Compositions: coating or plastic – Coating or plastic compositions – Corrosion inhibiting coating composition
Reexamination Certificate
1999-07-29
2001-07-17
Green, Anthony (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Corrosion inhibiting coating composition
C106S014050, C106S014420, C106S014440, C252S390000, C252S391000, C252S392000, C252S394000, C422S007000, C422S009000, C422S012000, C422S013000, C422S016000
Reexamination Certificate
active
06261346
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a 35 U.S.C. §371 national stage application based on International Patent Application No. EP97/06451, filed Nov. 19, 1997.
BACKGROUND OF THE INVENTION
The corrosion of metals in liquid or gaseous media is an age-old problem. In the field of geological exploration in particular, the metal surfaces of the equipment used have to be protected against corrosion, for example under the effect of the mildly acidic or deaerated saline aqueous solutions which are used in the production and processing of petroleum and natural gas. Petroleum and natural gas and the water accompanying them contain corrosive constituents, for example CO
2
or H
2
S and salts, which lead to serious corrosion of metal surfaces. In addition, the working fluids, for example drilling muds, used in this field also contribute towards corrosion.
Accordingly, so-called corrosion inhibitors are used to provide protection against corrosion, being added to the liquids or gases which come into contact with the metal surfaces. The corrosion inhibitors either form a film on the metal surface or reduce the corrosion process by physicochemical reactions on the metal surface (cf. P. H. Ogden, Chemicals in the Oil Industry, The Royal Society of Chemistry, 1991, pages 21-22 and O. Lahodny-{haeck over (S)}arc, Corrosion Inhibition in Oil and Gas Drilling and Production Operations, Eur. Fed. Corros., Publ. 1994, 11, pages 104-112).
Various substances, normally containing nitrogen, have already been proposed as corrosion inhibitors (O. Lahodny-{haeck over (S)}arc, pages 112-113). Mitzlaff et al. (Werkstoff und Korrosion, 40, 629-634 (1989)) describe quaternary ammonium compounds as corrosion inhibitors for the production of petroleum and natural gas. Phillips et al. (Proceedings of the 8th European Symposium on Corrosion Inhibitors, Suppl. N. 10, 1995, 1213-1227) describe certain betaines, for example cocoamidopropyl compounds, for the same purpose. EP 320 769 A2 discloses ethoxylated quaternized ammonium compounds specifically for use in the w/o emulsions encountered in the production and processing of petroleum.
More recently, corrosion inhibitors have also had to satisfy more stringent requirements in regard to their biodegradability and aquatic toxicity. EP 651 074 describes N-ethoxyimidazolines substituted in the 2-position which not only have a favorable corrosion-inhibiting effect, they also show low aquatic toxicity (EC
50
in
Skeletonema costatum
<1 ppm).
Since it is precisely the chemicals used in the production of petroleum and natural gas which are having to meet increasingly more stringent environmental compatibility requirements, there is still a need to protect metal surfaces exposed to corrosive liquid or gaseous media against corrosion without using substances which have only limited environmental compatibility.
It has now been found that certain quaternized ammonium compounds which contain at least one ester group in the molecule have a favorable corrosion-inhibiting effect, are readily biodegradable and show low aquatic toxicity.
SUMMARY OF THE INVENTION
The present invention relates to processes for protecting metal surfaces against corrosion in liquid aqueous or non-aqueous or gaseous media and to the use of certain quatenized ammonium compounds as corrosion inhibitors.
Accordingly, the present invention relates to a process for protecting metal surfaces against corrosion in liquid aqueous or non-aqueous or gaseous media, characterized in that compounds corresponding to formula (I):
in which R
1
, R
2
and R
3
independently of one another represent an alkyl or hydroxyalkyl group containing 1 to 4 carbon atoms, an aryl or alkylaryl group or a group corresponding to formula (II):
A
−
is an anion, n is the number 2 or 3, p is a number of 1 to 3 and R
5
is an alkyl or alkenyl group containing 7 to 23 carbon atoms and 0, 1, 2 or 3 double bonds,
and R
4
is a group corresponding to formula (II) or (III):
where R
1
, R
2
and R
3
are as defined above and Z is a group —(CH
2
)
m
— or a group corresponding to formula (IV):
and m is an integer of 1 to 6, X is a group NH or an oxygen atom and D is a dimer fatty acid residue containing on average 36 to 54 carbon atoms, are added to the media.
DETAILED DESCRIPTION OF THE INVENTION
The process according to the invention is preferably used to protect metal surfaces, such as occur in the technical equipment used in drilling operations, i.e. for example in pipelines, valves or delivery tubes, against corrosion in liquid aqueous or non-aqueous or gaseous media. The equipment in question is generally made of steel. However, the process according to the invention may also be used to prevent corrosion in other metals, for example aluminium, lead or copper, or alloys containing these metals.
The media to which the metals are exposed may be liquid or gaseous. In geological exploration work, the principal gaseous medium encountered is natural gas. A typical liquid non-aqueous medium is, for example, crude oil. Typical aqueous media preferably contain between 10 and 90% by weight of water. The water encountered in oil and gas production can have salt contents from 0.2% to saturation level and, accordingly, can seriously corrode metal surfaces. However, purely aqueous media can also be encountered, for example in the drilling of drinking water wells. Another medium often encountered are water/oil mixtures or emulsions used, for example, as drilling muds which can contain up to 99% by weight of oil. Besides crude oil, the oil phase can also contain environmentally compatible organic esters, for example of the type described in EP 374 671 A1, EP 374 672 A1 or EP 386 636 A1. In addition, the drilling muds contain suspended clay and other additives which are used to control the properties of the drilling mud.
The compounds corresponding to formula (I) are known and today are mainly used as fabric-softening components or for the antistatic finishing of fabrics. Examples of compounds corresponding to formula (I) where R
4
is a group of formula (II) can be found in applicants' WO 94/06899 and DE 42 03 489 A1 which disclose diester amine compounds in fabric softeners. EP 239 910 A1 also describes fabric softeners containing readily biodegradable quaternized mono- and diester amine compounds. In addition, it is known from the literature that ammonium compounds of the type in question are distinguished by ready biodegradability (Hauswirtschaft und Wissenschaft, Vol. 42, No. 2, 1994, pages 72-74 and S. T. Giolano et al., Chemosphere, Vol. 30, No. 6, pages 1067-1083, 1995).
Compounds corresponding to formula (I), in which R
4
is a group of formula (III), are described in DE 195 03 277 C1. These compounds are readily biodegradable and, by virtue of their softening and antistatic effect, are used as fiber and textile auxiliaries and in hair cosmetics. However, the corrosion-inhibiting properties of these substances are neither mentioned nor suggested in any of the documents mentioned above.
Compounds corresponding to formula (I) where R
4
is a group of formula (II) are preferably used in the process according to the invention. These compounds are technically quaternized mono-, di- or trifatty acid amine ester compounds which can be obtained by known synthesis methods. Compounds containing one and preferably two fatty acid ester groups are normally used. The quatemized compounds may be obtained, for example, by esterification of tertiary mono-, di- or trialkanolamines, preferably triethanolamine or triisopropanolamine, with fatty acid chlorides and subsequent quaternization of the esters formed with methyl chloride, benzyl chloride or dimethyl sulfate. Particulars of the production of these cationic ester amine compounds can be found, for example in EP 293 955 A2 and EP 293 953 A2.
Besides the preferred compounds of formula (I) where R
4
is a group corresponding to formula (II), compounds containing two quaternized nitrogen atoms per molecule corresponding to formula (I), where R
4
is a group of formula (III), m
Breuer Wolfgang
Herold Claus-Peter
Pi Rafael
Schuetz Robert
Uphues Guenther
Cognis Deutschland GmbH
Drach John E.
Ettelman Aaron R.
Green Anthony
Murphy Glenn E. J.
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