An efficient polyphosphate ester flame retardant and its preparation method

Abstract

The present invention discloses an efficient polyphosphate ester flame retardant and its preparation method, belonging to the technical field of flame retardants. It includes phenoxyphosphoryl dichloride, modified diol and a catalyst, and the molar ratio of the three is 1:0.8 - 1.2:0.01 - 0.03. The polyphosphate ester flame retardant uses phenoxyphosphoryl dichloride as one of the raw materials, endowing the flame retardant with high heat stability; the prepared polyphosphate ester flame retardant is solid, which is easier to transport compared with the liquid flame retardants on the market; the modified diol is prepared through two-step reaction, and as one of the raw materials, the modified diol contains various functional groups in its molecule, which can greatly enhance the flame retardant effect of the flame retardant and improve the heat stability of the flame retardant; in summary, the polyphosphate ester flame retardant prepared by the present invention has good flame retardant effect, convenient transportation, and strong heat stability, and has important application value in the technical field of flame retardants.

Description

Technical Field

[0001] The present invention belongs to the technical field of flame retardants, and specifically relates to a high-efficiency polyphosphate flame retardant and a preparation method thereof. Background Art

[0002] With the wide application of polymer materials in fields such as construction, electronics, and transportation, the potential safety hazards caused by their flammability have attracted increasing attention. As a key additive for suppressing material combustion, the technological development of flame retardants has always revolved around three core issues: flame retardancy efficiency, environmental friendliness, and compatibility with substrates. Among various flame retardant systems, phosphorus-based flame retardants have gradually become the mainstream choice to replace traditional halogen-based flame retardants due to their low smoke, low toxicity, and high efficiency.

[0003] Polyphosphates are a class of polymers with a phosphorus-oxygen bond (P-O) as the main chain, formed by repeated connection of phosphate ester structural units. These compounds can play a flame retardant role through multiple pathways during combustion: in the condensed phase, the polyphosphoric acid generated by the thermal decomposition of polyphosphates can catalyze the formation of a dense carbon layer on the material surface, isolating the transfer of oxygen and heat; in the gas phase, the phosphorus-containing free radicals (such as PO·) generated by decomposition can capture the active free radicals (H·, OH·) in the combustion chain reaction, inhibiting flame spread. Moreover, compared with small molecule phosphates, the high molecular weight characteristics of polyphosphates significantly reduce their mobility in the substrate, thereby prolonging the flame retardant time effect. At the same time, their compatibility with the polymer matrix can be further optimized through molecular structure design, reducing the negative impact on the mechanical properties of the material. It is regarded as an important research direction for the new generation of flame retardants.

[0004] The current synthesis route of polyphosphate flame retardants is mainly based on the polycondensation reaction of phosphate monomers, but there are still many technical bottlenecks in practical applications. Traditional preparation processes often use polyphosphoric acid or phosphorus pentoxide as the phosphorus source. Although these strong dehydrating agents can accelerate the reaction process, they are prone to cause side reactions, resulting in a wide molecular weight distribution and insufficient purity of the product, thereby affecting the stability of the flame retardant performance. For example, in the esterification reaction of polyphosphoric acid and polyols, the intense exothermic effect often causes local overheating, leading to molecular chain breakage or excessive crosslinking, and it is difficult to balance the thermal stability and processing fluidity of the final product. Therefore, aiming at the above technical pain points, it is urgent to develop a polyphosphate flame retardant with excellent flame retardant effect and good heat stability to meet the higher requirements in the technical field of flame retardants. Summary of the Invention

[0005] The purpose of the present invention is to overcome the defects of the prior art and provide a preparation method of aluminum titanate nanofibers.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] A preparation method of a high-efficiency polyphosphate flame retardant, comprising the following steps:

[0008] A1. Add phenoxyphosphoryl dichloride, modified diol and a catalyst into a reaction kettle equipped with a hydrogen chloride gas discharging device. Introduce a protective gas and continuously heat up to 90 - 100 °C. Continuously stir until the reactants are completely in a liquid state. Then raise the temperature to 140 - 160 °C for reaction until the system becomes viscous and the "climbing rod" phenomenon appears. Raise the temperature again until it reaches 200 - 210 °C and continue to stir and react for 3 - 6 h. After the reaction is completed, stop stirring.

[0009] A2. Vacuumize the reaction kettle to remove the residual hydrogen chloride gas in the system. Then cool it. Dissolve the obtained solid in dichloroethane and precipitate with petroleum ether. After filtration, drying and pulverization, a high - efficiency polyphosphate flame retardant is obtained.

[0010] Further, the molar ratio of the phenoxyphosphoryl dichloride, the modified diol and the catalyst is 1:0.8 - 1.2:0.01 - 0.03.

[0011] Further, the catalyst is one of anhydrous calcium chloride and anhydrous aluminum chloride.

[0012] Further, the protective gas is nitrogen.

[0013] Further, the drying conditions are drying in an oven at 80 - 100 °C for 6 - 12 h.

[0014] Using phenoxyphosphoryl dichloride as one of the raw materials, it contains a benzene ring and belongs to aryl. The π - π conjugate system in aromatic compounds has high thermal stability, which can effectively disperse heat and improve the heat resistance of polyphosphate. In addition, most of the polyphosphate flame retardants on the market are in a liquid state, having defects such as inconvenient transportation and easy penetration. While the polyphosphate flame retardant of the present invention is in a solid state, which is convenient for transportation.

[0015] Further, the modified diol is prepared through the following steps:

[0016] Step 1. Add 1,3 - bis(aminopropyl)tetramethyldisiloxane and N,N - dimethylformamide into a three - necked round - bottom flask equipped with a thermometer, a magnetic stirring system and a spherical condenser. Under the condition of an ice - water bath, dropwise add formaldehyde solution (mass fraction 12%) and continuously stir. After the dropping is completed, add 4 - hydroxystyrene. Raise the temperature until the temperature of the reaction system reaches 70 °C and reflux for 8 h. After the reaction is completed, cool to room temperature, rotary evaporate to remove part of the solvent, and carry out column chromatography purification using a benzene - ethyl acetate (3:2, v / v) elution system. Finally, remove the residual eluent by vacuum distillation to obtain an intermediate product.

[0017] 1,3 - Bis(aminopropyl)tetramethyldisiloxane underwent a Mannich condensation reaction with 4 - hydroxystyrene, and the molar ratio of 1,3 - bis(aminopropyl)tetramethyldisiloxane to 4 - hydroxystyrene was adjusted to be close to 1:2 (4 - hydroxystyrene was slightly in excess) to ensure that two amino groups on 1,3 - bis(aminopropyl)tetramethyldisiloxane participated in the reaction, obtaining an intermediate product; the specific reaction process is as follows:

[0018]

[0019] Step 2: Add the intermediate product, azobisisobutyronitrile (AIBN), and N,N - dimethylformamide into a three - necked round - bottom flask equipped with a thermometer, a magnetic stirring system, and a spherical condenser. After stirring and mixing evenly, use a constant - pressure dropping funnel to drop 3 - mercaptopropanol into the flask. During the dropping process, keep stirring. After the dropping is completed, raise the temperature until the temperature of the reaction system reaches 85 °C, and reflux for 8 h. After the reaction is completed, cool to room temperature, rotary evaporate to remove part of the solvent, and perform column chromatography purification using a benzene - ethyl acetate (5:3, v / v) elution system. Finally, remove the residual eluent by vacuum distillation to obtain the modified diol;

[0020] Under the action of azobisisobutyronitrile, the unsaturated carbon - carbon double bonds on the intermediate product reacted with the mercapto groups on 3 - mercaptopropanol in a thiol - ene click reaction, and the molar ratio of the intermediate product to 3 - mercaptopropanol was adjusted to be close to 1:2 (3 - mercaptopropanol was slightly in excess) to ensure that two double bonds on the intermediate product participated in the reaction, obtaining the modified diol; the specific reaction process is as follows:

[0021]

[0022] The prepared modified diol molecules are used as raw materials for preparing polyphosphate flame retardants. The molecules are centered around the - Si - O - Si - segment. Since the Si - O bond has a high bond energy, it can improve the heat - resistant stability of the flame retardant. The introduced benzoxazine structure contains a benzene ring and an oxazine ring, and the conjugated structure of the two imparts high rigidity to the molecular chain, restricts the movement of the chain segments, and reduces the absorption of thermal vibration energy at high temperatures. In addition, the lone - pair electrons of nitrogen and oxygen atoms form a conjugated system with the benzene ring, enhancing the electron delocalization within the molecule and further enhancing the heat - resistant stability of the flame retardant; moreover, the modified diol molecules contain a variety of heteroatoms, including Si, N, and S. Among them, the silicon - containing element decomposes into silicon dioxide or a silicon - oxy - carbon network structure at high temperatures, and these products can catalyze the formation of a dense and stable carbon layer on the surface of the substrate, improving the flame - retardant performance; nitrogen decomposes into nitrogen - containing gases at high temperatures, reducing the oxygen concentration and improving the flame - retardant performance; finally, sulfur can release strong acids such as sulfuric acid under high - temperature conditions, promoting the dehydration and carbonization of the substrate and also showing excellent flame - retardant performance in the condensed phase. These heteroatoms can play a synergistic role with polyphosphate, greatly enhancing the flame - retardant effect of the flame retardant.

[0023] Further, in step 1, the dosage ratio of 1,3-bis(aminopropyl)tetramethyldisiloxane, N,N-dimethylformamide, formaldehyde solution, and 4-hydroxystyrene is 24.8 g: 100 mL: 15 mL: 26.7 g.

[0024] Further, in step 2, the dosage ratio of the intermediate product, azobisisobutyronitrile, N,N-dimethylformamide, and 3-mercaptopropanol is 53.6 g: 0.3 g: 150 mL: 20.3 g.

[0025] Advantages of the present invention:

[0026] 1. The polyphosphate ester flame retardant prepared by the present invention uses phenoxyphosphoryl dichloride as one of the raw materials, endowing the flame retardant with high heat stability;

[0027] 2. The prepared polyphosphate ester flame retardant is solid, which is easier to transport compared with the liquid flame retardants on the market;

[0028] 3. The modified diol is prepared through two-step reactions. As one of the raw materials, the modified diol contains multiple functional groups in its molecule, which can greatly enhance the flame retardant effect of the flame retardant and improve the heat stability of the flame retardant;

[0029] In summary, the polyphosphate ester flame retardant prepared by the present invention has good flame retardant effect, is convenient for transportation, and has strong heat stability, and has important application value in the field of flame retardant technology. Description of the Drawings

[0030] The present invention will be further described below with reference to the accompanying drawings.

[0031] Figure 1 SEM image of the residual carbon after the combustion test of the high-efficiency polyphosphate ester flame retardant prepared in Example 5 of the present invention added to polypropylene. Specific Embodiments

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. 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.

[0033] Example 1

[0034] Preparation of modified diol:

[0035] Step 1: Add 24.8 g of 1,3-bis(aminopropyl)tetramethyldisiloxane and 100 mL of N,N-dimethylformamide into a three-necked round-bottom flask equipped with a thermometer, a magnetic stirring system and a spherical condenser. Under an ice-water bath condition, slowly add 15 mL of formaldehyde solution (mass fraction 12%) drop by drop, and continuously stir. After the addition is completed, add 26.7 g of 4-hydroxystyrene, then raise the temperature until the temperature of the reaction system reaches 70 °C, and reflux for 8 h. After the reaction is completed, cool to room temperature, rotary evaporate to remove part of the solvent, carry out column chromatography purification using a benzene-ethyl acetate (3:2, v / v) elution system, and finally remove the residual eluent by vacuum distillation to obtain the intermediate product;

[0036] Step 2: Add 53.6 g of the intermediate product, 0.3 g of azobisisobutyronitrile and 150 mL of N,N-dimethylformamide into a three-necked round-bottom flask equipped with a thermometer, a magnetic stirring system and a spherical condenser. After stirring and mixing evenly, use a constant pressure dropping funnel to add 20.3 g of 3-mercaptopropanol drop by drop into the flask, continuously stir during the addition process. After the addition is completed, raise the temperature until the temperature of the reaction system reaches 85 °C, and reflux for 8 h. After the reaction is completed, cool to room temperature, rotary evaporate to remove part of the solvent, carry out column chromatography purification using a benzene-ethyl acetate (5:3, v / v) elution system, and finally remove the residual eluent by vacuum distillation to obtain the modified diol.

[0037] Example 2

[0038] Preparation of modified diol:

[0039] Step 1: Add 49.6 g of 1,3-bis(aminopropyl)tetramethyldisiloxane and 200 mL of N,N-dimethylformamide into a three-necked round-bottom flask equipped with a thermometer, a magnetic stirring system and a spherical condenser. Under an ice-water bath condition, slowly add 30 mL of formaldehyde solution (mass fraction 12%) drop by drop, and continuously stir. After the addition is completed, add 53.4 g of 4-hydroxystyrene, then raise the temperature until the temperature of the reaction system reaches 70 °C, and reflux for 8 h. After the reaction is completed, cool to room temperature, rotary evaporate to remove part of the solvent, carry out column chromatography purification using a benzene-ethyl acetate (3:2, v / v) elution system, and finally remove the residual eluent by vacuum distillation to obtain the intermediate product;

[0040] Step 2: Add 107.2 g of the intermediate product, 0.6 g of azobisisobutyronitrile, and 300 mL of N,N-dimethylformamide into a three-necked round-bottom flask equipped with a thermometer, a magnetic stirring system, and a spherical condenser. After stirring and mixing evenly, use a constant-pressure dropping funnel to add 40.6 g of 3-mercaptopropanol dropwise into the flask. Keep stirring during the dropping process. After the dropping is completed, raise the temperature until the temperature of the reaction system reaches 85 °C, and reflux for 8 h. After the reaction is completed, cool to room temperature, rotary evaporate to remove part of the solvent, perform column chromatography purification using a benzene-ethyl acetate (5:3, v / v) elution system, and finally remove the residual eluent by vacuum distillation to obtain the modified diol.

[0041] Example 3

[0042] Preparation of high-efficiency polyphosphate flame retardant:

[0043] A1: Add 21.1 g of phenoxyphosphoryl dichloride, 57.7 g of the modified diol prepared in Example 1, and 0.1 g of anhydrous calcium chloride into a reaction kettle equipped with a hydrogen chloride gas discharge device. Introduce nitrogen as a protective gas, continuously raise the temperature until 90 °C, and continuously stir until the reactants are completely in a liquid state. Then raise the temperature to 140 °C and carry out the reaction until the system becomes viscous and the rod climbing phenomenon appears. Raise the temperature again until the temperature reaches 200 °C, and continue to stir and react for 3 h. After the reaction is completed, stop stirring;

[0044] A2: Evacuate the reaction kettle to remove the residual hydrogen chloride gas in the system, then cool it. Dissolve the obtained solid in dichloroethane, precipitate with petroleum ether, filter, and dry in an oven at 80 °C for 6 h. After pulverization, obtain the high-efficiency polyphosphate flame retardant.

[0045] Example 4

[0046] Preparation of high-efficiency polyphosphate flame retardant:

[0047] A1: Add 21.1 g of phenoxyphosphoryl dichloride, 72.1 g of the modified diol prepared in Example 2, and 0.2 g of anhydrous calcium chloride into a reaction kettle equipped with a hydrogen chloride gas discharge device. Introduce nitrogen as a protective gas, continuously raise the temperature until 100 °C, and continuously stir until the reactants are completely in a liquid state. Then raise the temperature to 150 °C and carry out the reaction until the system becomes viscous and the rod climbing phenomenon appears. Raise the temperature again until the temperature reaches 210 °C, and continue to stir and react for 5 h. After the reaction is completed, stop stirring;

[0048] A2: Evacuate the reaction kettle to remove the residual hydrogen chloride gas in the system, then cool it. Dissolve the obtained solid in dichloroethane, precipitate with petroleum ether, filter, and dry in an oven at 100 °C for 12 h. After pulverization, obtain the high-efficiency polyphosphate flame retardant.

[0049] Example 5

[0050] Preparation of a highly efficient polyphosphate flame retardant:

[0051] A1. Add 21.1 g of phenoxyphosphoryl dichloride, 86.5 g of the modified diol prepared in Example 2, and 0.3 g of anhydrous calcium chloride into a reaction kettle equipped with a hydrogen chloride gas discharge device. Introduce nitrogen as the protective gas, continuously heat up to 100 °C, and continuously stir until the reactants are completely in a liquid state. Then raise the temperature to 160 °C for reaction until the system becomes viscous and shows the phenomenon of climbing the rod. Raise the temperature again until it reaches 200 °C, continue stirring and reacting for 6 h. After the reaction is completed, stop stirring;

[0052] A2. Evacuate the reaction kettle to remove the residual hydrogen chloride gas in the system. Then cool it. Dissolve the obtained solid in dichloroethane, precipitate with petroleum ether, filter, and dry in an oven at 100 °C for 12 h. After pulverization, a highly efficient polyphosphate flame retardant is obtained;

[0053] Mix the flame retardant prepared in Example 5 with polypropylene at a mass ratio of 12:100, add it to a twin-screw extruder for melt blending. After extrusion, conduct a combustion test, and use a scanning electron microscope to measure the SEM image of the char residue after combustion, as Figure 1 shown.

[0054] Comparative Example 1

[0055] Replace the modified diol in Example 5 with 1,4-butanediol of the same mass, and the remaining steps are the same as those in Example 5 to prepare a flame retardant.

[0056] Comparative Example 2

[0057] Use a commercially available polyphosphate flame retardant.

[0058] Respectively mix Examples 3, 4, 5 and Comparative Examples 1, 2 with polypropylene at a mass ratio of 12:100, add them to a twin-screw extruder for melt blending, extrusion, and pelletization. Then conduct the following performance tests:

[0059] Use the national standard GB / T 2406-2008 "Test Method for Flammability of Plastics" to measure the limiting oxygen index of the specimens;

[0060] Place the specimens in an environment of 140 °C, oxidize them with hot air for 72 h, then measure the limiting oxygen index (test standard GB / T2406-2008), and calculate the retention rate of the limiting oxygen index; Retention rate of limiting oxygen index = Limiting oxygen index after testing / Limiting oxygen index before testing × 100%;

[0061] The measured results are shown in Table 1:

[0062] Table 1

[0063]

[0064] As can be seen from Table 1, the flame retardancy and heat resistance stability of the polyphosphate flame retardant prepared in the embodiments of the present invention are higher than those of the comparative examples. Moreover, in Examples 3, 4, and 5, with the continuous increase of the dosage of the modified diol, the flame retardancy and heat stability of the flame retardant are enhanced. From Figure 1 it can be seen that when Example 5 is added to polypropylene, there are fewer pores, and a carbon layer with better compactness is formed, covering the surface of the material and improving the flame retardancy of the material. In summary, the present invention has important application value in the field of flame retardant technology.

[0065] In the description of the specification, the descriptions referring to terms such as "one embodiment", "example", "specific example", etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0066] The above content is only an example and illustration of the present invention. Those skilled in the art of the present technology can make various modifications or supplements to the described specific embodiments or use similar methods for substitution. As long as they do not deviate from the invention or exceed the scope defined by the claims of the present invention, they should fall within the protection scope of the present invention.

Claims

1. A preparation method of an efficient polyphosphate ester flame retardant, characterized in that, It includes the following steps: A1. Add phenoxyphosphoryl dichloride, modified diol and catalyst into a reaction kettle, introduce a protective gas, continuously heat up to 90 - 100 °C, continuously stir until the reactants are completely in a liquid state, then raise the temperature to 140 - 160 °C for reaction until the system becomes viscous and shows the phenomenon of climbing rod, then raise the temperature again until the temperature reaches 200 - 210 °C, stir and react for 3 - 6 h, after the reaction is completed, stop stirring; A2. Vacuumize the reaction kettle, then cool it. Dissolve the obtained solid in dichloroethane, precipitate with petroleum ether, filter, dry, and pulverize to obtain a high - efficiency polyphosphate flame retardant; Among them, the modified diol is prepared through the following steps: Step 1. Add 1,3 - bis(aminopropyl)tetramethyldisiloxane and N,N - dimethylformamide into a flask. Under the condition of an ice - water bath, dropwise add formaldehyde solution and continuously stir. After the addition is completed, add 4 - hydroxystyrene, reflux and react at 70 °C for 8 h. After the reaction is completed, cool, rotary evaporate, purify by column chromatography, and distill under reduced pressure to obtain an intermediate product; Step 2. Add the intermediate product, azobisisobutyronitrile and N,N - dimethylformamide into a flask. After stirring and mixing evenly, add 3 - mercaptopropanol. Stir continuously during the dropping process. After the dropping is completed, reflux and react at 85 °C for 8 h. After the reaction is completed, cool to room temperature, rotary evaporate, purify by column chromatography, and distill under reduced pressure to obtain the modified diol.

2. The preparation method of an efficient polyphosphate ester flame retardant according to claim 1, characterized in that The molar ratio of the phenoxyphosphoryl dichloride, modified diol and catalyst is 1:0.8 - 1.2:0.01 - 0.

03.

3. The preparation method of an efficient polyphosphate flame retardant according to claim 1, characterized in that, In Step 1, the dosage ratio of 1,3 - bis(aminopropyl)tetramethyldisiloxane, N,N - dimethylformamide, formaldehyde solution, and 4 - hydroxystyrene is 24.8 g:100 mL:15 mL:26.7 g.

4. The preparation method of an efficient polyphosphate ester flame retardant according to claim 1, wherein, In Step 2, the dosage ratio of the intermediate product, azobisisobutyronitrile, N,N - dimethylformamide, and 3 - mercaptopropanol is 53.6 g:0.3 g:150 mL:20.3 g.

5. The preparation method of an efficient polyphosphate ester flame retardant according to claim 1, characterized in that, The catalyst is one of anhydrous calcium chloride and anhydrous aluminum chloride.

6. The preparation method of an efficient polyphosphate ester flame retardant according to claim 1, wherein The protective gas is nitrogen.

7. The preparation method of an efficient polyphosphate ester flame retardant according to claim 1, characterized in that, The drying condition is drying in an oven at 80 - 100 °C for 6 - 12 h.

8. An efficient polyphosphate ester flame retardant, characterized in that, Prepared by the method according to any one of claims 1 - 7.

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