WO2021111730A1 - Cellulose particles and method for producing cellulose particles - Google Patents

Cellulose particles and method for producing cellulose particles Download PDF

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Publication number
WO2021111730A1
WO2021111730A1 PCT/JP2020/038105 JP2020038105W WO2021111730A1 WO 2021111730 A1 WO2021111730 A1 WO 2021111730A1 JP 2020038105 W JP2020038105 W JP 2020038105W WO 2021111730 A1 WO2021111730 A1 WO 2021111730A1
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Prior art keywords
cellulose
particles
cellulose acetate
water
cellulose particles
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PCT/JP2020/038105
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French (fr)
Japanese (ja)
Inventor
恵子 西田
慶 長谷川
要 田村
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根上工業株式会社
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Priority to JP2021562480A priority Critical patent/JP7199763B2/en
Priority to CN202080069174.7A priority patent/CN114555678B/en
Publication of WO2021111730A1 publication Critical patent/WO2021111730A1/en

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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J3/00—Processes of treating or compounding macromolecular substances
    • C08J3/12—Powdering or granulating
    • C08J3/16—Powdering or granulating by coagulating dispersions
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
    • C08B3/00—Preparation of cellulose esters of organic acids
    • C08B3/06—Cellulose acetate, e.g. mono-acetate, di-acetate or tri-acetate
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
    • C08B3/00—Preparation of cellulose esters of organic acids
    • C08B3/22—Post-esterification treatments, including purification
    • C08B3/24—Hydrolysis or ripening
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2301/00—Characterised by the use of cellulose, modified cellulose or cellulose derivatives
    • C08J2301/08—Cellulose derivatives
    • C08J2301/10—Esters of organic acids
    • C08J2301/12—Cellulose acetate

Definitions

  • the present invention relates to cellulose particles and a method for producing cellulose particles.
  • the present application claims priority based on Japanese Patent Application No. 2019-220328 filed in Japan on December 5, 2019, the contents of which are incorporated herein by reference.
  • particles such as acrylic beads, polystyrene beads, and polyurethane beads have been used in various products such as paints, plastics, adhesives, and cosmetics.
  • the issue of microplastics in the marine environment has been widely addressed, and the need for micrometer-scale cellulose particles made from natural products is increasing.
  • Patent Document 1 As a method for producing cellulose particles, the method described in Patent Document 1 is known.
  • Patent Document 1 describes the following methods 1 and 2.
  • -Method 1 Using a solution of cellulose ester in an organic solvent as a stock solution, the filament of cellulose ester produced by the dry spinning method is cut into chips, and the chips are heated and melted in a medium to form spherical particles of cellulose ester. And then the method of saponifying spherical particles.
  • Method 2 Using a solution of cellulose ester in an organic solvent as a stock solution, suspend the stock solution in a medium in which the stock solution is insoluble or slightly soluble in the organic solvent, and heat the medium containing the suspended particles to heat the organic solvent.
  • the cellulose particles obtained by Methods 1 and 2 contain a mixture of cellulose acetate and cellulose as the main component, the proportion of cellulose acetate is high, and the acetic acid odor may remain in the particles. Cellulose particles with residual acetic acid odor may limit the use of these products when applied to products such as paints, plastics, adhesives, and cosmetics.
  • a solution in which cellulose acetate is dissolved in an organic solvent has a significantly high viscosity. Therefore, if the concentration of cellulose acetate in the cellulose acetate solution is lowered so that the viscosity can be formed into droplets, the amount of cellulose acetate charged is reduced, and the yield of cellulose particles is lowered. On the other hand, if the concentration of cellulose acetate in the cellulose acetate solution is increased, it is difficult to make the cellulose acetate solution into droplets. As described above, the conventional method cannot produce micrometer-scale cellulose particles at low cost. Therefore, the present invention provides cellulose particles in which the odor of acetic acid is suppressed; a method for producing cellulose particles, which can easily produce the cellulose particles at low cost.
  • the present invention has the following aspects.
  • [1] Cellulose particles having an average particle size of 1 to 300 ⁇ m and an acetic acid concentration of 0.5 ppm or less.
  • [2] Cellulose particles of [1], which are spherical.
  • [3] Cellulose particles of [1] or [2] having a cellulose content of 92% by mass or more.
  • [4] A cellulose acetate solution in which cellulose acetate is dissolved in an organic solvent is suspended in water to prepare a suspension in which cellulose acetate particles are dispersed in water, and the organic solvent is removed from the suspension to obtain an acetic acid concentration.
  • a method for producing cellulose particles wherein the cellulose acetate particles are saponified to obtain cellulose particles so that the amount is 0.5 ppm or less.
  • water is added to the cellulose acetate solution, and then the aqueous phase and the organic solvent phase are reversed to suspend the cellulose acetate solution in water.
  • Method for producing cellulose particles [6] The method for producing cellulose particles according to [4] or [5], wherein the cellulose acetate solution has a viscosity of 2000 to 300,000 mPa ⁇ s.
  • the cellulose acetate solution is suspended in water in the presence of at least one cellulosic water-soluble resin selected from the group consisting of methyl cellulose, hydroxyethyl cellulose, hydroxypropyl methyl cellulose and carboxymethyl cellulose, [4] to The method for producing cellulose particles according to any one of [6]. [8] The method for producing cellulose particles according to any one of [4] to [7], wherein the cellulose acetate solution is suspended in water in the presence of a surfactant.
  • cellulose particles having suppressed acetic acid odor are provided. According to the present invention, there is provided a method for producing cellulose particles, which can easily produce cellulose particles having suppressed acetic acid odor at low cost.
  • the cellulose particles of the present invention are particles containing cellulose.
  • the cellulose particles are spherical particles.
  • the shape of the cellulose particles is not limited to a spherical shape.
  • agglomerates in which two or more particles are bonded and irregularly shaped cellulose particles may be unintentionally mixed in during production, although the amount is small.
  • the acetic acid concentration of the cellulose particles of the present invention is reduced to an extremely low level as described later, it can be said that the particles are substantially composed of cellulose.
  • the cellulose particles of the present invention are high-purity cellulose particles having a very high proportion of cellulose.
  • the cellulose particles of the present invention may further contain components other than cellulose as long as the effects of the present invention are not impaired.
  • examples of other components include trace amounts of cellulose acetate, suspension stabilizers, surfactants, water, organic solvents remaining during production, organic fillers, inorganic fillers, pigments, pharmaceutical materials and the like.
  • other components are not limited to these examples.
  • the content of cellulose is preferably 92% by mass or more, more preferably 95% by mass or more, and 98% by mass with respect to 100% by mass of one cellulose particle. % Or more is more preferable.
  • the water content is preferably 8% by mass or less, more preferably 5% by mass or less, still more preferably 2% by mass or less, based on 100% by mass of one cellulose particle.
  • the content of the organic solvent is preferably 0.01% by mass or less, more preferably 0.008% by mass or less, still more preferably 0.005% by mass or less, based on 100% by mass of one cellulose particle.
  • the acetic acid concentration is 0.5 ppm or less.
  • the acetic acid concentration is not particularly limited, and the acetic acid concentration can be appropriately changed depending on the product to which the cellulose particles are applied and the application of the product.
  • the acetic acid concentration is preferably 0.3 ppm or less, more preferably 0.2 ppm or less.
  • the acetic acid concentration of the cellulose particles can be measured using a headspace-gas chromatograph-mass spectrometer (for example, "Agilent 7697A Headspace Sampler, Agilent 7890B GCsystem, Agilent 5977B MSD” manufactured by Agilent).
  • the volume average particle diameter of the cellulose particles is 1 to 300 ⁇ m. Within the above numerical range, the volume average particle diameter of the cellulose particles can be appropriately changed depending on the product to which the cellulose particles are applied and the application of the product.
  • the volume average particle diameter of the cellulose particles is, for example, preferably 1 to 150 ⁇ m, more preferably 1 to 50 ⁇ m.
  • the volume average particle size of the cellulose particles is an integrated volume of 50% particle size obtained from the data obtained by measuring with a laser diffraction type particle size distribution meter (for example, "SALD2100" manufactured by Shimadzu Corporation). ..
  • a cellulose acetate solution in which cellulose acetate is dissolved in an organic solvent is suspended in water, a suspension in which cellulose acetate particles are dispersed in water is prepared, and the organic is prepared from the suspension.
  • the solvent is removed, and the cellulose acetate particles are saponified to obtain cellulose particles so that the acetate concentration becomes 0.5 ppm or less.
  • water may be further removed by solid-liquid separation to dry the cellulose particles.
  • the method for producing cellulose particles of the present invention has the following steps (a) to (c), and further includes the following steps (d) in addition to the steps (a) to (c). It can be said that it is also good.
  • step (a) a cellulose acetate solution in which cellulose acetate is dissolved in an organic solvent is suspended in water to prepare a suspension in which cellulose acetate particles are dispersed in water.
  • the cellulose acetate solution since cellulose acetate is dissolved in an organic solvent, when cellulose acetate is suspended in water, the cellulose acetate solution becomes oil and disperses in water to form oil droplets, and cellulose acetate is in water. A suspension dispersed in is obtained.
  • the cellulose acetate in the present invention is not particularly limited in the degree of substitution of acetyl groups, the vinegarization rate and the like.
  • Examples of cellulose acetate include monoacetyl cellulose, diacetyl cellulose, triacetyl cellulose and the like. One of these may be used alone, or two or more thereof may be used in combination.
  • the organic solvent is not particularly limited as long as it is a compound capable of dissolving cellulose acetate. However, as the organic solvent, one having low solubility in water is preferable.
  • the organic solvent preferably has a co-boiling point with water at 1013 hPa of 100 ° C. or lower.
  • Examples of the organic solvent having a co-boiling point with water at 1013 hPa of 100 ° C. or lower include aromatic compounds (for example, toluene, benzene, etc.), ester compounds (for example, methyl acetate, ethyl acetate, butyl acetate, etc.), and ketone compounds.
  • acetone, methyl ethyl ketone, etc. saturated aliphatic hydrocarbons (for example, n-heptane, n-hexane, n-octane, etc.) and the like can be mentioned.
  • saturated aliphatic hydrocarbons for example, n-heptane, n-hexane, n-octane, etc.
  • organic solvents may be used alone or in combination of two or more.
  • step (a) it is preferable to suspend the cellulose acetate solution in water by adding water to the cellulose acetate solution and then reversing the aqueous phase and the organic solvent phase.
  • reversing the aqueous phase and the organic solvent phase means changing the dispersed state of the mixture of the cellulose solution and water from the following state 1 to state 2.
  • -State 1 A state in which the aqueous phase is dispersed with respect to the organic solvent phase.
  • -State 2 A state in which the organic solvent phase is dispersed with respect to the aqueous phase.
  • a method can be adopted in which water or an aqueous solution of a dispersion medium described later is added to a cellulose acetate solution prepared in a container such as a beaker or a flask, and then the aqueous phase and the organic solvent phase are reversed.
  • a cellulose acetate solution prepared in a container such as a beaker or a flask
  • the aqueous phase and the organic solvent phase are reversed.
  • the cellulose acetate particles can be easily atomized on the micrometer scale by using water having a relatively low viscosity or an aqueous solution of a dispersion medium.
  • the cellulose particles can be produced more easily because they can be granulated on the micrometer scale regardless of the viscosity of the cellulose acetate solution. It becomes possible to do.
  • the ratio (W2 / W1) of the mass W2 of water to the mass W1 of the cellulose acetate solution when water is added to the cellulose acetate solution is preferably 0.2 to 3.0, more preferably 0.25 to 2.0. It is preferable, and 0.3 to 1.0 is more preferable.
  • the ratio (W2 / W1) is not more than the lower limit value, it is considered that the amount of water used for the organic solvent is sufficient after ensuring a sufficient amount of cellulose acetate to be charged, and suspension is easy.
  • the ratio (W2 / W1) is not more than the upper limit value, it is considered that the amount of water added to the organic solvent is unlikely to be excessive.
  • the viscosity of the cellulose acetate solution is appropriately set according to the intended use, but is preferably 2000 to 300,000 mPa ⁇ s, more preferably 5000 to 250,000 mPa ⁇ s, and even more preferably 10,000 to 200,000 mPa ⁇ s.
  • the viscosity of the cellulose acetate solution is not more than the above upper limit value, problems such as the cellulose acetate solution getting entangled with the shaft of the manufacturing machine are less likely to occur, and particle formation is easy.
  • the viscosity of the cellulose acetate solution is at least the above lower limit value, the yield of the cellulose particles in one production becomes sufficiently large, and the cellulose particles can be obtained at a lower cost.
  • the viscosity is a value measured under the condition of a temperature of 25 ° C. using a BL type rotational viscometer (for example, "RB-85L” manufactured by Toki Sangyo Co., Ltd.).
  • suspension stabilizer may be added in advance to, for example, water as a dispersion medium.
  • the suspension state tends to be stabilized, and cellulose particles can be produced more easily.
  • the suspension stabilizer include cellulosic water-soluble resins (methyl cellulose, hydroxyethyl cellulose, hydroxypropyl methyl cellulose, carboxymethyl cellulose, etc.), polyvinyl alcohol, polyacrylates, polyethylene glycol, polyvinylpyrrolidone, polyacrylamide, and tertiary phosphates. And so on. These suspension stabilizers may be used alone or in combination of two or more.
  • a surfactant may be added in advance to, for example, water as a dispersion medium.
  • the surfactant is not particularly limited, and may be an anionic surfactant, a cationic surfactant, a nonionic surfactant, or an amphoteric surfactant. These surfactants may be used alone or in combination of two or more.
  • a dispersion medium aqueous solution is prepared in advance, the dispersion medium aqueous solution and the cellulose acetate solution are mixed, the cellulose acetate solution is suspended in the dispersion medium aqueous solution, and the suspension in which the cellulose acetate particles are dispersed in water is prepared. It is preferable to obtain it.
  • aqueous solution of the dispersion medium a liquid containing water, the above-mentioned suspension stabilizer and the above-mentioned surfactant is preferable.
  • the content of the suspension stabilizer in the aqueous solution of the dispersion medium is preferably 0 to 10% by mass, more preferably 0.2 to 8% by mass, and further preferably 0.3 to 7% by mass with respect to 100% by mass of water. preferable.
  • the content of the suspension stabilizer is at least the above lower limit value, the suspended state of the cellulose acetate particles is likely to be stable, and the cellulose particles can be produced more easily.
  • the content of the surfactant in the dispersion medium aqueous solution is preferably 0 to 5% by mass, more preferably 0.1 to 3% by mass, and 0.2 to 1.5% by mass with respect to 100% by mass of water. More preferred.
  • the content of the surfactant in the aqueous solution of the dispersion medium is at least the above lower limit value, the suspended state of the cellulose acetate particles is likely to be stable, and the cellulose particles can be produced more easily.
  • the content of the surfactant in the aqueous solution of the dispersion medium is not more than the above upper limit value, foaming of the suspension due to stirring is less likely to occur, and the production of cellulose particles becomes easier.
  • step (b) the organic solvent is removed from the suspension.
  • the suspension it is considered that the cellulose acetate particles and the organic solvent are dispersed in water as oil. Therefore, by removing the organic solvent from the suspension in the step (b), an aqueous dispersion in which the cellulose acetate particles are dispersed in water can be obtained.
  • it is preferable to remove the organic solvent by heating the suspension in which the cellulose acetate particles are dispersed to a boiling point equal to or higher than the boiling point of the organic solvent with water. By heating the organic solvent to a boiling point equal to or higher than that of water in the step (b), the organic solvent can be sufficiently removed and the amount of the organic solvent remaining in the cellulose particles can be reduced to an extremely low level.
  • the heating temperature is preferably 1013 hPa and 100 ° C. or lower.
  • the cellulose acetate particles are in the form of a slurry dispersed in water.
  • the heating temperature of the cellulose acetate particles exceeds 100 ° C., water is volatilized and removed together with the organic solvent, so that the cellulose acetate particles may be fused to each other.
  • the cellulose acetate particles are saponified to obtain cellulose particles so that the acetic acid concentration of the cellulose particles is 0.5 ppm or less.
  • the saponification reaction can be carried out, for example, by mixing an aqueous dispersion in which cellulose acetate particles are dispersed in water and a basic compound, and heating as necessary.
  • the basic compound used for saponification is not particularly limited. For example, sodium hydroxide, potassium hydroxide, ammonia, triethylamine and the like can be mentioned.
  • the cellulose acetate particles are saponified so that the acetic acid concentration of the cellulose particles is 0.5 ppm or less.
  • Specific means for saponifying the cellulose particles so that the acetic acid concentration is 0.5 ppm or less include, for example, the following means 1 to 3.
  • the following means 1 to 3 may be used alone or in combination of two or more.
  • -Means 1 A method of sufficiently lengthening the reaction time of the saponification reaction so that the acetic acid concentration of the cellulose particles is 0.5 ppm or less.
  • -Means 2 A method of sufficiently raising the reaction temperature of the saponification reaction so that the acetic acid concentration of the cellulose particles is 0.5 ppm or less.
  • -Means 3 The amount of substance of the hydroxyl group in the basic compound used for saponification is appropriately adjusted according to the degree of substitution of the acetyl group in cellulose acetate and the vinegarization rate, and the acetic acid concentration of the cellulose particles is set to 0.5 ppm or less. Method.
  • the reaction time of the saponification reaction is preferably 1.5 hours or more, more preferably 2 hours or more, and even more preferably 3 hours or more.
  • the reaction time of the saponification reaction is at least the above lower limit value, a saponification reaction sufficient to reduce the acetic acid odor occurs, deacetylation is likely to proceed sufficiently, and the acetic acid odor of the cellulose particles is likely to be reduced.
  • the upper limit of the reaction time of the saponification reaction can be appropriately set in consideration of the production efficiency.
  • the reaction time of the saponification reaction is, for example, preferably 4 hours or less, more preferably 3 hours or less, still more preferably 2 hours or less.
  • the reaction time of the saponification reaction is not more than the above upper limit value, the time required for one production step can be shortened and the production efficiency becomes high.
  • the reaction temperature of the saponification reaction is preferably 90 ° C. or higher, more preferably 93 ° C. or higher, and even more preferably 95 ° C. or higher.
  • the reaction temperature of the saponification reaction is preferably 100 ° C. or lower, more preferably 98 ° C. or lower, and even more preferably 95 ° C. or lower.
  • the amount of substance of the hydroxyl group in the basic compound is preferably 90 mol% or more, more preferably 95 mol% or more, based on 100 mol% of the number of moles of the acetyl group of cellulose acetate. , 98 mol% or more is more preferable.
  • the upper limit of the amount of substance of the hydroxyl group in the basic compound can be appropriately set in consideration of the production cost.
  • the amount of substance of the hydroxyl group in the basic compound is preferably 100 mol% or less, for example, with respect to 100 mol% of the number of moles of the acetyl group of cellulose acetate.
  • step (d) water is removed from the saponified aqueous dispersion obtained in the step (c), and the cellulose particles are dried.
  • the method for removing water from the saponified aqueous dispersion is not particularly limited.
  • a method of removing water by solid-liquid separation can be mentioned.
  • the time and temperature of solid-liquid separation can be appropriately set according to the use of the cellulose particles.
  • the details and preferred embodiments of the cellulose particles obtained by the method for producing cellulose particles of the present invention can be the same as those described in the above section ⁇ Cellulose particles>.
  • a cellulose acetate solution is suspended in water to prepare a suspension in which the cellulose acetate particles are dispersed in water. Therefore, it is not necessary to make the cellulose acetate solution into droplets when the cellulose particles are made into particles. Therefore, a highly viscous cellulose acetate solution that makes it difficult to form droplets can be used for producing cellulose particles, and the concentration of cellulose acetate in the cellulose acetate solution can be increased. As a result, the amount of cellulose acetate charged can be increased, the yield of the cellulose particles obtained in one production step can be increased, and the cellulose particles can be produced at low cost.
  • the cellulose acetate particles are saponified to obtain cellulose particles so that the acetic acid concentration is 0.5 ppm or less. Therefore, the acetic acid odor of the obtained cellulose particles is reduced.
  • the cellulose particles according to the present invention can be used as environmentally friendly microbeads used in fillers such as paints, plastics, adhesives, cosmetics, paper coating materials, textile processing materials, writing tools, and markers.
  • acetic acid concentration was measured using a headspace-gas chromatograph-mass spectrometer (Agilent 7697A Headspace Sampler, Agilent 7890B GCsystem, Agilent 5977B MSD).
  • volume average particle size The volume average particle size of the cellulose particles was measured as a 50% integrated volume particle size obtained from the data obtained by measuring with a laser diffraction type particle size distribution meter (“SALD2100” manufactured by Shimadzu Corporation).
  • Viscosity of cellulose solution The viscosity of the cellulose solution was measured under the condition of a temperature of 25 ° C. using a BL type rotational viscometer (“RB-85L” manufactured by Toki Sangyo Co., Ltd.).
  • Example 1 720 g of ethyl acetate was placed in a separable flask equipped with a 2 L stirrer, and 180 g of cellulose acetate (vinegarization degree 55%) was dissolved therein to prepare a cellulose acetate solution.
  • the viscosity of this solution at 25 ° C. was 146000 mPa ⁇ s.
  • 300 g of water was placed in a separable flask equipped with a 2 L stirrer, and 5.0 g of hydroxypropyl methylcellulose (Metro's 90SH-100, manufactured by Shin-Etsu Chemical Co., Ltd.) and 1.0 g of sodium lauryl sulfate were dissolved therein.
  • a dispersion medium aqueous solution was prepared.
  • a dispersion medium aqueous solution was added to the cellulose acetate solution to prepare a suspension.
  • the suspension was heated to 90 ° C. while stirring at a rotation speed of 300 rpm of the stirrer, and ethyl acetate was volatilized from the suspension over 2 hours.
  • the temperature was raised to 95 ° C., 70 g of sodium hydroxide was added, and the mixture was held for 1.5 hours to remove the acetyl group from the cellulose acetate particles to obtain cellulose particles.
  • a slurry in which cellulose particles were dispersed in water was obtained.
  • Example 1 The acetic acid concentration of the cellulose particles obtained in Example 1 was 0.00 ppm, and there was no acetic acid odor.
  • Example 2 783 g of ethyl acetate was placed in a separable flask equipped with a 2 L stirrer, and 117 g of cellulose acetate (vinegarization degree 55%) was dissolved therein to prepare a cellulose acetate solution.
  • the viscosity of this solution at 25 ° C. was 6200 mPa ⁇ s.
  • 300 g of water was placed in a separable flask equipped with a 2 L stirrer, and 4.0 g of hydroxypropyl methylcellulose (Metro's 90SH-100, manufactured by Shin-Etsu Chemical Co., Ltd.) and 1.0 g of sodium lauryl sulfate were dissolved therein.
  • a dispersion medium aqueous solution was prepared.
  • a dispersion medium aqueous solution was added to the cellulose acetate solution to prepare a suspension.
  • the suspension was heated to 90 ° C. while stirring at a rotation speed of 300 rpm of the stirrer, and ethyl acetate was volatilized from the suspension over 2 hours.
  • the temperature was raised to 95 ° C., 70 g of sodium hydroxide was added, and the mixture was held for 1.5 hours to remove the acetyl group from the cellulose acetate particles to obtain cellulose particles.
  • a slurry in which cellulose particles were dispersed in water was obtained.
  • Example 2 The acetic acid concentration of the cellulose particles obtained in Example 2 was 0.00 ppm, and there was no acetic acid odor.
  • Example 3 720 g of ethyl acetate was placed in a separable flask equipped with a 2 L stirrer, and 180 g of cellulose acetate (vinegarization degree 55%) was dissolved therein to prepare a cellulose acetate solution.
  • the viscosity of this solution at 25 ° C. was 146000 mPa ⁇ s.
  • 300 g of water was placed in a separable flask equipped with a 2 L stirrer, and 0.8 g of hydroxypropyl methylcellulose (Metro's 90SH-100, manufactured by Shin-Etsu Chemical Co., Ltd.) and 1.0 g of sodium lauryl sulfate were dissolved therein.
  • a dispersion medium aqueous solution was prepared.
  • a dispersion medium aqueous solution was added to the cellulose acetate solution to prepare a suspension.
  • the suspension was heated to 90 ° C. while stirring at a rotation speed of 300 rpm of the stirrer, and ethyl acetate was volatilized from the suspension over 2 hours.
  • the temperature was raised to 95 ° C., 70 g of sodium hydroxide was added, and the mixture was held for 1.5 hours to remove the acetyl group from the cellulose acetate particles to obtain cellulose particles.
  • a slurry in which cellulose particles were dispersed in water was obtained.
  • Example 3 The acetic acid concentration of the cellulose particles obtained in Example 3 was 0.03 ppm, and there was no acetic acid odor.
  • Example 4 360 g of ethyl acetate and 360 g of MEK (methyl ethyl ketone) were charged in a separable flask equipped with a 2 L stirrer, and 180 g of cellulose acetate (vinegarization degree 55%) was dissolved therein to prepare a cellulose acetate solution.
  • the viscosity of this solution at 25 ° C. was 51100 mPa ⁇ s.
  • Example 5 576 g of ethyl acetate and 144 g of acetone were charged in a separable flask equipped with a 2 L stirrer, and 180 g of cellulose acetate (degree of vinegarization 55%) was dissolved therein to prepare a cellulose acetate solution.
  • the viscosity of this solution at 25 ° C. was 54,800 mPa ⁇ s.
  • Example 6 576 g of ethyl acetate and 144 g of MEK were charged in a separable flask equipped with a 2 L stirrer, and 180 g of cellulose acetate (degree of vinegarization 55%) was dissolved therein to prepare a cellulose acetate solution.
  • the viscosity of this solution at 25 ° C. was 54,800 mPa ⁇ s.
  • Example 7 705 g of ethyl acetate was placed in a separable flask equipped with a 2 L stirrer, and 45 g of cellulose acetate (vinegarization degree 55%) was dissolved therein to prepare a cellulose acetate solution.
  • the viscosity of this solution at 25 ° C. was 2300 mPa ⁇ s.
  • 750 g of water was placed in a separable flask equipped with a 2 L stirrer, and 25.0 g of hydroxypropyl methylcellulose (Metroze 90SH-100, manufactured by Shin-Etsu Chemical Co., Ltd.) and 4.0 g of sodium lauryl sulfate were dissolved therein.
  • a dispersion medium aqueous solution was prepared.
  • a dispersion medium aqueous solution was added to the cellulose acetate solution to prepare a suspension.
  • the suspension was heated to 90 ° C. while stirring at a rotation speed of 300 rpm of the stirrer, and ethyl acetate was volatilized from the suspension over 2 hours.
  • the temperature was raised to 95 ° C., 70 g of sodium hydroxide was added, and the mixture was held for 1.5 hours to remove the acetyl group from the cellulose acetate particles to obtain cellulose particles.
  • a slurry in which cellulose particles were dispersed in water was obtained.
  • Example 7 The acetic acid concentration of the cellulose particles obtained in Example 7 was 0.00 ppm, and there was no acetic acid odor.
  • Example 8 702 g of ethyl acetate was placed in a separable flask equipped with a 2 L stirrer, and 198 g of cellulose acetate (vinegarization degree 55%) was dissolved therein to prepare a cellulose acetate solution.
  • the viscosity of this solution at 25 ° C. was 295,000 mPa ⁇ s.
  • 300 g of water was placed in a separable flask equipped with a 2 L stirrer, and 5.0 g of hydroxypropyl methylcellulose (Metro's 90SH-100, manufactured by Shin-Etsu Chemical Co., Ltd.) and 1.0 g of sodium lauryl sulfate were dissolved therein.
  • a dispersion medium aqueous solution was prepared.
  • a dispersion medium aqueous solution was added to the cellulose acetate solution to prepare a suspension.
  • the suspension was heated to 90 ° C. while stirring at a rotation speed of 300 rpm of the stirrer, and ethyl acetate was volatilized from the suspension over 2 hours.
  • the temperature was raised to 95 ° C., 70 g of sodium hydroxide was added, and the mixture was held for 1.5 hours to remove the acetyl group from the cellulose acetate particles to obtain cellulose particles.
  • a slurry in which cellulose particles were dispersed in water was obtained.
  • Example 8 The acetic acid concentration of the cellulose particles obtained in Example 8 was 0.01 ppm, and there was no acetic acid odor.
  • ⁇ Comparative example 1> 720 g of ethyl acetate was placed in a separable flask equipped with a 2 L stirrer, and 180 g of cellulose acetate (vinegarization degree 55%) was dissolved therein to prepare a cellulose acetate solution.
  • the viscosity of this solution at 25 ° C. was 146000 mPa ⁇ s.
  • 300 g of water was placed in a separable flask equipped with a 2 L stirrer, and 5.0 g of hydroxypropyl methylcellulose (Metro's 90SH-100, manufactured by Shin-Etsu Chemical Co., Ltd.) and 1.0 g of sodium lauryl sulfate were dissolved therein.
  • a dispersion medium aqueous solution was prepared.
  • a dispersion medium aqueous solution was added to the cellulose acetate solution to prepare a suspension.
  • the suspension was heated to 90 ° C. while stirring at a rotation speed of 300 rpm of the stirrer, and ethyl acetate was volatilized from the suspension over 2 hours.
  • the temperature was raised to 95 ° C., 70 g of sodium hydroxide was added, and the mixture was held for 1.0 hour to remove the acetyl group from the cellulose acetate particles to obtain cellulose particles.
  • a slurry in which cellulose particles were dispersed in water was obtained.

Abstract

The present invention provides: cellulose particles which are suppressed in acetic acid odor; and a method for producing cellulose particles, by which the above-described cellulose particles are able to be easily produced at low cost.　Cellulose particles according to the present invention have an average particle diameter of from 1 to 300 μm, while having an acetic acid concentration of 0.5 ppm or less. In a method for producing cellulose particles according to the present invention, a cellulose acetate solution obtained by dissolving cellulose acetate into an organic solvent is suspended in water, thereby preparing a suspension liquid wherein cellulose acetate particles are dispersed in water; the organic solvent is removed from the suspension liquid; and the cellulose acetate particles are saponified so that the acetic acid concentration is 0.5 ppm or less, thereby obtaining cellulose particles.

Description

セルロース粒子、セルロース粒子の製造方法Cellulose particles, manufacturing method of cellulose particles
　本発明は、セルロース粒子、セルロース粒子の製造方法に関する。
　本願は、２０１９年１２月５日に、日本に出願された特願２０１９－２２０３２８号に基づき優先権を主張し、その内容をここに援用する。 The present invention relates to cellulose particles and a method for producing cellulose particles.
The present application claims priority based on Japanese Patent Application No. 2019-220328 filed in Japan on December 5, 2019, the contents of which are incorporated herein by reference.
　従来、アクリルビーズ、ポリスチレンビーズ、ポリウレタンビーズ等の粒子が、塗料、プラスチック、粘着剤、化粧品等の種々の製品に使用されている。
　近年、海洋環境におけるマイクロプラスチックの問題が大きく取り上げられているため、天然物を原料とするマイクロメートルスケールのセルロース粒子のニーズが高まっている。 Conventionally, particles such as acrylic beads, polystyrene beads, and polyurethane beads have been used in various products such as paints, plastics, adhesives, and cosmetics.
In recent years, the issue of microplastics in the marine environment has been widely addressed, and the need for micrometer-scale cellulose particles made from natural products is increasing.
　セルロース粒子の製造方法としては、特許文献１に記載の方法が知られている。特許文献１には下記の方法１、２が記載されている。
・方法１：セルロースエステルの有機溶媒中の溶液を原液として、乾式紡糸法により製造したセルロースエステルのフィラメントを切断してチップとし、チップを媒体中で加熱溶融することによりセルロースエステルの球状粒子を形成し、次いで球状粒子を鹸化する方法。
・方法２：セルロースエステルの有機溶媒中の溶液を原液として、原液をその有機溶媒に溶解しないかまたはわずかしか溶解しない媒体中に懸濁させ、懸濁粒子を含有する媒体を加熱して有機溶媒を蒸発させることにより、セルロースエステルの球状粒子を形成し、次いで球状粒子を鹸化する方法。 As a method for producing cellulose particles, the method described in Patent Document 1 is known. Patent Document 1 describes the following methods 1 and 2.
-Method 1: Using a solution of cellulose ester in an organic solvent as a stock solution, the filament of cellulose ester produced by the dry spinning method is cut into chips, and the chips are heated and melted in a medium to form spherical particles of cellulose ester. And then the method of saponifying spherical particles.
Method 2: Using a solution of cellulose ester in an organic solvent as a stock solution, suspend the stock solution in a medium in which the stock solution is insoluble or slightly soluble in the organic solvent, and heat the medium containing the suspended particles to heat the organic solvent. A method of forming spherical particles of cellulose ester by evaporating the above, and then saponifying the spherical particles.
特公昭５５－４０６１８号公報Special Publication No. 55-40618
　しかし、方法１、２で得られるセルロース粒子にあっては、酢酸セルロースとセルロースの混合物を主成分とするため、酢酸セルロースの割合が高くなり、粒子に酢酸臭が残る場合がある。酢酸臭が残存したセルロース粒子にあっては、塗料、プラスチック、粘着剤、化粧品等の製品に適用した際に、これらの製品の用途が限定されるおそれがある。 However, since the cellulose particles obtained by Methods 1 and 2 contain a mixture of cellulose acetate and cellulose as the main component, the proportion of cellulose acetate is high, and the acetic acid odor may remain in the particles. Cellulose particles with residual acetic acid odor may limit the use of these products when applied to products such as paints, plastics, adhesives, and cosmetics.
　加えて、一般に酢酸セルロースが有機溶媒に溶解した溶液は粘度が著しく高くなる。そのため、液滴化できる程度の粘度となるように酢酸セルロース溶液中の酢酸セルロースの濃度を低くすると、酢酸セルロースの仕込み量が少なくなり、セルロース粒子の収量が低下する。一方で、酢酸セルロース溶液中の酢酸セルロースの濃度を高くすると、酢酸セルロース溶液の液滴化が困難である。
　このように従来の方法では、低コストでマイクロメートルスケールのセルロース粒子を製造できない。
　そこで本発明は、酢酸臭が抑えられたセルロース粒子；前記セルロース粒子を低コストで簡便に製造できるセルロース粒子の製造方法を提供する。 In addition, in general, a solution in which cellulose acetate is dissolved in an organic solvent has a significantly high viscosity. Therefore, if the concentration of cellulose acetate in the cellulose acetate solution is lowered so that the viscosity can be formed into droplets, the amount of cellulose acetate charged is reduced, and the yield of cellulose particles is lowered. On the other hand, if the concentration of cellulose acetate in the cellulose acetate solution is increased, it is difficult to make the cellulose acetate solution into droplets.
As described above, the conventional method cannot produce micrometer-scale cellulose particles at low cost.
Therefore, the present invention provides cellulose particles in which the odor of acetic acid is suppressed; a method for producing cellulose particles, which can easily produce the cellulose particles at low cost.
　本発明は下記の態様を有する。
［１］　平均粒子径が１～３００μｍであり、酢酸濃度が０．５ｐｐｍ以下である、セルロース粒子。
［２］　球状である、［１］のセルロース粒子。
［３］　セルロースの含有量が９２質量％以上である、［１］または［２］のセルロース粒子。
［４］　酢酸セルロースが有機溶媒に溶解した酢酸セルロース溶液を水中に懸濁させ、酢酸セルロース粒子が水中に分散した懸濁液を調製し、前記懸濁液から前記有機溶媒を除去し、酢酸濃度が０．５ｐｐｍ以下となるように、前記酢酸セルロース粒子を鹸化してセルロース粒子とする、セルロース粒子の製造方法。
［５］　前記懸濁液を調製する際に、前記酢酸セルロース溶液に水を添加し、次いで、水相と有機溶媒相とを逆転させることにより、前記酢酸セルロース溶液を水中に懸濁させる、［４］のセルロース粒子の製造方法。
［６］　前記酢酸セルロース溶液の粘度が２０００～３０００００ｍＰａ・ｓである、［４］または［５］のセルロース粒子の製造方法。
［７］　メチルセルロース、ヒドロキシエチルセルロース、ヒドロキシプロピルメチルセルロースおよびカルボキシメチルセルロースからなる群から選ばれる少なくとも一つ以上のセルロース系水溶性樹脂の存在下で、前記酢酸セルロース溶液を水中に懸濁させる、［４］～［６］のいずれかのセルロース粒子の製造方法。
［８］　界面活性剤の存在下で前記酢酸セルロース溶液を水中に懸濁させる、［４］～［７］のいずれかのセルロース粒子の製造方法。 The present invention has the following aspects.
[1] Cellulose particles having an average particle size of 1 to 300 μm and an acetic acid concentration of 0.5 ppm or less.
[2] Cellulose particles of [1], which are spherical.
[3] Cellulose particles of [1] or [2] having a cellulose content of 92% by mass or more.
[4] A cellulose acetate solution in which cellulose acetate is dissolved in an organic solvent is suspended in water to prepare a suspension in which cellulose acetate particles are dispersed in water, and the organic solvent is removed from the suspension to obtain an acetic acid concentration. A method for producing cellulose particles, wherein the cellulose acetate particles are saponified to obtain cellulose particles so that the amount is 0.5 ppm or less.
[5] When preparing the suspension, water is added to the cellulose acetate solution, and then the aqueous phase and the organic solvent phase are reversed to suspend the cellulose acetate solution in water. 4] Method for producing cellulose particles.
[6] The method for producing cellulose particles according to [4] or [5], wherein the cellulose acetate solution has a viscosity of 2000 to 300,000 mPa · s.
[7] The cellulose acetate solution is suspended in water in the presence of at least one cellulosic water-soluble resin selected from the group consisting of methyl cellulose, hydroxyethyl cellulose, hydroxypropyl methyl cellulose and carboxymethyl cellulose, [4] to The method for producing cellulose particles according to any one of [6].
[8] The method for producing cellulose particles according to any one of [4] to [7], wherein the cellulose acetate solution is suspended in water in the presence of a surfactant.
　本発明によれば、酢酸臭が抑えられたセルロース粒子が提供される。
　本発明によれば、酢酸臭が抑えられたセルロース粒子を低コストで簡便に製造できるセルロース粒子の製造方法が提供される。 According to the present invention, cellulose particles having suppressed acetic acid odor are provided.
According to the present invention, there is provided a method for producing cellulose particles, which can easily produce cellulose particles having suppressed acetic acid odor at low cost.
＜セルロース粒子＞
　本発明のセルロース粒子は、セルロースを含む粒子である。通常、セルロース粒子は球状の粒子である。ただし、セルロース粒子の形状は球状に限定されない。２以上の粒子が結合した凝集物、異形のセルロース粒子が微量ながらも製造の際に意図せずに混入する可能性がある。
　本発明のセルロース粒子は、後述のように酢酸濃度がきわめて低水準に低減されていることから、実質的にセルロースからなる粒子であるとも言える。このように本発明のセルロース粒子は、セルロースの割合が非常に高く、高純度のセルロース粒子である。
　本発明のセルロース粒子は、本発明の効果を損なわない範囲内で、セルロース以外の他の成分をさらに含んでもよい。他の成分としては、例えば、微量の酢酸セルロース、懸濁安定剤、界面活性剤、水分、製造時に残存した有機溶媒、有機フィラー、無機フィラー、顔料、薬材等が挙げられる。ただし、他の成分はこれらの例示に限定されない。
　ここで、セルロース粒子の主要な成分の組成について言及すると、セルロースの含有量は、１粒のセルロース粒子１００質量％に対して、９２質量％以上が好ましく、９５質量％以上がより好ましく、９８質量％以上がさらに好ましい。
　水分の含有量は、１粒のセルロース粒子１００質量％に対して、８質量％以下が好ましく、５質量％以下がより好ましく、２質量％以下がさらに好ましい。
　有機溶媒の含有量は、１粒のセルロース粒子１００質量％に対して、０．０１質量％以下が好ましく、０．００８質量％以下がより好ましく、０．００５質量％以下がさらに好ましい。 <Cellulose particles>
The cellulose particles of the present invention are particles containing cellulose. Usually, the cellulose particles are spherical particles. However, the shape of the cellulose particles is not limited to a spherical shape. There is a possibility that agglomerates in which two or more particles are bonded and irregularly shaped cellulose particles may be unintentionally mixed in during production, although the amount is small.
Since the acetic acid concentration of the cellulose particles of the present invention is reduced to an extremely low level as described later, it can be said that the particles are substantially composed of cellulose. As described above, the cellulose particles of the present invention are high-purity cellulose particles having a very high proportion of cellulose.
The cellulose particles of the present invention may further contain components other than cellulose as long as the effects of the present invention are not impaired. Examples of other components include trace amounts of cellulose acetate, suspension stabilizers, surfactants, water, organic solvents remaining during production, organic fillers, inorganic fillers, pigments, pharmaceutical materials and the like. However, other components are not limited to these examples.
Here, referring to the composition of the main components of the cellulose particles, the content of cellulose is preferably 92% by mass or more, more preferably 95% by mass or more, and 98% by mass with respect to 100% by mass of one cellulose particle. % Or more is more preferable.
The water content is preferably 8% by mass or less, more preferably 5% by mass or less, still more preferably 2% by mass or less, based on 100% by mass of one cellulose particle.
The content of the organic solvent is preferably 0.01% by mass or less, more preferably 0.008% by mass or less, still more preferably 0.005% by mass or less, based on 100% by mass of one cellulose particle.
　本発明のセルロース粒子においては、酢酸濃度が０．５ｐｐｍ以下である。酢酸濃度が０．５ｐｐｍ以下の範囲内であれば、酢酸濃度は特に限定されず、セルロース粒子が適用される製品、製品の用途に応じて、酢酸濃度は適宜変更できる。例えば、酢酸濃度は、０．３ｐｐｍ以下が好ましく、０．２ｐｐｍ以下がより好ましい。酢酸濃度が０．５ｐｐｍ以下であることにより、セルロース粒子において脱アセチル化の進行が充分であり、酢酸セルロースの残存が極めて低水準に低減され、酢酸臭が抑えられる。一方、酢酸濃度が０．５ｐｐｍを超えると、脱アセチル化の進行が不充分であり、粒子に酢酸セルロースが残存し、酢酸臭が残る。
　ここで、セルロース粒子の酢酸濃度は、ヘッドスペース－ガスクロマトグラフ－質量分析計（例えば、Ａｇｉｌｅｎｔ社製「Ａｇｉｌｅｎｔ ７６９７Ａ ＨｅａｄｓｐａｃｅＳａｍｐｌｅｒ、Ａｇｉｌｅｎｔ ７８９０Ｂ ＧＣｓｙｓｔｅｍ、Ａｇｉｌｅｎｔ ５９７７Ｂ ＭＳＤ」）を用いて測定できる。 In the cellulose particles of the present invention, the acetic acid concentration is 0.5 ppm or less. As long as the acetic acid concentration is within the range of 0.5 ppm or less, the acetic acid concentration is not particularly limited, and the acetic acid concentration can be appropriately changed depending on the product to which the cellulose particles are applied and the application of the product. For example, the acetic acid concentration is preferably 0.3 ppm or less, more preferably 0.2 ppm or less. When the acetic acid concentration is 0.5 ppm or less, the progress of deacetylation of the cellulose particles is sufficient, the residual cellulose acetate is reduced to an extremely low level, and the acetic acid odor is suppressed. On the other hand, when the acetic acid concentration exceeds 0.5 ppm, the progress of deacetylation is insufficient, cellulose acetate remains in the particles, and an acetic acid odor remains.
Here, the acetic acid concentration of the cellulose particles can be measured using a headspace-gas chromatograph-mass spectrometer (for example, "Agilent 7697A Headspace Sampler, Agilent 7890B GCsystem, Agilent 5977B MSD" manufactured by Agilent).
　セルロース粒子の体積平均粒子径は、１～３００μｍである。前記数値範囲内であれば、セルロース粒子が適用される製品、製品の用途に応じて、セルロース粒子の体積平均粒子径は適宜変更できる。セルロース粒子の体積平均粒子径は、例えば、１～１５０μｍが好ましく、１～５０μｍがより好ましい。セルロース粒子の体積平均粒子径が１～３００μｍの範囲内であると、球状のセルロース粒子の製造が容易である。
　ここで、セルロース粒子の体積平均粒子径は、レーザー回折式粒度分布計（例えば、株式会社島津製作所製「ＳＡＬＤ２１００」）を用いて測定し得られたデータより求めた積算体積５０％粒子径である。 The volume average particle diameter of the cellulose particles is 1 to 300 μm. Within the above numerical range, the volume average particle diameter of the cellulose particles can be appropriately changed depending on the product to which the cellulose particles are applied and the application of the product. The volume average particle diameter of the cellulose particles is, for example, preferably 1 to 150 μm, more preferably 1 to 50 μm. When the volume average particle diameter of the cellulose particles is in the range of 1 to 300 μm, it is easy to produce spherical cellulose particles.
Here, the volume average particle size of the cellulose particles is an integrated volume of 50% particle size obtained from the data obtained by measuring with a laser diffraction type particle size distribution meter (for example, "SALD2100" manufactured by Shimadzu Corporation). ..
（作用効果）
　以上説明した本発明のセルロース粒子は、酢酸濃度が０．５ｐｐｍ以下であるため、後述の実施例で示すように、セルロース粒子の酢酸臭が低減される。 (Action effect)
Since the cellulose particles of the present invention described above have an acetic acid concentration of 0.5 ppm or less, the acetic acid odor of the cellulose particles is reduced as shown in Examples described later.
＜セルロース粒子の製造方法＞
　本発明のセルロース粒子の製造方法では、酢酸セルロースが有機溶媒に溶解した酢酸セルロース溶液を水中に懸濁させ、酢酸セルロース粒子が水中に分散した懸濁液を調製し、前記懸濁液から前記有機溶媒を除去し、酢酸濃度が０．５ｐｐｍ以下となるように、前記酢酸セルロース粒子を鹸化してセルロース粒子とする。酢酸セルロース粒子を鹸化してセルロース粒子とした後さらに、固液分離により水を除去し、セルロース粒子を乾燥させてもよい。
　本発明のセルロース粒子の製造方法は、下記の工程（ａ）～工程（ｃ）を有するとも言え、工程（ａ）～工程（ｃ）に加えて下記の工程（ｄ）をさらに有してもよいとも言える。
　工程（ａ）：酢酸セルロースが有機溶媒に溶解した酢酸セルロース溶液を水中に懸濁させ、酢酸セルロース粒子が水中に分散した懸濁液を調製する工程。
　工程（ｂ）：前記懸濁液から前記有機溶媒を除去する工程。
　工程（ｃ）：酢酸濃度が０．５ｐｐｍ以下となるように、前記酢酸セルロース粒子を鹸化してセルロース粒子とする工程。
　工程（ｄ）：工程（ｃ）で得られた鹸化後の水性分散液から水を除去し、セルロース粒子を乾燥させる工程。 <Manufacturing method of cellulose particles>
In the method for producing cellulose particles of the present invention, a cellulose acetate solution in which cellulose acetate is dissolved in an organic solvent is suspended in water, a suspension in which cellulose acetate particles are dispersed in water is prepared, and the organic is prepared from the suspension. The solvent is removed, and the cellulose acetate particles are saponified to obtain cellulose particles so that the acetate concentration becomes 0.5 ppm or less. After the cellulose acetate particles are saponified into cellulose particles, water may be further removed by solid-liquid separation to dry the cellulose particles.
It can be said that the method for producing cellulose particles of the present invention has the following steps (a) to (c), and further includes the following steps (d) in addition to the steps (a) to (c). It can be said that it is also good.
Step (a): A step of suspending a cellulose acetate solution in which cellulose acetate is dissolved in an organic solvent in water to prepare a suspension in which cellulose acetate particles are dispersed in water.
Step (b): A step of removing the organic solvent from the suspension.
Step (c): A step of saponifying the cellulose acetate particles into cellulose particles so that the acetic acid concentration is 0.5 ppm or less.
Step (d): A step of removing water from the saponified aqueous dispersion obtained in step (c) and drying the cellulose particles.
　工程（ａ）では、酢酸セルロースが有機溶媒に溶解した酢酸セルロース溶液を水中に懸濁させ、酢酸セルロース粒子が水中に分散した懸濁液を調製する。酢酸セルロース溶液において、酢酸セルロースは有機溶媒に溶解しているため、酢酸セルロースを水中に懸濁させると、酢酸セルロース溶液が油分となり、水中に分散して、油滴を形成し、酢酸セルロースが水中に分散した懸濁液が得られる。 In step (a), a cellulose acetate solution in which cellulose acetate is dissolved in an organic solvent is suspended in water to prepare a suspension in which cellulose acetate particles are dispersed in water. In the cellulose acetate solution, since cellulose acetate is dissolved in an organic solvent, when cellulose acetate is suspended in water, the cellulose acetate solution becomes oil and disperses in water to form oil droplets, and cellulose acetate is in water. A suspension dispersed in is obtained.
　本発明における酢酸セルロースは、アセチル基の置換度、酢化率等に特に制限はない。
　酢酸セルロースとしては、例えば、モノアセチルセルロース、ジアセチルセルロース、トリアセチルセルロース等が挙げられる。これらは１種を単独で使用してもよく、２種以上を併用してもよい。 The cellulose acetate in the present invention is not particularly limited in the degree of substitution of acetyl groups, the vinegarization rate and the like.
Examples of cellulose acetate include monoacetyl cellulose, diacetyl cellulose, triacetyl cellulose and the like. One of these may be used alone, or two or more thereof may be used in combination.
　有機溶媒としては、酢酸セルロースを溶解し得る化合物であれば特に制限されない。ただし、有機溶媒としては、水への溶解度が低いものが好ましい。また、有機溶媒としては、１０１３ｈＰａにおける水との共沸点が１００℃以下であるものが好ましい。
　１０１３ｈＰａにおける水との共沸点が１００℃以下である有機溶媒としては、例えば、芳香族化合物（例えば、トルエン、ベンゼン等）、エステル化合物（例えば、酢酸メチル、酢酸エチル、酢酸ブチル等）、ケトン化合物（例えば、アセトン、メチルエチルケトン等）、飽和脂肪族炭化水素（例えば、ｎ－ヘプタン、ｎ－ヘキサン、ｎ－オクタン等）等が挙げられる。これらの有機溶媒は、１種を単独で使用してもよく、２種以上を併用してもよい。 The organic solvent is not particularly limited as long as it is a compound capable of dissolving cellulose acetate. However, as the organic solvent, one having low solubility in water is preferable. The organic solvent preferably has a co-boiling point with water at 1013 hPa of 100 ° C. or lower.
Examples of the organic solvent having a co-boiling point with water at 1013 hPa of 100 ° C. or lower include aromatic compounds (for example, toluene, benzene, etc.), ester compounds (for example, methyl acetate, ethyl acetate, butyl acetate, etc.), and ketone compounds. (For example, acetone, methyl ethyl ketone, etc.), saturated aliphatic hydrocarbons (for example, n-heptane, n-hexane, n-octane, etc.) and the like can be mentioned. These organic solvents may be used alone or in combination of two or more.
　工程（ａ）では、酢酸セルロース溶液に水を添加し、次いで、水相と有機溶媒相を逆転させることにより、酢酸セルロース溶液を水中に懸濁させることが好ましい。ここで、「水相と有機溶媒相を逆転させる」とは、セルロース溶液と水の混合液の分散状態を下記の状態１から状態２に変化させることを意味する。
・状態１：水相が有機溶媒相に対して分散している状態。
・状態２：有機溶媒相が水相に対して分散している状態。
　例えば、ビーカー、フラスコ等の容器に調製した酢酸セルロース溶液に、水又は後述の分散媒水溶液を添加し、次いで、水相と有機溶媒相とを逆転させる、という手法を採用できる。この場合、酢酸セルロース溶液の粘度が相対的に高い場合であっても、相対的に粘度の低い水又は分散媒水溶液を使用することで、酢酸セルロース粒子をマイクロメートルスケールで粒子化しやすくなる。このように、酢酸セルロース溶液に対して、水を添加するという手法を採用すると、酢酸セルロース溶液の粘度にかかわらず、マイクロメートルスケールで粒子化することができる点で、さらに簡便にセルロース粒子を製造することが可能となる。
　水相と有機溶媒相とを逆転させる際には、撹拌機を使用して攪拌するとよい。 In step (a), it is preferable to suspend the cellulose acetate solution in water by adding water to the cellulose acetate solution and then reversing the aqueous phase and the organic solvent phase. Here, "reversing the aqueous phase and the organic solvent phase" means changing the dispersed state of the mixture of the cellulose solution and water from the following state 1 to state 2.
-State 1: A state in which the aqueous phase is dispersed with respect to the organic solvent phase.
-State 2: A state in which the organic solvent phase is dispersed with respect to the aqueous phase.
For example, a method can be adopted in which water or an aqueous solution of a dispersion medium described later is added to a cellulose acetate solution prepared in a container such as a beaker or a flask, and then the aqueous phase and the organic solvent phase are reversed. In this case, even when the viscosity of the cellulose acetate solution is relatively high, the cellulose acetate particles can be easily atomized on the micrometer scale by using water having a relatively low viscosity or an aqueous solution of a dispersion medium. As described above, when the method of adding water to the cellulose acetate solution is adopted, the cellulose particles can be produced more easily because they can be granulated on the micrometer scale regardless of the viscosity of the cellulose acetate solution. It becomes possible to do.
When reversing the aqueous phase and the organic solvent phase, it is advisable to stir using a stirrer.
　酢酸セルロース溶液に、水を添加する際の酢酸セルロース溶液の質量Ｗ１に対する水の質量Ｗ２の比（Ｗ２／Ｗ１）は、０．２～３．０が好ましく、０．２５～２．０がより好ましく、０．３～１．０がさらに好ましい。前記比（Ｗ２／Ｗ１）が前記下限値以上であると、十分な酢酸セルロースの仕込み量を確保したうえで、有機溶媒に対する水の使用量が充分量となり、懸濁を行いやすいと考えられる。前記比（Ｗ２／Ｗ１）が前記上限値以下であると、有機溶媒に対する水の添加量が過剰量となりにくいと考えられる。 The ratio (W2 / W1) of the mass W2 of water to the mass W1 of the cellulose acetate solution when water is added to the cellulose acetate solution is preferably 0.2 to 3.0, more preferably 0.25 to 2.0. It is preferable, and 0.3 to 1.0 is more preferable. When the ratio (W2 / W1) is not more than the lower limit value, it is considered that the amount of water used for the organic solvent is sufficient after ensuring a sufficient amount of cellulose acetate to be charged, and suspension is easy. When the ratio (W2 / W1) is not more than the upper limit value, it is considered that the amount of water added to the organic solvent is unlikely to be excessive.
　酢酸セルロース溶液の粘度は、用途に応じて適宜設定されるが、２０００～３０００００ｍＰａ・ｓが好ましく、５０００～２５００００ｍＰａ・ｓがより好ましく、１００００～２０００００ｍＰａ・ｓがさらに好ましい。酢酸セルロース溶液の粘度が前記上限値以下であると、酢酸セルロース溶液が製造機械のシャフトに絡みつく等の問題が起きにくくなり、粒子化が容易である。酢酸セルロース溶液の粘度が前記下限値以上であると、一度の製造におけるセルロース粒子の収量が充分に多くなり、さらに低コストでセルロース粒子を得ることができる。
　ここで、粘度はＢＬ型回転粘度計（例えば、東機産業株式会社製「ＲＢ－８５Ｌ」）を用いて温度２５℃の条件下で測定される値である。 The viscosity of the cellulose acetate solution is appropriately set according to the intended use, but is preferably 2000 to 300,000 mPa · s, more preferably 5000 to 250,000 mPa · s, and even more preferably 10,000 to 200,000 mPa · s. When the viscosity of the cellulose acetate solution is not more than the above upper limit value, problems such as the cellulose acetate solution getting entangled with the shaft of the manufacturing machine are less likely to occur, and particle formation is easy. When the viscosity of the cellulose acetate solution is at least the above lower limit value, the yield of the cellulose particles in one production becomes sufficiently large, and the cellulose particles can be obtained at a lower cost.
Here, the viscosity is a value measured under the condition of a temperature of 25 ° C. using a BL type rotational viscometer (for example, "RB-85L" manufactured by Toki Sangyo Co., Ltd.).
　本発明のセルロース粒子の製造方法では、懸濁安定剤の存在下で酢酸セルロース溶液を水中に懸濁させることが好ましい。懸濁安定剤は、例えば、分散媒となる水にあらかじめ添加してもよい。懸濁安定剤を使用すると、懸濁状態が安定化する傾向があり、セルロース粒子をさらに簡便に製造できる。
　懸濁安定剤としては、例えば、セルロース系水溶性樹脂（メチルセルロース、ヒドロキシエチルセルロース、ヒドロキシプロピルメチルセルロース、カルボキシメチルセルロース等）、ポリビニルアルコール、ポリアクリル酸塩類、ポリエチレングリコール、ポリビニルピロリドン、ポリアクリルアミド、第３燐酸塩類等が挙げられる。これらの懸濁安定剤は、１種を単独で使用してもよく、２種以上を併用してもよい。 In the method for producing cellulose particles of the present invention, it is preferable to suspend the cellulose acetate solution in water in the presence of a suspension stabilizer. The suspension stabilizer may be added in advance to, for example, water as a dispersion medium. When a suspension stabilizer is used, the suspension state tends to be stabilized, and cellulose particles can be produced more easily.
Examples of the suspension stabilizer include cellulosic water-soluble resins (methyl cellulose, hydroxyethyl cellulose, hydroxypropyl methyl cellulose, carboxymethyl cellulose, etc.), polyvinyl alcohol, polyacrylates, polyethylene glycol, polyvinylpyrrolidone, polyacrylamide, and tertiary phosphates. And so on. These suspension stabilizers may be used alone or in combination of two or more.
　本発明のセルロース粒子の製造方法では、界面活性剤の存在下で酢酸セルロース溶液を水中に懸濁させることが好ましい。界面活性剤は、例えば、分散媒となる水にあらかじめ添加してもよい。界面活性剤を使用すると、懸濁状態が安定化する傾向があり、セルロース粒子をさらに簡便に製造できる。
　界面活性剤は特に限定されず、アニオン系界面活性剤でもよく、カチオン系界面活性剤でもよく、ノニオン系界面活性剤でもよく、両性界面活性剤でもよい。
　これらの界面活性剤は、１種を単独で使用してもよく、２種以上を併用してもよい。 In the method for producing cellulose particles of the present invention, it is preferable to suspend the cellulose acetate solution in water in the presence of a surfactant. The surfactant may be added in advance to, for example, water as a dispersion medium. When a surfactant is used, the suspension state tends to be stabilized, and cellulose particles can be produced more easily.
The surfactant is not particularly limited, and may be an anionic surfactant, a cationic surfactant, a nonionic surfactant, or an amphoteric surfactant.
These surfactants may be used alone or in combination of two or more.
　工程（ａ）では、分散媒水溶液をあらかじめ調製し、分散媒水溶液と酢酸セルロース溶液とを混合し、酢酸セルロース溶液を分散媒水溶液に懸濁させ、酢酸セルロース粒子が水中に分散した懸濁液を得ることが好ましい。分散媒水溶液と酢酸セルロース溶液との混合の際には、例えば、撹拌機を使用して攪拌するとよい。 In the step (a), a dispersion medium aqueous solution is prepared in advance, the dispersion medium aqueous solution and the cellulose acetate solution are mixed, the cellulose acetate solution is suspended in the dispersion medium aqueous solution, and the suspension in which the cellulose acetate particles are dispersed in water is prepared. It is preferable to obtain it. When mixing the dispersion medium aqueous solution and the cellulose acetate solution, for example, it is preferable to stir using a stirrer.
　分散媒水溶液としては、水と上述の懸濁安定剤と上述の界面活性剤とを含む液体が好ましい。
　分散媒水溶液中の懸濁安定剤の含有量は、水１００質量％に対して、０～１０質量％が好ましく、０．２～８質量％がより好ましく、０．３～７質量％がさらに好ましい。懸濁安定剤の含有量が前記下限値以上であると、酢酸セルロース粒子の懸濁状態が安定しやすく、セルロース粒子をさらに簡便に製造できる。懸濁安定剤の含有量が前記上限値以下であると、懸濁液の粘度が高くなり過ぎず、懸濁液が製造機械のシャフトに絡みつく等の問題が起きにくくなり、粒子化が容易である。
　分散媒水溶液中の界面活性剤の含有量は、水１００質量％に対して、０～５質量％が好ましく、０．１～３質量％がより好ましく、０．２～１．５質量％がさらに好ましい。分散媒水溶液中の界面活性剤の含有量が前記下限値以上であると、酢酸セルロース粒子の懸濁状態が安定しやすく、セルロース粒子をさらに簡便に製造できる。分散媒水溶液中の界面活性剤の含有量が前記上限値以下であると、攪拌による懸濁液の泡立ちが起きにくく、セルロース粒子の製造がさらに容易となる。 As the aqueous solution of the dispersion medium, a liquid containing water, the above-mentioned suspension stabilizer and the above-mentioned surfactant is preferable.
The content of the suspension stabilizer in the aqueous solution of the dispersion medium is preferably 0 to 10% by mass, more preferably 0.2 to 8% by mass, and further preferably 0.3 to 7% by mass with respect to 100% by mass of water. preferable. When the content of the suspension stabilizer is at least the above lower limit value, the suspended state of the cellulose acetate particles is likely to be stable, and the cellulose particles can be produced more easily. When the content of the suspension stabilizer is not more than the above upper limit value, the viscosity of the suspension does not become too high, problems such as the suspension getting entangled with the shaft of the manufacturing machine are less likely to occur, and particle formation is easy. is there.
The content of the surfactant in the dispersion medium aqueous solution is preferably 0 to 5% by mass, more preferably 0.1 to 3% by mass, and 0.2 to 1.5% by mass with respect to 100% by mass of water. More preferred. When the content of the surfactant in the aqueous solution of the dispersion medium is at least the above lower limit value, the suspended state of the cellulose acetate particles is likely to be stable, and the cellulose particles can be produced more easily. When the content of the surfactant in the aqueous solution of the dispersion medium is not more than the above upper limit value, foaming of the suspension due to stirring is less likely to occur, and the production of cellulose particles becomes easier.
　工程（ｂ）では、懸濁液から有機溶媒を除去する。懸濁液においては酢酸セルロース粒子および有機溶媒が油分として水中に分散していると考えられる。そのため、工程（ｂ）で有機溶媒を懸濁液から除去することで、酢酸セルロース粒子が水中に分散した水性分散液が得られる。
　工程（ｂ）では、酢酸セルロース粒子が分散した懸濁液を、前記有機溶媒の水との共沸点以上に加熱することで、有機溶媒を除去することが好ましい。工程（ｂ）で前記有機溶媒の水との共沸点以上に加熱することで、有機溶媒を充分に除去でき、セルロース粒子に残存する有機溶媒の量をきわめて低水準に低減できる。
　加熱温度は、１０１３ｈＰａで１００℃以下が好ましい。ここで有機溶媒を除去した後には、酢酸セルロース粒子は水に分散したスラリー状となっている。酢酸セルロース粒子の加熱温度を１００℃超とすると有機溶媒とともに水も揮発して除去されるため、酢酸セルロース粒子同士が融着するおそれがある。 In step (b), the organic solvent is removed from the suspension. In the suspension, it is considered that the cellulose acetate particles and the organic solvent are dispersed in water as oil. Therefore, by removing the organic solvent from the suspension in the step (b), an aqueous dispersion in which the cellulose acetate particles are dispersed in water can be obtained.
In step (b), it is preferable to remove the organic solvent by heating the suspension in which the cellulose acetate particles are dispersed to a boiling point equal to or higher than the boiling point of the organic solvent with water. By heating the organic solvent to a boiling point equal to or higher than that of water in the step (b), the organic solvent can be sufficiently removed and the amount of the organic solvent remaining in the cellulose particles can be reduced to an extremely low level.
The heating temperature is preferably 1013 hPa and 100 ° C. or lower. Here, after removing the organic solvent, the cellulose acetate particles are in the form of a slurry dispersed in water. When the heating temperature of the cellulose acetate particles exceeds 100 ° C., water is volatilized and removed together with the organic solvent, so that the cellulose acetate particles may be fused to each other.
　工程（ｃ）では、セルロース粒子の酢酸濃度が０．５ｐｐｍ以下となるように、酢酸セルロース粒子を鹸化してセルロース粒子とする。鹸化反応は、例えば、酢酸セルロース粒子が水中に分散した水性分散液と塩基性化合物とを混合し、必要に応じて加熱することで行うことができる。
　鹸化に使用する塩基性化合物は、特に制限されない。例えば、水酸化ナトリウム、水酸化カリウム、アンモニア、トリエチルアミン等が挙げられる。 In the step (c), the cellulose acetate particles are saponified to obtain cellulose particles so that the acetic acid concentration of the cellulose particles is 0.5 ppm or less. The saponification reaction can be carried out, for example, by mixing an aqueous dispersion in which cellulose acetate particles are dispersed in water and a basic compound, and heating as necessary.
The basic compound used for saponification is not particularly limited. For example, sodium hydroxide, potassium hydroxide, ammonia, triethylamine and the like can be mentioned.
　工程（ｃ）の鹸化の際には、セルロース粒子の酢酸濃度が０．５ｐｐｍ以下となるように酢酸セルロース粒子を鹸化する。
　セルロース粒子の酢酸濃度が０．５ｐｐｍ以下となるように鹸化するための具体的な手段としては、例えば下記の手段１～３が挙げられる。下記の手段１～３は１種を単独で使用してもよく、２種以上を組み合わせて併用してもよい。
・手段１：鹸化反応の反応時間をセルロース粒子の酢酸濃度が０．５ｐｐｍ以下となるように充分に長くする方法。
・手段２：鹸化反応の反応温度をセルロース粒子の酢酸濃度が０．５ｐｐｍ以下となるように充分に高くする方法。
・手段３：鹸化に使用する塩基性化合物中の水酸基の物質量を酢酸セルロース中のアセチル基の置換度、酢化率に応じて適宜調整し、セルロース粒子の酢酸濃度を０．５ｐｐｍ以下とする方法。 During the saponification in step (c), the cellulose acetate particles are saponified so that the acetic acid concentration of the cellulose particles is 0.5 ppm or less.
Specific means for saponifying the cellulose particles so that the acetic acid concentration is 0.5 ppm or less include, for example, the following means 1 to 3. The following means 1 to 3 may be used alone or in combination of two or more.
-Means 1: A method of sufficiently lengthening the reaction time of the saponification reaction so that the acetic acid concentration of the cellulose particles is 0.5 ppm or less.
-Means 2: A method of sufficiently raising the reaction temperature of the saponification reaction so that the acetic acid concentration of the cellulose particles is 0.5 ppm or less.
-Means 3: The amount of substance of the hydroxyl group in the basic compound used for saponification is appropriately adjusted according to the degree of substitution of the acetyl group in cellulose acetate and the vinegarization rate, and the acetic acid concentration of the cellulose particles is set to 0.5 ppm or less. Method.
　手段１に関し、鹸化反応の反応時間は１．５時間以上が好ましく、２時間以上がより好ましく、３時間以上がさらに好ましい。鹸化反応の反応時間が前記下限値以上であると、酢酸臭を低減するのに充分な鹸化反応が起き、脱アセチル化が充分に進行しやすく、セルロース粒子の酢酸臭を低減しやすい。鹸化反応の反応時間の上限値は、製造効率を考慮して適宜設定できる。鹸化反応の反応時間は、例えば、４時間以下が好ましく、３時間以下がより好ましく、２時間以下がさらに好ましい。鹸化反応の反応時間が前記上限値以下であると、一回の製造工程に要する時間を短縮でき、製造効率が高くなる。 Regarding means 1, the reaction time of the saponification reaction is preferably 1.5 hours or more, more preferably 2 hours or more, and even more preferably 3 hours or more. When the reaction time of the saponification reaction is at least the above lower limit value, a saponification reaction sufficient to reduce the acetic acid odor occurs, deacetylation is likely to proceed sufficiently, and the acetic acid odor of the cellulose particles is likely to be reduced. The upper limit of the reaction time of the saponification reaction can be appropriately set in consideration of the production efficiency. The reaction time of the saponification reaction is, for example, preferably 4 hours or less, more preferably 3 hours or less, still more preferably 2 hours or less. When the reaction time of the saponification reaction is not more than the above upper limit value, the time required for one production step can be shortened and the production efficiency becomes high.
　手段２に関し、鹸化反応の反応温度は、９０℃以上が好ましく、９３℃以上がより好ましく、９５℃以上がさらに好ましい。鹸化反応の反応時間が前記下限値以上であると、酢酸臭を低減するのに充分な鹸化反応が起き、脱アセチル化が充分に進行しやすく、セルロース粒子の酢酸臭を低減しやすい。鹸化反応の反応温度は、１００℃以下が好ましく、９８℃以下がより好ましく、９５℃以下がさらに好ましい。鹸化反応の反応温度が前記上限値以下であると、必要以上に反応液（酢酸セルロース粒子の水性分散液）を加温しなくて済み、低コストでセルロース粒子をさらに簡便に製造できる。 Regarding means 2, the reaction temperature of the saponification reaction is preferably 90 ° C. or higher, more preferably 93 ° C. or higher, and even more preferably 95 ° C. or higher. When the reaction time of the saponification reaction is at least the above lower limit value, a saponification reaction sufficient to reduce the acetic acid odor occurs, deacetylation is likely to proceed sufficiently, and the acetic acid odor of the cellulose particles is likely to be reduced. The reaction temperature of the saponification reaction is preferably 100 ° C. or lower, more preferably 98 ° C. or lower, and even more preferably 95 ° C. or lower. When the reaction temperature of the saponification reaction is not more than the above upper limit value, it is not necessary to heat the reaction solution (aqueous dispersion of cellulose acetate particles) more than necessary, and the cellulose particles can be produced more easily at low cost.
　手段３に関し、塩基性化合物中の水酸基の物質量は、酢酸セルロースのアセチル基のモル数１００モル％に対して、９０モル％以上とすることが好ましく、９５モル％以上とすることがより好ましく、９８モル％以上とすることがさらに好ましい。塩基性化合物中の水酸基の物質量が前記下限値以上であると、酢酸臭を低減するのに充分な鹸化反応が起き、脱アセチル化が充分に進行しやすく、セルロース粒子の酢酸臭を低減しやすい。塩基性化合物中の水酸基の物質量の上限値は、製造コストを考慮して適宜設定できる。塩基性化合物中の水酸基の物質量は、例えば、酢酸セルロースのアセチル基のモル数１００モル％に対して、１００モル％以下が好ましい。 Regarding the means 3, the amount of substance of the hydroxyl group in the basic compound is preferably 90 mol% or more, more preferably 95 mol% or more, based on 100 mol% of the number of moles of the acetyl group of cellulose acetate. , 98 mol% or more is more preferable. When the amount of substance of the hydroxyl group in the basic compound is equal to or higher than the above lower limit value, a saponification reaction sufficient to reduce the acetic acid odor occurs, deacetylation easily proceeds sufficiently, and the acetic acid odor of the cellulose particles is reduced. Cheap. The upper limit of the amount of substance of the hydroxyl group in the basic compound can be appropriately set in consideration of the production cost. The amount of substance of the hydroxyl group in the basic compound is preferably 100 mol% or less, for example, with respect to 100 mol% of the number of moles of the acetyl group of cellulose acetate.
　工程（ｄ）では、工程（ｃ）で得られた鹸化後の水性分散液から水を除去し、セルロース粒子を乾燥させる。鹸化後の水性分散液から水を除去する方法は、特に制限されない。例えば、固液分離により水を除去する方法が挙げられる。固液分離の時間、温度は、セルロース粒子の用途に応じて適宜設定できる。
　本発明のセルロース粒子の製造方法によって得られるセルロース粒子の詳細および好ましい態様は、上述の＜セルロース粒子＞の項で説明した内容と同内容とすることができる。 In the step (d), water is removed from the saponified aqueous dispersion obtained in the step (c), and the cellulose particles are dried. The method for removing water from the saponified aqueous dispersion is not particularly limited. For example, a method of removing water by solid-liquid separation can be mentioned. The time and temperature of solid-liquid separation can be appropriately set according to the use of the cellulose particles.
The details and preferred embodiments of the cellulose particles obtained by the method for producing cellulose particles of the present invention can be the same as those described in the above section <Cellulose particles>.
（作用効果）
　以上説明した本発明のセルロース粒子の製造方法では、酢酸セルロース溶液を水中に懸濁させ、酢酸セルロース粒子が水中に分散した懸濁液を調製する。そのため、セルロース粒子の粒子化に際して、酢酸セルロース溶液の液滴化をする必要がない。よって、液滴化が困難となるような高粘度の酢酸セルロース溶液をセルロース粒子の製造に使用でき、当該酢酸セルロース溶液中の酢酸セルロースの濃度を高くすることができる。その結果、酢酸セルロースの仕込み量を多くすることができ、一度の製造工程で得られるセルロース粒子の収量が上昇し、低コストでセルロース粒子を製造できる。
　以上説明した本発明のセルロース粒子の製造方法では、酢酸濃度が０．５ｐｐｍ以下となるように酢酸セルロース粒子を鹸化してセルロース粒子とする。そのため、得られるセルロース粒子の酢酸臭が低減される。 (Action effect)
In the method for producing cellulose particles of the present invention described above, a cellulose acetate solution is suspended in water to prepare a suspension in which the cellulose acetate particles are dispersed in water. Therefore, it is not necessary to make the cellulose acetate solution into droplets when the cellulose particles are made into particles. Therefore, a highly viscous cellulose acetate solution that makes it difficult to form droplets can be used for producing cellulose particles, and the concentration of cellulose acetate in the cellulose acetate solution can be increased. As a result, the amount of cellulose acetate charged can be increased, the yield of the cellulose particles obtained in one production step can be increased, and the cellulose particles can be produced at low cost.
In the method for producing cellulose particles of the present invention described above, the cellulose acetate particles are saponified to obtain cellulose particles so that the acetic acid concentration is 0.5 ppm or less. Therefore, the acetic acid odor of the obtained cellulose particles is reduced.
（用途）
　本発明に係るセルロース粒子は、塗料、プラスチック、粘着剤、化粧品、紙塗工材、繊維加工材、筆記具、マーカー等のフィラー等に使用される親環境的なマイクロビーズとして利用できる。 (Use)
The cellulose particles according to the present invention can be used as environmentally friendly microbeads used in fillers such as paints, plastics, adhesives, cosmetics, paper coating materials, textile processing materials, writing tools, and markers.
　以下、本発明を実施例により具体的に説明するが、本発明は以下の記載によっては限定されない。 Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to the following description.
＜測定方法＞
（酢酸濃度）
　酢酸濃度は、ヘッドスペース－ガスクロマトグラフ－質量分析計（Ａｇｉｌｅｎｔ社製「Ａｇｉｌｅｎｔ ７６９７Ａ Ｈｅａｄｓｐａｃｅ Ｓａｍｐｌｅｒ、Ａｇｉｌｅｎｔ ７８９０Ｂ ＧＣｓｙｓｔｅｍ、Ａｇｉｌｅｎｔ ５９７７Ｂ ＭＳＤ」）を用いて測定した。 <Measurement method>
(Acetic acid concentration)
The acetic acid concentration was measured using a headspace-gas chromatograph-mass spectrometer (Agilent 7697A Headspace Sampler, Agilent 7890B GCsystem, Agilent 5977B MSD).
（体積平均粒子径）
　セルロース粒子の体積平均粒子径は、レーザー回折式粒度分布計（株式会社島津製作所製「ＳＡＬＤ２１００」）を用いて測定し得られたデータより求めた積算体積５０％粒子径として測定した。 (Volume average particle size)
The volume average particle size of the cellulose particles was measured as a 50% integrated volume particle size obtained from the data obtained by measuring with a laser diffraction type particle size distribution meter (“SALD2100” manufactured by Shimadzu Corporation).
（セルロース溶液の粘度）
　セルロース溶液の粘度は、ＢＬ型回転粘度計（東機産業株式会社製「ＲＢ－８５Ｌ」）を用いて温度２５℃の条件下で測定した。 (Viscosity of cellulose solution)
The viscosity of the cellulose solution was measured under the condition of a temperature of 25 ° C. using a BL type rotational viscometer (“RB-85L” manufactured by Toki Sangyo Co., Ltd.).
＜実施例１＞
　２Ｌ攪拌機付きセパラブルフラスコに酢酸エチル７２０ｇを仕込み、この中に酢酸セルロース（酢化度５５％）１８０ｇを溶解して酢酸セルロース溶液を調製した。この溶液の２５℃における粘度は１４６０００ｍＰａ・ｓであった。
　これとは別に、２Ｌ攪拌機付きセパラブルフラスコに水３００ｇを仕込み、この中にヒドロキシプロピルメチルセルロース（メトローズ９０ＳＨ－１００、信越化学工業株式会社製）５．０ｇとラウリル硫酸ナトリウム１．０ｇを溶解して分散媒水溶液を調製した。
　酢酸セルロース溶液に分散媒水溶液を添加して、懸濁液を調製した。次いで、攪拌機の回転数３００ｒｐｍで攪拌しながら懸濁液を９０℃に昇温し、２時間かけて懸濁液から酢酸エチルを揮発させた。次いで、９５℃に昇温し、水酸化ナトリウムを７０ｇ添加して、１．５時間保持し、酢酸セルロース粒子からアセチル基を脱離させ、セルロース粒子を得た。これにより、水中にセルロース粒子が分散したスラリーを得た。
　次いで、スラリーを室温まで冷却した後、ろ過により固液分離し、回収した固形物を水で充分洗浄した後、７０℃で２０時間乾燥して、体積平均粒子径６．８μｍの球状のセルロース粒子を得た。
　実施例１で得たセルロース粒子の酢酸濃度は０．００ｐｐｍであり、酢酸臭は無かった。 <Example 1>
720 g of ethyl acetate was placed in a separable flask equipped with a 2 L stirrer, and 180 g of cellulose acetate (vinegarization degree 55%) was dissolved therein to prepare a cellulose acetate solution. The viscosity of this solution at 25 ° C. was 146000 mPa · s.
Separately, 300 g of water was placed in a separable flask equipped with a 2 L stirrer, and 5.0 g of hydroxypropyl methylcellulose (Metro's 90SH-100, manufactured by Shin-Etsu Chemical Co., Ltd.) and 1.0 g of sodium lauryl sulfate were dissolved therein. A dispersion medium aqueous solution was prepared.
A dispersion medium aqueous solution was added to the cellulose acetate solution to prepare a suspension. Then, the suspension was heated to 90 ° C. while stirring at a rotation speed of 300 rpm of the stirrer, and ethyl acetate was volatilized from the suspension over 2 hours. Then, the temperature was raised to 95 ° C., 70 g of sodium hydroxide was added, and the mixture was held for 1.5 hours to remove the acetyl group from the cellulose acetate particles to obtain cellulose particles. As a result, a slurry in which cellulose particles were dispersed in water was obtained.
Next, the slurry was cooled to room temperature, solid-liquid separated by filtration, and the recovered solid was thoroughly washed with water and then dried at 70 ° C. for 20 hours to obtain spherical cellulose particles having a volume average particle diameter of 6.8 μm. Got
The acetic acid concentration of the cellulose particles obtained in Example 1 was 0.00 ppm, and there was no acetic acid odor.
＜実施例２＞
　２Ｌ攪拌機付きセパラブルフラスコに酢酸エチル７８３ｇを仕込み、この中に酢酸セルロース（酢化度５５％）１１７ｇを溶解して酢酸セルロース溶液を調製した。この溶液の２５℃における粘度は６２００ｍＰａ・ｓであった。
　これとは別に、２Ｌ攪拌機付きセパラブルフラスコに水３００ｇを仕込み、この中にヒドロキシプロピルメチルセルロース（メトローズ９０ＳＨ－１００、信越化学工業株式会社製）４．０ｇとラウリル硫酸ナトリウム１．０ｇを溶解して分散媒水溶液を調製した。
　酢酸セルロース溶液に分散媒水溶液を添加して、懸濁液を調製した。次いで、攪拌機の回転数３００ｒｐｍで攪拌しながら懸濁液を９０℃に昇温し、２時間かけて懸濁液から酢酸エチルを揮発させた。次いで、９５℃に昇温し、水酸化ナトリウムを７０ｇ添加して、１．５時間保持し、酢酸セルロース粒子からアセチル基を脱離させ、セルロース粒子を得た。これにより、水中にセルロース粒子が分散したスラリーを得た。
　次いで、スラリーを室温まで冷却した後、ろ過により固液分離し、回収した固形物を水で充分洗浄した後、７０℃で２０時間乾燥して、体積平均粒子径６．９μｍの球状のセルロース粒子を得た。
　実施例２で得たセルロース粒子の酢酸濃度は０．００ｐｐｍであり、酢酸臭は無かった。 <Example 2>
783 g of ethyl acetate was placed in a separable flask equipped with a 2 L stirrer, and 117 g of cellulose acetate (vinegarization degree 55%) was dissolved therein to prepare a cellulose acetate solution. The viscosity of this solution at 25 ° C. was 6200 mPa · s.
Separately, 300 g of water was placed in a separable flask equipped with a 2 L stirrer, and 4.0 g of hydroxypropyl methylcellulose (Metro's 90SH-100, manufactured by Shin-Etsu Chemical Co., Ltd.) and 1.0 g of sodium lauryl sulfate were dissolved therein. A dispersion medium aqueous solution was prepared.
A dispersion medium aqueous solution was added to the cellulose acetate solution to prepare a suspension. Then, the suspension was heated to 90 ° C. while stirring at a rotation speed of 300 rpm of the stirrer, and ethyl acetate was volatilized from the suspension over 2 hours. Then, the temperature was raised to 95 ° C., 70 g of sodium hydroxide was added, and the mixture was held for 1.5 hours to remove the acetyl group from the cellulose acetate particles to obtain cellulose particles. As a result, a slurry in which cellulose particles were dispersed in water was obtained.
Next, the slurry was cooled to room temperature, solid-liquid separated by filtration, and the recovered solid was thoroughly washed with water and then dried at 70 ° C. for 20 hours to obtain spherical cellulose particles having a volume average particle diameter of 6.9 μm. Got
The acetic acid concentration of the cellulose particles obtained in Example 2 was 0.00 ppm, and there was no acetic acid odor.
＜実施例３＞
　２Ｌ攪拌機付きセパラブルフラスコに酢酸エチル７２０ｇを仕込み、この中に酢酸セルロース（酢化度５５％）１８０ｇを溶解して酢酸セルロース溶液を調製した。この溶液の２５℃における粘度は１４６０００ｍＰａ・ｓであった。
　これとは別に、２Ｌ攪拌機付きセパラブルフラスコに水３００ｇを仕込み、この中にヒドロキシプロピルメチルセルロース（メトローズ９０ＳＨ－１００、信越化学工業株式会社製）０．８ｇとラウリル硫酸ナトリウム１．０ｇを溶解して分散媒水溶液を調製した。
　酢酸セルロース溶液に分散媒水溶液を添加して、懸濁液を調製した。次いで、攪拌機の回転数３００ｒｐｍで攪拌しながら懸濁液を９０℃に昇温し、２時間かけて懸濁液から酢酸エチルを揮発させた。次いで、９５℃に昇温し、水酸化ナトリウムを７０ｇ添加して、１．５時間保持し、酢酸セルロース粒子からアセチル基を脱離させ、セルロース粒子を得た。これにより、水中にセルロース粒子が分散したスラリーを得た。
　次いで、スラリーを室温まで冷却した後、ろ過により固液分離し、回収した固形物を水で充分洗浄した後、７０℃で２０時間乾燥して、体積平均粒子径１３６．３μｍの球状のセルロース粒子を得た。
　実施例３で得たセルロース粒子の酢酸濃度は０．０３ｐｐｍであり、酢酸臭は無かった。 <Example 3>
720 g of ethyl acetate was placed in a separable flask equipped with a 2 L stirrer, and 180 g of cellulose acetate (vinegarization degree 55%) was dissolved therein to prepare a cellulose acetate solution. The viscosity of this solution at 25 ° C. was 146000 mPa · s.
Separately, 300 g of water was placed in a separable flask equipped with a 2 L stirrer, and 0.8 g of hydroxypropyl methylcellulose (Metro's 90SH-100, manufactured by Shin-Etsu Chemical Co., Ltd.) and 1.0 g of sodium lauryl sulfate were dissolved therein. A dispersion medium aqueous solution was prepared.
A dispersion medium aqueous solution was added to the cellulose acetate solution to prepare a suspension. Then, the suspension was heated to 90 ° C. while stirring at a rotation speed of 300 rpm of the stirrer, and ethyl acetate was volatilized from the suspension over 2 hours. Then, the temperature was raised to 95 ° C., 70 g of sodium hydroxide was added, and the mixture was held for 1.5 hours to remove the acetyl group from the cellulose acetate particles to obtain cellulose particles. As a result, a slurry in which cellulose particles were dispersed in water was obtained.
Next, the slurry was cooled to room temperature, solid-liquid separated by filtration, and the recovered solid was thoroughly washed with water and then dried at 70 ° C. for 20 hours to obtain spherical cellulose particles having a volume average particle diameter of 136.3 μm. Got
The acetic acid concentration of the cellulose particles obtained in Example 3 was 0.03 ppm, and there was no acetic acid odor.
＜実施例４＞
　２Ｌ攪拌機付きセパラブルフラスコに酢酸エチル３６０ｇとＭＥＫ（メチルエチルケトン）３６０ｇを仕込み、この中に酢酸セルロース（酢化度５５％）１８０ｇを溶解して酢酸セルロース溶液を調製した。この溶液の２５℃における粘度は５１１００ｍＰａ・ｓであった。
　これとは別に、２Ｌ攪拌機付きセパラブルフラスコに水３００ｇを仕込み、この中にヒドロキシプロピルメチルセルロース（メトローズ９０ＳＨ－１００、信越化学工業株式会社製）４．０ｇとラウリル硫酸ナトリウム１．０ｇを溶解して分散媒水溶液を調製した。
　酢酸セルロース溶液に分散媒水溶液を添加して、懸濁液を調製した。次いで、攪拌機の回転数３００ｒｐｍで攪拌しながら懸濁液を９０℃に昇温し、２時間かけて懸濁液から酢酸エチルを揮発させた。次いで、９５℃に昇温し、水酸化ナトリウムを７０ｇ添加して、１．５時間保持し、酢酸セルロース粒子からアセチル基を脱離させ、セルロース粒子を得た。これにより、水中にセルロース粒子が分散したスラリーを得た。
　次いで、スラリーを室温まで冷却した後、ろ過により固液分離し、回収した固形物を水で充分洗浄した後、７０℃で２０時間乾燥して、体積平均粒子径１３．８μｍの球状のセルロース粒子を得た。
　実施例４で得たセルロース粒子の酢酸濃度は０．０１ｐｐｍであり、酢酸臭は無かった。 <Example 4>
360 g of ethyl acetate and 360 g of MEK (methyl ethyl ketone) were charged in a separable flask equipped with a 2 L stirrer, and 180 g of cellulose acetate (vinegarization degree 55%) was dissolved therein to prepare a cellulose acetate solution. The viscosity of this solution at 25 ° C. was 51100 mPa · s.
Separately, 300 g of water was placed in a separable flask equipped with a 2 L stirrer, and 4.0 g of hydroxypropyl methylcellulose (Metro's 90SH-100, manufactured by Shin-Etsu Chemical Co., Ltd.) and 1.0 g of sodium lauryl sulfate were dissolved therein. A dispersion medium aqueous solution was prepared.
A dispersion medium aqueous solution was added to the cellulose acetate solution to prepare a suspension. Then, the suspension was heated to 90 ° C. while stirring at a rotation speed of 300 rpm of the stirrer, and ethyl acetate was volatilized from the suspension over 2 hours. Then, the temperature was raised to 95 ° C., 70 g of sodium hydroxide was added, and the mixture was held for 1.5 hours to remove the acetyl group from the cellulose acetate particles to obtain cellulose particles. As a result, a slurry in which cellulose particles were dispersed in water was obtained.
Next, the slurry was cooled to room temperature, solid-liquid separated by filtration, and the recovered solid was thoroughly washed with water and then dried at 70 ° C. for 20 hours to obtain spherical cellulose particles having a volume average particle diameter of 13.8 μm. Got
The acetic acid concentration of the cellulose particles obtained in Example 4 was 0.01 ppm, and there was no acetic acid odor.
＜実施例５＞
　２Ｌ攪拌機付きセパラブルフラスコに酢酸エチル５７６ｇとアセトン１４４ｇを仕込み、この中に酢酸セルロース（酢化度５５％）１８０ｇを溶解して酢酸セルロース溶液を調製した。この溶液の２５℃における粘度は５４８００ｍＰａ・ｓであった。
　これとは別に、２Ｌ攪拌機付きセパラブルフラスコに水３００ｇを仕込み、この中にヒドロキシプロピルメチルセルロース（メトローズ９０ＳＨ－１００、信越化学工業株式会社製）４．０ｇとラウリル硫酸ナトリウム１．０ｇを溶解して分散媒水溶液を調製した。
　酢酸セルロース溶液に分散媒水溶液を添加して、懸濁液を調製した。次いで、攪拌機の回転数３００ｒｐｍで攪拌しながら懸濁液を９０℃に昇温し、２時間かけて懸濁液から酢酸エチルを揮発させた。次いで、９５℃に昇温し、水酸化ナトリウムを７０ｇ添加して、１．５時間保持し、酢酸セルロース粒子からアセチル基を脱離させ、セルロース粒子を得た。これにより、水中にセルロース粒子が分散したスラリーを得た。
　次いで、スラリーを室温まで冷却した後、ろ過により固液分離し、回収した固形物を水で充分洗浄した後、７０℃で２０時間乾燥して、体積平均粒子径４２．２μｍの球状のセルロース粒子を得た。
　実施例５で得たセルロース粒子の酢酸濃度は０．０２ｐｐｍであり、酢酸臭は無かった。 <Example 5>
576 g of ethyl acetate and 144 g of acetone were charged in a separable flask equipped with a 2 L stirrer, and 180 g of cellulose acetate (degree of vinegarization 55%) was dissolved therein to prepare a cellulose acetate solution. The viscosity of this solution at 25 ° C. was 54,800 mPa · s.
Separately, 300 g of water was placed in a separable flask equipped with a 2 L stirrer, and 4.0 g of hydroxypropyl methylcellulose (Metro's 90SH-100, manufactured by Shin-Etsu Chemical Co., Ltd.) and 1.0 g of sodium lauryl sulfate were dissolved therein. A dispersion medium aqueous solution was prepared.
A dispersion medium aqueous solution was added to the cellulose acetate solution to prepare a suspension. Then, the suspension was heated to 90 ° C. while stirring at a rotation speed of 300 rpm of the stirrer, and ethyl acetate was volatilized from the suspension over 2 hours. Then, the temperature was raised to 95 ° C., 70 g of sodium hydroxide was added, and the mixture was held for 1.5 hours to remove the acetyl group from the cellulose acetate particles to obtain cellulose particles. As a result, a slurry in which cellulose particles were dispersed in water was obtained.
Next, the slurry was cooled to room temperature, solid-liquid separated by filtration, and the recovered solid was thoroughly washed with water and then dried at 70 ° C. for 20 hours to obtain spherical cellulose particles having a volume average particle diameter of 42.2 μm. Got
The acetic acid concentration of the cellulose particles obtained in Example 5 was 0.02 ppm, and there was no acetic acid odor.
＜実施例６＞
　２Ｌ攪拌機付きセパラブルフラスコに酢酸エチル５７６ｇとＭＥＫ１４４ｇを仕込み、この中に酢酸セルロース（酢化度５５％）１８０ｇを溶解して酢酸セルロース溶液を調製した。この溶液の２５℃における粘度は５４８００ｍＰａ・ｓであった。
　これとは別に、２Ｌ攪拌機付きセパラブルフラスコに水３００ｇを仕込み、この中にポリビニルアルコール（けん化度８８％）４．０ｇとラウリル硫酸ナトリウム１．０ｇを溶解して分散媒水溶液を調製した。
　酢酸セルロース溶液に分散媒水溶液を添加して、懸濁液を調製した。次いで、攪拌機の回転数３００ｒｐｍで攪拌しながら懸濁液を９０℃に昇温し、２時間かけて懸濁液から酢酸エチルを揮発させた。次いで、９５℃に昇温し、水酸化ナトリウムを７０ｇ添加して、１．５時間保持し、酢酸セルロース粒子からアセチル基を脱離させ、セルロース粒子を得た。これにより、水中にセルロース粒子が分散したスラリーを得た。
　次いで、スラリーを室温まで冷却した後、ろ過により固液分離し、回収した固形物を水で充分洗浄した後、７０℃で２０時間乾燥して、体積平均粒子径８．８μｍの球状のセルロース粒子を得た。
　実施例６で得たセルロース粒子の酢酸濃度は０．００ｐｐｍであり、酢酸臭は無かった。 <Example 6>
576 g of ethyl acetate and 144 g of MEK were charged in a separable flask equipped with a 2 L stirrer, and 180 g of cellulose acetate (degree of vinegarization 55%) was dissolved therein to prepare a cellulose acetate solution. The viscosity of this solution at 25 ° C. was 54,800 mPa · s.
Separately, 300 g of water was charged into a separable flask equipped with a 2 L stirrer, and 4.0 g of polyvinyl alcohol (saponification degree 88%) and 1.0 g of sodium lauryl sulfate were dissolved therein to prepare a dispersion medium aqueous solution.
A dispersion medium aqueous solution was added to the cellulose acetate solution to prepare a suspension. Then, the suspension was heated to 90 ° C. while stirring at a rotation speed of 300 rpm of the stirrer, and ethyl acetate was volatilized from the suspension over 2 hours. Then, the temperature was raised to 95 ° C., 70 g of sodium hydroxide was added, and the mixture was held for 1.5 hours to remove the acetyl group from the cellulose acetate particles to obtain cellulose particles. As a result, a slurry in which cellulose particles were dispersed in water was obtained.
Next, the slurry was cooled to room temperature, solid-liquid separated by filtration, and the recovered solid was thoroughly washed with water and then dried at 70 ° C. for 20 hours to obtain spherical cellulose particles having a volume average particle diameter of 8.8 μm. Got
The acetic acid concentration of the cellulose particles obtained in Example 6 was 0.00 ppm, and there was no acetic acid odor.
＜実施例７＞
　２Ｌ攪拌機付きセパラブルフラスコに酢酸エチル７０５ｇを仕込み、この中に酢酸セルロース（酢化度５５％）４５ｇを溶解して酢酸セルロース溶液を調製した。この溶液の２５℃における粘度は２３００ｍＰａ・ｓであった。
　これとは別に、２Ｌ攪拌機付きセパラブルフラスコに水７５０ｇを仕込み、この中にヒドロキシプロピルメチルセルロース（メトローズ９０ＳＨ－１００、信越化学工業株式会社製）２５．０ｇとラウリル硫酸ナトリウム４．０ｇを溶解して分散媒水溶液を調製した。
　酢酸セルロース溶液に分散媒水溶液を添加して、懸濁液を調製した。次いで、攪拌機の回転数３００ｒｐｍで攪拌しながら懸濁液を９０℃に昇温し、２時間かけて懸濁液から酢酸エチルを揮発させた。次いで、９５℃に昇温し、水酸化ナトリウムを７０ｇ添加して、１．５時間保持し、酢酸セルロース粒子からアセチル基を脱離させ、セルロース粒子を得た。これにより、水中にセルロース粒子が分散したスラリーを得た。
　次いで、スラリーを室温まで冷却した後、ろ過により固液分離し、回収した固形物を水で充分洗浄した後、７０℃で２０時間乾燥して、体積平均粒子径１０．３μｍの球状のセルロース粒子を得た。
　実施例７で得たセルロース粒子の酢酸濃度は０．００ｐｐｍであり、酢酸臭は無かった。 <Example 7>
705 g of ethyl acetate was placed in a separable flask equipped with a 2 L stirrer, and 45 g of cellulose acetate (vinegarization degree 55%) was dissolved therein to prepare a cellulose acetate solution. The viscosity of this solution at 25 ° C. was 2300 mPa · s.
Separately, 750 g of water was placed in a separable flask equipped with a 2 L stirrer, and 25.0 g of hydroxypropyl methylcellulose (Metroze 90SH-100, manufactured by Shin-Etsu Chemical Co., Ltd.) and 4.0 g of sodium lauryl sulfate were dissolved therein. A dispersion medium aqueous solution was prepared.
A dispersion medium aqueous solution was added to the cellulose acetate solution to prepare a suspension. Then, the suspension was heated to 90 ° C. while stirring at a rotation speed of 300 rpm of the stirrer, and ethyl acetate was volatilized from the suspension over 2 hours. Then, the temperature was raised to 95 ° C., 70 g of sodium hydroxide was added, and the mixture was held for 1.5 hours to remove the acetyl group from the cellulose acetate particles to obtain cellulose particles. As a result, a slurry in which cellulose particles were dispersed in water was obtained.
Next, the slurry was cooled to room temperature, solid-liquid separated by filtration, and the recovered solid was thoroughly washed with water and then dried at 70 ° C. for 20 hours to obtain spherical cellulose particles having a volume average particle diameter of 10.3 μm. Got
The acetic acid concentration of the cellulose particles obtained in Example 7 was 0.00 ppm, and there was no acetic acid odor.
＜実施例８＞
　２Ｌ攪拌機付きセパラブルフラスコに酢酸エチル７０２ｇを仕込み、この中に酢酸セルロース（酢化度５５％）１９８ｇを溶解して酢酸セルロース溶液を調製した。この溶液の２５℃における粘度は２９５０００ｍＰａ・ｓであった。
　これとは別に、２Ｌ攪拌機付きセパラブルフラスコに水３００ｇを仕込み、この中にヒドロキシプロピルメチルセルロース（メトローズ９０ＳＨ－１００、信越化学工業株式会社製）５．０ｇとラウリル硫酸ナトリウム１．０ｇを溶解して分散媒水溶液を調製した。
　酢酸セルロース溶液に分散媒水溶液を添加して、懸濁液を調製した。次いで、攪拌機の回転数３００ｒｐｍで攪拌しながら懸濁液を９０℃に昇温し、２時間かけて懸濁液から酢酸エチルを揮発させた。次いで、９５℃に昇温し、水酸化ナトリウムを７０ｇ添加して、１．５時間保持し、酢酸セルロース粒子からアセチル基を脱離させ、セルロース粒子を得た。これにより、水中にセルロース粒子が分散したスラリーを得た。
　次いで、スラリーを室温まで冷却した後、ろ過により固液分離し、回収した固形物を水で充分洗浄した後、７０℃で２０時間乾燥して、体積平均粒子径１４．４μｍの球状のセルロース粒子を得た。
　実施例８で得たセルロース粒子の酢酸濃度は０．０１ｐｐｍであり、酢酸臭は無かった。 <Example 8>
702 g of ethyl acetate was placed in a separable flask equipped with a 2 L stirrer, and 198 g of cellulose acetate (vinegarization degree 55%) was dissolved therein to prepare a cellulose acetate solution. The viscosity of this solution at 25 ° C. was 295,000 mPa · s.
Separately, 300 g of water was placed in a separable flask equipped with a 2 L stirrer, and 5.0 g of hydroxypropyl methylcellulose (Metro's 90SH-100, manufactured by Shin-Etsu Chemical Co., Ltd.) and 1.0 g of sodium lauryl sulfate were dissolved therein. A dispersion medium aqueous solution was prepared.
A dispersion medium aqueous solution was added to the cellulose acetate solution to prepare a suspension. Then, the suspension was heated to 90 ° C. while stirring at a rotation speed of 300 rpm of the stirrer, and ethyl acetate was volatilized from the suspension over 2 hours. Then, the temperature was raised to 95 ° C., 70 g of sodium hydroxide was added, and the mixture was held for 1.5 hours to remove the acetyl group from the cellulose acetate particles to obtain cellulose particles. As a result, a slurry in which cellulose particles were dispersed in water was obtained.
Next, the slurry was cooled to room temperature, solid-liquid separated by filtration, the recovered solid was thoroughly washed with water, and then dried at 70 ° C. for 20 hours to obtain spherical cellulose particles having a volume average particle diameter of 14.4 μm. Got
The acetic acid concentration of the cellulose particles obtained in Example 8 was 0.01 ppm, and there was no acetic acid odor.
＜比較例１＞
　２Ｌ攪拌機付きセパラブルフラスコに酢酸エチル７２０ｇを仕込み、この中に酢酸セルロース（酢化度５５％）１８０ｇを溶解して酢酸セルロース溶液を調製した。この溶液の２５℃における粘度は１４６０００ｍＰａ・ｓであった。
　これとは別に、２Ｌ攪拌機付きセパラブルフラスコに水３００ｇを仕込み、この中にヒドロキシプロピルメチルセルロース（メトローズ９０ＳＨ－１００、信越化学工業株式会社製）５．０ｇとラウリル硫酸ナトリウム１．０ｇを溶解して分散媒水溶液を調製した。
　酢酸セルロース溶液に分散媒水溶液を添加して、懸濁液を調製した。次いで、攪拌機の回転数３００ｒｐｍで攪拌しながら懸濁液を９０℃に昇温し、２時間かけて懸濁液から酢酸エチルを揮発させた。次いで、９５℃に昇温し、水酸化ナトリウムを７０ｇ添加して、１．０時間保持し、酢酸セルロース粒子からアセチル基を脱離させ、セルロース粒子を得た。これにより、水中にセルロース粒子が分散したスラリーを得た。
　次いで、スラリーを室温まで冷却した後、ろ過により固液分離し、回収した固形物を水で充分洗浄した後、７０℃で２０時間乾燥して、体積平均粒子径６．８μｍの球状のセルロース粒子を得た。
　比較例１で得たセルロース粒子の酢酸濃度は１．３３ｐｐｍであり、酢酸臭があった。 <Comparative example 1>
720 g of ethyl acetate was placed in a separable flask equipped with a 2 L stirrer, and 180 g of cellulose acetate (vinegarization degree 55%) was dissolved therein to prepare a cellulose acetate solution. The viscosity of this solution at 25 ° C. was 146000 mPa · s.
Separately, 300 g of water was placed in a separable flask equipped with a 2 L stirrer, and 5.0 g of hydroxypropyl methylcellulose (Metro's 90SH-100, manufactured by Shin-Etsu Chemical Co., Ltd.) and 1.0 g of sodium lauryl sulfate were dissolved therein. A dispersion medium aqueous solution was prepared.
A dispersion medium aqueous solution was added to the cellulose acetate solution to prepare a suspension. Then, the suspension was heated to 90 ° C. while stirring at a rotation speed of 300 rpm of the stirrer, and ethyl acetate was volatilized from the suspension over 2 hours. Then, the temperature was raised to 95 ° C., 70 g of sodium hydroxide was added, and the mixture was held for 1.0 hour to remove the acetyl group from the cellulose acetate particles to obtain cellulose particles. As a result, a slurry in which cellulose particles were dispersed in water was obtained.
Next, the slurry was cooled to room temperature, solid-liquid separated by filtration, and the recovered solid was thoroughly washed with water and then dried at 70 ° C. for 20 hours to obtain spherical cellulose particles having a volume average particle diameter of 6.8 μm. Got
The acetic acid concentration of the cellulose particles obtained in Comparative Example 1 was 1.33 ppm, and there was an acetic acid odor.
　以上説明した実施例の結果から、酢酸臭が抑えられたセルロース粒子が得られたことを確認した。また、酢酸セルロースの仕込み量を多くすることができ、酢酸臭が抑えられたセルロース粒子を低コストで簡便に製造できることを確認した。 From the results of the examples described above, it was confirmed that cellulose particles with suppressed acetic acid odor were obtained. It was also confirmed that the amount of cellulose acetate charged can be increased, and that cellulose particles having an suppressed acetic acid odor can be easily produced at low cost.

Claims (8)

  1. 　平均粒子径が１～３００μｍであり、酢酸濃度が０．５ｐｐｍ以下である、セルロース粒子。 Cellulose particles with an average particle size of 1 to 300 μm and an acetic acid concentration of 0.5 ppm or less.
  2. 　球状である、請求項１に記載のセルロース粒子。 The cellulose particles according to claim 1, which are spherical.
  3. 　セルロースの含有量が９２質量％以上である、請求項１または２に記載のセルロース粒子。 The cellulose particles according to claim 1 or 2, wherein the cellulose content is 92% by mass or more.
  4. 　酢酸セルロースが有機溶媒に溶解した酢酸セルロース溶液を水中に懸濁させ、酢酸セルロース粒子が水中に分散した懸濁液を調製し、
    　前記懸濁液から前記有機溶媒を除去し、
    　酢酸濃度が０．５ｐｐｍ以下となるように、前記酢酸セルロース粒子を鹸化してセルロース粒子とする、セルロース粒子の製造方法。     A cellulose acetate solution in which cellulose acetate is dissolved in an organic solvent is suspended in water to prepare a suspension in which cellulose acetate particles are dispersed in water.
    The organic solvent is removed from the suspension and
    A method for producing cellulose particles, wherein the cellulose acetate particles are saponified into cellulose particles so that the acetic acid concentration is 0.5 ppm or less.
  5. 　前記懸濁液を調製する際に、前記酢酸セルロース溶液に水を添加し、次いで、水相と有機溶媒相とを逆転させることにより、前記酢酸セルロース溶液を水中に懸濁させる、請求項４に記載のセルロース粒子の製造方法。 According to claim 4, when preparing the suspension, water is added to the cellulose acetate solution, and then the aqueous phase and the organic solvent phase are reversed to suspend the cellulose acetate solution in water. The method for producing cellulose particles according to the above.
  6. 　前記酢酸セルロース溶液の粘度が２０００～３０００００ｍＰａ・ｓである、請求項４または５に記載のセルロース粒子の製造方法。 The method for producing cellulose particles according to claim 4 or 5, wherein the cellulose acetate solution has a viscosity of 2000 to 300,000 mPa · s.
  7. 　メチルセルロース、ヒドロキシエチルセルロース、ヒドロキシプロピルメチルセルロースおよびカルボキシメチルセルロースからなる群から選ばれる少なくとも一つ以上のセルロース系水溶性樹脂の存在下で、前記酢酸セルロース溶液を水中に懸濁させる、請求項４～６のいずれか一項に記載のセルロース粒子の製造方法。 Any of claims 4 to 6, wherein the cellulose acetate solution is suspended in water in the presence of at least one cellulosic water-soluble resin selected from the group consisting of methyl cellulose, hydroxyethyl cellulose, hydroxypropyl methyl cellulose and carboxymethyl cellulose. The method for producing cellulose particles according to item 1.
  8. 　界面活性剤の存在下で前記酢酸セルロース溶液を水中に懸濁させる、請求項４～７のいずれか一項に記載のセルロース粒子の製造方法。 The method for producing cellulose particles according to any one of claims 4 to 7, wherein the cellulose acetate solution is suspended in water in the presence of a surfactant.
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