Antibacterial urea resin and preparation method thereof

Abstract

The present invention relates to the field of resin technology, and more specifically to an antibacterial urea resin and a method for preparing the same. The present invention involves modifying chitosan using dimethylaminoethyl chloride hydrochloride as a quaternizing agent, followed by oxidation with potassium periodate to obtain quaternized oxidized chitosan. This quaternized oxidized chitosan is then reacted with urea and formaldehyde as a crosslinking agent to produce an antibacterial urea resin. The antibacterial urea resin prepared by the present invention has a high solids content and viscosity, a moderate curing time, excellent antibacterial properties, and an extremely low free formaldehyde content, resulting in excellent environmental protection and safety.

Description

Technical Field

[0001] The present invention relates to the technical field of resins, in particular to an antibacterial urea resin and a preparation method thereof. Background Art

[0002] Urea resin is an important thermosetting resin. Due to its low cost, excellent performance and mature process, it is widely used in plywood, furniture manufacturing, decorative materials and other fields. However, traditional urea resin has the problem of high free formaldehyde content. It releases formaldehyde during use, causing serious harm to the environment and human health, and it is difficult to meet increasingly stringent environmental protection standards. In addition, urea resin itself does not have antibacterial properties and is prone to breeding bacteria and mold in humid environments, affecting the service life and hygienic performance of the product, further limiting its application in fields with high environmental protection and high hygiene requirements. With the increasingly stringent environmental regulations and people's concern for health and safety, the development of urea resin with low formaldehyde emission and antibacterial properties has become a hot topic and difficulty in current research.

[0003] Chitosan, a widely available natural polysaccharide, has attracted widespread attention due to its excellent biocompatibility, antimicrobial properties, and environmental friendliness. The introduction of chitosan can impart antimicrobial properties to urea resins and improve their environmental performance. However, chitosan has poor dispersibility in urea resins and lacks sufficient bonding to the urea resin network, resulting in limited modification effectiveness. Summary of the Invention

[0004] In view of this, the object of the present invention is to provide an antibacterial urea resin and a preparation method thereof, so as to solve the problems of high formaldehyde emission and lack of antibacterial performance of urea resin.

[0005] Based on the above purpose, the present invention provides a method for preparing an antibacterial urea resin, comprising the following steps:

[0006] (1) chitosan is added to an N-methyl-2-pyrrolidone solution containing 0.8 wt%-1.2 wt% acetic acid, stirred for 20-40 min, then sodium iodide is added, the temperature is raised to 55-65°C, stirred for 20-40 min, then dimethylaminoethyl chloride hydrochloride is added, the stirring reaction is continued for 2.5-3.5 h, and finally washed and dried under reduced pressure to obtain quaternized chitosan;

[0007] (2) adding quaternized chitosan to deionized water, adjusting the pH to 3.5-4.5 with acetic acid solution, then adding potassium periodate, stirring and reacting at room temperature in the dark for 3-5 hours, adding anhydrous ethanol to stop the reaction, finally washing, and drying under reduced pressure to obtain quaternized oxidized chitosan;

[0008] (3) adding quaternized chitosan oxide to a 37 wt% formaldehyde solution, adding deionized water, adjusting the pH to 10.5-11.5 with sodium hydroxide solution, then adding urea, heating to 75-85° C., stirring and reacting for 50-70 minutes, and cooling to obtain a prepolymer solution;

[0009] (4) The pH of the prepolymer solution is adjusted to 8-9 with formic acid solution, a formaldehyde solution with a concentration of 37 wt% and urea are added, the temperature is raised to 55-65°C, and the mixture is stirred and reacted for 25-35 minutes. The pH is then adjusted to 4.8-5.5 with formic acid solution, quaternized oxidized chitosan and urea are added, the temperature is raised to 75-85°C, the mixture is stirred and reacted for 50-70 minutes, the temperature is then lowered to 55-65°C, urea is added, and the mixture is stirred for 20-40 minutes. The pH is adjusted to 7.9-8.3 with sodium hydroxide solution, and the mixture is cooled to room temperature to obtain an antibacterial urea resin.

[0010] Preferably, the weight ratio of chitosan, sodium iodide and dimethylaminoethyl chloride hydrochloride in step (1) is 5-15:20-60:2-8.

[0011] Preferably, the amount of N-methyl-2-pyrrolidone solution used in step (1) is 8-12 times the weight of chitosan.

[0012] Preferably, in step (2), the weight ratio of quaternized chitosan to potassium periodate is 5-15:2-5.

[0013] Preferably, in step (2), the amount of deionized water used is 40-60 times the weight of the quaternized chitosan, and the amount of anhydrous ethanol used is 1.5-3 times the weight of the deionized water.

[0014] Preferably, the concentration of the acetic acid solution in step (2) is 5 wt%-15 wt%.

[0015] Preferably, the concentration of the sodium hydroxide solution in step (3) and step (4) is 25wt%-35wt%.

[0016] Preferably, in step (3), the weight ratio of quaternized oxidized chitosan, formaldehyde solution, deionized water and urea is 1-3:15-25:22-38:12-21.

[0017] Preferably, in step (4), the weight ratio of the prepolymer solution, the formaldehyde solution, the quaternized oxidized chitosan and the urea is 50-90:58-98:6-10:35-55.

[0018] Preferably, the concentration of the formic acid solution in step (4) is 45wt%-55wt%

[0019] Preferably, in step (4), the weight ratio of urea added in sequence is 15-25:15-25:5.

[0020] Furthermore, the present invention also provides an antibacterial urea resin obtained by the above-mentioned preparation method of the antibacterial urea resin.

[0021] Beneficial effects of the present invention:

[0022] The present invention significantly improves the comprehensive performance of urea resin by introducing oxidized quaternized chitosan, including higher solid content and viscosity, moderate curing time and excellent antibacterial properties, while significantly reducing the free formaldehyde content. The environmental performance and safety of the resin are significantly improved, meeting more stringent environmental protection requirements. The plywood prepared using the antibacterial urea resin has a bonding strength of more than 1MPa, meeting the national requirements for the use of Class II plywood, and the formaldehyde emission is as low as 0.5mg / L, significantly reducing the harm to human health and indoor air quality, meeting green environmental protection standards, and is suitable for fields with high environmental protection requirements such as interior decoration and furniture manufacturing.

[0023] The oxidized quaternized chitosan provided by the present invention forms crosslinking sites through its active aldehyde groups, which are crosslinked in the urea resin network, thereby improving the dispersibility and cohesion of the chitosan in the resin, significantly improving the adhesive strength of the resin, and reducing the amount of formaldehyde used, reducing the free formaldehyde content and formaldehyde release. In addition, the batch addition of the quaternized oxidized chitosan effectively avoids the excessive reaction of urea with the aldehyde groups, preventing the chitosan from agglomerating to form insoluble aggregates, thereby further reducing the free formaldehyde content and improving the antibacterial and adhesive properties of the resin.

[0024] In summary, the present invention not only significantly improves the basic properties of urea resin by optimizing the formula and process, but also gives it excellent antibacterial properties and environmental protection characteristics. The prepared plywood has the characteristics of high strength and low formaldehyde emission, is suitable for a variety of application scenarios with high environmental protection requirements, and has broad market prospects. DETAILED DESCRIPTION

[0025] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to specific embodiments.

[0026] Example 1:

[0027] (1) 5 g of chitosan was added to 40 g of N-methyl-2-pyrrolidone solution containing 0.8 wt% acetic acid, stirred for 20 min, then 20 g of sodium iodide was added, the temperature was raised to 55°C, stirred for 20 min, then 2 g of dimethylaminochloroethane hydrochloride was added, and the stirring reaction was continued for 2.5 h. Finally, the chitosan was washed with anhydrous ethanol 3 times and acetone 3 times, and dried under reduced pressure to obtain quaternized chitosan.

[0028] (2) 5 g of quaternized chitosan was added to 200 g of deionized water, and the pH was adjusted to 4.4 with a 5 wt% acetic acid solution. 2 g of potassium periodate was then added, and the mixture was stirred and reacted for 3 h at room temperature in the dark. 300 g of anhydrous ethanol was added to stop the reaction, and the mixture was washed with deionized water 3 times and anhydrous ethanol 3 times, and dried under reduced pressure to obtain quaternized oxidized chitosan.

[0029] (3) 1 g of quaternized chitosan oxide was added to 15 g of a 37 wt% formaldehyde solution, 22 g of deionized water was added, the pH was adjusted to 10.5 with a 25 wt% sodium hydroxide solution, and 12 g of urea was added. The mixture was heated to 75° C., stirred for 50 min, and cooled to obtain a prepolymer solution.

[0030] (4) The pH of 50 g of the prepolymer solution was adjusted to 8.1 with a 45 wt % formic acid solution, 58 g of a 37 wt % formaldehyde solution and 15 g of urea were added, the temperature was raised to 55°C, and the mixture was stirred for 20 min. The pH was then adjusted to 3.5 with a 50 wt % formic acid solution, 6 g of quaternized oxidized chitosan and 15 g of urea were added, the temperature was raised to 75°C, the mixture was stirred for 50 min, the temperature was then lowered to 55°C, 5 g of urea was added, and the mixture was stirred for 20 min. The pH was adjusted to 7.9 with a 20 wt % sodium hydroxide solution, and the mixture was cooled to room temperature to obtain an antibacterial urea resin.

[0031] Example 2:

[0032] (1) 10 g of chitosan was added to 100 g of N-methyl-2-pyrrolidone solution containing 1 wt% acetic acid, stirred for 30 min, then 40 g of sodium iodide was added, the temperature was raised to 60°C, stirred for 30 min, then 4.5 g of dimethylaminoethyl chloride hydrochloride was added, and the stirring reaction was continued for 3 h. Finally, the mixture was washed with anhydrous ethanol 3 times and acetone 3 times, and dried under reduced pressure to obtain quaternized chitosan;

[0033] (2) 10 g of quaternized chitosan was added to 500 g of deionized water, and the pH was adjusted to 4.0 with a 10 wt% acetic acid solution. 3 g of potassium periodate was then added, and the mixture was stirred and reacted at room temperature in the dark for 4 h. 1000 g of anhydrous ethanol was added to stop the reaction. The mixture was washed with deionized water 3 times and anhydrous ethanol 3 times, and dried under reduced pressure to obtain quaternized oxidized chitosan.

[0034] (3) 2 g of quaternized chitosan oxide was added to 20 g of a 37 wt % formaldehyde solution, 30 g of deionized water was added, the pH was adjusted to 11 with a 30 wt % sodium hydroxide solution, and 15 g of urea was added. The temperature was raised to 80° C., stirred for 60 min, and cooled to obtain a prepolymer solution.

[0035] (4) The pH value of 70 g of the prepolymer solution was adjusted to 8.5 with a 50 wt % formic acid solution, 75 g of a 37 wt % formaldehyde solution and 20 g of urea were added, the temperature was raised to 60°C, and the mixture was stirred for reaction for 30 min. The pH value was then adjusted to 5.2 with a 50 wt % formic acid solution, 8 g of quaternized oxidized chitosan and 20 g of urea were added, the temperature was raised to 80°C, the mixture was stirred for reaction for 60 min, the temperature was then lowered to 60°C, 5 g of urea was added, and the mixture was stirred for 30 min. The pH value was adjusted to 8.1 with a 30 wt % sodium hydroxide solution, and the mixture was cooled to room temperature to obtain an antibacterial urea resin.

[0036] Example 3:

[0037] (1) 15 g of chitosan was added to 180 g of N-methyl-2-pyrrolidone solution containing 1.2 wt% acetic acid, stirred for 40 min, then 60 g of sodium iodide was added, the temperature was raised to 65°C, stirred for 40 min, then 8 g of dimethylaminoethyl chloride hydrochloride was added, and the stirring reaction was continued for 4 h. Finally, the chitosan was washed with anhydrous ethanol 3 times and acetone 3 times, and dried under reduced pressure to obtain quaternized chitosan;

[0038] (2) 15 g of quaternized chitosan was added to 900 g of deionized water, and the pH was adjusted to 4.5 with a 15 wt% acetic acid solution. 5 g of potassium periodate was then added, and the mixture was stirred and reacted at room temperature in the dark for 5 h. 2700 g of anhydrous ethanol was added to stop the reaction. The mixture was washed with deionized water three times and anhydrous ethanol three times, and dried under reduced pressure to obtain quaternized oxidized chitosan.

[0039] (3) 3 g of quaternized chitosan oxide was added to 25 g of a 37 wt % formaldehyde solution, 38 g of deionized water was added, the pH was adjusted to 11.4 with a 35 wt % sodium hydroxide solution, and 21 g of urea was added. The temperature was raised to 85° C., stirred for 70 min, and cooled to obtain a prepolymer solution.

[0040] (4) The pH value of 90 g of the prepolymer solution was adjusted to 8.5 with a 55 wt % formic acid solution, 98 g of a 37 wt % formaldehyde solution and 25 g of urea were added, the temperature was raised to 65° C., and the mixture was stirred for 40 min. The pH value was then adjusted to 5.5 with a 50 wt % formic acid solution, 10 g of quaternized oxidized chitosan and 25 g of urea were added, the temperature was raised to 85° C., the mixture was stirred for 70 min, the temperature was then lowered to 65° C., 5 g of urea was added, and the mixture was stirred for 40 min. The pH value was adjusted to 8.3 with a 35 wt % sodium hydroxide solution, and the mixture was cooled to room temperature to obtain an antibacterial urea resin.

[0041] Comparative Example 1:

[0042] The difference between Comparative Example 1 and Example 2 is that the quaternized oxidized chitosan in step (3) and step (4) is replaced by quaternized chitosan;

[0043] The specific steps are as follows:

[0044] (1) 10 g of chitosan was added to 100 g of N-methyl-2-pyrrolidone solution containing 1 wt% acetic acid, stirred for 30 min, then 40 g of sodium iodide was added, the temperature was raised to 60°C, stirred for 30 min, then 4.5 g of dimethylaminoethyl chloride hydrochloride was added, and the stirring reaction was continued for 3 h. Finally, the mixture was washed with anhydrous ethanol 3 times and acetone 3 times, and dried under reduced pressure to obtain quaternized chitosan;

[0045] (2) 2 g of quaternized chitosan was added to 20 g of a 37 wt % formaldehyde solution, 30 g of deionized water was added, the pH was adjusted to 11 with a 30 wt % sodium hydroxide solution, 15 g of urea was added, the temperature was raised to 80° C., the mixture was stirred for 60 min, and the temperature was lowered to obtain a prepolymer solution;

[0046] (3) The pH of 70 g of the prepolymer solution was adjusted to 8.5 with a 50 wt % formic acid solution, 75 g of a 37 wt % formaldehyde solution and 20 g of urea were added, the temperature was raised to 60° C., and the mixture was stirred for reaction for 30 min. The pH was then adjusted to 5.2 with a 50 wt % formic acid solution, 8 g of quaternized chitosan and 20 g of urea were added, the temperature was raised to 80° C., the mixture was stirred for reaction for 60 min, the temperature was then lowered to 60° C., 5 g of urea was added, and the mixture was stirred for 30 min. The pH was adjusted to 8.1 with a 30 wt % sodium hydroxide solution, and the mixture was cooled to room temperature to obtain a urea resin.

[0047] Comparative Example 2:

[0048] The difference between Comparative Example 2 and Example 2 is that the amount of quaternized oxidized chitosan used in step (3) is 10 g, and quaternized oxidized chitosan is not added in step (4);

[0049] The specific steps are as follows:

[0050] (1) 10 g of chitosan was added to 100 g of N-methyl-2-pyrrolidone solution containing 1 wt% acetic acid, stirred for 30 min, then 40 g of sodium iodide was added, the temperature was raised to 60°C, stirred for 30 min, then 4.5 g of dimethylaminoethyl chloride hydrochloride was added, and the stirring reaction was continued for 3 h. Finally, the mixture was washed with anhydrous ethanol 3 times and acetone 3 times, and dried under reduced pressure to obtain quaternized chitosan;

[0051] (2) 10 g of quaternized chitosan was added to 500 g of deionized water, and the pH was adjusted to 4.0 with a 10 wt% acetic acid solution. 3 g of potassium periodate was then added, and the mixture was stirred and reacted at room temperature in the dark for 4 h. 1000 g of anhydrous ethanol was added to stop the reaction. The mixture was washed with deionized water 3 times and anhydrous ethanol 3 times, and dried under reduced pressure to obtain quaternized oxidized chitosan.

[0052] (3) 10 g of quaternized chitosan oxide was added to 20 g of a 37 wt % formaldehyde solution, 30 g of deionized water was added, the pH was adjusted to 11 with a 30 wt % sodium hydroxide solution, and 15 g of urea was added. The temperature was raised to 80° C., stirred for 60 min, and cooled to obtain a prepolymer solution.

[0053] (4) The pH of 70 g of the prepolymer solution was adjusted to 8.5 with a 50 wt % formic acid solution, 75 g of a 37 wt % formaldehyde solution and 20 g of urea were added, the temperature was raised to 60° C., and the mixture was stirred for reaction for 30 min. The pH was then adjusted to 5.2 with a 50 wt % formic acid solution, 20 g of urea was added, the temperature was raised to 80° C., and the mixture was stirred for reaction for 60 min. The temperature was then lowered to 60° C., 5 g of urea was added, and the mixture was stirred for 30 min. The pH was adjusted to 8.1 with a 30 wt % sodium hydroxide solution, and the temperature was lowered to room temperature to obtain a urea resin.

[0054] Comparative Example 3:

[0055] The difference between Comparative Example 3 and Example 2 is that the amount of quaternized oxidized chitosan used in step (4) is 10 g, and quaternized oxidized chitosan is not added in step (3);

[0056] The specific steps are as follows:

[0057] (1) 10 g of chitosan was added to 100 g of N-methyl-2-pyrrolidone solution containing 1 wt% acetic acid, stirred for 30 min, then 40 g of sodium iodide was added, the temperature was raised to 60°C, stirred for 30 min, then 4.5 g of dimethylaminoethyl chloride hydrochloride was added, and the stirring reaction was continued for 3 h. Finally, the mixture was washed with anhydrous ethanol 3 times and acetone 3 times, and dried under reduced pressure to obtain quaternized chitosan;

[0058] (2) 10 g of quaternized chitosan was added to 500 g of deionized water, and the pH was adjusted to 4.0 with a 10 wt% acetic acid solution. 3 g of potassium periodate was then added, and the mixture was stirred and reacted at room temperature in the dark for 4 h. 1000 g of anhydrous ethanol was added to stop the reaction. The mixture was washed with deionized water 3 times and anhydrous ethanol 3 times, and dried under reduced pressure to obtain quaternized oxidized chitosan.

[0059] (3) 20 g of 37 wt% formaldehyde solution and 30 g of deionized water were mixed, the pH was adjusted to 11 with 30 wt% sodium hydroxide solution, and then 15 g of urea was added. The temperature was raised to 80° C., stirred for 60 min, and cooled to obtain a prepolymer solution.

[0060] (4) The pH of 70 g of the prepolymer solution was adjusted to 8.5 with a 50 wt % formic acid solution, 75 g of a 37 wt % formaldehyde solution and 20 g of urea were added, the temperature was raised to 60° C., and the mixture was stirred for reaction for 30 min. The pH was then adjusted to 5.2 with a 50 wt % formic acid solution, 10 g of quaternized oxidized chitosan and 20 g of urea were added, the temperature was raised to 80° C., the mixture was stirred for reaction for 60 min, the temperature was then lowered to 60° C., 5 g of urea was added, and the mixture was stirred for 30 min. The pH was adjusted to 8.1 with a 30 wt % sodium hydroxide solution, and the mixture was cooled to room temperature to obtain a urea resin.

[0061] Comparative Example 4:

[0062] The difference between Comparative Example 4 and Example 2 is that: quaternized oxidized chitosan is not added in step (3) and step (4);

[0063] The specific steps are as follows:

[0064] (1) 10 g of chitosan was added to 100 g of N-methyl-2-pyrrolidone solution containing 1 wt% acetic acid, stirred for 30 min, then 40 g of sodium iodide was added, the temperature was raised to 60°C, stirred for 30 min, then 4.5 g of dimethylaminoethyl chloride hydrochloride was added, and the stirring reaction was continued for 3 h. Finally, the mixture was washed with anhydrous ethanol 3 times and acetone 3 times, and dried under reduced pressure to obtain quaternized chitosan;

[0065] (2) 10 g of quaternized chitosan was added to 500 g of deionized water, and the pH was adjusted to 4.0 with a 10 wt% acetic acid solution. 3 g of potassium periodate was then added, and the mixture was stirred and reacted at room temperature in the dark for 4 h. 1000 g of anhydrous ethanol was added to stop the reaction. The mixture was washed with deionized water 3 times and anhydrous ethanol 3 times, and dried under reduced pressure to obtain quaternized oxidized chitosan.

[0066] (3) 20 g of 37 wt% formaldehyde solution and 30 g of deionized water were mixed, the pH was adjusted to 11 with 30 wt% sodium hydroxide solution, and then 15 g of urea was added. The temperature was raised to 80° C., stirred for 60 min, and cooled to obtain a prepolymer solution.

[0067] (4) The pH of 70 g of the prepolymer solution was adjusted to 8.5 with a 50 wt % formic acid solution, 75 g of a 37 wt % formaldehyde solution and 20 g of urea were added, the temperature was raised to 60° C., and the mixture was stirred for reaction for 30 min. The pH was then adjusted to 5.2 with a 50 wt % formic acid solution, 20 g of urea was added, the temperature was raised to 80° C., and the mixture was stirred for reaction for 60 min. The temperature was then lowered to 60° C., 5 g of urea was added, and the mixture was stirred for 30 min. The pH was adjusted to 8.1 with a 30 wt % sodium hydroxide solution, and the temperature was lowered to room temperature to obtain a urea resin.

[0068] Performance testing:

[0069] Basic performance tests: solid content, viscosity, curing time, and free formaldehyde content were tested according to GB / T14074-2006 standard. The results are shown in Table 1.

[0070] Preparation of plywood: The urea resin prepared in the examples and comparative examples was used as the main adhesive, 1% of the resin mass of ammonium chloride was added as a curing agent, and 20% of flour was added as a filler to prepare the adhesive. The adhesive was applied manually, and the core board was double-sided with a glue amount of 300g / m 2 After gluing, aging and assembly, the veneer is hot pressed at a temperature of 120°C. The prepared plywood is placed in a constant temperature and humidity environment at a temperature of 20±2°C and a humidity of 65±2% for one week before the plywood performance is measured.

[0071] Plywood bonding strength and formaldehyde emission test: The test is carried out according to GB / T17657-2013 standard, and the bonding strength is tested according to the standard method for Class II plywood.

[0072] Antibacterial performance test: Separate the plywood layers and add 8×10 5 4 ml of Escherichia coli solution with a concentration of cfu / mL was prepared, and a blank control plate was used as a control. The culture time was transferred to a constant temperature and humidity chamber, the temperature was controlled at 38°C, and the relative humidity was 95%. The antibacterial rate was calculated by the plate count method. The results are shown in Table 1.

[0073] Table 1 Performance test results

[0074]

[0075] Data Analysis:

[0076] As can be seen from the data of Examples 1-3 in Table 1, the antimicrobial urea resin prepared by the present invention has a high solids content and viscosity, a moderate curing time, and excellent antimicrobial properties. Most importantly, it has an extremely low free formaldehyde content, which helps reduce environmental pollution, improve the product's environmental performance, enhance safety, and meet more stringent environmental protection requirements. Plywood prepared using this antimicrobial urea resin has a bonding strength of over 1 MPa, meeting the use requirements of Class II plywood in national standards. Furthermore, the formaldehyde emission is as low as 0.5 mg / L. This extremely low formaldehyde emission significantly reduces harm to human health and indoor air quality, meeting green environmental protection standards and making it suitable for use in environmentally demanding applications such as interior decoration and furniture manufacturing.

[0077] From the data of Example 2 and Comparative Example 1 in Table 1, it can be seen that the oxidized quaternized chitosan helps to increase the solid content and viscosity of the antibacterial urea resin and can further improve the antibacterial performance. This is mainly because the oxidized quaternized chitosan has active aldehyde groups, which can form cross-linking sites and cross-link in the urea resin network, thereby effectively improving the dispersion of the quaternized chitosan in the urea resin, thereby improving the overall performance of the urea resin, and the cross-linked quaternized chitosan can provide higher cohesion, so that the plywood prepared therefrom has higher bonding strength. Furthermore, the active aldehyde groups of the oxidized quaternized chitosan can effectively reduce the amount of formaldehyde used, thereby reducing the free formaldehyde content and reducing the formaldehyde release of the plywood.

[0078] It can be seen from the data of Example 2 and Comparative Examples 2-3 in Table 1 that the batchwise addition of quaternized oxidized chitosan can effectively improve the comprehensive properties of the antibacterial urea resin, especially the antibacterial properties and the free formaldehyde content. This is mainly because the batchwise addition of quaternized oxidized chitosan helps to avoid excessively rapid reaction between urea and aldehyde groups, which leads to agglomeration of the quaternized oxidized chitosan, thereby forming insoluble agglomerates, resulting in the presence of a large amount of free formaldehyde in the agglomerates, which is difficult to react with urea, thereby leading to an increase in the free formaldehyde content. In addition, after being prepared into plywood, the adhesive properties decrease and the formaldehyde release increases.

[0079] From the data of Example 2 and Comparative Example 4 in Table 1, it can be seen that quaternized oxidized chitosan can effectively optimize the basic properties of urea resin and impart it with strong antibacterial properties, and reduce formaldehyde emission while improving bonding strength.

[0080] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present invention is limited to these examples. Within the scope of the present invention, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity.

Claims

1. A method for preparing an antibacterial urea resin, characterized in that: The following steps are involved: (1) chitosan is added to an N-methyl-2-pyrrolidone solution containing 0.8 wt%-1.2 wt% acetic acid, stirred for 20-40 min, then sodium iodide is added, the temperature is raised to 55-65°C, stirred for 20-40 min, then dimethylaminoethyl chloride hydrochloride is added, the stirring reaction is continued for 2.5-3.5 h, and finally washed and dried under reduced pressure to obtain quaternized chitosan; (2) adding quaternized chitosan to deionized water, adjusting the pH to 3.5-4.5 with acetic acid solution, then adding potassium periodate, stirring and reacting at room temperature in the dark for 3-5 hours, adding anhydrous ethanol to stop the reaction, finally washing, and drying under reduced pressure to obtain quaternized oxidized chitosan; (3) adding quaternized chitosan oxide to a 37 wt% formaldehyde solution, adding deionized water, adjusting the pH to 10.5-11.5 with sodium hydroxide solution, then adding urea, heating to 75-85° C., stirring and reacting for 50-70 minutes, and cooling to obtain a prepolymer solution; (4) adjusting the pH of the prepolymer solution to 8-9 with a formic acid solution, adding a 37 wt% formaldehyde solution and urea, heating to 55-65° C., stirring and reacting for 25-35 minutes, then adjusting the pH to 4.8-5.5 with a formic acid solution, adding quaternized oxidized chitosan and urea, heating to 75-85° C., stirring and reacting for 50-70 minutes, then cooling to 55-65° C., adding urea, stirring for 20-40 minutes, adjusting the pH to 7.9-8.3 with a sodium hydroxide solution, and cooling to room temperature to obtain an antibacterial urea resin; In the step (1), the weight ratio of chitosan, sodium iodide and dimethylaminoethyl chloride hydrochloride is 5-15:20-60:2-8; In the step (3), the weight ratio of quaternized oxidized chitosan, formaldehyde solution, deionized water and urea is 1-3:15-25:22-38:12-21; In the step (4), the weight ratio of the prepolymer solution, the formaldehyde solution, the quaternized oxidized chitosan and the urea is 50-90:58-98:6-10:35-55.

2. The method for preparing the antibacterial urea resin according to claim 1, wherein The amount of N-methyl-2-pyrrolidone solution used in step (1) is 8-12 times the weight of chitosan.

3. The method for preparing the antibacterial urea resin according to claim 1, wherein In the step (2), the weight ratio of quaternized chitosan to potassium periodate is 5-15:2-5.

4. The method for preparing the antibacterial urea resin according to claim 1, wherein In the step (2), the amount of deionized water used is 40-60 times the weight of the quaternized chitosan, and the amount of anhydrous ethanol used is 1.5-3 times the weight of the deionized water.

5. The method for preparing the antibacterial urea resin according to claim 1, wherein The concentration of the acetic acid solution in step (2) is 5 wt%-15 wt%.

6. The method for preparing the antibacterial urea resin according to claim 1, wherein The concentration of the sodium hydroxide solution in step (3) and step (4) is 25 wt%-35 wt%.

7. The method for preparing the antibacterial urea resin according to claim 1, wherein The concentration of the formic acid solution in step (4) is 45 wt%-55 wt%.

8. The method for preparing the antibacterial urea resin according to claim 1, wherein In the step (4), the weight ratio of urea added in sequence is 15-25:15-25:

5.

9. An antibacterial urea resin, characterized in that The antibacterial urea resin is obtained by the preparation method of any one of claims 1 to 8.

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