A sandwich structure braided polyolefin foam material and its preparation method and application

Abstract

The application discloses a sandwich structure braided polyolefin foam material and a preparation method and application thereof. The sandwich structure braided polyolefin foam material comprises the following materials in parts by weight: 80-95 parts of polyolefin resin, 5-20 parts of fiber, 0.2-2 parts of heterogeneous nucleating agent and 0-5 parts of colorant. The sandwich structure braided polyolefin foam material has a sandwich structure of a cellular structure-solid structure-cellular structure in the inside. The sandwich structure braided polyolefin foam material has excellent mechanical properties, light weight, smooth surface, heat insulation performance and braiding characteristics. The preparation method has the advantages of low production cost, simple process, high efficiency and controllable structure, and the sandwich structure braided polyolefin foam material can be braided into different shapes after coloring according to requirements, and is applied to cushioning liners, cup sleeves, heat insulation pads and the like.

Description

Technical Field

[0001] The present application relates to a sandwich structure braided polyolefin foam material and its preparation method and application, belonging to the field of polymer foam material processing. Background Art

[0002] Foam materials are widely used in various fields of life due to their lightweight, weather-resistant, chemical-resistant, and high-temperature-resistant properties. They offer excellent thermal, sound-proofing, and moisture-proofing properties. However, they are often used in the form of foam boxes or blocks, which lack the flexibility to shape or color. If foam materials could be made multidimensionally weavable and possess excellent mechanical properties without sacrificing their inherent advantages, this would facilitate their widespread adoption and use in real life.

[0003] Furthermore, polyolefin foams are widely used in daily life due to their wide availability, stable performance, ease of processing, and recyclability, particularly in polymers such as polypropylene and polyethylene. Furthermore, plant fibers are produced from a large number of agricultural and industrial byproducts. Utilizing these can reduce the use of petroleum-based plastics, lower production costs, and increase the utilization of materials such as straw.

[0004] Composite foam materials with excellent mechanical properties and weavable characteristics can be produced on a large scale through a continuous production process, and can be used in the fields of cushioning liners, cup sleeves, placemats, etc. For example, Chinese patent CN 104513430 A discloses a rattan-like polypropylene foam material and its preparation method. The foam material is prepared by extrusion foaming using a supercritical fluid as a foaming agent, and polyethylene is added to the polypropylene matrix to regulate the mechanical properties of the foam material. The surface quality of the foam material is improved by abrasives and matting agents. This method has the advantages of high production efficiency and low cost. However, the material is shaped by the shape of the extrusion die head, and it is difficult to regulate the macroscopic morphology of the material in the later stage. In addition, the density is relatively high, making it difficult to apply to more applications.

[0005] In addition, the comprehensive performance of foam materials can be improved by adding fibers. For example, Chinese patent CN 105623098A discloses a long-fiber-reinforced polypropylene microporous foam material. This material is prepared by a series extrusion foaming method. The modulus of the prepared foam material is significantly improved compared with the foam material without the addition of long fibers. At the same time, this method uses a supercritical fluid as a physical foaming agent and improves the interfacial compatibility between polypropylene and fibers through a compatibilizer, which has the benefits of being safe, non-toxic, and environmentally friendly.

[0006] The mechanical properties of polyolefin foam materials are influenced not only by their matrix components but also by their pore structure and expansion ratio. A high expansion ratio is beneficial for imparting thermal insulation, insulation, and heat-insulating properties to foam materials, and continuous extrusion foaming facilitates efficient production of foam materials. For example, Chinese patent CN 107972297A discloses a continuous preparation method for high-expansion polypropylene foam sheets. This application utilizes supercritical fluid extrusion foaming to produce foam sheets with expansion ratios ranging from 5 to 40 times. By controlling the screw speed and die pressure, the morphology and pore size of the foam sheets can be controlled. The method boasts a simple preparation process, high efficiency, and environmental safety.

[0007] In summary, the mechanical properties and foam ratio of foam materials can be improved by adjusting the composition of the polymer system and adding fillers such as fibers. However, there are few reports on technologies that can control the macromorphology, controllable adjust the pore structure, and improve the mechanical properties of the material after foaming, and then apply them to the preparation of foam braided materials. Summary of the Invention

[0008] This application provides a sandwich-structured braided polyolefin foam material, its preparation method, and its applications. This sandwich-structured braided polyolefin foam material exhibits excellent mechanical properties, is lightweight, has a smooth surface, offers thermal insulation, and is braidable. The preparation method offers advantages such as low production cost, simple process, high efficiency, and controllable structure. Furthermore, the material can be colored and braided into various shapes as needed, and is suitable for applications such as cushioning liners, cup sleeves, and thermal insulation pads.

[0009] A sandwich structure braided polyolefin foam material, the sandwich structure braided polyolefin foam material comprising the following materials in parts by weight:

[0010]

[0011] The sandwich structure may be a sandwich structure in which the interior of the woven polyolefin foam material is a cellular structure-solid structure-cellular structure.

[0012] Optionally, the cross-section of the sandwich structure woven polyolefin foam material is a rounded rectangle, and the whole structure is in the shape of a flat strip.

[0013] Optionally, the sandwich structure may be woven from polyolefin foam material having an apparent density of 0.02 to 0.50 g / cm 3 The average diameter of the bubbles is 30 to 400 μm.

[0014] Optionally, the sandwich structure may be woven from polyolefin foam material having an apparent density of 0.035 to 0.20 g / cm 3 .

[0015] Optionally, the sandwich structure may be woven from polyolefin foam material having an apparent density of 0.035 to 0.07 g / cm 3 The average diameter of the bubbles is 240-260 μm.

[0016] Optionally, the sandwich structure braided polyolefin foam material is composed of a cellular layer-solid layer-cellular layer, the solid layer has a thickness of 5 to 800 μm, and the cellular layers on both sides of the sandwich layer have a thickness of 500 to 3500 μm.

[0017] Optionally, the thickness of the solid layer is 40 to 100 μm, and the thickness of the cellular layers on both sides of the sandwich layer is 800 to 3100 μm.

[0018] Optionally, the sandwich structure can be made of a woven polyolefin foam material with an elongation at break of 10-300%, a modulus of 2.5-50 MPa, and a specific modulus of 50-600 MPa·cm 3 / g.

[0019] Optionally, the sandwich structure can be made of a braided polyolefin foam material having an elongation at break of 35-55%, a modulus of 4.5-30 MPa, and a specific modulus of 140-360 MPa·cm 3 / g.

[0020] Optionally, the sandwich structure may be woven from polyolefin foam material with a width of 5 to 50 mm and an overall thickness of 0.5 to 8 mm.

[0021] Optionally, the sandwich structure may be woven from polyolefin foam material with a width of 10 to 15 mm and an overall thickness of 1.5 to 6.5 mm.

[0022] Optionally, the polyolefin resin is selected from at least one of polypropylene, polyethylene, ethylene-propylene rubber, ethylene-vinyl acetate copolymer, and ethylene-octene copolymer.

[0023] Preferably, the polypropylene is high melt strength polypropylene; and the polyethylene is high melt strength polyethylene.

[0024] Optionally, the fibers are selected from micro-nano fibers;

[0025] Preferably, the micro-nano fibers are selected from at least one of bamboo fibers, flax fibers, and wheat straw fibers.

[0026] Optionally, the heterogeneous nucleating agent is selected from at least one of talc, palygorskite, montmorillonite, magnesium hydroxide, diatomaceous earth, kaolin, silicon dioxide, wollastonite powder, aluminum hydroxide, calcium carbonate, barium carbonate, barium sulfate, and clay. The heterogeneous nucleating agent primarily provides cell nucleation sites during the foaming process, thereby reducing the nucleation energy barrier.

[0027] Masterbatch can be selected in different colors according to actual needs, such as yellow, red, purple masterbatch and master powder.

[0028] According to a second aspect of the present application, a method for preparing the aforementioned sandwich-structured braided polyolefin foam material is provided. After extrusion foaming, a double-roll calender is used to calender and shape the cylindrical foam strips at a predetermined distance from the extruder die head, thereby changing the internal cell structure, eliminating the central cells and transforming them into a solid structure, thereby obtaining a sandwich-structured foam material composed of a cell structure-solid structure-cell structure. Due to the formation of the internal solid structure, the foam has improved modulus and elongation at break, while also having good thermal insulation and braidability. After calendering, the foam material is wound and collected by a winder.

[0029] The method for preparing the above-mentioned sandwich structure braided polyolefin foam material comprises the following steps:

[0030] S1. Evenly mix the polyolefin resin, fiber, heterogeneous nucleating agent, and colorant to obtain a premixed material;

[0031] S2, adding the premixed materials into a first-stage extruder for hot melting, and adding a supercritical fluid into the first-stage extruder to obtain a polymer / supercritical fluid homogeneous system;

[0032] S3, sending the polymer / supercritical fluid homogeneous system into a second-stage extruder for processing, and conveying it to the extruder die head for pressure relief and foaming;

[0033] S4, rolling and shaping the pressure-released foamed material through a calender at the rear end of the extruder, and collecting it through a winder to obtain the sandwich structure braided polyolefin foam material.

[0034] The usage ratio of the polyolefin resin, fiber, heterogeneous nucleating agent and colorant is the same as above. The polyolefin resin is dried before use.

[0035] Optionally, in step S2, the temperature of the first-stage extruder is 150-220°C, the pressure is 6.0-16.0 MPa, and the screw speed is 15-40 rpm.

[0036] Preferably, in step S2, the temperature of the first-stage extruder is 175-200°C, the pressure is 7.0-10.0 MPa, and the screw speed is 30-35 rpm.

[0037] Optionally, in step S2, the supercritical fluid is selected from supercritical carbon dioxide and / or supercritical nitrogen.

[0038] Optionally, the injection pressure of the supercritical fluid is 15 to 30 MPa, and the content of the supercritical fluid is 0.5 to 5 parts by weight.

[0039] Optionally, in step S3, the polymer / supercritical fluid homogeneous system is fed into a second-stage extruder via a gear pump;

[0040] The rotation speed of the gear pump is 5-20 rpm.

[0041] Preferably, the rotation speed of the gear pump is 8-15 rpm.

[0042] Optionally, in step S3, the temperature of the second-stage extruder is 115-180° C., the pressure is 2-15 MPa, and the screw speed is 2-20 rpm.

[0043] Preferably, in step S3, the temperature of the second-stage extruder is 140-165° C., the pressure is 5-8 MPa, and the screw speed is 4-6 rpm.

[0044] Optionally, in step S3, the extruder die head contains 1 to 5 die openings, and the die opening diameter is 0.3 to 3.0 mm.

[0045] Preferably, the extruder die head contains 1 to 3 die openings, and the die opening diameter is 0.5 to 1.5 mm.

[0046] Optionally, the temperature of the extruder die head is 180-130° C., and the pressure is 3.0-10.0 MPa.

[0047] Optionally, the temperature of the extruder die head is 165-140° C., and the pressure is 6.0-9.0 MPa.

[0048] Optionally, in step S4, the distance between the two rollers of the calender is 0.5 to 20 mm; and the rotation speed of the calender is 5 to 300 rpm.

[0049] Optionally, in step S4, the distance between the two rollers of the calender is 1 to 6 mm; and the rotation speed of the calender is 80 to 120 rpm.

[0050] The calender features adjustable roller gap and roller speed, with both upper and lower rollers rotating at the same speed throughout the entire calendering process. The width and thickness of the foam are controlled by the extrusion foaming speed, the gap between the calender rollers, and the calendering speed. The calender speed can be adjusted based on the extrusion foaming speed. Controlling the production conditions ensures a smooth foam surface and stable width and thickness. The post-calendering winder speed matches the calender speed to prevent breakage of the foam during collection.

[0051] Optionally, the first-stage extruder and the second-stage extruder are independently selected from a single-screw extrusion foaming machine or a twin-screw extrusion foaming machine.

[0052] In the present application, the sandwich structure can be woven polyolefin foam material prepared by using an extruder of a two-stage single-screw series extruder, but is not limited to such equipment, and any extrusion foaming equipment having a similar extrusion foaming function is included, such as a single-screw extrusion foaming machine, a double-screw extrusion foaming machine, an extrusion foaming machine with a first-stage double screw and a second-stage single screw, and various types of series machines.

[0053] Further, the sandwich structure can be woven polyolefin foam material prepared by using a series extrusion foaming equipment, which is composed of an extruder, a supercritical fluid injection metering pump, a gear pump, a static mixer, an extrusion die, and the like; the supercritical fluid injection metering pump is connected to the first-stage single-screw extruder through a pipeline, the first-stage extruder is connected to the gear pump, the gear pump is connected to the second-stage extruder, and the second-stage extruder, the static mixer, and the extrusion die are sequentially connected.

[0054] The high-pressure fluid injection pump used in cooperation with the above-mentioned extrusion foaming machine is used to stably inject the supercritical fluid into the base body.

[0055] As a specific embodiment, the preparation method of the sandwich structure polyolefin foaming foam material prepared by using the two-stage series extrusion foaming machine includes the following steps: (1) polyolefin, bamboo fiber, and nucleating agent are uniformly mixed in a certain proportion by using a mixer; (2) the pre-mixed material in (1) is added to the first-stage extruder through a hopper to be mixed with the supercritical fluid to obtain a polymer / supercritical fluid uniform system; (3) the polymer / supercritical fluid uniform system in (2) is sent to the second-stage extruder through the gear pump, and the melt temperature is controlled to the foaming temperature; the pressure is within the range set by the equipment; (4) the polymer melt is delivered to the extrusion die of the second-stage extruder to be depressurized and foamed; (5) the extrusion die is rolled and shaped by the calender machine at the rear end of the extruder, and the foam material with constant width and thickness is collected by the winding machine.

[0056] According to a third aspect of the present application, the application of the sandwich structure can be woven polyolefin foam material described above is provided.

[0057] The application of the sandwich structure can be woven polyolefin foam material described above, and the sandwich structure can be woven polyolefin foam material prepared by the preparation method described above in the cushioning liner, the cup sleeve, and the heat insulation pad.

[0058] The beneficial effects that can be produced by the present application include:

[0059] The sandwich structure provided in the present application can be woven into a polyolefin foam material with excellent mechanical properties, light weight, smooth surface, heat insulation performance and weavability, stable shape, no shrinkage, and can be stored for a long time; extrusion foaming is coordinated with the back-end calendering equipment, and the width, thickness and density of the foam material can be controlled by controlling the temperature and pressure of the extrusion foaming and the roller gap of the double-roll calender. The method is simple and easy to operate, low in cost and high in production efficiency. It can be dyed by masterbatch to obtain a foam material with good gloss and bright color; it can be applied to cushioning linings, cup sleeves, thermal insulation pads, etc., and has good industrial prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 3D schematic diagram of a two-stage series extrusion foaming unit and a rear-end calendering and collecting device in the embodiment;

[0061] Figure 2 Schematic diagram of the structure of the sandwich structure braided polyolefin foam material in Example 1;

[0062] Figure 3 The electron microscope images of the microstructure of the sandwich structure braided polyolefin foam material in Example 1 are shown. The scale bar in Figure a is 500 μm, and the scale bar in Figure b is 100 μm.

[0063] Figure 4 Schematic diagram of the columnar foam structure in Comparative Example 1;

[0064] Figure 5 The electron microscope images of the columnar foam microstructure in Comparative Example 1 are shown. The scale bar in Figure a is 500 μm, and the scale bar in Figure b is 100 μm. DETAILED DESCRIPTION

[0065] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0066] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0067] The high melt strength polypropylene was purchased from Sinopec Ningbo Zhenhai Refining and Chemical Co., Ltd.

[0068] Unless otherwise specified, conventional methods were used for testing, and instrument settings were those recommended by the manufacturer.

[0069] The analysis method in the examples of this application is as follows:

[0070] The morphological characteristics were tested and analyzed by scanning electron microscopy (SEM). The analysis instrument was a large-cavity scanning electron microscope (EVO18) with a test condition of 20 kV and different magnifications.

[0071] The apparent density was analyzed using a density balance (BT224S).

[0072] The average cell diameter was analyzed using image analysis software (Nano measurer).

[0073] The elongation at break, modulus and specific modulus were tested and analyzed using a universal mechanical testing machine (Instron 5567).

[0074] like Figure 1 As shown in the figure, it is a three-dimensional schematic diagram of the double-stage series extrusion foaming unit and the rear-end calendering and collection device in the embodiment: the foam preparation device is shown in the figure as a first-stage extruder and a second-stage extruder connected in series, and the foam preparation process is as follows:

[0075] (1) Polyolefin, bamboo fiber and nucleating agent are uniformly mixed in a certain proportion by a mixer; (2) The premixed material in (1) is added to a first-stage extruder through a hopper to be melted and mixed with a supercritical fluid to obtain a polymer / supercritical fluid homogeneous system; (3) The polymer / supercritical fluid homogeneous system described in (2) is sent to a second-stage extruder through a gear pump, and the melt temperature is controlled to the foaming temperature, and the foaming pressure is within the set range of the equipment; (4) The polymer melt is transported to the extruder die head through the second-stage extruder to release pressure and foam; (5) It is rolled and formed by a calender at the rear end of the extruder, and collected by a winder to obtain a foam material with constant width and thickness.

[0076] The foam prepared under the set extrusion foaming conditions is shaped by the calender at the rear end, while adjusting its internal structure and improving its mechanical properties, and is further wound and collected by a winder.

[0077] Example 1

[0078] 87 parts by weight (8700 g) of high melt strength polypropylene, 10 parts by weight (1000 g) of bamboo fiber, 3 parts by weight (300 g) of red masterbatch and 1.0 part by weight (100 g) of talc powder as a nucleating agent accounting for the total mass of the system are mixed uniformly according to the mass ratio;

[0079] Inject carbon dioxide into the 3 / 4 position of the first-stage extruder at a rate of 4 mL / min and an injection pressure of 18 MPa. The final amount is 2.5 parts by weight.

[0080] The temperature of the first-stage screw heating unit was set to 175°C, 190°C, 200°C, 200°C, 200°C, 200°C, 200°C, the speed was 35 rpm, and the pressure was 10 MPa;

[0081] The gear pump speed is 10 rpm;

[0082] The temperature of the second-stage screw heating unit was set to 158°C, 158°C, 158°C, 158°C, 160°C, the speed was 7 rpm, and the pressure was 7 MPa;

[0083] The outlet end of the extruder is provided with a circular extruder die head with a die opening of 1.5 mm in diameter. The temperature of the die head is 160° C., and the pressure relief foaming pressure is 7 MPa.

[0084] The gap between the two rollers of the calender was 1.2 mm, and the speed of the calender was 100 rpm;

[0085] Figure 2 The schematic diagram of the structure of the obtained sandwich-structured braided polyolefin foam material shows that the center of the foam is a narrow solid area, with pore structures oriented along the solid area on both sides; Figure 3 The microstructure electron microscope image of the obtained sandwich structure woven polyolefin foam material, the scale of Figure a is 500μm, and the scale of Figure b is 100μm. It can be seen that the inside of the foam is as follows Figure 2 The solid structure and the cellular structure areas distributed on both sides are shown.

[0086] The prepared foam material has a sandwich structure and a density of 0.07 g / cm 3 , thickness is 1.8mm, width is 14.5mm, average cell diameter is 260μm, solid layer thickness is 100μm, thickness of the cell layers on both sides is 850μm, elongation at break is 53%, modulus is 27.12MPa, specific modulus is 350.4MPa·cm 3 / g.

[0087] Example 2

[0088] 85 parts by weight (8500 g) of high melt strength polypropylene, 10 parts by weight (1000 g) of bamboo fiber, 5 parts by weight (500 g) of red masterbatch and 1.0 part by weight (100 g) of talc as a nucleating agent accounting for the total mass of the system were mixed uniformly according to the mass ratio; carbon dioxide was injected into the 3 / 4 position of the first-stage extruder at a speed of 4 mL / min and an injection pressure of 18 MPa. The final amount was 2.5 parts by weight;

[0089] The temperature of the first-stage screw heating unit was set to 175°C, 190°C, 200°C, 200°C, 200°C, 200°C, 200°C, the speed was 35 rpm, and the pressure was 10 MPa;

[0090] The gear pump speed is 10 rpm;

[0091] The temperature of the second-stage screw heating unit was set to 158°C, 158°C, 158°C, 158°C, 160°C, the speed was 7 rpm, and the pressure was 7 MPa;

[0092] The outlet end of the extruder is provided with a circular extruder die head with a die opening of 1.5 mm in diameter. The temperature of the die head is 160° C., and the pressure relief foaming pressure is 7 MPa.

[0093] The gap between the two rollers of the calender was 3.0 mm, and the speed of the calender was 100 rpm;

[0094] The prepared foam material has a sandwich structure and a density of 0.05 g / cm 3 , thickness is 4.0mm, width is 12.3mm, average cell diameter is 240μm, solid layer thickness is 70μm, thickness of the cell layers on both sides is 1965μm, elongation at break is 46.5%, modulus is 7.6MPa, specific modulus is 146.5MPa·cm 3 / g.

[0095] Example 3

[0096] 85 parts by weight (8500g) of high melt strength polypropylene, 10 parts by weight (1000g) of bamboo fiber, 5 parts by weight (500g) of red masterbatch and 1.0 parts by weight (100g) of talc pink masterbatch as a nucleating agent accounting for the total mass of the system were mixed uniformly according to the mass ratio; carbon dioxide was injected into the 3 / 4 position of the first-stage extruder at a speed of 4mL / min and an injection pressure of 18MPa, and the final amount was 2.5 parts by weight;

[0097] The temperature of the first-stage screw heating unit was set to 175°C, 190°C, 200°C, 200°C, 200°C, 200°C, 200°C, the speed was 35 rpm, and the pressure was 10 MPa;

[0098] The gear pump speed is 10 rpm;

[0099] The temperature of the second-stage screw heating unit was set to 158°C, 158°C, 158°C, 158°C, 160°C, the speed was 7 rpm, and the pressure was 7 MPa;

[0100] The outlet end of the extruder is provided with a circular extruder die head with a die opening of 1.5 mm in diameter. The temperature of the die head is 160° C., and the pressure relief foaming pressure is 7 MPa.

[0101] The gap between the two rollers of the calender was 5.2 mm, and the speed of the calender was 100 rpm;

[0102] The prepared foam material has a sandwich structure and a density of 0.035 g / cm 3, thickness is 6.2mm, width is 11.5mm, average cell diameter is 260μm, solid layer thickness is 40μm, thickness of the cell layers on both sides is 3080μm, elongation at break is 39.9%, modulus is 4.6MPa, specific modulus is 150.0MPa·cm 3 / g.

[0103] Comparative Example 1

[0104] 87 parts by weight (8700 g) of high melt strength polypropylene, 10 parts by weight (1000 g) of bamboo fiber, 3 parts by weight (300 g) of red masterbatch and 1.0 part by weight (100 g) of talc powder as a nucleating agent accounting for the total mass of the system are mixed uniformly according to the mass ratio;

[0105] Inject carbon dioxide into the 3 / 4 position of the first-stage extruder at a rate of 4 mL / min and an injection pressure of 18 MPa. The final amount is 2.5 parts by weight.

[0106] The temperature of the first-stage screw heating unit was set to 175°C, 190°C, 200°C, 200°C, 200°C, 200°C, 200°C, the speed was 35 rpm, and the pressure was 10 MPa;

[0107] The gear pump speed is 10 rpm;

[0108] The temperature of the second-stage screw heating unit was set to 158°C, 158°C, 158°C, 158°C, 160°C, the speed was 7 rpm, and the pressure was 7 MPa;

[0109] The outlet end of the extruder is provided with a circular extruder die head with a die opening of 1.5 mm in diameter. The temperature of the die head is 160° C., and the pressure relief foaming pressure is 7 MPa.

[0110] The gap between the two rollers of the calender is such that the two rollers do not contact the foam, that is, no calendering effect is produced on the foam.

[0111] Figure 4 Figure 1 is a schematic diagram of the obtained columnar foam structure. It can be seen that the foam cross-section is circular, the interior is a typical irregular cell shape, and there is no solid area in the center except the cell wall; Figure 5 The electron microscope images of the obtained columnar foam microstructure, the scale of Figure a is 500μm, and that of Figure b is 100μm. It can be seen that the foam without back-end calendering presents a cylindrical macroscopic morphology, and the internal pore structure is a typical polyhedron structure. There is no solid structure in the center of the foam except the bubble wall, which is in sharp contrast to the strip structure of the foam after calendering and the solid structure inside it.

[0112] The prepared columnar foam material does not have a sandwich structure and has a density of 0.036 g / cm 3, the foam diameter is 8.2mm, the elongation at break is 14.5%, the modulus is 4.2MPa, and the specific modulus is 66.5MPa·cm 3 / g.

[0113] The above descriptions are merely a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application discloses the preferred embodiments as above, they are not intended to limit the present application. Any technical personnel familiar with the present profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A sandwich structure braided polyolefin foam material, characterized in that: The sandwich structure braided polyolefin foam material includes the following materials in parts by weight: 80-95 parts of polyolefin resin; Fiber 5-20 parts; 0.2-2 parts of heterogeneous nucleating agent; Colorant 0-5 parts; The sandwich structure can be a sandwich structure in which the interior of the woven polyolefin foam material is a cellular structure-solid structure-cellular structure; The method for preparing the sandwich structure braided polyolefin foam material comprises the following steps: S1, mixing polyolefin resin, fiber, heterogeneous nucleating agent, and colorant to obtain a premixed uniform material; S2, adding the premixed materials into a first-stage extruder for hot melting, and adding a supercritical fluid into the first-stage extruder to obtain a polymer / supercritical fluid homogeneous system; S3, sending the polymer / supercritical fluid homogeneous system into a second-stage extruder for processing, and conveying it to the extruder die head for pressure relief and foaming; S4, rolling and shaping the pressure-released foamed material through a calender at the rear end of the extruder, and collecting it through a winder to obtain the sandwich structure braided polyolefin foam material.

2. The sandwich structure braided polyolefin foam material according to claim 1, characterized in that: The cross section of the sandwich structure can be a woven polyolefin foam material with rounded corners and is in the shape of a flat strip as a whole.

3. The sandwich structure braided polyolefin foam material according to claim 1, characterized in that: The sandwich structure can be woven with polyolefin foam material with an apparent density of 0.02 to 0.50 g / cm 3 The average diameter of the pores is 30-400 μm.

4. The sandwich structure braided polyolefin foam material according to claim 1, characterized in that: The sandwich structure can be woven from polyolefin foam material with an elongation at break of 10-300%, a modulus of 2.5-50 MPa, and a specific modulus of 50-600 MPa·cm 3 / g.

5. The sandwich structure braided polyolefin foam material according to claim 1, characterized in that: The sandwich structure braided polyolefin foam material is composed of a cellular layer, a solid layer, and a cellular layer. The thickness of the solid layer is 5 to 800 μm, and the thickness of the cellular layers on both sides is 500 to 3500 μm.

6. The sandwich structure braided polyolefin foam material according to claim 1, characterized in that: The sandwich structure can be woven with polyolefin foam material with a width of 5 to 50 mm and a thickness of 0.5 to 8 mm.

7. The sandwich structure braided polyolefin foam material according to claim 1, characterized in that: The polyolefin resin is selected from at least one of polypropylene, polyethylene, ethylene-propylene rubber, ethylene-vinyl acetate copolymer, and ethylene-octene copolymer.

8. The sandwich structure braidable polyolefin foam material according to claim 7, characterized in that: The polypropylene is high melt strength polypropylene; the polyethylene is high melt strength polyethylene.

9. The sandwich structure braidable polyolefin foam material according to claim 1, characterized in that: The fibers are selected from micro-nano fibers.

10. The sandwich structure braided polyolefin foam material according to claim 9, characterized in that: The micro-nano fiber is selected from at least one of bamboo fiber, flax fiber and wheat straw fiber.

11. The sandwich structure braided polyolefin foam material according to claim 1, characterized in that: The heterogeneous nucleating agent is selected from at least one of talc, palygorskite, montmorillonite, magnesium hydroxide, diatomaceous earth, kaolin, silicon dioxide, wollastonite powder, aluminum hydroxide, calcium carbonate, barium carbonate, barium sulfate, and clay.

12. The sandwich structure braided polyolefin foam material according to claim 1, characterized in that: In step S2, the temperature of the first-stage extruder is 150-220°C, the pressure is 6.0-16.0 MPa, and the screw speed is 15-40 rpm.

13. The sandwich structure braided polyolefin foam material according to claim 1, characterized in that: In step S2, the temperature of the first-stage extruder is 175-200°C, the pressure is 7.0-10.0 MPa, and the screw speed is 30-35 rpm.

14. The sandwich structure braidable polyolefin foam material according to claim 1, characterized in that: In step S2, the supercritical fluid is selected from supercritical carbon dioxide and / or supercritical nitrogen.

15. The sandwich structure braided polyolefin foam material according to claim 1, characterized in that: In step S2, the injection pressure of the supercritical fluid is 15-30 MPa, and the content of the supercritical fluid is 0.5-5 parts by weight.

16. The sandwich structure braided polyolefin foam material according to claim 1, characterized in that: In step S3, the polymer / supercritical fluid homogeneous system is fed into a second-stage extruder via a gear pump; The rotation speed of the gear pump is 5 to 20 rpm.

17. The sandwich structure braidable polyolefin foam material according to claim 16, characterized in that: The rotation speed of the gear pump is 8 to 15 rpm.

18. The sandwich structure braidable polyolefin foam material according to claim 1, characterized in that: In step S3, the temperature of the second-stage extruder is 115-180° C., the pressure is 2-15 MPa, and the screw speed is 2-20 rpm.

19. The sandwich structure braided polyolefin foam material according to claim 1, characterized in that: In step S3, the temperature of the second-stage extruder is 140-165° C., the pressure is 5-8 MPa, and the screw speed is 4-6 rpm.

20. The sandwich structure braidable polyolefin foam material according to claim 1, characterized in that: In step S3, the extruder die head contains 1 to 5 die openings, and the die opening diameter is 0.3 to 3.0 mm.

21. The sandwich structure braidable polyolefin foam material according to claim 1, characterized in that: In step S3, the extruder die head contains 1 to 3 die openings, and the die opening diameter is 0.5 to 1.5 mm.

22. The sandwich structure braidable polyolefin foam material according to claim 1, characterized in that: In step S3, the temperature of the extruder die head is 180-130° C., and the pressure is 3.0-10.0 MPa.

23. The sandwich structure braidable polyolefin foam material according to claim 1, characterized in that: In step S3, the temperature of the extruder die head is 165-140° C., and the pressure is 6.0-9.0 MPa.

24. The sandwich structure braidable polyolefin foam material according to claim 1, characterized in that: In step S4, the distance between the two rollers of the calender is 0.5 to 20 mm; and the rotation speed of the calender is 5 to 300 rpm.

25. Use of the sandwich structure braided polyolefin foam material according to any one of claims 1 to 24 in cushioning linings, cup sleeves, and thermal insulation pads.

Images