Type II bacterial cellulose slurry as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of cellulose, and particularly relates to type II bacterial cellulose slurry as well as a preparation method and application thereof. Compared with the prior art, the preparation method has the advantages that the bacterial cellulose gel is modified to be converted into a cellulose type II from a cellulose type I, the stacking structure and the hydrophilic performance of a bacterial cellulose molecular chain are changed, and the bacterial cellulose pulp from the nanometer level to the millimeter level is further obtained through pulping treatment; the product is milky white, odorless, tasteless, controllable in granularity and adjustable in hydrophilic performance, can be quickly dispersed after being added with water and stirred, and can be applied to the fields of preparation of degradable materials, reinforcement of composite materials, papermaking and packaging industry, biomedicine and health, daily chemical industry, cosmetics and the like; and the preparation method greatly reduces the dosage of the poor alkali solvent and the recovery energy consumption, is simple in process, does not need special equipment, and is green and environment-friendly.

Description

Technical Field

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

[0002] Cellulose pulp refers to fibrous substances, primarily composed of cellulose, separated from plant materials through chemical or mechanical methods. It is an indispensable bio-based material in modern industrial society. Originating from natural plants, it is processed into various forms of products and serves as a fundamental raw material for many industries, including papermaking, synthetic fibers (such as viscose fiber), and coatings, permeating all aspects of life. With increasing demands for environmental protection and sustainable development, utilizing fast-growing forests (such as eucalyptus), bamboo, and agricultural waste (such as straw) to produce pulp, as well as developing more environmentally friendly pulping and bleaching technologies (such as elemental chlorine-free bleaching ECF and total chlorine-free bleaching TCF), has become an important development trend in this industry.

[0003] Chemical pulp is produced by cooking plant materials with chemicals (such as caustic soda and sodium sulfide) under high temperature and pressure, dissolving most of the lignin and hemicellulose, thereby separating cellulose fibers. These fibers have high purity, few impurities, good strength, and a lighter color, making them the main type of pulp used for producing high-grade paper and synthetic fibers. The main production methods include sulfate pulping (the most mainstream method, the product of which is also known as "kraft pulp") and sulfite pulping.

[0004] Mechanical pulping involves grinding wood through mechanical friction to separate fibers. It yields a high pulp rate (up to 90-95%) and is low in cost. However, it retains almost all of the lignin, making the paper prone to yellowing, brittleness, and poor durability. It is mainly used for newsprint, low-grade magazine paper, and other papers that do not require long-term storage.

[0005] Chemimechanical pulp is produced by first subjecting wood chips to a slight chemical pretreatment, followed by mechanical pulping. It falls between chemical pulp and mechanical pulp, balancing high pulp yield and good fiber strength. It is mainly used in paperboard, coated white paperboard, and tissue paper.

[0006] Compared with plant cellulose, bacterial cellulose does not contain impurities such as lignin and hemicellulose, and does not require complex pulping pretreatment such as delignification and bleaching. Its purity can reach more than 99%, resulting in high pulp purity. However, due to its unique nanostructure, it is prone to agglomeration at high concentrations. Direct use of nanocellulose dispersions results in low content and limited applications. Summary of the Invention

[0007] In view of this, the technical problem to be solved by the present invention is to provide a type II bacterial cellulose slurry with controllable particle size, adjustable hydrophilicity and rapid dispersion upon addition of water, as well as its preparation method and application.

[0008] This invention provides a method for preparing type II bacterial cellulose slurry, comprising the following steps:

[0009] S1) Pretreatment of bacterial cellulose gel;

[0010] S2) The pretreated bacterial cellulose gel is immersed in an alkaline solution to obtain an alkaline bacterial cellulose gel; the alkaline solution includes an alkaline substance.

[0011] S3) The alkaline bacterial cellulose gel is compressed to obtain compressed alkaline cellulose gel.

[0012] S4) The alkaline bacterial cellulose gel is subjected to alkaline condensation modification in a poor solvent containing an alkaline substance to obtain modified bacterial cellulose; the poor solvent is miscible with water;

[0013] S5) The modified bacterial cellulose is pulped to obtain type II bacterial cellulose pulp.

[0014] Preferably, the alkaline substance is selected from one or more of sodium hydroxide, potassium hydroxide, and quaternary ammonium bases;

[0015] The quaternary ammonium base is selected from tetraalkylammonium hydroxide; the alkyl group has 1 to 4 carbon atoms;

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

[0017] The alkaline bacterial cellulose gel has a mass concentration of 2% to 5%.

[0018] Preferably, in step S3), the material is compressed to 1 / 2 to 1 / 12 of the mass of the alkaline bacterial cellulose gel.

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

[0020] Preferably, the mass of the undesirable solvent is 2 to 5 times that of the alkaline bacterial cellulose gel system;

[0021] The alkali condensation modification time is 2-6 h.

[0022] Preferably, the pretreatment in step S1) includes cleaning and cutting; the cutting is to at least one size greater than or equal to 1 cm and less than or equal to 3 cm;

[0023] After alkali condensation modification in step S4), the product is washed with acid solution until neutral, then washed with water to obtain modified bacterial cellulose.

[0024] Preferably, the pulping process in step S5) includes beating and refining.

[0025] After pulping, the pulp is compressed, dehydrated, and sterilized to obtain type II bacterial cellulose pulp.

[0026] Preferably, the pulping speed is 200~400 r / min;

[0027] The grinding process is carried out by grinding or high-pressure homogenization; the grinding speed is 900~3000 r / min; the pressure of the high-pressure homogenization is 30~200 MPa.

[0028] After grinding, the pulp is compressed, dehydrated, and sterilized to obtain type II bacterial cellulose pulp.

[0029] The present invention also provides a type II bacterial cellulose slurry prepared by the above preparation method.

[0030] The present invention also provides an application of the type II bacterial cellulose slurry prepared by the above preparation method in the preparation of biodegradable materials, composite material reinforcing agents, paper and packaging industrial products, biomedical and health products, or daily chemical products.

[0031] Compared with existing technologies, this invention modifies bacterial cellulose gel, transforming it from cellulose type I to cellulose type II, thereby altering the packing structure and hydrophilic properties of the bacterial cellulose molecular chains. Further pulping treatment yields bacterial cellulose slurries ranging from nanometer to millimeter scale. The products are milky white, odorless, tasteless, with controllable particle size and adjustable hydrophilic properties. They disperse rapidly upon addition of water and stirring, making them suitable for preparing biodegradable materials, reinforcing composite materials, and applications in the paper and packaging industries, biomedicine and health fields, and daily chemical and cosmetic products. Furthermore, this preparation method significantly reduces the amount of alkaline solvents used and the energy consumption for recycling; the process is simple, requires no special equipment, and is environmentally friendly.

[0032] Experiments show that the type II bacterial cellulose slurry prepared by this invention is milky white, odorless, tasteless, has controllable cellulose particle size, adjustable hydrophilicity, and good dispersibility. It can be customized to provide different products for different application scenarios, further expanding the application range of bacterial cellulose. In addition, the amount of alkaline substances used as poor solvents and the energy consumption for recycling are reduced by 50% to 90%. Attached Figure Description

[0033] Figure 1 A schematic diagram of the preparation process of a type II bacterial cellulose slurry provided by the present invention;

[0034] Figure 2 This is a packaging image of the compressed bacterial cellulose gel used in the embodiments of the present invention;

[0035] Figure 3This is a photograph of the type II bacterial cellulose slurry prepared in Example 1 of the present invention. Detailed Implementation

[0036] 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.

[0037] This invention provides a method for preparing type II bacterial cellulose slurry, comprising the following steps: S1) pretreating bacterial cellulose gel; S2) immersing the pretreated bacterial cellulose gel in an alkaline solution to obtain alkaline bacterial cellulose gel; wherein the alkaline solution includes an alkaline substance; S3) compressing the alkaline bacterial cellulose gel to obtain compressed alkaline cellulose gel; S4) subjecting the alkaline bacterial cellulose gel to alkaline condensation modification in a poor solvent containing an alkaline substance to obtain modified bacterial cellulose; wherein the poor solvent is miscible with water; S5) pulping the modified bacterial cellulose to obtain type II bacterial cellulose slurry.

[0038] See Figure 1 , Figure 1 This is a schematic diagram of the preparation process of the type II bacterial cellulose slurry provided by the present invention.

[0039] In this invention, there are no special restrictions on the source of any raw materials; they can be commercially available.

[0040] In this invention, the bacterial cellulose gel can be obtained by compressing and soaking bacterial cellulose.

[0041] 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 preferably uses water for soaking and stirring 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; 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.

[0042] The pretreated bacterial cellulose gel is then subjected to alkali treatment in an alkaline solution to obtain an alkaline bacterial cellulose gel. The alkaline solution contains an alkaline substance. The alkaline substance can be any alkaline substance 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 base. The quaternary ammonium base is preferably tetraalkylammonium hydroxide. The number of carbon atoms in the alkyl group is preferably 1 to 4, specifically 1, 2, 3, or 4. 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 special restrictions; the mass concentration of alkaline substances in the alkaline bacterial cellulose gel obtained by alkali impregnation is 2%~5%; optionally, the mass concentration of alkaline substances in the alkaline bacterial cellulose gel is 2%, 3%, 4%, 5%, or any two of the above values; if the alkali concentration is too low, the resulting bacterial cellulose slurry will have high water absorption, which is not conducive to dispersion, and if the alkali concentration is too high, it will not be conducive to the recovery and reuse of alkali.

[0043] The alkaline bacterial cellulose gel is compressed to obtain a compressed alkaline cellulose gel; the compression is preferably to 1 / 2 to 1 / 12 of the mass of the alkaline bacterial cellulose gel; 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, or any two of the above values. A higher compression ratio results in a lower alkali content, which can lead to incomplete subsequent alkali shrinkage.

[0044] The alkaline bacterial cellulose gel is subjected to alkali condensation modification in a poor solvent containing an alkaline substance to obtain modified bacterial cellulose. In a specific embodiment of the present invention, the mass of the poor solvent is preferably 2 to 5 times that of the alkaline bacterial cellulose gel. If the amount of poor solvent is too low, the alkali condensation modification time will be long, while if the amount is too high, the cost of recycling and reuse will increase. Optionally, the mass of the poor solvent is preferably 2, 3, 4, 5 times that of the alkaline bacterial cellulose gel or any two of the above values. The poor 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, and there are no special limitations. In the present invention, one or more of dimethyl sulfoxide, N,N-dimethylformamide, and N,N-dimethylacetamide are preferred.

[0045] In one specific embodiment of the present invention, the alkali condensation modification is preferably carried out under stirring conditions.

[0046] In a specific embodiment of the present invention, the alkali-modified solution is preferably dehydrated by distillation to obtain a mixture of alkaline substance and undesirable solvent, which is further separated by filtration to obtain the alkaline substance and undesirable solvent. The alkaline substance can be reused by alkali impregnation, and the undesirable solvent can be reused by alkali-modification. The preparation method provided by the present invention solves the technical problems of large amounts of undesirable solvent and high energy consumption in the recovery of bacterial cellulose during alkali condensation.

[0047] 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.

[0048] 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; 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 restrictions, but dilute hydrochloric acid is preferred in the present invention; the number of water washings is preferably 2 to 3 times.

[0049] The modified bacterial cellulose was pulped to obtain type II bacterial cellulose pulp.

[0050] In one specific embodiment of the present invention, the pulping process includes beating and grinding. Pulp can be obtained by pulping; the pulping method is a method well known to those skilled in the art and is not particularly limited. In this invention, a pulper is preferably used; the pulper can be any pulper well known to those skilled in the art and is not particularly limited. This invention includes, but is not limited to, vertical hydraulic pulpers, horizontal hydraulic pulpers, drum pulpers, and high-consistency hydraulic pulpers, etc.; the pulping speed is preferably 200~3000 r / min; the pulping speed is 200 r / min, 400 r / min, 600 r / min, 800 r / min, 1000 r / min, 1200 r / min, 1400 r / min, 1500 r / min, 1600 r / min, 1800 r / min, 2000 r / min, 2200 r / min, 2400 r / min, 2500 r / min, 2600 r / min, 2800 r / min, etc. r / min, 3000 r / min, or any two of the above values.

[0051] The pulp prepared by pulping can be further subjected to fiber separation, fibrillation, and swelling. The pulping is preferably carried out by grinding or high-pressure homogenization. Grinding is preferably performed using a pulping machine, including but not limited to disc mills, conical mills, and double-disc mills. The grinding speed is preferably 900~3000 r / min; optionally, the grinding speed is 900 r / min, 1000 r / min, 1200 r / min, 1400 r / min, 1500 r / min, 1600 r / min, 1800 r / min, 2000 r / min, 2200 r / min, 2400 r / min, 2500 r / min, 2600 r / min, 2800 r / min, 3000 r / min, or any two of the above values. The particle size of the pulp obtained by grinding is in the millimeter range. The pressure of the high-pressure homogenization is preferably 30~200 MPa; optionally, the pressure of the high-pressure homogenization is 30 MPa. MPa, 60 MPa, 90 MPa, 120 MPa, 150 MPa, 180 MPa, 200 MPa or any two of the above values; the resulting slurry has a particle size in the nanometer range.

[0052] In one specific embodiment of the present invention, depending on the desired particle size of the type II bacterial cellulose slurry, such as if nano-sized particles are required, after grinding, it can be further processed using a high-pressure homogenizer or a microfluidic nano-dispersion device to obtain nano-sized type II bacterial cellulose slurry.

[0053] In a specific embodiment of the present invention, after pulping, the pulp is compressed, dehydrated, and sterilized to obtain type II bacterial cellulose pulp; the sterilization temperature is preferably 120℃~125℃; and the sterilization time is preferably 15~25 min.

[0054] This invention modifies bacterial cellulose gel, transforming it from cellulose type I to cellulose type II, thereby altering the molecular chain stacking structure and hydrophilic properties of bacterial cellulose. Further pulping treatment yields bacterial cellulose slurries with particle sizes ranging from nanometers to millimeters. The products are milky white, odorless, tasteless, with controllable particle size, adjustable hydrophilicity, and rapid dispersion upon addition of water and stirring. They can be used in the preparation of biodegradable materials, composite material reinforcement, paper and packaging industries, biomedicine and health fields, and daily chemical and cosmetic products. Furthermore, this preparation method significantly reduces the amount of alkaline solvents used and the energy consumption for recycling; the process is simple, requires no special equipment, and is environmentally friendly.

[0055] The present invention also provides a type II bacterial cellulose slurry prepared by the above preparation method.

[0056] This invention also provides an application of the type II bacterial cellulose slurry prepared by the above preparation method in the preparation of biodegradable materials, composite material reinforcing agents, paper and packaging industrial products, biomedical and health products, and daily chemical products.

[0057] To further illustrate the present invention, the following detailed description, in conjunction with embodiments, provides a type II bacterial cellulose slurry, its preparation method, and its application.

[0058] 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%.

[0059] Example 1

[0060] 1.1 Soak the compressed bacterial cellulose gel in tap water to rehydrate it, while stirring and cleaning to remove surface dirt.

[0061] 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.

[0062] 1.3 The mixture was 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.

[0063] 1.4 The alkaline bacterial cellulose gel is fed into a compression system and compressed to remove alkali to 1 / 12 of its original mass, resulting in a compressed alkaline cellulose gel system.

[0064] 1.5 Then, the compressed alkaline cellulose gel system was transferred to the modification tank and 4 times the mass of the alkaline bacterial cellulose gel system was injected while stirring. The mixture was stirred for 4 hours for modification. After the modification was completed, the dimethyl sulfoxide solution was drained from the bottom.

[0065] 1.6 The sample was washed with dilute hydrochloric acid solution until neutral, and then washed twice with pure water to obtain modified bacterial cellulose.

[0066] 1.7 The dimethyl sulfoxide solution recovered in step 1.5 above is subjected to distillation and dehydration to obtain sodium hydroxide and dimethyl sulfoxide. The sodium hydroxide and dimethyl sulfoxide are further separated by filtration. The sodium hydroxide is recycled into the alkali leaching process for reuse, and the dimethyl sulfoxide is recycled into the modification process for reuse.

[0067] 1.8 The modified bacterial cellulose was conveyed into a horizontal hydraulic pulper using a conveyor belt and the rotation speed was set to 1000 r / min for pulping. Then it was fed into a double-disc refiner at 2500 r / min for refining. The bacterial cellulose pulp was taken for testing and a bacterial cellulose pulp with a size of 300~500 microns was obtained.

[0068] 1.9 The qualified slurry is discharged from the bottom and fed into the dewatering system for compression and dewatering, and then sealed and packaged.

[0069] 1.10 The packaged bacterial cellulose slurry was transferred to a sterilization system and sterilized at 121°C for 20 minutes to obtain a type II bacterial cellulose slurry with a crystal size of 300-500 micrometers (X-ray diffraction analysis showed that the bacterial cellulose crystals in the slurry were of type II). The photograph is shown below. Figure 3 As shown, it can be used in biomedicine and tissue engineering, papermaking, composite materials, and daily chemical and consumer products.

[0070] Example 2

[0071] 2.1 Soak the compressed bacterial cellulose gel in tap water to rehydrate it, while stirring and cleaning to remove surface dirt.

[0072] 2.2 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.

[0073] 2.3 The mixture was 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.

[0074] 2.4 The alkaline bacterial cellulose gel particles are fed into a compression system for compression and dealkalization to 1 / 10 of their original mass, resulting in a compressed alkaline cellulose gel system.

[0075] 2.5 Then, the compressed alkaline cellulose gel system was transferred into the modification tank and three times the mass of the alkaline bacterial cellulose gel system was injected while stirring. Stirring was continued for 3.5 hours for modification. After modification, the dimethyl sulfoxide solution was drained from the bottom.

[0076] 2.6 Wash with dilute hydrochloric acid solution until neutral, then wash twice with pure water to obtain modified bacterial cellulose.

[0077] 2.7 The dimethyl sulfoxide solution recovered in step 2.5 above is subjected to distillation and dehydration to obtain sodium hydroxide and dimethyl sulfoxide. The sodium hydroxide and dimethyl sulfoxide are further separated by filtration. The sodium hydroxide is recycled into the alkali leaching process for reuse, and the dimethyl sulfoxide is recycled into the modification process for reuse.

[0078] 2.8 The modified bacterial cellulose was conveyed into a vertical hydraulic pulper using a conveyor belt and the rotation speed was set to 400 r / min for pulping. Then it was fed into a double-disc refiner at 2000 r / min for refining. The bacterial cellulose pulp was taken for testing and a bacterial cellulose pulp with a size of 500~800 microns was obtained.

[0079] 2.9 The qualified slurry is discharged from the bottom and fed into the dewatering system for compression and dewatering, and then sealed and packaged.

[0080] 2.10 The bacterial cellulose slurry is fed into a sterilization system and sterilized at 121°C for 20 min to obtain a 500-800 micrometer-sized type II bacterial cellulose slurry (X-ray diffraction analysis shows that the bacterial cellulose crystal form in the slurry is type II). It can be used in high-grade paper and specialty paper, composite material reinforcing agent, thickener and rheology modifier, and 3D printing materials, etc.

[0081] Example 3

[0082] 3.1 Soak the compressed bacterial cellulose gel in tap water to rehydrate it, while stirring and cleaning to remove surface dirt.

[0083] 3.2 The cleaned bacterial cellulose gel is conveyed into an automatic cutting system via a conveyor belt and cut into irregular shapes.

[0084] 3.3 The mixture is conveyed into an 8% potassium hydroxide tank via a conveyor belt and stirred for another 3 hours to obtain a 4% potassium hydroxide bacterial cellulose gel system.

[0085] 3.4 The alkaline bacterial cellulose gel is fed into a compression system and compressed to remove alkali to 1 / 8 of its original mass, resulting in a compressed alkaline cellulose gel system.

[0086] 3.5 The compressed alkaline cellulose gel system was transferred into the modification tank, and N,N-dimethylacetamide was injected at a ratio of 3 times the mass of the alkaline bacterial cellulose gel system while stirring. Stirring was continued for 4 h. After modification was completed, the N,N-dimethylacetamide solution was discharged from the bottom.

[0087] 3.6 Wash with dilute hydrochloric acid solution until neutral, then wash twice with pure water to obtain modified bacterial cellulose.

[0088] 3.7 The N,N-dimethylacetamide solution recovered in step 3.5 above is subjected to distillation and dehydration to obtain potassium hydroxide and N,N-dimethylacetamide. The potassium hydroxide and N,N-dimethylacetamide are further separated by filtration. The potassium hydroxide is recycled into the alkali leaching process for reuse; the N,N-dimethylacetamide is recycled into the modification process for reuse.

[0089] 3.8 The modified bacterial cellulose was conveyed into a horizontal hydraulic pulper using a conveyor belt and the rotation speed was set to 2000 r / min for pulping. Then, it was fed into a high-pressure homogenizer at 60 MPa for 20 cycles. The bacterial cellulose slurry was taken for testing and a bacterial cellulose slurry of 200~500 nanometers was obtained.

[0090] 3.9 The qualified slurry is discharged from the bottom and fed into the dewatering system for compression and dewatering. After dewatering, it is sealed and packaged.

[0091] 3.10 The packaged nano-bacterial cellulose slurry is transferred to a sterilization system and sterilized at 121°C for 20 minutes to obtain a 200-500 nm type II bacterial cellulose slurry (X-ray diffraction analysis shows that the bacterial cellulose crystal form in the slurry is type II). It can be used in the paper and packaging industry, as a composite material reinforcing agent, in electronic and optical devices, coatings, inks and adhesives, etc.

[0092] Example 4

[0093] 4.1 Soak the compressed bacterial cellulose gel in tap water to rehydrate it, while stirring and cleaning to remove surface dirt.

[0094] 4.2 The cleaned bacterial cellulose gel is conveyed into an automatic cutting system via a conveyor belt and cut into strips of bacterial cellulose gel, each 2 cm wide.

[0095] 4.3 The mixture was conveyed into a mixed alkali tank containing 9% sodium hydroxide and potassium hydroxide (mass ratio 1:1) via a conveyor belt, and sonicated at 25 KH for 1 h while stirring to obtain a 4.5% mixed alkali bacterial cellulose gel system.

[0096] 4.4 The alkaline bacterial cellulose gel strip is fed into a compression system for compression and dealkalization to 1 / 4 of its original mass, resulting in a compressed alkaline cellulose gel system.

[0097] 4.5 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 4 h. After modification is completed, the N,N-dimethylformamide solution is discharged from the bottom.

[0098] 4.6 Inject dilute hydrochloric acid solution to wash until neutral, then wash twice with pure water to obtain modified bacterial cellulose.

[0099] 4.7 The solution recovered in step 4.5 above is subjected to distillation and dehydration to obtain a mixture of mixed alkali and N,N-dimethylformamide. The mixed alkali and N,N-dimethylformamide are further separated by filtration. The mixed alkali is recycled into the alkali leaching process for reuse; the N,N-dimethylformamide is recycled into the modification process for reuse.

[0100] 4.8 Neutral modified bacterial cellulose was conveyed into a vertical hydraulic pulper using a conveyor belt at a speed of 2000 r / min for pulping. Then, it was fed into a double-disc refiner at 2800 r / min for refining. The bacterial cellulose pulp was taken for testing, and a bacterial cellulose pulp with a size of 200-400 microns was obtained.

[0101] 4.9 The qualified slurry is discharged from the bottom and enters the dewatering system for compression and dewatering. After dewatering, it is sealed and packaged.

[0102] 4.10 The packaged modified bacterial cellulose slurry is transferred into a sterilization system and sterilized at 121°C for 20 minutes to obtain a type II bacterial cellulose slurry with a diameter of 200-400 micrometers (X-ray diffraction analysis shows that the bacterial cellulose crystal form in the slurry is type II). It can be used as a reinforcing agent for high-grade paper and specialty paper, a thickener and rheology modifier, and a 3D printing material.

[0103] Example 5

[0104] 5.1 Soak the compressed bacterial cellulose gel in tap water to rehydrate it, while stirring and cleaning to remove surface dirt.

[0105] 5.2 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.

[0106] 5.3 The mixture is conveyed by a conveyor belt into a mixed alkali tank containing 10% sodium hydroxide and potassium hydroxide (ratio 1:1), and sonicated at 25 KH for 1.5 h while stirring to obtain a bacterial cellulose gel system with a mixed alkali content of 5%.

[0107] 5.4 The alkaline bacterial cellulose gel particles are fed into a compression system for compression and dealkalization to half of their original mass, resulting in a compressed alkaline cellulose gel system.

[0108] 5.5 The compressed alkaline cellulose gel system is transferred into the modification tank. While stirring, an anhydrous N,N-dimethylformamide and N,N-dimethylacetamide (mass ratio 1:1) mixture of 2 times the alkaline bacterial cellulose gel system is injected. Stirring is continued for 4 h. After modification is completed, the N,N-dimethylformamide and N,N-dimethylacetamide (1:1 ratio) mixture is discharged from the bottom.

[0109] 5.6 Wash with dilute hydrochloric acid solution until neutral, then wash twice with pure water to obtain modified bacterial cellulose.

[0110] 5.7 The mixed solution of N,N-dimethylformamide and N,N-dimethylacetamide (ratio 1:1) recovered in step 5.5 above is subjected to distillation and dehydration to obtain a mixed alkali, a mixture of N,N-dimethylformamide and N,N-dimethylacetamide, and a further filtration solution to separate the mixed alkali and N,N-dimethylformamide and N,N-dimethylacetamide. The mixed alkali is recycled into the alkali leaching process for reuse; the N,N-dimethylformamide and N,N-dimethylacetamide are recycled into the modification process for reuse.

[0111] 5.8 Neutral modified bacterial cellulose was conveyed into a horizontal hydraulic pulper using a conveyor belt at a speed of 2500 r / min for pulping. Then, it was fed into a high-pressure homogenizer at 60 MPa for 30 cycles. The bacterial cellulose slurry was then tested to obtain bacterial cellulose slurry with a particle size of 100-300 nanometers.

[0112] 5.9 The qualified slurry is discharged from the bottom and enters the dewatering system for compression and dewatering. After dewatering, it is sealed and packaged.

[0113] 5.10 The bagged bacterial cellulose slurry after packaging is conveyed into the sterilization system and sterilized at 121°C for 20 minutes to obtain a 100-300 nm type II bacterial cellulose slurry (X-ray diffraction analysis shows that the bacterial cellulose crystal form in the slurry is type II). It can be used in the paper and packaging industry, as a reinforcing agent for composite materials, electronic and optical devices, coatings, inks and adhesives, etc.

[0114] Comparative Example 1

[0115] Step 1.4, compression and dealkali removal, is omitted; all other operations are the same as in Example 1.

[0116] Compared with Example 1, the amount of dimethyl sulfoxide used increased by 11 times, the energy consumption for distillation recovery of dimethyl sulfoxide and alkali also increased by 11 times, and the alkali reduction time increased by 2.6 times.

[0117] Comparative Example 2

[0118] 2.1 Add the bacterial nanocellulose dispersion to sodium hydroxide solution and stir continuously to adjust the concentration to obtain a 5% sodium hydroxide bacterial nanocellulose dispersion, and let it stand for 4 h.

[0119] 2.2 Add a high concentration of sodium hydroxide to the above sodium hydroxide bacterial nanocellulose dispersion while stirring to obtain a 15% sodium hydroxide bacterial nanocellulose dispersion. Stir for 20 min. Filter quickly to separate the modified bacterial nanocellulose precipitate and sodium hydroxide solution.

[0120] 2.3 Take the above sodium hydroxide solution and recycle it in step 1 for reuse.

[0121] 2.4 Take the precipitate separated in step 2.2, wash it with dilute hydrochloric acid until neutral, wash it twice with pure water, and further filter it to obtain neutral modified bacterial nanocellulose colloid.

[0122] 2.5 The above-mentioned neutral modified nanocellulose is compressed and dehydrated, and then sealed and packaged.

[0123] 2.6 The packaged bacterial cellulose slurry is then transferred to a sterilization system and sterilized at 121°C for 20 min to obtain type II micro-nano bacterial cellulose slurry.

[0124] Products made from bacterial cellulose slurry obtained using high-concentration alkali have significantly reduced mechanical properties.

[0125] Comparative Example 3

[0126] 3.1 Add the bacterial nanocellulose dispersion to sodium hydroxide solution and stir continuously to adjust the concentration to obtain a sodium hydroxide cellulose nanofiber dispersion with a content of 3%, and sonicate for 30 min.

[0127] 3.2 Add 3 times the mass of dimethyl sulfoxide to the above sodium hydroxide and bacterial nanocellulose system while stirring for 120 min. Compress and filter to separate the precipitate and solvent.

[0128] 3.3 The above solvent is subjected to distillation and dehydration, followed by filtration to separate sodium hydroxide and dimethyl sulfoxide. Sodium hydroxide and dimethyl sulfoxide are obtained. The sodium hydroxide is recycled for reuse in the alkali leaching process, and the dimethyl sulfoxide is recycled for reuse in the modification process.

[0129] 3.4 Take the precipitate from step 3.2, wash it with dilute hydrochloric acid until neutral, wash it twice with pure water, and further filter it to obtain neutral modified nanocellulose.

[0130] 3.5 The above-mentioned neutral modified nanocellulose is compressed and dehydrated, and then sealed and packaged.

[0131] 3.6 The bagged bacterial cellulose slurry after packaging is transferred into a sterilization system and sterilized at 121℃ for 20 min to obtain type II micro-nano bacterial cellulose slurry.

[0132] Compared with Example 1, when the cellulose concentration in the bacterial cellulose dispersion is high, agglomeration is more likely to occur during alkali condensation. When producing the same concentration of modified bacterial cellulose, the amount of dimethyl sulfoxide used increases by more than 10 times, and the energy consumption for distillation recovery of dimethyl sulfoxide and alkali also increases by more than 10 times.

[0133] 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 process for the preparation of a type II bacterial cellulose slurry, characterized in that, The method comprises the following steps: S1) pretreating the bacterial cellulose gel; S2) immersing the pretreated bacterial cellulose gel in an alkali solution to obtain an alkaline bacterial cellulose gel; the alkali solution comprises an alkaline substance; S3) compressing the alkaline bacterial cellulose gel to obtain a compressed alkaline cellulose gel; S4) modifying the alkaline bacterial cellulose gel in a poor solvent of the alkaline substance to obtain a modified bacterial cellulose; the poor solvent is miscible with water; S5) pulping the modified bacterial cellulose to obtain a type II bacterial cellulose pulp.

2. The production method according to claim 1, characterized by, The alkaline substance is selected from one or more of sodium hydroxide, potassium hydroxide and quaternary ammonium base; The quaternary ammonium base is selected from tetraalkylammonium hydroxide; the number of carbon atoms of the alkyl group is 1-4; The mass concentration of the alkaline substance in the alkali solution is 4%-10%; The mass concentration of the alkaline substance in the alkaline bacterial cellulose gel is 2%-5%.

3. The method of claim 1, wherein, The compression in step S3) is to 1 / 2-1 / 12 of the mass of the alkaline bacterial cellulose gel.

4. The method of claim 1, wherein, The poor solvent is selected from one or more of dimethyl sulfoxide, N,N-dimethylformamide and N,N-dimethylacetamide.

5. The preparation method according to claim 1, characterized in that, The mass of the poor solvent is 2-5 times that of the alkaline bacterial cellulose gel system; The time for the alkaline modification is 2-6 h.

6. The method of claim 1, wherein, The pretreatment in step S1) comprises washing and cutting; the cutting is to a size of at least 1 cm and at most 3 cm; After the alkaline modification in step S4), the modified bacterial cellulose is obtained by washing with an acid solution to neutral, and washing with water.

7. The preparation method according to claim 1, characterized in that, The pulping in step S5) comprises beating and grinding; After the pulping, compression dewatering, sterilization are performed to obtain the type II bacterial cellulose pulp.

8. The preparation method according to claim 7, characterized in that, The rotation speed of the beating is 200-400 r / min; The grinding is performed by grinding or high-pressure homogenization; the rotation speed of the grinding is 900-3000 r / min; the pressure of the high-pressure homogenization is 30-200 MPa; After the grinding, compression dewatering, sterilization are performed to obtain the type II bacterial cellulose pulp.

9. The type II bacterial cellulose pulp prepared by the preparation method of any one of claims 1-8.

10. The use of the type II bacterial cellulose pulp prepared by the preparation method of any one of claims 1-8 in preparing degradable materials, composite material reinforcing agents, products in the papermaking and packaging industries, products in the biomedical and health fields, or daily chemical products.

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