Pha plant-based composite aqueous emulsion, and preparation method and application thereof

Abstract

The application discloses a PHA plant-based composite water-based emulsion and a preparation method and application thereof, and belongs to the technical field of water-based polymer dispersions and coating layers. The composite water-based emulsion takes water as a continuous phase, and takes dispersed particles containing a polyhydroxy fatty acid ester component and a rosin-based component as a dispersed phase; the dry solid mass ratio of the polyhydroxy fatty acid ester component to the rosin-based component is 1:4 to 4:1; the solid content is 10 to 70 wt%; the dispersed particle D 50 0.20 to 0.90 microns, D 90 ≤4.0 microns; an emulsion stabilizing system is constructed by means of internal emulsification ion group and rosin-based reactive emulsifier, and the dosage of additional non-fluorine surfactant is 0 to 0.5 wt%. The application can be used for preparing protective coating layers on the surfaces of metals, plastics and composite materials.

Description

Technical Field

[0001] This invention belongs to the field of waterborne polymer dispersions and coating technology, specifically relating to PHA plant-based composite waterborne emulsions, their preparation methods, and applications. Background Technology

[0002] Waterborne coatings are widely used for surface protection of metals, plastics, wood, and composite materials due to their advantages such as low volatile organic compound (VOC) emissions, safe application, and environmental friendliness. However, existing waterborne acrylic, polyurethane, and epoxy systems are usually petrochemical-based, resulting in insufficient bio-based content and a high carbon footprint. Furthermore, they still require further optimization in scenarios requiring high water resistance, high barrier properties, high solids content, and low migration.

[0003] Polyhydroxyalkanoates (PHAs) are aliphatic polyesters synthesized by microorganisms, possessing characteristics such as renewable sources, potential biodegradability, and barrier properties. Existing technologies have disclosed various preparation routes for aqueous dispersions or latexes of PHA, including techniques for obtaining PHA particles and forming dispersions in water through steps such as solvent removal, melt emulsification, high-shear emulsification, and high-pressure homogenization. These disclosed methods generally rely on the addition of external surfactants or stabilizers to achieve dispersion stability, with the core processes focusing on emulsification, homogenization, and particle size control.

[0004] Furthermore, existing technologies disclose the use of PHA as the main component in coatings or film formation. For example, CN112867766A discloses a scheme for forming a biodegradable coating based on an aqueous PHA dispersion. Simultaneously, literature also discloses the preparation and application research of poly(3-hydroxybutyric acid-3-hydroxyvalerate) copolyester (PHBV) aqueous dispersion in paper coatings. Regarding formulation design, there are also disclosures of using PHA as the main component and employing reactive emulsifiers to form an aqueous system, followed by compounding with tackifying resins, plasticizers, and waxes to obtain adhesive properties. For example, CN120944505A discloses a technical approach of introducing reactive emulsifiers into a pure bio-based PHA aqueous adhesive system and compounding with tackifying resins, plasticizers, and plant waxes, and in some embodiments, adding an aqueous dispersion of glycerol rosin ester as a tackifying component. The application scenarios of the aforementioned disclosures are mostly geared towards paper-based barrier or adhesive fields, and typically still rely on added surfactants or added tackifying components to balance stability and adhesive performance.

[0005] Rosin and its derivatives possess a rigid diterpenoid skeleton and are easily functionalized, exhibiting wetting, thickening, and interfacial interaction capabilities. Furthermore, they are derived from the resins and byproducts of pine trees, making the raw materials renewable. Relevant materials systematically summarize the applications of rosin acid, rosin esters, and their thickening and coating applications. Regarding patent disclosures, CN102010602B discloses an aqueous thickening resin emulsion and its preparation method, while CN112521637B discloses a rosin-based reactive thickening emulsion and its preparation and application. Existing technologies also include schemes that combine rosin-based resin emulsions or rosin thickening resin emulsions with other polymer emulsions.

[0006] Meanwhile, existing disclosures include schemes that combine PHA emulsions with multiple emulsions such as rosin emulsions to obtain paper-based heat-sealing or barrier coatings. For example, CN119265999A discloses an aqueous coating system containing PHA emulsions and rosin emulsions, using surfactants such as Tween 80 or Span 80 for emulsification and dispersion. These compounding schemes typically maintain system stability with added surfactants or stabilizers, but they are still prone to flocculation, stratification, or viscosity drift under high-solids concentration, freeze-thaw cycles, or long-term storage conditions, and surfactant migration may affect water resistance, media resistance, and durability. Other disclosures propose introducing reactive emulsifiers into aqueous PHA systems and compounding them with tackifying resins, plasticizers, and waxes to obtain adhesive or barrier properties. However, these disclosures lack a unified definition of the stability window under high-solids conditions, freeze-thaw resistance under low surfactant dosages, and pathways to improve adhesion and media resistance durability on metal or plastic substrates.

[0007] Therefore, an aqueous composite dispersion system is still needed: a rosin-based component is introduced to improve wetting and interfacial interactions while containing a PHA film-forming matrix, and simultaneously satisfying the following two points regarding emulsification stability: First, the ionizable groups in the rosin-based component are neutralized by alkaline substances to form internal emulsion ionic groups, thereby improving electrostatic or steric stability under high solids content; Second, a rosin-based reactive emulsifier containing hydrophobic groups, hydrophilic segments, and reactive anchoring groups is introduced, enabling it to covalently anchor with the dispersed particles during film formation and / or curing, thereby reducing the migration of added surfactants and improving water resistance, media resistance, and durability, thus achieving both storage stability and improved coating adhesion under wide formulation, wide solids content, and wide particle size window. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the prior art and provide PHA plant-based composite aqueous emulsion, its preparation method and application.

[0009] To achieve the above objectives, the present invention provides the following technical solution:

[0010] This invention proposes a polyhydroxyalkanoate (PHA) plant-based composite aqueous emulsion. The composite aqueous emulsion comprises water, dispersed particles, and an emulsion stabilizing system. The water is the continuous phase, the dispersed particles are the dispersed phase, and the emulsion stabilizing system is disposed on the surface and / or interface of the dispersed particles. The dispersed phase includes one or both of the following: composite particles simultaneously containing a PHA component and a rosin-based component; or a particle mixture system composed of PHA components and rosin-based particles, wherein the dry weight ratio of the PHA component to the rosin-based component is 1:4 to 4. The ratio can be 1:1, for example, 1:4, 2:8, 3:7, 7:13, 4:6, 6:9, 1:1, 10:10, 11:9, 6:4, 7:3, 8:2, 3:1, 4:1, etc. The solid content of the composite aqueous emulsion is 10-70 wt%, for example, 10 wt%, 15 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%, 53 wt%, 55 wt%, 57 wt%, 60 wt%, 65 wt%, 70 wt%, etc. The volume median diameter D of the overall volumetric particle size distribution of the dispersed particles is... 50 The diameter is 0.20 μm to 0.90 μm, for example, it can be 0.20 μm, 0.205 μm, 0.21 μm, 0.215 μm, 0.22 μm, 0.23 μm, 0.24 μm, 0.25 μm, 0.26 μm, 0.28 μm, 0.30 μm, 0.35 μm, 0.40 μm, 0.45 μm, 0.50 μm, 0.55 μm, 0.60 μm, 0.65 μm, 0.70 μm, 0.80 μm, 0.90 μm, etc., and the cumulative quantile diameter D in the volume distribution is 90%. 90The micrometer size is ≤4.0 μm, for example, it can be 0.50 μm, 0.55 μm, 0.58 μm, 0.60 μm, 0.62 μm, 0.65 μm, 0.70 μm, 0.75 μm, 0.80 μm, 0.85 μm, 0.90 μm, 1.00 μm, 1.20 μm, 1.50 μm, 1.80 μm, 2.00 μm, 2.50 μm, 3.00 μm, 3.50 μm, 3.80 μm, 4.00 μm, etc. The composite aqueous emulsion includes an emulsion stabilizing system, which is jointly provided by internal emulsifying ionic groups and rosin-based reactive emulsifiers. The internal emulsifying ionic groups are formed by ionized precursor groups provided by the rosin-based component under the action of an alkaline substance. The rosin-based reactive emulsifier comprises rosin hydrophobic groups, hydrophilic segments, and reactive anchoring groups. The reactive anchoring groups react chemically with the dispersed particles to form covalent bonds. The added surfactant is a non-fluorinated surfactant, and its dosage is 0-0.5 wt% of the total dry solid mass of the polyhydroxyalkanoate component and the rosin-based component. For example, it can be 0 wt%, 0.01 wt%, 0.05 wt%, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, etc. When the dosage is 0 wt%, the composite aqueous emulsion does not contain added surfactant, and the total fluorine content of the dry film of the composite aqueous emulsion, as measured by oxygen bomb combustion-ion chromatography, is less than 5 mg / kg.

[0011] The polyhydroxyalkanoate component is a base polyhydroxyalkanoate, or one or more of a blend, chain extender, or end-group modified product formed from the base polyhydroxyalkanoate; the base polyhydroxyalkanoate is selected from one or more of short-chain polyhydroxyalkanoates, medium- and long-chain polyhydroxyalkanoates, or copolymers between monomers forming short-chain polyhydroxyalkanoates and monomers forming medium- and long-chain polyhydroxyalkanoates, wherein the short-chain polyhydroxyalkanoate is selected from poly(3-hydroxybutyrate) (PHB), poly(3-hydroxybutyrate-3-hydroxyvalerate) copolyester (PHBV), and poly(3-hydroxybutyrate-3-hydroxyhexanoate) copolyester (PHBV). H), or one or more of poly(3-hydroxybutyrate-4-hydroxybutyrate) copolyester (P34HB), wherein the medium- and long-chain polyhydroxy fatty acid ester is selected from one or more of poly(3-hydroxyhexanoate), poly(3-hydroxyheptanoate), poly(3-hydroxyoctanoate), poly(3-hydroxynonanoate), poly(3-hydroxydecanoate), poly(3-hydroxyundecanoate), poly(3-hydroxydodecanoate), poly(3-hydroxytetrazoate), and poly(3-hydroxytetradecanoate), wherein the polyhydroxy fatty acid ester component contains reactive end groups, wherein the reactive end groups are selected from hydroxyl, carboxyl, epoxy, isocyanate, anhydride, acrylate, methacrylate, allyl, or combinations thereof.

[0012] The rosin-based component is selected from one or more of rosin acid and its derivatives, rosin esters and their derivatives, rosin-modified resins, rosin-based unsaturated monomers and their polymers, or combinations thereof. The rosin acid and its derivatives include rosin acid, dehydroabietic acid, hydrogenated rosin, disproportionated rosin, polymerized rosin, maleic rosin, fumaric rosin, rosin salts, or combinations thereof. The rosin esters and their derivatives include glycerol rosin esters, pentaerythritol rosin esters, rosin-modified polyol esters, or combinations thereof. The rosin-modified resins include rosin-modified polyesters, rosin-modified polyethers, rosin-modified polyurethanes, rosin-modified phenolic resins, rosin-modified terpene resins, or combinations thereof. The rosin-based unsaturated monomer is selected from dehydroabietic acid acrylate, dehydroabietic acid methacrylate, abietic acid acrylate, abietic acid methacrylate, rosin maleic anhydride adduct acrylate, rosin maleic anhydride adduct methacrylate, rosin-based allyl ester, rosin-based vinyl ether, or combinations thereof.

[0013] The internal emulsifying ionic group is derived from one or more of the carboxyl, anhydride, sulfonic acid, and phosphonic acid groups of the rosin-based component. The acid value of the component providing the ionization precursor group in the rosin-based component is 10-250 mg KOH / g, for example, it can be 10 mg KOH / g, 15 mg KOH / g, 20 mg KOH / g, 30 mg KOH / g, 36 mg KOH / g, 50 mg KOH / g, 100 mg KOH / g, 150 mg KOH / g, 180 mg KOH / g, 200 mg KOH / g, 250 mg KOH / g, etc. The internal emulsifying ionic group is formed by neutralizing the ionization precursor group by an alkaline substance at a rate of 30-80%. The degree of neutralization can be, for example, 30%, 35%, 40%, 50%, 55%, 60%, 70%, 75%, 80%, etc. The alkaline substance is selected from ammonia, alkanolamine, organic amine, alkali metal hydroxide, alkali metal carbonate, or a combination thereof.

[0014] The hydrophilic segment of the rosin-based reactive emulsifier is a polyether segment, and the reaction anchoring group is a cyclic anhydride group. The amount of the rosin-based reactive emulsifier is 0.2-5 wt% of the total dry solid mass of the polyhydroxyalkanoate component and the rosin-based component, for example, it can be 0.2 wt%, 0.5 wt%, 0.8 wt%, 1.0 wt%, 1.5 wt%, 2.0 wt%, 3.0 wt%, 4.0 wt%, 5.0 wt%, etc. The rosin-based reactive emulsifier is a rosin-polyether anhydride reactive emulsifier, which is obtained by esterification of dehydroabsic acid with polyethylene glycol monomethyl ether to obtain a rosin-polyether ester intermediate, and then reacting it with maleic anhydride to introduce a cyclic anhydride group.

[0015] The added surfactant is selected from anionic, nonionic, amphoteric, cationic, polymeric surfactants, or combinations thereof. When the pH of the composite aqueous emulsion is 7.8–8.2 and the solid content is 53–57 wt%, for example, pH 7.8, 7.9, 8.0, 8.1, 8.2, and solid content 53 wt%, 54 wt%, 55 wt%, 56 wt%, 57 wt%, the stratification height after storage at 50°C for 30 days does not exceed 2.5% of the sample height, for example, it can be 0.5%, 0.6%, 0.8%, 0.9%, 1.0%, 1.2%, 1.5%, 1.8%, 2.0%, 2.2%, 2.5%, etc., and the viscosity change rate after storage for 30 days is ≤12%, for example, it can be 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, etc., and the volume median diameter D of the dispersed particles is... 50 The rate of change is ≤12%, for example, it can be 3%, 4%, 5%, 6%, 8%, 9%, 10%, 12%, etc., and after ≥3 freeze-thaw cycles between -18℃ and 23℃, no irreversible condensation or irreversible stratification occurs, for example, after 3, 4, 5 or more cycles.

[0016] The dry film formed by the composite aqueous emulsion has a rosin-rich surface layer in the thickness direction, and the mass loss rate of the dry film after extraction with ethyl acetate at 23°C for 24 hours is 2.5% to 4.5%, for example, it can be 2.5%, 2.8%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.8%, 3.9%, 4.0%, 4.1%, 4.2%, 4.5%, etc.

[0017] The pH of the composite aqueous emulsion is 5.5 to 10.5, for example, it can be 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10.0, 10.5, etc., and further contains a chain extender or crosslinker. The chain extender or crosslinker is selected from polyfunctional epoxy compounds, polyfunctional isocyanate blocking agents, carbodiimides, metal complex crosslinkers, silane coupling agents, or combinations thereof. The amount of the chain extender or crosslinker is 0.01 to 15 wt% of the total dry solid mass of the polyhydroxy fatty acid ester component and the rosin-based component, for example, it can be 0.01 wt%, 0.1 wt%, 0.5 wt%, 1.0 wt%, 2.0 wt%, 3.0 wt%, 5.0 wt%, 10.0 wt%, 15.0 wt%, etc.

[0018] This invention also provides an aqueous coating composition comprising the aforementioned polyhydroxyalkanoate plant-based composite aqueous emulsion as a film-forming binder and water, wherein the composite aqueous emulsion accounts for 5-100 wt% of the total non-volatile matter of the aqueous coating composition on a dry solid basis, for example, 5 wt%, 10 wt%, 20 wt%, 30 wt%, 50 wt%, 60 wt%, 80 wt%, 90 wt%, 95 wt%, 100 wt%, etc., and the total non-volatile matter content of the aqueous coating composition is 2-80 wt%, for example, 2 wt%, 10 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, 70 wt%, 80 wt%, etc. When pigments or fillers are included, the pigments or fillers include one or more of inorganic pigments, anti-corrosion pigments, extender fillers, and nanofillers, wherein the inorganic pigments... The composition comprises titanium dioxide, iron oxide, carbon black, zinc oxide, or combinations thereof; the anti-corrosion pigment is selected from zinc phosphate, zinc phosphosilicate, molybdate anti-corrosion pigment, or combinations thereof; the extender filler is selected from barium sulfate, calcium carbonate, talc, mica powder, kaolin, wollastonite, silica, or combinations thereof; the nanofiller is selected from nano clay, nano silica, graphene, graphite, or combinations thereof; the water-based coating composition is suitable for application to the surface of a substrate and drying or curing to form a coating with a dry film thickness of 0.2–500 μm, for example, 0.2 μm, 0.5 μm, 1 μm, 5 μm, 10 μm, 20 μm, 25 μm, 30 μm, 40 μm, 50 μm, 100 μm, 150 μm, 200 μm, 300 μm, 400 μm, 500 μm, etc.; the substrate is selected from metal, alloy, galvanized sheet, aluminum, stainless steel, plastic, or composite materials thereof.

[0019] The waterborne coating composition further comprises one or more of the following: wetting and dispersing agent, defoamer, leveling agent, anti-corrosion and anti-mildew agent, thickener, rheology modifier, anti-settling agent, film-forming aid, plasticizer, bio-based wax, adhesion promoter, flash rust inhibitor, or crosslinking agent, wherein the crosslinking agent is selected from polyfunctional epoxy compounds, polyfunctional isocyanate blocking agents, carbodiimide, hydrazine crosslinking agents, aziridine, metal complex crosslinking agents, silane crosslinking agents, or combinations thereof, and the wetting and dispersing agent, leveling agent, and defoamer are non-fluorinated additives.

[0020] This invention also provides a method for preparing the above-mentioned polyhydroxyalkanoate plant-based composite aqueous emulsion, specifically comprising:

[0021] Step 1. Add deionized water, the rosin-based reactive emulsifier, and the added surfactant to the reaction vessel, and stir for 10 minutes using a high-shear emulsifying disperser to obtain an aqueous phase mixture. The added surfactant is a non-fluorinated surfactant. When the amount of added surfactant is 0 wt%, no added surfactant is added.

[0022] Step 2. Mix the polyhydroxyalkanoate component and the rosin-based component according to the formulation ratio and stir for 30 min to obtain a dispersed phase precursor. The polyhydroxyalkanoate component is a polyhydroxyalkanoate resin or a polyhydroxyalkanoate aqueous emulsion, and the rosin-based component is a rosin-based resin or a rosin-based aqueous emulsion. When the rosin-based component is a solid or high-viscosity resin and the polyhydroxyalkanoate component is a polyhydroxyalkanoate resin, heat the rosin-based component to 160°C to melt it and then add it to the polyhydroxyalkanoate resin. When the rosin-based component is a solid or high-viscosity resin and the polyhydroxyalkanoate component is a polyhydroxyalkanoate aqueous emulsion, slowly add the melted rosin-based component to the polyhydroxyalkanoate aqueous emulsion while stirring, and stir for 30 min to obtain the dispersed phase precursor.

[0023] Step 3. Add the dispersed phase precursor obtained in Step 2 to the aqueous phase mixture obtained in Step 1, emulsify in a high-shear emulsifying disperser for 15 min, and add an alkaline substance during the emulsification process to neutralize the ionized precursor groups to obtain a pre-emulsion;

[0024] Step 4. Process the preemulsion obtained in Step 3 using a high-pressure homogenizer. The homogenization pressure is 50–150 MPa, for example, 50 MPa, 80 MPa, 100 MPa, 120 MPa, 150 MPa, etc., and the homogenization is performed 1–5 times, for example, 1 time, 2 times, 3 times, 4 times, 5 times, etc., while controlling the median volume diameter D. 50 The particle size is 0.20–0.90 μm, and then the mixture is kept at 70–100°C, for example, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, etc., for 10–60 min, for example, 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, etc., so that the reaction anchoring groups of the rosin-based reactive emulsifier are chemically anchored to the dispersed particles, thereby obtaining the crude emulsion.

[0025] Step 5. Dilute the crude emulsion obtained in Step 4 with water or vacuum concentrate and dehydrate it to adjust the solid content to 10-70 wt%, and stir evenly to obtain a composite aqueous emulsion.

[0026] Step 2 adopts at least one of the following routes:

[0027] Route 1. The polyhydroxy fatty acid ester component and the rosin-based component are melted and stirred in a reactor to obtain a dispersed phase precursor. The dispersed phase precursor is added to the aqueous phase mixture obtained in step 1 and emulsified using a high-shear emulsifying disperser. After cooling, dispersed particles are obtained.

[0028] Route 2. First, prepare a polyhydroxyalkanoate emulsion, and then prepare a rosin-based emulsion, wherein the median volume diameter D of the polyhydroxyalkanoate emulsion is... 50 The diameter of the polyhydroxyalkanoate emulsion is 0.20–0.90 μm. The polyhydroxyalkanoate emulsion and the rosin-based emulsion are compounded at a dry-to-solid mass ratio of 1:4–4:1 and stirred evenly to obtain a compounded emulsion. An alkaline substance is added to the compounded emulsion to neutralize and form internal emulsion ionic groups, resulting in a neutralized compound emulsion. The neutralized compound emulsion is then treated with a high-pressure homogenizer at a pressure of 50–150 MPa for 1–5 passes, controlling the volume median diameter (D) of the neutralized compound emulsion. 50 The particle size is 0.20–0.90 μm. The homogenized neutralized compound emulsion is kept at 70–100 °C for 10–60 min to allow the reaction anchoring groups of the rosin-based reactive emulsifier to chemically anchor the dispersed particles, thereby obtaining dispersed particles.

[0029] The present invention also provides a use of the aforementioned water-based coating composition, wherein the aforementioned water-based coating composition is used in the preparation of protective coatings, barrier coatings, water-resistant coatings, media-resistant coatings, corrosion-resistant coatings, wear-resistant coatings, damp heat-resistant coatings, or composite material surface coatings on the surface of metal or plastic substrates.

[0030] Compared with the prior art, the following significant advantages can be obtained by using the present invention:

[0031] Excellent emulsion stability: This invention employs a dual-stabilization system constructed from internal emulsifying ionic groups and rosin-based reactive emulsifiers. With extremely low or zero added surfactant dosage, it achieves long-term storage stability of high-solids emulsions and excellent freeze-thaw resistance, solving the problem of traditional PHA emulsions relying on high amounts of surfactants and exhibiting poor stability.

[0032] Excellent adhesion and wettability: By introducing rosin-based components with a rigid diterpenoid skeleton and forming a rosin-rich surface layer during film formation, the wettability and interfacial interaction of the coating on metal, plastic and composite substrates are significantly improved, so that the coating exhibits excellent adhesion of grade 0 to 1 on difficult-to-adhere substrates such as aluminum plates and PET.

[0033] Significant water and media resistance and durability: By utilizing the chemical anchoring effect of rosin-based reactive emulsifiers, the emulsifiers are covalently bonded to the dispersed particles or film-forming network, effectively reducing the migration of small molecules. This results in coatings with extremely low water whitening tendency, excellent contact angle retention, and outstanding resistance to acids, alkalis, solvents, and salt spray.

[0034] Excellent barrier properties: The dense cross-linked network and the filling effect of the rosin rigid skeleton constructed in this invention significantly reduce the water vapor transmission rate (WVTR) and oxygen transmission rate (OTR) of the coating, providing an efficient bio-based barrier solution for the packaging and corrosion protection fields.

[0035] Environmentally friendly and low migration characteristics: The formulation of this invention is completely free of fluorinated surfactants and fluorinated additives, the total fluorine content of the dry film is less than 5 mg / kg, and the mass loss rate after extraction with ethyl acetate is low, which meets the high standards of environmental protection and food contact safety. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the microscopic cross-sectional structure of the composite coating formed after the polyhydroxy fatty acid ester plant-based composite aqueous emulsion of the present invention is coated on a substrate and dried and cured.

[0037] In the figure, 1-substrate; 2-coating; 3-dispersed particles; 4-nanofiller; 5-rosin-based reactive emulsifier. Detailed Implementation

[0038] 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.

[0039] Figure 1 This is a schematic diagram of the coating structure of the present invention. In this schematic structure, the dispersed particles 3 are film-forming units containing polyhydroxy fatty acid ester components and / or rosin-based components; the rosin-based reactive emulsifier 5 is preferably distributed on the surface of the dispersed particles and at the interparticle interfaces, and forms covalent bonds with reactive groups during the preparation or film formation process; the nanofiller 4 fills the interparticle gaps, thereby improving the overall density of the coating.

[0040] The main reagents and raw materials are shown in Table 1.

[0041] Table 1. Main reagent and raw material names, product models and manufacturers:

[0042]

[0043] 1 Note: The acid value is 36 mg KOH / g;

[0044] 2Note: The acid value is 15 mg KOH / g;

[0045] 3 Note: The acid value is 180 mg KOH / g;

[0046] 4 Note: The acid value is 8 mg KOH / g.

[0047] The main analytical and testing instruments are listed in Table 2.

[0048] Table 2 mainly analyzes the names, models, and manufacturers of the testing instruments:

[0049]

[0050] The main testing standards are shown in Table 3.

[0051] Table 3. Main test items, test standard numbers, and standard names:

[0052]

[0053] General preparation process for self-made materials:

[0054] (1) Preparation process of rosin-polyether anhydride reactive emulsifier:

[0055] Step 1. Add dehydroabietic acid and polyethylene glycol monomethyl ether to the reaction vessel, wherein the ratio of the carboxyl equivalent of dehydroabietic acid to the hydroxyl equivalent of polyethylene glycol monomethyl ether is 1.00:1; heat and stir, and connect a vacuum pump to evacuate to an absolute pressure of 20 kPa to remove small molecules, control the reaction temperature at 200℃, and react for 4 hours to obtain the esterification reaction mixture; during the reaction, take samples to determine the acid value according to GB / T 6743. When the acid value is ≤20 mg KOH / g and the difference between two consecutive measurements is ≤2 mg KOH / g, the esterification is considered to have reached the endpoint.

[0056] Step 2. Add maleic anhydride (MAH) to the esterification reaction mixture from Step 1, wherein the amount of MAH is 0.50 times the molar amount of dehydroabietic acid; and add hydroquinone monomethyl ether as an inhibitor. Stir the reaction mixture at 105°C for 2 hours to obtain a modified reaction mixture with cyclic anhydride groups introduced. The reaction endpoint is defined as an acid value that reaches and stabilizes at 120 mg KOH / g with a difference of ≤2 mg KOH / g between two consecutive measurements.

[0057] Step 3. Cool the modified reaction mixture from Step 2 to 70°C, discharge and filter it using a 200-mesh stainless steel filter to obtain a rosin-polyether anhydride reactive emulsifier.

[0058] (2) Preparation process of rosin-modified polyester:

[0059] Step 1. Dehydroabsic acid, adipic acid, 1,6-hexanediol and neopentyl glycol are added to a reactor, wherein the carboxyl equivalent of dehydroabsic acid and adipic acid accounts for 40% of the total carboxyl equivalent. Tetrabutyl titanate is added as an esterification / polymerization catalyst at an amount of 0.05 wt% of the total feed. The temperature is raised to 180°C for esterification for 2 hours, and then raised to 220°C for polymerization for 3 hours, followed by continuous dehydration to obtain a polyester reaction mixture.

[0060] Step 2. Continue to reduce the pressure of the polyester reaction mixture from Step 1 and react it under absolute pressure of 15 kPa until the acid value reaches 20 mg KOH / g (determined according to GB / T 6743). Then, cool down and discharge the material to obtain rosin-modified polyester.

[0061] (3) Preparation process of terminal hydroxyl PHBV:

[0062] Step 1. Add PHBV and ethylene glycol to the reaction vessel, wherein the mass ratio of PHBV to ethylene glycol is 100:10; heat and stir to carry out alcoholysis at 170℃ for 2 hours to obtain the alcoholysis reaction mixture.

[0063] Step 2. Remove excess ethylene glycol from the alcoholysis reaction mixture from Step 1 under reduced pressure and cool and pulverize to obtain terminal hydroxyl PHBV; wherein the target molecular weight level of terminal hydroxyl PHBV is based on the supplier's nominal Mn or the Mn determined by gel permeation chromatography (GPC), and the Mn target is 50,000.

[0064] General process parameters for composite aqueous emulsions (unless otherwise specified in the examples, the following fixed conditions are used):

[0065] Step 1. Add deionized water, rosin-based reactive emulsifier, and added surfactant to the reactor, and stir at 10000 r / min for 10 min using a high-shear emulsifying disperser to obtain an aqueous phase system; when the amount of added surfactant in the formula is 0 wt%, no added surfactant is added;

[0066] Step 2. Heat the rosin-based component to 160°C until completely melted, then lower it to 120°C and keep it warm for later use; add the PHA aqueous emulsion (BioTen series) to the reactor and heat it to 85°C, stirring at 500 r / min; then slowly add the rosin-based melt to the reactor and maintain the temperature at 85°C while stirring for 30 min to obtain the compound dispersion;

[0067] Step 3. The compound dispersion is dispersed at 12000 r / min for 15 min using a high-shear emulsifying disperser. During the dispersion process, dimethylethanolamine (DMEA) is added to complete the internal emulsification and neutralization of the rosin-based components, resulting in a pre-emulsion. The degree of neutralization is defined by equivalent: Degree of neutralization (%) = n(base equivalent provided by the alkaline substance) / n(equivalent of ionized precursor groups) × 100%. The equivalent of ionized precursor groups is calculated by converting the acid value of the rosin-based components that provide carboxyl and / or anhydride groups with the amount of feed. When the rosin-based components are a multi-component mixture, only the components that provide carboxyl and / or anhydride groups are included in the equivalent of ionized precursor groups. Components such as low-acid-value rosin esters that do not provide or provide virtually no ionized precursor groups are not included.

[0068] Step 4. The pre-emulsion is processed by a high-pressure homogenizer at a pressure of 100 MPa for 3 passes. After homogenization, it is kept at 85°C for 30 min to allow the reactive anchoring groups in the rosin-based reactive emulsifier to undergo ring-opening / addition reactions with the reactive end groups in the dispersed particles and form covalent bonds, thus obtaining the crude emulsion.

[0069] Step 5. When the formulation contains chain extenders or cross-linking agents, cool the crude emulsion to 50°C, add the chain extender or cross-linking agent, and stir for 20 minutes. The amount of chain extender or cross-linking agent added is based on the non-volatile part of its effective component, and the actual weighing amount is converted according to the supplier's nominal solid content or the measured solid content. When the formulation does not contain chain extenders or cross-linking agents, this step is not performed.

[0070] Step 6. Dilute the crude emulsion with water or vacuum concentrate and dehydrate it to adjust the solid content to 10-70 wt% and adjust the pH to 8.0. Stir evenly to obtain a composite aqueous emulsion. Except as otherwise specified in Example 10, the solid content of the samples in each example is uniformly adjusted to 55 wt%. For samples requiring high solid content, vacuum concentrate to 70 wt%. For samples requiring low solid content, dilute with water to 10 wt%.

[0071] Example:

[0072] Example 1: Preparation Method: The polyhydroxyalkanoate (PHA) rosin-based composite aqueous emulsion of Example 1 was prepared according to the general preparation process described in the "General Process Parameters for Composite Aqueous Emulsions" section of this specification; the dry weight ratio of the PHA component to the rosin-based component was 11:9. General Formulation: 11 parts by weight of PHBV aqueous emulsion (BioTen 1031, on a dry weight basis); 5 parts by weight of maleic rosin; 4 parts by weight of hydrogenated rosin glycerol ester. Emulsion Stabilization System: The rosin-based reactive emulsifier was a rosin-polyether anhydride reactive emulsifier, used at 1.0 wt% of the total dry weight; the neutralization degree of dimethylethanolamine was 50%; the added surfactant was a mixture of sodium dodecylbenzenesulfonate (SDBS) and fatty alcohol polyoxyethylene ether (AEO-9) in a 1:1 mass ratio, and was a non-fluorinated surfactant, used at a total amount of 0.5 wt% of the total dry weight; chain extender or crosslinking agent: none.

[0073] Example 2: Preparation Method: The polyhydroxyalkanoate (PHA) rosin-based composite aqueous emulsion of Example 2 was prepared according to the melt emulsification preparation process described in the "General Process Parameters for Composite Aqueous Emulsions" of this specification, and dispersed particles were formed; the dry weight ratio of the PHA component to the rosin-based component was 7:3. General Formulation: 7 parts by weight of PHBH aqueous emulsion (BioTen 1033, on a dry weight basis); 3 parts by weight of maleic rosin. Emulsion Stabilization System: The rosin-based reactive emulsifier was a rosin-polyether anhydride reactive emulsifier, used at 1.0 wt% of the total dry weight; the neutralization degree of dimethylethanolamine was 60%; the added surfactant was a non-fluorinated surfactant, a mixture of sodium dodecylbenzenesulfonate (SDBS) and fatty alcohol polyoxyethylene ether (AEO-9) in a 1:1 mass ratio, used at 0.5 wt% of the total dry weight; chain extender or crosslinker: none.

[0074] Example 3: Preparation Method: The polyhydroxyalkanoate (PHA) rosin-based composite aqueous emulsion of Example 3 was prepared according to the melt emulsification preparation process described in the "General Process Parameters for Composite Aqueous Emulsions" of this specification, and dispersed particles were formed; the dry weight ratio of the PHA component to the rosin-based component was 10:10. General Formulation: 10 parts by weight of P34HB aqueous emulsion (BioTen 1032, on a dry weight basis); 9 parts by weight of pentaerythritol rosin ester; 1 part by weight of maleic rosin. Emulsion Stabilization System: The rosin-based reactive emulsifier was a rosin-polyether anhydride reactive emulsifier, used at 2.0 wt% of the total dry weight; the neutralization degree of dimethylethanolamine was 50%; the added surfactant was sodium dodecylbenzenesulfonate (SDBS) and fatty alcohol polyoxyethylene ether (AEO-9) in a 1:1 mass ratio, and was a non-fluorinated surfactant, used at 0.5 wt% of the total dry weight; chain extender or crosslinking agent: none.

[0075] Example 4: Preparation Method: The polyhydroxyalkanoate (PHA) rosin-based composite aqueous emulsion of Example 4 was prepared according to the melt emulsification preparation process described in the 'General Process Parameters for Composite Aqueous Emulsions' section of this specification, and dispersed particles were formed; the dry solid mass ratio of the PHA component to the rosin-based component was 11:9. General Formulation: Terminal hydroxyl PHBV (obtained from PV3000G through alcoholysis modification, GPC determination M...) n The total dry weight is 50,000, prepared as an aqueous dispersion (11 parts by weight, dry weight); maleic rosin 5 parts by weight; rosin-modified polyester 4 parts by weight. Emulsification stabilization system: 1.0 wt% of total dry weight is used as a rosin-polyether anhydride reactive emulsifier; the degree of neutralization of dimethyl ethanolamine is 50%; the added surfactant is sodium dodecylbenzenesulfonate (SDBS) and fatty alcohol polyoxyethylene ether (AEO-9) in a 1:1 mass ratio, totaling 0.5 wt% of total dry weight, and is a non-fluorinated surfactant. Chain extender or crosslinking agent: The amount of epoxy chain extender is 2.0 wt% of the total dry solids, and the amount of carbodiimide is 1.0 wt% of the total dry solids; the epoxy chain extender and carbodiimide are added during step 5 of the "General Process Parameters for Composite Aqueous Emulsions" in this specification (i.e., added at 50°C), and after stirring for 20 min, proceed to step 6 of the "General Process Parameters for Composite Aqueous Emulsions" in this specification to adjust the solids content and pH.

[0076] Example 5: Preparation method: The polyhydroxyalkanoate (PHA) rosin-based composite aqueous emulsion of Example 5 was prepared according to the preparation process described in this specification; the dry weight ratio of the PHA component to the rosin-based component was 6:4; the median volume diameter D was directly selected. 50 A waterborne emulsion (BioTen 1033) of poly(3-hydroxybutyric acid-3-hydroxyhexanoic acid) copolyester (PHBH) with a thickness of 0.55 μm was prepared. The rosin-based emulsion was prepared by melting pentaerythritol rosin ester at 160 °C and adding it to an aqueous phase containing a rosin-polyether anhydride reactive emulsifier (1.0 wt% of the dry rosin mass) and an added surfactant (SDBS and AEO-9 compounded at a mass ratio of 1:1, 0.5 wt% of the dry rosin mass). The emulsification was carried out at 85 °C using a high-shear emulsifying disperser at 12000 r / min for 15 min, followed by homogenization three times using a high-pressure homogenizer at 100 MPa to obtain the rosin-based emulsion. The PHBH aqueous emulsion and the rosin-based emulsion were compounded and stirred at 85°C and 500 r / min for 20 min at a dry-solid mass ratio of 6:4. Then, DMEA was added to achieve a neutralization degree of 50%. Finally, the compounded emulsion was homogenized twice using a high-pressure homogenizer at 100 MPa to control the D... 50 The wavelength is 240 nm; finally, it is kept at 85℃ for 30 min to allow the reaction anchoring groups to undergo covalent anchoring. General formulation: 6 parts by weight of PHBH aqueous emulsion (on a dry solid basis); 4 parts by weight of pentaerythritol rosin ester.

[0077] Example 6: Preparation method: The polyhydroxyalkanoate (PHA) rosin-based composite aqueous emulsion of Example 6 was prepared according to the preparation process described in this specification; the dry weight ratio of the PHA component to the rosin-based component was 4:6; PHBH aqueous emulsion (BioTen) was directly selected. 1033); The preparation of rosin-based emulsion is as follows: Maleic rosin and pentaerythritol rosin ester are melted at 160°C and added to an aqueous phase, wherein the aqueous phase contains a rosin-polyether anhydride reactive emulsifier (the amount is 1.0 wt% of the total dry solid mass of maleic rosin and pentaerythritol rosin ester) and an added surfactant (SDBS and AEO-9 are compounded at a mass ratio of 1:1, the amount is 0.5 wt% of the total dry solid mass of the rosin components); emulsification is carried out at 85°C with a high-shear emulsifying disperser at 12000 r / min for 15 min, followed by homogenization three times with a high-pressure homogenizer at 100 MPa to obtain a rosin-based emulsion; the PHBH aqueous emulsion and the rosin-based emulsion are compounded at a dry solid mass ratio and stirred at 85°C and 500 r / min for 20 min, then DMEA is added to complete the neutralization, and then homogenized twice with a high-pressure homogenizer at 100 MPa to control the D of the compounded emulsion. 50 The thickness is 0.60 μm, and the final temperature is maintained at 85℃ for 30 min to allow the reaction anchoring groups to undergo covalent anchoring. General formulation: PHA component is 4 parts by weight of PHBH aqueous emulsion (BioTen 1033, on a dry solids basis); maleic rosin is 3 parts by weight; pentaerythritol rosin ester is 3 parts by weight. Emulsion stabilization system: Rosin-based reactive emulsifier is a rosin-polyether anhydride reactive emulsifier, used at 1.0 wt% of total dry solids; dimethylethanolamine neutralization degree is 60%; the added surfactant is sodium dodecylbenzenesulfonate (SDBS) and fatty alcohol polyoxyethylene ether (AEO-9) in a 1:1 mass ratio, and is a non-fluorinated surfactant, used at 0.5 wt% of total dry solids; chain extender or crosslinker: none.

[0078] Example 7: Preparation Method: The polyhydroxyalkanoate (PHA) rosin-based composite aqueous emulsion of Example 7 was prepared according to the preparation process described in this specification; the dry weight ratio of the PHA component to the rosin-based component was 2:8; PHBH aqueous emulsion (BioTen) was directly selected. 1033); The preparation of the rosin-based emulsion is as follows: Maleic rosin and hydrogenated rosin glycerol ester are melted at 160°C and added to an aqueous phase, wherein the aqueous phase contains a rosin-polyether anhydride reactive emulsifier (the amount is 1.0 wt% of the total dry solid mass of maleic rosin and hydrogenated rosin glycerol ester) and an added surfactant (SDBS and AEO-9 are compounded at a mass ratio of 1:1, the amount is 0.5 wt% of the total dry solid mass of the rosin components); emulsification is carried out at 85°C using a high-shear emulsifying disperser at 12000 r / min for 15 min, followed by homogenization three times at 100 MPa using a high-pressure homogenizer to obtain the rosin-based emulsion; the PHBH aqueous emulsion and the rosin-based emulsion are compounded at a dry solid mass ratio and stirred at 85°C and 500 r / min for 20 min, then DMEA is added to complete the neutralization, and then homogenized twice at 100 MPa using a high-pressure homogenizer to control the D of the compounded emulsion. 50 The thickness is 0.90 μm, and the final temperature is maintained at 85℃ for 30 min to allow the reaction anchoring groups to undergo covalent anchoring. General formulation: 2 parts by weight of PHA component PHBH aqueous emulsion (BioTen 1033, on a dry solids basis); 4 parts by weight of maleic rosin; 4 parts by weight of hydrogenated rosin glycerol ester. Emulsion stabilization system: The rosin-based reactive emulsifier is a rosin-polyether anhydride reactive emulsifier, used at 1.0 wt% of total dry solids; dimethylethanolamine neutralization degree 70%; the added surfactant is sodium dodecylbenzenesulfonate (SDBS) and fatty alcohol polyoxyethylene ether (AEO-9) in a 1:1 mass ratio, and is a non-fluorinated surfactant, used at 0.5 wt% of total dry solids; chain extender or crosslinking agent: none.

[0079] Example 8:

[0080] Preparation method: The polyhydroxyalkanoate (PHA) rosin-based composite aqueous emulsion of Example 8 was prepared according to the melt emulsification preparation process described in the "General Process Parameters for Composite Aqueous Emulsions" of this specification, and dispersed particles were formed; the dry weight ratio of the PHA component to the rosin-based component was 8:2. General formulation: 8 parts by weight of PHA component PHBV aqueous emulsion (BioTen 1031, on a dry weight basis); 1 part by weight of maleic rosin; 1 part by weight of hydrogenated rosin glycerol ester. Emulsion stabilization system: The rosin-based reactive emulsifier was a rosin-polyether anhydride reactive emulsifier, used at 1.0 wt% of the total dry weight; the neutralization degree of dimethyl ethanolamine was 30%; the added surfactant was a compound of sodium dodecylbenzenesulfonate (SDBS) and fatty alcohol polyoxyethylene ether (AEO-9) in a mass ratio of 1:1, and was a non-fluorinated surfactant, used at 0.5 wt% of the total dry weight; chain extender or crosslinker: none.

[0081] Example 9:

[0082] Preparation method: The polyhydroxyalkanoate (PHA) rosin-based composite aqueous emulsion of Example 9 was prepared according to the melt emulsification preparation process described in the "General Process Parameters for Composite Aqueous Emulsions" of this specification, and dispersed particles were formed; the dry weight ratio of the PHA component to the rosin-based component was 11:9. General formulation: 11 parts by weight of PHBV aqueous emulsion (BioTen 1031, on a dry weight basis); 5 parts by weight of maleic rosin; 4 parts by weight of hydrogenated rosin glycerol ester. Emulsion stabilization system: The rosin-based reactive emulsifier was a rosin-polyether anhydride reactive emulsifier, used at 1.0 wt% of the total dry weight; the degree of neutralization of dimethylethanolamine was 50%; the amount of added surfactant was 0 wt%, and no added surfactant was used; chain extender or crosslinker: none.

[0083] Example 10:

[0084] Preparation method: The polyhydroxyalkanoate (PHA) rosin-based composite aqueous emulsion of Example 10 was prepared according to the melt emulsification preparation process described in the "General Process Parameters for Composite Aqueous Emulsions" of this specification, and dispersed particles were formed; the dry weight ratio of the PHA component to the rosin-based component was 11:9. General formulation: 11 parts by weight of PHBV aqueous emulsion (BioTen 1031, on a dry weight basis); 5 parts by weight of maleic rosin; 4 parts by weight of hydrogenated rosin glycerol ester. Emulsion stabilization system: The rosin-based reactive emulsifier was a rosin-polyether anhydride reactive emulsifier, used at 1.0 wt% of the total dry weight; the neutralization degree of dimethyl ethanolamine was 50%; the added surfactant was sodium dodecylbenzene sulfonate (SDBS) and fatty alcohol polyoxyethylene ether (AEO-9) compounded at a mass ratio of 1:1, used at 0.5 wt% of the total dry weight. In step 6 of the "General Process Parameters for Composite Aqueous Emulsions" in this manual, the solid content is adjusted to 70 wt% by vacuum concentration, and the pH is adjusted to 8.0; chain extender or crosslinking agent: none.

[0085] Example 11:

[0086] Preparation method: The polyhydroxyalkanoate (PHA) rosin-based composite aqueous emulsion of Example 11 was prepared according to the melt emulsification preparation process described in the "General Process Parameters for Composite Aqueous Emulsions" of this specification and dispersed particles were formed; the dry weight ratio of the PHA component to the rosin-based component was 11:9. General formulation: 11 parts by weight of PHBV aqueous emulsion (BioTen 1031, on a dry weight basis); 5 parts by weight of fumarated rosin (acid value 180 mg KOH / g); 4 parts by weight of hydrogenated rosin glycerol ester. Emulsion stabilization system: The rosin-based reactive emulsifier was a rosin-polyether anhydride reactive emulsifier, used at 0.2 wt% of the total dry weight; the neutralization degree of dimethylethanolamine was 80%; the added surfactant was sodium dodecylbenzenesulfonate (SDBS) and fatty alcohol polyoxyethylene ether (AEO-9) compounded at a mass ratio of 1:1, used at 0.5 wt% of the total dry weight; chain extender or crosslinking agent: none.

[0087] Example 12:

[0088] Preparation method: The polyhydroxyalkanoate (PHA) rosin-based composite aqueous emulsion of Example 12 was prepared according to the melt emulsification preparation process described in the "General Process Parameters for Composite Aqueous Emulsions" of this specification and dispersed particles were formed; the dry weight ratio of the PHA component to the rosin-based component was 11:9. General formulation: 11 parts by weight of PHBV aqueous emulsion (BioTen 1031, on a dry weight basis); 9 parts by weight of low acid value rosin ester (acid value 8 mg KOH / g). Emulsion stabilization system: The rosin-based reactive emulsifier was a rosin-polyether anhydride reactive emulsifier, with an amount of 5.0 wt% of the total dry weight; the neutralization degree of dimethylethanolamine was 30%; the added surfactant was sodium dodecylbenzenesulfonate (SDBS) and fatty alcohol polyoxyethylene ether (AEO-9) compounded at a mass ratio of 1:1, with an amount of 0.5 wt% of the total dry weight; chain extender or crosslinking agent: none.

[0089] Example 13:

[0090] Preparation method: The polyhydroxyalkanoate (PHA) rosin-based composite aqueous emulsion of Example 13 was prepared according to the melt emulsification preparation process described in the "General Process Parameters for Composite Aqueous Emulsions" of this specification and dispersed particles were formed; the dry weight ratio of the PHA component to the rosin-based component was 11:9. General formulation: 11 parts by weight of terminal hydroxyl PHBV; 5 parts by weight of maleic rosin; 4 parts by weight of rosin-modified polyester. Emulsion stabilization system: The rosin-based reactive emulsifier was a rosin-polyether anhydride reactive emulsifier, with an amount of 1.0 wt% of the total dry weight; the neutralization degree of dimethylethanolamine was 50%; the added surfactant was sodium dodecylbenzenesulfonate (SDBS) and fatty alcohol polyoxyethylene ether (AEO-9) compounded at a mass ratio of 1:1, with an amount of 0.5 wt% of the total dry weight. Chain extender or crosslinking agent: The total amount of epoxy chain extender and carbodiimide is 15.0 wt% of the total dry solids (of which epoxy chain extender is 10.0 wt% and carbodiimide is 5.0 wt%). After cooling the crude emulsion obtained in step 4 of the "General Process Parameters for Composite Aqueous Emulsions" in this specification to 50°C, add the above-mentioned epoxy chain extender and carbodiimide, stir for 20 min, and then proceed to step 6 of the "General Process Parameters for Composite Aqueous Emulsions" in this specification to adjust the solids content and pH.

[0091] Comparative Examples: Unless otherwise specified in Comparative Example 4, the samples obtained from Comparative Examples 1 to 7 were all processed according to step 6 of the "General Process Parameters for Composite Aqueous Emulsions" in this manual after completing their respective preparation steps. This involved uniformly adjusting the solid content to 55 wt% and the pH to 8.0, followed by thorough stirring to obtain the emulsion to be tested. Comparative Example 4 experienced irreversible demulsification and gelation during homogenization, making it impossible to obtain a stable finished emulsion. For any test items requiring a stable emulsion or continuous film formation, the results for this sample are indicated by '-'.

[0092] Comparative Example 1: The preparation process is the same as in Example 1, except that: in step 1 of the "General Process Parameters for Composite Aqueous Emulsions" in this specification, no rosin-based reactive emulsifier is added; in step 2 of the "General Process Parameters for Composite Aqueous Emulsions" in this specification, no rosin-based component is added, and PHBV aqueous emulsion (BioTen) is used directly. 1031 (on a dry solids basis) 20 parts by mass were used as the dispersed phase precursor; in step 3 of the "General Process Parameters for Composite Aqueous Emulsions" in this specification, dimethylethanolamine was not added, and no neutralization or internal emulsification was performed; the added surfactant was changed to sodium dodecylbenzenesulfonate (SDBS) and fatty alcohol polyoxyethylene ether (AEO-9) in a mass ratio of 1:1, with a total amount of 2.0 wt% of the total dry solids; in step 4 of the "General Process Parameters for Composite Aqueous Emulsions" in this specification, homogenization was still performed 3 times at 100 MPa; in step 5 of the "General Process Parameters for Composite Aqueous Emulsions" in this specification, no chain extender or crosslinking agent was added; in step 6 of the "General Process Parameters for Composite Aqueous Emulsions" in this specification, the solids content was adjusted to 55 wt%, and the pH was finely adjusted to 8.0 using 0.1 mol / L sodium hydroxide solution. This pH adjustment was not considered as internal emulsification or neutralization treatment, and the final product was the Comparative Example 1 emulsion containing only the PHA component.

[0093] Comparative Example 2: The preparation process is the same as in Example 1, except that: in step 1 of the "General Process Parameters for Composite Aqueous Emulsions" in this specification, no PHA component or rosin-based reactive emulsifier is added; in step 2 of the "General Process Parameters for Composite Aqueous Emulsions" in this specification, no PHA aqueous emulsion is added, and only 6 parts by weight of maleic rosin and 4 parts by weight of pentaerythritol rosin ester are added to the reaction vessel, melted at 160°C and stirred for 30 min to obtain the rosin-based dispersed phase precursor; in step 3 of the "General Process Parameters for Composite Aqueous Emulsions" in this specification, dimethylethanolamine is added to ionize the precursor groups provided by maleic rosin. The neutralization degree is 60%; the added surfactant is sodium dodecylbenzenesulfonate (SDBS) and fatty alcohol polyoxyethylene ether (AEO-9) in a mass ratio of 1:1, with a total amount of 2.0 wt% of the total dry solids; step 4 in the "General Process Parameters for Composite Aqueous Emulsions" of this specification still uses homogenization at 100 MPa for 3 times; step 5 in the "General Process Parameters for Composite Aqueous Emulsions" of this specification does not add chain extenders or crosslinking agents; step 6 in the "General Process Parameters for Composite Aqueous Emulsions" of this specification adjusts the solid content to 55 wt% and the pH to 8.0, finally obtaining the Comparative Example 2 emulsion containing only rosin-based components.

[0094] Comparative Example 3: The preparation process is the same as in Example 1, except that: 5 parts by weight of maleic rosin and 4 parts by weight of hydrogenated rosin glycerol ester in Example 1 are replaced with 9 parts by weight of pentaerythritol rosin ester; rosin-based reactive emulsifiers are not added in step 1 of the "General Process Parameters for Composite Aqueous Emulsions" in this specification; dimethylethanolamine is not added in step 3 of the "General Process Parameters for Composite Aqueous Emulsions" in this specification, and neutralization and internal emulsification are not performed; the added surfactant is replaced with sodium dodecylbenzenesulfonate (SDBS) and fatty alcohol polyoxyethylene ether (AEO-9) in a mass ratio. The mixture is compounded at a ratio of 1:1, with a total dosage of 2.0 wt% of the total dry solids. Step 4 in the "General Process Parameters for Composite Aqueous Emulsions" of this manual still uses homogenization at 100 MPa for 3 times. Step 5 in the "General Process Parameters for Composite Aqueous Emulsions" of this manual does not add chain extenders or crosslinking agents. Step 6 in the "General Process Parameters for Composite Aqueous Emulsions" of this manual adjusts the solid content to 55 wt% and uses 0.1 mol / L sodium hydroxide solution to fine-tune the pH to 8.0, finally obtaining Comparative Example 3 emulsion, which is mainly a physical compound of PHBV and pentaerythritol rosin ester.

[0095] Comparative Example 4: The preparation process was the same as in Example 1, except that the amounts of PHBV aqueous emulsion, maleic rosin, and hydrogenated rosin glycerol ester in Example 1 were adjusted to 10 parts by mass, 5 parts by mass, and 5 parts by mass, respectively; rosin-based reactive emulsifiers were not added in step 1 of the "General Process Parameters for Composite Aqueous Emulsions" in this specification; dimethylethanolamine was not added in step 3 of the "General Process Parameters for Composite Aqueous Emulsions" in this specification, and neutralization and internal emulsification were not performed; the added surfactant was replaced with sodium dodecylbenzenesulfonate (SDBS) and fatty alcohol polyoxyethylene ether (AEO-9) in a mass ratio of 1:1, with a total amount of 2.0 wt% of the total dry solids. When high-shear emulsification and homogenization at 100 MPa for 3 passes were performed under the same conditions as in Example 1, irreversible demulsification and gelation occurred during the homogenization process, making it impossible to obtain a stable finished emulsion. Therefore, the effective finished product adjustment in step 6 of the "General Process Parameters for Composite Aqueous Emulsions" in this specification was no longer performed.

[0096] Comparative Example 5: The preparation process was the same as in Example 5, except that: 4 parts by mass of pentaerythritol rosin ester in Example 5 were replaced with 4 parts by mass of hydrogenated rosin glycerol ester, the acid value of which was 7 mg KOH / g, and maleic rosin or other high-acid-value rosin-based components were no longer introduced; when preparing the rosin-based emulsion, a rosin-polyether anhydride reactive emulsifier was still added to the aqueous phase at a dosage of 1.0 wt% of the total dry solids, and the added surfactant was still sodium dodecylbenzene sulfonate (SDBS) and fatty alcohol polyoxyethylene ether (AEO-9) in a 1:1 mass ratio at a dosage of 0.5 wt% of the total dry solids; when preparing the rosin-based emulsion, the hydrogenated rosin glycerol ester was heated to 160°C to melt, and then the rosin-based emulsion was prepared in the same manner as in Example 5; after being compounded with PHBH aqueous emulsion, the residual acid value of the hydrogenated rosin glycerol ester was 7 mg KOH / g. The amount of dimethylethanolamine added was calculated based on the carboxyl equivalent of KOH / g to achieve a nominal neutralization degree of 50%. The remaining compounding, homogenization at 100MPa twice, and heat treatment at 85℃ for 30 min were the same as in Example 5. In step 6 of the "General Process Parameters for Composite Aqueous Emulsions" in this specification, the solid content was adjusted to 55wt%, and the pH was adjusted to 8.0, finally obtaining the emulsion of Comparative Example 5.

[0097] Comparative Example 6: The preparation process is the same as that of Example 1, except that the total dry solids content of the added surfactant is increased from 0.5 wt% in Example 1 to 2.0 wt%. The added surfactant is still sodium dodecylbenzenesulfonate (SDBS) and fatty alcohol polyoxyethylene ether (AEO-9) in a mass ratio of 1:1. All other conditions are the same as those of Example 1, namely, 11 parts by mass of PHBV aqueous emulsion (BioTen 1031, on a dry solids basis), 5 parts by mass of maleic rosin, 4 parts by mass of hydrogenated rosin glycerol ester, 1.0 wt% of total dry solids amount of rosin-polyether anhydride reactive emulsifier, 50% neutralization degree of dimethyl ethanolamine, and no chain extender or crosslinking agent is added. In step 6 of the "General Process Parameters for Composite Aqueous Emulsions" in this specification, the solids content is adjusted to 55 wt% and the pH is adjusted to 8.0 to obtain the emulsion of Comparative Example 6.

[0098] Comparative Example 7: The preparation process is the same as in Example 1, except that the dry weight ratio of the PHA component to the rosin-based component in Example 1 is adjusted from 11:9 to 1:6. Specifically, the ratio is 2.8 parts by weight of PHBV aqueous emulsion (BioTen 1031, on a dry weight basis), 8.5 parts by weight of maleic rosin, and 8.7 parts by weight of hydrogenated rosin glycerol ester. The remaining emulsification stabilization system is the same as in Example 1, namely, the amount of rosin-polyether anhydride reactive emulsifier is 1.0 wt% of the total dry weight, the degree of neutralization of dimethyl ethanolamine is 50%, the added surfactant is sodium dodecylbenzene sulfonate (SDBS) and fatty alcohol polyoxyethylene ether (AEO-9) in a mass ratio of 1:1 and the amount is 0.5 wt% of the total dry weight, and no chain extender or crosslinking agent is added. In step 6 of the "General Process Parameters for Composite Aqueous Emulsions" in this specification, the solid content is adjusted to 55 wt%, and the pH is adjusted to 8.0, finally obtaining the emulsion of Comparative Example 7.

[0099] Application example:

[0100] Application Example 1: Evaluation of the basic physical, mechanical and protective properties of coatings.

[0101] This application example primarily evaluates the basic physical and mechanical properties and protective performance of various polyhydroxyalkanoate plant-based composite aqueous emulsions after film formation. In the experiment, the aluminum plate (Q-Panel standard test plate) first underwent rigorous degreasing and cleaning treatment. The cleaning process included rinsing with deionized water, immersion in a 2wt% sodium hydroxide solution at 50°C for 2 minutes, rinsing with deionized water, immersion in a 1wt% hydrochloric acid solution for 30 seconds, and a final rinse with deionized water. It was then dried in a 60°C forced-air drying oven for later use. The PET film was wiped with ethanol and then dried for later use. For the PET adhesion test, the PET film was first flatly attached to a 2mm thick glass plate, and then a cross-cut adhesion test was performed according to GB / T9286-2021. The emulsions from each example and comparative example were formulated into coatings according to a unified formula (90 parts emulsion dried to solid state, 3 parts film-forming aid Texanol Ester Alcohol, 0.5 parts wetting agent BYK-346, 0.2 parts defoamer BYK-024, and 0.5 parts HEUR thickener Acrysol RM-8W), and the Stormer viscosity was adjusted to 100 KU. Wet films were prepared on the treated substrate and polytetrafluoroethylene (PTFE) plates using an automatic coating machine, with the dry film thickness controlled at 25 μm. The curing conditions were set as follows: surface drying in a constant temperature and humidity chamber at 23°C and 50% relative humidity for 24 hours, followed by baking in a 60°C oven for 30 minutes, and then placing at 23°C for 6 days to complete complete curing. The water droplet contact angle was determined using the static drop method according to GB / T 30693-2014. The droplet volume was 3.0 μL, and the contact angle was read 5 seconds after the drop was added. Five different locations were tested for each sample, and the average value was taken. The contact angle retention rate after immersion in water for 24 hours was calculated according to formula (1): Contact angle retention rate (%) = θ24 h / θ0×100%(1), where θ0 is the contact angle of the water droplet before immersion, θ 24 h is the water droplet contact angle measured after immersion in water for 24 hours and drying of the surface.

[0102] Among them, water-resistant whitening is observed after immersion in water for 24 hours according to GB / T 1733-1993, and graded according to the defect rating method of GB / T 1766-2008: Grade 0 is no whitening, Grade 1 is slight whitening, Grade 2 is obvious whitening, Grade 3 is severe whitening, Grade 4 is extremely severe whitening, and Grade 5 is film layer damage or large-area peeling.

[0103] The foaming level is graded according to the defect rating method of GB / T 1766-2008: level 0 is no foaming, and levels 1 to 5 are progressively more severe foaming.

[0104] Salt spray resistance time is defined as the cumulative time from exposure to neutral salt spray conditions according to GB / T 10125-2021 until the sample shows a blistering level ≥2 or corrosion points / corrosion area ≥0.5%. For samples that have not reached the failure level, the upper limit of observation is used.

[0105] Table 4 shows the basic performance test results of Application Example 1:

[0106]

[0107] Note: The grade data in the table represent the worst values ​​from parallel tests. Comparative Example 4, due to the lack of an effective stabilizing component, exhibited extremely poor emulsion stability, resulting in severe pinholes and cracking in the coating. Therefore, a continuous free film meeting the test requirements could not be obtained, and its water absorption rate, salt spray resistance, foaming grade, hardness, and contact angle data are marked as "-". Comparative Example 1, although exhibiting high pencil hardness, demonstrated brittle cracking.

[0108] Analysis: As can be seen from the experimental data in Table 4, the overall performance of the samples in each example is significantly better than that of the comparative examples. Examples 1-13 all exhibited excellent adhesion on aluminum plates and PET substrates, mainly due to the excellent wettability of the rosin-based component and its van der Waals forces with the substrate. Among them, Example 9, which uses a system without added surfactant (0 wt% added surfactant), achieved a water whitening resistance grade of 0 and a contact angle retention rate as high as 97%, indicating that the system lacks easily migrating hydrophilic small molecules, significantly improving water resistance. Example 13, by introducing a high content of crosslinking agent (15 wt%), formed a dense crosslinking network, which not only increased the hardness to 3H but also achieved a salt spray resistance time of 400 hours and a water absorption rate of 2.5%, exhibiting the best protective performance. In contrast, although Comparative Example 1 (without rosin-based component) had higher hardness, it had poor adhesion and was brittle; Comparative Example 2 (without polyhydroxyalkanoate component) had a softer coating and insufficient water resistance. Of particular note is Comparative Example 6, where the amount of added surfactant increased to 2.0 wt%, resulting in severe water whitening (level 4), a significant decrease in contact angle retention to 78%, and an increase in water absorption. This verifies the importance of strictly controlling the amount of added surfactant for ensuring the water resistance of the coating. Comparative Example 7, due to an imbalance in the ratio of polyhydroxyalkanoate to rosin-based components (1:6), exhibited poor compatibility of the film-forming substances, leading to increased coating brittleness and decreased adhesion. In summary, the emulsion described in this invention, through the synergistic effect of internal emulsification and reactive emulsification mechanisms, effectively solves the problem of poor water resistance in traditional water-based coatings while ensuring high adhesion.

[0109] Application Example 2: Evaluation of the gas and water vapor barrier performance of the coating.

[0110] This application example focuses on evaluating the barrier properties of coatings, specifically their ability to block water vapor and oxygen, which is crucial for packaging materials and metal corrosion protection. In the experiment, the coating prepared in Application Example 1 was applied to a polytetrafluoroethylene (PTFE) plate, dried, cured, and carefully peeled off to obtain a free film. Samples with uniform thickness (40 μm) were selected using a thickness gauge. Before testing, all samples were conditioned for 48 hours at 23°C and 50% relative humidity according to GB / T 9278 standard. Water vapor transmission rate (WVTR) was measured using the infrared detector method (GB / T 26253), with a stringent test environment of 38°C and 90% relative humidity to simulate a high-temperature and high-humidity environment. Oxygen transmission rate (OTR) was measured using the differential pressure method (GB / T 1038.1), with a test environment of 23°C, dry conditions (0% RH), and a pressure difference of 0.1 MPa.

[0111] Table 5. Barrier performance test results for Application Example 2:

[0112]

[0113] Note: Comparative Example 4 could not form a complete, pinhole-free free membrane, so gas permeability testing could not be performed. Furthermore, its extremely poor film quality meant that the barrier performance failed. Therefore, the data is marked as "-".

[0114] Analysis: The data in Table 5 clearly demonstrate the advantages of the formulation described in this invention in terms of barrier performance. The water vapor transmission rate (WVTR) and oxygen transmission rate (OTR) of Examples 1-13 are generally lower than those of the comparative examples. Example 13 performs the best, with a WVTR as low as 45 g / m³. 2 ·d, OTR as low as 60cm 3 / (m 2 The high cross-linking density of the dense network structure effectively extends the diffusion path of gas molecules (24h·0.1MPa). Examples 6 and 7 optimize the mass ratio of polyhydroxyalkanoate to rosin-based components, utilizing the rigid rosin skeleton to fill the free volume of the polymer, while also achieving good barrier performance. Comparing Example 1 and Comparative Example 6, it can be found that when the amount of added surfactant increases from 0.5wt% to 2.0wt%, the WVTR increases from 88 to 115, and the OTR increases from 150 to 210. This indicates that excessive surfactant forms hydrophilic channels inside the coating, destroying the density of the coating and thus reducing the barrier performance. Although Comparative Example 2 (pure rosin-based) is rigid, it is brittle in film formation and prone to microcracks, resulting in poor barrier performance. Comparative Example 7 also has poor barrier performance due to the imbalance of the two-phase ratio and severe microphase separation, failing to form a tightly packed structure. Experimental results confirm that the gas barrier properties of bio-based coatings can be significantly improved through reasonable component blending, internal emulsification technology, and appropriate cross-linking.

[0115] Application Example 3: Evaluation of the coating's resistance to chemical media and its durability.

[0116] This application example aims to investigate the durability of the coating under harsh conditions such as chemical corrosion, solvent wiping, and physical abrasion. The coating preparation method is the same as in Application Example 1, with an aluminum plate as the substrate. Solvent wiping resistance was tested according to GB / T 23989, using methyl ethyl ketone (MEK) as the solvent. A load of 1 kg was applied, and the coating was wiped repeatedly at a frequency of 60 times / minute. The number of wiping cycles until the coating exposed the substrate or showed significant softening was recorded. Chemical resistance was tested using the drop method, adding 5 wt% NaOH and 5 wt% HCl solutions respectively. After covering for 24 hours, surface changes were observed, and the chemical resistance level was given according to the defect rating method of GB / T 1766: Level 0: no change; Level 1: slight change; Level 2: moderate change; Level 3: significant change; Level 4: severe change; Level 5: film damage or large-area peeling. Abrasion resistance was tested using a Taber abrasion tester with a CS-10 grinding wheel, a load of 1000 g, and the abrasion weight loss was measured after 1000 revolutions. The damp heat resistance test was conducted according to GB / T1740-2007. After being placed in an environment of 40℃ and 95% RH for 240 hours, the aluminum plate was removed and restored, and the adhesion was tested within 1 hour.

[0117] Table 6. Durability test results for Application Example 3:

[0118]

[0119] Note: The grade data in the table are the worst values ​​of parallel tests. The upper limit for the number of methyl ethyl ketone (MEK) double rubs is set at 200 times. Example 13 reached the upper limit but did not fail, so it is recorded as 200 in the table. Comparative Example 4 could not be tested for solvent resistance and abrasion resistance due to discontinuous film formation. The media resistance and wet heat adhesion tests directly showed that the coating blistered and peeled off (level 5).

[0120] Analysis: The durability test results (Table 6) show that the embodiments of the present invention exhibit outstanding performance in terms of chemical resistance and mechanical abrasion resistance. Example 13, with an addition of 15 wt% crosslinking agent, constructed a highly crosslinked three-dimensional structure, with methyl ethyl ketone (MEK) resistance exceeding 200 rub cycles, abrasion weight loss of only 15 mg, and an acid and alkali resistance rating of 0, demonstrating excellent chemical inertness and physical strength. Example 9 (soap-free system) showed a 0-1 grade of adhesion after humid heat resistance, significantly better than the 3 grade of Comparative Example 6 (containing 2.0 wt% surfactant), further proving that reducing or eliminating hydrophilic added surfactants can significantly improve the interfacial stability of the coating in humid heat environments, preventing blistering and peeling caused by moisture penetration. Example 4 introduced a reactive emulsifier to participate in crosslinking, and its rub resistance (150 cycles) was significantly better than that of Comparative Example 3 (30 cycles) without a reactive emulsifier, indicating that chemical anchoring effectively improved the solvent resistance of the coating. Comparative Example 7 showed decreased coating cohesion and significant abrasion weight loss (75 mg) due to improper formulation, and its adhesion was severely reduced after humid heat. These data strongly support the technical approach of this invention, which improves the durability of bio-based coatings through chemically anchored emulsifiers, internal emulsification technology, and crosslinking modification.

[0121] Application Example 4: Evaluation of storage stability and freeze-thaw resistance of composite aqueous emulsions.

[0122] This application example focuses on the storage stability of emulsions under different conditions, a key indicator for product commercialization. The emulsion samples from each example and comparative example (unless otherwise specified, the solid content was adjusted to 55 wt% with deionized water and the pH was adjusted to 8.0 with dimethylethanolamine) were divided into two groups. One group was stored in a 50°C incubator for 30 days (accelerated thermal aging test), while the other group underwent freeze-thaw cycles from -18°C to 23°C. Test parameters included initial particle size (D0). 50 D 90 The following parameters were considered after heat storage: percentage of stratification height, viscosity change rate, particle size change rate, and number of freeze-thaw cycles. Stratification height percentage (%) = h / H × 100%, where h is the height of the supernatant after sample settling, and H is the total sample height; viscosity change rate (%) = |viscosity after 30 days - initial viscosity| / initial viscosity × 100%; D 50 Rate of change (%) = |D after 30 days 50 -Initial D 50 | / Initial D 50×100%. One freeze-thaw cycle was defined as the sample being placed at (-18±2)℃ for 18 hours and then restored at (23±2)℃ for 6 hours. After each cycle, irreversible agglomeration or irreversible stratification was observed, and the maximum number of cycles passed was recorded as the freeze-thaw cycle number. For Example 1, its stability under pH 5.5 and pH 10.5 conditions was also tested. For Example 10, the sample solid content was tested according to the original 70wt% sample prepared in Example 10. Acid value and degree of neutralization were calculated based on raw material parameters and feed amounts.

[0123] Table 7. Application Example 4: Emulsion stability test results:

[0124]

[0125] Note: Comparative Example 4 showed rapid stratification and demulsification immediately after preparation, making it impossible to determine the initial particle size and the rate of change after aging.

[0126] Analysis: The stability data in Table 7 show that the emulsions described in this invention exhibit excellent colloidal stability under a wide range of process conditions. After storage at 50°C for 30 days, Examples 1-13 showed a stratification height of no more than 2.5%, viscosity change rate, and particle size change rate all controlled within 12%, and all passed at least three freeze-thaw cycles. Example 10 maintained stratification at 2.0% with a solid content of 70 wt%, indicating that the system has acceptable storage stability under high solid content conditions. Example 9, as a soap-free emulsion, achieved stability comparable to or even better than the soap-containing system (stratification 1.2%, 5 freeze-thaw cycles) by relying on the chemical anchoring of internally emulsifying ionic groups and reactive emulsifiers. In the extreme pH test, Example 1 maintained basic stability at pH 5.5 and 10.5, demonstrating the system's tolerance to acidic and alkaline environments. Conversely, Comparative Example 5, due to the low acid value of the hydrogenated rosin glycerol ester used (7 mg KOH / g), could not provide sufficient electrostatic repulsion, resulting in severe stratification (6.5%). Although Comparative Example 6 contained a relatively large amount of added surfactant, it may have caused competitive adsorption or exacerbated Ostwald ripening, resulting in a larger particle size change rate (14%) and decreased freeze-thaw resistance. Comparative Example 7, due to an imbalanced component ratio and unstable particle structure, exhibited the worst stability in all indicators. These results fully validate the crucial role of the dual stabilization mechanism of internal emulsification combined with reactive emulsifiers in improving the storage and freeze-thaw stability of emulsions.

[0127] Application Example 5: Determination of total fluorine content in coatings and verification of fluorine-free properties.

[0128] This application example uses oxygen bomb combustion-ion chromatography (CIC) to quantitatively determine the total fluorine (TF) content in each coating sample to verify the fluorine-free surfactant and fluorine-free additive characteristics of the product of this invention. In the experiment, 0.10 g of the pulverized coating free membrane sample was accurately weighed and placed in an oxygen bomb; the oxygen bomb was charged at an oxygen pressure of 3.0 MPa, and the sample was ignited to ensure complete combustion; the combustion products were absorbed with 10 mL of 0.01 mol / L sodium hydroxide absorbent and the volume was adjusted to 50 mL, and then the fluoride ion concentration in the absorbent was determined using an ion chromatograph. The total fluoride (TF) was calculated according to formula (2): TF (mg / kg) = (F in the sample absorbent) / (F in the sample absorbent) - Concentration - F in blank absorption solution - Concentration) × final volume × dilution factor / sample mass (2). The detection limit was determined to be 5 mg / kg under the experimental conditions, and the test method was performed in accordance with EN 14582:2016.

[0129] Table 8. Total Fluorine Test Results for Application Example 5:

[0130]

[0131] Analysis: The test results in Table 8 show that, for both the examples and comparative examples, the total fluorine content of all samples was "not detected" (detection limit ≤ 5 mg / kg). This result objectively confirms the strict control exercised in the formulation design and raw material screening stages of this invention, namely, the complete exclusion of the use of fluorinated surfactants, fluorinated additives, and fluorinated monomers. The total fluorine content of the samples after film formation described in this specification is ≤ 5 mg / kg, indicating that fluorinated surfactants, fluorinated additives, and fluorinated monomers were not introduced into the formulation design, thereby reducing the possibility of introducing fluorinated substances into the coating.

[0132] Application Example 6: Evaluation of the adaptability and comprehensive performance of industrial anti-corrosion coating formulations.

[0133] This application example aims to verify the universal applicability and performance of the emulsion described in this invention as a base material in high-performance industrial anti-corrosion coating formulations. The experiment used a uniform optimized anti-corrosion coating formulation: 80 parts emulsion (on a dry solids basis), 10 parts anti-corrosion pigment (zinc phosphate), 5 parts white pigment (titanium dioxide), 2 parts barrier filler (nanoclay, organically modified), 2 parts film-forming aid, 0.5 parts wetting agent, 0.2 parts defoamer, 0.5 parts thickener, with the remainder being deionized water for viscosity adjustment. The dispersion process employs a rigorous two-step method: First, the emulsion, wetting agent, and defoamer are added to the dispersion tank and pre-dispersed at 10,000 rpm for 2 minutes. Second, premixed pigment and filler powders are slowly added while stirring, the rotation speed is increased to 15,000 rpm and maintained for 10 minutes, utilizing high shear force to ensure the intercalation and depolymerization of the nanoclay and the uniform dispersion of the pigments. Finally, the rotation speed is reduced, film-forming aids and thickeners are added, the Stormer viscosity is adjusted to 105 KU, and the mixture is allowed to stand for degassing for 30 minutes before use. The board preparation and curing conditions are the same as in Application Example 1, but the observation time in the salt spray resistance test is extended to 1000 hours, and a methyl ethyl ketone solvent resistance wiping test is added to evaluate the change in density after the addition of pigments and fillers.

[0134] Table 9 shows the performance test results of the optimized formulation in Application Example 6:

[0135]

[0136] Note: The graded data in the table represent the worst values ​​from parallel tests. The upper limit for observation of the salt spray resistance test is set at 1000 hours; samples that do not fail after reaching this limit are recorded as 1000 in the table. The upper limit for observation of the methyl ethyl ketone (MEK) double-rub test is set at 250 times; samples that do not fail after reaching this limit are recorded as 250 in the table. Comparative Example 4, due to its extremely poor emulsion stability, experienced demulsification and gelation during the high-speed dispersion of pigments and fillers, making it impossible to prepare a uniform coating for application. Therefore, all performance indicators are marked as "-".

[0137] Analysis: The results in Table 9 show that the emulsion described in this invention exhibits excellent carrying capacity and synergistic effect in the pigment and filler system. The salt spray resistance times of Examples 4, 5, 7, 9, 11, and 13 all reached the upper limit of 1000 hours, a result far exceeding the film-forming performance of the pure emulsion, demonstrating a good interfacial bond between the emulsion, zinc phosphate anticorrosive pigment, and nano-clay. In particular, Example 13, under the dual action of the crosslinking agent and nano-filler, showed a 24-hour water absorption rate reduced to 1.5%, and a WVTR reduced to 25 g / m³. 2• The methyl ethyl ketone (MEK) withstands over 250 wiping cycles, meeting the performance standards for heavy-duty anti-corrosion coatings. Example 9 (soap-free system) showed no flocculation during pigment and filler dispersion, and the final coating exhibited excellent water whitening resistance (grade 0), indicating that the internally emulsified particles possess sufficient charge or steric hindrance to stabilize the high content of pigments and fillers. In contrast, Comparative Examples 1-7 showed limited performance improvement after the addition of pigments and fillers. Comparative Example 6, due to excessive added surfactant, experienced increased hydrophilicity of the coating, allowing water to easily penetrate along the pigment / base interface, resulting in a salt spray resistance of only 240 hours. Comparative Example 7, due to poor compatibility of the base material itself, may have seen the addition of pigments and fillers become stress concentration points, leading to further deterioration of adhesion (grades 2-3). These data confirm that the emulsion of this invention not only possesses excellent performance but also exhibits strong formulation adaptability, enabling it to meet higher-requirement industrial application scenarios through formulation optimization.

[0138] Application Example 7: Microstructure and elemental distribution analysis of coating surface.

[0139] This application example utilizes X-ray photoelectron spectroscopy (XPS) to analyze the microscopic surface elemental distribution of each emulsion after film formation, verifying the structural characteristics of the 'rosin-rich outer layer'. The emulsions from each example and comparative example were drop-coated onto the surface of a rigorously cleaned silicon wafer (ultrasonic cleaning with ethanol for 10 min followed by drying), and then naturally dried at 23°C and 50% RH for 48 h to form films. Broadband scanning and high-resolution C1s and O1s scans were performed using a monochromatic Al Kα source to analyze the oxygen-to-carbon atomic ratio (O / C) of the outermost layer of the coating (analysis depth approximately 5–10 nm). Subsequently, an argon ion beam (Ar) was used to further analyze the film. + The sample surface was sputter-exfoliated for 60 seconds (exfoliation depth approximately 20–30 nm), and the O / C ratio of the inner layer after exfoliation was measured again. Δ(O / C) was defined as (O / C)inner layer - (O / C)surface. When Δ(O / C) ≥ 0.08, it was judged as 'surface enriched with rosin'; when 0.03 ≤ Δ(O / C) < 0.08, it was judged as 'slightly uneven distribution'; when Δ(O / C) < 0.03, it was judged as 'uniform distribution'. Based on the difference in oxygen content between the rosin component and the polyhydroxyalkanoate, the distribution gradient of the component in the film thickness direction was determined by Δ(O / C).

[0140] Table 10. Elemental analysis results of XPS surface in Application Example 7:

[0141]

[0142] Note: Comparative Example 4 could not form a complete film layer for XPS testing, so it is marked as "-".

[0143] Analysis: The XPS analysis results in Table 10 reveal the unique microstructure of the composite particles of this invention. The surface O / C ratio (0.15–0.20) of all the sample examples was significantly lower than the inner layer O / C ratio (0.28–0.31), with the difference remaining stable between 0.11 and 0.13. This indicates that during film formation, the low surface energy rosin-based component spontaneously migrates to the air interface, forming a dense, rosin-rich, rigid, hydrophobic outer layer. This "rosin-rich outer layer" structure effectively shields the relatively hydrophilic ester bonds inside, explaining the excellent water whitening resistance and contact angle data of the sample examples. In contrast, the surface and inner layer O / C ratios of Comparative Example 1 (pure PHA) and Comparative Example 2 (pure rosin) were essentially consistent, showing a homogeneous structure. Comparative Example 5, due to its low acid value and insufficient internal emulsification ability, failed to form a significant rosin-based surface enrichment layer, resulting in a very small O / C difference (0.02). Although Comparative Example 6 also exhibits an O / C gradient, its surface O / C ratio (0.21) is slightly higher than that of Example 1 (0.18). This may be because excess hydrophilic surfactants (typically containing polyether segments and high oxygen content) also migrate to the surface, interfering with the rosin enrichment layer, which also explains the decrease in its water resistance. These microscopic analysis results provide solid physical evidence for the structural features described in this invention.

[0144] Application Example 8: Verification of chemical anchoring effect and covalent bonding structure.

[0145] This application example uses solvent extraction combined with infrared spectroscopy to quantitatively verify the existence and extent of the 'chemical anchoring' effect in emulsion systems. Free membranes prepared in each example and comparative example were selected, and a precise mass m0 (0.500 g) was weighed and placed in 50 mL of ethyl acetate solvent. The membranes were then sealed and extracted at 23°C for 24 h. After extraction, the membrane samples were removed, washed three times with fresh solvent, dried at 60°C to constant weight, and the mass m1 was weighed. The ethyl acetate extraction mass loss rate was calculated as (m0-m1) / m0×100%. Subsequently, Fourier transform infrared spectroscopy (FTIR) with an ATR (attenuated total reflectance) accessory was used to scan the membrane samples before and after extraction, focusing on monitoring the characteristic cyclic anhydride carbonyl absorption peak (1850 cm⁻¹) in rosin-based reactive emulsifiers. -1 and 1780cm -1 ) and the absorption peak of the ester carbonyl group (1730 cm⁻¹) -1 Changes in the vicinity (around 1850cm). -1 and 1780cm -1 Peak relative to 1450cm -1 The area ratio of the internal standard peaks was used as a criterion: when the relative area ratio of both acid anhydride peaks decreased by more than 80% after extraction compared to before extraction, and the peak area ratio at 1730 cm⁻¹ was within the range of 1730 cm⁻¹, the criteria were met. -1When the ester carbonyl peak is enhanced or remains stable, it is determined as 'chemical anchoring has occurred'; when it decreases by 30% to 80%, it is determined as 'partial anchoring / insufficient anchoring'; when it decreases by less than 30%, it is determined as 'no chemical anchoring'.

[0146] Table 11 Validation results of chemical anchoring and covalent coupling structures in Application Example 8:

[0147]

[0148] Note: Comparative Example 4 could not obtain a complete free membrane for extraction testing, and is marked with "-". The low loss rate of Comparative Example 1 is because PHA itself has limited solubility in ethyl acetate and is a high molecular weight polymer, not because small molecules are anchored.

[0149] Analysis: The data in Table 11 strongly demonstrate the effectiveness of the chemical anchoring mechanism. The ethyl acetate extraction mass loss rates in Examples 1–13 were all controlled at a low level of 2.5%–4.5%, and the characteristic anhydride peaks of the reactive emulsifiers disappeared in the FTIR spectra, replaced by enhanced ester bond absorption peaks. This indicates that the active groups in the rosin-based reactive emulsifier underwent a covalent reaction with the end groups of the polyhydroxy fatty acid ester or the hydroxyl groups in the rosin-based resin during preparation or film formation, fixing the potentially migrating small-molecule emulsifier within the dispersed particles and film-forming network. In contrast, Comparative Example 3 (without reactive emulsifier, only physically mixed rosin esters) had a mass loss rate as high as 14.8%, indicating that a large amount of rosin ester components were extracted by the solvent, which corresponds to the poor performance results in the durability test. Although Comparative Example 6 exhibited chemical anchoring, the addition of 2.0 wt% non-reactive surfactant led to a total mass loss rate of 6.5%, indicating that the presence of non-reactive small molecules increases the risk of dissolution and migration. Example 13 showed the lowest loss rate (2.5%), attributed to the added crosslinking agent further locking the entire network structure. These chemical analysis results validate at the molecular level the technical approach of this invention, which combines internal emulsification with chemical anchoring by reactive emulsifiers to reduce migration and improve durability.

[0150] Experimental Results and Analysis:

[0151] Based on the systematic test data from Examples 1-13, Comparative Examples 1-7, and Application Examples 1-8, the performance and mechanism of action of the PHA plant-based composite aqueous emulsion and its coating described in this invention are analyzed as follows:

[0152] Analysis of the emulsion dispersion stability mechanism: As can be seen from the storage stability and freeze-thaw cycle test results of Application Example 4, the present invention significantly broadens the stability window of bio-based emulsions through the dual stabilization mechanism constructed by "internal emulsifying ionic groups" and "rosin-based reactive emulsifier".

[0153] Electrostatic stabilizing effect of internal emulsification: Examples 1-13 provided the main electrostatic repulsion force by neutralizing carboxyl groups and other groups in the rosin base component, resulting in the stratification height of the emulsion being controlled within 2.5% after 30 days of heat storage at 50°C. In contrast, Comparative Example 5 used rosin raw material with a low acid value (7 mg KOH / g), which could not provide sufficient surface charge density, resulting in a stratification height as high as 6.5% during heat storage and a decrease in freeze-thaw resistance.

[0154] Steric hindrance stabilization and limited ripening effect of reactive emulsifiers: Data from the examples show that an appropriate amount (0.2–5 wt%) of rosin-based reactive emulsifier not only provides steric hindrance but also inhibits the dynamic migration of small molecules through chemical anchoring. Comparing Example 1 (0.5 wt% added surfactant) and Comparative Example 6 (2.0 wt% added surfactant), excessive added non-reactive surfactant actually exacerbated Ostwald ripening, resulting in a larger particle size change rate (14%) and decreased freeze-thaw resistance in Comparative Example 6. This confirms the necessity of limiting the amount of added surfactant for maintaining the long-term stability of the system.

[0155] Influence of component compatibility: Data from the examples verified the good compatibility between the PHA component and the rosin-based component in a mass ratio range of 1:4 to 4:1. In Comparative Example 7 (PHA:rosin = 1:6), the excess rosin component disrupted the internal phase structure equilibrium of the dispersed particles, leading to a wider emulsion particle size distribution (D...). 90 The particle size distribution reached 4.50 μm and exhibited the worst storage stability (12.0% separation), indicating that the ratio of the two phases is crucial to the integrity of the particle structure.

[0156] Data from Application Examples 1 and 7, which analyze coating adhesion and microstructure, reveal the source of the excellent adhesion of the coatings.

[0157] Rosin-based surface enrichment effect: XPS depth profiling (Application Example 7) confirmed that the surface O / C ratio of the sample in the examples was significantly lower than that of the inner layer, indicating that the low surface energy, hydrophobic rosin-based components with a rigid framework spontaneously migrated and enriched to the surface during film formation. This "rosin-based enriched surface layer" improved the wettability of the coating on substrates such as aluminum plates and PET, resulting in adhesion grades of 0 to 1 in all examples.

[0158] Comparative analysis: Comparative Example 1 (pure PHA) lacks rosin components, resulting in high internal stress and poor wettability in the coating, leading to an adhesion grade of only 3-4. Comparative Example 2 (pure rosin), while exhibiting good wettability, suffers from low cohesive strength and compromised adhesion. This demonstrates that the toughness of PHA and the adhesiveness of rosin achieve organic complementarity and synergy in this invention.

[0159] The data from Application Examples 1, 2, and 8, which highlight the advantages of water resistance, barrier properties, and "zero / low" surfactants, effectively validate the mechanism by which water resistance and barrier properties are improved.

[0160] Chemical anchoring blocks hydrophilic channels: Solvent extraction and FTIR analysis in Example 8 showed that the rosin-based reactive emulsifier was covalently anchored in the polymer network through reactions such as anhydride ring-opening (extraction loss rate <4.5%), eliminating free small molecules. In contrast, Comparative Example 6 (high surfactant) and Comparative Example 3 (physically mixed rosin esters) contained a large amount of free hydrophilic components, resulting in severe water whitening (grade 3-4) and increased water vapor transmission rate (WVTR).

[0161] Breakthrough in soap-free systems: Example 9 achieved Grade 0 water resistance whitening and excellent barrier properties (WVTR = 40 g / m³) through internal emulsification and chemical anchoring without the addition of any external surfactant (0 wt%). 2 ·d) demonstrates the feasibility of the technical route of this invention in preparing high-performance "soap-free" bio-based emulsions.

[0162] Densification Barrier: Example 13 further densified the coating network by introducing a high crosslinking density (15 wt% crosslinking agent), achieving the lowest WVTR (25 g / m²). 2 ·d) and OTR indicate that moderate crosslinking is an effective means to improve the barrier properties of bio-based coatings.

[0163] Application Examples 3 and 6, which comprehensively evaluate durability and corrosion resistance, demonstrate the performance of the coating in harsh environments.

[0164] Chemical inertness and corrosion resistance: Benefiting from the crystallinity of PHA itself and the hydrophobic shielding effect of the rosin skeleton, combined with the reduced defects caused by chemical anchoring, the coatings in the examples exhibited excellent performance in acid and alkali resistance tests. In the anti-corrosion formulation (Application Example 6), the salt spray resistance time of some examples reached the upper limit of 1000 hours, while the remaining examples reached 850–980 hours, far exceeding the comparative examples. This indicates that the emulsion, as a base material, can effectively encapsulate pigments and fillers, blocking the penetration path of corrosive media.

[0165] Solvent and abrasion resistance: The MEK in Example 13 reached the upper limit of 250 wiping cycles without failure and showed low abrasion weight loss, which confirmed that the three-dimensional network constructed by end-group reaction and added crosslinking agent significantly improved the mechanical strength and solvent resistance of the coating, overcoming the defects of traditional thermoplastic bio-based resins in poor heat and solvent resistance.

[0166] The total fluoride test results (not detected, ≤5 mg / kg) of the environmental compliance application example 5 confirm that the technical solution of the present invention achieves excellent hydrophobic and stain-resistant properties through structural design without relying on fluorine-containing additives, and complies with current and future environmental regulations restricting per- and polyfluoroalkyl substances (PFAS).

[0167] In summary, this invention, by controlling the specific ratio of PHA to rosin-based components, innovatively combines "alkali-neutralized internal emulsification" and "chemical anchoring of reactive emulsifiers" technologies to successfully prepare a composite waterborne emulsion with high stability, high bio-based content, high adhesion, and high barrier properties. This technical solution effectively solves the common problems of traditional bio-based waterborne coatings, such as the difficulty in balancing stability and water resistance, poor adhesion, and reliance on added surfactants. It provides a high-performance, environmentally friendly bio-based solution for metal corrosion protection, packaging barrier, and industrial protection.

[0168] Those skilled in the art should understand that the above embodiments are merely exemplary and are not intended to limit the scope of the present invention. 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 protection scope of the present invention.

Claims

1. A polyhydroxyalkanoate plant-based composite aqueous emulsion, characterized in that, The composite aqueous emulsion comprises water, dispersed particles, and an emulsion stabilizing system, wherein the water is the continuous phase, the dispersed particles are the dispersed phase, and the emulsion stabilizing system is disposed on the surface and / or interface of the dispersed particles; the dispersed particles include one or both of the following: Composite particles containing both polyhydroxyalkanoate components and rosin-based components; A particle mixture system consisting of polyhydroxyalkanoate particles and rosin-based particles; Wherein, the dry solid mass ratio of the polyhydroxyalkanoate component to the rosin-based component is 1:4 to 4:1; the solid content of the composite aqueous emulsion is 10 to 70 wt%; and the volume median diameter D of the overall volume particle size distribution of the dispersed particles is... 50 The diameter ranges from 0.20 μm to 0.90 μm, and the cumulative quantile diameter D in the volume distribution is 90%. 90 ≤4.0μm; The emulsification stabilization system is provided by internal emulsifying ionic groups and rosin-based reactive emulsifiers; The internal emulsifying ionic group is formed by the ionized precursor group provided by the rosin-based component under the action of an alkaline substance; the rosin-based reactive emulsifier includes rosin hydrophobic groups, hydrophilic segments, and reaction anchoring groups, and the reaction anchoring groups react chemically with the dispersed particles to form a covalent bond; The added surfactant is a non-fluorinated surfactant, and its dosage is 0 to 0.5 wt% of the total dry solid mass of the polyhydroxyalkanoate component and the rosin-based component; when the dosage is 0 wt%, the composite aqueous emulsion does not contain added surfactant. The total fluorine content of the dry film of the composite aqueous emulsion, as determined by oxygen bomb combustion-ion chromatography, is less than 5 mg / kg.

2. The polyhydroxyalkanoate plant-based composite aqueous emulsion according to claim 1, characterized in that: The polyhydroxyalkanoate component is a basic polyhydroxyalkanoate, or one or more of a blend, chain extender, or end-group modified product formed from the basic polyhydroxyalkanoate. The base polyhydroxy fatty acid ester is selected from one or more of short-chain polyhydroxy fatty acid esters, medium- and long-chain polyhydroxy fatty acid esters, or copolymers between monomers that form short-chain polyhydroxy fatty acid esters and monomers that form 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), poly(3-hydroxybutyrate-3-hydroxyvalerate copolyester), poly(3-hydroxybutyrate-3-hydroxyhexanoate copolyester), and poly(3-hydroxybutyrate-4-hydroxybutyrate copolyester; The medium- and long-chain polyhydroxy fatty acid esters are selected from one or more of poly(3-hydroxyhexanoate), poly(3-hydroxyheptanoate), poly(3-hydroxyoctanoate), poly(3-hydroxynonanoate), poly(3-hydroxydecanoate), poly(3-hydroxyundecanoate), poly(3-hydroxydodecanoate), poly(3-hydroxytridecanoate), and poly(3-hydroxytetradecanoate). The polyhydroxy fatty acid ester component contains reactive end groups, which are selected from hydroxyl, carboxyl, epoxy, isocyanate, anhydride, acrylate, methacrylate, allyl, or combinations thereof.

3. The polyhydroxyalkanoate plant-based composite aqueous emulsion according to claim 1, characterized in that: The rosin-based component is selected from one or more of the following: rosin acid and its derivatives, rosin esters and their derivatives, rosin-modified resins, rosin-based unsaturated monomers and their polymers, or combinations thereof. The rosin acid and its derivatives include rosin acid, dehydroabsic acid, hydrogenated rosin, disproportionated rosin, polymerized rosin, maleated rosin, fumarated rosin, rosin salt or combinations thereof; The rosin esters and their derivatives include glycerol rosin esters, pentaerythritol rosin esters, rosin-modified polyol esters, or combinations thereof; The rosin-modified resin includes rosin-modified polyester, rosin-modified polyether, rosin-modified polyurethane, rosin-modified phenolic resin, rosin-modified terpene resin, or a combination thereof. The rosin-based unsaturated monomer is selected from dehydroabsic acid acrylate, dehydroabsic acid methacrylate, abietic acid acrylate, abietic acid methacrylate, rosin maleic anhydride adduct acrylate, rosin maleic anhydride adduct methacrylate, rosin-based allyl ester, rosin-based vinyl ether, or a combination thereof.

4. The polyhydroxyalkanoate plant-based composite aqueous emulsion according to claim 1, characterized in that: The internal emulsifying ionic group is derived from one or more of the carboxyl group, acid anhydride group, sulfonic acid group, and phosphonic acid group of the rosin-based component; The acid value of the component providing the ionized precursor group in the rosin-based component is 10-250 mg KOH / g; and the ionized precursor group is neutralized by 30-80% with an alkaline substance to form the internal emulsion ionized group, wherein the alkaline substance is selected from ammonia, alkanolamine, organic amine, alkali metal hydroxide, alkali metal carbonate or a combination thereof.

5. The polyhydroxyalkanoate plant-based composite aqueous emulsion according to claim 1, characterized in that: The hydrophilic segment of the rosin-based reactive emulsifier is a polyether segment, and the reaction anchoring group is a cyclic anhydride group; and the amount of the rosin-based reactive emulsifier is 0.2 to 5 wt% of the total dry solid mass of the polyhydroxy fatty acid ester component and the rosin-based component; the rosin-based reactive emulsifier is a rosin-polyether anhydride reactive emulsifier, which is obtained by esterification of dehydroabietic acid with polyethylene glycol monomethyl ether to obtain a rosin-polyether ester intermediate, and then reacting it with maleic anhydride to introduce a cyclic anhydride group.

6. The polyhydroxyalkanoate plant-based composite aqueous emulsion according to claim 1, characterized in that: The added surfactant is selected from anionic, nonionic, amphoteric, cationic, polymeric surfactants or combinations thereof; When the pH of the composite aqueous emulsion is 7.8–8.2 and the solid content is 53–57 wt%, the stratification height after storage at 50°C for 30 days does not exceed 2.5% of the sample height, and the viscosity change rate after 30 days of storage is ≤12%, and the median diameter D of the dispersed particles is... 50 The rate of change is ≤12%, and no irreversible condensation or irreversible stratification occurs after ≥3 freeze-thaw cycles between -18℃ and 23℃.

7. The polyhydroxyalkanoate plant-based composite aqueous emulsion according to claim 1, characterized in that: The dry film formed by the composite aqueous emulsion has a rosin-rich surface layer in the thickness direction, and the mass loss rate of the dry film after extraction with ethyl acetate at 23°C for 24 hours is 2.5% to 4.5%.

8. The polyhydroxyalkanoate plant-based composite aqueous emulsion according to claim 1, characterized in that: The composite aqueous emulsion has a pH of 5.5 to 10.5 and contains a chain extender or crosslinker selected from polyfunctional epoxy compounds, polyfunctional isocyanate blocking agents, carbodiimides, metal complex crosslinking agents, silane coupling agents, or combinations thereof, and is used in an amount of 0.01 to 15 wt% of the total dry solid mass of the polyhydroxy fatty acid ester component and the rosin-based component.

9. A method for preparing the polyhydroxyalkanoate plant-based composite aqueous emulsion according to claim 1, characterized in that, The preparation method includes: Step 1. Add deionized water, the rosin-based reactive emulsifier, and the added surfactant to the reaction vessel, and stir for 10 minutes using a high-shear emulsifying disperser to obtain an aqueous phase mixture; wherein the added surfactant is a non-fluorinated surfactant; when the amount of added surfactant is 0 wt%, no added surfactant is added; Step 2. Mix the polyhydroxyalkanoate component and the rosin-based component according to the formulation ratio and stir for 30 min to obtain a dispersed phase precursor; wherein the polyhydroxyalkanoate component is a polyhydroxyalkanoate resin or a polyhydroxyalkanoate aqueous emulsion, and the rosin-based component is a rosin-based resin or a rosin-based aqueous emulsion; when the rosin-based component is a solid or high-viscosity resin and the polyhydroxyalkanoate component is a polyhydroxyalkanoate resin, heat the rosin-based component to 160°C to melt it and then add it to the polyhydroxyalkanoate resin; when the rosin-based component is a solid or high-viscosity resin and the polyhydroxyalkanoate component is a polyhydroxyalkanoate aqueous emulsion, slowly add the molten rosin-based component to the polyhydroxyalkanoate aqueous emulsion under stirring, and stir for 30 min to obtain a dispersed phase precursor; Step 3. Add the dispersed phase precursor obtained in Step 2 to the aqueous phase mixture obtained in Step 1, emulsify in a high-shear emulsifying disperser for 15 min, and add an alkaline substance during the emulsification process to neutralize the ionized precursor groups to obtain a pre-emulsion; Step 4. Process the preemulsion obtained in Step 3 using a high-pressure homogenizer at a pressure of 50–150 MPa for 1–5 passes, controlling the median volume diameter D. 50 The particle size is 0.20–0.90 μm, and then the mixture is kept at 70–100 °C for 10–60 min to allow the reaction anchoring groups of the rosin-based reactive emulsifier to chemically anchor the dispersed particles, thereby obtaining a crude emulsion. Step 5. Dilute the crude emulsion obtained in Step 4 with water or vacuum concentrate and dehydrate it to adjust the solid content to 10-70 wt%, and stir evenly to obtain a composite aqueous emulsion.

10. The method according to claim 9, characterized in that, Step 2 employs one or more of the following routes: Route 1. The polyhydroxy fatty acid ester component and the rosin-based component are melted and stirred in a reactor to obtain a dispersed phase precursor; the dispersed phase precursor is added to the aqueous phase mixture obtained in step 1 and emulsified using a high-shear emulsifying disperser, and then cooled to obtain dispersed particles; Route 2. First, prepare a polyhydroxyalkanoate emulsion separately to obtain a polyhydroxyalkanoate emulsion; and then prepare a rosin-based emulsion to obtain a rosin-based emulsion; wherein the median volume diameter D of the polyhydroxyalkanoate emulsion is... 50 The diameter of the polyhydroxyalkanoate emulsion is 0.20–0.90 μm. The polyhydroxyalkanoate emulsion and the rosin-based emulsion are compounded at a dry-to-solid mass ratio of 1:4–4:1 and stirred evenly to obtain a compounded emulsion. An alkaline substance is added to the compounded emulsion to neutralize and form internal emulsion ionic groups, resulting in a neutralized compound emulsion. The neutralized compound emulsion is then treated with a high-pressure homogenizer at a pressure of 50–150 MPa for 1–5 passes, controlling the median volume diameter (D) of the neutralized compound emulsion. 50 The particle size is 0.20–0.90 μm; the homogenized neutralized compound emulsion is kept at 70–100 °C for 10–60 min to allow the reaction anchoring groups of the rosin-based reactive emulsifier to chemically anchor the dispersed particles, thereby obtaining dispersed particles.

11. A water-based coating composition, characterized in that: The waterborne coating composition comprises the polyhydroxyalkanoate plant-based composite waterborne emulsion as described in any one of claims 1 to 8 as a film-forming binder and water; wherein the composite waterborne emulsion accounts for 5 to 100 wt% of the total non-volatile matter in the waterborne coating composition on a dry solid basis, and the total non-volatile matter content of the waterborne coating composition is 2 to 80 wt%. When pigments or fillers are included, the pigments or fillers include one or more of inorganic pigments, anti-corrosion pigments, extender fillers, and nanofillers; The inorganic pigment is selected from titanium dioxide, iron oxide, carbon black, zinc oxide, or combinations thereof; the anti-corrosion pigment is selected from zinc phosphate, zinc phosphosilicate, molybdate anti-corrosion pigment, or combinations thereof; the extender filler is selected from barium sulfate, calcium carbonate, talc, mica powder, kaolin, wollastonite, silicon dioxide, or combinations thereof; the nanofiller is selected from nano clay, nano silicon dioxide, graphene, graphite, or combinations thereof. The water-based coating composition is suitable for application to the surface of a substrate and drying or curing to form a coating with a dry film thickness of 0.2 to 500 μm; the substrate is selected from metals, alloys, galvanized sheets, aluminum, stainless steel, plastics or composite materials thereof.

12. The water-based coating composition according to claim 11, characterized in that: The water-based coating composition comprises one or more of the following: wetting and dispersing agents, defoamers, leveling agents, anti-corrosion and anti-mildew agents, thickeners, rheology modifiers, anti-settling agents, film-forming aids, plasticizers, bio-based waxes, adhesion promoters, flash rust inhibitors, or crosslinking agents. The crosslinking agent is selected from polyfunctional epoxy compounds, polyfunctional isocyanate blocking agents, carbodiimides, hydrazine crosslinking agents, aziridine, metal complex crosslinking agents, silane crosslinking agents, or combinations thereof; Furthermore, the wetting and dispersing agent, leveling agent, and defoamer are non-fluorinated additives.

13. The use of the water-based coating composition of claim 11, characterized in that, The intended use is the application of the water-based coating composition in the preparation of protective coatings, barrier coatings, water-resistant coatings, media-resistant coatings, corrosion-resistant coatings, wear-resistant coatings, damp heat-resistant coatings, or composite material surface coatings on the surface of metal or plastic substrates.

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