JP2010115574A - Functional filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a functional filter which is composed of cellulose nonwoven fabric having a fine porous structure and an extremely large surface area as well as high strength, is excellent in heat resistance and dimensional stability, and is disposable by incineration. <P>SOLUTION: The functional filter is composed of cellulose nonwoven fabric composed of cellulose microfibril or composed of a multi-layered structure containing the nonwoven fabric as one layer. The filter is characterized in that a Metsuke (weight of fabric per unit area) amount is ≥3 g/m<SP>2</SP>and ≤150 g/m<SP>2</SP>and that air permeability resistance is ≥10 s/100 ml and ≤2,000 s/100 ml. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a functional filter. Specifically, clean room air filters used in the fields of semiconductor manufacturing industry, pharmaceutical manufacturing industry, food industry, hospitals, filters for office air conditioners or home air conditioners, engine oil, fuel, water treatment, electric discharge machines The present invention relates to a filter for liquid filtration, such as removal of microorganisms in chemical and food manufacturing processes.

Conventional filters that efficiently collect particles in the air and particles in liquids (1) Excellent air permeability or liquid permeability, low pressure loss, and (2) Good collection efficiency , (3) Excellent workability, (4) Less decrease in strength during use, fiber dropout, etc. (5) In view of waste problems, incineration or biodegradation is required. (See Patent Document 1).
As the filter base material, a highly beaten wood pulp or a fibrillated pulp fiber is used. For example, as a mask for preventing the entry of pollen and cold viruses, a sheet made of a thin polyolefin fiber is electretized to increase the collection efficiency. Although not a filter, the speaker cone is partly made of high-density sheet or bacterial cellulose synthesized by acetic acid bacteria. This bacterial cellulose is a material well known as a fiber having a very small fiber diameter.

  On the other hand, the inorganic fiber-containing filter has an advantage that high collection efficiency can be obtained with a low pressure loss due to the rigidity of the inorganic fiber and the small fiber diameter. However, there is a problem that the rigidity of the inorganic fibers decreases the workability. In addition, if fine inorganic fibers fall off when used as an air filter, there is a concern about the influence on the human body. When inorganic fibers fall off from a filter material such as an engine oil filter of a machine, there is a concern that the sliding part of the machine may be damaged. Furthermore, there is a waste problem that inorganic fibers cannot be incinerated. Therefore, in the inorganic fiber-containing filter medium, it is desired to reduce the content of the inorganic fiber due to processability, problems due to falling off during use, waste problems, and the like.

Also, resin filters are widely used for ease of processing and fine fiber production. For example, polyacrylonitrile resin, polymethyl methacrylate resin, polysulfone resin, polyvinylidene fluoride resin, polyethylene resin, polycarbonate resin Are used for ultrafiltration membranes, microfiltration membranes, and the like. However, these materials are not satisfactory in terms of solvent elution, heat resistance and chemical resistance contained (see Patent Document 2).
On the other hand, cellulose has excellent structural stability, heat resistance, and organic solvent resistance, and is suitable for a filter substrate having a high dimensional stability requirement. In addition, because it is a naturally derived material, there is little environmental impact when it is discarded. However, since it is a strong structure, it is difficult to produce a nonwoven sheet having highly refined cellulose by the conventional method, and a highly refined cellulose sheet for making a high-performance filter substrate has been desired. .
JP 2008-652 A JP-A-8-257380

  An object of the present invention is to provide a functional filter comprising a cellulose nonwoven fabric having a fine pore structure and an extremely large surface area and having high strength, heat resistance, excellent dimensional stability, and capable of being incinerated.

  As a result of intensive studies, the present inventors can solve the above-mentioned problem by controlling a cellulose nonwoven fabric composed of fine cellulose fibers so as to be within a specific air resistance resistance range under a suitable basis weight. It has been found that a functional filter can be provided. Further, an appropriate amount of one or more water-soluble compounds (hereinafter referred to as “specific water-soluble compounds”) selected from the group consisting of sugars, polyhydric alcohols, alcohol derivatives, and water-soluble polymers. It has been found that the strength can be further improved by adding it to the cellulose nonwoven fabric, and a more preferable functional filter has been completed.

That is, the present invention is a functional filter comprising the following cellulose nonwoven fabric or a multilayered sheet containing the nonwoven fabric.
[1] A cellulose nonwoven fabric composed of cellulose microfibrils or a functional filter composed of a multilayer structure including the nonwoven fabric as a layer, having a basis weight of 3 g / m ² or more and 150 g / m ² or less, and an air permeability resistance of 10 s A functional filter characterized by being / 100 ml or more and 2000 s / 100 ml or less.
[2] The functional filter according to [1], wherein the number average fiber diameter of the fibers constituting the cellulose nonwoven fabric is 300 nm or less.
[3] When the cellulose nonwoven fabric contains one or more water-soluble compounds selected from the group consisting of sugars, polyhydric alcohols, alcohol derivatives, and water-soluble polymers, the total weight of the cellulose nonwoven fabric is 100%. The functional filter according to any one of [1] and [2], wherein the functional filter is a nonwoven fabric containing 5% by weight or more and 20% by weight or less.

  According to the present invention, it is possible to provide a functional filter having a fine pore structure, an extremely large surface area, and having a high-strength cellulose nonwoven fabric, having heat resistance, excellent dimensional stability, and capable of being incinerated.

The present invention relates to a functional filter. There are two types of filter functions: (1) size separation function by micropores, and (2) adsorption function by extremely large specific surface area.
(1) As functional filters using the size separation function by micropores, in the gas system, filters for vacuum cleaners for home and business, filters for ventilation fans, deodorizing filters, filters for air conditioners, filters for various air purifiers, etc. Examples of water filters include coffee filters and tea bag filters, and oil systems include various types of functional filters such as household and commercial oil filter paper, automotive oil filters, automotive fuel filters, and other various filter papers. . Moreover, it can be used suitably also for the industrial liquid filter aiming at the removal of the microparticles | fine-particles contained in the liquid in a production process. In addition, for example, beverages (beer, sake, wine, soft drinks), foods (edible oil, vinegar, soy sauce, honey), cosmetics (liquid hair styling, eau de cologne, perfume), pharmaceuticals (injections, eye drops, other liquid pharmaceuticals) It can also be used as final filtration (clarification, sterilization) of various liquids such as water (raw water, feed water, washing water, pure water for semiconductors), chemicals (resins, paints, varnishes).

(2) Functional filters that use an adsorption function with a very large specific surface area include pollen adsorption filters based on charge modification, capture filters for microorganisms such as airborne viruses, and blood substance specific substance capture filters and viruses based on antibody immobilization modifications. It can also be used as a filter for removing microorganisms such as cells, a culture filter for cells and microorganisms by immobilization modification of cell adhesion substances such as collagen, and a filter for coated wounds subjected to antibacterial treatment.

The functional filter of the present invention will be described more specifically.
The present invention relates to a cellulose nonwoven fabric having a fine network structure composed of cellulose microfibrils, or a functional filter composed of a multilayer structure including the cellulose nonwoven fabric as a layer. More specifically, the sheet-like structure composed of the cellulose nonwoven fabric, or the sheet-like structure itself composed of a multilayer structure including the cellulose nonwoven fabric as a layer, or the functionality based on these sheet-like structures. Regarding filters.

  In the present invention, the present inventors first focused on the amphiphilic surface characteristics of cellulose having an affinity for water and oil. In addition, the fact that it is effective for non-woven fabrics composed of fine fibers as a functional filter is already known for functional filters such as HEPA filters. Thus, an attempt was made to greatly improve the performance of the functional filter made of conventional fine fibers. If the conditions are selected, cellulose can be made into microfibers having a fiber diameter of several nanometers to 200 nm, called microfibrils, or microfibers having a fiber diameter of several tens to several hundreds of nanometers when the microfibrils are converged. Since it is known (in the present invention, these are collectively referred to as “cellulose microfibrils”), the cellulose non-woven fabric in which cellulose microfibrils are formed into a sheet helps the surface characteristics of cellulose, and exhibits remarkable performance as a functional filter. Therefore, the present invention has been completed.

  In the present invention, according to the 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” The sheet-like structure made of cellulose used in the 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 that make up the nonwoven fabric are cellulose fibers that are about two orders of magnitude thinner than cellulose fibers as the raw material of conventional paper. This is not a so-called paper use but a more suitable function in an application field where a non-woven fabric is used.

Here, in order for the cellulose nonwoven fabric composed of cellulose microfibrils to function suitably as the functional filter of the present invention, it is necessary to prevent the cellulose microfibrils from fusing together to reduce the surface area. In other words, it is important that the cellulose nonwoven fabric has a fine network structure and a certain air permeability. That is, the functional filter of the present invention is a functional filter composed of a cellulose nonwoven fabric composed of cellulose microfibrils or a multilayered structure including the nonwoven fabric as a layer, and has a basis weight of 3 g / m ² or more and 150 g / m ² or less. The air resistance is preferably 10 s / 100 ml or more and 2000 s / 100 ml or less.

The basis weight is more preferably 5 g / m ² or more and 100 g / m ² or less, and still more preferably 8 g / m ² or more and 80 g / m ² or less. A sheet having a basis weight of less than 3 g / m ² is not preferable because the sheet is too thin and the operability is significantly deteriorated. On the other hand, if the basis weight is greater than 150 g / m ² , the sheet lacks flexibility and the processing operability is deteriorated. It is not preferable. In the present invention, the basis weight (basis weight) is measured in accordance with JIS P 8124.

  In addition, the functional filter of the present invention needs to be in an appropriate range of air resistance for the reasons described above. When the air resistance is in the range of 10 s / 100 ml to 2000 s / 100 ml, preferably 20 s / 100 ml to 1000 s / 100 ml, various functions as the functional filter claimed by the present invention are suitably expressed. It becomes possible. Here, in the functional filter of the present invention, it is difficult to make a filter whose air resistance is smaller than 10 s / 100 ml due to the fineness of the network, and it is easy to make a filter whose air resistance exceeds 2000 s / 100 ml. However, since the porosity is low, the air resistance is increased, and the material has a poor original function as a functional filter, it is not preferable.

Here, the air resistance is a result of measuring the permeation time (unit: s / 100 ml) of 100 ml of air at room temperature using a Gurley type densometer (manufactured by Toyo Seiki Co., Ltd., model G-B2C). Means. For the measurement, five points are measured at various different positions for one sheet sample, and the average value is obtained.
When the number average fiber diameter of the fibers constituting the cellulose nonwoven fabric used in the present invention is in the range of 2 nm to 300 nm, preferably 10 nm to 150 nm, a nonwoven fabric or nonwoven fabric layer having a fine and uniform network structure is produced. It is effective because it can. 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. Further, when the number average fiber diameter is larger than 300 nm, it is difficult to become a non-woven fabric having a fine and uniform pore diameter based on a fine network structure, and therefore, the effect expected from the functional filter of the present invention is less likely to appear. Absent.

  Here, the number average fiber diameter of the cellulose microfibril is defined as follows. That is, regarding the surface of the functional filter of the present invention, at least two spots are randomly observed with a scanning electron microscope (SEM) at a magnification in which the fiber diameter can be clearly recognized within a range equivalent to 10,000 times or more and 30,000 times or less. . With respect to the obtained SEM image, a line is drawn in the horizontal direction and the vertical direction with respect to the screen, and the fiber diameter of the fiber intersecting the line is measured from the enlarged image, and the number of intersecting fibers and the fiber diameter of each fiber are counted. 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.

  In the cellulose nonwoven fabric or cellulose nonwoven fabric layer in the functional filter of the present invention, a total of 0.5 weight of one or more water-soluble compounds selected from the group consisting of sugars, polyhydric alcohols, alcohol derivatives, and water-soluble polymers. % To 20% by weight, preferably 0.8% to 15% by weight, more preferably 1.0% to 10% by weight, when the water-soluble compound is contained between fine cellulose microfibrils. Since it functions as a binder which reinforces the contact point strength, it is more preferable.

  Here, as sugar, glucose, mannose, galactose, fructose, xylose, trehalose, cellobiose and maltose, as polyhydric alcohol, ethylene glycol, propylene glycol, diethylene glycol and glycerin, as alcohol derivative, ethylene glycol monomethyl ether , Ethylene glycol monoethyl ether, ethylene glycol mono n-butyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, and diethylene glycol dimethyl ether, water-soluble polymers include polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene glycol, polypropylene glycol, polyacrylic acid, Polymethacrylic acid, water-soluble polysaccharides, and Soluble polysaccharide derivatives, and the like, but not limited thereto.

  Here, the water-soluble polysaccharide means a water-soluble polysaccharide, and various compounds exist as natural products. For example, α-1,4-glucan represented by starch, solubilized starch, amylose and pullulan, α-1,6-glucan represented by dextran, curdlan and β-1,3-glucan represented by lentinan Examples include glucan, amylopectin, branched sugars typified by glycogen, xylan, galactan, mannan, glucomannan, glucomannoglycan, galactoglucomannoglycan, and heteroglycans typified by guaran. It is not something.

  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.

Of the water-soluble compounds described above, water-soluble polysaccharides and water-soluble polysaccharide derivatives, which are water-soluble polymers, are often highly heat-resistant and have a large effect of improving the strength of cellulose nonwoven fabrics. If a polysaccharide and a water-soluble polysaccharide derivative are used, the cellulose nonwoven fabric obtained is particularly preferable because it has a high strength that does not impair the heat resistance inherent in cellulose.
Furthermore, the functional filter of the present invention is a sheet comprising a multilayer structure containing the cellulose nonwoven fabric described above as a layer (hereinafter also referred to as “multilayered sheet”), or a functional filter based on the multilayered sheet. It is.

The multilayered sheet is formed by laminating the above-described cellulose nonwoven fabric composed of cellulose microfibrils on a support such as another kind of nonwoven fabric or paper having air permeability (a nonwoven fabric or paper composed of fibers having a fiber diameter generally used). Even in a two-layer structure, whether it has a three-layer structure in which another type of non-woven fabric that is air permeable is sandwiched between the front and back sides of the cellulose nonwoven fabric, or has a different kind of layer, the basis weight described above as a multilayer sheet If the range of air permeability resistance is maintained, the function which the cellulose nonwoven fabric of this invention asserts can be expressed suitably. However, in consideration of the effect of the present invention that the filtration efficiency is remarkably improved by the nonwoven fabric layer having a fine network structure composed of cellulose microfibrils existing on the outermost surface, the cellulose nonwoven fabric layer is either one of the outermost surfaces. Or it is preferable to be located in both.
Moreover, the functional filter of the present invention may be a functional filter based on either the above-described cellulose nonwoven fabric or a multilayered sheet including the cellulose nonwoven fabric as a layer.

  The functional filter of the present invention described above is a vacuum cleaner filter for household or commercial use, a fan filter, a deodorizing filter, an air conditioner filter, a filter for various air purifiers, etc. in a gas system, or a coffee filter or tea bag in an aqueous system. Oil filters for household and commercial use, oil filters for automobiles, oil filters for automobiles, fuel filters for automobiles, other various types of filter paper, various functional papers, and liquids in the production process It can also be suitably used for industrial liquid filters intended to remove contained fine particles. Furthermore, for example, beverages (beer, sake, wine, soft drinks), foods (edible oil, vinegar, soy sauce, honey), cosmetics (liquid hairdressing, eau de cologne, perfume), pharmaceuticals (injection, eye drops, other liquid pharmaceuticals) Highly efficient filtration is possible even in the final filtration (clarification, sterilization) of various liquids such as water (raw water, feed water, washing water, pure water for semiconductors), chemicals (resin, paint, varnish), etc. In addition, the heat resistance and solvent resistance of cellulose can be used in a wide range of environments. The fine network structure of cellulose microfibrils present on at least the outermost surface of the functional filter of the present invention has a fine structure that captures both surface characteristics having affinity for both water and oily compounds and minute separation objects. It is thought that high filtration performance is expressed by having it together. Furthermore, the functional filter of the present invention can be provided as a material capable of being incinerated with less environmental load because the cellulose nonwoven fabric or the cellulose nonwoven fabric layer is the main component of the substrate.

Next, the example of the manufacturing method of the functional filter of this invention is demonstrated. Since the cellulose nonwoven fabric composed of cellulose microfibrils, or the sheet-like structure of a multilayered sheet containing the nonwoven fabric as a layer is the main component of the functional filter, the cellulose nonwoven fabric composed of cellulose microfibrils or the nonwoven fabric will be described below. The example of the preferable manufacturing method of the multilayered sheet | seat included as one layer is described.
The cellulose nonwoven fabric used in the present invention is obtained by first preparing an aqueous dispersion of cellulose microfibrils and forming a film by the method described below using the dispersion.

  Cellulose microfibril means a cellulose fiber having a fiber diameter of 2 nm to 200 nm or a bundle thereof called microfibril. 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, FW) obtained by refining with a highly shearing device such as a high-pressure homogenizer or grinder Snyder and KRSandberg, “Microfibrilated 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)).

  As raw materials 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.

Next, a method for fibrillation of cellulose fibers will be described.
In refining from raw pulp to microfibrillated cellulose, it is easy to make raw pulp fine by autoclave treatment, beating treatment, enzyme treatment, etc. under water impregnation at a temperature of 100 to 150 ° C. It is effective to pre-process. These pretreatments not only reduce the load of the micronization process, but also discharge impurity components such as lignin and hemicellulose present on the surface and gaps of the microfibrils that make up the cellulose fibers to the aqueous phase, resulting in a finer process. Since there is also an effect of increasing the α-cellulose purity of the formed fiber, it may be very effective in improving the heat resistance of the cellulose nonwoven fabric.

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 the high-pressure homogenizer used include NS type high-pressure homogenizer manufactured by Niro Soabi (Italy), SMT Co., Ltd., Ranier type (R model) pressure-type homogenizer, and Sanwa Kikai Co., Ltd. high-pressure type homogenizer. 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 miniaturization machines such as Mizuho Kogyo Co., Ltd. microfluidizer, Yoshida Kikai Kogyo Co., Ltd. Nanomizer, and Sugino Machine Ultimate 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).

Next, the manufacturing method of the cellulose nonwoven fabric used by this invention is described. Film forming methods can be roughly classified into coating methods and paper making methods.
Among these, in the coating method, 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. Therefore, an organic solvent having a lower surface tension than water (for example, for example, It is necessary to use an organic solvent-based dispersion liquid in which microfibrils are dispersed in a mixed solution of water (alcohol such as isopropanol or ethyl cellosolve) and water. Therefore, the predetermined specific water-soluble polymer is dissolved 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 unexpectedly difficult to uniformly form the high-viscosity dispersion, and this is disadvantageous in terms of cost because a large amount of an 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 described below.

There are two more methods for producing a cellulose nonwoven fabric having air permeability made of cellulose microfibrils by a papermaking method.
In the first method, cellulose microfibrils are dispersed in water while controlling them in an appropriate dispersion state, paper is made on a fine filter cloth, and water in the obtained wet paper is replaced with an organic solvent. It is a method of replacing with an organic solvent and drying. About the detail of this method, the literature (patent document 3; international publication 2006/004012 pamphlet) by the present inventors follows.

  When the specific water-soluble compound described above by this method is contained in the cellulose nonwoven fabric, it is preferably dissolved in the papermaking dispersion or the organic solvent substitution bath and contained in the cellulose nonwoven fabric. Among these, in the method of dissolving in the papermaking dispersion in advance, the fixing rate of the specific water-soluble compound on the cellulose microfibril surface in the dispersion may not be so high. In the organic solvent replacement step, which is a step, there is a possibility that the specific water-soluble compound once fixed may be removed, so that it is not preferable as a method for efficiently producing a cellulose nonwoven fabric used in the present invention. On the other hand, in the replacement step, the specific water-soluble compound is dissolved in the replacement bath, and simultaneously with the solvent replacement, the specific water-soluble compound is introduced as a binder for reinforcing the network of microfibrils, The specific water-soluble compound 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 compound is completely dissolved, there are restrictions on setting conditions, and a certain amount of the specific water-soluble compound in the substitution solvent. It is necessary to dissolve the active compound, and there is a disadvantage that it cannot be said to be an efficient introduction method.

On the other hand, it is preferable to manufacture the cellulose nonwoven fabric used by this invention with the 2nd method in a papermaking method, ie, the manufacturing method described below.
That is, (1) Cellulose microfibrils of 0.05% by weight or more and 0.5% by weight or less, an oily compound having a boiling point range of 50 ° C. or more and 200 ° C. or less at atmospheric pressure of 0.5% by weight to 10% by weight, sugar , One or more water-soluble compounds selected from the group consisting of polyhydric alcohols, alcohol derivatives, and water-soluble polymers, and a total of 0.003% to 0.3% by weight and water 85% to 99.5% A preparation step of preparing an aqueous dispersion containing less than wt%, wherein the oily compound is an emulsion in which the aqueous compound is dispersed in an aqueous phase, (2) a part of the water constituting the aqueous dispersion is obtained by a paper machine A papermaking step of obtaining a concentrated composition in which the concentration of cellulose microfibrils and the concentration of oily compounds are increased from the aqueous dispersion by dehydration, (3) by heating the concentrated composition, Drying step of removing oily compound and evaporating a portion of the water from the concentrate composition is a 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 is expressed as an “emulsion papermaking method” for simplicity.
First, the details of the three steps described above will be described. The emulsion papermaking method 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 used in the preparation step is cellulose microfibril 0.05 wt% or more and 0.5 wt% or less, and an oily compound having a boiling point range of 50 ° C or more and 200 ° C or less at atmospheric pressure of 0.5 wt% or more and 10 wt% or less. A total of 0.003% by weight or more and 0.3% by weight or less of one or more water-soluble polymers selected from the group consisting of sugars, polyhydric alcohols, alcohol derivatives and water-soluble polymers, and water 85 It is necessary to be an aqueous dispersion containing from 9% to 99.5% by weight.

  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. 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).

  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 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 specific water-soluble compound contained in the cellulose nonwoven fabric used in the present invention may be dissolved in these oily compounds. However, the mixing amount of the specific water-soluble compound at this time 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 preparation process. 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, the above-mentioned specific water-soluble compound may be dissolved in the aqueous phase in the aqueous dispersion for emulsion papermaking. 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 3; 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. The specific water-soluble compounds localized on the surface of the oil droplets are incorporated in the oil droplets into the mechanism of the emulsion paper making process described above, that is, the loose association pairs formed by cellulose microfibrils, and remain in the wet paper during the paper making process. Therefore, it remains in the wet paper with a high residual rate.

In the emulsion papermaking method, by using a specific water-soluble compound, the specific water-soluble compound 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 for producing the cellulose nonwoven fabric used in the present invention.
As described above, in the aqueous dispersion for emulsion papermaking, it is necessary that the specific water-soluble compound described above is dissolved in the aqueous phase. The concentration of the specific water-soluble polymer is as follows: 0.003 wt% or more and 0.3 wt% or less, more preferably 0.005 wt% or more and 0.08 wt% or less, and still more preferably 0.006 wt% or more and 0.07 wt% or less. In addition, the cellulose nonwoven fabric used in the present invention is easily obtained, and at the same time, the state of the aqueous dispersion is often stabilized, which is preferable. If the concentration is less than 0.003% by weight, the effect of adding the specific water-soluble compound is hardly exhibited, and it is not preferable. If the concentration exceeds 0.3% by weight, the amount of addition such as foaming increases. Since a negative effect tends to appear, it is not preferable. For the purpose of stabilizing the emulsion, a surfactant may be contained in the aqueous dispersion in addition to the specific water-soluble compound, and the total amount of the surfactant and the specific water-soluble polymer may be included in the 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, various additives may be added to the aqueous dispersion according to the purpose. For example, high porosity structure of the present invention such as silica particles, alumina particles, titanium oxide particles, inorganic particulate compounds such as calcium carbonate particles, resin fine particles, various salts, organic solvents that do not inhibit the stability of the emulsion, etc. It can be added within a range that does not adversely affect the production of the body (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 emulsion paper making method is a paper making step of filtering the 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.
A method for papermaking an aqueous dispersion prepared using microfibrillated cellulose or the like is basically a technique described in a document by the present inventors (Patent Document 3; International Publication No. 2006/004012 pamphlet). According to The difference between Patent Document 3 and the emulsion papermaking method is that an emulsion composed of an oily compound and water is contained in an aqueous dispersion for papermaking, but it is better depending on the papermaking conditions disclosed in Patent Document 3. Paper making can be performed. The reason is considered to be that the emulsion component is incorporated in the aggregate (soft agglomerate) composed of microfibrillated cellulose in the aqueous dispersion prepared in the preparation 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 also be used for extremely fine microfibrillated cellulose fibers include TETEXMONODW07-8435-SK010 (PET) manufactured by SEFAR (Switzerland), and NT20 (PET / nylon blend) manufactured by Shikishima Canvas. However, 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 emulsion papermaking method, the emulsion is concentrated by the papermaking process, and the concentration of the oily compound in the wet paper after the dehydration process is preferably about 5 times or more compared to the oily compound concentration in the aqueous dispersion before the dehydration. In such a case, 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 after drying is further subjected to a smoothing process by a calender device, thereby making it possible to reduce the thickness of the cellulose non-woven fabric of the present invention with a wide range of combinations of film thickness / air permeability / strength. It becomes possible to provide. 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. A cellulose nonwoven fabric having various physical property balances can be obtained by selecting materials (material hardness) and linear pressures on both sides of the rolls 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 cellulose nonwoven fabric manufacturing process, the surface of the resulting nonwoven fabric is significantly longer than the fiber length of cellulose microfibrils used as a papermaking raw material, because the pitch of the surface irregularities of the wire mesh and filter fabric used during the manufacturing process is significantly longer. Unevenness of wire mesh and filter cloth is easily 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 used by this invention. When extremely precise filtration is required, it is more effective that the surface of the functional filter is in close contact with the fine mesh structure. In such cases, smoothing by calendaring is effective. There is. What is necessary is just to select the process regarding surface unevenness | corrugation control according to the objective of a functional filter.

In particular, in order to continuously form a cellulose nonwoven fabric used in the present invention, it is necessary to continuously perform the paper making process, the drying process, and, in some cases, the smoothing process by calendaring, 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 paper making process by the paper machine, a sheet-like support having water permeability is placed on the paper machine, and a part of water constituting the aqueous dispersion is dehydrated (paper making) on the support, and the support By laminating and integrating wet paper of cellulose nonwoven fabric made of cellulose microfibrils on the body, a multilayered sheet made of a multilayer structure of at least two layers can be produced.

  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.

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 described above can be provided as having a tensile strength equivalent to a basis weight of 10 g / m ² when it is suitable and having a strength of 6 N / 15 mm or more, and more preferably 8 N / 15 mm or more. it can.

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 and 2 and Comparative Example 1
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, and the amount of slurry added to the paper machine was adjusted so as to have the basis weight of Examples 1 and 2 shown in Table 1, and emulsified and dispersed for 4 minutes with a home mixer. To obtain an aqueous dispersion for papermaking. In Examples 1 and 2, a 5 wt% aqueous solution of hydroxypropylmethylcellulose (Hypromellose 60SH-4000 manufactured by Shin-Etsu Chemical Co., Ltd.) was prepared in advance as a specific water-soluble compound so that the final concentration was 0.012 wt%. Blended into

A plain fabric made of PET / nylon blend (NT20, manufactured by Shikishima Kanbus Co., Ltd.) having the ability to filter out 99% or more of microfibrillated cellulose by filtration at 25 ° C under atmospheric pressure with respect to the aqueous dispersion. Batch-type paper machine (Ryu 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. The filter cloth is peeled from the cellulose sheet-like structure from the dried two-layered body, and the cellulose nonwoven fabric S1 (weight: 11.3 g / m ² ) and S2 (weight: 23.1 g / m) made of white uniform cellulose. ² ) (corresponding to Example 1 and Example 2 respectively). In all cases, the yield of cellulose microfibrils was almost 100%.

  All the samples were white and air-permeable sheets having a porosity of around 80%. When SEM image analysis was performed on the surface of S1 at a magnification of 10,000 times, the number average fiber diameter of the microfibrillated cellulose on the surface of S1 was 108 nm. Further, the image analysis of S2 was performed, and the same result was obtained.

From the above, S1 and S2 were both cellulose nonwoven fabrics that can be used in the filter 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 Examples 1 and 2 is about 0.2 μm, which is an extremely small oil It was presumed that a fine network structure was formed by taking the droplets into a wet paper made of cellulose microfibrils and drying it. The residual water-soluble polysaccharide in the filtrate after papermaking was measured by gas chromatography (manufactured by Shimadzu Corporation, GC-2014). As a result, the cellulose nonwoven fabric contained 4.2% by weight of hydroxypropylmethylcellulose.

  Using the aqueous dispersion M0 obtained only in the beating treatment obtained in Example 1, a papermaking dispersion 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 (number average fiber diameter is 859 nm), the film has poor uniformity, low strength, high It has been found that a cellulose nonwoven fabric that can be used in the filter of the present invention cannot be produced even using fibrillated cellulose beaten in the above. When the residual water-soluble polysaccharide in the filtrate after papermaking was measured in the same manner as in the Examples, the cellulose nonwoven fabric contained only 0.3% by weight of hydroxypropylmethylcellulose. The reason why the content of the specific water-soluble compound in the non-woven fabric was small is presumed to be because 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.

The film thickness (d (μm)) measurement was 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.
The air resistance was measured by measuring the permeation time (unit: s / 100 ml) of 100 ml of air at room temperature using a Gurley type densometer (Model G-B2C, manufactured by Toyo Seiki Co., Ltd.). If the result is zs / 100 ml, the following formula 10 × z / w (s / 100 ml) (1)
Is defined by Here, z is an average value obtained by measuring five points at various different positions for one nonwoven fabric sample.

The collection efficiency (%), which is the dust collection performance, is obtained by ventilating (filtering) air containing dioctyl phthalate particles with an average particle size of 0.3 μm at a flow rate of 5.3 cm / sec and sampling the air before and after the filter material. Then, the number of each particle was measured with a particle counter (manufactured by Lion Co., Ltd., type KM-27) and calculated from the following equation.
Collection efficiency = {(number of particles before filtration−number of particles after filtration) / number of particles before filtration} × 100 (2)

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. Considering the difference in the basis weight, the evaluation was made with a value corresponding to a 10 g basis weight.
By using the above-mentioned cellulose non-woven fabric or a multilayered sheet comprising the non-woven fabric as a base material, various functional filters, in detail, (1) Size separation function by micropores as described above, and (2) Very large specific surface area. Shows effective properties for applications with adsorption function.
The results for the sheets obtained in Examples 1 and 2 and Comparative Example 1 are shown in Table 1.

  Examples 1 and 2 are non-woven fabrics of the present invention having microfibrillated cellulose, and the collection efficiency showed a high filtration capacity of 98% or more. In Comparative Example 1, the fiber was not microfibrillated and the filterability was poor because a fine structure could not be obtained.

  The functional filter having the cellulose nonwoven fabric of the present invention and the multilayered sheet comprising the nonwoven fabric as a single layer is a vacuum cleaner filter for household use and business use, a filter for a ventilation fan, a deodorizing filter, a filter for an air conditioner, etc. Various functions, such as filters for air purifiers, coffee filters for water systems, filters for tea bags, etc. for oil systems, oil filter paper for household and business use, oil filters for automobiles, fuel filters for automobiles, and other various filter papers It can be used for filters and various functional papers, and can also be suitably used for industrial liquid filters for the purpose of removing fine particles contained in the liquid in the production process.

  In addition, for example, beverages (beer, sake, wine, soft drinks), foods (edible oil, vinegar, soy sauce, honey), cosmetics (liquid hair styling, eau de cologne, perfume), pharmaceuticals (injections, eye drops, other liquid pharmaceuticals) It can also be used as final filtration (clarification, sterilization) of various liquids such as water (raw water, feed water, washing water, pure water for semiconductors), chemicals (resins, paints, varnishes). In addition, pollen adsorption filters by charge modification, supplementation filters for microorganisms such as airborne viruses, specific substance supplement filters for blood components by modification of antibody immobilization, removal filters for microorganisms such as viruses, cells by immobilization modification of cell adhesion substances such as collagen, It can also be used for microorganism culture filters, antibacterial coated wound filters, and the like.

Claims (3)

A functional filter comprising a cellulose nonwoven fabric composed of cellulose microfibrils or a multilayer structure comprising the nonwoven fabric as a layer, wherein the basis weight is 3 g / m ² or more and 150 g / m ² or less, and the air resistance is 10 s / 100 ml or more A functional filter characterized by being 2000 s / 100 ml or less.   The functional filter according to claim 1, wherein the number-average fiber diameter of fibers constituting the cellulose nonwoven fabric is 300 nm or less.   When the cellulose nonwoven fabric is composed of one or more water-soluble compounds selected from the group consisting of sugars, polyhydric alcohols, alcohol derivatives, and water-soluble polymers, the total weight of the cellulose nonwoven fabric is 0.5% by weight. The functional filter according to claim 1, wherein the functional filter is a non-woven fabric containing 20% by weight or less.