Preparation method of piperazine diphosphate metal salt flame retardant

Abstract

The invention discloses a preparation method of a piperazine diphosphate metal salt flame retardant, which comprises the following steps: dropwise adding a metal salt aqueous solution into a 68 piperazine aqueous solution at room temperature under stirring, and carrying out primary reaction; dropwise adding a phosphoric acid aqueous solution into the reaction system, and carrying out secondary reaction; and filtering while the solution is hot, washing a filter cake, and drying to obtain the piperazine diphosphate metal salt. According to the preparation method, piperazine and the metal salt are subjected to a reaction, then phosphoric acid is directly added into the system for a reaction, an intermediate does not need to be separated, the piperazine diphosphate metal salt which is good in flame retardance, low in solubility and capable of solving the problem of precipitation can be prepared through a one-step method, and the method is simple and can replace part of piperazine pyrophosphate to be used.

Description

Technical Field

[0001] This invention relates to the field of flame retardant technology, and specifically to a method for preparing a piperazine diphosphate metal salt flame retardant. Background Technology

[0002] Phosphorus-nitrogen flame retardants are widely used in polyolefins, engineering plastics, and their composites due to their advantages such as promoting char formation, suppressing smoke, and being low-halogen / halogen-free. Among them, piperazine phosphate flame retardants, which use piperazine as the nitrogen-containing component and phosphate / pyrophosphate as the phosphorus-containing component, can provide a synergistic effect of gas-phase dilution and condensed-phase char formation during combustion, forming an expanded char layer that effectively blocks the transfer of heat and combustible gases, thus exhibiting good flame retardant performance.

[0003] In existing technologies, piperazine pyrophosphate, as a commonly used phosphorus-nitrogen flame retardant, exhibits outstanding flame-retardant properties. However, its molecular structure contains numerous hydrophilic groups, leading to strong hygroscopicity. This makes it prone to moisture absorption, aggregation, and clumping during storage and transportation, affecting metering and dispersion. Furthermore, if piperazine pyrophosphate is not adequately dehydrated during preparation or use, or undergoes hydrolysis in humid environments, it can easily introduce free water or generate soluble components. This can cause defects such as processing foaming, bubbles, and silver streaks during plastic processing, and migration and precipitation during long-term use, affecting the appearance and performance stability of the product. Therefore, reducing the hygroscopicity, hydrolysis, and precipitation tendency of flame retardants while ensuring flame-retardant efficacy, and improving their processing adaptability and long-term stability, are urgent technical problems that need to be solved in the practical application of this type of flame-retardant system.

[0004] To address the aforementioned issues, piperazine diphosphate metal salts, by introducing metal ions to form a stable salt structure with phosphate groups, can typically reduce the solubility and migration tendency of the system. To a certain extent, they can be used to replace some piperazine pyrophosphate, alleviating precipitation problems caused by moisture absorption and hydrolysis, while maintaining the flame-retardant contribution of the phosphorus-nitrogen system. However, existing technologies for the preparation of piperazine diphosphate metal salts are limited, and the processes are lengthy and energy-intensive, hindering large-scale applications.

[0005] Patent CN112778237A (Synthesis Method of Piperazine Pyrophosphate Metal Salt) discloses a method for preparing piperazine pyrophosphate metal salt: 1. First, phosphoric acid and piperazine are prepared into piperazine diphosphate; 2. Piperazine diphosphate is dehydrated at high temperature to obtain piperazine pyrophosphate; 3. Then, piperazine pyrophosphate is reacted with metal oxide and hydroxide at high temperature to form piperazine pyrophosphate metal salt. The above method is complex and energy-intensive. Summary of the Invention

[0006] In view of this, the present invention provides a method for preparing a piperazine diphosphate metal salt flame retardant. The method first reacts piperazine with a metal salt, and then directly adds phosphoric acid to the above system for reaction. There is no need to separate intermediates. The piperazine diphosphate metal salt with good flame retardancy and low solubility can be prepared in one step, thereby solving the precipitation problem. This method is simple and can replace part of the piperazine pyrophosphate.

[0007] To better solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0008] A method for preparing a piperazine diphosphate metal salt flame retardant includes the following steps:

[0009] At room temperature and with stirring, an aqueous solution of a metal salt was added dropwise to an aqueous solution of piperazine at 68°C to carry out a single reaction.

[0010] Add an aqueous solution of phosphoric acid dropwise to the above reaction system to carry out a secondary reaction;

[0011] Filter while hot, wash and dry the filter cake to obtain piperazine diphosphate metal salt.

[0012] Preferably, the metal salt is one of metal oxides, metal hydroxides, metal carbonates, and metal acetates.

[0013] Preferably, the metal in the metal salt is one of magnesium, aluminum, or zinc.

[0014] Preferably, the amounts of each component by weight are as follows: 60 parts of 68-piperazine, 50 parts of metal salt, and 300 parts of deionized water; the concentration of the metal salt aqueous solution is 12-14 wt%, the concentration of the 68-piperazine solution is 14-16 wt%, and the mass ratio of the 68-piperazine aqueous solution to the metal salt aqueous solution is (1.0-1.2):1.

[0015] Preferably, the metal salt aqueous solution is added over a period of 30-60 minutes, and the dropping rate of the metal salt aqueous solution is 5-10 ml / min.

[0016] Preferably, the temperature of a single reaction is 60-90℃ and the time is 1-1.5h.

[0017] Preferably, the concentration of the phosphoric acid aqueous solution is 80-90 wt%, and the amount of phosphoric acid aqueous solution added is 1.5-2 times the mass of the 68 piperazine aqueous solution.

[0018] Preferably, the dropping rate of the phosphoric acid aqueous solution is (5-10 g / min).

[0019] Preferably, the temperature of the secondary reaction is 80-90℃ and the time is 2-4h.

[0020] Preferably, deionized water at a temperature of 60-80℃ is used to wash the filter cake.

[0021] Compared with the prior art, the present invention has at least the following advantages:

[0022] 1. In this invention, a metal salt aqueous solution and a 68-piperazine aqueous solution are reacted first, and then a phosphoric acid aqueous solution is directly added dropwise to the same system for a second reaction. The product can be obtained by hot filtration, washing and drying. There is no need to separate, transfer or additionally process the intermediates. The preparation process is shorter and the operation is simpler.

[0023] 2. In the method of the present invention, the primary reaction temperature is 60-90°C and the secondary reaction temperature is 80-90°C. The entire reaction process is carried out under relatively mild conditions, avoiding the high-temperature dehydration and high-temperature solid-phase reaction steps in the prior art. This results in lower energy consumption, higher safety, and greater suitability for industrial production.

[0024] 3. The piperazine diphosphate metal salt prepared by this invention forms a more stable salt system with metal ions and phosphate, resulting in a lower overall solubility of the flame retardant. This effectively alleviates problems such as precipitation and whitening caused by moisture or hydrolysis in practical applications, and improves the appearance and performance stability of the material during long-term use.

[0025] 4. Compared with piperazine pyrophosphate, which is prone to moisture absorption and agglomeration and causes foaming during processing due to incomplete dehydration, the flame retardant prepared by this invention is more conducive to reducing defects such as moisture carryover and foaming during processing, and improving the stability of extrusion, injection molding and other processing processes and the quality of product molding.

[0026] 5. The piperazine diphosphate metal salt prepared by this invention also belongs to the phosphorus-nitrogen flame retardant system. It can be used to replace part of the piperazine pyrophosphate without significantly weakening the flame retardant effect, so as to achieve a comprehensive balance of flame retardant performance, precipitation control and processing stability. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 The infrared spectrum is that of zinc piperazine diphosphate prepared in Example 1. Detailed Implementation

[0029] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0030] Example 1

[0031] A method for preparing a zinc piperazine diphosphate flame retardant includes the following steps:

[0032] 63.34 g of 68-piperazine was dissolved in 350 mL of deionized water to obtain an aqueous solution of 68-piperazine; 54.88 g of anhydrous zinc acetate was dissolved in 350 mL of deionized water to obtain an aqueous solution of zinc acetate; at room temperature, the aqueous solution of zinc acetate was added dropwise to the aqueous solution of 68-piperazine over a period of 45 minutes, and after the addition was completed, the temperature was raised to 60 °C and the reaction was carried out for 1 hour.

[0033] Weigh 115.28 g of 85% phosphoric acid aqueous solution and add it dropwise to the above reaction system over 12 minutes. After the addition is complete, raise the temperature to 90°C and react for 3 hours.

[0034] After the reaction was completed, the mixture was filtered while hot. The filter cake was washed twice with deionized water at 90°C and then dried in an oven at 105°C until the moisture content was <0.5wt%, thus obtaining zinc piperazine diphosphate flame retardant.

[0035] from Figure 1 It can be seen that in the 500-600cm range -1 The presence of strong absorption peaks within the range corresponds to the bending vibrations of the Zn-O bonds in zinc oxide. Furthermore, the main characteristic peaks of this infrared spectrum include vibrational absorptions of Zn-O, PO, CN, and NH bonds, confirming the successful synthesis of the target flame retardant.

[0036] Example 2

[0037] The difference between this example and Example 1 is that an equal amount of zinc oxide is used to replace the anhydrous zinc acetate in Example 1, while the other operations are the same as in Example 1, to obtain the zinc piperazine diphosphate flame retardant.

[0038] Example 3

[0039] A method for preparing a zinc piperazine diphosphate flame retardant includes the following steps:

[0040] 63.34 g of piperazine was dissolved in 350 mL of deionized water to obtain an aqueous solution of piperazine; 54.88 g of basic zinc carbonate was dissolved in 350 mL of deionized water to obtain an aqueous solution of basic zinc carbonate; at room temperature, the aqueous solution of basic zinc carbonate was added dropwise to the aqueous solution of piperazine over a period of 45 minutes, and after the addition was completed, the temperature was raised to 60 °C and the reaction was carried out for 1 hour.

[0041] Weigh 115.28 g of 85% phosphoric acid aqueous solution and add it dropwise to the above reaction system over 12 minutes. After the addition is complete, raise the temperature to 80°C and react for 3 hours.

[0042] After the reaction is complete, filter while hot. Wash the filter cake twice with deionized water at 80°C, and then dry it in an oven at 120°C until the moisture content is <0.5wt%, to obtain zinc piperazine diphosphate flame retardant.

[0043] Example 4

[0044] The difference between this example and Example 3 is that an equal amount of zinc hydroxide is used to replace the basic zinc carbonate in Example 3, while the other operations are the same as in Example 3, to obtain the zinc piperazine diphosphate flame retardant.

[0045] Comparative Example 1

[0046] Commercially available zinc piperazine pyrophosphate.

[0047] Comparative Example 2

[0048] The difference between this example and Example 1 is that the zinc acetate aqueous solution was added over a time of 30 minutes, while the other operations were the same as in Example 1.

[0049] Comparative Example 3

[0050] The difference between this example and Example 1 is that the phosphoric acid aqueous solution was added over a time of 23 minutes, while the other operations were the same as in Example 1.

[0051] I. Solubility Test:

[0052] The solubility of the flame retardants in the above embodiments and comparative examples is shown in Table 1.

[0053] Table 1

[0054]

[0055] As can be seen from the test results in Table 1, the solubility of the piperazine diphosphate metal salt flame retardant prepared in this invention is significantly lower than that of commercially available piperazine pyrophosphate, which can improve the problems of flame retardant agglomeration, stickiness, and hygroscopicity. A comparison between Comparative Example 2 and Example 1 shows that the faster dropping speed of zinc acetate leads to a more rapid reaction, resulting in smaller particle size and a denser structure of the reaction product, thus increasing its solubility compared to Example 1.

[0056] II. Flame retardant performance test:

[0057] By weight, 4 parts of the flame retardant prepared in Examples 1-4 and Comparative Examples 2 and 3 were mixed with 9 parts of zinc piperazine pyrophosphate from Comparative Example 1, 76 parts of PP resin (EP300M, CNOOC Shell), 12 parts of melamine phosphate (Sichuan Fine Chemicals, MPP), 0.4 parts of anti-dripping agent (Pushin, DB-105), and 0.3 parts of antioxidant (AT-215) to prepare samples, which were denoted as samples A-1, A-2, A-3, A-4, D-2, and D-3, respectively.

[0058] By weight, 12 parts of zinc piperazine pyrophosphate from Comparative Example 1 were mixed with 76 parts of PP resin (EP300M, CNOOC Shell), 12 parts of melamine phosphate (Sichuan Fine Chemicals, MPP), 0.4 parts of anti-dripping agent (Pushin, DB-105), and 0.3 parts of antioxidant (AT-215) to prepare a sample, which was denoted as sample D-1.

[0059] Double 85 reliability test: The above samples were placed at 85±2℃ and 85±5% RH for 500h respectively, and then subjected to UL94 (1.6mm) flame retardancy test.

[0060] The UL94 (1.6mm) flame retardant test standard is as follows:

[0061] According to the UL94 vertical burning standard, the test strips were subjected to two 10±1s flame tests. The extinguishing time t1 and t2 of the test strips after each flame test were recorded, as well as whether dripping ignited the absorbent cotton below. Five test strips were tested for each sample. If the total burning time of the five test strips t1+t2 does not exceed 50s and there is no dripping ignition, it is judged as V-0. If there is no dripping ignition and the total burning time is between 50-250s, it is judged as V-1. If dripping ignition occurs and the total burning time is between 50-250s, it is judged as V-2.

[0062] The test results are shown in Table 2.

[0063] Table 2

[0064]

[0065] As shown in Table 2, replacing 25 wt% of PAPP piperazine pyrophosphate with the piperazine diphosphate metal salt flame retardant prepared according to this invention has no impact on the flame retardant performance of the products, and both can achieve V0 rating. After 500 hours of high temperature and high humidity treatment, the flame retardant system with 25 wt% piperazine diphosphate metal salt has better anti-precipitation and flame retardant performance, and both can achieve V0 rating. However, the flame retardant system without piperazine diphosphate metal salt showed a significant decrease in flame retardant performance after double 85 treatment. This is because piperazine pyrophosphate has high hygroscopicity and is prone to migration and precipitation inside or on the surface of the material, resulting in interface defects, a decrease in local flame retardant concentration, and a poorer ability to form a continuous char layer during combustion. At the same time, moisture absorption also changes the melting and dripping behavior, resulting in a significant decrease in the flame retardant performance of the products. The flame retardant system of Comparative Example 2 also showed a certain degree of decrease in flame retardant performance after double 85 treatment. This is because the metal salt solution drop acceleration was too fast, resulting in incomplete reaction, producing more impurities, and making them more prone to precipitation, which in turn affected the flame retardant performance, leading to drip ignition or a longer total combustion time.

[0066] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing a piperazine diphosphate metal salt flame retardant, characterized in that, Includes the following steps: At room temperature and with stirring, an aqueous solution of a metal salt was added dropwise to an aqueous solution of piperazine at 68°C to carry out a single reaction. Add an aqueous solution of phosphoric acid dropwise to the above reaction system to carry out a secondary reaction; Filter while hot, wash and dry the filter cake to obtain piperazine diphosphate metal salt.

2. The method for preparing a piperazine diphosphate metal salt flame retardant according to claim 1, characterized in that, Metal salts are one of the following: metal oxides, metal hydroxides, metal carbonates, and metal acetates.

3. The method for preparing a piperazine diphosphate metal salt flame retardant according to claim 1, characterized in that, The metal in the metal salt is one of magnesium, aluminum, or zinc.

4. The method for preparing a piperazine diphosphate metal salt flame retardant according to claim 1, characterized in that, The components are used in the following amounts by weight: 60 parts of 68-piperazine, 50 parts of metal salt, and 300 parts of deionized water; the concentration of the metal salt aqueous solution is 12-14 wt%, the concentration of the 68-piperazine solution is 14-16 wt%, and the mass ratio of the 68-piperazine aqueous solution to the metal salt aqueous solution is (1.0-1.2):

1.

5. The method for preparing a piperazine diphosphate metal salt flame retardant according to claim 1, characterized in that, The metal salt aqueous solution is added over a period of 30-60 minutes, and the dropping rate of the metal salt aqueous solution is 5-10 ml / min.

6. The method for preparing a piperazine diphosphate metal salt flame retardant according to claim 1, characterized in that, The temperature for one reaction is 60-90℃, and the time is 1-1.5h.

7. The method for preparing a piperazine diphosphate metal salt flame retardant according to claim 1, characterized in that, The concentration of the phosphoric acid aqueous solution is 80-90 wt%, and the amount of phosphoric acid aqueous solution added is 1.5-2 times the mass of the 68 piperazine aqueous solution.

8. The method for preparing a piperazine diphosphate metal salt flame retardant according to claim 1, characterized in that, The dropping rate of the phosphoric acid aqueous solution is 5-10 g / min.

9. The method for preparing a piperazine diphosphate metal salt flame retardant according to claim 1, characterized in that, The secondary reaction is carried out at a temperature of 80-90℃ for 2-4 hours.

10. The method for preparing a piperazine diphosphate metal salt flame retardant according to claim 1, characterized in that, Deionized water at a temperature of 60-80℃ is used to wash the filter cake.

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