JP5300398B2 - Cellulose nonwoven fabric and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cellulose nonwoven fabric having air permeability and high strength and comprising fine cellulose fibers. <P>SOLUTION: There is provided the cellulose nonwoven fabric comprising cellulose microfibrils contains one or more water-soluble polymers selected from the group consisting of water-soluble polysaccharides and water-soluble polysaccharide derivatives in a total amount of 0.5-20 wt.%, a METSUKE (basis weight) of 3-80 g/m<SP>2</SP>, and an air transmission-resistant rate(corresponding to a METSUKE of 10 g/m<SP>2</SP>) of 10-500 s/100mL. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a cellulose nonwoven fabric made of fine cellulose fibers and having air permeability, and a method for producing the same.

In the sheet material which consists of a fine cellulose fiber, the fiber diameter of the cellulose fiber to comprise is very thin. Therefore, in the sheet material specifically designed to have high porosity and air permeability, a very fine network structure is formed inside the nonwoven fabric, and can be provided as a nonwoven fabric corresponding to a small pore size comparable to a microporous membrane. . In addition, since the fibers are thin, it is possible to provide a nonwoven fabric with high homogeneity even when designed with a low basis weight of about 10 g / m ² or less, and a low basis weight sheet material that cannot be provided by conventional papermaking technology. It is also possible to reduce the film thickness.
The present inventors have studied a technique for providing a cellulose nonwoven fabric having air permeability composed of the above-described fine cellulose fibers (see Patent Document 1).

However, in a cellulose nonwoven fabric composed of such fine cellulose fibers, if a design with a low basis weight is attempted by making use of the characteristics, the strength is naturally reduced. Therefore, for practical use, there is a limit to the range in which the weight per unit area can be lowered in terms of strength.
On the other hand, one of the characteristics of cellulose as a material is high heat resistance (see Patent Document 2 and Patent Document 3). This is due to the extremely rigid and stable packing structure of the molecular chain by both the hydrogen bond in the molecular chain formed inside the cellulose solid and the hydrogen bond between the molecular chains. In order to improve the strength of cellulose nonwoven fabric made of cellulose fibers, we can devise reinforcement technology with binder polymers at the contact points with cellulose fibers, but we mix binder polymers within the range that does not impair the high heat resistance characteristics of cellulose materials In order to achieve this, there is a restriction that the binder polymer itself has high heat resistance.

On the other hand, in the sheet made of fine cellulose fibers disclosed as specific examples in the above-mentioned Patent Documents 1 to 3, there is no specific illustration about the reinforcing effect of the sheet strength by the binder polymer, and the same technique No specific exemplification is given for the disclosed Patent Documents 4 to 6.
International Publication 2006/004012 Pamphlet Japanese Patent Laid-Open No. 9-129509 JP 2003-201695 A JP-A-9-140493 JP 2007-23219 A JP 2006-241450 A

That is, in a cellulose nonwoven fabric composed of fine cellulose fibers, it is needless to say that the sheet strength is not limited to a low basis weight. As one means for solving the problem, a technique for increasing the strength of the contact point by causing the binder polymer to act on the entanglement point of the network can be considered, but at least one of the advantages of the cellulose material is heat resistance. At present, there is no technology that can achieve this problem while maintaining the above.
An object of this invention is to provide the air permeable and high intensity | strength cellulose nonwoven fabric which consists of a fine cellulose fiber.

  As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by containing an appropriate amount of a water-soluble polysaccharide or a water-soluble polysaccharide derivative in a cellulose nonwoven fabric composed of fine cellulose fibers. Further, the above-mentioned method is effectively achieved by forming a film by a papermaking method and drying using an aqueous dispersion obtained by mixing an emulsion of the water-soluble polysaccharide or water-soluble polysaccharide derivative and an oily compound in an aqueous dispersion of fine cellulose fibers. The present inventors have found that the problems can be solved and completed the present invention.

That is, this invention is the following cellulose nonwoven fabrics, the multilayered sheet containing this nonwoven fabric, the manufacturing method of this nonwoven fabric, and the manufacturing method of this multilayered sheet.
[1] A cellulose nonwoven fabric composed of cellulose microfibrils, containing a total of 0.5% by weight or more and 20% by weight or less of one or more water-soluble polymers selected from the group consisting of water-soluble polysaccharides and water-soluble polysaccharide derivatives A cellulose nonwoven fabric having a basis weight of 3 g / m ² or more and 80 g / m ² or less, and an air resistance corresponding to a basis weight of 10 g / m ² is 10 s / 100 ml or more and 500 s / 100 ml or less.
[2] The cellulose nonwoven fabric according to [1], wherein the number-average fiber diameter of the fibers constituting the cellulose nonwoven fabric is 300 nm or less.
[3] The average transmittance T _{r, av} defined by the following formula (1) obtained by scanning light with a wavelength of 850 nm perpendicularly to the nonwoven fabric in a state of being immersed in toluene is 10 g / The cellulose nonwoven fabric according to [1] or [2], wherein a value converted to a value corresponding to m ² is 0.70 or more.
(However, _{Tr, av} is filled with toluene in a state where the nonwoven fabric is adhered to the inner surface of the test tube, irradiated with light having a wavelength of 850 nm from the direction perpendicular to the nonwoven fabric, and along the test tube. In the state where only the toluene is injected except for the average value _{Tr, 1 of the} transmittance obtained when scanning a total length of 30,000 μm (data points: 750) every 40 μm in the length direction, and the nonwoven fabric. (It is defined by the following equation by the ratio of the average value T _{r, 2} of the transmittance obtained by performing the same measurement.)
T _{r, av} = T _{r, 1} / T _{r, 2} (1)

[4] Any of [1] to [3], wherein the basis weight is 5 g / m ² or more and 30 g / m ² or less, and the air resistance corresponding to the basis weight is 10 g / m ² is 20 s / 100 ml or more and 300 s / 100 ml or less. The cellulose nonwoven fabric as described.
[5] The cellulose nonwoven fabric according to any one of [1] to [4], wherein the water-soluble polymer is a water-soluble cellulose derivative.
[6] A multilayered sheet formed by laminating a plurality of layers, including the cellulose nonwoven fabric layer according to any one of [1] to [5], and having a basis weight of 8 g / m ² or more and 100 g / m ² or less. And a multilayer sheet having an air resistance of 10 s / 100 ml or more and 1000 s / 100 ml or less.

[7] A method for producing a cellulose nonwoven fabric according to any one of [1] to [5],
(1) Cellulose microfibrils 0.05% by weight or more and 0.5% by weight or less, oily compounds having a boiling point range of 50 ° C. or more and 200 ° C. or less under atmospheric pressure 0.15% by weight or more and 10% by weight or less, water-soluble polysaccharide And a water system comprising a total of 0.003% by weight or more and 0.1% by weight or less of water-soluble polymer and one or more water-soluble polymers selected from the group consisting of water-soluble polysaccharide derivatives and 85% by weight or more and 99.5% by weight or less of water A preparation step of preparing an aqueous dispersion, which is an emulsion in which the oily compound is dispersed in an aqueous phase; (2) by dehydrating a part of water constituting the aqueous dispersion with a paper machine, A paper-making process for obtaining a concentrated composition in which the concentration of microfibrils and the concentration of oily compound are increased from the aqueous dispersion; (3) heating the concentrated composition to remove the oily compound from the concentrated composition. Drying step of removing by evaporation a portion of the beauty water,
The manufacturing method of the cellulose nonwoven fabric containing these 3 processes.

[8] At least one selected from the group consisting of softwood pulp, hardwood pulp, cotton-derived pulp, hemp-derived pulp, bagasse-derived pulp, kenaf-derived pulp, bamboo-derived pulp, and straw-derived pulp is used as a raw material for cellulose microfibrils The manufacturing method of the cellulose nonwoven fabric as described in [7] which is the microfibrillated cellulose obtained.
[9] The cellulose nonwoven fabric according to [8], wherein the cellulose microfibril is a microfibrillated cellulose obtained from at least one selected from raw pulps having an α-cellulose content of 95% by weight or more. Production method.
[10] The method for producing a cellulose nonwoven fabric according to any one of [7] to [9], wherein the oily compound has a carbon number of 5 to 9 and contains a monovalent and primary alcohol.
[11] The method for producing a cellulose nonwoven fabric according to [10], wherein the oily compound contains at least one compound selected from the group consisting of 1-pentanol, 1-hexanol, and 1-heptanol.
[12] The cellulose nonwoven fabric according to any one of [7] to [11], wherein the cellulose nonwoven fabric obtained after drying is subjected to a smoothing process after the drying step by a calendering device. Production method.

[13] A method for producing a multilayered sheet according to [6],
(1) Cellulose microfibrils 0.05% by weight or more and 0.5% by weight or less, oily compounds having a boiling point range of 50 ° C. or more and 200 ° C. or less under atmospheric pressure 0.15% by weight or more and 10% by weight or less, water-soluble polysaccharide And a water system comprising a total of 0.003% by weight or more and 0.1% by weight or less of water-soluble polymer and one or more water-soluble polymers selected from the group consisting of water-soluble polysaccharide derivatives and 85% by weight or more and 99.5% by weight or less of water A preparation step for preparing an aqueous dispersion, which is an emulsion in which the oily compound is dispersed in an aqueous phase; (2) placing a water-permeable sheet-like support on a paper machine, A layer composed of a concentrated composition in which the concentration of cellulose microfibrils and the concentration of oily compounds are increased on the support by dehydrating a part of the constituent water on the support is laminated and integrated. Conversion By heating the paper making process (3) supported integrated with the concentrate composition body to a drying step to remove by evaporation a portion of the oily compound and water from the concentrate composition,
The manufacturing method of the multilayer sheet | seat containing these 3 processes.

[14] Using at least one selected from the group consisting of softwood pulp, hardwood pulp, cotton-derived pulp, hemp-derived pulp, bagasse-derived pulp, kenaf-derived pulp, bamboo-derived pulp, and straw-derived pulp as a raw material for cellulose microfibrils The method for producing a multilayered sheet according to [13], which is a microfibrillated cellulose obtained.
[15] The multilayered sheet according to [14], wherein the cellulose microfibril is a microfibrillated cellulose obtained from at least one selected from raw pulps having an α-cellulose content of 95% by weight or more. Manufacturing method.
[16] The method for producing a multilayered sheet according to any one of [13] to [15], wherein the oily compound has a carbon number of 5 to 9 and contains a monovalent and primary alcohol.
[17] The method for producing a multilayer sheet according to [16], wherein the oily compound includes at least one compound selected from the group consisting of 1-pentanol, 1-hexanol, and 1-heptanol.
[18] The multi-layering according to any one of [13] to [17], further comprising a smoothing step of performing a smoothing process on the multi-layered sheet obtained after drying by a calender device after the drying step Sheet manufacturing method.

  According to the present invention, it is possible to provide a cellulose nonwoven fabric having air permeability and high strength made of fine cellulose fibers.

The present invention will be described in further detail.
The present invention relates to a cellulose nonwoven fabric and a method for producing the same. Here, in the present invention, a general definition of a nonwoven fabric “a structure in which fibers are bonded or combined by a chemical method, a mechanical method, or a combination thereof without weaving or knitting the fibers”. Therefore, the structure of the present invention is regarded as a category of wet nonwoven fabric and is called a cellulose nonwoven fabric. What is not darely called paper is a material that differs greatly in that the main cellulose fibers constituting the nonwoven fabric of the present invention are cellulose fibers that are about two orders of magnitude thinner than the cellulose fibers as the raw material of conventional paper, This is because the function is more suitably expressed not in the so-called paper application but in the application field where the nonwoven fabric is used.

The cellulose nonwoven fabric of the present invention comprises cellulose microfibrils, and contains one or more water-soluble polymers selected from the group consisting of water-soluble polysaccharides and water-soluble polysaccharide derivatives in a total amount of 0.5% by weight to 20% by weight. The basis weight is 3 g / m ² or more and 80 g / m ² or less, and the air resistance corresponding to the basis weight 10 g / m ² is 10 s / 100 ml or more and 500 s / 100 ml or less.
Here, the cellulose microfibril means a cellulose fiber having a fiber diameter of several nm to 200 nm called a microfibril or a bundle thereof. More specifically, cellulose derived from acetic acid bacteria and bacteria, which is called bacterial cellulose, or plant-derived cellulose such as pulp or animal-derived cellulose such as squirt cellulose, called microfibrillated cellulose, is used as a high-pressure homogenizer or super Independent microfibrils that have been peeled off from the fiber surface or fine fibers in which they converge (Non-patent Document 1; AFTurbak, FWSnyder and) KRSandberg, "Microfibrillated Cellulose, A New Cellulose Product: Properties, Uses, and Commercial Potential" J. Appl. Polym. Sci .: Appl. Polym. Symp., 37, 815 (1983)). Among these, in the present invention, it is more preferable to use microfibrillated cellulose as a raw material from the viewpoint of cost and quality control.

  Here, the cellulose which comprises the surface of a cellulose microfibril may be chemically modified. For example, some or most of the hydroxyl groups present on the surface of fine cellulose fibers are esterified including acetic esterification, etherified including methyl ether, carboxyethyl ether, cyanoethyl ether, 6-position hydroxyl group Can be oxidized to form a carboxyl group (including acid type and salt type). Examples of such microfibrils having a chemically modified surface include, for example, microfibrils having a carboxylated surface obtained by treating pulp with a TEMPO oxidation catalyst (Non-patent Document 2; T. Saito, Y. Nishiyama, JL. Putaux, M. Vignon and A. Isogai, “Homogeneous Suspensions of Individualized Microfibrils from TEMPO-Catalyzed Oxidation of Natural Cellulose” Biomacromolecules, 7, 1687 (2006)).

  Next, as a raw material when using microfibrillated cellulose, so-called wood pulp and non-wood pulp such as softwood pulp and hardwood pulp can be used. Examples of non-wood pulp include cotton-derived pulp including 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, straw-derived pulp are cotton lint, cotton linter, hemp-based abaca (for example, many from Ecuador or the Philippines), It means a refined pulp obtained through a refining process such as delignification by a digestion process or a bleaching process for raw materials such as zaisal, bagasse, kenaf, bamboo, and straw. In addition, purified seaweed-derived cellulose and sea squirt cellulose can also be used as raw materials for microfibrillated cellulose.

  Further, the raw material of the microfibrillated cellulose is at least one selected from conifer pulp, hardwood pulp, cotton-derived pulp, hemp-derived pulp, bagasse-derived pulp, kenaf-derived pulp, bamboo-derived pulp and straw-derived pulp. And it is more preferable that the α-cellulose content is 95% by weight or more because the cellulose nonwoven fabric of the present invention having high heat resistance and solvent resistance can be produced. This is because if impurities such as lignin component and hemicellulose mainly contained in the plant raw material of the pulp remain, the heat resistance and solvent resistance are adversely affected.

Here, the evaluation of the content of α-cellulose in the raw pulp is described in Non-Patent Document 3 (edited by the Wood Society of Japan, Wood Science Experiment Manual, Bunnendo Publishing, p95-p96, issued April 10, 2000). According to the evaluation method of the total cellulose amount, the total cellulose amount x ₁ g in the sample x ₀ g is first evaluated, and then the total cellulose sample obtained by x ₁ g is used, and the method described in the literature is followed. The amount of α-cellulose is evaluated. When the amount of α-cellulose obtained here is x ₂ g, the α-cellulose content from the sample weight (x ₀ g) used first, x ₂ × 100 / x ₀ (%) is α- Defined as cellulose content.

  Among raw pulps, components other than α-cellulose (impurities) include lignin (the main component of the sample minus the total cellulose content) and hemicelluloses (the total cellulose content minus the α-cellulose content). Although some of these components are eluted into the aqueous phase in the beating and refining process of the present invention and discharged out of the system in the papermaking process, some of these components are cellulose microfibrils. It may remain in the vicinity of the surface and the like, and the heat resistance and durability of the cellulose nonwoven fabric of the present invention may be impaired. Therefore, the raw material pulp used in the present invention preferably has a high α-cellulose content.

  If the number average fiber diameter of the fibers constituting the cellulose nonwoven fabric of the present invention is in the range of 2 nm to 300 nm, preferably 10 nm to 150 nm, a nonwoven fabric having a fine and uniform network structure can be obtained with a low basis weight. This is particularly effective when such a nonwoven fabric is desired. There are no reports on cellulose microfibrils having a number average fiber diameter of less than 2 nm in the literature, and it is considered difficult to make them practically. In addition, when the number average fiber diameter is larger than 300 nm, it becomes difficult to become a non-woven fabric having a fine pore diameter based on a fine network structure, and thus the effect expected from the cellulose non-woven fabric of the present invention is difficult to appear (for general paper). Discriminatory).

  Here, the number average fiber diameter of the microfibrillated cellulose is defined as follows. That is, with respect to the surface of the cellulose nonwoven fabric obtained by molding and drying the microfibrillated cellulose into a sheet shape, at least two spots at random, the observation by a scanning electron microscope (SEM) is equivalent to 10,000 times or more and 30000 times or less. In the range, the magnification is such that the fiber diameter can be clearly recognized. With respect to the obtained SEM image (for example, FIG. 1), a line is drawn in the horizontal direction and the vertical direction with respect to the screen, and the fiber diameter of the fiber that intersects the line is measured from the enlarged image. Count the fiber diameter. In this way, the number average fiber diameter is calculated using the fiber diameter measurement results for all the fibers that intersect the two lines. Further, the number average fiber diameter is calculated in the same manner for the SEM image of the same magnification obtained by photographing another place observed for the same sample, and the average value of the results for the total of two images is used as the number average fiber diameter of the sample. To do. Here, the number average fiber diameter of the sample shown in FIG. 1 is 108 nm.

  In refining from raw pulp to microfibrillated cellulose, raw pulp is easily refined by autoclave treatment, beating treatment, enzyme treatment, etc. under impregnation in water at a temperature of 100 ° C. or higher, or a combination thereof. It is effective to pre-process. These treatments not only reduce the load of the micronization process, but also discharge impurities components such as lignin and hemicellulose that exist on the surface and gaps of the microfibrils that make up the cellulose fibers to the water phase, resulting in micronization. Since it also has the effect of increasing the α-cellulose purity of the prepared fibers, it may be very effective.

For example, in the beating treatment step, the raw material pulp is 0.5 wt% or more and 4 wt% or less, preferably 0.8 wt% or more and 3 wt% or less, more preferably 1.0 wt% or more and 2.5 wt% or less. First, fibrillation is promoted to a high degree by a beating device such as a beater or a 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) and processing is performed, extremely advanced beating (fibrillation) proceeds. It may be effective because the conditions for the conversion process can be relaxed.
A preferable degree of beating processing is determined as follows. When cellulose dispersed in water was evaluated by the CSF value of Canadian Standard Freeness Test Method (hereinafter, CSF method) of pulp defined in JIS P 8121, the CSF value decreased with time as the beating treatment was performed. Once it was close to zero, it was confirmed that it continued to increase as the beating process continued.

  The microfibrillated cellulose used for adjusting the aqueous dispersion is preferably beaten until the CSF value is once increased to a state where the CSF value is increased to zero after the beating treatment is continued. In the present invention, the CSF value in the process of decreasing the CSF value from unbeaten is expressed as *** ↓, and the CSF value in a tendency to increase after becoming zero is expressed as *** ↑. In the beating process, it is preferable that the CSF value has a value of *** ↑ which is at least zero or increases thereafter. In an aqueous dispersion (hereinafter also referred to as “slurry”) prepared to such a beating degree, fibrillation is highly advanced and at the same time the homogeneity of the slurry is increased. This is preferable because it can reduce clogging, and the processing condition can be connected to a condition with less burden (for example, reduction of the number of passes).

  For the production of microfibrillated cellulose, a high-pressure homogenizer, an ultra-high pressure homogenizer, a grinder or the like can be used. In this case, the solid content concentration in the aqueous dispersion is 0.5% by weight or more and 4% by weight or less, preferably 0.8% by weight or more and 3% by weight or less, more preferably 1.0%, in accordance with the beating treatment described above. If the solid content concentration is in the range of not less than 2.5% by weight, clogging does not occur and an efficient miniaturization process can be achieved.

Examples of high-pressure homogenizers used include NS type high-pressure homogenizers from Niro Soabi (Italy), SMT's Lanier type (R model) pressure-type homogenizers, and Sanwa Kikai Co., Ltd. high-pressure homogenizers. Any device other than these devices may be used as long as the device performs miniaturization by a mechanism substantially similar to those of these devices. Ultra-high pressure homogenizers mean high-pressure collision type miniaturizers such as Mizuho Kogyo Co., Ltd. microfluidizer, Yoshida Kikai Kogyo Co., Ltd. Nanomizer, and Suginoma Machine Co., Ltd. Any device other than these devices may be used as long as the device performs miniaturization with a substantially similar mechanism. Examples of the grinder-type miniaturization device include the pure fine mill of Kurita Machinery Co., Ltd. and the stone mill type milling die represented by Masuyuki Sangyo Co., Ltd. Any device other than these may be used as long as the device performs miniaturization by this mechanism.
The fiber diameter of the microfibrillated cellulose is determined by the conditions of the refinement using a high-pressure homogenizer (selection of equipment and operating pressure and the number of passes) or the pretreatment conditions before the refinement (for example, autoclave treatment, enzyme treatment, beating Control).

  In the cellulose nonwoven fabric of the present invention, the total of one or more water-soluble polymers selected from the group consisting of water-soluble polysaccharides and water-soluble polysaccharide derivatives is 0.5 wt% or more and 20 wt% or less, preferably 0.8 wt%. It is very important that the content is not less than 15% and not more than 15% by weight, more preferably not less than 1.0% and not more than 10% by weight. Here, the role of the water-soluble polymer is to strengthen the contact point strength of a network made of cellulose microfibril as a binder. The present inventors have an excellent effect in expressing tensile strength in a cellulose nonwoven fabric by allowing a water-soluble polysaccharide or a water-soluble polysaccharide derivative having a similar chemical structure to coexist with cellulose microfibril as a base material. I found out.

  Here, the water-soluble polysaccharide means a water-soluble polysaccharide, and various compounds exist as natural products. For example, α-1,4-glucans represented by starch, solubilized starch, amylose and pullulan, α-1,6-glucans represented by dextran, β-1, represented by curdlan and lentinan, Examples include compounds consisting of 3-glycan, amylopectin, branched saccharide represented by glycogen, xylan, galactan, mannan, glucomannan, glucomannoglycan, galactoglucomannoglycan, and heteroglycan represented by guaran. However, it is not limited to these.

  The water-soluble polysaccharide derivative includes the above-mentioned water-soluble polysaccharide derivatives, such as alkylated products, hydroxyalkylated products, and acetylated products, which are water-soluble. Alternatively, even if the polysaccharide before derivatization is insoluble in water such as cellulose, starch, etc., the water-solubilized one by derivatization, for example, hydroxyalkylation, alkylation, carboxyalkylation is also said water-soluble Included in polysaccharide derivatives. Specifically, hydroxyalkyl celluloses such as hydroxyethyl cellulose and hydroxypropyl cellulose, hydroxyalkyl starches such as hydroxyethyl starch and hydroxypropyl starch, methylcellulose, carboxymethylcellulose, and 2 such as hydroxyethylmethylcellulose and hydroxypropylmethylcellulose. Water-soluble polysaccharide derivatives derivatized with more than one type of functional group are also included, but are not limited thereto.

  Among these, in particular, the water-soluble cellulose derivative has a molecular chain skeleton having the same structure as cellulose in the cellulose microfibril base material, and the interaction force (adhesion force) to the surface of the cellulose microfibril is often strong. On the other hand, derivatives having a wide range of structures are industrially produced and easily available. In particular, when the cellulose nonwoven fabric of the present invention is produced by papermaking from an emulsion stock solution described later, emulsion stabilization (that is, an emulsifier) Alternatively, it is particularly preferable because it functions as an emulsion stabilizer). In this respect, among the water-soluble cellulose derivatives described above, since hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxyethyl methyl cellulose and hydroxypropyl methyl cellulose are also excellent in emulsifying performance, water-soluble polysaccharide derivatives having binder performance used in the present invention Is particularly preferred.

  In addition, many of the water-soluble polysaccharides and water-soluble polysaccharide derivatives described above have high heat resistance, and if a water-soluble polysaccharide and a water-soluble polysaccharide derivative having such properties are used, the cellulose nonwoven fabric obtained originally has cellulose. Heat resistance is not impaired. Specific examples are illustrated in Examples 8 and 9 and Comparative Example 3 and Reference Example 1 described later.

  The water-soluble polysaccharide and the water-soluble polysaccharide derivative in the cellulose nonwoven fabric of the present invention mean the corresponding components extracted by the following method, and the total amount of the content is evaluated as follows. That is, 1 g of non-woven fabric is dispersed in 500 g of cold water (using ion-exchanged water of 5 ° C. or lower) and is dispersed for 5 minutes with a home mixer. Next, while maintaining the temperature of the dispersion at 5 ° C. or lower, stirring is continued for 30 minutes under gentle stirring to completely dissolve the water-soluble polymer adhering to the fibers into the aqueous phase. Thereafter, the obtained fiber dispersion is filtered through a glass filter or the like, and the filtrate is recovered. The filtrate is further concentrated by an evaporator, and the resulting concentrate is added to heavy water to which an internal standard is added. Dissolve and evaluate the concentration of each component dissolved by the peak intensity of 1H-NMR.

  Considering the amount of the concentrated solution dissolved in heavy water, the concentration of the concentration step performed previously, and the like, the content of the dissolved component in the cellulose nonwoven fabric is calculated from the concentration of the dissolved component by 1H-NMR. If a water-soluble component that is neither a water-soluble polysaccharide nor a water-soluble polysaccharide derivative is contained in the concentrate, and the peak position of the water-soluble component in 1H-NMR is the peak position of the water-soluble polysaccharide or water-soluble polysaccharide derivative. In the case of overlapping, 1H-NMR analysis is carried out after separating each component by a liquid chromatograph or gel permeation chromatograph under an appropriate concentration condition.

Next, the cellulose nonwoven fabric of the present invention has a basis weight of 3 g / m ² or more and 80 g / m ² or less, more preferably 5 g / m ² or more and 50 g / m ² or less, more preferably 5 g / m ² or more and 30 g / m ² or less. ^When it is ² or less, it becomes possible to express various functions claimed by the present invention. Here, when the basis weight is smaller than 3 g / m ² , not only is it difficult to ensure the uniformity of the nonwoven fabric in a wide area, but also the strength is remarkably reduced based on an increase in partial defect frequency, which is not preferable. In addition, those having a basis weight larger than 80 g / m ² are difficult to produce from the viewpoint of productivity, and at the same time have characteristics based on the structure of the cellulose nonwoven fabric of the present invention that have a fine network and air permeability. (For example, if the basis weight becomes too large, the absolute value of the air permeability resistance described later increases and naturally the air permeability is remarkably lowered), it is also not preferable. The cellulose nonwoven fabric of the present invention is a cellulose nonwoven fabric having a relatively high basis weight obtained by laminating the cellulose nonwoven fabric of the present invention having a low basis weight by pressure bonding or the like (for example, 3 sheets of the same nonwoven fabric of the present invention having a basis weight of 15 g / m ² ). Even if it is divided into a single piece of cellulose nonwoven fabric with a basis weight of 45 g / m ² ), it does not matter as long as it satisfies the requirements of the present invention.

Furthermore, the cellulose nonwoven fabric of the present invention claims that the air resistance corresponding to a basis weight of 10 g / m ² is 10 s / 100 ml or more and 500 s / 100 ml or less, preferably 20 s / 100 ml or more and 300 s / 100 ml or less. Various functions can be suitably expressed. Here, in the cellulose nonwoven fabric composed of the cellulose microfibril of the present invention, it is difficult to make the air resistance less than 10 s / 100 ml due to the fineness of the network, and the air resistance exceeds 500 s / 100 ml. Although it can be easily produced, it is still not preferable because it is a material with poor differentiation from other materials (for example, a microporous film).
More preferably, it is a cellulose nonwoven fabric having a basis weight in the range of 5 g / m ^{2 to} 30 g / m ² and an air resistance equivalent to a basis weight of 10 g / m ² of 20 s / 100 ml to 300 s / 100 ml.

Here, the air permeation resistance corresponding to a basis weight of 10 g / m ² is a permeation of 100 ml of air using a Gurley type densometer (Model G-B2C, manufactured by Toyo Seiki Co., Ltd.) on a sample having a basis weight of wg / m ² If the result of measuring time (unit: s / 100 ml) at room temperature is zs / 100 ml, the following formula 10 × z / w (s / 100 ml) (2)
Is defined by Here, z is an average value obtained by measuring five points at various different positions for one nonwoven fabric sample.

By satisfying the above conditions, it is possible to provide a microporous cellulose nonwoven fabric that is excellent in heat resistance, weather resistance, solvent resistance, etc., has a fine network structure, and is breathable and has high strength. For example, the cellulose nonwoven fabric of the present invention, when suitable, has a tensile strength equivalent to a basis weight of 10 g / m ² (as defined in terms of the air resistance in the above equation (2)). It can be provided as having a strength of 6 N / 15 mm or more, and more preferably 8 N / 15 mm or more.
Here, the tensile strength of each sample was evaluated according to the method defined in JIS P 8113, using a tabletop horizontal tensile tester (No. 2000) manufactured by Kumagai Riki Kogyo Co., Ltd., and a sample having a width of 15 mm. Ten points were measured, and the average value was taken as the tensile strength. In addition, in the case of a sample made by continuous film formation in which strength anisotropy is likely to appear in the longitudinal and lateral directions of the nonwoven fabric with respect to batch type film formation, the tensile strength in the present invention is the tensile strength in the running direction (MD). Shall mean.

Next, the cellulose nonwoven fabric of the present invention is defined by the following formula (1) obtained by scanning light with a wavelength of 850 nm perpendicularly to the nonwoven fabric in a state of being immersed in toluene. _{Tr, av} = T _{r, 1} / T _{r, 2} (1)
The average transmittance T _{r, av} to be converted into a value corresponding to a weight per unit area of 10 g / m ² , that is, a measured value T _{r, av} of a sample having a per unit area wg / m ² is defined by the following formula (3). Value 1- (1-T _{r, av} ) × 10 / w (3)
When it is 0.70 or more, more preferably 0.75 or more, various functions claimed by the present invention can be expressed more clearly.

Here, _{Tr, av} is filled with toluene in a state where the nonwoven fabric is adhered to the inner surface of the test tube, irradiated with light having a wavelength of 850 nm from the direction perpendicular to the nonwoven fabric, and along the test tube. In the state where only the toluene is injected except for the average value _{Tr, 1 of the} transmittance obtained when scanning a total length of 30,000 μm (data points: 750) every 40 μm in the length direction, and the nonwoven fabric. The ratio of the average transmittance T _{r, 2} obtained by performing the same measurement is defined by the above formula (1). If _{Tr, av} converted to a value corresponding to a weight per unit area of 10 g / m ² is within this range, a microporous property that can be differentiated from other materials as a nanofiber nonwoven fabric is secured, and at the same time, for example, it is combined with a resin. In this case, a material having high transparency can be suitably obtained. This is due to the following reason.

Non-Patent Document 4: Non-Patent Document 4; “Polymer Handbook, 3rd Edition” Ed. By J. Brandrup and EH Immergood, for toluene with a refractive index of 1.496 at 20 ° C. According to John Wiley & Sons, New York, 1989, pp V126, the fibers constituting the nonwoven fabric when the refractive index is in the range of 1.51-1.62 depending on the type of cellulose and the orientation of the sample. In the case where a large number of fibers having a fiber diameter not sufficiently smaller than the visible wavelength of about 400 nm are included, scattering at the interface serves as an inhibitor of light transmission of the nonwoven fabric film, so the average transmittance value under the above conditions is The physical property value reflects the fineness of the constituent fibers of the nonwoven fabric or the fineness of the network structure of the nonwoven fabric. When the space in the nonwoven fabric containing cellulose is filled with a resin to make a composite, the average transmittance T _{r, av} obtained under the above conditions naturally correlates with the transparency of the obtained composite.

Here, in the present invention, Turboscan ^TM MA-2000 (Eihiro Seiki Co., Ltd.) is used in the measurement of _{Tr and av} . This device was originally developed to evaluate the aging stability of solutions and dispersions, but the nonwoven fabrics that are the subject of the present invention were immersed in toluene and the measurements described below were performed. Is very sensitive to the information on the diameter of the fibers constituting the nonwoven fabric and the information on the fineness of the network structure in the nonwoven fabric, and the physical property values correlated with the remaining amount of fiber diameter of a certain thickness or more contained in the nonwoven fabric. Is extremely effective.
Next, it is a multilayered sheet formed by laminating a plurality of layers including the above-mentioned cellulose nonwoven fabric layer, and the basis weight is 8 g / m ² or more and 100 g / m ² or less, and the air resistance is 10 s / 100 ml or more and 1000 s. A multilayered sheet that is 100 ml or less will be described.

The layer of the cellulose nonwoven fabric of the present invention that satisfies the above-mentioned requirements is included as a multilayer structure, and the basis weight as a multilayered sheet is 8 g / m ² or more and 100 g / m ² or less, preferably 10 g / m ² or more and 90 g / m. ² or less, and further, the air permeability resistance is 10 s / 100 ml or more and 1000 s / 100 ml or less, preferably 20 s / 100 ml or more and 500 s / 100 ml or less. Various functions of the cellulose nonwoven fabric claimed in the present invention are expressed. It becomes possible to provide a multilayered sheet that can be formed. Here, a multilayered sheet having a basis weight of less than 8 g / m ² is not suitable because it is difficult to produce stably, and if the basis weight is larger than 100 g / m ^2, a sheet having a permeability resistance range described later is structured. Since it is difficult to keep the balance above, it is not preferable. In addition, if the sheet has a resistance to air permeability smaller than 10 s / 100 ml, the physical properties due to the network composed of fine pores claimed by the present invention cannot be expected, so that the air resistance is not suitable. A sheet larger than the above is not preferable because the characteristic of the cellulose nonwoven fabric of the present invention that it has air permeability is impaired.

Even if the multilayered sheet has a two-layer structure in which the cellulose nonwoven fabric of the present invention is laminated on a support such as a breathable nonwoven fabric, the cellulose nonwoven fabric of the present invention is sandwiched between the front and back sides by a breathable support. Even if it has a three-layer structure, or even a different layer, the functions claimed by the cellulose nonwoven fabric of the present invention are preferably expressed as long as the above-mentioned basis weight and air resistance range are maintained. can do.
It describes about the manufacturing method of the cellulose nonwoven fabric of this invention. Basically, the cellulose nonwoven fabric of the present invention has a specified air resistance within the range of weight per unit area defined by the present invention when a nonwoven fabric composed of cellulose microfibrils, which are nanofibers, is formed. One or more water-soluble polymers (hereinafter also referred to as “specific water-soluble polymers”) selected from the group consisting of water-soluble polysaccharides and water-soluble polysaccharide derivatives may be controlled to a predetermined content. The film forming method can be roughly classified into a coating method and a paper making method.

  Among these, in the coating method, as described in Patent Document 1, a non-woven fabric having a predetermined air permeability resistance range cannot be obtained from an aqueous dispersion in which microfibrils are dispersed in water. It is necessary to use an organic solvent dispersion in which microfibrils are dispersed in a mixed solution of an organic solvent (for example, alcohol such as isopropanol or ethyl cellosolve) having a surface tension lower than that of water and water. Therefore, the predetermined specific water-soluble polymer is dispersed in the organic solvent dispersion, cast, and dried to form a film. It should be noted that by setting the composition of the organic solvent in the dispersion medium large, it becomes possible to control the air resistance to a predetermined degree. However, in the dispersion of cellulose microfibrils, it is difficult to increase the concentration of cellulose microfibrils to 2% by weight or more due to rheological restrictions (thus increasing the viscosity significantly), and the dispersion medium is dried from the dispersion. The sheet (nonwoven fabric) to be obtained is limited to those having an extremely low basis weight. In addition, it is surprisingly difficult to uniformly form the above-mentioned highly viscous dispersion, and this is disadvantageous in terms of cost because a large amount of organic solvent is required to produce a sheet having a constant area. In this respect, although the coating method is effective depending on conditions (film formation with a very low basis weight), the method for producing the cellulose nonwoven fabric of the present invention is more preferably based on the papermaking method.

  Patent Document 1 describes in detail a method for producing an air-permeable cellulose nonwoven fabric made of cellulose microfibrils by a papermaking method. In the production method disclosed in the document, cellulose microfibrils are dispersed in water while being controlled in an appropriate dispersion state, paper is made on a fine filter cloth, and water in the obtained wet paper is used as an organic solvent. In the substitution step, the organic solvent is substituted and dried.

  When the production method is applied to the present invention, it is preferable that a specific water-soluble polymer, which is an essential condition in the present invention, is dissolved in a papermaking dispersion or an organic solvent substitution bath and impregnated into a cellulose nonwoven fabric. . Among these, in the method of preliminarily dispersing in the papermaking dispersion, there is a possibility that the fixing rate of the specific water-soluble polymer on the cellulose microfibril surface in the dispersion is not so high, In the organic solvent replacement step, which is the next step, the specific water-soluble polymer once fixed may be detached, and thus cannot be said to be a method for efficiently producing the cellulose nonwoven fabric of the present invention. On the other hand, in the replacement step, the specific water-soluble polymer is dissolved in the replacement bath, and simultaneously with the solvent replacement, the specific water-soluble polymer is introduced as a binder for reinforcing the network of microfibrils. The specific water-soluble polymer remaining in the wet paper after the solvent replacement surely remains in the nonwoven fabric, and may be effective depending on conditions. However, in the introduction in the substitution step, it is necessary to adopt a solvent configuration in which the specific water-soluble polymer is completely dissolved, there are restrictions on the condition setting, and a certain amount of the specific water in the substitution solvent. It is necessary to dissolve the water-soluble polymer, and there is a disadvantage that it cannot be said to be an efficient introduction method.

  In contrast, in the present invention, the present inventors have found that the cellulose nonwoven fabric of the present invention can be efficiently produced by the following production method. 1) Cellulose microfibrils 0.05% by weight or more and 0.5% by weight or less, oily compounds having a boiling point range of 50 ° C. or more and 200 ° C. or less under atmospheric pressure 0.5% by weight or more and 10% by weight or less, water-soluble One or more water-soluble polymers selected from the group consisting of polysaccharides and water-soluble polysaccharide derivatives contain a total of 0.003% by weight to 0.1% by weight and water 85% by weight to 99.5% by weight Preparation step for preparing an aqueous dispersion, which is an emulsion in which the oily compound is dispersed in an aqueous phase, and 2) by dehydrating a part of the water constituting the aqueous dispersion with a paper machine, A papermaking process for obtaining a concentrated composition in which the concentration of microfibrils and the concentration of oily compounds are increased from the aqueous dispersion, and 3) heating the concentrated composition to form an oily compound from the concentrated composition. And drying the partially evaporated to remove the water, method for producing a cellulose nonwoven fabric containing three steps.

Below, the manufacturing method of the cellulose nonwoven fabric by the papermaking method using the emulsion type aqueous dispersion prescribed | regulated by this invention is expressed as an emulsion papermaking method for the sake of simplicity.
First, the details of the three steps described above will be described. The production method of the present invention is a simple method in which a wet paper is formed from a predetermined aqueous dispersion of cellulose microfibrils by a paper making method and the wet paper is dried.
The aqueous dispersion to be prepared in the preparation process is an oily compound having a cellulose microfibril of 0.05% by weight or more and 0.5% by weight or less and a boiling point range of 50 ° C. or more and 200 ° C. or less at atmospheric pressure of 0.5% by weight to 10%. The total of one or more water-soluble polymers selected from the group consisting of water-soluble polysaccharides and water-soluble polysaccharide derivatives is 0.003% to 0.1% by weight, and water is 85% to 99%. An aqueous dispersion containing 5% by weight or less is required.

  The concentration of cellulose microfibrils in the aqueous dispersion for emulsion papermaking is 0.05 to 0.5% by weight, preferably 0.08 to 0.35% by weight. Stable papermaking can be performed. If the cellulose microfibril concentration in the aqueous dispersion is lower than 0.05% by weight, the drainage time becomes very long, the productivity is remarkably lowered, and the film quality uniformity (texture) is also remarkably deteriorated. On the other hand, if the cellulose microfibril concentration is higher than 0.5% by weight, the viscosity of the dispersion is excessively increased, which makes it difficult to form a uniform film, which is also not preferable.

  Next, in the aqueous dispersion prepared in the preparation step, an oily compound having a boiling point range of 50 ° C. or more and 200 ° C. or less at atmospheric pressure of 0.15 wt% or more and 10 wt% or less is used as an emulsion. It is preferably dispersed in an aqueous phase composed of water of not less than 9% and not more than 99.5% by weight. This is due to the fact that the cellulose microfibrils contained in the aqueous dispersion have the property of interacting with and stabilizing the O / W emulsion composed of an oily compound (Non-Patent Document 5; H. Ono). , Y. Shimaya, T. Hongo and C. Yamane, ”New Aqueous Dispersion of Cellulose Sub-micron Particles: Preparation and Properties of Transparent Cellulose HydroGel (TCG)” Trans.Matr.Soc.Jpn., 26, 569 (2001) ).

  In the emulsion papermaking method, in the emulsion formed under the above-described conditions, the oily compound does not move to the filtrate side by the papermaking process, which means filtration in a papermaking machine, compared to water, and is highly water-insoluble and highly hydrophilic. It is characterized by efficiently remaining in the vicinity of cellulose as a molecule and substantially concentrating oily compounds. That is, when reaching the drying step, the water-insoluble hydrophilic polymer is surrounded by an oily compound having a lower surface tension than water, which prevents fusion between the polymers during drying and has air permeability. It becomes a driving force for forming a cellulose nonwoven fabric (in principle, the same as the above-described replacement method using an organic solvent). In order to create such an environment, it is an essential condition of the present invention that an emulsion composed of an oily compound and water is contained in a certain ratio.

  Since the air-permeable nonwoven fabric cannot be obtained unless the oily compound is removed during drying, the oily compound to be used must be removable in the drying step. Therefore, in the present invention, the oily compound contained as an emulsion in the aqueous dispersion must be in a certain boiling range, and specifically, the boiling point under atmospheric pressure is 50 ° C. or more and 200 ° C. or less. It is preferable. More preferably, when the temperature is 60 ° C. or higher and 190 ° C. or lower, the aqueous dispersion can be easily operated as 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 it under low temperature control in order to handle the aqueous dispersion stably, which is not preferable in terms of efficiency, and further the boiling point of the oily compound under atmospheric pressure. When the temperature exceeds 200 ° C., too much energy is required to heat and remove the oily compound in the drying step, which is also not preferable.

Furthermore, the solubility of the oily compound in water at 25 ° C. is 5% by weight or less, preferably 2% by weight or less, and more preferably 1% by weight or less for efficient formation of the necessary structure of the oily compound. It is desirable from the viewpoint of making a positive contribution. Specific examples of the oily compound are shown below.
For example, hydrocarbons having 6 to 14 carbon atoms, specifically n-hexane, n-heptane, n-octane, n-decane, n-undecane and isomers thereof (for example, isohexane, isooctane , Isodecane), chain saturated hydrocarbons such as cyclohexane and cyclohexene, chain or cyclic unsaturated hydrocarbons such as diisobutylene and cyclohexene, and benzene, toluene and xylene. Such aromatic hydrocarbons, followed by monohydric and primary alcohols having 5 to 9 carbon atoms, specifically n-pentanol, n-hexanol, n-heptanol, n-octanol , Isohexanol, isoheptanol, (Z) -3-hexen-1-ol, 2-methyl-1-pentanol, 2-ethyl- -Butanol, 4-methyl-1-pentanol, 3,3-dimethyl-1-butanol, (2E, 4E) -2,4-hexadien-1-ol, 2-methyl-2-hexanol, isoheptanol, Examples include 2-ethyl-1-hexanol, isooctanol, 1,3-benzodioxole-5-methanol, but are not limited thereto. Although not a primary alcohol, 4-methyl-2-pentanol, 3-methyl-3-pentanol, 2-methyl-2-hexanol, 2-heptanol, cycloheptanol, 4-heptanol, 1-methylcyclohexanol 1-ethynylcyclopentanol, 2-octanol, (S) -2-octanol, cyclooctanol, 3,5-dimethyl-1-hexyn-3-ol, 1-ethynylcyclohexanol, 1-octin-3-ol Monohydric alcohols having a carbon number in the range of 5 to 9 can also be suitably used as the oily compound.

Among the oily compounds described above, in particular, the oily compound is in the range of 5 to 9 carbon atoms, and is preferably at least one compound selected from monovalent and primary alcohols, more preferably 1 of the alcohols. The cellulose nonwoven fabric of the present invention can be particularly preferably produced by using at least one compound selected from pentanol, 1-hexanol, and 1-heptanol. This is considered to be suitable for the production of a nonwoven fabric having a high porosity and a fine porous structure because the oil droplet size of the emulsion is extremely small (1 μm or less under normal emulsification conditions).
These oil compounds may be blended as a simple substance, or a plurality of mixtures may be blended. Furthermore, in order to control the emulsion characteristics to an appropriate state, a small amount of a water-soluble organic solvent such as water-soluble alcohols such as ethyl cellosolve may be used in these oil compounds. In this case, the water-soluble organic solvent is preferably 25% by weight or less based on the oily compound. If the amount is more than this, the ability to form an emulsion of an oily compound is lowered, which is not preferable.

Next, the concentration of the oily compound in the aqueous dispersion for papermaking is 0.15% by weight to 10% by weight, preferably 0.3% by weight to 5% by weight, more preferably 0.5% by weight to 3%. % By weight or less. Even if the concentration of the oily compound exceeds 10% by weight, the cellulose nonwoven fabric of the present invention can be obtained. However, the amount of the oily compound used as a production process increases, and accordingly, the necessity of safety measures and cost increase. This is not preferable because of the restrictions. Further, if the concentration of the oily compound is less than 0.15% by weight, it is not preferable because only a sheet having an air resistance higher than a predetermined air resistance range can be obtained.
It is important that the oily compound described above is dispersed as an emulsion in the aqueous dispersion in the adjusting step. In this case, it is an O / W type emulsion in which oil droplets are dispersed in an aqueous phase. Since the network structure corresponding to the oil droplet size is reflected in the structure after drying, the oil droplet size is preferably small and stably dispersed.

  Here, it is important that the above-mentioned specific water-soluble polymer is dissolved in the aqueous phase in the aqueous dispersion for emulsion papermaking of the present invention. The action of these water-soluble polymers in the O / W type emulsion is known as a protective colloid in the field of colloid science (Non-patent Document 6; Masami Kawaguchi, “Polymer Interface / Colloid Science” 1999). Corona, p. 170). That is, the water-soluble polymer has a strong tendency to localize near the surface of the oil droplet particles dispersed in the aqueous phase (the interface between the water and the oil droplets), and contributes to the stabilization of the emulsion. Among water-soluble polymers, those having particularly high emulsification performance are considered to have a high localization rate on the surface of oil droplets. Thus, the water-soluble polymer localized on the surface of the oil droplets is taken up together with the oil droplets into the above-mentioned mechanism of emulsion papermaking, that is, the loose association pair formed by cellulose microfibrils, and remains in the wet paper in the papermaking process. Therefore, it remains in the wet paper with a high residual rate.

In the production method of the present invention, by using a specific water-soluble polymer, the specific water-soluble polymer remains in the wet paper, that is, in the cellulose nonwoven fabric after drying with high efficiency. In that respect, the emulsion papermaking method is a more preferable method as a method for producing the cellulose nonwoven fabric of the present invention.
As described above, in the aqueous dispersion for emulsion papermaking of the present invention, it is necessary that the specific water-soluble polymer described above is dissolved in the aqueous phase. The concentration of is 0.003% to 0.1% by weight, more preferably 0.005% to 0.08% by weight, and still more preferably 0.006% to 0.07% by weight. This amount is preferable because the cellulose nonwoven fabric of the present invention is easily obtained and the state of the aqueous dispersion is often stabilized. If the concentration is less than 0.003% by weight, the effect of adding the specific water-soluble polymer is hardly exhibited, and it is not preferable. If the concentration exceeds 0.1% by weight, the amount of addition such as foaming is increased. Since the accompanying negative effect tends to appear, it is not preferable. For the purpose of stabilizing the emulsion, in addition to the specific water-soluble polymer, at least one of a surfactant and other water-soluble polymer in the aqueous dispersion is a total amount of the specific water-soluble polymer. May be included in the above concentration range.

  As the surfactant in this case, anionic surfactants such as alkyl sulfate ester salt, polyoxyethylene alkyl sulfate ester salt, alkylbenzene sulfonate, α-olefin sulfonate, alkyltrimethylammonium chloride, dialkyldimethylammonium chloride, Examples include cationic surfactants such as benzalkonium chloride, amphoteric surfactants such as alkyldimethylaminoacetic acid betaines and alkylamidodimethylaminoacetic acid betaines, and nonionic surfactants such as alkylpolyoxyethylene ethers and fatty acid glycerol esters. However, it is not limited to these.

  In addition, as other water-soluble polymers described above, specific examples include polyvinyl alcohol (grades with a degree of saponification that is not too high contribute to stabilization, and those with terminal alkyl modification are also effective as stabilizers. ), Vinyl alcohol / ethylene copolymers (low ethylene composition, water-soluble grade), those having a copolymer structure of vinyl alcohol and other monomers such as butyral, polyethylene oxide or alkyl-terminated ends thereof Nonionic water-soluble polymers such as polypropylene oxide, polybutyral resin (water-soluble grade), acrylic acid monomer units and acrylate monomer units, methacrylic acid monomer units and methacrylate monomer units Anionic monomer units contained in the molecular chain skeleton Anionic water-soluble polymer, an organic amino derivative ester of acrylic acid, an organic amino derivative ester of methacrylic acid, a cationic water-soluble polymer in which a cationic monomer unit such as an ethyleneimine derivative is contained in the molecular chain skeleton, Alternatively, an amphoteric water-soluble polymer in which both an anionic monomer unit and a cationic monomer unit are contained in the molecular chain skeleton can be exemplified, but the invention is not limited thereto.

In addition, various additives may be added to the aqueous dispersion according to the purpose. For example, inorganic particulate compounds such as silica particles, alumina particles, titanium oxide particles, calcium carbonate particles, resin fine particles, various salts, seasonings, foodstuffs, food additives, organic solvents that do not hinder the stability of the emulsion For example, the cellulose non-woven fabric of the present invention can be added within a range that does not adversely affect the production (selection of type and selection of composition).
The aqueous dispersion prepared in the preparation step is an emulsion composition composed of the above-described compound group, but any method of emulsification can be employed in forming the emulsion. That is, an O / W emulsion is prepared by a method such as mechanical emulsification, phase inversion emulsification, liquid crystal emulsification, phase inversion temperature emulsification, D phase emulsification, or ultrafine emulsification (microemulsion emulsification) using a solubilized region.

Here, in the final aqueous dispersion, components other than water are 85 wt% or more and 99.5 wt% or less, preferably 90 wt% or more and 99.4 wt% or less, more preferably 92 wt% or more and 99.99 wt% or less. It is preferably dispersed or dissolved in water having a composition of 2% or less. When the composition of water in the aqueous dispersion is lower than 85% by weight, the viscosity often increases and it becomes difficult to uniformly disperse the emulsion in the dispersion, and a cellulose nonwoven fabric having a uniform structure and air permeability can be obtained. Since it becomes difficult, it is not preferable. On the other hand, when the composition of water in the aqueous dispersion exceeds 99.5% by weight, the content of the emulsion is reduced as a blended composition, the concentration of the oily compound in the concentrated composition is lowered, and the breathable structure Is also not preferable because it is difficult to obtain.
The aqueous dispersion is prepared by mixing all additives into water and preparing an aqueous emulsion dispersion by an appropriate emulsification method, or by preparing an aqueous emulsion previously composed of an oily compound and an emulsifier by an appropriate emulsification method as described above. What is necessary is just to prepare and mix with the aqueous dispersion liquid which consists of the cellulose microfibril prepared separately, and another additive, and just to make an aqueous dispersion liquid.

  Next, the second step of the present invention is a papermaking step of filtering cellulose microfibrils and concentrating the emulsion concentration by dehydrating the aqueous dispersion prepared in the first step with a paper machine. The papermaking process is basically an operation using a filter or filter cloth (also called a wire in the technical field of papermaking) that dehydrates water from a water-containing dispersion and retains a water-insoluble hydrophilic polymer. Any apparatus may be used as long as it is present. As described above, since the oil droplets in the emulsion have the property of being localized in the vicinity of the cellulose microfibrils, even if the liquid phase is discharged out of the system by the dehydration operation, the oil droplets remain on the filter or filter cloth, substantially. Concentration of the emulsion components will proceed.

As the paper machine, if a device such as an inclined wire type paper machine, a long net type paper machine, or a circular net type paper machine is used, a sheet-like cellulose nonwoven fabric with few defects can be suitably obtained. Whether the paper machine is a continuous type or a batch type, it may be properly used according to the purpose.
The method of papermaking an aqueous dispersion prepared using microfibrillated cellulose or the like basically conforms to the technique described in Patent Document 1 by the present inventors. The difference between Patent Document 1 and the present invention is that an emulsion composed of an oily compound and water is contained in an aqueous dispersion for papermaking. However, the papermaking condition is better due to the papermaking conditions disclosed in Patent Document 1. Can be implemented. The reason is considered to be that the emulsion component is incorporated in the aggregate (soft agglomerate) made of microfibrillated cellulose in the aqueous dispersion prepared in the adjustment step.

That is, dewatering is performed by the papermaking process using the aqueous dispersion obtained by the preparation process (aqueous dispersion for papermaking), but the papermaking is fine cellulose dispersed in the aqueous dispersion using a wire or filter cloth, etc. Therefore, the size of the wire or the filter cloth is important. In the present invention, essentially, a water-based dispersion for papermaking prepared under the above-described conditions, the yield ratio of water-insoluble components including cellulose and the like contained in the dispersion is 70% by weight or more, preferably Any wire or filter cloth that can make paper at 95% by weight or more, more preferably 99% by weight or more can be used. However, even if the yield ratio of cellulose or the like is 70% by weight or more, if the drainage is not high, it takes time to make paper and the production efficiency is remarkably deteriorated. When the amount is preferably 0.005 ml / cm ² · s or more, and more preferably 0.01 ml / cm ² · s or more, suitable papermaking can be performed from the viewpoint of productivity. When the yield ratio of the water-insoluble component is lower than 70% by weight, not only the productivity is remarkably reduced, but also the water-insoluble component such as cellulose is clogged in the wire or filter cloth to be used. The peelability of the subsequent cellulose non-woven fabric is also significantly deteriorated.

Here, the water permeation amount of the wire or the filter cloth at 25 ° C. under atmospheric pressure is evaluated as follows. When installing a wire or filter cloth to be evaluated on a batch paper machine (for example, an automatic square sheet machine manufactured by Kumagai Riki Kogyo Co., Ltd.), in the case of a wire, 80 to 120 mesh in the case of a filter cloth. A filter cloth is placed on a metal mesh (assuming that there is almost no drainage resistance), a sufficient amount (yml) of water is poured into a paper machine having a papermaking area of xcm ² , and filtered under atmospheric pressure. Measure time. The amount of water permeation when the drainage time is zs (seconds) is defined as y / (xz) (ml / cm ² · s).

  Wires and filter cloths that satisfy the above conditions that can be used for paper making of microfibrillated cellulose are limited. Examples of filters or filter cloths that can be used for extremely fine microfibrillated cellulose fibers include TETEXMONODW07-8435-SK010 (PET) manufactured by SEFAR (Switzerland), NT20 (PET / nylon blend) manufactured by Shikishima Kanbus. It can mention, but it is not limited to these.

  In the dehydration by the papermaking process, high solid differentiation proceeds simultaneously with the concentration of the emulsion, and a wet paper which is a concentrated composition in which the concentration of cellulose microfibrils and the concentration of oily compounds are increased from the aqueous dispersion is obtained. The solid content ratio of the wet paper is controlled by the degree of dehydration by the suction pressure (wet suction or dry suction) of the papermaking or pressing process, preferably the solid content concentration is 6 wt% or more and 25 wt% or less, more preferably the solid content. The concentration is adjusted in the range of 8 wt% to 20 wt%. If the solid content of the wet paper is lower than 6% by weight, there is no self-supporting property as the wet paper and problems in the process are likely to occur. Further, when the solid content of the wet paper is dehydrated to a concentration exceeding 25% by weight, not only the aqueous phase but also the concentrated emulsion is discharged out of the system, and the presence of the aqueous layer in the vicinity of the cellulose microfibrils makes it an oily compound. Therefore, the cellulose non-woven fabric having air permeability cannot be formed effectively, which is not suitable. As described above, in the present invention, the emulsion is concentrated by the papermaking process, and the oily compound concentration in the wet paper after the dehydration process is about 5 times or more that of the oily compound concentration in the aqueous dispersion before the dehydration. In some cases, it is concentrated 10 times or more.

  The wet paper obtained in the paper making process becomes a cellulose nonwoven fabric by evaporating a part of the oily compound and water in the drying process by heating. The drying process is a constant-length drying type that can dry water and an oily compound (hereinafter referred to as “dispersion medium” together with water and an oily compound) in a state where the width is constant as in a drum dryer. Use of a dryer is preferable because a cellulose nonwoven fabric having a lower air resistance can be stably obtained. The drying temperature may be appropriately selected according to the conditions, but preferably 45 ° C. or higher and 180 ° C. or lower, more preferably 60 ° C. or higher and 150 ° C. or lower. Can be manufactured. When the drying temperature is less than 45 ° C., the volatilization rate of the dispersion medium is slow in many cases, which is not preferable because productivity cannot be secured. When the drying temperature is higher than 180 ° C., the hydrophilic polymer constituting the structure is heated. There are cases in which denaturation occurs, and energy efficiency affecting the cost is also reduced, which is also not preferable. Depending on the case, the composition is prepared by low-temperature drying at 100 ° C. or lower, and multistage drying in which the composition is dried at a temperature of 100 ° C. or higher in the next stage is also effective in obtaining a highly uniform cellulose nonwoven fabric. is there.

Next, you may provide the smoothing process which smoothes the cellulose nonwoven fabric obtained at the drying process mentioned above with a calendar apparatus. By passing through the smoothing step, the cellulose nonwoven fabric of the present invention whose surface is smoothed and thinned can also be obtained. The outline will be described below.
That is, the cellulose non-woven fabric of the present invention after drying is further subjected to a smoothing process by a calender device, so that a thin film can be formed, and a wide range of film thickness / breathability / strength combinations of the present invention. A cellulose nonwoven fabric can be provided. For example, it is possible to easily produce a cellulose nonwoven fabric having a film thickness of 20 μm or less (lower limit is about 3 μm) under a basis weight setting of 10 g / m ² or less. As the calendar device, in addition to a normal calendar device using a single press roll, a super calendar device having a structure in which these are installed in a multistage manner may be used. The cellulose nonwoven fabric of the present invention having various physical property balances can be obtained by selecting the materials (material hardness) and linear pressures on both sides of the roll during the calendar process according to the purpose.

  There are two possible operating principles of the calendar treatment for the dried cellulose nonwoven fabric. First, in the manufacturing process of the cellulose nonwoven fabric of the present invention, the pitch of the surface irregularities of the wire mesh and filter cloth used at the time of manufacture is significantly longer than the fiber length of the cellulose microfibril used as a papermaking raw material. As for the surface of this, the unevenness of a wire mesh or a filter cloth is easy to be transferred. As a first point, the calendar process has an effect of flattening the unevenness. The second point is the effect of crushing the network structure itself of the nonwoven fabric having a certain porosity. Due to the second effect, the porosity of the non-woven fabric is reduced and the average pore diameter is also reduced. As a result, the air resistance is increased, and the tensile strength and the piercing strength may be increased. Actually, the first effect and the second effect are mixed according to the set calendar processing conditions (with various contribution ratios), and the structure and physical properties of the resulting cellulose nonwoven fabric are determined. Moreover, the cellulose nonwoven fabric which added the unevenness | corrugation by arbitrary surface patterns using the metal roll for calendering which gave the surface the embossing can also be used suitably as a cellulose nonwoven fabric of this invention.

In particular, in order to continuously form the cellulose nonwoven fabric of the present invention, it is necessary to continuously perform the paper making process, the drying process, and, in some cases, the smoothing process by calendering, except for the preparation process. At this time, the wire mesh to be used (hereinafter also simply referred to as “wire”) is an endless specification, and the entire process is performed with one wire, or the endless wire or the endless felt cloth of the next process is picked up in the middle. Or transfer and transfer, or all or part of the continuous film-forming process may be a roll-to-roll process using a filter cloth.
Further, in the present invention, in the paper making process by the paper machine, a sheet-like support having water permeability is placed on the paper machine, and a part of the water constituting the aqueous dispersion is dehydrated (paper making) on the support. A multilayered sheet having a laminated structure of at least two layers can be produced by laminating and integrating the wet paper of the cellulose nonwoven fabric of the present invention on the support.

  The support used for the production of such a multilayered sheet is preferably a nonwoven fabric or a porous membrane having a high porosity and water permeability. Specifically, cellulose, polyethylene terephthalate, 6,6-nylon, 6-nylon, polyvinyl alcohol, various polyurethane nonwoven fabrics, or cellulose, polyethylene terephthalate, 6,6-nylon, 6 -The porous film made from nylon, the product made from polyvinyl alcohol, and various polyurethanes can be mentioned, However, It is not limited to these. When a nonwoven fabric called microweb or a microporous membrane having a number average fiber diameter of 2 μm or less of fibers constituting the nonwoven fabric is used, the nonwoven fabric itself forms a film from an aqueous dispersion of microfibrillated cellulose in the present invention. Therefore, a high-porosity structure having an integrated multilayer structure can be produced without using a wire or filter cloth as described above during papermaking. In order to produce a multilayered sheet having three or more layers, a support having a multilayer structure having two or more layers may be used. Moreover, it is good also as a multilayer sheet | seat of three or more layers by performing the multistage papermaking of this invention of two or more layers on a support body.

  The cellulose nonwoven fabric of the present invention and the multilayered sheet comprising the nonwoven fabric as one layer are various functional filters, various functional papers, separators for various power storage devices, precision cleaning wipers, precision polishing pads, absorbent materials, and medical materials. It can be used in a wide range of fields such as a support and a functional membrane. Furthermore, by compounding with various resins such as epoxy resin, it can be applied as a substrate for semiconductor devices and wiring boards, as a base material for low linear expansion coefficient materials, etc. It is not limited.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples of the present invention, but the present invention is not limited to these Examples.

(Examples 1-5)
Obtained after using cotton linter pulp (Nippon Paper Pulp Shoji Co., Ltd.) as the cellulose raw material, immersing the pulp in water to a solid content of 10% by weight and subjecting to autoclave treatment at 130 ° C. for 4 hours. The swollen pulp was repeatedly washed with water to obtain a swollen pulp impregnated with water. When the α-cellulose content of the dried swelling pulp was measured, it was 98.0% by weight (total cellulose content was 100% by weight).

  The swollen pulp is dispersed in water to a solid content of 1.5% by weight to form a water dispersion (400 L). As a disk refiner device, SDR14 type laboratory refiner (pressure type DISK type) manufactured by Aikawa Tekko Co., Ltd. is used. The beating process was continued for 20 minutes on the 400 L water dispersion with a disc clearance of 1 mm, and then the beating process was continued under conditions where the clearance was reduced to almost zero. . Sampling was carried out over time, and the CSF value of the Canadian standard freeness test method (hereinafter referred to as CSF method) of pulp defined by JIS P 8121 was evaluated for the sampling slurry. Then, once it was close to zero, if the beating process continued further, a tendency to increase was confirmed. The beating treatment was continued under the above conditions for 10 minutes after the clearance was reduced to near zero, and a beating slurry having a CSF value of 73 ml ↑ (the beating slurry was designated as an aqueous dispersion M0) was obtained. The obtained beating slurry was subjected to micronization treatment 5 times under an operating pressure of 100 MPa using a high-pressure homogenizer (NS3015H manufactured by Niro Soabi (Italy)) as it was, and an aqueous dispersion (solid content) of microfibrillated cellulose. Concentration: 1.5% by weight), M1 was obtained.

Next, using M1, various components were added to prepare the compositions of Examples 1 to 5 shown in Table 1, emulsified and dispersed with a home mixer for 4 minutes, and an aqueous dispersion for papermaking. A liquid was obtained. In Examples 1 to 5, a 5% by weight aqueous solution of hydroxypropylmethylcellulose (Hypromellose 60SH-4000 manufactured by Shin-Etsu Chemical Co., Ltd.) was prepared in advance as a water-soluble polysaccharide derivative, and was mixed in a corresponding amount.
A plain fabric made of PET / nylon blend having the ability to filter out 99% or more of microfibrillated cellulose by filtration at 25 ° C under atmospheric pressure from the aqueous dispersion (NT20, manufactured by Shikishima Kanbus Co., Ltd.) Batch-type paper machine (Ri Kumagai) using a filter cloth made by cutting water permeation amount: 0.03ml / cm ² · s) to the size of square metal wire (25cm x 25cm) used below. Paper making (dehydration) was performed using an automatic square sheet machine manufactured by Kogyo Co., Ltd. The above-mentioned PET fabric is placed on a rectangular metal wire (25 cm × 25 cm, 80 mesh) incorporated in the paper machine, and a predetermined amount of paper dispersion is injected into the paper machine from above, and suction ( Pressure reducing device) Paper making was carried out at a reduced pressure with respect to atmospheric pressure of 4 KPa.

  The wet paper made of the concentrated composition on the obtained filter cloth is peeled off from the wire and the wet paper surface is brought into contact with the drum surface so that the wet paper / filter cloth has a two-layer surface. It was pasted on a drum dryer manufactured by Kumagai Riki Kogyo Co., Ltd. whose temperature was set to 60 ° C. and dried for about 120 seconds. Two layers of wet paper / filter cloth thus coarsely dried were dried for about 120 seconds with a drum dryer whose surface temperature was set to 130 ° C. so that the wet paper was still in contact with the drum surface. Cellulose nonwoven fabrics S1, S2, S3, S4, and S5 made of white uniform cellulose are peeled off from the dried two-layer body from the cellulose sheet-like structure (Examples 1, 2, and 5 respectively). 3, corresponding to Example 4 and Example 5). In all cases, the yield of cellulose microfibrils was almost 100%.

Table 2 shows the content of the specific water-soluble polymer (hydroxypropylmethylcellulose) contained in S1 to S5. Furthermore, the physical properties of S1 to S5 are as shown in Table 2. Here, the film thickness (d (μm)) means an average value of five or more measured values measured by a film thickness meter for one nonwoven fabric sample. In particular, the film thickness meter is a surface contact type film thickness meter (Code No. 547-401 manufactured by Mitutoyo Co., Ltd.) from the viewpoint that it can be evaluated without crushing the nonwoven fabric sample of the present invention having a high porosity. ))It was used.
Furthermore, the porosity was calculated by the following (4) from the film thickness d (μm) of the sample and the basis weight w (g / m ² ).
Pr (%) = (1−w × 0.94 / (1.5 × d)) × 100 (4)

All the samples were white and air-permeable sheets having a porosity of around 80%. An SEM image at a magnification of 10,000 times the surface of S1 is shown in FIG. As a result of analysis of photographs of two SEM images relating to the surface of S1 including FIG. 1, the number average fiber diameter of the microfibrillated cellulose on the surface of S1 was 108 nm.
From the above, S1 to S5 were all cellulose nonwoven fabrics of the present invention. From the results of the scattering-type particle size distribution measurement of the aqueous dispersion for papermaking, the oil droplet diameter of the emulsion in the aqueous dispersion for papermaking in Example 1 is about 0.2 μm, and very small oil droplets are formed from cellulose microfibrils. It was presumed that a fine network structure as shown in FIG. 1 was formed by taking in the wet paper and drying it.

(Examples 6 and 7)
Using the aqueous dispersion M1 of microfibrillated cellulose prepared in Example 1, the aqueous dispersion for papermaking having the composition shown in Table 1 was continuously formed using the continuous paper machine. did. However, in the emulsification operation, the disc refiner used as the beating apparatus in Example 1 was used, and the aqueous dispersion liquid 330 Kg blended in a predetermined composition was continuously circulated at a rate of 335 L / min. The clearance between the discs was reduced, and the treatment was continued for 17 minutes from the point when it became almost zero, and the resulting white emulsion was used as an aqueous dispersion for papermaking.

  Using the aqueous dispersion for papermaking, a polymer is produced using an inclined wire type continuous papermaking apparatus (manufactured by Saito Iron Works Co., Ltd.) having a papermaking width of 0.65 m and a suction line length of 1.5 m set at an inclination angle of 5 °. PET / nylon plain woven fabric (NT-20, width 0.76 m × length 100 m) similar to that used in Example 1 on a 200 mesh wire made by Nippon Filcon Co., Ltd. The papermaking dispersion liquid is continuously installed at a feed rate of 6.24 L / min, and the papermaking travel speed is 5. The continuous paper making was performed by operating the wet suction (inclined part) and the dry suction at 0 m / min. A press dehydration step using a metal roll was not provided immediately after papermaking, and the cellulose concentration of the wet paper made of the concentrated composition immediately after papermaking was 12% by weight.

  Transfer the wet paper to the drum dryer (two steps) set at 100 ° C in the two layers of wet paper / filter cloth so that the wet paper contacts the dryer surface, and peel the cellulose nonwoven fabric from the filter cloth immediately after drying. The continuous nonwoven fabric S6 (about 100 m long) of the cellulose of the present invention was wound up. As shown in Table 2, S6 was the cellulose nonwoven fabric of the present invention having air permeability, white color and high uniformity (Example 6).

  Next, a calendar process was applied to S6. In this embodiment, the upper roll is a metal mirror roll and the lower roll is a rubber roll (hardness A98), and a calendar process is performed at a running speed of 2 m / min at a linear pressure of 2.0 tons at room temperature. White cellulose nonwoven fabric S7 was obtained. The physical properties and the like of S7 are as shown in Table 2. Although the film thickness of S7 is less than half that of S6, the air resistance and the like satisfy the requirements of the present invention, and S7 is the cellulose nonwoven fabric of the present invention.

(Examples 8 and 9)
Next, the effects of the corresponding water-soluble polymer other than hydroxypropylmethylcellulose used as the specific water-soluble polymer contained in the cellulose of the present invention in Examples 1 to 7 are shown.
The aqueous dispersion for papermaking was prepared in the same manner as in Example 1, and the specific water-soluble polymer used was starch (soluble) (Wako Pure Chemical Industries, Ltd., code: 191-03985) (Example) 8) and hydroxyethyl cellulose (4,500-6,500 cps 2% in water at 25 ° C., code: H0392 manufactured by Tokyo Chemical Industry Co., Ltd.) (Example 9) were used for papermaking as the composition shown in Table 1.

In this case, a 1% by weight aqueous solution was prepared in advance at 80 ° C., and this was mixed with other compositions, followed by a mixer treatment at room temperature for 4 minutes to emulsify and disperse to obtain an aqueous dispersion for papermaking. .
The paper making method and the drying method were carried out in the same manner as in Example 1 to obtain a white and uniform cellulose nonwoven fabric of the present invention. The samples obtained in Example 8 and Example 9 were designated as S8 and S9, respectively. The physical properties of each sample are shown in Table 2. Although the intensity | strength of S8 is low in the sample obtained in the Example of S1-S9, it was produced from the same M1 dispersion liquid of the comparative example 2 and the comparative example 4 which are the cellulose nonwoven fabrics which do not contain a water-soluble polymer. The strength was clearly increased as compared with Samples H2 and H4, and the reinforcing effect of these binders was confirmed. As a result of a heat resistance test described later, both S8 and S9 were confirmed to be sheets having a small degree of discoloration and excellent heat resistance even after a high temperature history of 180 ° C. and 70 hours.

(Comparative Example 1)
Using the aqueous dispersion M0 obtained only in the beating treatment obtained in Example 1, a papermaking dispersion having the composition shown in Table 1 was prepared by the same emulsification and dispersion method as in Example 1. Paper making was performed using the obtained aqueous dispersion under the same batch-type paper making conditions as in Example 1. After paper making, the obtained wet paper was immediately dried in the same manner as in Example 1 to obtain a white sheet sample H1 with poor uniformity (Comparative Example 1).
From the SEM image of the surface of H1, the surface of H1 contains a considerable amount of fibers of several μm to 10 μm. As can be seen from the physical property table shown in Table 3, hydroxy, which is a water-soluble polysaccharide derivative. The content of propylmethylcellulose was as low as 0.4% by weight, which was not a cellulose nonwoven fabric of the present invention. It was found that the cellulose nonwoven fabric of the present invention could not be produced using fibrillated cellulose with poor film uniformity, low strength, and high beating. The value of T _{r, av} corresponding to a basis weight of 10 g / m ² was also 0.68, which was lower than each sample of the example. It is estimated that the reason why the content of the water-soluble polysaccharide derivative in the nonwoven fabric was small was that the oil droplets of the emulsion could not be effectively captured in the wet paper because the surface area of the cellulose fiber was low.

(Comparative Example 2)
Using the aqueous dispersion M1 of microfibrillated cellulose prepared in Example 1, as shown in Table 1, a water-based dispersion for papermaking having a composition not containing a water-soluble polysaccharide or a water-soluble polysaccharide derivative is the same as in Example 1. It was prepared by an emulsification and dispersion method. Although some oil droplets were floating on the surface of the obtained aqueous dispersion, the whole was a white emulsion.
Using the aqueous dispersion for papermaking, papermaking was performed immediately after preparation under the same batch-type papermaking conditions as in Example 1. After paper making, the obtained wet paper was immediately dried in the same manner as in Example 1 to obtain a uniform white sheet-like sample H2 (Comparative Example 2).
The physical properties of H2 are shown in Table 3. H2 is not a cellulose nonwoven fabric of the present invention consisting only of cellulose microfibrils, but is significantly lower in strength corresponding to 10 g / m ² than any of the samples obtained in Examples 1 to 7, and is water-soluble in the present invention. The effect of containing a water-soluble polysaccharide or a water-soluble polysaccharide derivative was confirmed.

(Comparative Example 3)
Using the aqueous dispersion M1 of microfibrillated cellulose prepared in Example 1, a papermaking aqueous dispersion having the composition shown in Table 1 was prepared in the same manner as in Example 1. However, as the water-soluble polymer, a polyvinyl alcohol resin (PVA-224C (R) manufactured by Kuraray Chemical Co., Ltd.) that is not the water-soluble polysaccharide or water-soluble polysaccharide derivative specified in the present invention is prepared in advance as a 5 wt% aqueous solution. , Mixed, emulsified and dispersed. Using a predetermined amount of the aqueous dispersion for papermaking, a paper sample H3 having high whiteness uniformity was obtained through the same steps of papermaking and drying as in Example 1. The physical properties of H3 are shown in Table 3.

H3 had a binder effect due to the addition of a water-soluble polymer by comparison with the strength of H2, but was lower than any of the samples of Examples 1 to 7 when compared with a strength corresponding to a basis weight of 10 g / m ^2. Value. Further, in order to investigate the effect of binder addition on the heat resistance, a discoloration test was conducted when S6 and S7 obtained in Example 6 and Example 7 were held at 180 ° C. for 70 hours in an air atmosphere. As a result, it was found that browning clearly progressed in H3 compared to S6 and S7. The added PVA-224C is a polymer that contains some vinyl acetate units, and it is estimated that elimination of acetic acid from the units and impurities such as metal salts contained in the PVA-224C itself reduce heat resistance. It was done.

(Comparative Examples 4 and 5)
As a method for obtaining a breathable cellulose nonwoven fabric composed of cellulose microfibrils, disclosed in Patent Document 1 and the like, by a method obtained by substituting a wet paper obtained by film formation from an aqueous dispersion with an organic solvent. Comparison with the obtained cellulose nonwoven fabric was performed.

The aqueous dispersion M1 prepared in Example 1 was diluted with water (Comparative Example 4) or water and a hydroxypropylmethylcellulose aqueous solution (Comparative Example 5), respectively, to give the composition shown in Table 1, and for 4 minutes with a household mixer. Emulsification and dispersion were carried out to obtain an aqueous dispersion for papermaking.
Batch papermaking was performed using the aqueous dispersion prepared under each condition in the same manner as in Example 1 to obtain a wet paper having a solid content of about 11% by weight. The wet paper obtained from each was subjected to solvent replacement and drying by the following methods. The wet paper on the obtained filter cloth was further covered with the same filter cloth, and was pressed for 1 minute at a pressure of 0.5 MPa using a square sheet machine press manufactured by Kumagai Riki Kogyo Co., Ltd. The solid content was about 15% by weight. Next, it is immersed for 15 minutes in a substitution bath in which 1 kg of isobutyl alcohol is mixed in the vat in the state of three layers of filter cloth / wet paper / filter cloth (substitution treatment), and once with the above-mentioned sheet machine press. Press treatment was performed at a pressure of 0.5 MPa for 1 minute. Furthermore, again, 1 kg of isobutyl alcohol was newly immersed in a substitution bath mixed in the vat and allowed to stand for 15 minutes. Next, the three-layer body of filter cloth / wet paper / filter cloth taken out from the substitution bath was pressed with a sheet machine press at a pressure of 0.5 MPa for 1 minute, and then the surface temperature of the three-layer body was set to 105 ° C. It was affixed on the drum dryer and dried for about 120 seconds. The cellulose nonwoven fabric was peeled from the resulting three-layer filter cloth to obtain white uniform cellulose nonwoven fabrics H4 (Comparative Example 4) and H5 (Comparative Example 5).

The physical properties of H4 and H5 are shown in Table 3. Although it was possible to obtain a breathable uniform cellulose nonwoven fabric by the solvent replacement and drying methods disclosed in Patent Document 1 and the like, in terms of strength, it was clearer than any sample of Examples 1-7. It was inferior. Furthermore, in Comparative Example 5, hydroxypropylmethylcellulose as a water-soluble polysaccharide derivative used in the present invention was blended into a papermaking dispersion by the method of Patent Document 1 or the like. In the obtained cellulose nonwoven fabric (H5), It was not contained in an amount of 0.2% by weight, and H5 was not a cellulose nonwoven fabric of the present invention. As a result, H5 did not show a clear reinforcing effect with respect to H4, and it was also shown that the method disclosed in Patent Document 1 and the like is not sufficient as the method for producing the cellulose nonwoven fabric of the present invention.
In Comparative Example 5, a considerable amount of the water-soluble polysaccharide derivative is discharged as a filtrate in the papermaking process, and further diffuses into the solvent in the subsequent solvent replacement process and does not stay on the cellulose surface. Was considered.

(Reference Example 1)
Abaca A 'pulp (Toho Special Pulp Co., Ltd.) is used as the cellulose raw material, and the pulp is made into an aqueous dispersion (400 L) with a solid content of 1.5% by weight. The beating process was continued for 10 minutes against 400L of slurry with a 1 mm diameter, and then the beating process was continued under the condition that the clearance was reduced to almost zero, and sampling was performed over time. On the other hand, when the CSF value by the CSF method was evaluated, as in Example 1, the CSF value decreased with time, and once it became close to zero, it further increased when the beating process was continued. The tendency to go was confirmed. The beating treatment was continued under the above conditions for 20 minutes after the clearance was reduced to near zero, and 60 ↑ ml of beating slurry with a CSF value was obtained. The obtained beating slurry was subjected to refinement treatment 5 times under an operating pressure of 100 MPa using a high-pressure homogenizer as it was, and an aqueous dispersion of microfibrillated cellulose (solid content concentration: 1.5% by weight), M2 Obtained. The α-cellulose content of Abaca A ′ pulp as a raw material was measured and found to be 85.2% by weight (total cellulose content was 94.3% by weight).

In order to prepare an aqueous dispersion for papermaking having the composition shown in Table 1 using the aqueous dispersion M2, dilution and dispersion were carried out with a home mixer for 4 minutes to obtain an aqueous dispersion for papermaking.
Through the same steps of paper making, press treatment, solvent replacement, and drying as in Comparative Example 4, a white sheet-like sample R1 having high uniformity was obtained. The physical properties of R1 are shown in Table 3. From the analysis of the image including the surface SEM image of R1, the number average fiber diameter of the microfibrillated cellulose constituting R1 was 78 nm. R1 is not the cellulose nonwoven fabric of the present invention because it does not contain the specific water-soluble polymer contained in the cellulose nonwoven fabric of the present invention, but possessed high strength comparable to the sample group of the examples.

  However, it was confirmed that the following heat resistance was inferior to the sample group of the examples. That is, when the discoloration test was performed in Comparative Example 3 when held in an oven environment at 180 ° C. for 70 hours in the atmosphere, clear discoloration was confirmed, and in terms of heat resistance and durability, the test was performed. It was confirmed that it did not reach the sample of the example. This was considered that impurities (lignin and hemicelluloses) other than α-cellulose contained in the pulp used as a raw material in Reference Example 1 had an adverse effect on heat resistance.

  The cellulose nonwoven fabric of the present invention and the multilayered sheet comprising the nonwoven fabric as one layer are various functional filters, various functional papers, separators for various power storage devices, precision cleaning wipers, precision polishing pads, absorbent materials, and medical materials. In addition, it can be used as a substrate for a semiconductor device or a wiring board, a base material for a low linear expansion coefficient material, and the like by being combined with various resins such as an epoxy resin.

The SEM image of the surface of the nonwoven fabric sample (S1) produced with the microfibrillated cellulose obtained from the cotton linter pulp in Example 1 (magnification: 10000 times, one scale on the lower right scale corresponds to 0.5 μm).

Claims (7)

A cellulose nonwoven fabric composed of cellulose microfibrils, containing one or more water-soluble polymers selected from the group consisting of water-soluble polysaccharides and water-soluble polysaccharide derivatives in a total amount of 0.5 wt% or more and 20 wt% or less. A method for producing a cellulose nonwoven fabric , wherein the air permeation resistance corresponding to 3 g / m ² or more and 80 g / m ² or less and the basis weight of 10 g / m ² is 10 s / 100 ml or more and 500 s / 100 ml or less ,
(1) Cellulose microfibrils 0.05% by weight or more and 0.5% by weight or less, oily compounds having a boiling point range of 50 ° C. or more and 200 ° C. or less under atmospheric pressure 0.15% by weight or more and 10% by weight or less, water-soluble polysaccharide And a water system comprising a total of 0.003% by weight or more and 0.1% by weight or less of water-soluble polymer and one or more water-soluble polymers selected from the group consisting of water-soluble polysaccharide derivatives and 85% by weight or more and 99.5% by weight or less of water A preparation step of preparing an aqueous dispersion, which is an emulsion in which the oily compound is dispersed in an aqueous phase; (2) by dehydrating a part of water constituting the aqueous dispersion with a paper machine, A paper-making process for obtaining a concentrated composition in which the concentration of microfibrils and the concentration of oily compound are increased from the aqueous dispersion; (3) heating the concentrated composition to remove the oily compound from the concentrated composition. Drying step of removing by evaporation a portion of the beauty water,
The manufacturing method of the cellulose nonwoven fabric containing these 3 processes. A multilayered sheet in which a plurality of layers are laminated, and is a cellulose non-woven fabric composed of cellulose microfibrils, and a total of one or a plurality of water-soluble polymers selected from the group consisting of a water-soluble polysaccharide and a water-soluble polysaccharide derivative is 0. A cellulose nonwoven fabric containing 5% by weight or more and 20% by weight or less, having a basis weight of 3 g / m ² or more and 80 g / m ² or less, and an air resistance corresponding to a basis weight of 10 g / m ² is 10 s / 100 ml or more and 500 s / 100 ml or less. A method for producing a multilayered sheet comprising a layer, having a basis weight of 8 g / m ² or more and 100 g / m ² or less, and a gas permeability resistance of 10 s / 100 ml or more and 1000 s / 100 ml or less ,
(1) Cellulose microfibrils 0.05% by weight or more and 0.5% by weight or less, oily compounds having a boiling point range of 50 ° C. or more and 200 ° C. or less under atmospheric pressure 0.15% by weight or more and 10% by weight or less, water-soluble polysaccharide And a water system comprising a total of 0.003% by weight or more and 0.1% by weight or less of water-soluble polymer and one or more water-soluble polymers selected from the group consisting of water-soluble polysaccharide derivatives and 85% by weight or more and 99.5% by weight or less of water A preparation step for preparing an aqueous dispersion, which is an emulsion in which the oily compound is dispersed in an aqueous phase; (2) placing a water-permeable sheet-like support on a paper machine, A layer composed of a concentrated composition in which the concentration of cellulose microfibrils and the concentration of oily compounds are increased on the support by dehydrating a part of the constituent water on the support is laminated and integrated. Conversion By heating the paper making process (3) supported integrated with the concentrate composition body to a drying step to remove by evaporation a portion of the oily compound and water from the concentrate composition,
The manufacturing method of the multilayer sheet | seat containing these 3 processes. Cellulose microfibril is obtained by using at least one selected from the group consisting of softwood pulp, hardwood pulp, cotton-derived pulp, hemp-derived pulp, bagasse-derived pulp, kenaf-derived pulp, bamboo-derived pulp, and straw-derived pulp as a raw material. It is a fibrillated cellulose, The manufacturing method of the cellulose nonwoven fabric of Claim 1 or 2 . The method for producing a cellulose nonwoven fabric according to claim 3 , wherein the cellulose microfibril is a microfibrillated cellulose obtained from at least one selected from raw pulps having an α-cellulose content of 95% by weight or more. The method for producing a cellulose nonwoven fabric according to any one of claims 1 to 4 , wherein the oily compound has a carbon number of 5 to 9 and contains a monovalent and primary alcohol. The method for producing a cellulose nonwoven fabric according to claim 5 , wherein the oily compound contains at least one compound selected from the group consisting of 1-pentanol, 1-hexanol, and 1-heptanol. The cellulose nonwoven fabric according to any one of claims 1 to 6 , further comprising a smoothing step of subjecting the cellulose nonwoven fabric or multilayered sheet obtained after drying to a smoothing process by a calender device after the drying step. Manufacturing method.