JPH11343301A - Fine cellulose particle and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve water dispersibility and satisfy the effect of thickening, emulsion stabilization or the like in an aqueous solution by setting a longitudinal size of a bar-like cellulose particle dispersed in water to a specified dimension. SOLUTION: A longitudinal size of a cellulose particle is set to a dimension up to a maximum of 2 μm, preferably up to a maximum of 500 nm. Preferably, a longitudinal size of not less than 50% of the particles is set to a dimension of 0.01-100 mm or a longitudinal size of not less than 40% thereof is set to a dimension of 0.01-50 nm. The fine cellulose particle can be produced by hydrolyzing a cellulose (e.g. a conifer wood pulp) in an aqueous solution containing one or more inorganic acids, preferably selected from hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, phosphotungstic acid and phosphomolybdic acid. The concentration of an inorganic acid is preferably 0.01-12 mol/l and the hydrolysis is preferably carried out in an aqueous solution of an inorganic acid at a temperature of 10-110 deg.C for not less than 1 min.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to finely divided cellulose and a method for producing the same. Such particulate cellulose is
It is used as a thickener, a stabilizer, and a water-absorbing agent in the fields of food, cosmetics, pharmaceuticals, inks, and paints. [0002] Cellulose is a polysaccharide composed of glucose which is a main component of cell walls of plants such as wood, cotton and hemp, and which is also present in ascidian skin and seaweed. Cellulose is uniaxially arranged in a living body and exists as cellulose microfibrils. As a commercial product, a product obtained by slightly hydrolyzing a highly purified pulp with an inorganic acid is commercially available. In addition, the raw material is not only refined pulp, but also, for example, Acetobacter xylinu.
Fermentation production by microorganisms such as m. These celluloses are usually, when dispersed in water, several mm to
It is several μm in size, and the smallest particles are 1 μm to 100 μm.
The particle size is nm. However, conventional cellulose has poor dispersibility in water, and is dispersed by applying a strong shearing force, or is dispersed by coating the cellulose surface with another polysaccharide. Have been attempted, but these methods have been insufficient and often resulted in precipitation. on the other hand,
Nothing satisfying the effect of increasing the viscosity in an aqueous solution, the effect of stabilizing the emulsion, the effect of dispersing another composition, and the effect of a water absorbing agent has not been obtained. Means for Solving the Problems The inventors of the present invention have conducted intensive studies in order to achieve the above-mentioned problems. As a result, it has been found that cellulose has an excellent affinity for water by being finely divided. The present inventors have found fine-particle cellulose having dispersibility in water, thickening, protective colloid, and water absorption, and completed the present invention. The present invention relates to fine-particle cellulose which is a fine-particle cellulose having a maximum size of 2 μm or less in the major axis direction of rod-like cellulose particles dispersed in water. The particulate cellulose of the present invention can be generally obtained by hydrolyzing cellulose with an aqueous solution containing an inorganic acid. Hereinafter, the present invention will be described in detail. As described above, the fine-particle cellulose of the present invention can be generally obtained by hydrolyzing cellulose with an aqueous solution containing an inorganic acid. The raw material cellulose used for producing the fine particle cellulose of the present invention is not particularly limited as long as it is a natural product having a high cellulose content and a processed product thereof. For example, plants such as wood, cotton, and hemp, plant epidermis, plant seed epidermis, various seaweeds, ascidian sac, wood pulp, paper, microcrystalline cellulose, etc., and Acetobac
Examples include fermented cellulose by ter xylinum and the like. In order to produce the fine particle cellulose of the present invention, cellulose is heated in an aqueous solution of an inorganic acid. As the inorganic acid, two or more elements selected from hydrogen, oxygen, nitrogen, phosphorus, chlorine, sulfur, tungsten, and molybdenum are used. Inorganic acids are preferred, and two or more inorganic acids may be mixed and used at the same time. In particular, hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, phosphotungstic acid, and phosphomolybdic acid are preferable as the catalytic action of hydrolysis. Further, in the case of a divalent or higher valent inorganic acid, a part thereof may be neutralized with a metal, an amine, a pyridine or the like. The concentration of the inorganic acid in the aqueous solution containing an inorganic acid is preferably 0.01 to 12 mol / l. However, when sulfuric acid, nitric acid or phosphoric acid is used at a high concentration, the microcrystalline cellulose has a substituent as an acid ester. Is introduced, and advantages such as improvement in the hydrophilicity of cellulose are produced. The temperature and time for the hydrolysis cannot be unequivocally defined depending on the strength of the acid and the concentration of the acid, but it is suitably 1 minute or more at 10 to 110 ° C. The stronger the acid or the higher the acid concentration, the lower the temperature and the shorter the heating conditions. For example, at an inorganic acid concentration of 0.1 mol / l or more, at 10 to 30 ° C. for 3 days or more, or 30 to 6 ° C.
Desirably, it is 6 hours or more at 0 ° C or 30 minutes or more at 60 to 110 ° C. For inorganic acid concentration of 1 mol / l or more, 10
It is desirable that the heating time is 4 hours or more at 30 to 30 ° C, 1 hour or more at 30 to 60 ° C, or 10 minutes or more at 60 to 110 ° C. More preferably, the concentration of the inorganic acid is 1 mol / l or more,
It is 1 to 12 hours or more at 50 to 100 ° C. Even under these conditions, heating for a relatively short time on the high temperature side and heating for a relatively long time on the low temperature side are preferable. If the heating temperature is less than 10 ° C, hydrolysis is not sufficient, and if it exceeds 110 ° C, the possibility of coloring generally increases. The heating is performed in an aqueous solution, in which a solvent that does not react with cellulose and a solvent may be appropriately added. Examples include alcohols such as methanol, ethanol, propanol and glycerin, and organic acids such as acetic acid, but are not particularly limited. In addition, if the reaction is performed in the presence of oxygen in air or the like, there is a possibility of coloration. Therefore, it is preferable to hydrolyze by sealing under reduced pressure after removing oxygen, or by blowing in an inert gas. Examples of the inert gas include a nitrogen gas, a helium gas, a carbon dioxide gas, and steam, but are not particularly limited. [0007] Isolation of the fine cellulose particles obtained after the hydrolysis treatment can be carried out by neutralizing the inorganic acid with an alkali or the like or removing the inorganic acid, followed by drying. The removal of the inorganic acid is performed, for example, by filtering the heat-treated liquid and washing the cake with a low-boiling solvent such as water or ethanol as necessary, or applying the heat-treated liquid to a centrifuge and washing the cake several times with water or the like. Alternatively, there is a method of treating the heat-treated solution with a dialysis membrane, but the method is not limited thereto. Fine-particle cellulose produced by the above method differs from conventional cellulose in the size of cellulose particles in the aqueous solution. That is, the particulate cellulose of the present invention refers to a particulate cellulose having a maximum size of 2 μm or less in the major axis direction in an aqueous solution. More preferably, it is at most 500 nm or less. The size distribution is 0.01 to 100 nm.
Is preferably 50% by weight or more. More preferably, it is a fine-particle cellulose in which cellulose particles having a size of 0.01 to 50 nm have a weight ratio of 40% or more. Commercially available cellulose usually has a size of several millimeters to several micrometers in an aqueous solution, and even the so-called microcrystalline cellulose having a small particle size has a minimum particle size of 100 to 200 nm. Microcrystalline cellulose is amazing. [0008] The particulate cellulose of the present invention can be used in the same applications as conventional cellulose, but at that time, it is improved as a thickener, an emulsion stabilizer, a dispersant, and a water absorbing agent as compared with conventional products. Further, the fine particle cellulose can be easily dispersed in water because the affinity for water is increased. By using the fine particle cellulose of the present invention alone or in combination with another water-soluble gelling agent, water-soluble thickener or emulsifier, a stable gel, viscous substance or emulsion can be obtained. Therefore, the fine-particle cellulose of the present invention can be used as a thickener, a stabilizer, and a water-absorbing agent in general industrial fields including inks and coatings, including the fields of foods, cosmetics, and pharmaceuticals. The present invention will be specifically described below with reference to Examples, Comparative Examples and Reference Examples, which are intended to exemplify the present invention and do not limit the present invention in any way. Example 1 10 g of softwood pulp was added to an aqueous sulfuric acid solution or aqueous hydrochloric acid solution and hydrolyzed by heating. Centrifugation was repeated while adding water to the hydrolyzate to remove the acid. After the supernatant liquid became cloudy (pH 4-5), it was dialyzed and dried. The softwood wood pulp and the particulate cellulose of the present invention were dispersed in water, the state of dispersion was examined, and the size of the particles was observed with a transmission electron micrograph. The results are shown in Table 1. [Table 1] From these results, it can be seen that the obtained particulate cellulose has improved dispersibility in water and viscosity characteristics. Example 2 20 g of commercially available microcrystalline cellulose (Avicel PH-10)
1) was added to hydrochloric acid, nitric acid, and phosphoric acid aqueous solution and hydrolyzed by heating. The hydrolyzate was dialyzed to remove the acid and dried. Microcrystalline cellulose and fine-particle cellulose of the present invention were dispersed in water, the state of dispersion was examined, and the size of the particles was observed with a transmission electron micrograph. Table 2 shows the results. [Table 2] From these results, it can be seen that the obtained particulate cellulose has improved dispersibility in water and viscosity characteristics. Example 3 20 g of soybean hulls were added to an aqueous solution of phosphotungstic acid and phosphomolybdic acid and heated and hydrolyzed. Centrifugation was repeated while adding water to the hydrolyzate to remove the acid. After the supernatant became cloudy (pH 4), it was dialyzed and dried. Soybean husks and the fine-particle cellulose of the product of the present invention were dispersed in water, the state of dispersion was examined, and the size of the particles was observed with a transmission electron micrograph. The results are shown in Table 3. [Table 3] From these results, it can be seen that the obtained particulate cellulose has improved dispersibility in water and viscosity characteristics. Example 4 30 g of fermented cellulose was added to an aqueous hydrochloric acid solution and hydrolyzed by heating. The hydrolyzate was dialyzed to remove the acid and dried. The fermented cellulose and the particulate cellulose of the present invention were dispersed in water, the state of dispersion was examined, and the size of the particles was observed with a transmission electron micrograph. The results are shown in Table 4. [Table 4] From these results, it can be seen that the obtained particulate cellulose has improved dispersibility in water and viscosity characteristics. Example 5 30 g of ramie was added to an aqueous solution of sulfuric acid and hydrolyzed by heating. The hydrolyzate was dialyzed to remove the acid and dried. Lamy and the cellulose cellulose of the present invention were dispersed in water, the state of dispersion was examined, and the size of the particles was observed with a transmission electron micrograph. The results are shown in Table 5. [Table 5] From these results, it can be seen that the obtained particulate cellulose has improved dispersibility in water and viscosity characteristics. The fine particle cellulose of the present invention is an extremely excellent polysaccharide having a viscosity several times that of conventional cellulose, and has improved water dispersibility and good workability.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a TEM photograph of particulate cellulose of the product 9 of the present invention.

Claims (1)

Claims: 1. Fine particle cellulose, characterized in that rod-shaped cellulose particles dispersed in water have a maximum size of 2 μm or less in the major axis direction. 3. The fine-particle cellulose according to claim 1, wherein the size of the rod-shaped cellulose particles in the major axis direction is 500 nm or less at maximum. 3. The particle of 50% or more of the rod-shaped cellulose particles dispersed in water. The size in the long axis direction is 0.01 to 1
3. The fine particle cellulose according to claim 1, which has a thickness of 00 nm. 4. The size of the rod-like cellulose particles dispersed in water in the major axis direction of at least 40% of the particles is 0.01 to 5%.
3. The fine particle cellulose according to claim 1, which has a thickness of 0 nm. 5. A method for producing fine-particle cellulose, comprising hydrolyzing cellulose with an aqueous solution containing an inorganic acid. 6. The inorganic acid is selected from hydrogen, oxygen, nitrogen, phosphorus, chlorine, sulfur, tungsten and molybdenum.
The method according to claim 5, wherein the inorganic acid is composed of at least one kind of element. 7. The method according to claim 1, wherein the inorganic acid is hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid,
1 selected from phosphotungstic acid and phosphomolybdic acid
The method for producing fine-particle cellulose according to claim 5, wherein the method is one or more kinds of inorganic acids. 8. An inorganic acid-containing aqueous solution having an inorganic acid concentration of:
The method for producing finely divided cellulose according to any one of claims 5 to 7, wherein the hydrolysis is performed in an aqueous solution of an inorganic acid.
The method for producing fine-particle cellulose according to any one of claims 5 to 8, wherein the treatment is performed at a temperature of 1 to 110 ° C for 1 minute or more. 10. The method according to claim 5, wherein the hydrolysis is carried out in an aqueous solution of an inorganic acid having an inorganic acid concentration of 0.1 mol / l or more at 10 to 30 ° C. for 3 days or more. The method for producing finely divided cellulose according to the above item. 11. The method according to claim 5, wherein the hydrolysis is carried out in an aqueous solution of an inorganic acid having an inorganic acid concentration of 0.1 mol / l or more at 30 to 60 ° C. for 6 hours or more. The method for producing finely divided cellulose according to the above item. 12. The hydrolysis conditions are as follows: in an inorganic acid aqueous solution having an inorganic acid concentration of 0.1 mol / l or more at 60 to 110 ° C.
The method for producing fine-particle cellulose according to any one of claims 5 to 9, wherein the treatment is performed for 0 minute or more. 13. The method according to claim 5, wherein the hydrolysis is performed in an aqueous solution of an inorganic acid having an inorganic acid concentration of 1 mol / l or more at 10 to 30 ° C. for 4 hours or more.
The method for producing finely divided cellulose according to the above item. 14. The method according to claim 5, wherein the hydrolysis is performed in an aqueous solution of an inorganic acid having an inorganic acid concentration of 1 mol / l or more at 30 to 60 ° C. for 1 hour or more.
The method for producing finely divided cellulose according to the above item. 15. The method according to claim 5, wherein the hydrolysis is performed in an aqueous solution of an inorganic acid having an inorganic acid concentration of 1 mol / l or more at 60 to 110 ° C. for 10 minutes or more. Production method of fine particle cellulose. 16. The hydrolysis condition is 1 to 1 in an inorganic acid aqueous solution having an inorganic acid concentration of 1 mol / l or more at 50 to 100 ° C.
The method for producing fine-particle cellulose according to any one of claims 5 to 9, wherein the treatment is performed for 2 hours.