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Title:
BIODEGRADABLE CORROSION INHIBITORS
Document Type and Number:
WIPO Patent Application WO/1999/059958
Kind Code:
A1
Abstract:
Compounds of formula (I), wherein R is the $g(a)-side chain of an amino acid, R1 is a straight or branched chain alkyl or alkenyl residue containing 1 to 30 carbon atoms or a cycloalkyl or aryl residue having from 5 to 12 carbon atoms; R2 is hydrogen or aryl or a straight chain alkyl or alkenyl residue having from 1 to 30 carbon atoms or together with R is the $g(a)-side chain of an amino acid; X is a linking moiety and Y is a suitable backbone moiety on which to append the N-acylated amino acid moieties via X linkages; and n is a number between 1 and the total number of available reactive substituents on Y; are corrosion inhibitors and/or scale inhibitors.

Inventors:
Thompson, Russell Martin (The Associated Octel Company Limited Oil Sites Road P.O. Box 17 Ellesmere Port Cheshire CH65 4HF, GB)
Application Number:
PCT/GB1999/001602
Publication Date:
November 25, 1999
Filing Date:
May 20, 1999
Export Citation:
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Assignee:
THE ASSOCIATED OCTEL COMPANY LIMITED (Berkeley Square House Berkeley Square London W1X 6DT, GB)
Thompson, Russell Martin (The Associated Octel Company Limited Oil Sites Road P.O. Box 17 Ellesmere Port Cheshire CH65 4HF, GB)
International Classes:
C07C233/47; C07C237/22; C09K8/528; C09K8/54; C10L1/14; C10L1/224; C10L1/238; C10L1/24; C10L10/04; C10M133/16; C23F11/14; C10L1/18; C10L1/22; C10L1/26; (IPC1-7): C07C233/47; C07C237/22; C23F11/14
Domestic Patent References:
1998-07-02
Foreign References:
EP0434464A11991-06-26
EP0839515A21998-05-06
GB2045738A1980-11-05
GB1465719A1977-03-02
DE2015075A11970-10-08
Other References:
CHEMICAL ABSTRACTS, vol. 90, no. 24, 11 June 1979 (1979-06-11) Columbus, Ohio, US; abstract no. 187959, YUZAWA, MOTOYASU ET AL: "Additives for polyolefin compositions" XP002086931 & JP 54 006039 A (AJINOMOTO CO., INC., JAPAN;MITSUI PETROCHEMICAL INDUSTRIES, LTD.)
PATENT ABSTRACTS OF JAPAN vol. 097, no. 004, 30 April 1997 (1997-04-30) & JP 08 337563 A (KASHIMA SEKIYU KK), 24 December 1996 (1996-12-24)
Attorney, Agent or Firm:
Matthews, Derek Peter (Frank B. Dehn & Co. 179 Queen Victoria Street London EC4V 4EL, GB)
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Claims:
Claims
1. A compound of formula: wherein R is the aside chain of an amino acid, R1 is a straight or branched chain alkyl or alkenyl residue containing 1 to 30 carbon atoms or a cycloalkyl or aryl residue having from 5 to 12 carbon atoms; R2 is hydrogen or aryl or a straight chain alkyl or alkenyl residue having from 1 to 30 carbon atoms or together with R is the aside chain of an amino acid; X is a linking moiety and Y is a suitable backbone moiety on which to append the Nacylated amino acid moieties via X linkages; and n is a number between 1 and the total number of available reactive substituents on Y.
2. A compound of formula: wherein m is 1 or 2; R1 is a straight or branched chain alkyl or alkenyl residue containing 1 to 30 carbon atoms or a cycloalkyl or aryl residue having from 5 to 12 carbon atoms; R2 is hydrogen or aryl or a straight chain alkyl or alkenyl residue having from 1 to 30 carbon atoms; M is hydrogen or a watersoluble cation or an optionally substituted quaternary ammonium cation; X is a linking moiety and Y is a suitable backbone moiety on which to append the Nacylated amino acid moieties via X linkages; and n is a number between 1 and the total number of available reactive substituents on Y.
3. A compound as claimed in claim 1 or claim 2 wherein X isOorSorN (R3) (R3 is H or Cl20 alkyl or alkenyl or Cs12 aryl or alkylaryl) derived from hydroxyl (OH), thiol (SH) or amine groupings (NHR3) on Y, and Y is a straight or branched chain or cyclic or aromatic carbon chain structure containing hydroxyl (OH), thiol (SH) or amine (NHR3) substituents capable of reacting to form said linking moieties X.
4. A compound as claimed in any preceding claim wherein n is from 210.
5. A compound as claimed in any preceding claim wherein Y is polyoxyalkylene, polyalkyleneamine or polyoxyalkyleneamine.
6. An aqueous or hydrocarbon composition comprising a compound as claimed in any preceding claim, in an amount sufficient to inhibit corrosion of, and/or scale formation on, a surface in contact with the composition.
7. A composition as claimed in claim 6 comprising a further polycarboxylic acid, phosphonate, phosphonocarboxylic acid, amino acid, imidazoline, trialkanolamine, fatty amine or watersoluble azole corrosion inhibitor or scale inhibitor.
8. A composition as claimed in claim 6 or 7 comprising one or more of a cosolvent, a surfactant, a buffer, a demulsifier, an antifoam, a biocide or an oxygen scavenger.
9. A method of inhibiting corrosion of, and/or scale formation on, a surface in contact with an aqueous or hydrocarbon medium, comprising addition to said medium of a compound as claimed in any of claims 1 to 5, in an amount sufficient to inhibit said corrosion and/or scale formation.
10. A method as claimed in claim 9 wherein said amount is from 0.1 parts per million to 5t by weight of said medium.
Description:
Biodegradable Corrosion Inhibitors Background of the Invention Field of the invention The subject invention relates to compounds and compositions which are useful in preventing or inhibiting corrosion and scale formation in a wide range of applications including water and boiler scale treatment, oilfield, pipelines, cutting fluids and hydraulic fluids, in particular where they come into contact with the natural environment. The subject compositions are based on environmentally compliant substances, which have low adverse environmental impact.

Specifically, the subject invention relates to water-and hydrocarbon-soluble corrosion-and scale-inhibitor compositions, which are biodegradable. Said compositions are very versatile for inhibiting corrosion and scale formation and may be used in aqueous media and in hydrocarbon media in contact with water.

The subject invention also relates to processes for manufacture of the subject compositions.

Description of the Prior and Related Art Growing awareness that reducing corrosion can increase profitability in many industries (from chemicals and petroleum refining to construction and machinery) has lead to a demand for additives to combat these problems. Internal corrosion is particularly a problem in automotive fuel distribution systems, refineries, and oilfield pipelines. However, legislative change, and awareness by large companies of the influence of environmental or"green"issues on market share, is turning against the use of (hazardous) potentially biologically toxic materials.

Corrosion inhibitors provide a cost-effective method of minimising the problems of corrosion for a wide variety of materials in an equally wide variety of corrosive environments. Unlike the material selection for a plant which must be made at the design stage, the choice of corrosion inhibitor may be changed during its operation.

Consequently, the inhibitor can be modified or changed as the process conditions vary. This flexibility maximises the versatility of the process equipment. Corrosion inhibitors provide an extra level of security against the premature failure of a system and the safety and financial consequences that such a failure entails. In the case of the oil and gas exploration and production industry, the application of production chemicals such as corrosion inhibitors, scale inhibitors, biocides and demulsifiers is essential to the successful operation of most oil and gas fields. But with this is the risk of their subsequent entry into the surrounding environment. The environmental impact of speciality chemicals for use in hydrocarbon production and processing is receiving increased attention, especially in cases where they find their way into the sea since it is normal practice to discharge the process water into the sea along with entrained chemicals.

Environmental concerns are increasingly likely to influence the choice of oilfield production and drilling chemicals. Attention has now begun to focus on the oil

production chemicals including corrosion inhibitors, which may be present in the process waters. There is an increasing realisation that whilst such chemicals are highly effective, their impact on the environment is not fully understood. Indeed, it is clear that many of these chemicals are immediately harmful to some forms of marine life.

Despite this, there are currently no clear universally accepted guidelines on the use and discharge of oil production chemicals. Individual countries are introducing their own legislation and in Europe, the EC has charged the Paris Commission (PARCOM) with providing a framework for legislation, particularly in the North Sea.

Chemical hazard assessment and risk management schemes also exist to investigate an appropriate balance between biodegradation, bioaccumulation and toxicity issues. Due to uncertainties surrounding what future legislation will bring, little genuinely new chemistry has appeared. This fact together with regulatory hurdles such as the European Inventory of Existing Commercial Chemical Substance (EINECS) has meant that product development is somewhat tentative. However, there is increasing concern that production chemicals should be available which are environmentally friendly or"green". But, there appears to be little evidence for high performance corrosion and/or scale inhibitor chemistry, which is genuinely biodegradable.

An organic chemical substance is said to be biodegradable if it can be broken down (degraded) by the metabolic action of living (micro) organisms such as bacteria, fungi, algae, and yeast. Biodegradation is one of the most important processes governing the fate of a chemical after its release into the environment. The biodegradability of all substances released to the environment is an important factor in defining the levels of a substance in the environment and hence assessing its potential for causing environmental damage. At present, the main strategy for assessing the biodegradability of a chemical is the experimental approach; a set of standardised biodegradability tests is performed in order to distinguish environmental acceptability.

The Organisation for Economic Cooperation and Development (OECD) define three such levels of tests namely the'Ready','Inherent', and'Simulation'biodegradation tests. All the tests use an innoculum derived either from domestic sewage biological treatment or from soil or surface water, and incubation at room temperature.

Biological (or biochemical) Oxygen Demand (BOD) is a standard estimate of the degree of contamination in an industrial water supply. It is a test that determines the oxygen required for wastewaters for biochemical degradation of organic material.

BOD is important because high values lead to oxygen depletion, which may kill fish in the sea, rivers and lakes. The BOD value is dependent on the time over which a test is run. Chemical Oxygen Demand (COD) is a measure of the oxygen equivalent from strong chemical oxidants that can degrade the organic material under fixed laboratory conditions. The COD value is independent of time. One sample gives one result. The ratio BOD/COD is used as an index of waste disposability or as an assessment of the degree of biodegradability, where a high BOD/COD ratio is desired.

'Ready Biodegradation'is the potential to degrade quickly in unadapted systems. A number of test methods are available to assess this. The general principle of these tests is the incubation of a small amount of bacterial innoculum containing a variety of aerobic microorganisms in a suitable medium under controlled conditions. A small amount of test material (2-100 mg/1) is added to this medium and acts as a sole source

of carbon and energy. Results > 60% as BOD/COD are regarded as indicating the material to be readily biodegradable. The principle of these tests is that they are so stringent that a substance judged to be readily biodegradable will biodegrade in all situations where biodegradation is possible. It is important to note that the converse is not true. A substance, which does not meet the ready criteria, may in practice be very satisfactorily degraded over a longer period of time, and additional testing is necessary to determine this.

The OECD takes account of this through'Inherent Biodegradability'. The OECD pass level for a substance to be considered inherently biodegradable on a primary degradation is 20%. This is based on a philosophy that if a substance will break down 20% in a certain test period then there is no reason why it should not break down 100% given sufficient time. That is, it is inherently biodegradable. This test methodology allows for a higher level of bacterial innoculum and an extended contact period for acclimatisation of the microorganisms and other conditions, which favour biodegradation. Negative results in the'inherent biodegradability'test assume non- biodegradability of the test substance. The least stringent'simulation'biodegradation tests provide rate data under environmentally relevant conditions.

To minimise the effects of metallic corrosion and scale formation, an armoury of chemical inhibitors has been developed. Although corrosion and scale inhibitors of many types are known, the materials which have been found to be the most effective in practice have the disadvantage of toxicity to the marine and freshwater environment. Use in a marine or freshwater environment is intended to mean use in an environment in which the compound is likely to come into contact with an area of seawater or freshwater including during the time the compound is acting to inhibit corrosion and scale formation, and after its disposal.

Much attention has focussed on the use of amino acids as possible corrosion inhibitors. Acylated amino acids are known inhibitors [see for example A Frignani et. al., Corrosion Science, 52 (3), 177-182, (1996)]. Ciba Geigy in 1979 claimed biodegradable water-soluble corrosion inhibitors for cooling water systems based on N-acylated methylaminosuccinate salts [B Holt, D R Clark and A Marshall, GB 2045738A] However, no biodegradability data was contained therein. Ethyl in 1990 [D K Waters and A S Thomas, EP 0434464A1], claimed metal-free lubricant compositions useful as hydraulic fluids, which contain an amino succinate compound as a corrosion inhibitor. Exxon Chemical in 1992 claimed corrosion inhibitors useful for inhibiting the corrosion of metals in oil-and gas-field application which also show low toxicity to marine organisms [J A Haselgrave, N Carruthers, W M Hedges and T M O'Brien, EP 0526251A1].

Several polypeptide homopolymers have been tested as environmentally friendly, water-soluble corrosion inhibitors in synthetic oilfield formation brines under conditions appropriate for use in the North Sea [A J McMahon and D Harrop, NACE "Corrosion/95"Meeting Orlando 2/23-31/95, Paper N. 32]. However, the efficiencies of these polymers were much less that that of commercially used inhibitors. More importantly, they are expensive in use. Economics of corrosion inhibitor use is an important requirement and includes inhibitor costs, treating level, any non-routine treating procedures, monitoring, volumes of water to be treated and development costs for these factors.

In addition to performing well in their own right, these additives need to be fully compatible with the components of a commercial package including: other corrosion and scale inhibitors, cosolvents, surfactant, buffers, demulsifiers, antifoams, biocides, oxygen scavengers and the like. Corrosion inhibitors are used in a wide variety of other applications including cleaning products, pulp and paper processing, water treatment, metal working, and oil field chemistry.

Scale inhibitors can be used in industrial processes whenever precipitates of Ca, Mg and other heavy metal and alkaline earth salts are a nuisance and are to be prevented.

They are used for preventing scale deposits and encrustation in kettles, pipelines, vessels, heat exchangers, evaporators, and filters spray nozzles or generally on smooth surfaces.

Scale formation, caused by the use of hard water, not only affects the efficiency of thermal systems, but also eventually may lead to corrosion. The organic chemicals can be used alone or combined with other inhibiting agents, such as polymers, which also exhibit their own threshold effects. One significant disadvantage of most common corrosion and scale inhibitors is that they are not environmentally compatible and therefore not easily degraded in the environment Waste disposal of metal working fluids is a major issue confronting the metalworking industry. Rising costs of waste disposal and environmental concerns are forcing metalworking fluid users to choose products for their ease of disposal.

Objects of the Invention It is therefore an object of the present invention to provide a compound or composition useful in preventing or inhibiting corrosion and scale formation on surfaces, preferably metallic surfaces. It is a particular object of the present invention to provide a corrosion or scale inhibitor compound or composition that is biodegradable.

The present invention creates a method that enables N-acylated amino acid moieties to be appended onto suitable substrates and to be manufactured simply and cheaply and in high yields. We have found that the molecules of the subject invention have high corrosion and scale inhibitor efficiencies. Moreover, these adducts contain the additional advantage of being biodegradable.

The composition of matter, the compositions containing such additives and moieties and the use of such reaction products to improve the performance properties are all believed to be unique and novel.

SUMMARY OF THE INVENTION The objects of the present invention are provided by a biodegradable compound or composition for inhibiting corrosion and/or scale formation in aqueous systems and hydrocarbon systems in contact with water, of general formula:

where R, where appropriate together with R2, is the a-side chain grouping of an a- amino acid, including glycine, alanine, valine, leucine, isoleucine, proline, phenylalanine, tyrosine, tryptophan, cysteine, methionine, lysine, arginine, histidine aspartic acid, glutamic acid, asparagine, glutamine, serine and threonine, RI, X and Y are as defined below and R2 is as defined below or together with R is the a-side chain grouping of an a-amino acid.

An especially preferred embodiment of the present invention is a biodegradable compound or composition for inhibiting metallic corrosion and/or scale formation in aqueous systems and hydrocarbon systems in contact with water, of formula derived from either of the dicarboxylic amino acids aspartic and glutamic acids, giving the formula: wherein m is 1 or 2 and Rl is a straight or branched chain alkyl or alkenyl residue containing 1 to 30 carbon atoms, for example 1 to 19 carbon atoms, or a cycloalkyl or aryl residue having from 5 to 12 carbon atoms; R2 is hydrogen or aryl or a straight chain alkyl or alkenyl residue having from 1 to 30 carbon atoms, for example 1 to 20 carbon atoms; M is hydrogen or a water-soluble cation (comprising alkali metal or alkaline earth metal) or an optionally substituted quaternary ammonium cation; X is a linking moiety optionally-O-or-S-or-N (R3)- (R3 is H or alkyl or alkenyl or aryl or alkylaryl) derived from hydroxyl (-OH), thiol (-SH) or amine groupings (-NHR3) on Y.

Y is a suitable backbone moiety on which to append the N-acylated amino acid moieties via X linkages, and can be straight or branched chain or cyclic or aromatic carbon chain structures containing hydroxyl (-OH), thiol (-SH) or amine (-NHR3) substituents, capable of reacting to form the products of the subject invention. n is a number between 1 and the total number of available reactive substituents on Y.

Preferably n is from 2-10. Optionally, Y may contain additional functionality

(carboxyl,-COOH, amine,-N (R4)-; ether,-O-; thioether,-S-; sulphonate,-S03H; phosphino,-P (R4)- ; R4 = H or C, 2o alkyl or C5, 2 are; and phosphonate,-PO3H2), either in the backbone of Y or as pendant functionality. Without being bound by any theories it is believed that these additional coordinating functionalities are capable of coordinating to a metallic surface and/or interacting with the crystal surface of precipitated scale species.

We have found that the subject invention reaction products of N-acyl aspartic or glutamic acid anhydrides and activated esters to have excellent corrosion and scale inhibition properties and the added advantage of good biodegradability. We have found that the physical effect of covalently bonding together more than one of these N-acylated amino acid moieties with a suitable backbone linkage Y is to increase the efficiency of corrosion inhibition and scale inhibition properties markedly. Moreover, by choice of the correct Y backbone one is able to moderate the biodegradability performance and also solubility and other solution characteristics such as partition coefficient between oil (hydrocarbon) and water phases.

Structures derived from L-aspartic or glutamic acids would be expected to be the most biodegradable structures. Aspartic and glutamic acid is understood to mean in particular the L-amino acid and also the D-form, as well as the D, L-form.

The subject invention relates to corrosion and scale inhibitor compounds and compositions comprising chelating moieties containing amide, ester and thioester derivatives of N-acylated amino acids. These compounds are designed to be chelating corrosion inhibitors. Without being bound by any theories, it is believed that organic corrosion inhibitors which contain more than one functional group can chelate the metal'ion'whilst it is still part of the metallic substrate, the metal ion is thus blocked from formation of a soluble ion. These chelating additives thus represent a novel class of multifunctional additive.

The invention thus provides additive products having superior and/or improved multifunctional characteristics for corrosion and scale inhibition that are biodegradable.

The present invention also provides a process for preparing the intermediates and final corrosion inhibitors comprising: 1. Reacting the amino acid or a monoester thereof with acyl halide compound of formula RU COCU or RICOBr to give N-acylated amino acid or N-acylated amino acid monoester product.

2. Reacting the resulting N-acylated amino acid product with acetic anhydride or acetyl chloride to give an N-acylated amino acid anhydride product.

3. Reacting either the N-acylated anhydride or monoester product with amine, hydroxyl or thiol functional group (X group in backbone moiety Y) or mixtures thereof to give the novel N-acylated amino acid amides, esters or thioesters corrosion and scale inhibitor products.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS It has been unexpectedly found that appending N-acylated amino acid containing moieties to suitable substrates (Y) provides a means to very efficiently inhibit

corrosion and/or scale formation for use in systems in contact with aqueous media and/or hydrocarbon media in contact with water.

Furthermore, said compositions are very versatile in their solubility characteristics.

The term'moiety'is used as understood by those skilled in the art to mean part of a molecule, molecular fragment, or molecular structural fragment.

In a preferred embodiment this application is more particularly directed to the reaction products provided when an acylated aspartic or glutamic acid anhydride or suitable activated ester product is reacted further with a suitable nucleophilic group.

Nucleophilic in this instance is meant to be functional groups (hydroxyl, amine, and thiol) which can effect the ring opening of the cyclic anhydride and or displacement of the activated ester function herein. Said reaction products exhibit excellent corrosion and scale inhibition performance. More specifically this application is directed to compositions containing these compounds.

To be acceptable, performance must be at least equivalent to that of current products.

The new product must provide equal performance at the same cost.

As used herein the compositions comprise compounds selected from the group consisting of N-acylated amino acid derivatives including N-acylated amino acid amides, esters, and thioesters. A further embodiment of the present invention is that the N-acylated amino acid derivative may be comprised of derivatives of any of the common a-amino acids including glycine, alanine, valine, leucine, isoleucine, proline, phenylalanine, tyrosine, tryptophan, cysteine, methionine, lysine, arginine, histidine aspartic acid, glutamic acid, asparagine, glutamine, serine and threonine. Where the a- amino acid is proline then R and R2 together from the propylene a-side chain grouping. Especially preferred N-acylated amino acid derivatives in the present invention are N-acylated derivatives of the dicarboxylic amino acids aspartic and glutamic acids. Both D-and L-amino acid isomers and D, L- are effective in the subject invention. Natural amino acids (L-isomers) are preferred.

Aliphatic carboxylic acid halides, which may be used in this invention for use in the N-acylation reaction, may have a saturated or (singly or multiply) unsaturated straight chain or branched aliphatic acyl (RlCO-) group. As used herein acyl means carbon containing chains which may be straight, branched or cyclic; substituted or unsubstituted, saturated, monounsaturated (i. e., one double or triple bond in the carbon chain) or polyunsaturated (i. e., two or more double bonds in the carbon chain; two or more triple bonds in the carbon chain, one or more double bonds and one or more triple bonds in the carbon chain). Acetyl, propionyl, butyryl, pivaloyl, decanoyl, lauroyl myristoyl, palmitoyl, and stearoyl are examples of saturated, straight chain or branched acyl groups in this respect, while oleoyl and linoleyl are examples of unsaturated acyl groups. Aliphatic C220 carboxylic acid halides that are preferred in the process of the invention are decanoyl, lauroyl (dodecanoyl), palmitoyl, and oleoyl or mixtures thereof. An especially preferred compound acid halide is lauroyl chloride.

Alternatively carboxylic acid halides prepared from mixtures of fatty acids derived from tall oil fatty acids or beef tallow or similar including vegetable oils derived from, for example, sunflower oil, rapeseed oil, coriander oil, castor oil, soybean oil, cottonseed oil, peanut oil, may be used in the present invention. Alternatively, the acid halide may be prepared from a diacid, for example, a dimer acid formed by

dimerisation of unsaturated fatty acids such as linoleic or oleic acid or mixtures thereof.

Many methods of making long chain N-acyl amino acids are known in the art (for example JP 09040624 assigned to Kao Corporation exemplifies useful methods for preparing these materials for use as surfactants). Typically, the acylation reaction used in the preferred embodiment of this invention is generally carried out at temperatures less than 5°C, the best yield being attained at reaction temperatures around 0°C. If reaction temperatures are too high, an appreciable hydrolysis of the acid chloride competes with the acylation reaction. If the reaction temperature is too low, the long chain acyl chloride is too poorly soluble to enable reasonably complete reaction.

There are many ways of making monoester, monamide and thioester derivatives of dicarboxylic acids known in the art [see for example pages 1152,1168 and 1173 respectively of'Advanced Organic Chemistry', J March, Third Edition, Wiley Interscience (1985)]; particularly preferred in this invention are amination and alcoholysis of N-acylated aspartic acid anhydride, and amination and transesterification of N-acylated aspartic or glutamic acid monoester. Monoester formation from anhydride is a relatively easy step, and is selective because diester formation is not as easy. The monoester product has all the attributes of a carboxylic acid and hence the second step of the esterification is an equilibrium process requiring the use of a catalyst or forcing conditions to remove the water product of reaction.

A preferred embodiment of the subject invention includes N-acyl amino acid amides and esters having the structure wherein the aspartic acid moiety may be functionalised in either its a-or p-forms: a-ester or amide ester or amide derivative derivative Glutamic acid moiety may be similarly functionalised at the a-or y-carboxyl residues.

Optionally, the backbone moiety Y may contain additional functionality either in the backbone of Y or as pendant functionality, capable of coordinating to a metallic surface and/or interacting with the crystal surface of precipitated scale species. The additional coordinating functionality on Y may be comprised of nitrogenous donor ligand systems selected from any or all of pyridines, (including bipyridines, phenanthrolines and terpyridines), pyridazines, pyrimidines, purines, pyrazines, naphthyridines, pyrazoles and imidazoles, amines, amides, hydrazides, diazenides, nitrenes, imides, imines, oximes, nitriles, and guanidines; from phosphorus donor ligands including phosphines and phosphides, from oxygen donor ligands selected

from hydroxyl, alcoxide, phenoxide, ether, ketone (diketonate), tropolonate, ester, amide, carboxyl, carbamate, pyridine N-oxide, phosphine oxide, hydroxamate phosphorus-containing oxo anions (including phosphonate and polyphosphate) and sulphur-containing oxo anions (including sulphonate); from sulphur donor ligands including thiol, thioether, thioester, dithiocarbamate, and dithiophosphate; and from miscellaneous ligand donor systems including substituted ureas, thioureas, semicarbazides, and thiosemicarbazides. A convenient classification of coordinating functionality (ligands) by donor atom type is given in Chapter 4, pp 107-194 of 'Advanced Inorganic Chemistry'by F A Cotton and G Wilkinson, 4"'Edition, Wiley Interscience (1980).

A preferred embodiment of the present invention is where Y is polyoxyalkylene or polyalkyleneamine or polyoxyalkyleneamine of formula: Where x is 1 to 20, Ry is H, alkyl or aryl, preferably H or Me and z is 0 to 2 for the glycols and n is 1,2,3 or 4, m is 1 to 20, and R3 is H or alkyl or aryl for the polyalkyleneamines and polyoxyalkyleneamines.

The alkylene glycols included herein are diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, tetraethylene glycol, tetrapropylene glycol and polyethylene glycols, polypropylene glycols, and polybutylene glycols of molecular weight up to 5000, preferably 200-3000, most preferably 200-1600, for example 200 to 600. The alkylene glycol ester derivatives are readily prepared by reaction of the anhydride intermediate dissolved in a suitable inert solvent such as toluene or xylene, by adding the required amount of glycol and heating under reflux. Alternatively, the glycol may be used in excess as both reactant and as a solvent for the esterification reaction. Usefully, these reactions are carried out at temperatures of from 50°C to 150°C, preferably 100°C to 140°C, depending on the solvent or solvent mixture used.

The amine reactants may be widely diverse in chemical structure and include straight, branched chain and cyclic amines which can be unsubstituted or substituted with other functional groups, such as one or more ester groups, ether linkages, carbonyl groups, oxirane groups, carboxyl groups, thioether linkages, thiol groups and hydroxyl groups, and many others such as those described above for coordinating fur. ctionality on Y. A few representative examples include ethylenediamine, propylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, dipropylenetriamine, tetrapropylenepentamine, and ethanolamines including monoethanolamine, diethanolamine and triethanolamine as well as polyalkyleneamines of molecular weight 200 to 1000 and the aminoglycols of which 2,2'- (ethylenedioxy) bisethyl-amine) is a particularly preferred example which is exemplified in Example 14. Other aliphatic polyamino compounds that may be used are N-aminoalkylpiperazines, e. g., N- (2-aminoethyl) piperazine.

Another preferred embodiment is where Y includes substituted aromatic alcohols (phenols), amines and benzoic acids such as anilines, phenylenediamines, aminophenols, catechols, salicylic acids, and anthranilic acids or mixtures thereof.

The subsequent reaction of the N-acylated amino acid anhydrides or activated esters with polyoxyalkylene or polyamine or polyoxyalkylene amines of formula above gives rise to mono-, bis-, tris-, and poly-substituted amides and esters.

Reaction of N-acylated amino acid anhydrides or activated esters with azamacrocycles, azacrown ethers and azacrown thioethers or combinations thereof gives rise to'claw-like'chelating structures. Preferred azamacrocycles are 1,4,7- triazacyclononanane (tacn), 1,4,8,11-tetraazacyclododecane (cyclen) and 1,4,7,10- tetraazacyclotetradecane (cylam) (as exemplified in Example 23). tacn cyclen cyclam Chelating agents based on azacrown ether bearing moieties have attracted considerable interest due to their enhanced ligating abilities.

Other suitable Y linkages include various polyols and carbohydrates including sugars and oligo-and polysaccharides, thiols, aminothiols, and substituted thioethers.

Preferred compounds include aminocarboxylates, aminodeoxysorbitol and hydroxyacids including citric acid, gluconic acid, tartaric acid, and malic acid.

Preferred polyhydric alcohols include one or a mixture of compounds such as glycerol, erythritol, pentaerythritol, dipentaerythritol, tripentaerythritol, glyceraldehyde, glucose, sucrose, 1,7-heptanediol, 1,10-decanediol and 1,2,3- hexanetriol and other similar carbohydrates. The functionalisation of tartaric acid with two equivalents of N-acyl aspartic acid anhydride is seen to give the novel compound of formula (as exemplified in Example 21): Preferred polysaccharides for use as suitable Y linkages include starches (amyloses, amylopectins), celluloses, inulins, pectins, and various gums including locust bean gum and guar gum.

A further embodiment of the present invention is that Y may consist of any of the common a-amino acids including glycine, alanine, valine, leucine, isoleucine, proline, phenylalanine, tyrosine, tryptophan, cysteine, methionine, lysine, arginine, histidine aspartic acid, glutamic acid, asparagine, glutamine, serine and threonine where the X linkage to be acylated consists of the a-amino group of the amino acid. Especially preferred embodiments of the present invention are where Y consists of those a- amino acids which contain additional (Z) functionality in the a-side chain such as tyrosine, serine and threonine (Z =OH); lysine, arginine, asparagine, glutamine (Z = NH2); proline and histidine (Z =-NH-); and cysteine (Z = SH). Alternatively, Y may consist of oligomers and polymers of any or all of the common a-amino acids such as polypeptides (including polyaspartic acid) and water soluble proteins or protein hydrolysates.

In another embodiment of the present invention, the source of the amino acid or polypeptide or protein may come from use of the dilute waste streams from amino acid-using and/or amino acid-producing processes such that saleable corrosion and/or scale inhibitor products may be produced from said waste streams.

In general it is envisaged that the derivatives will either be used singly in solution or in mixtures; in combination with various other additives selected from other corrosion and scale inhibitors, cosolvents, surfactant, buffers, demulsifiers, antifoams, biocides, oxygen scavengers and the like well known in the art. The derivatives will be used in amounts up to and including 5% by weight: <10 ppm, <100 ppm, <1000 ppm, >10 ppm, > 100 ppm, > 1000 ppm, preferably in the active concentrations 0.1-1 ppm, 1-5 ppm, 1-10 ppm, 10-20 ppm, 20-50 ppm, 20-100 ppm, 100-200 ppm, 200-1000 ppm, 1000-2000 ppm, 2000-5000 ppm, 5000-10000 (1%), < 5%.

Usefulness (Utility) Of the Invention Biodegradable corrosion and scale inhibitors are useful; for instance, in applications where the resulting clean-up costs of using environmentally hazardous chemicals will be avoided.

The following preparations and examples are included herein as further description and illustrative of the present invention.

EXAMPLES Example 1: N-Decanoyl-L-Aspartic Acid L-Aspartic acid (133.1 g, 1 mole) and DMAP (4.05 g, 3.3 mole %) were added to distilled water (1000 ml) in a 2 litre stirred reactor and cooled using an icebath.

Decanoyl chloride (190.71 g, 1 mole) and enough 30% NaOH solution were added to maintain a temperature of < 5°C and pH 2 10. The mixture was stirred at room temperature for 30 minutes before acidification to pH 2 with concentrated HCI. After stirring for an additional 30 minutes, the product was collected by filtration and thoroughly washed with water (3 x 250 ml). The white solid isolated was dried overnight in a vacuum oven at 40°C (yield 74%, 212.9 g).

Conversion of a small portion of the solid product (0.5 g) to the dimethyl ester in methanol using acetyl chloride (0.5 ml) at 50°C with stirring, indicated a product purity of 96% (3.4% methyl decanoate) by GC analysis.

Example 2: N-Dodecanoyl-D, L-Aspartic Acid D, L-Aspartic acid (82.52 g, 0.62 mole), DMAP (2.5 g, 3.3 mole %) and distilled water (600 ml) were charged to a 1 litre stirred reactor and the mixture cooled to 0°C.

Dodecanoyl chloride (135.6 g, 144 ml, 0.62 mole) and aqueous 25% NaOH solution <BR> <BR> were added dropwise to maintain the temperature at-0°C and the pH 2 10. The mixture was stirred for an additional 30 minutes before acidification to pH 2 with concentrated HCI. The product was collected by filtration and washed thoroughly with water (2 x 750 ml) and dried in vacuo (yield 178.2 g, 91%).

Product purity was estimated as 92 % by GC analysis of a sample of dimethyl ester derivative.

Example 3: N-Decanoyl-L-Aspartic Anhydride N-Decanoyl-L-aspartic acid (10 g, 34.8 mmol) was added to ethyl acetate (50 ml). The mixture was warmed to 50 °C with magnetic stirring. Acetic anhydride (3.91 g, 38.3 mmol, 1.1 mol equivalents) was added and the mixture stirred at reaction temperature for 2 hours.

The mixture was then filtered hot and 40-60°C petroleum ether (75 ml) added to the filtrate. The mixture was cooled to 5°C, and the resulting solid isolated by filtration.

After washing with cold petroleum ether the product was dried in vacuo (Yield 5.6 g, 60%). Product purity was estimated as > 96% by GCMS.

Example 4: N-Dodecanoyl-D, L-Aspartic Anhydride N-Dodecanoyl-D, L-aspartic acid (170 g, 0.539 mol) and ethyl acetate (500 ml) were added to a 2 litre stirred reactor. Acetic anhydride (60.54 g, 0.593 mol 1.1 mole equivalents) was added to the reaction mixture with stirring. The mixture was warmed to 50°C and held at reaction temperature for 2 hours.

After cooling to room temperature, petroleum ether (320 ml) was added with cooling to-5°C. The product was collected by filtration, washed with cold petroleum ether (3

x 100 ml portions) and dried in vacuo (Yield 118.2 g, 74%). GCMS analysis indicated product purity to be > 99%.

Examples of Ester Products Diester Products Example 5: Bis (N-Decanoyl-L-Aspartic Acid) Diethylene Glycol Diester N-Decanoyl-L-aspartic anhydride (5 g, 18.7 mmol) and diethylene glycol (0.985 g, 9.35 mmol) were added to toluene (50 ml) and the mixture was heated under reflux for 2 hours.

The product was isolated by removal of the solvent was in vacuo.

Example 6: BisfN-Decanoyl-L-AsparticAcid) Triethylene Glycol Diester N-Decanoyl-L-aspartic anhydride (10.8 g, 40 mmol), triethylene glycol (3 g, 20 mmol) and toluene (200 ml) were added to a 250 ml stirred reactor and the mixture was heated under reflux for 2 hours.

The solvent was removed in vacuo giving a pale pink product.

Example 7: Bis (N-Dodecanoyl-D, L-Aspartic Acid) Ethylene Glycol Diester N-Dodecanoyl-D, L-aspartic anhydride (10 g, 33.6 mmol), ethylene glycol (0.99 g, 0.5 equivalents) and toluene (200 ml) were added to a 250 ml stirred reactor and heated under reflux for 2 hours.

On cooling, the white solid product was isolated by filtration, washed with toluene and dried in vacuo (Yield 3.6 g). Further product was recovered by concentration of the filtrate in vacuo.

Example 8: Bis (N-Dodecanoyl-D, L-Aspartic Acid) Diethylene Glycol Diester N-Dodecanoyl-D, L-aspartic anhydride (10 g, 33.6 mmol), diethylene glycol (1.68 g, 0.5 equivalents) and toluene (200 ml) were added to a 250 ml stirred reactor and gently heated under reflux for 2 hours.

After cooling, the white solid product was collected by filtration, washed with toluene and dried in vacuo. Elemental analysis was consistent with the desired product.

Further product was recovered by concentration of the filtrate in vacuo.

Example 9: Bis (N-Dodecanoyl-D, L-Aspartic Acid) Triethylene Glycol Diester N-Dodecanoyl-D, L-aspartic anhydride (5 g, 16.8 mmol), triethylene glycol (1. 26 g, 0.5 equivalents, 8.4 mmol) and toluene (200 ml) were added to a 250 ml stirred reactor and gently heated under reflux for 1 hours.

The solvent was evaporated in vacuo giving the product as a pale yellow oil.

Monoester Products Example 10: N-Dodecanoyl-D, L-Aspartic Acid Ethylene Glycol Monoester N-Dodecanoyl-D, L-aspartic anhydride (10 g, 33.6 mmol), excess ethylene glycol (10.4 g, 5 mole equivalents) and toluene (200 ml) were added to a 250 ml stirred reactor and gently heated under reflux for 2 hours.

The solvent mixture was removed by distillation giving a pale yellow oil as product.

Example 11: N-Dodecanoyl-D, L-Aspartic Acid Diethylene Glycol Monoester N-Dodecanoyl-D, L-aspartic anhydride (5 g, 16.8 mmol), diethylene glycol (1.78 g, 16.8 mmol) and toluene (75 ml) were added to a 100 ml stirred reactor and heated under reflux for 2 hours.

The product was recovered by solvent removal in vacuo.

Example 12: N-Dodecanoyl-D, L-Aspartic Acid Triethylene Glycol Monoester N-Dodecanoyl-D, L-aspartic anhydride (5 g, 16.8 mmol), triethylene glycol (2.52 g, 16.8 mmol) and toluene (75 ml) were added to a 100 ml stirred reactor and heated under reflux for 2 hours.

The product was isolated by solvent removal in vacuo leaving the product as a pale pink oil.

Examples of Amide Products Diamide Products Example 13: Bis (N-Dodecanoyl-DL-Aspartic Acid) Diethylene Triamine Diamide N-Dodecanoyl-D, L-aspartic anhydride (10 g, 33.6 mmol), diethylenetriamine (1.736 g, 16.8 mmol) and toluene (120 ml) were added to a 250 ml stirred reactor and heated under reflux for 2 hours.

The off-white product was isolated by solvent removal in vacuo (Yield 11.44 g).

Example 14: Bis (N-Dodecanoyl-DL-Aspartic Acid) 2,2'- (ethylenedioxy) bisethyl- amine) Diamide N-Dodecanoyl-D, L-aspartic anhydride (10 g, 33.6 mmol), 2,2'- (ethylenedioxy) bisethyl-amine) (2.50 g, 16.8 mmol) and toluene (130 ml) were added to a 250 ml stirred reactor and heated under reflux for 2 hours.

The tan product was isolated by solvent removal in vacuo (Yield 12.36 g).

Monoamide Products Example 15: N-Dodecanoyl-D, L-AsparticAcid Ethanolamine Monoamide N-Dodecanoyl-D, L-aspartic anhydride (10 g, 33.6 mmol), ethanolamine (2.054 g, 33.6 mmol) and toluene (130 ml) were added to a 250 ml stirred reactor and heated under reflux for 30 minutes.

The product was isolated by solvent removal in vacuo (Yield 11.51 g).

Example 16: N-Dodecanoyl-D, L-AsparticAcid Diethanolamine Monoamide N-Dodecanoyl-D, L-aspartic anhydride (10 g, 33.6 mmol), diethanolamine (3.54 g, 33.6 mmol) and toluene (130 ml) were added to a 250 ml stirred reactor and heated under reflux for 30 minutes.

The product was isolated by solvent removal in vacuo (Yield 13.3 g).

Other Products Example 17: Aspartic Acid Methyl Ester Hydrochloride Salt L-Aspartic acid was suspended in methanol solvent at-10°C with stirring in an ice bath. Excess thionyl chloride was added slowly dropwise with cooling. After complete addition, the reaction mixture was allowed to slowly warm to room temperature.

Excess diethyl ether was added with vigorous stirring to precipitate the product salt in good yield Example 18: N-Dodecanoyl-Aspartic Acid Methyl Ester Using the reaction conditions exemplified in Example 2, the aspartic acid methyl ester was acylated in good yield.

Example 19 The product from Example 18, N-Dodecanoyl-Aspartic Acid Methyl Ester and diethanolamine were heated under reflux in toluene solvent to effect transformation to the amide product exemplified in Example 16 in good yield.

Example 20: N-Dodecanoyl-L-Glutamic Acid Under the reaction conditions exemplified in example 2, L-glutamic acid was acylated with dodecanoyl chloride in good yield (yield 223 g, 99%). Conversion of a small portion of the solid product to the dimethyl ester in methanol using acetyl chloride, indicated a product purity of 91% (8% methyl dodecanoate) by GCMS analysis.

Example 21: Bis (N-Decanoyl-L-Aspartic Acid)-L-Tartaric acid Diester N-Decanoyl-L-aspartic anhydride (19.55 g, 72.6 mmol), L-tartaric acid (5.45 g, 36.3 mmol) and toluene (200 ml) were added to a 250 ml stirred reactor. The resulting slurry was heated under reflux for 5 hours (nitrogen atmosphere).

The solvent was removed in vacuo giving the product as a pale yellow oil.

Example 22: N-Decanoyl-L-Aspartic Acid Citric acid Monoester N-Decanoyl-L-aspartic anhydride (14.6 g, 54.2 mmol), citric acid (10.41 g, 54.2 mmol) and toluene (200 ml) were added to a 250 ml stirred reactor. The resulting slurry was heated under reflux for 4 hours (nitrogen atmosphere).

The solvent was removed in vacuo giving the product as a pale yellow oil in good yield. <BR> <BR> <BR> <BR> <BR> <BR> <P>Example 23: Tetra (N-Decanoyl-L-Aspartic Acid) Tetraazacyclotetradecane Tetra- amide <BR> <BR> <BR> <BR> <BR> <BR> <BR> N-Decanoyl-L-aspartic anhydride (5.38 g, 20 mmol), tetraazacyclotetradecane (1 g, 5 mmol) and toluene (100 ml) were added to a 250 ml stirred reactor. The mixture was heated under reflux for 3 hours (nitrogen atmosphere).

The solvent was removed in vacuo giving the product as a white crystalline powder in good yield.

Example 24: Corrosion Inhibitor Performance Testing Corrosion rate data were determined using a combination of established electrochemical techniques [Linear Polarisation Resistance, Potentiodynamic Polarisation Scanning, A C Impedance Spectroscopy, Electrochemical Noise] well known in the art. Two test environments were used: 1. A test using seawater and diesel under air to simulate corrosion conditions in hydrocarbon containing systems.

2. The BP Bubble Test method, using deaerated seawater, purged with CO2, specifically to simulate corrosion conditions in oil & gas fields.

METHOD ONE: SEAWATER WITH DIESEL 1. Test solution consists of a mix of 70% standard diesel fuel and 30% ASTM seawater.

2. Test electrodes consist of three BS970: EN8 (080M40) cylindrical electrodes attached to a PTFE holder with brass rods. Rubber or PTFE seals are used. The electrode surface finish is 600 grit. Electrode dimensions are usually 15mm long by 10mm diameter 3. Place fluids into a suitably sized container and emulsify for 5 minutes using an air driven magnetic stirrer.

4. Inject the required amount of corrosion inhibitor, taking into account the active concentration.

5. Maintain the emulsion for 5 minutes.

6. Insert the electrodes into the emulsified fluids.

7. Maintain the emulsion for approximately 16 hours.

8. Turn off stirrer, and allow the fluids to separate. Ensure that all of the electrode surfaces are in the separated water phase.

9. Allow the electrodes to stabilise in the aqueous phase for a minimum of 30 minutes before commencing testing. Stability may be monitored by taking potential readings. If using identical materials; the potential difference between the working electrode

10. If required perform electrochemical noise tests at 10 Hz and 2 Hz.

11. If required perform electrochemical impedance spectroscopy test between 100mHz and l OmHz, using a wave amplitude of 10 to 20 mV.

12. Perform a cathodic potentiodynamic polarisation scan at 20mV/minute, to a potential difference of-200mV with respect to the rest potential.

13. Re-emulsify the fluids, and allow the working electrode to restabilise over a 60 minute period, and then perform an anodic potentiodynamic polarisation scan at 20mV/minute, to a potential difference of +200mV with respect to the rest potential, and then reverse 14. Allow the electrodes to stabilise in the aqueous phase for a minimum of 30 minutes before commencing testing. Stability may be monitored by taking potential readings. If using identical materials, the potential difference between the working electrode 15. On completion of the tests, examine the working electrode for signs of pitting.

METHOD TWO: THE BP TEST METHOD (SEAWATER ONLY) 1. Test solution consists of 100% ASTM seawater.

2. Test electrodes consist of three BS970: EN8 (080M40) cylindrical electrodes attached to a PTFE holder with brass rods. Rubber or PTFE seals are used. The electrode surface finish is 600 grit. Electrode dimensions are usually 15mm long by 10mm diameter 3. Place fluid into a suitably sized container, inject nitrogen into the water through a glass frit at approximately 0.5 to 1 litre/minute, and stir vigorously for one hour using an air driven magnetic flea. Suitably seal the vessel to allow gases to escape 4. Stop nitrogen injection into the water, raise the frit up into the gas phase at the top of the vessel, and continue the nitrogen flow at approximately 0.1 to 0.2 litres/minute.

5. Inject carbon dioxide gas into the bottom of the vessel at a slow rate -approximately 0.1 to 0.2 litres/minute, and continue for the entire test duration.

6. Inject the required amount of corrosion inhibitor, taking into account the active concentration.

7. Maintain stirring for 5 minutes.

8. Insert the electrodes into the fluid.

9. Maintain stirring for approximately 16 hours.

10. Turn off stirrer. Ensure that all of the electrode surfaces are in the water.

1 l. Allow the electrodes to stabilise in the aqueous phase for a minimum of 30 minutes before commencing testing. Stability may be monitored by taking potential readings. If using identical materials, the potential difference between the working electrode 12. If required perform electrochemical noise tests at 10 Hz and 2 Hz.

13. If required perform electrochemical impedance spectroscopy test between 100mHz and 1 OmHz, using a wave amplitude of 10 to 20 mV.

14. Perform a cathodic potentiodynamic polarisation scan at 20mV/minute, to a potential difference of-200mV with respect to the rest potential.

15. Allow the working electrode to re-stabilise over a 60 minute period, and then perform an anodic potentiodynamic polarisation scan at 20mV/minute, to a potential difference of +200mV with respect to the rest potential, and then reverse the scan back to the rest 16. On completion of the tests, examine the working electrode for signs of pitting.

Table 1. Corrosion Inhibitor Performance Test Results Inhibitor Solvent Active method 1: Method 2: Concentration (ppm) hydrocarbon/water/air seawater/carbon dioxide Corrosion Rate Efficiency Corrosion Rate Efficiency (mm yr-1) (%) (mm yr-1) (%) Example 2 water 50 0.0004 99.62 0.0145 90.40 20 0.0061 94.13 Example 5 shellsol 50 0.00986 90.52 Example 6 toluene 50 0.00248 97.62 0.0102 93.25 water 0.00361 96.53 toluene 10 0.0959 54.33 water 0.0583 72.24 Example 7 toluene 50 0.0149 90.13 water 0.0578 72.48 Example 9 toluene 50 0.0229 84.83 water 0.0523 75.10 0.052 65.56 toluene 20 0.0279 81.52 Example 10 toluene 50 0.0325 84.52 0.00771 94.89 water 0.0231 89.00 0.00821 94.56 water 0.0153 89.87 0.0187 87.62 Example 12 water 50 0.0522 75.14 0.0169 88.81 toluene 0.0492 76.57 0.0252 83.31 water 0.0368 75.63 Example 13 water 50 0.0199 80.87 0.0499 66.95 shellsol 0.0061 94.13 0.0774 48.74 Example 14 water 50 0.00454 95.63 0.0158 89.54 shellsol 0.00686 93.88 0.0441 70.79 water 0.0489 67.62 shellsol 10 0.0199 90.52 water 0.0135 87.02 0.0507 66.42 Example 15 water 50 0.0145 86.06 0.0339 77.55 10 0.0515 75.48 Example 16 water 50 0.0187 82.02 0.00839 94.44 10 0.0284 72.69 0.0321 78.74 Baseline Corrosion 0.104 0.15 Rate CRUNINHIBITED-CRINHIBITED<BR> %Efficiency= #100<BR> CRUNINHIBITED

Example 25: Scale Inhibitor Performance Testing The NACE International Standard Test Method TM0374-95 was used to assess the ability of some of the molecules according to the present invention, in prevention of the precipitation of calcium carbonate scale from solution (for oil and gas production systems).

The calcium concentrations of the filtrate supernatant were determined either by titration with EDTA or atomic absorption spectroscopy according to ASTM Method D 1126-96 (Standard Test Method for Hardness in Water).

Compounds according to the invention herein (Table 2) show good scale inhibition properties. Without being bound by theory it is believed that scale inhibition efficiency (%) illustrates Ca"complexing ability.

Table 2 NACE CaCO3 Scale Inhibition Test Results

Example 26: Biodegradability Testing Biodegradability was assessed in a 28-day biological (biochemical) oxygen demand screening test. The extent of biodegradation, the % biodegradability is expressed as the ratio BOD/COD (mg g-l) as a %. Results are given for selected inhibitors in Table 3.

Table 3 Biodegradability Results Inhibitor % Biodegradability Day 7 Day 14 Day 28 Example 1 66. 9 70. 2 84. 9 Example38.754.128.1 Example13 26. 0 32. 9 42. 4 Example 14 30. 0 39. 2 40. 9 Example15 45. 4 45. 8 54. 9 Example16 44. 8 51. 3 57 reference 74. 7 83. 4 89. 3