Pressure-resistant anti-aging composite foam box and manufacturing method thereof

Abstract

The invention belongs to the technical field of foam materials, and particularly relates to a pressure-resistant anti-aging composite foam box and a manufacturing method thereof. The method comprises the following steps: S1, preparing raw materials containing polypropylene and modified polypropylene; s2, mixing the raw materials, and performing melt blending granulation to obtain a modified polypropylene composite material; s3, the modified polypropylene composite material is fed into a hopper of a microcellular foaming injection molding machine to be preheated to be in a plasticized state, and then supercritical carbon dioxide is injected to serve as a foaming agent; s4, the polymer melt containing the supercritical carbon dioxide is injected into a cavity of the box forming mold with the preset temperature for pressure maintaining; the volume of a mold cavity is increased by controlling a mold core on one side of the movable mold to retreat, so that the pressure in the polymer melt is reduced, a foaming body is formed, and the target polypropylene composite foam box body is obtained after cooling and curing. The pressure-resistant anti-aging composite foam box prepared by the method disclosed by the invention has excellent buffering property, pressure resistance, aging resistance and environmental protection property.

Description

Technical Field

[0001] The invention belongs to the technical field of foaming materials, and in particular relates to a pressure-resistant and anti-aging composite foam box and a manufacturing method thereof. Background Art

[0002] With the development of economic globalization, the logistics and packaging industries have ushered in unprecedented development opportunities. In this context, the performance requirements for packaging materials are also constantly increasing, especially for those products that need to be transported over long distances, stored for a long time or used in harsh environments, high-performance packaging materials are particularly important.

[0003] Traditional foam packaging materials, such as polystyrene (EPS) foam, although they have certain cushioning properties, have obvious deficiencies in terms of pressure resistance, anti-aging and environmental protection. For example, EPS foam is prone to permanent deformation when subjected to high pressure, resulting in damage to the internal items; at the same time, due to its poor anti-aging performance, long-term exposure to sunlight will accelerate the aging of the material and shorten its service life. In addition, the foaming process of EPS foam and its own non-degradability also bring additional burdens to the environment, which does not meet the requirements of modern green packaging. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a pressure-resistant and anti-aging composite foam box and a manufacturing method thereof, which has excellent cushioning, pressure resistance, anti-aging and environmental protection properties.

[0005] The first aspect of the present invention is to provide a pressure-resistant and anti-aging composite foam box and a manufacturing method thereof, comprising the following steps:

[0006] Step S1: preparing raw materials including polypropylene and modified polypropylene;

[0007] Step S2: mixing the raw materials, and granulating them by melt blending to obtain a modified polypropylene composite material;

[0008] Step S3: feeding the modified polypropylene composite material into a hopper of a microcellular foaming injection molding machine and preheating it to a plasticized state, and then injecting supercritical carbon dioxide as a foaming agent;

[0009] Step S4: injecting a polymer melt containing supercritical carbon dioxide into a cavity of a box-forming mold at a preset temperature and maintaining the pressure; by controlling the core on one side of the movable mold to retreat, the volume of the mold cavity is increased, resulting in a decrease in the pressure in the polymer melt and the formation of a foamed body, and after cooling and solidification, the target polypropylene composite foam box is obtained.

[0010] As a further optimization scheme of the manufacturing method of the pressure-resistant and anti-aging composite foam box, in step S1, the raw materials include:

[0011] Polypropylene (PP): 1000 parts by mass;

[0012] Modified polypropylene: 30-50 parts by mass;

[0013] Mica powder: 30-50 parts by mass;

[0014] Ethylene-octene copolymer: 15-35 parts by mass;

[0015] Light stabilizer: 5-10 parts by mass;

[0016] Antioxidant: 5-8 parts by weight;

[0017] Nucleating agent: 10-20 parts by mass;

[0018] Polylactic acid: 70-90 parts by mass;

[0019] Thermoplastic polyurethane: 20-40 parts by mass.

[0020] As a further optimization scheme for the method for manufacturing the pressure-resistant and anti-aging composite foam box, in step S1, the light stabilizer is selected from one or more of Tinuvin 770, Tinuvin 328, and Chimassorb 944.

[0021] As a further optimization scheme for the method for manufacturing the pressure-resistant and anti-aging composite foam box, in step S1, the antioxidant is selected from one or more of Irganox 1010, Irganox 1076, and Irgafos 168.

[0022] As a further optimization scheme for the method for manufacturing the pressure-resistant and anti-aging composite foam box, in step S1, the nucleating agent is selected from one or more of talc and calcium carbonate.

[0023] As a further optimization scheme for the manufacturing method of the pressure-resistant and anti-aging composite foam box, in step S2, polypropylene, modified polypropylene, mica powder, ethylene-octene copolymer, light stabilizer, antioxidant, nucleating agent, polylactic acid and thermoplastic polyurethane are uniformly mixed in proportion; a twin-screw extruder is used for melt blending, the screw temperature is 190-230°C, the screw speed is 50-150rpm, and extrusion granulation is performed to obtain a modified polypropylene composite material.

[0024] As a further optimization scheme for the manufacturing method of the pressure-resistant and anti-aging composite foam box, in step S3, the modified polypropylene composite material particles are fed into the hopper of the microcellular foaming injection molding machine to be gradually plasticized and melted, and the screw temperature is 190-230°C; supercritical carbon dioxide (SC-CO 2 ) is used as a foaming agent, the pressure is 18-25MPa, and the mass fraction of the foaming agent in the composite material is 2-6%.

[0025] As a further optimization scheme for the manufacturing method of the pressure-resistant and anti-aging composite foam box, in step S4, a high-pressure full injection method is adopted to inject the polymer melt into the box molding mold cavity, the injection speed is 250-350 mm / s, the injection pressure is 150-180 MPa, the mold temperature is 45-55°C, the holding pressure is 65-80 MPa, and the holding time is 3-8s; then the mold core on one side of the movable mold retreats to increase the mold cavity volume, the movable mold moves at a speed of 8-15 mm / s, and the moving distance is 3-8 mm; the polymer melt pressure is reduced to form a foamed body, and the polypropylene composite foam box is obtained after the foamed melt is cooled.

[0026] As a further optimization scheme for the manufacturing method of the pressure-resistant and anti-aging composite foam box, the modified polypropylene is prepared by the following steps:

[0027] Polypropylene, 2-hydroxypropyl methacrylate and diisopropyl peroxide were mixed uniformly in a mass ratio of 100:1.2:0.7; under nitrogen protection, the mixture was added to a reactor filled with xylene, heated to 135°C, and reacted for 2.5 hours; after the reaction was completed, the reaction mixture was added to ethyl acetate, the mass of ethyl acetate was 5 times the mass of xylene, and the mixture was allowed to stand for 2 hours, filtered, and the filter cake was dried at 85°C for 12 hours to obtain hydroxy-modified polypropylene; the hydroxy-modified polypropylene was added to toluene, heated to 100°C, and stirred under reflux for 2 hours under nitrogen protection; 3-(methacryloyloxy)propyltrimethoxysilane (KH-570) was added dropwise, and the hydroxy-modified polypropylene, toluene, KH-57 0 is 15:100:1.2, and stirring and refluxing are continued for 3 hours; after the reaction is completed, centrifugation is performed at 1200r / min, and the centrifugal precipitate is washed 3 times with anhydrous ethanol at room temperature to obtain the washed centrifugal precipitate; the washed centrifugal precipitate is added to 98.5% ethanol by mass percentage, heated at 65°C for reaction for 3 hours, filtered after the reaction, and the filter cake is dried at 85°C for 12 hours to obtain silane-modified polypropylene; silane-modified polypropylene and maleic anhydride grafted polyethylene are uniformly mixed at a mass ratio of 100:22.5; a twin-screw extruder is used for melt blending, the screw temperature is 190-230°C, the screw speed is 150rpm, and extrusion granulation is performed to obtain the modified polypropylene.

[0028] On the basis of the above method, the present invention also provides a pressure-resistant and anti-aging composite foam box made by the above method.

[0029] Beneficial Effects

[0030] The present invention provides a method for manufacturing a pressure-resistant and anti-aging composite foam box, which significantly improves the physical and mechanical properties of the foam box. By combining materials such as polypropylene, modified polypropylene, mica powder, ethylene-octene copolymer, light stabilizer, antioxidant, nucleating agent, polylactic acid and thermoplastic polyurethane, the foam box has high tensile strength and compression strength while having low density, thereby ensuring its structural stability and impact resistance when subjected to external pressure. These characteristics not only enable the box to effectively protect the internal items and reduce the risk of damage during transportation, but also reduce logistics costs due to the lightweight of the materials.

[0031] The invention greatly improves the anti-aging performance of the foam box by adding light stabilizers and antioxidants, prolongs the service life of the product, and meets the needs of long-term storage and outdoor use. The use of supercritical carbon dioxide as a foaming agent not only ensures the efficiency and controllability of the foaming process, but also avoids the environmental pollution problems that may be caused by traditional chemical foaming agents. DETAILED DESCRIPTION

[0032] The present invention is further illustrated by specific examples below. These examples are exemplary and are intended to illustrate the problem and explain the present invention, but are not intended to be limiting.

[0033] The invention discloses a method for manufacturing a pressure-resistant and anti-aging composite foam box, aiming at improving the pressure-resistant performance, anti-aging performance and environmental protection of the foam box.

[0034] 1. Raw material preparation

[0035] Polypropylene (PP): 1000 parts by mass;

[0036] Modified polypropylene: 30-50 parts by mass;

[0037] Mica powder: 30-50 parts by mass;

[0038] Ethylene-octene copolymer (EOC): 15-35 parts by mass;

[0039] Light stabilizer: 5-10 parts by mass;

[0040] Antioxidant: 5-8 parts by weight;

[0041] Nucleating agent: 10-20 parts by mass;

[0042] Polylactic acid (PLA): 70-90 parts by mass;

[0043] Thermoplastic polyurethane (TPU): 20-40 parts by mass.

[0044] Among them, polypropylene (PP) is selected as the basic material, which has good heat resistance, mechanical properties and environmental protection performance. Modified polypropylene is introduced as a reinforcing material to enhance the melt strength and mechanical properties of PP. Light stabilizers and antioxidants are added, selected from hindered amine light stabilizers and phenolic antioxidants to improve the anti-aging properties of the material. Among them, the light stabilizer is selected from Tinuvin 770, Tinuvin 328, Chimassorb 944; the antioxidant is selected from Irganox1010, Irganox1076, Irgafos 168. The added nucleating agent is selected from talc and calcium carbonate to improve the uniformity and density of the foam. Polylactic acid (PLA) and thermoplastic polyurethane (TPU) are introduced as toughening agents to improve the elasticity and toughness of the material.

[0045] During the bubble process, supercritical carbon dioxide (SC-CO 2 ) as a foaming agent to ensure the environmental protection and high efficiency of the foaming process.

[0046] In each embodiment, the manufacturing process of modified polypropylene is as follows:

[0047] Polypropylene, 2-hydroxypropyl methacrylate (HEMA), and diisopropyl peroxide (DCP) were mixed uniformly in a mass ratio of 100:1.2:0.7. Under nitrogen protection, the mixture was added to a reactor containing xylene, heated to 135°C, and reacted for 2.5 hours. After the reaction was completed, the reaction mixture was added to ethyl acetate, the mass of ethyl acetate was 5 times the mass of xylene, and the mixture was allowed to stand for 2 hours, filtered, and the filter cake was dried at 85°C for 12 hours to obtain hydroxy-modified polypropylene (Hydroxy-PP). Hydroxy-modified polypropylene was added to toluene, heated to 100°C, and stirred and refluxed for 2 hours under nitrogen protection. 3-(Methacryloyloxy)propyltrimethoxysilane (KH-570) was added dropwise, and the mass ratio of hydroxy-modified polypropylene, toluene, and KH-570 was 15:100:1.2, and stirring and refluxing were continued for 3 hours. After the reaction is completed, centrifuge at 1200r / min, wash the centrifugal precipitate with anhydrous ethanol at room temperature for 3 times to obtain the washed centrifugal precipitate. Add the washed centrifugal precipitate to ethanol (98.5% by mass), heat at 65°C for 3 hours, filter after the reaction, and dry the filter cake at 85°C for 12 hours to obtain silane-modified polypropylene (Silane-PP). Silane-modified polypropylene and maleic anhydride grafted polyethylene (MAPE) are mixed uniformly at a mass ratio of 100:22.5. Use a twin-screw extruder for melt blending, the screw temperature is 190-230°C, the screw speed is 150rpm, and extrusion granulation is performed to obtain the final modified polypropylene.

[0048] 2. Raw material mixing

[0049] Polypropylene, modified polypropylene, mica powder, ethylene-octene copolymer, light stabilizer, antioxidant, nucleating agent, polylactic acid and thermoplastic polyurethane are uniformly mixed in proportion, melt blended by a twin-screw extruder, with a screw temperature of 190-230° C. and a screw speed of 50-150 rpm, and extruded into granules to obtain a modified polypropylene composite material.

[0050] 3. Pre-foaming treatment

[0051] The modified polypropylene composite material particles are fed into the hopper of the microcellular foam injection molding machine to be gradually plasticized and melted, and the screw temperature is 190-230°C. Supercritical carbon dioxide (SC-CO 2 ) is used as a foaming agent, the pressure is 18-25MPa, and the mass fraction of the foaming agent in the composite material is 2-6%.

[0052] 4. Injection molding

[0053] The polymer melt is injected into the cavity of the box molding mold by high-pressure full injection. The injection speed is 250-350mm / s, the injection pressure is 150-180MPa, the mold temperature is 45-55℃, the holding pressure is 65-80MPa, and the holding time is 3-8s. Then the metal mold core on one side of the movable mold retreats to increase the volume of the mold cavity. The movable mold moves at a speed of 8-15mm / s and a moving distance of 3-8mm. In this process, the pressure of the polymer melt decreases to form foaming. After the foaming melt is cooled, the polypropylene composite foam box is obtained.

[0054] Example 1

[0055] 1. Raw material preparation

[0056] Polypropylene (PP): 1000 parts by mass;

[0057] Modified polypropylene: 30 parts by mass;

[0058] Mica powder: 30 parts by mass;

[0059] Ethylene-octene copolymer (EOC): 15 parts by mass;

[0060] Light stabilizer Tinuvin 770: 5 parts by mass;

[0061] Antioxidant Irganox 1010: 5 parts by mass;

[0062] Nucleating agent talc: 10 parts by mass;

[0063] Polylactic acid (PLA): 70 parts by mass;

[0064] Thermoplastic polyurethane (TPU): 20 parts by mass.

[0065] 2. Raw material mixing

[0066] Polypropylene, modified polypropylene, mica powder, ethylene-octene copolymer, light stabilizer, antioxidant, nucleating agent, polylactic acid and thermoplastic polyurethane are mixed uniformly according to proportion, melt blended by a twin-screw extruder, with a screw temperature of 200° C. and a screw speed of 100 rpm, and extruded into granules to obtain a modified polypropylene composite material.

[0067] 3. Pre-foaming treatment

[0068] The modified polypropylene composite material particles were fed into the hopper of the microcellular foam injection molding machine to be gradually plasticized and melted. The screw temperature was 200°C. Supercritical carbon dioxide (SC-CO 2 ) is used as a foaming agent, the pressure is 22MPa, and the mass fraction of the foaming agent in the composite material is 4%.

[0069] 4. Injection molding

[0070] The polymer melt is injected into the cavity of the box molding mold by high-pressure full injection. The injection speed is 320 mm / s, the injection pressure is 165 MPa, the mold temperature is 52°C, the holding pressure is 75 MPa, and the holding time is 5 seconds. Then the metal mold core on one side of the movable mold retreats to increase the volume of the mold cavity. The movable mold moves at a speed of 12 mm / s and a moving distance of 6 mm. In this process, the polymer melt pressure decreases to form a foam body. After the foam body is cooled, a polypropylene composite foam box is obtained.

[0071] Example 2

[0072] 1. Raw material preparation

[0073] Polypropylene (PP): 1000 parts by mass;

[0074] Modified polypropylene: 50 parts by mass;

[0075] Mica powder: 50 parts by mass;

[0076] Ethylene-octene copolymer (EOC): 35 parts by mass;

[0077] Light stabilizer Tinuvin 770: 10 parts by mass;

[0078] Antioxidant Irganox 1010: 8 parts by mass;

[0079] Nucleating agent talc: 20 parts by mass;

[0080] Polylactic acid (PLA): 90 parts by mass;

[0081] Thermoplastic polyurethane (TPU): 40 parts by mass.

[0082] 2. Raw material mixing

[0083] Polypropylene, modified polypropylene, mica powder, ethylene-octene copolymer, light stabilizer, antioxidant, nucleating agent, polylactic acid and thermoplastic polyurethane are mixed uniformly according to proportion, melt blended by a twin-screw extruder, with a screw temperature of 200° C. and a screw speed of 100 rpm, and extruded into granules to obtain a modified polypropylene composite material.

[0084] 3. Pre-foaming treatment

[0085] The modified polypropylene composite material particles were fed into the hopper of the microcellular foam injection molding machine to be gradually plasticized and melted. The screw temperature was 200°C. Supercritical carbon dioxide (SC-CO 2 ) is used as a foaming agent, the pressure is 22MPa, and the mass fraction of the foaming agent in the composite material is 4%.

[0086] 4. Injection molding

[0087] The polymer melt is injected into the cavity of the box molding mold by high-pressure full injection. The injection speed is 320 mm / s, the injection pressure is 165 MPa, the mold temperature is 52°C, the holding pressure is 75 MPa, and the holding time is 5 seconds. Then the metal mold core on one side of the movable mold retreats to increase the volume of the mold cavity. The movable mold moves at a speed of 12 mm / s and a moving distance of 6 mm. In this process, the polymer melt pressure decreases to form a foam body. After the foam body is cooled, a polypropylene composite foam box is obtained.

[0088] Example 3

[0089] 1. Raw material preparation

[0090] Polypropylene (PP): 1000 parts by mass;

[0091] Modified polypropylene: 40 parts by mass;

[0092] Mica powder: 42 parts by mass;

[0093] Ethylene-octene copolymer (EOC): 18 parts by mass;

[0094] Light stabilizer Tinuvin 770: 7 parts by mass;

[0095] Antioxidant Irganox 1010: 7 parts by mass;

[0096] Nucleating agent talc: 15 parts by mass;

[0097] Polylactic acid (PLA): 80 parts by mass;

[0098] Thermoplastic polyurethane (TPU): 30 parts by mass.

[0099] 2. Raw material mixing

[0100] Polypropylene, modified polypropylene, mica powder, ethylene-octene copolymer, light stabilizer, antioxidant, nucleating agent, polylactic acid and thermoplastic polyurethane are mixed uniformly according to proportion, melt blended by a twin-screw extruder, with a screw temperature of 200° C. and a screw speed of 100 rpm, and extruded into granules to obtain a modified polypropylene composite material.

[0101] 3. Pre-foaming treatment

[0102] The modified polypropylene composite material particles were fed into the hopper of the microcellular foam injection molding machine to be gradually plasticized and melted. The screw temperature was 200°C. Supercritical carbon dioxide (SC-CO 2 ) is used as a foaming agent, the pressure is 22MPa, and the mass fraction of the foaming agent in the composite material is 4%.

[0103] 4. Injection molding

[0104] The polymer melt is injected into the cavity of the box molding mold by high-pressure full injection. The injection speed is 320 mm / s, the injection pressure is 165 MPa, the mold temperature is 52°C, the holding pressure is 75 MPa, and the holding time is 5 seconds. Then the metal mold core on one side of the movable mold retreats to increase the volume of the mold cavity. The movable mold moves at a speed of 12 mm / s and a moving distance of 6 mm. In this process, the polymer melt pressure decreases to form a foam body. After the foam body is cooled, a polypropylene composite foam box is obtained.

[0105] Example 4

[0106] 1. Raw material preparation

[0107] Polypropylene (PP): 1000 parts by mass;

[0108] Modified polypropylene: 40 parts by mass;

[0109] Mica powder: 42 parts by mass;

[0110] Ethylene-octene copolymer (EOC): 18 parts by mass;

[0111] Light stabilizer Tinuvin 328: 7 parts by mass;

[0112] Antioxidant Irganox 1076: 7 parts by mass;

[0113] Nucleating agent calcium carbonate: 15 parts by mass;

[0114] Polylactic acid (PLA): 80 parts by mass;

[0115] Thermoplastic polyurethane (TPU): 30 parts by mass.

[0116] 2. Raw material mixing

[0117] Polypropylene, modified polypropylene, mica powder, ethylene-octene copolymer, light stabilizer, antioxidant, nucleating agent, polylactic acid and thermoplastic polyurethane are mixed uniformly according to proportion, melt blended by a twin-screw extruder, with a screw temperature of 200° C. and a screw speed of 100 rpm, and extruded into granules to obtain a modified polypropylene composite material.

[0118] 3. Pre-foaming treatment

[0119] The modified polypropylene composite material particles were fed into the hopper of the microcellular foam injection molding machine to be gradually plasticized and melted. The screw temperature was 200°C. Supercritical carbon dioxide (SC-CO 2 ) is used as a foaming agent, the pressure is 18 MPa, and the mass fraction of the foaming agent in the composite material is 2%.

[0120] 4. Injection molding

[0121] The polymer melt is injected into the cavity of the box molding mold by high-pressure full injection. The injection speed is 320 mm / s, the injection pressure is 165 MPa, the mold temperature is 52°C, the holding pressure is 75 MPa, and the holding time is 5 seconds. Then the metal mold core on one side of the movable mold retreats to increase the volume of the mold cavity. The movable mold moves at a speed of 12 mm / s and a moving distance of 6 mm. In this process, the polymer melt pressure decreases to form a foam body. After the foam body is cooled, a polypropylene composite foam box is obtained.

[0122] Example 5

[0123] 1. Raw material preparation

[0124] Polypropylene (PP): 1000 parts by mass;

[0125] Modified polypropylene: 40 parts by mass;

[0126] Mica powder: 42 parts by mass;

[0127] Ethylene-octene copolymer (EOC): 18 parts by mass;

[0128] Light stabilizer Chimassorb 944: 7 parts by mass;

[0129] Antioxidant Irgafos 168: 7 parts by weight;

[0130] Nucleating agent calcium carbonate: 15 parts by mass;

[0131] Polylactic acid (PLA): 80 parts by mass;

[0132] Thermoplastic polyurethane (TPU): 30 parts by mass.

[0133] 2. Raw material mixing

[0134] Polypropylene, modified polypropylene, mica powder, ethylene-octene copolymer, light stabilizer, antioxidant, nucleating agent, polylactic acid and thermoplastic polyurethane are mixed uniformly according to proportion, melt blended by a twin-screw extruder, with a screw temperature of 200° C. and a screw speed of 100 rpm, and extruded into granules to obtain a modified polypropylene composite material.

[0135] 3. Pre-foaming treatment

[0136] The modified polypropylene composite material particles were fed into the hopper of the microcellular foam injection molding machine to be gradually plasticized and melted. The screw temperature was 200°C. Supercritical carbon dioxide (SC-CO 2 ) is used as a foaming agent, the pressure is 25MPa, and the mass fraction of the foaming agent in the composite material is 6%.

[0137] 4. Injection molding

[0138] The polymer melt is injected into the cavity of the box molding mold by high-pressure full injection. The injection speed is 320 mm / s, the injection pressure is 165 MPa, the mold temperature is 52°C, the holding pressure is 75 MPa, and the holding time is 5 seconds. Then the metal mold core on one side of the movable mold retreats to increase the volume of the mold cavity. The movable mold moves at a speed of 12 mm / s and a moving distance of 6 mm. In this process, the polymer melt pressure decreases to form a foam body. After the foam body is cooled, a polypropylene composite foam box is obtained.

[0139] Example 6

[0140] 1. Raw material preparation

[0141] Polypropylene (PP): 1000 parts by mass;

[0142] Modified polypropylene: 40 parts by mass;

[0143] Mica powder: 42 parts by mass;

[0144] Ethylene-octene copolymer (EOC): 18 parts by mass;

[0145] Light stabilizer Chimassorb 944: 6 parts by mass;

[0146] Antioxidant Irgafos 168: 8 parts by mass;

[0147] Nucleating agent calcium carbonate: 15 parts by mass;

[0148] Polylactic acid (PLA): 80 parts by mass;

[0149] Thermoplastic polyurethane (TPU): 30 parts by mass.

[0150] 2. Raw material mixing

[0151] Polypropylene, modified polypropylene, mica powder, ethylene-octene copolymer, light stabilizer, antioxidant, nucleating agent, polylactic acid and thermoplastic polyurethane are mixed uniformly according to proportion, melt blended by a twin-screw extruder, with a screw temperature of 200° C. and a screw speed of 100 rpm, and extruded into granules to obtain a modified polypropylene composite material.

[0152] 3. Pre-foaming treatment

[0153] The modified polypropylene composite material particles were fed into the hopper of the microcellular foam injection molding machine to be gradually plasticized and melted. The screw temperature was 200°C. Supercritical carbon dioxide (SC-CO 2 ) is used as a foaming agent, the pressure is 25MPa, and the mass fraction of the foaming agent in the composite material is 4%.

[0154] 4. Injection molding

[0155] The polymer melt is injected into the cavity of the box molding mold by high-pressure full injection. The injection speed is 320 mm / s, the injection pressure is 165 MPa, the mold temperature is 52°C, the holding pressure is 75 MPa, and the holding time is 5 seconds. Then the metal mold core on one side of the movable mold retreats to increase the volume of the mold cavity. The movable mold moves at a speed of 12 mm / s and a moving distance of 6 mm. In this process, the polymer melt pressure decreases to form a foam body. After the foam body is cooled, a polypropylene composite foam box is obtained.

[0156] Performance Testing

[0157] Test pieces were cut from the foam boxes prepared in various embodiments and subjected to density measurement and mechanical property testing.

[0158] Density measurement:

[0159] First, use an electronic balance to accurately measure the mass of the test block. Then, use a vernier caliper to measure the length L, width W and height H of the test block with an accuracy of 0.01mm. Based on the measurement results, calculate the volume V = L × W × H of the test block. Calculate the apparent density of the test block.

[0160] Tensile strength test:

[0161] Refer to the national standard GB / T6344-2008 "Determination of tensile strength and elongation at break of flexible foam polymer materials". Prepare standard rectangular cross-section specimens from the test blocks to ensure that the specimens have no obvious defects and a thickness of 10mm to 15mm. Before the test, measure the thickness of the specimen to ensure that the thickness difference does not exceed ±2%. Draw two parallel markings on the specimen as the gauge length, and the gauge length measurement accuracy is ±1%. Clamp the specimen to the fixture of the tensile testing machine, adjust the specimen so that the tensile force is evenly distributed on the cross section of the specimen, and apply a prestress of 0.1kPa or a pre-elongation of 0.5%. Start the tensile testing machine, set the tensile speed to 500mm / min, and record the maximum load during the stretching process and the distance between the two markings at the moment of specimen rupture, accurate to ±1% and ±1.25mm. Repeat each test condition 5 times to obtain a reliable average value.

[0162] Refer to the national standard GB / T8813-2008 "Determination of compression properties of rigid foam plastics". The sample is conditioned under standard environmental conditions, that is, the temperature is (23±2)°C, the relative humidity is (50±5)%, and the conditioning time is not less than 24 hours. Measure the initial dimensions of the sample, including length, width, and height, and record them. Place the sample in the center of the compression fixture to ensure that the upper and lower end surfaces of the sample are parallel and evenly in contact with the contact surface of the fixture. Set the loading speed of the testing machine to 5mm / min. Start the testing machine and compress the sample at the set loading speed until the sample is obviously damaged or deformed to the specified degree (the compression deformation reaches 50% of the initial thickness of the sample). Record the maximum load value displayed on the testing machine, as well as the deformation of the sample when the maximum load is reached. Repeat the test 5 times for each embodiment.

[0163] The test results are shown in Table 1.

[0164] Table 1 Performance test results

[0165]

[0166] The results of the above performance tests show that the pressure-resistant and anti-aging composite foam box of the present invention has excellent physical and mechanical properties. In terms of apparent density, the composite foam boxes of all embodiments show a relatively low density, ranging from 0.047 g / cm 3 Up to 0.056g / cm 3 The low density not only helps to reduce the weight of the finished product and reduce transportation costs, but also effectively reduces material consumption for packaging applications, meeting the requirements of green production and sustainable development.

[0167] Secondly, the data of tensile strength and compressive strength reflect the pressure resistance and impact resistance of the composite foam box in practical applications. The tensile strength of all embodiments is higher than 25MPa, with the highest reaching 27.6MPa (Example 3), while the compressive strength is generally maintained between 45.7MPa and 46.3MPa. This shows that even when subjected to a large external force, the composite foam box can maintain structural integrity, is not prone to permanent deformation or rupture, and can effectively protect the internal items from damage. Among them, Example 3 has the best comprehensive performance by optimizing the raw material composition and ratio.

[0168] In addition, by adding light stabilizers and antioxidants, the anti-aging performance of the foam box is effectively improved and the service life is extended. Using supercritical carbon dioxide as a foaming agent, the entire foaming process is environmentally friendly and pollution-free.

[0169] In summary, the pressure-resistant and anti-aging composite foam box provided by the present invention not only meets the requirements of light weight and high strength, but also has good anti-aging and environmental protection performance, and is an ideal packaging material container.

[0170] The above embodiments are exemplary, and their purpose is to illustrate the technical concept and features of the present invention so that people familiar with the technology in this field can understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for manufacturing a pressure-resistant and anti-aging composite foam box, characterized in that: The following steps are involved: Step S1: preparing raw materials including polypropylene and modified polypropylene; Step S2: mixing the raw materials, and granulating them by melt blending to obtain a modified polypropylene composite material; Step S3: feeding the modified polypropylene composite material into a hopper of a microcellular foaming injection molding machine and preheating it to a plasticized state, and then injecting supercritical carbon dioxide as a foaming agent; Step S4: injecting a polymer melt containing supercritical carbon dioxide into a cavity of a box-forming mold at a preset temperature and maintaining the pressure; by controlling the core on one side of the movable mold to retreat, the volume of the mold cavity is increased, resulting in a decrease in the pressure in the polymer melt and the formation of a foamed body, and after cooling and solidification, the target polypropylene composite foam box is obtained.

2. The method for manufacturing the pressure-resistant and anti-aging composite foam box according to claim 1, characterized in that: In step S1, the raw materials include: Polypropylene (PP): 1000 parts by mass; Modified polypropylene: 30-50 parts by mass; Mica powder: 30-50 parts by mass; Ethylene-octene copolymer: 15-35 parts by mass; Light stabilizer: 5-10 parts by mass; Antioxidant: 5-8 parts by weight; Nucleating agent: 10-20 parts by mass; Polylactic acid: 70-90 parts by mass; Thermoplastic polyurethane: 20-40 parts by mass.

3. The method for manufacturing the pressure-resistant and anti-aging composite foam box according to claim 2, characterized in that: In step S1, the light stabilizer is selected from one or more of Tinuvin 770, Tinuvin 328, and Chimassorb 944.

4. The method for manufacturing the pressure-resistant and anti-aging composite foam box according to claim 2, characterized in that: In step S1, the antioxidant is selected from one or more of Irganox 1010, Irganox 1076, and Irgafos 168.

5. The method for manufacturing the pressure-resistant and anti-aging composite foam box according to claim 2, characterized in that: In step S1, the nucleating agent is selected from one or more of talc and calcium carbonate.

6. The method for manufacturing the pressure-resistant and anti-aging composite foam box according to claim 2, characterized in that: In step S2, polypropylene, modified polypropylene, mica powder, ethylene-octene copolymer, light stabilizer, antioxidant, nucleating agent, polylactic acid and thermoplastic polyurethane are uniformly mixed in proportion; a twin-screw extruder is used for melt blending, the screw temperature is 190-230° C., the screw speed is 50-150 rpm, and extrusion granulation is performed to obtain a modified polypropylene composite material.

7. The method for manufacturing the pressure-resistant and anti-aging composite foam box according to claim 2, characterized in that: In step S3, the modified polypropylene composite material particles are fed into the hopper of a microcellular foaming injection molding machine to be gradually plasticized and melted, and the screw temperature is 190-230°C; supercritical carbon dioxide (SC-CO2) is injected as a foaming agent at a pressure of 18-25MPa, and the mass fraction of the foaming agent in the composite material is 2-6%.

8. The method for manufacturing the pressure-resistant and anti-aging composite foam box according to claim 2, characterized in that: In step S4, a high-pressure full injection method is used to inject the polymer melt into the box molding mold cavity, the injection speed is 250-350 mm / s, the injection pressure is 150-180 MPa, the mold temperature is 45-55°C, the holding pressure is 65-80 MPa, and the holding time is 3-8s; then the mold core on one side of the movable mold retreats to increase the mold cavity volume, the movable mold moves at a speed of 8-15 mm / s, and the moving distance is 3-8 mm; the polymer melt pressure is reduced to form a foamed body, and the polypropylene composite foam box is obtained after the foamed melt is cooled.

9. The method for manufacturing a pressure-resistant and anti-aging composite foam box according to any one of claims 1 to 8, characterized in that: The modified polypropylene is prepared by the following steps: Polypropylene, 2-hydroxypropyl methacrylate and diisopropylbenzene peroxide were mixed uniformly in a mass ratio of 100:1.2:0.7; under nitrogen protection, the mixture was added to a reactor filled with xylene, heated to 135°C, and reacted for 2.5 hours; after the reaction was completed, the reaction mixture was added to ethyl acetate, the mass of ethyl acetate was 5 times the mass of xylene, and the mixture was allowed to stand for 2 hours, filtered, and the filter cake was dried at 85°C for 12 hours to obtain hydroxy-modified polypropylene; the hydroxy-modified polypropylene was added to toluene, heated to 100°C, and stirred and refluxed for 2 hours under nitrogen protection; 3-(methacryloyloxy)propyltrimethoxysilane (KH-570) was added dropwise, the mass ratio of hydroxy-modified polypropylene, toluene and KH-570 was 15:100:1.2, and stirring and refluxing was continued for 3 hours; After the reaction is completed, centrifugation is performed at 1200 r / min, and the centrifugal precipitate is washed three times with anhydrous ethanol at room temperature to obtain the washed centrifugal precipitate; the washed centrifugal precipitate is added to 98.5% ethanol by mass, heated at 65°C for reaction for 3 hours, filtered after the reaction, and the filter cake is dried at 85°C for 12 hours to obtain silane-modified polypropylene; silane-modified polypropylene and maleic anhydride grafted polyethylene are uniformly mixed at a mass ratio of 100:22.5; a twin-screw extruder is used for melt blending, the screw temperature is 190-230°C, the screw speed is 150 rpm, and extrusion granulation is performed to obtain the modified polypropylene.

10. A pressure-resistant and anti-aging composite foam box, characterized in that: The method according to any one of claims 1 to 9 is used to prepare the product.

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