SU330160A1 - METHOD OF OBTAINING THE HIGH ALKYL ETHER AREAS OF METACRYLIC ACID - Google Patents

Description

A known method of producing higher alkyl esters of methacrylic acid by transesterification of lower alkyl esters of methacrylic acid with higher alcohols in the presence of a polymerization inhibitor and w, Christmas trees or their alcohols as a catalyst. The yield of the product is about 80% of theory.

The described method has a number of drawbacks, since alcohols, Christmas metals, in particular methylsilicate, have a high reactivity and, under the conditions of the transesterification process, catalyze a number of side reactions: addition of alcohols by double bond, resinification of reagents, saponification of methacrylic esters with the formation of sodium methacrylic acid, the polymerization of the starting and ending esters. Sodium methylate in the process of transesterification must be introduced in several stages in the course of the reaction. The process produces a significant amount of tar precipitation, which complicates the selection of the target products. Working with alkali metals and their alcohols, in connection with fire and explosion hazards, requires special precautions, which complicates the use of such catalysts in industry.

characterized in that the transesterification of lower alkyl methacrylates, such as methyl methacrylate, with higher alkanols, is dried in the presence of a polymerization inhibitor and alkaline earth metals, such as magnesium or calcium, or their alkoxides as a catalyst.

Alkaline earth metals and their alcohols by their catalytic activity in reactions

transesterifications are not inferior to silk metals and their alcohol there. At the same time, due to their lower reactivity, they catalyze side reactions to a lesser extent; do not cause tarring and staining of the reaction mixture and do not form a precipitate of methacrylic acid, even after prolonged boiling of the reaction mixture.

Liquids of magnesium or calcium are introduced into the mixture of reagents in one step, which simplifies

process. It is also possible to add the nosteic acid alkaline earth metal alkoxides to the reaction mixture, such as magnesium methoxide, as a solution in methanol. Apply alkaline earth metals and their alcohols do not require special precautions that must be observed when working with alkali metals and their alcohols.

takrilato.m, for example, methyl metal atom, polymerization inhibitor and alkaline earth metal alcoholate are heated in a flask attached to a distillation column. The lower alkanol formed in the reaction with an excess of lower alkyl ether (methanol mixed with an excess of methyl methacrylate) is distilled off. The methanol content in the stripping mixture is determined by refractometry or by gas-liquid chromatography. After distillation of the calculated amount of lower alkanol (methanol) from the mixture, ne reacted lower alkyl methacrylate is distilled. The remaining higher ester is purified by distillation or another method.

In the case of alkaline earth metal, the latter is previously dissolved in the original higher alkanol with heating in the presence of traces of iodine, then the lower alkyl ester is added to the resulting alcoholate solution and the inhibitor and then the reaction is carried out in the same manner as described.

As a result of transesterification i; in the presence of alkoxides of alkaline-earth metals, the initial higher alkanol is almost completely converted within a short time, and the products are slightly stained, and higher alkyl methacrylates can be isolated from the reaction products sufficiently pure without distillation in a vacuum.

To this end, the reaction products after distillation of an excess of lower alkyl methacrylate are purified from the catalyst and inhibitor, either by washing with an alkali solution and water, or by passing through an ion exchange resin, or by another method. As a result, higher alkyl methacrylates are obtained in high yields in the form of colorless or slightly colored liquids, which, according to physicochemical constants, analysis data and ability to polymerization, practically do not differ from samples isolated by distillation in vacuum.

The molar ratio of lower alkyl methacrylate to the higher alkanol can be from 1.2: 1 to 5: 1, preferably from 1.5: 1 to 3: 1; the amount of catalyst is from 0.1 to 10 mol. % better from 0.5 to 4.0 mol. %, calculated on the higher alcohol reacted. Phenols, naphthols, aromatic amines, amnophenols and other compounds are used as polymerization inhibitors, for example, hydroquinone, phenothiazine, a-nitroso-p-naphthol.

Example 1. Getting -butylmetac) lat.

f

CH-i- С - С - О - SI, - CHf СНз

II

a) In a flask equipped with a thermometer and a device for the periodical introduction of a catalyst attached to a reactor (an accumulation column, 74.1 g are charged

(1.0 g mol of n-butyl sheerat, 150 g (1.5 g mol) of methyl methacrylate and 1 g of hydroquinone. The mixture is heated to boiling and 12 ml of 8.5% magnesium methoxide are added over 15 min. in dry methanol. The methanol formed in the reaction and introduced together with the catalyst is distilled off in a mixture with methyl methacrylate through the top of the column at a vapor temperature of 64-66 ° C;

At the end of the reaction, the methanol is distilled off at a higher temperature (up to 70-80 ° C). Within two hours, 52 g of a mixture containing 39.8 g of methanol is distilled off, which, taking into account methane; 1L, introduced into the reaction with the catalyst, corresponds to a 97% conversion of the original n-butanol.

When distillation of the reaction products in vacuum on a short column, one gets, in addition to methyl methacrylate that does not react,

134.5 g (94.7% of theory) n-butyl methacrylate

with t. kip. 50 ° C / 10 mm, p; 1.4230.

b) 74 g (1.0 g-mol of n-butanol, 6.5 g of magnesium chips and a crystal of iodine are loaded into the flask. The mixture is boiled for 10 minutes

 to dissolve the magnesium, 150 g (1.5 g-mol of methyl methacrylate with 1 g of hydroquinone dissolved in it are added and reacted as described in Example 1a. 41.3 g of a mixture containing 31.35 g methanol, which corresponds to a 98% conversion of the starting n-butanol. During the distillation of the reaction products, 135.1 g are obtained (95.3% of the theory of n-butyLMETCrylate with a bale of 56-57 ° C / 14 mm.

Example 2. Getting "-decylmethacrylamide About

CNG-C-C-O-CH -iGHoJg-Cl-b

79 g are loaded into the transesterification apparatus (0.5 g-mol of c-decyl syirt, 100 g

(1.0 g-mol) of methyl methacrylate, 1 g of fentiazine and 3 g of solid magnesium butylate. The mixture is heated, and the methanol formed in the reaction is distilled in a mixture with methyl methacrylate. Within 115 minutes, 19.7 g of a mixture containing 15.4 g of methanol (96.2% of the calculated amount) are distilled off. By distillation of the reaction products in vacuum, 103.2 g (91.4% of theory: fi-decylmethacrylate) were obtained with a bale. 97--100 ° C / 1, 5 mm, 1.4420.

Paydeno,%: C 74.57, 74.32; H 11.62, 11.67. Calculated,%: C, 74.30; P 11.58.

C14H2b02

Similar results are obtained when replacing magnesium butylate with an equivalent amount of calcium ethoxide, m, oddyak, the reaction time increases slightly. In addition to fentazine, diphenyl-paraphenylenediamine, p-oxydiphenyl.min, Greg-octylpyroxymethyl 3 are also successfully inhibited by polymerization. Preparation of n-hexadecyl methacrylate.

SNZ Oh

 - C-0-SNg-1CH:.), - SLZ

a) 72.7 g (0.3 g-mol of cetyl alcohol (n-hexadecanol), 80 g (0.8 g-mol of methyl methyl acrylate, 2 g of hydroquinone and 2.5 g of solid magnesium butylate) are loaded into the device for re-stratification. The reaction proceeds at 98% (for the amount of methanol released) for 160 minutes. Unreacted methyl methacrylate is distilled from the mixture in vacuum, the residue is diluted with an equal volume of diethyl ether, washed with 10% aqueous sodium hydroxide solution until the coloration of r the tree layer, then with water. The organic layer is filtered, the diethyl ether is distilled off, not heated va monomer above 50 ° C, the remaining monomer incubated 20-30 min at I-a residual pressure of 3 mm Hg. v. to remove trace diethyl ether, methyl methacrylate and water.

89.1 g (95.6% of theory) of n-hexadecyl methacrylate are obtained in the form of slightly colored

transparent lg pait lty d d ittpt-hl f 11

liquids with l1, 4518.

b) The experiment was carried out under the conditions of the example of Za, but 1 g of a-nitrosor-naphthol is taken as an inhibitor. After completion of the reaction, unreacted methyl methacrylate is distilled off, the residue is distilled in good vacuum. 87.6 g (94.2% of theory) of n-hexadecyl methacrylate are obtained with m kip. 154-155 ° C / 0.35 mm,

ng 1.4516.

For impurity removal, the.. -Nitroso-3-naphthol monomer is diluted with diethyl ether and washed with 10% sodium hydroxide solution and adjusted as described in Example A above. 83.9 g (90.1% of theory) of n-hexadecyl methacrylate are obtained with m.p. 15, PC, n-, 1.4512.

: C, 77.8, 77.64; H

Found

12.46, 12.54.

С2оНз8О2.

%: C 77.36; H

Calculated, 2.33.

Subject invention

The method of producing higher alkyl esters of methacrylic acid by transesterification 1 and lower alkyl esters of methacrylic acid with higher alcohols with a boiling temperature of the reaction mixture in the presence of a polymerization inhibitor and a catalyst, in which the process increases and the range of catalysts increases, Alkaline earth metals or their alcohols are used as the latter.