Chemistry: analytical and immunological testing – Oxygen containing – Molecular oxygen
Reexamination Certificate
2002-10-23
2004-03-09
Wallenhorst, Maureen M. (Department: 1743)
Chemistry: analytical and immunological testing
Oxygen containing
Molecular oxygen
C436S008000, C436S127000, C436S138000, C436S164000, C436S166000, C436S169000, C436S904000, C422S051000, C422S051000, C252S408100
Reexamination Certificate
active
06703245
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an oxygen detecting composition, more particularly, relates to an oxygen detecting composition capable of indicating the presence or absence of oxygen or the degree of oxygen concentration by its color change, and exhibiting a good light and heat stability. The present invention further relates to an oxygen detecting agent and an oxygen detecting ink pigment each comprising the oxygen detecting composition.
2. Description of the Prior Art
Hitherto, there have been proposed oxygen detecting agents utilizing the reversible color change of organic colorants by oxidation-reduction reaction. For example, Japanese Patent Application Laid-Open Nos. 53-117495 and 53-120493 disclose solid oxygen detecting agents comprising an organic colorant such as thiazine dye, azine dye and oxazine dye, a reducing agent and a basic substance. Japanese Patent Application Laid-Open No. 56-84772 discloses an oxygen indicator ink composition prepared by dissolving or dispersing a thiazine dye or the like together with a reducing sugar and an alkaline substance into a resin solution. A commercially available oxygen detecting agent (for example, “AGELESS EYE”, trademark of Mitsubishi Gas Chemical Company, Inc.) is a functional product for indicating a deoxygenated condition (oxygen content of less than 0.1% by volume) of a transparent packaging container in a simple manner by its color change, and has been used together with an oxygen-absorbing agent (for example, “AGELESS”, trademark of Mitsubishi Gas Chemical Company, Inc.) to maintain a freshness of foods and to prevent the degradation of medical and pharmaceutical products.
The conventional oxygen detecting agent, however, is insufficient in the light and heat resistance, for example, tends to cause discoloration or deterioration in color change function upon exposure to light as well as cause browning or deterioration in color change function under high temperatures. To maintain its clear color for a long period of time, therefore, the conventional oxygen detecting agent must be stored by screening from light at low temperatures. This tendency is remarkable in case of a printed oxygen detecting agent comprising an ink having an oxygen detecting function.
In addition, the conventional oxygen detecting agent is opaque to hide the packaged contents such as foods, medical products and pharmaceutical products, thereby unfavorably making the contents invisible outwardly.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a light-resistant and heat-resistant oxygen detecting composition and an oxygen detecting agent. Another object of the present invention is to provide a transparent or translucent solid oxygen detecting agent and an oxygen detecting ink pigment.
As a result of extensive research, the inventors have found that an oxygen detecting composition comprising a composite material prepared by mixing a layered silicate (sheet silicate), a cationic surfactant, an organic colorant, a reducing agent and an optional basic substance is excellent in the heat resistance and the light resistance. The inventors have further found that an oxygen detecting agent and an oxygen detecting ink pigment each comprising a composite material of a layered silicate intercalated with a cationic surfactant, an organic colorant, a reducing agent and an optional basic substance is not only excellent in the light resistance and the heat resistance, but also transparent or translucent. The present invention has been accomplished on the basis of these findings.
DETAILED DESCRIPTION OF THE INVENTION
The oxygen detecting composition according to the present invention contains, as the essential constituting components, a cationic surfactant, an organic colorant, a reducing agent and a layered silicate (sheet silicate), or a cationic surfactant, an organic colorant, a reducing agent, a basic substance and a layered silicate. Preferably, the cationic surfactant, the organic colorant, the reducing agent and the optional basic substance are intercalated into the layered silicate.
The cationic surfactants usable in the present invention are those having cationic atoms and lipophilic groups in their molecules, and being capable of generating organic cations in water by ionization. As the cationic surfactant, a quaternary ammonium salt is typically mentioned, with a quaternary ammonium salt having four carbon groups including at least one lipophilic group bonded to the nitrogen atom being preferred.
The lipophilic group means a non-polar atomic group having a strong affinity for oil, but less interacting with water. Examples of the lipophilic group include chain- and cyclic hydrocarbon groups, aromatic hydrocarbon groups, halogenated alkyl groups, organosilicone groups, and fluorocarbon groups.
The cationic surfactant is preferably cetyltrimethylammonium bromide, cetyltrimethylammonium chloride, stearyltrimethylammonium chloride, stearyltri(methylbenzyl)ammonium chloride, distearyldimethylammonium chloride, or distearyldi(methylbenzyl)ammonium chloride.
The organic colorant usable in the present invention is an aromatic compound having a long conjugated double bond system containing mobile &pgr; electrons, and is capable of reversibly changing its color by oxidation-reduction reaction. Examples of the organic colorant include oxidation-reduction indicators, thiazine dyes, azine dyes, oxazine dyes, indigoid dyes, and thioindigoid dyes. Specific examples include methylene blue, new methylene blue, methylene green, variamine blue B, diphenylamine, ferroin, capri blue, safranine T, indigo, indigo carmine, indigo white, and indirubin. Of these, preferred are triazine dyes represented by methylene blue.
The reducing agent used in the present invention is a compound capable of reducing the organic colorant in an atmosphere having an oxygen concentration lower than that of atmospheric air. Examples of the reducing agents include monosaccharides such as glucose, fructose and xylose; reducing disaccharides such as maltose; ascorbic acid and its salts; dithionous acid and its salts; and cysteine and its salts.
In some cases, it is preferred to combinedly use the basic substance to enhance the reduction activity of the reducing agent. As the basic substance, there may be used hydroxides such as sodium hydroxide, potassium hydroxide and calcium hydroxide; and carbonates such as sodium carbonate, potassium carbonate and sodium hydrogen carbonate. The amount of the basic substance, if used, is preferably 0.001 to 10 parts by weight, more preferably 0.01 to 1 part by weight based on one part by weight of the layered silicate.
The layered silicate (sheet silicate) used in the present invention has a layered structure that comprises a number of sheets repeatedly stacked in parallel, each sheet being constituted by the atomic groups (inclusive of ioncontaining groups) arranged in plane. Specifically, the layered silicate is an inorganic layered compound that is constructed by tetrahedron sheets composed of silicon atoms, aluminum atoms and oxygen atoms and octahedron sheets composed of aluminum atoms, magnesium atoms, oxygen atoms and hydrogen atoms in a ratio of 1:1 or 2:1.
Further, in addition to the above atoms, the tetrahedron sheet may contain iron atoms, and the octahedron sheet may contain iron atoms, chromium atoms, manganese atoms, nickel atoms or lithium atoms. In addition to molecules of water, cations such as potassium ion, sodium ion or calcium ion may be present as exchangeable cations between the layers of the layered silicate.
The layered silicate used in the present invention is preferably a smectite group silicate, for example, a natural layered silicate such as montmorillonite, beidellite, saponite, hectorite and sauconite which are belonging to smectite group (natural smectite). A layered silicate belonging to smectite group that is produced from an inorganic compound by hydrothermal synthesis (synthetic smectite) is also usable. Of these, preferred is the synthetic smectite.
Inoue Haruo
Sugito Ken
Sumitani Makoto
Antonelli Terry Stout & Kraus LLP
Mitsubishi Gas Chemical Company Inc.
Wallenhorst Maureen M.
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