A light-weight container having a thermoformed preform thin-walled base body and a post-injection reinforcing rib and a method for producing the same

Abstract

The application discloses a kind of lightweight container with thermoforming preform thin-walled matrix and secondary injection reinforcing rib and preparation method, and the lightweight container includes container matrix, and segmented reinforcing structure is evenly or unevenly distributed along the mouth, and the container matrix sidewall, container bottom, container cover are provided with evenly or unevenly distributed reinforcing rib, and the reinforcing structure along the mouth and reinforcing rib can be integrally formed by secondary injection molding process;Reinforcing rib is one or more of horizontal, vertical, arc, radial or irregular shape;Container matrix is prepared as thin-walled structure by vacuum positive and negative pressure thermoforming, and then reinforcing rib is formed by secondary injection molding process in key stress area and container along mouth position.The application realizes the purpose that the structure strength of finished product is not lower than traditional container and the container is greatly reduced in weight by using two-step forming process, and simultaneously has the characteristics of appearance beauty, process is adapted to various degradable environmental protection materials, and meets the requirements of mass production.

Description

Technical Field

[0001] This application relates to the field of disposable food container technology, and in particular to a lightweight container with a thermoformed pre-formed thin-walled substrate and secondary injection molding reinforcement, and a method for preparing the same. Background Technology

[0002] Disposable food containers are widely used in takeout packaging, fresh food delivery, and other scenarios, requiring high standards for structural strength, heat resistance, and environmental biodegradability. With the advancement of environmental policies, the demand for lightweight containers is increasing, leading to the development of various molding technologies.

[0003] The first method is vacuum positive and negative pressure thermoforming. This process uses plastic sheets as raw materials and can stably produce ultra-thin-walled container substrates with outstanding lightweight effects. However, due to the limitations of the sheet stretching and forming process, the structural strength of the formed thin-walled substrate is relatively low. The side walls, corners, bottoms, and other stress-bearing parts are prone to deformation and damage, and it cannot meet the requirements for daily load-bearing and stacking when used alone. If it is thickened, the weight reduction target cannot be achieved.

[0004] The second type is the traditional one-piece injection molding process. Due to limitations in melt flowability and mold filling properties, the thickness of the container base wall produced by this process is difficult to achieve the ultra-thin level of thermoforming, resulting in very limited space for weight reduction. At the same time, constrained by process conditions such as injection channels and cooling shrinkage, the thickness of the reinforcing ribs added to the product usually cannot exceed 50% of the base wall thickness, greatly reducing the reinforcement effect and making it difficult to effectively improve the overall structural strength of the container.

[0005] The third approach is to achieve lightweighting using a foamed sandwich structure. This structure reduces the weight of the container by foaming the material, but the heat resistance temperature of foamed materials is usually only around 60°C, which is not suitable for high-temperature food preparation scenarios; the foamed layers are prone to damage and have insufficient interlayer bonding during use; at the same time, the food contact safety and environmental biodegradability of foamed materials are also limited, making them unsuitable for widespread use in scenarios with high environmental protection requirements.

[0006] In summary, all three approaches have varying degrees of technical shortcomings. Achieving significant weight reduction while ensuring the structural strength of the container, and simultaneously considering the process compatibility and large-scale production of biodegradable materials, remains a pressing technical challenge for the disposable food container industry. Summary of the Invention

[0007] To address the aforementioned shortcomings of existing technologies, the present invention aims to provide a lightweight container with a thermoformed pre-fabricated thin-walled matrix and secondary injection-molded reinforcing ribs, and a method for preparing the same, thereby solving the following problems in the prior art: 1) Vacuum positive and negative pressure thermoforming can produce ultra-thin-walled substrates to achieve deep weight reduction, but the rigidity of the product body is insufficient, and the stressed parts are prone to deformation and damage; one-piece injection molding is difficult to achieve the ultra-thin wall thickness of thermoforming, the weight reduction space is limited, and due to process limitations, the thickness of the reinforcing ribs can only be within 50% of the substrate wall thickness, and the reinforcement effect is weak; traditional one-piece injection molding process is limited by material flowability and mold filling pressure, making it difficult to produce ultra-thin-walled substrates, the weight reduction of the container is small, and it cannot meet the requirements of deep lightweighting; 2) Existing lightweight technologies generally suffer from the problem of "weight reduction inevitably leads to strength reduction", making it impossible to provide localized and differentiated reinforcement at key stress points of the container, and it is difficult to balance weight reduction and structural strength. At the same time, foamed sandwich structures also have defects such as poor heat resistance, easy breakage, and insufficient adaptability to food use and environmental protection.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A lightweight container with a thermoformed pre-fabricated thin-walled substrate and secondary injection-molded reinforcing ribs includes a container substrate; the sidewalls and / or bottom of the container substrate are provided with reinforcing ribs to improve the overall strength, the reinforcing ribs are formed on the outside of the container substrate by secondary injection molding, and the reinforcing ribs are one or more of the following shapes: horizontal, vertical, arc-shaped, radial, and irregular.

[0009] As an embodiment of the present invention, the lightweight container further includes a container lid adapted to the container base, and the container lid is provided with reinforcing ribs.

[0010] As an embodiment of the present invention, the reinforcing ribs are evenly distributed on the outer side wall and / or bottom of the container base, and their structural form is one or more of the following: straight line, curve, broken line, wavy line, horizontal, vertical, arc, radial, and irregular shape.

[0011] As an embodiment of the present invention, the outer sidewall is provided with a plurality of uniformly distributed vertical main reinforcing ribs along the height direction of the container.

[0012] As an embodiment of the present invention, the container base is provided with a full-circle or segmented reinforcing structure at the opening edge. The segmented reinforcing structure can be uniformly or non-uniformly distributed. The edge reinforcing structure and the reinforcing ribs of the side wall and bottom are integrally formed by secondary injection molding.

[0013] As an embodiment of the present invention, the sidewall is provided with a plurality of vertical main reinforcing ribs, and transverse auxiliary reinforcing ribs are evenly arranged between adjacent vertical main reinforcing ribs; the vertical main reinforcing ribs and transverse auxiliary reinforcing ribs are interwoven to form a composite reinforcing rib.

[0014] As an embodiment of the present invention, the vertical main reinforcing rib and the horizontal auxiliary reinforcing rib are arc-shaped curve structures.

[0015] As an embodiment of the present invention, the cross-section of the reinforcing rib is cylindrical, elliptical, square, or trapezoidal.

[0016] As an embodiment of the present invention, the cross-section of the vertical main stiffener is larger than the cross-section of the transverse auxiliary stiffener.

[0017] As an embodiment of the present invention, the bottom of the container and / or the container lid are provided with radial reinforcing ribs that are evenly distributed radially outward from the center of the bottom of the container and / or the container lid.

[0018] As an embodiment of the present invention, corner reinforcing ribs are provided at the connection between the side wall and the bottom of the container, and at the corners where adjacent side walls are connected.

[0019] As an embodiment of the present invention, the container base is provided with composite aesthetic reinforcing ribs, the composite aesthetic reinforcing ribs comprising: Vertical main stiffeners and horizontal auxiliary stiffeners are staggered and arranged on the side wall; Corner reinforcing ribs are provided at the connection between adjacent side walls of the container base and / or at the corner where the side wall and the bottom of the container are connected; And radial reinforcing ribs are provided at the bottom of the container, extending radially and evenly outward from the center.

[0020] As an embodiment of the present invention, the cross-sectional dimension of the corner stiffener is larger than that of the vertical main stiffener.

[0021] As an embodiment of the present invention, the cross-sectional dimension of the bottom radial reinforcing rib is larger than the cross-sectional dimension of the transverse auxiliary reinforcing rib.

[0022] As an embodiment of the present invention, the lightweight container is in the form of a circle, ellipse, frustum, rectangle, square or multi-compartment structure.

[0023] As an embodiment of the present invention, when the lightweight container has a rectangular or square structure, corner reinforcing ribs extending from the vertices along the edges are respectively provided at the vertices where the three edges intersect.

[0024] As an embodiment of the present invention, each side wall is provided with multiple vertical main reinforcing ribs, and transverse auxiliary reinforcing ribs are evenly arranged between adjacent vertical main reinforcing ribs; an arc-shaped transition rib is provided at the connection between the vertical main reinforcing ribs and the transverse auxiliary reinforcing ribs, and the arc-shaped transition rib is smoothly connected to the two types of ribs without sharp edges.

[0025] As an embodiment of the present invention, the lightweight container is sealed by heat sealing, ordinary cap sealing, or screw cap sealing.

[0026] As an embodiment of the present invention, the container base is a smooth thin-walled cavity with a side wall thickness of 0.1 to 0.6 mm, preferably 0.15 to 0.25 mm.

[0027] The lightweight container is made by thermoforming equipment, preferably by vacuum positive and negative pressure thermoforming. Secondary injection molding reinforcing ribs are fixed to the outer wall, corners and key stress positions of the container base. While significantly reducing weight, the overall structural strength of the container is not lower than that of traditional containers, and the aesthetic appearance and compatibility with the large-scale mass production of biodegradable materials are also taken into account.

[0028] As an embodiment of the present invention, the sidewall composite aesthetic reinforcing rib is composed of vertical main ribs, horizontal auxiliary ribs and arc-shaped transition ribs; the cross-sectional thickness of the vertical main reinforcing rib is 100% to 200% of the container base wall thickness, the cross-sectional thickness of the horizontal auxiliary reinforcing rib is 30% to 100% of the container base wall thickness, the cross-sectional thickness of the arc-shaped transition rib is 50% to 150% of the container base wall thickness, the cross-sectional thickness of the corner reinforcing rib is 300% to 600% of the container base wall thickness, and the cross-sectional thickness of the bottom radial rib is 100% to 200% of the container base wall thickness.

[0029] As an embodiment of the present invention, 2 to 3 vertical main reinforcing ribs are provided on each side of the outer wall of the container base, and 1 to 2 horizontal auxiliary reinforcing ribs are evenly arranged between the vertical main reinforcing ribs.

[0030] As an embodiment of the present invention, 2 to 3 vertical main reinforcing ribs are provided on each side outer wall of the container base, and 1 to 2 horizontal auxiliary reinforcing ribs are evenly arranged between the vertical main reinforcing ribs. Arc-shaped transition ribs are provided at the connection between the vertical main reinforcing ribs and the horizontal auxiliary reinforcing ribs. The arc-shaped transition ribs are smoothly connected to the vertical main reinforcing ribs and the horizontal auxiliary reinforcing ribs without sharp edges.

[0031] As an embodiment of the present invention, the container base is provided with a full-circle or segmented reinforcing structure around the opening. The segmented reinforcing structure is uniformly or non-uniformly distributed, and the reinforcing structure is made by secondary injection molding.

[0032] As an embodiment of the present invention, the container substrate is made by vacuum positive and negative pressure thermoforming in a thermoforming machine.

[0033] As an embodiment of the present invention, the container base and the secondary injection molding reinforcing ribs are made of food-grade PP material or biodegradable and environmentally friendly material.

[0034] The present invention also provides a method for preparing a lightweight container with reinforcing ribs, comprising the following steps: S1. Prepare the raw materials into sheets and prefabricate the ultra-thin-walled container substrate using a vacuum positive and negative pressure thermoforming process; S2. Use independent injection molding equipment to perform secondary local composite injection molding reinforcement at key stress locations of the container substrate.

[0035] This method overcomes the bottleneck of traditional one-piece injection molding, which makes it difficult to form ultra-thin walls. By combining a two-step molding process, it can achieve significant weight reduction while ensuring the overall structural strength of the container.

[0036] As an embodiment of the present invention, food-grade PP sheets or biodegradable sheets are used for vacuum positive and negative pressure thermoforming. The thermoforming process can stably produce smooth thin-walled cavities with uniform wall thickness, no internal stress accumulation, and no wall thickness deviation, providing a regular reference surface for subsequent secondary injection molding and reinforcement, and ensuring the composite accuracy of the reinforcing ribs and the substrate.

[0037] In one embodiment of the present invention, the secondary injection-molded reinforcing rib and the thin-walled container substrate are connected by injection molding using the same material. This same-material connection ensures good compatibility and bonding between the reinforcing rib and the thin-walled substrate, avoiding interface delamination or rib separation due to material differences, and ensuring the structural integrity of the container.

[0038] As an embodiment of the present invention, the container substrate is made of a biodegradable and environmentally friendly material, which includes one or a blend of multiple materials such as polylactic acid, polybutylene adipate-butyl terephthalate, corn starch-based biodegradable material, rice husk-based composite biodegradable material, polyhydroxyalkanoate, bamboo fiber-based composite biodegradable material, and wheat bran-based biodegradable material.

[0039] All of the above-mentioned biodegradable materials have been verified for process compatibility and are fully compatible with existing thermoforming and secondary injection molding processes, enabling large-scale mass production and meeting environmental protection policy requirements.

[0040] As an embodiment of the present invention, the corn starch-based biodegradable material is made by blending corn starch and polylactic acid.

[0041] Preferably, the corn starch and polylactic acid are blended in a mass ratio of 4:6 to 6:4. As an embodiment of the present invention, the rice husk-based composite biodegradable material is made by blending rice husk powder, polybutylene adipate-butyl terephthalate (PBAT), and polylactic acid (PLA).

[0042] Preferably, the rice husk powder, PBAT and PLA are blended in a mass ratio of 2:3:5 to 3:4:3. As an embodiment of the present invention, the bamboo fiber-based composite biodegradable material is made by blending bamboo fiber, polylactic acid (PLA) and polybutylene adipate-butyl terephthalate (PBAT).

[0043] Preferably, the bamboo fiber, PLA and PBAT are blended in a mass ratio of 1:4:5 to 2:5:3.

[0044] As an embodiment of the present invention, the bran-based biodegradable material is made by blending wheat bran powder with polylactic acid.

[0045] Preferably, the wheat bran powder and PLA are blended in a mass ratio of 4:6 to 5:5.

[0046] By using multi-component blending modification, the molding defects of various natural-based biodegradable materials, such as easy cracking, poor flowability, and uneven dispersion, are solved when used alone, so that they can meet the process requirements of thermoforming and secondary injection molding.

[0047] The beneficial effects of this invention are: 1) Thermoforming is the core support for achieving ultra-thin walls and lightweight construction. It offers excellent adaptability for ultra-thin wall molding, enabling stable and large-scale production of ultra-thin, homogeneous thin-walled substrates ranging from 0.1mm to 0.6mm. This avoids the pain points of one-piece injection molding, such as the inability to form ultra-thin cavities, flow marks and shrinkage during high-pressure molding, and cavity deformation and warping. It provides the basic structural conditions for approximately 30% weight reduction and also provides a good benchmark for injection molding of aesthetically pleasing composite reinforcing ribs on the sidewalls. Thermoforming produces smooth, thin-walled cavities without reinforcing ribs, overcoming the technical bottleneck of the inability to stably form ultra-thin walls using a single injection molding process. The thin-walled substrate has no internal stress accumulation or wall thickness deviation, resulting in stable molding quality and providing the basic structural conditions for significant weight reduction. Furthermore, the continuous closed-loop production line operation of thermoforming seamlessly integrates with the secondary injection molding process, offering significant advantages for large-scale mass production.

[0048] 2) By using secondary local injection molding to precisely composite reinforcing ribs at key stress locations on the sidewalls, corners, and bottom of the container, a combination of aesthetically pleasing composite reinforcing ribs on the sidewalls, triangular ribs at the corners, and radial ribs at the bottom is adopted to achieve differentiated local reinforcement for different stress locations. While significantly reducing weight, the overall structural strength of the container is not lower than that of traditional containers, thus completely solving the technical pain point of "weight reduction inevitably leads to reduced strength" in existing technologies.

[0049] 3) This application provides a lightweight container with a thermoformed prefabricated thin-walled substrate reinforced by secondary injection molding. The core improvement lies in the adoption of a two-step molding structure: "prefabricated thin-walled substrate + secondary local injection molding of reinforcing ribs." A smooth, thin-walled cavity without reinforcing ribs is prepared using thermoforming, overcoming the technical bottleneck of traditional one-time injection molding processes that cannot stably form ultra-thin-walled substrates. Then, secondary local injection molding of composite reinforcing ribs is performed at key stress-bearing locations on the container's sidewalls, corners, and bottom using an independent injection molding machine. The reinforcing ribs employ a combination of aesthetically pleasing composite reinforcing ribs on the sidewalls, corner triangular ribs, and bottom radial ribs. The aesthetically pleasing composite reinforcing ribs on the sidewalls are composed of vertical main reinforcing ribs, horizontal auxiliary reinforcing ribs, and arc-shaped transition ribs. Unlike traditional single vertical ribs, these ribs have smooth lines and an aesthetically pleasing appearance, significantly improving the container's appearance quality while balancing structural strength and aesthetics. This achieves significant weight reduction while ensuring the overall structural strength of the container is no less than that of traditional containers.

[0050] 4) Food safety and environmental protection can be balanced. The thin-walled container base and reinforcing ribs are compatible with food-grade PP material and a variety of biodegradable and environmentally friendly materials. The food-grade PP material is formed by low-temperature stretching throughout the process, with no risk of thermal degradation of raw materials, and meets food contact standards. All biodegradable materials have been verified for process compatibility and are fully compatible with thermoforming and secondary injection molding processes, enabling large-scale mass production and meeting the requirements of environmental protection policies for biodegradable packaging. It is suitable for various usage scenarios such as takeout packaging and fresh food delivery.

[0051] 5) Strong feasibility for mass production: The single-cavity molding efficiency of this solution is on par with that of traditional single-cavity molding. The thermoforming process is a continuous closed-loop production line operation, which is seamlessly connected with the secondary injection molding process. The tonnage requirements of the injection molding equipment are significantly reduced, eliminating the need for large-tonnage high-pressure injection molding equipment, thus reducing equipment investment and maintenance costs. At the same time, the process is smoothly connected, with no excess waste or matrix damage during the molding process, resulting in a significant increase in yield and further reducing unit production costs. It has outstanding advantages for large-scale implementation.

[0052] 6) The tooling has a high degree of fit and conformity. The thermoformed prefabricated thin-walled substrate has a regular shape and straight edges. After being placed into the special positioning and limiting tooling, the fitting accuracy is high. There is no displacement, no collapse, and no deformation during the secondary injection molding process, which ensures that the reinforcing ribs are firmly bonded to the substrate without delamination or detachment. At the same time, it ensures the forming accuracy and appearance of the reinforcing ribs.

[0053] 7) Lower overall mass production cost: The thermoforming mold has a simple structure and low cost. Equipment energy consumption and maintenance losses are lower than those of large-tonnage injection molding equipment. Combined with approximately 30% savings in raw material consumption, the overall cost is reduced in both directions. Furthermore, the composite reinforcing ribs do not require additional raw material consumption; aesthetics are achieved solely through layout optimization, making it suitable for large-scale implementation. Strong pattern expansion compatibility allows for adaptation to prefabrication of various container sizes, enabling rapid product changeovers and a wide range of flexible production options.

[0054] 8) The container base and container lid of the present invention can be used together or separately. When the container base is used alone, the sealing method can be one of the following: no sealing, heat sealing, ordinary cap sealing, or screw cap sealing. The reinforcing ribs can be evenly or non-evenly distributed; the form of the reinforcing ribs is selected from one or more combinations of transverse reinforcing ribs, vertical reinforcing ribs, arc-shaped reinforcing ribs, radial reinforcing ribs, and irregularly shaped reinforcing ribs.

[0055] In summary, the synergistic effect of thermoforming and secondary injection molding with local reinforcement can stably achieve lightweight and energy-saving mass production without reducing the performance of the container, taking into account environmental protection, aesthetics, and process adaptability, and making up for the shortcomings of existing technologies. Therefore, the present invention designs a lightweight container with reasonable structure, reliable strength, stable weight reduction of about 30%, compatibility with a variety of biodegradable materials, strong process adaptability, suitable for high-speed mass production, and also taking into account the aesthetic appearance. Attached Figure Description

[0056] Figure 1 A schematic diagram of the overall structure of a lightweight container with secondary injection molding reinforcement for a thermoformed prefabricated thin-walled container substrate; Figure 2 A schematic diagram of the bottom structure of a container with radial reinforcing ribs; Figure 3 A schematic diagram of the structure of a container lid with radial reinforcing ribs.

[0057] Reference numerals: 10-Container base; 11-Side wall; 12-Container bottom; 20-Container lid; 31-Vertical main stiffener; 32-Transverse auxiliary stiffener; 33-Radial stiffener. Detailed Implementation

[0058] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0059] Embodiments of the present invention, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The terms “first,” “second,” “third,” etc. (if present) in the specification, claims, and drawings of the present invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the objects thus described can be interchanged where appropriate. Furthermore, the terms “comprising” and “having,” and any variations thereof, are intended to cover non-exclusive inclusion. Directional terms used in the present invention, such as: up, down, left, right, front, back, inside, outside, side, etc., are only for the purpose of referring to the drawings. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. Furthermore, the present invention repeats reference numerals and / or reference letters in different examples; this repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, the present invention provides examples of various specific processes and materials, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0060] Example 1 This embodiment provides a lightweight container with a thermoformed prefabricated thin-walled substrate reinforced by secondary injection molding. It has a square structure with a length of 180mm, a width of 120mm, and a height of 80mm, which is suitable for conventional takeout packaging sizes. The thin-walled container substrate is made of food-grade homopolymer polypropylene.

[0061] like Figure 1 As shown, the container in this embodiment is composed of a thin-walled container base and secondary injection molding reinforcing ribs. The thin-walled base is a smooth thin-walled cavity without reinforcing ribs.

[0062] Food-grade homopolymer polypropylene particles are melt-extruded into sheets with a thickness of 0.7 mm. The sheets are free of impurities, bubbles, and scratches, and comply with the GB / T 18006.1-2009 standard for disposable plastic containers for food packaging.

[0063] The above sheet material is fed into a thermoforming machine, and the heating temperature is set to 160℃, the vacuum negative pressure value is -0.08MPa, the stretching rate is 50mm / s, the cooling temperature is 30℃, and the cooling time is 2.5s. A smooth, unreinforced thin-walled container substrate 1 with a wall thickness of 0.20mm is prepared by vacuum positive and negative pressure thermoforming.

[0064] After molding, the container substrate has no warping, no wall thickness deviation (deviation not exceeding ±0.01mm), and no internal stress accumulation. The substrate weight is 12.3g, providing a regular reference surface for subsequent secondary injection molding and reinforcement.

[0065] The thin-walled container substrate 1 is placed into a special positioning fixture. The fixture adopts an elastic limiting structure with a positioning accuracy of ±0.05mm and an elastic limiting pressure of 0.4MPa to prevent the substrate from shifting, collapsing, or deforming during secondary injection molding.

[0066] The positioning fixture containing the thin-walled container substrate 1 is fed into an independent injection molding machine. The reinforcing rib material for injection is homopolymer polypropylene granules. The injection temperature is set to 245℃, the holding pressure to 8MPa, the injection rate to 35mm / s, the cooling temperature to 25℃, the cooling time to 1.5s, and the holding time to 2s. Composite reinforcing ribs are injected at key stress locations on the container.

[0067] The reinforcing ribs adopt a combination layout of side wall composite aesthetic reinforcing ribs, corner triangular ribs (4 in total) and bottom radial ribs (8 in total).

[0068] The composite aesthetic reinforcement of the side wall adopts a composite design of vertical main reinforcement and horizontal auxiliary reinforcement. Two vertical main reinforcements are set on each side wall, with a spacing of 45mm between adjacent vertical main reinforcements. Two horizontal auxiliary reinforcements are evenly arranged between the vertical main reinforcements, with a spacing of 30mm between adjacent horizontal auxiliary reinforcements.

[0069] The thickness of the reinforcing ribs in each part is set as follows: the thickness of the vertical main reinforcing rib 31 is 150% of the base thickness, i.e., 0.3mm; the thickness of the horizontal auxiliary reinforcing rib 32 is 50% of the base thickness, i.e., 0.1mm. The corner triangular ribs are arranged at each corner of the container, with a thickness of 600% of the base thickness, i.e., 1.2mm, to bear the maximum corner support strength.

[0070] The bottom radial ribs 4 are evenly distributed radially outward from the center of the bottom of the container, with a thickness of 200% of the base thickness, i.e., 0.4 mm, to evenly distribute the force at the bottom.

[0071] The reinforcing ribs and the thin-walled container substrate are bonded together using the same material (food-grade polypropylene), with no delamination or rib separation, and the bonding strength is not less than 25MPa.

[0072] After injection molding, maintain pressure for 2 seconds, cool and solidify, then demold using a flexible demolding mechanism, stack, and bag.

[0073] By adopting a two-step molding structure of thermoformed prefabricated ultrathin-walled substrate and secondary local injection molding reinforcement, the wall thickness of the thin-walled substrate can be stably prepared down to 0.2mm, breaking through the technical bottleneck that traditional one-time injection molding process cannot form ultrathin walls, thereby achieving a significant weight reduction.

[0074] Testing revealed that the finished container weighs 17.8g, a 32.1% reduction compared to a traditional one-time injection molded polypropylene container (same size, 0.4mm thickness, 26.2g). Its compressive strength is 1200N, higher than the traditional one-time injection molded container (1150N). It can be stacked up to 25 layers without deformation or damage. Its impact resistance meets GB / T 18006.1-2009 standards. In terms of appearance, the composite reinforcing ribs have smooth lines, achieving an aesthetic score (out of 10) of 8.5 or higher, significantly higher than the traditional container (5.2).

[0075] Example 2 Based on Example 1, this embodiment further specifies the materials of the thin-walled container matrix and the secondary injection molding reinforcing ribs. The food-grade polypropylene is replaced with a biodegradable blend of polylactic acid and polybutylene adipate-butyl terephthalate in a mass ratio of 7:3.

[0076] Polylactic acid (PLA) and polybutylene adipate-butylene terephthalate (PET) particles were blended at a mass ratio of 7:3 and melt-extruded to produce a biodegradable sheet with a thickness of 0.8 mm. The melt flow rate was 2.0–3.0 g / 10 min, and the density was 1.20–1.25 g / cm³. 3 The tensile strength is not less than 25 MPa, and the flexural strength is not less than 30 MPa.

[0077] The biodegradable sheet was fed into a thermoforming machine, and the heating temperature was set to 155℃, the vacuum negative pressure value to be -0.08MPa, the stretching rate to be 50mm / s, the cooling temperature to be 30℃, and the cooling time to be 3.5s. A smooth, unreinforced thin-walled substrate 1 with a wall thickness of 0.25mm was prepared. After molding, the substrate had no warping or wall thickness deviation, and the substrate weight was 15.4g.

[0078] The thin-walled container substrate is placed into a special positioning fixture and sent into an independent injection molding machine. The injection temperature is set to 205°C, the holding pressure to 8MPa, the injection rate to 35mm / s, the cooling temperature to 25°C, the cooling time to 2s, and the holding time to 2.5s. The composite reinforcing ribs are injection molded according to the same reinforcing rib layout and thickness ratio as in Example 1.

[0079] The reinforcing ribs and the thin-walled container substrate are bonded together using the same material (a biodegradable blend of polylactic acid and polybutylene adipate-butyl terephthalate), with a bonding strength of not less than 25 MPa, and no delamination or rib detachment.

[0080] This embodiment solves the problem of easy cracking in thermoforming of polylactic acid by using polylactic acid and polybutylene adipate-butylene terephthalate as a blend modification, thus balancing rigidity and flexibility and making it suitable for large-scale mass production.

[0081] Testing revealed that the finished container weighs 21.2g, a 19.2% reduction compared to a traditional one-time injection molded polypropylene container (same size, 0.4mm thickness, 26.2g); and a 35.9% reduction compared to a traditional one-time environmentally friendly container of the same material (same size, 0.5mm thickness, 33.1g). Its compressive strength is 1180N, no less than that of a traditional one-time injection molded container (1150N). It can be stacked up to 25 layers without deformation or damage. The finished product can completely degrade in natural environments within 180–270 days, meeting environmental policy requirements.

[0082] Example 3 The difference between this embodiment and Embodiment 1 is that the material of the thin-walled matrix and the secondary injection-molded reinforcing ribs is replaced with a bamboo fiber-based composite biodegradable material, and the mass ratio of bamboo fiber, polylactic acid and polybutylene adipate-butyl terephthalate is 2:5:3.

[0083] Bamboo fiber, polylactic acid, and polybutylene adipate-butyl terephthalate particles were blended in a mass ratio of 2:5:3 and melt-extruded to produce a biodegradable sheet with a thickness of 0.8 mm. The melt flow rate was 2.2 g / 10 min, and the density was 1.26 g / cm³. 3 Tensile strength 24MPa, flexural strength 29MPa.

[0084] Biodegradable sheets were fed into a thermoforming machine. The heating temperature was set to 155℃, the vacuum negative pressure value to be -0.08MPa, the stretching rate to be 50mm / s, the cooling temperature to be 30℃, and the cooling time to be 3.5s. A smooth, unreinforced thin-walled container substrate with a wall thickness of 0.25mm was prepared. After molding, the substrate had no warping or wall thickness deviation, and the substrate weight was 16.2g.

[0085] The thin-walled container substrate is placed into a special positioning fixture (positioning accuracy ±0.05mm, elastic limiting pressure 0.4MPa), and sent into an independent injection molding machine. The injection temperature is set to 200℃, the holding pressure to 8MPa, the injection rate to 35mm / s, the cooling temperature to 25℃, the cooling time to 2s, and the holding time to 2.5s. Composite reinforcing ribs are injection molded according to the same reinforcing rib layout and thickness ratio as in Example 1. The thickness range of the reinforcing ribs is 0.1mm to 1.2mm.

[0086] The reinforcing ribs and the thin-walled substrate 1 are bonded together using the same material (bamboo fiber-based composite biodegradable material), with a bonding strength of not less than 25MPa, and no delamination or detachment.

[0087] After injection molding, maintain pressure for 2 seconds, cool for 2.5 seconds, and then demold using a flexible demolding mechanism for trimming.

[0088] The addition of bamboo fiber enhances the rigidity of the matrix, and the reinforcing ribs have a fine texture, making it suitable for high-end takeaway packaging scenarios where high appearance and texture are required. At the same time, the degradation cycle of this material is 150 to 210 days, making it more environmentally friendly than containers made of polylactic acid alone.

[0089] Testing revealed that the finished container weighs 22.6g, a 13.74% reduction compared to a traditional one-time injection molded polypropylene container (same size, 0.4mm thickness, 26.2g); and a 40.3% reduction compared to a traditional disposable environmentally friendly container of the same material (same size, 0.5mm thickness, 37.91g). Its compressive strength is 1160N, no less than that of the traditional container (1150N); it can be stacked up to 25 layers without deformation or damage; and the finished product can completely degrade in natural environments within 150–210 days.

[0090] Example 4 This embodiment provides another way to implement a natural-based biodegradable material. The difference from Embodiment 1 is that the material of the thin-walled matrix and the secondary injection-molded reinforcing ribs is replaced with a corn starch-based biodegradable material, and the mass ratio of corn starch to polylactic acid is 6:4.

[0091] Corn starch and polylactic acid (PLA) particles were blended at a mass ratio of 6:4. After PLA blending modification, the molding defects of pure corn starch, such as brittleness and poor flowability, were solved. The resulting material was melt-extruded into a biodegradable sheet with a thickness of 0.8 mm and a density of 1.22–1.28 g / cm³. 3 The tensile strength is not less than 22 MPa, and the flexural strength is not less than 28 MPa.

[0092] The biodegradable sheet was fed into a thermoforming machine, and the heating temperature was set to 155℃, the vacuum negative pressure value to be -0.08MPa, the stretching rate to be 50mm / s, the cooling temperature to be 30℃, and the cooling time to be 3.5s. A smooth, unreinforced thin-walled substrate 1 with a wall thickness of 0.25mm was prepared. After molding, the substrate had no warping or wall thickness deviation, and the substrate weight was 16.3g.

[0093] The thin-walled substrate is placed into a special positioning fixture and fed into an independent injection molding machine. The injection temperature is set to 190°C, the holding pressure to 8MPa, the injection rate to 35mm / s, the cooling temperature to 25°C, the cooling time to 2s, and the holding time to 2.5s. The composite reinforcing ribs are injection molded according to the same reinforcing rib layout and thickness ratio as in Example 1.

[0094] The reinforcing ribs and the thin-walled container substrate are bonded together using the same material (corn starch-based biodegradable material), with a bonding strength of not less than 25 MPa, and no delamination or rib separation.

[0095] Made with corn starch-based biodegradable material, the reinforcing ribs have a natural texture. The raw material cost is low. The natural biodegradable material combines environmental protection and economy, making it suitable for cost-sensitive large-volume takeout packaging scenarios. The degradation period is 150-210 days.

[0096] Testing revealed that the finished container weighs 22.7g, a 13.36% reduction compared to a traditional one-time injection molded polypropylene container (same size, 0.4mm thickness, 26.2g); and a 40.73% reduction compared to a traditional disposable environmentally friendly container of the same material (same size, 0.5mm thickness, 38.3g). Its compressive strength is 1150N, no less than that of a traditional one-time injection molded container; it can be stacked up to 25 layers without deformation or damage; and the finished product can completely degrade in natural environments within 150–210 days.

[0097] To further verify the technical advantages of this application, a traditional one-piece injection molded polypropylene container (same size, 0.4 mm thickness, 26.2 g weight), a thermoforming process (same preparation method as in Example 1, except without reinforcing ribs, same size, 0.3 mm thickness, 9.7 g weight, 20% weight reduction), and a conventional foamed weight-reducing container in the prior art (same size, 8.5 g weight, 30% weight reduction, without reinforcing ribs) were compared with the finished polypropylene container of Example 1 in terms of performance and appearance. The comparison results are shown in Table 1 below.

[0098] Table 1

[0099] As shown in the table above, while the weight reduction of this application is not much different from that of foaming, its compressive strength is significantly higher than that of the three comparative containers, its heat resistance temperature is higher than that of the foaming weight-reduced container, its appearance is significantly better than that of the three comparative containers, and it supports biodegradable materials. Its comprehensive performance advantages are outstanding, and it completely solves the technical pain point of "weight reduction inevitably leads to strength reduction" in the existing technology.

[0100] It is understandable that the shape of the thin-walled substrate 1 is not limited to square, but can also be round, elliptical or other shapes that meet the needs of takeout packaging, and thermoforming processes can be used to form it stably.

[0101] The number of vertical main reinforcing ribs is not limited to 2 on each side, but can also be 3 on each side. The number of transverse auxiliary reinforcing ribs between adjacent vertical main reinforcing ribs can be appropriately adjusted to 1 or 2 according to the height of the side wall.

[0102] The number of bottom radial ribs 4 is not limited to 8, and can be increased or decreased appropriately according to the size of the bottom of the container, with the principle of ensuring that the force is evenly distributed at the bottom.

[0103] Obviously, the materials of the thin-walled substrate 1 and the secondary injection molding reinforcing ribs are not limited to the materials listed in the above four embodiments. Any food-grade material or biodegradable and environmentally friendly material that is suitable for thermoforming and secondary injection molding processes and meets food contact safety standards is within the scope of protection of this application.

[0104] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A lightweight container having a thermoformed prefabricated thin-walled matrix and secondary injection-molded reinforcing ribs, characterized in that, Includes a container base (10); the container base (10) has reinforcing ribs on its sidewalls (11) and / or container bottom (12) to enhance the strength of the lightweight container; The reinforcing rib is integrally prepared by injection molding on the container base (10) and / or the container bottom (12) through a secondary injection molding process. The reinforcing rib is one or more of the following shapes: horizontal, vertical, arc-shaped, radial, or irregular.

2. The lightweight container according to claim 1, characterized in that, It also includes a container lid (20) adapted to the container base (10), and the container lid (20) is provided with reinforcing ribs; The container base (10) is provided with a full ring or segmented reinforcing structure around the opening. The segmented reinforcing structure is uniformly or non-uniformly distributed. The reinforcing structure is made by secondary injection molding. Preferably, the reinforcing ribs are evenly distributed on the outer side of the sidewall (11) of the container base (10) and / or the bottom (12) of the container. Preferably, the sidewall (11) is provided with a plurality of evenly distributed vertical main reinforcing ribs (31) along the height direction of the container. Preferably, the sidewall (11) is provided with multiple vertical main reinforcing ribs (31) on the outside, and transverse auxiliary reinforcing ribs (32) are evenly arranged between adjacent vertical main reinforcing ribs (31); the vertical main reinforcing ribs (31) and transverse auxiliary reinforcing ribs (32) are interwoven to form a composite reinforcing rib.

3. The lightweight container according to claim 1, characterized in that, The reinforcing rib is selected from one or more of the shapes of straight lines, curves, broken lines, wavy lines and arcs; the cross-section of the reinforcing rib is cylindrical, elliptical, square or trapezoidal. Preferably, the container base (10) is a smooth thin-walled cavity, and the wall thickness of the side wall (11) of the container base (10) is 0.1 to 0.6 mm, preferably 0.15 to 0.25 mm.

4. The lightweight container according to claim 2, characterized in that, The container bottom (12) and / or container lid (20) are provided with radial reinforcing ribs (33) that extend radially outward from the center and are evenly distributed. Preferably, the cross-sectional dimension of the bottom radial reinforcing rib (33) is larger than the cross-sectional dimension of the transverse auxiliary reinforcing rib (32); Preferably, the cross-sectional thickness of the reinforcing rib is 30% to 600% of the thickness of the corresponding container base.

5. The lightweight container according to claim 1, characterized in that, It also includes corner reinforcing ribs (34) provided at the connection of adjacent sidewalls (11) of the container base (10) and / or at the corner where the sidewall (11) and the container bottom (12) are connected. Preferably, the cross-sectional dimension of the corner stiffener (34) is larger than the cross-sectional dimension of the vertical main stiffener (31).

6. The lightweight container according to claim 1, characterized in that, The container base (10) is provided with composite aesthetic reinforcing ribs, the composite aesthetic reinforcing ribs comprising: Vertical main reinforcing ribs (31) and transverse auxiliary reinforcing ribs (32) are intersecting and formed on the side wall (11). Corner reinforcing ribs (34) are provided at the junction of adjacent sidewalls (11) of the container base (10) and / or at the corner where the sidewall (11) and the container bottom (12) meet; and Radial reinforcing ribs (33) are evenly distributed radially outward from the center at the bottom (12) of the container.

7. The lightweight container according to claim 1, characterized in that, The lightweight container can be circular, elliptical, frustum-shaped, rectangular, square, or have a multi-compartment structure. Preferably, when the lightweight container has a rectangular or square structure, corner reinforcing ribs extending from the vertices along the edges are provided at the vertices where the three edges intersect. Preferably, when the lightweight container has a rectangular or square structure, 2 to 3 vertical main reinforcing ribs are provided on each side wall of the container base (10), and 1 to 2 horizontal auxiliary reinforcing ribs are evenly provided between the vertical main reinforcing ribs; Preferably, an arc-shaped transition rib is provided at the connection between the vertical main reinforcing rib and the horizontal auxiliary reinforcing rib. The arc-shaped transition rib is smoothly connected to the vertical main reinforcing rib and the horizontal auxiliary reinforcing rib without sharp edges.

8. The lightweight container according to claim 1, characterized in that, Both the reinforcing ribs and the thin-walled container base (10) are made of biodegradable and environmentally friendly materials; The biodegradable and environmentally friendly materials include one or more of the following: polylactic acid, polybutylene adipate-butyl terephthalate, corn starch-based biodegradable materials, rice husk-based composite biodegradable materials, polyhydroxyalkanoates, bamboo fiber-based composite biodegradable materials, and wheat bran-based biodegradable materials.

9. A method for preparing a lightweight container having a thermoformed prefabricated thin-walled matrix and secondary injection-molded reinforcing ribs as described in any one of claims 1 to 8, characterized in that, Includes the following steps: Biodegradable and environmentally friendly materials are prepared into sheets, and ultra-thin-walled container substrates are prefabricated using a vacuum positive and negative pressure thermoforming process. Then, secondary local composite injection molding of reinforcing ribs is performed at key stress locations in the container substrate through independent injection molding.

10. The preparation method according to claim 9, characterized in that, The secondary injection-molded reinforcing ribs and the thin-walled container base (10) are connected by injection molding using the same material; the container base (10) is made of biodegradable and environmentally friendly material; The biodegradable and environmentally friendly materials include one or more of the following: polylactic acid, polybutylene adipate-butyl terephthalate, corn starch-based biodegradable materials, rice husk-based composite biodegradable materials, polyhydroxyalkanoates, bamboo fiber-based composite biodegradable materials, and wheat bran-based biodegradable materials. Preferably, the corn starch-based biodegradable material is made by blending corn starch and polylactic acid, wherein the corn starch and polylactic acid are blended in a mass ratio of 4:6 to 6:

4. Preferably, the rice husk-based composite biodegradable material is made by blending rice husk powder, polybutylene adipate-butyl terephthalate and polylactic acid, wherein the rice husk powder, PBAT and PLA are blended in a mass ratio of 2:3:5 to 3:4:

3. Preferably, the bamboo fiber-based composite biodegradable material is a blend of bamboo fiber, polylactic acid, and polybutylene adipate-butyl terephthalate; the bamboo fiber, PLA, and PBAT are blended in a mass ratio of 1:4:5 to 2:5:

3. Preferably, the bran-based biodegradable material is made by blending bran powder with polylactic acid, wherein the bran powder and PLA are blended in a mass ratio of 4:6 to 5:5.

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