CN111944178B

CN111944178B - Preparation method of nano holocellulose reinforced composite membrane and prepared composite membrane

Info

Publication number: CN111944178B
Application number: CN202010897415.9A
Authority: CN
Inventors: 关莹; 高慧; 吴玉乐; 吴汉
Original assignee: Anhui Agricultural University AHAU
Current assignee: Anhui Agricultural University AHAU
Priority date: 2020-08-31
Filing date: 2020-08-31
Publication date: 2021-11-30
Anticipated expiration: 2040-08-31
Also published as: CN111944178A

Abstract

The invention discloses a preparation method of a nano-hedocellulose reinforced composite membrane, which relates to the application field of biomass lignocellulose and is proposed based on the problems of poor mechanical properties and poor heat resistance of the existing composite membranes. The present invention includes the following steps: (1) preparing holocellulose; (2) preparing nano-holocellulose; (3) preparing composite film: preparing hemicellulose, chitosan and epichlorohydrin into a solution, and then The obtained nanohelocellulose is mixed according to a certain volume ratio, stirred for a period of time, and then air-dried to obtain a composite membrane. The present invention also provides a composite membrane prepared by the above-mentioned preparation method of the nanohedocellulose reinforced composite membrane. In the present invention, after fully mixing the nano-hemocellulose solution, the hemicellulose solution and the chitosan solution, the composite film is formed by the casting film forming method, and the prepared composite film has the characteristics of high strength, good heat resistance and the like. The tensile strength of the composite film is up to 34.93MPa.

Description

Preparation method of nano holocellulose reinforced composite membrane and prepared composite membrane

Technical Field

The invention relates to the application field of biomass lignocellulose, in particular to a preparation method of a nano holocellulose reinforced composite membrane and the prepared composite membrane.

Background

In recent years, renewable biomass resources replacing stone resources such as petroleum and the like have become the preferential development theme of various countries in the world, wherein lignocellulose resources such as agricultural straws, forest processing residues, cellulose-rich industrial processing wastes and natural plants are important raw materials for replacing petroleum. The nano material is always reproducible, has a high specific surface area, has higher catalytic activity and chemical reaction activity, is small in expansion degree, high in strength and hardness, light in weight, easy to modify surface hydroxyl and wide in application. The nano material can be generally used as a reinforcing agent, and is an effective way for improving the mechanical property and the service performance of the material.

The holocellulose is a polysaccharide compound except lignin and an extract in natural biomass, and mainly comprises cellulose and hemicellulose. The research and the utilization of cellulose are extremely wide, but the comprehensive utilization of the holocellulose is very little. The physical and chemical properties of the holocellulose are similar to those of cellulose, but the preparation process is simpler and more convenient than the cellulose. Therefore, the method for directly preparing the holocellulose into the nano material has important significance.

Patent CN104693464B discloses a preparation method of a lignin nanocellulose reinforced polylactic acid composite membrane, the raw materials include polylactic acid, lignin nanocellulose and N, N-dimethylacetamide, the lignin-containing nanocellulose is compounded with polylactic acid, and the polylactic acid is reinforced by nano materials. Patent CN108610517A discloses a method for preparing a nano-cellulose reinforced hemicellulose-based composite membrane, which comprises the steps of respectively dissolving and uniformly mixing hemicellulose, isolated soy protein and nano-cellulose according to a proportion, adding a plasticizer, fully and uniformly mixing, adding water to prepare a solution with the concentration of 2-6%, ultrasonically degassing, forming a membrane by adopting a tape casting method, placing the membrane in a constant temperature oven at 40-60 ℃ for 4-7 hours, drying and then uncovering the membrane to obtain the nano-cellulose reinforced hemicellulose-based composite membrane. Document "preparation and application of composite membrane with reinforced function of nano-cellulose" discloses a method for preparing composite membrane with reinforced function of nano-cellulose by mixing nano-cellulose and chitosan.

The problems with the above technique are as follows: the prepared composite film has poor mechanical property and heat resistance.

Disclosure of Invention

The invention aims to provide a preparation method of a nano holocellulose reinforced composite membrane with high strength and good heat resistance.

The invention adopts the following technical scheme to solve the technical problems:

the invention provides a preparation method of a nano holocellulose reinforced composite membrane, which comprises the following steps:

(1) crushing and sieving a wheat straw raw material to obtain wheat straw powder for later use;

(2) adding the wheat straw powder obtained in the step (1) into a benzene-alcohol mixed solution according to a bath ratio of w/v to 1:25, and heating and extracting in a constant-temperature water bath kettle at 80-90 ℃ to obtain an extract-free sample;

(3) adding the sample without the extract prepared in the step (2) and sodium chlorite into glacial acetic acid according to a bath ratio of w/w/v being 4:1.2:1, heating for 1-3h in a constant-temperature water bath kettle at 60-80 ℃, filtering the mixture after the reaction is finished, washing the mixture to be neutral by distilled water, and drying for 4-8h at 103-;

(4) ball-milling the holocellulose prepared in the step (3), swelling the ball-milled holocellulose with deionized water, adjusting the swollen holocellulose to a suspension with the concentration of 0.5-2.0% of the holocellulose solution, treating the obtained suspension with an ultramicron disc mill, and repeatedly disc-milling for multiple times at the disc mill rotation speed of 1000-3000r/min for 10-30min to prepare the nano holocellulose;

(5) mixing a hemicellulose solution and a chitosan solution according to a volume ratio of 50:50:1:5-50:50:6:5, stirring for 1-2h to fully mix, adding nano holocellulose and epoxy chloropropane into the mixed solution respectively, then stirring continuously, reacting for 1-3h at 60-80 ℃, casting the mixed solution into a film after the reaction is finished, and drying at room temperature to obtain the composite film sample.

According to the invention, the nano holocellulose solution, the hemicellulose solution and the chitosan solution are fully mixed, and then the casting film forming method is adopted to form the composite film, and the prepared composite film has the characteristics of high strength, good heat resistance and the like.

Preferably, the wheat straw in the step (1) is sieved by a 40-50 mesh sieve.

Preferably, the volume ratio of benzene to alcohol in the benzene-alcohol mixed solution in the step (2) is 2: 1.

Preferably, the extraction time in the step (2) is 6 to 8 hours.

Preferably, the distance between the sample and the grinding disc in the step (4) is-9-0 mm.

Preferably, the disc mill is repeated 5 to 10 times in the step (4).

Preferably, the concentration of the hemicellulose solution in the step (5) is 1-2%.

Preferably, the concentration of the chitosan solution in the step (5) is 1-2%.

Preferably, in the step (5), the hemicellulose solution, the chitosan solution and the nano holocellulose solution are mixed and then formed into a film by adopting a casting film forming method.

The invention also provides a composite membrane prepared by the preparation method of the nano holocellulose reinforced composite membrane.

The invention has the beneficial effects that:

(1) according to the invention, the nano holocellulose solution, the hemicellulose solution and the chitosan solution are fully mixed, and then the casting film forming method is adopted to form the composite film, and the prepared composite film has the characteristics of high strength, good heat resistance and the like.

(2) The method has the characteristics of low cost, simple process, easy industrial production investment, simple operation, high efficiency and little pollution, and can become a way for preparing novel functional materials by efficiently utilizing biomass raw materials.

Drawings

FIG. 1 is an AFM image of nano-sized holocellulose prepared in example 2 of the present invention;

FIG. 2 is an infrared spectrum of the raw material and composite film of examples 1 to 4 of the present invention and comparative example 1;

FIG. 3 is an X-ray diffraction pattern of the raw materials and composite films of examples 1-4 of the present invention and comparative example 1;

FIG. 4 is a result of light transmittance of the composite films of examples 1 to 4 of the present invention and comparative example 1;

FIG. 5 is a stress-strain diagram of composite films of examples 1-4 of the present invention and comparative example 1.

Detailed Description

The present invention will be described in further detail below.

Test materials, reagents and the like used in the following examples are commercially available unless otherwise specified.

The specific techniques or conditions not specified in the examples can be performed according to the techniques or conditions described in the literature in the field or according to the product specification.

Comparative example 1

Mixing 5mL of 2% hemicellulose solution and 5mL of 2% chitosan solution, stirring for 1h to fully mix the two solutions, adding 0.5mL of epoxy chloropropane into the mixed solution, continuing stirring, reacting at 60 ℃ for 1h, casting the mixed solution into a film after the reaction is finished, and drying at room temperature to obtain a composite film sample which is marked as HC-1;

performance test: the composite film prepared by the comparative example has the tensile strength of 19.42MPa, the elongation at break of 8.51 percent and the Young modulus of 7.04 MPa.

Example 1

A preparation method of a nano holocellulose reinforced composite membrane comprises the following steps:

(1) crushing a wheat straw raw material, and sieving the crushed wheat straw raw material with a 40-mesh sieve to obtain wheat straw powder for later use;

(2) adding the wheat straw powder obtained in the step (1) into a benzene-alcohol mixed solution (the volume ratio of benzene to alcohol is 2:1) according to a bath ratio of w/v being 1:25, and heating and extracting for 8 hours in a constant-temperature water bath kettle at 90 ℃ to obtain an extract-free sample;

(3) adding the sample without the extract prepared in the step (2) and sodium chlorite into glacial acetic acid according to a bath ratio of w/w/v being 4:1.2:1, heating the mixture in a constant-temperature water bath kettle at 75 ℃ for 1h, filtering the mixture after the reaction is finished, washing the mixture to be neutral by distilled water, and drying the mixture at 105 ℃ for 6h to obtain the holocellulose;

(4) ball-milling the holocellulose prepared in the step (3), swelling the ball-milled holocellulose with deionized water, adjusting the swollen holocellulose to a suspension with the concentration of 0.5% of the holocellulose solution, treating the obtained suspension with an ultramicron disc mill (MKCA6-2, Japan Masuko), and circularly disc-milling at the interval of-9 at the rotating speed of 1500r/min for 15min for 6 times to obtain the nano holocellulose;

(5) mixing 5mL of 2% hemicellulose solution and 5mL of 2% chitosan solution, stirring for 1h to fully mix the solutions, adding 0.1mL of nano holocellulose and 0.5mL of epoxy chloropropane into the mixed solution respectively, continuing stirring, reacting for 1h at 60 ℃, casting the mixed solution into a film after the reaction is finished, and drying at room temperature to obtain a composite film sample which is marked as HC-2.

Performance test: the tensile strength of the composite film prepared in this example was 29.15MPa, the elongation at break was 22.23%, and the Young's modulus was 5.58 MPa.

Example 2

(4) ball-milling the holocellulose prepared in the step (3), swelling the ball-milled holocellulose with deionized water, adjusting the swollen holocellulose to a suspension with the concentration of 0.5-2.0 of the holocellulose solution, treating the obtained suspension with an ultramicron disc mill (MKCA6-2, Japan Masuko), circularly disc-milling at the interval of-9 at the rotating speed of 1500r/min for 15min for 6 times to obtain nano holocellulose;

(5) mixing 5mL of 2% hemicellulose solution and 5mL of 2% chitosan solution, stirring for 1h to fully mix the solutions, adding 0.2mL of nano holocellulose and 0.5mL of epoxy chloropropane into the mixed solution respectively, continuing stirring, reacting for 1h at 60 ℃, casting the mixed solution into a film after the reaction is finished, and drying at room temperature to obtain a composite film sample which is marked as HC-3.

Performance test: the tensile strength of the composite film prepared in the example was 34.93MPa, the elongation at break was 27.91%, and the Young's modulus was 8.23 MPa.

As can be seen from figure 1, after mechanical treatment, the holocellulose still keeps a fibrous structure, and the fibers are intertwined with each other and have the length of between 300 and 1000 nm.

Example 3

(5) mixing 5mL of 2% hemicellulose solution and 5mL of 2% chitosan solution, stirring for 1h to fully mix the solutions, adding 0.4mL of nano holocellulose and 0.5mL of epoxy chloropropane into the mixed solution respectively, continuing stirring, reacting for 1h at 60 ℃, casting the mixed solution into a film after the reaction is finished, and drying at room temperature to obtain a composite film sample which is marked as HC-4.

Performance test: the tensile strength of the composite film prepared in the embodiment is 26.23MPa, the elongation at break is 26.22%, and the Young modulus is 6.76 MPa.

Example 4

(5) mixing 5mL of 2% hemicellulose solution and 5mL of 2% chitosan solution, stirring for 1h to fully mix the solutions, adding 0.6mL of nano holocellulose and 0.5mL of epoxy chloropropane into the mixed solution respectively, continuing stirring, reacting for 1h at 60 ℃, casting the mixed solution into a film after the reaction is finished, and drying at room temperature to obtain a composite film sample which is marked as HC-5.

Performance test: the tensile strength of the composite film prepared in the embodiment is 24.36MPa, the elongation at break is 12.87%, and the Young modulus is 9.98 MPa.

FIG. 2 is an infrared spectrum of the raw material and the composite film of examples 1 to 4 of the present invention and comparative example 1, and the results show that the addition of the nano holocellulose as a reinforcing phase to the hemicellulose/chitosan composite film is physically combined and does not cause a chemical reaction.

Fig. 3 is an X-ray diffraction spectrum of the raw materials and the composite films of examples 1 to 4 and comparative example 1, and the results show that characteristic peaks appear in five composite films at 2 θ of 21 to 24 °, and the crystal form change of the composite films is not changed by adding the nano holocellulose.

FIG. 4 is the results of transmittance of the composite films of examples 1 to 4 and comparative example 1, showing that the transmittance of 5 composite films is not changed with the addition of nano holocellulose, and is all above 80%, wherein the transmittance of the composite film sample prepared in example 2 is the highest, reaching 90%; meanwhile, the light transmittance of the composite film in an ultraviolet light wave band is close to 0, and the composite film has better ultraviolet resistance.

FIG. 5 is a stress-strain diagram of the composite films of examples 1 to 4 and comparative example 1, and the results show that the mechanical strength of the hemicellulose-based composite film can be significantly improved by adding nano holocellulose; according to the invention, after the nano holocellulose solution, the hemicellulose solution and the chitosan solution are fully mixed, the composite film is formed by adopting a tape casting film forming method, the prepared composite film has the characteristics of good mechanical property, high strength, good heat resistance and the like, and when 0.2mL of nano holocellulose with the concentration of 0.5% is added, the tensile strength of the prepared composite film is up to 34.93 MPa.

The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above examples, and various process schemes having no substantial difference from the concept of the present invention are within the protection scope of the present invention.

Claims

1. a preparation method of nano-hedocellulose reinforced composite membrane, is characterized in that, comprises the following steps:

(1) the wheat grass raw material is pulverized, sieved to obtain the wheat grass powder, for subsequent use;

(2) adding the wheatgrass powder in step (1) to the benzene alcohol mixture according to the liquor ratio of w/v=1:25, and heating and extracting in a constant temperature water bath at 90°C to obtain a sample without extractables ;

(3) According to the liquor ratio of w/w/v=4:1.2:1, add the non-extractable sample and sodium chlorite obtained in step (2) into glacial acetic acid, and put it in a constant temperature water bath at 75°C Heating for 1 hour, after the reaction was over, the mixture was filtered, washed with distilled water until neutral, and dried at 105°C for 6 hours to obtain holocellulose;

(4) ball-milling the holocellulose prepared in step (3), moistening the ball-milled holocellulose with deionized water, and adjusting it to a suspension with a concentration of the holocellulose solution of 0.5%, the obtained The suspension was processed with an ultra-fine particle disc mill, the distance between the sample and the disc was -9mm, and the disc milling was repeated for many times, the disc milling speed was 1500 r/min, and the disc milling time was 15 min to obtain nano-helocellulose;

(5) According to the volume ratio of 50:50:1:5-50:50:4:5, first mix the hemicellulose solution with the chitosan solution, the concentration of the hemicellulose solution is 2%, and the chitosan solution The concentration is 2%, stir for 1-2 h to make it fully mixed, add nano-hedocellulose and epichlorohydrin to the mixed solution, continue to stir, and react at 60 °C for 1 h. After the reaction, the mixed solution is cast into a The composite membrane samples were obtained after drying at room temperature.

2 . The method for preparing a nanohedocellulose reinforced composite membrane according to claim 1 , wherein in the step (1), the wheat straw is passed through a 40-mesh sieve. 3 .

3. The method for preparing a nanohedocellulose reinforced composite membrane according to claim 1, wherein the volume ratio of benzene to alcohol in the benzene alcohol mixed solution of the step (2) is 2:1.

4 . The method for preparing a nanohedocellulose reinforced composite membrane according to claim 1 , wherein the extraction time in the step (2) is 8h. 5 .

5 . The method for preparing a nanohedocellulose reinforced composite membrane according to claim 1 , wherein the disc grinding is repeated 6 times in the step (4). 6 .

6. A composite membrane prepared by the method for preparing a nanohedocellulose reinforced composite membrane according to any one of claims 1-5.