Preparation method of mineral fiber reinforced halogen-free flame-retardant plastic master batch

Abstract

The invention discloses a preparation method of mineral fiber reinforced halogen-free flame-retardant plastic master batch, which is characterized in that high-activity magnesium oxide powder is used as a raw material to prepare first active flame-retardant micro powder, and a hydration process is 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, is in a square sheet shape, and is small in particle size and good in dispersity. The components of the second reinforced flame-retardant composite micro-powder obtained through the composite reaction of the wollastonite fibers and the brucite fibers comprise hydrated calcium magnesium silicate and linear polyphosphate, the excellent characteristics of micro-nano particles can be effectively utilized, the surface properties of the micro-powder are changed, and the flame-retardant effect is further enhanced. A co-rotating twin-screw extruder is adopted for granulation, the flame retardant property of the prepared plastic master batch is greatly improved, the mechanical property is remarkably improved, the mass ratio of the master batch with the particle size of 1-3 mm after grain cutting is larger than 90%, the dust content in the master batch is remarkably reduced, the production cost is saved, and the occupational environment is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and relates to a production technology of an environmentally friendly halogen-free flame-retardant composite material, in particular to a method for preparing a mineral fiber reinforced halogen-free flame-retardant plastic masterbatch. Background Art

[0002] Polymer materials are widely used, but their flame retardancy is poor and they are easy to burn when exposed to fire. For example, the oxygen index of polypropylene is about 17 to 18, which greatly limits its scope of use. Adding flame retardant masterbatch during the preparation of polymer materials can improve the flame retardant effect of the materials. Halogen flame retardants are usually used to prepare flame retardant masterbatch, but they have many disadvantages such as large smoke production and easy generation of corrosive and toxic gases. In addition, they are not very stable and have poor compatibility with polymers, which has a great impact on the mechanical properties of the added materials.

[0003] Plastic masterbatch (also known as masterbatch) is a plastic processing aid developed in the 1980s. In the process of plastic processing and molding, for the convenience of operation, the required various additives, fillers and a small amount of carrier resin are first mixed and kneaded, and then the granular material is obtained through the process of metering, mixing, melting, extrusion, pelletizing and other processing by extruders and other equipment. Masterbatch is a granular solid with a particle size not exceeding 3mm. Particles with a particle size of 0.1-1μm are usually called ultrafine powders, 1-10μm are called fine powders, and 0.1-1.0mm are called powders composed of microparticles. The smaller the particle size, the easier it is for the particles to adsorb and agglomerate with each other. This agglomerated powder is not easy to be opened when mixed with other solid particles, and it is also difficult to be dispersed in the plastic melt. It is even more difficult to achieve uniform mixing when two powders with large particle sizes are mixed. The existing method for making masterbatch is not perfect enough, the dispersion of additives in the masterbatch is uneven, and the obtained masterbatch has a large proportion of fillers, poor mechanical properties, and poor quality stability. As a result, during production, transportation, and use, the masterbatch particles are worn and broken due to insufficient strength to produce a large amount of dust. For example, the content of dust less than 1.0mm in the masterbatch obtained by the die surface hot cutting process is about 20%, which not only pollutes the environment, but also wastes resources and increases production costs. Summary of the invention

[0004] In order to overcome the defects of the above-mentioned prior art, the present invention uses high-activity magnesium oxide powder as a raw material, performs surface modification during hydration reaction, and obtains a first active flame-retardant micropowder; wollastonite fiber and brucite fiber are polymerized by surface acidification and mechanical kneading to form a second enhanced flame-retardant composite micropowder; the first and second micropowders after activation treatment have excellent compatibility and dispersibility with polyolefin resins, effectively reducing the amount of flame retardant required for preparing composite materials, improving the flame retardant properties of the materials, significantly improving the mechanical properties of the masterbatch, and greatly improving the mechanical strength; the mass proportion of the particle size of 1 to 3 mm in the masterbatch after pelletizing is greater than 90%, and the mass proportion of the powder with a particle size of less than 0.1 mm does not exceed 0.5%, which significantly reduces the dust content of the masterbatch, saves production costs, and improves the working environment.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides a method for preparing a mineral fiber reinforced halogen-free flame retardant plastic masterbatch, comprising the following steps:

[0006] ① Preparation of the first active flame-retardant micropowder: using high-activity magnesium oxide powder as raw material, adding 2% to 3% of the mass of magnesium oxide as a hydration activator and 3% to 4% of the mass of magnesium oxide as a surface modifier, adding water to form a high-pressure steam reaction environment, stirring the hydration reaction at a pressure of 0.1 to 0.2 MPa and a temperature of 105°C to 120°C for 3 to 4 hours; obtaining a blade-shaped nanoscale first active flame-retardant micropowder.

[0007] Based on mechanical activation technology, crystal form regulation is achieved, and saturated vapor pressure conditions are formed to shorten the reaction time of the hydration process and reduce 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, fully developed grains, and the magnesium hydroxide flame retardant particles finally obtained are square flakes, small in size, and good in dispersibility. The amount of water required is calculated according to the complete hydration reaction of magnesium oxide, so that the generated flame retardant product does not need to be dried again; and surface modification is carried out at the same time as the hydration reaction to overcome the agglomeration of magnesium hydroxide particles, thereby preparing a blade-shaped nano-scale first active flame retardant micropowder with uniform crystal form.

[0008] Furthermore, in 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; by increasing the activity of magnesium oxide, the activation energy of the hydration reaction is reduced, the energy of the reaction molecules is increased, and the reaction speed is accelerated, which is beneficial to the crystal form control.

[0009] Furthermore, the hydration activator in step ① is magnesium oxalate powder, the surface modifier in step ① is a silane coupling agent, the amount of water required for step ① is calculated according to the 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 degree of influence on the hydration reaction of magnesium oxide. After magnesium oxalate is dissolved in water, it dissociates into CH 3 COO - , CH 3 COO - Compared with other anions, it has stronger complexing ability, promotes hydration reaction, and plays a significant role in promoting the hydration process of magnesium oxide; adding a surface modifier makes it adsorb on the surface of magnesium hydroxide microcrystals to form a protective film, reduce surface energy, effectively prevent magnesium hydroxide from agglomerating, and reduce the average particle size of magnesium hydroxide. Control the amount of water added to reduce the presence of excess water while ensuring the water required for the hydration reaction, so that the generated magnesium hydroxide active flame retardant can meet the process requirements without re-drying; stirring has a mechanical activation function, which is conducive to the hydration activation reaction and can realize the crystal form regulation of the product; finally, the hydration rate of the high-pressure steam hydration reaction of the first active flame retardant micropowder is greater than 90%, and the water content of the obtained product is reduced to below 1.0%.

[0010] ② Preparation of the second enhanced flame-retardant composite micropowder: adding 0.1 mol / L phosphoric acid at a concentration of 0.5% to 1.0% of the mass of the wollastonite fiber, stirring the reaction at 30°C to 40°C for 10 to 15 minutes, and the stirring rate is 300 to 400 r / min; then adding brucite fiber at a mass of 8% to 10% of the mass of the wollastonite fiber, and then adding a surfactant at a mass of 2% to 3% of the mass of the wollastonite fiber, adding water to form a pressure of 2.0 to 3.0 MPa and a temperature of 210°C to 235°C, and stirring for 30 to 40 minutes, and the stirring rate is 500 to 600 r / min; the components of the obtained second enhanced flame-retardant composite micropowder include hydrated calcium magnesium silicate and linear polyphosphate.

[0011] Furthermore, the particle size of the wollastonite fiber in step ② is 4-6 μm, and the aspect ratio is 15-20:1; the particle size of the brucite fiber is 1-3 μm, and the aspect ratio is 15-20:1. The surfactant in step ② is a silane coupling agent or a titanate coupling agent; the amount of water added in step ② is controlled to be 1.2-1.5 times the mass of water required for the hydration reaction of the wollastonite fiber and the brucite fiber. Wollastonite fiber CaSiO 3 It is weakly alkaline, and phosphoric acid is used to acidify the surface to form ionic bonds; the ionic bonds play the role of connecting nodes, promoting the monomer phosphate molecule Mg(H 2 PO 4 ) 2Polymerization occurs to generate linear polyphosphates, thereby forming stable reinforced flame retardant composite particles.

[0012] Wollastonite fiber has high heat resistance, a melting point of 1540°C, no ignition loss, and good flame retardant effect; Wollastonite fiber and brucite fiber undergo the following chemical reaction to generate hydrated calcium magnesium silicate composite flame retardant particles, which further enhance the flame retardant effect; at the same time, this particle size level can produce the nano effect of inorganic materials, and through heat storage and heat conduction, the material does not reach the thermal decomposition temperature and obtains a flame retardant effect.

[0013] CaSiO 3 +0.17H 2 O+Mg(OH) 2 =CaMgSiO 4 1.17H 2 O

[0014] The hydration reaction makes the magnesium hydroxide nanoparticles evenly dispersed or grown on the surface of the wollastonite micron particles, which can effectively utilize the excellent characteristics of the nanoparticles and change the surface properties of the micron powder; the sharp edges and corners on the surface of the mineral fiber particles are passivated, and the smooth cleavage surface becomes rough due to the presence 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 smooth crystal cleavage surface, and can significantly improve the composite effect, thereby obtaining a high-performance composite material.

[0015] ③ Adopt intermeshing co-rotating twin-screw extruder for granulation: the twin-screw extruder can be divided into conveying section, melting and plasticizing section, exhaust section, mixing section (including lateral feeding section), vacuum exhaust section, homogenizing section and other parts according to the material running path; the screw speed is 400r / min, the feeding frequency is 4.5Hz, the temperatures of extruder zones 1 to 9 are set to 180℃, 190℃, 195℃, 200℃, 210℃, 210℃, 220℃, 215℃ and 210℃, and the head temperature is 195℃.

[0016] The twin-screw extruder has good shearing, plasticizing, blending, exhaust and devolatilization functions, and the screws and screw functional areas are arranged as follows: the first and second sections of the screw barrel are material conveying sections, which are used to convey the mixed material; the third and fourth sections of the screw barrel are melt plasticizing sections, which are used to melt and plasticize the various components of the material; the fifth section is set as an exhaust section for water vapor discharge; the sixth to eighth sections of the screw barrel are mixing sections, among which the sixth section of the screw barrel is provided with a side feeding port (side feeding section) for side feeding of powders, glass fiber, additives, etc.; the seventh and eighth sections are provided with meshing blocks for dispersion, distribution and mixing of the various components; the ninth section is a vacuum exhaust section, which plays a devolatilization role; the tenth section is a homogenizing section.

[0017] In the preparation process of fiber-reinforced granules, if both the fiber and the solid polymer are added from the first feed port, the fiber will be excessively broken during the solid conveying process, and the inner surface of the screw and the barrel will also be severely worn due to direct contact with the fiber. The subsequent feeding method is adopted. Because the fiber is added to the molten polymer, the melt and the fiber are mixed and the fiber is wrapped up, which plays a lubricating and protective role, reduces the excessive breakage of the fiber and the wear of the screw and the barrel, and is conducive to the dispersion and distribution of the fiber in the melt. Therefore, the first (main) feed port is set in the first section (material conveying section) of the screw functional area, and the first active flame retardant particles and polypropylene and other additives are added from the main feed port. A side feed port is set in the fourth section (mixing section) of the screw functional area, and the second reinforced flame retardant composite micropowder is added from the side feed port using a side feeding device.

[0018] ④ Feeding: The first active flame retardant micropowder, polypropylene and other additives are added from the main feeding port, and the second enhanced flame retardant composite micropowder is added from the side feeding port using a side feeding device. The raw material components include: 40-45 parts of polypropylene, 30-35 parts of the first active flame retardant micropowder, 20-25 parts of the second enhanced flame retardant composite micropowder, and 4-6 parts of other additives.

[0019] Polypropylene is a general-purpose thermoplastic plastic with excellent comprehensive performance. It has the characteristics of easy processing, low density and low production cost, so polypropylene is widely used in household appliances, daily necessities, packaging materials, automotive industry and other industries. However, polypropylene also has some disadvantages, such as poor creep resistance, low melting point, poor dimensional stability, low heat deformation temperature, low-temperature brittleness, etc. These technical defects restrict its application as an engineering stress-bearing material. This technical solution improves the flame retardancy and mechanical strength of polypropylene by modifying it, so as to further broaden its application range.

[0020] ⑤ Pelletizing: The die surface hot cutting and air cooling process is adopted, and the particle size range of plastic masterbatch is 1 to 3 mm.

[0021] The masterbatch is composed of granular solids with a particle size of no more than 3mm. If the powder content of less than 1mm in the masterbatch is too large, it will affect its use and fail to achieve the expected technical effect. Therefore, it is required that the mass proportion of particles with a particle size of 1 to 3mm in the masterbatch after pelletizing is greater than 90%, and the mass proportion of powder with a particle size of less than 0.1mm is controlled to be no more than 0.5%.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] ① Based on mechanical activation technology, crystal form regulation is achieved, and saturated vapor pressure conditions are formed to shorten the reaction time of the hydration process and reduce 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, fully developed grains, and the magnesium hydroxide particles finally obtained are square flakes, small in size, and good in dispersibility. The amount of water required is calculated according to the complete hydration reaction of magnesium oxide, so that the generated flame retardant product does not require a secondary drying process; and surface modification is carried out at the same time as the hydration reaction to overcome the agglomeration of magnesium hydroxide particles.

[0024] ② The second reinforced flame retardant composite micropowder obtained by the composite reaction of wollastonite fiber and brucite fiber includes hydrated calcium magnesium silicate and linear polyphosphate, which can not only effectively utilize the excellent characteristics of nanoparticles, but also change the surface properties of micron powders, further enhance the flame retardant effect, and improve the mechanical strength, so as to obtain high-performance composite materials.

[0025] ③ The mechanical properties of the obtained plastic masterbatch are significantly improved. The mass proportion of particles with a particle size of 1 to 3 mm in the masterbatch after pelletizing is greater than 90%, and the mass proportion of powder with a particle size below 0.1 mm does not exceed 0.5%, which significantly reduces the dust content of the masterbatch, saves production costs, and improves the working environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a SEM image of the first active flame retardant micropowder sample prepared in Example 1;

[0027] Figure 2 This is a SEM image of the first active flame retardant micropowder sample prepared in Example 2;

[0028] Figure 3 This is the SEM image of the first active flame retardant micropowder sample prepared in Example 3. DETAILED DESCRIPTION

[0029] The present invention is further described below in conjunction with specific examples, but the present invention is not limited in any way. To avoid redundant description, the raw materials in the following examples are all commercially available products unless otherwise specified, and the methods used are all conventional methods unless otherwise specified.

[0030] The processing equipment used was a co-rotating parallel twin-screw extruder produced by Nanjing Ouli Extrusion Machinery Co., Ltd., model THE-52D / 600-90-40; the WDW-100 electronic universal testing machine of Jinan Star Testing Technology Co., Ltd. was used to test the bending and tensile properties of the test samples; the bending properties were tested in accordance with GB / T9341-2008, with a sample size of 80mm×10mm×4mm, a span of 64mm, and a loading rate of 2mm / min; the tensile properties were tested in accordance with GB / T1040-2018, using type I specimens, a gauge length of 50mm, and a loading rate of 2mm / min. The impact properties were measured using the HIT-2494 pendulum impact tester of Chengde Jinjian Testing Instrument Co., Ltd. in accordance with GB / T1843-2008, using a B-type 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. According to GB / T 2406.2-2009, the OI was measured using the PX-01-005 oxygen index instrument of Suzhou Phoenix Quality Inspection Instrument Co., Ltd. The specimen size was 80mm×10mm×4mm, with 15 parallel samples in each group. The vertical method test standard for plastic combustion performance is IEC60695 and UL94, where the flame retardant performance is ranked from best to worst as V0, V1, V2 and NV.

[0031] The hydration rate of magnesium oxide is calculated according to the following formula: α = 40 (m 1 -m 2 ) / 18m 2 ×100%; where α: hydration rate of magnesium oxide, %; m 1 : The mass of the hydrated product without calcination, g; m 2 : The mass of the hydrated product after calcination, g; 40 / 18: MgO and H 2 O molar mass ratio.

[0032] A method for preparing a mineral fiber reinforced halogen-free flame-retardant plastic masterbatch comprises the following steps:

[0033] ① Preparation of the first active flame retardant micropowder: Using high-activity magnesium oxide powder as raw material, add 2% to 3% of magnesium oxide mass hydration activator and 3% to 4% of magnesium oxide mass surface modifier, add water to form a high-pressure saturated steam reaction environment, stir the hydration reaction at a pressure of 0.1 to 0.2 MPa and a temperature of 105°C to 120°C for 3 to 4 hours; obtain a blade-shaped nanoscale first active flame retardant micropowder. The particle size of the high-activity magnesium oxide powder is 8μm, and the specific surface area is 56m 2 / g, and the chloride ion absorption value is 34mol / kg.

[0034] ② Preparation of the second enhanced flame retardant composite powder: adding 0.1 mol / L phosphoric acid at a concentration of 0.5% to 1.0% of the mass of the wollastonite fiber, stirring the reaction at 30°C to 40°C for 10 to 15 minutes, and the stirring rate is 300 to 400 r / min; then adding brucite fiber at 8% to 10% of the mass of the wollastonite fiber, and then adding a surfactant at 2% to 3% of the mass of the wollastonite fiber, adding water to form a pressure of 2.0 to 3.0 MPa, a temperature of 210°C to 235°C, and stirring for 30 to 40 minutes, and the stirring rate is 500 to 600 r / min.

[0035] ③ Use an intermeshing co-rotating twin-screw extruder for granulation: the screw speed is 400r / min, the feeding frequency is 4.5Hz, the temperatures of zones 1 to 9 of the extruder are set to 180℃, 190℃, 195℃, 200℃, 210℃, 210℃, 220℃, 215℃ and 210℃, and the head temperature is 195℃.

[0036] ④ Feeding: The first active flame retardant micropowder, polypropylene and other additives are added from the main feeding port, and the second enhanced flame retardant composite micropowder is added from the side feeding port using a side feeding device. The raw material components include: 40-45 parts of polypropylene, 30-35 parts of the first active flame retardant micropowder, 20-25 parts of the second enhanced flame retardant composite micropowder, and 4-6 parts of other additives.

[0037] ⑤ Pelletizing: The die surface hot cutting and air cooling process is adopted, and the particle size range of plastic masterbatch is 1 to 3 mm.

[0038] The plastic masterbatch prepared in the embodiment and the comparative example was placed in a vacuum oven at 80° C. and dried for 2 to 4 hours. The dried masterbatch was injection molded by an injection molding machine to prepare test specimens. The prepared specimens were placed for 48 hours and then tested for mechanical properties and flame retardancy.

[0039] The matters not described in the following embodiments are the same as the description of the above specific implementation methods.

[0040] Example 1

[0041] A method for preparing a mineral fiber reinforced halogen-free flame-retardant plastic masterbatch comprises the following steps:

[0042] ① Preparation of the first active flame retardant micropowder: using high-activity magnesium oxide powder as raw material, adding 2.5% of magnesium oxide mass as hydration activator magnesium oxalate powder and 3.5% of magnesium oxide mass as silane coupling agent, adding water to form a high-pressure saturated steam reaction environment, stirring the hydration reaction for 3.5 hours at a pressure of 0.15 MPa and a temperature of 110°C; obtaining a blade-shaped nanoscale first active flame retardant micropowder. The amount of water required for step ① is calculated according to the hydration reaction of all magnesium oxide, and the stirring rate is 1100r / min. Finally, the hydration rate of the high-pressure steam hydration reaction of the first active flame retardant micropowder is detected to be 94%, and the moisture content of the first active flame retardant micropowder product obtained is reduced to 0.6%.

[0043] ②Prepare the second enhanced flame-retardant composite micropowder: add 0.1mol / L phosphoric acid at 0.7% of the mass of wollastonite fiber, stir and react for 12 minutes at 35°C, and the stirring rate is 350r / min; then add brucite fiber at 9% of the mass of wollastonite fiber, and then add silane coupling agent at 2.5% of the mass of wollastonite fiber, add water to form a pressure of 2.5MPa and a temperature of 225°C, and stir for 35 minutes at a stirring rate of 550r / min. The particle size of the above-mentioned wollastonite fiber is 5um, and the aspect ratio is 18:1; the particle size of the brucite fiber is 2μm, and the aspect ratio is 18:1. The amount of water added in step ② is controlled by 1.4 times the mass of water required for the hydration reaction of wollastonite fiber and brucite fiber.

[0044] ③Use intermeshing co-rotating twin-screw extruder for granulation;

[0045] ④ Feeding: The raw material components include, by mass, 42 parts of polypropylene, 32 parts of the first active flame retardant micropowder, 21 parts of the second enhanced flame retardant composite micropowder, and 5 parts of other additives, wherein the other additives are antioxidants and lubricants.

[0046] ⑤ Pelletizing: The die surface hot cutting and air cooling process is adopted, and the particle size range of plastic masterbatch is 1 to 3 mm.

[0047] The first active flame retardant powder sample prepared in Example 1 was observed by SEM. Figure 1 As shown by Figure 1 It can be seen that the crystals of the first active flame retardant micropowder are blade-shaped, with a crystal length of 3 to 5 μm and a width of 1.0 to 1.5 μm; the thickness of a single piece is less than 100 nm, and the thickness of a multi-piece aggregate is within 200 nm. The particles are uniformly crystallized and not agglomerated.

[0048] The oxygen index OI value of the plastic masterbatch prepared in Example 1 is 39.4 (the oxygen index of polypropylene is about 17-18), and the vertical combustion performance test is V0 level, and the flame retardant performance is greatly improved.

[0049] The plastic masterbatch sample prepared in Example 1 has a tensile strength of 34 MPa, a flexural strength of 43 MPa, and a notched impact strength of 9 kJ / m 2 The mechanical properties of the plastic masterbatch prepared in Example 1 are significantly improved. The mass proportion of particles with a particle size of 1 to 3 mm in the masterbatch after pelletizing is 94%, and the mass proportion of powder with a particle size of less than 0.1 mm is 0.38%, which significantly reduces the dust content of the masterbatch, saves production costs, and improves the working environment.

[0050] Example 2

[0051] A method for preparing a mineral fiber reinforced halogen-free flame-retardant plastic masterbatch comprises the following steps:

[0052] ① Preparation of the first active flame retardant micropowder: using high-activity magnesium oxide powder as raw material, adding 2% magnesium oxide mass hydration activator magnesium oxalate powder and 3% magnesium oxide mass silane coupling agent, adding water to form a high-pressure saturated steam reaction environment, stirring the hydration reaction for 3 hours at a pressure of 0.1 MPa and a temperature of 105°C; obtaining a blade-shaped nanoscale first active flame retardant micropowder. Calculate the amount of water required for step ① according to the complete hydration reaction of magnesium oxide, and the stirring rate is 1000r / min. Finally, the hydration rate of the high-pressure steam hydration reaction of the first active flame retardant micropowder reaches 91%, and the moisture content of the product is reduced to 0.4%.

[0053] ②Prepare the second enhanced flame-retardant composite micropowder: add 0.1 mol / L phosphoric acid at 0.5% of the mass of wollastonite fiber, stir and react for 10 minutes at 30°C, and the stirring rate is 300r / min; then add brucite fiber at 8% of the mass of wollastonite fiber, and then add titanate coupling agent at 2% of the mass of wollastonite fiber, add water to form a pressure of 2.0MPa and a temperature of 210°C reaction conditions, and stir for 30 minutes at a stirring rate of 500r / min. The particle size of the wollastonite fiber is 6μm, and the aspect ratio is 15:1; the particle size of the brucite fiber is 3μm, and the aspect ratio is 15:1. The amount of water added in step ② is controlled by 1.2 times the mass of water required for the hydration reaction of wollastonite fiber and brucite fiber.

[0054] ③Use intermeshing co-rotating twin-screw extruder for granulation;

[0055] ④ Feeding: The first active flame retardant micropowder and polypropylene and other additives are added from the main feeding port, and the second enhanced flame retardant composite micropowder is added from the side feeding port using a side feeding device; the raw material components include, by mass: 41 parts of polypropylene, 30 parts of the first active flame retardant micropowder, 25 parts of the second enhanced flame retardant composite micropowder, and 4 parts of other additives. The other additives in step ④ include antioxidants, lubricants, and light stabilizers.

[0056] ⑤ Pelletizing: The die surface hot cutting and air cooling process is adopted, and the particle size range of plastic masterbatch is 1 to 3 mm.

[0057] The first active flame retardant micropowder sample prepared in Example 2 was observed by SEM. Figure 2 As shown by Figure 2 It can be seen that the crystals of the first active flame retardant micropowder are flaky and cubic and nearly equigranular, with good crystallization and a crystal size of about 200 nm.

[0058] The oxygen index OI value of the plastic masterbatch prepared in Example 2 is 40.2 (the oxygen index of polypropylene is about 17-18), and the vertical combustion performance test is V0 level, and the flame retardant performance is greatly improved.

[0059] The plastic masterbatch sample prepared in Example 2 has a tensile strength of 33 MPa, a flexural strength of 42 MPa, and a notched impact strength of 8 kJ / m 2 The mechanical properties of the plastic masterbatch obtained in Example 1 are significantly improved. The mass proportion of particles with a particle size of 1 to 3 mm in the masterbatch after pelletizing reaches 92%, and the mass proportion of powder with a particle size of less than 0.1 mm is 0.45%.

[0060] Example 3

[0061] A method for preparing a mineral fiber reinforced halogen-free flame-retardant plastic masterbatch comprises the following steps:

[0062] ① Preparation of the first active flame retardant micropowder: using high-activity magnesium oxide powder as raw material, adding 3% magnesium oxide mass hydration activator magnesium oxalate powder and 4% magnesium oxide mass silane coupling agent, adding water to form a high-pressure saturated steam reaction environment, stirring the hydration reaction for 4 hours at a pressure of 0.2MPa and a temperature of 120°C; obtaining a blade-shaped nanoscale first active flame retardant micropowder. Calculate the amount of water required for step ① according to the hydration reaction of all magnesium oxide, and the stirring rate is 1200r / min. Finally, the hydration rate of the high-pressure steam hydration reaction of the first active flame retardant micropowder reaches 95%, and the moisture content of the product is reduced to 0.8%.

[0063] ② Preparation of the second reinforced flame retardant composite powder: add 0.1 mol / L phosphoric acid at a concentration of 1.0% of the mass of wollastonite fiber, stir and react at 40°C for 15 minutes, and the stirring rate is 400r / min; then add brucite fiber at a mass of 10% of the mass of wollastonite fiber, and then add silane coupling agent at a mass of 3% of the mass of wollastonite fiber, add water to form a pressure of 3.0MPa, a temperature of 235°C, and stir for 40 minutes at a stirring rate of 600r / min.

[0064] In step ②, the particle size of the wollastonite fiber is 4 μm, and the aspect ratio is 20:1; the particle size of the brucite fiber is 1 μm, and the aspect ratio is 20:1. In step ②, the amount of water added is controlled to be 1.5 times the mass of water required for the hydration reaction of the wollastonite fiber and the brucite fiber.

[0065] ③Use intermeshing co-rotating twin-screw extruder for granulation;

[0066] ④ Feeding: The first active flame retardant micropowder and polypropylene and other additives are added from the main feeding port, and the second enhanced flame retardant composite micropowder is added from the side feeding port using a side feeding device; the raw material components include: 44 parts of polypropylene, 31 parts of the first active flame retardant micropowder, 21 parts of the second enhanced flame retardant composite micropowder, and 4 parts of other additives by mass. The other additives include antioxidants, lubricants, light stabilizers, and plasticizers.

[0067] ⑤ Pelletizing: The die surface hot cutting and air cooling process is adopted, and the particle size range of plastic masterbatch is 1 to 3 mm.

[0068] The first active flame retardant powder sample prepared in Example 3 was observed by SEM. Figure 3 As shown by Figure 3 It can be seen that the crystals of the first active flame retardant micropowder are blade-shaped, the crystals are aggregated in flakes, the length of a single flake is less than 1 μm, the width is about 100 nm, the particles are uniformly crystallized, and are not agglomerated.

[0069] The oxygen index OI value of the plastic masterbatch prepared in Example 3 is 41.8 (the oxygen index of polypropylene is about 17-18), and the vertical combustion performance test is V0 level, and the flame retardant performance is greatly improved.

[0070] The plastic masterbatch sample prepared in Example 3 has a tensile strength of 35 MPa, a flexural strength of 45 MPa, and a notched impact strength of 10 kJ / m 2 The mechanical properties of the plastic masterbatch obtained in Example 3 are significantly improved. The mass proportion of particles with a particle size of 1 to 3 mm in the masterbatch after pelletizing reaches 95%, and the mass proportion of powder with a particle size of less than 0.1 mm is 0.32%.

[0071] Comparative Example 1

[0072] Filling polypropylene with calcium carbonate powder to prepare plastic masterbatch includes the following steps:

[0073] Granulation was carried out using an intermeshing co-rotating twin-screw extruder, and the parameters of the twin-screw extruder were the same as those in Example 2. The raw material components included, by weight: 41 parts of polypropylene, 55 parts of 1250 mesh calcium carbonate, 1.5 parts of antioxidant, 1 part of lubricant, and 1.5 parts of surface modifier; all raw materials were added from the main feed port.

[0074] The plastic masterbatch prepared in Comparative Example 1 has a tensile strength of 21.7 MPa, a flexural strength of 37.2 MPa, and a notched impact strength of 1.6 kJ / m 2 The mass proportion of the masterbatch with a particle size of 1 to 3 mm after pelletizing is 79%, and the mass proportion of the powder with a particle size below 0.1 mm is 18.5%.

[0075] By comparing the performance of the plastic masterbatch prepared in Examples 1-3 and Comparative Example 1, it can be seen that the tensile strength of the embodiments is increased by 52.07% to 61.29% over that of the comparative example, the flexural strength is increased by 12.90% to 20.97% over that of the comparative example, and the notched impact strength is increased by 4 to 5.25 times over that of the comparative example; the mass proportion of particles with a particle size of 1 to 3 mm in the masterbatch after pelletizing is increased from about 80% to more than 90%, and the powder content is reduced from about 20% to about 0.4%, which significantly improves the product quality and yield rate.

[0076] For any technician familiar with the art, without departing from the scope of the technical solution of the present invention, the technical content disclosed above can be used to make many possible changes and modifications to the technical solution of the present invention, or modified into equivalent embodiments with equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention should still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preparing a mineral fiber reinforced halogen-free flame-retardant plastic masterbatch, characterized in that: The preparation method comprises the following steps: ① Preparation of the first active flame retardant micropowder: using high-activity magnesium oxide powder as raw material, adding 2% to 3% of the mass of magnesium oxide as a hydration activator and 3% to 4% of the mass of magnesium oxide as a surface modifier, adding water to form a high-pressure saturated steam reaction environment, stirring the hydration reaction at a pressure of 0.1 to 0.2 MPa and a temperature of 105° C. to 120° C. for 3 to 4 hours; obtaining a blade-shaped nanoscale first active flame retardant micropowder; ② Preparation of the second enhanced flame retardant composite powder: adding 0.1 mol / L phosphoric acid at a concentration of 0.5% to 1.0% of the mass of wollastonite fiber, stirring and reacting at 30°C to 40°C for 10 to 15 minutes, and the stirring rate is 300 to 400 r / min; then adding brucite fiber at a mass of 8% to 10% of the mass of wollastonite fiber, and then adding a surfactant at a mass of 2% to 3% of the mass of wollastonite fiber, adding water to form a pressure of 2.0 to 3.0 MPa and a temperature of 210°C to 235°C, and stirring for 30 to 40 minutes, and the stirring rate is 500 to 600 r / min; ③ Adopt intermeshing co-rotating twin-screw extruder for granulation: screw speed is 400r / min, the temperature of zones 1 to 9 of the extruder is set to 180℃, 190℃, 195℃, 200℃, 210℃, 210℃, 220℃, 215℃ and 210℃, and the die temperature is 195℃; ④ Feeding: The first active flame retardant micropowder, polypropylene and other additives are added from the main feeding port, and the second enhanced flame retardant composite micropowder is added from the side feeding port using a side feeding device; The raw material components include, by mass: 40-45 parts of polypropylene, 30-35 parts of the first active flame retardant micropowder, 20-25 parts of the second enhanced flame retardant composite micropowder, and 4-6 parts of other additives; ⑤ Pelletizing: The die surface hot cutting and air cooling process is adopted, and the particle size range of plastic masterbatch is 1 to 3 mm.

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, and the surface modifier in step ① is a silane coupling agent; the amount of water required for step ① is calculated according to 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: The particle size of the wollastonite fiber in step ② is 4 to 6 μm, and the aspect ratio is 15 to 20:1; the particle size of the brucite fiber in step ② is 1 to 3 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 surfactant is a silane coupling agent or a titanate coupling agent.

6. The preparation method according to claim 1, characterized in that: The amount of water added in step ② is controlled to be 1.2 to 1.5 times the mass of water required for the hydration reaction of the wollastonite fiber and the brucite fiber.

7. The preparation method according to claim 1, characterized in that: The other additives in step ④ include one or more of antioxidants, lubricants, light stabilizers, and plasticizers.

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