Preparation method of piperazine pyrophosphate

Abstract

The invention discloses a preparation method of piperazine pyrophosphate, which belongs to the field of chemical preparation, and comprises the following steps: M1, taking acid ammonium pyrophosphate powder; m2, piperazine is dissolved in water, acid is added for neutralization, and cooling is carried out; m3, adding acid ammonium pyrophosphate powder into the solution of M2, reacting for 2-4 hours under the acidic condition and the temperature of 7-12 DEG C, filtering, cleaning and drying to obtain piperazine pyrophosphate; the molar ratio of the piperazine to the acid ammonium pyrophosphate powder is (0.8-1.5): 1. The raw material cost is reduced, the use amount of hydrochloric acid is reduced, and the by-product ammonium chloride can be used as a fertilizer.

Description

Technical Field

[0001] This invention specifically relates to a method for preparing piperazine pyrophosphate. Background Technology

[0002] Ammonium pyrophosphate is an acid salt of ammonium pyrophosphate. The pyrophosphate ion has strong coordination properties and is commonly used in industry as a chelating agent and cleaning agent. In the food industry, it is commonly used as a preservative, stabilizer, and emulsifier. Common salts include sodium pyrophosphate, disodium dihydrogen pyrophosphate, and potassium pyrophosphate. Ammonium pyrophosphate salts are commonly used as flame retardants and fertilizers. For example, fertilizer-grade ammonium polyphosphate often contains some ammonium pyrophosphate salts.

[0003] Currently, there are no reports of production processes specifically for producing ammonium pyrophosphate salts. Most production processes are those used for fertilizer-grade ammonium polyphosphate, which contains a portion of ammonium pyrophosphate.

[0004] CN201210119676.3 discloses a method for preparing a low-polymerization-degree ammonium polyphosphate aqueous solution. Using 100% to 120% polyphosphoric acid as the main raw material, and adjusting with an appropriate amount of water, the solution is mixed, stirred, and reacted with ammonium bicarbonate under natural, low-temperature, and normal pressure conditions. This method produces a low-polymerization-degree ammonium polyphosphate aqueous solution with a nitrogen content higher than 11% and a phosphorus pentoxide content higher than 37%, with a polymerization degree of 71%, primarily composed of dimer (ammonium pyrophosphate). However, this method suffers from two drawbacks: firstly, the cost of the polyphosphoric acid used as a raw material is relatively high; secondly, the proportion of ammonium pyrophosphate in the produced product only reaches 70%.

[0005] CN202110285470.7 discloses a two-step method for preparing water-soluble ammonium polyphosphate. The method involves feeding molten monoammonium phosphate and molten urea into a reaction vessel to obtain an acidic ammonium polyphosphate melt. The polyphosphate melt is then fed into a kneading reactor for a secondary reaction with solid urea, yielding a semi-finished ammonium polyphosphate product. The semi-finished product is cooled and crushed to obtain the water-soluble ammonium polyphosphate product. The preparation method is carried out in two steps: the first reaction is conducted at a higher temperature (200-260℃) to obtain a polyphosphate melt with a wide degree of polymerization distribution; the second reaction is conducted at a lower temperature (approximately 120-160℃) to further increase the polymerization rate. The ammonium polyphosphate obtained by this method has a wide degree of polymerization distribution, with ammonium pyrophosphate accounting for 16-36%.

[0006] CN201610479295.4 discloses a method for preparing high-polymerization-rate water-soluble ammonium polyphosphate. The method involves adding monoammonium phosphate and urea in a molar ratio of (0.8-1.8):1 into a reaction vessel, stirring, heating, and controlling the material temperature at 110-180℃ to induce a condensation reaction, thereby generating high-polymerization-rate water-soluble ammonium polyphosphate powder. This method yields short-chain ammonium polyphosphate with an average degree of polymerization of approximately 3.5 and high water solubility.

[0007] Piperazine pyrophosphate (PPAP) is a novel, environmentally friendly flame retardant with a nitrogen-phosphorus synergistic effect, suitable for flame retardant applications in polyolefins, thermoplastic elastomers, and other products. Due to its excellent flame-retardant properties, it is a hot research topic in phosphorus-based flame-retardant materials.

[0008] In recent decades, there have been numerous reports on the preparation of pyrophosphate pyridine. These generally include the following methods: (1) Metathesis precipitation method: The metathesis precipitation method mentioned in US Patent US3810850A is as follows: anhydrous piperazine and anhydrous sodium pyrophosphate react in hydrochloric acid solution. The generated PPAP is sparingly soluble in water and precipitates out. After separation, the PPAP product can be obtained. Subsequently, US4599375A disclosed a similar method, the specific process of which is as follows: 750g of sodium pyrophosphate decahydrate is added to a 5L reactor and fully dissolved in 2500mL of water. The material is then cooled to 10°C and acidified with 563mL of hydrochloric acid (concentration 37wt%) while the system temperature does not exceed 12°C. The acidified sodium pyrophosphate solution is then added to a piperazine solution (149g of piperazine dissolved in 625mL of water). After crystals precipitate (pH 3~4), stirring is maintained for 2~3 hours (temperature maintained at around 7°C). The filter cake is then washed with water after filtration and dried in a vacuum drying oven at 105°C for 6 hours to obtain 235g of PPAP (yield 53%). The thermal stability of the product is above 280°C. The problem with this method is that the low solubility of sodium pyrophosphate in hydrochloric acid solution leads to a low concentration of reactants and a low product yield during the reaction. At the same time, some sodium ions are difficult to wash off, which reduces the flame retardant efficiency and affects its application in electronic products.

[0009] (2) Phosphorus pentoxide method: This method involves reacting phosphoric acid with phosphoric acid to generate pyrophosphate, which is then reacted with piperazine to generate PPAP. ​​This method suffers from low purity pyrophosphate due to the difficulty in controlling the degree of P2O5 depolymerization. Furthermore, slightly higher temperatures can cause piperazine volatilization, carbonization, and pyrophosphate decomposition, resulting in a low actual yield. Therefore, a new method for preparing piperazine pyrophosphate with high yield (Guangdong Chemical Industry, Zhang Xiuqin, 2017, 44(15):86-87) has been developed to improve this method. The process is as follows: P2O5 and phosphoric acid in an equimolar ratio are reacted at 200℃ for 1 hour, then the temperature is lowered to 80℃. Glacial acetic acid is added and stirred to dissolve for 0.5 hours. Anhydrous piperazine is then added, and the temperature is raised to 120℃ for 2 hours to obtain the product, with a yield of 96.5%. Using glacial acetic acid as a solvent makes the material easier to disperse, and the low reaction temperature results in non-sticky product particles, thus greatly improving the yield. The product is also white in color. However, glacial acetic acid recovery is difficult and corrodes equipment. In practice, there are also problems such as the difficulty in controlling the degree of P2O5 depolymerization and the easy decomposition of pyrophosphate.

[0010] (3) Piperazine diphosphate condensation method: This method first prepares piperazine diphosphate by reacting phosphoric acid and piperazine, and then prepares piperazine pyrophosphate (PPAP) by dehydration. US7449577 B2 and US2012 / 0190779A1 respectively disclose the preparation of piperazine diphosphate in aqueous solution, and then dehydration at a high temperature above 200°C to prepare piperazine pyrophosphate. CN102304100A proposes to first react piperazine with phosphoric acid to generate piperazine phosphate, and then mix piperazine phosphate and phosphoric acid in a 1:1 ratio and dehydrate and condense at high temperature to prepare piperazine pyrophosphate.

[0011] (4) Solid pyrophosphate method: CN202410781582.5 discloses a method for preparing piperazine pyrophosphate. This method uses piperazine, water and solid pyrophosphate powder as raw materials and prepares piperazine pyrophosphate by kneading reaction in a kneader. This method uses solid pyrophosphate powder, which is expensive and has a high production cost. Summary of the Invention

[0012] To address the aforementioned shortcomings, this invention provides a method for preparing piperazine pyrophosphate. This method reduces raw material costs and hydrochloric acid usage, while the byproduct ammonium chloride can be utilized as fertilizer. Furthermore, due to the extremely high solubility of ammonium pyrophosphate, water consumption is reduced, increasing the first-pass yield of the product, which also exhibits high whiteness and purity. It is sodium ion-free, making it suitable for most polymer materials and applications.

[0013] A method for preparing piperazine pyrophosphate includes the following steps: M1, take acidic ammonium pyrophosphate powder; M2, dissolve piperazine in water, add acid to neutralize, and cool; M3, add acidic ammonium pyrophosphate powder to the solution of M2, react at acidic temperature of 7℃~12℃ for 2~4 hours, filter, wash, dry to obtain piperazine pyrophosphate; The molar ratio of piperazine to ammonium pyrophosphate powder is 0.8~1.5:1.

[0014] In one or more optional embodiments of the present invention, the acidic ammonium pyrophosphate powder is prepared by the following steps: S1, phosphoric acid, monoammonium phosphate, and some urea react at 150℃~180℃ for 1 to 3 hours; The mixture after S2 and S1 reaction, the polymerization inhibitor, and the remaining urea are reacted at 185℃~210℃ for 1 hour to 3 hours. S3, cooling down, yields ammonium acid pyrophosphate; In S1, the mass ratio of phosphoric acid to monoammonium phosphate is 98:103.5 to 98:127.5, and the molar ratio of urea to phosphoric acid is 1:0.05 to 1:0.1; in S2, the molar ratio of urea to phosphoric acid is 1:0.2 to 1:0.5.

[0015] In one or more alternative embodiments of the present invention, the amount of the polymerization inhibitor is 0.05% to 0.2% of the total mass of phosphoric acid and monoammonium phosphate.

[0016] In one or more alternative embodiments of the present invention, in S2, urea is added slowly over a period of 15 to 35 minutes.

[0017] In one or more alternative embodiments of the present invention, the pH value of the reaction system in M3 is 3 to 4.

[0018] In one or more alternative embodiments of the present invention, the acid is hydrochloric acid.

[0019] In one or more alternative embodiments of the present invention, the amount of hydrochloric acid added is based on the pH value of the reaction system.

[0020] In one or more alternative embodiments of the present invention, the concentration of hydrochloric acid is 28 wt% to 32 wt%.

[0021] In one or more alternative embodiments of the present invention, the total weight of ammonium pyrophosphate powder and piperazine is denoted as Q, and the water content: Q = 1.5:1 to 4:1.

[0022] Invention principle and beneficial effects: This invention uses acidic ammonium pyrophosphate instead of solid pyrophosphate powder, reducing raw material costs. The use of acidic ammonium pyrophosphate reduces hydrochloric acid usage, and the byproduct ammonium chloride can be used as fertilizer. Furthermore, due to the extremely high solubility of ammonium pyrophosphate, water consumption is reduced, increasing the first-pass yield of the product, while also resulting in high whiteness and purity. It is sodium ion-free, making it suitable for most polymer materials and applications.

[0023] In the preparation method of acidic ammonium pyrophosphate of the present invention, the first step reaction is carried out under strong acid and urea dehydration conditions, which allows most of the orthophosphate ions to polymerize to form pyrophosphate. Water generated during the condensation of urea and phosphoric acid undergoes hydrolysis, resulting in rapid dehydration. The amount of urea used is strictly controlled to avoid the formation of more trimerized or higher-order products. In the second step reaction, urea and a polymerization inhibitor are added at a reaction temperature higher than that of the first step reaction, ensuring complete reaction of unreacted orthophosphate ions and preventing further dehydration of oligophosphates, thus achieving a higher yield of pyrophosphate. The acidic ammonium pyrophosphate salt prepared by the present invention has a pyrophosphate ion content of 90%~99% of the total phosphorus, exhibits an acidity of 2.5~5.5, and can be used in any proportion of macronutrients for compounding. It can also be used as an intermediate in flame retardant products. Detailed Implementation

[0025] The present invention will be further described below.

[0026] As used in this article: "Prepared from" is synonymous with "comprising". The terms "comprising", "including", "having", "containing", or any other variations thereof as used herein are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0027] The conjunction "composed of..." excludes any unspecified elements, steps, or components. If used in a claim, this phrase makes the claim closed, excluding materials other than those described, except for associated conventional impurities. When the phrase "composed of..." appears in a clause of the body of a claim rather than immediately following it, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0028] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1–5” is disclosed, the described range should be interpreted as including ranges “1–4”, “1–3”, “1–2”, “1–2 and 4–5”, “1–3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0029] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified, specific conditions in the embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Reagents (materials) or instruments (equipment) used without a specified manufacturer are all commercially available conventional products.

[0031] In these embodiments, unless otherwise specified, the portions and percentages are all by weight.

[0032] "Parts by mass" refers to the basic unit of measurement that expresses the mass ratio of multiple components. One part can represent any unit mass, such as 1g or 2.689g. If we say that component A has "a" parts by mass and component B has "b" parts by mass, it means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, it can mean that the mass of component A is aK and the mass of component B is bK (K is any number representing a multiplier). It is important to understand that, unlike the number of parts by mass, the sum of the mass parts of all components is not limited to 100 parts.

[0033] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0034] In this invention, the phosphoric acid is 98 wt% phosphoric acid purchased from the market, the monoammonium phosphate is 99 wt% monoammonium phosphate purchased from the market, and the ammonium persulfate and urea are purchased from the market.

[0035] Example 1 A method for preparing acidic ammonium pyrophosphate includes the following steps: S1. Weigh 100g of phosphoric acid and 116g of monoammonium phosphate, add them to a kneader, turn on the stirrer, add 6g of urea, and raise the temperature to 160℃ to react for 2 hours.

[0036] S2, add 0.216 g of ammonium persulfate, heat to 190°C, slowly add 24 g of urea, controlling the addition time to 30 minutes, and then keep the reaction at this temperature for 1.5 hours.

[0037] S3, cooling down, after the material becomes semi-solid, start discharging. After the discharged material is cooled, it is crushed to obtain 216 grams of acidic ammonium pyrophosphate.

[0038] Example 2 A method for preparing acidic ammonium pyrophosphate includes the following steps: S1. Weigh 100g of phosphoric acid and 116g of monoammonium phosphate, add them to a kneader, turn on the stirrer, add 6g of urea, and raise the temperature to 160℃ to react for 2 hours.

[0039] S2, add 0.216 g of ammonium persulfate, heat to 190°C, slowly add 12 g of urea, controlling the addition time to 30 minutes, and then keep the reaction at this temperature for 1.5 hours.

[0040] S3, cooling down, after the material becomes semi-solid, start discharging. After the discharged material is cooled, it is crushed to obtain 210 grams of acidic ammonium pyrophosphate.

[0041] Example 3 A method for preparing acidic ammonium pyrophosphate includes the following steps: S1. Weigh 100g of phosphoric acid and 116g of monoammonium phosphate, add them to a kneader, turn on the stirrer, add 6g of urea, and raise the temperature to 180℃ to react for 2 hours.

[0042] S2, add 0.216 g of ammonium persulfate, heat to 210°C, slowly add 12 g of urea, controlling the addition time to 30 minutes, and then keep the reaction at this temperature for 1.5 hours.

[0043] S3, cooling down, after the material becomes semi-solid, start discharging. After the discharged material is cooled, it is crushed to obtain 209 grams of acidic ammonium pyrophosphate.

[0044] Example 4 A method for preparing acidic ammonium pyrophosphate includes the following steps: S1. Weigh 100g of phosphoric acid and 104.5g of monoammonium phosphate, add them to a kneader, turn on the stirrer, add 6g of urea, and raise the temperature to 160℃ to react for 2 hours.

[0045] S2, add 0.216 g of ammonium persulfate, heat to 190°C, slowly add 24 g of urea, controlling the addition time to 30 minutes, and then keep the reaction at this temperature for 1.5 hours.

[0046] S3, cooling down, after the material becomes semi-solid, start discharging. After the discharged material is cooled, it is crushed to obtain 204 grams of acidic ammonium pyrophosphate.

[0047] Example 5 A method for preparing acidic ammonium pyrophosphate includes the following steps: S1. Weigh 100g of phosphoric acid and 127.5g of monoammonium phosphate, add them to a kneader, turn on the stirrer, add 6g of urea, and raise the temperature to 160℃ to react for 2 hours.

[0048] S2, add 0.216 g of ammonium persulfate, heat to 190°C, slowly add 24 g of urea, controlling the addition time to 30 minutes, and then keep the reaction at this temperature for 1.5 hours.

[0049] S3, cooling down, after the material becomes semi-solidified, the material is discharged. After being cooled, the discharged material is crushed to obtain 225 grams of acidic ammonium pyrophosphate.

[0050] Comparative Example 1 A method for preparing acidic ammonium pyrophosphate includes the following steps: S1. Weigh 100g of phosphoric acid and 116g of monoammonium phosphate, add them to a kneader, turn on the stirrer, add 24g of urea, and raise the temperature to 160℃ to react for 2 hours.

[0051] S2, add 0.216 g of ammonium persulfate, heat to 190°C, slowly add 6 g of urea, controlling the addition time to 30 minutes, and then keep the reaction at this temperature for 1.5 hours.

[0052] S3, cooling down, after the material becomes semi-solidified, the material is discharged. After being cooled, the discharged material is crushed to obtain 214 grams of acidic ammonium pyrophosphate.

[0053] Comparative Example 2 A method for preparing acidic ammonium pyrophosphate includes the following steps: S1. Weigh 100g of phosphoric acid and 116g of monoammonium phosphate, add them to a kneader, turn on the stirrer, add 6g of urea, and raise the temperature to 190℃ to react for 2 hours.

[0054] S2, add 0.216 g of ammonium persulfate, heat to 160°C, slowly add 24 g of urea, controlling the addition time to 30 minutes, and then keep the reaction at this temperature for 1.5 hours.

[0055] S3, cooling down, after the material becomes semi-solidified, start discharging. After the discharged material is cooled, it is crushed to obtain 215 grams of acidic ammonium pyrophosphate.

[0056] Comparative Example 3 A method for preparing acidic ammonium pyrophosphate includes the following steps: S1. Weigh 100g of phosphoric acid and 116g of monoammonium phosphate, add them to a kneader, turn on the stirrer, add 30g of urea and 0.216g of ammonium persulfate, heat to 190℃, and then keep the temperature for 3.5 hours.

[0057] S2, cooling down, after the material becomes semi-solid, the material is discharged. After being cooled, the discharged material is crushed to obtain 220 grams of acidic ammonium pyrophosphate.

[0058] Comparative Example 4 A method for preparing acidic ammonium pyrophosphate includes the following steps: S1. Weigh 100g of phosphoric acid and 116g of monoammonium phosphate, add them to a kneader, turn on the stirrer, add 30g of urea, heat to 190℃, and then keep the temperature for 3.5 hours.

[0059] S2, cooling down, after the material becomes semi-solid, the material is discharged. After cooling, the material is crushed to obtain 210 grams of acidic ammonium pyrophosphate.

[0060] The acidic ammonium pyrophosphate products obtained in Examples 1-5 and Comparative Examples 1-4 were tested, and the results are shown in Table 1 below.

[0061] Table 1 Example 6 A method for preparing piperazine pyrophosphate includes the following steps: M1, 216g of ammonium pyrophosphate powder was obtained according to the preparation method of Example 1.

[0062] M2, dissolve 78 g of piperazine in 500 g of water, add 203 g of 31 wt% hydrochloric acid, neutralize, and then cool to 10°C.

[0063] M3, slowly add 200 g of the acidic ammonium pyrophosphate powder obtained in M1, controlling the addition time to 1 hour. After the addition is complete, the pH of the reaction system is 3.4; keep the reaction at 7℃~12℃ for 3 hours, filter, wash with ice water 2~3 times, then dry, and pulverize and sieve to obtain 229.7 g of piperazine pyrophosphate.

[0064] Example 7 A method for preparing piperazine pyrophosphate includes the following steps: M1, 210g of ammonium pyrophosphate powder was obtained according to the preparation method of Example 2.

[0065] M2, dissolve 79.8 g of piperazine in 500 g of water, add 146 g of 31 wt% hydrochloric acid, neutralize, and then cool to 10°C.

[0066] M3, slowly add 200 g of the acidic ammonium pyrophosphate powder obtained in M1, controlling the addition time to 1 hour. After the addition is complete, the pH of the reaction system is 3.4; keep the reaction at 7℃~12℃ for 3 hours, filter, wash with ice water 2~3 times, then dry, and pulverize and sieve to obtain 235.8 g of piperazine pyrophosphate.

[0067] Example 8 A method for preparing piperazine pyrophosphate includes the following steps: M1, 209g of ammonium pyrophosphate powder was obtained according to the preparation method of Example 3.

[0068] M2, dissolve 77.7 g of piperazine in 500 g of water, add 152 g of 31 wt% hydrochloric acid, neutralize, and then cool to 10 °C.

[0069] M3, slowly add 200 g of the acidic ammonium pyrophosphate powder obtained in M1, controlling the addition time to 1 hour. After the addition is complete, the pH of the reaction system is 3.4; keep the reaction at 7℃~12℃ for 3 hours, filter, wash with ice water 2~3 times, then dry, and pulverize and sieve to obtain 229.5 g of piperazine pyrophosphate.

[0070] Example 9 A method for preparing piperazine pyrophosphate includes the following steps: M1, 204g of ammonium pyrophosphate powder was obtained according to the preparation method of Example 4.

[0071] M2, dissolve 78.1 g of piperazine in 500 g of water, add 205 g of 31 wt% hydrochloric acid, neutralize, and then cool to 10°C.

[0072] M3, slowly add 200 g of the acidic ammonium pyrophosphate powder obtained in M1, controlling the addition time to 1 hour. After the addition is complete, the pH of the reaction system is 3.4; keep the reaction at 7℃~12℃ for 3 hours, filter, wash with ice water 2~3 times, then dry, and pulverize and sieve to obtain 230.1 g of piperazine pyrophosphate.

[0073] Example 10 A method for preparing piperazine pyrophosphate includes the following steps: M1, 225g of ammonium pyrophosphate powder was obtained according to the preparation method of Example 5.

[0074] M2, dissolve 76.5 g of piperazine in 500 g of water, add 201 g of 31 wt% hydrochloric acid, neutralize, and then cool to 10°C.

[0075] M3, slowly add 200 g of the acidic ammonium pyrophosphate powder obtained in M1, controlling the addition time to 1 hour. After the addition is complete, the pH of the reaction system is 3.4; keep the reaction at 7℃~12℃ for 3 hours, filter, wash with ice water 2~3 times, then dry, and obtain 225.0 g of piperazine pyrophosphate after crushing and sieving.

[0076] Comparative Example 5 A method for preparing piperazine pyrophosphate includes the following steps: M1, 214g of ammonium acid pyrophosphate powder was obtained according to the preparation method of Comparative Example 1.

[0077] M2, dissolve 48.8 g of piperazine in 500 g of water, add 135 g of 31 wt% hydrochloric acid, neutralize, and then cool to 10°C.

[0078] M3, slowly add 200 g of the acidic ammonium pyrophosphate powder obtained in M1, controlling the addition time to 1 hour. After the addition is complete, the pH of the reaction system is 3.4; keep the reaction at 7℃~12℃ for 3 hours, filter, wash with ice water 2~3 times, then dry, and pulverize and sieve to obtain 140.8 g of piperazine pyrophosphate.

[0079] Comparative Example 6 A method for preparing piperazine pyrophosphate includes the following steps: M1, 215g of ammonium pyrophosphate powder was obtained according to the preparation method of Comparative Example 2.

[0080] M2, dissolve 63.3 g of piperazine in 500 g of water, add 170 g of 31 wt% hydrochloric acid, neutralize, and then cool to 10°C.

[0081] M3, slowly add 200 g of the acidic ammonium pyrophosphate powder obtained in M1, controlling the addition time to 1 hour. After the addition is complete, the pH of the reaction system is 3.4; keep the reaction at 7℃~12℃ for 3 hours, filter, wash with ice water 2~3 times, then dry, and pulverize and sieve to obtain 185.2 g of piperazine pyrophosphate.

[0082] Comparative Example 7 A method for preparing piperazine pyrophosphate includes the following steps: M1, 220g of ammonium acid pyrophosphate powder was obtained according to the preparation method of Comparative Example 3.

[0083] M2, dissolve 65.7 g of piperazine in 500 g of water, add 175 g of 31 wt% hydrochloric acid, neutralize, and cool to 10°C.

[0084] M3, slowly add 200 g of the acidic ammonium pyrophosphate powder obtained in M1, controlling the addition time to 1 hour. After the addition is complete, the pH of the reaction system is 3.4; keep the reaction at 7℃~12℃ for 3 hours, filter, wash with ice water 2~3 times, then dry, and pulverize and sieve to obtain 192.3 g of piperazine pyrophosphate.

[0085] Comparative Example 8 A method for preparing piperazine pyrophosphate includes the following steps: M1, 210g of ammonium acid pyrophosphate powder was obtained according to the preparation method of Comparative Example 4.

[0086] M2, dissolve 33.5 g of piperazine in 500 g of water, add 90 g of 31 wt% hydrochloric acid, neutralize, and then cool to 10°C.

[0087] M3, slowly add 200 g of the acidic ammonium pyrophosphate powder obtained in M1, controlling the addition time to 1 hour. After the addition is complete, the pH of the reaction system is 3.4; keep the reaction at 7℃~12℃ for 3 hours, filter, wash with ice water 2~3 times, then dry, and obtain 94.4 g of piperazine pyrophosphate after crushing and sieving.

[0088] The piperazine pyrophosphate products obtained in Examples 6-7 and Comparative Examples 5-8 were tested, and the results are shown in Table 2 below.

[0089] Table 2 The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing piperazine pyrophosphate, comprising the following steps: M1, take acidic ammonium pyrophosphate powder; M2, dissolve piperazine in water, add acid to neutralize, and cool; M3, add acidic ammonium pyrophosphate powder to the solution of M2, react at acidic temperature of 7℃~12℃ for 2~4 hours, filter, wash, dry to obtain piperazine pyrophosphate; The molar ratio of piperazine to ammonium pyrophosphate powder is 0.8~1.5:

1.

2. The method for preparing piperazine pyrophosphate according to claim 1, characterized in that, The acidic ammonium pyrophosphate powder is prepared by the following steps: S1, phosphoric acid, monoammonium phosphate, and some urea react at 150℃~180℃ for 1 to 3 hours; The mixture after S2 and S1 reaction, the polymerization inhibitor, and the remaining urea are reacted at 185℃~210℃ for 1 hour to 3 hours. S3, cooling down, yields ammonium acid pyrophosphate; In S1, the mass ratio of phosphoric acid to monoammonium phosphate is 98:103.5 to 98:127.5, and the molar ratio of urea to phosphoric acid is 1:0.05 to 1:0.1; in S2, the molar ratio of urea to phosphoric acid is 1:0.2 to 1:0.

5.

3. The method for preparing piperazine pyrophosphate according to claim 2, characterized in that, The amount of the polymerization inhibitor is 0.05% to 0.2% of the total mass of phosphoric acid and monoammonium phosphate.

4. The method for preparing piperazine pyrophosphate according to claim 2, characterized in that, In S2, urea is added slowly over a period of 15 to 35 minutes.

5. The method for preparing piperazine pyrophosphate according to claim 3, characterized in that, In M3, the pH value of the reaction system is 3~4.

6. The method for preparing piperazine pyrophosphate according to claim 5, characterized in that, The acid is hydrochloric acid.

7. The method for preparing piperazine pyrophosphate according to claim 6, characterized in that, The amount of hydrochloric acid added is based on the pH value of the reaction system.

8. The method for preparing piperazine pyrophosphate according to claim 6, characterized in that, The concentration of the hydrochloric acid is 28wt%~32wt%.

9. The method for preparing piperazine pyrophosphate according to claim 1, characterized in that, The total weight of ammonium pyrophosphate powder and piperazine is denoted as Q, and the water content is Q = 1.5:1~4:1.

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