Antibacterial emulsion as well as preparation method and application thereof
Through soy protein isolate modification and graft copolymerization reaction of acrylic coatings, combined with antibiotics, the problems of poor hydrophilicity and low solid content of antibacterial coatings were solved, and efficient antibacterial emulsion was prepared, achieving long-term efficient antibacterial effect on the surface of the instrument .
Patent Information
- Application Number
- CN202411396204.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-08
- Publication Date
- 2024-12-31
AI Technical Summary
During the use of existing antibacterial coatings, there are problems such as poor hydrophilicity, low solid content and high synthesis cost, making it difficult to effectively coat the surface of the instrument and maintain the antibacterial effect for a long time.
The soy protein isolate modification step is used to combine with acrylic coatings, and an antibacterial emulsion with good hydrophilicity and high solids content is prepared by graft copolymerization and cross-linking reaction, and antibiotics such as sulfameguanidine are added to enhance antibacterial properties.
The surface energy of the prepared antibacterial emulsion is large, with a bacterium-inhibiting rate of up to 91.72%, and the bacterium-inhibiting rate remains 90.89% after 15 days. It can be effectively coated on the surface of wood materials, significantly improving the application effect of antibacterial coatings.
Smart Images
Figure CN119219863A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of antibacterial coatings, and in particular relates to an antibacterial emulsion, a preparation method and application thereof. Background Art
[0002] Bacterial infection and spread pose a serious threat to human health. Statistics show that most human diseases are directly or indirectly related to bacteria, such as food poisoning and skin infections caused by certain bacteria. Therefore, antibacterial has attracted widespread attention. In life, there are many daily necessities with antibacterial properties, such as soap, wet wipes, textiles, etc. At present, the coating field has also begun to develop antibacterial coatings. Applying antibacterial coatings on wood products is one of the most effective ways to hinder the spread of pathogenic microorganisms. Therefore, people's demand for antibacterial coatings is increasing, especially in shipbuilding plants, wooden furniture factories, construction and other industries. Antibacterial coatings are simply a type of coating that combines an emulsion matrix with an antibacterial agent. Acrylic coatings are one of the most common matrix coatings, mainly homopolymers or copolymers synthesized by emulsion polymerization of olefin monomers containing unsaturated bonds such as acrylates and methacrylic acid. The main chain of acrylic coatings is a carbon chain, which exhibits special light, heat and chemical stability, and has properties such as good gloss, high toughness and strong adhesion.
[0003] At present, antimicrobial agents mainly include four categories: inorganic antimicrobial agents, polymer antimicrobial agents, natural antimicrobial agents, and organic antimicrobial agents. Among them, inorganic antimicrobial agents mainly include antimicrobial agents prepared from metals or ions such as silver, zinc, copper, and titanium. They are easily oxidized and discolored during use, and the antimicrobial effect will also be affected. In addition, they are expensive. Polymer antimicrobial agents are obtained by grafting small molecule antimicrobial agents into high molecular polymers. They have high chemical stability and good antimicrobial properties, but the synthesis cost of polymer antimicrobial agents is high and it is difficult to apply them on a large scale. Natural antimicrobial agents mainly come from extracts of natural substances and can be roughly divided into three categories: animal, plant, and microbial. The antimicrobial substances of natural antimicrobial agents include chitosan, catechin, curcumin, etc., but their antimicrobial effects are weak and their heat resistance is poor, which limits their development in the antimicrobial field. Therefore, how to prepare antimicrobial coatings with good solid content based on organic antimicrobial agents is an urgent problem to be solved. Summary of the invention
[0004] In view of the shortcomings of the prior art, the technical problem to be solved by the present invention is to overcome at least one of the above-mentioned shortcomings of the existing antibacterial coatings, and to propose an antibacterial emulsion with good hydrophilicity, antibacterial properties and solid content, which can be used as an antibacterial coating for coating on the surface of an appliance, and a preparation method and application thereof.
[0005] In order to solve the technical problem, the technical solution adopted by the present invention is: The present invention discloses a method for preparing an antibacterial emulsion, comprising: The soy protein isolate modification step comprises: putting the soy protein isolate into an alkaline solution, stirring in a water bath, cooling, adding nonylphenol polyoxyethylene ether and stirring, adding diacetone acrylamide and adipic anhydride while stirring and keeping the pH stable, and ultrasonically treating after the reaction is completed to obtain a modified soy protein isolate hydrosol; The reaction solution preparation step includes preparing an emulsifier solution containing sodium lauryl sulfate and alkylphenol polyoxyethylene ether, an initiator solution containing persulfate, and a reaction precursor solution containing methyl methacrylate and ethylene glycol acetoacetate; The intermediate emulsion preparation step comprises mixing the emulsifier solution, part of the initiator solution and part of the reaction precursor solution to obtain a reaction system; pre-emulsifying under stirring in a water bath until the reaction system is blue; dropping the remaining initiator solution and the reaction precursor solution into the reaction system, and after the dropping is completed, dropping the modified soy protein isolate hydrosol into the reaction system, and obtaining an intermediate emulsion after reaction; The step of preparing the product by cross-linking includes adding acrylic acid and an aqueous solution of antibiotics into the intermediate emulsion under stirring in a water bath, adjusting the pH of the system to 7-8, and obtaining an antibacterial emulsion.
[0006] Preferably, the antibiotic used in the cross-linking product preparation step is selected from sulfaguanidine; and the persulfate in the reaction solution preparation step is selected from ammonium persulfate.
[0007] Preferably, in the intermediate emulsion preparation step, part of the initiator solution and part of the reaction precursor solution account for 1 / 6-1 / 4 of the total volume of the initiator solution and the total volume of the reaction precursor solution.
[0008] Preferably, in the soy protein isolate modification step, the mass ratio of the soy protein isolate, the nonylphenol polyoxyethylene ether, the diacetone acrylamide and the adipic anhydride is 1:(0.15-0.25):(0.1-0.3):(0.05-0.15); after the soy protein isolate is put into the alkaline solution, the mass concentration of the soy protein isolate is 95-105 mg / mL.
[0009] Preferably, in the soy protein isolate modification step, the water bath stirring is a 95°C water bath and stirring at a speed of 700 rpm; the cooling is to adjust the temperature to 85°C; and the pH is kept stable by continuing to add the alkaline solution to maintain the pH at 8.0±0.2.
[0010] Preferably, in the reaction solution preparation step, the concentration of the initiator solution is 3.0-3.5 mg / mL; in the emulsifier solution, the mass ratio of the sodium dodecyl sulfate, the alkylphenol polyoxyethylene ether and water is (1.5-2.5):1:(7-8); in the reaction precursor solution, the mass ratio of the methyl methacrylate and the ethylene glycol acetoacetate is (24-36):9.
[0011] Preferably, in the intermediate emulsion preparation step, the volume ratio of the emulsifier solution, the initiator solution, the reaction precursor solution and the modified soy protein isolate hydrosol is selected from (40-50): (10-20): (35-45): (25-35).
[0012] Preferably, in the cross-linking step of preparing the product, the volume ratio of the acrylic acid, the antibiotic aqueous solution and the intermediate emulsion is (0.5-1.5):(35-45):(120-140); the concentration of the antibiotic in the antibiotic aqueous solution is selected from 7-8 wt%.
[0013] Another aspect of the present invention discloses an antibacterial emulsion prepared by the method for preparing the antibacterial emulsion described in any of the above technical solutions.
[0014] The invention also discloses the application of the antibacterial emulsion described in the technical solution in coatings.
[0015] Compared with the prior art, the present invention has the following beneficial effects: The invention discloses a method for preparing an antibacterial emulsion, which uses methyl methacrylate and ethylene glycol acetoacetate as main raw materials, adds soy protein isolate for graft copolymerization, and then adds antibiotics for cross-linking reaction. The prepared antibacterial emulsion has good hydrophilicity, antibacterial property and solid content, and can be used as an antibacterial coating for coating on the surface of a device. The present invention provides an antibacterial emulsion, which has a large surface energy and a bacteriostatic rate of up to 91.72%. After the antibacterial emulsion is placed for 15 days, the bacteriostatic rate is still 90.89%, and has a continuous bacteriostatic effect. The present invention provides the application of the antibacterial emulsion described in the above technical solution in coatings, and the surface energy of the coating can reach 72.5 mJ / m 2 , which can be better coated on the surface of wood materials where existing emulsions are difficult to use. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] Figure 1 A flow chart for preparing the SG / SPI / acrylic acid type antibacterial emulsion provided by the present invention; Figure 2The infrared spectrum of the SG / SPI / acrylic acid type antibacterial emulsion prepared in Example 1; Figure 3 is the water contact angle of the antibacterial emulsion at different SPI contents in Test Example 4; Figure 4 The antibacterial properties of the antibacterial emulsions at different sulfaguanidine contents in Test Example 5 are shown in Table 5, wherein a. contains no sulfaguanidine emulsion; b. contains 2.5 wt% sulfaguanidine emulsion; c. contains 5.0 wt% sulfaguanidine emulsion; d. contains 7.5 wt% sulfaguanidine saline; e. contains 7.5 wt% sulfaguanidine emulsion; f. contains 10.0 wt% sulfaguanidine emulsion; Figure 5 The antibacterial properties of the antibacterial emulsion under different storage time in Test Example 6. DETAILED DESCRIPTION
[0017] The technical scheme in the specific embodiment of the present invention is described in detail and completely below. Obviously, the described embodiment is only a part of the specific implementation of the overall technical scheme of the present invention, rather than all implementations. Based on the overall concept of the present invention, all other embodiments obtained by ordinary technicians in this field fall within the scope of protection of the present invention.
[0018] The present invention discloses a method for preparing an antibacterial emulsion. Figure 1 As shown, including: The soy protein isolate modification step comprises: putting the soy protein isolate into an alkaline solution, stirring in a water bath, cooling, adding nonylphenol polyoxyethylene ether and stirring, adding diacetone acrylamide and adipic anhydride while stirring and keeping the pH stable, and ultrasonically treating after the reaction is completed to obtain a modified soy protein isolate hydrosol; The reaction solution preparation step includes preparing an emulsifier solution containing sodium lauryl sulfate and alkylphenol polyoxyethylene ether, an initiator solution containing persulfate, and a reaction precursor solution containing methyl methacrylate and ethylene glycol acetoacetate; The intermediate emulsion preparation step comprises mixing the emulsifier solution, part of the initiator solution and part of the reaction precursor solution to obtain a reaction system; pre-emulsifying under stirring in a water bath until the reaction system is blue; dropping the remaining initiator solution and the reaction precursor solution into the reaction system, and after the dropping is completed, dropping the modified soy protein isolate hydrosol into the reaction system, and obtaining an intermediate emulsion after reaction; The step of preparing the product by cross-linking includes adding acrylic acid and an aqueous solution of antibiotics into the intermediate emulsion under stirring in a water bath, adjusting the pH of the system to 7-8, and obtaining an antibacterial emulsion.
[0019] Soy protein isolate (SPI) is a biological raw material that is renewable, easily degradable, and environmentally friendly. The protein content in soy protein isolate is as high as 90%, and the protein macromolecule chain contains -NH2, -OH, -COOH and -SH groups, which are hydrophilic. Under high temperature or acidic or alkaline conditions, the structure of SPI changes, and the -NH2, -OH, -COOH and -SH groups are exposed, which will react chemically with other substances under certain conditions. Acrylic antibacterial emulsion is an emulsion with an acrylic emulsion as the skeleton and antibacterial groups. In 2017, Wei Ding et al. modified polyhexamethyleneguanidine hydrochloride (PHMG) by grafting antibacterial vinyl monomer glycidyl methacrylate (GMA) to develop water-based polyacrylate with antibacterial properties, and the solid content of the emulsion was only 27 wt%; in 2022, Xiaopei Zhou used styrene as a hard monomer, butyl acrylate as a soft monomer, acrylic acid as a hydrophilic functional monomer, and methacrylate containing a thiazole structure as an antibacterial functional monomer to prepare a series of antibacterial emulsions containing thiazole structures, with an emulsion solid content of 26.47 wt% and a contact angle of 57.8°; in 2023, Wang Lijie selected 4 plant-derived natural antibacterial agents to prepare different antibacterial starch grafted styrene-acrylate emulsions, with the solid content of the emulsion ranging from 25.2-27.3 wt%, and the contact angle between 65°-75°. Most of the above-prepared acrylic antibacterial emulsions have defects such as poor hydrophilicity and low solid content, and the preparation process is complicated.
[0020] In the above-mentioned preparation method provided in the present application, methyl methacrylate and ethylene glycol acetoacetate are used as monomers, persulfate is used as an initiator, sodium dodecyl sulfate is used as an emulsifier, and water is used as a solvent. The modified SPI is used to undergo a graft copolymerization reaction with the acrylate monomer to improve the hydrophilicity of the acrylic emulsion, and then a cross-linking reaction is carried out with an antibiotic (sulfaguanidine) to prepare an acrylic emulsion with good hydrophilicity, strong antibacterial property and high solid content.
[0021] In a preferred embodiment, the antibiotic used in the cross-linking step of preparing the product is selected from sulfaguanidine; the persulfate in the reaction solution preparation step is selected from ammonium persulfate. The technical solution specifically limits the antibiotic to be selected from sulfaguanidine, because it is effective against streptococci, pneumococci, staphylococci, gonococci, meningococci, influenza bacillus, Escherichia coli, typhoid bacillus, dysentery bacillus, etc. in bacteria, but is ineffective against viruses, rickettsia, mycoplasma, spirochetes, fungi, etc. The present invention is to inhibit Escherichia coli, so the antibiotics that can inhibit Escherichia coli are within the protection scope of the present invention, such as cephalosporin antibiotics / penicillin antibiotics, etc. However, some strains of Escherichia coli may be resistant to cephalosporins or penicillins due to gene mutations or acquired resistance genes. In this case, traditional antibiotics may not be able to effectively treat infections caused by these resistant Escherichia coli. However, sulfaguanidine may still remain active against these resistant strains because it exerts its antibacterial effect by interfering with the folic acid metabolism of bacteria, which is a mechanism different from cephalosporins and penicillins. Therefore, the present invention further limits the antibiotic to be selected from sulfaguanidine.
[0022] Sulfadiazine (SG) is a highly effective antibiotic. It has a similar structure to p-aminobenzoic acid (PABA), the raw material of dihydrofolate synthase, a substance necessary for DNA synthesis. The structural formulas of SG and PABA are shown in Formula I and Formula II. SG interferes with the absorption of PABA by bacteria, thereby hindering the synthesis of bacterial DNA and affecting bacterial growth and reproduction.
[0023] In a preferred embodiment, in the intermediate emulsion preparation step, part of the initiator solution and part of the reaction precursor solution account for 1 / 6-1 / 4 of the total volume of the initiator solution and the total volume of the reaction precursor solution. Preferably, during the first mixing, the added initiator solution and the reaction precursor solution account for 1 / 5 of the total volume of the initiator solution and the total volume of the reaction precursor solution, respectively. In addition, the dripping speed of the initiator solution is 15-25 s / drop, the dripping speed of the reaction precursor is 2-8 s / drop, and the dripping speed of the SPI hydrosol is 2-8 s / drop. Further, the dripping speed of the initiator solution is 20s / drop, the dripping speed of the reaction precursor solution is 5 s / drop, and the dripping speed of the SPI hydrosol is 5 s / drop.
[0024] In a preferred embodiment, in the soy protein isolate modification step, the mass ratio of the soy protein isolate, the nonylphenol polyoxyethylene ether, the diacetone acrylamide and the adipic anhydride is 1:(0.15-0.25):(0.1-0.3):(0.05-0.15); after the soy protein isolate is put into the alkaline solution, the mass concentration of the soy protein isolate is 95-105 mg / mL. Further preferably, the mass ratio of SPI, nonylphenol polyoxyethylene ether, diacetone acrylamide and adipic anhydride is 1:0.2:0.2:0.1; after SPI is put into the alkaline solution, the mass concentration of SPI is 100 mg / mL. More preferably, the alkaline solution uses a NaOH solution with a concentration of 0.05M.
[0025] In a preferred embodiment, in the soy protein isolate modification step, the water bath stirring is a 95°C water bath and stirring at a speed of 700 rpm; the cooling is to adjust the temperature to 85°C; the pH is maintained stable by continuing to add the alkaline solution to maintain the pH at 8.0±0.2.
[0026] In a preferred embodiment, in the reaction solution configuration step, the concentration of the initiator solution is 3.0-3.5 mg / mL; in the emulsifier solution, the mass ratio of the sodium dodecyl sulfate, the alkylphenol polyoxyethylene ether and water is (1.5-2.5):1:(7-8); in the reaction precursor solution, the mass ratio of the methyl methacrylate and the ethylene glycol acetoacetate is (24-36):9. Further preferably, the concentration of the initiator solution is 3.33 mg / mL; the mass ratio of sodium dodecyl sulfate, the alkylphenol polyoxyethylene ether and water is 2:1:7.5; the mass ratio of methyl methacrylate and ethylene glycol acetoacetate is 30:9. In addition, in the reaction solution configuration step, the methyl methacrylate is washed three times with an alkaline solution and deionized water respectively before use to remove hydroquinone; wherein the alkaline solution is a NaOH solution with a concentration of 0.1M.
[0027] In a preferred embodiment, in the intermediate emulsion preparation step, the volume ratio of the emulsifier solution, the initiator solution, the reaction precursor solution and the modified soy protein isolate hydrosol is selected from (40-50): (10-20): (35-45): (25-35). Further, the volume ratio of the emulsifier solution, the initiator solution, the reaction precursor solution and the SPI aqueous solution is 45:15:40:30.
[0028] In a preferred embodiment, in the cross-linking step of preparing the product, the volume ratio of the acrylic acid, the antibiotic aqueous solution and the intermediate emulsion is (0.5-1.5):(35-45):(120-140); the concentration of the antibiotic in the antibiotic aqueous solution is selected from 7-8 wt%. Further, the volume ratio of the acrylic acid, the sulfaguanidine aqueous solution and the intermediate emulsion is 1:40:130; the concentration of sulfaguanidine in the sulfaguanidine aqueous solution is 7.5 wt%.
[0029] Another aspect of the present invention discloses an antibacterial emulsion prepared by the preparation method of the antibacterial emulsion described in any of the above technical solutions. The antibacterial emulsion prepared by the preparation method using the above limited conditions can achieve a solid content of 64.6-66.4%, an antibacterial rate of up to 90%, and the prepared coating can have a water contact angle of 12.2°, and a water absorption rate range of 12.2-13.0%, proving that the antibacterial emulsion has good hydrophilicity and water resistance, and the surface energy of the coating can reach 72.5 mJ / m 2 , indicating that the emulsion can be better coated on the surface of wood materials where existing emulsions are difficult to use.
[0030] The present invention also discloses the application of the antibacterial emulsion described in the above technical solution in coatings. Further, the present invention also discloses the application of the antibacterial emulsion described in the above technical solution in coatings for wood materials. Specifically, the antibacterial effect is achieved by coating on the surface of the material, with each coating thickness of 350-400 microns, 2-3 coatings, a total thickness of about 700-1200 microns, and a dry film thickness of about 420-720 microns.
[0031] In order to more clearly and in detail introduce the antibacterial emulsion provided by the embodiments of the present invention, its preparation method and application, the following will be described in conjunction with specific embodiments.
[0032] Example 1S1. Modification of soy protein isolate (SPI) 5 g of SPI was put into 50.0 mL of 0.05 mol / L sodium hydroxide solution, stirred in a water bath at 95 °C for 1 h, cooled to 85 °C, added with 1.0 g of nonylphenol polyoxyethylene ether and stirred for 1 h. While stirring, 1 g of diacetone acrylamide and 0.5 g of adipic anhydride were added, and 0.05 mol / L NaOH solution was used to keep the pH of the entire reaction system stable at 8.0. After the reaction was completed, ultrasonic treatment was performed at 500 W for 15 min to obtain the modified SPI hydrosol; wherein, the mass ratio of diacetone acrylamide: adipic anhydride: SPI was 0.20:0.10:1.
[0033] S2. Reaction solution preparation 1.20 g of sodium dodecyl sulfate and 0.60 g of alkylphenol polyoxyethylene ether were added into 45.0 mL of water to prepare an emulsifier solution, 0.05 g of ammonium persulfate was dissolved in 15.0 mL of water to prepare an initiator solution, 30.0 g of methyl methacrylate and 9.00 g of ethylene glycol acetoacetate were mixed to prepare a reaction precursor.
[0034] S3. Preparation of intermediate emulsion The emulsifier solution, 1 / 5 of the initiator solution and 1 / 5 of the reaction precursor are mixed, and pre-emulsified for 15 min under stirring in a water bath until the system turns blue, and the remaining initiator solution, the reaction precursor and the SPI hydrosol prepared in step S1 are added dropwise to the system at a certain addition rate to obtain an intermediate emulsion after reaction; Among them, the initiator dropping rate is controlled at 20 s / drop, and the monomer is controlled at 5 s / drop. After the monomer and initiator are added, 3.00 g of modified soy protein isolate hydrosol is added using a constant pressure dropping funnel. The soy protein isolate hydrosol is added to the emulsion at a speed of 5 s / drop to participate in the graft copolymerization reaction to obtain a SPI / acrylic acid type emulsion, which is milky white.
[0035] S4. Cross-linking preparation product 1.0 mL of acrylic acid and 3.0 g of sulfaguanidine aqueous solution were added to the intermediate emulsion prepared in step S3 under stirring in a water bath, and the pH of the system was adjusted to 7-8 to obtain a SG / SPI / acrylic acid type antibacterial emulsion.
[0036] During the preparation process, the reactions involved are as follows:
[0037] Wherein, formula III is the preparation formula of the intermediate emulsion, and formula IV is the preparation formula of the SG / SPI / acrylic acid type antibacterial emulsion.
[0038] In step S1, the mass ratio of SPI, nonylphenol polyoxyethylene ether, diacetone acrylamide and adipic anhydride is 1:0.2:0.2:0.1; after SPI is added to the alkaline solution, the mass concentration of SPI is 100 mg / mL. More preferably, the alkaline solution is a NaOH solution with a concentration of 0.05M.
[0039] In step S2, the mass concentration of the initiator solution is 3.33 mg / mL.
[0040] In step S4, the volume ratio of acrylic acid, sulfaguanidine aqueous solution and intermediate emulsion is 1:40:130; the concentration of sulfaguanidine in the sulfaguanidine aqueous solution is 7.5 wt%.
[0041] The product obtained in this example was characterized by structure. Figure 2As shown in the infrared spectrum, 3320 cm -1 The peaks are the stretching vibration peaks of -OH and -NH, 1670 cm -1 Infrared absorption of -NH2 at 1530 cm -1 The infrared absorption of -COOH at 3316 cm -1 -CH stretching vibration on the benzene ring, 1621 cm -1 are aromatic -C=N resonance vibration peaks, which are characteristic peaks of SG; at 1670 cm -1 The amide I band (-C=O stretching vibration peak) and 1540 cm -1 The peaks are amide II bands (-NH bending vibration and -CN stretching vibration), which confirm that soy protein isolate and sulfaguanidine have been successfully grafted onto polyacrylate.
[0042] The dried coating was immersed in deionized water for 48 h, and the initial mass was recorded as m 1 , after immersion in water, the mass is m 2 , calculate the water absorption rate. Three parallel experiments were carried out for each emulsion sample, and the average value of the results was taken. The water absorption rate of the emulsion was calculated according to formula (5): Water absorption rate = (5) m 1 is the amount of coating after drying, g; m 2 It is the mass of the coating after being immersed in water for 48 hours, g.
[0043] Table 1 shows the water absorption of the latex coating film in water after drying. The average water absorption rate of the latex after drying is 12.4%, and the coating film has strong water resistance.
[0044] Table 1 Water absorption test
[0045] The difference between Comparative Example 1 and Example 1 is that unmodified soy protein isolate is used.
[0046] The difference between Comparative Example 2 and Example 1 is that sulfaguanidine is not used.
[0047] The hydrophilicity, antibacterial property and solid content of the emulsions prepared in Example 1 and Comparative Examples 1-2 are compared. The results are shown in Table 2.
[0048] Table 2 Related performance results of Example 1 and Comparative Examples 1-2
[0049] In addition, the following test examples of the present invention also explore the influence of different experimental conditions on the results.
[0050] Test Example 1: Effect of reaction time on emulsion solid content Take 30.00 g of methyl methacrylate and 9.00 g of ethylene glycol acetoacetate as raw materials, use 0.05 g of ammonium persulfate as initiator, add 3.00 g of SPI hydrosol for graft copolymerization, and then add 3.00 g of sulfaguanidine for cross-linking reaction. The reaction temperature is 90 ° C. The optimal reaction time of the emulsion is determined by the solid content of the emulsion. The solid content of the emulsion is tested after 2 h, 4 h, 6 h, and 8 h of reaction under the same conditions. In order to reduce the experimental error, three parallel experiments are carried out.
[0051] The results are shown in Table 3. When the reaction time is 8 h, the solid content of the emulsion is the highest, which is 60.90%. However, when the reaction time is 6 h, the solid content of the emulsion is 59.61%, which is not much different from 8 h. In order to save energy, the optimal reaction time for emulsion synthesis is 6 h.
[0052] Table 3 Effect of reaction time of acrylic acid, sulfaguanidine aqueous solution and intermediate emulsion in step S4 on solid content of emulsion
[0053] Among them, the method for determining the solid content is as follows: Weigh 5.00 g of the emulsion sample on an electronic balance. m b In a dry beaker, after removing water and forming a film in an oven at 110°C, the total mass of the beaker and the film was measured after cooling. m a Each emulsion sample was measured 3 times, and the average value was taken. The solid content of the emulsion was calculated according to formula (1): Solid content = (1) in, m b is the mass of the beaker, g; m a is the total mass of beaker and coating, g.
[0054] Test Example 2: Effect of reaction temperature on emulsion solid content Take 30.00 g of methyl methacrylate and 9.00 g of ethylene glycol acetoacetate as raw materials, use 0.02 g of ammonium persulfate as initiator, add 3.00 g of SPI for graft copolymerization, and then add 3.00 g of sulfaguanidine for cross-linking reaction. The reaction time is 6 h. The optimal reaction temperature of the emulsion is determined based on the solid content of the emulsion. In order to reduce the error, three parallel experiments are carried out.
[0055] The results are shown in Table 4. When the reaction temperature is 95°C, the solid content of the emulsion is the highest, which is 61.77%. However, when the reaction temperature is 85°C, the solid content of the emulsion is 60.74%, which is not much different from 95°C. Compared with the increase in solid content, in order to save energy, the optimal reaction temperature of the emulsion reaction is selected as 85°C.
[0056] Table 4 Effect of reaction temperature of acrylic acid, sulfaguanidine aqueous solution and intermediate emulsion on emulsion solid content
[0057] Test Example 3: Effect of the amount of initiator on the solid content of the emulsion Take 30.00 g of methyl methacrylate and 9.00 g of ethylene glycol acetoacetate as raw materials, add 3.00 g of SPI for graft copolymerization, and then add 3.00 g of sulfaguanidine for cross-linking copolymerization. The reaction temperature is 85°C and the reaction time is 6 h. The solid content of the emulsion is used as an indicator to determine the optimal amount of initiator required for the emulsion reaction. In order to reduce the error, three parallel experiments are carried out.
[0058] The results are shown in Table 5. When the amount of initiator is 0.08 g, the solid content of the emulsion is the highest, which is 60.79%. However, when the amount of initiator is 0.05 g, the solid content of the emulsion is 60.74%, which is not much different from the initiator amount of 0.08 g. Compared with the increase in solid content, in order to save reagents, the optimal initiator amount of the emulsion reaction is selected as 0.05 g.
[0059] Table 5 Effect of initiator on emulsion solid content
[0060] Test Example 4: Water contact angle at different SPI addition amounts In step S3 of Example 1, the SPI dosage is set as shown in Table 6, and the contact angle and surface energy of water and diiodomethane are measured. The measured parameters are shown in Table 6. Table 6 Contact angles and surface energies of soy protein isolate emulsion coatings with different weight fractions in water and diiodomethane
[0061] In the table, the contact angle determination method is as follows: apply the prepared emulsion on a glass slide with a brush, dry it in an oven at a suitable temperature, keep the surface of the dried emulsion smooth and flat, and then use a contact angle meter to test the contact angle of the substance. Use water and diiodomethane as the medium to test the contact angle of SG / SPI / acrylic emulsions with different weight fractions of soy protein isolate, and take the average of the three results.
[0062] The surface energy is calculated using the Owens two-liquid method:
[0063] In the formula , and They are the surface energy, dispersion force and polar force of the solid; , and It is the surface energy, dispersion force and polar force of the liquid.
[0064] The two liquids used in this experiment are distilled water and diiodomethane. Their related parameters are shown in Table 7. The dispersion force and polar force of the two liquids can be obtained from Table 7. The surface energy of the two liquids can be calculated by formula (3), and then substituted into formula (4) together with the contact angle generated by the two liquids. The two sets of equations and two unknowns are solved to obtain the dispersion force and polar force of the solid, and then the surface energy of the coating is calculated by formula (2).
[0065] Table 7 Dispersion force and polarity force of distilled water and diiodomethane
[0066] The measured value of the contact angle can intuitively reflect the hydrophilicity and hydrophobicity of the material. Figure 3 The contact angles of SG / SPI / acrylic emulsion coatings containing different weight fractions of soy protein isolate and water medium. The contact angles and surface energy values of the emulsion coatings for water and diiodomethane at different SPI addition amounts are shown in Table 5. From Table 5, it can be seen that with the increase in the amount of SPI added, the contact angle of the coating with water gradually decreases from 41.1° to 10.1°, indicating that the hydrophilicity of the emulsion increases, and the surface energy of the coating increases from 48.32 mJ / m2 to 72.50 mJ / m2. The increase in surface energy indicates that the emulsion can be better coated on wooden materials.
[0067] Test Example 5 The emulsion without sulfaguanidine was used as the blank control group, and the antibacterial ability of the emulsion containing 2.5 wt% sulfaguanidine, the emulsion containing 5.0 wt% sulfaguanidine, the emulsion containing 7.5 wt% sulfaguanidine, the saline containing 7.5 wt% sulfaguanidine and the emulsion containing 10.00 wt% sulfaguanidine was tested for 24 h. To reduce the experimental error, three parallel experiments were performed for each group of experiments. The test results are shown in Figure 2. Figure 4 shown. Figure 4The data of the antibacterial rate of each sample are shown in Table 1, where a. does not contain sulfaguanidine emulsion; b. contains 2.5 wt% sulfaguanidine emulsion; c. contains 5.0 wt% sulfaguanidine emulsion; d. contains 7.5 wt% sulfaguanidine saline; e. contains 7.5 wt% sulfaguanidine emulsion; f. contains 10.0 wt% sulfaguanidine emulsion. Analysis shows that the antibacterial performance of the emulsion containing the same weight fraction of sulfaguanidine is better than that of saline, indicating that the antibacterial effect of the emulsion and sulfaguanidine is synergistic; the emulsion containing 7.5 wt% sulfaguanidine has the best antibacterial effect, with an antibacterial rate of 91.72%; the emulsion containing 10.00 wt% sulfaguanidine has an antibacterial rate of 90.34%. When the amount of sulfaguanidine in the emulsion reaches 10.00 wt%, the compatibility of sulfaguanidine with the emulsion becomes worse, and the antibacterial rate of the emulsion decreases.
[0068] Test Example 6 In order to test the antibacterial durability of the emulsion, the emulsion prepared in Example 1 was placed in the air for 3 days, 6 days, 9 days, 12 days and 15 days, and the emulsions exposed to the air for different lengths were taken out and the antibacterial rates of the emulsions were tested respectively.
[0069] The measured results are as follows Figure 5 As shown, when the emulsion was placed in the air for 3 days, 6 days, 9 days, 12 days and 15 days, the antibacterial rate of the emulsion changed from 91.72% to 90.89%, which was basically the same, indicating that the emulsion has a sustained antibacterial effect.
Claims
1. A method for preparing an antibacterial emulsion, characterized in that: include: The soy protein isolate modification step comprises: putting the soy protein isolate into an alkaline solution, stirring in a water bath, cooling, adding nonylphenol polyoxyethylene ether and stirring, adding diacetone acrylamide and adipic anhydride while stirring and keeping the pH stable, and ultrasonically treating after the reaction is completed to obtain a modified soy protein isolate hydrosol; The reaction solution preparation step includes preparing an emulsifier solution containing sodium lauryl sulfate and alkylphenol polyoxyethylene ether, an initiator solution containing persulfate, and a reaction precursor solution containing methyl methacrylate and ethylene glycol acetoacetate; The intermediate emulsion preparation step comprises mixing the emulsifier solution, part of the initiator solution and part of the reaction precursor solution to obtain a reaction system; pre-emulsifying under stirring in a water bath until the reaction system is blue; dropping the remaining initiator solution and the reaction precursor solution into the reaction system, and after the dropping is completed, dropping the modified soy protein isolate hydrosol into the reaction system, and obtaining an intermediate emulsion after reaction; The step of preparing the product by cross-linking includes adding acrylic acid and an aqueous solution of antibiotics into the intermediate emulsion under stirring in a water bath, adjusting the pH of the system to 7-8, and obtaining an antibacterial emulsion.
2. The method for preparing the antibacterial emulsion according to claim 1, characterized in that: The antibiotic used in the cross-linking product preparation step is selected from sulfaguanidine; the persulfate in the reaction solution preparation step is selected from ammonium persulfate.
3. The method for preparing the antibacterial emulsion according to claim 1, characterized in that: In the intermediate emulsion preparation step, part of the initiator solution and part of the reaction precursor solution account for 1 / 6-1 / 4 of the total volume of the initiator solution and the total volume of the reaction precursor solution.
4. The method for preparing the antibacterial emulsion according to claim 1, characterized in that: In the soy protein isolate modification step, the mass ratio of the soy protein isolate, the nonylphenol polyoxyethylene ether, the diacetone acrylamide and the adipic anhydride is 1:(0.15-0.25):(0.1-0.3):(0.05-0.15); after the soy protein isolate is put into the alkaline solution, the mass concentration of the soy protein isolate is 95-105 mg / mL.
5. The method for preparing the antibacterial emulsion according to claim 1, characterized in that: In the soy protein isolate modification step, the water bath stirring is a 95° C. water bath and stirring at a speed of 700 rpm; the cooling is to adjust the temperature to 85° C.; the pH is maintained stable by continuing to add the alkaline solution to maintain the pH at 8.0±0.
2.
6. The method for preparing the antibacterial emulsion according to claim 1, characterized in that: In the reaction solution preparation step, the concentration of the initiator solution is 3.0-3.5 mg / mL; in the emulsifier solution, the mass ratio of the sodium dodecyl sulfate, the alkylphenol polyoxyethylene ether and water is (1.5-2.5):1:(7-8); in the reaction precursor solution, the mass ratio of the methyl methacrylate and the ethylene glycol acetoacetate is (24-36):
9.
7. The method for preparing the antibacterial emulsion according to claim 1, characterized in that: In the intermediate emulsion preparation step, the volume ratio of the emulsifier solution, the initiator solution, the reaction precursor solution and the modified soy protein isolate hydrosol is selected from (40-50): (10-20): (35-45): (25-35).
8. The method for preparing the antibacterial emulsion according to claim 1, characterized in that: In the cross-linking product preparation step, the volume ratio of the acrylic acid, the antibiotic aqueous solution and the intermediate emulsion is (0.5-1.5):(35-45):(120-140); the concentration of the antibiotic in the antibiotic aqueous solution is selected from 7-8 wt%.
9. The antibacterial emulsion prepared according to the method for preparing the antibacterial emulsion according to any one of claims 1 to 8.
10. Use of the antibacterial emulsion according to claim 9 in coatings.