Core-shell foaming agent, micro-foaming material as well as preparation method and application of micro-foaming material

Abstract

The invention provides a core-shell foaming agent, a micro-foaming material as well as a preparation method and application of the micro-foaming material. The core of the core-shell foaming agent is a temperature-resistant foaming agent, and the shell of the core-shell foaming agent is at least one of a polymer of an acrylate monomer and a derivative thereof and a copolymer of the acrylate monomer and the derivative thereof and a comonomer; the preparation method comprises the following steps: dispersing the temperature-resistant foaming agent in an organic solvent, adding the acrylate monomer and the derivative thereof, the optional comonomer, the cross-linking agent and the initiator for reaction in the atmosphere of protective gas, and performing post-treatment to obtain the temperature-resistant foaming agent. The micro-foaming type material comprises the following components in parts by weight: 100 parts of matrix resin, 5-100 parts of reinforced fibers subjected to surface treatment, 1-6 parts of a core-shell type foaming agent, 1-20 parts of a functional auxiliary agent and 0.1-5 parts of a flow improving auxiliary agent, the core-shell foaming agent prepared by the invention can be applied to the field of high-temperature foaming, and a micro-foaming material has excellent strength, rigidity and dielectric properties.

Description

Technical Field

[0001] The present invention relates to the field of polymer composites. Further, it relates to a core-shell foaming agent, a micro-foamed material, and a preparation method and application thereof. Background Art

[0002] Micro-foamed materials are a type of foaming materials prepared by special processing and forming processes, having micro-nano scale pore diameters. When stressed, they generate crazes to prevent cracks from growing continuously. At the same time, the foam can share the stress and reduce stress concentration, having excellent mechanical properties. Compared with unfoamed pure plastic materials, micro-foamed materials have a small density and are light in weight, can save material costs, improve the use performance and processing performance of materials to a certain extent, and also have excellent high specific strength, high fatigue life, heat preservation, heat insulation, sound absorption, sound insulation, good dimensional stability, and dielectric properties. They have been widely used in fields such as automotive parts, aerospace, and household appliances. The existing problems are that there are obvious deficiencies in aspects such as material strength, stiffness, and heat resistance. In addition, for high-performance resin-based micro-foamed materials, due to their high processing temperature and the low decomposition temperature of conventional foaming agents, they are not suitable for temperature-resistant foaming systems. Therefore, high-performance development has become a new direction and hot spot in the research of micro-foamed materials.

[0003] Patents CN217916425U and CN116535802A also disclose the melt direct extrusion method, the supercritical micro-foaming technology, etc. Currently, the preparation of micro-foamed materials is mainly achieved through the injection molding method. The uniformly mixed plastic material and chemical foaming agent are heated and plasticized in the barrel, or the physical foaming agent is directly injected into the plastic melt. Then, the melt is injected into the mold cavity at high pressure and high speed, and then rapidly depressurized to form a supersaturated gas. The bubbles instantaneously nucleate and grow and are shaped to form micro-foamed materials. This method has a short molding cycle, can be molded in one step for products with complex shapes, and is easy to realize automated production. However, the foaming mechanism of the injection molding method is relatively complex, the process is difficult to control, and it is not easy to foam for thicker products. Therefore, the injection molding method is limited in practical applications. Chemical foaming injection molding is the inevitable way for future lightweight products.

[0004] Existing foaming agents generally belong to foaming aids for materials such as polyurethane, polyolefin, and thermoplastic elastomer in the medium and low temperature ranges, and are not suitable for high temperature ranges. At the same time, after foaming and molding, the strength of the pore material is significantly lower than that before foaming, especially for structural profiles with high strength requirements, this problem is more prominent. In addition, when preparing high-temperature resistant foaming materials, conventional foaming agents and foaming processes are not easy to control, resulting in difficult control of pore construction, structure, and their distribution, which is instead not conducive to the regulation of the dielectric properties of materials. Therefore, it is necessary to continuously optimize and improve the type, mechanism, structural composition and performance of foaming agents for micro-foamed materials, as well as the injection foaming process. Summary of the Invention

[0005] To solve the technical problems existing in the prior art, the present invention provides a core-shell foaming agent, a micro-foamed material, and their preparation methods and applications.

[0006] The present invention solves the problems of poor high-temperature resistance of the foaming agent, poor strength of the foamed material, and large dielectric loss existing in the prior art. The core-shell foaming agent prepared by the present invention has a shell composed of an acrylate polymer or copolymer. The shell layer of the polymer coating structure can protect the foaming agent from reacting prematurely during the material preparation process, which is beneficial to the dispersion of the foaming agent and can more effectively foam in situ during molding. Its core is a high-temperature-resistant foaming agent, which decomposes carbon dioxide, nitrogen, and ammonia only at a high processing temperature above 300 °C and can be applied to the field of high-temperature foaming.

[0007] For the micro-foamed material prepared by the present invention, a high-temperature-resistant matrix resin is selected, and the fibers are surface-modified with a hydroxyalkyl polyepoxy carboxylate coupling agent, which endows the micro-foamed material with better mechanical properties and improves its high-temperature resistance at the same time; the core-shell foaming agent makes its dispersion performance better and can foam in situ. When introduced into the system together with a flow improvement aid with a branched structure, etc., the micro-foamed material is endowed with excellent strength, rigidity, and dielectric properties.

[0008] The preparation method of the present invention is simple and easy to implement, and it is easy to realize production scale-up. The micro-foamed material can be widely applied in the fields of communication, electronics, automotive, medical, aerospace, etc.

[0009] One of the purposes of the present invention is to provide a core-shell foaming agent, wherein the core of the core-shell foaming agent is a high-temperature-resistant foaming agent; the shell of the core-shell foaming agent is at least one of a polymer of an acrylate monomer or its derivative, and a copolymer of an acrylate monomer or its derivative and a comonomer.

[0010] The raw materials of the shell of the core-shell foaming agent must contain acrylate monomers and their derivatives to ensure good compatibility between the core-shell foaming agent and the matrix resin of the micro-foamed material; the derivative refers to a compound further derived from the acrylate monomer, such as different substituents.

[0011] In a preferred embodiment of the present invention,

[0012] The high-temperature-resistant foaming agent is at least one of calcium carbonate, sodium carbonate, potassium carbonate, barium carbonate, magnesium carbonate, p-toluenesulfonyl semicarbazide, 4,4'-oxybis(benzenesulfonyl semicarbazide), trihydrazinotriazine, and 5-phenyltetrazole; preferably a composition of at least one of sodium carbonate and potassium carbonate and at least one of p-toluenesulfonyl semicarbazide, 4,4'-oxybis(benzenesulfonyl semicarbazide), and trihydrazinotriazine; more preferably a composition of sodium carbonate and trihydrazinotriazine.

[0013] In a preferred embodiment of the present invention,

[0014] The particle size of the core-shell foaming agent is 0.1 to 50 microns, preferably 0.25 to 40 microns, and more preferably 5 to 30 microns;

[0015] The thickness of the shell layer of the core-shell foaming agent is 50 nanometers to 10 microns, preferably 100 nanometers to 5 microns, and more preferably 0.5 to 5 microns;

[0016] The diameter of the core layer of the core-shell foaming agent is 50 nanometers to 40 microns, preferably 150 nanometers to 25 microns, and more preferably 200 nanometers to 8 microns.

[0017] The second object of the present invention is to provide a method for preparing a core-shell foaming agent, comprising:

[0018] Disperse the heat-resistant foaming agent in an organic solvent, and in a protective gas atmosphere, add acrylate monomers and their derivatives, crosslinking agents and initiators, and optional comonomers, and carry out a reaction, and obtain the core-shell foaming agent after post-treatment.

[0019] In a preferred embodiment of the present invention,

[0020] The acrylate monomers and their derivatives are at least one of methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, methyl 3-methoxyacrylate, 1-adamantyl acrylate, 1-adamantyl methacrylate, 1-adamantyl 3-methoxyacrylate;

[0021] The comonomer is at least one of ethylene, propylene, 1-butene, 1-hexene, 1-octene, styrene, acrylonitrile, butadiene, isoprene, maleic anhydride, vinyl acetate;

[0022] The organic solvent is at least one of cyclohexane, hexane, octane, chloroform, ethylbenzene;

[0023] The crosslinking agent is at least one of polyisocyanate, ethylene glycol diacrylate, propylene glycol diacrylate, butylene glycol diacrylate, hexylene glycol diacrylate, polyethylene glycol diacrylate, polypropylene glycol diacrylate, polybutylene glycol diacrylate, polyhexylene glycol diacrylate, epoxy resin-based diacrylate;

[0024] The initiator is at least one of azo initiators and peroxide initiators, preferably at least one of azodiisobutyronitrile, azodiisovaleronitrile, azodiisoheptonitrile, dicumyl peroxide, benzoyl peroxide, tert-butyl peroxybenzoate, methyl ethyl ketone peroxide, 1,1-di-tert-butylperoxycyclohexane, 1,1-di-tert-butylperoxy-3,3,5-trimethylcyclohexane, di-tert-butyl peroxide, di-tert-amyl peroxide, ditertiary pentyl peroxide;

[0025] The protective gas is at least one of nitrogen and inert gas; the inert gas is preferably argon.

[0026] In a preferred embodiment of the present invention,

[0027] The mass ratio of the temperature-resistant foaming agent to the total mass of acrylate monomers, their derivatives and comonomers is (2-10):100, preferably (4-6):100;

[0028] The mass ratio of the comonomer to the acrylate monomers and their derivatives is (0-100):100, preferably (5-50):100, more preferably (9-20):100;

[0029] The mass ratio of the total mass of the acrylate monomers, their derivatives and comonomers to the mass of the organic solvent is (1-200):100, preferably (10-150):100, more preferably (80-120):100; and / or,

[0030] The mass ratio of the crosslinking agent to the total mass of the acrylate monomers, their derivatives and comonomers is (0.01-5):100, preferably (0.1-3):100, more preferably (0.8-1.2):100;

[0031] The mass ratio of the initiator to the total mass of the acrylate monomers, their derivatives and comonomers is (0.001-1):100, preferably (0.005-0.85):100, more preferably (0.1-0.4):100.

[0032] In a preferred embodiment of the present invention,

[0033] The temperature-resistant foaming agent is dispersed in the organic solvent at room temperature under shear; the shear is achieved by stirring, and the stirring speed is preferably 100-1000 revolutions / min, more preferably 200-800 revolutions / min; and / or,

[0034] The reaction temperature is 40-95°C, preferably 50-90°C;

[0035] The reaction time is 0.5 to 12 h, preferably 1.5 to 10 h;

[0036] The post-treatment method is the usual operation in the art, including suction filtration, washing, and drying treatments.

[0037] The third object of the present invention is to provide a core-shell foaming agent obtained by the above preparation method.

[0038] The fourth object of the present invention is to provide a micro-foamed material. Based on 100 parts by weight of the matrix resin, the micro-foamed material comprises the following components:

[0039]

[0040] The core-shell foaming agent is the above-mentioned core-shell foaming agent;

[0041] The surface-treated reinforcing fiber is obtained by surface-treating the reinforcing fiber with a coupling agent.

[0042] In a preferred embodiment of the present invention,

[0043] The matrix resin is at least one of semi-aromatic polyamide, fully aromatic polyamide, aliphatic long-chain polyamide with 8 to 20 carbon atoms in the polymer monomer, polyphenylene sulfide, polyphenylene ether, polyimide, polyether amide, polyarylamide, polyarylate, polyether arylamide, polyether arylate, polyether ketone ketone, and polyether ether ketone; optionally, it further includes aliphatic short-chain polyamide with 4 to 6 carbon atoms in the polymer monomer, such as polyamide 6, polyamide 66, etc.; the aliphatic short-chain polyamide accounts for 5 to 35% of the total mass of the matrix resin;

[0044] The reinforcing fiber is at least one of carbon fiber, glass fiber, aramid fiber, plant fiber, basalt fiber, metal fiber, and natural fiber; the diameter of the reinforcing fiber is preferably 5 to 20 microns, more preferably 9 to 17 microns;

[0045] The functional additive is at least one of a flame retardant, a plasticizer, a heat stabilizer, a lubricant, and a UV absorber; preferably,

[0046] The flame retardant is at least one of triphenyl phosphate, triisopropylphenyl phosphate, tributyl phosphate, and trioctyl phosphate;

[0047] The plasticizer is at least one of phthalate, glyceryl tristearate, and epoxidized soybean oil;

[0048] The heat stabilizer is at least one of triphenyl phosphite, tris-(2,6-dimethylphenyl) phosphite, trimethyl phosphate, dimethyl phenyl phosphate, and benzotriazole;

[0049] The lubricant is at least one of methyl stearate, polyethylene glycol, and polypropylene glycol;

[0050] The UV absorber is at least one of hydroxybenzodiazole, hydroxybenzotriazine, hydroxydibenzophenone, benzoxazinone, nano-titanium dioxide, and nano-zinc oxide;

[0051] Based on 100 parts by weight of the matrix resin, it includes:

[0052] The dosage of the flame retardant is 0.5 to 9 parts by weight;

[0053] The dosage of the plasticizer is 0.05 to 2 parts by weight;

[0054] The dosage of the heat stabilizer is 0.05 to 2 parts by weight;

[0055] The dosage of the lubricant is 0.2 to 5 parts by weight;

[0056] The dosage of the UV absorber is 0.5 to 2 parts by weight.

[0057] The flow improver is at least one of polyolefin with a branched structure, polyester with a branched structure, polyether with a branched structure, polyamide with a branched structure, polystyrene with a branched structure, polydiene with a branched structure, and polyacrylate with a branched structure; and / or,

[0058] The coupling agent is prepared by the method in Chinese invention patent CN112225944A (invention name: "LDS additive with good dispersibility, LDS material containing the additive and application"), and its structural formula is as shown in formula (I):

[0059]

[0060] In formula (I), R is an aliphatic hydrocarbon group or an aromatic hydrocarbon group of C 1 ~C 18 ; X is -O-, -NH-, -COO- or -C 6 H 4 O-; p is any number selected from 0 to 20; q is any number selected from 1 to 20; M is hydrogen, an alkali metal, an alkaline earth metal, ammonium or aluminum; n is 1, 2 or 3; and / or,

[0061] The preparation method of the surface-treated reinforcing fiber includes: dispersing the coupling agent in water to obtain a coupling agent dispersion liquid, infiltrating the reinforcing fiber into the coupling agent dispersion liquid, and obtaining the surface-treated reinforcing fiber after ultrasonic treatment, infiltration, and drying; preferably,

[0062] The time of ultrasonic treatment is 20 to 40 min; and / or,

[0063] The infiltration time is 1 to 3 h; and / or,

[0064] Drying is carried out by the usual method of the prior art, such as hot air drying at a temperature of 60 to 90 °C; and / or,

[0065] The mass ratio of the reinforcing fiber to the coupling agent is 100:(0.01 to 2), preferably 100:(0.4 to 1.2); and / or,

[0066] The mass ratio of the coupling agent to water is (0.01 to 0.5):100, preferably (0.2 to 0.4):100.

[0067] The fifth object of the present invention is to provide a method for preparing a micro-foamed material, including:

[0068] After melting and mixing all the components in the above weight parts, extruding, calendering or injection molding is carried out to obtain the micro-foamed material; preferably,

[0069] After mixing the components evenly in a high-speed mixer, first carry out molding pressing in a molding press, and then carry out molding pressing in a cold molding machine; more preferably,

[0070] In the molding press,

[0071] The molding pressing temperature is 200 to 340 °C;

[0072] The molding pressing pressure is 10 to 20 MPa;

[0073] The molding pressing time is 10 to 60 min;

[0074] The melting of the matrix resin has a certain process. Different molding pressing gradient temperatures can be set at 200 to 340 °C to ensure good heat melting of the matrix resin, and at the same time, adjust the molding pressing at 10 to 20 MPa to make it take shape.

[0075] In the cold molding machine,

[0076] The cold molding pressing temperature is 10 to 30 °C;

[0077] The cold molding pressing pressure is 5 to 15 MPa;

[0078] The cold molding pressing time is 5 to 20 min.

[0079] The sixth object of the present invention is to provide an application of a core-shell foaming agent and a micro-foamed material in the fields of communication, electronics, automobiles, medical treatment, and aerospace, preferably in the applications of electronic and electrical, 5G communication, and radar.

[0080] Compared with the prior art, the beneficial effects of the present invention:

[0081] The present invention solves the problems existing in the prior art that the foaming agent is not resistant to high temperatures, the foaming material has poor strength, and the dielectric loss is large. The core-shell foaming agent prepared by the present invention has an outer shell composed of an acrylic polymer or copolymer, and the shell layer of the polymer coating structure can protect the foaming agent from reacting prematurely during the material preparation process, which is beneficial to the dispersion of the foaming agent and more effectively foams in situ during molding. The core is a temperature-resistant foaming agent, which decomposes carbon dioxide, nitrogen and ammonia at a high processing temperature above 300°C, and can be applied to the field of high-temperature foaming.

[0082] The micro-foamed material prepared by the present invention selects a high-temperature resistant base resin, and the fiber is surface-modified by a hydrocarbon-based polyepoxy carboxylate coupling agent, thereby giving the micro-foamed material better mechanical properties and improving its high-temperature resistance. The core-shell foaming agent makes the micro-foamed material more dispersible and capable of in-situ foaming, and is introduced into the system together with a flow improving agent with a branched structure, thereby giving the micro-foamed material excellent strength, rigidity, dielectric properties and processing properties, thereby achieving better technical effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0083] Figure 1 This is a scanning electron microscope image of the cross-section microstructure of the micro-foamed material prepared in Example 2;

[0084] Figure 2 This is a scanning electron microscope image of the cross-sectional microstructure of the non-foamed material prepared in Comparative Example 2. DETAILED DESCRIPTION

[0085] The present invention is described in detail below in conjunction with specific drawings and embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by those skilled in the art based on the content of the present invention still fall within the scope of protection of the present invention.

[0086] The raw materials used in the examples are all conventional commercially available raw materials;

[0087] The coupling agent used for the reinforcing fiber is prepared according to the method in Chinese invention patent CN112225944A:

[0088] Coupling agent A (p-tert-butylbenzoyloxy polypropylene oxide (3) / ethylene oxide (3) carboxylate magnesium), coupling agent B (n-dodecylamino polypropylene oxide (2) / ethylene oxide (2) carboxylate potassium):

[0089] Preparation method of coupling agent A: In a glass reaction kettle equipped with a reflux pipe, a thermometer and a stirrer, add 100 parts of p-tert-butylbenzoyloxy poly(propylene oxide)(3) / ethylene oxide(3). At 75 °C, slowly add 140 parts of 70% aqueous sodium chloroacetate solution dropwise through a dropping funnel. After the addition is completed, react for 7.5 h, and adjust the pH to 7.0 with 10% hydrochloric acid solution to obtain p-tert-butylbenzoyloxy poly(propylene oxide)(3) / ethylene oxide(3) carboxylic acid; then adjust the pH to 7.5 with a saturated aqueous solution of magnesium hydroxide, wash three times with saturated brine, and dry to obtain magnesium p-tert-butylbenzoyloxy poly(propylene oxide)(3) / ethylene oxide(3) carboxylate.

[0090] Preparation method of coupling agent B: In a glass reaction kettle equipped with a reflux pipe, a thermometer and a stirrer, add 150 parts of n-dodecylamino poly(propylene oxide)(2) / ethylene oxide(2). At 75 °C, slowly add 60 parts of 70% aqueous sodium chloroacetate solution dropwise through a dropping funnel. After the addition is completed, react for 7.5 h, and adjust the pH to 7.0 with 10% hydrochloric acid solution to obtain n-dodecylamino poly(propylene oxide)(2) / ethylene oxide(2) carboxylic acid; then adjust the pH to 9.0 with a saturated aqueous solution of potassium hydroxide, wash three times with saturated brine, and dry to obtain potassium n-dodecylamino poly(propylene oxide)(2) / ethylene oxide(2) carboxylate.

[0091] The main raw materials used in the examples are as follows:

[0092] Polyether amide: Sabic;

[0093] Polyphenylene sulfide: Solvay;

[0094] Polyamide 10T: Kingfa Science & Technology Co., Ltd.;

[0095] Polyamide 6 / 66(75 / 25): Relative viscosity 2.75, Sinopec Hunan Petrochemical Co., Ltd.;

[0096] Polyamide 6: Relative viscosity 3.98, Sinopec Hunan Petrochemical Co., Ltd.;

[0097] Basalt fiber: Diameter 12 μm, Changzhou Tianyi Engineering Co., Ltd.;

[0098] Glass fiber: Diameter 17 μm, Jushi Group Co., Ltd.;

[0099] Triisopropylphenyl phosphate: Jining Sanshi Technology Co., Ltd.;

[0100] Glycerol tristearate: Hai'an Petrochemical Co., Ltd.;

[0101] Benzotriazole: Jinan Xinshuangyue Chemical Co., Ltd.;

[0102] Methyl stearate / Sodium carbonate / 2-Hydroxyethyl acrylate / Maleic anhydride / Vinyl acetate / Cyclohexane / Ethylene glycol diacrylate / Diisopropyl peroxydicarbonate / 2,2'-Azobis(2,4-dimethylvaleronitrile): Aladdin;

[0103] Nano zinc oxide: Beijing Daojin Technology Co., Ltd.;

[0104] Branched polyamide: Chenyuan Molecular Co., Ltd.;

[0105] Trihydrazinotriazine: Wuhan Kemic Biopharmaceutical Co., Ltd.;

[0106] Styrene: Shandong Duoju Chemical Co., Ltd.;

[0107] Methyl 3-methoxyacrylate: Wuhan Shu'er Biotechnology Co., Ltd.;

[0108] Polyethylene glycol diacrylate: Sigma-Aldrich (Shanghai) Co., Ltd.

[0109] The properties of the present invention are measured by the following methods:

[0110] Flexural strength: Measured by an Instron 3344 material testing machine according to ISO 178 standard, with a flexural rate of 2 mm / min.

[0111] Elastic modulus: Measured by an Instron 3367 material testing machine according to ISO 527-2 standard, with a tensile rate of 5 mm / min.

[0112] Dielectric constant / Dielectric loss: Measured according to ASTM D150-11 standard, with a frequency of 1 MHz.

[0113] Volume resistivity: Measured according to IEC 60093 standard, with a voltage of 500 V.

[0114] The parts in the following examples and comparative examples all refer to parts by weight.

[0115]

Example 1

[0116] 1. Surface pretreatment of reinforcing fibers:

[0117] Disperse 0.5 part of magnesium p-tert-butylbenzoyloxy poly(propylene oxide)(3) / ethylene oxide(3) carboxylate in 200 parts of water, immerse 100 parts of glass fiber in the dispersion solution, perform ultrasonic treatment for 30 min, soak for 2 h, drain, and then dry with hot air at 70 °C to obtain surface-pretreated glass fiber Fiber-A.

[0118] 2. Preparation of core-shell foaming agent:

[0119] Disperse 5 parts of trihydrazinotriazine in a reaction kettle with a reflux device containing 125 parts of cyclohexane under stirring at room temperature and 300 rpm. After purging with nitrogen, introduce 90 parts of hydroxyethyl acrylate monomer, 15 parts of styrene comonomer, 1 part of ethylene glycol diacrylate crosslinking agent, and 0.3 part of diisopropylbenzene peroxide initiator. Heat up to 90 °C and continue the reaction for 6 h. After filtration, washing, and drying, the core-shell foaming agent Foam-1 is obtained, with a particle size of 20 microns, a core layer diameter of 18 microns, and a shell layer thickness of 2 microns.

[0120] 3. Preparation of microcellular foamed materials:

[0121] Put 100 parts of polyamide 10T, 30 parts of surface-treated glass fiber Fiber-A, 3.5 parts of branched polyamide, 5 parts of core-shell foaming agent Foam-1, 5.5 parts of triisopropylphenyl phosphate, 0.2 part of glyceryl tristearate, 0.4 part of benzotriazole, 0.8 part of methyl stearate, and 1 part of nano-zinc oxide into a high-speed mixer and mix thoroughly. Spread the mixed material evenly in a mold of a molding press, keep the pressure at 10 MPa for 35 min at a mold temperature of 280 °C, then keep the pressure at 20 MPa for 10 min at a mold temperature of 335 °C, and then keep the pressure at 20 MPa for 5 min at a mold temperature of 200 °C. Then place the mold in a cold mold machine and keep the pressure at 10 MPa for 10 min at a mold temperature of 20 °C. Demold to obtain the microcellular foamed material A. The comprehensive performance test results are shown in Table 1.

[0122]

Example 2

[0123] The difference from Example 1 is that in the preparation of the microcellular foamed material, 100 parts of polyamide 10T in Example 1 is replaced by 80 parts of polyamide 10T and 20 parts of polyamide 6;

[0124] Except for the above differences, other conditions in Example 2 are the same as those in Example 1, and the microcellular foamed material B is obtained. The comprehensive performance test results are shown in Table 1.

[0125]

Example 3

[0126] The difference from Example 1 is that in the preparation of the microcellular foamed material, the amount of branched polyamide used is 5 parts;

[0127] Except for the above differences, other conditions in Example 3 are the same as those in Example 1, and the microcellular foamed material C is obtained. The comprehensive performance test results are shown in Table 1.

[0128]

Example 4

[0129] The difference from Example 1 is that in the preparation of the microcellular foamed material, the amount of surface-treated glass fiber Fiber-A used is 50 parts, and the amount of branched polyamide used is 5 parts;

[0130] Except for the above differences, all other conditions of Example 4 are the same as those of Example 1, and microcellular material D is obtained. The comprehensive performance test results are shown in Table 1.

[0131]

Example 5

[0132] The difference from Example 1 is that in the preparation of the microcellular material, the dosage of surface-treated glass fiber Fiber-A is 80 parts, and the dosage of branched polyamide is 5 parts;

[0133] Except for the above differences, all other conditions of Example 5 are the same as those of Example 1, and microcellular material E is obtained. The comprehensive performance test results are shown in Table 1.

[0134]

Comparative Example 1

[0135] The difference from Example 4 is that in the preparation of the microcellular material, branched polyamide is not added;

[0136] Except for the above differences, all other conditions of Comparative Example 1 are the same as those of Example 3, and microcellular material a is obtained. The comprehensive performance test results are shown in Table 1.

[0137]

Comparative Example 2

[0138] The difference from Example 2 is that in the preparation of the microcellular material, core-shell foaming agent Foam-1 is not added;

[0139] Except for the above differences, all other conditions of Comparative Example 2 are the same as those of Example 2, and microcellular material b is obtained. The comprehensive performance test results are shown in Table 1.

[0140]

Comparative Example 3

[0141] The difference from Example 3 is that in the preparation of the microcellular material, the 30 parts of glass fiber used is untreated glass fiber;

[0142] Except for the above differences, all other conditions of Comparative Example 3 are the same as those of Example 3, and microcellular material c is obtained. The comprehensive performance test results are shown in Table 1.

[0143] Table 1 Performance test results of microcellular materials prepared in Examples 1-5 and Comparative Examples 1-3

[0144]

[0145] It can be seen from Table 1 that:

[0146] Comparing Comparative Example 1 with Example 4, no branched polyamide was added; the mechanical properties, dielectric properties, and volume resistivity of Example 4 were all superior to those of Comparative Example 1, proving that the branched polyamide can improve the mechanical properties of the microfoamed material, reduce the interfacial impedance, and endow the material with excellent electrostatic inhibition effect;

[0147] Comparing Comparative Example 2 with Example 2, no core-shell foaming agent was added; the mechanical properties, dielectric properties, and volume resistivity of Example 2 were all superior to those of Comparative Example 2, proving that the core-shell foaming agent has excellent temperature resistance, and the copolymer cross-linked outer shell controls the foaming process of the foaming agent, and nitrogen and ammonia are decomposed only at a high processing temperature above 300 °C, and a micro-nano scale pore structure can be formed in the high-temperature resistant polyamide 10T composite system, endowing the microfoamed material with excellent low dielectric properties and antistatic properties;

[0148] Comparing Comparative Example 3 with Example 3, the glass fiber added was not surface-treated with a coupling agent; the mechanical properties, dielectric properties, and volume resistivity of Example 3 were all superior to those of Comparative Example 3, proving that using a hydrocarbon-based copolymer ether-based carboxylate surface treatment agent to couple the surface of the reinforcing fiber can endow the fiber and nylon 10T composite system with excellent surface and interface compatibility performance, improve the mechanical properties of the material, and reduce the dielectric constant and loss.

[0149] Figure 1 It is the scanning electron microscope image of the cross-sectional microstructure of the microfoamed material prepared in Example 2, Figure 2 It is the scanning electron microscope image of the cross-sectional microstructure of the non-foamed material prepared in Comparative Example 2; Figures 1 - 2 In comparison, in the polyamide 10T, polyamide 6, and glass fiber composite system, by introducing a core-shell foaming agent with a surface coating structure, a dense micro-nano scale microporous structure can be in-situ foamed inside the composite material sheet during the subsequent compression molding process, endowing the microfoamed material with excellent dielectric properties.

[0150]

Example 6

[0151] 1. Surface pretreatment of reinforcing fiber:

[0152] Disperse 0.2 parts of dodecylaminopoly(propylene oxide)(2) / ethylene oxide(2) potassium carboxylate in 100 parts of water, immerse 20 parts of glass fiber in the dispersion solution, ultrasonically treat for 30 min, immerse for 2 h, drain, and then dry with hot air at 70 °C to obtain the surface-pretreated glass fiber Fiber-B.

[0153] 2. Preparation of core-shell foaming agent:

[0154] 3 parts of trihydrazinotriazine and 3 parts of sodium carbonate were dispersed in a reaction kettle with a reflux device containing 120 parts of cyclohexane under stirring at room temperature and 300 r / min. After purging with nitrogen, 95 parts of hydroxyethyl acrylate monomer, 10 parts of styrene copolymer monomer, 3 parts of maleic anhydride copolymer monomer, 1.2 parts of ethylene glycol diacrylate crosslinking agent, and 0.25 part of diisopropylbenzene peroxide initiator were introduced. The temperature was raised to 90 °C and the reaction was continued for 8 h. After filtration, washing, and drying, the core-shell foaming agent Foam-2 was obtained, with a particle size of 22 μm, a core layer diameter of 18 μm, and a shell layer thickness of 4 μm.

[0155] 3. Preparation of micro-foamed materials:

[0156] 80 parts of polyphenylene sulfide, 20 parts of polyether amide, 20 parts of surface-treated basalt fiber Fiber-B, 4 parts of branched polyamide, 3 parts of core-shell foaming agent Foam-2, 5 parts of triisopropylphenyl phosphate, 0.3 part of glyceryl tristearate, 0.3 part of benzotriazole, 1 part of methyl stearate, and 0.7 part of nano-zinc oxide were put into a high-speed mixer and mixed thoroughly. The mixed materials were spread evenly in a mold of a molding press and kept under pressure at a mold temperature of 290 °C and a molding pressure of 10 MPa for 35 min, then at a mold temperature of 335 °C and a molding pressure of 20 MPa for 15 min, and then at a mold temperature of 220 °C and a molding pressure of 20 MPa for 5 min. Then the mold was placed in a cold mold machine and kept under pressure at a mold temperature of 20 °C and a molding pressure of 10 MPa for 10 min, and the micro-foamed material F was demolded. The comprehensive performance test results are shown in Table 2.

[0157]

Example 7

[0158] The difference from Example 6 is that in the preparation of the core-shell foaming agent, the temperature-resistant foaming agent is 4.5 parts of trihydrazinotriazine and 1.5 parts of sodium carbonate; the core-shell foaming agent Foam-3 is obtained, with a particle size of 21.6 μm, a core layer diameter of 19 μm, and a shell layer thickness of 2.6 μm;

[0159] In the preparation of the micro-foamed material, the prepared core-shell foaming agent Foam-3 was used;

[0160] Except for the above differences, other conditions in Example 7 were the same as those in Example 6, and the micro-foamed material G was obtained. The comprehensive performance test results are shown in Table 2.

[0161]

Example 8

[0162] The difference from Example 6 is that in the preparation of the core-shell foaming agent, the temperature-resistant foaming agent is 1 part of trihydrazinotriazine and 5 parts of sodium carbonate; the core-shell foaming agent Foam-4 is obtained, with a particle size of 24 μm, a core layer diameter of 21 μm, and a shell layer thickness of 3 μm;

[0163] In the preparation of the micro-foamed material, the prepared core-shell foaming agent Foam-4 was used;

[0164] Except for the above differences, other conditions of Example 8 were the same as those of Example 6, and the micro-foamed material H was obtained. The comprehensive performance test results are shown in Table 2.

[0165]

Example 9

[0166] The difference from Example 6 was that in the preparation of the core-shell foaming agent, styrene comonomer and maleic anhydride comonomer were not added, and the amount of 2-hydroxyethyl acrylate monomer was changed to 108 parts; the core-shell foaming agent Foam-5 was obtained, with a particle size of 19.3 microns, a core layer diameter of 18 microns, and a shell layer thickness of 1.3 microns;

[0167] In the preparation of the micro-foamed material, the prepared core-shell foaming agent Foam-5 was used;

[0168] Except for the above differences, other conditions of Example 9 were the same as those of Example 6, and the micro-foamed material I was obtained. The comprehensive performance test results are shown in Table 2.

[0169]

Example 10

[0170] The difference from Example 6 was that in the preparation of the core-shell foaming agent, styrene comonomer was not added, and the amount of maleic anhydride comonomer was changed to 13 parts; the core-shell foaming agent Foam-6 was obtained, with a particle size of 25.1 microns, a core layer diameter of 18 microns, and a shell layer thickness of 7.1 microns;

[0171] In the preparation of the micro-foamed material, the prepared core-shell foaming agent Foam-6 was used;

[0172] Except for the above differences, other conditions of Example 10 were the same as those of Example 6, and the micro-foamed material I was obtained. The comprehensive performance test results are shown in Table 2.

[0173]

Comparative Example 4

[0174] The difference from Example 6 was that in the preparation of the core-shell foaming agent, 2-hydroxyethyl acrylate monomer was not added, and the amount of styrene comonomer was changed to 105 parts; the core-shell foaming agent Foam-7 was obtained, with a particle size of 24.5 microns, a core layer diameter of 18 microns, and a shell layer thickness of 6.5 microns;

[0175] In the preparation of the micro-foamed material, the prepared core-shell foaming agent Foam-7 was used;

[0176] Except for the above differences, other conditions of Comparative Example 4 were the same as those of Example 6, and the micro-foamed material d was obtained. The comprehensive performance test results are shown in Table 2.

[0177] Table 2 Performance test results of the micro-foamed materials prepared in Examples 6 - 10 and Comparative Example 4

[0178]

[0179] It can be seen from Table 2 that:

[0180] In Comparative Example 4, compared with Examples 6, 9 - 10, hydroxyethyl acrylate monomer was not added, and all of it was replaced equally with styrene copolymer monomer; the mechanical properties, dielectric properties, and volume resistivity of Examples 6, 9 - 10 were much better than those of Comparative Example 4, proving that by regulating the copolymer monomer ratio, the formed cross-linked shell can improve the comprehensive performance of the micro-foamed material, and the reasonable combination of acrylate monomers and copolymer monomers such as styrene and / or maleic anhydride has better performance than the combination of styrene / maleic anhydride copolymer.

[0181] In the core-shell foaming agents of Examples 6 - 10, trihydrazinotriazine and sodium carbonate are organic / inorganic composite foaming agents, which have gradient thermal decomposition temperatures respectively; at appropriate ratios, the two have excellent thermal decomposition matching degrees at high temperatures. By controlling the foaming process of the foaming agent through the copolymer cross-linked shell, carbon dioxide, nitrogen, and ammonia are decomposed only at high processing temperatures above 300 °C, forming micro-nano pore structures inside the polyphenylene sulfide / polyether amide composite material, endowing the micro-foamed material with excellent low dielectric properties, antistatic properties, and mechanical strength.

[0182]

Example 11

[0183] 1. Surface pretreatment of reinforcing fibers:

[0184] Disperse 0.15 parts of magnesium p-tert-butylbenzoyloxy poly(propylene oxide)(3) / ethylene oxide(3) carboxylate and 0.15 parts of potassium n-dodecylaminopoly(propylene oxide)(2) / ethylene oxide(2) carboxylate in 100 parts of water. Immerse 30 parts of glass fibers in the dispersion solution, ultrasonically treat for 30 min, soak for 3 h, drain, and then dry with hot air at 70 °C to obtain surface-pretreated glass fiber Fiber-C.

[0185] 2. Preparation of core-shell foaming agent:

[0186] 5 parts of trihydrazinotriazine and 2.2 parts of sodium carbonate were dispersed in a reaction kettle with a reflux device containing 100 parts of cyclohexane under stirring at room temperature and 200 rpm. After purging with nitrogen, 100 parts of hydroxyethyl acrylate monomer, 10 parts of methyl 3-methoxyacrylate monomer, 10 parts of vinyl acetate copolymer monomer, 1.44 parts of polyethylene glycol diacrylate crosslinking agent, and 0.48 part of azodiisobutyronitrile initiator were introduced. The temperature was raised to 50 °C and the reaction was continued for 1.5 h. After filtration, washing, and drying, the core-shell foaming agent Foam-8 was obtained, with a particle size of 16.8 μm, a core layer diameter of 15.5 μm, and a shell layer thickness of 1.3 μm.

[0187] 3. Preparation of micro-foamed materials:

[0188] 65 parts of polyamide 10T, 35 parts of polyamide 6 / 66, 90 parts of surface-treated glass fiber Fiber-C, 0.25 part of branched polyamide, 5 parts of core-shell foaming agent Foam-8, 0.9 part of tris(isopropylphenyl) phosphate, 0.4 part of glyceryl tristearate, 0.3 part of benzotriazole, 0.2 part of methyl stearate, and 0.2 part of nano-zinc oxide were put into a high-speed mixer and mixed thoroughly. The mixed material was spread evenly in a mold of a molding press and kept under pressure at a mold temperature of 290 °C and a molding pressure of 10 MPa for 20 min, then at a mold temperature of 335 °C and a molding pressure of 20 MPa for 12 min, and then at a mold temperature of 220 °C and a molding pressure of 20 MPa for 8 min. Then the mold was placed in a cold mold machine and kept under pressure at a mold temperature of 20 °C and a molding pressure of 10 MPa for 8 min, and then demolded to obtain the micro-foamed material K. The comprehensive performance test results are shown in Table 3.

[0189]

Example 12

[0190] The difference from Example 11 is that the preparation of the micro-foamed material is different;

[0191] Specifically:

[0192] 65 parts of polyamide 10T, 35 parts of polyamide 6 / 66, 90 parts of surface-treated glass fiber Fiber-C, 0.25 part of branched polyamide, 2 parts of core-shell foaming agent Foam-8, 5 parts of tris(isopropylphenyl) phosphate, 4 parts of glyceryl tristearate, 2 parts of benzotriazole, 1 part of methyl stearate, and 3 parts of nano-zinc oxide were put into a high-speed mixer and mixed thoroughly. The mixed material was spread evenly in a mold of a molding press and kept under pressure at a mold temperature of 290 °C and a molding pressure of 10 MPa for 30 min, then at a mold temperature of 335 °C and a molding pressure of 20 MPa for 15 min, and then at a mold temperature of 220 °C and a molding pressure of 20 MPa for 15 min. Then the mold was placed in a cold mold machine and kept under pressure at a mold temperature of 20 °C and a molding pressure of 10 MPa for 5 min;

[0193] Except for the above differences, other conditions of Example 12 were the same as those of Example 11, and a microcellular material L was obtained by demolding. The comprehensive performance test results are shown in Table 3.

[0194]

Example 13

[0195] The difference from Example 11 was that the preparation of the microcellular material was different;

[0196] Specifically:

[0197] 75 parts of polyamide 10T, 20 parts of polyether amide, 5 parts of polyamide 6, 50 parts of surface-treated basalt fiber Fiber-C, 4 parts of branched polyamide, 2.5 parts of core-shell foaming agent Foam-4, 1.5 parts of core-shell foaming agent Foam-8, 3 parts of triisopropylphenyl phosphate, 2 parts of glyceryl tristearate, 1 part of benzotriazole, 0.5 part of methyl stearate, and 0.3 part of nano-zinc oxide were put into a high-speed mixer and mixed thoroughly. The mixed material was laid flat in a mold press mold, and held at a mold temperature of 290 °C and a molding pressure of 10 MPa for 15 min, then held at a mold temperature of 335 °C and a molding pressure of 20 MPa for 10 min, and then held at a mold temperature of 220 °C and a molding pressure of 20 MPa for 20 min. Then the mold was placed in a cold mold machine and held at a mold temperature of 20 °C and a molding pressure of 10 MPa for 5 min;

[0198] Except for the above differences, other conditions of Example 13 were the same as those of Example 11, and a microcellular material M was obtained by demolding. The comprehensive performance test results are shown in Table 3.

[0199] Table 3 Performance test results of the microcellular materials prepared in Examples 11 - 13

[0200]

[0201] In Examples 1 - 13, core-shell foaming agents were prepared. The outer shell was composed of acrylate polymers or copolymers. The shell layer of the polymer coating structure could protect the foaming agent from reacting prematurely during the material preparation process, which was beneficial to the dispersion of the foaming agent and more effectively in-situ foaming during molding. Its inner core was a heat-resistant foaming agent that decomposed into carbon dioxide, nitrogen, and ammonia only at a high processing temperature above 300 °C, and could be applied to the field of high-temperature foaming.

[0202] Examples 1 to 13 The microcellular materials prepared by using the prepared core-shell blowing agent have fibers surface-modified with a hydrocarbyl polyepoxy carboxylate coupling agent, endowing the microcellular materials with better mechanical properties and at the same time improving their high-temperature resistance; the core-shell blowing agent makes their dispersion performance better and can foam in-situ. When introduced into the system together with a flow improver with a branched structure, etc., the microcellular materials are endowed with excellent strength, rigidity and dielectric properties. The preparation method is simple and easy to implement, and it is easy to achieve production scale-up, and can be applied to fields such as communication, electronics, automotive, medical, aerospace, etc.

Claims

1. A core-shell foaming agent, wherein the core of the core-shell foaming agent is a heat-resistant foaming agent; the shell of the core-shell foaming agent is at least one of a polymer of an acrylate monomer or its derivative, and a copolymer of an acrylate monomer or its derivative and a comonomer.

2. The core-shell foaming agent according to claim 1, characterized in that: the heat-resistant foaming agent is at least one of calcium carbonate, sodium carbonate, potassium carbonate, barium carbonate, magnesium carbonate, p-toluenesulfonyl semicarbazide, 4,4'-oxybis (benzenesulfonyl semicarbazide), trihydrazinotriazine, 5-phenyltetrazole; preferably a composition of at least one of sodium carbonate and potassium carbonate and at least one of p-toluenesulfonyl semicarbazide, 4,4'-oxybis (benzenesulfonyl semicarbazide), trihydrazinotriazine; more preferably a composition of sodium carbonate and trihydrazinotriazine.

3. The core-shell foaming agent according to claim 1 or 2, characterized in that: the particle size of the core-shell foaming agent is 0.1 to 50 microns, preferably 0.25 to 40 microns, more preferably 5 to 30 microns; and / or, the thickness of the shell layer of the core-shell foaming agent is 50 nanometers to 10 microns, preferably 100 nanometers to 5 microns, more preferably 0.5 to 5 microns; and / or, the diameter of the core layer of the core-shell foaming agent is 50 nanometers to 40 microns, preferably 150 nanometers to 25 microns, more preferably 4.5 to 25 microns.

4. A method for preparing a core-shell foaming agent according to any one of claims 1 to 3, comprising: Disperse the heat-resistant foaming agent in an organic solvent, and in a protective gas atmosphere, add an acrylate monomer and its derivative, a crosslinking agent and an initiator, and an optional comonomer, and carry out a reaction and then post-treatment to obtain the core-shell foaming agent.

5. The method for preparing a core-shell foaming agent according to claim 4, characterized in that: the acrylate monomer and its derivative are at least one of methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, methyl 3-methoxyacrylate, 1-adamantyl acrylate, 1-adamantyl methacrylate, 1-adamantyl 3-methoxyacrylate; and / or, the comonomer is at least one of ethylene, propylene, 1-butene, 1-hexene, 1-octene, styrene, acrylonitrile, butadiene, isoprene, maleic anhydride, vinyl acetate; and / or, the organic solvent is at least one of cyclohexane, hexane, octane, chloroform, ethylbenzene; and / or, the crosslinking agent is at least one of polyisocyanate, ethylene glycol diacrylate, propylene glycol diacrylate, butanediol diacrylate, hexanediol diacrylate, polyethylene glycol diacrylate, polypropylene glycol diacrylate, polybutylene glycol diacrylate, polyhexylene glycol diacrylate, epoxy resin-based diacrylate; and / or, The initiator is at least one of azo initiators and peroxide initiators, preferably at least one of azobisisobutyronitrile, azobisisovaleronitrile, azobisisoheptonitrile, dicumyl peroxide, benzoyl peroxide, tert-butyl benzoyl peroxide, methyl ethyl ketone peroxide, 1,1-di-tert-butyl peroxide cyclohexane, 1,1-di-tert-butyl peroxide-3,3,5-trimethylcyclohexane, di-tert-butyl peroxide, di-tert-amyl peroxide, and di-tert-pentyl peroxide; and / or, The protective gas is at least one of nitrogen and inert gases; the inert gas is preferably argon.

6. The method for preparing the core-shell foaming agent according to claim 4, characterized in that: The mass ratio of the temperature-resistant foaming agent to the total mass of acrylate monomers and their derivatives and comonomers is (2-10):100, preferably (4-6):100; and / or, The mass ratio of the comonomer to the acrylate monomers and their derivatives is (0-100):100, preferably (5-50):100, more preferably (9-20):100; and / or, The mass ratio of the total mass of the acrylate monomers and their derivatives and comonomers to the mass of the organic solvent is (1-200):100, preferably (10-150):100, more preferably (80-120):100; and / or, The ratio of the mass of the cross-linking agent to the total mass of the acrylate monomers and their derivatives and comonomers is (0.01-5):100, preferably (0.1-3):100, more preferably (0.8-1.2):100; and / or, The mass ratio of the initiator to the total mass of the acrylate monomers and their derivatives and comonomers is (0.001-1):100, preferably (0.005-0.85):100, more preferably (0.1-0.4):

100.

7. The method for preparing the core-shell foaming agent according to claim 4, characterized in that: The temperature-resistant foaming agent is dispersed in an organic solvent at room temperature under shear; the shear is achieved by stirring, and the stirring speed is preferably 100-1000 revolutions / min, more preferably 200-800 revolutions / min; and / or, The reaction temperature is 40-95°C, preferably 50-90°C; and / or, The reaction time is 0.5-12 h, preferably 1.5-10 h; and / or, The post-treatment includes suction filtration, washing, and drying.

8. A core-shell foaming agent obtained by the preparation method according to any one of claims 4-7.

9. A micro-foamed material, based on 100 parts by weight of the matrix resin, the micro-foamed material comprises the following components: The core-shell foaming agent is the core-shell foaming agent according to any one of claims 1-3, 8; The surface-treated reinforcing fiber is obtained by surface-treating the reinforcing fiber with a coupling agent.

10. The micro-foamed material according to claim 9, characterized in that: The matrix resin is at least one of semi-aromatic polyamide, wholly aromatic polyamide, aliphatic long-chain polyamide with 8-20 carbon atoms in the polymer monomer, polyphenylene sulfide, polyphenylene ether, polyimide, polyether amide, polyaramide, polyarylate, polyether aramide, polyether arylate, polyether ketone ketone, and polyether ether ketone; optionally, it further includes aliphatic short-chain polyamide with 4-6 carbon atoms in the polymer monomer; the aliphatic short-chain polyamide accounts for 5-35% of the total mass of the matrix resin; and / or, The reinforcing fiber is at least one of carbon fiber, glass fiber, aramid fiber, plant fiber, basalt fiber, metal fiber, and natural fiber; the diameter of the reinforcing fiber is preferably 5-20 microns, more preferably 9-17 microns; and / or, The functional additive is at least one of flame retardant, plasticizer, heat stabilizer, lubricant, and UV absorber; preferably, The flame retardant is at least one of triphenyl phosphate, triisopropylphenyl phosphate, tributyl phosphate, and trioctyl phosphate; and / or, The plasticizer is at least one of phthalate, glyceryl tristearate, and epoxidized soybean oil; and / or, The heat stabilizer is at least one of triphenyl phosphite, tris-(2,6-dimethylphenyl) phosphite, trimethyl phosphate, dimethylphenyl phosphate, and benzotriazole; and / or, The lubricant is at least one of methyl stearate, polyethylene glycol, and polypropylene glycol; and / or, The UV absorber is at least one of hydroxybenzodiazole, hydroxybenzotriazine, hydroxydibenzophenone, benzoxazinone, nano titanium dioxide, and nano zinc oxide; and / or, Based on 100 parts by weight of the matrix resin, The dosage of the flame retardant is 0.5-9 parts by weight; and / or, The dosage of the plasticizer is 0.05-2 parts by weight; and / or, The dosage of the heat stabilizer is 0.05-2 parts by weight; and / or, The dosage of the lubricant is 0.2-5 parts by weight; and / or, The dosage of the UV absorber is 0.5-2 parts by weight; and / or, The flow improver is at least one of polyolefin with a branched structure, polyester with a branched structure, polyether with a branched structure, polyamide with a branched structure, polystyrene with a branched structure, polydiene with a branched structure, and polyacrylate with a branched structure; and / or, The structural formula of the coupling agent is as shown in formula (I): In formula (I), R is an aliphatic hydrocarbon group or an aromatic hydrocarbon group of C 1 ~C 18 ; X is -O-, -NH-, -COO- or -C 6 H 4 O-; p is any number selected from 0 to 20; q is any number selected from 1 to 20; M is hydrogen, an alkali metal, an alkaline earth metal, ammonium or aluminum; n is 1, 2 or 3; and / or, The preparation method of the surface-treated reinforcing fiber includes: dispersing the coupling agent in water to obtain a coupling agent dispersion liquid, immersing the reinforcing fiber in the coupling agent dispersion liquid, and obtaining the surface-treated reinforcing fiber after ultrasonic treatment, immersion, and drying; preferably, The time of ultrasonic treatment is 20-40 min; and / or, The time of immersion is 1-3 h; and / or, The mass ratio of the reinforcing fiber to the coupling agent is 100:(0.01-2), preferably 100:(0.4-1.2); and / or, The mass ratio of the coupling agent to water is (0.01-0.5):100, preferably (0.2-0.4):

100.

11. A method for preparing the micro-foamed material as claimed in claim 9 or 10, Comprising: Extruding, calendering or injection molding the total components in the stated parts by weight after melting and mixing to obtain the micro-foamed material; preferably, Mixing the components evenly in a high-speed mixer, first performing compression molding in a compression molding machine, and then performing compression molding in a cold molding machine; more preferably, In the compression molding machine, The compression molding temperature is 200 - 340 °C; and / or, The compression molding pressure is 10 - 20 MPa; and / or, The compression molding time is 10 - 60 min; and / or, In the cold molding machine, The cold compression molding temperature is 10 - 30 °C; and / or, The cold compression molding pressure is 5 - 15 MPa; and / or, The cold compression molding time is 5 - 20 min.

12. Application of the core-shell foaming agent according to any one of claims 1 to 3, 8 and the micro-foamed material according to claim 9 or 10 in the fields of communication, electronics, automotive, medical, and aerospace, preferably in the applications of electronic and electrical, 5G communication, and radar.

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