JPS6042350A - Production of fluorine-containing unsaturated ester - Google Patents

Abstract

PURPOSE:To improve the yield of the titled substance which is an industrially important fluorine-containing monomer useful for the production of a fluorine- containing functional polymer, economically, in the production of the substance by the reaction of an unsaturated basic acid with a fluorine-containing alcohol, by using fuming sulfuric acid as a dehydration agent. CONSTITUTION:The unsaturated basic acid of formula I [R1 is H or COOH; R2 is H, CH3 or (CH2)nCOOH; n is 0 or 1], e.g. acrylic acid, methacrylic acid, fumaric acid, maleic acid, etc. is made to react with a fluorine-containing alcohol of formula II (R3 is lower alkyl, H or polyfluoroalkyl), e.g. 2,2,2- trifluoroethanol in the presence of fuming sulfuric acid to obtain the objective compound. The concentration of sulfuric anhydride in the fuming sulfuric acid is 5-50wt%, especially 10-30wt%. When the unsaturated basic acid and the fluorine-containing unsaturated ester are liable to polymerize, it is preferable to add a polymerization inhibitor such as hydroquinone to the reaction system.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the production of fluorine-containing unsaturated tooth mouth esters, and more particularly to the production of fluorine-containing unsaturated tooth mouth esters by the reaction of acrylic acid, methacrylic acid, or unsaturated polybasic acids with fluorine-containing alcohols. The present invention provides an inexpensive and industrially advantageous method for using fuming sulfuric acid as a dehydrating agent in producing unsaturated esters.

Fluorine-containing unsaturated esters such as fluorine-containing methacrylic acid esters and fluorine-containing acrylic esters are used as industrially important fluorine-containing monomers in the production of various fluorine-based functional polymers. 1. For example, fiber treatment agents that take advantage of the water and oil repellency of fluorine, fluorine rubber or plastic that takes advantage of chemical resistance, plastic optical fiber that takes advantage of low refractive properties, and other resist materials, contact lenses, dental materials, etc. The application of this material to medical paulownia materials has been studied, and many have been put into practical use.

A conventional method for producing fluorine-containing unsaturated esters is a method in which an acid chloride of a corresponding unsaturated acid and a fluorine-based alcohol are reacted in the presence of a base. Triethylamine, pyridine, etc. are used as the base.

However, this method is a laboratory method, and considering the toxicity of acid chloride, it cannot be said to be an industrially advantageous and economical method.

On the other hand, as an economical method, there is a method in which an ester of an unsaturated acid such as methyl ester or ethyl ester is transesterified with a fluorine alcohol in the presence of a catalyst. This method is industrially advantageous when the fluorinated alcohol is a compound with a large number of carbon atoms and a high boiling point. However, since the transesterification reaction is an equilibrium reaction, when a low-boiling fluorine-based alcohol is used, the fluorine-based alcohol is discharged from the reaction system together with methanol, ethanol, etc., and the reaction either has a low yield or does not proceed at all.

The simplest method has been proposed to produce esters from unsaturated basic acids and fluorinated alcohols using a strong dehydrating agent. In this case, concentrated sulfuric acid is usually used, but fluorinated alcohols In this case, even if a large amount of concentrated sulfuric acid is used, the reaction will not proceed and the yield will remain low. Therefore, a dehydrating agent that allows the reaction to proceed with the highest yield is trifluoroacetic anhydride.

In this case, esters are produced under relatively mild conditions near room temperature. However, it is necessary to use trifluoroacetic anhydride in an equivalent molar amount to that of the fluorinated alcohol or unsaturated basic acid, and since trifluoroacetic anhydride is an industrially very expensive compound, The method cannot be called economical. As a result of various studies, the present inventors have found that the purpose can be achieved in high yield by using fuming sulfuric acid as a dehydrating agent. This method is economical because fuming sulfuric acid is cheap, and after the reaction, the crude fluorinated unsaturated ester is removed directly from the reactor by simple distillation, and the purity is 99.9% or higher by washing with water etc. Since the method can be changed and the equipment can be simplified, it is extremely efficient, and the yield is generally superior to that of known methods.

7 Flucols include 2.2゜Todorifluoroethanol, hexafluoroisopropanol, s,
Examples include s, -trifluoropropanol-21.1°I-trifluorobutanol-2. The fuming sulfuric acid may be ordinary industrial grade, but the concentration of sulfuric anhydride should be 5 to 5.
A content of 10% by weight, preferably 10 to 30% by weight, is suitable for handling. There is usually no need to use a solvent in the reaction system, but for those that are likely to polymerize unsaturated basic acids and fluorine-containing unsaturated esters, use hydroquinone or 2,6-ditertiary butyl as a polymerization inhibitor. ← It is better to add phenols such as methylphenol to the reaction system.

Examples of the present invention will be described in detail below.

Example! .

Acrylic acid 1085' and hexafluoroisopropanol 168 were charged with 2,6-ditarjacyl-4-methylphenol Iff as a polymerization inhibitor into a 3-bottle round-bottomed flask equipped with a reflux condenser and a thermometer, and the SO2 concentration was adjusted while stirring the inside. 20 g of fuming sulfuric acid 56Q was added dropwise.

Then, the reaction was carried out for 4 hours while maintaining the system at 60°C. Furthermore, the entire reaction system was depressurized and distillation was performed to obtain a crude ester. The crude ester was washed with water and a 1% potassium carbonate aqueous solution, and then dried over calcium chloride. The gas chromatography purity of this pure ester was 99.5%, and the yield was 65 molti based on the hexafluoroinpropertool. Furthermore, we performed vacuum distillation purification to obtain 42'C/150n
A 12:5y fraction of Hy was obtained. The gas chromatography purity of this high purity ester was 99.99%.

This product was confirmed to be hexafluoroisofurobyl acrylate by 'H-NMR and 'F-NMR spectra.

'H-NMR (CDOR,: TMEt) :CH2-
C! H=(5,9ppm multiplet)/゛-CH(5,4ppm multiplet) \l″F-NMR(CDCl2: (!F,,0OOH
) Knee cF, (-3, 3ppm double line) Comparative example! .

In the same manner as in Example 1, acrylic acid 108f1 hexafluoroinglopanol 168^98 and concentrated sulfuric acid 160p
'ii Reaction was carried out, and the gas chromatography purity of the pure ester was 99.4, but the yield relative to hexafluoroisopropanol was 18 mol.

Example 2゜Itaconic acid 91P1 Hexafluoroisopropanol 235820% Fuming sulfuric acid 22
Gas chromatograph of pure ester from 0F
A yield of 99.6% was obtained based on hexafluoroisopropanol in the order of 50 molar.

This product was confirmed to be dihexafluoroimprobyl itaconate by 'H-NMR and 'F-NMR spectra.

”F-NMRCODoll: OFF 0OOH):
C! F3 (-4.2 ppm double line) Comparative Example 2 Itacon [965F 2.2.
2. -Trifluoroethanol 100jF, anhydrous trifluoroacetic acid rβ263ff were placed in a reactor and heated at 50°C for 4 hours.
．． The reaction was carried out for 5 hours. The gas chromatography purity of the pure ester obtained was 12.2% with a purity of 99.9%. -) The yield relative to refluoroethanol was 17 mol.

Example 3: Fumaric acid 1169. Hexafluoroisopropanol 3365E, 20% oleum 30
From 2y, a pure ester with a purity of 99.2% as determined by NMR was obtained in a yield of 32 molti based on hexafluoroisopropanol. This product was a solid with a melting point of 53 to 55° C., and was confirmed to be dihexafluoroisoprobyl fumarate by H-NMR and F-NMR spectra.

: -0F3 (-4.8 ppm 2-line) Example.

In the same manner as in Example 1, methacrylic acid 129 formula 2.2.
1-) Refluoroethanol 100F, 20% oleum 160p? After reacting at 75°C for 3 hours, the crude ester was washed with water and purified by vacuum distillation to obtain a boiling point of 36.5.
The fraction of °C/40 mmHg was completely exhausted. 2.2.2. -) Yield based on refluoroethanol is 70 mol/1 ton N
12.2.- by MR and F-NMR spectra
) Lifluoroether methacrylate (purity 99.9% by Cass chromatography).

5.75ppm - heavy line), -0H3 (1,75ppm
- double line) -OH2- (4,1 ppm quartet line)

Claims (1)

[Claims] ■) A method for producing a fluorine-containing unsaturated ester by reacting an unsaturated basic acid represented by the general formula % with a fluorine-containing alcohol represented by the presence of fuming sulfuric acid. 2) A method in which the fluorine-containing unsaturated ester is represented by the general formula (1). RtHmfc is (n%, -11) (n is an integer) or 3
2.) The method according to claim 1, wherein the sulfuric anhydride (sOs) concentration in the fuming sulfuric acid is 5 to 50% by weight.