A composition based on hollow glass microbeads and a process for the production thereof

Abstract

The application discloses a kind of composition based on hollow glass microsphere and preparation method thereof, it is related to material science technology field.The application first by constructing a kind of pre-composite functional microsphere with specific hierarchical structure as core basic functional unit, then with thermosetting resin matrix, latent curing system, functional synergistic additive package and composite solvent system multiple components, and matching preparation process synergistic effect, preparation a kind of composition based on hollow glass microsphere, to ensure the integrity of hollow glass microsphere structure under the premise, realize the uniform dispersion of hollow glass microsphere in coating system and the strong bonding of micro interface, to obtain the high-performance composite coating material with ultralight, high heat insulation efficiency, excellent mechanical strength and long-term service stability.

Description

Technical Field

[0001] This invention relates to the field of materials science and technology, specifically to a composition based on hollow glass microspheres and its preparation method. Background Technology

[0002] With increasingly stringent requirements for material performance in modern industry, functional coatings, as an important means of surface protection and functional enhancement, have become a research hotspot in the field of materials science and engineering. These coatings, with their unique thermal insulation, lightweight, corrosion resistance, and other specific physicochemical properties, demonstrate irreplaceable application value in many high-tech fields such as building energy conservation, industrial protection, transportation, and even aerospace. Of particular note is the coating system based on hollow glass microspheres (HGM), which, due to its significant ultra-lightweight characteristics and excellent thermal insulation performance, has broad application prospects in reducing structural weight and improving thermal management efficiency, and is gradually becoming an important direction for the development of high-performance coatings.

[0003] Existing technologies have made some progress in improving the overall performance of coatings. For example, Chinese patent document CN114106666B discloses a composition aimed at improving the mechanical properties and chemical resistance of coating films. This solution mainly constructs a resin matrix with balanced performance by optimizing the ratio of aromatic epoxy compounds, amine curing agents, silane coupling agents, and specific solvents. This technology has indeed effectively solved key problems such as coating hardness, adhesion, and resistance to chemical media erosion in a certain period, providing a reliable solution for industrial corrosion prevention and structural protection. However, due to inherent deficiencies in lightweighting and thermal insulation performance, this technology cannot meet the market's urgent demand for high-efficiency energy-saving coatings. Specifically, its relatively high coating density significantly limits its application in scenarios requiring strict weight control or pursuing ultimate thermal insulation effects (such as aircraft interiors and high-energy-consuming building exteriors). In addition, this technology has strict requirements for solvent selection; the use of high-volatile organic compounds may not only increase production costs but also pose potential environmental pressures, contradicting current environmental regulations and the concept of sustainable development.

[0004] Building upon this, another Chinese patent document, CN11594104B, focuses on improving the non-flammability and weather resistance of the composition. This technical solution, through the careful selection of flame retardants and anti-aging components, enables the coating to maintain structural integrity and functional stability even under extreme temperatures or prolonged outdoor exposure. This is significant for applications with high fire safety requirements or those exposed to harsh climates for extended periods. However, while this technology emphasizes safety and durability, it falls short in core areas such as lightweighting and thermal insulation, making it difficult to meet market demands for multifunctional, integrated coatings. Furthermore, to ensure the material's non-flammability and excellent weather resistance, the coating's preparation process often places high demands on the purity of raw materials and reaction conditions. This can lead to complex production processes, reduced production efficiency, and consequently, increased manufacturing costs, hindering large-scale industrial application.

[0005] As the application scenarios for functional coatings expand and the market demands more stringent integrated performance indicators, the inherent characteristics of the aforementioned existing technologies at the principle level are gradually revealing their limitations in addressing new challenges. Specifically, while hollow glass microspheres are ideal lightweight and heat-insulating fillers, their introduction has brought about multiple deep-seated technical contradictions.

[0006] First, the extremely low density of hollow glass microspheres differs significantly from the density of the organic resin matrix. Combined with their spherical structure and high specific surface area, this makes them highly prone to settling or floating in viscous coating systems, leading to severe agglomeration. This uneven dispersion directly results in structural defects within the coating, preventing the coating from fully and stably achieving its lightweight and thermal insulation properties. It may even create localized stress concentration points, weakening the overall mechanical properties of the coating. The fundamental reason is that traditional stirring or dispersion methods may struggle to overcome the van der Waals forces between the microspheres and the insufficient shear forces within the liquid, thus failing to maintain a stable suspension system.

[0007] Secondly, hollow glass microspheres are essentially inorganic glass materials, and their surfaces are typically hydrophilic, while the resin matrix in coatings is mostly organic polymers, which are hydrophobic. This inherent difference in chemical properties leads to poor interfacial compatibility and weak interfacial bonding between the two. During the coating curing process, the hollow glass microspheres and the resin matrix fail to form effective chemical bonds or physical entanglement, making the interface the weakest area in the coating. As a result, although the coating achieves overall lightweighting and thermal insulation, its mechanical strength (such as tensile strength, impact resistance, and abrasion resistance) and durability will significantly decrease, especially during long-term service or under external stress, making it prone to failure modes such as cracking and delamination. This sharply contradicts the inherent requirements of functional coatings for high strength and long service life in harsh application environments (such as industrial corrosion protection and aerospace structural components).

[0008] Furthermore, the inherent thin-walled and brittle structure of hollow glass microspheres makes them extremely prone to breakage under the mechanical shear stress during coating preparation. In industrial production, high-intensity stirring, grinding, or pumping are typically required to achieve thorough mixing of components and initial dispersion of microspheres. However, the shear or impact forces generated by these processes often far exceed the tolerance limits of the hollow glass microspheres, leading to the breakage of a large number of microspheres. Once the microspheres break, their internal cavity structure is destroyed, resulting in the loss of their core functions of lightweighting and thermal insulation. Moreover, the broken glass fragments may become harmful stress concentration points, further deteriorating the mechanical properties of the coating. This presents a dilemma: insufficient stirring intensity leads to uneven dispersion; excessive stirring intensity results in microsphere breakage, neither of which achieves the desired effect. In addition, for solvent-based systems, selecting a solvent system that can effectively dissolve the resin, effectively disperse the microspheres, and is environmentally friendly is also a challenge that current technologies urgently need to address.

[0009] In summary, the core technical challenge currently facing the coatings industry is not simply adding hollow glass microspheres to existing systems, but rather how to develop a composition and its preparation method that can effectively solve the deep-seated technical problems such as poor dispersion uniformity of hollow glass microspheres in the coating matrix, weak interfacial bonding, and fragility during processing, while taking into account environmental protection and preparation process efficiency, thereby achieving a synergistic improvement in multiple properties of coatings, including lightweighting, thermal insulation, mechanical strength, weather resistance, and environmental friendliness. This has become a key challenge and an urgent technical problem for those skilled in the art. Summary of the Invention

[0010] This invention provides a composition based on hollow glass microspheres and its preparation method, aiming to fundamentally overcome the triple technical bottlenecks in the prior art, namely, uneven dispersion, weak interfacial bonding, and easy breakage caused by the inherent low density, surface chemical inertness, and thin-wall brittleness of hollow glass microspheres during the composite process with organic resin matrices. This invention constructs a pre-composite functional microsphere with a specific hierarchical structure as the core functional unit and matches it with a synergistic preparation process. The goal is to achieve macroscopic uniform dispersion and strong microscopic interfacial bonding of the hollow glass microspheres in the coating system while ensuring the structural integrity of the hollow glass microspheres, thereby obtaining a high-performance composite coating material that combines ultra-lightweight properties, high thermal insulation efficiency, excellent mechanical strength, and long-term service stability.

[0011] The technical solution adopted in this invention is as follows:

[0012] One objective of this invention is to provide a composition based on hollow glass microspheres, comprising the following components in parts by weight:

[0013] 15-45 parts of hierarchical pre-composite functional microspheres;

[0014] 40-70 parts of thermosetting resin matrix;

[0015] 5-20 parts of the latent curing system;

[0016] Functional synergistic agent pack 1-5 portions;

[0017] And 20-40 parts of the composite solvent system;

[0018] The hierarchical pre-composite functional microspheres are a three-layer core-shell structure, which consists of the following components: a hollow glass microsphere core, accounting for 70-90% of the total mass of the microspheres; an interface-strengthening transition layer, accounting for 2-10% of the total mass of the microspheres, wherein the interface-strengthening transition layer is a functional molecular layer in situ chemically grafted onto the outer surface of the hollow glass microsphere core, and is formed by copolymerization and crosslinking of at least two synergistic silane coupling agents; and a controllable dissolution and release shell, accounting for 8-20% of the total mass of the microspheres, wherein the controllable dissolution and release shell is a thermoplastic block copolymer coating the interface-strengthening transition layer.

[0019] In this invention, the interface toughening transition layer serves to improve the mechanical properties of the microbead nucleus and its wettability with the resin matrix; the controllable dissolution and release shell serves to act as a robust physical barrier during the early high-energy dispersion stage of coating preparation, completely encapsulating the internal hollow glass microbead nucleus and protecting it from direct impact and breakage by mechanical shear forces; and in the later stage of preparation, the shell can be controllably dissolved under the action of a specific solvent, releasing the surface-toughened microbead nucleus in situ and uniformly into the resin matrix.

[0020] Furthermore, the hollow glass microsphere core is a borosilicate glass microsphere with a particle size distribution of 30–80 μm and a standard deviation of particle size distribution not exceeding 15 μm; its wall thickness is 1.5–3.0 μm; and its true density is 0.35–0.55 g / cm³. 3 Its compressive strength is not less than 35 MPa; its outer surface has a nanoscale porous morphology formed by acid etching and rapid cooling process, with a surface roughness Ra value of 80~150nm. This structure is designed to provide physical anchoring points for the subsequent interface layer.

[0021] Furthermore, there are two types of silane coupling agents used to form the interface toughening transition layer. The first type of silane coupling agent is an aminosilane containing long-chain alkyl groups, which functions by reacting the amino group with another silane coupling agent and the epoxy groups in the subsequent resin matrix to form a stable covalent bond. The second type of silane coupling agent is a silane containing epoxy functional groups, which functions by allowing self-polymerization between epoxy groups and forming a dense protective layer with a three-dimensional network structure on the surface of the microspheres. This protective layer not only enhances the mechanical strength of the microspheres but also improves their wettability with the resin matrix.

[0022] Furthermore, the aminosilane is specifically N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and the silane containing epoxy functional groups is specifically 3-glycidyl etheroxypropyltrimethoxysilane. The molar ratio of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane to 3-glycidyl etheroxypropyltrimethoxysilane is 1:1 to 3. The thickness of the interface toughening transition layer is 50 to 100 nm. The molar ratio of the two silane coupling agents is set to 1:1 to 1:3 to ensure that the formed transition layer has both flexibility and rigidity, effectively alleviating interface stress concentration.

[0023] Furthermore, the thermoplastic block copolymer is composed of A block and B block, wherein the A block is a polycaprolactone block, which has good physical adsorption and entanglement with the interface toughening transition layer and plays a toughening effect in the final cured product; the B block is a polymethyl methacrylate block, which has excellent compatibility with the thermosetting resin matrix (such as epoxy resin); the number average molecular weight of the block copolymer is controlled at 8000~15000, and the mass ratio of polycaprolactone to polymethyl methacrylate is 3~7:7.

[0024] Furthermore, the thermosetting resin matrix is ​​a bisphenol A type epoxy resin. This type of epoxy resin is chosen because it has excellent chemical compatibility with the PMMA blocks and interfacial toughening transition layer in the hierarchical pre-composite functional microspheres, which is beneficial for forming a uniform and stable curing network. The latent curing system is a microencapsulated modified aliphatic amine curing agent. The capsule wall material is a polyurethane-urea copolymer, and the core material is a flexible amine adduct prepared by pre-reaction of m-phenylenediamine and liquid polysulfide rubber. The average particle size of the microcapsules is 5~10μm, and the capsule wall thickness is 0.5~1μm. This capsule wall thickness is sufficient to maintain the structural integrity under room temperature and conventional stirring conditions, without releasing the curing agent. Its latent activation mechanism is as follows: after the coating is applied, heating at 60~80℃ for 10~20 minutes, or after the composite solvent system has completely evaporated, causes the capsule wall to rupture due to changes in osmotic pressure, thereby releasing the active curing agent and initiating the cross-linking curing reaction of the epoxy resin. This latent curing system significantly extends the pot life of the composition and ensures that the curing reaction only begins after all components have reached their optimal dispersion state, avoiding performance degradation caused by premature gelation. The functional synergistic additive package contains the following components by weight: 0.5-1.5 parts of organically modified montmorillonite thixotropic agent, which rapidly establishes a three-dimensional network structure in the system after the microsphere shell dissolves and the microspheres are released, effectively inhibiting the sedimentation or floating of the microspheres using its yield value characteristics; 0.3-1.0 parts of polyether-modified polydimethylsiloxane leveling agent, which reduces the surface tension of the coating film, improves leveling, and eliminates surface defects such as pinholes and orange peel; and nano-dimethylsiloxane... 0.2-2.5 parts of titanium dioxide light stabilizer, which adopts the rutile crystal form with an average particle size of less than 50 nm and is coated with organosilicon, are used to absorb ultraviolet light and protect the polymer matrix from photodegradation, thereby improving the weather resistance of the coating. The composite solvent system consists of methyl isobutyl ketone (MIBK) and butyl acetate in a volume ratio of 2-4:1. MIBK has a strong dissolving ability for the thermosetting resin matrix but does not dissolve the controllable dissolution and release shell layer, and is used in the initial high-energy dispersion stage of the preparation process. Butyl acetate has excellent solubility for the controllable dissolution and release shell layer and is added as a "trigger solvent" in the later stage of the preparation process to achieve the controllable dissolution of the shell layer. This dual-solvent system design is the key to realizing the "protection-release" mechanism in the preparation method of the present invention.

[0025] A second objective of this invention is to provide a unique preparation method that matches the above-described composition, the preparation method comprising the following steps:

[0026] (1) Preparation of hierarchical pre-composite functional microspheres;

[0027] (2) High-energy pre-dispersion: In a closed high-speed dispersion vessel, all the metered graded pre-composite functional microspheres, all the metered thermosetting resin matrix, all the metered functional synergistic additives and 70-80% methyl isobutyl ketone are mixed, and the high-speed disperser is started to perform strong dispersion at a speed of 1500-2500 r / min for 30-45 minutes. During this stage, because the microspheres are protected by a strong shell, they can withstand high shear force and remain unbroken. At the same time, the heavier pre-composite microspheres are easy to achieve macroscopic uniform distribution in the viscous resin liquid.

[0028] (3) Low-energy dissolution and release and homogenization: Keep the stirred tank sealed and reduce the speed to a low-speed stirring state of 300~500 r / min. Slowly add all the metered butyl acetate and the remaining methyl isobutyl ketone by a drop pump. After the addition is completed, continue stirring at this low speed for 60~90 minutes to ensure that the controllable dissolution and release shell is completely dissolved and the surface-reinforced microbead core is released into the resin matrix in a smooth and uniform manner to form a stable suspension system. This process avoids any mechanical damage to the released bare microbeads.

[0029] (4) Introduction of curing system and packaging of finished product: Cool the base slurry obtained in step (3) to room temperature, add all the metered latent curing system to the base slurry under extremely low stirring speed of less than 200 r / min, stir slowly for 10 to 15 minutes to make it evenly mixed, filter through a 100 mesh filter, perform vacuum degassing treatment, and then seal and package to obtain the composition.

[0030] Furthermore, the preparation process of the hierarchical pre-composite functional microspheres includes the following steps:

[0031] (1.1) Grafting of interface toughening transition layer: The hollow glass microsphere core is placed in toluene solvent, ultrasonically dispersed for 15 minutes, heated to 110℃, and a pre-mixed solution of at least two synergistic silane coupling agents is added dropwise. The mixture is refluxed for 4-6 hours. After the reaction is completed, the modified microspheres with interface toughening transition layer grafted on the surface are obtained by centrifugation, washing and drying.

[0032] (1.2) Controllable dissolution and release shell coating: The modified microspheres obtained in step (1.1) are used as fluidized particles in a fluidized bed coating process. The thermoplastic block copolymer is dissolved in dichloromethane to form a coating solution with a concentration of 5-10%. The coating solution is atomized and sprayed into the fluidized bed through the bottom nozzle. At an air inlet temperature of 40-50°C, the coating solution is uniformly attached to the surface of the modified microspheres. After the solvent evaporates quickly, a uniform and dense shell is formed. By controlling the amount of spraying, the shell thickness is precisely controlled, and the hierarchical pre-composite functional microspheres are finally obtained.

[0033] Furthermore, the preparation process of the hollow glass microsphere core is as follows: using water glass as the silicon source and boric acid as the boron source, polyethylene glycol, a pore-forming agent, is added to the solution, and precursor powder is prepared by spray drying; subsequently, the precursor powder is calcined and foamed at high temperature in a tube furnace at 800~950℃, while a nitrogen atmosphere containing trace amounts of hydrogen fluoride is introduced. The hydrogen fluoride gas etches the surface of the microspheres to form a nanoscale porous structure; after calcination, it is rapidly cooled under nitrogen protection to obtain the hollow glass microsphere core; in the glass composition of the prepared hollow glass microsphere core, the mass percentage of silicon dioxide is 65~75%, the mass percentage of boron trioxide is 10~18%, and the sum of the mass percentages of sodium oxide and potassium oxide is less than 5%. This ratio ensures that the core has a low coefficient of thermal expansion and excellent chemical stability.

[0034] The third objective of this invention is to disclose the application of the described composition as a surface treatment material in the preparation of industrial corrosion protection, aerospace structural components, transportation components, and exterior walls of high-energy-consuming buildings.

[0035] In summary, compared with the prior art, the present invention has the following advantages and benefits:

[0036] 1. This invention solves the problem of the fragility of hollow glass microspheres in processing by creating hierarchical pre-composite functional microspheres. The introduction of process-assisted shell layers enables high-energy dispersion, ensuring the macroscopic uniformity of functional fillers in the matrix. The subsequent controllable dissolution and release mechanism ensures that the structural integrity of the microspheres is as high as 99% or more at the moment of release, far exceeding the traditional mixing process.

[0037] 2. This invention fundamentally improves the interfacial compatibility between inorganic microspheres and the organic resin matrix by constructing a toughened interfacial transition layer. The interfacial layer with a three-dimensional network structure formed by bissilane copolymerization and crosslinking, combined with the nanoporous anchoring structure on the surface of the microsphere core, achieves a multi-scale, strong interfacial bond from physical entanglement to chemical bonding. This results in a more than 30% improvement in the tensile strength, impact resistance, and wear resistance of the cured coating compared to systems modified with only a single coupling agent.

[0038] 3. This invention achieves precise process control of "protection first, release later" for microspheres by matching a unique two-stage dispersion process with a dual solvent system. This process decouples macroscopic dispersion and microscopic homogenization, breaking through the limitation of traditional processes where dispersion effect and microsphere integrity cannot be simultaneously achieved. This results in a final coating without agglomeration or defects, thereby maximizing and stably maintaining its thermal insulation performance, with a thermal conductivity consistently below 0.06 W / (m·K).

[0039] 4. By employing a latent curing system, this invention provides the composition with an extremely long storage period and application window, while ensuring that the curing reaction takes place under the most ideal material distribution conditions, thus guaranteeing the uniformity and repeatability of the final coating performance and providing a solid technical guarantee for large-scale industrial production and application.

[0040] In summary, compared with existing technologies, this invention provides a systematic solution that achieves a comprehensive breakthrough in the preparation process, structural performance, and application reliability of hollow glass microsphere functional coatings. The novel composition prepared can be widely used in industrial corrosion protection, aerospace structural components, transportation components, and surface treatment of high-energy-consuming building exteriors. Attached Figure Description

[0041] Figure 1 The diagram shows the structure of the hierarchical pre-composite functional microspheres described in this invention. The numbers in the diagram represent: 1. Hollow glass microsphere core; 2. Interface toughening transition layer; 3. Controllable dissolution and release shell.

[0042] Figure 2 The process flow diagram for preparing the hierarchical pre-composite functional microspheres described in Example 1 is shown below.

[0043] Figure 3 This is a scanning electron microscope (SEM) image of the hollow glass microsphere core prepared in Example 1.

[0044] Figure 4 A schematic diagram of the preparation method of the composition provided by the present invention. Detailed Implementation

[0045] The present invention will be described in detail below with reference to specific embodiments and examples, thereby making the advantages and various effects of the present invention more clearly apparent. Those skilled in the art should understand that these specific embodiments and examples are for illustrative purposes only and are not intended to limit the present invention.

[0046] Throughout this specification, unless otherwise specified, the terminology used herein should be understood as having the meaning commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In the event of any conflict, this specification shall prevail.

[0047] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0048] This invention discloses a systematic technical solution, the core of which lies in a specially structurally designed composition and a precisely matched preparation method. This solution aims to fundamentally solve a series of technical challenges faced when applying hollow glass microspheres in an organic resin matrix. The composition, as a multi-component synergistic system, comprises, by weight: hierarchical pre-composite functional microspheres in the range of 15-45 parts; a thermosetting resin matrix in the range of 40-70 parts; a latent curing system in the range of 5-20 parts; a functional synergistic agent package in the range of 1-5 parts; and a composite solvent system composed of methyl isobutyl ketone and butyl acetate in the range of 20-40 parts. These components are organically combined through the preparation method detailed later, ultimately forming a high-performance final composition.

[0049] In one specific embodiment, the hierarchical pre-composite functional microspheres are the core carrier of the technical concept of this invention, and are themselves a precise composite with a multi-layered core-shell structure. (Refer to...) Figure 1 The microsphere comprises, from the inside out, a hollow glass microsphere core 1, an interface-strengthening transition layer 2, and a controllable dissolution and release shell 3. In the total mass composition of the hierarchical pre-composite functional microsphere, the hollow glass microsphere core 1, as the core functional unit, accounts for the vast majority of the mass, ranging from 70% to 90%; the interface-strengthening transition layer 2, which acts as a key interface bridge, accounts for 2% to 10% of the mass; and the controllable dissolution and release shell 3, which serves as a temporary protective structure, accounts for 8% to 20% of the mass.

[0050] Furthermore, the physicochemical properties of the hollow glass microsphere core 1 were strictly defined to ensure its performance as a lightweight and heat-insulating functional component. The core is a borosilicate glass sphere manufactured using a specific process. Its average particle size is precisely controlled within the range of 30–80 μm, and through meticulous process control, the standard deviation of its particle size distribution is no greater than 15 μm. This narrow distribution characteristic is crucial for obtaining a uniform coating structure. The wall thickness of the microspheres ranges from 1.5 to 3.0 μm, an optimized result that maximizes the hollowness to achieve lightweighting while ensuring sufficient mechanical strength. Its actual density is controlled between 0.35 and 0.55 g / cm³. 3The extremely low temperature is the foundation for achieving the final ultra-lightweight coating. In terms of mechanical properties, its compressive strength is no less than 35 MPa, obtained through hydrostatic testing under 90% survival rate conditions, ensuring its structural stability under certain processing and service stresses. Crucially, the outer surface of the core exhibits a nanoscale porous morphology formed through a synergistic process of acid etching and rapid cooling, with its surface roughness Ra value controlled between 80 and 150 nm. This microporous structure significantly increases the specific surface area and provides a solid foundation for the physical anchoring of the subsequent interface toughening transition layer 2. Chemically, its glass formulation has been optimized, with a silica mass content of 65-75%, a boron trioxide mass content of 10-18%, and the total content of sodium oxide and potassium oxide, serving as network ions, strictly limited to below 5%. This ratio endows the core with an extremely low coefficient of thermal expansion and excellent resistance to chemical corrosion.

[0051] As a crucial bridge connecting the inorganic core and the organic matrix, the interface-strengthening transition layer 2 is a functional nanomolecular layer directly grown on the outer surface of the hollow glass microsphere core 1 using in-situ chemical grafting technology. The uniqueness of this transition layer lies in its formation by copolymerization and crosslinking reaction of at least two silane coupling agents with specific functions. The first silane coupling agent is an aminosilane containing a long-chain alkyl group; a specific example is N-(2-aminoethyl)-3-aminopropyltrimethoxysilane. The trimethoxysilyl group of this molecule hydrolyzes to a silanol group in the presence of water, forming a stable -Si-O-Si- chemical bond with the surface of the core 1. The amino group (-NH2) at the other end acts as an active functional group, capable of undergoing a ring-opening addition reaction with the epoxy groups in the thermosetting resin matrix during subsequent curing, thereby establishing a strong covalent bond between the inorganic core and the organic matrix. The second type of silane coupling agent is a silane containing epoxy functional groups. A specific example is 3-glycidyl etheroxypropyltrimethoxysilane. This silane molecule is also bonded to the surface of the core 1 through its trimethoxysilane end. The epoxy functional groups it carries have a dual function: some epoxy groups can undergo self-polymerization to form a dense cross-linked layer with a three-dimensional network structure on the surface of the microspheres. This cross-linked layer is like a "nano-armor", which significantly enhances the mechanical strength of the microsphere core itself. The other part of the unreacted epoxy groups greatly improves the wettability and compatibility between the surface of the microspheres and the epoxy resin matrix. In order to obtain an optimized interface that combines flexibility and rigidity, the molar ratio of the two silane coupling agents is set in a specific range, namely 1:1 to 1:3. This synergistic effect effectively alleviates the stress concentration phenomenon at the interface caused by the difference in modulus. The thickness of the interface toughening transition layer 2 is precisely controlled on the scale of 50 to 100 nm.

[0052] In a preferred embodiment of the present invention, the controllable dissolution and release shell 3 is a functional outer shell that plays a temporary, sacrificial role in the composition preparation process. Its material is a non-reactive thermoplastic block copolymer that is highly compatible with the thermosetting resin matrix. Specifically, this block copolymer consists of A-blocks and B-blocks, namely a polycaprolactone-block-polymethyl methacrylate (PCL-b-PMMA) copolymer. The polycaprolactone (PCL) segment, as the A-block, exhibits good physical adsorption and molecular chain entanglement with the interface toughening transition layer 2 already formed on the surface of the microspheres due to its molecular structure characteristics, ensuring a tight fit between the controllable dissolution and release shell 3 and the interface toughening transition layer 2. Simultaneously, the PCL segment itself possesses good toughness, and even a small amount of residue in the final cured product can still provide a certain toughening effect. The polymethyl methacrylate (PMMA) segment, as the B-block, exhibits excellent thermodynamic compatibility with the subsequently introduced thermosetting resin matrix (specifically epoxy resin), which is beneficial for the uniformity and stability of the system after the shell dissolves. The number-average molecular weight of this PCL-b-PMMA block copolymer is controlled within the range of 8000~15000, while the mass ratio of the two blocks, PCL and PMMA, is controlled at 3~7:7. The core technical function of this controllable dissolution and release shell 3 is manifested in the high-energy dispersion stage in the early stage of coating preparation, where high shear forces must be applied. It acts as a robust and resilient physical barrier, completely encapsulating the fragile, surface-modified hollow glass microspheres inside, enabling them to withstand the direct impact and fluid shear forces from the high-speed stirring blades, thereby preventing breakage. In the subsequent stages of the preparation process, the controllable dissolution and release shell 3 can be completely and controllably dissolved under the action of a specific solvent (i.e., butyl acetate), thereby releasing the hollow glass microsphere core 1, which has undergone interface toughening modification, in situ, uniformly and without damage into the thermosetting resin matrix.

[0053] In the overall formulation of the composition, the thermosetting resin matrix is ​​a bisphenol A type epoxy resin with excellent comprehensive performance. To ensure the density and performance of the cured network, its epoxy equivalent (EEW) is limited to the range of 184-192 g per ounce. This specific type of epoxy resin is selected based on the precise matching of its molecular structure with the chemical properties of each layer in the hierarchical pre-composite functional microspheres. Its epoxy groups can not only react with the amino groups on the interfacial toughening transition layer 2, but also achieve good intermolecular forces with the PMMA blocks in the controllable dissolution and release shell layer 3, thereby forming a uniform and stable three-dimensional cross-linked network without obvious interfacial defects after the entire system is cured.

[0054] To achieve precise control over the curing process and impart a long shelf life and application period to the composition, this invention employs an advanced latent curing system. The core component of this system is a microencapsulated modified aliphatic amine curing agent. The capsule wall material is a polyurethane-urea copolymer with excellent mechanical strength and chemical stability. The core material is a flexible amine adduct, prepared by pre-reacting m-phenylenediamine with liquid polysulfide rubber under specific conditions. This design imparts a certain degree of internal toughening effect to the curing agent. The average particle size of the microcapsules is controlled at 5–10 μm, and the capsule wall thickness is 0.5–1 μm. This wall thickness is sufficient to ensure that the structure remains intact under room temperature storage and conventional stirring conditions, preventing premature release of the active amine curing agent within the core. Its latent activation mechanism has a dual triggering mode: after the coating is applied to the substrate surface, applying gentle heat, such as baking at 60-80°C for 10-20 minutes, will soften or rupture the capsule wall; alternatively, without heating, the osmotic pressure of the system changes significantly as the composite solvent evaporates, and this osmotic pressure difference can also cause the capsule wall to rupture. Once the capsule wall ruptures, the highly active curing agent is rapidly released and undergoes a cross-linking and curing reaction with the surrounding epoxy resin matrix. This latent curing system successfully separates the material mixing and dispersion process from the chemical curing process in time, ensuring that the curing reaction only starts after all components (especially hollow glass microspheres) have reached their most ideal and uniform dispersion state. This fundamentally avoids microsphere agglomeration, sedimentation, and severe degradation of the final coating performance caused by premature gelation.

[0055] To further optimize the overall performance and application properties of the coating, the composition also includes a functional synergistic agent package. This agent package is composed of a variety of functional additives, and its specific components, by weight, include: 0.5 to 1.5 parts of organically modified montmorillonite thixotropic agent. Its function is to rapidly establish a reversible three-dimensional physical network structure in the entire liquid system after the controlled dissolution and release of the shell layer 3 of the hierarchical pre-composite functional microspheres and the release of the hollow glass microsphere core 1 into the resin matrix. Utilizing its shear thinning and high yield value under static conditions, it effectively inhibits the sedimentation or floating of the extremely low-density hollow glass microspheres due to gravity, ensuring that they remain in a uniform suspension state until curing is complete. The additive package also contains 0.3–1.0 parts of polyether-modified polydimethylsiloxane leveling agent, which significantly reduces the surface tension of the liquid coating, improves its spreading and leveling properties on the substrate, and effectively eliminates surface defects such as pinholes, craters, and orange peel that may occur during the drying and curing process, resulting in a smooth and even coating appearance. In addition, the additive package also contains 0.2–2.5 parts of nano-titanium dioxide light stabilizer. This light stabilizer uses a rutile crystal form with low photocatalytic activity and high UV shielding efficiency, with an average particle size of less than 50 nm, and its particle surface is coated with silicone. This surface treatment not only improves its dispersibility in the organic resin but, more importantly, passivates the photoactive sites on its surface. Its main function is to efficiently absorb ultraviolet energy from sunlight, protecting the polymer resin matrix from photodegradation and chain scission, thereby significantly improving the long-term weather resistance and service life of the final coating.

[0056] Another key feature of this invention lies in its unique composite solvent system, which consists of a first solvent and a second solvent in a specific volume ratio. This system forms the chemical basis for the aforementioned "protection-release" preparation strategy. The first solvent is methyl isobutyl ketone (MIBK), and the second solvent is butyl acetate. Throughout the composite solvent system, the volume ratio of the first solvent to the second solvent is controlled within the range of 2 to 4:1. The selection and use of these two solvents are carefully designed: the first solvent, MIBK, has extremely strong dissolving power for the thermosetting resin matrix, forming a low-viscosity resin solution that facilitates subsequent high-energy dispersion; however, MIBK is essentially insoluble in the PCL-b-PMMA block copolymer that constitutes the controllable dissolution-release shell 3. This characteristic ensures that the protective shell of the microspheres remains intact during the initial high-energy dispersion stage of the preparation process. The second solvent, butyl acetate, is a solvent with excellent dissolving properties for the PCL-b-PMMA block copolymer. Therefore, it plays the role of a "trigger solvent" in the preparation process, added at specific process stages to achieve the dissolution of the shell as needed and in a controllable manner. This dual-solvent system design based on solubility differences is the core key to realizing the unique "protect first, release later" process flow in the preparation method described in this invention.

[0057] In conjunction with the carefully designed composition described above, this invention also provides a unique and ordered preparation method. The entire preparation process can be divided into two main steps: preparation of hierarchical pre-composite functional microspheres and preparation of the composition based on two-stage dispersion.

[0058] First, hierarchical pre-composite functional microspheres are prepared. This step is further subdivided into, for example... Figure 2 The steps shown are described in detail below:

[0059] Preparation of Hollow Glass Microsphere Core 1: The process begins with the preparation of precursor powder. Water glass (sodium silicate solution) is used as the silicon source, boric acid as the boron source, and an appropriate amount of polyethylene glycol is added to the aqueous solution as a pore-forming agent. The mixed solution is atomized by spray drying and rapidly dried in a hot gas stream to obtain uniform spherical precursor powder. Subsequently, the obtained precursor powder is placed in a tube furnace and calcined and foamed at a high temperature of 800-950 degrees Celsius. During this process, the precursor powder softens, and the internal pore-forming agent decomposes to generate gas, causing the powder to expand and form a hollow structure. Simultaneously, nitrogen gas containing a trace amount (e.g., 50-200 ppm) of hydrogen fluoride is introduced into the tube furnace as a carrier gas. The trace amount of hydrogen fluoride gas performs slight chemical etching on the surface of the forming high-temperature microspheres, thereby forming the desired nanoscale porous structure on the surface. After calcination, foaming, and etching, the hollow glass microspheres are rapidly cooled under a nitrogen atmosphere to quench their high-temperature structure, thus obtaining the hollow glass microsphere core 1 with specific physicochemical properties. Its microstructure is as follows: Figure 3 As shown, its surface has a nanoscale porous morphology.

[0060] Grafting of the interface-strengthening transition layer 2: The hollow glass microsphere core 1 obtained in the previous step was placed in a sufficient amount of toluene solvent and ultrasonically dispersed for 15 minutes using an ultrasonic generator to ensure that all microspheres were fully wetted and any possible agglomerates were broken. Subsequently, the suspension was transferred to a reactor equipped with a reflux condenser and heated to the boiling point of toluene (approximately 110°C). Under vigorous stirring, a pre-mixed solution of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane and 3-glycidyl etheroxypropyltrimethoxysilane, which had been uniformly mixed in a specific molar ratio (e.g., 1:2), was slowly added dropwise through a constant-pressure dropping funnel. After the addition was complete, the reaction was maintained under reflux for 4–6 hours to ensure that the silane coupling agent underwent sufficient hydrolysis and graft copolymerization on the surface of the microsphere core 1. After the reaction was completed, the reaction mixture was cooled to room temperature, and the modified microspheres were collected by centrifugation and washed repeatedly with toluene and anhydrous ethanol to remove unreacted monomers and oligomers. Finally, the washed product was dried in a vacuum oven at 80°C for 6 hours to obtain modified microspheres with a uniformly grafted interfacial toughening transition layer 2 on the surface.

[0061] Controlled Dissolution and Release of Shell 3 Coating: This step employs advanced fluidized bed coating technology. The modified microspheres obtained in the previous step are used as the fluidized particles to be coated and are fed into a fluidized bed reactor. Additionally, the aforementioned PCL-b-PMMA block copolymer is dissolved in dichloromethane to prepare a coating solution with a concentration of 5-10% (mass percentage). This coating solution is then uniformly sprayed into the fluidized microsphere bed in a mist form through nozzles located at the bottom of the fluidized bed. Simultaneously, the inlet air temperature of the fluidized bed is controlled between 40-50°C. This temperature promotes rapid evaporation of the dichloromethane solvent without causing thermal damage to the block copolymer or the internal microspheres. The atomized coating solution droplets uniformly adhere to the surface of the rapidly moving modified microspheres. As the solvent rapidly evaporates, the PCL-b-PMMA copolymer deposits on the microsphere surface, forming a uniform, dense, and controllable thickness protective shell layer. By precisely controlling the total amount and rate of coating liquid spraying, the thickness of the final controllable dissolution and release shell 3 can be precisely adjusted, thereby completing the preparation of the hierarchical pre-composite functional microspheres.

[0062] Secondly, such as Figure 4 As shown, the preparation of the composition is carried out. This step is the core embodiment of the process methodology of this invention, which creatively adopts a two-stage dispersion process, specifically including the following four stages:

[0063] Phase 1, the high-energy pre-dispersion stage. In a sealed high-speed dispersion vessel, all the metered quantities of the hierarchical pre-composite functional microspheres, all the metered quantities of the thermosetting resin matrix, all the metered quantities of the functional synergistic additives, and 70-80% of methyl isobutyl ketone are mixed. The high-speed disperser is started and vigorously dispersed at a speed of 1500-2500 r / min for 30-45 minutes. In this stage, because each hollow glass microsphere is protected by a robust and tough controllable dissolution-release shell 3, they can withstand such high mechanical shear forces while maintaining structural integrity and not breaking. At the same time, because the overall density of the hierarchical pre-composite functional microspheres is much higher than that of the bare hollow microspheres, and the system viscosity is moderate, these microspheres are easily and efficiently dispersed in the viscous resin liquid, achieving uniform distribution on a macroscopic scale.

[0064] Phase two, namely the low-energy dissolution and homogenization phase, follows the high-energy pre-dispersion phase. After the high-energy phase, the stirred tank is kept sealed, and the stirring speed is reduced to a low speed of 300-500 r / min. Using a drop pump, all the metered butyl acetate and the remaining methyl isobutyl ketone are slowly added dropwise. After the addition is complete, stirring continues at this low speed for 60-90 minutes to ensure the complete dissolution of the controllable dissolution shell layer and the smooth, uniform release of the surface-reinforced microbead core into the resin matrix, forming a stable suspension system. During this process, as butyl acetate, acting as a "trigger solvent," is introduced into the system, it begins to dissolve the controllable dissolution shell layer 3 encapsulated on the surface of the microbeads. The dropwise addition process typically continues for a period of time to ensure a smooth and controllable dissolution process. After the addition is complete, continue stirring at a low speed for 60-90 minutes. This gentle stirring during this time ensures that all controllable dissolution and release shell layers 3 are completely and thoroughly dissolved. Simultaneously, the modified microspheres, with their surface-toughening treatment, are released in situ and uniformly into the epoxy resin matrix in an extremely smooth and non-destructive manner, ultimately forming a stable, non-agglomerated microsphere suspension system. This process, employing low-speed stirring, cleverly avoids any mechanical damage to the exposed, restored-fragile hollow glass microspheres.

[0065] Phase three involves introducing the curing system. The base slurry obtained in the previous phase is cooled to room temperature using a jacket cooling method. After ensuring the system temperature is stable, the entire metered latent curing system is added to the base slurry at an extremely low stirring speed of less than 200 r / min. The mixture is then stirred slowly at this extremely low speed for 10-15 minutes to ensure uniform mixing. The purpose is solely to ensure that the curing agent microcapsules are evenly dispersed in the base slurry, thus avoiding accidental rupture of the microcapsules due to excessive shear force. After uniform mixing, the resulting material is filtered through a 100-mesh filter to remove any impurities or poorly dispersed microgel particles. The filtered material is then subjected to vacuum degassing to remove air introduced during mixing and dissolved in the solvent, thereby ensuring a dense and non-porous final coating.

[0066] Finally, in stage four, the finished product is packaged. After degassing, the finished product is immediately sealed under inert gas protection to obtain the finished product of the hollow glass microsphere composition described in this invention.

[0067] To illustrate the technical effects of the present invention more specifically, an embodiment and a comparative example are given below.

[0068] Example 1

[0069] This embodiment aims to prepare composition 1 according to the following steps and parameters:

[0070] (1) Preparation of hierarchical pre-composite functional microspheres:

[0071] First, hollow glass microsphere cores were prepared using water glass as the silicon source and boric acid as the boron source. Polyethylene glycol, a pore-forming agent, was added to the solution, and precursor powder was prepared by spray drying. Subsequently, the precursor powder was calcined and foamed in a tube furnace at 800–950°C while a nitrogen atmosphere containing 100 ppm HF was introduced. Hydrogen fluoride gas etched the surface of the microspheres, forming a nanoscale porous structure. After calcination, the microspheres were rapidly cooled under nitrogen protection to obtain the hollow glass microsphere cores. The glass composition of the prepared hollow glass microsphere cores contained 73% silicon dioxide, 17% boron trioxide, 3% sodium oxide, and 1% potassium oxide. Glass microspheres with a particle size distribution of 50–65 μm and an average wall thickness of 1.5–3.0 μm were selected for use. In this embodiment, the overall true density of the selected glass microspheres was 0.45 g / cm³. 3 It has a compressive strength of 40MPa and its outer surface has a nanoscale porous morphology formed by acid etching and rapid cooling process, with a surface roughness Ra value of 100nm.

[0072] Next, the interface toughening transition layer was grafted. The hollow glass microsphere core selected in this embodiment was placed in toluene solvent. N-(2-aminoethyl)-3-aminopropyltrimethoxysilane and 3-glycidyl etheroxypropyltrimethoxysilane were mixed at a molar ratio of 1:2 and added dropwise to the system. The mixture was refluxed for 5 hours to obtain modified microspheres containing a transition layer with a thickness of about 80 nm.

[0073] Finally, a shell coating was performed. The PCL-b-PMMA block copolymer (number average molecular weight 12000, where the mass ratio of PCL to PMMA is 2:3) was dissolved in dichloromethane to prepare an 8% coating solution. The modified microspheres were coated in a fluidized bed at 45°C. In the final hierarchical pre-composite functional microspheres, the hollow glass microsphere core accounted for 80% of the mass percentage, the transition layer accounted for 5% of the mass percentage, and the shell accounted for 15% of the mass percentage.

[0074] (2) Preparation of the composition:

[0075] The following mass ratios are used for feeding: 30 kg of hierarchical pre-composite functional microspheres; 55 kg of bisphenol A type epoxy resin (EEW ​​188); 10 kg of latent curing system (microencapsulated modified fatty amine); 3.0 kg of functional synergistic additive package (containing 1.0 kg of organic modified montmorillonite, 0.7 kg of polyether modified polydimethylsiloxane leveling agent, and 1.3 kg of nano titanium dioxide light stabilizer); and 30 kg of composite solvent system, of which the first solvent MIBK is 20 kg and the second solvent butyl acetate is 10 kg (volume ratio approximately 3:1).

[0076] First, in the high-energy pre-dispersion stage, 30 kg of microspheres, 55 kg of epoxy resin, 3.0 kg of additive package and 15 kg of MIBK were mixed and dispersed at 2000 r / min for 40 minutes.

[0077] Then, during the dissolution, release, and homogenization stage, the speed was reduced to 400 r / min, and 10 kg of butyl acetate and the remaining 5 kg of MIBK were slowly added dropwise, while stirring was continued for 80 minutes.

[0078] Finally, after cooling to 25°C, 10 kg of latent curing system was added at 150 r / min, mixed for 15 minutes, filtered, vacuum degassed, and then encapsulated to obtain composition 1.

[0079] Example 2

[0080] This embodiment is based on Example 1, except that the hollow glass microsphere core is replaced with commercially available hollow glass microspheres with similar parameters. These commercially available hollow glass microspheres have a silica content of 75%, boron trioxide content of 15%, sodium oxide content of 2%, and potassium oxide content of 2%. The microspheres have a particle size distribution of 60-75 μm and an average wall thickness of 1.5-2.0 μm, with an overall true density of 0.47 g / cm³. 3 It has a compressive strength of 42 MPa and an outer surface roughness Ra value of 80 nm.

[0081] The other steps and parameters are the same as in Example 1, and composition 2 is prepared.

[0082] Comparative Example 1

[0083] This comparative example differs from Example 1 only in the preparation process of the hollow glass microsphere core. During high-temperature calcination and foaming, a pure nitrogen atmosphere without HF was introduced; all other treatments remained the same. Glass microspheres with a particle size distribution of 50–65 μm and an average wall thickness of 1.5–3.0 μm were selected for use. The overall true density of the selected glass microspheres in this comparative example was 0.55 g / cm³. 3 It has a compressive strength of 42 MPa, and its outer surface does not have obvious nanoscale porous morphology. The surface roughness Ra value is 30 nm.

[0084] The other steps and parameters are the same as in Example 1, and composition 3 is prepared.

[0085] Comparative Example 2

[0086] This comparative example aims to prepare a composition of hollow glass microspheres modified with a single silane coupling agent. The main difference between this composition and Example 1 is that only N-(2-aminoethyl)-3-aminopropyltrimethoxysilane is used when grafting the interface toughening transition layer.

[0087] The other steps and parameters are the same as in Example 1, and composition 4 is prepared.

[0088] Comparative Example 3

[0089] This comparative example aims to prepare a composition of hollow glass microspheres modified with a single silane coupling agent. The main difference between this composition and Example 1 is that only 3-glycidyl etheroxypropyltrimethoxysilane is used when grafting the interface toughening transition layer.

[0090] The other steps and parameters are the same as in Example 1, and composition 5 is prepared.

[0091] Comparative Example 4

[0092] This comparative example aims to prepare a composition based on conventional hollow glass microspheres. The main difference between this example and Example 1 is that it does not use hierarchical pre-composite functional microspheres, but instead directly mixes the modified hollow glass microspheres with resin, etc., that is, it only omits the shell coating operation of Example 1.

[0093] The other steps and parameters are the same as in Example 1, and composition 6 is prepared.

[0094] Comparative Example 5

[0095] This comparative example aims to prepare a composition using a conventional process, which differs from Example 1 in that all components are mixed and dispersed at 2000 r / min for 40 minutes during the preparation of the composition.

[0096] The other steps and parameters are the same as in Example 1, and composition 7 is prepared.

[0097] The compositions obtained in Examples 1-2 and Comparative Examples 1-5 were coated onto steel plates and baked at 80°C for 2 hours to fully cure them. After cooling to room temperature for 24 hours, the properties of the coatings were tested. Simultaneously, samples of the prepared liquid compositions were taken, and the integrity rate of the hollow glass microspheres was observed under a microscope. The test results are summarized in Table 1.

[0098] Table 1 Performance indicators of each group of compositions

[0099]

[0100] As can be seen from the data in the table above, the composition 1 (Example 1) prepared by the technical solution of the present invention exhibits significant superiority in all key performance aspects. The integrity rate of its hollow glass microspheres is as high as 99% or more. This is directly attributed to the effective protective role of the process-assisted controllable dissolution and release shell in the high-energy dispersion stage, as well as the precise process control of the two-stage dispersion process. Composition 2, obtained by modifying commercially available hollow glass microspheres with similar parameters, showed slightly inferior performance compared to Composition 1, but the difference was not significant, indicating that the preparation process of hollow glass microspheres had little impact. Compared to Composition 1, Comparative Example 1 (Composition 3) had a smaller surface roughness due to the lack of HF etching, resulting in a significant decrease in performance, indicating that the surface roughness of hollow glass microspheres had a greater impact. The performance of Comparative Examples 2 and 3 (Compositions 4 and 5) modified with a single silane coupling agent also decreased significantly, indicating that the combined modification with two silane coupling agents could bring about a more significant improvement effect. Comparative Example 4 (Composition 6) lacked the protection of a controllable dissolution and release shell, and under the same high-speed dispersion conditions, about one-quarter of the microspheres were sheared and broken. This not only led to a significant increase in the dry film density of the coating, but also seriously deteriorated its core thermal insulation performance, with a thermal conductivity much higher than that of Example 1. Furthermore, the high integrity rate of the microspheres in Example 1 and the strong interfacial bonding constructed through the dual silane system resulted in coating mechanical properties (tensile strength and impact strength) far exceeding those of Comparative Example 4. In Comparative Example 4, the numerous broken microspheres became stress concentration points, weakening the matrix strength. Comparative Example 5 (composition 7) directly mixed all components and dispersed at 2000 r / min for 40 minutes, and its performance was close to that of Comparative Example 4. This indicates that the failure of the controlled dissolution-release shell during the high-energy pre-dispersion stage is essentially equivalent to not applying the controlled dissolution-release shell. The controlled dissolution-release shell should be used in conjunction with the two-stage dispersion process of this invention to achieve the desired effect. In addition, since all schemes in Examples 1-2 and Comparative Examples 1-5 adopted a latent curing system, they all exhibited excellent pot life.

[0101] Finally, it should be noted that the terms "comprising," "including," or any other variations are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make further changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0102] The embodiments described above merely illustrate specific implementation methods of this application, and while the descriptions are detailed and specific, they should not be construed as limiting the scope of protection of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the technical solution of this application, and these modifications and improvements all fall within the scope of protection of this application.

Claims

1. A composition based on hollow glass microspheres, characterized in that, By weight, it contains the following components: 15-45 parts of hierarchical pre-composite functional microspheres; 40-70 parts of thermosetting resin matrix; 5-20 parts of the latent curing system; Functional synergistic agent pack 1-5 portions; And 20-40 parts of the composite solvent system; The hierarchical pre-composite functional microspheres are a three-layer core-shell structure, which consists of the following components: a hollow glass microsphere core, accounting for 70-90% of the total mass of the microspheres; the hollow glass microsphere core is a borosilicate glass microsphere with a particle size distribution of 30-80 μm and a standard deviation of particle size distribution not exceeding 15 μm; its wall thickness is 1.5-3.0 μm; and its true density is 0.35-0.55 g / cm³. 3 Its compressive strength is not less than 35 MPa; its outer surface has a nanoscale porous morphology formed by acid etching and rapid cooling process, with a surface roughness Ra value of 80~150 nm; an interface toughening transition layer, accounting for 2~10% of the total mass of the microspheres, the interface toughening transition layer is a functional molecular layer in situ chemically grafted onto the outer surface of the hollow glass microsphere core, formed by copolymerization and crosslinking of at least two synergistic silane coupling agents; a controllable dissolution and release shell layer, accounting for 8~20% of the total mass of the microspheres, the controllable dissolution and release shell layer is a thermoplastic block copolymer coating the interface toughening transition layer, the thermoplastic block copolymer is composed of A block and B block, wherein the A block is a polycaprolactone block and the B block is a polymethyl methacrylate block; the number average molecular weight of the block copolymer is controlled at 8000~15000, and the mass ratio of polycaprolactone to polymethyl methacrylate is 3~7:7; The composite solvent system is composed of methyl isobutyl ketone and butyl acetate in a volume ratio of 2 to 4:

1.

2. The composition according to claim 1, characterized in that, There are two types of silane coupling agents that form the interface toughening transition layer. The first type of silane coupling agent is an aminosilane containing a long-chain alkyl group, and the second type of silane coupling agent is a silane containing an epoxy functional group.

3. The composition according to claim 2, characterized in that, The aminosilane is specifically N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and the silane containing the epoxy functional group is specifically 3-glycidyl etheroxypropyltrimethoxysilane. The molar ratio of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane to 3-glycidyl etheroxypropyltrimethoxysilane is 1:1~3, and the thickness of the interface toughening transition layer is 50~100 nm.

4. The composition according to claim 1, characterized in that, The thermosetting resin matrix is ​​bisphenol A type epoxy resin; the latent curing system is a microencapsulated modified aliphatic amine curing agent, the capsule wall material of which is a polyurethane-urea copolymer, and the core material is a flexible amine adduct prepared by pre-reaction of m-phenylenediamine and liquid polysulfide rubber. The average particle size of the microcapsules is 5~10μm, and the capsule wall thickness is 0.5~1μm; the functional synergistic additive package contains the following components by weight: 0.5~1.5 parts of organic modified montmorillonite thixotropic agent; 0.3~1.0 parts of polyether modified polydimethylsiloxane leveling agent; and 0.2~2.5 parts of rutile crystal nano titanium dioxide light stabilizer, with an average particle size of less than 50nm, and is treated with organosilicon coating.

5. A method for preparing the composition according to any one of claims 1 to 4, characterized in that, Includes the following steps: (1) Preparation of hierarchical pre-composite functional microspheres; (2) High-energy pre-dispersion: In a closed high-speed dispersion vessel, all the metered graded pre-composite functional microspheres, all the metered thermosetting resin matrix, all the metered functional synergistic additive package and 70-80% methyl isobutyl ketone are mixed, and the high-speed disperser is started to perform strong dispersion at a speed of 1500-2500 r / min for 30-45 minutes. (3) Low-energy dissolution and release and homogenization: Keep the stirred tank sealed and reduce the speed to a low-speed stirring state of 300~500 r / min. Use a drop pump to slowly add all the metered butyl acetate and the remaining methyl isobutyl ketone. After the addition is complete, continue stirring at this low speed for 60~90 minutes to ensure that the controllable dissolution and release shell is completely dissolved and the surface-strengthened microbead core is released into the resin matrix in a smooth and uniform manner to form a stable suspension system. (4) Introduction of curing system and packaging of finished product: Cool the base slurry obtained in step (3) to room temperature, add all the metered latent curing system to the base slurry under extremely low stirring speed of less than 200 r / min, stir slowly for 10~15 minutes to make it evenly mixed, filter through a 100 mesh filter, perform vacuum degassing treatment, and then seal and package to obtain the composition.

6. The preparation method according to claim 5, characterized in that, The preparation process of the hierarchical pre-composite functional microspheres includes the following steps: (1.1) Grafting of interface toughening transition layer: The hollow glass microsphere core is placed in toluene solvent, ultrasonically dispersed for 15 minutes, heated to 110℃, and a pre-mixed solution of at least two synergistic silane coupling agents is added dropwise. The mixture is refluxed for 4-6 hours. After the reaction is completed, the modified microspheres with interface toughening transition layer grafted on the surface are obtained by centrifugation, washing and drying. (1.2) Controllable dissolution and release shell coating: The modified microspheres obtained in step (1.1) are used as fluidized particles in a fluidized bed coating process. The thermoplastic block copolymer is dissolved in dichloromethane to form a coating solution with a concentration of 5-10%. The coating solution is atomized and sprayed into the fluidized bed through the bottom nozzle. At an air inlet temperature of 40-50°C, the coating solution is uniformly attached to the surface of the modified microspheres. After the solvent evaporates quickly, a uniform and dense shell is formed. By controlling the amount of spraying, the shell thickness is precisely controlled, and the hierarchical pre-composite functional microspheres are finally obtained.

7. The preparation method according to claim 6, characterized in that, The preparation process of the hollow glass microsphere core is as follows: using water glass as the silicon source and boric acid as the boron source, polyethylene glycol, a pore-forming agent, is added to the solution, and precursor powder is prepared by spray drying; then the precursor powder is calcined and foamed at high temperature in a tube furnace at 800~950℃, while a nitrogen atmosphere containing trace amounts of hydrogen fluoride is introduced. The hydrogen fluoride gas etches the surface of the microspheres to form a nanoscale porous structure; after calcination, it is rapidly cooled under nitrogen protection to obtain the hollow glass microsphere core; in the glass composition of the prepared hollow glass microsphere core, the mass percentage of silicon dioxide is 65~75%, the mass percentage of boron trioxide is 10~18%, and the sum of the mass percentages of sodium oxide and potassium oxide is less than 5%.

8. The application of the composition according to any one of claims 1 to 4 as a surface treatment material in the preparation of aerospace structural components, transportation components, and exterior walls of high-energy-consuming buildings.

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