulsifying type). May be. Both of the emulsions obtained by the respective methods have anionic, nonionic, or cationic hydrophilic groups exposed on the surface.

The self-emulsifying block polyisocyanate is a block polyisocyanate skeleton to which an active hydrogen group-containing compound having an anionic group, a nonionic group or a cationic group is bonded.

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 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 dihydroxylcarboxylic acids such as 2,2-dimethylolacetic acid and 2,2-dimethylollactic acid, for example, 1-carboxy-1,5-pentyl. Examples thereof include diaminocarboxylic acids such as diamine 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 and 1,3-phenylenediamine-4,6-disulfonic acid. Can be mentioned.
Examples of the active hydrogen group-containing compound having a phosphoric acid 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 reacting a tertiary amine such as N-methyldiethanolamine with 1,3-propanesultone. ..
Further, these active hydrogen group-containing compounds having an anionic group may be modified into alkylene oxides by adding alkylene oxides such as ethylene oxide and propylene oxide.
In addition, these active hydrogen group-containing compounds having an anionic group can be used alone or in combination of two or more kinds.

The active hydrogen group-containing compound having a nonionic group is not particularly limited, but, for example, polyalkylene ether polyol having an ordinary alkoxy group as a nonionic group or the like is 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, for example, N , N-dimethylethanolamine, N-methyldiethanolamine, N,N-dimethylethylenediamine and the like. It is also possible to use N,N,N-trimethylolamine and N,N,N-triethanolamine having a tertiary amine. Among them, a polyhydroxy compound having a tertiary amino group and containing two or more active hydrogens reactive with an isocyanate group is preferable.
The active hydrogen group-containing compound having a cationic group may be modified into an alkylene oxide by adding an alkylene oxide such as ethylene oxide or propylene oxide. Further, these active hydrogen group-containing compounds having a cationic group can be used alone or in combination of two or more kinds.

By neutralizing the cationic group with a compound having an anionic group, it can be easily dispersed in water in the form of a salt. Examples of the anionic group include a carboxyl group, a sulfonic acid group, a phosphoric acid group and the like. As the compound having a carboxyl group, for example, formic acid, acetic acid, propionic acid, butyric acid, lactic acid, etc., as the compound having a sulfonic group, for example, ethanesulfonic acid, etc., as the compound having a phosphoric acid group, for example, Examples thereof include acids and acidic phosphoric acid esters. A compound having a carboxyl group is preferable, and acetic acid, propionic acid, and butyric acid are more preferable. When neutralized, 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. Further, the introduced tertiary amino group can be quaternized with dimethyl sulfate, diethyl sulfate or the like.

In the present embodiment, the blocked polyisocyanate is reacted with the active hydrogen group-containing compound for the purpose of introducing the hydrophilic group, the equivalent ratio of isocyanate group/active hydrogen group is preferably 1.05 to 1000, 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 does not become too low, so that the curing speed of the blocked polyisocyanate is good and the brittleness of the cured product does not easily occur. The cross-linking points with the fine cellulose fibers do not become too small, and the water-based Wet strength and the non-water-based Wet strength of the porous fine cellulose fiber sheet and the porous fine cellulose fiber laminated sheet are good. When the equivalent ratio is 1000 or less, the effect of lowering the interfacial tension is great and hydrophilicity is well expressed. In addition, as a method of reacting the polyisocyanate compound having two or more isocyanate groups in one molecule with the active hydrogen group-containing compound in the present embodiment, a method of mixing both and performing a normal urethanization reaction is exemplified. it can.

The forced emulsification type block polyisocyanate is a well-known general anionic surfactant, nonionic surfactant, cationic surfactant, amphoteric surfactant, polymer surfactant, reactive surfactant, etc. A compound in which an isocyanate is emulsified and dispersed. Of these, anionic surfactants, nonionic surfactants, and cationic surfactants are preferable because they are low in cost and good emulsification can be obtained.

Examples of the anionic surfactant include an alkylcarboxylic acid salt-based compound, an alkyl sulfate-based compound, and an alkyl phosphate.
Examples of the nonionic surfactant 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 alkylenediamines. Examples include adducts.

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

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

The above-mentioned block polyisocyanate aqueous dispersion may contain a solvent other than water, preferably up to 20% by mass, in both the self-emulsifying type and the forced emulsifying type. The solvent in this case is not particularly limited, but 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 mass or more, and specifically, dipropylene glycol dimethyl ether and dipropylene glycol monomethyl ether are preferable.

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

The surface of the above-mentioned block polyisocyanate aqueous dispersion may be any of anionic, nonionic and cationic, but is more preferably cationic. The reason is that at the stage of producing the slurry, a block polyisocyanate aqueous dispersion (solid content concentration of 0.0001 to 0.5%) is added to a dilute fine cellulose fiber slurry (solid content concentration of 0.01 to 0.5% by mass). This is because it is effective to utilize electrostatic interaction to effectively adsorb (% by mass) to the fine cellulose fibers. It is known that the surface of a general cellulose fiber is anionic (zeta potential of -30 to -20 mV in distilled water) (Non-patent document 1 J. Brandrup (editor) and E.H. Imager (editor) "Polymer". See Handbook 3rd edition “V-153 to V-155). Therefore, the surface of the blocked polyisocyanate aqueous dispersion is more preferably cationic. However, even if it is nonionic, it can be sufficiently adsorbed on the fine cellulose fibers depending on the polymer chain length of the hydrophilic group of the emulsion and the rigidity. Further, even when adsorption is more difficult due to electrostatic repulsion such as anionic property, it is possible to adsorb onto the fine cellulose fibers by using a generally known cationic adsorption aid. Examples of the cationic adsorption aid include polymers having a primary amino group, a secondary amino group, a tertiary amino group, a quaternary ammonium salt group, pyridinium, imidazolium, and a quaternized pyrrolidone. Examples thereof 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 fine cellulose fiber sheet and the porous fine cellulose fiber composite sheet of the present embodiment contains polyurethane, the water-based Wet strength and the non-water-based Wet strength are enhanced, and the sheet in water and in an organic solvent is used. Is easier to use. Further, when the porosifying agent and polyurethane are used in combination in the present embodiment, the porosity is maintained well even if the wet-drying operation is performed. Although the use of polyurethane alone enhances the water-based Wet strength and the non-water-based Wet strength, it tends to be difficult to maintain the porosity in the wet-drying operation. It will be easier.

The fine cellulose fiber layers of the porous fine cellulose fiber sheet and the porous fine cellulose fiber composite sheet of the present embodiment are each one selected from the group consisting of inorganic particles, polymer particles, inorganic fibers and polymer fibers. You may include the said filler material.

The inorganic particles are not particularly limited, but for example, chemically stable metal particles such as gold, silver, copper, iron, zinc, tin, nickel, titanium and various alloys (for example, stainless steel), alumina, titanium oxide, zinc oxide, Iron oxide, tin oxide, copper oxide, silver oxide, metal oxide particles such as 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 nanotubes.

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

The inorganic fiber is not particularly limited, and examples thereof include fibers that are insoluble in the dispersion medium described below, and include carbon fibers such as carbon nanotubes obtained by firing and carbonizing glass fibers, metal fibers or 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 beaten regenerated cellulose fibers or finely fibrillated by high-pressure homogenizer etc., fine fibers obtained by electrospinning method using various polymers as raw materials, meltblown method using various polymers as raw materials The obtained fine fibers and the like can be mentioned, but not limited thereto. Among these, Tiara (registered trademark) (manufactured by Daicel Chemical Industries, Ltd.), a fine fibrous aramid obtained by refining aramid fibers which are wholly aromatic polyamide by a high-pressure homogenizer, has an average fiber diameter of 0.2 to 0. It has an average fiber length of 3 μm and an average fiber length of 500 to 600 μm, and 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 fine cellulose fiber sheet of the present embodiment is preferably 1% by mass or more and 50% by mass or less of the sheet weight, more preferably 1% by mass or more and 30% by mass or less, and 1% by mass or more and 10% by mass. The following are more preferable.

The filler material contained in the porous fine cellulose fiber composite sheet of the present embodiment is preferably 0.1% by mass or more and 50% by mass or less of the sheet weight, more preferably 0.1% by mass or more and 30% by mass or less, and More preferably, it is 1% by mass or more and 10% by mass or less.

The porous fine cellulose fiber sheet and the porous fine cellulose fiber composite sheet of the present embodiment are a filler, a paper strength enhancer, a sizing agent, a retention improver, a drainage improver, a sulfuric acid band, a wet paper strength enhancer, and a coloring. Known papermaking materials such as dyes, color pigments, fluorescent whitening agents, fluorescent decoloring agents, and pitch control agents can be appropriately used within a range that does not impair the intended effects of the present embodiment.

As a method for producing the porous fine cellulose fiber sheet of this embodiment, a papermaking method and a coating method are preferable. The papermaking method typically includes (1) a step of producing fine cellulose fibers by refining cellulose fibers, (2) a step of preparing a papermaking slurry containing the fine cellulose fibers, and (3) filtering the papermaking slurry (that is, dehydration). ) To form a wet paper web, and (4) a drying step of drying the wet paper web to obtain a dry sheet. In addition, the coating method is typically a step of preparing a coating slurry by the same steps as the above (1) and (2), and (3) coating the coating slurry on a support to form a coating sheet. And (4) a drying step of drying the coated sheet. In this case, a base sheet may be used as the support. Hereinafter, a method for preparing a papermaking slurry or coating slurry containing fine cellulose fibers of the present embodiment and a method for forming a porous fine cellulose fiber sheet by a papermaking method will be described.

The present embodiment is a method for producing a porous fine cellulose fiber sheet of the present disclosure, in which a porosifying agent, a fine cellulose fiber, and a preparing step of preparing a slurry containing water, the slurry is dehydrated by a papermaking method. A film forming step of forming a wet paper web by doing the above, and a porous fine cellulose fiber sheet forming step of obtaining a porous fine cellulose fiber sheet by at least drying the wet paper web are provided.
The present embodiment is also a method for producing a porous fine cellulose fiber laminated sheet, in which a preparing step of preparing a slurry containing a porosifying agent, fine cellulose fibers, and water, the slurry on a base sheet A film forming step of forming a multilayer wet paper web by dehydration by a paper making method, and a porous fine cellulose fiber laminate sheet forming step of obtaining a porous fine cellulose fiber laminate sheet by drying at least the multilayer wet paper web. Including, providing a method.

As the fine cellulose fibers constituting the porous fine cellulose fiber sheet of the present embodiment, 1) fine cellulose fibers produced by bacteria, 2) fine cellulose fibers of regenerated cellulose or cellulose derivative obtained by electrospinning method, 3 ) Microfibrillated cellulose obtained by subjecting natural cellulose fibers, regenerated cellulose fibers or cellulose derivative fibers, which are bundles of cellulose microfibrils, to micronization treatment can be used. From the viewpoint of cost and quality control, microfibrillated cellulose is preferable.

As raw materials for microfibrillated cellulose, animal-derived cellulose fibers (such as ascidian cellulose), higher plant-derived cellulose fibers, regenerated cellulose fibers, and chemically synthesized cellulose derivative fibers can be mentioned.

Cellulose fibers derived from higher plants include, for example, wood pulp obtained from wood species (hardwood or conifer), non-wood pulp obtained from non-wood species (bamboo, hemp fiber, bagasse, kenaf, linter, etc.), and these Refined pulp (refined linter, etc.) can be used. As non-wood pulp, cotton-derived pulp including cotton linter pulp, hemp-derived pulp, bagasse-derived pulp, kenaf-derived pulp, bamboo-derived pulp, straw-derived pulp and the like can be used. Cotton-derived pulp, hemp-derived pulp, bagasse-derived pulp, kenaf-derived pulp, bamboo-derived pulp, and straw-derived pulp are cotton lint, cotton linter, hemp-based abaca (for example, from Ecuador or the Philippines), and Zaisal. , Bagasse, kenaf, bamboo, straw and the like. These raw materials are provided as refined pulp through a refining process such as delignification by a digestion process and a bleaching process, and the residual lignin amount and hemicellulose amount in the pulp can be changed depending on the purpose.

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

Examples of the cellulose derivative fiber 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; Mixed acid esters such as cellulose nitrate acetate; hydroxyalkyl cellulose such as hydroxyethyl cellulose and hydroxypropyl cellulose; carboxyalkyl cellulose such as carboxymethyl cellulose and carboxyethyl cellulose; alkyl cellulose such as methyl cellulose and ethyl cellulose.
These fibers can be used alone or in combination of two or more.

It is preferable that the fine cellulose fiber of the present embodiment is subjected to a cellulose fiber raw material pretreatment step, a beating step, and a finer step if necessary. In the pretreatment step, the purpose is to keep the cellulose fiber raw material in a state in which it can be easily miniaturized by autoclave treatment under water impregnation at 100 to 150° C., chemical treatment, enzyme treatment, or the like, or a combination thereof. To do.

ㆍChemical treatment is a method of introducing anion groups or cation groups into microfibrils. Due to the presence of these functional groups, electrostatic repulsion and osmotic pressure effects are exhibited, and it is possible to obtain fine cellulose fibers with a small amount of energy without using a finer device that requires high energy such as a high pressure homogenizer.

Examples of the anionizing agent include carboxylic acids having a plurality of carboxyl groups or anhydrides thereof, salts thereof, oxo acids containing phosphorus atoms or salts thereof, ozone, 2,2,6,6-tetramethylpiperidinooxy. Radicals and the like can be mentioned.
Examples of the cationizing agent include glycidyltrialkylammonium halides or halohydrin-type compounds thereof.

　Enzyme treatment is a treatment that mainly decomposes cellulose in the amorphous part by cellulase.

These pretreatments not only reduce the load of the micronization treatment, but also discharge the impurities such as lignin and hemicellulose existing on the surface and interstices of the microfibrils constituting the cellulose fiber into the aqueous phase, and as a result, Since it also has the effect of increasing the α-cellulose purity of the cellulose fibers, it is effective in improving the heat resistance of the porous fine cellulose fiber sheet and the porous fine cellulose fiber laminated sheet.

In the beating step, the raw material pulp is preferably 0.5% by mass or more and 4% by mass or less, more preferably 0.8% by mass or more and 3% by mass or less, still more preferably 1.0% by mass or more and 2.5% by mass. It is dispersed in water so as to have the following solid content concentration, and fibrillation is highly promoted by a beating device such as a beater, a conical refiner, or a disc refiner (double disc refiner). Since an extremely high degree of beating (fibrillation) proceeds depending on the treatment conditions, the conditions for the micronization treatment with a high-pressure homogenizer or the like can be relaxed, which may be effective.

For the production of fine cellulose fibers, it is preferable to carry out a refining treatment with a high pressure homogenizer, an ultrahigh pressure homogenizer, a grinder or the like, following the beating step described above, depending on the desired number average fiber diameter. The solid content concentration in the aqueous dispersion at this time is in accordance with the beating treatment described above, preferably 0.5% by mass or more and 4% by mass or less, more preferably 0.8% by mass or more and 3% by mass or less, and further preferably It is 1.0% by mass or more and 2.5% by mass or less. When the solid content concentration is within this range, clogging does not occur, and moreover, efficient micronization processing can be achieved.

Examples of the high-pressure homogenizer to be used include NS type high-pressure homogenizer manufactured by Niro Soavi Inc. (Italy), Lanie type (R model) pressure homogenizer manufactured by SMT Co., Ltd., and high-pressure homogenizer manufactured by Sanwa Machinery Co., Ltd. be able to. Examples of the ultra-high pressure homogenizer include a high-pressure collision type miniaturization processor such as Microfluidizer manufactured by Mizuho Industry Co., Ltd., Nanomizer manufactured by Yoshida Kikai Co., Ltd., and Ultimateizer manufactured by Sugino Machine Co., Ltd. Examples of the grinder type refining device include a pure fine mill manufactured by Kurita Kikai Seisakusho Co., Ltd. and a stone mill type typified by a supermass colloider manufactured by Masuyuki Sangyo Co., Ltd. It should be noted that any device other than these may be used as long as it is a device that performs miniaturization with substantially the same mechanism.

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 fine cellulose fibers chemically treated on the surface 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% by mass or more and 2.0% by mass or less, and 0.01% by mass or more and 1.5% by mass or less of the mass of the papermaking slurry. It is more preferably 0.05 mass% or more and 1.0 mass% or less. When the content is 0.01% by mass or more, the drainage time does not become too long, the productivity is good, and at the same time, the uniformity of the film quality is good, which is preferable. Further, when the content is 2.0% by mass or less, the viscosity of the dispersion liquid does not increase excessively, and it is easy and uniform to form a film, which is preferable.

Further, in the coating slurry preparation step, the fine cellulose fibers contained in the slurry are preferably 75% by mass or more and 99.5% by mass or less of the coating slurry mass, more preferably 80% by mass or more and 99.0% by mass or less, It is more preferably 85% by mass or more and 98.0% by mass or less. When the content is 75% by mass or more and 99.5% by mass or less, the viscosity of the coating slurry facilitates film formation, and thus the film quality uniformity is good, which is preferable.

In the papermaking slurry preparation step, the porosifying agent added is preferably 0.0001 mass% or more and 2.0 mass% or less, more preferably 0.0001 mass% or more and 1.5 mass% or less, and 0.0005 mass% or less of the slurry mass. More preferably, it is not less than mass% and not more than 1.0 mass %. When the content is 0.0001% by mass or more, the porosifying agent can have a good solubility in general, depending on its type, so that the effect of making the porosity large. When the content is 2.0% by mass or less, the slurry viscosity does not increase excessively, the generation of bubbles due to stirring is suppressed, and uniform film formation is facilitated.

In addition, in the coating slurry preparation step, the amount of the porosifying agent added is preferably 0.005% by mass or more and 25.0% by mass or less of the mass of the slurry, and more preferably 0.01% by mass or more and 20.0% by mass or less. It is more preferably 0.05% by mass or more and 15.0% by mass or less, and particularly preferably 0.05% by mass or more and 10.0% by mass or less.

As a mixing device for uniformly dispersing the porosifying agent in the slurry, an agitator, a homomixer, a pipeline mixer, a high-speed homogenizer of a type such as a blender that rotates a blade having a cutting function at a high speed, and a high-pressure homogenizer can be given. To be The stirring device is not particularly limited as long as the fine cellulose fibers and the porosifying agent are uniformly dispersed without generating bubbles. In particular, when the porosifying agent self-emulsifies in water, or when it has already been 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 does not emulsify, a strong shear mixing method such as a homomixer or a high pressure homogenizer is more preferable.

In the papermaking slurry or coating slurry, a water-dispersible block polyisocyanate, the known papermaking material, or a filler material can be appropriately used within a range that does not impair the intended effect of the present embodiment. It can be arbitrarily changed within the range of 0.0001% by weight to 10.0% by weight in the slurry. Further, even in the coating slurry, the amount can be arbitrarily changed within the range of 0.005% by weight or more and 25.0% by weight or less.
The order of adding other additives such as the porosifying agent and the blocked polyisocyanate is not particularly limited as long as the intended effect of the present embodiment is not impaired.

In the papermaking slurry or the coating slurry, an organic solvent can be appropriately used within a range that does not impair the intended effect of the present embodiment, for the purpose of promoting the porosity of the sheet. It can be arbitrarily changed within the range of 0.0001% by weight or more and 10.0% by weight or less. Further, even in the coating slurry, the amount can be arbitrarily changed within the range of 0.005% by weight or more and 25.0% by weight or less.
The organic solvent is not particularly limited, but it is preferable that it is water-soluble because a uniform slurry can be obtained. Further, when the boiling point of the organic solvent is 100° C. or higher, the organic solvent is more likely to remain in the porous fine cellulose fiber sheet than water during drying, so that a porous fine cellulose fiber sheet having a higher porosity can be obtained. Therefore, it is preferable. A hydrophobic organic solvent can also be used in the form of an emulsion so that it can be uniformly present in the slurry.

In the papermaking process of this embodiment, a wet paper is formed by filtering a papermaking slurry on a water-permeable substrate.
In this papermaking process, any device may be used as long as it is an operation using 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, an apparatus such as a slanted wire type paper machine, a Fourdrinier paper machine, and a cylinder paper machine can be preferably used to obtain a porous fine cellulose fiber sheet with few defects. The paper machine may be a continuous type or a batch type and may be used properly according to the purpose.

In the coating step of the present embodiment, a spray coater, an air doctor coater, a blade coater, a knife coater, a rod coater, a squeeze coater, an impregnation coater, a gravure coater, a kiss roll coater, a die coater, a reverse roll coater, a transfer roll coater, etc. A wet paper can be obtained by applying the prepared coating slurry to a water-soluble base material or a non-porous sheet by using. When a water-permeable substrate is used, the degree of dehydration of the wet paper is controlled by the same method as the suction step or pressing step in paper making described below, or a method similar thereto, and preferably the solid content concentration is 6% by mass or more and 25% by mass or more. % Or less, and more preferably, the solid content concentration is adjusted to a range of 8% by mass or more and 20% by mass or less.

The size of the wire or filter cloth is important because the papermaking process is a step of filtering soft aggregates such as fine cellulose fibers dispersed in the papermaking slurry using a wire or filter cloth. In the present embodiment, essentially, the yield ratio of the water-insoluble component containing fine cellulose fibers etc. contained in the papermaking slurry is, for example, 70% by mass or more, preferably 80% by mass or more, more preferably 90% by mass, It is possible to use any wire or filter cloth capable of making paper at a content of 95% by mass or more, particularly preferably 99% by mass.

However, even if the yield ratio of fine cellulose fibers or the like is 70% by mass or more, if the drainage is not high, it takes time to make the paper, and the production efficiency is significantly deteriorated. When the amount of water permeation is preferably 0.005 ml/(cm ² ·sec) or more, more preferably 0.01 ml/(cm ² ·sec) or more, suitable papermaking becomes possible from the viewpoint of productivity. .. When the yield ratio of the water-insoluble component is 70% by mass or more, the productivity is good, the phenomenon that the water-insoluble component such as fine cellulose fibers is clogged in the wire or filter cloth used, or the porosity after film formation. It is possible to avoid deterioration of the releasability of the fine cellulose fiber sheet.

The water permeation amount of the wire or filter cloth under atmospheric pressure is evaluated as follows. A wire or filter cloth to be evaluated is installed on a batch type paper machine (for example, an automatic square sheet machine manufactured by Kumagai Riki Kogyo Co., Ltd.), and in the case of the wire, the wire or filter cloth of 80 to 120 mesh is used as it is. Place a filter cloth on a metal mesh (assuming that there is almost no resistance to drainage), inject a sufficient amount (y (ml)) of water into a paper machine with a paper making area of x (cm ² ), and Measure the drainage time under atmospheric pressure. The water permeation amount when the drainage time was z (sec) is defined as y/(x·z) (ml/(cm ² ·s)).

Examples of the wire or filter cloth of the present embodiment include TETEXMONODLW07-8435-SK010 (PET) manufactured by SEFAR (Switzerland), NT20 (PET/nylon mixed spinning) manufactured by Shikishima Canvas, and TT30 (PET). However, the present invention is not limited to these.

In the dehydration by the papermaking process of the present embodiment, high solidification progresses, and a wet paper having a concentrated composition higher than the concentration of fine cellulose fibers in the papermaking slurry is obtained. The solid content of the wet paper is controlled by controlling the suction pressure (wet suction or dry suction) of the papermaking and the pressing step, and the solid content is preferably 6% by mass or more and 25% by mass or less, more preferably the solid content. The concentration is adjusted within the range of 8% by mass or more and 20% by mass or less. When the solid content of the wet paper is 6% by mass or more, the wet paper has good self-supporting property, and problems in the process hardly occur. When the wet paper web is dehydrated to a concentration of 25% by mass or less, the fine cellulose fibers do not significantly penetrate into the wire or filter cloth, and unevenness is transferred to the sheet, or the wire or filter cloth. It is possible to avoid problems such as clogging of the.

In the production of the porous fine cellulose fiber laminated sheet of the present embodiment, a multi-layer wet paper can be obtained by placing the base material sheet on a wire or a filter cloth and performing paper making during the paper making. Further, in the coating method, a multilayer wet paper can be obtained by using a base material sheet of a porous fine cellulose fiber laminated sheet as a water-permeable base material on which the coating slurry is applied.

The base sheet preferably has an air resistance of 100 sec/100 ml or less and a thickness of 1 μm or more and 1000 μm or less, or 100 μm or more and 750 μm or less, or 200 μm or more and 500 μm or less. The base material sheet in the porous fine cellulose fiber composite sheet may have one layer or two or more layers. In the case of two or more layers, the total thickness of the base material sheet portion in the porous fine cellulose fiber composite sheet may be 2 μm or more and 2000 μm or less, or 200 μm or more and 1500 μm or less, or 400 μm or more and 1000 μm or less. The method of measuring the air resistance is in accordance with the method of measuring the air resistance of the porous fine cellulose fiber sheet. The thickness can be measured by using a porous fine cellulose fiber laminated sheet (20 cm x 20 cm) left standing for 1 day in an environment of 23° C. and 50% RH, and in the case of a porous fine cellulose fiber laminated sheet, a desktop offline contact type. Using a film thickness meter (for example, TOF-5R01 manufactured by Yamabun Denki Co., Ltd.), a length of 150 mm is measured once at a pitch of 0.1 mm, and the number average value is taken as the film thickness (μm). Further, in the case of a porous fine cellulose composite sheet, the cross section of the composite sheet is cut out, and SEM observation or optical microscope observation is arbitrarily performed at 10 places, and the thickness of the base material sheet is measured at each place. The obtained measurement value x the number average value at the above 10 points is calculated to obtain the substrate sheet thickness (μm).

The surface of the base sheet of this embodiment is preferably hydrophilic. It is preferable that the surface of the base material sheet is hydrophilic because the adhesiveness of the porous fine cellulose fiber laminated sheet is excellent and the drainage property at the time of producing the porous fine cellulose fiber laminated sheet by a papermaking method is improved. The hydrophilic functional group is not particularly limited, but it may be a hydroxyl group, a thiol group, a carboxyl group, a sulfonic acid group, a sulfuric acid ester group, a phosphoric acid group, a sulfuric acid group or -OM, -COOM, -SO ₃ M, -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.

Also, a functional group having active hydrogen may be introduced on the surface of the base material sheet. When the functional group on the surface of the base material sheet is a functional group having active hydrogen, a chemical bond by polyurethane can be formed, and the base material sheet and the porous fine cellulose fiber sheet are firmly bonded via the polyurethane, which is preferable. .. The functional group having active hydrogen as used herein means, for example, a hydroxyl group, an amino group, a thiol group, a carboxyl group or 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 or the like is formed.

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

It is also possible to apply an organic solvent to the wet paper or immerse the wet paper and replace the contained water with the organic solvent. Substitution with an organic solvent can further promote the formation of porosity. The organic solvent is not particularly limited, but it is preferable that the organic solvent is water-soluble because substitution with water occurs quickly. Further, when the boiling point of the organic solvent is 100° C. or higher, the organic solvent is more likely to remain in the porous fine cellulose fiber sheet than water during drying, so that a porous fine cellulose fiber sheet having a higher porosity can be obtained. Therefore, it is preferable. A hydrophobic organic solvent can also be used once it has been replaced with a water-soluble organic solvent.

In the drying step of the present embodiment, the porous fine cellulose fiber sheet or the porous fine cellulose fiber laminated sheet is obtained by evaporating the water by heating the wet paper obtained in the paper making step (film forming step) described above. Obtainable. The drying method is not particularly limited, but when a constant length drying type drier capable of drying water in a fixed width such as a drum dryer or a pin tenter is used, the air permeability resistance It is preferable because a porous fine cellulose fiber sheet or a porous fine cellulose fiber laminated sheet having a low viscosity can be stably obtained. The drying temperature may be appropriately selected according to the conditions, but is preferably in the range of 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 high in many cases, so that good productivity can be secured, which is preferable. When the drying temperature is 250° C. or lower, the porosifying agent is thermally denatured. This is preferable because it can avoid the case of causing the above-mentioned problem, and has good energy efficiency and low cost.

In a preferred embodiment, the slurry further contains a blocked polyisocyanate, and the porous fine cellulose fiber sheet forming step or the porous fine cellulose fiber laminated sheet forming step is a heat curing treatment performed after drying the wet paper or the multilayer wet paper. including. That is, when the block polyisocyanate is used, the cured sheet obtained by drying the wet paper or the multilayer wet paper is subjected to heat curing treatment (heat treatment) to dissociate the block groups of the block polyisocyanate contained in the sheet, and A chemical bond is formed with the subsequent fine cellulosic fibers. Further, in the porous fine cellulose fiber laminated sheet, the block polyisocyanate simultaneously promotes crosslinking between the base sheet and the fine cellulose fibers.

For the heat cure treatment, a known method using convective heat transfer, conductive heat transfer, radiant heat transfer, etc. can be adopted, and heating by hot air, infrared rays, or thermal contact can be used. From the viewpoint of uniform and short-time heat treatment, contact heating with a heating roller is preferable. The amount of heat energy that ignites the sheet can be adjusted by the roll temperature, roll diameter, feed rate, and the like.

Block polyisocyanate is stable at room temperature, but by heat treatment above the dissociation temperature of the blocking agent, the block group dissociates and the isocyanate group is regenerated, forming a chemical bond with the functional group containing active hydrogen. The heating temperature varies depending on the blocking agent used, but is, for example, 80° C. or higher and 300° C. or lower, preferably 100° C. or higher and 280° C. or lower, and more preferably 120° C. or higher and 250° C. or lower. .. When the temperature is lower than the dissociation temperature of the block group, the isocyanate group does not regenerate, and thus crosslinking does not occur. Moreover, it is preferable to heat at a temperature of 300° C. or less, because thermal degradation of the fine cellulose fibers and the block polyisocyanate and the coloring due to this can be avoided.

The heating time has a lower limit of, for example, 1 second or more and an upper limit of, for example, 10 minutes or less, preferably 5 minutes or less, more preferably 3 minutes or less, and further preferably 1 minute or less. When the heating temperature is sufficiently higher than the dissociation temperature of the block group, the heating time can be shortened. In addition, when the heating temperature is 200° C. or higher, the water content in the sheet is extremely reduced if the sheet is heated for more than 5 minutes, so heating within 5 minutes avoids embrittlement of the sheet immediately after heating. It is preferable in that it is easy to handle.

In a preferred embodiment, the step of forming a porous fine cellulose fiber sheet includes calendering performed after drying the wet paper web or the multilayer wet paper web. That is, the dried sheet obtained by drying may be subjected to calendering (smoothing) with a calendering device. It is also possible to obtain a porous fine cellulose fiber sheet or a porous fine cellulose fiber laminated sheet, the surface of which has been smoothed by a calendering treatment to form a thin film. That is, by further subjecting the dried sheet to a smoothing treatment with a calendering device, it becomes possible to form a thin film, and a wide range of film thickness/permeation resistance/strength combinations of the porous fine cellulose fiber sheet of the present embodiment or A porous fine cellulose fiber laminated sheet can be provided. For example, it is possible to easily produce a porous fine cellulose fiber sheet having a film thickness of 200 μm or less and a porous fine cellulose fiber laminated sheet under the setting of the basis weight of 100 g/m ² or less. As the calendering device, in addition to a normal calendering device using a single press roll, a super calendering device having a structure in which these are installed in multiple stages may be used. The material (material hardness) and the linear pressure of each of these devices and both sides of the roll at the time of calendering may be selected according to the purpose.

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

A method for manufacturing the porous fine cellulose fiber composite sheet of this embodiment will be described.
The porous fine cellulose fiber composite sheet of the present embodiment is manufactured by impregnating the above-mentioned porous fine cellulose fiber sheet with a thermoplastic resin. As the impregnation method, a porous fine cellulose fiber sheet and a thermoplastic resin sheet are stacked and pressed hot press, vacuum press, vacuum pressure hot press, or the thermoplastic resin is made into an emulsion to obtain porous fine cellulose. Examples of the method include, but are not limited to, a method in which a fiber sheet is impregnated, a solvent is dried, and then pressure hot pressing, vacuum pressing, and vacuum pressure hot pressing are performed. Further, the porous fine cellulose fiber composite sheet of the present embodiment also includes a plurality of porous fine cellulose fiber composite sheets impregnated with a thermoplastic resin, which are superposed and joined by a pressure hot press or the like.

The mixing ratio (mass basis) of the porous fine cellulose fiber sheet and the thermoplastic resin is not particularly limited, but 1:99 to 99:1 is preferable from the viewpoint of impregnating the thermoplastic resin into the porous fine cellulose fiber sheet, It is more preferably 3:97 to 90:10, particularly preferably 5:95 to 70:30.

The thermoplastic resin is not particularly limited, and examples thereof include styrene resin, acrylic resin, polycarbonate resin, polyester resin, polyolefin resin, polyamide resin, polyphenylene ether resin, polyimide resin, polyacetal resin, polysulfone resin, and fluorine resin. , From the viewpoint that the porous fine cellulose fiber sheet is not deteriorated by heat, and from the viewpoint that the porous fine cellulose fiber composite sheet is preferably used as an outer panel part for automobiles, a polyolefin resin, a polyamide resin, a polyester resin, a polyacetal resin, poly(meth) Acrylate resins and polyphenylene ether resins are preferably used. The thermosetting resin may be used alone or two or more different resins may be used.

The porous fine cellulose fiber composite sheet of the present embodiment may use a thermosetting resin and/or a photocurable resin in addition to the thermoplastic resin.

Examples of the thermosetting resin include epoxy resin, acrylic resin, oxetane resin, phenol resin, urea resin, melamine resin, unsaturated polyester resin, silicone resin, polyurethane resin, allyl ester resin and diallyl phthalate resin. Not limited.

Examples of the photocurable resin include, but are not limited to, precursors such as epoxy resin, acrylic resin, and oxetane resin.

In one aspect, the total thickness of the porous fine cellulose fiber composite sheet may be 50 μm to 4000 μm, or 100 μm to 3000 μm, or 200 μm to 2000 μm. In one embodiment, the ratio of [total thickness of porous fine cellulose fiber sheet portion]/[total thickness of base material sheet] in the porous fine cellulose fiber composite sheet is 1/20 to 1/1, or 1/10. It may be ˜19/20, or ⅕ to 9/10.

The linear thermal expansion coefficient (CTE) of the porous fine cellulose fiber composite sheet of the present embodiment is preferably 50 ppm or less in the temperature range of 0° C. to 60° C. from the viewpoint of use as an automobile outer panel component, and It is preferably 40 ppm/K or less, more preferably 30 ppm/K or less, and further preferably 20 ppm/K or less. The lower the CTE, the more preferable, but it may be, for example, 10 ppm/k or more, or 15 ppm/k or more from the viewpoint of the ease of manufacturing the porous fine cellulose fiber composite sheet.
The CTE of the porous fine cellulose fiber composite sheet was measured by cutting the porous fine cellulose fiber composite sheet into a length of 4 mm and a width of 4 mm with a precision cutting saw, measuring at a temperature range of -10 to 80°C, and measuring at 0°C. Calculate the expansion coefficient between ~60°C.

The CTE aspect ratio (anisotropy) of the porous fine cellulose fiber composite sheet of the present embodiment is preferably 0.5 or more and 2.0 or less, more preferably 0.6 or more and 1.5 or less, and further preferably 0. 0.7 or more and 1.3 or less, more preferably 0.8 or more and 1.2 or less, particularly preferably 0.9 or more and 1.1 or less, and most preferably 0.95 or more and 1.05 or less. The aspect ratio of CTE is preferably 0.5 or more and 2.0 or less from the viewpoint that strain does not easily occur when a resin molded body is manufactured and joined to a component made of another material. In the CTE measurement sample, the vertical direction can be arbitrarily determined, the horizontal direction is a direction perpendicular to the vertical direction, and the numerical range of the aspect ratio of the CTE described above is defined as any direction of the CTE measurement sample. Also in this case, it is intended that the value of the aspect ratio is within the above range.

In the porous fine cellulose fiber composite sheet of the present embodiment, from the viewpoint of reducing the coefficient of linear thermal expansion, the porous fine cellulose fiber sheet has a length (that is, a breaking length of the sheet) of 1 cm or more, and a width (that is, a break occurs). The maximum width of the inter-sheet gap) is more preferably not more than 1 mm, more preferably not more than 0.5 cm in length and not more than 1 mm in width, and most preferably no break. The presence or absence of the above-mentioned fractured portion can be confirmed by visual observation of the porous fine cellulose fiber composite sheet.

In the porous fine cellulose fiber composite sheet of the present embodiment, from the viewpoint of mechanical properties and low thermal linear expansion, it is preferable that the pores of the porous fine cellulose fiber sheet to be contained are impregnated with resin. Whether or not the resin is impregnated inside the pores of the porous fine cellulose fiber sheet is confirmed by observing with a cross-section SEM (scanning electron microscope) or optical microscope of the porous fine cellulose fiber composite sheet. be able to. FIG. 1 is a view showing a cross-sectional SEM image of a porous fine cellulose fiber composite sheet. FIG. 1 shows that the pores of the porous fine cellulose fiber sheet A are impregnated with the thermoplastic resin B. When the resin is not impregnated inside the pores of the porous fine cellulose fiber sheet, bubbles are observed inside the composite sheet. As sites where bubbles are observed in the composite sheet, there are three locations inside the pores of the porous fine cellulose fiber sheet to be included, between the porous fine cellulose fiber sheet and the resin layer, and inside the resin layer. However, the bubble ratio in all three locations is preferably 0.5% or less, more preferably 0.1% or less, further preferably 0.01% or less, Is most preferable. When the bubble ratio is 0.5% or less, it is easy to improve the mechanical properties and the coefficient of linear thermal expansion of the porous fine cellulose fiber composite sheet. In the present disclosure, the bubble ratio is a value obtained as an area ratio in a SEM (scanning electron microscope) cross-section observation image of a porous fine cellulose fiber composite sheet.

The method for extracting the fine cellulose fibers from the porous fine cellulose fiber composite sheet is not particularly limited, but a method for extracting the fine cellulose fibers using a resin dissolving agent that selectively dissolves only the thermoplastic resin is preferably used. .. For example, in the case of a porous fine cellulose fiber composite sheet using a polyamide resin, hexafluoroisopropanol, the fine cellulose fibers are separated by dissolving with a resin dissolving agent such as formic acid, after sufficiently washed with the resin dissolving agent, The resin solubilizer can be extracted by substituting the desired solvent to be stored.

The porous fine cellulose fiber composite sheet of the present embodiment is a fender, a front bumper, a rear bumper, a door module, a roof, a hood, a back door module, an underbody panel, a chassis, etc., an automobile outer panel component, an automobile structural component, etc. Can be suitably used. In particular, the outer panel part for automobiles is more preferable because the linear expansion coefficient of the porous fine cellulose fiber composite sheet of the present embodiment and the linear expansion coefficient of the adjacent metal parts are close to each other, so that interference between the parts is reduced. .. Therefore, one aspect of the present invention is an automobile outer panel component including a cellulose nanofiber reinforced resin molded article (a thermoformed article in one aspect) that includes the porous fine cellulose fiber composite sheet of the present disclosure.

Hereinafter, the present embodiment will be specifically described with reference to examples, but the present invention is not limited to these examples. The main measured values of physical properties were measured by the following methods.

(1) Number average fiber diameter of fine cellulose fibers The number average fiber diameter of fine cellulose fibers was determined by measuring the specific surface area of a porous sample obtained by tert-butanol substitution. First, a concentrate was obtained by centrifuging the fine cellulose fiber slurries A-1 to A-3 (solid content 5% by mass or more). Subsequently, the concentrate containing 0.5 g of fine cellulose fibers was dispersed in tert-butanol so that the concentration became 0.2% by mass, and further, ultrasonication or the like was performed to eliminate aggregates. Distributed processing was performed. 100 g of the obtained tert-butanol dispersion liquid was filtered on a filter paper (5C, Advantech, diameter 90 mm), and the wet paper web formed on the filter was dried at 150° C. to obtain a porous sample. The air permeation resistance of this sheet was 100 sec/100 ml or less per 10 g/m ^{2 of} sheet weight, which was measured as a porous sample.
After measuring the basis weight W (g/m ² ) of the porous sample that was left standing for 1 day in an environment of 23° C. and 50% RH, Oken type air resistance tester (manufactured by Asahi Seiko Co., Ltd., model EG01) Was used to measure the air resistance R (sec/100 ml). At this time, the value per 10 g/m ² basis weight was calculated according to the following formula (14).
Air permeability resistance per unit weight of 10 g/m ² (sec/100 ml)=R/W×10 Formula (14)
Subsequently, with a specific surface area/pore distribution measuring device (Nova-4200e, manufactured by Kantachrome Instruments, Inc.), about 0.2 g of a porous sample was dried under vacuum at 120° C. for 2 hours, and then liquid nitrogen was used. After measuring the adsorption amount of nitrogen gas at the boiling point of 5 points at a relative vapor pressure (P/P ₀ ) in the range of 0.05 to 0.2 (multipoint method), the BET specific surface area ( m ² / g) was calculated. The obtained BET specific surface area was substituted into the following formula (15), and the number average fiber diameter of the fine cellulose fibers was calculated.
D (nm)=2667/BET specific surface area (m ² /g) Formula (15)

(2) Presence or absence of fine cellulose fibers having a branched structure The presence or absence of the fine cellulose fibers having a branched structure is determined by using a high shear homogenizer prepared by dispersing a fine cellulose fiber slurry (solid content: 0.5% by mass) dispersed in tert-butanol. (For example, manufactured by Nippon Seiki Co., Ltd., trade name “Excel Auto Homogenizer ED-7”), and treatment conditions: an aqueous dispersion dispersed at a rotation speed of 15,000 rpm×5 minutes is tert up to 0.1% by mass. -10 fields of view with a scanning microscope (SEM) at a magnification of 2000 times (field size is 60 μm×60 μm), which was diluted with butanol, cast on a hydrophilized Si substrate, and air-dried. I observed. Of the 10 fields of view, the presence of one or more fields of fine cellulose fibers having a branched structure in which a thin trunk having a fiber diameter of 2 to 1000 nm branches from the thick trunk having a fiber diameter of 1 μm to 30 μm was confirmed as “yes”, and absolutely confirmed. When it was not done, it was set as "none".

(3) Unit weight A porous fine cellulose fiber sheet stored for 24 hours in an environment controlled at room temperature of 23° C. and humidity of 50% RH is cut into 20 cm×20 cm (area 0.04 m ² ) and mass W1 (g) is obtained. It was measured and calculated from the following formula (16).
Basis weight W (g/m ² )=W1/0.04 formula (16)

(4) Degree of acetylation (DS)
The acetylation degree (DS) of the fine cellulose fiber was calculated by infrared spectroscopy. The infrared spectroscopic spectrum of the porous sample by the ATR-IR method was measured with a Fourier transform infrared spectrophotometer (FT/IR-6200 manufactured by JASCO). The infrared spectroscopic spectrum was measured under the following conditions.
Total number of times: 64 times
Wave number resolution: 4 cm ^-1 ,
Measuring wave number range: 4000-600 cm ^-1 ,
ATR crystal: diamond,
Incident angle: 45°
The IR index is calculated from the obtained IR spectrum by the following formula (17):
IR index=H1730/H1030 Formula (17)
Was calculated according to. In the formula, H1730 and H1030 are absorbances at 1730 cm ⁻¹ and 1030 cm ⁻¹ (absorption band of cellulose skeleton chain CO stretching vibration). However, the line connecting 1900 cm ⁻¹ and 1500 cm ⁻¹ and the line connecting 800 cm ⁻¹ and 1500 cm ⁻¹ are taken as the baseline, and the absorbance when the baseline is set to 0 is meant.
Then, the average substitution degree (DS) of the fine cellulose fibers was calculated from the IR index according to the following formula (18).
DS=4.13×IR index formula (18)

(5) CTE
Two sample pieces of 4 mm x 4 mm were cut out from a porous fine cellulose fiber composite sheet stored for 24 hours in an environment controlled at room temperature of 23°C and humidity of 50% RH, and were perforated by a thermomechanical analyzer Q400 manufactured by TA Instruments. The fine and fine cellulose fiber sheet was measured in the longitudinal and transverse directions in a temperature range of -10 to 80°C, and the CTE of 0 to 60°C was calculated. In the CTE measurement sample, the vertical direction was arbitrarily determined from the sample pieces, and the horizontal direction was the direction perpendicular to the vertical direction.

(6) Film Thickness of Porous Fine Cellulose Fiber Sheet A sample piece is arbitrarily cut out from 10 locations from the porous fine cellulose fiber composite sheet stored for 24 hours in an environment controlled at room temperature of 23° C. and humidity of 50% RH, All the thickness of the porous fine cellulose fiber sheet portion was measured by the cross-section SEM. The obtained measured value×the number average value at the above 10 points was taken as the film thickness (μm) of the porous fine cellulose fiber sheet.

(7) Sheet thickness 10 pieces of sample pieces were arbitrarily cut from the porous fine cellulose fiber composite sheet stored for 24 hours in an environment controlled at room temperature of 23° C. and humidity of 50% RH, and each piece was made porous by an optical microscope. The total thickness of the fine cellulose fiber composite sheet was measured. The average value of the thickness at 10 places was defined as the sheet thickness (μm).

(8) Bubble ratio 10 pieces of sample pieces were arbitrarily cut out from the porous fine cellulose fiber composite sheet stored for 24 hours in an environment controlled at room temperature of 23°C and humidity of 50% RH, and cross-sectional SEM observation was performed at 1000 times each. I went. The bubble ratio in the cross-sectional visual field including the front surface to the back surface of the composite sheet can be expressed by the following formula.
Bubble ratio (%) = bubble area/composite sheet cross-sectional area x 100 (average value of 10 fields of view; SEM)

(9) Presence or absence of sheet breakage When visually observing from above the porous fine cellulose fiber composite sheet stored for 24 hours in an environment controlled at room temperature of 23° C. and humidity of 50% RH, a length of 1 cm or more, The sheet was broken when there was a break with a width of 1 mm or more, and the sheet was not broken when there was no break. An example of a porous fine cellulose composite sheet having a rupture portion having a sheet length of 1 cm or more and a width of 1 mm or more is shown in FIG. 2 (see the rupture portion C in FIG. 2). An example of a porous fine cellulose composite sheet having no breakage is shown in FIG.

(10) Presence or absence of impregnation of the thermoplastic resin into the porous fine cellulose fiber sheet Using the sample arbitrarily cut at 10 locations in (8), cross-sectional SEM observation was performed at 1000 times magnification, and the composite sheet was obtained. The presence or absence of voids was observed in the porous fine cellulosic fiber sheet that was encapsulated. Impregnation was carried out when no void having a diameter of 1 μm or more was observed, and no impregnation was conducted when a void having a diameter of 1 μm or more was observed.

(11) Fiber content The porous fine cellulose fiber composite sheet is immersed in hexafluoroisopropanol to dissolve the resin component, and then the fine cellulose fiber is separated by a centrifuge, washed with water and air-dried to obtain fine cellulose fiber. Was measured. The mass percentage of the above-mentioned fine cellulose fibers to the porous fine cellulose fiber composite sheet was defined as the fiber content (mass %).

(12) Amount of Porosifying Agent Included in Porous Fine Cellulose Fiber Composite Sheet Using the porous fine cellulose fiber composite sheet, Soxhlet extraction was performed with chloroform in the following manner, and the porosifying agent was measured by solution NMR. Was quantitatively analyzed. From the obtained results, the amount (mass %) of the porosifying agent contained in the porous fine cellulose fiber composite sheet was determined.

<Soxhlet treatment>
0.5755 g of the porous fine cellulose fiber composite sheet was Soxhlet extracted (80° C./10 hours) with 120 ml of chloroform, and concentrated and dried by nitrogen blowing. The obtained solidified product was made up to 10 ml with acetone, 4 ml was obtained from this solution, and concentrated to dryness by nitrogen blowing to obtain a sample for ¹ H-NMR measurement. To the above sample, 0.75 ml of the solvent CDC1 ₃ was added, and 100 μl of a DMF solution (CDCl ₃ solution containing 1000 mass ppm of DMF) was added as an internal standard to obtain a sample for ¹ H-NMR measurement.
<Measurement conditions>
Device: JEOL-ECZ500
Observation nucleus: 1H
Pulse width: 45°
Wait time: 5 seconds Integration: 128 times Solvent: CDCl ₃
Temperature: 23 ℃
Chemical shift standard: TMS 0.00ppm

Three types of fine cellulose fiber slurries were produced by the following method.
[Production Example 1-1]
Cotton linter pulp obtained from Nippon Pulp and Paper Co., Ltd. was immersed in water so as to be 10% by mass, and heat-treated at 130° C. for 4 hours in an autoclave. The obtained swollen pulp was washed with water to obtain a purified pulp containing water. Subsequently, the refined pulp was dispersed in water so as to have a solid content of 1.5% by mass, and a disk refiner SDR14 type lab refiner (pressurized DISK type) manufactured by Aikawa Iron Works Co., Ltd. was used, and clearance between the discs was used. Was beaten at 1 mm for 20 minutes. Subsequent to that, thorough beating under conditions where the clearance was reduced to a level close to zero to obtain a fine cellulose fiber slurry A-1 (solid content concentration: 1.5% by mass).

[Production Example 1-2]
In order to replace the solvent of the fine cellulose fiber slurry A-1 with water and dimethyl sulfoxide (DMSO), 10 parts by mass of the CNF slurry was concentrated with a dehydrator to a solid content of 10% by mass or more and then placed in an explosion-proof disperser tank. The concentrated slurry was charged into 100 parts by mass of DMSO charged, stirred for 20 minutes, and then concentrated by a dehydrator until the solid content became 10% by mass or more. After performing this operation two more times, the re-concentrated slurry was put into 100 parts by mass of DMSO in an explosion-proof disperser tank, stirred for 30 minutes, and then 3 parts by mass of vinyl acetate and 1 part by mass of baking soda were put in the tank. The temperature was set to 40° C. and stirring was performed for 60 minutes. The obtained slurry was dispersed in 100 parts by mass of pure water, stirred, and then concentrated with a dehydrator. Subsequently, the obtained wet cake was again dispersed in 100 parts by mass of pure water, and the washing operation of stirring and concentrating was repeated 3 times in total to remove the unreacted reagent solvent and the like. The washing operation was repeated 3 times, and finally pure water was added to obtain acetylated fine cellulose fiber slurry A-2 (solid content: 1.5% by mass). The degree of acetylation (DS) was 0.5.

[Production Example 1-3]
The fine cellulose fiber slurry A-1 (solid content concentration: 1.5% by mass) obtained in Production Example 1-1 was directly used for a high pressure homogenizer (NSO15H manufactured by Niro Soavi (Italy) Co., Ltd.) under an operating pressure of 100 MPa. Was subjected to 10 times of refining treatment to obtain a fine cellulose fiber slurry A-3 (solid content concentration: 1.5% by mass).

[Production Examples 2-1 to 2-5]
While stirring any one of the fine cellulose fiber slurries A-1 to A-3 with a three-one motor, the following porosifying agent C (1.0 mass% aqueous solution) and/or the following block polyisocyanate D (solid content concentration) 1.0% by mass dispersion) or isopropanol (ratio of 15 ml to 100 ml of slurry) was added dropwise with the composition shown in Table 1, and the mixture was stirred for 3 minutes to prepare one of the papermaking slurries B-1 to B-5. Got one. Since the porosity-imparting agent is not dissolved in water, it was shaken vigorously by hand just before addition and then collected. The weight of the solid content of the added porosifying agent and the weight of the solid content of the blocked polyisocyanate were both adjusted to 6% with respect to the weight of the fine cellulose fibers.
C: Emulgen 103 (also referred to as E103), polyoxyethylene lauryl ether, HLB8.1, manufactured by Kao Corporation (number average molecular weight: 324)
D: Meikanate CX (also called CX), manufactured by Meisei Chemical Industry Co., Ltd.

[Examples 1 to 5, Comparative Examples 1 to 4]
Plain woven fabric made of PET/nylon blend (NT20, manufactured by Shikishima Canvas Co., Ltd., water permeation amount at atmospheric temperature 25° C.: 0.03 ml/(cm ² ·s), fine cellulose fiber by filtration at atmospheric pressure 25° C. 99 Percentage of Eg/m ² porous fine cellulose fiber sheet is used as a guide in a batch type paper machine (manufactured by Kumagai Riki Kogyo Co., Ltd., automatic square sheet machine 25 cm x 25 cm, 80 mesh) set with the ability to filter more than 100%. Then, the papermaking slurry was added thereto, and then the papermaking (dehydration) was carried out at a reduced pressure degree with respect to atmospheric pressure of 4 KPa to obtain a wet paper.
The obtained wet paper was covered with the same PET/nylon mixed-spun plain fabric as a cloth, and then the whole filter cloth was peeled off from the paper machine. Then, after sandwiching it in a cardboard and pressing it at a pressure of 1 kg/cm ² for 1 minute, cover it with a drum dryer whose surface temperature is set to 130° C. and let it dry for about 120 seconds so that the cloth surface contacts the drum surface. It was By peeling the covering cloth and the filter cloth from the obtained three-layered body of covering cloth/sheet/filter cloth, a porous fine cellulose fiber sheet (25 cm×25 cm) composed of fine cellulose fibers was obtained.
The sheet containing the blocked polyisocyanate was heat-cured in an oven at 170° C. for 5 minutes while being sandwiched between 25 cm square metal frames.

Water was evenly sprayed on the obtained porous fine cellulose fiber sheet and then dried again in an oven at 130° C. for 5 hours. After cutting the dried porous fine cellulose fiber sheet into 10 cm squares, both sides were sandwiched with nylon 6 film (also referred to as PA6, film thickness: F μm), and vacuum hot press was performed at a temperature of 250° C. under a surface pressure of 3 MPa. It carried out for 10 minutes. As the vacuum heat press device, IMC-1AE4 manufactured by Imoto Machinery Co., Ltd. was used. The results of the obtained porous fine cellulose fiber composite sheet are shown in Table 2. As the nylon 6 film, a film formed by T-die using 1013B manufactured by Ube Industries was used. After that, for the sample with good resin impregnation and good sheet breakage under a surface pressure of 3 MPa, the pressure was increased by 1 MPa until the resin impregnation was poor or the sheet breakage was poor, and the resin impregnation was good and The maximum pressure at which the sheet did not break was calculated. Further, conversely, the pressure was lowered from 3 MPa by 1 MPa to a pressure at which resin impregnation was poor or sheet breakage was poor, and the minimum pressure at which the sheet did not break and the resin impregnation was good was determined. On the other hand, in the case of the resin impregnation failure or the sheet breakage failure under the condition of 3 MPa, the pressure was decreased by 1 MPa, and the minimum pressure and the maximum pressure were similarly obtained. The difference between the minimum pressure and the maximum pressure was defined as the pressing range.
The obtained porous fine cellulose fiber composite sheet was dissolved in hexafluoroisopropanol, and the fine cellulose fibers were extracted to evaluate the average fiber diameter of cellulose, the presence or absence of a branched structure, and the degree of acetylation. The value was the same as the value (described in Table 1) of the porous fine cellulose fiber sheet used for.
Tables 1 and 2 show the composition and conditions for papermaking and resin compounding.

[Example 6]
Ten porous fine cellulose fiber composite sheets obtained in Example 5 were superposed and heated and pressed under a surface pressure of 5 MPa to obtain a porous fine cellulose composite sheet having a sheet thickness of 2250 μm. The obtained porous fine cellulose fiber composite sheet was dissolved in hexafluoroisopropanol, and the fine cellulose fibers were extracted to evaluate the average fiber diameter of cellulose, the presence or absence of a branched structure, and the degree of acetylation. The value was the same as the value (described in Table 1) of the porous fine cellulose fiber sheet used for. Tables 1 and 2 show the composition and conditions for papermaking and resin compounding.

The porous fine cellulose fiber composite sheet of this embodiment can be suitably applied as an outer panel component and a structural component for automobiles. The porous fine cellulose fiber composite sheet of the present embodiment is characterized in that it is manufactured by impregnating a material recyclable thermoplastic resin, for example, as a substitute for a steel plate, carbon fiber reinforced plastic, and glass fiber reinforced plastic. Can also be preferably used. The porous fine cellulose fiber composite sheet of the present embodiment is specifically used as a vehicle member such as a fender, a front bumper, a rear bumper, a door module, a roof, a hood, a back door module, an underbody panel, a chassis and the like. It can be preferably used.

Claims (16)

1. The following requirements (1) to (4):
   (1) Containing one or more layers of porous fine cellulose fiber sheet having an average fiber diameter of 2 nm or more and 1000 nm or less,
   (2) The porous fine cellulose fiber sheet is arranged with a film thickness of 25 μm or more and 2000 μm or less,
   (3) Including a thermoplastic resin,
   (4) Including a porosifying agent,
   A porous fine cellulose fiber composite sheet that satisfies all of the above.
2. The following requirements (1) to (4):
   (1) One or more layers of porous fine cellulose fiber sheet having an average fiber diameter of 2 nm or more and 1000 nm or less are included (2) The porous fine cellulose fiber sheet is arranged with a film thickness of 25 μm or more and 4000 μm or less,
   (3) Including a thermoplastic resin,
   (4) The porous fine cellulose fiber sheet is impregnated with the thermoplastic resin,
   A porous fine cellulose fiber composite sheet that satisfies all of the above.
3. The porous fine cellulose fiber composite sheet according to claim 2, wherein the sheet thickness of the porous fine cellulose fiber composite sheet is 50 μm or more and 4000 μm or less.
4. The porous fine cellulose fiber composite sheet according to claim 2 or 3, further comprising a porosifying agent.
5. The porous fine cellulose fiber composite sheet according to claim 1 or 4, wherein the porous agent is contained in an amount of 0.1% by mass or more and 100% by mass or less based on 100% by mass of the fine cellulose fiber.
6. The porous fine cellulose fiber composite sheet according to any one of claims 1 to 5, wherein the porous fine cellulose fiber composite sheet has an air bubble ratio of 0.5% or less.
7. The porous fine cellulose fiber composite sheet according to any one of claims 1 to 6, further comprising a blocked polyisocyanate or a crosslinked product thereof.
8. The porous fine cellulose fiber composite sheet according to any one of claims 1 to 7, wherein the porous fine cellulose fiber sheet does not have a broken portion having a length of 1 cm or more and a width of 1 mm or more.
9. 9. The porous fine cellulose fiber sheet contains fine cellulose fibers having a branched structure in which a thick trunk having a fiber diameter of 1 μm to 30 μm branches fine branches having a fiber diameter of 2 to 1000 nm. The porous fine cellulose fiber-composite sheet according to [4].
10. The porous fine cellulose fiber composite sheet according to any one of claims 1 to 9, wherein the porous fine cellulose fiber sheet contains a cellulose type I crystal.
11. The porous fine cellulose fiber composite sheet according to any one of claims 1 to 10, wherein the porous fine cellulose fiber sheet contains acetylated cellulose having an acetylation degree of 0.1 to 1.5.
12. The porous fine cellulose fiber composite sheet according to any one of claims 1 to 11, which comprises one or more base material sheet layers.
13. The thermoplastic resin contains at least one selected from the group consisting of a polyolefin resin, a polyamide resin, a polyester resin, a polyacetal resin, a poly(meth)acrylate resin, and a polyphenylene ether resin. The porous fine cellulose fiber-composite sheet according to [4].
14. A molded body comprising the porous fine cellulose fiber composite sheet according to any one of claims 1 to 13, wherein a heat ray of 0°C to 60°C in two mutually perpendicular directions in the molded body. A cellulose nanofiber reinforced resin molded product having an expansion coefficient of 50 ppm/K or less.
15. An automobile outer panel component including the cellulose nanofiber-reinforced resin molded product according to claim 14.
16. Slurry preparing step for preparing a slurry containing a porosifying agent, fine cellulose fibers, and water,
    A film forming step of forming a wet paper web by dehydrating the slurry by a paper making method,
    A porous fine cellulose fiber sheet forming step of obtaining a porous fine cellulose fiber sheet by drying at least the wet paper, and a porous fine cellulose fiber composite sheet obtained by impregnating the porous fine cellulose fiber sheet with a thermoplastic resin. A compounding process to obtain
    A method for producing a porous fine cellulose fiber composite sheet, comprising:

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