Bacterial cellulose particles as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of cellulose, and particularly relates to bacterial cellulose particles as well as a preparation method and application thereof. Compared with the prior art, physical modification and a mechanical method are combined, so that the bacterial cellulose is converted from the cellulose type I to the cellulose type II, and then the bacterial cellulose type II particle product is obtained through mechanical crushing; in the preparation process, the accumulation structure and crystallinity of a cellulose molecular chain are changed by adjusting the concentration of alkali and the content of alkali liquor in alkaline bacterial cellulose gel, so that the hardness of the bacterial cellulose particles is regulated and controlled, a novel method for regulating and controlling the hardness of the bacterial cellulose particles is created, and the process is simple, does not need special equipment and is green and environment-friendly; and the obtained bacterial cellulose particle product is off-white, odorless and tasteless, the hardness of the cellulose particles is controllable, and the bacterial cellulose particle can be used in the fields of degradable materials, composite materials, daily chemical industry, cosmetics, foods and the like, and has huge scientific value and economic benefit.

Description

Technical Field

[0001] This invention belongs to the field of cellulose technology, and particularly relates to a bacterial cellulose particle, its preparation method, and its application. Background Technology

[0002] Cellulose particles are granular substances made from cellulose. Cellulose is a large polysaccharide composed of glucose and is a major component of plant cell walls. It can be used as a pharmaceutical excipient, such as microcrystalline cellulose, which is commonly used as a diluent, adsorbent, and disintegrant in oral tablets and capsules. Wheat cellulose particles can be used to treat constipation and regulate intestinal function. They can also be used in the production of cosmetics. For example, researchers at the University of Jena in Germany found that cellulose particles with a size of 50 to 250 nm have stability and multiple affinities, and can bind to active substances such as vitamin A and vitamin E, carrying them into the skin to improve skincare effects. They are also used in biopharmaceutical manufacturing; for example, cellulose particles can be used as chromatographic packing materials to remove aggregates of antibody drugs.

[0003] The main methods for preparing cellulose particles include mechanical, chemical, and biological methods.

[0004] Mechanical methods include high-pressure homogenization and high-energy ball milling. High-pressure homogenization disperses cellulose suspensions into nanoscale particles under high-speed shearing and collision through high-pressure homogenizing equipment; high-energy ball milling uses high-speed rotating milling jars and balls to grind cellulose into nanoscale particles.

[0005] Chemical methods include acid hydrolysis, enzymatic hydrolysis, and chemical oxidation. Acid hydrolysis uses strong acids such as concentrated sulfuric acid or hydrochloric acid to hydrolyze the polymer chains of cellulose under acidic conditions; enzymatic hydrolysis uses cellulase to hydrolyze cellulose; and chemical oxidation uses oxidants such as chromic acid or hydrogen peroxide to oxidize the hydroxyl and methyl groups of cellulose, causing it to decompose into nano-sized cellulose.

[0006] Biological methods include microbial fermentation and tissue culture. Microbial fermentation utilizes specific microorganisms such as acetic acid bacteria to produce nanocellulose through a biosynthetic process; tissue culture utilizes plant tissue culture technology to prepare nanocellulose by culturing and growing plant cells.

[0007] However, none of the above methods can adjust the hardness of cellulose particles. Summary of the Invention

[0008] In view of this, the technical problem to be solved by the present invention is to provide a bacterial cellulose particle, a method for preparing the same, and its application, wherein the preparation method can adjust the hardness of the bacterial cellulose.

[0009] This invention provides a method for preparing bacterial cellulose particles, comprising the following steps:

[0010] S1) Pretreatment of bacterial cellulose gel;

[0011] S2) The pretreated bacterial cellulose gel is mixed with an alkaline solution to obtain an alkaline bacterial cellulose gel system; the alkaline solution includes an alkaline substance.

[0012] S3) The alkaline bacterial cellulose gel system is subjected to alkali condensation modification to obtain modified bacterial cellulose gel;

[0013] S4) The modified bacterial cellulose gel is dried and pulverized to obtain bacterial cellulose particles.

[0014] Preferably, the pretreatment in step S1) includes cleaning and cutting; the target size of the cutting is greater than or equal to 1 cm and less than or equal to 3 cm in at least one direction.

[0015] Preferably, the alkaline substance is selected from one or more of sodium hydroxide, potassium hydroxide, and quaternary ammonium bases;

[0016] The mass concentration of the alkaline substance in the alkaline solution is 4% to 10%.

[0017] The mass concentration of alkaline substances in the alkaline bacterial cellulose gel system is 2% to 6%.

[0018] Preferably, the alkali condensation modification in step S3) is carried out by adding an alkaline substance to a poor solvent or a high-concentration alkaline solution; the mass concentration of the high-concentration alkaline solution is greater than or equal to 15%; the poor solvent is miscible with water.

[0019] Preferably, the undesirable solvent is selected from one or more of dimethyl sulfoxide, N,N-dimethylformamide, and N,N-dimethylacetamide;

[0020] The high-concentration alkaline solution includes one or more of sodium hydroxide, potassium hydroxide, and quaternary ammonium bases.

[0021] Preferably, the mass of the undesirable solvent is 2 to 5 times the mass of the alkaline bacterial cellulose gel system;

[0022] Alternatively, the mass of the high-concentration alkaline solution is 2 to 5 times the mass of the alkaline bacterial cellulose gel system.

[0023] Preferably, the alkaline bacterial cellulose gel system is compressed before alkali shrinkage modification; the compression is to 1 / 2 to 1 / 12 of the mass of the alkaline bacterial cellulose gel system.

[0024] Preferably, the alkali condensation modification time is 2-6 hours.

[0025] The present invention also provides bacterial cellulose particles prepared by the above preparation method.

[0026] The present invention also provides an application of the bacterial cellulose particles prepared by the above preparation method in the preparation of biodegradable materials, composite material reinforcing agents, composite material fillers, friction agents for daily chemical products, or animal feed additives.

[0027] Compared with existing technologies, this invention combines physical modification and mechanical methods to convert bacterial cellulose from cellulose type I to cellulose type II. Then, it obtains type II bacterial cellulose granules through mechanical pulverization. During the preparation process, the hardness of the bacterial cellulose granules is controlled by adjusting the concentration of alkali and the content of alkali solution in the alkaline bacterial cellulose gel, thereby altering the packing structure and crystallinity of the cellulose molecular chains. This pioneering method for controlling the hardness of bacterial cellulose granules is simple, requires no special equipment, and is environmentally friendly; all reagents used are recyclable. Furthermore, the resulting bacterial cellulose granules are off-white, odorless, tasteless, and have controllable hardness. They can be used in biodegradable materials, composite materials, daily chemical and cosmetic products, and food, possessing significant scientific value and economic benefits. It can also be extended to the development of related products such as plant cellulose and animal cellulose. Attached Figure Description

[0028] Figure 1 A schematic diagram of the preparation process of bacterial cellulose particles provided by the present invention;

[0029] Figure 2 This is a packaging image of the compressed bacterial cellulose gel used in the examples;

[0030] Figure 3 This is a photograph of the bacterial cellulose particles prepared in Example 1 of the present invention. Detailed Implementation

[0031] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0032] This invention provides a method for preparing bacterial cellulose particles, comprising the following steps: S1) pretreating bacterial cellulose gel; S2) mixing the pretreated bacterial cellulose gel with an alkaline solution to obtain an alkaline bacterial cellulose gel system; wherein the alkaline solution includes an alkaline substance; S3) subjecting the alkaline bacterial cellulose gel system to alkali condensation modification to obtain a modified bacterial cellulose gel; S4) drying and pulverizing the modified bacterial cellulose gel to obtain bacterial cellulose particles.

[0033] See Figure 1 , Figure 1 This is a schematic diagram of the preparation process of bacterial cellulose particles provided by the present invention.

[0034] In this invention, there are no special restrictions on the source of any raw materials; they can be commercially available.

[0035] In this invention, the bacterial cellulose gel can be obtained by compressing and soaking bacterial cellulose.

[0036] First, the bacterial cellulose gel is pretreated. In a specific embodiment of the present invention, the pretreatment preferably includes washing and cutting, more preferably washing first and then cutting. The washing is preferably done by soaking and stirring with tap water to remove surface contaminants. The present invention does not have any special restrictions on the target shape of the cutting, which can be strip-shaped, granular, or irregular. The target size of the cutting is preferably greater than or equal to 1 cm and less than or equal to 3 cm in at least one direction. If the size is too small, it will be difficult to separate, and if it is too large, it will lead to excessively long alkali soaking and alkali shrinkage modification time, reducing production efficiency and increasing production costs.

[0037] The pretreated bacterial cellulose gel is then mixed with an alkaline solution and impregnated to obtain an alkaline bacterial cellulose gel system. The alkaline solution includes an alkaline substance. The alkaline substance can be any alkaline substance well known to those skilled in the art and is not particularly limited. In this invention, it is preferably one or more of sodium hydroxide, potassium hydroxide, and quaternary ammonium alkali. The mass concentration of the alkaline substance in the alkaline solution is preferably 4% to 10%. Optionally, the mass concentration of the alkaline substance in the alkaline solution is 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any two of the above values. After mixing evenly, it can be left to stand, stirred, or ultrasonically treated, without any particular limitation. The mass concentration of the alkaline substance in the alkaline bacterial cellulose gel system obtained by impregnation is 2% to 6%. Optionally, the mass concentration of the alkaline substance in the alkaline bacterial cellulose gel system is 2%, 3%, 4%, 5%, 6%, or any two of the above values. If the alkali concentration is too low, the subsequent alkali condensation modification time will be longer, and the resulting bacterial cellulose particles will have lower hardness. If the alkali concentration is too high, the cellulose will degrade and it will not be conducive to the recycling and reuse of the alkali.

[0038] The alkaline bacterial cellulose gel system is subjected to alkali condensation modification; the alkali condensation modification is preferably carried out by adding an alkaline substance to a poor solvent or a high-concentration alkaline solution.

[0039] In a specific embodiment of the present invention, the mass of the unsuitable solvent is preferably 2 to 5 times the mass of the alkaline bacterial cellulose gel system. If the amount of unsuitable solvent is too low, the alkali condensation modification time will be long, while if the amount is too high, the cost of recycling and reusing the dehydrating agent will increase. Optionally, the mass of the unsuitable solvent is preferably 2, 3, 4, or 5 times the mass of the alkaline bacterial cellulose gel system, or any two of the above values. The unsuitable solvent is any solvent known to those skilled in the art that is insoluble, sparingly soluble, or slightly soluble in alkaline substances, and miscible with water. There are no special limitations. In the present invention, one or more of dimethyl sulfoxide, N,N-dimethylformamide, and N,N-dimethylacetamide are preferred.

[0040] In a specific embodiment of the present invention, the mass of the high-concentration alkaline solution is preferably 2 to 5 times the mass of the alkaline bacterial cellulose gel system; optionally, the mass of the high-concentration alkaline solution is preferably 2, 3, 4, or 5 times the mass of the alkaline bacterial cellulose gel system, or any two of the above values; the high-concentration alkaline solution includes one or more of sodium hydroxide, potassium hydroxide, and quaternary ammonium bases, and the alkaline substance therein may be the same as or different from the alkaline substance in the alkaline solution in step S2), without any particular limitation; the mass concentration of the high-concentration alkaline solution is preferably greater than or equal to 15%, more preferably 15% to 30%; optionally, the mass concentration of the high-concentration alkaline solution is 15%, 20%, 25%, or 30%, or any two of the above values.

[0041] In a specific embodiment of the present invention, the alkaline bacterial cellulose gel system is preferably compressed before alkali shrinkage modification; the compression is preferably to 1 / 2 to 1 / 12 of the mass of the alkaline bacterial cellulose gel system; optionally, the compression is preferably to 1 / 2, 1 / 3, 1 / 4, 1 / 5, 1 / 6, 1 / 7, 1 / 8, 1 / 9, 1 / 10, 1 / 11, 1 / 12 of the mass of the alkaline bacterial cellulose gel system, or a range between any two of the above values. A higher compression ratio results in a lower alkali content, leading to incomplete subsequent alkali shrinkage and lower particle size and hardness after alkali shrinkage modification.

[0042] In one specific embodiment of the present invention, the alkali condensation modification is preferably carried out under stirring conditions.

[0043] In one specific embodiment of the present invention, the alkali condensation modification time is preferably 2 to 6 hours; optionally, the alkali condensation modification time is 2 hours, 3 hours, 4 hours, 5 hours, 6 hours or any two of the above values.

[0044] In a specific embodiment of the present invention, after alkali condensation modification, the product is preferably washed with an acid solution until neutral, followed by water washing to obtain modified bacterial cellulose gel; specifically, the washing can be performed in small amounts and multiple times; the acid solution can be any acidic solution known to those skilled in the art, and there are no special limitations, but dilute hydrochloric acid is preferred in the present invention; the number of water washings is preferably 2 to 3 times.

[0045] The modified bacterial cellulose gel is dried; in a specific embodiment of the present invention, the drying preferably includes compression dehydration and heating drying; the compression dehydration is preferably compressed until no water drips; the heating drying temperature is preferably 80℃~105℃; optionally, the heating drying temperature is 80℃, 85℃, 90℃, 95℃, 100℃, 105℃ or any two of the above values.

[0046] After drying, the material is pulverized to obtain bacterial cellulose particles. In a specific embodiment of the present invention, the pulverization is specifically mechanical pulverization, and more specifically, a conventional pulverizer, an ultrafine pulverizer, or a ball mill can be used. The pulverization speed is preferably 1000~7000 r / min; optionally, the pulverization speed is 1000 r / min, 2000 r / min, 3000 r / min, 4000 r / min, 5000 r / min, 6000 r / min, 7000 r / min, or any two of the above values. Since the modified bacterial cellulose material has increased hardness, it is beneficial for rapid pulverization, so a conventional pulverizer fully meets the production requirements. After pulverization, it is preferable to sieve the material to obtain bacterial cellulose particles of different sizes; the particle size of these bacterial cellulose particles is in the micrometer range.

[0047] In another specific embodiment of the present invention, after pulverization, the material is soaked in water, homogenized under high pressure, and then spray-dried to obtain bacterial cellulose particles. The soaking time is preferably 1 to 4 hours; optionally, the soaking time is 1 hour, 2 hours, 3 hours, 4 hours, or any two of the above values. The pressure of the high-pressure homogenization is 30 to 200 MPa; optionally, the pressure of the high-pressure homogenization is 30 MPa, 60 MPa, 90 MPa, 120 MPa, 150 MPa, 180 MPa, 200 MPa, or any two of the above values. The bacterial cellulose particles obtained at this time have a particle size in the nanometer range.

[0048] This invention modifies the stacking structure and crystallinity of cellulose molecular chains by adjusting the concentration and content of alkali in alkaline bacterial cellulose gel, thereby controlling the hardness of bacterial cellulose particles. It pioneers a new method for controlling the hardness of bacterial cellulose particles, featuring a simple process, no special equipment required, and environmental friendliness, with all reagents being recyclable. The resulting bacterial cellulose particles are off-white, odorless, tasteless, and have controllable hardness, making them suitable for use in biodegradable materials, composite materials, daily chemicals, cosmetics, and food, among other fields. It possesses significant scientific value and economic benefits and can be further extended to the development of related products such as plant cellulose and animal cellulose.

[0049] The present invention also provides bacterial cellulose particles prepared by the above preparation method.

[0050] In one specific embodiment of the present invention, the hardness of the bacterial cellulose particles is preferably 120~320 MPa; optionally, the hardness of the bacterial cellulose particles is 120 MPa, 150 MPa, 190 MPa, 200 MPa, 220 MPa, 250 MPa, 270 MPa, 290 MPa, 300 MPa, 310 MPa, 315 MPa, 320 MPa or any two of the above values.

[0051] In one specific embodiment of the present invention, when the particle size of the bacterial cellulose particles is in the micrometer range, its hardness can be tested using a nanoindenter; when the particle size of the bacterial cellulose particles is in the nanometer range, its hardness can be tested by in-situ compression using a transmission electron microscope (TEM).

[0052] In one specific embodiment of the present invention, the bacterial cellulose particles are cellulose type II particles.

[0053] The present invention also provides the application of bacterial cellulose particles prepared by the above preparation method in the preparation of biodegradable materials, composite material reinforcing agents, composite material fillers, friction agents for daily chemical products, or animal feed additives.

[0054] To further illustrate the present invention, the following detailed description of a bacterial cellulose particle, its preparation method, and its application is provided in conjunction with embodiments.

[0055] All reagents used in the following examples are commercially available; the compressed bacterial cellulose gel used in the examples was imported from Vietnam, manufactured by Guangming Shunda Plastics Co., Ltd., and the product name is Coconut Jelly. The product packaging image is shown below. Figure 2 As shown, the cellulose content after rehydration is approximately 1%.

[0056] Example 1

[0057] 1.1 Soak the compressed bacterial cellulose gel in tap water to rehydrate it, while simultaneously soaking, stirring, and cleaning it to remove surface contaminants.

[0058] 1.2 The cleaned bacterial cellulose gel is conveyed into an automatic cutting system via a conveyor belt and cut into strips of bacterial cellulose gel with a width of 1 cm.

[0059] 1.3 The mixture was conveyed into an 8% sodium hydroxide alkaline tank via a conveyor belt and stirred for 4 hours to obtain a 4% sodium hydroxide bacterial cellulose gel system.

[0060] 1.4 The alkaline bacterial cellulose gel was transferred into the modification tank and stirred while adding 3 times the mass of the alkaline bacterial cellulose gel system of dimethyl sulfoxide. Stirring was continued for about 3 hours to carry out alkaline condensation modification. After the modification was completed, the dimethyl sulfoxide solution was drained from the bottom.

[0061] 1.5 The sample was washed with dilute hydrochloric acid solution until neutral, and then washed twice with pure water to obtain modified bacterial cellulose.

[0062] 1.6 The modified bacterial cellulose is conveyed into a compression dehydration device using a conveyor belt for rapid dehydration, and then conveyed to a drying system for drying at 105°C.

[0063] 1.7 The dried sample was fed into the pulverizing system and pulverized at 3000 r / min. After sieving, bacterial cellulose particles with a particle size of 250 μm were obtained. X-ray diffraction showed that the cellulose particles were of type II crystal form, and the hardness was tested to be 315.3 MPa using a nanoindenter.

[0064] 1.8 After packaging, 250 μm bacterial cellulose particles are obtained, which can be added to facial cleansers or scrubs as exfoliating particles.

[0065] Figure 3 This is a photograph of the bacterial cellulose particles prepared in Example 1.

[0066] Example 2

[0067] 2.1 Soak the compressed bacterial cellulose gel in tap water to rehydrate it, while stirring and cleaning to remove surface dirt.

[0068] 2.2 The cleaned bacterial cellulose gel is conveyed into an automatic cutting system via a conveyor belt and cut into irregular shapes with a width of about 2cm.

[0069] 2.3 The mixture was conveyed into an 8% potassium hydroxide tank via a conveyor belt and stirred for 3 hours to obtain a 6% potassium hydroxide bacterial cellulose gel system.

[0070] 2.4 The alkaline cellulose gel system was transferred into the modification tank, and N,N-dimethylacetamide with a mass of 3 times that of the alkaline bacterial cellulose gel system was injected while stirring. Stirring was continued for 4 h. After the alkaline condensation modification was completed, the N,N-dimethylacetamide solution was discharged from the bottom.

[0071] 2.5 Wash with dilute hydrochloric acid solution until neutral, then wash twice with pure water to obtain modified bacterial cellulose.

[0072] 2.6 The modified bacterial cellulose is conveyed into a compression dehydration device using a conveyor belt for rapid dehydration, and then conveyed to a drying system for drying at 105°C.

[0073] 2.7 The dried sample was fed into the pulverizing system and pulverized at 4000 r / min. After sieving, bacterial cellulose particles with a particle size of 50 μm were obtained. X-ray diffraction showed that the cellulose particles were of type II crystal form, and the hardness was tested to be 290.5 MPa using a nanoindenter.

[0074] 2.8 After packaging, 50 μm bacterial cellulose particles are obtained, which can be added to toothpaste as a mild polishing agent, or used as a filter aid or to form a filter layer for separating particulate impurities in high-grade lubricating oils.

[0075] Example 3

[0076] 3.1 Soak the compressed bacterial cellulose gel in tap water to rehydrate it, while stirring and cleaning to remove surface dirt.

[0077] 3.2 The cleaned bacterial cellulose gel is conveyed into an automatic cutting system via a conveyor belt and cut into strips of bacterial cellulose gel with a width of 1 cm.

[0078] 3.3 The mixture is conveyed into a 6% sodium hydroxide alkaline tank via a conveyor belt and stirred for 4 hours to obtain a 3% sodium hydroxide bacterial cellulose gel system.

[0079] 3.4 The above-mentioned alkaline bacterial cellulose gel is fed into a compression system for compression and dealkalization to 1 / 2 of its original mass, to obtain an alkaline cellulose gel system.

[0080] 3.5 The compressed alkaline cellulose gel system is transferred into the modification tank, and N,N-dimethylformamide of 3 times the alkaline bacterial cellulose gel system is injected while stirring. Stirring is continued for 3 h. After modification is completed, the N,N-dimethylformamide solution is discharged from the bottom.

[0081] 3.6 Wash with dilute hydrochloric acid solution until neutral, then wash twice with pure water to obtain modified bacterial cellulose.

[0082] 3.7 The modified bacterial cellulose is conveyed into a compression dehydration device using a conveyor belt for rapid dehydration, and then conveyed to a drying system for drying at 105°C.

[0083] 3.8 The dried sample was fed into the pulverizing system and pulverized at 3500 r / min. After sieving, bacterial cellulose particles with a particle size of 250 μm were obtained. X-ray diffraction showed that the cellulose particles were of type II crystal form, and the hardness was tested to be 272.5 MPa using a nanoindenter.

[0084] 3.9 After packaging, 250 μm bacterial cellulose particles are obtained, which can be added to facial cleansers or scrubs as exfoliating particles.

[0085] Example 4

[0086] 4.1 Soak and rehydrate the compressed bacterial cellulose gel with tap water while stirring and cleaning to remove surface contaminants.

[0087] 4.2 The cleaned bacterial cellulose gel is conveyed into an automatic cutting system via a conveyor belt and cut into granular bacterial cellulose gels with a width of 3×3×3 cm.

[0088] 4.3 The mixture was conveyed into a 10% sodium hydroxide and potassium hydroxide (1:1 ratio) mixed alkali tank via a conveyor belt, and sonicated at 25 KH for 2 h while stirring to obtain a bacterial cellulose gel system with a 3% mixed alkali content.

[0089] 4.4 The above alkaline bacterial cellulose gel is fed into a compression system and compressed to 1 / 10 to obtain a compressed alkaline cellulose gel system.

[0090] 4.5 The compressed alkaline cellulose gel system is transferred into the modification tank. While stirring, an anhydrous N,N-dimethylformamide and N,N-dimethylacetamide (ratio 1:1) mixture of 3 times the alkaline bacterial cellulose gel system is injected. Stirring is continued for 2.5 h. After modification is completed, the N,N-dimethylformamide and N,N-dimethylacetamide (ratio 1:1) mixture is discharged from the bottom.

[0091] 4.6 Wash with dilute hydrochloric acid solution until neutral, then wash twice with pure water to obtain modified bacterial cellulose.

[0092] 4.7 The modified bacterial cellulose is conveyed into a compression dehydration unit by a conveyor belt for rapid dehydration, and then conveyed to a drying system at 105°C for drying.

[0093] 4.8 The dried sample was fed into the pulverizing system and pulverized at 5000 r / min. After sieving, bacterial cellulose particles with a particle size of 150 μm were obtained. The particles were soaked in pure water for 2 h, fed into a high-pressure homogenizer and circulated 20 times at 60 MPa, and spray-dried to obtain 200 nm bacterial cellulose nanoparticles. X-ray diffraction analysis showed that the cellulose nanoparticles were of type II crystal form, and the hardness was measured to be 190.8 MPa using in-situ compression testing in TEM.

[0094] 4.9 After packaging, the product is a 200 nm bacterial cellulose nanopowder, which can be used in 3D printing materials; added to biodegradable plastics such as polylactic acid (PLA) and polyhydroxyalkanoates (PHA) as a reinforcing agent or as a surface coating in papermaking; it can also be used as a highly efficient thickener and rheology control agent in coatings.

[0095] Example 5

[0096] 5.1 Soak the compressed bacterial cellulose gel in tap water to rehydrate it, while stirring and cleaning to remove surface dirt.

[0097] 5.2 The cleaned bacterial cellulose gel is conveyed into an automatic cutting system via a conveyor belt and cut into bacterial cellulose gel particles with a width of 2×2×2 cm.

[0098] 5.3 The mixture is conveyed into an 8% sodium hydroxide alkaline tank via a conveyor belt and stirred for 3 hours to obtain a 4% sodium hydroxide bacterial cellulose gel system.

[0099] 5.4 The alkaline bacterial cellulose gel was transferred into the modification tank and 3 times its mass of 20% sodium hydroxide was injected while stirring. Stirring was continued for 6 hours for alkali condensation modification. After the modification was completed, the sodium hydroxide solution was drained from the bottom.

[0100] 5.5 Inject dilute hydrochloric acid solution and wash until neutral, then wash twice with pure water to obtain modified bacterial cellulose.

[0101] 5.6 The modified bacterial cellulose is conveyed into a compression dehydration device using a conveyor belt for rapid dehydration, and then conveyed to a drying system for drying at 105°C.

[0102] 5.7 The dried sample was fed into the pulverizing system and pulverized at 5000 r / min. After sieving, bacterial cellulose particles with a particle size of 150 μm were obtained. X-ray diffraction showed that the cellulose particles were of type II crystal form, and the hardness was tested to be 122.5 MPa using a nanoindenter.

[0103] 5.8 After packaging, 150 μm bacterial cellulose particles are obtained, which can be added to plastics, rubber or resins as reinforcing agents to improve the rigidity, strength and heat resistance of the materials.

[0104] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing bacterial cellulose particles, characterized in that, Includes the following steps: S1) Pretreatment of bacterial cellulose gel; S2) The pretreated bacterial cellulose gel is mixed with an alkaline solution to obtain an alkaline bacterial cellulose gel system; the alkaline solution includes an alkaline substance. S3) The alkaline bacterial cellulose gel system is subjected to alkali condensation modification to obtain modified bacterial cellulose gel; S4) The modified bacterial cellulose gel is dried and pulverized to obtain bacterial cellulose particles.

2. The preparation method according to claim 1, characterized in that, The pretreatment in step S1) includes cleaning and cutting; the target size of the cutting is greater than or equal to 1 cm and less than or equal to 3 cm in at least one direction.

3. The preparation method according to claim 1, characterized in that, The alkaline substance is selected from one or more of sodium hydroxide, potassium hydroxide, and quaternary ammonium bases; The mass concentration of the alkaline substance in the alkaline solution is 4% to 10%. The mass concentration of alkaline substances in the alkaline bacterial cellulose gel system is 2% to 6%.

4. The preparation method according to claim 1, characterized in that, The alkali condensation modification in step S3) is carried out by adding an alkaline substance to a poor solvent or a high-concentration alkaline solution; the mass concentration of the high-concentration alkaline solution is greater than or equal to 15%; the poor solvent is miscible with water.

5. The preparation method according to claim 4, characterized in that, The undesirable solvent is selected from one or more of dimethyl sulfoxide, N,N-dimethylformamide and N,N-dimethylacetamide; The high-concentration alkaline solution includes one or more of sodium hydroxide, potassium hydroxide, and quaternary ammonium bases.

6. The preparation method according to claim 4, characterized in that, The mass of the unsuitable solvent is 2 to 5 times the mass of the alkaline bacterial cellulose gel system; Alternatively, the mass of the high-concentration alkaline solution is 2 to 5 times the mass of the alkaline bacterial cellulose gel system.

7. The preparation method according to claim 4, characterized in that, The alkaline bacterial cellulose gel system is compressed before alkali shrinkage modification; the compression is carried out to 1 / 2 to 1 / 12 of the mass of the alkaline bacterial cellulose gel system.

8. The preparation method according to claim 4, characterized in that, The alkali condensation modification time is 2-6 h.

9. Bacterial cellulose particles prepared by the preparation method according to any one of claims 1 to 8.

10. The application of bacterial cellulose particles prepared by the preparation method according to any one of claims 1 to 8 in the preparation of biodegradable materials, composite material reinforcing agents, composite material fillers, friction agents for daily chemical products, or animal feed additives.

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