CN114349664B - Preparation method of isocyanate with low bromine content - Google Patents
Preparation method of isocyanate with low bromine content Download PDFInfo
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- CN114349664B CN114349664B CN202210050590.3A CN202210050590A CN114349664B CN 114349664 B CN114349664 B CN 114349664B CN 202210050590 A CN202210050590 A CN 202210050590A CN 114349664 B CN114349664 B CN 114349664B
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Abstract
The invention discloses a method for preparing isocyanate with low bromine content. Organic sulfonate reacts with the crude isocyanate product, a sedimentation-assisting agent is added to promote the precipitation of the product, the sediment is removed by adopting a negative pressure suction filtration mode, and the solvent is removed by reduced pressure distillation to obtain the isocyanate product. The method can reduce the content of brominated impurities in the crude product of isocyanate from 200ppm to less than 10ppm on the premise that the recovery rate of isocyanate is more than 90%. The method can obviously reduce the color number of downstream products and improve the quality of the downstream products because the content of brominated impurities in the isocyanate obtained by the treatment method is low.
Description
Technical Field
The invention belongs to the field of isocyanate, and particularly relates to a purification method of isocyanate and a preparation method of low-bromine-content isocyanate.
Background
Isocyanate is a substance containing-NCO groups and is widely applied to high-end fields such as coating, foaming materials, optical resin materials and the like. The isocyanate is prepared by a phosgenation method at present, and generally, amine and phosgene react under the existence of an inert solvent and at a certain temperature and pressure to obtain photochemical reaction liquid, and then a series of technological processes for removing solvent, impurities and hydrogen chloride are carried out to obtain the isocyanate product.
In the production process, bromine impurities carried by raw materials enter a reaction system, and brominated impurities are generated in the photochemical reaction process. Because of their close structural and nature to the isocyanate and some by-products, they enter the product along with other impurities in the system. Brominated impurities can affect the color number of isocyanate products, and can have adverse quality effects on downstream products, such as the polymerization degree and light transmittance of the material in high-end fields such as optical resins. There is thus a need to reduce the brominated impurity content of isocyanate products during the production process.
The effect of brominated impurities on the color number of the product is even greater than that of chlorinated impurities. In the literature and patents, different processes for the production of light-colored isocyanates by reduction of chlorinated impurities are reported, which include reduction of by-product formation by control of process parameters, purification of raw materials and intermediates by means of stripping, extraction, rectification, etc., or reaction with chlorinated impurities by addition of additives, at different stages of phosgene synthesis, photochemical reaction, desolventizing and crude purification. And the research of further improving the color number of the product by controlling the content of brominated impurities is only a few reports in the current literature and patents.
Patent CN1087312C discloses a preparation of a mixture of diphenylmethane diisocyanate and polyphenyl polymethylene polyisocyanate having a low iodine color number and a low chlorine content, adding water and hydroxypolyoxyalkenol to the reaction solution to react with impurities, and obtaining isocyanate having a low iodine number.
Patent CN102471071a proposes a process for preparing light-colored isocyanates of the diphenylmethane diisocyanate series, by fractionating chlorine to obtain a chlorine fraction with low content of free and compound bromine, iodine, reacting with primary amines after preparing phosgene to obtain light-colored isocyanates.
Patent CN112239416a discloses a process for preparing toluene diisocyanate with low hydrolysis chlorine and hydrolysis bromine, which comprises preparing TDI by cold-hot two-step phosgene method, subjecting the hot reaction liquid to high-temperature stripping treatment by mixed gas formed by phosgene tail gas rich in carbon monoxide and nitrogen dioxide, and controlling the content of chlorine and bromine impurities.
In the method or the process, a relatively complex process is required for controlling bromine-containing impurities, so that the stability and the safety of the production process are reduced, the yield of isocyanate is influenced, or the problem that the added substances are easy to cause corrosion under the action of hydrogen chloride in a system exists.
Disclosure of Invention
The invention provides a simple method capable of efficiently reducing the content of brominated impurities in isocyanate without reducing the yield of the product. In an organic solvent, organic sulfonate reacts with brominated impurities in the crude isocyanate product, a sedimentation-assisting agent is added to promote the precipitation of a product, the sediment is removed by adopting a negative pressure suction filtration mode, and the solvent is removed by reduced pressure distillation to obtain an isocyanate product.
In order to solve the technical problems, the invention adopts the following technical scheme:
the preparation method of the isocyanate with low bromine content comprises the following steps:
(1) Adding an inert organic solvent into the crude isocyanate product;
(2) Adding organic sulfonate according to the content of brominated impurities in the crude isocyanate product;
(3) Weighing a sedimentation aid according to the content of brominated impurities in the crude isocyanate product, adding the sedimentation aid into the solution, fully stirring and mixing, heating to 30-120 ℃, and reacting for 10-250 min;
(4) And removing sediment by negative pressure suction filtration of the obtained product, and then performing reduced pressure distillation to obtain the isocyanate with low bromine content.
The crude isocyanate product of the present invention is an aliphatic isocyanate prepared by an photochemical reaction, including but not limited to hexamethylene diisocyanate, cyclohexyl isocyanate, dicyclohexylmethane diisocyanate, isophorone diisocyanate, 1, 5-pentanediisocyanate, and preferably hexamethylene diisocyanate.
The isocyanate has high reactivity and can react with various reagents such as proton solvents, and the like rapidly, so that the reaction solvent needs to be an inert organic solvent which does not react with the isocyanate when the isocyanate exists.
The inert organic solvent is a polar organic solvent, and is selected from one or more of acetone, chlorobenzene, acetonitrile, N-dimethylformamide and N, N-dimethylacetamide, preferably acetone.
The mass ratio of the inert organic solvent to the crude isocyanate product is preferably 2:1-5:1, more preferably 2:1-3:1.
The organic sulfonate in the step (2) is aryl sulfonate, and the mass ratio of the aryl sulfonate to brominated impurities in the crude isocyanate product is 1:1-5:1, preferably 2:1-4:1.
The aryl sulfonate is one or more of compounds shown in formula I:
in formula I, M represents a metal ion, preferably M is sodium, potassium or calcium; ar is aryl with various substituents, preferably Ar is phenyl, C1-C6 alkyl substituted phenyl, amino substituted phenyl, thiomethyl substituted phenyl, thienyl, biphenyl, naphthyl.
In certain embodiments of the invention, compound i is sodium phenylsulfonate, sodium sulfanilate, sodium p-toluenesulfonate, respectively.
The sedimentation aid is alkyl or aryl carboxylate, and the mass ratio of the sedimentation aid to brominated impurities in the crude isocyanate is 1:1-5:1, preferably 2:1-4:1.
The alkyl or aryl carboxylate is one or more of compounds of formula II:
in formula II, M1 represents a metal ion, preferably M1 is sodium, potassium or calcium; r represents a straight chain of C1-C10 and an alkyl group with 1-2 branched chains of C1-C3, or an aryl group with a substituent of C6-C15, wherein the substituent can be methyl, sulfhydryl or amino, and preferably, R is amyl, hexyl, phenyl or tolyl.
In certain embodiments of the present invention, compound ii is sodium caproate, potassium caproate, sodium benzoate, respectively.
The brominated impurities are brominated alkyl NCO substances, specific examples include but are not limited to 1-bromohexyl isocyanate, 2-bromohexyl isocyanate, 4-bromocyclohexyl isocyanate and the like, and the content of the brominated impurities in the crude isocyanate is usually 150-250 ppm.
Taking 1-bromohexamethylene isocyanate as one of the bromocompounds in hexamethylene diisocyanate, and adopting sodium phenylsulfonate for reaction removal as an example, the action principle is as follows:
in an inert polar organic solvent, the aromatic sulfonate of the compound I has sufficient solubility due to the existence of the aromatic sulfonate, and is fully contacted with isocyanate brominated impurities. As shown above, bromine in isocyanate bromide reacts nucleophilic to attack metal M in aromatic sulfonate of compound I, and the metal M is combined with the isocyanate bromide and falls off to form small molecular bromine salt MBr which is easy to separate out to form precipitate; and alkyl connected with bromine in isocyanate bromide reacts electrophilically and combines with aryl sulfonic acid group to form macromolecular organic matter-aryl sulfonic acid alkyl isocyanate. The auxiliary sedimentation agent alkyl or aromatic carboxylate is in a suspension state in the polar organic solvent, and the generated macromolecular organic matters are separated out to form a precipitate under the synergistic effect of the auxiliary sedimentation agent, so that the balance of the reaction is ensured to shift right, and the reaction removal rate of isocyanate brominated impurities is improved.
In step (3) of the present invention, the reaction temperature is controlled to 30 to 120 ℃, preferably 40 to 100 ℃, more preferably 50 to 80 ℃. With increasing temperature, the reaction rate increases, but too high a temperature results in severe evaporation of part of the solvent and polymerization of part of the isocyanate at temperatures exceeding 120℃results in loss and darkening of the color. The reaction time is 10min-250min, preferably 30min-180min, more preferably 30min-60min.
The absolute pressure of the reduced pressure distillation system in the step (4) is controlled to be 3-10 kPa, and the temperature of the tower kettle is controlled to be 120-130 ℃.
The isocyanate with low bromine content prepared by the method can reduce the content of brominated impurities to below 10ppm, and the yield can reach above 90%.
Detailed Description
The invention will now be further illustrated by means of specific examples which are given solely by way of illustration of the invention and do not limit the scope thereof.
In the examples below, the analysis of the brominated impurity content of the isocyanate was carried out using a gas chromatography analysis, FID detector (manufacturer, agilent, usa).
[ example 1 ]
200g of hexamethylene diisocyanate crude product (the content of brominated substances is 200 ppm), 400g of acetone solvent is added, 0.1g of sodium benzenesulfonate powder is weighed and added into the solution, 0.12g of sodium caproate powder is weighed and added, after the sodium caproate powder is fully and uniformly mixed, the solution is heated to 50 ℃ to react for 60min, the solution is cooled to room temperature, solid impurities in the solution are removed by suction filtration under negative pressure, filtrate is collected, the filtrate is subjected to reduced pressure distillation, the absolute pressure of a system is controlled to 3kPa, the temperature of a tower bottom is 120 ℃, and the liquid produced from the tower bottom is collected, so that the hexamethylene diisocyanate product with lower brominated substances is obtained. The bromine content of the hexamethylene diisocyanate product was 7ppm by gas chromatography.
[ example 2 ]
200g of crude isophorone diisocyanate (the content of brominated substances is 200 ppm) is weighed, 600g of chlorobenzene solvent is added, 0.16g of sodium sulfanilate powder is weighed and added into the solution, then 0.12g of potassium caproate powder is weighed and added, the solution is heated to 80 ℃ to react for 30min, then the solution is cooled to room temperature, solid impurities in the solution are removed by suction filtration under negative pressure, filtrate is collected, reduced pressure distillation is carried out on the filtrate, the absolute pressure of a system is controlled to 3kPa, the temperature of a tower bottom is 120 ℃, and liquid produced from the tower bottom is collected, so that the product of the isophorone diisocyanate with lower content of brominated substances is obtained. The bromine content of the isophorone diisocyanate product was analyzed by gas chromatography to 5ppm.
[ example 3 ]
200g of crude cyclohexyl isocyanate (with 150ppm of brominated substance) is weighed, 500g of N, N-dimethylformamide solvent is added, 0.12g of sodium paratoluenesulfonate powder is weighed and added into the solution, then 0.12g of sodium benzoate is weighed and added, the solution is heated to 65 ℃ to react for 45min, then the solution is cooled to room temperature, solid impurities in the solution are removed by suction filtration under negative pressure, filtrate is collected, reduced pressure distillation is carried out on the filtrate, the absolute pressure of a system is controlled to 3kPa, the temperature of a tower bottom is 120 ℃, and liquid produced from the tower bottom is collected, so that the cyclohexyl isocyanate product with lower brominated substance content is obtained. The cyclohexyl isocyanate product was analyzed by gas chromatography for bromide content 5ppm.
Comparative example 1
Crude hexamethylene diisocyanate was treated according to the procedure and parameters of example 1, except that: no sedimentation aid sodium caproate was added.
The hexamethylene diisocyanate product obtained in this comparative example had a bromide content of 33ppm.
Comparative example 2
Crude hexamethylene diisocyanate was treated according to the procedure and parameters of example 1, except that: sodium benzenesulfonate was not added. The hexamethylene diisocyanate product obtained in this comparative example had a bromide content of 52ppm.
Comparative example 3
Crude hexamethylene diisocyanate was treated according to the procedure and parameters of example 1, except that: sodium phenolsulfonate was replaced with sodium phenolsulfonate.
The hexamethylene diisocyanate product obtained in this comparative example had a bromide content of 48ppm.
The analysis results of the bromine compounds in the raw materials and the products in each example are shown in the following table:
TABLE 1 analysis results of raw materials and products
| Initial bromo/ppm | Bromine in the product/ppm | Yield/% | |
| Example 1 | 200 | 7 | 95 |
| Example 2 | 200 | 5 | 94 |
| Example 3 | 150 | 5 | 94 |
| Comparative example 1 | 200 | 33 | 92 |
| Comparative example 2 | 200 | 52 | 93 |
| Comparative example 3 | 200 | 48 | 87 |
In comparative example 1, organic sulfonate is added, but no sedimentation aid is used, macromolecular substances generated by the reaction cannot be effectively separated out from the solution, and the progress of the reaction is limited; in comparative example 2, the added sedimentation aid alkyl carboxylate has an effect of removing isocyanate brominated impurities to some extent, but has no structure and charge characteristics of the aromatic sulfonate, has limited solubility and exists in a suspended state, and has an insufficient removal rate of brominated impurities. In comparative example 3, the organic sulfonate is replaced by the phenolate, and the removal rate of brominated impurities is not high; and the isocyanate yield is lower due to side reactions caused by the phenoxide.
The foregoing is merely a preferred embodiment of the present invention, and it should be noted that modifications and additions may be made to those skilled in the art without departing from the method of the present invention, which modifications and additions are also to be considered as within the scope of the present invention.
Claims (12)
1. A process for preparing an isocyanate having a low bromine content comprising the steps of:
(1) Mixing the crude isocyanate product with an inert organic solvent;
(2) Adding organic sulfonate and a sedimentation aid into the solution in the step (1) for reaction;
wherein the organic sulfonate is one or more of compounds of formula I:
wherein M represents sodium, potassium or calcium;
ar is phenyl, C1-C6 alkyl substituted phenyl, amino substituted phenyl, thiomethyl substituted benzene, thienyl, biphenyl and naphthyl;
the sedimentation aid is selected from one or more of compounds of formula II:
wherein M1 is sodium, potassium or calcium;
r represents a C1-C10 straight chain or an alkyl group with 1-2C 1-C3 branched chains, or a phenyl group or a tolyl group.
2. The method according to claim 1, characterized in that the method further comprises the steps of: and (3) removing sediment by negative pressure suction filtration of the product obtained in the step (2), and performing reduced pressure distillation to obtain the isocyanate with low bromine content.
3. The process according to claim 1 or 2, characterized in that the inert organic solvent is selected from one or more of acetone, chlorobenzene, acetonitrile, N-dimethylformamide, N-dimethylacetamide.
4. A process according to claim 3, characterized in that the mass ratio of inert organic solvent to crude isocyanate is 2:1-5:1.
5. The method of claim 1, wherein the organic sulfonate is selected from the group consisting of sodium phenylsulfonate, sodium sulfanilate, and sodium p-toluenesulfonate.
6. The process according to claim 1 or 5, characterized in that the mass ratio of the organic sulfonate to brominated impurities in the crude isocyanate product is 1:1 to 5:1.
7. The method according to claim 6, wherein the mass ratio of the organic sulfonate to brominated impurities in the crude isocyanate product is 2:1-4:1.
8. The method of claim 1, wherein R is pentyl, hexyl, phenyl, tolyl.
9. The method of claim 8, wherein the sedimentation aid is selected from the group consisting of sodium caproate, potassium caproate, and sodium benzoate.
10. The method according to claim 1, 8 or 9, wherein the mass ratio of the sedimentation aid to brominated impurities in the crude isocyanate product is 1:1-5:1.
11. The method of claim 10, wherein the mass ratio of the sedimentation aid to brominated impurities in the crude isocyanate product is 2:1-4:1.
12. The process according to any one of claims 1-2, wherein the reaction temperature in step (2) is 30-120 ℃ and the reaction time is 10-250 min.
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1148056A (en) * | 1995-06-30 | 1997-04-23 | 巴斯福股份公司 | Prepn. of mixtures of diphenylmethane diisocyanates and polyphenylpolymethylene polyisocyanates having reduced iodine color number and reduced chlorine content |
| CN1356980A (en) * | 1999-06-23 | 2002-07-03 | 巴斯福股份公司 | Light isocyanates, method for producing them and use thereof |
| CN102471071A (en) * | 2009-07-16 | 2012-05-23 | 巴斯夫欧洲公司 | Process for the preparation of light-colored isocyanates of the diphenylmethanediisocyanate series |
| CN102471241A (en) * | 2009-07-14 | 2012-05-23 | 巴斯夫欧洲公司 | Process for preparing light-coloured isocyanates of the diphenylmethane series |
| CN107382777A (en) * | 2017-07-12 | 2017-11-24 | 黄河三角洲京博化工研究院有限公司 | A kind of method of chlorinated derivative content in reduction isocyanates |
| CN110396057A (en) * | 2019-07-16 | 2019-11-01 | 万华化学（宁波）有限公司 | A method of preparing the isocyanates of low chlorine content |
| CN112239416A (en) * | 2020-11-02 | 2021-01-19 | 万华化学集团股份有限公司 | Preparation process of toluene diisocyanate with low chlorine and bromine hydrolysis |
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- 2022-01-17 CN CN202210050590.3A patent/CN114349664B/en active Active
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1148056A (en) * | 1995-06-30 | 1997-04-23 | 巴斯福股份公司 | Prepn. of mixtures of diphenylmethane diisocyanates and polyphenylpolymethylene polyisocyanates having reduced iodine color number and reduced chlorine content |
| CN1356980A (en) * | 1999-06-23 | 2002-07-03 | 巴斯福股份公司 | Light isocyanates, method for producing them and use thereof |
| CN102471241A (en) * | 2009-07-14 | 2012-05-23 | 巴斯夫欧洲公司 | Process for preparing light-coloured isocyanates of the diphenylmethane series |
| CN102471071A (en) * | 2009-07-16 | 2012-05-23 | 巴斯夫欧洲公司 | Process for the preparation of light-colored isocyanates of the diphenylmethanediisocyanate series |
| CN107382777A (en) * | 2017-07-12 | 2017-11-24 | 黄河三角洲京博化工研究院有限公司 | A kind of method of chlorinated derivative content in reduction isocyanates |
| CN110396057A (en) * | 2019-07-16 | 2019-11-01 | 万华化学（宁波）有限公司 | A method of preparing the isocyanates of low chlorine content |
| CN112239416A (en) * | 2020-11-02 | 2021-01-19 | 万华化学集团股份有限公司 | Preparation process of toluene diisocyanate with low chlorine and bromine hydrolysis |
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