Hydro-magnesite composite material hybridized by multi-level silicon-nitrogen bonding layer as well as preparation method and application of hydromagnesite composite material

Abstract

The invention provides a multi-level silicon-nitrogen bonding layer hybridized hydromagnesite composite material as well as a preparation method and application thereof, and belongs to the technical field of functional materials. The preparation method comprises the following steps: firstly, mixing amino acid and amino silane to obtain a mixed modifier, then mutually combining the mixed modifier with natural hydromagnesite mineral powder, and then carrying out physical adsorption modification by using aldehyde silane, thereby realizing the construction of the multi-level organic-inorganic composite powder. The multi-level amino acid silicon nitrogen bonding layer hybrid natural hydromagnesite composite powder is constructed in a mode of combining amino acid chemical modification and aromatic aldehyde group silane cross coupling, the yield is high, and the preparation method is suitable for large-scale industrial production and manufacturing; and moreover, the added value enhancement and functional enhancement effects of the bio-based organic functional molecules in the natural mineral powder can be effectively expanded, and the application range of a traditional bio-based material is expanded.

Description

Technical Field

[0001] The present invention relates to the technical field of functional materials, and in particular to a multi-level silicon-nitrogen bonding layer hybridized hydromagnesite composite material, a preparation method and an application thereof. Background Art

[0002] Efficient utilization of natural stone is a key development direction for inorganic non-metallic mineral powders. Designing surface functional layers is a rapid and efficient way to enhance the performance of natural stone micropowders. Natural hydromagnesite, primarily composed of basic magnesium carbonate, is a highly promising natural inorganic mineral powder that is environmentally friendly, safe, non-toxic, smoke-suppressing, and cost-effective. With increasing temperature, its inherent water of crystallization is released between 210 and 395°C. This is followed by a significant release of CO2 between 460 and 515°C. Finally, within the temperature range of 515 to 640°C, the magnesium carbonate framework collapses, forming an extremely heat-resistant MgO ceramic precursor with excellent physical flame retardancy and ablation resistance. However, the high polarity and abundant hydroxyl groups inherent in natural hydromagnesite limit its application. In-situ surface modification can effectively shield its surface hydroxyl groups and reduce its surface polarity. Silicon and nitrogen are core elements in a variety of highly effective flame-retardant materials with excellent thermal stability and zero secondary pollution. Currently, synthetic silicon- and nitrogen-based flame retardants are widely used. However, traditional silanes lack significant functionality. They are primarily interconnected via alkane bonds, making them neither heat-resistant nor flame-retardant, and may even promote combustion. They also struggle to form synergistic effects with the natural hydromagnesite within. Furthermore, due to their artificial synthesis, they are expensive and often rely on high concentrations, multiple components, and strong formulations to achieve surface passivation and modification. Therefore, there is an urgent need to develop surface functional layers with multiple functionalities that can enhance functionality and optimize multi-level structures with natural hydromagnesite, significantly increasing its added value. Large-scale industrial production can also make costs manageable and meet widespread industrial application. Summary of the Invention

[0003] The purpose of the present invention is to provide a multi-level silicon-nitrogen bonding layer hybridized hydromagnesite composite material, its preparation method and application, and to use biomass amino acid molecules to enhance the function of natural hydromagnesite, which can solve the problems in the existing technology of lack of surface modification function of natural mineral powder, poor thermal stability, difficulty in carbonization and low internal and external synergy.

[0004] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0005] The present invention provides a method for preparing a multi-level silicon-nitrogen bonding layer hybrid hydromagnesite composite material, comprising the following steps:

[0006] performing a first mixing of the amino acid and the first solvent to obtain an amino acid solution;

[0007] performing a second mixing of the aminosilane and the second solvent to obtain an aminosilane solution;

[0008] performing a third mixing of the amino acid solution and the aminosilane solution to obtain a mixed modifier;

[0009] The mixed modifier is mixed with the hydromagnesite ore powder for the fourth time, and subjected to the first modification to obtain a modified hydromagnesite composite powder;

[0010] After the aldehyde silane and the third solvent are mixed for the fifth time, the obtained aldehyde silane dispersion is mixed with the modified hydromagnesia composite powder and subjected to the second modification to obtain a hydromagnesia composite material with a multi-level silicon-nitrogen bonding layer hybridization.

[0011] Preferably, the amino acids include one or more of alanine, glycine, proline, serine, aspartic acid, cysteine, and threonine;

[0012] The first solvent is a water-alcohol mixture, the volume ratio of water to alcohol in the first solvent is 1:1~20:1, the first mixing conditions include: temperature of 45~75°C, time of 0.5~2.0h, stirring rate of 500~1500 rpm, and the concentration of the amino acid solution is 1~10M.

[0013] Preferably, the aminosilane includes one or more of 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, N-2-aminoethyl-3-aminopropyltriethoxysilane, N-2-aminoethyl-3-aminopropyltrimethoxysilane, N-2-aminoethyl-3-aminopropylmethyldiethoxysilane, diethylenetriaminopropyltrimethoxysilane and N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane; the molar ratio of the aminosilane to the amino acid is 1:1 to 1:10.

[0014] Preferably, the second solvent is a water-alcohol mixture, the volume ratio of water to alcohol in the second solvent is 1:1-1:20, the second mixing conditions include: temperature of 30-60°C, time of 0.1-1.2 h, stirring rate of 100-900 rpm, and the concentration of the aminosilane solution is 1-10M;

[0015] The third mixing method is constant-speed addition, with an addition rate of 1-10 mL / min, a stirring rate of 600-1600 rpm during addition, and continuous stirring for 0.5-2.0 h after the addition is completed.

[0016] Preferably, the molar amount of the aminosilane and the mass ratio of the hydromagnesite powder is 1-5 mol:10 kg; the particle size D of the hydromagnesite powder is 50 =0.9~3.9μm, the total content of magnesium carbonate and magnesium hydroxide is ≥90wt%; the temperature of the first modification is 65~85℃, and the time is 0.3~1.2h.

[0017] Preferably, the formaldehyde silane includes tetra(4-formylphenyl)silane, the third solvent is a water-alcohol mixture, and the volume ratio of water to alcohol in the third solvent is 1:1~1:20; the fifth mixing conditions include: temperature of 25~45°C, time of 0.2~1.6 h, and stirring rate of 100~900 rpm; the concentration of the formaldehyde silane dispersion is 0.1~5M.

[0018] Preferably, the molar ratio of the aldehyde silane to the mass of the hydromagnesite powder is 1-10 mol:20 kg; the second modification comprises reacting at 70-90°C for 0.1-0.5 h, cooling to room temperature for 0.1-0.3 h, and cooling to 5-15°C for 0.1-1.0 h.

[0019] The present invention provides a multi-level silicon-nitrogen bonding layer hybridized hydromagnesite composite material prepared by the preparation method described in the above technical solution.

[0020] The present invention provides the use of the multi-level silicon-nitrogen bonding layer hybridized hydromagnesia composite material described in the above technical solution in ethylene-vinyl acetate copolymer cable masterbatch.

[0021] Preferably, the application method comprises the following steps: first mixing the EVA resin and the processing aid, adding the multi-level silicon nitrogen bonding layer hybridized hydromagnesia composite material for second mixing, and then cooling and cutting in sequence to obtain the EVA cable masterbatch.

[0022] The present invention provides a preparation method of a multi-level silicon-nitrogen bonding layer hybridized hydromagnesite composite material (SiN-cr-NWM). Amino acids and aminosilanes are first mixed to obtain a mixed modifier, the mixed modifier is then combined with natural hydromagnesite mineral powder, and then cross-linked and modified with aldehyde silane to achieve the construction of a multi-level organic-inorganic composite powder.

[0023] The present invention adopts amino acid and aminosilane to coat the surface of natural hydromagnesite to form a composite powder hybridized with multiple natural products, which has typical green and environmentally friendly characteristics.

[0024] The present invention utilizes aldehyde silane to cross-link and couple amino acids and aminosilanes together through chemical cross-linking. Specifically, the aldehyde group on the aromatic aldehyde silane reacts with the amino group on the amino acid and the aminosilane to achieve cross-coupling and coating of the natural hydromagnesite surface, thereby forming a multi-level silicon-nitrogen bonding functional layer on the surface of the natural hydromagnesite. The formed multi-level silicon-nitrogen bonding layer can significantly reduce the surface polarity of the natural hydromagnesite powder, effectively shield active sites such as hydroxyl groups on the surface, reduce the oil absorption value of the composite powder, and significantly reduce processing costs. Moreover, the silicon-nitrogen bonding layer fully integrates elements such as silicon, nitrogen-containing aromatic heterocycles, and a cross-linked C=N structure. During the combustion process, it can quickly form carbon, act as a physical barrier layer, and protect the polymer matrix under the combustion front. The natural hydromagnesite inside will quickly form a large amount of MgO ceramic precursors when burning, which has good heat resistance (improves thermal stability) and can serve as an inorganic ablation-resistant skeleton to support the external carbon layer, which can greatly improve the flame retardant and smoke suppression properties of the composite powder, forming an internal and external synergistic effect; and the organic biomass amino acid functional molecules are widely available, low-priced, and naturally degradable, and the natural hydromagnesite is non-toxic, price-controlled, and has a high magnesium content. These characteristics make this type of composite powder extremely advantageous in terms of comprehensive performance, price control, and adjustable structure after being combined with each other; and the melting points of the amino acids used are all greater than 220°C, which is greater than the processing temperature of most resins, and can effectively ensure the thermal stability of the composite powder during processing, effectively avoiding premature dehydration and pyrolysis.

[0025] The present invention constructs a multi-level amino acid silicon-nitrogen bonding layer hybrid natural hydromagnesite composite powder by combining amino acid chemical modification and aromatic aldehyde silane cross-coupling. The yield is high, the preparation process is simple and easy, and it is suitable for large-scale industrial production. The obtained composite material is white or off-white or light yellow powder, which is conducive to subsequent coloring, and can effectively expand the added value enhancement and functional strengthening effect of bio-based organic functional molecules in natural mineral powders, expand the application range of traditional bio-based materials, and provide new ideas for the reconstruction and optimization combination of natural products with multiple components.

[0026] The present invention is the first to use biomass amino acid molecules to enhance the functionality of natural hydromagnesite powder. Amino acids, as a nitrogen-containing heterocyclic organic functional molecule, contain multiple active reaction sites and can provide opportunities for subsequent further structural modification. The present invention uses amino acids, aminosilanes and aldehyde silanes to perform multi-level reconstruction of natural hydromagnesite, which can significantly improve the functionality of the surface modification layer. This method can not only significantly improve the surface properties of natural hydromagnesite, but also avoid the consumption of a large amount of organic reagents during the production and preparation process, and can achieve the green and low-carbon sustainable production goals, which is of great significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1Schematic diagram of the structure of the multi-level silicon-nitrogen bonding layer hybridized hydromagnesia composite powder prepared in Example 1;

[0028] Figure 2 This is a scanning electron microscope (SEM) image of the multi-level silicon-nitrogen bonding layer hybridized hydromagnesia composite powder prepared in Example 1;

[0029] Figure 3 This is a particle size distribution diagram of the multi-level silicon-nitrogen bonding layer hybridized hydromagnesite composite powder prepared in Example 1. DETAILED DESCRIPTION

[0030] In the present invention, unless otherwise specified, the required raw materials or reagents are commercially available products well known to those skilled in the art.

[0031] The present invention provides a method for preparing a multi-level silicon-nitrogen bonding layer hybrid hydromagnesite composite material, comprising the following steps:

[0032] performing a first mixing of the amino acid and the first solvent to obtain an amino acid solution;

[0033] performing a second mixing of the aminosilane and the second solvent to obtain an aminosilane solution;

[0034] performing a third mixing of the amino acid solution and the aminosilane solution to obtain a mixed modifier;

[0035] The mixed modifier is mixed with the hydromagnesite ore powder for the fourth time, and subjected to the first modification to obtain a modified hydromagnesite composite powder;

[0036] After the aldehyde silane and the third solvent are mixed for the fifth time, the obtained aldehyde silane dispersion is mixed with the modified hydromagnesia composite powder and subjected to the second modification to obtain a hydromagnesia composite material with a multi-level silicon-nitrogen bonding layer hybridization.

[0037] In the present invention, the amino acids preferably include one or more of alanine, glycine, proline, serine, aspartic acid, cysteine, and threonine; when the amino acids are two or more of the above, the present invention has no special limitation on the ratio of different types of amino acids, and any ratio is acceptable.

[0038] In the present invention, the first solvent is preferably a water-alcohol mixture, and the volume ratio of water to alcohol in the first solvent is preferably 1:1 to 20:1, more preferably 5 to 10:1. The first mixing conditions preferably include: a temperature of 45 to 75°C, more preferably 50 to 60°C, and further preferably 50°C; a time of 0.5 to 2.0 h, more preferably 0.8 to 1.5 h, and further preferably 1.0 h; a stirring rate of 500 to 1500 rpm, more preferably 800 to 1200 rpm, and further preferably 1000 rpm; and the concentration of the amino acid solution is preferably 1 to 10 M, more preferably 2 to 8 M, and further preferably 5 M.

[0039] In the present invention, the aminosilane preferably includes one or more of 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, N-2-aminoethyl-3-aminopropyltriethoxysilane, N-2-aminoethyl-3-aminopropyltrimethoxysilane, N-2-aminoethyl-3-aminopropylmethyldiethoxysilane, diethylenetriaminopropyltrimethoxysilane and N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane; when the aminosilane is two or more of the above, the present invention has no special limitation on the ratio of different types of aminosilanes, and any ratio is acceptable.

[0040] In the present invention, the molar ratio of the aminosilane to the amino acid is preferably 1:1 to 1:10, more preferably 1:2 to 1:8, and even more preferably 1:5.

[0041] In the present invention, the second solvent is preferably a water-alcohol mixture, and the volume ratio of water to alcohol in the second solvent is preferably 1:1-1:20, more preferably 1:5-1:15, and further preferably 1:10. The second mixing conditions preferably include: a temperature of 30-60°C, more preferably 40-55°C, and further preferably 50°C; a time of 0.1-1.2 h, more preferably 0.3-1.0 h, and further preferably 0.5-0.8 h; a stirring rate of 100-900 rpm, more preferably 300-600 rpm, and further preferably 500 rpm; and the concentration of the aminosilane solution is preferably 1-10 M, more preferably 2-8 M, and further preferably 5 M.

[0042] The present invention preferably adds the amino acid solution to the aminosilane solution, and the third mixing method is preferably constant rate addition, the addition rate is preferably 1-10 mL / min, more preferably 5 mL / min, and the stirring rate during addition is preferably 600-1600 rpm, more preferably 1200 rpm. After the addition is completed, stirring is continued for 0.5-2.0 h, more preferably 1.0 h, to obtain a mixed modifier.

[0043] In the present invention, the particle size D of the hydromagnesite powder is 50 =0.9~3.9μm, more preferably 1.2~3.0μm, further preferably 1.8μm, the total content of magnesium carbonate and magnesium hydroxide is ≥90wt%; obtained by physical grinding using natural hydromagnesite; the molar amount of the aminosilane to the mass ratio of the hydromagnesite powder is preferably 1~5 mol:10 kg, more preferably 3 mol:10 kg.

[0044] In the present invention, before the fourth mixing, the hydromagnesite powder is preferably preheated in a high-speed stirrer for 0.1 to 0.5 h (more preferably 0.3 h), with a stirring rate of 100 to 300 r / min, more preferably 200 r / min, and a preheating temperature of 45 to 65 ° C, more preferably 55 ° C, and then the mixed modifier is added to the high-speed rotating hydromagnesite powder at a uniform speed, and the addition rate is preferably 1 to 60 mL / min, more preferably 30 mL / min. During the addition, the stirring rate is increased to 300 to 900 r / min, more preferably 600 r / min, at which time the temperature rises to 65 to 85 ° C (the temperature of the first modification), until the addition is completed, and the first modification is carried out under continuous stirring conditions.

[0045] In the present invention, the temperature of the first modification is preferably 65-85°C, more preferably 70-75°C; the time is preferably 0.3-1.2 h, more preferably 0.5-1.0 h, and further preferably 0.8 h.

[0046] In the present invention, the formaldehyde silane preferably includes tetrakis(4-formylphenyl)silane, the third solvent is preferably a water-alcohol mixture, the volume ratio of water to alcohol in the third solvent is preferably 1:1~1:20, more preferably 1:10~15, and the fifth mixing conditions preferably include: temperature of 25~45°C, more preferably 30~35°C, time of 0.2~1.6 h, more preferably 0.8~1.2 h, stirring rate of 100~900 rpm, more preferably 300~600 rpm, further preferably 500 rpm; the concentration of the formaldehyde silane dispersion is preferably 0.1~5M, more preferably 1~4M, further preferably 3M.

[0047] In the present invention, the alcohol used in the first solvent, the second solvent and the third solvent independently preferably includes one or more of methanol, ethanol, propanol, ethylene glycol and 1,3-propylene glycol, more preferably ethanol; and the water is preferably distilled water.

[0048] In the present application, the ratio of the molar amount of the aldehyde-based silane to the mass of the water-magnesite ore powder is preferably 1-10 mol:20 kg, and more preferably 5 mol:20 kg. When the molar-to-mass ratio of the aldehyde-based silane to the water-magnesite ore powder is less than 1 mol:20 kg, the amount of the aldehyde-based silane added can be too low, making it difficult to effectively cover and shield the natural water-magnesite ore powder (NWM), and the functionalization enhancement effect is limited, and the comprehensive performance of the composite powder is not good. On the other hand, when the molar-to-mass ratio of the aldehyde-based silane to the natural water-magnesite ore powder (NWM) is higher than 10 mol:20 kg, the content of the aldehyde-based silane can be too large, and too much of the aldehyde-based silane can accumulate on the surface of the natural water-magnesite ore powder. Most of the aldehyde-based silane is physically weakly adsorbed on the surface of the natural water-magnesite ore powder (NWM) and can be unevenly dispersed. In the subsequent powder modification and processing, the aldehyde-based silane can be easily mechanically stripped, and the composite powder can be unevenly dispersed in the polymer matrix, and even multiple natural water-magnesite ore powder (NWM) particles can be wrapped, which can easily cause defect-induced fracture when subjected to external impact, and is not conducive to the mechanical retention and functional enhancement of the composite substrate.

[0049] In the present application, the step of mixing the aldehyde-based silane dispersion liquid with the modified water-magnesite composite powder is preferably spraying the aldehyde-based silane dispersion liquid into the modified water-magnesite composite powder rotating at high speed. The spraying rate is preferably 1-40 mL / min, and more preferably 20-30 mL / min. The spraying is performed while stirring, and the stirring rate is preferably 500-1200 r / min, and more preferably 800-1000 r / min. The stirring temperature during spraying is 70-90 °C, and more preferably 75-85 °C, and further preferably 80 °C. The spraying is performed until completion.

[0050] After the spraying is completed, the obtained mixture is subjected to a second modification. Specifically, the stirring is continued at 70-90 °C (more preferably 80 °C) for 0.1-0.5 h, and more preferably 0.3 h. Then, the mixture is cooled to room temperature (25 °C), and stirred at room temperature for 0.1-0.3 h, and more preferably 0.2 h. The stirring rate is 400-1000 r / min, and more preferably 700-800 r / min. Then, the mixture is cooled to 5-15 °C, and more preferably 10 °C, and stirred at low temperature for 0.1-1.0 h, and more preferably 0.5 h. The stirring rate is 300-800 r / min, and more preferably 500 r / min. The stirring is stopped, and the mixture is subjected to static settling, dust removal, and drying in sequence, to obtain a water-magnesite composite material with multiple levels of silicon-nitrogen adhesion layer hybridization.

[0051] In the present invention, the static sedimentation time is preferably 0.3-0.8 h, more preferably 0.5 h; the dust removal is preferably carried out by a cyclone separator, the dust removal rotation rate is preferably 300-1000 r / min, more preferably 600 r / min, the air inlet rate is preferably 3-12 m / s, more preferably 6 m / s, the power is preferably 200-600 W, more preferably 400 W; the drying method is preferably flash drying, the drying temperature is preferably 100-125 ° C, more preferably 110 ° C, the time is preferably 5-20 min, more preferably 10 min, and the air inlet volume is preferably 500-1000 m 3 / h, more preferably 800 m 3 / h.

[0052] The present invention provides a multi-level silicon-nitrogen bonding layer hybridized hydromagnesia composite material prepared by the preparation method described in the above technical solution. In the present invention, the median particle size D of the multi-level silicon-nitrogen bonding layer hybridized hydromagnesia composite material is 50 =1.0~4.0μm, more preferably 2.0μm.

[0053] The present invention provides the use of the multi-level silicon-nitrogen bonding layer hybridized hydromagnesia composite material described in the above technical solution in ethylene-vinyl acetate copolymer (EVA) cable masterbatch.

[0054] In the present invention, the application method preferably includes the following steps: performing a first mixing of EVA resin and a processing aid in a mixing-type internal mixer, adding a multi-level silicon-nitrogen bonding layer hybridized hydromagnesia composite material for a second mixing, and then cooling and cutting in sequence to obtain EVA cable masterbatch.

[0055] In the present invention, the processing aid preferably includes a compatibilizer, an antioxidant and a lubricant; the lubricant is preferably a silicone masterbatch.

[0056] In the present invention, the mass ratio of the EVA resin, compatibilizer, antioxidant, lubricant and multi-level silicon nitrogen bonding layer hybridized hydromagnesia composite material is preferably 54~79:5:0.2:0.8:15~40, more preferably 54~65:5:0.2:0.8:15~30, and further preferably 54:5:0.2:0.8:30.

[0057] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited by the specific embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. The experimental methods described in the embodiments of the present invention are all conventional methods unless otherwise specified.

[0058] The following experimental methods and detection methods, unless otherwise specified, are conventional methods; the following reagents and raw materials, unless otherwise specified, are commercially available.

[0059] In the following examples, natural hydromagnesite powder is obtained by physical grinding of natural hydromagnesite. The particle size D of the natural hydromagnesite powder is 50 =1.8μm, total content of magnesium carbonate and magnesium hydroxide ≥90wt%.

[0060] Example 1

[0061] 1) Alanine was dissolved in a mixture of water and ethanol at a volume ratio of 10:1. The mixture was stirred at 50°C for 1 h at a stirring rate of 1000 rpm to obtain Solution 1. The concentration of Solution 1 was 5 M.

[0062] 2) Dissolve 3-aminopropylmethyldimethoxysilane in a mixture of water and ethanol at a volume ratio of 1:10, a mixing temperature of 50°C, a stirring time of 0.8 h, and a stirring rate of 500 rpm to obtain Solution 2. The concentration of Solution 2 is 5 M.

[0063] Solution 1 was added to solution 2 at a rate of 5 mL / min and stirred at a stirring rate of 1200 rpm until the addition was complete. After the addition was complete, stirring was continued for 1.0 h to obtain solution 3, wherein the molar ratio of 3-aminopropylmethyldimethylsilane to alanine was 1:5;

[0064] 3) adding solution 3 to the high-speed rotating natural hydromagnesite powder at a uniform speed, controlling the addition rate to be 30 mL / min. Before addition, the natural hydromagnesite powder was preheated in a high-speed stirrer for 0.3 h, with a stirring rate of 200 r / min and a preheating temperature of 55°C. During addition, the stirring rate was increased to 600 r / min, and the temperature was raised to 75°C. Stirring was continued for 0.8 h until the addition was completed to obtain a modified hydromagnesite composite powder. The molar to mass ratio of the 3-aminopropylmethyldimethylsilane to the natural hydromagnesite powder was 3 mol:10 kg.

[0065] 4) Tetrakis(4-formylphenyl)silane was stirred and dispersed in a mixture of water and ethanol at a volume ratio of 1:10, at a stirring temperature of 35°C, a stirring time of 0.8 h, and a stirring rate of 500 rpm to obtain Solution 4. The concentration of Solution 4 was 3 M.

[0066] 5) Solution 4 was added to the high-speed rotating modified hydromagnesite composite powder in the form of a spray, and the molar to mass ratio of tetra(4-formylphenyl)silane and natural hydromagnesite powder was controlled to be 5 mol: 20 kg. The spray rate was 20 mL / min, and the spraying was carried out while stirring. The stirring rate was 800 r / min, and the stirring temperature during spraying was 80 °C until the spraying was completed. Then, stirring was continued for 0.3 h, and then cooled to room temperature (25 °C). Stirred at room temperature for 0.2 h at a stirring rate of 700 r / min, and further cooled to 10 °C, stirred at low temperature for 0.5 h at a stirring rate of 500 r / min, and then stopped stirring. The mixture was allowed to settle for 0.5 h, and then dusted by a cyclone separator. The dust removal rotation rate was controlled to be 600 r / min, the air inlet rate was 6 m / s, and the power was 400 W. Then, flash drying was further adopted, and the drying temperature was 110 °C, the drying time was 10 min, and the air inlet volume was 800 m 3 / h, a multi-level silicon-nitrogen bonding layer hybrid hydromagnesia composite powder (SiN-cr-NWM) was obtained, and the median particle size of the product was D 50 =2.0μm.

[0067] like Figure 1 As shown, in the outer layer of natural hydromagnesite, natural biomass amino acids with amino groups and aminosilanes are fully coupled by aromatic aldehyde silane to construct a silane layer and amino acid bonding layer with a multi-level structure, so that it can better form a multi-level shielding and modification of the internal natural hydromagnesite, and effectively form a better multi-layer core-shell structure.

[0068] Example 2

[0069] 1) Glycine was dissolved in a mixture of water and ethanol at a volume ratio of 1:1. The mixture was stirred at 45°C for 2.0 h at a stirring rate of 500 rpm to obtain Solution 1. The concentration of Solution 1 was 1 M.

[0070] 2) Dissolve 3-aminopropylmethyldiethoxysilane in a mixture of water and ethanol at a volume ratio of 1:1 at 30°C, stirring for 1.2 h at a stirring rate of 100 rpm to obtain Solution 2. The concentration of Solution 2 was 1 M.

[0071] Solution 1 was added to solution 2 at a rate of 1 mL / min and stirred at 600 rpm until the addition was complete. Stirring was continued for 2.0 h after the addition was complete to obtain solution 3, wherein the molar ratio of 3-aminopropylmethyldiethylsilane to glycine was 1:1;

[0072] 3) adding solution 3 to the high-speed rotating natural hydromagnesite powder at a uniform speed, controlling the addition rate to be 1 mL / min. Before addition, the natural hydromagnesite powder was preheated in a high-speed stirrer for 0.1 h, with a stirring rate of 100 r / min and a preheating temperature of 45°C. During addition, the stirring rate was increased to 300 r / min, at which time the temperature rose to 65°C. Stirring was continued for 1.2 h until the addition was complete to obtain a modified hydromagnesite composite powder. The molar to mass ratio of the 3-aminopropylmethyldiethoxysilane to the natural hydromagnesite powder was 1 mol:10 kg.

[0073] 4) Tetrakis(4-formylphenyl)silane was stirred and dispersed in a mixture of water and ethanol at a volume ratio of 1:1 at 25°C for 1.6 h at a stirring rate of 100 rpm to obtain Solution 4. The concentration of Solution 4 was 0.1 M.

[0074] 5) Solution 4 was added to the high-speed rotating modified hydromagnesite composite powder in the form of a spray, and the molar to mass ratio of tetra(4-formylphenyl)silane and natural hydromagnesite mineral powder was controlled to be 1 mol:20 kg, wherein the spray rate was 1 mL / min, and the spraying was carried out while stirring. The stirring rate was 500 r / min, and the stirring temperature during spraying was 70 °C until the spraying was completed. Then, stirring was continued for 0.5 h, and then cooled to room temperature (25 °C), stirred at room temperature for 0.3 h, and stirred at a stirring rate of 400 r / min, and further cooled to 5 °C, stirred at low temperature for 1.0 h, and stirred at a stirring rate of 300 r / min. After that, stirring was stopped, and the mixture was allowed to settle for 0.3 h. Then, a cyclone separator was used for dust removal, and the dust removal rotation rate was controlled to be 300 r / min, the air inlet rate was 3 m / s, and the power was 200 W. Then, flash drying was further adopted, and the drying temperature was 100 °C, the drying time was 20 min, and the air inlet volume was 500m 3 / h, a multi-level silicon-nitrogen bonding layer hybrid hydromagnesia composite powder (SiN-cr-NWM) was obtained, and the median particle size of the product was D 50 =2.0 μm.

[0075] Example 3

[0076] 1) Proline was dissolved in a mixture of water and ethanol at a volume ratio of 20:1. The mixture was stirred at 75°C for 0.5 h at a stirring rate of 1500 rpm to obtain Solution 1, where the concentration of Solution 1 was 10 M.

[0077] 2) Dissolve 3-aminopropyltriethoxysilane in a mixture of water and ethanol at a volume ratio of 1:20, a mixing temperature of 60°C, a stirring time of 0.1 h, and a stirring rate of 900 rpm to obtain Solution 2. The concentration of Solution 2 is 10 M.

[0078] Solution 1 was added to solution 2 at a rate of 10 mL / min and stirred at a stirring rate of 1600 rpm until the addition was complete. Stirring was continued for 0.5 h after the addition was complete to obtain solution 3, wherein the molar ratio of 3-aminopropyltriethoxysilane to proline was 1:10;

[0079] 3) adding solution 3 to the high-speed rotating natural hydromagnesite powder at a uniform speed, controlling the addition rate to be 60 mL / min. Before addition, the natural hydromagnesite powder was preheated in a high-speed stirrer for 0.5 h, with a stirring rate of 300 r / min and a preheating temperature of 65°C. During addition, the stirring rate was increased to 900 r / min, at which time the temperature rose to 85°C. Stirring was continued for 0.3 h until the addition was complete to obtain a modified hydromagnesite composite powder. The molar to mass ratio of the 3-aminopropyltriethoxysilane to the natural hydromagnesite powder was 5 mol:10 kg.

[0080] 4) Tetrakis(4-formylphenyl)silane was stirred and dispersed in a mixture of water and ethanol at a volume ratio of 1:20, a stirring temperature of 45°C, a stirring time of 0.2 h, and a stirring rate of 900 rpm to obtain Solution 4. The concentration of Solution 4 was 5 M.

[0081] 5) Solution 4 was added to the high-speed rotating modified hydromagnesite composite powder in the form of a spray, and the molar to mass ratio of tetra(4-formylphenyl)silane and natural hydromagnesite mineral powder was controlled to be 10 mol:20 kg, wherein the spray rate was 40 mL / min, and the spraying was carried out while stirring. The stirring rate was 1200 r / min, and the stirring temperature during spraying was 90 °C until the spraying was completed. Then, stirring was continued for 0.1 h, and then cooled to room temperature (25 °C), stirred at room temperature for 0.1 h, and stirred at a stirring rate of 800 r / min, and further cooled to 15 °C, stirred at low temperature for 0.1 h, and stirred at a stirring rate of 800 r / min. Then, stirring was stopped, and the mixture was allowed to settle for 0.8 h. Then, a cyclone separator was used for dust removal, and the dust removal rotation rate was controlled to be 1000 r / min, the air inlet rate was 12 m / s, and the power was 600 W. Then, flash drying was further adopted, the drying temperature was 125 °C, and the drying time was 5 min, air intake volume is 1000 m 3 / h, a multi-level silicon-nitrogen bonding layer hybrid hydromagnesia composite powder (SiN-cr-NWM) was obtained, with a median particle size of D 50 =2.0μm.

[0082] Comparative Example 1

[0083] Steps (1), (2), (3), and (4) are the same as those in Example 1;

[0084] (5) Solution 4 was added to the high-speed rotating modified hydromagnesite composite powder in the form of a spray, and the molar to mass ratio of tetra(4-formylphenyl)silane and natural hydromagnesite powder was controlled to be 0.5 mol:20 kg, wherein the spray rate was 20 mL / min, and the spraying was carried out while stirring, the stirring rate was 800 r / min, and the stirring temperature during spraying was 80 ℃ until the spraying was completed. Then, stirring was continued for 0.3 h, and then cooled to room temperature (25 ℃), stirred at room temperature for 0.2 h, and the stirring rate was 700 r / min, and further cooled to 10 ℃, stirred at low temperature for 0.5 h, and the stirring rate was 500 r / min. Then, stirring was stopped, and the mixture was allowed to settle for 0.5 h. Then, a cyclone separator was used for dust removal, and the dust removal rotation rate was controlled to be 600 r / min, the air inlet rate was 6 m / s, and the power was 400 W. Then, flash drying was further adopted, and the drying temperature was 110 ℃, the drying time was 10 min, and the air inlet volume was 800 m 3 / h, a multi-level silicon-nitrogen bonding layer hybridized hydromagnesia composite powder was obtained, and the median particle size of the product was D 50 =2.0μm.

[0085] Comparative Example 2

[0086] Steps (1), (2), (3), and (4) are the same as those in Example 1;

[0087] (5) Solution 4 was added to the high-speed rotating modified hydromagnesite composite powder in the form of a spray, and the molar to mass ratio of tetra(4-formylphenyl)silane and natural hydromagnesite powder was controlled to be 30 mol:20 kg, wherein the spray rate was 20 mL / min, and the spraying was carried out while stirring, the stirring rate was 800 r / min, and the stirring temperature during spraying was 80 ℃ until the spraying was completed. Then, the stirring was continued for 0.3 h, and then cooled to room temperature (25 ℃), stirred at room temperature for 0.2 h, and the stirring rate was 700 r / min, and further cooled to 10 ℃, stirred at low temperature for 0.5 h, and the stirring rate was 500 r / min. Then, the stirring was stopped, and the mixture was allowed to settle for 0.5 h. Then, the mixture was dusted by a cyclone separator, and the dust removal rotation rate was controlled to be 600 r / min, the air inlet rate was 6 m / s, and the power was 400 W. Then, flash drying was further adopted, and the drying temperature was 110 ℃, the drying time was 10 min, and the air inlet volume was 800 m 3 / h, a multi-level silicon-nitrogen bonding layer hybridized hydromagnesia composite powder was obtained, and the median particle size of the product was D50 =2.0μm.

[0088] Comparative Example 3

[0089] Natural hydromagnesite powder, the median particle size of the product is D 50 =1.8 μm.

[0090] Structural characterization and performance testing

[0091] 1) The microscopic morphology of the multi-layer silicon-nitrogen bonding layer hybridized hydromagnesia composite powder prepared in Example 1 was characterized by scanning electron microscopy. Figure 2 As shown, there is a relatively dense irregular coating layer on the surface of the composite powder.

[0092] 2) Figure 3 The particle size distribution diagram of the multi-level silicon-nitrogen bonding layer hybridized hydromagnesia composite powder prepared in Example 1; Figure 3 It can be seen that the median particle size of the obtained multi-level silicon-nitrogen bonding layer hybridized hydromagnesia composite powder (SiN-cr-NWM) is about 2.0 μm, showing a good normal distribution.

[0093] 3) The activation rate, oil absorption value, and contact angle of the multi-layer silicon-nitrogen bonding layer hybrid hydromagnesite composite materials (SiN-cr-NWM) prepared in Examples 1 to 3 and Comparative Examples 1 to 3 and the natural hydromagnesite mineral powder were tested. The test method is as follows:

[0094] Activation rate: The dry powder is tested by weighing method.

[0095] Oil absorption value: tested in accordance with DB / T5211.15-2014 standard.

[0096] Contact angle: The contact angle of the sample was measured using a contact angle meter.

[0097] The test results are shown in Table 1.

[0098] Table 1 Performance test results of products prepared in Examples 1 to 3 and Comparative Examples 1 to 3

[0099]

[0100] From the test results of examples 1-3 and comparative example 3 in table 1, it can be found that the multi-level efficient modification of natural water-magnesite powder can be achieved by introducing multi-component amino acid to form a silicon-nitrogen cross-linking layer, and the obtained composite powder has significant advantages in activation rate, oil absorption value and contact angle. Especially in terms of oil absorption value, it is reduced from 40 mL / 100g of natural water-magnesite powder to 22 mL / 100g. The hydrophilic and hydrophobic properties of the powder surface are significantly changed, realizing the transformation from hydrophilic to hydrophobic. Such changes make the composite powder exhibit typical hydrophobicity and low polarity, which can effectively reduce the adsorption of natural mineral powder to processing aids, greatly reduce the processing cost, and have great advantages for industrial large-scale application. From the test results of the composite powders of comparative examples 1-2, it can be found that when the ratio of aldehyde-silane on the surface to natural water-magnesite powder is not appropriate, the activation rate and oil absorption performance of the final composite powder are limitedly improved, and the hydrophobic performance of the composite powder is also poor in terms of contact angle.

[0101] Application example

[0102] The multi-level silicon-nitrogen adhesive layer hybrid water-magnesite composite powders (SiN-cr-NWM) of examples 1-3 and comparative examples 1-2 and the natural water-magnesite mineral powder in comparative example 3 were added to ethylene-vinyl acetate copolymer (EVA) cable master batch, and the performance of the cable material was tested. The specific method is as follows:

[0103] The EVA resin and processing aids (54 parts of EVA resin, 5 parts of compatibilizer MC226, 0.2 parts of antioxidant 1010, and 0.8 parts of industrial-grade silicone master batch) were first densified at 140 ℃ for 5 min, then 30 parts of the multi-level silicon-nitrogen adhesive layer hybrid water-magnesite composite powders (SiN-cr-NWM) prepared in examples 1-3 and comparative examples 1-2 and the natural water-magnesite mineral powder in comparative example 3 were added and densified for 8 min, then taken out and fixed on the open mill for shaping, the temperature was controlled at 150 ℃, the back pressure was 15 MPa, and the hot pressing time was 10 min, then cold pressing, to prepare various test samples for use.

[0104] Thermogravimetric test: nitrogen atmosphere, heating rate 10 ℃ / min, 30-800 ℃.

[0105] Limiting oxygen index: GBT 2406-1993 test.

[0106] Vertical burning: ASTM D3801-2010.

[0107] Processing performance test: blending temperature 150 ℃, rotation speed 40 r / min.

[0108] Tensile strength test: GB / T1040-2006, at 23±2 ℃.

[0109] Raman spectroscopy test: Bruker FRS-100S, 500~3000 cm -1 , I D is located at 1340 cm -1 The D-band peak, I G is located at 1570 cm -1 G-band peak.

[0110] The test results are shown in Table 2.

[0111] Table 2 Performance test results of EVA composite substrates prepared using the powders obtained in Examples 1 to 3 and Comparative Examples 1 to 3

[0112]

[0113] By comparing the data on the carbon residue quality of the EVA composite substrates prepared by the powders in Examples 1 to 3 and Comparative Example 3, it can be seen that when the hydromagnesite composite powder modified by silicon-nitrogen cross-linking silane is compounded, the carbon residue quality of EVA at high temperature can be significantly improved, and the maximum value increases from 12.1% to 34.6%. This may be because the silicon-nitrogen cross-linked modification layer on the surface can quickly form carbon during the combustion process and can significantly promote the deposition of matrix combustion molecular chain fragments in the carbon layer, effectively improving the physical barrier property of the combustion front; in terms of combustion performance, the LOI value of the composite substrate increases from 21.1% to 30.0% at a maximum, which transforms the composite material from a combustible material to a flame retardant material. It can be seen that in terms of barrier The combustion performance has been effectively improved; at the same time, in the vertical combustion test, when the hydromagnesite composite powder modified with silicon-nitrogen cross-linked silane is compounded, the vertical combustion of the composite substrate can pass the V-0 level; in contrast, when the hydromagnesite powder that has not been effectively modified is added to the EVA composite substrate, the vertical combustion level has a more significant decrease, and the macroscopic combustion performance has decreased; in terms of processing performance, the introduction of the hydromagnesite composite powder modified with silicon-nitrogen cross-linked layer can reduce the balance torque of the composite substrate to a certain extent, indicating that the effectively modified hydromagnesite composite powder can be more evenly dispersed in the polymer matrix, which may be due to the introduction of silicon-nitrogen into the composite powder. After the cross-linking layer, it can be used as an internal plasticizer to effectively promote the relative flow and slip of molecular chains during processing. In contrast, natural hydromagnesite composite powders that have not been effectively modified on the surface may cause serious agglomeration during the melt mixing process due to their high surface energy and large polarity, resulting in uneven mixing, which seriously hinders the movement of EVA molecular chains and causes an increase in equilibrium torque. In terms of mechanical tensile strength, the introduction of hydromagnesite composite powders modified with a silicon-nitrogen cross-linking layer can improve the dispersion and compatibility of the composite powders in the polymer matrix, effectively improving the mechanical tensile properties of the EVA composite substrate. In contrast, the surface modification effect is poor or not effectively modified. Due to its high polarity, natural hydromagnesite mineral powder has poor bonding with lipophilic EVA, making it easy to become a stress concentration point, resulting in a decrease in the tensile strength of the EVA substrate; in terms of carbonization effect, after adding hydromagnesite composite powder modified with a silicon-nitrogen cross-linking layer, the ID / IG of the carbon layer has a more significant downward trend, and can drop from 1.31 to a maximum of 0.80, indicating that the degree of order of the carbon layer has been greatly improved, which can better enhance the physical barrier properties. This shows that the introduction of the amino acid silicon-nitrogen bonding layer can enhance the internal and external synergistic effect, thereby playing a significant role in improving the quality and quantity of residual carbon, and effectively improving its processing performance and tensile strength.In comparison, Comparative Examples 1-2 are inferior to Examples 1-3 in terms of both char quality and quantity, and the combustion performance test is not as obvious as that of Examples 1-3. The performance improvement in tensile strength and processing fluidity is also limited. This may be due to the unbalanced proportion of the introduced silicon-nitrogen cross-linked silane layer, which limits the modification effect on natural hydromagnesite and leads to a decline in performance in multiple aspects.

[0114] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing a multi-level silicon-nitrogen bonding layer hybrid hydromagnesite composite material, characterized in that: The following steps are involved: performing a first mixing of the amino acid and the first solvent to obtain an amino acid solution; performing a second mixing of the aminosilane and the second solvent to obtain an aminosilane solution; performing a third mixing of the amino acid solution and the aminosilane solution to obtain a mixed modifier; The mixed modifier is mixed with the hydromagnesite ore powder for the fourth time, and subjected to the first modification to obtain a modified hydromagnesite composite powder; After the aldehyde silane and the third solvent are mixed for the fifth time, the obtained aldehyde silane dispersion is mixed with the modified hydromagnesia composite powder and subjected to the second modification to obtain a hydromagnesia composite material with a multi-level silicon-nitrogen bonding layer hybridization.

2. The preparation method according to claim 1, characterized in that The amino acids include one or more of alanine, glycine, proline, serine, aspartic acid, cysteine, and threonine; The first solvent is a water-alcohol mixture, the volume ratio of water to alcohol in the first solvent is 1:1~20:1, the first mixing conditions include: temperature of 45~75°C, time of 0.5~2.0 h, stirring rate of 500~1500 rpm, and the concentration of the amino acid solution is 1~10M.

3. The preparation method according to claim 1, characterized in that The aminosilane includes one or more of 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, N-2-aminoethyl-3-aminopropyltriethoxysilane, N-2-aminoethyl-3-aminopropyltrimethoxysilane, N-2-aminoethyl-3-aminopropylmethyldiethoxysilane, diethylenetriaminopropyltrimethoxysilane and N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane; the molar ratio of the aminosilane to the amino acid is 1:1 to 1:

10.

4. The preparation method according to claim 1, characterized in that The second solvent is a water-alcohol mixture, the volume ratio of water to alcohol in the second solvent is 1:1 to 1:20, the second mixing conditions include: temperature of 30 to 60° C., time of 0.1 to 1.2 h, stirring rate of 100 to 900 rpm, and the concentration of the aminosilane solution is 1 to 10 M; The third mixing method is constant-speed addition, with an addition rate of 1-10 mL / min, a stirring rate of 600-1600 rpm during addition, and continuous stirring for 0.5-2.0 h after the addition is completed.

5. The preparation method according to claim 1, characterized in that The molar ratio of the aminosilane to the hydromagnesite powder is 1-5 mol:10 kg; the particle size of the hydromagnesite powder is D 50 =0.9~3.9μm, the total content of magnesium carbonate and magnesium hydroxide is ≥90wt%; the temperature of the first modification is 65~85℃, and the time is 0.3~1.2 h.

6. The preparation method according to claim 1, characterized in that The formaldehyde silane includes tetra(4-formylphenyl)silane, the third solvent is a water-alcohol mixture, and the volume ratio of water to alcohol in the third solvent is 1:1~1:20; the fifth mixing conditions include: temperature of 25~45°C, time of 0.2~1.6 h, and stirring rate of 100~900 rpm; the concentration of the formaldehyde silane dispersion is 0.1~5M.

7. The preparation method according to claim 1, characterized in that The molar ratio of the aldehyde silane to the mass of the hydromagnesite powder is 1-10 mol:20 kg; the second modification includes reacting at 70-90° C. for 0.1-0.5 h, cooling to room temperature for 0.1-0.3 h, and cooling to 5-15° C. for 0.1-1.0 h.

8. The multi-level silicon-nitrogen bonding layer hybridized hydromagnesite composite material prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the multi-level silicon-nitrogen bonding layer hybridized hydromagnesia composite material according to claim 8 in ethylene-vinyl acetate copolymer cable masterbatch.

10. The use according to claim 9, characterized in that The application method comprises the following steps: first kneading EVA resin and processing aid, adding a multi-level silicon-nitrogen bonding layer hybridized hydromagnesia composite material for second kneading, and then sequentially cooling and cutting to obtain EVA cable masterbatch.

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