A method and device for preparing flame-retardant modified polypropylene for woven bags

Abstract

The invention discloses a method and device for preparing flame-retardant modified polypropylene for woven bags, and belongs to the technical field of woven bags. The flame-retardant modified polypropylene for woven bags comprises the following components: by weight, by weight, 60-70 parts of polypropylene, 10-20 parts of microcapsules coated with modified zirconium phosphate hydrotalcite, and 15-25 parts of modified EPDM. The preparation method is as follows: (1) polypropylene and modified EPDM are mixed in a screw extruder to obtain a mixture, which is extruded into a centralized extruder; (2) microcapsules coated with modified zirconium phosphate hydrotalcite are extruded into a centralized extruder; (3) the mixture and the microcapsules coated with modified zirconium phosphate hydrotalcite are extruded from the centralized extruder at the same time to obtain filaments; (4) the filaments are cooled in a cooling device, and then extruded by an extrusion roller to obtain flat embryo wires. The present invention can improve the flame retardant properties, toughness, anti-aging properties and the like of polypropylene for woven bags, and extend its service life.

Description

Technical Field

[0001] The invention relates to a method and a device for preparing flame-retardant modified polypropylene for woven bags, belonging to the technical field of woven bags. Background Art

[0002] The main raw material for domestic woven bag production is polypropylene, which is a thermoplastic resin made by polymerization of propylene. It is usually a translucent colorless solid, odorless and non-toxic. Due to its regular structure and high degree of crystallization, polypropylene has a high melting point and is heat-resistant. Its products can be sterilized by steam, and its density is 0.90g / cm 3 , is a lightweight general-purpose plastic that also has excellent strength, rigidity and corrosion resistance.

[0003] However, polypropylene also has many disadvantages when used in woven bags, such as poor anti-aging performance, poor flame retardancy, poor toughness, etc. These disadvantages limit the use of polypropylene for woven bags. Therefore, it is very important to choose a suitable method to improve the performance of polypropylene for woven bags and prepare a polypropylene for woven bags with excellent performance. ` Summary of the invention

[0004] In view of the deficiencies of the prior art, the object of the present invention is to provide a method and device for preparing flame-retardant modified polypropylene for woven bags, so as to improve the flame retardant properties of polypropylene for woven bags and extend its service life.

[0005] In order to solve the above technical problems, the technical solutions provided by the present invention are as follows:

[0006] A flame-retardant modified polypropylene for woven bags comprises the following components: by mass, 60-70 parts of polypropylene, 10-20 parts of microcapsules coated with modified zirconium phosphate-hydrotalcite, and 15-25 parts of modified EPDM.

[0007] Furthermore, the surface layer of the flame-retardant modified polypropylene for the woven bag is a microcapsule coated with modified zirconium phosphate-hydrotalcite, and the inner layer is a mixture of polypropylene and modified EPDM. During combustion, the outer microcapsule wall material breaks, and the inner modified zirconium phosphate-hydrotalcite releases a large amount of water and carbon dioxide when thermally decomposed, absorbs a large amount of heat, can reduce the temperature of the combustion system, and generates carbides to form a dense protective layer, which can coat the polypropylene on the inside to prevent the inner layer of polypropylene from further burning. And the modified zirconium phosphate-hydrotalcite is coated inside with microcapsules, which can prevent the modified zirconium phosphate-hydrotalcite from being denatured when in contact with air, etc., affecting its flame retardant effect, and can also improve the moisture absorption resistance of polypropylene and extend the service life of the polypropylene woven bag.

[0008] A method for preparing flame-retardant modified polypropylene for woven bags comprises the following steps:

[0009] (1) Adding polypropylene and modified EPDM from the feed port I (1), mixing in the screw extruder I (2) to obtain a mixture, and then extruding through the extrusion port I (3) into the centralized extruder (8);

[0010] (2) adding microcapsules coated with modified zirconium phosphate-hydrotalcite from the feed port (5) and extruding through the extrusion port II (7) into the centralized extruder (8);

[0011] (3) the mixture and the microcapsules coated with modified zirconium phosphate-hydrotalcite are simultaneously extruded from a centralized extruder (8) to obtain filaments;

[0012] (4) The temperature controller (4) is turned on, the filaments are cooled in the cooling device (9), and then extruded by the extrusion roller (10) to obtain flat embryo filaments, thereby obtaining modified polypropylene for woven bags.

[0013] Furthermore, the preparation method of the microcapsules coated with modified zirconium phosphate-hydrotalcite is:

[0014] (1) Dissolve zirconium phosphate in water, add methylamine, stir, then add isopropanol, ultrasonicate for 30-40 minutes, filter, dry, and calcine for 1-6 hours to obtain zirconium phosphate peeling powder;

[0015] (2) mixing the acid-treated hollow microspheres and rare earth element salt, dissolving them in water, adding zirconium phosphate peeling powder, fully stirring and ultrasonically dispersing for 30-40 minutes, then heating the mixed solution to dryness, calcining, and performing low-temperature plasma treatment to obtain hollow microspheres and modified zirconium phosphate modified with rare earth elements;

[0016] (3) adding hollow microspheres and a modified zirconium phosphate solution modified with a rare earth element to an aqueous solution of magnesium salt and aluminum salt, adjusting the pH to 5-6, reacting at 80-85°C with stirring for 2-3 hours, then adjusting the pH to 10-11 with an alkaline solution, stirring at 70-80°C for 20-30 hours, filtering, washing, and drying at 100-120°C to obtain a modified zirconium phosphate-hydrotalcite;

[0017] (4) Modified zirconium phosphate-hydrotalcite, ethanol and sodium dodecylbenzene sulfonate aqueous solution are stirred at a temperature of 30-35°C and a stirring rate of 800-1200 r·min -1 The mixture was stirred for 30-45 minutes, and then a mixed solution of melamine and formaldehyde was added, the pH was adjusted to 3-4, and the mixture was stirred for 20-30 minutes, and then filtered, washed and dried to obtain microcapsules coated with modified zirconium phosphate-hydrotalcite.

[0018] The microcapsules encapsulate the modified zirconium phosphate-hydrotalcite to prevent the modified zirconium phosphate-hydrotalcite from being denatured when in contact with air and the like, which would affect its flame retardant effect. Moreover, both the microcapsules and the modified polyethylene are organic materials, and when the two are in contact, the interface bonding force between them is stronger, and the performance of the flame retardant modified polypropylene is more excellent.

[0019] Furthermore, in step (1), the ratio of zirconium phosphate to water is 1 g: 100-120 mL, and the mass ratio of zirconium phosphate to methylamine is 1: 2.5-3.0. The purpose of stirring is to mix the zirconium phosphate and methylamine evenly and make them gel.

[0020] Furthermore, in step (1), the calcination conditions are: N2 atmosphere, temperature 300-600°C.

[0021] Furthermore, in step (2), the acid-treated hollow microspheres are hollow microspheres that have been corroded by acid and have a rough surface, which is convenient for loading with zirconium phosphate, and the acid is one of hydrofluoric acid and nitric acid.

[0022] Furthermore, in step (2), the power of the plasma generator of the low-temperature plasma treatment is 7W, and the treatment time is 0.5-1h. Low-temperature plasma treatment can make the hollow microspheres and rare earth elements disperse better.

[0023] Furthermore, in step (3), the structure of the modified zirconium phosphate-hydrotalcite is: the structure of the modified zirconium phosphate-hydrotalcite is: the main layer of the hydrotalcite is magnesium and aluminum hydroxide, the interlayer is modified zirconium phosphate and anions, wherein the matrix of the modified zirconium phosphate is zirconium phosphate peeling, and the surface of the matrix is ​​loaded with hollow microspheres and rare earth elements. The addition of hollow microspheres can improve the hardness, stability, and weather resistance of the product, and has excellent heat insulation effect. When burning, it can isolate heat and reduce the loss of internal polypropylene.

[0024] Furthermore, the rare earth element is Ce. Ce can absorb ultraviolet rays and infrared rays, and after being added, it can enhance the anti-aging performance of the modified polypropylene and extend the service life of the polypropylene woven bag.

[0025] Furthermore, in step (3), the molar ratio of the magnesium salt to the aluminum salt is 2-3:1.

[0026] Furthermore, in step (3), the alkaline solution is a mixed solution of NaOH and Na2CO3.

[0027] Furthermore, in step (4), the melamine and formaldehyde mixed solution is prepared by mixing melamine and formaldehyde solutions at a mass ratio of 10:15-25, adjusting the pH to 7-8, and stirring for 15-25 minutes.

[0028] Furthermore, the preparation method of the modified EPDM is:

[0029] (1) Dissolve the nano-montmorillonite in deionized water, ultrasonicate for 20-30 min, add chitosan, disperse and stir at high speed for 15-20 min, filter and dry to obtain modified nano-montmorillonite;

[0030] (2) Melt EPDM in an internal mixer at a temperature of 170-200°C, add modified nano-montmorillonite, blend at a speed of 25-35 rpm for 10-15 minutes, and then vulcanize and crush to obtain modified EPDM.

[0031] Chitosan is introduced to modify montmorillonite to increase the compatibility of montmorillonite and EPDM. The modified montmorillonite is evenly mixed with EPDM and added to polypropylene. The modified montmorillonite has good stiffness and heat resistance, which can improve the hardness, flame retardancy and wear resistance of polypropylene, effectively prevent the damage of oxygen and ultraviolet light to polypropylene, and delay the aging of polypropylene. The addition of modified EPDM can increase the toughness of polypropylene, solve the problem of poor toughness of polypropylene, and improve the performance of polypropylene woven bags.

[0032] A preparation device for flame-retardant modified polypropylene for woven bags, comprising a centralized extruder (8), a cooling device (9) and an extrusion roller (10), wherein the centralized extruder (8), a screw extruder (2) and a screw extruder (6) are connected via a pipeline, the centralized extruder (8), the cooling device (9) and the extrusion roller (10) are connected in sequence, and the centralized extruder (8) comprises extrusion ports arranged in parallel.

[0033] Furthermore, the extrusion port includes an inner tube and an outer tube, the inner tube extrude a mixture of polypropylene and modified EPDM, and the outer tube extrude microcapsules coated with modified zirconium phosphate-hydrotalcite, and the two are extruded simultaneously to obtain modified polyethylene with a sandwich structure.

[0034] Furthermore, the extrusion roller (10) is connected to a winding system (11). By setting the temperature of the extrusion roller, the modified polypropylene is extruded by the roller to obtain a polypropylene flat yarn for woven bags. The flat yarn is heat-set by a hot roller in the winding system, shrunk at a low traction speed, and then treated at a low temperature by a cold roller, and finally wound into shape.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] (1) The flame-retardant modified polypropylene for woven bags of the present invention has a surface layer of microcapsules coated with modified zirconium phosphate-hydrotalcite, and an inner layer of a mixture of polypropylene and modified EPDM. When burning, the outer microcapsule wall material breaks, and the inner modified zirconium phosphate-hydrotalcite releases a large amount of water and carbon dioxide when it is thermally decomposed, absorbs a large amount of heat, can reduce the temperature of the combustion system, and generates carbides to form a dense protective layer, which coats the polypropylene on the inner side, thereby preventing the inner polypropylene from further burning.

[0037] (2) The present invention uses microcapsules to encapsulate the modified zirconium phosphate-hydrotalcite, which can prevent the modified zirconium phosphate-hydrotalcite from being denatured when in contact with air and the like, thereby affecting its flame retardant effect. The rare earth elements, hollow microbeads, etc. in the microcapsules can absorb ultraviolet rays and infrared rays, thereby enhancing the anti-aging, weather resistance, strength and other properties of the modified polypropylene. At the same time, it can also improve the anti-moisture absorption performance of polypropylene and extend the service life of the polypropylene woven bag.

[0038] (3) The present invention uniformly mixes modified montmorillonite and EPDM and then adds them to polypropylene. The modified montmorillonite can effectively prevent the damage of oxygen and ultraviolet light to polypropylene and delay the aging of polypropylene. The addition of modified EPDM can increase the toughness of polypropylene, solve the problem of poor toughness of polypropylene, and improve the performance of polypropylene woven bags.

[0039] (4) The present invention only needs to use the prepared three components to produce flame-retardant modified polypropylene using a preparation device, without the need to add components such as a compatibilizer. The operation method is simple. The prepared flame-retardant modified polypropylene has multiple excellent properties such as good toughness and anti-aging, thereby broadening the application market of woven bags.

[0040] (5) The device of the present invention directly cools the polypropylene filaments and then extrude them into flat wires through rollers, and cuts the flat wires into different lengths for woven bags of different specifications. The operation is simple and convenient, and there is no need to cut them into embryonic wires and then draw them, thereby reducing the number of processes, saving manpower and material resources, and reducing production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a preparation device for flame-retardant modified polypropylene for woven bags;

[0042] Figure 2 This is a schematic diagram of the extrusion port arrangement of the centralized extruder;

[0043] Figure 3 It is a schematic diagram of a single extrusion port in a centralized extruder;

[0044] Among them, 1. feeding port Ⅰ; 2. screw extruder Ⅰ; 3. extrusion port Ⅰ; 4. temperature controller; 5. feeding port Ⅱ; 6. screw extruder Ⅱ; 7. extrusion port Ⅱ; 8. centralized extruder; 9. cooling device; 10. extrusion roller; 11. winding system. DETAILED DESCRIPTION

[0045] Example 1

[0046] A flame-retardant modified polypropylene for woven bags comprises the following components: by mass, 60 parts of polypropylene, 20 parts of microcapsules coated with modified zirconium phosphate-hydrotalcite, and 20 parts of modified EPDM.

[0047] The preparation method of the microcapsules coated with modified zirconium phosphate-hydrotalcite is as follows:

[0048] (1) Dissolve zirconium phosphate in water, add methylamine, stir, then add isopropanol, ultrasonicate for 30 min, filter, dry, and calcine for 6 h to obtain zirconium phosphate exfoliation powder;

[0049] (2) hollow microspheres and rare earth element salts are mixed and dissolved in water to prepare an impregnation solution, zirconium phosphate exfoliation powder is added, fully stirred and ultrasonically dispersed for 40 minutes, and then the mixed solution is heated to evaporate and calcined, and low-temperature plasma treatment is performed to obtain hollow microspheres and modified zirconium phosphate modified with rare earth elements;

[0050] (3) adding hollow microspheres and a modified zirconium phosphate solution modified with a rare earth element to an aqueous solution of magnesium salt and aluminum salt, adjusting the pH to 5, reacting at 80°C for 3 hours under stirring, then adjusting the pH to 10 with an alkaline solution, stirring at 70°C for 30 hours, filtering, collecting the precipitate, washing, and drying at 120°C to obtain a modified zirconium phosphate-hydrotalcite;

[0051] (4) Modified zirconium phosphate-hydrotalcite, ethanol and sodium dodecylbenzene sulfonate aqueous solution were stirred at 30 °C and 1200 r·min. -1 The mixture was stirred for 30 min, and then melamine and formaldehyde mixture was added to adjust the pH to 3. The mixture was stirred for 30 min, and then filtered, washed and dried to obtain microcapsules coated with modified zirconium phosphate-hydrotalcite.

[0052] Note: EPDM is ethylene propylene diene monomer rubber.

[0053] Example 2

[0054] A flame-retardant modified polypropylene for woven bags comprises the following components: by mass, 70 parts of polypropylene, 10 parts of microcapsules coated with modified zirconium phosphate-hydrotalcite, and 20 parts of modified EPDM.

[0055] The preparation method of the microcapsules coated with modified zirconium phosphate-hydrotalcite is as follows:

[0056] (1) Dissolve zirconium phosphate in water, add methylamine, stir, then add isopropanol, ultrasonicate for 40 min, filter, dry, and calcine for 1 h to obtain zirconium phosphate exfoliation powder;

[0057] (2) hollow microspheres and rare earth element salts are mixed and dissolved in water to prepare an impregnation solution, zirconium phosphate exfoliation powder is added, fully stirred and ultrasonically dispersed for 30 minutes, and then the mixed solution is heated to evaporate and calcined, and low-temperature plasma treatment is performed to obtain hollow microspheres and modified zirconium phosphate modified with rare earth elements;

[0058] (3) adding hollow microspheres and modified zirconium phosphate solution modified by rare earth elements to the magnesium salt and aluminum salt aqueous solution, adjusting the pH to 6, reacting at 85°C with stirring for 2 hours, then adjusting the pH to 11 with an alkaline solution, stirring at 80°C for 20 hours, filtering, collecting the precipitate, washing, and drying at 100°C to obtain modified zirconium phosphate-hydrotalcite;

[0059] (4) Modified zirconium phosphate-hydrotalcite, ethanol and sodium dodecylbenzene sulfonate aqueous solution were stirred at 35 °C and 800 r·min -1 The mixture was stirred for 45 min, and then a mixture of melamine and formaldehyde was added, the pH was adjusted to 4, and the mixture was stirred for 20 min. The mixture was then filtered, washed, and dried to obtain microcapsules coated with modified zirconium phosphate-hydrotalcite.

[0060] Example 3

[0061] A flame-retardant modified polypropylene for woven bags comprises the following components: by mass, 65 parts of polypropylene, 15 parts of microcapsules coated with modified zirconium phosphate-hydrotalcite, and 20 parts of modified EPDM.

[0062] The preparation method of the microcapsules coated with modified zirconium phosphate-hydrotalcite is as follows:

[0063] (1) Dissolve zirconium phosphate in water, add methylamine, stir, then add isopropanol, ultrasonicate for 35 minutes, filter, dry, and calcine for 4 hours to obtain zirconium phosphate exfoliation powder;

[0064] (2) hollow microspheres and rare earth element salts are mixed and dissolved in water to prepare an impregnation solution, zirconium phosphate exfoliation powder is added, fully stirred and ultrasonically dispersed for 35 minutes, and then the mixed solution is heated to evaporate and calcined, and low-temperature plasma treatment is performed to obtain hollow microspheres and rare earth element modified zirconium phosphate;

[0065] (3) adding hollow microspheres and modified zirconium phosphate solution modified by rare earth elements to the magnesium salt and aluminum salt aqueous solution, adjusting the pH to 5, reacting at 80°C with stirring for 3 hours, then adjusting the pH to 10 with an alkaline solution, stirring at 75°C for 25 hours, filtering, collecting the precipitate, washing, and drying at 110°C to obtain modified zirconium phosphate-hydrotalcite;

[0066] (4) Modified zirconium phosphate-hydrotalcite, ethanol and sodium dodecylbenzene sulfonate aqueous solution were stirred at 30 °C and 1000 r·min. -1 The mixture was stirred for 40 min, and then a mixture of melamine and formaldehyde was added, the pH was adjusted to 4, and the mixture was stirred for 25 min. The mixture was then filtered, washed, and dried to obtain microcapsules coated with modified zirconium phosphate-hydrotalcite.

[0067] Example 4

[0068] A flame-retardant modified polypropylene for woven bags comprises the following components: by mass, 60 parts of polypropylene, 15 parts of microcapsules coated with modified zirconium phosphate-hydrotalcite, and 25 parts of modified EPDM.

[0069] The preparation method of the microcapsules coated with modified zirconium phosphate-hydrotalcite is as follows:

[0070] (1) Dissolve zirconium phosphate in water, add methylamine, stir, then add isopropanol, ultrasonicate for 30 minutes, filter, dry, and calcine for 3 hours to obtain zirconium phosphate exfoliation powder;

[0071] (2) hollow microspheres and rare earth element salts are mixed and dissolved in water to prepare an impregnation solution, zirconium phosphate exfoliation powder is added, fully stirred and ultrasonically dispersed for 35 minutes, and then the mixed solution is heated to evaporate and calcined, and low-temperature plasma treatment is performed to obtain hollow microspheres and rare earth element modified zirconium phosphate;

[0072] (3) adding hollow microspheres and a modified zirconium phosphate solution modified with a rare earth element to an aqueous solution of magnesium salt and aluminum salt, adjusting the pH to 6, reacting at 85°C with stirring for 3 hours, then adjusting the pH to 11 with an alkaline solution, stirring at 75°C for 25 hours, filtering, collecting the precipitate, washing, and drying at 110°C to obtain a modified zirconium phosphate-hydrotalcite;

[0073] (4) Modified zirconium phosphate-hydrotalcite, ethanol and sodium dodecylbenzene sulfonate aqueous solution were stirred at a temperature of 35°C and a stirring rate of 1100 r·min. -1 The mixture was stirred for 35 min, and then a mixed solution of melamine and formaldehyde was added, the pH was adjusted to 3, and the mixture was stirred for 25 min. The mixture was then filtered, washed, and dried to obtain microcapsules coated with modified zirconium phosphate-hydrotalcite.

[0074] Example 5

[0075] A flame-retardant modified polypropylene for woven bags comprises the following components: by mass, 65 parts of polypropylene, 25 parts of microcapsules coated with modified zirconium phosphate-hydrotalcite, and 20 parts of modified EPDM.

[0076] The preparation method of the microcapsules coated with modified zirconium phosphate-hydrotalcite is as follows:

[0077] (1) Dissolve zirconium phosphate in water, add methylamine, stir, then add isopropanol, ultrasonicate for 30 minutes, filter, dry, and calcine for 3 hours to obtain zirconium phosphate exfoliation powder;

[0078] (2) hollow microspheres and rare earth element salts are mixed and dissolved in water to prepare an impregnation solution, zirconium phosphate exfoliation powder is added, fully stirred and ultrasonically dispersed for 35 minutes, and then the mixed solution is heated to evaporate and calcined, and low-temperature plasma treatment is performed to obtain hollow microspheres and rare earth element modified zirconium phosphate;

[0079] (3) adding hollow microspheres and a modified zirconium phosphate solution modified with a rare earth element to an aqueous solution of magnesium salt and aluminum salt, adjusting the pH to 6, reacting at 85°C with stirring for 3 hours, then adjusting the pH to 11 with an alkaline solution, stirring at 70°C for 25 hours, filtering, collecting the precipitate, washing, and drying at 110°C to obtain a modified zirconium phosphate-hydrotalcite;

[0080] (4) Modified zirconium phosphate-hydrotalcite, ethanol and sodium dodecylbenzene sulfonate aqueous solution were stirred at a temperature of 35°C and a stirring rate of 1100 r·min. -1 The mixture was stirred for 35 min, and then a mixed solution of melamine and formaldehyde was added, and the pH was adjusted to 4. The mixture was stirred for 25 min, and then filtered, washed and dried to obtain microcapsules coated with modified zirconium phosphate-hydrotalcite.

[0081] Comparative Example 1

[0082] A flame retardant modified polypropylene for woven bags comprises the following components: 65 parts of polypropylene and 15 parts of modified EPDM, by weight, and is prepared in the same steps as in Example 3 according to the method and device of the present invention.

[0083] Comparative Example 2

[0084] Without adding hollow microbeads, the remaining steps were the same as those in Example 3.

[0085] Comparative Example 3

[0086] No rare earth element is added, and the remaining steps are the same as those in Example 3.

[0087] Comparative Example 4

[0088] Step (4) is not performed, and the remaining steps are the same as those in Example 3.

[0089] Comparative Example 5

[0090] A flame retardant modified polypropylene for woven bags comprises the following components: by weight, 65 parts of polypropylene and 15 parts of microcapsules coated with modified zirconium phosphate-hydrotalcite. The steps are the same as those in Example 3 and the material is prepared according to the method and device of the present invention.

[0091] Comparative Example 6

[0092] A flame retardant modified polypropylene for woven bags comprises the following components: by mass, 65 parts of polypropylene, 15 parts of microcapsules coated with modified zirconium phosphate-hydrotalcite, and 20 parts of modified EPDM. The steps are the same as those in Example 3, but the preparation is carried out according to a conventional method and apparatus, that is, the above three raw materials are first mixed and then the mixture is extruded and drawn.

[0093] Experimental Example 1

[0094] The flame retardant modified polypropylene of Examples 1-5 was tested according to the test method specified in GB / T2406.2-2009 "Determination of Combustion Behavior of Plastics by Oxygen Index Method Part 2: Room Temperature Test" to test its oxygen index, and the test was repeated three times to take the average value. The test results are listed in Table 1.

[0095] Table 1. Oxygen index test

[0096]

[0097] As can be seen from Table 1, the oxygen index of the flame retardant modified polypropylene in Example 1 is 34.8%, the oxygen index of the flame retardant modified polypropylene in Example 2 is 35.2%, the oxygen index of the flame retardant modified polypropylene in Example 3 is 35.4%, the oxygen index of the flame retardant modified polypropylene in Example 4 is 35.1%, and the oxygen index of the flame retardant modified polypropylene in Example 5 is 34.9%. It can be seen that the oxygen index of the flame retardant modified polypropylene prepared by the present invention is greater than 34.8%, indicating that the flame retardant modified polypropylene prepared by the present invention has good flame retardant properties.

[0098] Experimental Example 2

[0099] The flame retardant modified polypropylene of Example 1-5 was irradiated with an intensity of 600 W / m 2 The cumulative irradiation is 400kWh / m 2 , respectively, the tensile strength, impact strength and impact strength retention of the samples before and after light aging were tested. The tests were repeated three times and the average values ​​were taken. The test results are listed in Table 2.

[0100] Table 2. Toughness and anti-aging performance test

[0101]

[0102] As shown in Table 2, the tensile strength of the flame retardant modified polypropylene of Examples 1-5 is 80.9-81.7 MPa, the tensile strength after light aging is 73.5-75.9 MPa, and the impact strength is 56.3-57.2 kJ / m 2 The impact strength after light aging is 54.6-55.6 kJ / m 2 The impact strength retention rate is greater than 96.2%, indicating that the flame retardant modified polypropylene prepared by the present invention has excellent toughness and anti-aging properties.

[0103] Experimental Example 3

[0104] The flame retardant modified polypropylene of Example 3 and Comparative Examples 1-5 was tested according to the test method specified in GB / T2406.2-2009 "Determination of Combustion Behavior of Plastics by Oxygen Index Method Part 2: Room Temperature Test" to test its oxygen index, and the test was repeated three times to take the average value. The test results are listed in Table 3.

[0105] Table 3. Flame retardant performance test

[0106]

[0107] As can be seen from Table 3, in Comparative Example 1, the oxygen index of the flame retardant modified polypropylene prepared without adding microcapsules coated with modified zirconium phosphate-hydrotalcite is 22.1%, in Comparative Example 2, the oxygen index of the flame retardant modified polypropylene prepared without adding hollow microspheres is 26.3%, in Comparative Example 3, the oxygen index of the flame retardant modified polypropylene prepared without adding rare earth elements is 29.9%, in Comparative Example 4, the oxygen index of the flame retardant modified polypropylene prepared without coating modified zirconium phosphate-hydrotalcite is 30.7%, in Comparative Example 5, the oxygen index of the flame retardant modified polypropylene prepared without adding EPDM is 32.0%, and in Comparative Example 6, the oxygen index of the flame retardant modified polypropylene prepared by conventional blending is 29.4%, because the surface of the modified polypropylene prepared after blending is partially exposed to flammable polypropylene. The oxygen index of the flame retardant modified polypropylene of Comparative Examples 1-6 is lower than that of Example 3. It can be seen that the preparation method and device of the present invention and the addition of hollow microspheres, rare earth elements and other substances can improve the flame retardant properties of flame retardant modified polypropylene to varying degrees.

[0108] Experimental Example 4

[0109] The flame retardant modified polypropylene of Example 3 and Comparative Examples 1-6 was irradiated with an intensity of 600 W / m 2 The cumulative irradiation is 400kWh / m 2 , respectively, the tensile strength, impact strength and impact strength retention of the samples before and after light aging were tested. The tests were repeated three times and the average values ​​were taken. The test results are listed in Table 4.

[0110] Table 4. Toughness and anti-aging performance test

[0111]

[0112] As can be seen from Table 4, the tensile strength and impact strength of the flame retardant modified polypropylene of Comparative Examples 1-6 before and after light aging are lower than those of Example 3, and the impact strength retention rate is also lower than that of Example 3, indicating that the preparation method and device of the present invention and the addition of hollow microspheres, rare earth elements and other substances can improve the toughness and anti-aging properties of the flame retardant modified polypropylene to varying degrees.

[0113] Experimental Example 5

[0114] The flame retardant modified polypropylene of Example 3, Comparative Example 4 and Comparative Example 6 were placed in the same outdoor environment for 0, 3, 6 and 12 months, and tested according to the test method specified in GB / T2406.2-2009 "Determination of Combustion Behavior of Plastics by Oxygen Index Method Part 2: Room Temperature Test" to test their oxygen index, and the test was repeated three times to take the average value. The test results are listed in Table 5.

[0115] Table 5. Flame retardant performance test

[0116]

[0117] It can be seen from Table 5 that after the flame retardant modified polypropylene of Example 3 was placed in an outdoor environment for 12 months, the oxygen index decreased from 35.4% to 34.1%, a decrease of 1.3%. After the flame retardant modified polypropylene of Comparative Example 4 was placed in an outdoor environment for 12 months, the oxygen index decreased from 30.7% to 26.9%, a decrease of 3.8%. After the flame retardant modified polypropylene of Comparative Example 6 was placed in an outdoor environment for 12 months, the oxygen index decreased from 29.4% to 26.6%, a decrease of 2.8%. It can be seen that the present invention uses microcapsules to encapsulate the modified zirconium phosphate-hydrotalcite, and uses the microcapsules encapsulating the modified zirconium phosphate-hydrotalcite as the surface layer of the flame retardant modified polypropylene, which can prevent the modified zirconium phosphate-hydrotalcite from being denatured when in contact with air, etc., and affect the flame retardant effect of the flame retardant modified polypropylene.

Claims

1. A flame retardant modified polypropylene for woven bags, characterized in that: The invention comprises the following components: by weight, 60-70 parts of polypropylene, 10-20 parts of microcapsules coated with modified zirconium phosphate-hydrotalcite, and 15-25 parts of modified EPDM; The surface layer of the flame-retardant modified polypropylene for woven bags is microcapsules coated with modified zirconium phosphate-hydrotalcite, and the inner layer is a mixture of polypropylene and modified EPDM; the structure of the modified zirconium phosphate-hydrotalcite is: the main layer of the hydrotalcite is magnesium and aluminum hydroxide, and the interlayer is modified zirconium phosphate and anions, wherein the matrix of the modified zirconium phosphate is zirconium phosphate peeling, and the surface of the matrix is ​​loaded with hollow microspheres and rare earth elements; The preparation method of the microcapsules coated with modified zirconium phosphate-hydrotalcite is: (1) Dissolve zirconium phosphate in water, add methylamine, stir, then add isopropanol, ultrasonicate for 30-40 minutes, filter, dry, and calcine for 1-6 hours to obtain zirconium phosphate peeling powder; (2) mixing the acid-treated hollow microspheres and rare earth element salt, dissolving them in water, adding zirconium phosphate peeling powder, fully stirring and ultrasonically dispersing for 30-40 minutes, then heating the mixed solution to dryness, calcining, and performing low-temperature plasma treatment to obtain hollow microspheres and modified zirconium phosphate modified with rare earth elements; (3) adding hollow microspheres and a modified zirconium phosphate solution modified with a rare earth element to an aqueous solution of magnesium salt and aluminum salt, adjusting the pH to 5-6, reacting at 80-85°C with stirring for 2-3 hours, then adjusting the pH to 10-11 with an alkaline solution, stirring at 70-80°C for 20-30 hours, filtering, washing, and drying at 100-120°C to obtain a modified zirconium phosphate-hydrotalcite; (4) Modified zirconium phosphate-hydrotalcite, ethanol and sodium dodecylbenzene sulfonate aqueous solution are stirred at a temperature of 30-35°C and a stirring rate of 800-1200 r·min -1 The mixture was stirred for 30-45 minutes, and then a mixture of melamine and formaldehyde was added to adjust the pH to 3-4, and stirred for 20-30 minutes, and then filtered, washed, and dried to obtain microcapsules coated with modified zirconium phosphate-hydrotalcite; The preparation device of flame-retardant modified polypropylene for woven bags comprises a centralized extruder (8), a cooling device (9) and an extrusion roller (10), wherein the centralized extruder (8) is connected to a screw extruder I (2) and a screw extruder II (6) via a pipeline, and the centralized extruder (8), the cooling device (9) and the extrusion roller (10) are connected in sequence, and the centralized extruder (8) comprises extrusion ports arranged in parallel; the extrusion ports comprise an inner tube and an outer tube, the inner tube extruding a mixture of polypropylene and modified EPDM, and the outer tube extruding microcapsules coated with modified zirconium phosphate-hydrotalcite, and the two are extruded simultaneously to obtain a modified polyethylene with a sandwich structure.

2. The flame retardant modified polypropylene for woven bags according to claim 1, characterized in that: The squeezing roller (10) is connected to the winding system (11).

3. The flame retardant modified polypropylene for woven bags according to claim 1, characterized in that: In step (1), the ratio of zirconium phosphate to water is 1 g:100-120 mL, and the mass ratio of zirconium phosphate to methylamine is 1:2.5-3.

0.

4. A method for preparing the flame retardant modified polypropylene for woven bags according to claim 1, characterized in that: The steps include: (1) Adding polypropylene and modified EPDM from the feed port I (1), mixing in the screw extruder I (2) to obtain a mixture, and then extruding through the extrusion port I (3) into the centralized extruder (8); (2) adding microcapsules coated with modified zirconium phosphate-hydrotalcite from the feed port II (5), and extruding through the extrusion port II (7) into the centralized extruder (8); (3) the mixture and the microcapsules coated with modified zirconium phosphate-hydrotalcite are simultaneously extruded from a centralized extruder (8) to obtain filaments; (4) The temperature controller (4) is turned on, the filaments are cooled in the cooling device (9), and then extruded by the extrusion roller (10) to obtain flat embryo filaments, thereby obtaining modified polypropylene for woven bags.

5. The method for preparing flame retardant modified polypropylene for woven bags according to claim 4, characterized in that: In step (1), the preparation method of the modified EPDM is: (1) Dissolve the nano-montmorillonite in deionized water, ultrasonicate for 20-30 min, add chitosan, disperse and stir at high speed for 15-20 min, filter and dry to obtain modified nano-montmorillonite; (2) Melt EPDM in an internal mixer at a temperature of 170-200°C, add modified nano-montmorillonite, blend at a speed of 25-35 rpm for 10-15 minutes, and then vulcanize and crush to obtain modified EPDM.

Images