阅读说明：本技术 一种两性纳米纤维素的制备方法、应用 (Preparation method and application of amphoteric nanocellulose ) 是由 罗屹东 余镇城 王国忠 李玉柱 于 2021-08-18 设计创作，主要内容包括：本发明提供了一种两性纳米纤维素的制备方法,通过季铵化改性和羧基化改性制备得到的两性纳米纤维素,具有显著的取代度；本发明的两性纳米纤维素在改性完毕后就能达到纳米级别,无需再通过超声波粉碎、超高速打碎等处理,有助于简化生产工艺,进而降低生产耗能,降低生产成本；本发明的两性纳米纤维素的高亲水性、具有阴离子基团羧酸根和阳离子基团三甲基季铵盐的特征,使其能够吸附具有正电荷和负电荷的有机物大分子,因此可以应用于有机废水的处理中；本发明两性纳米纤维素的制备工艺整体条件温和、操作简便,有利于批量生产。(The invention provides a preparation method of amphoteric nanocellulose, which is characterized in that the amphoteric nanocellulose prepared by quaternization modification and carboxylation modification has obvious substitution degree; the amphoteric nanocellulose can reach the nano level after being modified, and does not need to be subjected to ultrasonic crushing, ultrahigh-speed crushing and other treatments, so that the production process is facilitated to be simplified, the production energy consumption is reduced, and the production cost is reduced; the amphoteric nano-cellulose has the characteristics of high hydrophilicity, anion group carboxylate radical and cation group trimethyl quaternary ammonium salt, so that the amphoteric nano-cellulose can adsorb organic macromolecules with positive charges and negative charges, and can be applied to the treatment of organic wastewater; the preparation process of the amphoteric nano-cellulose has mild overall conditions and simple and convenient operation, and is beneficial to batch production.)

1. The preparation method of the amphoteric nanocellulose is characterized by comprising the following steps:

shearing and crushing cellulose, drying and freezing for later use;

adding NaOH and urea into water, uniformly stirring to obtain a first reaction solvent system, and then placing the first reaction solvent system at the temperature of-18 ℃ for later use;

adding the frozen cellulose into the first reaction solvent system, and stirring until the cellulose is completely dissolved to obtain a mixed solution;

dripping a cationic etherifying agent into the mixed solution, stirring and reacting, and filtering to obtain quaternized cellulose;

mixing TEMPO, NaBr and NaClO to obtain a second reaction solvent system, then adding the quaternized cellulose into the second reaction solvent system, uniformly stirring, adjusting the pH to 9.8-10.2, reacting for 6-10 h, continuously adjusting the pH to 7, repeatedly cleaning with deionized water, performing suction filtration treatment, and drying to obtain the amphoteric nanocellulose.

2. The method for preparing amphoteric nanocellulose according to claim 1, wherein the cellulose is one or both of pulp cellulose and cotton cellulose.

3. The method according to claim 1, wherein the temperature of the freezing treatment is from-20 ℃ to-10 ℃.

4. The method according to claim 1, wherein the first reaction solvent system comprises NaOH, urea and water at a mass ratio of 7:12: 81.

5. The method of claim 1, wherein the absolute dry cellulose is 2 wt% of the first reaction solvent system.

6. The method for producing amphoteric nanocellulose according to claim 1, wherein a sieve having a 200-mesh sieve is used for the filtration treatment.

7. The method according to claim 1, wherein the mass ratio of TEMPO, NaBr and NaClO in the second reaction solvent system is 0.64:6: 223-246.

8. The method according to claim 1, wherein the ratio of the cellulose to the cationic etherifying agent is 1:7 to 25 by mass.

9. The method according to claim 8, wherein the mass ratio of the quaternized cellulose to the second reaction solvent system is 1:100 to 1: 150.

10. Use of the amphoteric nanocellulose according to any one of claims 1 to 9, characterized in that it is used in the adsorption of impurities from organic waste water or in the preparation of paints or in the preparation of household chemical products.

Technical Field

The invention relates to the field of preparation of functional materials, in particular to a preparation method and application of amphoteric nanocellulose.

Background

Nanocellulose is a renewable nanomaterial of natural polymers. Unmodified nanocellulose is suitable for adsorption of cationic molecules since it exposes a large number of surface hydroxyl groups and, possibly depending on the preparation process, other negatively charged groups, such as sulphate or carboxylate groups. The high specific surface area nanocellulose aerogel prepared by oxidation of 2,2,6, 6-tetramethylpyridin-1-oxyl in the prior art has been shown to adsorb and remove the cationic dye malachite green, and chemical modification, such as introduction of positively charged amino groups, is usually required in order to produce nanocellulose adsorbents for anionic dyes. However, nanocellulose having only positive/negative charge groups is difficult to apply to practical organic wastewater treatment applications. Zheng G Z et al (Journal of Polymer Science Part B Polymer Physics,1995,33(6): 867-. Zhangming et al (applied chemistry, 1998, 015 (004): 5-8.) require the use of isopropanol as the reaction medium and the addition of a cationic etherifying agent under nitrogen conditions for quaternization substitution. According to the two preparation schemes reported above, the substitution degree of quaternization in the prepared amphoteric cellulose is low, the size of the amphoteric cellulose cannot reach the nanometer level after the reaction is finished, nitrogen needs to be introduced for protection and dialysis treatment in the preparation process, the reaction is complicated, and water resources are wasted. However, the amphoteric nanocellulose with the size reaching the nanometer level and high hydrophilicity and surface activity and carrying anion and cation groups are directly obtained after modification treatment, and related technical schemes are not reported.

In summary, the above problems still remain to be solved in the field of preparing amphoteric nanocellulose.

Disclosure of Invention

Based on the above, in order to solve the problems of low substitution degree, low yield and unsuitability for application in organic wastewater in the prior art for preparing cellulose, the invention provides a preparation method of amphoteric nanocellulose, and the specific technical scheme is as follows:

a preparation method of amphoteric nanocellulose comprises the following steps:

shearing and crushing cellulose, drying and freezing for later use;

adding NaOH and urea into water, uniformly stirring to obtain a first reaction solvent system, and then placing the first reaction solvent system at the temperature of-18 ℃ for later use;

adding the frozen cellulose into the first reaction solvent system, and stirring until the cellulose is completely dissolved to obtain a mixed solution;

dripping a cationic etherifying agent into the mixed solution, stirring and reacting, and filtering to obtain quaternized cellulose;

mixing TEMPO, NaBr and NaClO to obtain a second reaction solvent system, then adding the quaternized cellulose into the second reaction solvent system, uniformly stirring, adjusting the pH to 9.8-10.2, reacting for 6-10 h, continuously adjusting the pH to 7, repeatedly cleaning with deionized water, performing suction filtration treatment, and drying to obtain the amphoteric nanocellulose.

Preferably, the cellulose is one or two of pulp cellulose and cotton cellulose.

Preferably, the temperature of the freezing treatment is-20 ℃ to-10 ℃.

Preferably, in the first reaction solvent system, the mass ratio of NaOH to urea to water is 7:12: 81.

Preferably, the absolute cellulose comprises 2 wt% of the first reaction solvent system.

Preferably, a 200 mesh sieve is used in the filtration treatment.

Preferably, in the second reaction solvent system, the mass ratio of TEMPO, NaBr and NaClO is 0.64:6: 223-246.

Preferably, the ratio of the cellulose to the cationic etherifying agent is 1: 7-25 by mass.

Preferably, the mass ratio of the quaternized cellulose to the second reaction solvent system is 1:100 to 1: 150.

In addition, the amphoteric nano-cellulose is applied to impurity adsorption of organic wastewater or a preparation process of a coating or a preparation process of a daily chemical product.

The amphoteric nanocellulose prepared by quaternization modification and carboxylation modification in the scheme has obvious substitution degree; the amphoteric nanocellulose can reach the nano level after being modified, and does not need to be subjected to ultrasonic crushing, ultrahigh-speed crushing and other treatments, so that the production process is facilitated to be simplified, the production energy consumption is reduced, and the production cost is reduced; the amphoteric nano-cellulose has the characteristics of high hydrophilicity, anion group carboxylate radical and cation group trimethyl quaternary ammonium salt, so that the amphoteric nano-cellulose can adsorb organic macromolecules with positive charges and negative charges, and can be applied to the treatment of organic wastewater; the preparation process of the amphoteric nano-cellulose has the advantages of mild overall conditions, simple and convenient operation, high yield and contribution to batch production.

Drawings

FIG. 1 is a graphical representation of the infrared spectra of quaternized-carboxylated cellulose, carboxylated-quaternized cellulose, and unmodified pulp cellulose;

FIG. 2 is a schematic representation of an embodiment of the amphoteric nanocellulose prepared in example 1;

FIG. 3 is a schematic representation of an embodiment of the amphoteric cellulose prepared in comparative example 1;

FIG. 4 is a schematic representation of the infrared spectra of quaternized-carboxylated cellulose, quaternized cellulose, unmodified pulp cellulose;

fig. 5 is a graph of the static saturation adsorption capacity of the amphoteric nanocellulose aerogel prepared in example 1 to congo red and methylene blue dye solutions.

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 amphoteric nanocellulose in one embodiment of the invention comprises the following steps:

shearing and crushing cellulose, drying and freezing for later use;

adding NaOH and urea into water, uniformly stirring to obtain a first reaction solvent system, and then placing the first reaction solvent system at the temperature of-18 ℃ for later use;

adding the frozen cellulose into the first reaction solvent system, and stirring until the cellulose is completely dissolved to obtain a mixed solution;

dripping a cationic etherifying agent into the mixed solution, stirring and reacting, and filtering to obtain quaternized cellulose;

mixing TEMPO, NaBr and NaClO to obtain a second reaction solvent system, then adding the quaternized cellulose into the second reaction solvent system, uniformly stirring, adjusting the pH to 9.8-10.2, reacting for 6-10 h, continuously adjusting the pH to 7, repeatedly cleaning with deionized water, performing suction filtration treatment, and drying to obtain the amphoteric nanocellulose.

In one embodiment, the cellulose is one or both of pulp cellulose and cotton cellulose.

In one embodiment, the time of the shear breaking process is 30-60 s.

In one embodiment, the temperature of the freezing treatment is-20 ℃ to-10 ℃.

In one embodiment, the mass ratio of NaOH, urea, and water in the first reaction solvent system is 7:12: 81.

In one embodiment, the absolutely dry cellulose comprises 2 wt% of the first reaction solvent system.

In one embodiment, the mixing speed is 1500r/min-2000r/min when preparing the mixed solution.

In one embodiment, the cationic etherifying agent is 3-chloro-2-hydroxypropyl-trimethylammonium chloride, hereinafter CHPTMAC.

In one embodiment, the reaction time is 8h to 16h while stirring to prepare the quaternized cellulose.

In one embodiment, a 200 mesh screen is used in the filtration process.

In one embodiment, in the second reaction solvent system, the mass ratio of TEMPO, NaBr and NaClO is 0.64:6: 223-246.

In one embodiment, the ratio of the cellulose to the cationic etherifying agent is 1: 7-25 by mass.

In one embodiment, the mass ratio of the quaternized cellulose to the second reaction solvent system is 1:100 to 1: 150.

In one embodiment, the amphoteric nanocellulose is applied to impurity adsorption of organic wastewater.

In one embodiment, the amphoteric nanocellulose is applied to a preparation process of a coating.

In one embodiment, the amphoteric nanocellulose is applied to a preparation process of a daily chemical product.

The amphoteric nanocellulose prepared by quaternization modification and carboxylation modification in the scheme has obvious amphoteric substitution degree; the amphoteric nanocellulose can reach the nano level after being modified, and does not need to be subjected to ultrasonic crushing, ultrahigh-speed crushing and other treatments, so that the production process is facilitated to be simplified, the production energy consumption is reduced, and the production cost is reduced; the amphoteric nano-cellulose has the characteristics of high hydrophilicity, anion group carboxylate radical and cation group trimethyl quaternary ammonium salt, so that the amphoteric nano-cellulose can adsorb organic macromolecules with positive charges and negative charges, and can be applied to the treatment of organic wastewater; the preparation process of the amphoteric nano-cellulose has the advantages of mild overall conditions, simple and convenient operation, high yield and contribution to batch production.

Embodiments of the present invention will be described in detail below with reference to specific examples.

Example 1:

putting 10g of paper pulp cellulose into a powder grinding machine for shearing and crushing for 60s, drying to obtain the absolute dry cellulose, and then putting the absolute dry cellulose at the temperature of-14 ℃ for freezing for later use;

according to the mass ratio of 7%: 12%: 81% NaOH: urea: mixing water, stirring uniformly to obtain 500mL of a first reaction solvent system, and then placing the first reaction solvent system at the temperature of-18 ℃ for later use;

adding the absolute dry cellulose accounting for 2 wt% of the first reaction solvent system into the first reaction solvent system, and stirring under the stirring condition of 1500r/min until the absolute dry cellulose is completely dissolved to obtain a mixed solution;

dripping 151.3g of CHPTMAC into the mixed solution, stirring and reacting for 8h under the stirring condition of 1500r/min, and filtering the reaction solution by using a 200-mesh filter screen to obtain quaternized pulp cellulose;

mixing TEMPO, NaBr and NaClO in a mass ratio of 0.64:6:223 to obtain a second reaction solvent system, and then mixing the TEMPO, NaBr and NaClO according to a mass ratio of 1: and 100, adding the quaternized cellulose into the second reaction solvent system, uniformly stirring, adjusting the pH to 9.8-10.2, reacting for 6 hours, neutralizing the reaction solution with 10% hydrochloric acid to adjust the pH to 7, repeatedly washing with deionized water, performing suction filtration treatment, and drying to obtain the amphoteric nanocellulose.

Example 2:

putting 10g of cotton cellulose into a powder grinding machine, shearing and crushing for 30s, drying to obtain absolutely dry cotton cellulose, and then putting the absolutely dry cotton cellulose at the temperature of-20 ℃ for freezing treatment for later use;

according to the mass ratio of 7%: 12%: 81% NaOH: urea: mixing water, stirring uniformly to obtain 500mL of a first reaction solvent system, and then placing the first reaction solvent system at the temperature of-18 ℃ for later use;

adding the oven-dried cotton cellulose accounting for 2 wt% of the first reaction solvent system into the first reaction solvent system, and stirring under the stirring condition of 2000r/min until the oven-dried cotton cellulose is completely dissolved to obtain a mixed solution;

dropping 117.6g of CHPTMAC into the mixed solution, stirring and reacting for 16h under the stirring condition of 2000r/min, and filtering the reaction solution by using a 200-mesh filter screen to obtain quaternized cotton cellulose;

mixing TEMPO, NaBr and NaClO in a mass ratio of 0.64:6:223 to obtain a second reaction solvent system, and then mixing the TEMPO, the NaBr and the NaClO according to a mass ratio of 1:150, adding the quaternized cotton cellulose into the second reaction solvent system, uniformly stirring, adjusting the pH value to 9.8-10.2, reacting for 6 hours, neutralizing the reaction solution with 10% hydrochloric acid to adjust the pH value to 7, repeatedly washing with deionized water, performing suction filtration treatment, and drying to obtain the amphoteric nano cellulose.

Example 3:

putting 10g of pulp cellulose into a powder grinding machine, shearing and crushing for 45s, drying to obtain oven-dried pulp cellulose, and then putting the oven-dried pulp cellulose at the temperature of-15 ℃ for freezing for later use;

according to the mass ratio of 7%: 12%: 81% NaOH: urea: mixing water, stirring uniformly to obtain 500mL of a first reaction solvent system, and then placing the first reaction solvent system at the temperature of-18 ℃ for later use;

adding the oven-dried pulp cellulose accounting for 2 wt% of the first reaction solvent system into the first reaction solvent system, and stirring under the stirring condition of 1750r/min until the oven-dried pulp cellulose is completely dissolved to obtain a mixed solution;

201.7g of CHPTMAC is dropped into the mixed solution, the mixture is stirred and reacted for 12 hours under the stirring condition of 1750r/min, and a 200-mesh filter screen is used for filtering the reaction solution to obtain quaternized pulp cellulose;

mixing TEMPO, NaBr and NaClO in a mass ratio of 0.64:6:223 to obtain a second reaction solvent system, and then mixing the TEMPO, NaBr and NaClO according to a mass ratio of 1: 125 adding the quaternized pulp cellulose into the second reaction solvent system, uniformly stirring, adjusting the pH value to 9.8-10.2, reacting for 6 hours, neutralizing the reaction solution with 10% hydrochloric acid to adjust the pH value to 7, repeatedly washing with deionized water, performing suction filtration treatment, and drying to obtain the amphoteric nano cellulose.

Comparative example 1:

6g of carboxylated pulp cellulose is added into 100mL of reaction medium containing 29.63mM CHPTMAC, 64.75mM NaOH and isopropanol, and stirred and dispersed at the stirring speed of 1500r/min to obtain a mixture; adding the mixture into polyethylene bag, heating to 60 deg.C, activating for 30min, taking out every 10min, and kneading; adding CHPTMAC, reacting at 60 deg.C for 120min, taking out every 20min, and kneading uniformly; after the reaction is finished, washing the cellulose by using 20 mass percent ethanol for 2 times, washing the cellulose by using deionized water for 3 times, and then carrying out suction filtration and drying to obtain a product, namely the carboxylated-quaternized cellulose.

Fig. 1 is a graphical representation of the infrared spectra of quaternized-carboxylated cellulose, carboxylated-quaternized cellulose, and unmodified pulp cellulose, and the amphoteric nanocellulose prepared according to the present invention is quaternized-carboxylated cellulose, as compared to the carboxylated-quaternized cellulose and unmodified pulp cellulose prepared according to comparative example 1, showing that: 1475cm of quaternized-carboxylated cellulose^-1Cationic trimethyl quaternary ammonium salt (-N)⁺(CH₃)₃Cl^-) The characteristic peak is more remarkable than that of carboxylated-quaternized cellulose, and can pass 1712cm of C ═ O stretching vibration representing COOH^-1Peak position, it is clear that the carboxyl group of the quaternized-carboxylated cellulose. And with reference to the schematic infrared spectrum of fig. 4, fig. 4 is a schematic infrared spectrum of quaternized-carboxylated cellulose, quaternized cellulose, unmodified pulp cellulose, showing that: for unmodified pulp cellulose, at 3343, 2900cm^-1The absorption peaks at the positions are O-H stretching vibration and C-H stretching vibration respectively. At 1430 and 1031cm^-1Has an absorption peak of C₆Shear vibration of OH and CH on₂C-H bending deformation vibration of (2). 1640cm^-1It is likely that the C ═ O stretching vibration absorption peak of a small amount of hemicellulose in pulp cellulose. For quaternized cellulose, 1475cm^-1And 962cm^-1Is trimethyl quaternary ammonium salt (-N)⁺(CH₃)₃Cl^-) Characteristic peak. Para quaternized carboxylated cellulose, 1712cm^-1C ═ O stretching vibration for COOH, 1731cm^-1C ═ O stretching vibration for CHO. 1604cm^-1Stretching vibration of C ═ O after TEMPO oxidation. 1475cm^-1And 962cm^-1Is trimethyl quaternary ammonium salt (-N)⁺(CH₃)₃Cl^-) Characteristic peaks, indicating that the quaternized-carboxylated cellulose prepared herein has both cationic and anionic groups with a significant degree of amphoteric substitution.

Fig. 2 is a schematic diagram of an embodiment of the amphoteric nanocellulose (quaternized-carboxylated cellulose) prepared in example 1, and it can be seen that the appearance is gel-like and has more excellent hydrophilic characteristics.

Fig. 3 is a schematic representation of an embodiment of the amphoteric cellulose (carboxylated-quaternized cellulose) prepared in comparative example 1, which has substantially the same morphology as unmodified pulp cellulose, and has poor hydrophilic properties, and is significantly different from the amphoteric nanocellulose prepared in the present application.

Fig. 5 is a graph of the static saturation adsorption capacity of the amphoteric nanocellulose (quaternized-carboxylated cellulose) aerogel prepared in example 1 on congo red and methylene blue dyebaths. The conditions of the adsorption experiment were: the adsorption ambient temperature is 25 ℃, the pH value of the adsorbed dye is an initial value, the initial concentration is 250mg/L, and the adsorption time is 16 h. As can be seen from the figure, the static saturated adsorption capacity of the quaternized-carboxylated cellulose to the anionic dye Congo red and the cationic dye methylene blue reaches 148.8mg/g162.4mg/g respectively, which shows that the amphoteric nanocellulose prepared by the invention has excellent adsorption capacity of the anionic dye and the cationic dye. In addition, the amphoteric nano-cellulose prepared by the method has a large number of cationic groups and anionic groups, and can be widely applied to adsorption and removal of organic macromolecules, so that excellent adsorption effect can be embodied when the amphoteric nano-cellulose is applied to organic wastewater. In other experiments, the amphoteric nanocelluloses prepared in examples 2-3 also have the same effects as those of the amphoteric nanocellulose prepared in example 1, and therefore, the details are not repeated.

In other application examples, the amphoteric nanocellulose prepared by the invention can be loaded with TiO in the coating through a three-dimensional network structure₂While improving TiO by virtue of its amphoteric polyelectrolyte properties₂Dispersion of (2). Meanwhile, the coating is endowed with good water retention and rheological property, and the obtained coating is more environment-friendly and green. The nano three-dimensional network structure can be used for loading small molecular components in daily chemical articles; meanwhile, the thickener can be used as a thickening agent to improve the viscosity of daily chemical products.

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 more specific and detailed, but not construed 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.