Piperazine pyrophosphate compound resistant to yellowing at high temperature and preparation method thereof

Abstract

The invention relates to the technical field of pyrophosphate piperazine salt flame retardants, and discloses a high-temperature yellowing-resistant pyrophosphate piperazine salt compound and a preparation method thereof.The preparation method comprises the following steps that 1, pyrophosphate piperazine salt is subjected to constant-temperature heat treatment and cooled to the room temperature for use; 2) blending an auxiliary agent I and an auxiliary agent II according to a ratio of 1: 3-3: 1 to obtain a complexing agent; (3) diluting and blending the complexing agent and the pyrophosphoric acid piperazine salt treated in the step (1) according to the ratio of 1: 5-1: 9, and drying for later use to obtain a premixing agent; (4) adding a premixing agent into the piperazine pyrophosphate treated in the step (1) according to the addition amount of 0.5-5%, blending at 60-150 DEG C, and drying to obtain a high-temperature yellowing-resistant piperazine pyrophosphate compound prepared by a low-temperature method; according to the invention, the low-temperature-method piperazine pyrophosphate is taken as an object, the yellowing problem of the piperazine pyrophosphate is solved through heat treatment and addition of the auxiliary agent, and the application performance of the piperazine pyrophosphate in plastics is improved.

Description

Technical Field

[0001] The invention relates to the technical field of piperazine pyrophosphate flame retardants, and in particular to a high-temperature yellowing-resistant piperazine pyrophosphate composite and a preparation method thereof. Background Art

[0002] Piperazine pyrophosphate (PAPP) is an intumescent flame retardant that integrates acid source, carbon source and gas source. It has high carbonization efficiency and can be used in polypropylene (PP), polyethylene (PE), ethylene-vinyl acetate copolymer (EVA), epoxy resin (EP) and other fields. Currently, PAPP is most widely used in the field of polypropylene. Compared with other intumescent flame retardants, PAPP itself has good heat resistance, hydrolysis resistance and excellent flame retardant properties. PAPP compounds are widely used in extrusion sheet technology and injection molding technology. As downstream users have higher flame retardant requirements for plastic products, the amount of PAPP compound added is increased accordingly. However, if the processing temperature of the combustion aid is too low, the plasticization of the plastic is poor, resulting in uneven dispersion of the flame retardant in the resin, and plastic products will have quality defects such as white spots and unstable flame retardant properties. If the processing temperature is too high, the plastic products will turn yellow.

[0003] In order to solve the problem of yellowing of plastic products, the existing technology mainly focuses on the plastic itself. The main means is to select piperazine pyrophosphate salt with better whiteness, or add anti-yellowing agents to plastic products, but it does not consider that the flame retardant piperazine pyrophosphate salt itself will also turn yellow. Therefore, there has been no technical means to solve the yellowing of plastic products from the preparation process of piperazine pyrophosphate salt. At present, the preparation methods of polypiperazine phosphate flame retardant are roughly: 1) double decomposition method; 2) phosphorus pentoxide method; 3) diammonium phosphate method; 4) dipiperazine diphosphate condensation method. Most of the above preparation methods require high temperature. The high temperature process not only consumes a lot of energy but also requires good temperature control. A slightly higher temperature is easy to cause piperazine carbonization, which affects the flame retardant efficiency. In addition, polypiperazine phosphate is more likely to turn yellow at high temperature, and the whiteness is reduced, which affects its performance.

[0004] Therefore, the use of low-temperature method to prepare piperazine pyrophosphate has become a new trend. The piperazine pyrophosphate salt prepared in the process of the process has good whiteness, and the preparation of piperazine pyrophosphate is environmentally friendly, low in energy consumption, easy to clean equipment, and safe to operate. Under high temperature heating, piperazine pyrophosphate salt will still turn yellow. This may be due to the presence of nitrides or other impurities in piperazine pyrophosphate salt that are oxidized to chromogenic functional groups at high temperatures. Piperazine and piperazine orthophosphate are present in the volatile impurities that are removed, and these impurities will also undergo oxidation and yellowing. In addition, under acidic conditions, the functional groups of piperazine pyrophosphate salts subjected to high temperatures are more easily oxidized to chromogenic groups. Summary of the invention

[0005] The invention provides a high-temperature yellowing-resistant piperazine pyrophosphate salt composite and a preparation method thereof, which solves the problem in the prior art that piperazine polyphosphate is easily yellowed, resulting in performance being affected.

[0006] The scheme of the present invention is:

[0007] A method for preparing a high-temperature yellowing-resistant piperazine pyrophosphate salt complex comprises the following steps:

[0008] 1) subjecting the piperazine pyrophosphate to a constant temperature heat treatment and cooling to room temperature for later use;

[0009] 2) Mixing the additive 1 and the additive 2 in a ratio of 1:0.25-4 to form a composite agent;

[0010] 3) blending the composite agent with the piperazine pyrophosphate salt heat-treated in step 1) at a mass ratio of 1:5 to 9, drying and setting aside to obtain a premix;

[0011] 4) blending the premix with the piperazine pyrophosphate heat-treated in step 1) at 60° C. to 150° C., and drying to obtain a low-temperature process piperazine pyrophosphate complex that is resistant to yellowing at high temperatures;

[0012] The first auxiliary agent is alkaline hydrotalcite; the second auxiliary agent is one of polysiloxane and micro-sized silica.

[0013] As a preferred technical solution, in 1), pyrophosphoric acid and piperazine are mixed in an aqueous phase at room temperature to prepare the pyrophosphate piperazine salt; the temperature of the constant temperature heat treatment is 60-150° C., and the insulation time is 0.5-4 hours.

[0014] As a preferred technical solution, in the step 2), the stirring speed of the blending of the auxiliary agent 1 and the auxiliary agent 2 is 500 to 2000 rad / min, and the time is 2 to 8 minutes.

[0015] As a preferred technical solution, in the step 3), the stirring speed of the blending of the composite agent and the heat-treated piperazine pyrophosphate salt in step 1) is 500 to 2000 rad / min, and the stirring time is 2 to 8 min.

[0016] As a preferred technical solution, the mass ratio of the premix in step 4) to the heat-treated piperazine pyrophosphate is 0.005 to 0.05:1, the stirring speed of the premix in step 4) and the heat-treated piperazine pyrophosphate in step 1) is 500 to 2000 rad / min, and the stirring time is 2 to 8 min.

[0017] As a preferred technical solution, the alkaline hydrotalcite is one or more of calcium magnesium tin hydrotalcite, calcium magnesium aluminum hydrotalcite, and aluminum magnesium hydrotalcite.

[0018] As a preferred technical solution, the particle size of the micro-sized silicon dioxide is 50 to 200 nm.

[0019] As a preferred technical solution, the polysiloxane is solid at room temperature and melts above 60°C, and is selected from Chengdu Silike Technology Co., Ltd., and the model is one or both of SILIMER6150 and SILIMER5500.

[0020] The invention also discloses a method for preparing a high-temperature yellowing-resistant low-temperature piperazine pyrophosphate salt complex to obtain the high-temperature yellowing-resistant low-temperature piperazine pyrophosphate salt complex.

[0021] Advantages of the present invention:

[0022] 1. The present invention is based on low-temperature piperazine pyrophosphate salt. Since the low-temperature piperazine pyrophosphate salt preparation process does not undergo high-temperature treatment, the piperazine pyrophosphate salt prepared contains volatile impurities such as piperazine and piperazine orthophosphate. In the steps of the present invention, impurities such as piperazine and piperazine orthophosphate are removed by constant temperature heat treatment. The presence of these impurities will cause the piperazine pyrophosphate salt to yellow at high temperatures during use.

[0023] 2. Piperazine pyrophosphate is more likely to turn yellow under acidic and high temperature conditions. Alkaline hydrotalcite can reduce the acidity of piperazine pyrophosphate. At the same time, through uniform blending, the alkaline hydrotalcite can be evenly coated on the surface of piperazine pyrophosphate to form a protective layer, which plays a role of heat insulation on the surface of piperazine pyrophosphate, further reducing the yellowing of piperazine pyrophosphate caused by high temperature. The addition ratio of alkaline hydrotalcite needs to be controlled, and the addition amount should not be too much, otherwise it will not only fail to achieve the protective effect, but also affect the stability and flame retardant properties of piperazine pyrophosphate.

[0024] 3. The polysiloxane in the auxiliary agent 2 of the present invention, which is solid at room temperature, can be melted at the temperature of step 4), and after melting, it is uniformly stirred and attached to the surface of piperazine pyrophosphate to form a protective layer, which can play a heat insulation effect and reduce the yellowing of piperazine pyrophosphate at high temperature; at the same time, it will not affect the flame retardant properties of the flame retardant; in addition, after the polysiloxane is melted, it can play a lubricating role, reduce the temperature increase caused by friction that causes the yellowing of piperazine pyrophosphate, and after the polysiloxane is melted, it is beneficial to the uniform dispersion of the auxiliary agent 1, which is beneficial for the auxiliary agent 1 to further play its role;

[0025] 4. The micro-sized silica in the second additive of the present invention has extremely strong dispersibility and high surface energy, which makes the alkaline hydrotalcite more dispersible and has a certain encapsulation performance for piperazine pyrophosphate, so that the first additive and the second additive can work together to improve the anti-yellowing effect of piperazine pyrophosphate salt.

[0026] 5. The present invention uses a polysiloxane that is solid at room temperature, which is convenient to add and easy to disperse. There is no need to add equipment such as a liquid additive loss-in-weight scale. Instead, a premix is ​​prepared first, and the premix is ​​then blended with piperazine pyrophosphate to ensure that the solid additives one and two are more evenly dispersed, and the premix wraps the pyrophosphate more fully. The hydrotalcite used in the present invention is an alkaline hydrotalcite. Adding hydrotalcite under anhydrous conditions will not only not affect the stability of piperazine pyrophosphate, but the presence of alkali metals can also reduce the acidity and thereby prevent or slow down oxidation to chromophores. DETAILED DESCRIPTION

[0027] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further described below in conjunction with specific embodiments.

[0028] Embodiment 1:

[0029] A high temperature yellowing resistant piperazine pyrophosphate salt complex and a preparation method thereof, comprising the following steps:

[0030] 1) pyrophosphoric acid and piperazine are mixed in an aqueous phase at room temperature to obtain the piperazine pyrophosphate salt, the piperazine pyrophosphate salt is subjected to a constant temperature heat treatment, and cooled to room temperature for standby use;

[0031] 2) Mixing the additive 1 and the additive 2 in a ratio of 1:3 to 3:1 to form a composite agent;

[0032] 3) diluting the composite agent and the piperazine pyrophosphate salt treated in step 1) at a ratio of 1:9, mixing, drying and setting aside to obtain a premix;

[0033] 4) adding the premix in an amount of 0.5% to 5% to the piperazine pyrophosphate salt to be used after the treatment in step 1), blending and drying at 60° C. to 150° C. to obtain a low-temperature process piperazine pyrophosphate salt composite that is resistant to yellowing at high temperatures;

[0034] The first auxiliary agent is alkaline hydrotalcite; the second auxiliary agent is polysiloxane or micro-sized silica in a solid state at room temperature;

[0035] The temperature of the constant temperature heat treatment is 60-150°C, and the insulation time is 0.5-4h;

[0036] In the step 2), the stirring speed of the blending of the auxiliary agent 1 and the auxiliary agent 2 is 500 to 2000 rad / min, and the time is 2 to 8 minutes;

[0037] The stirring speed of the composite agent and the piperazine pyrophosphate salt treated in step 1) is 500 to 2000 rad / min, and the stirring time is 2 to 8 minutes;

[0038] In the step 4), the stirring speed of the premix and the piperazine pyrophosphate salt treated in step 1) is 500 to 2000 rad / min, and the stirring time is 2 to 8 min;

[0039] The auxiliary agent is selected from one or more of calcium magnesium tin hydrotalcite, calcium magnesium aluminum hydrotalcite, and aluminum magnesium hydrotalcite;

[0040] The particle size of the micro-sized silicon dioxide is 50 to 200 nm;

[0041] The polysiloxane is solid at room temperature and melts above 60° C. and is selected from Chengdu Silike Technology Co., Ltd., and the model is one or both of SILIMER6150 and SILIMER5500.

[0042] The piperazine pyrophosphate salt (i.e., PAPP complex) prepared by the above method is mixed according to the following formula requirements, and then high-speed blending (200-2000 rad / min), extrusion (processing temperature 190-230°C), pelletizing, injection molding, and constant temperature and humidity treatment are performed to obtain flame-retardant polypropylene.

[0043] Flame retardant polypropylene formulations consist of the following mass groups:

[0044]

[0045] The mass ratio of each component in the compound antioxidant is: main antioxidant 3114: auxiliary antioxidant 168=1:1.

[0046] Embodiment 2

[0047] Different piperazine pyrophosphates were prepared according to Table 1 below, and flame-retardant polypropylene was prepared according to the flame-retardant polypropylene formula and method of Example 1. The properties thereof were tested, and the results are shown in Table 2.

[0048] Table 1:

[0049]

[0050]

[0051] Note: 1) The premix of S13, S14, S15, S16 and S17 contains 90% pure PAPP + 10% compound;

[0052] 2) The compounding agent in the premixes of S13, S14, S15, S16 and S17 is prepared by mixing auxiliary agent 1 and auxiliary agent 2 in a ratio of 1:1.

[0053] Table 2 Test results

[0054]

[0055]

[0056] Note: The treated PAPP compound contains 15% PAPP complex, 7.5% MPP, 2% zinc oxide, and 0.5% compound antioxidant.

[0057] As can be seen from Table 2, the present invention significantly improves the high-temperature yellowing resistance of PAPP after heat treatment of PAPP alone, among which the high-temperature yellowing resistance is the best after heat treatment at 110°C. The high-temperature yellowing resistance of PAPP alone can be improved after using CaMgAl-DHT, MgAl-DHT, CaMgSn-DHT or nano-SiO2, 6150, 5500 and other additives, but it will affect the processing performance (melting index is seriously reduced) and flame retardant performance of PAPP to a certain extent, among which aluminum-magnesium hydrotalcite has a more obvious effect on high-temperature yellowing; polysiloxane 6150 and polysiloxane 5500 alone obviously provide PAPP processing performance (melting index is significantly improved) and flame retardant performance without obvious effect, among which polysiloxane 5500 has the best high-temperature yellowing resistance. After CaMgAl-DHT, MgAl-DHT and nano-SiO2, 6150, 5500 are compounded and premixed, the high-temperature yellowing resistance of PAPP pure product is improved to varying degrees. Among them, the flame retardant performance, processing performance, high temperature anti-yellowing performance and other comprehensive performances are the best after the premix (MgAl-DHT: nano-SiO2=1:1 compound, and then diluted 10 times with PAPP) is blended with PAPP. The reason is that MgAl-DHT is an alkaline substance, and it reacts with piperazine pyrophosphate to make PAPP have higher color stability. In addition, nano-SiO2 has extremely strong dispersibility and high surface energy, which makes MgAl-DHT more dispersible and has certain wrapping performance for PAPP. Therefore, MgAl-DHT and nano-SiO2 have a synergistic effect on the anti-yellowing performance of PAPP.

[0058] It can be seen from Table 2 that without heat treatment, even with the addition of additives 1 and 2, the high-temperature yellowing resistance of PAPP cannot be significantly improved, indicating that the constant temperature heat treatment step of the present invention has an impact on the effectiveness of additives 1 and 2, and only by heat treatment to remove certain volatile impurities, without the addition of additives 1 and 2, the high-temperature yellowing resistance of PAPP cannot be greatly improved. This proves that the reason for the yellowing of low-temperature piperazine pyrophosphate, in addition to the volatile impurities contained therein, may also be due to the self-oxidation of piperazine pyrophosphate under high temperature acidity to produce chromogenic functional groups.

[0059] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for preparing a high temperature yellowing resistant piperazine pyrophosphate salt complex, characterized in that: The following steps are involved: 1) subjecting the piperazine pyrophosphate to a constant temperature heat treatment and cooling to room temperature for later use; 2) Mixing the additive 1 and the additive 2 in a ratio of 1:3 to 3:1 to form a composite agent; 3) blending the composite agent with the piperazine pyrophosphate salt heat-treated in step 1) at a mass ratio of 1:5 to 9, drying and setting aside to obtain a premix; 4) blending the premix with the piperazine pyrophosphate heat-treated in step 1) at 60° C. to 150° C., and drying to obtain a low-temperature process piperazine pyrophosphate complex that is resistant to yellowing at high temperatures; The first auxiliary agent is alkaline hydrotalcite; the second auxiliary agent is one of polysiloxane and micro-sized silica.

2. The method for preparing a high temperature yellowing resistant piperazine pyrophosphate salt complex according to claim 1, characterized in that: In the step 1), pyrophosphoric acid and piperazine are mixed in an aqueous phase at room temperature to obtain the piperazine pyrophosphate salt; the temperature of the constant temperature heat treatment is 60-150° C., and the insulation time is 0.5-4 hours.

3. The method for preparing a high temperature yellowing resistant piperazine pyrophosphate complex according to claim 1, characterized in that: In the step 2), the stirring speed of the blending of the auxiliary agent 1 and the auxiliary agent 2 is 500 to 2000 rad / min, and the time is 2 to 8 minutes.

4. The method for preparing a high temperature yellowing resistant piperazine pyrophosphate salt complex according to claim 1, characterized in that: In the step 3), the stirring speed of blending the composite agent with the heat-treated piperazine pyrophosphate salt in step 1) is 500 to 2000 rad / min, and the stirring time is 2 to 8 minutes.

5. The method for preparing a high temperature yellowing resistant piperazine pyrophosphate complex according to claim 1, characterized in that: The mass ratio of the premix in step 4) to the heat-treated piperazine pyrophosphate is 0.005 to 0.05:1, and the stirring speed of the premix in step 4) and the heat-treated piperazine pyrophosphate in step 1) is 500 to 2000 rad / min, and the stirring time is 2 to 8 minutes.

6. The method for preparing a high temperature yellowing resistant piperazine pyrophosphate complex according to claim 1, characterized in that: The alkaline hydrotalcite is one or more of calcium magnesium tin hydrotalcite, calcium magnesium aluminum hydrotalcite, and aluminum magnesium hydrotalcite.

7. The method for preparing a high temperature yellowing resistant piperazine pyrophosphate salt complex according to claim 1, characterized in that: The particle size of the micro-sized silicon dioxide is 50 to 200 nm.

8. The method for preparing a high temperature yellowing resistant piperazine pyrophosphate complex according to claim 1, characterized in that: The polysiloxane is solid at room temperature and melts above 60°C.

9. A high-temperature yellowing-resistant low-temperature piperazine pyrophosphate complex prepared by the method for preparing a high-temperature yellowing-resistant low-temperature piperazine pyrophosphate complex according to any one of claims 1 to 8.

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