Microcapsule-coated wood mildew preventive based on plant source extract and preparation method of microcapsule-coated wood mildew preventive

Abstract

The invention relates to the technical field of wood mildewproof agents, in particular to a microcapsule-coated wood mildewproof agent based on plant source extracts and a preparation method of the microcapsule-coated wood mildewproof agent. According to the preparation method, various medicaments such as chitosan, glacial acetic acid, span80 and glutaraldehyde react with a plant source extract to prepare the wood mildew preventive which can endow wood with hydrophobicity, mildew resistance, thermal stability and the like at the same time, the wood mildew preventive combines a conventional plant source mildew preventive with a microcapsule technology, the efficient and environment-friendly characteristics of the plant source mildew preventive are reserved, and meanwhile, the wood mildew preventive has a good application prospect. And the problems of poor stability and short timeliness of natural extracts are solved, so that the mildew preventive can efficiently and stably play a role in a long-acting manner in an environment-friendly manner, and the lasting mildew prevention effect on wood is successfully achieved. The agent is wide in raw material source, low in price and simple to prepare, and can be used for mildew-proof treatment of wood structure buildings.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wood mildew inhibitor, in particular to a wood mildew inhibitor based on plant extract microcapsule coating and its preparation method. BACKGROUND

[0002] As the main fast-growing timber tree species in southern China, Pinus massoniana is widely used in construction, furniture, pulp and papermaking due to its light and soft texture and easy processing. However, it is easily infected by mold due to the internal abundance of starch and sugar substances, leading to mold and blue stain of wood, which seriously restricts its service life and economic value. Although traditional mildew inhibitors can inhibit bacteria, they have problems such as high toxicity and environmental residues. Although the existing plant source mildew inhibitor is natural and environmentally friendly, it is difficult to meet the long-term protection needs due to its poor stability and short time limit. Therefore, it is of great significance to develop an environmentally friendly, efficient and long-lasting plant source mildew inhibitor for the green and sustainable use of Pinus massoniana.

[0003] So far, some of the traditional mildew and blue stain prevention agents and methods that have been developed have some adverse effects on the human body and the environment, some have high processing costs and are not suitable for widespread promotion, or have negative effects on the physical and mechanical properties of wood. Therefore, it is particularly important to explore environmentally friendly, efficient and low-cost mildew and blue stain prevention agents.

[0004] New mildew inhibitors prepared from plant extracts have received more and more attention and research in recent years. Compared with traditional mildew inhibitors, wood mildew inhibitors prepared from plant extracts are made from natural plants, which are environmentally friendly and pollution-free, improving the safety of the environment and human and animal use. This kind of mildew inhibitor has greater development potential and wider application prospects than ordinary mildew inhibitors due to its characteristics. Radix Draconis is also known as Xianxiefei and Xiashantiger, which was first recorded in Bencao Tujing. It is a semi-woody evergreen plant of the Rutaceae family. Its pharmacological effects include dispersing blood stasis, stopping bleeding, relieving swelling and pain, and anti-inflammatory and analgesic effects. This plant has varying degrees of antibacterial properties and can be used to prepare environmentally friendly and pollution-free natural plant extract mildew inhibitors.

[0005] In order to improve the anti-loss performance and durability of the plant extract antifungal agent, the plant extract is made into nano microcapsule preparation. Microcapsule is a kind of micro container or micro packaging material composed of core and wall material. Through microcapsule technology, the physical form of core material can be controlled, the components can be separated and the target controlled release can be achieved. The wall material system mainly includes three categories: natural, semi-synthetic and synthetic. Among these materials, natural polymers are concerned due to their superior biocompatibility, easy availability of raw materials and environmental friendliness. Chitosan is a biological macromolecule, as a natural polysaccharide polymer, its global reserves are abundant, and it has many excellent properties. Chitosan is used as a wall material, and the extract selected by the method of combining microcapsule technology with plant source antifungal agent is microencapsulated, so that the plant source antifungal agent with excellent thermal stability is prepared, and the long-acting plant source antifungal agent is realized, which lays a foundation for promoting the development and utilization of long-acting plant source antifungal agent. SUMMARY

[0006] In order to solve the above technical problems existing in the prior art, the present application provides a kind of wood antifungal agent based on plant source extract microcapsule and its preparation method, as follows: A kind of wood antifungal agent based on plant source extract microcapsule and its preparation method, comprising the following steps: (1) take acetic acid 1.5-5 parts, 92-98 parts, chitosan 0.5-3 parts, and dragon blood extract 0.1-2 parts by volume fraction;Mix acetic acid, chitosan and distilled water evenly; (2) mix the dragon blood extract with the acetic acid chitosan solution and stand by; (3) take the oil phase (liquid paraffin) with the water phase (acetic acid chitosan solution of dragon blood extract) in the proportion of (5:1) ~ (11:1), then add surfactant Span 80 to the oil phase (liquid paraffin), control the reaction temperature at 30-60 ℃, keep the stirring speed at 600-1000 rpm, and get the emulsifier;The liquid paraffin is the external phase of water-in-oil emulsion, the water phase is dispersed in the form of small droplets, the viscosity of the oil phase affects the shear force of the emulsification process and the particle size distribution of the final microcapsule, but it is chemically inert and does not participate in the crosslinking reaction of chitosan, which can be removed by washing finally; (4) add the prepared dragon blood chitosan acetic acid solution of step (2) to the emulsifier prepared in step (3), and then add the crosslinking agent after the solution is fully dispersed; (5) after the reaction is completed, the solution is centrifuged, the precipitate is washed with petroleum ether and anhydrous ethanol respectively, and then the sample is vacuum dried to obtain the product.

[0007] Further, the step (1) is that the volume ratio of each raw material is 3 parts of acetic acid, 97 parts of distilled water, 1 part of chitosan and 0.28 parts of the extract of Aspidistra elatior.

[0008] Further, the step (2) is that the acetic acid, the chitosan and the distilled water are uniformly mixed and then placed in a 4 ℃ environment for standing.

[0009] Further, the extract of Aspidistra elatior is obtained by extracting the leaves of Aspidistra elatior, and the extract is sealed and stored in the dark before use to reduce the volatilization of active ingredients as much as possible. The extract has various bacteriostatic effects, and the natural and efficient bacteriostatic effect helps to improve the mildew resistance of wood.

[0010] Further, the configuration sequence in the step (1) is that the distilled water is added first, then the acetic acid is added, the chitosan is added after uniform stirring, and the solution is placed in a refrigerator for standing after complete dissolution.

[0011] Further, the configuration sequence in the step (2) is that the extract of Aspidistra elatior is added to the acetic acid chitosan solution to uniformly disperse the extract in the acetic acid chitosan solution.

[0012] Further, the configuration sequence in the step (3) is that the emulsifier is configured and stirred, the extract of Aspidistra elatior acetic acid chitosan solution is added while stirring after 15 min of stirring, and the crosslinking agent is finally added after complete dispersion of the solution.

[0013] Chitosan is a natural high molecular compound, and has spectrum antibacterial and mildew resistance activity. As the wall material of the microcapsule, chitosan can enhance the effect of the extract of Aspidistra elatior and has a good coating effect on the extract of Aspidistra elatior. Without affecting the bacteriostatic effect of the extract, the chitosan can not only release the bacteriostatic effect of the extract, but also enhance the stability of the extract.

[0014] Further, the step (3) is that 0.2-4 parts of 25% glutaraldehyde are added for reaction for 1-5 h. Preferably, 0.99 parts of 25% glutaraldehyde are added for reaction for 3 h. The glutaraldehyde as the crosslinking agent can harden and dissolve the wall material, and the crosslinking significantly improves the mechanical stability of the microcapsule, so that the microcapsule can withstand physical stress in the process of processing, storage and use, and the amount of the glutaraldehyde greatly affects the compactness of the wall material, that is, the release speed of the core material of the microcapsule.

[0015] The wood mildew inhibitor coated with the microcapsule based on the plant extract is prepared by the preparation method of the wood mildew inhibitor coated with the microcapsule based on the plant extract.

[0016] Compared with the prior art, the technical effects of the application are embodied in the following aspects. 1.The present application uses natural and environmentally friendly materials as raw materials, uses plant source antifungal agent as core material, and uses chitosan as wall material, so that the prepared antifungal agent has high efficiency and environmental protection of the plant source antifungal agent, and improves the stability and slow release performance; 2.The prepared microcapsule particle size can effectively penetrate the key internal structure (pits, tracheids) of the wood of Pinus massoniana, and realize deep antifungal from the surface to the inside; 3.The present application provides good antifungal performance while strictly maintaining the original chemical composition of the wood, maintaining the natural nature and original performance of the wood, avoiding the adverse chemical influence on the wood matrix, forming a hydrophobic covering layer on the surface of the wood treated by the present application, improving the hydrophobic performance of the wood surface, and helping to reduce the moisture intrusion, thereby enhancing the wood antifungal effect; 4.The whole system of the present application is based on natural renewable materials, is environmentally friendly, has high biocompatibility and biodegradability, and meets the green chemistry and sustainable development trend. DETAILED DESCRIPTION

[0017] The technical solutions of the present application will be further limited in combination with specific implementation manners, but the scope of protection is not limited to the description.

[0018] Example 1 (1) Take 0.15 mL of acetic acid, 4.85 mL of distilled water, and then add 0.05 g of chitosan, mix uniformly, and then put into a 4 DEG C refrigerator for standby; (2) Take 11 mg of extract of Dracaena cochinchinensis and mix with the chitosan acetic acid solution, and then stand by; (3) In a three-necked flask, add liquid paraffin in a proportion of 5:1 of oil phase (liquid paraffin) to water phase (chitosan acetic acid solution), and then add 0.5 mL of surfactant Span 80, control the reaction temperature to be 30 DEG C, and keep the stirring speed to be 600 rpm for 10 min; (4) Add the prepared chitosan acetic acid solution of Dracaena cochinchinensis into the three-necked flask, after the solution is fully dispersed, add 0.1 mL of 25% volume fraction of glutaraldehyde for 1 h reaction; (5) After the reaction is completed, the solution is centrifuged, the precipitate is washed with petroleum ether and anhydrous ethanol respectively, and then the sample is vacuum dried to obtain the product.

[0019] Example 2 (1) Take 0.075 mL of acetic acid, 4.925 mL of distilled water, and then add 0.1 g of chitosan, mix uniformly, and then put into a 4 DEG C refrigerator for standby; (2) Take 13 mg of extract of Dracaena cochinchinensis and mix with the chitosan acetic acid solution, and then stand by; (3) In a three-necked flask, liquid paraffin was added in the proportion of 7:1 of oil phase (liquid paraffin) to water phase (chitosan acetate solution), and then 0.5 mL of surfactant Span 80 was added. The reaction temperature was controlled at 40 ℃, and the stirring speed was kept at 700 rpm for 20 min; (4) The prepared solution of Asclepiadaceae L. chitosan acetate was added to the three-necked flask, and after the solution was fully dispersed, 0.2 mL of 25% glutaraldehyde was added for 2 h of reaction; (5) After the reaction was completed, the solution was centrifuged, and the precipitate was washed with petroleum ether and anhydrous ethanol, respectively. The sample was vacuum dried to obtain the product.

[0020] Example 3 (1) 0.25 mL of acetic acid, 4.75 mL of distilled water, and 0.025 g of chitosan were mixed and placed in a 4 ℃ refrigerator for standby; (2) 14 mg of Asclepiadaceae L. extract was mixed with the chitosan acetate solution and left to stand; (3) In a three-necked flask, liquid paraffin was added in the proportion of 9:1 of oil phase (liquid paraffin) to water phase (chitosan acetate solution), and then 2 mL of surfactant Span 80 was added. The reaction temperature was controlled at 50 ℃, and the stirring speed was kept at 900 rpm for 15 min; (4) The prepared solution of Asclepiadaceae L. chitosan acetate was added to the three-necked flask, and after the solution was fully dispersed, 1 mL of 25% glutaraldehyde was added for 3 h of reaction; (5) After the reaction was completed, the solution was centrifuged, and the precipitate was washed with petroleum ether and anhydrous ethanol, respectively. The sample was vacuum dried to obtain the product.

[0021] Example 4 (1) 0.15 mL of acetic acid, 4.85 mL of distilled water, and 0.05 g of chitosan were mixed and placed in a 4 ℃ refrigerator for standby; (2) 14 mg of Asclepiadaceae L. extract was mixed with the chitosan acetate solution and left to stand; (3) In a three-necked flask, liquid paraffin was added in the proportion of 9:1 of oil phase (liquid paraffin) to water phase (chitosan acetate solution), and then 0.5 mL of surfactant Span 80 was added. The reaction temperature was controlled at 60 ℃, and the stirring speed was kept at 800 rpm for 15 min; (4) The prepared solution of Asclepiadaceae L. chitosan acetate was added to the three-necked flask, and after the solution was fully dispersed, 0.5 mL of 25% glutaraldehyde was added for 3 h of reaction; (5) After the reaction, the solution was centrifuged, the precipitate was washed with petroleum ether and anhydrous ethanol, and the sample was vacuum dried to obtain the product.

[0022] Example 5 (1) Take 0.1 mL of acetic acid, 4.9 mL of distilled water, and then add 0.075 g of chitosan. Mix well and place in a 4°C refrigerator for standby; (2) Take 17 mg of extract of Aspidistra elatior and mix with the chitosan acetate solution, and then stand by; (3) In a three-necked flask, add liquid paraffin in a ratio of 11:1 of oil phase (liquid paraffin) to water phase (chitosan acetate solution), and then add 2.5 mL of surfactant Span 80. Control the reaction temperature at 60°C, and keep the stirring speed at 1000 rpm for 25 min; (4) Add the prepared chitosan acetate solution of Aspidistra elatior to the three-necked flask. After the solution is fully dispersed, add 2 mL of 25% glutaraldehyde by volume fraction for 5 h reaction; (5) After the reaction, the solution was centrifuged, the precipitate was washed with petroleum ether and anhydrous ethanol, and the sample was vacuum dried to obtain the product.

[0023] Comparative Example 1 (1) Take 0.4 mL of acetic acid, 4.6 mL of distilled water, and then add 0.005 g of chitosan. Mix well and place in a 4°C refrigerator for standby; (2) Take 7 mg of extract of Aspidistra elatior and mix with the chitosan acetate solution, and then stand by; (3) In a three-necked flask, add liquid paraffin in a ratio of 3:1 of oil phase (liquid paraffin) to water phase (chitosan acetate solution), and then add 0.5 mL of surfactant Span 80. Control the reaction temperature at 20°C, and keep the stirring speed at 600 rpm for 5 min; (4) Add the prepared chitosan acetate solution of Aspidistra elatior to the three-necked flask. After the solution is fully dispersed, add 0.1 mL of 25% glutaraldehyde by volume fraction for 1 h reaction; (5) The solution formed by the reaction is milky white, and the crosslinking reaction fails, so the experiment cannot continue.

[0024] Comparative Example 2 (1) Take 0.1 mL of acetic acid, 4.9 mL of distilled water, and then add 0.075 g of chitosan. Mix well and place in a 4°C refrigerator for standby; (2) Take 4 mg of extract of Aspidistra elatior and mix with the chitosan acetate solution, and then stand by; (3) In a three-necked flask, liquid paraffin was added in the proportion of 13:1 of oil phase (liquid paraffin) to water phase (chitosan acetate solution), then 5 mL of surfactant Span 80 was added, the reaction temperature was controlled at 80 ℃, and the stirring speed was kept at 1000 rpm for 10 min; (4) The prepared solution of Asclepiadaceae Loddigesii chitosan acetate was added to the three-necked flask, and after the solution was fully dispersed, 5 mL of 25% glutaraldehyde was added for 2 h of reaction; (5) After the reaction was completed, the solution was centrifuged, the precipitate was washed with petroleum ether and anhydrous ethanol respectively, and then the sample was vacuum dried to obtain the product.

[0025] Comparative Example 3 (1) Acetic acid 0.5 mL, distilled water 4.5 mL, and chitosan 0.25 g were mixed and placed in a 4 ℃ refrigerator for standby; (2) Asclepiadaceae Loddigesii extract 25 mg was mixed with the chitosan acetate solution and placed for standby; (3) In a three-necked flask, liquid paraffin was added in the proportion of 15:1 of oil phase (liquid paraffin) to water phase (chitosan acetate solution), then 2.5 mL of surfactant Span 80 was added, the reaction temperature was controlled at 60 ℃, and the stirring speed was kept at 800 rpm for 15 min; (4) The prepared solution of Asclepiadaceae Loddigesii chitosan acetate was added to the three-necked flask, and after the solution was fully dispersed, 3 mL of 25% glutaraldehyde was added for 4 h of reaction; (5) After the reaction was completed, the solution was centrifuged, the precipitate was washed with petroleum ether and anhydrous ethanol respectively, and then the sample was vacuum dried to obtain the product.

[0026] Comparative Example 4 (1) Acetic acid 1 mL, distilled water 4 mL, and chitosan 0.5 g were mixed and placed in a 4 ℃ refrigerator for standby; (2) Asclepiadaceae Loddigesii extract 30 mg was mixed with the chitosan acetate solution and placed for standby; (3) In a three-necked flask, liquid paraffin was added in the proportion of 15:1 of oil phase (liquid paraffin) to water phase (chitosan acetate solution), then 5 mL of surfactant Span 80 was added, the reaction temperature was controlled at 80 ℃, and the stirring speed was kept at 1200 rpm for 5 min; (4) The prepared solution of Asclepiadaceae Loddigesii chitosan acetate was added to the three-necked flask, and after the solution was fully dispersed, 0.1 mL of 25% glutaraldehyde was added for 6 h of reaction; (5) After the reaction was completed, the solution was milky white and too viscous, and the experiment could not continue.

[0027] The encapsulation rates of the examples and comparative examples are compared: Table 1 encapsulation rates of each ratio

[0028] Performance detection: the wood treated by each example and comparative example is then measured for mildew resistance and contact angle after treatment.

[0029] 1. Wood treatment method: (1) Number, classify and weigh the wood blocks; (2) Mix the microcapsule powder prepared in the above step with anhydrous ethanol at a microcapsule powder mass fraction of 1.25% to configure a microcapsule mildew inhibitor, immerse the wood in the microcapsule mildew inhibitor, and place it in a vacuum pressurized device. First, use a vacuum pump to draw the vacuum degree in the device to 0.085-0.095 MPa, and maintain this vacuum degree for 30-60 min; (3) Gradually restore the vacuum state of the pressurized device to normal pressure, so that the microcapsule mildew inhibitor can enter the wood cells under the action of pressure difference. After the immersion is completed, place the wood at normal temperature and pressure for 18-24 h; (4) After the immersion is completed, clean the surface of the wood. Then place the wood in an electric heat air drying oven until the mass does not change (put the sample wood block into the oven, take it out after baking at 60 ℃ for 6 h, and weigh it until the difference between the two masses is not significant, that is, the sample wood block is considered to be fully dried), and then adjust it in a constant temperature and humidity chamber at 25 ℃ and 60% relative humidity for 14 days before performance detection.

[0030] 2. Source of raw materials: the wood used in the experiment is Pinus massoniana Lamb. grown in Huaxi District, Guiyang City, Guizhou Province. The sapwood of Pinus massoniana Lamb. with moderate annual ring width and no obvious discoloration is used as the sample material. The sample specifications and sample purposes are as follows: Table 2 sample specifications

[0031] 3. The indicators followed in this experiment are international or forestry standard indicators, which are as follows: (1) Mildew resistance: determined according to GB / T 18261-2013 "Test method for mildew resistance of wood preservatives".

[0032] 4. Experimental results 4.1 Mildew resistance The wood blocks with the size of 20mmx5mmx50mm were sterilized and then placed in the culture dish full of mold and put in the constant temperature and humidity incubator at 25℃ and relative humidity of 85%, and cultured for 4 weeks. The wood blocks were taken out, and the infected area of the wood blocks by 10 kinds of fungi was measured to determine the damage value of the sample and the prevention efficiency. The smaller the damage value, the higher the control efficiency, indicating that the antifungal effect is better. The results are as follows: Table 5 Antifungal test results

[0033] 4.2 Contact angle test According to international requirements, the sample wood blocks with the size of 20mmx5mmx50mm were subjected to contact angle test, and the contact angle of the sample wood blocks was measured. The results are as follows: Table 7 Water absorption test results

[0034] The above data comparison shows that the wood treated by the plant source microcapsule antifungal agent of the present application has significantly improved antifungal performance compared with the untreated control sample. The treated wood shows excellent inhibition effect on the ten kinds of fungi tested, effectively blocking the growth and spread of mold on the surface of the wood. At the same time, the contact angle test results confirm that the treatment forms a hydrophobic covering layer on the surface of the wood, resulting in an increase in the contact angle and giving the wood stronger hydrophobic properties. This hydrophobic effect not only reduces the retention and penetration of water on the surface of the wood, but also creates an environment that is not conducive to the growth of mold, further synergistically enhancing the antifungal effect of the plant source active ingredient, thereby achieving double protection against mold growth of the wood.

[0035] Finally, it should be pointed out that the above examples are only more representative examples of the present application. Obviously, the technical solutions of the present application are not limited to the above examples, but can also have many variations. All variations that can be directly derived or inferred from the content disclosed in the present application by those of ordinary skill in the art should be considered as falling within the scope of protection of the present application.

Claims

1. A method for preparing a wood antifungal agent based on plant-derived extract microcapsules, characterized in that, Includes the following steps: (1) Take 1.5-5 parts acetic acid, 92-98 parts chitosan, 0.5-3 parts paisleya extract and 0.1-2 parts paisleya extract by volume; mix acetic acid, chitosan and distilled water evenly; (2) Mix the blood extract of the gypsy palm with the chitosan acetate solution and let it stand for later use; (3) Take the oil phase (liquid paraffin) and the water phase (acetic acid chitosan solution of spatholobus suberectus extract) in a ratio of (5:1) to (11:1), and then add the surfactant Span 80 to the oil phase (liquid paraffin). Control the reaction temperature at 30-60 ℃ and keep stirring at a speed of 600-1000 rpm to obtain the emulsifier. (4) Add the prepared *Pterocarya stenoptera* blood chitosan acetate solution from step (2) to the emulsifier prepared in step (3). After the solution is fully dispersed, add the crosslinking agent to react. (5) After the reaction is complete, the solution is centrifuged, the precipitate is washed with petroleum ether and anhydrous ethanol respectively, and the sample is dried under vacuum to obtain the final product.

2. The method for preparing the microcapsule-encapsulated wood mildew inhibitor based on plant-derived extracts according to claim 1, characterized in that, In step (1), the volume ratio of each raw material is 3 parts acetic acid, 97 parts distilled water, 1 part chitosan, and 0.28 parts scabra blood extract.

3. The method for preparing a microcapsule-encapsulated wood antifungal agent based on plant-derived extracts according to claim 1, characterized in that, In step (2), after the acetic acid, chitosan and distilled water are mixed evenly, they are placed at 4 ℃ and left to stand for later use.

4. The method for preparing a microcapsule-encapsulated wood antifungal agent based on plant-derived extracts according to claim 1, characterized in that, The *Pterocarya stenoptera* extract is obtained by extracting the leaves of the *Pterocarya stenoptera* plant.

5. The method for preparing a microcapsule-encapsulated wood antifungal agent based on plant-derived extracts according to claim 1, characterized in that, The order of preparation in step (1) is to first add distilled water, then add acetic acid, stir evenly, then add chitosan, and after it is completely dissolved, put it in the refrigerator to stand.

6. The method for preparing a microcapsule-encapsulated wood antifungal agent based on plant-derived extracts according to claim 1, characterized in that, The configuration sequence in step (2) is to add the blood extract of *Pterocarya stenoptera* to the chitosan acetate solution and disperse it evenly in the chitosan acetate solution.

7. The method for preparing a microcapsule-encapsulated wood antifungal agent based on plant-derived extracts according to claim 1, characterized in that, The configuration sequence in step (3) is as follows: the emulsifier is prepared and stirred for 15 minutes, and then the acetic acid chitosan solution of the *Pterocarya stenoptera* blood extract is added while stirring. After the solution is completely dispersed, the crosslinking agent is added for reaction.

8. The method for preparing a microcapsule-encapsulated wood antifungal agent based on plant-derived extracts according to claim 1, characterized in that, The crosslinking agent reaction in step (3) involves adding 0.2-4 parts of 25% glutaraldehyde by volume and reacting for 1-5 hours.

9. The method for preparing a microcapsule-encapsulated wood antifungal agent based on plant-derived extracts according to claim 8, characterized in that, The reaction in step (3) involves adding 0.99 parts of glutaraldehyde (25% by volume) and reacting for 3 hours.

10. A wood antifungal agent based on plant extracts prepared by the method for preparing a microcapsule-encapsulated wood antifungal agent based on plant extracts as described in claims 1-9.

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