A high-phosphorus-content hydrolysis-resistant flame retardant and its preparation method

Abstract

The present invention relates to a high-phosphorus-content hydrolysis-resistant flame retardant and a preparation method thereof. The structural formula of the high-phosphorus-content hydrolysis-resistant flame retardant is as follows: The preparation method of the high-phosphorus-content hydrolysis-resistant flame retardant is: carrying out a transesterification reaction between methyl phytate and phenylpropyl alcohol ester, and then obtaining the high-phosphorus-content hydrolysis-resistant flame retardant through high-vacuum impurity removal; the molar ratio of phenylpropyl alcohol ester to methyl phytate is greater than 12. First, the present invention realizes the esterification of the terminal carboxyl group of phytate through an esterification reaction. By carrying out a transesterification reaction between phenylpropyl alcohol with a reactive terminal hydroxyl group structure and phytate with an esterified terminal carboxyl group, a phenylpropyl structure with a large steric hindrance and a long chain segment is grafted onto the phosphoric acid structure on the surface of phytate, forming a cluster-like structure, improving the hydrolysis resistance and high-temperature resistance of the phytate structure, and solving the problems of hydrolysis resistance and high-temperature resistance of phytate.

Description

Technical Field

[0001] The present invention belongs to the technical field of flame retardant modification, and relates to a high-phosphorus-content hydrolysis-resistant flame retardant and a preparation method thereof. Background Art

[0002] Nowadays, polymer materials are widely used in all aspects of people's lives, but their flammability poses a serious threat to people's lives and property. Therefore, people increasingly attach importance to the development and utilization of flame retardant materials.

[0003] A flame retardant is an auxiliary agent that can prevent a material from being ignited or inhibit the spread of a flame. The existing flame retardant modification technologies for improving polymers are mainly divided into two methods: additive and reactive. As the main traditional flame retardant series, halogen-based and organophosphorus-based flame retardant materials have excellent flame retardant properties. Halogen-based flame retardants have good flame retardant properties, but their combustion will produce a large amount of toxic smoke, which is not conducive to environmental protection. For organophosphorus-based flame retardants, due to the limitation of the flame retardant mechanism, they need to contain a large amount of hydrogen and oxygen elements in themselves or in the modified material structure in order to form a char layer during combustion. At the same time, organophosphorus-based flame retardants also have a low addition amount, resulting in poor flame retardant effects, and problems such as poor hydrolysis resistance and high temperature resistance, so their application scope is limited.

[0004] Phytic acid, also known as inositol hexaphosphate, is an organic phosphorus compound extracted from plant seeds. It is a biomass flame retardant. The phosphorus content in phytic acid is as high as 28%, and the phosphoric acid and metaphosphoric acid structures generated by the phosphonate group during combustion can promote the formation of a carbon layer. However, phytic acid itself is a water-soluble substance as a flame retardant, and its concentration in water reaches 30wt%. Therefore, it is often used as a flame retardant for flame retardant modification of cotton fibers and paper. It mainly reacts the phosphoric acid group on the phytic acid with the hydroxyl group, amino group and other structures on the cellulose to be grafted on the cellulose surface, so as to cover the fiber surface and achieve the purpose of flame retardant modification. However, since phytic acid itself contains more hydrophilic phosphoric acid groups, it is easy to combine with water and the like and dissolve, resulting in poor hydrolysis resistance of phytic acid; and under high temperature environment, the phosphoric acid group is hydrolyzed, and the decomposed acidic structure will catalyze the hydrolysis of the phosphoric acid group, so that the hydrolysis of phytic acid is accelerated, and finally the decomposition temperature of phytic acid is low, and it is carbonized after decomposition. At the same time, the acidic structure of phytic acid itself has the effect of easily catalyzing the hydrolysis of ester bonds and amide groups on polyesters, polyamides, etc., so it is difficult to be applied to material systems such as polyesters, polyamides and polyurethanes. In order to improve the high temperature resistance and hydrolysis resistance of phytic acid, metal salt compounds phytates are formed by reacting with phytic acid, such as calcium phytate, magnesium phytate, iron phytate and other phytate structures. As an inorganic salt structure with a high phosphorus content, it has a high melting point and is difficult to dissolve in water, but it is difficult to have a good dispersion in the polymer matrix, which will lead to a decrease in the overall performance of the polymer matrix and a lack of a regular molecular structure, such as causing problems such as a decrease in thermal stability and mechanical properties. At the same time, phytate itself is affected by the six-membered ring structure and has a relatively low decomposition temperature. Therefore, as a blended modified flame retardant, the flame retardant efficiency needs to be further improved. while Ammonium phytate is synthesized by reacting phytic acid with ammonium salt in an alkaline environment. Ammonium phytate has a good phosphorus-nitrogen synergistic flame retardant effect. However, due to the solubility of ammonium phytate itself, especially in water systems, it has a large solubility and is greatly affected by temperature. At the same time, it has a low melting point.

[0005] Therefore, it is of great significance to develop an organophosphorus flame retardant with high phosphorus content, good flame retardant effect, hydrolysis resistance and high temperature resistance. Summary of the invention

[0006] The purpose of the present invention is to solve the above problems existing in the prior art, and to provide a high phosphorus content hydrolysis-resistant flame retardant and a preparation method thereof. The present invention uses phytic acid, methanol and phenylpropanol as raw materials, undergoes esterification reaction of phytic acid and methanol, then undergoes ester exchange reaction with phenylpropanol, and then undergoes high vacuum impurity removal to obtain an organic phosphine flame retardant with high phosphorus content, good flame retardant effect, hydrolysis resistance and good high temperature resistance. This flame retardant has important application prospects for flame retardant modification of plastics and fibers such as polyolefins, polyesters and polyamides.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] A hydrolyzable flame retardant with a high phosphorus content, and the structural formula of the hydrolyzable flame retardant with a high phosphorus content is as follows:

[0009]

[0010] The molecular formula of the hydrolyzable flame retardant with a high phosphorus content is C 114 H 138 O 24 P6.

[0011] As a preferred technical solution:

[0012] For a hydrolyzable flame retardant with a high phosphorus content as described above, the melting point of the hydrolyzable flame retardant with a high phosphorus content is 56-58 °C, the weight loss rate of the hydrolyzable flame retardant with a high phosphorus content after heat treatment in an air atmosphere at 300 °C for 24 h is <5%, and the phosphorus content retention rate of the hydrolyzable flame retardant with a high phosphorus content after being treated in a sodium hydroxide solution at a temperature of 80 °C and a concentration of 0.1 mol / L for 8 h is >99%.

[0013] The present invention also provides a preparation method of a hydrolyzable flame retardant with a high phosphorus content as described above. Methyl phytate and phenylpropyl alcohol ester are subjected to transesterification reaction, and then high-vacuum impurity removal under 200-300 Pa (the high-vacuum environment can ensure that unreacted raw materials and small-molecule products are removed from the flame retardant, and a high-purity hydrolyzable flame retardant with a high phosphorus content is obtained) to prepare a hydrolyzable flame retardant with a high phosphorus content;

[0014] Using phenylpropyl alcohol as the transesterification raw material is because phenylpropyl alcohol has a certain chain segment length, which increases the alkyl length, making the hydrolysis resistance increase, and contains a benzene ring structure, improving the high-temperature resistance. If phenylpentanol with a longer alkyl chain segment is used, etc., the phosphorus content will decrease, and the longer chain segments will entangle, which is not conducive to reflecting the performance of the flame retardant. Using shorter chain segments will result in the inability to connect to the terminal carboxyl group structure on the phosphate group due to steric hindrance effects. Therefore, using phenylpropyl alcohol can endow phytate with excellent hydrolysis resistance and high-temperature resistance at the same time.

[0015] The molar ratio of phenylpropyl alcohol ester to methyl phytate is greater than 12.

[0016] As a preferred technical solution:

[0017] The preparation method of a hydrolyzable flame retardant with a high phosphorus content as described above specifically comprises the following steps:

[0018] (1) Preparation of methyl phytate;

[0019] Phytic acid, methanol, a catalyst, an anti-aging agent, and an anti-etherification agent are added to a reaction kettle, a condensation reflux device is assembled, nitrogen protection is passed, the stirring rate is 100 rpm, a certain reaction temperature and reaction time are controlled, and methyl phytate, a transparent substance, is obtained.

[0020] (2) Preparation of the phytic acid phenylpropanol crude polymer;

[0021] Phenylpropanol is added to the methyl phytate reaction kettle, a condensation device is assembled, nitrogen protection is passed, the stirring rate is 200 rpm, a certain reaction temperature and reaction time are controlled, and the reaction is stopped when the water output reaches 90% of the theoretical value, and the phytic acid phenylpropanol crude polymer is obtained.

[0022] (3) Preparation of the high-phosphorus-content hydrolysis-resistant flame retardant;

[0023] The reaction kettle in the transesterification stage is equipped with a vacuum device. The phytic acid phenylpropanol crude polymer is first subjected to vacuum polymerization at a certain temperature and then vacuum purified at an increased temperature to obtain the high-phosphorus-content hydrolysis-resistant flame retardant.

[0024] In the preparation method of a high-phosphorus-content hydrolysis-resistant flame retardant as described above, in step (1), the molar ratio of phytic acid to methanol is 1:14 - 16. Setting the molar ratio of phytic acid to methanol within this range is to ensure that all 12 terminal carboxyl groups of phytic acid are esterified by methanol to form ester groups, providing a basis for the subsequent transesterification reaction. The reaction temperature is 75 - 90 °C, and the reaction time is 4 - 5.5 h.

[0025] In the preparation method of a high-phosphorus-content hydrolysis-resistant flame retardant as described above, in step (1), the catalyst is an antimony-based catalyst, such as antimony glycolate or antimony acetate. The catalyst addition amount is 100 ppm of the total mass of phytic acid, methanol, and phenylpropanol. The anti-aging agent is sodium acetate, and the anti-aging agent addition amount is 100 ppm of the total mass of phytic acid, methanol, and phenylpropanol. The anti-etherification agent is trimethyl phosphite or triphenyl phosphite, and the anti-etherification agent addition amount is 150 ppm of the total mass of phytic acid, methanol, and phenylpropanol.

[0026] In the preparation method of a high-phosphorus-content hydrolysis-resistant flame retardant as described above, in step (2), the molar ratio of methyl phytate to phenylpropanol is 1:13 - 15. The molar ratio of phenylpropanol ester to methyl phytate must be greater than 12 for the reaction to proceed smoothly. However, to ensure the continuous progress of the reaction, an excessive amount of phenylpropanol ester will cause the transesterification reaction to reach equilibrium earlier, which is not conducive to the preparation of a high-yield and high-phosphorus-content water-resistant flame retardant. Therefore, the molar ratio of methyl phytate to phenylpropanol ester needs to be limited to 1:13 - 15 to ensure the comprehensive performance of the final organophosphorus flame retardant. The reaction temperature is 105 - 115 °C, and the reaction time is 2 - 3 h.

[0027] A preparation method of a high-phosphorus-content hydrolysis-resistant flame retardant as described above. In step (3), the phytic acid phenylpropanol crude polymer is first subjected to vacuum polymerization at 110-120 °C with a stirring rate of 150 rpm and a vacuum degree of 300-500 Pa, and the reaction time is controlled to be 1-1.5 h. Then, it is subjected to vacuum purification at 125-130 °C with a vacuum degree of 200-300 Pa, and the reaction time is controlled to be 20-30 min.

[0028] The vacuum purification described above is divided into two stages to first ensure that the reaction of the crude polymer is complete, and then to extract the excess phenylpropanol at a temperature higher than the boiling point of phenylpropanol to achieve the purification effect.

[0029] A preparation method of a high-phosphorus-content hydrolysis-resistant flame retardant as described above. In step (3), the transesterification temperature is 75-90 °C, which is higher than the boiling point of methanol. Using high-temperature reflux reaction, methanol molecules are more active, which will accelerate the reaction rate with phytic acid.

[0030] The principle of the present invention is as follows:

[0031] The present invention utilizes the high phosphorus content of phytic acid. By introducing a benzene ring structure with a high heat-resistant temperature in the molecular structure design and using a simple transesterification reaction, the hydrophobic chain segment phenylpropanyloxy structure is reacted on phytic acid, so that the flame retardant forms a heat-resistant and hydrophobic phenylpropanyloxy group on the outer layer, and the inner layer is a six-membered cyclic phosphonate structure of phytic acid, avoiding the decomposition of the phytic acid molecular structure, and at the same time maintaining the high phosphorus content design of phytic acid; at the same time, the large rigid benzene ring in the phenylpropanyloxy structure has an excellent steric hindrance effect, improving the stability of the outer layer structure of the flame retardant and the shielding effect on the inner layer, and the rigid carbon-forming structure of the benzene ring also endows the flame retardant with certain flame-retardant carbon-forming properties.

[0032] Beneficial effects:

[0033] (1) In the preparation method of a high-phosphorus-content hydrolysis-resistant flame retardant of the present invention, the terminal carboxyl group of phytic acid is first esterified through an esterification reaction. By carrying out a transesterification reaction between phytic acid with an esterified terminal carboxyl group and phenylpropanol with a reactive terminal hydroxyl group structure, the phosphoric acid structure on the surface of phytic acid is grafted with a large steric hindrance and long-chain phenylpropyl structure, forming a cluster-like structure, improving the hydrolysis resistance and high-temperature resistance of the phytic acid structure, and solving the problems of hydrolysis resistance and high-temperature resistance of phytic acid.

[0034] (2) The preparation method of a high-phosphorus-content hydrolysis-resistant flame retardant of the present invention has a simple process, a high phosphorus content, good flame retardant performance, and phytic acid belongs to a biomass material, which is green and environmentally friendly, and responds to the national "carbon neutrality" policy. Description of the drawings

[0035] Figure 1 It is a schematic diagram of the chemical structure of the high-phosphorus-content hydrolysis-resistant flame retardant of the present invention;

[0036] Figure 2 This is the nuclear magnetic resonance spectrum of the high-phosphorus-content hydrolysis-resistant flame retardant of the present invention. Detailed implementation manners

[0037] The present invention will be further described below in conjunction with the detailed implementation manners. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0038] The present invention adopts the following test methods:

[0039] (1) Melting point: It is measured by a Q20 differential scanning calorimeter, using nitrogen as the protective gas, with a gas flow rate of 50 mL / min, and heating at a rate of 10 °C / min. The maximum melting peak during the heating process is the melting point;

[0040] (2) Weight loss rate: In an air atmosphere, in an oven at 300 °C, with 5 samples in a batch, test and weigh, and test the thermal weight loss rate after 24 h;

[0041] (3) Phosphorus content retention rate: The phosphorus content of the high-phosphorus-content hydrolysis-resistant flame retardant is measured by an elemental analyzer. The phosphorus content of the flame retardant before hydrolysis resistance test is P0, and the phosphorus content of the flame retardant after hydrolysis resistance test is P t , and its phosphorus content retention rate is P d =(P t / P0)*100%.

[0042] Example 1

[0043] A preparation method of a high-phosphorus-content hydrolysis-resistant flame retardant is as follows:

[0044] (1) Preparation of methyl phytate;

[0045] Phytic acid, methanol, antimony glycolate, sodium acetate and triphenyl phosphite are added to a reaction kettle, a condensation reflux device is configured, and nitrogen protection is passed. The stirring rate is 100 rpm, the reaction temperature is controlled at 90 °C, and the reaction time is 4 h to obtain a transparent substance, methyl phytate;

[0046] Among them, the molar ratio of phytic acid to methanol is 1:14; the addition amount of antimony glycolate is 100 ppm of the total mass of phytic acid, methanol and phenylpropanol; the addition amount of sodium acetate is 100 ppm of the total mass of phytic acid, methanol and phenylpropanol; the addition amount of triphenyl phosphite is 150 ppm of the total mass of phytic acid, methanol and phenylpropanol;

[0047] (2) Preparation of phytic acid phenylpropanol crude polymer;

[0048] Add phenylpropanol to the reaction kettle for methyl phytate. The molar ratio of methyl phytate to phenylpropanol is 1:13. Assemble the condensation device and pass nitrogen for protection. The stirring rate is 200 rpm. Control the reaction temperature at 105 °C and the reaction time at 3 h. Record the water output and stop the reaction when it reaches 90% of the theoretical value to obtain the crude phytate phenylpropanol polymer.

[0049] (3) Preparation of the high-phosphorus-content hydrolysis-resistant flame retardant;

[0050] Equip the reaction kettle in the transesterification stage (transesterification temperature is 90 °C) with a vacuum device. First, carry out vacuum polymerization of the crude phytate phenylpropanol polymer at 110 °C with a stirring rate of 150 rpm. Control the reaction time at 1 h and the vacuum degree at 300 Pa. Raise the temperature to 125 °C for vacuum purification, control the reaction time at 20 min and the vacuum degree at 200 Pa. Finally, obtain the high-phosphorus-content hydrolysis-resistant flame retardant. Its chemical structure schematic diagram is as Figure 1 shown.

[0051] The melting point of the prepared high-phosphorus-content hydrolysis-resistant flame retardant is 56 °C. The weight loss rate is 4% after heat treatment in an air atmosphere at 300 °C for 24 h. After treatment in a sodium hydroxide solution at 80 °C and a concentration of 0.1 mol / L for 8 h, the phosphorus content retention rate is 99.5%.

[0052] From Figure 1 it can be seen that phytate forms a hydrolysis-resistant and high-temperature-resistant structure centered on phytate with 12 phenylpropanols, and the nuclear magnetic resonance spectrum ( Figure 2 ) proves that this structure is indeed synthesized; Figure 2 In, the resonance peak at δ = 3.33 ppm corresponds to the peak of C-H on the benzene ring of phytate (c); it proves the benzene ring structure; the peak at δ = 4.03 ppm is the proton peak of the hydrogen atoms of the two methylene groups (b) connected to the oxygen atom on phenylpropanol; the peak at δ = 2.55 pmm corresponds to the -CH2- proton peak (d) near the benzene ring in phenylpropanol; the peak at δ = 1.99 ppm corresponds to the proton peak of the hydrogen atoms on the middle methylene group (e) in phenylpropanol. The multiplet proton peaks appearing at δ = 7.08 - 7.21 ppm are the hydrogen proton peaks of the benzene ring on phenylpropanol, indicating that the high-phosphorus-content hydrolysis-resistant flame retardant is successfully synthesized.

[0053] Example 2

[0054] A preparation method of a high-phosphorus-content hydrolysis-resistant flame retardant, the specific steps are as follows:

[0055] (1) Preparation of methyl phytate;

[0056] Phytic acid, methanol, antimony glycolate, sodium acetate and triphenyl phosphite were added to a reaction kettle, a condensation reflux device was assembled, nitrogen protection was applied, the stirring rate was 100 rpm, the reaction temperature was controlled at 75 °C, and the reaction time was 5.5 h to obtain methyl phytate, a transparent substance;

[0057] Among them, the molar ratio of phytic acid to methanol was 1:16; the addition amount of antimony glycolate was 100 ppm of the total mass of phytic acid, methanol and phenylpropanol; the addition amount of sodium acetate was 100 ppm of the total mass of phytic acid, methanol and phenylpropanol; the addition amount of triphenyl phosphite was 150 ppm of the total mass of phytic acid, methanol and phenylpropanol;

[0058] (2) Preparation of phytic acid phenylpropanol crude polymer;

[0059] Phenylpropanol was added to the reaction kettle for methyl phytate. The molar ratio of methyl phytate to phenylpropanol was 1:15. A condensation device was assembled, nitrogen protection was applied, the stirring rate was 200 rpm, the reaction temperature was controlled at 115 °C, and the reaction time was 2 h. The reaction was stopped when the water output reached 90% of the theoretical value to obtain phytic acid phenylpropanol crude polymer;

[0060] (3) Preparation of high-phosphorus-content hydrolysis-resistant flame retardant;

[0061] The reaction kettle in the transesterification stage (transesterification temperature of 75 °C) was equipped with a vacuum device. The phytic acid phenylpropanol crude polymer was first subjected to vacuum polymerization at 120 °C with a stirring rate of 150 rpm, the reaction time was controlled at 1.5 h, and the vacuum degree was 500 Pa. The temperature was raised to 130 °C for vacuum purification, the reaction time was controlled at 30 min, and the vacuum degree was 300 Pa. Finally, a high-phosphorus-content hydrolysis-resistant flame retardant was obtained.

[0062] The prepared high-phosphorus-content hydrolysis-resistant flame retardant had a melting point of 58 °C, a weight loss rate of 1% after heat treatment in an air atmosphere at 300 °C for 24 h, and a phosphorus content retention rate of 99.7% after treatment in a sodium hydroxide solution at 80 °C and a concentration of 0.1 mol / L for 8 h.

[0063] Example 3

[0064] A preparation method of a high-phosphorus-content hydrolysis-resistant flame retardant is as follows:

[0065] (1) Preparation of methyl phytate;

[0066] Phytic acid, methanol, antimony glycolate, sodium acetate and triphenyl phosphite were added to a reaction kettle, a condensation reflux device was assembled, nitrogen protection was applied, the stirring rate was 100 rpm, the reaction temperature was controlled at 85 °C, and the reaction time was 4.5 h to obtain methyl phytate, a transparent substance;

[0067] Among them, the molar ratio of phytic acid to methanol is 1:15; the addition amount of antimony glycolate is 100 ppm of the total mass of phytic acid, methanol and phenylpropanol; the addition amount of sodium acetate is 100 ppm of the total mass of phytic acid, methanol and phenylpropanol; the addition amount of triphenyl phosphite is 150 ppm of the total mass of phytic acid, methanol and phenylpropanol;

[0068] (2) Preparation of phytic acid phenylpropanol crude polymer;

[0069] Add phenylpropanol to the phytic acid methyl ester reaction kettle. The molar ratio of phytic acid methyl ester to phenylpropanol is 1:14. Assemble the condensation device and protect it with nitrogen. The stirring rate is 200 rpm. Control the reaction temperature at 110 °C and the reaction time at 2.5 h. Record and stop the reaction when the water output reaches 90% of the theoretical value to obtain the phytic acid phenylpropanol crude polymer;

[0070] (3) Preparation of high-phosphorus-content hydrolysis-resistant flame retardant;

[0071] Assemble a vacuum device for the reaction kettle in the transesterification stage (transesterification temperature is 90 °C). First, carry out vacuum polymerization of the phytic acid phenylpropanol crude polymer at 120 °C. The stirring rate is 150 rpm. Control the reaction time at 1.5 h and the vacuum degree at 400 Pa. Raise the temperature to 130 °C for vacuum purification. Control the reaction time at 30 min and the vacuum degree at 200 Pa. Finally, obtain the high-phosphorus-content hydrolysis-resistant flame retardant.

[0072] The melting point of the prepared high-phosphorus-content hydrolysis-resistant flame retardant is 57 °C. The weight loss rate is 2% after heat treatment in an air atmosphere at 300 °C for 24 h. After treatment in a sodium hydroxide solution at 80 °C with a concentration of 0.1 mol / L for 8 h, the phosphorus content retention rate is 99.5%.

[0073] Comparative Example 1

[0074] A preparation method of a flame retardant is basically the same as that of Example 3, except that "phenylpropanol" in step (2) is replaced with "phenylbutanol";

[0075] The melting point of the prepared flame retardant is 35 °C. The weight loss rate is 52% after heat treatment in an air atmosphere at 300 °C for 24 h. After treatment in a sodium hydroxide solution at 80 °C with a concentration of 0.1 mol / L for 8 h, the phosphorus content retention rate is 65%.

[0076] Comparing Comparative Example 1 with Example 3, it can be found that the flame retardant obtained in Comparative Example 1 has a lower melting point and phosphorus content retention rate, while having a higher weight loss rate. This is because the molecular weight of phenylbutanol is relatively high, which causes the phosphorus content of the flame retardant to decrease. Moreover, the alkyl chain segment length of the flame retardant is too long, making it easy for the chain segments of the flame retardant to entangle and curl, resulting in incomplete reaction of the phosphate groups and reduced high-temperature resistance, ultimately causing an increase in the weight loss rate. Since phenylbutanol has a longer alkyl chain segment than phenylpropanol, the benzene ring structure is unevenly dispersed, which makes it easier for water molecules to attack phytic acid, reducing the hydrolysis resistance and heat resistance of the flame retardant.

[0077] Comparative Example 2

[0078] A preparation method of a flame retardant is basically the same as that of Example 3, except that "phenylpropanol" in step (2) is replaced with "phenylethanol".

[0079] The melting point of the prepared flame retardant is 20 °C, the weight loss rate after heat treatment in an air atmosphere at 300 °C for 24 h is 60%, and the phosphorus content retention rate is 30% after treatment in a sodium hydroxide solution at 80 °C and a concentration of 0.1 mol / L for 8 h.

[0080] Comparing Comparative Example 2 with Example 3, it can be found that the flame retardant obtained in Comparative Example 2 has a lower melting point and phosphorus content retention rate, while having a higher weight loss rate. This is because after using phenylethanol, the alkyl chain segment is short. Due to the steric hindrance effect of the benzene ring, one phosphate group cannot connect two phenylethanols, forming a group where one phosphate group connects one phenylethanol and one methanol. The flame retardant does not form a coated structure, which makes the flame retardant have a lower melting point, poor high-temperature resistance, and the existing methanol structure is more likely to decompose.

[0081] Comparative Example 3

[0082] A preparation method of a flame retardant is basically the same as that of Example 3, except that "methanol" is not added in step (1).

[0083] The structure of the flame retardant cannot be obtained, and the obtained structure is black carbon material. This is because the phytic acid structure itself is a strong acidic structure with a high phosphorus content. Although it can react with phenylpropanol, the high temperature during the reaction between phytic acid and phenylpropanol causes the flame retardant to carbonize and form black carbon material.

[0084] Comparative Example 4

[0085] A preparation method of a flame retardant is basically the same as that of Example 3, except that "phenylpropanol" in step (2) is replaced with "bisphenol A".

[0086] The prepared flame retardant has a melting point of 33 °C, a weight loss rate of 8% after heat treatment in an air atmosphere at 300 °C for 24 h, and a phosphorus content retention rate of 10% after treatment in a sodium hydroxide solution at 80 °C and a concentration of 0.1 mol / L for 8 h.

[0087] Comparing Comparative Example 4 with Example 3, it can be found that the flame retardant obtained in Comparative Example 4 has a lower melting point and a decline in thermal stability. This is because bisphenol A has no alkyl chain ends. After being attached to phytic acid, there are excess hydroxyl groups exposed to the environment, which makes the flame retardant have poor hydrolysis resistance. And because bisphenol A has two benzene rings, it has a high steric hindrance, so it cannot form a fully encapsulated structure, resulting in a decline in its hydrolysis stability in a high-temperature environment.

[0088] Example 4

[0089] A preparation method of a high-phosphorus-content hydrolysis-resistant flame retardant is as follows:

[0090] (1) Preparation of methyl phytate;

[0091] Add phytic acid, methanol, antimony acetate, sodium acetate, and trimethyl phosphite to a reaction kettle, configure a condensation reflux device, and protect with nitrogen. The stirring rate is 100 rpm, control the reaction temperature at 80 °C and the reaction time at 4.2 h to obtain a transparent substance, methyl phytate;

[0092] Among them, the molar ratio of phytic acid to methanol is 1:14; the addition amount of antimony acetate is 100 ppm of the total mass of phytic acid, methanol, and phenylpropanol; the addition amount of sodium acetate is 100 ppm of the total mass of phytic acid, methanol, and phenylpropanol; the addition amount of trimethyl phosphite is 150 ppm of the total mass of phytic acid, methanol, and phenylpropanol;

[0093] (2) Preparation of phytic acid phenylpropanol crude polymer;

[0094] Add phenylpropanol to the methyl phytate reaction kettle. The molar ratio of methyl phytate to phenylpropanol is 1:15. Configure a condensation device and protect with nitrogen. The stirring rate is 200 rpm, control the reaction temperature at 115 °C and the reaction time at 2.2 h. Record and stop the reaction when the water output reaches 90% of the theoretical value to obtain phytic acid phenylpropanol crude polymer;

[0095] (3) Preparation of high-phosphorus-content hydrolysis-resistant flame retardant;

[0096] Assemble a vacuum device for the reaction kettle in the transesterification stage (transesterification temperature is 85 °C). First, carry out vacuum polymerization of the phytic acid phenylpropanol crude polymer at 115 °C with a stirring rate of 150 rpm, control the reaction time at 1.2 h and the vacuum degree at 500 Pa. Raise the temperature to 126 °C for vacuum purification, control the reaction time at 20 min and the vacuum degree at 280 Pa, and finally obtain a high-phosphorus-content hydrolysis-resistant flame retardant.

[0097] The prepared hydrolysis-resistant flame retardant with high phosphorus content has a melting point of 57 °C, a weight loss rate of 4% after heat treatment in an air atmosphere at 300 °C for 24 h, and a phosphorus content retention rate of 99.6% after treatment in a sodium hydroxide solution at 80 °C with a concentration of 0.1 mol / L for 8 h.

[0098] Example 5

[0099] A preparation method of a hydrolysis-resistant flame retardant with high phosphorus content is as follows:

[0100] (1) Preparation of methyl phytate;

[0101] Phytic acid, methanol, antimony acetate, sodium acetate and trimethyl phosphite are added to a reaction kettle, a condensation reflux device is equipped, nitrogen protection is passed, the stirring rate is 100 rpm, the reaction temperature is controlled at 85 °C, and the reaction time is 4.8 h to obtain a transparent substance, methyl phytate;

[0102] Among them, the molar ratio of phytic acid to methanol is 1:15; the addition amount of antimony acetate is 100 ppm of the total mass of phytic acid, methanol and phenylpropanol; the addition amount of sodium acetate is 100 ppm of the total mass of phytic acid, methanol and phenylpropanol; the addition amount of trimethyl phosphite is 150 ppm of the total mass of phytic acid, methanol and phenylpropanol;

[0103] (2) Preparation of phytic acid phenylpropanol crude polymer;

[0104] Phenylpropanol is added to the reaction kettle of methyl phytate. The molar ratio of methyl phytate to phenylpropanol is 1:14. A condensation device is equipped and nitrogen protection is passed. The stirring rate is 200 rpm. The reaction temperature is controlled at 110 °C and the reaction time is 2.5 h. Record and stop the reaction when the water output reaches 90% of the theoretical value to obtain phytic acid phenylpropanol crude polymer;

[0105] (3) Preparation of hydrolysis-resistant flame retardant with high phosphorus content;

[0106] The reaction kettle in the transesterification stage (transesterification temperature is 90 °C) is equipped with a vacuum device. The phytic acid phenylpropanol crude polymer is first subjected to vacuum polymerization at 120 °C, the stirring rate is 150 rpm, the reaction time is controlled at 1.2 h, and the vacuum degree is 400 Pa. The temperature is raised to 128 °C for vacuum purification, the reaction time is controlled at 30 min, and the vacuum degree is 250 Pa. Finally, a hydrolysis-resistant flame retardant with high phosphorus content is obtained.

[0107] The prepared hydrolysis-resistant flame retardant with high phosphorus content has a melting point of 58 °C, a weight loss rate of 3% after heat treatment in an air atmosphere at 300 °C for 24 h, and a phosphorus content retention rate of 99.5% after treatment in a sodium hydroxide solution at 80 °C with a concentration of 0.1 mol / L for 8 h.

[0108] Example 6

[0109] A preparation method of a high-phosphorus-content hydrolysis-resistant flame retardant is as follows:

[0110] (1) Preparation of methyl phytate;

[0111] Phytic acid, methanol, antimony acetate, sodium acetate and trimethyl phosphite are added to a reaction kettle, a condensation reflux device is configured, and nitrogen protection is passed. The stirring rate is 100 rpm, the reaction temperature is controlled at 90 °C, and the reaction time is 5 h to obtain a transparent substance, methyl phytate;

[0112] Among them, the molar ratio of phytic acid to methanol is 1:16; the addition amount of antimony acetate is 100 ppm of the total mass of phytic acid, methanol and phenylpropanol; the addition amount of sodium acetate is 100 ppm of the total mass of phytic acid, methanol and phenylpropanol; the addition amount of trimethyl phosphite is 150 ppm of the total mass of phytic acid, methanol and phenylpropanol;

[0113] (2) Preparation of a crude phytic acid phenylpropanol polymer;

[0114] Phenylpropanol is added to the methyl phytate reaction kettle. The molar ratio of methyl phytate to phenylpropanol is 1:13. A condensation device is configured, and nitrogen protection is passed. The stirring rate is 200 rpm, the reaction temperature is controlled at 105 °C, and the reaction time is 2.8 h. Record and stop the reaction when the water output reaches 90% of the theoretical value to obtain a crude phytic acid phenylpropanol polymer;

[0115] (3) Preparation of a high-phosphorus-content hydrolysis-resistant flame retardant;

[0116] The reaction kettle in the transesterification stage (transesterification temperature is 90 °C) is equipped with a vacuum device. The crude phytic acid phenylpropanol polymer is first subjected to vacuum polymerization at 110 °C, the stirring rate is 150 rpm, the reaction time is controlled at 1.5 h, and the vacuum degree is 300 Pa. The temperature is raised to 125 °C for vacuum purification, the reaction time is controlled at 25 min, and the vacuum degree is 220 Pa. Finally, a high-phosphorus-content hydrolysis-resistant flame retardant is obtained.

[0117] The melting point of the prepared high-phosphorus-content hydrolysis-resistant flame retardant is 58 °C. The weight loss rate is 4% after heat treatment in an air atmosphere at 300 °C for 24 h. After being treated in a sodium hydroxide solution at a temperature of 80 °C and a concentration of 0.1 mol / L for 8 h, the phosphorus content retention rate is 99.3%.

Claims

1. A preparation method of a hydrolysis-resistant flame retardant with a high phosphorus content, characterized in that: Methyl phytate is subjected to transesterification reaction with phenylpropyl alcohol ester, and then high - phosphorus - content hydrolysis - resistant flame retardant is prepared by removing impurities under a high vacuum of 200 - 300 Pa; The molar ratio of phenylpropyl alcohol ester to methyl phytate is greater than 12; The preparation steps of methyl phytate are as follows: Phytic acid, methanol, a catalyst, an anti - aging agent and an anti - ether agent are added to a reaction kettle, a condensation reflux device is configured, nitrogen protection is passed, the stirring rate is 100 rpm, a certain reaction temperature and reaction time are controlled, and transparent methyl phytate is obtained; The catalyst is an antimony - based catalyst, the anti - aging agent is sodium acetate, and the anti - ether agent is trimethyl phosphite or triphenyl phosphite; The structural formula of the high - phosphorus - content hydrolysis - resistant flame retardant is as follows: The melting point of the high - phosphorus - content hydrolysis - resistant flame retardant is 56 - 58 °C. The weight loss rate of the high - phosphorus - content hydrolysis - resistant flame retardant is <5% after heat treatment in an air atmosphere at 300 °C for 24 h. After being treated in a sodium hydroxide solution with a temperature of 80 °C and a concentration of 0.1 mol / L for 8 h, the phosphorus content retention rate of the high - phosphorus - content hydrolysis - resistant flame retardant is >99%; 2. The preparation method of a high-phosphorus-content hydrolysis-resistant flame retardant according to claim 1, characterized in that, The specific steps are as follows: (1) Preparation of phytic acid phenylpropyl alcohol crude polymer; Phenylpropyl alcohol is added to a methyl phytate reaction kettle, a condensation device is configured, nitrogen protection is passed, the stirring rate is 200 rpm, a certain reaction temperature and reaction time are controlled, and the reaction is stopped when the measured methanol amount reaches 90% of the theoretical value, and phytic acid phenylpropyl alcohol crude polymer is obtained; (2) Preparation of high - phosphorus - content hydrolysis - resistant flame retardant; The reaction kettle in the transesterification stage is equipped with a vacuum device. The phytic acid phenylpropyl alcohol crude polymer is first subjected to vacuum polymerization at a certain temperature, and then the temperature is raised for vacuum purification to obtain a high - phosphorus - content hydrolysis - resistant flame retardant.

3. The preparation method of a high-phosphorus-content hydrolysis-resistant flame retardant according to claim 2, characterized in that, The molar ratio of phytic acid to methanol is 1:14 - 16, the reaction temperature is 75 - 90 °C, and the reaction time is 4 - 5.5 h.

4. The preparation method of a high-phosphorus-content hydrolysis-resistant flame retardant according to claim 2, characterized in that, The addition amount of the catalyst is 100 ppm of the total mass of phytic acid, methanol and phenylpropyl alcohol, the addition amount of the anti - aging agent is 100 ppm of the total mass of phytic acid, methanol and phenylpropyl alcohol, and the addition amount of the anti - ether agent is 150 ppm of the total mass of phytic acid, methanol and phenylpropyl alcohol.

5. The preparation method of a high-phosphorus-content hydrolysis-resistant flame retardant according to claim 2, wherein, In step (1), the molar ratio of methyl phytate to phenylpropyl alcohol is 1:13 - 15, and the reaction temperature is 105 - 115 °C.

6. The preparation method of a high-phosphorus-content hydrolysis-resistant flame retardant according to claim 2, characterized in that, In step (2), the phytic acid phenylpropyl alcohol crude polymer is first subjected to vacuum polymerization at 110 - 120 °C, the stirring rate is 150 rpm, the vacuum degree is 300 - 500 Pa, the reaction time is controlled for 1 - 1.5 h, and then vacuum purification is carried out at 125 - 130 °C, the vacuum degree is 200 - 300 Pa, and the reaction time is controlled for 20 - 30 min.

7. The preparation method of a high-phosphorus-content hydrolysis-resistant flame retardant according to claim 2, characterized in that, In step (2), the transesterification temperature is 75 - 90 °C.

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