1. A novel phosphorus-nitrogen flame retardant and a preparation method thereof are disclosed, wherein the flame retardant is characterized by having excellent flame retardant efficiency and thermal stability.

2. The process according to claim 1, wherein phosphorus oxychloride is reacted with piperazine or methylpiperazine to give a chlorophosphamide compound. Hydrolyzing the chlorophosphoramide compound to obtain the phosphoric acid amide compound. The final flame retardant, the pyrophosphoamide compound, is prepared by intermolecular dehydration reaction of the phosphoramidate compound in an inert atmosphere or a high boiling point solvent.

3. The reaction between phosphorus oxychloride and piperazine or methylpiperazine according to claim 2, characterized in that the molar ratio between phosphorus oxychloride and piperazine or methylpiperazine is 2: 1 or 1:1, adding piperazine and methyl piperazine in a slow mode, wherein the reaction temperature is 0-10 ℃, the reaction time is 0.5-3 hours, and the reaction solvent is selected from anhydrous solvents.

4. The hydrolysis reaction according to claim 2, wherein an excess amount of water is added to the system after the reaction according to claim 3, the reaction temperature is 80 ℃ and the reaction time is 1 to 3 hours.

5. The hydrolysis reaction of claim 2, which is carried out in an inert atmosphere or in a high boiling solvent at a temperature of 250 ℃ to 320 ℃ for a period of 1 to 3 hours.

6. The reaction conditions as claimed in claim 5, wherein the apparatus is selected from the group consisting of kneaders, vacuum rakes, and orbital furnaces, and the solvent is selected from the group consisting of triphenyl phosphate.

Background

Polymeric materials are commonly used, but are extremely flammable. The inflammability of the high polymer material leads to multiple accidents, and harms the life and property safety of people and the development of various industries. The flame retardant can effectively inhibit the inflammability of the high polymer material and reduce the fire risk. The development of the halogen-containing flame retardant is early, the application is wide, but with the annual improvement of the environmental protection requirement, the increment of the halogen-free flame retardant is obviously considered as the development trend of the future flame retardant. The phosphorus-nitrogen flame retardant has excellent performance in the halogen-free flame retardant due to the phosphorus-nitrogen synergistic effect. However, the phosphorus-nitrogen flame retardants in the current market are few in types and mainly comprise ammonium polyphosphate, melamine polyphosphate, piperazine pyrophosphate and melamine cyanurate.

Piperazine contains nitrogen source and has excellent carbon forming performance, so that the flame retardant performance of piperazine pyrophosphate is excellent. However, since phosphoric acid is ionically bonded to piperazine, thermal stability is limited, and the use of phosphoric acid is limited to polyolefin materials, and degradation and discoloration problems occur during thermal processing.

In conclusion, the invention provides a novel phosphorus-nitrogen flame retardant, wherein piperazine reacts with phosphorus oxychloride to directly generate phosphorus-nitrogen bonds and generate a polyphosphoric acid structure, so that the thermal stability and the flame retardant efficiency are improved.

Disclosure of Invention

The invention provides a novel phosphorus-nitrogen flame retardant and a preparation method thereof. The material can be used as a novel halogen-free environment-friendly phosphorus-nitrogen flame retardant, and the heat stability and the flame retardant efficiency are improved by using a phosphoric acid amide and polyphosphoric acid structure. The material has good thermal stability and flame retardant property, and the preparation method is practical and suitable for industrial production.

The technical scheme of the invention is as follows:

phosphorus oxychloride and piperazine or methylpiperazine in a molar ratio of 2: 1 or 1:1, and the reaction temperature is 0-10 ℃ to obtain the chlorophosphamide compound. Hydrolyzing the chlorophosphoramide compound to obtain the phosphoric acid amide compound. The phosphoric acid amide compound is dehydrated in inert atmosphere or high boiling point solvent to prepare the pyrophosphoric acid amide compound, and the reaction temperature is 250-320 ℃. As shown in fig. 2.

In one embodiment, a molar ratio of 2: 1, phosphorus oxychloride and piperazine, and anhydrous toluene as solvent, wherein the reaction temperature is 0 ℃, and the reaction time is 0.5-3 hours. The product is a white chlorophosphoric acid amide compound.

In one embodiment, excess water is added into a reaction system of phosphorus oxychloride and piperazine, and the reaction is carried out under the protection of inert gas, wherein the reaction temperature is 80 ℃, and the reaction time is 1-3 hours. The inert gas is nitrogen, carbon dioxide or argon.

In one embodiment, the phosphoramidate compound is subjected to intermolecular dehydration reaction in an inert atmosphere or a high boiling point solvent to obtain a pyrophosphoamide product, wherein the reaction temperature is 250 ℃ to 320 ℃ and the reaction time is 1 to 3 hours. The equipment can be selected from a kneader, a vacuum rake machine and an orbital furnace, and the solvent can be selected from triphenyl phosphate.

In one embodiment, a molar ratio of 1:1 phosphorus oxychloride and methylpiperazine, anhydrous toluene as solvent, the reaction temperature is 0 ℃, the reaction time is 0.5-3 hours. The product is a white chlorophosphoric acid amide compound.

In one embodiment, excessive water is added into a reaction system of phosphorus oxychloride and methylpiperazine, and the reaction is carried out under the protection of inert gas, wherein the reaction temperature is 80 ℃, and the reaction time is 1-3 hours. The inert gas is nitrogen, carbon dioxide or argon.

In one embodiment, the phosphoramidate compound is subjected to intermolecular dehydration reaction in an inert atmosphere or a high boiling point solvent to obtain a pyrophosphoamide product, wherein the reaction temperature is 250 ℃ to 320 ℃ and the reaction time is 1 to 3 hours. The equipment can be selected from a kneader, a vacuum rake machine and an orbital furnace, and the solvent can be selected from triphenyl phosphate.

In one embodiment, adding PP, nylon 6 or nylon 66 and a flame retardant into a mixer, and uniformly stirring to obtain a premix; adding the premix into a hopper of a double-screw extruder feeder, adding fibers from a side feeding port, and performing melt mixing, extrusion and granulation to obtain the flame-retardant composite material.

Advantageous effects

Novel phosphorus-nitrogen synergistic environment-friendly flame retardant. The piperazine ring is not only a nitrogen source provider, but also the aliphatic ring structure thereof can effectively induce carbon formation, thereby improving the flame retardant efficiency. The piperazine structure is connected with the phosphoric acid structure by an N-P phosphorus-nitrogen bond, so that the thermal stability is improved.

The preparation method of the flame retardant is simple, convenient and practical, and is suitable for industrial production.

Drawings

FIG. 1 is a schematic representation of a novel phosphorus-nitrogen flame retardant of the present application;

FIG. 2 is a chemical reaction equation for the synthesis of phosphoric acid amide compounds and polyphosphoric acid amide compounds according to the present application;

FIG. 3 is a thermogravimetric analysis of the pyrophosphoric piperazine amide of the present application.

Detailed Description

Reference throughout this specification to "one embodiment," "another embodiment," "an implementation," or the like, means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment described generally throughout this application. The appearances of the same phrase in various places in the specification are not necessarily all referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with any embodiment, it is submitted that it is within the purview of this application to effect such feature, structure, or characteristic in connection with other ones of the embodiments.

The present invention will be described in further detail with reference to the following embodiments. It will be understood by those skilled in the art that the following examples are illustrative of the present invention only and should not be taken as limiting the scope of the invention. The examples do not specify particular techniques or conditions, and are performed according to the techniques or conditions described in the literature in the art or according to the product specifications. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products commercially available.

Example 1

10 kg of phosphorus oxychloride is added into the reaction kettle, the rotating speed is increased to 60rmp, and the temperature is reduced to 0 ℃. 2.8 kg of piperazine were added in a slow manner and the reaction was carried out for 1 hour. After adding excessive distilled water, the temperature was raised to 80 ℃ and the reaction was carried out for 1.5 hours to obtain 11.1 kg of piperazine phosphate amide white solid. Adding phosphoric piperazine amide into a vacuum kneader, increasing the rotating speed to 50rpm, replacing the nitrogen for more than three times, heating to 280 ℃, and reacting for 3 hours to obtain the product of the pyrophosphoric piperazine amide, wherein the weight of the product is 10.5 kg.

Example 2

10 kg of phosphorus oxychloride is added into the reaction kettle, the rotating speed is increased to 60rmp, and the temperature is reduced to 10 ℃. Dissolving 2.8 kg of piperazine by using anhydrous toluene as a solvent, slowly adding the piperazine into phosphorus oxychloride, and reacting for 1 hour. After adding excessive distilled water, the temperature is raised to 80 ℃, and after 1.5 hours of reaction, toluene and water are distilled out under reduced pressure to obtain 11.5 kg of piperazine phosphate amide white solid. Adding phosphoric piperazine amide into a vacuum kneader, increasing the rotating speed to 50rpm, replacing the nitrogen for more than three times, heating to 280 ℃, and reacting for 3 hours to obtain 11 kg of pyrophosphoric piperazine amide product.

Example 3

10 kg of phosphorus oxychloride is added into the reaction kettle, the rotating speed is increased to 60rmp, and the temperature is reduced to 10 ℃. 6.5 kg of methyl piperazine is dissolved by taking anhydrous toluene as a solvent, and the methyl piperazine is slowly added into phosphorus oxychloride for reaction for 1 hour. After adding excessive distilled water, raising the temperature to 80 ℃, reacting for 2 hours, and distilling out toluene and water under reduced pressure to obtain 15.3 kg of methylpiperazine amide white solid. Adding phosphoric piperazine amide into a vacuum kneader, increasing the rotating speed to 50rpm, replacing the nitrogen for more than three times, heating to 280 ℃, and reacting for 3 hours to obtain 14.5 kg of pyrophosphoric piperazine amide product.

Example 4

10 kg of phosphorus oxychloride is added into the reaction kettle, the rotating speed is increased to 60rmp, and the temperature is reduced to 5 ℃. Dissolving 2.8 kg of piperazine by using anhydrous toluene as a solvent, slowly adding the piperazine into phosphorus oxychloride, and reacting for 1 hour. After adding excessive distilled water, raising the temperature to 90 ℃, reacting for 2 hours, and distilling out toluene and water under reduced pressure to obtain 11.3 kg of piperazine phosphate amide white solid. Adding phosphoric piperazine amide into a vacuum rake dryer, increasing the rotating speed to 50rpm, replacing the nitrogen for more than three times, increasing the temperature to 265 ℃, and reacting for 5 hours to obtain 10.9 kg of pyrophosphoric piperazine amide product.

Example 5

Taking the matrix resin as nylon 66 as an example: 63% of nylon 66 and 7% of pyrophosphate piperazine amide are weighed according to the weight. Adding the mixture into a mixer and uniformly stirring to obtain a premix; adding the premix into a hopper of a double-screw extruder feeder, adding 30% of fibers from a side feeding port, and performing melt mixing, extrusion and granulation. The temperature of each section of the extrusion process is respectively as follows: the nylon-burning flame retardant material is prepared at the temperature of 250-260 ℃ in the conveying section, 270-290 ℃ in the melting section, 270-290 ℃ in the shearing section, 260-280 ℃ in the exhaust section and 260-280 ℃ in the extrusion section. The spline combustion test shows that the UL94-V2 rating is achieved.

Example 6

Taking the matrix resin as nylon 66 as an example: 60% of nylon 66 and 10% of pyrophosphate piperazine amide are weighed. Adding the mixture into a mixer and uniformly stirring to obtain a premix; adding the premix into a hopper of a double-screw extruder feeder, adding 30% of fibers from a side feeding port, and performing melt mixing, extrusion and granulation. The temperature of each section of the extrusion process is respectively as follows: the nylon-burning flame retardant material is prepared at the temperature of 250-260 ℃ in the conveying section, 270-290 ℃ in the melting section, 270-290 ℃ in the shearing section, 260-280 ℃ in the exhaust section and 260-280 ℃ in the extrusion section. The spline combustion test shows that the UL94-V1 rating is achieved.

Example 7

Taking the matrix resin as nylon 66 as an example: weighing 55% of nylon 66 and 15% of pyrophosphate piperazine amide by weight. Adding the mixture into a mixer and uniformly stirring to obtain a premix; adding the premix into a hopper of a double-screw extruder feeder, adding 30% of fibers from a side feeding port, and performing melt mixing, extrusion and granulation. The temperature of each section of the extrusion process is respectively as follows: the nylon-burning flame retardant material is prepared at the temperature of 250-260 ℃ in the conveying section, 270-290 ℃ in the melting section, 270-290 ℃ in the shearing section, 260-280 ℃ in the exhaust section and 260-280 ℃ in the extrusion section. The spline combustion test shows that the UL94-V0 rating is achieved.

Comparative example 1

Taking the matrix resin as nylon 66 as an example: nylon 66 was weighed 60% by weight, and a commercial flame retardant 10%. Adding the mixture into a mixer and uniformly stirring to obtain a premix; adding the premix into a hopper of a double-screw extruder feeder, adding 30% of fibers from a side feeding port, and performing melt mixing, extrusion and granulation. The temperature of each section of the extrusion process is respectively as follows: the nylon-burning flame retardant material is prepared at the temperature of 250-260 ℃ in the conveying section, 270-290 ℃ in the melting section, 270-290 ℃ in the shearing section, 260-280 ℃ in the exhaust section and 260-280 ℃ in the extrusion section. The spline combustion test shows that the UL94-V2 rating is achieved.

Comparative example 2

Taking the matrix resin as nylon 66 as an example: nylon 66 was weighed 56% by weight, and a commercially available flame retardant 14%. Adding the mixture into a mixer and uniformly stirring to obtain a premix; adding the premix into a hopper of a double-screw extruder feeder, adding 30% of fibers from a side feeding port, and performing melt mixing, extrusion and granulation. The temperature of each section of the extrusion process is respectively as follows: the nylon-burning flame retardant material is prepared at the temperature of 250-260 ℃ in the conveying section, 270-290 ℃ in the melting section, 270-290 ℃ in the shearing section, 260-280 ℃ in the exhaust section and 260-280 ℃ in the extrusion section. The spline combustion test shows that the UL94-V2 rating is achieved.

Comparative example 3

Taking the matrix resin as nylon 66 as an example: 50% by weight of nylon 66 and 20% by weight of a commercially available flame retardant were weighed. Adding the mixture into a mixer and uniformly stirring to obtain a premix; adding the premix into a hopper of a double-screw extruder feeder, adding 30% of fibers from a side feeding port, and performing melt mixing, extrusion and granulation. The temperature of each section of the extrusion process is respectively as follows: the nylon-burning flame retardant material is prepared at the temperature of 250-260 ℃ in the conveying section, 270-290 ℃ in the melting section, 270-290 ℃ in the shearing section, 260-280 ℃ in the exhaust section and 260-280 ℃ in the extrusion section. The spline combustion test shows that the UL94-V2 rating is achieved.

TABLE 1 flame retardancy test results of examples and comparative examples

As is apparent from the test results of the examples and comparative examples in table 1: under the condition of reaching the same flame retardant grade, the dosage of the novel flame retardant is obviously less than that of the commercially available flame retardant. For the glass fiber reinforced nylon material, the flame retardant can achieve satisfactory effect with less addition amount of the novel flame retardant under the condition of not needing complex modification. As seen from the second graph, the 1% thermal decomposition temperature of the novel flame retardant is as high as 390 ℃, and the thermal stability is excellent. The flame-retardant nylon reinforced material added with the pyrophosphoric piperazine amide flame retardant obviously inhibits the yellowing phenomenon during processing.