Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acids and salts thereof
Reexamination Certificate
2000-05-18
2003-01-28
Gitomer, Ralph (Department: 1627)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acids and salts thereof
Reexamination Certificate
active
06512142
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a granulated product of potassium sorbate, to a process for producing the granulated product, and to a process for producing potassium sorbate. Such potassium sorbate is useful as, for example, a food additive.
2. Description of the Related Art
Sorbic acid and its salts have antiseptic and antimicrobial activities and are substantially nontoxic to the human body in normal concentrations in use. These compounds are therefore useful as food additives. In a variety of known processes for producing sorbic acid, a commercially important pathway is a process of polymerizing crotonaldehyde and ketene to form an intermediate polyester, and decomposing the polyester to yield sorbic acid. The thus-prepared sorbic acid contains various colored substances and other impurities, and is generally subjected to a treatment with activated carbon, distillation, recrystallization or another purification operation, and the purified sorbic acid is neutralized with potassium hydroxide to yield potassium sorbate. The prepared potassium sorbate is usually supplied as a granule obtained through a granulation operation.
Potassium sorbate generally shows a denser coloring, a stronger odor and a deteriorated quality with the passage of time from preparation. As possible solutions to the quality deterioration problem, different measures have been proposed. Such measures include a production technique of removing colored substances in the manufacture to improve the hue of the product immediately after the manufacture and a storage technique of sealing the product with an inert gas or of packing the product with a water-impermeable packaging after the manufacture.
However, these techniques do not always have commercially satisfactory effects and costs.
SUMMARY OF THE INVENTION
Accordingly, an object of the invention is to provide a granulated product of potassium sorbate having a satisfactory stability of hue over time, and to provide a production process of the granulated product.
Another object of the invention is to provide a process for producing potassium sorbate which is useful in the production of a granulated product of potassium sorbate having a satisfactory stability of hue over time.
The present inventors noted a synthesis operation of potassium sorbate in a series of production operations of potassium sorbate, and made intensive investigations on a relationship between deterioration of hue during a long-term storage of a granulated product of potassium sorbate and the amounts of impurities in the granulated product. They found a relation between an Na content of the granulated product and the degree of deterioration of hue. This lead the present inventors to a supposition that Na contaminating as an alkali into potassium sorbate is converted into a colored substance after a long-term storage. The inventors also made detailed consideration on a production process of potassium sorbate and found that the Na is predominantly derived from potassium hydroxide used as a material. Furthermore, the inventors determined an overall pore volume of a granulated potassium sorbate and made a detailed investigation on a relation between the overall pore volume and deterioration of hue after a long-time storage. As a result, they found a link between the overall pore volume and the degree of deterioration of hue. This finding indicates that the hygroscopicity of the granulated product is involved in the stability of hue. From these findings, it was speculated that Na-containing impurities in a granulated product of potassium sorbate absorb moisture to form colored substances. Likewise, the inventors found a link between the hardness and Na content of the granulated product and the stability of hue.
Based on the above finding, the present inventors further found that deterioration of hue in a granulated product of potassium sorbate can be prevented by specifying the overall pore volume and/or Na content of the granulated product within a specific range, or by specifying a granule hardness and the Na content of the granulated product within specific ranges. The present invention has been accomplished based on these findings.
Specifically, the present invention provides in an aspect a granulated product of potassium sorbate. The granulated product has (i) an overall pore volume of equal to or less than 0.3 ml/g, (ii) an Na content of equal to or less than 450 ppm, or (iii) an overall pore volume of equal to or less than 0.4 ml/g or a granule hardness of equal to or less than 15% and an Na content of equal to or less than 1000 ppm.
In another aspect, the invention provides a process for producing a granulated product of potassium sorbate. This process includes the step of subjecting an aqueous solution of potassium sorbate to fluidized bed granulation drying to yield the aforementioned granulated product of potassium sorbate.
In a further aspect, the invention provides a process for producing a granulated product of potassium sorbate. This process includes the steps of neutralizing sorbic acid with a potassium hydroxide having a molar ratio of Na to K (Na/K) of equal to or less than 0.0024 to yield potassium sorbate, and granulating the potassium sorbate.
The invention further provides, in yet another aspect, a process for producing a granulated product of potassium sorbate. The process includes the steps of neutralizing sorbic acid with a potassium hydroxide having a molar ratio of Na to K (Na/K) of equal to or less than 0.006 to yield potassium sorbate, 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 moisture-conditioned potassium sorbate to extrusion granulation.
In addition and advantageously, the invention provides a process for producing potassium sorbate. The process includes the step of neutralizing sorbic acid with a potassium hydroxide having a molar ratio of Na to K (Na/K) of equal to or less than 0.006.
The term “ppm” as used herein means parts per million by weight.
Granular potassium sorbate (granulated product of potassium sorbate) is formed by adhesion of crystal masses with each other, and voids are formed between crystals in this process. The voids can be regarded as pores, and the diameters and volumes of the voids can be determined by a method for the determination of pore size for use in the evaluation of properties of catalysts. The term “pore(s)” as used herein also includes the voids.
The term “granule hardness” is defined in the following manner. A sample (a granule) is shifted through a standard sieve (Zenno; 500 &mgr;m) to yield a residue on sieve. About 100 g of the residue on sieve is weighed (W
0
g) and placed in a magnetic pot (100 mm in inner diameter, 100 mm in depth) of a variable horizontal roller ball mill with three pieces of a magnetic ball (30±2 mm in diameter, 35±3 g in weight) . The sample is milled and pulverized by rotating the mill at a roller rotary rate of 75 rpm for 15 minutes. The pulverized sample is then shifted through the same sieve as above, and a powder passing the sieve is weighed (W g). The granule hardness is calculated according to the following equation:
Granule hardness (%)=W/W
0
×100
DESCRIPTION OF THE PREFERRED EMBODIMENT
The invented granulated product of potassium sorbate is distinguished by (i) having an overall pore volume of 0.3 ml/g or less (preferably 0.25 ml/g or less), (ii) having an Na content of 450 ppm or less (preferably 400 ppm or less), or (iii) having an overall pore volume of 0.4 ml/g or less (preferably 0.38 ml/g or less) or a granule hardness of 15% or less (preferably 12% or less), and an Na content of 1000 ppm or less (preferably 800 ppm or less) . If the overall pore volume and Na content or granule hardness of the granulated product of potassium sorbate are out of the above-specified ranges, the granulated product is more markedly colored with time.
A granulated product having an overall p
Kamei Noboru
Kouno Mitsuhiro
Matsuoka Kazuyuki
Okada Masayuki
Daicel Chemical Industries Ltd.
Gitomer Ralph
LandOfFree
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