Hydrolysis-resistant reactive phosphorus flame retardant and preparation method thereof

Abstract

The invention discloses a hydrolysis-resistant reactive phosphorus flame retardant and a preparation method thereof, and belongs to the technical field of flame retardants, the key point of the technical scheme is that the preparation method comprises the following preparation steps: S1, mixing p-bromostyrene, 3, 3 '-dibromostyrene and 3, 3'-dibromostyrene; the method comprises the following steps: mixing 2, 5-dimethyl-4-chlorophenylboronic acid, a catalyst, a polymerization inhibitor and a mixed solution of a potassium carbonate solution bubbled by nitrogen and dichloromethane, heating to 70-95 DEG C under the protection of nitrogen, reacting for 4-10 hours, extracting after the reaction is finished, and carrying out column chromatography to obtain a styrene derivative; s2, dissolving diethyl phosphine oxide in dioxane, adding sodium hydroxide under the condition of ice-water bath, stirring and reacting to form phosphate, and performing suction filtration to take a solid for later use; and S3, adding the styrene derivative obtained in the step S1 into a solvent, adding a phase transfer catalyst, uniformly stirring, adding a polymerization inhibitor, adding the phosphate obtained in the step S2, reacting for 1-5 hours, extracting after the reaction is finished, and performing reduced-pressure rotary evaporation to obtain the reactive phosphorus flame retardant, thereby achieving the effect of improving the hydrolysis resistance of the reactive phosphorus flame retardant.

Description

Technical Field

[0001] The invention relates to the technical field of flame retardants, in particular to a hydrolysis-resistant reactive phosphorus flame retardant and a preparation method thereof. Background Art

[0002] Flame retardants are functional additives that can reduce the flammability, self-extinguishing or smoke suppression of flammable or combustible materials and improve the flame retardancy of materials. They have broad market prospects in various fields such as chemical building materials, food, clothing, housing, transportation, and electronic appliances. There are many types of flame retardants. Generally, based on the method of treating the flame retardant and the substrate, they can be divided into additive flame retardants and reactive flame retardants. In the process of flame retardant finishing the substrate, the additive flame retardant will not react chemically with other components in the substrate. It only enters the substrate in the form of physical blending or disperses on the surface of the substrate to make it flame retardant. The process of this type of flame retardant is relatively simple, but the requirements for the flame retardant itself are high. For example, in terms of the degree of micronization, the smaller the particles, the more uniform the blending of the flame retardant and the substrate, and the better the flame retardant effect. However, there is a certain degree of incompatibility between the additive flame retardant and the material, and precipitation and decomposition will occur during the processing, thereby affecting the mechanical properties of the material.

[0003] During the flame retardant finishing process, the reactive flame retardant undergoes polymerization or polycondensation reaction with the substrate and combines with the molecular chain of the polymer to play a flame retardant role. Representative flame retardants of reactive flame retardants are halogen-based, intumescent flame retardants, phosphorus-based, nitrogen-based and inorganic hydroxides. Among them, halogen-based flame retardants are one of the organic flame retardants with the highest global output and an important series of flame retardants. They are widely used at home and abroad because of their wide range of applications, high thermal stability, low price, high flame retardant efficiency and good compatibility. However, halogen-based flame retardants produce a lot of smoke and harmful gases during combustion, which poses a huge threat to the environment and human health. In recent years, it has been found that some brominated flame retardants themselves also have potential hazards to the environment and human health, which is obviously contrary to today's environmental protection requirements. Therefore, the transition of flame retardants to non-brominated and the development of halogen-free flame retardants have become a trend in the field of flame retardancy around the world.

[0004] Phosphorus-based flame retardants are the most important type of flame retardants, and are also the most complex and well-studied of all types of flame retardants. They are widely used in all walks of life. The flame retardant effect of phosphorus compounds in different reaction zones can be divided into flame retardant mechanisms in the condensed phase and flame retardant mechanisms in the vapor phase. The mechanism of organic phosphorus-based flame retardants in the condensed phase is as follows: during combustion, phosphorus compounds decompose to form a non-flammable liquid film of phosphoric acid, whose boiling point can reach 300°C. At the same time, phosphoric acid is further dehydrated to form metaphosphoric acid, which is further polymerized to form polymetaphosphoric acid. In this process, not only does the covering layer generated by phosphoric acid play a covering effect, but also because the generated polymetaphosphoric acid is a strong acid and a strong dehydrating agent, the polymer is dehydrated and carbonized, which changes the mode of the polymer combustion process and forms a film on its surface to isolate the air, thereby exerting a stronger flame retardant effect. Phosphorus flame retardant is also a free radical scavenger. Using mass spectrometry technology, it is found that any phosphorus-containing compound will form PO· when the polymer burns. It can combine with hydrogen atoms in the flame area to suppress the flame. In addition, the moisture generated by phosphorus flame retardants during the flame retardant process can, on the one hand, reduce the temperature of the condensed phase, and on the other hand, dilute the concentration of combustibles in the gas phase, thereby better playing a flame retardant role. Therefore, phosphorus flame retardants have attracted much attention from scholars in recent years.

[0005] However, the traditional phosphate structure is easily hydrolyzed by changes in environmental pH, resulting in a decrease in the reactivity of phosphorus flame retardants. Summary of the invention

[0006] In order to solve the problems in the prior art, the present invention provides a hydrolysis-resistant reactive phosphorus flame retardant and a preparation method thereof.

[0007] The first aspect of the present invention is to provide a method for preparing a hydrolysis-resistant reactive phosphorus flame retardant, which adopts the following technical scheme: A method for preparing a hydrolysis-resistant reactive phosphorus flame retardant comprises the following preparation steps: S1. Synthesis of styrene derivatives The reaction equation is as follows: After mixing p-bromostyrene, 3,5-dimethyl-4-chlorophenylboric acid, a catalyst, an inhibitor, and a mixed solution of a potassium carbonate solution and dichloromethane after nitrogen bubbling, the mixture is heated to 70-95° C. under nitrogen protection for reaction for 4-10 hours. After the reaction is completed, extraction and column chromatography are performed to obtain a styrene derivative; S2. Phosphate preparation Dissolve diethylphosphine oxide in dioxane, add sodium hydroxide in an ice-water bath and stir to react to form phosphate, and filter out the solid for later use; S3. Synthesis of flame retardant The reaction equation is as follows: The styrene derivative obtained in step S1 is mixed with a solvent, a phase transfer catalyst is added, and then the mixture is stirred evenly. Then, a polymerization inhibitor is added, and then the phosphate obtained in step S2 is added to react for 1-5 hours. After the reaction is completed, extraction is performed, and vacuum rotary evaporation is performed to obtain a reactive phosphorus flame retardant.

[0008] In a preferred embodiment, the molar ratio of bromostyrene to 3,5-dimethyl-4-chlorophenylboronic acid in step S1 is 1:(0.8-1.2).

[0009] In a preferred embodiment, the molar ratio of bromostyrene to 3,5-dimethyl-4-chlorophenylboronic acid in step S1 is 1:(1.05-1.2) In a preferred embodiment, the reaction temperature of step S1 is 80-95° C., and the reaction time is 8-10 h.

[0010] In a preferred embodiment, the molar ratio of the styrene derivative to diethylphosphine oxide in S3 is 1:(0.8-1.3).

[0011] In a preferred embodiment, the molar ratio of the styrene derivative to diethylphosphine oxide in S3 is 1:(1.2-1.3).

[0012] In a preferred embodiment, the solvent in step S3 is one of toluene, benzene, dichloromethane, ethyl acetate, DMF, and dioxane.

[0013] In a preferred embodiment, the solvent is dioxane.

[0014] In a preferred embodiment, the reaction time in step S2 is 4-5 hours.

[0015] The second aspect of the present invention is to provide a reactive phosphorus flame retardant obtained by the preparation method of the above-mentioned hydrolysis-resistant reactive phosphorus flame retardant.

[0016] In summary, the present invention has the following beneficial effects: the present invention increases the steric hindrance of the structures on both sides of the phosphate ester, thereby greatly reducing the degree of hydrolysis reaction of the reactive phosphorus flame retardant, effectively improving the hydrolysis resistance of the reactive phosphorus flame retardant, and the reactive phosphorus flame retardant obtained in the present invention has a high phosphorus content and high reactivity, so the reactive phosphorus flame retardant obtained in the present invention can be used in industrial fields such as aerospace, machinery, and electronics. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is the H-NMR spectrum of the styrene derivative obtained in Preparation Example 1.

[0018] Figure 2 This is the H-NMR spectrum of the reactive phosphorus flame retardant obtained in Example 1. DETAILED DESCRIPTION

[0019] The present invention is further described in detail below in conjunction with the accompanying drawings.

[0020] Preparation Example 1 A synthesis of a styrene derivative comprises the following preparation steps: The synthetic reaction equation of styrene derivatives is as follows: 1 mol of p-bromostyrene, 1.05 mol of 3,5-dimethyl-4-chlorophenylboronic acid, 0.02 mol of (triphenylphosphine) palladium catalyst, and 0.01 mol of inhibitor p-hydroxyanisole were added to a flask, 100 mL of 3 mol / L potassium carbonate solution was prepared, and 300 mL of dichloromethane was added and mixed thoroughly. Nitrogen was bubbled to form a mixed solution, and the bubbled mixed solution was added to a flask and mixed thoroughly with other raw materials until completely dissolved. The mixture was heated to 85° C. under nitrogen protection for reaction for 8 h. After the reaction, a mixed system of dichloromethane and water was used for extraction, and the solvent was dried by spin drying after extraction. Column chromatography was used for dry loading for separation and purification (eluent was dichloromethane / petroleum ether). After the purification was completed, the solvent was removed by spin evaporation to obtain a styrene derivative with a purity greater than 99%, and the yield was 88.6%. The H-NMR spectrum is shown as follows Figure 1 shown.

[0021] Preparation Example 2-3 The synthesis of a styrene derivative is different from that of Preparation Example 1 in that the molar ratio of p-bromostyrene to 3,5-dimethyl-4-chlorophenylboronic acid is different, and the other conditions are the same. The yield of the obtained styrene derivative is shown in the following table.

[0022] It can be seen from the table that the yield of the styrene derivative is the highest when the molar ratio of p-bromostyrene to 3,5-dimethyl-4-chlorophenylboronic acid is 1:1.05.

[0023] Preparation Example 4-6 The synthesis of a styrene derivative is different from that of Preparation Example 1 in that the reaction temperature is different, that is, the reaction temperature is changed on the basis of a molar ratio of p-bromostyrene to 3,5-dimethyl-4-chlorophenylboronic acid of 1:1.05, while the other conditions are the same. The yields of styrene derivatives obtained at different reaction temperatures are shown in the following table. project Preparation Example 1 Preparation Example 4 Preparation Example 5 Preparation Example 6 Reaction temperature℃ 85 70 80 95 Yield % 88.6 68.2 81.3 82.4

[0024] It can be seen from the table that, under the premise of keeping the molar ratio and reaction time unchanged, the yield of styrene derivatives increases with increasing temperature, but when the temperature reaches 85°C, the yield begins to decrease. It can be seen that the optimal reaction temperature is 85°C.

[0025] Preparation Example 7-10 The synthesis of a styrene derivative is different from that of Preparation Example 1 in that the reaction time is different, that is, the reaction time is changed under the conditions that the molar ratio of p-bromostyrene to 3,5-dimethyl-4-chlorophenylboronic acid is 1:1.05 and the reaction temperature is 85°C, while the other conditions are the same. The yields of styrene derivatives obtained at different reaction times are shown in the following table. project Preparation Example 1 Preparation Example 7 Preparation Example 8 Preparation Example 10 Reaction time 8 4 6 10 Yield % 88.6 55.8 69.3 88.7

[0026] It can be seen from the above preparation examples that when the molar ratio of bromostyrene to 3,5-dimethyl-4-chlorophenylboronic acid is 1:1.05, the reaction temperature is 85°C, and the reaction time is 8h, the yield of the obtained styrene derivative is 88.6%. Although the yield after 10h of reaction in Preparation Example 10 is 88.7%, it is only 0.1% higher than that of the Preparation Example. Based on this, considering the production cost, the styrene derivative obtained in Preparation Example 1 is selected as the synthetic raw material for the reactive flame retardant.

[0027] Example 1 A method for preparing a hydrolysis-resistant reactive phosphorus flame retardant comprises the following preparation steps: S1. Phosphate preparation Dissolve 1.2 mol of diethylphosphine oxide in dioxane, add 1 mol of sodium hydroxide in an ice-water bath and stir for 1 hour to form phosphate, and filter out the solid for later use; S2. Synthesis of flame retardant The reaction equation is as follows: Take 1 mol of the styrene derivative obtained in Preparation Example 1 and add it to 300 mL of dioxane, then add the phase transfer catalyst benzyltriethylammonium chloride and stir evenly, then add the inhibitor p-hydroxyanisole and then add the phosphate obtained in step S2 to react for 4 hours. After the reaction is completed, extract and take the organic phase, and vacuum rotary evaporate for 0.5 hours to obtain a reactive phosphorus flame retardant with a yield of 79.3%. The H-NMR spectrum is as shown in Figure 2 As shown, the added amount of the phase transfer catalyst is 3% of the total mass of the styrene derivative and the phosphate, and the added amount of the polymerization inhibitor is 0.3% of the total mass of the styrene derivative and the phosphate.

[0028] Example 2 A method for preparing a hydrolysis-resistant reactive phosphorus flame retardant comprises the following preparation steps: S1. Phosphate preparation Dissolve 0.8 mol of diethylphosphine oxide in dioxane, add 1 mol of sodium hydroxide in an ice-water bath and stir for 1 hour to form phosphate, and filter out the solid for later use; S2. Synthesis of flame retardant Take 1 mol of the styrene derivative obtained in Preparation Example 1 and add it to 300 mL of dioxane, then add the phase transfer catalyst benzyltriethylammonium chloride and stir evenly, then add the inhibitor p-hydroxyanisole and then add the phosphate obtained in step S2 to react for 4 hours, extract after the reaction, take the organic phase, and evaporate under reduced pressure for 2 hours to obtain a reactive phosphorus flame retardant with a yield of 68.1%, wherein the amount of the phase transfer catalyst added is 3% of the total mass of the styrene derivative and the phosphate, and the inhibitor is 0.3% of the total mass of the styrene derivative and the phosphate.

[0029] Example 3 A method for preparing a hydrolysis-resistant reactive phosphorus flame retardant comprises the following preparation steps: S1. Phosphate preparation Dissolve 1.3 mol of diethylphosphine oxide in dioxane, add 1 mol of sodium hydroxide in an ice-water bath and stir for 1 hour to form phosphate, and filter out the solid for later use; S2. Synthesis of flame retardant Take 1 mol of the styrene derivative obtained in Preparation Example 1 and add it to 300 mL of dioxane, then add the phase transfer catalyst benzyltriethylammonium chloride and stir evenly, then add the inhibitor p-hydroxyanisole and then add the phosphate obtained in step S2 to react for 4 hours, extract after the reaction, take the organic phase, and evaporate under reduced pressure for 3 hours to obtain a reactive phosphorus flame retardant with a yield of 79.1%, wherein the amount of the phase transfer catalyst added is 3% of the total mass of the styrene derivative and the phosphate, and the inhibitor is 0.3% of the total mass of the styrene derivative and the phosphate.

[0030] Compared with Example 1, after only changing the molar ratio of styrene derivatives and diethylphosphine oxide, the yields of reactive phosphorus flame retardants obtained in Examples 2-3 are lower than the yield in Example 1, indicating that the molar ratio of styrene derivatives and diethylphosphine oxide in Example 1 is better.

[0031] Embodiment 4-8 A method for preparing a hydrolysis-resistant reactive phosphorus flame retardant is different from that of Example 1 in that the solvent for dissolving the styrene derivative is different, and the rest is the same as Example 1. The yield of the flame retardant obtained is shown in the following table. project Example 1 Example 4 Example 5 Example 6 Example 7 Example 8 Solvents Dioxane Toluene benzene Dichloromethane Ethyl acetate DMF Yield % 79.3 64.8 53.7 48.3 72.5 69.7

[0032] It can be seen from the table that when the amount of styrene derivatives, phosphates, reaction temperature and time are the same, the yields of the reactive phosphorus flame retardants obtained by using toluene, benzene, dichloromethane, ethyl acetate and DMF as solvents are lower than the yield when dioxane is used in Example 1. It can be seen that the yield of the reactive phosphorus flame retardant can be effectively improved when dioxane is used as the solvent.

[0033] Examples 9-11 A method for preparing a hydrolysis-resistant reactive phosphorus flame retardant is different from that of Example 1 in that the reaction time of the styrene derivative and the phosphate is different, and the other conditions are the same as those of Example 1. The yield of the flame retardant obtained is shown in the following table. project Example 1 Example 9 Example 10 Embodiment 11 Reaction time 4 1 3 5 Yield % 79.3 24.1 66.2 79.2

[0034] It can be seen from the table that when the amount of styrene derivatives, phosphates, reaction temperature, and solvent type are the same, the yield of the reactive phosphorus flame retardant gradually increases with the increase of reaction time. However, compared with Example 1, the yield of Example 11 begins to decrease, indicating that the optimal reaction time is 4 h.

[0035] Therefore, in summary, the yield of the reactive phosphorus flame retardant is the highest when the molar ratio of styrene derivative to diethylphosphine oxide is 1:1.2, the reaction time is 4 hours, and dioxane is used as the solvent.

[0036] The embodiments of this specific implementation method are all preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Therefore, all equivalent changes made based on the structure, shape, and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a hydrolysis-resistant reactive phosphorus flame retardant, characterized in that , comprising the following preparation steps: S1. Synthesis of styrene derivatives After mixing p-bromostyrene, 3,5-dimethyl-4-chlorophenylboric acid, a catalyst, an inhibitor, and a mixed solution of a potassium carbonate solution and dichloromethane after nitrogen bubbling, the mixture is heated to 70-95° C. under nitrogen protection for reaction for 4-10 hours. After the reaction is completed, extraction and column chromatography are performed to obtain a styrene derivative; S2. Phosphate preparation Dissolve diethylphosphine oxide in dioxane, add sodium hydroxide in an ice-water bath and stir to react to form phosphate, and filter out the solid for later use; S3. Synthesis of flame retardant The styrene derivative obtained in step S1 is mixed with a solvent, a phase transfer catalyst is added, and then the mixture is stirred evenly. Then, a polymerization inhibitor is added, and then the phosphate obtained in step S2 is added to react for 1-5 hours. After the reaction is completed, extraction is performed, and vacuum rotary evaporation is performed to obtain a reactive phosphorus flame retardant.

2. The method for preparing a hydrolysis-resistant reactive phosphorus flame retardant according to claim 1, characterized in that: In the step S1, the molar ratio of bromostyrene to 3,5-dimethyl-4-chlorophenylboronic acid is 1:(0.8-1.2).

3. The method for preparing a hydrolysis-resistant reactive phosphorus flame retardant according to claim 1, characterized in that: The molar ratio of bromostyrene to 3,5-dimethyl-4-chlorophenylboronic acid in step S1 is 1:(1.05-1.2) The method for preparing a hydrolysis-resistant reactive phosphorus flame retardant according to claim 1 is characterized in that the reaction temperature of step S1 is 80-95° C. and the reaction time is 8-10 h.

4. The method for preparing a hydrolysis-resistant reactive phosphorus flame retardant according to claim 1, characterized in that: The molar ratio of the styrene derivative to diethylphosphine oxide in S3 is 1:(0.8-1.3).

5. The method for preparing a hydrolysis-resistant reactive phosphorus flame retardant according to claim 1, characterized in that: The molar ratio of the styrene derivative to diethylphosphine oxide in S3 is 1:(1.2-1.3).

6. The method for preparing a hydrolysis-resistant reactive phosphorus flame retardant according to claim 1, characterized in that: The solvent in step S3 is one of toluene, benzene, dichloromethane, ethyl acetate, DMF and dioxane.

7. The method for preparing a hydrolysis-resistant reactive phosphorus flame retardant according to claim 7, characterized in that: The solvent used is dioxane.

8. The method for preparing a hydrolysis-resistant reactive phosphorus flame retardant according to claim 1, characterized in that: The reaction time in step S2 is 4-5h.

9. A reactive phosphorus flame retardant obtained by the method for preparing a hydrolysis-resistant reactive phosphorus flame retardant according to any one of claims 1 to 9.

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