Antibacterial self-repairing microcapsules for water-based coatings on wood surfaces and preparation methods

Abstract

The invention discloses an antibacterial self-repairing microcapsule for water-based coating on wood surface and a preparation method thereof. The microcapsule comprises the following raw materials: urea, formaldehyde aqueous solution, polyvinyl alcohol, triethanolamine, ethanol extract of grapefruit peel, sodium dodecylbenzene sulfonate, distilled water and sodium chloride. The invention uses urea and formaldehyde as capsule wall raw materials, adds polyvinyl alcohol to prepare modified wall materials, uses grapefruit peel extract as capsule core, prepares modified urea-formaldehyde resin-coated grapefruit peel ethanol extract microcapsules, utilizes antibacterial components such as naringin and naringenin in the grapefruit peel extract, utilizes esters such as phellodendron lactone in the grapefruit peel extract to self-heal microcracks in the coating, uses microcapsule technology to synthesize a material with integrated antibacterial self-repairing function, and applies it to water-based coating, thereby ensuring the use performance of water-based coating on the surface of wood products, and enabling the surface coating of wood materials to have low gloss, wear resistance, impact resistance and antibacterial self-repairing compatibility.

Description

Technical Field

[0001] The present invention relates to the field of coatings, and in particular to an antibacterial self-repairing integrated microcapsule of grapefruit peel ethanol extract used in water-based coatings on wood surfaces and a preparation method thereof, referred to as an antibacterial self-repairing microcapsule used in water-based coatings on wood surfaces and a preparation method thereof. Background Art

[0002] Wood furniture materials easily absorb moisture from the air during use, providing a good environment for bacterial growth. At the same time, the glucose produced by wood during degradation can easily cause wood materials to decay, mold, and insect damage. Bacteria may be transmitted indirectly through the surface coating as a carrier, so the antibacterial properties of the coating are an effective way to block indirect transmission. Pomelo peel extract contains flavonoids, terpenes, aldehydes, alcohols, esters and other compounds with antibacterial and self-repairing effects. It has excellent antibacterial properties, a wide range of sources, and is easy to extract. It has a strong antibacterial effect on Staphylococcus aureus, large intestine, dysentery and typhoid bacillus. It is a natural antibacterial agent that can effectively resist bacteria and is safe, harmless and non-irritating. Microcapsule technology is used to modify natural antibacterial agents to enhance their performance. After extensive research by domestic and foreign scholars, the use of antibacterial coatings is one of the most effective ways to reduce the density of indoor bacteria. It has good antibacterial properties and is simple to operate, and can be directly applied to home environments.

[0003] Therefore, in order to address the problem that wooden furniture materials easily absorb moisture in the air during use, causing mildew, bacteria, etc., and indirectly spread through contact with the surface coating, it is necessary to provide an antibacterial self-healing integrated microcapsule that can be used in water-based coatings on the surface of wooden materials to effectively improve the antibacterial and mechanical properties of wooden products and their coating surfaces. Summary of the invention

[0004] The purpose of the present invention is to provide an antibacterial self-repairing microcapsule for use in water-based coatings on wood surfaces and a preparation method thereof, in order to address the problem that wood furniture materials easily absorb moisture in the air during use to produce mildew, bacteria, etc., and spread the bacteria indirectly through the surface coating. The microcapsule has high-efficiency antibacterial properties, can effectively improve the antibacterial properties of wood products and their coating surfaces, and at the same time improve the mechanical properties of water-based coatings on wood surfaces.

[0005] In order to achieve the above technical objectives, the technical solution adopted by the present invention is:

[0006] The antibacterial self-repairing microcapsules used in water-based coatings on wood surfaces include the following raw materials in parts by weight:

[0007] 15 to 30 parts by weight of urea, 30 to 50 parts by weight of 37% formaldehyde aqueous solution, 0.5 to 1 parts by weight of polyvinyl alcohol, 10 to 20 parts by weight of triethanolamine, 10 to 25 parts by weight of grapefruit peel ethanol extract, 0.005 to 2 parts by weight of sodium dodecylbenzene sulfonate, 5 to 20 parts by weight of distilled water and 0.75 to 2.5 parts by weight of sodium chloride.

[0008] As a further improved preferred embodiment of the present invention, the raw materials include the following parts by weight:

[0009] 20-27 parts by weight of urea, 34-44 parts by weight of 37% formaldehyde aqueous solution, 0.6-0.9 parts by weight of polyvinyl alcohol, 12-16 parts by weight of triethanolamine, 15-22 parts by weight of grapefruit peel ethanol extract, 0.2-1.5 parts by weight of sodium dodecylbenzene sulfonate, 6-18 parts by weight of distilled water and 1-2 parts by weight of sodium chloride.

[0010] Polyvinyl alcohol can reduce the free formaldehyde content, enhance the water resistance of the water-based coating / wood material interface, reduce the brittleness of the coating, and improve toughness and stability.

[0011] NaCl can prevent microcapsule particles from agglomerating and agglomerating with each other, making the microcapsule material stronger.

[0012] In order to achieve the above technical purpose, another technical solution adopted by the present invention is:

[0013] A method for preparing antibacterial self-repairing microcapsules for use in water-based coatings on wood surfaces, comprising the following steps:

[0014] (1) extracting the dried grapefruit peel powder and ethanol in a certain ratio by water bath heating, freeze crystallizing and air drying to obtain the grapefruit peel ethanol extract;

[0015] (2) Mixing urea and formaldehyde aqueous solution, stirring thoroughly until urea is dissolved, and adjusting the pH with triethanolamine;

[0016] (3) adding polyvinyl alcohol, stirring thoroughly, placing a magnetic stirrer, stirring evenly in a constant temperature water bath to obtain a modified urea-formaldehyde prepolymer solution, and rapidly cooling to room temperature for standby use;

[0017] (4) adding sodium dodecylbenzene sulfonate to distilled water and stirring until completely dissolved to obtain an aqueous solution of sodium dodecylbenzene sulfonate as an emulsifier;

[0018] (5) heating the grapefruit peel ethanol extract in a water bath until the ethanol is completely volatilized, adding an aqueous solution of sodium dodecylbenzene sulfonate, adding a magnetic stirrer to stir, stirring and emulsifying in a water bath at a certain temperature to obtain a stable core material emulsion;

[0019] (6) The modified urea-formaldehyde resin prepolymer solution is slowly dripped into the core material emulsion at a preset speed, and citric acid crystals are added gradually. Then, NaCl powder is added, and the temperature is slowly raised to a certain temperature. Stirring and reacting are continued, and the obtained product is filtered and dried. The obtained powder is the antibacterial self-healing microcapsule used in the water-based coating on the wood surface.

[0020] As a further improved technical solution of the present invention, in step (1), the dried grapefruit peel powder and ethanol are subjected to water bath heating extraction in a ratio of 1:3, the water bath temperature is 45° C., and the reaction time is 60 min; and the grapefruit peel ethanol extract is obtained by freeze crystallization and air drying.

[0021] As a further improved technical solution of the present invention, in step (2), urea and 37% formaldehyde aqueous solution are added to a three-necked flask, stirred thoroughly until the urea is dissolved, and the pH is adjusted to 9.0 with triethanolamine.

[0022] As a further improved technical solution of the present invention, in step (3), the water bath temperature is 70°C.

[0023] As a further improved technical solution of the present invention, in step (5), the grapefruit peel ethanol extract is heated in a water bath at 60° C. until the ethanol is completely volatilized, and an aqueous solution of sodium dodecylbenzenesulfonate is added, and a magnetic stirrer is added for stirring. The mixture is stirred and emulsified in a water bath at 50° C., the stirring speed is 900 r / min, and the emulsification time is 45 min to obtain a core material emulsion.

[0024] As a further improved technical solution of the present invention, in step (6), the modified urea-formaldehyde resin prepolymer solution is slowly dripped into the core material emulsion at a speed of 350 r / min, and citric acid crystals are gradually added to adjust the pH to 2.5-3.0. Thereafter, NaCl powder is added, and the temperature is slowly raised to 65°C and continuously stirred and reacted for 2 hours. The obtained product is filtered and dried, and the obtained powder is the antibacterial self-healing microcapsule used in the water-based coating on the wood surface.

[0025] As a further improved technical solution of the present invention, in step (6), the drying temperature is 40° C. and the drying time is 24 hours.

[0026] The beneficial effects of the present invention are:

[0027] Natural antimicrobial agents are abundant in resources, highly efficient, non-toxic, pollution-free and easy to obtain. With grapefruit peel extract as the core material, it is coated by the microencapsulation method to obtain microcapsules with excellent antibacterial properties of 5-10μm. It can keep the biologically active substances of natural antimicrobial agents in their original physical state, enhance stability, reduce volatility, prolong shelf life, and also have functions such as sustained release and controlled release. Naringin and naringenin in grapefruit peel extract have good antibacterial effects, and esters such as phellodendron lactone in grapefruit peel extract can self-heal microcracks in the coating. Adding polyvinyl alcohol during the synthesis of urea-formaldehyde resin enhances the flexibility, moisture resistance and stability of the microcapsule wall material. The microcapsule reaction is carried out under acidic conditions, that is, in the acid-catalyzed prepolymer condensation process, adding NaCl can increase the ionic strength of the solution, destroy the double-layer structure formed by the prepolymer adsorbing charged ions, increase the collision opportunities between prepolymers, prevent microcapsule particles from sticking to each other and agglomerating, and make the microcapsule material stronger.

[0028] The present invention uses urea and formaldehyde as capsule wall raw materials, adds polyvinyl alcohol to prepare modified wall materials, uses grapefruit peel extract as capsule core, prepares modified urea-formaldehyde resin-coated grapefruit peel ethanol extract microcapsules, utilizes antibacterial components such as naringin and naringenin in the grapefruit peel extract, and utilizes esters such as phellodendron lactone in the grapefruit peel extract to self-heal coating microcracks, and uses microcapsule technology to synthesize materials with integrated antibacterial self-repairing functions for application in water-based coatings, thereby ensuring the use performance of water-based coatings on the surface of wood products, and enabling the surface coating of wood materials to have low gloss, wear resistance, impact resistance, and antibacterial self-repairing compatibility.

[0029] The present invention mainly uses the experiment of modifying water-based paint with microcapsules to make the coating have low gloss and wear resistance, impact resistance and antibacterial ability. The microcapsules of the present invention are added in an amount of 5-15% in the water-based paint on the surface of the wood material (the water-based paint is Dulux water-based acrylic varnish, and the wood material is basswood). After adding the microcapsules, they are coated on the surface of basswood boards (100mm×100mm×12mm). According to the national standard GB / T 4893.6-2013, the gloss of the coating film is matte, according to the national standard GB / T 4893.8-2013, the wear resistance of the coating film is grade 1 (abrasion revolution number 5000 revolutions), according to the national standard GB / T 4893.9-2013, the impact resistance is grade 2, according to the national standard GB / T 21866-2008, the antibacterial property of the paint film is detected, and according to GB / T The antibacterial property of the paint film was evaluated as Grade I or Grade II according to 21866-2008. The self-repair rate of the paint film was tested. A 8×19㎜ single-sided blade was used to scratch the surface of the test sample. The scratch width was immediately observed under a microscope and marked as H0. Five days later, the scratch width was observed again under a microscope and marked as H1. The self-repair rate was calculated as H=(H0-H1) / H0·100%. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0031] The specific embodiments of the present invention are further described below according to the accompanying drawings:

[0032] Embodiment 1:

[0033] like Figure 1 As shown, this embodiment provides an antibacterial self-repairing microcapsule for use in a water-based coating on a wood surface and a preparation method thereof, comprising the following steps:

[0034] (1) extracting dried grapefruit peel powder and ethanol in a ratio of 1:3 by heating in a water bath at 45° C. for 60 min, freeze-crystallizing and air-drying to obtain grapefruit peel ethanol extract;

[0035] (2) Add 20 g of urea and 36 g of 37% formaldehyde aqueous solution into a three-necked flask, stir thoroughly until the urea is dissolved, and adjust the pH to 9.0 with 15 g of triethanolamine;

[0036] (3) adding 0.8 g of polyvinyl alcohol, stirring thoroughly, placing in a magnetic stirrer, stirring evenly in a constant temperature water bath at 70° C. to obtain a modified urea-formaldehyde resin prepolymer solution, and rapidly cooling to room temperature for later use;

[0037] (4) adding 1 g of sodium dodecylbenzene sulfonate to 10 g of distilled water and stirring until completely dissolved to obtain an aqueous solution of sodium dodecylbenzene sulfonate as an emulsifier;

[0038] (5) heating 16 g of grapefruit peel ethanol extract in a water bath at 60° C. until the ethanol is completely volatilized, adding an aqueous solution of sodium dodecylbenzenesulfonate to the obtained grapefruit peel ethanol extract, adding a magnetic stirrer for stirring, stirring and emulsifying at a speed of 900 r / min in a water bath at 50° C. for 45 minutes to obtain a stable core material emulsion;

[0039] (6) At a speed of 350 r / min, the modified urea-formaldehyde resin prepolymer solution is slowly dripped into the core material emulsion, and citric acid crystals are added gradually. The pH value is tested with pH test paper. After the pH is adjusted to 2.5-3, 1.2 g of NaCl powder is added, and the temperature is slowly raised to 65 °C and stirred for 2 h. The obtained product is filtered and distilled water is added to wash away the excess emulsifier. Finally, the product is placed in a drying oven and heated and dried at 40 °C for 24 hours. The obtained powder is the required microcapsule.

[0040] Embodiment 2:

[0041] like Figure 1As shown, this embodiment provides an antibacterial self-repairing microcapsule for use in a water-based coating on a wood surface and a preparation method thereof, comprising the following steps:

[0042] (1) extracting dried grapefruit peel powder and ethanol in a ratio of 1:3 by heating in a water bath at 45° C. for 60 min, freeze-crystallizing and air-drying to obtain grapefruit peel ethanol extract;

[0043] (2) Add 30 g of urea and 32 g of 37% formaldehyde aqueous solution into a three-necked flask, stir thoroughly until the urea is dissolved, and adjust the pH to 9.0 with 10 g of triethanolamine;

[0044] (3) adding 0.9 g of polyvinyl alcohol, stirring thoroughly, placing in a magnetic stirrer, stirring evenly in a constant temperature water bath at 70° C. to obtain a modified urea-formaldehyde resin prepolymer solution, and rapidly cooling to room temperature for later use;

[0045] (4) adding 0.5 g of sodium dodecylbenzene sulfonate to 6 g of distilled water and stirring until completely dissolved to obtain an aqueous solution of sodium dodecylbenzene sulfonate as an emulsifier;

[0046] (5) heating 19 g of grapefruit peel ethanol extract in a water bath at 60° C. until the ethanol is completely volatilized, adding an aqueous solution of sodium dodecylbenzenesulfonate to the obtained grapefruit peel ethanol extract, adding a magnetic stirrer for stirring, stirring and emulsifying at a speed of 900 r / min in a water bath at 50° C. for 45 minutes to obtain a stable core material emulsion;

[0047] (6) At a speed of 350 r / min, the modified urea-formaldehyde resin prepolymer solution is slowly dripped into the core material emulsion, and citric acid crystals are added gradually. The pH value is tested with pH test paper. After the pH is adjusted to 2.5-3, 1.6 g of NaCl powder is added, and the temperature is slowly raised to 65°C and stirred for 2 h. The obtained product is filtered and distilled water is added to wash away the excess emulsifier. Finally, the product is placed in a drying oven and heated and dried at 40°C for 24 hours. The obtained powder is the required microcapsule.

[0048] Embodiment 3:

[0049] like Figure 1 As shown, this embodiment provides an antibacterial self-repairing microcapsule for use in a water-based coating on a wood surface and a preparation method thereof, comprising the following steps:

[0050] (1) extracting dried grapefruit peel powder and ethanol in a ratio of 1:3 by heating in a water bath at 45° C. for 60 min, freeze-crystallizing and air-drying to obtain grapefruit peel ethanol extract;

[0051] (2) Add 24 g of urea and 38 g of 37% formaldehyde aqueous solution into a three-necked flask, stir thoroughly until the urea is dissolved, and adjust the pH to 9.0 with 12 g of triethanolamine;

[0052] (3) adding 0.7 g of polyvinyl alcohol, stirring thoroughly, placing in a magnetic stirrer, stirring evenly in a constant temperature water bath at 70° C. to obtain a modified urea-formaldehyde resin prepolymer solution, and rapidly cooling to room temperature for later use;

[0053] (4) adding 0.8 g of sodium dodecylbenzene sulfonate to 5 g of distilled water and stirring until completely dissolved to obtain an aqueous solution of sodium dodecylbenzene sulfonate as an emulsifier;

[0054] (5) 18 g of grapefruit peel ethanol extract was heated in a water bath at 60° C. until the ethanol was completely volatilized, and an aqueous solution of sodium dodecylbenzene sulfonate was added to the obtained grapefruit peel ethanol extract, and a magnetic stirrer was added for stirring. The mixture was stirred and emulsified in a water bath at 50° C. at a speed of 900 r / min for 45 minutes to obtain a stable core material emulsion;

[0055] (6) At a speed of 350 r / min, slowly drip the modified urea-formaldehyde resin prepolymer solution into the core material emulsion, gradually add citric acid crystals, test the pH value with pH test paper, adjust the pH to 2.5-3, add 1.5 g NaCl powder, slowly raise the temperature to 65 °C and continue stirring for 2 h. Filter the obtained product and add distilled water to rinse off the excess emulsifier. Finally, place the product in a drying oven and heat it at 40 °C for 24 hours to obtain the desired microcapsules.

[0056] Embodiment 4:

[0057] like Figure 1 As shown, this embodiment provides an antibacterial self-repairing microcapsule for use in a water-based coating on a wood surface and a preparation method thereof, comprising the following steps:

[0058] (1) extracting dried grapefruit peel powder and ethanol in a ratio of 1:3 by heating in a water bath at 45° C. for 60 min, freeze-crystallizing and air-drying to obtain grapefruit peel ethanol extract;

[0059] (2) Add 15 g of urea and 30 g of 37% formaldehyde aqueous solution into a three-necked flask, stir thoroughly until the urea is dissolved, and adjust the pH to 9.0 with 20 g of triethanolamine;

[0060] (3) adding 0.5 g of polyvinyl alcohol, stirring thoroughly, placing in a magnetic stirrer, stirring evenly in a constant temperature water bath at 70° C. to obtain a modified urea-formaldehyde resin prepolymer solution, and rapidly cooling to room temperature for later use;

[0061] (4) adding 1.3 g of sodium dodecylbenzene sulfonate to 11 g of distilled water and stirring until completely dissolved to obtain an aqueous solution of sodium dodecylbenzene sulfonate as an emulsifier;

[0062] (5) heating 20 g of grapefruit peel ethanol extract in a water bath at 60° C. until the ethanol is completely volatilized, adding an aqueous solution of sodium dodecylbenzenesulfonate to the obtained grapefruit peel ethanol extract, adding a magnetic stirrer for stirring, stirring and emulsifying at a speed of 900 r / min in a water bath at 50° C. for 45 minutes to obtain a stable core material emulsion;

[0063] (6) At a speed of 350 r / min, the modified urea-formaldehyde resin prepolymer solution is slowly dripped into the core material emulsion, and citric acid crystals are added gradually. The pH value is tested with pH test paper. After the pH is adjusted to 2.5-3, 2.2 g of NaCl powder is added, and the temperature is slowly raised to 65°C and stirred for 2 h. The obtained product is filtered and distilled water is added to wash away the excess emulsifier. Finally, the product is placed in a drying oven and heated and dried at 40°C for 24 hours. The obtained powder is the required microcapsule.

[0064] Embodiment 5:

[0065] like Figure 1 As shown, this embodiment provides an antibacterial self-repairing microcapsule for use in a water-based coating on a wood surface and a preparation method thereof, comprising the following steps:

[0066] (1) extracting dried grapefruit peel powder and ethanol in a ratio of 1:3 by heating in a water bath at 45° C. for 60 min, freeze-crystallizing and air-drying to obtain grapefruit peel ethanol extract;

[0067] (2) Add 20 g of urea and 50 g of 37% formaldehyde aqueous solution into a three-necked flask, stir thoroughly until the urea is dissolved, and adjust the pH to 9.0 with 11 g of triethanolamine;

[0068] (3) adding 0.755 g of polyvinyl alcohol, stirring thoroughly, placing in a magnetic stirrer, stirring evenly in a constant temperature water bath at 70° C. to obtain a modified urea-formaldehyde resin prepolymer solution, and rapidly cooling to room temperature for later use;

[0069] (4) adding 0.75 g of sodium dodecylbenzene sulfonate to 6 g of distilled water and stirring until completely dissolved to obtain an aqueous solution of sodium dodecylbenzene sulfonate as an emulsifier;

[0070] (5) heating 10 g of grapefruit peel ethanol extract in a water bath at 60° C. until the ethanol is completely volatilized, adding an aqueous solution of sodium dodecylbenzenesulfonate to the obtained grapefruit peel ethanol extract, adding a magnetic stirrer for stirring, stirring and emulsifying at a speed of 900 r / min in a water bath at 50° C. for 45 minutes to obtain a stable core material emulsion;

[0071] (6) At a speed of 350 r / min, the modified urea-formaldehyde resin prepolymer solution is slowly dripped into the core material emulsion, and citric acid crystals are added gradually. The pH value is tested with pH test paper. After the pH is adjusted to 2.5-3, 1.495 g of NaCl powder is added, and the temperature is slowly raised to 65 °C and stirred for 2 h. The obtained product is filtered and distilled water is added to wash away the excess emulsifier. Finally, the product is placed in a drying oven and heated and dried at 40 °C for 24 hours. The obtained powder is the required microcapsule.

[0072] Embodiment 6:

[0073] like Figure 1 As shown, this embodiment provides an antibacterial self-repairing microcapsule for use in a water-based coating on a wood surface and a preparation method thereof, comprising the following steps:

[0074] (1) extracting dried grapefruit peel powder and ethanol in a ratio of 1:3 by heating in a water bath at 45° C. for 60 min, freeze-crystallizing and air-drying to obtain grapefruit peel ethanol extract;

[0075] (2) Add 18 g of urea and 32 g of 37% formaldehyde aqueous solution into a three-necked flask, stir thoroughly until the urea is dissolved, and adjust the pH to 9.0 with 16.245 g of triethanolamine;

[0076] (3) Add 1 g of polyvinyl alcohol, stir thoroughly, put in a magnetic stirrer, stir evenly in a constant temperature water bath at 70° C. to obtain a modified urea-formaldehyde resin prepolymer solution, and quickly cool to room temperature for use;

[0077] (4) adding 0.005 g of sodium dodecylbenzene sulfonate to 7 g of distilled water and stirring until completely dissolved to obtain an aqueous solution of sodium dodecylbenzene sulfonate as an emulsifier;

[0078] (5) heating 25 g of grapefruit peel ethanol extract in a water bath at 60° C. until the ethanol is completely volatilized, adding an aqueous solution of sodium dodecylbenzene sulfonate to the obtained grapefruit peel ethanol extract, adding a magnetic stirrer for stirring, stirring and emulsifying at a speed of 900 r / min in a water bath at 50° C. for 45 minutes to obtain a stable core material emulsion;

[0079] (6) At a speed of 350 r / min, the modified urea-formaldehyde resin prepolymer solution is slowly dripped into the core material emulsion, and citric acid crystals are added gradually. The pH value is tested with pH test paper. After the pH is adjusted to 2.5-3, 0.75 g of NaCl powder is added, and the temperature is slowly raised to 65 °C and stirred for 2 h. The obtained product is filtered and distilled water is added to wash away the excess emulsifier. Finally, the product is placed in a drying oven and heated and dried at 40 °C for 24 hours. The obtained powder is the required microcapsule.

[0080] Embodiment 7:

[0081] like Figure 1 As shown, this embodiment provides an antibacterial self-repairing microcapsule for use in a water-based coating on a wood surface and a preparation method thereof, comprising the following steps:

[0082] (1) extracting dried grapefruit peel powder and ethanol in a ratio of 1:3 by heating in a water bath at 45° C. for 60 min, freeze-crystallizing and air-drying to obtain grapefruit peel ethanol extract;

[0083] (2) Add 19 g of urea and 31 g of 37% formaldehyde aqueous solution into a three-necked flask, stir thoroughly until the urea is dissolved, and adjust the pH to 9.0 with 12.9 g of triethanolamine;

[0084] (3) adding 0.6 g of polyvinyl alcohol, stirring thoroughly, placing in a magnetic stirrer, stirring evenly in a constant temperature water bath at 70° C. to obtain a modified urea-formaldehyde resin prepolymer solution, and rapidly cooling to room temperature for later use;

[0085] (4) adding 2 g of sodium dodecylbenzene sulfonate to 20 g of distilled water and stirring until completely dissolved to obtain an aqueous solution of sodium dodecylbenzene sulfonate as an emulsifier;

[0086] (5) heating 12 g of grapefruit peel ethanol extract in a water bath at 60° C. until the ethanol is completely volatilized, adding an aqueous solution of sodium dodecylbenzene sulfonate to the obtained grapefruit peel ethanol extract, adding a magnetic stirrer for stirring, stirring and emulsifying at a speed of 900 r / min in a water bath at 50° C. for 45 minutes to obtain a stable core material emulsion;

[0087] (6) At a speed of 350 r / min, the modified urea-formaldehyde resin prepolymer solution is slowly dripped into the core material emulsion, and citric acid crystals are added gradually. The pH value is tested with pH test paper. After the pH is adjusted to 2.5-3, 2.5 g of NaCl powder is added, and the temperature is slowly raised to 65 °C and stirred for 2 h. The obtained product is filtered and distilled water is added to wash away the excess emulsifier. Finally, the product is placed in a drying oven and heated and dried at 40 °C for 24 hours. The obtained powder is the required microcapsule.

[0088] Performance Testing:

[0089] The microcapsules of Examples 1-7 were added to Dulux water-based acrylic topcoat in an amount of 5 wt %. Both the primer and the topcoat were Dulux water-based acrylic varnish. Basswood was used as the substrate and coated on the surface of a basswood board (100 mm × 100 mm × 12 mm). The process for coating the basswood board was manual brushing, with two layers of primer and two layers of topcoat applied, and the coating amount of each layer was 78 g / m 2 , the total coating weight is 312g / m 2, the coating thickness is about 80μm. Then, according to GB / T 4893.6-2013, the glossiness of the paint film was tested using a gloss meter; according to GB / T 4893.8-2013, the wear resistance of the coating film was tested using the wear resistance determination method; according to GB / T 4893.9-2013, the impact resistance of the coating film was tested using a coating impact resistance tester; according to GB / T21866-2008, the antibacterial property of the paint film was tested; using a scratch test, the self-repair rate of the paint film was tested, and compared with the water-based acrylic paint on the surface of the basswood substrate before adding microcapsules. The test results are shown in Table 1 below.

[0090] The present invention mainly uses the experiment of modifying water-based paint with microcapsules to make the coating have low gloss and wear resistance, impact resistance and antibacterial ability. The microcapsules of the present invention are added in an amount of 5-15% in the water-based paint on the surface of the wood material (the water-based paint is Dulux water-based acrylic varnish, and the wood material is basswood). After adding the microcapsules, they are coated on the surface of basswood boards (100mm×100mm×12mm). According to the national standard GB / T 4893.6-2013, the gloss of the coating film is matte, according to the national standard GB / T 4893.8-2013, the wear resistance of the coating film is grade 1 (abrasion revolution number 5000 revolutions), according to the national standard GB / T 4893.9-2013, the impact resistance is grade 2, according to the national standard GB / T 21866-2008, the antibacterial property of the paint film is detected, and according to GB / T The antibacterial property of the paint film was evaluated as Grade I or Grade II according to 21866-2008. The self-repair rate of the paint film was tested. A 8×19㎜ single-sided blade was used to scratch the surface of the test sample. The scratch width was immediately observed under a microscope and marked as H0. Five days later, the scratch width was observed again under a microscope and marked as H1. The self-repair rate was calculated as H=(H0-H1) / H0·100%.

[0091] Table 1 shows the test results:

[0092]

[0093] The protection scope of the present invention includes but is not limited to the above embodiments. The protection scope of the present invention shall be based on the claims. Any replacement, deformation, and improvement of the technology that can be easily thought of by technicians in this field shall fall within the protection scope of the present invention.

Claims

1. A method for preparing antibacterial self-repairing microcapsules for water-based coatings on wood surfaces, characterized in that: The antibacterial self-repairing microcapsules include the following raw materials in parts by weight: 15 to 30 parts by weight of urea, 30 to 50 parts by weight of 37% formaldehyde aqueous solution, 0.5 to 1 parts by weight of polyvinyl alcohol, 10 to 20 parts by weight of triethanolamine, 10 to 25 parts by weight of grapefruit peel ethanol extract, 0.005 to 2 parts by weight of sodium dodecylbenzene sulfonate, 5 to 20 parts by weight of distilled water and 0.75 to 2.5 parts by weight of sodium chloride; The preparation method of antibacterial self-repairing microcapsules comprises the following steps: (1) extracting the dried grapefruit peel powder and ethanol in a certain ratio by water bath heating, freezing, crystallizing and air-drying to obtain the grapefruit peel ethanol extract; (2) Mix urea and formaldehyde aqueous solution, stir thoroughly until urea is dissolved, and adjust the pH with triethanolamine; (3) Add polyvinyl alcohol, stir thoroughly, put in a magnetic stirrer, stir evenly in a constant temperature water bath to obtain a modified urea-formaldehyde prepolymer solution, and quickly cool to room temperature for standby use; (4) adding sodium dodecylbenzene sulfonate to distilled water and stirring until completely dissolved to obtain an aqueous solution of sodium dodecylbenzene sulfonate as an emulsifier; (5) heating the grapefruit peel ethanol extract in a water bath until the ethanol is completely volatilized, adding an aqueous solution of sodium dodecylbenzene sulfonate, adding a magnetic stirrer to stir, stirring and emulsifying in a water bath at a certain temperature to obtain a core material emulsion; (6) The modified urea-formaldehyde resin prepolymer solution is slowly dripped into the core material emulsion at a preset speed, and citric acid crystals are gradually added. Then, NaCl powder is added, and the temperature is slowly raised to a certain temperature. The mixture is continuously stirred and reacted. The obtained product is filtered and dried. The obtained powder is the antibacterial self-healing microcapsule used in the water-based coating on the wood surface.

2. The method for preparing antibacterial self-repairing microcapsules for water-based coatings on wood surfaces according to claim 1, characterized in that: The antibacterial self-repairing microcapsules include the following raw materials in parts by weight: 20-27 parts by weight of urea, 34-44 parts by weight of 37% formaldehyde aqueous solution, 0.6-0.9 parts by weight of polyvinyl alcohol, 12-16 parts by weight of triethanolamine, 15-22 parts by weight of grapefruit peel ethanol extract, 0.2-1.5 parts by weight of sodium dodecylbenzene sulfonate, 6-18 parts by weight of distilled water and 1-2 parts by weight of sodium chloride.

3. The method for preparing antibacterial self-repairing microcapsules for water-based coatings on wood surfaces according to claim 1, characterized in that: In step (1), the dried grapefruit peel powder and ethanol are subjected to water bath heating extraction in a ratio of 1:3, the water bath temperature is 45° C., and the reaction time is 60 min; and the grapefruit peel ethanol extract is obtained by freeze crystallization and air drying.

4. The method for preparing antibacterial self-repairing microcapsules for water-based coatings on wood surfaces according to claim 1, characterized in that: In step (2), urea and 37% formaldehyde aqueous solution are added into a three-necked flask, stirred thoroughly until the urea is dissolved, and the pH is adjusted to 9.0 with triethanolamine.

5. The method for preparing antibacterial self-repairing microcapsules for water-based coatings on wood surfaces according to claim 1, characterized in that: In step (3), the water bath temperature is 70°C.

6. The method for preparing antibacterial self-repairing microcapsules for water-based coatings on wood surfaces according to claim 1, characterized in that: In step (5), the grapefruit peel ethanol extract is heated in a water bath at 60° C. until the ethanol is completely volatilized, and an aqueous solution of sodium dodecylbenzene sulfonate is added, and a magnetic stirrer is added for stirring. The mixture is stirred and emulsified in a water bath at 50° C., the stirring speed is 900 r / min, and the emulsification time is 45 min to obtain a core material emulsion.

7. The method for preparing antibacterial self-repairing microcapsules for water-based coatings on wood surfaces according to claim 1, characterized in that: In step (6), the modified urea-formaldehyde resin prepolymer solution is slowly dripped into the core material emulsion at a speed of 350 r / min, and citric acid crystals are gradually added to adjust the pH to 2.5-3.

0. Then, NaCl powder is added, and the temperature is slowly raised to 65°C and continuously stirred and reacted for 2 hours. The obtained product is filtered and dried, and the obtained powder is the antibacterial self-healing microcapsule used in the water-based coating on the wood surface.

8. The method for preparing antibacterial self-repairing microcapsules for water-based coatings on wood surfaces according to claim 7, characterized in that: In step (6), the drying temperature is 40° C. and the drying time is 24 h.

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