US2379625A

US2379625A - Manufacture of methacrylic acid

Info

Publication number: US2379625A
Application number: US352935A
Authority: US
Inventors: Jr Loring Coes
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1940-08-16
Filing date: 1940-08-16
Publication date: 1945-07-03
Anticipated expiration: 1962-07-03

Description

July 3, 1945. L, CQES1 JR- 2,379,625

MANUFAGTURE OF METHACRYLIG` ACID l Filed Aug. 1e, 1940 v 2 sheets-sheet 1 o c: o QfFFrCHZgI-H';

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WM l WM July 3, 1945. GOES, JR 2,379,625

MANUFACTURE OF METHACRYLICACIDv Filed Aug. 1e, 1940 2 sheets-sheet 2 CH3-COQHjEHQQHMHCHB-cog cHzff H o CH3 CH3 @HCD-ww l (|:H3 CLH-CofCHa (cHfocoa'cmz Hce+ z CHZr-clz-COQH CQ Cea L 7H/N5 E055 JR.

-ffrcw' Patented July 3, 1945 Aaazaszs MANUFACTURE oF METHACRYLIC ACID Loring Coes, Jr., Brookiield, Mass., assignor, by mesne assignments, to E; I. du Pont de Nemours & Company, Wilmington,

Delaware Del., a corporation of Application August 16, 1940, Serial No. 352,935

4 Claims.

The invention relates tothe manufacture of methacrylic acid and its esters.

One object of the invention is to provide a simple process for making methacrylic acid. Another object of the invention is to provide a cheap process for making methacrylic acid. Another object of the invention is to provide a process for the manufacture of methyl methacrylate via preparation of methacrylic acid which shall be as cheap as or cheaper than any method heretofore known. Anotherrobject of the invention is to provide a cheap way of obtaining other derivatives f methacrylio acid, for example besides the methyl ester, ethyl, propyl and butyl and other alkylesters, also phenol esters, `metal salts, the anhydride of the acid, and many other derivatives of methacrylic acid. Another object is to' provide a process of the type indicated free from 1 the use of dangerous or poisonous chemicals.

Other objects will be in part obvious or in party pointed out hereinafter.

The invention accordingly consists in the combinations of elements, arrangements of parts, and in the several steps and relation and order of each of said steps to one or more of the others thereof, all as will be illustratively described herein, Vand the scope of the application of which will be indicated in the following claims.

In the accompanying drawings illustrating an important step in two of many possible embodiments of my invention:

In Figures 1, 2 and 3 are chemical equations showing three reactions involvedin one method according to the present invention;

Figures 4, 5, 6 and '7 are chemical equations showing the reactions involved in another method according to the present invention.

As `a starting material, I use methyl ethyl ketone. In the cracking of petroleum, butanol 2 is produced. From this, methyl ethyl ketone can be readily manufactured in a well known manner.v Methyl ethyl ketone in fairly pure form is readily available on the market and as of the present date has a price around ve cents a pound.

Other ingredients used in my process are formaldehyde, chloride of lime, hydrochloric acid, and a small amount of sulphuric acid. Formaldehyde is inexpensive, being at present about seven cents per pound in a 40% solution in water. Ordinary bleaching powder is good enough chloride of lime and this at present has a price of about two cents a pound. Hydrochloric acid costs about two cents a. pound and sulphuric acid, of which little is used; about one cent a pound. Therefore, the ingre- (Cl. 26o-531) dients in the manufacture of methacrylic acid according to the present invention are all linexpensive. For the manufacture of methyl methacrylate, the most valuable product to be derived from the acid, methyl alcohol is used which is still relatively inexpensive, costing at present about live cents a pound.

Considering now in detail the manufacturev of the acid, I take 500 grams of methyl ethyl ketone, 3'75 grams of 40% formaldehydesolution in water, and 10 cc. of 2 normal sodium hydroxide. I cool it to below 30 C. and let it stand for 24 hours. I distill this mixture and collect the fraction, boiling between 90 C. and 120l'C. at 20 millimeters of mercury. This is beta methyl gamma keto butanol.

This is the rst `step inthe process and the re-V actionmay be indicated as follows:

This reaction per se` however, is not novel.

The second step in the'total process which is.

believed to be novel, as awhole, may be carried out as follows: I take 2'75 grams of commercial bleaching powder (an impure chloride of limeAV containing 33% of available chlorine) and suspend it inV 800 cc. of water. I then add a solution of 40 grams of the foregoing beta-methyl gamma keto butanol inv 40 grams of water. The addition should be made gradually and the mixture should be stirred for about two hours at between 30 and 50 C.

To the foregoing mixture I then add 150 co. of concentrated hydrochloric acid, keeping the temperature below 50 C. I then heat the mixture to approximately C. for one hour and then extract continuously with ethyl ether. The ether extract is then distilled to drive 01T the ether and there remains methacrylic acid with some impurities. The methacrylic acid can be purified in known manners or else in the impure -form it can be esterified to methyl methacrylate and the latter can be purified in known manners.

In carrying out the second step' in the process, I provide a quantity of copper or other suitable linhibitor to prevent polymerization of the methacrylic acid during its manufacture. I believe the reactions will definitely convert all of the beta methyl gamma keto butanol to methacrylic acid, and the thing to bev particularly guarded against is polymerization of the methacrylic acid. Since the reaction may proceed at low temperatures and polymerization is slower at low temperatures,V it

is possible to obtain a relatively high yield of methacrylic acid in monomeric form. The use of copper as an inhibitor is a distinct aid in carrying out this step of the process. Other inhibitors which can be used are hydroquinone and pyrogallol.

In the foregoing, commercial bleaching powder has been selected as it is the cheapest of the group consisting of the alkaline earth hypochlorites and alkali hypochlorites that I know of. The process, however, can be carried out using an alkali hypochlorite such as sodium hypochloride NaOCl. Other alkali metals can be substituted, so also other alkaline earth metals. Also other halogens can be substituted for the chlorine. However, so far as I know, there is no advantage in using anything but the cheapest.

Other acid hydrolyzing and dehydrating agents besides HC1 .can be used, for example, sulphuric acid and phosphoric acid.

It does not seem necessary to describe esterification of methacrylic acid to methyl methacrylate since this is now well known. Equally other monohydric alcohols can be used to obtain the corresponding esters of methacrylic acid and, in fact, other products ,can be made from it, such as the salts. By adding acetic anhydride, the anhydride of methacrylic acid can be produced. As set forth in co-pending application of Carl E. Barnes, Serial No. 326,974 led March 30', 1940, a hard transparent resin highly useful for optical purposes, for windows and especially for airplanes, can be produced by copolymerizing methyl methacrylate with a small quantity of methacrylic anhydride.

Referring now to the accompanying drawings, Figure 1 shows a halogenation reaction in which beta methyl gamma keto butanol is converted to delta delta delta trichloro beta` methyl gamma keto butanol. At the same time, three molecules of calcium hydroxide are formed. The delta delta delta trichloro beta methyl gamma keto butanol immediately breaks down, as shown in Figure 2, in a chloroform reaction, producing two molecules of chloroform and a molecule of calcium beta'hydroxyisobutyrate. The reaction indicated in Figure 3 produces methacrylic acid, calcium chloride and water. This weak acid is liberated by treating the salt with a strong acid and dehydration occurs at the same time.

Other haloform reactions could be substituted for that shown in Figure 2 if for the hypochlorite a. hypohalite having a halogen other than chlorine were selected.

A similar process for the manufacture of methacrylic acid within the scope of the present invention is illustrated in Figures 4 to '7 inclusive. Figure 4 illustrates the dehydrating of beta methyl gamma keto butanol to methyl isopropenyl ketone. As shown in Figures 5 and 6, this is then 'reacted with a hypohalite (using bleaching powder preferably) to produce calcium methacrylate which is then, as shown in Figure '7, reacted with a strong acid to produce the methacrylic acid. In the reaction shown in Figure 5,

calcium hydroxide and trichloro-methyl isopropenyl ketone are produced from the calcium hypochlorite and methyl isopropenyl ketone. In the reaction shown in Figure 6 calcium methacrylate and chloroform are produced from the calcium hydroxide and trichloro-methyl isopropenyl ketone. As an example of this embodiment of the invention, I may take 40 grams of beta methyl gamma keto butanol, put it in a flask and warm it with 10 cc. of hydrochloric acid. I then add sodium carbonate to neutralize the HC1 and then proceed as in the first example. However, from the -metal methacrylate the esters may be made directly.

It will thus be seen that there has been provided by this invention methods and compositions of matter in which the various objects hereinabove set forth together with many thoroughly.

practical advantages are successfully achieved. As various possible embodiments might be made of the chemical features of the above invention and as the art herein described might be varied in various parts, all without departing from the scope of the invention, it is to be understood that all matter hereinbefore set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

I claim:

1. In the process of producing methacrylic acid, the steps comprising reacting beta methyl gamma keto butanol and a hypohalite from the group consisting of alkaline and alkaline earth metal hypohalites, in an aqueous medium and, thereafter, treating said reaction mixture with an acid dehydrating agent from the group consisting of concentrated hydrochloric, sulfuric and Vphosphoric acids.

2. In the process of producing methacrylic acid, the steps comprising reacting beta methyl gamma keto butanol and calcium hypochlorite in an aqueous medium and, thereafter, treating said reaction mixture with concentrated hydrochloric acid.

3. In the process of producing methacrylic acid, the steps comprising reacting beta methyl gamma keto butanol and a hypohalite from the group consisting of alkaline and alkaline earth metal hypohalites, in an aqueous medium for at least about two hours at 30 C.-50 C. and, thereafter, adding to the reaction mixture an acid dehydrating agent from the group consisting of Iconcentrated hydrochloric, sulfuric and phosphoric acids, and maintaining said reaction mixture at about '75 C. for at least about one hour.

4. In the process of producing methacrylic acid, the steps comprising reacting beta methyl gamma keto butanol and calcium hypochlorite in an aqueous medium for at least about two hours at 30 C.-50 C. and, thereafter, adding concentrated hydrochloric -acid to the reaction mixture and maintaining said reaction mixture at about C. for at least about one hour.

LORING COES, JR.