A high-whiteness piperazine pyrophosphate and its preparation method and application

Abstract

The invention discloses a high-whiteness piperazine pyrophosphate and a preparation method and application thereof. The whiteness value of the piperazine pyrophosphate of the invention is ≥97.7. The preparation method of the invention comprises the following steps: adsorbing a piperazine diphosphate solution with a concentration of 19-58wt.%, so that the chromaticity of the piperazine diphosphate solution after adsorption treatment is ≤100 Hazen units; then crystallizing, filtering and drying the piperazine diphosphate solution to obtain pretreated piperazine diphosphate particles; in a flowing inert gas environment or under continuous vacuum conditions, the pretreated piperazine diphosphate particles are subjected to a dehydration condensation reaction to obtain high-whiteness piperazine pyrophosphate. By adsorbing the piperazine diphosphate solution and then precipitating crystals, colored impurities in the piperazine diphosphate are removed from the source to prevent the impurities from being embedded in the crystals; in a flowing inert gas atmosphere or under continuous vacuum conditions, the piperazine diphosphate is dehydrated and condensed, effectively improving the whiteness of the piperazine pyrophosphate.

Description

Technical Field

[0001] The invention relates to the technical field of flame retardant preparation, and more specifically to high-whiteness piperazine pyrophosphate and a preparation method and application thereof. Background Art

[0002] Piperazine pyrophosphate, as a phosphorus-nitrogen-containing halogen-free flame retardant, has excellent flame retardant properties and is a halogen-free flame retardant with great market potential. It is mainly used in polyolefin materials. Since flame-retardant polyolefin materials are mainly used in the field of household appliance materials, they have high requirements for appearance, especially whiteness, so the whiteness problem of piperazine pyrophosphate has always been the focus of research.

[0003] The conventional preparation method of piperazine pyrophosphate is to first prepare piperazine diphosphate, and then perform high-temperature dehydration condensation on the piperazine diphosphate to obtain piperazine pyrophosphate. The piperazine pyrophosphate obtained by this preparation method is usually gray or brown, which seriously affects its application in white flame-retardant polyolefin materials. In the prior art, the improvement of the whiteness of piperazine pyrophosphate is mainly studied around the step of high-temperature dehydration condensation, but the color of piperazine diphosphate is not controlled.

[0004] Chinese patent application CN 105541758 A discloses a method for preparing piperazine pyrophosphate, comprising: adding 85% phosphoric acid aqueous solution to phosphorus pentoxide at high temperature, keeping the temperature for a period of time and then cooling appropriately; adding glacial acetic acid, stirring for a period of time and then adding anhydrous piperazine in batches, and obtaining piperazine pyrophosphate crystals after reaction and post-treatment. The whiteness of the piperazine pyrophosphate can reach 94-45. Chinese patent application CN 102482239 A discloses a method for preparing (poly) piperazine pyrophosphate powder, by dehydrating and condensing diphosphate piperazine under an inert gas atmosphere to obtain (poly) piperazine pyrophosphate with a whiteness of 95-97.

[0005] However, for some flame-retardant polyolefin products with extremely high requirements on appearance, the above-mentioned piperazine pyrophosphate still cannot meet the actual high whiteness requirements. Therefore, it is necessary to develop a piperazine pyrophosphate with higher whiteness. Summary of the invention

[0006] The present invention provides a high-whiteness piperazine pyrophosphate to overcome the defect of low whiteness in the prior art. The whiteness value of the piperazine pyrophosphate in the present invention is ≥97.7.

[0007] Another object of the present invention is to provide a method for preparing piperazine pyrophosphate with high whiteness, by adsorbing a piperazine diphosphate solution so that the chromaticity of the piperazine diphosphate solution is ≤100 Hazen units, and combining a dynamic dehydration method to effectively improve the whiteness of piperazine pyrophosphate.

[0008] Another object of the present invention is to provide the use of the piperazine pyrophosphate in the preparation of white polyolefin products.

[0009] Another object of the present invention is to provide a continuous preparation method of high-whiteness piperazine pyrophosphate.

[0010] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0011] A high-whiteness piperazine pyrophosphate, wherein the whiteness value (W value) of the piperazine pyrophosphate is ≥97.7.

[0012] The whiteness detection method of piperazine pyrophosphate is: according to the CIE1983 whiteness formula, based on the three primary colors (red, green, blue) stimulus values ​​X, Y, Z (X is the sensing value of red, Y is the sensing value of green, and Z is the sensing value of blue) calculated by the following formula:

[0013] W value = Y + 800 (x n -x)+1700(y n -y);

[0014] In the above formula, x and y are the chromaticity coordinates of the sample in the XYZ colorimetric system, x n ,y n is the value of the chromaticity coordinate in the XYZ colorimetric system of the completely diffuse reflecting surface.

[0015] The present invention also protects a method for preparing the high-whiteness piperazine pyrophosphate, comprising the following steps:

[0016] S1. A piperazine diphosphate solution having a concentration of 19 to 58 wt.% is subjected to adsorption treatment, so that the chromaticity of the piperazine diphosphate solution subjected to adsorption treatment is ≤100 black units;

[0017] Then, the piperazine diphosphate solution is crystallized and filtered to collect crude crystals, and the crude crystals are dried to obtain pretreated piperazine diphosphate particles;

[0018] The chromaticity detection method is in accordance with GB / T 3143-1982;

[0019] S2. In a flowing inert gas environment or under continuous vacuum conditions, the pretreated piperazine diphosphate particles undergo a dehydration condensation reaction to obtain piperazine pyrophosphate with high whiteness.

[0020] Piperazine diphosphate usually contains trace colored impurities and is light brown. The inventor has found that if piperazine diphosphate is not pre-treated, directly dehydrated, condensed or dried, the trace impurities in piperazine diphosphate cannot be removed, and colored impurities will be embedded in piperazine diphosphate crystals instead, affecting the whiteness of final piperazine pyrophosphate. By adsorption treatment of piperazine diphosphate solution and then crystallization, impurities can be removed from the source, colored impurities are avoided from being embedded in crystals, and the whiteness of piperazine pyrophosphate is finally improved.

[0021] The colorimetric detection method of piperazine diphosphate solution is in accordance with GB / T 3143-1982 "Color determination method for liquid chemical products (Hazen unit-platinum-cobalt color number)".

[0022] Generally speaking, the chromaticity of the piperazine diphosphate solution without adsorption treatment is ≥ 200 Hazen units. Through adsorption treatment, the chromaticity of the piperazine diphosphate solution after adsorption treatment is controlled to be ≤ 100 Hazen units, which can remove colored impurities in piperazine diphosphate and improve the whiteness of piperazine pyrophosphate.

[0023] At the same time, the method of dynamic dehydration is used to dehydrate and condense piperazine diphosphate in a flowing inert gas environment or under continuous vacuum conditions. The water molecules removed from piperazine diphosphate are promptly taken away by the flowing inert gas or are quickly drawn away under continuous vacuum conditions. On the one hand, the efficiency of the dehydration condensation reaction is improved. On the other hand, if water molecules gather in the dehydration reaction device, they are likely to produce heterochromatic spots on the surface of piperazine pyrophosphate, affecting the whiteness of the product.

[0024] Preferably, in step S1, the adsorption treatment is performed using a fixed bed adsorber.

[0025] The piperazine diphosphate solution is adsorbed by using a fixed bed adsorber. The piperazine diphosphate solution can be passed through the fixed bed adsorber. The adsorption operation is more convenient and the adsorption efficiency is high.

[0026] Generally, adsorption treatment using a fixed bed adsorber is divided into two types: gravity filtration adsorption and pressure filtration adsorption. Gravity filtration adsorption is preferred in the present invention.

[0027] The inventors have found that the adsorption efficiency of the dipiperazine diphosphate solution is higher using gravity filtration adsorption, while pressure filtration adsorption easily leads to incomplete adsorption of colored impurities in the dipiperazine diphosphate.

[0028] Preferably, the fixed bed adsorber uses one or more of activated carbon, clay or adsorption resin as adsorbent filler.

[0029] Preferably, the fixed bed adsorber uses activated carbon as the adsorbent filler.

[0030] Activated carbon as an adsorbent filler not only has good adsorption effect, but also is a bio-based material with a wide range of sources. The waste activated carbon after adsorption treatment is more convenient to handle.

[0031] Preferably, the activated carbon is in a honeycomb, columnar, powdery, granular, spherical or crushed shape.

[0032] In order to lower the chromaticity of the dipiperazine phosphate solution after adsorption treatment, the adsorption treatment time can be appropriately extended, or multi-stage adsorption treatment can be carried out, or a long tubular fixed bed adsorber can be used to allow the dipiperazine phosphate solution to be adsorbed to pass through the adsorbent filler in a small interface and long path manner.

[0033] Preferably, in step S1, the chromaticity of the piperazine diphosphate solution subjected to the adsorption treatment is ≤50 Hazen units.

[0034] Preferably, in step S1, the concentration of the piperazine diphosphate solution is 25-40 wt.%.

[0035] The concentration of the piperazine diphosphate solution for adsorption treatment cannot be too high, as too high a concentration will cause a large amount of piperazine diphosphate to precipitate during adsorption treatment; at the same time, the concentration of piperazine diphosphate should not be too low, as too low a concentration will result in high evaporation energy consumption during subsequent crystallization. According to a large number of experiments, the inventors found that the adsorption treatment effect of the piperazine diphosphate solution is optimal when the concentration is 25 to 40 wt.%.

[0036] Preferably, the flow rate of the inert gas in step S2 is 15-90 m / h.

[0037] More preferably, the flow rate of the inert gas in step S2 is 30-60 m / h.

[0038] Further preferably, the flow rate of the inert gas in step S2 is 40-50 m / h.

[0039] The flow rate of the inert gas should not be too high or too low. When the flow rate is too high, the temperature of the dehydration condensation reaction will drop, affecting the reaction efficiency; when the flow rate is too low, the removed water molecules cannot be taken away in time.

[0040] Preferably, the inert gas is nitrogen or helium.

[0041] Preferably, the continuous vacuuming in step S2 is to maintain an absolute pressure between 100 and 300 Pa.

[0042] Preferably, the reaction temperature of the dehydration condensation reaction is 240-260° C., and the reaction time is 0.5-2 h.

[0043] The present invention also protects the use of the high-whiteness piperazine pyrophosphate in the preparation of white polyolefin products.

[0044] Preferably, the white polyolefin product is a white socket wiring board, air conditioning panel, data transmission cable or charging cable.

[0045] The present invention also protects a continuous preparation method of high-whiteness piperazine pyrophosphate, comprising the following steps:

[0046] M1. Anhydrous piperazine and phosphoric acid are added to a saturated piperazine diphosphate solution, and the anhydrous piperazine and phosphoric acid are completely dissolved by heat of solution and reaction to obtain a reaction solution having a piperazine diphosphate concentration of 19 to 58wt.%;

[0047] The molar ratio of anhydrous piperazine to phosphoric acid is 1:1.98-2.02;

[0048] M2. The reaction solution is subjected to adsorption treatment so that the chromaticity of the dipiperazine diphosphate solution subjected to the adsorption treatment is ≤100 Hazen units, and then crystallization is performed and filtration is performed to obtain crude crystals and a filtrate, and the crude crystals are dried to obtain pretreated dipiperazine diphosphate particles; the filtrate is concentrated to saturation, and the obtained saturated dipiperazine diphosphate solution is applied to step M1; the chromaticity detection method is in accordance with GB / T 3143-1982;

[0049] M3. In a flowing inert gas environment, or under continuous vacuum conditions, the pretreated piperazine diphosphate particles are subjected to a dehydration condensation reaction to obtain high-whiteness piperazine pyrophosphate;

[0050] The whiteness value of the high-whiteness piperazine pyrophosphate is ≥97.7.

[0051] When anhydrous piperazine and phosphoric acid are added to a saturated piperazine diphosphate solution, a large amount of dissolution heat is generated when the phosphoric acid dissolves, causing the temperature of the solution system to rise, thereby promoting the dissolution of anhydrous piperazine; at the same time, the dissolved anhydrous piperazine reacts with the phosphoric acid to generate piperazine diphosphate, while also generating a large amount of reaction heat, further increasing the temperature of the solution system, causing the piperazine diphosphate solution to change from a saturated state to an unsaturated state.

[0052] After the reaction liquid is subjected to adsorption treatment, the temperature is lowered, crystals are precipitated, and the pretreated diphosphate piperazine particles are obtained by filtration and drying, with a yield of ≥98%. After the filtrate is concentrated to saturation, it is continuously applied to the initial step of M1, and can be used for industrial continuous production of high-whiteness pyrophosphate piperazine.

[0053] The filtrate described in step M2 is the filtrate after crystallization and filtration. As dipiperazine diphosphate crystals are precipitated, the obtained filtrate is cooled to room temperature, that is, it is in a saturated state, that is, a saturated dipiperazine diphosphate solution; the saturated dipiperazine diphosphate solution can be directly used in the initial step of M1, anhydrous piperazine and phosphoric acid are added thereto, and the M1 step is repeated to continuously produce high-whiteness pyrophosphate piperazine.

[0054] The molar ratio of anhydrous piperazine to phosphoric acid should be as close to 1:2 as possible, so as to avoid free phosphoric acid affecting the color of piperazine pyrophosphate after dehydration condensation, and to avoid excess piperazine and solution piperazine diphosphate to form piperazine monophosphate impurities. In the industrial production process, the addition of anhydrous piperazine and phosphoric acid usually has an error of less than 1%, which is an acceptable range.

[0055] Compared with the prior art, the present invention has the following beneficial effects:

[0056] (1) The present invention removes colored impurities in piperazine diphosphate from the source by adsorption treatment of the piperazine diphosphate solution and then crystallization, thereby preventing the impurities from being embedded in the crystals; at the same time, the present invention combines the method of dynamic dehydration to dehydrate and condense piperazine diphosphate under a flowing inert gas atmosphere or under continuous vacuum conditions, thereby effectively improving the whiteness of piperazine pyrophosphate. The whiteness of piperazine pyrophosphate prepared by the preparation method is ≥97.7.

[0057] (2) The present invention also provides a method for continuously preparing high-whiteness piperazine pyrophosphate, by adding anhydrous piperazine and phosphoric acid in proportion to a saturated piperazine diphosphate solution, then subjecting the reaction solution to adsorption treatment and crystallization, and applying the piperazine diphosphate filtrate, high-whiteness piperazine pyrophosphate can be continuously produced. DETAILED DESCRIPTION

[0058] The present invention will be further described below in conjunction with specific implementation modes.

[0059] The raw materials in the embodiments and comparative examples can be obtained from commercial sources, among which:

[0060] Anhydrous piperazine, Changzhou Puhua Chemical Technology Co., Ltd., purity> 99wt.%;

[0061] Phosphoric acid, Hubei Yichang Xingfa Group, phosphoric acid purity 85wt.%;

[0062] Piperazine diphosphate, homemade, obtained by mixing anhydrous piperazine and phosphoric acid;

[0063] White clay, Anji Zhongxin Activated White Clay Co., Ltd., HT-1A;

[0064] Activated carbon, Jiangsu Tianlun Activated Carbon Co., Ltd., TL-622;

[0065] Adsorption resin, Suqing Group, DA201-D.

[0066] Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the present technical field.

[0067] Examples 1 to 14

[0068] Embodiments 1 to 14 provide a kind of piperazine pyrophosphate, and the preparation method is as follows:

[0069] S1. using a fixed bed adsorber to adsorb the piperazine diphosphate solution, and obtaining pretreated piperazine diphosphate particles by crystallization, filtration and drying;

[0070] S2. In a flowing nitrogen environment or under continuous vacuum conditions, the pretreated dipiperazine phosphate particles prepared in S1 are subjected to a dehydration condensation reaction to obtain high-whiteness piperazine pyrophosphate.

[0071] The specific parameters in the preparation method are shown in Table 1;

[0072] The activated carbon used in Examples 1 to 6 and Examples 9 to 14 is wood activated carbon with a particle size of 20 to 60 meshes and a specific surface area of ​​1000 to 1200 m 2 / g, Examples 1 to 8, Examples 11 to 12 use a long tubular fixed bed adsorber for one-stage adsorption treatment, Example 9 uses a two-stage adsorption treatment, and Example 10 uses a three-stage adsorption treatment; the white clay used in Example 7 is modified bentonite with a particle size of 180 to 200 mesh; the adsorption resin used in Example 8 is an ion exchange resin with a specific surface area of ​​500 to 600 m 2 / g, average pore diameter 8-10nm, pore volume 1.3-1.6mL / g;

[0073] All adsorbents were used in a single amount of 5 wt.% of the filtrate solution.

[0074] Table 1 Preparation method parameters of Examples 1 to 14

[0075]

[0076] Embodiment 15

[0077] Example 15 provides a continuous preparation method of piperazine pyrophosphate, comprising the following steps:

[0078] S1. Anhydrous piperazine with a purity of >99wt.% and phosphoric acid with a purity of 85wt.% are added to a saturated piperazine diphosphate solution in a net molar ratio of anhydrous piperazine: phosphoric acid of 1:2, and the anhydrous piperazine and phosphoric acid are completely dissolved by heat of dissolution and heat of reaction to obtain a reaction solution;

[0079] The reaction liquid is subjected to adsorption treatment using a fixed bed adsorber whose adsorbent filler is activated carbon. The chromaticity of the reaction liquid after adsorption treatment is 60 Hazen units. Pretreated dipiperazine diphosphate particles are obtained by crystallization, filtration and drying.

[0080] The filtrate is concentrated to saturation, and the obtained saturated piperazine diphosphate solution is used mechanically;

[0081] S2. Under the condition of a nitrogen flow rate of 40 m / h, the pretreated dipiperazine diphosphate particles prepared in S1 are subjected to a dehydration condensation reaction at a reaction temperature of 250° C. for a reaction time of 1 h to obtain pyropiperazine phosphate.

[0082] Comparative Example 1

[0083] Comparative Example 1 provides a piperazine pyrophosphate, and the preparation method is different from that of Example 1 in that:

[0084] In step S1, the piperazine diphosphate solution is not subjected to adsorption treatment, but is directly crystallized, filtered, and dried to obtain piperazine diphosphate particles.

[0085] Comparative Example 2

[0086] Comparative Example 2 provides a piperazine pyrophosphate, and the preparation method is different from that of Example 1 in that:

[0087] The flow rate of the inert gas in step S2 is 0 m / h, that is, the inert gas does not flow.

[0088] Comparative Example 3

[0089] Comparative Example 3 provides a piperazine pyrophosphate, the preparation method of which differs from that of Example 6 in that:

[0090] In step S2, the dehydration condensation reaction is carried out under the condition of non-continuous vacuuming, that is, only the initial absolute pressure is controlled to be 200Pa. As the dehydration condensation reaction proceeds, the removed water molecules become water vapor and remain in the reactor, and the vacuuming is not continued.

[0091] Comparative Example 4

[0092] Comparative Example 4 provides a kind of piperazine pyrophosphate, and the preparation method is different from that of Example 1 in that:

[0093] The concentration of the piperazine diphosphate solution was 59 wt.%.

[0094] Comparative Example 5

[0095] Comparative Example 5 provides a kind of piperazine pyrophosphate, and the preparation method is different from that of Example 1 in that:

[0096] The tube diameter of the fixed bed adsorber is relatively large, and the path of the piperazine diphosphate solution to be adsorbed through the adsorbent filler is relatively short, so that the chromaticity of the piperazine diphosphate solution after adsorption is 115 Hazen units.

[0097] Comparative Example 6

[0098] Comparative Example 6 provides a continuous preparation method of piperazine pyrophosphate, which differs from that of Example 15 in that:

[0099] In step S1, the molar ratio of anhydrous piperazine to phosphoric acid is 1:3.

[0100] Performance Testing

[0101] The piperazine pyrophosphate obtained in the above examples and comparative examples was tested, and the specific method is as follows:

[0102] Whiteness value (W value): According to the CIE1983 whiteness formula, based on the three primary colors (red, green, blue) stimulus values ​​X, Y, Z (X is the sensing value of red, Y is the sensing value of green, and Z is the sensing value of blue), it is calculated by the following formula:

[0103] W value = Y + 800 (x n -x)+1700(y n -y);

[0104] In the above formula, x and y are the chromaticity coordinates of the sample in the XYZ colorimetric system, x n ,y n is the value of the chromaticity coordinate in the XYZ colorimetric system of the completely diffuse reflecting surface.

[0105] Piperazine diphosphate yield: calculated according to the following formula:

[0106] Wherein, Yield represents the yield of piperazine diphosphate; m 1 Indicates the mass of 85wt.% pure phosphoric acid added, in g; m 2 Indicates the mass of anhydrous piperazine added, in g; m 3 It indicates the mass of the obtained piperazine diphosphate dry product, in g; in the continuous production of high-whiteness piperazine pyrophosphate, the saturated piperazine diphosphate solution obtained by M2 is tested and calculated for its single piperazine diphosphate yield after each application.

[0107] The test results of Examples 1 to 14 are shown in Table 3.

[0108] Table 3 Test results of Examples 1 to 14

[0109]

[0110] The whiteness value of the piperazine pyrophosphate obtained in Example 15 was 98.1, and the yield of piperazine diphosphate was 98.8%.

[0111] The test results of Comparative Examples 1 to 5 are shown in Table 4.

[0112] Table 4 Test results of comparative examples 1 to 5

[0113] Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Whiteness 94.3 Slightly yellow 88.4 96.5 95.1

[0114] The whiteness value of the piperazine pyrophosphate obtained in Comparative Example 6 was 91.0, and the yield of piperazine diphosphate was 87.2%.

[0115] According to the test results in Table 3, the whiteness of the piperazine pyrophosphate prepared in various embodiments of the present invention is ≥97.7, and the whiteness of the piperazine pyrophosphate in some embodiments is above 99, which has an excellent whiteness value.

[0116] According to Examples 2 to 8, under a flowing inert gas environment or under continuous vacuum conditions, the piperazine diphosphate particles can be subjected to a dehydration condensation reaction to obtain high-whiteness piperazine pyrophosphate. The inert gas flow rate is preferably 15 to 90 m / h, more preferably 40 to 50 m / h. According to Examples 1 to 2 and Examples 9 to 12, the concentration of piperazine diphosphate in the reaction solution is preferably 25 to 40 wt.%. According to Examples 2 and Examples 11 to 12, the chromaticity of the piperazine diphosphate solution after adsorption treatment is preferably ≤50 Hazen units.

[0117] According to the test results of the diphosphate piperazine yield of Example 15, according to the continuous production method of the present invention, anhydrous piperazine and phosphoric acid are added to a saturated diphosphate piperazine solution in a molar ratio of 1:2, and then subjected to adsorption treatment, filtration, and drying. The pretreated diphosphate piperazine particles obtained are used for dehydration condensation to synthesize pyrophosphate piperazine, and the filtrate is then used. After five times of application, the average value of the diphosphate piperazine yield is calculated to be 98.8%, indicating that the continuous production method of the present invention is suitable for industrial large-scale production of high-whiteness pyrophosphate piperazine.

[0118] According to the test result of Table 4, when piperazine diphosphate was not subjected to adsorption treatment, the whiteness of piperazine pyrophosphate obtained was only 94.3. By Comparative Examples 2 and 3, when the dehydration condensation process was not subjected to flowing inert gas, or when vacuuming was not continuously performed, piperazine pyrophosphate was difficult to reach the requirement of high whiteness. Wherein, although the reaction was carried out under an inert gas atmosphere in Comparative Example 2, its flow rate was 0, and the color of piperazine pyrophosphate obtained was slightly yellow. In Comparative Example 4, the concentration of piperazine diphosphate solution was too high, and piperazine diphosphate was precipitated in a large number during adsorption treatment in the production process, and the whiteness of piperazine pyrophosphate obtained was on the low side. In Comparative Example 5, although piperazine diphosphate was subjected to adsorption treatment, the chromaticity after adsorption treatment was still relatively high, being 115 black units, so that the whiteness value of piperazine pyrophosphate finally obtained was only 95.1, which did not meet the high whiteness requirement. In the continuous production process of Comparative Example 6, the molar ratio of anhydrous piperazine to phosphoric acid was 1:3, resulting in a large amount of free phosphoric acid in the reaction solution, causing the whiteness value of piperazine pyrophosphate to be only 91 and a low yield of piperazine diphosphate.

[0119] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A method for preparing piperazine pyrophosphate, characterized in that: The steps include: S1. A 25 to 40 wt.% piperazine diphosphate solution is subjected to adsorption treatment, so that the chromaticity of the piperazine diphosphate solution subjected to adsorption treatment is ≤60 black units; Then, the piperazine diphosphate solution is crystallized and filtered to collect crude crystals, and the crude crystals are dried to obtain pretreated piperazine diphosphate particles; The chromaticity detection method is in accordance with GB / T 3143-1982; S2. In a flowing inert gas environment or under continuous vacuum conditions, the pretreated dipiperazine diphosphate particles undergo a dehydration condensation reaction to obtain high-whiteness piperazine pyrophosphate; the flow rate of the inert gas is 40 to 50 m / h, and the continuous vacuum is such that the absolute pressure is maintained between 100 and 300 Pa; the whiteness value of the piperazine pyrophosphate is ≥98.

3.

2. The preparation method according to claim 1, characterized in that: In step S1, the adsorption treatment is performed using a fixed bed adsorber.

3. The preparation method according to claim 2, characterized in that: The fixed bed adsorber uses one or more of activated carbon, clay or adsorption resin as adsorbent filler.

4. The preparation method according to claim 1, characterized in that: In step S1, the chromaticity of the piperazine diphosphate solution after adsorption treatment is ≤50 Hazen units.

5. A continuous preparation method of high-whiteness piperazine pyrophosphate, characterized in that: The steps include: M1. adding anhydrous piperazine and phosphoric acid to a saturated piperazine diphosphate solution, using the heat of dissolution and the heat of reaction to completely dissolve the added anhydrous piperazine and phosphoric acid to obtain a reaction solution having a piperazine diphosphate concentration of 25 to 40 wt.%; the molar ratio of anhydrous piperazine to phosphoric acid is 1:1.98 to 2.02; M2. The reaction solution is subjected to adsorption treatment so that the chromaticity of the diphosphate piperazine solution subjected to adsorption treatment is ≤60 black units, and then crystallization is performed, filtration is performed, crude crystals and a filtrate are obtained, and the crude crystals are dried to obtain pretreated diphosphate piperazine particles; the filtrate is concentrated to saturation, and the obtained saturated diphosphate piperazine solution is applied to step M1; The chromaticity detection method is in accordance with GB / T 3143-1982; M3. In a flowing inert gas environment or under continuous vacuum conditions, the pretreated piperazine diphosphate particles are subjected to a dehydration condensation reaction to obtain high-whiteness piperazine pyrophosphate; the flow rate of the inert gas is 40 to 50 m / h, and the continuous vacuum is maintained at an absolute pressure of 100 to 300 Pa; The whiteness value of the high-whiteness piperazine pyrophosphate is ≥98.1.

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