Migration-resistant piperazine pyrophosphate flame retardant and synthesis method thereof

Abstract

The invention provides a migration-resistant piperazine pyrophosphate flame retardant and a synthesis method thereof, and relates to the field of flame retardants. Comprising the following steps: S1, mixing anhydrous piperazine with water, heating, dropwise adding a phosphoric acid solution into a system, performing microwave heating to 80-90 DEG C, and keeping the temperature for 2-3 hours; adding a coupling agent, uniformly stirring, cooling to room temperature, filtering and drying to obtain modified piperazine diphosphate; s2, mixing the modified piperazine diphosphate prepared in the step S1 with a catalyst, adding the mixture into a kneading machine, heating to 180-220 DEG C, reacting for 2-3 hours, cooling and crushing to obtain a piperazine pyrophosphate crude product; s3, uniformly mixing modified montmorillonite, methyl hydrogen-containing silica oil and a coupling agent, then adding the piperazine pyrophosphate crude product in the step S2 and ammonia water, and performing ultrasonic oscillation, uniform mixing, drying and crushing to obtain the piperazine pyrophosphate flame retardant. The piperazine pyrophosphate is subjected to surface modification, so that the bonding strength of the piperazine pyrophosphate and a resin matrix is improved, and the problem that traditional piperazine pyrophosphate is not resistant to flame retardance and migration is solved.

Description

Technical Field

[0001] The present invention relates to the field of flame retardants, and more particularly, to a migration-resistant piperazine pyrophosphate flame retardant and a method for synthesizing the same. Background Art

[0002] Piperazine pyrophosphate (PAPP), with the chemical formula C 10 H 14 N3O4P, is a highly efficient halogen-free and environmentally friendly flame retardant with nitrogen-phosphorus synergy. Piperazine pyrophosphate is usually a white or off-white powder, odorless and tasteless, and has stable chemical properties. It is soluble in water and some organic solvents. Piperazine pyrophosphate can be better mixed and dispersed with other components, thereby improving the flame retardant effect. In addition, piperazine pyrophosphate also has good thermal stability and char-forming properties, and can maintain its molecular structure and flame retardant properties at high temperatures, and is not easily decomposed or inactivated.

[0003] The flame retardant mechanism of piperazine pyrophosphate mainly depends on the phosphorus and nitrogen elements in its molecular structure. During the combustion process, the phosphorus and nitrogen elements play a synergistic role to form a dense carbon layer, thereby blocking the transfer of oxygen and heat and achieving the flame retardant effect. Piperazine pyrophosphate flame retardant has a wide range of applications in polyolefins, ethylene-propylene-diene rubber and TPE elastomer materials. It is mainly used as a char-forming agent in polypropylene resin and can replace traditional char-forming agents such as pentaerythritol, pentaerythritol phosphate, and triazine char-forming agents. It can also be used for flame retardant modification of materials such as PP, PE, and ABS. However, the dispersibility of piperazine pyrophosphate flame retardant in resin is poor, and it is easy to agglomerate itself, which affects its application in resin.

[0004] To solve the above problems, during the preparation of piperazine pyrophosphate, by adding a dispersant to form an intermolecular repulsive force, or using the encapsulation effect of microcapsules to produce an anti-aggregation effect, high-purity and high-dispersibility piperazine pyrophosphate can be obtained. This not only improves the storage stability of the flame retardant product, but also makes the flame retardant more environmentally friendly and efficient. Although methods such as adding a dispersant and encapsulation effect can improve the dispersion performance of piperazine pyrophosphate in the resin matrix, the binding strength between piperazine pyrophosphate and the resin matrix is low. During the use of resin products, the piperazine pyrophosphate flame retardant is likely to migrate in the resin matrix, resulting in uneven dispersion of the flame retardant and affecting the flame retardancy of the resin products. Summary of the Invention

[0005] The purpose of the present invention is to provide a migration-resistant piperazine pyrophosphate flame retardant. By surface-modifying piperazine pyrophosphate, its binding strength with the resin matrix is improved, thereby solving the problem of poor migration resistance of traditional piperazine pyrophosphate flame retardants.

[0006] Another object of the present invention is to provide a preparation method for a migration-resistant piperazine pyrophosphate flame retardant. By modifying the raw materials and the surface of piperazine pyrophosphate, the bonding strength with the resin matrix is improved, thereby solving the problem of poor migration resistance of traditional piperazine pyrophosphate flame retardants.

[0007] The present invention solves its technical problems by adopting the following technical solutions.

[0008] On the one hand, an embodiment of the present invention provides a synthesis method for a migration-resistant piperazine pyrophosphate flame retardant, including the following steps:

[0009] S1. Mix anhydrous piperazine with water, heat, then dropwise add phosphoric acid solution to the system, microwave heat to 80 - 90 °C and keep warm for 2 - 3 h; add a coupling agent, stir evenly, then cool to room temperature, filter and dry to obtain modified dipiperazine pyrophosphate;

[0010] S2. Mix the modified dipiperazine pyrophosphate obtained in step S1 with a catalyst, add it to a kneader, heat to 180 - 220 °C, react for 2 - 3 h, cool, and pulverize to obtain a crude piperazine pyrophosphate product;

[0011] S3. Mix modified montmorillonite, methyl hydrogen siloxane oil, and a coupling agent evenly, then add the crude piperazine pyrophosphate product obtained in step S2 and ammonia water, ultrasonically oscillate, mix evenly, dry and pulverize to obtain the piperazine pyrophosphate flame retardant.

[0012] In some embodiments of the present invention, in steps S1 and S3, the coupling agent is a double-bond silane coupling agent, including one or a mixture of more than one of vinyltrimethoxysilane, vinyltriethoxysilane, 3-(methacryloyloxy)propyltrimethoxysilane, and allyl tris(β-methoxyethoxy)silane.

[0013] In some embodiments of the present invention, in step S2, the catalyst is a mixture of P2O5 and calcium hydride, and the mass ratio of the two is 1:(0.1 - 0.5).

[0014] In some embodiments of the present invention, the modified montmorillonite is prepared by the following method:

[0015] Mix montmorillonite with water, stir evenly, then add tetradecyldimethyl tertiary amine and a sulfuric acid metal salt solution, mix evenly, filter and dry to obtain the modified montmorillonite.

[0016] In some embodiments of the present invention, the sulfuric acid metal salt solution is a mixture of one or both of zinc sulfate and magnesium sulfate.

[0017] In some embodiments of the present invention, the mass ratio of the montmorillonite, tetradecyldimethylamine, and metal sulfate is 1:(0.5 - 1):(0.5 - 1).

[0018] In some embodiments of the present invention, in step S3, the mass ratio of the modified montmorillonite, methylhydrogen siloxane oil, coupling agent, and piperazine pyrophosphate crude product is (1 - 2):(1 - 2):(0.5 - 1):(2 - 3).

[0019] In some embodiments of the present invention, the frequency of the ultrasonic oscillation is 50 - 80 KHz, and the time is 1 - 2 h.

[0020] In some embodiments of the present invention, in step S1, the mass ratio of anhydrous piperazine to the coupling agent is 1:(1 - 1.5).

[0021] On the other hand, an embodiment of the present invention provides a migration-resistant piperazine pyrophosphate flame retardant prepared by the above method. Compared with the prior art, the embodiments of the present invention have at least the following advantages or beneficial effects:

[0022] The synthesis method of the piperazine pyrophosphate flame retardant provided by the present invention first prepares piperazine diphosphate from anhydrous piperazine and phosphoric acid solution, and a coupling agent is added. The coupling agent can combine with piperazine diphosphate to improve the dispersibility of piperazine diphosphate; subsequently, piperazine diphosphate undergoes dehydration condensation under the action of a catalyst to obtain a piperazine pyrophosphate crude product. In this process, one end of the coupling agent molecule can further combine with the piperazine pyrophosphate molecule to form a piperazine pyrophosphate crude product carrying a free-end coupling agent molecular chain. Subsequently, under the action of modified montmorillonite, methylhydrogen siloxane oil, and coupling agent, the surface of the piperazine pyrophosphate crude product is further surface-modified. Methylhydrogen siloxane oil can form a hydrophobic structure on the surface of piperazine pyrophosphate, providing the dispersibility of piperazine pyrophosphate and reducing the caking of piperazine pyrophosphate; under the action of the coupling agent, the modified montmorillonite can be loaded on the surface of piperazine pyrophosphate to form a wrapped state.

[0023] When using this piperazine pyrophosphate flame retardant, the montmorillonite on its surface can be embedded into the network structure of the resin matrix, that is, the binding strength between the piperazine pyrophosphate flame retardant and the resin matrix is improved. Secondly, the coupling agent also participates in the resin polymerization reaction, further improving the binding strength between the piperazine pyrophosphate flame retardant and the resin and enhancing the migration resistance of the piperazine pyrophosphate flame retardant. On the other hand, the montmorillonite on the surface of piperazine pyrophosphate can improve the flame retardant performance of the flame retardant. Detailed Embodiments

[0024] 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. For those not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0025] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to specific embodiments.

[0026] An embodiment of the present invention provides a method for synthesizing a migration-resistant piperazine pyrophosphate flame retardant, including the following steps:

[0027] S1. Mix anhydrous piperazine with water, heat it, then dropwise add a phosphoric acid solution to the system, and microwave heat it to 80 - 90 °C and keep it warm for 2 - 3 h; add a coupling agent, stir evenly, then cool it to room temperature, filter, and dry to obtain modified dipiperazine phosphate; wherein, the mass ratio of anhydrous piperazine to the coupling agent is 1:(1 - 1.5). In steps S1 and S3, the coupling agent is a double-bond silane coupling agent, including one or a mixture of more of vinyltrimethoxysilane, vinyltriethoxysilane, 3-(methacryloyloxy)propyltrimethoxysilane, and allyltris(β-methoxyethoxy)silane.

[0028] In step S1, through microwave heating, the molecules of each raw material can be made more active, increasing the active sites, so as to improve the reaction rate, and at the same time, the binding rate of the coupling agent to dipiperazine phosphate can also be improved.

[0029] S2. Mix the modified dipiperazine phosphate obtained in step S1 with a catalyst, add it to a kneader, heat it to 180 - 220 °C, react for 2 - 3 h, cool it, and pulverize it to obtain a crude product of piperazine pyrophosphate; wherein, the catalyst is a mixture of P2O5 and calcium hydride, and the mass ratio of the two is 1:(0.1 - 0.5). Under the action of the catalyst, the modified dipiperazine phosphate undergoes dehydration condensation to obtain piperazine pyrophosphate. During the dehydration condensation process, a part of the double bonds of the coupling agent are opened and participate in the dehydration condensation, chemically bonding with piperazine pyrophosphate; a part of the coupling agent binds to piperazine pyrophosphate through intermolecular electrostatic adsorption, cross-winding, etc., making the binding of the silane coupling agent to piperazine pyrophosphate tighter.

[0030] S3. Mix the modified montmorillonite, methyl hydrogen siloxane oil, and coupling agent evenly, then add the crude piperazine pyrophosphate from step S2 and ammonia water, and ultrasonically agitate to mix evenly. Dry and pulverize to obtain the piperazine pyrophosphate flame retardant. The mass ratio of the modified montmorillonite, methyl hydrogen siloxane oil, coupling agent, and crude piperazine pyrophosphate is (1 - 2):(1 - 2):(0.5 - 1):(2 - 3). The frequency of ultrasonic agitation is 50 - 80 KHz, and the time is 1 - 2 h. Under the action of ultrasonic agitation, each raw material is more evenly dispersed, and under the action of ultrasonic waves, the coupling agent on the crude piperazine pyrophosphate and the free coupling agent can combine with the modified montmorillonite, making the combination of montmorillonite and piperazine pyrophosphate firmer.

[0031] In the present invention, the modified montmorillonite is prepared by the following method:

[0032] Mix montmorillonite with water, stir evenly, then add tetradecyldimethyl tertiary amine and a sulfuric acid metal salt solution, mix evenly, filter, and dry to obtain the modified montmorillonite. The sulfuric acid metal salt solution is one or a mixture of two of zinc sulfate and magnesium sulfate. The mass ratio of montmorillonite, tetradecyldimethyl tertiary amine, and sulfuric acid metal salt is 1:(0.5 - 1):(0.5 - 1).

[0033] Montmorillonite has a layered structure. When montmorillonite is mixed with tetradecyldimethyl tertiary amine, the molecular chain of tetradecyldimethyl tertiary amine can enter the interlayer of montmorillonite, making montmorillonite combine with tetradecyldimethyl tertiary amine to obtain organically modified montmorillonite. The modified montmorillonite has a higher degree of combination and improved binding strength with the resin matrix and piperazine pyrophosphate. Secondly, the metal ions in the sulfuric acid metal salt can undergo a coordination or complexation reaction with tetradecyldimethyl tertiary amine, that is, the sulfuric acid metal salt can combine with montmorillonite through tetradecyldimethyl tertiary amine. That is to say, the modified montmorillonite is grafted with tetradecyldimethyl tertiary amine and sulfuric acid metal salt. In step S3, tetradecyldimethyl tertiary amine can combine with the coupling agent, and the sulfuric acid metal salt hydrolyzes into metal hydroxide in an alkaline solution to wrap on the surface of piperazine pyrophosphate, and at the same time load montmorillonite on the surface of piperazine pyrophosphate. When using this piperazine pyrophosphate flame retardant, montmorillonite can be embedded into the network structure of the resin matrix to play a strengthening role. At the same time, montmorillonite has flame retardancy and can also improve the flame retardancy of the resin. On the other hand, by combining montmorillonite and piperazine pyrophosphate through metal hydroxide, the binding strength between the piperazine pyrophosphate flame retardant and the resin matrix can be improved, thereby improving the migration resistance of the flame retardant and prolonging the flame retardant life of the resin.

[0034] The features and properties of the present invention are further described in detail below in conjunction with examples.

[0035] Example 1

[0036] Prepare modified montmorillonite:

[0037] Mix montmorillonite with water, stir evenly, then add tetradecyldimethylamine and zinc sulfate solution, mix evenly, filter, and dry to obtain modified montmorillonite. Among them, the mass ratio of montmorillonite, tetradecyldimethylamine and zinc sulfate is 1:1:1.

[0038] Prepare the pyrophosphate flame retardant of this example according to the following method:

[0039] S1, Mix anhydrous piperazine with water, heat to 40 °C, then dropwise add a phosphoric acid solution with a mass fraction of 85% to the system, microwave heat to 80 °C and keep warm for 3 h; add vinyltrimethoxysilane, stir evenly and then cool to room temperature, filter and dry to obtain modified dipiperazine pyrophosphate; among them, the mass ratio of anhydrous piperazine to vinyltrimethoxysilane is 1:1, and the molar ratio of anhydrous piperazine to phosphoric acid is 1:2.

[0040] S2, Mix the modified dipiperazine pyrophosphate obtained in step S1 with a catalyst, add it to a kneader, heat to 200 °C, react for 3 h, cool and crush to obtain the crude pyrophosphate piperazine; among them, the catalyst is a mixture of P2O5 and calcium hydride, and the mass ratio of the two is 1:0.5. The mass ratio of modified dipiperazine pyrophosphate to the catalyst is 1:0.01.

[0041] S3, Mix the modified montmorillonite, methylhydrogen siloxane oil and coupling agent evenly, then add the crude pyrophosphate piperazine obtained in step S2 and ammonia water with a mass fraction of 5%, adjust the pH value to 8, then ultrasonically vibrate at 50 KHz for 2 h, mix evenly, dry and crush to obtain the pyrophosphate piperazine flame retardant. The mass ratio of modified montmorillonite, methylhydrogen siloxane oil, coupling agent and crude pyrophosphate piperazine is 1:1:0.5:2.

[0042] Example 2

[0043] Prepare the pyrophosphate flame retardant of this example according to the following method:

[0044] S1, Mix anhydrous piperazine with water, heat to 40 °C, then dropwise add a phosphoric acid solution with a mass fraction of 85% to the system, microwave heat to 80 °C and keep warm for 3 h; add vinyltriethoxysilane, stir evenly and then cool to room temperature, filter and dry to obtain modified dipiperazine pyrophosphate; among them, the mass ratio of anhydrous piperazine to vinyltriethoxysilane is 1:1, and the molar ratio of anhydrous piperazine to phosphoric acid is 1:2.

[0045] S2, Mix the modified dipiperazine pyrophosphate obtained in step S1 with a catalyst, add it to a kneader, heat to 200 °C, react for 3 h, cool and crush to obtain the crude pyrophosphate piperazine; among them, the catalyst is a mixture of P2O5 and calcium hydride, and the mass ratio of the two is 1:0.3. The mass ratio of modified dipiperazine pyrophosphate to the catalyst is 1:0.01.

[0046] S3. Mix the modified montmorillonite, methyl hydrogen siloxane oil, and coupling agent evenly, then add the crude piperazine pyrophosphate from step S2 and 5% ammonia water by mass fraction, adjust the pH value to 8, then ultrasonically vibrate at a frequency of 60 KHz for 1.5 h, mix evenly, dry and pulverize to obtain the piperazine pyrophosphate flame retardant. The mass ratio of the modified montmorillonite, methyl hydrogen siloxane oil, coupling agent, and crude piperazine pyrophosphate is 2:1.5:1:2.

[0047] Example 3

[0048] The piperazine pyrophosphate flame retardant of this example is prepared by the following method:

[0049] S1. Mix anhydrous piperazine with water, heat to 40 °C, then dropwise add 85% phosphoric acid solution by mass fraction to the system, microwave heat to 90 °C and keep warm for 2 h; add 3-(methacryloyloxy)propyltrimethoxysilane, stir evenly and then cool to room temperature, filter and dry to obtain modified dipiperazine pyrophosphate; among them, the mass ratio of anhydrous piperazine to 3-(methacryloyloxy)propyltrimethoxysilane is 1:1. The molar ratio of anhydrous piperazine to phosphoric acid is 1:2.

[0050] S2. Mix the modified dipiperazine pyrophosphate obtained in step S1 with a catalyst, add it to a kneader, heat to 180 °C, react for 3 h, cool and pulverize to obtain the crude piperazine pyrophosphate; among them, the catalyst is a mixture of P2O5 and calcium hydride, and the mass ratio of the two is 1:0.5. The mass ratio of the modified dipiperazine pyrophosphate to the catalyst is 1:0.01.

[0051] S3. Mix the modified montmorillonite, methyl hydrogen siloxane oil, and coupling agent of Example 1 evenly, then add the crude piperazine pyrophosphate from step S2 and 5% ammonia water by mass fraction, adjust the pH value to 8, then ultrasonically vibrate at a frequency of 80 KHz for 1 h, mix evenly, dry and pulverize to obtain the piperazine pyrophosphate flame retardant. The mass ratio of the modified montmorillonite, methyl hydrogen siloxane oil, coupling agent, and crude piperazine pyrophosphate is 2:1:1:2.

[0052] Example 4

[0053] The piperazine pyrophosphate flame retardant of this example is prepared by the following method:

[0054] S1. Mix anhydrous piperazine with water, heat to 40 °C, then dropwise add 85% phosphoric acid solution by mass fraction to the system, microwave heat to 80 °C and keep warm for 3 h; add allyl tris(β-methoxyethoxy)silane, stir evenly and then cool to room temperature, filter and dry to obtain modified dipiperazine pyrophosphate; among them, the mass ratio of anhydrous piperazine to allyl tris(β-methoxyethoxy)silane is 1:1.5. The molar ratio of anhydrous piperazine to phosphoric acid is 1:2.

[0055] S2. Mix the modified piperazine diphosphate prepared in step S1 with a catalyst, add it to a kneader, heat to 180 - 220 °C, react for 2 - 3 h, cool, and pulverize to obtain the crude piperazine pyrophosphate. Among them, the catalyst is a mixture of P2O5 and calcium hydride, and the mass ratio of the two is 1:0.1. The mass ratio of the modified piperazine diphosphate to the catalyst is 1:0.01.

[0056] S3. Mix the modified montmorillonite, methyl hydrogen siloxane oil, and coupling agent in Example 1 evenly, then add the crude piperazine pyrophosphate from step S2 and ammonia water with a mass fraction of 5%, adjust the pH value to 8, then perform ultrasonic oscillation at a frequency of 50 KHz for 2 h, mix evenly, dry, and pulverize to obtain the piperazine pyrophosphate flame retardant. The mass ratio of the modified montmorillonite, methyl hydrogen siloxane oil, coupling agent, and crude piperazine pyrophosphate is 1:1:1:3.

[0057] Example 5

[0058] The piperazine pyrophosphate flame retardant of this example is prepared by the following method:

[0059] S1. Mix anhydrous piperazine with water, heat to 40 °C, then dropwise add a phosphoric acid solution with a mass fraction of 85% to the system, microwave heat to 80 °C and keep warm for 3 h; add allyl tris(β - methoxyethoxy)silane, stir evenly and then cool to room temperature, filter and dry to obtain the modified piperazine diphosphate. Among them, the mass ratio of anhydrous piperazine to allyl tris(β - methoxyethoxy)silane is 1:1.5.

[0060] S2. Mix the modified piperazine diphosphate prepared in step S1 with a catalyst, add it to a kneader, heat to 200 °C, react for 3 h, cool, and pulverize to obtain the crude piperazine pyrophosphate. Among them, the catalyst is a mixture of P2O5 and calcium hydride, and the mass ratio of the two is 1:0.5. The mass ratio of the modified piperazine diphosphate to the catalyst is 1:0.02.

[0061] S3. Mix the modified montmorillonite, methyl hydrogen siloxane oil, and coupling agent evenly, then add the crude piperazine pyrophosphate from step S2 and ammonia water with a mass fraction of 5%, adjust the pH value to 8, then perform ultrasonic oscillation at a frequency of 80 KHz for 2 h, mix evenly, dry, and pulverize to obtain the piperazine pyrophosphate flame retardant. The mass ratio of the modified montmorillonite, methyl hydrogen siloxane oil, coupling agent, and crude piperazine pyrophosphate is 2:2:1:2.

[0062] Example 6

[0063] The difference from Example 1 is that the preparation method of the modified montmorillonite is as follows:

[0064] Mix montmorillonite with water, stir evenly, then add tetradecyldimethylamine and zinc sulfate solution, mix evenly, filter, and dry to obtain modified montmorillonite. Among them, the mass ratio of montmorillonite, tetradecyldimethylamine, and zinc sulfate is 1:0.5:0.5.

[0065] Example 7

[0066] The difference from Example 1 is that the preparation method of the modified montmorillonite is as follows:

[0067] Mix montmorillonite with water, stir evenly, then add tetradecyldimethylamine and zinc sulfate solution, mix evenly, filter, and dry to obtain modified montmorillonite. Among them, the mass ratio of montmorillonite, tetradecyldimethylamine, and zinc sulfate is 1:0.5:1.

[0068] Example 8

[0069] The difference from Example 1 is that the preparation method of the modified montmorillonite is as follows:

[0070] Mix montmorillonite with water, stir evenly, then add tetradecyldimethylamine and zinc sulfate solution, mix evenly, filter, and dry to obtain modified montmorillonite. Among them, the mass ratio of montmorillonite, tetradecyldimethylamine, and zinc sulfate is 1:1:0.5.

[0071] Comparative Example 1

[0072] The difference from Example 1 is that in this comparative example, in step S1, the coupling agent is not added, and the remaining steps, raw materials, etc. are the same as those in Example 1.

[0073] Comparative Example 2

[0074] The difference from Example 1 is that in this comparative example, in step S3, the montmorillonite is not modified and the montmorillonite is directly used, and the remaining steps, raw materials, etc. are the same as those in Example 1.

[0075] Comparative Example 3

[0076] The difference from Example 1 is that in this comparative example, in step S3, methylhydrogen siloxane oil is not added, and the remaining steps, raw materials, etc. are the same as those in Example 1.

[0077] Comparative Example 4

[0078] The difference from Example 1 is that in this comparative example, in step S3, methylhydrogen siloxane oil and the coupling agent are not added, and the remaining steps, raw materials, etc. are the same as those in Example 1.

[0079] Experimental Example

[0080] The flame retardants of Examples 1-5 and Comparative Examples 1-4 were used to prepare flame-retardant polypropylene, and the specific method is as follows:

[0081] The polypropylene masterbatch and the flame retardant were added to a screw extrusion molding machine according to a mass ratio of 95:5 to obtain polypropylene resin.

[0082] The oxygen index performance and UL94 flame retardancy of the above polypropylene resin were tested, and the results are shown in Table 1:

[0083] Table 1 Flame Retardant Properties of Each Resin

[0084] LOI(%) Flame retardancy Example 1 31.2 V1 Example 2 32.3 V1 Example 3 30.8 V1 Example 4 30.9 V1 Example 5 32.7 V1 Comparative Example 1 21.5 V2 Comparative Example 2 18.3 V2 Comparative Example 3 22.3 V2 Comparative Example 4 20.1 V2 Polypropylene masterbatch 16.8 V2

[0085] It can be seen from Table 1 that compared with the polypropylene masterbatch, after adding the flame retardants of Examples 1-5, the LOI of the resin increased and the flame retardant grade reached V1. The flame retardant of Comparative Example 1 did not add a coupling agent in S1, and its LOI was lower than that of Examples 1-5, and the flame retardant performance was poor. In Comparative Example 2, the montmorillonite was not modified, and the flame retardant performance of the resin decreased significantly. It can be seen that adding modified montmorillonite can significantly improve the flame retardant performance of the resin agent.

[0086] After aging treatment (ultraviolet light irradiation at 60 °C for 24 h) of the resins of Examples 1-5 and Comparative 1-4, the oxygen index performance and UL94 flame retardant performance were tested, and the results are shown in Table 2.

[0087] Table 2 Flame Retardant Properties of Each Resin after Aging Treatment

[0088] LOI(%) Flame retardancy Example 1 30.2 V1 Example 2 31.4 V1 Example 3 29.5 V1 Example 4 28.3 V1 Example 5 31.4 V1 Comparative Example 1 17.3 V2 Comparative Example 2 10.2 V3 Comparative Example 3 19.3 V2 Comparative Example 4 17.4 V2 Polypropylene masterbatch 13.6 V3

[0089] It can be seen from Table 2 that after aging treatment, the flame retardant performance of the resins of Examples 1-5 changed little. In Comparative Example 2, the montmorillonite was not modified, and during the aging treatment, the flame retardant migrated in the resin, resulting in a low concentration of the flame retardant on the resin surface and poor flame retardant performance; in Comparative Example 1, no coupling agent was added, but under the action of the modified montmorillonite, the binding strength between the flame retardant and the resin was better than that of Comparative Example 3, and the influence of the flame retardant on the migration resistance was small, but the flame retardant performance was still superior to that of Comparative Example 3. In Comparative Examples 3 and 4, no methyl hydrogen siloxane oil was added, and the dispersion of the flame retardant in the resin was worse than that of Examples 1-5. Therefore, the flame retardancy of the obtained resin was also poor. It can be seen that modified montmorillonite can improve the binding strength between the flame retardant and the resin, reduce the migration of the flame retardant, and cooperate with the coupling agent and methyl hydrogen siloxane oil to synergistically enhance the flame retardancy of the resin, reduce the migration of the flame retardant, and improve the migration resistance of the flame retardant.

[0090] The embodiments described above are some, but not all, of the embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely represents selected 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 fall within the scope of protection of the present invention.

Claims

1. A method for synthesizing a migration-resistant piperazine pyrophosphate flame retardant, characterized in that: The following steps are involved: S1, mixing anhydrous piperazine with water, heating, then dropping a phosphoric acid solution into the system, heating to 80-90°C by microwave and keeping the temperature for 2-3h; adding a coupling agent, stirring evenly, cooling to room temperature, filtering, and drying to obtain modified diphosphate piperazine; S2, mixing the modified piperazine diphosphate obtained in step S1 with a catalyst, adding the mixture to a kneader, heating to 180-220° C., reacting for 2-3 hours, cooling, and crushing to obtain a crude piperazine pyrophosphate; S3, uniformly mixing the modified montmorillonite, methyl hydrogen silicone oil and coupling agent, then adding the crude piperazine pyrophosphate and ammonia water of step S2, ultrasonically shaking, uniformly mixing, drying and crushing to obtain the piperazine pyrophosphate flame retardant.

2. The method for synthesizing the migration-resistant piperazine pyrophosphate flame retardant according to claim 1, characterized in that: In the steps S1 and S3, the coupling agent is a double bond silane coupling agent, including a mixture of one or more of vinyl trimethoxy silane, vinyl triethoxy silane, 3-(methacryloyloxy)propyl trimethoxy silane, and acryl tri(β-methoxyethoxy) silane.

3. The method for synthesizing the migration-resistant piperazine pyrophosphate flame retardant according to claim 1, characterized in that: In step S2, the catalyst is a mixture of P2O5 and calcium hydride, and the mass ratio of the two is 1:(0.1-0.5).

4. The method for synthesizing the migration-resistant piperazine pyrophosphate flame retardant according to claim 1, characterized in that: The modified montmorillonite is prepared by the following method: The montmorillonite is mixed with water, stirred evenly, and then tetradecyl dimethyl tertiary amine and a metal sulfate solution are added, mixed evenly, filtered, and dried to obtain the modified montmorillonite.

5. The method for synthesizing the migration-resistant piperazine pyrophosphate flame retardant according to claim 4, characterized in that: The metal sulfate solution is zinc sulfate, magnesium sulfate or a mixture of the two.

6. The method for synthesizing the migration-resistant piperazine pyrophosphate flame retardant according to claim 4, characterized in that: The mass ratio of the montmorillonite, tetradecyl dimethyl tertiary amine and the metal sulfate is 1:(0.5-1):(0.5-1).

7. The method for synthesizing the migration-resistant piperazine pyrophosphate flame retardant according to claim 1, characterized in that: In step S3, the mass ratio of modified montmorillonite, methyl hydrogen silicone oil, coupling agent and crude piperazine pyrophosphate is (1-2): (1-2): (0.5-1): (2-3).

8. The method for synthesizing the migration-resistant piperazine pyrophosphate flame retardant according to claim 1, characterized in that: The frequency of the ultrasonic oscillation is 50-80KHz, and the duration is 1-2h.

9. The method for synthesizing the migration-resistant piperazine pyrophosphate flame retardant according to claim 1, characterized in that: In step S1, the mass ratio of anhydrous piperazine to coupling agent is 1:(1-1.5).

10. A migration-resistant piperazine pyrophosphate flame retardant, characterized in that: Prepared by the synthesis method according to any one of claims 1 to 9.