Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
2001-04-23
2003-03-18
Gerstl, Robert (Department: 1626)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
C252S391000
Reexamination Certificate
active
06534659
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to sulfidoamidocarboxylic acids, a method for the production thereof, and uses therefor. More particularly, it relates to sulfidoamidocarboxylic acids, a method for the production thereof, and a corrosion inhibitor for metals, a composition comprising a sulfidoamidocarboxylic acid and a polyamine, a salt formed by the reaction of a sulfidoamidocarboxylic acid with a polyamine, and a corrosion inhibitor for metals containing the composition and/or the salt.
2. Description of the Related Art
When water is used as a working medium, the water exerts various effects on the metal. One of the effects is corrosion of metals. The corrosion of metals is an important problem in the maintenance and management of various facilities and devices that handle aqueous media. For this problem, corrosion inhibitors for metals are generally used.
The corrosion inhibitors for metals are known in numerous kinds including inorganic inhibitors such as chromates and phosphates and organic inhibitors such as alkyl amines and alkyl ammoniums. They are useful under specific conditions.
SUMMARY OF THE INVENTION
By situation of application, corrosion inhibitors for metals are used in two modes, i.e., closed system and open system. The use in the open system is particularly important because it directly relates to the environmental conservation. There are some cases when the chromates may possibly prove problematic in safety and the phosphates in eutrophication of the aqueous environment. Most alkyl amines and alkyl ammoniums manifest relatively high toxicity. From the viewpoint of protecting the environment, it is important to develop corrosion inhibitors for metals that enjoys high safety because of low toxicity, exerts only a small load on the environment, and proves highly effective.
I have found that low molecular weight sulfidoamines such as dimethylthiazolidine have an effect of corrosion inhibition for metals. When these amines do not call for gasifiability, there is a limit to use because of strong odor.
Except for the problem of the toxicity, the organic corrosion inhibitors, which are liable to decompose relatively easily in the natural environment, are attractive. The alkyl amines and the alkyl ammoniums exhibit toxicity. A cause for the toxicity is considered to have the nature of cationic soap, since this inference is supported by that the fatty acids (salts) having hydrocarbon groups of an equal size generally exhibit low toxicity. Since the fatty acids (salts) are surfactants, they generally do not seem to be used by themselves as a corrosion inhibitor for metals though are utilized as a component for corrosion inhibitors for metals.
Most fatty acids (salts) generally exhibit low toxicity as compared with the corresponding amines and ammoniums. An effort to improve their effects on corrosion inhibition and heightening the manifestation speed of such effects, constitute themselves important tasks for the development of corrosion inhibitors for metals expected to be low toxicity. Since the task of heightening the effect of corrosion inhibition automatically entails a decrease in the amount of an inhibitor to be used, it has an important significance in decreasing the load to be exerted on the environment.
When such a fatty acid (salt) is modified in molecular structure and consequently enabled to increase the effect of corrosion inhibition for metals, it is thought to provide a corrosion inhibitor for metals of low toxicity. Further, this fatty acid can be expected to exhibit high biodegradability when a partial structure liable to be decomposed with an enzyme is incorporated into the molecular structure.
On the basis of this theory, I have taken notice of carboxylic acids (salts) with an amide bond (amide bonds) in the molecular structures thereof. Such carboxylic acids with the amide bond can be expected to subject to hydrolysis caused by the amidases of microorganisms.
I have performed a study on sulfidoamidocarboxylic acids (salts) and have consequently found that the sulfidoamidocarboxylic acids (salts), i.e. the derivatives of dimethylthiazolidine, manifest an excellent effect of corrosion inhibition for metals. Moreover, these sulfidoamidocarboxylic acids (salts) emit only weak odor as compared with low molecular weight sulfidoamines such as dimethylthiazolidine (DMT) that generally entail the problem of emitting strong odor. It has been found by this study that sulfidoamidocarboxylic acids (salts) are useful as a corrosion inhibitor for metals. This invention has been perfected as a result.
It is an object of this invention to provide novel sulfidoamidocarboxylic acids (salts), a method for the production thereof, and uses therefor.
This invention concerns sulfidoamidocarboxylic acids (salts) represented by the formula I:
wherein CnHm and Cn′Hm′ denote independently a hydrocarbon chain, CiHj denotes a hydrocarbon chain, n stands for an integer of 1-12, m for an integer of 2 to 2n, n′ for an integer of 1-15, m′ for an integer of 2 to 2n′, i for an integer of 2-20, j for an integer of 0 to 2i+2−k−z, k for an integer of 1-5, and z for an integer of 1-5, and M represents a hydrogen atom or a metal atom or an ammonium, i.e. an ammonium originating in NH
3
or amines.
This invention also concerns a method for the production of sulfidoamidocarboxylic acids (salts) represented by the formula:
wherein CnHm and Cn′Hm′ denote independently a hydrocarbon chain, CiHj denotes a hydrocarbon chain, n stands for an integer of 1-12, m for an integer of 2 to 2n, n′ for an integer of to 1-15, m′ for an integer of 2 to 2n′, i for an integer of 2-20, j for an integer of 0 to 2i+2−k−z, k for an integer of 1-5, and z for an integer of 1-5, and M represents a hydrogen atom or a metal atom or an ammonium, i.e. an ammonium originating in NH
3
or amines, characterized by causing a sulfidoamine to react with an acid anhydride.
Further, this invention relates to a corrosion inhibitor for metals containing a sulfidoamidocarboxylic acid (salt) mentioned above.
In the following description, the group of compounds represented by the formula (I) will be referred to as “sulfidoamidocarboxylic acids (salts).”
Though the sulfidoamidocarboxylic acid (salt) indeed manifests a high effect on corrosion inhibition for metals even at a low concentration, the speed of manifestion of the corrosion inhibition does not necessary deserve such a designation as “very high”. On use in the circumstance, it is desirable to increase the speed at manifestion of corrosion inhibition without decreasing the maximal level of corrosion inhibition observed in the sulfidocarboxylic acid (salt). I have made a diligent study in search of a method for using sulfidocarboxylic acid (salt).
Polyethyleneimine effectively functions as a corrosion inhibitor in a bath for acid washing metal materials (JP-A-10-140379), and I have made a study on this action thereof in detail. As a result, I have found that this compound, when used at a low concentration in a neutral or weakly acidic aqueous medium, promotes the effect of sulfidoamidocarboxylic acids (salts) on corrosion inhibition for metals. The result means polyethyleneimine functioned as synergy for corrsion inhibition for metals.
I have made a diligent study in search of a method for using sulfidoamidocarboxylic acid (salt). This invention has been perfected as a result. A theory has prevailed that when the polyamine and the sulfidoamidocarboxylic acid (salt) independently functioned, their coexistance brings an effect that is the sum of their respective characteristic properties. From their respective characteristic properties, it has been impossible to infer the effect that forms the essence of this invention, i.e. the fact that their coexistence greatly increases the speed of manifestation of corrosion inhibition for metals.
This invention provides a novel composition for inhibiting corrosion of metals. The present invention conce
Fish & Richardson P.C.
Gerstl Robert
Nippon Shokubai Co. , Ltd.
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