An ultra-low melt index high-filled halogen-free flame-retardant polypropylene material and its preparation method

Abstract

The present invention relates to the field of polypropylene materials, and particularly relates to an ultra-low melt index, highly filled, halogen-free flame-retardant polypropylene material and a preparation method thereof. The preparation method feeds raw material components into a twin-screw extruder, and after co-mixing and melting and extrusion, a polypropylene material is obtained; the thread blocks in the kneading section of the twin-screw extruder sequentially include a forward conveying type thread block, a multi-head kneading thread block, a forward conveying type thread block, a multi-head kneading thread block, a forward conveying type thread block, a forward shearing thread block, and a forward conveying type thread block along the material conveying direction; the present invention solves the problems that powder is easily accumulated at the feeding port and the powder at the feeding port is easily scattered during the processing of ultra-low melt index, highly filled, halogen-free flame-retardant polypropylene; it solves the problems of hollow polypropylene material particles, particle foaming, and unqualified flame retardancy, and improves the stability of the quality of the products in the manufacturing process; the polypropylene material prepared by this preparation method has excellent flame-retardant performance and maintains good mechanical properties.

Description

Technical Field

[0001] The present invention relates to the field of polypropylene materials, and particularly to an ultra-low melt index, high-fill, halogen-free flame-retardant polypropylene material and a preparation method thereof. Background Art

[0002] Polypropylene (PP for short) is a semi-crystalline thermoplastic. It has high impact resistance, strong mechanical properties, and is resistant to a variety of organic solvents and acid-base corrosion. It is widely used in fields such as household appliances and automobiles. In order to make it have flame-retardant safety, flame retardants are added and the flame-retardant effect is improved by blending through a twin-screw extruder.

[0003] Brominated flame retardants are widely used in flame-retardant PP materials due to their high flame-retardant efficiency. However, when a fire occurs, the materials modified with brominated flame retardants will produce toxic gases during combustion, causing secondary harm. At present, many fields promote halogen-free flame retardants (such as nitrogen-phosphorus flame retardants). Different from halogen-containing flame retardants, the special environmental-friendly halogen-free flame retardant for PP achieves the purpose of flame retardancy by generating a dense expanded carbon layer during combustion, and there will be no irritating hydrogen halide gas and black smoke. It is an environmental-friendly flame retardant. However, when preparing an ultra-low melt index, high-fill, halogen-free flame-retardant polypropylene material by adding a halogen-free flame retardant, the halogen-free flame retardant is in powder form. Due to the high filling ratio of the halogen-free flame retardant, the feeding port is prone to powder accumulation during the processing process, and there is a lot of powder. The powder at the feeding port and the exhaust port is easy to disperse, affecting the on-site environment. In addition, the particles of the polypropylene material are prone to foaming during the extrusion process, and the foaming characteristics lead to porous particles that are easy to absorb water, which not only causes poor appearance of the particles but also results in unqualified flame retardancy.

[0004] Therefore, how to avoid the above problems: the problems of easy powder accumulation at the feeding port and easy dispersion of powder at the feeding port during the processing of the ultra-low melt index, high-fill, halogen-free flame-retardant polypropylene material, and the problems that the particles of the prepared polypropylene material are prone to foaming during the extrusion process, the particles are porous and easy to absorb water, which not only causes poor appearance of the particles but also results in unqualified flame retardancy, are exactly what the technical field urgently needs to solve. Summary of the Invention

[0005] To solve the deficiencies and defects of the existing solutions mentioned in the above background art, the present invention provides a preparation method of an ultra-low melt index, high-fill, halogen-free flame-retardant polypropylene material.

[0006] The technical solution of the preparation method of the ultra-low melt index, high-fill, halogen-free flame-retardant polypropylene material is as follows:

[0007] The raw material components are fed into a twin-screw extruder, and a polypropylene material is obtained after blending, melting, and extrusion. By weight, the raw material components include 61-66 parts of polypropylene resin, 32-37 parts of a halogen-free flame retardant, and 1.6-2.2 parts of other additives. The twin-screw extruder sequentially includes a feeding section, a melting and plasticizing section, a kneading section, a degassing section, and a metering section along the material conveying direction. The screw blocks in the kneading section sequentially include forward conveying screw blocks, multi-head kneading screw blocks, forward conveying screw blocks, multi-head kneading screw blocks, forward conveying screw blocks, forward shearing screw blocks, and forward conveying screw blocks along the material conveying direction. A main feeding port is provided on the feeding section, and a side feeding port is provided on the kneading section. The polypropylene resin, other additives, and the first part of the halogen-free flame retardant are fed through the main feeding port, and the second part of the halogen-free flame retardant is fed through the side feeding port. The sum of the weights of the first part of the halogen-free flame retardant and the second part of the halogen-free flame retardant is the total amount of the halogen-free flame retardant.

[0008] In view of the above-mentioned formulation of the polypropylene material with a high filling of halogen-free flame retardant, according to the characteristics of the high addition amount of the halogen-free flame retardant, the halogen-free flame retardant is divided into two parts. One part is fed into the twin-screw extruder through the main feeding port, and the other part is fed into the twin-screw extruder through the side feeding port. By adopting this optimized feeding method in combination with the screw combination method, the problems of powder accumulation and powder floating at the feeding port during the processing can be solved. Among them, the present invention optimizes the arrangement of the screw blocks in the kneading section, and sets the screw blocks in the kneading section to sequentially include forward conveying screw blocks, multi-head kneading screw blocks, forward conveying screw blocks, multi-head kneading screw blocks, forward conveying screw blocks, forward shearing screw blocks, and forward conveying screw blocks along the material conveying direction. Among them, the conventionally arranged shearing elements (i.e., shearing screw blocks) are used to shear, mix, and melt the material, and the conventionally arranged conveying elements (i.e., conveying screw blocks) are used to convey the material, and pressure is established through the changes in the pitch and the screw groove. The present invention specifically introduces multi-head kneading screw blocks (FKB elements) into the kneading section to strengthen the dispersion distribution in the kneading section. The multi-head kneading screw element is a screw element with multiple heads in the middle and two heads at both ends. When the multi-head kneading screw element is used in the kneading section, the middle has multiple heads and both ends have two heads, and the shearing is uniform, overcoming the drawback of uneven shearing of the two-head screw element, and having the advantages of uniform shearing, achieving better melting, and improving the ability of dispersion distribution.

[0009] In summary, through the optimization of the feeding methods of different materials at the main feeding port and the side feeding port, and the synchronous optimization of the screw combination arrangement, the present invention introduces FKB elements in the kneading section in cooperation with the conveying screw blocks and the forward shearing screw blocks. Therefore, during the processing of the ultra-low melt index and high filling halogen-free flame retardant polypropylene material of the present invention, there is no powder accumulation at the feeding port, the powder at the discharging port does not float, and the obtained polypropylene material particles have no holes, have excellent flame retardant properties, and maintain good mechanical properties.

[0010] In one embodiment, the weight ratio of the first part of the halogen-free flame retardant to the second part of the halogen-free flame retardant is (20 - 25):(10 - 15).

[0011] In one embodiment, the kneading section is sequentially composed of the following screw blocks along the material conveying direction: 96 / 96*2, 72 / 72*2, FKB90 / 7 / 75*1, 56 / 56*2, FKB90 / 7 / 75*1, 44 / 44*3, K60 / 4 / 44*2, 44 / 44*2.

[0012] In one embodiment, the other additives include an antioxidant, a lubricant, and a black masterbatch; by weight, the raw material components include 61 - 66 parts of polypropylene resin, 32 - 37 parts of halogen-free flame retardant, 0.3 - 0.6 parts of antioxidant, 0.3 - 0.6 parts of lubricant, and 1 part of black masterbatch.

[0013] In one embodiment, the length-diameter ratio of the screw of the twin-screw extruder is ( 40 - 48 ) :1, the barrel temperature is 180°C - 200°C, and the screw speed is ( 400 - 500 ) rpm.

[0014] In one embodiment, the feeding section includes a forward conveying type screw block; the melting and plasticizing section sequentially includes a forward shearing screw block and a reverse conveying type screw block along the material conveying direction.

[0015] In one embodiment, the exhaust section sequentially includes a reverse conveying type screw block and a forward conveying type screw block along the material conveying direction; the metering section sequentially includes a forward conveying type screw block, a forward shearing screw block, and a forward conveying type screw block along the material conveying direction.

[0016] In one embodiment, the misalignment angle of the sheet-shaped shear slices of the forward shearing screw block is 45° or 60° or 90°, the actual length of the sheet-shaped shear slices is 44 - 72, and the number of discs of the sheet-shaped shear slices is 3 or 4 or 5.

[0017] In one embodiment, the feeding section is sequentially composed of the following screw blocks along the material conveying direction: 56 / 56A, 96 / 96*3, 72 / 72, 56 / 56*3; the melting and plasticizing section is sequentially composed of the following screw blocks along the material conveying direction: K45 / 5 / 72, K45 / 5 / 56*4, K60 / 4 / 44, 44 / 22L; the exhaust section is sequentially composed of the following screw blocks along the material conveying direction: 44 / 22L, 96 / 96*2, 72 / 72; the metering section is sequentially composed of the following screw blocks along the material conveying direction: 56 / 56*2, K45 / 5 / 44, 44 / 44*2.

[0018] The present invention also provides an ultra-low melt index, highly filled, halogen-free flame-retardant polypropylene material, which is prepared by the preparation method of the ultra-low melt index, highly filled, halogen-free flame-retardant polypropylene material as described above.

[0019] The preparation method of the ultra-low melt index, highly filled, halogen-free flame-retardant polypropylene material provided by the present invention has the following beneficial effects compared with the prior art:

[0020] Through the optimization of process conditions, the present invention solves the problems that the feeding port is prone to powder accumulation and the powder at the feeding port is prone to dispersion during the processing of ultra-low melt index, highly filled, halogen-free flame-retardant polypropylene, and avoids the impact of floating powder on the on-site environment; through the optimization of the screw combination, the dispersion and distribution uniformity of polypropylene resin and flame retardant are strengthened, and the problems of hollow particles, foamed particles and unqualified flame retardancy of polypropylene materials are solved, improving the stability of the product quality in the manufacturing process; the polypropylene material prepared by this preparation method has excellent flame retardant performance and maintains good mechanical properties. Description of the Drawings

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0022] Figure 1 Schematic diagram of the screw combination structure of Embodiment 1 provided by the present invention;

[0023] Figure 2 Schematic diagram of the structure of the FKB element;

[0024] Figure 3 Appearance diagram of the polypropylene material particles prepared in Comparative Example 1 provided by the present invention;

[0025] Figure 4 Appearance diagram of the polypropylene material particles prepared in Comparative Example 2 provided by the present invention;

[0026] Figure 5 Appearance diagram of the polypropylene material particles prepared in Comparative Example 3 provided by the present invention;

[0027] Figure 6 Appearance diagram of the polypropylene material particles prepared in Embodiment 1 provided by the present invention;

[0028] Reference Signs:

[0029] A feeding section, B melting and plasticizing section, C kneading section

[0030] D Exhaust section, E Metering section, 100 Main feeding port

[0031] 200 Side feeding port, 300 Exhaust port

[0032] 1 - 10 indicate the barrel area Specific implementation manner

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0034] The present invention provides a preferred implementation scheme for a preparation method of an ultra - low melt index, high - filled, halogen - free flame - retardant polypropylene material:

[0035] Feed the raw material components into a twin - screw extruder, and obtain the polypropylene material after co - blending, melting, and pelletizing. The specific steps are as follows:

[0036] (1) Weigh the raw material components according to a certain weight. Stir and mix the polypropylene resin, masterbatch, antioxidant, lubricant, and the first part of the halogen - free flame - retardant in a high - speed mixer to obtain a mixture M;

[0037] (2) Feed the mixture M into the main feeding port 100 of the feeding section A of the twin - screw extruder, and the second part of the halogen - free flame - retardant passes through the side feeding port 200. Then, the raw material components are co - blended, melted, and pelletized in the twin - screw extruder to obtain the polypropylene material.

[0038] Among them, the twin - screw extruder successively includes a feeding section A, a melting and plasticizing section B, a mixing section C, an exhaust section D, and a metering section E along the material conveying direction; the screw blocks in the mixing section C successively include forward - conveying screw blocks, multi - head kneading screw blocks, forward - conveying screw blocks, multi - head kneading screw blocks, forward - conveying screw blocks, forward - shearing screw blocks, and forward - conveying screw blocks.

[0039] Among them, the present invention also provides a formula for the raw material components of this polypropylene material. By weight, the raw material components include: 61 - 66 parts of polypropylene resin, 32 - 37 parts of halogen - free flame - retardant, 0.3 - 0.6 parts of antioxidant, 0.3 - 0.6 parts of lubricant, and 1 part of masterbatch. The sum of the weights of the first part of the halogen - free flame - retardant and the second part of the halogen - free flame - retardant is the total amount of the halogen - free flame - retardant.

[0040] The present invention also provides the following examples and comparative examples:

[0041] The feeding schemes and process parameters shown in Table 1 below are adopted in the examples and comparative examples:

[0042] Table 1

[0043]

[0044] The specific feeding schemes for Scheme 1 to Scheme 4 are as follows:

[0045] Scheme 1: By mass percentage, 63% polypropylene resin, 35% halogen-free flame retardant, 1% masterbatch, 0.4% antioxidant and 0.6% lubricant are put into a high-speed mixer through the main feeding port 100, and stirred at 200 rpm for 120 seconds to obtain mixture 1. The mixture 1 is put into a twin-screw extruder for melt mixing and then pelletized.

[0046] Scheme 2: By mass percentage, 63% polypropylene resin, 25% halogen-free flame retardant, 1% masterbatch, 0.4% antioxidant and 0.6% lubricant are put into a high-speed mixer, and stirred at 200 rpm for 120 seconds to obtain mixture 2. The mixture 2 is put into a twin-screw extruder through the main feeding port 100, and 10% halogen-free flame retardant is put into the twin-screw extruder through the side feeding port 200, and the materials are melt mixed and then pelletized.

[0047] Scheme 3: By mass percentage, 63% polypropylene resin, 20% halogen-free flame retardant, 1% masterbatch, 0.4% antioxidant and 0.6% lubricant are put into a high-speed mixer, and stirred at 200 rpm for 120 seconds to obtain mixture 3. The mixture 3 is put into a twin-screw extruder through the main feeding port 100, and 15% halogen-free flame retardant is put into the twin-screw extruder through the side feeding port 200, and the materials are melt mixed and then pelletized.

[0048] Scheme 4: By mass percentage, 63% polypropylene resin, 20% halogen-free flame retardant, 1% masterbatch, 0.4% antioxidant and 0.6% lubricant are put into a high-speed mixer, and stirred at 200 rpm for 120 seconds to obtain mixture 3. The mixture 3 is put into a twin-screw extruder through the main feeding port 100, and 15% halogen-free flame retardant is put into the twin-screw extruder through the side feeding port 200, and the materials are melt mixed and then pelletized.

[0049] Among them, the polypropylene resin is T4401 from Guangzhou Petrochemical, the halogen-free flame retardant is HS-FP20 from Guangzhou Hocheng Industry Co., Ltd., the antioxidant is THANOX1010 from Lion Chemical Supply Chain Management Co., Ltd., the lubricant is EBS-SF from Shanghai Canal Material Technology Co., Ltd., and the masterbatch is 2718 from Xiamen Huiyu Chemical Co., Ltd.

[0050] The following screw combination methods shown in Table 2 below are adopted in the examples and comparative examples:

[0051] Table 2

[0052]

[0053]

[0054] Among them, the order of the screw combinations in Table 2 is from front to back along the material conveying direction; Figure 1 is a schematic structural diagram of the twin-screw extruder in Embodiment 1 of the present invention, Figure 2 is a schematic structural diagram of the FKB element. The expression method of the thread block in this article is the conventional and general thread block model and parameter expression method in the art, specifically:

[0055] Expression method of the forward conveying type thread block: numerical value x / numerical value y × numerical value z, which represents numerical value z forward conveying type thread blocks with a lead of numerical value x mm and an actual length of numerical value y mm. Among them, if there is no suffix of "× numerical value z", it indicates that there is only 1 forward conveying type thread block. If the suffix "A" is added (i.e., numerical value x / numerical value y × numerical value z A), where "A" indicates that it is the starting element of the screw;

[0056] Expression method of the reverse conveying type thread block: numerical value x / numerical value y × numerical value z L, which represents z reverse conveying type thread blocks with a lead of numerical value x mm and an actual length of numerical value y mm, where "L" represents reverse;

[0057] Expression method of the forward shearing thread block: K numerical value x / numerical value y / numerical value z × numerical value p, which represents numerical value p forward shearing thread blocks, the misalignment angle of the sheet-like shear slices is numerical value x°, the number of discs of the sheet-like shear slices is numerical value y, and the actual length of the shear thread block is numerical value z mm;

[0058] Expression method of the multi-head kneading thread element: FKB numerical value x / numerical value y / numerical value z × numerical value p, which represents p multi-head kneading thread elements, the staggered angle of the kneading discs is numerical value x°, the number of kneading discs is numerical value y, and the element length is numerical value z mm of the multi-head kneading thread element FKB, with multiple heads in the middle and double heads at both ends.

[0059] Specifically, the feeding methods and screw combinations shown in Table 3 below are adopted in the comparative example and the embodiment for preparation:

[0060] Table 3

[0061] Item Comparative Example 1 Comparative Example 2 Comparative Example 3 Example 1 Feeding Method Item Scheme 1 Scheme 2 Scheme 3 Scheme 4 Screw Combination Combination 1 Combination 1 Combination 1 Combination 2

[0062] The specific preparation methods of the embodiment and the comparative example include the following steps:

[0063] The specific preparation methods of the examples and comparative examples include the following steps: According to the feeding scheme in Table 3 and the screw combination conditions, each material is put into a twin-screw extruder, and after blending, melting, extrusion, and water cooling, pellets are made to obtain polypropylene materials;

[0064] Among them, the twin-screw extruder is a Nanjing Ruia 65 machine. The length-diameter ratio of the screw of the twin-screw extruder is 40:1, and there are a total of 10 barrel sections (from Zone 1 to Zone 10 in the direction of material transportation). The barrel temperature is 180°C to 200°C, the screw speed is as shown in Table 1, and the production capacity of the twin-screw extruder is 300 kg / h. Among them, as Figure 1 shown, the main feeding port 100 is located in the feeding section A, the side feeding port 200 is located in the mixing section C (on the 6th barrel section), and the exhaust port 300 is located on the exhaust section D; specifically, the temperatures of the barrel sections 1 to 10 of the twin-screw extruder are 180°C, 200°C, 200°C, 200°C, 180°C, 180°C, 180°C, 180°C, 200°C, and 200°C in sequence along the direction of material transportation.

[0065] The polypropylene materials obtained in the examples and comparative examples are injection molded into test specimens under the same injection molding conditions using an injection molding machine. The specific injection molding conditions are as shown in Table 4 below:

[0066] Table 4

[0067]

[0068] The processing and preparation processes of the examples and comparative examples are observed, and the specimens injection molded from the polypropylene materials of the examples and comparative examples are tested for relevant performance indicators. The test results are shown in Table 5 below:

[0069] Table 5

[0070]

[0071] Among them, the characterization test methods for the prepared polypropylene materials are as follows: The test standard for tensile strength is GB / T 1040.1-2018, the test standard for flexural strength is GB / T 9341-2008, the test standard for the notched Izod impact strength of a simply supported beam is GB / T 1043.1-2008; the test standard for melt flow rate is GB / T 3682.1-2018; the test standard for the vertical method of the combustion performance of materials is IEC60695, UL94, and among them, the flame retardant performance is in descending order as V0, V1, V2, and NV.

[0072] The instruments and equipment used in the preparation and testing processes and their models are as shown in Table 6 below:

[0073] Table 6

[0074] Instrument Name Model Manufacturer High-Speed Mixer SHR200 Suzhou Songyuan Co-Rotating Parallel Twin-Screw Extruder RTX-65 Nanjing Ruiya Pendulum Impact Tester ZBC8400-C Meters Electronic Universal Testing Machine AGS-X-10KN Shimadzu Melt Flow Rate Tester MFI-2322S Jinjian Injection Molding Machine EM80-V Haitian Injection Molding Machine Horizontal and Vertical Burning Tester AUTO-SPA Odyssey Innovation

[0075] In summary, it can be seen from the test results in Table 5 that:

[0076] In Example 1, based on Comparative Example 3, the screw optimization combination 2 is adopted, and the dispersion distribution of the kneading section C is strengthened by the FKB mixing element. The FKB overcomes the drawback of uneven shear of the double-headed thread element, has uniform shear, realizes better melting, improves the ability of dispersion distribution, and optimizes the feeding methods of different materials at the main feeding port 100 and the side feeding port 200. The above comprehensive process optimization methods make the powder not accumulate at the discharging port during the processing of Example 1, the powder at the discharging port does not disperse, and as Figure 6 shown, the prepared polypropylene material particles have no pores, have excellent flame retardant properties and maintain good mechanical properties;

[0077] During the processing of Comparative Example 1, powder accumulates at the discharging port, as Figure 3 shown, the prepared polypropylene material particles are porous, its flame retardant property grade is NV, and its flame retardant properties are all unqualified;

[0078] During the processing of Comparative Example 2, powder accumulates at the discharging port, as Figure 4 shown, the prepared polypropylene material particles are porous, the flame retardant property grade is NV, and its melt index and flame retardant properties are unqualified;

[0079] During the processing of Comparative Example 3, powder accumulates at the discharging port, as Figure 5 shown, the prepared polypropylene material particles have a small number of single pores, and its flame retardant property grade is only V1, the flame retardant is unqualified, and it is difficult to achieve the excellent effect of the example.

[0080] For the above-mentioned formula of the polypropylene material with high filling and halogen-free flame retardant, the present invention optimizes the feeding methods of different materials at the main feeding port 100 and the side feeding port 200, synchronously optimizes the arrangement of the screw combination, and introduces the FKB element in the kneading section C to cooperate with the conveying type thread block and the positive shear thread block. Thus, during the processing of the ultra-low melt index, high filling and halogen-free flame retardant polypropylene material of the present invention, the material does not accumulate at the discharging port, the powder at the discharging port does not disperse, and the prepared polypropylene material particles have no pores, have excellent flame retardant properties and maintain good mechanical properties.

[0081] To sum up, through the optimization of process conditions, the present invention solves the problems that the discharging port is easy to accumulate powder and the powder at the discharging port is easy to disperse during the processing of ultra-low melt index, high filling and halogen-free flame retardant polypropylene, and avoids the influence of floating powder on the on-site environment; through the optimization of the screw combination, it strengthens the uniformity of the dispersion distribution of the polypropylene resin and the flame retardant, solves the problems of hollow polypropylene material particles, particle foaming and unqualified flame retardant, and improves the stability of the product quality in the manufacturing process; the polypropylene material prepared by this preparation method has excellent flame retardant properties and maintains good mechanical properties.

[0082] It should be noted that:

[0083] According to the general expression method of thread blocks in this field, "L" indicates that the thread block is reverse. For the forward (right-handed) one, it generally does not need to be marked. A thread block without being specifically marked as reverse (left-handed) indicates that it is forward.

[0084] The expression "in sequence along the material conveying direction" described in this article is the conventional expression method of screw elements in this field. It is well known in this field that in this field, it is generally defaulted to express the sequence according to the material conveying direction, that is, the processing procedure sequence, that is, from the feeding section A - the melting and plasticizing section B - the kneading section C - the degassing section D to the metering section E is the conveying direction of the material from front to back.

[0085] In addition to the actual selections reflected in the above specific embodiments, the present invention mainly aims at the process improvement of polypropylene materials added with high-content halogen-free flame retardants. For the addition, type selection and ratio determination of other auxiliaries and other raw material components in the raw material components of polypropylene materials, those skilled in the art can make adaptive adjustments, including but not limited to the actual selections reflected in the above embodiments.

[0086] Finally, it should be noted that: The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: They can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A preparation method of an ultra-low melt index high-filled halogen-free flame-retardant polypropylene material, characterized in that: The raw material components are fed into a twin-screw extruder, and a polypropylene material is prepared after blending, melting, and extrusion. By weight, the raw material components include 61-66 parts of polypropylene resin, 32-37 parts of a halogen-free flame retardant, and 1.6-2.2 parts of other additives. The twin-screw extruder sequentially includes a feeding section, a melting and plasticizing section, a kneading section, a venting section, and a metering section along the material conveying direction. A main feeding port is provided on the feeding section, and a side feeding port is provided on the kneading section. The polypropylene resin, other additives, and the first part of the halogen-free flame retardant are fed through the main feeding port, and the second part of the halogen-free flame retardant is fed through the side feeding port. The sum of the weights of the first part of the halogen-free flame retardant and the second part of the halogen-free flame retardant is the total amount of the halogen-free flame retardant, and the weight ratio of the first part of the halogen-free flame retardant to the second part of the halogen-free flame retardant is (20-25):(10-15). The screw blocks in the kneading section sequentially include forward conveying screw blocks, multi-head kneading screw blocks, forward conveying screw blocks, multi-head kneading screw blocks, forward conveying screw blocks, forward shearing screw blocks, and forward conveying screw blocks along the material conveying direction. The kneading section is sequentially composed of the following screw block combinations along the material conveying direction: 96 / 96*2, 72 / 72*2, FKB90 / 7 / 75*1, 56 / 56*2, FKB90 / 7 / 75*1, 44 / 44*3, K60 / 4 / 44*2, 44 / 44*2. The feeding section includes forward conveying screw blocks. The feeding section is sequentially composed of the following screw block combinations along the material conveying direction: 56 / 56A, 96 / 96*3, 72 / 72, 56 / 56*3. The melting and plasticizing section sequentially includes forward shearing screw blocks and reverse conveying screw blocks along the material conveying direction. The melting and plasticizing section is sequentially composed of the following screw block combinations along the material conveying direction: K45 / 5 / 72, K45 / 5 / 56*4, K60 / 4 / 44, 44 / 22L. The venting section sequentially includes reverse conveying screw blocks and forward conveying screw blocks along the material conveying direction. The venting section is sequentially composed of the following screw block combinations along the material conveying direction: 44 / 22L, 96 / 96*2, 72 / 72. The metering section sequentially includes forward conveying screw blocks, forward shearing screw blocks, and forward conveying screw blocks along the material conveying direction. The metering section is sequentially composed of the following screw block combinations along the material conveying direction: 56 / 56*2, K45 / 5 / 44, 44 / 44*2. Among them, the expression of the forward conveying screw block: numerical value x / numerical value y×numerical value z, which means numerical value z forward conveying screw blocks with a lead of numerical value xmm and an actual length of numerical value ymm. Among them, if there is no suffix of "×numerical value z", it means there is only 1 forward conveying screw block. If the suffix "A" is added, that is, numerical value x / numerical value y×numerical value z A, where "A" indicates that it is the starting element of the screw. Reverse conveying type thread block expression: numerical value x / numerical value y×numerical value zL, which represents z reverse conveying type thread blocks with a lead of numerical value xmm and an actual length of numerical value ymm, where "L" represents reverse; Forward shearing thread block expression: K numerical value x / numerical value y / numerical value z×numerical value p, representing numerical value p forward shearing thread blocks, the dislocation angle of the flaky shear slices is numerical value x°, the number of discs of the flaky shear slices is numerical value y, and the actual length of the shearing thread block is numerical value zmm; Multi-headed kneading thread element expression: FKB numerical value x / numerical value y / numerical value z×numerical value p, representing p multi-headed kneading thread elements, the staggered angle of the kneading discs is numerical value x°, the number of kneading discs is numerical value y, and the element length is numerical value zmm of the multi-headed kneading thread element FKB, with multiple heads in the middle and double heads at both ends.

2. The preparation method of the ultra-low melt index highly filled halogen-free flame-retardant polypropylene material according to claim 1, characterized in that: The other additives include antioxidants, lubricants and masterbatch; By weight, the raw material components include 61-66 parts of polypropylene resin, 32-37 parts of halogen-free flame retardant, 0.3-0.6 parts of antioxidant, 0.3-0.6 parts of lubricant and 1 part of masterbatch.

3. The preparation method of the ultra-low melt index and high-fill halogen-free flame-retardant polypropylene material according to claim 1, characterized in that: The length-diameter ratio of the screw of the twin-screw extruder is (40-48):1, the barrel temperature is 180°C-200°C, and the screw speed is (400-500) rpm.

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