A method for preparing a composite enhanced active halogen-free flame retardant

Abstract

This invention discloses a method for preparing a composite-enhanced active halogen-free flame retardant. Using highly active magnesium oxide powder as raw material, a first active flame-retardant micropowder is obtained by stirring and hydrating the powder under pressure of 0.1–0.2 MPa and temperature of 105–120 °C for 3–4 hours. Based on mechanical activation technology and the formation of saturated vapor pressure conditions, the hydration process has a short reaction time and low energy consumption. The wet-evaporation hydration product has a better crystal morphology, with square-shaped flakes, small particle size, and good dispersibility. The first active flame-retardant micropowder is then combined with wollastonite fibers to obtain a halogen-free flame retardant containing hydrated calcium magnesium silicate and linear polyphosphate. This effectively utilizes the excellent properties of nanoparticles and alters the surface properties of the micropowder, further enhancing the flame-retardant effect. The mechanical properties of the composite material with this flame retardant are also significantly improved. This solves the technical defect that requires a high addition amount of magnesium hydroxide to achieve the flame-retardant effect and that this affects the mechanical properties of the material.

Description

Technical Field

[0001] This invention belongs to the field of plastic additives processing and relates to the production technology of environmentally friendly halogen-free flame retardant materials, specifically a method for preparing a composite reinforced active halogen-free flame retardant. Background Technology

[0002] The wide range of applications for polymers necessitates excellent flame-retardant properties to meet the fire protection requirements of various application scenarios. Adding flame retardants has become a common flame-retardant method for polymer materials due to its flexible design, wide application, and ideal results. Currently, the mainstream flame retardants include halogenated and halogen-free flame retardants. However, halogenated flame retardants easily produce large amounts of toxic gases and fumes during combustion and decomposition, which not only endangers human health but also exhibits low stability and poor compatibility with polymers, significantly impacting the mechanical properties of the added material.

[0003] Magnesium-based flame retardant materials, as halogen-free flame retardants, have multiple advantages such as flame retardancy, low smoke, non-toxicity, and no secondary pollution to the environment. In particular, their high smoke suppression performance is more in line with the current development trend of material safety. my country is one of the countries with the richest magnesium resources in the world. Transforming the abundant magnesium ore resources into flame retardant products and effectively improving the actual flame retardant effect of magnesium-based flame retardant materials is conducive to the sustainable development of the inorganic flame retardant industry and can overcome the drawbacks of halogen-based flame retardant materials producing a large amount of toxic and corrosive gases during combustion. Magnesium hydroxide is widely used as an environmentally friendly material due to its wide availability of raw materials, good thermal stability, non-volatility, and lack of precipitation. However, magnesium hydroxide flame retardants produced by grinding and processing natural brucite have many technical problems. These magnesium hydroxide flame retardants are mostly hexagonal crystals, and due to the polarity between particles, they are prone to agglomeration, resulting in poor dispersion in polymers and a significant impact on the mechanical properties of polymer materials. At the same time, this type of magnesium hydroxide requires a high addition amount to meet the flame retardant requirements. For example, the patent with publication number CN1465618A, "A Halogen-Free Flame Retardant Polypropylene Composite Material of Magnesium Hydroxide," requires a maximum addition amount of 200 parts of magnesium hydroxide per 100 parts by weight of polypropylene to meet the flame retardant requirements, which seriously affects the mechanical and processing properties of the composite material.

[0004] Existing methods for synthesizing magnesium hydroxide mainly include selective calcination of dolomite, electrolytic brine, and magnesium salt precipitation. Among these, selective calcination of dolomite is limited by process constraints and can only produce low-quality magnesium hydroxide. The electrolytic method relies on electrolytic purification of high-concentration magnesium chloride solution, resulting in high energy consumption and production costs. The magnesium salt precipitation method requires large amounts of acid and alkali, leading to cumbersome and expensive subsequent processing. Furthermore, the magnesium hydroxide solution generated in the aforementioned liquid environments requires filtration and drying processes, which not only increases energy consumption but also causes particle agglomeration, reducing the performance of flame retardants. Summary of the Invention

[0005] To overcome the shortcomings of the existing technology, this invention uses highly active magnesium oxide powder as raw material and prepares nano-scale flake-shaped first active flame retardant micro powder through hydration reaction; then, wollastonite fiber is combined with the first active flame retardant micro powder through surface acidification and mechanical kneading to form an active halogen-free flame retardant; this flame retardant has excellent compatibility and dispersibility with polyolefin resin, effectively reducing the amount of flame retardant required to prepare composite materials, improving the flame retardant performance of the materials, and significantly improving the mechanical properties and mechanical strength of the composite materials.

[0006] To achieve the above-mentioned objective, this invention provides a method for preparing a composite enhanced active halogen-free flame retardant, comprising the following steps:

[0007] ① Add highly active magnesium oxide powder into a reaction vessel, add 2% to 3% of the magnesium oxide mass as a hydration activator, add water to form a high-pressure saturated steam reaction environment, and stir and hydrate for 3 to 4 hours under the conditions of pressure 0.1 to 0.2 MPa and temperature 105℃ to 120℃; obtain nano-scale flake-shaped first active flame retardant micro powder.

[0008] Based on mechanical activation technology, crystal form regulation is achieved, and saturated vapor pressure conditions are formed to shorten the hydration process reaction time and reduce energy consumption. After high-pressure steam hydration reaction, magnesium hydroxide with a hydration rate of more than 90% can be obtained. The wet steam hydration product has a better crystal morphology and fully developed crystal grains. The final magnesium hydroxide flame retardant particles are square flakes with small particle size and good dispersibility.

[0009] Furthermore, the particle size of the highly active magnesium oxide powder in step ① is 6–18 μm, and the specific surface area is 15–60 m². 2 / g, with an absorption value of 30-40 mol / kg of chloride ions; by increasing the activity of magnesium oxide, the activation energy of the hydration reaction is reduced, the energy of the reaction molecules is increased, thereby accelerating the reaction rate and facilitating crystal form control.

[0010] Furthermore, the hydration activator in step ① is magnesium oxalate powder. The amount of water required for step ① is calculated based on the complete hydration reaction of magnesium oxide, and the stirring speed is 1000–1200 r / min. The hydration activator not only alters the morphology of magnesium hydroxide particles but also has a certain influence on the hydration reaction of magnesium oxide. After magnesium oxalate dissolves in water, it dissociates into CH3COO. - CH3COO -Compared to other anions, it has a stronger complexing ability, promoting the hydration reaction and playing a significant role in the hydration of magnesium oxide. By controlling the amount of water added, the excess water is reduced while ensuring the water required for the hydration reaction, so that the generated magnesium hydroxide active flame retardant does not need to be dried to meet the process requirements; the amount of water required for step ① is calculated based on the complete hydration reaction of magnesium oxide, so that the generated flame retardant product does not require a drying process; stirring has a mechanical activation function, which is conducive to the hydration activation reaction and realizes the crystal form control of the product; ultimately, the hydration rate of the high-pressure steam hydration reaction of the first active flame retardant powder can be greater than 90%, and the moisture content of the obtained product can be reduced to below 0.5%.

[0011] ② Take wollastonite fibers at 80% to 160% of the mass of magnesium oxide and add phosphoric acid at a concentration of 0.05 to 0.1 mol / L for surface acidification.

[0012] Furthermore, the wollastonite fibers described in step ② have a particle size of 5–20 μm and an aspect ratio of 15–20:1; the amount of phosphoric acid added in step ② is 0.5%–1.0% of the mass of the wollastonite fibers, and the acidification time is 5–8 min. Wollastonite fibers (CaSiO3) are weakly alkaline. Surface acidification with phosphoric acid causes the formation of ionic bonds. These ionic bonds act as connecting nodes, promoting the polymerization of monomeric phosphate molecules Mg(H2PO4)2 to form linear polyphosphates, thereby creating stable reinforced flame-retardant composite particles.

[0013] ③ Add the acidified wollastonite fiber to the reactor and mix it with the first active flame retardant micro powder obtained in step ①. Stir and react at 30℃~40℃ for 10~15min at a stirring rate of 300~400r / min.

[0014] Wollastonite fiber has a high heat resistance temperature, a melting point of 1540℃, no loss on ignition, and good flame retardant effect. Wollastonite fiber undergoes the following chemical reaction with the first active flame retardant micropowder to generate hydrated calcium magnesium silicate composite flame retardant particles, further enhancing the flame retardant effect. At the same time, this particle size can generate the nano-effect of inorganic materials, achieving a flame retardant effect by preventing the material from reaching the thermal decomposition temperature through heat storage and conduction.

[0015] CaSiO3+0.17H2O+Mg(OH)2=CaMgSiO4·1.17H2O

[0016] The hydration reaction causes the nanoparticles of the first active flame retardant powder to be uniformly dispersed or grown on the surface of wollastonite microparticles. This not only effectively utilizes the excellent properties of nanoparticles but also changes the surface properties of the microparticles. The sharp edges of the mineral fiber particles are blunted, and their smooth cleavage surfaces become rough due to the presence of the micro- and nanoparticle structures. When filled into the resin matrix, this can alleviate the problem of local stress concentration inside the composite material caused by sharp edges and smooth crystal cleavage surfaces, which can significantly improve the composite effect and thus obtain a high-performance composite material.

[0017] ④ Add water to the reactor to form reaction conditions of 2.0-3.0 MPa pressure and 210-235℃ temperature, and stir for 30-40 min at a stirring rate of 500-600 r / min; then add surfactant at 2%-5% of the mass of wollastonite fiber, and continue stirring for 50-60 min at a stirring rate of 200-300 r / min.

[0018] Furthermore, the surfactant used in step ④ is selected as a silane coupling agent or a titanate coupling agent, and the amount of water added in step ④ is controlled to be 1.2 to 1.5 times the mass of water required for the hydration reaction of wollastonite fibers and magnesia fibers. A saturated vapor pressure environment can promote the hydration reaction, and surface modification is carried out simultaneously with the hydration reaction to overcome the agglomeration of composite flame-retardant particles; the surface modifier adsorbs onto the microcrystalline surface to form a protective film, reducing surface energy and effectively preventing the agglomeration of composite flame-retardant particles, further reducing the average particle size of the composite flame-retardant particles.

[0019] ⑤ The material obtained in step ④ is aged at 120℃~140℃ for 3~4 hours to obtain a composite reinforced active halogen-free flame retardant. Controlling the aging conditions is beneficial to crystal growth. When the aging reaction is fully completed, the excess attached water evaporates to generate gas, which can be released through the one-way exhaust port on the equipment, so that the product reaches a dry state.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] Based on mechanical activation technology, crystal form control is achieved, and saturated vapor pressure conditions are formed, resulting in a short reaction time and low energy consumption for the hydration process. After high-pressure steam hydration, magnesium hydroxide with a hydration rate of more than 90% can be obtained. The wet steam hydration product has a better crystal morphology and fully developed crystal grains. The obtained first active flame retardant microparticles are square flakes with small particle size and good dispersibility. The amount of water required is calculated based on the complete hydration reaction of magnesium oxide, so that the generated flame retardant product does not require a drying process, thus saving energy and increasing efficiency.

[0022] Wollastonite fiber and first active flame-retardant micro powder react to generate hydrated calcium magnesium silicate composite flame-retardant particles. The composite powder contains hydrated calcium magnesium silicate and linear polyphosphate, which can effectively utilize the excellent properties of nanoparticles and change the surface properties of micron powder, further enhancing the flame-retardant effect and improving mechanical strength, thereby obtaining high-performance composite materials. Attached Figure Description

[0023] Figure 1 Here is an SEM image of the first active flame retardant micropowder sample prepared in Example 1;

[0024] Figure 2 This is a SEM image of the composite reinforced active halogen-free flame retardant powder sample prepared in Example 1. Detailed Implementation

[0025] The present invention will be further described below with reference to specific embodiments, but this does not limit the invention in any way. To avoid redundancy, unless otherwise specified, the raw materials used in the following embodiments are all commercially available products, and the methods used are all conventional methods unless otherwise specified.

[0026] The processing equipment used was a co-rotating parallel twin-screw extruder, model THE-52D / 600-90-40, manufactured by Nanjing Euroextrusion Machinery Co., Ltd. The bending and tensile properties of the test samples were tested using a WDW-100 electronic universal testing machine from Jinan Sida Testing Technology Co., Ltd. Bending properties were tested according to GB / T9341-2008, with a sample size of 80mm×10mm×4mm, a span of 64mm, and a loading rate of 2mm / min. Tensile properties were tested according to GB / T1040-2018, using type I specimens, a gauge length of 50mm, and a loading rate of 2mm / min. Impact performance was determined using a HIT-2494 pendulum impact testing machine from Chengde Jinjian Testing Instruments Co., Ltd., according to GB / T1843-2008, using a type B notch, a sample size of 80mm×10mm×4mm, a span of 64mm, and a pendulum impact capacity of 15J. At least 5 specimens were tested in each group, and the arithmetic mean was taken as the final result. Oxygen index (OI) was determined using a PX-01-005 oxygen index meter from Suzhou Phoenix Contact Instruments Co., Ltd., in accordance with GB / T 2406.2-2009. The specimen size was 80mm × 10mm × 4mm, with 15 parallel samples per group. The vertical method test standards for plastic flammability were IEC60695 and UL94, with flame retardant performance ranked from best to worst as V0, V1, V2, and NV.

[0027] The hydration rate of magnesium oxide is calculated using the following formula: α = 40(m1-m2) / 18m2 × 100%; where α: hydration rate of magnesium oxide, %; m1: mass of the hydrated product before calcination, g; m2: mass of the hydrated product after calcination, g; 40 / 18: molar mass ratio of MgO to H2O.

[0028] A method for preparing a composite enhanced active halogen-free flame retardant includes the following steps:

[0029] ① Add highly active magnesium oxide powder into a reaction vessel, add 2% to 3% of the magnesium oxide mass as a hydration activator, add water to form a high-pressure saturated steam reaction environment, and stir the hydration reaction for 3 to 4 hours under the conditions of pressure 0.1 to 0.2 MPa and temperature 105℃ to 120℃; to obtain nano-scale flake-shaped first active flame retardant micro powder;

[0030] ② Take wollastonite fibers at 80% to 160% of the mass of magnesium oxide, and add phosphoric acid at a concentration of 0.05 to 0.1 mol / L for surface acidification;

[0031] ③ Add the acidified wollastonite fiber to the reactor and mix it with the first active flame retardant micro powder obtained in step ①. Stir and react at 30℃~40℃ for 10~15min at a stirring rate of 300~400r / min.

[0032] ④ Add water to create a reaction condition with a pressure of 2.0-3.0 MPa and a temperature of 210℃-235℃, and stir for 30-40 minutes at a stirring rate of 500-600 r / min; then add surfactant at 2%-5% of the mass of wollastonite fiber, and continue stirring for 50-60 minutes at a stirring rate of 200-300 r / min.

[0033] ⑤ The material obtained in step ④ is aged at a temperature of 120℃~140℃ for 3~4 hours to obtain a composite enhanced active halogen-free flame retardant.

[0034] Any aspects not described in the following embodiments are the same as those described in the specific embodiments above.

[0035] Example 1

[0036] A method for preparing a composite enhanced active halogen-free flame retardant includes the following steps:

[0037] ① High-activity magnesium oxide powder was added to a reaction vessel, along with 2.5% (by weight of magnesium oxide) of hydration activator. Water was added to create a high-pressure saturated steam reaction environment. The hydration reaction was carried out under stirring at a pressure of 0.15 MPa and a temperature of 110°C for 3.5 hours to obtain nano-sized, flake-shaped, first-activity flame-retardant micro-powder. The high-activity magnesium oxide powder had a particle size of 12 μm and a specific surface area of ​​35 m². 2 / g, with an absorbed chloride ion value of 35mol / kg; the hydration activator is magnesium oxalate powder, and the amount of water required for step ① is calculated based on the complete hydration reaction of magnesium oxide; the stirring rate is 1100 r / min. The hydration rate of the highly active magnesium oxide powder in step ① was tested to be 94.8%.

[0038] ② Take 120% of the mass of magnesium oxide wollastonite fiber and add 0.08 mol / L phosphoric acid for surface acidification; the particle size of the wollastonite fiber is 12 μm and the aspect ratio is 18:1; the amount of phosphoric acid added in step ② is 0.8% of the mass of wollastonite fiber, and the acidification time is 7 min.

[0039] ③ Add the acidified wollastonite fiber to the reactor and mix it with the first active flame retardant micro powder obtained in step ①. Stir and react at 35°C for 12 minutes at a stirring rate of 350 r / min.

[0040] ④ Add water to create reaction conditions of 2.5 MPa pressure and 218°C in the reactor, and stir for 35 min at a stirring rate of 550 r / min; then add surfactant at 3% of the mass of wollastonite fiber, and continue stirring for 55 min at a stirring rate of 250 r / min; the surfactant is selected as a silane coupling agent, and the amount of water added in step ④ is controlled to be 1.4 times the mass of water required for the hydration reaction of wollastonite fiber and magnesia fiber.

[0041] ⑤ The material obtained in step ④ is aged at 130℃ for 3.5 hours to obtain a composite enhanced active halogen-free flame retardant.

[0042] The first active flame-retardant micropowder sample prepared in Example 1 was observed by SEM, as follows: Figure 1 As shown, by Figure 1 It can be seen that the crystals of the first active flame retardant micropowder are square-shaped, with a crystal particle size of about 200 nm and a single-piece thickness of less than 100 nm. The particles are uniformly crystallized and do not agglomerate. The microstructure of the composite reinforced active halogen-free flame retardant powder sample prepared in Example 1 is as follows: Figure 2 As shown, the hydration reaction causes the nanoparticles of the first active flame retardant powder to be uniformly dispersed or grown on the surface of the wollastonite microparticles, resulting in good dispersibility, no agglomeration, and good composite effect; the moisture content of the obtained product is reduced to 0.28%, eliminating the need for further drying.

[0043] 53 parts by weight of the composite reinforced active halogen-free flame retardant prepared in Example 1 were premixed with 42 parts by weight of polypropylene and 5 parts by weight of other additives in a high-speed mixer until homogeneous. The mixture was then extruded on a twin-screw extruder, water-cooled, and granulated to obtain a composite reinforced flame-retardant polypropylene composite material. The mechanical and flame-retardant properties of the obtained composite material were tested as follows: tensile strength 31.8 MPa, flexural strength 42.6 MPa, and notched impact strength 9.4 kJ / m². 2 The oxygen index (OI) value was 36.4 (the oxygen index of polypropylene is about 17-18), and the vertical burning performance test was V0. It can be seen that the mechanical properties of the plastic sample with the addition of the halogen-free flame retardant prepared in Example 1 were significantly improved, and the flame retardant performance was excellent. The hydrated calcium magnesium silicate composite flame retardant particles improved the oxygen index (OI) value of the composite material, which can meet the application requirements.

[0044] Example 2

[0045] A method for preparing a composite enhanced active halogen-free flame retardant includes the following steps:

[0046] ① High-activity magnesium oxide powder was added to a reactor, along with a hydration activator at 2% of the magnesium oxide mass. Water was added to create a high-pressure saturated steam reaction environment. The hydration reaction was carried out under stirring at a pressure of 0.1 MPa and a temperature of 105℃ for 3 hours to obtain nano-scale flake-shaped first-activity flame-retardant micro-powder. The particle size of the high-activity magnesium oxide powder was 6 μm, and the specific surface area was 60 m². 2 / g, with an absorbed chloride ion value of 40 mol / kg; the hydration activator is magnesium oxalate powder, and the required water addition is calculated based on the complete hydration reaction of magnesium oxide; the stirring rate is 1080 r / min. The hydration rate of the highly active magnesium oxide powder in step ① was tested to be 95.6%.

[0047] ② Take 80% of the mass of magnesium oxide wollastonite fiber and add 0.05 mol / L phosphoric acid for surface acidification; the particle size of the wollastonite fiber is 5 μm and the aspect ratio is 15:1; the amount of phosphoric acid added in step ② is 0.5% of the mass of wollastonite fiber, and the acidification time is 5 min.

[0048] ③ Add the acidified wollastonite fiber to the reactor and mix it with the first active flame retardant micro powder obtained in step ①. Stir and react at 30°C for 10 min at a stirring rate of 300 r / min.

[0049] ④ Add water to create reaction conditions of 2.0 MPa and 210°C in the reactor, and stir for 30 min at a stirring rate of 500 r / min; then add surfactant at 2% of the mass of wollastonite fiber, and continue stirring for 50 min at a stirring rate of 200 r / min; the surfactant is selected as titanate coupling agent, and the amount of water added in step ④ is controlled to be 1.2 times the mass of water required for the hydration reaction of wollastonite fiber and magnesia fiber.

[0050] ⑤ The material obtained in step ④ is aged at 120℃ for 3 hours to obtain a composite enhanced active halogen-free flame retardant.

[0051] SEM observation of the first active flame retardant micropowder sample prepared in Example 2 revealed that the crystals of the first active flame retardant micropowder were square-shaped flakes with a particle size of approximately 180 nm and a single flake thickness of less than 90 nm. The particles exhibited uniform crystallization and minimal agglomeration. The moisture content of the composite reinforced active halogen-free flame retardant product prepared in Example 2 was reduced to 0.24%, eliminating the need for further drying. The hydration reaction resulted in the uniform dispersion or growth of the nanoparticles of the first active flame retardant micropowder on the surface of the wollastonite microparticles, exhibiting good dispersibility, no agglomeration, and a good composite effect.

[0052] 55 parts by weight of the composite reinforced active halogen-free flame retardant prepared in Example 2 were premixed with 41 parts by weight of polypropylene and 4 parts by weight of other additives in a high-speed mixer until homogeneous. The mixture was then extruded on a twin-screw extruder, water-cooled, and granulated to obtain a composite reinforced flame-retardant polypropylene composite material. The mechanical and flame-retardant properties of the obtained composite material were tested as follows: tensile strength 30.6 MPa, flexural strength 41.7 MPa, and notched impact strength 8.9 kJ / m². 2 The oxygen index (OI) value was 37.2, and the vertical burning performance test was rated as V0. It can be seen that the mechanical properties of the plastic sample with the addition of the halogen-free flame retardant prepared in Example 2 were significantly improved, and the flame retardant performance was excellent.

[0053] Example 3

[0054] A method for preparing a composite enhanced active halogen-free flame retardant includes the following steps:

[0055] ① High-activity magnesium oxide powder was added to a reaction vessel, along with a hydration activator at a mass of 3% of the magnesium oxide. Water was added to create a high-pressure saturated steam reaction environment. The hydration reaction was carried out under stirring at a pressure of 0.2 MPa and a temperature of 120°C for 4 hours to obtain nano-sized, flake-shaped, first-activity flame-retardant micro-powder. The high-activity magnesium oxide powder had a particle size of 18 μm and a specific surface area of ​​15 m². 2 / g, with an absorbed chloride ion value of 30 mol / kg; the hydration activator is magnesium oxalate powder, and the required water addition is calculated based on the complete hydration reaction of magnesium oxide; the stirring rate is 1200 r / min. The hydration rate of the highly active magnesium oxide powder in step ① was tested to be 94.7%.

[0056] ② Take 160% of the mass of magnesium oxide wollastonite fiber and add 0.1 mol / L phosphoric acid for surface acidification; the particle size of the wollastonite fiber is 20 μm and the aspect ratio is 20:1; the amount of phosphoric acid added in step ② is 1.0% of the mass of wollastonite fiber, and the acidification time is 8 min.

[0057] ③ Add the acidified wollastonite fiber to the reactor and mix it with the first active flame retardant micro powder obtained in step ①. Stir and react at 40℃ for 15 minutes at a stirring rate of 400 r / min.

[0058] ④ Add water to create reaction conditions of 3.0 MPa and 235°C in the reactor, and stir for 40 min at a stirring rate of 600 r / min; then add surfactant at 5% of the mass of wollastonite fiber, and continue stirring for 60 min at a stirring rate of 300 r / min; the surfactant is selected as a silane coupling agent, and the amount of water added in step ④ is controlled to be 1.5 times the mass of water required for the hydration reaction of wollastonite fiber and magnesia fiber.

[0059] ⑤ The material obtained in step ④ is aged at 140℃ for 4 hours to obtain a composite enhanced active halogen-free flame retardant.

[0060] SEM observation of the first active flame retardant micropowder sample prepared in Example 3 showed that the crystals of the first active flame retardant micropowder sample were square-shaped plates with a particle size of about 190 nm and a single plate thickness of less than 90 nm. The particles were uniformly crystallized with no obvious agglomeration. The moisture content of the composite reinforced active halogen-free flame retardant product prepared in Example 3 was reduced to 0.19%, eliminating the need for a drying process. The hydration reaction caused the nanoparticles of the first active flame retardant micropowder to be uniformly dispersed or grown on the surface of the wollastonite microparticles, exhibiting good dispersibility, no agglomeration, and a good composite effect.

[0061] 52 parts by weight of the composite reinforced active halogen-free flame retardant prepared in Example 3 were premixed with 44 parts by weight of polypropylene and 4 parts by weight of other additives in a high-speed mixer until homogeneous. The mixture was then extruded on a twin-screw extruder, water-cooled, and granulated to obtain a composite reinforced flame-retardant polypropylene composite material. The mechanical properties and flame retardancy data of the obtained composite material are as follows: tensile strength 32.4 MPa, flexural strength 44.9 MPa, notched impact strength 9.8 kJ / m². 2The oxygen index (OI) value was 38.8, and the vertical burning performance test was rated as V0. It can be seen that the mechanical properties of the plastic sample with the addition of the halogen-free flame retardant prepared in Example 3 were significantly improved, and the flame retardant performance was excellent.

[0062] Comparative Example 1

[0063] Using the technical solution of Example 4 of Patent CN1465618A, "A Halogen-Free Flame-Retardant Polypropylene Composite Material of Magnesium Hydroxide," as Comparative Example 1, the preparation process of its composite material includes the following steps:

[0064] 1200 g of natural mineral magnesium hydroxide powder with a particle size of 5 μm was premixed with 600 g of homopolymer polypropylene, 120 g of ethylene-octene elastomer, and 3.84 g of pentaerythritol di(2,4-di-tert-butylphenyl) phosphite in a high-speed mixer in a specific ratio. The mixture was then extruded on a twin-screw extruder at 220 °C, water-cooled, and granulated to obtain a flame-retardant polypropylene composite material. The mechanical properties, processing properties, and flame retardancy data of the obtained material are as follows: tensile strength 17.3 MPa, flexural strength 26.8 MPa, flexural modulus 1468.0 MPa, melt index 0.1 g / 10 min, and flame retardancy FV-1.

[0065] By comparing the performance of the plastic samples prepared in Examples 1-3 and Comparative Example 1, it can be seen that the tensile strength of Examples 1-3 is 78.88% to 87.28% higher than that of Comparative Example 1, and the flexural strength is 55.60% to 67.54% higher than that of Comparative Example 1, and the mechanical properties are significantly improved. At the same time, the hydrated calcium magnesium silicate composite flame retardant particles of Examples 1-3 improve the oxygen index (OI) of the composite material and exhibit excellent flame retardant performance.

[0066] For anyone skilled in the art, many possible variations and modifications can be made to the technical solutions of this invention, or equivalent embodiments can be modified based on the disclosed technical content, without departing from the scope of the technical solutions of this invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of this invention without departing from the content of the technical solutions of this invention should still fall within the protection scope of the technical solutions of this invention.

Claims

1. A method for preparing a composite reinforced active halogen-free flame retardant, characterized in that, The preparation method includes the following steps: ① Add highly active magnesium oxide powder into a reaction vessel, add 2% to 3% of the magnesium oxide mass as a hydration activator, add water to form a high-pressure saturated steam reaction environment, and stir the hydration reaction for 3 to 4 hours under the conditions of pressure 0.1 to 0.2 MPa and temperature 105℃ to 120℃; to obtain nano-scale flake-shaped first active flame retardant micro powder; ② Take wollastonite fibers at 80% to 160% of the mass of magnesium oxide, and add phosphoric acid at a concentration of 0.05 to 0.1 mol / L for surface acidification; ③ Add the acidified wollastonite fiber to the reactor and mix it with the first active flame retardant micro powder obtained in step ①. Stir and react at 30℃~40℃ for 10~15min at a stirring rate of 300~400r / min. ④ Add water to create a reaction condition with a pressure of 2.0-3.0 MPa and a temperature of 210℃-235℃, and stir for 30-40 minutes at a stirring rate of 500-600 r / min; then add surfactant at 2%-5% of the mass of wollastonite fiber, and continue stirring for 50-60 minutes at a stirring rate of 200-300 r / min. ⑤ The material obtained in step ④ is aged at a temperature of 120℃~140℃ for 3~4 hours to obtain a composite enhanced active halogen-free flame retardant.

2. The preparation method according to claim 1, characterized in that, The highly active magnesium oxide powder in step ① has a particle size of 6–18 μm and a specific surface area of ​​15–60 m². 2 / g, with an absorption value of 30-40 mol / kg for chloride ions.

3. The preparation method according to claim 1, characterized in that, The hydration activator in step ① is magnesium oxalate powder. The amount of water required for step ① is calculated based on the complete hydration reaction of magnesium oxide, and the stirring rate is 1000-1200 r / min.

4. The preparation method according to claim 1, characterized in that, The wollastonite fibers described in step ② have a particle size of 5–20 μm and an aspect ratio of 15–20:

1.

5. The preparation method according to claim 1, characterized in that, In step ②, the amount of phosphoric acid added is 0.5% to 1.0% of the mass of wollastonite fiber, and the acidification time is 5 to 8 minutes.

6. The preparation method according to claim 1, characterized in that, The surfactant mentioned in step ④ is a silane coupling agent or a titanate coupling agent.

7. The preparation method according to claim 1, characterized in that, Step ④ The amount of water added should be controlled at 1.2 to 1.5 times the mass of water required for the hydration reaction of wollastonite fiber and the first active flame retardant micro powder.

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