A bio-based root-resistant waterproof coating and a preparation method and application thereof

Abstract

This invention provides a bio-based root-penetration resistant waterproof coating, its preparation method, and its application. The coating consists of component A and component B in a mass ratio of 100:25-100:35. By weight, component A comprises: 35-45 parts castor oil-based polyurethane prepolymer, 18-28 parts polysiloxane-modified acrylate resin, 6-10 parts rosin-based dynamic borate crosslinking agent, 8-15 parts pH-responsive root-barrier microcapsules, 10-12 parts flaky kaolin, 3-4 parts cellulose nanofibers, 1-3 parts cashew phenol glycidyl ether, 0.15-0.35 parts organic bismuth catalyst, and 3-6 parts hydrophobic fumed silica. Component B comprises: 25-35 parts cashew phenol polyamine curing agent, 10-18 parts deionized water, 5-10 parts propylene glycol methyl ether acetate, and 1-2 parts nonionic emulsifier. The components in this invention work synergistically to impart excellent mechanical properties, root penetration resistance, self-healing properties, and waterproof properties to the coating film, and it also has a high bio-based content, which meets environmental protection requirements.

Description

Technical Field

[0001] This invention relates to the field of waterproof coating technology, specifically to a bio-based root-penetration resistant waterproof coating, its preparation method, and its application. Background Technology

[0002] With the development of green building and ecological greening industries, scenarios such as green roofs and underground garage roofs place higher demands on the root penetration resistance and environmental friendliness of waterproofing materials. Traditional waterproofing coatings mostly rely on petrochemical-based raw materials, which not only face resource dependence and shortage issues, but may also be accompanied by volatile organic compound (VOC) emissions throughout their entire life cycle, which is inconsistent with the "dual carbon" strategy and environmental protection development trends. Existing root penetration resistant waterproofing materials often achieve their function through a single physical barrier or chemical root barrier method, and there is still room for improvement in the balance between mechanical properties, durability, and environmental friendliness.

[0003] Currently, most root-penetration resistant waterproof coatings suffer from low bio-based content, making it difficult to fully meet environmental protection requirements. Furthermore, some products are prone to micro-cracks due to external forces during long-term use, lacking effective self-healing capabilities, leading to a decline in waterproofing and root-penetration resistance, and insufficient synergy between mechanical properties and core functions. Therefore, developing a waterproof coating with high bio-based content, excellent root-penetration resistance and waterproofing performance, and self-healing capabilities has become an urgent technical problem to be solved in this field. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a bio-based root-penetration resistant waterproof coating, its preparation method, and its application.

[0005] To achieve the above objectives, the present invention provides the following technical solution: This invention discloses a bio-based root-penetration resistant waterproof coating, composed of component A and component B, in parts by weight: The raw materials for preparing component A include: 35-45 parts of castor oil-based polyurethane prepolymer, 18-28 parts of polysiloxane-modified acrylate resin, 6-10 parts of rosin-based dynamic borate crosslinking agent, 8-15 parts of pH-responsive root-barrier microcapsules, 10-12 parts of flake kaolin, 3-4 parts of cellulose nanofibers, 1-3 parts of cashew phenol glycidyl ether, 0.15-0.35 parts of organic bismuth catalyst, and 3-6 parts of hydrophobic fumed silica. The raw materials for preparing component B include: 25-35 parts of cashew phenol polyamine curing agent, 10-18 parts of deionized water, 5-10 parts of propylene glycol methyl ether acetate, and 1-2 parts of nonionic emulsifier (Tween 80); the mass ratio of component A to component B is 100:25-100:35.

[0006] Using the above technical solutions, the castor oil-based polyurethane prepolymer of component A can provide a bio-based carbon chain skeleton and react with cashew phenol polyamine curing agent to form a polymer network, giving the coating film basic flexibility and adhesion properties; polysiloxane-modified acrylate resin can introduce hydrophobic segments, improving the hydrophobicity and weather resistance of the coating film; rosin-based dynamic borate ester crosslinking agent can achieve self-repair function after coating film damage through reversible breaking and recombination of dynamic borate ester bonds, and enhance the mechanical strength of the coating film with its rigid structure; pH-responsive root-blocking microcapsules can directionally release the active ingredients of the core material under the condition of local pH change caused by acidic substances secreted by plant roots, achieving precise inhibition of root growth and giving the coating film root penetration resistance; flaky kaolin can form a two A physical barrier layer extends the penetration path of water and roots; cellulose nanofibers construct a reinforcing skeleton, improving the tensile strength of the coating and bridging microcracks; cashew phenol glycidyl ether participates in the cross-linking reaction through epoxy groups, enhancing interfacial bonding; an organic bismuth catalyst catalyzes the curing reaction, increasing the density of the cross-linked network; hydrophobic fumed silica fills the pores of the coating, further improving its density and hydrophobicity; the cashew phenol polyamine curing agent in component B reacts with the active groups in component A to form a cross-linked network, improving the mechanical properties and adhesion strength of the coating; deionized water provides the curing medium; propylene glycol methyl ether acetate improves the leveling and coatability of the coating, enhancing its application performance; Tween 80 improves the compatibility of components A and B. The synergistic effect of these components endows the coating with excellent mechanical properties, root penetration resistance, self-healing properties, and waterproofing properties, and has a high bio-based content, meeting environmental protection requirements.

[0007] Preferably, the castor oil-based polyurethane prepolymer has an NCO content of 4.5%-5.5% and a viscosity of 3200-3600 mPa·s at 25°C; the polysiloxane-modified acrylate resin has a hydroxyl value of 55-65 mgKOH / g; the flaky kaolin has a sheet diameter of 0.8-3.0 μm and an aspect ratio of 15-25; and the cellulose nanofibers have a diameter of 20-50 nm and a length of 1-3 μm.

[0008] Using the above technical solutions, the NCO content and viscosity limits of the castor oil-based polyurethane prepolymer ensure its full reaction with the curing agent and other components, forming a stable polyurethane network that imparts flexibility and adhesion to the coating film. The hydroxyl value limits of the polysiloxane-modified acrylate resin promote the formation of an interpenetrating network with the castor oil-based polyurethane prepolymer, enhancing the interfacial bonding and weather resistance of the coating film. The limits on the flake diameter and aspect ratio of the flaky kaolin allow it to form a continuous two-dimensional physical barrier layer in the coating film, extending the penetration path of water and roots. The size limits of the cellulose nanofibers allow them to be uniformly dispersed in the system, constructing a one-dimensional reinforcing skeleton, bridging microcracks, and synergistically improving the mechanical properties of the coating film with the flaky kaolin.

[0009] Preferably, the rosin-based dynamic borate ester crosslinking agent is made from the following raw materials in parts by weight: 50-60 parts of dehydroabsic acid, 10-15 parts of 1,4-butanediol, 4-6 parts of boric acid, 8-12 parts of 3-methacryloyloxypropyltrimethoxysilane, 0.3-0.6 parts of p-toluenesulfonic acid, and 70-80 parts of xylene.

[0010] Using the above technical solution, dehydroabsic acid provides a rigid framework, 1,4-butanediol can undergo esterification with dehydroabsic acid to generate an intermediate, which further reacts with boric acid to form dynamic borate ester bonds; 3-methacryloyloxypropyltrimethoxysilane provides reactive groups, which facilitates the participation of crosslinking agents in the coating curing reaction to form a crosslinking network; p-toluenesulfonic acid, as a catalyst, can promote the esterification reaction, and xylene, as a solvent, can ensure the uniform dispersion of each raw material to achieve a smooth reaction; the rosin-based dynamic borate ester crosslinking agent prepared by the synergistic effect of each raw material can endow the waterproof coating with excellent mechanical reinforcement and self-healing properties, while improving the crosslinking density and structural stability of the coating film.

[0011] Preferably, the preparation method of the rosin-based dynamic borate ester crosslinking agent includes the following steps: 1) Add dehydroabsic acid, 1,4-butanediol, p-toluenesulfonic acid and xylene to the reaction vessel and mix them evenly. At 25-30℃, purge the air in the vessel with nitrogen at a rate of 0.5-1.0 L / min for 15-20 min. Then, under nitrogen protection, raise the temperature to 125-135℃ and stir and reflux at 180-250 r / min for 3-4 h. Remove the water generated in the reaction through a water separator to obtain the rosin-based diol intermediate. 2) Cool the system obtained in step 1) to 95-105℃, add boric acid, maintain the temperature and stir the reaction at 150-200r / min for 2-3h, remove the water generated in the reaction to form a borate ester skeleton; 3) Cool the system obtained in step 2) to 70-80℃, slowly add 3-methacryloyloxypropyltrimethoxysilane dropwise over 35-45 min, keep the temperature after the addition is complete, and stir the reaction at 120-180 r / min for 3-5 h. 4) Remove xylene from the system obtained in step 3) by vacuum distillation at 130-145℃ and 5-10kPa absolute pressure for 1.5-2.5h to obtain the rosin-based dynamic borate ester crosslinking agent.

[0012] The above technical solution utilizes nitrogen protection to ensure the stability of the reaction system and reduce oxidation side reactions. Stepwise removal of reaction water promotes the forward esterification and borate esterification reactions, ensuring the effective formation of dynamic borate ester bonds. Slowly adding 3-methacryloyloxypropyltrimethoxysilane ensures a uniform and complete end-capping reaction, and the introduced reactive groups enhance the compatibility and reactivity of the rosin-based dynamic borate ester crosslinking agent with the coating system. Finally, solvent removal by vacuum distillation ensures product purity. The synergistic effect of these operations prepares a rosin-based dynamic borate ester crosslinking agent with a rigid tricyclic phenanthrene backbone and a stable dynamic borate ester bond structure. This crosslinking agent effectively improves the mechanical strength of waterproof coatings and imparts self-healing properties to the coating film.

[0013] Preferably, the raw materials for preparing the pH-responsive root-blocking microcapsules, by weight, include: 18-25 parts of matrine extract, 10-15 parts of carboxymethyl chitosan, 5-8 parts of sodium alginate, 1.0-1.6 parts of sorbitan oleate (Span 80), 50-70 parts of calcium chloride aqueous solution with a mass fraction of 8%-10%, 120-180 parts of acetic acid solution with a mass fraction of 1%-2%, and 120-160 parts of liquid paraffin.

[0014] Using the above technical solution, matrine extract, as the core material, can provide root-blocking active ingredients; carboxymethyl chitosan and sodium alginate can form a composite wall material, and carboxymethyl chitosan has pH-responsive characteristics; Span 80, as an emulsifier, combined with liquid paraffin, acetic acid solution and calcium chloride aqueous solution, can ensure the stable progress of the emulsification process, promote the dissolution of carboxymethyl chitosan and the cross-linking and solidification of sodium alginate, and achieve uniform coating of matrine extract; the synergistic effect of each raw material enables the prepared pH-responsive root-blocking microcapsules to release matrine under specific pH conditions to exert the root-blocking effect, while ensuring the structural stability of the microcapsules and the coating effect of the core material.

[0015] Preferably, the preparation method of the pH-responsive root-barrier microcapsules includes the following steps: (1) Dissolve carboxymethyl chitosan in acetic acid solution, add matrine extract and sodium alginate, stir at 250-400 r / min at 45-55℃ to dissolve, and obtain aqueous phase; (2) Add the aqueous phase to liquid paraffin containing Span 80 and emulsify it at 35-45℃ with a high-speed shearing of 5000-6000 r / min for 10-15 min to form a W / O emulsion; (3) Under the stirring conditions of 30-40℃ and 200-300r / min, the calcium chloride aqueous solution is slowly added dropwise to the W / O emulsion and stirred continuously at 200-300r / min for 40-50min to allow sodium alginate to crosslink with carboxymethyl chitosan ions to form a wall material; (4) Add 2.0-2.5 times the total volume of ethyl acetate to the system obtained in step (3), centrifuge at 3500-4500 r / min for 6-10 min, collect the solid product, wash the product with ethyl acetate and deionized water 2-3 times each, the amount of washing solution used each time is 3-5 times the mass of the product, centrifuge after washing to collect the solid phase; (5) Fluidized bed spray drying was adopted, with the inlet air temperature controlled at 85-95℃, the outlet air temperature at 55-65℃, the atomization pressure at 0.3-0.4MPa, and the drying time at 20-30min, to obtain pH-responsive root-barrier microcapsules with an average particle size of 5-15μm.

[0016] Using the above technical solution, carboxymethyl chitosan, matrine extract and sodium alginate are fully dissolved by heating and stirring to form a uniform aqueous phase. Under high-speed shearing, emulsification is carried out to form a stable W / O emulsion, ensuring uniform dispersion of the core material. Sodium alginate and carboxymethyl chitosan are cross-linked by calcium chloride aqueous solution to form a structurally stable composite wall material. Impurities are removed by centrifugation and washing to improve product purity. Then, by controlling the parameters of fluidized bed spray drying, pH-responsive root-barrier microcapsule powder with uniform average particle size is obtained.

[0017] Preferably, the epoxy value of the cashew phenol glycidyl ether is 0.35-0.45 mol / 100g; the bismuth content of the organic bismuth catalyst is 20%-25%; and the amine value of the cashew phenol polyamine curing agent is 350-380 mgKOH / g.

[0018] By employing the above technical solutions, limiting the epoxy value of cashew phenol glycidyl ether ensures a suitable reaction ratio between its epoxy groups and the amine groups of the cashew phenol polyamine curing agent, promoting a full interfacial bonding reaction. Limiting the bismuth content of the organic bismuth catalyst provides highly efficient catalytic activity, selectively accelerating the NCO-OH reaction process and regulating the curing rate. Limiting the amine value of the cashew phenol polyamine curing agent provides sufficient amine groups to participate in the crosslinking reaction, working synergistically with the epoxy groups of cashew phenol glycidyl ether and the NCO groups of castor oil-based polyurethane prepolymer to ensure the formation of a dense and stable crosslinking network in the coating system, thereby improving the mechanical properties and interfacial bonding of the coating film, while ensuring the controllability and stability of the curing reaction during construction.

[0019] This invention also discloses a method for preparing a bio-based root-penetration resistant waterproof coating, comprising the following steps: Preparation of S1 and A components: S11. Prepolymer modification: Castor oil-based polyurethane prepolymer, polysiloxane-modified acrylate resin, and cashew phenol glycidyl ether are added to a planetary mixer and mixed for 30-40 minutes at 40-50℃ and 10-20kPa absolute pressure with a revolution speed of 30-40 r / min and a rotation speed of 1200-1600 r / min. S12, Nano-dispersion: Under nitrogen protection, add sheet-like kaolin, cellulose nanofibers, and hydrophobic fumed silica sequentially to the system obtained in step S11. Disperse at 30-40 r / min revolution and 1200-1600 r / min rotation for 45-60 min. Use circulating cooling water to control the temperature of the material to ≤60℃. Then, ultrasonically disperse at 18-22 kHz and 300-500 W for 10-15 min. S13, Functional Combination: Keep the system obtained in step S12 at 50-60℃ and under an absolute pressure of 10-20kPa, add rosin-based dynamic borate ester crosslinking agent and organic bismuth catalyst in sequence, and mix at a revolution speed of 20-25 r / min and a rotation speed of 400-600 r / min for 20-30 min; then cool the system to 30-40℃, add pH-responsive root-barrier microcapsules, and mix at a revolution speed of 10-15 r / min and a rotation speed of 200-300 r / min for 10-15 min; S14. Vacuum degassing: Degas for 20-30 minutes under an absolute pressure of 10-20 kPa and a temperature of 25-35℃, and then seal to obtain component A. Preparation of S2 and B components: Cashew phenol polyamine curing agent, deionized water, propylene glycol methyl ether acetate, and Tween 80 are stirred at 600-800 r / min for 10-15 min, filtered through a 120-150 mesh filter under normal pressure, the filtrate is collected, and after standing for 10-15 min, the supernatant is taken to obtain component B.

[0020] By employing the above technical solution, the temperature, pressure, and stirring parameters during the prepolymer modification stage are controlled to promote the full pre-reaction of castor oil-based polyurethane prepolymer, polysiloxane-modified acrylate resin, and cashew phenol glycidyl ether, thereby improving the compatibility between components. In the nano-dispersion stage, nitrogen protection, temperature control, and ultrasonic-assisted dispersion work synergistically to achieve uniform dispersion of sheet-like kaolin, cellulose nanofibers, and hydrophobic fumed silica, avoiding agglomeration. In the functional composite stage, staged temperature and pressure control and stirring speed adjustment ensure the full integration of the rosin-based dynamic borate crosslinking agent and organic bismuth catalyst with the system, while maintaining the structural integrity of the pH-responsive root-barrier microcapsules. Vacuum degassing removes air bubbles from component A, improving the system's density. The stirring, filtration, and settling steps of component B yield a uniform and pure cured system. The synergistic effect of these steps enables the preparation of uniformly dispersed and structurally stable components A and B, ensuring the formation of a high-performance bio-based root-penetration-resistant waterproof coating after subsequent mixing.

[0021] Preferably, during construction, component A and component B are stirred at 400-600 r / min for 2-3 minutes, allowed to stand for 3-5 minutes for defoaming treatment, and then applied to a substrate surface free of dust, oil, and cracks; the construction environment temperature is 10-30℃, and the relative humidity is 45%-65%; the wet film thickness is 0.8-1.0 mm, 2-3 coats are applied, and the total dry film thickness is 1.5-2.7 mm.

[0022] By employing the above technical solutions, stirring at specific speeds and times ensures thorough mixing of components A and B, guaranteeing uniform subsequent curing reactions. Static defoaming treatment reduces air bubbles in the coating, lowering the film porosity. Cleaning the substrate surface enhances the interfacial bonding strength between the coating and the substrate. Suitable application temperature and humidity conditions provide a stable environment for coating curing, ensuring the orderly progress of the curing reaction. Coating in multiple coats and controlling specific wet and dry film thicknesses create a continuous, complete, and uniformly thick coating, enabling it to fully utilize its waterproof and root-penetration-resistant properties, ensuring the coating's performance stability and durability during service.

[0023] This invention also discloses the application of a bio-based root-penetration resistant waterproof coating in green roof planting systems, underground garage roof planting projects, or waterproofing of vertical green walls.

[0024] Using the above technical solution, the coating film cured by the bio-based root-penetration resistant waterproof coating can effectively resist the erosion of plant roots, effectively block water penetration, reduce the risk of damage to related waterproof substrates, and meet the long-term service requirements of the above-mentioned planting waterproof projects.

[0025] The beneficial effects of this invention are as follows: Component A, castor oil-based polyurethane prepolymer, provides a bio-based carbon chain backbone and reacts with cashew phenol polyamine curing agent to form a polymer network, giving the coating basic flexibility and adhesion properties; polysiloxane-modified acrylate resin introduces hydrophobic segments, improving the coating's hydrophobicity and weather resistance; rosin-based dynamic borate ester crosslinking agent achieves self-repair function after coating damage through reversible breaking and recombination of dynamic borate ester bonds, and enhances the coating's mechanical strength through its rigid structure; pH-responsive root-barrier microcapsules can directionally release the core material's active ingredients under conditions of local pH changes caused by acidic substances secreted by plant roots, achieving precise inhibition of root growth and giving the coating root penetration resistance; flaky kaolin forms a two-dimensional physical barrier. The coating consists of several components: a layer that extends the penetration path of water and roots; cellulose nanofibers that construct a reinforcing skeleton, improving the tensile strength of the coating and bridging microcracks; cashew phenol glycidyl ether that participates in the cross-linking reaction through epoxy groups, enhancing interfacial bonding; an organobismuth catalyst that catalyzes the curing reaction, increasing the density of the cross-linking network; hydrophobic fumed silica that fills the pores of the coating, further improving its density and hydrophobicity; and cashew phenol polyamine curing agent in component B that reacts with the active groups in component A to form a cross-linking network, improving the mechanical properties and adhesion strength of the coating. Deionized water provides the medium for the curing reaction; propylene glycol methyl ether acetate that improves the leveling and coatability of the coating, enhancing its application performance; and Tween 80 that improves the compatibility of components A and B. Through the synergistic effect of these components, the coating acquires excellent mechanical properties, root penetration resistance, self-healing properties, and waterproofing properties, and has a high bio-based content, meeting environmental protection requirements.

[0026] Dehydroabsic acid provides a rigid framework, while 1,4-butanediol can undergo esterification with dehydroabsic acid to generate an intermediate. This intermediate further reacts with boric acid to form dynamic borate ester bonds. 3-Methacryloxypropyltrimethoxysilane provides reactive groups, which facilitates the participation of crosslinking agents in the coating curing reaction to form a crosslinking network. Toluenesulfonic acid acts as a catalyst to promote the esterification reaction, while xylene acts as a solvent to ensure uniform dispersion of the raw materials for a smooth reaction. The rosin-based dynamic borate ester crosslinking agent prepared by the synergistic effect of the raw materials can endow waterproof coatings with excellent mechanical reinforcement and self-healing properties, while improving the crosslinking density and structural stability of the coating film. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] The specific information on the raw materials used in the embodiments of the present invention is shown in Table 1.

[0029] Table 1. Raw material names and sources

[0030] Example 1: This embodiment discloses a bio-based root-penetration resistant waterproof coating, composed of component A and component B in a mass ratio of 100:25, in parts by weight: The raw materials for preparing component A include: 35 parts of castor oil-based polyurethane prepolymer, 18 parts of polysiloxane-modified acrylate resin, 6 parts of rosin-based dynamic borate crosslinking agent, 8 parts of pH-responsive root-barrier microcapsules, 10 parts of flake kaolin, 3 parts of cellulose nanofibers, 1 part of cashew phenol glycidyl ether, 0.15 parts of organic bismuth catalyst, and 3 parts of hydrophobic fumed silica. The raw materials for preparing component B include: 25 parts cashew phenol polyamine curing agent, 10 parts deionized water, 5 parts propylene glycol methyl ether acetate, and 1 part Tween 80.

[0031] The castor oil-based polyurethane prepolymer has an NCO content of 4.5% and a viscosity of 3200 mPa·s at 25℃; the polysiloxane-modified acrylate resin has a hydroxyl value of 55 mgKOH / g; the flake kaolin has a flake diameter of 0.8 μm and an aspect ratio of 15; the cellulose nanofibers have a diameter of 20 nm and a length of 1 μm. The cashew phenol glycidyl ether has an epoxy value of 0.35 mol / 100 g; the organic bismuth catalyst has a bismuth content of 20%; and the cashew phenol polyamine curing agent has an amine value of 350 mgKOH / g.

[0032] The rosin-based dynamic borate ester crosslinking agent is made from the following raw materials in parts by weight: 50 parts dehydroabsic acid, 10 parts 1,4-butanediol, 4 parts boric acid, 8 parts 3-methacryloyloxypropyltrimethoxysilane, 0.3 parts p-toluenesulfonic acid, and 70 parts xylene.

[0033] The preparation method of rosin-based dynamic borate ester crosslinking agent includes the following steps: 1) Add dehydroabsic acid, 1,4-butanediol, p-toluenesulfonic acid and xylene to the reaction vessel and mix well. At 25°C, purge the air in the vessel with nitrogen at a rate of 0.5 L / min for 15 min. Then, under nitrogen protection, raise the temperature to 125°C and stir and reflux at 180 r / min for 3 h. Remove the water generated in the reaction through a water separator to obtain the rosin-based diol intermediate. 2) Cool the system obtained in step 1) to 95°C, add boric acid, maintain the temperature and stir at 150 r / min for 2 h, remove the water generated in the reaction to form a borate ester skeleton; 3) Cool the system obtained in step 2) to 70°C, slowly add 3-methacryloyloxypropyltrimethoxysilane dropwise over 35 min, keep the temperature after the addition is complete, and stir the reaction at 120 r / min for 3 h. 4) The system obtained in step 3) was subjected to vacuum distillation at 130℃ and 5kPa absolute pressure for 1.5h to remove xylene, thereby obtaining rosin-based dynamic borate ester crosslinking agent.

[0034] The raw materials for preparing pH-responsive root-blocking microcapsules, by weight, include: 18 parts matrine extract, 10 parts carboxymethyl chitosan, 5 parts sodium alginate, 1 part Span 80, 50 parts calcium chloride aqueous solution with a mass fraction of 8%, 120 parts acetic acid solution with a mass fraction of 1%, and 120 parts liquid paraffin.

[0035] The preparation method of pH-responsive root-barrier microcapsules includes the following steps: (1) Dissolve carboxymethyl chitosan in acetic acid solution, add matrine extract and sodium alginate, stir at 250 r / min at 45℃ to dissolve, and obtain an aqueous phase; (2) Add the aqueous phase to liquid paraffin containing Span 80 and emulsify it at 35°C and 5000 r / min for 10 min to form a W / O emulsion; (3) Under the stirring conditions of 30℃ and 200r / min, calcium chloride aqueous solution was slowly added dropwise to W / O emulsion and stirred continuously at 200r / min for 40min to allow sodium alginate and carboxymethyl chitosan ions to crosslink and form wall material; (4) Add ethyl acetate twice the total volume of the system to the system obtained in step (3), centrifuge at 3500 r / min for 6 min, collect the solid product, wash the product twice with ethyl acetate and deionized water each time, and use 3 times the mass of the product each time. After washing, centrifuge to separate and collect the solid phase. (5) Fluidized bed spray drying was used, with the inlet air temperature controlled at 85℃, the outlet air temperature at 55℃, the atomization pressure at 0.3MPa, and the drying time at 20min, to obtain pH-responsive root-barrier microcapsules with an average particle size of 5μm.

[0036] This embodiment also discloses a method for preparing a bio-based root-penetration resistant waterproof coating, comprising the following steps: Preparation of S1 and A components: S11. Prepolymer modification: Castor oil-based polyurethane prepolymer, polysiloxane-modified acrylate resin, and cashew phenol glycidyl ether are added to a planetary mixer and mixed for 30 min at 30 r / min revolution and 1200 r / min rotation under the conditions of 40℃ and 10 kPa absolute pressure. S12, Nano-dispersion: Under nitrogen protection, flaky kaolin, cellulose nanofibers and hydrophobic fumed silica are added sequentially to the system obtained in step S11. The mixture is dispersed for 45 min at a revolution speed of 30 r / min and a rotation speed of 1200 r / min. The temperature is controlled by circulating cooling water to keep the material temperature ≤60℃. Then, the mixture is ultrasonically dispersed for 10 min at 18 kHz and 300 W. S13, Functional Combination: The system obtained in step S12 is kept at 50°C and under an absolute pressure of 10 kPa, rosin-based dynamic borate ester crosslinking agent and organic bismuth catalyst are added sequentially, and mixed at a revolution speed of 20 r / min and a rotation speed of 400 r / min for 20 min; then the system is cooled to 30°C, pH-responsive root-barrier microcapsules are added, and mixed at a revolution speed of 10 r / min and a rotation speed of 200 r / min for 10 min; S14, Vacuum degassing: Degas for 20 minutes under an absolute pressure of 10 kPa and a temperature of 25°C, and then seal to obtain component A; Preparation of S2 and B components: Cashew phenol polyamine curing agent, deionized water, propylene glycol methyl ether acetate, and Tween 80 were stirred at 600 r / min for 10 min, filtered through a 120 mesh filter under normal pressure, the filtrate was collected, and after standing for 10 min, the supernatant was taken to obtain component B.

[0037] During construction, mix component A and component B at 400 r / min for 2 min, let stand for 3 min to defoam, and then apply to a substrate surface free of dust, oil, and cracks; the construction environment temperature is 10℃ and the relative humidity is 45%; the wet film thickness is 0.8 mm, apply 2 coats, and the total dry film thickness is 1.5 mm.

[0038] This invention also discloses the application of a bio-based root-penetration resistant waterproof coating in a green roof planting system.

[0039] Example 2: This embodiment discloses a bio-based root-penetration resistant waterproof coating, composed of component A and component B in a mass ratio of 100:35, in parts by weight: The raw materials for preparing component A include: 45 parts of castor oil-based polyurethane prepolymer, 28 parts of polysiloxane-modified acrylate resin, 10 parts of rosin-based dynamic borate crosslinking agent, 15 parts of pH-responsive root-barrier microcapsules, 12 parts of flake kaolin, 4 parts of cellulose nanofibers, 3 parts of cashew phenol glycidyl ether, 0.35 parts of organic bismuth catalyst, and 6 parts of hydrophobic fumed silica. The raw materials for preparing component B include: 35 parts cashew phenol polyamine curing agent, 18 parts deionized water, 10 parts propylene glycol methyl ether acetate, and 2 parts Tween 80.

[0040] The castor oil-based polyurethane prepolymer has an NCO content of 5.5% and a viscosity of 3600 mPa·s at 25℃; the polysiloxane-modified acrylate resin has a hydroxyl value of 65 mgKOH / g; the flake kaolin has a sheet diameter of 3.0 μm and an aspect ratio of 25; the cellulose nanofibers have a diameter of 50 nm and a length of 3 μm. The cashew phenol glycidyl ether has an epoxy value of 0.45 mol / 100 g; the organic bismuth catalyst has a bismuth content of 25%; and the cashew phenol polyamine curing agent has an amine value of 380 mgKOH / g.

[0041] The rosin-based dynamic borate ester crosslinking agent is made from the following raw materials in parts by weight: 60 parts dehydroabsic acid, 15 parts 1,4-butanediol, 6 parts boric acid, 12 parts 3-methacryloyloxypropyltrimethoxysilane, 0.6 parts p-toluenesulfonic acid, and 80 parts xylene.

[0042] The preparation method of rosin-based dynamic borate ester crosslinking agent includes the following steps: 1) Add dehydroabsic acid, 1,4-butanediol, p-toluenesulfonic acid and xylene to the reaction vessel and mix well. At 30°C, purge the air in the vessel with nitrogen at a rate of 1.0 L / min for 20 min. Then, under nitrogen protection, raise the temperature to 135°C and stir and reflux at 250 r / min for 4 h. Remove the water generated in the reaction through a water separator to obtain the rosin-based diol intermediate. 2) Cool the system obtained in step 1) to 105℃, add boric acid, maintain the temperature and stir at 200r / min for 3h, remove the water generated in the reaction to form a borate ester skeleton; 3) Cool the system obtained in step 2) to 80°C, slowly add 3-methacryloyloxypropyltrimethoxysilane dropwise over 45 min, keep the temperature after the addition is complete, and stir the reaction at 180 r / min for 5 h. 4) The system obtained in step 3) was subjected to vacuum distillation at 145℃ and 10kPa for 2.5h to remove xylene, thereby obtaining rosin-based dynamic borate ester crosslinking agent.

[0043] The raw materials for preparing pH-responsive root-blocking microcapsules, by weight, include: 25 parts matrine extract, 15 parts carboxymethyl chitosan, 8 parts sodium alginate, 1.6 parts Span 80, 70 parts calcium chloride aqueous solution with a mass fraction of 10%, 180 parts acetic acid solution with a mass fraction of 2%, and 160 parts liquid paraffin.

[0044] The preparation method of pH-responsive root-barrier microcapsules includes the following steps: (1) Dissolve carboxymethyl chitosan in acetic acid solution, add matrine extract and sodium alginate, stir at 400 r / min at 55℃ to dissolve, and obtain an aqueous phase; (2) Add the aqueous phase to liquid paraffin containing Span 80 and emulsify it at 45°C and 6000 r / min for 15 min to form a W / O emulsion; (3) Under the stirring conditions of 40℃ and 300r / min, calcium chloride aqueous solution was slowly added dropwise to W / O emulsion and stirred continuously at 300r / min for 50min to allow sodium alginate to crosslink with carboxymethyl chitosan ions to form wall material; (4) Add 2.5 times the total volume of ethyl acetate to the system obtained in step (3), centrifuge at 4500 r / min for 10 min, collect the solid product, wash the product with ethyl acetate and deionized water 3 times each, and use 5 times the mass of the product each time. After washing, centrifuge to separate and collect the solid phase. (5) Fluidized bed spray drying was used, with the inlet air temperature controlled at 95℃, the outlet air temperature at 65℃, the atomization pressure at 0.4MPa, and the drying time at 30min, to obtain pH-responsive root-barrier microcapsules with an average particle size of 15μm.

[0045] This embodiment also discloses a method for preparing a bio-based root-penetration resistant waterproof coating, comprising the following steps: Preparation of S1 and A components: S11, Prepolymer Modification: Castor oil-based polyurethane prepolymer, polysiloxane-modified acrylate resin, and cashew phenol glycidyl ether are added to a planetary mixer and mixed for 40 min at 50°C and 20 kPa absolute pressure with a revolution speed of 40 r / min and a rotation speed of 1600 r / min. S12, Nano-dispersion: Under nitrogen protection, flaky kaolin, cellulose nanofibers and hydrophobic fumed silica are added sequentially to the system obtained in step S11. The mixture is dispersed for 60 min at a revolution speed of 40 r / min and a rotation speed of 1600 r / min. The temperature is controlled by circulating cooling water to keep the material temperature ≤60℃. Then, the mixture is ultrasonically dispersed for 15 min at 22 kHz and 500 W. S13, Functional Combination: The system obtained in step S12 is kept at 60°C and under an absolute pressure of 20 kPa, rosin-based dynamic borate ester crosslinking agent and organic bismuth catalyst are added sequentially, and mixed at a revolution speed of 25 r / min and a rotation speed of 600 r / min for 30 min; then the system is cooled to 40°C, pH-responsive root-barrier microcapsules are added, and mixed at a revolution speed of 15 r / min and a rotation speed of 300 r / min for 15 min; S14, Vacuum degassing: Degas for 30 minutes under an absolute pressure of 20 kPa and a temperature of 35°C, and then seal to obtain component A; Preparation of S2 and B components: Cashew phenol polyamine curing agent, deionized water, propylene glycol methyl ether acetate, and Tween 80 were stirred at 800 r / min for 15 min, filtered through a 150 mesh filter under normal pressure, the filtrate was collected, and after standing for 15 min, the supernatant was taken to obtain component B.

[0046] During construction, mix component A and component B at 600 rpm for 3 minutes, let stand for 5 minutes to defoam, and then apply to a substrate surface free of dust, oil, and cracks; the construction environment temperature is 30℃ and the relative humidity is 65%; the wet film thickness is 1.0 mm, apply 3 coats, and the total dry film thickness is 2.7 mm.

[0047] This invention also discloses the application of a bio-based root-penetration resistant waterproof coating in underground garage roof planting projects.

[0048] Example 3: This embodiment discloses a bio-based root-penetration resistant waterproof coating, composed of component A and component B in a mass ratio of 100:30, in parts by weight: The raw materials for preparing component A include: 40 parts of castor oil-based polyurethane prepolymer, 23 parts of polysiloxane-modified acrylate resin, 8 parts of rosin-based dynamic borate crosslinking agent, 11 parts of pH-responsive root-barrier microcapsules, 11 parts of flake kaolin, 3.5 parts of cellulose nanofibers, 2 parts of cashew phenol glycidyl ether, 0.25 parts of organic bismuth catalyst, and 4.5 parts of hydrophobic fumed silica. The raw materials for preparing component B include: 30 parts cashew phenol polyamine curing agent, 14 parts deionized water, 7.5 parts propylene glycol methyl ether acetate, and 1.5 parts Tween 80.

[0049] The castor oil-based polyurethane prepolymer has an NCO content of 5% and a viscosity of 3400 mPa·s at 25℃; the polysiloxane-modified acrylate resin has a hydroxyl value of 60 mg KOH / g; the flake kaolin has a flake diameter of 2.0 μm and an aspect ratio of 20; the cellulose nanofibers have a diameter of 35 nm and a length of 2 μm. The cashew phenol glycidyl ether has an epoxy value of 0.4 mol / 100 g; the organic bismuth catalyst has a bismuth content of 22%; and the cashew phenol polyamine curing agent has an amine value of 365 mg KOH / g.

[0050] The rosin-based dynamic borate ester crosslinking agent is made from the following raw materials in parts by weight: 55 parts dehydroabsic acid, 12 parts 1,4-butanediol, 4 parts boric acid, 10 parts 3-methacryloyloxypropyltrimethoxysilane, 0.4 parts p-toluenesulfonic acid, and 75 parts xylene.

[0051] The preparation method of rosin-based dynamic borate ester crosslinking agent includes the following steps: 1) Add dehydroabsic acid, 1,4-butanediol, p-toluenesulfonic acid and xylene to the reactor and mix well. At 27°C, purge the air in the reactor with nitrogen at a rate of 0.7 L / min for 17 min. Then, under nitrogen protection, raise the temperature to 130°C and stir and reflux at 210 r / min for 3.5 h. Remove the water generated in the reaction through a water separator to obtain the rosin-based diol intermediate. 2) Cool the system obtained in step 1) to 100℃, add boric acid, maintain the temperature and stir the reaction at 175r / min for 2.5h, remove the water generated in the reaction to form a borate ester skeleton; 3) Cool the system obtained in step 2) to 75°C, slowly add 3-methacryloyloxypropyltrimethoxysilane dropwise over 40 min, keep the temperature after the addition is complete, and stir the reaction at 150 r / min for 4 h. 4) The system obtained in step 3) was subjected to vacuum distillation at 138℃ and 7kPa for 2 hours to remove xylene, thereby obtaining rosin-based dynamic borate ester crosslinking agent.

[0052] The raw materials for preparing pH-responsive root-blocking microcapsules, by weight, include: 21 parts matrine extract, 12 parts carboxymethyl chitosan, 6.5 parts sodium alginate, 1.3 parts Span 80, 60 parts calcium chloride aqueous solution with a mass fraction of 9%, 150 parts acetic acid solution with a mass fraction of 1.5%, and 140 parts liquid paraffin.

[0053] The preparation method of pH-responsive root-barrier microcapsules includes the following steps: (1) Dissolve carboxymethyl chitosan in acetic acid solution, add matrine extract and sodium alginate, stir at 320 r / min at 50℃ to dissolve, and obtain aqueous phase; (2) Add the aqueous phase to liquid paraffin containing Span 80 and emulsify it at 40°C and 5500 r / min for 12 min to form a W / O emulsion; (3) Under the stirring conditions of 35℃ and 250r / min, calcium chloride aqueous solution was slowly added dropwise to W / O emulsion and stirred continuously at 250r / min for 45min to allow sodium alginate to crosslink with carboxymethyl chitosan ions to form wall material; (4) Add 2.5 times the total volume of ethyl acetate to the system obtained in step (3), centrifuge at 4000 r / min for 8 min, collect the solid product, wash the product with ethyl acetate and deionized water 3 times each, and use 4 times the mass of the product each time. After washing, centrifuge to separate and collect the solid phase. (5) Fluidized bed spray drying was used, with the inlet air temperature controlled at 90℃, the outlet air temperature at 60℃, the atomization pressure at 0.35MPa, and the drying time at 25min, to obtain pH-responsive root-barrier microcapsules with an average particle size of 10μm.

[0054] This embodiment also discloses a method for preparing a bio-based root-penetration resistant waterproof coating, comprising the following steps: Preparation of S1 and A components: S11, Prepolymer Modification: Castor oil-based polyurethane prepolymer, polysiloxane-modified acrylate resin, and cashew phenol glycidyl ether are added to a planetary mixer and mixed for 35 min at 35 r / min revolution and 1400 r / min rotation under the conditions of 45℃ and 15 kPa absolute pressure. S12, Nano-dispersion: Under nitrogen protection, flaky kaolin, cellulose nanofibers and hydrophobic fumed silica are added sequentially to the system obtained in step S11. The mixture is dispersed at 35 r / min revolution and 1400 r / min rotation for 52 min. The temperature is controlled by circulating cooling water to keep the material temperature ≤60℃. Then, it is ultrasonically dispersed at 20 kHz and 400 W for 12 min. S13, Functional Combination: The system obtained in step S12 is kept at 55°C and under an absolute pressure of 15 kPa, rosin-based dynamic borate ester crosslinking agent and organic bismuth catalyst are added sequentially, and mixed at a revolution speed of 22 r / min and a rotation speed of 500 r / min for 25 min; then the system is cooled to 35°C, pH-responsive root-barrier microcapsules are added, and mixed at a revolution speed of 12 r / min and a rotation speed of 250 r / min for 12 min; S14, Vacuum degassing: Degas for 25 minutes under an absolute pressure of 15 kPa and a temperature of 30°C, and then seal to obtain component A; Preparation of S2 and B components: Cashew phenol polyamine curing agent, deionized water, propylene glycol methyl ether acetate, and Tween 80 were stirred at 700 r / min for 12 min, filtered through a 135 mesh filter under normal pressure, the filtrate was collected, and after standing for 12 min, the supernatant was taken to obtain component B.

[0055] During construction, mix component A and component B at 500 r / min for 2.5 min, let stand for 4.5 min to defoam, and then apply to a substrate surface free of dust, oil, and cracks; the construction environment temperature is 20℃ and the relative humidity is 55%; the wet film thickness is 0.9 mm, apply 3 coats, and the total dry film thickness is 2.5 mm.

[0056] This invention also discloses the application of a bio-based root-penetration resistant waterproof coating in waterproofing vertical green walls.

[0057] Comparative Example 1: A bio-based root-penetration resistant waterproof coating, its preparation method and application, differs from Example 3 only in that: no rosin-based dynamic borate ester crosslinking agent is added.

[0058] Comparative Example 2: A bio-based root-penetration resistant waterproof coating, its preparation method and application, differs from Example 3 only in that: pH-responsive root-barrier microcapsules are not added.

[0059] Comparative Example 3: A bio-based root-penetration resistant waterproof coating, its preparation method and application, differs from Example 3 only in that the pH-responsive root-barrier microcapsules are replaced with an equal amount of root-barrier agent 2-(4-chloro-2-methylphenoxy)propionate (Beijing Bailingwei Technology Co., Ltd., CAS: 23844-56-6).

[0060] Comparative Example 4: A bio-based root-penetration resistant waterproof coating, its preparation method and application, differs from Example 3 only in that: no flaky kaolin is added.

[0061] Comparative Example 5: A bio-based root-penetration resistant waterproof coating, its preparation method and application, differs from Example 3 only in that: cellulose nanofibers are replaced with an equal mass of ordinary calcium carbonate whiskers (Shanghai Jiadeer Chemical Technology Co., Ltd., CAS: 471-34-1).

[0062] Comparative Example 6: A bio-based root-penetration resistant waterproof coating, its preparation method and application, differs from Example 3 only in that: no polysiloxane-modified acrylate resin is added.

[0063] Comparative Example 7: A bio-based root-penetration resistant waterproof coating, its preparation method and application, differs from Example 3 only in that hydrophobic fumed silica is not added.

[0064] Comparative Example 8: A bio-based root-penetration resistant waterproof coating, its preparation method and application, differs from Example 3 only in that the mixing mass ratio of component A to component B is changed to 100:20 (the amount of curing agent is lower).

[0065] Comparative Example 9: A bio-based root-penetration resistant waterproof coating, its preparation method and application, differs from Example 3 only in that: in step S12, the planetary dispersion step is omitted, and only high-speed stirring dispersion is used, with a stirring speed of 1400 r / min and a time of 52 min.

[0066] The waterproof coatings obtained in Examples 1-3 and Comparative Examples 1-9 were subjected to performance tests for VOC content, tensile strength, bond strength, root penetration resistance, self-healing efficiency, xenon lamp aging resistance, water contact angle, water absorption rate, and storage stability. The test methods and standards for each performance are as follows: 1. Volatile Organic Compound (VOC) Content Detection: The determination was carried out according to the method specified in the national standard GB 18582-2020 "Limits of Harmful Substances in Wall Coatings for Buildings". The coating sample was baked at 105±2℃ for 1 hour, and the volatile content was detected by gas chromatography.

[0067] 2. Tensile property testing: In accordance with the national standard GB / T 16777-2008 "Test Methods for Waterproof Coatings for Buildings", a 2mm thick coating film was prepared and cut into dumbbell-shaped specimens. The tensile strength and elongation at break were determined using a universal testing machine at a tensile speed of 200mm / min. The distance between the markings on the specimens was 25mm. The average value of 5 specimens was taken as the result.

[0068] 3. Bond strength test: According to the method specified in national standard GB / T 16777-2008, the coating is applied to the surface of a standard concrete substrate. After it is fully dry, the bond strength with the concrete is determined by the figure-eight tensile test at a tensile speed of 10 mm / min.

[0069] 4. Root penetration resistance test: According to the national standard GB / T 35468-2017 "Root penetration resistant waterproof membrane for green roof", the coating sample was placed in a planting box, sown with tall fescue grass seeds, and cultured under standard plant growth conditions for 18 months. The root penetration was observed and the root barrier efficiency was calculated. Root barrier efficiency = [(dry weight of roots in the blank group - dry weight of roots in the test group) / dry weight of roots in the blank group] × 100%.

[0070] 5. Self-healing efficiency test: Referring to the scratch repair method in "Evaluation Methods for Self-Healing Polymer Materials" (Polymer Testing, 2021, 93: 106859), a scratch with a depth of 15μm and a width of 80μm was created on the coating surface using a micron indenter. After curing for 7 days at a temperature of 23-27℃ and a relative humidity of 50±5%, the scratch depth recovery rate was measured by laser confocal microscopy. The self-healing efficiency = [(initial depth - depth after curing) / initial depth] × 100%.

[0071] 6. Xenon lamp aging performance test: Based on the national standard GB / T 18244-2000 "Aging Test Method for Building Waterproofing Materials", a xenon arc lamp aging chamber was used with an irradiance of 0.51 W / m². 2 The tensile strength retention rate was measured after aging for 1500 hours with a wavelength of 340 nm, a blackboard temperature of 65 ± 3 ℃, a water spray cycle of 18 min / 102 min, and a wavelength of 340 nm.

[0072] 7. Water contact angle test: According to the national standard GB / T 30693-2014 "Determination of contact angle between plastic film and water", a contact angle measuring instrument is used. 3μL of deionized water is dropped onto the coating surface, and the static contact angle is measured at 5 different positions. The arithmetic mean is taken.

[0073] 8. Water absorption rate test: According to the national standard GB / T 1738-1979 "Determination of water absorption rate of insulating varnish film", the coating film is cut into 20mm×20mm test pieces, dried at 50±2℃ to constant weight m0, immersed in deionized water at 23±2℃ for 24h, taken out, the surface moisture is absorbed with filter paper, and weighed m1. Water absorption rate = [(m1-m0) / m0]×100%.

[0074] 9. Storage stability test: After sealing component A, place it at a temperature of 23±2℃ and a relative humidity of 50±5%. Take samples every 30 days to measure the changes in NCO content and viscosity. When the decrease rate of NCO content is >15% or the increase rate of viscosity is >50%, the storage period is considered to be over.

[0075] 10. Bio-based content is determined according to ASTM D6866-16 standard and calculated based on the ratio of bio-carbon to total carbon.

[0076] The results are shown in Tables 2 and 3.

[0077] Table 2. Test results of basic physical and mechanical properties of the waterproof coatings obtained in Examples 1-3 and Comparative Examples 1-9

[0078] Table 3. Test results of the functional and durability properties of the waterproof coatings obtained in Examples 1-3 and Comparative Examples 1-9

[0079] Comparison of Comparative Example 1 (without rosin-based dynamic borate ester crosslinking agent) and Example 3 The tensile strength decreased from 6.5 MPa to 4.5 MPa, a drop of 30.8%; the self-healing efficiency decreased from 70% to 12%, a drop of 82.9%; and the strength retention rate after xenon lamp aging decreased from 85% to 65%, a drop of 23.5%. This is because the rosin-based dynamic borate ester crosslinking agent simultaneously provides three functions: rigid tricyclic phenanthrene framework reinforcement, dynamic borate ester bond self-healing, and reactive end-capping groups. Without this component, the coating loses its stress dissipation capacity, and cracks are prone to irreversible propagation; simultaneously, the reinforcing effect of the rigid framework disappears, leading to a significant deterioration in mechanical properties and weather resistance.

[0080] Comparison of Comparative Example 2 (without pH-responsive root-barrier microcapsules) and Example 3 The root barrier efficiency dropped sharply from 96.5% to 48.2%, a decrease of 50.1%, and two penetrations occurred within the 18-month test period. The high root barrier efficiency in Example 3 was due to the intelligent release mechanism of the microcapsules, while Comparative Example 2, which did not add this component, relied solely on physical barrier and could not effectively inhibit root growth. These results confirm that the chemical inhibitory component plays a decisive role in the long-term root barrier effect.

[0081] Comparative Example 3 (2-(4-chloro-2-methylphenoxy)propionate as a root inhibitor replacing pH-responsive root-inhibiting microcapsules) compared with Example 3 Root inhibition efficiency decreased from 96.5% to 85.5%, a drop of 11.4%, with one penetration occurring after 18 months. Compared to the complete absence in Comparative Example 2, while the chemical root inhibitor provided some inhibition, it lacked the protection and sustained-release mechanism of microcapsules. The small-molecule root inhibitor migrated and decomposed during aging, resulting in insufficient long-term effectiveness. The strength retention rate after xenon lamp aging decreased from 85% to 78%, indicating poor compatibility between the chemical root inhibitor and the resin, affecting the coating's weather resistance.

[0082] Comparison of Example 4 (without added flaky kaolin) and Example 3 Tensile strength decreased from 6.5 MPa to 5.0 MPa, a decrease of 23.1%; bond strength decreased from 2.5 MPa to 1.9 MPa, a decrease of 24.0%; and water absorption increased from 2.5% to 4.2%, an increase of 68.0%. Two-dimensional kaolinite forms a physical barrier layer in the coating and enhances mechanical properties. Its absence leads to decreased coating density, increased water penetration pathways, and the disappearance of the nano-reinforcing effect, resulting in a decline in mechanical properties.

[0083] Comparative Example 5 (cellulose nanofibers replaced with ordinary calcium carbonate whiskers) compared with Example 3 Tensile strength decreased from 6.5 MPa to 5.4 MPa, a drop of 16.9%; self-healing efficiency decreased from 70% to 45%, a drop of 35.7%; and strength retention after xenon lamp aging decreased from 85% to 66%, a drop of 22.4%. Ordinary calcium carbonate whiskers have an aspect ratio of only 5-10, far lower than the 30-60 of cellulose nanofibers, making it impossible to construct an effective skeletal reinforcement structure. Furthermore, the lack of crack bridging by nanofibers leads to a simultaneous decline in mechanical properties, self-healing function, and durability.

[0084] Comparison Example 6 (acrylate resin without added polysiloxane) with Example 3 The water contact angle decreased from 135° to 105°, a reduction of 22.2%; the water absorption rate increased from 2.5% to 5.8%, an increase of 1.32 times; and the VOC increased from 6.8 g / L to 8.5 g / L, an increase of 25.0%. Organosilicon segments are crucial for constructing hydrophobic surfaces; their absence increases the surface energy of the coating, deteriorates water resistance, and reduces environmental performance.

[0085] Comparison Example 7 (without hydrophobic fumed silica) with Example 3 The water contact angle decreased from 135° to 88°, a reduction of 34.8%; the water absorption rate increased sharply from 2.5% to 8.5%, an increase of 2.4 times. Hydrophobic fumed silica can construct micro-nano rough structures on the coating surface, synergistically enhancing hydrophobic properties with polysiloxane-modified acrylate resin; its absence leads to a decrease in coating surface roughness, a reduction in the water contact angle, and an increase in water absorption rate, which will severely affect the long-term durability of the coating.

[0086] Comparison of Comparative Example 8 (lower amount of curing agent) and Example 3 The bond strength decreased from 2.5 MPa to 1.5 MPa, a drop of 40.0%; the surface drying time increased from 1.5 h to 2.8 h, an increase of 86.7%; and the storage stability decreased from 6 months to 5 months. The use of a curing agent below the stoichiometric ratio resulted in insufficient crosslinking density, incomplete reaction of NCO groups, and significant deterioration of mechanical and workability properties, while also weakening the effect of the latent curing agent.

[0087] Comparison of Comparative Example 9 (step S12 cancels planetary dispersion) with Example 3 Tensile strength decreased from 6.5 MPa to 5.4 MPa, a decrease of 16.9%; bond strength decreased from 2.5 MPa to 1.9 MPa, a decrease of 24.0%; and root barrier efficiency decreased from 96.5% to 91.5%, a decrease of 5.2%. The synergistic effect of planetary dispersion's revolution and rotation can generate strong shear forces, while simple high-speed stirring is insufficient to generate enough shear forces, leading to the aggregation of nanomaterials, the formation of defects, and a decrease in coating density.

[0088] In summary, rosin-based dynamic borate ester crosslinking agents can achieve self-repair function after coating damage through the reversible breaking and recombination of dynamic borate ester bonds, and enhance the mechanical strength of the coating through their rigid structure. pH-responsive root-barrier microcapsules can directionally release the active ingredients of the core material under conditions of local pH changes caused by acidic substances secreted by plant roots, achieving precise inhibition of root growth and endowing the coating with root penetration resistance. Flaky kaolin can form a two-dimensional physical barrier layer, extending the penetration path of water and roots. Cellulose nanofibers can construct a reinforcing skeleton, improving the tensile strength of the coating and bridging microcracks. The synergistic effect of these components endows the coating with excellent mechanical properties, root penetration resistance, self-healing properties, and waterproofing properties, and has a high bio-based content, meeting environmental protection requirements.

[0089] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A bio-based root-penetration resistant waterproof coating, characterized in that, Composed of component A and component B, in parts by weight: The raw materials for preparing component A include: 35-45 parts of castor oil-based polyurethane prepolymer, 18-28 parts of polysiloxane-modified acrylate resin, 6-10 parts of rosin-based dynamic borate crosslinking agent, 8-15 parts of pH-responsive root-barrier microcapsules, 10-12 parts of flake kaolin, 3-4 parts of cellulose nanofibers, 1-3 parts of cashew phenol glycidyl ether, 0.15-0.35 parts of organic bismuth catalyst, and 3-6 parts of hydrophobic fumed silica. The raw materials for preparing component B include: 25-35 parts cashew phenol polyamine curing agent, 10-18 parts deionized water, 5-10 parts propylene glycol methyl ether acetate, and 1-2 parts nonionic emulsifier; the mass ratio of component A to component B is 100:25-100:

35.

2. The bio-based root-penetration resistant waterproof coating according to claim 1, characterized in that, The castor oil-based polyurethane prepolymer has an NCO content of 4.5%-5.5% and a viscosity of 3200-3600 mPa·s at 25°C; the polysiloxane-modified acrylate resin has a hydroxyl value of 55-65 mgKOH / g; the flaky kaolin has a sheet diameter of 0.8-3.0 μm and an aspect ratio of 15-25; the cellulose nanofibers have a diameter of 20-50 nm and a length of 1-3 μm.

3. The bio-based root-penetration resistant waterproof coating according to claim 1, characterized in that, The rosin-based dynamic borate ester crosslinking agent is made from the following raw materials in parts by weight: 50-60 parts of dehydroabsic acid, 10-15 parts of 1,4-butanediol, 4-6 parts of boric acid, 8-12 parts of 3-methacryloyloxypropyltrimethoxysilane, 0.3-0.6 parts of p-toluenesulfonic acid, and 70-80 parts of xylene.

4. The bio-based root-penetration resistant waterproof coating according to claim 3, characterized in that, The preparation method of the rosin-based dynamic borate ester crosslinking agent includes the following steps: 1) Add dehydroabsic acid, 1,4-butanediol, p-toluenesulfonic acid and xylene to the reactor and mix well. At 25-30℃, purge the air in the reactor with nitrogen at a rate of 0.5-1.0 L / min for 15-20 min. Then, under nitrogen protection, raise the temperature to 125-135℃ and stir and reflux at 180-250 r / min for 3-4 h. Remove the water generated in the reaction. 2) Cool the system obtained in step 1) to 95-105℃, add boric acid, maintain the temperature and stir the reaction at 150-200r / min for 2-3h, and remove the water generated in the reaction; 3) Cool the system obtained in step 2) to 70-80℃, slowly add 3-methacryloyloxypropyltrimethoxysilane dropwise over 35-45 min, keep the temperature after the addition is complete, and stir the reaction at 120-180 r / min for 3-5 h. 4) Remove xylene from the system obtained in step 3) by vacuum distillation at 130-145℃ and 5-10kPa absolute pressure for 1.5-2.5h to obtain the rosin-based dynamic borate ester crosslinking agent.

5. The bio-based root-penetration resistant waterproof coating according to claim 1, characterized in that, The raw materials for preparing the pH-responsive root-blocking microcapsules, by weight, include: 18-25 parts of matrine extract, 10-15 parts of carboxymethyl chitosan, 5-8 parts of sodium alginate, 1.0-1.6 parts of Span 80, 50-70 parts of calcium chloride aqueous solution with a mass fraction of 8%-10%, 120-180 parts of acetic acid solution with a mass fraction of 1%-2%, and 120-160 parts of liquid paraffin.

6. The bio-based root-penetration resistant waterproof coating according to claim 5, characterized in that, The preparation method of the pH-responsive root-barrier microcapsules includes the following steps: (1) Dissolve carboxymethyl chitosan in acetic acid solution, add matrine extract and sodium alginate, stir at 250-400 r / min at 45-55℃ to dissolve, and obtain aqueous phase; (2) Add the aqueous phase to liquid paraffin containing Span 80 and emulsify it at 35-45℃ with a high-speed shearing of 5000-6000 r / min for 10-15 min to form a W / O emulsion; (3) Under stirring conditions of 30-40℃ and 200-300r / min, calcium chloride aqueous solution is slowly added dropwise to W / O emulsion, and stirring is continued at 200-300r / min for 40-50min; (4) Add 2.0-2.5 times the total volume of ethyl acetate to the system obtained in step (3), centrifuge at 3500-4500 r / min for 6-10 min, collect the solid product, wash the product with ethyl acetate and deionized water 2-3 times each, the amount of washing solution used each time is 3-5 times the mass of the product, centrifuge after washing to collect the solid phase; (5) Fluidized bed spray drying was used, with the inlet air temperature controlled at 85-95℃, the outlet air temperature at 55-65℃, the atomization pressure at 0.3-0.4MPa, and the drying time at 20-30min, to obtain pH-responsive root-barrier microcapsules.

7. The bio-based root-penetration resistant waterproof coating according to claim 1, characterized in that, The cashew phenol glycidyl ether has an epoxy value of 0.35-0.45 mol / 100g; the organic bismuth catalyst has a bismuth content of 20%-25%; and the cashew phenol polyamine curing agent has an amine value of 350-380 mgKOH / g.

8. A method for preparing a bio-based root-penetration resistant waterproof coating as described in any one of claims 1-7, characterized in that, Includes the following steps: Preparation of S1 and A components: S11. Prepolymer modification: Castor oil-based polyurethane prepolymer, polysiloxane-modified acrylate resin, and cashew phenol glycidyl ether are added to a planetary mixer and mixed for 30-40 minutes at 40-50℃ and 10-20kPa absolute pressure with a revolution speed of 30-40 r / min and a rotation speed of 1200-1600 r / min. S12, Nano-dispersion: Under nitrogen protection, add sheet-like kaolin, cellulose nanofibers, and hydrophobic fumed silica sequentially to the system obtained in step S11. Disperse at 30-40 r / min revolution and 1200-1600 r / min rotation for 45-60 min. Use circulating cooling water to control the temperature of the material to ≤60℃. Then, ultrasonically disperse at 18-22 kHz and 300-500 W for 10-15 min. S13, Functional Combination: Keep the system obtained in step S12 at 50-60℃ and under an absolute pressure of 10-20kPa, add rosin-based dynamic borate ester crosslinking agent and organic bismuth catalyst in sequence, and mix at a revolution speed of 20-25 r / min and a rotation speed of 400-600 r / min for 20-30 min; then cool the system to 30-40℃, add pH-responsive root-barrier microcapsules, and mix at a revolution speed of 10-15 r / min and a rotation speed of 200-300 r / min for 10-15 min; S14. Vacuum degassing: Degas for 20-30 minutes under an absolute pressure of 10-20 kPa and a temperature of 25-35℃, and then seal to obtain component A. Preparation of S2 and B components: Cashew phenol polyamine curing agent, deionized water, propylene glycol methyl ether acetate, and nonionic emulsifier are stirred at 600-800 r / min for 10-15 min, filtered through a 120-150 mesh filter under normal pressure, the filtrate is collected, and after standing for 10-15 min, the supernatant is taken to obtain component B.

9. The method for preparing the bio-based root-penetration resistant waterproof coating according to claim 8, characterized in that, During application, mix component A and component B at 400-600 rpm for 2-3 minutes, let stand for 3-5 minutes to defoam, and then apply to a substrate surface free of dust, oil, and cracks. The ambient temperature during application should be 10-30℃, and the relative humidity should be 45%-65%. The wet film thickness should be 0.8-1.0 mm, and 2-3 coats should be applied. The total dry film thickness should be 1.5-2.7 mm.

10. The application of a bio-based root-penetration resistant waterproof coating as described in any one of claims 1-7 in green roof planting systems, underground garage roof planting projects, or waterproofing of vertical green walls.

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