A foamed masterbatch, a method for preparing the same and a foamed material composition

Abstract

This application provides a foaming masterbatch comprising 20wt%–69wt% carrier resin, 12wt%–60wt% foaming agent, 2wt%–4wt% dispersant, and the balance being additives; the carrier resin has a melting point not exceeding 80°C; the foaming agent is selected from one or more of hydrogen phosphate, bicarbonate, and citrate. This application also provides a method for preparing the foaming masterbatch, a foaming material composition, and a composite packaging material. This application uses hydrogen phosphate, bicarbonate, and citrate as foaming agents and a resin with a melting point not exceeding 80°C as a carrier, enabling the preparation of foaming masterbatch at temperatures not exceeding 90°C without loss of the foaming agent. The resulting foaming masterbatch produces a continuous and stable foaming effect, allowing a sufficient number of microbubbles to form in the plastic at an addition amount as low as 1wt%, achieving a significant weight reduction effect.

Description

Technical Field

[0001] This invention relates to the field of packaging materials technology, and in particular to a foaming masterbatch, its preparation method, and a foaming material composition. Background Technology

[0002] Plastic microfoaming technology reduces material density by introducing tiny air bubbles into a plastic matrix, while simultaneously improving the material's mechanical and thermal insulation properties. This technology is widely used in the automotive, electronics, and packaging industries to achieve goals such as lightweighting, energy saving, and improved product performance.

[0003] A foaming agent is a chemical substance that generates gas under specific conditions. The gas produced by its decomposition forms tiny pores in the plastic. Current technology typically involves preparing a foaming masterbatch by combining the foaming agent with a carrier resin, which is then added to the plastic matrix for foaming. The preparation of the foaming masterbatch requires high-temperature processing, such as above 150°C. Therefore, foaming masterbatches generally use azodicarbonamide, which has a high decomposition temperature, as the foaming agent component. However, azodicarbonamide produces highly toxic components such as cyanic acid during decomposition and foaming, making the resulting foamed film unsuitable for use as food packaging material. Summary of the Invention

[0004] In view of this, the technical problem to be solved by the present invention is to provide a foaming masterbatch, its preparation method and foaming material composition. The foaming masterbatch provided in this application will not produce highly toxic components when preparing foamed film. The obtained foamed film can be used as food packaging material and can achieve good foaming effect with low addition amount.

[0005] The applicant found in the research that inorganic foaming agents such as sodium bicarbonate (NaHCO3) and sodium citrate (C6H5Na3O7) have advantages such as low cost and non-toxicity. However, when they are used as foaming components to prepare foaming masterbatch, a large amount of them is required to obtain a good foaming weight reduction effect.

[0006] Based on this, the present invention provides a foaming masterbatch comprising 20wt% to 69wt% of a carrier resin, 12wt% to 60wt% of a foaming agent, 2wt% to 4wt% of a dispersant, and the balance being an additive; wherein the melting point of the carrier resin does not exceed 80°C; and the foaming agent is selected from one or more of hydrogen phosphate, bicarbonate, and citrate.

[0007] This application uses inorganic salts such as hydrogen phosphate, bicarbonate, and citrate as foaming agents and resins with a melting point not exceeding 80°C as carrier resins. It enables the preparation of foaming masterbatches at temperatures not exceeding 90°C without loss of the foaming agent components. The resulting foaming masterbatches produce a continuous and stable foaming effect, exhibiting good foaming performance even at addition levels as low as 1 wt%. This results in the formation of a sufficient number of microbubbles within the plastic, achieving significant weight reduction. Furthermore, in the foaming masterbatches provided by this application, the foaming agent does not form large bubbles inside or on the surface of the carrier resin, thus not affecting the processing and performance of subsequent products.

[0008] The foaming masterbatch provided in this application includes a carrier resin with a melting point not exceeding 80°C, enabling it to be melted at a processing temperature below 90°C to prepare the foaming masterbatch. In some specific implementations, the carrier resin is selected from one or more of ethylene-vinyl acetate copolymer resin, PE wax, PP wax, synthetic wax, and polyethylene resin powder. When the carrier resin is selected from a combination of multiple substances, this application does not impose any special restrictions on the specific proportions of each substance. In some specific implementations, the carrier resin is preferably one or more of ethylene-vinyl acetate copolymer resin, PE wax, and polyethylene resin powder. For example, it can be ethylene-vinyl acetate copolymer resin or PE wax, a mixture of ethylene-vinyl acetate copolymer resin and PE wax, or a mixture of ethylene-vinyl acetate copolymer resin and polyethylene resin powder. When the carrier resin contains polyethylene resin powder, it preferably also includes ethylene-vinyl acetate copolymer resin, PE wax, PP wax, and synthetic wax. During low-temperature processing, the ethylene-vinyl acetate copolymer resin, PE wax, PP wax, and synthetic wax can encapsulate the polyethylene resin powder without affecting the foaming performance of the obtained foaming masterbatch. In some specific implementations, the mass ratio of the ethylene-vinyl acetate copolymer resin, PE wax, PP wax and / or synthetic wax to the polyethylene resin powder is 50-60:15-25. In some specific implementations, the amount of the carrier resin is 20wt%-69wt%, preferably 21wt%-60wt%, and more preferably 22wt%-50wt%.

[0009] The foaming masterbatch provided in this application includes a foaming agent selected from one or more of hydrogen phosphate, bicarbonate, and citrate. When the foaming agent is a combination of multiple types, this application does not impose any particular limitation on the proportion of each specific component. In some specific implementations, the foaming agent is preferably a combination of sodium bicarbonate and sodium citrate, wherein the mass ratio of sodium bicarbonate to sodium citrate is 1–3:1–4, preferably 1–2.5:1.3–3.8. In some specific implementations, the content of the foaming agent is 12 wt%–60 wt%, preferably 25 wt%–60 wt%, and more preferably 30 wt%–58 wt%.

[0010] The foaming masterbatch provided in this application includes a dispersant, which includes, but is not limited to, one or more of silicones, amides, stearic acids, fatty acids, and esters, such as glyceryl monostearate and oleamide. This application does not impose any particular limitation on the dispersant; it can be selected as needed. In some specific implementations, the amount of the dispersant is 2wt% to 4wt%, preferably 2.5wt% to 3.5wt%.

[0011] The foaming masterbatch provided in this application also includes additives, including but not limited to lubricants, antioxidants, inorganic fillers, antistatic agents, and crosslinking agents, which may be one or more of these. When there are multiple additives, this application does not impose any special restrictions on the content of each specific additive. In some specific implementations, the lubricants include but are not limited to silicones, amides, stearic acid, fatty acids, esters, and metal oxides, such as zinc oxide; the antioxidants include but are not limited to light stabilizers and UV stabilizers; the inorganic fillers include but are not limited to calcium carbonate, talc, titanium dioxide, and silica; the antistatic agents include but are not limited to anionic antistatic agents, cationic antistatic agents, and nonionic antistatic agents; and the crosslinking agents include but are not limited to polyesters.

[0012] Specifically, the foaming masterbatch provided in this application includes:

[0013] 40wt%–50wt% ethylene-vinyl acetate polymer; 15wt%–25wt% sodium bicarbonate; 20wt%–30wt% sodium citrate; 1wt%–5wt% dispersant and balance additives;

[0014] Alternatively, the foaming masterbatch provided in this application may include:

[0015] 15wt%–25wt% ethylene-vinyl acetate polymer; 20wt%–30wt% PE wax; 10wt%–15wt% sodium bicarbonate; 30wt%–40wt% sodium citrate; 1wt%–5wt% dispersant and balance additives.

[0016] Alternatively, the foaming masterbatch provided in this application may include:

[0017] 30wt%–40wt% PE wax; 15wt%–25wt% sodium bicarbonate; 30wt%–40wt% sodium citrate; 1wt%–5wt% dispersant and balance additives.

[0018] Alternatively, the foaming masterbatch provided in this application may include:

[0019] 50wt%–60wt% ethylene-vinyl acetate polymer; 15wt%–25wt% polyethylene resin powder; 10wt%–15wt% sodium bicarbonate; 10wt%–15wt% sodium citrate; 1wt%–5wt% dispersant and balance additives.

[0020] In some specific implementations, the dispersant comprises glyceryl monostearate and oleamide, wherein the mass ratio of glyceryl monostearate to oleamide is 1–5:0.01–1, preferably 2–4:0.05–0.5. In some specific implementations, the auxiliary agent is zinc oxide, wherein the content of zinc oxide is 0.01 wt%–5 wt%, preferably 0.1 wt%–1 wt%.

[0021] In some specific implementations, the particles in the foaming masterbatch, such as fillers and polyethylene resin powder, have a particle size of 5 to 15 μm, preferably 6 to 12 μm. A suitable and uniform particle size can ensure the continuous and stable foaming ability of the foaming masterbatch.

[0022] This application also provides a method for preparing foaming masterbatch, comprising the following steps:

[0023] The carrier resin (20wt%–69wt%), foaming agent (12wt%–29wt%), dispersant (2wt%–4wt%), and the balance of additives are mixed evenly and then subjected to intensive mixing at a temperature not exceeding 80°C. The melting point of the carrier resin is not exceeding 80°C. The foaming agent is selected from one or more of hydrogen phosphate, bicarbonate, and citrate.

[0024] The mixed material is granulated or shaped at a temperature not exceeding 90°C.

[0025] This application first mixes the carrier resin, foaming agent, dispersant, and additives evenly to obtain a mixture. In some specific implementations, this application preferably mixes the materials evenly under stirring conditions, wherein the stirring speed is ≥1200 r / min, preferably 1500 r / min to 3000 r / min, and the stirring time is not less than 5 min, preferably 5 min to 25 min, and more preferably 10 min to 20 min. If foaming occurs during the mixing process, the stirring speed needs to be paused and adjusted until foaming stops.

[0026] The resulting mixture is preferably ground to control the particle size, ensuring that the particle diameter is ≤15μm, preferably 5μm~15μm, and more preferably 6μm~12μm. This application does not impose any special limitations on the grinding method and parameters, as long as the above objective is achieved.

[0027] After grinding, the obtained material is subjected to intensive mixing in an internal mixer. During the mixing process, the temperature of the internal mixer, i.e., the mixing temperature, shall not exceed 80°C, preferably not exceed 75°C, more preferably 52°C to 60°C, and even more preferably 52°C to 58°C. This temperature is sufficient to melt the carrier resin without causing the decomposition of the foaming agent, which is one of the key steps to prevent the loss of the effective components of the foaming agent. This application does not impose any special limitations on the mixing time; those skilled in the art can select the appropriate time as needed.

[0028] After mixing, the obtained material is preferably crushed to particles of 3mm to 5mm and then sieved to ensure uniform particle size. The resulting granules are then granulated at a temperature not exceeding 90℃.

[0029] In some specific implementations, this application allows extrusion granulation to be performed in an extruder. The temperature of the first two sections of the extruder does not exceed 50°C, for example, 40°C to 50°C; the temperature of other sections does not exceed 80°C, for example, 70°C to 80°C; and the die temperature does not exceed 85°C, for example, 80°C to 85°C. This application does not impose any special limitations on the extruder; it can be a single-screw extruder, preferably a single-screw extruder with low shear force. This application also does not impose any special limitations on the die of the extruder; it can be single-hole or multi-hole. To reduce the loss of foaming agent, the granulation method can be selected after extrusion based on the choice of carrier resin. For example, the extrudate can be drawn and cooled to obtain fine strips before pelletizing, or the extrudate can be extruded underwater for pelletizing. Specifically, when the carrier resin is ethylene-vinyl acetate copolymer resin, extrusion granulation can be carried out by cooling first and then pelletizing; when the carrier resin is a mixture of two or more of ethylene-vinyl acetate copolymer resin, PE wax, PP wax, and synthetic wax, and the content of ethylene-vinyl acetate copolymer resin is less than 40% of the carrier, underwater pelletizing is preferred during extrusion granulation; when the carrier resin is a mixture of one or more of PE wax, PP wax, and synthetic wax, underwater pelletizing is used during extrusion granulation; when the carrier resin is polyethylene resin powder or two or more of PE wax, PP wax, and synthetic wax, underwater pelletizing is used during extrusion granulation.

[0030] In some specific implementations, the molding process includes: calendering the internally mixed material at a temperature above 40°C, and then cutting or pressing it into sheets to obtain foaming masterbatch. Specifically, after internal mixing, the material is calendered before cooling to below 40°C, and simultaneously cut or pressed into sheets. After cooling, foaming masterbatch is obtained. The particle size of the foaming masterbatch obtained after cutting or pressing is preferably 3mm to 5mm.

[0031] This application prepares foaming masterbatch at a processing temperature below 90°C, resulting in minimal loss of the foaming agent. The resulting foaming masterbatch is both stable in molding and exhibits continuous and stable foaming effects. This allows the foaming masterbatch to achieve excellent foaming performance at addition levels as low as 1 wt%, forming a sufficient number of microbubbles within the plastic to achieve significant weight reduction and performance improvement. Furthermore, in the foaming masterbatch provided by this application, the foaming agent does not form large bubbles inside or on the surface of the carrier resin, thus not affecting the processing and performance of subsequent products.

[0032] Based on this, this application provides a foaming material composition, comprising:

[0033] 0.1wt% to 1wt% of foaming masterbatch, wherein the foaming masterbatch is the foaming masterbatch described in the above technical solution or the foaming masterbatch prepared by the preparation method described in the above technical solution;

[0034] The remaining amount of matrix resin.

[0035] This application does not impose any special limitations on the matrix resin, which may include, but is not limited to, polyethylene, polypropylene, polylactic acid, or polystyrene, and may be one or more of these. This application achieves good foaming effect and reduces the weight of the packaging material by adding 0.1 wt% to 1 wt% of the foaming masterbatch described above to the matrix resin.

[0036] This application also provides a composite packaging material, including a microfoamed film, wherein the microfoamed film comprises an outer layer, a microfoamed intermediate layer and an inner layer sequentially laminated together;

[0037] The microbubble intermediate layer is formed by foaming the foaming material composition described in the above technical solution.

[0038] The composite packaging material provided in this application includes a microfoamed film, which comprises an outer layer, a microfoamed intermediate layer, and an inner layer that are sequentially laminated. Foaming is achieved with a low amount of foaming masterbatch, forming a sufficient number of micro-bubbles, and the weight of the composite packaging material is reduced.

[0039] The microbubble intermediate layer is formed by foaming the foaming material composition described in the above technical solution, which will not be repeated here.

[0040] In some specific implementations, the outer and inner layers of the microbubble membrane can be configured according to usage requirements, and each layer independently comprises a matrix resin and additives; this application does not impose any special restrictions on this. The matrix resin of the inner and outer layers can be the same as or different from the matrix resin of the microbubble intermediate layer, but is preferably the same as the matrix resin of the microbubble intermediate layer.

[0041] This application uses inorganic salts such as hydrogen phosphate, bicarbonate, and citrate as foaming agents and resins with a melting point not exceeding 80°C as carrier resins. It enables the preparation of foaming masterbatches at temperatures not exceeding 90°C without loss of the foaming agent components. The resulting foaming masterbatches produce a continuous and stable foaming effect, exhibiting good foaming performance even at addition levels as low as 1 wt%. This results in the formation of a sufficient number of microbubbles within the plastic, leading to significant weight reduction and performance improvement. Furthermore, in the foaming masterbatches provided by this application, the foaming agent does not form large bubbles inside or on the surface of the carrier resin, thus not affecting the processing and performance of subsequent products. Attached Figure Description

[0042] Figure 1 Photographs of the foaming masterbatches prepared in Example 1 and Comparative Example 1 of this application;

[0043] Figure 2 A photograph of the foaming masterbatch prepared in Comparative Example 3 of this application, before it was cut after extrusion in an extruder;

[0044] Figure 3 Photograph of the foaming masterbatch prepared in Example 4 of this application;

[0045] Figure 4 This is a photograph of the foaming masterbatch prepared in Example 5 of this application. Detailed Implementation

[0046] This invention provides a foaming masterbatch, its preparation method, and a foaming material composition. Those skilled in the art can refer to the content herein and appropriately modify the process parameters to achieve the desired results. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention. The methods and applications of this invention have been described through preferred embodiments. Those skilled in the art can clearly modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit, and scope of this invention to realize and apply the technology of this invention.

[0047] Example 1

[0048] This invention provides a foaming masterbatch and its preparation method, using the following raw materials: ethylene-vinyl acetate polymer, sodium citrate, sodium bicarbonate, glyceryl monostearate, oleamide, and zinc oxide.

[0049] Based on the total mass of the foaming masterbatch, prepare 10kg of foaming masterbatch, the raw materials of which include: 4.8kg of ethylene-vinyl acetate polymer, 2.1kg of sodium bicarbonate, 2.8g of sodium citrate, 0.26kg of glyceryl monostearate, 0.02kg of oleamide, and 0.02kg of zinc oxide.

[0050] The preparation method of the above-mentioned foaming masterbatch is as follows:

[0051] (1) Weighing: Determine the total amount of target foaming masterbatch to be added, and weigh out ethylene-vinyl acetate polymer, sodium citrate, sodium bicarbonate, glyceryl monostearate, oleamide, zinc oxide and crosslinking agent according to the proportion.

[0052] (2) Raw material mixing: All the weighed raw materials are mixed in the same clean mixing tank and stirred for 15 minutes to make them evenly mixed.

[0053] (3) Particle size uniformity: Grind the uniformly mixed raw materials to a particle diameter ≤15μm, then continue stirring for 20min until uniform, and package for later use.

[0054] (4) Internal mixing: Place the raw materials that have been mixed evenly in step (3) into an internal mixer for internal mixing. The internal mixing temperature is 55±3℃.

[0055] (5) Crushing: After the material is intensively mixed, it is cut into pieces and crushed into powder particles with a particle size of 3 to 5 mm. The smaller or larger particles are removed by sieving.

[0056] (6) Extruder granulation: Granulation is performed using a single-screw, low-shear extruder. The temperature of the first two sections of the extruder, starting from the feed port, should not exceed 50°C, and the temperature of other sections of the barrel should not exceed 75°C. The die temperature is set at 83°C to obtain foamed masterbatch. See also Figure 1 , Figure 1 These are photographs of the foaming masterbatches prepared in Example 1 and Comparative Example 1 of this application. Figure 1 (a) is a photograph of the foaming masterbatch prepared in Comparative Example 1. Figure 1 (b) is a photograph of the foaming masterbatch prepared in Example 1.

[0057] The foaming masterbatch prepared by the above method is used for PE film blowing, and the process is as follows:

[0058] Three-layer extrusion blown film was produced using 75:25 linear low-density polyethylene 0220AA and low-density polyethylene 2420H as outer layer materials, 40:59.5:0.5 polyethylene 2426H, linear low-density polyethylene 1002BU, and foaming masterbatch as intermediate microbubble layer materials, and 40:30:30 linear low-density polyethylene 5401G, linear low-density polyethylene 0220KJ, and polyethylene 2426H as inner layer materials. During the production process, temperature parameters needed to be adjusted multiple times until the cells were uniform and dense. The temperatures of the main processing sections after foaming were stabilized were 165℃ in zone 1, 168℃ in zone 2, 171℃ in zone 3, and 150℃ in zone 4, resulting in a micro-foamed PE film comprising an outer layer, an intermediate microbubble layer, and an inner layer. The thickness ratio of the outer, intermediate, and inner layers was 1:1.5:1, and the total film thickness was 100μm. The foamed PE film has dense pores with a pore size of 30-62 μm and a density of 0.77 g / cm³. Compared with a PE film obtained using the same method and raw materials but without adding foaming masterbatch to the intermediate layer (density 0.92 g / cm³), the PE film prepared by adding foaming masterbatch has an overall weight reduction of 16%.

[0059] Comparative Example 1

[0060] The preparation of the foaming masterbatch differs from Example 1 in that polyethylene resin particles are used instead of the ethylene-vinyl acetate polymer. The mixing temperature is controlled at 55±3℃, the temperatures of the first two sections of the extruder are 50℃ and 80℃ respectively, the temperatures of the other barrel sections are 95℃, and the die temperature is set at 95℃. The foaming masterbatch is obtained by extrusion. See [link to relevant documentation]. Figure 1 , Figure 1 These are photographs of the foaming masterbatches prepared in Example 1 and Comparative Example 1 of this application. Figure 1 (a) is a photograph of the foaming masterbatch prepared in Comparative Example 1. Figure 1 (b) is a photograph of the foaming masterbatch prepared in Example 1. Figure 1 It can be seen that the foaming masterbatch prepared in Example 1 has a particle size of 2-3 μm and no pores; while the foaming masterbatch prepared in Comparative Example 1 has a particle size of 3-4 μm and obvious pores are generated on its end face, indicating that the foaming agent in Comparative Example 1 decomposes and produces gas when heated.

[0061] Comparative Example 2

[0062] A PE film comprising an outer layer, a middle microbubble layer, and an inner layer was prepared using the same raw materials and methods as in Example 1. The difference from Example 1 is that the formulation of the middle microbubble layer is 40:59:1 of 2426H:1002BU:commercial foaming masterbatch. The foamed PE film has sparse pores with a pore size of 60-87 μm and a density of 0.89 g / cm³. Compared with a PE film obtained using the same method and raw materials but without adding foaming masterbatch to the middle layer (density 0.92 g / cm³), the PE film prepared with adding foaming masterbatch has an overall weight reduction of 3%.

[0063] Compared with Comparative Example 2, the foaming masterbatch prepared in Example 1 showed significantly better foaming performance than Comparative Example 1, even with a 50% reduction in usage.

[0064] Example 2

[0065] This invention provides a foaming masterbatch for plastics and its preparation method. The raw materials for preparation are as follows: ethylene-vinyl acetate polymer, PE wax, sodium citrate, sodium bicarbonate, glyceryl monostearate, oleamide, and zinc oxide.

[0066] Based on the total mass of the foaming masterbatch, prepare 10kg of foaming masterbatch, including: 2.2kg of ethylene-vinyl acetate polymer, 2.6kg of PE wax, 1.1kg of sodium bicarbonate, 3.8kg of sodium citrate, 0.343kg of glyceryl monostearate, 0.03kg of oleamide, and 0.027kg of zinc oxide.

[0067] The preparation method of the above-mentioned foaming masterbatch is as follows:

[0068] (1) Weighing: Determine the total amount of target foaming masterbatch to be added, and weigh out ethylene-vinyl acetate polymer, PE wax, sodium citrate, sodium bicarbonate, glyceryl monostearate, oleamide, zinc oxide and crosslinking agent according to the proportion.

[0069] (2) Raw material mixing: All the weighed raw materials except PE wax are mixed in the same clean mixing tank and stirred for 15 minutes to make them evenly mixed.

[0070] (3) Particle size uniformity: Grind the uniformly mixed raw materials to a particle diameter ≤15μm, then continue stirring for 20min until uniform, and package for later use.

[0071] (4) Internal mixing: Place the evenly mixed raw materials in an internal mixer for internal mixing at a temperature of 55±3℃.

[0072] (5) Crushing: After the material is intensively mixed, it is cut into pieces and crushed into powder particles with a particle size of 3 to 5 mm. The smaller or larger particles are removed by sieving.

[0073] (6) Secondary mixing: The weighed PE wax is mixed with the above-mentioned crushed particles for secondary mixing and then set aside.

[0074] (7) Extruder granulation: A single-screw, low-shear extruder is used for granulation. The temperature of the first section is 50℃, the temperature of the second section is 57℃, and the temperature of other barrel sections does not exceed 92℃. The die temperature is set at 83℃ to obtain foamed masterbatch. The foamed masterbatch has a particle size of 2-3μm and no bubbles.

[0075] The foaming masterbatch prepared by the above method is used for PE film blowing, and the process is as follows:

[0076] Three-layer extrusion blown film was produced using 75:25 linear low-density polyethylene 0220AA and low-density polyethylene 2420H as outer layer materials, 40:59.5:0.5 polyethylene 2426H, linear low-density polyethylene 1002BU, and foaming masterbatch as intermediate microbubble layer materials, and 40:30:30 linear low-density polyethylene 5401G, linear low-density polyethylene 0220KJ, and polyethylene 2426H as inner layer materials. During the production process, temperature parameters needed to be adjusted multiple times until the cells were uniform and dense. The temperatures of the main processing sections after foaming were stabilized were 165℃ in zone 1, 168℃ in zone 2, 171℃ in zone 3, and 150℃ in zone 4, resulting in a micro-foamed PE film comprising an outer layer, an intermediate microbubble layer, and an inner layer. The thickness ratio of the outer, intermediate, and inner layers was 1:1.5:1, and the total film thickness was 100μm. The foamed PE film has dense pores with a pore size of 33–58 μm and a density of 0.79 g / cm³. Compared with a PE film obtained using the same method and raw materials but without adding foaming masterbatch to the intermediate layer (density 0.92 g / cm³), the PE film prepared with added foaming masterbatch has an overall weight reduction of 14%.

[0077] Comparative Example 3

[0078] The preparation of the foaming masterbatch differs from Example 2 in that polyethylene resin particles are used instead of ethylene-vinyl acetate polymer and PE wax. The mixing temperature is controlled at 60±3℃, the temperatures of the first two sections of the extruder are 55℃ and 78℃ respectively, the temperatures of the other barrel sections are 100℃, and the die temperature is set at 90℃. The foaming masterbatch is obtained by extrusion. See [link to relevant documentation]. Figure 2 , Figure 2 This is a photograph of the foaming masterbatch prepared in Comparative Example 3 of this application, before it was cut after extrusion in an extruder. Figure 2 It can be seen that the foaming masterbatch prepared in Comparative Example 3 has a particle size of 3-4 μm and obvious pores are generated, indicating that the foaming agent in Comparative Example 3 decomposes and produces gas upon heating.

[0079] Comparative Example 4

[0080] A PPE film comprising an outer layer, a middle microbubble layer, and an inner layer was prepared using the same raw materials and methods as in Example 2. The difference from Example 2 is that the formulation of the middle microbubble layer is 40:59:1 2426H:1002BU:commercial foaming masterbatch. The foamed PE film has sparse pores with a pore size of 100-150 μm and a density of 0.87 g / cm³. Compared with a PE film obtained without adding foaming masterbatch to the middle layer using the same method and raw materials (density 0.92 g / cm³), the overall weight reduction of the PE film prepared by adding foaming masterbatch is only 5%.

[0081] Compared with Comparative Example 4, the foaming masterbatch prepared in Example 2 showed a significant improvement in foaming effect with a 50% reduction in usage, resulting in denser cells and a more concentrated pore size distribution.

[0082] Example 3

[0083] This invention provides a foaming masterbatch for plastics and its preparation method. The raw materials for preparation are as follows: PE wax, sodium citrate, sodium bicarbonate, glyceryl monostearate, oleamide, and zinc oxide.

[0084] Based on the total mass of the foaming masterbatch, prepare 10kg of foaming masterbatch, including: 3.8kg of PE wax, 2.0kg of sodium bicarbonate, 3.8kg of sodium citrate, 0.343kg of glyceryl monostearate, 0.03kg of oleamide, and 0.027kg of zinc oxide.

[0085] The preparation method of the above-mentioned foaming masterbatch is as follows:

[0086] (1) Weighing: Determine the total amount of target foaming masterbatch to be added, and weigh PE wax, sodium citrate, sodium bicarbonate, glyceryl monostearate, oleamide, zinc oxide and crosslinking agent according to the proportion.

[0087] (2) Raw material mixing: All the weighed raw materials are mixed in the same clean mixing tank and stirred for 15 minutes to make them evenly mixed.

[0088] (3) Particle size uniformity: Grind the uniformly mixed raw materials to a particle diameter ≤15μm, then continue stirring for 20min until uniform, and package for later use.

[0089] (4) Internal mixing: The uniformly mixed raw materials are placed in an internal mixer for internal mixing. The temperature during the internal mixing process is 85±3℃.

[0090] (5) Crushing: After the material is intensively mixed, it is cut into pieces and crushed into powder particles with a particle size of 3 to 5 mm. The smaller or larger particles are removed by sieving.

[0091] (6) Extruder granulation: The temperature of the first section is 50℃, the temperature of the second section is 59℃, the temperature of other barrel areas is 90℃, and the die head temperature is set at 86℃ to obtain foamed masterbatch.

[0092] The foaming masterbatch prepared by the above method is used for PE film blowing, and the process is as follows:

[0093] A three-layer extrusion blown film was produced using 75:25 linear low-density polyethylene (LLDPE) 0220AA and LLDPE 2420H as the outer layer material, 40:59.7:0.3 polyethylene 2426H, LLDPE 1002BU, and foaming masterbatch as the intermediate microbubble layer material, and 40:30:30 linear LLDPE 5401G, LLDPE 0220KJ, and polyethylene 2426H as the inner layer material. During production, temperature parameters needed to be adjusted multiple times until the cells were uniform and dense. The temperatures of the main processing sections after foaming stability were 165℃ in zone 1, 168℃ in zone 2, 171℃ in zone 3, and 150℃ in zone 4, resulting in a micro-foamed PE film comprising an outer layer, an intermediate microbubble layer, and an inner layer. The thickness ratio of the outer, intermediate, and inner layers was 1:1.5:1, and the total film thickness was 100 μm. The foamed PE film has dense pores with a pore size of 30–59 μm and a density of 0.75 g / cm³. Compared with a PE film obtained using the same method and raw materials but without adding foaming masterbatch to the intermediate layer (density 0.92 g / cm³), the PE film prepared with added foaming masterbatch has an overall weight reduction of 14%.

[0094] Comparative Example 5

[0095] The preparation of foaming masterbatch differed from Example 3 in that polyethylene was used instead of PE wax, the mixing temperature was controlled at 70±3℃, the temperatures of the first two sections of the extruder were 47℃ and 65℃ respectively, the temperatures of the other barrel sections were 76℃ and 96℃ respectively, and the die temperature was set at 90℃. The resulting foaming masterbatch showed obvious decomposition, similar to Comparative Example 2.

[0096] Comparative Example 6

[0097] A PPE film comprising an outer layer, a middle microbubble layer, and an inner layer was prepared using the same raw materials and methods as in Example 3. The difference from Example 3 is that the formulation of the middle microbubble layer is 40:59:1 2426H:1002BU:commercial foaming masterbatch. The foamed PE film has sparse pores, with pore sizes ranging from 61 to 120 μm and a relatively large pore size variation. The density is 0.88 g / cm³. Compared with a PE film obtained using the same method and raw materials but without adding foaming masterbatch to the middle layer (density 0.92 g / cm³), the PE film prepared with adding foaming masterbatch has an overall weight reduction of 4%.

[0098] Compared with Comparative Example 6, the foaming masterbatch prepared in Example 3 showed a significant improvement in foaming effect with a 70% reduction in usage, resulting in denser foam pores and a more concentrated pore size distribution.

[0099] Example 4

[0100] This invention provides a foaming masterbatch for plastics and its preparation method. The raw materials for preparation are as follows: ethylene-vinyl acetate polymer, polyethylene resin powder, sodium citrate, sodium bicarbonate, glyceryl monostearate, oleamide, and zinc oxide.

[0101] Based on the total mass of the foaming masterbatch, prepare 10kg of foaming masterbatch, including: 5.3kg of ethylene-vinyl acetate polymer, 1.9kg of polyethylene resin powder, 1.1kg of sodium bicarbonate, 1.3kg of sodium citrate, 0.343kg of glyceryl monostearate, 0.03kg of oleamide, and 0.027kg of zinc oxide.

[0102] The preparation method of the above-mentioned foaming masterbatch is as follows:

[0103] (1) Weighing: Determine the total amount of target foaming masterbatch to be added, and weigh out ethylene-vinyl acetate polymer, polyethylene resin powder, sodium citrate, sodium bicarbonate, glyceryl monostearate, oleamide, zinc oxide and crosslinking agent according to the proportion.

[0104] (2) Raw material mixing: All the weighed raw materials are mixed in the same clean mixing tank and stirred for 15 minutes to make them evenly mixed.

[0105] (3) Particle size uniformity: Grind the uniformly mixed raw materials to a particle diameter ≤15μm, then continue stirring for 20min until uniform, and package for later use.

[0106] (4) Internal mixing: The uniformly mixed raw materials are placed in an internal mixer for internal mixing. The temperature during the internal mixing process is 65±3℃.

[0107] (5) Calendering: After the material is cut into blocks, it is calendered directly before the temperature drops (around 50°C). The thickness of the calendered material is 4mm.

[0108] (6) Cutting: After calendering, the sheet is cut into cylindrical, square or irregular particles with a particle size of 4mm.

[0109] See Figure 3 , Figure 3 The image shows the foaming masterbatch prepared in Example 4 of this application. There are no pores on its end face and surface.

[0110] Example 5

[0111] This invention provides a foaming masterbatch for plastics and its preparation method. The raw materials for preparation are as follows: ethylene-vinyl acetate polymer, polyethylene resin powder, sodium citrate, sodium bicarbonate, glyceryl monostearate, oleamide, and zinc oxide.

[0112] Based on the total mass of the foaming masterbatch, prepare 10 kg of foaming masterbatch, including: 5.3 kg of ethylene-vinyl acetate polymer, 1.9 kg of polyethylene resin powder, 1.1 kg of sodium bicarbonate, 1.3 kg of sodium citrate, 0.343 kg of glyceryl monostearate, 0.03 kg of oleamide, and 0.027 kg of zinc oxide.

[0113] The preparation method of the above-mentioned foaming masterbatch is as follows:

[0114] (1) Weighing: Determine the total amount of target foaming masterbatch to be added, and weigh out ethylene-vinyl acetate polymer, polyethylene resin powder, sodium citrate, sodium bicarbonate, glyceryl monostearate, oleamide, zinc oxide and crosslinking agent according to the proportion.

[0115] (2) Raw material mixing: All the weighed raw materials are mixed in the same clean mixing tank and stirred for 15 minutes to make them evenly mixed.

[0116] (3) Particle size uniformity: Grind the uniformly mixed raw materials to a particle diameter ≤15μm, then continue stirring for 20min until uniform, and package for later use.

[0117] (4) Internal mixing: The uniformly mixed raw materials are placed in an internal mixer for internal mixing. The temperature during the internal mixing process is 65±3℃.

[0118] (5) Tableting: The mixed material is tableted using a tableting machine. The particle size is controlled at 3-5 mm. The shape of the tableted material is elliptical or cylindrical.

[0119] See Figure 4 , Figure 4 The image shows the foamed masterbatch prepared in Example 5 of this application. There are no pores on its surface and end faces.

[0120] The materials used in the above embodiments all comply with GB9685 and GB4806.6 and meet the requirements for food materials.

[0121] Unless otherwise specified, the materials, reagents, and experimental equipment involved in the embodiments of this invention are all commercially available products in the field of polymer formulation. The above is only one specific embodiment, and the proportions and types of each component can be adjusted according to actual needs.

[0122] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A foaming masterbatch, characterized in that, It consists of 20wt% to 69wt% carrier resin, 12wt% to 60wt% foaming agent, 2wt% to 4wt% dispersant and the balance of additives; The melting point of the carrier resin does not exceed 80°C; The foaming agent is selected from one or more of hydrogen phosphate, bicarbonate and citrate.

2. The foaming masterbatch according to claim 1, characterized in that, The carrier resin is selected from one or more of ethylene-vinyl acetate copolymer resin, PE wax, PP wax, synthetic wax and polyethylene resin powder.

3. The foaming masterbatch according to claim 1, characterized in that, The content of the foaming agent is 25wt% to 60wt%; The foaming agent is selected from sodium bicarbonate and sodium citrate in a mass ratio of 1-3:1-4.

4. The foaming masterbatch according to claim 1, characterized in that, The additives are selected from one or more of lubricants, antioxidants, inorganic fillers, antistatic agents, and crosslinking agents.

5. The foaming masterbatch according to any one of claims 1 to 4, characterized in that, include: 40wt% to 50wt% ethylene-vinyl acetate polymer; Sodium bicarbonate, 15wt% to 25wt%; 20wt%–30wt% sodium citrate; 1wt%–5wt% dispersant and balance additives; Or include: 15wt%–25wt% ethylene-vinyl acetate polymer; 20wt%–30wt% PE wax; 10wt%–15wt% sodium bicarbonate; 30wt%–40wt% sodium citrate; 1wt%–5wt% dispersant and balance additives; Or include: 30wt%–40wt% PE wax; 15wt%–25wt% sodium bicarbonate; 30wt%–40wt% sodium citrate; 1wt%–5wt% dispersant and balance additives; Or include: 50wt%–60wt% ethylene-vinyl acetate polymer; 15wt%–25wt% polyethylene resin powder; 10wt%–15wt% sodium bicarbonate; 10wt%–15wt% sodium citrate; 1wt%–5wt% dispersant and balance additives.

6. A method for preparing foaming masterbatch, comprising the following steps: The carrier resin (20wt%–69wt%), foaming agent (12wt%–29wt%), dispersant (2wt%–4wt%), and the balance of additives are mixed evenly and then subjected to intensive mixing at a temperature not exceeding 80°C. The melting point of the carrier resin is not exceeding 80°C. The foaming agent is selected from one or more of hydrogen phosphate, bicarbonate, and citrate. The mixed material is granulated or shaped at a temperature not exceeding 90°C.

7. The preparation method according to claim 6, characterized in that, Before the mixture is thoroughly mixed with 20wt% to 69wt% of carrier resin, 12wt% to 29wt% of foaming agent, 2wt% to 4wt% of dispersant and the balance of additives, the mixture is ground to ensure that the particle size of the mixture does not exceed 15μm.

8. The preparation method according to claim 6, characterized in that, The granulation process specifically includes: After the material is pulverized, it is extruded and granulated. During the extrusion process, the temperature of the first two sections of the extruder does not exceed 50℃, the temperature of other sections does not exceed 80℃, and the die temperature does not exceed 85℃.

9. The preparation method according to claim 8, characterized in that, The intensively mixed material is crushed, extruded, and then granulated in water.

10. The preparation method according to claim 6, characterized in that, The molding process specifically includes: The mixed material is calendered at a temperature above 40°C, and then cut or pressed into sheets to obtain foaming masterbatch.

11. A foaming material composition, characterized in that, include: 0.1 wt% to 1 wt% of foaming masterbatch, wherein the foaming masterbatch is the foaming masterbatch according to any one of claims 1 to 5 or the foaming masterbatch prepared by the preparation method according to any one of claims 6 to 10; The remaining amount of matrix resin.

12. The foaming material composition according to claim 1, characterized in that, The matrix resin is selected from one or more of polyethylene, polypropylene, polylactic acid, or polystyrene.

13. A composite packaging material, characterized in that, The microbubble membrane includes an outer layer, a microbubble intermediate layer, and an inner layer that are sequentially laminated together. The microbubble intermediate layer is formed by foaming the foaming material composition of claim 11 or 12.

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