Efficient polyphosphate flame retardant and preparation method thereof

Abstract

The invention discloses an efficient polyphosphate flame retardant and a preparation method thereof, and belongs to the technical field of flame retardants. Comprising phenoxy phosphoryl dichloride, modified dihydric alcohol and a catalyst, and the molar ratio of phenoxy phosphoryl dichloride to modified dihydric alcohol to catalyst is 1: (0.8-1.2): (0.01-0.03). The polyphosphate flame retardant takes phenoxy phosphoryl dichloride as one of the raw materials, so that the flame retardant is endowed with relatively high heat-resistant stability; the prepared polyphosphate flame retardant is in a solid state, and is easier to transport compared with a liquid flame retardant in the market; the modified dihydric alcohol is prepared through two-step reaction, the modified dihydric alcohol serves as one of raw materials, molecules of the modified dihydric alcohol contain multiple functional groups, the flame retardant effect of the flame retardant can be greatly enhanced, and the heat-resistant stability of the flame retardant is improved; in conclusion, the prepared polyphosphate flame retardant is good in flame retardant effect, convenient to transport and high in heat-resistant stability, and has important application value in the technical field of flame retardants.

Description

Technical Field

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

[0002] With the widespread application of polymer materials in the fields of construction, electronics, transportation, etc., the safety hazards caused by their flammability have received increasing attention. As a key auxiliary agent to inhibit material combustion, the technical development of flame retardants has always revolved around the three core issues of flame retardant efficiency, environmental friendliness and compatibility with substrates. Among the many flame retardant systems, phosphorus-based flame retardants have gradually become the mainstream choice to replace traditional halogen-based flame retardants due to their low smoke, low toxicity and high efficiency.

[0003] Polyphosphates are a type of polymer with a phosphorus-oxygen bond (PO) as the main chain and formed by repeated connection of phosphate structural units. This type of compound can play a flame retardant role in multiple ways during combustion: in the condensed phase, the polyphosphoric acid generated by the thermal decomposition of polyphosphates can catalyze the formation of a dense carbon layer on the surface of the material, isolating oxygen and heat transfer; in the gas phase, the phosphorus-containing free radicals (such as PO·) produced by decomposition can capture the active free radicals (H·, OH·) in the combustion chain reaction, inhibiting the spread of flames. Compared with small molecule phosphates, the high molecular weight characteristics of polyphosphates significantly reduce their mobility in the substrate, thereby extending the flame retardant time. At the same time, their compatibility with the polymer matrix can be further optimized through molecular structure design to reduce the negative impact on the mechanical properties of the material. It is regarded as an important research direction for the new generation of flame retardants.

[0004] The current synthesis route of polyphosphate flame retardants is mainly based on the polycondensation reaction of phosphate monomers, but there are still many technical bottlenecks in practical applications. Traditional preparation processes mostly use polyphosphoric acid or phosphorus pentoxide as the phosphorus source. Although such strong dehydrating agents can accelerate the reaction process, they are prone to cause side reactions, resulting in a wide molecular weight distribution and insufficient purity of the product, which in turn affects the stability of the flame retardant properties. For example, in the esterification reaction of polyphosphoric acid and polyols, the violent exothermic effect often causes local overheating, leading to molecular chain breakage or excessive cross-linking, and it is difficult to balance the thermal stability and processing fluidity of the final product. Therefore, in view of the above-mentioned technical pain points, it is urgent to develop a polyphosphate flame retardant with excellent flame retardant effect and good heat resistance stability to meet the higher requirements in the field of flame retardant technology. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects of the prior art and provide a method for preparing aluminum titanate nanofibers.

[0006] The purpose of the present invention can be achieved through the following technical solutions: A method for preparing a high-efficiency polyphosphate flame retardant comprises the following steps: A1. Add phenoxyphosphoryl dichloride, modified diol and catalyst into a reactor with a hydrogen chloride gas exhaust device, introduce protective gas, continuously raise the temperature to 90-100°C, continuously stir until the reactants are completely liquid, then raise the temperature to 140-160°C, react until the system becomes viscous and a pole climbing phenomenon occurs, raise the temperature again until the temperature reaches 200-210°C, continue stirring and react for 3-6 hours, and stop stirring when the reaction is complete; A2. The reactor was evacuated to remove the residual hydrogen chloride gas in the system, and then cooled. The obtained solid was dissolved with ethylene dichloride, precipitated with petroleum ether, filtered, dried, and crushed to obtain a high-efficiency polyphosphate flame retardant.

[0007] Furthermore, the molar ratio of the phenoxyphosphoryl dichloride, the modified diol and the catalyst is 1:0.8-1.2:0.01-0.03.

[0008] Furthermore, the catalyst is one of anhydrous calcium chloride and anhydrous aluminum chloride.

[0009] Furthermore, the protective gas is nitrogen.

[0010] Furthermore, the drying condition is to dry in an oven at 80-100° C. for 6-12 hours.

[0011] Phenoxyphosphoryl dichloride is used as one of the raw materials, and contains a benzene ring, which belongs to an aromatic group. The π-π conjugated system in the aromatic compound has high thermal stability, can effectively disperse heat, and improves the heat resistance of polyphosphate. In addition, most polyphosphate flame retardants on the market are in liquid form, which has the defects of inconvenient transportation and easy penetration, while the present invention is in solid form and convenient for transportation.

[0012] Further, the modified diol is prepared by the following steps: Step 1, 1,3-bis(aminopropyl)tetramethyldisiloxane and N,N-dimethylformamide are added to a three-necked round-bottom flask equipped with a thermometer, a magnetic stirring system and a spherical condenser, and formaldehyde solution (mass fraction 12%) is added dropwise under an ice-water bath condition, and stirring is continued until the addition is completed, and then 4-hydroxystyrene is added, and the temperature is increased until the temperature of the reaction system reaches 70°C, and reflux reaction is carried out for 8 hours. After the reaction is completed, the reaction is cooled to room temperature, and part of the solvent is removed by rotary evaporation, and column chromatography purification is carried out using a benzene-ethyl acetate (3:2, v / v) elution system, and finally the residual eluent is removed by reduced pressure distillation to obtain an intermediate product; 1,3-bis(aminopropyl)tetramethyldisiloxane and 4-hydroxystyrene undergo a Mannich condensation reaction, and the molar ratio of 1,3-bis(aminopropyl)tetramethyldisiloxane to 4-hydroxystyrene is adjusted to close to 1:2 (4-hydroxystyrene is slightly excessive), ensuring that two amino groups on 1,3-bis(aminopropyl)tetramethyldisiloxane participate in the reaction to obtain an intermediate product; the specific reaction process is as follows:

[0013] Step 2, the intermediate product, azobisisobutyronitrile (AIBN) and N, N-dimethylformamide are added to a three-necked round-bottom flask equipped with a thermometer, a magnetic stirring system and a spherical condenser, and after stirring and mixing evenly, 3-mercaptopropanol is added dropwise to the flask using a constant pressure dropping funnel, and the dropping process is continuously stirred. After the dropping is completed, the temperature is increased until the temperature of the reaction system reaches 85°C, and the reaction is refluxed for 8 hours. After the reaction is completed, the mixture is cooled to room temperature, and part of the solvent is removed by rotary evaporation. Column chromatography purification is performed using a benzene-ethyl acetate (5:3, v / v) elution system, and the residual eluent is finally removed by reduced pressure distillation to obtain a modified diol; Under the action of azobisisobutyronitrile, the unsaturated carbon-carbon double bond on the intermediate product undergoes a thiol-ene click reaction with the thiol group on 3-mercaptopropanol, and the molar ratio of the intermediate product to 3-mercaptopropanol is adjusted to close to 1:2 (3-mercaptopropanol is slightly excessive) to ensure that two double bonds on the intermediate product participate in the reaction to obtain a modified diol; the specific reaction process is as follows:

[0014] The obtained modified diol molecule is used as a raw material for preparing polyphosphate flame retardant. The molecule is centered on the -Si-O-Si- segment. Since the Si-O bond has a high bond energy, it can improve the heat stability of the flame retardant. The introduced benzoxazine structure contains a benzene ring and an oxazine ring. The conjugated structure of the two gives the molecular chain high rigidity, restricts the movement of the chain segment, and reduces the absorption of thermal vibration energy at high temperature. In addition, the lone pair of electrons of nitrogen and oxygen atoms forms a conjugated system with the benzene ring, which enhances the electron delocalization in the molecule and can further enhance the heat stability of the flame retardant. In addition, the modified diol molecule It contains a variety of heteroatoms, including Si, N and S. The silicon-containing element decomposes at high temperature to form silicon dioxide or silicon-oxygen-carbon network structure. These products can catalyze the formation of a dense and stable carbon layer on the surface of the substrate, thereby improving the flame retardant properties. The nitrogen element decomposes at high temperature to form nitrogen-containing gas, which reduces the oxygen concentration and improves the flame retardant properties. Finally, the sulfur element can release strong acids such as sulfuric acid under high temperature conditions, promote the dehydration of the substrate into carbon, and can also exhibit excellent flame retardant properties in the condensed phase. These heteroatoms can play a synergistic role with polyphosphate esters, greatly enhancing the flame retardant effect of the flame retardant.

[0015] Furthermore, in step 1, the ratio of 1,3-bis(aminopropyl)tetramethyldisiloxane, N,N-dimethylformamide, formaldehyde solution, and 4-hydroxystyrene is 24.8 g: 100 mL: 15 mL: 26.7 g.

[0016] Furthermore, in step 2, the ratio of the amount of the intermediate product, azobisisobutyronitrile, N,N-dimethylformamide, and 3-mercaptopropanol is 53.6 g:0.3 g:150 mL:20.3 g.

[0017] Beneficial effects of the present invention: 1. The polyphosphate flame retardant prepared by the present invention uses phenoxyphosphoryl dichloride as one of the raw materials, which gives the flame retardant higher heat resistance stability; 2. The prepared polyphosphate flame retardant is solid, which is easier to transport than the liquid flame retardant on the market; 3. The modified diol is obtained through a two-step reaction. As one of the raw materials, the modified diol contains a variety of functional groups in the molecule, which can greatly enhance the flame retardant effect of the flame retardant and improve the heat stability of the flame retardant; In summary, the polyphosphate flame retardant prepared by the present invention has good flame retardant effect, is convenient to transport, and has strong heat resistance and stability, and has important application value in the field of flame retardant technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will be further described below in conjunction with the accompanying drawings.

[0019] Figure 1 This is a SEM picture of the carbon residue after the combustion test of the high-efficiency polyphosphate flame retardant prepared in Example 5 of the present invention added to polypropylene. DETAILED DESCRIPTION

[0020] 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.

[0021] Embodiment 1 Preparation of modified diols: Step 1, 24.8g 1,3-bis(aminopropyl)tetramethyldisiloxane and 100mL N,N-dimethylformamide are added to a three-necked round-bottom flask equipped with a thermometer, a magnetic stirring system and a spherical condenser, and 15mL formaldehyde solution (mass fraction 12%) is added dropwise under an ice-water bath condition, and stirring is continued until the addition is completed, and then 26.7g 4-hydroxystyrene is added, and the temperature is increased until the temperature of the reaction system reaches 70°C, and the reaction is refluxed for 8h. After the reaction is completed, the mixture is cooled to room temperature, and part of the solvent is removed by rotary evaporation, and column chromatography purification is performed using a benzene-ethyl acetate (3:2, v / v) elution system, and finally the residual eluent is removed by reduced pressure distillation to obtain an intermediate product; Step 2, 53.6g of the intermediate product, 0.3g of azobisisobutyronitrile and 150mL of N,N-dimethylformamide were added to a three-necked round-bottom flask with a thermometer, a magnetic stirring system and a spherical condenser. After stirring and mixing evenly, 20.3g of 3-mercaptopropanol was added dropwise to the flask using a constant pressure dropping funnel. The dropping process was continuously stirred. After the dropping was completed, the temperature was increased until the temperature of the reaction system reached 85°C, and the reaction was refluxed for 8h. After the reaction was completed, it was cooled to room temperature, and part of the solvent was removed by rotary evaporation. Column chromatography purification was performed using a benzene-ethyl acetate (5:3, v / v) elution system, and the residual eluent was finally removed by reduced pressure distillation to obtain a modified diol.

[0022] Embodiment 2 Preparation of modified diols: Step 1, 49.6g 1,3-bis(aminopropyl)tetramethyldisiloxane and 200mL N,N-dimethylformamide were added to a three-necked round-bottom flask equipped with a thermometer, a magnetic stirring system and a spherical condenser. Under an ice-water bath, 30mL formaldehyde solution (mass fraction 12%) was added dropwise, and stirring was continued until the addition was completed, and then 53.4g 4-hydroxystyrene was added, and the temperature was increased until the temperature of the reaction system reached 70°C. The reaction was refluxed for 8h. After the reaction was completed, the mixture was cooled to room temperature, and part of the solvent was removed by rotary evaporation. Column chromatography purification was performed using a benzene-ethyl acetate (3:2, v / v) elution system, and the residual eluent was finally removed by reduced pressure distillation to obtain an intermediate product; Step 2, 107.2g of the intermediate product, 0.6g of azobisisobutyronitrile and 300mL of N,N-dimethylformamide were added to a three-necked round-bottom flask with a thermometer, a magnetic stirring system and a spherical condenser. After stirring and mixing evenly, 40.6g of 3-mercaptopropanol was added dropwise to the flask using a constant pressure dropping funnel. The dropping process was continuously stirred. After the dropping was completed, the temperature was increased until the temperature of the reaction system reached 85°C, and the reaction was refluxed for 8h. After the reaction was completed, it was cooled to room temperature, and part of the solvent was removed by rotary evaporation. Column chromatography purification was performed using a benzene-ethyl acetate (5:3, v / v) elution system, and the residual eluent was finally removed by reduced pressure distillation to obtain a modified diol.

[0023] Embodiment 3 Preparation of high-efficiency polyphosphate flame retardant: A1. Add 21.1 g of phenoxyphosphoryl dichloride, 57.7 g of the modified diol obtained in Example 1 and 0.1 g of anhydrous calcium chloride to a reactor with a hydrogen chloride gas exhaust device, introduce nitrogen as a protective gas, and continuously heat up to 90° C., stir continuously until the reactants are completely liquid, then raise the temperature to 140° C., react until the system becomes viscous and a pole climbing phenomenon occurs, and heat again until the temperature reaches 200° C., continue stirring the reaction for 3 h, and stop stirring when the reaction is complete; A2. The reactor was evacuated to remove the residual hydrogen chloride gas in the system, and then cooled. The obtained solid was dissolved with dichloroethane, precipitated with petroleum ether, filtered, dried in an oven at 80° C. for 6 h, and crushed to obtain a high-efficiency polyphosphate flame retardant.

[0024] Embodiment 4 Preparation of high-efficiency polyphosphate flame retardant: A1. Add 21.1 g of phenoxyphosphoryl dichloride, 72.1 g of the modified diol obtained in Example 2 and 0.2 g of anhydrous calcium chloride to a reactor with a hydrogen chloride gas exhaust device, introduce nitrogen as a protective gas, and continuously heat up to 100° C., stir continuously until the reactants are completely liquid, then raise the temperature to 150° C., react until the system becomes viscous and a pole climbing phenomenon occurs, and heat again until the temperature reaches 210° C., continue stirring the reaction for 5 h, and stop stirring when the reaction is complete; A2. The reactor was evacuated to remove the residual hydrogen chloride gas in the system, and then cooled. The obtained solid was dissolved with dichloroethane, precipitated with petroleum ether, filtered, dried in an oven at 100° C. for 12 h, and crushed to obtain a high-efficiency polyphosphate flame retardant.

[0025] Embodiment 5 Preparation of high-efficiency polyphosphate flame retardant: A1. Add 21.1 g of phenoxyphosphoryl dichloride, 86.5 g of the modified diol obtained in Example 2 and 0.3 g of anhydrous calcium chloride to a reactor with a hydrogen chloride gas exhaust device, introduce nitrogen as a protective gas, and continuously heat up to 100° C., stir continuously until the reactants are completely liquid, then raise the temperature to 160° C., react until the system becomes viscous and a pole climbing phenomenon occurs, and heat again until the temperature reaches 200° C., continue stirring the reaction for 6 h, and stop stirring when the reaction is complete; A2. The reactor was evacuated to remove the residual hydrogen chloride gas in the system, and then cooled. The obtained solid was dissolved with dichloroethane, precipitated with petroleum ether, filtered, dried in an oven at 100° C. for 12 h, and crushed to obtain a high-efficiency polyphosphate flame retardant; The flame retardant prepared in Example 5 was mixed with polypropylene at a mass ratio of 12:100, added to a twin-screw extruder, melt blended, and extruded. A combustion test was performed, and a SEM image of the residual carbon after combustion was measured using a scanning electron microscope. Figure 1 shown.

[0026] Comparative Example 1 The modified diol in Example 5 was replaced by 1,4-butanediol of equal mass, and the remaining steps were the same as those in Example 5 to prepare a flame retardant.

[0027] Comparative Example 2 A commercially available polyphosphate flame retardant was used.

[0028] The examples 3, 4, 5 and the comparative examples 1 and 2 were mixed with polypropylene at a mass ratio of 12:100, added into a twin-screw extruder, melt blended, extruded, granulated, and then the following performance tests were performed: The national standard GB / T 2406-2008 "Test method for combustion performance of plastics" is used to determine the limiting oxygen index of the sample; Place the sample in an environment of 140°C and oxidize it with hot air for 72 hours, then measure the limiting oxygen index (test standard GB / T2406-2008) and calculate the retention rate of the limiting oxygen index; the retention rate of the limiting oxygen index = limiting oxygen index after test / limiting oxygen index before test × 100%; The measured results are shown in Table 1: Table 1

[0029] As shown in Table 1, the flame retardant performance and thermal stability of the polyphosphate flame retardant prepared in the embodiment of the present invention are higher than those in the comparative example, and the flame retardant performance and thermal stability of the flame retardant are enhanced as the amount of modified diol used in the embodiments 3, 4 and 5 increases. Figure 1 It can be seen that when Example 5 is added to polypropylene, fewer pores are formed, forming a carbon layer with good density, which covers the surface of the material and improves the flame retardant properties of the material; in summary, the present invention has important application value in the field of flame retardant technology.

[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-efficiency polyphosphate flame retardant, characterized in that: The steps include: A1. Add phenoxyphosphoryl dichloride, modified diol and catalyst into a reactor, introduce protective gas, continuously raise the temperature to 90-100°C, and continuously stir until the reactants are completely liquid. Then raise the temperature to 140-160°C and react until the system becomes viscous and a pole climbing phenomenon occurs. Then raise the temperature again until the temperature reaches 200-210°C, stir and react for 3-6 hours, and stop stirring when the reaction is complete. A2, the reactor was evacuated, then cooled, the obtained solid was dissolved with ethylene dichloride, precipitated with petroleum ether, filtered, dried, and crushed to obtain a high-efficiency polyphosphate flame retardant; Wherein, the modified diol is prepared by the following steps: Step 1, 1,3-bis(aminopropyl)tetramethyldisiloxane and N,N-dimethylformamide are added to a flask, and formaldehyde solution is added dropwise under an ice-water bath, and stirring is continued until the addition is complete, and then 4-hydroxystyrene is added, and reflux reaction is carried out at 70° C. for 8 hours. After the reaction is completed, the mixture is cooled, rotary evaporated, purified by column chromatography, and distilled under reduced pressure to obtain an intermediate product; Step 2: Add the intermediate product, azobisisobutyronitrile and N,N-dimethylformamide into a flask, stir and mix evenly, then add 3-mercaptopropanol, stirring continuously during the addition process. After the addition is completed, reflux at 85° C. for 8 hours. After the reaction is completed, cool to room temperature, rotary evaporate, purify by column chromatography, and distill under reduced pressure to obtain a modified diol.

2. The method for preparing a high-efficiency polyphosphate flame retardant according to claim 1, characterized in that: The molar ratio of the phenoxyphosphoryl dichloride, the modified diol and the catalyst is 1:0.8-1.2:0.01-0.

03.

3. The method for preparing a high-efficiency polyphosphate flame retardant according to claim 1, characterized in that: In step 1, the ratio of 1,3-bis(aminopropyl)tetramethyldisiloxane, N,N-dimethylformamide, formaldehyde solution and 4-hydroxystyrene is 24.8 g:100 mL:15 mL:26.7 g.

4. The method for preparing a high-efficiency polyphosphate flame retardant according to claim 1, characterized in that: In step 2, the ratio of the amount of the intermediate product, azobisisobutyronitrile, N,N-dimethylformamide, and 3-mercaptopropanol is 53.6 g:0.3 g:150 mL:20.3 g.

5. The method for preparing a high-efficiency polyphosphate flame retardant according to claim 1, characterized in that: The catalyst is one of anhydrous calcium chloride and anhydrous aluminum chloride.

6. The method for preparing a high-efficiency polyphosphate flame retardant according to claim 1, characterized in that: The protective gas is nitrogen.

7. The method for preparing a high-efficiency polyphosphate flame retardant according to claim 1, characterized in that: The drying condition is to dry in an oven at 80-100° C. for 6-12 hours.

8. A high-efficiency polyphosphate flame retardant, characterized in that: Prepared according to the method according to any one of claims 1 to 7.

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