JP7327952B2 - Process for producing dispersions, structures and crosslinked structures containing fine cellulose fibers - Google Patents

Description

The present invention relates to methods for producing dispersions, structures and crosslinked structures containing fine cellulose fibers and organic fibers.

In recent years, from the viewpoint of environmental protection, it has been proposed to manufacture various articles (eg, sheets, moldings, etc.) using materials that have less environmental impact during manufacture, use, and/or disposal. For example, a molded body composed of a material mainly composed of organic fibers has advantages such as being lightweight and being inexpensive to dispose of. In particular, if the organic fibers are biodegradable materials such as cellulosic fibers, the molding itself will be a material that meets modern needs from the viewpoint of sustainability. For example, Patent Document 1 describes a composite container consisting of an outer container mainly made of paper and an inner container mainly made of plastic, and having a sealed lid member. and mentions an isocyanate-based resin as an interlaminar strength enhancer.

Conventionally, various paper strength enhancers have been proposed as a method for increasing the mechanical strength of paper (that is, a sheet-like material mainly composed of cellulose fibers, which are organic fibers). and a water-soluble heat-reactive urethane prepolymer having isocyanate groups blocked with a blocking agent that dissociates upon heat treatment; and (b) a cationic compound that increases the cationicity of the urethane prepolymer in an aqueous solution. We describe a wet strength agent characterized by: In recent years, fine cellulose fibers obtained by beating and pulverizing cellulose fibers at a high level to make them finer (fibrillated) to a fiber diameter of 1 μm or less have attracted attention. , Patent Document 3 is composed of fine cellulose fibers having an average fiber diameter of 2 nm or more and 1000 nm or less, the weight ratio of the fine cellulose fibers is 50% by weight or more and 99% by weight, and the aggregate of block polyisocyanate is included in the weight of the fine cellulose fibers. A fine cellulose fiber sheet containing 1 to 100% by weight is described.

JP 2014-168340 A JP-A-2003-138497 WO2015/008868

To obtain articles (sheets, moldings, etc.) useful for a wide range of applications by using a molding material mainly composed of organic fibers alone (that is, without requiring combination with other members (laminating, etc.)) It is desirable that the molding material has various properties required for articles (e.g. moldability (especially shape followability to mold), mechanical strength, water resistance and solvent resistance). be The container described in Patent Document 1 has an outer container mainly made of paper, but has a complicated structure in which the outer container and the inner container are combined, and there is room for improvement in terms of cost and convenience. There is Further, Patent Document 2 provides a paper strength enhancer in which the adsorption rate of the urethane prepolymer to cellulose fibers is improved by increasing the cationicity of the water-soluble urethane prepolymer in combination with a cationic compound, and Patent Document 3 provides , provides a fine cellulose fiber sheet having various excellent physical properties by using a blocked polyisocyanate. It does not provide molding materials that give articles having mechanical strength, water resistance and solvent resistance.

The present invention solves the above problems, and provides an organic fiber-based article (sheet, molded article, etc.) having good moldability (especially shape followability to a molding die), mechanical strength, water resistance, and solvent resistance. It is an object of the present invention to provide a method for producing a dispersion and a structure, and a crosslinked structure formed from the structure and usable as various forms of articles.

As a result of intensive studies conducted by the present inventors to solve the above problems, the above problems can be solved by a dispersion containing fine cellulose fibers with a specific average fiber diameter, organic fibers with a specific average fiber diameter, and blocked polyisocyanate. We found that and completed the present invention.
The present invention includes the following aspects.

[1] A method for producing a dispersion containing fine cellulose fibers, organic fibers, and blocked isocyanate, comprising:
A method comprising mixing fine cellulose fibers having an average fiber diameter of 2 nm or more and 1000 nm or less, organic fibers having an average fiber diameter of more than 3000 nm, blocked polyisocyanate, and water.
[2] The method according to Aspect 1, wherein the dispersion contains the blocked polyisocyanate in an amount of 0.1 to 120 parts by mass based on 100 parts by mass of the fine cellulose fibers.
[3] The method according to aspect 1 or 2 above, wherein the blocked polyisocyanate is a cationic blocked polyisocyanate.
[4] the mass ratio of the fine cellulose fibers and the organic fibers in the dispersion (fine cellulose fibers/organic fibers) is 0.2/99.8 to 30/70;
The method according to any one of aspects 1 to 3 above, wherein the dispersion has a solid content ratio of 0.1% by mass to 55% by mass.
[5] The method according to any one of aspects 1 to 4, wherein the organic fibers include fibers having hydroxyl groups and/or amide groups on at least their surfaces.
[6] The method according to any one of aspects 1 to 5, wherein the organic fibers comprise cellulose fibers.
[7] Any one of the above aspects 1 to 6, wherein the mixing is performed by mixing fine cellulose fibers, blocked polyisocyanate and water to prepare a premix, and then mixing the premix and organic fibers. The method described in .
[8] Any one of the above aspects 1 to 7, wherein the mixing is performed by mixing fine cellulose fibers, organic fibers and water to prepare a pre-mixture, and then mixing the pre-mixture with the blocked polyisocyanate. The method described in .
[9] The method according to any one of aspects 1 to 8 above, wherein the mixing is performed at a temperature of 5°C to 60°C.
[10] a dispersion preparation step of preparing a dispersion by the method according to any one of the above aspects 1 to 9;
A structure comprising a concentration step of dehydrating the dispersion to form a water-containing concentrate, and a structure-forming step of drying the water-containing concentrate at 80° C. or higher and 120° C. or lower to form a structure. Production method.
[11] A structure, wherein a dispersion is prepared by the method according to any one of the above aspects 1 to 9, and a structure is formed by drying the dispersion at 80°C or higher and 120°C or lower. A method of manufacturing a structure, comprising a forming step.
[12] The method according to aspect 10 or 11, wherein the structure is a sheet or a molded body.
[13] The method according to any one of the above aspects 10 to 12, wherein the blocked polyisocyanate is uniformly distributed within the structure.
[14] a dispersion preparation step of preparing a dispersion by the method according to any one of the above aspects 1 to 9;
a concentration step of dehydrating the dispersion to form a hydrous concentrate; and drying the hydrous concentrate at 80° C. to 120° C., and subsequently or simultaneously with the drying, blocking in the blocked polyisocyanate. A crosslinked structure forming step of forming a crosslinked structure by crosslinking the blocked polyisocyanate and the fine cellulose fibers and/or the organic fibers by heating at a group elimination temperature or higher. Production method.
[15] A dispersion preparation step of preparing a dispersion by the method according to any one of the above aspects 1 to 9, and drying the dispersion at 80 ° C. or higher and 120 ° C. or lower, followed by the drying or the drying At the same time, a crosslinked structure is formed by crosslinking the blocked polyisocyanate and the fine cellulose fibers and/or the organic fibers by heating at a temperature equal to or higher than the elimination temperature of the blocking groups in the blocked polyisocyanate. A method for producing a crosslinked structure, comprising a forming step.
[16] The method according to aspect 14 or 15, wherein the crosslinked structure has a wet/dry strength ratio of 0.4 to 1.2.
[17] The method according to any one of aspects 14 to 16 above, wherein the heating is performed at a temperature of 130°C to 220°C.

INDUSTRIAL APPLICABILITY According to the present invention, a dispersion and a structure, as well as the structure, which provide an organic fiber-based article having good moldability (especially conformability to a mold), mechanical strength, water resistance and solvent resistance A method is provided for producing crosslinked structures that are formed from and that can be used as articles of various forms.

Illustrative embodiments of the invention will be described below, but the invention is not limited to these embodiments.

One aspect of the present invention includes fine cellulose fibers with an average fiber diameter of 2 nm or more and 1000 nm or less (hereinafter sometimes simply referred to as fine cellulose fibers) and organic fibers with an average fiber diameter of more than 3000 nm (hereinafter simply referred to as organic fibers). ), a method for producing a dispersion containing blocked polyisocyanate and water, fine cellulose fibers having an average fiber diameter of 2 nm or more and 1000 nm or less, organic fibers having an average fiber diameter of more than 3000 nm, and blocked polyisocyanate. A method is provided for manufacturing a structure comprising: In one aspect, the structure may be formed using the dispersion. Another aspect of the present invention provides a method for producing a crosslinked structure by crosslinking the structure.

According to the structure containing the combination of the fine cellulose fibers and the organic fibers, the fine cellulose fibers are dispersed among the organic fibers and function as a filler. Obtainable. However, since fine cellulose fibers are easily aggregated due to their fine structure, simply combining fine cellulose fibers with organic fibers cannot sufficiently improve the physical properties of fine cellulose fibers. Further, since fine cellulose fibers are inherently hydrophilic, they are not necessarily suitable as fillers for articles requiring water resistance. Furthermore, a molding material that is simply a combination of fine cellulose fibers and organic fibers does not have sufficient moldability (particularly shape followability to a molding die). The present inventors found that when combining fine cellulose fibers and organic fibers, the presence of block polyisocyanate (1) prevents fine cellulose fibers from aggregating and allows them to be well dispersed and interposed between organic fibers, ( 2) Mainly using fine cellulose fibers as a scaffold for water resistance, and (3) providing a structure as a molding material with good moldability (especially shape followability to a molding die). I found

A blocked polyisocyanate is a compound having a structure in which the isocyanate groups of a polyisocyanate (that is, a polyfunctional compound having two or more isocyanate groups per molecule) are blocked with blocking groups, and is substantially non-reactive at room temperature. On the other hand, at the elimination temperature of the blocking group or higher, two or more free isocyanate groups are generated per molecule, and a functional group having reactivity with the isocyanate group (for example, a functional group having an active hydrogen) reacts with it. Form a crosslinked structure. Fine cellulose fibers have hydroxyl groups, which are functional groups reactive with isocyanate groups, but blocked polyisocyanates retain blocking groups in the dispersion or structure, so they do not react with fine cellulose fibers. However, it adsorbs to the fine cellulose fibers and functions as a dispersant for the fine cellulose fibers, contributing to the uniform dispersion of the fine cellulose fibers between the organic fibers. When the dispersion or structure is heated above the desorption temperature of the blocking group, the polyisocyanates themselves and the fine cellulose fibers and the polyisocyanate are chemically bonded to form polyisocyanate-polyisocyanate and polyisocyanate-polyisocyanate- A crosslinked structure is formed between fine cellulose fibers. Moreover, when the organic fiber has a functional group having an active hydrogen, a crosslinked structure between the polyisocyanate and the organic fiber is also formed. Due to the above-mentioned crosslinked structure formed by using the blocked polyisocyanate, the fine cellulose fibers maintain their fine structure in the crosslinked structure (that is, aggregation of the fine cellulose fibers is avoided) and a stable three-dimensional network is formed. is formed, and furthermore, the physical properties of the crosslinked structure can be improved more remarkably because the hydroxyl groups are reduced (due to the reaction with the isocyanate group) to be water resistant.

In the crosslinked structure of the present embodiment, the fine cellulose fibers spread between the organic fibers are not only dispersed between the organic fibers, but also form a three-dimensional network due to the crosslinked structure derived from the block polyisocyanate. Therefore, it can be molded into a complicated shape and has good mechanical strength, water resistance and solvent resistance. Therefore, the crosslinked structure of the present embodiment can be used, for example, in a wide range of applications such as various containers for food, various containers used as daily necessities, stationery, etc., packaging materials, packaging materials, board materials such as decorative boards, and interior products. It can be suitably applied to the intended use. Exemplary embodiments of dispersions, structures, crosslinked structures, and methods of making these are described below.

<Dispersion and method for producing the same>
The dispersion produced in this embodiment contains fine cellulose fibers with an average fiber diameter of 2 nm or more and 1000 nm or less, organic fibers with a fiber diameter of more than 3000 nm, blocked polyisocyanate, and water.

In one embodiment, the dispersion may comprise 0.01-15% by weight fine cellulose fibers, 0.02-30% by weight organic fibers, 0.0001-10% by weight blocked polyisocyanate, and water.

(fine cellulose fiber)
The fine cellulose fibers have an average fiber diameter of 2 nm or more and 1000 nm or less. Here, the average fiber diameter of the fine cellulose fibers means the average fiber diameter recognized from the surface SEM image or TEM image, and its measurement conforms to the evaluation means described in International Publication No. WO2006/4012. Cellulose with an average fiber diameter of less than 2 nm does not have a clear difference from molecular chains such as hemicellulose dissolved in water. Inadequate as a body reinforcement. On the other hand, cellulose having an average fiber diameter of more than 1000 nm is not sufficiently effective in functioning as a reinforcing material by uniformly distributing it among organic fibers. From the viewpoint of obtaining good physical properties as a reinforcing material, the average fiber diameter is preferably 10 nm or more, more preferably 15 nm or more, and still more preferably 20 nm or more, and the fine cellulose fibers are uniformly distributed among the organic fibers for reinforcement. From the viewpoint of functioning well as a material, the thickness is preferably 800 nm or less, more preferably 600 nm or less, and even more preferably 500 nm or less.

The fine cellulose fibers may be short fibers (staple) or continuous long fibers (filaments), but short fibers are preferred.

The degree of polymerization (DP) of the fine cellulose fibers is preferably 100 or more and 12,000 or less. The degree of polymerization of fine cellulose fibers is the number of repeating glucose rings forming the cellulose molecular chain. The degree of polymerization of fine cellulose fibers is measured by measuring the viscosity of a copper ethylenediamine solution by the copper ethylenediamine method. The viscosity-average degree of polymerization DP is obtained from the following viscosity formula. where [η] is the intrinsic viscosity.
DP=175×[η]
When the degree of polymerization of the fine cellulose fibers is 100 or more, the tensile strength and elastic modulus of the fibers themselves are improved, and as a result, the mechanical strength and handleability of the structure are improved. The degree of polymerization is more preferably 150 or higher, still more preferably 300 or higher. There is no particular upper limit to the degree of polymerization of the fine cellulose fibers, but since cellulose with a degree of polymerization exceeding 12,000 is practically difficult to obtain, the degree of polymerization is usually 12,000 or less, which is convenient for handling and industrial use. From the viewpoint of practical implementation, it is preferably 8,000 or less, more preferably 6,000 or less.

As fine cellulose fibers, both chemically unmodified (that is, unmodified) fibers and chemically modified fibers can be used. Chemical modifications include esterification (e.g., acetate esterification, nitrate esterification, or sulfate esterification) and etherification (e.g., methyl ether) of some or most of the hydroxyl groups present on the surface of the fine cellulose fibers. Etherification with an alkyl ether, a carboxy ether typified by carboxymethyl ether, or a cyano ether typified by cyanoethyl ether), oxidation (for example, with a TEMPO oxidation catalyst, the carboxyl group of the hydroxyl group at the 6-position of the glucose ring (acid type, including salt type)), and the like. In a preferred embodiment, the fine cellulose fibers desirably have hydroxyl groups remaining on the surface in consideration of reactivity with the blocked polyisocyanate. That is, the fine cellulose fibers are preferably fibers whose surfaces are not chemically modified, but even if the fibers are chemically modified with acetyl groups, carboxyl groups, phosphate ester groups, etc., hydroxyl groups remain on the surface. If so, it can be suitably used as the fine cellulose fibers used in the present invention.

The mass ratio of fine cellulose fibers to the total mass of the dispersion is preferably 0.1% by mass or more and 5% by mass or less. When the mass ratio of fine cellulose fibers is 0.1% by mass or more, a uniform structure can be produced with high productivity. On the other hand, when the mass ratio of the fine cellulose fibers is 5% by mass or less, the viscosity of the dispersion does not become too high and a uniform structure can be easily produced. It is easy to keep good, and the handleability is also good. The mass ratio of the fine cellulose fibers is more preferably 0.15% by mass or more and 4% by mass or less, and still more preferably 0.2% by mass or more and 3% by mass or less.

Raw materials for fine cellulose fibers include so-called wood pulp such as softwood pulp and hardwood pulp, and non-wood pulp. Non-wood pulps include cotton-derived pulp such as cotton linter pulp, hemp-derived pulp, bagasse-derived pulp, kenaf-derived pulp, bamboo-derived pulp, and straw-derived pulp. Cotton-derived pulp, hemp-derived pulp, bagasse-derived pulp, kenaf-derived pulp, bamboo-derived pulp, and straw-derived pulp are cotton lints or cotton linters, hemp-based abaca (e.g., often from Ecuador or the Philippines), respectively. , zaisal, bagasse, kenaf, bamboo, straw, etc., through a refining process and a bleaching process for the purpose of delignification and hemicellulose removal by cooking treatment. In addition, refined products such as seaweed-derived cellulose and sea squirt cellulose can also be used as raw materials for fine cellulose fibers. Furthermore, cut yarns of regenerated cellulose fibers and cut yarns of cellulose derivative fibers can also be used as a raw material for fine cellulose fibers. It can be used as a raw material or fine cellulose fibers themselves. Among these, refined pulp derived from cotton lint or cotton linter, hemp-based abaca (e.g., mostly from Ecuador or the Philippines), zaisal, bagasse, kenaf, bamboo, straw, etc., is a fine cellulose fiber with a long fiber length. is easily obtained, and the reinforcing effect as a filler due to entanglement is also high, so it is particularly preferable.

Next, a method for refining cellulose fibers will be described. It is preferable that the cellulose fibers be refined through a pretreatment process, a beating process and a refinement process. In the pretreatment step, it is effective to make the raw pulp into a state that facilitates pulverization by autoclave treatment under water immersion at a temperature of 100 to 150° C., enzyme treatment, or a combination thereof. These pretreatments not only reduce the load of microfibrillation, but also remove impurities such as lignin and hemicellulose present on the surface and interstices of the microfibrils that make up the cellulose fibers into the aqueous phase. Since it also has the effect of increasing the purity of the α-cellulose of the converted fibers, it may be effective in improving the heat resistance of fine cellulose fiber nonwoven fabrics.

In the beating step, the raw pulp is 0.5% by mass or more and 4% by mass or less, preferably 0.8% by mass or more and 3% by mass or less, more preferably 1.0% by mass or more and 2.5% by mass or less of solids. It is dispersed in water so as to have a concentration of 10%, and is highly fibrillated with a beating device such as a beater or disc refiner (double disc refiner). When using a disc refiner, if the clearance between the discs is set as narrow as possible (for example, 0.1 mm or less), extremely high beating (fibrillation) will proceed, so use a high-pressure homogenizer or the like. In some cases, the conditions for miniaturization can be relaxed, which is effective.

A preferred degree of beating treatment is defined as follows. In the study by the present inventors, as the beating treatment was performed, the CSF value (indicating the degree of beating of cellulose, evaluated by the Canadian standard freeness test method for pulp defined in JIS P 8121) decreased over time. It was found that after the beating treatment was continued, it increased again after it became close to zero. As a result, it was found that it is preferable to continue beating treatment until the CSF value is increased after the CSF value once becomes close to zero. In the present disclosure, the CSF value in the process in which the CSF value decreases from unbeaten is expressed as ***↓, and the CSF value in the tendency to increase after reaching zero is expressed as ***↑. In the beating treatment, the CSF value is preferably at least zero, more preferably CSF30↑. In an aqueous dispersion prepared to such a beating degree, fibrillation progresses to a high degree, and a homogeneous sheet consisting of fine cellulose fibers having a number average fiber diameter of 1000 nm or less can be obtained. At the same time, the resulting fine cellulose fiber sheet tends to have improved tensile strength, possibly due to an increase in adhesion points between cellulose microfibrils. In addition, a highly beaten aqueous dispersion with a CSF value of at least zero or a value of ***↑ that increases thereafter has increased uniformity, and can reduce clogging in the subsequent refinement treatment using a high-pressure homogenizer or the like. There are efficiency advantages.

In the production of fine cellulose fibers, it is preferable to carry out a refinement treatment using a high-pressure homogenizer, an ultrahigh-pressure homogenizer, a grinder, or the like, following the beating step described above. At this time, the solid content concentration in the water dispersion is 0.5% by mass or more and 4% by mass or less, preferably 0.8% by mass or more and 3% by mass or less, more preferably 1.0% by mass, according to the beating treatment described above. It is more than mass % and below 2.5 mass %. In the case of the solid content concentration within this range, clogging does not occur, and moreover efficient pulverization treatment can be achieved.

Examples of the high-pressure homogenizer to be used include an NS-type high-pressure homogenizer manufactured by Niro Soavi (Italy), a Rannie type (R model) pressure-type homogenizer manufactured by SM T Co., Ltd., and a high-pressure homogenizer manufactured by Sanwa Kikai Co., Ltd. Any device other than these devices may be used as long as it can perform the miniaturization with substantially the same mechanism as these devices. The ultra-high pressure homogenizer means a high pressure collision type atomization processor such as Mizuho Kogyo Co., Ltd. Microfluidizer, Yoshida Kikai Kogyo Co., Ltd. Nanomizer, Sugino Machine Co., Ltd. Ultimizer. Any device other than these may be used as long as it implements miniaturization with substantially the same mechanism. As the grinder-type miniaturization device, there is a stone mill-type grinding type typified by Pure Fine Mill manufactured by Kurita Machinery Co., Ltd. and Super Mascolloider manufactured by Masuko Sangyo Co., Ltd. These devices are almost the same. Any device other than these may be used as long as the device implements miniaturization by the mechanism of (1).

The average fiber diameter of the fine cellulose fibers depends on the conditions of micronization by a high-pressure homogenizer or the like (selection of equipment, operating pressure and number of passes) or the conditions of pretreatment before the micronization (e.g., autoclave treatment, enzyme treatment, beating processing, etc.).

When using, for example, fibers whose surfaces have been chemically modified as the fine cellulose fibers, various surface chemical treatments are applied according to the purpose, for example, to remove some or most of the hydroxyl groups present on the surfaces of the fine cellulose fibers. , Esterified to acetate ester, nitrate ester, sulfate ester, etc., or etherified to alkyl ether typified by methyl ether, carboxy ether typified by carboxymethyl ether, cyano ether typified by cyanoethyl ether, etc. , can be prepared and used as appropriate. In addition, when using cellulose-based fine fibers in which the hydroxyl group at the 6-position is oxidized by a TEMPO oxidation catalyst and becomes a carboxyl group (including acid type and salt type), high energy such as a high-pressure homogenizer is necessarily required. A dispersion of fine cellulose can be obtained without the need to use a micronizer. For example, as described in the literature (A. Isogai et al., Biomacromolecules, 7, 1687-1691 (2006)), 2,2,6,6-tetramethylpiperidinooxy is added to an aqueous dispersion of natural cellulose. A radical-like catalyst called TEMPO and an alkyl halide are allowed to coexist, an oxidizing agent such as hypochlorous acid is added, and the reaction is allowed to proceed for a certain period of time. A dispersion of fine cellulose fibers can be obtained very easily by the treatment.
In one aspect, two or more types of fine cellulose fibers having different raw materials, degrees of fibrillation, surface chemical treatments, etc. may be combined in an arbitrary ratio.

(organic fiber)
The dispersion contains organic fibers with an average fiber diameter greater than 3000 nm. The average fiber diameter of the organic fibers is more than 3000 nm (3 μm), preferably 3.5 μm or more, more preferably 4 μm or more from the viewpoint of maintaining a viscosity suitable for mixing the dispersion, and the fine cellulose fibers are fillers. It is preferably 30 μm or less, more preferably 27 μm or less, and even more preferably 25 μm or less, from the viewpoint of uniformly dispersing and functioning as a.

The organic fibers preferably have functional groups having active hydrogen (for example, hydroxyl groups, amide groups, amino groups, carboxyl groups, thiol groups, etc.). In a preferred embodiment, the organic fibers comprise or consist of fibers having at least surface hydroxyl groups and/or amide groups. Suitable examples of organic fibers having hydroxyl groups and/or amide groups include cellulose fibers, starch fibers, chitin fibers, chitosan fibers and other polysaccharide fibers (poly-α-1,3-glucan, poly-β-1,3- glucan, etc.), cellulose acetate fiber, polyamide fiber (PA-6 fiber, PA-6,6 fiber, PA-12 fiber, aromatic polyamide fiber such as Kevlar fiber, etc.), polyvinyl alcohol fiber (vinyl acetate including copolymers having monomer units). In particular, when polysaccharide fibers such as cellulose fibers are used, many of them are highly oriented fibers derived from nature. It is particularly preferable because interaction such as entanglement becomes easier. Similarly, highly oriented polyamide fibers are preferable because they can increase the entanglement effect by fibrillation treatment such as beating treatment, but the effects of the present invention are effectively exhibited even if they are used without beating treatment. sometimes. The mass ratio of the organic fibers having hydroxyl groups and/or amide groups to the total mass of the organic fibers is preferably 20% by mass or more, more preferably 30% by mass or more, in that the organic fibers can be satisfactorily crosslinked with the blocked polyisocyanate. , more preferably 40% by mass or more. The above mass ratio may be 100% by mass, but from the viewpoint of obtaining the advantage of using fibers having no hydroxyl group and/or amide group (for example, imparting water resistance to the structure), for example, 95% by mass or less, or 90% by mass % or less, or 85% by mass or less.

The mass ratio of the organic fiber to the total mass of the dispersion is preferably 5 to 65% by mass, more preferably 8 to 55% by mass, and still more preferably 10 to 50% by mass, from the viewpoint of handleability during structure production. be.

The mass ratio of the fine cellulose fibers to the organic fibers in the dispersion (fine cellulose fibers/organic fibers) is preferably 0.2/99 from the viewpoint that the fine cellulose fibers enter between the organic fibers and exhibit a good reinforcing effect. .8 to 30/70, more preferably 0.5/99.5 to 25/75, still more preferably 1/99 to 20/80.

The solid content ratio of the dispersion is preferably 1% by mass or more, more preferably 3% by mass or more, and still more preferably 5% by mass or more, and from the viewpoint of handling of the dispersion, preferably 55% by mass or less, more It is preferably 50% by mass or less, more preferably 40% by mass or less.

(blocked polyisocyanate)
The dispersion contains a blocked polyisocyanate. Block polyisocyanate means (1) polyisocyanate compounds such as polyisocyanate and polyisocyanate derivatives as a basic skeleton, and (2) the isocyanate groups are blocked with blocking groups to prevent the reaction between the isocyanate groups and water. (3) Does not react with functional groups having active hydrogen at room temperature (specifically, 30° C. or lower); (4) Blocking groups are eliminated by heat treatment at the elimination temperature or higher to regenerate active isocyanate groups. is a compound that reacts with a functional group having an active hydrogen to form a bond. Polyisocyanate means polyfunctional isocyanate having two or more isocyanate groups. Similarly, blocked polyisocyanate means a polyisocyanate whose isocyanate groups have been blocked by blocking groups. When the blocked polyisocyanate is heated in the dispersion and in the structure at a temperature higher than the elimination temperature of the blocking group, the fine cellulose fibers and the organic fibers according to one embodiment (functional groups having active hydrogen are (if it has) to form a crosslinked structure.

The blocked polyisocyanate is selected from compounds obtained by substituting isocyanate groups of polyisocyanates (that is, compounds having two or more isocyanate groups in the molecule) with blocking groups. Examples of the basic skeleton of polyisocyanate include aromatic polyisocyanate, alicyclic polyisocyanate, and aliphatic polyisocyanate. Among them, alicyclic polyisocyanates and aliphatic polyisocyanates are more preferable from the viewpoint of little yellowing.

Examples of aromatic polyisocyanates include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate and mixtures thereof (TDI), diphenylmethane-4,4'-diisocyanate (MDI), naphthalene-1,5-diisocyanate. , 3,3-dimethyl-4,4-biphenylene diisocyanate, crude TDI, polymethylene polyphenyl diisocyanate, crude MDI, phenylene diisocyanate and xylylene diisocyanate.
Alicyclic polyisocyanates include, for example, alicyclic diisocyanates such as 1,3-cyclopentane diisocyanate, 1,3-cyclopentene diisocyanate and cyclohexane diisocyanate.
Examples of aliphatic polyisocyanates include aliphatic diisocyanates such as trimethylene diisocyanate, 1,2-propylene diisocyanate, butylene diisocyanate, pentamethylene diisocyanate and hexamethylene diisocyanate.

Examples of the polyisocyanate derivative as the basic skeleton of the blocked polyisocyanate include, in addition to the above polyisocyanate polymers (e.g., dimers, trimers, pentamers, heptamers, etc.), active hydrogen-containing Examples include reaction products obtained by reacting one or more compounds. Examples of the reaction product include allophanate modified products (e.g., polyisocyanate and allophanate modified products produced by reaction with alcohols, etc.), polyol modified products (e.g., polyol modified products produced by reaction of polyisocyanate and alcohols) (alcohol adduct), etc.), modified biuret (e.g., biuret modified by reaction of polyisocyanate with water or amines), modified urea (e.g., generated by reaction of polyisocyanate and diamine) urea modified product, etc.), oxadiazinetrione modified product (e.g., oxadiazinetrione produced by the reaction of polyisocyanate and carbon dioxide), carbodiimide modified product (carbodiimide-modified product produced by the decarboxylation condensation reaction of polyisocyanate and the like), modified uretdione, modified uretonimine, and the like.

Active hydrogen-containing compounds include, for example, monovalent to hexavalent hydroxyl group-containing compounds (eg, polyester polyols, polyether polyols, etc.), amino group-containing compounds, thiol group-containing compounds, carboxyl group-containing compounds, and the like. Water, carbon dioxide, etc. present in the air or in the reaction field can also be active hydrogen-containing compounds.

Mono- to hexahydric alcohols (that is, polyols) include, for example, non-polymerized polyols and polymerized polyols. A non-polymerized polyol is a polyol that has not undergone polymerization, and a polymerized polyol is a polyol obtained by polymerizing a monomer.

Examples of non-polymerized polyols include monoalcohols, diols, triols, tetraols and the like. Examples of monoalcohols include, but are not limited to, methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, s-butanol, n-pentanol, n-hexanol, n-octanol, n-nonanol, 2-ethylbutanol, 2,2-dimethylhexanol, 2-ethylhexanol, cyclohexanol, methylcyclohexanol, ethylcyclohexanol and the like. Examples of diols include, but are not limited to, 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-propanediol, phloroglucin, pyrogallol, catechol, hydroquinone, bisphenol A, bisphenol F, bisphenol S and the like. Examples of triols include, but are not particularly limited to, glycerin, trimethylolpropane, and the like. Moreover, the tetraols are not particularly limited, but include, for example, pentaerythritol, 1,3,6,8-tetrahydroxynaphthalene, 1,4,5,8-tetrahydroxyanthracene, and the like.

Examples of polymerized polyols include, but are not limited to, polyester polyols, polyether polyols, acrylic polyols, and polyolefin polyols.
The polyester polyol is not particularly limited. Propylene glycol, diethylene glycol, neopentyl glycol, trimethylolpropane, polyester polyol obtained by condensation reaction with a mixture of polyhydric alcohols such as glycerin, and obtained by ring-opening polymerization of ε-caprolactone using polyhydric alcohol Examples include polycaprolactones such as those described above.

Examples of polyether polyols include, but are not limited to, hydroxides of lithium, sodium, potassium, etc.; alcoholates, strongly basic catalysts such as alkylamines; metal porphyrins; Polyethers obtained by random or block addition of alkylene oxides such as ethylene oxide, propylene oxide, butylene oxide, cyclohexene oxide, and styrene oxide, alone or in mixtures, to polyhydric hydroxy compounds alone or in mixtures, etc. Examples include polyols and polyether polyols obtained by reacting polyamine compounds such as ethylenediamines with alkylene oxides. So-called polymer polyols 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, rhamnitol;
(3) monosaccharides such as arabinose, ribose, xylose, glucose, mannose, galactose, fructose, sorbose, rhamnose, fucose, ribodesose;
(4) disaccharides such as trehalose, sucrose, maltose, cellobiose, gentiobiose, lactose and melibiose;
(5) trisaccharides such as raffinose, gentianose, melezitose;
(6) tetrasaccharides, such as stachyose;
etc.

Examples of acrylic polyols 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. monoesters, acrylic acid monoesters or methacrylic acid monoesters of trimethylolpropane, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 3-hydroxypropyl methacrylate, methacrylic acid-4-hydroxybutyl methacrylate and the like selected from the group of methacrylic acid esters having active hydrogen, either singly or as a mixture, as an essential component, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, Acrylic esters such as 2-ethylhexyl acrylate, methacrylic esters such as methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-hexyl methacrylate, and lauryl methacrylate , unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid and itaconic acid; unsaturated amides such as acrylamide, N-methylolacrylamide and diacetone acrylamide; and glycidyl methacrylate, styrene, vinyl toluene, vinyl acetate, acrylonitrile, Presence of other polymerizable monomers selected from the group of vinyl monomers having a hydrolyzable silyl group such as dibutyl fumarate, vinyltrimethoxysilane, vinylmethyldimethoxysilane, γ-methacryloxypropylmethoxysilane, and the like, singly or as a mixture. acrylic polyols obtained by polymerization in the presence or absence of

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

Examples of amino group-containing compounds include monohydrocarbylamines having 1 to 20 carbon atoms [alkylamine (butylamine, etc.), benzylamine and aniline], 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 of numbers 2 to 20 (piperazine and N-aminoethylpiperazine, etc.), alkanolamines (monoethanolamine, diethanolamine, triethanolamine, etc.), polyamidepolyamines obtained by condensation of dicarboxylic acids and excess polyamines, polyether polyamines, hydrazines (such as hydrazine and monoalkylhydrazine), dihydrazides (such as dihydrazide succinate and dihydrazide terephthalate), guanidines (such as butylguanidine and 1-cyanoguanidine) and dicyandiamide.

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

Examples of carboxyl group-containing compounds 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 terephthalic aromatic dicarboxylic acids such as acids) and the like.

The blocking group is added to and blocks the isocyanate group of the polyisocyanate compound. This blocking group is stable at room temperature, but when heated to a predetermined elimination temperature (usually about 100 to about 200° C.), the blocking group is eliminated and the free isocyanate group can be regenerated.

As a blocking agent that provides a blocking group that satisfies such requirements,
(1) alcohols such as methanol, ethanol, 2-propanol, n-butanol, sec-butanol, 2-ethyl-1-hexanol, 2-methoxyethanol, 2-ethoxyethanol and 2-butoxyethanol;
(2) Alkylphenols: 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 and di-n-nonylphenol,
(3) Phenol-based: phenol, cresol, ethylphenol, styrenated phenol, hydroxybenzoic acid ester, etc.
(4) active methylene system: dimethyl malonate, diethyl malonate, methyl acetoacetate, ethyl acetoacetate, acetylacetone, etc.;
(5) Mercaptans: butyl mercaptan, dodecyl mercaptan, etc.
(6) acid amides: acetanilide, acetic amide, ε-caprolactam, δ-valerolactam, γ-butyrolactam, etc.
(7) Acid imide type: succinimide, maleic acid imide, etc.
(8) imidazole series: imidazole, 2-methylimidazole, 3,5-dimethylpyrazole, 3-methylpyrazole, etc.;
(9) Urea-based: urea, thiourea, ethylene urea, etc.
(10) oxime series: formaldoxime, acetoaldoxime, acetoxime, methylethylketoxime, cyclohexanone oxime, etc.;
(11) Amines: diphenylamine, aniline, carbazole, di-n-propylamine, diisopropylamine, isopropylethylamine, etc.
These blocking agents can be used alone or in combination of two or more.

The blocked polyisocyanate may be anionic, nonionic or cationic, preferably cationic blocked polyisocyanate. Cationic blocked polyisocyanates are advantageous in that they are easily adsorbed to fine cellulose fibers due to electrostatic interaction. That is, it is known that the general cellulose fiber surface is anionic (zeta potential of −30 to −20 mV in distilled water) (Non-Patent Document 1 J. Brandrup (editor) and EH Immergut (editor) "Polymer Handbook 3rd Edition" V-153 to V-155), the blocked polyisocyanate is preferably cationic in terms of electrostatic interaction.

However, even if the blocked polyisocyanate is nonionic, it is possible to favorably adsorb the blocked polyisocyanate to the fine cellulose fibers by adjusting the polymer chain length, rigidity, etc. of the hydrophilic group of the blocked polyisocyanate. be. Furthermore, even for blocked polyisocyanates that are more difficult to adsorb due to electrostatic repulsion with fine cellulose fibers, such as anionic blocked polyisocyanates, generally well-known cationic adsorption aids or cationic polymers are used. Thus, the blocked polyisocyanate can be adsorbed onto the fine cellulose fibers.

In the dispersion, the amount of the blocked polyisocyanate relative to 100 parts by mass of the fine cellulose fibers is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, from the viewpoint of obtaining the advantages of using the blocked polyisocyanate. , more preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and still more preferably 3 parts by mass or more, to reduce the residual unreacted blocked polyisocyanate in the crosslinked structure, From the viewpoint of satisfactorily preventing problems such as the occurrence of cracks, the amount is preferably 120 parts by mass or less, more preferably 100 parts by mass or less, and even more preferably 90 parts by mass or less.

The amount of the blocked polyisocyanate with respect to the total of 100 parts by mass of the fine cellulose fibers and the organic fibers in the dispersion is preferably 0.5 parts by mass or more, more preferably 0.5 parts by mass or more, from the viewpoint of obtaining the advantages of using the blocked polyisocyanate. It is 1 part by mass or more, more preferably 1.5 parts by mass or more, and preferably 80 parts by mass or less, more preferably 50 parts by mass or less from the viewpoint of reducing the amount of unreacted blocked polyisocyanate remaining in the crosslinked structure. and more preferably 30 parts by mass or less.

The amount of the blocked polyisocyanate in the dispersion is preferably 0.0001% by mass or more, more preferably 0.001% by mass or more, and still more preferably 0.005% by mass, from the viewpoint of obtaining the advantages of using the blocked polyisocyanate. From the viewpoint of reducing the amount of unreacted blocked polyisocyanate remaining in the crosslinked structure, the amount is preferably 10% by mass or less, more preferably 6% by mass or less, and even more preferably 4% by mass or less.

The blocked polyisocyanate is preferably present in the dispersion in the form of a water dispersion (e.g. an emulsion), in which case the blocked polyisocyanate has better dispersibility in the dispersion. Examples of emulsions include self-emulsifying emulsions and forced emulsifying emulsions. Anionic, nonionic, or cationic hydrophilic groups are exposed on the surface of both self-emulsifying and forced emulsifying emulsions.

A self-emulsifying emulsion is an emulsion obtained by directly bonding a hydrophilic compound (for example, an active hydrogen group-containing compound having an anionic group, a nonionic group, or a cationic group) to a blocked polyisocyanate and emulsifying it. . Examples of active hydrogen group-containing compounds having an anionic group include, but are not limited to, compounds having one anionic group and two or more active hydrogen groups.

Examples of anionic groups include carboxyl groups, sulfonic acid groups, phosphoric acid groups, betaine structure-containing groups, and the like. More specifically, active hydrogen group-containing compounds having a carboxyl group include, for example, dihydroxycarboxylic acids such as 2,2-dimethylolacetic acid and 2,2-dimethylollactic acid, 1-carboxy-1,5-pentyl Diamines, diaminocarboxylic acids such as dihydroxybenzoic acid, half ester compounds of polyoxypropylene triol and maleic anhydride and/or phthalic anhydride, and the like can be mentioned.

Examples of active hydrogen group-containing compounds having a sulfonic acid group include N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid and 1,3-phenylenediamine-4,6-disulfonic acid. be done.
Examples of active hydrogen group-containing compounds having a phosphoric acid group include 2,3-dihydroxypropylphenyl phosphate.
Examples of active hydrogen group-containing compounds having betaine structure-containing groups include sulfobetaine group-containing compounds obtained by reacting tertiary amines such as N-methyldiethanolamine with 1,3-propanesultone. can.

The active hydrogen group-containing compound having an anionic group may be modified with an alkylene oxide by adding an alkylene oxide such as ethylene oxide or propylene oxide. The active hydrogen group-containing compound having an anionic group can be used alone or in combination of two or more.

The active hydrogen group-containing compound having a nonionic group is not particularly limited, but for example, a polyalkylene ether polyol containing an ordinary alkoxy group as a nonionic group is used. Ordinary nonionic group-containing polyester polyols, polycarbonate polyols, and the like are also used.
As the polymer polyol, those having a number average molecular weight of 500 to 10,000, particularly 500 to 5,000 are preferably used.

The active hydrogen group-containing compound having a cationic group is not particularly limited, but an aliphatic compound having an active hydrogen-containing group such as a hydroxyl group or a primary amino group and a tertiary amino group, such as N,N-dimethylethanolamine, N-methyldiethanolamine, N,N-dimethylethylenediamine and the like. Further, N,N,N-trimethylolamine, N,N,N-triethanolamine, etc. having a tertiary amine can also be used. Among them, a polyhydroxy compound having a tertiary amino group and containing two or more active hydrogens reactive with an isocyanate group is preferred.

The active hydrogen group-containing compound having a cationic group may be modified with an alkylene oxide by adding an alkylene oxide such as ethylene oxide or propylene oxide. Active hydrogen group-containing compounds having a cationic group can be used alone or in combination of two or more.

The cationic group can also be neutralized with a compound having an anionic group to make it easier to disperse in water in the form of a salt. Examples of anionic groups include carboxyl groups, sulfonic acid groups, and phosphoric acid groups. Examples of compounds having a carboxyl group include formic acid, acetic acid, propionic acid, butyric acid, and lactic acid. Examples of compounds having a sulfone group include ethanesulfonic acid. Examples of compounds having a phosphate group include phosphoric acid. acids, acidic phosphate esters, and the like. A compound having a carboxyl group is preferred, and acetic acid, propionic acid and butyric acid are more preferred. The equivalent ratio of the cationic group introduced into the blocked polyisocyanate to the anionic group when neutralization is carried out is preferably from 1:0.5 to 1:3, more preferably from 1:1 to 1:1. 5. Moreover, when introducing a tertiary amino group, the tertiary amino group can be quaternized with dimethyl sulfate, diethyl sulfate, or the like.

The reaction ratio between the blocked polyisocyanate and the active hydrogen group-containing compound is such that the isocyanate group/active hydrogen group equivalent ratio is preferably 1.05 to 1000, more preferably 2 to 200, and still more preferably 4 to 100. Range. When the equivalent ratio is 1.05 or more, the isocyanate group content in the hydrophilic polyisocyanate does not become too low, and a decrease in the curing speed of the blocked polyisocyanate and weakening of the cured product can be avoided. By increasing the number of cross-linking points with isocyanate groups, the blocked polyisocyanate works well as a waterproofing agent and a fixing agent for fine cellulose fibers. When the equivalent ratio is 1000 or less, the effect of lowering the interfacial tension is good, and hydrophilicity is well expressed. As a method for reacting a polyisocyanate compound (that is, a compound having two or more isocyanate groups in one molecule) and an active hydrogen group-containing compound, a method of mixing the two to carry out a normal urethanization reaction may be used. can be done.

The forcibly emulsified emulsion is an emulsion obtained by forcibly emulsifying a blocked polyisocyanate with a surfactant or the like. Forced emulsification type emulsions are well-known general emulsifiers (e.g., anionic surfactants, nonionic surfactants, cationic surfactants, amphoteric surfactants, polymeric surfactants, reactive surfactants, etc.) It may be a compound emulsified and dispersed with. Among emulsifiers, anionic surfactants, nonionic surfactants and cationic surfactants are preferred because they are inexpensive and can provide good emulsification.

Examples of anionic surfactants include alkylcarboxylate-based compounds, alkylsulfate-based compounds, and alkylphosphates.
Examples of nonionic surfactants include ethylene oxide and/or propylene oxide adducts of alcohols having 1 to 18 carbon atoms, ethylene oxide and/or propylene oxide adducts of alkylphenols, ethylene oxide and/or alkylene glycols and/or alkylenediamines. Or a propylene oxide adduct etc. are mentioned.
Examples of cationic surfactants include primary to tertiary amine salts, pyridinium salts, alkylpyridinium salts, quaternary ammonium salts such as halogenated alkyl quaternary ammonium salts, and the like.

The amount of these emulsifiers to be used is not particularly limited, but is preferably 0.01 parts by mass or more in terms of mass ratio to 1 part by mass of the blocked polyisocyanate because good dispersibility can be obtained, and is preferably 0.3 parts by mass or less. It is preferable because it satisfactorily exerts its action as a water resistance and a functionalizing agent or a fixing agent. The amount used is more preferably 0.05 to 0.2 parts by mass.

Both the self-emulsifying type and the forced emulsifying type water-dispersible block polyisocyanate can contain a solvent other than water, for example, in an amount of 20% by mass or less. Examples of the solvent include, but are not limited to, ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol dimethyl 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 the dispersibility of the solvent in water, the solvent preferably has a solubility in water of 5% by mass or more, and specifically, dipropylene glycol monomethyl ether and dipropylene glycol dimethyl ether are preferred.

The average dispersed particle size of the water-dispersible blocked polyisocyanate is preferably 1 to 1000 nm, more preferably 10 to 500 nm, and still more preferably 10 to 200 nm. The above average dispersed particle size is a value measured by a static light scattering laser particle size measurement method.

(additional ingredients)
The dispersion may further comprise additional ingredients in addition to the fine cellulose fibers, organic fibers, blocked polyisocyanate and water. Additional ingredients include inorganic fibers, filler particles, functionalizing agents, and the like.

Glass fiber, carbon fiber, and the like can be used as the inorganic fiber. Regarding the amount of inorganic fibers, the ratio of inorganic fibers is, for example, 1 to 40% by mass, or 2 to 30% by mass, or 3 to 20% by mass with respect to 100% by mass of the total mass of organic fibers and inorganic fibers. good.

Examples of filler particles include silica particles, alumina particles, titanium oxide particles, calcium carbonate particles, polymer particles and the like.

In one aspect, a functionalizing agent for imparting a certain function to the molded article may be contained, and the functionalizing agent includes a water repellent agent, a water and oil repellent agent, an antibacterial polymer, an oily compound, It is one or more selected from the group consisting of thermoplastic resins, thermosetting resins, and photocurable resins. In the dispersion, the mass ratio of the functionalizing agent based on solid content is preferably 0.1 to 20% by mass, more preferably 0.2 to 15% by mass, and still more preferably 0.3 to 10% by mass. .

Examples of the water-repellent agent or water-repellent and oil-repellent agent include various organic resins containing fluorine. In particular, polymers of unsaturated monomers such as perfluoroalkyl group-containing acrylic acid esters, methacrylic acid esters, alkyl acrylamides, alkyl vinyl ethers, vinyl alkyl ketones, or the above perfluoroalkyl group-containing unsaturated monomers and acrylic acid, acrylic Copolymers with unsaturated monomers containing no perfluoroalkyl groups, such as acid esters, methacrylic acid, methacrylic acid esters, vinyl chloride, acrylonitrile, maleic acid esters, polyoxyethylene group-containing unsaturated monomers, are preferred. In addition, as a water-repellent agent or water- and oil-repellent agent that does not contain a fluorine-based compound, a silicone compound such as methylhydrogenpolysiloxane, dimethylsiloxane, reactive (OH group-terminated) dimethylpolysiloxane, wax-based Compounds, waxes such as ordinary waxes, synthetic paraffin waxes, paraffin waxes, and the like. A mixture of paraffin and an acrylic acid ester-based polymer can also be used to exhibit the desired effects. Also, wax-zirconium-based compounds, that is, reaction products of the aforementioned wax-based compounds and zirconium-based compounds (specifically, zirconium acetate, zirconium hydrochloride, zirconium nitrate, basic zirconium with potassium hydroxide, etc.), alkylene urea higher fatty acid amide derivatives such as compounds (eg, octadecylethylene urea or modified products thereof), aliphatic amide compounds (eg, N-methylolstearylamide or modified products thereof), and the like. These may be used alone or may be contained in combination of two or more.

Antibacterial polymers such as polyhexamethylenebiguanide hydrochloride, chlorhexidine, 2-acrylamido-2-methylpropanesulfonic acid copolymer, polymethacrylic acid, mixture of polyacrylate and zinc sulfate, phosphate ester Quaternary ammonium salt compound of copolymer of monomers, dicyanamide/diethylenetriamine/ammonium chloride condensate, dicyandiamide/polyalkylene/polyamine ammonium polycondensate, (poly β-1,4)-N-acetyl-D-glucosamine portion Reaction product of deacetylated compound and hexamethylenebis(3-chloro-2-hydroxypropyldimethylammonium chloride, acrylonitrile-acrylic acid copolymer copper cross-linked product, acrylamide-diallylamine hydrochloride copolymer, methacrylate copolymer, Hydroxypropyl chitosan, crosslinked chitosan, chitosan organic acid salt, chitosan fine powder (polyglucosamine), chitin fiber, chitin, N-acetyl-D-glucosamine, etc. For example, these antibacterial polymers are blocked on the surface of the structure. Immobilization with polyisocyanate is advantageous, as one aspect of the structure, in that it provides, for example, an antibacterial clothing fabric (sheet) with excellent washing resistance.

The antibacterial evaluation can be performed, for example, by the antibacterial test method for textile products (unified method) established by JIS-1902-1998. Specifically, 2 g of a sample is placed in advance on the bottom of a closed container, and 0.2 ml of a staphylococcus aureus (test strain: AATCC-6538P) solution diluted with 1/50 broth that has been cultured in advance is sown on this sample. After standing in an incubator at 37° C. for 18 hours, 20 mL of SCDLP medium is added and thoroughly shaken to wash off the bacteria. This is placed on a nutrient agar medium, and after 24 hours, the number of bacteria is counted, and the number of bacteria is compared with the number of bacteria obtained from an unprocessed sample cloth, which was performed at the same time, to determine the antibacterial properties.
D = (Ma - Mb) - (Mc - Md)
During the ceremony,
Ma: Logarithm of the number of viable bacteria after 18-hour culture of the unprocessed sample (average of 3 samples)
Mb: Logarithm of viable count immediately after inoculation of unprocessed sample (average of 3 samples)
Mc: Logarithm of viable count after 18 hours culture on processed cloth Md: Logarithm of viable count immediately after inoculation in processed cloth culture D: Bacteriostatic activity value.
When the bacteriostatic activity value D≧2.2, it is judged to have antibacterial properties. Therefore, it is preferable that the fine cellulose fiber sheet also has a bacteriostatic activity value D≧2.2.

As the oily compound, an oily compound having a boiling point range of 50° C. or higher and 200° C. or lower under atmospheric pressure is preferable. The oily compound is preferably dispersed in the dispersion in the form of an emulsion at a concentration of 0.15% by mass or more and 10% by mass or less. The concentration of the oily compound in the dispersion is preferably 0.15% by mass or more and 10% by mass or less, more preferably 0.3% by mass or more and 5% by mass or less, and still more preferably 0.5% by mass or more and 3% by mass. % or less. Although a structure can be obtained even if the concentration of the oily compound exceeds 10% by mass, the amount of the oily compound used in the manufacturing process increases, and the accompanying need for safety measures and cost restrictions. It is not desirable because it occurs. Further, when the concentration of the oily compound is 0.15% by mass or more, the degree of air permeation resistance can be lowered, which is preferable.

Since the oily compound is removed during drying (that is, during the production of the structure), it is desirable that the oily compound can be easily removed by drying. Therefore, the boiling point of the oily compound under atmospheric pressure is preferably 50°C or higher and 200°C or lower, more preferably 60°C or higher and 190°C or lower. When the boiling point is within the above range, the papermaking slurry can be easily manipulated in an industrial production process, and can be removed by heating relatively efficiently. If the boiling point of the oily compound under atmospheric pressure is less than 50°C, it is necessary to handle the papermaking slurry under low temperature control in order to handle it stably, which is not preferable in terms of efficiency. Furthermore, if the boiling point of the oily compound exceeds 200° C. under atmospheric pressure, a large amount of energy is required to heat and remove the oily compound in the drying step, which is also not preferred.
Furthermore, the solubility of the oily compound in water at 25° C. is 5% by mass or less, preferably 2% by mass or less, and more preferably 1% by mass or less. It is desirable from the viewpoint of a significant contribution.

Examples of oily compounds include hydrocarbons having 6 to 14 carbon atoms, chain saturated hydrocarbons, cyclic hydrocarbons, chain or cyclic unsaturated hydrocarbons, aromatic hydrocarbons, carbon number Monohydric and primary alcohols in the range of 5 to 9 carbon atoms are included. In particular, the use of at least one compound selected from 1-pentanol, 1-hexanol and 1-heptanol makes it possible to produce the fine cellulose fiber porous sheet of the present invention particularly preferably. This is considered to be suitable for producing a nonwoven fabric having a high porosity and a fine porous structure, since the size of oil droplets in the emulsion is extremely small (1 μm or less under normal emulsifying conditions).
These oily compounds may be blended as a single substance, or may be blended as a mixture of two or more. Furthermore, a water-soluble compound may be dissolved in the papermaking slurry in order to control the emulsion properties to an appropriate state.

Surfactants include anionic surfactants such as alkyl sulfates, polyoxyethylene alkyl sulfates, alkylbenzene sulfonates, α-olefin sulfonates, alkyltrimethylammonium chloride, dialkyldimethylammonium chloride, benzalcochloride. amphoteric surfactants such as betaine alkyldimethylaminoacetate and betaine alkylamidodimethylaminoacetate; and nonionic surfactants such as alkylpolyoxyethylene ethers and fatty acid glycerol esters. It is not limited to these.

Examples of thermoplastic resins include styrene resins, acrylic resins, aromatic polycarbonate resins, aliphatic polycarbonate resins, aromatic polyester resins, aliphatic polyester resins, aliphatic polyolefin resins, cyclic olefin resins, and polyamides. resins, polyphenylene ether-based resins, thermoplastic polyimide-based resins, polyacetal-based resins, polysulfone-based resins, amorphous fluorine-based resins, and the like. The number average molecular weight of these thermoplastic resins is generally 1,000 or more, preferably 5,000 or more and 5,000,000 or less, and more preferably 10,000 or more and 1,000,000 or less. These thermoplastic resins may be used alone or in combination of two or more. When two or more thermoplastic resins are contained, it is preferable because the refractive index of the resin can be adjusted by the content ratio. For example, if polymethyl methacrylate (refractive index of about 1.49) and acrylonitrile styrene (acrylonitrile content of about 21%, refractive index of about 1.57) are contained at a ratio of 50:50, a resin with a refractive index of about 1.53 is obtained. .

The thermosetting resin is not particularly limited, but specific examples include epoxy resin, thermosetting modified polyphenylene ether resin, thermosetting polyimide resin, urea resin, allyl resin, silicon resin, Benzoxazine resins, phenolic resins, unsaturated polyester resins, bismaleimide triazine resins, alkyd resins, furan resins, melamine resins, polyurethane resins, aniline resins, other industrially available resins, and mixtures of two or more of these resins. resins obtained by Among them, epoxy resins, allyl resins, unsaturated polyester resins, vinyl ester resins, thermosetting polyimide resins, and the like have transparency and are suitable for use as optical materials.
Examples of photocurable resins include epoxy resins containing a latent photocationic polymerization initiator. These thermosetting resins or photocurable resins may be contained singly or in combination of two or more.

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

Curing agents and curing catalysts are not particularly limited as long as they are used for curing thermosetting resins and photocurable resins. Specific examples of curing agents include polyfunctional amines, polyamides, acid anhydrides, and phenolic resins, and specific examples of curing catalysts include imidazole and the like. may be contained in

The functionalizing agent is preferably bound to the blocked polyisocyanate, and for this purpose, as described later, it is preferable to perform a heat treatment for forming a chemical bond (covalent bond) with the blocked polyisocyanate. By chemically bonding the blocked polyisocyanate to the fine cellulose fibers and also bonding to the functionalizing agent, the functionalizing agent is immobilized inside and/or on the surface of the crosslinked structure of the present embodiment. This allows the function derived from the functionalizing agent to be maintained well even after long-term use in water, for example.

The mass proportion of water in the dispersion may preferably be 45% by mass or more and 99.9% by mass or less. For example, when the dispersion is used as a slurry for papermaking, the mass ratio of water is such that the viscosity does not become excessively high, the fine cellulose fibers and organic fibers can be uniformly dispersed in the dispersion, and a structure with a uniform structure can be obtained. In terms of the above, it is preferably 55% by mass or more, more preferably 70% by mass or more. is preferably 99.9% by mass or less, more preferably 99.4% by mass or less, and even more preferably 99.2% by mass or less. For example, when the dispersion is used as a coating slurry, the mass ratio of water is preferably 80% by mass or more and 99.5% by mass or less, more preferably 85% by mass or more and 99% by mass or less.

The dispersions of this embodiment provide good moldability that allows the formation of complex shaped crosslinked structures. For example, the dispersion can be formed into a sheet by a papermaking method, formed into a wet cake molded body by a suitable mold papermaking apparatus, dried and heat-treated, or molded into an appropriate shape by a pulp molding method and then dried and heat-treated. can produce the molded article of the present invention. It is important to adjust the viscosity of the dispersion during molding, and the viscosity is adjusted to suit the molding method. For example, even in cases where the degree of freedom in dispersion casting is high, such as in the case of sheeting, the proper viscosity differs depending on whether the sheet is thin or thick (thicker sheets preferably have a higher solid content and a higher viscosity dispersion). . Furthermore, in the case of molding by the coating method, a dispersion having a high solid content and a high viscosity is preferable compared to the papermaking method, considering the load in the subsequent drying process. In the case of the pulp molding method, it is preferable to use a high-concentration dispersion (for example, 10% by mass or more) as compared with the papermaking method or the coating method. In order to reduce the drying load, the viscosity becomes high when the concentration is increased. can flow and form the shape of the compact.

The dispersion is produced by a method comprising mixing fine cellulose fibers with an average fiber diameter of 2 nm or more and 1000 nm or less, organic fibers with an average fiber diameter of more than 3000 nm, blocked polyisocyanate, and water. For mixing, for example, (1) fine cellulose fibers, blocked polyisocyanate, and water are mixed to prepare a premix, and then the premix and organic fibers (organic fibers alone or in the form of an aqueous dispersion of organic fibers, etc.) can be used. or (2) mixing fine cellulose fibers, organic fibers and water to prepare a pre-mixture, and then mixing the pre-mixture with the blocked polyisocyanate;
can be done by

Among the methods (1) and (2) above, the method (1) mixes the blocked polyisocyanate with the fine cellulose fibers prior to the organic fibers. It is preferable because it can be adsorbed more (that is, selectively), and the effect of improving the dispersibility of fine cellulose fibers and the effect of cross-linking by the blocked polyisocyanate are improved. In particular, when the blocked polyisocyanate is a cationic blocked polyisocyanate and has an electrostatic interaction with the fine cellulose fibers, the method (1) is used when the blocked polyisocyanate has a high affinity with the fine cellulose fibers. Adsorption of the blocked polyisocyanate to the fine cellulose fibers in advance is extremely advantageous in localizing the blocked polyisocyanate around the fine cellulose fibers. On the other hand, even in the above method (2), fine cellulose fibers have a larger surface area per unit mass than, for example, organic fibers due to their fine structure. It is possible to adsorb a proportion of the polyisocyanate to the fine cellulose fibers, and the method (2) may be advantageous when, for example, the blocked polyisocyanate is adsorbed to both the fine cellulose fibers and the organic fibers. Therefore, the addition order and mode of addition of each component in the production of the dispersion may be appropriately designed according to the type and amount of the component contained in the dispersion, the application of the dispersion, and the like.

For example, when a plurality of additives are added, a system in which the additives aggregate (for example, a cationic polymer and an anionic polymer are present in the dispersion, and these form an ion complex. system), the order of addition of additives may change the dispersion state, zeta potential, etc. of the dispersion. The amount and order of addition of the additive are appropriately selected according to the desired dispersion state of the dispersion.

A device for uniformly mixing and dispersing the components of the dispersion is appropriately selected according to the viscosity and state of the dispersion. For example, when the dispersion has a low viscosity (a fluid state), a dispersing machine such as an agitator, a homomixer, a pipeline mixer, and a blender that can also have a cutting function, a high-pressure homogenizer, and the like can be used. When the dispersion is so viscous that it lacks fluidity, it is preferable to use various kneaders driven at low speed. However, when using an emulsion such as a water-dispersible block polyisocyanate, a high-pressure homogenizer, a grinder-type pulverizing device, a stone-mill-type grinding device, etc. are used from the viewpoint of preventing the emulsion from collapsing due to excessive shear stress. preferably not used.

The mixing temperature is preferably 5° C. or higher, 7° C. or higher, or 9° C. or higher from the viewpoint of mixing efficiency, and preferably 60° C. or lower, or 55° C. or lower from the viewpoint of preventing the reaction of the blocked isocyanate. , or 50° C. or less.

<Structure and its manufacturing method>
One aspect of the present invention provides a method for producing a structure containing fine cellulose fibers with an average fiber diameter of 2 nm or more and 1000 nm or less, organic fibers with an average fiber diameter of more than 3000 nm, and blocked polyisocyanate.
In one aspect, a method of manufacturing a structure comprises:
Dispersion preparation step of preparing a dispersion by the method for producing a dispersion described above,
A concentration step of dehydrating the dispersion to form a water-containing concentrate, and a structure-forming step of drying the water-containing concentrate (preferably at 80° C. or higher and 120° C. or lower) to form a structure. .
In one aspect, a method of manufacturing a structure comprises:
Dispersion preparation step of preparing a dispersion by the method for producing a dispersion described above,
A structure forming step of drying the dispersion (preferably at 80° C. or higher and 120° C. or lower) to form a structure.

That is, when the structure is formed, the dispersion is once dehydrated (that is, concentrated) by papermaking or the like and then molded and then dried, or the dispersion is molded as it is without the process of dehydrating (that is, concentrating). , and drying are effective. In the former case, the solid content ratio of the dispersion should be in the range of 0.1% by mass to 20% by mass, more preferably in the range of 0.2% by mass to 15% by mass, from the viewpoint of the degree of freedom in molding by papermaking. . In the latter case, the solid content ratio of the dispersion should be in the range of 10% by mass to 55% by mass, more preferably in the range of 15% by mass to 45% by mass, from the viewpoint of viscosity suitable for molding. In either case, using a suitable mold for molding, it is possible to form not only sheets but also complex shaped structures. Here, preferred aspects of each of the fine cellulose fibers, organic fibers, blocked polyisocyanate, and additional components, and preferred quantitative ratios thereof, may be the same as those exemplified in the preparation of the dispersion. For example, the structure contains blocked polyisocyanate in an amount of preferably 0.1 to 30 parts by weight per 100 parts by weight of fine cellulose fibers. Further, the mass ratio of the fine cellulose fibers and the organic fibers in the structure (fine cellulose fibers/organic fibers) is 0.2/99.8 to 30/70.

(Dispersion preparation step)
In this step, the dispersion is obtained by the method described above as the method for producing the dispersion.

(Structure forming step)
In the structure-forming step, the dispersion can be dehydrated and dried by a papermaking method, a coating method, or the like, or the dispersion can be directly dried (ie, without the dehydration step) to form the structure. The structure may be formed alone or laminated on another member (for example, a sheet), and in the latter case, a coating method is suitable.
In the papermaking process, after the step of preparing a papermaking slurry (as a dispersion of the present disclosure), the papermaking slurry is filtered over a porous substrate to dehydrate (i.e., concentrate) while producing wet paper (as a wet concentrate). A structure can be manufactured through a step of forming (papermaking step) and a step of drying the wet paper to obtain a dried compact (drying step). After that, the dried sheet is further heat-treated to eliminate the blocking groups from the blocked polyisocyanate and to proceed with the cross-linking reaction, whereby a cross-linked structure can be produced.

In the coating method, after the step of preparing a coating slurry or a highly viscous dispersion (as the dispersion of the present disclosure), a member (for example, an organic polymer sheet) is placed on a flat or complex-shaped mold set After applying the slurry for coating on top by spray coating, gravure coating, dip coating, etc. or spreading a highly viscous dispersion like paper clay and molding it (pulp molding method), either directly from the wet state ( That is, the structure can be manufactured by a step of drying without going through a concentration step of dehydration. After that, a crosslinked structure can be manufactured through a heat treatment step.

An example of a procedure for producing a structure and a crosslinked structure will be described below using the papermaking method as an example.

Paper Making Process In the paper making process, the paper making slurry is filtered to form wet paper. Drainage time during filtration may be, for example, 60 seconds or less, preferably 30 seconds or less, and more preferably 10 seconds or less, from the viewpoint of manufacturing efficiency of the structure. Evaluation of drainage time is carried out as follows. Paper made using a batch-type paper machine (manufactured by Kumagai Riki Kogyo Co., Ltd., automatic square sheet machine 25 cm × 25 cm, 80 mesh) set with a metal mesh equivalent to 80 mesh with a basis weight of 50 g / m ² as a guide. The slurry is charged, and then paper making (dehydration) is performed at a pressure reduction of 4 KPa with respect to the atmospheric pressure. The time required for dehydration at this time is measured as drainage time.
The drainage time of the papermaking slurry can also be adjusted by increasing or decreasing the degree of pressure reduction.

In the papermaking process, any paper machine can be used that has wires of a mesh size such that the papermaking slurry is dewatered and the fine cellulosic and organic fibers are retained. When a sheet is obtained as a papermaking apparatus, a sheet-like structure with few defects is preferably obtained by using an apparatus such as an inclined wire paper machine, a fourdrinier paper machine, or a cylinder paper machine as a paper machine. can be done. The paper machine may be a continuous type or a batch type, depending on the purpose. When producing a molded body with a complicated shape (for example, a bottle or a box), a mold with a dewaterable mesh surface attached to the entire surface of the molded body is used, and the slurry is poured into the mold and then dewatered. (that is, condensing) to form a wet paper web having a complicated shape, followed by drying to form a structure.

In the present embodiment, when forming a composite of the structure and an additional member in order to produce a composite of the crosslinked structure and an additional member (for example, an organic polymer sheet), the additional member can be used as a support for papermaking. In this case, as the wire or filter cloth of the paper machine, a material is selected that satisfies the requirements relating to the yield ratio and the water permeation rate in combination with the support.

In the dehydration in the papermaking process, high solidification progresses to obtain wet paper. The solids content of the wet paper is controlled by the suction pressure (wet suction or dry suction) of papermaking and the pressing process, and preferably the solids concentration is 6 mass% or more and 50 mass% or less, more preferably solid content The concentration is adjusted to the range of 8% by mass or more and 45% by mass or less. If the solid content of the wet paper is lower than 6% by mass, the wet paper does not stand on its own, and problems are likely to occur in the process. Further, when the wet paper is dehydrated to a concentration exceeding 50% by mass, the wet paper tends to crack, which is not preferable.

In addition, by using a method in which papermaking is performed on a wire or a mesh in a mold, water in the resulting wet paper is replaced with an organic solvent in the process of replacing with an organic solvent, and then dried, a porous structure can be obtained after drying. Since it becomes a structure, for example, it is possible to impart heat insulation to the structure. For details of this method, refer to WO 2006/004012 pamphlet by the present inventors.
In the case of producing a composite of a crosslinked structure and an additional member (for example, an organic polymer sheet), when using the additional member (for example, an organic polymer sheet) as a support, for example, a wire is used. The support is placed on the set paper machine, part of the water constituting the papermaking slurry is dehydrated (papermaking) on the support, and the wet paper is laminated on the support and integrated. A multi-layered sheet comprising a multi-layered structure of at least two layers can be produced. In order to produce a multi-layered sheet having three or more layers, a support having a multi-layer structure of two or more layers may be used. Also, a multi-layer sheet having three or more layers may be obtained by multistage papermaking of a structure having two or more layers on a support.

Drying Process The wet material (wet paper, etc.) obtained in the papermaking or coating process described above becomes the structure of the present embodiment by evaporating water in a drying process by heating. In the drying process, in the case of a sheet-like structure, if a constant length drying type dryer such as a drum dryer or a pin tenter that can dry water with a constant width is used, air resistance is preferable because a structure having a high value can be stably obtained. On the other hand, in the case of producing a molded body with a complicated shape, as in the pulp molding method, the structure in a wet state once molded in a mold is removed from the mold and dried in a batch or continuously with a dryer such as a hot air dryer. Drying may be applied. The drying temperature may be appropriately selected according to the conditions, preferably 45° C. or higher and 180° C. or lower, more preferably 60° C. or higher and 150° C. or lower, and still more preferably 80° C. or higher and 120° C. or lower. A highly breathable structure can be manufactured. The air permeability of the structure can be controlled by the compositional ratio of the fine cellulose fibers and the organic fibers constituting the dispersion, and the lower the mass ratio of the fine cellulose fibers, the higher the air permeability of the structure. The drying temperature is preferably 80° C. or higher, or 85° C. or higher, or 90° C. or higher from the viewpoint of drying efficiency (especially the viewpoint of obtaining good productivity by increasing the evaporation rate of water). The temperature is preferably 120° C. or lower, or 115° C. or lower, or 110° C. or lower from the viewpoints of prevention of thermal denaturation of the hydrophilic polymer constituting the structure, and prevention of reduction in energy efficiency that affects cost. For example, low-temperature drying at a temperature of 100° C. or lower first, followed by multistage drying at a temperature exceeding 100° C. is also effective in obtaining a highly uniform structure.
A structure can be formed by the procedure described above.

In one aspect, the structure is a sheet or molded body. The average thickness of the sheet or molding may be, for example, 10-50000 μm, or 20-40000 μm, or 30-30000 μm. The molded body may have various shapes such as a box shape, a bottle shape, a bowl shape, or a shape obtained by applying complex unevenness to these shapes. (thickness at the point where is the smallest) may be, for example, 5 to 45,000 μm, or 10 to 40,000 μm, or 15 to 35,000 μm.

In a preferred embodiment, the blocked polyisocyanate is uniformly distributed in the structure in the planar direction and the thickness direction. In the present disclosure, "the blocked polyisocyanate is uniformly distributed in the structure in the planar direction and the thickness direction" is defined as follows.
Uniformity in the planar direction means that the ratio (W1/W2) of the amount of blocked polyisocyanate (W1) and the amount of cellulose (W2) at any point on the surface of the structure is always constant. Here, "constantly constant" means a coefficient of variation of 50% or less of W1/W2 variation at arbitrary four locations when four 1 cm x 1 cm regions are selected on the surface of the structure. means that
Further, uniformity in the thickness direction means that the ratio of the amount of blocked polyisocyanate and the amount of cellulose is the same in each of the upper, middle and lower parts when the structure is divided into three equal parts in the thickness direction. In addition, when the structure is a molded body having a complicated shape, the thickness direction is measured on four surfaces that can be sampled from an area of 1 cm×1 cm of the molded body. Here, "same" means that four 1 cm × 1 cm regions are selected on the surface of the structure, and the average of W1/W2 in the upper part, the average of W1/W2 in the middle part, and the lower part means that when the average of W1/W2 is calculated, the variation of the three average values is a coefficient of variation of 50% or less.

The coefficient of variation of the distribution of the blocked polyisocyanate in the plane direction and the thickness direction is preferably 50% or less. When the coefficient of variation is 50% or less, physical properties such as tensile strength (dry and wet) and biodegradation resistance are better than structures containing the same amount of blocked polyisocyanate and having a coefficient of variation of more than 50%. be. The coefficient of variation is a value representing relative variation, and can be calculated by the following formula: coefficient of variation (CV)=(standard deviation/arithmetic mean)×100.

In the structure, the ratio between the amount of blocked polyisocyanate (W1) and the amount of cellulose (W2) is obtained from three-dimensional composition analysis by TOF-SIMS accompanied by sputter etching, for example. TOF-SIMS can analyze the elemental composition and chemical structure of the extreme surface of the sample. When a sample is irradiated with a primary ion beam under ultra-high vacuum, secondary ions are emitted from the extreme surface (1 to 3 nm) of the sample. By introducing secondary ions into a time-of-flight (TOF) mass spectrometer, a mass spectrum of the extreme surface of the sample is obtained. At this time, by suppressing the primary ion irradiation dose to a low level, surface components can be detected as molecular ions that retain their chemical structure and partially cleaved fragments, and information on the elemental composition and chemical structure in the planar direction of the extreme surface can be obtained. is obtained. At this time, by repeating sputter etching with a sputter etching gun and measurement of secondary ions with a primary ion gun, information on the elemental composition and chemical structure in the depth direction can be obtained, enabling three-dimensional composition and chemical structure analysis. .

W1/W2 is calculated by TOF-SIMS, for example, as follows. Samples of 0.5 cm square are collected from four equally divided portions in a structure of 1 cm×1 cm. A three-dimensional TOF-SIMS compositional analysis of the four samples is performed. The ratio of the amount of blocked polyisocyanate to the amount of cellulose is the count number (C1) of m/z = 26 (fragment ion: CN) derived from blocked polyisocyanate and m/z = 59 (fragment ion: C ₂ H ₃ O ₂ ) It can be obtained from the count number (C2) as W1/W2=C1/C2. For example, CNO (m/z=42) may be used as fragment ions derived from other blocked polyisocyanates. Further, as other fragment ions derived from cellulose, for example, C ₃ H ₃ O ₂ (m/z=71) may be used. Note that the observed fragment ions may vary depending on the composition of the blocked polyisocyanate, the cellulose raw material, and the like, and are not limited to the above fragment ions.
Measurement conditions of TOF-SIMS to be used are, for example, as follows.

(Measurement condition)
Equipment used: nanoTOF (manufactured by ULVAC-PHI)
Primary ion: Bi ₃ ⁺⁺
Accelerating voltage: 30 kV
Ion current: about 0.1 nA (as DC)
Analysis area: 200 μm × 200 μm
Analysis time: about 6 sec/cycle
Detected ions: Negative ions Neutralization: Using an electron gun (sputtering conditions)
Sputter ion: Ar2500 ⁺
Accelerating voltage: 20 kV
Ion current: about 5nA
Sputtering area: 500 μm×500 μm
Sputtering time: 60 sec/cycle
Neutralization: use electron gun

<Crosslinked structure and method for producing the same>
One aspect of the present invention provides a method for producing a crosslinked structure by cross-linking the block polyisocyanate of the structure of the present disclosure described above.
In one aspect, the method for producing a crosslinked structure comprises:
Dispersion preparation step of preparing a dispersion by the method for producing a dispersion described above,
a concentration step of dehydrating the dispersion to form a hydrous concentrate; and drying the hydrous concentrate (preferably at 80° C. or higher and 120° C. or lower); A crosslinked structure forming step is included in which the blocked polyisocyanate and the fine cellulose fibers and/or organic fibers are crosslinked by heating at a temperature equal to or higher than the elimination temperature of the blocking groups in the isocyanate to form a crosslinked structure.
In one aspect, the method for producing a crosslinked structure comprises:
A dispersion preparation step of preparing a dispersion by the dispersion manufacturing method described above, and drying the dispersion (preferably at 80 ° C. or higher and 120 ° C. or lower), following the drying or at the same time as the drying, A crosslinked structure forming step of forming a crosslinked structure by crosslinking the blocked polyisocyanate and the fine cellulose fibers and/or organic fibers by heating at a temperature equal to or higher than the elimination temperature of the blocking groups in the blocked polyisocyanate.

In one aspect, the cross-linking is between polyisocyanates derived from blocked polyisocyanates and/or between polyisocyanates derived from blocked polyisocyanates and fine cellulosic fibers and/or organic fibers (typically fine cellulosic fibers and optionally organic fibers). formed between In typical embodiments, the blocked polyisocyanate-derived structures are present as aggregates in the crosslinked structure. Such aggregates are significantly formed when a crosslinked structure is produced using a dispersion containing, for example, the above-mentioned water-dispersible blocked polyisocyanate as the blocked polyisocyanate. The agglomerates are formed in one embodiment in a film-like manner on fine cellulose fibers and optionally on organic fibers.

When the blocked polyisocyanate is heated at a predetermined elimination temperature or higher according to the blocking group, the blocking group is eliminated to generate a free isocyanate group. It reacts with a group (hydroxy group, amido group, amino group, thiol group, carboxyl group, etc.) to form a covalent bond. Since the fine cellulose fibers have at least hydroxyl groups, the covalent bonds are formed at least three-dimensionally with respect to the fine cellulose fibers. Moreover, when the organic fiber has a functional group having an active hydrogen, a three-dimensional covalent bond is also formed with the organic fiber. By forming such covalent bonds, good mechanical strength, water resistance and solvent resistance are imparted to the crosslinked structure, and block polyisocyanate and polyisocyanate derived therefrom are eluted (e.g., into water or a solvent). elution) is suppressed.

(Dispersion preparation step)
In this step, the dispersion is obtained by the method described above as the method for producing the dispersion.

(Crosslinked structure forming step (heat treatment step))
In this step, following drying (this drying may be carried out in the same manner as the drying of the dispersion described above in the method for producing a structure) or simultaneously with drying, the to crosslink the blocked polyisocyanate with the fine cellulose fibers and/or the organic fibers (typically the fine cellulose fibers and optionally the organic fibers).

For example, if the structure is in the form of a sheet, the heat treatment process should be performed using a constant heating method such as a drum dryer or a pin tenter that heats the structure with a fixed width from the viewpoint of uniform heat treatment and suppression of shrinkage of the structure due to heating. It is preferable to use a long-drying heat treatment device. When a dryer such as a drum dryer is used, the feeding speed can be adjusted and the diameter of the roll can be adjusted. In addition, when the structure is not a sheet but a complex-shaped molded body, the dried solid mounted in the mold may be heat-treated while mounted in the mold, or the dried solid (molded body) may be removed from the mold after drying. The body) may be removed and heat-treated in a free state with a hot air treatment device such as an electric heating type. As in the case of the sheet shape, the former case is preferable in some cases from the viewpoint of securing uniformity of physical properties and preventing the occurrence of cracks because the heat treatment is performed in a fixed length.

As described above, blocked polyisocyanate is stable at room temperature, but isocyanate groups can be regenerated by heat treatment above the desorption temperature of the blocking groups, and chemical bonds can be formed with functional groups having active hydrogen. The heating temperature varies depending on the blocked polyisocyanate used, but is preferably 130° C. or higher and 220° C. or lower, more preferably 140° C. or higher and 210° C. or lower, at a temperature higher than the elimination temperature of the blocking group. At a heating temperature lower than the elimination temperature of the blocking group, the isocyanate group is not regenerated, and the cross-linking reaction does not proceed. On the other hand, if heating is performed at a temperature exceeding 220°C, the fine cellulose fibers and the blocked polyisocyanate, and depending on the type, may be colored due to thermal deterioration of the organic fibers.

The heating time is preferably 5 seconds or more and 10 minutes or less, more preferably 7 seconds or more and 3 minutes or less. If the heating temperature is sufficiently higher than the elimination temperature of the blocking group, the heating time can be shortened.

The dry tensile strength of the crosslinked structure per 50 g/m ² basis weight is preferably 5 N/15 mm or more. The dry tensile strength of the crosslinked structure is affected by its basis weight, but when the dry tensile strength per 50 g/m ² basis weight is 5 N/15 mm or more, the crosslinked structure is less likely to break, which is preferable. The dry tensile strength per 50 g/m ² basis weight is more preferably 7 N/15 mm or more, and still more preferably 10 N/15 mm or more. On the other hand, there is no particular upper limit for the dry tensile strength per 50 g/m ² of basis weight, but from the viewpoint of ease of production, it is preferably 300 N/15 mm or less, more preferably 250 N/15 mm or less, and still more preferably 220 N/15 mm or less. be. The dry tensile strength is measured after storage for 24 hours in an environment controlled at room temperature of 20° C. and humidity of 50% RH in accordance with JIS P 8113. A test sheet, which will be described later, is used as a measurement sample.

The wet tensile strength per 50 g/m ² basis weight of the crosslinked structure is preferably 3 N/15 mm or more. The wet tensile strength of the crosslinked structure is affected by the size of its ^basis weight. Hard to break. The wet tensile strength per 50 g/m ² basis weight is more preferably 5 N/15 mm or more, and still more preferably 7 N/15 mm or more. On the other hand, there is no particular upper limit for wet tensile strength per 50 g/m ² of basis weight, but from the viewpoint of ease of production, it is preferably 300 N/15 mm or less, more preferably 250 N/15 mm or less, and still more preferably 220 N/15 mm or less. be. The wet tensile strength is measured by immersing a test sheet prepared in the same manner as the dry tensile strength test sheet in a container filled with water sufficient to immerse the sheet for 5 minutes, and then measuring the dry tensile strength. It is a value of tensile strength measured by a similar method.

As a test sheet as a sample for measuring dry tensile strength and wet tensile strength, one prepared by the following procedure is used. That is, from the dispersion of the present embodiment used as a material for the crosslinked structure to be measured, a basis weight of 50 g/m ² is obtained by a sheeting method (papermaking method, coating method, etc.) corresponding to the molding method of the crosslinked structure to be measured. A test sheet is obtained by cutting a crosslinked structure sheet of 20 cm long and 15 mm wide. The crosslinked structure of the present embodiment is obtained by optionally dehydrating, drying, and heat-treating the dispersion of the present embodiment. It may vary depending on the site of the crosslinked structure. Therefore, in the present disclosure, the dry tensile strength and wet tensile strength of the crosslinked structure are defined by the values obtained by the above method for convenience.

The wet/dry strength ratio is a value calculated by the following formula from the above dry tensile strength and wet tensile strength.
Wet/dry strength ratio (%) = (wet tensile strength) / (dry tensile strength) x 100

The wet/dry strength ratio of the crosslinked structure is preferably between 0.4 and 1.2. From the viewpoint of obtaining a crosslinked structure with good durability even in applications where the crosslinked structure is used in a liquid such as water, the wet/dry strength ratio is preferably 0.4 or more, more preferably 0.5 or more, and further It is preferably 0.6 or more, and the wet/dry strength ratio is preferably 1.2 or less from the viewpoint of not intending to increase the resin ratio of the organic fiber such as block polyisocyanate and create a structure that is the same as plastic. , more preferably 1.1 or less, and still more preferably 1.0 or less.

In one aspect, the crosslinked structure may be biodegradable to cellulase. Cellulase is a general term for enzyme proteins that catalyze hydrolysis reactions of β-1,4 glucosidic bonds in cellulose molecular chains. Cellulases are produced by microorganisms such as bacteria, insects, and the like, and are widely present in the living world and readily available. Various types of cellulase are known, and by selecting an appropriate type, cellulose can be efficiently hydrolyzed to glucose units. However, from the viewpoint of industrial use of cellulosic materials, cellulase is a material that significantly deteriorates the materials. Therefore, it is preferable that the crosslinked structure of the present embodiment has biodegradation resistance to cellulase.

As a method for quantitatively evaluating the biodegradation resistance of the crosslinked structure of the present embodiment to cellulase, for example, cellulose is hydrolyzed with a cellulase mixture containing endoglucanase, exoglucanase, and β-glucosidase, and the reaction is performed. A method of evaluation by quantifying the amount of glucose in the liquid can be mentioned. The amount of glucose produced can be quantified by the glucose oxidase method. In addition, quantification using a kit such as Glucose Test Wako II manufactured by Wako Pure Chemical Industries, Ltd. is also possible. If the amount of glucose produced is small, it means that the hydrolysis reaction of cellulose is difficult to proceed, and it can be said that the biodegradation resistance is high. i.e. the following formula:
Glucose yield (%) = (amount of glucose produced)/(absolute dry mass of sample) x 100
can be used to determine the glucose yield. And the biodegradation resistance index is the following formula:
Biodegradation resistance index = 1/(glucose yield/100)
can be evaluated using The higher the biodegradability index, the lower the biodegradability.
The biodegradation resistance index of the crosslinked structure is preferably at least twice the biodegradation resistance index of a comparative crosslinked structure containing no blocked polyisocyanate. Such a high biodegradation resistance index is particularly advantageous in applications such as water treatment filters, which are assumed to be used in environments where cellulases may exist.

In the crosslinked structure, the hydrophilicity/hydrophobicity may be appropriately controlled. The hydrophilicity/hydrophobicity of the crosslinked structure is determined, for example, when a hydrophilic compound or a hydrophobic compound is applied onto the crosslinked structure or impregnated with the crosslinked structure for a predetermined purpose depending on the application. It greatly affects the coating amount or impregnation amount of the hydrophilic compound or hydrophobic compound and the operability of coating or impregnation. In addition, the crosslinked structure has applications in separation membranes utilizing its hydrophilicity and hydrophobicity. In particular, the degree of hydrophobization of the crosslinked structure obtained by heat-treating the structure varies considerably depending on the type and amount of the blocked polyisocyanate. Therefore, it is possible to control the hydrophilicity/hydrophobicity of the crosslinked structure by selecting or designing an appropriate blocked polyisocyanate.

Furthermore, adding a compound having hydrophobic or water-repellent properties with which the blocked polyisocyanate can react as a component in the dispersion is also a means of improving the wet/dry strength ratio or controlling hydrophilicity/hydrophobicity. It is valid. Examples of compounds having hydrophobic or water-repellent properties to be contained include, for example, various organic resins containing fluorine. In particular, polymers of unsaturated monomers such as perfluoroalkyl group-containing acrylic acid esters, methacrylic acid esters, alkyl acrylamides, alkyl vinyl ethers, vinyl alkyl ketones, or the above perfluoroalkyl group-containing unsaturated monomers and acrylic acid, acrylic Copolymers with unsaturated monomers containing no perfluoroalkyl groups, such as acid esters, methacrylic acid, methacrylic acid esters, vinyl chloride, acrylonitrile, maleic acid esters, polyoxyethylene group-containing unsaturated monomers, are preferred. In addition, as a water-repellent agent or water- and oil-repellent agent that does not contain a fluorine-based compound, a silicone compound such as methylhydrogenpolysiloxane, dimethylsiloxane, reactive (OH group-terminated) dimethylpolysiloxane, wax-based Compounds, waxes such as ordinary waxes, synthetic paraffin waxes, paraffin waxes, and the like. There are many types of synthetic paraffin, such as those with a low melting point and those with a high melting point, and paraffin wax with a high melting point is preferable. A modified paraffin in which an acrylic acid ester-based polymer is allowed to coexist can also be used to exhibit the desired effects. In addition, wax-zirconium compounds, that is, the above-mentioned wax compounds reacted with zirconium compounds, specifically zirconium acetate, zirconium hydrochloride, zirconium nitrate, potassium hydroxide, etc., and alkylene urea compounds. , for example, octadecyl ethylene urea, modified products thereof, aliphatic amide compounds, such as N-methylolstearylamide, higher fatty acid amide derivatives such as modified products thereof, and the like. These may be used alone or may be contained in combination of two or more.

There are several methods for evaluating hydrophilicity/hydrophobicity, and a method may be selected according to the purpose. Also, since the hydrophilicity/hydrophobicity is a relative index, it is determined by comparison with a reference substance. For example, using a sheet composed only of fine cellulose fibers and organic fibers as a reference material, the hydrophilicity/hydrophobicity of a sheet to which block polyisocyanate and various functionalizing agents are added is determined. As an evaluation method, for example, a static contact angle measurement of a water droplet is exemplified. 4 μL of distilled water (20° C.) is dropped, and the static contact angle 1 second after the drop is applied is measured with an automatic contact angle meter (eg, trade name: “DM-301” manufactured by Kyowa Interface Science Co., Ltd.). At this time, it can be said that the smaller the static contact angle, the more hydrophilic, and the larger the static contact angle, the more hydrophobic. Another method is to measure the time it takes for water droplets to absorb. In this method, 4 μL of distilled water (20° C.) is dropped and the time required for the droplets to absorb water is measured. The longer the water absorption time, the more hydrophobic it is judged.

The crosslinked structure of this embodiment can be controlled to have a desired air resistance. For example, air permeation resistance is defined as a value equivalent to a sheet with a basis weight of 50 g/m ² in the same manner as tensile strength, and may be 5 to 990,000 sec/100 ml, 10 to 800,000 sec/100 ml, or 15 to 700,000 sec/100 ml.

The control of air resistance can be changed by selecting the average fiber diameters of the fine cellulose fibers and organic fibers to be used and the mixing ratio of a plurality of types of fibers having different average fiber diameters. The smaller the average fiber diameter, the more dense the crosslinked structure can be formed. However, it is possible to greatly change the degree of air resistance by selecting the kind of blocked polyisocyanate and the amount of addition.

The air permeability resistance is the permeation time of 100 ml of air using a Gurley densometer (manufactured by Toyo Seiki Co., Ltd., model G-B2C) for samples with air resistance of 1,000 sec/100 ml or less. means the result of measuring A sheet having a basis weight of 50 g/m ² of the crosslinked structure is cut out from the crosslinked structure, and 10 measurements are taken at various different positions, and the average value is taken as the measurement. Note that the range of air resistance that can be measured by this measurement method is between 1 and 1,800 sec/100 ml due to restrictions on the time required for measurement. In addition, for samples with an air resistance of 1,000 sec/100 ml or more, measurement was performed at room temperature with an Oken type air resistance tester (manufactured by Asahi Seiko Co., Ltd., model EG01), and the average value of 10 points was calculated. Take.

<Composite and its manufacturing method>
One aspect of the invention provides a composite of the aforementioned crosslinked structure and an additional member. In one aspect, the composite is a laminate of a crosslinked structure sheet and an organic polymer sheet (hereinafter also simply referred to as an organic polymer sheet) as an additional member. In one aspect, in such a laminate, the mechanical strength such as tensile strength is further enhanced by the organic polymer sheet, and the handleability as a sheet can be improved. The laminate is particularly suitable for various applications such as various containers for food, various containers used as daily necessities, stationery, etc., packaging materials, packaging materials, board materials such as decorative boards, and interior products. The material of the organic polymer sheet is not particularly specified, but the required performance such as the desired laminate shape, hardness, mechanical properties, thermal properties, durability, water resistance, air resistance, etc. , or is appropriately selected depending on the use of the laminate. In one aspect, it is preferred that the crosslinked structure and the additional member are chemically crosslinked with a blocked polyisocyanate. From this point of view, preferred materials for the additional members include materials having functional groups having active hydrogen, specifically cellulose, nylon, polyvinyl alcohol, polycarboxylic acid, and the like. In the case of materials that do not have functional groups with active hydrogen (for example, polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate, etc.), the functional groups are activated by surface activation treatment such as corona discharge treatment and plasma treatment. can be introduced. For example, after laminating the structure (that is, the structure before cross-linking) and the additional member, the composite is cross-linked with the blocked polyisocyanate under the conditions described above so that the cross-linked structure and the additional member are locked polyisocyanate It can be produced by a method of obtaining a composite crosslinked by the crosslinker of (1), a method of laminating a crosslinked structure and an additional member, or the like.

EXAMPLES The present invention will be specifically described below with reference to examples. In addition, the main measured values of physical properties were measured by the following methods.

(1) Average fiber diameter of fine cellulose fibers A wet paper sheet was prepared by a filtration method from a dispersion liquid in which tert-butanol was gradually substituted for an aqueous dispersion of fine cellulose fibers, dried, and used for fiber diameter evaluation. samples were obtained. The surface of the evaluation sample was observed with a scanning electron microscope (SEM) at a magnification of 10,000 to 100,000 times depending on the average fiber diameter of the fine fibers. From the obtained SEM image, the fiber diameter of each fiber was measured, and the number average value was defined as the average fiber diameter.

(2) Fabric weight The fabric weight of the sheet was calculated according to JIS P8124.

(3) Dry/Wet Strength Ratio of Tensile Strength As described above, the dry/wet strength of the corresponding molded body was measured for a sample having a basis weight of 50 g/m ² prepared from the same dispersion by the same method.
First, the dry tensile strength was evaluated according to the method defined in JIS P 8113, using a desktop horizontal tensile tester (No. 2000) manufactured by Kumagai Riki Kogyo Co., Ltd. About 10 samples with a width of 15 mm The average value was taken as the dry strength (N/15 mm). In the same manner, the sheet was immersed for 5 minutes in a container filled with enough water to immerse the sheet, and 10 samples were measured, and the average value was taken as the wet strength (N/15 mm).
From the dry strength and wet elongation evaluated above, the following formula:
Dry-wet strength ratio (%) = (wet strength) / (dry strength) x 100
Calculated by Here, neither the dry strength nor the wet strength is converted to equivalent of 10 g/m ² per unit area.
When the dry/wet strength ratio was 70% or more, it was evaluated as ◯; when it was 50% or more and less than 70%, it was evaluated as Δ;

(4) Dry-wet strength ratio after immersion in solvent A sample of 25 cm x 25 cm was immersed for one day in a container lined with iso-butanol. After that, the sample was dried in vacuum at room temperature, and the dry/wet strength ratio of the tensile strength was calculated by the above method. When the dry/wet strength ratio was 70% or more, it was evaluated as ◯; when it was 50% or more and less than 70%, it was evaluated as Δ;

(5) Evaluation of Block Polyisocyanate Distribution in Structure Sheet First, 1 cm square samples were taken from arbitrary four locations in a 25 cm×25 cm sheet. Three-dimensional TOF-SIMS compositional analysis was performed on the four samples.
[Uniformity in planar direction]
Block polyisocyanate-derived m/z=26 (fragment ion: CN) counts (C1) and cellulose-derived m/z=59 (fragment ions: C ₂ H ₃ O ₂ ) counts (C2) of four samples. ) was normalized for C2 (C1/C2). The uniformity in the planar direction was evaluated by ◯ when the variation coefficient of the C1/C2 value of each sample was less than 50%, and x when it was 50% or more.
[Uniformity in thickness direction]
For the four samples, C1/C2 was calculated for the upper, middle and lower parts when the sheet was divided into three equal parts in the thickness direction. C1 and C2 are m / z = 26 (fragment ion: CN) count number (C1) derived from blocked polyisocyanate and m / z = 59 (fragment ion: C ₂ H ₃ O ₂ ) count number (C2) derived from cellulose ). Furthermore, the average of four C1/C2 values for each of the upper, middle, and lower regions was calculated. At this time, the uniformity in the thickness direction was evaluated with ○ when the coefficient of variation for the three average values was less than 50%, and x when it was 50% or more.

The TOF-SIMS measurement conditions are as follows.
(Measurement condition)
Equipment used: nanoTOF (manufactured by ULVAC-PHI)
Primary ion: Bi ₃ ⁺⁺
Accelerating voltage: 30 kV
Ion current: about 0.1 nA (as DC)
Analysis area: 200 μm × 200 μm
Analysis time: about 6 sec/cycle
Detected ions: Negative ions Neutralization: Using an electron gun (sputtering conditions)
Sputter ion: Ar2500 ⁺
Accelerating voltage: 20 kV
Ion current: about 5nA
Sputtering area: 500 μm×500 μm
Sputtering time: 60 sec/cycle
Neutralization: use electron gun

(6) Initial static contact angle evaluation The initial static contact angle of the sample before and after pretreatment was measured by dropping 4 μL of distilled water (20 ° C.) on the sheet, and automatically contacting the contact angle 1 second after contact. A goniometer (trade name: “DM-301”, manufactured by Kyowa Interface Science Co., Ltd.) was used to measure video. An initial contact angle of 90° or more was evaluated as ◯, an initial contact angle of 30° or more and less than 90° was evaluated as Δ, and an initial contact angle of less than 30° was evaluated as x.
(7) Hydrophobicity evaluation (liquid absorption time)
4 μL of distilled water (20° C.) is dropped onto the fine cellulose fiber sheet, and the time required for the droplet to absorb water is measured. It was judged that the longer the water absorption time, the more hydrophobic.
(8) Air Resistance Humidity was adjusted in an atmosphere with a room temperature of 20° C. and a humidity of 50% RH. The humidity-conditioned sample was measured with a Gurley densometer (manufactured by Toyo Seiki Co., Ltd., model G-B2C) or an Oken type air resistance tester (manufactured by Asahi Seiko Co., Ltd., model EG01) for air permeability resistance of 10 points. The average value was taken as the air resistance of the sample.

(9) Thickness A sample conditioned in an atmosphere of room temperature of 20° C. and humidity of 50% RH was measured for thickness at 10 points using an automatic micrometer manufactured by Hybridge Manufacturing Co., Ltd., and the average value was taken as the thickness of the sample.

<Fine cellulose fiber slurry production example 1>
As a raw material, natural cellulose linter pulp obtained from Nippon Pulp & Paper Co., Ltd. was used and immersed in water so that the linter pulp content was 4% by mass. After that, heat treatment was carried out at 130° C. for 4 hours in an autoclave, and the resulting swollen pulp was washed with water several times to obtain purified linter pulp impregnated with water. Thereafter, the purified linter pulp thus obtained was dispersed in water so as to have a solid content of 1.5% by mass to obtain 400 L of dispersion. Using an SDR14 type laboratory refiner (pressurized DISK type) manufactured by Aikawa Iron Works Co., Ltd. as a disc refiner, the water dispersion of 400 L was beaten for 20 minutes with a clearance between discs of 1 mm. Subsequently, the beating process was continued under conditions that reduced the clearance to a level close to zero. Sampling was performed over time, and the sampled slurry was evaluated for the CSF value of the Canadian standard freeness test method for pulp defined in JIS P 8121 (hereinafter referred to as the CSF method), and the CSF value decreased over time. It gradually became close to zero for a while. It was confirmed that the CSF value tended to increase as the beating treatment was continued. The beating treatment was continued under the above conditions for 10 minutes after the clearance was brought to near zero to obtain a beating slurry having a CSF value of 100 ml or more. The resulting slurry of beating water was directly subjected to a high-pressure homogenizer (NS015H manufactured by Nilo Soavi (Italy)) for 5 times at an operating pressure of 100 MPa to obtain a slurry S1 of fine cellulose fibers (solid concentration: 1.5 MPa). 5% by mass) was obtained. The average fiber diameter of the fine cellulose fibers contained in S1 was 102 nm.

<Fine cellulose fiber slurry production example 2>
LBKP, which is softwood pulp obtained from Japan Pulp & Paper Co., Ltd., was used as a raw material. LBKP was put into water so as to be 1.5% by mass, swollen and dispersed by pulper treatment, and then subjected to beating treatment in the same manner as in Production Example 1 to prepare a slurry of cellulose fine fibers (solid content concentration: 1 .5 mass %) was obtained. After passing through zero once, the CSF value was 50 ml or more after continuing the beating treatment. The beaten slurry was finely treated five times with a high-pressure homogenizer at an operating pressure of 100 MPa in the same manner as in Production Example 1 to obtain a fine cellulose fiber slurry S2 (solid concentration: 1.5% by mass). The average fiber diameter of the fine cellulose fibers contained in S2 was 85 nm.

<Example of manufacturing organic fiber slurry>
LBKP, which is softwood pulp obtained from Japan Pulp & Paper Co., Ltd., was used as a raw material. LBKP was put into water so that the amount of LBKP was 1.5% by mass, and after swelling and dispersing by pulper treatment, the clearance between the discs was set to 1 mm in the same manner as in Production Example 1, and 400 L of the aqueous dispersion was added to 20 A beating treatment was performed for a minute to obtain a slurry of cellulose fibers having a CSF value of about 550 ml (solid concentration: 1.5% by mass). The slurry was filtered and concentrated to obtain a cellulose fiber/water dispersion D0 having a solid content of 40% by mass. When the average fiber diameter of the cellulose fibers contained in S1 was observed with an optical microscope, it was approximately 18 μm.

<Example of preparation of dispersion for molding>
10 parts by mass of fine cellulose fiber/aqueous dispersion S1 and cationic block polyisocyanate (trade name "Meikanate WEB", manufactured by Meisei Chemical Industry Co., Ltd.) are added to 100 parts by mass of fine cellulose fiber in a stirring tank previously filled with water. The fine cellulose concentration was adjusted to 0.5% by mass by adding an amount equivalent to 1 part, and the mixture was stirred with an agitator for 5 minutes. Further, while continuing to stir with the agitator, the cellulose fiber/aqueous dispersion D0 was added so that the fine cellulose fiber/cellulose fiber mass ratio was 10/90. got

Under the preparation conditions of SA1, the fine cellulose fiber/aqueous dispersion S1 was changed to S2, and the other preparation method was the same as the preparation of SA1 to obtain dispersion SA2.

Under the preparation conditions of SA1, a cationic block polyisocyanate (trade name “Meikanate WEB”, manufactured by Meisei Chemical Industry Co., Ltd.) is used as a nonionic block polyisocyanate (trade name “NY30”, manufactured by Nicca Chemical Co., Ltd.), and other Dispersion SA3 was obtained by the same preparation method as SA1.

Under the preparation conditions of SA1, the amount of blocked isocyanate is 5 parts by mass, 90 parts by mass or 15 parts by mass, the fine cellulose fiber/cellulose fiber mass ratio is 5/95 or 20/80, and the other preparation method is SA1. Dispersions SA4, SA5 and SA6 were obtained respectively by analogous preparation.

Dispersion RA1 was obtained under the same preparation conditions as SA1 without adding cationic blocked polyisocyanate.

10 parts by mass of fine cellulose fiber/aqueous dispersion S1 and cationic block polyisocyanate (trade name "Meikanate WEB", manufactured by Meisei Chemical Industry Co., Ltd.) are added to 100 parts by mass of fine cellulose fiber in a stirring tank previously filled with water. The fine cellulose concentration was adjusted to 0.5% by mass, and the mixture was stirred with an agitator for 5 minutes to obtain Dispersion RA2.

Cellulose fiber/aqueous dispersion D0 and cationic block polyisocyanate (trade name "Meikanate WEB", manufactured by Meisei Chemical Industry Co., Ltd.) are added to 100 parts by weight of cellulose fiber in a stirring tank filled with water in advance, equivalent to 10 parts by weight. and water were added to adjust the fine cellulose concentration to 5% by mass, and the mixture was stirred with an agitator for 5 minutes to obtain Dispersion RA3.

Table 1 shows the preparation conditions of the dispersion for moldings.

[Examples 1 to 6]
Using a batch-type paper machine (manufactured by Kumagai Riki Kogyo Co., Ltd., automatic square sheet machine), the dispersion SA1 was poured onto a square metal wire (25 cm × 25 cm, 80 mesh) to make paper with a basis weight of 50 g/m ² . went. A suction (decompression device) was used to prepare a wet paper at a pressure reduction of 4 KPa relative to the atmospheric pressure, followed by dehydration pressing and drying with a drum dryer set at 100°C to obtain a sheet-like sample SB1. After that, a cross-linking treatment was carried out by heat treatment for 5 minutes in a constant length state using a hot air dryer set at 170° C. to obtain a sheet-like structure SB1 (Example 1).

Forming dispersion SA1 in Example 1 was replaced with SA2, SA3, SA4, SA5, and SA6, and according to the same production method as Structure SB1, sheet-like structure SB2 having a basis weight of 50 g/m ² (Example 2) , SB3 (Example 3), SB4 (Example 4), SB5 (Example 5), and SB6 (Example 6) were obtained.

For each of the structural bodies SB1 to SB6 obtained in Examples 1 to 6, the average film thickness, the dry-wet strength ratio, the dry-wet strength ratio after immersion in a solvent, and the distribution evaluation of the blocked polyisocyanate in the structural sheet ( plane direction and thickness direction), initial contact angle, hydrophobization degree (water absorption time), and air resistance were evaluated. Table 2 shows the results. All of SB1 to SB6 were sheets excellent in visual homogeneity, water resistance and hydrophobicity.

[Example 7]
A box-shaped container (planar size: 100 mm × 100 mm, height: 30 mm, container thickness (clearance) of 5 mm on all surfaces) with dehydration meshes on all outer surfaces (at the center in the plane direction) After injecting the dispersion SA1 from the conduit, dehydration under reduced pressure is performed outside the mesh surface at a reduced pressure of 4 KPa against the atmospheric pressure, and a wet paper layer is deposited on the mesh surface. After wet paper was formed, the entire mold was dried in a hot air dryer at a temperature of 100° C., the mold was disassembled, and the dried compact was taken out. The molded body was further heat-treated in a hot air dryer at 170° C. in a free state for 5 minutes to obtain a foil-type structure SB7. The average thickness in the plane direction and height direction was measured for SB7. In addition, the initial contact angle, hydrophobization degree (water absorption time), and air permeability resistance of the plane portion were evaluated. SB7 was a uniform and strong box in both the plane direction and the thickness direction, and no swelling was visually confirmed even when immersed in water.

[Comparative Examples 1 to 3]
In the method for producing the sheet-like structure SB1 in Example 1, the dispersion SA1 was replaced with the dispersions RA1, RA2, and RA3, respectively, and the sheet-like structure RB1 having a sheet basis weight of 50 g/m ² (Comparative Example 1), RB2 (Comparative Example 2) and RB3 (Comparative Example 3) were obtained. However, in papermaking from the dispersion RA2 of fine cellulose fibers only, a PET/nylon blended plain fabric (NT20, manufactured by Shikishima Canvas Co., Ltd.) was placed on a rectangular metal wire (25 cm × 25 cm, 80 mesh) used in batch paper making. ) was placed as a filter cloth, and Dispersion RA2 was poured into a paper machine from above to carry out papermaking.

For each of the structural bodies RB1 to RB3 obtained in Comparative Examples 1 to 3, the average film thickness, the dry-wet strength ratio, the dry-wet strength ratio after immersion in a solvent, and the distribution evaluation of the blocked polyisocyanate in the structural sheet ( plane direction and thickness direction), initial contact angle, hydrophobicity (water absorption time), and air resistance. Table 2 shows the results. All of RB1 to SB3 were visually superior in homogeneity, but excluding RB2, the sheets were clearly inferior in water resistance and hydrophobicity to SB1 to SB6. In addition, in RB2, it took a long time of 420 sec to obtain a self-supporting wet paper in the dehydration process by suction, and similarly, it took less than 60 sec to obtain a self-supporting wet paper. It was found that there was a problem in productivity compared with other examples and comparative examples.

[Comparative Example 4]
Dispersion SA1 in Example 7 was changed to RA3 to obtain foil-type structure RB4. The average thickness in the plane direction and height direction was measured for RB4. In addition, the initial contact angle, hydrophobization degree (water absorption time), and air permeation resistance of the flat (bottom) portion were evaluated. RB4 was a uniform and strong box in both the plane direction and the thickness direction, but swelling occurred clearly even when immersed in water, and a part of the structure was observed to collapse. It turns out there is.

Since the crosslinked structure obtained from the dispersion and structure of the present disclosure simultaneously achieves excellent moldability, mechanical strength, water resistance and solvent resistance, it can be used in various containers for food, daily necessities, It can be suitably applied to a wide range of applications such as various containers used as stationery, packaging materials, packaging materials, board materials such as decorative boards, and interior products. In particular, when cellulose fiber is used as the organic fiber, it can be used as a sustainable and highly environmentally compatible material.

Claims (16)

A method for producing a dispersion comprising fine cellulose fibers, organic fibers and blocked isocyanate, comprising:
mixing fine cellulose fibers with an average fiber diameter of 2 nm or more and 1000 nm or less, organic fibers with an average fiber diameter of more than 3000 nm, blocked polyisocyanate, and water;
The mass ratio of the fine cellulose fibers and the organic fibers in the dispersion (fine cellulose fibers/organic fibers) is 0.2/99.8 to 30/70,
The method , wherein the dispersion has a solid content ratio of 0.1% to 55% by weight . The method of claim 1, wherein said dispersion comprises said blocked polyisocyanate in an amount of 0.1 to 120 parts by weight per 100 parts by weight of said fine cellulose fibers. 3. The method of claim 1 or 2, wherein the blocked polyisocyanate is a cationic blocked polyisocyanate. The method according to any one of claims 1 to 3 , wherein the organic fibers comprise fibers having at least surface hydroxyl groups and/or amide groups. A method according to any preceding claim, wherein the organic fibers comprise cellulose fibers. 6. The method according to any one of claims 1 to 5 , wherein said mixing is carried out by mixing fine cellulose fibers, blocked polyisocyanate and water to prepare a pre-mixture, and then mixing said pre-mixture with organic fibers. described method. 7. The method according to any one of claims 1 to 6 , wherein said mixing is carried out by mixing fine cellulose fibers, organic fibers and water to prepare a pre-mixture, and then mixing said pre-mixture with blocked polyisocyanate. described method. A method according to any one of the preceding claims, wherein said mixing is carried out at a temperature between 5°C and 60 °C. A dispersion preparation step of preparing a dispersion by the method according to any one of claims 1 to 8 ,
A structure comprising a concentration step of dehydrating the dispersion to form a water-containing concentrate, and a structure-forming step of drying the water-containing concentrate at 80° C. or higher and 120° C. or lower to form a structure. Production method. A dispersion preparation step of preparing a dispersion by the method according to any one of claims 1 to 8 , and a structure formation by drying the dispersion at 80 ° C. or higher and 120 ° C. or lower to form a structure. A method of manufacturing a structure, comprising: 11. A method according to claim 9 or 10 , wherein said structure is a sheet or molded body. A method according to any one of claims 9 to 11 , wherein said blocked polyisocyanate is uniformly distributed within said structure. A dispersion preparation step of preparing a dispersion by the method according to any one of claims 1 to 8 ,
a concentration step of dehydrating the dispersion to form a hydrous concentrate; and drying the hydrous concentrate at 80° C. to 120° C., and subsequently or simultaneously with the drying, blocking in the blocked polyisocyanate. A crosslinked structure forming step of forming a crosslinked structure by crosslinking the blocked polyisocyanate and the fine cellulose fibers and/or the organic fibers by heating at a group elimination temperature or higher. Production method. A dispersion preparation step of preparing a dispersion by the method according to any one of claims 1 to 8 , and drying the dispersion at 80 ° C. or higher and 120 ° C. or lower, following the drying or with the drying At the same time, the block polyisocyanate and the fine cellulose fibers and/or the organic fibers are crosslinked to form a crosslinked structure by heating at a temperature equal to or higher than the elimination temperature of the blocking groups in the blocked polyisocyanate. A method for producing a crosslinked structure, comprising steps. A method according to claim 13 or 14 , wherein the crosslinked structure has a wet/dry strength ratio of 0.4 to 1.2. A method according to any one of claims 13 to 15 , wherein said heating is carried out at a temperature between 130°C and 220°C.