A method for manufacturing a cover for aseptic liquid food packaging by using an aqueous fiber molding

Abstract

The application provides a method for manufacturing a sterile liquid food packaging cover by using a water-containing fiber molding method, which comprises the following steps: S1, providing a bottom layer, a base layer comprising a water-containing fiber, an isolation layer and a surface layer; S2, stacking the bottom layer, the base layer, the isolation layer and the surface layer to form a stacked body; and S3, molding the stacked body by using a mold, wherein the bottom layer, the base layer and the surface layer are deformed in the mold, and the bottom layer and the surface layer are combined along the periphery of the base layer to form a high-density combined part, and the combined part, the surface layer and the bottom layer seal the base layer. By the above method, on the one hand, the base layer and the isolation layer are sealed in a cavity formed by the surface layer and the bottom layer, and on the other hand, the base layer and the isolation layer form excellent oxygen barrier performance, which meets the needs of packaging of sterile liquid food such as milk, and meanwhile, the above method can use the existing mold, and the modification cost is low.

Description

Technical Field

[0001] This invention relates to a method for preparing a sealing device, and more particularly to a method for manufacturing a sterile liquid food packaging cap using water-containing fiber molding. Background Technology

[0002] Hydrous fibers, especially widely used pulp materials composed of cellulose fibers, are generally considered good environmentally friendly materials because they can be recycled and reused. However, when prepared using molding processes, their poor barrier properties and permeability generally make them unsuitable for packaging aseptic liquid foods. Nevertheless, the good shape retention of hydrous fibers during molding has led to increasing interest in their application as lids or lid connectors.

[0003] For example, EP4045436A1 discloses a portioning container made of biodegradable fibrous material, a fiber molding system, and a method for producing such a portioning container, including a container for receiving luxury goods. The container and lid are made from pulp, which is a liquid solution containing biodegradable fibrous material, using a fiber molding process through a fiber molding system. At least the container, preferably also the lid, has a barrier layer system having a barrier substance that at least prevents the penetration of moisture, water, fragrances, flavorings, odorants, and / or substances incompatible with food.

[0004] However, the above-mentioned barrier layer system still cannot meet the needs of liquid foods such as milk. There is a desire to develop a method for preparing a cap with higher barrier performance, especially with higher oxygen barrier performance.

[0005] Therefore, a new technical solution is needed to address the aforementioned technical problems. Summary of the Invention

[0006] To address these technical problems, the present invention provides a method for manufacturing sterile liquid food packaging caps using water-containing fiber molding.

[0007] A method for manufacturing a sterile liquid food packaging cap using water-containing fiber molding includes:

[0008] S1: Provides a base layer, including a matrix containing water-containing fibers, an isolation layer, and a top layer;

[0009] S2: A laminate is formed by stacking the bottom layer, the substrate, the isolation layer, and the top layer;

[0010] S3: The laminate is molded using a mold. Inside the mold, the bottom layer, the substrate, and the top layer are deformed. The bottom layer and the top layer are bonded together along the periphery of the substrate to form a high-density bond. The bond, the top layer, and the bottom layer enclose the substrate.

[0011] It includes a skeleton formed by cross-arranged water-containing fibers and a thermoplastic resin filling the spaces between the skeleton. The water-containing fibers are one of wood pulp fibers, cotton fibers, sugarcane fibers, or bamboo fibers. The thermoplastic resin can be polyvinyl chloride, polyvinylidene chloride, polyethylene, polypropylene, or a polymer formed by polyethylene and polypropylene.

[0012] In step S2, the area of ​​the substrate and the isolation layer is smaller than that of the bottom layer and the top layer. The shape of the substrate and the isolation layer is the same as the area. The bottom layer includes a first end surrounded around the periphery of the substrate, and the top layer includes a second end surrounded around the periphery of the substrate. The first end and the second end are annular.

[0013] The mold includes an upper mold and a lower mold. The upper mold and the lower mold include a cavity. The upper mold also includes a pressing device. The pressing device is configured to move movably toward the center of the cavity. In step S3, the pressing device moves movably toward the center of the cavity and applies pressure to the second end of the surface layer to form a joint with the first end. The density of the joint is greater than the density of the surface layer or the bottom layer.

[0014] The density of the joint is greater than or equal to 150% of the density of the surface layer or the bottom layer.

[0015] The isolation layer includes a barrier substrate layer and a barrier coating layer disposed on the barrier substrate layer. The barrier substrate layer is a polymer film, and the barrier coating layer is an aluminum metal or aluminum oxide coating with a thickness of 10-30 nm.

[0016] The barrier substrate layer is a multilayer composite film with a gradient distribution of crystallinity, and the barrier substrate layer includes at least three structural layers, with a crystallinity difference of more than 5% between adjacent structural layers.

[0017] The barrier substrate layer is an MDOPE film, and the crystallinity of each structural layer ranges from 40% to 80%. The barrier substrate layer includes five structural layers, namely an outer structural layer, an inner structural layer, and an intermediate layer, a second intermediate layer, and a third intermediate layer located between the outer structural layers. The crystallinity decreases sequentially from the outer structural layer to the inner structural layer, and the difference in crystallinity between adjacent structural layers is 5% to 15%.

[0018] The skeleton is a nonwoven fabric formed from wood pulp fibers.

[0019] The lower mold includes a first heating device, and the upper mold includes a second heating device. In step S3, the first heating device heats the bottom layer, causing at least a portion of the bottom layer to melt and form an integral part with the substrate. The second heating device heats the surface layer, causing at least a portion of the surface layer to melt and form an integral part with the isolation layer.

[0020] Beneficial Effects: This invention provides a method for manufacturing aseptic liquid food packaging caps using water-containing fiber molding, comprising: S1: providing a bottom layer, a substrate including water-containing fibers, an isolation layer, and a top layer; S2: stacking the bottom layer, substrate, isolation layer, and top layer to form a laminate; S3: molding the laminate using a mold, wherein the bottom layer, substrate, and top layer deform within the mold, and the bottom layer and top layer bond along the periphery of the substrate to form a high-density joint, wherein the joint, the top layer, and the bottom layer enclose the substrate. Through the above method, on the one hand, the substrate and isolation layer are enclosed within the cavity formed by the top layer and the bottom layer; on the other hand, the substrate and the isolation layer form excellent oxygen barrier properties, meeting the requirements for aseptic liquid food packaging such as milk. Furthermore, the above method can utilize existing molds, resulting in low modification costs. Attached Figure Description

[0021] Figure 1 A schematic diagram of the cover structure according to an embodiment of the present invention;

[0022] Figure 2 form Figure 1 The diagram shows the flow chart of the cover.

[0023] Component descriptions in the diagram:

[0024] Laminated body 10; bottom layer 11; first end 111; substrate 12; isolation layer 13; surface layer 14; second end 141; joint 142; mold 20; lower mold 21; first heating device 211; upper mold 22; second heating device 221; pressing device 222. Detailed Implementation

[0025] Please refer to Figure 1 and Figure 2 This invention provides a method for manufacturing a sterile liquid food packaging cap using water-containing fiber molding, thereby preparing a cap with high barrier properties.

[0026] The final cover, from the inside out, includes a bottom layer 11, a base layer 12, an isolation layer 13, and a top layer 14. The top layer 14 and the bottom layer 11 are joined at their edges to form a high-density joint 142. The joint 142 allows the top layer 14 and the bottom layer 11 to form a closed space, enclosing the base layer 12 and the isolation layer 13 within this closed space. The high density means that the density of the joint 142 is greater than the density of the top layer 14 and the bottom layer 11. Typically, the density of the joint 142 should be greater than or equal to 150% of the density of the top layer 14 or the bottom layer 11.

[0027] In the following description, the following terms shall have the following meanings:

[0028] "Polymer" refers to a polymeric compound prepared by polymerizing the same or different types of monomers.

[0029] A copolymer is a polymer prepared by polymerizing at least two different types of monomers.

[0030] "Ethylene-based polymers" refers to polymers that contain a majority amount of ethylene monomers (by weight of the polymer) in polymeric form and may optionally contain one or more comonomers.

[0031] “EVOH” refers to a polymer containing repeating units of ethylene and vinyl alcohol.

[0032] Understandably, the cover includes a bottom plate and side plates extending downward from the bottom plate, and the joint 142 is located at the end of the side plate away from the bottom plate.

[0033] The bottom layer 11 is a thermoplastic plastic, preferably selected from at least one of polyolefins, vinyl polymers, polyacrylates, polyamides, polyurethanes, polyureas, polyimides, polyesters, polyethers, polystyrene, PMMA, SAN, TPO, TPU, and POM.

[0034] Furthermore, since the bottom layer 11 is adjacent to the liquid food and may come into contact with the food, preferably, the bottom layer 11 is made of olefin resins such as polyethylene and polypropylene, including low-density polyethylene, linear low-density polyethylene, metallocene linear low-density polyethylene, high-density polyethylene, medium-density polyethylene, ethylene / vinyl acetate copolymer, ethylene / acrylic acid copolymer, ethylene / ethyl acrylate copolymer, etc., and can also be used in appropriate combinations. More preferably, the bottom layer 11 is mainly made of polyethylene.

[0035] Furthermore, the melt flow index (190℃ / 2.16kg) of the bottom layer 11 ranges from 5 to 20 g / 10 min, and the density ranges from 0.910 to 0.930 g / cm³. 3 The weight of the bottom layer 11 can range from 10 to 30 g / m³.2 Within the range.

[0036] Furthermore, the bottom layer 11 has a thickness of 0.5 to 5 mm.

[0037] The matrix 12 includes a skeleton formed by cross-arranged water-containing fibers and a thermoplastic resin filling the spaces between the skeleton. The water-containing fibers can be water-containing acidified fibers, or more specifically, the fibers are natural cellulose fibers, such as wood pulp fibers, cotton fibers, sugarcane fibers, or bamboo fibers. The thermoplastic resin can be polyvinyl chloride, polyvinylidene chloride, polyethylene, polypropylene, or a polymer formed by polyethylene and polypropylene.

[0038] In one specific embodiment, the substrate 12 is formed by impregnating the skeleton in a thermoplastic resin and then pressing it into a sheet. In another embodiment, the skeleton is a network structure formed of water-containing fibers. More specifically, the skeleton is a nonwoven fabric formed of wood pulp fibers. In this embodiment, the substrate 12 is formed by impregnating the nonwoven fabric in polyethylene and then cooling and hot-pressing it into a sheet.

[0039] The isolation layer 13 includes a barrier substrate layer and a barrier coating disposed on the barrier substrate layer. The barrier substrate layer is used to provide support for the barrier coating and to bond the isolation layer 13 to the surface layer 14. In this embodiment, the barrier substrate layer can be a polymer film. Specifically, the polymer film can be a film formed by blending at least one or more polymers whose monomers are esters, amides, or olefins. Preferably, the barrier substrate 12 is a polyolefin film, specifically, it can be uniaxial or biaxially oriented polypropylene (PP, OPP, BOPP), polyethylene, such as oriented or non-oriented high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE), and cyclic olefin copolymers (COC), etc.

[0040] In a preferred embodiment, the barrier substrate layer is a multilayer composite film with a gradient distribution of crystallinity. The gradient distribution means that the difference in crystallinity between adjacent layers is greater than 5%. For example, in one embodiment, the barrier substrate layer includes at least three structural layers, and the difference in crystallinity between adjacent structural layers is greater than 5%. In another embodiment, the barrier substrate layer includes five structural layers, specifically an outer structural layer, an inner structural layer, and an intermediate layer, a second intermediate layer, and a third intermediate layer located between the outer structural layers. The crystallinity decreases sequentially from the outer structural layer to the inner structural layer, and the difference in crystallinity between adjacent structural layers is 5%-15%. Studies have found that configuring the crystallinity of the structural layers into a gradient distribution causes changes in the microstructure of adjacent structural layers. When oxygen moves from one type of microstructure to another different microstructure, a greater resistance is formed at the interface, thus improving the barrier performance against oxygen. The difference in crystallinity between adjacent structural layers refers to the difference between the higher crystallinity and the lower crystallinity in adjacent structural layers.

[0041] Furthermore, the crystallinity of the outer structural layer is 78%–85%, and the crystallinity of the inner structural layer is 35%–50%.

[0042] Furthermore, the barrier substrate layer is an MDOPE film, and the crystallinity of each structural layer ranges from 40% to 80%. Within this range, it can not only satisfy excellent barrier properties, but also provide good support for the barrier layer and better adaptability for subsequent vapor deposition or coating processes.

[0043] Furthermore, the barrier layer has a basis weight of 20-30 g / m².

[0044] The barrier coating is basically composed of aluminum metal or aluminum oxide and can be deposited on the barrier substrate layer by physical vapor deposition (PVD) or chemical vapor deposition (CVD). The barrier coating has a thickness of 10-30 nm. Studies have found that within this range, it can provide sufficient oxygen barrier performance and at the same time ensure that the isolation layer 13 and the substrate 12 are bonded together without delamination.

[0045] Furthermore, the barrier coating has a thickness of 18–28 nm, or more preferably 22–26 nm.

[0046] In addition, since the barrier coating is mainly composed of aluminum oxide, it is more brittle. In this case, a thickness of 15 to 25 nm can be selected.

[0047] Furthermore, a metal foil layer is laminated on one side of the barrier substrate layer to form better oxygen barrier performance. The metal foil layer is disposed on the side opposite to the barrier coating, and the thickness of the metal foil layer is 1-6 μm.

[0048] The surface layer 14 is a thermoplastic plastic, preferably selected from at least one of polyolefins, vinyl polymers, polyacrylates, polyamides, polyurethanes, polyureas, polyimides, polyesters, polyethers, polystyrene, PMMA, SAN, TPO, TPU, and POM.

[0049] Furthermore, the surface layer 14 is made of olefin resins such as polyethylene and polypropylene, including low-density polyethylene, linear low-density polyethylene, metallocene linear low-density polyethylene, high-density polyethylene, medium-density polyethylene, ethylene / vinyl acetate copolymer, ethylene / acrylic acid copolymer, ethylene / ethyl acrylate copolymer, etc., and can also be used in appropriate combinations. More preferably, the surface layer 14 is mainly made of polyethylene.

[0050] Furthermore, the melt flow index (190℃ / 2.16kg) of the surface layer 14 ranges from 5 to 20 g / 10 min, and the density ranges from 0.910 to 0.930 g / cm³. 3 The weight of the bottom layer 11 can range from 10 to 30 g / m³. 2 Within the range.

[0051] Furthermore, the bottom layer 11 has a thickness of 0.5 to 5 mm.

[0052] In a preferred embodiment, the surface layer 14 is made of the same material as the bottom layer 11, so that the bottom layer 11 and the surface layer 14 can be better bonded together.

[0053] The following section will further explain the preparation method of the cover.

[0054] S1: Provides a bottom layer 11, including a matrix 12 containing water-containing fibers, an isolation layer 13, and a top layer 14;

[0055] The bottom layer 11, substrate 12, isolation layer 13 and top layer 14 have been described in detail above and will not be repeated here.

[0056] S2: The bottom layer 11, the substrate 12, the isolation layer 13 and the top layer 14 are stacked to form the laminate 10;

[0057] The laminate 10 is formed by stacking the bottom layer 11, the substrate 12, the isolation layer 13 and the top layer 14. It is understood that the barrier coating of the isolation layer 13 is located between the substrate 12 and the barrier substrate layer. In a preferred embodiment, an adhesive is also provided between the substrate 12 and the isolation layer 13 to form a fixed bond between the substrate 12 and the isolation layer 13.

[0058] In this embodiment, the area of ​​the substrate 12 and the isolation layer 13 is smaller than that of the bottom layer 11 and the top layer 14. More specifically, the shape and area of ​​the substrate 12 and the isolation layer 13 are the same, so that the substrate 12 and the isolation layer 13 overlap. The projection of the substrate 12 on the bottom layer 11 is located inside the bottom layer 11, so that the bottom layer 11 includes a first end 111 surrounding the periphery of the substrate 12. The first end 111 is annular. Similarly, the top layer 14 also includes a second end 141 surrounding the periphery of the substrate 12. The second end 141 is also annular.

[0059] S3: The laminate 10 is molded by a mold 20. Inside the mold 20, the bottom layer 11, the substrate 12 and the surface layer 14 are deformed. The bottom layer 11 and the surface layer 14 are bonded together along the periphery of the substrate 12 to form a high-density area, and the high-density area closes the substrate 12.

[0060] Please refer to this as well. Figure 2 ,exist Figure 2 The mold 20 is shown in the figure. The mold 20 includes a lower mold 21 and an upper mold 22. After the upper mold 22 and the lower mold 21 are closed, they include a cavity. It can be understood that the cavity corresponds to the shape of the cover so that the laminate 10 is molded to form a cover after the upper mold 22 and the lower mold 21 are closed.

[0061] Understandably, after the upper mold 22 and the lower mold 21 are closed, when the laminate 10 is molded, the bottom layer 11, the base 12 and the surface layer 14 are deformed, so that a part of them forms a bottom plate and another part of them forms a side plate.

[0062] The lower mold 21 includes a first heating device 211 for heating the bottom layer 11 and causing at least a portion of the bottom layer 11 to melt and form an integral with the substrate 12. Similarly, the upper mold 22 includes a second heating device 221 for heating the surface layer 14 and causing at least a portion of the surface layer 14 to melt and form an integral with the isolation layer 13.

[0063] In a preferred embodiment, the first heating device 211 and the second heating device 221 are configured to give the bottom layer 11 and the top layer 14 a temperature of 180°C to 250°C.

[0064] The upper mold 22 further includes a pressing device 222, which is configured to move movably toward the center of the cavity to apply pressure to the second end 141 of the surface layer 14 and combine with the first end 111 to form a joint 142, wherein the density of the joint 142 is greater than the density of the surface layer 14 or the bottom layer 11.

[0065] Furthermore, the density of the joint 142 is greater than or equal to 150% of the density of the surface layer 14 or the bottom layer 11.

[0066] Furthermore, the pressure applied by the pressing device 222 to the second end 141 is greater than the mold closing pressure.

[0067] In this way, on the one hand, the substrate and the insulating layer are sealed within the cavity formed by the top and bottom layers; on the other hand, the excellent oxygen barrier properties formed by the substrate and the insulating layer ensure that the OTR of the cap is <1cm. 3 / m 2 At 1 atm, 23°C, and 50% RH, it forms an excellent barrier effect, meeting the needs of aseptic liquid food packaging such as milk. At the same time, the above method can be used with existing molds, resulting in low modification costs.

[0068] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for manufacturing sterile liquid food packaging caps using water-containing fiber molding, characterized in that, include: S1: Provides a base layer, including a matrix containing water-containing fibers, an isolation layer, and a top layer; S2: A laminate is formed by stacking the bottom layer, the substrate, the isolation layer, and the top layer; S3: The laminate is molded using a mold. Inside the mold, the bottom layer, the substrate, and the top layer are deformed. The bottom layer and the top layer bond together along the periphery of the substrate to form a high-density bond. The bond, the top layer, and the bottom layer seal the substrate. In step S2, the area of ​​the substrate and the isolation layer is smaller than that of the bottom layer and the top layer. The shape of the substrate and the isolation layer is the same as the area. The bottom layer includes a first end surrounding the periphery of the substrate, and the top layer includes a second end surrounding the periphery of the substrate. The first end and the second end are annular. The mold includes an upper mold and a lower mold. When the upper mold and the lower mold include a cavity, the upper mold also includes a pressing device. The pressing device is configured to move movably towards the center of the cavity. In step S3, the pressing device moves movably towards the center of the cavity and applies pressure to the second end of the top layer to combine with the first end to form a joint. The density of the joint is greater than or equal to 150% of the density of the top layer or the bottom layer.

2. The method as described in claim 1, characterized in that, It includes a skeleton formed by cross-arranged water-containing fibers and a thermoplastic resin filling the spaces between the skeleton. The water-containing fibers are one of wood pulp fibers, cotton fibers, sugarcane fibers, or bamboo fibers, and the thermoplastic resin is polyvinyl chloride, polyvinylidene chloride, polyethylene, polypropylene, or a polymer formed by polyethylene and polypropylene.

3. The method as described in claim 2, characterized in that, The isolation layer includes a barrier substrate layer and a barrier coating disposed on the barrier substrate layer. The barrier substrate layer is a polymer film, and the barrier coating is an aluminum metal or aluminum oxide coating with a thickness of 10-30 nm.

4. The method as described in claim 3, characterized in that, The barrier substrate layer is a multilayer composite film with a gradient distribution of crystallinity. The barrier substrate layer includes at least three structural layers. The barrier substrate layer is an MDOPE film, and the crystallinity of each structural layer ranges from 40% to 80%. The barrier substrate layer includes five structural layers, namely an outer structural layer, an inner structural layer, and an intermediate layer, a second intermediate layer, and a third intermediate layer located between the outer structural layers. The crystallinity decreases sequentially from the outer structural layer to the inner structural layer, and the crystallinity difference between adjacent structural layers is 5% to 15%.

5. The method as described in claim 4, characterized in that, The skeleton is a nonwoven fabric formed from wood pulp fibers.

6. The method as described in claim 4, characterized in that, The lower mold includes a first heating device, and the upper mold includes a second heating device. In step S3, the first heating device heats the bottom layer, causing at least a portion of the bottom layer to melt and form an integral part with the substrate. The second heating device heats the surface layer, causing at least a portion of the surface layer to melt and form an integral part with the isolation layer.

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