WO2018054212A1 - 石墨烯复合物、其制备方法及用途、制备纳米纤维素的方法及所得纳米纤维素、高性能的石墨烯复合纳米纤维素及其制备方法 - Google Patents

石墨烯复合物、其制备方法及用途、制备纳米纤维素的方法及所得纳米纤维素、高性能的石墨烯复合纳米纤维素及其制备方法 Download PDF

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WO2018054212A1
WO2018054212A1 PCT/CN2017/100249 CN2017100249W WO2018054212A1 WO 2018054212 A1 WO2018054212 A1 WO 2018054212A1 CN 2017100249 W CN2017100249 W CN 2017100249W WO 2018054212 A1 WO2018054212 A1 WO 2018054212A1
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graphene
nanocellulose
group
cellulose
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PCT/CN2017/100249
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English (en)
French (fr)
Inventor
唐一林
张金柱
王鹏辉
郑应福
许日鹏
刘顶
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济南圣泉集团股份有限公司
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Priority claimed from CN201610835479.XA external-priority patent/CN106832425A/zh
Priority claimed from CN201611143799.5A external-priority patent/CN106832426A/zh
Priority claimed from CN201611160905.0A external-priority patent/CN106829944B/zh
Application filed by 济南圣泉集团股份有限公司 filed Critical 济南圣泉集团股份有限公司
Publication of WO2018054212A1 publication Critical patent/WO2018054212A1/zh

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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/15—Nano-sized carbon materials
    • C01B32/182—Graphene
    • C01B32/194—After-treatment

Definitions

  • the invention relates to the field of nano materials, in particular to a graphene composite, a preparation method thereof and use thereof, a method for preparing nano cellulose, a obtained nano cellulose, a high performance graphene composite nano cellulose and a preparation method thereof .
  • Graphene is a two-dimensional material of a honeycomb structure composed of a single layer of sp2 hybridized carbon atoms, and has many excellent properties. Since its discovery in 2004, graphene has become a research hotspot in the scientific community. While studying the physicochemical properties of graphene, graphene-related composite materials are also emerging. In the direction of nanoscience, graphene is also used to prepare related nanocomposites, especially graphene/metal or graphene/metal oxide nanocomposites. Due to the excellent properties of graphene, these nanocomposites have broad research prospects in new energy, biosensing, catalysis, optical materials and other fields.
  • Graphene on the market is generally divided into powders and slurries.
  • powders strong ultrasound is required before application, and even dispersants are needed to assist dispersion.
  • slurry the situation is slightly better, but ultrasound is also required before use, and there will also be a dispersant in the dispersion.
  • the graphene is generally modified or a better dispersant is selected, or the graphene concentration is as low as possible, and the concentration of the graphene slurry on the market is generally 0.5 wt%. Below, otherwise the dispersion effect will be poor and precipitation will occur easily. This not only increases transportation costs, but also causes a large amount of solvent contamination, and requires removal of the dispersion during downstream applications, which inevitably increases process complexity and cost.
  • Nanocrystalline cellulose is a widely existing and renewable resource on earth.
  • the nanocrystalline cellulose is a cellulose crystal obtained by removing the amorphous region and the low crystallinity crystalline region in the cellulose after the natural cellulose is treated (for example, acid hydrolysis, biological enzymatic hydrolysis, etc.).
  • Nanocrystalline cellulose prepared from natural cellulose not only has the basic structure and properties of cellulose, but also has a large specific surface area, high crystallinity (>70%), high hydrophilicity, high Young's modulus, high strength. (7500MPa), ultra-fine structure and high transparency, good biodegradability and biocompatibility as well as stable chemical properties.
  • nano-microcrystalline cellulose has great potential for chemical modification, which promotes its application in papermaking, medicine, food, composite materials and other fields. It’s hot.
  • a graphene composite comprising a graphene composite mainly composed of nanocellulose and graphene, wherein nanocellulose At least a portion is interposed between the graphene species.
  • the graphene-based substance includes a mixture of one or more of graphene, biomass graphene, graphene oxide, and graphene derivatives.
  • Graphene is a layered structure or a pleated sheet structure, and the sheet size is on the order of nanometers, because of the intermolecular force, it is easy to cause agglomeration.
  • Nanocellulose is also nano-scale, but has a long-to-diameter ratio, which is equivalent to a rod-like structure. When two different nanomaterials are mixed together, it is generally believed that they will still reunite.
  • the present inventors have unexpectedly found that nanocellulose and graphene-like substances are sufficiently dispersed, and the obtained graphene composite is very easily dispersed in a liquid without using an ultrasonic or dispersing agent.
  • the diameter of the nanocellulose is smaller than the diameter of the graphene-based material. Without being bound by theory, it is believed that during the mixing of the two, the small diameter of the nanocellulose is easily inserted between the graphene sheets, and the graphene is weakened by the length of the nanocellulose, which weakens the graphene sheet. The intermolecular forces between the layers make the graphene-based materials easy to disperse later after agglomeration.
  • the number of layers of the graphene is 1-10 layers; preferably, the graphene is selected from one of single layer graphene, double layer graphene, and a few layers of graphene having 3-10 layers or A variety.
  • the biomass graphene is a monolayer graphene, a small layer graphene, a graphene nanosheet layer structure prepared by a catalytic or carbonization process using biomass resources as a main raw material, and is loaded with metal/non-metal.
  • a composite carbon material of a metal compound is a monolayer graphene, a small layer graphene, a graphene nanosheet layer structure prepared by a catalytic or carbonization process using biomass resources as a main raw material, and is loaded with metal/non-metal.
  • a composite carbon material of a metal compound is a monolayer graphene, a small layer graphene, a graphene nanosheet layer structure prepared by a catalytic or carbonization process using biomass resources as a main raw material, and is loaded with metal/non-metal.
  • the graphene derivative comprises any one or a combination of at least two of elemental doped graphene or functionalized graphene.
  • the graphene derivation comprises any one or a combination of at least two of elemental doped graphene or functionalized graphene.
  • the element doped graphene comprises any one or a combination of at least two of metal doped graphene or non-metal element doped graphene.
  • the metal element in the metal doped graphene comprises potassium, sodium, gold, silver, iron, copper, nickel, chrome titanium, vanadium or cobalt.
  • the non-metallic elements in the non-metallic element doped graphene include nitrogen, phosphorus, silicon, boron or silicon.
  • the non-metal element doped graphene comprises any one or a combination of at least two of nitrogen-doped graphene, phosphorus-doped graphene or sulfur-doped graphene.
  • the functionalized graphene comprises graphene grafted with a functional group.
  • the functionalized graphene includes graphene grafted with any one or a combination of at least two of a hydroxyl group, a carboxyl group or an amino group.
  • the hydroxyl group comprises R1-OH, and R1 is an alkyl group; preferably, the hydroxyl group is selected from the group consisting of methylhydroxyl, ethylhydroxyl, and propyl One or more of a hydroxy group, a butyl hydroxy group, a pentyl hydroxy group, and a hexyl hydroxy group.
  • the carboxyl group comprises R2-COOH, and R2 is an alkyl group; preferably, the carboxyl group is selected from the group consisting of methylcarboxyl, ethylcarboxy, propylcarboxy, butylcarboxy, pentylcarboxy, hexylcarboxyl One or more of them.
  • the amino group comprises R3-NH3, and the R3 comprises an alkyl group; preferably, the amino group is selected from the group consisting of methylhydroxyl, ethylhydroxy, propylhydroxy, butylhydroxy,pentylhydroxy,hexylhydroxyl One or more of them.
  • the graphene-based material is subjected to TEMPO catalytic oxidation treatment.
  • Graphene-based substances treated by the TEMPO catalytic oxidation system have more carboxyl groups added between the graphene sheets, and thus the intercalation effect of the nanocellulose is added to make the dispersion effect more excellent.
  • the TEMPO catalytic oxidation system comprises an aqueous solution system comprising TEMPO and/or a derivative thereof, hypochlorite or a bromide salt; more preferably TEMPO (2,2,6,6-tetramethylpiperidine)
  • the TEMPO derivative is selected from the group consisting of 2-azaadamantane-N-oxyl, 1-methyl-2-aza-adamantane-N-oxyl, 1,3-dimethyl-2-nitrogen
  • a heteroadamantane-N-oxyl group a 4-hydroxy TEMPO derivative.
  • the TEMPO and/or its derivative is added in an amount of 0.05 to 5% by weight, preferably 0.1 to 3%, more preferably 0.3% to 2%, still more preferably 0.5 to 1% by weight of the graphene-based substance; 0.1%, 0.3%, 0.8%, 1%, 1.2%, 1.5%, 2.5%, 3.5%, 4%, 4.5%, and the like.
  • the hypochlorite is added in an amount of 10 to 500%, preferably 30% to 90%, more preferably 40 to 75%, and may be 50%, 70%, 100%, 120%, by weight of the graphene-based substance. 135%, 160%, 200%, 300%, 400%, 450%, etc.
  • the chlorinated salt is added in an amount of 0.5 to 50%, preferably 10 to 30%, more preferably 3% to 20%, still more preferably 5% to 10%, and may be 3% or 8% by weight of the graphene-based substance. , 10%, 12%, 15%, 18%, 25%, 35%, 45%, etc.
  • TEMPO is a typical process for treating graphenes by mixing TEMPO and/or its derivatives with a halogen salt (such as a bromide salt such as NaBr), stirring and dissolving, then adding graphene to continue stirring, and then stirring.
  • a hypochlorite such as sodium hypochlorite solution is added to control the pH between 10-11.
  • the particle size of the graphene composite of the present invention is not critical, and of course, the smaller the particle size, the better.
  • the present invention splits the large particles into small particles by introducing nanocellulose, or interpolates the nanocellulose inside the large particles, which has weakened the agglomeration between the graphenes and is easily dispersed.
  • the graphene has a particle size of 50 ⁇ m.
  • the nanocellulose enters the interior of the particle, and the graphene sheet is disassembled to form a particle having a particle size of 30 ⁇ m.
  • nanofibers may still exist inside the 30 ⁇ m particle.
  • the graphene composite has a D90 of 30 ⁇ m or less, preferably 15 ⁇ m or less, preferably 10 ⁇ m or less, preferably 5 ⁇ m or less, preferably 1 ⁇ m or less, more preferably 0.51 ⁇ m or less, further preferably 0.4 ⁇ m or less. Still more preferably 0.3 ⁇ m or less, and most preferably 0.2 ⁇ m or less.
  • the graphene composite particles have a D90 in the range of 0.001-30 ⁇ m, 0.01-25 ⁇ m, 0.015-20 ⁇ m, 0.02-15 ⁇ m, 0.03-10 ⁇ m, 0.04-9 ⁇ m, 0.05-8 ⁇ m, 0.06-6 ⁇ m, 0.07-5 ⁇ m, 0.08-3 ⁇ m, 0.09-1 ⁇ m, or 0.1-0.5 ⁇ m.
  • the content of nanocellulose in the graphene composite is within 10 wt%, preferably within 8 wt%, preferably within 5 wt%, preferably within 3 wt%, preferably within 1 wt%, preferably at 0.5. Less than wt%. According to some embodiments, the content of nanocellulose ranges from 0.1 wt% to 10 wt%, between 0.2 wt% and 8 wt%, between 0.3 wt% and 5 wt%, between 0.4 wt% and 3 wt%, 0.5 wt%. Between -2 wt% or 0.1 wt% - 1 wt%.
  • Nanocellulose is used as an additive for graphenes, and excessive addition is likely to cause side effects.
  • Nano-cellulose itself is a nano-material, which has a long-diameter ratio. If it is added in too much, it is easy to agglomerate itself. In addition, the diameter is small and the length is long. It is easy to form a entanglement to wrap the graphene-like substances together, but instead Adding the reaction of agglomeration, and thus controlling the amount of addition thereof, is also one of the innovations of the present invention.
  • the nanocellulose content of the invention is preferably controlled within 10 wt%, of course, the most preferred range is between 0.1 wt% and 1 wt%, the amount of nanocellulose added is small, and the problem of dispersion of graphene is solved. Affects downstream applications of graphene.
  • the nanocellulose is selected to have a diameter within 30 nm, preferably within 20 nm, more preferably within 10 nm, more preferably within 5 nm; and the aspect ratio of nanocellulose is (5-200):1, It is preferably (10-100): 1, more preferably (15-40): 1.
  • the length of the cellulose is too long, and the diameter is too small, which may cause the nanocellulose to adsorb on the surface of the graphene and lose its proper function.
  • the nanocellulose preparation raw material is derived from a crop such as corn cob, plant straw, cotton, and wood; preferably, the nanocellulose is a nanocellulose selected from the group consisting of corncob cellulose as a raw material;
  • the nanocellulose is prepared by purifying and bleaching corncob cellulose.
  • the present inventors have found that nanocellulose prepared by corncob cellulose has a better dispersion effect on graphene, especially for dispersing biomass graphene.
  • the invention further relates to a method for preparing a graphene composite comprising: dispersing nanocellulose and graphene in a solution into a suspension.
  • the method further comprises: removing the suspension from the solution, washing, and drying.
  • solution removal includes centrifugation, filtration, or a combination thereof.
  • the drying comprises vacuum drying, freeze drying, air flow drying, microwave drying, infrared drying, high frequency drying or a combination thereof.
  • the drying is freeze drying.
  • the dispersion is performed by one of high speed agitation or shearing, sonication, and grinding, or a combination thereof, preferably by dispersion, by sonication and milling.
  • the frequency of the milling is between 25 and 35 Hz, more preferably between 27 and 32 Hz, and the time of milling is controlled between 4 and 6 hours, more preferably between 5 and 5.5 hours.
  • the time of the ultrasonic dispersion treatment is from 15 to 60 min, more preferably from 30 to 50 min.
  • the power of the ultrasonic dispersion treatment is from 500 to 1500 kW, more preferably from 1,000 to 1,200 kW.
  • the graphene composite of the present invention can be obtained by physically blending graphene-based materials with nano-cellulose, but the effect is worse.
  • the solution itself also acts to disperse the graphene-like substance and the nano-cellulose, and it is easier to interpolate the nano-cellulose into the graphene material and increase Nanocellulose and graphene The number of collisions and the angle of collision are more conducive to the combination of the two.
  • the invention also relates to the use of graphene composites according to the invention in textiles, pharmaceuticals, environmental protection, food packaging, composite materials.
  • the invention also relates to a graphene composite nanocellulose with high performance, wherein the graphene material can maintain a high content, the graphene particles are still uniformly dispersed, the particle size is relatively uniform, and the agglomeration is achieved.
  • the particles are less produced, and the graphenes are added in the process of preparing the nanocellulose, so that the graphenes can be opened in the non-crystalline region of the cellulose and intercalated with the nanocellulose to achieve in-situ recombination, which is more effective.
  • Embodiments of the present invention provide a high-performance graphene composite nanocellulose product, which is mainly composed of a graphene-based substance and nano-cellulose, and the graphene-based substance and nano-cellulose are carried in situ with each other;
  • the content of the graphene-based substance is 20% by weight or less, further 10% by weight or less, and further preferably 0.5% by weight to 5% by weight.
  • the graphene composite nanocellulose has a graphene content of less than 20 wt%, because if the graphene content is too high, the graphene and the nanocellulose are easily separated, and the graphene particles are agglomerated in the nanocellulose.
  • the dispersibility is not good, which in turn affects the performance of the final product. Therefore, the content of graphene substances needs to be controlled within a suitable range to ensure excellent dispersibility. This range is also a comparison optimized by the inventors through a large amount of practical experience.
  • a suitable content more preferably, the content of the graphene-based substance is controlled to be 10% by weight or less, and may be between 0.5% by weight and 5% by weight, and other than, for example, 1% by weight, 1.5% by weight, 2% by weight, and 2.5% by weight. , 3.5 wt%, 4 wt%, and the like.
  • the graphene composite nanocellulose of the present invention has a relatively high graphene content, but the particle dispersion is relatively uniform, and additionally imparts excellent antibacterial properties, excellent toughness, hot water resistance and antistatic property to the nanocellulose material.
  • the raw material cost is low and the investment is small. This further expands the market application range of the fiber material, increases the added value of the product, and is also beneficial for further promotion and application.
  • the nanocellulose is prepared from corncob cellulose, and preferably, the nanocellulose is prepared by purifying and bleaching corncob cellulose.
  • the raw material for preparing nanocellulose of the present invention is preferably corncob cellulose, because corncob cellulose itself is equivalent to waste recycling, realizing reasonable redistribution of resources, and the use of such cellulose makes the prepared graphene composite nanometer.
  • Cellulose products have a more uniform particle size.
  • corncob cellulose to be purified and bleached prior to preparation of nanocellulose
  • the corncob raw material is subjected to acid hydrolysis, and the pentose sugar solution and the acid hydrolysis residue are obtained after separation; the acid used is a common acid solution such as sulfuric acid, hydrochloric acid, phosphoric acid, sulfurous acid, etc., and the amount of the acid is 1-10% by weight of the corncob raw material.
  • hydrolysis temperature is 100-150 ° C, time is 0.5-3h;
  • the above acid hydrolysis residue is treated with an alkali solution, and after separation, an alkali solution and an alkali residue are obtained.
  • the alkali used is sodium hydroxide, the amount of the base is 1-15 wt% of the corn cob raw material, the treatment temperature is 40-100 ° C, and the time is 1-6 h;
  • bleaching the above-mentioned alkaline residue which comprises one or more of sodium hypochlorite bleaching, hydrogen peroxide bleaching, alkali treatment, acid treatment and the like.
  • corncob cellulose After the above purification treatment, corncob cellulose can be obtained, and the main indexes are cellulose content: 80-95%, whiteness 70-90%, ash 0.1-2%, and fiber length 0.05-0.5 mm.
  • the aspect ratio of the nanocellulose is controlled to be (5-1000):1, preferably (10-300):1, more preferably (15-200):1.
  • the minimum diameter of the nanocellulose is less than 20 nm, preferably 10 nm or less, more preferably 5 nm or less.
  • the graphene-based substance used in the present invention includes one or a mixture of graphene, biomass graphene, graphene oxide, and graphene derivatives, and the graphene derivative is a modified graphene.
  • the graphene derivation comprises any one or a combination of at least two of elemental doped graphene or functionalized graphene.
  • the element doped graphene comprises any one or a combination of at least two of metal doped graphene or non-metal element doped graphene.
  • the metal-doped metal element typically, but not limited to, includes potassium, sodium, gold, silver, iron, copper, nickel, chrome titanium, vanadium or cobalt.
  • the non-metallic element doped graphene typically includes, but is not limited to, nitrogen, phosphorus, silicon, boron or silicon.
  • the non-metal element doped graphene comprises any one or a combination of at least two of nitrogen-doped graphene, phosphorus-doped graphene or sulfur-doped graphene.
  • the functionalized graphene comprises graphene grafted with a functional group.
  • the functionalized graphene comprises graphene grafted with any one or a combination of at least two of a hydroxyl group, a carboxyl group or an amino group.
  • the hydroxyl group of the present invention includes -R1-OH, and the R1 includes an alkane group, and a typical but non-limiting hydroxyl group may be a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group or the like. .
  • the carboxyl group of the present invention includes -R2-COOH, and the R2 includes an alkane group, and a typical but non-limiting hydroxyl group may be a methylhydroxy group, an ethylhydroxy group, a propylhydroxy group, a butylhydroxy group, a pentylhydroxy group, a hexylhydroxy group, or the like. .
  • the carboxyl group of the present invention includes -R3-NH3, and the R3 includes an alkane group, and a typical but non-limiting hydroxyl group may be a methylhydroxy group, an ethylhydroxy group, a propylhydroxy group, a butylhydroxy group, a pentylhydroxy group, a hexylhydroxy group, or the like. .
  • biomass graphene is a two-dimensional nanometer containing a single layer of graphene, a small layer of graphene, a graphene nanosheet layer structure, and supporting a metal/nonmetal compound with a layer number of not more than 10 layers.
  • the carbon material may even be a composite carbon material containing graphitized carbon or a metal/nonmetal compound on the basis of the above.
  • the invention also provides a preparation method of the above-mentioned high-performance graphene composite nanocellulose, wherein the preparation method has a close connection before and after, and the method is simple and quick, and no chemical agent such as acid and alkali is used in the whole preparation process, and the environment is green and there is no
  • the production of waste acid caustic soda, and the preparation method of the present invention also achieves the advantages of using acidification to prepare nanocellulose, such as a suitable aspect ratio.
  • the preparation method has the advantages of simple and easy operation, mild operating conditions, and industrialized production of graphene composite nanocellulose, and good economic benefits.
  • the invention also provides the above-mentioned application of high performance graphene composite nanocellulose, which is widely used and can be widely applied in various industries.
  • the present invention also provides a method for preparing the graphene composite nanocellulose, which comprises the following steps: (A) cellulose, graphene materials and Ionized water is mixed and ultrasonically dispersed and ground to obtain a suspension; (B) the suspension is ultrasonicated, centrifuged, and freeze-dried to obtain graphene composite nanocellulose.
  • the synthesis processes of nanocellulose mainly include the following:
  • MFC microfibrillated cellulose
  • NCC is a rigid rod-shaped cellulose having a diameter of 1 to 100 nm and a length of several tens to several hundreds of nanometers. It generally has a crystalline form of natural cellulose I and forms a stable suspension in water. Specifically, it includes enzymatic hydrolysis method, enzymatic hydrolysis method and biological method.
  • the preparation of NCC by enzymatic hydrolysis method produces a large amount of waste acid and impurities, which requires high reaction equipment, and the residue after reaction is difficult to recover, but the preparation process is relatively mature and has been realized. Industrial production.
  • Biological methods Cellulose prepared by microbial synthesis is commonly referred to as bacterial cellulose, and the physical and chemical properties of bacterial cellulose are similar to those of natural cellulose.
  • the preparation of NCC by biological methods can regulate the structure, crystal form and particle size distribution of NCC, and thus it is easy to realize industrialization and commercialization.
  • the preparation process of bacterial cellulose is complicated, time consuming, high in cost, expensive, and low in yield.
  • the mechanical method is prone to the problem of uneven particle size distribution.
  • the chemical method itself is not environmentally friendly, pollutes the environment, and has a certain degree of damage to the health of the operator.
  • the graphite of the present invention The preparation method of the olefin composite nanocellulose not only solves the problem of uneven distribution of mechanical particle size, but also avoids the problem of serious environmental pollution by using the chemical method, and the operation cost of the whole preparation method is relatively low.
  • the particle size index of the graphene-containing substance is also strictly required, and the D90 index of the graphene-based substance is controlled to be 70 ⁇ m or less, and the D10 index is controlled to be 20 ⁇ m or less.
  • graphene composite nanocellulose products only limited the graphene content, but neglected the important parameter of the particle size index of the graphenes themselves.
  • the inventors of the present invention have conducted a large number of creative experiments by using graphene. The content of the substance and the particle size index are limited to a suitable range, and the interaction of these indexes works together to finally achieve the object of the present invention, and the problem of uneven dispersion of the graphene particles is surely solved.
  • the D90 index of the graphene-based substance is preferably controlled to be less than 50 ⁇ m, and more preferably the D90 index is controlled to be 30 ⁇ m or less, more preferably 5 to 25 ⁇ m. Between, for example, it can be 45um, 40um, 35um, 30um and so on.
  • the control of D90 index below 70 ⁇ m means that the particle size below 100um accounts for 90% of the whole, that is, the maximum particle size of 90% is 100um, which ensures the dispersibility of graphene and ensures the graphene particles.
  • the uniformity of size avoids the occurrence of particle agglomeration.
  • the D90 index of the graphene-based substance is preferably controlled to 20 times or less, preferably 10 times or less, more preferably 5 times or less, or 8 times or less, 11 times or less, 12 times or less, or 13 times, of the D10 index. Less than or less than 14 times.
  • the purpose of this is to Try to maintain the large structure of graphene materials, ensure that graphenes do not agglomerate between layers, and prevent the problem of stress concentration point breakage caused by graphitic materials with different diameters, because the particle size is too large or too small. It is not conducive to the formation of a uniform substance with nanocellulose, so that the performance of all aspects of the composite nanocellulose product is excellent, so it is better to control the particle size index of the graphene material within a suitable range.
  • the specific control of graphene D90, D10 indicators need to adopt a graded pretreatment method, including: mixing graphene materials with deionized water, leaving the bottom precipitate after centrifugation at 2000-3000 rpm.
  • the supernatant liquid is centrifuged at 5000-7000 rpm to obtain a second bottom precipitate and a secondary supernatant, respectively, wherein the fractionated centrifugation liquid comprises a bottom sediment, a secondary bottom precipitate, and a secondary supernatant. It is preferred to have a secondary bottom precipitate.
  • the rate of centrifugation of the bottom precipitate is relatively low, and the rate of further centrifugation of the supernatant is relatively high, because the particle size of the precipitate is generally large, and if the rate is too fast, it is not conducive to the deposition of large particles.
  • the particle size of the supernatant is generally small, so the rate needs to be faster so that the less granular material is present in the supernatant.
  • Such graphene materials with relatively uniform particle size are classified and precipitated at the bottom, or precipitated at the second bottom, or in the secondary supernatant.
  • the fractionated centrate can select any of the above-mentioned classified materials.
  • Graphene materials with uniform particle size can be ensured, and the size of the particles is also suitable, so as to ensure the uniformity of the film diameter, which is beneficial to the subsequent performance of the prepared product.
  • the time of centrifugation operation at 2000-3000 rpm is preferably controlled between 20-40 min, and the time of centrifugation operation at 5000-7000 rpm is preferably controlled between 10-30 min, and the control is more favorable in better operation time.
  • the particle size fractionation treatment is more thorough, so that the particle size distribution is more uniform.
  • the main purpose of the ultrasonic dispersion treatment is to achieve the effect of separation and degradation by mechanical dispersion and ultrasonic cavitation effect, and the time of the ultrasonic dispersion treatment is preferably controlled at 15-60 min, more preferably 30. -50min, the power of the ultrasonic dispersion treatment is preferably controlled between 500-1500kw, more preferably between 1000-1200kw.
  • a certain grinding operation is generally performed before the ultrasonic dispersion treatment, depending on The mutual friction between the grinding beads and the fibers achieves the effect of separating and degrading the fibers, which also correspondingly improves the overall working efficiency.
  • the grinding frequency is preferably controlled between 25-35 Hz, more preferably between 27-32 Hz.
  • the grinding time is preferably controlled between 4 and 6 h, more preferably between 5 and 5.5 h.
  • the graphene material used is preferably subjected to a certain grinding pretreatment before being mixed with the cellulose and deionized water, and more preferably, only the wall of the container after the pretreatment is used. Residual graphenes, mixed with cellulose and deionized water. Since the graphene on the wall of the vessel has better nano-characteristics and a lamellar structure, the graphene-like substance on the wall of the vessel is more preferably selected.
  • the concentration of cellulose is preferably controlled between 1% by weight and 10% by weight, more preferably between 2% by weight and 8% by weight, and may be other than 3wt%, 4wt%, 5wt%, 6wt. %, 7wt%, etc.
  • the method for preparing graphene composite nanocellulose according to the embodiment of the invention improves the efficiency of the grinding itself and shortens the grinding time by adding the graphene material, especially the use of biomass graphene to make the nanocellulose have antibacterial inhibition The functions of bacteria and far infrared are more prominent.
  • the graphene composite nanocellulose prepared by the above preparation method further doubles the mechanical properties of the nanocellulose itself, and additionally imparts excellent antibacterial properties, far infrared properties, excellent toughness, hot water resistance and the nanocellulose.
  • Antistatic performance widely used, has a wide range of applications in pharmaceutical, environmental protection, food packaging, composite materials.
  • the invention also provides a method for preparing nano cellulose, which solves the problems of high energy consumption, serious environmental pollution and easy agglomeration of nano cellulose.
  • the present invention provides the following technical solution: a method for preparing nanocellulose, comprising the following steps:
  • the graphene-based substance is selected from the group consisting of graphene and its derivatives, graphene oxide and its derivatives One or more of the biomass, biomass graphene, and derivatives thereof, preferably graphene oxide/biographene.
  • the above method utilizes a sheet-like structure of a graphene substance to be inserted into an amorphous region in cellulose, and disperses it into a uniformly dispersed nano-scale structure, and the friction of physical grinding is more advantageous for graphene-based materials and fibers.
  • the contact of the element, and the cutting effect of the graphene sheet structure is further realized by grinding external force.
  • the above method of the present invention prevents the nanocrystalline cellulose from agglomerating by cutting to form nanocrystalline cellulose, and then utilizing the physical barrier action of the graphene to form a nanocrystalline cellulose which is stable in performance and easy to transport.
  • the present invention does not require strong mechanical force or high temperature reaction, and thus has low energy consumption and no environmental pollution.
  • the biomass graphene according to the present invention is a monolayer graphene, a small layer graphene, a graphene nanosheet layer structure prepared by a catalytic or carbonization process using biomass resources as a main raw material, and is loaded with metal/non-metal.
  • a composite carbon material of a metal element is a monolayer graphene, a small layer graphene, a graphene nanosheet layer structure prepared by a catalytic or carbonization process using biomass resources as a main raw material, and is loaded with metal/non-metal.
  • the graphene oxide according to the present invention may be a commercially available graphene, or may be a product of oxidation of graphene prepared by partial reduction crosslinking, or may be an oxidized product of graphene prepared by PECVD. It is a graphene oxide produced by other methods.
  • the graphene oxide derivative comprises any one or a combination of at least two of elemental doped graphene oxide or functionalized graphene oxide.
  • the element-doped graphene oxide comprises any one or a combination of at least two of metal-doped graphene oxide or non-metal element-doped graphene oxide.
  • the metal-doped metal element typically, but not limited to, includes potassium, sodium, gold, silver, iron, copper, nickel, chrome titanium, vanadium or cobalt.
  • the non-metallic element doped graphene typically includes, but is not limited to, nitrogen, phosphorus, sulfur, silicon, boron or silicon.
  • the non-metal element doped graphene oxide comprises any one or a combination of at least two of nitrogen-doped graphene oxide, phosphorus-doped graphene oxide or sulfur-doped graphene oxide.
  • the functionalized graphene oxide comprises graphene oxide grafted with a functional group.
  • the functionalized graphene oxide comprises graphene oxide grafted with any one or a combination of at least two of a hydroxyl group, a carboxyl group or an amino group.
  • the hydroxyl group of the present invention includes -R1-OH, and the R1 includes an alkane group, and a typical but non-limiting hydroxyl group may be a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group or the like. .
  • the carboxyl group of the present invention includes -R2-COOH, and the R2 includes an alkane group, and a typical but non-limiting hydroxyl group may be a methyl group.
  • the amino group of the present invention includes -R3-NH3, and the R3 includes an alkane group, and a typical but non-limiting hydroxyl group may be a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group or the like. .
  • the graphene derivative and the biomass graphene derivative are the same as the above graphene oxide derivative.
  • the graphene-based substance is added in an amount of 5 wt% or less, preferably 2 wt% or less, preferably 1 wt% or less, more preferably 0.6 wt% or less, of the aqueous solution of the cellulose precursor.
  • the graphene-like substance has a particle size of ⁇ 30 ⁇ m, preferably ⁇ 15 ⁇ m, preferably ⁇ 3 ⁇ m, preferably ⁇ 500 nm, preferably ⁇ 100 nm, and may be 28 ⁇ m, 25 ⁇ m, 20 ⁇ m, 10 ⁇ m, 5 ⁇ m, 2 ⁇ m, 1 ⁇ m, 200 nm and the like.
  • the cellulose is selected from one or more of a mixture of lignocellulose, corncob cellulose, microcrystalline cellulose, bacterial cellulose, pulp.
  • the pulp is selected from the group consisting of bleached wood pulp, bleached straw pulp, corn core pulp, cotton pulp, hemp pulp, bamboo pulp, mash pulp, dissolving pulp, rag pulp, unbleached wood pulp, and unbleached straw pulp.
  • the grinding according to the present invention does not require the same high requirements as the conventional mechanical method. Since graphene is a two-dimensional material, it has the effects of enhancing the lubricating effect and reducing the friction. Therefore, the introduction of graphene by the grinding process is more advantageous for grinding. The effect is to reduce energy consumption. If the grinding force is too large to favor the action of graphene, the preferred grinding conditions are:
  • Dispersing treatment at a stirring speed of 1000 to 13600 rpm for 1 to 30 minutes, preferably at a stirring speed of 1000 to 3000 rpm for 10 to 20 minutes using an ultrasonic homogenizer having a power of 200 to 400 W; or using a mechanical stirrer or a magnetic stirrer
  • the mixture is continuously stirred at a rate of 300 to 500 rpm for 1 to 72 hours, preferably for 1 to 3 hours.
  • the polishing temperature is 4 to 50 ° C, and more preferably 4 to 10 ° C.
  • the present invention can also combine chemical measures such as acid hydrolysis and TEMPO catalytic oxidation to improve production efficiency.
  • chemical measures such as acid hydrolysis and TEMPO catalytic oxidation to improve production efficiency.
  • an acid is added for acid hydrolysis before or during the grinding:
  • TEMPO catalytic oxidation system is additionally added to the oxidation treatment before or during the grinding:
  • the reaction is stirred at a pH of 10 to 11, 10-40 ° C for 2 to 24 hours under the action of a TEMPO catalytic oxidation system;
  • the catalytic oxidation time is not strictly limited, and generally, depending on the degree of the reaction, for example, when the hydroxyl group is depleted, the catalytic oxidation reaction is terminated, and the consumption of the hydroxyl group may be controlled according to the time.
  • the TEMPO catalytic oxidation system can oxidize some or all of the hydroxyl groups of the cellulose to a carboxyl group, and can also catalyze the oxidation of a hydroxyl group or an epoxy functional group of a graphene substance to a carboxyl group.
  • the TEMPO system partially oxidizes the non-crystalline regions of cellulose into macromolecular structures and allows the crystallization regions to open apart from each other, but also facilitates the shearing of graphenes.
  • graphite is passed through the TEMPO system.
  • the hydroxyl group of the olefinic substance is also oxidized to a carboxyl group, which reduces the thickness of the graphene and is more favorable for the shearing action of the graphene-based substance.
  • the TEMPO catalytic oxidation system is an aqueous system containing TEMPO and/or its derivatives, hypochlorite, bromide and/or perchlorate; more preferably TEMPO, sodium hypochlorite, sodium bromide and / or aqueous solution of sodium perchlorate;
  • the TEMPO derivative is selected from the group consisting of 2-azaadamantane-N-oxyl, 1-methyl-2-aza-adamantane-N-oxyl, 1,3-dimethyl-2-nitrogen
  • 2-azaadamantane-N-oxyl 1-methyl-2-aza-adamantane-N-oxyl, 1,3-dimethyl-2-nitrogen
  • 2-hydroxy TEMPO derivative 4-hydroxy TEMPO derivative
  • the TEMPO and/or its derivative is added in an amount of 0.05% to 5% by weight, preferably 0.1% to 3%, more preferably 0.3% to 2%, still more preferably 0.5% to 1%; %, 0.3%, 0.8%, 1%, 1.2%, 1.5%, 2.5%, 3.5%, 4%, 4.5%, etc.;
  • the hypochlorite is added in an amount of 10% to 500%, preferably 30% to 95%, more preferably 40% to 75% by weight of the cellulose; 50%, 70%, 100%, 120%, 135%, 160%, 200%, 300%, 400%, 450%, etc.;
  • the bromide salt and/or perchlorate is added in an amount of 0.5% to 50%, preferably 10% to 30%, more preferably 3% to 20%, still more preferably 5% to 10% by weight of the cellulose; 3%, 8%, 10%, 12%, 15%, 18%, 25%, 35%, 45%, etc.;
  • the hypochlorite is added at a concentration of from 5 to 15% by weight.
  • the nanocellulose aqueous solution is subjected to solution removal, washing, and drying;
  • the solution removal comprises centrifugation, filtration or a combination thereof;
  • the drying comprises vacuum drying, freeze drying, air drying, microwave drying, spray drying, infrared drying, high frequency drying or a combination thereof; preferably, the drying is freeze drying.
  • the drying conditions have an important influence on the stability of the product.
  • the product is frozen at -20 to -25 ° C for 10 to 20 hours, and then placed in a cold trap of a freeze dryer for pre-preparation.
  • the freezing and freezing dryer has a cold trap temperature of -50 to -80 ° C; after the pre-freezing, it is freeze-dried at a vacuum of 1 to 10 Pa for 24 to 48 hours.
  • the graphene composite of the present invention is very easy to disperse in a solvent and is not easily agglomerated, even without the aid of an ultrasonic or dispersing agent.
  • the high-performance graphene composite nanocellulose provided by the invention can maintain a high content of graphene materials, the graphene particles are still uniformly dispersed, the particle size is relatively uniform, the agglomerated particles are less produced, and the properties are stable;
  • the preparation method of the high-performance graphene composite nanocellulose of the invention has a close connection before and after, and the method is simple and quick, and no chemical agent such as acid and alkali is used in the whole preparation process, and the environment is green and has no waste.
  • the production of acid waste alkali, and the preparation method of the present invention also achieves the advantages of using acidification to prepare nanocellulose, such as a suitable aspect ratio.
  • the preparation method has the advantages of simple and easy operation, mild operating conditions, industrialized production of graphene composite nanocellulose, and good economic benefit;
  • the high-performance graphene composite para-aramid fiber of the invention has a wide application and has wide application in various industries such as medicine, environmental protection, food packaging and composite materials.
  • the prepared nanocellulose has an aspect ratio of 100 or more, especially 200 or more, or even 300 or more; and the diameter can reach 20 nm or less, especially 10 nm or less, or even 5 nm or less.
  • the preparation method has low energy consumption and no environmental pollution.
  • Biomass graphene A The preparation method is Example 4 of Chinese Patent Publication No. CN105502330A.
  • Biomass graphene B The preparation method is Example 7 of Chinese Patent Publication No. CN104016341A.
  • Biomass graphene C The preparation method is Example 1 of Chinese Patent Publication No. CN104724699A.
  • Graphene F Model produced by Changzhou Sixth Element Materials Technology Co., Ltd.: SE1430.
  • Graphene oxide G Model produced by Changzhou Sixth Element Materials Technology Co., Ltd.: SE2430W.
  • Example 2 The difference from Example 1 was that 0.001 g of corncob nanocellulose having a diameter of 5-10 nm and an aspect ratio of 20-30 (the nanocellulose content in the solution was 1.5 wt%) was added.
  • Example 2 The difference from Example 1 was that 0.005 g of corncob nanocellulose having a diameter of 3-5 nm and an aspect ratio of 15-20 (the nanocellulose content in the solution was 2.5 wt%) was added.
  • Example 2 The difference from Example 1 was that 0.03 g of corncob nanocellulose having a diameter of 12-15 nm and an aspect ratio of 10-15 (the nanocellulose content in the solution was 0.5 wt%) was added.
  • Example 2 The difference from Example 1 was that 0.05 g of corncob nanocellulose having a diameter of 1-3 nm and an aspect ratio of 80-100 (the nanocellulose content in the solution was 1.5 wt%) was added.
  • Example 2 The difference from Example 1 was that 0.1 g of corncob nanocellulose having a diameter of 20 to 25 and an aspect ratio of 5 to 10 (having a nanocellulose content of 1.5 wt% in solution) was added.
  • Example 1 The difference from Example 1 is that the corncob nanocellulose is replaced with wood nanocellulose and cotton nanocellulose.
  • Example 1 The difference from Example 1 is that biomass graphene A is replaced with biomass graphene B, biomass graphene C, graphene D, graphene E, graphene F, and graphene oxide G, respectively.
  • Example 2 The difference from Example 2 is that TEMPO catalytic oxidation treatment is performed on the biomass graphene A.
  • the specific steps are as follows: a. Take 1 g of biomass graphene A, add 200 g of water to stir to form a uniform slurry, and then add TEMPO catalytic oxidation combination. The reaction (0.01 g TEMPO, 1 g sodium hypochlorite, 0.05 g sodium bromide) was stirred, and the pH of the reaction system was maintained in the range of 10.5-11 by adjusting with 0.5 wt% sodium hydroxide solution and 1 wt% glacial acetic acid solution. After the change, the reaction was stopped to obtain a suspension, and the reaction time was 2.5 h; b.
  • the suspension obtained in the step a was filtered, and washed repeatedly with water, and centrifuged at a speed of 1000 rpm, each time of centrifugation for 5 minutes, and finally The pH of the suspension was neutral after washing, and dried to obtain a modified graphene powder.
  • Example 1 The difference from Example 1 is that 1 g of biomass graphene A is taken in step (1) and added to 0.01 g of corncob nanocellulose having a diameter of 3-5 nm and a length to diameter ratio of 15-20 (the nanocellulose content in the solution is 2 wt. Stirring was continued for 30 min in an aqueous solution of %).
  • Example 2 The difference from Example 1 is that the grinding step is increased before the drying of the step (2), as follows:
  • the product and the distilled water were mixed into a solution at a mass ratio of 1:10, and subjected to dispersion treatment at a stirring speed of 10,000 rpm for 30 minutes at a normal temperature using an ultrasonic homogenizer having a power of 400 W.
  • Example 2 The difference from Example 1 is that the step of (2) is increased before the drying step, as follows:
  • the product was made into a solution with distilled water at a mass ratio of 1:1000, and continuously stirred at a temperature of 500 rpm for 72 hours at room temperature using a mechanical stirrer.
  • Biomass graphene A, biomass graphene B, biomass graphene C, graphene D, graphene E, graphene F, and graphene oxide G, respectively, without nanocellulose were used as comparative examples.
  • the modified graphene powder obtained in Example 1-18 and the graphene-like substance in the comparative example were directly dispersed in water and ethanol solution, respectively, without any dispersing agent, and ultrasonicated for 20 min, and the specific operation was as follows:
  • Example 1 It was found through further experiments that the graphene composite powder obtained in Example 1 was dispersed in water, and the maximum dispersion amount without precipitation for 24 hours was 5% by weight.
  • the solution obtained in the step (1) was ultrasonically centrifuged to collect a precipitate. Then, the precipitate is frozen at -20 to -25 ° C for 10 h, and then placed in a cold trap of a freeze dryer for pre-freezing, and the cold trap temperature of the freeze dryer is -70 to -80 ° C; After the end of the freezing, it was freeze-dried at a vacuum of 1 Pa for 24 hours to obtain a nanocellulose solid.
  • Example 2 The difference from Example 1 is that the solid content of the biomass graphene A in the aqueous solution in the step (1) is 0.05 g, 0.2 g, 0.5 g, 0.7 g, 1 g.
  • Example 19 The difference from Example 19 was that the grinding method of the step (1) was different: continuous stirring was carried out at a temperature of 500 rpm for 3 hours at room temperature using a mechanical stirrer or a magnetic stirrer.
  • Example 19 The difference from Example 19 was that the grinding method of the step (1) was different: continuous stirring was carried out at a temperature of 400 rpm for 20 hours at room temperature using a mechanical stirrer or a magnetic stirrer.
  • Example 19 The difference from Example 19 is that biomass graphene A is replaced with biomass graphene B, biomass graphene C, graphene D, graphene E, graphene F, and graphene oxide G, respectively.
  • Example 19 The difference from Example 19 was that the corncob cellulose was replaced with lignocellulose, bleached wood pulp, respectively.
  • the solution obtained in the step (1) was ultrasonically centrifuged to collect a precipitate. Then, the precipitate is frozen at -20 to -25 ° C for 10 h, and then placed in a cold trap of a freeze dryer for pre-freezing, and the cold trap temperature of the freeze dryer is -70 to -80 ° C; After the end of the freezing, it was freeze-dried at a vacuum of 1 Pa for 24 hours to obtain a nanocellulose solid.
  • the aspect ratio, diameter, and degree of agglomeration of all of the above examples were tested and the results are shown in Table 3.
  • the test method for the degree of agglomeration is as follows: 1 g of the solid nanocellulose prepared in the example is added to 30 g of the aqueous solution, and the sedimentation time is observed after a simple physical stirring.
  • the preparation method of the bleached corncob cellulose is as follows: 1) acid hydrolysis of the corn cob raw material is first performed, and the pentose solution and the sulfuric acid hydrolysis residue are obtained after separation; the acid amount is 6 wt% of the corn cob raw material, and the hydrolysis temperature is 130 ° C, time. 2h; then the above acid hydrolysis residue is treated with sodium hydroxide solution, and the alkali solution and the alkali residue are obtained after separation.
  • the amount of the alkali is 7 wt% of the corn cob raw material, the treatment temperature is 90 ° C, and the time is 3 h; 2)
  • the above-mentioned alkali hydrolysis residue is bleached, and the treatment method is hydrogen peroxide bleaching, the amount of hydrogen peroxide is 6 wt% of the dry weight of the alkali residue, the slurry concentration is 10 wt%, the temperature is 90 ° C, the bleaching time is 2 h, after the above purification treatment Corncob cellulose can be obtained, the main indicators of which are whiteness of 75% and fiber length of 0.16 mm.
  • the preparation method of high performance graphene composite nanocellulose is as follows:
  • the preparation method of high performance graphene composite nanocellulose is as follows:
  • the preparation method of high performance graphene composite nanocellulose is as follows:
  • the preparation method of high performance graphene composite nanocellulose is as follows:
  • the specific process steps are substantially the same as those of the embodiment 40, and the difference from the embodiment 40 is that the selected graphene oxide fractionated centrate is the first bottom precipitate (D90 is 70 um, D10 is 30 um).
  • the specific process steps are substantially the same as those of the embodiment 40, and the difference from the embodiment 40 is that the selected graphene oxide fractionated centrate is the first bottom precipitate (D90 is 370 um, D10 is 120 um).
  • the specific process steps are basically the same as those of the embodiment 40, and the difference from the embodiment 40 is that the selected graphene oxide fractionated centrate is the second supernatant (D90 is 20 um, and D10 is 0.5 um).
  • the specific process steps are basically the same as those of the embodiment 40, and the difference from the embodiment 40 is that the selected graphene oxide fractionated centrate (30 um for D90 and 10 um for D10).
  • Example 40 The specific process steps are substantially the same as those of Example 40, and the difference from Example 40 is that the selected graphene oxide fractionated centrate (590 for D90 and 0.25um for D10).
  • Example 40 The specific process steps are substantially the same as in Example 40, and the difference from Example 40 is that the selected graphene oxide fractionated centrate (25 um for D90 and 5 um for D10).
  • the specific process steps are basically the same as those in the embodiment 40, and the difference from the embodiment 40 is that the selected graphene oxide fractionated centrate (D90 is 70 um, D10 is 20 um).
  • Example 44 The difference from Example 44 is that in the step 1), the graphene oxide is replaced with the biomass graphene.
  • Example 44 The difference from Example 44 is that in the step 1), the graphene oxide is replaced with redox graphene.
  • Example 44 The difference from Example 44 is that in the step 1), the graphene oxide is replaced by a mixture of nitrogen-doped graphene and graphene oxide (mass is 1:1).
  • Example 40 The difference from Example 40 is that in the step 1), 10 g of graphene oxide, 390 g of corncob cellulose, and 13 L of deionized water.
  • Example 40 The difference from Example 40 is that in the step 1), 10 g of graphene oxide, 990 g of corncob cellulose, and 99 L of deionized water.
  • Example 40 The difference from Example 40 is that in the step 1), 10 g of graphene oxide, 2000 g of corncob cellulose, and 40 L of deionized water.
  • step 1) the corn cob cellulose obtained in Preparation Example 1 was replaced with corn cob cellulose which was not purified and purified.
  • Example 40 The difference from Example 40 is that in the step 1), the corn cob cellulose obtained in the preparation example was replaced with poplar cellulose.
  • Example 40 The difference from Example 40 is that in the step 1), the corn cob cellulose obtained in the preparation example was replaced with reed cellulose.
  • the diameter of the prepared nanocellulose is more nanometerized, and the aspect ratio is larger and fluctuates within a certain range, which is more favorable for subsequent applications.
  • the graphene composite nanocellulose prepared in Examples 44 and 48 of the present invention was respectively replaced with Patent Publication No. CN102344685A, and the name is "a method for preparing a nanocellulose microfiber reinforced polymer composite material".
  • the nanocellulose materials used in the preparation or the preparation process thereof are as follows:
  • Example 1 The tensile strength of the composite film was 47 MPa, the tensile modulus was 1.5 GPa;
  • Example 2 The strength of the composite fiber was: 4.5 cN/dtex;
  • Example 3 The strength of the composite fiber was: 5.5 cN/ Dtex;
  • Example 4 The tensile strength of the composite film reached 150 MPa, the tensile modulus reached 4.6 GPa;
  • Example 5 The strength of the composite fiber was 4.3 cN/dtex;
  • Example 6 The strength of the composite fiber was: 6.4cN/dtex.
  • Example 1 The tensile strength of the composite film was 49 MPa, the tensile modulus was 1.7 GPa;
  • Example 2 The strength of the composite fiber was: 4.8 cN/dtex;
  • Example 3 The strength of the composite fiber was: 5.9 cN/ Dtex;
  • Example 4 The tensile strength of the composite film reached 160 MPa, the tensile modulus reached 4.9 GPa;
  • Example 5 The strength of the composite fiber was 4.6 cN/dtex;
  • Example 6 The strength of the composite fiber was: 6.7cN/dtex.
  • the invention solves the problems that the existing graphene composite is easy to disperse in the solvent, easy to agglomerate, etc., wherein the high-performance graphene composite nanocellulose preparation method is environmentally friendly and easy to operate, and the prepared graphene nanocellulose is widely used. It has a wide range of applications in many industries such as medicine, environmental protection, food packaging and composite materials.

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Abstract

涉及石墨烯复合物、其制备方法及用途、制备纳米纤维素的方法及所得纳米纤维素、高性能的石墨烯复合纳米纤维素及其制备方法。石墨烯复合物包括纳米纤维素与石墨烯类物质，其中纳米纤维素的至少一部分插入在石墨烯类物质之间。该石墨烯复合物在溶剂中非常容易分散，不易团聚，甚至无需超声或分散剂的帮助。制备纳米纤维素的方法包括：在纤维素水溶液的研磨过程中加入石墨烯类物质。解决了耗能高、环境污染重、纳米纤维素易团聚的问题。高性能的石墨烯复合纳米纤维素，主要由纳米纤维素与石墨烯类物质相互原位搭载，其中石墨烯类物质含量较高，分散较均匀，颗粒大小较均一，团聚颗粒产生少，并且还具有其他优异性能。

Description

石墨烯复合物、其制备方法及用途、制备纳米纤维素的方法及所得纳米纤维素、高性能的石墨烯复合纳米纤维素及其制备方法
本申请要求于2016年12月15日提交中国专利局的申请号为CN201611160905.0、名称为“一种石墨烯复合物、其制备方法和用途”的中国专利申请以及2016年12月12日提交中国专利局的申请号为CN201611143799.5、名称为“一种制备纳米纤维素的方法及所得纳米纤维素”的中国专利申请以及2016年09月20日提交中国专利局的申请号为CN201610835479.X、名称为“高性能的石墨烯复合纳米纤维素及其制备方法、应用”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本发明涉及纳米材料领域，具体而言，涉及一种石墨烯复合物、其制备方法及用途、制备纳米纤维素的方法及所得纳米纤维素、高性能的石墨烯复合纳米纤维素及其制备方法。
背景技术
石墨烯是一种由单层sp2杂化碳原子组成的蜂窝状结构的二维材料，具有许多优异的性能。自从2004年被发现起，石墨烯就成为了科学界的一大研究热点。在对石墨烯的物理化学性质进行研究的同时，与石墨烯相关的复合材料也层出不穷。在纳米科学方向上，石墨烯也被用来制备相关的纳米复合材料，尤其是石墨烯/金属或石墨烯/金属氧化物的纳米复合材料。由于石墨烯的优异性能，这些纳米复合材料在新型能源、生物传感、催化、光学材料等领域有着广阔的研究前景。
但是目前石墨烯的应用是个难题，最主要的原因之一就是分散性问题。因为石墨烯粒径小，容易团聚，团聚后性能大幅降低，导致石墨烯的优良性能难以体现。
市面上的石墨烯一般分粉体和浆料。对于粉体来讲，应用之前需要强力的超声，甚至需要有分散剂协助分散。对于浆料来言，情况稍好一些，但是使用之前也需要超声，并且分散液中也会有分散剂。为了更好地提高分散性，一般情况下都会对石墨烯进行改性或者选择更好的分散剂，或者将石墨烯浓度越低越好，市面上的石墨烯浆料的浓度一般为0.5wt％以下，否则分散效果会很差，容易产生沉淀。这样不但增加了运输成本，还造成了大量的溶剂污染，并且在下游应用时需要去除分散液，无形之中增加了工艺复杂性和成本。
纤维素是地球上广泛存在且可再生的资源。纳米微晶纤维素，是天然纤维素经过处理(如酸水解、生物酶水解等)后，纤维素中的无定形区及低结晶度的结晶区被破除，而得到的一种纤维素结晶体。由天然纤维素制备的纳米微晶纤维素不但具有纤维素的基本结构与性能，还具有巨大的比表面积、高结晶度(＞70％)、高亲水性、高杨氏模量、高强度(7500MPa)、超精细结构和高透明性，良好的生物可降解性与生物相容性以及稳定的化学性能。另外，因纤维素表面裸露出大量羟基、还原性及非还原性末端基，使得纳米微晶纤维素具有巨大的化学改性潜力，促使其在造纸、医药、食品、复合材料等领域的应用研究炙手可热。
但是，如何制备长径比更高、直径更小的纳米纤维素是一个难题，目前比较成熟的办法为机械法、化学法和机械化学法，但是存在耗能高、环境污染严重等问题，都没有大规模生产。另一个问题，当制备得到的纳米纤维素尺寸越小、长径比越高时，获得的纳米纤维素固体容易团聚，造成应用时性能下降，如果利用纳米纤维素溶液会造成不易运输的麻烦。
发明内容
本发明人出人意料地发现，石墨烯难以分散的问题能够通过以下技术手段解决：一种石墨烯复合物，包括主要由纳米纤维素与石墨烯类物质组成的石墨烯复合物，其中纳米纤维素的至少一部分插入在石墨烯类物质之间。
所述石墨烯类物质包括石墨烯、生物质石墨烯、氧化石墨烯、石墨烯衍生物的一种或几种的混合。
石墨烯为层状结构或者褶皱片状结构，且片层尺寸为纳米级别，因为存在分子间作用力，容易导致其团聚。而纳米纤维素也为纳米级别，但是存在长径比，相当于一根一根的棒状结构。当两种不同的纳米材料混合在一起时，通常认为他们也仍然会团聚。本发明人出人意料地发现，纳米纤维素与石墨烯类物质充分分散，所得到的石墨烯复合物无需超声或分散剂也非常容易分散在液体中。
本发明中，纳米纤维素的直径要小于石墨烯类物质的片径。不受理论限制，认为在两者混合过程中，由于纳米纤维素的小直径很容易插入石墨烯片层之间，又因为纳米纤维素的长度将石墨烯之间撑开，减弱了石墨烯片层之间的分子间作用力，使得石墨烯类材料团聚后易于后期分散。
优选地，所述石墨烯的层数为1-10层；优选地，所述石墨烯选自单层石墨烯、双层石墨烯以及具有3-10层的少层石墨烯中的一种或多种。
优选的，所述生物质石墨烯为以生物质资源为主要原料，经过催化、碳化工艺制备而成的含有单层石墨烯、少层石墨烯、石墨烯纳米片层结构，并负载金属/非金属化合物的复合炭材料。
优选地，所述石墨烯衍生物包括元素掺杂石墨烯或官能团化石墨烯物中的任意一种或至少两种的组合。
优选地，所述石墨烯衍生包括元素掺杂石墨烯或官能团化石墨烯物中的任意一种或至少两种的组合。优选地，所述元素掺杂石墨烯包括金属掺杂石墨烯或非金属元素掺杂石墨烯中的任意1种或至少2种的组合。
优选地，所述金属掺杂石墨烯中的金属元素包括钾、钠、金、银、铁、铜、镍、铬钛、钒或钴。
优选地，非金属元素掺杂石墨烯中的非金属元素包括氮、磷、硅、硼或硅。
优选地，所述非金属元素掺杂石墨烯包括氮掺杂石墨烯、磷掺杂石墨烯或硫掺杂石墨烯中的任意一种或至少两种的组合。
优选地，所述官能团化石墨烯包括接枝有官能团的石墨烯。优选地，所述官能团化石墨烯包括接枝有羟基基团、羧基基团或氨基基团中的任意1种或至少2种的组合的石墨烯。
优选地，所述羟基基团包括R1-OH，R1为烷基；优选地，羟基基团选自甲基羟基、乙基羟基、丙 基羟基、丁基羟基、戊基羟基、己基羟基中的一种或多种。
优选地，所述羧基基团包括R2-COOH，所述R2为烷基；优选地，羧基基团选自甲基羧基、乙基羧基、丙基羧基、丁基羧基、戊基羧基、己基羧基中的一种或多种。
优选地，所述氨基基团包括R3-NH3，所述R3包括烷基；优选地，氨基基团选自甲基羟基、乙基羟基、丙基羟基、丁基羟基、戊基羟基、己基羟基中的一种或多种。
优选地，石墨烯类物质为经过TEMPO催化氧化处理过的。
通过TEMPO催化氧化体系处理过的石墨烯类物质，石墨烯片层之间由于增加了更多的羧基，因此再加上纳米纤维素的穿插作用，使得分散效果更加优异。
具体的，所述TEMPO催化氧化体系包括含有TEMPO和/或其衍生物、次氯酸盐、溴化盐的水溶液体系；更优选为含有TEMPO(2,2,6,6-四甲基哌啶-氮-氧化物)、次氯酸钠、溴化钠的水溶液体系；所述催化氧化pH反应的优选为9.5-11.5，更优选10-11。
优选地，所述TEMPO衍生物选自2-氮杂金刚烷-N-氧基、1-甲基-2-氮杂金刚烷-N-氧基、1,3-二甲基-2-氮杂金刚烷-N-氧基、4-羟基TEMPO衍生物中的一种或多种。优选地，所述TEMPO和/或其衍生物的加入量是石墨烯类物质重量的0.05～5％，优选0.1～3％，再优选0.3％～2％,更优选0.5～1％；可以为0.1％、0.3％、0.8％、1％、1.2％、1.5％、2.5％、3.5％、4％、4.5％等。
优选地，次氯酸盐的加入量是石墨烯类物质重量的10～500％，优选30％～90％，再优选40～75％，可以为50％、70％、100％、120％、135％、160％、200％、300％、400％、450％等。
优选地，氯化盐的加入量是石墨烯类物质重量的0.5～50％，优选10～30％，再优选3％～20％，更优选5％～10％，可以为3％、8％、10％、12％、15％、18％、25％、35％、45％等。
TEMPO处理石墨烯类物质的典型工艺为：将TEMPO和/或其衍生物和与卤盐(例如溴化盐如NaBr)配成水溶液，搅拌溶解完，随后加入石墨烯类物质继续搅拌，然后再加入次氯酸盐如次氯酸钠溶液控制pH在10-11之间反应。
本发明所述石墨烯复合物的粒径没有严格要求，当然粒径越小越好。本发明通过引入纳米纤维素，将大颗粒拆分成小颗粒，或者将大颗粒内部穿插上纳米纤维素，已经减弱了石墨烯间的团聚，很容易分散。举例来说，石墨烯粒径在50μm，通过纳米纤维素的加入，使得纳米纤维素进入颗粒内部，将石墨烯片层拆开，成为粒径30μm的颗粒，但是或许30μm颗粒内部仍然存在纳米纤维素，只不过没有将其完全拆开，而是削弱片层之间作用力，等到外力搅拌或者分散到水中后，将变成粒径小于30μm的颗粒或片状物。在一些实施方式中，所述石墨烯复合物的D90在30μm以下，优选为15μm以下，优选为10μm以下，优选为5μm以下，优选为1μm以下，更优选0.51μm以下，进一步优选0.4μm以下，还进一步优选0.3μm以下，最优选0.2μm以下。根据一些实施方式，石墨烯复合物颗粒的D90范围在0.001-30μm，0.01-25μm，0.015-20μm，0.02-15μm，0.03-10μm，0.04-9μm，0.05-8μm，0.06-6μm，0.07-5μm，0.08-3μm，0.09-1μm，或0.1-0.5μm。
在一些实施方式中，所述石墨烯复合物中纳米纤维素的含量在10wt％以内，优选在8wt％以内，优选在5wt％以内，优选在3wt％以内，优选在1wt％以内，优选在0.5wt％以内。根据一些实施方式，纳米纤维素的含量范围在0.1wt％-10wt％之间，0.2wt％-8wt％之间，0.3wt％-5wt％之间，0.4wt％-3wt％之间，0.5wt％-2wt％之间或0.1wt％-1wt％。
一般情况下，纳米纤维素作为石墨烯类物质的添加剂，加入量过多容易起到副作用。纳米纤维素本身即为纳米材料，存在长径比，加入量过多，自身也容易发生团聚，再加上直径小，长度长，很容易形成缠绕将石墨烯类物质包裹在一起，反而起到加团聚的反作用，因此控制其加入量也是本发明的创新点之一。本发明纳米纤维素含量最好选择控制在10wt％以内，当然最优选的范围在0.1wt％-1wt％之间，纳米纤维素的加入量既少，还解决了石墨烯的分散问题，还不影响石墨烯的下游应用。
在一些实施方式中，所述纳米纤维素选的直径在30nm以内，优选20nm以内，再优选在10nm以内，更优选在5nm以内；纳米纤维素的长径比为(5-200)：1，优选为(10-100)：1，更优选为(15-40)：1。
纳米纤维素的直径越小，越容易插入石墨烯片层之间，常规来讲长径比越大，越利于将石墨烯片层分离，但是选择合适的长径比更容易实现，原因在于纳米纤维素长度太长，直径太小容易导致纳米纤维素吸附在石墨烯表面，失去应有的作用。
优选地，所述纳米纤维素制备原料源自农作物如玉米芯、植物秸秆、棉花、林木；优选地，所述纳米纤维素为选自以玉米芯纤维素为原料制备得到的纳米纤维素；优选地，所述纳米纤维素为经过提纯漂白处理过的玉米芯纤维素制备得到。本发明发现用玉米芯纤维素制备得到的纳米纤维素对于石墨烯的分散效果要更好一些，尤其是用它分散生物质石墨烯。
本发明还涉及一种石墨烯复合物的制备方法，包括：使纳米纤维素和石墨烯类物质在溶液中分散成悬浮液。
优选的，该方法进一步包括：对悬浮液经过溶液去除，洗涤，干燥。在一些实施方式中，溶液去除包括离心、过滤或其结合。优选地，干燥包括真空干燥、冷冻干燥、气流干燥、微波干燥、红外线干燥、高频率干燥或其结合。优选地，干燥为冷冻干燥。
在一些实施方式中，分散通过高速搅拌或剪切、超声、以及研磨中的一种或其结合来进行，优选地所述分散通过超声和研磨进行。在一些实施方式中，研磨的频率在25-35Hz，更优选为27-32Hz，研磨的时间控制在4-6h，更优选为5-5.5h。
在一些实施方式中，超声分散处理的时间在15-60min，更优选为30-50min。超声分散处理的功率在500-1500kw，更优选为1000-1200kw。
本发明所述的石墨烯复合物完全可以是石墨烯类物质与纳米纤维素通过物理共混，研磨得到，只不过效果要差一些。
而通过将石墨烯类物质与纳米纤维素在溶液中混合，溶液本身也会起到分散石墨烯类物质和纳米纤维素的作用，更容易的将纳米纤维素穿插到石墨烯材料内部，并且增加了纳米纤维素与石墨烯类物质的 碰撞次数和碰撞角度，更有利于两者的复合。
本发明还涉及根据本发明的石墨烯复合物在纺织、医药、环保、食品包装、复合材料中的应用。
本发明还涉及一种具有高性能的石墨烯复合纳米纤维素，该复合型纤维素中，石墨烯类物质可以保持较高的含量，石墨烯颗粒依然分散比较均匀，颗粒大小也比较均一，团聚颗粒产生较少，且石墨烯类物质是在制备纳米纤维素过程中加入的，使得石墨烯类物质通过穿插打开纤维素非结晶区并与纳米纤维素相互搭载，实现原位复合，更有效的实现分散的均匀性和保持石墨烯和纳米纤维素各自的性能，并且还额外赋予了纳米纤维素优异的抗菌性能、远红外性能，优良的韧性、耐热水性和抗静电性能，采用的原料成本低，投资少，如此一来进一步扩大了纳米纤维素的市场应用范围，提高了产品的附加值，也有利于进一步推广应用。
为了实现本发明的上述目的，特采用以下技术方案：
本发明实施例提供了一种高性能的石墨烯复合纳米纤维素产品，其主要由石墨烯类物质与纳米纤维素组成，所述石墨烯类物质与纳米纤维素相互原位搭载；
所述石墨烯复合纳米纤维素中，石墨烯类物质的含量在20wt％以下，进一步的为10wt％以下，更进一步的为0.5wt％-5wt％之间。
其中，该石墨烯复合纳米纤维素中，石墨烯类物质的含量在20wt％以下，因为石墨烯含量如果太高会容易导致石墨烯与纳米纤维素脱离，石墨烯颗粒在纳米纤维素中发生团聚，分散性不好，进而影响到最终产品的性能，因此石墨烯类物质的含量需要控制在适宜的范围内以保证优良的分散性，这个范围也是发明人通过大量的实践经验最终优化出的比较适宜的含量，更优的石墨烯类物质的含量控制在10wt％以下，还可以为0.5wt％-5wt％之间，除此之外例如为1wt％、1.5wt％、2wt％、2.5wt％、3.5wt％、4wt％等。
总之，本发明的石墨烯复合纳米纤维素中，石墨烯含量本身比较高，但是颗粒分散比较均一，还额外赋予了纳米纤维素材料优异的抗菌性能、优良的韧性、耐热水性和抗静电性能，采用的原料成本低，投资少，如此一来进一步扩大了纤维材料的市场应用范围，提高了产品的附加值，也有利于进一步推广应用。
进一步的，纳米纤维素由玉米芯纤维素制备得到，优选地，所述纳米纤维素为经过提纯漂白处理过的玉米芯纤维素制备得到。
本发明制备纳米纤维素的原料优选为玉米芯纤维素，因为玉米芯纤维素本身相当于废物再利用，实现了资源的合理再分配，并且采用这种纤维素会使得制备得到的石墨烯复合纳米纤维素产品的粒径更加均一。
玉米芯纤维素在制备纳米纤维素之前经过提纯漂白处理的具体方法包括：
a.对玉米芯原料进行酸水解，分离后得到戊糖溶液和酸水解残渣；所用酸为硫酸、盐酸、磷酸、亚硫酸等常用的酸液，酸的用量为玉米芯原料的1-10wt％，水解温度为100-150℃，时间为0.5-3h；
b.用碱溶液处理上述的酸水解残渣，分离后得到碱解液和碱解残渣。所用碱为氢氧化钠，碱的用量为玉米芯原料的1-15wt％，处理温度为40-100℃，时间为1-6h；
c.对上述的碱解残渣进行漂白处理，处理方式包括次氯酸钠漂白、双氧水漂白、碱处理、酸处理等方式中的一种或几种。
经过上述提纯处理后，可以得到玉米芯纤维素，其主要的指标为纤维素含量：80-95％，白度70-90％，灰分0.1-2％，纤维长度0.05-0.5mm。
更进一步的，纳米纤维素的长径比控制在(5-1000)：1，优选为(10-300)：1，更优选为(15-200)：1。
实际操作时，纳米纤维素的最小直径小于20nm，优选为10nm以下，更优选为5nm以下。
本发明所采用的石墨烯类物质包括石墨烯、生物质石墨烯、氧化石墨烯、石墨烯衍生物的一种或几种混合，所述石墨烯衍生物为经过改性的石墨烯。优选地，所述石墨烯衍生包括元素掺杂石墨烯或官能团化石墨烯物中的任意1种或至少2种的组合。优选地，所述元素掺杂石墨烯包括金属掺杂石墨烯或非金属元素掺杂石墨烯中的任意1种或至少2种的组合。
所述金属掺杂的金属元素典型但非限制性的包括钾、钠、金、银、铁、铜、镍、铬钛、钒或钴。所述非金属元素掺杂石墨烯典型但非限制性的包括氮、磷、硅、硼或硅。
优选地，所述非金属元素掺杂石墨烯包括氮掺杂石墨烯、磷掺杂石墨烯或硫掺杂石墨烯中的任意1种或至少2种的组合。优选地，所述官能团化石墨烯包括接枝有官能团的石墨烯。优选地，所述官能团化石墨烯包括接枝有羟基、羧基或氨基中的任意1种或至少2种的组合的石墨烯。
本发明所述羟基包括-R1-OH，所述R1包括烷烃基，典型但非限制性的羟基可以是甲基羟基、乙基羟基、丙基羟基、丁基羟基、戊基羟基、己基羟基等。
本发明所述羧基包括-R2-COOH，所述R2包括烷烃基，典型但非限制性的羟基可以是甲基羟基、乙基羟基、丙基羟基、丁基羟基、戊基羟基、己基羟基等。
本发明所述羧基包括-R3-NH3，所述R3包括烷烃基，典型但非限制性的羟基可以是甲基羟基、乙基羟基、丙基羟基、丁基羟基、戊基羟基、己基羟基等。
另外，生物质石墨烯是以生物质为原料制备的含有单层石墨烯、少层石墨烯、石墨烯纳米片层结构，并负载金属/非金属化合物，层数不大于10层的二维纳米炭材料，甚至可以是在以上基础上包含石墨化炭、金属/非金属化合物的复合炭材料。
本发明还提供一种上述高性能的石墨烯复合纳米纤维素的制备方法，该制备方法前后步骤衔接紧密，方法简单快捷，整个制备过程中没有使用酸碱等任何化学药剂，绿色环保，也没有废酸废碱的产生，并且采用本发明的制备方法同样达到了采用了酸化制备纳米纤维素所具有的优点，比如适宜的长径比。而且该制备方法具有方法简单易于操作，操作条件温和，可实现石墨烯复合纳米纤维素的工业化生产、经济效益良好。本发明还提供上述具有高性能的石墨烯复合纳米纤维素的应用，该纳米纤维素产品应用非常广泛，可广泛应用于各个行业。
本发明除了提供了一种高性能的石墨烯复合纳米纤维素产品，还提供了该石墨烯复合纳米纤维素的制备方法，具体包括如下步骤：(A)将纤维素、石墨烯类物质以及去离子水混合超声分散、研磨得到悬浮液；(B)将悬浮液超声、离心，冷冻干燥成型即得石墨烯复合纳米纤维素。
现有技术中，纳米纤维素的合成工艺主要有以下几种：
1、机械法：天然纤维素经高压机械处理，得到一种新型高度润胀的胶体状纳米纤维素，一般称之为微纤化纤维素(MFC)。MFC是由一些长的线状微细纤维组成的无规则网状物，保留了微细纤维的外形，其纤维直径为10-50nm，长度为直径的10-20倍。通过机械法制备MFC，无需化学试剂，对环境影响小。但采用这种方法制备的MFC粒径分布宽，且制备设备特殊，能量消耗高，因此该方法目前应用较少。高压均质法和化学机械法都属于机械制备法。
2、化学法：天然纤维素经酸水解或酶解后，得到NCC。NCC是一种直径为1～100nm、长度为几十到几百纳米的刚性棒状纤维素，一般具有天然纤维素Ⅰ的晶型，可在水中形成稳定的悬浮液。具体包括酶水解法、酶解法以及生物法，其中酶水解法制备NCC会产生大量的废酸和杂质，对反应设备要求高，且反应后残留物较难回收，但制备工艺比较成熟，已实现工业化生产。
3、生物法：通过微生物合成法制备的纤维素通常被称为细菌纤维素，细菌纤维素的物理和化学性质与天然纤维素相近。生物法制备NCC时可调控NCC的结构、晶型和粒径分布等，因此容易实现工业化和商业化。但是细菌纤维素制备过程复杂、耗时长、成本高、价格贵、得率低。
上述现有技术中常用的纳米纤维素的制备工艺中，机械法容易出现粒度分布不均的问题，化学法本身不环保，污染环境，对操作人员的健康也有一定程度的损害，本发明的石墨烯复合纳米纤维素的制备方法既解决了机械法粒度分布不均的问题，还避免了采用化学法对环境污染严重的问题，整个制备方法操作成本也比较低。
在本发明中，步骤(A)中，加入石墨烯类物质的粒度指标也是有严格的要求的，石墨烯类物质的D90指标控制在70μm以下，D10指标控制在20um以下。以往的石墨烯复合纳米纤维素产品只对石墨烯含量进行了一定的限定，但是忽略了石墨烯类物质本身的粒度指标这个重要参数，本发明的发明人经过大量的创造性实验，通过将石墨烯类物质的含量、粒度指标限定在适宜的范围内，通过这些指标的互相配合共同发挥作用，最终达到了本发明的发明目的，确实解决了石墨烯颗粒分散不均匀的问题。
优选地，为了进一步提高石墨烯复合纳米纤维素中石墨烯类物质的分散性能，石墨烯类物质的D90指标最好控制在50μm以下，更优D90指标控制在30μm以下，更优选为5-25μm之间，例如还可以为45um，40um，35um，30um等等。这里D90指标控制在70μm以下是指100um以下粒径物质占整体的90％，即这90％里面最大粒径为100um，这样在保证了石墨烯类物质的分散性，同时也保证了石墨烯颗粒的大小均一性，避免了颗粒团聚的发生。
更进一步的，石墨烯类物质的D90指标最好控制在D10指标的20倍以下，优选10倍以下，更优选为5倍以下，还可以为8倍以下、11倍以下、12倍以下、13倍以下、14倍以下等。这样的目的是为 了尽量保持石墨烯类物质的大片结构，确保石墨烯类物质不会发生层间团聚，防止不同片径石墨烯类物质带来的应力集中点断裂的问题，因为颗粒度太大、或者太小均不利于与纳米纤维素形成均一的物质，从而使得复合纳米纤维素产品各方面性能表现俱佳，因此最好将石墨烯类物质的粒度指标控制在适宜的范围内。
当然，实际操作时，具体控制石墨烯类物质D90、D10指标需要采用分级预处理方法，包括：将石墨烯类物质与去离子水混合后，2000-3000rpm条件下离心操作后保留底部沉淀，上清液在5000-7000rpm条件下离心操作后分别得到二次底部沉淀与二次上清液，其中所述分级离心液包括底部沉淀、二次底部沉淀、二次上清液中的任意一种制备得到，优选二次底部沉淀。
第一步得到底部沉淀的离心操作速率比较低，后面上清液进一步离心操作的速率则比较高，因为沉淀中的物质颗粒度一般比较大，如果速率过快不利于大颗粒的物质沉积，后续上清液中的物质颗粒度一般比较小，因此速率需要快一些，以使颗粒度小的物质上浮存在上清液中。这样颗粒度比较一致的石墨烯类物质经过归类后在底部沉淀、或在二次底部沉淀、或在二次上清液中，分级离心液可以选择上述经过分级处理的任意一种物质，均能保证具有颗粒度比较一致的石墨烯类物质，并且粒度的大小也比较适宜，以充分保证了片径的均一性，有利于后续保证制备出的产品的性能。
其中，2000-3000rpm条件下离心操作的时间最好控制在20-40min之间，5000-7000rpm条件下离心操作的时间最好控制在10-30min之间，控制在较优的操作时间内更利于粒径分级处理的更为彻底，从而粒径分布的更加均匀。
其中，步骤(A)中，超声分散处理主要的目的是为了依靠机械分散以及超声空化效应使得纤维达到分离降解的效果，一般超声分散处理的时间最好控制在15-60min，更优选为30-50min，超声分散处理的功率最好控制在500-1500kw之间，更优选为1000-1200kw之间，为了提升纤维分离、降解的效果，一般在超声分散处理之前先进行一定的研磨操作，依靠研磨珠与纤维之间的相互摩擦作用达到使纤维分离、降解的效果，这样也相应的提高了总体工作效率，研磨的频率最好控制在25-35Hz之间，更优选为27-32Hz之间，研磨的时间最好控制在4-6h之间，更优选为5-5.5h。
为了充分改善复合产品本身的分散性能，所用的石墨烯类物质在与纤维素、去离子水混合之前最好先进行一定的研磨预处理，更优的，只选用研磨预处理后的容器壁上残留的石墨烯类物质，与纤维素、去离子水混合。因为容器壁上的石墨烯具有更好的纳米特性以及片层结构，因此更优选择容器壁上的石墨烯类物质。
另外悬浮液中，纤维素的浓度最好控制在1wt％-10wt％之间，更优的为2wt％-8wt％之间，除此之外还可以为3wt％、4wt％、5wt％、6wt％、7wt％等。
本发明实施例的石墨烯复合纳米纤维素的制备方法，通过添加了石墨烯材料后，提高了研磨本身的效率，缩短了研磨的时间，尤其是采用生物质石墨烯使得纳米纤维素具有抗菌抑菌、远红外等功能性更为突出。
采用上述制备方法制备得到的石墨烯复合纳米纤维素进一步翻倍提升纳米纤维素本身的力学性能，并且还额外赋予了纳米纤维素优异的抗菌性能、远红外性能，优良的韧性、耐热水性和抗静电性能，应用非常广泛，在医药、环保、食品包装、复合材料多个行业均有很广阔的应用。
本发明的还提供一种制备纳米纤维素的方法，所述的方法解决了耗能高、环境污染严重、纳米纤维素易团聚的问题。
为了实现以上目的，本发明提供了以下技术方案：一种制备纳米纤维素的方法，包括下列步骤：
在纤维素水溶液的研磨过程中加入重量为纤维素10wt％以下的石墨烯类物质，即得纳米纤维素水溶液；所述石墨烯类物质选自石墨烯及其衍生物、氧化石墨烯及其衍生物、生物质石墨烯及其衍生物中的一种或多种，优选氧化石墨烯/生物质石墨烯。
上述的方法利用石墨烯类物质的片状结构插入纤维素中的无定形区，将其分散为均匀分散的纳米级结构，再加上物理研磨的摩擦作用，更加有利于石墨烯类物质与纤维素的接触，并通过研磨外力更进一步地实现石墨烯片层结构的切割效果。通过引入石墨烯类物质，使其与纤维素混合在一起，有效防止已形成的纳米微晶纤维素的自团聚。综上，本发明上述方法通过切割形成纳米微晶纤维素，再利用石墨烯类物质的物理阻隔作用防止纳米微晶纤维素团聚，从而制成性能稳定、容易运输的纳米微晶纤维素。
其次，与常规的机械法、化学法和机械化学法相比，本发明并不需要较强的机械力或者高温反应，因此耗能低、无环境污染。
本发明所述的生物质石墨烯为以生物质资源为主要原料，经过催化、碳化工艺制备而成的含有单层石墨烯、少层石墨烯、石墨烯纳米片层结构，并负载金属/非金属元素的复合炭材料。
本发明所述的氧化石墨烯可以为市售的石墨烯，也可以是部分还原交联制备的石墨烯经氧化后的产物，亦可以是PECVD法制备的石墨烯经氧化后的产物，也可以是其它方法制得的氧化石墨烯。
优选地，所述氧化石墨烯衍生物包括元素掺杂氧化石墨烯或官能团化氧化石墨烯物中的任意1种或至少2种的组合。优选地，所述元素掺杂氧化石墨烯包括金属掺杂氧化石墨烯或非金属元素掺杂氧化石墨烯中的任意1种或至少2种的组合。
所述金属掺杂的金属元素典型但非限制性的包括钾、钠、金、银、铁、铜、镍、铬钛、钒或钴。
所述非金属元素掺杂石墨烯典型但非限制性的包括氮、磷、硫、硅、硼或硅。
优选地，所述非金属元素掺杂氧化石墨烯包括氮掺杂氧化石墨烯、磷掺杂氧化石墨烯或硫掺杂氧化石墨烯中的任意1种或至少2种的组合。
优选地，所述官能团化氧化石墨烯包括接枝有官能团的氧化石墨烯。优选地，所述官能团化氧化石墨烯包括接枝有羟基、羧基或氨基中的任意1种或至少2种的组合的氧化石墨烯。
本发明所述羟基包括－R1－OH，所述R1包括烷烃基，典型但非限制性的羟基可以是甲基羟基、乙基羟基、丙基羟基、丁基羟基、戊基羟基、己基羟基等。
本发明所述羧基包括－R2－COOH，所述R2包括烷烃基，典型但非限制性的羟基可以是甲基羟基、 乙基羟基、丙基羟基、丁基羟基、戊基羟基、己基羟基等。
本发明所述氨基包括－R3－NH3，所述R3包括烷烃基，典型但非限制性的羟基可以是甲基羟基、乙基羟基、丙基羟基、丁基羟基、戊基羟基、己基羟基等。
所述的石墨烯衍生物以及生物质石墨烯衍生物同上述氧化石墨烯衍生物。
优选地，所述石墨烯类物质的加入量为纤维素前驱体水溶液的5wt％以下，优选2wt％以下，优选1wt％以下，更优选0.6wt％以下。
优选地，所述石墨烯类物质粒径≤30μm，优选≤15μm，优选≤3μm，优选≤500nm，优选≤100nm，可以是28μm，25μm，20μm，10μm，5μm，2μm，1μm，200nm等。
一般而言，石墨烯的粒径越小，片层越薄，越利于对纤维素的剪切。优选地，所述纤维素选自木质纤维素、玉米芯纤维素、微晶纤维素、细菌纤维素、纸浆中的一种或多种混合。
优选地，所述纸浆选自漂白木浆、漂白草浆、玉米芯浆、棉浆、麻浆、竹浆、苇浆、溶解浆、破布浆、未漂木浆、未漂草浆中的一种或几种的混合。本发明所述的研磨不需要与常规机械法同样高的要求，由于石墨烯为二维材料，具有增强润滑效果、减小摩擦力的作用，因此通过研磨过程引入石墨烯类物质更加有利于研磨效果，减小能耗。若研磨力度过大反而不利于石墨烯类物质的作用，优选的研磨条件为：
使用功率为200－400W的超声匀质分散机以1000～13600rpm的搅拌速度进行分散处理1～30min，优选1000～3000rpm的搅拌速度进行分散处理10～20min；或使用机械搅拌器或磁力搅拌器以300～500rpm的速度连续搅拌1～72h，优选搅拌1～3h。优选地，研磨温度为4～50℃，进一步优选为4～10℃。
除了加入石墨烯类物质研磨的方法外，本发明还可以结合酸解、TEMPO催化氧化等化学措施，以提高生产效率。例如，优选地，在所述研磨前或研磨过程中还加入酸进行酸解：
加入55～64wt％的H2SO4，在40～60℃下搅拌进行酸解，反应1～2小时后加入去离子水，再离心一次或多次，收集沉淀。
优选地，在所述研磨前或研磨过程中还加入TEMPO催化氧化体系进行氧化处理：
在TEMPO催化氧化体系的作用下，在pH 10～11、10－40℃下搅拌反应2～24小时；
对催化氧化时间没有严格的限定，一般根据反应程度，例如当羟基耗尽则催化氧化反应结束，也可以根据时间控制羟基的消耗量。
在这里，TEMPO催化氧化体系一方面可以将纤维素部分或全部羟基氧化为羧基，也可以将石墨烯类物质的羟基或者环氧官能团催化氧化为羧基。由此一来，不但通过TEMPO体系将纤维素非结晶区部分氧化成大分子结构并使得结晶区相互撑开，而且更有利于石墨烯类物质的剪切，更进一步的，通过TEMPO体系将石墨烯类物质的羟基也氧化为羧基，减小了石墨烯厚度，更有利于石墨烯类物质的剪切作用。
优选地，所述TEMPO催化氧化体系为含有TEMPO和/或其衍生物、次氯酸盐、溴化盐和/或高氯酸盐的水溶液体系；更优选为含有TEMPO、次氯酸钠、溴化钠和/或高氯酸钠的水溶液体系；
优选地，所述TEMPO衍生物选自2－氮杂金刚烷－N－氧基、1－甲基－2－氮杂金刚烷－N－氧基、1，3－二甲基－2－氮杂金刚烷－N－氧基、4－羟基TEMPO衍生物中的一种或多种；
优选地，TEMPO和/或其衍生物的加入量是纤维素重量的0.05％～5％，优选0.1％～3％，再优选0.3％～2％，更优选0.5％－1％；可以为0.1％、0.3％、0.8％、1％、1.2％、1.5％、2.5％、3.5％、4％、4.5％等；
优选地，次氯酸盐的加入量是纤维素重量的10％～500％，优选30％～95％，再优选40％－75％；可以为50％、70％、100％、120％、135％、160％、200％、300％、400％、450％等；
优选地，溴化盐和/或高氯酸盐的加入量是纤维素重量的0.5％～50％，优选10％～30，再优选3％～20％，更优选5％～10％；可以为3％、8％、10％、12％、15％、18％、25％、35％、45％等；
优选地，次氯酸盐加入浓度为5－15wt％。
优选地，对所述纳米纤维素水溶液进行，溶液去除，洗涤，干燥；
优选地，溶液去除包括离心、过滤或其结合；
优选地，干燥包括真空干燥、冷冻干燥、气流干燥、微波干燥、喷雾干燥、红外线干燥、高频率干燥或其结合；优选地，干燥为冷冻干燥。
其中，干燥的条件对产品的稳定性有重要影响，优选为：将产品置于－20～－25℃的条件下冷冻处理10～20h，然后将其放置于冷冻干燥机的冷阱中进行预冻，冷冻干燥机的冷阱温度为－50～－80℃；预冻结束后在真空度1～10Pa下冷冻干燥24～48h。
与现有技术相比，本发明的有益效果为：
本发明的石墨烯复合物在溶剂中非常容易分散，并且不易团聚，甚至无需超声或分散剂的帮助。
本发明提供的高性能的石墨烯复合纳米纤维素，石墨烯类物质可以保持较高的含量，石墨烯颗粒依然分散比较均匀，颗粒大小也比较均一，团聚颗粒产生较少，各项性能稳定；
(2)本发明的高性能的石墨烯复合纳米纤维素的制备方法，该制备方法前后步骤衔接紧密，方法简单快捷，整个制备过程中没有使用酸碱等任何化学药剂，绿色环保，也没有废酸废碱的产生，并且采用本发明的制备方法同样达到了采用了酸化制备纳米纤维素所具有的优点，比如适宜的长径比。而且该制备方法具有方法简单易于操作，操作条件温和，可实现石墨烯复合纳米纤维素的工业化生产、经济效益良好；
(3)本发明的高性能的石墨烯复合对位芳纶纤维应用非常广泛，在医药、环保、食品包装、复合材料多个行业均有很广阔的应用。
本发明提供的纤维素的制备方法达到了以下技术效果：
(1)制备的纳米纤维素长径比可以达到100以上，尤其200以上，甚至300以上；直径可以达到20nm以下，尤其10nm以下，甚至5nm以下。(2)制备方法耗能低、无环境污染。
具体实施方式
下面将结合具体实施例对本发明的实施方案进行详细描述，但是本领域技术人员将会理解，下列实施例仅用于说明本发明，而不应视为限制本发明的范围。实施例中未注明具体条件者，按照常规条件或制造商建议的条件进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购买获得的常规产品。
石墨烯类物质：
生物质石墨烯A：制备方法为中国专利公开号为CN105502330A实施例4。
生物质石墨烯B：制备方法为中国专利公开号为CN104016341A实施例7。
生物质石墨烯C：制备方法为中国专利公开号为CN104724699A实施例1。
石墨烯D：常州第六元素材料科技股份有限公司生产的型号：SE1231。
石墨烯E：常州第六元素材料科技股份有限公司生产的型号：SE1132。
石墨烯F：常州第六元素材料科技股份有限公司生产的型号：SE1430。
氧化石墨烯G：常州第六元素材料科技股份有限公司生产的型号：SE2430W。
实施例1
(1)取1g生物质石墨烯A，加入200g水搅拌形成均匀的浆液，然后再加入0.01g直径3-5nm、长径比15-20的玉米芯纳米纤维素(溶液中纳米纤维素含量为2wt％的水溶液)，继续搅拌30min。
(2)将步骤(1)得到的悬浮液过滤，并用水进行多次洗涤、离心，每次离心速度为1000rpm，每次离心时间为5min，冷冻干燥后得到石墨烯复合物。
实施例2
与实施例1的区别在于加入0.001g直径5-10nm、长径比20-30的玉米芯纳米纤维素(溶液中纳米纤维素含量为1.5wt％)。
实施例3
与实施例1的区别在于加入0.005g直径3-5nm、长径比15-20的玉米芯纳米纤维素(溶液中纳米纤维素含量为2.5wt％)。
实施例4
与实施例1的区别在于加入0.03g直径为12-15nm、长径比为10-15的玉米芯纳米纤维素(溶液中纳米纤维素含量为0.5wt％)。
实施例5
与实施例1的区别在于加入0.05g直径为1-3nm、长径比为80-100的玉米芯纳米纤维素(溶液中纳米纤维素含量为1.5wt％)。
实施例6
与实施例1的区别在于加入0.1g直径为20-25、长径比为5-10的玉米芯纳米纤维素(溶液中纳米纤维素含量为1.5wt％)。
实施例7-8
与实施例1的区别在于将玉米芯纳米纤维素换成木质纳米纤维素和棉花纳米纤维素。
实施例9-14
与实施例1的区别在于将生物质石墨烯A分别替换为生物质石墨烯B、生物质石墨烯C、石墨烯D、石墨烯E、石墨烯F和氧化石墨烯G。
实施例15
与实施例2的区别在于，对生物质石墨烯A进行TEMPO催化氧化处理，具体步骤为：a.取1g生物质石墨烯A，加入200g水搅拌形成均匀的浆液，然后再加入TEMPO催化氧化组合物(0.01gTEMPO、1g次氯酸钠、0.05g溴化钠)搅拌反应，通过0.5wt％的氢氧化钠溶液和1wt％的冰醋酸溶液调节使反应体系的pH保持在10.5-11范围内，当pH不再变化后停止反应得到悬浮液，反应时间为2.5h；b.将步骤a得到的悬浮液过滤，并用水进行多次洗涤、离心，每次离心速度为1000rpm，每次离心时间为5min，最终洗涤至悬浮液的pH为中性，干燥后得到改性石墨烯粉体。
实施例16
与实施例1的区别在于将步骤(1)取1g生物质石墨烯A，加入到0.01g直径3-5nm、长径比15-20的玉米芯纳米纤维素(溶液中纳米纤维素含量为2wt％)的水溶液中，继续搅拌30min。
实施例17
与实施例1的区别在于在步骤(2)干燥之前增加研磨步骤，具体如下：
将产品与蒸馏水以1：10的质量比配成溶液，常温下使用功率为400W的超声匀质分散机以10000rpm的搅拌速度进行分散处理30min。
实施例18
与实施例1的区别在于步骤(2)干燥之前增加研磨步骤，具体如下：
将产品与蒸馏水以1：1000的质量比配成溶液，常温下使用机械搅拌器以500rpm的速度连续搅拌72h。
对比例1
分别以不加纳米纤维素的生物质石墨烯A、生物质石墨烯B、生物质石墨烯C、石墨烯D、石墨烯E、石墨烯F和氧化石墨烯G为对比例。
测试
将实施例1-18所得改性石墨烯粉体和对比例的石墨烯类物质分别直接分散于水、乙醇溶液中，不加任何分散剂，超声20min，具体操作如下：
(1)将1g实施例1-18所得改性石墨烯粉体和对比例的石墨烯类物质分别分散于100ml水、100ml乙醇溶液中，观察出现沉淀时间，结果如表1。
表1
Figure PCTCN2017100249-appb-000001
Figure PCTCN2017100249-appb-000002
将实施例4和实施例6的石墨烯复合物粉体分散于水溶液后，其D90分别为5.2μm和7.8μm。
(2)将3g实施例1-17所得改性石墨烯粉体和对比例的石墨烯类物质分别分散于100ml水、100ml乙醇溶液中，观察出现沉淀时间，结果如表2。
表2
Figure PCTCN2017100249-appb-000003
Figure PCTCN2017100249-appb-000004
经过进一步实验发现，实施例1所得石墨烯复合物粉体分散于水中，24h不沉淀的最大分散量为5wt％。
实施例19
(1)将10g玉米芯纤维素加入到500mL固含为0.1g的生物质石墨烯A的水溶液中，然后在室温下，使用功率为400W的超声匀质分散机以3000rpm的搅拌速度进行研磨分散处理15min，得到纳米纤维素水溶液；
(2)将(1)步所得溶液超声离心，收集沉淀。然后将沉淀置于－20～－25℃的条件下冷冻处理10h，然后将其放置于冷冻干燥机的冷阱中进行预冻，冷冻干燥机的冷阱温度为－70～－80℃；预冻结束后在真空度1Pa下冷冻干燥24h，得到纳米纤维素固体。
实施例20－24
与实施例1的区别在于步骤(1)中生物质石墨烯A在水溶液中的固含为0.05g，0.2g，0.5g，0.7g，1g。
实施例25
与实施例19的区别在于步骤(1)的研磨方法不同，为：在室温下，使用机械搅拌器或磁力搅拌器以500rpm的速度连续搅拌3h。
实施例26
与实施例19的区别在于步骤(1)的研磨方法不同，为：在室温下，使用机械搅拌器或磁力搅拌器以400rpm的速度连续搅拌20h。
实施例27－32
与实施例19的区别在于将生物质石墨烯A分别替换为生物质石墨烯B、生物质石墨烯C、石墨烯D、石墨烯E、石墨烯F和氧化石墨烯G。
实施例33－34
与实施例19的区别在于将玉米芯纤维素分别替换为木质纤维素、漂白木浆。
实施例35
(1)将10g玉米芯纤维素先用55wt％的硫酸处理2h，水洗得到固体后加入到500mL固含为0.1g的生物质石墨烯A的水溶液中，然后在室温下，使用功率为400W的超声匀质分散机以3000rpm的搅拌速度进行研磨分散处理15min，得到纳米纤维素水溶液；
(2)将(1)步所得溶液超声离心，收集沉淀。然后将沉淀置于－20～－25℃的条件下冷冻处理10h，然后将其放置于冷冻干燥机的冷阱中进行预冻，冷冻干燥机的冷阱温度为－70～－80℃；预冻结束后在真空度1Pa下冷冻干燥24h，得到纳米纤维素固体。
实施例36
(1)将10g玉米芯纤维素加入到500mL固含为0.1g的生物质石墨烯A的水溶液中，然后再加入TEMPO催化氧化组合物(0.1gTEMPO、10g次氯酸钠、0.5g溴化钠)搅拌反应，通过0.5wt％的氢氧化钠溶液和1wt％的冰醋酸溶液调节使反应体系的pH保持在10.5－11范围内，当pH不再变化后停止反应得到悬浮液，反应时间为2.5h；
(2)将步骤(1)所得溶液通过超声离心洗涤至中性，收集沉淀。然后真空干燥得到纳米纤维素。
对比例2
(1)将10g玉米芯纤维素加入到500mL的水溶液中，然后在室温下，使用功率为400W的超声匀质分散机以3000rpm的搅拌速度进行研磨分散处理15min，得到纳米纤维素水溶液；
(2)将1步所得溶液超声离心，收集沉淀。然后将沉淀置于－20～－25℃的条件下冷冻处理10h，然后将其放置于冷冻干燥机的冷阱中进行预冻，冷冻干燥机的冷阱温度为－70～－80℃；预冻结束后在真空度1Pa下冷冻干燥24h，得到纳米纤维素固体。
实验
测试上文所有实施例产品的长径比、直径、团聚程度，结果如表3所示。其中团聚程度的测试方法为：将实施例制备得到的1g固体纳米纤维素加入到30g水溶液中，简单的物理搅拌后观察出现沉降时间。
表3
Figure PCTCN2017100249-appb-000005
Figure PCTCN2017100249-appb-000006
制备例1
漂白玉米芯纤维素的制备方法如下：1)先对玉米芯原料进行酸水解，分离后得到戊糖溶液和硫酸水解残渣；酸的用量为玉米芯原料的6wt％，水解温度为130℃，时间为2h；然后用氢氧化钠溶液处理上述的酸水解残渣，分离后得到碱解液和碱解残渣，碱的用量为玉米芯原料的7wt％，处理温度为90℃，时间为3h；2)对上述的碱解残渣进行漂白处理，处理方式为双氧水漂白，双氧水用量占碱解残渣绝干重量的6wt％，浆浓为10wt％，温度为90℃，漂白时间为2h，经过上述提纯处理后，可以得到玉米芯纤维素，其主要的指标为白度75％，纤维长度0.16mm。
实施例37
高性能的石墨烯复合纳米纤维素的制备方法如下：
1)将制备例1得到的玉米芯纤维素80g与20g氧化石墨烯以及800ml去离子水混合配成浆料，在研磨机内以频率25Hz进行研磨4h，得到悬浮液；
2)将上述的悬浮液在1500kw功率下超声60min、离心、冷冻干燥，得到复合纳米纤维素。
实施例38
高性能的石墨烯复合纳米纤维素的制备方法如下：
1)先将10g氧化石墨烯进行研磨4h后，加入制备例1得到的90g玉米芯纤维素、以及1000ml去离子水混合配成浆料，在研磨机内以频率35Hz进行研磨6h，得到悬浮液；
2)将上述的悬浮液在700kw功率下超声30min、离心、冷冻干燥，得到复合纳米纤维素。
实施例39
高性能的石墨烯复合纳米纤维素的制备方法如下：
1)先将氧化石墨烯进行研磨4h后，选择残留在容器壁上面的10g氧化石墨烯中加入制备例1得到的90g玉米芯纤维素、以及1000ml去离子水混合配成浆料，在研磨机内以频率27Hz进行研磨5h，得到悬浮液；
2)将上述的悬浮液在500kw功率下超声15min、离心、冷冻干燥，得到复合纳米纤维素。
实施例40
高性能的石墨烯复合纳米纤维素的制备方法如下：
1)将氧化石墨烯与去离子水混合，在2000-3000rpm条件下离心操作20-40min后保留第一次底部沉淀，上清液在5000-7000rpm条件下离心操作10-30min后分别得到二次底部沉淀与二次上清液，选择二次底部沉淀得到的10g氧化石墨烯分级离心液(D90为50um，D10为12um)，与制备例1得到的190g玉米芯纤维素、以及3800ml去离子水混合配成浆料，在研磨机内以频率32Hz进行研磨5.5h，得到悬浮液；
2)将上述的悬浮液在1000kw功率下超声50min、离心、冷冻干燥，得到复合纳米纤维素。
实施例41
具体工艺步骤与实施例40基本相同，与实施例40的区别在于，选用的氧化石墨烯分级离心液为第一次底部沉淀(D90为70um，D10为30um)。
实施例42
具体工艺步骤与实施例40基本相同，与实施例40的区别在于，选用的氧化石墨烯分级离心液为第一次底部沉淀(D90为370um，D10为120um)。
实施例43
具体工艺步骤与实施例40基本相同，与实施例40的区别在于，选用的氧化石墨烯分级离心液为第二次上清液(D90为20um，D10为0.5um)。
实施例44
具体工艺步骤与实施例40基本相同，与实施例40的区别在于，选用的氧化石墨烯分级离心液(D90为30um，D10为10um)。
实施例45
具体工艺步骤与实施例40基本相同，与实施例40的区别在于，选用的氧化石墨烯分级离心液(D90为5um，D10为0.25um)。
实施例46
具体工艺步骤与实施例40基本相同，与实施例40的区别在于，选用的氧化石墨烯分级离心液(D90为25um，D10为5um)。
实施例47
具体工艺步骤与实施例40基本相同，与实施例40的区别在于，选用的氧化石墨烯分级离心液(D90为70um，D10为20um)
实施例48
与实施例44的区别点在于步骤1)中，氧化石墨烯替换为生物质石墨烯。
实施例49
与实施例44的区别点在于步骤1)中，氧化石墨烯替换为氧化还原石墨烯。
实施例50
与实施例44的区别点在于步骤1)中，氧化石墨烯替换为氮掺杂石墨烯和氧化石墨烯的混合物(质量为为1:1)。
实施例51
与实施例40的区别点在于步骤1)中，氧化石墨烯10g，玉米芯纤维素390g，去离子水13L。
实施例52
与实施例40的区别点在于步骤1)中，氧化石墨烯10g，玉米芯纤维素990g，去离子水99L。
实施例53
与实施例40的区别点在于步骤1)中，氧化石墨烯10g，玉米芯纤维素2000g，去离子水40L。
实施例54
与实施例40的区别点在于步骤1)中，将制备例1得到的玉米芯纤维素替换为未经过纯化漂白的玉米芯纤维素。
实施例55
与实施例40的区别点在于步骤1)中，制备例得到的玉米芯纤维素替换为杨树纤维素。
实施例56
与实施例40的区别点在于步骤1)中，制备例得到的玉米芯纤维素替换为芦苇纤维素。
对比例3
CN101509209B“一种棒状纳米纤维素的制备方法”专利中，实施例1制备得到的纳米纤维素产品。
对比例4
CN102433786A“一种机械力化学法制备微纳米纤维素的方法”专利中实施例1制备得到的纳米纤维素产品。
实验
将本发明实施例37-56以及对比例3-4的纳米纤维素产品进行性能检测，具体结果如下表4所示：
表4性能指标对比
Figure PCTCN2017100249-appb-000007
Figure PCTCN2017100249-appb-000008
通过实施例37-56数据和对比例3、4对比，可以看出添加石墨烯类物质后，利用纯机械方法就能达到化学法的效果，甚至更好，这样减少了废酸碱的产生，有利于保护环境；并且通过对比，实施例制备的纳米纤维素的长度和直径的范围要远远窄于对比例3和4，说明制备得到的纳米纤维素粒径更加均匀，均一性好。
尤其是对石墨烯类物质进行前处理之后，使得制备的纳米纤维素的直径更加纳米化，并使得长径比更大，并在一定范围内波动，更有利于后续的应用。
应用例1
将本发明实施例44和48制备得到的石墨烯复合纳米纤维素分别替换专利公开号为CN102344685A，名称为“一种制备纳米纤维素微纤增强聚合物复合材料的方法”的实施例1-6中所用的纳米纤维素材料或者其制备过程，测试数据如下：
本发明实施例44制备得到的石墨烯复合纳米纤维素对应数据如下：
实施例1：复合材料膜的拉伸强度为47MPa，拉伸模量为1.5GPa；实施例2：复合纤维的强度为:4.5cN/dtex；实施例3：复合纤维的强度为:5.5cN/dtex；实施例4：复合材料膜的拉伸强度达到150MPa，拉伸模量达到4.6GPa；实施例5：复合材料纤维的强度为4.3cN/dtex；实施例6：复合材料纤维的强度为:6.4cN/dtex。
本发明实施例48制备得到的石墨烯复合纳米纤维素对应数据如下：
实施例1：复合材料膜的拉伸强度为49MPa，拉伸模量为1.7GPa；实施例2：复合纤维的强度为:4.8cN/dtex；实施例3：复合纤维的强度为:5.9cN/dtex；实施例4：复合材料膜的拉伸强度达到160MPa，拉伸模量达到4.9GPa；实施例5：复合材料纤维的强度为4.6cN/dtex；实施例6：复合材料纤维的强度为:6.7cN/dtex。
工业实用性
本发明解决了现有石墨烯复合物在溶剂中容易分散，易团聚等问题，其中，高性能的石墨烯复合纳米纤维素制备方法环保易操作，制备而得的石墨烯纳米纤维素应用非常广泛，在医药、环保、食品包装、复合材料多个行业均有很广阔的应用。

Claims (30)

  1. 一种石墨烯复合物，其特征在于，所述石墨烯复合物包括纳米纤维素与石墨烯类物质，其中所述纳米纤维素的至少一部分插入在所述石墨烯类物质之间。
  2. 根据权利要求1所述的石墨烯复合物，其特征在于，所述石墨烯类物质包括石墨烯、生物质石墨烯、氧化石墨烯、石墨烯衍生物的一种或几种的混合；
    优选地，所述石墨烯的层数为1-10层；优选地，所述石墨烯选自单层石墨烯、双层石墨烯以及具有3-10层的少层石墨烯中的一种或多种；
    优选的，所述生物质石墨烯为以生物质资源为主要原料，经过催化、碳化工艺制备而成的含有单层石墨烯、少层石墨烯、石墨烯纳米片层结构，并负载金属/非金属化合物的复合炭材料；
    优选地，所述石墨烯衍生物包括元素掺杂石墨烯或官能团化石墨烯中的任意一种或至少两种的组合；
    优选地，所述元素掺杂石墨烯包括金属掺杂石墨烯或非金属元素掺杂石墨烯中的任意1种或至少2种的组合；
    优选地，所述金属掺杂石墨烯中的金属元素包括钾、钠、金、银、铁、铜、镍、铬钛、钒或钴；
    优选地，所述非金属元素掺杂石墨烯中的非金属元素包括氮、磷、硅、硼或硅；
    优选地，所述非金属元素掺杂石墨烯包括氮掺杂石墨烯、磷掺杂石墨烯或硫掺杂石墨烯中的任意一种或至少两种的组合；
    优选地，所述官能团化石墨烯包括接枝有官能团的石墨烯；
    优选地，所述官能团化石墨烯包括接枝有羟基基团、羧基基团或氨基基团中的任意1种或至少2种的组合的石墨烯；
    优选地，所述羟基基团包括R1-OH，R1为烷基；优选地，羟基基团选自甲基羟基、乙基羟基、丙基羟基、丁基羟基、戊基羟基、己基羟基中的一种或多种；
    优选地，所述羧基基团包括R2-COOH，所述R2为烷基；优选地，羧基基团选自甲基羧基、乙基羧基、丙基羧基、丁基羧基、戊基羧基、己基羧基中的一种或多种；
    优选地，所述氨基基团包括R3-NH3，所述R3包括烷基；优选地，氨基基团选自甲基羟基、乙基羟基、丙基羟基、丁基羟基、戊基羟基、己基羟基中的一种或多种；
    优选地，石墨烯类物质为经过TEMPO催化氧化处理过的。
  3. 根据权利要求1所述的石墨烯复合物，其特征在于，所述石墨烯复合物的D90在30μm以下，优选为15μm以下，优选为10μm以下，优选为5μm以下，优选为1μm以下，更优选0.51μm以下，进一步优选0.4μm以下，还进一步优选0.3μm以下，最优选0.2μm以下。
  4. 根据权利要求1所述的石墨烯复合物，其特征在于，所述石墨烯复合物中纳米纤维素的含量在10wt％以内，优选在8wt％以内，优选在5wt％以内，优选在3wt％以内，优选在1wt％以内，优选在0.5wt％以内。
  5. 根据权利要求1所述的石墨烯复合物，其特征在于，所述纳米纤维素的直径在30nm以内，优选20nm以内，再优选在10nm以内，更优选在5nm以内。
  6. 根据权利要求1所述的石墨烯复合物，其特征在于，所述纳米纤维素的长径比为(5-200)：1，优选为(10-100)：1，更优选为(15-40)：1；
    优选地，所述纳米纤维素制备原料源自农作物如玉米芯、植物秸秆、棉花、林木；
    优选地，所述纳米纤维素为选自以玉米芯纤维素为原料制备得到的纳米纤维素；
    优选地，所述纳米纤维素为经过提纯漂白处理过的玉米芯纤维素制备得到。
  7. 根据权利要求1至6中任一项所述的石墨烯复合物的制备方法，其特征在于，包括：使纳米纤维素和石墨烯类物质在溶液中分散成悬浮液。
  8. 根据权利要求7所述的方法，其特征在于，进一步包括：对悬浮液经过溶液去除，洗涤，干燥；
    优选地，所述溶液去除包括离心、过滤或其结合；
    优选地，所述干燥包括真空干燥、冷冻干燥、气流干燥、微波干燥、红外线干燥、高频率干燥或其结合；
    优选地，所述干燥为冷冻干燥。
  9. 根据权利要求7所述的方法，其特征在于，所述分散通过高速搅拌或剪切、超声、以及研磨中的一种或其结合来进行，优选地所述分散通过超声和研磨进行。
  10. 根据权利要求1至6中任一项所述的石墨烯复合物在纺织、医药、环保、食品包装、复合材料中的应用。
  11. 一种制备纳米纤维素的方法，其特征在于，包括下列步骤：
    在纤维素水溶液的研磨过程中加入重量为纤维素10wt％以下的石墨烯类物质，即得纳米纤维素水溶液；
    所述石墨烯类物质选自石墨烯及其衍生物、氧化石墨烯及其衍生物、生物质石墨烯及其衍生物中的一种或多种，优选氧化石墨烯/生物质石墨烯。
  12. 根据权利要求11所述的制备纳米纤维素的方法，其特征在于，
    所述石墨烯类物质的加入量为纤维素水溶液的5wt％以下，优选2wt％以下，更优选1wt％以下，再优选0.6wt％以下。
  13. 根据权利要求11或12所述的制备纳米纤维素的方法，其特征在于，
    所述石墨烯类物质粒径≤30μm，优选≤15μm，更优选≤3μm，再优选≤500nm，进一步优选≤100nm。
  14. 根据权利要求11所述的制备纳米纤维素的方法，其特征在于，所述纤维素选自木质纤维素、玉米芯纤维素、微晶纤维素、细菌纤维素和纸浆中的一种或多种混合；
    优选地，所述纸浆选自漂白木浆、漂白草浆、玉米芯浆、棉浆、麻浆、竹浆、苇浆、溶解浆、破布浆、未漂木浆和未漂草浆中的一种或几种的混合。
  15. 根据权利要求11所述的制备纳米纤维素的方法，其特征在于，所述研磨的条件为：使用功率为200-400W的超声匀质分散机以1000～13600rpm的搅拌速度进行分散处理1～30min，或者，使用机械搅拌器或磁力搅拌器以300～500rpm的速度连续搅拌1～72h；研磨温度优选为4～50℃，进一步优选为4～10℃。
  16. 根据权利要求11所述的制备纳米纤维素的方法，其特征在于，在所述研磨前或研磨过程中还加入酸进行酸解：
    加入55～64wt％的H2SO4，在40～60℃下搅拌进行酸解，反应1～2小时后加入去离子水，再离心一次或多次，收集沉淀。
  17. 根据权利要求11所述的制备纳米纤维素的方法，其特征在于，在所述研磨前或研磨过程中还加入TEMPO催化氧化体系进行氧化处理：在TEMPO催化氧化体系的作用下，在pH10～11、10-40℃下搅拌反应2～24小时；
    优选地，所述TEMPO催化氧化体系为含有TEMPO和/或其衍生物、次氯酸盐、溴化盐和/或高氯酸盐的水溶液体系；更优选为含有TEMPO、次氯酸钠、溴化钠和/或高氯酸钠的水溶液体系；
    优选地，所述TEMPO衍生物选自2-氮杂金刚烷-N-氧基、1-甲基-2-氮杂金刚烷-N-氧基、1，3-二甲基-2-氮杂金刚烷-N-氧基和4-羟基TEMPO衍生物中的一种或多种；
    优选地，TEMPO和/或其衍生物的加入量是纤维素重量的0.05％～5％，优选0.1％～3％，再优选0.3％～2％，更优选0.5％-1％；
    优选地，次氯酸盐的加入量是纤维素重量的10％～500％，优选30％～95％，再优选40％-75％；
    优选地，溴化盐和/或高氯酸盐的加入量是纤维素重量的0.5％～50％，优选10％～30，再优选3％～20％，更优选5％～10％；
    优选地，次氯酸盐的加入浓度为5-15wt％。
  18. 根据权利要求11所述的制备纳米纤维素的方法，其特征在于，对所述纳米纤维素水溶液进行溶液去除，洗涤，干燥；优选地，所述溶液去除包括离心、过滤或其结合；优选地，所述干燥包括真空干燥、冷冻干燥、气流干燥、喷雾干燥、微波干燥、红外线干燥、高频率干燥或其结合；优选地，所述干燥为冷冻干燥。
  19. 根据权利要求18所述的制备纳米纤维素的方法，其特征在于，所述冷冻干燥的方法为：
    将产品置于-20～-25℃的条件下冷冻处理10～20h，然后将其放置于冷冻干燥机的冷阱中进行预冻，冷冻干燥机的冷阱温度为-50～-80℃；预冻结束后在真空度1～10Pa下冷冻干燥24～48h。
  20. 一种纳米纤维素，其特征在于，利用权利要求1-9任一项所述的制备纳米纤维素的方法制得。
  21. 一种高性能的石墨烯复合纳米纤维素，其特征在于，主要由纳米纤维素与石墨烯类物质组成，所述石墨烯类物质与纳米纤维素相互原位搭载；
    所述石墨烯复合纳米纤维素中，石墨烯类物质的含量在20wt％以下，进一步优选的为10wt％以下，更进一步优选的为0.5wt％-5wt％之间。
  22. 根据权利要求21所述的石墨烯复合纳米纤维素，其特征在于，所述纳米纤维素由玉米芯纤维素制备得到；
    优选地，所述纳米纤维素为经过提纯漂白处理过的玉米芯纤维素制备得到。
  23. 根据权利要求21所述的石墨烯复合纳米纤维素，其特征在于，所述纳米纤维素的长径比为(5-1000)：1，优选为(10-300)：1，更优选为(15-200)：1。
  24. 根据权利要求21-23任一项所述的石墨烯复合纳米纤维素，其特征在于，石墨烯类物质包括石墨烯、生物质石墨烯、氧化石墨烯和石墨烯衍生物的一种或几种的混合，所述石墨烯衍生物包括元素掺杂的石墨烯；
    优选地，所述石墨烯衍生包括元素掺杂石墨烯或官能团化石墨烯物中的任意1种或至少2种的组合；
    优选地，所述元素掺杂石墨烯包括金属掺杂石墨烯或非金属元素掺杂石墨烯中的任意1种或至少2种的组合；
    所述金属掺杂的金属元素典型但非限制性的包括钾、钠、金、银、铁、铜、镍、铬钛、钒或钴；所述非金属元素掺杂石墨烯包括氮、磷、硅、硼或硅；
    优选地，所述非金属元素掺杂石墨烯包括氮掺杂石墨烯、磷掺杂石墨烯和硫掺杂石墨烯中的任意1种或至少2种的组合；
    优选地，所述官能团化石墨烯包括接枝有官能团的石墨烯；
    优选地，所述官能团化石墨烯包括接枝有羟基、羧基和氨基中的任意1种或至少2种的组合的石墨烯；
    其中，所述羟基包括R1-OH，所述R1包括烷烃基，所述羟基包括甲基羟基、乙基羟基、丙基羟基、丁基羟基、戊基羟基和己基羟基中的其中一种；
    所述羧基包括R2-COOH，所述R2包括烷烃基，所述羟基包括甲基羟基、乙基羟基、丙基羟基、丁基羟基、戊基羟基和己基羟基中的其中一种；
    所述羧基包括R3-NH3，所述R3包括烷烃基，所述羟基包括甲基羟基、乙基羟基、丙基羟基、丁基羟基、戊基羟基和己基羟基中的其中一种。
  25. 权利要求21-24任一项所述的石墨烯复合纳米纤维素的制备方法，其特征在于，包括如下步骤：
    (A)将纤维素、石墨烯类物质以及去离子水混合超声分散、研磨得到悬浮液；
    (B)将悬浮液超声、离心，冷冻干燥成型即得石墨烯复合纳米纤维素；
    优选地，所述悬浮液中，纤维素的浓度为1wt％-10wt％。
  26. 根据权利要求25所述的石墨烯复合纳米纤维素的制备方法，其特征在于，所述悬浮液中，石墨烯类物质的D90指标控制在70μm以下，D10指标控制在20um以下；
    优选地，石墨烯类物质的D90指标控制在50μm以下，再优选为30μm以下，更优选为5-25μm之间；
    优选地，D90指标控制在D10指标的20倍以下，优选10倍以下，更优选为5倍以下。
  27. 根据权利要求26所述的石墨烯复合纳米纤维素的制备方法，其特征在于，所述石墨烯类物质D90和D10指标的控制方法包括：将石墨烯类物质与去离子水混合分级预处理后得到分级离心液，再将所述分级离心液与纳米纤维素混合超声分散、研磨得到悬浮液；
    优选地，所述分级预处理的方法包括：将石墨烯类物质与去离子水混合后，2000-3000rpm条件下离心操作后保留底部沉淀，上清液在5000-7000rpm条件下离心操作后分别得到二次底部沉淀与二次上清液；
    其中，所述分级离心液包括底部沉淀、二次底部沉淀和二次上清液中的任意一种制备得到，优选二次底部沉淀；
    优选地，2000-3000rpm条件下离心操作的时间控制在20-40min，
    优选地，5000-7000rpm条件下离心操作的时间控制在10-30min。
  28. 根据权利要求25所述的石墨烯复合纳米纤维素的制备方法，其特征在于，所述步骤(A)中，石墨烯类物质进行研磨预处理后再与纤维素和去离子水混合；
    优选地，将研磨预处理后的容器壁上残留的石墨烯类物质与纤维素和去离子水混合。
  29. 根据权利要求25所述的石墨烯复合纳米纤维素的制备方法，其特征在于，所述步骤(A)中，研磨的频率控制在25-35Hz，更优选为27-32Hz；
    优选地，研磨的时间控制在4-6h，更优选为5-5.5h；
    优选地，超声分散处理的时间控制在15-60min，更优选为30-50min；
    优选地，超声分散处理的功率控制在500-1500kw，更优选为1000-1200kw。
  30. 权利要求21-24任一项所述的石墨烯复合纳米纤维素在医药、环保、食品包装或复合材料方面的应用。
PCT/CN2017/100249 2016-09-20 2017-09-01 石墨烯复合物、其制备方法及用途、制备纳米纤维素的方法及所得纳米纤维素、高性能的石墨烯复合纳米纤维素及其制备方法 WO2018054212A1 (zh)

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