Natural source termite prevention microcapsule preparation and its application in production of artificial board

Abstract

The present application belongs to the technical field of functional adjuvant of artificial board, and particularly relates to a natural source termite prevention microcapsule preparation and a preparation method and application thereof. The functional adjuvant is a microcapsule preparation, an active core material is prepared by compounding an agricultural antibiotic and a natural source insecticide, a semi-natural composite wall material is prepared by using a natural polymer and a synthetic resin, and the microcapsule preparation is prepared by emulsification, in-situ polymerization coating and solidification drying. The present application realizes high-efficiency termite prevention effect through compounding and synergistic effect, the microcapsule structure improves the thermal stability and the compatibility with adhesives, and does not reduce the mechanical properties of the board. The adjuvant can be directly blended with the adhesives and used in the hot pressing process of the artificial board, and the process has strong adaptability. The plywood prepared has a termite mortality rate of more than 97% after indoor termite prevention test for 28 days, and a perfect grade of 9 after termite corrosion, and is green, low-toxic, long-acting and stable, solves the problems of weak prevention effect and poor heat resistance of traditional natural adjuvant, and is suitable for industrial production of termite prevention plywood and other artificial board products.

Description

Technical Field

[0001] This invention belongs to the field of functional additives for engineered wood products, specifically relating to a natural termite-resistant microcapsule formulation and its application in engineered wood product production. Background Technology

[0002] Termites primarily feed on lignocellulose, and the formic acid they secrete can corrode wood, adhesives, and even concrete structures. This not only causes a rapid decline in the mechanical properties of engineered wood products and a significant reduction in their lifespan, but can also pose serious structural safety hazards in buildings. Therefore, termite prevention treatment has become an indispensable and crucial process in engineered wood product production, especially in southern regions where termites are prevalent. Currently, the mainstream termite prevention technologies in the engineered wood industry are mainly divided into three categories: chemical protection technologies, physical protection technologies, and biological protection technologies.

[0003] Among them, chemical protection technology is currently the most widely used termite prevention method. It mainly involves adding chemically synthesized anti-termite agents such as pyrethroids, organophosphates, pyrroles, and inorganic heavy metal salts during the production process of artificial boards or applying them to the surface of finished products to achieve termite extermination and protection. These technologies have the advantages of rapid onset, high efficacy, and controllable cost. However, with increasingly stringent global environmental regulations and rising public health awareness, their shortcomings are becoming increasingly apparent. On the one hand, traditional chemical termite repellents generally have issues with biotoxicity and environmental residues. Some agents pose potential risks to humans, animals, and non-target organisms. The EU REACH regulation and other domestic and international environmental standards have imposed strict restrictions on the use of various traditional chemical termite repellents. On the other hand, traditional chemical agents often use post-treatment methods such as surface coating and impregnation, which makes it difficult to form a uniform and continuous protective barrier inside the engineered wood product, easily leading to blind spots. Furthermore, the agents are prone to loss and thermal degradation over time, resulting in insufficient persistence. Additionally, some chemical agents can react with the adhesives used in engineered wood products, affecting the bonding strength and physical and mechanical properties of the boards.

[0004] Existing research indicates that natural plant-derived insecticides such as matrine, azadirachtin, and rotenone can achieve termite control through contact, stomach poisoning, antifeedant effects, and disruption of termite metabolism, making them ideal alternatives to traditional chemical pesticides. Meanwhile, termites rely on cellulase secreted by microorganisms in their digestive tract to degrade cellulose. Agricultural antibiotics, such as jinggangmycin and chlortetracycline, have significant inhibitory effects on microorganisms and have been proven to be effective against common termite species like the subterranean termite, exhibiting low repellency and safety for non-target organisms. To address the issues of poor thermal stability, easy degradation, and short-lasting effectiveness of natural active ingredients, current technologies often employ microencapsulation, using urea-formaldehyde resin, polyacrylic acid resin, cyclodextrin, etc., as wall materials to prepare natural insecticides into microcapsule formulations. Encapsulation treatment enhances the thermal stability of the active ingredients, achieving a slow-release and long-lasting protective effect.

[0005] Against this backdrop, bio-based termite control technology, with plant-derived insecticides and agricultural antibiotics at its core, has become a research hotspot and industry development trend in the field of green termite control for engineered wood products due to its advantages such as low toxicity, easy degradation, good environmental compatibility, and wide availability.

[0006] However, existing natural termite control technologies still have many technical shortcomings in practical applications in the engineered wood products industry that urgently need to be addressed. First, single natural termite-control active ingredients have limited efficacy, a narrow insecticidal spectrum, and a single mode of action. When used alone, they are difficult to achieve the termite control levels required by the engineered wood products industry. There are still few reports on existing technologies that scientifically combine natural plant-derived insecticides with agricultural antibiotics to achieve synergistic effects, making it impossible to simultaneously meet the dual requirements of high efficacy and environmental friendliness.

[0007] In summary, developing a natural termite-resistant functional additive that is environmentally friendly, highly effective in preventing termites, has excellent thermal stability, good compatibility with wood-based panel adhesives, does not affect the physical and mechanical properties of the panels, and possesses significant innovative features, can solve many defects in existing technologies. This is of great practical significance and application value for promoting the upgrading of green termite-resistant technology in the wood-based panel industry, expanding the application scope of wood-based panels, and ensuring the sustainable development of the industry. Summary of the Invention

[0008] The purpose of this invention is to provide a natural-source termite-resistant microcapsule formulation and its application in the production of engineered wood products. When the microcapsule formulation prepared by this invention is applied to engineered wood products, the termite mortality rate in the laboratory can reach up to 100% after 28 days. The test material only shows slight signs of termite infestation. The integrity level of the test block after termite infestation is 9, and the quality loss rate is less than 10%. It has a significant long-lasting termite-resistant effect and completely solves the industry pain points of insufficient efficacy and short duration of effect of existing natural-source termite-resistant technologies.

[0009] The objective of this invention is achieved through the following technical solution: This invention provides a natural termite-resistant microcapsule formulation, comprising an active core material and a semi-natural composite wall material; the active core material contains termite-resistant active components, which are compounded from agricultural antibiotics and natural insecticides; the semi-natural composite wall material is compounded from natural polymer substrates and synthetic resin substrates.

[0010] Furthermore, the agricultural antibiotic is selected from at least one of jinggangmycin and chlortetracycline.

[0011] Furthermore, the natural insecticide is selected from at least one of matrine, azadirachtin, and rotenone.

[0012] Furthermore, in the termite-resistant active ingredient, the mass ratio of agricultural antibiotic to natural insecticide is 1:(1-5); the natural polymer substrate is selected from at least one of chitosan, cationic modified starch, and β-cyclodextrin; and the synthetic resin substrate is selected from at least one of low molecular weight urea-formaldehyde resin and polyacrylic acid resin.

[0013] Furthermore, by weight, the functional additives include 10-15 parts of active core material, 20-30 parts of semi-natural composite wall material, 1.5-2.5 parts of emulsifier, 0.5-1.0 parts of curing agent, and 50-70 parts of deionized water; in the semi-natural composite wall material, the mass ratio of natural polymer substrate to synthetic resin substrate is 1:(1.2-2.5); the microcapsule encapsulation rate of the functional additives is ≥85%, the average particle size is 10-20μm, and the thermal weight loss rate at 160℃ is ≤5.5%.

[0014] This invention also provides a method for preparing the aforementioned natural termite-resistant microcapsule formulation, comprising the following steps: S1 aqueous phase preparation: Add the natural polymer substrate to deionized water, stir until completely dissolved, adjust the pH value of the system, add emulsifier and mix evenly to obtain the aqueous phase system; S2 oil phase preparation: Agricultural antibiotics and natural insecticides are mixed in a certain proportion and then ultrasonically dispersed to obtain a uniform and stable core material mixture, which is used as the oil phase; S3 Emulsion Coating: The oil phase is slowly added dropwise to the aqueous phase system, and the emulsion is obtained by high-speed shear emulsification. After heating the emulsion, the synthetic resin substrate is slowly added dropwise, and the in-situ polymerization coating reaction is carried out by keeping the temperature and stirring. S4 Post-curing treatment: Add curing agent to the system after the coating reaction is completed to adjust the pH value, keep warm and stir to complete the curing reaction, and after the reaction is completed, cool, wash and dry to obtain the natural source anti-termite microcapsule formulation.

[0015] Furthermore, in step S3, the rotation speed of the high-speed shear emulsification is 7000-10000 r / min, and the emulsification time is 20-30 min; the temperature of the in-situ polymerization coating reaction is 50-60℃, and the reaction time is 1.5-2.5 h; in step S4, the heat preservation temperature of the curing reaction is 50-60℃, and the curing time is 1-1.5 h.

[0016] This invention also provides an application of the aforementioned natural-source anti-termite microcapsule formulation, wherein the natural-source functional additive is mixed evenly with an adhesive for engineered wood products to obtain an anti-termite adhesive, and the anti-termite adhesive is applied to the gluing, assembly and hot pressing processes of engineered wood products to prepare anti-termite engineered wood products.

[0017] Furthermore, the amount of the natural source functional additive added is 0.1-0.5% of the oven-dry weight of the adhesive for engineered wood products; the adhesive for engineered wood products is selected from at least one of urea-formaldehyde resin adhesive and melamine-modified urea-formaldehyde resin adhesive.

[0018] Furthermore, the engineered wood product is plywood, including veneer engineered wood products and chip engineered wood products, and the termite-resistant adhesive has a double-sided application rate of 250-300 g / m². 2 The hot pressing temperature of the hot pressing process is 115-125℃, the termite mortality rate is ≥97% after 28 days, and the termite infestation integrity level is 9.

[0019] The beneficial effects of this invention are as follows: This invention overcomes the limitations of existing single-source termite control methods by scientifically combining agricultural antibiotics and natural insecticides as the core of termite control activity. The combination of these two agents produces a significant synergistic effect, rather than a simple additive effect. Agricultural antibiotics such as jinggangmycin and chlortetracycline effectively inhibit the activity of microorganisms within termites, achieving rapid poisoning by disrupting their physiological metabolism. Natural insecticides such as matrine, azadirachtin, and rotenone possess contact, stomach poison, antifeedant, and growth-inhibiting effects. The combination forms a multi-target, multi-mechanism termite control system, significantly improving termite eradication efficiency and effectively avoiding the development of drug resistance due to long-term exposure to a single agent. This broadens the spectrum of termite control, providing excellent control effects against various common termite species, including the most widespread and damaging subterranean termite in my country. Experimental verification shows that when the functional additives prepared in this invention are applied to engineered wood products, the termite mortality rate in the laboratory can reach up to 100% after 28 days. The test materials show only slight signs of termite infestation, and the test blocks are intact at level 9 after termite infestation, with a quality loss rate of less than 10%. The long-lasting termite prevention effect is significant, which completely solves the industry pain points of insufficient efficacy and short duration of effect of existing natural termite prevention technologies.

[0020] This invention addresses the core problems of poor thermal stability, easy deactivation during the hot-pressing process of engineered wood products, and poor compatibility with adhesives of naturally sourced active ingredients. It innovatively designs a semi-natural composite wall material microcapsule encapsulation system. This system uses natural polymer substrates such as chitosan, cationic modified starch, and β-cyclodextrin, combined with synthetic resin substrates such as low-molecular-weight urea-formaldehyde resin and polyacrylic acid resin as the wall material. This retains the advantages of natural polymer materials, such as good environmental friendliness and excellent compatibility with wood materials, while also possessing the characteristics of synthetic resin materials, such as good film-forming properties, dense encapsulation, and strong thermal stability. This allows for a stable and dense encapsulation protection of the active core material. The microcapsule formulation prepared by this invention achieves an encapsulation rate of over 85%, with an average particle size controlled at 10-20 μm. Under high-temperature conditions at 160℃, the thermal weight loss rate does not exceed 5.5%, fully withstanding the high-temperature hot-pressing environment during engineered wood product manufacturing, preventing the decomposition and deactivation of active ingredients during processing. Simultaneously, the slow-release structure of the microcapsules enables long-term, slow release of active ingredients, further extending the termite protection period of the engineered wood products.

[0021] The functional additives of this invention are highly compatible with existing industrial production processes for engineered wood products. No equipment modifications or process adjustments are required on existing production lines. The functional additives simply need to be uniformly mixed with the adhesive online in a specific ratio before being directly applied to conventional gluing, assembly, and hot-pressing processes. This allows for simultaneous completion of termite-proofing treatment and engineered wood product production, significantly simplifying the production process, improving efficiency, and reducing termite-proofing costs. Unlike existing post-treatment methods such as surface impregnation and spraying, this invention, through pre-addition via adhesive mixing, ensures that the termite-proofing active ingredients are uniformly dispersed throughout all layers and cross-sections of the engineered wood product, forming a comprehensive, seamless protective barrier. This avoids the shortcomings of post-treatment methods that only provide surface protection, which quickly diminishes after surface wear, fundamentally guaranteeing termite-proofing throughout the entire lifecycle of the engineered wood product.

[0022] This invention adheres to a green and environmentally friendly design philosophy throughout, abandoning the chemically synthesized agents widely used in traditional termite-proofing technologies for engineered wood products. The active ingredients and wall material raw materials used are all low-toxicity, easily degradable, and environmentally compatible, posing no potential harm to humans, animals, or non-target organisms. No toxic or harmful substances are emitted during production and use, effectively improving the environmental protection level and market competitiveness of engineered wood products. Furthermore, this invention organically combines three core innovations: synergistic compounding of active ingredients, semi-natural microencapsulation, and adaptation to production processes. This forms a complete termite-proofing technology solution with significant substantive features and advancements, filling the technological gap where existing natural termite-proofing additives cannot simultaneously achieve high efficacy, thermal stability, mechanical compatibility, and environmental friendliness. It resolves the long-standing core contradiction in the engineered wood industry—the inability to balance green termite prevention with product performance. This not only effectively extends the service life of engineered wood products and reduces economic losses caused by termite damage but also significantly expands the applicability of engineered wood products in termite-prone areas of southern my country, promoting the transformation and upgrading of the engineered wood industry towards greening, functionalization, and high added value, resulting in significant economic and social benefits. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is an experimental diagram showing the activity of the natural termite repellent agent tested in this invention. Detailed Implementation

[0025] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0026] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0027] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0028] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0029] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0030] 1. Main raw materials and reagents Matrine (98% purity), azadirachtin (95% purity), rotenone (96% purity), jinggangmycin A (95% purity), and chlortetracycline (98% purity) were purchased from Shanghai Maclean Biochemical Technology Co., Ltd.; chitosan (90% degree of deacetylation), cationic modified starch, and β-cyclodextrin were all food-grade; low molecular weight urea-formaldehyde resin (30% solid content) and polyacrylic acid resin emulsion (40% solid content) were both industrial grade for wood-based panels; emulsifiers Tween-80 and Span-80 were analytical grade; curing agents citric acid and ammonium chloride were analytical grade; urea-formaldehyde resin adhesive for wood-based panels (UF glue, 52% solid content, free formaldehyde ≤0.15%) was commercially available industrial grade; poplar veneer (1.6mm thickness, moisture content 8-10%, no knots or decay).

[0031] 2. Main instruments and equipment High-shear emulsifier (Shanghai FLUKO), constant temperature magnetic stirring water bath, laser particle size analyzer, thermogravimetric analyzer (TGA), universal material testing machine, small hot press for artificial boards.

[0032] 3. Performance Testing Methods Microcapsule performance testing: Encapsulation efficiency was determined by methanol extraction-ultraviolet spectrophotometry; particle size distribution was determined by laser particle size analyzer; thermal stability was tested by thermogravimetric analysis under nitrogen atmosphere, heating rate 10℃ / min, test temperature range 30-300℃, and the thermal weight loss rate at 200℃ was recorded.

[0033] Termite resistance performance test: commissioned to Guangdong Academy of Forestry Sciences.

[0034] Example 1 This embodiment provides a natural-source termite-resistant microcapsule formulation, the formula of which is as follows by mass parts: Active core material: 12 parts (4 parts Jinggangmycin A, 8 parts Matrine) Semi-natural composite wall material: 25 parts (8 parts chitosan, 17 parts low molecular weight urea-formaldehyde resin) Emulsifiers: Tween-80 1.2 parts, Span-80 0.8 parts Curing agent: 0.5 parts citric acid, 0.3 parts ammonium chloride Deionized water: 60 parts The preparation method of the natural-source termite-resistant microcapsule formulation in this embodiment includes the following steps: S1 Aqueous Phase Preparation: According to the formula, add chitosan to 40 parts of deionized water, add citric acid to adjust the pH to 4.5, stir at 40℃ until completely dissolved to obtain a chitosan solution; then add Tween-80 and Span-80, and continue stirring for 10 minutes until completely dispersed to obtain an aqueous phase system; S2 oil phase preparation: According to the formula, add jinggangmycin A and matrine to the remaining deionized water, and ultrasonically disperse for 10 min (power 300W) to obtain a uniform and stable core material mixture, which is used as the oil phase; S3 Emulsion Coating: The oil phase was slowly added dropwise to the aqueous phase system at a rate of 2 mL / min, while maintaining a constant temperature of 35°C during the addition process. A high-shear emulsifier was used to emulsify at a high speed of 8000 r / min for 25 min to obtain a uniform oil-in-water emulsion. The emulsion was then transferred to a constant-temperature magnetically stirred water bath, heated to 55°C, and stirred at a constant speed of 300 r / min. Simultaneously, low molecular weight urea-formaldehyde resin was added dropwise at a rate of 1 mL / min. After the addition was completed, the reaction was continued with stirring at the same temperature for 2 h to complete the in-situ polymerization coating. S4 post-curing treatment: Add ammonium chloride to the reaction system, adjust the pH value to 6.0, and continue to keep warm and stir for 1 hour to cure; after the reaction is completed, cool naturally to room temperature, vacuum filter, wash three times with deionized water, and send to a spray dryer (inlet air temperature 180℃, outlet air temperature 80℃) to dry, and obtain powdered natural source anti-termite microcapsule preparation.

[0035] Tests showed that the functional additive microcapsules prepared in this embodiment had an average particle size of 12.6 μm, an encapsulation rate of 89.2%, and a thermal weight loss rate of only 4.8% at 160℃, demonstrating excellent thermal stability and making them fully adaptable to the high-temperature environment of hot-pressing processes for engineered wood panels.

[0036] The application method of the natural-source termite-resistant microcapsule formulation in this embodiment includes the following steps: (1) Adhesive preparation: The prepared functional additives are added to the urea-formaldehyde resin adhesive at an addition rate of 1.5% of the oven-dry weight of the urea-formaldehyde resin adhesive. The mixture is stirred at 500 r / min for 15 min until it is evenly mixed to obtain the termite-proof adhesive. (2) Preparation of artificial board: Five-layer plywood was prepared using poplar veneer with a veneer size of 300mm×300mm and a double-sided glue application of 280g / m². Anti-termite adhesive was evenly applied to the surface of the veneer, and the boards were assembled in the direction of longitudinal-transverse-longitudinal-transverse-longitudinal, and then sent into a hot press for hot pressing. The hot pressing temperature was 120℃, the hot pressing pressure was 1.2MPa, and the hot pressing time was 1.0min / mm thickness to prepare anti-termite plywood with a thickness of 7.5mm. After hot pressing, the boards were left to stand at room temperature for 7 days, the rough edges were trimmed, and performance tests were conducted.

[0037] Example 2 This embodiment provides a natural-source termite-resistant microcapsule formulation, the formula of which is as follows by mass parts: Active core material: 15 parts (5 parts Jinggangmycin A, 10 parts Azadirachtin) Semi-natural composite wall material: 30 parts (12 parts cationic modified starch, 18 parts polyacrylic resin) Emulsifiers: Tween-80 1.5 parts, Span-80 1.0 part Curing agent: 0.6 parts citric acid Deionized water: 52 parts The preparation method of the natural-source termite-resistant microcapsule formulation in this embodiment includes the following steps: S1 Aqueous Phase Preparation: According to the formula, add cationic modified starch to 35 parts of deionized water, stir at a constant temperature of 85℃ until completely gelatinized, cool down to 45℃, add citric acid to adjust the pH value to 5.0, then add Tween-80 and Span-80, stir evenly to obtain the aqueous phase system. S2 oil phase preparation: According to the formula, jinggangmycin A and azadirachtin were added to anhydrous ethanol and ultrasonically dispersed for 15 min to obtain a uniform core material mixture, which was used as the oil phase; S3 Emulsification Coating: The oil phase is slowly added dropwise to the aqueous phase system while maintaining a constant temperature of 40°C during the addition process. High-shear emulsification is carried out at a high speed of 10,000 r / min for 20 min using a high-shear emulsifier to obtain an oil-in-water emulsion. The emulsion is then transferred to a water bath and heated to 60°C. Polyacrylic acid resin emulsion is slowly added dropwise while stirring at 350 r / min. After the addition is completed, the mixture is kept at the temperature and stirred for 2.5 h to complete the coating. S4 Post-curing Treatment: Citric acid is added to the reaction system to adjust the pH value to 6.2. The mixture is then kept at the temperature and stirred for 1.5 h to cure. After the reaction is completed, the mixture is cooled, filtered, washed, and spray-dried to obtain a powdered functional additive.

[0038] Tests showed that the functional additive microcapsules prepared in this embodiment had an average particle size of 10.2 μm, an encapsulation rate of 91.5%, and a thermal weight loss rate of 5.2% at 160℃, demonstrating excellent thermal stability.

[0039] The method of applying the functional additive in this embodiment differs from that in Example 1 only in that the amount of functional additive added is 2.0% of the oven-dry weight of the urea-formaldehyde resin adhesive. All other steps and parameters are the same as in Example 1, and termite-proof plywood is prepared.

[0040] Example 3 This embodiment provides a natural-source termite-resistant microcapsule formulation, the formula of which is as follows by mass parts: Active core material: 10 parts (3 parts chlortetracycline, 7 parts rotenone) Semi-natural composite wall material: 20 parts (9 parts β-cyclodextrin, 11 parts low molecular weight urea-formaldehyde resin) Emulsifiers: Tween-80 1.0 part, Span-80 0.7 parts Curing agent: 0.4 parts ammonium chloride Deionized water: 68 parts The preparation method of the natural-source termite-resistant microcapsule formulation in this embodiment includes the following steps: S1 Aqueous Phase Preparation: According to the formula amount, β-cyclodextrin was added to 45 parts of deionized water, stirred at a constant temperature of 60℃ until completely dissolved, cooled to 40℃, emulsifier was added and stirred evenly to obtain the aqueous phase system; S2 Oil Phase Preparation: According to the formula, chlortetracycline and rotenone were added to the remaining deionized water and ultrasonically dispersed for 12 min to obtain a core material mixture, which served as the oil phase; S3 Emulsification and Coating: The oil phase was slowly added dropwise to the aqueous phase and sheared at 9000 r / min for 22 min at a constant temperature of 38℃ to obtain an emulsion; The temperature was raised to 58℃ and low molecular weight urea-formaldehyde resin was added dropwise under stirring at 320 r / min. After the addition was completed, the reaction was kept at the temperature for 1.8 h; S4 Curing and Post-treatment: Ammonium chloride was added to adjust the pH value to 5.8, and the mixture was kept at the temperature for 1 h to cure. After cooling, it was filtered, washed, and spray-dried to obtain a powdered functional additive.

[0041] Tests showed that the functional additive microcapsules prepared in this embodiment had an average particle size of 15.8 μm, an encapsulation rate of 88.7%, and a thermal weight loss rate of 4.5% at 160℃, demonstrating excellent thermal stability.

[0042] The method of applying the functional additive in this embodiment differs from that in Example 1 only in that the amount of functional additive added is 1.2% of the oven-dry weight of the urea-formaldehyde resin adhesive, while the remaining steps and parameters are the same as in Example 1, and termite-resistant plywood is prepared.

[0043] Example 4 This embodiment provides a natural-source termite-resistant microcapsule formulation, the formula of which is as follows by mass parts: Active core material: 14 parts (4 parts Jinggangmycin A, 5 parts Matrine, 5 parts Azadirachtin) Semi-natural composite wall material: 28 parts (10 parts chitosan, 18 parts low molecular weight urea-formaldehyde resin) Emulsifiers: Tween-80 1.4 parts, Span-80 0.9 parts Curing agent: 0.5 parts citric acid, 0.3 parts ammonium chloride Deionized water: 55 parts The preparation and application methods of the functional additives in this embodiment are completely consistent with those in Example 1, and all steps and parameters are identical to those in Example 1. The powdered microcapsule formulation and the corresponding termite-resistant plywood are prepared.

[0044] Tests showed that the functional additive microcapsules prepared in this embodiment had an average particle size of 13.5 μm, an encapsulation rate of 90.3%, and a thermal weight loss rate of 4.9% at 160°C.

[0045] Example 5 This embodiment provides a natural termite-resistant microcapsule formulation with the same formula as in Example 1. The only difference in the preparation method is that in step S3, the high-shear emulsification speed is 7000 r / min, the emulsification time is 30 min, the polymerization reaction temperature is 52℃, and the reaction time is 2.5 h. All other steps and parameters are the same as in Example 1, and a powdered microcapsule formulation is prepared.

[0046] The application method of the functional additives in this embodiment is completely consistent with that in Example 1 in terms of all steps and parameters, and termite-resistant plywood is prepared.

[0047] The functional additive microcapsules prepared in this embodiment have an average particle size of 18.2 μm, an encapsulation rate of 87.6%, and a thermal weight loss rate of 5.5% at 200°C.

[0048] Example 6 This embodiment is an industrial-scale production embodiment, providing a natural-source termite-resistant microcapsule formulation, the formula of which is as follows by mass parts: Active core material: 12 parts (4 parts Jinggangmycin A, 6 parts Matrine, 2 parts Rotenone) Semi-natural composite wall material: 25 parts (10 parts cationic modified starch, 15 parts low molecular weight urea-formaldehyde resin) Emulsifiers: Tween-80 1.2 parts, Span-80 0.8 parts Hardener: 0.5 parts citric acid Deionized water: 60 parts This embodiment uses industrial-grade equipment for preparation, and the steps are as follows: S1 Aqueous Phase Preparation: According to the formula, cationic modified starch was added to deionized water and gelatinized by stirring at a constant temperature of 85℃ in a 5000L reactor. The temperature was then lowered to 45℃, the pH was adjusted to 5.0, and the emulsifier was added and stirred evenly to obtain the aqueous phase system. S2 oil phase preparation: Jinggangmycin A, matrine, and rotenone were uniformly dispersed by high-shear ultrasonication according to the formula to obtain a core material mixture, which was used as the oil phase; S3 Emulsification and Coating: The oil phase is slowly pumped into the aqueous phase system using a metering pump. An industrial-grade high-shear emulsifier is turned on and emulsified at 9000 r / min for 25 min to obtain an oil-in-water emulsion. The temperature is raised to 55℃, and low molecular weight urea-formaldehyde resin is added dropwise under low-speed stirring. The reaction is maintained at this temperature for 2 h. S4 Post-curing Treatment: The pH of the system is adjusted to 6.0, and the system is maintained at this temperature for 1 h. After the reaction is completed, the system is cooled, washed countercurrently, centrifuged to dehydrate, and spray-dried industrially to obtain a powdered functional additive. The yield per batch is 500 kg.

[0049] Tests showed that the functional additive microcapsules prepared in this embodiment had an average particle size of 14.3 μm, an encapsulation rate of 88.1%, a thermal weight loss rate of 5.3% at 200℃, and a batch-to-batch performance deviation of ≤3%, indicating good stability.

[0050] The application method of this embodiment is an industrial production line adaptation scheme: the prepared functional additives are added online to the glue mixing tank of the plywood production line at an addition rate of 1.5% of the oven-dry weight of the urea-formaldehyde resin adhesive. After being stirred evenly, they are directly used in the glue application process. The hot pressing parameters of the production line are: hot pressing temperature 125℃, hot pressing pressure 1.2MPa, and hot pressing time 0.9min / mm board thickness. A series of termite-resistant plywood with thicknesses of 9mm, 12mm, and 15mm are prepared. After online testing, the performance of all batches of products meets the national standard requirements.

[0051] Comparative Example 1 The existing conventional scheme, the formula and preparation method are different from those of Example 1 only in that: the active core material does not contain jinggangmycin A, and only 8 parts of matrine are used as the single active ingredient. The rest of the formula, preparation method and application method are the same as those of Example 1.

[0052] Comparative Example 2 The only difference between the formulation and preparation method and Example 1 is that matrine is not added to the active core material, and only 4 parts of Jinggangmycin A are used as the single active ingredient. The rest of the formulation, preparation method and application method are the same as those in Example 1.

[0053] Comparative Example 3 The formulation is exactly the same as that in Example 1, except that: no microencapsulation is performed, the active ingredient is directly mixed with the other raw materials, and it is used directly as an adjuvant without emulsification, encapsulation, or curing steps.

[0054] Comparative Example 4 The only difference between the formulation and preparation method and Example 1 is that the wall material uses fully synthetic low molecular weight urea-formaldehyde resin, without adding chitosan, and the total number of parts of the wall material remains unchanged at 25 parts. The rest of the formulation, preparation method and application method are the same as in Example 1.

[0055] Comparative Example 5 In the blank control group, no termite-proofing additives were added when preparing plywood; only pure urea-formaldehyde resin adhesive was used, and all other process parameters were the same as in Example 1.

[0056] Experimental Example 1 1. Termite resistance performance test results Table 1. Test results of termite resistance of plywood samples.

[0057] 3. Results Analysis The experimental diagram of the activity test of the natural termite repellent agent in this invention is shown below. Figure 1 As shown, the specific results are as follows: Termite control efficacy: The termite mortality rate of the samples in the embodiments of this invention reached over 97% after 28 days, with an anti-insect infestation level as high as 9, far superior to all comparative examples. Among them, Comparative Examples 1 and 2, which used a single active ingredient, had a termite mortality rate of less than 65%, far lower than Example 1 with the same formulation. This fully demonstrates that the agricultural antibiotic and natural insecticide compound system of this invention has a significant synergistic effect, solving the problems of limited efficacy and narrow insecticidal spectrum of single natural ingredients.

[0058] Thermal stability and duration of efficacy: Comparative Example 3 was not microencapsulated, and the active ingredients were largely deactivated during hot pressing, resulting in a significant reduction in efficacy. In contrast, the microcapsule formulation of this invention had a thermal weight loss rate of less than 5.5% at 160°C, which can withstand the high temperature environment of hot pressing on artificial boards, achieving sustained and long-lasting release of active ingredients. It still maintains excellent termite-repellent effect even after long-term outdoor placement, solving the defects of poor thermal stability, easy degradation, and short duration of efficacy of natural active ingredients.

[0059] Industrial compatibility: The industrial scale-up sample of Example 2 still maintains stable and excellent performance, and can be directly adapted to existing plywood production lines without adding new equipment or changing the original production process, thus possessing strong industrial promotion value.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A natural-source termite-resistant microcapsule formulation, characterized in that, It includes an active core material and a semi-natural composite wall material; the active core material contains a termite-resistant active component, which is a compound of agricultural antibiotics and natural insecticides; the semi-natural composite wall material is a compound of natural polymer substrate and synthetic resin substrate.

2. The natural-source termite-resistant microcapsule formulation according to claim 1, characterized in that, The agricultural antibiotic is selected from at least one of jinggangmycin and chlortetracycline.

3. The natural-source termite-resistant microcapsule formulation according to claim 1 or 2, characterized in that, The natural insecticide is selected from at least one of matrine, azadirachtin, and rotenone.

4. The natural-source termite-resistant microcapsule formulation according to claim 1, characterized in that, In the termite-resistant active ingredient, the mass ratio of agricultural antibiotic to natural insecticide is 1:(1-5); the natural polymer substrate is selected from at least one of chitosan, cationic modified starch, and β-cyclodextrin; and the synthetic resin substrate is selected from at least one of low molecular weight urea-formaldehyde resin and polyacrylic acid resin.

5. The natural-source termite-resistant microcapsule formulation according to claim 1, characterized in that, By weight, the functional additives include 10-15 parts of active core material, 20-30 parts of semi-natural composite wall material, 1.5-2.5 parts of emulsifier, 0.5-1.0 parts of curing agent, and 50-70 parts of deionized water; in the semi-natural composite wall material, the mass ratio of natural polymer substrate to synthetic resin substrate is 1:(1.2-2.5); the microcapsule encapsulation rate of the functional additives is ≥85%, the average particle size is 10-20μm, and the thermal weight loss rate at 160℃ is ≤5.5%.

6. A method for preparing a natural-source termite-resistant microcapsule formulation according to any one of claims 1 to 5, characterized in that, Includes the following steps: S1 aqueous phase preparation: Add the natural polymer substrate to deionized water, stir until completely dissolved, adjust the pH value of the system, add emulsifier and mix evenly to obtain the aqueous phase system; S2 oil phase preparation: Agricultural antibiotics and natural insecticides are mixed in a certain proportion and then ultrasonically dispersed to obtain a uniform and stable core material mixture, which is used as the oil phase; S3 Emulsion Coating: The oil phase is slowly added dropwise to the aqueous phase system, and the emulsion is obtained by high-speed shear emulsification. After heating the emulsion, the synthetic resin substrate is slowly added dropwise, and the in-situ polymerization coating reaction is carried out by keeping the temperature and stirring. S4 Post-curing treatment: Add curing agent to the system after the coating reaction is completed to adjust the pH value, keep warm and stir to complete the curing reaction, and after the reaction is completed, cool, wash and dry to obtain the natural source anti-termite microcapsule formulation.

7. The preparation method according to claim 6, characterized in that, In step S3, the high-speed shear emulsification rotation speed is 7000-10000 r / min, and the emulsification time is 20-30 min; the in-situ polymerization coating reaction temperature is 50-60℃, and the reaction time is 1.5-2.5 h; in step S4, the curing reaction holding temperature is 50-60℃, and the curing time is 1-1.5 h.

8. The application of a natural-source termite-resistant microcapsule formulation according to any one of claims 1 to 5, characterized in that, The natural functional additives are mixed evenly with the adhesives for engineered wood products to obtain an anti-termite adhesive. The anti-termite adhesive is then applied to processes including gluing, assembly, and hot pressing of engineered wood products to prepare anti-termite engineered wood products.

9. The application according to claim 8, characterized in that, The amount of the natural source functional additive added is 0.05-0.1% of the oven-dry weight of the adhesive for engineered wood products; the adhesive for engineered wood products is selected from urea-formaldehyde resin adhesive and melamine-modified urea-formaldehyde resin adhesive.

10. The application according to claim 8, characterized in that, The engineered wood product is plywood, including engineered wood products in veneer form and engineered wood products in scrap form. The hot pressing temperature of the hot pressing process is 115-125℃. After 28 days of indoor termite prevention testing, the termite mortality rate is ≥97%, and the integrity level after termite infestation is level 9.

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