Preparation method of composite reinforced active halogen-free flame retardant

Abstract

The invention discloses a preparation method of a composite reinforced active halogen-free flame retardant, which comprises the following steps: by taking high-activity magnesium oxide powder as a raw material, stirring and carrying out hydration reaction for 3-4 hours under the conditions that the pressure is 0.1-0.2 MPa and the temperature is 105-120 DEG C to obtain first active flame-retardant micro powder, and enabling the hydration process to be short in reaction time and low in energy consumption on the basis of a mechanical activation technology and under a saturated vapor pressure condition; the wet steaming hydration product has a better crystal form, the crystal form is in a square sheet shape, the particle size is small, and the dispersity is good; the first active flame-retardant micro powder and wollastonite fibers are subjected to a composite reaction to obtain the halogen-free flame retardant, the halogen-free flame retardant comprises hydrated calcium magnesium silicate and linear polyphosphate, the excellent characteristics of nano particles can be effectively utilized, the surface property of the micro powder is changed, the flame-retardant effect is further enhanced, and the flame-retardant effect is further improved. The mechanical property of the composite material added with the flame retardant is also remarkably improved; therefore, the technical defects that the flame-retardant effect can be achieved only by high addition amount of magnesium hydroxide and the mechanical property of the material is influenced are overcome.

Description

Technical Field

[0001] The present invention belongs to the field of plastic additive processing, relates to the production technology of environment-friendly halogen-free flame retardant materials, and specifically relates to a preparation method of a composite reinforced active halogen-free flame retardant. Background Art

[0002] The wide application range of polymer materials requires them to have good flame retardant properties to meet the fire prevention requirements of different application scenarios. Adding flame retardants has become a common flame retardant method for polymer materials due to its flexible design, wide application, and ideal effect. Currently, the mainstream flame retardants include halogen-based flame retardants and halogen-free flame retardants. Since halogen-based flame retardants are prone to generate a large amount of poisonous gas and smoke during combustion and decomposition, they not only endanger human health, but also have low stability, poor compatibility with polymers, and have a greater impact on the mechanical properties of the added materials.

[0003] As a halogen-free flame retardant, magnesium-based flame retardant materials have the advantages of multiple flame retardancy, low smoke, non-toxicity, and no secondary pollution to the environment. In particular, their high-efficiency smoke suppression performance is more in line with the current development trend of material safety. China is one of the countries with the richest magnesium resources in the world. Converting the rich magnesium ore resources into flame retardant products and effectively improving the actual flame retardant effect of magnesium-based flame retardant materials is beneficial to the sustainable development of the inorganic flame retardant industry and can overcome the drawbacks of halogen-based flame retardant materials generating a large amount of toxic and corrosive gases during the combustion process. Magnesium hydroxide is widely used as an environment-friendly material due to its wide range of raw material sources, good thermal stability, non-volatility, and no precipitation. However, magnesium hydroxide flame retardants produced by grinding and processing natural brucite have many technical problems. This kind of magnesium hydroxide flame retardant is mostly hexagonal crystal form. Due to the polarity between particles, it is easy to agglomerate, has poor dispersion effect in polymer materials, and has a greater impact on the mechanical properties of polymer materials. At the same time, this kind of magnesium hydroxide requires a high addition amount to meet the flame retardant effect requirements. For example, in the patent "A Magnesium Hydroxide Halogen-Free Flame Retardant Polypropylene Composite Material" with the publication number CN1465618A, the addition amount of magnesium hydroxide in every 100 parts by mass of polypropylene can reach up to 200 parts at most to meet the flame retardant requirements, seriously affecting the mechanical properties and processing properties of the composite material.

[0004] The existing production methods for synthesizing magnesium hydroxide mainly include dolomite selective calcination method, electrolytic brine method, and magnesium salt precipitation method, etc. Among them, the dolomite selective calcination method can only produce magnesium hydroxide of low quality grade due to process limitations; the electrolytic method relies on electrolyzing refined high-concentration magnesium chloride solution, with high power consumption and high production cost; the magnesium salt precipitation method requires a large amount of acids and alkalis, and the subsequent treatment is cumbersome and costly. At the same time, the magnesium hydroxide solution generated in the above liquid environment requires filtration and drying processes, which not only increases energy consumption, but also causes particle agglomeration, reducing the application performance of the flame retardant. Summary of the Invention

[0005] To overcome the defects of the above-mentioned prior art, the present invention uses high-activity magnesium oxide powder as a raw material, and prepares nanoscale flaky first active flame-retardant micro-powder through a hydration reaction; wollastonite fibers are compounded with the first active flame-retardant micro-powder through surface acidification and mechanical kneading to form an active halogen-free flame retardant; the compatibility and dispersibility of this flame retardant with polyolefin resin are excellent, effectively reducing the amount of flame retardant required for preparing the composite material, improving the flame retardant performance of the material, and significantly improving the mechanical properties of the composite material, with a substantial increase in mechanical strength.

[0006] To achieve the above-mentioned invention purpose, the present invention provides a preparation method of a composite reinforced active halogen-free flame retardant, including the following steps:

[0007] ① Put high-activity magnesium oxide powder into a reaction kettle, add a hydration activator accounting for 2% - 3% of the mass of magnesium oxide, add water to form a high-pressure saturated steam reaction environment, and stir and hydrate for 3 - 4 hours under the conditions of a pressure of 0.1 - 0.2 MPa and a temperature of 105°C - 120°C; obtain nanoscale flaky first active flame-retardant micro-powder.

[0008] Based on mechanical activation technology to achieve crystal form control, forming a saturated vapor pressure condition makes the hydration process have a short reaction time and low energy consumption; after high-pressure steam hydration reaction, magnesium hydroxide with a hydration rate greater than 90% can be obtained, and the product of wet steam hydration has a better crystal form, with fully developed crystal grains. Finally, the obtained magnesium hydroxide flame-retardant particles are square flakes, with small particle size and good dispersibility.

[0009] Further, the particle size of the high-activity magnesium oxide powder in step ① is 6 - 18 μm, the specific surface area is 15 - 60 m 2 / g, and the chloride ion absorption value is 30 - 40 mol / kg; by increasing the activity of magnesium oxide, the activation energy of the hydration reaction is reduced, the energy of reaction molecules is increased, and thus the reaction rate is accelerated, which is beneficial to crystal form control.

[0010] Further, the hydration activator in step ① is magnesium oxalate powder. Calculate the water addition amount required in step ① according to the complete hydration reaction of magnesium oxide, and the stirring rate is 1000 - 1200 r / min. The hydration activator can not only change 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 CH 3 COO - CH 3 COO -It has a stronger complexing ability compared to other anions, promotes the hydration reaction, and plays a significant promoting role in the hydration process of magnesium oxide. By controlling the water addition amount, while ensuring the water required for the hydration reaction, the existence of excess water is reduced, so that the produced magnesium hydroxide active flame retardant can meet the process requirements without drying; calculating the water addition amount required in step ① according to the complete hydration reaction of magnesium oxide, so that the produced flame retardant product does not require a drying process; stirring has a mechanical activation function, which is conducive to the progress of the hydration activation reaction and realizes the crystal form control of the product; finally, the hydration rate of the high-pressure steam hydration reaction of the first active flame retardant micropowder can be greater than 90%, and the water content of the obtained product is reduced to less than 0.5%.

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

[0012] Further, the particle size of the wollastonite fibers in step ② is 5 - 20 μm, and the aspect ratio is 15 - 20:1; the addition amount of the phosphoric acid 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 CaSiO 3 are weakly alkaline. Surface acidification is carried out with phosphoric acid to generate ionic bonds; the ionic bonds play a role in connecting nodes, promoting the monomer phosphate molecule Mg(H 2 PO 4 ) 2 to polymerize and generate linear polyphosphates to form stable enhanced flame retardant composite particles.

[0013] ③ Add the acidified wollastonite fibers to the reaction kettle, mix them with the first active flame retardant micropowder obtained in step ①, and stir and react at 30°C - 40°C for 10 - 15 min, and the stirring rate is 300 - 400 r / min.

[0014] Wollastonite fibers have a high heat-resistant temperature, a melting point of 1540°C, no loss on ignition, and good flame retardant effect; wollastonite fibers react with the first active flame retardant micropowder to generate calcium magnesium hydrosilicate composite flame retardant particles through the following chemical reaction, further strengthening the flame retardant effect; at the same time, this particle size level can produce the nano effect of inorganic materials, and the material cannot reach the thermal decomposition temperature through heat storage and heat conduction to obtain the flame retardant effect.

[0015] CaSiO 3 +0.17H 2 O+Mg(OH) 2 =CaMgSiO 4 ·1.17H 2 O

[0016] The hydration reaction evenly disperses or grows the nanoparticles of the first active flame retardant micropowder on the surface of wollastonite microparticles, which can not only effectively utilize the excellent properties of the nanoparticles but also change the surface properties of the micropowder; the sharp edges and corners on the surface of the mineral fiber particles are passivated, and its flat and smooth cleavage plane becomes rough due to the existence of the micro-nano particle structure. Filling it into the resin matrix can alleviate the local stress concentration problem inside the composite material caused by the sharp edges and corners and the flat crystal cleavage plane, significantly improving the composite effect and thus obtaining a high-performance composite material.

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

[0018] Furthermore, the surfactant described in step ④ is selected from silane coupling agents or titanate coupling agents, and the water addition amount in step ④ is controlled according to 1.2 - 1.5 times the mass of water required for the hydration reaction of wollastonite fiber and brucite fiber. The saturated vapor pressure environment can promote the progress of the hydration reaction, and surface modification is carried out simultaneously during the hydration reaction to overcome the agglomeration phenomenon of the composite flame retardant particles; the surface modifier adsorbs on the surface of the microcrystals to form a protective film, reducing the surface energy and effectively preventing the agglomeration of the composite flame retardant particles, further reducing the average particle size of the composite flame retardant particles.

[0019] ⑤ Age and develop the material obtained in step ④ for 3 - 4 h at a temperature of 120°C - 140°C to prepare a composite enhanced active halogen-free flame retardant. Controlling the aging and development conditions is beneficial to crystal growth. When the aging and development reaction is fully completed, the excess attached water evaporates to form gas and can be discharged through the one-way exhaust hole set on the equipment, making the product reach a dry state.

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

[0021] Based on the mechanical activation technology, crystal form regulation is realized, forming a saturated vapor pressure condition, so that the hydration process has a short reaction time and low energy consumption; after the high-pressure steam hydration reaction, magnesium hydroxide with a hydration rate greater than 90% can be obtained. The product of wet steam hydration has a better crystal morphology, the crystal grains are fully developed, and the obtained first active flame retardant micropowder particles are square flakes, with small particle size and good dispersibility; the water addition amount is calculated according to all the magnesium oxide undergoing the hydration reaction, so that the generated flame retardant product does not require a drying process, saving energy and increasing efficiency.

[0022] The wollastonite fiber reacts with the first active flame retardant fine powder to generate hydrated calcium magnesium silicate composite flame retardant particles. The components of the composite powder include hydrated calcium magnesium silicate and linear polyphosphate, which can not only effectively utilize the excellent properties of nanoparticles, but also change the surface properties of the micro-powder, further enhancing the flame retardant effect and improving the mechanical strength, so as to obtain high-performance composite materials. Description of the Drawings

[0023] Figure 1 SEM image of the first active flame retardant fine powder sample prepared in Example 1;

[0024] Figure 2 SEM image of the composite enhanced active halogen-free flame retardant powder sample prepared in Example 1. Detailed Embodiments

[0025] The present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited in any way. To avoid repetition, in the following embodiments, the raw materials are commercially available products without special instructions, and the methods used are conventional methods without special instructions.

[0026] The processing equipment uses a co-rotating parallel twin-screw extruder produced by Nanjing Ouli Extrusion Machinery Co., Ltd., model THE-52D / 600-90-40; a WDW-100 type electronic universal testing machine produced by Jinan Sida Testing Technology Co., Ltd. is used to detect the bending performance and tensile performance of the test samples; the bending performance is tested according to GB / T9341-2008, the specimen size is 80mm×10mm×4mm, the span is 64mm, and the loading rate is 2mm / min; the tensile performance is tested with reference to GB / T1040-2018, using type I specimens, the gauge length is 50mm, and the loading rate is 2mm / min. The impact performance is measured with reference to GB / T1843-2008 using a HIT-2494 type pendulum impact tester produced by Chengde Jinjian Testing Instrument Co., Ltd., using a B-type notch, the specimen size is 80mm×10mm×4mm, the span is 64mm, and the pendulum impact energy is 15J; at least 5 specimens are tested in each group, and the arithmetic mean is taken as the final result. The OI is measured using a PX-01-005 type oxygen index meter produced by Suzhou Phoenix Quality Inspection Instrument Co., Ltd. according to GB / T 2406.2-2009, the specimen size is 80mm×10mm×4mm, and there are 15 parallel samples in each group. The vertical method test standard for the combustion performance of plastics is IEC60695 and UL94, and the flame retardant performance from excellent to poor is V0, V1, V2, and NV in turn.

[0027] Calculate the hydration rate of magnesium oxide according to the following formula: α = 40(m 1 -m 2 ) / 18m 2× 100%; where α: the hydration rate of magnesium oxide, %; m 1 : the mass of uncalcined hydrated product, g; m 2 : the mass of the calcined hydrated product, g; 40 / 18: the molar mass ratio of MgO to H 2 O

[0028] A preparation method of a composite reinforced active halogen-free flame retardant, comprising the following steps:

[0029] ① Put high-activity magnesium oxide powder into a reaction kettle, add a hydration activator accounting for 2% - 3% of the mass of magnesium oxide, add water to form a high-pressure saturated steam reaction environment, and stir and hydrate react for 3 - 4 h under the conditions of a pressure of 0.1 - 0.2 MPa and a temperature of 105°C - 120°C; obtain nano-scale flaky first active flame retardant micro-powder;

[0030] ② Take wollastonite fiber according to 80% - 160% of the mass of magnesium oxide, and carry out surface acidification with phosphoric acid with a concentration of 0.05 - 0.1 mol / L;

[0031] ③ Add the acidified wollastonite fiber into the reaction kettle, mix it with the first active flame retardant micro-powder obtained in step ①, and stir and react at 30°C - 40°C for 10 - 15 min, with a stirring rate of 300 - 400 r / min;

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

[0033] ⑤ Age and develop the material obtained in step ④ at a temperature of 120°C - 140°C for 3 - 4 h to prepare a composite reinforced active halogen-free flame retardant.

[0034] For those not described in the following examples, they are the same as the description content of the above specific implementation manners.

[0035] Example 1

[0036] A preparation method of a composite reinforced active halogen-free flame retardant, comprising the following steps:

[0037] ① Put high-activity magnesium oxide powder into a reaction kettle, add a hydration activator accounting for 2.5% of the mass of magnesium oxide, add water to form a high-pressure saturated steam reaction environment, and stir and hydrate react for 3.5 h under the conditions of a pressure of 0.15 MPa and a temperature of 110°C; obtain nano-scale flaky first active flame retardant micro-powder; the particle size of the high-activity magnesium oxide powder is 12 μm, and the specific surface area is 35 m 2 / g, the chloride ion absorption value is 35 mol / kg; the hydrated activator is magnesium oxalate powder. Calculate the amount of water required in step ① according to 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 is detected to be 94.8%.

[0038] ② Take wollastonite fibers at 120% of the mass of magnesium oxide and add phosphoric acid with a concentration of 0.08 mol / L for surface acidification; the particle size of the wollastonite fibers 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 the wollastonite fibers, and the acidification time is 7 min.

[0039] ③ Add the acidified wollastonite fibers to the reaction kettle and mix with the first active flame retardant micropowder obtained in step ①, and stir and react at 35 °C for 12 min. The stirring rate is 350 r / min.

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

[0041] ⑤ Age and develop the material obtained in step ④ at a temperature of 130 °C for 3.5 h to prepare a composite enhanced active halogen-free flame retardant.

[0042] Perform SEM observation on the first active flame retardant micropowder sample prepared in Example 1, as Figure 1 shown. It can be seen from Figure 1 that the crystals of the prepared first active flame retardant micropowder are square flakes, the crystal particle size is about 200 nm, the single sheet thickness is less than 100 nm, the particle crystallization is uniform, and there is no agglomeration. The microstructure of the composite enhanced active halogen-free flame retardant powder sample prepared in Example 1 is as Figure 2 shown. The hydration reaction makes the nanoparticles of the first active flame retardant powder uniformly disperse or grow on the surface of the wollastonite micron particles, with good dispersion, no agglomeration, and good composite effect; the water content of the obtained product is reduced to 0.28%, and there is no need to dry it again.

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

[0044] Example 2

[0045] A preparation method of a composite enhanced halogen-free flame retardant, comprising the following steps:

[0046] ① Put the high-activity magnesium oxide powder into the reaction kettle, add a hydration activator accounting for 2% of the mass of magnesium oxide, add water to form a high-pressure saturated steam reaction environment, and stir and hydrate for 3 h under the conditions of a pressure of 0.1 MPa and a temperature of 105 °C; obtain nano-scale flaky first active flame-retardant micropowder; the particle size of the high-activity magnesium oxide powder is 6 μm, the specific surface area is 60 m 2 / g, and the chloride ion absorption value is 40 mol / kg; the hydration activator is magnesium oxalate powder, and the amount of water to be added is calculated according to the complete hydration reaction of magnesium oxide, and the stirring rate is 1080 r / min. The hydration rate of the high-activity magnesium oxide powder in step ① was detected to be 95.6%.

[0047] ② Take wollastonite fiber according to 80% of the mass of magnesium oxide, and add phosphoric acid with a concentration of 0.05 mol / L 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 the wollastonite fiber, and the acidification time is 5 min.

[0048] ③ Add the acidified wollastonite fiber to the reaction kettle, mix it with the first active flame-retardant micropowder obtained in step ①, and stir and react at 30 °C for 10 min, and the stirring rate is 300 r / min.

[0049] ④ Add water to form a reaction condition with a pressure of 2.0 MPa and a temperature of 210 °C in the reaction kettle, and stir for 30 min at a stirring rate of 500 r / min; then add a surfactant at 2% of the mass of wollastonite fiber and continue to stir for 50 min at a stirring rate of 200 r / min; the surfactant is selected as titanate coupling agent, and the water addition amount in step ④ is controlled at 1.2 times the mass of water required for the hydration reaction of wollastonite fiber and brucite fiber.

[0050] ⑤ Age and develop the material obtained in step ④ for 3 h at a temperature of 120 °C to obtain a composite enhanced active halogen-free flame retardant.

[0051] Perform SEM observation on the first active flame retardant micro-powder sample prepared in Example 2. The crystals of the prepared first active flame retardant micro-powder are square flakes, the crystal particle size is about 180 nm, the single-piece thickness is less than 90 nm, the particle crystallization is uniform, and the agglomeration is not obvious. The water content of the composite enhanced active halogen-free flame retardant product prepared in Example 2 is reduced to 0.24%, and there is no need for secondary drying; the hydration reaction enables the nano-particles of the first active flame retardant micro-powder to be uniformly dispersed or grown on the surface of wollastonite micron particles, with good dispersibility, no agglomeration, and good composite effect.

[0052] Pre-mix 55 parts by mass of the composite enhanced active halogen-free flame retardant prepared in Example 2, 41 parts by mass of polypropylene, and 4 parts by mass of other additives uniformly in a high-speed mixer, and then extrude on a twin-screw extruder, cool with water, and pelletize to obtain a composite enhanced flame-retardant polypropylene composite material. The mechanical properties and flame retardant properties of the obtained composite material are tested as follows: tensile strength 30.6 MPa, flexural strength 41.7 MPa, notched impact strength 8.9 kJ / m 2 ; oxygen index OI value 37.2, vertical burning performance test is V0 grade; it can be seen that the mechanical properties of the plastic specimen added with the halogen-free flame retardant prepared in Example 2 are significantly improved, and the flame retardant performance is excellent.

[0053] Example 3

[0054] A preparation method of a composite enhanced active halogen-free flame retardant, comprising the following steps:

[0055] ① Put the high-activity magnesium oxide powder into the reaction kettle, add a hydration activator at 3% of the mass of magnesium oxide, add water to form a high-pressure saturated steam reaction environment, and stir and hydrate for 4 h under the conditions of a pressure of 0.2 MPa and a temperature of 120 °C; obtain nano-scale flaky first active flame retardant micro-powder; the particle size of the high-activity magnesium oxide powder is 18 μm, and the specific surface area is 15 m 2 / g, the chloride ion absorption value is 30 mol / kg; the hydrated activator is magnesium oxalate powder, and the water addition amount is calculated according to 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 is detected to be 94.7%.

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

[0057] ③ Add the acidified wollastonite fibers to the reaction kettle, mix with the first active flame retardant powder obtained in step ①, and stir and react at 40 °C for 15 min, and the stirring rate is 400 r / min.

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

[0059] ⑤ Age and develop the material obtained in step ④ at a temperature of 140 °C for 4 h to obtain a composite enhanced active halogen-free flame retardant.

[0060] Perform SEM observation on the first active flame retardant powder sample prepared in Example 3. The crystals of the prepared first active flame retardant powder sample are square flakes, the crystal particle size is about 190 nm, the single sheet thickness is less than 90 nm, the particle crystallization is uniform, and the agglomeration is not obvious. The water content of the composite enhanced active halogen-free flame retardant product prepared in Example 3 is reduced to 0.19%, and there is no need to perform the drying process again; the hydration reaction makes the nanoparticles of the first active flame retardant powder evenly disperse or grow on the surface of the wollastonite micron particles, with good dispersibility, no agglomeration, and good composite effect.

[0061] Premix 52 parts by mass of the composite enhanced active halogen-free flame retardant prepared in Example 3, 44 parts by mass of polypropylene, and 4 parts by mass of other additives evenly in a high-speed mixer, and then extrude on a twin-screw extruder, cool with water, and pelletize to obtain a composite enhanced 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 / m 2; The oxygen index OI value is 38.8, and the vertical burning performance test is at V0 level; It can be seen that the mechanical properties of the plastic specimen added with the halogen-free flame retardant prepared in Example 3 are significantly improved, and the flame retardant performance is excellent.

[0062] Comparative Example 1

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

[0064] 1200 grams of natural mineral magnesium hydroxide powder with a particle size of 5 μm, 600 grams of homopolypropylene, 120 grams of ethylene-octene elastomer, and 3.84 grams of bis(2,4-di-tert-butylphenyl) pentaerythritol diphosphite are pre-mixed evenly in a high-speed mixer according to the proportion, and then extruded on a twin-screw extruder. The extrusion temperature is 220 °C, water-cooled, pelletized, and a flame-retardant polypropylene composite material is obtained. 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, flame retardancy FV-1.

[0065] Through the performance comparison of the plastic specimens prepared in Examples 1-3 and Comparative Example 1, it can be seen that the tensile strength of Examples 1-3 is increased by 78.88% - 87.28% compared with Comparative Example 1, and the flexural strength is increased by 55.60% - 67.54% compared with Comparative Example 1, and the mechanical properties are significantly improved; at the same time, the calcium magnesium hydrosilicate composite flame retardant particles in Examples 1-3 increase the oxygen index OI value of the composite material, and the flame retardant performance is excellent.

[0066] For any person skilled in the art, without departing from the scope of the technical solution of the present invention, many possible changes and modifications can be made to the technical solution of the present invention by using the above-disclosed technical content, or modified into equivalent embodiments with equivalent changes. Therefore, any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

Claims

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

2. The preparation method according to claim 1, characterized in that: Step ① The particle size of the highly active magnesium oxide powder is 6 to 18 μm, and the specific surface area is 15 to 60 m 2 / g, and the chloride ion absorption value is 30-40 mol / kg.

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 in step ① is calculated based on the hydration reaction of all magnesium oxide, and the stirring rate is 1000-1200r / min.

4. The preparation method according to claim 1, characterized in that: In step ②, the particle size of the wollastonite fiber is 5 to 20 μm, and the aspect ratio is 15 to 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 the wollastonite fiber, and the acidification time is 5 to 8 minutes.

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

7. The preparation method according to claim 1, characterized in that: 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 between the wollastonite fiber and the first active flame retardant micropowder.

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