Daicel Chemical Industries, Ltd.

Mitsuhiro Kouno

Noboru Kamei

Akira Yamashita

Kazuyuki Matsuoka

Tadayuki Mitani

Masayuki Okada

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

A process produces sorbic acid by hydrolyzing a polyester with an aqueous hydrochloric acid solution having a concentration of 15% by weight or less under the application of pressure or at a temperature of 100&deg; C. or higher, which polyester is obtained by reaction between crotonaldehyde and ketene. In this process, the polyester may be hydrolyzed with a 3 to 10% by weight aqueous hydrochloric acid solution at a temperature of from 115&deg; C. to 140&deg; C. A reaction mixture after hydrolysis of the polyester may be subjected to solid-liquid separation and the resulting filtrate may be recycled and reused in the hydrolysis reaction of the polyester. This process can significantly reduce the amount of tar formed during decomposition of the polyester, can produce sorbic acid in a high yield, and can reduce the load on the treatment of waste filtrates formed during purification operation.

Process for producing sorbic acid

A granulated product of potassium sorbate (i) has an overall pore volume of 0.3 ml/g or less, (ii) has an Na content of 450 ppm or less, or (iii) has an overall pore volume of 0.4 ml/g or less, or a granule hardness of 15% or less, and an Na content of 1000 ppm or less. The granulated product is obtained, for example, (i) by granulating a potassium sorbate aqueous solution through fluidized bed granulation drying, (ii) by neutralizing sorbic acid with a potassium sorbate having a molar ratio of Na to K (Na/K) of 0.0024 or less to yield potassium sorbate, and granulating the potassium sorbate, or (iii) by neutralizing sorbic acid with a potassium sorbate having a molar ratio of Na to K (Na/K) of 0.006 or less to yield potassium sorbate, and moisture-conditioning 100 parts by weight of the potassium sorbate with 1 to 8.5 parts by weight of water and 1 to 8 parts by weight of a water-soluble organic solvent and subjecting the resulting mixture to extrusion granulation. The granulated product of potassium sorbate has a highly stable hue over time.

Potassium sorbate granulate and production processes thereof

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

A process produces sorbic acid or its salt and includes the step of retaining a slurry or solution containing sorbic acid or its salt while holding an oxygen concentration of a gaseous phase at 4% by volume or less, the gaseous phase being in contact with the slurry or solution containing sorbic acid or its salt. In the process, the oxygen concentration of the gaseous phase may be held at 4% by volume or less while introducing an inert gas into a gaseous phase of a reservoir holding the slurry or solution and/or of a conduit adjacent to the reservoir. Such an inert gases includes, for example, nitrogen gas. The oxygen concentration of the gaseous phase is preferably held at 1% by volume or less. The process can prevent the formation of new color-inducing substances in a purification operation of sorbic acid or its salt, and the obtained sorbic acid or its salt has a minimized degree of coloring and a minimized deterioration of hue over time.

Process for producing sorbic acid or salts thereof

An aqueous potassium sorbate solution has a dissolved oxygen concentration of not more than 3.0 mg/l. The aqueous potassium sorbate solution can be obtained (i) by degassing an aqueous potassium sorbate solution to thereby control the dissolved oxygen concentration to 3.0 mg/l or less, or (ii) by performing a reaction in a system, in which the oxygen concentrations of the gas phase and of materials to be reacted are reduced, in the production of an aqueous potassium sorbate solution by a reaction of sorbic acid and potassium hydroxide in the presence of water. The resulting aqueous potassium sorbate solution exhibits successively stable hue.

Methods of storing aqueous potassium sorbate solution

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

Mitsuhiro Kouno