CN116082541B - Hydrolysis method of polyvinyl dimethyl phosphonate - Google Patents

Abstract

A method for hydrolyzing dimethyl polyvinylphosphonate, comprising the steps of: 1) Adding polymethyl vinylphosphonate and pure water into a hydrolysis kettle, wherein the mass ratio of the polymethyl vinylphosphonate to the pure water is 1:2-3, the hydrolysis temperature is 100-130 ℃, the hydrolysis pressure is saturated steam pressure which maintains the temperature of 100-130 ℃, the hydrolysis time is 12-24 hours, and the vapor phase is discharged through an automatic pressure relief device; 2) Adding 1-2 times of pure water into the hydrolysate obtained in the step 1), adding the hydrolysate into a hydrolysis kettle, wherein the hydrolysis temperature is 130-160 ℃, the hydrolysis pressure is saturated steam pressure which maintains the temperature at 130-160 ℃, the hydrolysis time is 12-24h, and discharging a vapor phase through an automatic pressure relief device; 3) And (3) carrying out light component removal and crystallization on the hydrolysate obtained in the step (2) to obtain a hydrolysate. The method has the advantages of high hydrolysis efficiency, convenient separation of the decomposition products, high separation purity and environmental protection and no pollution.

Description

A method for hydrolyzing dimethyl polyvinylphosphonate

Technical Field

The invention relates to the field of chemical industry, and in particular to a method for hydrolyzing dimethyl polyvinylphosphonate.

Background Art

In recent years, phosphorus-containing polymers have become the focus of research due to their wide applications in the fields of proton conductivity, biomedicine and flame retardant materials. Among them, polyvinylphosphonic acid and its derivatives have attracted the attention of more and more researchers due to their simple structure and excellent performance. As a type of polymer with a large number of phosphonic acid groups in the side chain, polyvinylphosphonic acid has similar properties to small molecule phosphonic acid, but has higher thermal stability and chemical stability. At the same time, due to its diprotic acid structure and the special properties of phosphorus-containing polymers, polyvinylphosphonic acid has better performance than monoprotic acids such as poly(meth)acrylic acid and polyvinyl sulfonic acid.

Polyvinylphosphonic acid is usually prepared by the following two methods: 1) self-polymerization of vinylphosphonic acid to generate polyvinylphosphonic acid; 2) hydrolysis of polyvinylphosphonic acid derivatives. When polyvinylphosphonic acid is generated by free radical polymerization of vinylphosphonic acid, the polymerization is carried out in a cyclopolymerization manner, that is, first an intermediate such as vinylphosphonic anhydride is formed, and then a six-membered ring or five-membered ring structure with a methylene or methine free radical is formed through intramolecular growth, and then growth is carried out on the free radical site. The polymer formed by this growth method is random, and the main chain has both head-to-head and head-to-tail linked structures. The titration curve shows that its performance is more like a monoprotic acid. In addition, due to the formation of anhydride, the number of charges carried by polyvinylphosphonic acid is reduced, which also hinders the transfer of charges between adjacent segments, and also leads to the poor hygroscopicity of polyvinylphosphonic acid, and the conductivity will be further affected. The polyvinylphosphonic acid obtained by hydrolysis of polyvinylphosphonic acid derivatives does not have the above situation. The polyvinylphosphonic acid generated by this method usually has a certain stereoregularity.

Although the hydrolysis of polyvinylphosphonic acid derivatives to prepare polyvinylphosphonic acid is the main method for preparing stereoregular polyvinylphosphonic acid, there are few studies on the hydrolysis process of vinylphosphonic acid derivatives, and most studies are only briefly mentioned. At present, hydrolysis is usually carried out in an excess of halogenated hydrogen solution. Hartmut Komber ^[1] , baharBingol ^[2] and others hydrolyzed vinylphosphonic acid derivatives in saturated HBr solution, and Renaud Perrin ^[3] , Takashi Takahashi, Keisuke Matsushita ^[4] hydrolyzed vinylphosphonic acid derivatives in fuming hydrochloric acid. Using halogenated hydrogen solution for hydrolysis will introduce halogen ions into vinylphosphonic acid, making separation difficult; and the concentration during hydrolysis is very high, which will cause serious corrosion to the equipment.

Therefore, it is of great significance to develop a method for hydrolyzing vinylphosphonic acid derivatives without using halogenated hydrogen.

Summary of the invention

The purpose of the present invention is to provide a method for hydrolyzing polyvinyl dimethyl phosphonate in view of the deficiencies in the prior art, which has high hydrolysis efficiency, convenient separation of decomposition products, high separation purity, and is a green and pollution-free hydrolysis method.

The technical solution of the present invention is: a method for hydrolyzing polyvinyl dimethyl phosphonate, comprising the following steps:

1) Take polyvinyl dimethyl phosphate and pure water, add them into a hydrolysis kettle, the mass ratio of polyvinyl dimethyl phosphate to pure water is 1:2-3, the hydrolysis temperature is 100-130°C, the hydrolysis pressure is the saturated steam pressure maintaining the temperature at 100-130°C, the hydrolysis time is 12-24h, and the vapor phase is discharged through an automatic pressure relief device;

2) The hydrolyzate obtained in step 1) is supplemented with 1-2 times the mass of pure water and added into a hydrolysis kettle. The hydrolysis temperature is 130-160° C. The hydrolysis pressure is a saturated steam pressure maintaining a temperature of 130-160° C. The hydrolysis time is 12-24 hours, and the vapor phase is discharged through an automatic pressure relief device;

3) The hydrolyzate obtained in step 2) is subjected to light removal and crystallization to obtain a hydrolyzate.

Furthermore, in step 1), polyvinyl phosphoric acid is added as a catalyst, and the mass ratio of polyvinyl phosphoric acid to polyvinyl dimethyl phosphate is 0-0.05:1.

Furthermore, the mother liquor separated after the crystallization in step 3) is returned to step 1) as a catalyst.

Furthermore, the mother liquor separated after crystallization in step 3) is returned to step 2) and mixed with the hydrolyzate.

Furthermore, in step 3), the hydrolyzate is added to the light removal kettle, the kettle temperature is controlled to 85-110°C, the fraction with the top temperature of 67-90°C is collected, methanol is recovered by distillation, and the fraction with the top temperature of 90-100°C is collected as pure water for step 1) and/or step 2), and then vacuum dehydration is carried out until the water content in the kettle liquid is less than 5wt%.

Furthermore, the vapor phase discharged from step 1) and/or the vapor phase discharged from step 2) is condensed and then distilled to recover methanol.

Furthermore, the crystallization in step 3) is performed by cooling the temperature to 0-50°C.

The above technical solution has the following beneficial effects:

1. The present invention utilizes a secondary hydrolysis process, and controls the mass ratio of polyvinyl dimethyl phosphate and pure water to be 1:2-3, the hydrolysis temperature to be 100-130°C, and the hydrolysis pressure to be a saturated steam pressure at a temperature of 100-130°C, so that the hydrolysis rate of polyvinyl dimethyl phosphate reaches about 80%. By maintaining the hydrolysis temperature at 100-130°C and the reaction under the saturated steam pressure, the reaction rate can be increased, and the generated methanol can be discharged in time to promote the forward reaction of the hydrolysis; if the temperature is lower than 100°C, the reaction can also proceed, but the reaction rate is slow. After the first hydrolysis is completed, pure water of 1-2 times the mass is added, the hydrolysis temperature is controlled to be 130-160°C, and the hydrolysis pressure is a saturated steam pressure at a temperature of 130-160°C, so that the hydrolysis rate of polyvinyl dimethyl phosphate finally reaches more than 95%, which can effectively improve the utilization efficiency of raw materials.

2. In the present invention, polyvinylphosphonic acid or mother liquor (containing a small amount of polyvinylphosphonic acid) is added as a catalyst during the first hydrolysis. The added polyvinylphosphonic acid provides an acidic environment at the initial stage of the reaction, effectively improving the initial hydrolysis rate of polyvinyl dimethyl phosphate and shortening the reaction time.

3. In the two hydrolysis processes of the present invention, the vapor phase, especially the by-product methanol, is discharged through the automatic pressure relief device, so that the hydrolysis reaction proceeds in the forward direction.

4. The secondary hydrolysis process of the present invention can produce a vapor phase (methanol-water mixture), a light phase produced by light removal, and a mother liquor separated after crystallization, which can be recycled to avoid the discharge of phosphorus. This can effectively avoid the waste of raw materials and is a green and environmentally friendly hydrolysis method.

The applicant has verified through experiments that the hydrolysis method of the present invention can achieve a hydrolysis rate of polyvinyl dimethyl phosphate of more than 95%, a yield of the target product of more than 90% (the remaining mother liquor can be recycled, and the comprehensive yield exceeds 98%), and a product purity of more than 97%.

The following is a further description in conjunction with specific implementation methods.

DETAILED DESCRIPTION

In the present invention, the used dimethyl vinylphosphonate (wt%=99.5%) and dimethyl polyvinylphosphonate (MV=61000, Mv/Mn=5.51, GPC) are both made by Chongqing Chemical Research Institute; pure water (resistivity>18.2MΩ).

Example 1

Hydrolysis 1: 200g of dimethyl vinylphosphonate, 600g of pure water and 20g of vinylphosphonic acid were added to the enamel hydrolysis kettle 1, the hydrolysis temperature was controlled to 128°C, the pressure in the hydrolysis kettle was 0.26Mpa, and the methanol vapor generated by the byproduct was removed in time using an automatic pressure relief device. The reaction time was 12h. After the hydrolysis 1 reaction was completed, 690g of the reaction liquid was transferred to the enamel hydrolysis kettle 2, 700g of pure water was added, the hydrolysis temperature was increased to 150°C, the pressure in the hydrolysis kettle was 0.48Mpa, and the methanol vapor generated by the byproduct was removed in time using an automatic pressure relief device. The reaction time was about 12h. After the hydrolysis 2 reaction was completed, 1330g of the hydrolyzate was transferred to the light removal kettle for light removal, and the light was removed by vacuum distillation. 50g of light components containing methanol at 64-80°C were collected at -0.01Mpa, and 1090g of water was recovered from the 81-110°C fraction to obtain 170g of kettle liquid. The kettle liquid after light removal was transferred to the crystallization kettle, cooled to 0-10°C for crystallization, and 145g of crystal product and 30g of mother liquor were collected. The purity of the crystal product was 97.2% and the yield was 91.3%.

Example 2

Take 200g of polyvinylphosphonic acid dimethyl ester (MV = 61000, Mv / Mn = 5.51, GPC) and 600g of pure water and put them into the enamel reactor 1, control the hydrolysis temperature to 130 ° C, the pressure in the hydrolysis reactor to 0.28Mpa, use the automatic pressure relief device to remove the methanol generated by the byproduct in time, and the reaction time is 36h. After the hydrolysis 1 reaction is completed, transfer 785g of the reaction liquid to the enamel hydrolysis reactor 2, add 785g of pure water, increase the hydrolysis temperature to 160 ° C, the pressure in the hydrolysis reactor to 0.6Mpa, use the automatic pressure relief device to remove the methanol generated by the byproduct in time, and the reaction time is about 12h. After the hydrolysis 2 reaction is completed, transfer 1320g of the hydrolyzate to the de-light reactor to de-lighten, collect 42g of 64-80°C methanol-containing light components at -0.01Mpa, collect 1062g of 81-110°C distillate water, and obtain 216g of kettle liquid. The kettle liquid after light removal was transferred to the crystallization kettle, cooled to 20-30°C for crystallization, and 135g of crystal product and 81g of mother liquor were collected, with a yield of about 85.0%.

Example 3

Hydrolysis 1: 600g of polyvinylphosphonic acid dimethyl ester (MV=61000, Mv/Mn=5.51, GPC), 1200g of pure water and 20g of the crystallization mother liquor prepared in Example 2 were put into the enamel reactor 1, the hydrolysis temperature was controlled to 130°C, the pressure in the hydrolysis reactor was 0.28Mpa, and the methanol generated as a by-product was removed in time using an automatic pressure relief device, and the reaction time was 26h. After the hydrolysis 1 reaction was completed, 1380g of the reaction solution was transferred to the enamel hydrolysis reactor 2, 1380g of pure water was added, the hydrolysis temperature was increased to 160°C, the pressure in the hydrolysis reactor was 0.6Mpa, and the methanol generated as a by-product was removed in time using an automatic pressure relief device, and the reaction time was about 8h. After the hydrolysis 2 reaction was completed, 2496g of the hydrolyzate was transferred to a light removal kettle for light removal, 31g of methanol-containing light components at 64-80°C were collected at -0.01Mpa, 1975g of water was recovered from the 81-110°C fraction, and 490g of kettle liquid was obtained. The kettle liquid after light removal was transferred to a crystallization kettle, cooled to 20-30°C for crystallization, 400g of crystal product and 90g of mother liquor were collected, and the yield was about 84.0%.

Claims (5)

1. A method for hydrolyzing polymethyl vinyl phosphonate, which is characterized by comprising the following steps:

1) Adding polymethyl vinylphosphonate and pure water into a hydrolysis kettle, wherein the mass ratio of the polymethyl vinylphosphonate to the pure water is 1:2-3, the hydrolysis temperature is 100-130 ℃, the hydrolysis pressure is saturated steam pressure which maintains the temperature at 100-130 ℃, the hydrolysis time is 12-24 hours, the vapor phase is discharged through an automatic pressure relief device, polyvinyl phosphonic acid is added as a catalyst, and the mass ratio of polyvinyl phosphonic acid to polymethyl phosphonate is 0-0.05:1, a step of;

2) Adding 1-2 times of pure water into the hydrolysate obtained in the step 1), adding the hydrolysate into a hydrolysis kettle, wherein the hydrolysis temperature is 130-160 ℃, the hydrolysis pressure is saturated steam pressure which maintains the temperature at 130-160 ℃, the hydrolysis time is 12-24h, and discharging a vapor phase through an automatic pressure relief device;

3) The hydrolysate obtained in the step 2) is subjected to light component removal and crystallization to obtain a hydrolysate, and mother liquor separated after crystallization is returned to the step 1) to be used as a catalyst.

2. The hydrolysis method according to claim 1, wherein the mother liquor separated after crystallization in step 3) is returned to step 2) to be mixed with the hydrolysis liquid.

3. The hydrolysis method according to claim 1, wherein the light component is removed in the step 3), the hydrolysis liquid is added into a light component removing kettle, the kettle temperature is controlled to be 85-110 ℃, the fraction with the top temperature of 67-90 ℃ is collected, the methanol is recovered by rectification, the fraction with the top temperature of 90-100 ℃ is collected as the pure water in the step 1) and/or the step 2), and then the water content in the kettle liquid is reduced to be lower than 5wt%.

4. Hydrolysis method according to claim 1, characterized in that the vapor phase discharged in step 1) and/or the vapor phase discharged in step 2) is condensed and then distilled to recover methanol.

5. The hydrolysis method according to claim 1, wherein the crystallization in step 3) is crystallization at a temperature of 0 to 50 ℃.