Daicel Chemical Industries, Ltd.

Akira Yamashita

Mitsuhiro Kouno

Noboru Kamei

Fumihiko Shoji

The invented process for producing a polyester supplies a crotonaldehyde with a purity of 95% by weight or more to a reaction system in the reaction of ketene with crotonaldehyde. In this process, unreacted crotonaldehyde may be recovered from a reaction mixture obtained by the reaction of ketene with crotonaldehyde and may be recycled to the reaction system. The &agr;vinylcrotonaldehyde content of the crotonaldehyde to be supplied to the reaction system is, for example, less than 0.5% by weight, and the paraldehyde content of the crotonaldehyde to be supplied to the reaction system is, for example, less than 5% by weight. By decomposing the above-prepared polyester with, for example, hydrochloric acid, a sorbic acid having a satisfactory hue can be efficiently obtained.

Processes for producing polyesters and producing sorbic acid

The invented process for producing sorbic acid includes the step of decomposing a polyester at temperatures of 100&deg; C. or less with hydrochloric acid, which polyester is obtained from ketene and crotonaldehyde. In the process, the reaction temperature after the initiation of a polyester decomposition reaction is controlled by adding a hydrochloric acid to a reaction mixture, which hydrochloric acid has a temperature lower than that of the reaction mixture, for example, a temperature of 50&deg; C. or less. Such hydrochloric acid for reaction control may have a concentration of, for example, 23% by weight or more. This process can yield sorbic acid in a short time in a high yield and can highly efficiently produce sorbic acid.

Process for the preparation of sorbic acid

The invented process produces sorbic acid or its salt through the decomposition of a polyester obtained from ketene and aldehyde, and includes the step of treating a solution containing-sorbic acid or its salt with a chemically activated carbon, which sorbic acid or its salt is produced by the decomposition of the polyester. The treatment with activated carbon is performed, for example, at pH ranging from 5.8 to 7.5 at temperatures ranging from 30&deg; C. to 80&deg; C. The invented process can efficiently remove colored substances and can easily yield a high quality sorbic acid having a satisfactory hue in a high yield.

Process for the preparation of sorbic acid or salts thereof

The invented process produces sorbic acid. The process includes the steps of adding a crude sorbic acid to a hot water having a temperature exceeding 100&deg; C., which crude sorbic acid is obtained by the decomposition of a polyester formed through a reaction of ketene with crotonaldehyde, and performing at least one treatment selected from (A) a hot water extraction treatment for extracting sorbic acid with the hot water, and (B) a treatment with an activated carbon in the hot water. The temperature of the hot water is, for example, 120&deg; C. or lower. The amount of sorbic acid to be treated is, for example, equal to or less than the saturated dissolution amount of sorbic acid with respect to the hot water at a treating temperature. The invented process can easily and efficiently remove tar substances and other impurities by-produced in the decomposition of the polyester and can produce a highly purified sorbic acid with a high productivity.

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Arai, Japan

Akira Yamashita