CN112694537B - Preparation method of oxidized nanocellulose - Google Patents
Preparation method of oxidized nanocellulose Download PDFInfo
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- CN112694537B CN112694537B CN202011525354.XA CN202011525354A CN112694537B CN 112694537 B CN112694537 B CN 112694537B CN 202011525354 A CN202011525354 A CN 202011525354A CN 112694537 B CN112694537 B CN 112694537B
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- 238000002360 preparation method Methods 0.000 title claims abstract description 25
- 229920001046 Nanocellulose Polymers 0.000 title claims description 29
- 229920002678 cellulose Polymers 0.000 claims abstract description 164
- 239000001913 cellulose Substances 0.000 claims abstract description 164
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims abstract description 48
- 238000006243 chemical reaction Methods 0.000 claims abstract description 44
- SUKJFIGYRHOWBL-UHFFFAOYSA-N sodium hypochlorite Chemical compound [Na+].Cl[O-] SUKJFIGYRHOWBL-UHFFFAOYSA-N 0.000 claims abstract description 17
- 150000005846 sugar alcohols Polymers 0.000 claims abstract description 8
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 claims description 120
- 239000000243 solution Substances 0.000 claims description 54
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 31
- 239000007864 aqueous solution Substances 0.000 claims description 30
- 239000002994 raw material Substances 0.000 claims description 29
- JHJLBTNAGRQEKS-UHFFFAOYSA-M sodium bromide Chemical compound [Na+].[Br-] JHJLBTNAGRQEKS-UHFFFAOYSA-M 0.000 claims description 28
- 239000012634 fragment Substances 0.000 claims description 25
- 238000003756 stirring Methods 0.000 claims description 24
- 239000000725 suspension Substances 0.000 claims description 24
- 239000007787 solid Substances 0.000 claims description 23
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 claims description 19
- 239000008367 deionised water Substances 0.000 claims description 17
- 229910021641 deionized water Inorganic materials 0.000 claims description 17
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 16
- 230000007935 neutral effect Effects 0.000 claims description 16
- 239000003513 alkali Substances 0.000 claims description 15
- GDOPTJXRTPNYNR-UHFFFAOYSA-N methyl-cyclopentane Natural products CC1CCCC1 GDOPTJXRTPNYNR-UHFFFAOYSA-N 0.000 claims description 15
- 238000005406 washing Methods 0.000 claims description 15
- 238000000967 suction filtration Methods 0.000 claims description 12
- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerine Chemical compound OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 claims description 9
- 238000010438 heat treatment Methods 0.000 claims description 8
- 238000000034 method Methods 0.000 claims description 8
- 238000012544 monitoring process Methods 0.000 claims description 3
- YASYEJJMZJALEJ-UHFFFAOYSA-N Citric acid monohydrate Chemical compound O.OC(=O)CC(O)(C(O)=O)CC(O)=O YASYEJJMZJALEJ-UHFFFAOYSA-N 0.000 claims 1
- 230000003647 oxidation Effects 0.000 abstract description 4
- 238000007254 oxidation reaction Methods 0.000 abstract description 4
- 239000005708 Sodium hypochlorite Substances 0.000 abstract description 3
- 238000006555 catalytic reaction Methods 0.000 abstract description 3
- 238000004519 manufacturing process Methods 0.000 abstract description 3
- 238000007086 side reaction Methods 0.000 abstract description 3
- 230000009286 beneficial effect Effects 0.000 abstract description 2
- 235000010980 cellulose Nutrition 0.000 description 101
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 39
- 229920001131 Pulp (paper) Polymers 0.000 description 9
- 239000000706 filtrate Substances 0.000 description 8
- 235000017166 Bambusa arundinacea Nutrition 0.000 description 7
- 235000017491 Bambusa tulda Nutrition 0.000 description 7
- 241001330002 Bambuseae Species 0.000 description 7
- 235000015334 Phyllostachys viridis Nutrition 0.000 description 7
- 239000011425 bamboo Substances 0.000 description 7
- 230000000052 comparative effect Effects 0.000 description 6
- 229920000742 Cotton Polymers 0.000 description 5
- 150000001735 carboxylic acids Chemical class 0.000 description 5
- 238000001704 evaporation Methods 0.000 description 5
- 239000000835 fiber Substances 0.000 description 5
- 239000000843 powder Substances 0.000 description 5
- 238000005070 sampling Methods 0.000 description 5
- 239000010902 straw Substances 0.000 description 5
- 238000001914 filtration Methods 0.000 description 4
- 229920005862 polyol Polymers 0.000 description 4
- 150000003077 polyols Chemical class 0.000 description 4
- 239000002253 acid Substances 0.000 description 3
- 238000004061 bleaching Methods 0.000 description 3
- 239000013078 crystal Substances 0.000 description 3
- 238000000265 homogenisation Methods 0.000 description 3
- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 description 2
- 238000004821 distillation Methods 0.000 description 2
- 235000013312 flour Nutrition 0.000 description 2
- WGCNASOHLSPBMP-UHFFFAOYSA-N hydroxyacetaldehyde Natural products OCC=O WGCNASOHLSPBMP-UHFFFAOYSA-N 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 238000004448 titration Methods 0.000 description 2
- 241000609240 Ambelania acida Species 0.000 description 1
- 229920000168 Microcrystalline cellulose Polymers 0.000 description 1
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 1
- 238000003917 TEM image Methods 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000001580 bacterial effect Effects 0.000 description 1
- 239000010905 bagasse Substances 0.000 description 1
- 238000010170 biological method Methods 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 239000000084 colloidal system Substances 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000007405 data analysis Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 125000000524 functional group Chemical group 0.000 description 1
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 235000019813 microcrystalline cellulose Nutrition 0.000 description 1
- 239000008108 microcrystalline cellulose Substances 0.000 description 1
- 229940016286 microcrystalline cellulose Drugs 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000003020 moisturizing effect Effects 0.000 description 1
- 239000002159 nanocrystal Substances 0.000 description 1
- 239000002121 nanofiber Substances 0.000 description 1
- 239000002086 nanomaterial Substances 0.000 description 1
- 238000000053 physical method Methods 0.000 description 1
- 239000012086 standard solution Substances 0.000 description 1
- 239000002023 wood Substances 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
- C08B15/00—Preparation of other cellulose derivatives or modified cellulose, e.g. complexes
- C08B15/02—Oxycellulose; Hydrocellulose; Cellulosehydrate, e.g. microcrystalline cellulose
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- Chemical & Material Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Biochemistry (AREA)
- Materials Engineering (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Polysaccharides And Polysaccharide Derivatives (AREA)
Abstract
The invention provides a preparation method of oxidized nano-cellulose, which can ensure the reaction efficiency and inhibit side reactions in the reaction process by adding polyalcohol and under the catalysis of sulfuric acid; the preparation method disclosed by the invention is environment-friendly and low in cost, and can ensure the yield of the cellulose in unit time, thereby being beneficial to reducing the production cost; in addition, sodium hypochlorite solution is added to ensure that the reaction is gentle, so that the oxidation of the nano-cellulose is more uniform, and the oxidized nano-cellulose with better uniformity and quality is obtained. The problems that the preparation of the nano-cellulose in the prior art is not environment-friendly enough, equipment is easy to corrode and the nano-cellulose is not uniformly oxidized can be solved.
Description
Technical Field
The invention relates to the field of preparation of nanocellulose, in particular to a preparation method of oxidized nanocellulose.
Background
Nanocellulose is a cellulose with a nano-scale, and can be classified into Cellulose Nanocrystals (CNC), cellulose Nanofibrils (CNF), and bacterial synthetic nanofibers (BNC) according to material sources, preparation methods, and fiber forms. The nano-cellulose as a novel green nano-material has good flexibility and mechanical property, and the fibers are connected in a staggered manner, so that a porous structure convenient for ion and electron transmission is easily formed; the fiber surface is also attached with hydrophilic functional groups such as hydroxyl, carboxyl and the like, and has good moisturizing capability. Generally, nanocellulose is a cellulose crystal in the nanoscale range separated from a fiber raw material by a chemical method, a physical method, a biological method or the like, and the diameter of the cellulose crystal is generally between 1 nm and 100nm, and the cellulose crystal can be dispersed in an aqueous solution to form a stable colloid. The chemical method is to treat fiber raw materials by using chemical reagents such as TEMPO, sulfuric acid and the like to obtain the nano-cellulose with uniform size. However, the problem of serious pollution and equipment corrosion in the preparation of the nano-cellulose in the prior art and the problem of uneven oxidation of the prepared nano-cellulose exist.
In view of the above, there are still problems to be solved in the field of nanocellulose preparation.
Disclosure of Invention
Based on the above, in order to solve the problems that the preparation of the nano-cellulose in the prior art is not environment-friendly enough, equipment is easy to corrode, and the nano-cellulose is oxidized unevenly, the invention provides a preparation method of oxidized nano-cellulose, which has the following specific technical scheme:
a preparation method of oxidized nano-cellulose comprises the following steps:
crushing a cellulose raw material into fragments to obtain cellulose fragments;
adding cellulose fragments into an aqueous solution containing citric acid, then adding a solution containing polyalcohol and sulfuric acid, uniformly stirring, heating to 95-100 ℃, and standing for reaction for 3-5 hours to obtain a cellulose suspension;
carrying out suction filtration on the cellulose suspension under a vacuum condition, and recovering the citric acid to obtain cellulose pulp;
washing cellulose pulp with deionized water, and adjusting the pH value of the cellulose pulp to be neutral by using alkali liquor;
adding water into cellulose pulp, adjusting the solid content of the cellulose pulp to be 1-5% by mass, adding NaBr and TEMPO under the stirring condition, dropwise adding NaClO solution after uniform stirring, and controlling the pH of a reaction system to be 9.5-10.0 under the real-time monitoring of precise pH;
when the pH of the reaction system is stabilized at 9.5-10.0 within 15min, adding ethanol, and stopping the reaction to obtain cellulose pulp;
and adding deionized water into the cellulose pulp, carrying out suction filtration under a vacuum condition, and then washing until the pH value is neutral to obtain the oxidized nano cellulose.
Preferably, the cellulose fragments are less than 10mm in diameter and length.
Preferably, the polyol is one of ethylene glycol and glycerol.
Preferably, the content of sulfuric acid in the sulfuric acid solution is 30% by mass.
Preferably, the alkali content in the alkali liquor is 0.5-10% by mass percent.
Preferably, the addition amount of NaBr is as follows: 0.08g to 0.15g of NaBr was added to 1g of a cellulose raw material.
Preferably, the amount of TEMPO added is: 1g of cellulose raw material is added with 0.01g to 0.02g of TEMPO.
Preferably, the addition amount of the NaClO is as follows: 5mmol-12mmol of NaClO was added to 1g of the cellulose raw material.
Preferably, the content of the citric acid in the citric acid aqueous solution is 65-85% by mass percent.
Preferably, the cellulose fragments account for 3-10% of the aqueous solution of citric acid by mass percent.
In the scheme, by adding the polyol and under the catalysis of sulfuric acid, not only can the reaction efficiency be ensured, but also side reactions occurring in the reaction process can be inhibited; the preparation method disclosed by the invention is environment-friendly, equipment is not easy to corrode, the cost is lower, the yield of the cellulose in unit time can be ensured, and the production cost is further reduced; in addition, sodium hypochlorite solution is added to enable the reaction to be smooth, so that the oxidation of the nano-cellulose is more uniform, and oxidized nano-cellulose with better uniformity and quality is obtained.
Drawings
FIG. 1 is a TEM image of an oxidized nanocellulose of example 1;
FIG. 2 is a length statistic of an oxidized nanocellulose in example 1;
fig. 3 is a schematic view of an oxidized nanocellulose in comparative example 1.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to embodiments thereof. It should be understood that the detailed description and specific examples, while indicating the scope of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
The preparation method of the oxidized nano-cellulose in one embodiment of the invention comprises the following steps:
crushing a cellulose raw material into fragments to obtain cellulose fragments;
adding cellulose fragments into an aqueous solution containing citric acid, then adding a solution containing polyalcohol and sulfuric acid, uniformly stirring, heating to 95-100 ℃, and standing for reaction for 3-5 hours to obtain a cellulose suspension;
carrying out suction filtration on the cellulose suspension under a vacuum condition, and recovering the citric acid to obtain cellulose pulp;
washing cellulose pulp by deionized water, and adjusting the pH value of the cellulose pulp to be neutral by alkali liquor;
adding water into cellulose pulp, adjusting the solid content of the cellulose pulp to be 1-5% by mass, adding NaBr and TEMPO under the stirring condition, dropwise adding NaClO solution after uniform stirring, and controlling the pH of a reaction system to be 9.5-10.0 under the real-time monitoring of precise pH;
after the pH value of the reaction system is kept stable at 9.5-10.0 within 15min, adding ethanol, and stopping the reaction to obtain cellulose pulp;
and adding deionized water into the cellulose pulp, carrying out suction filtration under a vacuum condition, and washing until the pH value is neutral to obtain the oxidized nano cellulose.
In one embodiment, the preparation method further comprises the following steps: adding a proper amount of water into the oxidized nano-cellulose to ensure that the solid content of the oxidized nano-cellulose in the solution is 0.5-2% by mass, and homogenizing under high pressure to obtain the oxidized nano-cellulose suspension.
In one embodiment, the cellulose chips are less than 10mm in diameter and length.
In one embodiment, the polyol is one of ethylene glycol and glycerol.
In one embodiment, the sulfuric acid solution contains 30% sulfuric acid by mass.
In one embodiment, the alkali content in the alkali liquor is 0.5-10% by mass percent.
In one embodiment, the addition amount of NaBr is: 0.08-0.15 g NaBr was added per 1g of cellulose raw material.
In one embodiment, TEMPO is added in an amount of: 0.01g-0.02g TEMPO is added to 1g cellulose raw material.
In one embodiment, the addition amount of the NaClO is as follows: 5mmol-12mmol NaClO is added to 1g of the cellulose raw material.
In one embodiment, the citric acid content of the citric acid aqueous solution is 65-85% by mass percent.
In one embodiment, the cellulose fragments comprise 3-10% by mass of the aqueous solution of citric acid.
In one embodiment, the cellulose raw material is one or more of microcrystalline cellulose, bagasse pulp, wood pulp, straw pulp, cotton pulp and bamboo pulp.
In one embodiment, the cellulose material is one of wood flour subjected to alkali or acid bleaching treatment, bamboo flour subjected to alkali or acid bleaching treatment, and cotton fiber subjected to alkali or acid bleaching treatment.
In one embodiment, the high-pressure homogenizing pressure is 50MPa-150MPa.
In one embodiment, the high-pressure homogenization is performed 1-10 times.
In one embodiment, the addition amount of the polyol is 1-10% of the aqueous solution of citric acid by mass percent.
In one embodiment, the addition amount of the sulfuric acid solution is 1-10% of the citric acid aqueous solution according to the mass percentage.
In one embodiment, the alkali solution is sodium hydroxide or potassium hydroxide solution.
In the scheme, the polyhydric alcohol is added under the catalysis of sulfuric acid, so that the reaction efficiency can be ensured, and side reactions in the reaction process can be inhibited; the preparation method disclosed by the invention is environment-friendly and low in cost, and can ensure the yield of the cellulose in unit time, thereby being beneficial to reducing the production cost; in addition, sodium hypochlorite solution is added to enable the reaction to be smooth, so that the oxidation of the nano-cellulose is more uniform, and oxidized nano-cellulose with better uniformity and quality is obtained.
Embodiments of the present invention will be described in detail below with reference to specific examples.
Example 1
A preparation method of oxidized nano-cellulose comprises the following steps:
crushing the wood pulp board into wood pulp board fragments with the diameter and the length of less than 10mm by a crusher;
adding wood pulp board fragments into an aqueous solution of citric acid with the mass percent content of 80%, wherein the mass of the wood pulp board fragments accounts for 8% of the mass of the aqueous solution of the citric acid, adding glycol accounting for 10% of the mass of the aqueous solution of the citric acid, finally adding a sulfuric acid solution accounting for 5% of the mass of the aqueous solution of the citric acid, wherein the solid content of the added sulfuric acid solution accounts for 30% by mass, uniformly stirring, heating to 95 ℃, standing and reacting for 3 hours to obtain a cellulose suspension;
carrying out suction filtration on the cellulose suspension under a vacuum condition, and evaporating and recrystallizing filtrate at normal temperature or distilling the filtrate under reduced pressure to recover citric acid to obtain cellulose pulp;
washing cellulose pulp with deionized water, adjusting the pH value to be neutral by using a sodium hydroxide solution with the mass percent of 0.5%, sampling, measuring the solid content and calculating the cellulose yield;
adding a proper amount of water into the cellulose pulp until the solid content is 3 percent by mass, continuously stirring the cellulose pulp by using a stirrer at room temperature, and simultaneously sequentially adding NaBr (0.1g -1 Cellulose raw material), TEMPO (0.015g.g. -1 Cellulose raw material), stirring uniformly, and then gradually dropwise adding NaClO (5mmol -1 Cellulose raw material), the whole reaction process is monitored in real time by a precise pH meter, and 0.5mol.L is added -1 NaOH solution is used for controlling the pH value of the reaction system to be 9.5-10.0, and ethanol (1mL. G) is used when the pH value of the reaction system is 9.5-10.0 and is not changed within 15min -1 Cellulose raw material) and filtering the reaction solution by using a large amount of deionized water under a vacuum condition, and washing the reaction solution until the pH value is neutral to obtain oxidized nano-cellulose;
adding a proper amount of water into the oxidized nano-cellulose to ensure that the solid content of the oxidized nano-cellulose in the solution is 2% by mass, and homogenizing for 1 time under the homogenizing pressure of 100Mpa to obtain the oxidized nano-cellulose suspension.
Example 2:
a preparation method of oxidized nano-cellulose comprises the following steps:
crushing the straw pulp board into straw pulp board fragments with the diameter and the length of less than 10mm by a crusher;
adding straw pulp board fragments into a citric acid aqueous solution with the mass percentage content of 65%, wherein the mass of the straw pulp board fragments accounts for 10% of the mass of the citric acid aqueous solution, adding ethylene glycol with the mass of 1% of the mass of the citric acid aqueous solution, finally adding a sulfuric acid solution with the mass of 1% of the mass of the citric acid aqueous solution, wherein the solid content of the added sulfuric acid solution is 30%, uniformly stirring, heating to 100 ℃, standing and reacting for 5 hours to obtain a cellulose suspension;
carrying out suction filtration on the cellulose suspension under a vacuum condition, and evaporating and recrystallizing filtrate at normal temperature or distilling the filtrate under reduced pressure to recover citric acid to obtain cellulose pulp;
washing cellulose pulp with deionized water, adjusting the pH value to be neutral by using a sodium hydroxide solution with the mass percent of 5%, sampling, measuring the solid content and calculating the cellulose yield;
adding a proper amount of water into cellulose pulp until the solid content is 5 percent by mass, continuously stirring the cellulose pulp by using a stirrer at room temperature, and simultaneously sequentially adding NaBr (0.2g.g.into the pulp -1 Cellulose feedstock), TEMPO (0.01g.g) -1 Cellulose raw material), stirring uniformly, and then gradually adding NaClO (10mmol.g) dropwise -1 Cellulose raw material), the whole reaction process is monitored in real time by a precise pH meter, and 0.5mol.L is added -1 NaOH solution is used for controlling the pH value of the reaction system to be 9.5-10.0, and ethanol (1mL. G) is used when the pH value of the reaction system is 9.5-10.0 and is not changed within 15min -1 Cellulose raw material) and filtering the reaction solution by using a large amount of deionized water under a vacuum condition, and washing the reaction solution until the pH value is neutral to obtain oxidized nano-cellulose;
adding a proper amount of water into the oxidized nano-cellulose to ensure that the solid content of the oxidized nano-cellulose in the solution is 1% by mass, and homogenizing for 10 times under the homogenization pressure of 50Mpa to obtain the oxidized nano-cellulose suspension.
Example 3:
a preparation method of oxidized nano-cellulose comprises the following steps:
crushing the bamboo powder treated by the alkali liquor into bamboo powder fragments with the diameter and the length of less than 10mm by using a crusher;
adding bamboo powder chips into a citric acid aqueous solution with the mass percent of 75%, adding ethylene glycol with the mass percent of 5% of the citric acid aqueous solution into the bamboo powder chips, and finally adding a sulfuric acid solution with the mass percent of 5% of the citric acid aqueous solution into the bamboo powder chips, wherein the solid content of the added sulfuric acid solution is 30%, uniformly stirring, heating to 100 ℃, standing and reacting for 4 hours to obtain a cellulose suspension;
carrying out suction filtration on the cellulose suspension under a vacuum condition, and evaporating and recrystallizing filtrate at normal temperature or distilling the filtrate under reduced pressure to recover citric acid to obtain cellulose pulp;
washing cellulose pulp with deionized water, adjusting the pH value to be neutral by using a sodium hydroxide solution with the mass percent of 5%, sampling, measuring the solid content and calculating the cellulose yield;
adding a proper amount of water into cellulose pulp until the solid content is 5 mass percent, continuously stirring the cellulose pulp by using a stirrer at room temperature, and simultaneously sequentially adding 0.2g.g.NaBr into the pulp -1 Cellulose feedstock), TEMPO (0.01g.g.) -1 Cellulose raw material), stirring uniformly, and gradually dropwise adding NaClO (7mmol.g) -1 Cellulose feedstock), the entire reaction process was monitored in real time with a precision pH meter by adding 1mol -1 NaOH solution is used for controlling the pH value of the reaction system to be 9.5-10.0, and ethanol (1mL. G) is used when the pH value of the reaction system is 9.5-10.0 and is not changed within 15min -1 Cellulose raw material) and filtering the reaction solution by using a large amount of deionized water under a vacuum condition, and washing the reaction solution until the pH value is neutral to obtain oxidized nano-cellulose;
adding a proper amount of water into the oxidized nanocellulose to enable the solid content of the oxidized nanocellulose in the solution to be 1% by mass, and homogenizing for 3 times under the condition that the homogenization pressure is 100Mpa to obtain the oxidized nanocellulose.
Example 4:
a preparation method of oxidized nano-cellulose comprises the following steps:
crushing the cotton fiber treated by the alkali liquor into cotton fiber fragments with the diameter and the length of less than 10mm by using a crusher;
adding cotton fiber fragments into an aqueous solution of citric acid with the mass percent of 85%, adding glycol with the mass percent of 6% of the aqueous solution of citric acid, finally adding a sulfuric acid solution with the mass percent of 7% of the aqueous solution of citric acid, stirring uniformly, heating to 98 ℃, standing and reacting for 4 hours to obtain a cellulose suspension;
carrying out suction filtration on the cellulose suspension under a vacuum condition, and evaporating and recrystallizing filtrate at normal temperature or carrying out reduced pressure distillation to recover citric acid to obtain cellulose pulp;
washing cellulose pulp with deionized water, adjusting the pH value to be neutral by using a sodium hydroxide solution with the mass percent of 5%, sampling, measuring the solid content and calculating the cellulose yield;
adding a proper amount of water into cellulose pulp until the solid content is 1 percent by mass, continuously stirring the cellulose pulp by using a stirrer at room temperature, and simultaneously sequentially adding NaBr (0.2g.g.into the pulp -1 Cellulose feedstock), TEMPO (0.02g.g -1 Cellulose raw material), stirring uniformly, and gradually dropwise adding NaClO (12mmol -1 Cellulose feedstock) solution, the entire reaction process was monitored in real time using a precision pH meter by adding 2mol -1 NaOH solution is used for controlling the pH value of the reaction system to be 9.5-10.0, and ethanol (1mL. G) is used when the pH value of the reaction system is 9.5-10.0 and is not changed within 15min -1 Cellulose raw material) and filtering the reaction solution by using a large amount of deionized water under a vacuum condition, and washing the reaction solution until the pH value is neutral to obtain oxidized nano-cellulose;
adding a proper amount of water into the oxidized nano-cellulose to ensure that the solid content of the oxidized nano-cellulose in the solution is 1% by mass, and homogenizing for 5 times under the homogenizing pressure of 80Mpa to obtain the oxidized nano-cellulose suspension.
Comparative example 1:
a preparation method of oxidized nano-cellulose comprises the following steps:
crushing the wood pulp board into wood pulp board fragments with the diameter and the length of less than 10mm by a crusher;
adding wood pulp board fragments into an aqueous solution of citric acid with the mass percentage content of 80%, wherein the mass of the wood pulp board fragments accounts for 8% of the mass of the aqueous solution of the citric acid, adding a sulfuric acid solution with the mass of 5% of the mass of the aqueous solution of the citric acid, wherein the solid content of the added sulfuric acid solution accounts for 30% by mass, uniformly stirring, heating to 95 ℃, standing and reacting for 3 hours, and obtaining a cellulose suspension;
carrying out suction filtration on the cellulose suspension under a vacuum condition, and evaporating and recrystallizing filtrate at normal temperature or carrying out reduced pressure distillation to recover citric acid to obtain cellulose pulp;
washing cellulose pulp with deionized water, adjusting the pH value to be neutral by using a sodium hydroxide solution with the mass percent of 0.5%, sampling, measuring the solid content and calculating the cellulose yield;
adding a proper amount of water into cellulose pulp until the solid content is 3 percent by mass, continuously stirring the cellulose pulp by using a stirrer at room temperature, and simultaneously sequentially adding NaBr (0.1g.g.into the pulp) -1 Cellulose raw material), TEMPO (0.015g.g. -1 Cellulose raw material), stirring uniformly, and then gradually dropwise adding NaClO (5mmol -1 Cellulose feedstock), the entire reaction process was monitored in real time with a precision pH meter by adding 0.5mol.l -1 Controlling the pH of the reaction system to be 9.5-10.0 by NaOH solution, and using ethanol (1mL. G) when the pH of the reaction system is 9.5-10.0 and is not changed within 15min -1 Cellulose raw material) is stopped, a large amount of deionized water is used for suction filtration under the vacuum condition, and the obtained product is washed until the pH value is neutral, so that oxidized nano-cellulose is obtained;
adding a proper amount of water into the oxidized nano-cellulose to ensure that the solid content of the oxidized nano-cellulose in the solution is 2% by mass, and homogenizing for 1 time under the homogenizing pressure of 100Mpa to obtain the oxidized nano-cellulose suspension.
The cellulose pulps obtained in the preparation process of examples 1 to 4 and comparative example 1 were examined, while the resulting oxidized nanocellulose suspensions were examined.
Wherein, the content determination of carboxylic acid: 0.1g of absolutely dry cellulose pulp or oxidized nano-cellulose suspension is uniformly dispersed in 55mL of deionized water, 5mL of KCl solution with the concentration of about 0.01mol/L is added, and after uniform dispersion, the pH value of the suspension is adjusted to 2.5-3.0 by using 0.1mol/L HCl solution. And (2) dropwise adding 0.05mol/LNaOH standard solution into the solution successively at a dropping rate of 0.1mL/min, recording the conductivity change of each dropping by using a conductivity meter, drawing a curve graph according to data, and calculating the content of carboxylic acid according to the difference value of the V2 value at the titration end point and the V1 value at the titration initial point in the curve graph according to the following formula:
carboxylic acid content: [ COOH]＝(C NaOH V 2 －C NaOH V 1 )/m(mmol/g)
The results obtained are shown in table 1 below.
Table 1:
as can be seen from the data analysis in Table 1 and the analysis in combination with FIGS. 1-3, the carboxylic acid content of the oxidized nanocellulose prepared by the present invention is high, specifically 0.8-1.5mmol/g, while the carboxylic acid content of the oxidized nanocellulose obtained in comparative example 1 without the treatment with the polyhydric alcohol is 0.2, which is significantly different from examples 1-4 and inferior to examples 1-4; the oxidized nanocellulose prepared by the method is large in diameter and long in length, but the oxidized nanocellulose in comparative example 1 is degraded, so that the oxidized nanocellulose large in diameter and long in length cannot be obtained; the oxidized nanocelluloses prepared in examples 1 to 4 were high in yield and colorless and transparent oxidized nanocellulose was obtained, but the oxidized nanocellulose prepared in comparative example 1 was low in yield, dark in color, and easily oxidized to a darker product.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is specific and detailed, but not to be understood as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (7)
1. A preparation method of oxidized nano-cellulose is characterized by comprising the following steps:
crushing a cellulose raw material into fragments to obtain cellulose fragments;
adding cellulose fragments into an aqueous solution containing citric acid, then adding a solution containing polyalcohol and sulfuric acid, uniformly stirring, heating to 95-100 ℃, and standing for reaction for 3-5 hours to obtain a cellulose suspension;
carrying out suction filtration on the cellulose suspension under a vacuum condition, and recovering the citric acid to obtain cellulose pulp;
washing cellulose pulp with deionized water, and adjusting the pH value of the cellulose pulp to be neutral by using alkali liquor;
adding water into cellulose pulp, adjusting the solid content of the cellulose pulp to be 1-5% by mass, adding NaBr and TEMPO under the stirring condition, dropwise adding NaClO solution after uniform stirring, and controlling the pH of a reaction system to be 9.5-10.0 under the real-time monitoring of precise pH;
after the pH value of the reaction system is kept stable at 9.5-10.0 within 15min, adding ethanol, and stopping the reaction to obtain cellulose pulp;
adding deionized water into the cellulose pulp, carrying out suction filtration under a vacuum condition, and washing until the pH value is neutral to obtain oxidized nano cellulose;
wherein the polyalcohol is one of ethylene glycol and glycerol;
according to the mass percentage, the adding amount of the polyhydric alcohol is 1-10% of the aqueous solution of the citric acid;
according to the mass percentage, the addition amount of the sulfuric acid solution is 1-10% of the aqueous solution of the citric acid;
according to the mass percentage, the content of the sulfuric acid in the sulfuric acid solution is 30%;
according to the mass percentage, the content of the citric acid in the citric acid water solution is 65-85%.
2. The method of claim 1, wherein the cellulose fragments have a diameter and a length of less than 10mm.
3. The method according to claim 1, wherein the amount of NaBr added is: 0.08-0.15 g NaBr was added per 1g of cellulose raw material.
4. The preparation method of oxidized nanocellulose according to claim 1, characterized in that, by mass percentage, the alkali content in the alkali solution is 0.5% -10%.
5. The method for preparing oxidized nanocellulose according to claim 1, characterized in that the amount of TEMPO added is: 0.01g-0.02g TEMPO is added to 1g cellulose raw material.
6. The method for preparing oxidized nanocellulose according to claim 1, characterized in that the amount of said NaClO added is: 5mmol-12mmol of NaClO is added to 1g of the cellulose raw material.
7. The method for preparing oxidized nanocellulose according to claim 6, characterized in that the cellulose pieces account for 3% -10% by mass of the aqueous solution of citric acid.
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