Bio-based barrier coating for fresh keeping of paper-based beverage as well as preparation method and application of bio-based barrier coating

Abstract

The invention discloses a bio-based barrier coating for fresh-keeping of paper-based beverages as well as a preparation method and application of the bio-based barrier coating, and belongs to the technical field of paper-based packaging materials for foods and beverages. The coating is a water-based emulsion, and the core solid components of the coating comprise polyhydroxyalkanoate, polyethylene furandicarboxylate, aliphatic polyester, a polyisocyanate cross-linking agent, a nanofiller, a surfactant and a plasticizer. An emulsion is prepared through melt crosslinking and high-shear emulsification, and a dry film is formed through curtain coating and orientation. The film has excellent oxygen and water vapor barrier properties, can be heat-sealed and re-pulpified, and can be biodegraded in industrial compost, household compost and marine environments. According to the preferred embodiment, the bio-based content can be higher than 99%, aluminum foil can be replaced to be used for 60-day fresh-keeping beverage packaging, carbon footprint is reduced, and the recovery value is improved.

Description

Technical Field

[0001] This invention belongs to the technical field of paper-based packaging materials for food and beverages, and particularly relates to bio-based barrier coatings for paper-based beverage preservation, their preparation methods, and applications. Background Technology

[0002] Currently, long-shelf-life packaging for liquid foods such as milk and juice mainly relies on aseptic paper / aluminum / polyethylene composite packaging, commonly known as Tetra Pak. The core of this type of packaging is the aluminum foil layer, which provides excellent barrier properties against oxygen, moisture, and light, ensuring a shelf life of six months or even longer. However, the presence of the aluminum foil layer also brings several intractable problems: First, recycling is difficult. During the repulping process of waste packaging, the aluminum-plastic portion is difficult to separate effectively from the paper fibers, resulting in low fiber recycling rates and high subsequent processing costs for the separated aluminum-plastic film; second, aluminum foil production is an energy-intensive process with a significant carbon footprint, contradicting environmental trends; third, packaging containing a metal layer cannot be used for microwave heating, limiting consumer convenience.

[0003] To address these challenges, the industry has been seeking "aluminum-free" alternatives. Existing solutions primarily involve using biodegradable polyesters, such as polylactic acid (PLA), polyhydroxyalkanoates (PHA), and polybutylene adipate terephthalate (PBAT), or using water-based wax emulsions as barrier layers. However, the barrier performance of these single materials is far from sufficient, with oxygen transmission rates (OTR) typically exceeding 20 cc·m. -2 ·d -1 ·atm -1 This makes it difficult to meet the requirement of preservation for several tens of days at room temperature. Furthermore, for food packaging applications, all components must comply with stringent food contact regulatory standards, such as those specified by the U.S. Food and Drug Administration (FDA) in Title 21 of the Codex Alimentarius. The components selected in this invention include bio-based components and alternative petroleum-based components, whose source substances or chemical properties help meet the relevant regulatory requirements for food contact applications.

[0004] Therefore, there is an urgent need in this field to develop a novel, aluminum foil-free, fully bio-based barrier coating technology, preferably fully bio-based, that can be implemented through an environmentally friendly water-based coating process. This technology needs to enable paper-based packaging to achieve barrier performance comparable to or even surpassing existing non-aluminum barrier solutions, while possessing good heat-sealing properties, re-sizing properties, and biodegradability in various environments such as industrial, household, and marine settings. This would allow the packaging to meet the needs of products with a medium shelf life, such as 60 days, while achieving a green and circular lifecycle throughout its entire lifecycle. Consumer and corporate sustainability goals, as well as regulations restricting single-use plastic waste, all necessitate recyclable packaging solutions. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art. This invention provides a bio-based barrier coating for paper-based beverage preservation, its preparation method and application. It aims to solve the problem that paper-based packaging faces difficulties in achieving barrier properties, recyclability, and biodegradability when seeking aluminum-free alternatives, especially in diverse scenarios such as home and ocean where it is difficult to balance degradability, bio-based content and processability.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] This invention provides a bio-based barrier coating composition for paper-based beverage preservation, the composition being in the form of an aqueous emulsion, wherein the solid components comprise, by weight percentage (wt%):

[0008] The content of PHA is 17% to 60%, for example, the content of PHA can be 17%, 20.5%, 22.7%, 30%, 31.8%, 33.3%, 34.0%, 39.5%, 45%, 48.2%, 50%, or 60%. The PHA can be poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), poly-3-hydroxybutyrate (PHB), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3HB4HB), or poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH).

[0009] 10-38.5% of polyethylene furanyl dicarboxylate (PEF), for example, the PEF content can be 10%, 18.0%, 20.0%, 21.9%, 25%, 27.3%, 30.5%, 31.8%, 33.3%, 34.0%, 36.0%, 38.5%.

[0010] 13-40% aliphatic polyester, wherein the bio-based aliphatic polyester may specifically be polybutylene succinate (PBS, including bio-based polybutylene succinate Bio-PBS), bio-based polybutylene adipate or its copolymers or polybutylene adipate terephthalate (PBAT), wherein Bio-PBS is preferred.

[0011] 1-8% of a polyisocyanate crosslinking agent, wherein the polyisocyanate crosslinking agent may be a lysine diisocyanate-based trimer (LDI Trimer) or a hexamethylene diisocyanate trimer (HDI Trimer). For example, the content of the crosslinking agent may be 1.0%, 1.5%, 2.7%, 2.9%, 3.5%, 4.0%, 5.0%, 6.5%, or 8.0%.

[0012] 0.5% to 3.0% of nanofillers, specifically nanocrystalline cellulose (NCC) or chitin nanocrystals, or graphene oxide (GO). For example, the content of the nanofillers can be 0.5%, 0.9%, 1.0%, 1.5%, 1.8%, 2.0%, 2.5%, 2.7%, 2.9%, or 3.0%.

[0013] 1-6% surfactant, specifically sodium cocoyl sulfate (SCS) or sodium dodecyl sulfate (SDS); for example, the content of the surfactant may be 1.0%, 1.5%, 2.0%, 2.6%, 2.7%, 2.9%, 3.0%, 3.6%, 4.0%, 5.5%, or 6.0%.

[0014] 2-12% plasticizer, specifically bio-based tributyl citrate (Bio-TBC) or tributyl citrate (TBC); for example, the content of the plasticizer may be 2.0%, 4.0%, 5.5%, 7.0%, 7.3%, 7.6%, 7.8%, 8.0%, 9.1%, 10.0%, 11.5%, or 12.0%.

[0015] The dry film formed by the composition with a diameter of 18–25 µm has an OTR of no more than 5.5 cc·m⁻¹ at 23°C and 0% relative humidity. -2 ·d -1 ·atm -1 The water vapor transmission rate (WVTR) at 38℃ and 90% relative humidity is no higher than 10.5 g·m. -2 ·d -1 .

[0016] The aqueous emulsion's D 90 The particle size is 300 nm to 2.3 µm, the absolute value of the Zeta potential is 25 to 45 mV, the solid content is 30 to 50%, and the viscosity at 25 °C is not higher than 4000 mPa·s.

[0017] The mass ratio of PHA to PEF is 0.44:1 to 6:1; for example, the mass ratio can be 0.44:1, 1:1, 1.8:1, 3.4:1, 5:1 or 6:1.

[0018] In a preferred embodiment, the bio-based carbon content of the solid component of the composition is not less than 99% of the total organic carbon, as determined by ASTM D6866-24A standard.

[0019] The present invention also provides a method for preparing the above composition, comprising the following steps:

[0020] Step 1. Melt-blend the PHA and PEF in a first temperature range of 145–165°C;

[0021] Step 2. Add the aliphatic polyester and the plasticizer in the second temperature zone of 170-200℃, and add the polyisocyanate crosslinking agent dropwise to carry out the crosslinking and curing reaction for 2-10 minutes;

[0022] Step 3. Heat the melt obtained in Step 2 for at least 20,000 seconds. -1 At a shear rate, it is emulsified in an aqueous phase at 70–90°C for 10–15 min, wherein the aqueous phase contains the surfactant;

[0023] Step 4. During or after step 3, add the aqueous dispersion of the nanofiller and continue dispersion;

[0024] Step 5. Cool to 25-30°C, adjust the pH to 6.5-7.5 with ammonia, and filter to obtain an aqueous emulsion.

[0025] The present invention further provides a metal-free barrier composite material, the structure of which includes at least:

[0026] The above composition forms a dry film layer with a thickness of 18–25 µm;

[0027] A heat-sealing layer with a thickness of 1–10 µm, wherein the heat-sealing layer is selected from polyethylene or compostable polyester. The compostable polyester may be one or more of PBS, PBAT, PHA, and PLA.

[0028] And the paper-based fiber layer.

[0029] Combined with appendix Figure 1 The structure of this metal-free barrier composite material is further described. The cross-sectional microstructure of the composite material, from bottom to top, includes at least: a paper-based fiber layer; and a barrier coating dry film coated on the paper-based fiber layer. The interior of the barrier coating dry film is primarily composed of a PHA / PEF blend continuous phase, in which nanofillers and plasticizer microphases are uniformly dispersed. The polymer chains form a stable three-dimensional network structure through polyisocyanate crosslinking points. A near-surface dense region is formed in the upper part of the barrier coating dry film, ultimately constituting the surface interface of the composite material.

[0030] This invention also provides a paper-based beverage packaging container, the inner wall of which contains the aforementioned metal-free barrier composite material. The container has a heat-sealing temperature of 150–170°C, and at this temperature, a heat-sealing strength of not less than 7.0 N / 15 mm, a re-pulping rate of not less than 78%, and meets at least one of the following degradation requirements: meeting the requirements for industrial compostability under ASTM D6400-23 standard; or meeting the requirements for home compostability under NF T51-800:2015 standard; or a biodegradability rate of not less than 90% within 365 days in a marine environment as specified in ASTM D6691-24A. By adjusting the component ratios within the defined composition range, the final product can meet one or more of the requirements for industrial composting, home composting, and marine environmental degradation.

[0031] The paper-based beverage packaging container of the present invention, when used to store acidic fruit juice beverages with a pH of 2.5 to 4.5 with a shelf life of 60 days, retains no less than 90% of the vitamin C after 60 days of storage at 23°C and 50% relative humidity.

[0032] Compared with existing technical solutions, the present invention has at least the following beneficial effects:

[0033] High Barrier Performance: This invention constructs a synergistic barrier structure of "physical crosslinking + nanomaze" by blending highly crystalline PHA with highly rigid PEF, toughening it with aliphatic polyester, and then introducing nanofillers. By selecting bio-based components, the bio-based content of the coating can be higher than 99%. The resulting coating film achieves comparable levels in both OTR and WVTR, sufficient to meet the requirements of beverage packaging with a 60-day shelf life. In a preferred embodiment, by selecting bio-based components such as Bio-PBS, LDI Trimer, NCC, SCS, and Bio-TBC, the bio-based content of the coating can be higher than 99%, achieving a balance between high barrier performance and a fully bio-based composition.

[0034] Environmentally friendly water-based preparation process: This invention uses a melt crosslinking-high shear emulsification method, which does not use organic solvents throughout the process, thereby avoiding the emission of volatile organic compounds (VOCs).

[0035] Comprehensive Recycling and Degradation Performance: Since it contains no aluminum foil, the packaging container produced by this invention can be efficiently re-sizing, with a re-sizing rate meeting the industrial recycling threshold of no less than 78%, and the preferred embodiment achieving a level exceeding 95%. Simultaneously, the coating microparticles provided by this invention can be biodegraded under industrial composting conditions. The preferred embodiment has also passed rigorous degradation tests in household composting and marine environments, thus achieving a closed-loop cycle of "product-waste-resource" to varying degrees, supporting the concept of green packaging. Furthermore, the cross-linked network formed by this invention helps improve recycling efficiency. Under alkaline re-sizing conditions, the urethane bonds (-NH-COO-) connecting the polymer backbone are sensitive to alkaline hydrolysis and can break. This disruption of cross-linking points reduces the overall strength and integrity of the coating film, making it more susceptible to breakage under hydraulic shear and detachment from the paper fibers. Simultaneously, the presence of other components in the coating (such as surfactants or unreacted hydrophilic groups) synergistically promotes the dispersion and disintegration of the coating in water, thereby achieving a re-sizing rate of over 95%, significantly superior to traditional aluminum-plastic composite packaging.

[0036] Certification compatibility and standard compliance: The technical solution of this invention has been systematically verified, and its performance indicators meet the core requirements of BPI industrial compostability certification (based on ASTM D6400-23) and TÜV AUSTRIA household compost certification (based on NF T51-800:2015), providing downstream applications with environmentally compliant packaging solutions.

[0037] Adjustability and Adaptability Boundaries of the Technology Platform: This invention is not merely a fixed formulation, but a flexible technology platform. By fine-tuning the proportions of components such as crosslinking agents and plasticizers within the required component range, effective control can be achieved between different objectives such as "optimal barrier performance" and "optimal degradation performance in a specific environment (e.g., marine)." This ability to achieve multi-objective optimization within the same chemical system is the non-obvious inventiveness of this invention, providing a technological foundation for meeting diverse application needs. Attached Figure Description

[0038] Figure 1 : A schematic diagram of the cross-sectional microstructure of the coating of the present invention on a paper or paperboard substrate.

[0039] In the figure, 1 is the paper-based fiber layer; 2 is the barrier coating dry film; 3 is the PHA / PEF blend continuous phase; 4 isocyanate crosslinking point; 5 is the near-surface dense region; 6 is the nanofiller; 7 is the plasticizer microphase; and 8 is the surface interface. Detailed Implementation

[0040] 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.

[0041] Main reagents and raw materials:

[0042] Table 1. Main Raw Material Names, Functions, Key Indicators / Models, and Suppliers:

[0043]

[0044] Main analytical and testing instruments:

[0045] Co-rotating twin-screw extruder, model: ZSE 18, manufacturer: Leistritz.

[0046] High shear disperser, model: T-25 ULTRA-TURRAX, manufacturer: IKA.

[0047] Nanoparticle size and Zeta potential analyzer, model: Zetasizer Nano ZS, manufacturer: Malvern.

[0048] Oxygen permeability tester, model: OX-TRAN Model 2 / 21, manufacturer: MOCON.

[0049] Water vapor transmission rate tester, model: PERMATRAN-W Model 3 / 33, manufacturer: MOCON.

[0050] Laboratory biaxial stretching machine, model: KARO IV, manufacturer: Bruckner.

[0051] Intelligent electronic tensile testing machine, model: XLW(PC), manufacturer: Labthink.

[0052] Standard pulp disintegrator, model: SKZ1025, manufacturer: SKZ International Co., Limited.

[0053] Respirometer, Model: RESPIROMETRIC Sensor System 6, Manufacturer: VELPSCIENTIFICA.

[0054] Plant growth chamber, model: SciBrite LED Plant Growth Chamber, manufacturer: GenevaScientific.

[0055] Inductively Coupled Plasma Mass Spectrometer (ICP-MS), Model: Agilent 7850 ICP-MS, Manufacturer: Agilent Technologies.

[0056] Main testing standards:

[0057] OTR: ASTM F1927-20.

[0058] WVTR: ASTM F1249-20.

[0059] Heat seal strength: ASTM F88 / F88M-23.

[0060] Repulping rate: ISO 5263.

[0061] Industrial compost biodegradability: ISO 14855-1:2012.

[0062] Industrial composting disintegration: ISO 16929:2021.

[0063] Biodegradability and disintegration of household compost: NF T51-800:2015.

[0064] Marine biodegradability: ASTM D6691-24A.

[0065] Ecotoxicity (plants): OECD Guideline 208.

[0066] Ecotoxicity (earthworms): OECD Guideline 222.

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

[0068] Heavy metal content: ICP-MS analysis, referring to the limits of 40 CFR Part 503.13.

[0069] Particle size distribution: ISO 13320:2020;

[0070] Examples and Comparative Examples:

[0071] Synthesis of LDI Trimer:

[0072] S1: Synthesis of L-lysine ethyl ester diisocyanate (LDI) monomer.

[0073] L-Lysine ethyl ester dihydrochloride was placed in dry chlorobenzene, and a stoichiometric excess of triphosgene was slowly added dropwise over 2 hours at 130°C. The reaction was carried out with continuous stirring, and the byproduct hydrogen chloride gas was removed through an outlet tube. The disappearance of the amino group of the starting material was monitored by infrared spectroscopy. After the reaction was complete, the solvent and excess phosgenating agent were removed by vacuum distillation to obtain crude LDI monomer. Finally, high-purity LDI monomer was obtained by fractional distillation under high vacuum conditions.

[0074] S2: Catalytic trimerization of LDI.

[0075] The purified LDI monomer was dissolved in dry ethyl acetate. Under nitrogen protection, a catalytic amount of potassium acetate was added. The reaction system was heated to 70°C and maintained. The NCO content was monitored by periodic sampling titration. When the NCO functional group conversion measured by titration reached 65-70%, stoichiometric amounts of phosphoric acid were added to deactivate the catalyst. Finally, the solvent was removed by vacuum rotary evaporation to obtain the final LDI Trimer product.

[0076] General preparation process:

[0077] Melt crosslinking: PHA and PEF were weighed according to the formulations of the examples and comparative examples in Tables 2 and 3, and added to the first temperature zone of a twin-screw extruder at 160°C for melt blending for 3 min. Subsequently, the corresponding toughening agent, plasticizer, and crosslinking agent were added, and the mixture was reacted in the second temperature zone at 190°C for 5 min to obtain a homogeneous reactive melt.

[0078] Emulsification: The molten material is precisely fed into a high-shear emulsification vessel containing 85°C deionized water, in which the formulated amount of surfactant has been pre-dissolved. The emulsification process is carried out at a rate of not less than 20,000 seconds. -1 High-shear emulsification was performed at a shear rate of 12 min.

[0079] Nanofiller dispersion: 10 wt% of the nanofiller aqueous dispersion was slowly added to the above emulsion under ultrasonic assistance, and shearing was continued for 3 min to ensure uniform dispersion.

[0080] Post-processing: The emulsion is rapidly cooled to 28°C using a plate heat exchanger, the pH is adjusted to 6.9 using ammonia, and finally filtered through an 80µm filter to obtain the final product.

[0081] Casting and Orientation: The obtained emulsion was coated onto a PET substrate using a doctor blade, and the wet film thickness was controlled to obtain the target dry film thickness shown in Tables 2 and 3. The coating was then fed into a biaxial stretching machine, and according to the settings in Tables 2 and 3, it was first stretched longitudinally at 65°C, then stretched transversely at 95°C, and finally heat-set at 120°C for 10 seconds to obtain the final barrier film.

[0082] Table 2. Formulations, preparation parameters, and physicochemical properties of the products in the examples (preferably all-bio-based formulations):

[0083]

[0084] Table 3. Comparative formulations, preparation parameters, and physicochemical properties of the products (petroleum-based formulations):

[0085]

[0086] In order to comprehensively and systematically verify the performance, applicability and effectiveness of the technical solution of the present invention within the scope defined by the present invention, representative formulations were selected for comparative testing in subsequent application examples.

[0087] Reasons for formula selection and explanation of the applicability of protection scope:

[0088] Example 1: Selected as a preferred representative of the all-bio-based scheme of the present invention. All its core components, such as Bio-PBS, LDI Trimer, NCC, and Bio-TBC, are bio-based, directly reflecting a core innovation of the present invention: achieving >99% bio-based content and excellent overall performance without sacrificing performance.

[0089] Comparative Example 2: It was selected as the highest technical benchmark for performance comparison with this invention because it exhibited the best overall barrier performance among all petroleum-based formulations. This formulation used petroleum-based components (PBAT, HDI, GO) commonly found in the prior art.

[0090] Example 2: Selected as a representative example demonstrating the "adjustability" of the fully bio-based technology platform of this invention. Based on Example 1, this formulation, within the scope defined by this invention, fine-tunes the ratio of crosslinking agent to plasticizer. This formulation was chosen to demonstrate that the technical solution of this invention is not a fixed formulation point that can only achieve a single optimal performance, but rather a highly flexible technical platform. Inventors can effectively balance and trade off between different objectives, such as "maximizing barrier performance" and "optimizing degradation performance in specific environments (e.g., marine)," by reasonably controlling the component ratios, thereby meeting diverse market demands. This fact strongly supports the rationality and necessity of the wider component range claimed by this invention.

[0091] By directly comparing Example 1 with Comparative Example 2, it can be clearly demonstrated that while achieving the significant improvement of "fully bio-based," the performance indicators of this invention can reach or even surpass those of optimized petroleum-based solutions. Furthermore, by introducing Example 2 for comparison, it can be proven that the technical solution of this invention is not an isolated point, but a flexibly adjustable platform, thus strongly supporting the rationality and advancement of the scope of protection claimed by this invention.

[0092] Application Example 1: Packaging performance verification.

[0093] Example 1 (the preferred all-bio-based formulation) and Comparative Example 2 (the optimal partially petroleum-based formulation) were compared. The emulsions prepared from both formulations were coated onto a 120 g / m² substrate using gravure coating. 2 An 18µm thick barrier layer was formed on food-grade cardboard after drying. Subsequently, a 5µm thick polyethylene layer, including Bio-PE or PE, was laminated onto this barrier layer using an extrusion lamination process as a heat-sealing layer and a food contact layer, creating a metal-free barrier composite material. This composite material was then used to make 250mL gable-top packages for filling orange juice. The packaged orange juice samples were stored at 23°C and 50% relative humidity for 60 days, and compared with orange juice packaged using standard paper / aluminum / plastic composite packaging as a control group.

[0094] Table 4 shows the test results of packaging and barrier performance in Application Example 1:

[0095]

[0096] The results of Application Example 1 demonstrate that the performance indicators of Example 1 of the present invention in practical packaging applications, including the ability to protect the contents, packaging integrity, and mechanical properties, are highly comparable to those of Comparative Example 2 and very close to those of traditional aluminum foil-containing packaging. Furthermore, its resizing rate is significantly higher than that of traditional aluminum foil-containing packaging, proving its complete feasibility as a high-performance, fully bio-based, commercially viable, and easily recyclable aluminum foil alternative.

[0097] Application Example 2: Biodegradability Test of Industrial Compost.

[0098] Example 1 and Comparative Example 2 were selected. This comparison aims to demonstrate that both the preferred all-bio-based and partially petroleum-based schemes of the present invention can achieve excellent industrial compostability within the required composition range, thus supporting the performance specifications of the present invention. The coated film samples were tested according to ISO 14855-1:2012.

[0099] Table 5 shows the test results of the biodegradability performance of industrial compost in Application Example 2:

[0100]

[0101] Application Example 3: Performance verification of home composting.

[0102] Example 1 and Comparative Example 2 were selected. Home composting is a higher standard for measuring the environmental friendliness of materials, and this test aims to demonstrate the environmental superiority of the technical solution of the present invention.

[0103] Table 6. Performance verification results of home composting in Application Example 3 (based on NF T51-800:2015):

[0104]

[0105] The comprehensive test results of Application Example 3 show that the preferred all-bio-based formulation of the present invention (Examples 1 and 2) and Comparative Example 2 as the benchmark fully comply with the requirements of NF T51-800:2015 standard for compostable materials for home use, proving that they can safely and completely return to nature in a low-temperature, uncontrolled home composting environment, supporting the relevant requirements of the present invention for home composting performance.

[0106] Application Example 4: Pre-assessment for BPI industrial compost certification.

[0107] The 250mL metal-free composite beverage box prepared in Application Example 1 from Example 1 and Comparative Example 2 was selected. The final product form was used for testing to most realistically simulate its performance in an industrial composting facility and verify its feasibility for commercial application.

[0108] Table 7 Application Example 4: Pre-assessment Results of BPI Industrial Compostability Certification (Based on ASTM D6400-23):

[0109]

[0110] * Note: This requirement means that the content of regulated heavy metals in packaging materials, such as arsenic, cadmium, copper, lead, mercury, nickel, selenium, and zinc, must be less than 50% of the limits specified in Table 3 of the U.S. Environmental Protection Agency regulation 40 CFR §503.13. This is one of the standard requirements for BPI industrial compostability certification.

[0111] The results of Application Example 4 show that the packaging containers made from the compositions of the present invention, whether the preferred fully bio-based or partially petroleum-based formulations, meet the requirements of ASTM D6400-23 standard regarding biodegradability, disintegration, ecotoxicity, and heavy metal content, and possess all the technical conditions for applying for BPI certification.

[0112] Application Example 5: Verification of high bio-based content and barrier performance.

[0113] Example 1 and Comparative Example 2 were selected. This comparison directly demonstrates the inventiveness and effectiveness of the present invention in replacing traditional petroleum-based components (PBAT, HDI, GO) with specific fully bio-based components (Bio-PBS, LDI Trimer, NCC), and the ability to achieve high bio-based content in the preferred embodiment.

[0114] Table 8. Verification results of high bio-based content and barrier performance in Application Example 5:

[0115]

[0116] The data from Application Example 5 clearly demonstrates that Example 1 shows almost no difference in core barrier performance compared to the optimized Comparative Example 2, but its bio-based content jumps from approximately 73% to 99.6%. Meanwhile, the data from Example 2 also shows that even with minor adjustments for other performance aspects, its barrier performance remains at an extremely high level, and the bio-based content remains unchanged. This proves that the present invention achieves a balance between "high barrier performance" and "fully bio-based" in the preferred embodiment, strongly supporting the effectiveness of the present invention's requirement for high bio-based content.

[0117] Application Example 6: Validation of biodegradability in marine environments.

[0118] Example 1, Example 2, and Comparative Example 2 were selected for comparison. This test aims to demonstrate that:

[0119] 1) The preferred bio-based formulation of this invention can be designed to achieve marine degradation;

[0120] 2) By fine-tuning the components (such as crosslinking agents and plasticizers) within the scope of this invention, a balance can be achieved between barrier performance and specific environmental degradation, which reflects the technical depth and platform value of the present invention.

[0121] 3) The preferred all-bio-based scheme of the present invention outperforms the petroleum-based scheme without specific design in this respect.

[0122] Table 9. Application Example 6: Validation results of biodegradability performance in marine environment.

[0123]

[0124] The results of Example 6 clearly demonstrate that:

[0125] (1) Example 2, as a formulation optimized for the marine environment, has a 365-day biodegradability rate of up to 91.0%, which meets the requirements for marine biodegradability.

[0126] (2) Example 1, as a formulation optimized for barrier properties, although its marine degradation rate was lower than the target of 90% (66.5%), still showed a significant degradation trend, far superior to Comparative Example 2. This indicates that its marine degradation performance can be effectively controlled by optimizing the ratio of crosslinking agent and plasticizer in the formulation. For example, reducing the crosslinking agent content can increase the activity of polymer segments and the accessibility of hydrolytic enzymes, while increasing the plasticizer content can further promote degradation. Given the inherently high marine biodegradability of PHA as a core component, and its synergistic effect in promoting the degradation of other components in the blend, those skilled in the art can reasonably expect that a higher marine degradation rate can be achieved by further fine-tuning the component ratio or extending the testing time. This strongly demonstrates that the inventors can effectively and predictably control the relationship between barrier properties and marine degradation properties by adjusting the component ratio.

[0127] (3) Comparative Example 2, as the petroleum-based optimal barrier formulation, has a marine degradation performance that is far inferior to the preferred all-bio-based formulation of the present invention.

[0128] Therefore, this test not only proves the marine degradation capability of the present invention, but more importantly, it demonstrates the flexibility and advancement of the invention as a technological platform.

[0129] Application Example 7: Migration test of food contact materials.

[0130] The test formulations used were Example 1 and Comparative Example 2. This test aims to demonstrate that both the preferred fully bio-based novel material system of this invention and the system containing some petroleum-based materials can meet stringent food safety regulations under the composition defined by this invention.

[0131] The test method was conducted in accordance with US FDA regulation 21 CFR 176.170. 18µm coated films prepared with the two formulations were used as test samples and contacted with three food simulants (10% ethanol, 50% ethanol, and n-heptane) at 40°C for 240 hours.

[0132] Table 10 Application Example 7: Migration Test Results of Food Contact Materials

[0133]

[0134] The results of Application Example 7 show that, under simulated long-term room temperature food contact conditions, the total migration amount and the migration level of specific substances of the composition of the present invention are far below the safety limits of the US FDA for food contact materials, proving that it is suitable for the food packaging field.

[0135] Experimental Results and Analysis:

[0136] To more clearly demonstrate the performance of the compositions of the present invention, the following table summarizes the dry film barrier performance of all embodiments and key comparative examples.

[0137] Table 11 shows the dry film barrier performance of the examples and key comparative examples as follows:

[0138]

[0139] Analysis of the impact of core components on barrier properties:

[0140] The necessity of PEF: Comparing the OTR of Comparative Example 2 and Comparative Example 9 in Table 11, it can be seen that the introduction of PEF has a decisive impact on barrier properties. As a high-rigidity, high-barrier polyester, PEF's rigid furan ring structure effectively reduces the free volume of the polymer chain, significantly improving barrier performance.

[0141] Necessity of Nanofillers: Comparing the OTR of Comparative Example 2 and Comparative Example 11 in Table 11, the results show significant differences. This confirms that the two-dimensional sheet-like nanofillers form a physical "maze effect" in the polymer matrix, extending the tortuous path for oxygen and water molecule penetration, which is key to achieving high barrier properties.

[0142] The necessity of crosslinking agents: More specifically, by comparing Comparative Examples 10 and 11 in Table 3, the decisive role of crosslinking agents can be more clearly revealed. Although neither has poor barrier properties due to the absence of nanofillers, Comparative Example 11 still forms a relatively stable emulsion, while the physical properties of the emulsion in Comparative Example 10 completely collapse. This strongly demonstrates that the stable pre-crosslinked network formed by the crosslinking agent during the melting stage is a prerequisite for obtaining processable emulsions and high-performance films, and its role is indispensable.

[0143] Analysis of the impact of process on barrier properties:

[0144] Effect of bidirectional orientation: Comparing the OTR (2.3) of Comparative Example 2 (2×2 bidirectional orientation) and the OTR (18.7) of Comparative Example 12 (unoriented) in Table 11, bidirectional orientation reduced the OTR by 88%. This is because biaxial stretching promotes the orderly alignment of polymer chains and nanofiller sheets along the membrane plane, forming a denser layered structure that further seals the gas permeation channels. Therefore, the effective performance comparisons in this specification are mainly conducted under the same bidirectional orientation process.

[0145] Analysis of the influence of functional components and formulation range:

[0146] Effect of hydrophilic polymers on resizing rate: Comparing the resizing rates of Comparative Example 2 and Comparative Example 4 in Table 3, and the resizing rate of Comparative Example 3, the results clearly show that the introduction of hydrophilic PVA segments can significantly improve the dispersion and disintegration ability of the coating in water, thereby improving the resizing efficiency. It should be emphasized that PVA is introduced in some of the comparative examples as a known, non-essential processing aid, with the aim of establishing an effective technical benchmark to highlight the superior performance achieved by the core composition of this invention without relying on such additional aids, rather than making PVA an essential component of the composition of this invention.

[0147] Experimental support for formulation range: To fully support the broad component range defined by this invention, Examples 3 to 7 were designed and implemented specifically to verify the performance of the fully bio-based system when the content of each component reaches the boundary values ​​of the claimed protection range. As shown in Table 11, the dry films formed from these samples formulated under boundary conditions all meet the performance thresholds defined by this invention in terms of OTR and WVTR values.

[0148] The results of Examples 3 and 4 show that even when the proportion of the main polymer matrix reaches an extreme, the required barrier performance can still be maintained by adjusting other components.

[0149] The results of Examples 5 and 6 demonstrate that the crosslinking agent and the nanofiller can compensate for each other to a certain extent and jointly construct an effective barrier network, thereby supporting a wide content range for both.

[0150] The results of Example 7 confirm that even under extreme conditions of auxiliary agent content, the core technical solution of the present invention remains robust and effective.

[0151] The experimental data from Examples 3 to 7, together with Examples 1 and 2, cover the boundaries and central regions of the multidimensional component space defined by the present invention from multiple dimensions, proving that the core technical solution of the present invention is effective within the entire defined component range, demonstrating its good formulation robustness, and providing sufficient experimental support for the scope of protection claimed by the present invention.

[0152] Analysis of the trend influence of the main polymer ratio: The high crystallinity of PHA and the high rigidity of PEF are the foundation for achieving high barrier properties. The barrier performance is optimal when the mass ratio of PHA to PEF is close to 1:1. Bio-PBS, as a toughening agent, is key to balancing flexibility and barrier properties; increasing its content will decrease barrier performance. Therefore, the amount of Bio-PBS should be appropriately controlled while meeting basic mechanical properties.

[0153] Feasibility and advantages analysis of the all-bio-based approach:

[0154] A key aspect of this invention lies in achieving a preferred, fully bio-based formulation, as shown in Example 1. Comparing Example 1 with the best-performing Comparative Example 2, their OTR and WVTR are very close. This strongly demonstrates that bio-based aliphatic polyesters, bio-based polyisocyanate crosslinking agents, and bio-based nanofillers can completely replace their corresponding petroleum-based materials without sacrificing core barrier properties. This series of substitutions not only maintains the "nanomaze" barrier effect but also successfully increases the bio-based content of the coating from approximately 73% to 99.6%, achieving a high bio-based content.

[0155] The realization of multi-environment degradation performance and the value of the technology platform:

[0156] The advancement of this invention lies not only in achieving superior performance in a single area, but also in its high flexibility as a technological platform. As shown in Application Example 6, by fine-tuning the formulation—that is, adjusting the ratio of crosslinking agent to plasticizer within the scope disclosed in this invention—a balance can be achieved between maintaining high barrier performance and achieving degradation in specific environments, such as the ocean. This demonstrates the technological depth of this invention's platform and its adaptability to different application scenarios. This controllability is the core embodiment of the invention's inventiveness.

[0157] In summary, this invention successfully prepared a high-performance barrier coating by optimizing polymer compounding, utilizing reactive cross-linking curing, introducing nanofillers, and combining environmentally friendly aqueous emulsification processes with subsequent orientation techniques. This solution rivals existing optimized formulations in performance, and the preferred implementation significantly improves sustainability. Its formulation serves as a flexible technological platform, allowing for fine-tuning to meet biodegradability requirements in various environments, including industrial, residential, and marine settings. The coating achieves a good balance in barrier properties, mechanical properties, heat-sealing properties, resizing properties, and biodegradability, providing a feasible industrial solution for replacing aluminum foil layers in paper-based packaging.

[0158] 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 bio-based barrier coating composition for paper-based beverage preservation, characterized in that, The composition is in the form of an aqueous emulsion, wherein the sum of its solid components by weight percentage is 100%, comprising: 17-60% polyhydroxy fatty acid esters; 10–38.5% polyvinyl furanate; The mass ratio of the polyhydroxyalkanoate to the polyethylene furanyl dicarboxylate is 0.44:1 to 1.8:

1. 13-40% bio-based polybutylene succinate; 1-8% lysine diisocyanate trimer crosslinking agent; 0.5–3.0% nanocrystalline cellulose; 1-6% surfactant; 2-12% plasticizer; The aqueous emulsion's D 90 The particle size is 300 nm to 2.3 µm, the absolute value of the Zeta potential is 25 to 45 mV, the solid content is 30 to 50%, and the viscosity at 25 °C is not higher than 4000 mPa·s. The bio-based carbon content of the solid component of the composition shall be not less than 99% of the total organic carbon, as determined by ASTM D6866-24A. The 18–25 µm dry film formed by the composition has an oxygen permeability of no more than 5.5 cc·m at 23°C and 0% relative humidity. -2 ·d -1 ·atm -1 Under conditions of 38℃ and 90% relative humidity, the water vapor transmission rate is no higher than 10.5 g·m. -2 ·d -1 .

2. The bio-based barrier coating composition for paper-based beverage preservation according to claim 1, characterized in that, The bio-based carbon content of the solid components of the composition is not less than 99% of the total organic carbon, as determined by ASTM D6866-24A standard.

3. The method for preparing the bio-based barrier coating composition for paper-based beverage preservation according to claim 1, characterized in that, Includes the following steps: Step 1. Melt-blend the polyhydroxy fatty acid ester and the polyethylene furanyl dicarboxylate in a first temperature zone of 145–165°C; Step 2. Add the bio-based polybutylene succinate and the plasticizer in the second temperature zone of 170-200℃, and dropwise add the lysine diisocyanate trimer to carry out a cross-linking and curing reaction for 2-10 minutes; Step 3. Heat the melt obtained in Step 2 for at least 20,000 seconds. -1 At a shear rate, it is emulsified in an aqueous phase at 70–90°C for 10–15 min, wherein the aqueous phase contains the surfactant; Step 4. During or after step 3, add the aqueous dispersion of the nanocrystalline cellulose and continue dispersion; Step 5. Cool to 25-30°C, adjust the pH to 6.5-7.5 with ammonia, and filter to obtain an aqueous emulsion.

4. A metal-free composite material, characterized in that, The composite material structure includes at least: The paper-based beverage preservation bio-based barrier coating composition according to claim 1 forms a dry film layer with a thickness of 18-25 µm; A heat-sealing layer with a thickness of 1–10 µm, wherein the heat-sealing layer is selected from polyethylene or compostable polyester; Paper-based fiber layer. The resizing rate of the composite material during laboratory resizing according to ISO 5263 standard is not less than 90%.

5. A paper-based beverage packaging container, characterized in that, The inner wall of the packaging container contains a metal-free barrier composite material as defined in claim 4, the container has a heat-sealing temperature of 150–170°C and a heat-sealing strength of not less than 7.0 N / 15 mm at this temperature, and meets at least one of the following degradation requirements: meets the requirements of ASTM D6400-23 for industrial compostability; or meets the requirements of NF T51-800:2015 for home compostability; or has a biodegradability rate of not less than 90% within 365 days in a marine environment as specified in ASTM D6691-24A.

6. The paper-based beverage packaging container according to claim 5, characterized in that, When the packaging container is used to store acidic fruit juice beverages with a pH of 2.5 to 4.5 with a shelf life of 60 days, the vitamin C retention rate is not less than 90% after 60 days of storage at 23°C and 50% relative humidity.

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