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WO-2026091216-A1 - MULTI-LAYER COEXTRUDED FLAME-RETARDANT POLYOLEFIN FOAM PARTICLE WAVE-ABSORBING MATERIAL AND PREPARATION METHOD THEREFOR

WO2026091216A1WO 2026091216 A1WO2026091216 A1WO 2026091216A1WO-2026091216-A1

Abstract

Provided in the present invention are a multi-layer coextruded flame-retardant polyolefin foam particle wave-absorbing material and a preparation method therefor. In the method, polyolefin resins having different properties are compounded, and a polyolefin resin A is highly filled with a flame retardant filler to form a flame-retardant polyolefin layer that serves as an inner layer of a particle; a polyolefin resin B is filled with a conductive agent to form a conductive polyolefin layer that serves as an outer layer of the particle; the compounded polyolefin resin particle is foamed under foaming conditions for the polyolefin resin B, thereby preparing a polyolefin resin wave-absorbing foam particle having an unfoamed or slightly foamed inner layer and a foamed outer layer; and then a wave-absorbing material is prepared by means of a foam forming process. Therefore, the flame retardance, environmental protection properties and economic value of a thermoplastic foam wave-absorbing material are improved, the production efficiency is improved, and good application prospects are exhibited.

Inventors

  • WANG, Junyao
  • AI, WENBO

Assignees

  • 无锡敬仁电子材料科技有限公司

Dates

Publication Date
20260507
Application Date
20241127
Priority Date
20241101

Claims (10)

  1. A multilayer co-extruded flame-retardant polyolefin foam particle microwave absorbing material, characterized in that: each foam particle has a layered structure, including a flame-retardant polyolefin layer and a conductive polyolefin layer, wherein the flame-retardant polyolefin layer is the inner layer and the conductive polyolefin layer is the outer layer; or the flame-retardant polyolefin layer is the middle layer and the conductive polyolefin layer is both the inner and outer layers; or the flame-retardant polyolefin layer is the outer layer and the conductive polyolefin layer is the inner layer.
  2. According to claim 1, the multilayer co-extruded flame-retardant polyolefin foam particle microwave absorbing material is characterized in that, by weight, the flame-retardant polyolefin comprises: 20-80 parts of polyolefin resin A, 20-80 parts of flame retardant A, 0-15 parts of conductive masterbatch, and 0-20 parts of functional additive masterbatch A, which are mixed and then extruded into flame-retardant polyolefin masterbatch A particles.
  3. According to claim 2, the multilayer co-extruded flame-retardant polyolefin foam particle microwave absorbing material is characterized in that: the flame retardant A is selected from one or more of organic flame retardants, inorganic flame retardants, ammonium salt flame retardants, organosilicon flame retardants, and halogen flame retardants.
  4. According to claim 1, the multilayer co-extruded flame-retardant polyolefin foam particle microwave absorbing material is characterized in that, by weight, the conductive polyolefin comprises: 2-98 parts of polyolefin resin, 1-20 parts of flame-retardant masterbatch, 0.1-95 parts of conductive masterbatch, and 1-20 parts of functional additive masterbatch.
  5. According to claim 4, the multilayer co-extruded flame-retardant polyolefin foam particle microwave absorbing material is characterized in that: the flame-retardant masterbatch B comprises a polyolefin resin and a flame retardant B, wherein the polyolefin resin is selected from one or more of polypropylene, polyethylene, ethylene-acrylic acid copolymer, and chlorinated polyolefin resin; and the flame retardant B is selected from one or more of organic flame retardants, inorganic flame retardants, ammonium salt flame retardants, organosilicon flame retardants, and halogenated flame retardants, and the mixture is extruded to obtain flame-retardant masterbatch B particles.
  6. According to claim 5, the multilayer co-extruded flame-retardant polyolefin foam particle microwave absorbing material is characterized in that: the flame retardant B accounts for 1-20% of the total mass of the conductive polyolefin by mass percentage.
  7. The multilayer co-extruded flame-retardant polyolefin foam particle microwave absorbing material according to claim 2 or 4 is characterized in that: the polyolefin resin A and polyolefin resin B are respectively selected from one or more of polypropylene resin, polyethylene resin, maleic anhydride grafted polypropylene, ethylene acrylic acid copolymer, and chlorinated polyolefin resin.
  8. The multilayer co-extruded flame-retardant polyolefin foam particle microwave absorbing material according to claim 2 or 4 is characterized in that: the conductive masterbatch includes polypropylene resin or polyethylene resin, microwave absorbing powder and/or dispersing lubricant, wherein the microwave absorbing powder is selected from one or more of carbon black, graphite, carbon nanotubes, graphene, and carbon fiber.
  9. The multilayer co-extruded flame-retardant polyolefin foam particle microwave absorbing material according to claim 2 or 4 is characterized in that: the functional additive masterbatch A comprises a polyolefin resin and a functional additive A, wherein the polyolefin resin is selected from one or more of polypropylene, polyethylene, maleic anhydride-grafted polypropylene, ethylene-acrylic acid copolymer, and chlorinated polyolefin resin, and the functional additive A is selected from one or more of antioxidants, ultraviolet absorbers, antibacterial agents, dispersing lubricants, and molecular weight regulators; the functional additive masterbatch B comprises a polyolefin resin and a functional additive B, wherein the polyolefin resin is selected from one or more of polypropylene, polyethylene, maleic anhydride-grafted polypropylene, ethylene-acrylic acid copolymer, and chlorinated polyolefin resin, and the functional additive B is selected from one or more of nucleating agents, antioxidants, ultraviolet absorbers, antibacterial agents, and dispersing lubricants.
  10. A method for preparing a multilayer co-extruded flame-retardant polyolefin foam particle microwave absorbing material, characterized by comprising the following steps: Step S1: Mix polyolefin resin A, flame retardant A, conductive masterbatch, and functional additive masterbatch A, and then extrude them into flame retardant masterbatch A granules. Step S2: Add the flame-retardant masterbatch A particles obtained in step S1 to extruder A. Simultaneously, add polyolefin resin B, flame-retardant masterbatch B, conductive masterbatch, and functional additive masterbatch B to extruder B. Extrude through a two-layer co-extrusion die to obtain columnar or ring-shaped polyolefin resin microwave-absorbing particles with an inner layer of flame-retardant polyolefin and an outer layer of conductive polyolefin, or vice versa. By replacing the extruder die with a 3-layer co-extrusion die, columnar or ring-shaped polyolefin resin microwave absorbing particles with flame-retardant polyolefin as the middle layer and conductive polyolefin as the inner and outer layers are obtained. Step S3: Add the polyolefin resin microwave absorbing particles obtained in step S2 to the reactor, add water and dispersant to the high-pressure reactor, stir, heat and pressurize by introducing carbon dioxide, continue heating until the melting point of the conductive polyolefin layer resin is reached, and release the material to obtain polyolefin microwave absorbing foam particles with flame retardant polyolefin layer that does not foam or micro-foams while conductive polyolefin layer foams. Step S4: The polyolefin absorbing foam particles obtained in step S3 are molded into absorbing materials.

Description

A multilayer co-extruded flame-retardant polyolefin foam particle microwave absorbing material and its preparation method Technical Field This invention relates to the field of polyolefin foam microwave absorbing materials, specifically to a multilayer co-extruded flame-retardant polyolefin foam particle microwave absorbing material and its preparation method. Background Technology In the field of microwave absorbing materials, most polyolefin foam microwave absorbing materials have the advantages of low water absorption, high hardness, odorless and environmentally friendly properties, and stable performance over long-term use. They are the main replacement products for sponge-type microwave absorbing materials in the future. However, when used in electromagnetic anechoic chambers, poor flame retardant performance is a major drawback of polyolefin foam microwave absorbing materials. Common polyolefin foam microwave absorbing materials include polystyrene foam, polypropylene, and polyethylene foam. Polystyrene foam uses pentane as a blowing agent, which has a strong pungent odor at high temperatures and poor mechanical properties, resulting in a high damage rate during use. Its temperature resistance is generally worse than that of polypropylene or polyethylene. Therefore, carbon dioxide-foamed polypropylene or polyethylene foam has higher mechanical properties and temperature resistance than polystyrene foam. Currently, commercially available foamed polypropylene or polyethylene microwave absorbing materials are made by mixing polypropylene or polyethylene resin, microwave absorbing agents, and flame retardants, granulating the mixture, and then preparing it through a carbon dioxide foaming process. To ensure microwave absorption performance, a larger amount of microwave absorbing agent needs to be added, which necessitates a reduction in the proportion of flame retardant. This affects the flame retardant performance, and ultimately, the oxygen index of the resulting polypropylene or polyethylene foam microwave absorbing material cannot meet the requirement of a greater than 28 in the "Technical Specification for Electromagnetic Anechoic Chamber Engineering GB50826-2012". In existing technologies, adhesives are typically mixed with flame retardants to prepare polypropylene or polyethylene microwave absorbing foam particles, so that the microwave absorbing and flame retardant coating is coated on the surface of the polymer foam particles. However, in this production process, dissolving the adhesive requires the addition of organic solvents. The use of general organic solvents may pose significant safety hazards and is not environmentally friendly, which can have a certain impact on the physical and mental health of the operators. Moreover, the process is complex, requiring extrusion, granulation, foaming, coating, and molding. Since the polymer foam has a large volume, the operation becomes more difficult, often resulting in low production efficiency. Typically, the coating of microwave-absorbing and flame-retardant materials does not significantly increase the volume of the foam particles. Ignoring the weight of the coating, calculations show that when mixing polypropylene or polyethylene microwave-absorbing foam particles with the coating in a 2-cubic-meter mixing tank, the mixing, discharging, and drying process takes approximately one hour per tank. Since only 50%-70% of the space in a 2-cubic-meter mixing tank can be utilized, only about 40-56 kg of foam particles with a density of 40 kg/cubic meter can be produced per hour. Only with continuous 24-hour production could approximately 1120 kg of foam particles be produced per day. Generally, the average consumption of microwave-absorbing material for microwave anechoic chambers is about 15 kg per square meter. A large microwave anechoic chamber of 10,000 square meters requires approximately 150 tons of absorbing material. Even with 24-hour continuous production, producing 150 tons of material would take 133 days. Many customers with large anechoic chambers have very strict deadline requirements, and the production efficiency described above is simply insufficient to meet the needs of large-scale market applications. Summary of the Invention To address the insufficient production capacity of existing technologies, the inventors have developed a high-capacity, high-efficiency production process for producing polyolefin foam particle microwave absorbing materials with high flame retardant properties and high economic value through continuous research and development. This process utilizes composite polyolefin resins with different properties. A flame retardant filler is highly filled into polyolefin resin A as the inner layer of the particles, while a conductive agent is filled into polyolefin resin B as the outer layer. The composite polyolefin particles are placed in a reactor and foamed under the foaming conditions of polyolefin resin B, resulting in pol