Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acid esters
Reexamination Certificate
1992-11-18
2001-06-26
Gerstl, Robert (Department: 1626)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acid esters
C568S417000, C568S904000, C585S005000
Reexamination Certificate
active
06252106
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method for the stabilization of a higher unsaturated organic compound having at least one double bond in a molecule such as those compounds used in the control of insect pests by the method of mating disruption as a sex pheromone of the insect or, more particularly, to a method for the stabilization of an ester, alcohol, ketone or hydrocarbon compound having at least 10 carbon atoms and at least one double bond in a molecule.
In relation to the pest control in agriculture by using agricultural chemicals, serious problems are noted in recent years including increased resistance against chemicals acquired by the insect species and the toxicity of the chemicals against the health of the agricultural workers as well as consumers of the agricultural products due to the residual amount of the chemicals in the products. As a countermeasure for these problems, biological methods for insect pest control are now under way of intensive investigations, of which the most promising is the method of mating disruption by utilizing various kinds of chemically synthesized sex pheromone compounds as a secretion of the insect females to attract males. It is very important in this method of pest control to keep a constant rate of release of the sex pheromone compound in the field over a long period of time, for example, by the use of the sustained-release dispensers disclosed in Japanese Patent Publication No. 61-16361. In this regard, difficulties are encountered in the use of the sex pheromone compounds for the insect pests belonging to the order of Lepidoptera which are each a long-chain aliphatic compound having at least 10 carbon atoms and at least one double bond in a molecule. The presence of double bonds in such a compound is responsible for the denaturation of the compound by the reaction of oxidation, isomerization, oligomerization and the like at the double bond when the sex pheromone compound is kept under outdoor conditions.
With an object to solve this problem, a method is proposed for the stabilization of a sex pheromone compound by the admixture thereof with an antioxidant or ultraviolet absorber. For example, it is reported in Journal of Chemical Ecology, volume 14, No. 8, page 1659 (1988) that the stability of a sex pheromone compound can be improved by the addition of an antioxidant such as di-tert-butyl hydroxytoluene or tert-butyl hydroxyanisole in combination with an ultraviolet absorber such as 2-hydroxy-4-methoxy benzo-phenone and the like. Further, Japanese Patent Publication 63-12452 teaches that the stability of a higher unsaturated aliphatic aldehyde compound can be increased by the combined admixture of a benzophenone compound as an ultraviolet absorber with an antioxidant and a tertiary amine compound.
Although it is indeed that combined use of a specific antioxidant and a specific ultraviolet absorber synergistically contributes more to the improvement of the stability of a sex pheromone compound having a double bond in the molecular structure than in the use of either one of them alone, no quite satisfactory stabilizing effect can be obtained with any combinations of heretofore known antioxidants and known ultraviolet absorbers. Accordingly, it is eagerly desired to obtain a high stabilizing effect on various sex pheromone compounds by the combined addition of stabilizing agents.
It is proposed in U.S. Pat. No. 4,568,771 that a higher aliphatic unsaturated aldehyde compound can be stabilized against oxidation by the admixture of a tertiary amine compound, benzophenone compound, salicylate compound, benzotriazole compound or cyanoacrylate compound together with or without further admixture of an antioxidant. When the sex pheromone compound is not an aldehyde but an ester, alcohol, ketone or hydrocarbon compound, no very effective method is known for the stabilization of such a compound.
SUMMARY OF THE INVENTION
The present invention accordingly has an object to provide a very efficient method for the stabilization of a sex pheromone compound which is a long-chain aliphatic ester, alcohol, ketone or hydrocarbon compound having at least 10 carbon atoms in a molecule and at least one double bond in the molecular structure by the admixture of compounds having a stabilizing and antioxidizing effects thereon in combination to exhibit a synergistic effect.
Thus, the method of the present invention for the stabilization of a compound belonging to one of the above named classes, which is a long-chain aliphatic compound having at least 10 carbon atoms in a molecule and at least one double bond in the molecular structure, comprises: admixing the compound with 2-(2′-hydroxy-5′-methyl-phenyl) benzotriazole and a phenolic compound as an antioxidant in combination each in an amount in the range from 0.1 to 10% by weight based on the amount of the compound to be stabilized.
It is preferable, in particular, that the above mentioned phenolic compound as an antioxidant is selected from the group consisting of tert-butyl hydroquinone, 2,5-di-tert-butyl hydroquinone and 2,5-di-tert-amyl hydroquinone.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The above described method of the invention for the stabilization of a higher aliphatic unsaturated compound, the scope of which consists in the combined admixture of a specific benzotriazole compound and an antioxidant or, in particular, a specific hydroquinone compound, has been established as a result of the extensive studies undertaken by the inventors with an object to discover a combination of stabilizing agents capable of synergistically stabilizing such an unsaturated compound even when it is not a long-chain aliphatic aldehyde compound having at least one double bond in a molecule, which is notoriously unstable to cause denaturation by the reaction of oxidation, isomerization and oligomerization at the double bond as well as the autoxidation reaction of the aldehyde resulting in the formation of a carboxylic acid or an oligomer. It has been unexpectedly discovered that the above described combination of the specific stabilizing agents has a strong stabilizing effect on the long-chain unsaturated aliphatic ester, alcohol, ketone and hydrocarbon compounds belonging to the classes of sex pheromone compounds having at least one double bond in a molecule. It is important that the specific benzotriazole compound and an antioxidant or, in particular, the specific hydroquinone compound are used in combination in order to exhibit a strong synergistic effect. If desired, other types of stabilizing agents can be used in combination with these two compounds.
The amounts of addition of these specific benzotriazole compound and antioxidant are each in the range from 0.1 to 10% by weight based on the amount of the higher aliphatic unsaturated compound. In particular, the amount of the benzotriazole compound is preferably in the range from 1 to 5% by weight based on the amount of the higher aliphatic unsaturated compound. When the amount of either one of the compounds is too small, the desired stabilizing effect cannot be fully exhibited as a matter of course while no further improvement can be obtained by increasing the amount thereof to exceed the above mentioned upper limit rather with an economical disadvantage.
Examples of the phenolic compounds as an antioxidant which can be used in combination with the specific benzotriazole compound include tert-butyl hydroquinone, 2,5-di-tert-butyl hydroquinone, 2,5-di-tert-amyl hydroquinone, 4-methoxy phenol, 2-tert-butyl-4-methoxy phenol, 3-tert-butyl-4-methoxy phenol, 2,6-di-tert-butyl-4-methoxy phenol, 2,6-di-tert-butyl-4-methyl phenol, 2,5-di-tert-butyl-3-hydroxy phenol, hydroquinone, 4,4′-methylene bis-(2,6-di-tert-butyl phenol) and the like, of which tert-butyl hydroquinone, 2,5-di-tert-butyl hydroquinone and 2,5-di-tert-amyl hydroquinone are particularly preferable in view of the high stabilizing effect on and good miscibility with the higher aliphatic unsaturated ester, alcohol, ketone or hydrocarbon compound.
The met
Saguchi Ryuichi
Sakurada Toyohisa
Yamamoto Akira
Gerstl Robert
Shin-Etsu Chemical Co. , Ltd.
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