Composite intumescent flame retardant and preparation method thereof

Abstract

The invention provides a composite intumescent flame retardant and a preparation method thereof.The preparation method comprises the following steps that S1, phosphoric acid is added into a melamine aqueous solution for a reaction, and a mixture A is obtained; s2, adding a piperazine aqueous solution into the mixture A for reaction, and filtering and drying to obtain an intermediate; and S3, placing the intermediate in an inert gas atmosphere, and carrying out a heating reaction to obtain the intumescent flame retardant. The flame retardant obtained by the invention has the characteristics of high P and N content and excellent flame retardant property, can be used in resin systems such as polypropylene and the like, and is used for improving the flame retardant effect of resin.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of environment-friendly phosphorus-based intumescent flame retardant, and particularly relates to a composite intumescent flame retardant and a preparation method thereof. BACKGROUND

[0002] Intumescent flame retardant (IFR) is a kind of environmentally friendly green flame retardant, which does not contain halogen and does not use antimony oxide as a synergist. The system itself has synergistic effect. The plastic containing intumescent flame retardant can generate a carbon foam layer on the surface during combustion, which can play the role of heat insulation, oxygen insulation, smoke suppression and drip prevention, has excellent flame retardant performance, and is low in smoke and toxicity, and does not produce corrosive gas, which meets the research and development direction of future flame retardants, and has become one of the most active flame retardant research fields at home and abroad.

[0003] When the intumescent flame retardant is added to the polymer material, it is required to have good thermal stability and can withstand high temperature above 200℃ in the polymer processing process; a large amount of volatile substances are released due to thermal degradation, and residues are formed, so the process should not have adverse effects on the intumescent foaming process; the flame retardant is uniformly distributed in the polymer, and can form an expanded carbon layer completely covering the surface of the material during material combustion; the flame retardant must have good compatibility with the flame-retardant high polymer, and cannot have adverse effects with the high polymer and additives, and cannot excessively deteriorate the physical and mechanical properties of the material. The intumescent flame retardant is superior to the general flame retardant in that it is halogen-free and antimony-free, low in smoke and toxicity, and free of corrosive gas; the carbon layer generated by the intumescent flame retardant can absorb the molten polymer on fire to prevent the molten polymer from dripping and spreading the fire.

[0004] Patent CN105837855A discloses a halogen-free flame retardant, a preparation method thereof and a flame-retardant polyolefin composition composed of the flame retardant. Melamine, phosphoric acid and piperazine are blended according to a molar ratio of 1: (5-10): (1-5), and then high-temperature dehydration condensation is performed to obtain a composite halogen-free flame retardant. In the patent, the amount of phosphoric acid added is 5-10 times that of melamine, and the flame-retardant efficiency is improved by adding a large amount of phosphoric acid. However, the product is troublesome to process after a large amount of phosphoric acid is added, the excess phosphoric acid introduced into the resin corrodes the equipment in the processing process, and the excess phosphoric acid also affects the mechanical properties of the base body. SUMMARY

[0005] The present application provides a preparation method of intumescent flame retardant, which comprises the following steps: S1, adding phosphoric acid into a melamine aqueous solution to react, to obtain a mixture A; S2, adding a piperazine aqueous solution into the mixture A to react, and then filtering and drying to obtain an intermediate; S3, placing the intermediate in an inert gas atmosphere to react under heating, to obtain an intumescent flame retardant.

[0006] Further, the molar ratio of phosphoric acid, melamine and piperazine is (3-7):(1-5):1.

[0007] Further, the molar ratio of phosphoric acid, melamine and piperazine is (3-7):(1-5):1.

[0008] Further, the phosphoric acid is a water solution with a mass content of 85%; the purity of the melamine is ≥99.0%; and the purity of the piperazine is ≥99.0% with no water content. Further, the mass concentration of the melamine water solution is 2%-20%; and the mass concentration of the piperazine water solution is 5%-10%.

[0009] Further, the reaction condition of S1 is 70-95℃ for 1-2h; and the reaction condition of S2 is 70-95℃ for 2-3h.

[0010] Further, the reaction condition of S3 is stepwise heating, the first segment temperature is 200-220℃ for 0.5-1.5h; and the second segment temperature is 260-300℃ for 1.5-2.5h.

[0011] The application further provides a composite intumescent flame retardant comprising the intumescent flame retardant prepared by the preparation method.

[0012] Further, the P content of the intumescent flame retardant is 16wt%-25wt%, and the N content is 35wt%-45wt%.

[0013] Further, the composite intumescent flame retardant further comprises a flame-retardant synergist; the flame-retardant synergist comprises zinc oxide, and the addition amount is 1%-6% of the composite intumescent flame retardant.

[0014] The application further provides a polypropylene composite material comprising 70-90 parts of polypropylene resin and 15-25 parts of the intumescent flame retardant or the composite intumescent flame retardant.

[0015] The application has the following advantages: The preparation method of the flame retardant can significantly improve the P and N contents of the flame retardant, thereby improving the flame-retardant effect; and when the flame retardant is added to the resin without adding an anti-dripping agent (such as polytetrafluoroethylene), the vertical burning level can reach V-0, and the oxygen index is >30%. DETAILED DESCRIPTION

[0016] The embodiments of the application will be described in detail below with reference to the examples, which are only used to illustrate the application and should not be regarded as limiting the scope of the application.

[0017] Example 1 The molar ratio of phosphoric acid, melamine and piperazine is 0.25:0.15:0.1.

[0018] Take 18.9g of melamine and 500g of pure water into the reaction bottle, heat to 85℃, after the melamine is dissolved, add 28.8g of 85% phosphoric acid into the reaction bottle at the rate of two seconds per drop, control the temperature at 90℃, and keep it at 90℃ for 2h, then add 100g of piperazine aqueous solution containing 8.6g of piperazine into the reaction bottle, keep it at 95℃ for 2h. After the reaction is completed, place the material in an ice water bath for 4h, reduce the temperature to 20℃. After filtering the cooled material, place it in a forced air drying oven at 100℃ for drying, then grind it to obtain the intermediate.

[0019] Place the obtained intermediate in a tube furnace, heat it in stages under nitrogen atmosphere, the first stage temperature is 200℃, keep it for 1h, the second stage temperature is 260℃, keep it for 2h, to obtain the intumescent flame retardant.

[0020] Then put zinc oxide and intumescent flame retardant together into a laboratory high-speed homogenizer at a mass ratio of 3:97, stir at 3000rpm for 2min to obtain the target product, composite intumescent flame retardant.

[0021] A polypropylene composite material is prepared, 76 parts of polypropylene resin and 24 parts of the above-mentioned composite intumescent flame retardant are added into a mixing mill, melt blended at 200℃, then placed in a flat vulcanizing machine, press molded at 200℃ for 5min, and pressed into a sheet to prepare a polypropylene composite material sample for testing.

[0022] Example 2 The molar ratio of phosphoric acid, melamine and piperazine is 0.325:0.225:0.1.

[0023] Take 28.35g of melamine and 500g of pure water into the reaction bottle, heat to 85℃, after the melamine is dissolved, add 37.5g of 85% phosphoric acid into the reaction bottle at the rate of two seconds per drop, control the temperature at 90℃, and keep it at 90℃ for 2h, then add 100g of piperazine aqueous solution containing 8.6g of piperazine into the reaction bottle, keep it at 95℃ for 2h. After the reaction is completed, place the material in an ice water bath for 4h, reduce the temperature to 20℃. After filtering the cooled material, place it in a forced air drying oven at 100℃ for drying, then grind it to obtain the intermediate.

[0024] Place the obtained intermediate in a tube furnace, heat it in stages under nitrogen atmosphere, the first stage temperature is 200℃, keep it for 1h, the second stage temperature is 260℃, keep it for 2h, to obtain the intumescent flame retardant.

[0025] The zinc oxide and the intumescent flame retardant are put into a laboratory high-speed cell disrupter together according to a mass ratio of 3:97, stirred at 3000 rpm for 2 min, and the target product, a composite intumescent flame retardant, is obtained.

[0026] A polypropylene composite material is prepared as follows: 76 parts of polypropylene resin and 24 parts of the composite intumescent flame retardant are added into a mixing mill, fully melt-blended at 200℃, and then put into a flat vulcanizing machine to be pressure molded at 200℃ for 5 min to prepare a polypropylene composite material sample for testing.

[0027] Example 3 The molar ratio of phosphoric acid, melamine and piperazine is 0.4:0.3:0.1.

[0028] 37.8 g of melamine and 500 g of pure water are weighed into a reaction bottle, heated to 85℃, and after the melamine is dissolved, 46.1 g of 85% phosphoric acid is added dropwise into the reaction bottle at a rate of two drops per second, the temperature is controlled at 90℃, and the temperature is kept at 90℃ for 2 h, then 100 g of an aqueous piperazine solution containing 8.6 g of piperazine is added dropwise into the reaction bottle, and the temperature is kept at 95℃ for 2 h. After the reaction is completed, the material is placed in an ice water bath for 4 h, and the temperature is reduced to 20℃. The cooled material is filtered and placed in a forced air drying oven at 100℃ for drying, and then ground to obtain an intermediate.

[0029] The obtained intermediate is placed in a tube furnace and heated in a nitrogen atmosphere in stages, the first stage temperature is 200℃, and the temperature is kept for 1 h; the second stage temperature is 260℃, and the temperature is kept for 2 h; and an intumescent flame retardant is obtained.

[0030] The zinc oxide and the intumescent flame retardant are put into a laboratory high-speed cell disrupter together according to a mass ratio of 3:97, stirred at 3000 rpm for 2 min, and the target product, a composite intumescent flame retardant, is obtained.

[0031] A polypropylene composite material is prepared as follows: 76 parts of polypropylene resin and 24 parts of the composite intumescent flame retardant are added into a mixing mill, fully melt-blended at 200℃, and then put into a flat vulcanizing machine to be pressure molded at 200℃ for 5 min to prepare a polypropylene composite material sample for testing.

[0032] Example 4 The molar ratio of phosphoric acid, melamine and piperazine is 0.475:0.375:0.1.

[0033] Take 47.25g melamine and 500g pure water into the reaction bottle, heat to 85℃, after the melamine is dissolved, add 54.8g 85% phosphoric acid into the reaction bottle at the rate of two seconds per drop, control the temperature at 90℃, and keep at 90℃ for 2h, then add 100g piperazine aqueous solution containing 8.6g piperazine into the reaction bottle, keep at 95℃ for 2h. After the reaction is completed, the material is placed in an ice water bath for 4h, and the temperature is reduced to 20℃. After the cooled material is filtered, it is placed in a forced air drying oven at 100℃ for drying, then ground to obtain the intermediate.

[0034] Put the obtained intermediate into a tube furnace, heat in stages under nitrogen atmosphere, the first stage temperature is 200℃, keep for 1h; the second stage temperature is 260℃, keep for 2h, to obtain the intumescent flame retardant.

[0035] Put zinc oxide and intumescent flame retardant into a laboratory high-speed cell disrupter at a mass ratio of 3:97, stir at 3000rpm for 2min to obtain the target product, composite intumescent flame retardant.

[0036] A polypropylene composite material is prepared, 76 parts of polypropylene resin and 24 parts of the above-mentioned composite intumescent flame retardant are added into a banbury mixer, fully melt blended at 200℃, then put into a flat curing machine, press at 200℃ for 5min, and press into a sheet to prepare a polypropylene composite material sample for testing.

[0037] Example 5 The molar ratio of phosphoric acid, melamine and piperazine is 0.55:0.45:0.1.

[0038] Take 47.25g melamine and 500g pure water into the reaction bottle, heat to 85℃, after the melamine is dissolved, add 54.8g 85% phosphoric acid into the reaction bottle at the rate of two seconds per drop, control the temperature at 90℃, and keep at 90℃ for 2h, then add 100g piperazine aqueous solution containing 8.6g piperazine into the reaction bottle, keep at 95℃ for 2h. After the reaction is completed, the material is placed in an ice water bath for 4h, and the temperature is reduced to 20℃. After the cooled material is filtered, it is placed in a forced air drying oven at 100℃ for drying, then ground to obtain the intermediate.

[0039] Put the obtained intermediate into a tube furnace, heat in stages under nitrogen atmosphere, the first stage temperature is 200℃, keep for 1h; the second stage temperature is 260℃, keep for 2h, to obtain the intumescent flame retardant.

[0040] Put zinc oxide and intumescent flame retardant into a laboratory high-speed cell disrupter at a mass ratio of 3:97, stir at 3000rpm for 2min to obtain the target product, composite intumescent flame retardant.

[0041] A polypropylene composite material is prepared by adding 76 parts by weight of polypropylene resin and 24 parts by weight of the above-mentioned composite intumescent flame retardant into a mixing mill, fully melting and blending at 200°C, and then putting into a flat vulcanizing machine to be pressed and molded at 200°C for 5 minutes to prepare a polypropylene composite material sample for testing.

[0042] Example 6 The molar ratio of phosphoric acid, melamine and piperazine is 0.4:0.3:0.1.

[0043] 37.8g of melamine and 500g of pure water are weighed into a reaction bottle, heated to 85°C, and after the melamine is dissolved, 46.1g of 85% phosphoric acid is added dropwise into the reaction bottle at a rate of two drops per second, the temperature is controlled at 90°C, and the reaction is kept at 90°C for 2 hours, then 100g of an aqueous piperazine solution containing 8.6g of piperazine is added dropwise into the reaction bottle, and the reaction is kept at 95°C for 2 hours. After the reaction is completed, the material is placed in an ice water bath for 4 hours to reduce the temperature to 20°C. The cooled material is filtered and placed in a forced air drying oven at 100°C for drying, and then ground to obtain the intermediate.

[0044] The obtained intermediate is placed in a tube furnace and heated in a nitrogen atmosphere in stages, the first stage temperature is 200°C, and the temperature is kept for 1 hour; the second stage temperature is 260°C, and the temperature is kept for 2 hours to obtain the intumescent flame retardant.

[0045] Zinc oxide and the intumescent flame retardant are placed in a laboratory high-speed cell disrupter at a mass ratio of 3:97, stirred at 3000rpm for 2 minutes to obtain the target product, a composite intumescent flame retardant.

[0046] A polypropylene composite material is prepared by adding 76 parts by weight of polypropylene resin and 24 parts by weight of the above-mentioned composite intumescent flame retardant into a mixing mill, fully melting and blending at 200°C, and then putting into a flat vulcanizing machine to be pressed and molded at 200°C for 5 minutes to prepare a polypropylene composite material sample for testing.

[0047] Example 7 The molar ratio of phosphoric acid, melamine and piperazine is 0.4:0.3:0.1.

[0048] Take 37.8g melamine and 500g pure water into the reaction bottle, heat to 85℃, after the melamine is dissolved, add 46.1g 85% phosphoric acid into the reaction bottle at the rate of two seconds per drop, control the temperature at 90℃, and keep at 90℃ for 2h, then add 100g piperazine aqueous solution containing 8.6g piperazine into the reaction bottle, keep at 95℃ for 2h. After the reaction is completed, the material is placed in an ice water bath for 4h, and the temperature is reduced to 20℃. After the cooled material is filtered, it is placed in a forced air drying oven at 100℃ for drying, then ground to obtain the intermediate.

[0049] Put the obtained intermediate into a tube furnace, heat in stages under nitrogen atmosphere, the first stage temperature is 200℃, keep for 1h; the second stage temperature is 260℃, keep for 2h, to obtain the intumescent flame retardant.

[0050] A polypropylene composite material is prepared, 85 parts of polypropylene resin and 15 parts of the intumescent flame retardant are added into a mixing mill, fully melt blended at 200℃, then put into a flat vulcanizing machine, press at 200℃ for 5min, and press into a sheet to prepare a polypropylene composite material sample for testing.

[0051] Example 8 Different from example 1, no stepwise heating is performed, i.e. the obtained intermediate is placed in a tube furnace, kept at 260℃ for 3h under nitrogen atmosphere to obtain the intumescent flame retardant. The rest is the same as example 1.

[0052] The molar ratio of phosphoric acid, melamine and piperazine is 0.25:0.15:0.1.

[0053] Take 37.8g melamine and 500g pure water into the reaction bottle, heat to 85℃, after the melamine is dissolved, add 46.1g 85% phosphoric acid into the reaction bottle at the rate of two seconds per drop, control the temperature at 90℃, and keep at 90℃ for 2h, then add 100g piperazine aqueous solution containing 8.6g piperazine into the reaction bottle, keep at 95℃ for 2h. After the reaction is completed, the material is placed in an ice water bath for 4h, and the temperature is reduced to 20℃. After the cooled material is filtered, it is placed in a forced air drying oven at 100℃ for drying, then ground to obtain the intermediate.

[0054] Put the obtained intermediate into a tube furnace, heat at 260℃ for 3h under nitrogen atmosphere; to obtain the intumescent flame retardant.

[0055] Then put zinc oxide and the intumescent flame retardant together into a laboratory high-speed homogenizer at a mass ratio of 3:97, stir at 3000rpm for 2min to obtain the target product, composite intumescent flame retardant.

[0056] The preparation of a polypropylene composite material involves adding 76 parts by weight of polypropylene resin and 24 parts by weight of the above-mentioned composite intumescent flame retardant into a mixer, fully melting and mixing at 200°C, then placing it in a flat vulcanizing machine and pressing it at 200°C for 5 minutes to compress and form a polypropylene composite material sample for testing.

[0057] Comparative Example 1 The molar ratio of phosphoric acid to melamine is 0.15:0.15.

[0058] Weigh 18.9g of melamine and 500g of pure water and add them to a reaction flask. Heat the mixture to 85℃ and, after the melamine dissolves, add 17.3g of 85% phosphoric acid dropwise at a rate of one drop every two seconds, controlling the dropping temperature at 90℃. Maintain this temperature for 2 hours. After the reaction is complete, place the material in an ice-water bath for 4 hours, then lower the temperature to 20℃. Filter the cooled material and dry it in a forced-air drying oven at 100℃. Then grind the dried material to obtain an intermediate.

[0059] The obtained intermediate was placed in a tube furnace and heated in a nitrogen atmosphere in stages. The first stage temperature was 200℃ and held for 1 hour; the second stage temperature was 260℃ and held for 2 hours to obtain an intumescent flame retardant.

[0060] Zinc oxide and intumescent flame retardant were placed together in a laboratory high-speed blender at a mass ratio of 3:97 and stirred at 3000 rpm for 2 minutes to obtain the target product, melamine polyphosphate.

[0061] The preparation of a polypropylene composite material involves adding 76 parts by weight of polypropylene resin and 24 parts by weight of the above-mentioned melamine polyphosphate flame retardant into a mixer, fully melting and mixing at 200°C, then placing it in a flat vulcanizing machine and pressing it at 200°C for 5 minutes to compress and form a polypropylene composite material sample for testing.

[0062] Comparative Example 2 The molar ratio of phosphoric acid to piperazine is 0.2:0.1.

[0063] Weigh 500g of pure water and add it to a reaction flask. Heat the flask to 85℃, then add 23.1g of 85% phosphoric acid dropwise, controlling the addition temperature at 90℃, and maintain this temperature for 2 hours. Next, add 100g of a piperazine aqueous solution containing 8.6g of piperazine dropwise to the reaction flask, and maintain the temperature at 95℃ for 2 hours. After the reaction is complete, place the material in an ice-water bath for 4 hours, then lower the temperature to 20℃. Filter the cooled material, dry it in a forced-air drying oven at 100℃, and then grind it to obtain an intermediate.

[0064] The obtained intermediate is placed in a tube furnace, and is subjected to stepwise temperature rising under a nitrogen atmosphere, the first section temperature is 200 DEG C, and the holding time is 1h; the second section temperature is 260 DEG C, and the holding time is 2h, to obtain the intumescent flame retardant.

[0065] The zinc oxide and the intumescent flame retardant are placed in a laboratory high-speed wall breaking machine at a mass ratio of 3:97, and are stirred at 3000 rpm for 2 min to obtain the target product piperazine pyrophosphate.

[0066] A polypropylene composite material is prepared, and 76 parts of polypropylene resin and 24 parts of the above-mentioned piperazine pyrophosphate flame retardant are added into a mixing mill, and are fully melt blended at 200 DEG C, and then are placed into a flat vulcanizing machine, and are subjected to pressure molding at 200 DEG C for 5 min to prepare a polypropylene composite material sample for testing.

[0067] The polypropylene composite materials obtained in the above examples and comparative examples are tested, and the P and N contents of the intumescent flame retardant are tested; the test standards or methods are as follows: The oxygen index is determined according to the national standard GB / T 2406.1-2008; The UL94 vertical burning grade (thickness 1.6mm) is determined according to the national standard GB / T 2408-2021; The tensile strength is tested according to the national standard GB / T 1040.3-2006; The phosphorus content test method is a quinoline molybdenum ketone weight method after digestion; The nitrogen content test method is determined by an elemental analyzer; The test results are shown in Table 1.

[0068] Table 1

[0069] The present application synthesizes a composite intumescent flame retardant for the flame retardance of a polypropylene composite material. As can be seen from Table 1, the oxygen index of the composite intumescent flame retardant prepared by adding different molar ratios is effectively improved. Without adding an anti-dripping agent, the vertical burning grade can reach V-0.

Claims

1. A method for preparing an intumescent flame retardant, characterized in that, Includes the following steps: S1. Phosphoric acid is added to an aqueous solution of melamine to react and obtain mixture A; S2. Add the piperazine aqueous solution to mixture A to carry out the reaction, filter and dry to obtain the intermediate; S3. The intermediate is heated in an inert gas atmosphere to react and obtain an intumescent flame retardant.

2. The method for preparing an intumescent flame retardant according to claim 1, characterized in that, The molar ratio of phosphoric acid to melamine is (1.2-2):

1.

3. The method for preparing an intumescent flame retardant according to claim 1, characterized in that, The molar ratio of phosphoric acid, melamine and piperazine is (3-7):(1-5):

1.

4. The method for preparing an intumescent flame retardant according to claim 1, characterized in that, The phosphoric acid is an aqueous solution with a phosphoric acid content of 85% by mass; the melamine has a purity of ≥99.0%; the piperazine has a purity of ≥99.0% and the water content is anhydrous. The melamine aqueous solution has a mass concentration of 2%-20%; the piperazine aqueous solution has a mass concentration of 5%-10%.

5. The method for preparing an intumescent flame retardant according to claim 1, characterized in that, The reaction conditions described in S1 are: 70-95℃ for 1-2 hours; the reaction conditions described in S2 are: 70-95℃ for 2-3 hours.

6. The method for preparing an intumescent flame retardant according to claim 1, characterized in that, The reaction conditions described in S3 are a stepwise increase in temperature, with the first stage temperature being 200-220℃ and held for 0.5-1.5 hours; and the second stage temperature being 260-300℃ and held for 1.5-2.5 hours.

7. A composite intumescent flame retardant, characterized in that, Including intumescent flame retardants prepared by the preparation method according to any one of claims 1-6.

8. The composite intumescent flame retardant according to claim 7, characterized in that, The intumescent flame retardant has a phosphorus content of 16wt%-25wt% and an nitrogen content of 35wt%-45wt%.

9. The composite intumescent flame retardant according to claim 7, characterized in that, It also includes flame retardant synergists; the flame retardant synergists include zinc oxide, and the amount added accounts for 1%-6% of the composite intumescent flame retardant.

10. A polypropylene composite material, characterized in that, It includes 70-90 parts of polypropylene resin and 15-25 parts of the intumescent flame retardant as described in claim 7.

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