A sodium bicarbonate foamed lightweight compression-resistant plastic fruit basket

Abstract

The utility model discloses a kind of sodium bicarbonate foamed lightweight pressure-resistant plastic fruit baskets, including basket body, basket body periphery surface and bottom are all provided with vent hole and are provided with reinforcing rib, reinforcing rib is grid-like distribution, it is characterized in that: basket body includes surface dense layer and core foamed layer, the single surface thickness of surface dense layer is 0.3mm-0.4mm, its density is greater than or equal to 1g / cm³, the thickness of core foamed layer is 0.8mm-2.2mm, its density is less than 0.85g / cm³.The utility model has lightweight and structural strength, significantly reduce the self weight of basket body by core foamed layer, realize lightweight target;Surface dense layer completely wraps core foamed layer, provides excellent surface hardness, impact resistance and overall structure rigidity;Eliminate shrinkage pit, product surface is regular and flat.

Description

Technical Field

[0001] This utility model relates to the field of injection molding foaming technology, specifically to a lightweight, pressure-resistant plastic fruit basket made of sodium bicarbonate foam. Background Technology

[0002] Traditional plastic fruit baskets, in order to ensure sufficient structural strength, have thick walls and are quite heavy. Although they have some ventilation holes, they still consume a significant amount of plastic raw materials. The cost of plastic raw materials constitutes a major part of the production cost of fruit baskets. This not only significantly increases the direct production costs of manufacturers, eroding their profit margins and survival index, but also significantly increases energy consumption in the logistics and transportation process, which runs counter to the current concept of energy conservation, emission reduction, and green environmental protection for sustainable development. In order to achieve the goal of lightweighting, current technologies involve structural design of the basket body, adding a large number of ventilation holes without sacrificing structural strength, further increasing the wall thickness of the basket, and adding a large number of ventilation holes on all four sides of the basket body. However, with the rapid increase in production scale and the fast turnover of logistics and transportation, these fruit baskets still have problems such as heavy weight and high consumption of plastic raw materials. In order to further achieve the goal of lightweighting plastic fruit baskets, this utility model provides a solution. Utility Model Content

[0003] The technical solution adopted by this utility model to solve the above-mentioned technical problems is as follows:

[0004] A lightweight, pressure-resistant plastic fruit basket made of sodium bicarbonate foam includes a basket body with ventilation holes and reinforcing ribs on all four sides and bottom. The reinforcing ribs are distributed in a grid pattern. The basket body includes a surface dense layer and a core foam layer. The surface dense layer has a single-sided thickness of 0.3mm-0.4mm and a density ≥1g / cm³. The core foam layer has a thickness of 0.8mm-2.2mm and a density <0.85g / cm³.

[0005] Furthermore, the wall thickness of the basket is 2mm-3mm, and there is a transition layer between the surface dense layer and the core foam layer of the basket, with a single-sided thickness of 0.1mm-0.2mm.

[0006] Furthermore, the thickness of the reinforcing ribs is 5mm-9mm.

[0007] Furthermore, the wall thickness of the basket is 3mm, the single-sided thickness of the surface dense layer is 0.4mm, the single-sided thickness of the transition layer is 0.2mm, the thickness of the core foam layer is 1.8mm, and the thickness of the reinforcing ribs is 7mm.

[0008] Furthermore, the bottom diagonal of the basket also has diagonal bracing ribs.

[0009] The beneficial effects of this utility model are:

[0010] Combining lightweight design with structural strength, the core foam layer significantly reduces the weight of the housing, achieving the goal of lightweight construction. The dense surface layer completely encapsulates the core foam layer, providing excellent surface hardness, impact resistance, and overall structural rigidity.

[0011] By saving raw materials and reducing costs, the core foam layer uses gas expansion to replace a large amount of solid plastic, which greatly reduces the raw material consumption required per unit product, thereby reducing raw material costs from the source and bringing direct and considerable economic benefits to enterprises.

[0012] The surface is regular and flat. The foaming expansion force counteracts the cooling contraction force, eliminating shrinkage pits. The smooth surface increases the adhesion of the surface, which is helpful for printing words and affixing trademarks and labels. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the surface dense layer and the core foam layer of this utility model;

[0014] Figure 2 This is a flowchart of the process flow of this utility model.

[0015] The figure shows: 1. Surface dense layer; 2. Transition layer; 3. Core foam layer. Detailed Implementation

[0016] The present invention will be further described below with reference to the accompanying drawings and embodiments. The accompanying drawings of this utility model are only schematic illustrations of structural features, for example... Figure 1 The layer thickness ratio, foam pore shape and size shown are for structural principle demonstration only and do not constitute a limitation on specific values.

[0017] This utility model discloses a lightweight, pressure-resistant plastic fruit basket made of sodium bicarbonate foam, such as... Figure 1 As shown, a gradient foaming layer structure is adopted, which forms a dense surface layer and a foamed core layer in the basket. Compared with the traditional structure, the two-layer foaming structure is more lightweight and breathable. In addition, the traditional foaming agents commonly used in the prior art (such as AC azodicarbonamide foaming agent) leave harmful substances. This utility model uses non-toxic inorganic foaming agent sodium bicarbonate (commonly known as baking soda).

[0018] The process employs a three-stage controlled-pressure foaming method: high-pressure filling, medium-pressure expansion, and low-pressure foaming. 5-8% sodium bicarbonate by weight is added to the polypropylene raw material, stirred thoroughly, and then fed into the injection molding machine hopper. The raw material mixed with sodium bicarbonate enters the screw barrel, where it is heated to 175℃-195℃ and completely melted to form a plastic melt. Sodium bicarbonate decomposes at 60℃, at which point it produces carbon dioxide gas. Since there is no space for expansion within the screw barrel, it cannot yet foam.

[0019] In the high-pressure filling section, the injection speed of the injection molding machine is set to 120-150 mm / s, and the injection pressure is maintained at 10-12 MPa. The plastic melt is quickly filled into the mold. Because the injection speed is very fast, there is no time or space for the plastic melt to expand, which avoids the phenomenon of uneven foaming and surface bulging caused by premature foaming of the melt.

[0020] After the mold is filled with molten plastic, the medium-pressure stretching stage begins. At this point, the mold cavity is filled with the rapidly injected melt, and the pressure can reach up to 12 MPa. Then, the pressure holding stage begins, maintaining the mold cavity pressure at 10-12 MPa for 8-12 seconds. The purpose is to control the densification of the surface layer, forming a dense skin layer of 0.3mm-0.4mm on one side (0.6mm-0.8mm on both sides). At this time, the high-temperature melt adheres tightly to the mold wall under high pressure. The steel of the mold conducts heat extremely quickly, and the temperature of the melt in contact with the mold can drop rapidly from 170℃ to below 80℃ in a very short time. The polypropylene melt crystallizes and solidifies during the rapid heat dissipation process, forming a dense surface layer. The optimal pressure holding time is controlled at 8-12 seconds.

[0021] Table 1: Experimental data on pressure holding time

[0022] Pressure holding time Epidermal thickness Surface condition 3 seconds 0.1mm bubble pattern 5 seconds 0.18mm Slight pockmarks 8 seconds 0.3mm Smooth as a mirror 12 seconds 0.4mm ideal state 15 seconds 0.5mm Insufficient foaming

[0023] The holding time should not be too short, otherwise the surface will not be smooth and dense enough. It should not be too long either, as too long a time will cause more heat dissipation and solidification of the melt, which will create hidden dangers for the subsequent foaming process and result in insufficient foaming.

[0024] After the pressure holding period ends, the low-pressure foaming stage begins. Within 0.5 seconds, the molding pressure is quickly released and the mold is opened again by 1.5-2.0 mm, which provides space for gas expansion in the core melt. The pressure reduction and venting allow the pressure reduction rate to reach 15 MPa / s, triggering explosive foaming.

[0025] After foaming, wait for it to cool completely, then open the mold and take out the basket to obtain a fruit basket with a gradient foam layer structure, which has a dense surface layer and a foam core layer.

[0026] Table 2: Foaming Structure Parameters

[0027] area Average density (g / cm³) Pore ​​size distribution (μm) Bubble morphology Surface dense layer ≥1 10-30 Closed-pore spherical transition layer 0.85-1 50-100 ellipsoidal closed hole Core foam layer <0.85 150-300 Connecting opening

[0028] The wall thickness of the basket is 2mm-3mm, of which the thickness of the single side of the surface dense layer is 0.3mm-0.4mm and its density is ≥1g / cm³. There is also a transition layer between the surface dense layer and the core foam layer. The transition layer is formed due to the gradual heat dissipation and solidification of the melt from the outside to the inside. Its density is between that of the surface dense layer and the core foam layer, and its single side thickness is between 0.1mm-0.2mm. The thickness of the core foam layer is 0.8mm-2.2mm and its density is <0.85g / cm³.

[0029] Ventilation holes are provided on all four sides and the bottom of the basket, and reinforcing ribs are distributed in a grid pattern, with a thickness of 5mm-9mm. The bottom of the basket also has diagonal bracing ribs.

[0030] In one specific embodiment, the plastic fruit basket has a wall thickness of 3mm, a single-sided thickness of 0.4mm for the surface dense layer, a single-sided thickness of 0.2mm for the transition layer, a core foam layer thickness of 1.8mm, and a reinforcing rib thickness of 7mm.

[0031] Table 3: Performance Verification Data

[0032] Testing items Traditional solid basket The foam basket in this case Weight of a single basket (35L) 1.55kg 1.35kg Stacking deformation (8 layers) 12mm 8mm Drop damage height 1.8m 3.0m Water absorption rate (24h) 0.3% 0.9%

[0033] This invention significantly reduces the weight of the basket: the density of the core foam layer is reduced to <0.85g / cm³, and the 35L basket weighs only 1.35kg (15% lighter than traditional baskets), resulting in a reduction of over 15% in raw material costs. The dense surface layer provides fundamental strength, reducing stacking deformation to 8mm and drop breakage height to 3.0m. Reinforcing ribs allow for localized reinforcement. Combining lightweight and strength, its overall performance surpasses traditional solid baskets, saving raw materials and reducing production costs.

[0034] Secondly, plastic products typically have smooth surfaces, which increases adhesion and facilitates printing and labeling. However, injection-molded plastic products generally exhibit surface shrinkage, meaning their dimensions before cooling are larger than their dimensions after cooling. This shrinkage is related to thermal expansion and contraction and other properties.

[0035] Shrinkage rate is closely related to wall thickness. Because the cooling time is different for different wall thicknesses, the shrinkage rate is different in the fruit basket with many reinforcing ribs of different thicknesses. This results in uneven shrinkage, causing pits on the product surface, affecting the product's appearance and texture, making the surface irregular and flat, and reducing surface adhesion.

[0036] Plastic fruit baskets made by injection molding with added sodium bicarbonate foam have an outward expansion force that counteracts the inward contraction during cooling, preventing shrinkage pits on the surface of the plastic product. This results in a smooth and regular surface, making it easier to engrave or affix labels and trademarks to the product later.

[0037] This utility model is not limited to the above-described preferred embodiments. Any other products that are the same as or similar to this utility model and derived by anyone under the guidance of this utility model shall fall within the protection scope of this utility model.

Claims

1. A lightweight, pressure-resistant plastic fruit basket made of sodium bicarbonate foam, comprising a basket body, wherein the basket body has ventilation holes on all four sides and the bottom, and is provided with reinforcing ribs arranged in a grid pattern, characterized in that: The housing consists of a dense surface layer and a foamed core layer. The dense surface layer has a single-sided thickness of 0.3mm–0.4mm and a density ≥1g / cm³. The foamed core layer has a thickness of 0.8mm–2.2mm. Its density is <0.85g / cm³.

2. The lightweight, pressure-resistant plastic fruit basket made of sodium bicarbonate foam according to claim 1, characterized in that: The wall thickness of the basket is 2mm-3mm. There is also a transition layer between the surface dense layer and the core foam layer of the basket. The thickness of the transition layer on one side is between 0.1mm-0.2mm.

3. The lightweight, pressure-resistant plastic fruit basket made of sodium bicarbonate foam according to claim 1, characterized in that: The thickness of the reinforcing ribs is 5mm-9mm.

4. The lightweight, pressure-resistant plastic fruit basket made of sodium bicarbonate foam according to claim 3, characterized in that: The wall thickness of the basket is 3mm, the single-sided thickness of the surface dense layer is 0.4mm, the single-sided thickness of the transition layer is 0.2mm, the thickness of the core foam layer is 1.8mm, and the thickness of the reinforcing ribs is 7mm.

5. The lightweight, pressure-resistant plastic fruit basket made of sodium bicarbonate foam according to claim 1, characterized in that: The bottom diagonal of the basket also has diagonal bracing ribs.

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