Microfoamed packaging material and microfoamed process for its preparation

Abstract

The application relates to the technical field of foaming packaging materials, and discloses a micro-foaming packaging material and a micro-foaming preparation process thereof. The micro-foaming packaging material comprises the following components by weight: 85-100 parts of polyethylene, 5-7 parts of silane-modified calcium carbonate, 0.4-0.8 parts of a lubricant, 0.8-1.5 parts of sodium bicarbonate, 0.8-1.2 parts of a pH regulator, 0.5-1 part of an antioxidant, 1-2 parts of a nucleating agent and 4-8 parts of a compatilizer. The preparation method of the nucleating agent comprises the following steps: dispersing talcum powder in a solvent, and coating and modifying the talcum powder by adding a composite silicon source precursor to obtain the nucleating agent, wherein the composite silicon source precursor comprises tetraethyl orthosilicate and methyl triethoxysilane. The above technical scheme solves the problem of low strength of the foaming packaging material in the related art.

Description

Technical Field

[0001] This invention relates to the field of foamed packaging materials technology, specifically to a micro-foamed packaging material and its micro-foaming preparation process. Background Technology

[0002] With the packaging industry's increasing demand for "lightweight, environmentally friendly, and high-performance" materials, microfoamed packaging materials are finding wider application in food packaging caps, electronic cushioning liners, and transport protective sleeves due to their combination of low density, excellent cushioning and protection, and good thermal and moisture insulation. Microfoamed packaging materials typically use polyolefins as the main raw material, combined with foaming agents, nucleating agents, and other additives to construct a complete microfoamed system. In the preparation of microfoamed materials, the nucleating agent is the core additive that determines the bubble structure and final performance. However, existing technologies mostly use a single inorganic nucleating agent. These nucleating agents have uneven distribution of nucleation sites, resulting in large differences in bubble size, which in turn causes microscopic defects within the material. Ultimately, this leads to lower strength in the microfoamed material, making it difficult to meet the needs of high-end packaging applications and limiting its application range. Therefore, developing a high-strength microfoamed packaging material is of great significance for expanding its application scope. Summary of the Invention

[0003] This invention proposes a micro-foamed packaging material and its micro-foaming preparation process, which solves the problem of low strength of foamed packaging materials in related technologies.

[0004] The technical solution of the present invention is as follows:

[0005] This invention proposes a microfoamed packaging material comprising the following raw materials in parts by weight: 85-100 parts polyethylene, 5-7 parts silane-modified calcium carbonate, 0.4-0.8 parts lubricant, 0.8-1.5 parts sodium bicarbonate, 0.8-1.2 parts pH adjuster, 0.5-1 part antioxidant, 1-2 parts nucleating agent, and 4-8 parts compatibilizer;

[0006] The preparation method of the nucleating agent includes the following steps: dispersing talc powder in a solvent, adding a composite silicon source precursor to coat and modify it, and obtaining the nucleating agent;

[0007] The composite silicon source precursor includes tetraethyl orthosilicate and methyltriethoxysilane.

[0008] As a further technical solution, the coating modification method includes the following steps: adding a composite silicon source precursor to a solvent in which talc powder is dispersed, mixing, adjusting the pH to alkaline, concentrating, and drying to obtain a nucleating agent.

[0009] As a further technical solution, the mass ratio of tetraethyl orthosilicate to methyltriethoxysilane is 7~8.5:2, preferably 7.8:2.

[0010] As a further technical solution, the mass ratio of the talc powder to the composite silicon source precursor is 6~8:1, preferably 7:1.

[0011] As a further technical solution, the solvent is composed of water, isopropanol and ammonia in a volume ratio of 1:10:1.

[0012] As a further technical solution, the mass-to-volume ratio of the talc powder and the solvent is 1g:12mL.

[0013] As a further technical solution, when the pH is adjusted to be alkaline, the pH value is 8-9.

[0014] As a further technical solution, the lubricant is composed of pentaerythritol distearate and polyethylene glycol stearate in a mass ratio of 1.2 to 2.8:1, preferably 2.1:1.

[0015] In the microfoamed packaging material of this invention, the lubricant is composed of pentaerythritol distearate and polyethylene glycol stearate in a mass ratio of 1.2 to 2.8:1. When the mass ratio of pentaerythritol distearate to polyethylene glycol stearate is less than 1.2 to 2.8:1, the internal lubrication of pentaerythritol distearate is insufficient, making it difficult to effectively reduce the viscosity of polyethylene melt. This leads to uneven dispersion of solid components such as silane-modified calcium carbonate and nucleating agents in the melt, easily forming local agglomerates, and consequently causing a decrease in the strength of the microfoamed material. When the mass ratio of pentaerythritol distearate to polyethylene glycol stearate is greater than 1.2 to 2.8:1, the strong internal lubrication of pentaerythritol distearate will reduce the melt viscosity. Strength is easily compromised by the formation of interconnected pores or collapsed bubbles, leading to internal structural defects and a decrease in the mechanical strength of microfoamed packaging materials. When the lubricant is composed of pentaerythritol distearate and polyethylene glycol stearate in a mass ratio of 1.2 to 2.8:1, the pentaerythritol distearate can achieve efficient dispersion of the components, while the polyethylene glycol stearate can maintain the strength of the melt during the foaming process, ensuring a uniform and dense bubble structure, thereby further improving the mechanical strength of microfoamed packaging materials.

[0016] As a further technical solution, the preparation method of the silane-modified calcium carbonate includes the following steps: dispersing calcium carbonate in a 75wt% ethanol solution, adding a silane coupling agent to mix, concentrating, and drying to obtain silane-modified calcium carbonate.

[0017] As a further technical solution, the mass of the silane coupling agent is 3% to 5% of the mass of calcium carbonate, and the mass-to-volume ratio of the calcium carbonate to the ethanol solution is 1g:10mL.

[0018] As a further technical solution, the silane coupling agent includes one or more of KH-550, KH-560, and KH-570, preferably KH-560.

[0019] As a further technical solution, in the preparation method of silane-modified calcium carbonate, the mixing temperature is 50~60℃ and the mixing time is 3~4h.

[0020] As a further technical solution, the pH adjuster includes one or both of sodium citrate and citric acid.

[0021] As a further technical solution, the antioxidant includes one or both of antioxidant 1010 and antioxidant 1076.

[0022] As a further technical solution, the compatibilizer is one or both of maleic anhydride-grafted polyethylene and maleic anhydride-grafted ethylene-octene copolymer.

[0023] The present invention also proposes a micro-foaming preparation process for micro-foamed packaging materials, comprising the following steps: mixing raw materials and then melting and extruding them to obtain micro-foamed packaging materials.

[0024] As a further technical solution, in the micro-foaming preparation process of micro-foamed packaging materials, the mixing speed is 250~350rpm and the mixing time is 2~3min.

[0025] As a further technical solution, during the melt extrusion, the screw speed is 80~100rpm, the barrel temperature is 160~180℃, and the die temperature is 200~220℃.

[0026] The working principle and beneficial effects of this invention are as follows:

[0027] In this invention, a composite silicon source precursor composed of tetraethyl orthosilicate and methyltriethoxysilane is used to coat and modify talc powder to prepare a nucleating agent, which can synergistically improve the mechanical strength of the microfoamed packaging material. The silica shell formed by the hydrolysis of tetraethyl orthosilicate in the composite silicon source precursor provides a large number of uniform nucleation sites for talc powder, ensuring fine and regular bubbles and reducing stress concentration caused by uneven bubble size. The methyl groups introduced by methyltriethoxysilane can reduce the surface polarity of the nucleating agent, enhance its compatibility with the polyethylene matrix, and reduce interface defects. The synergistic effect of these two components achieves a dual optimization of the cell structure and interface compatibility, significantly improving the tensile strength of the microfoamed packaging material. Detailed Implementation

[0028] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0029] In the following examples and comparative examples: polyethylene, grade DMDA-8920; maleic anhydride-grafted polyethylene, purchased from Dongguan Dinghai Plastic & Chemical Co., Ltd., grade DINGHAI; maleic anhydride-grafted ethylene-octene copolymer, purchased from Shenzhen Huixin Plastic & Chemical Co., Ltd., model PE8190; calcium carbonate, particle size 48μm; talc, particle size 5μm.

[0030] Example 1

[0031] A microfoamed packaging material comprises the following raw materials in parts by weight: 85 parts polyethylene, 5 parts silane-modified calcium carbonate, 0.4 parts lubricant, 0.8 parts sodium bicarbonate, 0.8 parts citric acid, 0.5 parts antioxidant 1010, 1 part nucleating agent, and 4 parts maleic anhydride-grafted polyethylene; wherein the lubricant is only pentaerythritol distearate.

[0032] The preparation method of the nucleating agent includes the following steps: dispersing talc powder in a solvent composed of water, isopropanol and ammonia in a volume ratio of 1:10:1, adding a composite silicon source precursor composed of tetraethyl orthosilicate and methyltriethoxysilane in a mass ratio of 7:2, adjusting the pH to 8, concentrating, and drying to obtain the nucleating agent; wherein the mass-volume ratio of talc powder to solvent is 1g:12mL, and the mass ratio of talc powder to composite silicon source precursor is 7:1;

[0033] The preparation method of silane-modified calcium carbonate includes the following steps: dispersing calcium carbonate in a 75wt% ethanol solution, adding silane coupling agent KH-560, ultrasonically dispersing at 55℃ for 3.5h, concentrating, and drying to obtain silane-modified calcium carbonate; wherein, the mass of silane coupling agent is 4% of the mass of calcium carbonate, and the mass-volume ratio of calcium carbonate to ethanol solution is 1g:10mL;

[0034] A micro-foamed packaging material preparation process includes the following steps: adding raw materials into a mixer, mixing for 3 minutes at a speed of 300 rpm, then placing the mixture in a screw extruder, and melting and extruding it at a screw speed of 90 rpm, a barrel temperature of 170°C, and a die temperature of 210°C to obtain the micro-foamed packaging material.

[0035] Example 2

[0036] Compared with Example 1, the only difference in Example 2 is that the microfoamed packaging material in this example includes the following raw materials in parts by weight: 93 parts polyethylene, 6 parts silane-modified calcium carbonate, 0.6 parts lubricant, 1.2 parts sodium bicarbonate, 1 part sodium citrate, 0.7 parts antioxidant 1076, 1.5 parts nucleating agent, and 6 parts maleic anhydride-grafted ethylene-octene copolymer; wherein, the lubricant is only pentaerythritol distearate.

[0037] Example 3

[0038] Compared with Example 1, the only difference in Example 3 is that the microfoamed packaging material in this example includes the following raw materials in parts by weight: 100 parts of polyethylene, 7 parts of silane-modified calcium carbonate, 0.8 parts of lubricant, 1.5 parts of sodium bicarbonate, 1.2 parts of citric acid, 1 part of antioxidant 1010, 2 parts of nucleating agent, and 8 parts of maleic anhydride-grafted polyethylene; wherein, the lubricant is only pentaerythritol distearate.

[0039] Example 4

[0040] Compared with Example 1, the only difference in Example 4 is that in the preparation method of the nucleating agent in this example, the composite silicon source precursor is composed of tetraethyl orthosilicate and methyltriethoxysilane in a mass ratio of 7.8:2.

[0041] Example 5

[0042] Compared with Example 1, the only difference in Example 5 is that in the preparation method of the nucleating agent in this example, the composite silicon source precursor is composed of tetraethyl orthosilicate and methyltriethoxysilane in a mass ratio of 8.5:2.

[0043] Example 6

[0044] Compared with Example 1, the only difference in Example 6 is that the lubricant in this example is composed of pentaerythritol distearate and polyethylene glycol stearate in a mass ratio of 1.2:1.

[0045] Example 7

[0046] Compared with Example 1, the only difference in Example 7 is that the lubricant in this example is composed of pentaerythritol distearate and polyethylene glycol stearate in a mass ratio of 2.1:1.

[0047] Example 8

[0048] Compared with Example 1, the only difference in Example 8 is that the lubricant in this example is composed of pentaerythritol distearate and polyethylene glycol stearate in a mass ratio of 2.8:1.

[0049] Example 9

[0050] Compared with Example 1, the only difference in Example 9 is that the lubricant in this example is only polyethylene glycol stearate.

[0051] Comparative Example 1

[0052] Compared with Example 1, the only difference in Comparative Example 1 is that the composite silicon source precursor in this comparative example is only tetraethyl orthosilicate.

[0053] Comparative Example 2

[0054] Compared with Example 1, the only difference in Comparative Example 2 is that the composite silicon source precursor in this comparative example is only methyltriethoxysilane.

[0055] Comparative Example 3

[0056] Compared with Example 1, the only difference in Comparative Example 3 is that the nucleating agent in this comparative example is only talc.

[0057] The microcellular packaging materials prepared in Examples 1-9 and Comparative Examples 1-3 were tested according to the following methods:

[0058] 1. Tensile strength test method: The tensile strength of the micro-foamed packaging material specimens shall be tested in accordance with the test method specified in GB / T 1040.2-2022 "Determination of tensile properties of plastics - Part 2: Test conditions for molded and extruded plastics", wherein the specimen size is 1A type specimen.

[0059] The test results are shown in Tables 1 and 2:

[0060] Table 1 Tensile strength test results of microfoamed packaging materials

[0061]

[0062] As shown in Table 1, the comparison between Examples 1-5 and Comparative Examples 1-3 indicates that when the nucleating agent is talc modified with a composite silicon source precursor composed of tetraethyl orthosilicate and methyltriethoxysilane, the tensile strength of the microfoamed packaging material can be further improved.

[0063] Table 2 Tensile strength test results of microfoamed packaging materials

[0064]

[0065] As shown in Table 2, the comparison of Examples 1, 6-9 indicates that when the lubricant is composed of pentaerythritol distearate and polyethylene glycol stearate, the tensile strength of the microfoamed packaging material can be further improved.

[0066] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A micro-foamed packaging material, characterized in that, The raw materials include the following components by weight: polyethylene 85-100 parts, silane modified calcium carbonate 5-7 parts, lubricant 0.4-0.8 parts, sodium bicarbonate 0.8-1.5 parts, pH regulator 0.8-1.2 parts, antioxidant 0.5-1 part, nucleating agent 1-2 parts, and compatibilizer 4-8 parts; The preparation method of the nucleating agent comprises the following steps: dispersing talcum powder in a solvent, and coating and modifying the talcum powder by adding a composite silicon source precursor to obtain the nucleating agent; The composite silicon source precursor comprises tetraethyl orthosilicate and methyl triethoxysilane in a mass ratio of 7-8.5:

2. The mass ratio of the talcum powder to the composite silicon source precursor is 6-8:

1.

2. A micro-foamed packaging material according to claim 1, characterized in that, The lubricant is composed of pentaerythritol distearate and polyethylene glycol stearate in a mass ratio of 1.2-2.8:

1.

3. A micro-foamed packaging material according to claim 1, characterized in that, The solvent is composed of water, isopropyl alcohol and ammonia water in a volume ratio of 1:10:

1.

4. A micro-foamed packaging material according to claim 1, characterized in that, The preparation method of the silane modified calcium carbonate comprises the following steps: dispersing calcium carbonate in a 75wt% ethanol solution, adding a silane coupling agent, mixing, concentrating, and drying to obtain the silane modified calcium carbonate.

5. A micro-foamed packaging material according to claim 1, wherein, The pH regulator comprises one or both of sodium citrate and citric acid.

6. A process for the microfoaming preparation of a microfoamed packaging material for the preparation of a microfoamed packaging material according to any one of claims 1 to 5, characterized in that, The method comprises the following steps: After the raw materials are mixed, micro-foamed packaging material is obtained by melt extrusion.

7. A process for the microfoaming of a microfoamed packaging material according to claim 6, characterized in that, During the mixing, the rotation speed is 250-350 rpm, and the mixing time is 2-3 min.

8. A process for the microfoaming of a microfoamed packaging material according to claim 6, characterized in that, During the melt extrusion, a screw extruder is used, the screw rotation speed of the screw extruder is 80-100 rpm, the barrel temperature is 160-180℃, and the die temperature is 200-220℃.

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