CN108084101A - Melamine polyphosphate and preparation method thereof - Google Patents

Abstract

The preparation method of melamine polyphosphate comprises the following steps: a. dissolving melamine in a solvent, heating and raising the temperature to dissolve the melamine, dripping polyphosphoric acid, then heating up to solvent boiling and reacting for 0.5h-2h, cooling after completion of the reaction The intermediate is obtained; b. add a treatment agent to the intermediate obtained in step a and mix uniformly to obtain a mixture, and the treatment agent is selected from one or more of urea, ammonium bicarbonate or biuret; c . The mixture obtained in step b is heat-treated at a temperature of 180-260° C., and cooled after the heat treatment is completed to obtain the melamine polyphosphate described in the present invention. The melamine polyphosphate finally obtained according to the preparation method provided by the present invention has higher degree of polymerization, lower water solubility, excellent thermal stability, and no color change. Compared with the existing technology, it is significantly lower and the production energy consumption is reduced, and it has extremely broad application prospects.

Description

Melamine polyphosphate and preparation method thereof

technical field

The invention relates to the field of preparation of melamine polyphosphate, in particular to melamine polyphosphate and a preparation method thereof.

Background technique

With the wide application of flame retardant materials and people's emphasis on environmental protection, the development of environmentally friendly flame retardants has attracted more and more attention. As a representative of halogen-free environmentally friendly flame retardants, melamine polyphosphate (MPP) It has also become a hot spot of research and development. The flame retardant can be used in almost all plastics, especially for engineering plastics with high processing temperature, such as glass fiber reinforced nylon, polyester and other polymer materials.

At present, melamine polyphosphate is usually obtained by the reaction of melamine and polyphosphoric acid, as follows: melamine and polyphosphoric acid are reacted under heating conditions to obtain an intermediate, which is a melamine polyphosphate with a large difference in the degree of polymerization and molecular weight distribution. The mixture of phosphates has a low degree of polymerization and poor thermal stability. In order to change these intermediates obtained by the reaction of melamine and polyphosphoric acid into melamine polyphosphate with a higher degree of polymerization to enhance its thermal stability, commonly used The best method is to heat treat the intermediate at high temperature. According to actual production experience, the intermediate must be heat treated at a high temperature above 320°C for a period of time to improve the thermal stability of the melamine polyphosphate. However, the defects of heat treatment at such a high temperature are also more obvious. First of all, although the final product melamine polyphosphate has improved to a certain extent relative to the thermal stability of the intermediate after heat treatment at high temperature, after the thermogravimetric analysis test, It is found that when the weight loss is 1%, the decomposition temperature is much lower than 360 °C, and the thermal stability still needs to be further improved; secondly, the color of the final melamine polyphosphate will be yellowish when the heat treatment temperature is too high, which limits its use in Application in light-colored plastics; in addition, heat treatment at high temperature will also lead to waste of energy and increase production costs.

Contents of the invention

The technical problem to be solved by the present invention is to provide a preparation method of melamine polyphosphate, which can effectively reduce production energy consumption and save production cost.

In order to solve the problems of the technologies described above, the present invention adopts the following technical solutions: a preparation method of melamine polyphosphate, comprising the following steps:

a. Dissolve melamine in a solvent, heat up to dissolve the melamine, drop polyphosphoric acid, then heat up to solvent boiling and react for 0.5h-2h, after the reaction is completed, cool to obtain the intermediate;

b. Add a treatment agent to the intermediate obtained in step a and mix uniformly to obtain a blend, the treatment agent is selected from one or more of urea, ammonium bicarbonate or biuret;

c. heat-treat the mixture obtained in step b at a temperature of 180° C. to 260° C., and cool after the heat treatment to obtain the melamine polyphosphate described in the present invention.

Preferably, the mass ratio of melamine to polyphosphoric acid described in step a is 1.5:1-3:1.

Preferably, the solvent in step a is selected from one or more of glacial acetic acid, methanol or ethanol.

Preferably, filtering, washing and drying are also carried out after cooling in step a.

More preferably, the drying is carried out under vacuum conditions, the drying temperature is 130°C-140°C, and the drying time is 2h-3h.

Preferably, the mass ratio between the intermediate and the treatment agent in step b is 1:0.01-1:0.2.

Preferably, the temperature of the heat treatment in step c is 180°C-230°C.

More preferably, the heat treatment time in step c is 1h-5h.

Melamine polyphosphate is prepared by the above preparation method.

Compared with the prior art, the present invention has the following beneficial effects:

The present invention first obtains the intermediate by reacting melamine and polyphosphoric acid, and the intermediate is a mixture of melamine polyphosphate with various degrees of polymerization and molecular weight distributions, and then adds specific treatment agents (urea, bicarbonate) to the intermediate. One or more of ammonium or biuret), and heat treatment in a specific temperature range of 180°C-260°C, the final melamine polyphosphate has a high degree of polymerization, low water solubility, and thermal stability Excellent, after detection, it is found that the temperature of 1% weight loss of the finally obtained melamine polyphosphate is higher than 380 °C, because the temperature of the heat treatment of the intermediate in the present invention is low, not only prevents the final product melamine polyphosphate due to excessive temperature It becomes khaki, reduces production energy consumption, saves cost, and has extremely broad application prospects.

Detailed ways

The following examples are provided below to specifically describe the present invention. It is necessary to point out that the following examples are only used to further illustrate the present invention, and cannot be interpreted as limiting the protection scope of the present invention. Some non-essential improvements or adjustments made by the embodiments to the present invention still belong to the protection scope of the present invention.

Example 1

The preparation method of melamine polyphosphate comprises the following steps:

a. Put 56.7g of melamine in a 1000mL four-necked flask equipped with an electric stirrer, a thermometer, a reflux condenser and a constant pressure dropping funnel, add 200mL of glacial acetic acid to the four-necked flask, heat up and stir to dissolve the melamine , slowly drop into the glacial acetic acid solution of polyphosphoric acid (obtained by dissolving 33.8g of polyphosphoric acid in 100mL of glacial acetic acid) through a constant pressure dropping funnel. The reaction was continued at reflux temperature for 1 hour. After the reaction was completed, it was cooled, filtered, and washed, and finally vacuum-dried at 130° C. for 2 hours to obtain 79.8 g of the intermediate;

b. add 7g urea to the intermediate obtained in step a and mix homogeneously to obtain a blend;

c. heat-treat the mixture obtained in step b at a temperature of 260° C. for 1 hour, and cool down after the heat treatment to obtain the product melamine polyphosphate, with a product weight of 76.9 g.

Example 2

The preparation method of melamine polyphosphate comprises the following steps:

a. 81.9g melamine is placed in the 1000mL four-neck flask equipped with electric stirrer, thermometer, reflux condenser and constant pressure dropping funnel, 250mL ethanol is added in the four-necked flask, after heating and stirring the melamine is dissolved, Slowly drop in the ethanol solution of polyphosphoric acid (33.8g polyphosphoric acid dissolved in 120mL ethanol) through the constant pressure dropping funnel, the time for adding is 1h, continue to heat until the ethanol boils and reflux, and keep the ethanol at the reflux temperature to continue the reaction 1h, after the reaction was completed, cooling, filtering, and washing were carried out, and finally vacuum-dried at 135°C for 2 hours to obtain 80.9g of the intermediate;

b. add 10g ammonium bicarbonate to the intermediate obtained in step a and mix homogeneously to obtain a blend;

c. heat-treat the mixture obtained in step b at 180° C. for 5 hours, and cool down after the heat treatment to obtain the product melamine polyphosphate, with a product weight of 77.6 g.

Example 3

The preparation method of melamine polyphosphate comprises the following steps:

a. 126g melamine is placed in the 1000mL four-necked flask that electric stirrer, thermometer, reflux condenser and constant pressure dropping funnel are housed, in the four-necked flask, add 300mL glacial acetic acid, heat up and stir after melamine is dissolved, Slowly drop the glacial acetic acid solution of polyphosphoric acid (obtained by dissolving 67.6g polyphosphoric acid in 200mL ethanol) through the constant pressure dropping funnel, and the dropping time is 1h, continue to heat until the glacial acetic acid boils and refluxes, and keep the glacial acetic acid at the reflux temperature The reaction was continued for 1 h at low temperature, and after the reaction was completed, it was cooled, filtered, and washed, and finally vacuum-dried at 140 ° C for 2 hours to obtain the intermediate;

b. Add 16.2g biuret to the intermediate obtained in step a and mix uniformly to obtain a mixture;

c. heat-treat the mixture obtained in step b at 230° C. for 3 hours, and cool down after the heat treatment to obtain the product melamine polyphosphate, with a product weight of 157.2 g.

Comparative example 1

Compared with Example 1, the only difference in the preparation method of melamine polyphosphate is that step b is omitted, that is, the intermediate obtained in step a is directly subjected to heat treatment and cooling in step c to obtain product melamine polyphosphate.

Comparative example 2

Compared with Example 2, the only difference in the preparation method of melamine polyphosphate is that step b is omitted, that is, the intermediate obtained in step a is directly subjected to heat treatment and cooling in step c to obtain product melamine polyphosphate.

Comparative example 3

Compared with Example 3, the only difference in the preparation method of melamine polyphosphate is that step b is omitted, that is, the intermediate obtained in step a is directly subjected to heat treatment and cooling in step c to obtain product melamine polyphosphate.

Comparative example 4

Compared with Example 2, the only difference in the preparation method of melamine polyphosphate is that the heat treatment temperature in step c is changed from 180°C to 320°C, and the others are consistent with Example 2.

Performance Data Test Method

Thermal stability test: adopt thermogravimetric analysis method, promptly take a small amount of intermediate and product melamine polyphosphate obtained in embodiment 1-3 and comparative example 1-4 respectively as sample, use thermobalance as testing instrument, sample is heated After the sample is heated, the weight change causes the balance displacement to be converted into an electromagnetic quantity. After the small electric quantity is amplified by the amplifier, it is sent to the recorder for recording, and the magnitude of the electric quantity is proportional to the weight change of the sample. When the weight of the measured substance changes during the heating process, the thermogravimetric curve will drop. By analyzing the thermogravimetric curve, it can be known how much weight changes the tested sample occurs at what degree. The specific implementation of the present invention What is tested in the method is the temperature when the sample weight is reduced by 1%.

Water Solubility Test: A small amount of product melamine polyphosphate in Examples 1-3 and Comparative Examples 1-4 will be taken as a sample, and a 2wt% slurry will be obtained by adding 49 times the weight of the sample, and then the melamine polyphosphate in the slurry will be tested Salt solubility.

The test results of performance parameters of the intermediate and product melamine polyphosphate of Examples 1-3 and Comparative Examples 1-4 are shown in Table 1 below.

As can be seen from Table 1, after the melamine polyphosphate prepared by the method provided by the present invention is tested by thermogravimetric analysis, it is found that the temperature of the melamine polyphosphate can reach 1% weight loss above 380°C, and its solubility in water is 0.015g Within /100mL, the thermal stability and water solubility of the melamine polyphosphate finally prepared in the present invention are relatively excellent, while Comparative Examples 1-3 did not add treatment to the intermediate before heat treatment at 180°C-260°C agent, resulting in its final product melamine polyphosphate weight loss 1% temperature relative to the intermediate does not increase, and the solubility is significantly higher than that of Examples 1-3.

In addition, as can be seen from Comparative Example 4 and Example 2 in Table 1, because the heat treatment temperature of Comparative Example 4 is too high, the melamine polyphosphate finally obtained is khaki, and the thermal stability and water solubility obtained by the test are also poor. In Example 2.

Claims (9)

1. the preparation method of melamine polyphosphate is characterized in that: comprise the following steps: a. Dissolve melamine in a solvent, heat up to dissolve the melamine, drop polyphosphoric acid, then heat up to solvent boiling and react for 0.5h-2h, after the reaction is completed, cool to obtain the intermediate; b. Add a treatment agent to the intermediate obtained in step a and mix uniformly to obtain a blend, the treatment agent is selected from one or more of urea, ammonium bicarbonate or biuret; c. heat-treat the mixture obtained in step b at a temperature of 180° C. to 260° C., and cool after the heat treatment to obtain the melamine polyphosphate described in the present invention. 2. according to the preparation method of melamine polyphosphate described in claim 1, it is characterized in that: the mass ratio of melamine and polyphosphoric acid described in step a is 1.5:1-3:1. 3. according to the preparation method of melamine polyphosphate described in claim 1, it is characterized in that: solvent described in step a is selected from one or more in glacial acetic acid, methyl alcohol or ethanol. 4. according to the preparation method of melamine polyphosphate described in claim 1, it is characterized in that: also carry out filtering, washing, drying after cooling in step a. 5 . The method for preparing melamine polyphosphate according to claim 4 , characterized in that: the drying is carried out under vacuum condition, the drying temperature is 130°C-140°C, and the drying time is 2h-3h. 6. According to the preparation method of melamine polyphosphate described in claim 1, it is characterized in that: the mass ratio between the intermediate and the treatment agent in step b is 1:0.01-1:0.2. 7. The method for preparing melamine polyphosphate according to claim 1, characterized in that: the temperature of the heat treatment in step c is 180°C-230°C. 8. according to the preparation method of the melamine polyphosphate described in any one of claim 1-7, it is characterized in that: the time of heat treatment described in step c is 1h-5h. 9. Melamine polyphosphate is characterized in that it is prepared by the preparation method described in any one of claims 1-8.