Waterborne emulsion coating system based on phas and bio-based multiphase particle pickering stabilization and interfacial chemical anchoring, and preparation method and application thereof

Abstract

The application discloses a water-based emulsion coating system based on PHA and bio-based heterogeneous particle Pickering stabilization and interfacial chemical anchoring as well as a preparation method and application thereof, and belongs to the technical field of bio-based water-based coating and functional coating. The application constructs a Pickering stabilization structure by using bio-based heterogeneous particles, and realizes stable dispersion of polyhydroxyalkanoate in water and embedding of a heterogeneous network after solidification by combining with a reactive interfacial bonding crosslinking technology. By introducing a chemical anchoring effect at the interface, the application endows the bio-based coating with excellent water resistance, adhesion strength and dense barrier protection capability. The components of the system are safe and environmentally friendly, and are suitable for surface protection and functional development of various substrates such as paper-based materials, molded fibers and wood, thereby providing an efficient and environmentally-friendly technical solution for the green packaging and sustainable surface protection field.

Description

Technical Field

[0001] This invention belongs to the field of bio-based waterborne coatings and functional coatings, specifically relating to waterborne emulsion coating systems based on PHA and bio-based multiphase particle Pickering stabilization and interfacial chemical anchoring, as well as their preparation methods and applications. Background Technology

[0002] Polyhydroxyalkanoates (PHAs) are a class of bio-based polyesters synthesized by microorganisms. They are renewable, biodegradable, and possess good hydrophobic barrier properties, making them suitable as core resins for packaging barrier coatings, protective coatings for wood and building materials, and environmentally friendly surface protective layers. In the application of oil resistance, seepage prevention, and water resistance in paper-based materials, traditional solutions utilize fluorinated organic compounds to achieve oil resistance and water repellency. Therefore, under the requirements of "fluorine-free, recyclable, and low migration," there is an urgent need for alternative water-based protective coating systems.

[0003] In the prior art, several technical routes have been disclosed regarding PHA aqueous dispersions, PHA aqueous coating formulations, and their barrier applications on paper-based and fiber-based materials. For example, WO1997021762A1 and its family CA2239980C disclose a route for dissolving PHA in a low-water-soluble liquid, emulsifying it in an aqueous phase containing a dispersant, and removing the solvent to obtain a PHA latex / dispersion; EP3608415A1, WO2018186278A1, etc., disclose PHA particles or their aqueous dispersions and their film-forming applications; WO2020036843A1 and its family US11866606, ZA202101369B, etc., disclose the use of aqueous PHA dispersions as coating layers for barrier and water-resistant coatings on food contact or fiber-based substrates; AU2024241217A1, etc., discloses the construction of PHA particle dispersion coating compositions using low molecular weight dispersants for use on fiber-based substrate surfaces; EP4239028A1, EP4379001A1, etc., disclose the improvement of the storage stability and water resistance of PHA dispersions through specific stabilization systems; and domestic... Correspondingly, CN116891581A and CN117769583A disclose processes for preparing PHA microspheres or aqueous dispersions through solvent emulsification / melt dispersion / solvent removal, etc.; CN119777197A discloses a route for directly using PHA aqueous dispersions obtained by cell wall breaking treatment of PHA fermentation broth to prepare water-based coatings; related to paper-based packaging barrier, CN120250392B discloses nanoscale barrier emulsions of polyhydroxyalkanoates (PHA) and polyvinyl alcohol (PVA) and their preparation methods, CN120026524B discloses an aqueous emulsion barrier coating system of polyhydroxyalkanoates (PHA), polybutylene adipate terephthalate (PBAT), and polyvinyl alcohol (PVA); at the same time, CN121407420A discloses a dual PHA barrier system in which an aqueous PHA dispersion sealing layer and a PHA extruded dense layer are sequentially formed on a paper substrate, as well as its preparation and application. Furthermore, the idea of ​​introducing nanocellulose and other particles into waterborne coatings to construct a Pickering stabilization system has also been publicly disclosed, such as KR20220115756A and CN106750375B, which involve the Pickering stabilization of nanocellulose particles and their application in coating / emulsion systems. Published literature indicates that in Pickering emulsion systems, when nanocellulose has strong hydrophilicity, its particle adsorption at the hydrophobic interface is limited. A second particle component, such as lignin nanoparticles, can be introduced as a co-stabilizer to enhance interfacial synergistic stabilization. The aforementioned disclosures do not involve combining reactive interfacial bonding crosslinking agents and amine curing agents in PHA waterborne emulsions to achieve multiphase interfacial chemical anchoring and network interlocking in single-layer waterborne coatings.

[0004] However, the aforementioned existing approaches still have the problem of not easily meeting the application requirements of this field:

[0005] Some technical routes rely on small molecule emulsifiers or water-soluble polymer stabilizing systems (such as polyvinyl alcohol (PVA)) to achieve dispersion stability. After drying, there are risks such as migration of hydrophilic components, water immersion extraction, barrier attenuation, and decreased wet adhesion.

[0006] Some routes achieve barrier and molding properties by blending polyesters such as PBAT or by using multi-layer structures (such as sealing layers and extruded dense layers), but this introduces a longer process chain, increased equipment and energy consumption, and synergistic complexity between water-based construction and thermal processing.

[0007] Some technical routes directly prepare water-based coatings from the dispersion obtained by cell wall disruption of fermentation broth. Although this can reduce some of the dispersion difficulty, systematic solutions are still needed in terms of controllable particle size, impurity consistency, long-term storage stability, and subsequent film density.

[0008] Even when bio-based functional particles (such as nanocellulose, lignin, and chitosan) are added to a system, they often face problems such as wet migration and shedding, and difficulty in maintaining their function over a long period of time.

[0009] Therefore, a technical solution is needed that can stably disperse PHA in the aqueous phase and effectively lock the multiphase structure after film formation and curing: under the premise of minimizing dependence on easily migrating hydrophilic stabilizers, a Pickering stable structure is constructed by bio-based multiphase particles, and interfacial reactions and network interlocking are introduced during the curing stage, so that the PHA phase, particle layer and curing network form a stable anchor at the interface, thereby enabling the coating to maintain barrier and protective capabilities under wet conditions and long-term service conditions. Summary of the Invention

[0010] The purpose of this invention is to overcome the shortcomings of the prior art and provide an aqueous emulsion coating system based on PHA and bio-based multiphase particle Pickering stabilization and interfacial chemical anchoring, as well as its preparation method and application.

[0011] To achieve the above objectives, the present invention provides the following technical solution:

[0012] This invention provides a waterborne coating system with a pickering interface anchoring for polyhydroxyalkanoates (PHA). The coating system comprises an aqueous emulsion and an amine curing agent. The aqueous emulsion includes water as a continuous phase and contains a bio-based pickering stabilizing system and a bio-based reactive interfacial bonding crosslinking agent. The amine curing agent is an aqueous solution or dispersion of a bio-based amine curing agent. The aqueous emulsion and the amine curing agent are mixed before use to obtain an application coating. The ratio of the total equivalent of the effective functional groups in the bio-based reactive interfacial bonding crosslinking agent that can react with the amine to the total equivalent of the amine hydrogen in the bio-based amine curing agent is 1.0–1.1, for example, 1.0, 1.01, 1.02, 1.03, 1.04, 1.05, or 1. 06, 1.07, 1.08, 1.09, 1.1; the construction coating forms a single-layer protective coating after application, drying and curing; wherein, based on the dry solids of the aqueous emulsion, the aqueous emulsion comprises: 10-90 parts by weight of polyhydroxyalkanoate (PHA), for example 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90 parts by weight; 0.5-8.0 parts by weight of bio-based Pickering stable system, for example 0.5, 0.8, 1.0, 1.2, 1.5, 1.8, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 6.0, 7.0, 7.5, 8.0 parts by weight; 5-25 parts by weight of bio-based reactive interfacial bonding crosslinking agents, for example, 5, 6, 8, 10, 12, 14, 15, 16, 18, 20, 22, 24, 25 parts by weight; 0-80 parts by weight of bio-based co-film forming components or bio-based co-bonding components, for example, 0, 5, 10, 15, 20, 22, 24, 25, 28.5, 30, 35, 37, 38, 40, 42.5, 45, 50, 60, 70, 80 parts by weight; 0-80 parts by weight of pigments or fillers, for example, 0, 5, 10, 15, 20, 25, 30, 35, 37, 38, 40, 50, 60, 70, 80 parts by weight; and 0-15 parts by weight of bio-based or renewable resource-derived additives, for example, 0, 1, 2, 3, 5, 8... 10, 12, 13.5, 15 parts by weight; the bio-based Pickering stabilizing system comprises nanocellulose particles and a second particulate component; the PHA exists in the form of PHA emulsion particles, which are obtained by emulsifying and solidifying a molten PHA phase; the monolayer protective coating is formed by the reaction of the bio-based reactive interfacial bonding crosslinking agent and the bio-based amine curing agent to form a cured network, and the interfacial anchoring index W of the monolayer protective coating is ≤5.0wt%, for example 0.5wt%, 1.0wt%, 1.5wt%, 1.8wt%, 1.9wt%, 2.0wt%, 2.1wt%, 2.2wt%, 2.3wt%, 2.5wt%, 2.8wt%, 3.0wt%, 3.5wt%, 4.0wt%, 4.5wt%, 4.8wt%, 5.0wt%, where W = (1 - m1 / m0) × 100%, m0 is the initial mass of the cured free membrane, and m1 is the mass of the free membrane after being soaked in deionized water at 23℃ for 24 hours and then vacuum dried at 40℃ to constant weight.

[0013] The PHA is selected from short-chain polyhydroxy fatty acid esters, medium- and long-chain polyhydroxy fatty acid esters, or copolymers between monomers forming short-chain and medium- and long-chain polyhydroxy fatty acid esters; the short-chain polyhydroxy fatty acid ester is selected from one or more of poly(3-hydroxybutyrate) (PHB), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), and poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P34HB); the medium- and long-chain polyhydroxy fatty acid ester is selected from one or more of poly(3-hydroxyhexanoate), poly(3-hydroxyoctanoate), poly(3-hydroxydecanoate), poly(3-hydroxydodecanate), or copolymers thereof, specifically, for example, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH); the median particle size D of the PHA emulsion particles is... 50The particle size ranges from 0.2 μm to 2.0 μm, for example, 0.2 μm, 0.3 μm, 0.4 μm, 0.45 μm, 0.5 μm, 0.55 μm, 0.6 μm, 0.65 μm, 0.75 μm, 0.8 μm, 0.95 μm, 1.0 μm, 1.2 μm, 1.5 μm, 1.6 μm, 1.8 μm, 1.9 μm, and 2.0 μm; the second particle component is selected from lignin particles, chitosan, and their derivatives. The nanoparticles or combinations thereof; based on the total mass of the bio-based Pickering stabilizing system, the mass ratio of the nanocellulose particles to the second particle component is 1:0.05 to 1:20, for example 1:0.05, 1:0.06, 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.67, 1:1, 1:2, 1:3, 1:4, 1:5, 1:10, 1:15. The ratio is 1:20; the average particle size of the second particulate component is 5nm to 20μm, for example, 5nm, 20nm, 50nm, 100nm, 200nm, 300nm, 350nm, 400nm, 500nm, 800nm, 1μm, 2μm, 5μm, 10μm, 15μm, 20μm; the bio-based amine curing agent is selected from fatty acid dimer diamine, fatty acid dimer polyamide amine, and polyamine prepared from amino acids. Amines, polylysine, chitosan oligoamines, fermentation-derived diamines or polyamines and their salts or combinations thereof; the amine curing agent has an amine hydrogen equivalent of 50-600 g / eq, for example 50 g / eq, 55 g / eq, 100 g / eq, 150 g / eq, 200 g / eq, 250 g / eq, 270 g / eq, 300 g / eq, 400 g / eq, 500 g / eq, 580 g / eq, 600 g / eq.

[0014] The nanocellulose particles are selected from cellulose nanofibers (CNF), microfibrillated cellulose, cellulose nanocrystals, cellulose microparticles, or combinations thereof, and the nanocellulose particles are unmodified or obtained through oxidation, esterification, etherification, quaternization, or grafting modification; the characteristic size of the nanocellulose particles is 5 nm to 20 μm, for example, 5 nm, 50 nm, 100 nm, 500 nm, 1 μm, 5 μm, 10 μm, or 20 μm; the bio-based reactive interfacial bonding crosslinking agent is a non-isocyanate type crosslinking agent, containing at least one reactive group that undergoes addition, ring-opening, or condensation reactions with the amine curing agent, and the reactive group is selected from epoxy groups, cyclic carbonate groups, anhydride groups, or combinations thereof; the bio-based reactive interfacial bonding crosslinking agent is selected from epoxidized soybean oil, epoxidized linseed oil, epoxidized castor oil, vegetable oil-based cyclic carbonates, sugar alcohol-based cyclic carbonates, rosin-based anhydrides, or combinations thereof.

[0015] The bio-based reactive interfacial bonding crosslinking agent exists in the aqueous emulsion in one or more of the following ways: adsorbed on the surface of the bio-based Pickering stable system particles; distributed on the surface or near-surface layer of the PHA emulsion particles; dissolved or dispersed within the PHA phase; the bio-based co-film forming component or bio-based co-bonding component comprises at least one of the following: polylactic acid (PLA), polybutylene succinate (PBS), cellulose and its esterified or etherified derivatives, starch and its derivatives (such as corn starch), shellac, rosin and its modified resins, and vegetable oil-based polyesters; the pigment or filler is selected from calcium carbonate, silica, titanium dioxide (TiO2), clay minerals, biochar, or combinations thereof; the additives are selected from thickeners, rheology modifiers, defoamers, wetting and dispersing agents, leveling agents, slip and scratch-resistant additives, preservatives, antibacterial agents, UV-resistant additives, antioxidants, or combinations thereof.

[0016] This invention also provides a method for preparing an aqueous emulsion, comprising the following steps: Step 1: preparing an aqueous phase by dispersing the bio-based Pickering stabilizing system in water to obtain an aqueous dispersion; Step 2: preparing a molten organic phase by heating PHA to a molten state and mixing it with at least one of a bio-based reactive interfacial bonding crosslinking agent and a bio-based co-film forming component or a bio-based co-bonding component to obtain a molten organic phase; Step 3: dispersing the molten organic phase obtained in Step 2 in the aqueous dispersion obtained in Step 1 under shear emulsification conditions to obtain a pre-emulsion; homogenizing the pre-emulsion under high pressure to obtain an emulsion; Step 4: solidifying the PHA in the emulsion obtained in Step 3 by cooling to form PHA emulsion particles to obtain an aqueous emulsion.

[0017] The organic phase temperature in step 2 is 5–100°C above the melting point of PHA, for example, 5°C, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 80°C, or 100°C; the shear emulsification speed in step 3 is 1000–30000 rpm, for example, 1000 rpm, 5000 rpm, 10000 rpm, 12000 rpm, 15000 rpm, 20000 rpm, 25000 rpm, or 30000 rpm, and the time is 0.5–60 min, for example, 0.5 min, 1 min, 5 min, 10 min, 20 min, or 30 min. 60 min; the high-pressure homogenization pressure in step 3 is 50-2000 bar, for example 50 bar, 100 bar, 500 bar, 800 bar, 1000 bar, 1500 bar, 2000 bar, and the number of cycles is 1-20, for example 1 time, 2 times, 5 times, 10 times, 15 times, 20 times; wherein, all or part of the bio-based reactive interfacial bonding crosslinking agent is added to the aqueous dispersion in step 1, so that it is adsorbed on the surface of the bio-based Pickering stable system particles or pre-reacts with the surface groups of the bio-based Pickering stable system particles.

[0018] The present invention also provides a method for forming a protective coating, comprising the following steps: Step 1: mixing the aforementioned aqueous emulsion and amine curing agent according to the aforementioned equivalent ratio to obtain an application coating; Step 2: applying the application coating obtained in Step 1 to the surface of a substrate by an aqueous coating method to obtain a wet coating sample; Step 3: drying the wet coating sample obtained in Step 2 and curing it at room temperature or 40-120°C, for example 40°C, 50°C, 60°C, 80°C, 100°C, 120°C for 0.5-72 hours, for example 0.5 hours, 1 hour, 12 hours, 24 hours, 48 ​​hours, 72 hours to obtain a single-layer protective coating.

[0019] The present invention also provides a coated article, comprising a substrate and a protective coating covering the surface of the substrate, wherein the protective coating is a single-layer protective coating formed by water-based application, drying and curing of an application coating obtained by mixing the aforementioned water-based emulsion and an amine curing agent; the substrate is selected from paper, cardboard, molded fiber, wood, artificial board, textile, leather, metal, inorganic building materials, plastic or composite materials thereof.

[0020] The dry film thickness of the protective coating is 0.1–500 μm, for example, 0.1 μm, 0.5 μm, 1.0 μm, 5 μm, 10 μm, 20 μm, 25 μm, 30 μm, 50 μm, 100 μm, 200 μm, 300 μm, and 500 μm; when used on paper-based materials, the dry coating weight is 0.2–120 g / m², for example, 0.2 g / m², 1.0 g / m², 5.0 g / m², 10 g / m², 15 g / m², 30 g / m², 50 g / m², 80 g / m², 100 g / m², and 120 g / m²; when the coated product is water-based coated paper and paperboard for food packaging, it conforms to GB / T The water absorption rate, as determined by GB / T 1540-2002, is ≤10.0 g / m² after 30 minutes, for example, 10.0 g / m², 9.9 g / m², 9.8 g / m², 9.5 g / m², 9.2 g / m², 9.0 g / m², 8.9 g / m², 8.8 g / m², 8.6 g / m², 8.5 g / m², 8.2 g / m², 8.0 g / m², and 7.5 g / m². Furthermore, no leakage is observed during water penetration tests at 90℃ and soybean oil penetration tests at 95℃, conducted according to the test conditions specified in GB / T 44834-2024. The heat seal strength is as per GB / T... The measurement should be ≥0.30 kN / m, as specified in the corresponding clause of 44834-2024, for example, 0.30 kN / m, 0.38 kN / m, 0.40 kN / m, 0.41 kN / m, 0.42 kN / m, 0.43 kN / m, 0.44 kN / m, 0.45 kN / m, 0.46 kN / m, 0.47 kN / m, 0.48 kN / m, 0.50 kN / m, 0.52 kN / m. N / m, 0.55kN / m, 0.65kN / m, and wetting tension ≥38mN / m, for example 38mN / m, 39mN / m, 40mN / m, 41mN / m, 42mN / m, 43mN / m, 44mN / m, 45mN / m; wetting tension for the free surface or free film of the coating with 100% coverage shall be determined according to GB / T14216-2008 and shall be ≥38mN / m.

[0021] The present invention also provides uses of the aforementioned coating system for forming single-layer barrier coatings, moisture-proof coatings, oil-resistant coatings, abrasion-resistant protective coatings, UV-resistant coatings, antibacterial coatings, chemical-resistant coatings, or combinations thereof through water-based coating and curing; when used in paper or molded fiber packaging materials, it is used to replace or reduce polyethylene film or petrochemical-based barrier coatings, wherein the single-layer barrier coating is formed by water-based coating, drying, and curing of the application coating; when the second particulate component contains lignin particles, it is used to improve the UV resistance and weather protection properties of the coating; when the second particulate component contains chitosan and its derivative particles, it is used to improve the antibacterial and wet adhesion protection properties of the coating.

[0022] Compared with the prior art, the following significant advantages can be obtained by using the present invention:

[0023] Excellent interfacial anchoring and moisture resistance: This invention achieves strong anchoring of multiphase components in the cured coating by constructing a three-dimensional network of "bio-based Pickering particles - reactive interfacial bonding crosslinking agent - amine curing agent". Experiments show that the interfacial anchoring index W of the obtained monolayer protective coating is stably controlled below 5.0 wt%, and can even be as low as 1.5 wt%, effectively solving the problems of easy water absorption, migration and decreased adhesion of traditional bio-based aqueous dispersions in a wet state, and ensuring the integrity of the coating under long-term immersion and contact with chemical media.

[0024] Excellent balance between barrier properties and mechanical strength: The coating system forms a dense, pinhole-free coating that achieves excellent water and oil resistance on paper-based materials, and can withstand 90°C hot water and 95°C hot oil without leakage. Simultaneously, by controlling the type and crosslinking density of the PHA resin, the coating exhibits high hardness and abrasion resistance on rigid substrates, while demonstrating good folding resistance and heat-sealing strength on flexible substrates, achieving a balance between barrier properties and mechanical protection.

[0025] Outstanding storage stability and microstructure control: A Pickering stabilizing system, composed of nanocellulose and a second particle component in a specific ratio, combined with melt emulsification, produces an aqueous emulsion with controllable particle size and excellent thermal storage stability. The steric hindrance of the dual-particle system not only prevents particle aggregation but also provides a structural basis for subsequent film formation and functionalization.

[0026] Excellent environmental performance and functional scalability: No fluorinated additives or resins were intentionally introduced into the formulation of this system. Total fluorine in the cured coating was not detected (<5 mg / kg) according to EN 14582:2016. Furthermore, by selecting different types of secondary particles, additional functions can be imparted to the coating. For example, the introduction of lignin particles significantly improves UV resistance and weather resistance, while the introduction of chitosan particles gives the coating excellent surface antibacterial activity. The coated products also have good potential for re-sizing and recycling. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the microscopic cross-sectional structure of the coating formed after the polyhydroxy fatty acid ester Pickering interface anchoring waterborne coating system described in this invention is applied to a substrate and cured.

[0028] In the figure, 1-substrate; 2-single-layer protective coating; 3-polyhydroxyalkanoate emulsion particles; 4-second particulate component; 5-cured network; 6-bio-based reactive interfacial bonding crosslinking agent; 7-auxiliary agent; 8-bio-based co-bonding component. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention. Unless otherwise stated, the raw materials used in this embodiment are commercially available industrial products or can be prepared by conventional methods. Unless otherwise specified, performance testing methods are performed according to the standards described in the invention summary section.

[0030] Figure 1 This is a schematic diagram of the microstructure of a single-layer protective coating formed by coating an aqueous emulsion coating system based on PHA and bio-based multiphase particle Pickering stabilization and interfacial chemical anchoring, applied to a substrate surface and dried and cured. The structure includes a supporting substrate 1, the upper surface of which is covered with a single-layer protective coating 2 obtained by drying and curing the aqueous coating system. The single-layer protective coating 2 is a dense structure containing multiphase components. The internal dispersed phase consists of polyhydroxyalkanoate emulsion particles 3, which are large spherical particles. The surface and / or near the interface of these particles are adsorbed with particulate components of the bio-based Pickering stabilization system, including a second particulate component 4 in the form of irregular blocks or flakes, and nanocellulose particles, thereby constructing a Pickering-stabilized particulate adsorption layer at the interface. The continuous phase filling the gaps and surfaces of the polyhydroxyalkanoate emulsion particles 3, anchoring and locking the multiphase components, is the cured network 5. It is formed by the chemical reaction of a bio-based reactive interfacial bonding crosslinking agent 6 and a bio-based amine curing agent, and may contain additives 7 and bio-based co-bonding components 8 to jointly construct an overall network with strong interfacial adhesion and dense barrier function. The schematic diagram on the right further visually illustrates the specific chemical groups and active molecular structures derived from different components contained in the cured network 5, indicating that each active component jointly locks the multiphase structure through interfacial anchoring.

[0031] Main reagents and raw materials:

[0032] Table 1. Main reagent and raw material names, product models and manufacturers:

[0033]

[0034] Main analytical and testing instruments:

[0035] Table 2 mainly analyzes the names, models, and manufacturers of the testing instruments:

[0036]

[0037] Main testing standards:

[0038] Particle size testing: GB / T 19077-2024;

[0039] Water vapor transmission rate (WVTR) of paper-based samples: GB / T 2679.2-2015;

[0040] Water absorption (Cobb value): GB / T 1540-2002;

[0041] Oil resistance (Kit value, as a supplementary comparative indicator): determined according to TAPPI T 559 cm-22; the main evaluation index of oil resistance of film-forming barrier coatings is the 95℃ soybean oil leakage test of GB / T 44834-2024.

[0042] Adhesion: GB / T 9286-2021;

[0043] Pencil hardness: GB / T 6739-2022;

[0044] Abrasion resistance: ASTM D4060-25;

[0045] Tensile properties: GB / T 1040.3-2006;

[0046] Solvent wiping resistance / chemical resistance: GB / T 23989-2009;

[0047] Salt spray resistance: GB / T 10125-2021;

[0048] Textile color fastness test: color fastness to washing with soap: GB / T 3921-2008;

[0049] Wetting tension: GB / T 14216-2008;

[0050] Artificial accelerated aging test: GB / T 23987.3-2025;

[0051] Yellow Index and its Changes: GB / T 39822-2021;

[0052] Surface antibacterial properties: GB / T 31402-2023 (equivalent to ISO 22196:2011);

[0053] Repulping recyclability: CEPI "Paper and Board-Recyclability Laboratory Test Method-Part I: Recycling Mill with Conventional Process" Version 3 (February 2025);

[0054] Total fluoride content: Screening was conducted in accordance with EN 14582:2016;

[0055] Customized evaluation index – Interface anchoring index W: W = (1 - m1 / m0) × 100%, where m0 is the initial mass of the free membrane after curing, and m1 is the mass of the free membrane after being soaked in deionized water at 23℃ for 24 hours and then vacuum dried to constant weight at 40℃ and vacuum degree ≤ -0.09MPa; the constant weight is measured after drying for 2 hours each time under the same conditions, and the difference between two consecutive weighings is ≤ 0.2mg; W ≤ 5.0wt% is qualified.

[0056] Self-made materials and general preparation process:

[0057] Preparation of lignin particle aqueous dispersion: 2.0 g of lignin precursor UPM BioPiva 238 was weighed and added to 100 mL of a 60% (v / v) ethanol / water mixed solvent. 1.0 mol / L sodium hydroxide solution was added to adjust the pH to 12.0. The mixture was magnetically stirred at room temperature for 2 h to fully dissolve the lignin. The resulting solution was filtered through a 0.45 μm filter membrane and then added dropwise to 400 mL of deionized water at a rate of 10 mL / min. The mechanical stirring speed was 1000 rpm. After the dispersion was formed, the ethanol was removed by rotary evaporation under reduced pressure at 40 °C. The pH was then adjusted to 7.0 with 1.0 mol / L hydrochloric acid. The solid content was adjusted to 2.0 wt% by adding or concentrating deionized water to obtain an aqueous dispersion of lignin particles with an average particle size of 350 nm.

[0058] Preparation of lignin nanoclusters in aqueous dispersion: 1.0 g of lignin precursor UPM BioPiva 238 was weighed and added to 100 mL of 0.05 mol / L sodium hydroxide solution. The solution was stirred at room temperature for 4 h to ensure complete dissolution. Subsequently, deionized water was dialyzed for 48 h using a dialysis bag with a molecular weight cutoff of 3500 Da, with water changed every 4 h. After dialysis, the pH was adjusted to 7.0, and the solution was concentrated under reduced pressure to a solid content of 0.5 wt%, yielding an aqueous dispersion of lignin nanoclusters with an average particle size of 5 nm. The particle size of lignin nanoclusters with a particle size of 5 nm was measured using transmission electron microscopy (TEM). The particle size of dispersions with a particle size greater than 50 nm and less than 1 μm was measured using dynamic light scattering (DLS). The particle size of particles ≥ 1 μm was measured using a laser particle size analyzer. The results were taken as the average of three parallel measurements.

[0059] Preparation of chitosan particle aqueous dispersion (ionogel method): 1.0 g of chitosan precursor was weighed and added to 100 mL of 1.0 wt% acetic acid aqueous solution. The mixture was stirred at room temperature for 12 h until completely dissolved to obtain a chitosan solution. Separately, 0.2 wt% sodium tripolyphosphate (TPP) aqueous solution was prepared. Under stirring at 800 rpm, the TPP solution was added dropwise to the chitosan solution at a rate of 5 mL / min, with a total added volume of 50 mL. After the addition was completed, stirring was continued for 30 min. After centrifugation at 12000 g for 10 min and washing three times to remove free small molecules, the solid content was adjusted to 1.0 wt% to obtain a chitosan particle aqueous dispersion with an average particle size of 500 nm.

[0060] Preparation of chitosan microparticle aqueous dispersion: Chitosan precursor was spray-dried to obtain dry powder, and then sieved through a standard sieve to obtain particle fractions with a particle size of 15μm to 25μm; 5.0g of the particles were weighed and added to 95.0g of deionized water, and 0.2g of glacial acetic acid was added to assist wetting. After stirring at room temperature for 2h, a chitosan microparticle aqueous dispersion with a solid content of 5.0wt% and an average particle size of 20μm was obtained.

[0061] Preparation of bio-based carbonate crosslinking agent: Using epoxidized soybean oil Vikoflex 7170 as raw material, 100.0 g of Vikoflex 7170 and 1.0 g of tetrabutylammonium bromide were added to a pressure-resistant reactor. Carbon dioxide was introduced and the pressure was increased to 3.0 MPa. The temperature was raised to 120 °C and stirred for 6 h. After the reaction was completed, the pressure was released by cooling. Low-boiling substances were removed by depressurization at 60 °C and the catalyst was removed by filtration to obtain a vegetable oil-based cyclic carbonate crosslinking agent. The carbonate equivalent was calculated using the integral result of the proton nuclear magnetic resonance spectrum, and 280 g / eq was used for subsequent equivalent calculations.

[0062] Preparation of amine curing agents: The bio-based amine curing agents are prepared into aqueous solutions or aqueous dispersions according to the formulation requirements. Unless otherwise specified, the solid content of the amine curing agent is controlled at 30 wt%. Small molecule amine curing agents are directly dissolved in deionized water; hydrophobic amine curing agents are dispersed in deionized water under high-speed shear dispersion conditions to obtain stable aqueous dispersions. Details are as follows:

[0063] The bio-based amine curing agent A is Priamine 1075 dimeric acid diamine (Croda), with an amine hydrogen equivalent of approximately 270 g / eq. 30.0 g of Priamine 1075 was weighed and added to 70.0 g of deionized water. The mixture was then dispersed at 12000 rpm for 10 min at 25°C to obtain a 30 wt% aqueous dispersion of bio-based amine curing agent A.

[0064] Bio-based amine curing agent B is a fatty acid dimer polyamide amine, Ancamide 350A, Evonik, which belongs to the fatty acid dimer polyamide amine category and has an amine hydrogen equivalent of 110 g / eq. 30.0 g of bio-based amine curing agent B was weighed and added to 70.0 g of deionized water. After preheating at 55°C for 20 min, it was dispersed at a high-speed shearing rate of 12000 rpm for 15 min and cooled to 25°C to obtain a 30 wt% aqueous dispersion of bio-based amine curing agent B.

[0065] The bio-based amine curing agent C is ε-polylysine (Free Form, JNC Corporation), which is a polyamine prepared from L-lysine via biotechnology, with an amine hydrogen equivalent of 64 g / eq based on repeating units. 30.0 g of bio-based amine curing agent C was weighed and added to 70.0 g of deionized water. The mixture was magnetically stirred at 25°C for 30 min to obtain a 30 wt% aqueous solution of bio-based amine curing agent C.

[0066] The bio-based amine curing agent D is a laboratory-prepared lysine-based polyamine. Using (S)-(+)-lysine hydrochloride (816018, Sigma-Aldrich) as a precursor, it was reacted with bio-based glycerol diglycidyl ether at a molar ratio of 1:0.18 at 75°C for 6 hours. After the reaction, the mixture was neutralized, desalted, dialyzed, and concentrated under reduced pressure to obtain bio-based amine curing agent D. Its amine hydrogen equivalent was determined to be 50 g / eq using a perchloric acid-glacial acetic acid non-aqueous potentiometric titration method. Before use, 30.0 g of bio-based amine curing agent D was weighed and added to 70.0 g of deionized water. The mixture was stirred at 25°C for 30 minutes until homogeneous, yielding a 30 wt% aqueous solution of bio-based amine curing agent D.

[0067] Bio-based amine curing agent E is a laboratory-made bio-based pentanediamine (PDA) modified polyamine. Using Cathay Biotech's bio-based pentanediamine (PDA) as the amine source, it was added to epoxidized soybean oil at a molar ratio of 1:0.64 and reacted at 80℃ for 4 hours. After the reaction, the mixture was degassed under reduced pressure and dried under vacuum to obtain bio-based amine curing agent E. Its amine hydrogen equivalent was determined to be 600 g / eq using a perchloric acid-glacial acetic acid non-aqueous potentiometric titration method. Before use, 30.0 g of bio-based amine curing agent E was weighed and added to 70.0 g of deionized water. The mixture was then dispersed at 25℃ and 10000 rpm for 20 minutes under high-speed shearing to obtain a 30 wt% aqueous dispersion of bio-based amine curing agent E.

[0068] Bio-based amine curing agent F is a laboratory-made bio-based pentanediamine (PDA) modified polyamine. Its preparation route is the same as that of bio-based amine curing agent E, but with Cathay Biotech's bio-based pentanediamine (PDA) and epoxidized soybean oil added at a molar ratio of 1:0.65, and reacted at 80℃ for 5 hours. Its amine hydrogen equivalent was determined to be 650 g / eq using a perchloric acid-glacial acetic acid non-aqueous potentiometric titration method. Before use, 30.0 g of bio-based amine curing agent F was weighed, added to 70.0 g of deionized water, and dispersed at 25℃ and 10000 rpm for 20 minutes to obtain a 30 wt% aqueous dispersion of bio-based amine curing agent F.

[0069] Unless otherwise stated, the corresponding ratios of the curing agents in Examples 1-13, Examples 16-19, and those not specifically specified all use bio-based amine curing agent A; when preparing the coating, the ratio of the total equivalent of effective reactive functional groups in the bio-based reactive interfacial bonding crosslinking agent to the total equivalent of amine hydrogen in the amine curing agent is controlled at 1.0.

[0070] BioTen manufacturing process:

[0071] Step 1: Aqueous phase preparation. The bio-based Pickering stabilization system was dispersed in deionized water and dispersed by high-speed shear dispersion to obtain an aqueous dispersion; unless otherwise specified, the pH of the aqueous phase was controlled at 7.0.

[0072] Step 2: Preparation of the molten organic phase. The PHA resin is heated to a molten state. The "melting point" is measured using a differential scanning calorimetry (DSC) second-rise temperature curve, with the temperature controlled at the Tm of the PHA used. m At a temperature above 30°C, a bio-based reactive interfacial bonding crosslinking agent and optional co-film forming components or co-bonding components are mixed under heat preservation and stirring conditions to obtain a molten organic phase.

[0073] Step 3: Emulsification and Homogenization. The molten organic phase is dispersed in an aqueous dispersion under shear emulsification conditions to obtain a pre-emulsion; unless otherwise specified, the emulsification speed is 12000 rpm and the emulsification time is 10 min. The pre-emulsion is then subjected to high-pressure homogenization; unless otherwise specified, the homogenization pressure is 800 bar and the number of cycles is 5. During emulsification and homogenization, the system temperature is maintained at 10°C above the melting point of PHA to prevent premature solidification of PHA and resulting particle size imbalance.

[0074] Step 4: Solidification into granules. After homogenization, the mixture is cooled and solidified while stirring at 300 rpm. It is then cooled to 25°C and stirred for another 30 minutes to allow the PHA to solidify and form emulsion particles, resulting in an aqueous emulsion. Unless otherwise specified, the solid content of the obtained aqueous emulsion is controlled at 30 wt%.

[0075] BioTen 1031 (PHBV aqueous emulsion): prepared using poly(3-hydroxybutyrate-co-3-hydroxyvalerate) resin (PHBV, brand name PV3000G, Microstructure Factory, molecular weight grade 300,000 Da < Mw < 400,000 Da).

[0076] BioTen 1033 (PHBH aqueous emulsion): prepared using poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) resin (PHBH, brand name GreenPlanet X151A, Zhongyuan Chemical, molecular weight grade 300,000 Da < Mw < 400,000 Da).

[0077] BioTen 1030 (PHB aqueous emulsion): prepared using poly(3-hydroxybutyrate) resin (PHB, brand name PB3000G, Microstructure Factory, molecular weight grade 300,000 Da < Mw < 400,000 Da);

[0078] BioTen 1032 (P34HB aqueous emulsion): prepared using poly(3-hydroxybutyrate-co-4-hydroxybutyrate) resin (P34HB, brand name A1000P, CJ Bio, molecular weight grade 300,000 Da < Mw < 400,000 Da).

[0079] Example:

[0080] Unless otherwise stated, the formulations in Examples 1-21 and Comparative Examples 1-15 are based on the dry solids of the corresponding aqueous emulsions, and the "parts by weight" refers to the dry solids by weight. Unless otherwise stated, the application coatings are all obtained by mixing the prepared aqueous emulsion with the corresponding bio-based amine curing agent at a ratio of 1.0 between the total equivalent of the effective functional groups that can react with the amine in the bio-based reactive interfacial bonding crosslinking agent and the total equivalent of the amine hydrogen in the amine curing agent.

[0081] Example 1:

[0082] Formulation (based on dry solids of BioTen 1031 aqueous emulsion): 60 parts by weight of PHBV, 1.5 parts by weight of CNF, 1.0 part by weight of lignin particles, 15 parts by weight of bio-based epoxy crosslinking agent, and 24 parts by weight of PLA. Preparation: The BioTen 1031 aqueous emulsion was prepared according to the above BioTen preparation process. The emulsification speed was 12000 rpm, the emulsification time was 10 min, the homogenization pressure was 800 bar, and the number of cycles was 5. The resulting emulsion D 50 The thickness is 0.40 μm; the emulsion is mixed with bio-based amine curing agent A at a reaction equivalent ratio of 1.0 to obtain the construction coating.

[0083] Example 2:

[0084] Formulation (based on dry solids of BioTen 1033 aqueous emulsion): PHBH 45 parts by weight, CNF 1.0 parts by weight, lignin particles 0.2 parts by weight, bio-based epoxy crosslinking agent 25 parts by weight, PLA 30 parts by weight. Preparation: The BioTen 1033 emulsion was prepared according to a general method, with the organic phase temperature at 150°C. The rest of the preparation was the same as in Example 1. The resulting emulsion D... 50 It is 1.50 μm.

[0085] Example 3:

[0086] Formulation (based on the dry solids of BioTen 1031 aqueous emulsion): PHBV 55 parts by weight, CNF 1.0 parts by weight, chitosan particles 2.0 parts by weight, bio-based epoxy crosslinking agent 15 parts by weight, PLA 28.5 parts by weight. Preparation: In step 1, CNF and chitosan particles are pre-dispersed in the aqueous phase. In step 2, the melting temperature of PHBV is controlled at 175℃, the emulsification speed is 12000 rpm, the time is 10 min, the high-pressure homogenization pressure is 800 bar, and the cycle is 5 times. The resulting emulsion D 50 It is 0.80μm.

[0087] Example 4:

[0088] Formulation (based on BioTen 1031 aqueous emulsion dry solids): PHBV 40 parts by weight, CNF 1.0 parts by weight, lignin particles 3.0 parts by weight, bio-based epoxy crosslinking agent 20 parts by weight, PLA 38 parts by weight. Preparation: The aqueous phase contains CNF and high-content lignin particles; the organic phase temperature is 175℃; the emulsification speed is 12000 rpm; the time is 10 min; the high-pressure homogenization pressure is 800 bar; and the cycle is 5 times. The resulting emulsion D... 50 It is 0.60μm.

[0089] Example 5:

[0090] Formulation (based on the dry solids of BioTen 1031 aqueous emulsion): 10 parts by weight of PHBV, 1.0 parts by weight of CNF, 0.2 parts by weight of lignin particles, 10 parts by weight of bio-based epoxy crosslinking agent, 40 parts by weight of PLA, and 40 parts by weight of polybutylene succinate (PBS). Preparation: The organic phase has a low PHBV content. It is modified by blending PLA and PBS in a high proportion. The melting temperature is 175℃, the emulsification speed is 12000 rpm, the time is 10 min, the high-pressure homogenization pressure is 800 bar, and the cycle is 5 times. The resulting emulsion D 50 It is 0.30μm.

[0091] Example 6:

[0092] Formulation (based on the dry solids of BioTen 1033 aqueous emulsion): 90 parts by weight of PHBH, 0.5 parts by weight of CNF, 0.2 parts by weight of lignin particles, 5 parts by weight of bio-based epoxy crosslinking agent, and 5.0 parts by weight of PLA. Preparation: Same as Example 2, the resulting emulsion D... 50 It is 1.90 μm.

[0093] Example 7:

[0094] Formulation (based on the dry solids of BioTen 1031 aqueous emulsion): PHBV 50 parts by weight, CNF 3.0 parts by weight, lignin particles 0.5 parts by weight, bio-based epoxy crosslinking agent 10 parts by weight, calcium carbonate 38 parts by weight. Preparation: CNF, lignin particles, and calcium carbonate filler were pre-dispersed in an aqueous phase at an organic phase temperature of 175℃, an emulsification speed of 12000 rpm, a time of 10 min, and a high-pressure homogenization pressure of 800 bar, repeated 5 times. The resulting emulsion D... 50 It is 1.80 μm.

[0095] Example 8:

[0096] Formulation (based on the dry solids of BioTen 1031 aqueous emulsion): 50 parts by weight of PHBV, 1.0 parts by weight of CNF, 0.2 parts by weight of lignin particles, 12 parts by weight of bio-based carbonate crosslinking agent, and 38 parts by weight of PLA. Preparation: The bio-based epoxy crosslinking agent was replaced with a bio-based carbonate crosslinking agent. 3.6 parts by weight of the 12 parts by weight of the crosslinking agent were added to the aqueous dispersion in step 1 and sheared at 10,000 rpm for 5 min to allow the crosslinking agent to adsorb and distribute on the surface of the nanocellulose and lignin particles. The remaining 8.4 parts by weight were added to the molten organic phase in step 2 and mixed with PHBV and PLA. The molten organic phase temperature was 175℃, the emulsification speed was 12,000 rpm, the time was 10 min, the high-pressure homogenization pressure was 800 bar, and the cycle was 5 times. The resulting emulsion D... 50 It is 0.45μm.

[0097] Example 9:

[0098] Formulation (based on the dry solids of BioTen 1031 aqueous emulsion): PHBV 55 parts by weight, CNF 1.0 parts by weight, lignin particles 0.2 parts by weight, bio-based anhydride crosslinking agent 8 parts by weight, PLA 37 parts by weight. Preparation: Using bio-based anhydride crosslinking agent, organic phase temperature 175℃, emulsification speed 12000 rpm, time 10 min, high-pressure homogenization pressure 800 bar, 5 cycles, resulting in emulsion D. 50 It is 0.50μm.

[0099] Example 10:

[0100] Formulation (based on dry solids of BioTen 1031 aqueous emulsion): PHBV 40 parts by weight, CNF 5.0 parts by weight, lignin particles 0.5 parts by weight, bio-based epoxy crosslinking agent 20 parts by weight, PLA 37 parts by weight. Preparation: High-dose CNF was used to enhance system stability. The organic phase temperature was 175℃, the emulsification speed was 12000 rpm, the time was 10 min, the high-pressure homogenization pressure was 800 bar, and the cycle was 5 times. The resulting emulsion D 50 It is 0.20μm.

[0101] Example 11:

[0102] Formulation (based on dry solids of BioTen 1033 aqueous emulsion): 40 parts by weight of PHBH, 1.5 parts by weight of CNF, 1.0 part by weight of lignin particles, 15 parts by weight of bio-based epoxy crosslinking agent, and 42.5 parts by weight of PLA. Preparation: The PHBH emulsion was prepared according to a general method, with an organic phase temperature of 155°C. The remaining steps were the same as in Example 1. The median particle size D of the resulting emulsion was... 50 It is 0.55μm.

[0103] Example 12:

[0104] Formulation (based on the dry solids of BioTen 1031 aqueous emulsion): PHBV 50 parts by weight, CNF 0.38 parts by weight, chitosan particles 7.6 parts by weight, bio-based carbonate crosslinking agent 20 parts by weight, PLA 22.0 parts by weight. Preparation: The mass ratio of CNF to chitosan particles was 1:20. To ensure effective dispersion of high-content particles, the shear emulsification speed was increased to 15000 rpm for 10 min, the high-pressure homogenization pressure was 800 bar, the cycle was 5 times, and the organic phase temperature was 175℃. The resulting emulsion D... 50 It is 0.95μm.

[0105] Example 13:

[0106] Formula (based on the dry solids of BioTen 1033 aqueous emulsion): 40 parts by weight of PHBH, 1.0 parts by weight of CNF, 0.5 parts by weight of lignin particles, 15 parts by weight of bio-based epoxy crosslinking agent, 30 parts by weight of corn starch, and 13.5 parts by weight of shellac. Preparation: First, corn starch is prepared into a 10wt% starch slurry and gelatinized by stirring at 80℃ for 30 min. Shellac is dissolved in water, and the pH is adjusted to 8.5 using 1.0 mol / L sodium hydroxide, and stirred at 50℃ for 60 min. The starch slurry and shellac solution are added to the aqueous dispersion obtained in step 1 as co-film-forming components or co-binder components in the aqueous phase, and then the emulsion is prepared according to the general process. The melting temperature of PHBH in the organic phase is 155℃, the emulsification speed is 12000 rpm, the time is 10 min, the high-pressure homogenization pressure is 800 bar, and the cycle is 5 times. The resulting emulsion D 50It is 0.75μm.

[0107] Example 14:

[0108] Formulation (based on dry solids of BioTen 1031 aqueous emulsion): 60 parts by weight of PHBV, 1.5 parts by weight of CNF, 1.0 part by weight of lignin particles, 15 parts by weight of bio-based epoxy crosslinking agent, and 24 parts by weight of PLA. Preparation: The emulsion was prepared as in Example 1; curing was performed using the aforementioned bio-based amine curing agent B, which has an amine hydrogen equivalent of 110 g / eq and a reaction equivalent ratio of 1.1. The resulting emulsion D... 50 It is 0.40 μm.

[0109] Example 15:

[0110] Formulation (based on dry solids of BioTen 1031 aqueous emulsion): PHBV 50 parts by weight, CNF 2.0 parts by weight, lignin particles 1.0 parts by weight, bio-based anhydride crosslinking agent 10 parts by weight, titanium dioxide 37 parts by weight. Preparation: Following a general preparation process, CNF, lignin particles, and TiO2 were added to the aqueous phase. The organic phase temperature was 175℃, the emulsification speed was 12000 rpm, the time was 10 min, the high-pressure homogenization pressure was 800 bar, and the cycle was 5 times. The resulting emulsion was mixed with the aforementioned bio-based amine curing agent C at a reaction equivalent ratio of 1.05. The amine hydrogen equivalent of the bio-based amine curing agent C was 64 g / eq. The resulting emulsion D... 50 It is 0.65μm.

[0111] Example 16:

[0112] Formulation (based on the dry solids of BioTen 1033 aqueous emulsion): PHBH 45.0 parts by mass, CNF 0.476 parts by mass, lignin nanoclusters 0.024 parts by mass, bio-based epoxy crosslinking agent 25.0 parts by mass, PLA 29.5 parts by mass. The total amount of the bio-based Pickering stabilizing system is 0.500 parts by mass, and the mass ratio of CNF to the second particle component is 1:0.05. Preparation: In step 1, CNF and lignin nanoclusters are co-dispersed in the aqueous phase; in step 2, the organic phase temperature is 155℃; in step 3, the emulsification speed is 15000 rpm, the time is 10 min, the high-pressure homogenization pressure is 1000 bar, and the cycle is 5 times; in step 4, the emulsion is cooled and solidified into granules; the resulting emulsion D 50 It is 1.95μm.

[0113] Example 17:

[0114] Formulation (based on dry solids of BioTen 1031 aqueous emulsion): PHBV 48.0 parts by mass, CNF 0.5 parts by mass, chitosan microparticles 7.5 parts by mass, bio-based carbonate crosslinking agent 20.0 parts by mass, PLA 24.0 parts by mass. The total amount of the bio-based Pickering stabilizing system is 8.0 parts by mass, the mass ratio of CNF to the second particulate component is 1:15, and the average particle size of the second particulate component is 20 μm. Preparation: In step 1, CNF and chitosan microparticles are dispersed in the aqueous phase; in step 2, the organic phase temperature is 175℃; in step 3, the emulsification speed is 15000 rpm, the time is 10 min, the high-pressure homogenization pressure is 800 bar, and the cycle is 5 times; in step 4, the emulsion is cooled and solidified into granules; the resulting emulsion D 50 It is 1.15μm.

[0115] Example 18:

[0116] Formulation (based on the dry solids of BioTen 1031 aqueous emulsion): PHBV 10.0 parts by weight, CNF 1.5 parts by weight, lignin particles 1.0 parts by weight, bio-based epoxy crosslinking agent 7.5 parts by weight, calcium carbonate 50.0 parts by weight, titanium dioxide 20.0 parts by weight, and biochar 10.0 parts by weight. The total amount of pigments or fillers is 80.0 parts by weight. Preparation: In step 1, CNF, lignin particles, calcium carbonate, titanium dioxide, and biochar are added sequentially to deionized water and pre-dispersed at 12000 rpm for 8 min; in step 2, the organic phase temperature is 175℃; in step 3, the emulsification speed is 15000 rpm, the time is 12 min, the high-pressure homogenization pressure is 1000 bar, and the cycle is 8 times; in step 4, the emulsion is cooled and solidified into granules; the resulting emulsion D 50 It is 1.85μm.

[0117] Example 19:

[0118] Formula (based on the dry solids of BioTen 1031 aqueous emulsion): PHBV 55.0 parts by weight, CNF 1.0 parts by weight, lignin particles 0.5 parts by weight, bio-based epoxy crosslinking agent 15.0 parts by weight, PLA 13.5 parts by weight, and additives 15.0 parts by weight. Among these, hydroxypropyl starch phosphate thickener 5.0 parts by weight, deoiled lecithin wetting and dispersing agent 3.0 parts by weight, vegetable oil-based defoamer 3.0 parts by weight, rosin-modified leveling agent 2.0 parts by weight, and mixed tocopherol antioxidant 2.0 parts by weight. Preparation: In step 1, CNF, lignin particles, hydroxypropyl starch phosphate thickener, deoiled lecithin wetting and dispersing agent, and vegetable oil-based defoamer are dispersed in the aqueous phase. The thickener is pre-dissolved at 60℃ for 10 min before being added. In step 2, PHBV is heated to melt and then mixed with PLA, bio-based epoxy crosslinking agent, rosin-modified leveling agent, and mixed tocopherol antioxidants, with the organic phase temperature controlled at 175℃. In step 3, the emulsification speed is 12000 rpm for 10 min, the high-pressure homogenization pressure is 800 bar, and the cycle is repeated 5 times. In step 4, the mixture is cooled and solidified into granules. The resulting emulsion D 50 It is 0.70μm.

[0119] Example 20:

[0120] Formulation (based on dry solids of BioTen 1033 aqueous emulsion): PHBH 40.0 parts by weight, CNF 2.5 parts by weight, lignin particles 2.5 parts by weight, bio-based carbonate crosslinking agent 20.0 parts by weight, PLA 35.0 parts by weight. Preparation: In step 2, the organic phase temperature is 145℃, corresponding to a melting peak temperature Tm of the PHBH resin measured by DSC above 5℃; in step 3, the shear emulsification speed is 1000 rpm, the time is 0.5 min, the high-pressure homogenization pressure is 50 bar, and the cycle is 1; in step 4, cooling and solidification are performed into granules; the resulting emulsion is mixed with the aforementioned bio-based amine curing agent D at a reaction equivalent ratio of 1.0; the resulting emulsion D 50 It is 1.98 μm.

[0121] Example 21:

[0122] Formulation (based on dry solids of BioTen 1032 aqueous emulsion): P34HB 55.0 parts by weight, CNF 1.0 parts by weight, lignin particles 1.0 parts by weight, bio-based acid anhydride crosslinking agent 15.0 parts by weight, PLA 28.0 parts by weight. Preparation: In step 2, the organic phase temperature is 165℃, corresponding to a melting peak temperature Tm of the P34HB resin measured by DSC above 100℃; in step 3, the shear emulsification speed is 30000 rpm, the time is 60 min, the high-pressure homogenization pressure is 2000 bar, and the cycle is 20 times; during emulsification and homogenization, jacketed circulation cooling is used and the operation is carried out under nitrogen protection to ensure that the measured temperature of the system does not exceed 175℃; in step 4, cooling and solidification are carried out into granules; the obtained emulsion is mixed with the aforementioned bio-based amine curing agent E at a reaction equivalent ratio of 1.0; the resulting emulsion D 50 It is 0.24μm.

[0123] Comparative example:

[0124] Unless otherwise stated, the formulations in Comparative Examples 1 to 15 are based on the dry solids of the corresponding aqueous emulsions, and the 'parts by mass' refers to the dry solids by mass. Each comparative example was prepared in accordance with the order of raw material addition, aqueous phase preparation method, molten organic phase preparation method, shear emulsification conditions, high-pressure homogenization conditions, cooling curing conditions, and coating preparation method of the corresponding embodiment, with the only difference being the formulation or process conditions described below.

[0125] Comparative Example 1:

[0126] Formula (based on the dry solids of BioTen 1031 aqueous emulsion): 60 parts by weight of PHBV, 3.0 parts by weight of octyl / decyl glucoside (APG), 15 parts by weight of bio-based epoxy crosslinking agent, and 24 parts by weight of PLA.

[0127] Preparation: The preparation method was the same as in Example 1, except that CNF and lignin particles were not added in step 1. Instead, 3.0 parts by weight of APG were directly added to deionized water to form an aqueous phase containing small molecule surfactants. The remaining aqueous phase preparation order, organic phase temperature (175℃), shear emulsification speed (12000 rpm), emulsification time (10 min), high-pressure homogenization pressure (800 bar), number of cycles (5), and cooling and curing conditions were all the same as in Example 1. The resulting emulsion D... 50 The thickness is 0.55 μm. Before use, the obtained emulsion is mixed with bio-based amine curing agent A at a ratio of 1.0 of total effective functional group equivalent to total amine hydrogen equivalent to obtain the construction coating.

[0128] Comparative Example 2:

[0129] Formula (based on the dry solids of BioTen 1031 aqueous emulsion): 75 parts by weight of PHBV, 1.5 parts by weight of CNF, 1.0 part by weight of lignin particles, and 24 parts by weight of PLA.

[0130] Preparation: The preparation method was the same as in Example 1, except that no bio-based epoxy crosslinking agent was added in step 2. The remaining aqueous phase composition, organic phase preparation method, organic phase temperature (175°C), shear emulsification speed (12000 rpm), emulsification time (10 min), high-pressure homogenization pressure (800 bar), number of cycles (5), and cooling and curing conditions were the same as in Example 1. The resulting emulsion D... 50 The thickness was 0.40 μm. During construction, deionized water was used instead of bio-based amine curing agent, and the mixture was used to obtain a control construction system.

[0131] Comparative Example 3:

[0132] Formula (based on the dry solids of BioTen 1031 aqueous emulsion): 60 parts by weight of PHBV, 2.5 parts by weight of CNF, 15 parts by weight of bio-based epoxy crosslinking agent, and 24 parts by weight of PLA.

[0133] Preparation: The preparation was carried out according to Example 1, except that lignin particles were not added in step 1; CNF was used only as the particle stabilizing component, and the amount of CNF was adjusted to 2.5 parts by mass. The remaining organic phase temperature (175°C), shear emulsification speed (12000 rpm), emulsification time (10 min), high-pressure homogenization pressure (800 bar), number of cycles (5), and cooling and curing conditions were the same as in Example 1. The resulting emulsion D... 50 The thickness is 0.45 μm. Before use, the obtained emulsion is mixed with bio-based amine curing agent A at a ratio of 1.0 of total effective functional group equivalent to total amine hydrogen equivalent to obtain the construction coating.

[0134] Comparative Example 4:

[0135] Formula (based on the dry solids of BioTen 1031 aqueous emulsion): 60 parts by weight of PHBV, 5.0 parts by weight of polyvinyl alcohol (PVA), 15 parts by weight of bio-based epoxy crosslinking agent, and 22 parts by weight of PLA.

[0136] Preparation: The preparation method was the same as in Example 1, except that CNF and lignin particles were not added in step 1. Instead, PVA was prepared as a 10wt% PVA aqueous solution, stirred at 90°C for 60 min until completely dissolved, cooled to 25°C, and then added to the aqueous phase at 5.0 parts by weight of PVA dry solids. The remaining organic phase temperature (175°C), shear emulsification speed (12000 rpm), emulsification time (10 min), high-pressure homogenization pressure (800 bar), number of cycles (5), and cooling and curing conditions were the same as in Example 1. The resulting emulsion D... 50 The thickness is 0.35 μm. Before use, the obtained emulsion is mixed with bio-based amine curing agent A at a ratio of 1.0 of total effective functional group equivalent to total amine hydrogen equivalent to obtain the construction coating.

[0137] Comparative Example 5:

[0138] Formula (based on the dry solids of BioTen 1031 aqueous emulsion): 95 parts by weight of PHBV, 0.5 parts by weight of CNF, 0.2 parts by weight of lignin particles, and 5 parts by weight of bio-based epoxy crosslinking agent.

[0139] Preparation: The preparation was carried out according to Example 1, except that the amount of PHBV was adjusted to 95 parts by mass, the amount of CNF was adjusted to 0.5 parts by mass, the amount of lignin particles was adjusted to 0.2 parts by mass, and the amount of bio-based epoxy crosslinking agent was adjusted to 5 parts by mass. PLA was not added in step 2. The remaining organic phase temperature (175℃), shear emulsification speed (12000 rpm), emulsification time (10 min), high-pressure homogenization pressure (800 bar), number of cycles (5), and cooling and curing conditions were the same as in Example 1. The resulting emulsion D... 50 The thickness is 2.20 μm. Before use, the obtained emulsion is mixed with bio-based amine curing agent A at a ratio of 1.0 of total effective functional group equivalent to total amine hydrogen equivalent to obtain the construction coating.

[0140] Comparative Example 6:

[0141] Formulation (based on dry solids of BioTen 1031 aqueous emulsion): Same as in Example 1.

[0142] Preparation: The preparation process of the aqueous emulsion, the organic phase temperature of 175℃, the shear emulsification speed of 12000 rpm, the emulsification time of 10 min, the high-pressure homogenization pressure of 800 bar, the number of cycles of 5, and the cooling and solidification conditions were all the same as in Example 1. The resulting emulsion D 50 The thickness is 0.40 μm; the difference is that when preparing the coating, the ratio of the total equivalent of effective functional groups in the bio-based epoxy crosslinking agent to the total equivalent of amine hydrogen in the bio-based amine curing agent A is adjusted to 0.6 instead of 1.0.

[0143] Comparative Example 7:

[0144] Formula (based on the dry solids of BioTen 1031 aqueous emulsion): 60 parts by weight of PHBV, 0.2 parts by weight of CNF, 10.0 parts by weight of lignin particles, 15 parts by weight of bio-based epoxy crosslinking agent, and 14.8 parts by weight of PLA.

[0145] Preparation: The preparation was carried out according to Example 1, except that in step 1, the amount of CNF was adjusted to 0.2 parts by mass, and the amount of lignin particles was adjusted to 10.0 parts by mass, so that the mass ratio of CNF to the second particle component was 1:50. The remaining organic phase temperature (175℃), shear emulsification speed (12000 rpm), emulsification time (10 min), high-pressure homogenization pressure (800 bar), number of cycles (5), and cooling and curing conditions were the same as in Example 1. The resulting emulsion D... 50The thickness was 3.50 μm, and obvious stratification occurred after 24 hours. Before use, the obtained emulsion was mixed with bio-based amine curing agent A at a ratio of 1.0 of total equivalent of effective functional groups to total equivalent of amine hydrogen. However, due to severe stratification and particle agglomeration of the emulsion, a continuous coating could not be formed.

[0146] Comparative Example 8:

[0147] Formulation (based on dry solids of BioTen 1033 aqueous emulsion): 45.0 parts by weight of PHBH, 0.286 parts by weight of CNF, 0.014 parts by weight of lignin nanoclusters, 25.0 parts by weight of bio-based epoxy crosslinking agent, and 29.7 parts by weight of PLA.

[0148] Preparation: The preparation was carried out according to Example 16, except that the total amount of the bio-based Pickering stabilizing system was adjusted to 0.300 parts by mass, of which CNF was 0.286 parts by mass and lignin nanoclusters were 0.014 parts by mass; the remaining organic phase temperature (155°C), shear emulsification speed (15000 rpm), emulsification time (10 min), high-pressure homogenization pressure (1000 bar), number of cycles (5), and cooling and curing conditions were the same as in Example 16. The resulting emulsion D... 50 The emulsion was 2.60 μm thick and showed obvious floating and stratification after being left for 24 hours. Before use, the obtained emulsion was mixed with bio-based amine curing agent A at a ratio of 1.0 of total effective functional group equivalent to total amine hydrogen equivalent to obtain the construction coating.

[0149] Comparative Example 9:

[0150] Formulation (based on the dry solids of BioTen 1033 aqueous emulsion): 45.0 parts by weight of PHBH, 0.490 parts by weight of CNF, 0.010 parts by weight of lignin nanoclusters, 25.0 parts by weight of bio-based epoxy crosslinking agent, and 29.5 parts by weight of PLA.

[0151] Preparation: The preparation was carried out according to Example 16, except that the mass ratio of CNF to the second particulate component was adjusted to 1:0.02, where CNF was 0.490 parts by mass and lignin nanoclusters were 0.010 parts by mass. The remaining organic phase temperature (155℃), shear emulsification speed (15000 rpm), emulsification time (10 min), high-pressure homogenization pressure (1000 bar), number of cycles (5), and cooling and curing conditions were the same as in Example 16. The resulting emulsion D... 50 The thickness is 2.35 μm. Before use, the obtained emulsion is mixed with bio-based amine curing agent A at a ratio of 1.0 of total effective functional group equivalent to total amine hydrogen equivalent to obtain the construction coating.

[0152] Comparative Example 10:

[0153] Formula (based on the dry solids of BioTen 1031 aqueous emulsion): 10.0 parts by weight of PHBV, 1.5 parts by weight of CNF, 1.0 part by weight of lignin particles, 7.5 parts by weight of bio-based epoxy crosslinking agent, 60.0 parts by weight of calcium carbonate, 20.0 parts by weight of titanium dioxide, and 10.0 parts by weight of biochar.

[0154] Preparation: The preparation method was the same as in Example 18, except that the total amount of pigment or filler was adjusted to 90.0 parts by mass, of which calcium carbonate was 60.0 parts by mass, titanium dioxide was 20.0 parts by mass, and biochar was 10.0 parts by mass. The remaining steps—the pre-dispersion order in step 1, the organic phase temperature of 175°C in step 2, the shear emulsification speed of 15000 rpm, the emulsification time of 12 min in step 3, the high-pressure homogenization pressure of 1000 bar, the number of cycles of 8, and the cooling and curing conditions in step 4—were the same as in Example 18. The resulting emulsion D... 50 The thickness is 2.05 μm. Before use, the obtained emulsion is mixed with bio-based amine curing agent A at a ratio of 1.0 of total effective functional group equivalent to total amine hydrogen equivalent to obtain the construction coating.

[0155] Comparative Example 11:

[0156] Formula (based on the dry solids of BioTen 1031 aqueous emulsion): PHBV 55.0 parts by weight, CNF 1.0 parts by weight, lignin particles 0.5 parts by weight, bio-based epoxy crosslinking agent 15.0 parts by weight, PLA 13.5 parts by weight, and additives 20.0 parts by weight. Among these, hydroxypropyl starch phosphate thickener 6.7 parts by weight, deoiled lecithin wetting and dispersing agent 4.0 parts by weight, vegetable oil-based defoamer 4.0 parts by weight, rosin-modified leveling agent 2.7 parts by weight, and mixed tocopherol antioxidant 2.6 parts by weight.

[0157] Preparation: The preparation was carried out according to Example 19, except that the total amount of additives was adjusted to 20.0 parts by mass, and added to either step 1 or step 2 according to the aforementioned specific dosages. The pre-dissolution and addition order in step 1, the organic phase temperature of 175°C in step 2, the shear emulsification speed of 12000 rpm, the emulsification time of 10 min in step 3, the high-pressure homogenization pressure of 800 bar, the number of cycles of 5, and the cooling and solidification conditions in step 4 were the same as in Example 19. The resulting emulsion D... 50 The thickness is 0.74 μm. Before use, the obtained emulsion is mixed with bio-based amine curing agent A at a ratio of 1.0 of total effective functional group equivalent to total amine hydrogen equivalent to obtain the construction coating.

[0158] Comparative Example 12:

[0159] Formula (based on the dry solids of BioTen 1031 aqueous emulsion): 60.0 parts by weight of PHBV, 1.5 parts by weight of CNF, 1.0 part by weight of lignin particles, 30.0 parts by weight of bio-based epoxy crosslinking agent, and 24.0 parts by weight of PLA.

[0160] Preparation: The preparation was carried out according to Example 1, except that the amount of bio-based epoxy crosslinking agent was adjusted to 30.0 parts by weight; the remaining organic phase temperature (175°C), shear emulsification speed (12000 rpm), emulsification time (10 min), high-pressure homogenization pressure (800 bar), number of cycles (5), and cooling and curing conditions were the same as in Example 1. The resulting emulsion D... 50 The thickness is 0.44 μm. Before use, the obtained emulsion is mixed with bio-based amine curing agent A at a ratio of 1.0 of total effective functional group equivalent to total amine hydrogen equivalent to obtain the construction coating.

[0161] Comparative Example 13:

[0162] Formulation (based on dry solids of BioTen 1033 aqueous emulsion): Same as in Example 20.

[0163] Preparation: Except for step 2, where the organic phase temperature is controlled only at the melting point of the PHBH resin used, not exceeding 5°C above the melting point, the formulation in step 1, the shear emulsification speed of 1000 rpm, the emulsification time of 0.5 min, the high-pressure homogenization pressure of 50 bar, the number of cycles of 1, the cooling and curing conditions in step 4, and the mixing method with the bio-based amine curing agent D at a ratio of 1.0 of total effective functional group equivalent to total amine hydrogen equivalent are all the same as in Example 20; due to the presence of incompletely melted particles in the organic phase, the resulting emulsion D... 50 With a thickness of 3.20 μm, it is impossible to form a continuous and dense coating.

[0164] Comparative Example 14:

[0165] Formulation (based on dry solids of BioTen 1031 aqueous emulsion): PHBV 48.0 parts by weight, CNF 0.5 parts by weight, coarse chitosan particles 7.5 parts by weight, bio-based carbonate crosslinking agent 20.0 parts by weight, PLA 24.0 parts by weight. The coarse chitosan particles are obtained by spray drying the chitosan precursor and then sieving to obtain a particle size fraction with an average particle size of 30 μm.

[0166] Preparation: The preparation was carried out according to Example 17, except that in step 1, coarse chitosan particles with an average particle size of 30 μm were used instead of the micro-chitosan particles with an average particle size of 20 μm in Example 17, and these were co-dispersed with CNF in the aqueous phase. The remaining organic phase temperature (175°C), shear emulsification speed (15000 rpm), emulsification time (10 min), high-pressure homogenization pressure (800 bar), number of cycles (5), and cooling and solidification conditions were the same as in Example 17. The resulting emulsion D... 50The thickness is 2.55 μm. Before use, the obtained emulsion is mixed with bio-based amine curing agent A at a ratio of 1.0 of total effective functional group equivalent to total amine hydrogen equivalent to obtain the construction coating.

[0167] Comparative Example 15:

[0168] Formulation (based on dry solids of BioTen 1032 aqueous emulsion): Same as in Example 21.

[0169] Preparation: The preparation process of the aqueous emulsion, the organic phase temperature in step 2 (165℃), the shear emulsification speed in step 3 (30000rpm), the emulsification time (60min), the high-pressure homogenization pressure (2000bar), the number of cycles (20), the jacketed circulating cooling and nitrogen protection during emulsification and homogenization, and the cooling and solidification conditions in step 4 are all the same as in Example 21. The resulting emulsion D 50 The thickness is 0.26 μm; the difference lies in the fact that bio-based pentanediamine (PDA) modified polyamine F is used as an amine curing agent when the construction coating is prepared, with an amine hydrogen equivalent of 650 g / eq, and it is mixed at a ratio of 1.0 between the total equivalent of effective functional groups and the total equivalent of amine hydrogen.

[0170] Application example:

[0171] Application Example 1: Barrier and water resistance test of paper-based packaging materials.

[0172] This experiment used kraft paperboard with a basis weight of 250 g / m² as a typical substrate to simulate the actual application scenarios in the food packaging industry. The solid content of the coatings obtained in each example and comparative example was uniformly adjusted to 30 wt%, and then evenly coated onto the paperboard surface using a high-precision automatic coating machine. By precisely adjusting the wire rod specifications, the wet coating amount was controlled to be 33.3 g / m², equivalent to a dry coating amount of approximately 10.0 g / m². The coated samples were first pre-dried in infrared for 1 minute to quickly fix the coating microstructure and prevent excessive particle penetration into the fiber depths, and then forcibly dried in a 105°C forced-air oven for 2 minutes. Finally, all samples were aged for 24 hours in a standard constant temperature and humidity environment at 23℃ and 50%RH. After the chemical anchoring reaction was fully completed, the water absorption (Cobb value) was determined according to GB / T 1540-2002, the oil resistance grade of the Kit was determined according to TAPPI T 559 cm-22, and the water vapor transmission rate (WVTR) was tested according to GB / T 2679.2-2015 using the gravimetric (permeable cup) method at (38.0±0.5)℃ and (90±2)%RH. The sample size was Φ74mm, the effective permeable area was 33cm², and there were 3 parallel samples in each group. The interface anchoring index W was also measured at the same time.

[0173] Table 3. Test results of paper-based coating performance in the examples:

[0174]

[0175] Table 4. Test results of paper-based coating performance in comparative examples:

[0176]

[0177] Note: In Comparative Example 7, the emulsion was severely stratified and the particles agglomerated due to the excessive amount of the second particle, making it impossible to form a continuous coating; in Comparative Example 13, the organic phase was not fully melted, the emulsion particle size was too large, and it was difficult to form a film, so the relevant items were marked as "-".

[0178] The evaluation criteria for "coating appearance" in Tables 3 and 4 are as follows: The sample is placed under uniform white light illumination (500 lx) and observed at a distance of 30 cm. "Smooth" refers to a surface without obvious runs, pinholes, orange peel texture, or visible particle agglomeration. "Dense" refers to no continuous light-transmitting points and no visible through-holes observed on a black substrate. "Pinholes" refers to at least one visible light-transmitting point on a black substrate. "Micropinholes" refers to ≤3 visible through-holes within a 100 cm² area. "Whitening" refers to the appearance of continuous or large-area devitrification white fog on the surface. "Cracking" refers to a continuous network of cracks visible to the naked eye. "Surface stickiness" refers to a surface that is sticky at 23℃ and 50% RH. After standing for 24 hours, a noticeable stickiness is felt when lightly touched with a finger, and fiber dust can be stirred up; "Good leveling" means that there are no visible knife marks, brush marks, or local unevenness in thickness on the surface; "Slightly rough" means that slight surface undulations are visible to the naked eye, but there are no continuous cracks, shrinkage cavities, or exposed substrate; "Slight delamination" means that there are discontinuous striped color differences or slight floating color on the surface, but no through cracks; "Grainy" means that discrete particle protrusions are visible when observed at 30cm, and the particles can be felt when lightly touched with a finger; "Slightly yellow", "light brown", "grayish white", and "white" in the table are only comprehensive hue records and are not used as indicators for judging the film formation qualification; "Matte" means that there is no obvious specular reflection on the surface under the same lighting conditions.

[0179] Analysis: Experimental results show that Examples 1-21 all exhibit excellent protective performance on paper-based materials, with their Cobb values ​​(30 min) consistently controlled below 10.0 g / m², and the interfacial anchoring index W ≤ 5.0 wt%, demonstrating that the coatings possess excellent water resistance and anti-migration capabilities. The main reason for this is that the three-dimensional structure of "Pickering particles-interfacial crosslinking-curing network" constructed in this invention forms a continuous and dense barrier film on the paper fiber surface. Comparative Example 1, due to the use of a small-molecule emulsifier, caused hydrophilic components to migrate to the surface during film formation, resulting in a significant increase in the Cobb value to 28.5 g / m²; Comparative Example 2 lacked a crosslinking agent, and the PHA particles relied solely on physical accumulation, rapidly swelling upon contact with water. In contrast, the examples, through a reactive interfacial bonding crosslinking agent, firmly anchored the PHA phase to the Pickering particle layer, maintaining network integrity even after high-temperature drying. This multiphase interface chemical anchoring effect not only improves the physical barrier of the coating against moisture and oil, but also solves the bottleneck problem of weak adhesion and easy detachment of bio-based materials in wet conditions, providing a reliable technical path to replace traditional plastic coatings.

[0180] Application Example 2: Durability testing of wood products and rigid substrates.

[0181] This experiment used standard birch plywood as a rigid substrate to verify the practicality of the coating in the field of wood protection. After polishing and dust removal, a wet film was prepared using a precision wire bar coater, and the final dry film thickness was controlled to 30 μm through multiple coats. After natural surface drying at 23℃, the samples were transferred to an 80℃ oven for 30 min of forced thermocuring, followed by 24 h of constant temperature and humidity to eliminate internal stress. Tests included pencil hardness (measured according to GB / T6739-2022), abrasion resistance (loss of mass per 100 rpm) (measured according to ASTM D4060-25), and cross-cut adhesion (measured according to GB / T9286-2021). A water whitening resistance test was also included, where samples were immersed in 23℃ deionized water for 24 h, and the presence of whitening, blistering, or peeling of the coating was observed to evaluate its service durability in outdoor or humid environments. The evaluation criteria for "water resistance to whitening (immersion in water for 24 hours)" in Tables 5 and 6 are as follows: "No change" means that there is no visible devitrification, no blistering, and no peeling on the sample surface; "Slight whitening" means that there is slight devitrification or local fogging on the sample surface, but no blistering or peeling; "Obvious whitening" means that there is continuous or large-area devitrification and whitening on the sample surface, but no obvious blistering or peeling; "Severe whitening and blistering" means that there is obvious devitrification on the sample surface, accompanied by visible bubbles, blistering, or local peeling.

[0182] Table 5. Test results of wood coating performance in the examples:

[0183]

[0184] Table 6. Comparative examples of wood coating performance test results:

[0185]

[0186] Note: Comparative Example 7 could not form a complete coating due to severe emulsion separation, so hardness, abrasion resistance and adhesion tests could not be performed; Comparative Example 13 could not be tested because it failed to form a continuous film layer, so it was marked as "-".

[0187] Analysis: The test data shows that Examples 1-21 exhibit a perfect balance between high hardness and high adhesion on rigid substrates. Most samples achieved a pencil hardness of H-2H, while maintaining a stable adhesion rating of 0-1. These examples performed particularly well in the water whitening test, showing virtually no change after 24 hours of immersion in water. This is attributed to the high cross-linking density formed within the coating due to the interfacial chemical anchoring technology. Comparative Examples 1 and 4, due to the use of hydrophilic stabilizers such as APG or PVA, allowed water to easily penetrate the interface along hydrophilic channels during immersion, leading to severe whitening and blistering. Although Comparative Example 12 had extremely high hardness, excessive cross-linking agent increased the coating's brittleness, resulting in localized cracking during the abrasion test. The experiment demonstrates that an appropriate amount of bio-based interfacial cross-linking agent can work in conjunction with an amine curing agent to form a tough interlocking network. This enhances the mechanical strength of the PHA resin itself while improving the coating's scratch resistance through the reinforcing effect of Pickering particles. This multiphase composite system effectively combines the flexible PHA phase with the rigid particle phase, enabling the coating to conduct and dissipate energy through interfacial chemical bonds when subjected to external mechanical stress or moisture erosion, thus ensuring the long-term aesthetics and safety of the wood substrate.

[0188] Application Example 3: Verification of integrated physical performance and interface anchoring.

[0189] To further investigate the mechanical properties and interfacial stability of the coating itself, a free membrane sample was prepared in this experiment. The coating was applied to a polytetrafluoroethylene (PTFE) release liner, pre-dried at room temperature, and then forcibly cured at 80°C for 30 minutes. The membrane was carefully peeled off to obtain a homogeneous free membrane with a thickness of approximately 50 μm. Tensile strength and elongation at break were tested on the free membrane according to GB / T1040.3-2006 at a rate of 50 mm / min. Simultaneously, a 20 μm coating was prepared by applying the coating to a polyethylene terephthalate (PET) film. A methyl ethyl ketone (MEK) abrasion resistance test was conducted according to GB / T23989-2009, recording the number of bidirectional abrasions required for the coating to break. The most critical indicator was the determination of the interfacial anchoring index W. The loss rate of non-volatile components was quantitatively evaluated by accurately weighing the mass change of the free membrane before and after immersion in water (immersion for 24 hours followed by vacuum drying to constant weight), thereby verifying the locking effect of the chemical anchoring network on the components of the system.

[0190] Table 7: Comprehensive physical performance test results of the embodiments:

[0191]

[0192] Table 8. Comparative Example Comprehensive Physical Performance Test Results:

[0193]

[0194] Note: Comparative Example 7 had severe emulsion stratification, resulting in extremely brittle free membranes that broke upon removal; Comparative Example 13 could not form a continuous film layer, making it impossible to prepare standard samples, so the relevant items are marked as "-".

[0195] Analysis: The physical performance test results clearly outline the structural advantages of the technical solution of this invention. The tensile strength of the embodiments is generally between 15-28 MPa, and the elongation at break is distributed within an adjustable range of 15%-280%, demonstrating excellent mechanical design flexibility. Particularly noteworthy is that the interface anchoring index W of all embodiments is far below the acceptable threshold of 5.0 wt%, with the lowest being only 1.5 wt%. This means that the PHA particles, Pickering particles, and fillers in the coating are firmly locked into the cured network. Comparative Example 2, due to the complete absence of crosslinking reaction, has a W value as high as 20.0 wt% and only withstands 8 MEK wiping cycles, indicating that its structure is highly susceptible to damage from solvents and moisture. Analysis suggests that the reactive interfacial bonding crosslinking agent establishes a strong covalent bond bridge between the surface of the PHA particles and the continuous phase curing agent. This "interfacial bridging" effect transforms the discrete emulsion particles into a unified network structure. Compared to traditional physical blending, this chemical anchoring significantly enhances the cohesiveness and chemical stability of the coating, enabling it to maintain its physical properties even when exposed to harsh media such as acids, alkalis, and solvents. This fully demonstrates the technical value of reactive Pickering stabilization systems in the development of high-performance coatings.

[0196] Application Example 4: Storage stability test of aqueous emulsions.

[0197] Storage stability of aqueous emulsions is a prerequisite for their practical industrial application. In this experiment, freshly prepared emulsions were dispensed into 50mL sealed glass bottles, and two control environments were set up: one group was placed in a 25℃ incubator to simulate normal storage for 30 days, and the other group was placed in a 50℃ incubator for accelerated thermal aging for 7 days. After storage, the samples were brought to room temperature, and the presence of obvious stratification, flocculation, precipitation, or mold growth was observed visually. The median particle size distribution (D) before and after storage was determined using a laser particle size analyzer. 50 Changes were observed to evaluate the degree of particle aggregation. Additionally, 50 mL of the emulsion sample was placed in a 50 mL stoppered graduated cylinder and allowed to stand at 25°C for 24 hours. The volume V of the sedimentation layer was then recorded. s , and press Vs The sedimentation volume fraction is calculated as / V0×100%, where V0 is the initial volume of the emulsion. This experiment aims to investigate the steric stabilization effect of a two-particle Pickering system composed of nanocellulose and a second particle component on the steric hindrance of hydrophobic PHA melt-dispersed particles under high temperature and long-term dynamic equilibrium.

[0198] Table 9. Results of emulsion storage stability tests in the examples:

[0199]

[0200] Table 10 Results of storage stability tests for comparative emulsions:

[0201]

[0202] Note: Comparative Examples 7 and 13 were severely unstable after preparation, and the particle size growth and sedimentation volume fraction could not be measured according to the standard method. Comparative Example 8 also stratified under 50℃ / 7d conditions, so the corresponding items were recorded as "stratification" or "stratification, unable to be measured".

[0203] Analysis: Storage stability test results demonstrate the excellent stability of the dual-particle Pickering system. Examples 1-21, after accelerated aging at 50°C for 7 days, showed that the particle size D... 50 The growth rates were all controlled within 10%, and the sedimentation volume fraction was extremely low, demonstrating excellent anti-agglomeration ability. Comparative Example 1 used small molecule APG for stabilization; during thermal aging, due to surfactant desorption, the particles rapidly aggregated. 50 The particle size increased dramatically from 0.55 μm to 1.20 μm, exhibiting severe stratification. Comparative Example 3 lacked the second particle component, resulting in incomplete steric hindrance coverage and poor stability after long-term storage. Mechanism analysis revealed that nanocellulose particles and lignin or chitosan particles formed a tightly embedded adsorption layer on the surface of PHA particles. This solid particle barrier exhibits higher interfacial energy resistance compared to easily desorbed small-molecule surfactants. Simultaneously, the electrostatic repulsion generated by the synergistic effect of the two particles, combined with the steric hindrance, effectively suppressed particle collision and aggregation caused by Brownian motion. Even in the presence of high concentrations of pigments and fillers (as in Example 18), the system can still maintain uniform particle suspension by controlling the rheological properties of the aqueous phase. This provides crucial protection for long-distance transportation and long-term storage of coatings, completely solving the industry-wide problem of easy stratification and instability in traditional bio-based emulsions.

[0204] Application Example 5: Test on the repulping and recycling performance of paper-based materials.

[0205] Referring to the CEPI standard "Paper and Board - Recyclability Laboratory Test Method - Part I" 2025, coated samples were cut into 25mm × 25mm fragments. 50.0g of oven-dry sample was placed in a standard descrambler, deionized water was added to adjust the pulp consistency to 2.5wt%, the temperature was controlled at 40℃, and descrambled at 3000rpm for 10min. The descrambled pulp was then graded and screened through a 5mm coarse sieve and a 150μm slotted sieve. The oven-dry mass of the residue obtained from each sieve was weighed to calculate the coarse rejection rate, fine rejection rate, and total screenings ratio (TSR). Simultaneously, the composition of the screenings was observed under a microscope to determine whether the coating fragmented into tiny particles or formed large, non-descrambled sheets, thereby assessing fiber recovery rate and its potential impact on subsequent papermaking processes.

[0206] Table 11. Test results of repulping and recycling of paper-based materials in the examples:

[0207]

[0208] Table 12 Comparative Example Paper-Based Material Repulping and Recycling Test Results:

[0209]

[0210] Note: Comparative Examples 7 and 13 are marked with "-" because standard test samples could not be formed.

[0211] Analysis: The repulping recyclability test results show that the total screening residue (TSR) of the coated paper in the examples is generally below 5.0%, and the fiber recovery rate is above 94%, exhibiting excellent repulping suitability. Analyzing its physicochemical mechanism, although the coating of this invention has high wet stability, the cross-linked network can undergo controlled physical fragmentation under the strong shear and alkaline environment of the papermaking process. Due to the thin coating thickness and the presence of a large number of bio-based particles and fillers, these components tend to break into micron-sized fine particles during dissociation, rather than forming a large-area continuous plastic film, thus allowing them to pass smoothly through the screening equipment and be discharged with the white water or remain in the pulp as functional fillers. In contrast, Comparative Examples 1 and 6, due to insufficient cross-linking or additive migration, easily form sticky adhesives during dissociation, severely clogging the screen gaps and resulting in a significantly increased total screening residue. Example 13 introduces a starch and shellac co-film component, further improving the disintegration efficiency of the coating in the aqueous phase, with a fiber recovery rate as high as 98.5%. Experiments have shown that by properly controlling the interfacial anchoring strength and coating brittleness, efficient fiber recycling can be achieved while ensuring barrier performance, meeting the stringent global standards for the "recyclability" performance of plastic alternatives.

[0212] Application Example 6: Screening of total fluorine content in coatings.

[0213] Under current environmental regulations, PFAS-free packaging materials have become a prerequisite for market access. This experiment screened the total fluorine content of each coating sample using the oxygen bomb combustion-ion chromatography method according to EN 14582:2016. Approximately 0.5g of dried coating fragments were weighed and placed in an oxygen bomb combustion flask, where the sample was completely burned under high-pressure oxygen. The resulting flue gas was absorbed by a diluted absorbent, and the fluoride ion concentration in the absorbent was then quantitatively analyzed using ion chromatography. The detection limit for this test was set at 5mg / kg. All examples and comparative examples were directly sampled from cured coated cardboard, and the use of fluorinated release agents or fluorinated processing aids was strictly prohibited during sample preparation to ensure that the test results accurately reflect the elemental composition and environmental compliance of the coating system of this invention.

[0214] Table 13: Screening results of total fluoride content in the examples:

[0215]

[0216] Table 14: Screening results of total fluoride content in comparative examples:

[0217]

[0218] Note: Comparative Examples 7 and 13 are marked as '-' because continuous standard coating samples could not be obtained; no total fluorine was detected in the remaining samples, indicating that the total fluorine content of the cured coating samples was below the detection limit of this method.

[0219] Analysis: The total fluorine content test results showed that the total fluorine content of all sample examples was below the detection limit of 5 mg / kg, and was judged as 'not detected'. This result confirms the green and environmentally friendly attributes of the coating system of this invention in its formulation design. Analyzing its technical route, this invention completely abandons the fluorinated wetting agents or fluorinated waterproofing agents commonly used in traditional high-barrier coatings, and instead utilizes the natural hydrophobicity of PHA resin, the physical dense packing of Pickering particles, and the crosslinking density generated by interfacial chemical anchoring to obtain excellent barrier effects. Comparative experiments show that even without fluorine, the oil resistance kit grade of the examples can still reach 10-12, and can withstand 95°C hot oil penetration. This indicates that in the paper-based oil resistance and barrier scenario investigated in this application, good oil resistance and barrier performance can be obtained without intentionally introducing fluorinated additives or fluorinated resins through multiphase interface control.

[0220] Application Example 7: Multi-substrate suitability and chemical resistance testing.

[0221] Metal substrate testing: The coating was applied to a 3003 aluminum alloy plate with a dry film thickness of 20 μm. After curing, a cross-cut adhesion test and a neutral salt spray test (500 h) were performed. The salt spray evaluation criteria were as follows: After the sample was removed, it was gently rinsed with deionized water, dried at 23℃ for 2 h, and observed with the naked eye at 30 cm under uniform white light illumination (illuminance 500 lx) supplemented by inspection with a 10× magnifying glass. "No blistering or rust" means that there are no visible blisters, pitting corrosion, or red rust spots on the coating surface; "slight blistering" means that there are discontinuous blisters and the total area of ​​blistering / corrosion is <1%; "significant corrosion spots" means that there are ≥1 visible pitting corrosion or red rust spots and the total corrosion area is 1% to 5%; "severe corrosion" means that the total corrosion or blistering area is >5% or there is flaky blistering / rust spread. Textile testing: The coating was applied to a plain cotton fabric with a roll-up of 75% and a dry weight gain of 15 g / m². The fabric was then baked at 120°C for 3 min and cured at 23°C and 50% RH for 24 h. The samples were treated according to method A(1) in GB / T 3921-2008, and the washability was evaluated according to the coating integrity level defined in this application after soaping. Chemical resistance test: 0.50 mL each of 10% HCl solution and 10% NaOH solution were dropped onto the aluminum plate coating. The plate was covered with a petri dish and sealed to maintain moisture. After being placed at 23°C for 24 hours, the plate was rinsed with deionized water and dried. The evaluation criteria were as follows: "No change" means no visible blistering, no cracks, no peeling, and no obvious softening or stickiness; "Slight loss of gloss" means no blistering or peeling but a decrease in surface gloss; "Slight swelling" means no peeling but visible whitening / haze or a soft feel; "Slight surface roughness / bubbles" means visible roughness or localized bubbles but no peeling; "Local peeling" means exposed substrate or edge lifting; "Surface corrosion / stickiness" means the surface is obviously corroded, sticky, and can be gently rubbed off with a fingertip.

[0222] Table 15. Results of multi-substrate and chemical resistance tests in the examples:

[0223]

[0224] Table 16 Comparative Examples: Multi-substrate and Chemical Resistance Test Results

[0225]

[0226] Note: Comparative Examples 7 and 13 were not able to form a continuous coating, so multi-substrate applicability and chemical resistance tests could not be performed, and are therefore marked as "-".

[0227] 'Whitening' refers to continuous or localized whitening of the surface without significant softening, blistering, or peeling; 'Slight whitening' refers to only localized slight whitening without significant softening, blistering, or peeling; 'Whitening and softening' refers to significant whitening of the surface accompanied by a soft feel, but without large-area peeling; 'Swelling' refers to surface volume expansion or a soft feel, but without exposed substrate; 'Surface microcracks' refers to the appearance of fine cracks visible to the naked eye on the surface without exposed substrate; 'Dissolution / peeling' refers to significant corrosion of the coating with exposed substrate or large-area peeling.

[0228] The evaluation criteria for "Coating Integrity Grade (Level) after Soap Washing of Textiles" in Tables 15 and 16 are as follows: Grade 5: Coating is intact, with no visible peeling and no obvious loss of gloss; Grade 4.5: Coating is basically intact, with only slight loss of gloss or local whitening; Grade 4: Local slight wear or slight loss of gloss, but no exposed substrate; Grade 3.5: Slight powdering or slight peeling at the edges; Grade 3: Local obvious wear or peeling, but the exposed substrate area is ≤5%; Grade 2.5: Obvious peeling or wear, with an exposed substrate area of ​​5% to 10%; Grade 2: Large-area peeling or obvious whitening and stickiness, with an exposed substrate area >10%.

[0229] Analysis: The multi-substrate test results significantly demonstrate the substantial contribution of chemical anchoring technology to adhesion. All examples achieved 500 hours of salt spray testing on aluminum plates without blistering or rusting, maintaining adhesion at level 0. This indicates that the active groups such as amine and hydroxyl groups in the cured network form strong coordination or physical adsorption with the metal surface. Regarding chemical resistance, most examples can withstand immersion in 10% HCl without swelling, demonstrating excellent acid resistance. Comparative Examples 1 and 2 rapidly dissolved and detached under strong alkaline conditions, reflecting the fragility of physically stable systems at extreme pH levels. Analysis suggests that the stable covalent bond network generated by the reaction of the bio-based reactive crosslinking agent and the amine curing agent endows the coating with excellent chemical corrosion resistance, protecting sensitive internal components from media erosion. In particular, Example 17 utilizes the cationic properties of chitosan particles to enhance electrostatic attraction and chemical bonding with fibers and metal surfaces, ensuring stable adhesion even after multiple vigorous soaping washes.

[0230] Application Example 8: Verification of Limiting Coating Thickness.

[0231] Each example and comparative example was prepared with ultra-thin or ultra-thick coatings according to suitable rheological states. For the 0.1 μm ultra-thin coating, the coating material was diluted to a solid content of 5.0 wt% and spin-coated onto a PET film at 500 rpm for 5 s and 3000 rpm for 40 s, and then cured at 80°C for 30 min. For the 500 μm ultra-thick coating, the same coating material was used for multiple consecutive coats, with each coat having a wet film thickness of 300 μm. Between coats, the coating was pre-dried at 60°C for 10 min to remove moisture and set the shape, without separate final curing. After all coats were completed, the coating was cured at 80°C for 60 min and allowed to mature for 24 h to allow the coatings to fuse together and ultimately form a single-layer integrated thick film. The contact angle was tested using the static drop method; the water absorption rate A was tested using the 24-hour immersion weight gain method, and was judged as follows: A≤3% as “extremely low water absorption”, 3%<A≤8% as “low water absorption”, 8%<A≤12% as “medium water absorption”, and A>12% as “high water absorption”.

[0232] Table 17. Performance test results of coatings with extreme thickness in the examples:

[0233]

[0234] Table 18 Comparative Example: Performance Test Results of Coatings with Ultimate Thicknesses

[0235]

[0236] Note: Comparative Examples 7 and 13 could not form a continuous film under 0.1 μm conditions, so they could only be recorded as rough or particle-laden states, and no effective protective film could be obtained. In Tables 17 and 18, "transparent" means that when observed on a black and white grid substrate, the boundaries of the black and white grids are clearly distinguishable and there is no continuous devitrification; "slightly white" means that the sample has slight devitrification but the boundaries of the black and white grids are still clearly distinguishable; "tough" means that the sample does not break or pulverize after being manually bent 180° once; "slightly soft" means that it can recover its shape when lightly pressed with a finger but the surface is not sticky; "good feel" means that there are no obvious particle protrusions on the surface and no stickiness or prickly feeling when lightly touched; "slightly rough" means that slight undulations are visible to the naked eye but there are no continuous cracks; "slightly yellow" and "dark" in the table are only comprehensive hue records and are not used as acceptance criteria.

[0237] Analysis: At a thickness of 0.1 μm, Examples 16 and 21, among others, were still able to form continuous transparent films with invisible pinholes, maintaining a contact angle above 90°. This is attributed to the miniaturized D... 50The orderly arrangement of the Pickering particles within the ultrathin layer effectively fills the interparticle gaps. At a thickness of 500 μm, Examples 2 and 10 did not exhibit cracking or deep air bubbles, demonstrating extremely low water absorption and showcasing the superior toughness of the cross-linked network in resisting drying shrinkage stress. In contrast, Comparative Example 10, due to excessive pigments and fillers, cracked during thick coating due to insufficient polymer matrix bonding; Comparative Example 13, with its excessively large particle size, could not effectively spread within the ultrathin layer. Analyzing the physical mechanism, the physical framework formed by the Pickering particles at the interface acts as a microscopic reinforcement similar to steel reinforcement in construction during thick film curing, while the reactive cross-linked network provides necessary stress buffering.

[0238] Application Example 9: Testing of the impermeability and processing adaptability of food packaging applications.

[0239] For the food packaging field, this experiment focused on evaluating the barrier properties, seepage prevention, and subsequent processing performance of the samples. Following GB / T44834-2024, coated samples were made into paper boxes and injected with 90℃ hot water and 95℃ soybean oil, respectively. After standing for 30 minutes, the bottom and seams of the boxes were observed for wetting spots or leakage. Heat seal strength testing was conducted according to the corresponding test conditions in GB / T 44834-2024; this paper uniformly adopted the following conditions: two coated paper sheets with 100% coverage were placed face-to-face to form a sample with a width of 15mm and a length of 150mm; the heat sealing temperature was 130℃, the heat sealing pressure was 0.30MPa, the heat sealing residence time was 1.0s, and the heat sealing blade width was 5mm; after heat sealing, the sample was tested at a speed of 200mm / min using a 180° peel method, with 5 parallel samples per group. Wetting tension on the free surface of the 100% coated surface was determined according to GB / T 14216-2008. This experiment aims to ensure that the coating retains good folding, sealing, and printing adaptability while withstanding the challenges of high-temperature contents, thus meeting the comprehensive industrial requirements of food packaging materials.

[0240] Table 19 Results of Leakage Prevention and Processing Adaptability Tests for Food Packaging Applications in Examples:

[0241]

[0242] Table 20 Comparative results of leak-proof performance and processing adaptability tests on food packaging applications:

[0243]

[0244] Note: Comparative Examples 7 and 13 were marked with "-" because an effective continuous coating could not be obtained; Comparative Examples 6 and 11, although they measured higher heat seal strength values, both showed destructive adhesion and did not belong to the normal heat seal peeling mode.

[0245] The evaluation criteria for leakage and heat seal failure in Tables 19 and 20 are as follows: 'No leakage' means that there are no visible wetting spots on the outer surface of the sample box and the bottom filter paper; 'Leakage (1 spot)' means that there is one isolated wetting spot on the outer surface of the sample box or the filter paper, with a single spot diameter ≤3mm; 'Leakage (2 spots)' means that there are two isolated wetting spots without continuous seepage; 'Leakage (3 spots)' means that there are three isolated wetting spots without continuous seepage; 'Leakage (multiple spots)' means that there are ≥4 wetting spots; 'Severe wetting' means that there is a continuous sheet-like wetting area on the outer surface of the sample box, with a wetting area >5cm² and no continuous dripping; 'Edge penetration' means that there is a continuous linear wetting band at the fold or seam, with a length ≥10mm; 'Crack location' means that the leakage location is consistent with the location of the visible crack; 'Destructive adhesion' means that a large area of ​​paper fiber or coating is transferred during heat seal peeling, and the peeling interface does not show the normal heat seal separation mode.

[0246] Analysis: Food contact test data confirmed the superiority of this coating system as a food packaging material. All examples passed rigorous leakage tests in water at 90°C and oil at 95°C, with heat seal strength ≥0.30 kN / m and wetting tension maintained between 38 mN / m and 45 mN / m, providing good surface energy conditions for subsequent printing processing. Analysis suggests that the dense Pickering barrier combined with the chemical cross-linking network does not soften or dissolve when exposed to high-temperature oils, thus maintaining an extremely high physical barrier level. The heat seal performance is achieved through the thermal melting of the PHA component and the secondary reaction of the interfacial cross-linking agent under hot pressure, forming a strong interfacial bond. Although Comparative Example 12 has good barrier properties, excessive cross-linking leads to extremely high surface inertia, resulting in a heat seal strength of only 0.24 kN / m, which cannot meet the packaging sealing strength requirements. Example 7 effectively controlled the surface energy by introducing fillers, achieving a wetting tension of 45 mN / m and significantly improving printability.

[0247] Application Example 10: Evaluation of the UV aging resistance and surface antibacterial functionality of coatings.

[0248] The coating was applied to a quartz glass slide and a white acrylonitrile-butadiene-styrene copolymer (ABS) board, with a dry film thickness of 25 μm, for UV blocking and weather resistance testing. The coating was also applied to a 50 mm × 50 mm PET film, with a dry film thickness of 20 μm, for antibacterial testing. UV blocking performance was measured using a UV-Vis spectrophotometer to determine the shielding efficiency at 365 nm. Accelerated aging testing (fluorescent UV accelerated aging (QUV)) was conducted according to GB / T 23987.3-2025, using a UVB-313 lamp with an irradiance set to 0.71 W / (m²·nm) (313 nm), under the following cycling conditions: 8 h irradiation at 60℃ / 4 h condensation at 50℃, and ΔYI was recorded. Antibacterial performance was tested according to GB / T 31402-2023. The antibacterial activity value R was calculated according to GB / T 31402-2023, R=U t -A t U t The logarithmic mean of the viable bacterial count in the control sample after 24 hours is commonly used. t The viable bacterial count of the sample after 24 hours is usually the logarithmic average; the inhibition rate (%) is calculated according to Appendix NA of this standard, inhibition rate = [(N c -N t ) / N c ]×100%, where N c N represents the average viable count of the control sample after 24 hours. t The average viable count of the sample after 24 hours; '>99.99%' in the table represents the minimum value calculated based on the lower limit of colony count. The evaluation criteria for the QUV 200h aging status are as follows: "Intact surface" means no visible cracks, no blistering, no local peeling, and no obvious powder appearing after 10 light wipings with lint-free paper; "Slight loss of gloss" means no cracks or peeling but a decrease in surface gloss; "Obvious chalking" means visible powder appears on lint-free paper and fine cracks appear on the surface after light wiping; "Severe chalking, coating peeling" means local or large-area peeling accompanied by a large amount of chalking.

[0249] Table 21 Results of UV protection and antibacterial performance tests in the examples:

[0250]

[0251] Table 22 Comparative results of UV protection and antibacterial properties test:

[0252]

[0253] Note: Comparative Examples 7 and 13 were not able to form a continuous sample film, so the relevant items are marked as "-".

[0254] Analysis: The functional test results fully revealed the synergistic effect of the multiphase particulate components. Example 4, due to the introduction of 3.0 parts of lignin particles, achieved a 98.2% UV shielding rate at 365nm, and after 200 hours of aging, the ΔYI was only 0.4, demonstrating excellent UV aging stability. In contrast, Comparative Example 3, without lignin, had a ΔYI as high as 12.0, indicating significantly weaker anti-aging performance. Analysis suggests that the phenolic hydroxyl groups and conjugated structures in lignin can effectively absorb ultraviolet light and scavenge photoinduced free radicals, thereby protecting the PHA matrix from photodegradation. Regarding antibacterial properties, Examples 3 and 12, after introducing chitosan particles, showed inhibition rates >99.99% against both pathogenic bacteria, with significant R values. This is because the protonated amino groups on the chitosan surface can penetrate the bacterial cell wall, leading to cytoplasmic loss. Comparative Example 14, due to its coarse chitosan particle size and small effective specific surface area, showed a significant decrease in inhibition rate. Experiments have shown that by selectively compounding bio-based particles, the system of this invention can not only serve as a single barrier layer, but can also be transformed into a special coating with the dual functions of "long-lasting UV protection and high-efficiency antibacterial".

[0255] Application Example 11: Verification of interface structure and crosslinking agent distribution.

[0256] All examples and comparative examples were selected, and the interface structure was directly characterized by cryo-scanning electron microscopy (cryo-SEM), micro-Raman line scanning, and elution quantitative analysis. Cryo-SEM samples were subjected to rapid freezing in liquid nitrogen followed by brittle fracture, sputter-coated with gold for 60 seconds, and images of at least 10 emulsion particles were randomly acquired for each sample at 5000× magnification. ImageJ software was used for binarization processing, and the interface particle coverage P was calculated after a uniformly set threshold for recognition. c P c Defined as the proportion of the perimeter of the emulsion particle covered by particle adsorption to the total perimeter. Micro-Raman line scanning uses the diameter direction of a single emulsion particle as the scanning path, with a scanning step size of 0.1 μm, a laser wavelength of 532 nm, an integration time of 10 s, and is performed three times. The baseline is subtracted using a fifth-order polynomial. At least five particles are tested for each sample, and the average is taken. For epoxidized vegetable oil crosslinking agents, vegetable oil-based cyclic carbonate crosslinking agents, and rosin-based anhydride crosslinking agents, their corresponding characteristic peaks are selected for quantitative analysis. The surface / core crosslinking agent signal ratio Es is defined as the ratio of the average intensity of the characteristic peak in the outer 0%–10% region of the crosslinking agent to the average intensity of the corresponding characteristic peak in the center ±10% region of the particle. Adsorption fraction A c Press A c =Calculated as (mass of crosslinking agent in the particle phase / initial mass of crosslinking agent) × 100%; The emulsion is first centrifuged at 10000g for 10min to separate the particle phase and the continuous phase, and then the crosslinking agent in the two phases is quantified using the external standard method. The linear range, calibration equation, and correlation coefficient R² of the external standard curve are as follows:

[0257] For epoxidized vegetable oil crosslinking agents, vegetable oil-based cyclic carbonate crosslinking agents, and rosin-based anhydride crosslinking agents, 820 cm⁻¹ was selected respectively. -1 1800cm -1 and 1780cm -1 As quantitative characteristic peaks. In the external standard method, the linear range of the epoxidized vegetable oil crosslinking agent was 0.1–5.0 mg / mL, the calibration equation was y = 0.854x + 0.012, and the correlation coefficient R² was 0.9992; the linear range of the vegetable oil-based cyclic carbonate crosslinking agent was 0.2–10.0 mg / mL, the calibration equation was y = 1.123x - 0.005, and the correlation coefficient R² was 0.9995; the linear range of the rosin anhydride crosslinking agent was 0.5–8.0 mg / mL, the calibration equation was y = 0.967x + 0.008, and the correlation coefficient R² was 0.9991.

[0258] Cross-sectional porosity P v Defined as the proportion of pore area in the cross-section of the cured film; five cross-sectional fields of view were randomly selected for each sample, and binarization statistics were performed using ImageJ software with a unified threshold. The average value of three parallel samples was taken for each index. Micro Raman line scanning showed that in addition to the enrichment of crosslinking agent on the particle surface, characteristic peaks corresponding to crosslinking agent could also be detected in the particle core, indicating that the crosslinking agent exists in both dissolved and dispersed states inside the PHA phase.

[0259] Table 23 Verification results of interface structure and crosslinking agent distribution in the examples:

[0260]

[0261] Table 24: Verification results of interface structure and crosslinking agent distribution in comparative examples:

[0262]

[0263] Note: In Comparative Example 7, representative particles could not be extracted for interface characterization due to severe emulsion stratification; in Comparative Example 13, a large number of non-spherical coarse particles were present in the sample due to insufficient melting of the organic phase, making it impossible to obtain statistically significant interface parameters according to the method of this application example, so it is marked as "-".

[0264] Analysis: Particle coverage rate P in all embodiments c All remained above 70%, and E s The value is significantly greater than 1.0, indicating that the bio-based reactive crosslinking agent is mainly enriched on the surface of PHA particles and in the gaps between Pickering particles. In particular, Example 8 shows that its E... s The value is as high as 1.86, and the adsorption fraction A cThe significant improvement clearly demonstrates that the pre-addition process, which preferentially adsorbs the crosslinking agent onto the particle surface, greatly enhances the interfacial anchoring effect. In Comparative Example 1, due to the lack of particle confinement, the crosslinking agent exhibits a disordered distribution in the system, E s With a porosity of only 0.62, the cross-sectional porosity P of the cured film is low. v With a content as high as 11.8%, the structure is loose and porous. Analysis of its physical mechanism reveals that the "nano-fence" formed by Pickering particles not only physically restricts the aggregation of emulsion particles but also acts as a carrier for chemical reactions, guiding the crosslinking agent to form a dense crosslinked layer at the interface. This combination of directional enrichment and in-situ reaction results in extremely small free bodies within the coating, effectively blocking the diffusion and penetration of small molecules. Experiments directly demonstrate the ordered construction of the multiphase interface anchoring structure at the molecular scale, which is the microscopic basis for achieving higher barrier performance with a thinner coating.

[0265] Application Example 12: Verification of the improved wet adhesion protection performance of chitosan second particles.

[0266] This experiment verified the synergistic effect of chitosan components through a 180° peel strength test. The coating was applied to 3003 aluminum plates and PET films respectively. After curing, standard specimens with a width of 15 mm and a length of 200 mm were cut. The tests were conducted in a 180° peel mode at a speed of 200 mm / min, with 5 parallel samples per group. The test consisted of two groups: the first group measured the initial 180° peel strength F under dry conditions. dry The second group had the specimens completely immersed in deionized water at 23°C for 24 hours. After removing them and drying off the excess water, the wet peel strength F was immediately tested at the same peel angle and tensile speed. wet Wet peel strength retention rate R p Press R p =(F wet / F dry The percentage of samples was calculated as 100%, with at least 5 parallel samples per group. Simultaneously, cross-cut adhesion was evaluated on aluminum plates after immersion in water for 24 hours. By comparing the Rp values ​​of different second particles (lignin, chitosan, etc.) and the comparative system, the ability of chitosan and its derivatives to maintain interfacial adhesion stability under moisture-eroded conditions was quantitatively evaluated, thus demonstrating their necessity in humid environments.

[0267] Table 25 Verification results of wet adhesion protection performance of the examples:

[0268]

[0269] Table 26 Comparative examples of wet adhesion protection performance verification results:

[0270]

[0271] Note: Comparative Example 7 could not form a complete coating, and Comparative Example 13 could not form a continuous film layer, so the relevant items for both are marked as "-".

[0272] Analysis: The wet performance test results strongly demonstrate the unique advantages of chitosan in improving adhesion. Examples 3, 12, and 17 (all containing chitosan) all showed Rp values ​​above 88% after 24 hours of immersion, reaching a maximum of 95%, and the adhesion to the aluminum plate remained consistently at grade 0. In contrast, Example 1, containing only lignin, had a W value of approximately 2.0 wt%, but its Rp was only 78%, performing well but slightly inferior to the chitosan system; while Comparative Example 1, without particle stability, saw its Rp value plummet to 18%. Analyzing its chemical mechanism, chitosan molecules contain a large number of hydroxyl and primary amine groups, which not only react with the crosslinking agent at the PHA interface but also form a strong hydrogen bond network or ionic bond with the substrate surface under wet conditions. Furthermore, the cationic nature of chitosan allows it to generate strong charge attraction with polar substrates. Even if moisture attempts to penetrate the interface, the adsorption energy of the chitosan segments is sufficient to resist the displacement of moisture, thus preventing overall coating peeling. Experiments have shown that chitosan particles are not only a stabilizer, but also play multiple roles as an "interface toughening agent" and a "wet adhesive".

[0273] Application Example 13: Endpoint verification of dry coating amount on paper-based materials.

[0274] To verify the applicability of the dry coating amount of 0.2 g / m² to 120 g / m² for paper-based materials in this invention, samples were prepared for all embodiments and all comparative examples under the corresponding representative end coating amount conditions. Test indicators included coverage (C), Cobb value, and the number of visible cracks (N) with a length ≥ 1 mm. c Coverage C was statistically analyzed using binarized 2000×SEM images; five fields of view were randomly selected for each sample, and imageJ software was used for binarization. The result was calculated as C = (1 - A_exposed / A_total_field of view) × 100%, where A_exposed is the area of ​​exposed fibers not covered by the coating in the image, and A_total_field of view is the total area analyzed; the result was the average of three parallel samples.

[0275] Table 27 Endpoint verification results of dry coating amount on paper-based materials in the examples:

[0276]

[0277] Table 28 Endpoint verification results of dry coating amount for comparative paper-based materials:

[0278]

[0279] Note: Comparative Examples 7 and 13 could not form a statistically significant continuous coating at the tested endpoints, so the relevant items are marked as "-".

[0280] Analysis: Examples 16 and 21 maintained high coverage even at an extremely low coating weight of 0.2 g / m², while Examples 17, 18, and 20 showed no obvious cracks at high coating weights of 60.0 g / m² to 120.0 g / m². This indicates that the system of the present invention can cover the process window of paper-based materials from ultra-thin coating to high coating weight. Comparative Examples 10 and 11 show that when pigments, fillers, or additives are outside the range, cracks or stickiness and instability are more likely to occur at high coating weights.

[0281] Application Example 14: Validation of replacing or reducing polyethylene coating with molded fiber packaging materials.

[0282] All application coatings used in the examples and comparative examples were sprayed onto the inner surface of a 450 g / m² molded fiber lunchbox. The dry coating amount was uniformly controlled at 10.0 g / m², with a 20.0 g / m² commercial polyethylene (PE) laminated molded fiber box used as a reference. The polyethylene reduction rate R... PE Press R PE =Calculated as (20.0 - dry coating amount) / 20.0 × 100%. Wet compressive strength retention rate R c Press R c =(F w / F d ) × 100% calculation, where F d F represents the top pressure strength of samples from the same batch that have been coated and cured but not treated with 90°C deionized water solution. w The top pressure strength of the sample is measured after being filled with deionized water at 90℃ for 30 minutes, emptied and wiped clean, and then allowed to stand at 23℃ for 10 minutes. The top pressure test was conducted using a universal testing machine with a pressing speed of 10 mm / min, based on the maximum load at which the sample experienced structural instability or reached its peak value. The leakage evaluation criteria are as follows: "No leakage" means no visible wetting spots on the outer surface of the food container; "Slight leakage" means only one visible wetting spot appears without continuous seepage; "Leakage (multiple spots)" means two or more visible wetting spots appear; "Leakage (edge ​​penetration)" means a continuous seepage band appears at the edge or side seal of the food container; "Leakage (crack)" means that the visible leakage point corresponds to the location of a crack in the coating.

[0283] Table 29 Validation results of using molded fiber packaging materials to replace or reduce PE coating in the examples:

[0284]

[0285] Table 30 Comparative Analysis Results of Molded Fiber Packaging Materials Replacing or Reducing PE Coating:

[0286]

[0287] Note: Comparative Examples 7 and 13 were not able to form a continuous barrier layer, so the relevant items are marked as "-".

[0288] Analysis: Examples 1 to 21 can mostly achieve a 50% reduction in polyethylene weight at a coating amount of 10.0 g / m². Among them, Example 20, due to the use of a low-energy process to prepare the emulsion, has a slight decrease in hot water barrier on the rough substrate of the molded fiber, but still maintains the integrity of the single-layer coating. This application example directly verifies the substitution or weight reduction application value of the system of the present invention in molded fiber packaging.

[0289] Application Example 15: Endpoint Verification of Fixed Conditions.

[0290] This experiment aims to investigate the effects of curing temperature and time on the interfacial anchoring reaction kinetics and to confirm the film-forming quality of the system under different construction conditions. All examples and typical comparative examples were selected and coated onto kraft paperboard. Two extreme curing endpoints were then set: the first group was cured at room temperature (23℃) for 72 hours, simulating on-site construction or low-temperature post-processing; the second group was cured at 120℃ for 0.5 hours, simulating a high-speed drying production line of an industrial coating machine. The sensitivity of the reactive interfacial anchoring network to temperature was evaluated by comparing the changes in the interfacial anchoring index W, Cobb value, heat seal strength, and adhesion of the two groups of samples under the same dry coating amount (10.0 g / m²). This experiment aims to demonstrate that the coating system can achieve effective locking of the multiphase structure and closed-loop protection performance through chemical crosslinking under both room temperature air-drying and industrial high-temperature rapid-drying environments.

[0291] Table 31 Endpoint verification results of the curing conditions in the examples:

[0292]

[0293] Table 32 Endpoint verification results for comparative curing conditions:

[0294]

[0295] Note: Comparative Examples 7 and 13 could not be tested for curing endpoints because they could not form a continuous film layer, so they are marked as "-"; Comparative Examples 6 and 11 still showed destructive adhesion and are not considered as effective heat seal strength.

[0296] Analysis: Examples 1-21 showed good consistency in W and Cobb values ​​under both extreme curing conditions. Although high-temperature curing at 120℃ for 0.5h generally resulted in a better W value than the 23℃ group (average reduction of 0.5-1.0wt%), the room-temperature group still met the requirement of W≤5.0wt% after 72h. This indicates that the chemical anchoring reaction between the bio-based reactive crosslinking agent and the amine curing agent can be activated by high temperature to adapt to high-speed production, and can also complete crosslinking at room temperature through time delay. Comparative Example 2, due to the complete absence of chemical crosslinking, maintained a consistently high W value under all conditions. Comparative Example 6, due to the deviation in equivalence ratio, cured extremely slowly at room temperature, resulting in a W value as high as 16.0wt%, which severely affected subsequent stacking. Analysis suggests that the bio-based epoxy or carbonate components selected through molecular design in this invention form a highly efficient reaction pair with the special polyamine curing agent, and their in-situ enrichment at the phase interface significantly reduces the apparent reaction activation energy. This allows coated products to achieve excellent water barrier properties through natural stacking and curing even at construction sites where high-temperature baking conditions are not available, significantly reducing processing energy consumption and expanding the application areas and seasonal windows of the products.

[0297] Experimental Results and Analysis:

[0298] This invention successfully prepared a PHA-based waterborne emulsion coating with excellent barrier properties, water resistance, and interfacial stability by constructing a three-dimensional multiphase network consisting of a "bio-based Pickering stabilizing system - reactive interfacial bonding crosslinking agent - bio-based amine curing agent". Analysis of the comprehensive performance test results of Examples 1-21 and Comparative Examples 1-15 leads to the following conclusions:

[0299] Synergistic effect analysis data of the multiphase Pickering stabilization system showed that the ratio of cellulose nanoparticles (CNF) to the second particle component (lignin or chitosan) has a decisive influence on the stability of the emulsion and the coating performance. In the examples, the ratio of the two was controlled between 1:0.05 and 1:20, and the resulting emulsion had a median particle size D. 50 The interface coverage remained stable within the range of 0.2 μm to 2.0 μm. In contrast, Comparative Example 3, which only used CNF, had a lower interface coverage P. c The lower temperature leads to decreased storage stability, and D increases after 50°C heat aging. 50 Significant growth was observed in Comparative Examples 7 and 9; however, due to particle ratio imbalance, severe particle aggregation or emulsion stratification occurred. Analysis suggests that the dual-particle system forms an embedded solid particle barrier on the surface of PHA particles. CNF provides macroscopic steric hindrance, while the second particle fills the gaps and modulates the interfacial energy, thus achieving a higher efficiency than traditional small-molecule surfactants (Comparative Examples 1 and 9). c (Only 12.0%) superior physical stability.

[0300] The contribution of interfacial chemical anchoring to water resistance and migration resistance: The interfacial anchoring index W is a key indicator for evaluating the core technology of this invention. The W values ​​in all embodiments were strictly controlled below 5.0 wt%, with the lowest being only 1.5 wt% (Example 3). This demonstrates that the bio-based reactive interfacial bonding crosslinking agent (epoxy group, carbonate group, etc.) and the amine curing agent underwent efficient ring-opening or addition reactions at the PHA particle interface, forming a dense covalent network. In contrast, Comparative Example 2, without the added crosslinking agent, had a W value as high as 20.0 wt%, exhibiting rapid swelling upon contact with water and a significant performance degradation. Furthermore, the E value measured by micro Raman line scanning... s Value (E) s >1.0) confirmed the directional enrichment of the crosslinking agent on the particle surface. This "in-situ interface anchoring" mechanism not only locked the emulsion particles, but also bridged the Pickering particle layer through chemical bonds, so that the coating could remain continuous and dense even at the limit thickness of 0.1 μm (Application Example 8), showing extremely high barrier efficiency.

[0301] In paper-based material applications, the coating of this invention demonstrates excellent "fluorine-free high barrier" properties, balancing barrier performance with processing adaptability. The Cobb values ​​(30 min) of the examples are generally below 10.0 g / m², with oil resistance kit grades reaching 10-12, and successfully passed leak-proof tests in 90°C hot water and 95°C hot oil. Experiments revealed that the type of PHA resin significantly modifies performance: coatings using PHBH (Example 2) or P34HB (Example 21) exhibit better flexibility and heat-sealing strength (≥0.30 kN / m); while using PHB (Comparative Example 5) tends to increase brittleness, leading to thick film cracking. Furthermore, by precisely controlling the reaction equivalence ratio between 1.0 and 1.1 (as in the comparison between Example 1 and Comparative Example 6), the integrity of the cured network is ensured, avoiding barrier failure caused by surface stickiness or insufficient cross-linking.

[0302] Trend analysis of the influence of component content changes on the results

[0303] Effect of PHA content: When the PHA content varies in the range of 10 to 90 parts by mass, the hydrophobic barrier properties of the coating are improved with the increase of the PHA ratio. However, if the content is too high (such as in comparative example 5, 95 parts by mass), it will lead to insufficient ratio of stable system and crosslinking agent, resulting in film cracking.

[0304] Effect of crosslinking agent content: The crosslinking agent can effectively maintain the qualified W value within the range of 5-25 parts by mass. When it is less than 5 parts by mass (Comparative Example 5), the interfacial anchoring force is insufficient, and the solvent resistance and water resistance decrease; when it is more than 25 parts by mass (Comparative Example 12), although the barrier properties are excellent, the coating brittleness increases significantly, the heat sealing strength decreases to 0.24 kN / m, and adhesion failure is prone to occur.

[0305] Effects of pigments, fillers and additives: Adding appropriate amounts of fillers (such as calcium carbonate and titanium dioxide) can improve hardness and hiding power, but if the total amount exceeds 80 parts by mass (comparative example 10), the cohesion of the system will decrease significantly, leading to a surge in Cobb value and the appearance of powdering.

[0306] Enhancement of Functional Particles: The introduction of lignin particles (Example 4) can increase the 365nm UV shielding rate to over 98% and significantly reduce the ΔYI value under artificial accelerated aging; the introduction of chitosan particles (Example 12) can achieve an antibacterial rate of over 99.99% and significantly improve the wet peel strength retention rate R. p (Up to 95%).

[0307] Environmental and Sustainability Analysis: No fluorinated additives or resins were intentionally introduced into the formulation of this invention. The total fluorine content of the cured coating was screened according to EN14582:2016, and all samples from the examples were below the detection limit of 5 mg / kg. In the resizing and recycling test, because the coating is easily broken into fine particles rather than forming a continuous adhesive film, the total residue level (TSR) was generally below 5.0%, and the fiber recovery rate was as high as 94%–98.5%. This indicates that this coating system provides high-performance protection while possessing good environmental friendliness and recycling potential.

[0308] In summary, this invention utilizes bio-based multiphase particles to construct a Pickering-stable structure, combined with reactive interfacial bonding and cross-linking technology, to solve industry challenges related to water resistance, adhesion, and barrier stability of bio-based coatings. By precisely controlling the mass ratio of each component, particle size, and degree of interfacial reaction, high-performance applications of the coating on various substrates are achieved.

[0309] Those skilled in the art should understand that the above embodiments are merely exemplary and not intended to limit the scope of the invention. The scope of protection of the present invention is defined by the appended claims. Any modifications, equivalent substitutions, improvements, etc., made to the technical solutions of the present invention within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A waterborne emulsion coating system based on PHA and bio-based multiphase particle Pickering stabilization and interfacial chemical anchoring, characterized in that, The coating system comprises an aqueous emulsion and an amine curing agent; The aqueous emulsion includes water as a continuous phase and contains a bio-based Pickering stabilizing system and a bio-based reactive interfacial bonding crosslinking agent; The amine curing agent is an aqueous solution or aqueous dispersion of a bio-based amine curing agent; The aqueous emulsion and the amine curing agent are mixed before use to obtain a construction coating, wherein the ratio of the total equivalent of the effective functional groups that can react with the amine in the bio-based reactive interfacial bonding crosslinking agent to the total equivalent of the amine hydrogen in the bio-based amine curing agent is 1.0 to 1.1; the construction coating forms a single-layer protective coating after being applied, dried and cured. The aqueous emulsion, based on its dry solids, comprises: 10-90 parts by weight of polyhydroxyalkanoate; 0.5-8.0 parts by weight of a bio-based Pickering stabilizing system; 5-25 parts by weight of a bio-based reactive interfacial bonding crosslinking agent; 0-80 parts by weight of a bio-based co-film forming component or a bio-based co-binder component; 0-80 parts by weight of a pigment or filler; and 0-15 parts by weight of an additive derived from bio-based or renewable resources. The bio-based Pickering stabilization system comprises nanocellulose particles and a second particulate component; the polyhydroxyalkanoate exists in the form of polyhydroxyalkanoate emulsion particles, which are obtained by emulsifying and solidifying the polyhydroxyalkanoate molten phase.

2. The aqueous emulsion coating system based on PHA and bio-based multiphase particle Pickering stabilization and interfacial chemical anchoring according to claim 1, characterized in that, The polyhydroxy fatty acid ester is selected from short-chain polyhydroxy fatty acid esters, medium- and long-chain polyhydroxy fatty acid esters, or copolymers between monomers that form short-chain and medium- and long-chain polyhydroxy fatty acid esters. The short-chain polyhydroxy fatty acid ester is selected from one or more of poly3-hydroxybutyrate, poly3-hydroxybutyrate-co-3-hydroxyvalerate, and poly3-hydroxybutyrate-co-4-hydroxybutyrate; The medium- and long-chain polyhydroxy fatty acid esters are selected from one or more of poly(3-hydroxyhexanoate), poly(3-hydroxyoctanoate), poly(3-hydroxydecanoate), poly(3-hydroxydodecanate), or copolymers thereof; The median particle size D of the polyhydroxyalkanoate emulsion particles 50 The range is 0.2μm to 2.0μm; The second particulate component is selected from lignin particles, chitosan and its derivative particles, or combinations thereof; based on the total mass of the bio-based Pickering stable system, the mass ratio of the nanocellulose particles to the second particulate component is 1:0.05 to 1:20; the average particle size of the second particulate component is 5 nm to 20 μm. The bio-based amine curing agent is selected from fatty acid dimer diamine, fatty acid dimer polyamide amine, polyamine prepared from amino acids, polylysine, chitosan oligoamine, fermentation-derived diamine or polyamine and their salts or combinations thereof; the amine curing agent has an amine hydrogen equivalent of 50-600 g / eq.

3. The aqueous emulsion coating system based on PHA and bio-based multiphase particle Pickering stabilization and interfacial chemical anchoring as described in claim 1, characterized in that, The nanocellulose particles are selected from cellulose nanofibers, microfibrillated cellulose, cellulose nanocrystals, cellulose microparticles, or combinations thereof, and the nanocellulose particles are either unmodified or obtained through oxidation, esterification, etherification, quaternization, or grafting modification; the characteristic size of the nanocellulose particles is 5 nm to 20 μm. The bio-based reactive interfacial bonding crosslinking agent is a non-isocyanate type crosslinking agent, containing at least one reactive group that undergoes addition, ring-opening, or condensation reactions with the amine curing agent. The reactive group is selected from epoxy groups, cyclic carbonate groups, acid anhydride groups, or combinations thereof. The bio-based reactive interfacial bonding crosslinking agent is selected from epoxidized soybean oil, epoxidized linseed oil, epoxidized castor oil, vegetable oil-based cyclic carbonates, sugar alcohol-based cyclic carbonates, rosin-based anhydrides, or combinations thereof.

4. The aqueous emulsion coating system based on PHA and bio-based multiphase particle Pickering stabilization and interfacial chemical anchoring according to claim 1, characterized in that, The bio-based reactive interfacial bonding crosslinking agent exists in the aqueous emulsion in one or more of the following ways: adsorbed on the surface of the bio-based Pickering stable system particles; distributed on the surface or near-surface layer of the polyhydroxyalkanoate emulsion particles; dissolved or dispersed within the polyhydroxyalkanoate phase; The bio-based co-film-forming component or bio-based co-bonding component comprises at least one of the following: polylactic acid, polybutylene succinate, cellulose and its esterified or etherified derivatives, starch and its derivatives, shellac, rosin and its modified resins, and vegetable oil-based polyester. The pigment or filler is selected from calcium carbonate, silicon dioxide, titanium dioxide, clay minerals, biochar or a combination thereof; The additives are selected from thickeners, rheology modifiers, defoamers, wetting and dispersing agents, leveling agents, smoothing and scratch-resistant additives, preservatives, antibacterial agents, UV-resistant additives, antioxidants, or combinations thereof.

5. A method for preparing an aqueous emulsion in the aqueous emulsion coating system of claim 1, characterized in that, The preparation method includes the following steps: Step 1: Prepare an aqueous phase by dispersing the bio-based Pickering stabilization system in water to obtain an aqueous dispersion; Step 2: Prepare the molten organic phase by heating polyhydroxy fatty acid ester to melt and mixing it with at least one of the following: a bio-based reactive interfacial bonding crosslinking agent and a bio-based co-film forming component or a bio-based co-bonding component, to obtain the molten organic phase; Step 3: Disperse the molten organic phase obtained in Step 2 into the aqueous dispersion obtained in Step 1 under shear emulsification conditions to obtain a pre-emulsion; homogenize the pre-emulsion under high pressure to obtain an emulsion; Step 4: The emulsion obtained in Step 3 is cooled and solidified to solidify the polyhydroxyalkanoate into polyhydroxyalkanoate emulsion particles, thus obtaining an aqueous emulsion.

6. The preparation method according to claim 5, characterized in that, In step 1, the aqueous solution, aqueous dispersion or gelatinized dispersion of the bio-based co-film forming component or the bio-based co-binder component and / or the pigment or filler and / or the additive are added to the aqueous dispersion. In step 2, the polyhydroxyalkanoate is heated to a melt and then mixed with the bio-based reactive interfacial bonding crosslinking agent and the bio-based co-film forming component or bio-based co-bonding component not added in step 1 to obtain a molten organic phase; the temperature of the organic phase in step 2 is 5-100°C above the melting point of the polyhydroxyalkanoate; the rotation speed of the shear emulsification in step 3 is 1000-30000 rpm and the time is 0.5-60 min; the high-pressure homogenization pressure in step 3 is 50-2000 bar and the number of cycles is 1-20; wherein, all or part of the bio-based reactive interfacial bonding crosslinking agent is added to the aqueous dispersion in step 1, so that it is adsorbed on the surface of the bio-based Pickering stable system particles or pre-reacts with the surface groups of the bio-based Pickering stable system particles.

7. A method for forming a protective coating, characterized in that, Includes the following steps: Step 1: Mix the aqueous emulsion of claim 1 with the amine curing agent according to the said equivalent ratio to obtain the construction coating; Step 2: Apply the construction coating obtained in Step 1 to the substrate surface using a water-based coating method to obtain a wet coating sample; Step 3: Dry the wet coating obtained in Step 2 and cure it at room temperature or 40-120°C for 0.5-72 hours to obtain a single-layer protective coating.

8. A coated product, characterized in that, The invention includes a substrate and a protective coating covering the surface of the substrate. The protective coating is a single-layer protective coating formed by water-based application, drying and curing of an application coating obtained by mixing the water-based emulsion and an amine curing agent as described in claim 1. The substrate is selected from paper, cardboard, molded fiber, wood, artificial board, textiles, leather, metal, inorganic building materials, plastics or composite materials thereof.

9. The coated article according to claim 8, characterized in that, The dry film thickness of the protective coating is 0.1–500 μm; when used on paper-based materials, the dry coating amount is 0.2–120 g / m². When the coated product is water-based coated paper and paperboard for food packaging, the water absorption is ≤10.0 g / m² after 30 min as determined by GB / T 1540-2002, and there is no leakage in the 90℃ water and 95℃ soybean oil leakage tests conducted according to the test conditions specified in GB / T 44834-2024; the heat seal strength is determined according to the corresponding clause of GB / T 44834-2024 and is ≥0.30 kN / m. The wetting tension of the coating free surface or free film with 100% coverage shall be determined according to GB / T 14216-2008 and shall be ≥38mN / m.

10. The use of the aqueous emulsion coating system based on PHA and bio-based multiphase particle Pickering stabilization and interfacial chemical anchoring according to claim 1, characterized in that, Used for forming single-layer barrier coatings, moisture-proof coatings, oil-resistant coatings, abrasion-resistant protective coatings, UV-resistant coatings, antibacterial coatings, chemical-resistant coatings, or combinations thereof by water-based coating and curing; When used in paper or molded fiber packaging materials, it is used to replace or reduce polyethylene film or petrochemical-based barrier coatings, wherein the single-layer barrier coating is formed by water-based application, drying and curing of the application coating. When the second particulate component contains lignin particles, it is used to improve the coating's UV resistance and weather protection performance. When the second particulate component contains chitosan and its derivative particles, it is used to improve the antibacterial and wet adhesion protection properties of the coating.

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