Preparation method of a high-performance composite modified polypropylene granule

Abstract

The present invention discloses a preparation method of high-performance composite modified polypropylene particles, which relates to the technical field of polypropylene. In the present invention, partial alcohol hydroxyl groups and aldehyde groups of lignin are first oxidized into carboxyl groups, and aluminum nitrate is added to cobalt salts. The cobalt salts react simultaneously to form metal layered double hydroxide precipitates that bind to the surface of lignin, synergistically achieving a dual-effect flame retardancy. Secondly, attapulgite has a special fibrous porous crystal structure, but the dispersibility and binding degree of attapulgite in polypropylene are not high. Therefore, in the present invention, the catalyst citric acid is used to increase the layer spacing or cause exfoliation, and then propylene monomers are intercalated into the expanded attapulgite to polymerize and form an inorganic-organic hybrid composite material. Finally, the flame retardant filler is added to the composite material, and the free radicals on the surface of the attapulgite aerogel combine with those of the flame retardant filler, causing the overall binding of the polypropylene particle material and improving its flame retardancy and high-temperature resistance. The polypropylene particles prepared by the present invention have the effects of high-performance high-temperature resistance and flame retardancy.

Description

Technical Field

[0001] The present invention relates to the technical field of polypropylene, and particularly to a preparation method of high-performance composite modified polypropylene particles. Background Art

[0002] Polypropylene is a polymer formed by the addition polymerization of propylene. It is a white waxy material with a transparent and light appearance. It is a thermoplastic synthetic resin with excellent mechanical properties, safety and non-toxicity. It has chemical resistance, heat resistance, electrical insulation, high-strength mechanical properties and good high-abrasion processing properties, etc. At present, it has been widely used in many fields such as clothing, fiber products, medical devices, automobiles, bicycles, parts, conveying pipelines, food, chemical containers, etc.

[0003] However, the flammable characteristics of such resin materials lead to certain safety hazards, limit their application space, and hinder the further development of polypropylene resins. In existing flame-retardant polypropylene materials, usually means such as adding flame retardants and other components are adopted to improve the flame-retardant performance. However, the compatibility between inorganic fillers and polypropylene is poor, resulting in uneven distribution and poor stability. And increasing the addition amount of fillers will cause the comprehensive performance of polypropylene materials to decline. Therefore, there are still many defects and it is difficult to meet the needs of consumers. The present invention improves the dispersibility and compatibility of attapulgite in polypropylene through intercalation modification, so as to improve the comprehensive performance of polypropylene particles. At the same time, combined with composite flame-retardant materials, a preparation method of high-performance composite modified polypropylene particles is provided to solve the above problems. Summary of the Invention

[0004] The purpose of the present invention is to provide a preparation method of high-performance composite modified polypropylene particles to solve the problems existing in the prior art.

[0005] To solve the above technical problems, the present invention provides the following technical solutions: A preparation method of high-performance composite modified polypropylene particles, including the following preparation steps:

[0006] (1) Prepare a lignin solution with a concentration of 30 wt% by mixing lignin and deionized water in proportion. Then, use an air compressor to press air into the air distributor in the reaction kettle and mix it evenly with the lignin solution under stirring. The stirring speed is 350 - 550 rpm. Add a composite catalyst to the lignin solution and react at 50 - 140 °C for 30 - 480 min to obtain a carboxylated lignin solution; slowly add 0.5 - 1.5 parts of aluminum nitrate to 5 - 10 parts of the carboxylated lignin solution, and stir the mixture at 100 rpm for 20 - 40 min to dissolve the aluminum nitrate. The dissolved mixed solution is vigorously stirred at 80 - 100 °C for 18 - 30 h. After the reaction is completed, filter to obtain the precipitate, wash it 3 times with deionized water, and dry it at normal temperature and pressure for 24 h to obtain a flame-retardant filler;

[0007] (2) Under the protection of inert gas, evacuate to -0.085 MPa, then heat attapulgite to 70 - 400 °C for dehydroxylation treatment for 2 - 12 h to obtain pretreated attapulgite; mix the pretreated attapulgite with citric acid in proportion, first ultrasonicate at 20 kHz power for 30 min, then stir at 200 rpm at 70 - 90 °C for 12 h to obtain delaminated attapulgite; dissolve 0.008 - 0.014 parts of catalyst in 50 parts of toluene, stir at 100 rpm for 20 min to obtain a catalytic solution; place 0.5 parts of delaminated attapulgite in a round-bottom three-necked flask equipped with a condenser, evacuate to 1.5 kPa to displace the inert gas protection, add 50 parts of toluene, stir at 100 rpm for 20 min to obtain an attapulgite suspension; drop the prepared catalytic solution into the attapulgite suspension, the volume ratio of the two solutions is 1:1, the dropping is controlled within 30 min, after dropping, heat and reflux for 6 - 10 h, the temperature is 40 °C, after the reaction is completed, filter, then wash with toluene at 40 °C by stirring for 10 min, repeat 3 times, evacuate to 0.085 MPa and dry at room temperature for 4 h to obtain modified attapulgite; introduce propylene into the three-necked flask replaced by nitrogen and propylene, then add 100 parts of toluene, keep the propylene pressure in the flask at 770 mmHg under the condition of stirring at 60 rpm, the temperature is 50 - 90 °C, add 0.001 - 0.005 parts of catalyst, keep stirring at the original speed for 2 - 10 min, then add 0.2 - 0.4 parts of modified attapulgite, after reacting for 40 - 120 min, add acidified ethanol to terminate the polymerization reaction, and wash with toluene in the same way as above, then dry under vacuum at room temperature at 0.085 MPa for 6 - 8 h to obtain a polypropylene-attapulgite composite;

[0008] (3) Put the antioxidant, polypropylene wax, polypropylene-attapulgite composite and flame retardant filler into a rotary mixer according to the mass ratio of 0.2 - 0.6:20:5 - 10:2 - 5 and mix for 10 - 20 min, the rotational speed of the molten rotary mixer is 70 - 110 rpm, and this mixture is melt granulated by a twin-screw extruder at a temperature of 180 - 210 °C to obtain modified polypropylene particles.

[0009] Further, it is characterized in that the pressure during the carboxylation reaction in step (1) is maintained at 0.02 - 1.0 MPa.

[0010] Further, it is characterized in that the mass ratio of the composite catalyst to the lignin solution in step (1) is 1 - 3:40.

[0011] Further, it is characterized in that the preparation method of the composite catalyst in the step (1) is: cerium acetate, cobalt octoate and deionized water are mixed according to a mass ratio of 1:3 - 10:200, and stirred at a speed of 60 rpm for 10 min to obtain the composite catalyst.

[0012] Further, the stirring speed of the vigorous stirring in the step (1) is 800 - 1200 rpm.

[0013] Further, the inert gas in the step (2) is nitrogen.

[0014] Further, the mass ratio of attapulgite to citric acid in the step (2) is 10:0.5 - 2.5.

[0015] Further, the catalyst in the step (2) is a Ziegler catalyst.

[0016] Further, the solid-liquid ratio during toluene washing in the step (2) is 1:5.

[0017] Further, the antioxidant in the step (3) is compounded by antioxidant 1010 and antioxidant 168 according to a mass ratio of 5:4.

[0018] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0019] The present invention uses lignin and layered double hydroxides to prepare a flame retardant filler, and propylene intercalated attapulgite as a raw material to mix and prepare polypropylene particles, so as to achieve the effects of high temperature resistance and flame retardancy.

[0020] First, by using the large number of phenolic hydroxyl groups and aldehyde groups contained in the lignin molecular structure, air is used as an oxidant, and lignin is oxidized in the presence of a cobalt salt as a catalyst. Some of the alcohol hydroxyl groups and aldehyde groups are oxidized into carboxyl groups, and the remaining phenolic hydroxyl groups achieve the effect of high temperature resistance by strongly capturing free radicals; after carboxylation of lignin, aluminum nitrate is added to the cobalt salt, and the nitrate group reacts with the carboxyl group to combine, and reacts with the cobalt salt at the same time to form a metal layered double hydroxide precipitate bound to the surface of lignin, generating a flame retardant filler; lignin is rich in carbon content and can be used as a carbon source during the thermal decomposition process, and has a strong carbon-forming ability during combustion, which can prevent the combustion of olefin polymers. Combining with the metal hydroxide on the surface of lignin, metal ions can react with free radicals in the gas during the combustion process to form relatively stable compounds, achieving synergistic dual-effect flame retardancy;

[0021] Secondly, attapulgite has a special fibrous porous crystal structure. Making full use of its structure and applying it to polypropylene particles can achieve high thermal stability and flame retardant effects. However, the dispersibility and bonding degree of attapulgite in polypropylene are not high. Therefore, in this invention, the catalyst citric acid is introduced into the interlayer of attapulgite clay, which increases the interlayer spacing of attapulgite clay or causes peeling between layers. Then, propylene monomers are intercalated into the expanded attapulgite clay, and then polymerized to form an inorganic-organic hybrid composite. Finally, flame retardant fillers are added to the composite. The free radicals on the surface of attapulgite aerogel and the flame retardant fillers combine, enabling the overall bonding of polypropylene pellets and improving their flame retardancy and high temperature resistance. Detailed implementation mode

[0022] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0023] In order to more clearly illustrate the method provided by the present invention, it is described in detail through the following embodiments. The test methods for each index of a kind of high-performance composite modified polypropylene pellet prepared in the following embodiments are as follows:

[0024] High temperature resistance: The high temperature resistance of the samples prepared in the examples and comparative examples is detected in accordance with GB / T1633-2000 "Determination of Vicat softening temperature (VST) of thermoplastics".

[0025] Flame retardancy: Performance tests are carried out on the samples prepared in the examples and comparative examples, and the flame retardant performance is determined according to standards such as UL-94 and GB / T5169.12-2006.

[0026] Example 1; (1) Lignin and deionized water were mixed in proportion to prepare a lignin solution with a concentration of 30 wt%. Then, air was pressed into the air distributor in the reaction kettle by an air compressor, and the pressure was maintained at 0.02 MPa. The air was fully mixed with the lignin solution under stirring at a stirring speed of 350 rpm. A composite catalyst was added to the lignin solution, and the mass ratio of the composite catalyst to the lignin solution was 1:40. The reaction was carried out at 50 °C for 30 min to obtain a carboxylated lignin solution. The preparation method of the composite catalyst was as follows: Cerium acetate, cobalt octanoate and deionized water were mixed in a mass ratio of 1:3:200 and stirred at a speed of 60 rpm for 10 min to obtain the composite catalyst. 0.5 part of aluminum nitrate was slowly added to 5 parts of the carboxylated lignin solution. After mixing, it was fully stirred at 100 rpm for 20 min to dissolve the aluminum nitrate. The dissolved mixed solution was vigorously stirred at 80 °C for 18 h at a stirring speed of 800 rpm. After the reaction, the precipitate was filtered, washed 3 times with deionized water, and then dried at normal temperature and pressure for 24 h to obtain a flame retardant filler;

[0027] (2) Under the protection of nitrogen, the vacuum was pumped to -0.085 MPa, and then attapulgite was heated to 70 °C for dehydroxylation treatment for 2 h to obtain pretreated attapulgite. The pretreated attapulgite and citric acid were mixed in a mass ratio of 10:0.5. First, ultrasonic treatment was carried out at a power of 20 kHz for 30 min, and then stirred at a speed of 200 rpm at 70 °C for 12 h to obtain delaminated attapulgite. 0.008 part of Ziegler catalyst was dissolved in 50 parts of toluene and stirred at a speed of 100 rpm for 20 min to obtain a catalytic solution. 0.5 part of delaminated attapulgite was placed in a round-bottom three-necked flask equipped with a condenser. The vacuum was pumped to 1.5 kPa to displace nitrogen for protection, 50 parts of toluene was added, and it was stirred at a speed of 100 rpm for 20 min to obtain an attapulgite suspension. The prepared catalytic solution was added dropwise to the attapulgite suspension, and the volume ratio of the two solutions was 1:1. The dropping was controlled within 30 min. After the dropping was completed, the reaction was heated under reflux for 6 h at a temperature of 40 °C. After the reaction, it was filtered, and then washed with toluene at 40 °C by stirring for 10 min, and the solid-liquid ratio was 1:5. After repeating 3 times, the vacuum was pumped to 0.085 MPa and dried at normal temperature for 4 h to obtain modified attapulgite. Propylene was introduced into the three-necked flask replaced by nitrogen and propylene, and then 100 parts of toluene was added. Under the condition of stirring at a speed of 60 rpm, the propylene pressure in the flask was maintained at 770 mmHg and the temperature was 50 °C. 0.001 part of Ziegler catalyst was added. After maintaining the original speed of stirring for 2 min, 0.2 part of modified attapulgite was added. After reacting for 40 min, acidified ethanol was added to terminate the polymerization reaction, and it was washed in the same way as above with toluene, and then dried under vacuum at normal temperature at 0.085 MPa for 6 h to obtain a polypropylene-attapulgite composite;

[0028] (3) Antioxidant 1010 and antioxidant 168 are compounded into an antioxidant in a mass ratio of 5:4; the antioxidant, polypropylene wax, polypropylene-attapulgite composite, and flame retardant filler are put into a rotary mixer according to a mass ratio of 0.2:20:5:2 and mixed for 10 min. The rotational speed of the molten rotary mixer is 70 rpm. The mixture is melt granulated by a twin-screw extruder at a temperature of 180 °C to obtain modified polypropylene particles.

[0029] Example 2; (1) Lignin and deionized water are configured into a lignin solution with a concentration of 30 wt% according to a ratio. Then, air is pressed into the air distributor in the reaction kettle through an air compressor, and the pressure is maintained at 0.5 MPa. The air is fully mixed with the lignin solution under stirring, and the stirring speed is 450 rpm. A composite catalyst is added to the lignin solution, and the mass ratio of the composite catalyst to the lignin solution is 2:40. The reaction is carried out at 95 °C for 250 min to obtain a carboxylated lignin solution; the preparation method of the composite catalyst is: cerium acetate, cobalt octanoate, and deionized water are mixed according to a mass ratio of 1:6.5:200 and stirred at a speed of 60 rpm for 10 min to obtain the composite catalyst; 1 part of aluminum nitrate is slowly added to 7.5 parts of the carboxylated lignin solution. After mixing, it is fully stirred at 100 rpm for 30 min to dissolve the aluminum nitrate. The dissolved mixed solution is vigorously stirred at 90 °C for 24 h, and the stirring speed is 1000 rpm. After the reaction, the precipitate is filtered, washed 3 times with deionized water, and dried at normal temperature and pressure for 24 h to obtain the flame retardant filler;

[0030] (2) Under the protection of nitrogen, evacuate to -0.085 MPa, then heat attapulgite to 235 °C for dehydroxylation treatment for 7 h to obtain pretreated attapulgite; mix the pretreated attapulgite and citric acid at a mass ratio of 10:1.5, first ultrasonicate at a power of 20 kHz for 30 min, and then stir at 80 °C at a speed of 200 rpm for 12 h to obtain delaminated attapulgite; dissolve 0.011 parts of Ziegler catalyst in 50 parts of toluene, stir at a speed of 100 rpm for 20 min to obtain a catalytic solution; place 0.5 parts of delaminated attapulgite in a round-bottom three-necked flask equipped with a condenser, evacuate to 1.5 kPa to displace nitrogen for protection, add 50 parts of toluene, and stir at a speed of 100 rpm for 20 min to obtain an attapulgite suspension; add the prepared catalytic solution dropwise to the attapulgite suspension, with the volume ratio of the two solutions being 1:1, and control the dropping within 30 min. After the dropping is completed, heat under reflux for 8 h at a temperature of 40 °C. After the reaction is completed, filter, and then wash with toluene at 40 °C by stirring for 10 min, with a solid-liquid ratio of 1:5. Repeat 3 times, then evacuate to 0.085 MPa and dry at room temperature for 4 h to obtain modified attapulgite; introduce propylene into a three-necked flask replaced with nitrogen and propylene, then add 100 parts of toluene, and maintain the propylene pressure in the flask at 770 mmHg and the temperature at 70 °C under the condition of stirring at a speed of 60 rpm. Add 0.003 parts of Ziegler catalyst, keep stirring at the original speed for 6 min, then add 0.3 parts of modified attapulgite. After reacting for 80 min, add acidified ethanol to terminate the polymerization reaction, and wash with toluene in the same way as above, and then dry under vacuum at room temperature at 0.085 MPa for 7 h to obtain a polypropylene-attapulgite composite;

[0031] (3) Compound antioxidant 1010 and antioxidant 168 at a mass ratio of 5:4 to form an antioxidant; put the antioxidant, polypropylene wax, polypropylene-attapulgite composite, and flame retardant filler into a rotary mixer and mix for 15 min according to a mass ratio of 0.4:20:7.5:3.5. The rotational speed of the molten rotary mixer is 90 rpm. The mixture is melt granulated by a twin-screw extruder at a temperature of 195 °C to obtain modified polypropylene particles.

[0032] Example 3; (1) Lignin and deionized water were configured into a lignin solution with a concentration of 30 wt% according to a ratio. Then, air was pressed into the air distributor in the reaction kettle by an air compressor, and the pressure was maintained at 1.0 MPa. It was fully mixed with the lignin solution under stirring, and the stirring speed was 550 rpm. A composite catalyst was added to the lignin solution, and the mass ratio of the composite catalyst to the lignin solution was 3:40. The reaction was carried out at 140 °C for 480 min to obtain a carboxylated lignin solution. The preparation method of the composite catalyst was: cerium acetate, cobalt octanoate and deionized water were mixed according to a mass ratio of 1:10:200, and stirred at a speed of 60 rpm for 10 min to obtain the composite catalyst. 1.5 parts of aluminum nitrate were slowly added to 10 parts of the carboxylated lignin solution. After mixing, it was fully stirred at 100 rpm for 40 min to dissolve the aluminum nitrate. The dissolved mixed solution was vigorously stirred at 100 °C for 30 h, and the stirring speed was 1200 rpm. After the reaction, the precipitate was filtered, washed 3 times with deionized water, and dried at normal temperature and pressure for 24 h to obtain a flame retardant filler;

[0033] (2) Under the protection of nitrogen, the vacuum was pumped to -0.085 MPa, and then attapulgite was heated to 400 °C for dehydroxylation treatment for 12 h to obtain pretreated attapulgite. The pretreated attapulgite and citric acid were mixed according to a mass ratio of 10:2.5. First, ultrasonic treatment was carried out at a power of 20 kHz for 30 min, and then stirred at a speed of 200 rpm at 90 °C for 12 h to obtain delaminated attapulgite. 0.014 parts of Ziegler catalyst were dissolved in 50 parts of toluene and stirred at a speed of 100 rpm for 20 min to obtain a catalytic solution. 0.5 parts of delaminated attapulgite were placed in a round-bottom three-necked flask equipped with a condenser, and the vacuum was pumped to 1.5 kPa to displace nitrogen for protection. 50 parts of toluene were added and stirred at a speed of 100 rpm for 20 min to obtain an attapulgite suspension. The prepared catalytic solution was added dropwise to the attapulgite suspension, and the volume ratio of the two solutions was 1:1. The addition was controlled within 30 min. After the addition was completed, the reaction was carried out under reflux for 10 h at a temperature of 40 °C. After the reaction, it was filtered, and then washed with toluene at 40 °C by stirring for 10 min, and the solid-liquid ratio was 1:5. After repeating 3 times, the vacuum was pumped to 0.085 MPa and dried at normal temperature for 4 h to obtain modified attapulgite. Propylene was introduced into the three-necked flask replaced by nitrogen and propylene, and then 100 parts of toluene were added. Under the condition of stirring at a speed of 60 rpm, the propylene pressure in the flask was maintained at 770 mmHg and the temperature was 90 °C. 0.005 parts of Ziegler catalyst were added. After stirring at the original speed for 10 min, 0.4 parts of modified attapulgite were added. After reacting for 120 min, acidified ethanol was added to terminate the polymerization reaction, and it was washed in the same way as above with toluene, and then vacuum dried at 0.085 MPa at normal temperature for 8 h to obtain a polypropylene-attapulgite composite;

[0034] (3) Antioxidant is compounded by antioxidant 1010 and antioxidant 168 at a mass ratio of 5:4; the antioxidant, polypropylene wax, polypropylene-attapulgite composite and flame retardant filler are put into a rotary mixer and mixed for 20 min according to a mass ratio of 0.6:20:10:5. The rotation speed of the melting rotary mixer is 110 rpm. The mixture is melt granulated by a twin-screw extruder at a temperature of 210 °C to obtain modified polypropylene particles.

[0035] Comparative Example 1; The difference between Comparative Example 1 and Example 2 lies in step (1). Step (1) is changed to: lignin and deionized water are configured into a lignin solution with a concentration of 30 wt%. The preparation method of the composite catalyst is: cerium acetate, cobalt octanoate and deionized water are mixed according to a mass ratio of 1:6.5:200 and stirred at a speed of 60 rpm for 10 min to obtain the composite catalyst; 1 part of aluminum nitrate is slowly added to 7.5 parts of the lignin solution. After mixing, it is fully stirred at 100 rpm for 30 min to dissolve the aluminum nitrate. The dissolved mixed solution is vigorously stirred at 90 °C for 24 h, and the stirring speed is 1000 rpm. After the reaction is completed, the precipitate is filtered, washed 3 times with deionized water, and dried at normal temperature and pressure for 24 h to obtain the flame retardant filler; the remaining steps are the same as those in Example 2.

[0036] Comparative Example 2; The difference between Comparative Example 2 and Example 2 is that there is no step (1). Step (3) is changed to: antioxidant is compounded by antioxidant 1010 and antioxidant 168 at a mass ratio of 5:4; the antioxidant, polypropylene wax, polypropylene-attapulgite composite, lignin, and talcum powder are put into a rotary mixer and mixed for 15 min according to a mass ratio of 0.4:20:7.5:2:1.5. The rotation speed of the melting rotary mixer is 90 rpm. The mixture is melt granulated by a twin-screw extruder at a temperature of 195 °C to obtain modified polypropylene particles; the remaining steps are the same as those in Example 2.

[0037] Comparative Example 3 (without hydroxide); The difference between Comparative Example 3 and Example 2 lies in step (1). Step (1) is changed to: lignin and deionized water are configured into a lignin solution with a concentration of 30 wt%. Then, air is pressed into the air distributor in the reaction kettle by an air compressor, and the pressure is maintained at 0.5 MPa and fully mixed with the lignin solution under stirring. The stirring speed is 450 rpm. The composite catalyst is added to the lignin solution, and the mass ratio of the composite catalyst to the lignin solution is 2:40. The reaction is carried out at 95 °C for 250 min. After the reaction is completed, the precipitate is filtered, washed 3 times with deionized water, and dried at normal temperature and pressure for 24 h to obtain the flame retardant filler; the remaining steps are the same as those in Example 2.

[0038] Comparative Example 4; The difference between Comparative Example 4 and Example 2 is that step (2) is not carried out, and step (3) is changed to: Antioxidant 1010 and antioxidant 168 are compounded into an antioxidant in a mass ratio of 5:4; The antioxidant, polypropylene wax, attapulgite clay complex and flame retardant filler are put into a rotary mixer and mixed for 15 min according to a mass ratio of 0.4:25:4.5:3.5, the rotational speed of the melting rotary mixer is 90 rpm, and this mixture is melt granulated at a temperature of 195 °C by a twin-screw extruder to obtain modified polypropylene particles; The remaining steps are the same as those in Example 2.

[0039] Comparative Example 5; The difference between Comparative Example 5 and Example 2 lies in step (2). Step (2) is changed to: 0.011 part of Ziegler catalyst is dissolved in 50 parts of toluene, and stirred at a speed of 100 rpm for 20 min to obtain a catalytic solution; 0.5 part of attapulgite clay is placed in a round-bottom three-necked flask equipped with a condenser, evacuated to 1.5 kPa to displace nitrogen for protection, 50 parts of toluene is added, and stirred at a speed of 100 rpm for 20 min to obtain an attapulgite clay suspension; The prepared catalytic solution is added dropwise to the attapulgite clay suspension, and the volume ratio of the two solutions is 1:1. The dropping is controlled within 30 min. After the dropping is completed, heat reflux reaction is carried out for 8 h at a temperature of 40 °C. After the reaction is completed, filtration is carried out, and then washed with toluene at 40 °C by stirring for 10 min, and the solid-liquid ratio is 1:5. After repeating 3 times, evacuate to 0.085 MPa and dry at room temperature for 4 h to obtain modified attapulgite clay; Propylene is introduced into a three-necked flask replaced with nitrogen and propylene, then 100 parts of toluene is added, and the propylene pressure in the flask is maintained at 770 mmHg at a stirring speed of 60 rpm and a temperature of 70 °C. 0.003 part of Ziegler catalyst is added, and after stirring at the original speed for 6 min, 0.3 part of modified attapulgite clay is added. After reacting for 80 min, acidified ethanol is added to terminate the polymerization reaction, and washed with toluene in the same way as above, and then dried under vacuum at room temperature at 0.085 MPa for 7 h to obtain a polypropylene-attapulgite clay complex; The remaining steps are the same as those in Example 2.

[0040] Effect Example

[0041] The performance analysis results of a kind of high-performance composite modified polypropylene particles using Examples 1 to 3 and Comparative Examples 1 to 5 of the present invention are given in Table 1 below.

[0042] Table 1

[0043] Flame retardancy / 1.6 mm Vicat softening temperature / °C Example 1 V0 162 Example 2 V0 165 Example 3 V0 164 Comparative Example 1 V1 135 Comparative Example 2 V1 138 Comparative Example 3 V2 125 Comparative Example 4 V1 145 Comparative Example 5 V1 140

[0044] From the comparison of the experimental data on high-temperature resistance between the examples and the comparative examples, it can be found that in the present invention, a large number of phenolic hydroxyl groups and aldehyde groups contained in the lignin molecular structure are utilized. Using air as an oxidant and cobalt salt as a catalyst, lignin is oxidized, and some alcohol hydroxyl groups and aldehyde groups are oxidized into carboxyl groups. The retained phenolic hydroxyl groups achieve the effect of high-temperature resistance by strongly capturing free radicals. From the comparison of the experimental data on flame retardancy between the examples and the comparative examples, it can be found that in the present invention, aluminum nitrate is added to the carboxylated lignin and cobalt salt. The nitrate group reacts and combines with the carboxyl group, and reacts with the cobalt salt simultaneously to form a metal layered double hydroxide precipitate, which binds to the surface of the lignin to form a flame retardant filler. The lignin is rich in carbon content and can serve as a carbon source during the thermal decomposition process. It has a strong carbon-forming ability during combustion and can prevent the combustion of olefin polymers. Combining with the metal hydroxide on the surface of the lignin, metal ions can react with free radicals in the gas during the combustion process to form relatively stable compounds, achieving a synergistic dual-effect flame retardancy. The added attapulgite has a special fibrous porous crystal structure. Making full use of its structure and applying it to polypropylene particles can achieve high thermal stability and flame retardancy effects. However, the dispersibility and binding degree of attapulgite in polypropylene are not high. Therefore, in the present invention, the catalyst citric acid enters the interlayer of attapulgite clay, increasing the interlayer spacing of attapulgite clay or causing the layers to peel off from each other. Then, propylene monomers are intercalated into the expanded attapulgite clay, and then polymerized to form an inorganic-organic hybrid composite material. Finally, the flame retardant filler is added to the composite material. The attapulgite aerogel combines with the free radicals on the surface of the flame retardant filler, making the polypropylene particle material integrally combined, and improving its flame retardancy and high-temperature resistance performance.

[0045] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be construed as limiting the claimed rights.

Claims

1. A preparation method of a high-performance composite modified polypropylene particle, characterized in that, It includes the following preparation steps: (1) Prepare a lignin solution with a concentration of 30 wt% by mixing lignin and deionized water in proportion. Then, press air into the air distributor in the reaction kettle through an air compressor, and fully mix it with the lignin solution under stirring. The stirring speed is 350 - 550 rpm. Add a composite catalyst to the lignin solution and react at 50 - 140 °C for 30 - 480 min to obtain a carboxylated lignin solution. Slowly add 0.5 - 1.5 parts of aluminum nitrate to 5 - 10 parts of the carboxylated lignin solution, fully stir at 100 rpm for 20 - 40 min after mixing to dissolve the aluminum nitrate. The dissolved mixed solution is vigorously stirred at 80 - 100 °C for 18 - 30 h. After the reaction ends, filter to obtain the precipitate, wash it 3 times with deionized water, and dry it at normal temperature and pressure for 24 h to prepare a flame retardant filler; (2) Under the protection of an inert gas, evacuate to -0.085 MPa, and then heat attapulgite to 70 - 400 °C for dehydroxylation treatment for 2 - 12 h to obtain pretreated attapulgite. Mix the pretreated attapulgite and citric acid in proportion, first ultrasonic at 20 kHz power for 30 min, and then stir at 200 rpm at 70 - 90 °C for 12 h to obtain delaminated attapulgite. Dissolve 0.008 - 0.014 parts of the catalyst in 50 parts of toluene, stir at 100 rpm for 20 min to prepare a catalytic solution. Place 0.5 part of delaminated attapulgite in a round-bottom three-necked flask equipped with a condenser, evacuate to 1.5 kPa to displace the inert gas protection, add 50 parts of toluene, and stir at 100 rpm for 20 min to prepare an attapulgite suspension. Drop the prepared catalytic solution into the attapulgite suspension, and the volume ratio of the two solutions is 1:

1. The dropping is controlled within 30 min. After the dropping is completed, heat and reflux for 6 - 10 h at a temperature of 40 °C. After the reaction ends, filter, and then wash with toluene stirred at 40 °C for 10 min, repeat 3 times, evacuate to 0.085 MPa and dry at normal temperature for 4 h to obtain modified attapulgite. Introduce propylene into a three-necked flask replaced with nitrogen and propylene, then add 100 parts of toluene, keep the propylene pressure in the flask at 770 mmHg under stirring at 60 rpm, at a temperature of 50 - 90 °C, add 0.001 - 0.005 parts of the catalyst, keep stirring at the original speed for 2 - 10 min, then add 0.2 - 0.4 part of modified attapulgite, react for 40 - 120 min, add acidified ethanol to terminate the polymerization reaction, and wash in the same way as above with toluene, and then dry at 0.085 MPa under vacuum at normal temperature for 6 - 8 h to obtain a polypropylene-attapulgite composite; (3) Put the antioxidant, polypropylene wax, polypropylene-attapulgite complex, and flame retardant filler into a rotary mixer in a mass ratio of 0.2 - 0.6:20:5 - 10:2 - 5 and mix for 10 - 20 min. The rotational speed of the molten rotary mixer is 70 - 110 rpm. This mixture is melt granulated using a twin-screw extruder at a temperature of 180 - 210 °C to obtain modified polypropylene particles.

2. The preparation method of a high-performance composite modified polypropylene particle according to claim 1, wherein, In the step (1), the pressure during the carboxylation reaction is maintained at 0.02 - 1.0 MPa.

3. The preparation method of a high-performance composite modified polypropylene particle according to claim 1, wherein In the step (1), the mass ratio of the composite catalyst to the lignin solution is 1 - 3:

40.

4. The preparation method of a high-performance composite modified polypropylene particle according to claim 1, characterized in that, In the step (1), the preparation method of the composite catalyst is as follows: Mix cerium acetate, cobalt octanoate, and deionized water in a mass ratio of 1:3 - 10:200, and stir at a speed of 60 rpm for 10 min to obtain the composite catalyst.

5. The preparation method of a high-performance composite modified polypropylene particle according to claim 1, characterized in that, In the step (1), the stirring speed of the vigorous stirring is 800 - 1200 rpm.

6. The preparation method of a high-performance composite modified polypropylene particle according to claim 1, characterized in that, In the step (2), the inert gas is nitrogen.

7. The preparation method of a high-performance composite modified polypropylene particle according to claim 1, wherein, In the step (2), the mass ratio of attapulgite to citric acid is 10:0.5 - 2.

5.

8. The preparation method of a high-performance composite modified polypropylene particle according to claim 1, wherein, In the step (2), the catalyst is a Ziegler catalyst.

9. The preparation method of a high-performance composite modified polypropylene particle according to claim 1, wherein, In the step (2), the solid-liquid ratio during toluene washing is 1:

5.

10. The preparation method of a high-performance composite modified polypropylene particle according to claim 1, wherein, In the step (3), the antioxidant is a compound prepared by mixing antioxidant 1010 and antioxidant 168 in a mass ratio of 5:4.