Flame-retardant MPP pipe and preparation method thereof

Abstract

The invention discloses a flame-retardant MPP tube and a preparation method thereof, and belongs to the technical field of high polymer materials, the flame-retardant MPP tube comprises the following raw materials: polypropylene and a modified filler, the addition amount of the modified filler is 20-40% of the mass of the polypropylene, and the modified filler is a poly (diethylaminoethyl methacrylate) grafted polydopamine functionalized filler. The preparation method comprises the following steps: adding the modified filler and the polypropylene resin into a high-speed mixer, stirring, then adding the uniformly mixed material into a double-screw extruder, extruding and granulating, drying the obtained particles, and carrying out injection molding to obtain the flame-retardant MPP pipe. The prepared flame-retardant MPP pipe has good flame retardance and mechanical property, the modified filler can improve the flame retardance of the flame-retardant MPP pipe and can be evenly dispersed in polypropylene, the interface bonding performance of the filler and the polypropylene is improved, and the reinforcing and toughening functions are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and particularly relates to a flame-retardant MPP pipe and a preparation method thereof. Background Art

[0002] MPP pipe, also known as MPP power cable protection pipe, is a pipe widely used in the fields of electricity, communications, etc. It is mainly used to protect cables and other facilities to prevent them from being damaged by external environmental factors (such as soil corrosion, mechanical damage, etc.). MPP pipe uses modified polypropylene as the main raw material and has the characteristics of high temperature resistance and external pressure resistance. However, the flame retardancy of MPP pipes is poor and it is easy to cause fire hazards. For example, in cable laying projects in the power, communications and other industries, the flame retardancy of MPP pipes will be subject to certain restrictions. With the continuous development of the industry and the continuous advancement of science and technology, MPP pipes have gradually ushered in new challenges. Therefore, the improvement of the comprehensive properties of MPP pipes such as heat resistance and flame retardancy to meet its application requirements in different fields has become a research hotspot.

[0003] In order to improve the flame retardancy of MPP pipes, flame retardants can be added to improve the flame retardant performance of MPP pipes. Due to the structural differences between flame retardants and the components of MPP power pipes, the large-scale use of flame retardants will form a weak interface layer in the MPP power pipe, resulting in a decrease in the mechanical properties of the MPP power pipe. The invention patent with application number CN108276659A discloses a flame retardant and highly heat-resistant MPP pipe and its preparation method. By adding heat-resistant fillers and flame retardants to the matrix raw materials, although the application guarantees certain mechanical properties of the pipe by controlling the synergistic effect between the raw materials, the flame retardant in the application uses bromine-containing flame retardants. Although the flame retardant effect is good, it will produce toxic hydrogen halide gas during combustion, and the environmental protection is poor. Adding flame retardants to MPP power pipes usually improves the flame retardant performance of MPP power pipes through the flame retardant itself. There is a lack of synergy between the flame retardant and the components of MPP, and the flame retardant performance of MPP power pipes needs to be further improved. Summary of the invention

[0004] The object of the present invention is to provide a flame retardant MPP pipe and a preparation method thereof, so as to solve the problem that the mechanical properties of the flame retardant MPP pipe are poor.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A flame retardant MPP pipe comprises the following raw materials: polypropylene and modified filler, wherein the addition amount of the modified filler is 20% to 40% of the mass of the polypropylene, and the modified filler is a polydopamine functional filler grafted with diethylaminoethyl methacrylate.

[0007] Furthermore, the polydopamine functionalized filler is prepared by self-polymerization of dopamine onto the surface of the flame retardant filler.

[0008] Furthermore, the flame retardant filler is one of magnesium hydroxide, aluminum hydroxide, magnesium aluminum hydrotalcite, calcium carbonate, talcum powder and barium sulfate. The flame retardant filler can not only improve the flame retardant performance of the material, but also can be used as a reinforcing filler.

[0009] Furthermore, the particle size of the flame retardant filler is 1.5-3 μm.

[0010] Furthermore, the polydopamine functionalized filler is prepared by the following steps:

[0011] The flame retardant filler is added to a 20% by mass ethanol aqueous solution, and tris(hydroxymethyl)aminomethane hydrochloride) is added while stirring to adjust the pH value of the system to 8.5, and dopamine hydrochloride is added, and stirring is continued for 5-10 hours. After the reaction is completed, the mixture is centrifuged, washed with ethanol, washed with water, and dried in sequence to obtain a polydopamine functional filler.

[0012] Furthermore, 3 mg of dopamine hydrochloride is added to each milliliter of ethanol aqueous solution, and the mass ratio of the flame retardant filler to the ethanol aqueous solution is 1 g:100 mL.

[0013] Furthermore, the modified filler is prepared by the following steps:

[0014] Under nitrogen protection, polydopamine functional filler, diethylaminoethyl methacrylate and initiator were added to the solvent and mixed, and stirred at 60-70°C for 3 hours. After the reaction, the mixture was washed with ethanol, washed with water and dried to obtain a modified filler. In order to improve the poor dispersibility of general flame retardant fillers in polypropylene, dopamine was used as an active substance to adhere to the surface of the flame retardant filler to prepare a polydopamine functional filler, and then diethylaminoethyl methacrylate was grafted and polymerized on the polydopamine functional filler by an initiator to obtain a modified filler.

[0015] Furthermore, the mass ratio of the polydopamine functionalized filler and diethylaminoethyl methacrylate is 1:8-11; the amount of the initiator is 1% to 3% of the mass of diethylaminoethyl methacrylate. Polydiethylaminoethyl methacrylate has good compatibility with polypropylene, but the amount of polydiethylaminoethyl methacrylate should not be too much. The long chains of polydiethylaminoethyl methacrylate and polypropylene are easily entangled. When the amount of polydiethylaminoethyl methacrylate formed is too much, the modified filler will not have a nucleation effect, thereby affecting the mechanical properties of the modified filler. Therefore, the material performance can be further optimized by controlling the amount ratio of polydopamine functionalized filler and diethylaminoethyl methacrylate.

[0016] A method for preparing a flame retardant MPP pipe comprises the following steps:

[0017] The modified filler and polypropylene resin are added into a high-speed mixer and stirred, and then the uniformly mixed materials are added into a twin-screw extruder for extrusion granulation. The obtained particles are dried and injection molded to obtain a flame-retardant MPP tube.

[0018] Furthermore, the stirring time is 10-20 minutes; and the drying temperature is 80-85°C.

[0019] Beneficial effects of the present invention:

[0020] The flame retardant MPP pipe prepared by the present invention has good flame retardant properties and mechanical properties, wherein the modified filler can not only improve the flame retardant properties of the flame retardant MPP pipe, but also can be evenly dispersed in polypropylene, improve the interface bonding performance between the filler and polypropylene, and play a role in strengthening and toughening.

[0021] In the present invention, dopamine is used as an active substance to adhere to the surface of the flame retardant filler to prepare a polydopamine functionalized filler, and then diethylaminoethyl methacrylate is initiated by an initiator to undergo graft polymerization on the polydopamine functionalized filler to obtain a modified filler, wherein the modified filler is a polydopamine functionalized filler grafted with polydiethylaminoethyl methacrylate, and polydiethylaminoethyl methacrylate has excellent adhesion, and is conducive to the dispersion of the modified filler in polypropylene, improves the interfacial bonding performance between the filler and polypropylene, and plays a role in strengthening and toughening. In addition, the selection of dopamine as an active substance to adhere to the surface of the flame retardant filler in the present invention, and the selection of diethylaminoethyl methacrylate as an active monomer both have a certain flame retardant enhancement effect, therefore, there is a synergistic coordination between the modified filler (containing the flame retardant filler and the flame retardant element) and the components of the polypropylene, which not only improves the mechanical properties of the polypropylene material, but also improves the flame retardant effect of the polypropylene. DETAILED DESCRIPTION

[0022] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] Preparation Example 1

[0024] Preparation of modified fillers:

[0025] Add the flame retardant filler (magnesium hydroxide) to a 20% ethanol aqueous solution, add tris(hydroxymethyl)aminomethane hydrochloride to adjust the pH value of the system to 8.5 while stirring, add dopamine hydrochloride, continue stirring for 5 hours, centrifuge after the reaction, wash with ethanol, wash with water, and dry at 60°C to constant weight to obtain a polydopamine functional filler; add 3 mg dopamine hydrochloride per milliliter of ethanol aqueous solution, and the mass ratio of the flame retardant filler (magnesium hydroxide) to the ethanol aqueous solution is 1g:100mL. The particle size of the flame retardant filler is 1.5-3μm.

[0026] Under nitrogen protection, polydopamine functional filler, diethylaminoethyl methacrylate and initiator (benzoyl peroxide) were added to toluene and mixed, stirred at 65°C for 3 hours, and after the reaction, washed with ethanol and water in sequence, and dried at 50°C to obtain a modified filler. The mass ratio of polydopamine functional filler to diethylaminoethyl methacrylate was 1:8. The amount of initiator (benzoyl peroxide) was 2% of the mass of diethylaminoethyl methacrylate.

[0027] Preparation Example 2

[0028] Preparation of modified fillers:

[0029] Add the flame retardant filler (magnesium hydroxide) to a 20% ethanol aqueous solution, add tris(hydroxymethyl)aminomethane hydrochloride to adjust the pH value of the system to 8.5 while stirring, add dopamine hydrochloride, continue stirring for 5 hours, centrifuge after the reaction, wash with ethanol, wash with water, and dry at 60°C to constant weight to obtain a polydopamine functional filler; add 3 mg dopamine hydrochloride per milliliter of ethanol aqueous solution, and the mass ratio of the flame retardant filler (magnesium hydroxide) to the ethanol aqueous solution is 1g:100mL. The particle size of the flame retardant filler is 1.5-3μm.

[0030] Under nitrogen protection, polydopamine functional filler, diethylaminoethyl methacrylate and initiator (benzoyl peroxide) were added to toluene and mixed, stirred at 65°C for 3 hours, and after the reaction, washed with ethanol and water in sequence, and dried at 50°C to obtain a modified filler. The mass ratio of polydopamine functional filler to diethylaminoethyl methacrylate was 1:9. The amount of initiator (benzoyl peroxide) was 2% of the mass of diethylaminoethyl methacrylate.

[0031] Preparation Example 3

[0032] Preparation of modified fillers:

[0033] Add the flame retardant filler (magnesium hydroxide) to a 20% ethanol aqueous solution, add tris(hydroxymethyl)aminomethane hydrochloride to adjust the pH value of the system to 8.5 while stirring, add dopamine hydrochloride, continue stirring for 5 hours, centrifuge after the reaction, wash with ethanol, wash with water, and dry at 60°C to constant weight to obtain a polydopamine functional filler; add 3 mg dopamine hydrochloride per milliliter of ethanol aqueous solution, and the mass ratio of the flame retardant filler (magnesium hydroxide) to the ethanol aqueous solution is 1g:100mL. The particle size of the flame retardant filler is 1.5-3μm.

[0034] Under nitrogen protection, polydopamine functional filler, diethylaminoethyl methacrylate and initiator (benzoyl peroxide) were added to toluene and mixed, stirred at 65°C for 3 hours, and after the reaction, washed with ethanol and water in sequence, and dried at 50°C to obtain a modified filler. The mass ratio of polydopamine functional filler to diethylaminoethyl methacrylate was 1:10. The amount of initiator (benzoyl peroxide) was 2% of the mass of diethylaminoethyl methacrylate.

[0035] Preparation Example 4

[0036] Preparation of modified fillers:

[0037] Add the flame retardant filler (magnesium hydroxide) to a 20% ethanol aqueous solution, add tris(hydroxymethyl)aminomethane hydrochloride to adjust the pH value of the system to 8.5 while stirring, add dopamine hydrochloride, continue stirring for 5 hours, centrifuge after the reaction, wash with ethanol, wash with water, and dry at 60°C to constant weight to obtain a polydopamine functional filler; add 3 mg dopamine hydrochloride per milliliter of ethanol aqueous solution, and the mass ratio of the flame retardant filler (magnesium hydroxide) to the ethanol aqueous solution is 1g:100mL. The particle size of the flame retardant filler is 1.5-3μm.

[0038] Under nitrogen protection, polydopamine functional filler, diethylaminoethyl methacrylate and initiator (benzoyl peroxide) were added to toluene and mixed, stirred at 65°C for 3 hours, and after the reaction, washed with ethanol and water in sequence, and dried at 50°C to obtain a modified filler. The mass ratio of polydopamine functional filler to diethylaminoethyl methacrylate was 1:11. The amount of initiator (benzoyl peroxide) was 2% of the mass of diethylaminoethyl methacrylate.

[0039] Preparation Example 5

[0040] The modified filler in this preparation example is a polydopamine functionalized filler.

[0041] Add the flame retardant filler (magnesium hydroxide) to a 20% ethanol aqueous solution, add tris(hydroxymethyl)aminomethane hydrochloride to adjust the pH value of the system to 8.5 while stirring, add dopamine hydrochloride, continue stirring for 5 hours, centrifuge after the reaction, wash with ethanol, wash with water, and dry at 60°C to constant weight to obtain a polydopamine functional filler; add 3 mg dopamine hydrochloride per milliliter of ethanol aqueous solution, and the mass ratio of the flame retardant filler (magnesium hydroxide) to the ethanol aqueous solution is 1g:100mL. The particle size of the flame retardant filler is 1.5-3μm.

[0042] Example 1

[0043] This embodiment provides a flame retardant MPP tube, which is prepared by the following steps:

[0044] The modified filler and polypropylene resin prepared in Preparation Example 1 are added into a high-speed mixer, the amount of the modified filler added is 20% of the mass of the polypropylene, and stirred at high speed for 10 minutes. Then the evenly mixed material is added into a twin-screw extruder for extrusion granulation. The obtained particles are dried at 85°C and injection molded to obtain a flame-retardant MPP tube.

[0045] Example 2

[0046] This embodiment provides a flame retardant MPP tube, which is prepared by the following steps:

[0047] The modified filler and polypropylene resin prepared in Preparation Example 2 are added to a high-speed mixer, with the added amount of the modified filler being 20% ​​of the mass of the polypropylene. The mixture is stirred at high speed for 10 minutes, and then the evenly mixed material is added to a twin-screw extruder for extrusion granulation. The obtained particles are dried at 85°C and injection molded to obtain a flame-retardant MPP tube.

[0048] Example 3

[0049] This embodiment provides a flame retardant MPP tube, which is prepared by the following steps:

[0050] The modified filler and polypropylene resin prepared in Preparation Example 3 are added to a high-speed mixer, with the added amount of the modified filler being 20% ​​of the mass of the polypropylene. The mixture is stirred at high speed for 10 minutes, and then the evenly mixed material is added to a twin-screw extruder for extrusion granulation. The obtained particles are dried at 85°C and injection molded to obtain a flame-retardant MPP tube.

[0051] Example 4

[0052] This embodiment provides a flame retardant MPP tube, which is prepared by the following steps:

[0053] The modified filler and polypropylene resin prepared in Preparation Example 4 are added to a high-speed mixer, with the amount of modified filler added being 20% ​​of the mass of polypropylene. The mixture is stirred at high speed for 10 minutes, and then the evenly mixed material is added to a twin-screw extruder for extrusion granulation. The obtained particles are dried at 85°C and injection molded to obtain a flame-retardant MPP tube.

[0054] The samples prepared in Examples 1 to 4 were subjected to mechanical property tests: tensile strength, drop weight impact test and ring stiffness test were performed according to the method in the electric power industry standard DL / T802.7-2023. The test results are shown in Table 1 below:

[0055] Table 1

[0056]

[0057]

[0058] Example 5

[0059] This embodiment provides a flame retardant MPP tube, which is prepared by the following steps:

[0060] The modified filler and polypropylene resin prepared in Preparation Example 3 are added to a high-speed mixer, the added amount of the modified filler is 25% of the mass of the polypropylene, and stirred at high speed for 10 minutes. Then the evenly mixed material is added to a twin-screw extruder for extrusion granulation. The obtained particles are dried at 85°C and injection molded to obtain a flame-retardant MPP tube.

[0061] Example 6

[0062] This embodiment provides a flame retardant MPP tube, which is prepared by the following steps:

[0063] The modified filler and polypropylene resin prepared in Preparation Example 3 are added to a high-speed mixer, the added amount of the modified filler is 30% of the mass of the polypropylene, and stirred at high speed for 10 minutes. Then the evenly mixed material is added to a twin-screw extruder for extrusion granulation. The obtained particles are dried at 85°C and injection molded to obtain a flame-retardant MPP tube.

[0064] Example 7

[0065] This embodiment provides a flame retardant MPP tube, which is prepared by the following steps:

[0066] The modified filler and polypropylene resin prepared in Preparation Example 3 are added to a high-speed mixer, the added amount of the modified filler is 35% of the mass of the polypropylene, and stirred at high speed for 10 minutes. Then the evenly mixed material is added to a twin-screw extruder for extrusion granulation. The obtained particles are dried at 85°C and injection molded to obtain a flame-retardant MPP tube.

[0067] Example 8

[0068] This embodiment provides a flame retardant MPP tube, which is prepared by the following steps:

[0069] The modified filler and polypropylene resin prepared in Preparation Example 3 are added to a high-speed mixer, the added amount of the modified filler is 40% of the mass of the polypropylene, and stirred at high speed for 10 minutes. Then the evenly mixed material is added to a twin-screw extruder for extrusion granulation. The obtained particles are dried at 85°C and injection molded to obtain a flame-retardant MPP tube.

[0070] Comparative Example 1

[0071] Compared with Example 3, this comparative example replaces the modified filler with the modified filler (polydopamine functionalized filler) prepared in Preparation Example 5, and the remaining raw materials and preparation process remain the same as those in Example 3.

[0072] Comparative Example 2

[0073] Compared with Example 3, this comparative example replaces the modified filler with an untreated filler (magnesium hydroxide) with a particle size of 1.5-3 μm.

[0074] Mechanical properties and flame retardant properties were tested for Example 3, Example 5-Example 6 and Comparative Examples 1-Comparative Examples 2. In the flame retardant property test, the limiting oxygen index of the sample was tested using an oxygen index tester. The test standard was GB / T 2408-2021. The size of the oxygen index strip was 120 mm long, 6.5 mm wide and 3.0 mm thick. The results are shown in Table 2:

[0075] Table 2

[0076]

[0077] According to the test results recorded in Tables 1 and 2, the flame retardant MPP pipe prepared by the present invention has good flame retardant properties and mechanical properties, wherein the modified filler can not only improve the flame retardant properties of the flame retardant MPP pipe, but also can be evenly dispersed in polypropylene, improve the interface bonding performance between the filler and polypropylene, and play a role in strengthening and toughening.

[0078] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0079] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A flame retardant MPP tube, characterized in that: The invention comprises the following raw materials: polypropylene and modified filler, wherein the addition amount of the modified filler is 20% to 40% of the mass of the polypropylene, and the modified filler is a polydopamine functional filler grafted with diethylaminoethyl methacrylate.

2. The flame-retardant MPP tube according to claim 1, characterized in that: The polydopamine functionalized filler is prepared by self-polymerization of dopamine onto the surface of the flame retardant filler.

3. The flame-retardant MPP tube according to claim 2, characterized in that: The flame retardant filler is one of magnesium hydroxide, aluminum hydroxide, magnesium aluminum hydrotalcite, calcium carbonate, talcum powder and barium sulfate.

4. The flame-retardant MPP tube according to claim 3, characterized in that: The particle size of the flame retardant filler is 1.5-3 μm.

5. The flame-retardant MPP tube according to claim 1, characterized in that: The polydopamine functionalized filler is prepared by the following steps: The flame retardant filler is added to a 20% by mass ethanol aqueous solution, and tris(hydroxymethyl)aminomethane hydrochloride) is added while stirring to adjust the pH value of the system to 8.5, and dopamine hydrochloride is added, and stirring is continued for 5-10 hours. After the reaction is completed, the mixture is centrifuged, washed with ethanol, washed with water, and dried in sequence to obtain a polydopamine functionalized filler.

6. The flame-retardant MPP tube according to claim 5, characterized in that: 3 mg of dopamine hydrochloride was added to each ml of ethanol aqueous solution, and the mass ratio of flame retardant filler to ethanol aqueous solution was 1 g:100 mL.

7. The flame-retardant MPP tube according to claim 1, characterized in that: The modified filler is prepared by the following steps: Under nitrogen protection, polydopamine functional filler, diethylaminoethyl methacrylate and initiator are added to a solvent and mixed, and stirred for reaction at 60-70° C. for 3 hours. After the reaction, the mixture is washed with ethanol, washed with water and dried in sequence to obtain a modified filler.

8. The flame-retardant MPP tube according to claim 7, characterized in that: The mass ratio of the polydopamine functional filler to diethylaminoethyl methacrylate is 1:8-11; the amount of the initiator is 1% to 3% of the mass of the diethylaminoethyl methacrylate.

9. A method for preparing a flame-retardant MPP tube according to any one of claims 1 to 8, characterized in that: The steps include: The modified filler and polypropylene resin are added into a high-speed mixer and stirred, and then the uniformly mixed materials are added into a twin-screw extruder for extrusion granulation. The obtained particles are dried and injection molded to obtain a flame-retardant MPP tube.

10. The method for preparing the flame-retardant MPP pipe according to claim 9, characterized in that: The stirring time is 10-20 minutes; the drying temperature is 80-85°C.

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