CN118620218A - Preparation method of cellulose/keratin copolymer in homogeneous system - Google Patents

Abstract

The invention discloses a method for preparing a cellulose/keratin copolymer in a homogeneous system, including: preparing allyl cellulose using cellulose and allyl chloride, and preparing an allyl cellulose solution; adding a keratin solution to an allyl cellulose solution, obtaining an allyl cellulose/keratin homogeneous solution, wherein the mass ratio of keratin in the keratin solution to the allyl cellulose in the allyl cellulose solution is 1:1.5~9; causing a click chemical reaction in the allyl cellulose/keratin homogeneous solution to obtain a cellulose/keratin copolymer. The present invention utilizes allyl chloride to allylate cellulose, thereby introducing a carbon-carbon double bond on cellulose, and a thiol-ene click chemical reaction occurs between the carbon-carbon double bond and the sulfhydryl group (-SH) on the keratin, and bonding is performed, thereby not destroying the complete structure of the protein polypeptide chain, so that the prepared composite film and composite fiber have the advantages of high transparency and excellent mechanical properties.

Description

Preparation method of cellulose/keratin copolymer in homogeneous system

Technical Field

The invention discloses a method for preparing a cellulose/keratin copolymer in a homogeneous system, belonging to the technical field of composite materials.

Background Art

Cellulose is the natural polymer with the largest reserves and the widest source in nature. The rich hydroxyl groups in its structure make the materials made from it exhibit strong mechanical properties. Keratin is an abundant natural renewable resource in animals and is widely present in animal hair, feathers, and nails. The thiol, amino, and imino groups in its structure provide reactive sites for its chemical modification. In particular, the hydrophilic and hydrophobic groups in the structure and its own amphiphilic properties give it a self-assembly effect, which is conducive to the preparation of bio-based polymers with adjustable structure.

The preparation of cellulose/keratin copolymers in the prior art is mainly prepared by aldehyde-amino Schiff base reaction, aldehyde compounds, genipin or epichlorohydrin cross-linking. Among them, Schiff base reaction, aldehyde compounds and genipin cross-linking are carried out under heterogeneous conditions, which are mainly used to process cellulose/keratin composite films. However, since the molecular chains do not have time to rearrange during the film formation process, the formed film has poor uniformity and low transparency; in addition, the above method cannot process cellulose/keratin composite fibers. Cellulose/keratin composite fibers are mainly formed into spinning solutions by co-solvents such as ionic liquids, and then wet spinning to form cellulose/keratin composite fibers. However, due to the different phase separation speeds of the two and the strong self-assembly ability of keratin, keratin is distributed on the surface of cellulose fibers in the form of spherical aggregates during the formation of composite fibers, making it difficult to obtain ideal cellulose/keratin composite fibers, and there is a problem of insufficient mechanical properties. Although the researchers used epichlorohydrin to cross-link cellulose/protein copolymers in a homogeneous system, the complete structure of the protein polypeptide chain was destroyed during the reaction, causing keratin to lose its isoelectric point and pH response effect, resulting in the inability to control the structure of the cellulose/keratin copolymer and making it difficult to process it into a cellulose/protein composite membrane with excellent mechanical properties.

Summary of the invention

The purpose of the present application is to provide a method for preparing a cellulose/keratin copolymer in a homogeneous system, so as to solve the technical problem of destroying the intact structure of the protein polypeptide chain in the preparation process of the cellulose/keratin copolymer in the prior art.

The present invention provides a method for preparing a cellulose/keratin copolymer in a homogeneous system, comprising:

Step 1, preparing allyl cellulose by using cellulose and allyl chloride, and preparing an allyl cellulose solution by using the allyl cellulose;

Step 2, adding the keratin solution to the allyl cellulose solution to obtain an allyl cellulose/keratin homogeneous solution; the mass ratio of keratin in the keratin solution to allyl cellulose in the allyl cellulose solution is 1:1.5-9;

Step 3: preparing a cellulose/keratin copolymer using the allyl cellulose/keratin homogeneous solution.

Preferably, the allyl cellulose is used to prepare an allyl cellulose solution, which specifically comprises:

The allyl cellulose is dissolved in dimethyl sulfoxide, N'N-dimethylformamide or N'N-dimethylacetamide to prepare an allyl cellulose solution.

Preferably, allyl cellulose is prepared from cellulose and allyl chloride, specifically comprising:

preparing a cellulose solution;

Adding allyl chloride to the cellulose solution, and reacting in the dark to obtain a reaction solution;

A precipitant is added to the reaction solution to obtain allyl cellulose.

Preferably, adding a precipitant to the reaction solution to obtain allyl cellulose specifically comprises:

adding a precipitant to the reaction solution to obtain a precipitate;

The precipitate is placed in a dialysis bag with a molecular weight cutoff of 8 to 12k for dialysis, and the dialysis product is freeze-dried to obtain allyl cellulose.

Preferably, the molar ratio of the allyl chloride to the anhydroglucose unit in the cellulose is 6 to 18:1.

Preferably, the degree of substitution of the allyl cellulose is 1 to 1.2.

Preferably, the preparation method of the keratin solution is:

The wool is dissolved in an aqueous solution containing urea, sodium dodecyl sulfate and sodium bisulfite to obtain a keratin solution.

Preferably, the content of urea in the aqueous solution is 16-20 wt %, the content of sodium dodecyl sulfate is 3-4.5 wt %, and the content of sodium bisulfite is 4-6 wt %.

Preferably, the step 3 specifically includes:

A photoinitiator is added to the allyl cellulose/keratin homogeneous solution, and ultraviolet light is used to irradiate the allyl cellulose/keratin homogeneous solution to cause a click chemical reaction to occur, thereby obtaining a cellulose/keratin copolymer.

Preferably, the photoinitiator is 6-8% of the dry weight of keratin in the allyl cellulose/keratin homogeneous solution.

The method for preparing cellulose/keratin copolymer in a homogeneous system of the present invention has the following beneficial effects compared with the prior art:

In the present invention, cellulose is allylated by using allyl chloride, thereby introducing carbon-carbon double bonds on the cellulose, and the carbon-carbon double bonds undergo thiol-ene click chemical reaction with the thiol (-SH) on the keratin to form bonds, thereby not destroying the complete structure of the protein polypeptide chain, so that the cellulose/keratin composite film and composite fiber processed by using the prepared copolymer have the advantages of high transparency, excellent mechanical properties and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a flow chart of a method for preparing a cellulose/keratin copolymer in a homogeneous system of the present invention;

FIG2 is a stress-strain curve of the cellulose/keratin copolymer film obtained in Examples 1-3 of the present invention;

FIG3 is an infrared spectrum of the cellulose/keratin copolymer obtained in Examples 1-3 of the present invention;

FIG4 is an XPS high-resolution S2p spectrum of keratin and the obtained cellulose/keratin copolymer in an embodiment of the present invention;

FIG5 is an infrared peak fitting diagram of cellulose/keratin copolymer at 1600-1700 cm ^-1 in an embodiment of the present invention;

FIG6 is a stress-strain curve of the cellulose/keratin copolymer composite fiber obtained by Example 1 of the present invention;

FIG. 7 shows the breaking strength and elongation values of the cellulose/protein copolymer composite fibers obtained in the comparative example.

DETAILED DESCRIPTION

The embodiment of the present invention provides a method for preparing a cellulose/keratin copolymer in a homogeneous system, comprising:

Step 1, preparing an allyl cellulose solution using cellulose and allyl chloride, specifically comprising:

Step 1.1, preparing allyl cellulose using cellulose and allyl chloride, comprising:

Step 1.1.1, preparing a cellulose solution: dissolving cellulose in an aqueous solution of NaOH and urea at -10 to -15°C to obtain a cellulose solution, wherein the concentration of the cellulose solution is 3 to 5%. For example, the temperature may be -10°C, -12°C, -14°C, -15°C, etc., preferably -12°C; the concentration of the cellulose solution is 3%, 4%, 5%, etc., preferably 3%.

Step 1.1.2, slowly add allyl chloride to the cellulose solution, and obtain a reaction solution after the light-proof reaction is completed. The molar ratio of allyl chloride to the anhydroglucose unit in cellulose is 6 to 18:1, such as 6:1, 12:1, 18:1, etc., preferably 12:1; the temperature of the light-proof reaction is 30 to 40°C, such as 30°C, 35°C, 40°C, etc., and the time of the light-proof reaction is 70 to 80h, such as 70h, 72h, 75h, 80h, preferably 72h. The embodiment of the present invention controls the degree of allylation of cellulose by limiting the molar ratio of allyl chloride to the anhydroglucose unit in cellulose, so as to obtain allyl cellulose with a subsequent degree of substitution of 1 to 1.2.

Step 1.1.3, adding a precipitant to the reaction solution to obtain allyl cellulose with a degree of substitution of 1 to 1.2, specifically comprising:

(1) Adjusting the pH value of the reaction solution. For example, the reaction solution is neutralized with hydrochloric acid having a concentration of 36-38%, wherein the concentration of the hydrochloric acid is 36%, 37%, 37.5%, 38%, etc., preferably 37.5%.

(2) adding a precipitant to the reaction solution to obtain a precipitate, wherein the precipitant may be acetone.

(3) The precipitate is dialyzed in a dialysis bag with a molecular weight cutoff of 8 to 12k, and the dialyzed product is freeze-dried to obtain allyl cellulose with a degree of substitution of 1 to 1.2. The degree of substitution in the embodiment of the present invention can be 1, 1.1, 1.2, etc., preferably 1.1.

Step 1.2, dissolving allyl cellulose in dimethyl sulfoxide (DMSO), N'N-dimethylformamide (DMF) or N'N-dimethylacetamide (DMAC) to obtain an allyl cellulose solution.

In the embodiment of the present invention, the concentration of the allyl cellulose solution is 2-3%, for example, 2%, 2.5%, 3%, etc., preferably 2.5%.

Step 2: adding the keratin solution to the allyl cellulose solution to obtain an allyl cellulose/keratin homogeneous solution.

The preparation method of the keratin solution is as follows:

The wool is dissolved in an aqueous solution containing urea, sodium dodecyl sulfate and sodium bisulfite in a 100° C. water bath, and the undissolved wool is removed by centrifugation. The supernatant is separated to obtain a keratin solution, wherein the stirring and dissolving time is 2 to 4 hours, for example, 2 hours, 3 hours, 4 hours, and preferably 3 hours; the centrifugal speed is 7000 to 9000 r/min, for example, 7000 r/min, 8000 r/min, 9000 r/min, etc., and preferably 8000 r/min; the centrifugal time is 5 to 10 minutes, for example, 5 minutes, 8 minutes, 10 minutes, etc., and preferably 5 minutes.

The content of urea in the aqueous solution is 16-20wt%, such as 16wt%, 18wt%, 19wt%, 20wt%, etc., preferably 18wt%; the content of sodium dodecyl sulfate is 3-4.5wt%, such as 3wt%, 3.75wt%, 4wt%, 4.5wt%, etc., preferably 3.75wt%; the content of sodium bisulfite is 4-6wt%, such as 4wt%, 5wt%, 6wt%, etc., preferably 5wt%. The components and proportions of the aqueous solution can better dissolve wool to obtain a keratin solution.

After obtaining the keratin solution, the keratin solution is slowly added to the allyl cellulose solution and stirred evenly, for example, at room temperature for 1 to 2 hours, illustratively, for 1 hour, 1.5 hours, 2 hours, etc., preferably for 1 hour, to obtain an allyl cellulose/keratin homogeneous solution. The mass ratio of keratin in the keratin solution to allyl cellulose in the allyl cellulose solution is 1:1.5 to 9, for example, 1:9, 2:8, 3:7, 4:6, etc., preferably 1:9. Within this ratio range, the transparency and mechanical properties of the composite film and composite fiber prepared using the final copolymer can be ensured to be optimal, wherein the mechanical properties include breaking strength and breaking elongation, etc.

Step 3, preparing a cellulose/keratin copolymer using an allyl cellulose/keratin homogeneous solution, specifically comprising:

A photoinitiator is added to the allyl cellulose/keratin homogeneous solution, and ultraviolet light is used to irradiate the allyl cellulose/keratin homogeneous solution to cause a click chemistry reaction to occur, thereby obtaining a cellulose/keratin copolymer. The photoinitiator is 6 to 8% of the dry amount of keratin in the allyl cellulose/keratin homogeneous solution, for example, 6%, 7%, 8%, etc., preferably 7%. Exemplarily, the photoinitiator may be 2,2-dimethoxy-2-phenylacetophenone (DMPA). The dosage range of the photoinitiator in the embodiment of the present invention can avoid the problem of incomplete click chemistry reaction due to too little dosage or out-of-control reaction due to excessive dosage or affecting the performance of the prepared copolymer, and can significantly improve the preparation efficiency of the copolymer.

In the embodiment of the present invention, the time for click chemistry to occur can be 1-3 hours, such as 1 hour, 2 hours, 3 hours, etc., preferably 2 hours. After the reaction is completed, the cellulose/keratin copolymer is obtained by dialyzing through a dialysis bag with a molecular weight cutoff of 8k-12k and then freeze-drying.

The cellulose/keratin copolymer obtained in the embodiment of the present invention does not destroy the integrity of the polypeptide chain structure during the preparation process. Therefore, the cellulose/keratin composite film or cellulose/keratin composite fiber prepared using the copolymer has better mechanical properties and higher transparency.

The method for preparing the cellulose/keratin composite film is to dissolve the cellulose/keratin copolymer in DMSO or DMF, and then cast the solution and dry it to form a film.

The method for preparing the cellulose/keratin composite fiber is to use sodium chloride, magnesium sulfate or sodium carbonate aqueous solution as a coagulation bath and process the cellulose/keratin composite fiber by wet spinning.

The preparation method of cellulose/keratin copolymer in a homogeneous system of the present invention can solve the problem that the complete structure of the protein polypeptide chain cannot be retained in the cellulose/keratin homogeneous reaction, and avoids the defect of insufficient mechanical properties caused by different phase separation in the processing of cellulose/keratin composite film and composite fiber; at the same time, click chemistry is an efficient and controllable reaction method, which can significantly improve the preparation efficiency of cellulose/keratin copolymer. The cellulose/keratin copolymer developed by the present invention is environmentally friendly and has good processability. It can be easily processed into solutions, films, fibers, gels, and fabrics, and has broad application prospects. FTIR and XPS provide evidence for the bonding of keratin to the glucose unit of cellulose; the formed cellulose/keratin copolymer film exhibits high transparency and excellent mechanical properties.

The effectiveness of the method for preparing the cellulose/keratin copolymer in the homogeneous system of the present invention will be verified by more specific examples below.

Example 1

3 grams of cellulose was immersed in 97 grams of an aqueous solution containing 7wt% NaOH and 12wt% urea, and dissolved at -12°C to prepare a 3% cellulose solution; then 17 grams of allyl chloride (with a molar ratio of 12:1 to cellulose anhydroglucose unit) was slowly added, and the reaction was carried out at 35°C in the dark for 72 hours. After the reaction was completed, 37.5% hydrochloric acid was used for neutralization, and then acetone was used for precipitation. The precipitate was placed in a dialysis bag with a molecular weight cutoff of 8k-12k for dialyzing, and finally freeze-dried to obtain allyl cellulose with a degree of substitution of 1.1.

0.5 g of allyl cellulose was added to 19.5 g of DMSO to obtain a 2.5% allyl cellulose solution. 5 g of wool was immersed in 100 mL of an aqueous solution containing 18 wt% urea, 5 wt% sodium bisulfite and 3.75 wt% sodium dodecyl sulfate, stirred and dissolved at 100°C for 3 h, centrifuged at 8000 r/min for 5 min, and the supernatant was separated to obtain a keratin solution.

The keratin solution is added to the allyl cellulose solution (the mass ratio of keratin to allyl cellulose is 1:9), stirred and mixed evenly, DMPA (mass is 7% of the dry weight of keratin) is slowly added, and the mixture is reacted under ultraviolet light for 2 hours; after the reaction, it is placed in a dialysis bag with a molecular weight cutoff of 8k-12k for dialyzation, and finally freeze-dried to obtain a cellulose/keratin copolymer.

0.5g of cellulose/keratin copolymer was dissolved in 9.5g of DMSO to obtain a cellulose/keratin copolymer solution with a concentration of 5%, which was cast and dried to form a film. The transparency of the film was 91%, the breaking strength of the film was 44.93Mpa, and the breaking elongation was 22.29%.

Example 2

3 grams of cellulose was immersed in 97 grams of an aqueous solution containing 7wt% NaOH and 12wt% urea, and dissolved at -12°C to prepare a 3% cellulose solution; then 17 grams of allyl chloride (with a molar ratio of 12:1 to cellulose dehydrated glucose unit) was slowly added, and the reaction was carried out at 35°C in the dark for 72 hours. After the reaction was completed, 37.5% hydrochloric acid was used for neutralization, and then acetone was used for precipitation. The precipitate was placed in a dialysis bag with a molecular weight cutoff of 8k-12k for dialyzing, and finally freeze-dried to obtain allyl cellulose with a degree of substitution of 1.1.

0.5 g of allyl cellulose was added to 19.5 g of DMSO to obtain a 2.5% allyl cellulose solution. 5 g of wool was immersed in 100 mL of an aqueous solution containing 18 wt% urea, 5 wt% sodium bisulfite and 3.75 wt% sodium dodecyl sulfate, stirred and dissolved at 100°C for 3 h, centrifuged at 8000 r/min for 5 min, and the supernatant was separated to obtain a keratin solution.

The keratin solution is added to the allyl cellulose solution (the mass ratio of keratin to allyl cellulose is 2:8), stirred and mixed evenly, DMPA (mass is 7% of the dry weight of keratin) is slowly added, and the mixture is reacted under ultraviolet light for 2 hours; after the reaction, it is placed in a dialysis bag with a molecular weight cutoff of 8k-12k for dialyzation, and finally freeze-dried to obtain a cellulose/keratin copolymer.

0.5g of cellulose/keratin copolymer was dissolved in 9.5g of DMSO to obtain a cellulose/keratin copolymer solution with a concentration of 5%, which was cast and dried to form a film with a transparency of 90%, a breaking strength of 34.58Mpa, and a breaking elongation of 25.56%.

Example 3

3 grams of cellulose was immersed in 97 grams of an aqueous solution containing 7wt% NaOH and 12wt% urea, and dissolved at -12°C to prepare a 3% cellulose solution; then 17 grams of allyl chloride (with a molar ratio of 12:1 to cellulose anhydroglucose unit) was slowly added, and the reaction was carried out at 35°C in the dark for 72 hours. After the reaction was completed, 37.5% hydrochloric acid was used for neutralization, and then acetone was used for precipitation. The precipitate was placed in a dialysis bag with a molecular weight cutoff of 8k-12k for dialyzing, and finally freeze-dried to obtain allyl cellulose with a degree of substitution of 1.1.

0.5 g of allyl cellulose was added to 19.5 g of DMSO to obtain a 2.5% allyl cellulose solution. 5 g of wool was immersed in 100 mL of an aqueous solution containing 18 wt% urea, 5 wt% sodium bisulfite and 3.75 wt% sodium dodecyl sulfate, stirred and dissolved at 100°C for 3 h, centrifuged at 8000 r/min for 5 min, and the supernatant was separated to obtain a keratin solution.

The keratin solution is added to the allyl cellulose solution (the mass ratio of keratin to allyl cellulose is 3:7), stirred and mixed evenly, DMPA (mass is 7% of the dry weight of keratin) is slowly added, and the mixture is reacted under ultraviolet light for 2 hours; after the reaction, it is placed in a dialysis bag with a molecular weight cutoff of 8k-12k for dialyzation, and finally freeze-dried to obtain a cellulose/keratin copolymer.

0.5g of cellulose/keratin copolymer was dissolved in 9.5g of DMSO to obtain a cellulose/keratin copolymer solution with a concentration of 5%, which was cast and dried to form a film with a transparency of 88%, a breaking strength of 28.40Mpa, and a breaking elongation of 42.63%.

The stress-strain curves of the cellulose/keratin copolymer films obtained in Examples 1-3 above are shown in FIG2 .

The infrared spectra of the cellulose/keratin copolymers obtained in the above Examples 1-3, as well as cellulose, allyl cellulose, and keratin are shown in FIG3 . As can be seen from FIG3 , compared with the FTIR spectrum of cellulose, the characteristic peaks at 930 cm ^-1 and 1018 cm ^-1 in the spectrum of allyl cellulose correspond to the C=C stretching vibration and the COC stretching vibration band of the methoxy group, respectively. In the FTIR spectrum of keratin, the absorption peaks at 1205 cm ^-1 , 1530 cm ^-1 , and 1650 cm ^-1 belong to the characteristic peaks of the amide III band (CN bond stretching vibration), the amide II band (NH bending vibration), and the amide I band (C=O stretching and CN stretching vibration), respectively. The same characteristic peaks also appear in the spectrum of cellulose/keratin copolymers, and the intensity of the C=C characteristic peak at 930 cm ^-1 is reduced, which verifies the thiol-ene click reaction between allyl cellulose and keratin.

Furthermore, the XPS high-resolution S2p spectra of keratin and the obtained cellulose/keratin copolymer in Example 1 are shown in FIG. 4 . As can be seen from FIG. 4 , a C-S-C characteristic peak appears in the peak separation diagram of the cellulose/keratin copolymer, verifying the thiol-ene click reaction between allyl cellulose and keratin.

The infrared peak fitting diagram of the cellulose/keratin copolymer at 1600-1700 cm ^-1 in Example 1 is shown in FIG5 , and the secondary structure ratio obtained by peak fitting is shown in Table 1, indicating that the click chemistry reaction successfully retains the complete structure of keratin.

Table 1 Keratin secondary structure ratio obtained in Example 1

Secondary structure type β-fold Irregular curl Alpha helix β turn Percentage (%) 44.6354 17.1705 15.086 23.1081

Example 4

3 grams of cellulose was immersed in 97 grams of an aqueous solution containing 7 wt% NaOH and 12 wt% urea, and dissolved at -12°C to prepare a 3% cellulose solution; then 25.5 grams of allyl chloride (with a molar ratio of 18:1 to cellulose dehydrated glucose unit) was slowly added, and the reaction was carried out at 35°C in the dark for 72 hours. After the reaction was completed, 37.5% hydrochloric acid was used for neutralization, and then acetone was used for precipitation. The precipitate was placed in a dialysis bag with a molecular weight cutoff of 8k-12k for dialyzing, and finally freeze-dried to obtain allyl cellulose with a degree of substitution of 1.2.

0.5 g of allyl cellulose was added to 19.5 g of DMSO to obtain a 2.5% allyl cellulose solution. 5 g of wool was immersed in 100 mL of an aqueous solution containing 20 wt% urea, 4 wt% sodium bisulfite and 4.5 wt% sodium dodecyl sulfate, stirred and dissolved at 100°C for 3 h, centrifuged at 8000 r/min for 5 min, and the supernatant was separated to obtain a keratin solution.

The keratin solution is added to the allyl cellulose solution (the mass ratio of keratin to allyl cellulose is 1:9), stirred and mixed evenly, DMPA (mass is 6% of the dry weight of keratin) is slowly added, and the mixture is reacted under ultraviolet light for 2 hours; after the reaction, it is placed in a dialysis bag with a molecular weight cutoff of 8k-12k for dialyzation, and finally freeze-dried to obtain a cellulose/keratin copolymer.

0.5g of cellulose/keratin copolymer was dissolved in 9.5g of DMSO to obtain a 5% cellulose/keratin copolymer solution, which was cast and dried to form a film. The transparency of the film was 90.6%, the breaking strength of the film was 40.67Mpa, and the breaking elongation was 24.73%.

Example 5

3 grams of cellulose was immersed in 97 grams of an aqueous solution containing 7 wt% NaOH and 12 wt% urea, and dissolved at -12°C to prepare a 3% cellulose solution; then 8.5 grams of allyl chloride (with a molar ratio of 6:1 to cellulose dehydrated glucose unit) was slowly added, and the reaction was carried out at 35°C in the dark for 72 hours. After the reaction was completed, 37.5% hydrochloric acid was used for neutralization, and then acetone was used for precipitation. The precipitate was placed in a dialysis bag with a molecular weight cutoff of 8k-12k for dialyzing, and finally freeze-dried to obtain allyl cellulose with a degree of substitution of 1.

0.5 g of allyl cellulose was added to 19.5 g of DMSO to obtain a 2.5% allyl cellulose solution. 5 g of wool was immersed in 100 mL of an aqueous solution containing 16 wt% urea, 6 wt% sodium bisulfite and 3 wt% sodium dodecyl sulfate, stirred and dissolved at 100°C for 3 h, centrifuged at 8000 r/min for 5 min, and the supernatant was separated to obtain a keratin solution.

The keratin solution is added to the allyl cellulose solution (the mass ratio of keratin to allyl cellulose is 1:9), stirred and mixed evenly, DMPA (the mass is 8% of the dry weight of keratin) is slowly added, and the mixture is reacted under ultraviolet light for 2 hours; after the reaction, it is placed in a dialysis bag with a molecular weight cutoff of 8k-12k for dialyzation, and finally freeze-dried to obtain a cellulose/keratin copolymer.

0.5 g of cellulose/keratin copolymer was dissolved in 9.5 g of DMSO to obtain a 5% cellulose/keratin copolymer solution, which was cast and dried to form a film. The transparency of the film was 91.5%, the breaking strength of the film was 45.54 MPa, and the breaking elongation was 17.08%.

The properties of the composite membranes obtained in the above five embodiments are shown in Table 2.

Table 2 Properties of the composite membranes obtained in the examples of the present invention

Experimental methods Breaking strength(MPa) Elongation at break (%) Example 1 44.93±2.6 22.29±1.2 Example 2 34.58±1.5 25.56±0.8 Example 3 28.40±2.1 42.63±1.1 Example 4 40.67±0.9 24.73±1.3 Example 5 45.54±1.9 17.08±0.7

Comparative Example

The comparative example used in the present invention is a cellulose/protein copolymer obtained by cross-linking with epichlorohydrin in a homogeneous system, which is then cast and dried to form a film. The properties of the obtained composite film are shown in Table 3.

Table 3 Performance of the composite membrane obtained in the comparative example

Epichlorohydrin cross-linked film Breaking strength(MPa) Elongation at break (%) Cellulose/protein mass ratio 9:1 18±2.4 8.6±2.5 Cellulose/protein mass ratio 8:2 12.9±3.6 13.7±4.2 Cellulose/protein mass ratio 7:3 10.8±2.4 19.1±4.0

According to the performance of the composite membranes of the embodiments of the present invention and the comparative examples, it can be known that the composite membranes prepared by the preparation method of the present application have excellent mechanical properties.

Furthermore, the present invention also uses a sodium chloride aqueous solution as a coagulation bath to process the 5% cellulose/keratin copolymer solution obtained in Example 1 into cellulose/keratin composite fibers by wet spinning. The composite fibers have a breaking strength of 28.8 MPa and a breaking elongation of 14.85%, as shown in the stress-strain curve of FIG6 .

The cellulose/protein copolymer obtained in the comparative example was processed into cellulose/keratin composite fibers by wet spinning using sodium chloride aqueous solution as a coagulation bath. The breaking strength was 25 MPa and the breaking elongation was 4%, as shown in FIG. 7 . It can be seen that the mechanical properties are lower than those of the composite fibers prepared in the present invention.

The present invention treats cellulose with allylation in an alkali and urea system, and then undergoes a "thiol-ene" click chemical reaction with the thiol groups on the keratin structure to prepare a novel cellulose/keratin copolymer. By changing the mass ratio of cellulose to keratin, the degree of allylation, the reaction time, etc., a cellulose/keratin copolymer with adjustable structure is obtained, and a cellulose/keratin copolymer film/fiber is processed by solution casting and wet spinning. The influence of structural regulation on the performance characteristics of cellulose/keratin copolymer materials is studied, thereby obtaining a cellulose/keratin copolymer material with high transparency and excellent mechanical properties.

The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical contents disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims (10)

1. A process for the preparation of a cellulose/keratin copolymer in a homogeneous system, comprising:

step 1, preparing allyl cellulose by using cellulose and chloropropene, and preparing an allyl cellulose solution by using the allyl cellulose;

Step 2, adding a keratin solution into the allyl cellulose solution to obtain an allyl cellulose/keratin homogeneous solution; the mass ratio of the keratin in the keratin solution to the allyl cellulose in the allyl cellulose solution is 1:1.5-9;

and 3, preparing a cellulose/keratin copolymer by using the allyl cellulose/keratin homogeneous solution.

2. The method for preparing cellulose/keratin copolymer in a homogeneous system according to claim 1, characterized in that said allyl cellulose is used to prepare an allyl cellulose solution comprising in particular:

Dissolving the allyl cellulose in dimethyl sulfoxide, N 'N-dimethylformamide or N' N-dimethylacetamide to prepare an allyl cellulose solution.

3. The method for preparing cellulose/keratin copolymer in a homogeneous system according to claim 1, comprising the steps of:

preparing a cellulose solution;

adding chloropropene into the cellulose solution, and reacting in a dark place to obtain a reaction solution;

adding a precipitant into the reaction solution to obtain allyl cellulose.

4. A method for preparing cellulose/keratin copolymer in a homogeneous system according to claim 3, characterized in that adding a precipitant to said reaction solution, obtaining allyl cellulose, comprising:

Adding a precipitant into the reaction solution to obtain a precipitate;

And (3) placing the precipitate into a dialysis bag with the molecular weight cut-off of 8-12 k for dialysis, and freeze-drying the dialyzed product to obtain the allyl cellulose.

5. The method for preparing a cellulose/keratin copolymer in a homogeneous system according to claim 1, wherein the molar ratio of chloropropene to anhydroglucose units in the cellulose is from 6 to 18:1.

6. The method for producing a cellulose/keratin copolymer in a homogeneous system according to claim 5, wherein the substitution degree of the allyl cellulose is from 1 to 1.2.

7. The method for preparing a cellulose/keratin copolymer in a homogeneous system according to any one of claims 1 to 5, characterized in that said keratin solution is prepared by:

Wool is dissolved in an aqueous solution containing urea, sodium dodecyl sulfate and sodium bisulphite to obtain a keratin solution.

8. The method for preparing cellulose/keratin copolymer in a homogeneous system according to claim 7, wherein the urea content in the aqueous solution is 16 to 20% by weight, the sodium dodecyl sulfate content is 3 to 4.5% by weight, and the sodium bisulphite content is 4 to 6% by weight.

9. The method for preparing a cellulose/keratin copolymer in a homogeneous system according to any one of claims 1 to 5, characterized in that said step 3 comprises in particular:

And adding a photoinitiator into the allyl cellulose/keratin homogeneous solution, and irradiating the solution by using ultraviolet light to enable the allyl cellulose/keratin homogeneous solution to undergo click chemical reaction to obtain the cellulose/keratin copolymer.

10. The method for preparing cellulose/keratin copolymer in a homogeneous system according to claim 9, wherein said photoinitiator is 6-8% of the dry weight of keratin in the homogeneous solution of allyl cellulose/keratin.