WO2013016982A1

WO2013016982A1 - Cellulose acetate microsphere preparation method and product prepared thereby

Info

Publication number: WO2013016982A1
Application number: PCT/CN2012/077073
Authority: WO
Inventors: 曹建国; 窦峰; 彭为骏; 张�杰
Original assignee: 南通醋酸纤维有限公司
Priority date: 2011-08-04
Filing date: 2012-06-18
Publication date: 2013-02-07
Also published as: CN102911379A; CN102911379B

Abstract

The present invention relates to the technical field of chemical celluloses. Disclosed are a cellulose acetate microsphere preparation method and product prepared thereby. The cellulose acetate microsphere preparation method of the present invention comprises the following steps: dissolving in a mixed solvent a cellulose acetate tow containing a plasticizer and obtaining polymer slurry; then adding the obtained polymer slurry to a dispersion liquid, fully mixing and obtaining suspension liquid; reducing the solubility of the cellulose acetate and separating out the cellulose acetate microsphere. The cellulose acetate microsphere of the present invention has an average particle diameter of 5-1500μm, an average pore diameter of 2-200nm, a specific surface area of 0.6m2•g-1-10.0m2•g-1, the degree of substitution of the cellulose acetate acetyl is 2.0-2.6, and the level of the residual plasticizer is 1.0%-3.0% by weight of the cellulose acetate microsphere. The microsphere of the present invention has the advantages of easy regeneration, good biocompatibility and good hydrophilicity.

Description

Method for preparing cellulose acetate microspheres and products prepared by the method

The invention belongs to the technical field of chemical cellulose, and relates to a preparation method of cellulose acetate microspheres and a product prepared by the method. Background technique

Acetate fiber is also known as cellulose acetate, that is, cellulose acetate. A rayon fiber obtained by esterification of cellulose acetate with acetic acid and cellulose as raw materials. The lignocellulose is treated by acetification, hydrolysis, drying, etc. to obtain a sheet of cellulose diacetate sheet (referred to as "vinegar sheet"), and the vinegar sheet is spun to obtain a cellulose diacetate tow (referred to as "tow" for short). ).

Cellulose acetate can be directly esterified by cellulose such as cotton linter pulp or wood pulp under glacial acetic acid, acetic anhydride and sulfuric acid to obtain cellulose triacetate, and then partially hydrolyzed triacetate to obtain acetyl substitution degree. A cellulose diacetate product between 2.0 and 2.6.

As an important organic cellulose ester, cellulose diacetate is non-toxic and non-flammable, and is mainly used in the manufacture of cigarette filters. In order for the filter rod made from the tow to have a suitable hardness, it is necessary to add a plasticizer. A plasticizer is a low molecular weight compound or polymer that is added to a polymer that requires plasticization to increase the plasticity of the polymer. Plasticizers are generally high boiling point, less volatile liquids or low melting point solids, and are mostly ester organic compounds. It usually does not chemically react with the polymer, and the interaction with the polymer is mainly the swelling at elevated temperatures. Plasticizers are more comprehensive and easy to produce and use, and are widely used. The plasticizer used in the manufacture of cigarette filters for cellulose acetate tow is usually triacetin or ethylene glycol diacetate, and the amount of plasticizer used is 5% to 12% of the mass of cellulose acetate tow. . The waste tow produced during the processing of tobacco processing is mainly in the form of a mixture of plasticizers. Unless otherwise stated, the discarded tows described below are mixed with a plasticizer. China's annual consumption of acetate tow is 260,000 tons, and waste tow is produced every year from 2000 to 4000 tons.

In order to prevent loss control outside the tow, the China Tobacco Monopoly Administration stipulates that all discarded tows must be incinerated at a fixed point. Although incineration eliminates the way in which discarded tows enter the manufacturing process of counterfeit cigarettes, it inevitably leads to waste of resources and unnecessary carbon emissions. Earlier, it was reported in China that the waste tow was directly added to acetone and auxiliaries to form a polymer. After filtration and defoaming, dry spinning was used to make tow re-use (WCA) regenerated tobacco filter fiber research. Man-made fibers. 1989, 5: 1-4. ), but the plasticizer mixed in the discarded tow is difficult to remove by ordinary filtration, and the spinning process is prone to sticking. In the related patent, the waste tow is subjected to high-temperature water washing or enzymatic hydrolysis, and the plasticizer is removed, and then recycled to be used for reconstitution (US 5,328,934, US 5,504,119, US 5,504,120, Chinese Patent Application No. 200910064880.8). The patent proposes to increase the plasticizer removal efficiency by using high pressure/low temperature and low pressure/high temperature water washing in a closed container (US 5,402,893), but these methods require a large amount of water and energy and the washing wastewater is difficult to handle. There are also smashed waste tows, The tow is degraded to a monosaccharide (US 4,298,013) with a biological enzyme and reused, but the biodegradation rate is slow and the plasticizer in the discarded tow is also difficult to handle. It is also possible to add waste tow to the caustic soda to be hydrolyzed and mixed with cellulose for use in the paper industry (US 5,662,773, 2004/0214702 A1), but the industrial value of such a method is not high. There are also patents that disclose a method for recovering cellulose acetate using a mixed solvent (CN200910185996.7), but the toxic solvent used is not conducive to subsequent processing.

Cellulose acetate can be used in other applications (such as film, film or fiber) depending on its shape, and cellulose acetate microspheres are a special field of cellulose acetate application. Cellulose acetate microspheres not only retain the original properties of cellulose acetate, but also have hydrophilicity, porosity, large specific surface area and good swelling properties. They can be widely used as adsorbents in chromatography and separation techniques. Since the hydroxyl group in the cellulose molecule is substituted by the acetyl group, the force of the hydrogen bond is weakened, the inter-molecular distance is increased, and the affinity of the hydroxyl group and the carbonyl group in the molecule to the precious metal is greatly enhanced, so that it can be used as a precious metal. Adsorbent. Due to the unique microscopic properties of cellulose acetate microspheres, industrial adaptability is gradually gaining attention, and it is expected to be widely used in environmental protection, biochemistry, bioengineering, medicine, pharmacy and other fields. Daicel Corporation of Japan has disclosed the preparation of cellulose acetate microspheres by spraying method (US 4, 551, 389, US 4, 663, 447), and Nishikawa et al. of Japan also introduced the preparation method of "suspension method" of cellulose diacetate microspheres (US 4 , 390, 691, US 4, 461, 892), preparing microspheres using a halogenated hydrocarbon as a main solvent. Wagenknecht W et al. prepared a cellulose acetate deacetylated cellulose microsphere (EP 750007A1) by dispersing cellulose acetate in a mixed solution of ethoxylated alkylphenol and ethyl acetate under alkaline conditions and evaporating the solvent. . Summary of the invention

It is an object of the present invention to provide a process for the preparation of cellulose acetate microspheres.

Another object of the present invention is to provide a cellulose acetate microsphere prepared by the above method, which has the advantages of easy regeneration, good biocompatibility and good hydrophilicity.

The technical solution of the present invention is as follows:

The invention provides a preparation method of cellulose acetate microspheres, the method comprising the following steps:

Dissolving the cellulose acetate tow containing the plasticizer in a mixed solvent to obtain a polymer slurry, and then adding the obtained polymer slurry to the dispersion, thoroughly mixing to obtain a suspension, reducing the solubility of the cellulose acetate, and separating the cellulose acetate. Microspheres.

The plasticizer is selected from one of triacetin or ethylene glycol diacetate.

The cellulose acetate tow has an acetyl substitution degree of 2.0 to 2.6.

The mixed solvent is a mixture of an alcohol and an ester, wherein: the volume percentage of the alcohol is 1 to 40%, and the volume percentage of the ester is 60 to 99% _;

Wherein the alcohol contains 1-3 carbon atoms, further selected from the group consisting of methanol, ethanol, n-propanol or isopropanol; and the ester is selected from the group consisting of C ₂ ～C _{The 5} carboxylate is further selected from the group consisting of one or more of methyl acetate, ethyl acetate, n-propyl acetate or isopropyl acetate.

The dispersion includes a water-soluble salt, an emulsifier, a protective colloid, water, and an ester selected from the mixed solvent. The mass concentration of the water-soluble salt is 0.3 to 5% of the total mass of the dispersion, the mass concentration of the emulsifier is 0.1 to 1.5% of the total mass of the dispersion, and the mass concentration of the protective colloid is 0 to 1.5% of the total mass of the dispersion, mixing The mass concentration of the ester substance selected in the solvent is 5.0-15.0% of the total mass of the dispersion, and the mass concentration of water is 77.0-94.6% of the total mass of the dispersion;

Wherein: the water-soluble salt is a metal acetate salt, further selected from the group consisting of one or a mixture of sodium acetate or potassium acetate; the emulsifier is a nonionic surfactant, further selected from the group consisting of polyoxyethylene sorbitan lauric acid a mixture of one or both of ester or sorbitan monolaurate; a protective colloid selected from the group consisting of methyl cellulose, methyl cellulose mixed ether, gelatin or polyvinyl alcohol. .

The reducing the solubility of cellulose acetate is controlled by distilling the suspension under reduced pressure or adding the suspension to deionized water; wherein: the distillation temperature under reduced pressure is 40 ° C to 60 ° C, the degree of vacuum is 260 to 180 mbar _; The volume ratio of liquid to deionized water is 1: 30 to 1: 140.

The cellulose acetate microspheres contain a plasticizer in an amount of 1.0 to 3.0% by mass.

The present invention provides a cellulose acetate microspheres, the average particle size of the microspheres is _{5~1500μηι;} average pore diameter of 20~ lOOOnm; specific surface area of ^{^{0.6 m 2 'g - 1 ~}} 10.0m 2' g- 1; acetic acid The cellulose has an acetyl substitution degree of 2.0 to 2.6, and the residual plasticizer content is 1.0% to 3.0% by mass of the cellulose acetate microspheres.

The mixed solvent is a product in which two or more solvents are mixed together in a certain ratio. Any mixed solvent may be selected in the present invention as long as the mixed solvent is capable of dissolving cellulose acetate and a plasticizer in the waste tow to obtain a mixed polymer slurry containing cellulose acetate and a plasticizer; Each solvent component in the mixed solvent can be dispersed in the dispersion.

The dispersion liquid refers to an aqueous solution containing a component such as a water-soluble salt, an emulsifier, a protective colloid, etc., capable of dissolving a mixed solvent and a plasticizer in the polymer slurry; and at the same time, the cellulose acetate microparticle in the polymer slurry Soluble or insoluble in the dispersion, capable of being dispersed in the dispersion to obtain a suspension;

Among them, the water-soluble salt is a metal salt which is easily soluble in water, and its function is to improve the conductive property in the dispersion, adjust the δ potential of the dispersion in the dispersion, and improve the stability of the entire solution system;

An emulsifier is a type of surfactant which acts to form a film or an electric double layer when dispersed on the surface of a dispersion medium, so that the dispersed phase can be charged, and the droplets of the dispersed phase can be prevented from coagulating with each other, so that the formed milk The turbid liquid is more stable; at the same time, by changing the hydrophilic group or the hydrophobic group on the emulsifier molecule, the proportion and the position in the molecular structure, the desired hydrophilic-lipophilic balance can be achieved; It can effectively increase the solubility and stability of the mixed solvent component and the plasticizer component of the polymer slurry in the dispersion;

The protective colloid is a kind of water-soluble polymer which exhibits a network structure in the dispersion system and protects the cellulose acetate in the dispersion from mutual polymerization, thereby effectively improving the stability of the entire dispersion system.

A variety of methods can reduce the solubility of cellulose acetate in the suspension, and precipitate most of the cellulose acetate which is slightly soluble in the original suspension. By selecting the cellulose acetate precipitation method and conditions, the particle size of the cellulose acetate microspheres can be controlled, and the surface properties of the cellulose acetate microspheres can be improved. The present invention selects to reduce the solubility of cellulose acetate in the suspension by increasing the ratio of water/mixed solvent in the suspension. The vacuum distillation suspension can effectively distill the mixed solvent from the suspension to increase the ratio of water/mixed solvent in the suspension. Vacuum distillation is a technique well known to those skilled in the art, and the conditions selected by the present invention include: distillation temperature 40 ° C ~

60 ° C, vacuum 260~180 mbar.

Another way to increase the ratio of water/mixed solvent in the suspension is to add the suspension to a quantity of deionized water at a rate that is sufficiently agitated. In the present invention, the volume ratio of the suspension to the deionized water is 1:30 to 1:140, and most of the cellulose acetate is precipitated.

In addition, the cellulose acetate microspheres prepared by the above preparation steps can be subjected to a purification process such as separation, multiple water washing, centrifugation, and drying to obtain a final product. Washing with deionized water can effectively remove alcohols, esters, metal salts, emulsifiers and protective colloids present in cellulose acetate microspheres.

Further, the precipitated cellulose acetate microspheres are purified by the following purification steps:

The crude acetic acid microspheres after vacuum distillation are naturally cooled to room temperature, added with deionized water, transferred to a shaker, shaken, and transferred to a centrifuge for centrifugation again; the water washing oscillation-centrifugation step is repeated several times, the product is repeated. It is placed in a dry box and dried to finally obtain cellulose diacetate microspheres.

Compared with the prior art, the present invention has the following advantages and beneficial effects:

1. The method of preparing cellulose acetate microspheres of the present invention uses spent cellulose acetate tow to enable efficient utilization of spent cellulose acetate tow.

2. The cellulose acetate microspheres prepared by the invention can be recycled and recycled in the production process, and have little impact on the environment.

3. The cellulose acetate microspheres prepared by the present invention have porous characteristics and the particle size of the microspheres can be adjusted.

4. The cellulose acetate microspheres prepared by the invention have many reactive groups, and can modify various ligands, such as ion exchange ligands and affinity ligands, to meet various adsorption separation requirements.

5. The cellulose acetate microsphere prepared by the invention has good biocompatibility and good hydrophilicity, and can be used as an adsorbent, a cigarette harm reduction coke additive, an ion exchanger, a catalyst, a redox agent and a treatment of heavy metal ions and organic substances. , pigment waste water and gas separation, blood filtration, drug release, chromatographic separation of substances and other uses.

6. The invention aims to prepare a waste tow or vinegar sheet mixed with a plasticizer into cellulose acetate microspheres, as an additive for cigarette filter materials and cosmetics (foundation, lipstick, eye shadow, lotion, body lotion), Drug slow release agents, modifiers for pigments and paints, and sewage treatment engineering adsorbents. DRAWINGS

Fig. 1 is a scanning electron micrograph of cellulose acetate microspheres (particle diameter 300 μηι to 600 μηι according to the method of Example 1).

Figure 2 is a scanning electron micrograph of cellulose acetate microspheres (average particle size 100 μηι according to the method of Example 2).

Figure 3 is a scanning electron micrograph of cellulose acetate microspheres (average particle size 1500 μηι according to the method of Example 3).

Figure 4 is a scanning electron micrograph of cellulose acetate microspheres (particle size 5μηι~50μηι according to the method of Example 4). detailed description

The invention will be further described below in conjunction with the embodiments shown in the drawings.

In the present invention, unless otherwise defined, all percentages (%) are a component in a system, for example, the weight percentage of the solute in the solution; all "inside" include the terminal value, for example, average The particle size ranges from 100 μm to 150 μm and includes ΙΟΟμηι and 150 μm _; all RPMs represent revolutions per minute (rmin−, for example, 60 RPM means 60 rpm).

In the present invention, all the data units are in international units and auxiliary units, and the length units are in mm, μηι, nm, where 111^1 (mm) = 10 - (m), ^! ^ M - ⁶ ^ lnm (nanometer) = 10- ⁹ m; time units employed min, lmin (min) = 60s (seconds); vacuum unit employed ^{mbar, lmbar = 10 "3 bar} , lbar = 100000Pa = 0.98692327atm =! 750.06168mm Hg.

The plasticizer content detection method of the invention is gas chromatography detection, using Agilent 6890N gas chromatograph, 30mx0.53mmx l. (^m DB-1701 capillary column, column temperature oven temperature 170 ° C, flow rate 2.4mL / min, The injection temperature is 250 °C and the FID detector temperature is 300 °C.

The specific surface area detection of the present invention is tested by the ASAP2020M-V3 type automatic surface area and micropore tester of the American Micromeritics, liquid nitrogen protection, and the analysis bath temperature is -195.6 ° C, and the equilibrium time is 10 s.

The vacuum distillation operation of the present invention adopts a Buchi 250 type rotary evaporator of Swiss Buchi, the temperature of the water bath is 40 ° C to 60 ° C, the vacuum degree of the instrument is 260 to 180 mbar, and the rotation speed of the distillation flask is 30 to 150 RPM.

The centrifugation of the present invention was carried out using a Fisher company Accuspin 400 centrifuge with a set speed of 3600 RPM and a centrifugal separation time of 10 min.

The oscillator of the invention adopts the German KS260 circumferential oscillation instrument of IKA Company, and sets the rotation speed of 300 RPM and the oscillation time is 3 min.

The cellulose acetate tow used in the preparation of cellulose acetate microspheres, whether using new cellulose acetate tow (without plasticizer itself) or using discarded cellulose acetate tow (which contains The plasticizer) can achieve the object of the present invention. The cellulose acetate tow used in the present invention is a waste cellulose acetate tow, which is a waste product which is produced by adding a plasticizer to a filter for producing tobacco, and contains a plasticizer component.

Example 1

A sample of 13 g of waste cellulose acetate tow (in which the plasticizer triacetin content was 8.2% of the total mass of the sample, and the degree of acetyl substitution was 2.4) was dissolved in 160 ml of ethyl acetate and 28 ml of ethanol at room temperature. The polymer solution was taken up in a solvent. The obtained polymer solution is added to the dispersion at room temperature to obtain a suspension; (the mixed volume ratio of the polymer slurry to the dispersion is 1: 2.34) The dispersion is composed of 400 ml of water (mass concentration: 90.8%), 2.2 g. Water soluble methylcellulose (mass concentration 0.5%), 2.4 grams of sodium acetate (0.5% by mass), 2.0 grams of polyoxyethylene sorbitan lauric acid monoester and sorbitan monolaurate The mixture (mass ratio of the two components was 1:1) (mass concentration 0.5%) and 38 ml of ethyl acetate (mass concentration 7.7%). The whole suspension is transferred to a rotary evaporator, and rotated under a pressure of 260 to 180 mbar at 30 to 60 RPM in a water bath at 40 to 60 ° C to distill off most of the organic solvent and a small amount of water to precipitate vinegar. Acid cellulose microspheres. After about 150 minutes, the evaporator was turned off, naturally cooled to room temperature, centrifuged at 3600 RPM for 10 min in a centrifuge, and the precipitate was separated. After adding 100 mL of deionized water, it was shaken at 300 RPM for 3 min in a shaker, and then transferred to a centrifuge. Centrifuge again. This washing method (water washing shaking-centrifugation) was repeated 3 times, and the product was vacuum-dried at 105 ° C for 48 hours in a vacuum drying oven to finally obtain cellulose diacetate microspheres.

The cellulose diacetate microspheres were subjected to a screening test, and 95% of the particle size ranged from 300 μm to 600 μm. Figure 1 is a scanning electron micrograph of the prepared cellulose acetate microspheres, and the microspheres exhibited a highly porous structure. The microspheres were tested using a BET specific surface tester with a specific surface area of 1.0 m ² , g - ¹ to 5.01 μ·, and an average pore diameter of 20 to 50 nm. After gas chromatography analysis, the condensate was evaporated to a mixture of water, ethyl acetate and ethanol. The content of the plasticizer triacetin in the microspheres is from 1.4% to 2.5%. Example 2

A sample of 13 g of waste cellulose acetate tow (in which the plasticizer triacetin content was 8.2% of the total mass of the sample, and the degree of acetyl substitution was 2.4) was dissolved in 160 ml of ethyl acetate and 28 ml of ethanol at room temperature. The polymer solution was taken up in a solvent. The obtained polymer solution is added to the dispersion at room temperature to obtain a suspension; (the mixed volume ratio of the polymer slurry to the dispersion is 1: 2.34) The dispersion is composed of 400 ml of water (mass concentration: 90.8%), 2.2 g. Water soluble methylcellulose (mass concentration 0.5%), 2.4 grams of sodium acetate (0.5% by mass), 2.0 grams of polyoxyethylene sorbitan lauric acid monoester and sorbitan monolaurate The mixture (mass ratio of the two components was 1:1) (mass concentration 0.5%) and 38 ml of ethyl acetate (mass concentration 7.7%). The resulting suspension was slowly added to 48 L of deionized water at a rate of 5 to 20 mL/min at a temperature of 500 RPM, and the cellulose acetate microspheres were separated, and separated to obtain solid cellulose acetate microspheres;

The obtained solid cellulose acetate microspheres were added to 100 mL of deionized water, shaken at 300 RPM for 3 min in a shaker, and transferred to a centrifuge at 3600 RPM for 10 min. This washing method (washing shaking-centrifugation) was repeated 3 times, and the product was vacuum-dried at 105 ° C for 48 hours in a vacuum drying oven to finally obtain cellulose diacetate microspheres.

The cellulose diacetate microspheres were tested for particle size, and 95% of the particles ranged from 5 μm to 100 μm. Figure 2 is a scanning electron micrograph of the prepared cellulose acetate microspheres, and the microspheres exhibited a highly porous structure. The microspheres were tested using a BET specific surface tester with a specific surface area of

The average pore diameter is 70-150 nm. The content of the plasticizer triacetin in the microspheres was 1.0% to 2.2% by gas chromatography.

Example 3

A sample of 26 g of waste cellulose acetate tow (in which the plasticizer triacetin content was 8.2% of the total mass of the sample, and the degree of acetyl substitution was 2.3) was dissolved in 160 ml of ethyl acetate and 28 ml of ethanol at room temperature. The polymer solution was taken up in a solvent. The obtained polymer solution is added to the dispersion at room temperature to obtain a suspension; (the mixing ratio of the polymer slurry to the dispersion is 1: 2.30). The dispersion is composed of 400 ml of water (mass concentration: 90.8%), 2.2 g. Water soluble methylcellulose (mass concentration 0.5%), 2.4 grams of sodium acetate (0.5% by mass), 2.0 grams of polyoxyethylene sorbitan lauric acid monoester and sorbitan monolaurate The mixture (mass ratio of the two components was 1:1) (mass concentration 0.5%) and 38 ml of ethyl acetate (mass concentration 7.7%). The whole suspension is transferred to a rotary evaporator, and rotated at a temperature of 30 to 60 RPM in a water bath at 40 to 60 ° C under a pressure of 260 to 180 mbar, and most of the organic solvent and a small amount of water are distilled off. Cellulose acetate microspheres. After about 150 minutes, the evaporator was turned off, naturally cooled to room temperature, centrifuged at 3600 RPM for 10 min in a centrifuge, and the precipitate was separated and added to 100 mL of deionized water. After shaking at 300 RPM for 3 min in a shaker, it was transferred to a centrifuge again. Centrifugal separation. This washing method (water washing shaking-centrifugation) was repeated 3 times, and the product was vacuum-dried at 105 ° C for 48 hours in a vacuum drying oven to finally obtain cellulose diacetate microspheres.

The cellulose diacetate microspheres were subjected to a screening test, and 95% of the particle size ranged from 800 μm to 1600 μm. FIG. 3 is a scanning electron micrograph of the cellulose acetate microsphere prepared by the method of Example 3. The microspheres were highly elevated. porous structure. The microspheres were tested using a BET specific surface tester with a specific surface area of Ο.όη^ Ζ.Οηι ² · with an average pore diameter of 2-30 nm. After gas chromatography analysis, the condensate was evaporated to a mixture of water, ethyl acetate and ethanol. The content of the plasticizer triacetin in the microspheres is 1.6% to 2.6%.

Example 4

A sample of 13 g of waste cellulose acetate tow (in which the plasticizer triacetin content was 8.2% of the total mass of the sample, and the degree of acetyl substitution was 2.3) was dissolved in 160 ml of ethyl acetate and 28 ml of ethanol at room temperature. The polymer solution was taken up in a solvent. The obtained polymer solution is added to the dispersion at room temperature to obtain a suspension; (the mixing ratio of the polymer slurry to the dispersion is 1: 2.34) The dispersion is composed of 400 ml of water (mass concentration: 88.3%), 2.2 g. Water soluble methylcellulose (mass concentration 0.5%), 2.4 grams of sodium acetate (0.5% by mass), 2.0 grams of polyoxyethylene sorbitan lauric acid monoester and sorbitan monolaurate The mixture (mass ratio of the two components was 1:1) (mass concentration 0.5%) and 52 ml of ethyl acetate (mass concentration 10.2%). The whole suspension was transferred to a rotary evaporator, and rotated under a pressure of 260 to 180 mbar at a speed of 60 to 150 RPM in a water bath of 40 to 60 degrees Celsius to remove most of the organic solvent and a small amount of water. After about 150 minutes, the evaporator was turned off, naturally cooled to room temperature, centrifuged at 3600 RPM for 10 min in a centrifuge, and the precipitate was separated and added to 100 mL of deionized water. After shaking at 300 RPM for 3 min in a shaker, it was transferred to a centrifuge again. Centrifugal separation. This washing method (washing shaking-centrifugation) was repeated 3 times, and the product was vacuum-dried at 105 ° C for 48 hours to finally obtain cellulose diacetate microspheres.

The cellulose diacetate microspheres were tested for particle size, and 95% of the particles ranged from 5 μm to 50 μm. Figure 4 is a scanning electron micrograph of the prepared cellulose acetate microspheres, and the microspheres exhibited a highly porous structure. The microspheres were tested using a BET specific surface tester with a specific surface area of

The average pore diameter is 100-200 nm. After gas chromatography analysis, the condensate was evaporated to a mixture of water, ethyl acetate and ethanol. The content of the plasticizer triacetin in the microspheres is 1.0% to 2.2%.

The above description of the embodiments is intended to facilitate the understanding and application of the present invention by those skilled in the art. It will be obvious to those skilled in the art that various modifications can be made to these embodiments and the general principles described herein can be applied to other embodiments without the inventive work. Therefore, the present invention is not limited to the embodiments herein, and those skilled in the art, in light of the present invention, the modifications and modifications may be made without departing from the scope of the invention.

Claims

A method for producing cellulose acetate microspheres, comprising the steps of: dissolving a cellulose acetate tow containing a plasticizer in a mixed solvent to obtain a polymer slurry, and then obtaining the obtained polymerization. The slurry is added to the dispersion and thoroughly mixed to obtain a suspension, which lowers the solubility of cellulose acetate and precipitates cellulose acetate microspheres.

The method for producing cellulose acetate microspheres according to claim 1, wherein the plasticizer is one selected from the group consisting of triacetin or ethylene glycol diacetate.

The method for producing cellulose acetate microspheres according to claim 1, wherein the cellulose acetate tow has an acetyl substitution degree of 2.0 to 2.6.

The method for preparing cellulose acetate microspheres according to claim 1, wherein the mixed solvent is a mixture of alcohols and esters, wherein: the volume percentage of the alcohol is 1~ 40%, the volume percentage of the ester is 60 to 99%.

The method for preparing cellulose acetate microspheres according to claim 4, wherein the alcohol is selected from the group consisting of methanol, ethanol, n-propanol or isopropanol; The ester is selected from one or a mixture of methyl acetate, ethyl acetate, n-propyl acetate or isopropyl acetate.

The method for preparing cellulose acetate microspheres according to claim 1, wherein the composition of the dispersion comprises a water-soluble salt, an emulsifier, a protective colloid, water, and an ester selected from the mixed solvent. The mass concentration of the substance, the water-soluble salt is 0.3 to 5% of the total mass of the dispersion, the mass concentration of the emulsifier is 0.1 to 1.5% of the total mass of the dispersion, and the mass concentration of the protective colloid is 0 to 1.5% of the total mass of the dispersion. The mass concentration of the ester substance selected in the mixed solvent is 5.0-15.0% of the total mass of the dispersion, and the mass concentration of water is 77.0-94.6% of the total mass of the dispersion.

The method for producing cellulose acetate microspheres according to claim 6, wherein the water-soluble salt is a metal acetate.

The method for producing cellulose acetate microspheres according to claim 7, wherein the metal acetate is selected from one or a mixture of two of sodium acetate or potassium acetate.

The method for producing cellulose acetate microspheres according to claim 6, wherein the emulsifier is a nonionic surfactant.

10. The method for preparing cellulose acetate microspheres according to claim 9, wherein: the nonionic surfactant is selected from the group consisting of polyoxyethylene sorbitan laurate monoester or sorbitan monolauric One or a mixture of two esters.

The method for preparing cellulose acetate microspheres according to claim 6, wherein the protective colloid is selected from the group consisting of methyl cellulose, methyl cellulose mixed ether, gelatin or polyvinyl alcohol. Or a mixture of several.

12. The method for preparing cellulose acetate microspheres according to claim 1, wherein: said reducing acetic acid Cellulose solubility is achieved by distilling the suspension under reduced pressure or by adding the suspension to deionized water.

The method for preparing cellulose acetate microspheres according to claim 12, wherein the vacuum distillation has a temperature of 40 ° C to 60 ° C and a vacuum of 260 to 180 mbar.

The method for preparing cellulose acetate microspheres according to claim 12, wherein the volume ratio of the suspension to the deionized water is 1:30 to 1:140.

The method for producing cellulose acetate microspheres according to claim 1, wherein the cellulose acetate microspheres contain a plasticizer in an amount of 1.0 to 3.0% by mass.

16. The method for preparing cellulose acetate microspheres according to claim 1, wherein the precipitated cellulose acetate microspheres are purified by the following purification steps:

The cellulose acetate microsphere prepared by the method according to any one of claims 1 to 16, wherein the microsphere has an average particle diameter of 5 to 1500 μm _; an average pore diameter of 20 to 1000 nm; and a specific surface area of 0.6 m ² ' g ~ ! ^^ ^_1 _; cellulose acetate has an acetyl substitution degree of 2.0 to 2.6, and a plasticizer content of 1.0% to 3.0% by mass of cellulose acetate microspheres.