Preparation method of modified pyrophosphoric acid piperazine base halogen-free environment-friendly flame retardant with high thermal stability

Abstract

The application provides a preparation method of a modified pyrophosphoric acid piperazine-based halogen-free environment-friendly flame retardant with high thermal stability, and belongs to the technical field of flame retardants; the preparation method comprises a pyrophosphoric acid piperazine pretreatment, preparation of a modifier and a modification step; in the preparation of the modifier, composite fillers are added into N,N-dimethylformamide, ultrasonic dispersion is carried out, then dipentaerythritol and polyphosphoric acid are added, under a nitrogen atmosphere, 95-100 DEG C heat preservation is carried out for 15-18 min, then the temperature is increased to 132-137 DEG C, 0.01-0.02 MPa heat preservation is carried out for 4.0-4.5 h, the temperature is reduced to 115-120 DEG C, isophorone diisocyanate is added, 142-147 DEG C reaction is carried out for 2.5-3.0 h, and after cooling, filtration and drying, the modifier is prepared; the flame retardant prepared by the application has excellent flame retardance and thermal stability, has good compatibility with a PP matrix, and the comprehensive performance of the prepared PP composite material is excellent.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of flame retardants, and particularly relates to a preparation method of a modified pyrrolizidine pyrophosphoric acid halogen-free environmentally-friendly flame retardant with high thermal stability. BACKGROUND

[0002] With the increasingly stringent environmental regulations and the improvement of people's awareness of fire safety, the demand and requirement for flame-retardant materials are also increasingly high, and the research and development of halogen-free flame retardants have become the mainstream direction in the flame-retardant field; among numerous flame retardants, pyrrolizidine pyrophosphate, as a typical halogen-free phosphorus-nitrogen type flame retardant, has attracted widespread attention in the field of high polymer flame retardation;

[0003] Specifically, pyrrolizidine pyrophosphate has the following excellent performances:

[0004] First, pyrrolizidine pyrophosphate has excellent environmental performance, it does not contain halogen and will not release toxic and harmful hydrogen halide gas during combustion, and the amount of smoke is small; second, pyrrolizidine pyrophosphate has excellent flame retardant performance, it contains both phosphorus and nitrogen elements in the molecular structure, and can form a phosphorus-nitrogen synergistic flame retardant system during combustion, and realize high-efficiency flame retardation through the dual effects of forming a dense carbon layer and releasing inert gas; third, pyrrolizidine pyrophosphate has good water resistance, compared with traditional phosphate ester flame retardants, it has low water absorption, which can reduce the problems of flame retardant performance decline and mechanical property deterioration caused by water absorption.

[0005] However, pyrrolizidine pyrophosphate has obvious defects in practical application, especially in the field of plastics such as PP with high processing temperature, and mainly has the following shortcomings: first, pyrrolizidine pyrophosphate has insufficient thermal stability, its initial thermal decomposition temperature is about 280-300 DEG C, while the processing temperature of polypropylene is above 200 DEG C, under the conditions of screw shearing, local overheating and long-time processing, it is easy to decompose, resulting in discoloration of the material, decline of the flame retardant performance, and poor mechanical properties, which limits its application in high-performance PP materials; in addition, the compatibility with the high polymer matrix is poor, pyrrolizidine pyrophosphate, as a strong polar compound, has poor compatibility with the non-polar high polymer matrix, which further leads to uneven dispersion of pyrrolizidine pyrophosphate in the matrix, easy agglomeration, influence on the flame retardant performance, and formation of stress defect points at the interface between the two phases, which further affects the mechanical properties and mechanical stability of the composite material.

[0006] In order to improve the comprehensive performance of pyrrolizidine pyrophosphate, it is necessary to modify pyrrolizidine pyrophosphate, which can expand the application range in the field of high polymer materials, and the modification methods of pyrrolizidine pyrophosphate in the prior art include the following:

[0007] Microencapsulation modification: mainly using isocyanate, melamine formaldehyde resin and other resins to coat the surface of pyrithidyl pyrophosphate organically, and the thermal stability and compatibility with the polymer matrix are enhanced by forming a coating layer, but the viscosity of pyrithidyl pyrophosphate treated by isocyanate is large, which affects the mechanical properties of the composite material; melamine formaldehyde resin introduces formaldehyde and other components;

[0008] Surfactant coating: treated by anionic surfactant, which can improve the dispersion performance to a certain extent, but the improvement of thermal stability performance is limited;

[0009] Compound synergism: by introducing metal oxide or other flame retardants for compounding, which improves the flame retardant performance through the synergistic effect between components, but cannot fundamentally overcome the defects of poor thermal stability and poor compatibility.

[0010] Therefore, a modification method of pyrithidyl pyrophosphate is provided, which has good flame retardant performance, good thermal stability, good compatibility with high molecular matrix such as PP, and the prepared composite material has excellent flame retardant performance, mechanical properties and thermal stability. SUMMARY

[0011] In order to solve the technical problems existing in the prior art, the present application provides a preparation method of modified pyrithidyl pyrophosphate based halogen-free environmentally friendly flame retardant with high thermal stability, which improves the flame retardancy and thermal stability of pyrithidyl pyrophosphate, enhances the compatibility with PP matrix, and improves the flame retardancy, mechanical properties and thermal stability of PP composite material.

[0012] In view of the above technical problems, the present application adopts the following technical scheme:

[0013] A preparation method of modified pyrithidyl pyrophosphate based halogen-free environmentally friendly flame retardant with high thermal stability, including pyrithidyl pyrophosphate pretreatment, preparation of modifier, modification steps, as follows:

[0014] 1. Pyrithidyl pyrophosphate pretreatment

[0015] Add kH550 amino silane coupling agent to deionized water, raise the temperature to 62-67 DEG C, stir at 200-220 rpm for 30-35 min to obtain a pretreatment solution; put pyrithidyl pyrophosphate into deionized water, raise the temperature to 62-67 DEG C, add chitosan solution, stir for 15-20 min, then add the pretreatment solution, control the addition rate to 1.0-1.2 g / min, after adding, keep the temperature at 62-67 DEG C for 2.0-2.3 h, filter, wash and dry to obtain pretreated pyrithidyl pyrophosphate;

[0016] In the pretreatment solution, the mass ratio of deionized water to kH550 aminosilane coupling agent is 50:3.0-4.0;

[0017] The chitosan solution is prepared by mixing chitosan and a 4.0-5.0 wt% acetic acid solution, wherein the mass ratio of chitosan to the 4.0-5.0 wt% acetic acid solution is 0.5-1.0:8.0.

[0018] The mass ratio of piperazine pyrophosphate, deionized water, chitosan solution, and pretreatment solution is 10-12:100:8.5-9.0:25-30.

[0019] 2. Preparation of Modifier

[0020] A composite filler was added to N,N-dimethylformamide and ultrasonically dispersed. The ultrasonic time was controlled at 25-30 min, the ultrasonic power at 120-125 W, and the ultrasonic frequency at 28-34 kHz. After ultrasonic dispersion, dipentaerythritol and polyphosphoric acid were added. Under a nitrogen atmosphere, the temperature was increased to 95-100℃ at a rate of 2.5-3.0℃ / min and held for 15-18 min. Then, the temperature was increased to 132-137℃ at a rate of 1.4-1.8℃ / min and held at 0.01-0.02 MPa for 4.0-4.5 h. After the reaction was completed, the temperature was decreased to 115-120℃ at a rate of 1.5-2.0℃ / min, and isophorone diisocyanate was added. After stirring evenly, the temperature was increased to 142-147℃ at a rate of 1.2-1.6℃ / min and held for 2.5-3.0 h. After cooling, filtration, and drying, the modifier was obtained.

[0021] The mass ratio of N,N-dimethylformamide, composite filler, dipentaerythritol, polyphosphoric acid, and isophorone diisocyanate is 500:20-25:7.6-8.0:3.6-3.8:3.0-3.2.

[0022] The polyphosphoric acid has a mass content of 84-86% based on phosphorus pentoxide and a dynamic viscosity of 8500-10000 mPa·s at 25°C.

[0023] The composite filler is prepared by calcining kaolin and magnesium hydroxide, first raising the temperature to 215-225℃ at a rate of 4.5-5.0℃ / min and holding for 30-40 min, then raising the temperature to 330-350℃ at a rate of 1.6-2.2℃ / min and holding for 1.8-2.2 h, and allowing it to cool naturally to room temperature. The filler is then added to an ethanol solution, along with kH550 silane coupling agent, and the temperature is raised to 60-64℃ at a rate of 2.5-3.0℃ / min, held and stirred for 2.0-2.3 h. After filtration, washing, and drying, the composite filler is obtained.

[0024] The mass ratio of the kaolin, magnesium hydroxide, ethanol solution, kH550 silane coupling agent is 10-12:10-12:175-180:2.5-3.0;

[0025] The mass concentration of the ethanol solution is 35-40%.

[0026] 3. Modification

[0027] Pretreated pyrophosphoric acid piperazine is added to N, N-dimethylacetamide, stirred uniformly, then a modifier is added, the temperature is raised to 48-52℃ at a rate of 1.5-2.0℃ / min, and the mixture is kept stirring for 15-20min, then the temperature is raised to 78-84℃ at a rate of 1.0-1.2℃ / min, and the mixture is kept stirring for 3.5-4.0h, to obtain modified pyrophosphoric acid piperazine; the modified pyrophosphoric acid piperazine is mixed with melamine cyanurate, aluminum diethylphosphinate, melamine polyphosphate, stirred at 800-820rpm for 15-20min, then talc powder and polyethylene glycol 400 solution are added, stirred at 320-350rpm for 20-25min, and dried to obtain modified pyrophosphoric acid piperazine-based halogen-free environmentally friendly flame retardant;

[0028] The mass ratio of the N, N-dimethylacetamide, pretreated pyrophosphoric acid piperazine, and modifier is 100:12-15:4-7;

[0029] The mass ratio of the modified pyrophosphoric acid piperazine, melamine cyanurate, aluminum diethylphosphinate, melamine polyphosphate, talc powder, and polyethylene glycol 400 solution is 30-50:30-40:1-10:1-5:6-8:25-30;

[0030] The polyethylene glycol 400 solution is a mixture of polyethylene glycol 400 and deionized water, and the mass ratio of the polyethylene glycol 400 and deionized water is 1.0-1.4:100.

[0031] The application first pretreats pyrophosphoric piperazine with amino silane coupling agent, and after hydrolysis, the silicon hydroxyl at one end can be dehydrated and condensed with the hydroxyl of pyrophosphoric piperazine, and the amino at the other end serves as an anchor point for the subsequent modifier reaction, chitosan is rich in hydroxyl and amino, which can be wrapped on the surface of pyrophosphoric piperazine, and the amino can cooperate with the amino of the amino silane coupling agent to improve the compatibility with the PP matrix and improve the charring performance; in the modifier preparation step, kaolin and magnesium hydroxide are first treated with amino silane, which serves as an inorganic flame retardant synergist and reinforcing phase, which can not only improve the flame retardant performance, but also improve the compatibility with the PP matrix, enhance the mechanical properties, combine with dipentaerythritol and polyphosphoric acid components to form a stable intumescent flame retardant system, the introduction of isocyanate groups can not only enhance the flexibility of the molecular chain and improve the mechanical properties of the composite material, but also serve as a bridge to improve the compatibility between the modifier and the pretreated pyrophosphoric piperazine and the PP matrix, thereby ensuring the stability of the composite material, and then the pretreated pyrophosphoric piperazine and the modifier in the modification step are strongly combined, and other flame retardant components and processing aids are compounded to improve the environmental performance of the final product, and the homogeneity and stability of the product are enhanced, and the flame retardancy, mechanical properties and stability of the product are ensured.

[0032] Compared with the prior art, the application has the following beneficial effects:

[0033] 1. The modified pyrophosphoric piperazine-based halogen-free environmentally friendly flame retardant prepared by the application has an ultimate oxygen index of 40.97-42.83%, a notched impact strength of 9.53-10.45kJ / m 2 , a tensile strength of 34.88-36.61MPa, an elongation at break of 66.74-68.53%, and a bending strength of 43.35-45.26MPa;

[0034] 2. The modified pyrophosphoric piperazine-based halogen-free environmentally friendly flame retardant prepared by the application has a notched impact strength of 9.09-10.21kJ / m 2 , a tensile strength of 33.38-35.92MPa, an elongation at break of 63.40-66.62%, and a bending strength of 41.01-43.81MPa after being placed in an environment with a temperature of 85℃ and a humidity of 85% for 240h;

[0035] 3. The modified pyrophosphoric piperazine-based halogen-free environmentally friendly flame retardant prepared by the application has a notched impact strength of 8.79-9.83kJ / m 2The tensile strength is 32.30-34.60 MPa, the elongation at break is 61.01-63.94%, and the bending strength is 39.36-42.09 MPa. DETAILED DESCRIPTION

[0036] In order to more clearly understand the technical features, objectives and effects of the present application, the specific embodiments of the present application will now be described.

[0037] Example 1

[0038] 1. Pyrophosphoryl piperazine pretreatment

[0039] 4.0 g of kH550 amino silane coupling agent was added to 50 g of deionized water, the temperature was raised to 67℃, and stirring was carried out at 220 rpm for 35 min to obtain a pretreatment solution; 12 g of pyrophosphoryl piperazine was placed in 100 g of deionized water, the temperature was raised to 67℃, 9.0 g of chitosan solution was added, stirring was carried out for 20 min, then 30 g of the pretreatment solution was added at a rate of 1.2 g / min, after the addition was completed, the reaction was carried out at 67℃ for 2.3 h, and after filtration, washing and drying, pretreated pyrophosphoryl piperazine was obtained.

[0040] The chitosan solution was prepared by mixing chitosan and 5.0 wt% acetic acid solution, and the mass ratio of the chitosan and 5.0 wt% acetic acid solution was 1.0:8.0.

[0041] 2. Preparation of modifier

[0042] 25 g of composite filler was added to 500 g of N,N-dimethylformamide, ultrasonic dispersion was carried out, the ultrasonic time was controlled to be 30 min, the ultrasonic power was 125 W, the ultrasonic frequency was 34 kHz, after the ultrasonic dispersion was completed, 8.0 g of dipentaerythritol and 3.8 g of polyphosphoric acid were added, the temperature was raised to 100℃ at a rate of 3.0℃ / min under a nitrogen atmosphere, the temperature was kept at 100℃ for 18 min, then the temperature was raised to 137℃ at a rate of 1.8℃ / min, the reaction was carried out at 0.02 MPa for 4.5 h, after the reaction was completed, the temperature was lowered to 120℃ at a rate of 2.0℃ / min, 3.2 g of isophorone diisocyanate was added, after stirring was uniform, the temperature was raised to 147℃ at a rate of 1.6℃ / min, the reaction was carried out for 3.0 h, after cooling, filtration and drying, a modifier was prepared.

[0043] The mass content of the polyphosphoric acid, calculated as phosphorus pentoxide, was 86%, and the dynamic viscosity at 25℃ was 10000 mPa·s;

[0044] The preparation method of the composite filler is that 12 g of kaolin and 12 g of magnesium hydroxide are calcined, first increased to 225℃ at a rate of 5.0℃ / min, and kept for 40 min, then increased to 350℃ at a rate of 2.2℃ / min, and kept for 2.2 h, and then naturally cooled to room temperature, added to 180 g of 40 wt% ethanol solution, added 3.0 g of kH550 silane coupling agent, increased to 64℃ at a rate of 2.5℃ / min, and kept for 2.3 h of stirring, and then filtered, washed and dried to obtain the composite filler.

[0045] 3. Modification

[0046] To 100 g of N, N-dimethylacetamide, 15 g of pretreated pyrophosphoric acid piperazine is added, stirred uniformly, then 7 g of modifier is added, increased to 52℃ at a rate of 2.0℃ / min, and kept for 20 min of stirring, then increased to 84℃ at a rate of 1.2℃ / min, and kept for 4.0 h of stirring to obtain modified pyrophosphoric acid piperazine; 50 g of modified pyrophosphoric acid piperazine is mixed with 40 g of melamine cyanurate, 10 g of aluminum diethyl phosphinate, and 5 g of melamine polyphosphate, stirred at 820 rpm for 20 min, then 8 g of talc powder and 30 g of polyethylene glycol 400 solution are added, stirred at 350 rpm for 25 min, and then dried to obtain a modified pyrophosphoric acid piperazine-based halogen-free environmentally friendly flame retardant.

[0047] The polyethylene glycol 400 solution is a mixture of 1.4 g of polyethylene glycol 400 and 10 g of deionized water.

[0048] Example 2

[0049] 1. Pretreatment of pyrophosphoric acid piperazine

[0050] To 50 g of deionized water, 3.0 g of kH550 amino silane coupling agent is added, and the temperature is increased to 62℃, and stirred at 200 rpm for 30 min to obtain a pretreatment solution; 10 g of pyrophosphoric acid piperazine is placed in 100 g of deionized water, the temperature is increased to 62℃, 8.5 g of chitosan solution is added, stirred for 15 min, then 25 g of pretreatment solution is added at a rate of 1.0 g / min, after the addition is completed, the reaction is kept at 62℃ for 2.0 h, and then filtered, washed and dried to obtain pretreated pyrophosphoric acid piperazine;

[0051] The chitosan solution is prepared by mixing chitosan and 4.00 wt% acetic acid solution, and the mass ratio of chitosan to 4.0 wt% acetic acid solution is 0.5:8.0.

[0052] 2. Preparation of modifier

[0053] To 500g N, N-dimethylformamide, 20g composite filler was added, ultrasonic dispersion was carried out, the ultrasonic time was controlled to be 25min, the ultrasonic power was 1205W, the ultrasonic frequency was 28kHz, after the ultrasonic dispersion was completed, 7.60g dipentaerythritol and 3.6g polyphosphoric acid were added, the temperature was increased to 95℃ at a rate of 2.5℃ / min under a nitrogen atmosphere, and the temperature was kept for 15min, then the temperature was increased to 132℃ at a rate of 1.4℃ / min, and the temperature was kept for reaction for 4.0h under 0.01MPa, after the temperature keeping reaction was completed, the temperature was decreased to 115℃ at a rate of 1.5℃ / min, 3.0g isophorone diisocyanate was added, after stirring uniformly, the temperature was increased to 142℃ at a rate of 1.2℃ / min, and the temperature was kept for reaction for 2.5h, after cooling, filtration and drying, a modifier was prepared;

[0054] The mass content of the polyphosphoric acid, calculated based on the mass of the phosphorus pentoxide, was 84%, and the dynamic viscosity at 25℃ was 8500mPa·s;

[0055] The preparation method of the composite filler was as follows: 10g kaolin and 10g magnesium hydroxide were calcined, the temperature was first increased to 215℃ at a rate of 4.5℃ / min, and the temperature was kept for 30min, then the temperature was increased to 330℃ at a rate of 1.6℃ / min, and the temperature was kept for 1.8h, and after natural cooling to room temperature, the mixture was added into 175g 35wt% ethanol solution, 2.5g kH550 silane coupling agent was added, the temperature was increased to 60℃ at a rate of 3.0℃ / min, and the temperature was kept for stirring for 2.0h, and after filtration, washing and drying, the composite filler was obtained.

[0056] 3. Modification

[0057] To 100g N, N-dimethylacetamide, 12g pretreated piperazine pyrophosphate was added, after stirring uniformly, 4g modifier was added, the temperature was increased to 48℃ at a rate of 1.5℃ / min, and the temperature was kept for stirring for 150min, then the temperature was increased to 78℃ at a rate of 1.0℃ / min, and the temperature was kept for stirring for 3.5h, and modified piperazine pyrophosphate was obtained; 30g modified piperazine pyrophosphate, 30g melamine cyanurate, 2g aluminum diethyl phosphinate and 1g melamine polyphosphate were mixed, 6g talc powder and 25g polyethylene glycol 400 solution were added after stirring at 800rpm for 15min, and the mixture was stirred at 320rpm for 20min, and after drying, modified piperazine pyrophosphate-based halogen-free environment-friendly flame retardant was obtained;

[0058] The polyethylene glycol 400 solution was a mixture of 1.0g polyethylene glycol 400 and 10g deionized water.

[0059] Example 3

[0060] 1. Piperazine pyrophosphate pretreatment

[0061] Into 50 g of deionized water, 3.5 g of kH550 amino silane coupling agent was added, the temperature was raised to 65℃, and stirring was carried out at 210 rpm for 32 min to obtain a pretreatment solution; 12 g of piperazine pyrophosphate was put into 100 g of deionized water, the temperature was raised to 65℃, 8.8 g of chitosan solution was added, stirring was carried out for 18 min, then 27 g of the pretreatment solution was added, the addition rate was controlled at 1.2 g / min, after the addition was completed, the reaction was carried out at 65℃ for 2.2 h, and after filtration, washing and drying, the pretreated piperazine pyrophosphate was obtained;

[0062] The chitosan solution was prepared by mixing chitosan and 4.5wt% acetic acid solution, and the mass ratio of chitosan and 4.5wt% acetic acid solution was 0.8:8.0.

[0063] 2. Preparation of modifier

[0064] Into 500 g of N,N-dimethylformamide, 23 g of composite filler was added and ultrasonic dispersion was carried out, the ultrasonic time was controlled at 28 min, the ultrasonic power was 122 W, and the ultrasonic frequency was 30 kHz; after the ultrasonic dispersion was completed, 7.8 g of dipentaerythritol and 3.6 g of polyphosphoric acid were added, the temperature was raised to 98℃ at a rate of 2.8℃ / min under a nitrogen atmosphere, and the temperature was kept for 16 min; then the temperature was raised to 135℃ at a rate of 1.6℃ / min, and the reaction was carried out at 0.02 MPa for 4.2 h; after the reaction was completed, the temperature was lowered to 117℃ at a rate of 1.7℃ / min, 3.1 g of isophorone diisocyanate was added, stirring was carried out until it was uniform, the temperature was raised to 145℃ at a rate of 1.5℃ / min, and the reaction was carried out for 2.8 h; after cooling, filtration and drying, the modifier was prepared;

[0065] The mass content of polyphosphoric acid, calculated as phosphorus pentoxide, was 85%, and the dynamic viscosity at 25℃ was 9000 mPa·s;

[0066] The preparation method of the composite filler was as follows: 12 g of kaolin and 12 g of magnesium hydroxide were calcined, the temperature was raised to 220℃ at a rate of 4.8℃ / min, and the temperature was kept for 35 min; then the temperature was raised to 3450℃ at a rate of 1.8℃ / min, and the temperature was kept for 2.0 h; after natural cooling to room temperature, it was added to 178 g of 37wt% ethanol solution, 2.8 g of kH550 silane coupling agent was added, the temperature was raised to 62℃ at a rate of 2.55℃ / min, and the temperature was kept for 2.2 h with stirring; after filtration, washing and drying, the composite filler was obtained.

[0067] 3. Modification

[0068] To 100 g N, N-dimethylacetamide, 14 g of pre-processed pyrophosphoric acid piperazine was added, stirred uniformly, then 5 g of modifier was added, the temperature was raised to 50℃ at a rate of 1.8℃ / min, and the temperature was kept for 18 min, then the temperature was raised to 80℃ at a rate of 1.0℃ / min, and the temperature was kept for 3.80 h, to obtain modified pyrophosphoric acid piperazine; 40 g of modified pyrophosphoric acid piperazine was mixed with 350 g of cyanuric acid melamine, 8 g of aluminum diethyl phosphinate, and 4 g of melamine polyphosphate, stirred at 810 rpm for 18 min, then 7 g of talc powder and 28 g of polyethylene glycol 400 solution were added, stirred at 330 rpm for 23 min, and after drying, modified pyrophosphoric acid piperazine-based halogen-free environmentally friendly flame retardant was obtained.

[0069] The polyethylene glycol 400 solution is a mixture of 1.2 g of polyethylene glycol 400 and 10 g of deionized water.

[0070] Comparative Example 1

[0071] On the basis of Example 3, the following changes were made:

[0072] The pyrophosphoric acid piperazine pretreatment step was omitted; in the modification step, the pretreated pyrophosphoric acid piperazine was replaced with an equal amount of pyrophosphoric acid piperazine without any treatment; and the polyethylene glycol 400 solution was omitted.

[0073] The remaining operations were exactly the same as in Example 3.

[0074] Comparative Example 2

[0075] On the basis of Example 3, the following changes were made:

[0076] The preparation of the modifier was as follows: 23 g of composite filler was added to 500 g of deionized water, and ultrasonic dispersion was performed, with a control ultrasonic time of 28 min, an ultrasonic power of 122 W, and an ultrasonic frequency of 30 kHz; after ultrasonic dispersion, 7.8 g of dipentaerythritol was added and stirred uniformly to obtain the modifier;

[0077] The preparation method of the composite filler was as follows: 12 g of kaolin and 12 g of magnesium hydroxide were calcined, first at a rate of 4.8℃ / min to 220℃, kept for 35 min, then at a rate of 1.8℃ / min to 340℃, kept for 2.0 h, and then naturally cooled to room temperature to obtain the composite filler;

[0078] The remaining operations were exactly the same as in Example 3.

[0079] Application performance test

[0080] The modified pyrophosphoryl piperazinyl halogen-free environmentally friendly flame retardant prepared in Examples 1-3 and Comparative Examples 1-2 was used to prepare PP composite materials, respectively, and the comprehensive performance of the PP composite materials was tested; wherein, the preparation method of the PP composite material was that 16 g of PP (the mass ratio of PP1100N to PP K8003 was 1:1) was mixed with 2.7 g of the modified pyrophosphoryl piperazinyl halogen-free environmentally friendly flame retardant prepared in Examples 1-3 and Comparative Examples 1-2, respectively, and uniformly mixed, and then extruded and pelletized by an extruder, and the extrusion temperature was controlled at 185°C to obtain the PP composite material.

[0081] 1. Conventional performance

[0082] The performance of the PP composite materials prepared in Examples 1-3 and Comparative Examples 1-2, respectively, was tested, and the results were as follows:

[0083]

[0084] 2. High thermal stability performance

[0085] The PP composite materials prepared in Examples 1-3 and Comparative Examples 1-2, respectively, were placed in an environment with a temperature of 85°C and a humidity of 85% and allowed to stand and age, and the mechanical properties of the PP composite materials after standing and aging for 240 h were recorded, and the details were as follows:

[0086]

[0087] 3. Aging resistance performance

[0088] The PP composite materials prepared in Examples 1-3 and Comparative Examples 1-2, respectively, were placed in an environment with a temperature of 85°C and a humidity of 85% and allowed to stand for 12 h, and then immersed in deionized water at 20°C for 12 h, and the above operation was regarded as one treatment cycle, and after 14 treatment cycles, the mechanical properties of the PP composite materials were tested again, and the details were as follows:

[0089]

[0090] From the above results, it can be seen that Comparative Example 1 did not pretreat the pyrophosphoryl piperazine, and its compatibility with the PP matrix was poor, and it was easy to agglomerate in the PP, and it also omitted the polyethylene glycol solution, and could not form a uniform flame retardant barrier, thereby affecting the flame retardant performance and mechanical properties of the composite material, and the stability was poor; Comparative Example 2 only physically mixed the filler and dipentaerythritol as a modifier, and the interfacial bonding force with the PP matrix was poor, and it could not be stably combined with the pretreated pyrophosphoryl piperazine, and finally led to the destruction of the continuity of the PP by the flame retardant, thereby increasing the brittleness of the composite material, reducing the mechanical properties, and greatly reducing the flame retardant performance.

[0091] Unless otherwise specified, the percentages used in the present application are mass percentages.

[0092] It should be pointed out finally that the above only describes the preferred embodiments of the present application and is not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent replacements to some technical features. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a modified pyrophosphoryl piperazinyl halogen-free environmentally friendly flame retardant with high thermal stability, characterized in that, The preparation method comprises the following steps: preparing a modifier, a modification step, and a preparation step of the modified pyrophosphoric acid piperazine-based halogen-free environmentally friendly flame retardant. The pyrophosphoric acid piperazine pretreatment step is as follows: adding kH550 amino silane coupling agent into deionized water to obtain a pretreatment solution; adding pyrophosphoric acid piperazine into deionized water, heating to 62-67℃, adding chitosan solution and the pretreatment solution, and reacting at 62-67℃ for 2.0-2.3h to obtain pretreated pyrophosphoric acid piperazine. The preparation method of the composite filler is as follows: calcining kaolin and magnesium hydroxide, first increasing the temperature to 215-225℃ at a rate of 4.5-5.0℃ / min, and then increasing the temperature to 330-350℃ at a rate of 1.6-2.2℃ / min, and keeping the temperature for 1.8-2.2h, and then naturally cooling to room temperature, adding into an ethanol solution, adding kH550 silane coupling agent, increasing the temperature to 60-64℃ at a rate of 2.5-3.0℃ / min, and keeping the temperature for 2.0-2.3h, and then filtering, washing and drying to obtain the composite filler. The modification step is as follows: adding the pretreated pyrophosphoric acid piperazine into N,N-dimethylacetamide, uniformly stirring, adding the modifier, increasing the temperature to 48-52℃ at a rate of 1.5-2.0℃ / min, keeping the temperature for 15-20min, then increasing the temperature to 78-84℃ at a rate of 1.0-1.2℃ / min, and keeping the temperature for 3.5-4.0h to obtain modified pyrophosphoric acid piperazine; mixing the modified pyrophosphoric acid piperazine with melamine cyanurate, aluminum diethylphosphinate and melamine polyphosphate, stirring at 800-820rpm for 15-20min, then adding talcum powder and polyethylene glycol 400 solution, stirring at 320-350rpm for 20-25min, and then drying to obtain the modified pyrophosphoric acid piperazine-based halogen-free environmentally friendly flame retardant.

2. The preparation method of the modified pyrophosphoric acid piperazine-based halogen-free environmentally friendly flame retardant with high thermal stability according to claim 1, wherein, in the pyrophosphoric acid piperazine pretreatment step, the mass ratio of the pyrophosphoric acid piperazine, deionized water, chitosan solution and pretreatment solution is 10-12:100:8.5-9.0:25-30. ​ ​ The mass ratio of the deionized water and the kH550 amino silane coupling agent in the pretreatment solution is 50:3.0-4.0; The chitosan solution is prepared by mixing chitosan and 4.0-5.0wt% acetic acid solution, and the mass ratio of the chitosan and 4.0-5.0wt% acetic acid solution is 0.5-1.0:8.

0.

3. The preparation method of the modified pyrazinium pyrophosphate halogen-free environmentally friendly flame retardant with high thermal stability according to claim 1, characterized in that, The mass ratio of the N,N-dimethylformamide, the composite filler, the dipentaerythritol, the polyphosphoric acid and the isophorone diisocyanate in the preparation modifier is 500:20-25:7.6-8.0:3.6-3.8:3.0-3.2; The mass content of the polyphosphoric acid, calculated based on the mass content of the diaphosphorus pentoxide, is 84-86%, and the dynamic viscosity at 25℃ is 8500-10000mPa·s.

4. The preparation method of the modified pyrazinium pyrophosphate halogen-free environmentally friendly flame retardant with high thermal stability according to claim 1, characterized in that, The mass ratio of the kaolin, the magnesium hydroxide, the ethanol solution and the kH550 silane coupling agent in the preparation method of the composite filler is 10-12:10-12:175-180:2.5-3.0; The mass concentration of the ethanol solution is 35-40%.

5. The preparation method of the modified pyrazinium pyrophosphate halogen-free environmentally friendly flame retardant with high thermal stability according to claim 1, characterized in that, The mass ratio of the N,N-dimethylacetamide, the pretreated pyrazinium pyrophosphate and the modifier in the modification step is 100:12-15:4-7; The mass ratio of the modified pyrazinium pyrophosphate, the melamine cyanurate, the aluminum diethylphosphinate, the melamine polyphosphate, the talcum powder and the polyethylene glycol 400 solution is 30-50:30-40:1-10:1-5:6-8:25-30; The polyethylene glycol 400 solution is a mixture of polyethylene glycol 400 and deionized water, and the mass ratio of the polyethylene glycol 400 and the deionized water is 1.0-1.4:100.

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