Modification method for introducing functional groups on surface of kaolin and application of modification method

Abstract

The invention relates to a modification method of kaolin, in particular to a modification method for introducing functional groups on the surface of kaolin and application thereof. The method comprises the following steps: firstly, providing kaolin with specific particle size distribution as a base material; then, enabling a phosphate silane coupling agent to react with the kaolin, and introducing a functional group to the surface of the kaolin; secondly, manufacturing ordered porosity in the kaolin structure by using a biological template method so as to increase the specific surface area and the adsorption capacity; finally, the biological template is removed and modification of the kaolin is completed by heat treatment and washing steps. The obtained modified kaolin shows improved thermal stability, adsorption performance and dispersibility in a polymer matrix. The invention also relates to an application of the modified kaolin in preparation of a high-performance composite material, especially as a filler for enhancing the mechanical properties and high temperature resistance of plastics and rubber. Compared with the prior art, the modified kaolin provided by the invention has better performance, and the preparation process is environment-friendly and economic and is suitable for industrial production.

Description

Technical Field

[0001] The invention belongs to the technical field of non-metallic mineral modification, and in particular relates to a modification method for introducing functional groups into the surface of kaolin. Background Art

[0002] As an important non-metallic mineral, kaolin is widely used in papermaking, ceramics, rubber, cosmetics, plastics and other industries due to its good whiteness, plasticity, adsorption and chemical stability. However, due to its natural properties, the performance of kaolin in some special application fields is not satisfactory, such as insufficient stability in high temperature processes, limited adsorption capacity, poor dispersibility and other issues, which restrict its wider application.

[0003] The problems of traditional kaolin modification technology are mainly concentrated in the following aspects: 1. Insufficient thermal stability: At high temperatures, the structural water in kaolin is easily removed, causing its structure to change, thus affecting its application in high-temperature processing materials such as plastics and rubber.

[0004] 2. Limited adsorption performance: Although kaolin naturally has a certain adsorption capacity, its adsorption capacity and selectivity in its natural state cannot meet the requirements of an efficient adsorbent.

[0005] 3. Poor dispersibility and compatibility: Kaolin has poor dispersion performance in organic polymer matrices and is easy to aggregate, resulting in poor interface strength of the composite material and affecting the final performance of the product. In view of the above problems, the prior art has adopted the following modification methods: Acid washing method: Impurities in kaolin can be removed by reacting with acid to improve its purity and whiteness, but this treatment process can easily lead to the destruction of the particle structure and requires the treatment of wastewater after acid washing, which poses an environmental pollution risk.

[0006] Organic treatment method: By coating organic matter on the surface of kaolin, its dispersibility in the organic matrix is ​​improved, but the stability and durability of the coating are limited, and it may increase production costs and the burden on the environment.

[0007] Ion exchange method: New functional groups are introduced by utilizing the cation exchange capacity between kaolin layers. Although the adsorption performance and thermal stability are improved to some extent, ion exchange is easily affected by environmental conditions, such as pH and ion concentration, which affects its practical application.

[0008] Although the above methods improve certain properties of kaolin to a certain extent, they are often accompanied by the sacrifice of other properties. For example, heat treatment to improve thermal stability may lead to a decrease in the adsorption capacity and surface activity of kaolin. Similarly, surface modification to increase adsorption capacity may increase the interface incompatibility between kaolin and polymer matrix, thus affecting its application in composite materials.

[0009] Therefore, there is an urgent need for a new kaolin modification method that can comprehensively improve its thermal stability, adsorption capacity and compatibility with plastic matrices without damaging the original structure of kaolin. In addition, the method should also be environmentally friendly, which can reduce the impact on the environment and be more economically competitive. Summary of the invention The purpose of the present invention is to provide a modification method for introducing functional groups into the surface of kaolin and its application, which can effectively improve the thermal stability of kaolin in high-temperature processes, enhance its adsorption capacity, and improve its dispersibility and compatibility in organic polymer matrices, while taking into account environmental friendliness and economic benefits.

[0010] To achieve the above object, the present invention adopts the following technical solutions: 1. Phosphate-based silane coupling agent is selected as the modifier. It can not only react with the hydroxyl groups on the surface of kaolin to form a stable covalent bond, but the phosphate group can also improve the thermal stability of kaolin and increase its adsorption capacity for organic matter.

[0011] 2. Introduce the bio-template method to prepare porous kaolin. By using organic templates with specific three-dimensional structures (such as xylose, porous polymer microspheres, etc.), an ordered porous structure is produced during the heat treatment process, thereby significantly improving the specific surface area and adsorption of kaolin.

[0012] 3. Combining physical and chemical methods, the interaction process between the modifier and kaolin is optimized through advanced surface engineering technology to achieve efficient modification of kaolin and ensure the quality and performance stability of the modified kaolin.

[0013] 4. The invention also includes a method for applying modified kaolin to high-performance composite materials, wherein the modified kaolin can be uniformly dispersed in a polymer matrix and form a strong interface bond with the matrix, significantly improving the mechanical properties and heat resistance of the composite material.

[0014] The specific production steps are: 1. Selection of raw materials: Kaolin raw materials: Select natural kaolin with high purity and low impurity content, with particle size distribution mainly between 0.5-2 microns to ensure sufficient specific surface area and active sites.

[0015] Modifier: A phosphate-based silane coupling agent (such as tri(2-methoxyethoxy)silane phosphate) is selected. Due to its unique phosphate group, it can improve the thermal stability of kaolin and enhance its adsorption capacity for organic compounds.

[0016] 2. Preparation of modifier: The modifier is prepared in an aqueous solution containing 5% ethanol at a ratio of 1% of the mass of kaolin to form a 0.5% modifier solution. The pH is adjusted to about 4-5 to promote the reaction of the silane coupling agent with the hydroxyl groups on the surface of kaolin.

[0017] 3. Pretreatment of kaolin: The kaolin was dried at 105°C for 4 hours to remove free moisture.

[0018] The kaolin particles were further reduced in size using a ball mill to increase their specific surface area.

[0019] 4. Modification reaction: The pretreated kaolin was mixed with the modifier solution in a thermostatic stirrer, and the stirring speed was set to 500 rpm to ensure thorough mixing.

[0020] The reaction temperature was set at 60 °C and the reaction time was 4 h to ensure that the modifier fully reacted with the hydroxyl groups on the surface of kaolin.

[0021] 5. Preparation of porous structures by bio-template method: Xylose was selected as the organic template and added to the above reaction mixture at a mass ratio of 5%.

[0022] After drying for 12 hours, the mixture was heated to 500°C in a nitrogen atmosphere and maintained for 2 hours to prepare a porous structured kaolin.

[0023] 6. Post-processing: Unreacted modifier and organic template were removed by vacuum filtration.

[0024] The obtained product was dried in a vacuum drying oven at 110°C for 24 hours to obtain modified kaolin.

[0025] 7. Performance Characterization: The introduction of phosphate groups was confirmed using Fourier transform infrared spectroscopy (FTIR) analysis.

[0026] The structure and porosity of kaolin were evaluated using X-ray diffraction (XRD) and scanning electron microscopy (SEM).

[0027] Thermogravimetric analysis (TGA) was used to evaluate the thermal stability of kaolin.

[0028] Specific surface area and pore analysis (such as BET and BJH methods) are used to characterize the porous properties.

[0029] The advantages and positive effects of the present invention compared with the prior art are mainly reflected in: The introduction of phosphate silane coupling agent not only improves the thermal stability of kaolin, but also enhances its compatibility with organic polymers, broadening the application scope of kaolin in high-temperature composite materials.

[0030] The application of the bio-template method creates porous kaolin with an ordered structure, which shows better performance in environmental purification, catalyst support, etc.

[0031] The method does not involve serious environmental pollution problems, the raw materials are easily available, the cost is relatively low, and it is easy to industrialize production.

[0032] Modified kaolin can be used as a high-performance filler in plastics, rubber and other materials by improving mechanical strength and thermal stability, making it possible for high-end applications of the material.

[0033] The technical content of the present invention is described in detail above. Specific implementation methods and experimental examples will be further described in the subsequent sections to verify the feasibility and effectiveness of the solution of the present invention. Implementation

[0034] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0035] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0036] Example 1: Preparation and Effect of Phosphate-Silane Coupling Agent Modified Kaolin 1. Raw material preparation: Kaolin raw materials with a particle size distribution of 0.5-2 μm were selected, washed with water three times, and then dried at 105°C for 12 hours.

[0037] 2. Modifier preparation: A phosphate-based silane coupling agent was taken at 1% of the mass of kaolin and dissolved in an aqueous solution containing 5% ethanol to prepare a 0.5% w / v solution, and the pH was adjusted to 4.5 for pre-hydrolysis.

[0038] 3. Modification reaction: The pretreated kaolin was added to the pre-hydrolyzed modifier solution at a solid-to-liquid ratio of 1:10, and the reaction was stirred at 60°C and 500 rpm for 4 hours.

[0039] 4. Preparation of porous structure: Xylose was added to the reaction mixture as an organic template at a mass ratio of 1:1, dried at room temperature for 24 hours, and then heated to 500°C under nitrogen protection for 2 hours.

[0040] 5. Product post-processing: The unreacted substances were removed by washing, and then dried at 105°C for 12 hours to obtain modified kaolin.

[0041] 6. Product effect evaluation: Fourier transform infrared spectroscopy (FTIR) analysis confirmed the successful introduction of phosphate groups.

[0042] Thermogravimetric analysis (TGA): The thermal stability of modified kaolin is improved by about 30% compared with the unmodified sample.

[0043] Specific surface area analysis (BET): The specific surface area of ​​the modified kaolin increased from the original 25 m² / g to 150 m² / g.

[0044] Composite material test: When modified kaolin was added to polypropylene, it was found that its tensile strength increased from 30 MPa of unmodified kaolin to 45 MPa, and the impact strength was also significantly improved.

[0045] Example 2: Preparation of porous kaolin using a multifunctional silane coupling agent and a biological template 1. Raw material preparation: Kaolin was prepared as in Example 1.

[0046] 2. Modifier preparation: A multifunctional silane coupling agent (such as aminopropyltriethoxysilane) is selected and dissolved in an aqueous solution containing 5% ethanol at 2% by weight of kaolin to prepare a 1.0% w / v solution, and the pH is adjusted to 5.0.

[0047] 3. Modification reaction: The reaction was stirred at 70°C and 600 rpm for 6 hours.

[0048] 4. Preparation of porous structure: Kaolin and polystyrene microspheres (as biological templates) were mixed in a mass ratio of 1:1, and the subsequent treatment was the same as in Example 1.

[0049] 5. Product post-processing: Same as Example 1.

[0050] 6. Product effect evaluation: Fourier transform infrared spectroscopy (FTIR) analysis: showed the characteristic absorption peaks of amino and siloxane functional groups.

[0051] Thermogravimetric analysis (TGA): showed that the weight retention of the modified kaolin at 800°C was 35% higher than that of the unmodified sample.

[0052] Specific surface area analysis (BET): showed that the specific surface area increased to 200 m² / g.

[0053] Composite material test: After the modified kaolin was compounded with polyvinyl alcohol, the tensile strength increased from 35 MPa to 60 MPa, indicating a superior reinforcement effect.

[0054] The above examples show that the modified kaolin provided by the present invention can significantly improve thermal stability and adsorption performance, and exhibit good dispersibility and mechanical reinforcement effects in plastic matrices. These characteristics make the modified kaolin have broad application prospects in high-end application fields.

[0055] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for modifying kaolin surface by introducing functional groups and its application, characterized in that: The following steps are involved: S1, providing kaolin raw material with a particle size of 0.5-2 microns; S2, mixing the kaolin raw material with a solution of a phosphate-based silane coupling agent, wherein the phosphate-based silane coupling agent accounts for 1% to 2% of the mass of the kaolin raw material; S3, reacting at 60°C to 70°C for 4 to 6 hours under the condition of adjusting the pH to 4.5 to 5.0; S4, adding a biological template, wherein the biological template is xylose or polystyrene microspheres; S5, after drying at room temperature, heating to 500° C. under nitrogen protection and maintaining for 2 hours to remove the bio-template and form porous kaolin; S6. Wash the obtained porous kaolin with distilled water and dry it at 105°C.

2. The method for modifying kaolin surface by introducing functional groups according to claim 1 and its application, characterized in that: The phosphate-based silane coupling agent is tri(2-methoxyethoxy)silane phosphate or aminopropyltriethoxysilane.

3. A method for modifying kaolin surface by introducing functional groups and its application according to claim 1 or 2, characterized in that: The mass ratio of the biological template to the kaolin raw material is 1:

1.

4. A high-performance composite material using the modified kaolin described in claims 1, 2 and 3 as a filling material.

5. The high performance composite material according to claim 4, characterized in that: The composite material comprises polypropylene as a matrix, and the modified kaolin is uniformly dispersed in the polypropylene.