Polyphosphate flame retardant with high thermal stability and preparation method thereof

Abstract

The invention discloses a high-thermal-stability polyphosphate flame retardant and a preparation method thereof. Comprising the following steps: adding modified diol and aluminum chloride into a three-necked flask, introducing nitrogen, heating to 60-70 DEG C under a stirring condition, then adding phenyl dichlorophosphate, keeping the temperature to react for 4-5 hours, heating to 200-220 DEG C, reacting for 3-4 hours, cooling after the reaction is completed, crushing, washing with water, and drying in vacuum to obtain the polyphosphate flame retardant. The preparation method has the beneficial effects that a functionalized modified diol structure is prepared through multi-step chemical reaction, and the functionalized modified diol structure reacts with aluminum chloride and phenyl dichlorophosphate under specific conditions to obtain the polyphosphate flame retardant with high thermal stability.

Description

Technical Field

[0001] The invention belongs to the technical field of flame retardants, and in particular relates to a high thermal stability polyphosphate flame retardant and a preparation method thereof. Background Art

[0002] With the widespread application of polymer materials, the research and development of flame retardants has received increasing attention. Polyphosphate flame retardants have become one of the current research hotspots in the field of flame retardancy due to their high efficiency, low toxicity and environmental protection.

[0003] However, traditional polyphosphate flame retardants still have some key defects in practical applications. First, most polyphosphate flame retardants have insufficient thermal stability and are prone to decomposition during high-temperature processing or long-term use, resulting in a decrease in flame retardant efficiency and even affecting the mechanical properties of the base material. Secondly, polyphosphate flame retardants in the prior art often rely on a single flame retardant mechanism, such as gas phase flame retardancy or condensed phase carbonization, and it is difficult to provide comprehensive and effective flame retardant protection under complex combustion environments. In addition, some flame retardants have poor compatibility with the polymer matrix and are prone to migration and precipitation during processing or use, which not only reduces the flame retardant durability, but also may affect the surface properties of the material.

[0004] In view of the above problems, the prior art attempts to improve the thermal stability and flame retardant efficiency of flame retardants by introducing rigid structures or fluorine-containing groups, but these modification methods usually face problems such as complex synthesis process, high cost or limited modification effect. For example, although some fluorine-containing flame retardants can improve thermal stability, their compatibility with polymers is poor; and simply adding rigid structure flame retardants may lead to deterioration of material processing performance.

[0005] Therefore, in order to solve the above problems, the present invention provides a high thermal stability polyphosphate flame retardant and a preparation method thereof. Summary of the invention

[0006] The purpose of the present invention is to overcome the defects of the prior art and provide a high thermal stability polyphosphate flame retardant and a preparation method thereof.

[0007] The purpose of the present invention can be achieved through the following technical solutions: A preparation method of a high-thermal-stability polyphosphate flame retardant comprises the following process: adding modified diol and aluminum chloride into a three-necked flask, introducing nitrogen, heating to 60-70°C under stirring, then adding phenyl dichlorophosphate, maintaining the temperature for reaction for 4-5h, then heating to 200-220°C, reacting for 3-4h, cooling after the reaction is complete, crushing, washing with water, and vacuum drying to obtain the polyphosphate flame retardant.

[0008] More optimally, the polyphosphate flame retardant raw material includes the following substances: 200-250 parts of modified diol, 1-2 parts of aluminum chloride, and 210-230 parts of phenyl dichlorophosphate, by weight.

[0009] More optimally, the preparation process of the modified diol is: S1: trifluorodecanol, 4′-hydroxy-4-benzoic acid, p-toluenesulfonic acid and p-xylene were mixed, the temperature was raised to 70-80°C, and the reaction was carried out for 3-4 hours. After the reaction was completed, the mixture was filtered, washed three times with 50°C deionized water, and dried to obtain intermediate A; S2: Mix 4′-hydroxy-4-benzoic acid, sodium hydroxide and water, and stir for 3-5 minutes to obtain a mixed solution; then dissolve acryloyl chloride in acetic acid, add it to the mixed solution, react at room temperature for 5-6 hours, filter, wash and dry to obtain intermediate B; S3: Intermediate A, intermediate B, N,N′-dicyclohexylcarbodiimide, 4-dimethylaminopyridine and tetrahydrofuran are mixed, the temperature is raised to 35-40° C., and the reaction is carried out for 6-8 hours. After the reaction is completed, the solvent is removed in vacuo and purified to obtain intermediate C; S4: Under a protective atmosphere, the intermediate C, 3-mercapto-1,2-propylene glycol, dibenzoyl peroxide, and N,N-dimethylformamide are mixed, the temperature is raised to 50-60° C., the reaction is carried out for 3-4 hours, and post-processing is performed to obtain a modified diol.

[0010] In the scheme, trifluorodecanol and 4′-hydroxy-4-benzoic acid undergo esterification reaction under the catalysis of p-toluenesulfonic acid to generate intermediate A; p-xylene, as a high boiling point solvent, promotes the reaction equilibrium to move toward the product. The specific synthesis process is as follows:

[0011] In the scheme, 4′-hydroxy-4-benzoic acid is first neutralized with NaOH to generate sodium phenolate, and then reacts with acryloyl chloride to undergo a nucleophilic substitution reaction to generate an intermediate B containing acrylate. The specific synthesis process is as follows:

[0012] In the scheme, the carboxyl group of intermediate A and the hydroxyl group of intermediate B are esterified by DCC / DMAP to generate intermediate C (a bifunctional compound containing trifluorodecyl and acrylate). The specific synthesis process is as follows:

[0013] In the scheme, the acrylate double bond of intermediate C reacts with 3-mercapto-1,2-propanediol through a free radical-initiated mercapto-ene click reaction to generate a hydroxyl-containing modified diol, the structural formula of which is shown below:

[0014] More optimally, the intermediate A raw material includes the following components: by weight, 21-24 parts of trifluorodecanol, 13-15 parts of 4′-hydroxy-4-benzoic acid, 0.8-1 parts of p-toluenesulfonic acid, and 100-120 parts of p-xylene.

[0015] More optimally, the intermediate B raw material includes the following components: by weight, 13-15 parts of 4′-hydroxy-4-benzoic acid, 4-5 parts of sodium hydroxide, 40-50 parts of water, 9-10 parts of acryloyl chloride, and 70-80 parts of acetic acid.

[0016] More optimally, the intermediate C raw material includes the following components: by weight, 33-35 parts of intermediate A, 20-22 parts of intermediate B, 24-28 parts of N,N′-dicyclohexylcarbodiimide, 12-15 parts of 4-dimethylaminopyridine, and 300-350 parts of tetrahydrofuran.

[0017] More optimally, the modified diol raw material includes the following components: by weight, 50-55 parts of intermediate C, 21-22 parts of 3-mercapto-1,2-propylene glycol, 1-2 parts of dibenzoyl peroxide, and 250-300 parts of N,N-dimethylformamide.

[0018] Benefits: The present invention prepares a functionalized modified diol structure through multi-step chemical reactions, and reacts the functionalized modified diol structure with aluminum chloride and phenyl dichlorophosphate under specific conditions to obtain a polyphosphate flame retardant with high thermal stability. The details are as follows: First: In the scheme, the rigid groups (such as aromatic ring structures) introduced into the modified diol structure can significantly improve the flame retardant properties of the material. These rigid structures will be preferentially carbonized under high temperature conditions to form a continuous and dense carbon layer barrier. This carbon layer not only has excellent heat insulation and oxygen isolation properties, but also can effectively prevent the diffusion of combustible gases into the flame area. At the same time, the molecular chains of the rigid structure are stacked more tightly, which reduces the fluidity of the material at high temperatures, thereby delaying the droplet phenomenon during the combustion process. In addition, these rigid groups can also synergize with the phosphoric acid compounds produced by the decomposition of polyphosphate esters, and further enhance the quality and stability of the carbon layer by catalyzing the dehydration to carbonize reaction, forming a multi-level flame retardant protection mechanism.

[0019] Second: In the scheme, the short-chain fluoride component introduced by the polyphosphate flame retardant gives the material excellent thermal stability. The high bond energy characteristics of the CF bond enable these fluorinated groups to maintain structural integrity in high temperature environments, effectively delaying the decomposition process of the flame retardant itself. In the early stages of combustion, these fluorinated components can preferentially decompose and release fluorinated free radicals. These free radicals have a strong ability to capture active free radicals in the combustion chain reaction, thereby playing a significant flame retardant role in the gas phase. More importantly, the presence of fluorides can also form a thermally stable protective layer on the surface of the material. This protective film can not only reflect part of the thermal radiation, but also prevent oxygen from penetrating into the interior of the material, thereby maintaining the stability of the material under high temperature conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will be further described below in conjunction with the accompanying drawings.

[0021] Figure 1 The high-efficiency polyphosphate flame retardant prepared in Example 3 of the present invention is added to polypropylene, and the SEM image of the residual carbon after the combustion test. DETAILED DESCRIPTION

[0022] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] Embodiment 1: A method for preparing a polyphosphate flame retardant with high thermal stability, comprising the following process: adding 200 parts of modified diol and 1 part of aluminum chloride into a three-necked flask, introducing nitrogen, heating to 60°C under stirring, then adding 210 parts of phenyl dichlorophosphate, maintaining the temperature for reaction for 4 hours, then heating to 200°C, reacting for 3 hours, cooling after the reaction is complete, crushing, washing with water, and vacuum drying to obtain a polyphosphate flame retardant; Wherein, the preparation process of modified diol is: S1: 21 parts of trifluorodecanol, 13 parts of 4′-hydroxy-4-benzoic acid, 0.8 parts of p-toluenesulfonic acid, and 100 parts of p-xylene were mixed, the temperature was raised to 70°C, and the reaction was carried out for 3 hours. After the reaction was completed, the mixture was filtered, washed three times with 50°C deionized water, and dried to obtain intermediate A; S2: 13 parts of 4′-hydroxy-4-benzoic acid, 4 parts of sodium hydroxide and 40 parts of water were mixed and stirred for 3 minutes to obtain a mixed solution; then 9 parts of acryloyl chloride were dissolved in 70 parts of acetic acid, added to the mixed solution, reacted at room temperature for 5 hours, filtered, washed and dried to obtain intermediate B; S3: 33 parts of intermediate A, 20 parts of intermediate B, 24 parts of N,N′-dicyclohexylcarbodiimide, 12 parts of 4-dimethylaminopyridine and 300 parts of tetrahydrofuran were mixed, the temperature was raised to 35° C., and the reaction was carried out for 6 hours. After the reaction was completed, the solvent was removed in vacuo and purified to obtain intermediate C; S4: Under a protective atmosphere, 50 parts of intermediate C, 21 parts of 3-mercapto-1,2-propylene glycol, 1 part of dibenzoyl peroxide, and 250 parts of N,N-dimethylformamide were mixed, the temperature was raised to 50° C., the reaction was performed for 3 hours, and post-processing was performed to obtain a modified diol.

[0024] Example 2: A method for preparing a high thermal stability polyphosphate flame retardant, comprising the following process: adding 250 parts of modified diol and 2 parts of aluminum chloride into a three-necked flask, introducing nitrogen, heating to 70°C under stirring, then adding 230 parts of phenyl dichlorophosphate, maintaining the temperature for reaction for 5 hours, then heating to 220°C, reacting for 4 hours, cooling after the reaction is complete, crushing, washing with water, and vacuum drying to obtain a polyphosphate flame retardant; Wherein, the preparation process of modified diol is: S1: 24 parts of trifluorodecanol, 15 parts of 4′-hydroxy-4-benzoic acid, 1 part of p-toluenesulfonic acid, and 120 parts of p-xylene were mixed, the temperature was raised to 80°C, and the reaction was carried out for 4 hours. After the reaction was completed, the mixture was filtered, washed three times with 50°C deionized water, and dried to obtain intermediate A; S2: 15 parts of 4′-hydroxy-4-benzoic acid, 5 parts of sodium hydroxide and 50 parts of water were mixed and stirred for 5 minutes to obtain a mixed solution; then 10 parts of acryloyl chloride were dissolved in 80 parts of acetic acid, added to the mixed solution, reacted at room temperature for 6 hours, filtered, washed and dried to obtain intermediate B; S3: 35 parts of intermediate A, 22 parts of intermediate B, 28 parts of N,N′-dicyclohexylcarbodiimide, 15 parts of 4-dimethylaminopyridine, and 350 parts of tetrahydrofuran were mixed, the temperature was raised to 40°C, and the reaction was carried out for 8 hours. After the reaction was completed, the solvent was removed in vacuo and purified to obtain intermediate C; S4: Under a protective atmosphere, 55 parts of intermediate C, 22 parts of 3-mercapto-1,2-propylene glycol, 2 parts of dibenzoyl peroxide, and 300 parts of N,N-dimethylformamide were mixed, the temperature was raised to 60° C., the reaction was performed for 4 hours, and post-processing was performed to obtain a modified diol.

[0025] Example 3: A method for preparing a high thermal stability polyphosphate flame retardant, comprising the following process: adding 225 parts of modified diol and 1.5 parts of aluminum chloride into a three-necked flask, introducing nitrogen, heating to 65°C under stirring, then adding 220 parts of phenyl dichlorophosphate, maintaining the temperature for reaction for 4.5 hours, then heating to 210°C, reacting for 3.5 hours, cooling after the reaction is complete, crushing, washing with water, and vacuum drying to obtain a polyphosphate flame retardant; Wherein, the preparation process of modified diol is: S1: 22.5 parts of trifluorodecanol, 14 parts of 4′-hydroxy-4-benzoic acid, 0.9 parts of p-toluenesulfonic acid, and 110 parts of p-xylene were mixed, the temperature was raised to 75°C, and the reaction was carried out for 3.5 hours. After the reaction was completed, the mixture was filtered, washed three times with 50°C deionized water, and dried to obtain intermediate A; S2: 14 parts of 4′-hydroxy-4-benzoic acid, 4.5 parts of sodium hydroxide and 45 parts of water were mixed and stirred for 4 minutes to obtain a mixed solution; then 9.5 parts of acryloyl chloride were dissolved in 75 parts of acetic acid, added to the mixed solution, reacted at room temperature for 5.5 hours, filtered, washed and dried to obtain intermediate B; S3: 34 parts of intermediate A, 21 parts of intermediate B, 26 parts of N,N′-dicyclohexylcarbodiimide, 13.5 parts of 4-dimethylaminopyridine, and 325 parts of tetrahydrofuran were mixed, the temperature was raised to 37.5°C, and the reaction was carried out for 7 hours. After the reaction was completed, the solvent was removed in vacuo and purified to obtain intermediate C; S4: Under a protective atmosphere, 52.5 parts of intermediate C, 21.5 parts of 3-mercapto-1,2-propylene glycol, 1.5 parts of dibenzoyl peroxide, and 275 parts of N,N-dimethylformamide were mixed, the temperature was raised to 55° C., the reaction was performed for 3.5 hours, and post-processing was performed to obtain a modified diol; Comparative Example 1: Using biphenol instead of modified diol, the rest is the same as Example 3, specifically as follows: A method for preparing a high thermal stability polyphosphate flame retardant, comprising the following process: adding 180 parts of biphenol and 1.5 parts of aluminum chloride into a three-necked flask, passing nitrogen, heating to 65°C under stirring conditions, then adding 220 parts of phenyl dichlorophosphate, maintaining the temperature for reaction for 4.5 hours, then heating to 210°C, reacting for 3.5 hours, cooling after the reaction is complete, crushing, washing with water, and vacuum drying to obtain a polyphosphate flame retardant.

[0026] Comparative Example 2: Using a commercially available polyphosphate flame retardant.

[0027] Detection test: The polyphosphate flame retardant and polypropylene obtained in the embodiment and the comparative example were dried in a vacuum oven at 80°C for 12 hours, and after drying, they were mixed evenly in a mass ratio of 1:8, and then poured into a twin-screw extruder for extrusion molding at a processing temperature of 240°C; the extruded composite material was crushed and pelletized by a pelletizer, and relevant performance tests were performed: (1) The limiting oxygen index of the sample is determined using the national standard GB / T2406 "Test method for combustion performance of plastics"; (2) Place the sample in an environment of 180°C and oxidize it in hot air for 48 hours, then measure the limiting oxygen index (test standard GB / T2406-2008) and calculate the retention rate of the limiting oxygen index; A combustion test was carried out on Example 3, and the SEM image of the carbon residue after combustion was measured using a scanning electron microscope. Figure 1 shown.

[0028] The obtained data are shown in Table 1: Table 1

[0029] Conclusion: The present invention prepares a high thermal stability polyphosphate flame retardant through multi-step chemical reactions, and the rigid groups and short-chain fluoride components introduced into the modified diol structure significantly improve the thermal stability and flame retardant properties of the material. Experimental data show that the limiting oxygen index of Examples 1 to 3 are 34.8%, 35.6% and 37.8%, respectively, which are much higher than Comparative Example 1 (28.8%) and Comparative Example 2 (26.7%), and after 48 hours of hot air oxidation at 180°C, the limiting oxygen index retention rate of the embodiment is as high as 98.9%-99.4%, which is significantly better than 85.6% and 84.3% of the comparative example, indicating that the flame retardant has excellent stability in high temperature environments, can effectively delay decomposition and maintain flame retardant efficiency, and is suitable for flame retardant applications of polymer materials.

[0030] In the description of the specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0031] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the invention or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. A method for preparing a high thermal stability polyphosphate flame retardant, characterized in that: The method comprises the following steps: adding modified diol and aluminum chloride into a three-necked flask, introducing nitrogen, heating to 60-70° C. under stirring, then adding phenyl dichlorophosphate, maintaining the temperature for reaction for 4-5 hours, then heating to 200-220° C., reacting for 3-4 hours, cooling after the reaction is complete, crushing, washing with water, and vacuum drying to obtain a polyphosphate flame retardant; The preparation process of the modified diol is: S1: trifluorodecanol, 4′-hydroxy-4-benzoic acid, p-toluenesulfonic acid and p-xylene were mixed, the temperature was raised to 70-80°C, and the reaction was carried out for 3-4 hours. After the reaction was completed, the mixture was filtered, washed three times with 50°C deionized water, and dried to obtain intermediate A; S2: Mix 4′-hydroxy-4-benzoic acid, sodium hydroxide and water, and stir for 3-5 minutes to obtain a mixed solution; then dissolve acryloyl chloride in acetic acid, add it to the mixed solution, react at room temperature for 5-6 hours, filter, wash and dry to obtain intermediate B; S3: Intermediate A, intermediate B, N,N′-dicyclohexylcarbodiimide, 4-dimethylaminopyridine and tetrahydrofuran are mixed, the temperature is raised to 35-40° C., and the reaction is carried out for 6-8 hours. After the reaction is completed, the solvent is removed in vacuo and purified to obtain intermediate C; S4: Under a protective atmosphere, the intermediate C, 3-mercapto-1,2-propylene glycol, dibenzoyl peroxide, and N,N-dimethylformamide are mixed, the temperature is raised to 50-60° C., the reaction is carried out for 3-4 hours, and post-processing is performed to obtain a modified diol.

2. The method for preparing a high thermal stability polyphosphate flame retardant according to claim 1, characterized in that: Polyphosphate flame retardant raw material The invention comprises the following substances: by weight, 200-250 parts of modified diol, 1-2 parts of aluminum chloride and 210-230 parts of phenyl dichlorophosphate.

3. The method for preparing a high thermal stability polyphosphate flame retardant according to claim 1, characterized in that: The intermediate A raw material comprises the following components: by weight, 21-24 parts of trifluorodecanol, 13-15 parts of 4'-hydroxy-4-benzoic acid, 0.8-1 parts of p-toluenesulfonic acid, and 100-120 parts of p-xylene.

4. The method for preparing a high thermal stability polyphosphate flame retardant according to claim 1, characterized in that: The intermediate B raw material comprises the following components: by weight, 13-15 parts of 4'-hydroxy-4-benzoic acid, 4-5 parts of sodium hydroxide, 40-50 parts of water, 9-10 parts of acryloyl chloride, and 70-80 parts of acetic acid.

5. The method for preparing a high thermal stability polyphosphate flame retardant according to claim 1, characterized in that: The intermediate C raw material comprises the following components: by weight, 33-35 parts of intermediate A, 20-22 parts of intermediate B, 24-28 parts of N,N′-dicyclohexylcarbodiimide, 12-15 parts of 4-dimethylaminopyridine, and 300-350 parts of tetrahydrofuran.

6. The method for preparing a high thermal stability polyphosphate flame retardant according to claim 1, characterized in that: The modified diol raw material comprises the following components: by weight, 50-55 parts of intermediate C, 21-22 parts of 3-mercapto-1,2-propylene glycol, 1-2 parts of dibenzoyl peroxide, and 250-300 parts of N,N-dimethylformamide.

7. The polyphosphate flame retardant obtained according to the preparation method of a polyphosphate flame retardant with high thermal stability according to any one of claims 1 to 6.

Images