CN117186252A - Nanocellulose and preparation method of polyethylene sheet containing nanocellulose - Google Patents
Nanocellulose and preparation method of polyethylene sheet containing nanocellulose Download PDFInfo
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- CN117186252A CN117186252A CN202310676203.1A CN202310676203A CN117186252A CN 117186252 A CN117186252 A CN 117186252A CN 202310676203 A CN202310676203 A CN 202310676203A CN 117186252 A CN117186252 A CN 117186252A
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- 229920001046 Nanocellulose Polymers 0.000 title claims abstract description 100
- -1 polyethylene Polymers 0.000 title claims abstract description 61
- 239000004698 Polyethylene Substances 0.000 title claims abstract description 56
- 229920000573 polyethylene Polymers 0.000 title claims abstract description 56
- 238000002360 preparation method Methods 0.000 title abstract description 27
- 239000002253 acid Substances 0.000 claims abstract description 37
- 229920000168 Microcrystalline cellulose Polymers 0.000 claims abstract description 30
- 235000019813 microcrystalline cellulose Nutrition 0.000 claims abstract description 30
- 239000008108 microcrystalline cellulose Substances 0.000 claims abstract description 30
- 229940016286 microcrystalline cellulose Drugs 0.000 claims abstract description 30
- 238000002156 mixing Methods 0.000 claims abstract description 28
- 238000002137 ultrasound extraction Methods 0.000 claims abstract description 17
- 238000000944 Soxhlet extraction Methods 0.000 claims abstract description 16
- DBMJMQXJHONAFJ-UHFFFAOYSA-M Sodium laurylsulphate Chemical compound [Na+].CCCCCCCCCCCCOS([O-])(=O)=O DBMJMQXJHONAFJ-UHFFFAOYSA-M 0.000 claims abstract description 13
- 238000004108 freeze drying Methods 0.000 claims abstract description 13
- GVGUFUZHNYFZLC-UHFFFAOYSA-N dodecyl benzenesulfonate;sodium Chemical compound [Na].CCCCCCCCCCCCOS(=O)(=O)C1=CC=CC=C1 GVGUFUZHNYFZLC-UHFFFAOYSA-N 0.000 claims abstract description 5
- 229940080264 sodium dodecylbenzenesulfonate Drugs 0.000 claims abstract description 5
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 claims description 114
- BDAGIHXWWSANSR-UHFFFAOYSA-N methanoic acid Natural products OC=O BDAGIHXWWSANSR-UHFFFAOYSA-N 0.000 claims description 76
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 70
- OSWFIVFLDKOXQC-UHFFFAOYSA-N 4-(3-methoxyphenyl)aniline Chemical compound COC1=CC=CC(C=2C=CC(N)=CC=2)=C1 OSWFIVFLDKOXQC-UHFFFAOYSA-N 0.000 claims description 38
- 235000019253 formic acid Nutrition 0.000 claims description 38
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 32
- 238000000034 method Methods 0.000 claims description 24
- 239000000725 suspension Substances 0.000 claims description 24
- UIIMBOGNXHQVGW-UHFFFAOYSA-M Sodium bicarbonate Chemical compound [Na+].OC([O-])=O UIIMBOGNXHQVGW-UHFFFAOYSA-M 0.000 claims description 22
- 238000001816 cooling Methods 0.000 claims description 16
- 239000000243 solution Substances 0.000 claims description 15
- 239000003054 catalyst Substances 0.000 claims description 14
- 239000007788 liquid Substances 0.000 claims description 12
- 239000002904 solvent Substances 0.000 claims description 12
- 239000000203 mixture Substances 0.000 claims description 11
- 229910000030 sodium bicarbonate Inorganic materials 0.000 claims description 11
- 235000017557 sodium bicarbonate Nutrition 0.000 claims description 11
- 238000005406 washing Methods 0.000 claims description 11
- 238000011049 filling Methods 0.000 claims description 8
- 238000007731 hot pressing Methods 0.000 claims description 8
- 238000002844 melting Methods 0.000 claims description 8
- 230000008018 melting Effects 0.000 claims description 8
- 239000012778 molding material Substances 0.000 claims description 8
- 238000000465 moulding Methods 0.000 claims description 8
- 239000000843 powder Substances 0.000 claims description 8
- 238000007493 shaping process Methods 0.000 claims description 8
- 238000003892 spreading Methods 0.000 claims description 8
- 230000007480 spreading Effects 0.000 claims description 8
- 239000012670 alkaline solution Substances 0.000 claims description 7
- 229920002678 cellulose Polymers 0.000 claims description 7
- 239000001913 cellulose Substances 0.000 claims description 7
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims description 3
- 235000011114 ammonium hydroxide Nutrition 0.000 claims description 3
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 claims 1
- 239000011734 sodium Substances 0.000 claims 1
- 229910052708 sodium Inorganic materials 0.000 claims 1
- 238000006243 chemical reaction Methods 0.000 abstract description 9
- 239000011159 matrix material Substances 0.000 abstract description 5
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- 238000000605 extraction Methods 0.000 description 24
- 230000000052 comparative effect Effects 0.000 description 13
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 13
- 235000010980 cellulose Nutrition 0.000 description 6
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- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
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- 239000012620 biological material Substances 0.000 description 1
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Abstract
The invention belongs to the field of nano cellulose and polyethylene plate preparation, and in particular relates to a nano cellulose and a preparation method of a polyethylene plate containing the nano cellulose, wherein the nano cellulose is prepared by mixing commercial microcrystalline cellulose, mixed acid and sodium dodecyl sulfate or sodium dodecyl benzene sulfonate or polyoxyethylene octanol for reaction, and then obtaining the nano cellulose through freeze drying, ultrasonic extraction and Soxhlet extraction, and mixing the nano cellulose into polyethylene; the preparation time of the nanocellulose is shortened, and the yield of the nanocellulose is improved; evenly distributed in the polyethylene matrix material, so as to realize the mechanical property enhancement of the polyethylene matrix; endows the polyethylene composite material with self-degradation capability at normal temperature, and has wide application prospect in industrial production.
Description
Technical Field
The invention belongs to the field of nano cellulose and polyethylene plate preparation, and particularly relates to a nano cellulose and a preparation method of a polyethylene plate containing the nano cellulose.
Background
The nanocellulose is a natural pollution-free degradable novel polymer functional material extracted from natural cellulose, has a unique structure and excellent performance, and has the characteristics of light weight, degradability, reproducibility and the like of biological materials, so that the nanocomposite material, foods, biological medicines and the like are paid attention to by a plurality of researchers.
However, at present, high-concentration inorganic acid such as sulfuric acid, hydrochloric acid, phosphoric acid and the like is adopted for preparing the nanocellulose, the hydrolysis of the cellulose is serious, the cellulose is difficult to dissolve in water, and the problems of slow reaction and low yield and the like exist in the acid hydrolysis.
Polyethylene is widely applied to aspects of daily life in the world at present, is mainly used for manufacturing films, packaging materials, containers, pipelines, monofilaments, wires, cables, daily necessities and the like, can be used as high-frequency insulating materials for televisions, radars and the like, and is rapidly developed along with the development of petrochemical industry, and the yield is about 1/4 of the total yield of plastics; because of the huge yield of polyethylene, recycling and degradation of polyethylene have become a difficult problem, and although polyethylene can be degraded, the molecular structure of polyethylene determines that polyethylene is easy to crosslink and difficult to decompose, the decomposition needs to be carried out at high temperature, the degradation temperature is generally about 450 ℃, and the degradation speed is very slow, which tends to cause environmental pollution and high cost of recycling and centralized degradation.
Among them, polyethylene sheets are more difficult to degrade due to their good chemical stability, and polyethylene sheets are very sensitive to environmental stresses, and their mechanical properties often cannot meet the daily production requirements. Therefore, it is necessary to find a polyethylene sheet material which is degradable at normal temperature and has good mechanical properties.
Disclosure of Invention
The invention provides a nanocellulose and a preparation method of a polyethylene sheet containing the nanocellulose, which can realize the preparation of the nanocellulose, improve the yield of the nanocellulose, strengthen the mechanical property of the polyethylene sheet containing the nanocellulose and further endow the polyethylene composite material with self-degradation capability in normal temperature environment.
The technical scheme adopted for solving the technical problems is as follows:
a method for preparing nanocellulose, the method comprising the steps of:
1) Mixing commercial microcrystalline cellulose, a catalyst and mixed acid, reacting for 1-2 hours at 60-95 ℃, adding a weak alkaline solution to the mixture until the pH value is 7, and centrifuging and washing the mixture to obtain a suspension, wherein the weight and volume ratio of the commercial microcrystalline cellulose, the catalyst and the mixed acid is 1g:0.001-0.05g:50-100ml;
2) Freeze-drying the suspension liquid obtained in the step 1), adding an ethanol solvent, performing ultrasonic extraction for 20-40min by 200-300W, and performing Soxhlet extraction for 3-6h to obtain nanocellulose, wherein the weight-volume ratio of microcrystalline cellulose to ethanol is 1g:100-150ml.
In the present invention, the commercial microcrystalline cellulose and the catalyst are mixed with a mixed acid, and more preferably reacted at 80 to 90℃for 1 to 2 hours, at which temperature the acidolysis reaction of cellulose is more favored.
Further, the mixed acid comprises hydrochloric acid, formic acid and citric acid, the concentrations of the hydrochloric acid, the formic acid and the citric acid are respectively and independently 3-6M, and the volume ratio is V (hydrochloric acid) :V (formic acid) :V (citric acid) ＝(0-1):(1.5-7.5):(7.5-1)。
Further, the concentration of the hydrochloric acid, the formic acid and the citric acid is 3M, and the volume ratio is V (hydrochloric acid) :V (formic acid) :V (citric acid) ＝1:2:7。
Further, the weakly alkaline solution is selected from any one of 1-2% ammonia water and 0.5-1% sodium bicarbonate solution.
Further, the catalyst is sodium dodecyl sulfate or sodium dodecyl benzene sulfonate or polyoxyethylene octanol.
The catalyst can improve the contact angle of acid on the surface of microcrystalline cellulose, so that the acid can be fully contacted with the microcrystalline cellulose and negative charge is introduced to improve the surface stability of the microcrystalline cellulose, promote the reaction, reduce the reaction time and improve the reaction yield.
The method for extracting the ganaxolose by ultrasonic extraction ensures that the extraction efficiency is improved on the premise of ensuring the extraction effect of the product.
Further, the preparation method of the nanocellulose comprises the following steps:
1) Mixing commercial microcrystalline cellulose and sodium dodecyl sulfate with mixed acid, reacting for 1h at 80 ℃, adding weak alkaline solution, centrifuging, and washing with water to obtain suspension with pH of 7, wherein the weight-volume ratio of the commercial microcrystalline cellulose to the sodium dodecyl sulfate to the mixed acid is 1g:0.001g:100ml, wherein the mixed acid is hydrochloric acid, formic acid and citric acid, the concentrations of the hydrochloric acid, the formic acid and the citric acid are respectively 3M, and the volume ratio is V (hydrochloric acid) :V (formic acid) :V (citric acid) ＝1:2:7；
2) And 3) freeze-drying the suspension liquid obtained in the step 1), adding 1000ml of ethanol solvent, performing ultrasonic extraction for 20min by 300W, and performing Soxhlet extraction for 3h to obtain the nanocellulose.
The preparation method of the polyethylene board comprises the following steps:
1) Filling a die: the mass ratio of the nanocellulose to the polyethylene powder is 1: uniformly mixing 50-100, and spreading in a mould;
2) Hot pressing and melting: setting the temperature of the upper template to 140-150 ℃, reducing the molding pressure to 1-10MPa so as to improve the curing uniformity of the molding material, setting the temperature of the lower template to 230-240 ℃, placing the mold on the lower template which has reached the set temperature, and moving the upper template downwards to apply the pressure to the mold to 1-50MPa;
3) Cooling and solidifying: and taking out the die, placing the die on a plate vulcanizing machine for cold press shaping, cooling to room temperature, and taking out the die to obtain the nanocellulose-containing polyethylene plate.
The beneficial effects of the invention are as follows:
1) Shortens the preparation time of the nanocellulose and improves the extraction rate of the nanocellulose.
2) The nanocellulose molecules have a large number of functional groups, and are uniformly distributed in the polyethylene matrix material, so that the mechanical property of the polyethylene matrix is enhanced;
3) The nanocellulose belongs to a full-biodegradable nanofiller, endows the polyethylene composite material with self-degradation capability at normal temperature, and has wide application prospect in industrial production.
Detailed Description
The invention will be further illustrated with reference to specific examples. It is understood that these examples are provided only for illustrating the present invention and are not intended to limit the scope of the present invention. Further, it is understood that various changes and modifications of the present invention may be made by those skilled in the art after reading the disclosure of the present invention, and such equivalents are intended to fall within the scope of the present invention as defined by the appended claims.
The experimental methods used in the following examples are all conventional methods unless otherwise specified; the reagents, materials, etc. used in the examples described below are commercially available unless otherwise specified.
The invention provides a preparation method of nanocellulose, which comprises the following specific steps: 1) Mixing commercial microcrystalline cellulose, a catalyst and mixed acid, reacting for 1-2 hours at 60-95 ℃, adding a weak alkaline solution to the mixture until the pH value is 7, and centrifuging and washing the mixture to obtain a suspension, wherein the weight and volume ratio of the commercial microcrystalline cellulose, the catalyst and the mixed acid is 1g:0.001-0.05g:50-100ml;
2) Freeze-drying the suspension liquid obtained in the step 1), adding an ethanol solvent, performing ultrasonic extraction for 20-40min by 200-300W, and performing Soxhlet extraction for 3-6h to obtain nanocellulose, wherein the weight-volume ratio of microcrystalline cellulose to ethanol is 1g:100-150ml.
Wherein, the mixture of the commercial microcrystalline cellulose, the catalyst and the mixed acid is preferably reacted for 1-2 hours at 80-90 ℃ so as to be beneficial to the acidolysis reaction of the cellulose.
Wherein the catalyst is sodium dodecyl sulfate or sodium dodecyl benzene sulfonate or polyoxyethylene octanol, preferably sodium dodecyl sulfate, and the surface tension is reduced in the acidolysis reaction of microcrystalline cellulose and mixed acid, so that a layer of film is formed on the surface of microcrystalline cellulose with poor hydrophilicity, and the film is fully contacted and reacted with an acid solution, so that acidolysis solution is easier to enter the cellulose; the addition of the catalyst can change the pH value of the mixed acid reaction, buffer the ionic strength of the reaction solution and prevent the microcrystalline cellulose from being gelled or precipitated due to the ionic action.
The weak alkaline solution comprises ammonia water and sodium bicarbonate solution, preferably sodium bicarbonate solution, and is used for adjusting the pH value of the suspension and reducing the corrosion effect brought by the acidic solution.
The invention adopts the combination of the ultrasonic extraction method and the Soxhlet extraction method, and the Soxhlet extraction method is carried out after the ultrasonic extraction, thereby accelerating the extraction efficiency and taking the separation rate into account.
The preparation of the polyethylene board containing the nanocellulose comprises the following steps: 1) Filling a die: the mass ratio of the nanocellulose to the polyethylene powder is 1: uniformly mixing 50-100, and spreading in a mould;
2) Hot pressing and melting: setting the temperature of the upper template to 140-150 ℃, reducing the molding pressure to 1-10MPa so as to improve the curing uniformity of the molding material, setting the temperature of the lower template to 230-240 ℃, placing the mold on the lower template which has reached the set temperature, and moving the upper template downwards to apply the pressure to the mold to 1-50MPa;
3) Cooling and solidifying: and taking out the die, placing the die on a plate vulcanizing machine for cold press shaping, cooling to room temperature, and taking out the die to obtain the nanocellulose-containing polyethylene plate.
The invention will now be further illustrated with reference to specific examples, which are given solely for the purpose of illustration and are not to be construed as limiting the invention. The test specimens and test procedures used in the following examples include those (if the specific conditions of the experiment are not specified in the examples, generally according to conventional conditions or according to the recommended conditions of the reagent company; the reagents, consumables, etc. used in the examples described below are commercially available unless otherwise specified).
Example 1:
a preparation method of nanocellulose comprises the following steps:
1) Mixing 10g of commercial microcrystalline cellulose, 0.1g of sodium dodecyl sulfate and 1000ml of mixed acid, reacting for 1h at 85 ℃ in water bath, adding 0.5% sodium bicarbonate solution until the pH is equal to 7, centrifuging, washing with water to obtain suspension, mixing hydrochloric acid, formic acid and citric acid, wherein the concentration of the mixed acid, the formic acid and the citric acid is 3M respectively, and the volume ratio is V (hydrochloric acid) :V (formic acid) :V (citric acid) ＝1:2:7；
2) And 3) freeze-drying the suspension liquid obtained in the step 1), adding 1000ml of ethanol solvent, performing ultrasonic extraction for 20min by 300W, and performing Soxhlet extraction for 3h to obtain the nanocellulose, wherein the nanocellulose extraction rate is 83%.
The preparation method of the polyethylene board containing the nanocellulose comprises the following steps:
1) Filling a die: uniformly mixing 5g of the nanocellulose and 250g of the polyethylene powder, and spreading the mixture in a die;
2) Hot pressing and melting: setting the temperature of an upper template to 150 ℃, reducing the molding pressure to 10MPa so as to improve the curing uniformity of molding materials, setting the temperature of a lower template to 240 ℃, placing a die on the lower template which has reached the set temperature, and moving the upper template downwards to apply pressure to the die to 40MPa;
3) Cooling and solidifying: and taking out the die, placing the die on a plate vulcanizing machine for cold press shaping, cooling to room temperature, and taking out the die to obtain the nanocellulose-containing polyethylene plate.
Example 2:
a preparation method of nanocellulose comprises the following steps:
1) Mixing 10g of commercial microcrystalline cellulose, 0.1g of sodium dodecyl benzene sulfonate and 1000ml of mixed acid, reacting for 1h at 95 ℃, adding 0.5% sodium bicarbonate solution until the pH value is equal to 7, centrifuging, washing with water to obtain suspension, mixing hydrochloric acid, formic acid and citric acid, wherein the concentration of the mixed acid, the formic acid and the citric acid is 3M respectively, and the volume ratio is V (hydrochloric acid) :V (formic acid) :V (citric acid) ＝1:2:7；
2) And 3) freeze-drying the suspension liquid obtained in the step 1), adding 1000ml of ethanol solvent, performing ultrasonic extraction for 20min by 300W, and performing Soxhlet extraction for 3h to obtain the nanocellulose, wherein the nanocellulose extraction rate is 89%.
The preparation method of the polyethylene board containing the nanocellulose comprises the following steps:
1) Filling a die: uniformly mixing 10g of the nanocellulose and 250g of the polyethylene powder, and spreading the mixture in a die;
2) Hot pressing and melting: setting the temperature of an upper template to 140 ℃, reducing the molding pressure to 10MPa so as to improve the curing uniformity of molding materials, setting the temperature of a lower template to 230 ℃, placing a die on the lower template which has reached the set temperature, and moving the upper template downwards to apply pressure to the die to 40MPa;
3) Cooling and solidifying: and taking out the die, placing the die on a plate vulcanizing machine for cold press shaping, cooling to room temperature, and taking out the die to obtain the nanocellulose-containing polyethylene plate.
Example 3:
a preparation method of nanocellulose comprises the following steps:
1) Mixing 10g of commercial microcrystalline cellulose, 0.01g of polyoxyethylene octanol and 1000ml of mixed acid, reacting for 1h at 80 ℃, adding 0.5% sodium bicarbonate solution until the pH value is equal to 7, centrifuging, washing with water to obtain suspension, mixing hydrochloric acid, formic acid and citric acid, wherein the concentration of the mixed acid, the formic acid and the citric acid is 3M respectively, and the volume ratio is V (hydrochloric acid) :V (formic acid) :V (citric acid) ＝1:2:7；
2) And 3) freeze-drying the suspension liquid obtained in the step 1), adding 1000ml of ethanol solvent, performing ultrasonic extraction for 20min by 300W, and performing Soxhlet extraction for 3h to obtain the nanocellulose, wherein the nanocellulose extraction rate is 83%.
The preparation method of the polyethylene board containing the nanocellulose comprises the following steps:
1) Filling a die: uniformly mixing 15g of the nanocellulose and 250g of the polyethylene powder, and spreading the mixture in a die;
2) Hot pressing and melting: setting the temperature of an upper template to 140 ℃, reducing the molding pressure to 5MPa so as to improve the curing uniformity of molding materials, setting the temperature of a lower template to 230 ℃, placing a die on the lower template which has reached the set temperature, and moving the upper template downwards to apply pressure to the die to 40MPa;
3) Cooling and solidifying: and taking out the die, placing the die on a plate vulcanizing machine for cold press shaping, cooling to room temperature, and taking out the die to obtain the nanocellulose-containing polyethylene plate.
Example 4:
a preparation method of nanocellulose comprises the following steps:
1) Mixing 10g of commercial microcrystalline cellulose, 0.5g of sodium dodecyl sulfate and 1000ml of mixed acid, reacting for 1h at the temperature of 80 ℃ in a water bath, adding 0.5% sodium bicarbonate solution until the pH value is equal to 7, centrifuging, washing with water to obtain suspension, mixing hydrochloric acid, formic acid and citric acid, wherein the concentration of the mixed acid is 6M, and the volume ratio is V (hydrochloric acid) :V (formic acid) :V (citric acid) ＝1:2:7；
2) And 3) freeze-drying the suspension liquid obtained in the step 1), adding 1000ml of ethanol solvent, performing ultrasonic extraction for 20min by 150W, and performing Soxhlet extraction for 3h to obtain the nanocellulose, wherein the nanocellulose extraction rate is 86%.
The preparation method of the polyethylene board containing the nanocellulose comprises the following steps:
1) Filling a die: uniformly mixing 20g of the nanocellulose and 250g of the polyethylene powder, and spreading the mixture in a die;
2) Hot pressing and melting: setting the temperature of an upper template to 140 ℃, reducing the molding pressure to 5MPa so as to improve the curing uniformity of molding materials, setting the temperature of a lower template to 230 ℃, placing a die on the lower template which has reached the set temperature, and moving the upper template downwards to apply pressure to the die to 40MPa;
3) Cooling and solidifying: and taking out the die, placing the die on a plate vulcanizing machine for cold press shaping, cooling to room temperature, and taking out the die to obtain the nanocellulose-containing polyethylene plate.
Example 5:
the procedure is similar to example 1, except that V (hydrochloric acid) :V (formic acid) :V (citric acid) ＝1:7.5:1。
The final nanocellulose extraction rate was 78%.
Example 6:
the procedure is similar to that of example 1,the difference is that the V (hydrochloric acid) :V (formic acid) :V (citric acid) ＝1:6:3。
The final nanocellulose extraction rate was 80%.
Example 7:
the procedure is similar to example 1, except that V (hydrochloric acid) :V (formic acid) :V (citric acid) ＝1:4:5。
The final nanocellulose extraction rate was 82%.
Example 8:
the procedure is similar to example 1, except that V (hydrochloric acid) :V (formic acid) :V (citric acid) ＝1:3:6。
The final nanocellulose extraction rate was 84%.
Example 9:
the procedure is similar to example 1, except that V (hydrochloric acid) :V (formic acid) :V (citric acid) ＝1:1.5:7.5。
The final nanocellulose extraction rate was 88%.
Comparative example 1:
a preparation method of nanocellulose comprises the following steps:
1) Mixing 10g of commercial microcrystalline cellulose with 1000ml of mixed acid, reacting for 1h at 85 ℃ in water bath, adding 0.5% sodium bicarbonate solution until the pH is equal to 7, centrifuging, and washing with water to obtain suspension, wherein the mixed acid is prepared by mixing hydrochloric acid, formic acid and citric acid, the concentration of the mixed acid, the formic acid and the citric acid is 3M respectively, and the volume ratio is V (hydrochloric acid) :V (formic acid) :V (citric acid) ＝1:7:2；
2) And 3) freeze-drying the suspension liquid obtained in the step 1), adding 1000ml of ethanol solvent, performing ultrasonic extraction for 20min by 300W, and performing Soxhlet extraction for 3h to obtain the nanocellulose, wherein the nanocellulose extraction rate is 70%.
Comparative example 2:
a preparation method of nanocellulose comprises the following steps:
1) Mixing commercial microcrystalline cellulose 10g, sodium dodecyl sulfate 0.1g, and mixed acid 1000ml, reacting in water bath at 80deg.C for 1 hr, and adding 0.5%The sodium bicarbonate solution is centrifugated and washed until the pH value is equal to 7, the mixed acid is mixed with hydrochloric acid, formic acid and citric acid, the concentrations of the three are respectively 3M, and the volume ratio is V (hydrochloric acid) :V (formic acid) :V (citric acid) ＝1:7:2；
2) And 3) freeze-drying the suspension liquid obtained in the step 1), adding 1000ml of ethanol solvent, and performing ultrasonic extraction for 40min at 300W to obtain the nanocellulose, wherein the nanocellulose extraction rate is 60%.
Comparative example 3:
a preparation method of nanocellulose comprises the following steps:
1) Mixing 10g of commercial microcrystalline cellulose, 0.1g of sodium dodecyl sulfate and 1000ml of mixed acid, reacting for 1h at the temperature of 80 ℃ in a water bath, adding 0.5% sodium bicarbonate solution until the pH value is equal to 7, centrifuging, washing with water to obtain suspension, mixing hydrochloric acid, formic acid and citric acid, wherein the concentration of the mixed acid is 3M, and the volume ratio is V (hydrochloric acid) :V (formic acid) :V (citric acid) ＝1:7:2；
2) And 3) freeze-drying the suspension liquid obtained in the step 1), adding 1000ml of ethanol solvent, and extracting for 6 hours by a Soxhlet extraction method to obtain the nanocellulose, wherein the nanocellulose extraction rate is 75%.
Comparative example 4:
the procedure was similar to comparative example 3, except that nanocellulose was obtained by ultrasonic extraction at 300W for 120min, with a nanocellulose extraction rate of 75%.
Comparative example 5:
the procedure was similar to comparative example 3, except that nanocellulose was obtained by soxhlet extraction for 12 hours, with an extraction rate of nanocellulose of 85%.
Comparative example 6:
the preparation method of the polyethylene board containing the nanocellulose comprises the following steps:
1) Filling a die: spreading 250g of polyethylene powder in a mould;
2) Hot pressing and melting: setting the temperature of an upper template to 140 ℃, reducing the molding pressure to 5MPa so as to improve the curing uniformity of molding materials, setting the temperature of a lower template to 230 ℃, placing a die on the lower template which has reached the set temperature, and moving the upper template downwards to apply pressure to the die to 40MPa;
3) Cooling and solidifying: and taking out the die, placing the die on a plate vulcanizing machine for cold press shaping, cooling to room temperature, and taking out the die to obtain the nanocellulose-containing polyethylene plate.
Table 1 shows the tensile yield strength and tensile modulus of elasticity of nanocellulose polyethylene sheets prepared in examples 1-4 and comparative example 6.
Table 1 mechanical strength table of nanocellulose polyethylene sheets produced in examples 1-4 and comparative example 6
| Sample number | Tensile yield strength (MPa) | Tensile elastic modulus (MPa) |
| Example 1 | 17.8 | 465.3 |
| Example 2 | 18.1 | 489.2 |
| Example 3 | 17.6 | 457.4 |
| Example 4 | 17.9 | 462.1 |
| Comparative example 6 | 16.1 | 442.5 |
Compared with the common nanocellulose-free polyethylene plate, the nanocellulose polyethylene plate prepared by the invention has higher tensile yield strength and tensile elastic modulus, because strong interface interaction is generated between nanocellulose and a matrix of a polyethylene material, the mechanical strength of the nanocellulose polyethylene plate is greatly enhanced, and the more the nanocellulose addition amount is, the greater the mechanical strength is.
As can be seen from the comparison of comparative example 1 and example 1, the catalyst of the present invention can effectively improve the extraction yield of the present invention.
Examples 1-9 show that the smaller the ratio of the addition amount of formic acid to citric acid is, the higher the extraction rate of nanocellulose is, and the later is stable when the addition amount of hydrochloric acid is the same.
As can be seen from comparative examples 2-5, the ultrasonic extraction of nanocellulose is fast but has a low extraction rate, while the Soxhlet extraction method is slow but has a high extraction rate, and the combination of the two greatly shortens the extraction time and has a high extraction rate.
The preparation method of the nanocellulose and the polyethylene sheet containing the nanocellulose provided by the invention is described in detail above. The principles and embodiments of the present invention have been described herein with reference to specific examples, the description of which is intended only to facilitate an understanding of the method of the present invention and its core ideas. It should be noted that it will be apparent to those skilled in the art that various modifications and adaptations of the invention can be made without departing from the principles of the invention and these modifications and adaptations are intended to be within the scope of the invention as defined in the following claims.
Claims (7)
1. A method for preparing nanocellulose, which is characterized by comprising the following steps:
1) Mixing commercial microcrystalline cellulose, a catalyst and mixed acid, reacting for 1-2 hours at 60-95 ℃, adding a weak alkaline solution to the mixture until the pH value is 7, and centrifuging and washing the mixture to obtain a suspension, wherein the weight and volume ratio of the commercial microcrystalline cellulose, the catalyst and the mixed acid is 1g:0.001-0.05g:50-100ml;
2) Freeze-drying the suspension liquid obtained in the step 1), adding an ethanol solvent, performing ultrasonic extraction for 20-40min by 200-300W, and performing Soxhlet extraction for 3-6h to obtain nanocellulose, wherein the weight volume ratio of the commercial microcrystalline cellulose to the ethanol is 1g:100-150ml.
2. The method for preparing nanocellulose as claimed in claim 1 wherein: the mixed acid is prepared by mixing hydrochloric acid, formic acid and citric acid, the concentrations of the three are respectively and independently 3-6M, and the volume ratio is V (hydrochloric acid) :V (formic acid) :V (citric acid) ＝(0-1):(1.5-7.5):(1-7.5)。
3. The method for preparing nanocellulose as claimed in claim 2 wherein: the concentration of the hydrochloric acid, the formic acid and the citric acid is 3M, and the volume ratio is V (hydrochloric acid) :V (formic acid) :V (citric acid) ＝1:2:7。
4. The method for preparing nanocellulose as claimed in claim 1 wherein: the weak alkaline solution is selected from any one of ammonia water with the concentration of 1-2% and sodium bicarbonate solution with the concentration of 0.5-1%.
5. The method for preparing nanocellulose as claimed in claim 1 wherein: the catalyst is sodium dodecyl sulfate or sodium dodecyl benzene sulfonate or polyoxyethylene octanol.
6. The method for preparing nanocellulose as claimed in claim 1 wherein the method steps are:
1) Mixing commercial microcrystalline cellulose, sodium dodecyl sulfate and mixed acid, reacting at 80deg.C for 1 hr, and adding 0.5% bicarbonateAnd (3) centrifuging and washing the sodium solution to obtain a suspension with the pH of 7, wherein the weight-volume ratio of the commercial microcrystalline cellulose to the sodium dodecyl sulfate to the mixed acid is 1g:0.001g:100ml, the mixed acid is mixed by hydrochloric acid, formic acid and citric acid, the concentrations of the three are respectively 3M, and the volume ratio is V (hydrochloric acid) :V (formic acid) :V (citric acid) ＝1:2:7；
2) Freeze-drying the suspension liquid obtained in the step 1), adding an ethanol solvent, performing ultrasonic extraction for 20min by 300W, and performing Soxhlet extraction for 3h to obtain nano-cellulose, wherein the weight-volume ratio of the microcrystalline cellulose to the ethanol is 1g:100ml.
7. A method for preparing a polyethylene sheet, comprising the steps of:
1) Filling a die: the nano cellulose and polyethylene powder according to the mass ratio of 1: uniformly mixing 50-100, and spreading in a mould;
2) Hot pressing and melting: setting the temperature of the upper template to 140-150 ℃, reducing the molding pressure to 1-10MPa so as to improve the curing uniformity of the molding material, setting the temperature of the lower template to 230-240 ℃, placing the mold on the lower template which has reached the set temperature, and moving the upper template downwards to apply the pressure to the mold to 1-50MPa;
3) Cooling and solidifying: and taking out the die, placing the die on a plate vulcanizing machine for cold press shaping, cooling to room temperature, and taking out the die to obtain the polyethylene plate containing the nanocellulose.
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