United States Patent Office Patiented Jan

3,299,012 United States Patent Office Patiented Jan. 17, 1967 2 methacrylates, vinyl chloride, vinylidine chloride, vinyli 3,299,92 dine fluoride, vinyl acetate, ethylene, propylene, isobutyl PROCESS FOR THE PREPARATION OF ene, O-methylstyrene, and styrene. POLYLACTONES Rciand 5. Kern, Bridgeton, Mo., assignor to Monsanto According to the instant invention, a rearrangement re Conapany, a corporation of Delaware action, catalyzed by a Lewis acid, is used to prepare No Drawing. Filled Dec. 17, 1963, Ser. No. 331,096 polymeric substances characterized by lactone links and 12 Claims. (C. 269-78.5) also carboxylic acid groups or carboxylic acid ester groups along the polymer chain. This invention relates to a process for the preparation It will be understood that various vinyl ethers, as de of polylactones, and to ester derivatives of polylactones. 10 scribed above, can be used to prepare the polymeric re This invention particularly relates to lactones derived actant, however for convenience the invention is de from alternating copolymers of certain vinyl ethers and Scribed with reference to the tert-butyl vinyl ether co unsaturated carboxylic acid anhydrides. polymer. The process can be practiced when the group It is an object of this invention to provide a novel attached to the vinyl group through an ether link is one process for preparing polylactones. 5 known to form a stable carbonium ion. It is another object of this invention to provide a simple The rearrangement of the vinyl ether/olefinic carboxylic direct method for converting vinyl ether/unsaturated car anhydride copolymers is conducted in the presence of any boxylic acid anhydride copolymers to polymers charac of the materials known as acids within the concept of terized by lactone rings along the polymer chains, and Dr. G. N. Lewis, and commonly referred to as Lewis also containing carboxylic acid groups or ester groups 20 acids. These acids are regarded as electron acceptorS. along the polymer chain. Lewis acids include the inorganic acids such as HCl, It is another object of this invention to provide a HSO, HPO, HF, HNO3; the organic carboxylic acids process for the preparation of ester-lactones of polymers such as acetic acid, propionic acid, chloroacetic acid; and having excellent stiffness modulus properties over a broad BF, trialkylboranes such as trimethylborane, triethyl temperature range, and which also have excellent impact 25 borane, AlCl3, FeCl3, SnCl4, ZnCl2, PaOs, etc. strength properties at temperatures coinciding with the According to my invention, a polymer containing a temperature range where the polymers have excellent stiff tert-butyl ether linkage attached to the carbon-carbon ness modulus properties. polymer backbone is rearranged under the catalytic in The process of the invention involves the acid-catalyzed fluence of a Lewis acid. The ether linkage is usually ad rearrangement of vinyl ether copolymers obtained by 30 jacent to a carbonyl group which is incorporated into an copolymerization of a vinyl ether monomer, acid anhydride linkage. The rearrangement is accon plished through the splitting of the ether linkage and the R-O-CH-CH2 opening of the carboxylic anhydride ring with the forma wherein R represents a group which forms a stable car tion of the resulting lactone. bonium ion. 35 A typical equation for the reaction can be Written as The reaction of the present invention involves the ether follows: group attached to the polymer chain through the ether -CH-CH-CH-CH- COO oxygen atom, when said ether group is neighboring (or Lewis adjacent) to a carbonyl group. Internal lactonization O Co-C-ON aci d CH (H E. GH occurs with the formation of, generally, five membered 40 tert-likyl O x O Ce:O rings, although four and also six membered ring lactones wherein x is equivalent to the degree of polymerization, can also be formed. and generally will be 20 or more and can be as high as The polymeric reactant employed in the rearrangement 1000, and up to 10,000 or even greater. reaction is an alternating copolymer obtained in the The amount of Lewis acid required to rearrange to catalytic copolymerization of a vinyl ether, 45 polymers is a catalytic quantity, and it has been deter mined that as small a quantity as 0.01% by Weight, based with an unsaturated carboxylic acid anhydride, e.g., on the weight of the polymer, is effective. I prefer to maleic anhydride, itaconic anhydride, citraconic an employ from about 0.01% to about 1% by Weight of the hydride. The vinyl ether preferred for the preparation of acid based on the polymer weight. If the ester-lactone these copolymers is tert-butyl vinyl ether, although I can is to be prepared in one step, it may be advantageous to use any vinyl ether of the formula R-O-CH=CH2, use up to about 5% by weight of the Lewis acid, based wherein R represents an organic group which forms a on the polymer weight, depending upon the particular stable carbonium ion. The carbonium ion theory is de catalyst and alcohol selected. In certain instances the scribed by Whitmore in Chem. Eng. News, volume 26, 55 initial lactonization step can be conducted in the presence page 668 (1948). Stable carbonium ions are formed by of 0.01% to 0.2% of a Lewis acid, and then the esteri the tert-butyl group and other tert-alkyl groups of 5 to fication carried out with a higher, and additional quantity 12 carbon atoms, the benzyl group, the allyl group, and of Lewis acid, e.g., 0.1% to up to 5%, by weight based the 1-methylcyclohexyl group. Thus, suitable vinyl ether on the weight of initial polymer. It is understood that monomers, in addition to tert-butyl vinyl ether, include considerable latitude is permitted in the preparation of the tert-amyl vinyl ether, 3-methyl-3-pentyl vinyl ether, and . ester-lactones since the reactions can be carried out near any of the tert-alkyl vinyl ethers wherein the alkyl group ly simultaneously, or stepwise. If a tert-butyl vinyl ether has up to 12 carbon atoms, benzyl vinyl ether, allyl vinyl copolymer of an olefinically unsaturated carboxylic an ether and 1-methylcyclohexyl vinyl ether. The copoly hydride is used as a reactant, the initial rearrangement meric reactant is characterized by its content of equiva step yields isobutylene as byproduct, and it is sometimes lent amounts of vinyl ether monomer and unsaturated desirable to have a portion of the isobutylene driven from acid anhydride monomer. Although I normally prefer to the reactor prior to increasing the temperature to conclude conduct the rearrangement with the two-component co the esterification in order to avoid losses from the reactor polymer the novel reaction is applicable to polymers con due to entrainment. taining minor amounts, less than about 15 weight per TO Generally, the lactone-producing reaction can be car cent of the total polymer weight, of a third monomer. ried out at room temperature, although the temperature Suitable third monomers include the alkyl acrylates, alkyl can be increased to temperatures as high as 150° C. with 3,299,012 3. 4. out adverse effect; I prefer to operate in the range of about unit with the unsaturated acid anhydride. The tert-butyl 20 to 100° C. Temperature control can be maintained vinyl ether then participates to a lesser extent in the by the use of a refluxing inert organic diluent. The esteri polymerization, resulting in the reduction of the number fication reaction is normally conducted at a temperature of lactone rings that can be produced along the polymer sufficiently high to enable the ready removal of the water chain during the Lewis acid-catalyzed rearrangement step. of reaction. This water can be removed as an azeotrope The polymer obtained as the result of the rearrange by the use of refluxing benzene, toluene, xylene, or ethanol ment reaction contains the reactive lactone ring and addi or other azeotrope. Common organic solvents which boil tionally has activated caboxylic acid groups attached to in the range of 50 to 150 C. or higher can be employed the polymer backbone. The acid groups can be esterified, as diluents for the esterification. It will be further un O e.g. with alcohols of up to about 20 carbon atoms, to pro derstood that the reactions can be carried out at super duce other polymers having desirable physical properties atmospheric pressure, although generally I prefer to op including high modulus over a broad temperature range erate the reactor system at atmospheric pressure, or at and high impact strength. even lower pressures. I have found that the rearrangement reaction can be The polymers useful in the preparation of the lactone 15 conducted in the presence of an alcohol so that ester lac compositions can be essentially tert-butyl vinyl ether co tones can be produced in a single convenient reaction. polymers with maleic anhydride, citraconic anhydride, or The Lewis acid catalyst which is used to prepare the lac itaconic anhydride, although terpolymers containing up to tone can also be the esterification catalyst. about 15 weight percent of a third monomer can be used. It is of course known that copolymers of unsaturated These polymers can be prepared in the presence of a free 20 carboxylic anhydrides and alkyl vinyl ethers can be pre radical type catalyst for example, an organic peroxygen pared wherein the alkyl group is attached to the ether compound. The peroxygen compound can be activated OXygen through a primary or secondary carbon atom. by trialkylboranes in promoting the polymerization, to When these polymers are subjected to an attempted lacton prevent thermal rearrangement of the product during the ization, or lactonization-esterification reaction, the anhy polymerization step.

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