Preparation method of dispersed polypropylene carbon black composite flame-retardant master batch

Abstract

The invention discloses a preparation method of a dispersing type polypropylene carbon black composite flame-retardant master batch, which comprises the following steps: by taking polypropylene resin, a grafting monomer, a grafting accelerant, a free radical initiator and a free radical stabilizer as raw materials, synthesizing a polypropylene carrier with a side group containing a furan group through melt grafting reaction; the preparation method comprises the following steps: by taking polypropylene as a raw material, and then carrying out thermal reversible Diels-Alder reaction on the polypropylene and flame-retardant modified carbon black with maleimide groups on the surface, so that the carbon black is well and stably dispersed in a polypropylene matrix material, the interaction force between polypropylene and the carbon black is effectively improved, the composite material is endowed with excellent flame-retardant performance, and the comprehensive performance of the composite material is remarkably improved.

Description

Technical Field

[0001] The invention relates to a method for preparing an easily dispersible polypropylene carbon black flame retardant masterbatch, in particular to a method for preparing a polypropylene carbon black composite flame retardant masterbatch with good carbon black dispersion effect. Background Art

[0002] Carbon black is an important functional filler composed of carbon elements. It is widely used in the processing and application of polymer materials such as synthetic rubber, synthetic resin, synthetic fiber, coating, adhesive, etc. At the same time, there are many varieties of carbon black, and the performance differences are relatively large. The requirements and functions of different materials and application fields are also different. Carbon black is mainly used as a UV shielding agent and black colorant in the plastic, fiber and other industries. Only when carbon black is well and evenly dispersed in polymer materials can it exert its excellent UV shielding, coloring and other properties without causing a significant decrease in the mechanical properties of the matrix material. When carbon black is used in plastic and fiber formulations, its dosage is much lower than that in rubber material formulations, and its mass usually accounts for only 0.5~6% of the plastic or fiber matrix resin. If a small amount of carbon black powder (0.5-6%) is mixed with granular resin and then granulated through a twin-screw extruder commonly used in ordinary plastic modification, the carbon black cannot be well dispersed in the matrix resin. This is because carbon black, as an inorganic material, has low adhesion to the surface of the organic polymer matrix. In addition, because carbon black has a low apparent density and a large specific surface area, it is difficult to directly disperse it evenly through the processing equipment of common plastic products. This phenomenon is more significant for high-structure carbon black with a small original particle size and a large specific surface area. Therefore, how to achieve uniform dispersion of carbon black in plastic or fiber matrix resin has always been a problem that the industry has been constantly exploring and seeking improvements. Summary of the invention

[0003] By using special equipment and special formula to prepare carbon black masterbatch first, and then adding masterbatch containing pre-dispersed carbon black, carbon black can be evenly dispersed in the matrix resin in the processing of plastic or fiber products, which helps to maintain the stability of plastic or fiber performance and will not significantly reduce the performance of the product due to the addition of carbon black. To achieve this purpose, the present invention proposes a preparation method of dispersed polypropylene carbon black composite flame retardant masterbatch, which adopts thermally reversible dynamic covalent bonds to realize the covalent bond connection between polypropylene molecular chain and carbon black. Specifically, by constructing a covalent bond that can undergo thermally reversible Diels-Alder reaction (DA reaction) between polypropylene macromolecular chain and carbon black, the interaction between the two is fundamentally and thoroughly strengthened, and the mechanical properties of the material are significantly enhanced; at the same time, since the covalent bond formed by the DA reaction can be dissociated after heating, it will not affect the melt processing performance of polypropylene itself, so that the composite material can be molded under conventional processing conditions of polypropylene. In particular, the present invention proposes a method for preparing an easily dispersible flame-retardant polypropylene carbon black masterbatch. By functionalizing polypropylene, carbon black and flame retardant in advance, a covalent bond is conveniently established between the two through a DA reaction, thereby constructing a stable polypropylene-carbon black-flame retardant composite material structure. This structure is not only beneficial to improving the mechanical strength of the material, but also can obtain a high-carbon black content, easily dispersible high-performance carbon black masterbatch.

[0004] To achieve the above object, the present invention adopts the following technical solution: A method for preparing a dispersed polypropylene carbon black composite flame retardant masterbatch comprises the following steps: firstly, a polypropylene resin is subjected to a melt grafting reaction with a grafting monomer, a grafting accelerator, a free radical initiator and a free radical stabilizer to obtain a polypropylene carrier; then, the polypropylene carrier is mixed with a flame retardant modified carbon black and a fluorine processing aid, and then the dispersed polypropylene carbon black composite flame retardant masterbatch is prepared by a melt extrusion method.

[0005] Furthermore, the polypropylene resin is isotactic polypropylene.

[0006] Furthermore, the grafting monomer is a compound containing a furanyl group, and its structural formula is as follows: ; The amount of grafting monomer used is 0.01%~10% of the mass of polypropylene resin, preferably 0.1%~5%.

[0007] Furthermore, the grafting accelerator is diethyl diphenyl thiuram disulfide, and its usage is 0.01% to 5% of the mass of the polypropylene resin, preferably 0.05% to 2%.

[0008] Furthermore, the free radical initiator is a thermal decomposition free radical initiator, an organic peroxide or an azo initiator, preferably an alkyl peroxide, a hydroperoxide, an acyl peroxide, or a peroxycarbonate, and its usage is 0.01% to 1% of the mass of the polypropylene resin, preferably 0.05% to 0.5%.

[0009] Furthermore, the free radical stabilizer is at least one of hindered phenol, phosphite or alkyl ester stabilizers, and its usage is 0.05-1% of the mass of the polypropylene resin, preferably 0.1-0.5%.

[0010] Furthermore, the melt grafting reaction is carried out in an extruder, which is a twin-screw extruder having at least six zones, wherein the temperature of the first zone is 90°C~230°C, the temperature of the second zone is 150°C~230°C, the temperature of the third zone is 180°C~230°C, and the temperature of the subsequent zones is 190°C~230°C; the residence time of the material in the twin-screw extruder is 30 seconds~300 seconds.

[0011] Furthermore, the mass percentage ratio of the flame retardant modified carbon black to the polypropylene carrier is 50:50 to 2:98.

[0012] Furthermore, the flame retardant modified carbon black is a carbon black composite whose surface is grafted with maleimide groups and contains a flame retardant.

[0013] Furthermore, the flame retardant modified carbon black is prepared by esterifying silane-modified carbon black with carboxyl-substituted maleimide in the presence of a flame retardant, and the specific preparation steps are as follows: (1) Mix carbon black and 65% pure nitric acid and disperse them by ultrasonic for 30 minutes. After deoxygenation, heat the mixture in an oil bath at 100°C for 24 hours under stirring. After the reaction, cool the mixture to room temperature, filter it, and wash it repeatedly with deionized water until the pH of the filtrate is 7. Then, vacuum dry the filtered precipitate at 50°C to obtain carboxyl-modified carbon black (with a carboxyl content of 1.68 mmol / g). (2) 12 g of carboxyl-modified carbon black and 200 mL of thionyl chloride were mixed and ultrasonically dispersed for 15 minutes. After deoxygenation, the mixture was heated in an oil bath at 65°C for 24 hours under stirring. After the reaction, the mixture was cooled to room temperature, and the unreacted thionyl chloride was removed under reduced pressure. Then, 200 mL of ethylene glycol was added under inert gas protection, and the mixture was heated to 120°C for 24 hours. The mixture was filtered and repeatedly washed with deionized water and tetrahydrofuran. Finally, the filtered precipitate was vacuum dried at 50°C to obtain hydroxyl-modified carbon black CB-OH (wherein the hydroxyl content was 1.55 mmol / g). (3) Add 3-mercaptopropyltrimethoxysilane (MPTS) and sodium hydroxide in a molar ratio of 1:(2-3) to an ethanol solution with a mass concentration of 1-50%, control the reaction temperature to 0°C, then add hydroxyl-modified carbon black CB-OH with a molar amount of 10-30 times that of MPTS, react for 48 hours, filter, wash repeatedly with deionized water, and vacuum dry the filtered precipitate at 50°C to obtain silane-modified carbon black M-CB; (4) adding an organic solvent, silane-modified carbon black M-CB, carboxyl-substituted maleimide, flame retardant 2-carboxyethylphenylphosphinic acid (CEPPA) and a catalyst into a reaction container in sequence, and performing an esterification reaction at 0° C. to 60° C. for 1 to 72 hours. After the reaction is completed, filtering and drying are performed to obtain the flame retardant modified carbon black; Wherein, the particle size of the carbon black in step (1) is 5-25 nm, and the oil absorption value is ≥6010 5 m 3 / kg, color strength ≥120%, 45 μm sieve residue ≤100ppm; The organic solvent in step (4) is selected from chloroalkanes having 1 to 5 carbon atoms, dimethylformamide, tetrahydrofuran, acetonitrile or dimethyl sulfoxide; the catalyst is selected from one of inorganic acids, organic acids or carbodiimide compounds, and its amount accounts for 0.5 to 5% of the total mass of the reaction materials; in the esterification reaction, the reaction molar ratio of the hydroxyl group on the silane-modified carbon black to the carboxyl group on the carboxyl-substituted maleimide and the carboxyl group on the 2-carboxyethylphenylphosphinic acid is 0.01 to 0.5:1:0.01 to 0.5.

[0014] Furthermore, the amount of the fluorine processing aid is 0.05-1% of the mass of the polypropylene carrier, preferably 0.2-0.5%.

[0015] Furthermore, the extrusion temperature of the melt extrusion method is 170-220°C.

[0016] The present invention has the following beneficial effects: (1) The present invention adopts the introduction of grafting and thermally reversible dynamic covalent bonds. On the one hand, at a lower extrusion temperature, the melt strength of the polypropylene carrier is increased, which is beneficial to the transmission of shear stress, prompting the carbon black aggregates to open and form a void system, which is beneficial to achieve uniform dispersion of carbon black. On the other hand, in the preparation process of polypropylene molded products, a higher extrusion temperature can release the dynamic covalent bonds, making it less likely for carbon black to agglomerate.

[0017] (2) The present invention introduces a flame retardant into the system and connects the flame retardant with modified carbon black through an esterification reaction, thereby inhibiting the migration, volatilization and precipitation of small molecule flame retardants and promoting uniform dispersion of the flame retardant. According to experimental results, carbon black and 2-carboxyethylphenylphosphinic acid have a synergistic flame retardant effect and can give polypropylene carbon black composite masterbatch excellent flame retardant properties.

[0018] (3) The furan group of the polypropylene side group of the present invention and the maleimide group modified on the surface of the modified carbon black can be connected through a DA reaction, thereby forming a covalent bond between the polypropylene molecular chain and the modified carbon black, fundamentally enhancing the interaction between the two and significantly improving the mechanical properties of the material.

[0019] (3) The use of the polypropylene carbon black composite masterbatch of the present invention can achieve good dispersion of carbon black in the polypropylene matrix resin. DETAILED DESCRIPTION

[0020] A method for preparing a dispersed polypropylene carbon black composite flame retardant masterbatch, comprising the following steps: (1) mixing a polypropylene resin with a grafting monomer, a grafting accelerator, a free radical initiator, and a free radical stabilizer, and feeding the mixture into an extruder for melt grafting reaction to obtain a polypropylene carrier; (2) 20 g of carbon black and 200 mL of 65% pure nitric acid were mixed and ultrasonically dispersed for 30 minutes. After deoxygenation, the mixture was heated in an oil bath at 100°C for 24 hours under stirring. After the reaction, the mixture was cooled to room temperature, filtered, and repeatedly washed with deionized water until the pH of the filtrate was 7. The filtered precipitate was then vacuum dried at 50°C to obtain carboxyl-modified carbon black (with a carboxyl content of 1.68 mmol / g). (3) 12 g of carboxyl-modified carbon black and 200 mL of thionyl chloride were mixed and ultrasonically dispersed for 15 minutes. After deoxygenation, the mixture was heated in an oil bath at 65°C for 24 hours under stirring. After the reaction, the mixture was cooled to room temperature, and the unreacted thionyl chloride was removed under reduced pressure. Then, 200 mL of ethylene glycol was added under inert gas protection, and the mixture was heated to 120°C for 24 hours. The mixture was filtered and repeatedly washed with deionized water and tetrahydrofuran. Finally, the filtered precipitate was vacuum dried at 50°C to obtain hydroxyl-modified carbon black CB-OH (wherein the hydroxyl content was 1.55 mmol / g). (4) Add 3-mercaptopropyltrimethoxysilane (MPTS) and sodium hydroxide in a molar ratio of 1:(2-3) to an ethanol solution with a mass concentration of 1-50%, control the reaction temperature to 0°C, then add hydroxyl-modified carbon black CB-OH with a molar amount of 10-30 times that of MPTS, react for 48 hours, filter, repeatedly wash with deionized water, and vacuum dry the filtered precipitate at 50°C to obtain silane-modified carbon black M-CB; (5) adding an organic solvent, silane-modified carbon black M-CB, carboxyl-substituted maleimide, flame retardant 2-carboxyethylphenylphosphinic acid (CEPPA) and a catalyst into a reaction vessel in sequence, carrying out an esterification reaction at 0°C to 60°C for 1 to 72 hours, filtering and drying after the reaction to obtain a flame retardant modified carbon black; (6) The polypropylene carrier prepared in step (1), the flame retardant modified carbon black prepared in step (5) and the fluorine processing aid are mixed, and then melt-extruded at 170-220° C. to obtain a dispersed polypropylene carbon black composite flame retardant masterbatch.

[0021] Wherein, the polypropylene resin in step (1) is isotactic polypropylene. The grafting monomer is a compound containing a furan group ( ), and its dosage is 0.01%~10% of the mass of polypropylene resin. The grafting accelerator is diethyl diphenyl thiuram disulfide, and its dosage is 0.01%~5% of the mass of polypropylene resin. The free radical initiator is a thermal decomposition free radical initiator, an organic peroxide or an azo initiator, and its dosage is 0.01%~1% of the mass of polypropylene resin. The free radical stabilizer is at least one of hindered phenols, phosphites or alkyl ester stabilizers, and its dosage is 0.05~1% of the mass of polypropylene resin. The extruder is a twin-screw extruder with at least six zones, wherein the temperature of the first zone is 90℃~230℃, the temperature of the second zone is 150℃~230℃, the temperature of the third zone is 180℃~230℃, and the temperature of the subsequent zone is 190℃~230℃; the residence time of the material in the twin-screw extruder is 30 seconds~300 seconds.

[0022] The particle size of the carbon black in step (3) is 5-25 nm, and the oil absorption value is ≥6010 5 m 3 / kg, color strength ≥120%, 45 μm sieve residue ≤100ppm; The organic solvent in step (5) is selected from chloroalkanes having 1 to 5 carbon atoms, dimethylformamide, tetrahydrofuran, acetonitrile or dimethyl sulfoxide; the catalyst is selected from one of inorganic acids, organic acids or carbodiimide compounds, and its amount accounts for 0.5 to 5% of the total mass of the reaction materials; in the esterification reaction, the reaction molar ratio of the hydroxyl group on the silane-modified carbon black to the carboxyl group on the carboxyl-substituted maleimide and the carboxyl group on the 2-carboxyethylphenylphosphinic acid is 0.01 to 0.5:1:0.01 to 0.5.

[0023] The mass percentage ratio of the flame retardant modified carbon black to the polypropylene carrier used in step (6) is 50:50-2:98. The amount of the fluorine processing aid used is 0.05-1% of the mass of the polypropylene carrier.

[0024] In order to make the contents of the present invention easier to understand, the technical solution of the present invention is further described below in conjunction with specific implementation methods, but the present invention is not limited thereto.

[0025] The grafting monomers used in the examples are referenced to the literature " ACS Sustainable Chem. Eng. 2024, 12, 37,13798-13809” for synthesis.

[0026] The carboxyl-substituted maleimide used in the examples was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0027] Preparation of copolymers of polypropylene and olefins containing furan substituents: Comparative Example 1 In parts by mass, 100 parts of polypropylene (melt index MFR = 20 g / 10min, 230°C), 0.2 parts of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (free radical initiator), 0.1 parts of 1010 (free radical stabilizer), and 0.2 parts of 168 (free radical stabilizer) were mixed, and then the mixture was added to a twin-screw extruder for melting. The temperature of the first zone of the extruder was 100°C, the temperature of the second zone was 160°C, the temperature of the third zone was 190°C, the temperature of the fourth and fifth zones was 200°C, the temperature of the sixth zone was 190°C, the material residence time was 90 s, and the extruded product was cooled in a circulating water bath and pelletized to obtain the final product.

[0028] Comparative Example 2 In parts by mass, 100 parts of polypropylene (melt index MFR = 20 g / 10min, 230°C), 0.2 parts of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (free radical initiator), 0.1 parts of 1010 (free radical stabilizer), 0.2 parts of 168 (free radical stabilizer), and 1.0 parts of grafting monomer were mixed, and then the mixture was added to a twin-screw extruder for melting. The temperature of the first zone of the extruder was 100°C, the temperature of the second zone was 160°C, the temperature of the third zone was 190°C, the temperature of the fourth and fifth zones was 200°C, the temperature of the sixth zone was 190°C, the material residence time was 90 s, and the extruded product was cooled in a circulating water bath and pelletized to obtain the final product.

[0029] Example 1 In parts by mass, 100 parts of polypropylene (melt index MFR = 20 g / 10min, 230°C), 0.2 parts of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (free radical initiator), 0.1 parts of 1010 (free radical stabilizer), 0.2 parts of 168 (free radical stabilizer), 1.0 parts of grafting monomer, and 1.0 parts of diethyl diphenyl thiuram disulfide (grafting promoter) were mixed, and then the mixture was added to a twin-screw extruder for melting. The temperature of the first zone of the extruder was 100°C, the temperature of the second zone was 160°C, the temperature of the third zone was 190°C, the temperature of the fourth and fifth zones was 200°C, the temperature of the sixth zone was 190°C, the material residence time was 90 s, and the extruded product was cooled in a circulating water bath and pelletized to obtain the final product.

[0030] Example 2 In parts by mass, 100 parts of polypropylene (melt index MFR = 20 g / 10min, 230°C), 0.2 parts of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (free radical initiator), 0.1 parts of 1010 (free radical stabilizer), 0.2 parts of 168 (free radical stabilizer), 2.0 parts of grafting monomer, and 2.0 parts of diethyl diphenyl thiuram disulfide (grafting promoter) were mixed, and then the mixture was added to a twin-screw extruder for melting. The temperature of the first zone of the extruder was 100°C, the temperature of the second zone was 160°C, the temperature of the third zone was 190°C, the temperature of the fourth and fifth zones was 200°C, the temperature of the sixth zone was 190°C, the material residence time was 90 s, and the extruded product was cooled in a circulating water bath and pelletized to obtain the final product.

[0031] Example 3 In parts by mass, 100 parts of polypropylene (melt index MFR = 20 g / 10min, 230°C), 0.2 parts of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (free radical initiator), 0.1 parts of 1010 (free radical stabilizer), 0.2 parts of 168 (free radical stabilizer), 5.0 parts of grafting monomer, and 5.0 parts of diethyl diphenyl thiuram disulfide (grafting promoter) were mixed, and then the mixture was added to a twin-screw extruder for melting. The temperature of the first zone of the extruder was 100°C, the temperature of the second zone was 160°C, the temperature of the third zone was 190°C, the temperature of the fourth and fifth zones was 200°C, the temperature of the sixth zone was 190°C, the material residence time was 90 s, and the extruded product was cooled in a circulating water bath and pelletized to obtain the final product.

[0032] Preparation of flame retardant modified carbon black: Example 4 (1) Add 20 g of carbon black and 200 mL of 65% pure nitric acid into a 500 mL three-necked flask, deoxygenate the reaction system after ultrasonic dispersion for 30 minutes, and heat the reaction in a 100°C oil bath for 24 hours under stirring conditions. After the reaction is completed, cool to room temperature, filter, and repeatedly wash with deionized water until the pH of the filtrate is 7. Finally, the filtered precipitate is vacuum dried at 50°C to obtain carboxyl-modified carbon black CB-COOH (-COOH, 1.68 mmol / g).

[0033] (2) Add 12 g CB-COOH and 200 mL thionyl chloride to a 500 mL three-necked flask, deoxygenate the reaction system by ultrasonic dispersion for 15 minutes, and heat the reaction in a 65°C oil bath for 24 hours under stirring conditions. After the reaction is completed, cool to room temperature, remove the unreacted thionyl chloride under reduced pressure, add 200 mL ethylene glycol under inert gas protection, heat to 120°C, react for 24 hours, filter, and repeatedly wash with deionized water and tetrahydrofuran. Finally, dry the filtered precipitate in vacuum at 50°C to obtain CB-OH (-OH, 1.55 mmol / g).

[0034] (3) Add 1 mmol of 3-mercaptopropyltrimethoxysilane (MPTS) and 2 mmol of sodium hydroxide to 20 mL of 20% ethanol solution, control the reaction temperature to 0 °C, then add 10 mmol of CB-OH, react for 48 hours, filter, wash repeatedly with deionized water, and finally filter the precipitate at 50 °C. o C and dried in vacuum to obtain M-CB.

[0035] (4) Add 1 L of dichloromethane, 45 g of M-CB, 10 g of carboxyl-substituted maleimide, 5 g of flame retardant CEPPA, and 0.5 g of p-toluenesulfonic acid into a reaction container in sequence, and react at 0°C to 60°C for 1 to 72 hours; after the reaction is completed, filter and dry to obtain flame-retardant modified carbon black.

[0036] Preparation of polypropylene carbon black masterbatch: Comparative Example 3 In parts by mass, 60 parts of the polypropylene prepared in Comparative Example 1, 0.3 parts of PPA (fluorine processing aid), and 40 parts of the flame retardant modified carbon black prepared in Example 4 were mixed, and then the mixture was added to a twin-screw extruder, melt-extruded at 190° C., and the extruded product was cooled and pelletized to obtain the final product.

[0037] Comparative Example 4 In parts by mass, 60 parts of the polypropylene prepared in Comparative Example 2, 0.3 parts of PPA (fluorine processing aid), and 40 parts of the flame retardant modified carbon black prepared in Example 4 were mixed, and then the mixture was added to a twin-screw extruder, melt-extruded at 190° C., and the extruded product was cooled and pelletized to obtain the final product.

[0038] Example 5 In parts by mass, 60 parts of the polypropylene prepared in Example 1, 0.3 parts of PPA (fluorine processing aid), and 40 parts of the flame retardant modified carbon black prepared in Example 4 were mixed, and then the mixture was added to a twin-screw extruder, melt-extruded at 190° C., and the extruded product was cooled and pelletized to obtain the final product.

[0039] Example 6 In parts by mass, 60 parts of the polypropylene prepared in Example 2, 0.3 parts of PPA (fluorine processing aid), and 40 parts of the flame retardant modified carbon black prepared in Example 4 were mixed, and then the mixture was added to a twin-screw extruder, melt-extruded at 190° C., and the extruded product was cooled and pelletized to obtain the final product.

[0040] Example 7 In parts by mass, 60 parts of the polypropylene prepared in Example 3, 0.3 parts of PPA (fluorine processing aid), and 40 parts of the flame retardant modified carbon black prepared in Example 4 were mixed, and then the mixture was added to a twin-screw extruder, melt-extruded at 190° C., and the extruded product was cooled and pelletized to obtain the final product.

[0041] Comparative Example 5 In parts by mass, 60 parts of the polypropylene prepared in Example 3, 0.3 parts of PPA (fluorine processing aid), and 40 parts of carbon black were mixed, and then the mixture was added to a twin-screw extruder, melt-extruded at 190° C., and the extruded product was cooled and pelletized to obtain the final product.

[0042] Comparative Example 6 In parts by mass, 93 parts of the polypropylene prepared in Example 3, 0.3 parts of PPA (fluorine processing aid), 33 parts of carbon black, 5 parts of flame retardant CEPPA, and 2 parts of 3-mercaptopropyltrimethoxysilane were mixed, and then the mixture was added to a twin-screw extruder, melt-extruded at 190° C., and the extruded product was cooled and pelletized to obtain the final product.

[0043] The composite flame retardant masterbatch obtained in Examples 5 to 7 and Comparative Examples 3 to 6 was dispersed in the matrix resin polypropylene T30S (polypropylene: composite flame retardant masterbatch = 100:6), and the extrusion temperature was 190° C. The mechanical properties of the obtained polypropylene composite materials and the dispersion grade of carbon black are shown in Table 1.

[0044] Table 1 Performance comparison of polypropylene composites

[0045] It can be seen from Table 1 that: (1) Since the interaction between the polypropylene molecular chain and the flame-retardant modified carbon black is enhanced by the DA reaction, the mechanical properties of the obtained materials (Examples 5 to 7) are significantly improved compared with those of the ordinary blended samples without DA bonds (Comparative Examples 3 and 4), as shown by the significant improvement in yield strength and flexural strength, and the outstanding flame retardant effect.

[0046] (2) The flame retardant modified carbon black was used to prepare the composite flame retardant masterbatch. The mechanical properties of the obtained materials (Examples 5 to 7) were significantly improved compared with those of the unmodified carbon black (Comparative Examples 5 and 6). In addition, the agglomeration of carbon black was weakened, the dispersibility was significantly improved, and the flame retardant effect was also significantly improved.

[0047] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A method for preparing a dispersed polypropylene carbon black composite flame retardant masterbatch, characterized in that: First, a polypropylene carrier is obtained by melt grafting reaction of polypropylene resin with a grafting monomer, a grafting accelerator, a free radical initiator and a free radical stabilizer, and then the carrier is mixed with flame retardant modified carbon black and a fluorine processing aid to prepare the dispersed polypropylene carbon black composite flame retardant masterbatch by melt extrusion.

2. The method for preparing the dispersed polypropylene carbon black composite flame retardant masterbatch according to claim 1, characterized in that: The grafting monomer is a compound containing a furanyl group, and its structural formula is as follows: ; The amount of grafting monomer used is 0.01%~10% of the mass of polypropylene resin.

3. The method for preparing the dispersed polypropylene carbon black composite flame retardant masterbatch according to claim 1, characterized in that: The grafting accelerator is diethyl diphenyl thiuram disulfide, and its usage is 0.01% to 5% of the mass of the polypropylene resin.

4. The method for preparing the dispersed polypropylene carbon black composite flame retardant masterbatch according to claim 1, characterized in that: The free radical initiator is a thermal decomposition free radical initiator, an organic peroxide or an azo initiator, and its usage is 0.01% to 1% of the mass of the polypropylene resin.

5. The method for preparing the dispersed polypropylene carbon black composite flame retardant masterbatch according to claim 1, characterized in that: The free radical stabilizer is at least one of hindered phenol, phosphite or alkyl ester stabilizers, and its usage is 0.05-1% of the mass of the polypropylene resin.

6. The method for preparing the dispersed polypropylene carbon black composite flame retardant masterbatch according to claim 1, characterized in that: The melt grafting reaction is carried out in an extruder, which is a twin-screw extruder with at least six zones, wherein the temperature of the first zone is 90°C to 230°C, the temperature of the second zone is 150°C to 230°C, the temperature of the third zone is 180°C to 230°C, and the temperature of the subsequent zones is 190°C to 230°C; the residence time of the material in the twin-screw extruder is 30 seconds to 300 seconds.

7. The method for preparing the dispersed polypropylene carbon black composite flame retardant masterbatch according to claim 1, characterized in that: The flame retardant modified carbon black is a carbon black composite whose surface is grafted with maleimide groups and contains a flame retardant; the mass percentage ratio of the flame retardant modified carbon black to the polypropylene carrier is 50:50-2:

98.

8. The method for preparing the dispersed polypropylene carbon black composite flame retardant masterbatch according to claim 7, characterized in that: The specific preparation steps of the flame retardant modified carbon black are: (1) Mix carbon black and 65% pure nitric acid and disperse them by ultrasonic for 30 minutes. After deoxygenation, heat the mixture in an oil bath at 100°C for 24 hours under stirring. After the reaction, cool the mixture to room temperature, filter it, and wash it repeatedly with deionized water until the pH of the filtrate is 7. Then, vacuum dry the filtered precipitate at 50°C to obtain carboxyl-modified carbon black. (2) 12 g of carboxyl-modified carbon black and 200 mL of thionyl chloride were mixed and ultrasonically dispersed for 15 minutes. After deoxygenation, the mixture was heated in an oil bath at 65°C for 24 hours under stirring. After the reaction, the mixture was cooled to room temperature, and the unreacted thionyl chloride was removed under reduced pressure. Then, 200 mL of ethylene glycol was added under inert gas protection, and the mixture was heated to 120°C for 24 hours. The mixture was filtered and repeatedly washed with deionized water and tetrahydrofuran. Finally, the filtered precipitate was vacuum dried at 50°C to obtain hydroxyl-modified carbon black. (3) adding 3-mercaptopropyltrimethoxysilane and sodium hydroxide in a molar ratio of 1:(2-3) to an ethanol solution with a mass concentration of 1-50%, controlling the reaction temperature to 0°C, then adding hydroxyl-modified carbon black in an amount of 10-30 times the molar amount of 3-mercaptopropyltrimethoxysilane, reacting for 48 hours, filtering, repeatedly washing with deionized water, and vacuum drying the filtered precipitate at 50°C to obtain silane-modified carbon black; (4) adding an organic solvent, silane-modified carbon black, carboxyl-substituted maleimide, flame retardant 2-carboxyethylphenylphosphinic acid and a catalyst into a reaction container in sequence, and performing an esterification reaction at 0° C. to 60° C. for 1 to 72 hours. After the reaction is completed, filtering and drying are performed to obtain the flame retardant modified carbon black; Wherein, the particle size of the carbon black in step (1) is 5-25 nm, and the oil absorption value is ≥6010 5 m 3 / kg, color strength ≥120%, 45μm sieve residue ≤100ppm; The organic solvent in step (4) is selected from chloroalkanes having 1 to 5 carbon atoms, dimethylformamide, tetrahydrofuran, acetonitrile or dimethyl sulfoxide; the catalyst is selected from one of inorganic acids, organic acids or carbodiimide compounds, and its amount accounts for 0.5 to 5% of the total mass of the reaction materials; in the esterification reaction, the molar ratio of the hydroxyl group on the silane-modified carbon black to the carboxyl group on the carboxyl-substituted maleimide and the carboxyl group on the 2-carboxyethylphenylphosphinic acid is 0.01 to 0.5:1:0.01 to 0.

5.

9. The method for preparing the dispersed polypropylene carbon black composite flame retardant masterbatch according to claim 1, characterized in that: The amount of the fluorine processing aid is 0.05-1% of the mass of the polypropylene carrier.

10. The method for preparing the dispersed polypropylene carbon black composite flame retardant masterbatch according to claim 1, characterized in that: The extrusion temperature of the melt extrusion method is 170-220°C.

Images