Halogen-free flame retardant, preparation method and application in plastics

Abstract

The invention relates to the technical field of flame retardants, and discloses a halogen-free flame retardant, a preparation method and application of the halogen-free flame retardant in plastics. The preparation method comprises the following steps: synthesizing modified DOPO by taking DOPO, p-hydroxybenzaldehyde and phenol as raw materials, and mixing the modified DOPO with propargylamine and paraformaldehyde for reaction to obtain dialkynyl benzoxazine; the preparation method comprises the following steps: grafting dialkynyl benzoxazine and 1-azido adamantane through a click chemical reaction to obtain flame-retardant benzoxazine; the halogen-free flame retardant is obtained by carrying out in-situ polymerization on flame-retardant benzoxazine on the surface of the ammonium polyphosphate / molecular sieve composite material. The halogen-free flame retardant is excellent in flame retardant effect and good in compatibility in a matrix material, can effectively improve the flame retardant property and the mechanical property of the matrix material, and can be applied to plastic materials.

Description

Technical Field

[0001] The invention relates to the technical field of flame retardants, and in particular to a halogen-free flame retardant, a preparation method and application in plastics. Background Art

[0002] Flame retardants are additives used to improve the flame resistance of materials, reduce the probability of materials being ignited and inhibit further flame propagation. They are mainly used in polymer materials and are an important additive for composite materials. Flame retardants can be divided into halogen flame retardants, phosphorus flame retardants, nitrogen flame retardants, silicon flame retardants, inorganic flame retardants, nano flame retardants, etc. Halogen flame retardants are the flame retardants with the highest market share. They can achieve excellent flame retardant effects with very small addition amounts, and have good compatibility with matrix resins, etc., and basically do not affect the mechanical properties of the matrix materials. However, halogen flame retardants will generate a large amount of toxic gases during combustion, which are harmful to the environment and human health.

[0003] Ammonium polyphosphate, also known as ammonium polyphosphate or condensed ammonium phosphate, is a nitrogen-phosphorus composite high-efficiency halogen-free intumescent flame retardant (IFR) with broad application prospects. Due to its high nitrogen and phosphorus content, it has a good flame retardant effect; however, there are a large number of hydrophilic groups in the structure of ammonium polyphosphate, which has strong wettability, is not conducive to storage, and has poor compatibility with the matrix, so polymer materials usually have problems of decreased mechanical properties after adding ammonium polyphosphate modification. Prior art such as Chinese patent application CN102850592A discloses a method for preparing ammonium polyphosphate-polystyrene core-shell microspheres, through ultrasound-assisted in-situ polymerization, styrene is polymerized on the surface of ammonium polyphosphate to form a core-shell structure, improves the hydrophobicity of ammonium polyphosphate, and polystyrene as a shell layer also has a toughening effect, and the prepared ammonium polyphosphate-polystyrene core-shell microspheres have flame retardant, toughening and hydrophobic multiple functions, realizing the integration of toughening and flame retardant modification of polymer materials. However, although polystyrene improves the hydrophilicity of ammonium polyphosphate and improves its dispersibility in the polymer plastic matrix, polystyrene itself is not flame retardant and has no significant synergistic effect on improving the flame retardancy of the material. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a halogen-free flame retardant, a preparation method and an application in plastics. The halogen-free flame retardant has excellent flame retardant effect and good compatibility in a matrix material, and can be used as a flame retardant and toughening agent in the matrix material to improve the flame retardancy and mechanical properties of the matrix material.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing a halogen-free flame retardant comprises the following steps:

[0007] Step (1), mixing DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide), p-hydroxybenzaldehyde, phenol and p-toluenesulfonic acid, reacting, and after the reaction, purifying and drying to obtain modified DOPO;

[0008] Propargylamine, modified DOPO, paraformaldehyde and chloroform are mixed and stirred for reaction. After the reaction is completed, the reaction is continued. After the reaction is completed, the mixture is cooled and purified to obtain dialkynyl benzoxazine.

[0009] Step (2), mixing 1-azidoadamantane with N,N-dimethylformamide, adding tert-butyl alcohol and cuprous iodide in sequence and mixing evenly, then adding dialkynylbenzoxazine, reacting, and after the reaction is completed, precipitating, filtering, washing, and drying to obtain a flame-retardant benzoxazine;

[0010] Step (3), mixing the ammonium polyphosphate / molecular sieve composite material, flame-retardant benzoxazine, dimethyl silicone oil, and dichloromethane, ultrasonically dispersing, reacting, and continuing the reaction after the reaction is completed. After the reaction is completed, cooling, filtering, washing, and drying are performed to obtain a halogen-free flame retardant.

[0011] Preferably, in step (1), the mass ratio of DOPO, p-hydroxybenzaldehyde, phenol and p-toluenesulfonic acid is 11-15:6-7:25-35:0.3-0.4; when preparing modified DOPO, the reaction conditions are: reacting in a nitrogen atmosphere at a temperature of 120-130° C. for 24-26 hours.

[0012] Preferably, when preparing modified DOPO, the purification operation includes: obtaining a reaction product after the reaction is completed, adding ethanol 3-4 times the mass of the reaction product to mix and dissolve, after dissolution, adding 70-80°C hot water 3-4 times the mass of the reaction product to precipitate, repeating the dissolving and precipitating operation, and filtering.

[0013] Preferably, in the step (1), the mass ratio of propargylamine, modified DOPO, paraformaldehyde and chloroform is 5.5-6:20-22:6.5-7:200-250; when preparing dialkynylbenzoxazine, the reaction conditions are: stirring the reaction at 45-50°C for 0.5-1h, and the continued reaction conditions are: continuing the reaction at 60-70°C for 24-26h.

[0014] Preferably, when preparing dialkynylbenzoxazine, the purification operation includes: cooling to obtain a reaction product, adding 1 mol / L sodium hydroxide aqueous solution of 3-4 times the mass of the reaction product for mixed washing, separating the liquids, taking the organic phase, adding 3-4 times the mass of water of the organic phase for washing until neutral, separating the liquids to obtain the washed organic phase, and then adding 15-20% of the mass of the washed organic phase for dehydration with anhydrous sodium sulfate, filtering after dehydration, taking the filtrate, removing the solvent chloroform at a temperature of 35-45°C by rotary evaporation, and passing through a column.

[0015] Furthermore, the eluent in the column operation is prepared by mixing chloroform and acetone in a volume ratio of 40:1.

[0016] Preferably, in step (2), the mass ratio of 1-azidoadamantane, N,N-dimethylformamide, tert-butyl alcohol, cuprous iodide and dialkynylbenzoxazine is 23-25:110-150:15-17:0.1:55-60; and the reaction conditions are: reacting at a temperature of 25-30° C. for 24-26 hours.

[0017] Preferably, the precipitating agent used in the precipitation operation comprises water.

[0018] Preferably, in the step (3), the mass ratio of ammonium polyphosphate / molecular sieve composite material, flame retardant benzoxazine, dimethyl silicone oil and dichloromethane is 6-7:3-4:15-20:20-25; the reaction conditions are: react at a temperature of 150-160°C for 3-4h; and the continued reaction conditions are: continue to react at a temperature of 180°C for 1-1.5h.

[0019] Preferably, the washing agent used in the washing operation comprises dichloromethane.

[0020] Preferably, the ammonium polyphosphate / molecular sieve composite material in step (3) is prepared by the following steps:

[0021] The molecular sieve and the ammonium chloride aqueous solution are uniformly mixed, a regulator is added to adjust the pH value, and the reaction is carried out. After the reaction is completed, the mixture is cooled, filtered, and dried. After drying, a reaction product is obtained, and calcined to obtain an acidified molecular sieve;

[0022] The phosphoric acid aqueous solution is mixed with urea, heated, and an acidified molecular sieve is added to react. After the reaction is completed, the mixture is solidified. After solidification, the mixture is crushed and sieved to obtain an ammonium polyphosphate / molecular sieve composite material.

[0023] Preferably, in the preparation of the ammonium polyphosphate / molecular sieve composite material: the mass ratio of the molecular sieve to the ammonium chloride aqueous solution is 1:10-12, and the ammonium chloride aqueous solution is a 25wt% ammonium chloride aqueous solution; when preparing the acidified molecular sieve, the reaction conditions are: reacting at a pH value of 4.5-5, a rotation speed of 250-300r / min, and a temperature of 60-70°C for 4-5h; and the calcination conditions are: calcining at a temperature of 680-720°C in a muffle furnace for 4-5h.

[0024] Preferably, the regulator comprises a 1 mol / L aqueous solution of hydrogen chloride.

[0025] Preferably, in the preparation of the ammonium polyphosphate / molecular sieve composite material: the mass ratio of 85wt% phosphoric acid aqueous solution, urea, and acidified molecular sieve is 11.5-12:10.5-11:10, and the phosphoric acid aqueous solution is 85wt% phosphoric acid aqueous solution; the heating operation includes: heating to 120-130°C at a heating rate of 2-3°C / min; when preparing the ammonium polyphosphate / molecular sieve composite material, the reaction conditions are: reacting at a temperature of 120-130°C for 15-30min; the curing conditions are: curing at a temperature of 200-210°C for 2-3h; in the sieving operation, the mesh size is 100-150 meshes.

[0026] Preferably, a halogen-free flame retardant is prepared by the method for preparing a halogen-free flame retardant as described above.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The present invention compounds ammonium polyphosphate with molecular sieve to obtain an ammonium polyphosphate / molecular sieve composite material, and compounds the ammonium polyphosphate / molecular sieve composite material with flame-retardant benzoxazine, so that the flame-retardant benzoxazine is in-situ polymerized on the surface of the ammonium polyphosphate / molecular sieve composite material to form a polybenzoxazine resin structure. The prepared halogen-free flame retardant has excellent flame retardant effect, good compatibility in a matrix material, can effectively improve the flame retardant properties and mechanical properties of the matrix material, and can be applied to plastic materials.

[0029] The invention uses DOPO, p-hydroxybenzaldehyde and phenol as raw materials to synthesize a modified DOPO having a DOPO structure and two phenolic hydroxyl groups, uses the modified DOPO as a phenol intermediate, and reacts with propargylamine and polyformaldehyde to produce a Mannich reaction to prepare a bis-alkynyl benzoxazine having a DOPO structure and an alkynyl functional group; and undergoes a click chemical reaction between the bis-alkynyl benzoxazine and 1-azidoadamantane to graft the adamantane structure onto the benzoxazine monomer to prepare a flame-retardant benzoxazine; wherein the benzoxazine structure contains a six-membered heterocyclic ring composed of carbon and nitrogen, and the polybenzoxazine generated after ring-opening curing has a network cross-linked structure and contains a Mannich bond and a rigid benzene ring structure, so that the polybenzoxazine has It has excellent mechanical properties, heat resistance and high carbonization. By introducing the DOPO flame retardant structure into the benzoxazine monomer, the heat resistance and flame retardancy of the polybenzoxazine resin can be effectively improved. Adamantane is a cage structure composed of three cyclohexane rings. This special structure makes adamantane rigid, with excellent thermal stability and hydrophobicity. By introducing the adamantane structure into the benzoxazine monomer, the heat resistance and mechanical properties of the polybenzoxazine resin can be further improved, and the moisture resistance and hydrophobicity are also improved. In addition, the alkynyl group of the diacetyl benzoxazine and the azide group of the 1-azidoadamantane undergo a click chemical reaction to form a nitrogen-containing triazole ring structure. This structure also plays a positive addition role in the heat resistance and flame retardancy of the polybenzoxazine resin.

[0030] Ammonium polyphosphate is a nitrogen-phosphorus flame retardant with the advantages of low toxicity, low smoke and halogen-free. The present invention mixes the molecular sieve with an aqueous solution of ammonium chloride to exchange sodium ions with ammonium ions in the molecular sieve lattice. During calcination, the ammonium ions are removed to form ammonia gas, thereby forming Lewis acidic sites. The obtained acidified molecular sieve, as a solid Lewis acid, can effectively catalyze the cross-linking of the matrix material into carbon during combustion, thereby improving the flame retardant effect. Moreover, due to its large specific surface area, it can also play a role in suppressing smoke as an adsorbent. Ammonium polyphosphate is added to the surface of the acidified molecular sieve. The ammonium polyphosphate / molecular sieve composite material is obtained by in-situ polymerization. The ammonium polyphosphate / molecular sieve composite material is compounded with flame-retardant benzoxazine, so that the flame-retardant benzoxazine is in-situ polymerized on the surface of the ammonium polyphosphate / molecular sieve composite material to form a polybenzoxazine resin structure, thereby improving the hydrophilicity and compatibility of the ammonium polyphosphate / molecular sieve composite material with the matrix material. The prepared halogen-free flame retardant has excellent flame retardant effect and good compatibility in the matrix material, and can be used as a flame retardant and toughening agent in the matrix material to improve the flame retardancy and mechanical properties of the matrix material. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a process flow chart of preparing halogen-free flame retardant in the present invention;

[0032] Figure 2 is a schematic diagram of the reaction for preparing flame-retardant benzoxazine in the present invention;

[0033] Figure 3 It is a bar graph of the impact strength of EP samples 1-7 in the performance test of the present invention;

[0034] Figure 4 It is a bar graph of the limiting oxygen index of EP samples 1-7 in the performance test of the present invention. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0036] Example 1

[0037] This embodiment discloses a method for preparing a halogen-free flame retardant, comprising the following steps:

[0038] Step (1), DOPO, p-hydroxybenzaldehyde, phenol, and p-toluenesulfonic acid are mixed in a mass ratio of 13:6.5:30:0.35, and reacted at 125°C for 25 hours in a nitrogen atmosphere. After the reaction is completed, a reaction product is obtained, and ethanol 3 times the mass of the reaction product is added to mix and dissolve. After dissolution, hot water at 75°C 3 times the mass of the reaction product is added to precipitate. The operation of dissolving the precipitate is repeated once, and the mixture is filtered and dried at 25°C for 16 hours to obtain a modified DOPO.

[0039] Propylamine, modified DOPO, paraformaldehyde and chloroform are mixed in a mass ratio of 5.5:20:6.5:200, stirred at 45°C for 1 hour, and continued to react at 60°C for 26 hours after the reaction. After the reaction, the mixture is cooled to room temperature to obtain a reaction product, and a 1 mol / L sodium hydroxide aqueous solution of 3 times the mass of the reaction product is added for mixing and washing, and the mixture is separated to obtain an organic phase, and water of 3 times the mass of the organic phase is added for washing until neutrality, and the mixture is separated to obtain a washed organic phase, and anhydrous sodium sulfate of 15% of the mass of the washed organic phase is added for dehydration, and the mixture is filtered after dehydration, and the filtrate is taken, and the solvent chloroform is removed by rotary evaporation at 35°C, and the mixture is passed through a column to obtain dialkynylbenzoxazine;

[0040] The eluent in the column operation is a mixture of chloroform and acetone in a volume ratio of 40:1.

[0041] Step (2), 1-azidoadamantane is mixed with N,N-dimethylformamide, tert-butyl alcohol and cuprous iodide are added in sequence and mixed evenly, and then dialkynylbenzoxazine is added, the mass ratio of 1-azidoadamantane, N,N-dimethylformamide, tert-butyl alcohol, cuprous iodide and dialkynylbenzoxazine is 23:110:15:0.1:55, and the reaction is carried out at a temperature of 25° C. for 26 hours. After the reaction is completed, a reaction product is obtained, and water 5 times the mass of the reaction product is added to precipitate, and suction filtration is performed to obtain a filter cake, and water 5 times the mass of the filter cake is added to wash, and the filter cake is dried at a temperature of 50° C. for 24 hours to obtain a flame-retardant benzoxazine;

[0042] Step (3), mixing the ammonium polyphosphate / molecular sieve composite material, flame-retardant benzoxazine, dimethyl silicone oil, and dichloromethane in a mass ratio of 6:4:15:25, ultrasonically dispersing for 20 minutes, reacting at 150° C. for 4 hours, and continuing to react at 180° C. for 1 hour after the reaction. After the reaction, cooling to room temperature, filtering, taking the filter cake, adding dichloromethane 5 times the mass of the filter cake for washing, and drying at 50° C. for 24 hours to obtain a halogen-free flame retardant;

[0043] Wherein, the ammonium polyphosphate / molecular sieve composite material is prepared by the following steps:

[0044] The molecular sieve was mixed with a 25wt% aqueous solution of ammonium chloride at a mass ratio of 1:10, and a 1mol / L aqueous solution of hydrogen chloride was added to adjust the pH value to 4.5, and the mixture was reacted at a speed of 250r / min and a temperature of 60°C for 5h. After the reaction was completed, the mixture was cooled to room temperature, filtered, and the filter cake was taken and dried at a temperature of 70°C for 12h. After drying, a reaction product was obtained, and the reaction product was placed in a muffle furnace and calcined at a temperature of 680°C for 5h to obtain an acidified molecular sieve;

[0045] An 85 wt% phosphoric acid aqueous solution and urea are mixed at a temperature of 65°C, and the temperature is raised to 130°C at a heating rate of 3°C / min. An acidified molecular sieve is added, and the mass ratio of the 85 wt% phosphoric acid aqueous solution, urea, and the acidified molecular sieve is 11.5:10.5:10. The mixture is reacted at a temperature of 130°C for 15 minutes. After the reaction is completed, the mixture is cured at a temperature of 200°C for 3 hours. After curing, the mixture is crushed and passed through a 100-mesh sieve to obtain an ammonium polyphosphate / molecular sieve composite material.

[0046] Example 2

[0047] This embodiment discloses a method for preparing a halogen-free flame retardant, comprising the following steps:

[0048] Step (1), propargylamine, modified DOPO, paraformaldehyde, and chloroform are mixed in a mass ratio of 5.6:20.5:6.6:220, and stirred at 45°C for 1 hour. After the reaction, the reaction is continued at 65°C for 25 hours. After the reaction, the mixture is cooled to room temperature to obtain a reaction product, and a 1 mol / L sodium hydroxide aqueous solution with a mass of 3 times that of the reaction product is added for mixing and washing. The mixture is separated, and an organic phase is taken, and water with a mass of 3 times that of the organic phase is added for washing until neutrality. The organic phase is separated to obtain a washed organic phase, and anhydrous sodium sulfate with a mass of 15% of the mass of the washed organic phase is added for dehydration. After dehydration, the mixture is filtered, and the filtrate is taken, and the solvent chloroform is removed by rotary evaporation at 40°C, and the mixture is passed through a column to obtain dialkynylbenzoxazine;

[0049] The preparation of modified DOPO is the same as that in Example 1; the eluent in the column operation is a mixture of chloroform and acetone in a volume ratio of 40:1;

[0050] Step (2), 1-azidoadamantane is mixed with N,N-dimethylformamide, tert-butyl alcohol and cuprous iodide are added in sequence and mixed evenly, and then dialkynylbenzoxazine is added, the mass ratio of 1-azidoadamantane, N,N-dimethylformamide, tert-butyl alcohol, cuprous iodide and dialkynylbenzoxazine is 23.5:120:15.5:0.1:56, and the reaction is carried out at a temperature of 25° C. for 25 hours. After the reaction is completed, a reaction product is obtained, and water 5 times the mass of the reaction product is added to precipitate, and suction filtration is performed to obtain a filter cake, and water 6 times the mass of the filter cake is added to wash, and the filter cake is dried at a temperature of 55° C. for 20 hours to obtain a flame-retardant benzoxazine;

[0051] Step (3), mixing the ammonium polyphosphate / molecular sieve composite material, flame-retardant benzoxazine, dimethyl silicone oil, and dichloromethane in a mass ratio of 6.2:3.8:16:24, ultrasonically dispersing for 25 minutes, reacting at 155°C for 3.5 hours, and continuing to react at 180°C for 1 hour after the reaction. After the reaction, cooling to room temperature, filtering, taking the filter cake, adding dichloromethane 6 times the mass of the filter cake for washing, and drying at 55°C for 20 hours to obtain a halogen-free flame retardant;

[0052] Wherein, the ammonium polyphosphate / molecular sieve composite material is prepared by the following steps:

[0053] The molecular sieve was mixed with a 25wt% aqueous solution of ammonium chloride at a mass ratio of 1:10.5, and a 1mol / L aqueous solution of hydrogen chloride was added to adjust the pH value to 4.5, and the mixture was reacted at a speed of 260r / min and a temperature of 60°C for 4.5h. After the reaction was completed, the mixture was cooled to room temperature, filtered, and the filter cake was taken and dried at a temperature of 75°C for 11h. After drying, a reaction product was obtained, and the reaction product was placed in a muffle furnace and calcined at a temperature of 690°C for 4.5h to obtain an acidified molecular sieve;

[0054] 85wt% phosphoric acid aqueous solution and urea are mixed at 70°C, heated to 125°C at a heating rate of 2°C / min, and an acidified molecular sieve is added, the mass ratio of the 85wt% phosphoric acid aqueous solution, urea and the acidified molecular sieve is 11.6:10.6:10, and the mixture is reacted at 125°C for 25min. After the reaction is completed, the mixture is cured at 200°C for 3h. After curing, the mixture is crushed and passed through a 120-mesh sieve to obtain an ammonium polyphosphate / molecular sieve composite material.

[0055] Example 3

[0056] This embodiment discloses a method for preparing a halogen-free flame retardant, comprising the following steps:

[0057] Step (1), propargylamine, modified DOPO, paraformaldehyde and chloroform are mixed in a mass ratio of 5.8:21:6.8:230, stirred at 48°C for reaction for 0.8h, and continued to react at 65°C for 25h after the reaction. After the reaction, the mixture is cooled to room temperature to obtain a reaction product, and a 1 mol / L sodium hydroxide aqueous solution with a mass of 3 times that of the reaction product is added to mix and wash, separate the liquids, take the organic phase, add water with a mass of 3 times that of the organic phase to wash until neutral, separate the liquids to obtain the washed organic phase, and then add anhydrous sodium sulfate with a mass of 20% of the mass of the washed organic phase for dehydration, filter after dehydration, take the filtrate, remove the solvent chloroform at 40°C, and pass through a column to obtain dialkynyl benzoxazine;

[0058] The preparation of modified DOPO is the same as that in Example 1; the eluent in the column operation is a mixture of chloroform and acetone in a volume ratio of 40:1;

[0059] Step (2), 1-azidoadamantane is mixed with N,N-dimethylformamide, tert-butyl alcohol and cuprous iodide are added in sequence and mixed evenly, and then dialkynylbenzoxazine is added, the mass ratio of 1-azidoadamantane, N,N-dimethylformamide, tert-butyl alcohol, cuprous iodide and dialkynylbenzoxazine is 24:130:16:0.1:58, and the reaction is carried out at 28° C. for 25 hours. After the reaction is completed, a reaction product is obtained, and water 5 times the mass of the reaction product is added to precipitate, and suction filtration is performed to obtain a filter cake, and water 6 times the mass of the filter cake is added to wash, and the filter cake is dried at 55° C. for 20 hours to obtain a flame-retardant benzoxazine;

[0060] Step (3), mixing the ammonium polyphosphate / molecular sieve composite material, flame-retardant benzoxazine, dimethyl silicone oil, and dichloromethane in a mass ratio of 6.5:3.5:18:22, ultrasonically dispersing for 25 minutes, reacting at 155°C for 3.5 hours, and continuing to react at 180°C for 1 hour after the reaction. After the reaction, cooling to room temperature, filtering, taking the filter cake, adding dichloromethane 6 times the mass of the filter cake for washing, and drying at 55°C for 20 hours to obtain a halogen-free flame retardant;

[0061] Wherein, the ammonium polyphosphate / molecular sieve composite material is prepared by the following steps:

[0062] The molecular sieve was mixed with a 25wt% aqueous solution of ammonium chloride at a mass ratio of 1:11, and a 1mol / L aqueous solution of hydrogen chloride was added to adjust the pH value to 4.5, and the mixture was reacted at a speed of 280r / min and a temperature of 65°C for 4.5h. After the reaction was completed, the mixture was cooled to room temperature, filtered, and the filter cake was taken and dried at a temperature of 75°C for 11h. After drying, a reaction product was obtained, and the reaction product was placed in a muffle furnace and calcined at a temperature of 700°C for 4.5h to obtain an acidified molecular sieve;

[0063] An 85 wt% phosphoric acid aqueous solution and urea are mixed at 70°C, heated to 125°C at a heating rate of 2°C / min, and an acidified molecular sieve is added, wherein the mass ratio of the 85 wt% phosphoric acid aqueous solution, urea and the acidified molecular sieve is 11.8:10.8:10, and the mixture is reacted at 125°C for 25 minutes. After the reaction is completed, the mixture is cured at 205°C for 2.5 hours. After curing, the mixture is crushed and passed through a 120-mesh sieve to obtain an ammonium polyphosphate / molecular sieve composite material.

[0064] Example 4

[0065] This embodiment discloses a method for preparing a halogen-free flame retardant, comprising the following steps:

[0066] Step (1), propargylamine, modified DOPO, paraformaldehyde, and chloroform are mixed in a mass ratio of 5.9:21.5:6.9:240, and stirred at 50°C for 0.5h. After the reaction, the reaction is continued at 65°C for 25h. After the reaction is completed, the mixture is cooled to room temperature to obtain a reaction product, and a 1 mol / L sodium hydroxide aqueous solution with a mass of 4 times that of the reaction product is added to mix and wash, separate the liquids, take the organic phase, add water with a mass of 4 times that of the organic phase, wash until neutral, separate the liquids to obtain the washed organic phase, and then add anhydrous sodium sulfate with a mass of 20% of the mass of the washed organic phase for dehydration, filter after dehydration, take the filtrate, remove the solvent chloroform at 40°C, and pass through a column to obtain dialkynyl benzoxazine;

[0067] The preparation of modified DOPO is the same as that in Example 1; the eluent in the column operation is a mixture of chloroform and acetone in a volume ratio of 40:1;

[0068] Step (2), 1-azidoadamantane is mixed with N,N-dimethylformamide, tert-butyl alcohol and cuprous iodide are added in sequence and mixed evenly, and then dialkynylbenzoxazine is added, the mass ratio of 1-azidoadamantane, N,N-dimethylformamide, tert-butyl alcohol, cuprous iodide and dialkynylbenzoxazine is 24.5:140:16.5:0.1:59, and the reaction is carried out at 30° C. for 25 hours. After the reaction is completed, a reaction product is obtained, and water 5 times the mass of the reaction product is added to precipitate, and suction filtration is performed to obtain a filter cake, and water 6 times the mass of the filter cake is added to wash, and the filter cake is dried at 55° C. for 20 hours to obtain a flame-retardant benzoxazine;

[0069] Step (3), mixing the ammonium polyphosphate / molecular sieve composite material, flame-retardant benzoxazine, dimethyl silicone oil, and dichloromethane in a mass ratio of 6.8:3.2:20:20, ultrasonically dispersing for 30 minutes, reacting at 155°C for 3.5 hours, and continuing to react at 180°C for 1.5 hours. After the reaction is completed, cooling to room temperature, filtering, taking the filter cake, adding dichloromethane 6 times the mass of the filter cake for washing, and drying at 55°C for 20 hours to obtain a halogen-free flame retardant;

[0070] Wherein, the ammonium polyphosphate / molecular sieve composite material is prepared by the following steps:

[0071] The molecular sieve was mixed with a 25wt% aqueous solution of ammonium chloride at a mass ratio of 1:11.5, and a 1mol / L aqueous solution of hydrogen chloride was added to adjust the pH value to 5, and the mixture was reacted at a speed of 290r / min and a temperature of 70°C for 4h. After the reaction was completed, the mixture was cooled to room temperature, filtered, and the filter cake was taken and dried at a temperature of 75°C for 11h. After drying, a reaction product was obtained, and the reaction product was placed in a muffle furnace and calcined at a temperature of 710°C for 4.5h to obtain an acidified molecular sieve;

[0072] 85wt% phosphoric acid aqueous solution and urea are mixed at 70°C, heated to 130°C at a heating rate of 3°C / min, and an acidified molecular sieve is added, the mass ratio of the 85wt% phosphoric acid aqueous solution, urea and the acidified molecular sieve is 11.9:10.9:10, and the mixture is reacted at 130°C for 25min. After the reaction is completed, the mixture is cured at 210°C for 3h. After curing, the mixture is crushed and passed through a 120-mesh sieve to obtain an ammonium polyphosphate / molecular sieve composite material.

[0073] Example 5

[0074] This embodiment discloses a method for preparing a halogen-free flame retardant, comprising the following steps:

[0075] Step (1), propargylamine, modified DOPO, paraformaldehyde and chloroform are mixed in a mass ratio of 6:22:7:250, stirred at 50°C for 0.5h, and continued to react at 70°C for 24h after the reaction. After the reaction, the mixture is cooled to room temperature to obtain a reaction product, and a 1 mol / L sodium hydroxide aqueous solution with a mass of 4 times that of the reaction product is added to mix and wash, separate the liquids, take the organic phase, add water with a mass of 4 times that of the organic phase to wash until neutral, separate the liquids to obtain the washed organic phase, and then add anhydrous sodium sulfate with a mass of 20% of the mass of the washed organic phase for dehydration, filter after dehydration, take the filtrate, remove the solvent chloroform at 45°C, and pass through a column to obtain dialkynyl benzoxazine;

[0076] The preparation of modified DOPO is the same as that in Example 1; the eluent in the column operation is a mixture of chloroform and acetone in a volume ratio of 40:1;

[0077] Step (2), 1-azidoadamantane is mixed with N,N-dimethylformamide, tert-butyl alcohol and cuprous iodide are added in sequence and mixed evenly, and then dialkynylbenzoxazine is added, the mass ratio of 1-azidoadamantane, N,N-dimethylformamide, tert-butyl alcohol, cuprous iodide and dialkynylbenzoxazine is 25:150:17:0.1:60, and the reaction is carried out at 30° C. for 24 hours. After the reaction is completed, a reaction product is obtained, and water 6 times the mass of the reaction product is added to precipitate, and suction filtration is performed to obtain a filter cake, and water 8 times the mass of the filter cake is added to wash, and the filter cake is dried at 60° C. for 18 hours to obtain a flame-retardant benzoxazine;

[0078] Step (3), mixing the ammonium polyphosphate / molecular sieve composite material, flame-retardant benzoxazine, dimethyl silicone oil, and dichloromethane in a mass ratio of 7:3:20:20, ultrasonically dispersing for 30 minutes, reacting at 160° C. for 3 hours, and continuing to react at 180° C. for 1.5 hours after the reaction. After the reaction, cooling to room temperature, filtering, taking the filter cake, adding dichloromethane 8 times the mass of the filter cake for washing, and drying at 60° C. for 18 hours to obtain a halogen-free flame retardant;

[0079] Wherein, the ammonium polyphosphate / molecular sieve composite material is prepared by the following steps:

[0080] The molecular sieve was mixed with a 25wt% aqueous solution of ammonium chloride at a mass ratio of 1:12, and a 1mol / L aqueous solution of hydrogen chloride was added to adjust the pH value to 5, and the mixture was reacted at a speed of 300r / min and a temperature of 70°C for 4h. After the reaction was completed, the mixture was cooled to room temperature, filtered, and the filter cake was taken and dried at a temperature of 80°C for 10h. After drying, a reaction product was obtained, and the reaction product was placed in a muffle furnace and calcined at a temperature of 720°C for 4h to obtain an acidified molecular sieve;

[0081] An 85 wt% phosphoric acid aqueous solution and urea are mixed at a temperature of 75°C, and the temperature is raised to 120°C at a heating rate of 2°C / min. An acidified molecular sieve is added, and the mass ratio of the 85 wt% phosphoric acid aqueous solution, urea, and the acidified molecular sieve is 12:11:10. The mixture is reacted at a temperature of 120°C for 30 minutes. After the reaction is completed, the mixture is cured at a temperature of 210°C for 2 hours. After curing, the mixture is crushed and passed through a 150-mesh sieve to obtain an ammonium polyphosphate / molecular sieve composite material.

[0082] Comparative Example 1

[0083] This comparative example discloses a method for preparing a halogen-free flame retardant, comprising the following steps:

[0084] The molecular sieve was mixed with a 25wt% aqueous solution of ammonium chloride at a mass ratio of 1:10, and a 1mol / L aqueous solution of hydrogen chloride was added to adjust the pH value to 4.5, and the mixture was reacted at a speed of 250r / min and a temperature of 60°C for 5h. After the reaction was completed, the mixture was cooled to room temperature, filtered, and the filter cake was taken and dried at a temperature of 70°C for 12h. After drying, a reaction product was obtained, and the reaction product was placed in a muffle furnace and calcined at a temperature of 680°C for 5h to obtain an acidified molecular sieve;

[0085] 85wt% phosphoric acid aqueous solution and urea are mixed at 65°C, heated to 130°C at a heating rate of 3°C / min, and acidified molecular sieves are added. The mass ratio of 85wt% phosphoric acid aqueous solution, urea and acidified molecular sieves is 11.5:10.5:10. The mixture is reacted at 130°C for 15min. After the reaction is completed, the mixture is cured at 200°C for 3h. After curing, the mixture is crushed and passed through a 100-mesh sieve to obtain a halogen-free flame retardant.

[0086] Comparative Example 2

[0087] This comparative example discloses a method for preparing a halogen-free flame retardant, comprising the following steps:

[0088] Step (1), propargylamine, bisphenol A, paraformaldehyde and chloroform are mixed in a mass ratio of 5.5:11:6.5:200, stirred at 45°C for 1h, and continued to react at 60°C for 26h after the reaction. After the reaction, the mixture is cooled to room temperature to obtain a reaction product, 1 mol / L sodium hydroxide aqueous solution (3 times the mass of the reaction product) is added to mix and wash, the mixture is separated, an organic phase is taken, water (3 times the mass of the organic phase) is added to wash until neutral, the mixture is separated to obtain a washed organic phase, anhydrous sodium sulfate (15% the mass of the washed organic phase) is added for dehydration, the mixture is filtered after dehydration, the filtrate is taken, the solvent chloroform is removed by rotary evaporation at 35°C, and the mixture is passed through a column to obtain bis-alkynylbenzoxazine;

[0089] The eluent in the column operation is a mixture of chloroform and acetone in a volume ratio of 40:1.

[0090] Step (2), mixing the ammonium polyphosphate / molecular sieve composite material, diacetylene benzoxazine, dimethyl silicone oil, and dichloromethane in a mass ratio of 6:4:15:25, ultrasonically dispersing for 20 minutes, reacting at 150° C. for 4 hours, and continuing to react at 180° C. for 1 hour after the reaction. After the reaction, cooling to room temperature, filtering, taking the filter cake, adding dichloromethane 5 times the mass of the filter cake for washing, and drying at 50° C. for 24 hours to obtain a halogen-free flame retardant;

[0091] Wherein, the ammonium polyphosphate / molecular sieve composite material is prepared by the following steps:

[0092] The molecular sieve was mixed with a 25wt% aqueous solution of ammonium chloride at a mass ratio of 1:10, and a 1mol / L aqueous solution of hydrogen chloride was added to adjust the pH value to 4.5, and the mixture was reacted at a speed of 250r / min and a temperature of 60°C for 5h. After the reaction was completed, the mixture was cooled to room temperature, filtered, and the filter cake was taken and dried at a temperature of 70°C for 12h. After drying, a reaction product was obtained, and the reaction product was placed in a muffle furnace and calcined at a temperature of 680°C for 5h to obtain an acidified molecular sieve;

[0093] An 85 wt% phosphoric acid aqueous solution and urea are mixed at a temperature of 65°C, and the temperature is raised to 130°C at a heating rate of 3°C / min. An acidified molecular sieve is added, and the mass ratio of the 85 wt% phosphoric acid aqueous solution, urea, and the acidified molecular sieve is 11.5:10.5:10. The mixture is reacted at a temperature of 130°C for 15 minutes. After the reaction is completed, the mixture is cured at a temperature of 200°C for 3 hours. After curing, the mixture is crushed and passed through a 100-mesh sieve to obtain an ammonium polyphosphate / molecular sieve composite material.

[0094] In the above examples and comparative examples: DOPO is from AlfaAesar, CAS No.: 35948-25-5; p-hydroxybenzaldehyde is from Shandong Poly Chemical Co., Ltd., CAS No.: 123-08-0; propargylamine is from AlfaAesar, CAS No.: 2450-71-7; paraformaldehyde is from Shanghai Aladdin Biochemical Technology Co., Ltd., CAS No.: C104190, CAS No.: 30525-89-4; 1-azidoadamantane is from Shanghai Aladdin Biochemical Technology Co., Ltd., CAS No.: A346899, CA S number: 24886-73-5; bisphenol A comes from AlfaAesar, CAS number: 80-05-7; molecular sieve comes from Shanghai MacLean Biochemical Technology Co., Ltd., model sodium type 4A molecular sieve, particle size 50μm, item number M766916, CAS number: 70955-01-0; 85wt% phosphoric acid aqueous solution comes from Shanghai MacLean Biochemical Technology Co., Ltd., item number P816342; urea comes from Shanghai Aladdin Biochemical Technology Co., Ltd., model analytical grade, item number U111897, CAS number: 57-13-6.

[0095] Test example

[0096] The halogen-free flame retardants prepared in Examples 1-5 and Comparative Examples 1-2 were added to epoxy resin (EP), the addition amount of the halogen-free flame retardant was 10wt%, and the samples were cured at 150°C for 2h and further cured at 180°C for 2h. The flame-retardant epoxy plastics obtained after curing were recorded as EP samples 1-7. The specific test results are shown in Table 1:

[0097] Table 1

[0098]

[0099] The tests of various indicators in Table 1 are based on the following standards: impact strength is measured by GB / T1843-1996 "Plastic Izod Impact Test Method"; limiting oxygen index is measured by ISO4589-1981 "Plastic Oxygen Index Method for Determining Flammability"; vertical burning grade is measured by ASTM D3801 "Test Method for Measuring Vertical Burning of Solid Plastics".

[0100] It can be seen from the test results in Table 1 that the halogen-free flame retardant prepared by the present invention has excellent flame retardant effect, can effectively improve the flame retardant properties and mechanical properties of the base material, and can be applied to plastic materials.

[0101] The present invention prepares a bis-alkynyl benzoxazine having a DOPO structure and an alkynyl functional group, and grafts an adamantane structure onto a benzoxazine monomer through a click chemical reaction to prepare a flame-retardant benzoxazine; and in-situ polymerizes the flame-retardant benzoxazine on the surface of an ammonium polyphosphate / molecular sieve composite material to form a polybenzoxazine resin structure to obtain a halogen-free flame retardant. Among them, the polybenzoxazine resin improves the hydrophilicity and compatibility of the ammonium polyphosphate / molecular sieve composite material with the matrix material. After adding the halogen-free flame retardant to the epoxy resin, the polybenzoxazine has good compatibility with the epoxy resin, and the active groups on its surface can also catalyze the cross-linking and curing of the epoxy resin, increase the cross-linking density, and thus improve the mechanical properties of the flame-retardant epoxy plastic. During the combustion process, ammonium polyphosphate is easily decomposed to generate medium-strong acids such as polyphosphoric acid, which cooperates with the acidified molecular sieve as a solid Lewis acid to catalyze the cross-linking of the matrix material into carbon, providing an acid source for the flame retardant process. Ammonium polyphosphate, polybenzoxazine resin, and epoxy resin are initially degraded during combustion, and as a gas source and carbon source, they constitute an intumescent flame retardant system, thereby achieving an excellent flame retardant effect. In Comparative Example 1, no flame-retardant benzoxazine was added, and the ammonium polyphosphate / molecular sieve composite material had poor compatibility with the epoxy resin matrix and was easily agglomerated, which affected the flame retardant effect. In addition, the flame retardant toughening effect of the flame retardant benzoxazine was lacking, so the mechanical properties and flame retardant properties of EP sample 6 prepared from Comparative Example 1 were both reduced; in the preparation of Comparative Example 2, no DOPO intermediate and adamantane were added, and the effect of the DOPO structure on improving the flame retardant properties of the matrix material and the effect of the adamantane rigid structure on improving the flame retardancy and mechanical properties of the matrix material were lacking. In addition, the nitrogen-containing triazole ring structure formed by the click chemical reaction between the alkynyl group of diacetyl benzoxazine and the azide group of 1-azidoadamantane was lacking, so the mechanical properties and flame retardant properties of EP sample 7 prepared from Comparative Example 2 were both reduced.

[0102] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a halogen-free flame retardant, characterized in that: The following steps are involved: Step 1: mixing DOPO, p-hydroxybenzaldehyde, phenol and p-toluenesulfonic acid, reacting, purifying and drying after the reaction to obtain modified DOPO; Propargylamine, modified DOPO, paraformaldehyde and chloroform are mixed and stirred for reaction. After the reaction is completed, the reaction is continued. After the reaction is completed, the mixture is cooled and purified to obtain dialkynyl benzoxazine. Step 2: 1-azidoadamantane is mixed with N,N-dimethylformamide, tert-butyl alcohol and cuprous iodide are added in sequence and mixed evenly, and then dialkynylbenzoxazine is added to react. After the reaction is completed, precipitation is performed, suction filtration is performed, washing is performed, and drying is performed to obtain a flame-retardant benzoxazine; Step 3: Mix the ammonium polyphosphate / molecular sieve composite material, flame-retardant benzoxazine, dimethyl silicone oil, and dichloromethane, perform ultrasonic dispersion, react, continue the reaction after the reaction is completed, cool, filter, wash, and dry to obtain a halogen-free flame retardant.

2. The method for preparing a halogen-free flame retardant according to claim 1, characterized in that: In the step 1, the mass ratio of DOPO, p-hydroxybenzaldehyde, phenol and p-toluenesulfonic acid is 11-15:6-7:25-35:0.3-0.4; when preparing the modified DOPO, the reaction conditions are: reacting in a nitrogen atmosphere at a temperature of 120-130° C. for 24-26 hours.

3. The method for preparing a halogen-free flame retardant according to claim 1, characterized in that: In the step 1, the mass ratio of propargylamine, modified DOPO, paraformaldehyde and chloroform is 5.5-6:20-22:6.5-7:200-250; when preparing dialkynylbenzoxazine, the reaction conditions are: stirring the reaction at 45-50°C for 0.5-1h, and the continued reaction conditions are: continuing the reaction at 60-70°C for 24-26h.

4. The method for preparing a halogen-free flame retardant according to claim 1, characterized in that: In the step 2, the mass ratio of 1-azidoadamantane, N,N-dimethylformamide, tert-butyl alcohol, cuprous iodide and dialkynylbenzoxazine is 23-25:110-150:15-17:0.1:55-60; and the reaction conditions are: reacting at a temperature of 25-30° C. for 24-26 hours.

5. The method for preparing a halogen-free flame retardant according to claim 1, characterized in that: The ammonium polyphosphate / molecular sieve composite material in step 3 is prepared by the following steps: Step (1), mixing the molecular sieve and the ammonium chloride aqueous solution uniformly, adding a regulator to adjust the pH value, reacting, cooling after the reaction is completed, filtering, drying, and drying to obtain a reaction product, calcining to obtain an acidified molecular sieve; Step (2), mixing the phosphoric acid aqueous solution with urea, heating, adding the acidified molecular sieve, reacting, curing after the reaction, crushing and sieving after curing to obtain the ammonium polyphosphate / molecular sieve composite material.

6. The method for preparing a halogen-free flame retardant according to claim 5, characterized in that: In the step (1), the mass ratio of the molecular sieve to the aqueous ammonium chloride solution is 1:10-12, and the aqueous ammonium chloride solution is a 25wt% aqueous ammonium chloride solution; the reaction conditions are: reacting at a pH value of 4.5-5, a rotation speed of 250-300 r / min, and a temperature of 60-70° C. for 4-5 hours; and the calcination conditions are: calcining in a muffle furnace at a temperature of 680-720° C. for 4-5 hours.

7. The method for preparing a halogen-free flame retardant according to claim 5, characterized in that: The step (2): the mass ratio of 85wt% phosphoric acid aqueous solution, urea and acidified molecular sieve is 11.5-12:10.5-11:10, and the phosphoric acid aqueous solution is 85wt% phosphoric acid aqueous solution; the heating operation comprises: heating to 120-130°C at a heating rate of 2-3°C / min; the reaction conditions are: reacting at a temperature of 120-130°C for 15-30min; the curing conditions are: curing at a temperature of 200-210°C for 2-3h; in the sieving operation, the mesh size is 100-150 meshes.

8. The method for preparing a halogen-free flame retardant according to claim 1, characterized in that: In the step 3, the mass ratio of ammonium polyphosphate / molecular sieve composite material, flame retardant benzoxazine, dimethyl silicone oil and dichloromethane is 6-7:3-4:15-20:20-25; the reaction conditions are: react at a temperature of 150-160° C. for 3-4 hours; and the continued reaction conditions are: continue to react at a temperature of 180° C. for 1-1.5 hours.

9. A halogen-free flame retardant prepared by the method for preparing a halogen-free flame retardant according to any one of claims 1 to 8.

10. Use of the halogen-free flame retardant according to claim 9 in plastics.

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