JP5477265B2 - Method for producing fine fibrous cellulose composite porous sheet - Google Patents

Description

  The present invention relates to a method for efficiently producing a porous sheet in which fine fibrous cellulose and a polymer are combined.

In recent years, nanotechnology aimed at obtaining physical properties different from the bulk and molecular levels by making a material a nanometer size has attracted attention. On the other hand, attention is also focused on the application of natural fibers that can be regenerated due to the substitution of petroleum resources and the growing environmental awareness.
Among natural fibers, cellulose fibers, particularly wood-derived cellulose fibers (pulp) are widely used mainly as paper products. Most cellulose fibers used for paper have a width of 10 to 50 μm. Filter materials such as filter paper and filters are manufactured using such fibers and are widely used.
On the other hand, it is known that the fiber width becomes nanometer order when cellulose fiber is processed (beating, pulverizing) with a refiner, kneader, sand grinder, etc., and the cellulose fiber is refined (microfibril). Materials using cellulose have been proposed.

  Cellulose fibers are aggregates of cellulose crystals with a high modulus of elasticity and a low coefficient of thermal expansion, and heat resistant dimensional stability is improved by compositing cellulose fibers with polymers. Yes. The aqueous dispersion of fine fibrous cellulose having mechanically pulverized cellulose fibers and having a fiber width of 50 nm or less is transparent. On the other hand, since the fine fibrous cellulose sheet contains voids, it is diffusely reflected white and has high opacity. However, when the fine fibrous cellulose sheet is impregnated with a resin, the voids are filled, and a transparent sheet is obtained. Furthermore, the fibers of the fine fibrous cellulose sheet are an aggregate of cellulose crystals, very stiff, and because the fiber width is small, the number of fibers is dramatically increased at the same mass compared to ordinary cellulose sheets (paper). To be more. Therefore, when composited with a polymer, fine fibers are dispersed more uniformly and densely in the polymer, and the heat-resistant dimensional stability is dramatically improved. Moreover, since the fibers are thin, the transparency is high. A fine fibrous cellulose composite having such characteristics is expected to be very large as a flexible transparent substrate (a transparent substrate that can be bent or folded) for organic EL or liquid crystal displays. Further, it is known that the nonwoven fabric air filter generally improves the collection efficiency by reducing the fiber width, but increases the pressure loss. However, when the fiber width becomes narrower than a certain threshold, it is considered that the amount of increase in pressure loss decreases with respect to the decrease in fiber width. Therefore, in recent years, research on filters using nanofibers has become active. Yes. In addition, it is thought that the filter with fine pores made of nanofibers can be used for precision filters in water treatment and virus collection filters.

Fine fibrous cellulose with mechanically pulverized cellulose fibers and a fiber width of 50 nm or less can be applied to these nanofiber filters. In addition, improvement in elastic modulus, thermal dimensional stability, solvent resistance, etc. Although it can be expected, the above-mentioned nanofiber filter mainly uses a resin-based polymer.
In addition, nanofibers using structural polysaccharides such as cellulose and chitosan are also produced by electrospinning and the like. However, since they have undergone dissolution, the naturally derived ordered structure is lost. Therefore, high elastic modulus and thermal dimensional stability due to the microfibril structure cannot be expected.
When used in an aqueous system such as a water treatment filter, it is necessary to impart water resistance, and as one of the means, conjugation with a polymer can be considered. This not only provides the filter with water resistance, but also makes it possible to produce a high-performance filter that takes advantage of the characteristics of fine fibrous cellulose and polymer.

  There are many disclosures about the finer fiber technology and the composite technology with the polymer, but most of the technology to make the fine fibrous cellulose into a composite sheet while maintaining industrial productivity. The current situation is not.

  Specifically, Patent Documents 1 to 3 disclose a technique for making cellulose fibers into fine fibers. However, there is disclosure and suggestion of a technique for forming cellulose into a sheet at the same time that cellulose is formed into fine fibers. Absent.

  Patent Documents 4 to 10 disclose a technique for improving physical properties such as mechanical strength by compositing a fine fibrous cellulose to a polymer resin, but almost disclose a technique for facilitating compositing. It has not been. There is no porous composite sheet using fine fibrous cellulose.

Patent Documents 10 to 20 disclose a technique for forming fine fibrous cellulose into a sheet, but there is no technique disclosed for making a composite sheet porous.
Patent Documents 21 to 26 disclose a technique for producing a filter using nanofibers, but there is no filter using naturally derived fine fibrous cellulose.
Patent Document 27 is a technique for producing a porous material using fine fibrous cellulose, but is a technique for producing a porous material using a single cellulose fiber, and does not disclose a technique for producing a composite porous material. . Moreover, although the filter material which consists of the said fine fibrous cellulose is also reported, since the fiber of this filter is interacting mainly by the hydrogen bond, it is weak with respect to water and a use is limited.
Patent Document 28 discloses a technique of a porous composite sheet that includes a filler material composed of inorganic particles or polymer particles in cellulose microfibrils. In the present technology, after the porous sheet is manufactured, the polymer particles are fused to improve water resistance by heat calendering. However, when polymer particles having good film forming properties are mixed as a filler material in order to further enhance the water resistance, there is a problem that the binder is fused in the drying step during the paper making process and the porosity is lost.

JP-A 56-1000080 JP 2008-169497 A Japanese Patent No. 3036354 Japanese Patent No. 3641690 JP 9-509694 A JP 2006-316253 A JP-A-9-216952 JP-A-11-209401 JP 2008-106152 A JP-A-2005-060680 JP-A-8-188981 JP 2006-193858 A JP 2008-127893 A JP-A-5-148387 JP 2001-279016 A JP 2004-270064 A JP-A-8-188980 JP 2007-23218 A JP 2007-23219 A Japanese Patent Laid-Open No. 10-248872 JP 2009-148748 A JP 2009-6272 A JP 2008-101315 A JP 2007-254942 A JP 2006-289209 A JP 2005-305289 A JP 2010-115574 A JP 2010-202987 A

  In the present invention, a polymer emulsion having film-forming properties is mixed with an aqueous suspension containing fine fibrous cellulose, this mixed solution is dehydrated by filtration on a porous substrate, and then an organic solvent is applied and impregnated. In addition, the present invention provides a method for producing a composite porous sheet of fine fibrous cellulose and polymer obtained by drying.

  The inventors mixed a polymer emulsion having film-forming properties with an aqueous suspension containing fine fibrous cellulose, dehydrated the mixed solution by filtration on a porous substrate, and then applied an organic solvent. Various studies were made as to whether or not the composite sheet of fine fibrous cellulose and polymer containing a large amount of water could be efficiently made porous by impregnation and drying, and the present invention was completed based on such findings.

The present invention includes the following inventions.
A method for producing a composite porous sheet using fine fibrous cellulose and a polymer having film-forming properties, and mixing and mixing a polymer emulsion having film-forming properties with an aqueous suspension containing fine fibrous cellulose. A preparation step for producing a liquid, a paper making step for forming a sheet containing moisture by dehydrating the mixed solution on a porous substrate, a step for replacing the moisture-containing sheet with an organic solvent, an organic solvent It is a manufacturing method of the fine fibrous cellulose composite porous sheet which has a drying process which heat-drys the sheet | seat substituted by.

  The fine fibrous cellulose composite porous material according to (1), wherein the polymer is at least one selected from polyurethane, polyethylene, polypropylene, alkyl (meth) acrylate copolymer, and acid-modified styrene-butadiene copolymer. It is a manufacturing method of an adhesive sheet.

  The method for producing a fine fibrous cellulose composite porous sheet according to (1) or (2), wherein the polymer emulsion is cationic.

It is a manufacturing method of the fine fibrous cellulose composite porous sheet of any one of (1)-(3) which mix | blends a cellulose coagulant | flocculant with the said liquid mixture in the said preparation process.

  In the said preparation process, it is a manufacturing method of the fine fibrous cellulose composite porous sheet of any one of (1)-(4) whose fiber width of the fine fibrous cellulose to mix is 2-1000 nm.

  According to the present invention, it is possible to provide a production method capable of very efficiently producing a polymeric composite porous sheet having fine fibrous cellulose and film-forming properties, and improving the water resistance and porosity of the composite sheet. be able to.

Hereinafter, the present invention will be described in detail.
The fine fibrous cellulose in the present invention is a cellulose fiber or rod-like particle that is much narrower than the pulp fiber usually used in papermaking. Fine fibrous cellulose is an aggregate of crystalline cellulose molecules, and its crystal structure is type I (parallel chain). The width of the fine fibrous cellulose is preferably 2 nm to 1000 nm as observed with an electron microscope, more preferably 2 nm to 500 nm, still more preferably 4 nm to 100 nm. When the width of the fiber is less than 2 nm, since the cellulose molecule is dissolved in water, the physical properties (strength, rigidity, dimensional stability) as the fine fiber are not expressed. If it exceeds 1000 nm, it cannot be said that it is a fine fiber, and is merely a fiber contained in ordinary pulp, and physical properties (strength, rigidity, dimensional stability) as a fine fiber cannot be obtained. Moreover, when it is a use by which transparency is required for the composite of fine fibrous cellulose, the width of the fine fibers is preferably 50 nm or less.

  Here, the fact that the fine fibrous cellulose has a type I crystal structure is that 2θ = 14 in a diffraction profile obtained from a wide-angle X-ray diffraction photograph using CuKα (λ = 1.5418４) monochromatized with graphite. It can be identified by having typical peaks at two positions near -17 ° and 2θ = 22-23 °. Moreover, the measurement of the fiber width by electron microscope observation of fine fibrous cellulose is performed as follows. An aqueous suspension of fine fibrous cellulose having a concentration of 0.05 to 0.1% by mass is prepared, and the suspension is cast on a carbon film-coated grid subjected to a hydrophilic treatment to obtain a sample for TEM observation. When a wide fiber is included, an SEM image of the surface cast on glass may be observed. Observation with an electron microscope image is performed at a magnification of 5000 times, 10000 times, or 50000 times depending on the width of the constituent fibers. At this time, when an axis of arbitrary vertical and horizontal image width is assumed in the obtained image, a sample and observation conditions (magnification, etc.) are set so that at least 20 fibers intersect the axis at least with respect to the axis. With respect to the observation image satisfying this condition, two random axes are drawn vertically and horizontally for each image, and the fiber width of the fiber intersecting with the axis is visually read. In this way, images of at least three non-overlapping surface portions are observed with an electron microscope, and the fiber width values of the fibers where two axes intersect each other are read (at least 20 × 2 × 3 = 120 fiber widths).

  There are no particular restrictions on the method for producing fine fibrous cellulose, but it can be used for grinders (stone mills), high-pressure homogenizers, ultrahigh-pressure homogenizers, high-pressure collision type crushers, high-speed rotary defibrators, disk type refiners, conical refiners, etc. A method of thinning the cellulosic fibers by wet pulverization utilizing mechanical action is preferred. Further, it may be refined after chemical treatment such as TEMPO oxidation, ozone treatment, enzyme treatment or the like. Examples of cellulosic fibers to be refined include plant-derived cellulose, animal-derived cellulose, and bacterial-derived cellulose. More specifically, it is isolated from wood-based paper pulp such as conifer pulp and hardwood pulp, cotton pulp such as cotton linter and cotton lint, non-wood pulp such as hemp, straw and bagasse, sea squirt and seaweed. A cellulose etc. are mentioned. Among these, wood-based paper pulp and non-wood pulp are preferable in terms of easy availability.

In the present invention, a polymer emulsion having film-forming properties is mixed with an aqueous suspension obtained by suspending the fine fibrous cellulose in water.
Here, the polymer emulsion is an emulsion of a natural or synthetic polymer, and is a milky white liquid dispersed in water with fine polymer particles having a particle diameter of about 0.001 to 10 μm. These polymer emulsions are usually produced by emulsion polymerization, but are sometimes called polymer latexes. Emulsion polymerization is a kind of radical polymerization and is basically a polymerization method in which a monomer and an emulsifier that are hardly soluble in a medium are mixed in an aqueous medium, and a polymerization initiator that is soluble in the medium is added. The polymer emulsion is not particularly limited, but polystyrene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, ethylene-vinyl acetate copolymer, poly (meth) acrylic acid alkyl ester polymer, (meth) acrylic. Resin emulsion such as acid alkyl ester copolymer, poly (meth) acrylonitrile, polyester, polyurethane; natural rubber; styrene-butadiene copolymer; molecular chain terminal is —SH, —CSSH, —SO ₃ H, — (COO) _x M, — (SO ₃ ) _x M and —CO—R (wherein M is a cation, x is an integer of 1 to 3 depending on the valence of M, and R is an alkyl group) ) Styrene-butadiene copolymer modified with at least one functional group selected from the group of: acid-modified, amine-modified, Modified styrene-butadiene copolymer such as amide-modified, acrylic-modified, (meth) acrylonitrile-butadiene copolymer, polyisoprene, polychloroprene, styrene-butadiene-methyl methacrylate copolymer, styrene- (meth) acrylic acid alkyl ester A copolymer etc. are mentioned.
In addition, polymers such as polyethylene, polypropylene, polyurethane, ethylene-vinyl acetate copolymer and the like may be emulsified by a post-emulsification method.
As the polymer used in the polymer emulsion, it is necessary to select a polymer having excellent film forming properties. In order to improve the film formability, the glass transition temperature of the polymer needs to be 60 ° C. or lower, more preferably 50 ° C. or lower, and particularly preferably 40 ° C. or lower. The glass transition temperature referred to in the present invention is, for example, an amorphous material as described in Manabu Seneo, Kimio Kurita, Shoichiro Yano, Takashi Sawaguchi, “Basic Polymer Science” (Kyoritsu Publishing Co., Ltd., 2000). The temperature at which the polymer chain segment in the region starts the micro-Brownian motion, and in the case of a copolymer, the glass transition temperature calculated by the Fox equation described on pages 131-132 of the same document. That is, the glass transition temperature of the copolymer is calculated by the following formula.

In the above formula, Tg is the glass transition temperature of the copolymer and is calculated in terms of absolute temperature. _{Tg 1, Tg 2, ·····,} Tg n are the components 1, 2, ..., these homopolymers 1 and 2 n, ..., the glass transition temperature (absolute n Temperature display). W ₁ , W ₂ ,..., W _n are mass fractions of specific monomers in the copolymer component. Therefore, the glass transition temperature of the copolymer can be controlled within the desired range of the present invention by adjusting the mass fraction of the monomer constituting the homopolymer exhibiting various glass transition temperatures.

  Among the above polymers, at least one selected from polyurethane, polyethylene, polypropylene, (meth) acrylic acid alkyl ester copolymer, and acid-modified styrene-butadiene copolymer is preferable from the viewpoint of film formability.

A method for producing the polymer emulsion will be described.
First, the polymer emulsion used in the present invention has sufficient ability to emulsify radically polymerizable monomers in water by using an emulsifier and stabilize the emulsion formed by polymerization of these monomers in water. It has a polymer.
The production method of the polymer emulsion is based on a conventional traditional emulsion polymerization method. That is, radical polymerization of a radical polymerizable monomer (emulsion) in a suitable aqueous medium in the presence of a polymerization initiator such as a peroxide or an azo compound, or a chain transfer agent such as a thiol compound or a disulfide compound. Is.

  In the polymer emulsion, the emulsifier is contained in the range of 0.1 to 6% by mass with respect to all monomers. When the content is less than 0.1% by mass, the polymerization stability becomes insufficient, and aggregates may be generated during the reaction. On the other hand, if it exceeds 6% by mass, the particle size of the polymer emulsion becomes too small and the viscosity becomes high, which is not preferable.

  Examples of the emulsifier used in the polymer emulsion include potassium oleate, sodium laurate, sodium todecylbenzenesulfonate, sodium alkylnaphthalenesulfonate, sodium dialkylsulfosuccinate, polyoxyethylene alkylether sodium sulfate, and polyoxyethylene. Anionic emulsifiers such as sodium alkyl allyl ether sulfate, sodium polyoxyethylene dialkyl sulfate, polyoxyethylene alkyl ether phosphate ester, polyoxyethylene alkyl allyl ether phosphate ester, polyoxyethylene alkyl ether, polyoxyethylene alkyl allyl Ether, poly (oxyethylene-oxypropylene) block copolymer, polyethylene glycol fatty acid ester Ether, nonionic emulsifiers such as polyoxyethylene sorbitan fatty acid esters can be exemplified. Further, for example, alkyltrimethylammonium salt, dialkyldimethylammonium salt, alkyldimethylbenzylammonium salt, acylaminoethyldiethylammonium salt, acylaminoethyldiethylamine salt, alkylamidopropyldimethylbenzylammonium salt, alkylpyridinium salt, alkylpyridinium sulfate, Quaternary ammonium salts such as aramidmethylpyridinium salt, alkylquinolinium salt, alkylisoquinolinium salt, fatty acid polyethylene polyamide, acylaminoethylpyridinium salt, acylcoraminoformylmethylpyridinium salt, stearoxymethylpyridinium salt, Fatty acid triethanolamine, fatty acid triethanolamine formate, trioxyethylene fatty acid triethanolamine Ester bond amine such as cetyloxymethylpyridinium salt, p-isooctylphenoxyethoxyethyldimethylbenzylammonium salt, ether bond quaternary ammonium salt, alkylimidazoline, 1-hydroxyethyl-2-alkylimidazoline, 1-acetylaminoethyl- Heterocyclic amines such as 2-alkylimidazolines and 2-alkyl-4-methyl-4-hydroxymethyloxazolines, polyoxyethylene alkylamines, N-alkylpropylenediamines, N-alkylpolyethylenepolyamines, N-alkylpolyethylenepolyamine dimethyl sulfates And cationic emulsifiers such as amine derivatives such as alkyl biguanides and long chain amine oxides. Further, a relatively low molecular weight polymer compound having an emulsifying and dispersing ability, such as polyvinyl alcohol, and a modified product thereof, polyacrylamide, polyethylene glycol derivative, neutralized product of polycarboxylic acid copolymer, casein and the like alone or the above-mentioned Can be used in combination with emulsifiers.

  The concentration of the monomer during the polymerization is usually about 30 to 70% by mass, preferably about 40 to 60% by mass. Examples of the polymerization initiator used in the polymerization include benzoyl peroxide, lauroyl peroxide, t-butyl hydroperoxide, paramentane hydroperoxide, diisopropylbenzene hydroperoxide, 1,1,3,3- Tetramethylbutyl hydroperoxide, dicumyl peroxide, cyclohexane peroxide, succinic acid peroxide, potassium persulfate, ammonium persulfate, peroxide compounds such as hydrogen peroxide, 2,2′-azobis (4-methoxy-2, 4-dimethylvaleronitrile), 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobis (2-methylpropionitrile), 2,2'-azobis (2-methylbutyro) Nitrile), 1,1'-azobis Chlorohexane-1-carbonitrile), 1-[(1-cyano-1-methylethyl) azo] formamide, dimethyl 2,2′-azobis (2-methylpropionate), 4,4′-azobis (4 -Cyanovaleric acid), 2,2'-azobis (2,4,4-trimethylpentane), 2,2'-azobis {2-methyl-N- [1,1'-bis (hydroxymethyl) -2 -Hydroxyethyl] propionamide}, 2,2′-azobis {2- (2-imidazolin-2-yl) propane] dihydrochloride, 2,2′-azobis {2- (2-imidazolin-2-yl) Propane] disulfate dihydrate, 2,2′-azobis {2- [1- (2-hydroxyethyl) -2-imidazolin-2-yl) propane]} dihydrochloride, 2 , 2'-azobis (1-imino-1-pyrrolidino-2-methylpropane) dihydrochloride, 2,2'-azobis (2-methylpropionamidine) dihydrochloride, 2,2'-azobis [N- ( An azo compound such as 2-carboxyethyl) -2-methylpropionamidine] tetrahydrate can be used.

  As an aqueous medium for polymerizing the polymer emulsion, water or water, ethers such as tetrahydrofuran, dioxane, dimethoxyethane, ketones such as methyl ethyl ketone, methyl isobutyl ketone, acetone, and aromatics such as toluene, benzene, chlorobenzene, etc. , Halogenated hydrocarbons such as dichloromethane, 1,1,2-trichloroethane, dichloroethane, alcohols such as isopropanol, ethanol, methanol, methoxyethanol, and esters such as ethyl acetate can be appropriately selected.

  Specific examples of the monomer constituting the polymer emulsion used in the present invention include (meth) acrylic acid, crotonic acid, maleic acid, itaconic acid, fumaric acid, monoalkylmaleic acid, monoalkylfumarate. Ethylenically unsaturated carboxylic acid-containing monomers such as acids, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, ( Octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, vinyl acetate, vinyl chloride, vinylidene chloride, (meth) acrylonitrile, styrene, ethylene, propylene, Butadiene, isoprene, chloroprene, 2-hydroxyethyl (meth) a Relate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, polyethylene glycol (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, glycenol mono (meth) acrylate, ethylene glycol Di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate , Trimethylolpropane tri (meth) acrylate, tetramethylolmethane tetra (meth) acrylate, divinylbenzene, 1,4-butanediol di (meth) acrylate 1,6-hexanediol di (meth) acrylate, glycidyl (meth) acrylate, methyl glycidyl (meth) acrylate, N-methylol (meth) acrylamide, N-methoxymethyl (meth) acrylamide, N-butoxymethyl (meta) ) Acrylamide, N, N-methylenebis (meth) acrylamide and the like, and at least one of them can be used.

  Examples of chain transfer agents include mercaptans such as n-dodecyl mercaptan, octyl mercaptan, t-butyl mercaptan, thioglycolic acid, thiomalic acid, thiosalicylic acid, sulfides such as diisopropylxanthogen disulfide, diethylxanthogen disulfide, diethylthiuram disulfide, and iodoform. And the like, diphenylethylene, p-chlorodiphenylethylene, p-cyanodiphenylethylene, α-methylstyrene dimer, sulfur and the like can be used.

  Examples of the polymerization inhibitor include phenothiazine, 2,6-di-t-butyl-4-methylphenol, 2,2′-methylenebis (4-ethyl-6-t-butylphenol), tris (nonylphenyl) phosphite, 4 , 4'-thiobis (3-methyl-6-tert-butylphenol), N-phenyl-1-naphthylamine, 2,2'-methylenebis (4-methyl-6-tert-butylphenol), 2-mercaptobenzimidazole, hydroquinone N, N-diethylhydroxylamine and the like can be used.

The polymerization reaction is usually performed at a reaction temperature of about 40 to 95 ° C., preferably about 60 to 90 ° C. for 1 to 10 hours, preferably about 4 to 8 hours. As the monomer addition method, a batch addition method, a divided addition method, a continuous addition method, or the like, such as a monomer tap method or a monomer pre-emulsification tap method can be used. A monomer pre-emulsification tapping method is preferred by a continuous addition method.
The concentration of the polymer emulsion thus obtained is preferably 20 to 65% by mass, more preferably about 30 to 60% by mass.

  In the polymer emulsion (latex), when a copolymer containing a carboxyl group, a sulfo group or the like is copolymerized in the copolymer, for example, sodium hydroxide, potassium hydroxide, ammonia, various first types You may stabilize by neutralizing with suitable alkaline substances, such as a grade, a secondary, and a tertiary amine.

Next, a method for emulsifying the polymer by the post-emulsification method will be described.
Various methods are known for producing dispersions, so-called emulsions, in which thermoplastic resins such as polyethylene, polypropylene, and ethylene-vinyl acetate copolymer resins are dispersed in water using a dispersant such as an emulsifier or a protective colloid agent. Yes.

  For example, in the case of an ethylene-vinyl acetate copolymer, as described in JP-A-57-61035, the ethylene-vinyl acetate copolymer is first heated and melted, and then the anionic or nonionic type as described above. It is obtained by adding and stirring the emulsifier of the system, and then adding hot water and emulsifying using mechanical shearing force such as a homomixer.

  Many water-soluble or water-dispersible polyurethane emulsions are also known. One of them is a heat-reactive polyurethane emulsion having a relatively low to medium molecular weight range using a blocked isocyanate group. Another example is a relatively high molecular weight thermoplastic polyurethane emulsion mainly composed of a linear structure. These can be self-emulsified or dispersed by introducing anionic, cationic or nonionic hydrophilic groups into the urethane resin skeleton, or can be forcibly dispersed in water by adding an emulsifier as described above to a hydrophobic resin. Is.

In the present invention, in consideration of the yield and dehydration property when mixing an aqueous suspension of fine fibrous cellulose and a polymer emulsion to form a sheet, the particle size of the polymer emulsion is preferably large and too large. Therefore, 0.001 to 10 [mu] m which is an appropriate size suitable for the purpose is preferable. Especially, it is advantageous in terms of dispersion stability and yield that the polymer emulsion has a cationic surface charge.
Examples of a method for imparting cationicity to the polymer emulsion include a method of copolymerizing a cationic monomer, a method of polymerizing the dispersoid of the emulsion using a cationic emulsifier, and the like.

  A method for imparting cationicity will be specifically described with polyurethane as an example of the dispersoid of the emulsion. One method for imparting cationic properties to the urethane prepolymer is to introduce a tertiary amino group by reacting an active hydrogen compound having a tertiary amino group with the urethane prepolymer. Any active hydrogen compound having a tertiary amino group can be used. Preferred active hydrogen compounds include aliphatic compounds having an active hydrogen-containing group such as a hydroxyl group or a primary amino group and a tertiary amino group, such as N, N-dimethylethanolamine, N-methyldiethanolamine, N, N- Examples thereof include dimethylethylenediamine. Further, N, N, N-trimethylolamine and N, N, N-triethanolamine having a tertiary amine can also be used. Of these, polyhydroxy compounds having a tertiary amino group and containing two or more active hydrogens reactive with isocyanate groups are preferred.

The amine equivalent value of the urethane prepolymer introduced with these tertiary amino groups is preferably 10 mgKOH / g or more. If the amine equivalent value (indicating the total amount of 1,2,3 and tertiary amines, and the number of mg of KOH equivalent to hydrochloric acid required to neutralize 1 g of sample) is 10 mg KOH / g or more, the urethane prepolymer Sufficient hydrophilicity can be imparted.
The active hydrogen compound having a tertiary amino group is bonded to the urethane prepolymer by reacting the active hydrogen-containing group of the active hydrogen compound having the tertiary amino group with the isocyanate group in the urethane prepolymer. Thereafter, when the tertiary amino group is quaternized with a quaternizing agent, a water-soluble cationic urethane prepoly can be obtained.

  As the quaternizing agent, dimethyl sulfate or diethyl sulfate is preferably used from the viewpoint of non-chlorine. Alternatively, the water can be made water-soluble by neutralizing the tertiary amino group with an acid to form a salt without quaternization. The neutralizing acid is preferably an organic acid such as acetic acid, oxalic acid, malonic acid, succinic acid, malic acid, citric acid, glutaric acid, adipic acid, maleic acid, or an inorganic acid such as phosphoric acid or nitric acid.

As a second method for imparting cationicity to the urethane prepolymer, there is a method in which a cationic compound is blended in the urethane prepolymer and the urethane prepolymer is charged cationically. In this case, the amine equivalent value of the urethane prepolymer is preferably 10 mgKOH / g or less, and may be 0 mgKOH / g.
Examples of the cationic compound include a cationic emulsifier having a quaternary ammonium salt. Specific examples include dicyandiamide compounds such as alkyltrimethylammonium salts, alkyldimethylbenzylammonium salts, alkylpyridinium salts, and dicyandiamide / diethylenetriamine condensates.
By emulsifying the urethane prepolymer in water using an emulsifier containing a cationic compound, the urethane prepolymer can be rendered cationic.

  In addition, a polyhydroxy compound having a tertiary amino group and containing at least two active hydrogens reactive with an isocyanate group is reacted with a urethane prepolymer, and water is added using an emulsifier containing a cationic compound. It is also possible to impart cationicity to the urethane prepolymer by emulsifying it.

  In this way, after imparting cationicity to the urethane prepolymer, water is added to the urethane prepolymer to make the urethane prepolymer water-based (dissolve or disperse in water) while cross-linking isocyanate groups ( A urea bond is formed). The content of isocyanate groups in the urethane prepolymer is preferably in the range of 1 to 5% by mass. If the isocyanate group is in this range, the preparation of the urethane prepolymer is easy, and the resulting polyurethane sheet does not become too cohesive, and an excellent texture can be imparted to the resulting composite sheet.

Instead of water, a polyvalent amine having two or more active hydrogens in one molecule may be added, and the isocyanate group may be amine-crosslinked while emulsifying the urethane prepolymer in water.
Examples of the polyvalent amine having two or more active hydrogens in one molecule include ethylenediamine, propylenediamine, diethylenetriamine, hexylenediamine, triethylenetetramine, tetraethylenepentamine, isophoronediamine, piperazine, diphenylmethanediamine, hydrazine, And adipic acid dihydrazide.

  Thus, water or a polyvalent amine is added to the cationic urethane prepolymer, the chain extension reaction of the cationic urethane prepolymer is carried out while emulsifying, and then the solvent is removed to obtain a polyurethane emulsion.

  Although the density | concentration of the polymer emulsion used in this invention can be changed arbitrarily in the range of about 20-65 mass%, when the basic weight of a cellulose sheet becomes low, capture | acquisition by a fiber will lose | eliminate and there exists a possibility that a yield may fall extremely.

  The mixed liquid containing the fine fibrous cellulose and the polymer used in the present invention is prepared by adding the polymer emulsion to the fine fibrous cellulose aqueous suspension with stirring. As an agitation device, an agitator, a homomixer, a pipeline mixer or the like is used for uniform mixing and agitation.

  In this invention, it is preferable to mix | blend a cellulose coagulant | flocculant with the said liquid mixture at a preparation process. Examples of the cellulose coagulant include water-soluble inorganic salts and water-soluble organic compounds containing a cationic functional group. Water-soluble inorganic salts include sodium chloride, calcium chloride, potassium chloride, ammonium chloride, magnesium chloride, aluminum chloride, sodium sulfate, potassium sulfate, aluminum sulfate, magnesium sulfate, sodium nitrate, calcium nitrate, sodium carbonate, potassium carbonate, ammonium carbonate , Sodium phosphate, ammonium phosphate and the like.

  Examples of the water-soluble organic compound containing a cationic functional group include polyacrylamide, polyvinylamine, urea resin, melamine resin, melamine-formaldehyde resin, and a polymer obtained by polymerizing or copolymerizing a monomer containing a quaternary ammonium salt.

  The blending amount of the cellulose coagulant is added more than the amount that the aqueous suspension gels. Specifically, it is preferable to add 0.5 to 10 parts by mass of a cellulose coagulant to 100 parts by mass of fine fibrous cellulose. Incidentally, when the addition amount of the cellulose coagulant is less than 0.5 parts by mass, the gelation of the aqueous suspension becomes insufficient, and there is a possibility that the effect of improving drainage may be poor. When the addition amount exceeds 10 parts by mass, gelation may proceed excessively and handling of the aqueous suspension may be difficult. More preferably, it is the range of 1-8 mass parts. Here, the gelation according to the present invention is a state change in which the viscosity of the aqueous suspension suddenly and greatly increases and loses fluidity. However, the gel obtained here is jelly-like and easily broken by stirring. Judgment of gelation can be judged visually because it is in a state of rapidly losing fluidity, but the concentration of the aqueous suspension of fine fibrous cellulose containing the cellulose coagulant of the present invention is 0.5% by mass and the temperature is 25. Judged by the B-type viscosity (rotor No. 4, rotational speed 60 rpm) at ° C. The viscosity is preferably 1000 mPa · second or more, more preferably 2000 mPa · second or more, and particularly preferably 3000 mPa · second or more. Incidentally, if the B-type viscosity is less than 1000 mPa · s, gelation of the aqueous suspension becomes insufficient, and the effect of improving drainage may be poor.

In applications where transparency is required, it is preferable to use a compound having a weak cationic property as the cellulose coagulant. Examples of compounds having weak cationic properties include ammonium carbonate compounds such as ammonium carbonate and ammonium hydrogen carbonate, and organic carboxylate ammonium compounds such as ammonium formate, ammonium acetate, and ammonium propionate. Among these, ammonium carbonate and ammonium hydrogen carbonate which are decomposed and vaporized by heating at 60 ° C. or higher and released from the sheet are preferable.
Furthermore, organic cationic compounds such as polyamide compounds, polyamide polyurea compounds, polyamidoamine polyurea compounds and polyamidoamine compounds having a cationization degree measured by a colloid titration method of 1.0 to 3.0 meq / g. Molecules can also be used. Commercially available products include SPI-203 (modified amine-based resin, manufactured by Taoka Chemical Industries), SPI-106N (modified polyamide-based resin, manufactured by Taoka Chemical Industries), and SPI-102A (modified polyamide-based resin, manufactured by Taoka Chemical Industries). Manufactured) and the like.

[Colloidal titration method]
The colloidal titration method used to measure the degree of cationization is a polyelectrolyte titration method proposed by Hiroshi Terayama and Professor of Science at the University of Tokyo. The principle is that polycations and polyanions are ion-associated to form complexes instantly. It is based on forming. In addition, the metachromy phenomenon of dyes is used to detect the end point of titration. A “colloid titration set” (manufactured by Dojindo Laboratories, Inc.) can be used to measure the degree of cationization using a colloid titration method.

  About the said compound with weak cationic property, it is preferable to mix | blend 10-200 mass parts of cellulose coagulants with respect to 100 mass parts of fine fibrous cellulose, More preferably, it is 20-150 mass parts, More preferably, it is 30-100. It is the range of mass parts. If the blending amount of the cellulose coagulant having a weak cationic property is less than 10 parts by mass, the drainage may be deteriorated. On the contrary, if the blending amount exceeds 200 parts by mass, the transparency may be deteriorated.

  In the present invention, as a method for forming an aqueous suspension containing fine fibrous cellulose and a polymer resin, for example, a dispersion containing fine fibers described in Japanese Patent Application No. 2009-173136 is discharged onto the upper surface of an endless belt. A squeezing section for squeezing a dispersion medium from the discharged dispersion to produce a web, and a drying section for drying the web to produce a fiber sheet, from the squeezing section to the drying section. Examples thereof include a method using a manufacturing apparatus in which the endless belt is disposed and the web generated in the squeezing section is conveyed to the drying section while being placed on the endless belt.

  Examples of the dehydration method that can be used in the present invention include a dehydration method that is usually used in the manufacture of paper. A method of dehydrating with a long net, circular net, inclined wire or the like and then dehydrating with a roll press is preferable. Examples of the drying method include methods used in paper manufacture. For example, methods such as a cylinder dryer, a Yankee dryer, hot air drying, and an infrared heater are preferable.

  In addition, as a porous base material which can be used as a wire at the time of dehydration, a wire used for general papermaking can be mentioned. For example, metal wires such as stainless steel and bronze, and plastic wires such as polyester, polyamide, polypropylene, and polyvinylidene fluoride are preferable. Moreover, you may use the membrane filter, such as a cellulose acetate base material, and the nonwoven fabric which consists of plastics, paper, etc. as a wire. The opening of the wire is preferably 0.2 μm to 200 μm, more preferably 0.4 μm to 100 μm. If the mesh opening is less than 0.2 μm, the dehydration rate becomes extremely slow, which is not preferable. If it exceeds 200 μm, the yield of fine fibrous cellulose decreases, which is not preferable.

  In this case, the concentration of the mixed solution is preferably 3% by mass or less, more preferably 0.1 to 1% by mass, and particularly preferably 0.2 to 0.8% by mass. If the concentration of the mixed solution exceeds 3% by mass, the viscosity may be too high and handling may be difficult. The viscosity of the mixed solution is preferably about 100 to 5000 mPa · sec as a B-type viscosity.

The basis weight of the fine fibrous cellulose composite sheet obtained in the present invention is preferably 0.1~1000g / ^{m 2,} more preferably ^{1~500g / m 2, 5~100g / m} 2 is particularly preferred. If the basis weight is less than 0.1 g / m ² , the sheet strength becomes extremely weak and continuous production becomes difficult. If it exceeds 1000 g / m ² , dehydration takes a very long time and productivity is extremely lowered, which is not preferable.

  The thickness of the fine fibrous cellulose composite sheet obtained by the present invention is preferably 0.1 to 1000 μm, more preferably 1 to 500 μm, and particularly preferably 5 to 100 μm. When the thickness is less than 0.1 μm, the sheet strength becomes extremely weak and continuous production becomes difficult. If it exceeds 1000 μm, the dehydration rate takes a very long time, and productivity is extremely lowered, which is not preferable.

  The fine fibrous cellulose composite sheet obtained in the present invention may be processed by a size press, coating, or the like in a subsequent process in order to obtain the desired physical properties.

In the present invention, it is necessary to replace the water-containing fine fibrous cellulose sheet with an organic solvent, that is, to apply or impregnate the organic solvent. The organic solvent has a boiling point of 120 to 260 ° C. and is water-soluble. It is preferable that
If the boiling point of the organic solvent is lower than 120 ° C., the amount of the organic solvent that evaporates together when water is evaporated increases, and a porous sheet may not be obtained. On the other hand, if the boiling point exceeds 260 ° C., a high temperature is required to evaporate the organic solvent, and the fine fibers may be yellowed or the fiber strength may be reduced. Further, the solubility in water is preferably 10% or more at 20 ° C., more preferably 30% or more, and still more preferably 50% or more.

  Examples of such organic solvents include glycol ethers such as dipropylene glycol methyl ether, ethylene glycol mono n-butyl ether, ethylene glycol mono t-butyl ether, and diethylene glycol monoethyl ether, diethylene glycol dimethyl ether, diethylene glycol dibutyl ether, and tetraethylene glycol. Glymes such as dimethyl ether, triethylene glycol dimethyl ether, diethylene glycol diethyl ether, ethylene glycol diethyl ether, ethylene glycol dimethyl ether, diethylene glycol isopropyl methyl ether, dihydric alcohols such as 1,2-butanediol, 1,6 hexanediol, diethylene glycol mono Ethyl ether Tate, ethylene glycol monomethyl ether acetate. Two or more of these organic solvents may be used in combination.

  Of these, diethylene glycol dimethyl ether and diethylene glycol isopropyl methyl ether are particularly preferred because of their excellent solubility in water and a good balance of boiling point, surface tension, and molecular weight.

  In the present invention, the mass ratio of water and the organic solvent contained in the fine fibrous cellulose sheet containing the water and the organic solvent is preferably 100: 10 to 10: 100, more preferably 100: 30 to 30: 100, 100: 50 to 50: 100 is more preferable. If the ratio of the organic solvent is less than 10, the porosity of the sheet may decrease. Moreover, when the ratio of the organic solvent exceeds 100, the pulp concentration decreases too much and the papermaking efficiency decreases. When the ratio of the organic solvent exceeds 100 with the pulp concentration kept constant, the viscosity is too high or fine fibers are May cause agglomeration.

  As a method of applying or impregnating an organic solvent in the present invention, methods such as spray, curtain, gravure, bar, blade, size press, gate roll, cap coater, micro gravure, die coater, rod coater, comma coater, screen coater, etc. However, it is preferable to use at least one method selected from spray, curtain, gravure, bar, blade, and size press because it is easy to control the coating amount (impregnation amount) and can be made uniform. A sheet containing moisture is weak in strength, and when the coater head is brought into contact with the coater, streaks or unevenness occurs. Therefore, a non-contact coating method such as spray or curtain is most preferable.

  In the present invention, the drying process is not particularly limited, but a two-stage drying is a preferred embodiment. That is, water is evaporated in the first drying step, and then an organic solvent having a boiling point higher than that of water is evaporated in the second drying step. Moreover, as a drying method, the method normally used by paper manufacture is preferable, For example, methods, such as a cylinder dryer, a Yankee dryer, hot air drying (floating dryer), an infrared heater, are mentioned. Many fine voids are formed in the fine fibrous cellulose sheet obtained by this method, and it is extremely easy to impregnate the resin.

  The porous composite sheet produced by the present invention is a low-density sheet having a high elastic modulus derived from cellulose and having no wrinkles and many pores. In addition, it is possible to impart a function of a polymer resin such as improvement of water resistance or moisture resistance dimensional stability to a cellulose sheet that is inherently weak to water or has a large dimensional change with respect to humidity.

In the present invention, the term “porous” means that the density of the composite sheet is 0.9 g / cm ³ or less, the pore volume of 1 μm or less is 0.03 ml / g or more, and the pore mode diameter of 1 μm or less is 0.00. That which is 007 μm or more. Preferably density and ^{0.30~0.90g / cm 3, 0.40~0.85g / cm} 3 is particularly preferred. When the density is less than 0.30 g / cm ³ , the strength of the sheet is weak, and when the density exceeds 0.90 g / cm ³ , the porosity is low. The pore volume of 1 μm or less is preferably 0.03 ml / g to 0.60 ml / g, particularly preferably 0.05 ml / g to 0.55 ml / g. If it is less than 0.03 ml / g, the porosity is low. If it is 0.60 ml / g, the strength of the sheet is low. The pore mode diameter of 1 μm or less is preferably 0.007 μm to 0.20 μm, particularly preferably 0.01 μm to 0.10 μm. If it is less than 0.007 μm, the porosity is low. If it exceeds 0.20 μm, the strength of the sheet is low.

  Examples are given below to describe the present invention in more detail, but it goes without saying that the present invention is not limited thereto. Moreover, unless otherwise indicated, the part and% in an example show a mass part and mass%, respectively.

<Production of fine fibrous cellulose aqueous suspension>
After classifying bay pine chips used for pulp production into chips of 2 mm on with a chip thickness classification device, the moisture content of the chips in the sun (water content / total amount of chips including water content) Was adjusted to about 7% and used as a sample for wood dusting.
The chips were coarsely pulverized using a coarse pulverizer (Hammer Crusher HC-400) manufactured by Hadano Sangyo Co., Ltd. Without classifying it, it was first finely pulverized with the company's DD mill (screen 0.8 mmφ, DD-3 type), and then secondary pulverized with DD mill (screen 0.2 mmφ, DD-3 type). .
The wood flour was degreased at 90 ° C. for 5 hours with stirring in a 2% aqueous sodium carbonate solution. The treated raw material was washed with 10 times the amount of distilled water, dehydrated with a Buchner, and distilled water was added to adjust the concentration.
In the delignification step, acetic anhydride and 30% hydrogen peroxide were mixed at a volume ratio of 1: 1, and this delignification liquid was adjusted to a hydrogen peroxide equivalent of 4 with respect to the raw material after degreasing treatment (BD 30 g). 1.5 L of a peracid aqueous solution corresponding to 5% was added and treated at 90 ° C. for 1 hour.
The slurry-like delignified raw material (BD 30 g) was immersed in a 5% aqueous potassium hydroxide solution at room temperature for 24 hours and subjected to dehemicose treatment. It was washed with 10 times the amount of distilled water, dehydrated with Buchner, and distilled water was added to prepare a 2% pulp suspension.
The above pulp slurry is treated for 2 hours at a rotational speed of 7000 rpm with a high-speed rotating type defibrating machine (trade name: “CLEAMIX 9S” manufactured by M Technique Co., Ltd.), diluted to a concentration of 0.2%, and fine fibrous cellulose aqueous system A suspension was obtained.

<Example 1>
Anionic polypropylene resin emulsion (trade name: “HITECH P-5800” (glass transition temperature: 0 ° C., average particle size: 0) obtained by diluting the fine fibrous cellulose aqueous suspension to 50 parts and a concentration of 0.2%. .15 μm), manufactured by Toho Chemical Co., Ltd.), 50 parts of a cationic coagulant (trade name: “Fixage 614” manufactured by Kurita Kogyo Co., Ltd.) with a concentration of 0.2% was added and stirred for 1 minute. did. The obtained mixed solution was sucked and dehydrated on a non-woven fabric (trade name: “Techno Wiper”, manufactured by Technos Co., Ltd.) subjected to thermal calendaring at 180 ° C.
Ethylene glycol mono-tert-butyl ether (EG-t-BE) (manufactured by Tokyo Chemical Industry Co., Ltd., molecular weight 118, boiling point 152 ° C., surface tension 26.3 mN / m) on the obtained wet sheet 100 parts of wet sheet solid content 2400 parts were uniformly spray-coated. The pressure was further reduced to form a wet sheet containing water and an organic solvent. The wet sheet was dried for 40 minutes while being pressurized to 0.3 MPa with a cylinder dryer at 70 ° C. to obtain a sheet after the first drying. The sheet after the first drying was dried at 130 ° C. for 3 minutes (second drying step), and the sheet was peeled off from the techno wiper to obtain a 49.3 g / m ² fine fibrous cellulose composite porous sheet. The resulting sheet was white and opaque. The thickness was 68 μm.

  By adding the anionic polypropylene resin emulsion, the contact angle to water is increased compared to the case of cellulose alone, the humidity expansion / contraction rate is lowered, and in addition, temperature dimensional stability and strength performance can be improved. It was.

<Example 2>
44 In the same manner as in Example 1, except that an anionic polyethylene emulsion (trade name: “E-2213” (glass transition temperature: −120 ° C., average particle size: 0.07 μm), manufactured by Toho Chemical Industry Co., Ltd.) was used. A fine fibrous cellulose composite porous sheet of .7 g / m ² was obtained. The resulting sheet was white and opaque. The thickness was 61 μm.

<Example 3>
A cationic polyurethane emulsion (trade name: Superflex 650, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) (glass transition temperature: 40 ° C.) 50 diluted with 50 parts of the above fine fibrous cellulose aqueous suspension to a concentration of 0.2% After mixing with the part, the mixture was stirred for 1 minute. The obtained mixed solution was sucked and dehydrated on a non-woven fabric (trade name: “Techno Wiper”, manufactured by Technos Co., Ltd.) subjected to thermal calendaring at 180 ° C. Ethylene glycol mono-tert-butyl ether (EG-t-BE) (manufactured by Tokyo Chemical Industry Co., Ltd., molecular weight 118, boiling point 152 ° C., surface tension 26.3 mN / m) on the obtained wet sheet 100 parts of wet sheet solid content 2400 parts were uniformly spray-coated. The pressure was further reduced to form a wet sheet containing water and an organic solvent. The wet sheet was dried for 40 minutes while being pressurized to 0.3 MPa with a cylinder dryer at 70 ° C. to obtain a sheet after the first drying. The sheet after the first drying was dried at 130 ° C. for 3 minutes (second drying step), and the sheet was peeled off from the techno wiper to obtain a 45.7 g / m ² fine fibrous cellulose composite porous sheet. The resulting sheet was white and opaque. The thickness was 57 μm.

<Example 4>
After suction dehydration using the anionic polypropylene emulsion in the same manner as in Example 1, 1200 parts of ethylene glycol mono-tert-butyl ether was uniformly curtain coated on 100 parts of wet sheet solids. The pressure was further reduced to form a wet sheet containing water and an organic solvent. The wet sheet was dried for 40 minutes while being pressurized to 0.3 MPa with a cylinder dryer at 70 ° C. to obtain a sheet after the first drying. The sheet after the first drying was dried at 130 ° C. for 3 minutes (second drying step), and the sheet was peeled off from the techno wiper to obtain a 49.7 g / m ² fine fibrous cellulose composite porous sheet. The resulting sheet was white and opaque. The thickness was 66 μm.

<Example 5>
A 47.8 g / m ² fine fibrous cellulose composite porous sheet was prepared in the same manner as in Example 4 except that 4800 parts of ethylene glycol mono-tert-butyl ether was uniformly spray-coated on 100 parts of wet sheet solids. Obtained. The resulting sheet was white and opaque. The thickness was 69 μm.
By adding the anionic polyethylene emulsion, the contact angle of water increased compared to the case of cellulose alone, the humidity expansion / contraction rate decreased, and in addition, temperature dimensional stability and strength performance could be improved. .

<Comparative Example 1>
A fine fibrous cellulose porous sheet was obtained in the same manner as in Example 1 except that the fine fibrous cellulose aqueous suspension was 100 parts and no polymer emulsion was added.

<Comparative example 2>
A fine fibrous cellulose composite sheet was obtained in the same manner as in Example 1 except that ethylene glycol mono-tert-butyl ether (EG-t-BE) was not added on the wet sheet.

<Comparative Example 3>
A fine fibrous cellulose composite sheet was obtained in the same manner as in Example 2 except that ethylene glycol mono-tert-butyl ether (EG-t-BE) was not added on the wet sheet.

[Evaluation method]
1. Air Permeability The air permeability of the fine fibrous cellulose / polymer composite sheet was measured using the JAPAN TAPPI Paper Pulp Test Method No. It was measured according to 5-2: 2000 (Oken type). The lower the air permeability, the better the resin impregnation.

2. Pore volume and pore surface area The pore volume and pore surface area of a fine fibrous cellulose sheet having a diameter of 1 μm or less were measured with a mercury porosimeter (manufactured by Shimadzu Corporation, trade name: “Autopore IV9505”). The larger the pore volume and pore surface area, the better the impregnation of the resin. The pore volume is preferably 0.1 or more and 2 mL / g or less. When the pore volume is less than 0.1 mL / g, impregnation is impossible. When the pore volume exceeds 2 ml / g, the ratio of the fine fibrous cellulose to the impregnated resin becomes small, which is not preferable. The pore surface area is preferably 40 m ² / g or more and 200 m ² / g or less. If it is less than 40 m ² / g, the impregnation property of the resin deteriorates, and if it exceeds 200 m ² / g, the strength of the sheet is undesirably lowered.

3. Stekkit method sizing degree Stekking method sizing degree measurement was performed according to JIS P8122. The higher the size, the lower the water permeability.

4). Humidity expansion / contraction measurement The humidity expansion / contraction test was performed using a humidity expansion / contraction measurement apparatus manufactured by Sagawa Seisakusho. While applying a load with a 20 g weight, the humidity in the chamber is (a) 50% RH, (b) 85% RH, (c) 25% RH, (d) 85% RH, (e) 25% RH. After giving the history, it was further changed in the order of 80% RH and 25% RH, the amount of expansion / contraction of both was measured, and the humidity expansion / contraction rate was calculated by the following equation.
Humidity expansion / contraction rate (%) = (Expansion / contraction at humidity 80% RH−Expansion / contraction at 25% RH) / Span length × 100

5. Contact angle measurement According to TAPPI T558, 4 μL of distilled water (20 ° C.) was dropped, and the contact angle after 0.1 seconds was measured with a dynamic contact angle meter (trade name: “DAT 1100”, manufactured by FIBRO system ab). It was measured.

  As is clear from Table 1, the fine fibrous cellulose / polymer composite sheet of the present invention is a porous sheet and also has polymer characteristics such as water resistance. According to this manufacturing method, the composite porous sheet can be easily manufactured by a papermaking apparatus. And the humidity dimensional stability and moisture-proof performance are improved, and a porous sheet is obtained.

  According to the production method of the present invention, a fine fibrous cellulose and a polymer can be efficiently made into a porous composite sheet, and the obtained sheet also has excellent water resistance, humidity dimensional stability, and moisture resistance performance. It is shown and is useful for water resistant filters and the like.

Claims (5)

A method for producing a composite porous sheet using fine fibrous cellulose and a polymer having film-forming properties, and mixing and mixing a polymer emulsion having film-forming properties with an aqueous suspension containing fine fibrous cellulose. A preparation step for producing a liquid, a paper making step for forming a sheet containing moisture by dehydrating the mixed solution on a porous substrate, a step for replacing the moisture-containing sheet with an organic solvent, an organic solvent The manufacturing method of the fine fibrous cellulose composite porous sheet characterized by having the drying process which heat-drys the sheet | seat substituted by. The fine polymer according to claim 1, wherein the polymer is at least one selected from polyurethane, polyethylene, polypropylene, (meth) acrylic acid alkyl ester copolymer, and acid-modified styrene-butadiene copolymer. A method for producing a fibrous cellulose composite porous sheet. The method for producing a porous sheet of fine fibrous cellulose composite according to claim 1 or 2, wherein the polymer emulsion is cationic. In the said preparation process, a cellulose coagulant is mix | blended with the said liquid mixture, The manufacturing method of the fine fibrous cellulose composite porous sheet of any one of Claims 1-3 characterized by the above-mentioned. In the said preparation process, the fiber width of the fine fibrous cellulose to mix is 2-1000 nm, The manufacturing method of the fine fibrous cellulose composite porous sheet of any one of Claims 1-4 characterized by the above-mentioned.