A core-skin resin microparticle and a method for preparing the same, a foamed material, a composite foam material

Abstract

The application provides a core-skin resin particle and a preparation method thereof, a foaming material and a composite foam material. The core-skin resin particle is prepared by using a co-extrusion process, and a polymer base material and a conductive filler are selectively distributed in a skin layer and a core part, so that a structure design of separation of the conductive part and the insulating part is realized. In addition, the core-skin resin particle obtained by the application is foamed by a physical foaming process, so that the purpose of material lightening is achieved, and the foaming beads have improved electromagnetic shielding and absorbing characteristics. Further, the foaming beads obtained by the application can be processed by molding, so that a molded part with a designed shape and having the insulating and electromagnetic shielding properties can be obtained.

Description

Technical Field

[0001] This invention belongs to the field of polymer foaming material technology, specifically relating to a core-shell resin microparticle and its preparation method, a foaming material, and a composite foam material. Background Technology

[0002] In recent years, with the rapid development of electronic devices towards higher integration and higher frequency, electromagnetic interference (EMI) between electronic components has become increasingly prominent. Therefore, the development of EMI shielding materials has become a current research focus and hot topic. Currently, the EMI shielding performance of polymers can be achieved by introducing conductive or magnetic particle fillers. Studies have shown that special distribution / dispersion structures of fillers, such as 3D network structures, isolation structures, and porous foam structures, can effectively further enhance EMI shielding capabilities. Among these, the isolation network structure obtained through foaming technology is one of the most promising structures for endowing polymer matrices with lightweight and high EMI shielding properties.

[0003] Currently, with the increasing precision and integration of electronic devices, electromagnetic shielding materials used inside electronic devices must not only ensure high shielding effectiveness but also possess electrical insulation properties. However, excellent EMI shielding performance often requires good conductivity, which is the opposite of electrical insulation.

[0004] Currently, insulating electromagnetic shielding materials are generally prepared by stacking multiple layers of electromagnetic shielding and insulating layers. However, this method is complex and expensive. Furthermore, the resulting insulating electromagnetic shielding materials often suffer from high electromagnetic wave reflection and high density.

[0005] Therefore, developing materials that simultaneously possess electrical insulation and excellent EMI shielding capabilities remains a pressing issue that needs to be addressed. Summary of the Invention

[0006] In view of this, the purpose of this invention is to provide a core-shell resin microparticle and its preparation method, a foaming material, and a composite foam material. The composite foam material possesses adjustable electrical insulation and electromagnetic shielding functions, and has a low density.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a core-shell resin microparticle comprising a core and a shell, wherein the mass ratio of the core to the shell is (80~95):(5~20).

[0009] Preferably, the core comprises a polymer substrate and a conductive masterbatch; the conductive masterbatch includes conductive filler, and the mass content of the conductive filler in the conductive masterbatch is 20-45%.

[0010] Preferably, the skin layer comprises a polymer substrate, and the thickness of the skin layer is 5~50 μm.

[0011] Preferably, the aspect ratio of the core-shell resin microparticles is 1:1 to 3:1.

[0012] Preferably, the conductive filler includes carbon-based fillers and / or metal fillers.

[0013] Preferably, the carbon-based filler includes any one or more of carbon black, carbon nanotubes, graphene nanosheets, or expanded graphite; the metal filler includes any one or more of silver nanoparticles, silver nanowires, or copper powder.

[0014] Preferably, the size of the conductive filler is less than 10 μm.

[0015] Preferably, the conductive filler accounts for 4 to 20 wt% of the core mass.

[0016] Preferably, the mass of the core-shell resin microparticles is 0.5~3 mg.

[0017] Preferably, the conductive masterbatch comprises a polymer substrate, conductive fillers, and optional additives.

[0018] Preferably, the additives include, but are not limited to, any one or more of antioxidants, stabilizers, lubricants, nucleating agents, compatibilizers, reinforcing agents, or catalysts.

[0019] Preferably, the polymer substrate is selected from any one or more of rubber, thermoplastic resin, biodegradable resin, engineering plastics, or thermoplastic elastomers.

[0020] Preferably, the rubber comprises EVA.

[0021] Preferably, the thermoplastic resin includes any one or more of PP, PE, or PS.

[0022] The biodegradable resin includes any one or more of PLA, PBAT, or PPC.

[0023] Preferably, the engineering plastic includes any one or more of PA, PET, PBT, PPO, PES, or PEI.

[0024] Preferably, the thermoplastic elastomer includes any one or more of TPU, SEBS, OBC, or nylon elastomers.

[0025] Preferably, the conductive masterbatch comprises, by weight, 45-89 parts of polymer base material, 20-45 parts of conductive filler, and 1-10 parts of additives.

[0026] Preferably, the cortex further includes a nucleating agent.

[0027] Preferably, in the skin layer, the polymer substrate comprises 0.3 to 2 parts by weight of nucleating agent per 100 parts.

[0028] Secondly, the present invention provides a method for preparing the above-mentioned core-shell resin microparticles, comprising the following steps:

[0029] A polymer substrate and a conductive masterbatch are mixed to obtain a core mixture; a polymer substrate and an optional nucleating agent are mixed to obtain a skin material.

[0030] The core mixture and the outer layer material are melt-extruded to obtain core-outer resin microparticles.

[0031] Thirdly, the present invention provides a foaming material, characterized in that it is obtained by physically foaming the above-mentioned core-shell resin microparticles;

[0032] Preferably, the foaming material has a pore diameter of 10~300 μm.

[0033] Preferably, the physical foaming is carried out using supercritical carbon dioxide foaming.

[0034] Preferably, the physical foaming temperature is 50~300℃, the saturation time is 0.5~2 h, and the saturation pressure is 2~20MPa.

[0035] Fourthly, the present invention provides a composite foam material, which is obtained by molding the above-mentioned foam material.

[0036] Preferably, the molding process is either direct molding or molding after pre-pressing.

[0037] Preferably, the heat source used in the molding process includes any one or more of steam, hot air, or microwaves.

[0038] Preferably, the composite foam material is insulating, has an electromagnetic shielding effectiveness of 20~50 dB, and a density of 30~300 kg / m³. 3 .

[0039] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0040] This invention provides core-shell resin microparticles, comprising a core and a skin layer. The core includes a polymer substrate and a conductive masterbatch. The conductive masterbatch includes conductive fillers, with a mass content of 20-45%. The skin layer includes a polymer substrate. The skin layer can form an insulating structure, and the core forms island-structure units with electromagnetic shielding properties, enabling the core-shell resin microparticles to achieve electrical insulation and high absorption shielding.

[0041] This invention employs a co-extrusion process to prepare core-shell resin microparticles, selectively distributing polymer substrates and conductive fillers in the skin and core, achieving a structural design that separates the conductive and insulating components. Furthermore, the core-shell resin microparticles obtained by this invention are foamed using a physical foaming process, achieving material lightweighting. The resulting foamed beads have a porous core structure that enhances the material's electromagnetic shielding and absorption properties. Moreover, the foamed beads obtained by this invention can be molded to obtain customizable shapes of molded parts possessing both insulation and electromagnetic shielding properties (i.e., the aforementioned composite foam material).

[0042] The present invention also provides a method for preparing the above-mentioned composite foam material. This method micronizes macroscopic foam beads into multiple foam particle units, and each unit can maintain an independent structural principle, thus avoiding damage to the insulating and thermally conductive network. While ensuring excellent electromagnetic shielding performance, it also has excellent insulation properties. This method has the advantages of simple process, low cost, no pollution, and easy industrial production. Attached Figure Description

[0043] Figure 1 A schematic diagram of the structure of core-shell resin microparticles;

[0044] Figure 2 Here is an SEM image of the foamed beads obtained in Example 2;

[0045] Figure 3 The graph shows the electromagnetic shielding performance of the molded product obtained in Example 2. Detailed Implementation

[0046] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0047] To address the limitations of traditional electromagnetic shielding composite materials, such as high conductivity, low absorption, high density, restricted application range, and difficulty in fabricating complex, irregularly shaped parts, this invention provides a method for preparing a high-strength composite foam material that combines electrical insulation and adjustable electromagnetic shielding. This method involves first constructing insulating electromagnetic shielding core-shell resin microparticles, then controlling the electromagnetic shielding performance of the foamed core through physical foaming. The resulting foamed beads are then molded, with the skin layers bonding together to form an insulating isolation structure, while the core forms island-like structural units with electromagnetic shielding properties, ultimately achieving the goal of electrical insulation and high absorption shielding.

[0048] Specifically, the present invention first provides a core-shell resin microparticle, which includes a core and a skin layer.

[0049] In this invention, the core comprises a polymer substrate and a conductive masterbatch.

[0050] The polymer substrate is a common, foamable, extruded polymer substrate. Specifically, the polymer substrate is selected from any one or more of rubber, thermoplastic resin, biodegradable resin, engineering plastics, or thermoplastic elastomers.

[0051] In this invention, the rubber includes ethylene-vinyl acetate copolymer (EVA).

[0052] In this invention, the thermoplastic resin includes any one or more of polypropylene (PP), polyethylene (PE), or polystyrene (PS);

[0053] In this invention, the biodegradable resin includes any one or more of polylactic acid (PLA), polybutylene adipate / terephthalate (PBAT), or polypropylene carbonate (PPC).

[0054] In this invention, the engineering plastic includes any one or more of polyamide (PA), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyphenylene ether (PPO), polyethersulfone resin (PES), or polyetherimide (PEI).

[0055] In this invention, the thermoplastic elastomer includes any one or more of thermoplastic polyurethane elastomer (TPU), SEBS thermoplastic elastomer (SEBS), olefin block copolymer elastomer (OBC), or nylon elastomer.

[0056] In this invention, the conductive masterbatch includes conductive fillers, which include carbon-based fillers and / or metal fillers. The carbon-based fillers include any one or more of conductive carbon black, carbon nanotubes, graphene nanosheets, or expanded graphite, preferably conductive carbon black; the metal fillers include any one or more of silver nanoparticles, silver nanowires, or copper powder. The carbon-based or metal fillers in this invention preferably possess high conductivity, and the filler size is preferably less than 10 μm.

[0057] In this invention, the conductive masterbatch, in addition to the conductive filler, also includes a polymer substrate and optional additives. The term "optional additives" means that additives may or may not be added, and those skilled in the art can select them based on the actual polymer substrate and conductive filler system. In this invention, the additives include, but are not limited to, any one or more of antioxidants, stabilizers, lubricants, nucleating agents, compatibilizers, reinforcing agents, or catalysts. This invention does not impose any particular restrictions on the selection and source of the aforementioned antioxidants, stabilizers, lubricants, nucleating agents, compatibilizers, reinforcing agents, or catalysts; commonly available commercial products commonly used by those skilled in the art are acceptable.

[0058] In some embodiments of the present invention, the conductive masterbatch comprises, by weight, 45-89 parts of polymer base material, 20-45 parts of conductive filler, and 1-10 parts of additives. Preferably, the conductive masterbatch contains 20-35% by mass, such as 20%, 22%, 25%, 28%, 30%, 32%, or 35%.

[0059] In this invention, the conductive masterbatch is prepared by mixing polymer substrate, conductive filler, optional additives and other raw materials through steps such as extrusion granulation. The preparation process is a common industrial preparation process.

[0060] In some embodiments of the present invention, it is preferred to mix the polymer substrate and the conductive masterbatch to obtain a core mixture. The conductive filler content in the core mixture is 4-20 wt%, such as 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, etc.; preferably 5-15 wt%, to ensure that the core, after foaming, has the properties required to achieve 10 2 ~10 4 The stable electrostatic dissipation property of the surface resistivity of Ω results in an electromagnetic shielding effect. If the mass content of the conductive filler is less than 4%, the foamed core will hardly exhibit an electromagnetic shielding effect; conversely, if it is higher than 20%, the core-shell resin microparticles will be difficult to foam, and subsequent granulation processing of the microparticles will be difficult.

[0061] In this invention, the skin layer comprises a polymer substrate, and the thickness of the skin layer is 5~50 μm, preferably 10~40 μm. If the skin layer is too thin, it is difficult to guarantee the insulation properties of the skin layer; conversely, if the skin layer is too thick, the proportion of the conductive part in the core is small, the electromagnetic shielding performance of the foamed material decreases, and it is difficult to meet the overall shielding performance requirements.

[0062] In some preferred embodiments of the present invention, in order to adjust the cell structure of the core layer and the skin layer, a cell nucleating agent is preferably added to the core and skin layer of the resin particles. The cell nucleating agent can be selected from any one or more of inorganic powders such as talc, calcium carbonate, silica, zinc borate, or nano-clay. Specifically, the amount of cell nucleating agent used is controlled at 0.3 to 2 parts by weight per 100 parts by weight of polymer substrate, such as 0.3 parts by weight, 0.5 parts by weight, 0.8 parts by weight, 1 part by weight, 1.3 parts by weight, 1.5 parts by weight, 1.8 parts by weight, or 2 parts by weight, etc.

[0063] In this invention, the mass ratio of the core to the skin is (80~95):(5~20), such as 80:20, 83:17, 85:15, 90:10, 93:7, or 95:5. This ensures that the core has electromagnetic shielding properties while maintaining appropriate moldability of the subsequently expanded beads and the insulating physical properties of the resulting molded product. In preparing the core-skin resin microparticles, this invention further adjusts the weight ratio of the core to the skin by adjusting the ratio of the core component's feed amount to the skin component's feed amount. The conductivity of the core can be controlled by the amount of conductive masterbatch added; preferably, the mass content of conductive filler in the core is 4~20 wt%, more preferably 5~15 wt%.

[0064] In this invention, the mass of the prepared core-shell resin microparticles is 0.5~3 mg, such as 0.5 mg, 1 mg, 1.5 mg, 2 mg, 2.5 mg, or 3 mg. The aspect ratio of the core-shell resin microparticles is 1:1~3:1, such as 1:1, 1.5:1, 2:1, 2.5:1, or 3:1, etc. The length is controlled at 1.5~3 mm, such as 1.5 mm, 1.8 mm, 2 mm, 2.3 mm, 2.5 mm, 2.8 mm, or 3 mm, etc., and the diameter is 0.5~1 mm, such as 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, or 1 mm, etc. It should be noted that if the aspect ratio of the core-shell resin microparticles is less than 1, the core cross-section of the foamed material will be large, the insulation will be poor, and a complete insulating layer cannot be formed; if the aspect ratio is greater than 3, gaps / pores are easily formed between the particles in the product obtained after foaming beads are formed, resulting in poor appearance quality.

[0065] The present invention also provides a method for preparing the above-mentioned core-shell resin microparticles, comprising the following steps:

[0066] A polymer substrate and a conductive masterbatch are mixed to obtain a core mixture; a polymer substrate and an optional nucleating agent are mixed to obtain a skin material.

[0067] The core mixture and the outer layer material are melt-extruded to obtain core-outer resin microparticles.

[0068] In this invention, the melt extrusion is carried out using a co-extruder, and the specific process is a commonly used process in the field.

[0069] The present invention also provides a foamed material, which is obtained by physically foaming the above-mentioned core-shell resin microparticles to obtain a foamed material with pores. The average diameter of the pores in the foamed material is 10~300 μm.

[0070] In some embodiments of the present invention, the physical foaming is carried out using supercritical carbon dioxide foaming, followed by rapid depressurization to obtain foamed beads. The physical foaming temperature is 50~300℃, such as 50℃, 100℃, 150℃, 200℃, 250℃, or 300℃; the saturation time is 0.5~2 h, such as 0.5 h, 1 h, 1.5 h, or 2 h; and the saturation pressure is 2~20 MPa, such as 2 MPa, 5 MPa, 8 MPa, 10 MPa, 12 MPa, 15 MPa, 18 MPa, or 20 MPa.

[0071] In this invention, the physical foaming process is preferably carried out in a high-pressure sealed container. The foaming temperature, pressure, and saturation time are selected according to the characteristics of the polymer substrate and can be set according to the conditions reported in the literature. The preferred physical foaming temperature of this invention is 50~270℃, the saturation time is 0.5~2 h, and the saturation pressure is 2~20 MPa.

[0072] The present invention also provides a composite foam material (also known as a "molded article"), which is obtained by molding the above-mentioned foamed beads; the molding process is either direct molding or molding after pre-pressing; the heat source used in the molding process includes any one or more of steam, hot air or microwaves.

[0073] In this invention, the molding process can be carried out using common EPS or EPP steam molding equipment or high-pressure steam (0.4~3 MPa) molding equipment, or the foamed beads can be pre-pressed and filled into a mold, hot air / steam can be introduced, and the mixture can be molded to obtain a composite foam material that has both insulation and electromagnetic shielding properties.

[0074] In summary, this invention provides a method for preparing a composite foam material that combines insulation and electromagnetic shielding, comprising the following steps:

[0075] (1) The polymer substrate and the conductive masterbatch are physically blended to obtain composite particles A1; the mass of the conductive filler is 4~20 wt% of the total mass of the composite particles A1.

[0076] (2) The polymer substrate and the composite material particles A1 described in step (1) are melt-extruded through a co-extruder to obtain core-skin resin microparticles with a core conductive and skin insulating structure;

[0077] (3) The core resin microparticles obtained in step (2) are foamed with supercritical carbon dioxide to obtain foamed particles; the foamed particles are molded with steam / hot air to obtain a composite foam material with both insulation and electromagnetic shielding.

[0078] The porous structure of the foamed core provides electromagnetic shielding and high absorption, while the skin forming process maintains a complete insulating layer. Therefore, the foam material provided by this invention offers excellent absorption and shielding performance and mechanical properties while ensuring the insulation properties of the composite foam material.

[0079] Testing showed that the composite foam material prepared by this invention using polypropylene as the polymer base material has insulating properties, an electromagnetic shielding effectiveness of 20-50 dB, and a density of 30-300 kg / m³. 3 .

[0080] It is evident that the composite foam material obtained by foaming and molding the core-shell resin microparticles provided by this invention has both adjustable electrical insulation and electromagnetic shielding functions, and also has low density.

[0081] To further illustrate the present invention, the following embodiments provide a detailed description. The experimental materials used in the following embodiments of the present invention are all commercially available products.

[0082] The apparent density of the foamed beads and molded products mentioned below is measured by the water displacement method for foamed particles; the apparent density of the molded products is calculated as density = mass / volume.

[0083] The average pore diameter of the foamed beads was obtained by measuring and analyzing SEM images obtained through scanning electron microscopy.

[0084] Insulation is measured using a surface resistance tester. When the surface resistance is greater than 10... 12 When the symbol "◎" is used, it indicates that the material is insulating (represented by the symbol "◎").

[0085] Electromagnetic shielding performance was tested using a PAN-x vector network analyzer.

[0086] The following examples and comparative examples all provide a polypropylene molded article, and the preparation method is as follows:

[0087] 1) Preparation of core-shell resin microparticles: The conductive filler used in the preparation of conductive masterbatch CB1 is conductive carbon black with a particle size range of 20-50 nm and an oil absorption of 300-400 mL / 100 g dibutyl phthalate (DBP). Conductive masterbatch CB1, by mass fraction, includes: 55% polypropylene resin A, 40% conductive carbon black, and 5% other general-purpose additives (3.2% linear low-density polyethylene, 0.5% erucamide lubricant, 0.5% white oil dispersant, 0.5% zinc stearate, and 0.3% antioxidant B215). Polypropylene resin A is selected as propylene-ethylene random copolymer resin (PP, TPC w311). Polypropylene resin A and the aforementioned conductive masterbatch CB1 were mixed in a suitable ratio to obtain composite particles A1, which served as the core material. Polypropylene resin A (99.2%), nucleating agent (zinc borate, 0.5%), and antioxidant (B215, 0.3%) were weighed according to the formula, mixed at high speed, and the blend served as the skin layer. The mixture was extruded through a co-extrusion device, and pelletized using a dual-frequency pelletizer to obtain foamed core-skin structure resin microparticles (see schematic diagram). Figure 1 As shown in the figure, the skin layer is an insulating layer, and the core is a conductive composite material;

[0088] 2) Preparation of foamed beads:

[0089] 2 kg of core-shell resin microparticles and 6 L of water as dispersion medium were loaded into a 10 L autoclave. Simultaneously, 6 g of kaolin, 0.1 g of sodium alkylbenzene sulfonate, and 0.3 g of aluminum sulfate were added as dispersants. Then, carbon dioxide was injected into the autoclave as a foaming agent according to the required internal pressure (P). The contents were heated (40–60 min) to the foaming temperature (T) with stirring and held at this temperature for 20 min. Subsequently, the contents and water in the autoclave were released to atmospheric pressure to obtain foamed beads.

[0090] 3) Production of molded products:

[0091] The expanded beads are pre-compressed (saturated air pressure 0.15~0.25 MPa). These expanded beads are then placed in a mold cavity suitable for forming a flat plate with a length of 250 mm, a width of 250 mm, and a thickness of 50 mm. The mold is then heated by steam to obtain a plate-shaped foamed molded product. The steam heating molding process involves applying steam to the mold through single-sided preheating, double-sided heating, and water cooling to obtain the molded part. The molded product is removed from the mold cavity and aged in an 80°C oven for 12 hours to obtain the molded product made from the expanded beads.

[0092] According to the above method and the specific parameters in Table 1 below, the present invention prepared molded articles corresponding to Examples 1-5 and Comparative Examples 1-4. The density, insulation properties, and electromagnetic shielding properties of the obtained molded articles were tested, and the results are shown in Table 1 (Note: Insulation ◎: Surface resistivity > 10). 12 Ω, Antistatic / Conductive --: Surface resistivity ≤10 12 Ω, ----: indicates no electromagnetic shielding.

[0093] Table 1

[0094]

[0095] As shown in Table 1, the molded products obtained by foaming and molding the core-shell resin microparticles provided by the present invention have excellent insulation and electromagnetic shielding properties, and low density.

[0096] As shown in Comparative Example 1, when the sheath mass in the core-shell resin particles is 3 wt%, the insulation of the resulting molded product is significantly reduced. This indicates that if the sheath mass content is too low, it is difficult to maintain the integrity of the sheath (i.e., the insulating layer) in the molded product, resulting in the molded product exhibiting antistatic / conductive properties.

[0097] As can be seen from Comparative Example 2, when the aspect ratio of the foamed beads is 0.7, that is, the diameter of the foamed beads is larger than the length, it is easy to cause more core leakage, which in turn causes the molded product to exhibit antistatic / conductive properties.

[0098] As can be seen from Comparative Example 3, if the mass content of conductive masterbatch in the core layer is 15 wt%, the content of conductive filler will be lower, which will result in the molded product failing to exhibit electromagnetic shielding properties.

[0099] As can be seen from Comparative Example 4, the skin thickness of the foamed beads is 3 μm. It can be seen that the skin is too thin after foaming, and the molded product cannot show insulation properties after molding.

[0100] A schematic diagram of the core-shell resin particles obtained in Embodiment 2 of the present invention is shown below. Figure 1 As shown, the black part in the core is the area containing conductive filler.

[0101] The cross-sectional SEM image of the foamed beads obtained in Example 2 of the present invention is shown below. Figure 2 As shown, it has an ordered pore structure.

[0102] The electromagnetic shielding performance test image of the molded article obtained in Embodiment 2 of the present invention is shown below. Figure 3 As shown, the electromagnetic shielding performance reaches 25 dB, and its electromagnetic wave shielding is mainly absorption.

[0103] Example 6

[0104] 1) Preparation of conductive masterbatch: by mass fraction, it includes: 55% polyphenylene ether / high-impact polystyrene (mass ratio 6 / 4, Bluestar PPO powder LXR040, SECCO HIPS 622) alloy, 40% conductive carbon black (particle size range 20~50 nm, oil absorption of 300~400 mL / 100 g dibutyl phthalate (DBP)), and 5% other general-purpose additives (3.2% linear low-density polyethylene, 0.5% lubricant erucamide, 0.5% dispersant white oil, 0.5% zinc stearate, and 0.3% antioxidant B215). Polyphenylene ether / high-impact polystyrene (6 / 4) alloy is physically blended with the above-mentioned conductive masterbatch to obtain composite particles A1; the mass of the conductive filler (conductive carbon black) is 15 wt% of the total mass of the composite particles A1; the skin material polyphenylene ether / high-impact polystyrene (mass ratio: 6 / 4) and the composite particles A1 are melt-extruded through a co-extruder to obtain core-skin resin microparticles with a core conductive and skin insulating structure (core-skin ratio is 90:10, skin thickness is 10 μm).

[0105] 2) 2 kg of core-shell resin microparticles and 6 L of water (dispersion medium) were placed into a 10 L autoclave. Simultaneously, 6 g of kaolin, 0.1 g of sodium alkylbenzene sulfonate, and 0.3 g of aluminum sulfate were added as dispersants. Then, carbon dioxide was injected into the autoclave as a foaming agent, based on the internal pressure (15 MPa). The contents were heated (60 min) with stirring to the foaming temperature (160 °C). o C), and held at this foaming temperature for 20 min. Subsequently, the contents of the autoclave, along with water, were released to atmospheric pressure to obtain foamed beads;

[0106] 3) The foamed beads are steam-formed (0.35 MPa) to obtain a product that combines insulation and electromagnetic shielding (20 dB) with a density of 0.06 g / cm³. 3 Polylactic acid foam material.

[0107] Example 7

[0108] 1) Preparation of conductive masterbatch: By mass fraction, it includes: 65% polylactic acid (NatureWorks, 8052D), 30% graphite, and 5% other general-purpose additives (3.2% linear low-density polyethylene, 0.5% erucamide lubricant, 0.5% white oil dispersant, 0.5% zinc stearate, and 0.3% antioxidant B215). Polylactic acid is physically blended with the above conductive masterbatch to obtain composite particles A1; the mass of the conductive filler (graphite) is 18 wt% of the total mass of the composite particles A1; the polylactic acid skin material and the composite particles A1 are melt-extruded through a co-extruder to obtain core-skin resin microparticles with a conductive core and insulating skin structure (core-skin ratio of 95:5, skin thickness of 5 μm).

[0109] 2) 2 kg of core-shell resin microparticles and 6 L of water (dispersion medium) were placed into a 10 L autoclave. Simultaneously, 6 g of kaolin, 0.1 g of sodium alkylbenzene sulfonate, and 0.3 g of aluminum sulfate were added as dispersants. Then, carbon dioxide was injected into the autoclave as a foaming agent, based on the internal pressure (6 MPa). The contents were heated (80 min) with stirring to the foaming temperature (160 °C). o C), and held at this foaming temperature for 10 min. Subsequently, the contents of the autoclave, along with water, were released to atmospheric pressure to obtain foamed beads;

[0110] 3) The foamed beads are steam-formed (0.15 MPa) to obtain a product that combines insulation and electromagnetic shielding (30 dB) with a density of 0.06 g / cm³. 3 Polylactic acid foam material.

[0111] Example 8

[0112] 1) Preparation of conductive masterbatch: By mass fraction, it includes: 85% polyurethane (Lubrizol, 302EZ), 10% silver nanowires, and 5% other general-purpose additives (3.2% linear low-density polyethylene, 0.5% erucamide lubricant, 0.5% white oil dispersant, 0.5% zinc stearate, and 0.3% antioxidant B215). The polyurethane is physically blended with the above conductive masterbatch to obtain composite particles A1; the mass of the conductive filler (silver nanowires) is 5 wt% of the total mass of the composite particles A1; the polyurethane skin material and the above composite particles A1 are melt-extruded using a co-extruder to obtain core-skin resin microparticles with a conductive core and insulating skin structure (core-skin ratio of 96:4, skin thickness of 15 μm).

[0113] 2) 2 kg of core-shell resin microparticles and 6 L of water (dispersion medium) were placed into a 10 L autoclave. Simultaneously, 6 g of kaolin was added as a dispersant, 0.1 g of sodium alkylbenzene sulfonate, and 0.3 g of aluminum sulfate as dispersing aids. Then, based on the internal pressure (12 MPa) of the autoclave, carbon dioxide was injected as a foaming agent. The contents were heated (45 min) with stirring to the foaming temperature (115 °C). o C), and held at this foaming temperature for 5 minutes. Subsequently, the contents of the autoclave, along with water, were released to atmospheric pressure to obtain foamed beads;

[0114] 3) The foamed beads are processed through 120 o C-type steam molding yields a product that combines insulation and electromagnetic shielding (40 dB) with a density of 0.07 g / cm³. 3 Polyurethane foam material.

[0115] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A core-sheath resin microparticle characterized by, It includes a core and a sheath, wherein the mass ratio of the core to the sheath is (80~95):(5~20); The core comprises a polymer substrate and a conductive masterbatch; the conductive masterbatch includes conductive filler, and the mass content of the conductive filler in the conductive masterbatch is 20-45%. The skin layer comprises a polymer substrate, and the thickness of the skin layer is 5~50 μm; The aspect ratio of the core-shell resin microparticles is 1:1 to 3:1; The composite foam material prepared by foaming the core-shell resin microparticles and then molding it is insulated, has an electromagnetic shielding effectiveness of 20~50 dB, and a density of 30~300 kg / m³. 3 .

2. The core / sheath resin microparticle of claim 1, wherein The conductive filler includes carbon-based fillers and / or metal fillers; The carbon-based filler includes any one or more of carbon black, carbon nanotubes, graphene nanosheets, or expanded graphite; the metal filler includes any one or more of silver nanoparticles, silver nanowires, or copper powder. The size of the conductive filler is less than 10 μm; The conductive filler accounts for 4-20 wt% of the core mass; The mass of the core-shell resin particles is 0.5~3 mg.

3. The core / sheath resin microparticle according to claim 1 or 2, wherein The conductive masterbatch includes a polymer substrate, conductive fillers, and optional additives; The additives include any one or more of antioxidants, stabilizers, lubricants, nucleating agents, compatibilizers, reinforcing agents, or catalysts; The polymer substrate is selected from any one or more of rubber, thermoplastic resin, biodegradable resin, engineering plastics, or thermoplastic elastomers; The rubber includes EVA; The thermoplastic resin includes any one or more of PP, PE, or PS; The biodegradable resin includes any one or more of PLA, PBAT, or PPC. The engineering plastics include any one or more of PA, PET, PBT, PPO, PES, or PEI; The thermoplastic elastomer includes any one or more of TPU, SEBS, OBC, or nylon elastomers.

4. The core / sheath resin microparticle of claim 3, wherein The conductive masterbatch, by weight, comprises 45-89 parts of polymer base material, 20-45 parts of conductive filler, and 1-10 parts of additives.

5. The core / sheath resin microparticle of claim 1, wherein The cortex also includes a nucleating agent; In the skin layer, the polymer substrate is 100 parts by weight, and the nucleating agent is 0.3 to 2 parts by weight.

6. A process for producing the core / sheath resin microparticle according to any one of claims 1 to 5, characterized by, Includes the following steps: A polymer substrate and a conductive masterbatch are mixed to obtain a core mixture; a polymer substrate and an optional nucleating agent are mixed to obtain a skin material. The core mixture and the outer layer material are melt-extruded to obtain core-outer resin microparticles.

7. A foamed material, characterized by The product is obtained by physically foaming the core-shell resin microparticles prepared by any one of claims 1 to 5 or by the preparation method according to claim 6. The average diameter of the foamed material's pores is 10~300 μm.

8. The foamed material of claim 7, wherein, The physical foaming is carried out using supercritical carbon dioxide foaming. The physical foaming temperature is 50~300℃, the saturation time is 0.5~2 h, and the saturation pressure is 2~20 MPa.

9. A composite foam material, characterized by, Obtained by molding the foaming material as described in claim 7 or 8; The molding process is either direct molding or molding after pre-pressing; The heat source used in the molding process includes any one or more of steam, hot air, or microwaves.

10. The composite foam material of claim 9, wherein, The composite foam material is insulated, the electromagnetic shielding efficiency is 20-50 dB, and the density is 30-300 kg / m 3 .

Images