CN111333547A

CN111333547A - Green synthesis method of polyisocyanate suitable for industrial production

Info

Publication number: CN111333547A
Application number: CN202010152502.1A
Authority: CN
Inventors: 冉祥海; 高一星; 聂伟
Original assignee: Changchun Institute of Applied Chemistry of CAS
Current assignee: Changchun Institute of Applied Chemistry of CAS
Priority date: 2020-03-06
Filing date: 2020-03-06
Publication date: 2020-06-26

Abstract

The invention provides a method for synthesizing polyisocyanate, which comprises the following steps: r is to be₁OOC‑R‑COOR₁In NaOH and NH₂Reacting and neutralizing in the presence of HCl to obtain di-hydroxamic acid HO-NH-CO-R-CO-NH-OH; the R is₁The compound is selected from aliphatic alkyl of C1-C15, R is selected from one or more of phenylene, arylene of C6-C30 containing substituent groups, unsubstituted arylene of C6-C30, aliphatic hydrocarbon of C6-C20, alicyclic hydrocarbon of C6-C20 and naphthylene; and (3) rearranging the di-hydroxamic acid under alkaline conditions to obtain polyisocyanate OCN-R-NCO. The method does not adopt highly toxic gas, does not generate corrosive gas or intermediate in the reaction process, and does not need to adopt noble metal catalyst, so the method is green, environment-friendly and simple; the product selectivity in the reaction process is good, the side reaction is less, and the yield is higher.

Description

Green synthesis method of polyisocyanate suitable for industrial production

Technical Field

The invention belongs to the technical field of isocyanate, and particularly relates to a method for green synthesis of polyisocyanate suitable for industrial production.

Background

Isocyanates, in particular diisocyanates such as methylene diphenyl diisocyanate (MDI), Toluene Diisocyanate (TDI), 1, 6-Hexamethylene Diisocyanate (HDI) and the like, are important raw materials for producing polyurethanes in our national society. Currently, the worldwide production of isocyanates is close to 1000 ten thousand tons, and industrial isocyanates are mainly synthesized by the phosgene method. Although the technology is mature, the phosgene used is volatile and highly toxic, the environmental pollution is large, the energy consumption is large, the generated hydrogen chloride seriously corrodes equipment, the production equipment is high in cost, the technical requirement is complex, and the product contains chloride ion impurities which are difficult to remove from the purification process of the final product isocyanate, so that the cost is high. In view of environmental protection and social safety, there is an urgent need to develop a non-phosgene process for producing isocyanates.

The existing method for synthesizing isocyanate includes more than 20 methods, which can be divided into phosgenation method and non-phosgenation method, but has little industrial production value, so far the widely adopted industrial production method is still primary amine phosgene method, at present the non-phosgene method for producing isocyanate mainly includes four methods of triphosgene method, carbonization method, haloform β elimination method and carbamate anion dehydration method, the triphosgene method utilizes solid triphosgene to replace phosgene to prepare MDI, and has the advantages of convenient use, solid weighing, mild reaction condition and high yield, but when the solid triphosgene method is adopted, a large amount of hydrochloric acid can be still produced, equipment is corroded, and the problem of chloride contained in the product is not solved, the haloform β elimination method is that trihaloacetamide compounds generate isocyanate in the presence of diazabicyclo and dimethyl sulfoxide, although the whole reaction is mild and the reaction speed is high, the cost of the method is too high, and the method is lack of the basis of industrial application, and the carbamate anion dehydration method is based on CO₂Carbamate anion solution prepared from organic alkali-primary amine mixed solution and phosphorus-containing electrophilic reagent (POCL)₃、PCL₃、P₄O₁₀) The isocyanate is obtained by dehydration reaction, and the process has the characteristics of mild reaction conditions, high selectivity, low cost and the like, but cannot be popularized in a wider range due to generation of a large amount of waste salt which is difficult to treat. Currently, the most popular is the carbonization process, and among the carbonization processes, the most industrially feasible is the thermal decomposition of carbamate, which is carried out by a two-step process: the first step is the synthesis of urethane groups and the second step is the thermal decomposition of the urethane to form the target isocyanate, with CO or CO₂As a carbon source, the raw materials are easy to obtain and environment-friendly. During the second thermal decomposition, although the carbamate can be decomposed at high temperatureThe isocyanate is decomposed, but the reaction rate is slow, side reactions are more, and the industrial production is not facilitated, so that the introduction of a catalyst in the reaction process is necessary to improve the efficiency, most of the catalyst is VIII group metal, the price is high, the catalyst is easy to deactivate at high temperature, and even if the cheap catalyst is selected in individual methods, the economic cost and the energy consumption are increased due to the recovery and separation of the catalyst, so the industrial application of the method is limited.

In summary, the phosgene process, which is highly polluting, is the mainstream technology for the production of isocyanates, since the non-phosgene process still has different disadvantages. However, in the long run, with the enhancement of environmental awareness and the continuous progress of technology, phosgene method is inevitably replaced by non-phosgene method. Therefore, a non-phosgene synthesis method which is suitable for industrial production and is environmentally friendly is urgently required.

Disclosure of Invention

In view of the above, the present invention aims to provide a method for synthesizing polyisocyanate, which is environment-friendly, simple and high in yield.

The invention provides a method for synthesizing polyisocyanate, which comprises the following steps:

r is to be₁OOC-R-COOR₁In NaOH and NH₂Reacting and neutralizing in the presence of HCl to obtain di-hydroxamic acid HO-NH-CO-R-CO-NH-OH; the R is₁The compound is selected from aliphatic alkyl of C1-C15, R is selected from one or more of phenylene, arylene of C6-C30 containing substituent groups, unsubstituted arylene of C6-C30, aliphatic hydrocarbon of C6-C20, alicyclic hydrocarbon of C6-C20 and naphthylene;

and (3) rearranging the di-hydroxamic acid under alkaline conditions to obtain polyisocyanate OCN-R-NCO.

Preferably, R is selected from one or more of formula 101 to formula 111:

preferably, said R is₁Is selected from-C₂H₅。

Preferably, the compound R₁OOC-R-COOR₁In NaOH and NH₂The reaction in the presence of HCl specifically comprises:

r is to be₁OOC-R-COOR₁Dissolving in methanol to obtain R₁OOC-R-COOR₁A solution;

mixing a sodium hydroxide solution and a hydroxylamine hydrochloride solution to obtain an alkaline solution;

dropwise adding the alkaline solution to the R₁OOC-R-COOR₁In the solution, the reaction was carried out under stirring.

Preferably, said R is₁OOC-R-COOR₁The mass ratio of NaOH to NaOH was 1: 6-7;

the NaOH and NH₂Mass ratio of HCl 1: 1.

preferably, said R is₁OOC-R-COOR₁In NaOH and NH₂The reaction temperature is 50-60 ℃ in the presence of HCl;

the R is₁OOC-R-COOR₁In NaOH and NH₂The reaction time in the presence of HCl is 70-75 h.

Preferably, hydrochloric acid is used for neutralization.

Preferably, the basic conditions are achieved by 4-nitrobenzenesulfonyl chloride and triethylamine;

the mass ratio of the 4-nitrobenzenesulfonyl chloride to the triethylamine to the di-hydroxamic acid is 1.9-2.1: 3.8-4.2: 1.

preferably, the rearrangement temperature is 0-25 ℃, and the rearrangement time is 5-7 h; the rearrangement is carried out under stirring.

Preferably, the polyisocyanate is p-phenylene diisocyanate, toluene diisocyanate, or diphenylmethane diisocyanate.

The invention provides a method for synthesizing polyisocyanate, which comprises the following steps: r is to be₁OOC-R-COOR₁In NaOH and NH₂Presence of HClReacting and neutralizing to obtain the di-hydroxamic acid HO-NH-CO-R-CO-NH-OH; the R is₁The compound is selected from aliphatic alkyl of C1-C15, R is selected from one or more of phenylene, arylene of C6-C30 containing substituent groups, unsubstituted arylene of C6-C30, aliphatic hydrocarbon of C6-C20, alicyclic hydrocarbon of C6-C20 and naphthylene; and (3) rearranging the di-hydroxamic acid under alkaline conditions to obtain polyisocyanate OCN-R-NCO. The method does not adopt highly toxic gas, does not generate corrosive gas or intermediate in the reaction process, and does not need to adopt noble metal catalyst, so the method is green, environment-friendly and simple; the product selectivity in the reaction process is good, the side reaction is less, and the yield is higher. The method adopts ester bio-based raw materials, has wide sources and low cost, is renewable and meets the requirement of environmental protection. The experimental results show that: the yield of the p-phenylene diisocyanate is 85 percent, and the purity is 97 percent; the yield of toluene diisocyanate was 80% and the purity was 97%; the yield of diphenylmethane diisocyanate was 82% and the purity was 96%.

Drawings

FIG. 1 is a H-NMR spectrum of terephthalic hydroxamic acid in example 1 of the present invention;

FIG. 2 is a chart of H-NMR of p-phenylene diisocyanate prepared in example 1 of the present invention;

FIG. 3 shows the preparation of toluene diisocyanate according to example 2 of the present invention¹³A C-NMR spectrum;

FIG. 4 is a H-NMR spectrum of diphenylmethane diisocyanate obtained in example 3 of the present invention.

Detailed Description

The method does not adopt highly toxic gas, does not generate corrosive gas or intermediate in the reaction process, and does not need to adopt noble metal catalyst, so the method is green, environment-friendly and simple; the product selectivity in the reaction process is good, the side reaction is less, and the yield is higher. The method adopts ester bio-based raw materials, has wide sources and low cost, is renewable and meets the requirement of environmental protection.

In the present invention, said R₁OOC-R-COOR₁In R₁Selected from aliphatic alkyl of C1-C15, preferably selected from aliphatic alkyl of C2-C10, more preferably selected from-C₂H₅. The R is selected from one or more of phenylene, arylene of C6-C30 containing substituent groups, unsubstituted arylene of C6-C30, aliphatic alkylene of C6-C20, alicyclic alkylene of C6-C20 and naphthylene; preferably one or more selected from formula 101 to formula 111:

more preferably, R is selected from formula 101, formula 102 or formula 104.

In a specific embodiment of the invention, R is₁OOC-R-COOR₁In particular to ethyl diphenylmethane dicarboxylate, the structural formula is as follows:

or ethyl toluate with the structural formula

Or ethyl terephthalate with the structural formula

In the invention, R is₁OOC-R-COOR₁In NaOH and NH₂Presence of HClThe following reaction particularly preferably includes:

In the present invention, said R₁OOC-R-COOR₁The concentration of the solution is preferably 0.25-0.35 mol/L, and more preferably 0.3 mol/L; the temperature of the sodium hydroxide solution is preferably 8-10 mol/L, and more preferably 9 mol/L; the concentration of the hydroxylamine hydrochloride is preferably 13-14 mol/L, and more preferably 13.5 mol/L. The R is₁OOC-R-COOR₁The mass ratio to NaOH is preferably 1: 6-7, more preferably 1: 6; the NaOH and NH₂The mass ratio of HCl is preferably 1: 1.

in the present invention, said R₁OOC-R-COOR₁In NaOH and NH₂The reaction temperature in the presence of HCl is preferably 50-60 ℃, more preferably 52-58 ℃, and most preferably 55 ℃;

the R is₁OOC-R-COOR₁In NaOH and NH₂The reaction time in the presence of HCl is preferably 70-75 h, and more preferably 72-73 h.

The invention preferably adopts hydrochloric acid for neutralization, and more preferably adopts hydrochloric acid with the mass fraction of 5 percent for neutralization. The invention preferably neutralizes until the pH value is 6-7. Neutralizing, filtering, stirring the obtained solid in boiling methanol, removing redundant impurities, filtering and drying to obtain the di-hydroxamic acid HO-NH-CO-R-CO-NH-OH. In particular embodiments of the invention, the di-hydroxamic acid is specifically of formula 201, formula 202 or formula 203:

the present invention rearranges the di-hydroxamic acid under alkaline condition to obtain polyisocyanate OCN-R-NCO. In the invention, the alkaline condition is realized by 4-nitrobenzenesulfonyl chloride and triethylamine; the mass ratio of the 4-nitrobenzenesulfonyl chloride to the triethylamine to the di-hydroxamic acid is preferably 1.9-2.1: 3.8-4.2: 1, more preferably 2: 4: 1. the rearrangement is preferably carried out in tetrahydrofuran solvent; dissolving the di-hydroxamic acid, 4-nitrobenzenesulfonyl chloride and triethylamine in tetrahydrofuran; the rearrangement temperature is preferably 0-25 ℃, and more preferably 15-25 ℃; the rearrangement time is preferably 5-7 h, more preferably 5.5-6.5 h, and most preferably 6 h; the rearrangement is carried out under stirring.

Filtering after rearrangement is finished, concentrating the filtrate, and distilling under reduced pressure to obtain the polyisocyanate. In the present invention, the polyisocyanate is p-phenylene diisocyanate, toluene diisocyanate or diphenylmethane diisocyanate.

In order to further illustrate the present invention, a method for synthesizing polyisocyanates according to the present invention is described in detail with reference to the following examples, which should not be construed as limiting the scope of the present invention.

Example 1

In a 2L three-necked flask, 0.135mol of ethyl terephthalate was dissolved in 400ml of methanol at room temperature; dissolving 0.81mol of sodium hydroxide in 90ml of distilled water, dissolving 0.81mol of hydroxylamine hydrochloride in 60ml of distilled water, mixing the two alkaline solutions, dropwise adding the two alkaline solutions into a terephthalate solution at 5 ℃, and then stirring the reactants for 72 hours at 55 ℃; the mixture is neutralized to pH 6-7 with 700ml of 5% strength hydrochloric acid, the solution is then filtered and the solid obtained is stirred in 1L of boiling methanol; thereafter, the mixture was filtered to give a white solid of terephthalic hydroxamic acid, the yield of the reaction was 92%, and the purity of the product could reach 97%.

FIG. 1 is a H-NMR spectrum of terephthalic hydroxamic acid in example 1 of the present invention; as can be seen from fig. 1: monomodal 7.8ppm corresponds to 4H C-H aromatic compound, monomodal 9.1ppm corresponds to 2H O-H, and monomodal 11.2ppm corresponds to 2 HN-H.

Weighing a certain mass of the obtained white solid di-hydroxamic acid, adding 2 times of equivalent of 4-nitrobenzenesulfonyl chloride and 4 times of equivalent of triethylamine, completely dissolving the obtained mixture in excessive tetrahydrofuran, fully stirring the mixture for 6 hours at 0-25 ℃, filtering the mixture, concentrating the filtrate, and carrying out reduced pressure distillation and purification to obtain the p-phenylene diisocyanate, wherein the reaction yield is 85%, and the purity of the product reaches 97%.

FIG. 2 is a chart of H-NMR of p-phenylene diisocyanate prepared in example 1 of the present invention; as can be seen from fig. 2: the unimodal 6.75ppm corresponds to 4H C-H aromatics.

Example 2

In a 2L three-necked flask, 0.135mol of ethyl toluate was dissolved in 400ml of methanol at room temperature; dissolving 0.81mol of sodium hydroxide in 90ml of distilled water, dissolving hydroxylamine hydrochloride in 60ml of distilled water, mixing the two alkaline solutions, dropwise adding the mixture into a terephthalate solution at 5 ℃, and then stirring the reactants for 72 hours at 55 ℃; the mixture is neutralized with 700ml of 5% strength hydrochloric acid to a pH of 6 to 7, the solution is then filtered and the solid obtained is stirred in 1L of boiling methanol; thereafter, the mixture was filtered to give the hydroxamic acid as a white solid, and the yield of the reaction was 93%, and the purity of the product was 97%.

Weighing a certain mass of the obtained white solid di-hydroxamic acid, adding 2 times of equivalent of 4-nitrobenzenesulfonyl chloride and 4 times of equivalent of triethylamine, completely dissolving the mixture in excessive tetrahydrofuran, fully stirring the mixture at 0-25 ℃ for 6 hours, filtering the mixture, concentrating the filtrate, and purifying the toluene diisocyanate by reduced pressure distillation, wherein the reaction yield is 80%, and the purity of the product reaches 97%.

FIG. 3 shows the preparation of toluene diisocyanate according to example 2 of the present invention¹³C-NMR spectrum.

The carbon 1 peak shift was 133.34ppm, the carbon 2 peak shift was 132.17ppm, the carbon 3 peak shift was 131.47ppm, the carbon 4 peak shift was 130.65ppm, the carbon 5 peak shift was 124.98ppm, the carbon 6 peak shift was 122.25ppm, the carbon 7 peak shift was 121.02ppm, and the carbon 8 peak shift was 17.79 ppm.

Example 3

In a 2L three-necked flask, 0.135mol of ethyl diphenylmethane dicarboxylate was dissolved in 400ml of methanol at room temperature; dissolving 0.81mol of sodium hydroxide in 90ml of distilled water, dissolving hydroxylamine hydrochloride in 60ml of distilled water, mixing the two alkaline solutions, dropwise adding the mixture into a terephthalate solution at 5 ℃, and then stirring the reactants for 72 hours at 55 ℃; the mixture is neutralized to pH 6-7 with 700ml of 5% strength hydrochloric acid, the solution is then filtered and the solid obtained is stirred in 1L of boiling methanol. Thereafter, the mixture was filtered to give the hydroxamic acid as a white solid in 92% yield and 98% purity of the product.

Weighing a certain mass of the obtained white solid di-hydroxamic acid, adding 2 times of equivalent of 4-nitrobenzenesulfonyl chloride and 4 times of equivalent of triethylamine, completely dissolving the mixture in excessive tetrahydrofuran, fully stirring the mixture for 6 hours at 0-25 ℃, filtering the mixture, concentrating the filtrate, and purifying the diphenylmethane diisocyanate by reduced pressure distillation, wherein the reaction yield is 82%, and the purity of the product reaches 96%.

FIG. 4 is a chart of the H-NMR spectrum of diphenylmethane diisocyanate obtained in example 3 of the present invention, from which FIG. 4 it can be seen that: multiplet 3.89ppm corresponds to 2H C-H methylene compound and multiplet 6.9-7.16ppm corresponds to 4H C-H aromatic compound.

From the above examples, it can be seen that the present invention provides a process for the synthesis of a polyisocyanate comprising the steps of: r is to be₁OOC-R-COOR₁In NaOH and NH₂Reacting and neutralizing in the presence of HCl to obtain di-hydroxamic acid HO-NH-CO-R-CO-NH-OH; the R is₁The compound is selected from aliphatic alkyl of C1-C15, R is selected from one or more of phenylene, arylene of C6-C30 containing substituent groups, unsubstituted arylene of C6-C30, aliphatic hydrocarbon of C6-C20, alicyclic hydrocarbon of C6-C20 and naphthylene; and (3) rearranging the di-hydroxamic acid under alkaline conditions to obtain polyisocyanate OCN-R-NCO. The method does not adopt highly toxic gas, does not generate corrosive gas or intermediate in the reaction process, and does not need to adopt noble metal catalyst, so the method is green, environment-friendly and simple; the product selectivity in the reaction process is good, the side reaction is less, and the yield is higher. The method adopts ester bio-based raw materials, has wide sources and low cost, can be regenerated, and meets the requirements ofAnd (5) environmental protection requirements. The experimental results show that: the yield of the p-phenylene diisocyanate is 85 percent, and the purity is 97 percent; the yield of toluene diisocyanate was 80% and the purity was 97%; the yield of diphenylmethane diisocyanate was 82% and the purity was 96%.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims

1. A method of synthesizing a polyisocyanate comprising the steps of:

2. The method according to claim 1, wherein R is selected from one or more of formula 101 to formula 111:

3. the method of claim 1, wherein R is₁Is selected from-C₂H₅。

4. The method of claim 1, wherein R is₁OOC-R-COOR₁In NaOH and NH₂The reaction in the presence of HCl specifically comprises:

5. The method of claim 1, wherein R is₁OOC-R-COOR₁The mass ratio of NaOH to NaOH was 1: 6-7;

the NaOH and NH₂Mass ratio of HCl 1: 1.

6. the method of claim 1, wherein R is₁OOC-R-COOR₁In NaOH and NH₂The reaction temperature is 50-60 ℃ in the presence of HCl;

7. The method of claim 1, wherein the neutralization is with hydrochloric acid.

8. The process according to claim 1, characterized in that the basic conditions are achieved by 4-nitrobenzenesulfonyl chloride and triethylamine;

the mass ratio of the 4-nitrobenzenesulfonyl chloride to the triethylamine s to the di-hydroxamic acid is (1.9-2.1): 3.8-4.2: 1.

9. the method according to claim 1, wherein the temperature of the rearrangement is 0-25 ℃, and the time of the rearrangement is 5-7 h; the rearrangement is carried out under stirring.

10. The method of claim 1, wherein the polyisocyanate is p-phenylene diisocyanate, toluene diisocyanate, or diphenylmethane diisocyanate.