Preparation method of thermal insulation packaging material

Abstract

The invention belongs to the technical field of plastic products, and particularly relates to a preparation method of a heat-preservation packaging material, which comprises the following steps: carrying out methyl silicon oxidation treatment on cork powder and carrying out epoxy resin wrapping; alkalifying the surface of the pigmented nevus glass fiber; polypropylene resin, wrapped cork powder, alkalized glass fibers, stearic acid, an antioxidant 1010, polyvinyl alcohol and tributyl citrate are weighed and then mixed, and the thermal insulation plastic meal box is obtained through melt extrusion and plastic molding. The problem that a polypropylene lunch box is poor in heat preservation performance is solved, the heat preservation performance of the polypropylene plastic lunch box is effectively improved by utilizing the sealing air blocking structure of the cork powder and the heat insulation performance of the methyl silica structure in cooperation with the heat reflection and heat isolation effects of the methyl silica material and the alkalized glass fiber.

Description

Technical Field

[0001] The present invention belongs to the technical field of plastic products, and particularly relates to a preparation method of a heat-insulating packaging material. Background Art

[0002] Since the advent of plastic packaging in the 20th century, it has rapidly spread due to its light weight, durability, low cost and other characteristics. From food preservation to product protection, the application scope of plastic packaging has been continuously expanding. With the development of Internet technology, ordering takeout has become an important way for consumers to dine, and the demand for disposable lunch boxes made of plastic packaging materials is increasing. These disposable lunch boxes are mostly made of polypropylene plastic, which has the advantages of non-toxicity, chemical resistance, heat resistance, electrical insulation, etc. Its physical and chemical properties will not change within the range of -10~140°C, making it an ideal material for tableware. However, the heat preservation effect of such polypropylene lunch boxes is not good, resulting in the food in the lunch box being prone to getting cold. Therefore, there is a large demand in the market for heat-insulating polypropylene lunch boxes made of heat-insulating packaging materials. Summary of the Invention

[0003] Aiming at the problems in the prior art, the present invention provides a preparation method of a heat-insulating packaging material, which solves the problem of poor heat preservation of polypropylene lunch boxes. By utilizing the airtight air barrier structure of cork powder and the heat insulation property of the methyl silicone structure, and combining the heat reflection and heat isolation effects of methyl silicone materials and alkalized glass fibers, the heat preservation performance of polypropylene plastic lunch boxes is effectively improved.

[0004] To achieve the above technical objectives, the technical solution of the present invention is as follows: A preparation method of a heat-insulating packaging material, comprising the following steps: Step 1: Add cork powder into ether and stir evenly, then add trichloromethylsilane and perform low-temperature ultrasonic treatment for 20 - 30 min. After filtration, dry under reduced pressure to obtain coated cork powder; the concentration of the cork powder in ether is 100 - 300 g / L, the stirring speed for even stirring is 200 - 500 r / min, the concentration of trichloromethylsilane in ether is 80 - 150 g / L, the temperature for low-temperature ultrasonic treatment is 5 - 10 °C, the ultrasonic frequency is 70 - 90 kHz, the pressure for drying under reduced pressure is 80 - 90% of the atmospheric pressure, and the temperature is 30 - 32 °C; in this step, the cork powder is added into ether to form a homogeneous dispersion, and at the same time, the ether penetrates into the pore structure inside the cork powder to achieve homogeneous wetting inside and outside; trichloromethylsilane has good solubility in ether and can be quickly dissolved and dispersed. Therefore, trichloromethylsilane is dispersed inside and outside the cork powder; during filtration and drying under reduced pressure, the cork powder is directly stripped from the ether solution, and the ether is directly evaporated and removed during in-situ drying, thereby precipitating trichloromethylsilane in-situ and distributing it on the surface of the cork powder; the mesh number of the cork powder is controlled within 200 - 800 meshes; the mesh number of the cork powder defines the particle size of the cork powder. If the mesh number of the cork powder is too large, the cork powder particles become smaller, resulting in a smaller pore structure inside the cork powder and a decrease in the heat insulation effect; if the mesh number is too small, the cork powder particles increase, leading to a decline in the performance of the entire packaging material and a decrease in the supportability, making it difficult to meet the actual market demand; Step 2: Let the coated cork powder stand still for 20 - 30 minutes, and then keep it standing at a constant temperature for 2 - 4 hours. Then add it to the epoxy resin - acetone solution, stir for 20 - 30 minutes, filter, and then keep it standing at a constant temperature for 20 - 30 minutes to obtain the cork powder wrapped; the atmosphere for standing is a mixed atmosphere of nitrogen and water vapor, and the volume ratio of nitrogen to water vapor is 8 - 10:1. The temperature for standing is 20 - 30 °C, and the temperature for constant - temperature standing is 120 - 130 °C; the concentration of epoxy resin E - 44 in the epoxy resin - acetone solution is 100 - 300 g / L, the concentration of the coated cork powder in the epoxy resin - acetone solution is 80 - 100 g / L, the stirring speed is 20 - 50 r / min, and the temperature for constant - temperature standing is 30 - 40 °C; in this step, the coated cork powder is subjected to a standing treatment. With the standing atmosphere being a mixed atmosphere of nitrogen and water vapor, trichloromethylsilane contacts with water vapor in situ to form trihydroxymethylsilane, and during the constant - temperature standing process, trihydroxymethylsilane is polycondensed to form a methylsiloxane structure; the above - mentioned trichloromethylsilane is evenly distributed on the surface of the cork powder. Therefore, the subsequently formed methylsiloxane structure forms a stable silicon - oxygen support within the cork powder, solving the problems of easy compression and low strength of the cork powder; epoxy resin has good solubility in acetone, and the epoxy resin - acetone solution has a certain viscosity. When the cork powder wrapped with the methylsiloxane structure is put in and stirred, the epoxy resin - acetone liquid film will form a liquid film on the surface of the cork powder based on its own viscosity. However, it is difficult for epoxy resin to penetrate into the cork powder. Therefore, during standing and constant - temperature standing, due to the volatility of acetone itself and the increase in temperature, epoxy resin gradually precipitates and forms a wrapping film on the surface of the cork powder, thus obtaining the cork powder wrapped. The surface of the cork powder wrapped is coated with epoxy resin, and the pore structure within the cork powder is formed into a closed - type pore structure. At the same time, there is a silicon - oxygen structure formed on the inner wall of this closed - type pore structure to provide support, which not only ensures the reactivity of the cork powder but also ensures its mechanical properties and heat insulation properties; Step 3: Put the glass fiber into an ethanol aqueous solution and stir for 20 - 30 min. After filtration and drying, soak it in an alkali solution for 10 - 20 s, then filter and leave it to dry to obtain alkalized glass fiber. The concentration of the glass fiber in the ethanol aqueous solution is 300 - 500 g / L, and the volume percentage of ethanol in the ethanol aqueous solution is 40 - 50%. The stirring speed of the stirring treatment is 300 - 600 r / min, and the temperature for filtration and drying is 120 - 140 °C; the alkali solution is a sodium hydroxide solution with a pH of 11, and the temperature for leaving it to dry is 100 - 110 °C; this step uses the ethanol aqueous solution to remove impurities on the surface of the glass fiber, ensuring the cleanliness of the glass fiber surface and exposing the pores on the glass fiber surface; after rapid soaking in the alkali solution and leaving it to dry, a sodium hydroxide liquid film layer is formed on the glass fiber surface, and a reaction occurs between the two. The surface of the glass fiber is not only corroded to form a rough structure, but also active groups after alkalization are formed, reducing the reaction inertness on the glass fiber surface; Step 4: Mix polypropylene resin, wrapped cork powder, and alkalized glass fiber and stir evenly to obtain a first mixture. The addition amount of the wrapped cork powder is 8 - 10% of the mass of the polypropylene resin, and the addition amount of the alkalized glass fiber is 9 - 10% of the mass of the polypropylene resin. The stirring speed for even mixing is 20 - 30 r / min; Step 5: Add a dispersant, an antioxidant, and polyvinyl alcohol to the first mixture and stir at a low speed for 30 - 50 min, then add a plasticizer and stir at a constant temperature for 20 - 30 min to obtain a second mixture. The dispersant is stearic acid, and the addition amount of the dispersant is 3 - 5% of the mass of the polypropylene resin. The addition amount of the antioxidant is 0.6 - 0.8% of the mass of the polypropylene resin, and the antioxidant is antioxidant 1010. The addition amount of the polyvinyl alcohol is 0.5 - 1.2% of the mass of the polypropylene resin. The low-speed stirring speed is 10 - 30 r / min. The plasticizer is tributyl citrate, and the addition amount of the plasticizer is 3 - 5% of the mass of the polypropylene resin; Step 6: Put the second mixture into a twin-screw extruder for melt extrusion to obtain a mixed sheet, and then put the mixed sheet into a thermoforming machine for thermoforming to obtain a heat-insulated lunch box, that is, a heat-insulating packaging material; the temperature for melt extrusion is 175 - 180 °C.

[0005] The cork powder in this preparation method not only contains a support structure with a methylsiloxane structure as the scaffold, but also has an epoxy resin coating and sealing layer, which provides good reaction activity for the cork powder. In the entire thermal insulation material, the pores in the cork powder are coated with epoxy resin to form a sealed structure, achieving the purpose of blocking heat transfer by static air, and cooperating with the methylsiloxane structure to have good heat insulation, reducing heat transfer and ensuring the thermal insulation of the wrapped cork powder itself. At the same time, the cork powder contains various esters and various polar groups, which adsorb trichloromethylsilane, ensuring the adsorption and adhesion of trimethylol silane. Therefore, the siloxane structure closely adheres to the specific surface of the cork powder. Epoxy resin has good activity, and its molecular structure contains epoxy groups and polar groups, ensuring its excellent adhesion and reactivity. Therefore, the wrapped cork powder based on the epoxy resin on the surface shows good reaction activity and improves the connection stability of the cork powder. The alkalized glass fiber is subjected to cleaning treatment and alkalization treatment on the surface of the glass fiber, effectively improving the roughness of the glass fiber surface and activating the glass fiber with alkali, improving the connection stability of the glass fiber in the entire packaging material. At the same time, the glass fiber has heat insulation performance, effectively preventing heat dissipation, thus achieving the thermal insulation effect. Stearic acid can play a good dispersibility, effectively improving the material dispersion uniformity in the polypropylene resin. At the same time, stearic acid has good antioxidant properties, can form a synergistic antioxidant with antioxidant 1010, and cooperate with the weather resistance of stearic acid to ensure the stability and high temperature resistance of the polypropylene resin. Stearic acid has good plasticizing properties, can form a synergistic plasticizing effect with tributyl citrate, ensuring the processability and weather resistance of the polypropylene resin, and realizing the stability of the polypropylene resin in the use of lunch boxes. Polyvinyl alcohol has certain adhesiveness and excellent adhesion. At the same time, the epoxy resin is located on the surface of the cork powder, showing excellent adhesion reactivity and improving the connection stability of the entire lunch box.

[0006] From the above description, it can be seen that the present invention has the following advantages: 1. The present invention solves the problem of poor thermal insulation of polypropylene lunch boxes. By using the air-blocking structure of the sealed cork powder and the heat insulation of the methylsiloxane structure, and cooperating with the heat reflection and heat isolation effects of the methylsiloxane material and alkalized glass fiber, the thermal insulation of the polypropylene plastic lunch box is effectively improved. 2. The present invention uses wrapped cork powder as a thermal insulation agent to solve the problem of unstable mechanical properties of the cork powder itself. By using methyltrichlorosilane to form penetration and hydrolysis, it plays a role in supporting the internal structure of the cork powder. At the same time, the surface of the cork powder is coated with epoxy resin to seal the cork powder, solving the problem of insufficient reaction sites caused by the pore structure of the cork powder itself. Cooperating with the connection reaction between the epoxy resin and the hydroxyl groups in the methylsiloxane structure and the high reactivity of the epoxy resin, it ensures the fixation of the wrapped cork powder in the entire thermal insulation lunch box, improving the stability, connectivity and thermal insulation of the entire material. 3. The present invention uses glass fiber as a filler, and through the alkalization treatment of the glass fiber, the alkalization activity and surface roughening of the glass fiber are formed, solving the inertness problem on the surface of the glass fiber, improving the fixability and dispersibility of the glass fiber, and enhancing the weather resistance of the polypropylene lunch box; at the same time, the alkalized glass fiber and the wrapped cork powder effectively solve the subsequent powdering problem; 4. The polypropylene heat-insulating lunch box prepared by the present invention is light in weight, convenient for transportation and has good airtightness, showing excellent toughness and heat preservation performance. Specific Embodiments

[0007] The present invention will be described in detail in conjunction with the embodiments, but no limitations will be made to the claims of the present invention. Example 1

[0008] A heat-insulating packaging material is prepared by the following method: Step 1, add 1000 g of 200-mesh cork powder into 10 L of ether and stir at a speed of 200 r / min for 20 min, then add 80 g of trichloromethylsilane and perform ultrasonic treatment at an ultrasonic frequency of 70 kHz and a temperature of 5 °C for 20 min, and finally dry at 30 °C under a pressure of 80% atmospheric pressure to obtain coated cork powder; Step 2, keep the above-mentioned coated cork powder static at 20 °C for 20 min in an atmosphere with a volume ratio of nitrogen to water vapor of 8:1, and keep it static at 120 °C for 2 h, then add it to 10 L of an epoxy resin-acetone solution and stir at a speed of 20 r / min for 20 min, and filter and then keep it static at 30 °C for 20 min to obtain wrapped cork powder, wherein the concentration of epoxy resin E-44 in the epoxy resin-acetone solution is 100 g / L; Step 3, put 1000 g of glass fiber into an ethanol aqueous solution with an ethanol volume ratio of 40% in 3.33 L and stir at a speed of 300 r / min, filter and then dry at a temperature of 120 °C, then soak it in a sodium hydroxide solution with a pH of 11 for 10 s, filter and then keep it static and dry at a temperature of 100 °C to obtain alkalized glass fiber; Step 4, weigh 1000 g of polypropylene resin, 80 g of wrapped cork powder, 90 g of alkalized glass fiber, 30 g of stearic acid, 6 g of antioxidant 1010, 5 g of polyvinyl alcohol, and 30 g of tributyl citrate according to the formula; then mix the polypropylene resin, wrapped cork powder and alkalized glass fiber and stir evenly at a stirring speed of 20 r / min to obtain a first mixture; Step 5, add stearic acid, antioxidant 1010 and polyvinyl alcohol to the first mixture and stir at a speed of 10 r / min for 30 min, then add tributyl citrate and perform constant temperature stirring at a temperature of 20 °C and a stirring speed of 20 r / min to obtain a second mixture; Step 6: Put the second mixture into a twin-screw extruder and melt-extrude it at a temperature of 175°C. After forming a sheet, perform thermoforming to obtain a heat-insulating plastic lunch box. Example 2

[0009] A heat-insulating packaging material is prepared by the following method: Step 1: Add 1000 g of 400-mesh cork powder to 3.33 L of diethyl ether and stir at a speed of 500 r / min for 30 min. Then add 500 g of trichloromethylsilane and perform ultrasonic treatment at an ultrasonic frequency of 90 kHz and a temperature of 10°C for 30 min. Finally, dry it at 32°C under a pressure of 90% atmospheric pressure to obtain coated cork powder. Step 2: Keep the above-mentioned coated cork powder static at 30°C for 30 min in an atmosphere with a volume ratio of nitrogen to water vapor of 10:1, and keep it static at 130°C for 4 h. Then add it to a 12.5-L epoxy resin-acetone solution and stir at a speed of 50 r / min for 30 min. After filtration, keep it static at 40°C for 30 min to obtain encapsulated cork powder, where the concentration of epoxy resin E-44 in the epoxy resin-acetone solution is 300 g / L. Step 3: Put 1000 g of glass fiber into an ethanol aqueous solution with an ethanol volume ratio of 50% in 2 L and stir at a speed of 600 r / min. After filtration, dry it at a temperature of 140°C, then soak it in a sodium hydroxide solution with a pH of 11 for 20 s, and after filtration, keep it static and dry at a temperature of 110°C to obtain alkalized glass fiber. Step 4: Weigh 1000 g of polypropylene resin, 100 g of encapsulated cork powder, 100 g of alkalized glass fiber, 50 g of stearic acid, 8 g of antioxidant 1010, 12 g of polyvinyl alcohol, and 50 g of tributyl citrate according to the formula; then mix the polypropylene resin, encapsulated cork powder, and alkalized glass fiber and stir evenly at a stirring speed of 30 r / min to obtain a first mixture. Step 5: Add stearic acid, antioxidant 1010, and polyvinyl alcohol to the first mixture and stir at a speed of 30 r / min for 50 min. Then add tributyl citrate and perform constant-temperature stirring at a temperature of 20°C and a stirring speed of 20 r / min to obtain a second mixture. Step 6: Put the second mixture into a twin-screw extruder and melt-extrude it at a temperature of 180°C. After forming a sheet, perform thermoforming to obtain a heat-insulating plastic lunch box. Example 3

[0010] A heat-insulating packaging material is prepared by the following method: Step 1, add 1000 g of 800-mesh cork powder into 5 L of ether and stir at a speed of 400 r / min for 25 min. Then add 600 g of trichloromethylsilane and ultrasonically treat it at an ultrasonic frequency of 80 kHz and a temperature of 8 °C for 25 min. Finally, dry it at 31 °C under a pressure of 85% atmospheric pressure to obtain coated cork powder; Step 2, keep the above-mentioned coated cork powder static at 25 °C for 25 min in an atmosphere with a volume ratio of nitrogen to water vapor of 9:1, and keep it static at 125 °C for 3 h. Then add it into 12 L of epoxy resin-acetone solution and stir at a speed of 40 r / min for 25 min. After filtration, keep it static at 35 °C for 25 min to obtain encapsulated cork powder. Among them, the concentration of epoxy resin E-44 in the epoxy resin-acetone solution is 200 g / L; Step 3, put 1000 g of glass fiber into an ethanol aqueous solution with an ethanol volume ratio of 45% in 2.5 L and stir at a speed of 500 r / min. After filtration, dry it at a temperature of 130 °C, and then soak it in a sodium hydroxide solution with a pH of 11 for 15 s. After filtration, keep it static and dry at a temperature of 105 °C to obtain alkalized glass fiber; Step 4, weigh 1000 g of polypropylene resin, 90 g of encapsulated cork powder, 95 g of alkalized glass fiber, 40 g of stearic acid, 7 g of antioxidant 1010, 9 g of polyvinyl alcohol, and 40 g of tributyl citrate according to the formula; then mix the polypropylene resin, encapsulated cork powder and alkalized glass fiber and stir evenly at a stirring speed of 25 r / min to obtain a first mixture; Step 5, add stearic acid, antioxidant 1010 and polyvinyl alcohol to the first mixture and stir at a speed of 20 r / min for 40 min. Then add tributyl citrate and carry out constant temperature stirring at a temperature of 20 °C and a stirring speed of 20 r / min to obtain a second mixture; Step 6, put the second mixture into a twin-screw extruder and melt-extrude it at a temperature of 175 °C. After forming into a sheet, carry out thermoforming to obtain a heat-insulating plastic lunch box. Example 4

[0011] A heat-insulating packaging material is prepared by the following method: Step 1, add 1000 g of 600-mesh cork powder into 5 L of ether and stir at a speed of 400 r / min for 25 min. Then add 600 g of trichloromethylsilane and ultrasonically treat it at an ultrasonic frequency of 80 kHz and a temperature of 8 °C for 25 min. Finally, dry it at 31 °C under a pressure of 85% atmospheric pressure to obtain coated cork powder; Step 2: Keep the above-mentioned coated cork powder at 25°C for 25 min under the atmosphere with a volume ratio of nitrogen to water vapor of 9:1, then keep it at 125°C for 3 h. Then add it to a 12 L epoxy resin-acetone solution and stir at a speed of 40 r / min for 25 min. After filtration, keep it at 35°C for 25 min to obtain the coated cork powder. Among them, the concentration of epoxy resin E-44 in the epoxy resin-acetone solution is 200 g / L; Step 3: Put 1000 g of glass fiber into an ethanol aqueous solution with an ethanol volume ratio of 45% in 2.5 L and stir at a speed of 500 r / min. After filtration, dry it at a temperature of 130°C, then soak it in a sodium hydroxide solution with a pH of 11 for 15 s, and after filtration, keep it standing and drying at a temperature of 105°C to obtain alkalized glass fiber; Step 4: Weigh 1000 g of polypropylene resin, 90 g of coated cork powder, 95 g of alkalized glass fiber, 40 g of stearic acid, 7 g of antioxidant 1010, 9 g of polyvinyl alcohol, and 40 g of tributyl citrate according to the formula; then mix the polypropylene resin, coated cork powder, and alkalized glass fiber and stir evenly at a stirring speed of 25 r / min to obtain the first mixture; Step 5: Add stearic acid, antioxidant 1010, and polyvinyl alcohol to the first mixture and stir at a speed of 20 r / min for 40 min. Then add tributyl citrate and carry out constant-temperature stirring at a temperature of 20°C and a stirring speed of 20 r / min to obtain the second mixture; Step 6: Put the second mixture into a twin-screw extruder and melt-extrude it at a temperature of 180°C. After forming into a sheet, carry out thermoforming to obtain the heat-insulating plastic lunch box.

[0012] Comparative Example 1 A heat-insulating packaging material is prepared by the following method: Step 1: Put 1000 g of glass fiber into an ethanol aqueous solution with an ethanol volume ratio of 45% in 2.5 L and stir at a speed of 500 r / min. After filtration, dry it at a temperature of 130°C, then soak it in a sodium hydroxide solution with a pH of 11 for 15 s, and after filtration, keep it standing and drying at a temperature of 105°C to obtain alkalized glass fiber; Step 2: Weigh 1000 g of polypropylene resin, 90 g of cork powder, 95 g of alkalized glass fiber, 40 g of stearic acid, 7 g of antioxidant 1010, 9 g of polyvinyl alcohol, and 40 g of tributyl citrate according to the formula; then mix the polypropylene resin, cork powder, and alkalized glass fiber and stir evenly at a stirring speed of 25 r / min to obtain the first mixture; Step 3: Add stearic acid, antioxidant 1010, and polyvinyl alcohol to the first mixture, stir at a speed of 20 r / min for 40 min, then add tributyl citrate and conduct constant-temperature stirring at a temperature of 20°C and a stirring speed of 20 r / min to obtain a second mixture; Step 4: Put the second mixture into a twin-screw extruder and melt-extrude it at a temperature of 180°C, then perform thermoforming after forming a sheet to obtain a heat-insulating plastic lunch box.

[0013] Comparative Example 2 A heat-insulating packaging material is prepared by the following method: Step 1: Weigh 1000 g of polypropylene resin, 90 g of cork powder, 95 g of glass fiber, 40 g of stearic acid, 7 g of antioxidant 1010, 9 g of polyvinyl alcohol, and 40 g of tributyl citrate according to the formula; then mix the polypropylene resin, cork powder, and glass fiber and stir evenly at a stirring speed of 25 r / min to obtain a first mixture; Step 2: Add stearic acid, antioxidant 1010, and polyvinyl alcohol to the first mixture, stir at a speed of 20 r / min for 40 min, then add tributyl citrate and conduct constant-temperature stirring at a temperature of 20°C and a stirring speed of 20 r / min to obtain a second mixture; Step 3: Put the second mixture into a twin-screw extruder and melt-extrude it at a temperature of 180°C, then perform thermoforming after forming a sheet to obtain a heat-insulating plastic lunch box.

[0014] Comparative Example 3 A heat-insulating packaging material is prepared by the following method: Step 1: Weigh 1000 g of polypropylene resin, 90 g of cork powder, 95 g of calcium carbonate, 40 g of stearic acid, 7 g of antioxidant 1010, 9 g of polyvinyl alcohol, and 40 g of tributyl citrate according to the formula; then mix the polypropylene resin, cork powder, and glass fiber and stir evenly at a stirring speed of 25 r / min to obtain a first mixture; Step 2: Add stearic acid, antioxidant 1010, and polyvinyl alcohol to the first mixture, stir at a speed of 20 r / min for 40 min, then add tributyl citrate and conduct constant-temperature stirring at a temperature of 20°C and a stirring speed of 20 r / min to obtain a second mixture; Step 3: Put the second mixture into a twin-screw extruder and melt-extrude it at a temperature of 180°C, then perform thermoforming after forming a sheet to obtain a heat-insulating plastic lunch box.

[0015] Comparative Example 4 A packaging material is prepared by the following method: Step 1: Weigh 1000 g of polypropylene resin, 95 g of glass fiber, 40 g of stearic acid, 7 g of antioxidant 1010, 9 g of polyvinyl alcohol, and 40 g of tributyl citrate according to the formula; then mix the polypropylene resin and glass fiber and stir evenly at a stirring speed of 25 r / min to obtain a first mixture; Step 2: Add stearic acid, antioxidant 1010, and polyvinyl alcohol to the first mixture and stir at a speed of 20 r / min for 40 min, then add tributyl citrate and perform constant temperature stirring at a temperature of 20°C and a stirring speed of 20 r / min to obtain a second mixture; Step 3: Put the second mixture into a twin-screw extruder and melt-extrude it at a temperature of 180°C, then thermoform it after forming into a sheet to obtain a heat-insulating plastic lunch box.

[0016] Performance Testing (1) Use the plastic lunch boxes prepared in Examples 1-4 and Comparative Examples 1-4 as test samples to conduct Vicat softening temperature tests in accordance with GB / T 1633-2000; (2) Use the plastic lunch boxes prepared in Examples 1-4 and Comparative Examples 1-4 as test samples to conduct heat preservation conditions under different temperature environments: Inject 100 mL of water at 90-95°C into the lunch boxes of the test samples, and place them in constant temperature incubators at 0°C, 25°C, and 35°C respectively. After standing for 1 h, measure the temperature of the water in the lunch boxes; (3) Use the plastic lunch boxes of Example 4, Comparative Example 1, Comparative Example 2, and Comparative Example 4 as test samples to conduct mechanical property tests.

[0017] Table 1: Vicat softening temperature and water temperature test results of each example and each comparative example Vicat softening temperature At an ambient temperature of 0°C At an ambient temperature of 25°C At an ambient temperature of 35°C Example 1 163℃ 71℃ 75℃ 78℃ Example 2 168℃ 74℃ 78℃ 81℃ Example 3 165℃ 73℃ 76℃ 80℃ Example 4 167℃ 73℃ 76℃ 80℃ Comparative Example 1 154℃ 65℃ 69℃ 73℃ Comparative Example 2 152℃ 63℃ 68℃ 70℃ Comparative Example 3 151℃ 62℃ 64℃ 67℃ Comparative Example 4 143℃ 56℃ 59℃ 61℃ The above data show that in this technical solution, adding silica-oxygen-coated cork powder can effectively improve the Vicat softening problem of the heat-insulating packaging material, improve the heat preservation effect of the heat-insulating packaging material. At the same time, the use and activation of glass fiber can effectively reduce internal gaps, and combined with its own heat insulation characteristics, effectively improve the heat preservation performance of the packaging material.

[0018] It can be understood that the above specific description of the present invention is only for explaining the present invention and is not limited to the technical solutions described in the embodiments of the present invention. Those of ordinary skill in the art should understand that the present invention can still be modified or equivalently replaced to achieve the same technical effect; as long as it meets the use requirements, it is within the protection scope of the present invention.

Claims

1. A method for preparing a thermal insulation packaging material, characterized in that: The steps include: Step 1, adding cork powder to ether and stirring evenly, then adding trichloromethylsilane and performing low-temperature ultrasonic treatment for 20-30 minutes, filtering and drying under reduced pressure to obtain coated cork powder; Step 2, allowing the coated cork powder to stand for 20-30 minutes and stand at a constant temperature for 2-4 hours, then adding it to the epoxy resin-acetone solution, stirring for 20-30 minutes, filtering and standing at a constant temperature for 20-30 minutes to obtain coated cork powder; Step 3, placing the glass fiber in an ethanol aqueous solution and stirring for 20-30 minutes, filtering and drying, and then soaking in an alkali solution for 10-20 seconds, filtering, and then standing and drying to obtain an alkalized glass fiber; Step 4, mixing the polypropylene resin, the wrapped cork powder and the alkalized glass fiber and stirring them evenly to obtain a first mixture; Step 5, adding the dispersant, antioxidant and polyvinyl alcohol to the first mixture and stirring at a low speed for 30-50 minutes, and then adding the plasticizer and stirring at a constant temperature for 20-30 minutes to obtain a second mixture; Step 6, placing the second mixture into a twin-screw extruder for melt extrusion to obtain a mixed sheet, and then placing the mixed sheet into a blister machine for blister molding to obtain a heat-insulating lunch box, i.e., a heat-insulating packaging material.

2. The method for preparing the thermal insulation packaging material according to claim 1, characterized in that: The concentration of the cork powder in the ether in step 1 is 100-300 g / L, and the stirring speed for uniform stirring is 200-500 r / min.

3. The method for preparing the thermal insulation packaging material according to claim 1, characterized in that: The concentration of trichloromethylsilane in diethyl ether in step 1 is 80-150 g / L, the temperature of low-temperature ultrasound is 5-10° C., the ultrasonic frequency is 70-90 kHz, the pressure of the reduced pressure drying is 80-90% of the atmospheric pressure, and the temperature is 30-32° C.

4. The method for preparing the thermal insulation packaging material according to claim 1, characterized in that: The standing atmosphere in step 2 is a mixed atmosphere of nitrogen and water vapor, and the volume ratio of nitrogen to water vapor is 8-10:

1. The standing temperature is 20-30°C, and the constant temperature standing temperature is 120-130°C.

5. The method for preparing the thermal insulation packaging material according to claim 1, characterized in that: The concentration of epoxy resin E-44 in the epoxy resin-acetone solution in step 2 is 100-300 g / L, the concentration of coated cork powder in the epoxy resin-acetone solution is 80-100 g / L, the stirring speed is 20-50 r / min, and the constant temperature standing temperature is 30-40°C.

6. The method for preparing the thermal insulation packaging material according to claim 1, characterized in that: The concentration of the glass fiber in the ethanol aqueous solution in step 3 is 300-500 g / L, and the volume proportion of ethanol in the ethanol aqueous solution is 40-50%, the stirring speed of the stirring treatment is 300-600 r / min, and the temperature of the filtration and drying is 120-140°C; the alkali solution adopts a sodium hydroxide solution with a pH of 11, and the temperature of the static drying is 100-110°C.

7. The method for preparing the thermal insulation packaging material according to claim 1, characterized in that: The amount of the wrapped cork powder added in step 4 is 8-10% of the mass of the polypropylene resin, the amount of the alkalized glass fiber added is 9-10% of the mass of the polypropylene resin, and the stirring speed is 20-30r / min.

8. The method for preparing the thermal insulation packaging material according to claim 1, characterized in that: The dispersant in step 5 is stearic acid, and the amount of the dispersant added is 3-5% of the mass of the polypropylene resin, the amount of the antioxidant added is 0.6-0.8% of the mass of the polypropylene resin, and the antioxidant is antioxidant 1010, the amount of polyvinyl alcohol added is 0.5-1.2% of the mass of the polypropylene resin, and the speed of the low-speed stirring is 10-30r / min.

9. The method for preparing the thermal insulation packaging material according to claim 1, characterized in that: The plasticizer in step 5 is tributyl citrate, and the amount of the plasticizer added is 3-5% of the mass of the polypropylene resin.

10. The method for preparing the thermal insulation packaging material according to claim 1, characterized in that: The temperature of the melt extrusion in step 6 is 175-180°C.