JP5419120B2 - Method for imparting water repellency and oil resistance using cellulose nanofibers - Google Patents

Description

   The present invention relates to a method for imparting water repellency and oil resistance using cellulose nanofibers. More specifically, the present invention relates to the use of a bacterial cellulose facing collision-treated product for coating a surface of paper or the like. The present invention is particularly useful for protecting the surface of a food preservation paper molding.

  One type of acetic acid bacteria produces a gel-like cellulose membrane outside the cells when cultured. The cellulose produced by this fungus is called bacterial cellulose. Bacterial cellulose is secreted as highly crystalline ribbon-like cellulose nanofibers with an average width of about 50 nm and a thickness of about 10 nm, but a gel called a nano-sized mesh pellicle forms a random network immediately after secretion. A film is formed.

  As a method of using bacterial cellulose, it is considered to use a gel film as it is. Utilizing the fine mesh structure and good water retention, its use in separation membranes, medical and cosmetic pads, etc. is being studied. There is also an attempt to improve the strength and the like of the material by pulverizing the gel film into a mechanical treatment and kneading it into the material.

  Furthermore, the following has been proposed as a technique for using bacterial cellulose for coating the material surface. For example, Patent Document 1 discloses a coating liquid characterized by containing bacterial cellulose and a surfactant, and a recording medium using the same. Patent Document 2 discloses a coating liquid containing a chitosan salt and a divalent or higher anionic substance in a cellulose aqueous dispersion, and a recording medium using the same. Patent Document 3 discloses an organic fiber pulp obtained by fibrillating organic fibers, characterized in that bacterial cellulose is fixed to at least a part of the surface thereof. Patent Document 4 describes a cellulose solubilized product obtained from bacterial cellulose produced by stirring culture, a coating composition or composite containing the cellulose solubilized product, and a molding composition containing the cellulose solubilized product. An article or composite is disclosed.

  The present inventors have so far cultivated cellulose-producing bacteria on a cellulose template that is molecularly oriented in a uniaxial direction so that bacterial cellulose nanofibers secreted from the bacteria coincide with the orientation direction. As a result, the inventors succeeded in constructing a three-dimensional sheet structure in which nanofibers are oriented in one direction instead of a pellicle (Non-patent Document 1 and Patent Document 5).

On the other hand, the present inventors succeeded in water solubilization by opposing collision of microcrystalline cellulose fibers (degree of polymerization of about 200) derived from tree cell walls (Patent Document 6).
JP 2004-249573 A JP 2005-162897 A JP-A-2005-194648 Japanese Patent Laid-Open No. 10-77302 JP2002-142796 JP2005-270891 Kondo, T., Nojiri, M., Hishikawa, Y., Togawa, E., Romanovicz, D. and Brown, Jr., RM, Bio-directed epitaxial nanodeposition of polymers on oriented macromolecular templates, Proc. Natl. Acad. Sci. USA, 99 (22), 14008-14013 (2002)

  When using bacterial cellulose, this pellicle (membrane) is usually used instead of the nanofiber itself. However, the present inventors considered that it is necessary to take out bacterial cellulose as nanofibers in order to expand the application of bacterial cellulose. Further, according to the study by the present inventors, it has been clarified that the crystal surface of the bacterial cellulose nanofiber has a triclinic crystal structure called cellulose I alpha (alpha) different from plant-derived cotton. (unpublished). Therefore, if it can take out as a nanofiber as above-mentioned, it can anticipate as a fiber which expresses a new property.

On the other hand, biomass resources such as cellulose and chitin are polysaccharides composed of a glucopyranose skeleton. In this sugar skeleton molecular structure, there are hydrophilic sites derived from hydroxyl groups in a direction parallel to the skeleton, and hydrophobic sites derived from CH groups in a direction perpendicular to the skeleton (FIG. 1). Similarly, the cellulose natural fiber surface on which such molecules are assembled is divided into hydrophilic and hydrophobic sites having different properties. For example, although hydrophilic surface is affinity with water if Arawarere a solid surface, if hydrophobic surface is arranged on the surface, the surface will have a water-repellent Teflon ^TM comparable (Figure 2).

  The nano-sized natural fiber has a large specific surface area, and it is estimated that strong interaction is possible at the interface with the partner substance. In particular, if the material surface is coated with natural cellulose nanofibers that have an amphipathic property (hydrophilic and hydrophobic) and are likely to interact with each other, the fiber-side surface showing similar properties is adsorbed on the material surface, and the resulting surface is The effect of fibers exhibiting the opposite properties appears. That is, it is expected that the hydrophilic surface is made more hydrophobic, the hydrophobic surface is made more hydrophilic, and the property can be changed.

  The inventors of the present invention considered that surface modification based on the above-described concept would be possible if nanofibers were used, and the present invention was completed.

  In other words, the present invention provides a method for modifying a substrate surface, which includes a step of coating bacterial cellulose with cellulose nanofibers obtained by opposing collision treatment. In addition, the present invention provides a method for producing cellulose nanofibers, comprising a step of subjecting bacterial cellulose to an opposite collision treatment, and a treatment liquid containing cellulose nanofibers obtained by subjecting bacterial cellulose to an opposite collision treatment, and the substrate is applied to the treatment liquid. And / or a cellulose nanofiber coating formed by applying the treatment liquid to a substrate surface and drying.

  Cellulose nanofibers used for coating the base material are not pellicles but are single nanofibers, and have an average width of 25 nm or less (preferably 20 nm or less, more preferably 15 nm or less, more preferably 8 to 12 nm), The average thickness is 8-12 nm.

  In the present specification, the term “cellulose” is not limited in terms of origin, production method, properties and the like, and includes vegetable cellulose, bacterial cellulose, cellulose fiber, crystalline cellulose and the like.

As used herein, “bacterial cellulose” refers to cellulose produced by microorganisms (polysaccharides with β-1,4-glucoside bonds as the main binding form), and in the form of a gel-like film unless otherwise indicated. Point to. Bacterial cellulose can be produced by methods well known to those skilled in the art. The cellulose-producing bacteria, (also called Acetobactor xylinum or Gluconacetobactor xylinus) Acetobacter xylinum, Acetobacter pasteurianum (Acetobactor pasteurianum), acetic acid bacteria such as Acetobacter Ransensu (Acetobactor rancens), Sarcina Bentokyuri (Sarcina ventriculi), bacterium Kishiroidesu (Bacteirum Xyloides), Pseudomonas (Pseudomonas) genus, it is possible to use Agrobacterium (Agrobacterium) spp like. Those skilled in the art can appropriately determine the culture solution and culture conditions to be used.

  In the present specification, “cellulose nanofiber” refers to a cellulose fiber having an average width and an average thickness of 100 nm or less. The average width and average thickness of the cellulose fiber can be measured by methods well known to those skilled in the art, such as a light scattering device, a laser microscope, and an electron microscope. The average width is obtained by measuring several points, for example, 10 to 200 points, preferably 30 to 80 points, of the measured length, and taking the average value. The average thickness is obtained by measuring several points, for example, 10 to 200 points, preferably 30 to 80 points, of the measured length, and taking the average value. Preferred examples of the cellulose nanofibers used in the present invention have an average width and an average thickness equal to or less than that of bacterial cellulose (for example, an average width of 25 nm or less, preferably 20 nm or less, more preferably 15 nm or less, more preferably 8 ~ 12nm) with an average thickness of 8-12nm.

In the present specification, when “opposite collision (treatment)” is used, a dispersion of polysaccharide is sprayed from a pair of nozzles at a high pressure of 70 to 250 MPa, and the jet flow is collided with each other to pulverize cellulose fibers. The wet pulverization method. Details of this method are disclosed in JP-A-2005-270891 (Patent Document 6 ).

  Opposing collision treatment is a wet atomization method in which the material is ultrafine-grained using the collision energy of ultra-high pressure water. Compared to other pulverization methods, bead mill, jet mill, stirrer, high-pressure homogenizer, etc., it has various excellent advantages. For example, since no grinding media is used, there is no mixing of wear powder of the medium, and a uniform and sharp particle size distribution is obtained from the medium agitation type.Furthermore, continuous processing, large capacity is easy, contact time with the atmosphere is small, The point which can suppress the oxidation of a processed product as much as possible can be mentioned.

  As a device for the counter collision treatment, a high-pressure washing device or a high-pressure homogenizer device for pulverization / dispersion / emulsification can be used.

  Cellulose is dispersed in water during the counter collision process. Cellulose may be pulverized in advance if necessary. The dispersion concentration is preferably a concentration suitable for passing through the piping as a dispersion slurry, and preferably 0.1 to 10% by mass.

  In the counter-collision process, the dispersion liquid is ejected from the pair of nozzles at a high pressure of 70 to 250 MPa, and the jet streams collide with each other to be pulverized. By adjusting the number of times of pulverization by adjusting the number of jets of high-pressure fluid or adjusting the number of times of pulverization. While the average particle length of the fibers can be pulverized to 1/4 or less or 10 μm, a decrease in the degree of polymerization of cellulose can also be suppressed.

  The collision angle θ can be 95 to 178 °, for example, 100 to 170 °. If it is smaller than 95 °, for example, if it is made to collide at 90 °, structurally the collision dispersion liquid tends to directly collide with the wall of the chamber, and the degree of polymerization of cellulose in one collision The decrease in the number of cases often exceeds 10%. On the other hand, when the angle is larger than 178 °, for example, when the collision is 180 °, that is, when the collision is made in the face-to-face relationship, the energy of the collision is large, and the degree of polymerization in one collision may be drastically reduced.

  The number of collisions can be 1 to 200 times, for example, 5 to 120 times, ˜60 times, ˜30 times, ˜15 times, and ˜10 times. When the number of pulverization is large, the decrease in the degree of polymerization of cellulose may exceed 10%.

  The collision angle and / or the number of collisions can be appropriately designed in consideration of the decomposition efficiency by cellulose and the like. By adjusting the collision angle and / or the number of collisions, the average particle length of cellulose after collision treatment is 1/4 or less, 1/5 to 1/100, 1/6 to 1/50, 1/7 before treatment. ~ 1/20. Similarly, the average particle length can be 10 μm or less, 0.01 to 9 μm, 0.1 to 8 μm, or 0.1 to 5 μm. Cellulose fibers have a particle width in a direction perpendicular to the average particle length. This width is referred to as an average particle width, which can also be set to 10 μm or less, 0.01 to 9 μm, or 0.1 to 8 μm by adjusting the collision angle and / or the number of collisions.

  Since the temperature of the processed object rises as the number of counter collision processes increases, the processed object once subjected to the collision process is cooled to 4 to 20 ° C. or 5 to 15 ° C. as necessary. Also good. Equipment for cooling can be incorporated in the opposing collision processing apparatus.

  Further, in the present invention, as a method for taking out only the portion where the cellulose fibers are particularly fine from the treated product, the treated product is centrifuged to obtain a cellulose fine particle having an average particle length of less than 1 μm by separating the supernatant. Can do.

FIG. 1 is a diagram showing hydrophilic sites and hydrophobic sites of cellulose molecules. In molecules such as cellulose and chitin, there are hydrophilic sites derived from hydroxyl groups in the direction parallel to the skeleton and hydrophobic sites derived from C—H groups in the direction perpendicular to the skeleton. FIG. 2 is a diagram showing the influence of the orientation angle of the glucose ring on the surface on the surface characteristics. If the hydrophilic surface appears on the solid surface, it has an affinity for water. However, when the hydrophobic surface is arranged on the surface, the surface has water repellency equivalent to that of Teflon ^TM . FIG. 3 is a diagram including photographs showing changes in bacterial cellulose nanofibers before and after the opposing collision treatment. It was found that the nanofiber network structure in the pellicle was destroyed by the facing collision treatment and dispersed in water as a single fiber instead of the pellicle. Moreover, it became clear from the TEM photograph that the width of the nanofiber was reduced to about 10 nm and about ¼, and the cross section was a fiber having a shape close to a square. FIG. 4 is a photograph of the water repellency (water contact angle) measured on the surface of a filter paper coated with bacterial cellulose subjected to opposing collision treatment. In the case of the untreated filter paper, the contact angle could not be measured due to intense suction of water into the filter paper, but a value of 51 ° contact angle could be obtained by the coating treatment. FIG. 5 is a photograph when the oil resistance of the surface of the filter paper coated with the bacterial cellulose subjected to the counter collision treatment was tested. When the salad oil mixed with the red dye (Zudan IV) was dropped and the surface at that time was observed, the untreated filter paper penetrated quickly and exuded to the back side, but the salad oil was filtered by the coating process. Although it spread on the surface, it did not penetrate and oil did not ooze out on the back side. FIG. 6 is a photograph when the oil resistance of the surface of the filter paper coated with the plant-derived microcrystalline cellulose fiber subjected to the opposing collision treatment was tested. From the left, the number of coatings is 1, 3, and 5. Salad oil penetrated immediately, and when the number of times of application was 2 times or more, the applied one turned into a film and peeled off the filter paper. FIG. 7 is a photograph when the oil resistance of the filter paper surface coated with bacterial cellulose defibrated with a homogenizer was tested. From the left, the number of coatings is 1, 3, and 5. Salad oil penetrated immediately. FIG. 8 is a photograph of the bacterial cellulose that has been subjected to opposing collision treatment developed on a PET film. Bacterial cellulose adhered well to the PET film. FIG. 9 is a photograph of the microcrystalline cellulose fiber that has been subjected to opposing collision treatment when spread on a PET film. The development was peeled off the film. FIG. 10 is a photograph when the water resistance of the surface of the filter paper coated with the bacterial cellulose subjected to the counter collision treatment was tested. When a 1% solution of blue stain (Coomassie brilliant blue R-250) was dropped and the surface at that time was observed, the untreated filter paper penetrated quickly and exuded to the back side. The solution spread on the surface of the filter paper but did not penetrate and did not ooze out on the back side. FIG. 11 is a photograph when the water resistance and oil resistance of the surface of filter paper coated with reed-derived cellulose nanofibers subjected to opposing collision treatment were tested. When a 1% aqueous solution of blue stain (Coomassie brilliant blue R-250) was dropped, the solution spread on the surface of the filter paper but did not permeate, and water did not ooze out on the back side. (Left photo) Moreover, when salad oil mixed with a red dyeing agent (Zudan IV) was dropped, the salad oil spread on the surface of the filter paper but did not penetrate, and the oil did not ooze out on the back side (right photo). FIG. 12 is a photograph when the water resistance and oil resistance of the surface of the filter paper coated with the bamboo-derived cellulose nanofibers subjected to facing collision treatment were tested. When a 1% aqueous solution of blue stain (Coomassie brilliant blue R-250) was dropped, a slight soaking of water into the filter paper was observed, but the soaking speed was slow (left photo). Moreover, when salad oil mixed with a red dye (Zudan IV) was dropped, no soaking into the filter paper was observed (right photo). FIG. 13 is a photograph of the coating composition when tested for water resistance and oil resistance. The oil resistance and water repellency were maintained in the same manner as in Example 1.

[Coating method]
In the present invention, when the substrate surface is coated with a cellulose nanofiber coating (sometimes referred to as “coating”), the method is not particularly limited, but usually the substrate is impregnated (soaked) in the liquid. .) Or by applying the liquid to the substrate surface and drying. Impregnation and application may be performed in combination, or may be performed repeatedly. There is no restriction | limiting in particular in an application means, It can carry out with an air spray, a brush, a roller, etc. Drying can be performed by heat drying, forced drying, and / or room temperature drying.

[Examples of base materials and application of the present invention to paper and paper products]
According to the present invention, it is possible to coat an organic base material surface such as plastic, wood and paper; an inorganic base material surface such as concrete, stone, glass and ceramic; and a metal surface such as iron and aluminum. Preferred examples of substrates coated and modified according to the present invention are paper, polyethylene terephthalate, polyethylene, polypropylene. An example of a particularly suitable substrate is paper.

In the present specification, the term “paper” refers to a product made by intertwining and attaching plant fibers and other fibers. There are no particular limitations on the raw materials, the types of fibers to be formed, and the proportions of the components, and any form such as paperboard or molded product can be used. A pulp mold is also included. Further, it may contain a fungicidal component other than fibers, an antibacterial component and the like.

Cellulose nanofibers are 0.01 to 30 g / m ² (preferably 0.05 to 20 g / m ² , more preferably 0.1 to 10 g / m ² , more preferably 0.2 to 5 g / m ² ) on the paper surface. Coated. As a coating method, various methods used for coating a substrate, such as dipping, spraying, and the like, can be applied.

  When the coating of the present invention is applied to a substrate having a hydrophobic surface (water repellency) such as PET, the surface of the substrate is modified to be hydrophilic. If it is hydrophilic, it can be printed on the coated substrate with aqueous ink or pencil.

  The present invention is also a paper product or a paper-molded product in which a part or all of the surface is coated with a cellulose nanofiber coating; the cellulose nanofiber coating is formed by subjecting bacterial cellulose to opposing collision treatment and cellulose. The paper product or the paper product, which is formed by obtaining a treatment liquid containing nanofibers, impregnating the treatment liquid with a substrate and / or applying the treatment liquid to the surface of the substrate and drying. Provide paper moldings.

  Examples of paper products or paper moldings include food containers (for example, bento containers), tableware (paper cups, paper plates), bags, cards, books, magazines, printing paper, stationery, printing records Examples include paper, adhesive paper, and filters.

  The present invention is also a method of imparting water repellency or hydrophilicity, or oil and fat resistance to a substrate surface such as a paper product or a paper molded product; and imparting water resistance or hydrophilicity, and oil and fat resistance, By covering a part or all of the surface of a substrate such as a paper product or a paper molding with a cellulose nanofiber coating; the cellulose nanofiber coating is a cellulose fiber derived from bacterial cellulose or a plant of the grass family Formed by subjecting the substrate to an impingement treatment to obtain a treatment liquid containing cellulose nanofibers, impregnating the treatment liquid with a substrate, and / or applying the treatment liquid to the substrate surface and drying The method is provided.

  By the treatment of the present invention, various resistances can be imparted to the paper, particularly resistance to penetration of liquids and gases. Resistance to liquid includes water repellency, oil and fat resistance (oil resistance and oil resistance), and water resistance. Each evaluation method is well known to those skilled in the art. These evaluations are usually evaluated by dropping water or oil droplets on the surface, but not only immediately after landing of the droplets, but also depending on the intended use, the state after several hours after landing may be evaluated. . According to the study of the present inventor, even the porous filter paper that is most wettable can be easily given oil resistance by spraying, and this oil resistance did not change even after several hours after landing.

  As a result of the evaluation, when an effect suitable for the intended application is not recognized, it can be improved by modifying the coating method. For example, when sufficient water repellency cannot be obtained by wiping one to several times by spraying, it can be improved by immersion in a coating solution or repeated spraying.

[Coating composition]
This invention also provides the coating composition containing the cellulose nanofiber obtained by carrying out the opposing collision process of the cellulose fiber derived from bacterial cellulose . The coating composition of the present invention can be used as a paint or as an ink.

  The coating composition of the present invention may contain water, a pigment, and various additives as a developing agent in addition to cellulose nanofibers as a film-binding component. Examples of pigments include inorganic pigments, lakes, colored pigments, extender pigments, and bright pigments. Examples of additives include dispersants, emulsifiers, suspending agents, anti-coloring agents, drying agents, Anti-sagging agents, leveling agents, plasticizers, matting agents, antifoaming agents, fireproofing agents, antiseptics, fungicides, bactericides, and agents for imparting slipperiness to the coating film can be mentioned.

  The coating composition of the present invention can be applied to various substrate surfaces and old paint film surfaces. Examples of the substrate surface include organic substrate surfaces such as plastic, wood and paper; concrete, stone, glass, ceramic and the like. Inorganic base material surface: Metal surfaces such as iron and aluminum can be mentioned. As the old paint film, acrylic resin system, acrylic urethane resin system, polyurethane resin system, fluororesin system, silicon acrylic resin system, vinyl acetate resin system, Examples include old paint films such as epoxy resin and alkyd resin. The coating composition of the present invention can also be used in combination with an undercoat material or an overcoat material. The coating method of the coating composition of this invention is not specifically limited, It can carry out by immersion, an air spray, a brush, a roller, etc.

  Although most of the conventional coating compositions are used as water-based paints, they require a VOC (volatile organic compound) component that is one of the causes of sick house syndrome. It can be configured not to include. Such a coating composition of the present invention mainly includes general-purpose materials for interiors that do not require amenity (does not emit VOCs) and materials that are used in contact (for example, welfare materials for the elderly, metal substitutes used in hospitals) Particularly suitable for materials). Specific examples include architectural interior materials, automotive interior materials, food packaging, and plastic trays.

  In the coating composition of the present invention, the formed coating film strongly strengthens the substrate surface due to the strong adsorptivity of nanocellulose fibers to the substrate surface and the anchor effect to the material surface such as pigment components used together. It is thought that it can be coated. Therefore, the coating composition of this invention can be comprised so that a coating film may exhibit sufficient durability.

  With the coating composition of the present invention, painting or dyeing and oil resistance / water repellency treatment can be performed simultaneously.

[Surface structure and properties of cellulose nanofibers]
According to the present invention, cellulose nanofibers and cellulose nanofiber coatings are provided. Bacterial cellulose has recently been reported to exhibit biocompatibility not found in cotton wool, but this is because the difference in the structure of the surface reflects the difference in the effect on the cell at the contact surface. It seems to show that. As described above, the bacterial cellulose surface has a crystal form called I alpha (triclinic) in which the aggregate state is triclinic even if it is composed of the same cellulose molecules. On the other hand, the molecular morphology of the plant-derived surface is in the form of a monoclinic crystal called I beta (beta), so the properties of the surfaces of the nanofibers are different. The conventional plant cellulose fiber and the bacterial cellulose nanofiber according to the present invention are different in the arrangement of the constituent molecules, and as a result, the aggregation state of the molecules on the fiber surface is different, and therefore the properties exhibited by the fiber surface are considered to be different. It is done. According to the study by the present inventors, the opposite treatment product of the crystalline cellulose fiber derived from the woody plant did not obtain the same effect as the case of using the opposite treatment product of the bacterial cellulose (see Comparative Example). In addition, even when the bacterial cellulose was treated with a high-pressure homogenizer, the same effect as in the case of using a bacterial cellulose facing product was not obtained. The treatment with a high-pressure homogenizer may be useful from the viewpoint of water-solubilization of cellulose, but naturally it involves physical molecular cleavage, so that cellulose is reduced in molecular weight and the degree of polymerization is lowered. However, the opposing collision acts to peel off the molecules, and the degree of polymerization does not decrease so much. And it is anticipated that the aggregation state of molecules on the fiber surface will differ depending on the treatment method. Therefore, in the nano-size consideration, even if the starting material is the same, fibers with different surface properties are produced depending on the treatment method. Opposing collision treatment technology is important in that it is a non-destructive operation of molecular structure without lowering the degree of polymerization.

  In this sense, the present application provides the property that only bacterial cellulose that has been subjected to a counter collision process can be expressed at the present time. The present invention utilizes the surface properties of nanofibers, and at present, the surface structure and size of bacterial cellulose that has been subjected to an appropriate number of counter-collision treatments has the potential of being amphiphilic in cellulose molecules and aggregates thereof. This means that the special characteristics are expressed more clearly.

Example 1
Method:
<Preparation of bacterial cellulose nanofiber suspension>
Acetobacter xylinum (Acetobactor xylinum or Gluconacetobactor xylinus) (production strain: ATCC 53582). Culturing the (medium process for the preparation of for the bacterial cellulose cultures, Hestrin, S. & Schramm, M. (1954) Biochem J. 58, 345-352.) The obtained cellulose pellicle was cut into a 1 cm square size as it was and suspended in water, and then faced collision (device used: Ultimizer (Sugino Machine), pressure 200 mPa, Cellulosic nanofiber suspension was obtained by subjecting the suspension to 34 times and a solid concentration of the suspension of about 0.4%.

<Coating of filter paper surface with suspension>
The filter paper surface was coated with nanofibers by using filter paper as a substrate material, dipping in a suspension of cellulose nanofibers and drying at 105 ° C. The coating amount was 2-3 g / m ² .

  An attempt was made to evaluate how the surface condition of the filter paper coated with nanofibers changed, focusing on the correlation between the surface structure and hydrophobicity or oil resistance. First, using the contact angle method, the contact angle of water was measured, and the hydrophobicity of the surface was examined. As a method, 1 μl of ultrapure water was dropped, and the measurement was made 1 second after landing on the filter paper. Oil resistance is examined by mixing red oil (Zudan IV) with salad oil (manufacturer J-Oil Mills, product name AJINOMOTO salad oil 1500 g eco-bottle, raw material name edible soybean oil, edible rapeseed oil) and dripping onto filter paper. did.

result:
<Bacterial cellulose nanofiber suspension>
In order to examine the effect of the opposing collision treatment, particularly the influence on the fiber width size, the morphology of the cellulose nanofibers in the suspension was observed with a transmission electron microscope (TEM). FIG. 3 shows a TEM photograph. It was found that the nanofiber network structure in the pellicle was destroyed and dispersed in water as a single fiber rather than a pellicle. Furthermore, bacterial cellulose nanofibers are usually 40-60 nm wide and 10 nm thick, but after collision treatment, the width of the nanofibers is reduced to about 10 nm and 1/4, resulting in fibers having a cross-sectional shape close to a square. It was found from the TEM photograph.

  From this, it was considered that the fiber adsorption to the filter paper surface by purely the interaction between the nanofiber surface and the filter paper surface was significantly improved as compared with the case of bacterial nanofibers forming a pellicle. That is, since the filter paper is hydrophilic, the hydrophilic side of the nanofiber is adsorbed on the surface, and the hydrophobic side is directed to the air side, so that it is considered that the surface is given hydrophobicity.

<Coating of filter paper surface with suspension>
i) Influence with water (water repellency):
The contact angle of the surface of the filter paper immersed in the suspension was measured (Fig. 4). In the case of untreated filter paper, the suction angle of water into the filter paper was so strong that the contact angle could not be measured. However, in the filter paper that has been soaked, the suction of water is significantly slowed, the contact angle can be measured, and a numerical value of 51 ° can be obtained with a single soaking treatment, giving hydrophobicity. it was thought.

The water contact angle is 20 ° for glass, 45 ° for stainless steel and 70 ° for aluminum (DuPont HP HYPERLINK "http://www.dupont.co.jp/tc/seinou/" http: // www.dupont.co.jp/tc/seinou/ ). It is considered that the 51 ° numerical value of the filter paper that had been soaked was able to have the same water repellency as stainless steel.

ii) Effect with oil (oil resistance):
Oil (salad oil) was dropped onto the filter paper surface, and the surface at that time was observed (FIG. 5). Ordinary filter paper penetrated quickly and oozed out to the back, although not as much as water. However, with respect to the filter paper soaked, the salad oil spread on the surface of the filter paper but did not penetrate, and the oil did not ooze out on the back side. This showed oil resistance.

(Comparative Example 1)
Example except that plant-derived cellulose microcrystalline fiber (Funacel II: average particle size 80 micrometers: Funakoshi Co., Ltd.) was subjected to opposing collision treatment (number of collisions 30 times, solid concentration of suspension was about 0.5%) (The same conditions as in 1) were applied to the filter paper by spraying and dried at 105 ° C. to test the oil resistance of the filter paper (FIG. 6).

  The salad oil immediately penetrated the filter paper. In addition, when the number of times of coating was 2 times or more, the coated material turned into a film and peeled off from the filter paper. This was thought to be due to the fact that the interaction of the cellulose used with the filter paper was weaker than that of bacterial cellulose.

  Furthermore, the suspension obtained by treating bacterial cellulose with a homogenizer (product name: Hiscotron, manufactured by Microtec Nithion) at 20,000 rpm for 5 minutes was applied by spray, and other conditions were the same as in Example 1. The oil resistance of the filter paper was tested (Fig. 7).

  The salad oil immediately penetrated the filter paper. In addition, it was difficult to uniformly apply to the filter paper surface as compared with the case of facing collision treatment.

(Example 2)
The bacterial cellulose suspension obtained in Example 1 was developed on a PET film (FIG. 8). Bacterial cellulose treated with facing collision was in good contact with the PET film. Other than paper, PET, PP, PE and other substrates could be coated with bacterial cellulose.

(Comparative Example 2)
The suspension of plant-derived microcrystalline fibers obtained in Comparative Example 2 was developed on a PET film (FIG. 9). The developed material peeled off the film.

Example 3
In the same manner as in Example 1, spraying the bacterial cellulose suspension that had been subjected to the counter treatment 34 times and air-drying was repeated 15 times, and finally the water resistance of the filter paper obtained by drying at 40 ° C. for about 1 hour. Sex was evaluated.

  A solution prepared by dissolving Coomassie (registered trademark) brilliant blue R-250 in 1% water was dropped onto a filter paper, and the surface was observed (FIG. 10).

[Example 4 ] Coating composition A blue dyeing agent (Coomassie brilliant blue R-250) was added to the cellulose nanofiber suspension with 34 collisions obtained in Example 1 so as to have a concentration of 0.1%. A coating composition was obtained. This was applied to the filter paper surface by spraying and subjected to oil resistance and water repellency tests.

  The results are shown in FIG. Oil resistance and water repellency were maintained as in Example 1. From this, it was considered that the coating or dyeing and the oil resistance / water repellency treatment can be simultaneously performed by using the cellulose nanofiber suspension.

Claims (9)

A treatment liquid containing cellulose nanofibers is produced by a method in which a dispersion of bacterial cellulose pellicle is sprayed from a pair of nozzles at a high pressure of 70 to 250 MPa, and the jet flows collide with each other (hereinafter referred to as opposing collision treatment). And impregnating the substrate with the treatment liquid and / or coating the substrate surface with a cellulose nanofiber coating formed by applying the treatment liquid to the substrate surface and drying. A method for modifying a substrate surface. The method for modifying a substrate surface according to claim 1 , wherein the substrate is paper, polyethylene terephthalate, polyethylene or polypropylene. The method for modifying a substrate surface according to claim ² , wherein the cellulose nanofiber is coated on the substrate surface at 0.01 to 30 g / m2. The method for modifying a substrate surface according to claim 3 , wherein the substrate is imparted with water repellency or hydrophilicity, water resistance and / or oil resistance. The method for modifying the surface of a substrate according to claim 4 for protecting the surface of a molded product made of food storage paper. A paper product or a paper molding, part or all of which is coated with a cellulose nanofiber coating;
The cellulose nanofiber coating treats a dispersion of bacterial cellulose pellicle in a facing collision process to obtain a treatment liquid containing cellulose nanofibers, impregnates the treatment liquid with a substrate, and / or uses the treatment liquid as a substrate. The paper product or paper molded product, which is formed by applying to a surface and drying. A method of imparting water resistance and oil resistance to paper products or paper moldings;
The provision of water resistance and oil and fat resistance is due to coating part or all of the surface of the paper product or paper molding with a cellulose nanofiber coating;
The cellulose nanofiber coating treats a dispersion of bacterial cellulose pellicle in a facing collision process to obtain a treatment liquid containing cellulose nanofibers, impregnates the treatment liquid with a base material, and / or uses the treatment liquid as a base material. A method for modifying a substrate surface , which is formed by applying to a surface and drying. A treatment liquid containing cellulose nanofibers is obtained by opposing collision treatment of a dispersion of bacterial cellulose pellicle , the substrate is impregnated with the treatment liquid, and / or the treatment liquid is applied to the surface of the substrate and dried. A cellulose nanofiber coating formed by A coating composition comprising cellulose nanofibers obtained by subjecting a dispersion of a bacterial cellulose pellicle to an opposing collision treatment.