CN115477777A - Preparation method of cellulose nanocrystal film - Google Patents

Abstract

The invention discloses a preparation method of a cellulose nanocrystal film, and the specific steps are as follows: S1, acid hydrolyzes the pretreated cotton wool to obtain a cellulose nanocrystal suspension; S2, prepares the cellulose nanocrystal suspension with deionized water into a cellulose nanocrystal solution, ultrasonically treated, washed and concentrated in sequence to obtain a chiral nematic cellulose nanocrystal suspension with a mass concentration of 2-6%; S3, the chiral nematic cellulose nanocrystal The suspension is evaporated and self-assembled into a film to obtain a cellulose nanocrystal film. The invention obtains cellulose nanocrystals with uniform size and narrow distribution by adopting sulfuric acid hydrolysis and high-pressure homogenization, which solves the problem that conventional cellulose nanocrystals are not uniform in size and difficult to form a chiral nematic structure.

Description

A kind of preparation method of cellulose nano crystal film

technical field

The invention relates to the technical field of cellulose film preparation, in particular to a preparation method of a cellulose nanocrystal film.

Background technique

Cellulose is the most widely and abundantly known sugar substance in nature, accounting for about 50% of the total carbon content in the plant kingdom. Cellulose has the advantages of excellent mechanical properties, good biocompatibility, easy availability and low cost. The effective utilization of cellulose, especially the preparation of regenerated cellulose materials with multiple functions based on its unique properties at the microscopic scale, has broad application prospects.

Nanocellulose has a wide range of applications, including papermaking, additives, food industry and even medicine. Functional materials synthesized from nanocellulose have shown great promise in many potential applications, such as sensors, catalyst supports, nanofiltration, tissue engineering, electronics, solar cells, etc. The research and utilization of nanocellulose has become the mainstream direction today.

Nanocellulose itself is a tiny nano-scale material. When it is processed and modified, it will fully exert its light transmission.

How to obtain a method for preparing a cellulose nanocrystal film with a simple preparation method, short time consumption and low cost is an urgent problem to be solved by those skilled in the art.

Contents of the invention

In view of this, the invention provides a method for preparing a cellulose nanocrystal film.

In order to achieve the above object, the technical scheme adopted in the present invention is as follows:

A kind of preparation method of cellulose nano crystal thin film, concrete steps are as follows:

S1, acid hydrolysis pretreatment of cotton linters to obtain cellulose nanocrystal suspension;

S2, preparing the cellulose nanocrystal suspension and deionized water into a cellulose nanocrystal solution, performing ultrasonic treatment, washing and concentrating in sequence, to obtain a chiral nematic cellulose nanocrystal suspension with a mass concentration of 2-6%;

S3, the chiral nematic cellulose nanocrystal suspension is evaporated and self-assembled into a film by an evaporation film forming method to obtain a cellulose nanocrystal film.

Preferably, the acid hydrolysis pretreatment in the step S1 includes the following steps:

1) Grinding cotton wool to obtain particle I, soaking particle I in NaOH solution, washing with distilled water to obtain particle II;

2) Put the particle II into concentrated sulfuric acid, heat and stir for hydrolysis, the hydrolysis is complete, add distilled water to dilute, centrifuge, remove the residual acid until neutral, and obtain a suspension;

3) The suspension is treated by a micro-jet high-pressure homogenization method, and the size of the suspension is homogenized.

Preferably, the concentration of the NaOH solution in the step 1) is 3wt%, and the soaking time is 8-10h.

Preferably, the concentration of concentrated sulfuric acid in step 2) is 60-65wt.%, the temperature is controlled to be 50-60° C., and the stirring speed is 200-300 r/min during the heating and stirring hydrolysis process.

Preferably, the centrifugation speed in step 2) is 10000-12000r/min, and the centrifugation time is 8-10min.

Preferably, when the micro-jet high-pressure homogenization method is used in the step 3), the pressure is 1000-8000 MPa, and the number of times is 6-12.

Preferably, the mass ratio of cellulose nanocrystals and deionized water prepared into the cellulose nanocrystal solution in the step S2 is 1:30-250.

Preferably, the ultrasonic power of the ultrasonic treatment in the step S2 is 500-1500W, and the ultrasonic time is 10-20min.

Preferably, the humidity of the evaporation film forming method in the step S3 is 75%, and the evaporation time is 5-8 days.

The beneficial effects of the present invention are as follows:

The present invention obtains cellulose nanocrystals with uniform size and narrow distribution by using sulfuric acid hydrolysis and high-pressure homogenization, which solves the problem of non-uniform size of conventional cellulose nanocrystals and difficulty in forming a chiral nematic structure. Proportioning the nanocrystal suspension to obtain a cellulose nanocrystal solution and then performing ultrasonic treatment can control and change the fluidity of the cellulose nanocrystal to achieve full dispersion. The technological process of the invention is simple and the processing time is short. Using cotton linters as raw materials, combined with cellulose nanocrystals can improve mechanical properties.

detailed description

The following clearly and completely describes the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, but not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

Example 1

Embodiment 1 of the present invention discloses a preparation method of a cellulose nanocrystal film, and the specific steps are as follows:

S1, acid hydrolysis pretreatment of cotton linters to obtain cellulose nanocrystal suspension;

S2, the cellulose nanocrystal suspension and deionized water are prepared into a cellulose nanocrystal solution, and ultrasonic treatment is carried out, the ultrasonic power is 500W, and the ultrasonic wave is 20min, followed by washing and concentration to obtain chiral nematic cellulose with a mass concentration of 2%. Nanocrystal suspension, wherein, the mass ratio of the cellulose nanocrystals and deionized water prepared into the cellulose nanocrystal solution is 1:30;

S3, the chiral nematic cellulose nanocrystal suspension was evaporated and self-assembled into a film by evaporation film formation method, the humidity of the evaporation film formation method was 75%, and the evaporation time was 5 days to obtain a cellulose nanocrystal film.

Wherein, the acid hydrolysis pretreatment in the step S1 includes the following steps:

1) Grinding cotton wool to obtain granule I, soaking granule I in a NaOH solution with a concentration of 3 wt%, soaking for 8 hours, washing with distilled water to obtain granule II;

2) Put the particle II into concentrated sulfuric acid with a concentration of 60wt.%, heat and stir for hydrolysis, control the temperature to 50°C, and stir at a speed of 200r/min. When the hydrolysis is complete, add distilled water to dilute and centrifuge at a speed of 10000r/min. Centrifuge for 10 minutes to remove residual acid until neutral to obtain a suspension;

3) The suspension is treated by the micro-jet high-pressure homogenization method, the pressure is 1000 MPa, and the frequency is 12 times, and the size of the suspension is homogenized.

Example 2

Embodiment 2 of the present invention discloses a preparation method of a cellulose nanocrystal film, and the specific steps are as follows:

S1, acid hydrolysis pretreatment of cotton linters to obtain cellulose nanocrystal suspension;

S2, the cellulose nanocrystal suspension and deionized water are prepared into a cellulose nanocrystal solution, and ultrasonic treatment is performed, the ultrasonic power is 1500W, and the ultrasonic wave is 10min, followed by washing and concentration to obtain chiral nematic cellulose with a mass concentration of 6%. Nanocrystal suspension, wherein, the mass ratio of the cellulose nanocrystals and the deionized water prepared into the cellulose nanocrystal solution is 1:250;

S3, the chiral nematic cellulose nanocrystal suspension was evaporated and self-assembled into a film by evaporation film formation method, the humidity of the evaporation film formation method was 75%, and the evaporation time was 8 days to obtain a cellulose nanocrystal film.

Wherein, the acid hydrolysis pretreatment in the step S1 includes the following steps:

1) Grinding cotton wool to obtain granule I, soaking granule I in a NaOH solution with a concentration of 3 wt%, soaking for 10 h, washing with distilled water to obtain granule II;

2) Put the particle II into concentrated sulfuric acid with a concentration of 65wt.%, heat and stir for hydrolysis, control the temperature at 60°C, and stir at a speed of 300r/min. When the hydrolysis is complete, dilute with distilled water and centrifuge at a speed of 12000r/min. Centrifuge for 8 minutes to remove residual acid until neutral to obtain a suspension;

3) The suspension is treated by the micro-jet high-pressure homogenization method, the pressure is 8000 MPa, and the number of times is 6 times, and the size of the suspension is homogenized.

Example 3

Embodiment 3 of the present invention discloses a preparation method of a cellulose nanocrystal film, and the specific steps are as follows:

S1, acid hydrolysis pretreatment of cotton linters to obtain cellulose nanocrystal suspension;

S2, the cellulose nanocrystal suspension and deionized water are prepared into a cellulose nanocrystal solution, and ultrasonic treatment is carried out, the ultrasonic power is 1000W, and the ultrasonic wave is 15min, followed by washing and concentration to obtain chiral nematic cellulose with a mass concentration of 4%. Nanocrystal suspension, wherein the mass ratio of cellulose nanocrystals and deionized water prepared into the cellulose nanocrystal solution is 1:100;

S3, the chiral nematic cellulose nanocrystal suspension was evaporated and self-assembled into a film by evaporation film formation method, the humidity of the evaporation film formation method was 75%, and the evaporation time was 6 days to obtain a cellulose nanocrystal film.

Wherein, the acid hydrolysis pretreatment in the step S1 includes the following steps:

1) Grinding cotton wool to obtain granule I, soaking granule I in a NaOH solution with a concentration of 3 wt%, soaking for 9 hours, washing with distilled water to obtain granule II;

2) Put the particle II into concentrated sulfuric acid with a concentration of 62wt.%, heat and stir for hydrolysis, control the temperature at 55°C, and stir at a speed of 250r/min. When the hydrolysis is complete, dilute with distilled water and centrifuge at a speed of 11000r/min. Centrifuge for 9 minutes to remove residual acid until neutral to obtain a suspension;

3) The suspension is treated by the micro-jet high-pressure homogenization method, the pressure is 5000 MPa, and the number of times is 9 times, and the size of the suspension is homogenized.

Example 4

Embodiment 4 of the present invention discloses a preparation method of a cellulose nanocrystal film, and the specific steps are as follows:

S1, acid hydrolysis pretreatment of cotton linters to obtain cellulose nanocrystal suspension;

S2, the cellulose nanocrystal suspension and deionized water are prepared into a cellulose nanocrystal solution, and the ultrasonic treatment is performed at an ultrasonic power of 750W for 18 minutes, followed by washing and concentration to obtain chiral nematic cellulose with a mass concentration of 3%. Nanocrystal suspension, wherein, the mass ratio of the cellulose nanocrystals and deionized water prepared into the cellulose nanocrystal solution is 1:200;

S3, the chiral nematic cellulose nanocrystal suspension was evaporated and self-assembled into a film by evaporation film formation method, the humidity of the evaporation film formation method was 75%, and the evaporation time was 7 days to obtain a cellulose nanocrystal film.

Wherein, the acid hydrolysis pretreatment in the step S1 includes the following steps:

1) Grinding cotton wool to obtain granule I, soaking granule I in a NaOH solution with a concentration of 3 wt%, soaking for 8 hours, washing with distilled water to obtain granule II;

2) Put the particle II into concentrated sulfuric acid with a concentration of 63wt.%, heat and stir for hydrolysis, control the temperature at 52°C, and stir at a speed of 230r/min. When the hydrolysis is complete, dilute with distilled water and centrifuge at a speed of 10000r/min. Centrifuge for 10 minutes to remove residual acid until neutral to obtain a suspension;

3) The suspension is treated by the micro-jet high-pressure homogenization method, the pressure is 3000 MPa, and the number of times is 10 times, and the size of the suspension is homogenized.

Example 5

Embodiment 5 of the present invention discloses a preparation method of a cellulose nanocrystal film, and the specific steps are as follows:

S1, acid hydrolysis pretreatment of cotton linters to obtain cellulose nanocrystal suspension;

S2, the cellulose nanocrystal suspension and deionized water are prepared into a cellulose nanocrystal solution, and ultrasonic treatment is performed, the ultrasonic power is 1250W, and the ultrasonic wave is 12min, followed by washing and concentration to obtain chiral nematic cellulose with a mass concentration of 5%. Nanocrystal suspension, wherein, the mass ratio of the cellulose nanocrystals and deionized water prepared into the cellulose nanocrystal solution is 1:150;

S3, the chiral nematic cellulose nanocrystal suspension was evaporated and self-assembled into a film by evaporation film formation method, the humidity of the evaporation film formation method was 75%, and the evaporation time was 8 days to obtain a cellulose nanocrystal film.

Wherein, the acid hydrolysis pretreatment in the step S1 includes the following steps:

1) Grinding cotton wool to obtain granule I, soaking granule I in a NaOH solution with a concentration of 3 wt%, soaking for 9 hours, washing with distilled water to obtain granule II;

2) Put the particle II into concentrated sulfuric acid with a concentration of 64wt.%, heat and stir for hydrolysis, control the temperature at 57°C, and stir at a speed of 280r/min. After complete hydrolysis, add distilled water to dilute, and centrifuge at a speed of 12000r/min. Centrifuge for 8 minutes to remove residual acid until neutral to obtain a suspension;

3) The suspension is treated by the micro-jet high-pressure homogenization method, the pressure is 7000MPa, and the number of times is 8 times, and the size of the suspension is homogenized.

The above description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention will not be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (9)

1. A preparation method of a cellulose nanocrystal film is characterized by comprising the following specific steps:

s1, performing acid hydrolysis pretreatment on cotton linters to obtain a cellulose nanocrystal suspension;

s2, preparing a cellulose nanocrystal solution from the cellulose nanocrystal suspension and deionized water, carrying out ultrasonic treatment, and sequentially washing and concentrating to obtain a chiral nematic cellulose nanocrystal suspension with the mass concentration of 2-6%;

and S3, evaporating the chiral nematic cellulose nanocrystal suspension by adopting an evaporation film-forming method to form a film by self-assembly, so as to obtain the cellulose nanocrystal film.

2. The method for preparing a cellulose nanocrystal thin film according to claim 1, wherein the acid hydrolysis pretreatment in step S1 comprises the following steps:

1) Grinding cotton linters to obtain particles I, soaking the particles I in NaOH solution, and washing with distilled water to obtain particles II;

2) Putting the particles II into concentrated sulfuric acid, heating, stirring, hydrolyzing, adding distilled water for diluting, centrifuging, and removing residual acid until the particles are neutral to obtain a suspension;

3) And (3) processing the suspension by a micro-jet high-pressure homogenization method, and homogenizing the size of the suspension.

3. The method for preparing a cellulose nanocrystal film according to claim 2, wherein the concentration of the NaOH solution in step 1) is 3wt%, and the soaking time is 8-10h.

4. The method for preparing cellulose nanocrystal film according to claim 2, wherein the concentration of concentrated sulfuric acid in step 2) is 60-65wt.%, the temperature is controlled to be 50-60 ℃ during heating, stirring and hydrolyzing, and the stirring speed is 200-300r/min.

5. The method for preparing cellulose nanocrystal film according to claim 2, wherein the centrifugation speed in step 2) is 10000-12000r/min, and the centrifugation time is 8-10min.

6. The method for preparing cellulose nanocrystal film according to claim 2, wherein the pressure is 1000-8000MPa and the times is 6-12 times when the microfluid high pressure homogenization process is performed in step 3).

7. The method for preparing a cellulose nanocrystal film according to claim 1, wherein the mass ratio of the cellulose nanocrystals to the deionized water prepared into the cellulose nanocrystal solution in step S2 is 1:30-250.

8. The method for preparing a cellulose nanocrystal film according to claim 1, wherein the ultrasonic power of the ultrasonic treatment in step S2 is 500-1500W, and the ultrasonic time is 10-20min.

9. The method for preparing a cellulose nanocrystal thin film according to claim 1, wherein the humidity of the evaporation film forming method in the step S3 is 75%, and the evaporation time is 5 to 8 days.