Organic polymer catalyst and method for preparing cyclic phosphate flame retardant by using same

Abstract

The invention relates to the technical field of organophosphorus flame retardant synthesis, and particularly discloses an organic polymer catalyst and a method for preparing a cyclic phosphate flame retardant by using the organic polymer catalyst, the organic polymer catalyst contains methyl benzenesulfonate and imidazole ion groups and has bifunctional catalytic sites, imidazole ions can catalyze Michaelis-Arbuzov rearrangement reaction, and the molecular weight of the imidazole ions can be reduced to a certain degree. Methyl benzenesulfonate can catalyze isomerization of dimethyl phosphite, the organic polymer can be recycled through simple treatment after the catalytic reaction is completed, and high catalytic efficiency can still be obtained after the organic polymer is repeatedly used for multiple times.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of organic phosphorus flame retardant synthesis, and particularly relates to a functionalized organic polymer catalyst and a method for preparing a cyclic phosphate flame retardant using the catalyst. BACKGROUND

[0002] Polystyrene polymers are thermoplastic polymer materials prepared by polymerization of diphenyl ethylene and styrene as main monomers, the molecular chain is connected by carbon-carbon single bond, and benzene ring is distributed as a side group. The introduction of catalytic functional groups on the benzene ring can make polystyrene become a catalyst with great application potential and has many advantages: (1) excellent chemical stability, the polystyrene main chain is composed of carbon-carbon single bond, resistant to acid, alkali and various organic solvents; (2) environmental friendly and economic balance, the polystyrene polymerization process is mature, which can be quickly formed by injection molding, extrusion and other technologies to reduce cost, at the same time, polystyrene is odorless and non-toxic, which meets the food contact material standard, and can reduce the risk of heavy metal pollution as a catalyst carrier; (3) sustainable development potential, polystyrene catalyst is generally a heterogeneous catalytic system, which can be recycled and reused by simple filtration to reduce solid waste pollution.

[0003] Cyclic phosphonate is a kind of excellent performance of added polyester fabric flame retardant, the fabric after finishing has good washing performance, after 50 times washing still has good flame retardant performance, does not release HX and other toxic gases in the process of flame retardant, the phosphorus content reaches more than 20%, and the flame retardant is good, therefore, the synthesis of cyclic phosphonate is concerned. The commonly used method for preparing cyclic phosphonate is trimethyl phosphite method, Yang Jinfei (Flame Retardant Materials and Technology, 2008, (1): 6-8) reported that trimethyl phosphite, trimethylolpropane and dimethyl methylphosphonate were used as raw materials, triethylamine was used as catalyst, the first ester exchange was reacted at 80 DEG C for 5h to generate intermediate ethyl bicyclic phosphite; the second Michaelis-Arbuzov rearrangement was reacted at 185 DEG C for 16h, and the yield was 95.7%. Li Jinzhong et al. (CN 200910031843.7) reported a similar synthesis scheme, the first ester exchange reaction was catalyzed by inorganic acid, first reacted at 70-80 DEG C for 4-5h, and then heated to 160-170 DEG C for 1-2h; the second Michaelis-Arbuzov rearrangement was first catalyzed by strong base, reacted at 160-170 DEG C for 7-8h, and then catalyzed by bromoalkane for 4-5h. The above-mentioned method has two main problems: (1) the catalyst is difficult to completely remove, which affects the product quality; (2) the rearrangement reaction time of ethyl bicyclic phosphite and dimethyl methylphosphonate is too long, which leads to more than 30h of synthesis of a batch of products. Dong Chunmei et al. (Fine Chemicals, 2011, 28 (6): 581-584) used imidazole ionic liquid to catalyze the rearrangement reaction, the reaction time was shortened, and the yield reached 98%, but the catalyst residue problem still existed. Han Zhongshan et al. (CN 202010122268.8) improved the process, the first step was reacted at 70-120 DEG C for 2-4h to generate dimethyl ester and a small amount of ethyl bicyclic phosphite, and the second step was reacted at 170-180 DEG C for 1-3h to isomerize dimethyl ester to form cyclic phosphonate catalyzed by methyl phenyl sulfonate. The process still does not solve the problem of catalyst residue, in addition, the presence of a small amount of ethyl bicyclic phosphite also damages the quality of the product. Therefore, it is urgent to develop a new type of catalyst to solve the existing problems. SUMMARY

[0004] In view of the defects existing in the prior art for preparing cyclic phosphonate, the purpose of the present application is to provide a bifunctional organic polymer catalyst which is efficient and easy to recycle and reuse.

[0005] The organic polymer catalyst contains methyl phenyl sulfonate and imidazole ion, and the structural formula of the organic polymer catalyst is as follows:

[0006]

[0007] Another purpose of the present application is to provide a preparation method of the organic polymer catalyst, and the method is as follows:

[0008] (1) 1-methylimidazole and 4-chloromethylstyrene were dissolved in acetonitrile, heated to react, the solvent was evaporated under reduced pressure after the reaction, washed with diethyl ether, and dried under vacuum at room temperature to obtain colorless oily ionic liquid ImM, the reaction temperature was 50-80°C, the reaction time was 12-24h, and the molar ratio of 1-methylimidazole to 4-chloromethylstyrene was 1:1-1.5;

[0009] (2) 4-vinylbenzenesulfonic acid methyl ester, ionic liquid ImM, p-divinylbenzene, azobisisobutyronitrile and a mixture of tetrahydrofuran-water were heated and stirred under a nitrogen atmosphere, cooled to room temperature after the reaction was completed, filtered, the filter cake was Soxhlet extracted with tetrahydrofuran for 24 hours, and the obtained solid was dried under vacuum at 80°C overnight to obtain white solid PIS, the reaction temperature was 50-100°C, the time was 24-72h, and the molar ratio of ionic liquid ImM, 4-vinylbenzenesulfonic acid methyl ester, p-divinylbenzene and azobisisobutyronitrile was 1:2-4:4-12:0.2-0.4.

[0010] The reaction process is shown as follows:

[0011]

[0012] The present application also aims to provide a method for preparing cyclic phosphonate ester by using the catalyst.

[0013] The method for preparing cyclic phosphonate ester is as follows:

[0014] S1: using trimethylolpropane and trimethyl phosphite as raw materials, an intermediate product mixture of dimethyl phosphite and ethyl bicyclic phosphite was obtained through ester exchange reaction;

[0015] S2: the product of S1 was added with the catalyst, trimethyl phosphite was isomerized to dimethyl methylphosphonate, dimethyl phosphite was isomerized to cyclic phosphonate ester, and Michaelis-Arbuzov rearrangement occurred between ethyl bicyclic phosphite and dimethyl methylphosphonate to generate cyclic phosphonate ester.

[0016] The reaction process is shown as follows:

[0017]

[0018] The reaction process is divided into two steps, the first step is the ester exchange reaction of trimethylolpropane and trimethyl phosphite to generate dimethyl phosphite and a small amount of ethyl bicyclic phosphite, and the second step is that three reactions occur under the catalysis of PIS: ① trimethyl phosphite isomerizes into dimethyl methylphosphonate; ② dimethyl phosphite isomerizes into cyclic phosphonate; and ③ a small amount of ethyl bicyclic phosphite and dimethyl methylphosphonate generate cyclic phosphonate through Michaelis-Arbuzov rearrangement, and the ethyl bicyclic phosphite is completely consumed.

[0019] Further, in the step S1, the molar ratio of trimethylolpropane to trimethyl phosphite is 1:2-1:4, the oil bath temperature is 90-130°C, and the reaction time is 2-4h; in the step S2, the reaction temperature is 170-180°C, and the reaction time is 1-3h.

[0020] Further, in the step S2, the addition amount of the catalyst is 0.5%-3% of the mass of trimethylolpropane.

[0021] The beneficial effects of the present application are that the provided organic polymer catalyst has a dual functional catalytic site, the imidazole ion can catalyze the Michaelis-Arbuzov rearrangement reaction, the methyl phenyl sulfonate can catalyze the isomerization of dimethyl phosphite, the organic polymer can be recovered through simple treatment after the completion of the catalytic reaction, and a higher catalytic efficiency can still be obtained after repeated use for multiple times. DETAILED DESCRIPTION

[0022] The technical solutions of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art belong to the protection scope of the present application.

[0023] Embodiments 1-6: Preparation method of dual functional organic polymer catalyst.

[0024] Embodiment 1

[0025] 1-methylimidazole (3.25g, 40mmol) and 4-chloromethylstyrene (5g, 33mmol) were dissolved in 15mL of acetonitrile, heated to 70°C and reacted for 12h. After the completion of the reaction, the solvent was evaporated under reduced pressure, the obtained sticky product was washed with ether three times to remove the excess reactants, and then dried under vacuum at room temperature for 3 hours to obtain a colorless oily ionic liquid ImM 6.68g, with a yield of 87%;

[0026] The ionic liquid ImM (235 mg, 1.0 mmol), methyl 4-vinylbenzenesulfonate (396 mg, 2.0 mmol), p-divinylbenzene (521 mg, 4.0 mmol), azobisisobutyronitrile (34 mg, 0.21 mmol) were dissolved in 11 mL of a tetrahydrofuran-water mixture (10:1, V:V) under nitrogen atmosphere and the mixture was heated to 70 °C for 36 h. After the reaction was completed, it was cooled to room temperature, filtered and the filter cake was subjected to a soxhlet extraction with tetrahydrofuran for 24 h. The obtained solid was dried under vacuum at 80 °C overnight to obtain PIS-19 as a white solid 3.3 mg, 81% yield.

[0027] Example 2

[0028] The ionic liquid ImM (235 mg, 1.0 mmol), methyl 4-vinylbenzenesulfonate (396 mg, 2.0 mmol), p-divinylbenzene (521 mg, 4.0 mmol), azobisisobutyronitrile (34 mg, 0.21 mmol) were dissolved in 11 mL of a tetrahydrofuran-water mixture (10:1, V:V) under nitrogen atmosphere and the mixture was heated to 70 °C for 36 h. After the reaction was completed, it was cooled to room temperature, filtered and the filter cake was subjected to a soxhlet extraction with tetrahydrofuran for 24 h. The obtained solid was dried under vacuum at 80 °C overnight to obtain PIS-19 as a white solid 3.3 mg, 81% yield.

[0029] The ionic liquid ImM (235 mg, 1.0 mmol), methyl 4-vinylbenzenesulfonate (396 mg, 2.0 mmol), p-divinylbenzene (521 mg, 4.0 mmol), azobisisobutyronitrile (34 mg, 0.21 mmol) were dissolved in 11 mL of a tetrahydrofuran-water mixture (10:1, V:V) under nitrogen atmosphere and the mixture was heated to 70 °C for 36 h. After the reaction was completed, it was cooled to room temperature, filtered and the filter cake was subjected to a soxhlet extraction with tetrahydrofuran for 24 h. The obtained solid was dried under vacuum at 80 °C overnight to obtain PIS-19 as a white solid 3.3 mg, 81% yield.

[0030] Example 3

[0031] The ionic liquid ImM (235 mg, 1.0 mmol), methyl 4-vinylbenzenesulfonate (396 mg, 2.0 mmol), p-divinylbenzene (521 mg, 4.0 mmol), azobisisobutyronitrile (34 mg, 0.21 mmol) were dissolved in 11 mL of a tetrahydrofuran-water mixture (10:1, V:V) under nitrogen atmosphere and the mixture was heated to 70 °C for 36 h. After the reaction was completed, it was cooled to room temperature, filtered and the filter cake was subjected to a soxhlet extraction with tetrahydrofuran for 24 h. The obtained solid was dried under vacuum at 80 °C overnight to obtain PIS-19 as a white solid 3.3 mg, 81% yield.

[0032] Under a nitrogen atmosphere, ionic liquid 1 mM (235 mg, 1.0 mmol), methyl 4-vinylbenzenesulfonate (595 mg, 3.0 mmol), p-divinylbenzene (1042 mg, 8.0 mmol), and azobisisobutyronitrile (59 mg, 0.36 mmol) were dissolved in 19.8 mL of a 10:1, v:v, tetrahydrofuran (THF)-water mixture. The mixture was heated to 100°C and reacted for 24 hours. After completion of the reaction, the mixture was cooled to room temperature, filtered, and the filter cake was Soxhlet extracted with THF for 24 hours. The resulting solid was vacuum-dried at 80°C overnight to yield 1.68 g of PIS-3 as a white solid in a 90% yield.

[0033] Example 4

[0034] 1-Methylimidazole (2.95 g, 36 mmol) and 4-chloromethylstyrene (5 g, 33 mmol) were dissolved in 15 mL of acetonitrile and heated to 80°C for 24 hours. After completion of the reaction, the solvent was evaporated under reduced pressure. The resulting viscous product was washed three times with diethyl ether to remove excess reactants and then dried under vacuum at room temperature for 3 hours to obtain 6.99 g of a colorless oily ionic liquid (1 mM in 91% yield).

[0035] Under a nitrogen atmosphere, ionic liquid 1 mM (235 mg, 1.0 mmol), methyl 4-vinylbenzenesulfonate (396 mg, 2.0 mmol), p-divinylbenzene (521 mg, 4.0 mmol), and azobisisobutyronitrile (34 mg, 0.21 mmol) were dissolved in 11 mL of a 10:1, v:v, tetrahydrofuran (THF) mixture. The mixture was heated to 70°C and reacted for 36 hours. After completion of the reaction, the mixture was cooled to room temperature, filtered, and the filter cake was Soxhlet extracted with THF for 24 hours. The resulting solid was dried in vacuo at 80°C overnight to yield 933 mg of PIS-19 as a white solid in an 81% yield.

[0036] Example 5

[0037] 1-Methylimidazole (2.95 g, 36 mmol) and 4-chloromethylstyrene (5 g, 33 mmol) were dissolved in 15 mL of acetonitrile and heated to 80°C for 24 hours. After completion of the reaction, the solvent was evaporated under reduced pressure. The resulting viscous product was washed three times with diethyl ether to remove excess reactants and then dried under vacuum at room temperature for 3 hours to obtain 6.99 g of a colorless oily ionic liquid (1 mM in 91% yield).

[0038] The mixture was heated to 85 °C for 36 h under nitrogen atmosphere. The reaction was completed and cooled to room temperature, filtered, and the filter cake was Soxhlet extracted with tetrahydrofuran for 24 h. The obtained solid was dried under vacuum at 80 °C overnight to obtain white solid PIS-21.37 g, yield 85%.

[0039] Example 6

[0040] The 1-methylimidazole (2.95 g, 36 mmol) and 4-chloromethylstyrene (5 g, 33 mmol) were dissolved in 15 mL of acetonitrile and heated to 80 °C for 24 h. After the completion of the reaction, the solvent was evaporated under reduced pressure and the obtained viscous product was washed with diethyl ether three times to remove excess reactants and then dried under vacuum at room temperature for 3 h to obtain colorless oily ionic liquid ImM 6.99 g, yield 91%.

[0041] The mixture was heated to 85 °C for 36 h under nitrogen atmosphere. The reaction was completed and cooled to room temperature, filtered, and the filter cake was Soxhlet extracted with tetrahydrofuran for 24 h. The obtained solid was dried under vacuum at 80 °C overnight to obtain white solid PIS-21.37 g, yield 85%.

[0042] Examples 7-12: Synthesis of bifunctional polymer PIS catalyzed cyclic phosphonate ester.

[0043] Example 7

[0044] In a 250ml flask equipped with magnetic stirrer, fractionating column and thermometer, 96.7g trimethyl phosphite and 40.2g trimethylolpropane were added, and heated to 80-120°C under nitrogen protection, and the by-product methanol was separated by distillation during the reaction, the column top temperature of the methanol fraction was about 64°C, and the reaction distillation was carried out for 3h, and no obvious methanol reflux was observed, and the transesterification product was obtained. The fractionating column was replaced by reflux condenser, and then 2.2g catalyst PIS-1 was added, and heated to 170-180°C under nitrogen protection, and the reaction was carried out for 2.5h, and the crude product was obtained. The dimethyl methylphosphonate was removed by vacuum distillation under 0.0095-0.01MPa vacuum degree and 180-190°C oil bath temperature, and cooled to 90°C, and filtered hot, and the catalyst was recovered, and the filtrate was cooled, and the product 76.3g was obtained with a yield of 91.0%.

[0045] Example 8

[0046] In a 250ml flask equipped with magnetic stirrer, fractionating column and thermometer, 96.7g trimethyl phosphite and 40.2g trimethylolpropane were added, and heated to 80-120°C under nitrogen protection, and the by-product methanol was separated by distillation during the reaction, the column top temperature of the methanol fraction was about 64°C, and the reaction distillation was carried out for 3h, and no obvious methanol reflux was observed, and the transesterification product was obtained. The fractionating column was replaced by reflux condenser, and then 2.2g catalyst PIS-1 was added, and heated to 170-180°C under nitrogen protection, and the reaction was carried out for 2.5h, and the crude product was obtained. The dimethyl methylphosphonate was removed by vacuum distillation under 0.0095-0.01MPa vacuum degree and 180-190°C oil bath temperature, and cooled to 90°C, and filtered hot, and the catalyst was recovered, and the filtrate was cooled, and the product 76.3g was obtained with a yield of 91.0%.

[0047] Example 9

[0048] In a 250ml flask equipped with magnetic stirrer, fractionating column and thermometer, 96.7g trimethyl phosphite and 40.2g trimethylolpropane were added, and heated to 80-120°C under nitrogen protection, and the by-product methanol was separated by distillation during the reaction, the column top temperature of the methanol fraction was about 64°C, and the reaction distillation was carried out for 3h, and no obvious methanol reflux was observed, and the transesterification product was obtained. The fractionating column was replaced by reflux condenser, and then 2.2g catalyst PIS-1 was added, and heated to 170-180°C under nitrogen protection, and the reaction was carried out for 2.5h, and the crude product was obtained. The dimethyl methylphosphonate was removed by vacuum distillation under 0.0095-0.01MPa vacuum degree and 180-190°C oil bath temperature, and cooled to 90°C, and filtered hot, and the catalyst was recovered, and the filtrate was cooled, and the product 76.3g was obtained with a yield of 91.0%.

[0049] Example 10

[0050] In a 250ml flask equipped with magnetic stirrer, fractionating column and thermometer, 114.6g trimethyl phosphite and 41.3g trimethylolpropane were added, and heated to 80-120°C under nitrogen protection, and the by-product methanol was separated by distillation during the reaction, the column top temperature of the methanol fraction was about 64°C, the reaction distillation was carried out for 3h, and no obvious methanol reflux was observed, and the transesterification product was obtained. The fractionating column was replaced by reflux condenser, and then 2.5g catalyst PIS-2 was added, and heated to 170-180°C under nitrogen protection, and the reaction was carried out for 2h, and the crude product was obtained. The dimethyl methylphosphonate was removed by vacuum distillation under 0.0095-0.01MPa vacuum degree and 180-190°C oil bath temperature, and the temperature was lowered to 90°C, and the catalyst was recovered by hot filtration, and the filtrate was cooled to obtain the product 85.6g with a yield of 97.2%.

[0051] Example 11

[0052] In a 250ml flask equipped with magnetic stirrer, fractionating column and thermometer, 114.6g trimethyl phosphite and 41.3g trimethylolpropane were added, and heated to 80-120°C under nitrogen protection, and the by-product methanol was separated by distillation during the reaction, the column top temperature of the methanol fraction was about 64°C, the reaction distillation was carried out for 3h, and no obvious methanol reflux was observed, and the transesterification product was obtained. The fractionating column was replaced by reflux condenser, and then 2.5g catalyst PIS-2 was added, and heated to 170-180°C under nitrogen protection, and the reaction was carried out for 2h, and the crude product was obtained. The dimethyl methylphosphonate was removed by vacuum distillation under 0.0095-0.01MPa vacuum degree and 180-190°C oil bath temperature, and the temperature was lowered to 90°C, and the catalyst was recovered by hot filtration, and the filtrate was cooled to obtain the product 85.6g with a yield of 97.2%.

[0053] Example 12

[0054] In a 250ml flask equipped with magnetic stirrer, fractionating column and thermometer, 114.6g trimethyl phosphite and 41.3g trimethylolpropane were added, and heated to 80-120°C under nitrogen protection, and the by-product methanol was separated by distillation during the reaction, the column top temperature of the methanol fraction was about 64°C, the reaction distillation was carried out for 3h, and no obvious methanol reflux was observed, and the transesterification product was obtained. The fractionating column was replaced by reflux condenser, and then 2.5g catalyst PIS-2 was added, and heated to 170-180°C under nitrogen protection, and the reaction was carried out for 2h, and the crude product was obtained. The dimethyl methylphosphonate was removed by vacuum distillation under 0.0095-0.01MPa vacuum degree and 180-190°C oil bath temperature, and the temperature was lowered to 90°C, and the catalyst was recovered by hot filtration, and the filtrate was cooled to obtain the product 85.6g with a yield of 97.2%.

[0055] The recovered catalyst crude sample was washed with ethanol and dried to obtain the recovered catalyst PIS-2.

[0056] The recovered catalyst PIS-2 was used to catalyze the preparation of cyclic phosphonate ester under the same conditions. The recovery experiments were repeated 3 times under the same conditions, and the yields were 97.5%, 96.9%, and 97.3% respectively based on the amount of trimethylolpropane added.

[0057] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An organic polymer catalyst, characterized in that The organic polymer catalyst contains methyl benzenesulfonate and imidazolium ions, and the structural formula of the organic polymer catalyst is as follows:

2. The organic polymer catalyst according to claim 1, characterized in that The preparation method of the organic polymer catalyst is as follows: (1) 1-Methylimidazole and 4-chloromethylstyrene were dissolved in acetonitrile and heated for reaction. After the reaction, the solvent was evaporated under reduced pressure, washed with ether, and dried under vacuum at room temperature to obtain 1 mM colorless oily ionic liquid. The reaction temperature was 50-80°C, the reaction time was 12-24 h, and the molar ratio of 1-methylimidazole to 4-chloromethylstyrene was 1:1-1.5; (2) Under a nitrogen atmosphere, a mixture of methyl 4-vinylbenzenesulfonate, ionic liquid ImM, p-divinylbenzene, azobisisobutyronitrile and tetrahydrofuran-water was heated and stirred. After the reaction was completed, the mixture was cooled to room temperature and filtered. The filter cake was Soxhlet extracted with tetrahydrofuran for 24 hours. The obtained solid was vacuum dried at 80°C overnight to obtain a white solid PIS. The reaction temperature was 50-100°C and the reaction time was 24-72 hours. The molar ratio of ionic liquid ImM, methyl 4-vinylbenzenesulfonate, p-divinylbenzene and azobisisobutyronitrile was 1:2-4:4-12:0.2-0.

4.

3. A method for preparing a cyclic phosphate flame retardant using the catalyst according to any one of claims 1 to 2, characterized in that: Here are the steps: S1: using trimethylolpropane and trimethyl phosphite as raw materials, a mixture of dimethyl phosphite and ethyl bicyclophosphite as intermediate products is obtained through ester exchange reaction; S2: adding the catalyst to the product of S1, trimethyl phosphite isomerizes to dimethyl methylphosphonate, dimethyl phosphite isomerizes to cyclic phosphate, ethyl bicyclic phosphite and dimethyl methylphosphonate undergo Michaelis-Arbuzov rearrangement to generate cyclic phosphonate.

4. The method according to claim 3, characterized in that In step S1, the molar ratio of trimethylolpropane to trimethyl phosphite is 1:2 to 1:4, the oil bath temperature is 90 to 130° C., and the reaction time is 2 to 4 hours; in step S2, the reaction temperature is 170 to 180° C., and the reaction time is 1 to 3 hours.

5. The method according to claim 3, characterized in that In the step S2, the amount of the catalyst added is 0.5% to 3% of the mass of trimethylolpropane.

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