CN118812452A - A kind of melamine polyphosphate and preparation method thereof - Google Patents

Abstract

The invention discloses melamine polyphosphate and a preparation method thereof, wherein the melamine polyphosphate is prepared from the following components: melamine; phosphoric acid; ammonium dihydrogen phosphate and melamine diamide mixtures; and water; the melamine is taken as a reference, wherein the mole ratio of phosphoric acid to melamine is=0.9-1.2, the weight ratio of monoammonium phosphate to melamine diamide mixture to melamine is=0.04-0.2, and the weight ratio of water to melamine is=3-10. The melamine polyphosphate has higher linear property and better thermal stability.

Description

A kind of melamine polyphosphate and preparation method thereof

Technical Field

The present invention particularly relates to a melamine polyphosphate and a preparation method thereof.

Background Art

Melamine polyphosphate (MPP) is an environmentally friendly, highly efficient nitrogen-phosphorus flame retardant. It has the advantages of being halogen-free, low toxicity, and having good compatibility with substrates. Therefore, it is widely used and is suitable for engineering plastics such as PA66 and PBT with higher processing temperatures.

There are many synthetic routes for melamine polyphosphate, the most common ones are as follows:

(1) Synthesis of melamine and polyphosphoric acid. This process requires methanol as a solvent, the production workshop needs explosion-proof design, and the infrastructure investment is large;

(2) The synthesis of melamine and sodium polyphosphate requires the addition of hydrochloric acid. The product contains a large amount of sodium chloride and needs to be washed with water, which produces a large amount of industrial wastewater. If the washing is not thorough, the chloride ions in it will cause harm to plastic products.

(3) Using phosphorus pentoxide and diammonium hydrogen phosphate (or ammonium dihydrogen phosphate) as raw materials to catalyze the synthesis of MPOP. This process takes a long time to synthesize, requiring more than 10 hours, and the synthetic product loses a lot of weight at around 300°C;

(4) Synthesizing MPOP with melamine, phosphorus pentoxide and oxalic acid as raw materials. This process uses phosphorus pentoxide as raw material, resulting in a violent reaction and the release of toxic CO gas, making it difficult to control and obtain qualified MPOP;

(5) Using melamine and phosphoric acid as raw materials, melamine polyphosphate is synthesized by a two-step process. The first step is to react melamine with phosphoric acid to form a melamine phosphate intermediate, and the melamine phosphate intermediate is thermally polycondensed to obtain melamine polyphosphate.

The commonly used synthesis process in China is a two-step method for synthesizing melamine polyphosphate using melamine and phosphoric acid as raw materials, but the two-step method has the following defects:

In the first step of preparing melamine phosphate from phosphoric acid and melamine, the dropwise addition rate and stirring rate are difficult to control, resulting in uneven mixing of reactants and local side reactions, which affect the purity of the melamine phosphate intermediate and ultimately the quality of the polymerization product melamine polyphosphate.

Summary of the invention

In view of the above-mentioned defects, the present invention provides a melamine polyphosphate, which has higher linearity and better thermal stability.

The technical solution is: a melamine polyphosphate is made of the following ingredients:

Melamine;

Phosphoric acid;

A mixture of ammonium dihydrogen phosphate and melamine diamide; and

water;

Based on melamine, the molar ratio of phosphoric acid to melamine is 0.9-1.2, the weight ratio of the mixture of ammonium dihydrogen phosphate and melamine diamide to melamine is 0.04-0.2, and the weight ratio of water to melamine is 3-10.

Optionally, in the mixture of diammonium phosphate and melamine diamide, the weight ratio of diammonium phosphate to melamine diamide is 90-100:1-10.

Optionally, the preparation method of the melamine polyphosphate comprises the following steps:

S1, taking melamine, adding it into water, stirring and heating to 80-100°C; slowly dropping a mixed aqueous solution of ammonium dihydrogen phosphate and melamine diamide into the melamine solution, stirring while dropping; then dropping phosphoric acid into the melamine solution, stirring while dropping; after the dropping is completed, reacting for 1-4 hours; after the reaction is completed, cooling and crystallizing, filtering, drying, and crushing to obtain a melamine polyphosphate intermediate;

S2, placing the melamine polyphosphate intermediate of S1 into a rotary kiln for high temperature reaction to obtain melamine polyphosphate.

Optionally, the mixed aqueous solution of ammonium dihydrogen phosphate and melamine diamide is prepared by the following steps:

S01, take ammonium dihydrogen phosphate and melamine diamide, mix them evenly and dissolve them in water to form an ammonium dihydrogen phosphate-melamine diamide mixed solution.

Optionally, in S2, the rotation speed of the rotary kiln is 15-30 r/min, and the high-temperature reaction is a gradient temperature increase reaction.

The invention also provides a method for preparing melamine polyphosphate.

The technical solution is: a method for preparing melamine polyphosphate, comprising the following steps:

S1, taking melamine, adding it into water, stirring and heating to 80-100°C; slowly dropping a mixed aqueous solution of ammonium dihydrogen phosphate and melamine diamide into the melamine solution, stirring while dropping; then dropping phosphoric acid into the melamine solution, stirring while dropping; after the dropping is completed, reacting for 1-4 hours; after the reaction is completed, cooling and crystallizing, filtering, drying, and crushing to obtain a melamine polyphosphate intermediate;

S2, placing the melamine polyphosphate intermediate of S1 into a rotary kiln for high temperature reaction to obtain melamine polyphosphate;

Wherein, taking melamine as the basis, the molar ratio of phosphoric acid to melamine is 0.9-1.2, the weight ratio of the mixture of diammonium phosphate and melamine diamide to melamine is 0.04-0.2, and the weight ratio of water to melamine is 3-10.

Optionally, the mixed aqueous solution of ammonium dihydrogen phosphate and melamine diamide is prepared by the following steps:

S01, take ammonium dihydrogen phosphate and melamine diamide, mix them evenly and dissolve them in water to form an ammonium dihydrogen phosphate-melamine diamide mixed solution.

Optionally, in S1, the dripping speed of the mixed aqueous solution of ammonium dihydrogen phosphate and melamine diamide is controlled to be 3-6 minutes, and the dripping speed of phosphoric acid is controlled to be 3 seconds/drop.

Optionally, in S2, the rotation speed of the rotary kiln is 15-30 r/min, and the high-temperature reaction is a gradient temperature increase reaction.

Optionally, the gradient temperature increase reaction is to react at 250-270 degrees for 1-3 hours, 270-290 degrees for 1-3 hours, and 280-320 degrees for 1-5 hours.

Invention principle and beneficial effects:

Firstly, in the first step, monoammonium phosphate and melamine diacylate are added, wherein the monoammonium phosphate ensures that the phosphate ions in the solution are excessive, and at the same time, there are excessive ammonium ions, so that byproducts such as dimelamine phosphate and dimelamine phosphate are not easily generated during the synthesis process; and the addition of a trace amount of melamine diacylate destroys the hydrogen bond balance in the reaction system, making it difficult for the reaction system to produce over-condensation and the like, reducing the viscosity of the reaction system, ensuring the uniformity of the reaction, and thus obtaining a melamine phosphate intermediate with higher purity.

Secondly, in the second step, the melamine phosphate intermediate undergoes a thermal condensation reaction in a rotary kiln, which can effectively reduce the occurrence of side reactions, thereby obtaining a melamine polyphosphate with a higher linearity and better thermal stability.

DETAILED DESCRIPTION

The present invention will be further described below. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

In the following Examples 1 to 6 and Comparative Examples 1 to 2:

Phosphoric acid: commercially available, 85wt% industrial phosphoric acid;

Example 1

S01, take ammonium dihydrogen phosphate and melamine diamide (a total of 8.8 grams, wherein the weight ratio of ammonium dihydrogen phosphate to melamine diamide is 99:1), mix them evenly and dissolve them in 50 grams of water to obtain an ammonium dihydrogen phosphate-melamine diamide mixed solution 1.

S1, take 126 grams of melamine, add it to 500 grams of water, stir and heat it to 90°C; slowly drop the diammonium phosphate-melamine diamide mixed solution 1 into the melamine solution, stir while dropping, and control the dropping speed to 3-6 minutes; then drop 115 grams of phosphoric acid into the melamine solution, stir while dropping, and control the dropping speed to 3 seconds/drop; after the drop addition is completed, react at 90°C for 2 hours. After the reaction is completed, cool and crystallize, filter and wash with atomized water 3 times, then dry at 130 degrees for 4 hours, and crush to obtain a melamine polyphosphate intermediate.

S2, put the melamine polyphosphate intermediate of S1 into a rotary kiln, start the rotation (speed 20r/min), heat it to 260°C, react for 2 hours, heat it to 280°C, react for 2 hours, heat it to 300°C, react for 4 hours, and obtain melamine polyphosphate.

Example 2

S01, take ammonium dihydrogen phosphate and melamine diamide (a total of 8.8 grams, wherein the weight ratio of ammonium dihydrogen phosphate to melamine diamide is 90:10), mix them evenly and dissolve them in 50 grams of water to obtain an ammonium dihydrogen phosphate-melamine diamide mixed solution 2.

S1, take 126 grams of melamine, add it to 500 grams of water, stir and heat it to 90°C; slowly drop the diammonium phosphate-melamine diamide mixed solution 2 into the melamine solution, stir while dropping, and control the dropping speed to 3-6 minutes; then drop 115 grams of phosphoric acid into the melamine solution, stir while dropping, and control the dropping speed to 3 seconds/drop; after the drop addition is completed, react at 90°C for 2 hours. After the reaction is completed, cool and crystallize, filter and wash with atomized water 3 times, then dry at 130 degrees for 4 hours, and crush to obtain a melamine polyphosphate intermediate.

S2, put the melamine polyphosphate intermediate of S1 into a rotary kiln, start the rotation (speed 20r/min), heat it to 260°C, react for 2 hours, heat it to 280°C, react for 2 hours, heat it to 300°C, react for 4 hours, and obtain melamine polyphosphate.

Example 3

S01, take 8.8 grams of diammonium phosphate and dissolve it in 50 grams of water to obtain diammonium phosphate solution.

S1, take 126 grams of melamine, add it to 500 grams of water, stir and heat it to 90°C; slowly drop the diammonium phosphate solution into the melamine solution, stir while dropping, and control the dropping speed to 3-6 minutes; then drop 115 grams of phosphoric acid into the melamine solution, stir while dropping, and control the dropping speed to 3 seconds/drop; after the drop addition is completed, react at 90°C for 2 hours. After the reaction is completed, cool and crystallize, filter and wash with atomized water 3 times, then dry at 130 degrees for 4 hours, and crush to obtain melamine polyphosphate intermediate.

S2, put the melamine polyphosphate intermediate of S1 into a rotary kiln, start the rotation (speed 20r/min), heat it to 260°C, react for 2 hours, heat it to 280°C, react for 2 hours, heat it to 300°C, react for 4 hours, and obtain melamine polyphosphate.

Example 4

S01, take 8.8 grams of melamine diamide, dissolve it in 50 grams of water to obtain a melamine diamide solution.

S1, take 126 grams of melamine, add it to 500 grams of water, stir and heat it to 90°C; slowly add the melamine diamide solution dropwise into the melamine solution, stir while adding, and control the dropping speed to 3-6 minutes; then add 115 grams of phosphoric acid dropwise into the melamine solution, stir while adding, and control the dropping speed to 3 seconds/drop; after the dropping is completed, react at 90°C for 2 hours. After the reaction is completed, cool and crystallize, filter and wash with atomized water 3 times, then dry at 130 degrees for 4 hours, and crush to obtain a melamine polyphosphate intermediate.

S2, put the melamine polyphosphate intermediate of S1 into a rotary kiln, start the rotation (speed 20r/min), heat it to 260°C, react for 2 hours, heat it to 280°C, react for 2 hours, heat it to 300°C, react for 4 hours, and obtain melamine polyphosphate.

Example 5

S01, take ammonium dihydrogen phosphate and melamine diamide (a total of 8.8 grams, wherein the weight ratio of ammonium dihydrogen phosphate to melamine diamide is 90:10), mix them evenly and dissolve them in 50 grams of water to obtain an ammonium dihydrogen phosphate-melamine diamide mixed solution 3.

S1, take 126 grams of melamine, add it to 500 grams of water, stir and heat it to 90°C; slowly drop the diammonium phosphate-melamine diamide mixed solution 3 into the melamine solution, stir while dropping, and control the dropping speed to 3-6 minutes; then drop 113 grams of phosphoric acid into the melamine solution, stir while dropping, and control the dropping speed to 3 seconds/drop; after the drop addition is completed, react at 90°C for 2 hours. After the reaction is completed, cool and crystallize, filter and wash with atomized water 3 times, then dry at 130 degrees for 4 hours, and crush to obtain a melamine polyphosphate intermediate.

S2, put the melamine polyphosphate intermediate of S1 into a rotary kiln, start the rotation (speed 20r/min), heat it to 260°C, react for 2 hours, heat it to 280°C, react for 2 hours, heat it to 300°C, react for 4 hours, and obtain melamine polyphosphate.

Example 6

S01, take ammonium dihydrogen phosphate and melamine diamide (a total of 8.8 grams, wherein the weight ratio of ammonium dihydrogen phosphate to melamine diamide is 90:10), mix them evenly and dissolve them in 50 grams of water to obtain an ammonium dihydrogen phosphate-melamine diamide mixed solution 4.

S1, take 126 grams of melamine, add it to 500 grams of water, stir and heat it to 90°C; slowly drop the diammonium phosphate-melamine diamide mixed solution 4 into the melamine solution, stir while dropping, and control the dropping speed to 3-6 minutes; then drop 117.6 grams of phosphoric acid into the melamine solution, stir while dropping, and control the dropping speed to 3 seconds/drop; after the drop addition is completed, react at 90°C for 2 hours. After the reaction is completed, cool and crystallize, filter and wash with atomized water 3 times, then dry at 130 degrees for 4 hours, and crush to obtain a melamine polyphosphate intermediate.

S2, put the melamine polyphosphate intermediate of S1 into a rotary kiln, start the rotation (speed 20r/min), heat it to 260°C, react for 2 hours, heat it to 280°C, react for 2 hours, heat it to 300°C, react for 4 hours, and obtain melamine polyphosphate.

Comparative Example 1

Compared with Example 2, this comparative example differs only in S2. In this comparative example, the step S2 is:

S2, putting the melamine polyphosphate intermediate of S1 in Example 2 into a rotary kiln, starting the rotation (rotation speed 20 r/min), heating to 300° C., reacting for 8 hours, to obtain melamine polyphosphate.

Comparative Example 2

S1, take 126 grams of melamine, add it to 550 grams of water, stir and heat it to 90°C; add 115 grams of phosphoric acid dropwise into the melamine solution, stir while adding, and control the drop speed to 3 seconds/drop; after the dropwise addition is completed, react at 90°C for 2 hours. After the reaction is completed, cool and crystallize, filter and wash with atomized water 3 times, then dry at 130 degrees for 4 hours, and crush to obtain melamine polyphosphate intermediate.

S2, put the melamine polyphosphate intermediate of S1 into a rotary kiln, start the rotation (speed 20r/min), heat it to 260°C, react for 2 hours, heat it to 280°C, react for 2 hours, heat it to 300°C, react for 4 hours, and obtain melamine polyphosphate.

The melamine polyphosphate intermediates of the examples and comparative examples were tested for nitrogen (N) content, phosphorus (P) content, pH value and conductivity. The results are shown in Table 1 below.

Table 1

The melamine polyphosphates of the embodiments and comparative examples were tested for nitrogen (N) content, phosphorus (P) content, pH value, water solubility and weight loss temperature. The results are shown in Table 2 below.

Table 2

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims (10)

1. A melamine polyphosphate, characterized in that it is made from the following ingredients: Melamine; Phosphoric acid; A mixture of ammonium dihydrogen phosphate and melamine diamide; and water; Based on melamine, the molar ratio of phosphoric acid to melamine is 0.9-1.2, the weight ratio of the mixture of ammonium dihydrogen phosphate and melamine diamide to melamine is 0.04-0.2, and the weight ratio of water to melamine is 3-10. 2. The melamine polyphosphate according to claim 1, characterized in that in the mixture of diammonium phosphate and melamine diamide, the weight ratio of diammonium phosphate to melamine diamide is 90-100:1-10. 3. The melamine polyphosphate according to any one of claims 1 to 2, characterized in that the preparation method of the melamine polyphosphate comprises the following steps: S1, taking melamine, adding it into water, stirring and heating to 80-100°C; slowly dropping a mixed aqueous solution of ammonium dihydrogen phosphate and melamine diamide into the melamine solution, stirring while dropping; then dropping phosphoric acid into the melamine solution, stirring while dropping; after the dropping is completed, reacting for 1-4 hours; after the reaction is completed, cooling and crystallizing, filtering, drying, and crushing to obtain a melamine polyphosphate intermediate; S2, placing the melamine polyphosphate intermediate of S1 into a rotary kiln for high temperature reaction to obtain melamine polyphosphate. 4. The melamine polyphosphate according to claim 3, characterized in that the mixed aqueous solution of ammonium dihydrogen phosphate and melamine diamide is prepared by the following steps: S01, take ammonium dihydrogen phosphate and melamine diamide, mix them evenly and dissolve them in water to form an ammonium dihydrogen phosphate-melamine diamide mixed solution. 5. The melamine polyphosphate according to claim 3, characterized in that, in S2, the rotary kiln speed is 15-30 r/min, and the high temperature reaction is a gradient temperature increase reaction. 6. A method for preparing melamine polyphosphate, characterized in that it comprises the following steps: S1, taking melamine, adding it into water, stirring and heating to 80-100°C; slowly dropping a mixed aqueous solution of ammonium dihydrogen phosphate and melamine diamide into the melamine solution, stirring while dropping; then dropping phosphoric acid into the melamine solution, stirring while dropping; after the dropping is completed, reacting for 1-4 hours; after the reaction is completed, cooling and crystallizing, filtering, drying, and crushing to obtain a melamine polyphosphate intermediate; S2, placing the melamine polyphosphate intermediate of S1 into a rotary kiln for high temperature reaction to obtain melamine polyphosphate; Wherein, taking melamine as the basis, the molar ratio of phosphoric acid to melamine is 0.9-1.2, the weight ratio of the mixture of diammonium phosphate and melamine diamide to melamine is 0.04-0.2, and the weight ratio of water to melamine is 3-10. 7. The method for preparing melamine polyphosphate according to claim 6, characterized in that the mixed aqueous solution of ammonium dihydrogen phosphate and melamine diamide is prepared by the following steps: S01, take ammonium dihydrogen phosphate and melamine diamide, mix them evenly and dissolve them in water to form an ammonium dihydrogen phosphate-melamine diamide mixed solution. 8. The method for preparing melamine polyphosphate according to claim 6, characterized in that, in S1, the dropping speed of the mixed aqueous solution of ammonium dihydrogen phosphate and melamine diamide is controlled within 3-6 minutes, and the dropping speed of phosphoric acid is controlled within 3 seconds/drop. 9. The method for preparing melamine polyphosphate according to claim 6, characterized in that, in S2, the rotating speed of the rotary kiln is 15-30 r/min, and the high temperature reaction is a gradient temperature rising reaction. 10. The method for preparing melamine polyphosphate according to claim 9, characterized in that the gradient temperature reaction is 250-270 degrees for 1-3 hours, 270-290 degrees for 1-3 hours, and 280-320 degrees for 1-5 hours.