Process for the treatment of an ion exchange resin

A process for preparing and purifying an ethylenically unsaturated acid or ester of the following formula:—

• R1—C(═(CH2)m)—COOR2
• wherein R1 and R2 are each, independently, hydrogen or an alkyl group with 1 to 12 carbon atoms;
• and m is 1 or 2;
• the process comprising the steps of—
• a) contacting an alkanoic acid or ester of the formula R1—CH2—COOR3, wherein R1 is as defined for the ethylenically unsaturated acid or ester above and R3 is independently, hydrogen or an alkyl group with 1 to 12 carbon atoms, with a methylene or ethylene source of formula I, optionally in the presence of a suitable catalyst,
• where R5 and R6 are independently selected from C1-C12 hydrocarbons or H;
• X is either O or S;
• n is an integer from 1 to 100;
• and m is 1 or 2;
• and optionally in the presence of an alkanol to produce an impure ethylenically unsaturated acid or ester of the formula:—
• R1—C(═(CH2)m)COOR2;
• b) purifying the impure product of step a) by contact with an acidic ion exchange resin until the ion exchange resin is at least partially deactivated;
• and
• c) treating the at least partially deactivated ion exchange resin with an alkanol of formula R4OH, wherein R4 is an alkyl group with 1 to 12 carbon atoms, and a carboxylic acid of formula:—
• R1—CH2—COOH
• to thereby reactivate the acidic ion exchange resin and produce as a by-product an ester of formula:—
• R1—CH2—COOR4;
• d) optionally hydrolysing the ester of step c) to produce an acid of formula:—
• R1—CH2—COOH;
• e) recycling the said ester or acid of step c) or acid of step d) as a reactant in step a) with the proviso that when the ester of step c) is recycled, R4 and R3 are the same alkyl group.