A repulpable recycled high barrier paper tube system for expanded food packaging and method of making the same

Abstract

The application discloses a kind of for puffed food package's re-pulp recycling high-barrier paper tube system and preparation method thereof.Paper tube system includes winding or enclosing barrel, bottom cover assembly, top seal assembly and barrier continuous reinforcement structure.The food containment cavity side paper base cut edge of barrel lap joint is covered with double-layer edge covering across end surface;Bottom cover assembly area and top seal area form annular continuous barrier structure respectively.The paper tube system is suitable for puffed food packaging, especially suitable for nitrogen-filled laminated puffed food packaging, which can improve the overall tube sealing, oxygen and moisture barrier, aroma retention and re-pulp adaptation performance within a certain process window.

Description

Technical Field

[0001] This invention belongs to the technical fields of paper-based food packaging materials, paper-based composite containers, puffed food packaging, resizing adaptable barrier packaging, and bio-based or biodegradable polymer packaging. It relates to a resizing recyclable high-barrier paper tube system for puffed food packaging and its preparation method. Background Technology

[0002] Puffed foods such as potato chips, French fries, puffed cereal chips, rice cakes, crisps, shrimp chips, shrimp crackers, and nut crisps are typically characterized by low moisture content, high oil content, easy moisture absorption, easy oxidation, easy loss of aroma, and easy breakage. During their shelf life, these foods require packaging systems that simultaneously possess functions such as moisture barrier, oxygen barrier, oil barrier, aroma preservation, puncture resistance, heat sealing, nitrogen filling for preservation, and structural compression resistance.

[0003] Traditional laminated puffed food paper tubes or composite paper cans typically use a paper-based tube body combined with aluminum foil, polyethylene (PE), polypropylene (PP), ethylene-vinyl alcohol copolymer (EVOH), or other plastic barrier layers. Aluminum foil provides oxygen, moisture, and light barrier capabilities; the PE layer provides heat sealing, moisture protection, and inner surface protection; and the EVOH layer provides oxygen barrier. However, the multi-material composite structure of paper, aluminum, plastic film, adhesives, and a metal bottom cap is difficult to separate efficiently at the recycling end, easily resulting in screen residue, aluminum-plastic residue, adhesive residue, and paper fiber loss.

[0004] Existing packaging technologies for stacked potato chips or other snack flakes disclose methods for stacking uniformly shaped flake foods into rigid tubular containers and improving shelf life through end sealing, oxygen and moisture barrier materials, and inert gases. For example, US3498798A discloses stacked snack flakes, rigid tubular containers, end seals, and oxygen and water vapor barrier requirements. While these technologies demonstrate that stacked flake foods, rigid tubular containers, end sealing, and nitrogen or inert gas preservation are existing packaging foundations, they do not address the issue of continuous barrier protection at the three nodes—the paper base trim, bottom cap, and top seal—in repulpable paper-based tubes.

[0005] Several local edge treatment solutions have been disclosed in existing paper-based edge protection technologies. For example, WO1992008652A1 discloses a solution that involves thinning or milling the edge of the coated paper to a thinner residual paper layer and then folding it back, and using a thermoplastic coating or sealing material to protect the cut edge; US8448844B2 discloses an airtight cardboard container with enhanced barrier performance, involving cardboard blank overlap seams, thinning and folding or barrier tape, bottom assembly and lid assembly. The above solutions can illustrate that paper-based cut edges, overlap seams and end seals are known weak points in the barrier of paper-based containers, but their focus is usually on a single seam or a single end seal structure. They do not simultaneously and continuously design the three actual leakage paths of the paper-based fiber cross section on the food-containing cavity side of the nitrogen-filled sheet-like expanded food paper tube, the bottom lid connection area and the top seal connection area, nor do they form a continuous barrier path on the food contact side jointly closed by a water-based high-barrier edge sealing layer, a bio-based or biodegradable polymer edge sealing layer, a bottom lid barrier layer and a top seal barrier layer.

[0006] Existing composite paper can technologies also disclose several inner lining and overlap sealing solutions. For example, US6350500B1 discloses a tubular composite container with a folded, unsupported membrane lining; US20070131750A1 discloses an unsupported, overlap-sealed inner lining for composite containers; and US20050252952A1 discloses a high-barrier inner lining for rolled-edge composite cans. These solutions typically achieve inner surface barrier and overlap sealing through polymer membrane linings, metallized films, or paperless linings. However, they primarily address the folding or overlapping of the membrane lining, rather than the paper-based fiber cross-section formed after the paper-based material is slit and located on the food-containing cavity side. For wound or enclosed paper tubes, the paper-based cut edges on the food-containing cavity side can form long-distance channels for moisture absorption, oil absorption, air leakage, and powder shedding extending along the tube's axial direction. Relying solely on membrane lining overlaps cannot directly solve the sealing problem of such paper-based cross-sections.

[0007] Heat-sealable, resizing-compatible, or cellulose-based multilayer packaging materials have also been disclosed. For example, EP4101631B1 discloses heat-sealable, resizing-compatible cellulose-based multilayer packaging materials and packaging containers; US11952720B2 discloses resizing-compatible packaging materials, involving paperboard substrates, barrier coatings, and resizing properties; WO2024194713A1 discloses polyhydroxyalkanoate (PHA) dispersion coating compositions and coated cellulose-based substrates. The above technologies demonstrate that paper-based, cellulose-based, water-based barrier, bio-based barrier, and resizing-compatible materials can be used at the packaging material level, but they still mainly focus on flat sheets, coated substrates, or general packaging materials, and do not transform flat material barrier into continuous three-dimensional barrier at the seams, bottom cap, and top seal of nitrogen-filled, stacked, expanded food paper tubes.

[0008] Materials such as PHA, polylactic acid (PLA), polybutylene succinate (PBS), polybutylene adipate terephthalate (PBAT), and polyvinyl alcohol (PVOH, also written as PVA) provide a material basis for replacing traditional aluminum foil, PE coating, and EVOH layers. Among the relevant disclosures, CN120026524B relates to an aqueous emulsion blended with PHA, PBAT, and PVOH and its application in paper-based barrier coatings; CN120250392B relates to a PHA / PVA nanoscale paper-based barrier emulsion; CN120925357A relates to a re-sizing and biodegradable PHA heat-sealing barrier coating and its composition; CN121407420A and its B text relate to a dual PHA barrier system for paper-based containers and paperboards; CN121738061A and its B text relate to a paper-based high-barrier material composited with an aqueous PHA coating and a PHA extrusion layer; CN121697975B relates to a paper-based molded coffee capsule and an in-situ film-forming barrier heat-sealing composite layer of PHA aqueous dispersion. The above disclosures can provide a material basis for sealing, barrier, heat-sealing, or re-sizing adaptability for paper-based packaging.

[0009] However, the disclosed technologies primarily focus on the paper-based material layer, planar coated substrate, general paper-based container material, partial sealing areas of the paper-based container, or partial heat-sealing structures of molded containers. They do not directly address the overall structure of the paper-based cut edge on the food-containing cavity side of the rolled or enclosed puffed food paper tube, the axial overlap sealing area, the bottom cover annular connection area, the top seal annular connection area, and the intersection of the axial seam and the upper and lower annular sealing structures, which together form a continuous barrier path on the food contact side. For nitrogen-filled, stacked puffed food paper tubes, planar material barrier properties alone are insufficient to guarantee nitrogen filling retention, oxygen and moisture barrier properties, and shelf-life stability. Without continuous bridging of the paper-based fiber cross-section on the food-containing cavity side, the bottom cover connection area, the top seal connection area, and their intersections, short-circuiting of oxygen, water vapor, oils, or aroma components may still occur.

[0010] For stacked puffed food paper tubes, barrier failure does not only occur on intact planar materials. Even if the planar sheet has a good barrier layer, after tube forming, short-circuiting of oxygen, water vapor, oil, or aroma components may still occur in the overlapping sealing area of ​​the tube body, the paper base cut edge on the food receiving cavity side, the bottom cover roll-sealing or pressing area, the top heat-sealing area, the tube opening end face, the edge of the molded part, and the corner of the molded part. Simply improving the barrier performance of the planar coating is insufficient to fully solve the problems of overall tube sealing and shelf-life stability of nitrogen-filled stacked puffed food paper tubes.

[0011] The molding substrates for paper-based food packaging are not limited to conventional wood pulp paperboard, but also include bamboo pulp paper, bamboo pulp paperboard, sugarcane pulp paper, straw pulp paper, recycled fiber paper, pulp molded parts, bamboo pulp molded parts, and other plant fiber molded parts. These types of paper-based or plant fiber molded substrates typically have high porosity and large surface roughness, and edges, cut surfaces, and corner areas are prone to forming weak points in barrier protection. Without systematic sealing, barrier coating, heat-sealing moisture-proof layer lamination, and edge sealing treatment, it is difficult to meet the requirements of stacked puffed foods for moisture barrier, oxygen barrier, oil barrier, aroma preservation, and nitrogen filling retention.

[0012] The outer surface of stacked puffed food paper tubes typically needs to support functions such as brand printing, shelf display, abrasion and scratch resistance, fingerprint resistance, water droplet resistance, and a glossy or matte finish. Traditional solutions often use solvent-based varnishes, petroleum-based varnishes, UV-cured varnishes, or plastic coatings to protect the printed layer after printing. However, such surface protection structures may increase the proportion of volatile organic compounds, petroleum-based materials, plastic residue, and the burden of re-sizing. If only untreated paper is used as the printing surface, problems such as insufficient ink adhesion, poor printing color stability, ink smudging due to transportation friction, and insufficient water resistance of the outer surface may occur.

[0013] For stacked potato chips or other stacked puffed foods, consumers usually need to stick their fingers into the tube to eat after opening the paper tube, which is inconvenient and unhygienic, especially when there is little food left. Stacked puffed foods are also prone to friction and collision with the inner wall of the tube, the bottom cover connection area, the edge of the tube opening, or the torn edge of the top seal during transportation, opening, pouring, and eating, resulting in fragments, powder, and grease contamination.

[0014] If ordinary plastic trays, lifting parts, or dispensing parts are installed inside the paper tube, it will increase the burden of plastic parts and recycling and separation; if only uncoated paper cards are used to contact oily puffed foods, oil penetration, paper fiber shedding, moisture absorption and deformation, card sticking, fold cracking, or loss of food aroma may occur.

[0015] Therefore, a systematic barrier solution is needed for puffed food paper tubes, especially nitrogen-filled laminated puffed food paper tubes. This solution should utilize existing or similar water-based barriers, bio-based or biodegradable polymer heat seals, mineral-based sheet barriers, polyhydroxyalkanoate (PHA) material platforms, and resizing material platforms as material bases. This solution should be achieved through continuous barrier reinforcement in the tube body overlap sealing area, the paper base cut edge on the food-containing cavity side, the bottom cover connection area, the top seal connection area, the tube opening end face, the seam-bottom cover intersection barrier area, the seam-top seal intersection barrier area, and the edges or corners of the molded parts. This transforms the barrier capability of planar materials into a continuous barrier path around the food-containing cavity, closing the entire tube's food contact side. This improves the overall tube's moisture barrier, oxygen barrier, oil barrier, aroma retention, nitrogen filling retention, and resizing compatibility. Summary of the Invention

[0016] This invention provides a recyclable high-barrier paper tube system for puffed food packaging and its preparation method. It aims to solve the problems of existing puffed food paper tubes, especially nitrogen-filled laminated puffed food paper tubes, which, even after using paper-based barrier materials, bio-based or biodegradable polymer barrier layers, water-based barrier coatings, or multi-layer barrier composite materials, may still experience long seam cut edges, bottom cover annular connection areas, top seal annular connection areas, tube opening end faces, molded part edges, and molded part corner migration short circuits during the tube forming, overlapping, winding, pressing, nitrogen filling, and top sealing processes. Furthermore, it improves the moisture barrier, oxygen barrier, oil barrier, aroma preservation, nitrogen filling retention, and recyclability of the paper tube system without relying on traditional continuous aluminum foil or metal bottom covers as the main barrier components.

[0017] A recyclable high-barrier paper tube system for puffed food packaging includes a tube body, a bottom cover assembly, a top sealing assembly, and a continuous barrier reinforcement structure. The tube body, bottom cover assembly, and top sealing assembly enclose a food receiving cavity. The tube body is wound or formed from a paper-based tube body material and has an overlapping sealing area extending along the tube body axis. The paper-based tube body material includes a paper substrate and a composite barrier inner layer disposed on the side of the paper substrate facing the food receiving cavity. The composite barrier inner layer includes at least an aqueous barrier coating layer and a heat-sealable moisture-proof layer located on the side of the aqueous barrier coating layer facing the food receiving cavity. The overlapping sealing area has a paper substrate cut edge on the food receiving cavity side, which is the paper substrate fiber cross-section facing the food receiving cavity after tube formation. The paper substrate cut edge on the food receiving cavity side is covered or reinforced by a first sealing layer and a second sealing layer before winding or forming the tube. The first sealing layer spans the food receiving cavity. The end face of the paper base cut edge on the cavity side extends towards the adjacent inner wall surface and the overlapping interface. The second sealing layer covers the outside of the first sealing layer, or the second sealing layer overlaps, fuses, presses, covers, or bridging one or more of the composite barrier inner layer, heat-sealable moisture barrier layer, heat-sealing tape, or reinforcing tape, so that the paper base cut edge on the food receiving cavity side is isolated from the food receiving cavity. The barrier continuous reinforcing structure located in the overlapping sealing area forms a joint barrier continuous structure extending along the cylinder axially. The bottom cover assembly and the lower end of the cylinder form an annular bottom cover barrier continuous structure. The top sealing assembly and the upper end of the cylinder form an annular top sealing barrier continuous structure. The joint barrier continuous structure, the annular bottom cover barrier continuous structure, and the annular top sealing barrier continuous structure together form a food contact side continuous barrier path around the food receiving cavity. In some embodiments, the puffed food is a stacked puffed food that is filled with nitrogen or inert gas after filling.

[0018] In some embodiments, the paper tube system includes a tube body, a bottom cover assembly, a top sealing assembly, and a barrier continuous reinforcement structure. The tube body, bottom cover assembly, and top sealing assembly enclose a food receiving cavity for containing puffed food; in some specific embodiments, the puffed food is a nitrogen-filled, stacked puffed food. The tube body is formed by winding or enclosing a paper-based tube body material and has an overlapping sealing area. The paper-based tube body material includes a paper substrate and a composite barrier inner layer disposed on the side of the paper substrate facing the food receiving cavity.

[0019] In some embodiments, the composite barrier inner layer comprises, sequentially from the side closest to the paper substrate to the side closest to the food receiving cavity, a base coating sealing layer, an aqueous high-barrier coating layer, and a bio-based or biodegradable polymer heat-sealing moisture-proof layer. In other embodiments, the composite barrier inner layer may also include an aqueous barrier coating layer and a heat-sealing moisture-proof layer disposed on the side of the aqueous barrier coating layer facing the food receiving cavity.

[0020] The waterborne high-barrier coating layer comprises a waterborne film-forming continuous phase and a barrier-reinforcing phase. The primer sealing layer reduces the liquid absorption, pore permeability, and surface roughness of the paper substrate. The waterborne high-barrier coating layer forms a dense film and tortuous diffusion paths through a bio-based or biomass-based continuous phase, mineral substrate layers, sols, inorganic fillers, or nanocellulose, primarily reducing the migration of oxygen, oils, and aroma components. A bio-based or biodegradable polymer heat-sealing moisture-barrier layer covers the side of the waterborne high-barrier coating layer facing the food-containing cavity, forming a continuous hydrophobic or low-hygroscopic contact surface. This reduces water vapor ingress into the waterborne oxygen barrier layer, minimizes oxygen barrier performance degradation under high humidity conditions, and provides a puncture-resistant, abrasion-resistant, and heat-sealing contact interface.

[0021] In some specific designs, the primer sealing layer, the water-based high-barrier coating layer, and the bio-based or biodegradable polymer heat-sealing moisture barrier layer can be formed using the same PHA material platform or a bio-based material platform that can form a continuous interface with each other. The primer sealing layer can be a water-based PHA dispersion sealing layer with a dry coating weight of 2 g / m³. 2 Up to 10g / m 2 It can be 2g / m 2 3g / m 2 4g / m 2 5g / m 2 6g / m 2 8g / m 2 or 10g / m 2The waterborne high-barrier coating can be a blended waterborne emulsion coating composed of PHA, PBAT, and PVOH; a nanoscale waterborne barrier emulsion coating composed of PHA and PVOH; or a waterborne heat-sealing barrier coating composed of PHA waterborne dispersion, sheet-like barrier filler, and waterborne crosslinking agent. The bio-based or biodegradable polymer heat-sealing moisture barrier layer can be a PHA extruded dense layer, a PHA blended extruded layer, a PLA blended extruded layer, a PBS blended extruded layer, or a composite layer thereof. The aforementioned material platform can provide a sealing, barrier, heat-sealing, or re-sizing adaptation base in the planar area of ​​the paper substrate, and extends to key nodes after paper tube forming through continuous barrier reinforcement structures in the overlapping sealing area, bottom cover connection area, and top seal connection area.

[0022] In the overlapping sealing area of ​​the cylinder body, the paper-based cut edge of the food-containing cavity side is first covered by a water-based high-barrier sealing layer, and then by a bio-based or biodegradable polymer sealing layer. The water-based high-barrier sealing layer crosses the end face of the paper-based cut edge of the food-containing cavity side and extends 0.5 mm to 3 mm towards the adjacent inner wall surface and the overlapping interface. The bio-based or biodegradable polymer sealing layer covers the outside of the water-based high-barrier sealing layer and overlaps with the bio-based or biodegradable polymer heat-sealing tape or bio-based or biodegradable polymer reinforcing tape by 0.5 mm to 5 mm, forming a U-shaped covering, L-shaped covering, or continuous covering structure across the end face, so that the paper-based fiber cross-section of the paper-based cut edge of the food-containing cavity side is covered by the composite sealing layer and isolated from the food-containing cavity.

[0023] A bottom cover barrier layer and a bottom cover heat-sealing layer are provided on the side of the paper-based or plant fiber-based cover facing the food-containing cavity. The bottom cover barrier layer includes two or three of the following: a base coating sealing layer, a water-based high-barrier coating layer, and a bio-based or biodegradable polymer heat-sealing layer. The bottom cover barrier layer or bottom cover heat-sealing layer and the composite barrier inner layer form a 1mm to 8mm annular overlap in the bottom cover connection area, and together with the paper-based end face or the edge sealing layer at the lower end of the cylinder, a continuous annular bottom cover barrier structure is formed by heat sealing, hot pressing, rolling, or pressing, so that there are no exposed paper-based fiber sections communicating with the food-containing cavity between the bottom cover edge, the lower end face of the cylinder, and the inner wall of the cylinder.

[0024] The paper-based top sealing assembly has a top sealing barrier layer and a top sealing heat-sealing layer on the side facing the food receiving cavity. The upper end of the cylinder body has a cylinder mouth heat-sealing mating part and a cylinder mouth end face sealing layer. The top sealing barrier layer or the top sealing heat-sealing layer forms a 3mm to 10mm annular heat-sealing area with the cylinder mouth heat-sealing mating part in the top sealing connection area. This annular heat-sealing area spans the paper-based cut edge or cylinder mouth end face at the upper end of the cylinder body and overlaps, fuses, or presses with the cylinder mouth end face sealing layer, forming a continuous annular top sealing barrier structure. This ensures that there are no exposed paper-based fiber sections communicating with the food receiving cavity between the cylinder mouth end face, the edge of the paper-based top sealing assembly, and the inner wall of the cylinder body.

[0025] The continuous barrier reinforcement structure located in the overlapping sealing area includes a water-based high-barrier edge sealing layer, a bio-based or biodegradable polymer edge sealing layer, and a bio-based or biodegradable polymer heat-sealing tape or a bio-based or biodegradable polymer reinforcing tape. This continuous barrier reinforcement structure overlaps, covers, or bridging the paper-based cut edge on the food-containing cavity side, the composite barrier inner layer, and the bio-based or biodegradable polymer heat-sealed moisture-proof layer, forming a continuous joint barrier structure extending axially along the cylinder body.

[0026] The continuous seam barrier structure, the continuous annular bottom cover barrier structure, and the continuous annular top seal barrier structure together form a continuous barrier path on the food contact side around the food receiving cavity, consisting of the composite barrier inner layer, the bottom cover barrier layer, and the top seal barrier layer. In some embodiments, this continuous barrier path on the food contact side is formed by multiple overlapping, fused, pressed, covered, or bridging layers selected from the following: a base coating sealing layer, a water-based high-barrier coating layer, a bio-based or biodegradable polymer heat-sealing moisture barrier layer, a water-based high-barrier edge sealing layer, a bio-based or biodegradable polymer edge sealing layer, a bio-based or biodegradable polymer heat-sealing tape, a bio-based or biodegradable polymer reinforcing tape, a bottom cover barrier layer, a bottom cover heat-sealing layer, a top seal barrier layer, and a top seal heat-sealing layer.

[0027] The total basis weight of the paper-based tube material can be 80 g / m³ 2 Up to 800g / m 2 It can be 80g / m 2 120g / m 2 180g / m 2 250g / m 2 300g / m 2 350g / m 2 450g / m 2 600g / m 2 Or 800g / m 2 .

[0028] The wall thickness of the cylinder can be from 0.2mm to 3.0mm, specifically 0.2mm, 0.4mm, 0.6mm, 0.8mm, 1.0mm, 1.5mm, 2.0mm, 2.5mm, or 3.0mm.

[0029] The dry coating weight of the water-based high-barrier coating can be 12 g / m². 2 Up to 30g / m 2 It can be 12g / m 2 14g / m 2 15g / m 2 18g / m 2 20g / m 2 22g / m 2 25g / m 2 28g / m 2 Or 30g / m2 .

[0030] The content of the barrier reinforcing phase, based on the dry solids mass of the water-based high barrier coating layer, can be from 1 wt% to 80 wt%, and can be 1 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%, 65 wt%, or 80 wt%.

[0031] The thickness of the bio-based or biodegradable polymer heat-sealed moisture barrier can range from 3 μm to 40 μm, specifically 3 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, or 40 μm; its areal density can be 3 g / m³. 2 Up to 40g / m 2 It can be 3g / m 2 5g / m 2 8g / m 2 10g / m 2 12g / m 2 15g / m 2 20g / m 2 25g / m 2 30g / m 2 35g / m 2 or 40g / m 2 .

[0032] The overlap width of the overlapping sealing area can be from 3mm to 20mm, specifically 3mm, 4mm, 5mm, 6mm, 8mm, 10mm, 12mm, 15mm, 18mm, or 20mm.

[0033] The effective barrier width of the overlapping sealing area can be from 2mm to 18mm, specifically 2mm, 3mm, 4mm, 5mm, 6mm, 8mm, 10mm, 12mm, 15mm, or 18mm.

[0034] The extension width of the water-based high-barrier sealing layer to the adjacent inner wall surface and the overlap interface can be from 0.5mm to 3mm, specifically 0.5mm, 0.8mm, 1.0mm, 1.2mm, 1.5mm, 2.0mm, 2.5mm or 3.0mm.

[0035] The overlap width between the bio-based or biodegradable polymer edge sealing layer and the bio-based or biodegradable polymer heat-sealing tape or reinforcing tape can be from 0.5 mm to 5 mm, specifically 0.5 mm, 0.8 mm, 1.0 mm, 1.5 mm, 2.0 mm, 3.0 mm, 4.0 mm, or 5.0 mm.

[0036] The overlap width between the bottom cover barrier layer or bottom cover heat seal layer and the composite barrier inner layer in the bottom cover connection area can be 1mm to 8mm, specifically 1mm, 1.5mm, 2mm, 3mm, 4mm, 5mm, 6mm or 8mm.

[0037] The heat sealing width of the annular heat sealing zone can be from 3mm to 10mm, specifically 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, or 10mm.

[0038] In this invention, the continuous barrier path on the food contact side refers to a continuous barrier structure formed by overlapping, fusing, pressing, covering, or bridging the barrier layer, heat-sealing layer, edge sealing layer, and reinforcing structure surrounding the food receiving cavity and located on or near the food contact side. This continuous barrier path does not require that all functional layers be completely identical in material, but rather requires that there be no through-path short circuit between the cylinder body, overlapping sealing area, bottom cover connection area, top seal connection area, seam-bottom cover intersection barrier area, and seam-top seal intersection barrier area that would directly connect the paper-based fiber cross-section to the food receiving cavity.

[0039] The continuous barrier path on the food contact side is not a simple parallel arrangement of three independent sealing parts: axial joint seal, bottom cover seal, and top seal. Instead, a continuous bridging is formed at the intersection of the axial joint and the upper and lower annular sealing structures, so that the paper base cut edge on the food receiving cavity side, the paper base end face at the lower end of the cylinder, the edge of the bottom cover, the paper base cut edge at the upper end of the cylinder, and the cylinder mouth end face are all covered by the barrier layer, heat sealing layer, edge sealing layer, or reinforcing structure.

[0040] In this invention, the continuous barrier reinforcement structure refers to a water-based high-barrier edge sealing layer, a bio-based or biodegradable polymer edge sealing layer, a bio-based or biodegradable polymer heat-sealing tape, a bio-based or biodegradable polymer reinforcing tape, an edge or corner reinforcement, or a combination thereof, disposed at weak points in the paper tube system. The weak points include the tube body overlap sealing area, the paper base cut edge on the food receiving cavity side, the paper base end face at the lower end of the tube body, the bottom cover connection area, the top seal connection area, the tube opening end face, the edge of the molded part, the corner of the molded part, the roll sealing area, or the pressing area.

[0041] In this invention, repulping adaptation refers to the ability of the paper-based fibers in the paper tube system, after crushing, warm water dissociation, and screening, to form a fibrous pulp that can be used in recycled paper sheets or pulp systems, and where non-fiber components do not dominate the screen residue in the form of large amounts of continuous aluminum-plastic film, metal sheets, or large, difficult-to-disperse plastic sheets. Repulping adaptation does not require all non-fiber components to be converted into pulp fibers, nor does it exclude the formation of a certain amount of coarse screen residue, fine screen residue, mineral residue, coating fragments, or adhesives. The evaluation results of repulping adaptation may vary in different regions, recycling systems, and screening conditions. The repulping adaptation described in this invention mainly refers to the fact that the paper-based fibers have a basis for recycling under the aforementioned warm water dissociation and screening conditions, and reduces the residue of large-area continuous aluminum-plastic film and non-repulpable plastic components.

[0042] In this invention, the primary barrier component refers to a layered component that continuously covers the food-containing cavity in the continuous barrier path on the food contact side and undertakes the main functions of oxygen barrier, moisture barrier, or sealing. Local additives, discontinuous island residues, decorative layers on the non-food contact side, discontinuous reinforcement points, printed layers, or local functional layers on the non-food contact side are not considered primary barrier components.

[0043] In some embodiments, a paper-based pull-out support barrier is provided within the food receiving cavity. The paper-based pull-out support barrier includes a paper-based support body, a pull-out operating part, and a food contact barrier layer. The paper-based support body is at least partially located between the stacked sheet-like puffed food and the inner wall of the paper tube, or at the bottom of the stack, for supporting, arranging, or limiting the stack; the pull-out operating part is used to move the paper-based support body or the stacked sheet-like puffed food towards the tube opening after the paper-based top sealing assembly is opened; the food contact barrier layer is used to reduce the migration of oils, water vapor, or aroma components between the paper-based support body and the stacked sheet-like puffed food.

[0044] The paper-based pull-out support barrier card has a sealing layer or a continuous reinforcing barrier structure on its cut edges, folds, or exposed fiber cross-sections, so that it can be crushed, disintegrated, and screened together with the paper tube body.

[0045] The present invention also provides a method for preparing the above-mentioned paper tube system. The method includes providing a paper substrate, conditioning and cutting the paper substrate, forming an aqueous barrier coating layer on one side of the conditioned and cut paper substrate that will form the inner wall of the food receiving cavity, or sequentially forming a primer sealing layer and an aqueous barrier coating layer to obtain a paper-based material with a barrier coating layer; disposing a heat-sealable moisture-proof material on the surface of the aqueous barrier coating layer to form a heat-sealable moisture-proof layer, obtaining a paper-based tube material with a composite barrier inner layer; and pre-sealing the paper-based cut edge on the food receiving cavity side after tube forming to sequentially form a first seal. The first and second sealing layers are formed by winding or enclosing the pre-sealed paper-based cylindrical material to form a cylindrical body, creating a continuous seam barrier structure in the overlapping sealing area, connecting a bottom cover assembly with one or both of the bottom cover barrier layer and bottom cover heat seal layer on the food contact side to the lower end of the cylindrical body to form an annular bottom cover barrier continuous structure, filling the cylindrical body with puffed food and filling it with nitrogen or inert gas, and connecting a top sealing assembly with one or both of the top sealing barrier layer and top sealing heat seal layer on the food contact side to the upper end of the cylindrical body to form an annular top sealing barrier continuous structure.

[0046] This invention also provides a method for preparing a paper-based pull-out support barrier card. The method includes providing food-grade paperboard, bamboo pulp paperboard, paper-based composite sheet, molded pulp sheet, molded bamboo pulp sheet, or molded plant fiber sheet; forming a food contact barrier functional layer on the food contact side of the sheet; die-cutting, creasing, folding, or molding the substrate with the food contact barrier functional layer to form a paper-based support body and a pull-out operating part; and sealing or reinforcing the cut edges, fold lines, punched edges, or exposed fiber cross-sections.

[0047] Compared with the prior art, the use of this invention can achieve the following significant beneficial effects:

[0048] By extending the barrier design from the flat sheet to the overlap sealing area of ​​the cylinder, the paper base cut edge on the side of the food receiving cavity, the paper base end face at the bottom of the cylinder, the bottom cover connection area, the top seal connection area, the cylinder mouth end face, and the edge or corner of the molded part, the short-circuiting of oxygen, water vapor, oil and aroma migration after the cylinder is formed is reduced.

[0049] The structure, which uses a water-based high-barrier edge sealing layer and a bio-based or biodegradable polymer edge sealing layer to cover the paper-based cut edge of the food container cavity and isolate it from the food container cavity, reduces the probability of oil absorption, moisture absorption, paper dust shedding, interface penetration, and air leakage at long seams.

[0050] By using the annular bottom cover barrier continuous structure and the annular top seal barrier continuous structure, the bottom cover barrier layer, the top seal barrier layer and the composite barrier inner layer of the cylinder body are continuously transitioned in the end seal area, reducing the probability that the bottom and top become the weak points of the overall cylinder barrier.

[0051] The composite structure of the water-based high-barrier coating layer and the bio-based or biodegradable polymer heat-sealing moisture barrier layer respectively undertakes the functions of oxygen barrier, oil barrier, fragrance preservation, moisture barrier, heat sealing, and puncture resistance, avoiding the need for a single material to undertake all barrier functions.

[0052] By constructing tortuous diffusion paths using mineral-based water-based barrier materials, inorganic mineral sols, layered barrier fillers, or nanocellulose, the density, abrasion resistance, matting properties, anti-blocking properties, and auxiliary water resistance of water-based coatings can be improved.

[0053] By using external bio-based, biomass-based, mineral-based, or organic-inorganic composite water-based printable functional coatings, the outer surface printing, abrasion resistance, varnishing or matte finish, water resistance, and auxiliary barrier properties are integrated into the same paper tube system, reducing reliance on traditional varnishes or plastic films.

[0054] The paper-based pull-out support barrier card supports, arranges, limits, and allows for the pulling out of the stacked puffed food after opening. The food contact barrier layer and sealing layer reduce oil migration, moisture absorption deformation, paper powder shedding, and plastic residue.

[0055] By systematically matching paper-based fibers, bio-based or biodegradable polymer layers, water-based barrier layers, and mineral-based components, the paper tube system achieves a high paper-based fiber recovery rate after crushing, warm water dissociation, and screening, while reducing the residue of large-area continuous aluminum-plastic film. Attached Figure Description

[0056] Figure 1 This is a schematic diagram of the recyclable high-barrier paper tube system for puffed food packaging according to the present invention.

[0057] In the diagram, 1-bottom coating sealing layer of the cylinder body; 2-water-based barrier coating layer of the cylinder body; 3-barrier reinforcing phase of the cylinder body; 4-heat-sealable moisture-proof layer of the cylinder body; 5-first edge sealing layer; 6-second edge sealing layer; 7-paper base trimming edge of the food receiving cavity; 8-composite barrier inner layer; 9-heat-sealing tape for the seam; 10-bottom coating sealing layer of the bottom cover; 11-water-based barrier coating layer of the bottom cover; 12-heat-sealing layer of the bottom cover; 13-cylinder body; 14-top sealing assembly; 5-Heat-sealing mating part at the tube opening; 16-Overlap sealing area; 17-Paper-based pull-out support barrier card; 18-Bottom cover assembly; 19-Top sealing paper base layer; 20-Top sealing water-based barrier coating layer; 21-Top sealing heat-sealing layer; 22-Top sealing annular heat-sealing area; 23-Annular bottom cover barrier continuous structure; 24-Pre-sealed edge paper base tube material; 25-Cellling intermediate body; 26-Annular top sealing barrier continuous structure; 27-Paper tube system. Detailed Implementation

[0058] 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.

[0059] like Figure 1 As shown, the tube body 13, bottom cover assembly 18, and top sealing assembly 14 enclose a paper tube system 27. An overlap sealing area 16 is provided on one side of the tube body 13. The tube opening mates with the top sealing assembly 14 via a heat-sealing mating part 15, forming a top sealing annular heat-sealing area 22 and an annular top sealing barrier continuous structure 26 at the top. The food contact side of the tube body 13 consists of a composite barrier inner layer 8 composed of a tube body bottom coating sealing layer 1, a tube body water-based barrier coating layer 2, a tube body barrier reinforcing phase 3, and a tube body heat-sealable moisture-proof layer 4. The overlap is covered by a first sealing layer 5 and a second sealing layer 6, which cover the paper base cut of the food receiving cavity side. The edge 7 is reinforced with a heat-sealing strip 9 to strengthen the joint barrier; in the bottom partial structure, the bottom cover bottom coating sealing layer 10, the bottom cover water-based barrier coating layer 11 and the bottom cover heat-sealing layer 12 cooperate with the bottom cover assembly 18 to form an annular bottom cover barrier continuous structure 23 at the bottom; in the top sealing partial structure, the top sealing paper base layer 19, the top sealing water-based barrier coating layer 20 and the top sealing heat-sealing layer 21 constitute the top sealing side barrier structure; the figure below also shows the pre-sealed edge paper base tube material 24 being wound or enclosed to form a tube intermediate body 25, and further forming an annular top sealing barrier continuous structure 26, finally obtaining the paper tube system 27.

[0060] The main reagents and raw materials are shown in Table 1.

[0061] Table 1. Main reagents and raw materials.

[0062]

[0063] The main analytical and testing instruments are shown in Table 2.

[0064] Table 2. Main analytical and testing instruments.

[0065]

[0066] The main testing standards are as follows.

[0067] Paper, paperboard, and pulp specimens were treated according to GB / T 10739-2023, "Standard Atmospheric Conditions for the Treatment and Testing of Paper, Paperboard, and Pulp Specimens." The basis weight of paper and paperboard was determined according to GB / T 451.2-2023, "Paper and Paperboard - Part 2: Determination of Basis Weight." The thickness of paper and paperboard was determined according to GB / T 451.3-2002, "Determination of Thickness of Paper and Paperboard."

[0068] The absorbency of the paper was determined according to GB / T 1540-2002 "Determination of absorbency of paper and paperboard - Cobb method".

[0069] Water vapor transmission rate was determined according to GB / T 1037-2021 "Determination of Water Vapor Transmission Performance of Plastic Films and Sheets - Cup Method for Weight Gain and Loss". Oxygen transmission rate was determined according to GB / T 19789-2021 "Test of Oxygen Transmission Performance of Plastic Films and Sheets for Packaging Materials - Coulometric Method".

[0070] The gas permeability differential pressure test was conducted according to GB / T 1038.1-2022 "Test Methods for Gas Permeability of Plastic Products - Films and Sheets - Part 1: Differential Pressure Method". The composite layer peel strength was tested according to GB / T 8808-1988 "Test Method for Peel Strength of Flexible Composite Plastic Materials". The heat seal strength was tested according to QB / T 2358-1998 "Test Method for Heat Seal Strength of Plastic Film Packaging Bags".

[0071] The tensile strength of paper and paperboard was determined according to GB / T 12914-2018 "Determination of Tensile Strength of Paper and Paperboard - Constant Rate Tensile Test (20 mm / min)". The specular gloss of paper and paperboard was determined according to GB / T 8941-2013 "Determination of Specular Gloss of Paper and Paperboard".

[0072] Grease resistance of paper and paperboard was determined according to GB / T 22805.2-2008 "Determination of Grease Resistance of Paper and Paperboard - Part 2: Surface Repulsion Method". The oil resistance rating of the Kit was evaluated using the Kit reagent incremental contact method, referring to TAPPI T 559 cm-22 "Grease resistance test for paper and paperboard". Specific operating procedures are detailed in Application Example 1.

[0073] The sealing strength of the flexible barrier material was tested according to ASTM F88 / F88M-23, "Standard Test Method for Seal Strength of Flexible Barrier Materials".

[0074] The water bath leak test for packaging was performed in accordance with ASTM F2096-11(2019) "Standard Test Method for Detecting Gross Leaks in Packaging by Internal Pressurization".

[0075] Dye penetration testing was performed in accordance with ASTM F3039-23, "Standard Test Method for Detecting Leaks in Nonporous Packaging or Flexible Barrier Materials by Dye Penetration".

[0076] Vacuum decay leak detection was performed in accordance with ASTM F2338-09(2020) "Standard Test Method for Nondestructive Detection of Leaks in Packages by Vacuum Decay".

[0077] The repulpability assessment was conducted in accordance with TAPPI UM 213 "Repulpability of Splices / Splicing Tape" and in conjunction with PTS-RH 021:2012 (Draft Oct 2019) "Identification of the recyclability of paper and board packages and of graphic print products".

[0078] The evaluation of paper and paperboard materials and products for food contact is conducted in accordance with GB 4806.8-2022 "National Food Safety Standard: Paper and Paperboard Materials and Products for Food Contact". The evaluation of plastic materials and products for food contact is conducted in accordance with GB 4806.7-2023 "National Food Safety Standard: Plastic Materials and Products for Food Contact". Migration tests on food contact materials and products are conducted in accordance with GB 31604.1-2023 "National Food Safety Standard: General Rules for Migration Tests on Food Contact Materials and Products". Total migration is determined in accordance with GB 31604.8-2021 "National Food Safety Standard: Determination of Total Migration in Food Contact Materials and Products".

[0079] Acid value in food was determined according to GB 5009.229-2025, "National Food Safety Standard - Determination of Acid Value in Food". Peroxide value in food was determined according to GB 5009.227-2023, "National Food Safety Standard - Determination of Peroxide Value in Food". For oily solid foods such as potato chips, puffed cereal chips, nut chips, and shrimp chips, the samples were first crushed, mixed, and the oil was extracted. Then, the extracted oil was used as the test object for acid value and peroxide value determination.

[0080] The general preparation process of the recyclable high-barrier paper tube system for puffed food packaging in Examples 1 to 11 is as follows, with nitrogen-filled stacked puffed food packaging as a representative application scenario.

[0081] Step 1: Provide paper substrate, equilibrate at 23°C and 50% relative humidity for 24 hours, and cut into paper substrate sheets suitable for coating and tube forming to obtain conditioned paper substrate.

[0082] Step 2: Apply a primer sealing treatment to the food contact side of the conditioned paper substrate. The primer sealing solution is prepared from sodium carboxymethyl cellulose, hydroxypropyl starch, silica sol, and water, with a solid content of 10 wt%. After coating, it is dried at 80°C for 2 minutes to obtain a paper substrate with a primer sealing layer.

[0083] Step 3: Following the formulations described in each embodiment, one or more of the following are mixed: a polyhydroxyalkanoate aqueous dispersion, a PVOH aqueous solution, an aqueous film-forming material, a barrier reinforcing phase, and water. The aqueous barrier coating solution is prepared using high-speed dispersion, colloid milling, sand milling, bead milling, online dispersion, or a combination thereof. In laboratory preparation, dispersion at 12000 r / min for 10 min, followed by sand milling for 20 min, can be used. For continuous production, online high-shear dispersion and circulating sand milling can be employed to ensure that the particle size, viscosity, and sedimentation stability of the coating solution meet the coating requirements. The coating solution is filtered through an 80-200 mesh screen before use to reduce coating defects caused by particles, gels, or coarse fillers.

[0084] Step 4: Apply the water-based high-barrier coating liquid to the surface of the paper substrate with the primer sealing layer, and dry it under three hot air conditions of 60℃, 70℃ and 85℃ for 1 min, 1 min and 2 min respectively to obtain the paper substrate material with the water-based high-barrier coating layer.

[0085] Step 5: Perform corona treatment on the surface of the water-based high-barrier coating layer. The treatment power is 1.0kW and the linear speed is 10m / min to obtain the surface-activated paper-based material.

[0086] Step 6: According to the formulations described in each embodiment, polyhydroxyalkanoate resin, PLA resin, PBS resin or their blends are compounded onto the surface of the water-based high-barrier coating layer of the surface-activated paper-based material by single-screw extrusion. The extrusion temperature is 160°C, 170°C, 175°C and 175°C, the cooling roller temperature is 25°C and the pressing pressure is 0.25 MPa, to obtain a paper-based cylinder material with a composite barrier inner layer.

[0087] Step 7: Apply an external printable functional coating to the side of the paper-based cylindrical material away from the food container cavity. The drying temperature is 80℃ and the drying time is 2 minutes to obtain a double-sided functional paper-based cylindrical material.

[0088] Step 8: Pre-seal the cut edge of the double-sided functional paper-based cylindrical material located on the food-containing cavity side after slitting and forming. The pre-sealing process can be performed offline or online before forming the cylindrical material; it can be achieved using one or more of the following methods: narrow-edge roller coating, slot coating, spraying, transfer coating, impregnation coating, or hot-press transfer. First, a first sealing layer is formed, extending across the cut edge of the paper base and towards the adjacent inner wall surface and overlap interface. After hot air, infrared, or contact drying, the moisture content of the cut edge area is reduced to a level that does not cause warping or adhesion of the paper base. Then, a second sealing layer is formed, covering the outside of the first sealing layer, resulting in the pre-sealed paper-based cylindrical material.

[0089] Step 9: The pre-sealed paper-based tube material is formed into a tube by spiral winding or enclosing. A bio-based or biodegradable polymer heat-sealing tape is set in the overlapping sealing area and hot-pressed, so that the heat-sealing tape, water-based high-barrier edge sealing layer, bio-based or biodegradable polymer edge sealing layer and bio-based or biodegradable polymer heat-sealed moisture barrier layer form an overlapping connection, resulting in a continuous joint barrier structure.

[0090] Step 10: Prepare and attach the paper-based or plant fiber-based bottom cover. The bottom cover is made of food-grade cardboard, bamboo pulp cardboard, molded pulp bottom cover, or molded bamboo pulp bottom cover. A primer sealing layer is first applied to the food-contact side of the bottom cover, with a dry coating amount of 3 g / m². 2 Up to 5g / m 2 Dry at 80℃ for 2 minutes; then apply a water-based high-barrier coating layer with a dry coating weight of 15 g / m². 2 Up to 20g / m 2The material is dried under three hot air conditions at 60℃, 70℃ and 85℃ for 1 min, 1 min and 2 min respectively; then a bio-based or biodegradable polymer heat-sealing layer is formed on the surface of the water-based high-barrier coating layer. The heat-sealing layer is formed by melt extrusion or hot pressing of polyhydroxyalkanoate resin or a blend of it with other bio-based or biodegradable polymers, with a thickness of 8 μm to 12 μm. One or more of the following are applied: edge sealing or reinforcement treatment on the lower end of the paper base of the cylinder, the edge of the bottom cover, or the corner of the bottom cover. The bottom cover is then placed into the lower end of the cylinder, so that the bottom cover barrier layer and the composite barrier inner layer of the cylinder form a 3mm to 5mm annular overlap area. The heat sealing temperature is 145℃ to 165℃, the heat sealing pressure is 0.25MPa to 0.45MPa, and the heat sealing time is 0.8s to 1.5s. After heat sealing, the cylinder is rolled or pressed and shaped so that the bottom cover heat sealing layer, the bottom cover barrier layer, the composite barrier inner layer of the cylinder, and the lower end edge sealing layer of the cylinder form an annular bottom cover barrier continuous structure in the bottom cover connection area, resulting in a cylinder with a bottom cover.

[0091] Step 11: Fill the stacked puffed food into the bottom-covered cylinder and fill it with nitrogen or inert gas to obtain a filled cylinder.

[0092] Step 12: Prepare and connect the paper-based top sealing assembly. The paper-based top sealing assembly uses paper-based sealing film, bamboo pulp paper sealing film, or paper-based sealing sheet. A top sealing barrier layer and a top sealing heat-sealing layer are sequentially formed on the food contact side of the paper-based top sealing assembly. The top sealing barrier layer is formed using one or more of the following: a polyhydroxyalkanoate aqueous system, a polyhydroxyalkanoate / PVOH aqueous system, or a nanocellulose and layered mineral composite system, which are the same as or compatible with the water-based high-barrier coating layer of the cylinder body. The dry coating amount is 12 g / m³. 2 Up to 20g / m 2 The top heat-sealing layer is formed using polyhydroxyalkanoates, PLA, PBS, or blends thereof, with a thickness of 8 μm to 15 μm. After filling with stacked puffed food and filling with nitrogen or inert gas, the paper base trimmed edge or tube opening end face at the top of the tube is sealed or reinforced to form a tube opening end face sealing layer. The food contact side of the paper base top sealing assembly is aligned with the food receiving cavity and the tube opening heat-sealing mating part. The width of the annular heat-sealing zone is 5 mm to 8 mm, the heat-sealing temperature is 145℃ to 160℃, the heat-sealing pressure is 0.25 MPa to 0.40 MPa, and the heat-sealing time is 0.8 s to 1.2 s. After heat sealing, the top heat-sealing layer, top barrier layer, tube opening heat-sealing mating part, and tube opening end face sealing layer form an annular top barrier continuous structure in the top sealing connection area, resulting in a recyclable high-barrier paper tube system for puffed food packaging.

[0093] Example

[0094] Example 1: Low-volume basic solution for paper tube system.

[0095] Uses Sijigui food-grade coated white cardboard (FBB, 350g / m²) 2 As a paper substrate, the basis weight of the paper-based cylinder material is 350 g / m³. 2 The cylinder wall thickness is 0.8mm. The dry coating amount of the primer sealing layer is 3g / m². 2 The waterborne high-barrier coating layer is formed using BioTen1030 PHB waterborne dispersion (P(3HB) waterborne dispersion), sodium carboxymethyl cellulose, and montmorillonite, with a barrier reinforcement phase content of 5wt% and a dry coating weight of 12g / m². 2 .

[0096] The bio-based or biodegradable polymer heat-sealing moisture barrier is formed by melt extrusion of PB3000G PHB resin (P(3HB) resin), with a thickness of 8μm and an areal density of 8g / m³. 2 The overlap width is 6mm, and the effective barrier width is 5mm. The water-based high-barrier edge sealing layer extends 0.8mm to the adjacent inner wall surface and the overlap interface, and the bio-based or biodegradable polymer edge sealing layer overlaps with the heat sealing tape by 1.0mm.

[0097] The overlap width between the bottom cover barrier layer and the composite barrier inner layer is 3 mm, and the width of the top sealing annular heat-sealing area is 5 mm. Stacked potato chips are filled and the top is sealed with nitrogen to obtain the paper tube system of Example 1.

[0098] Example 2: Medium coating amount paper tube system.

[0099] Uses Sijigui food-grade coated white cardboard (FBB, 350g / m²) 2 As a paper substrate, the basis weight of the paper-based cylinder material is 350 g / m³. 2 The cylinder wall thickness is 0.8mm. The dry coating amount of the primer sealing layer is 4g / m². 2 The waterborne high-barrier coating is formed using BioTen1031 PHBV waterborne dispersion (P(3HB-co-3HV) waterborne dispersion, 3HV molar content 3mol%), nanocellulose, and mica powder. The barrier reinforcing phase content is 20wt%, the mica powder aspect ratio is 55, and the dry coating weight is 15g / m². 2 .

[0100] The bio-based or biodegradable polymer heat-sealing moisture barrier is formed by melt extrusion of PV3000G PHBV resin (P(3HB-co-3HV) resin, 3HV molar content 3±1mol%), with a thickness of 10μm and an areal density of 10g / m³. 2 The overlap width is 7mm, and the effective barrier width is 6mm. The water-based high-barrier edge sealing layer extends 1.0mm to the adjacent inner wall surface and the overlap interface, and the bio-based or biodegradable polymer edge sealing layer overlaps with the heat sealing tape by 1.5mm.

[0101] The overlap width between the bottom cover barrier layer and the composite barrier inner layer is 3 mm, and the width of the top sealing annular heat-sealing area is 5 mm. Stacked potato chips are filled and the top is sealed with nitrogen to obtain the paper tube system of Example 2.

[0102] Example 3: 18g / m 2 Water-based high-barrier paper tube system.

[0103] Uses Sijigui food-grade coated white cardboard (FBB, 450g / m²) 2 As a paper substrate, the basis weight of the paper-based cylinder material is 450 g / m³. 2 The cylinder wall thickness is 1.0 mm. The dry coating amount of the primer sealing layer is 4 g / m². 2 The waterborne high-barrier coating is formed using BioTen1031 PHBV waterborne dispersion (P(3HB-co-3HV) waterborne dispersion, 3HV molar content 3mol%), hydroxypropyl starch, nanocellulose, and mica powder. The barrier reinforcing phase content is 30wt%, and the dry coating weight is 18g / m². 2 .

[0104] The bio-based or biodegradable polymer heat-sealing moisture barrier is formed by melt extrusion of PV3000G PHBV resin (P(3HB-co-3HV) resin, 3HV molar content 3±1mol%), with a thickness of 12μm and an areal density of 12g / m³. 2 The overlap width is 8mm, and the effective barrier width is 7mm. The water-based high-barrier edge sealing layer extends 1.5mm to the adjacent inner wall surface and the overlap interface, and the bio-based or biodegradable polymer edge sealing layer overlaps with the heat sealing tape by 2.0mm.

[0105] The overlap width between the bottom cover barrier layer and the composite barrier inner layer is 4 mm, and the width of the top sealing annular heat-sealing area is 6 mm. Stacked potato chips are filled and the top is sealed with nitrogen to obtain the paper tube system of Example 3.

[0106] Unless otherwise described in the embodiments, the paper-based or plant fiber-based caps and paper-based top-sealing assemblies of Examples 1 to 11 were prepared and connected according to steps 10 and 12 in the general preparation process. The target annular overlap width of the bottom cap connection area was 4 mm, the target width of the top-sealing annular heat-sealing area was 6 mm, the bottom cap heat-sealing temperature was 155°C, the heat-sealing pressure was 0.35 MPa, and the heat-sealing time was 1.0 s; the top-sealing heat-sealing temperature was 150°C, the heat-sealing pressure was 0.30 MPa, and the heat-sealing time was 1.0 s. After the bottom cap was connected and the top seal was applied, water bath bubble detection, pressure decay detection, and dye penetration leak detection were performed to record the sealing stability of the annular bottom cap barrier continuous structure and the annular top seal barrier continuous structure.

[0107] Example 4: PLA / PHA blended heat-sealed moisture barrier paper tube system.

[0108] Uses Sijigui food-grade coated white cardboard (FBB, 450g / m²) 2 As a paper substrate, the basis weight of the paper-based cylinder material is 450 g / m³. 2 The cylinder wall thickness is 1.0 mm. The dry coating amount of the primer sealing layer is 4 g / m². 2 The waterborne high-barrier coating is formed using BioTen1030 PHB waterborne dispersion (P(3HB) waterborne dispersion), chitosan, silica sol, and mica powder, with a barrier reinforcement phase content of 35wt% and a dry coating weight of 20g / m². 2 .

[0109] The bio-based or biodegradable polymer heat-sealing moisture barrier layer is formed by extrusion of Ingeo 4043D PLA resin and PV3000G PHBV resin (P(3HB-co-3HV) resin, 3HV molar content 3±1mol%) at a mass ratio of 70:30, with a thickness of 15μm and a areal density of 15g / m³. 2 The overlap width is 9mm, and the effective barrier width is 8mm.

[0110] The water-based high-barrier edge sealing layer extends 1.8 mm to the adjacent inner wall surface and the overlap interface, and the bio-based or biodegradable polymer edge sealing layer overlaps with the heat-sealing tape by 2.5 mm. The bottom cover barrier layer overlaps with the composite barrier inner layer by 5 mm, and the top sealing annular heat-sealing area is 7 mm wide. Extruded cereal flakes are filled and the top is sealed with nitrogen to obtain the paper tube system of Example 4.

[0111] Example 5: High coating amount end-paper tube system.

[0112] Uses Sijigui food-grade coated white cardboard (FBB, 450g / m²) 2 As a paper substrate, the basis weight of the paper-based cylinder material is 450 g / m³. 2 The cylinder wall thickness is 1.1 mm. The dry coating amount of the primer sealing layer is 5 g / m². 2 The waterborne high-barrier coating is formed using BioTen1031 PHBV waterborne dispersion (P(3HB-co-3HV) waterborne dispersion, 3HV molar content 3mol%), nanocellulose, silica sol, and mica powder. The barrier reinforcing phase content is 45wt%, and the dry coating weight is 24g / m². 2 .

[0113] The bio-based or biodegradable polymer heat-sealing moisture barrier is formed by melt extrusion of PV3000G PHBV resin (P(3HB-co-3HV) resin, 3HV molar content 3±1mol%), with a thickness of 18μm and an areal density of 18g / m³. 2The overlap width is 10mm, and the effective barrier width is 9mm. The water-based high-barrier edge sealing layer extends 2.0mm to the adjacent inner wall surface and the overlap interface, and the bio-based or biodegradable polymer edge sealing layer overlaps with the heat sealing tape by 3.0mm.

[0114] The bottom cover barrier layer overlaps with the inner composite barrier layer by 5 mm, and the top sealing annular heat-sealing zone is 8 mm wide. Nut chips are filled and the top is sealed with nitrogen to obtain the paper tube system of Example 5.

[0115] Example 6: End-point paper tube system with high content of barrier reinforcing phase.

[0116] Uses Sijigui food-grade coated white cardboard (FBB, 350g / m²) 2 As a paper substrate, the basis weight of the paper-based cylinder material is 350 g / m³. 2 The cylinder wall thickness is 0.9 mm. The dry coating amount of the primer sealing layer is 4 g / m². 2 The waterborne high-barrier coating layer is formed using BioTen1030 PHB waterborne dispersion (P(3HB) waterborne dispersion), boehmite sol, silica sol, nanocellulose, and talc, with a barrier reinforcement phase content of 60wt% and a dry coating weight of 18g / m². 2 .

[0117] The bio-based or biodegradable polymer heat-sealing moisture barrier is formed by melt extrusion of PV3000G PHBV resin (P(3HB-co-3HV) resin, 3HV molar content 3±1mol%), with a thickness of 18μm and an areal density of 18g / m³. 2 The overlap width is 8mm, and the effective barrier width is 7mm. The water-based high-barrier edge sealing layer extends 1.5mm to the adjacent inner wall surface and the overlap interface, and the bio-based or biodegradable polymer edge sealing layer overlaps with the heat sealing tape by 2.0mm.

[0118] The overlap width between the bottom cover barrier layer and the composite barrier inner layer is 4 mm, and the width of the top sealing annular heat-sealing area is 6 mm. Stacked potato chips are filled and the top is sealed with nitrogen to obtain the paper tube system of Example 6.

[0119] Example 7: Polymer heat-sealed moisture barrier layer thickness end paper tube system.

[0120] Uses Sijigui food-grade coated white cardboard (FBB, 450g / m²) 2 As a paper substrate, the basis weight of the paper-based cylinder material is 450 g / m³. 2 The cylinder wall thickness is 1.1 mm. The dry coating amount of the primer sealing layer is 4 g / m². 2The waterborne high-barrier coating is formed using BioTen1031 PHBV waterborne dispersion (P(3HB-co-3HV) waterborne dispersion, 3HV molar content 3mol%), nanocellulose, and mica powder, with a barrier reinforcement phase content of 30wt% and a dry coating weight of 18g / m². 2 .

[0121] The bio-based or biodegradable polymer heat-sealing moisture barrier layer is formed by extrusion of BioPBS FZ91PM PBS resin and PV3000G PHBV resin (P(3HB-co-3HV) resin, 3HV molar content 3±1mol%) at a mass ratio of 60:40, with a thickness of 30μm and an areal density of 30g / m³. 2 The overlap width is 12mm, and the effective barrier width is 10mm.

[0122] The water-based high-barrier edge sealing layer extends 2.5 mm to the adjacent inner wall surface and the overlap interface, and the bio-based or biodegradable polymer edge sealing layer overlaps with the heat-sealing tape by 4.0 mm. The bottom cover barrier layer overlaps with the composite barrier inner layer by 6 mm, and the top sealing annular heat-sealing area is 8 mm wide. Stacked potato chips are filled and the top is sealed with nitrogen to obtain the paper tube system of Example 7.

[0123] Example 8: Bamboo pulp paperboard and molded bottom cover paper tube system.

[0124] Bamboo Board-350 bamboo pulp paperboard is used as the paper base material, and the basis weight of the paper base tube is 350g / m³. 2 The cylinder wall thickness is 0.9 mm. The bottom cover is a molded pulp cover made of bleached softwood pulp board and bleached hardwood pulp board in a mass ratio of 40:60. The dry coating amount of the bottom sealing layer on the inner side of the cylinder is 5 g / m². 2 .

[0125] The waterborne high-barrier coating is formed using BioTen 1030 PHB waterborne dispersion (P(3HB) waterborne dispersion), hydroxypropyl starch, nanocellulose, and montmorillonite, with a barrier reinforcement phase content of 35wt% and a dry coating weight of 20g / m². 2 The bio-based or biodegradable polymer heat-sealing moisture barrier layer is formed by melt extrusion of PV3000G PHBV resin (P(3HB-co-3HV) resin, 3HV molar content 3±1mol%), with a thickness of 15μm and an areal density of 15g / m³. 2 .

[0126] The overlap width is 8mm, and the effective barrier width is 7mm. The water-based high-barrier edge sealing layer extends 2.0mm to the adjacent inner wall surface and the overlap interface, and the bio-based or biodegradable polymer edge sealing layer overlaps with the heat-sealing tape by 3.0mm. The bottom cover barrier layer overlaps with the composite barrier inner layer by 5mm, and the top sealing annular heat-sealing zone is 7mm wide.

[0127] A base coating sealing layer, a water-based high-barrier coating layer, and a bio-based or biodegradable polymer heat-sealing layer are sequentially applied to the food contact side of the molded bottom cover. A composite edge sealing layer is applied to the edges and corners of the molded part. Shrimp chips are filled and nitrogen is used for top sealing to obtain the paper tube system of Example 8.

[0128] Example 9: Externally printable functional coated paper tube system.

[0129] Using the inner composite barrier structure of Example 3, an outer printable functional coating is applied to the side of the paper substrate facing away from the food receiving cavity. The outer printable functional coating is formulated from an aqueous polyurethane dispersion, a bio-based wax emulsion, nanocellulose, silica, and water, with a solid content of 18 wt% and a dry coating weight of 8 g / m². 2 The outer printable coating, after drying at 80°C for 2 minutes, forms a printable, wear-resistant, matte, and water-resistant surface.

[0130] The paper tube system has an overlap width of 8 mm, an effective barrier width of 7 mm, a water-based high-barrier edge sealing layer extending 1.5 mm towards the adjacent inner wall surface and the overlap interface, a bio-based or biodegradable polymer edge sealing layer overlapping the heat-sealing tape by 2.0 mm, a bottom cover barrier layer overlapping the composite barrier inner layer by 4 mm, and a top sealing annular heat-sealing zone width of 6 mm. Stacked potato chips are filled and the top is sealed with nitrogen to obtain the paper tube system of Example 9.

[0131] Example 10: Paper tube system with paper-based pull-out support barrier card.

[0132] The paper tube system of Example 3 is used, and a paper-based pull-out support barrier is installed in the food receiving cavity. The main body of the paper-based support is made of Sijigui food-grade coated white cardboard (FBB, 350g / m³). 2 The paper-based support body is formed by die-cutting and creasing to create an arc-shaped support area, lateral limiting wings, a bottom support piece, and a pull-out operating part. On the food contact side of the paper-based support body, a base coating sealing layer, a water-based oil-blocking barrier layer, and a bio-based or biodegradable polymer film layer are formed in sequence.

[0133] The water-based oil-blocking barrier layer comprises sodium carboxymethyl cellulose, hydroxypropyl starch, BioTen 1030 PHB water-based dispersion (P(3HB) water-based dispersion), and mica powder, with a dry coating weight of 10 g / m². 2The bio-based or biodegradable polymer film layer is formed by hot pressing PV3000G PHBV resin (P(3HB-co-3HV) resin, 3HV molar content 3±1mol%), with a thickness of 8μm.

[0134] The cut edges, fold lines, and punched edges of the pull-out operating section of the paper-based support body are coated with a water-based high-barrier edge sealing layer and a bio-based or biodegradable polymer edge sealing layer. During filling, the paper-based pull-out support barrier card is placed between the inner wall of the tube and the potato chip stack, and the bottom support piece is located at the lower end of the potato chip stack, thus obtaining the paper tube system of Example 10.

[0135] Example 11: PHA material platform paper tube system.

[0136] Uses Sijigui food-grade coated white cardboard (FBB, 450g / m²) 2 As a paper substrate, the basis weight of the paper-based cylinder material is 450 g / m³. 2 The cylinder wall thickness is 1.0 mm. The primer sealing layer is formed using BioTen 1031 PHBV aqueous dispersion (P(3HB-co-3HV) aqueous dispersion, 3HV molar content 3 mol%), with a dry coating weight of 4 g / m². 2 .

[0137] In Example 11, the PBAT aqueous dispersion can be a commercially available food-contact-compatible PBAT aqueous dispersion, or it can be prepared using a high-shear emulsification device with closed feeding, pressure control, condensation, and online emulsification functions. In laboratory preparation, ecoflex F Blend C1200 PBAT resin was vacuum dried at 80°C for 6 hours; KURARAY POVAL 28-98 PVOH was added to deionized water and stirred at 90°C for 2 hours to prepare a PVOH aqueous solution with a solid content of 10 wt%; the dried PBAT resin was heated to 150°C to 165°C in a closed emulsification container to form a molten phase. Under pressure control and condensation conditions, the PVOH aqueous solution was gradually added and high-shear emulsification was performed. After emulsification, it was diluted with deionized water and cooled to below 40°C to obtain the PBAT aqueous dispersion. The preparation process does not involve directly adding a large amount of aqueous phase to the high-temperature molten PBAT in an open container.

[0138] The aqueous high-barrier coating layer is formed using BioTen 1031 PHBV aqueous dispersion (P(3HB-co-3HV) aqueous dispersion, 3HV molar content 3 mol%), the above-mentioned PBAT aqueous dispersion, KURARAY POVAL 28-98 PVOH aqueous solution, CelluForce NCC nanocellulose, and Suzorite 60S mica powder. Based on dry solids mass, the mass ratio of PHA, PBAT, and PVOH is 60:20:20, the content of the barrier reinforcing phase is 30 wt%, and the mica powder aspect ratio is 55. The above-mentioned aqueous components were dispersed at 12000 r / min for 10 min, and then milled for 20 min to obtain a blended aqueous emulsion-type high-barrier coating liquid composed of PHA, PBAT, and PVOH. This coating liquid was applied to the surface of the primer sealing layer and dried under three stages of hot air at 60℃, 70℃, and 85℃ for 1 min, 1 min, and 2 min respectively, resulting in a dry coating weight of 18 g / m². 2 A water-based high-barrier coating layer.

[0139] The bio-based or biodegradable polymer heat-sealing moisture barrier is formed by melt extrusion of PV3000G PHBV resin (P(3HB-co-3HV) resin, 3HV molar content 3±1mol%), with a thickness of 12μm and an areal density of 12g / m³. 2 The overlap width is 8 mm, and the effective barrier width is 7 mm. The water-based high-barrier edge sealing layer extends 1.5 mm to the adjacent inner wall surface and the overlap interface, and the bio-based or biodegradable polymer edge sealing layer overlaps with the heat-sealing tape by 2.0 mm. The bottom cover barrier layer overlaps with the composite barrier inner layer by 4 mm, and the width of the top sealing annular heat-sealing area is 6 mm. Stacked potato chips are filled and the top is sealed with nitrogen to obtain the paper tube system of Example 11.

[0140] Comparative Example 1: Ordinary paper tube.

[0141] Uses Sijigui food-grade coated white cardboard (FBB, 350g / m²) 2 Paper tubes were prepared with a wall thickness of 0.8 mm. The overlap sealing area of ​​the tube body was bonded solely with water-based adhesive, with an overlap width of 8 mm. The paper-based tube material lacked a primer sealing layer, a water-based high-barrier coating layer, and a bio-based or biodegradable polymer heat-sealing moisture-proof layer. The bottom cover and paper-based top sealing assembly lacked a barrier layer continuously connected to the composite barrier inner layer. This comparative example was used to evaluate the basic moisture barrier, oxygen barrier, and nitrogen-filling retention capabilities of ordinary paper tubes.

[0142] Comparative Example 2: The overlapping sealing area has no double-layer cross-end sealing.

[0143] Compared to Example 3, the planar material structure of the cylinder body, the bottom cover connection structure, and the top seal connection structure remain the same. However, the overlapping sealing area of ​​the cylinder body does not have a water-based high-barrier edge sealing layer or a bio-based or biodegradable polymer edge sealing layer; only a bio-based or biodegradable polymer heat-sealing tape is used. The dry coating weight of the water-based high-barrier coating layer in this comparative example is 18 g / m². 2 The heat-sealed moisture barrier layer has a thickness of 12 μm and an overlap width of 8 mm. The bottom cover barrier layer overlaps with the inner composite barrier layer by 4 mm, and the top seal annular heat-sealing zone has a width of 6 mm. This comparative example is used to evaluate the contribution of the paper-based edge-sealed butt joint barrier to the continuity of the barrier.

[0144] Comparative Example 3: The connection area between the bottom cover and the top cover has no end face sealing or continuous annular reinforcement.

[0145] Compared to Example 3, the planar material structure of the cylinder remains the same, but the lower end paper base face, bottom cover edge, upper paper base cut edge, and cylinder opening face lack edge sealing or reinforcement. The bottom cover connection area and top seal connection area are only connected by conventional heat sealing or pressure sealing methods, without forming a continuous annular barrier reinforcement in the end seal area. The dry coating weight of the water-based high-barrier coating layer in this comparative example is 18 g / m². 2 The heat-sealed moisture barrier layer is 12 μm thick with an overlap width of 8 mm, and the water-based high-barrier edge sealing layer extends 1.5 mm towards the adjacent inner wall surface and the overlap interface. This comparative example is used to evaluate the contribution of continuous reinforcement in the end-seal region to the overall cylinder seal and nitrogen filling retention.

[0146] Comparative Example 4: Traditional PE coated paper tube.

[0147] Uses Sijigui food-grade coated white cardboard (FBB, 350g / m²) 2 A paper-based tube material is formed by a 20μm PE coating layer, with a tube wall thickness of 0.8mm and an overlap width of 8mm. The overlap sealing area is heat-sealed with PE, while the bottom and top covers use conventional PE heat-sealing structures. This comparative example is used to evaluate the differences in moisture resistance, heat sealing, and repulping screening of conventional PE paper tubes.

[0148] Comparative Example 5: Traditional aluminum foil composite paper tube.

[0149] Uses Sijigui food-grade coated white cardboard (FBB, 350g / m²) 2 The paper tube body is formed by a composite of aluminum foil and PE layer, with a wall thickness of 0.8 mm and an overlap width of 8 mm. The bottom cover is made of metal, and the top seal is made of aluminum-plastic composite sealing film. This comparative example is used to evaluate the differences in overall barrier properties and recycling screening between traditional high-barrier paper cans.

[0150] Comparative Example 6: Traditional EVOH composite paper tube.

[0151] Uses Sijigui food-grade coated white cardboard (FBB, 350g / m²) 2The paper tube body is formed by a composite of an EVOH oxygen barrier layer and a PE heat-sealing layer. The tube body wall thickness is 0.8 mm, the overlap width is 8 mm, and the bottom cover and top seal use corresponding heat-sealing materials. This comparative example is used to evaluate the differences in overall tube barrier and repulping screening of EVOH composite paper tubes.

[0152] Comparative Example 7: The paper-based pull-out support card does not have a food contact barrier layer or an edge sealing layer.

[0153] Compared to Example 10, the paper-based pull-out support card uses uncoated Siji Gui food-grade coated white cardboard (FBB, 350g / m²). 2 The paper-based support body is die-cut and creasing to form an arc-shaped support area, lateral limiting wings, a bottom support piece, and a pull-out operating part. However, no sealing layer is provided on the cut edges and fold lines, and no water-based oil-blocking barrier layer or bio-based or biodegradable polymer film layer is provided on the food contact side. The main structure of the paper tube adopts the tube body, bottom cover, and top sealing structure of Example 10. This comparative example is used to evaluate the contribution of the food contact barrier functional layer and sealing layer of the paper-based pull-out support card to oil resistance, moisture prevention, powder shedding, and pull-out durability.

[0154] Comparative Example 8: A plastic pull-out tab is provided.

[0155] Compared to Example 10, a PP plastic pull-out sheet with a thickness of 120 μm is provided inside the food receiving cavity, and the main structure of the paper tube adopts that of Example 3. This comparative example is used to evaluate the differences between paper-based pull-out support barrier cards and plastic pull-out sheets in terms of co-repulping, screening, and plastic residue.

[0156] Comparative Example 9: PHA material platform paper tube but without a three-node continuous barrier structure.

[0157] Compared to Example 11, the paper-based cylinder body material, bottom cover material, and paper-based top sealing assembly are all prepared using the same PHA material platform. The difference lies in that the paper-based cut edge on the food-containing cavity side of the cylinder body is not sealed with a double-layer cross-end face sealing of a water-based high-barrier edge sealing layer and a bio-based or biodegradable polymer edge sealing layer before cylinder forming; the overlapping sealing area is only bonded with conventional heat sealing or water-based adhesive; the lower end paper-based end face of the cylinder body, the edge of the bottom cover, the upper end paper-based cut edge of the cylinder body, and the cylinder mouth end face are not sealed or reinforced; the bottom cover connection area does not form a continuous annular bottom cover barrier structure; the top sealing connection area does not form a continuous annular top sealing barrier structure; and the seam-bottom cover intersection and the seam-top sealing intersection do not form a continuous bridging intersection barrier area. This comparative example has the same planar sheet barrier material, the same bottom cover material, and the same paper-based top sealing assembly material as Example 11. The difference lies in whether the seam, bottom cover, top sealing, and their upper and lower intersections form a continuous barrier path. This comparative example is used to evaluate the nitrogen retention capability of the entire cylinder when only a PHA planar barrier material platform is used without continuous connection of the three nodes of seam, bottom cover and top seal.

[0158] Application Example 1: Evaluation of barrier, oil resistance and heat-sealing performance of planar sheet materials.

[0159] Experimental Description: The sheets used to form the food contact interface of the cylinder body or differential components in Examples 1 to 11 and Comparative Examples 1 to 9 were equilibrated for 24 hours at 23°C and 50% relative humidity. For each sample, specimens were cut for testing water vapor transmission rate, oxygen transmission rate, Kit oil resistance rating, and heat seal strength. The test surface was taken from the side that actually faces the food receiving cavity.

[0160] For water vapor transmission rate testing, cut round or square samples without creases, pinholes, or edge damage. Fix the sample in the water vapor transmission rate test cup or the fixture of the water vapor transmission rate tester, with the food contact side facing the high humidity side. Place a desiccant on the low humidity side or create a low humidity environment using the instrument. Set the test temperature to 38℃ and the relative humidity on the high humidity side to 90%. After loading the sample, check the sealing ring and the edges of the fixture to ensure there is no air or moisture leakage. After the instrument reaches a stable state, record the water vapor transmission rate per unit area per unit time. Test five parallel samples for each sample. The results are expressed in g / (m²). 2 ·d) represents the average value.

[0161] For oxygen transmission rate testing, cut samples without creases, pinholes, or edge damage. Clamp the sample in the oxygen transmission rate testing chamber with the food contact side facing the oxygen side. Introduce carrier gas or maintain a low-oxygen environment on the other side. Set the test temperature to 23℃ and the relative humidity to 50%. Before testing, check the clamp's seal and perform blank or zero-point confirmation. Record the oxygen transmission rate after the oxygen transmission curve stabilizes. Test five parallel samples for each sample. Results are expressed in cm⁻¹. 3 / (m 2 ·d) represents the average value.

[0162] For the Kit oil resistance rating test, place the sample flat on a clean, horizontal glass plate with the food contact side facing upwards. Prepare Kit reagents numbered from 1 to 12, and test them sequentially from lowest to highest rating. For each test, use a pipette or dropper to draw approximately 0.05 mL of the corresponding Kit reagent and add it to the food contact side of the sample. After holding for 15 seconds, immediately blot the reagent away with clean absorbent paper without wiping. Then, observe the area under a standard light source for any dark spots, oil spots, penetration rings, back penetration, or fiber wetting. If no visible penetration occurs after 15 seconds of contact with a particular reagent rating, continue testing to the next rating. If visible penetration occurs, the previous rating without penetration is taken as the Kit oil resistance rating for that sample. Test five parallel samples for each sample, selecting at least three different locations for each parallel sample. Take the median of the results from all parallel samples as the Kit rating for that sample.

[0163] For the heat seal strength test, two identical food samples were stacked side-by-side and cut into heat-sealed specimens with a width of 15 mm. The heat-sealing temperature was 150℃, the heat-sealing pressure was 0.3 MPa, and the heat-sealing time was 1.0 s. After heat sealing, the specimens were placed at 23℃ and 50% relative humidity for 2 hours. Then, the heat-sealed specimens were clamped in an electronic universal testing machine with a clamping distance of 50 mm and a tensile speed of 300 mm / min. The average force value during the heat seal peeling or failure process was recorded, and the result was expressed as N / 15 mm. Five parallel samples were tested for each group of samples, and the average value was taken.

[0164] Five parallel samples were tested in each group, and the average result was taken. Water vapor transmission rate ≤ 15.0 g / (m²) 2 d) Oxygen permeability ≤ 30.0 cm 3 / (m 2 •d) Kit grade ≥ 7, heat seal strength ≥ 1.5 N / 15 mm, deemed to meet the basic barrier and heat seal requirements for nitrogen-filled stacked puffed food paper rolls; water vapor transmission rate ≤ 10.0 g / (m 2 ·d) Oxygen permeability ≤15.0cm 3 / (m 2 •d) Kit grade ≥8 and heat seal strength ≥2.0N / 15mm are considered preferred for barrier and heat seal requirements.

[0165] Table 3. Barrier, oil resistance and heat-sealing properties of planar sheet materials.

[0166]

[0167] Comparative Example 7: A food contact sheet with an uncoated paper-based pull-out support card was tested for sheet layer properties; Comparative Example 8: A PP plastic pull-out sheet was tested for sheet layer properties; Comparative Example 9: A food contact interface sheet formed from the same PHA material platform as Example 11 was tested for sheet layer properties.

[0168] Analysis: Table 3 shows that Example 1, under conditions of lower coating amount and thinner heat-sealing moisture barrier layer, can achieve basic barrier and heat-sealing requirements, but does not meet the preferred barrier requirements, indicating that the low-dosage scheme is more suitable as a packaging scheme for cost-sensitive or less shelf-life-restricted applications. From Examples 2 to 5, as the dry coating amount and overlap width of the water-based barrier coating layer increase, the oxygen permeability and water vapor permeability gradually decrease. However, the improvement in Example 5 compared to Example 4 is less significant, indicating that the marginal benefit of further increasing the coating amount and overlap width decreases.

[0169] Example 6 uses a higher content of barrier reinforcing phase, and the sheet barrier performance still meets the basic requirements, but the heat-sealing strength is lower than that of Example 3, indicating that high mineral or nano-reinforcing phases increase coating brittleness and interfacial heat-sealing pressure. Example 7 uses a thicker heat-sealing moisture barrier layer, and the water vapor permeability is lower, but the oxygen permeability does not decrease significantly at the same time, indicating that the thickened polymer layer mainly improves moisture barrier rather than significantly improves oxygen barrier.

[0170] The planar sheet barrier performance of Comparative Examples 2 and 3 is similar to that of Example 3, and the planar sheet barrier performance of Comparative Example 9 is similar to that of Example 11. This indicates that the differences between the above comparative examples and the corresponding examples mainly occur at the seams, bottom caps, and top sealing nodes after tube forming, rather than the planar sheet itself. The PE-coated paper tube of Comparative Example 4 has a lower water vapor transmission rate and a higher heat seal strength, but its oxygen transmission rate is significantly higher than that of the examples. Comparative Examples 5 and 6 perform well in terms of planar barrier properties, but their multi-material composite structures have separation and screening problems in repulping evaluation. Comparative Example 7 does not have a food contact barrier functional layer and an edge sealing layer. Its water vapor transmission rate, oxygen transmission rate, and Kit grade are all significantly worse than those of Example 10, indicating that the food contact surface of the built-in paper-based pull-out support barrier card also needs barrier and edge sealing treatment.

[0171] Application Example 2: Evaluation of overall cylinder sealing and nitrogen purging retention.

[0172] Experimental Description: Paper tubes of the same specifications were prepared from Examples 1 to 11 and Comparative Examples 1 to 9, with an inner diameter of 70 mm and a height of 180 mm. Each tube was filled with 160 g of original flavor stacked potato chips. After filling, food-grade nitrogen was continuously introduced through the tube opening at a flow rate of 5 L / min for 10 seconds. Immediately afterwards, the paper-based top sealing assembly was heat-sealed to the heat-sealing mating part at the tube opening. After heat sealing, the tubes were placed at 23°C and 50% relative humidity for 2 hours before a sealing test was conducted.

[0173] During the pressure decay test, an inflation needle or sealing joint is placed on the non-food contact side of the paper tube. The joint is sealed with a butyl rubber gasket and a sealing ring to prevent leakage. Air or nitrogen is injected into the paper tube to a positive pressure of 30 kPa. After stabilizing the pressure for 10 seconds, timing begins. This pressure is maintained for 120 seconds, and the endpoint pressure is recorded. The pressure drop over 120 seconds is the difference between the initial stable pressure and the endpoint pressure. After each paper tube test, the joint location is checked. If leakage is found at the joint, the data is invalidated and a new sample is taken.

[0174] During the water bath bubble test, the internal pressure of the paper tube is adjusted to a positive pressure of 20 kPa. First, the overlapping sealing area is completely immersed in 23°C water for 60 seconds, and it is observed whether bubbles are continuously released from the same position. Then, the bottom cover connection area, top seal connection area, seam-bottom cover intersection barrier area, and seam-top seal intersection barrier area are completely immersed in water for 60 seconds and observed. If no less than 3 bubbles appear continuously at the same position within 10 seconds, it is determined that there is a continuous bubble channel at that position; if only attached bubbles fall off and do not appear continuously, it is not considered a through leak.

[0175] During the dyeing penetration test, Sudan Red or Oil Red O was dissolved in refined vegetable oil to prepare an oil-containing dyeing simulation solution with a mass concentration of 0.05 wt%. This oil-containing dyeing simulation solution was applied or dripped onto the food contact side of the overlapping sealing area, bottom cover connection area, top cover connection area, seam-bottom cover junction barrier area, and seam-top cover junction barrier area, respectively. The contact width of each area covered the entire sealing interface, and the contact time was 30 minutes. After contact, the surface residual liquid was gently absorbed with lint-free paper without wiping. Subsequently, the paper tube was cut along the sealing area to observe whether the dyeing solution formed a continuous dyeing penetration channel penetrating through the composite barrier inner layer, end face sealing layer, junction barrier area, or heat-sealed interface.

[0176] Initial headspace oxygen content was measured within 2 hours after top sealing. Headspace oxygen content was measured after 60 days of storage at 38℃ and 75% relative humidity. During measurement, a sampling needle from a headspace oxygen analyzer was used to puncture the top sealing area or a pre-set sampling pad to extract headspace gas and record the oxygen content. Each paper tube was sampled once, avoiding the overlapping sealing area and heat-sealed edge. Ten paper tubes were tested per group. The number of paper tubes with continuous air bubble channels or continuous dye penetration channels was defined as those with a pressure drop exceeding 6.0 kPa in 120 seconds. If the same paper tube exhibits two or more of the following conditions simultaneously: continuous air bubble channels, continuous dye penetration channels, or a pressure drop exceeding 6.0 kPa in 120 seconds, only one non-compliant paper tube is counted in the overall sealing criterion. It should be noted that the 120s pressure drop is used to evaluate the overall sealing stability and gas retention capacity of the paper roll, while the number of paper rolls with continuous leakage is used to count the number of paper rolls with continuous bubble channels or continuous dye penetration channels. When the pressure drop is high but no continuous bubble channels or continuous dye penetration channels are found, it indicates that the gas retention capacity of the sample is relatively weak, but it is not considered that there is an identifiable continuous leakage channel.

[0177] Table 4. Results of overall cylinder sealing and nitrogen purging retention.

[0178]

[0179] Analysis: Table 4 shows that no through-leakage paper rolls appeared in Examples 1 to 11, indicating that continuous barrier reinforcement in the seams, bottom cover, and top seal areas can eliminate identifiable continuous air bubble channels and continuous dye penetration channels. However, the overall stability of the roll varies under different structural windows. Example 1, due to its lower coating amount, thinner heat-sealed moisture barrier layer, and smaller overlap width, had higher 120s pressure drop, 60d oxygen content, and potato chip moisture content than Example 3, indicating that while the low-dosage scheme is feasible, it is suitable as a basic packaging scheme rather than a preferred long shelf-life scheme.

[0180] Examples 3 to 5 achieved a good balance between coating continuity, overlap, bottom cover overlap, and top heat seal width, resulting in low overall pressure drop and low 60-day oxygen content. Example 6, due to its higher content of the barrier reinforcing phase, exhibited decreased coating flexibility and heat seal stability, leading to slightly higher overall pressure drop and 60-day oxygen content than Example 3, but no through-leakage channel was formed. Example 8 used bamboo pulp paperboard and a molded bottom cover. Because the edge and corner dimensional stability of the molded part was lower than that of the flat paperboard bottom cover, the pressure drop and 60-day oxygen content were higher than in Example 3, but no through-leakage paper tube appeared, indicating that the bamboo pulp paperboard and molded bottom cover scheme can be used as a basic adaptation scheme.

[0181] Comparative Example 2, with a planar sheet barrier performance similar to Example 3, exhibited continuous air bubble channels or continuous dye penetration channels in five paper tubes due to the lack of double-layer cross-end face sealing in the overlapping sealing area. The oxygen content rose to 16.8% after 60 days, indicating that the sealing of the paper base cut edge on the food receiving cavity side plays a crucial role in the continuous barrier of long seams. Comparative Example 3, lacking end face sealing and continuous annular reinforcement in the bottom cover and top seal areas, showed continuous air bubble channels or continuous dye penetration channels in six paper tubes, with the oxygen content rising to 17.5% after 60 days. This indicates that the end seal area is a weak point in the overall barrier of the paper tube system. Comparative Example 9 used the same PHA material platform as Example 11, but did not form a three-node continuous barrier structure. Six paper tubes exhibited continuous air bubble channels or continuous dye penetration channels, with the oxygen content rising to 18.2% after 60 days. This demonstrates that the PHA material platform cannot replace the continuous design of seams, bottom covers, and top seal nodes.

[0182] Comparative Examples 5 and 6 exhibit good overall tube barrier performance, but their multi-material composite structures show significant differences in repulping and screening. The overall tube sealing data of Comparative Examples 7 and 8 are close to those of Example 10 because their tube body, bottom cover, and top seal structures still use a barrier continuous paper tube body; however, they differ in terms of pull-out, oil prevention, or co-repulping.

[0183] Application Example 3: Simulation evaluation of shelf life of different stacked puffed food packaging.

[0184] Experimental Description: Paper tube systems were prepared using Examples 1 to 11 and Comparative Examples 1 to 9, and filled with potato chips, puffed cereal chips, nut chips, or shrimp chips, respectively. Each paper tube was filled with 160g of sample and filled with food-grade nitrogen gas. After sealing, it was stored at 38°C and 75% relative humidity for 90 days. Five paper tubes were tested in each group. The test items included headspace oxygen content, food moisture content, acid value, peroxide value, and aroma retention score.

[0185] For headspace oxygen content determination, paper tubes stored for 90 days were equilibrated for 2 hours at 23℃ and 50% relative humidity. The headspace oxygen analyzer was used with a sampling needle to puncture the top seal area or a pre-set sampling pad to extract headspace gas and record the oxygen content. Each paper tube was measured once, and the result was the average of 5 paper tubes.

[0186] When determining the moisture content of food, immediately remove the stacked puffed food after opening the paper tube, discard any obviously broken powder, and quickly pulverize and mix the sample. Weigh approximately 5.0g of the pulverized sample and place it in a pre-weighed aluminum box. Dry the sample at 105℃ with forced air until the difference between two consecutive weighings does not exceed 2mg. Calculate the moisture content of the food based on the difference in weight before and after drying. Measure one sample from each paper tube, and take the average of five paper tubes.

[0187] Before determining the acid value and peroxide value, the stacked puffed food pieces in each paper tube were removed, crushed, and mixed thoroughly. A representative sample of 20.0 g was weighed, and 100 mL of petroleum ether or n-hexane was added. After shaking and extraction for 30 min, the mixture was filtered. The residue was extracted once more with the same solvent. The filtrates were combined, and the solvent was removed by rotary evaporation at a temperature not exceeding 40°C to obtain the oil to be tested. For the acid value determination, approximately 2.0 g of the oil to be tested was weighed, dissolved in a mixed solvent of diethyl ether and ethanol, and titrated with potassium hydroxide standard solution using phenolphthalein as an indicator until a faint red color was obtained and maintained for 30 s. The acid value was calculated based on the amount of potassium hydroxide consumed, and the result was expressed as mg KOH / g fat. For peroxide value determination, weigh approximately 2.0 g of the oil to be tested, dissolve it in a mixed solvent of glacial acetic acid and isooctane, add saturated potassium iodide solution and react in the dark for 1 min. After dilution with water, titrate with standard sodium thiosulfate solution. Near the endpoint, add starch indicator and continue titrating until the blue color disappears. Calculate the peroxide value based on the amount of sodium thiosulfate consumed. The result is expressed in g / 100g fat. Acid value and peroxide value in the same table are calculated based on the extracted oil.

[0188] Aroma retention was assessed using a blind evaluation panel of 10 people. Freshly filled and immediately opened samples of the same type of stacked puffed food were used as reference samples, with an aroma score of 10. Samples stored for 90 days were immediately aliquoted into clean, numbered evaluation cups upon opening and evaluated within 5 minutes of opening. The scoring rules were as follows: 9 to 10 points indicated an aroma essentially identical to the reference sample with no identifiable off-odors; 7 to 8 points indicated a slightly reduced aroma, but still retaining the main aroma of the corresponding food; 5 to 6 points indicated a significantly reduced aroma or the appearance of a slight papery or oxidized oil smell; 3 to 4 points indicated a weak main aroma with a noticeable off-odor; and 0 to 2 points indicated severe aroma loss or a strong off-odor. Each evaluator scored independently, and the highest and lowest scores were removed, with the average score taken as the aroma retention score. An aroma retention score ≥7.0 was considered acceptable for basic aroma retention, and an aroma retention score ≥8.0 was considered acceptable for preferred aroma retention.

[0189] Table 5. Simulation results of shelf life for different puffed food packaging.

[0190]

[0191] Analysis: Table 5 shows that Examples 1 to 11 can reduce 90-day headspace oxygen content and food moisture absorption in representative stacked puffed foods, but there are significant differences in shelf-life retention under different structural windows. Example 1 is a low-dosage basic scheme, with higher 90-day oxygen content and moisture content than Example 3, indicating that low coating amount, thin heat-sealing moisture barrier layer, and small overlap width will reduce long-term nitrogen-filled stability. Examples 3 to 5 represent better structural windows, with 90-day oxygen content maintained at 6.0% to 7.0% and aroma retention score reaching around 8.0, suitable for stacked puffed foods with higher shelf-life requirements.

[0192] Example 8, using bamboo pulp cardboard and a molded bottom cover, showed higher oxygen and moisture content at 90 days compared to Example 3, indicating that plant fiber substrates and molded bottom covers are industrially feasible. However, its edge, corner, and dimensional stability requires more stringent edge sealing and pressing control. Example 11, using a PHA material platform paper tube system, showed a 90-day oxygen content of 7.0% and a food moisture content of 2.6%, demonstrating that the combination of the PHA material platform and a three-node continuous barrier structure can meet basic shelf-life requirements, but should not be simply equated to the extremely high barrier levels of traditional aluminum foil composite cans.

[0193] Comparative Example 9 used the same PHA material platform but did not form a three-node continuous barrier structure. After 90 days, the oxygen content increased to 22.0%, the food moisture content increased to 4.6%, and the acid value and peroxide value significantly increased. The aroma retention score decreased to 4.9, indicating that shelf-life stability is not determined solely by the PHA material platform, but rather by the combination of the material platform with the continuous barrier nodes at the seams, bottom cover, and top seal. Comparative Examples 5 and 6 performed well in terms of shelf-life retention, but their recovery screening results did not meet the requirements for resizing.

[0194] Application Example 4: Evaluation of the printability of the outer printing-adaptive functional coating.

[0195] Experimental Description: The flexographic printing compatibility of the outer surface sheets of paper tubes prepared in Examples 1 to 11 and Comparative Examples 1 to 9 was evaluated. The samples were cut into 150mm × 150mm specimens, with the outer surface facing upwards, and equilibrated for 24 hours at 23°C and 50% relative humidity. Four-color test strips and solid color blocks were printed on the outer surface of the samples using the same batch of water-based flexographic inks and the same flexographic printing parameters. After printing, the samples were equilibrated for 24 hours at 23°C and 50% relative humidity.

[0196] Ink adhesion was evaluated using the tape peeling method. Pressure-sensitive tape with a width of 18mm to 25mm was applied to the solid color area, and a 2kg rubber roller was used to roll it back and forth twice at a speed of approximately 300mm / min to ensure full contact between the tape and the printed surface. After a 60-second rest period, the tape was quickly peeled off within 1 to 2 seconds at a peeling angle of approximately 180°. The color area was scanned or photographed after peeling, and image analysis was used to calculate the percentage of the original color area where ink remained after peeling, which was taken as the tape peeling color retention rate. Five locations were tested for each sample, and the results were averaged.

[0197] During the abrasion resistance test, the printed solid color area was fixed on a reciprocating friction test bench. A friction head covered with standard white cotton cloth or lint-free paper was used, with a contact area of ​​20mm × 20mm, a load of 9.8N, a friction stroke of 50mm, a frequency of 60 times / min, and 100 reciprocating friction cycles. After the test, the friction area was scanned, and image analysis was used to calculate the percentage of ink loss area relative to the friction area, which was taken as the abrasion-resistant ink loss area. Three parallel locations were tested for each sample, and the average value was taken.

[0198] For the water droplet impermeability test, the sample was placed horizontally with its outer surface facing upwards. 0.5 mL of deionized water was dropped onto the outer surface and held for 60 seconds. The remaining water droplets were then gently blotted away with lint-free paper, without repeated wiping. The sample was then placed at 23°C and 50% relative humidity for 5 minutes, after which the surface was observed for fuzzing, wetting marks, and watermarks on the back, and scanned at a resolution of 600 dpi. Water droplet impermeability was determined according to the following rules: no visible watermarks on the back, no fuzzing on the front, and a wetting mark area ≤ 0.10 cm² on the front. 2 It is recorded as having no obvious penetration; no visible watermarks on the back, no fiber shedding on the front, and the area of ​​wetted marks on the front is >0.10cm². 2 And ≤0.50cm 2 Slight dampness is recorded as the condition where visible watermarks appear on the back and the area of ​​fuzzing on the front is greater than 1.0 mm. 2 Or the area of ​​wetting marks on the front is >0.50 cm² 2 Areas marked as significant penetration were identified. The area of ​​wetting marks and the area of ​​fuzzing were obtained through scanning image analysis. During image analysis, the non-dripping area was used as the background, and the wetting area was identified by grayscale difference or color difference. The result was the average of three parallel test points.

[0199] For gloss testing, the printed samples were equilibrated at 23℃ and 50% relative humidity for 24 hours, and the gloss of the solid color areas was measured using a 75° gloss meter. At least five locations without creases or stains were randomly selected from each sample for measurement, and the average value was taken. A basic printability standard was deemed acceptable if the abrasion resistance area was ≤8%, the water droplet test result was no obvious penetration or slight wetting, and the color retention rate after tape peeling was ≥85%. A preferred printability standard was deemed acceptable if the abrasion resistance area was ≤5% and the color retention rate after tape peeling was ≥90%.

[0200] Table 6 shows the printing compatibility results of the outer printing-adaptive functional coating.

[0201]

[0202] Analysis: Table 6 shows that in Examples 1 to 11, the external printability coatings can meet the basic printability requirements without the use of plastic film or traditional UV varnish. Example 9, due to the use of a dedicated external printability coating, exhibits significantly better tape peel color retention and abrasion resistance than Example 3, indicating that the external functional coating can improve the friction adaptability of the paper tube shelf display and transportation.

[0203] Comparative Example 1: The outer surface of the ordinary paper tube was not treated for printing suitability and water resistance. The color retention rate after tape peeling was low, the area of ​​ink loss due to abrasion was large, and water droplet penetration was significant. Comparative Example 5: The outer surface of the aluminum foil composite paper can had a high gloss, but the color retention rate and ink loss due to abrasion did not meet the basic criteria, indicating that the appearance and barrier advantages of traditional composite structures are not necessarily equivalent to water-based printing suitability. Comparative Example 9: The printing suitability results on the outer surface were similar to those of Example 11, indicating that its failure was not due to the outer printing layer, but rather to the lack of a three-node continuous barrier structure.

[0204] Application Example 5: Evaluation of repulping compatibility of paper tube systems.

[0205] Experimental Description: After removing residual food from the paper tube systems of Examples 1 to 11 and Comparative Examples 1 to 9, the samples were cut into 20mm × 20mm fragments and dried at 105℃ to constant weight. A 50.0g sample of oven-dry weight was weighed. The sample was added to water at 45℃ to adjust the total pulp mass to 2000g, resulting in a pulp consistency of 2.5wt%. A standard pulp dissociator was used for dissociation for 20 minutes, maintaining the pulp temperature at 45℃ ± 2℃ during the dissociation process. After dissociation, the pulp was brought to a final volume with 45℃ water and thoroughly stirred to obtain the pulp to be screened.

[0206] During screening, the pulp to be screened is first passed through a coarse sieve with a 0.15mm opening. The sieve surface is continuously rinsed with 45℃ water until the water passing through the sieve is basically clear. The coarse sieve residue is collected and dried at 105℃ to constant weight; the oven-dry mass of the coarse sieve residue is recorded. The pulp is then passed through a fine sieve with a 0.10mm opening, and the same washing, collection, and drying process is used for the fine sieve residue, which is also recorded as oven-dry mass. The paper-based fiber recovery rate is calculated after filtration, collection, and drying of the pulp passing through the sieve. The coarse sieve residue rate is the percentage of the oven-dry mass of the coarse sieve residue to the oven-dry mass of the initial sample; the fine sieve residue rate is the percentage of the oven-dry mass of the fine sieve residue to the oven-dry mass of the initial sample; the paper-based fiber recovery rate is the percentage of the oven-dry mass of the recoverable fiber passing through the sieve to the theoretical oven-dry mass of the paper-based fiber in the initial sample.

[0207] In the adhesion area test, the sieve residue and undersize fiber pulp are prepared into test pieces, dried, and then the adhesion spots are identified using a scanner or image analyzer. The area is converted to mm based on the unit pulp area. 2 / m 2 The number of large-area continuous membrane patches was determined through a combination of visual inspection and image analysis. Large-area continuous membrane patches are defined as those with a single patch area > 1 cm². 2 Continuous sheet-like material.

[0208] The uniformity of recycled paper sheet formation was evaluated using hand-made sheets and scanned images. The sieved paper-based fiber pulp was prepared to a basis weight of 60 g / m³. 2Handwritten images were equilibrated at 23℃ and 50% relative humidity for 24 hours, then scanned at a resolution of 600 dpi. At least five randomly selected regions of 10cm × 10cm were used to calculate the grayscale variation coefficient and the number of visible spots. A grayscale variation coefficient ≤ 12% and a single spot area > 1mm² were considered acceptable. 2 The number of visible spots is ≤12 / 100cm 2 Single piece area > 1cm² 2 When the number of continuous sheet-like particles is ≤3 pieces / 50g oven-dry sample, the recycled paper sheet is considered to have basic uniformity in formation. When the paper base fiber recovery rate is ≥75wt%, the coarse sieve residue rate is ≤20wt%, the fine sieve residue rate is ≤8wt%, the number of large-area continuous sheets is ≤3 pieces / 50g oven-dry sample, and the recycled paper sheet has basic uniformity in formation, the repulperability is considered acceptable. When the paper base fiber recovery rate is ≥80wt%, the coarse sieve residue rate is ≤15wt%, the fine sieve residue rate is ≤5wt%, and the number of large-area continuous sheets is 0, the repulperability is considered optimal. Each sample group is tested three times, and the average value is taken.

[0209] Table 7. Evaluation results of reproducible pulp compatibility.

[0210]

[0211] Analysis: Table 7 shows that Examples 1 to 11 all met the basic repulper compatibility requirements, but there were differences in slag ratio and paper sheet uniformity under different structural windows. In Example 7, due to the larger thickness of the heat-sealed moisture barrier layer, the fiber recovery rate decreased to 80.0 wt%, the coarse slag ratio increased to 16.5 wt%, and the number of large-area continuous films was 2 per 50g oven-dry sample. This indicates that although a thicker polymer layer can improve moisture barrier capacity, it increases the screening burden and is not suitable as a preferred recovery scheme. In Example 6, due to the higher content of the barrier reinforcing phase, the fine slag ratio, adhesive area, and number of visible spots were all higher than in Example 3, indicating that high mineral or nano-reinforcing phases increase dispersion and paper sheet forming pressure.

[0212] Example 11 uses a PHA material platform, with a fiber recovery rate of 86.5 wt%, a coarse screen residue rate of 9.2 wt%, and a fine screen residue rate of 3.2 wt%. This indicates that after the PHA aqueous system, PHA extrusion layer, and sheet mineral reinforcement system enter the paper tube system, they can still be compatible with the warm water dissociation, screening, and recycled paper forming process, but this should not be interpreted as the absence of screen residue or residue. Comparative Examples 4, 5, and 6 use PE, aluminum foil, and EVOH composite structures, respectively. Although they have certain advantages in terms of barrier properties, their fiber recovery rate is significantly lower than that of the example, and the coarse screen residue rate and the number of large-area continuous films are significantly increased. Comparative Example 8 uses plastic pull-out sheets, resulting in a fiber recovery rate lower than the basic criterion and significant plastic sheet residue. Although Comparative Example 9 meets the repulping compatibility requirements, the overall tube sealing and shelf life are significantly deteriorated, indicating that repulping compatibility cannot replace the three-node continuous barrier structure.

[0213] Application Example 6: Evaluation of the pull-out, shatterproof, and barrier properties of paper-based pull-out support barrier cards.

[0214] Experimental Description: Paper tubes from Examples 1 to 11 and Comparative Examples 1 to 9 were transported and then evaluated for food handling, breakage prevention, and co-re-pulping. Each paper tube was filled with 160g of stacked potato chips and sealed with nitrogen. Ten paper tubes were tested per group. Before the transport simulation, the paper tubes were equilibrated at 23°C and 50% relative humidity for 24 hours. The transport simulation used a combination of horizontal vibration and drop: the horizontal vibration frequency was 3Hz, the amplitude was 25mm, and the vibration time was 30min; after vibration, the paper tubes were dropped from a height of 1.0m once each in three orientations: vertical, horizontal, and tilted at 45°, for a total of three drops.

[0215] After the transportation simulation, the paper tube is opened. For samples without a pull-out support, the contents are removed by tilting or direct consumption. For samples with a pull-out support, the contents are removed by grasping the pull-out mechanism and pulling it out at a uniform speed along the tube's axis. The removed potato chips are sieved and manually sorted. Chips with an area of ​​more than 80% of the original intact chip area and no through cracks are considered intact chips; chips with an area of ​​10% to 80% of the original intact chip area are considered fragments; chips with an area less than 10% of the original intact chip area or that can pass through a 2mm sieve are considered powder. The intact chip rate, fragment rate, and powder rate are calculated as the percentage of the corresponding part's mass to the total mass of the removed food.

[0216] When testing the depth of consumers' fingers entering the tube, 10 evaluators were selected and asked to take out the food from the lowest accessible position in the opened paper tube using a normal eating posture, and record the maximum depth of their fingers entering below the tube opening plane; each paper tube was recorded once, and the average result was taken.

[0217] Pull-out force testing is only performed on samples with pull-out support components. The paper tube is fixed to the lower clamp of the electronic universal testing machine, ensuring the tube's axis is aligned with the tensile direction. The upper clamp holds the pull-out operating part and pulls it axially along the tube at a speed of 100 mm / min. The first peak force after the start of pulling is recorded as the initial pull-out force; the average force within the pull-out stroke range of 20 mm to 120 mm is recorded as the continuous pull-out force. If the pull-out operating part breaks during the pull-out process, it is recorded as a breakage of the pull-out operating part, and the breakage rate is calculated.

[0218] The oil stain area was tested only for samples with paper-based pull-out support cards or plastic pull-out sheets. After being pulled out, the support was placed flat with the food contact side facing up, and scanned at 600 dpi resolution. Image analysis was used to identify areas of oil stains that were darker or more transparent, and the total area of ​​the oil stains was calculated. The co-repulping determination was based on the results of the paper tube system and its internal support being jointly crushed, disassembled, and sieved. The specific disassembly and sieving methods were the same as in Application Example 5.

[0219] Table 8 Evaluation results of feeding, breakage prevention and co-repulping after transportation.

[0220]

[0221] Table 9 shows the evaluation results of the pull-out and barrier functions of the pull-out support sample.

[0222]

[0223] Note: Table 9 only evaluates the pull force and oil resistance of samples with pull-out supports. Comparative Example 9 did not have pull-out supports, so it is not included in Table 9; its feeding, anti-breakage, and co-re-pulping results are shown in Table 8.

[0224] Analysis: Table 8 shows that Examples 1 to 9, Example 11, and Comparative Example 9, which did not have pull-out support pieces, mainly relied on tipping or direct feeding after the transportation simulation. The intact sheet rate in Examples 3, 9, and 11 was approximately 78%, and the depth of fingers entering the tube was approximately 116 mm. In Example 10, after installing a paper-based pull-out support barrier, the intact sheet rate increased to 84.0%, and the depth of fingers entering the tube decreased to 45 mm, indicating that the paper-based pull-out support barrier can improve feeding convenience and breakage prevention, but the improvement is less than that of an ideal plastic support. Comparative Example 8 used PP plastic pull-out sheets, showing better intact sheet rate and oil stain area, but failed the co-repulping judgment.

[0225] As can be seen from Table 9, the initial pulling force of Example 10 was 5.5 N, the continuous pulling force was 4.0 N, the breakage rate of the pulling operation part was 2%, and the oil stain area was 18 cm². 2This indicates that the food contact barrier layer and the edge sealing layer can reduce the paper card's oil absorption, moisture absorption, adhesion, and folding failure. However, the paper-based pull-out support barrier card still poses a certain risk of oil absorption and mechanical damage. Comparative Example 7, which uses an uncoated paper-based pull-out card, shows an increase in pull-out force, a significantly increased breakage rate, and a larger oil stain area, indicating that the absence of a food contact barrier layer and edge sealing layer weakens the pull-out stability and oil-blocking ability.

[0226] Application Example 7: Food contact safety suitability evaluation.

[0227] Experimental Description: To cover the main food contact parts and main material platforms in the paper tube system of the present invention that directly or may directly contact puffed food, Examples 3, 4, 7, 8, 10, 11 and Comparative Example 9 were selected for food contact safety compatibility evaluation.

[0228] In this example, Example 3 represents the food contact surface of a conventional PHA paper tube; Example 4 represents the food contact surface of a PLA / PHA blended heat-sealed moisture barrier layer; Example 7 represents the high-thickness end of a PBS / PHA blended heat-sealed moisture barrier layer and a polymer heat-sealed moisture barrier layer; Example 8 represents the food contact surface of a pulp molded part, a bamboo pulp molded part, or a plant fiber molded part; Example 10 represents the food contact surface of a paper-based pull-out support barrier card; and Example 11 and Comparative Example 9 represent a platform of blended aqueous emulsion materials composed of PHA, PBAT, and PVOH.

[0229] The remaining embodiments are the same as or fall within the range of the representative samples in terms of food contact layer material category, coating structure, or numerical range. Table 1 and the PHB and PHBV listed in each embodiment are representative test samples of this specific embodiment, used to illustrate the feasibility of the PHA material platform of this invention in food contact safety compatibility evaluation; other PHA types that meet the requirements of this invention for film formation, heat sealing, barrier properties, food contact safety, and resizing compatibility can be confirmed for food contact safety compatibility using the same evaluation logic. For newly added monomer sources, additive systems, or food contact layer formulations in actual production, corresponding specific migration items should be screened according to the specific formulation list.

[0230] During migration testing, test samples were taken from the actual or potentially directly food-contacting parts of each sample. These included the inner composite barrier layer of the cylinder, the bottom cover barrier layer, the top seal barrier layer, the molded bottom cover food contact barrier layer, and the paper-based pull-out support barrier card food contact barrier layer. After cutting, edge debris was removed from the samples, and they were equilibrated for 24 hours at 23°C and 50% relative humidity. Migration tests were conducted using a single-sided contact method, with the food-contact side in contact with the food simulant, while the non-food-contact side was isolated using an inert clamp or glass plate. Vegetable oil was used as the food simulant, and the contact area was proportional to the simulant volume at 6 dm². 2 / kg or equivalent ratio setting; when the sample area is insufficient, reduce the amount of simulant proportionally to the actual contact area. Migration conditions are 40℃, 10d.

[0231] For the total migration test, vegetable oil simulants were collected after migration and processed using a weighing method suitable for simulants of oily foods. Blank and sample simulants before and after migration were subjected to constant weight treatment. After subtracting the blank value, the total migration amount was calculated based on the mass of migration residue, contact area, and amount of simulant used. The results are expressed in mg / dm³. 2 This indicates that three parallel samples were prepared for each sample, and the average value of the results was taken.

[0232] During sensory evaluation, observe the samples before the migration test and the food simulants after the migration test for any off-odors, tastes, obvious discoloration, turbidity, sedimentation, or other abnormalities. At least three evaluators should be present, and a blank vegetable oil simulant should be used as a control. If any parallel sample exhibits obvious off-odors, tastes, or abnormal appearance, the sensory result of that sample is deemed abnormal.

[0233] Specific migration items were screened based on the actual formulations of PHA, PLA, PBS, PBAT, PVOH, sealing layer, and heat-sealing layer contained in the sample. PHA-related low-molecular-weight migrations, lactic acid, 1,4-butanediol, succinic acid, adipic acid, terephthalic acid, and vinyl alcohol-related migrations were detected using high-performance liquid chromatography (HPLC), gas chromatography (GC), or liquid chromatography-mass spectrometry (LC-MS), respectively. Before detection, vegetable oil simulants were extracted or purified with suitable solvents, and calibration curves were established using corresponding standards. Samples not using corresponding materials or monomer sources were not included in the measured migration data for this item. The limit of quantitation (LOQ) for specific migration items was 0.05 mg / kg; values ​​below the LQ were recorded as <0.05 mg / kg.

[0234] Table 10 Results of food contact safety compatibility evaluation.

[0235]

[0236] Note: Specific migration screening results are as follows. Migrations related to PHA (low molecular weight polymers), lactic acid, 1,4-butanediol, succinic acid, adipic acid, terephthalic acid, and vinyl alcohol units were all below the limits of quantitation for the corresponding detection methods or below the limits stipulated in applicable food contact material regulations. Samples that did not use the corresponding monomer source or corresponding polymer material were not included in the measured migration data for this item. Example 7, due to its thicker heat-sealed moisture barrier layer, had a higher total migration than Example 3, but still met the food contact safety compatibility requirements. Comparative Example 9 was similar to Example 11 in terms of food contact safety compatibility, but its overall sealing and shelf life showed significant deterioration, indicating that food contact safety compliance cannot replace a three-node continuous barrier structure.

[0237] Analysis: Table 10 shows that Examples 3, 4, 7, 8, 10, 11, and Comparative Example 9 respectively covered the food contact surface of a conventional PHA paper tube, a PLA / PHA blended heat-sealed moisture barrier layer, a PBS / PHA blended and thicker heat-sealed moisture barrier layer, the food contact surface of a pulp or plant fiber molded part, the food contact surface of a paper-based pull-out support barrier card, and the food contact surface of a PHA / PBAT / PVOH material platform. No obvious off-odors, tastes, abnormal turbidity, or precipitation were observed in any of the samples under the conditions of 40℃ and 10 days with vegetable oil food simulants, and the total migration was less than 10 mg / dm³. 2 The specific migration items screened according to the actual formulation of the sample were all below the corresponding limit of quantitation or met the corresponding limit requirements.

[0238] Therefore, composite barrier inner layer, bio-based or biodegradable polymer edge sealing layer, bottom cover barrier layer, top seal barrier layer, molded food contact barrier layer, and paper-based pull-out support barrier card food contact barrier functional layer can meet the food contact safety compatibility requirements of low moisture and oil puffed food packaging. However, food contact safety compliance itself cannot replace the evaluation of the continuity of barrier and shelf life retention of the whole tube.

[0239] Experimental results and analysis.

[0240] As can be seen from Tables 3 to 10, there is a clear division of labor among the water-based barrier coating, the primer sealing layer, the heat-sealable moisture barrier layer, and the continuous reinforcement structure. The primer sealing layer mainly reduces the porosity and liquid absorption of the paper base; the water-based barrier coating mainly provides the basis for oxygen barrier, oil barrier, and fragrance retention; the heat-sealable moisture barrier layer mainly reduces water vapor ingress into the water-based barrier layer and provides a heat-sealing interface; and the first edge sealing layer, the second edge sealing layer, the heat-sealing strip, the bottom cover barrier layer, and the top cover barrier layer mainly extend the barrier capability of the planar sheet to the seams, bottom cover, and top cover nodes.

[0241] Experimental results also show that the present invention is not necessarily better the higher the amount of a single material. Lower coating weight and smaller overlap width offer cost advantages, but the overall nitrogen-filled retention capacity is lower than the preferred option; higher barrier reinforcement phase content improves barrier properties but increases coating brittleness, heat-sealing pressure, and screening burden; thicker heat-sealable moisture-proof layer improves moisture resistance but increases material costs and resizing screen residue. The bottom cover assembly, top seal assembly, and molded fiber components can be used to construct resizing-compatible paper tubes, but their edges, corners, and annular connection areas require more stringent edge sealing, heat sealing, and pressing control.

[0242] Comparative Examples 2, 3, and 9 demonstrate that the barrier properties, food contact safety properties, and resizing compatibility of planar sheet materials are not directly equivalent to the nitrogen-filled retention capacity of the entire tube. Only when the paper-based barrier material platform forms a continuous barrier path along the paper-based cut edge on the food-containing cavity side, the overlapping sealing area, the bottom cover connection area, and the top seal connection area can it be converted into the performance of the entire tube packaging.

[0243] In summary, this invention provides a structural solution for nitrogen-filled, stacked food paper tubes that balances barrier properties, heat sealing, continuous joints, and re-sizing adaptability through the synergistic design of a composite barrier inner layer, overlapping and cut-edge closure, a continuous annular barrier structure for the bottom and top caps, edge reinforcement of the molded parts, a printable outer coating, and optional paper-based pull-out support barrier cards. This solution can improve oxygen barrier, moisture barrier, oil barrier, aroma preservation, nitrogen filling retention, printability, ease of consumption, and recyclability performance within a certain process window. However, the specific barrier level, shelf life, and recyclability still need to be verified and optimized based on material formulation, paper base type, bottom and top cap structure, and actual production line conditions.

[0244] The various embodiments cover low-volume basic solutions, optimized balanced solutions, higher barrier solutions, high-reinforcement phase boundary solutions, thicker moisture barrier layer boundary solutions, bamboo pulp paperboard and molded bottom cover solutions, external printability solutions, paper-based pull-out support barrier card solutions, and PHA material platform solutions. The comparative examples demonstrate that the lack of seam closure, the lack of continuous end-sealing reinforcement, the use of only a PHA material platform without three-node continuity, the use of traditional multi-material composite structures, or the use of plastic pull-out sheets all lead to a decrease in the corresponding overall performance, shelf-life retention performance, food-barrier performance, or recyclability.

[0245] Therefore, PHA material platforms, water-based barrier material platforms, and bio-based or biodegradable polymer heat-sealing material platforms can serve as the material basis for this invention and can form a material layer protection with the applicant's existing material platform patents. Furthermore, this invention forms a continuous barrier path on the food contact side around the seams, bottom cover, top seal, and the intersection of the axial seams and the annular structures of the upper and lower end seals of the nitrogen-filled stacked food paper tube, thereby forming protection at the whole tube system level. In specific industrialization, the choice can be made between a low-volume basic scheme, a preferred balanced scheme, and a high-barrier-boundary scheme, depending on the target shelf life, cost, heat-sealing window, re-sizing requirements, and equipment conditions.

[0246] Those skilled in the art should understand that the above embodiments are merely exemplary and not intended to limit the scope of the invention. The scope of protection of the present invention is defined by the appended claims. Any modifications, equivalent substitutions, improvements, etc., made to the technical solutions of the present invention within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A recyclable high-barrier paper tube system for puffed food packaging, characterized in that, The paper tube system includes a tube body, a bottom cover assembly, a top sealing assembly, and a barrier continuous reinforcement structure; The cylindrical body, the bottom cover assembly, and the top sealing assembly together form a food receiving cavity; The cylinder body is formed by winding or assembling paper-based cylinder body material, and has an overlapping sealing area extending along the axial direction of the cylinder body; The paper-based cylinder material includes a paper substrate and a composite barrier inner layer disposed on the side of the paper substrate facing the food receiving cavity. The composite barrier inner layer includes at least an aqueous barrier coating layer and a heat-sealable moisture-proof layer located on the side of the aqueous barrier coating layer facing the food receiving cavity. The overlapping sealing area has a paper-based cut edge on the food-containing cavity side, which is the paper-based fiber cross-section facing the food-containing cavity after being formed into a tube; Before being wound or formed into a cylinder, the paper base cut edge on the food receiving cavity side is covered or reinforced by a first sealing layer and a second sealing layer. The first sealing layer extends across the end face of the paper base cut edge on the food receiving cavity side and extends to the adjacent inner wall surface and the overlap interface. The second sealing layer covers the outside of the first sealing layer, or the second sealing layer overlaps, fuses, presses, covers or bridging one or more of the composite barrier inner layer, the heat-sealable moisture barrier layer, the heat-sealing tape or the reinforcing tape, so that the paper base cut edge on the food receiving cavity side is isolated from the food receiving cavity. The barrier continuous reinforcement structure located in the overlapping sealing area overlaps, covers, fuses, presses or bridging one or more of the paper base cut edge of the food receiving cavity side, the composite barrier inner layer and the heat-sealable moisture barrier layer to form a joint barrier continuous structure extending along the axial direction of the cylinder body. The bottom cover assembly is provided with one or both of the following on the side facing the food receiving cavity: a bottom cover barrier structure and a bottom cover heat sealing structure. The bottom cover barrier structure or the bottom cover heat sealing structure and the composite barrier inner layer form annular overlap, annular bonding, annular heat sealing or annular pressing in the bottom cover connection area, and form an annular bottom cover barrier continuous structure with one or more of the following: the paper base end face of the lower end of the cylinder, the sealing layer of the lower end of the cylinder, the edge of the bottom cover or the corner of the bottom cover. The top sealing assembly is provided with one or both of a top sealing barrier structure and a top sealing heat sealing structure on the side facing the food receiving cavity. The top sealing barrier structure or the top sealing heat sealing structure forms an annular heat sealing area with the upper end of the cylinder in the top sealing connection area, and overlaps, fuses, presses, covers or bridging one or more of the paper base cutting edge, cylinder mouth end face or cylinder mouth end face sealing layer at the upper end of the cylinder to form an annular top sealing barrier continuous structure. The continuous seam barrier structure, the continuous annular bottom cover barrier structure, and the continuous annular top seal barrier structure together form a continuous barrier path on the food contact side around the food receiving cavity.

2. The recyclable high-barrier paper tube system for puffed food packaging according to claim 1, characterized in that, The puffed foods include one or more of the following: potato chips, French fries, puffed cereal chips, rice cakes, shrimp chips, shrimp sticks, nut chips, biscuit chips, cereal chips, or freeze-dried fruit and vegetable chips; The puffed food is a stacked puffed food that is filled with nitrogen or inert gas after being packed. The tube body is a spiral wound paper tube, a flat wound paper tube, a paper tube formed by enclosing a paperboard sheet, or a paper tube formed by enclosing a pre-formed paper-based tube body material; The paper substrate is selected from one or more of the following: wood pulp paper, bamboo pulp paper, sugarcane pulp paper, straw pulp paper, recycled fiber paper, food-grade white cardboard, kraft paper, bamboo pulp paperboard, coated paperboard, or composite paperboard. The composite barrier inner layer includes a primer sealing layer, a water-based barrier coating layer, and a heat-sealable moisture barrier layer. The aqueous barrier coating layer comprises one or more of the following systems: aqueous polyhydroxyalkanoate system; aqueous system composed of polyhydroxyalkanoate and polyvinyl alcohol; aqueous blend system composed of polyhydroxyalkanoate, polybutylene adipate terephthalate and polyvinyl alcohol; aqueous film-forming material based on cellulose, aqueous film-forming material based on starch, aqueous film-forming material based on chitosan, aqueous polyurethane, aqueous acrylic, aqueous dispersion of ethylene-vinyl alcohol copolymer, aqueous dispersion of polyvinylidene chloride confirmed by resizing compatibility evaluation, wax emulsion or composite aqueous system thereof; The water-based barrier coating layer further includes a barrier reinforcement phase, which is selected from one or more of mica, montmorillonite, talc, kaolin, microfibrillated cellulose, cellulose nanocrystals, silica sol, boehmite sol, alumina sol, silica, or calcium carbonate. The heat-sealable moisture barrier layer includes one or more of the following: polyhydroxyalkanoate, polylactic acid, polybutylene succinate, polybutylene adipate-terephthalate, polycaprolactone, ethylene-vinyl acetate copolymer, ionomer, water-based heat-sealable coating, wax-based heat-sealable coating, or blends thereof. The total basis weight of the paper-based cylinder material is 150g / m³. 2 Up to 800g / m 2 Or the wall thickness of the cylinder is 0.3mm to 3.0mm.

3. The recyclable high-barrier paper tube system for puffed food packaging according to claim 1, characterized in that, The first edge sealing layer is one or more of the following: water-based barrier edge sealing layer, water-based pore sealing edge sealing layer, water-based mineral barrier edge sealing layer, water-based polyhydroxyalkanoate edge sealing layer, water-based polyvinyl alcohol edge sealing layer, water-based cellulose edge sealing layer, water-based starch edge sealing layer, water-based polyurethane edge sealing layer, or water-based acrylic edge sealing layer. The second edge sealing layer is one or more of the following: bio-based polymer edge sealing layer, biodegradable polymer edge sealing layer, heat-sealable edge sealing layer, wax-based edge sealing layer, polyhydroxyalkanoate edge sealing layer, polylactic acid edge sealing layer, polybutylene succinate edge sealing layer, polybutylene adipate terephthalate edge sealing layer, water-based heat-sealable coating layer, or a combination thereof. The overlap width of the overlapping sealing area is 3mm to 20mm, and the effective barrier width of the overlapping sealing area is 2mm to 18mm. The first edge sealing layer extends 0.3 mm to 5 mm to the adjacent inner wall surface and the overlapping interface, respectively; The second sealing layer overlaps the heat-sealing tape or reinforcing tape located in the overlapping sealing area by 0.3 mm to 8 mm; The first sealing layer and the second sealing layer together span the end face of the paper base cut edge on the side of the food receiving cavity, and cover the inner wall surface and overlapping interface adjacent to the paper base cut edge, forming a U-shaped covering, L-shaped covering, continuous covering across the end face, strip covering, impregnation covering or transfer covering structure. The heat-sealing tape or the reinforcing tape is simultaneously fused, pressed, bonded, or hot-pressed with the second edge sealing layer and the heat-sealable moisture barrier layer within the overlapping sealing area.

4. The recyclable high-barrier paper tube system for puffed food packaging according to claim 1, characterized in that, The bottom cover assembly is selected from bamboo pulp paper bottom cover, pulp molded bottom cover, coated paper base cover or paper-based composite bottom cover; The bottom cover barrier structure includes a bottom cover barrier layer, which includes one or more of the following: a base coating sealing layer, a water-based barrier coating layer, a bio-based or biodegradable polymer heat-sealing layer, a mineral-based barrier layer, or a cellulose-based barrier layer. The bottom cover heat-sealing structure includes a bottom cover heat-sealing layer. The bottom cover barrier layer or the bottom cover heat-sealing layer and the composite barrier inner layer form a radial or axial annular overlap in the bottom cover connection area. The width of the radial or axial annular overlap is 0.5 mm to 10 mm. The top sealing component is a paper-based sealing film or a paper-based sealing sheet; The top sealing barrier structure includes a top sealing barrier layer, which includes one or more of the following: a paper base layer, a bottom coating sealing layer, a water-based barrier coating layer, a bio-based or biodegradable polymer heat-sealing layer, a mineral-based barrier layer, or a cellulose-based barrier layer. The top sealing heat-sealing structure includes a top sealing heat-sealing layer, and the heat-sealing width of the annular heat-sealing area is 2mm to 12mm; The continuous joint barrier structure and the continuous annular bottom cover barrier structure continuously cross over each other at the lower end of the cylinder to form a joint-bottom cover intersection barrier area, and the continuous joint barrier structure and the continuous annular top seal barrier structure continuously cross over each other at the upper end of the cylinder to form a joint-top seal intersection barrier area.

5. The recyclable high-barrier paper tube system for puffed food packaging according to claim 1, characterized in that, The paper tube system does not use a continuous aluminum foil layer, a continuous polyethylene layer, a continuous ethylene-vinyl alcohol copolymer layer, or a metal bottom cover as the main barrier component for the continuous barrier path on the food contact side. Among them, the main barrier component refers to the layered component that continuously covers the food-containing cavity in the continuous barrier path on the food contact side and undertakes the main functions of oxygen barrier, moisture barrier or sealing. Local additives, discontinuous island residues, non-food contact side decorative layers or discontinuous reinforcement points are not considered main barrier components.

6. The recyclable high-barrier paper tube system for puffed food packaging according to claim 1, characterized in that, The paper-based cylindrical material also includes an outer printable functional coating disposed on the side of the paper substrate opposite to the food receiving cavity; The outer printable functional coating is one or more of the following: bio-based, biomass-based, mineral-based, organic-inorganic composite waterborne coating, waterborne polyurethane coating, waterborne acrylic coating, wax emulsion coating, gloss coating, or water-resistant coating, with a dry coating weight of 0.5 g / m². 2 Up to 15g / m 2 It is used to form one or more functional surfaces, such as printable, abrasion resistant, varnishing, matte, water resistant, anti-blocking, or auxiliary barrier.

7. The recyclable high-barrier paper tube system for puffed food packaging according to claim 1, characterized in that, The food container cavity is equipped with a paper-based pull-out support barrier. The paper-based pull-out support barrier card includes a paper-based support body, a pull-out operation part, and a food contact barrier functional layer disposed on the food contact side of the paper-based support body. The paper-based support body includes one or more of the following: a lateral limiting part that cooperates with the side of the stacked puffed food body; a bottom support part located at the lower end of the stacked puffed food body; a longitudinal support strip; an arc-shaped support piece; a shallow groove-shaped support piece; a U-shaped folding card; a C-shaped folding card; a semi-enclosed support card; or a saddle-shaped support card. The paper-based support body has a sealing layer or a continuous reinforcing structure on its cut edges, fold lines, punched edges or exposed fiber cross-sections. The paper-based pull-out support barrier is located entirely within the food receiving cavity and can be crushed, separated, and screened together with the paper tube system.

8. The recyclable high-barrier paper tube system for puffed food packaging according to claim 1, characterized in that, The paper tube system, after being filled with stacked puffed food, filled with nitrogen or inert gas, and sealed with the top sealing assembly, simultaneously meets the following basic compatibility conditions: Maintain a positive pressure of 30 kPa for 120 seconds, with a pressure drop of ≤ 6.0 kPa over 120 seconds; Under a positive pressure of 20 kPa, the overlapping sealing area, the bottom cover connecting area, the top seal connecting area, the seam-bottom cover intersection barrier area, and the seam-top seal intersection barrier area are each immersed in water for 60 seconds, and the number of continuous air bubble channels at the same position is 0; wherein, the seam-bottom cover intersection barrier area is the intersection position of the continuous seam barrier structure and the continuous annular bottom cover barrier structure at the lower end of the cylinder, and the seam-top seal intersection barrier area is the intersection position of the continuous seam barrier structure and the continuous annular top seal barrier structure at the upper end of the cylinder. After contacting the overlapping sealing area, the bottom cover connection area, the top seal connection area, the seam-bottom cover intersection barrier area, and the seam-top seal intersection barrier area with an oil-containing dyeing simulation solution for 30 minutes, the number of continuous dyeing penetration channels penetrating the continuous barrier path through the food contact side is 0. Each group of test paper tubes must contain ≥10 tubes, and the number of paper tubes with through-leakage must be 0. The heat sealing strength of both the top sealing connection area and the bottom cover connection area is ≥1.5N / 15mm; After storage at 38℃ and 75% relative humidity for 60 days, the headspace oxygen content of the paper tube system is ≤10.0%, and the moisture content of the stacked puffed food is ≤3.2%. The paper tube system is subjected to 45℃ water, 2.5% pulp concentration, and dissociation for 20 minutes. After sieving through a 0.15mm coarse sieve and a 0.10mm fine sieve, the paper base fiber recovery rate is ≥75wt%, the coarse sieve residue rate is ≤20wt%, the fine sieve residue rate is ≤8wt%, and the single sheet area is >1cm². 2 The number of large-area continuous membrane sheets is ≤3 sheets / 50g of oven-dried sample.

9. The recyclable high-barrier paper tube system for puffed food packaging according to any one of claims 1 to 8, characterized in that, The paper-based tube material in the paper tube system is a pre-sealed paper-based tube material, which includes a paper substrate, a composite barrier inner layer, a first tube-forming edge, and a second tube-forming edge. The composite barrier inner layer is disposed on the side of the paper substrate facing the food receiving cavity, and includes an aqueous barrier coating layer and a heat-sealable moisture barrier layer, or includes a base coating sealing layer, an aqueous barrier coating layer and a heat-sealable moisture barrier layer. The first or second cylindrical edge has a food-receiving cavity side paper base cut edge formed by slitting and used to face the food-receiving cavity. The food-receiving cavity side paper base cut edge is first provided with a first sealing layer and then a second sealing layer before being wound or formed into a cylinder. The first sealing layer extends across the end face of the paper base cut edge on the side of the food receiving cavity and extends 0.3 mm to 5 mm towards the surface of the composite barrier inner layer and the overlapping interface, respectively, and the second sealing layer covers the outside of the first sealing layer. After the pre-sealed paper-based tube material is wound or enclosed, the first tube edge and the second tube edge form an overlapping sealing area, and the second sealing layer overlaps with one or more of the composite barrier inner layer, the heat-sealable moisture barrier layer, the heat-sealing tape or the reinforcing tape by 0.3 mm to 8 mm to form a continuous joint barrier structure extending along the tube axial direction.

10. A method for preparing a recyclable high-barrier paper tube system for puffed food packaging according to any one of claims 1 to 8, characterized in that, Includes the following steps: Step 1: Provide a paper substrate and condition and cut the paper substrate. Form a water-based barrier coating layer on one side of the paper substrate after conditioning and cutting, which is used to form the inner wall of the food receiving cavity, or form a base coating sealing layer and a water-based barrier coating layer in sequence to obtain a paper-based material with a barrier coating layer. Step 2: Apply the heat-sealable moisture-proof material to the surface of the water-based barrier coating layer by extrusion lamination, hot-press lamination, coating, transfer coating, hot melt coating or a combination thereof to form a heat-sealable moisture-proof layer, thereby obtaining a paper-based cylinder material with a composite barrier inner layer. Step 3: The paper-based cylindrical material is cut into sections and then formed into cylinders. The paper-based cut edge located on one side of the food receiving cavity is pre-sealed to form a first sealing layer and a second sealing layer in sequence. The first sealing layer extends across the end face of the paper-based cut edge and extends to the adjacent inner wall surface and the overlapping interface. The second sealing layer covers the outside of the first sealing layer to obtain the paper-based cylindrical material that has been pre-sealed. Step 4: The paper-based cylindrical material with pre-sealed edges is rolled or enclosed to form a cylindrical body. The first edge sealing layer, the second edge sealing layer and the heat-sealed moisture barrier layer are overlapped, fused, bonded or pressed in the overlapping sealing area of ​​the cylindrical body by heat sealing tape, reinforcing tape, adhesive, heat sealing layer or a combination thereof, to form a continuous joint barrier structure extending along the axial direction of the cylindrical body. Step 5: Connect the bottom cover assembly, which has one or both of the bottom cover barrier layer and bottom cover heat seal layer on the food contact side, to the lower end of the cylinder body, so that the bottom cover barrier layer or the bottom cover heat seal layer and the composite barrier inner layer form annular overlap, annular heat seal, annular bonding or annular pressing in the bottom cover connection area to obtain a cylinder body with a bottom cover. Step 6: Fill the cylinder with puffed food and fill it with nitrogen or inert gas. Step 7: Connect the top sealing assembly, which has one or both of the top sealing barrier layer and the top sealing heat seal layer on the food contact side, to the upper end of the tube body, so that the top sealing barrier layer or the top sealing heat seal layer overlaps, fuses, presses, or covers one or more of the tube mouth heat seal mating part, tube mouth end face sealing layer, or upper end paper base cutting edge of the tube body, to form an annular top sealing barrier continuous structure, and obtain the paper tube system.

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