Octaaminopropyl POSS (polyhedral oligomeric silsesquioxane) hydrochloride modified sepiolite and flame-retardant application thereof in plastics

Abstract

The invention provides octa-aminopropyl POSS (polyhedral oligomeric silsesquioxane) hydrochloride modified sepiolite and a flame retardant application of the octa-aminopropyl POSS hydrochloride modified sepiolite in plastics. The modified sepiolite is formed by compounding octa-aminopropyl POSS hydrochloride and sepiolite, the mass ratio of the octa-aminopropyl POSS hydrochloride to the sepiolite is (2-5): 10, and the POSS hydrochloride is synthesized from 3-aminopropyl triethoxy silane, methanol and concentrated hydrochloric acid according to the volume ratio of (5-15): (65-85): (10-20). According to the octa-aminopropyl POSS hydrochloride modified sepiolite, the modification process comprises the steps of sepiolite pretreatment, reaction of POSS and sepiolite and treatment after calcination, and dispersity and bonding strength are remarkably improved through variable-speed stirring and particle size control. In flame-retardant application, the octa-aminopropyl POSS hydrochloride modified sepiolite and a polypropylene plastic matrix or a cable material are mixed according to the mass ratio of (1-10): 100, and flame-retardant plastic is prepared by adopting a mechanical blending method. The flame retardant property, thermal stability and mechanical property of the plastic are remarkably improved, the environment-friendly requirement is met, a high-performance and low-cost halogen-free flame retardant solution is provided, and the halogen-free flame retardant plastic has important practical application value.

Description

Technical Field

[0001] The present invention relates to the field of materials science, and particularly to an octaaminopropyl POSS hydrochloride modified sepiolite and its flame retardant application in plastics. Background Art

[0002] Plastic is a material made of high molecular polymers. Due to its characteristics such as light weight, durability, and strong plasticity, it has been widely used in daily life and industrial fields. However, the flammability of plastics poses a fire risk during use, and even leads to serious safety accidents. Once plastic products come into contact with a fire source or a high-temperature environment, they are very likely to burn rapidly and release a large amount of heat and toxic smoke, resulting in the spread of the fire and bringing great difficulties to the evacuation of personnel and the extinguishment of the fire. Therefore, it is necessary to add flame retardants to plastics, conduct flame retardant treatment on them, and enhance their flame retardant performance to avoid unnecessary safety hazards.

[0003] Traditional halogen-based flame retardants (organic chlorides and organic bromides) have been widely used in plastic products in the past and have been favored because of their significant flame retardant effects. These flame retardants can capture free radicals during the combustion process and inhibit the spread of flames, thereby effectively reducing the burning rate of materials. However, with the enhancement of environmental awareness and the in-depth development of scientific research, people have gradually discovered that halogen-based flame retardants have serious environmental and health problems. First of all, halogen-based flame retardants will release a large amount of toxic and harmful gases during the combustion process, such as dioxins, polybrominated biphenyls, etc. These substances are not only harmful to human health but also cause serious environmental pollution. Secondly, halogen-based flame retardants have strong environmental persistence and bioaccumulation. They are difficult to degrade in the natural environment, will exist in soil, water bodies, and organisms for a long time, and will continuously accumulate through the transfer of the food chain, ultimately posing a potential threat to the ecosystem and human health. For example, polybrominated diphenyl ethers have been proven to be persistent organic pollutants, and their widespread presence in the environment has attracted global attention. Therefore, with the increasingly strict relevant regulations, the use of halogen-based flame retardants has been gradually restricted, and the development of new environmentally friendly flame retardants has become an urgent need in the field of flame retardant materials.

[0004] In the prior art, halogen-free flame retardants mainly include metal hydroxides, phosphorus-based compounds, and intumescent flame retardants, but there are problems such as high addition amounts and large losses of mechanical properties. Sepiolite, as a natural silicate mineral, has a high specific surface area and adsorption capacity and can be used as a flame retardant filler. However, its compatibility with the polymer matrix is poor, and its dispersibility needs to be improved through surface modification. Cage-like silsesquioxane (POSS) has a nanoscale cage-like structure and can be functionalized through chemical modification to synergistically enhance the flame retardant effect with inorganic fillers. However, the composite modification of POSS and sepiolite and its application in polypropylene and cable materials have not been systematically developed in the prior art. Summary of the Invention

[0005] The object of the present invention is to synthesize a new halogen-free flame retardant additive. This sepiolite additive uses octa(aminopropyl)silsesquioxane hydrochloride (POSS) and sepiolite as raw materials, and after modification, it is applied to plastics to improve their flame retardancy, thermal stability and mechanical properties, while meeting environmental protection requirements.

[0006] Both the octa(aminopropyl)POSS hydrochloride and sepiolite raw materials used in the present invention are substances harmless to the human body. Sepiolite is a natural mineral with good biocompatibility, rich resources and renewable. By using this natural material, the present invention not only reduces the dependence on non-renewable resources, but also reduces production costs. The POSS structure does not release toxic and harmful gases after combustion, and its residue is similar to the soil components, causing no pollution to the environment. The modified sepiolite of the present invention also does not produce harmful residues after combustion, and its residue is similar to the soil components, further reflecting sustainability. Therefore, the flame retardant of the present invention fully meets environmental protection requirements, is harmless to the environment and human health after combustion, and has remarkable environmental friendliness and safety.

[0007] The present invention provides an accurate chemical basis for synthesizing a new type of high-efficiency flame retardant additive by clarifying the raw material composition and its ratio of octa(aminopropyl)POSS hydrochloride modified sepiolite. Among them, the mass ratio of octa(aminopropyl)POSS hydrochloride to sepiolite ensures the optimal combination ratio between POSS and sepiolite, which can not only give full play to the flame retardant function of POSS, but also maintain the excellent adsorption performance and high specific surface area of sepiolite. At the same time, the volume ratio of 3-aminopropyltriethoxysilane, methanol and concentrated hydrochloric acid provides optimized reaction conditions for the synthesis of POSS, ensuring the high purity and functionality of the product. The precise setting of these ratios not only provides a guarantee for the repeatability and high efficiency of the synthesis of modified sepiolite, but also lays a solid material foundation for its flame retardant application in plastics, meeting the requirements of the modern plastics industry for high-performance and environmentally friendly flame retardant materials.

[0008] The present invention provides an octa(aminopropyl)POSS hydrochloride modified sepiolite, the raw materials of which include: octa(aminopropyl)POSS hydrochloride and sepiolite, and the mass ratio of the octa(aminopropyl)POSS hydrochloride to sepiolite is 2-5:10; the raw material composition of the octa(aminopropyl)POSS hydrochloride includes: 3-aminopropyltriethoxysilane, methanol and concentrated hydrochloric acid, and the volume ratio of the 3-aminopropyltriethoxysilane, methanol and concentrated hydrochloric acid is 5-15:65-85:10-20.

[0009] In the octaaminopropyl POSS hydrochloride modified sepiolite raw material of the present invention, the mass ratio of octaaminopropyl POSS hydrochloride to sepiolite of 20-50:100 determines the coverage degree and interaction strength of POSS on the surface of sepiolite. As a functional additive, the higher the content of POSS, the better the flame retardant effect usually is. However, excessive POSS leads to agglomeration and reduces dispersibility. An appropriate amount of POSS can enhance the interfacial bonding force between sepiolite and the plastic matrix, thereby improving the mechanical properties of the composite material. At the same time, a higher POSS content will increase the cost. Therefore, it is necessary to find a balance between performance and cost. The appropriate mass ratio selected in the present invention can ensure good compatibility between POSS and sepiolite, and avoid performance degradation caused by improper proportion.

[0010] In the octaaminopropyl POSS hydrochloride of the octaaminopropyl POSS hydrochloride modified sepiolite raw material of the present invention, the volume ratio of 3-aminopropyltriethoxysilane, methanol and concentrated hydrochloric acid of 5-15:65-85:10-20 determines the reactant concentration and reaction conditions during the POSS synthesis process, and directly affects the structure and performance of the product. 3-aminopropyltriethoxysilane is the core reactant of the POSS structure, and its content determines the number of amino groups and active sites of POSS. A higher proportion of 3-aminopropyltriethoxysilane can increase the amino group content of POSS, thereby improving the binding ability with sepiolite. As a solvent, methanol provides a reaction medium to ensure the uniform dispersion of reactants. The proportion of methanol needs to be high enough to ensure the fluidity of the reaction system and avoid side reactions caused by too high reactant concentration. As a catalyst, concentrated hydrochloric acid promotes the hydrolysis and polycondensation reactions of 3-aminopropyltriethoxysilane, and its proportion needs to be precisely controlled to avoid the reaction being too fast or too slow. Too fast will lead to an increase in by-products, and too slow will affect production efficiency.

[0011] The present invention ensures its high-quality synthesis and functionality by optimizing the preparation process of octaaminopropyl POSS hydrochloride. During the preparation process, by controlling the reaction temperature, reaction time and the dropping rate of concentrated hydrochloric acid, the reaction rate is precisely regulated to avoid the occurrence of side reactions, thereby improving the purity and stability of the product. At the same time, the post-treatment steps of washing with cold methanol multiple times and vacuum drying are used to further remove unreacted raw materials and impurities, ensuring the purity and performance of the final product. This preparation process not only improves the synthesis efficiency of octaaminopropyl POSS hydrochloride, but also provides a high-quality raw material guarantee for its application in sepiolite modification.

[0012] In the octa-aminopropyl POSS hydrochloride modified sepiolite raw material of the present invention, the preparation process of the octa-aminopropyl POSS hydrochloride includes: using 3-aminopropyltriethoxysilane as the reactant, concentrated hydrochloric acid as the catalyst, and methanol as the solvent. Under the water bath condition of 20-40 °C, the reaction is carried out by mechanical stirring. The reaction temperature of 20-40 °C controls the reaction rate and the stability of the product. A higher temperature can accelerate the hydrolysis and polycondensation reactions of 3-aminopropyltriethoxysilane, but too high a temperature will lead to a runaway reaction and generate a large amount of by-products. Secondly, a lower temperature helps to control the reaction rate, reduce side reactions, and improve the purity and stability of the product. At the same time, carrying out the reaction at a lower temperature can reduce energy consumption, which conforms to the concept of green chemistry. The reaction time for the preparation of octa-aminopropyl POSS hydrochloride in the present invention is 2-4 days, which determines the completeness of the reaction and the maturity of the product. A longer reaction time can ensure the full hydrolysis and polycondensation of 3-aminopropyltriethoxysilane to form a stable POSS structure. An appropriate reaction time can reduce the residue of unreacted raw materials and improve the purity of the product. Too long a reaction time will reduce production efficiency. Therefore, it is necessary to find a balance between the reaction completeness and production efficiency. During the reaction process, concentrated hydrochloric acid is slowly added dropwise to the reaction system through a constant pressure burette to control the reaction rate. The dropping rate of concentrated hydrochloric acid controls the reaction rate and the stability of the reaction system. Slowly adding concentrated hydrochloric acid can avoid too violent a reaction and reduce the generation of by-products. By controlling the dropping rate through a constant pressure burette, the pH value of the reaction system can be maintained stable to ensure the uniform progress of the reaction. After the reaction is completed, the product is separated by filtration and washed repeatedly with cold methanol to remove unreacted raw materials and by-products, improve the purity of the product, and cold methanol washing can prevent the product from decomposing or agglomerating at high temperature to ensure the stability of the product. Then the product is dried in a vacuum drying oven at 20-50 °C for 12-36 hours. A lower drying temperature can avoid the decomposition or structural change of the product and ensure its stability. An appropriate drying time can ensure the complete drying of the product, remove the residual solvent, improve the purity and performance of the product, and finally obtain octa-aminopropyl POSS hydrochloride.

[0013] The present invention ensures its high-quality synthesis and functionality by carefully optimizing the preparation process of octa-aminopropyl POSS hydrochloride. From the raw material ratio, reaction condition control to product post-treatment, each step is carefully designed: by precisely controlling the volume ratio of raw materials, reaction temperature, stirring speed, and the dropping rate of concentrated hydrochloric acid, the uniformity and stability of the reaction are ensured, and the occurrence of side reactions and violent reactions is avoided; cold methanol washing is used to remove impurities to ensure the product purity; finally, through vacuum drying and nano-scale particle size control, the dispersibility and application performance of the product are further improved. This fine preparation process not only improves the synthesis efficiency and quality of octa-aminopropyl POSS hydrochloride, but also provides high-performance guarantee for its application in sepiolite modification and subsequent flame retardancy.

[0014] Preferably, the preparation process of octaaminopropyl POSS hydrochloride in the octaaminopropyl POSS hydrochloride modified sepiolite raw material of the present invention specifically includes the following steps: S11 Raw material mixing and reaction initiation: Weigh 3-aminopropyltriethoxysilane, methanol, and concentrated hydrochloric acid with a mass fraction concentration of 37% at a volume ratio of 5-15:65-85:10-20. The raw material ratio determines the stoichiometric relationship of the reaction and the stability of the reaction system. Among them, 3-aminopropyltriethoxysilane is the core reactant for synthesizing the POSS structure, and its content determines the number of amino groups and active sites of POSS. Methanol serves as a solvent, providing a reaction medium to ensure the uniform dispersion of the reactants. The proportion of methanol is high enough to ensure the fluidity of the reaction system and avoid side reactions caused by too high reactant concentration. Concentrated hydrochloric acid acts as a catalyst to promote the hydrolysis and polycondensation reactions of 3-aminopropyltriethoxysilane. Add 3-aminopropyltriethoxysilane to a three-necked flask containing methanol and stir evenly to ensure its complete dissolution. Place the flask in a water bath at 20-40°C, start mechanical stirring, and set the stirring speed to 400-800 r / min. An appropriate stirring speed ensures the full dispersion of the reactants in the solution, avoids local high concentration, improves the reaction efficiency, and ensures the uniform progress of the reaction. Use a constant-pressure dropping funnel to slowly add concentrated hydrochloric acid to the reaction system at a speed of 8-12 ml / min for 20-40 minutes to control the reaction rate and avoid violent reactions. Control the dropping speed through the constant-pressure dropping funnel to maintain the stability of the pH value of the reaction system, ensure the uniform progress of the reaction, and slowly add concentrated hydrochloric acid to avoid overly violent reactions and reduce the generation of by-products.

[0015] S12 Reaction completion and product separation: During the addition of concentrated hydrochloric acid, keep the reaction system in a water bath at 20-40°C and maintain the stirring speed at 400-800 r / min. After the addition is completed, continue to stir and react for 24-48 hours under the same conditions to ensure complete reaction, improve the purity and quality of the product. Continue to stir after the addition is completed to ensure that all reactants in the reaction system react fully, reduce the residue of unreacted raw materials, and an appropriate stirring time can ensure the uniformity and stability of the product. After the reaction is completed, cool the reaction mixture to room temperature to reduce the decomposition or side reactions of the product at high temperature. Filter and collect the precipitate product to separate the reaction product, remove the unreacted substances and by-products in the reaction system, and ensure the purity of the product. Wash the precipitate product with cold methanol at 0-5°C multiple times, with each amount being 250-1000 ml, to remove unreacted raw materials and by-products and improve the purity of the product. Cold methanol can dissolve unreacted 3-aminopropyltriethoxysilane and by-products, and low-temperature washing can prevent the product from decomposing or agglomerating at high temperature, ensuring the stability of the product.

[0016] S13 Drying and Post-treatment: Place the washed precipitate product in a vacuum drying oven and dry it at 20 - 50 °C for 12 - 36 hours. A lower drying temperature can avoid the decomposition or structural change of the product, ensuring its stability. An appropriate drying time can ensure that the product is completely dried, remove residual solvents, improve the purity and quality of the product, and obtain a dried POSS product. The dried product is treated by grinding or ball milling to control the particle size of the product so that its particle size reaches 10 - 100 nanometers, improving its dispersibility and functionality, and obtaining octaaminopropyl POSS hydrochloride. Among them, a smaller particle size can improve the dispersibility of POSS on the surface of sepiolite, enhance the binding ability with sepiolite, and POSS with a nanoscale particle size can better exert its flame retardant and strengthening properties.

[0017] The present invention optimizes the preparation process of octaaminopropyl POSS hydrochloride modified sepiolite, ensuring the high-quality synthesis and excellent properties of the modified sepiolite. Reacting under specific pH conditions, combined with appropriate temperature and time control, and uniform mixing by mechanical stirring, can fully promote the chemical bonding between POSS and sepiolite, enhancing the bonding strength between the two. Through post-treatment steps such as centrifugal separation, drying, and particle size control, the purity and dispersibility of the modified sepiolite are further improved, enabling it to exhibit more excellent flame retardant properties and mechanical properties in plastics. This preparation process not only improves the production efficiency and quality stability of the modified sepiolite but also provides key technical support for the development of high-performance and environmentally friendly flame retardant materials.

[0018] Preferably, the octaaminopropyl POSS hydrochloride modified sepiolite provided by the present invention has a preparation process including: mixing octaaminopropyl POSS hydrochloride with sepiolite under specific pH conditions. The pH value determines the chemical reaction environment between octaaminopropyl POSS hydrochloride and sepiolite, affecting their interaction and binding strength; by adjusting the pH value, the surface of sepiolite is activated, making the silanol groups (-SiOH) on its surface more likely to undergo chemical bonding with the amino groups of POSS. An appropriate pH value can promote the reaction, while avoiding side reactions or product decomposition caused by too high or too low acidity or alkalinity. And under specific pH conditions, the charge distribution of POSS and sepiolite can be optimized, thereby improving their compatibility and dispersibility. The reaction temperature is from room temperature to 80 °C, and the reaction time is 12 - 36 hours; a higher temperature can accelerate the chemical bonding between POSS and sepiolite, but too high a temperature will cause product decomposition or side reactions. Conducting the reaction at a lower temperature can reduce the thermal decomposition of the product and ensure its structural integrity. Therefore, reacting within the range of room temperature to 80 °C can not only ensure the reaction efficiency but also reduce energy consumption; the reaction time of 12 - 36 hours determines the degree of completion of the reaction and the quality of the product. A longer reaction time can ensure sufficient reaction between POSS and sepiolite to form stable chemical bonds, but too long a reaction time will reduce production efficiency. Therefore, it is necessary to find a balance between the completeness of the reaction and production efficiency. An appropriate reaction time ensures the uniform distribution of POSS on the surface of sepiolite, avoiding local excess or deficiency. During the reaction process, mechanical stirring is used to fully mix the reactants and promote the reaction; mechanical stirring ensures the uniform distribution of POSS and sepiolite in the reaction system, avoiding agglomeration; stirring can accelerate the contact and reaction between the reactants, improve the reaction efficiency, and at the same time prevent side reactions or non-uniform products caused by too high local concentration. After the reaction, the product is collected by centrifugal separation to efficiently collect the modified sepiolite and remove unreacted POSS and other impurities; subsequently, it is dried under the condition of 60 - 80 °C to quickly remove the moisture in the product, ensuring its dryness while avoiding product decomposition or structural changes at high temperature, which not only ensures the efficiency but also reduces energy consumption; it is mechanically ground to a particle size range of 45 - 75 microns to improve the dispersibility of the modified sepiolite in the plastic matrix, avoid agglomeration, more effectively play the flame retardant role, improve the flame retardant performance of the plastic while reducing the negative impact on the mechanical properties of the plastic matrix, and obtain a highly efficient halogen-free flame retardant additive modified sepiolite.

[0019] The present invention further optimizes the preparation process of octaaminopropyl POSS hydrochloride modified sepiolite, and precisely controls the pH value, centrifugation speed, and stirring speed of the reaction system. This optimization enables flexible adaptation to the reaction requirements at different stages through wide-range pH value adjustment, ensuring efficient binding of POSS and sepiolite; adjustment of the centrifugation speed guarantees efficient separation and purification of the product; and precise control of the stirring speed promotes uniform mixing of the reactants and full progress of the reaction. The synergistic optimization of these parameters significantly improves the quality and performance of the modified sepiolite.

[0020] Furthermore, for the octaaminopropyl POSS hydrochloride modified sepiolite of the present invention, the pH value during the preparation process is 2 - 10, which controls the reaction environment and the surface properties of the reactants, avoids damage to the product structure caused by excessive acidity or alkalinity, and ensures the stability of the modified sepiolite; at a lower pH value (such as 2 - 4), the cation exchange performance of sepiolite is significantly improved, facilitating ion exchange with positively charged POSS molecules. In addition, acid treatment can increase the number of surface hydroxyl groups (-SiOH) on sepiolite, enhance the electrostatic interaction with cations, and promote the exchange reaction. At a higher pH value (such as 7 - 10), the silanol groups (-SiOH) on the surface of sepiolite are deprotonated, and the surface is negatively charged, which is conducive to chemical bonding with the amino group of POSS; the pH value range of 2 - 10 covers conditions from acidic to alkaline, ensuring that the binding of POSS and sepiolite can be optimized at different stages. The low pH value (2 - 4) is used for the pretreatment of sepiolite to activate its surface; the high pH value (7 - 10) is used for the reaction of POSS and sepiolite to promote the formation of chemical bonds. The centrifugation speed is 3000 - 10000 r / min, ensuring sufficient sedimentation of sepiolite particles for easy collection and subsequent processing; a higher centrifugation speed (such as 10000 r / min) can more effectively separate the modified sepiolite, remove unreacted substances and impurities in the reaction system, and ensure higher purity. However, too high a centrifugation speed will increase energy consumption, while low-speed centrifugation cannot completely separate the product. Therefore, it is necessary to balance the separation efficiency and energy consumption. The stirring speed of mechanical stirring is between 1000 - 6000 r / min, ensuring uniform mixing of the reactants and efficient progress of the reaction; a higher stirring speed ensures uniform distribution of POSS and sepiolite in the reaction system, avoiding agglomeration or incomplete reaction caused by excessive local concentration. However, too high a stirring speed leads to instability of the reaction system and even causes the generation of bubbles. Therefore, it is necessary to balance the mixing efficiency and system stability. An appropriate stirring speed accelerates the contact and reaction between the reactants, increases the reaction rate, and ensures the completeness of the reaction.

[0021] Through the adoption of a multi-step modification process, the present invention realizes the deep functionalization of octaaminopropyl POSS hydrochloride modified sepiolite. Firstly, the surface of sepiolite is activated by acid pretreatment to enhance its reactivity; subsequently, under alkaline conditions, POSS is chemically bonded to sepiolite to ensure the modification effect; finally, organic impurities are removed by calcination and the bonding strength is further enhanced, while the particle size is controlled to optimize its dispersion in plastics. This staged and refined process not only significantly improves the flame retardancy and thermal stability of the modified sepiolite, but also ensures its uniform dispersion in the plastic matrix.

[0022] In the preparation process of octaaminopropyl POSS hydrochloride modified sepiolite of the present invention, the multi-step modification process is adopted. By optimizing the surface activation of sepiolite, the grafting of POSS, and the post-treatment enhancement in stages, the deep functionalization of sepiolite is realized. It not only significantly improves the chemical bonding strength between sepiolite and octaaminopropyl POSS hydrochloride, but also further enhances the thermal stability of the modified sepiolite and its dispersion in the plastic matrix through calcination and particle size control, so that it exhibits more excellent flame retardancy and mechanical properties in plastics, meeting the environmental protection and application requirements of high-performance flame retardant materials.

[0023] Furthermore, for the octaaminopropyl POSS hydrochloride modified sepiolite of the present invention, the preparation process adopts a multi-step modification process, which specifically includes the following steps: The pretreatment steps of sepiolite determine the surface activation degree of sepiolite and its binding ability with POSS, remove impurities on the sepiolite surface, and improve its purity and reaction activity; activate the sepiolite surface by adjusting the pH value to increase its binding sites with POSS; stirring and centrifugal separation ensure the uniform dispersion of sepiolite in the solution and improve the reaction efficiency. The specific operations include: adding sepiolite powder into deionized water with a mass 2 - 5 times that of the sepiolite, and stirring evenly; an appropriate amount of deionized water ensures the full dispersion of sepiolite powder, controls the concentration of sepiolite in the solution, ensures its uniform dispersion, avoids agglomeration, improves the pretreatment efficiency, and ensures uniform surface activation. Use dilute hydrochloric acid or sulfuric acid to adjust the pH value of the solution to 2 - 4; acid treatment can dissolve some magnesium ions (such as Mg²⁺) and impurities (such as Fe and Al oxides) in sepiolite, dredge the pores and increase the specific surface area, thereby exposing more cation exchange sites to promote subsequent reactions. Acidic conditions are helpful for removing impurities and organic substances on the sepiolite surface. Stir and react at room temperature for 6 - 12 hours to ensure the full activation of the sepiolite surface; long-term stirring can ensure the full contact between the sepiolite surface and the acid, achieve uniform activation, and avoid structural damage caused by local over-fast reactions. After the reaction, collect sepiolite by centrifugal separation at 3000 - 5000 r / min for 5 - 15 minutes; an appropriate centrifugal speed ensures the separation of sepiolite particles from the solution, removes the unreacted acid, and at the same time ensures the full sedimentation of sepiolite particles for easy collection. Wash sepiolite with deionized water multiple times until the washing liquid is neutral; remove the residual acid to ensure that the subsequent reaction proceeds under neutral conditions and avoid being affected by the acidic environment in the subsequent reaction. Dry in an oven at 60 - 80 °C for 6 - 24 hours to remove moisture and obtain pretreated sepiolite; a lower drying temperature can avoid the thermal decomposition of the sepiolite structure.

[0024] Reaction of S2 POSS with sepiolite: Add the pretreated sepiolite into deionized water with a mass 2 - 5 times that of sepiolite, and stir evenly; adjust the pH value of the solution to 7 - 10 using sodium hydroxide or ammonia water; the alkaline condition can promote the deprotonation of silanol groups on the surface of sepiolite, and form chemical bonds with the amino groups of POSS, while avoiding side reactions caused by excessive alkalinity. Under alkaline conditions, the silanol groups on the surface of sepiolite are fully deprotonated, enhancing the covalent bonding with the amino groups of POSS, thereby improving the toughness of the composite material. Add octaaminopropyl POSS hydrochloride in a mass ratio of 20 - 50:100; in a water bath at 60 - 80 °C, mechanically stir at 3000 - 6000 r / min for 12 - 36 hours; stirring can accelerate the contact of reactants and improve the reaction efficiency. A higher stirring speed can ensure the uniform distribution of POSS on the surface of sepiolite, ensure the full mixing of POSS and sepiolite, and promote the reaction; a higher temperature accelerates the bonding of POSS and sepiolite, while avoiding thermal decomposition at high temperatures. During the reaction process, slowly add the alkali solution through a constant-pressure burette funnel to maintain the stability of the pH value of the reaction system, and avoid violent fluctuations in the pH value to ensure that the reaction proceeds under stable conditions. After the reaction, collect the product by centrifugal separation at 3000 - 5000 r / min for 5 - 15 minutes; wash the product with deionized water multiple times to remove unreacted POSS and by-products; dry in an oven at 60 - 80 °C for 6 - 24 hours to obtain preliminarily modified sepiolite; through centrifugal separation and multiple washings, remove unreacted POSS and other impurities to ensure the purity and stability of the product.

[0025] The post - calcination treatment steps in S3 determine the final properties and application effects of the modified sepiolite; through high - temperature calcination, organic impurities are removed, and the bonding strength between POSS and sepiolite is enhanced. Calcination can strengthen the chemical bonding between POSS and sepiolite, improving thermal stability; controlling the particle size range ensures the uniform dispersion of the modified sepiolite in plastics and avoids agglomeration; drying removes residual moisture to ensure the stability and performance of the modified sepiolite. Specifically, it includes: putting the preliminarily modified sepiolite into a muffle furnace and calcining it at a temperature of 200 - 300 °C for 2 - 4 hours to remove organic impurities and enhance the bonding strength between POSS and sepiolite; avoiding the decline in product performance caused by incomplete calcination. After calcination, it is naturally cooled to room temperature, and the calcined sepiolite is mechanically ground, controlling the particle size range to be 45 - 75 microns; a smaller particle size can improve the dispersion of the modified sepiolite in the plastic matrix, and the uniformly dispersed modified sepiolite can play a more effective flame - retardant role. Finally, the ground modified sepiolite is dried in an oven at 60 - 80 °C for 6 - 24 hours to obtain the final octa - aminopropyl POSS hydrochloride - modified sepiolite. In the post - calcination treatment of S3, calcination (200 - 300 °C) can remove most of the bound water and organic impurities, but the material after high - temperature calcination will re - adsorb trace amounts of moisture due to environmental humidity during the natural cooling process. Sepiolite is a porous silicate mineral with a high specific surface area and hygroscopicity, and it will adsorb moisture even when briefly exposed to air; mechanical grinding (controlling the particle size to 45 - 75 microns) will significantly increase the particle surface area and exacerbate the hygroscopic phenomenon, and the grinding operation will make the material directly contact environmental moisture; residual moisture will also affect the dispersion of the modified sepiolite in the plastic matrix, resulting in the agglomeration of the flame retardant or a decrease in the interfacial bonding force. Drying after grinding eliminates the hygroscopic effect, ensures the stability of the modified sepiolite and its uniform dispersion in plastics, makes the water content of the final product meet the industrial standard, and avoids performance fluctuations caused by moisture absorption during storage or application.

[0026] The variable speed stirring operation adopted in the preparation process of octaaminopropyl POSS hydrochloride modified sepiolite of the present invention adjusts the stirring speed according to the reaction demand at different stages, and realizes the accurate control of sepiolite pretreatment, POSS grafting reaction and post-processing process from rapid dispersion to uniform mixing to sedimentation separation; In the pre-processing stage, rapid stirring ensures that sepiolite powder is rapidly and uniformly dispersed, and then the stirring speed is reduced to promote the full progress of surface activation reaction; In the POSS grafting stage, uniform mixing is achieved by first rapid stirring, and then the speed is reduced to maintain reaction stability, ensuring that POSS is fully combined with sepiolite; In the post-processing stage, variable speed stirring helps to remove impurities and avoid particle agglomeration; The dispersibility and reaction uniformity of modified sepiolite are significantly improved, the bonding strength of POSS and sepiolite is enhanced, and the flame retardant and mechanical properties of modified sepiolite in plastic are finally improved. This variable speed stirring strategy not only improves the bonding efficiency of sepiolite and POSS, enhances the modification effect, but also effectively avoids particle agglomeration and impurity residues, and significantly improves the dispersibility and purity of modified sepiolite.

[0027] Furthermore, the preparation process of the octaaminopropyl POSS hydrochloride modified sepiolite of the present invention adopts variable speed stirring, specifically comprising the following operations: In the pretreatment stage of S1 sepiolite, after adding sepiolite powder to deionized water, turn on the stirring device, set the stirring speed to a high speed of 5000-6000r / min, and continue stirring for 10-20 minutes to quickly disperse the sepiolite powder and ensure that it is evenly distributed in the solution; the high stirring speed quickly disperses the sepiolite powder evenly in the deionized water to avoid particle agglomeration, ensure that the sepiolite powder is evenly distributed in the solution, and provide good initial conditions for subsequent reactions. After adjusting the pH value of the solution to 2-4, reduce the stirring speed to 3000-4000r / min, maintain this speed for stirring reaction for 6-12 hours to ensure that the surface of the sepiolite is fully in contact with the acidic solution and react; the lower stirring speed ensures that the surface of the sepiolite is fully in contact with the acidic solution, promotes surface activation reaction, and avoids excessive local concentration or uneven reaction caused by excessive stirring speed. After the reaction is completed, the stirring speed is reduced to 1000-2000r / min, and stirring is continued for 5-10 minutes to allow the sepiolite particles to fully settle before centrifugal separation; low stirring speed helps the sepiolite particles to fully settle, facilitating subsequent centrifugal separation and ensuring that after the particles settle, centrifugal separation can more efficiently remove unreacted acid and impurities.

[0028] In the reaction stage of S2 POSS and sepiolite, after adding the pretreated sepiolite into deionized water and adjusting the pH value to 7 - 10, set the stirring speed to 4000 - 5000 r / min and continuously stir for 10 - 20 minutes to uniformly disperse the sepiolite in the solution; the high stirring speed ensures that the pretreated sepiolite is uniformly dispersed in the solution, provides good conditions for the addition of POSS, prevents the agglomeration of sepiolite particles in the solution, and improves the reaction efficiency. After adding octaaminopropyl POSS hydrochloride according to the mass ratio, increase the stirring speed to 5000 - 6000 r / min and continuously stir for 10 - 20 minutes to promote the full contact and mixing of POSS and sepiolite; further increasing the stirring speed ensures the full contact and mixing of POSS and sepiolite, and rapid stirring helps the amino group of POSS to chemically bond with the silanol groups on the surface of sepiolite. Subsequently, reduce the stirring speed to 3000 - 4000 r / min and maintain this rotation speed for stirring reaction for 12 - 36 hours; the lower stirring speed can maintain the stability of the reaction system, avoid side reactions caused by violent stirring, and long-term stirring ensures the full reaction of POSS and sepiolite to form stable chemical bonds. After the reaction is completed, reduce the stirring speed to 1000 - 2000 r / min and continuously stir for 5 - 10 minutes to allow the product to fully settle and then perform centrifugal separation; the low stirring speed helps the product to fully settle, facilitating centrifugal separation, and removing unreacted POSS and other impurities through centrifugal separation to improve the product purity.

[0029] In the post-treatment stage of S3 calcination, when washing the preliminarily modified sepiolite, set the stirring speed to 3000 - 4000 r / min and continuously stir for 10 - 20 minutes to ensure the full removal of surface impurities; the high stirring speed ensures the full removal of surface impurities, improves the product purity, ensures the full contact of the washing liquid and the product, and removes residual reactants and by-products, but its crushing effect on hard materials such as calcined sepiolite is minimal and cannot replace the effect of grinding. The calcined sepiolite is ground through equipment such as ball mills, air mills, and vibration mills, and large particles are broken into small particles by mechanical forces (such as impact and friction), and the particle size is controlled within 45 - 75 microns. After high-speed stirring and washing of the modified sepiolite in the S3 stage, first achieve the target particle size through mechanical grinding, and then stir to ensure that the ground particles are uniformly dispersed before drying to avoid agglomeration caused by van der Waals forces or electrostatic adsorption. After mechanical grinding of the calcined sepiolite, set the stirring speed to 2000 - 3000 r / min and continuously stir for 10 - 20 minutes before drying to uniformly disperse the modified sepiolite and avoid particle agglomeration; after mechanical grinding of the calcined sepiolite, stirring can ensure the uniform dispersion of particles and avoid agglomeration, and the low stirring speed can avoid excessive particle breakage and ensure uniform dispersion at the same time.

[0030] The present invention provides an efficient method for preparing flame-retardant plastics by mixing octaaminopropyl POSS hydrochloride-modified sepiolite with a plastic matrix (polypropylene) in a specific mass ratio and performing melt blending by mechanical blending. By optimizing the mixing ratio, extrusion temperature, and screw speed, it ensures the uniform dispersion of the modified sepiolite in the plastic matrix, thereby significantly improving the flame-retardant performance of the plastics while maintaining their good mechanical properties and processing properties. This flame-retardant application not only meets the requirements of the plastic industry for environmentally friendly and efficient flame-retardant materials but also provides a practical technical solution for the development of high-performance flame-retardant composite materials, having important practical application value and market prospects.

[0031] The present invention provides a flame-retardant application of octaaminopropyl POSS hydrochloride-modified sepiolite in plastics. Parameters such as the mixing ratio, extrusion temperature, and screw speed during the preparation process of the flame-retardant plastics determine the dispersion of the modified sepiolite in the plastics and the properties of the composite materials; the mass ratio of the modified sepiolite to the plastic matrix determines the balance between the flame-retardant effect and the mechanical properties; the modified sepiolite is mixed with polypropylene by mechanical blending using a twin-screw extruder to ensure the uniform dispersion of the modified sepiolite in the polypropylene matrix. During the mixing process, a good interfacial bonding is formed between the modified sepiolite and the polypropylene matrix, enhancing the mechanical properties of the composite materials. An extrusion temperature of 180 - 220 °C ensures the complete melting of polypropylene, enables the uniform dispersion of the modified sepiolite in the matrix, and at the same time avoids the decomposition of the modified sepiolite or the degradation of polypropylene due to excessive temperature; a screw speed of 200 - 300 r / min ensures the uniform mixing and dispersion of the materials, avoids local overheating or agglomeration, and improves the quality of the composite materials. Specifically, it includes: mixing the modified sepiolite with the plastic matrix in a mass ratio of 1 - 10:100; adopting mechanical blending and performing melt blending through a twin-screw extruder, with an extrusion temperature of 180 - 220 °C and a screw speed of 200 - 300 r / min; granulating the extruded material using a granulator to obtain the flame-retardant plastic material, ensuring the uniformity and consistency of the composite materials.

[0032] The present invention provides an efficient and balanced solution for the flame-retardant modification of polypropylene by optimizing the mass ratio of octaaminopropyl POSS hydrochloride-modified sepiolite to polypropylene. This ratio not only ensures that the modified sepiolite can fully exert its flame-retardant performance in the polypropylene matrix, effectively inhibiting heat transfer and flame spread during combustion, but also takes into account the mechanical properties and processing properties of polypropylene, avoiding a decline in material properties or processing difficulties caused by excessive addition of flame retardants. This optimized mass ratio provides clear guidance for the development of high-performance and environmentally friendly flame-retardant polypropylene materials, meeting the dual requirements of the modern plastic industry for flame-retardant performance and comprehensive material properties.

[0033] Preferably, in the flame retardant application of octaaminopropyl POSS hydrochloride modified sepiolite in plastics, the plastic matrix is polypropylene, and the mass ratio of the modified sepiolite to polypropylene is 2-5:100.

[0034] In the flame retardant application of octaaminopropyl POSS hydrochloride modified sepiolite in plastics of the present invention, the mass ratio of octaaminopropyl POSS hydrochloride modified sepiolite to polypropylene is 2-5:100, achieving the optimization of flame retardant performance and the balance of mechanical properties. As a flame retardant, the addition amount of the modified sepiolite directly affects the flame retardant effect. A lower addition amount cannot provide sufficient flame retardant performance, while a higher addition amount leads to a decrease in mechanical properties or an increase in processing difficulty; polypropylene is a plastic with good mechanical properties, but adding too much flame retardant will weaken its strength and toughness; by optimizing the mass ratio, a balance can be found between flame retardant performance and mechanical properties. The appropriate mass ratio can ensure the uniform dispersion of the modified sepiolite in the polypropylene matrix, avoiding agglomeration or phase separation, thus ensuring the processing performance and molding quality of the material. Among them, the addition amount of the modified sepiolite directly affects the cost, and optimizing the mass ratio can reduce the material cost while meeting the flame retardant requirements.

[0035] The modified sepiolite provides flame retardant performance through the POSS structure on its surface. The nano-cage structure of POSS can form a stable carbon layer during combustion, inhibiting the transfer of heat and gas; the introduction of the POSS structure improves the thermal stability of sepiolite, making it not easily decomposed at high temperatures, thereby enhancing the thermal stability of polypropylene; the modified sepiolite has better compatibility with the polypropylene matrix and can be uniformly dispersed in polypropylene, avoiding agglomeration and phase separation; at the same time, the modified sepiolite can form a good interfacial bond with the polypropylene matrix, thereby enhancing the mechanical properties of the composite material to a certain extent.

[0036] Polypropylene is a lightweight, chemically resistant, and easily processed plastic, widely used in various fields. As a matrix material, it provides good mechanical properties and processing performance for the composite material; on the one hand, polypropylene provides a carrier for the modified sepiolite, enabling it to be uniformly dispersed in the composite material and play a flame retardant role; on the other hand, polypropylene has a low cost, and by optimizing the addition amount of the flame retardant, high-performance and economical flame retardant composite materials can be developed.

[0037] In summary, the present invention has the following beneficial effects: 1. Compared with traditional halogen-based flame retardants, the present invention uses octaaminopropyl POSS hydrochloride modified sepiolite as a flame retardant additive, which is completely halogen-free. Through the modification of sepiolite with octaaminopropyl POSS hydrochloride, the flame retardant performance of plastic materials is significantly improved; at the same time, it avoids the problem of releasing toxic and harmful gases (such as dioxins, polybrominated biphenyls, etc.) during the combustion process of traditional halogen-based flame retardants. The octaaminopropyl POSS hydrochloride and sepiolite raw materials used in the present invention are both substances harmless to the human body. The natural mineral sepiolite has good biocompatibility, and the POSS structure will not release toxic and harmful gases after combustion. Its residue is similar to soil components, is environmentally friendly, has significant environmental friendliness and safety, and meets environmental protection requirements; 2. The octaaminopropyl POSS hydrochloride modified sepiolite of the present invention forms a stable carbon layer during the combustion process through the POSS structure on its surface, effectively inhibiting the transfer of heat and gas, significantly reducing the combustion rate, and its flame retardant effect is better than that of traditional halogen-free flame retardants; moreover, the thermal stability of the modified sepiolite is better than that of traditional flame retardant fillers (such as ordinary silicate minerals), and it can maintain the structural integrity in a high-temperature environment, further enhancing the heat resistance of plastic composites; 3. The octaaminopropyl POSS hydrochloride modified sepiolite of the present invention forms a good interfacial bond with the plastic matrix, which not only improves the flame retardant performance of the composite material, but also maintains the thermal stability and original mechanical properties of the plastic material, avoiding the decrease in strength and toughness caused by the addition of flame retardants. Compared with traditional flame retardants, the composite material of the present invention shows a better balance in mechanical properties and is a multifunctional composite material additive; 4. Compared with the preparation process of conventional flame retardants, the present invention adopts a multi-step modification process and variable-speed stirring technology to achieve the uniform dispersion of modified sepiolite in the plastic matrix, avoiding particle agglomeration. This not only improves the overall performance of the composite material, but also ensures the high efficiency and repeatability of production. And by optimizing reaction conditions such as temperature, stirring speed, pH value, etc., the preparation process of the present invention is more controllable and suitable for industrial production; 5. Compared with traditional flame retardants, by optimizing the formula and process of modified sepiolite, the present invention achieves high-efficiency flame retardant performance while significantly reducing the usage amount of flame retardants, thereby reducing the material cost; the raw material sepiolite of the present invention is a natural mineral, which is rich in resources and renewable, reducing the dependence on non-renewable resources and lowering the production cost; its preparation process is simple and controllable, further enhancing the economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic diagram of the char formation of the test sample in Example 1 of the present invention; Figure 2 It is a schematic diagram of the char formation of the test sample in Example 2 of the present invention; Figure 3 Schematic diagram of char formation of the test sample in Example 3 of the present invention; Figure 4 Schematic diagram of char formation of the test sample in Comparative Example 1 of the present invention; Figure 5 Schematic diagram of char formation of the test sample in Comparative Example 2 of the present invention. Detailed implementation manners

[0039] This specific embodiment is only an explanation of the present invention, and it does not limit the present invention. After reading this specification, those skilled in the art can make modifications without creative contributions to this embodiment as needed, but as long as it is within the scope of the claims of the present invention, it is protected by the patent law.

[0040] Example 1

[0041] S1 Synthesis of octa(aminopropyl) POSS hydrochloride: Add 200 ml of 3-aminopropyltriethoxysilane into a three-necked flask, add 1500 ml of methanol, and stir evenly; place the flask in a water bath at 30 °C, stir at 400 r / min, and slowly add 280 ml of concentrated hydrochloric acid at a rate of 10 ml / min through a constant-pressure dropping funnel, and the dropping time is 28 minutes; after the dropping is completed, continue to stir and react at 30 °C for 48 hours; after the reaction is completed, filter to collect the precipitate product, wash it with cold methanol at 0-5 °C for several times, 500 ml each time, to remove unreacted raw materials and by-products; dry the washed precipitate product in a vacuum drying oven at 40 °C for 2 days to obtain octa(aminopropyl) POSS hydrochloride; S2 Preparation of POSS-modified sepiolite: Add 900 g of water into a flask, start stirring, and add 100 g of sepiolite; adjust the pH of the solution to 3, add 22.9 g of octa(aminopropyl) POSS hydrochloride, stir evenly, and react at 70 °C for 24 hours; after the reaction is completed, adjust the pH to neutral, centrifuge, collect the precipitate part and dry and grind it to obtain modified sepiolite.

[0042] S3 Application of modified sepiolite in polypropylene: Mix 50 g of modified sepiolite with 1000 g of polypropylene evenly; adopt the mechanical blending method, and carry out melt blending through a twin-screw extruder at an extrusion temperature of 180 °C and a screw speed of 200 r / min; the extruded material is made into pellets by a pelletizer, and then made into test samples by an injection molding machine.

[0043] Example 2

[0044] S1 Synthesis of octa(aminopropyl) POSS hydrochloride: The raw material ratio and operation steps are the same as those in Example 1; Preparation of POSS-modified sepiolite: Add 900 g of water into a flask, start stirring, and add 100 g of sepiolite; without adjusting the pH, directly add 22.9 g of octaaminopropyl POSS hydrochloride, stir evenly, and react at 70 °C for 24 hours; after the reaction, perform centrifugal separation, collect the precipitate part and dry and grind it to obtain modified sepiolite; S3 Application of modified sepiolite in polypropylene: The raw material ratio and operation steps are the same as those in Example 1.

[0045] Example 3

[0046] S1 Synthesis of octaaminopropyl POSS hydrochloride: The raw material ratio and operation steps are the same as those in Example 1; S2 Preparation of POSS-modified sepiolite: Add 900 g of water into a flask, start stirring, and add 100 g of sepiolite; adjust the pH of the solution to 10, add 22.9 g of octaaminopropyl POSS hydrochloride, stir evenly, and react at 70 °C for 24 hours; after the reaction, adjust the pH to neutral, perform centrifugal separation, collect the precipitate part and dry and grind it to obtain modified sepiolite; S3 Application of modified sepiolite in polypropylene: The raw material ratio and operation steps are the same as those in Example 1.

[0047] Example 4

[0048] S1 Synthesis of octaaminopropyl POSS hydrochloride and S2 Preparation of POSS-modified sepiolite: The raw material ratio and operation steps are the same as those in Example 1; S3 Application of modified sepiolite in cable compound: Mix 10 g of modified sepiolite with 200 g of cable compound, use the mechanical blending method, perform internal mixing through a torque rheometer, and carry out melt blending at a temperature of 155 °C and a screw speed of 50 r / min; then the material is hot-pressed into a sample plate by a flat vulcanizer at 180 °C, and then punched into test samples by a pneumatic impact puncher.

[0049] Example 5

[0050] S1 Synthesis of octaaminopropyl POSS hydrochloride: The raw material ratio and operation steps are the same as those in Example 1; S2 Preparation of POSS-modified sepiolite: The raw material ratio and operation steps are the same as those in Example 2; S3 Application of modified sepiolite in cable compound: The raw material ratio and operation steps are the same as those in Example 4.

[0051] Example 6

[0052] S1 Synthesis of octaaminopropyl POSS hydrochloride: The raw material ratio and operation steps are the same as those in Example 1; S2 Preparation of POSS-modified sepiolite: The raw material ratio and operation steps are the same as those in Example 3; Application of S3 modified sepiolite in cable materials: The raw material ratio and operation steps are the same as those in Example 4.

[0053] Comparative Example 1 Preparation of S1 sepiolite: Directly take 100 g of unmodified sepiolite without any treatment. Application of S2 sepiolite in polypropylene: Mix 50 g of unmodified sepiolite with 1000 g of polypropylene evenly. Using the mechanical blending method, melt blending is carried out through a twin-screw extruder at an extrusion temperature of 200 °C and a screw speed of 250 r / min. The extruded material is made into pellets by a granulator and then made into test samples by an injection molding machine.

[0054] Comparative Example 2 S1 raw material ratio: Directly take 1000 g of polypropylene without any treatment. S2 operation steps: For 1000 g of polypropylene, without adding any flame retardant, using the mechanical blending method, melt blending is carried out through a twin-screw extruder at an extrusion temperature of 200 °C and a screw speed of 250 r / min. The extruded material is made into pellets by a granulator and then made into test samples by an injection molding machine.

[0055] Comparative Example 3 S1 raw material ratio: Directly take 200 g of commercial cable material without any treatment. S2 operation steps: For 200 g of commercial cable material, without adding any flame retardant, using the mechanical blending method, mixing is carried out through a torque rheometer. Melt blending is carried out at a temperature of 155 °C and a screw speed of 50 r / min. Subsequently, the material is hot-pressed into a sample plate by a flat vulcanizer at 180 °C and then cut into test samples by a pneumatic impact slicing machine.

[0056] Performance detection is carried out on the test samples prepared in Examples 1-3 and Comparative Examples 1-2, including determination of loss on ignition, determination of char yield, determination of dripping time, and mechanical property tests (impact strength and tensile property). Oxygen index tests are carried out on the test samples prepared in Example 4, Example 5, Example 6, and Comparative Example 3.

[0057] 1. Determination of loss on ignition Detection method: According to the standard of "General test methods for insulating and sheathing materials of cables and optical cables - Part 11: Methods for determining the loss on ignition", accurately weigh about 1 g of the sample, accurate to 0.0001 g, and put the sample into a crucible that has been pre-dried to a constant weight. Put the crucible into a muffle furnace, with a heating rate of 10 °C / min, and heat up to 900 °C. Keep the temperature constant at 900 °C for 2 hours to completely burn the organic matter in the sample. Take out the crucible from the muffle furnace and put it into a desiccator to cool to room temperature. After cooling, weigh the total mass of the crucible and the residue, and calculate the loss on ignition.

[0058] 2. Determination of char yield Testing method: Make the sample into specimens with the size of 8×8×0.4 cm, ensuring that the surface of the specimens is flat and defect-free; for three square plates each time, after igniting with a blowtorch, remove from the fire, and check the char formation visually after extinguishing, and make a comparative evaluation; check whether the sample pieces are agglomerated by looking through light to evaluate the dispersion effect.

[0059] 3. Determination of dripping time Testing method: According to the standard of "UL-94 Test for Flammability of Plastic Materials", make the sample into specimens with standard sizes, ensuring that the surface of the specimens is flat and defect-free; use a combustion furnace or alcohol lamp as the heat source, and fix the specimens on a bracket; place a water collecting tray at the lower end of the specimens to collect the dripping melt; ignite the specimens and record the time from ignition to the dripping of the first drop of melt (dripping time); repeat the experiment 3 times and take the average value as the final result.

[0060] 4. Oxygen index test Testing method: Refer to the standard of "GB / T2406.2-2009 Plastics - Determination of burning behavior by the oxygen index method", make the sample into specimens with standard sizes, ensuring that the surface of the specimens is flat and defect-free. Take at least 15 standard specimens, draw a line at 50 mm from any end of the specimen, and insert the other end into the specimen clamp in the combustion column. By adjusting the flow rate, keep the mixed flow rate of nitrogen and oxygen at (10±0.5) L / min. After determining the initial oxygen concentration, stabilize the gas flow rate for 30 s, then ignite the top of the specimen with a lighter (flame length 12 mm - 20 mm), remove the lighter, and start timing immediately. Compare the continuous burning time of the specimen or the burning length of the specimen with the given criterion. Through a series of tests at different oxygen concentrations, determine the lowest oxygen concentration required for the specimen to burn for 3 min or 50 mm in length as the oxygen index.

[0061] 5. Mechanical property test Evaluate the change in the mechanical properties of the material after adding flame retardants, including impact strength and tensile properties, to ensure that the material still meets the usage requirements after flame retardant modification.

[0062] 5.1 Impact strength test Testing method: According to the standard of "ISO179-1:2010 Plastics - Determination of Charpy impact properties", make the sample into standard-sized impact specimens, ensuring that the surface of the specimens is defect-free and scratch-free; use a pendulum impact testing machine and set the impact energy to 50 J; place the specimens on the supports of the testing machine with the notch facing the direction of pendulum impact; start the testing machine and record the impact energy at the moment when the specimens break, and calculate the impact strength.

[0063] 5.2 Tensile property test Testing method: According to the standard of "ISO527-2:1993 Plastics - Determination of tensile properties", the sample is made into a tensile specimen with standard dimensions, ensuring that the surface of the specimen is flat and defect-free; a universal material testing machine is used, and the tensile speed is set at 50 mm / min; the specimen is clamped in the upper and lower fixtures of the testing machine, ensuring that the specimen is perpendicular to the fixtures; the testing machine is started, and the stress-strain curve during the tensile process of the specimen is recorded, and the tensile strength, tensile elastic modulus, and elongation at break are calculated.

[0064] Summary of the performance test results of the test samples in each group in Table 1

[0065] Summary of the limiting oxygen index test results of the test samples in each group in Table 2

[0066] Result analysis: The loss on ignition refers to the percentage of the mass reduction after the sample burns at high temperature and the organic matter is completely burned. The higher the loss on ignition, the higher the organic matter content in the sample, the more combustible gas and heat are generated during combustion, and the worse the combustion performance. The loss on ignition of Examples 1, 2, and 3 of the present invention are 96.25%, 96.13%, and 96.36% respectively, all lower than 96.83% of Comparative Example 1 and 100.00% of Comparative Example 2; the relatively low loss on ignition of Examples 1, 2, and 3 indicates that the modified sepiolite has a certain improvement effect on the combustion performance of polypropylene and reduces the organic matter content.

[0067] The char yield is the mass or volume ratio of the residual char formed after the material burns, and it is one of the important indicators to measure the flame retardancy of the material. The char yield reflects the proportion of the solid char layer formed by pyrolysis, cross-linking and other reactions during the high-temperature combustion process of the material. The char layer isolates oxygen, blocks heat transfer, and inhibits the diffusion of combustible gases, thereby delaying or terminating the combustion process. A high char yield means a dense and continuous char layer, effectively blocking oxygen and heat; a low char yield means a loose and incomplete char layer, poor flame retardancy, and a fast combustion rate. The char yield of Examples 1-3 of the present invention Figures 1-3 , the surface of the char layer shows a yellowish-brown color, with a large number of black holes distributed. The char layer is dense and continuous, with excellent blocking effect, high and evenly dispersed residual char amount after combustion, and good flame retardant effect; the char yield of Comparative Example 1 Figure 4 , there are obvious massive or irregular accumulations in the middle of the char layer, with a large difference in the structure from the surrounding char layer, poor overall structural uniformity, a loose and incomplete char layer, and limited flame retardant effect; Comparative Example 2 Figure 5The charring photograph shows that after combustion, the surface is transparent or semi-transparent, and no char layer is formed. There are adhered black impurities at the bottom. Due to the absence of a char layer structure, the lack of a heat-insulating air layer and free radical adsorption sites, the flame retardant performance of the polypropylene substrate is weak; it shows that the POSS structure introduced by the modified sepiolite in the present invention significantly optimizes the quality of the char layer.

[0068] The dripping time refers to the time from ignition to the first drop of melt dripping during the combustion of the sample. The longer the dripping time, the greater the melt viscosity of the sample, the less melt dripping generated during combustion, and the better the combustion performance. The dripping times of Examples 1, 2, and 3 are 17.0 s, 17.7 s, and 16.0 s respectively, all higher than 13.3 s of Comparative Example 1 and 9.3 s of Comparative Example 2; the longer dripping times of Examples 1, 2, and 3 indicate that the modified sepiolite increases the melt viscosity of polypropylene, reduces melt dripping, and improves the combustion performance.

[0069] The limiting oxygen index refers to the volume fraction concentration of oxygen when a polymer can just support its combustion in a mixed gas of oxygen and nitrogen, and it is an index characterizing the combustion behavior of materials. The higher the limiting oxygen index, the less flammable the material. The limiting oxygen indices of Examples 4, 5, and 6 are 34.3%, 34.5%, and 35.3% respectively, all higher than 32.6% of Comparative Example 3. The higher limiting oxygen indices of Examples 4, 5, and 6 indicate that the modified sepiolite improves the flame resistance of commercial cable materials.

[0070] The impact strength refers to the maximum energy that a material can withstand when subjected to an impact force. The higher the impact strength, the better the impact resistance of the material. The impact strengths of Examples 1, 2, and 3 are 3.227 kJ / m², 3.343 kJ / m², and 3.13 kJ / m² respectively, all higher than 3.03 kJ / m² of Comparative Example 1 and 3.08 kJ / m² of Comparative Example 2; the higher impact strengths of Examples 1, 2, and 3 indicate that the modified sepiolite has a certain enhancing effect on the impact resistance of polypropylene.

[0071] The tensile strength refers to the maximum stress that a material can withstand when subjected to a tensile force. The higher the tensile strength, the better the tensile performance of the material. The tensile strengths of Examples 1, 2, and 3 are 29.8 MPa, 29.8 MPa, and 27.6 MPa respectively, all higher than 27.2 MPa of Comparative Example 1 and 26.2 MPa of Comparative Example 2; the higher tensile strengths of Examples 1, 2, and 3 indicate that the modified sepiolite has a certain enhancing effect on the tensile performance of polypropylene.

[0072] The tensile modulus of elasticity refers to the ratio of stress to strain when the material is under tensile force. The higher the tensile modulus of elasticity, the greater the rigidity of the material. The tensile moduli of elasticity of Examples 1, 2, and 3 are 1027.3 MPa, 1030.8 MPa, and 1089.7 MPa respectively, all higher than 948.1 MPa of Comparative Example 1 and 681.0 MPa of Comparative Example 2; the relatively high tensile moduli of elasticity of Examples 1, 2, and 3 indicate that the modified sepiolite improves the rigidity of polypropylene.

[0073] The elongation at break refers to the ratio of the elongation at the time of fracture of the material to the original length. The higher the elongation at break, the better the toughness of the material. The elongations at break of Examples 1, 2, and 3 are 245.5%, 247.4%, and 287.7% respectively, all higher than 163.0% of Comparative Example 1 and 143.5% of Comparative Example 2; the relatively high elongations at break of Examples 1, 2, and 3 indicate that the modified sepiolite improves the toughness of polypropylene.

[0074] Generally speaking, the loss on ignition and the dripping time of Examples 1, 2, and 3 are better than those of Comparative Example 1 and Comparative Example 2, indicating that the modified sepiolite can reduce the organic matter content of polypropylene, increase the melt viscosity, reduce the melt dripping during combustion, and thus improve the combustion performance of polypropylene; the impact strength, tensile strength, tensile modulus of elasticity, and elongation at break of Examples 1, 2, and 3 are better than those of Comparative Example 1 and Comparative Example 2, indicating that the modified sepiolite can enhance the impact resistance, tensile property, rigidity, and toughness of polypropylene and improve the comprehensive mechanical properties of the material. The limiting oxygen indices of Examples 4, 5, and 6 are higher than that of Comparative Example 3, indicating that the modified sepiolite improves the combustion performance of ordinary commercial cable compounds. Thus, it is verified that the octaaminopropyl POSS hydrochloride modified sepiolite of the present invention can not only significantly improve the combustion performance and mechanical properties of polypropylene matrix plastics, reduce the loss on ignition, increase the dripping time, enhance the impact resistance, tensile property, rigidity, and toughness, but also improve the flame retardancy of commercial cable compounds.

Claims

1. An octaaminopropyl POSS hydrochloride modified sepiolite, characterized in that, Its raw materials include: octaaminopropyl POSS hydrochloride and sepiolite, and the mass ratio of octaaminopropyl POSS hydrochloride to sepiolite is 2 - 5:10; the raw material composition of octaaminopropyl POSS hydrochloride includes: 3-aminopropyltriethoxysilane, methanol and concentrated hydrochloric acid, and the volume ratio of 3-aminopropyltriethoxysilane, methanol and concentrated hydrochloric acid is 5 - 15:65 - 85:10 - 20.

2. The octaaminopropyl POSS hydrochloride modified sepiolite according to claim 1, characterized in that, The preparation process of octaaminopropyl POSS hydrochloride in its raw materials includes: using 3-aminopropyltriethoxysilane as the reactant, concentrated hydrochloric acid as the catalyst, and methanol as the solvent, reacting under the water bath condition of 20 - 40 °C through mechanical stirring, and the reaction time is 2 - 4 days; during the reaction process, concentrated hydrochloric acid is slowly added dropwise to the reaction system through a constant pressure burette funnel to control the reaction rate; after the reaction is completed, the product is separated by filtration and washed repeatedly with cold methanol to remove unreacted raw materials and by-products; finally, the product is dried in a vacuum drying oven at 20 - 50 °C for 12 - 36 hours to obtain octaaminopropyl POSS hydrochloride.

3. The octaaminopropyl POSS hydrochloride modified sepiolite according to claim 2, wherein, The preparation process of the octaaminopropyl POSS hydrochloride specifically includes the following steps: S11 Raw material mixing and reaction start: Add 3-aminopropyltriethoxysilane to a three-necked flask filled with methanol, stir evenly, place it in a water bath at 20 - 40 °C, stir mechanically, and use a constant pressure burette funnel to add concentrated hydrochloric acid to the reaction system at a rate of 8 - 12 ml / min within 20 - 40 minutes; S12 Reaction completion and product separation: During the process of adding concentrated hydrochloric acid, maintain a water bath at 20 - 40 °C and a stirring speed of 400 - 800 r / min. After the addition is completed, continue to react for 24 - 48 hours. After the reaction is completed, cool to room temperature, filter and collect the precipitate product, and wash it repeatedly with cold methanol at 0 - 5 °C; S13 Drying and post-treatment: Put the washed precipitate product into a vacuum drying oven, dry it at 20 - 50 °C for 12 - 36 hours, and then process it by grinding or ball milling to make its particle size reach 10 - 100 nanometers to obtain octaaminopropyl POSS hydrochloride.

4. The octaaminopropyl POSS hydrochloride modified sepiolite according to claim 1, wherein Its preparation process includes: mixing octaaminopropyl POSS hydrochloride and sepiolite under specific pH conditions, with the reaction temperature ranging from room temperature to 80 °C and the reaction time being 12 - 36 hours; during the reaction process, make the reactants fully mixed through mechanical stirring; after the reaction is completed, collect the product by centrifugal separation, and then dry it at 60 - 80 °C and mechanically grind it to a particle size range of 45 - 75 microns to obtain modified sepiolite.

5. The octaaminopropyl POSS hydrochloride modified sepiolite according to claim 4, wherein During its preparation process, the pH value is 2 - 10, the stirring speed of mechanical stirring is between 1000 - 6000 r / min, and the centrifugal speed is 3000 - 10000 r / min.

6. The octaaminopropyl POSS hydrochloride modified sepiolite according to claim 4, characterized in that, Its preparation process adopts a multi-step modification process, specifically including the following steps: S1 Pretreatment of sepiolite: Stir and add sepiolite powder to deionized water, adjust the pH value of the solution to 2 - 4 using dilute hydrochloric acid or sulfuric acid, and react for 6 - 12 hours; after the reaction is completed, collect sepiolite by centrifugal separation; wash sepiolite repeatedly with deionized water until the washing liquid is neutral, and dry to obtain pretreated sepiolite; Reaction of S2 POSS with sepiolite: Add the pretreated sepiolite into deionized water and stir evenly; adjust the pH value of the solution to 7 - 10 using sodium hydroxide or ammonia water, add octaaminopropyl POSS hydrochloride, and mechanically stir the reaction in a water bath for 12 - 36 hours; during the reaction process, add alkali solution dropwise through a constant pressure dropping funnel to maintain the pH balance of the system. After the reaction is completed, add dilute hydrochloric acid dropwise through a constant pressure titration funnel to adjust the pH of the system to neutral, and collect the product by centrifugation; wash the product with deionized water multiple times. At this time, the chloride ions in octaaminopropyl POSS hydrochloride have been washed away, and the preliminarily modified sepiolite is obtained after drying. S3 Post - calcination treatment: Put the preliminarily modified sepiolite into a muffle furnace and calcine for 2 - 4 hours. After natural cooling to room temperature, mechanically grind the powder, control the particle size range to be 45 - 75 microns, and obtain octaaminopropyl POSS hydrochloride - modified sepiolite after drying the ground powder.

7. The octaaminopropyl POSS hydrochloride modified sepiolite according to claim 6, wherein The preparation process uses variable - speed stirring, specifically including the following operations: In the S1 stage, after adding sepiolite powder into deionized water, set the stirring speed at 5000 - 6000 r / min and stir continuously for 10 - 20 minutes; after adjusting the pH value of the solution to 2 - 4, reduce the speed to 3000 - 4000 r / min and maintain the reaction for 6 - 12 hours; after the reaction is completed, reduce the speed to 1000 - 2000 r / min and stir continuously for 5 - 10 minutes. In the S2 stage, after adding the pretreated sepiolite into deionized water and adjusting the pH value to 7 - 10, stir at 4000 - 5000 r / min for 10 - 20 minutes. After adding octaaminopropyl POSS hydrochloride, stir at 5000 - 6000 r / min for 10 - 20 minutes; then reduce the speed to 3000 - 4000 r / min and maintain the reaction for 12 - 36 hours; after the reaction is completed, stir at 1000 - 2000 r / min for 5 - 10 minutes. In the S3 stage, when washing the preliminarily modified sepiolite, stir at 3000 - 4000 r / min for 10 - 20 minutes; after mechanically grinding the calcined sepiolite, stir and disperse at 2000 - 3000 r / min for 10 - 20 minutes before drying.

8. Flame retardant application of octaaminopropyl POSS hydrochloride modified sepiolite in plastics, characterized in that, Specifically including: S1 Mix the modified sepiolite and polypropylene plastic matrix at a mass ratio of 1 - 10:100; adopt the mechanical blending method, and carry out melt blending through a twin - screw extruder. The extrusion temperature is 180 - 220 °C, and the screw speed is 200 - 300 r / min; the extruded material is granulated by a granulator to obtain a flame - retardant plastic material. S2 Mix the modified sepiolite and cable material matrix at a mass ratio of 1 - 10:100; adopt the mechanical blending method, and carry out melt blending through a torque rheometer. The temperature is 140 - 180 °C, and the screw speed is 40 - 80 r / min; then the material is hot - pressed into a sample plate by a flat vulcanizer, and then blanked by a pneumatic impact punching machine to obtain a flame - retardant plastic material.

9. The flame retardant application of octaaminopropyl POSS hydrochloride modified sepiolite in plastics according to claim 8, characterized in that, The plastic matrix is polypropylene or cable material, and the mass ratio of the modified sepiolite to polypropylene or cable material is 2 - 5:100.

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