Ultrafine brominated polystyrene high-concentration dust-free flame-retardant master batch for eliminating dust explosion risk and preparation method thereof

Abstract

The application discloses superfine brominated polystyrene high-concentration dust-free flame-retardant master batch for eliminating dust explosion risk and a preparation method thereof, and belongs to the field of high polymer flame-retardant material modification and processing. In view of the safety hidden danger of superfine brominated polystyrene powder with high molecular weight, fine particle size and easy dust explosion, 60-75 parts of brominated polystyrene with a median diameter of 3-4 microns, a maximum particle size of less than 25 microns and a molecular weight of 300,000-500,000 are used as a flame retardant, 15-35 parts of ethylene-vinyl acetate copolymer is used as a carrier, 0.5-3 parts of ethylene bis-stearamide, 0.5-2 parts of an oily titanate coupling agent and 2-8 parts of polyethylene wax are used as accessories, and then the master batch is prepared through segmented mixing and melt extrusion granulation. The technology realizes high loading and good dispersibility by coating superfine flame-retardant powder with a carrier resin, completely eliminates the dust explosion risk in downstream use, and solves the use safety and processing problems of traditional superfine flame-retardant powder.

Description

Technical Field

[0001] This invention relates to the field of polymer flame retardant materials, specifically to a high-concentration dust-free flame retardant masterbatch of ethylene-vinyl acetate copolymer with high molecular weight ultrafine brominated polystyrene as the core flame retardant component and its preparation method. Technical Background

[0002] High molecular weight brominated polystyrene plays an irreplaceable role in high-end thin-wall injection molding due to its excellent thermal stability and non-precipitation properties. To eliminate "crystal point" defects on the surface of the product, this material must be air-jet milled to an ultrafine powder state with a median diameter (D50) of 3-4 μm and a maximum particle size (D100) of less than 25 μm. However, the direct unpacking, metering, and feeding of such micron-sized ultrafine powders in conventional open workshops not only poses extremely high safety production (dust explosion) and environmental compliance barriers, but also greatly increases the equipment operation risks and application thresholds for downstream manufacturers.

[0003] To circumvent the application bottlenecks of directly using ultrafine powders, masterbatch granulation of ultrafine flame-retardant powders is a theoretical direction for exploration. However, when the particle size of high molecular weight brominated polystyrene is reduced to the micrometer level, its specific surface area increases dramatically. When attempting to prepare high-concentration masterbatches with a loading exceeding 60%, conventional carrier resins and ordinary dispersion systems face serious rheological challenges: ultrafine powders are prone to severe agglomeration in the extrusion melt, leading to a sharp increase in the system melt viscosity, local shear friction overheating, and consequently, a surge in equipment melt pressure or even die blockage, making continuous granulation impossible.

[0004] Furthermore, conventional premixed extrusion processes struggle to achieve monomer dispersion of ultrafine flame retardants under high filler conditions. This microscopic agglomeration defect not only leads to brittle extruded material and breakage, but also causes severe stress concentration during downstream injection molding, resulting in a precipitous deterioration of the tensile strength and impact toughness of the final material. Therefore, the industry urgently needs to develop a novel masterbatch formulation and supporting preparation process to completely eliminate the risks associated with micronized powder applications, break through the limits of granulation processing under extremely high loads, and maintain the material's excellent melt flowability and synergistic mechanical enhancement effects. Summary of the Invention

[0005] The purpose of this invention is to overcome the aforementioned problems of the prior art and provide a high-concentration, dust-free, flame-retardant masterbatch. This invention utilizes a carrier resin to encapsulate and granulate highly explosive micron-sized high-molecular-weight brominated polystyrene powder, completely eliminating the risk of dust dispersion and explosion during downstream use. Simultaneously, through a specific coupling and lubrication system, it achieves extremely high loading capacity and excellent dispersibility of the ultrafine powder in the masterbatch.

[0006] To achieve the above-mentioned objectives, the technical solution of the present invention is as follows: A high-concentration, dust-free, flame-retardant masterbatch for ultrafine brominated polystyrene that eliminates the risk of dust explosion comprises the following formulation components in parts by weight: 60-75 parts of ultrafine brominated polystyrene with a particle size (D50) of 3-4 μm and a maximum particle size (D100) of less than 25 μm; 15-35 parts of ethylene-vinyl acetate copolymer (EVA); 0.5-3 parts of ethylene bis-stearamide (EBS); 0.5-2 parts of oily titanate coupling agent; and 2-8 parts of polyethylene wax.

[0007] Furthermore, the molecular weight of ultrafine brominated polystyrene with a particle size (D50) of 3~4 μm and a maximum particle size (D100) of less than 25 μm is 300,000~500,000.

[0008] Furthermore, the VA content of the ethylene-vinyl acetate copolymer is 18%~28%, and the melt mass flow rate is 2~8 g / 10 min.

[0009] Furthermore, the oily titanate coupling agent used is LD-144 produced by Yangzhou Lida Resin Co., Ltd.

[0010] Furthermore, the mass ratio of polyethylene wax to ethylene bis-stearamide is (3~4):1.

[0011] Furthermore, the melt mass flow rate (MFR) of the flame retardant masterbatch at 190°C and 2.16 kg load is 15.0~19.0 g / 10min.

[0012] A method for preparing ultrafine brominated polystyrene high-concentration dust-free flame-retardant masterbatch that eliminates the risk of dust explosion includes the following steps: The ethylene-vinyl acetate copolymer was heated and stirred, and then mixed with ultrafine brominated polystyrene in one step. Then, the oily titanate coupling agent LD-144 was added for a second step of mixing. Finally, ethylene bis-stearamide and polyethylene wax were added for a third step of mixing to obtain the flame retardant masterbatch precursor. The flame retardant masterbatch precursor is melt-extruded and granulated to obtain the flame retardant masterbatch.

[0013] Furthermore, the flame retardant masterbatch precursor is melted using a stepped zone temperature-controlled melt extrusion process, with the following conditions: zone 1 temperature 120~140℃, zone 2 temperature 130~160℃, zone 3 temperature 140~180℃, zone 4 temperature 130~170℃, barrel residence time 1~3 minutes, and melt pressure 5~10 MPa.

[0014] Furthermore, the heating temperature of the ethylene-vinyl acetate copolymer is 90~100 ℃, the stirring time is 10~30 minutes, and the stirring rate is 30~40 Hz; The mixing time is 10-15 minutes, and the stirring rate during mixing is 10-15 Hz; During the secondary mixing, the oily titanate coupling agent LD-144 is injected via atomization, the mixing time is 5-10 minutes, and the stirring rate during mixing is 10-15 Hz. The three mixing times are 2 to 5 minutes, and the stirring rate during mixing is 30 to 40 Hz.

[0015] This invention uses an ethylene-vinyl acetate copolymer as a matrix, with a high-flowability carrier resin coating the dust as a carrier for other components, thus imparting high mechanical properties to the ultrafine brominated polystyrene high-concentration dust-free flame-retardant masterbatch as raw material. Specifically, oily titanate LD-144 is used for surface coating modification of the ultrafine powder to prevent agglomeration of 3-4 μm powder. Polyethylene wax serves as an external lubricant and dispersant, reducing the melt viscosity of the high-filler system, achieving an extremely high loading of high molecular weight ultrafine brominated polystyrene powder in the masterbatch, and improving the excellent dispersibility and flame retardancy of the ultrafine brominated polystyrene high-concentration dust-free flame-retardant masterbatch. Furthermore, ethylene bis-stearamide effectively promotes the dispersion of each component in the melt extrusion process, ensuring the stable performance of the ultrafine brominated polystyrene high-concentration dust-free flame-retardant masterbatch. Detailed Implementation

[0016] Example 1: An ultrafine brominated polystyrene high-concentration dust-free flame retardant masterbatch that eliminates the risk of dust explosion, its composition by mass parts is as follows: Ethylene-vinyl acetate copolymer 25.9 copies Ethylene bis-stearamide 1.44 copies Oily titanate LD-144 0.96 copies Polyethylene wax 4.5 copies

[0017] The preparation method of the ultrafine brominated polystyrene high-concentration dust-free flame-retardant masterbatch that eliminates the risk of dust explosion is as follows: Weigh each component according to the above formula for ultrafine brominated polystyrene high-concentration dust-free flame retardant masterbatch; The ethylene-vinyl acetate copolymer was placed in a high-speed mixer, set to 100 ℃, and stirred at 30 Hz for 30 minutes. After the time was reached, the stirring was turned off, and the internal temperature was 95 ℃. The surface of the ethylene-vinyl acetate copolymer became sticky. Ultrafine brominated polystyrene with a molecular weight of 350,000 and a particle size of 3 μm was added, and the mixture was stirred at 10 Hz for 10 minutes. After stirring, the internal temperature rose to 97 ℃, and the stirring was turned on at 10 Hz. At this time, the oily titanate coupling agent LD-144 was sprayed in through atomization. After the coupling agent was added, the mixture was stirred at 10 Hz for 8 minutes. After stirring, the internal temperature rose to 99 ℃, and ethylene bis-stearamide and polyethylene wax were added. The mixture was stirred at 30 Hz for 3 minutes. After stirring, the high-concentration dust-free flame-retardant masterbatch precursor of ultrafine brominated polystyrene was obtained. The masterbatch precursor prepared above was placed in a twin-screw extruder and melt-extruded and granulated. The process conditions were: zone 1 temperature 120~140 ℃, zone 2 temperature 130~160 ℃, zone 3 temperature 140~180 ℃, zone 4 temperature 130~170 ℃, barrel residence time of 1 minute, and melt pressure of 7.8 MPa.

[0018] The prepared masterbatch strips are discharged smoothly, and the melt pressure is stable at 7.8±0.2 MPa. The surface of the masterbatch strips is smooth and flat, but it is brittle and easy to break. It needs to be slowly cooled and pelletized with water to obtain ultrafine brominated polystyrene high-concentration dust-free flame retardant masterbatch.

[0019] Example 2: An ultrafine brominated polystyrene high-concentration dust-free flame retardant masterbatch that eliminates the risk of dust explosion, its composition by mass parts is as follows: Ethylene-vinyl acetate copolymer 32 copies Ethylene bis-stearamide 1.5 copies Oily titanate LD-144 1.5 copies Polyethylene wax 5 copies

[0020] The preparation method of the ultrafine brominated polystyrene high-concentration dust-free flame-retardant masterbatch that eliminates the risk of dust explosion is as follows: Weigh each component according to the above formula for ultrafine brominated polystyrene high-concentration dust-free flame retardant masterbatch; The ethylene-vinyl acetate copolymer was placed in a high-speed mixer, set to 100 ℃, and stirred at 30 Hz for 30 minutes. After the time was reached, the stirring was turned off, and the internal temperature was 93 ℃. The surface of the ethylene-vinyl acetate copolymer became sticky. Ultrafine brominated polystyrene with a molecular weight of 400,000 and a particle size of 4 μm was added, and the mixture was stirred at 10 Hz for 10 minutes. After stirring, the internal temperature rose to 96 ℃, and the stirring was turned on at 10 Hz. At this time, the oily titanate coupling agent LD-144 was sprayed in through atomization. After the coupling agent was added, the mixture was stirred at 10 Hz for 8 minutes. After stirring, the internal temperature rose to 98 ℃, and ethylene bis-stearamide and polyethylene wax were added. The mixture was stirred at 30 Hz for 3 minutes. After stirring, the high-concentration dust-free flame-retardant masterbatch precursor of ultrafine brominated polystyrene was obtained. The masterbatch precursor prepared above was placed in a twin-screw extruder and melt-extruded and granulated. The process conditions were: zone 1 temperature 120~140 ℃, zone 2 temperature 130~160 ℃, zone 3 temperature 140~180 ℃, zone 4 temperature 130~170 ℃, barrel residence time of 2 minutes, and melt pressure of 7.2 MPa.

[0021] The prepared masterbatch strips are discharged smoothly, and the melting pressure is stable at 7.2±0.1MPa. The surface of the masterbatch strips is smooth and flat but brittle and easy to break. They can be normally granulated by water cooling to obtain ultrafine brominated polystyrene high-concentration dust-free flame retardant masterbatch.

[0022] Example 3: A high-concentration, dust-free flame-retardant masterbatch for ultrafine brominated polystyrene that eliminates the risk of dust explosion, with the following composition by mass parts: Ethylene-vinyl acetate copolymer 21.5 copies Ethylene bis-stearamide 0.7 copies Oily titanate LD-144 0.7 copies Polyethylene wax 2.1 copies

[0023] The preparation method of the ultrafine brominated polystyrene high-concentration dust-free flame-retardant masterbatch that eliminates the risk of dust explosion is as follows: Weigh each component according to the above formula for ultrafine brominated polystyrene high-concentration dust-free flame retardant masterbatch; Ethylene-vinyl acetate copolymer was placed in a high-speed mixer, set to 100 ℃, and stirred at 30 Hz for 30 minutes. After the time was reached, the stirring was turned off, and the internal temperature was 98 ℃. The surface of the ethylene-vinyl acetate copolymer became sticky. Ultrafine brominated polystyrene with a molecular weight of 300,000 and a particle size of 3.2 μm was added, and the mixture was stirred at 10 Hz for 10 minutes. After stirring, the internal temperature rose to 99 ℃, and the stirring was turned on at 10 Hz. At this time, the oily titanate coupling agent LD-144 was sprayed in through atomization. After the coupling agent was added, the mixture was stirred at 10 Hz for 8 minutes. After stirring, the internal temperature rose to 102 ℃, and ethylene bis-stearamide and polyethylene wax were added. The mixture was stirred at 30 Hz for 3 minutes. After stirring, the high-concentration dust-free flame-retardant masterbatch precursor of ultrafine brominated polystyrene was obtained. The masterbatch precursor prepared above was placed in a twin-screw extruder and melt-extruded and granulated. The process conditions were: zone 1 temperature 120~140 ℃, zone 2 temperature 130~160 ℃, zone 3 temperature 140~180 ℃, zone 4 temperature 130~170 ℃, barrel residence time of 3 minutes, and melt pressure of 8.3 MPa.

[0024] The prepared masterbatch strips are discharged smoothly but slowly, with a stable melt pressure of 8.3±0.2 MPa. The surface of the masterbatch strips is smooth and flat, and they can be normally water-cooled and pelletized to obtain ultrafine brominated polystyrene high-concentration dust-free flame-retardant masterbatch.

[0025] Comparative Example 1: Based on Example 1, the main ultrafine brominated polystyrene was changed to a 100,000 molecular weight variety, while the other steps remained unchanged. The proportions of the high-concentration dust-free flame-retardant ultrafine brominated polystyrene masterbatch for eliminating the risk of dust explosion were modified as follows: Ethylene-vinyl acetate copolymer 25.9 copies Ethylene bis-stearamide 1.44 copies Oily titanate LD-144 0.96 copies Polyethylene wax 4.5 copies

[0026] During the granulation and extrusion process, the prepared masterbatch strips are discharged smoothly and the melt pressure is stable at 7±0.2 MPa. However, the masterbatch strips appear slightly yellow, and the surface is smooth and flat but brittle and easy to break. They need to be slowly cooled and granulated with water to obtain ultrafine brominated polystyrene high-concentration dust-free flame-retardant masterbatch.

[0027] Comparative Example 2: Based on Example 1, with the remaining steps unchanged, the proportions of the ultrafine brominated polystyrene high-concentration dust-free flame-retardant masterbatch for eliminating the risk of dust explosion were modified as follows: Ethylene-vinyl acetate copolymer 12.5 copies Ethylene bis-stearamide 1.27 copies Oily titanate LD-144 0.13 copies Polyethylene wax 6.1 copies

[0028] During the entire granulation and extrusion process, in the early stage of equipment operation, the melt pressure is 8.5±0.5 MPa, which can produce relatively smooth masterbatch strips that can be normally water-cooled and pelletized. In the middle stage of equipment operation, the melt pressure rises to 9±1 MPa. At this time, the surface of the prepared masterbatch strips becomes rough, the discharge is not smooth, and the prepared masterbatch strips are brittle and easy to break. They can be normally water-cooled but require manual assistance for pelletizing. In the later stage of equipment operation, the melt pressure reaches the set protection value, causing the twin-screw extruder to stop suddenly. During the subsequent cleaning process, it was found that solid powder was blocked at the die extrusion point. This formula can be granulated in stages, but it cannot convert all the target formula material into ideal smooth rice grains.

[0029] Comparative Example 3: Based on Example 1, the dispersant ethylene bis-stearamide was replaced with zinc stearate, while the other steps remained unchanged. The proportions of the ultrafine brominated polystyrene high-concentration dust-free flame-retardant masterbatch for eliminating the risk of dust explosion were changed as follows: Ethylene-vinyl acetate copolymer 25.9 copies Zinc stearate 1.44 copies Oily titanate LD-144 0.96 copies Polyethylene wax 4.5 copies

[0030] During the granulation and extrusion process, the prepared masterbatch strips are discharged smoothly, and the melt pressure is stable at 7±0.5 MPa. However, the extruded masterbatch strips are prone to breakage after rapid cooling in the cooling water tank, which prevents the strips from being transported stably and continuously to the pelletizing equipment. To complete the finished product processing, it is necessary to assign a dedicated person to pick up the broken strips and manually feed them into the pelletizing machine to obtain ultrafine brominated polystyrene high-concentration dust-free flame-retardant masterbatch.

[0031] In the above examples and comparative examples, the ethylene-vinyl acetate copolymer used was USI-629 produced by Fujian Gulei Petrochemical Co., Ltd.

[0032] The following performance tests aim to evaluate the overall performance of injection molding samples made from different high-concentration dust-free flame retardant masterbatches or their preparations in terms of color swatch whiteness, melt flow properties, flame retardancy rating, and mechanical properties.

[0033] (1) Whiteness test of injection molded sample color swatch: The whiteness of the injection molded sample was measured using a YQ-Z-48A whiteness meter; (2) Masterbatch melt flow performance test: The melt mass flow rate (MFR) of high-concentration dust-free flame retardant masterbatch was tested using a melt flow rate tester according to ASTM D1238 standard. The test conditions were: temperature 190 °C, load 2.16 kg. (3) Flame retardant performance test of injection molded specimens: According to UL 94 standard, the vertical flammability rating of injection molded specimens was tested using a horizontal-vertical flammability tester. (4) Mechanical property testing of injection molded specimens: According to ASTM D638 standard, the tensile strength and elongation at break of injection-molded specimens were tested using a universal testing machine. According to ASTM D256 standard, the impact strength of injection-molded specimens with V-notches was tested using a cantilever beam impact testing machine. Five specimens were tested in each group, and the average value of the results was taken.

[0034] The overall test data is shown in the table below: Example 1 88.7 16.8 15.1 117.5 125.7 V0 Example 2 89.3 15.6 16.3 125.1 127.1 V0 Example 3 87.6 18.1 14.5 111.9 122.6 V0 Comparative Example 1 79.2 20.6 10.2 103.8 100.8 V0 Comparative Example 2 78.8 7.3 18.9 49.6 85.5 V1 Comparative Example 3 85.5 9.8 18.5 55.9 96.4 V0

[0035] The test data in the table above demonstrates the significant advantages of the masterbatch of this invention in downstream market applications.

[0036] First, the melt flow rate (MFR) data reflects the stability of the material formulation and normal dispersion. The MFR values ​​of Examples 1-3 are moderate (15.6-18.1 g / 10min), indicating that the melt flow of the high-concentration dust-free flame retardant masterbatch under this formulation is moderate, and the corresponding material processing performance, mechanical properties, and molding stability are at their best. The MFR value of Comparative Example 1 is significantly higher, indicating that the reduced molecular weight of the flame retardant leads to a decrease in heat resistance. The MFR values ​​of Comparative Examples 2 and 3 are lower, indicating insufficient flowability, which increases the processing difficulty and defect risk for downstream manufacturers. The problem in Comparative Example 2 is due to the high flame retardant filler content, which causes powder thickening. The problem in Comparative Example 3 is due to the lack of an effective dispersant, which fails to synergistically disperse the flame retardant, resulting in substandard tensile strength.

[0037] Secondly, in terms of mechanical properties, Examples 1-3 are significantly superior to all comparative examples in terms of tensile strength, elongation at break, and impact strength. This indicates that the masterbatch product of the present invention has excellent dispersibility and achieves effective reinforcement and toughening of the material.

Claims

1. A high-concentration, dust-free, flame-retardant masterbatch for ultrafine brominated polystyrene that eliminates the risk of dust explosion, characterized in that, The formulation comprises the following components in parts by weight: 60-75 parts of ultrafine brominated polystyrene with a median diameter (D50) of 3-4 μm and a maximum particle size (D100) of less than 25 μm; 15-35 parts of ethylene-vinyl acetate copolymer (EVA); 0.5-3 parts of ethylene bis-stearamide (EBS); 0.5-2 parts of oily titanate coupling agent; and 2-8 parts of polyethylene wax.

2. The ultrafine brominated polystyrene high-concentration dust-free flame-retardant masterbatch for eliminating the risk of dust explosion as described in claim 1, characterized in that: Ultrafine brominated polystyrene with a median diameter (D50) of 3-4 μm and a maximum particle size (D100) of less than 25 μm, and a molecular weight of 300,000-500,000.

3. The ultrafine brominated polystyrene high-concentration dust-free flame-retardant masterbatch for eliminating the risk of dust explosion as described in claim 1, characterized in that: The VA content of the ethylene-vinyl acetate copolymer is 18%~28%, and the melt mass flow rate is 2~8 g / 10min.

4. The ultrafine brominated polystyrene high-concentration dust-free flame-retardant masterbatch for eliminating the risk of dust explosion as described in claim 1, characterized in that: The oily titanate coupling agent used is LD-144 produced by Yangzhou Lida Resin Co., Ltd.

5. The ultrafine brominated polystyrene high-concentration dust-free flame-retardant masterbatch for eliminating the risk of dust explosion as described in claim 1, characterized in that: The mass ratio of the polyethylene wax to ethylene bis-stearamide is (3~4):

1.

6. The ultrafine brominated polystyrene high-concentration dust-free flame-retardant masterbatch for eliminating the risk of dust explosion according to claim 1, characterized in that: The melt mass flow rate (MFR) of the flame retardant masterbatch at 190°C and 2.16 kg load is 15.0~19.0 g / 10min.

7. A method for preparing ultrafine brominated polystyrene high-concentration dust-free flame-retardant masterbatch with dust explosion risk according to any one of claims 1 to 5, characterized in that, Includes the following steps: The ethylene-vinyl acetate copolymer was heated and stirred, and then mixed with ultrafine brominated polystyrene in one step. Then, the oily titanate coupling agent LD-144 was added for a second step of mixing. Finally, ethylene bis-stearamide and polyethylene wax were added for a third step of mixing to obtain the flame retardant masterbatch precursor. The flame retardant masterbatch precursor is melt-extruded and granulated to obtain the flame retardant masterbatch.

8. The method for preparing ultrafine brominated polystyrene high-concentration dust-free flame-retardant masterbatch with dust explosion risk according to claim 6, characterized in that: The flame retardant masterbatch precursor is melted using a stepped zone temperature-controlled melt extrusion process. The process conditions are: zone 1 temperature 120~140℃, zone 2 temperature 130~160℃, zone 3 temperature 140~180℃, zone 4 temperature 130~170℃, barrel residence time 1~3 minutes, and melt pressure 5~10 MPa.

9. The method for preparing ultrafine brominated polystyrene high-concentration dust-free flame-retardant masterbatch with dust explosion risk according to claim 6, characterized in that: The ethylene-vinyl acetate copolymer is heated at 90~100 ℃, stirred for 10~30 minutes, and stirred at a rate of 30~40 Hz. The mixing time is 10-15 minutes, and the stirring rate during mixing is 10-15 Hz; During the secondary mixing, the oily titanate coupling agent LD-144 is injected via atomization, the mixing time is 5-10 minutes, and the stirring rate during mixing is 10-15 Hz. The three mixing times are 2 to 5 minutes, and the stirring rate during mixing is 30 to 40 Hz.