Preparation method of cellulose nanocrystal modified full-bio-based polyacrylate composite emulsion with hydrophobic, antibacterial and ultraviolet resistant functions

Abstract

The invention discloses a preparation method of a cellulose nanocrystal-modified all-biobased polyacrylate composite emulsion with hydrophobic, antibacterial and anti-ultraviolet functions. The method comprises the following steps: 1. uniformly mixing a macromolecular RAFT agent, a vinyl monomer, an initiator and an organic solvent, heating the mixture under argon to obtain a product A, adding n-hexane to the product A, separating a precipitate, and drying the mixture to obtain an amphiphilic block copolymer; 2. uniformly mixing the amphiphilic block copolymer-modified cellulose nanocrystals, N,N-dimethylformamide and a catalyst, heating the mixture, centrifuging the mixture to obtain a crude product B, washing the mixture and drying the mixture to obtain an amphiphilic block copolymer-modified cellulose nanocrystal; 3. uniformly mixing the amphiphilic block copolymer-modified cellulose nanocrystals, deionized water and the vinyl monomer, and ultrasonically emulsifying the mixture to obtain a Pickering emulsion; and 4. heating the Pickering emulsion under argon, and then dropwise adding an initiator aqueous solution to react the mixture to obtain the cellulose nanocrystal-modified all-biobased polyacrylate composite emulsion with hydrophobic, antibacterial and anti-ultraviolet properties.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high polymer materials, and particularly relates to a preparation method of a cellulose nanocrystal modified full-bio-based polyacrylate composite emulsion with hydrophobic, antibacterial and ultraviolet resistant functions. BACKGROUND

[0002] Natural leather has the advantages of softness, comfortable touch and air permeability, and has been widely used in the manufacture of household products. However, in the actual use process, the following disadvantages also exist: 1) since the leather is composed of natural collagen fibers tightly woven in three-dimensional space, a large number of microporous structures are very suitable for the breeding and reproduction of microorganisms such as bacteria and fungi, which seriously threatens human health; 2) the collagen contains a large number of amino, carboxyl and hydroxyl groups, which makes the leather have a strong affinity for water, resulting in the leather surface being easy to harden and even crack, which seriously reduces the comfort and service life of the leather product; 3) ultraviolet rays can destroy the molecular structure of collagen, leading to the breakage or cross-linking reaction of the molecules of the leather material, thereby accelerating the aging process of the leather. Therefore, it is usually necessary to coat a coating material on the surface of the leather to form a protective film, so as to improve the performance of the leather.

[0003] Polyacrylate has excellent film-forming property and adhesion, and is usually coated on the surface of the leather in the form of a Pickering emulsion. The Pickering emulsion is a new type of emulsion prepared by using solid particles instead of traditional small molecule surfactants as stabilizers. Compared with traditional emulsions, the Pickering emulsion has the advantages of low or no toxicity, low cost and no pollution, and has been widely used in composite materials with special structure and function. However, the solid particles used as stabilizers in the Pickering emulsion are mostly small inorganic nanoparticles, which have the disadvantages of toxicity, non-renewability, poor biocompatibility and non-renewability, resulting in unsatisfactory performance of the polyacrylate emulsion film and environmental unfriendliness.

[0004] With the improvement of living quality, people pay more and more attention to the quality of leather, and pursue the functionality and green environmental protection of leather. Therefore, it is necessary to develop a new type of polyacrylate composite emulsion to endow the leather product with good hydrophobicity, antibacterial property and ultraviolet resistance. SUMMARY

[0005] In view of the deficiencies of the prior art, the purpose of the present application is to provide a preparation method of a cellulose nanocrystal modified full-bio-based polyacrylate composite emulsion with hydrophobic, antibacterial and ultraviolet resistant functions, so as to prepare a polyacrylate composite emulsion which is green and environmentally friendly and has excellent hydrophobicity, antibacterial property and ultraviolet resistance.

[0006] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0007] A method for preparing a cellulose nanocrystal-modified all-biobased polyacrylate composite emulsion having hydrophobic, antibacterial and anti-ultraviolet functions comprises the following steps:

[0008] Step 1: Preparation of amphiphilic block copolymer modified cellulose nanocrystals

[0009] Step 1.1. Add a macromolecular RAFT agent, a vinyl monomer, an initiator I, and an organic solvent to a three-necked flask equipped with a condenser reflux tube and a gas guide tube in a mass ratio of (10-45):(150-180):(3-5):(1600-6800), introduce argon into the three-necked flask, heat to 70-90° C., and stir for 7-9 hours to obtain product A. Add product A to a beaker containing n-hexane and stir. After precipitation, separate the precipitate and vacuum dry it to obtain an amphiphilic block copolymer.

[0010] Step 1.2, adding an amphiphilic block copolymer, cellulose nanocrystals, N,N-dimethylformamide, and a catalyst into a three-necked flask with a reflux tube in a mass ratio of (9-30):(3-10):(300-1000):(1-2), stirring for 20-30 hours in an oil bath at 45-55° C., centrifuging to separate a crude product B, then washing the crude product B with tetrahydrofuran to remove residual organic solvent, and then vacuum drying to obtain an amphiphilic block copolymer-modified cellulose nanocrystal;

[0011] Step 2: Prepare Pickering emulsion

[0012] The amphiphilic block copolymer modified cellulose nanocrystals, deionized water and vinyl monomer are uniformly mixed in a mass ratio of (1-3): (500-1000): (80-180), and ultrasonically emulsified at room temperature to obtain a Pickering emulsion;

[0013] Step 3: Preparation of a cellulose nanocrystal-modified all-biobased polyacrylate composite emulsion with hydrophobic, antibacterial and anti-ultraviolet functions

[0014] Step 3.1, taking initiator II according to 0.6% to 1.5% of the mass of the vinyl monomer in step 2, adding it to deionized water to prepare an initiator II aqueous solution with a mass fraction of 16.7% to 25%;

[0015] Step 3.2: Transfer the Pickering emulsion into a three-necked flask equipped with a condenser reflux tube and an air guide tube. Under argon protection, stir and heat to 75-85°C. Then, add the initiator II aqueous solution dropwise into the three-necked flask. After the addition of the initiator II aqueous solution is completed, keep warm for 90-120 minutes, and then cool to room temperature to obtain a cellulose nanocrystal-modified all-biobased polyacrylate composite emulsion with hydrophobic, antibacterial and anti-UV functions.

[0016] Further, the macromolecular RAFT agent in step 1.1 has the following structural formula:

[0017]

[0018] In the formula, R is isobutyryl or isoamyl; Z is C12 alkylthio or C11 alkylthio; R1 is -H or -CH3; R2 is -H or -CH3; m and n represent the average polymerization degree of glycidyl acrylate or glycidyl methacrylate, and m = 15-100, n = 15-100.

[0019] Further, the initiator I in step 1.1 is at least one of azobisisobutyronitrile, azobisisopentyl cyanide and azobisisoheptyl cyanide.

[0020] Further, the organic solvent in step 1.1 is n-hexane, 1,4-dioxane or N,N-dimethylformamide.

[0021] Further, the catalyst in step 1.2 is p-toluenesulfonic acid, triethylamine or pyridine.

[0022] Further, the temperature of vacuum drying in step 1.1 and step 1.2 is 40℃.

[0023] Further, the vinyl monomer in step 1.1 and step 2 is at least one of isobornyl acrylate, methyl vanillin acrylate, vanillin acrylate, lauryl acrylate, tetrahydrofurfuryl acrylate, lauryl methacrylate and tetrahydrofurfuryl methacrylate.

[0024] Further, the ultrasonic emulsification in step 2 is performed by using an ultrasonic crusher with a total power of 1500W, at an ultrasonic power of 8%-25% for 5-30min.

[0025] Further, the initiator II in step 3.1 is ammonium persulfate, potassium persulfate or sodium persulfate.

[0026] Further, the time for dropping the aqueous initiator II solution into the three-necked flask in step 3.2 is 60-120min.

[0027] Compared with the prior art, the present application has the following technical effects:

[0028] The cellulose nanocrystals CNC are a kind of abundant natural organic nanomaterials, have the characteristics of low density, high aspect ratio, high crystallinity and low cost, etc., the cellulose nanocrystals are grafted and modified by amphiphilic block copolymers, the modified cellulose nanocrystals with good wettability and dispersibility are obtained, the cellulose nanocrystal modified bio-based polyacrylate composite emulsion with good hydrophobicity, antibacterial property and ultraviolet resistance is obtained by taking the modified cellulose nanocrystals as a stabilizer of Pickering emulsion, the adverse effects of traditional small molecule surfactants on the performance of polyacrylate emulsion film and the environment are avoided, and the application range of the polyacrylate emulsion is widened.

[0029] The vinyl monomers selected in the application are all bio-based monomers, inherit the characteristics of lignin such as aromatic ring structure and rich in various active oxygen-containing functional groups (hydroxyl, aldehyde group), meanwhile, overcome the problems of uneven structure and poor designability of crosslinked macromolecular state when lignin is directly applied, therefore, the polyacrylate is modified by the vinyl monomers, not only the hydrophobic property, antibacterial property and ultraviolet resistance of the polyacrylate can be improved, but also the use of petroleum-based materials in the synthesis process is reduced, the scientific concept of green environmental protection is adhered, and the synthetic material has good degradation and recyclability. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The FT-IR spectrum of the cellulose nanocrystal modified full bio-based polyacrylate composite emulsion prepared in example 1 of the application is shown in the figure.

[0031] Figure 2 The water contact angle photo of the emulsion film formed by the cellulose nanocrystal modified full bio-based polyacrylate composite emulsion prepared in example 1 of the application is shown in the figure.

[0032] Figure 3 The ultraviolet shielding performance photo of the emulsion film formed by the cellulose nanocrystal modified full bio-based polyacrylate composite emulsion prepared in example 1 of the application is shown in the figure.

[0033] Figure 4 The antibacterial performance photo of the emulsion film formed by the cellulose nanocrystal modified full bio-based polyacrylate composite emulsion prepared in example 1 of the application is shown in the figure. DETAILED DESCRIPTION

[0034] The specific content of the application is further explained and described in detail in combination with the examples.

[0035] The macromolecular RAFT agent used in Examples 1-5 is synthesized according to C. H. Such, E. Rizzardo, A. K. Serelis, B. S. Hawkett, R. G. Gilbert, C. J. Ferguson, R. J. Hughes, E. Olejnik, Aqueous dispersions of polymer particles. 2006, and has the following structure:

[0036]

[0037] wherein R is isobutyrate or iso-valerate; Z is C12 alkylthio or C11 alkylthio; R1 is -H or -CH3; R2 is -H or -CH3; m and n each represent the average degree of polymerization of glycidyl acrylate or glycidyl methacrylate, and m = 15-100, n = 15-100.

[0038] Example 1

[0039] Step 1, preparation of amphiphilic block copolymer modified cellulose nanocrystals

[0040] Step 1.1, according to the mass ratio 10:150:3:1600, the macromolecular RAFT agent, vinyl monomer, azobisisobutyronitrile and 1,4-dioxane are added into a three-necked flask with a condenser reflux tube and a gas inlet tube, argon is introduced into the three-necked flask for 20 min, then heated to 70°C, and mechanically stirred at a speed of 200 rpm for 9 h to obtain product A. Product A is added to a beaker containing n-hexane and stirred. After precipitation, the precipitate is separated, then the precipitate is added to another beaker containing n-hexane, and the operation is repeated twice to remove residual organic solvents. The product is dried under vacuum at 40°C to obtain the amphiphilic block copolymer, wherein the vinyl monomer is a mixture of lauryl methacrylate and methyl vanillin acrylate in a mass ratio of 1:2;

[0041] Step 1.2, according to the mass ratio 9:3:300:1, the amphiphilic block copolymer, cellulose nanocrystals, N,N-dimethylformamide and triethylamine are added into a three-necked flask with a condenser reflux tube, and stirred at a speed of 300 rpm / min for 20 h in an oil bath at 45°C. The crude product B is separated by centrifugation and washed with tetrahydrofuran for 3 times, and then dried under vacuum at 40°C to obtain the amphiphilic block copolymer modified cellulose nanocrystals.

[0042] Step 2, preparation of Pickering emulsion

[0043] The amphiphilic block copolymer modified cellulose nanocrystals, deionized water and vinyl monomer were mixed uniformly according to the mass ratio of 1:500:80, and at room temperature, the Pickering emulsion was obtained by ultrasonic emulsification for 5 min using an ultrasonic crusher with a total power of 1500 W at an ultrasonic power of 25%, wherein the vinyl monomer was mixed by lauryl methacrylate and methyl vanillin acrylate according to the mass ratio of 4:1;

[0044] Step 3, preparation of cellulose nanocrystal modified full-bio-based polyacrylate composite emulsion with hydrophobic, antibacterial and ultraviolet resistant functions

[0045] Step 3.1, according to 1.1% of the mass of the vinyl monomer in step 2, take ammonium sulfate and add it to deionized water to prepare a 16.7% ammonium sulfate aqueous solution;

[0046] Step 3.2, the Pickering emulsion was transferred to a three-necked flask with a condensation reflux tube and a gas inlet tube, stirred at a speed of 220 r / min, and argon was introduced into the three-necked flask for 10 min. The three-necked flask was heated to 75°C, and the ammonium sulfate aqueous solution was added dropwise into the three-necked flask, and the ammonium sulfate aqueous solution was added dropwise within 60 min. After the ammonium sulfate aqueous solution was added dropwise, it was kept at 90 min, and then cooled to room temperature to obtain a cellulose nanocrystal modified full-bio-based polyacrylate composite emulsion with hydrophobic, antibacterial and ultraviolet resistant functions.

[0047] From Figure 1 It can be seen that the peaks at 2921 cm -1 and 2855 cm -1 are attributed to the stretching vibration absorption of -CH3 and -CH2-, the peak at 1721 cm -1 is attributed to the stretching vibration absorption of ester compound -C=O and -C=O in VMA, the absorption peaks at 1593 cm -1 and 1461 cm -1 are attributed to the stretching vibration of C=C in the benzene ring skeleton of VMA, the peaks at 1262 cm -1 and 1117 cm -1 are attributed to the stretching vibration of ester group C-O-C, indicating that the cellulose nanocrystal modified full-bio-based polyacrylate composite emulsion is successfully prepared.

[0048] The cellulose nanocrystal modified full-bio-based polyacrylate composite emulsion prepared in Example 1 was placed in a silica gel mold, molded at room temperature for 48 h, dried in an oven at 80°C to remove residual moisture, and then annealed at 120°C for 30 min to obtain a latex film, which was used to test the hydrophobicity, antibacterial property and ultraviolet resistant function, respectively, and the results are shown in Figures 2 to 4 .

[0049] Referring to Figure 2 It can be seen that the water contact angle of the latex film is 125.8°, indicating that the cellulose nanocrystal modified full-bio-based polyacrylate composite emulsion prepared in Example 1 has good hydrophobicity.

[0050] Referring to Figure 3 In the first graph from the left in FIG. 8, a piece of latex film is placed on the test area of the ultraviolet sensing card, then, referring to Figure 3 In the second graph from the left in FIG. 8, the ultraviolet sensing card with the latex film placed thereon is irradiated under a 365 nm ultraviolet light source, finally, the ultraviolet light source is turned off and the latex film is removed, and the result is shown in the third graph from the left in FIG. 8. Figure 3 It can be seen that the area of the ultraviolet sensing card covered by the latex film is white, and the area not covered by the latex film is purple, indicating that the cellulose nanocrystal modified full-bio-based polyacrylate composite emulsion prepared in Example 1 has good ultraviolet resistance function.

[0051] A piece of latex film is placed in the bacterial solution of Staphylococcus aureus as a test group, and the bacterial solution of Staphylococcus aureus without the latex film is used as a control group, and the number of Staphylococcus aureus in the test group and the control group is observed after 24 h, referring to Figure 4 It can be seen that the number of Staphylococcus aureus in the test group is significantly less than that in the control group, indicating that the cellulose nanocrystal modified full-bio-based polyacrylate composite emulsion prepared in Example 1 can inhibit the growth of Staphylococcus aureus and has good antibacterial performance.

[0052] Example 2

[0053] Step 1, preparation of amphiphilic block copolymer modified cellulose nanocrystal

[0054] Step 1.1, according to the mass ratio of 15:160:4:3000, the macromolecular RAFT reagent, the vinyl monomer, the azobisisoheptane and N,N-dimethylformamide are added into a three-necked flask with a condenser reflux tube and a gas inlet tube, argon is introduced into the three-necked flask for 25 min, heated to 80℃, and mechanically stirred at a speed of 300 rpm for 7 h to obtain product A, product A is added into a beaker containing n-hexane and stirred, after precipitation, the precipitate is separated and added into another beaker containing n-hexane, and the operation is repeated for 3 times to remove the residual organic solvent, and vacuum drying is carried out at 40℃ to obtain the amphiphilic block copolymer, wherein the vinyl monomer is mixed by lauryl methacrylate and vanillin acrylate according to the mass ratio of 1:1;

[0055] Step 1.2, the amphiphilic block copolymer, cellulose nanocrystals, N,N-dimethylformamide and pyridine were taken in a mass ratio of 14:5:450:1.5 and added into a three-necked flask with a condensation reflux tube, and stirred at a speed of 200 rpm / min in an oil bath at 50°C for 30h, and the crude product B was separated by centrifugation, washed with tetrahydrofuran for 2 times, and then dried at 40°C under vacuum to obtain the amphiphilic block copolymer modified cellulose nanocrystals;

[0056] Step 2, preparation of Pickering emulsion

[0057] The amphiphilic block copolymer modified cellulose nanocrystals, deionized water and vinyl-based monomer were mixed in a mass ratio of 2:600:100, and ultrasonic emulsification was carried out for 10min at room temperature using an ultrasonic crusher with a total power of 1500W at an ultrasonic power of 20%, to obtain a Pickering emulsion, wherein the vinyl-based monomer was mixed by lauryl methacrylate and vanillin acrylate in a mass ratio of 35:13;

[0058] Step 3, preparation of cellulose nanocrystal modified full-bio-based polyacrylate composite emulsion with hydrophobic, antibacterial and ultraviolet resistant functions

[0059] Step 3.1, ammonium sulfate was taken in an amount of 1.1% of the mass of the vinyl-based monomer in step 2 and added into deionized water to prepare an ammonium sulfate aqueous solution with a mass fraction of 18%;

[0060] Step 3.2, the Pickering emulsion was transferred into a three-necked flask with a condensation reflux tube and a gas inlet tube, and stirred at a speed of 250r / min while argon was introduced into the three-necked flask for 15min, heated to 85°C, and the ammonium sulfate aqueous solution was added dropwise into the three-necked flask, and the ammonium sulfate aqueous solution was added dropwise within 90min, and after the ammonium sulfate aqueous solution was added dropwise, the temperature was kept for 100min, and then cooled to room temperature to obtain a cellulose nanocrystal modified full-bio-based polyacrylate composite emulsion with hydrophobic, antibacterial and ultraviolet resistant functions.

[0061] Example 3

[0062] Step 1, preparation of amphiphilic block copolymer modified cellulose nanocrystals

[0063] Step 1.1, the macromolecular RAFT agent, vinyl monomer, azobisisobutyronitrile and 1,4-dioxane were added into a three-necked flask with a condenser reflux tube and a gas inlet tube according to a mass ratio of 45:180:5:6800, argon was introduced into the three-necked flask for 30 min, heated to 70°C, mechanically stirred at a speed of 200 rpm for 9 h, and the product A was obtained. The product A was added into a beaker containing n-hexane and stirred, the precipitate was separated and added into another beaker containing n-hexane, and the operation was repeated for 3 times, so as to remove the residual organic solvent, and vacuum drying was performed at 40°C, thereby obtaining the amphiphilic block copolymer, wherein the vinyl monomer was prepared by mixing isobornyl acrylate and methyl vanillin acrylate according to a mass ratio of 2:5;

[0064] Step 1.2, the amphiphilic block copolymer, cellulose nanocrystal, N,N-dimethylformamide and triethylamine were added into a three-necked flask with a condenser reflux tube according to a mass ratio of 30:10:1000:2, and stirring was performed at a speed of 200 rpm for 30 h under the condition of a 50°C oil bath, and the crude product B was separated by centrifugation, washed with tetrahydrofuran for 2 times, and vacuum dried at 40°C, thereby obtaining the amphiphilic block copolymer modified cellulose nanocrystal;

[0065] Step 2, preparation of Pickering emulsion

[0066] The amphiphilic block copolymer modified cellulose nanocrystal, deionized water and vinyl monomer were uniformly mixed according to a mass ratio of 3:1000:180, and ultrasonic emulsification was performed at a total power of 1500 W at room temperature for 30 min by using an ultrasonic crusher at an ultrasonic power of 8%, thereby obtaining the Pickering emulsion, wherein the vinyl monomer was prepared by mixing isobornyl acrylate, lauryl acrylate and tetrahydrofurfuryl acrylate according to a mass ratio of 1:2:1;

[0067] Step 3, preparation of cellulose nanocrystal modified full-bio-based polyacrylate composite emulsion with hydrophobic, antibacterial and ultraviolet resistant functions

[0068] Step 3.1, potassium persulfate was prepared according to 1.5% of the mass of the vinyl monomer in step 2, and was added into deionized water to prepare a potassium persulfate aqueous solution with a mass fraction of 25%;

[0069] Step 3.2, the Pickering emulsion is transferred into a three-necked flask with a condensation reflux tube and a gas inlet tube, while stirring at a speed of 150 r / min, argon is introduced into the three-necked flask for 20 min, heated to 80℃, and the potassium persulfate aqueous solution is added dropwise into the three-necked flask, and the potassium persulfate aqueous solution needs to be added dropwise within 120 min, after the potassium persulfate aqueous solution is added dropwise, the temperature is kept for 120 min, and then cooled to room temperature, to obtain a cellulose nanocrystal modified full-bio-based polyacrylate composite emulsion with hydrophobic, antibacterial and ultraviolet resistance functions.

[0070] Example 4

[0071] Step 1, preparation of amphiphilic block copolymer modified cellulose nanocrystal

[0072] Step 1.1, according to the mass ratio of 28:165:3:4200, the macromolecular RAFT agent, the vinyl monomer, the azobisisovaleronitrile and the n-hexane are added into a three-necked flask with a condensation reflux tube and a gas inlet tube, argon is introduced into the three-necked flask for 20 min, then heated to 80℃, and the mechanical stirring is carried out at a speed of 200 rpm for 8 h to obtain product A, the product A is added into a beaker containing n-hexane and stirred, after precipitation, the precipitate is separated, then the precipitate is added into another beaker containing n-hexane, and the operation is repeated for 3 times to remove the residual organic solvent, and the product is dried under vacuum at 40℃ to obtain the amphiphilic block copolymer, wherein the vinyl monomer is mixed by lauryl acrylate, tetrahydrofurfuryl acrylate and tetrahydrofurfuryl methacrylate according to the mass ratio of 1:1:1;

[0073] Step 1.2, according to the mass ratio of 20:6.5:650:1, the amphiphilic block copolymer, the cellulose nanocrystal, the N,N-dimethylformamide and the p-toluenesulfonic acid are added into a three-necked flask with a condensation reflux tube, stirred at a speed of 300 rpm / min for 20 h under the condition of an oil bath at 55℃, and the crude product B is separated by centrifugation, washed with tetrahydrofuran for 3 times, and dried under vacuum at 40℃ to obtain the amphiphilic block copolymer modified cellulose nanocrystal.

[0074] Step 2, preparation of Pickering emulsion

[0075] According to the mass ratio of 1.5:750:145, the amphiphilic block copolymer modified cellulose nanocrystal, deionized water and vinyl monomer are uniformly mixed, and the Pickering emulsion is obtained by ultrasonic emulsification for 20 min at room temperature by using an ultrasonic crusher with a total power of 1500 W at an ultrasonic power of 10%, wherein the vinyl monomer is mixed by tetrahydrofurfuryl acrylate and tetrahydrofurfuryl methacrylate according to the mass ratio of 3:1;

[0076] Step 3, preparation of cellulose nanocrystal modified full-bio-based polyacrylate composite emulsion with hydrophobic, antibacterial and ultraviolet resistant functions

[0077] Step 3.1, according to 1.3% of the mass of the vinyl monomer in step 2, take potassium persulfate and add it to deionized water to prepare a 23% mass fraction potassium persulfate aqueous solution;

[0078] Step 3.2, transfer the Pickering emulsion to a three-necked flask with a condensation reflux tube and a gas inlet tube, stir at a speed of 220 r / min, and at the same time, pass argon into the three-necked flask for 10 min, heat to 75℃, and drop the potassium persulfate aqueous solution into the three-necked flask, and the potassium persulfate aqueous solution is dropped in 70 min, after the potassium persulfate aqueous solution is dropped, keep warm for 110 min, then cool to room temperature, to obtain cellulose nanocrystal modified full-bio-based polyacrylate composite emulsion with hydrophobic, antibacterial and ultraviolet resistant functions.

[0079] Example 5

[0080] Step 1, preparation of amphiphilic block copolymer modified cellulose nanocrystal

[0081] Step 1.1, according to the mass ratio of 36:170:5:5500, add macromolecular RAFT reagent, vinyl monomer, azobisisobutyronitrile and 1,4-dioxane into a three-necked flask with a condensation reflux tube and a gas inlet tube, pass argon into the three-necked flask for 20 min, then heat to 90℃, mechanically stir at a speed of 250 rpm for 7 h to obtain product A, add product A into a beaker containing n-hexane and stir, after precipitation, separate the precipitate, then add the precipitate into another beaker containing n-hexane, repeat 4 times to remove residual organic solvents, and vacuum dry at 40℃ to obtain the amphiphilic block copolymer, wherein the vinyl monomer is isobornyl acrylate;

[0082] Step 1.2, according to the mass ratio of 25:8:800:2, take the amphiphilic block copolymer, cellulose nanocrystal, N,N-dimethylformamide and triethylamine, and add them into a three-necked flask with a condensation reflux tube, stir at a speed of 250 rpm / min under the condition of an oil bath at 45℃ for 25 h, centrifugally separate the crude product B, wash the crude product B with tetrahydrofuran for 3 times, and vacuum dry at 40℃ to obtain the amphiphilic block copolymer modified cellulose nanocrystal;

[0083] Step 2, preparation of Pickering emulsion

[0084] The amphiphilic block copolymer modified cellulose nanocrystals, deionized water and vinyl monomer are mixed uniformly according to the mass ratio of 2.5:900:160, at room temperature, using the ultrasonic crusher with a total power of 1500W, ultrasonic emulsification is carried out for 8min at 15% ultrasonic power, to obtain a Pickering emulsion, wherein: the vinyl monomer is vanillin acrylate;

[0085] Step 3, preparation of cellulose nanocrystal modified full-bio-based polyacrylate composite emulsion with hydrophobic, antibacterial and ultraviolet resistant functions

[0086] Step 3.1, according to 0.6% of the mass of the vinyl monomer in step 2, take sodium persulfate and add it to deionized water to prepare a 20% mass fraction sodium persulfate aqueous solution;

[0087] Step 3.2, the Pickering emulsion is transferred to a three-necked flask with a condensation reflux tube and a gas inlet tube, while stirring at a speed of 180r / min, argon is introduced into the three-necked flask for 10min, heated to 85℃, and the sodium persulfate aqueous solution is added dropwise into the three-necked flask, and the sodium persulfate aqueous solution is added dropwise within 100min, after the sodium persulfate aqueous solution is added dropwise, the temperature is kept for 100min, and then cooled to room temperature, to obtain a cellulose nanocrystal modified full-bio-based polyacrylate composite emulsion with hydrophobic, antibacterial and ultraviolet resistant functions.

Claims

1. A method for preparing a cellulose nanocrystal-modified all-biobased polyacrylate composite emulsion having hydrophobic, antibacterial and anti-ultraviolet functions, characterized in that: The steps include: Step 1: Preparation of amphiphilic block copolymer modified cellulose nanocrystals Step 1.

1. Add a macromolecular RAFT agent, a vinyl monomer, an initiator I, and an organic solvent to a three-necked flask equipped with a condenser reflux tube and a gas guide tube in a mass ratio of (10-45):(150-180):(3-5):(1600-6800), introduce argon into the three-necked flask, heat to 70-90° C., and stir for 7-9 hours to obtain product A. Add product A to a beaker containing n-hexane and stir. After precipitation, separate the precipitate and vacuum dry it to obtain an amphiphilic block copolymer. The structural formula of the macromolecular RAFT agent is as follows: In the formula, R is isobutyrate or isovalerate; Z is C12 alkylthio or C11 alkylthio; R1 is -H or -CH3; R2 is -H or -CH3; m and n both represent the average degree of polymerization of glycidyl acrylate or glycidyl methacrylate, and m = 15 to 100, n = 15 to 100; Step 1.2, adding an amphiphilic block copolymer, cellulose nanocrystals, N,N-dimethylformamide, and a catalyst into a three-necked flask with a reflux tube in a mass ratio of (9-30):(3-10):(300-1000):(1-2), stirring for 20-30 hours in an oil bath at 45-55° C., centrifuging to separate a crude product B, then washing the crude product B with tetrahydrofuran to remove residual organic solvent, and then vacuum drying to obtain an amphiphilic block copolymer-modified cellulose nanocrystal; Step 2: Prepare Pickering emulsion The amphiphilic block copolymer modified cellulose nanocrystals, deionized water and vinyl monomer are uniformly mixed in a mass ratio of (1-3): (500-1000): (80-180), and ultrasonically emulsified at room temperature to obtain a Pickering emulsion; Step 3: Preparation of a cellulose nanocrystal-modified all-biobased polyacrylate composite emulsion with hydrophobic, antibacterial and anti-ultraviolet functions Step 3.1, taking initiator II according to 0.6% to 1.5% of the mass of the vinyl monomer in step 2, and adding it to deionized water to prepare an initiator II aqueous solution with a mass fraction of 16.7% to 25%; Step 3.2: Transfer the Pickering emulsion into a three-necked flask equipped with a condenser reflux tube and an air guide tube. Under argon protection, stir and heat to 75-85°C. Then, add the initiator II aqueous solution dropwise into the three-necked flask. After the addition of the initiator II aqueous solution is completed, keep warm for 90-120 minutes, and then cool to room temperature to obtain a cellulose nanocrystal-modified all-biobased polyacrylate composite emulsion with hydrophobic, antibacterial and anti-UV functions.

2. The method for preparing the cellulose nanocrystal-modified all-biobased polyacrylate composite emulsion having hydrophobic, antibacterial and anti-ultraviolet functions according to claim 1, characterized in that: The initiator I in step 1.1 is at least one of azobisisobutyronitrile, azobisisovaleronitrile and azobisisoheptanenitrile.

3. The method for preparing the cellulose nanocrystal-modified all-biobased polyacrylate composite emulsion having hydrophobic, antibacterial and anti-ultraviolet functions according to claim 1, characterized in that: The organic solvent in step 1.1 is n-hexane, 1,4-dioxane or N,N-dimethylformamide.

4. The method for preparing the cellulose nanocrystal-modified all-biobased polyacrylate composite emulsion having hydrophobic, antibacterial and anti-ultraviolet functions according to claim 1, characterized in that: The catalyst in step 1.2 is p-toluenesulfonic acid, triethylamine or pyridine.

5. The method for preparing the cellulose nanocrystal-modified all-biobased polyacrylate composite emulsion having hydrophobic, antibacterial and anti-ultraviolet functions according to claim 1, characterized in that: The vacuum drying temperature in step 1.1 and step 1.2 is 40°C.

6. The method for preparing the cellulose nanocrystal-modified all-biobased polyacrylate composite emulsion having hydrophobic, antibacterial and anti-ultraviolet functions according to claim 1, characterized in that: The vinyl monomer in step 1.1 and step 2 is at least one of isobornyl acrylate, methyl vanillin acrylate, vanillin acrylate, lauryl acrylate, tetrahydrofurfuryl acrylate, lauryl methacrylate and tetrahydrofurfuryl methacrylate.

7. The method for preparing the cellulose nanocrystal-modified all-biobased polyacrylate composite emulsion having hydrophobic, antibacterial and anti-ultraviolet functions according to claim 1, characterized in that: The ultrasonic emulsification in step 2 is performed using an ultrasonic crusher with a total power of 1500W and an ultrasonic power of 8% to 25% for 5 to 30 minutes.

8. The method for preparing the cellulose nanocrystal-modified all-biobased polyacrylate composite emulsion having hydrophobic, antibacterial and anti-ultraviolet functions according to claim 1, characterized in that: The initiator II in step 3.1 is ammonium persulfate, potassium persulfate or sodium persulfate.

9. The method for preparing the cellulose nanocrystal-modified all-biobased polyacrylate composite emulsion having hydrophobic, antibacterial and anti-ultraviolet functions according to claim 1, characterized in that: In step 3.2, the time for adding the aqueous solution of initiator II dropwise into the three-necked flask is 60 to 120 minutes.

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