Piperazine pyrophosphate, its preparation method and application

Abstract

This application discloses a piperazine pyrophosphate, its preparation method, and its application, belonging to the field of flame retardant technology. The preparation method of piperazine pyrophosphate in this application uses piperazine diphosphate as raw material and employs a multi-stage temperature-switching condensation reaction and a multi-stage cooling treatment to ensure complete condensation of piperazine diphosphate while avoiding side reactions. This significantly improves the synthesis efficiency, product purity, batch stability, thermal stability, and whiteness of piperazine pyrophosphate. The preparation method of piperazine pyrophosphate in this application enables continuous reaction, achieving 24-hour uninterrupted production, greatly shortening the production cycle of piperazine pyrophosphate, and reducing environmental pollution.

Description

Technical Field

[0001] This application relates to the field of flame retardant technology, specifically to a piperazine pyrophosphate, its preparation method, and its application. Background Technology

[0002] In the fields of materials science and chemical engineering today, the research and application of flame retardants are of paramount importance. Piperazine pyrophosphate (structure shown below), as a high-performance, halogen-free, and environmentally friendly flame retardant, possesses excellent char-forming properties, enabling it to form a dense carbonized layer on the material surface. This effectively blocks the transfer of oxygen and heat, thus significantly improving the flame retardant performance of the material. When applied to the flame retardancy of polyolefins, thermoplastic elastomers, and other products, it can effectively reduce the flammability of these materials, improve product safety, and meet increasingly stringent fire safety standards.

[0003] Currently, there are several main methods for preparing piperazine pyrophosphate: (1) Sodium pyrophosphate acidification method: Patents such as US3810850 and US4599375 disclose the use of sodium pyrophosphate and piperazine in hydrochloric acid solution to generate water-insoluble piperazine pyrophosphate precipitate. This method cannot completely remove sodium chloride and sodium piperazine pyrophosphate produced by the side reaction. Adding them to flame retardant resin will affect the performance of the flame retardant resin, and the reaction yield and purity are low. (2) High-temperature dehydration method of piperazine diphosphate: Patent CN102304100A discloses the direct reaction synthesis of piperazine pyrophosphate using phosphoric acid and piperazine as raw materials. The pH of this method is difficult to control, and local uneven reaction is very likely to occur, resulting in an increase in product impurities and affecting the purity of piperazine pyrophosphate. At the same time, a large amount of heat is released during the reaction. If it cannot be removed in time and effectively, the reaction temperature will run out of control, causing side reactions and reducing the purity of piperazine pyrophosphate. Moreover, one of the raw materials, phosphoric acid, is expensive. Patent CN114605353A discloses the preparation of piperazine pyrophosphate by heating it to cause intermolecular dehydration condensation reaction using piperazine diphosphate as raw material. This method has low reaction efficiency and requires a long time to achieve a high conversion rate, which seriously restricts production efficiency. (3) Patent CN118324714A discloses the preparation of piperazine pyrophosphate using melamine, phosphoric acid and piperazine as raw materials. This method has complicated reaction steps, involves multiple reaction stages, has poor batch stability of piperazine pyrophosphate, high energy consumption, and complex equipment requirements.

[0004] Therefore, it is essential to develop a method for preparing piperazine pyrophosphate that has a wide range of raw material sources, low production costs, and high yield, purity, batch stability, thermal stability, and whiteness. Summary of the Invention

[0005] The purpose of this disclosure is to overcome the shortcomings of the prior art and provide a piperazine pyrophosphate, its preparation method, and its application.

[0006] To achieve the above objectives, the technical solution adopted in this disclosure is as follows: Firstly, a method for preparing piperazine pyrophosphate, characterized by comprising the following steps:

[0007] Piperazine diphosphate was added to a rotary kiln and condensed under the protection of an inert gas. After the reaction was completed, the temperature was lowered to obtain piperazine pyrophosphate.

[0008] The condensation reaction includes a first condensation reaction, a second condensation reaction, a third condensation reaction, a fourth condensation reaction, a fifth condensation reaction, a sixth condensation reaction, a seventh condensation reaction, and an eighth condensation reaction, carried out sequentially; the temperature of the first condensation reaction is 198-202℃; the temperature of the second condensation reaction is 213-217℃; the temperature of the third condensation reaction is 218-222℃; the temperature of the fourth condensation reaction is 223-227℃; the temperature of the fifth condensation reaction is 228-232℃; the temperature of the sixth condensation reaction is 233-237℃; and the temperatures of the seventh and eighth condensation reactions are each independently 238-242℃.

[0009] The cooling process includes a first cooling process, a second cooling process, and a third cooling process performed sequentially; the endpoint temperature of the first cooling process is 200°C; the endpoint temperature of the second cooling process is 150°C; and the endpoint temperature of the third cooling process is room temperature.

[0010] In some embodiments, the cooling rates of the first cooling process, the second cooling process, and the third cooling process are each independently 0.1-3℃ / min.

[0011] In some embodiments, the piperazine diphosphate has an average particle size of 40-200 μm and is in the form of flakes.

[0012] In some embodiments, the method for preparing the piperazine diphosphate includes the following steps:

[0013] After dissolving piperazine in water, phosphoric acid is added dropwise while stirring and at a temperature of 50-80℃. After the addition is complete, the temperature is raised to 80-90℃ and the reaction is maintained for 3-4 hours. After the reaction is complete, the temperature is lowered to room temperature at a rate of 1-2℃ / min and allowed to stand for 8-12 hours. The obtained product is then subjected to solid-liquid separation, dried, and pulverized to obtain piperazine diphosphate, wherein the molar ratio of piperazine to phosphoric acid is 1:(2-2.2).

[0014] In some embodiments, the dropping rate of the phosphoric acid is 30-50 mL / min;

[0015] In some embodiments, the stirring speed is 200-300 rpm;

[0016] In some embodiments, the mass-to-volume ratio of the piperazine to water is (1:2)-(1:5) g / L.

[0017] In some embodiments, the feed rate of the piperazine diphosphate into the rotary kiln is 50-200 kg / h.

[0018] In some embodiments, the rotary kiln rotates at a speed of 1-10 rpm;

[0019] In some embodiments, the tilt angle of the rotary kiln is 0.5-2°.

[0020] In some embodiments, the flow rate of the inert gas is 2-4 m³ / h. 3 / h;

[0021] In some embodiments, the inert gas is one of nitrogen or argon.

[0022] Secondly, a piperazine pyrophosphate is provided, which is prepared by the method for preparing the piperazine pyrophosphate.

[0023] Thirdly, a flame-retardant composition is provided, comprising the piperazine pyrophosphate.

[0024] Compared with existing technologies, the beneficial effects of this disclosure are as follows: The preparation method of piperazine pyrophosphate in this application uses piperazine diphosphate as raw material and achieves complete condensation of piperazine diphosphate through multi-stage temperature-varying condensation reaction and multi-stage cooling treatment, while avoiding side reactions. This significantly improves the synthesis efficiency, product purity, batch stability, thermal stability, and whiteness of piperazine pyrophosphate. The preparation method of piperazine pyrophosphate in this application enables continuous reaction, achieving 24-hour uninterrupted production, greatly shortening the production cycle of piperazine pyrophosphate, and reducing environmental pollution. Attached Figure Description

[0025] Figure 1 The TG curve for piperazine pyrophosphate in Example 5 is shown below.

[0026] Figure 2 The image shows the TG curve for piperazine pyrophosphate in Comparative Example 6. Detailed Implementation

[0027] To facilitate understanding of this disclosure, a more complete description will be provided below. However, this disclosure may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure.

[0028] As used in this article:

[0029] "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.

[0030] 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.

[0031] 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.

[0032] In these embodiments, unless otherwise specified, the portions and percentages are all by weight.

[0033] "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 that the mass ratio of component A to component B is a:b. It is important to understand that, unlike mass percentage content, the sum of the mass parts of all components is not limited to 100 parts.

[0034] "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).

[0035] According to a first aspect of this application, a method for preparing piperazine pyrophosphate includes the following steps:

[0036] Piperazine diphosphate was added to a rotary kiln and condensed under the protection of an inert gas. After the reaction was completed, the temperature was lowered to obtain piperazine pyrophosphate.

[0037] The condensation reaction includes a first condensation reaction, a second condensation reaction, a third condensation reaction, a fourth condensation reaction, a fifth condensation reaction, a sixth condensation reaction, a seventh condensation reaction, and an eighth condensation reaction, carried out sequentially; the temperature of the first condensation reaction is 198-202℃; the temperature of the second condensation reaction is 213-217℃; the temperature of the third condensation reaction is 218-222℃; the temperature of the fourth condensation reaction is 223-227℃; the temperature of the fifth condensation reaction is 228-232℃; the temperature of the sixth condensation reaction is 233-237℃; and the temperatures of the seventh and eighth condensation reactions are each independently 238-242℃.

[0038] The cooling process includes a first cooling process, a second cooling process, and a third cooling process performed sequentially; the endpoint temperature of the first cooling process is 200°C; the endpoint temperature of the second cooling process is 150°C; and the endpoint temperature of the third cooling process is room temperature.

[0039] Specifically, the temperature of the first condensation reaction can be, but is not limited to, 198°C, 198.5°C, 199°C, 199.5°C, 200°C, 200.5°C, 201°C, 201.5°C, or 202°C.

[0040] Specifically, the temperature of the second condensation reaction can be, but is not limited to, 213°C, 213.5°C, 214°C, 214.5°C, 215°C, 215.5°C, 216°C, 216.5°C, or 217°C.

[0041] Specifically, the temperature of the third condensation reaction can be, but is not limited to, 218°C, 218.5°C, 219°C, 219.5°C, 220°C, 220.5°C, 221°C, 221.5°C, or 222°C.

[0042] Specifically, the temperature of the fourth condensation reaction can be, but is not limited to, 223°C, 223.5°C, 224°C, 224.5°C, 225°C, 225.5°C, 226°C, 226.5°C, or 227°C.

[0043] Specifically, the temperature of the fifth condensation reaction can be, but is not limited to, 228°C, 228.5°C, 229°C, 229.5°C, 230°C, 230.5°C, 231°C, 231.5°C, or 232°C.

[0044] Specifically, the temperature of the sixth condensation reaction can be, but is not limited to, 233°C, 223.5°C, 234°C, 234.5°C, 235°C, 235.5°C, 236°C, 236.5°C, or 237°C.

[0045] Specifically, the temperatures of the seventh and eighth condensation reactions can be, but are not limited to, 238°C, 238.5°C, 239°C, 239.5°C, 240°C, 240.5°C, 241°C, 241.5°C, and 242°C.

[0046] The method for preparing piperazine pyrophosphate disclosed in this application uses piperazine diphosphate as a raw material. Through multi-stage temperature-varying condensation reaction and multi-stage cooling treatment, the condensation reaction of piperazine diphosphate is completed while avoiding side reactions, significantly improving the synthesis efficiency, product purity, batch stability, thermal stability, and whiteness of piperazine pyrophosphate. This method enables continuous reaction, achieving 24-hour uninterrupted production, greatly shortening the production cycle of piperazine pyrophosphate, and reducing environmental pollution.

[0047] In some embodiments, the cooling rates of the first cooling process, the second cooling process, and the third cooling process are each independently 0.1-3℃ / min, for example, but not limited to 0.1℃ / min, 0.5℃ / min, 1℃ / min, 1.5℃ / min, 2℃ / min, 2.5℃ / min, and 3℃ / min.

[0048] The applicant found that piperazine pyrophosphate exhibited higher thermal stability and whiteness within the aforementioned cooling rate range.

[0049] The applicant also found that the cooling rates of the first and third cooling treatments were lower than those of the second cooling treatment, which could further improve the thermal stability of piperazine pyrophosphate.

[0050] Specifically, holding the temperature at the end of the first and second cooling treatments for 10-20 minutes can further improve the thermal stability of piperazine pyrophosphate.

[0051] In some embodiments, the average particle size of the piperazine diphosphate is 40-200 μm, for example, but not limited to 40 μm, 60 μm, 80 μm, 100 μm, 120 μm, 140 μm, 160 μm, 180 μm, 200 μm; preferably 80-160 μm.

[0052] In some embodiments, the piperazine diphosphate is in the form of a sheet.

[0053] The applicant found that piperazine diphosphate with an average particle size and shape within the above range had better yield, purity, and thermal stability.

[0054] To obtain piperazine diphosphate with an average particle size of 40-200 μm, it can be obtained by crushing and sieving piperazine diphosphate.

[0055] Specifically, this application does not impose specific restrictions on the pulverization method, as long as it can pulverize piperazine diphosphate.

[0056] Specifically, the average particle size of piperazine diphosphate was determined by dispersing piperazine diphosphate in anhydrous ethanol, characterizing the morphology of piperazine diphosphate using scanning electron microscopy (SEM), and statistically analyzing 100 piperazine diphosphate particles to obtain the average particle size.

[0057] Specifically, the piperazine diphosphate can be obtained by purchasing commercially available products or by preparation methods known in the art.

[0058] Specifically, the preparation method of the piperazine diphosphate includes the following steps:

[0059] After dissolving piperazine in water, phosphoric acid is added dropwise while stirring and at a temperature of 50-80℃. After the addition is complete, the temperature is raised to 80-90℃ and the reaction is maintained for 3-4 hours. After the reaction is complete, the temperature is lowered to room temperature at a rate of 1-2℃ / min and allowed to stand for 8-12 hours. The obtained product is then subjected to solid-liquid separation, dried, and pulverized to obtain piperazine diphosphate, wherein the molar ratio of piperazine to phosphoric acid is 1:(2-2.2).

[0060] In this application, piperazine diphosphate with different shapes and average particle sizes is obtained by controlling the cooling rate.

[0061] In some embodiments, the dropping rate of the phosphoric acid is 30-50 mL / min; for example, but not limited to, 30 mL / min, 32 mL / min, 35 mL / min, 37 mL / min, 40 mL / min, 43 mL / min, 45 mL / min, 48 mL / min, and 50 mL / min; a dropping rate of 30-50 mL / min can avoid local overheating and improve the purity and yield of piperazine diphosphate.

[0062] In some embodiments, the stirring speed is 200-300 rpm; for example, it can be, but is not limited to, 200 rpm, 220 rpm, 240 rpm, 260 rpm, 280 rpm, or 300 rpm; stirring within the above speed range can prevent crystal nuclei from breaking, so as to obtain piperazine diphosphate with uniform particle size.

[0063] In some embodiments, the mass-to-volume ratio of piperazine to water is (1:2)-(1:5) g / L; for example, it can be, but is not limited to, 1:2 g / L, 1:3 g / L, 1:4 g / L, or 1:5 g / L.

[0064] In some embodiments, the feed rate of the piperazine diphosphate into the rotary kiln is 50-200 kg / h, for example, but not limited to 50 kg / h, 70 kg / h, 90 kg / h, 110 kg / h, 130 kg / h, 150 kg / h, 170 kg / h, and 200 kg / h.

[0065] In some embodiments, the rotary kiln rotates at a speed of 1-10 rpm; for example, but not limited to 1 rpm, 2 rpm, 4 rpm, 6 rpm, 8 rpm, or 10 rpm.

[0066] In some embodiments, the tilt angle of the rotary kiln is 0.5-2°, for example, but not limited to 0.5°, 0.7°, 0.9°, 1.1°, 1.3°, 1.5°, 1.7°, and 2°.

[0067] In some embodiments, the flow rate of the inert gas is 2-4 m³ / h. 3 / h; for example, it can be, but is not limited to, 2m. 3 / h, 2.2m 3 / h, 2.5m 3 / h, 2.7m 3 / h、3m 3 / h, 3.3m 3 / h, 3.5m 3 / h, 3.8m 3 / h、4m 3 / h.

[0068] The applicant discovered that by controlling the mass-to-volume ratio of piperazine and water, the feed rate of piperazine diphosphate, the rotational speed of the rotary kiln, the tilt angle of the rotary kiln, and the flow rate of the inert gas within the above-mentioned ranges, the synthesis efficiency, product purity, batch stability, thermal stability, and whiteness of piperazine pyrophosphate can be effectively improved.

[0069] In some embodiments, the inert gas is one of nitrogen or argon.

[0070] Specifically, the rotary kiln uses one of the following materials: high-temperature resistant and corrosion-resistant silicon carbide, alumina, and 316L stainless steel, with 316L stainless steel being preferred. 316L stainless steel possesses excellent mechanical properties and chemical stability, enabling it to withstand the harsh conditions of the piperazine diphosphate dehydration condensation reaction.

[0071] Specifically, the inner wall of the rotary kiln undergoes the following treatment: the surface of the inner wall is mechanically polished to achieve a high gloss (Ra≤0.2μm) to reduce micro-roughness and prevent material adhesion. Then, an alumina (Al2O3) coating with a thickness of 50-200μm is sprayed on to improve high temperature resistance and wear resistance. The treated inner wall surface of the rotary kiln is smooth and not prone to scaling, which can effectively reduce the adhesion of materials to the inner wall of the equipment and avoid problems such as unstable reaction conditions and product contamination caused by scaling.

[0072] Specifically, the rotary kiln is 15-25m long and 50-150cm in diameter.

[0073] Specifically, the room temperature in this application refers to 20-25°C.

[0074] A second aspect of this application provides a piperazine pyrophosphate, prepared by the method for preparing the piperazine pyrophosphate.

[0075] A third aspect of this application provides a flame retardant composition comprising the piperazine pyrophosphate.

[0076] The piperazine pyrophosphate of this application can be used as a flame retardant in flame retardant compositions.

[0077] Specifically, the flame-retardant composition includes a resin matrix. Specific examples of resin matrices include: polypropylene, high-density polyethylene, low-density polyethylene, linear low-density polyethylene, α-olefin polymers such as polybutene-1 and poly-3-methylpentene, or polyolefins and their copolymers such as ethylene-vinyl acetate copolymers and ethylene-propylene copolymers; polyvinyl chloride, polyvinylidene chloride, chlorinated polyethylene, chlorinated polypropylene, polyvinylidene fluoride, chlorinated rubber, vinyl chloride-vinyl acetate copolymers, vinyl chloride-ethylene copolymers, vinyl chloride-vinylidene chloride copolymers, vinyl chloride-vinylidene chloride-vinyl acetate terpolymers, vinyl chloride-acrylate copolymers, vinyl chloride-maleic ester copolymers, vinyl chloride-cyclohexylmaleimide copolymers, and other halogenated resins; petroleum resins; coumarone resins; polystyrene; polyvinyl acetate; and propylene glycol. The following are thermoplastic resins and mixtures thereof: acrylic resins, styrene and / or α-methylstyrene copolymers with other monomers (e.g., maleic anhydride, phenylmaleimide, methyl methacrylate, butadiene, acrylonitrile, etc.); polymethyl methacrylate, polyvinyl alcohol, polyvinyl methyl acetal, polyvinyl butyral, polyethylene terephthalate and polybutylene terephthalate, etc.; polyamides such as polyphenylene ether, polycaprolactam and polyhexamethylene adipamide; polycarbonate, polycarbonate / ABS resin, branched polycarbonate, polyacetal, polyphenylene sulfide, polyurethane, cellulose resins, etc.; or thermosetting resins such as phenolic resin, urea resin, melamine resin, epoxy resin, unsaturated polyester resin, etc., with polypropylene resin being particularly preferred.

[0078] When using piperazine pyrophosphate of the present invention as a flame retardant, it is preferable to mix 20-60 parts by weight relative to 100 parts by weight of the above-described resin matrix. Furthermore, other flame retardants such as melamine pyrophosphate, piperazine polyphosphate, melamine polyphosphate, polyphosphoramide, phosphate esters, and phosphate ester amides, as well as compounding agents such as polysiloxane compounds, metal oxides, silica, and higher aliphatic carboxylic acids, can be used in combination with piperazine pyrophosphate of the present invention. In this case, the amount of other flame retardants added relative to 100 parts by weight of piperazine pyrophosphate of the present invention is preferably 50-400 parts by weight, and the amount of compounding agents mixed relative to 100 parts by weight of the above-described resin matrix is ​​preferably 0.05-20 parts by weight. Alternatively, they can be pre-mixed as a flame retardant composition and added to the above-described resin matrix.

[0079] The flame-retardant composition comprising a resin matrix and piperazine pyrophosphate described above is used to form a molded article using conventional molding methods such as injection molding, extrusion molding, and pneumatic molding. This molded article is also one aspect of the present invention. As for the molded article of the present invention, there are no limitations on its shape; examples include power plugs, connectors, sleeves, boxes, wire sheaths, tape substrates, tubes, sheets, films, etc.

[0080] Furthermore, when obtaining injection-molded articles such as wire components as the molded articles of the present invention, injection molding can be performed at a barrel temperature of approximately 190°C and a nozzle temperature of approximately 190°C. An injection molding machine typically used for molding PVC resins can be used as the injection molding apparatus.

[0081] The raw materials used in the embodiments and comparative examples are described below, but are not limited to these materials:

[0082] Piperazine diphosphate A was prepared in-house, and its preparation method is as follows:

[0083] Piperazine was dissolved in water, and phosphoric acid was added dropwise at a rate of 40 mL / min while stirring at 250 rpm and at 65 °C. After the addition was completed, the temperature was raised to 85 °C and the reaction was maintained for 3 h. After the reaction was completed, the temperature was lowered to room temperature at a rate of 1.5 °C / min and allowed to stand for 10 h. The product was then subjected to solid-liquid separation, dried, and pulverized to obtain piperazine diphosphate A. The mass-to-volume ratio of piperazine to water was 1:3 g / L, the molar ratio of piperazine to phosphoric acid was 1:2.1, and the average particle size of piperazine diphosphate A was 80 μm, with a flake-like shape.

[0084] Piperazine diphosphate BF was obtained by adjusting and controlling at least one of the following parameters: stirring speed, dropping rate of phosphoric acid, reaction temperature, reaction time, cooling rate, and pulverization time.

[0085] Piperazine diphosphate B: average particle size is 120 μm, and the shape is flake-like;

[0086] Piperazine diphosphate C: average particle size is 160 μm, and the shape is flake-like;

[0087] Piperazine diphosphate D: average particle size is 200 μm, and the shape is flake-like;

[0088] Piperazine diphosphate E: average particle size is 40 μm, and the shape is flake-like;

[0089] Piperazine diphosphate F: The average particle size is 80 μm, and the shape is spherical.

[0090] Example 1

[0091] A method for preparing piperazine pyrophosphate includes the following steps:

[0092] Piperazine diphosphate A was continuously fed into the feed inlet of a 316L stainless steel rotary kiln at a feed rate of 180 kg / h using a mass flow meter. The rotary kiln was 20 m long, 100 cm in diameter, tilted at 1.5°, and rotated at 6 rpm. A nitrogen flow rate of 3 m³ / min was used. 3Under nitrogen protection at a concentration of / h, condensation reactions are carried out, including the first condensation reaction, the second condensation reaction, the third condensation reaction, the fourth condensation reaction, the fifth condensation reaction, the sixth condensation reaction, the seventh condensation reaction, and the eighth condensation reaction, carried out sequentially. The temperature of the first condensation reaction is 200℃, the temperature of the second condensation reaction is 215℃, the temperature of the third condensation reaction is 220℃, the temperature of the fourth condensation reaction is 225℃, the temperature of the fifth condensation reaction is 230℃, the temperature of the sixth condensation reaction is 235℃, and the temperature of the seventh and eighth condensation reactions is 240℃.

[0093] After the reaction was completed, a first cooling treatment, a second cooling treatment, and a third cooling treatment were performed sequentially. The endpoint temperature of the first cooling treatment was 200℃, the cooling rate was 2℃ / min, and the holding time was 10min. The endpoint temperature of the second cooling treatment was 150℃, the cooling rate was 3℃ / min, and the holding time was 15min. The endpoint temperature of the third cooling treatment was room temperature, and the cooling rate was 1℃ / min. Piperazine pyrophosphate was obtained.

[0094] Example 2

[0095] A method for preparing piperazine pyrophosphate includes the following steps:

[0096] Piperazine diphosphate A was continuously fed into the feed inlet of a 316L stainless steel rotary kiln at a feed rate of 180 kg / h using a mass flow meter. The rotary kiln was 20 m long, 100 cm in diameter, tilted at 1.5°, and rotated at 6 rpm. A nitrogen flow rate of 4 m³ / min was used. 3 Under nitrogen protection at a concentration of / h, condensation reactions are carried out, including the first condensation reaction, the second condensation reaction, the third condensation reaction, the fourth condensation reaction, the fifth condensation reaction, the sixth condensation reaction, the seventh condensation reaction, and the eighth condensation reaction, carried out sequentially. The temperature of the first condensation reaction is 198℃, the temperature of the second condensation reaction is 213℃, the temperature of the third condensation reaction is 218℃, the temperature of the fourth condensation reaction is 223℃, the temperature of the fifth condensation reaction is 228℃, the temperature of the sixth condensation reaction is 233℃, and the temperature of the seventh and eighth condensation reactions is 240℃.

[0097] After the reaction was completed, a first cooling treatment, a second cooling treatment, and a third cooling treatment were performed sequentially. The endpoint temperature of the first cooling treatment was 200℃, the cooling rate was 0.5℃ / min, and the holding time was 10min. The endpoint temperature of the second cooling treatment was 150℃, the cooling rate was 2℃ / min, and the holding time was 15min. The endpoint temperature of the third cooling treatment was room temperature, and the cooling rate was 1℃ / min. Piperazine pyrophosphate was obtained.

[0098] Example 3

[0099] A method for preparing piperazine pyrophosphate includes the following steps:

[0100] Piperazine diphosphate A was continuously fed into the feed inlet of a 316L stainless steel rotary kiln at a feed rate of 180 kg / h using a mass flow meter. The rotary kiln was 20 m long, 100 cm in diameter, tilted at 1.5°, and rotated at 6 rpm. A nitrogen flow rate of 2 m³ / min was used. 3 Under nitrogen protection at a concentration of / h, condensation reactions are carried out, including the first condensation reaction, the second condensation reaction, the third condensation reaction, the fourth condensation reaction, the fifth condensation reaction, the sixth condensation reaction, the seventh condensation reaction, and the eighth condensation reaction, carried out sequentially. The temperature of the first condensation reaction is 202℃, the temperature of the second condensation reaction is 217℃, the temperature of the third condensation reaction is 222℃, the temperature of the fourth condensation reaction is 228℃, the temperature of the fifth condensation reaction is 232℃, the temperature of the sixth condensation reaction is 237℃, and the temperature of the seventh and eighth condensation reactions is 242℃.

[0101] After the reaction was completed, a first cooling treatment, a second cooling treatment, and a third cooling treatment were performed sequentially. The endpoint temperature of the first cooling treatment was 200℃, the cooling rate was 2℃ / min, and the holding time was 10min. The endpoint temperature of the second cooling treatment was 150℃, the cooling rate was 3℃ / min, and the holding time was 15min. The endpoint temperature of the third cooling treatment was room temperature, and the cooling rate was 1℃ / min. Piperazine pyrophosphate was obtained.

[0102] Example 4

[0103] A method for preparing piperazine pyrophosphate differs from Example 1 only in that piperazine diphosphate B is used instead of piperazine diphosphate A, while the remaining steps and parameters are the same as in Example 1.

[0104] Example 5

[0105] A method for preparing piperazine pyrophosphate differs from Example 1 only in that piperazine diphosphate C is used instead of piperazine diphosphate A, while the remaining steps and parameters are the same as in Example 1.

[0106] Example 6

[0107] A method for preparing piperazine pyrophosphate differs from Example 1 only in that piperazine diphosphate D is used instead of piperazine diphosphate A, while the remaining steps and parameters are the same as in Example 1.

[0108] Example 7

[0109] A method for preparing piperazine pyrophosphate differs from Example 1 only in that piperazine diphosphate E is used instead of piperazine diphosphate A, while the remaining steps and parameters are the same as in Example 1.

[0110] Example 8

[0111] A method for preparing piperazine pyrophosphate differs from Example 1 only in that piperazine diphosphate F is used instead of piperazine diphosphate A, while the remaining steps and parameters are the same as in Example 1.

[0112] Example 9

[0113] A method for preparing piperazine pyrophosphate differs from Example 1 only in that the cooling rate of the first cooling treatment, the second cooling treatment, and the third cooling treatment is 2℃ / min, while the remaining steps and parameters are the same as in Example 1.

[0114] Example 10

[0115] A method for preparing piperazine pyrophosphate differs from Example 1 only in that the cooling rate of the first cooling treatment, the second cooling treatment, and the third cooling treatment is 6°C / min, while the remaining steps and parameters are the same as in Example 1.

[0116] Example 11

[0117] A method for preparing piperazine pyrophosphate differs from Example 1 only in that the cooling treatment steps are different. In this example, the cooling treatment steps are as follows: the endpoint temperature of the first cooling treatment is 200°C, and the cooling rate is 2°C / min; the endpoint temperature of the second cooling treatment is 150°C, and the cooling rate is 3°C / min; the endpoint temperature of the third cooling treatment is room temperature, and the cooling rate is 1°C / min. That is, in this example, no heat preservation is performed at the endpoint temperatures of the first and second cooling treatments.

[0118] Example 12

[0119] A method for preparing piperazine pyrophosphate differs from Example 1 only in that the feed rate of piperazine diphosphate is 100 kg / h, while the other steps and parameters are the same as in Example 1.

[0120] Example 13

[0121] A method for preparing piperazine pyrophosphate differs from Example 1 only in that the feed rate of piperazine diphosphate is 50 kg / h, while the remaining steps and parameters are the same as in Example 1.

[0122] Example 14

[0123] A method for preparing piperazine pyrophosphate differs from Example 1 only in that the feed rate of piperazine diphosphate is 200 kg / h, while the other steps and parameters are the same as in Example 1.

[0124] Example 15

[0125] A method for preparing piperazine pyrophosphate differs from Example 1 only in that the tilt angle of the rotary kiln is 1° and the kiln rotation speed is 3 rpm, while the remaining steps and parameters are the same as in Example 1.

[0126] Example 16

[0127] A method for preparing piperazine pyrophosphate differs from Example 1 only in that the tilt angle of the rotary kiln is 0.5° and the kiln rotation speed is 10 rpm, while the remaining steps and parameters are the same as in Example 1.

[0128] Example 17

[0129] A method for preparing piperazine pyrophosphate differs from Example 1 only in that the tilt angle of the rotary kiln is 2° and the kiln rotation speed is 1 rpm, while the remaining steps and parameters are the same as in Example 1.

[0130] Comparative Example 1

[0131] A method for preparing piperazine pyrophosphate includes the following steps:

[0132] 150 kg of piperazine diphosphate A was added to a batch reactor at once, and the reaction was carried out for 12 h at a stirring speed of 1200 rpm and a temperature of 220 °C to obtain piperazine pyrophosphate.

[0133] Comparative Example 2

[0134] A method for preparing piperazine pyrophosphate differs from Example 1 only in that the temperature of the first condensation reaction to the eighth condensation reaction is 220°C, while the remaining steps and parameters are the same as in Example 1.

[0135] Comparative Example 3

[0136] A method for preparing piperazine pyrophosphate differs from Example 1 only in that: the temperature of the first condensation reaction is 198°C, the temperature of the second condensation reaction is 208°C, the temperature of the third condensation reaction is 213°C, the temperature of the fourth condensation reaction is 220°C, the temperature of the fifth condensation reaction is 225°C, the temperature of the sixth condensation reaction is 230°C, and the temperatures of the seventh and eighth condensation reactions are both 240°C.

[0137] Comparative Example 4

[0138] A method for preparing piperazine pyrophosphate differs from Example 1 only in that the condensation reaction includes a first condensation reaction, a second condensation reaction, a third condensation reaction, and a fourth condensation reaction carried out sequentially; the temperature of the first condensation reaction is 198°C, the temperature of the second condensation reaction is 213°C, the temperature of the third condensation reaction is 223°C, the temperature of the fourth condensation reaction is 233°C, and the temperature of the fourth condensation reaction is 240°C.

[0139] Comparative Example 5

[0140] A preparation method of piperazine pyrophosphate, the difference from Example 1 is only that: the cooling treatment steps are different. The cooling treatment steps of this comparative example are: after the reaction ends, the obtained product is taken out from the furnace mouth of the rotary furnace and directly cooled to room temperature, and the remaining steps and parameters are the same as those in Example 1.

[0141] Comparative Example 6

[0142] A preparation method of piperazine pyrophosphate, the difference from Example 1 is only that: the end temperature of the first cooling treatment is 220°C; the end temperature of the second cooling treatment is 150°C; the end temperature of the third cooling treatment is room temperature.

[0143] Comparative Example 7

[0144] A preparation method of piperazine pyrophosphate, the difference from Example 1 is only that: the end temperature of the first cooling treatment is 200°C; the end temperature of the second cooling treatment is 130°C; the end temperature of the third cooling treatment is room temperature.

[0145] Performance Test

[0146] Test the yield, purity, batch stability, thermal stability and whiteness of the piperazine pyrophosphate obtained in the test examples and comparative examples. The test methods are as follows:

[0147] (1) Yield: By weighing the mass difference of the materials before and after the reaction, combined with the stoichiometric ratio of piperazine pyrophosphate, calculate the percentage of the actual product mass to the theoretical maximum yield; the formula is: Yield (%) = Actual product mass / Theoretical product mass × 100%;

[0148] (2) Purity: Measured by high performance liquid chromatography (HPLC, Agilent 1260 Infinity II), under the conditions that the mobile phase is acetonitrile - water (volume ratio 85:15) and the flow rate is 1.0 mL / min, measure the purity of piperazine pyrophosphate;

[0149] (3) Batch stability: Continuously produce 5 batches of samples under the same preparation method, respectively test the purity of the samples obtained in different batches, and calculate the relative standard deviation (RSD); RSD ≤ 1.5% is excellent, 1.5% < RSD ≤ 3% is good, RSD > 3% is poor;

[0150] (4) Thermal stability: Use a thermogravimetric analyzer (TGA,), in a nitrogen atmosphere, with a heating rate of 10°C / min, record the temperature at 1% mass loss (T1%); the higher the temperature, the better the thermal stability;

[0151] (5) Whiteness: The whiteness is measured using a whiteness meter (WSB-3A). The whiteness value is measured after the sample is pressed into a tablet, with a standard white plate (whiteness value 90%) as the reference. The higher the value, the better the whiteness.

[0152] The test results are shown in Table 1 and Figure 1-2 As shown.

[0153] Table 1

[0154]

[0155]

[0156] As shown in Table 1, the pyrophosphate piperazine prepared by the method of this application has a yield of ≥95.2%, purity of ≥95.1%, batch stability of ≤3.5%, 1% mass loss temperature of ≥292℃, and whiteness of ≥90.7. This indicates that the pyrophosphate piperazine prepared by the method of this application has high yield, purity, batch stability, thermal stability, and whiteness.

[0157] The experimental data from Examples 1 and 4-7 show that when the average particle size of piperazine diphosphate is 80-160 μm, the purity of the obtained piperazine pyrophosphate is ≥98.5%, the batch stability is ≤1.5%, the 1% mass loss temperature is ≥297℃, and the whiteness is ≥93.5. This indicates that when the average particle size of piperazine diphosphate is 80-160 μm, the purity, batch stability, thermal stability, and whiteness of piperazine pyrophosphate are high.

[0158] The experimental data from Examples 1 and 8 show that when piperazine diphosphate is in the form of flakes, the purity of the obtained piperazine pyrophosphate is 99.2%, the batch stability is 0.8%, the 1% mass loss temperature is 297°C, and the whiteness is 97. This indicates that when piperazine diphosphate is in the form of flakes, the purity, batch stability, thermal stability, and whiteness of piperazine pyrophosphate are high.

[0159] The experimental data from Examples 1 and 9-10 show that when the cooling rates of the first, second, and third cooling treatments are each independently 0.1-3℃ / min, the yield of piperazine pyrophosphate is ≥96.4%, the purity is ≥97.2%, the batch stability is ≤2.0%, the 1% mass loss temperature is ≥294℃, and the whiteness is ≥94.2. This indicates that when the cooling rates of the first, second, and third cooling treatments are each independently 0.1-3℃ / min, the yield, purity, batch stability, thermal stability, and whiteness of piperazine pyrophosphate are high. Furthermore, the cooling rates of the first and third cooling treatments are lower than that of the second cooling treatment, resulting in even higher yield, purity, batch stability, thermal stability, and whiteness of piperazine pyrophosphate.

[0160] The experimental data from Examples 1 and 11 show that when the endpoint temperatures of the first and second cooling treatments are maintained, the purity of the obtained piperazine pyrophosphate is 99.2%, the batch stability is 0.8%, the 1% mass loss temperature is 297°C, and the whiteness is 97. This indicates that maintaining the endpoint temperatures of the first and second cooling treatments can improve the purity, batch stability, thermal stability, and whiteness of piperazine pyrophosphate.

[0161] The experimental data from Examples 1 and 12-14 show that when the feed rate of piperazine diphosphate to the rotary kiln is 100-180 kg / h, the purity of the obtained piperazine pyrophosphate is ≥99%, the batch stability is ≤0.9%, the 1% mass loss temperature is ≥297℃, and the whiteness is ≥96.4. This indicates that when the feed rate of piperazine diphosphate to the rotary kiln is 100-180 kg / h, the purity, batch stability, thermal stability, and whiteness of piperazine pyrophosphate can be improved.

[0162] The experimental data from Examples 1 and 15-17 show that when the rotary kiln speed is 3-6 rpm, the purity of the obtained piperazine pyrophosphate is ≥98.3%, the batch stability is ≤1.6%, the 1% mass loss temperature is ≥297℃, and the whiteness is ≥94.4. This indicates that when the rotary kiln speed is 3-6 rpm, the purity, batch stability, thermal stability, and whiteness of piperazine pyrophosphate can be improved.

[0163] Experimental data from Examples 1 and Comparative Examples 1-7 show that when at least one of the following is outside the scope of protection of this application: the number of condensation reaction stages, the temperature of the condensation reaction, the number of cooling stages, and the endpoint temperature of a certain stage during the cooling process, the purity of the obtained piperazine pyrophosphate is ≤94.8%, the batch stability is ≥4.0%, the 1% mass loss temperature is ≤284℃, and the whiteness is ≤90.5. This indicates that only when the parameters in the preparation method of piperazine pyrophosphate are within the scope of protection of this application can piperazine pyrophosphate with high yield, purity, batch stability, thermal stability, and whiteness be obtained.

[0164] Finally, it should be noted that the above embodiments are used to illustrate the technical solutions of this disclosure and not to limit the scope of protection of this disclosure. Although this disclosure has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this disclosure without departing from the substance and scope of the technical solutions of this disclosure.

Claims

1. A method for preparing piperazine pyrophosphate, characterized in that, Includes the following steps: Piperazine diphosphate was added to a rotary kiln and condensed under the protection of an inert gas. After the reaction was completed, the temperature was lowered to obtain piperazine pyrophosphate. The condensation reaction includes a first condensation reaction, a second condensation reaction, a third condensation reaction, a fourth condensation reaction, a fifth condensation reaction, a sixth condensation reaction, a seventh condensation reaction, and an eighth condensation reaction, carried out sequentially; the temperature of the first condensation reaction is 198-202℃; the temperature of the second condensation reaction is 213-217℃; the temperature of the third condensation reaction is 218-222℃; the temperature of the fourth condensation reaction is 223-227℃; the temperature of the fifth condensation reaction is 228-232℃; the temperature of the sixth condensation reaction is 233-237℃; and the temperatures of the seventh and eighth condensation reactions are each independently 238-242℃. The cooling process includes a first cooling process, a second cooling process, and a third cooling process performed sequentially; the endpoint temperature of the first cooling process is 200°C; the endpoint temperature of the second cooling process is 150°C; and the endpoint temperature of the third cooling process is room temperature.

2. The method for preparing piperazine pyrophosphate as described in claim 1, characterized in that, The cooling rates of the first, second, and third cooling treatments are each 0.1-3℃ / min.

3. The method for preparing piperazine pyrophosphate as described in claim 1, characterized in that, The average particle size of the piperazine diphosphate is 40-200 μm, and the shape is flake-like.

4. The method for preparing piperazine pyrophosphate as described in claim 1, characterized in that, The method for preparing the piperazine diphosphate includes the following steps: After dissolving piperazine in water, phosphoric acid is added dropwise while stirring and at a temperature of 50-80℃. After the addition is complete, the temperature is raised to 80-90℃ and the reaction is maintained for 3-4 hours. After the reaction is complete, the temperature is lowered to room temperature at a rate of 1-2℃ / min and allowed to stand for 8-12 hours. The obtained product is then subjected to solid-liquid separation, dried, and pulverized to obtain piperazine diphosphate, wherein the molar ratio of piperazine to phosphoric acid is 1:(2-2.2).

5. The method for preparing piperazine pyrophosphate as described in claim 4, characterized in that, The dropping rate of the phosphoric acid is 30-50 mL / min; And / or, the stirring speed is 200-300 rpm; And / or, the mass-to-volume ratio of the piperazine to water is (1:2)-(1:5) g / L.

6. The method for preparing piperazine pyrophosphate as described in claim 1, characterized in that, The feed rate of piperazine diphosphate into the rotary kiln is 50-200 kg / h.

7. The method for preparing piperazine pyrophosphate as described in claim 1, characterized in that, The rotary kiln rotates at a speed of 1-10 revolutions per minute. And / or, the tilt angle of the rotary kiln is 0.5-2°.

8. The method for preparing piperazine pyrophosphate as described in claim 1, characterized in that, The flow rate of the inert gas is 2-4 m³ / h. 3 / h; And / or, the inert gas is one of nitrogen or argon.

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