Resizing waterborne bio-based high-barrier coating compositions, coated articles, their preparation methods and applications

Abstract

This invention discloses a resizing water-based bio-based high-barrier coating composition, coated products, their preparation methods, and applications, belonging to the field of green packaging materials technology. The composition consists of a functionalized core-shell structured acrylic polymer, polyhydroxyalkanoate particles, in-situ modified minerals, and a smart crosslinking system. This invention innovatively constructs a pH-sensitive organic-inorganic dual interpenetrating network, enabling the coating to exhibit excellent water and oil resistance and gas barrier properties under usage conditions, while rapidly undergoing network swelling and dissociation under alkaline recovery conditions. Compared to traditional technologies relying on high mineral fillers, this solution utilizes the synergistic enhancement effect of trace amounts of smart crosslinking agents and bio-based particles to achieve superior barrier effects with low filler content. It also imparts high fiber recovery yield and excellent industrial and household composting degradation performance to paper, and is completely free of fluorides, effectively solving the problem of simultaneously achieving barrier properties, resizing, and full biodegradability in paper-based packaging.

Description

Technical Field

[0001] This invention belongs to the field of green packaging materials technology, specifically relating to resizing water-based bio-based high-barrier coating compositions, coated products, their preparation methods and applications. Background Technology

[0002] With the increasing global awareness of environmental protection and the in-depth implementation of the "paper-for-plastic" strategy, traditional polyethylene (PE) coated paper is facing elimination due to its non-biodegradability and difficulty in achieving fiber separation and recycling through standard papermaking pulping processes. Developing green water-based barrier coatings that combine high-performance protection with environmental friendliness has become an inevitable trend in the food, medical, and industrial packaging materials industries.

[0003] However, existing waterborne barrier coating technologies generally face irreconcilable performance contradictions. The first type, conventional waterborne acrylic emulsion systems, often rely on high-density chemical cross-linking to achieve sufficient water resistance and barrier properties. This results in an overly dense coating network that is difficult to dissociate during the alkaline pulping process in paper recycling, easily forming large-sized stickies that clog screens or contaminate the pulp, failing to meet stringent resizing test standards such as PTS-RH 021:2012. The second type, bio-based materials such as pure polyhydroxyalkanoates (PHA) aqueous dispersions, while possessing excellent biodegradability and oil resistance, suffer from poor film-forming properties, high brittleness, and a tendency to crack after drying. Furthermore, they are costly and difficult to form films independently. The third type of blending modification system, such as combining PHA with polybutylene terephthalate (PBAT) or polyvinyl alcohol (PVOH), improves flexibility to some extent. However, the introduction of PBAT reduces the bio-based carbon content of the material, while the barrier properties of PVOH decrease sharply in high humidity environments, making it unsuitable for humid and hot applications. The fourth type of high-mineral filler technology, although using layered fillers to improve barrier properties, suffers from excessively high pigment-to-binder ratios that severely damage the mechanical properties of the coating, leading to brittle fracture and failure of the coating during paper cup forming or carton folding.

[0004] In summary, the industry urgently needs to develop a water-based coating composition that can balance high bio-based content and excellent mechanical flexibility, and that constructs an interpenetrating network structure with intelligent pH response characteristics. This composition should exhibit excellent water resistance, oil resistance, and high gas barrier properties in acidic to neutral environments, while also rapidly undergoing network swelling and dissociation under alkaline recovery conditions. This would completely solve the technical challenge of achieving both "long-lasting barrier" and "efficient repulping" in paper-based packaging materials. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a reslurryable waterborne bio-based high-barrier coating composition, coated articles, preparation methods thereof, and applications. To achieve the above objective, this invention provides the following technical solution:

[0006] This invention provides a reslurryable aqueous bio-based high-barrier coating composition. The composition is an aqueous dispersion system that, upon drying and curing, forms a dry coating film. This dry coating film forms a barrier layer with a multi-interpenetrating network structure. The composition comprises the following components by weight percentage based on the total dry weight of its solid components:

[0007] The film-forming matrix comprises 15wt% to 62wt%, specifically 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, 55wt%, 60wt%, or 62wt%, and is a functionalized acrylic polymer dispersion obtained by emulsion polymerization. The functionalized acrylic polymer is a core-shell or multiphase polymer. The core-shell structure includes a shell layer with a glass transition temperature of -15℃ to 10℃ and a core layer with a glass transition temperature of 80℃ to 110℃. Its polymer backbone contains 0.5wt% to 4.0wt% diacetone acrylamide. (DAAM) and / or acetoacetic acid group structural units and 0.2wt% to 2.0wt% of alkoxysilane structural units; the content of the DAAM and / or acetoacetic acid group structural units may specifically be 0.5wt%, 0.8wt%, 1.0wt%, 1.5wt%, 2.0wt%, 2.5wt%, 3.0wt%, 3.5wt% or 4.0wt%; the content of the alkoxysilane structural units may specifically be 0.2wt%, 0.5wt%, 0.8wt%, 1.0wt%, 1.2wt%, 1.5wt%, 1.8wt% or 2.0wt%;

[0008] The bio-based reinforcing phase comprises 10 wt% to 40 wt%, with specific contents of 10 wt%, 13.8 wt%, 15 wt%, 20 wt%, 25 wt%, 27.7 wt%, 30 wt%, 35 wt%, 35.8 wt%, 36 wt%, or 40 wt%, representing the median particle size D. 50 PHA particles ranging from 0.2 μm to 2.0 μm; the median particle size D 50 Specifically, the micrometer size can be 0.2μm, 0.5μm, 0.8μm, 1.0μm, 1.2μm, 1.5μm, 1.8μm, or 2.0μm;

[0009] The mineral barrier phase is 10wt% to 46wt%, and the specific content can be 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 37.5wt%, 40wt%, 45wt% or 46wt%, which is a sheet-like inorganic mineral material modified in situ by an alkoxysilane coupling agent.

[0010] The intelligent crosslinking system is 0.3wt% to 3.2wt%, and the specific content can be 0.3wt%, 0.5wt%, 1.0wt%, 1.2wt%, 1.5wt%, 2.0wt%, 2.5wt%, 3.0wt% or 3.2wt%, which is a crosslinking agent composition including polyhydrazine compounds and silane coupling agents containing epoxy or amino groups;

[0011] The weight percentage is calculated as 100wt% of the sum of the solid dry weights of the film-forming matrix, the bio-based reinforcing phase, the mineral barrier phase, and the smart crosslinking system.

[0012] The solid dry weight of the mineral barrier phase includes the dry weight of the sheet-like inorganic mineral material and the dry weight of the alkoxysilane coupling agent used for its in-situ modification.

[0013] The solid dry weight of the intelligent crosslinking system includes the dry weight of the polyhydrazine compound and the dry weight of the epoxy- or amino-containing silane coupling agent in the intelligent crosslinking system.

[0014] The composition further includes water as a dispersion medium and 0.1 wt% to 5.0 wt% of additives based on total dry weight of solids;

[0015] Based on a 100wt% standard, using the sum of the solid dry weights of the film-forming matrix, bio-based reinforcing phase, mineral barrier phase, and intelligent crosslinking system as a benchmark, the mass ratio of the bio-based reinforcing phase to the film-forming matrix is ​​0.25 to 2.5, specifically 0.25, 0.30, 0.40, 0.44, 0.50, 0.60, 0.625, 0.70, 0.80, 0.90, 1.0, 1.20, 1.40, 1.44, 1.60, 1.80, 2.0, 2.39, or 2.5; the mass ratio of the mineral barrier phase to the film-forming matrix is... The mass ratio of the film-forming substrate is from 0.15 to 3.2, specifically 0.15, 0.16, 0.30, 0.40, 0.50, 0.55, 0.60, 0.70, 0.75, 0.90, 1.0, 1.20, 1.40, 1.50, 2.0, 2.50, 3.0, 3.07, or 3.2; the film-forming substrate and the mineral barrier phase are chemically anchored in situ through siloxane covalent bonds, and the intelligent crosslinking system constructs an organic / inorganic dual crosslinking network in the dry coating film;

[0016] When the composition is coated onto the surface of a paper or paperboard substrate containing at least 50 wt% cellulose fibers, and tested under alkaline pulping conditions of pH > 10 and temperature of 40°C to 80°C according to the PTS-RH 021:2012 method, the fiber yield of the resulting paper is ≥ 90%, specifically 90%, 91%, 92%, 93%, 94%, 95%, 96%, 98%, or 99%. The adhesive on coarse and fine sieves does not form visible flakes with an area > 2 mm², and the total organic fluorine (TOF) content of the dry film of the coating is less than 5 mg / kg, i.e., undetectable, as determined by oxygen bomb combustion-ion chromatography.

[0017] The functionalized acrylic polymer dispersion has a core-shell structure, comprising:

[0018] The shell is a polyacrylic acid or polyacrylic acid comethacrylic acid structure rich in carboxyl groups. The shell is copolymerized from acidic monomers and monomers containing post-crosslinking groups. The acidic monomers are selected from one or more of acrylic acid, methacrylic acid, itaconic acid, fumaric acid and their half-esters. The monomers containing post-crosslinking groups are selected from one or more of DAAM, acetylacetoethyl methacrylate (AAEM) and acetylacetoethyl acrylate.

[0019] The core layer is a copolymer structure rich in hydrophobic monomers and functional silane monomers. The hydrophobic monomers are selected from one or more of aromatic vinyl monomers and C1 to C18 alkyl acrylate or methacrylate monomers. Aromatic vinyl monomers include styrene and α-methylstyrene. C1 to C18 alkyl acrylate or methacrylate monomers include one or more of butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, and butyl methacrylate. The functional silane monomers are selected from one or more of vinyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-aminopropyltriethoxysilane.

[0020] The bio-based reinforcing phase is composed of the PHA particles, wherein the PHA is selected from short-chain PHA, medium- and long-chain PHA, or copolymers formed by copolymerizing monomers that form short-chain PHA with monomers that form medium- and long-chain PHA.

[0021] The short-chain PHA is selected from one or more of poly(3-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), and poly(3-hydroxybutyrate-co-4-hydroxybutyrate).

[0022] The medium- and long-chain PHAs 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-hydroxydodecanate), and poly(3-hydroxytetradecanoate);

[0023] The PHA particles are filled in the polymer network pores of the film-forming matrix in the form of a semi-crystalline discrete phase in the dry coating film, and do not contain PBAT, PLA or other aliphatic or aliphatic aromatic polyesters.

[0024] The intelligent cross-linking system includes:

[0025] The first crosslinking agent is the polyhydrazine compound, which reacts with the carbonyl structural unit in the film-forming matrix to form an organic crosslinking framework through a ketone-hydrazine reaction. The polyhydrazine compound is selected from one or more of ADH, sebacic dihydrazide, succinic dihydrazide, isophthalic dihydrazide, and terephthalic dihydrazide.

[0026] The second crosslinking agent is the epoxy- or amino-containing silane coupling agent, which hydrolyzes and condenses in the aqueous dispersion system and undergoes a condensation reaction with the surface of the sheet-like inorganic mineral material and the film-forming matrix to form an inorganic / organic framework. The epoxy- or amino-containing silane coupling agent is selected from one or more of γ-glycidoxypropyltrimethoxysilane and γ-aminopropyltriethoxysilane.

[0027] The organic / inorganic dual crosslinked network remains stable under acidic to neutral conditions, and undergoes reversible dissociation or swelling under alkaline conditions.

[0028] The mineral barrier phase is a lamellar or layered inorganic mineral material with an aspect ratio ≥ 50, and is selected from one or more of the following categories:

[0029] Layered silicate minerals include kaolinite, montmorillonite, talc, muscovite, and sericite;

[0030] Layered silicates obtained through chemical exfoliation or synthesis;

[0031] During the preparation process, the mineral barrier phase is modified in situ by the alkoxysilane coupling agent, so that its surface is grafted with active groups that can undergo condensation reactions with hydroxyl, carboxyl or silanol groups in the film-forming matrix.

[0032] The composition exhibits shear-thinning rheological characteristics, with a low shear rate of 0.1 s⁻¹ at 25°C. -1The viscosity ranges from 1000 mPa·s to 5000 mPa·s, specifically 1000 mPa·s, 1500 mPa·s, 1800 mPa·s, 2000 mPa·s, 2600 mPa·s, 2800 mPa·s, 3100 mPa·s, 3200 mPa·s, 4000 mPa·s, 4800 mPa·s, or 5000 mPa·s; the high shear rate is 10000 s⁻¹. -1 The viscosity at that time ranges from 20 mPa·s to 200 mPa·s, specifically 20 mPa·s, 40 mPa·s, 45 mPa·s, 60 mPa·s, 75 mPa·s, 85 mPa·s, 90 mPa·s, 150 mPa·s, 190 mPa·s or 200 mPa·s.

[0033] The composition has a bio-based carbon content of ≥25% of the total organic carbon, and the specific proportion can be 25%, 28%, 30%, 35%, 40%, 41%, 42%, 50%, 55%, 60%, 65% or 70%.

[0034] The present invention also provides a paper-based barrier material, comprising a fiber substrate and a barrier coating coated on at least one side of the fiber substrate, wherein the barrier coating is formed by drying and curing the composition described above, the fiber substrate being paper, paperboard, or pulp molding article containing at least 50 wt% cellulose fibers, and the paper-based barrier material meeting one or more of the following comprehensive performance indicators:

[0035] 1) Repulpingability: Tested according to PTS-RH 021:2012 under alkaline pulping conditions with pH > 10 and temperature between 40°C and 80°C. Fiber yield ≥ 90%, specifically 90%, 91%, 92%, 93%, 94%, 95%, 96%, 98% or 99%. The adhesive on coarse and fine sieves does not form visible flakes with an area > 2 mm².

[0036] 2) Barrier properties: Water vapor transmission rate (WVTR) at 38℃ and 90% relative humidity ≤ 100 g / m²·d, with specific values ​​of 20 g / m²·d, 25 g / m²·d, 30 g / m²·d, 40 g / m²·d, 42 g / m²·d, 45 g / m²·d, 50 g / m²·d, 55 g / m²·d, 60 g / m²·d, 65 g / m²·d, 70 g / m²·d, 80 g / m²·d, 85 g / m²·d, 90 g / m²·d, 95 g / m²·d, or 100 g / m²·d; at 23℃, The oxygen transmission rate (OTR) under 50% relative humidity conditions is ≤500mL / m²·d, and the specific values ​​can be 50mL / m²·d, 80mL / m²·d, 100mL / m²·d, 150mL / m²·d, 200mL / m²·d, 240mL / m²·d, 250mL / m²·d, 260mL / m²·d, 280mL / m²·d, 300mL / m²·d, 350mL / m²·d, 400mL / m²·d, 420mL / m²·d, 450mL / m²·d or 500mL / m²·d;

[0037] 3) Oil resistance: Oil resistance grade ≥ 10 according to TAPPI T559 test;

[0038] 4) Heat resistance and adhesion: The adhesion grade is ≤ Grade 1 after being placed at 60℃ and 10kPa pressure for 24 hours;

[0039] 5) Compostability: The paper-based barrier material meets the degradation requirements for industrial and / or household composting. Specifically, under industrial composting conditions, tested according to EN 13432:2000, its 12-week disintegration rate is ≥90%, with specific values ​​of 90%, 90.5%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100%; its 180-day biodegradability (relative to cellulose reference) is ≥90%, with specific values ​​of 90%, 91%, 91.5%, 92%, 92.5%, 93%, 94%, 95%, or 96%. Under home composting conditions, and tested according to NF T 51-800:2015 standard, its 26-week disintegration rate is ≥90%, with specific values ​​of 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99%; its 12-month biodegradation rate is ≥90%, with specific values ​​of 90%, 90.2%, 91%, 91.5%, 92%, 93%, 94%, or 95%.

[0040] The paper-based barrier material is used in paper food packaging, industrial packaging, or medical packaging that requires alkaline pulp recycling. This paper food packaging, industrial packaging, or medical packaging is subjected to both humid and hot environments and / or oily media during use.

[0041] The paper food packaging includes at least one of the following: disposable paper cups, instant noodle paper buckets, paper bowls that can directly hold hot oil or hot soup, hamburger paper and similar high-fat food packaging paper, takeaway food boxes with the barrier coating on the inner wall, and paper pulp molded tableware inner wall coating.

[0042] The paper industrial packaging includes at least one of the following: a heavy-duty cardboard box waterproof layer for withstanding high humidity and condensation, and an inner paper bag for holding oily chemical raw materials or lubricating oil.

[0043] The paper medical packaging includes at least one of medical dialysis paper and medical sterile wrapping paper that need to be recycled into pulp after use.

[0044] The present invention also provides a method for preparing the above-described composition, comprising the following steps:

[0045] Step 1. Mineral Activation: Disperse the flaky inorganic mineral material in water, adjust the pH of the system to 9 to 11, specifically 9.0, 9.5, 10.0, 10.5 or 11.0, and stir at a shear rate of 800 r / min to 2000 r / min at 20℃ to 35℃ for 10 min to 40 min, specifically 20℃, 25℃, 30℃ or 35℃, and 800 r / min, 1000 r / min, 1200 r / min, 1500 r / min, 1800 r / min or 2000 r / min, and 10 min, 15 min, 20 min, 25 min, 30 min, 35 min or 40 min. Simultaneously, add the alkoxysilane coupling agent dropwise to allow the silane to undergo in-situ hydrolysis and condensation reaction on the mineral surface, obtaining a modified mineral slurry.

[0046] Step 2. Film-forming matrix composite: The functionalized acrylic polymer dispersion is slowly added to the modified mineral slurry obtained in Step 1, keeping the system temperature ≤40℃, specifically 20℃, 25℃, 30℃, 35℃ or 40℃, and the shear rate is 300r / min to 800r / min, specifically 300r / min, 400r / min, 500r / min, 600r / min, 700r / min or 800r / min. Stirring is continued for 10min to 30min, specifically 10min, 15min, 20min, 25min or 30min, to fully disperse the minerals in the film-forming matrix, thus obtaining a mineral-containing film-forming matrix dispersion system.

[0047] Step 3. Introduction of biological phase and pH adjustment: In the mineral-containing film-forming matrix dispersion system obtained in Step 2, the pH of the system is adjusted to 7.5 to 9.0, specifically 7.5, 8.0, 8.5 or 9.0. PHA particle dispersion is slowly added at a rate of 300 r / min to 600 r / min at a temperature of 20℃ to 30℃, specifically 20℃, 25℃ or 30℃, and the specific shear rate can be 300 r / min, 400 r / min, 500 r / min or 600 r / min. The addition time is 15 min to 60 min, specifically 15 min, 20 min, 30 min, 40 min, 50 min or 60 min, to reduce the damage of shear to the PHA crystal structure and obtain a PHA-containing composite dispersion system.

[0048] Step 4. Latent curing: In the composite dispersion system containing PHA obtained in step 3, add the smart crosslinking system composed of the polyhydrazine compound and the silane coupling agent containing epoxy or amino groups and the required additives at a system temperature ≤30℃. Stir for 10 min to 30 min until the mixture is uniform. The specific time can be 10 min, 15 min, 20 min, 25 min or 30 min. After filtering to remove coarse particles, the composition is obtained.

[0049] Compared with the prior art, the use of this invention can achieve the following significant beneficial effects:

[0050] An excellent balance between barrier properties and resizing properties is achieved. This invention utilizes the carbonyl structure in functionalized acrylic polymers to react with the ketone-hydrazine of polyhydrazine compounds to construct an organic crosslinking network. Simultaneously, a silane coupling agent is used to construct an inorganic-organic hybrid network between the inorganic minerals and the organic matrix. This dual intelligent crosslinking system is stable in acidic to neutral environments, endowing the coating with excellent water resistance, oil resistance, and gas barrier properties. Under alkaline pulping conditions, the ketone-hydrazine bonds can undergo a reverse reaction or network swelling. Combined with the effect of hydrophilic groups, the coating can quickly dissociate into fine fragments, avoiding the formation of large-sized adhesives and meeting the stringent PTS-RH 021:2012 resizing standard.

[0051] This invention improves the bio-based content and environmental friendliness of the material. By introducing micron-sized PHA particles as a bio-based reinforcing phase, not only is the bio-based carbon content of the coating increased, but the pores of the polymer network are also effectively filled, synergistically enhancing the barrier properties with the lamellar minerals. Furthermore, the composition of this invention is fluoride-free, and TOF content was undetectable, complying with increasingly stringent global food contact safety regulations and the trend towards banning plastics and limiting fluorine.

[0052] The processability, rheology, and mechanical properties of the coating are improved. The composition of this invention is designed with specific shear-thinning rheological characteristics, making it suitable for high-speed coating processes; the resulting dry film coating has both strength and toughness, and is not prone to cracking during processing such as paper cup forming and carton folding, ensuring the integrity and barrier effectiveness of the final packaged product. Attached Figure Description

[0053] Figure 1 This is a schematic cross-sectional view of the microstructure of the paper-based barrier material described in this invention.

[0054] In the figure, 1-fiber substrate; 2-film-forming matrix; 3-mineral barrier phase; 4-bio-based reinforcing phase; 5-siloxane covalent bond; 6-organic / inorganic dual crosslinking network. Detailed Implementation

[0055] 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.

[0056] Figure 1 This is a schematic cross-sectional view of the microstructure of a paper-based barrier material in one embodiment of the present invention, showing the underlying fiber substrate 1 and the coated dry film with a multi-interpenetrating network structure formed by coating and curing above it; in the coated dry film, the film-forming matrix 2, as a continuous phase, wraps around the horizontally arranged stacked lamellar mineral barrier phase 3 and the randomly distributed granular bio-based reinforcing phase 4, wherein the siloxane covalent bond 5 (indicated by dashed lines) specifically refers to the chemical connection at the interface between the mineral barrier phase lamellars and the film-forming matrix, while the grid-like solid lines throughout the matrix indicate the overall organic / inorganic dual cross-linked network 6.

[0057] Table 1. Main reagent and raw material names, product models / specifications, and manufacturers:

[0058]

[0059] Table 2 mainly analyzes the names, brands / specifications, and manufacturers of the testing instruments:

[0060]

[0061] Main testing standards:

[0062] WVTR: Tested according to ASTM F1249-25 at 38°C; wet-side relative humidity set to 90%, dry-side relative humidity set to 0%, and carrier gas is nitrogen.

[0063] OTR: Tested according to ASTM F1927-20 at 23°C and 50% relative humidity; pressure difference is converted to 1 atm and reported as mL / m²·d.

[0064] Oil resistance (Kit): Refer to TAPPI T 559 cm-22, grades 1 to 12.

[0065] Cobb absorbency 60 (Refer to TAPPI / ANSI T 441 om-24, test the water absorption in 60 seconds.)

[0066] Resizing properties: Refer to PTS-RH 021:2012 (Cat II, October 2021 edition), dissociation conditions are pH=10.5, 50℃.

[0067] Bio-based carbon content: Refer to ASTM D6866-24A.

[0068] Industrial composting performance: Refer to EN 13432:2000 "Packaging - Requirements for assessing the recyclability of packaging by synthetic and biodegradation - Test schemes and evaluation criteria", where the disintegration rate test refers to ISO 16929:2021 and the biodegradation rate test refers to ISO 14855-1:2012.

[0069] Home composting performance: Refer to NF T 51-800:2015 "Specifications for Plastics in Home Composting".

[0070] Static water contact angle: Using a contact angle meter (DSA100), 3.0 μL of deionized water was added at 23℃ and 50% relative humidity. The left and right contact angles were read 5 seconds after addition and averaged. Five different positions were tested for each sample and the average value was taken.

[0071] TOF content: determined using a method of "water extraction for inorganic fluorine removal + oxygen bomb combustion-ion chromatography", with the oxygen bomb combustion-ion chromatography portion following EN 14582:2016. The specific steps are as follows:

[0072] (1) Sample weighing and water extraction: After crushing the coated paper sample or the dry film of the coating, weigh m=1.00g, add 50mL of deionized water (liquid-solid ratio 50:1mL:g), and extract water for 60min at 60℃ and 200r / min under constant temperature shaking; after filtration (0.45μm aqueous filter membrane), discard the filtrate; repeat the water extraction twice.

[0073] (2) Drying: Place the water-extracted sample in a vacuum drying oven at 60℃ (-0.08MPa) for 4 hours until the mass is constant.

[0074] (3) Oxygen bomb combustion and absorption: The dry sample was placed in the oxygen bomb combustion device and the oxygen was pressurized to 3.0 MPa; after combustion, fluoride ions in the combustion products were absorbed by diluting the volume with 50.0 mL of absorption liquid (deionized water).

[0075] (4) Ion chromatography and calculation: The concentration of fluoride ions C (mg / L) in the absorption solution was determined by ion chromatography and converted according to TOF (mg / kg) = C (mg / L) × V (mL) / m (g).

[0076] The method detection limit (MDL) is determined by blank and low concentration spikes; when MDL = 5 mg / kg, a result lower than MDL is recorded as "<5 (not detected)".

[0077] Heat resistance adhesion: The following "Heat resistance adhesion test method" is used. The product is placed at 60℃ and 10kPa pressure for 24 hours, and the adhesion level is judged from 0 to 3.

[0078] Heavy-duty carton wet heat compressive strength: refer to GB / T 4857.4-2008.

[0079] Heat resistance adhesion test method:

[0080] Cut the coated and cured paper sample into two 50mm × 50mm pieces, ensuring the coated surfaces are facing each other. Place PTFE release film or silicone paper on both sides to prevent adhesion to the fixture. Place the pieces in a constant temperature and pressure adhesion test device and maintain pressure at 60℃ and 10kPa for 24 hours. After removal, place them at 23℃ and 50% relative humidity for 30 minutes. Then, manually or mechanically peel the two pieces apart at a stable speed and observe the coating surface damage and adhesion. Judge according to the following levels:

[0081] Grade 0: No adhesion, can be easily separated, and there is no visible damage to the coating surface;

[0082] Grade 1: Slight adhesion, slight resistance when separating, no tearing or only dot marks on the coating surface;

[0083] Level 2: Moderate adhesion, significant separation resistance, and flaky tears or migration on the coating surface;

[0084] Grade 3: Severe adhesion, difficult to separate or large-area tearing / transfer after separation.

[0085] Preparation of functionalized core-shell acrylic emulsions:

[0086] Step 1. Formulation and Pre-emulsification: Based on a total monomer content of 100 parts (by weight). Add 70 parts deionized water, 1.0 part sodium dodecyl sulfate, and 0.20 parts sodium bicarbonate to the reactor. After stirring and dissolving, purge with nitrogen for 30 minutes to remove oxygen, and then heat to 80°C. Prepare the core layer pre-emulsion: Mix 20 parts deionized water, 0.60 parts sodium dodecyl sulfate, and the core layer monomers, including 20.0 parts styrene, 39.0 parts butyl acrylate, and 1.0 part KH-570 (total core layer monomers 60.0 parts). Shear emulsify at 10000 r / min for 8 minutes to obtain the core layer pre-emulsion. Preparation of the shell preemulsion: 20 parts of deionized water, 0.40 parts of sodium dodecyl sulfate, and shell monomers were mixed. The shell monomers included 22.0 parts of methyl methacrylate, 12.0 parts of butyl acrylate, 4.0 parts of acrylic acid, 1.5 parts of DAAM, and 0.5 parts of AAEM (total shell monomers 40.0 parts). The mixture was sheared and emulsified at 10000 r / min for 8 min to obtain the shell preemulsion. Initiator solution: 0.70 parts of ammonium persulfate were dissolved in 10 parts of deionized water to obtain an ammonium persulfate aqueous solution.

[0087] Step 2. Polymerization and Post-treatment: 5% of the total amount of core layer pre-emulsion was added to the reactor as seed emulsion, along with 10% of the total amount of ammonium persulfate aqueous solution to initiate the polymerization reaction for 20 minutes. Then, the remaining core layer pre-emulsion was added dropwise over 2 hours, along with 45% of the total amount of ammonium persulfate aqueous solution. Next, the shell layer pre-emulsion was added dropwise over another 2 hours, along with the remaining ammonium persulfate aqueous solution. After the addition was complete, the temperature was raised to 85℃ and held for 2 hours to improve the conversion rate. The temperature was then lowered to 40℃, and the pH was adjusted to 7.8 with 10% sodium hydroxide solution. The mixture was filtered (using a 100μm filter) to obtain a functionalized core-shell structured acrylic emulsion with the following physicochemical properties: solid content 45.0%, Tg (shell layer) = -5℃, Tg (core layer) = 95℃. Note: Following the above steps and formulation, the polymer obtained contains a total of 2.0 parts by mass of DAAM and AAEM structural units, accounting for 2.0% of the total monomers; and 1.0 parts by mass of alkoxysilane structural units (derived from KH-570), accounting for 1.0% of the total monomers.

[0088] Preparation of low-crosslinking functionalized core-shell acrylic emulsions:

[0089] Step 1. Follow the steps in "Preparation of Functionalized Core-Shell Structure Acrylic Emulsion" above, except that, based on a total monomer content of 100 parts by mass: the amount of KH-570 in the core layer monomer is 0.2 parts, styrene is 20.0 parts, butyl acrylate is 39.8 parts, and the total amount of core layer monomer is 60.0 parts; the amount of other emulsifiers, initiators, dropping methods, temperature programs and post-treatment are the same as above, to obtain a low crosslinked core layer emulsion.

[0090] Step 2. Proceed as described in Step 2 of "Preparation of Functionalized Core-Shell Acrylic Emulsion" above. Add shell monomers dropwise to the low-crosslinked core emulsion. The difference lies in the following: the shell monomers are 0.4 parts DAAM, 0.1 parts AAEM, 4.0 parts acrylic acid, 12.0 parts butyl acrylate, and 23.5 parts methyl methacrylate, for a total of 40.0 parts shell monomers. The amounts of other emulsifiers and initiators, the dropping method, the temperature program, and the post-treatment are the same as above. The resulting emulsion has a solid content of 45.0%, thus obtaining a low-crosslinked functionalized core-shell acrylic emulsion.

[0091] Note: The total mass of DAAM and AAEM structural units in the obtained polymer is 0.5 parts, accounting for 0.5% of the total monomer; the alkoxysilane structural units derived from KH-570 are 0.2 parts by mass, accounting for 0.2% of the total monomer.

[0092] Preparation of highly cross-linked functionalized core-shell acrylic emulsions:

[0093] Step 1. Follow the steps in "Preparation of Functionalized Core-Shell Structure Acrylic Emulsion" above, except that, based on a total monomer content of 100 parts by mass: the amount of KH-570 in the core layer monomer is 2.0 parts, styrene is 20.0 parts, butyl acrylate is 38.0 parts, and the total amount of core layer monomer is 60.0 parts; the amount of other emulsifiers, initiators, dropping methods, temperature programs and post-treatment are the same as above, to obtain a highly cross-linked core layer emulsion.

[0094] Step 2. Proceed as described in Step 2 of "Preparation of Functionalized Core-Shell Structure Acrylic Emulsion" above. Add shell monomers dropwise to the highly cross-linked core emulsion. The difference is that the shell monomers contain 3.0 parts of DAAM, 1.0 parts of AAEM, 4.0 parts of acrylic acid, 12.0 parts of butyl acrylate, and 20.0 parts of methyl methacrylate, for a total of 40.0 parts of shell monomers. The amounts of other emulsifiers and initiators, the dropping method, the temperature program, and the post-treatment are the same as above. The resulting emulsion has a solid content of 45.0%, thus obtaining a highly cross-linked functionalized core-shell structure acrylic emulsion.

[0095] Note: The total mass of DAAM and AAEM structural units in the obtained polymer is 4.0 parts by mass, accounting for 4.0% of the total monomer; the alkoxysilane structural units derived from KH-570 are 2.0 parts by mass, accounting for 2.0% of the total monomer.

[0096] Preparation of ordinary styrene-acrylic emulsion:

[0097] Step 1. Formulation and Pre-emulsification: Based on a total monomer content of 100 parts (by weight). Add 70 parts deionized water, 1.0 part sodium dodecyl sulfate, and 0.20 parts sodium bicarbonate to the reactor. After stirring and dissolving, purge with nitrogen for 30 minutes to remove oxygen, then heat to 80°C. Prepare the mixed monomer pre-emulsion: Mix 40 parts deionized water and 1.0 part sodium dodecyl sulfate with the mixed monomers, which include 25.0 parts styrene, 70.0 parts butyl acrylate, and 5.0 parts acrylic acid. Shear emulsify at 10000 r / min for 8 minutes to obtain the mixed monomer pre-emulsion. Initiator Solution: Dissolve 0.70 parts ammonium persulfate in 10 parts deionized water to obtain an ammonium persulfate aqueous solution.

[0098] Step 2. Polymerization and Post-treatment: 5% of the total amount of the mixed monomer pre-emulsion was added to the reactor as a seed emulsion, and 10% of the total amount of ammonium persulfate aqueous solution was added to initiate the polymerization reaction for 20 min. Subsequently, the remaining mixed monomer pre-emulsion was added dropwise over 3 h, along with the remaining ammonium persulfate aqueous solution. After the addition was completed, the temperature was raised to 85℃ and held for 2 h. The temperature was then lowered to 40℃, and the pH was adjusted to 7.8 with 10% sodium hydroxide solution. The mixture was filtered (using a 100 μm filter) to obtain a common styrene-acrylic emulsion (solid content 45%), with a measured Tg of 15℃.

[0099] Preparation of aqueous dispersions of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV):

[0100] Step 1. Prepare the dispersion medium. Take 59.2 parts of laboratory deionized water, add 0.8 parts of wetting agent, and stir for 5 minutes to make it uniform.

[0101] Step 2. Add resin and shear dispersion. Slowly add 40.0 parts of PHBV resin and shear disperse at 10000 r / min for 30 min on a high-speed disperser. Control the temperature of the dispersion system to ≤35℃ by using an external circulating water bath or ice bath.

[0102] Step 3. Particle size control and filtration. Samples are taken every 10 minutes and the particle size distribution is measured using a laser particle size analyzer until D... 50 The particle size was reduced to 1.80 μm; then, coarse particles were removed by filtration through a 100 μm filter to obtain an aqueous dispersion of PHBV (solid content 40.0%).

[0103] Preparation of aqueous dispersions of poly(3-hydroxybutyrate) (PHB):

[0104] Step 1. Prepare the dispersion medium. Take 59.2 parts of laboratory deionized water, add 0.8 parts of wetting agent, and stir for 5 minutes to make it uniform.

[0105] Step 2. Add resin and shear dispersion. Slowly add 40.0 parts of PHB resin and shear disperse at 10000 r / min for 30 min on a high-speed disperser. Control the temperature of the dispersion system to ≤35℃ by using an external circulating water bath or ice bath.

[0106] Step 3. Particle size control and filtration. Samples are taken every 10 minutes and the particle size distribution is measured using a laser particle size analyzer until D... 50 The particle size was reduced to 1.50 μm; then, coarse particles were removed by filtration through a 100 μm filter to obtain an aqueous dispersion of PHB (40% solids content).

[0107] Example:

[0108] Note: In the following examples, unless otherwise stated, the amounts of each component are based on dry weight parts of solids; the functionalized core-shell acrylic emulsion and ordinary styrene-acrylic emulsion have a solid content of 45.0%, and the PHBV aqueous dispersion and PHB aqueous dispersion have a solid content of 40.0%; the crosslinking agent ADH is added based on its effective ingredient dry weight, prepared using a 20% (mass fraction) ADH aqueous solution, and the amount added is calculated based on dry weight parts; the wetting agent and defoamer are added in commercial form; the silane coupling agent is added in its original form. The prepared coating composition is finally filtered through a 100 μm filter to remove coarse particles.

[0109] Example 1: A balanced reslurry-type waterborne bio-based high-barrier coating composition.

[0110] Preparation method:

[0111] Step 1. Mineral activation: Disperse 30.00 parts (dry weight) of kaolin in 120.00 parts of deionized water to obtain a mineral slurry with a solid content of 20.0% (mass fraction); adjust the pH of the system to 9.5 using 1.0 mol / L sodium hydroxide solution; stir at 1200 r / min for 20 min at 25℃, while adding 0.15 parts of γ-glycidoxypropyltrimethoxysilane dropwise over 10 min; continue stirring for 10 min after the addition is complete to allow the silane to undergo in-situ hydrolysis and condensation reaction on the mineral surface, thus obtaining the modified mineral slurry.

[0112] Step 2. Film-forming matrix composite: In the modified mineral slurry obtained in Step 1, 40.00 parts (dry weight) of film-forming matrix are slowly added over 15 min, and 88.89 parts of functionalized core-shell acrylic emulsion with a solid content of 45.0% are added accordingly; the system temperature is maintained at 35℃ and the shear rate is 500 r / min, and stirring is continued for 15 min to fully disperse the minerals in the film-forming matrix, thus obtaining a mineral-containing film-forming matrix dispersion system.

[0113] Step 3. Introduction of biological phase and pH adjustment: The pH of the film-forming matrix dispersion system containing minerals obtained in Step 2 was adjusted to 8.0; the system was stirred at 400 r / min at 25℃, and PHBV aqueous dispersion was slowly added over 20 min. The amount added was equivalent to 25.00 parts of PHBV dry weight, corresponding to a solid content of 40.0% and D. 50 A composite dispersion system was obtained by dispersing 62.50 parts of PHBV aqueous dispersion with a particle size of 1.80 μm.

[0114] Step 4. Latent curing: In the composite dispersion system obtained in step 3, add 20% (mass fraction) ADH aqueous solution at 25°C. The amount added is equivalent to 0.40 parts of the dry weight of the effective ADH component, corresponding to 2.00 parts of 20% ADH aqueous solution. Then add 0.10 parts of γ-glycidyl etheroxypropyltrimethoxysilane. Next, add 0.20 parts of wetting agent and 0.10 parts of defoamer. Stir for 15 minutes until the mixture is uniform, and filter through a 100μm filter to obtain the composition.

[0115] Example 2: A coating composition with high bio-based content. The preparation method is the same as in Example 1, but the formulation is adjusted as follows: the amount of film-forming matrix is ​​35 parts by dry weight, the amount of PHBV aqueous dispersion is 35 parts by dry weight, the amount of mineral barrier phase is 25 parts by dry weight, and the amount of intelligent crosslinking system is 1.0 part (ADH is 0.8 parts and silane is 0.2 parts).

[0116] Example 3: An ultra-high barrier coating composition. The preparation method is the same as in Example 1, but the formulation is adjusted as follows: the amount of film-forming matrix is ​​25 parts by dry weight, the amount of PHBV aqueous dispersion is 15 parts by dry weight, the amount of mineral barrier phase is 35 parts by dry weight, and the amount of intelligent crosslinking system is 2.0 parts (ADH is 1.7 parts and silane is 0.3 parts).

[0117] Example 4: A highly flexible coating composition. The preparation method is the same as in Example 1, but the formulation is adjusted: the amount of film-forming substrate is 50 parts by dry weight, and PHB aqueous dispersion (D...) is used. 50 =1.50μm) 15 parts dry weight, mineral barrier phase 15 parts dry weight, smart crosslinking system 2.0 parts (ADH 1.7 parts, silane 0.3 parts).

[0118] Example 5: An economical coating composition. The preparation method is the same as in Example 1, but the formulation is adjusted as follows: the amount of film-forming matrix is ​​40 parts by dry weight, the amount of PHBV aqueous dispersion is 25 parts by dry weight, the amount of mineral barrier phase is 30 parts by dry weight, and the amount of intelligent crosslinking system is 3.0 parts (ADH is 2.6 parts and silane is 0.4 parts).

[0119] Example 6: A low-mineral-filled coating composition. The preparation method is the same as in Example 1, except that a low-crosslinking functionalized core-shell acrylic emulsion (solid content 45.0%) is used instead of the original film-forming matrix, and flake talc is used instead of kaolin. The formulation is adjusted as follows: the amount of film-forming matrix is ​​62 parts by dry weight, the amount of PHBV aqueous dispersion is 27.7 parts by dry weight, the amount of mineral barrier phase is 10 parts by dry weight, the amount of mineral modification silane is 0.10 parts by dry weight, and the amount of intelligent crosslinking system is 0.3 parts (ADH is 0.25 parts, and intelligent crosslinking silane is 0.05 parts).

[0120] Example 7: A high-mineral-filled coating composition. The preparation method is the same as in Example 1, except that a highly cross-linked functionalized core-shell acrylic emulsion (solid content 45.0%) is used instead of the original film-forming matrix, and sodium-based montmorillonite is used instead of kaolin. The formulation is adjusted as follows: the amount of film-forming matrix is ​​15 parts by dry weight, the amount of PHBV aqueous dispersion is 35.8 parts by dry weight, the amount of mineral barrier phase is 46 parts by dry weight, the amount of mineral-modifying silane is 0.20 parts by dry weight, and the amount of intelligent cross-linking system is 3.2 parts (ADH is 2.5 parts and intelligent cross-linking silane is 0.7 parts).

[0121] Example 8: A low bio-based coating composition. The preparation method is the same as in Example 1, but the formulation is adjusted as follows: the amount of film-forming matrix is ​​55 parts by dry weight, the amount of PHBV aqueous dispersion is 13.8 parts by dry weight, the amount of mineral barrier phase is 30 parts by dry weight, and the amount of intelligent crosslinking system is 1.2 parts (ADH is 1.0 part and silane is 0.2 parts).

[0122] Example 9: A high pigment-to-binder ratio coating composition. The preparation method is the same as in Example 1, but the formulation is adjusted as follows: the amount of film-forming matrix is ​​25 parts by dry weight, the amount of PHBV aqueous dispersion is 36 parts by dry weight, the amount of mineral barrier phase is 37.5 parts by dry weight, and the amount of intelligent crosslinking system is 1.5 parts (ADH is 1.2 parts and silane is 0.3 parts).

[0123] Comparative example:

[0124] Comparative Example 1: System without bio-based reinforcing phase. The preparation process was the same as in Example 1, but the formulation was adjusted as follows: 65 parts of film-forming matrix, 30 parts of mineral barrier phase, 0.5 parts of intelligent crosslinking system (0.4 parts of ADH and 0.1 parts of silane), without the addition of bio-based reinforcing phase.

[0125] Comparative Example 2: Silane-free anchoring system. The formulation is the same as in Example 1, except that γ-glycidoxypropyltrimethoxysilane is not added in preparation step (1), and no functionalized silane coupling agent is added in step (4), only ADH is added.

[0126] Comparative Example 3: No intelligent crosslinking system. The formulation is the same as in Example 1, except that no ADH crosslinking agent or silane-containing crosslinking components are added.

[0127] Comparative Example 4: Non-functionalized ordinary matrix system. The formulation is the same as in Example 1, except that an ordinary styrene-acrylic emulsion is used instead of the functionalized film-forming matrix.

[0128] Comparative Example 5: Mineral Barrier Phase Overload System. The formulation is the same as in Example 1, except that the amount of mineral barrier phase is significantly increased. The formulation is adjusted as follows: 30 parts film-forming matrix, 15 parts PHBV aqueous dispersion, 54 parts mineral barrier phase, and 0.75 parts intelligent crosslinking system (0.6 parts ADH and 0.15 parts silane).

[0129] Comparative Example 6: Smart Crosslinking Agent Overload System. The formulation is the same as in Example 1, except that the amount of smart crosslinking system is significantly increased. The formulation is adjusted as follows: 40 parts film-forming matrix, 25 parts PHBV aqueous dispersion, 30 parts mineral barrier phase, and 5.0 parts smart crosslinking system (4.2 parts ADH and 0.8 parts silane).

[0130] Comparative Example 7: Bio-based particle size exceeding the standard system. The formulation is the same as in Example 1, except that the median particle size D is used. 50 The original PHBV aqueous dispersion was replaced with a 5.0 μm PHBV particle dispersion, while the other components remained unchanged.

[0131] The formulations of the examples and comparative examples are summarized in Table 3.

[0132] Table 3 Summary of Formulations and Physical Properties of Examples and Comparative Examples (parts of solid dry weight):

[0133]

[0134] Application example:

[0135] Application Example 1: Evaluation of paper cup barrier and repulpability properties.

[0136] Experimental Description: Food-grade white cardboard with a basis weight of 250 g / m² was selected as the substrate (cellulose fiber content ≥ 50%). Single-sided coating was performed using a laboratory coating machine with a bar coating method. The linear speed was set to 2.0 m / min, and the appropriate bar type was selected to control the dry weight of the coating to 11.0 g / m². The coating amount was calibrated using a weighing method: the difference in paper sample weight before and after coating was recorded and converted to the dry coating weight per unit area. The coated paper samples were dried in a 105℃ oven for 2 minutes, followed by curing at 23℃ and 50% relative humidity for 24 hours.

[0137] WVTR was tested according to ASTM F1249-25 (38°C, 90% relative humidity); OTR was tested according to ASTM F1927-20 (23°C, 50% relative humidity); and oil resistance was rated according to the Kit grade of TAPPI T 559 cm-22.

[0138] Resizing properties were tested according to PTS-RH 021:2012: Cured coated paper was cut into approximately 20mm × 20mm pieces. A 30.0g sample, dried to constant weight, was taken. 1470mL of deionized water preheated to 50℃ was added to a standard disintegrator, and a 10% sodium hydroxide solution was added dropwise under stirring to adjust the pH to 10.5. Then, the 30.0g sample, dried to constant weight, was added to bring the pulp concentration to 2.0% (mass fraction). Disintegration was performed at 50℃, with a disintegration speed of 2980 r / min and a total disintegration revolution of 3.0 × 10⁴ revolutions (corresponding to a disintegration time of 10 min). After disintegration, the pulp was first sieved through a coarse sieve (0.7mm aperture) and then through a fine sieve (0.15mm slit width, i.e., 150μm).

[0139] Fiber yield is calculated using the following formula: Fiber yield (%) = (Dried mass of pulp received from coarse and fine sieves / Dried mass of sample) × 100%.

[0140] The evaluation of adhesives is divided into two parts: coarse sieve and fine sieve. The coarse sieve rejects and fine sieve rejects are collected on filter paper and dried to constant weight at 23℃ and 50% relative humidity. The coarse sieve rejects are inspected by the naked eye and with the aid of a magnifying glass, and the presence of visible flakes with an area >2mm² is recorded. The fine sieve rejects are scanned at 600dpi and the area of ​​a single flake is counted using image analysis software. The largest single flake area is recorded and the presence of visible flakes with an area >2mm² is determined.

[0141] Table 4 Performance test results of Application Example 1:

[0142]

[0143] Note:

[0144] Adhesive material determination: Fine sieve rejection material was obtained according to the PTS-RH 021:2012 sieving procedure. After drying, it was scanned and the area of ​​each piece was counted using image analysis software. In the table, "None" means no visible flakes (no visible flakes with an area > 2 mm²); "Trace fragments" means a small amount of fragments are present, but the area of ​​each piece is ≤ 2 mm²; "Present" means visible flakes with an area > 2 mm² were detected.

[0145] TOF determination: After removing inorganic fluorine from the sample by water extraction, the sample was determined by oxygen bomb combustion-ion chromatography. "<5" in the table indicates not detected, i.e., below the method detection limit (MDL=5 mg / kg).

[0146] Analysis: The experimental data from Application Example 1 comprehensively validated the excellent balance between barrier properties and resizing properties of the coating composition of the present invention, and all examples met stringent industrial application standards. Specifically, Example 6, using a low mineral (10%) and high matrix (62%) ratio, achieved a resizing yield of up to 99%, validating the advantages of the low-filler system in the recycling process; while Example 7, by introducing high aspect ratio montmorillonite and increasing the degree of crosslinking to the upper limit (3.2%), achieved an extremely low WVTR of 20 g / m²·d while maintaining a qualified fiber yield of 90%, demonstrating the effectiveness of the technical solution over a wide range. Comparative experiments profoundly revealed the critical boundaries of the formulation parameters: In Comparative Example 5, increasing the mineral / matrix mass ratio to 1.8, although the theoretical barrier path increased, the excessively high pigment-to-binder ratio led to microcracks during coating drying shrinkage, causing the WVTR to abnormally increase to 450 g / m²·d, and undispersed hard flakes appeared during resizing; In Comparative Example 6, increasing the total crosslinking agent to 5.0% resulted in excessively high crosslinking density locking the polymer network, leading to ineffective swelling under alkaline conditions, a sharp drop in resizing yield to 65%, and the generation of a large amount of adhesive; Comparative Example 7 confirmed that PHA particle sizes exceeding 2.0 μm would form surface defects, leading to barrier failure. In summary, the experiments confirmed the scientific validity and necessity of the limitations on component ratios and particle size ranges in the claims.

[0147] Application Example 2: Evaluation of the resistance and leakage performance of paper cups to hot water and hot oil.

[0148] The coating compositions of the examples and comparative examples were coated onto the surface of the paper cup base paper (as the side of the cup in contact with the liquid inside), and the dry weight of the coating was controlled at 11.0 g / m²; the coating, drying, and curing conditions were the same as in Application Example 1. The cured coated paper was processed into 12-ounce paper cups using a PMC2001S paper cup forming machine. The experiment was divided into two groups for durability testing: the first group was injected with hot water at 95°C and left to stand for 30 minutes; the second group was injected with refined rapeseed oil at 80°C and left to stand for 30 minutes.

[0149] Leakage determination: If visible droplets, continuous wet seepage marks, or leakage marks appear on the outer wall of the cup during and at the end of the settling process, the sample is considered to have leaked. The leakage rate is calculated based on the proportion of leaking samples out of 50. The cup deformation level is rated on a scale of 0 to 3, with 0 representing no deformation and 3 representing severe collapse. The width of the wetted zone at the cup rim is measured using calipers at four equally spaced points along the circumference of the cup rim, and the average value is recorded.

[0150] Table 5 Application Example 2: Leakage performance of paper cups in hot water and hot oil:

[0151]

[0152] Analysis: Application Example 2 further established the tolerance boundary of the coating formulation of the present invention by simulating the actual use of paper cups in a high-temperature liquid environment. All examples showed a 0% leakage rate in the 80°C hot oil test, proving that the dense organic / inorganic interpenetrating network effectively shields grease molecules. In the more challenging 95°C hot water test, Example 6 achieved zero leakage and no cup deformation due to the excellent flexibility provided by the high film-forming matrix content; while Examples 7 and 9, due to the near-upper limit of mineral content, had increased coating rigidity and generated slight stress concentration at the forming fold at the bottom of the cup, resulting in a slight leakage of 2%-4%, but still within the commercially acceptable range. In contrast, Comparative Example 5 suffered from catastrophic leakage of 100% due to the extremely brittle coating caused by mineral overload, resulting in mechanical fracture during the forming process; Comparative Example 4, due to the lack of a heat-resistant crosslinking network in the ordinary styrene-acrylic emulsion, had a hot water leakage rate as high as 20% and severe softening and deformation of the cup; Comparative Example 7 performed poorly in both hot oil and hot water tests due to surface pinhole defects caused by large PHA particles. These results strongly demonstrate the crucial role of a reasonable mineral / matrix ratio and functionalized cross-linked matrices in ensuring the structural integrity of paper containers under extreme humid and hot conditions.

[0153] Application Example 3: Evaluation of the compressive strength of the waterproof layer of heavy-duty cardboard boxes in a humid and hot environment.

[0154] Experimental Description: The corrugated cardboard structure selected was a three-layer composite structure of "face paper / core paper / liner paper": the face paper was made of 200g / m² high-strength corrugated base paper, the liner paper was made of 200g / m² liner paper (Testliner 3), and the core paper was made of 140g / m² corrugated core paper; starch adhesive (25% solid content) was used as the adhesive for corrugation, and the cardboard was laminated into single-wall corrugated cardboard (with consistent flute profile) under the same process conditions. Each coating composition was applied to the face paper, controlling the dry weight of the coating to 15g / m², and then dried at 105℃ for 2 minutes followed by curing for 24 hours before corrugation lamination.

[0155] The composite corrugated cardboard was used to create carton models with the same box type and dimensions (the box type and external dimensions remained consistent across all sample groups), with ≥5 carton samples prepared for each group. Before the dry test, the carton samples were conditioned at 23℃ and 50% relative humidity for 24 hours. For the wet test, the samples were placed in a constant temperature and humidity chamber at 50℃ and 90% relative humidity for 48 hours, and then subjected to a box compression test within 5 minutes. The box compression test was conducted according to GB / T 4857.4-2008, using a box compression testing machine to test the dry and wet compressive strengths respectively. The wet strength retention rate was calculated using the following formula: Wet strength retention rate (%) = (Wet strength / Dry strength) × 100%.

[0156] Table 6 Application Example 3: Compression strength (dry / wet) and wet strength retention rate of heavy-duty cardboard boxes:

[0157]

[0158] Analysis: Application Example 3 focused on the protective effect of the coating on the mechanical strength of the cardboard box under prolonged humid and hot fumigation. The experimental results highlighted the importance of the synergistic effect of the lamellar mineral barrier phase and the crosslinking network. Example 7 (containing 46% montmorillonite) and Example 3 (containing 35% kaolinite) showed the best wet strength retention rates, reaching 72% and 71% respectively. This is attributed to the high content and high aspect ratio of the mineral lamellars constructing a tortuous "maze path" within the coating, significantly delaying the penetration of water molecules into the cardboard fibers. Although Example 6 had a mineral content of only 10% and a slightly lower wet strength retention rate (50%), it was still significantly better than Comparative Example 3 (33%) with no crosslinking and Comparative Example 4 (37%) with a normal matrix system, demonstrating that the organic crosslinking network can provide basic protection even with low filler content. The most destructive result appeared in Comparative Example 5. Despite its high mineral content of 54%, the imbalance of pigment-to-binder ratio disrupted the physical continuity of the coating, resulting in a wet strength retention rate that dropped to the lowest of the entire experiment at 25%. This counterintuitive experimental result strongly confirms the necessity of setting the upper limit of the mineral barrier phase content to 46 wt%, indicating that only by increasing the mineral content can the damp heat protection performance be effectively improved, provided that the coating remains intact and continuous.

[0159] Application Example 4: Evaluation of barrier and repulpability properties of medical dialysis paper / medical sterile wrapping paper.

[0160] Experimental Description: Medical dialysis paper and sterile medical wrapping paper were selected as substrates (the mass percentage of cellulose fibers in each substrate ≥ 50 wt%). Single-sided coating was performed using the same laboratory coating machine as in Application Example 1, and the dry weight of the coating was controlled at 10 g / m². The coated paper samples were dried in an oven at 105°C for 2 minutes, and then cured at 23°C and 50% relative humidity for 24 hours.

[0161] Performance testing: WVTR was tested according to ASTM F1249-25 (38℃, 90% relative humidity); OTR was tested according to ASTM F1927-20 (23℃, 50% relative humidity); oil resistance was assessed according to TAPPI T 559 cm-22 Kit grade; resizing was tested according to PTS-RH 021:2012 (pH=10.5, 50℃), and the sieving and adhesive determination methods were the same as in Application Example 1.

[0162] Table 7. Performance test results of medical packaging substrate in Application Example 4:

[0163]

[0164] Analysis: Application Example 4 validated the dual requirements of barrier properties (antibacterial properties) and recyclability (environmental protection) for medical packaging. Examples 7 and 9 exhibited extremely low OTR (100-160 mL / m²·d), effectively preventing oxidation and microbial intrusion of medical devices. Although their resizing yield was slightly lower than other examples, the 88-91% figure was still far higher than the industry standard of 80%, and there were no large-sized adhesive residues, fully meeting the requirements for resource utilization of medical waste. Example 6 provided a highly recyclable solution with an ultra-high resizing yield of 99%. The experimental data of Comparative Example 6 constitutes an important technical warning. Its low fiber yield of 55% means that a large amount of fiber was lost due to being encapsulated by an undissociated, excessively cross-linked coating, and serious adhesive residue pollution was generated, directly negating the technical route of blindly increasing the degree of cross-linking to pursue barrier properties. Furthermore, the data from Comparative Example 4 show that ordinary latex lacking hydrophilic modification aggregates into adhesives larger than 5 mm² during resizing, which cannot pass through fine sieves, thus confirming the core value of the specific functionalized matrix of this invention for achieving "zero adhesive" recycling.

[0165] Application Example 5: Characterization of coating microstructure and verification of intelligent cross-linking network.

[0166] Experimental Description: This experiment comprehensively verified the emulsion morphology, dry film crosslinking network structure, and pH response behavior of various coating compositions to elucidate their barrier and resizing mechanisms.

[0167] (1) Structural characterization: The emulsions used in each formulation were diluted 100 times with deionized water and then subjected to D... 50 Particle size testing: Before particle size testing, the diluted emulsion was ultrasonically dispersed for 1 min to break weak flocculation. The diluted emulsion was dropped onto a 300-mesh carbon copper mesh, allowed to stand for 60 s, and then excess droplets were absorbed with filter paper. Subsequently, 2.0% (mass fraction) phosphotungstic acid aqueous solution (adjusted to pH 7.0) was added for negative staining for 30 s, then absorbed again and dried at room temperature. The core / shell interface morphology of the emulsion particles was observed and recorded using TEM. At the same time, the emulsion was allowed to form a film naturally on a polytetrafluoroethylene separator and then subjected to DSC testing (-50℃ to 150℃, heating rate 10℃ / min). The Tg quantity and value were recorded. The core-shell structure was determined by combining the TEM morphology and DSC dual Tg characteristics.

[0168] (2) Network and morphology verification: The compositions of each example and comparative example were prepared into free films with a thickness of 30 μm, dried and aged at 105 °C, and then characterized.

[0169] (3) pH response dissociation: Place a 10mm×10mm free membrane sample in an alkaline solution at pH 10.5 and 50℃, and record the time required for the membrane to completely dissociate (disperse into a paste without visible debris). If it remains intact or only breaks into pieces after more than 60 minutes, it is recorded as ">60 (difficult to dissociate)".

[0170] (4) Determination of mineral diameter-to-thickness ratio: The ultrafine kaolin samples used were dispersed and dripped onto a glass slide, dried, and observed by SEM; 100 mineral sheets were randomly selected, their equivalent diameter and thickness were measured, and the diameter-to-thickness ratio was calculated; the results showed that the median diameter-to-thickness ratio of the kaolin mineral sheets used was 80, and ≥90% of the sheets had a diameter-to-thickness ratio ≥50.

[0171] Table 8 Application Example 5: Coating microstructure parameters and alkaline dissociation properties:

[0172]

[0173] Analysis: Application Example 5, through microscopic morphology characterization and dissociation kinetic testing, deeply revealed the intrinsic mechanism of macroscopic performance differences. The DSC curves of Examples 1 to 9 all exhibited clear double Tg characteristics, which, combined with the core-shell structure observed by TEM, confirmed the successful synthesis of the functionalized matrix and the maintenance of the phase-separated structure. Alkaline dissociation time testing showed that Example 6 (low crosslinking) required only 6 minutes for complete dissociation, while Example 7 (high crosslinking) required 25 minutes. This time span perfectly covers the operating window of existing paper pulping processes (10-30 minutes), demonstrating the process adaptability of the intelligent crosslinking system design. In contrast, Comparative Example 6, with a crosslinking agent content of 5.0%, had a dissociation time exceeding 60 minutes, indicating that the network density had exceeded the threshold for alkali penetration and swelling. The SEM cross-section of Comparative Example 2 showed interfacial micropores, confirming that the lack of silane chemical anchoring led to organic / inorganic phase separation. The SEM image of Comparative Example 5 directly captured macroscopic physical cracks caused by excessive mineral accumulation. These microscopic evidences are highly consistent with the macroscopic application test results, and provide a complete mechanistic explanation as to why perfect unity of barrier and resizing can only be achieved within a specific range of component ratios and structural parameters.

[0174] Application Example 6: Verification of the mechanical properties of the dry film coating and the core-shell structure effect.

[0175] Experimental Description: This experiment aims to verify the contribution of the "soft shell, hard core" design in functionalized core-shell acrylic polymers to the mechanical properties of the coating, focusing on the balance between the film-forming flexibility and surface hardness of the coating.

[0176] Food-grade white cardboard with a density of 250 g / m² was selected as the substrate. The compositions of Examples 1-9 and Comparative Examples 1-7 were coated onto the surface of the substrate, and the dry weight of the coating was controlled to be 12 g / m² ± 0.5 g / m². After drying at 105°C for 2 min, the coating was cured at 23°C and 50% relative humidity for 24 h.

[0177] Test metrics and methods:

[0178] Cleavage resistance: Simulating the folding process in packaging manufacturing. Fold the coated paper sample 180 degrees with the coated side facing outwards, and apply pressure (rolled once with a 2kg weight) to the crease in this position. After unfolding, apply red ink to the crease area and observe the penetration and degree of cracking, rating it from 0 to 5.

[0179] 0 points: The coating at the crease is intact, without any cracks, and the red ink does not penetrate;

[0180] 1 point: There are only microscopic cracks at the crease, and the red ink has seeped in in dots;

[0181] 2 points: A few visible cracks appear, and the red ink seeps in discontinuous lines;

[0182] 3 points: Obvious cracks appear, and red ink seeps in a continuous line;

[0183] 4 points: The coating is severely cracked or peeling off at the creases;

[0184] 5 points: The coating is completely broken, exposing the substrate fibers.

[0185] Pendulum hardness: Referring to ISO 1522:2022, a König pendulum was used, and a pendulum hardness tester was used to test the damping time (seconds) of the coating surface. This index reflects the surface hardness and anti-adhesion potential of the coating; the higher the value, the higher the hardness and the more significant the contribution of the "hard core".

[0186] Table 9. Application Example 6: Coating crease resistance and pendulum stiffness test results:

[0187]

[0188] Analysis: The test results of Application Example 6 strongly confirm the key role of the "core-shell structure design" of the functionalized acrylic polymer in this invention.

[0189] The data shows that all embodiments using this specific core-shell structure substrate, such as Examples 1-9, exhibit excellent "rigid-flexible" characteristics. Taking Example 1 as an example, its crease resistance score is 0 (undamaged), while the pendulum stiffness remains at a high level of 58s. This performance is attributed to the carboxyl-rich shell layer with a Tg of -5℃ providing good particle integration and fusion with the substrate during film formation, giving the coating excellent continuity and crease resistance; while the hydrophobic core layer with a Tg of 95℃ acts as a rigid support framework, effectively improving the overall modulus and surface hardness of the coating, preventing the common problems of stickiness and poor wear resistance in soft coatings.

[0190] In contrast, Comparative Example 4 used a conventional homogeneous styrene-acrylic emulsion with a Tg of 15°C, which not only exhibited poor crease resistance (3 points, with obvious cracks appearing), but also had a pendulum hardness of only 35s. This is because the homogeneous structure cannot simultaneously achieve the softness required for film formation and the hardness required for use, representing a typical "performance compromise" product, thus demonstrating the advanced nature of the core-shell design of this invention.

[0191] Furthermore, the hardness of Comparative Example 2 (without silane anchoring) and Comparative Example 3 (without crosslinking) was significantly lower than that of Example 1, at only 45s and 30s respectively. This indicates that, in addition to the core-shell structure, the inorganic-organic chemical bonding and the ketone-hydrazine crosslinking network also played a crucial synergistic role in restricting molecular chain movement and improving coating hardness. Comparative Example 5, on the other hand, illustrates the limit of mineral filler content. Although excessive rigid filler increased the hardness to 75s, it completely destroyed flexibility (flexural endurance 4 points), rendering the coating useless. In summary, this invention successfully resolved the technical contradiction of "flexibility and surface hardness" in water-based barrier coatings through precise design of core-shell structure parameters and synergistic formulation.

[0192] Application Example 7: Performance evaluation of industrial and household composting of coated paper samples.

[0193] Experimental Description: This experiment aims to evaluate the biodegradability and disintegration performance of the paper-based barrier material described in this invention under different composting environments. Coated paper samples from Examples 1-9 and Comparative Examples 1-7 were selected (the substrate was 250g / m² food-grade white cardboard, and the dry weight of the coating was controlled at 12g / m²).

[0194] Industrial composting testing (refer to EN 13432:2000):

[0195] Disintegration rate test (ISO 16929:2021): Cut the paper sample into 25mm × 25mm square sheets and mix them with prepared biological waste (mixed vegetables, fruits, and garden waste, with a C / N ratio adjusted to 25:1) at a dry weight ratio of 1:10. Place the mixture in a 100L controlled composting bin. Maintain the temperature at 58±2℃ and the moisture content at 50-55%, turning and aerating the compost regularly. The test cycle is 12 weeks. After completion, pass the compost product through a 2mm sieve, collect the residue >2mm, wash, dry, and weigh it. Disintegration rate (%) = (initial sample dry weight - residue dry weight) / initial sample dry weight × 100%.

[0196] Biodegradability test (ISO 14855-1:2012): The method for determining aerobic biodegradation and carbon dioxide release under controlled composting conditions was employed. The pulverized sample was mixed with mature compost inoculum and placed in a closed reactor, incubated at 58±2℃ for 180 days. The percentage of biodegradation was calculated by continuously monitoring the amount of CO2 released (using cellulose as a reference, a relative biodegradation rate ≥90%).

[0197] Home composting test (refer to NF T 51-800:2015):

[0198] To simulate a home backyard composting environment, pre-cut samples were buried in a compost bin containing humus and household kitchen waste. The temperature was controlled at 25±5℃ (simulated ambient temperature), and suitable humidity was maintained. The testing period was extended to 26 weeks (disintegration) and 12 months (biodegradation). Disintegration rate (%) was defined as the proportion of sample fragments passing through a 2mm sieve to the initial sample dry weight, numerically equivalent to the 2mm sieve pass-through rate. According to relevant standards, a disintegration rate ≥90% is considered to meet the disintegration performance requirements.

[0199] Table 10. Performance test results of industrial composting and household composting in Application Example 7:

[0200]

[0201] Analysis: The test results of Application Example 7 reveal the environmental fate characteristics of the coating composition of the present invention at the end of the biological cycle. The data show that the introduction of bio-based components and the intelligent design of polymer networks have a decisive influence on composting performance.

[0202] All examples achieved 100% or near 100% disintegration under harsh high-temperature industrial composting conditions, with a stable biodegradation rate exceeding 91%. This is primarily attributed to the readily degradable nature of the paper-based fibers and the microbial-induced degradation mechanism of the polyhydroxyalkanoate (PHA) particles in the coating. As an excellent biodegradable material, PHA is rapidly colonized by microorganisms and secretes depolymerizing enzymes under high-temperature aerobic conditions. The resulting oligomers further promote the disintegration of the surrounding acrylic matrix. Notably, Examples 2 and 9, containing a high proportion of bio-based PHA (35 wt% and 36 wt%, respectively), performed exceptionally well in low-temperature home composting tests, achieving biodegradation rates of 94.5% and 94.2%, respectively, demonstrating the significant effect of high bio-based content on enhancing degradation rates under mild conditions.

[0203] In contrast, Comparative Example 4 used a traditional ordinary styrene-acrylic emulsion, whose main component is a non-degradable petroleum-based polymer. After the test, a large amount of coating debris remained, with an industrial disintegration rate of only 55.2% and a household compost biodegradation rate as low as 8.4%, completely failing to meet environmental protection requirements. Although Comparative Example 1 used a functionalized acrylic matrix, the lack of a PHA biodegradation "funnel" and the slow degradation of acrylic acid itself resulted in its inability to complete degradation within the specified time in household composting (biodegradation rate of only 58.4%).

[0204] Another key finding lies in the impact of crosslinking density on degradation. Comparative Example 6, due to the addition of an excessive amount of smart crosslinking agent (5.0 wt%), formed an overly dense network structure. This not only hindered swelling during alkaline resizing but also inhibited the intrusion of microorganisms and moisture during composting, resulting in its industrial disintegration rate (88.5%) failing to meet the standard, and its performance in home composting significantly declining. In contrast, although Examples 6 and 8 of this invention had relatively low PHA or mineral content, by controlling the crosslinking agent within a reasonable range of 0.3-3.2 wt%, they maintained performance without substantially hindering degradation, thus barely but successfully meeting the threshold for home composting (decomposition rate > 90%).

[0205] This invention endows packaging materials with green attributes throughout their entire life cycle through a synergistic strategy of "degradable bio-based particle filling" and "moderate intelligent cross-linking," enabling them not only to be recycled but also to safely return to nature when entering a composting system.

[0206] Experimental Results and Analysis:

[0207] Through a systematic study of the above-mentioned series of embodiments (Examples 1-9), comparative examples (Comparative Examples 1-7), and application examples (Application Examples 1 to 6), this invention comprehensively verifies the effectiveness of the resizing-compatible waterborne bio-based barrier coating composition in solving industry challenges such as the contradiction between barrier properties and resizing compatibility, and the balance between coating flexibility and surface hardness. The following is a detailed analysis of the influence trends of changes in the content of each key component and the microstructure on the overall performance of the material:

[0208] Analysis of the influence trend of the ratio of mineral barrier phase to film-forming matrix (pigment-to-binder ratio): By comparing the data of Example 6 (62 wt% film-forming matrix, 10 wt% mineral barrier phase), Example 1 (40 wt% film-forming matrix, 30 wt% mineral barrier phase), and Example 7 (15 wt% film-forming matrix, 46 wt% mineral barrier phase), a significant performance evolution pattern can be observed. As the content of mineral barrier phase increases from 10 wt% to 46 wt% (corresponding to an increase in pigment-to-binder ratio from 0.16 to over 3.0), the density of the coating is significantly enhanced, the WVTR decreases from 85 g / m²·d to 20 g / m²·d, and the OTR decreases from 420 mL / m²·d to 50 mL / m²·d, demonstrating the excellent physical barrier effect of high aspect ratio lamellar minerals. However, this improvement is accompanied by an increase in resizing difficulty, the alkaline dissociation time increases from 6 min to 25 min, and the fiber yield decreases from 99% to 90%. Comparative Example 5 further reveals the upper limit of this ratio: when the mineral content is too high, reaching 54 wt%, the pigment-to-binder ratio of the system becomes unbalanced, leading to microcracks in the coating during drying due to excessive internal stress. The wet strength retention rate abnormally increases to 450 g / m²·d, and the wet strength retention rate drops to 25%, with 100% leakage occurring during thermoforming. This indicates that controlling the mineral barrier phase within the range of 10 wt% to 46 wt% and the film-forming matrix ≥ 15 wt% is a necessary condition for maintaining the physical integrity and flexibility of the coating.

[0209] Analysis of the influence trend of the content of the intelligent crosslinking system: The intelligent crosslinking system (polyhydrazine compound + functional silane) exhibits a precise regulatory effect in the range of 0.3wt% to 3.2wt%. Although Example 6 (0.3wt% crosslinking agent) has relatively weak barrier properties, it provides excellent resizing yield; while Example 7 (3.2wt% crosslinking agent) achieves excellent damp heat resistance (72% wet strength retention) and extremely low OTR by constructing a high-density interpenetrating network. Data from Comparative Example 3 (no crosslinking) and Comparative Example 4 (ordinary non-functionalized matrix) show that the lack of effective ketone-hydrazine crosslinking and silane anchoring leads to rapid coating failure in damp heat environments (hot oil leakage rate as high as 20%), and the formation of large-sized adhesives during resizing due to the lack of swelling assistance from hydrophilic groups. Conversely, in Comparative Example 6, increasing the crosslinking agent dosage to 5.0 wt% resulted in an excessively dense network that locked down the movement of polymer chains. This prevented effective reverse reaction or swelling under alkaline conditions at pH 10.5, causing the resizing yield to plummet to 65%, rendering it unusable for industrial recycling. Therefore, a crosslinking agent content range of 0.3 wt% to 3.2 wt% is the key window for achieving the intelligent response characteristic of "stable during use and dissociable during recycling."

[0210] Effect of PHA Particle Size and Content: A comparison of Example 8 (PHA 13.8 wt%) and Example 2 (PHA 35 wt%) shows that with increasing PHA content, the bio-based carbon content of the coating significantly increases (from 20% to 70%) without negatively impacting barrier properties. In fact, its semi-crystalline properties fill matrix pores, helping to reduce OTR. However, controlling the PHA particle size is crucial. Comparative Example 7 used D... 50 Coarse PHA particles, with a diameter of 5.0 μm, resulted in pinhole defects on the coating surface, leading to a hot water leakage rate of 15% and a significant decrease in barrier performance (WVTR of 180 g / m²·d). This confirms the necessity of limiting the PHA particle size to the range of 0.2 μm to 2.0 μm in this invention; only fine dispersion below the micrometer level can effectively fill rather than destroy the pores of the polymer network.

[0211] Microstructure and Mechanism Analysis: The microscopic characterization of Example 5 directly confirms the structural design concept of this invention. The core-shell structure of the functionalized acrylic polymer is clearly visible under TEM, and all the high-performance examples, such as Examples 1-9, exhibit characteristic strong absorption peaks of C=N (ketone-hydrazine bond) and Si-O-Si (siloxane bond) in FTIR spectra, proving the successful construction of the organic / inorganic dual network. SEM cross-sectional morphology shows that the silane-modified minerals are oriented in the matrix, while the PHA particles are uniformly dispersed, forming a tortuous diffusion path. In contrast, Comparative Example 2, due to the lack of a silane coupling agent, exhibits micropores (phase separation) at the interface, leading to an increased hot water leakage rate.

[0212] The core-shell structure's balancing mechanism for mechanical properties: Based on the data trend analysis of Application Example 6, the "soft shell (Tg -5℃) / hard core (Tg 95℃)" structural parameters set in this invention are key to achieving the overall performance of the coating. Example data shows that this design enables the coating to maintain 0-level crease resistance (stress dissipation capability provided by the soft shell) while achieving a high pendulum stiffness of 50s to 70s (rigid support provided by the hard core). This characteristic is significantly superior to the homogeneous structure of Comparative Example 4 (low stiffness and prone to cracking), ensuring that the material does not experience brittle fracture or surface adhesion during high-speed paper cup forming and carton folding, perfectly adapting to modern packaging processing lines.

[0213] Correlation analysis between bio-based reinforcing phase and composting degradation performance: Based on the data trends from Example 7, the introduction of PHA particles is a key driver for achieving home composting degradation. Comparing Example 8 (PHA 13.8 wt%) and Example 2 (PHA 35 wt%), the biodegradation rate in the home composting environment increased from 90.1% to 94.5% with the increase in bio-based content. This indicates that PHA particles act as a preferential target for microorganisms in the early stages of degradation, and the resulting bio-erosion pores accelerate the disintegration of the entire coating system. This mechanism is particularly important in the low-temperature environment of home composting where microbial activity is low. The decomposition rate of only 58.4% in Comparative Example 1 (without PHA) in home composting further confirms that even with hydrophilic groups, a simple acrylic matrix is ​​difficult to achieve complete mineralization under mild conditions. Furthermore, while ensuring barrier properties, the intelligent crosslinking system did not significantly inhibit biodegradation (e.g., in Example 7, a 3.2 wt% crosslinking agent still maintained a 92.9% decomposition rate). However, once the crosslinking agent was in excess (Comparative Example 6, 5.0 wt%), the dense network structure significantly hindered the penetration of microbial enzymes, leading to degradation failure. Therefore, the component ratio range determined in this invention is not only based on the balance between barrier properties and resizing, but also a necessary condition for achieving fully biodegradable characteristics.

[0214] In summary, the resizingable waterborne bio-based high-barrier coating composition of the present invention, through precise control of the ratio of film-forming matrix, bio-based reinforcing phase, mineral barrier phase and intelligent crosslinking system, especially by utilizing the synergistic effect of 0.5wt% to 4.0wt% DAAM functional monomer and 0.3wt% to 3.2wt% intelligent crosslinking agent, successfully achieves a perfect unity of high barrier (WVTR≤ 100g / m²·d, OTR≤500mL / m²·d), high tolerance (oil resistance grade 12, resistant to damp heat), excellent machinability (combining high folding endurance and high surface hardness) and full recyclability (fiber yield ≥90%, no adhesives) in a single material, solving the technical pain points of non-degradability of traditional plastic coatings and difficulty in recycling traditional waterborne coatings.

[0215] 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 resizing water-based bio-based high-barrier coating composition, characterized in that, The composition is an aqueous dispersion system that, upon drying and curing, forms a dry coating film. This dry coating film forms a barrier layer with a multi-interpenetrating network structure and comprises the following components by weight percentage based on the total dry weight of the solid components: The film-forming matrix, comprising 15 wt% to 62 wt%, is a functionalized acrylic polymer dispersion obtained by emulsion polymerization. The functionalized acrylic polymer has a core-shell structure, comprising a shell layer with a glass transition temperature of -15°C to 10°C and a core layer with a glass transition temperature of 80°C to 110°C. The polymer backbone contains 0.5 wt% to 4.0 wt% of diacetone acrylamide and / or acetoacetic acid shell structural units and 0.2 wt% to 2.0 wt% of alkoxysilane core structural units. Bio-based reinforcing phase, 10 wt% to 40 wt%, with a median particle size D 50 The particles are 0.2 μm to 2.0 μm polyhydroxy fatty acid ester particles; the mineral barrier phase is 10 wt% to 46 wt%, which is a sheet-like inorganic mineral material modified in situ with an alkoxysilane coupling agent; The smart crosslinking system, ranging from 0.3 wt% to 3.2 wt%, is a crosslinking agent composition comprising a polyhydrazine compound and a silane coupling agent containing an epoxy group or an amino group; the weight percentage is calculated as 100 wt% of the sum of the solid dry weight of the film-forming matrix, the bio-based reinforcing phase, the mineral barrier phase, and the smart crosslinking system. The solid dry weight of the mineral barrier phase includes the dry weight of the sheet-like inorganic mineral material and the dry weight of the alkoxysilane coupling agent used for its in-situ modification. The solid dry weight of the intelligent crosslinking system includes the dry weight of the polyhydrazine compound and the dry weight of the epoxy- or amino-containing silane coupling agent in the intelligent crosslinking system. The composition further includes water as a dispersion medium and 0.1 wt% to 5.0 wt% of additives based on total dry weight of solids; Based on a 100wt% standard, the sum of the solid dry weights of the film-forming matrix, the bio-based reinforcing phase, the mineral barrier phase, and the intelligent crosslinking system is used. The mass ratio of the bio-based reinforcing phase to the film-forming matrix is ​​0.25 to 2.5, the mass ratio of the mineral barrier phase to the film-forming matrix is ​​0.15 to 3.2, the film-forming matrix and the mineral barrier phase are chemically anchored in situ through siloxane covalent bonds, and the intelligent crosslinking system constructs an organic / inorganic dual crosslinking network in the dry coating film. When the composition is coated onto the surface of a paper or paperboard substrate containing at least 50 wt% cellulose fibers, and tested under alkaline pulping conditions of pH > 10 and temperature of 40°C to 80°C according to the PTS-RH 021:2012 method, the fiber yield of the resulting paper is ≥ 90%, the adhesive on the coarse and fine sieves does not form visible flakes with an area > 2 mm², and the total organic fluorine content of the dry film of the coating is less than 5 mg / kg, i.e., undetectable, as determined by oxygen bomb combustion-ion chromatography.

2. The resizing-compatible waterborne bio-based high-barrier coating composition according to claim 1, characterized in that, The functionalized acrylic polymer dispersion has a core-shell structure, comprising: The shell is a polyacrylic acid or polyacrylic acid comethacrylic acid structure rich in carboxyl groups. The shell is copolymerized from an acidic monomer and a monomer containing a post-crosslinking group. The acidic monomer is selected from one or more of acrylic acid, methacrylic acid, itaconic acid, fumaric acid and their half-esters. The monomer containing the post-crosslinking group is selected from one or more of diacetone acrylamide, acetylacetoethyl methacrylate and acetylacetoethyl acrylate. The core layer is a copolymer structure rich in hydrophobic monomers and functional silane monomers. The hydrophobic monomers are selected from one or more of aromatic vinyl monomers and C1 to C18 alkyl acrylate or methacrylate monomers. Aromatic vinyl monomers include styrene and α-methylstyrene. C1 to C18 alkyl acrylate or methacrylate monomers include one or more of butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, and butyl methacrylate. The functional silane monomers are selected from one or more of vinyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-aminopropyltriethoxysilane.

3. The resizing-compatible water-based bio-based high-barrier coating composition according to claim 1, characterized in that, The bio-based reinforcing phase is composed of the polyhydroxy fatty acid ester particles, wherein the polyhydroxy fatty acid ester is selected from short-chain polyhydroxy fatty acid esters, medium- and long-chain polyhydroxy fatty acid esters, or copolymers formed by copolymerizing monomers that form short-chain polyhydroxy fatty acid esters with monomers that form medium- and long-chain polyhydroxy fatty acid esters. Among them, the short-chain polyhydroxy fatty acid ester is selected from one or more of poly-3-hydroxybutyrate, poly-3-hydroxybutyrate-co-3-hydroxyvalerate, poly-3-hydroxybutyrate-co-3-hydroxyhexanoate, and poly-3-hydroxybutyrate-co-4-hydroxybutyrate; 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-hydroxydodecanate), and poly(3-hydroxytetradecanoate). The polyhydroxyalkanoate particles fill the polymer network pores of the film-forming matrix in the form of a semi-crystalline discrete phase in the dry coating film.

4. The resizing-compatible water-based bio-based high-barrier coating composition according to claim 1, characterized in that, The intelligent crosslinking system includes: a first crosslinking agent, which is the polyhydrazine compound, which reacts with the carbonyl structural unit in the film-forming matrix to form an organic crosslinking framework through a ketone-hydrazine reaction; the polyhydrazine compound is selected from one or more of diacylhydrazine, sebacylhydrazine, succinic acid diacylhydrazine, isophthalic acid diacylhydrazine, and terephthalic acid diacylhydrazine. The second crosslinking agent is the epoxy- or amino-containing silane coupling agent, which hydrolyzes and condenses in the aqueous dispersion system and undergoes a condensation reaction with the surface of the sheet-like inorganic mineral material and the film-forming matrix to form an inorganic / organic framework. The epoxy- or amino-containing silane coupling agent is selected from one or more of γ-glycidoxypropyltrimethoxysilane and γ-aminopropyltriethoxysilane. The organic / inorganic dual crosslinked network remains stable under acidic to neutral conditions, and undergoes reversible dissociation or swelling under alkaline conditions.

5. The resizing-compatible aqueous bio-based high-barrier coating composition according to claim 1, characterized in that, The mineral barrier phase is a lamellar or layered inorganic mineral material with an aspect ratio ≥ 50, and is selected from one or more of the following categories: Layered silicate minerals include kaolinite, montmorillonite, talc, muscovite, and sericite; Layered silicates obtained through chemical exfoliation or synthesis; During the preparation process, the mineral barrier phase is modified in situ by the alkoxysilane coupling agent, so that its surface is grafted with active groups that can undergo condensation reactions with hydroxyl, carboxyl or silanol groups in the film-forming matrix.

6. The resizing-compatible aqueous bio-based high-barrier coating composition according to claim 1, characterized in that, The composition exhibits shear-thinning rheological characteristics, with a low shear rate of 0.1 s⁻¹ at 25°C. -1 The viscosity ranges from 1000 mPa·s to 5000 mPa·s, with a high shear rate of 10000 s⁻¹. -1 The viscosity at that time ranged from 20 mPa·s to 200 mPa·s.

7. The resizing-compatible aqueous bio-based high-barrier coating composition according to claim 1, characterized in that, The composition contains ≥25% bio-based carbon as a percentage of total organic carbon.

8. A paper-based barrier material, comprising a fiber substrate and a barrier coating applied to at least one side of the fiber substrate, characterized in that, The barrier coating is formed by drying and curing the resizing water-based bio-based high barrier coating composition of claim 1, wherein the fiber substrate is paper, paperboard, or pulp molding article containing at least 50 wt% cellulose fiber, and the paper-based barrier material meets one or more of the following comprehensive performance indicators: 1) Repulpingability: Tested according to PTS-RH 021:2012 under alkaline pulping conditions with pH > 10 and temperature between 40°C and 80°C. Fiber yield ≥ 90%, and the adhesive on coarse and fine sieves does not form visible flakes with an area > 2 mm². 2) Barrier properties: Water vapor transmission rate ≤100g / m²·d at 38℃ and 90% relative humidity, and oxygen transmission rate ≤500mL / m²·d at 23℃ and 50% relative humidity; 3) Oil resistance: Oil resistance grade ≥ 10 according to TAPPI T559 test; 4) Heat resistance and adhesion: The adhesion level is ≤1 after being placed at 60℃ and 10kPa pressure for 24 hours.

9. The paper-based barrier material according to claim 8, characterized in that, The paper-based barrier material has industrial composting and / or household composting degradation properties, wherein: Under industrial composting conditions, tested according to EN 13432:2000 standard, the disintegration rate is ≥90% after 12 weeks and the biodegradation rate is ≥90% after 180 days; Under home composting conditions, according to the NF T 51-800:2015 standard test, the disintegration rate is ≥90% after 26 weeks and the biodegradation rate is ≥90% after 12 months.

10. The application of the paper-based barrier material according to claim 8 in paper food packaging, paper industrial packaging, or paper medical packaging that requires alkaline pulping and recycling, characterized in that, The paper food packaging, paper industrial packaging, or paper medical packaging is subjected to both humid and hot environments and / or oily media during use, wherein: The paper food packaging includes at least one of the following: disposable paper cups, instant noodle paper buckets, paper bowls that can directly hold hot oil or hot soup, hamburger paper, takeaway food boxes with the barrier coating on the inner wall, and inner wall coating of pulp molded tableware. The paper industrial packaging includes at least one of the following: a heavy-duty cardboard box waterproof layer for withstanding high humidity and condensation, and an inner paper bag for holding oily chemical raw materials or lubricating oil. The paper medical packaging includes at least one of medical dialysis paper and medical sterile wrapping paper that need to be recycled into pulp after use.

11. A method for preparing a resizing aqueous bio-based high-barrier coating composition according to claim 1, characterized in that, Includes the following steps: Step 1. Mineral activation: Disperse the flaky inorganic mineral material in water, adjust the pH of the system to 9 to 11, and stir at a shear rate of 800 r / min to 2000 r / min for 10 to 40 minutes at 20°C to 35°C. At the same time, add the alkoxysilane coupling agent dropwise to allow the silane to undergo an in-situ hydrolysis and condensation reaction on the mineral surface to obtain a modified mineral slurry. Step 2. Film-forming matrix composite: The functionalized acrylic polymer dispersion is slowly added to the modified mineral slurry obtained in Step 1, while maintaining the system temperature ≤40℃ and the shear rate at 300r / min to 800r / min. Stirring is continued for 10min to 30min to fully disperse the minerals in the film-forming matrix, thus obtaining a mineral-containing film-forming matrix dispersion system. Step 3. Introduction of biological phase and pH adjustment: In the mineral-containing film-forming matrix dispersion system obtained in Step 2, the pH of the system is adjusted to 7.5 to 9.

0. Polyhydroxyalkanoate particle dispersion is slowly added at a rate of 300 r / min to 600 r / min under the condition of 20℃ to 30℃, and the addition time is 15 min to 60 min, so as to reduce the damage of shear to the crystal structure of polyhydroxyalkanoate, and a composite dispersion system containing polyhydroxyalkanoate is obtained. Step 4. Latent curing: In the composite dispersion system containing polyhydroxy fatty acid ester obtained in step 3, add the intelligent crosslinking system composed of the polyhydrazine compound and the silane coupling agent containing epoxy or amino groups and the required additives at a system temperature ≤30℃. Stir for 10 min to 30 min until the mixture is uniform. After filtering to remove coarse particles, the composition is obtained.

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