Continuous production method and device for halogen-free flame retardant melamine polyphosphate

Abstract

The invention relates to the technical field of flame retardants, in particular to a halogen-free flame retardant melamine polyphosphate continuous production method and device, and the method comprises the following steps: metering melamine and phosphoric acid through a metering pump, inputting the metered melamine and phosphoric acid into a reactor unit, and carrying out preliminary reaction to generate melamine phosphate; melamine phosphate is cooled by the screw conveyor and then collected in an MP receiving tank; melamine phosphate in the MP receiving tank is conveyed to the fluidized bed reactor through the MP metering pump, the melamine phosphate and heated nitrogen are subjected to a thermal condensation reaction in the fluidized bed reactor to obtain the melamine polyphosphate, the uniformity and the stability of the melamine polyphosphate prepared by the method and the device are ensured, the quality of the melamine polyphosphate is improved, and the production cost is reduced. By accurately controlling reaction conditions, unnecessary energy consumption and waste generation are reduced.

Description

Technical Field

[0001] This invention relates to the field of flame retardant technology, specifically to a continuous production method and apparatus for halogen-free flame retardant melamine polyphosphate. Background Technology

[0002] In recent years, with the increasing awareness of environmental protection, traditional halogenated flame retardants have faced challenges due to environmental problems, while halogen-free intumescent flame retardants have become the main direction for future development due to their excellent performance. Among them, melamine polyphosphate (MPP), as a new type of high-efficiency intumescent flame retardant, has broad application prospects in polymer materials.

[0003] Currently, the main preparation processes for MPP include the traditional two-step method and solid-state polycondensation, but these methods suffer from high energy consumption or poor product uniformity. Chinese patent application (publication number CN108084101A) discloses a method for preparing melamine polyphosphate, including the following steps: a. Dissolving melamine in a solvent, heating to dissolve the melamine, then adding polyphosphoric acid dropwise, and then heating to boiling and reacting for 0.5 hours. After 2 hours of reaction, the intermediate is obtained by cooling. b. A treatment agent is added to the intermediate obtained in step a and mixed thoroughly to obtain a homogeneous mixture. The treatment agent is selected from one or more of urea, ammonium bicarbonate, or biuret. c. The homogeneous mixture obtained in step b is heated at 180°C. Melamine polyphosphate is obtained by heat treatment at 260℃ followed by cooling. However, this method requires sophisticated equipment, is cumbersome to operate, generates large amounts of phosphorus-containing wastewater, has high treatment costs, and imposes a burden on the environment. Summary of the Invention

[0004] To address the aforementioned issues, this invention provides a continuous production method and apparatus for halogen-free flame retardant melamine polyphosphate. The melamine polyphosphate prepared using this method and apparatus ensures product uniformity and stability, improves product quality, and reduces unnecessary energy consumption and waste generation by precisely controlling reaction conditions.

[0005] This invention provides a continuous production method for halogen-free flame retardant melamine polyphosphate, comprising the following steps: melamine and phosphoric acid are metered into a reactor unit via a metering pump to undergo a preliminary reaction to generate melamine phosphate (MP); the melamine phosphate is cooled by a screw conveyor and collected in an MP receiving tank; the melamine phosphate in the MP receiving tank is transported to a fluidized bed reactor via an MP metering pump, where it undergoes a thermal condensation reaction with heated nitrogen gas to obtain melamine polyphosphate.

[0006] In one embodiment, the molar ratio of melamine to phosphoric acid is 0.6-1.2:1.

[0007] In one embodiment, the molar ratio of melamine to phosphoric acid is 0.665-1:1.

[0008] In one embodiment, the phosphoric acid is industrial phosphoric acid with a mass concentration of 70-80%, and the solvent is water.

[0009] In one embodiment, the industrial phosphoric acid has a mass concentration of 75% and the solvent is water.

[0010] In one embodiment, the number of reactor units is 1 to 5.

[0011] In one embodiment, when the number of reactor units is ≥2, each reactor unit is set up independently or connected in series through pipelines.

[0012] In one embodiment, the reactor unit includes reactor unit A and reactor unit B, which are independently arranged. The working volumes of reactor unit A and reactor unit B are the same, and the residence time of the materials in reactor unit A and reactor unit B is the same.

[0013] In one embodiment, the initial reaction temperature in the reactor unit is 90-110°C, and the initial reaction time is 1-3 hours.

[0014] In one embodiment, the initial reaction temperature in the reactor unit is 100°C, and the initial reaction time is 2 hours.

[0015] In one embodiment, the melamine phosphate is cooled to 80-100°C via a screw conveyor.

[0016] In one embodiment, the temperature of the thermal condensation reaction in the fluidized bed reactor is 350-390°C.

[0017] In one embodiment, the temperature of the thermal condensation reaction in the fluidized bed reactor is 370-380°C.

[0018] In one embodiment, the thermal condensation reaction time in the fluidized bed reactor is 1-2 hours.

[0019] This invention designs a continuous production process, which achieves continuous material flow through precise feeding by metering pumps, seamless connection of reactor units, screw conveyors, and fluidized bed reactors. This eliminates problems such as temperature fluctuations and material accumulation in intermittent production. The continuous process allows the thermal condensation reaction to take place under steady-state conditions, ensuring the large-scale and stable preparation of high-polymerization-degree MPP.

[0020] Specifically, by optimizing the molar ratio of melamine (ME) to phosphoric acid and controlling the reaction conditions in the initial reaction, the purity of the intermediate melamine phosphate was significantly improved. Combined with the control of the thermal condensation reaction conditions in the fluidized bed reactor, the thermal stability of the melamine polyphosphate generated by subsequent thermal condensation was significantly improved.

[0021] Furthermore, this invention ensures stable feed temperature in the fluidized bed reactor through screw cooling, while nitrogen mixing further optimizes heat transfer efficiency within the fluidized bed. Nitrogen, as an inert gas and heat transfer medium, suspends MP particles and heats them uniformly through the gas-solid fluidization effect of the fluidized bed reactor, while isolating oxygen to prevent oxidation side reactions. The directional flow of heated nitrogen promotes rapid heat transfer, accelerates the condensation reaction of phosphate groups, ensures the structural consistency of high-polymerization-degree MPP, and effectively improves energy utilization efficiency and reduces production costs.

[0022] Another aspect of the present invention provides a continuous production apparatus for halogen-free flame retardant melamine polyphosphate, comprising at least reactor unit A; reactor unit B; melamine inlet; phosphoric acid inlet; nitrogen inlet; screw conveyor; MP receiving tank; MP metering pump; fluidized bed reactor; MPP collection tank; gas outlet; and ton bag packaging machine. Melamine inlet and phosphoric acid inlet are respectively provided at the upper ends of reactor unit A and reactor unit B. Reactor unit A and reactor unit B are respectively connected to the screw conveyor via pipelines. The screw conveyor is connected to the MP receiving tank via pipelines. The MP receiving tank is connected to the fluidized bed reactor via pipelines. The MP metering pump is provided between the MP receiving tank and the fluidized bed reactor. A gas outlet is provided at the upper end of the fluidized bed reactor, and a nitrogen inlet is provided at the lower end of the fluidized bed reactor. The fluidized bed reactor, MPP collection tank, and ton bag packaging machine are sequentially connected via pipelines.

[0023] The present invention provides a continuous production device for halogen-free flame retardant melamine polyphosphate. The various components of the device are seamlessly connected through a precision pipeline and valve system. It features a high degree of automation, continuous operation, ease of operation, improved production efficiency, reduced production costs, and conforms to the concept of green and environmentally friendly production.

[0024] Beneficial effects 1. This invention provides a continuous production method and apparatus for halogen-free flame retardant melamine polyphosphate. The melamine polyphosphate prepared by this method and apparatus ensures the uniformity and stability of the product, improves the product quality, and reduces unnecessary energy consumption and waste generation by precisely controlling the reaction conditions.

[0025] 2. This invention designs a continuous production process, which achieves continuous material flow through precise feeding by metering pumps, seamless connection of reactor units, screw conveyors and fluidized bed reactors. This eliminates problems such as temperature fluctuations and material accumulation in intermittent production. The continuous process allows the thermal condensation reaction to take place under steady-state conditions, ensuring the large-scale and stable preparation of high-polymerization-degree MPP.

[0026] 3. This invention significantly improves the purity of the intermediate melamine phosphate by optimizing the molar ratio of melamine (ME) to phosphoric acid and controlling the reaction conditions in the initial reaction. Combined with the control of the thermal condensation reaction conditions in the fluidized bed reactor, the thermal stability of the melamine polyphosphate generated by subsequent thermal condensation is significantly improved.

[0027] 4. This invention ensures stable feed temperature in the fluidized bed reactor through screw cooling, while nitrogen mixing further optimizes heat transfer efficiency within the fluidized bed. Nitrogen, as an inert gas and heat transfer medium, suspends MP particles and heats them uniformly through the gas-solid fluidization effect of the fluidized bed reactor. At the same time, it isolates oxygen to prevent oxidation side reactions. The directional flow of heated nitrogen promotes rapid heat transfer, accelerates the condensation reaction of phosphate groups, ensures the structural consistency of high-polymerization-degree MPP, and effectively improves energy utilization efficiency and reduces production costs.

[0028] 5. The halogen-free flame retardant melamine polyphosphate continuous production device provided by the present invention has its components seamlessly connected through a precision pipeline and valve system. It features high automation, continuous operation, ease of operation, improved production efficiency, reduced production costs, and conforms to the concept of green and environmentally friendly production. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the continuous production apparatus for halogen-free flame retardant melamine polyphosphate provided in Example 1. In the diagram, 1 is reactor unit A; 2 is reactor unit B; 3 is melamine inlet; 4 is phosphoric acid inlet; 5 is nitrogen inlet; 6 is screw conveyor; 7 is MP receiving tank; 8 is MP metering pump; 9 is fluidized bed reactor; 10 is MPP collection tank; 11 is gas outlet; and 12 is ton bag packaging machine.

[0030] Figure 2 The image shows the TGA test result of melamine polyphosphate obtained in Example 1. Detailed Implementation

[0031] Example 1 Embodiment 1 of the present invention provides a continuous production method for halogen-free flame retardant melamine polyphosphate, comprising the following steps: melamine and phosphoric acid are metered into reactor unit A via a metering pump to undergo a preliminary reaction to generate melamine phosphate; the melamine phosphate is cooled by a screw conveyor 6 and collected in an MP receiving tank 7; the melamine phosphate in the MP receiving tank is transported to a fluidized bed reactor 9 via an MP metering pump 8, where it undergoes a thermal condensation reaction with heated nitrogen gas in the fluidized bed reactor 9 to obtain melamine polyphosphate; the melamine polyphosphate is collected in an MPP collecting tank 10 and packaged into finished products using a ton bag packaging machine 12.

[0032] The molar ratio of melamine to phosphoric acid is 0.665:1.

[0033] The phosphoric acid is industrial phosphoric acid with a mass concentration of 75%, and the solvent is water.

[0034] The reactor unit includes reactor unit A and reactor unit B, which are set up independently. Reactor unit A and reactor unit B have the same working volume and the same residence time of the material in reactor unit A and reactor unit B.

[0035] The initial reaction temperature in the reactor unit is 100℃, and the initial reaction time is 2 hours.

[0036] The melamine phosphate is cooled to 100°C via a screw conveyor.

[0037] The temperature of the thermal condensation reaction in the fluidized bed reactor is 350°C.

[0038] The thermal condensation reaction time in the fluidized bed reactor is 2 hours.

[0039] The melamine polyphosphate was subjected to thermogravimetric analysis (TGA), and the results were as follows: the temperature at which the weight loss was 1% was 360℃, the phosphorus content was 14.1%, and the nitrogen content was 41.3%.

[0040] See Figure 1In another aspect, Embodiment 1 of the present invention provides a continuous production apparatus for halogen-free flame retardant melamine polyphosphate, comprising at least reactor unit A1; reactor unit B2; melamine inlet 3; phosphoric acid inlet 4; nitrogen inlet 5; screw conveyor 6; MP receiving tank 7; MP metering pump 8; fluidized bed reactor 9; MPP collection tank 10; gas outlet 11; and ton bag packaging machine 12. Melamine inlet 3 and phosphoric acid inlet 4 are respectively provided at the upper ends of reactor unit A1 and reactor unit B2. 2 are connected to the screw conveyor 6 via pipelines. The screw conveyor 6 is connected to the MP receiving tank 7 via pipelines. The MP receiving tank 7 is connected to the fluidized bed reactor 9 via pipelines. An MP metering pump 8 is installed between the MP receiving tank 7 and the fluidized bed reactor 9. A gas outlet 11 is installed at the upper end of the fluidized bed reactor 9, and a nitrogen inlet 5 is installed at the lower end of the fluidized bed reactor 9. The fluidized bed reactor 9 is connected to the MPP collection tank 10 and the ton bag packaging machine 12 in sequence via pipelines.

[0041] Example 2 Example 2 of the present invention provides a continuous production method and apparatus for halogen-free flame retardant melamine polyphosphate. The specific implementation method is the same as that of Example 1, except that the temperature of the thermal condensation reaction in the fluidized bed reactor is 370°C, and the melamine polyphosphate is subjected to TGA testing. The test results are as follows: the temperature at which the weight loss is 1% is 378°C, the phosphorus content is 14.3%, and the nitrogen content is 41.5%.

[0042] Example 3 Example 3 of this invention provides a continuous production method and apparatus for halogen-free flame retardant melamine polyphosphate. The specific implementation is the same as in Example 1, except that the molar ratio of melamine to phosphoric acid is 1:1; the temperature of the thermal condensation reaction in the fluidized bed reactor is 378°C; and the melamine polyphosphate is subjected to TGA testing, with the following results: a 1% weight loss at 387°C, a phosphorus content of 14.3%, and a nitrogen content of 41.5%. (See [link to relevant documentation]). Figure 2 .

[0043] Example 4 Example 4 of the present invention provides a continuous production method and apparatus for halogen-free flame retardant melamine polyphosphate. The specific implementation method is the same as that of Example 1, except that the molar ratio of melamine to phosphoric acid is 1:1; the temperature of the thermal condensation reaction in the fluidized bed reactor is 380°C; and the melamine polyphosphate is subjected to TGA testing, and the test results are: the temperature at which the weight loss is 1% is 387°C, the phosphorus content is 14.3%, and the nitrogen content is 41.5%.

[0044] Example 5 Example 5 of the present invention provides a continuous production method and apparatus for halogen-free flame retardant melamine polyphosphate. The specific implementation method is the same as that of Example 1, except that the molar ratio of melamine to phosphoric acid is 1:1; the temperature of the thermal condensation reaction in the fluidized bed reactor is 390°C; and the melamine polyphosphate is subjected to TGA testing, and the test results are: the temperature at which the weight loss is 1% is 378°C, the phosphorus content is 14.3%, and the nitrogen content is 41.5%.

Claims

1. A continuous production method for halogen-free flame retardant melamine polyphosphate, characterized in that, The process includes the following steps: melamine and phosphoric acid are metered into the reactor unit via a metering pump to undergo a preliminary reaction to generate melamine phosphate; the melamine phosphate is cooled by a screw conveyor and collected in an MP receiving tank; the melamine phosphate in the MP receiving tank is transported to a fluidized bed reactor via an MP metering pump, where it undergoes a thermal condensation reaction with heated nitrogen gas to obtain melamine polyphosphate.

2. The continuous production method of halogen-free flame retardant melamine polyphosphate according to claim 1, characterized in that, The molar ratio of melamine to phosphoric acid is 0.6-1.2:

1.

3. The continuous production method of halogen-free flame retardant melamine polyphosphate according to claim 1, characterized in that, The phosphoric acid is industrial phosphoric acid with a mass concentration of 70-80%, and the solvent is water.

4. The continuous production method of halogen-free flame retardant melamine polyphosphate according to claim 3, characterized in that, The number of reactor units is 1-5.

5. The continuous production method of halogen-free flame retardant melamine polyphosphate according to claim 4, characterized in that, When the number of reactor units is ≥2, each reactor unit is set up independently or connected in series through pipelines.

6. The continuous production method of halogen-free flame retardant melamine polyphosphate according to claim 1, characterized in that, The initial reaction temperature in the reactor unit is 90-110℃, and the initial reaction time is 1-3 hours.

7. The continuous production method of halogen-free flame retardant melamine polyphosphate according to claim 1, characterized in that, The melamine phosphate is cooled to 80-100℃ via a screw conveyor.

8. The continuous production method of halogen-free flame retardant melamine polyphosphate according to claim 1, characterized in that, The temperature of the thermal condensation reaction in the fluidized bed reactor is 350-390℃.

9. The continuous production method of halogen-free flame retardant melamine polyphosphate according to claim 1, characterized in that, The thermal condensation reaction time in the fluidized bed reactor is 1-2 hours.

10. A continuous production apparatus for halogen-free flame retardant melamine polyphosphate, used in the continuous production method of halogen-free flame retardant melamine polyphosphate according to any one of claims 1-9, characterized in that, The system includes at least reactor unit A; reactor unit B; melamine inlet; phosphoric acid inlet; nitrogen inlet; screw conveyor; MP receiving tank; MP metering pump; fluidized bed reactor; MPP collection tank; gas outlet; and ton bag packaging machine. Melamine and phosphoric acid inlets are respectively located at the top ends of reactor units A and B. Reactor units A and B are connected to the screw conveyor via pipelines. The screw conveyor is connected to the MP receiving tank via a pipeline. The MP receiving tank is connected to the fluidized bed reactor via a pipeline. An MP metering pump is installed between the MP receiving tank and the fluidized bed reactor. A gas outlet is located at the top end of the fluidized bed reactor, and a nitrogen inlet is located at the bottom end. The fluidized bed reactor is sequentially connected to the MPP collection tank and the ton bag packaging machine via pipelines.

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