Fatty Imidazolines: Chemistry, Synthesis, Properties and Their Industrial Applications

＊ Divya BAJPAI and V.K. TYAGI Department of Oil and Paint Technology, Harcourt Butler Technological Institute (Kanpur- 208002, INDIA)

Edited by A. Noda, Shiseido Co., Ltd., and accepted January 5, 2006 (received for review December 19, 2005)

Abstract: Imidazoline surfactants belong to the category of cationic surfactants. Cationic surfactants are often quaternary nitrogen salts and are widely used both in non aqueous systems and in applications such as textile softeners, dispersants and emulsifiers. In the class of imidazoline compounds there is a presence of a pendant group, an imidazoline head group and a hydrocarbon tail. This paper reviews the imidazoline and its salts as an emerging class of cationic surfactants. It deals with the synthesis, various properties that prove its use in laundry detergent applications like good detergency, resiliency, foaming property, softening property, rewettability, good storage stability and less irritating property. In addition the film forming and corrosion inhibition properties tend them to varied and numerous industrial applications. Key words: imidazoline, fabric softener, laundry detergent, resiliency, biodegradability

1 Introduction 2Types of Imidazolines

Imidazoline surfactants belong to the category of 2･1 Cationic Imidazolines cationic surfactants. Cationic surfactants first found use The Cationic imidazolines have positive charge on as dye leveling agents in the textile industry in 1930s imidazoline nucleus and the electrical charge on the and their softening properties were discovered as side molecule is unaffected by pH changes. Positive charge benefit. Cationic surfactants are often quaternary nitro- remains in acidic, neutral and alkaline medium. They gen salts and are widely used both in non-aqueous sys- are used as textile softeners industrially and for home tems and aqueous systems. In household products, the use in the rinse cycle of washing machines and as water cationic surfactants are primarily applied in fabric soft- repellents, anti-corrosives, emulsifiers and dispersing eners, hair conditioners and other hair preparations. agents. This group include: Other applications of cationic surfactants include disin- 2･1･1 Hydroxyethyl imidazolines fectants, a wide variety of speciality materials, and are These type of cationic imidazolines are based on usually classified into fatty amine salts, fatty diamine fatty acid/aminoethyl ethanolamine in the ratio of 1:1 salts, quaternary ammonium compounds and imidazo- and are used as rheology modifiers, oil soluble,water line salts. Substituted imidazoline compounds possess soluble salts and adhesion promoters in lubricants, road desirable storage stability, viscosity, dispersibility and making, paint and ink industries. e.g. hydroxyl ethyl fabric conditioning properties(1) and are useful in laun- imidazoline. dry applications and various industrial applications.

＊ Correspondence to: V.K. TYAGI, Department of Oil and Paint Technology, Harcourt Butler Technological Institute, Kanpur- 208002, INDIA E-mail: [email protected], [email protected]

Journal of Oleo Science ISSN 1345-8957 print / ISSN 1347-3352 online 319 http://jos.jstage.jst.go.jp/en/ D. Bajpai and V.K. Tyagi

2･2･2 Alkyliminopropionates These may be obtained by the addition of ethyl acrylate to the reaction product of fatty acids and amines. e.g. disodium lauroamphodipropionate. 2･1･2 Aminoethyl imidazolines These types of cationic imidazolines are based on fatty acid/diethylenetriamine in the ratio of 1:1 and are used as corrosion inhibitiors, dispersants, dewatering agents and emulsifiers in oil fields, metal working, tex- 2･2･3 Alkylamphopropionates tiles and paper industries. e.g. aminoethyl imidazoline. These may be obtained by the addition of acrylatic acid to the reaction product of fatty acids and amines. e.g. sodium lauriminodipropionate.

2･1･3 Amidoethyl imidazolines These type of cationic imidazoline are based on fatty acid/diethylenetriamine in the ratio of 1:1 and are used as textile softeners, acid stable detergents and floccula- 3 Chemistry of Imidazolines tors in agriculture, maintenance chemicals and lapping compounds. e.g. amidoethyl imidazoline. Chemically imidazoline compounds belong to the heterocyclic compounds containing five membered ring having two nitrogen atoms in the ring. Cationic imidazolines are the ammonium mono quaternary salts of RnN+X– type that have an asymmetrical structure (according to the tetrahedral carbon scheme) determined by the cation. They are optically active in aque- 2･2 Amphoteric Imidazolines ous solution in which they are ionized (2). Chemically amphoteric imidazoline derivatives don’t Substitution of imidazolines takes place in the 1-, 2- have imidazoline ring in the molecule but during syn- & 3- positions (Fig. 1) with a fatty acid aminoethyl thesis of such compound, an intermediate imidazoline chain at the first position of ring, a long chain alkyl sub- ring structure formed , hence called imidazoline deriva- stituent at the second position and a methyl group at the tives.The derivatives of amphoteric imidazolines have third position (3). both of the charges on molecule and may show the The most widely used representative of this group is properties of anionics imidazolines at high pHs and the tallow alkyl derivative. It is applied as a liquid and those of cationics at low pHs and are used in products is easily processed to fabric softeners. Other approxi- like hair shampoos, liquid soaps and shower gels. Other mate composition of the fatty alkyl groups are given in major applications of this group include highly acidic Table 1 (5). and alkaline household cleaning agents. This group The unsaturated C18 contains one double bond in a include : cis isomer configuration “Unsaturation” in a fat tends to 2･2･1 Alkylamphoadiacetates lower the melting point and make it a liquid at room

These may be obtained by the addition of methyl temperature. The saturated C18 contains no double acrylate to the reaction product of fatty acids and bonds, giving rigidity to the molecule, raising the melt- amines. e.g. disodium lauroaphodiacetate. ing point and reducing fluidity. In general, imidazoline compounds present a pendant group, an imidazoline head group and a hydrocarbon tail, as shown in Fig. 2. Recent molecular modeling (6- 11) studies suggest that the head and pendant group promote bonding of the molecule to the surface, while

320 J. Oleo Sci., Vol. 55, No. 7, 319-329 (2006) Fatty Imidazolines: Chemistry, Synthesis, Properties & Industrial Applications

Fig. 1 Structure of Imidazolines. Fig. 2 Molecular Structure of Imidazolines. the hydrocarbon tail forms a protective monolayer. surfactants that were first introduced, in which 1-(2 Recent molecular modeling studies suggest that the hydroxy)-2-alkyl -imidazoline (H.E.A.I) was allowed to head and pendant group promote bonding of the react with sodium mono chlorate. molecule to the surface, while the hydrocarbon tail The production of the imidazoline compounds (12, forms a protective monolayer. 14) starts from fatty acid and diethylene triamine. They Introduction of extra nitrogen atom into the hetero- are condensed under ring closure and the imidazoline cyclic molecule imparts to the imidazoline and imida- formed is then converted with dimethyl sulfate to the zolidine nucleus, some specific features and advan- imidazolinium salts (Scheme 2). By condensation of tages, including increased ability to functional deriva- triethylene tetra amine with fatty acids and subsequent tion. The latter allows to study chemical reactions of ring closure with additional acid, 1, 3 bis (fatty acid various functional group of imidazoline radicals pro- amido ethyl)-2-alkyl imidazolinium salts are obtained. ceeding without loss of their paramagnetic properties. These bis-amidoethyl substituted imidazolinium deriva- Common reactions of ammonium quaternary salts of tives are particularly suitable for crystallization (15). imidazoline are Hoffman eliminations, rearrangements A large number of scientists synthesized imidazo- and displacing. Imidazoline ammonium salts react with lines by using different fatty acids and amines and stud- all organic and inorganic salts forming neutral salts that ied their performance in different fields of research. have got a rather great molecular weight and are always Cationic imidazoline (16) surfactants have been syn- non water soluble. thesized by H. Sheng Zhong. For this purpose, palmitic

4 Synthesis of Imidazoline and Its Salts If the amido amine is merely heated to a higher temperature, instead of being aloxylated, ring closure occurs at 350˚F to 450˚F as shown in Scheme 1 (12). Mannheimer(13) in 1950 synthesized imidazolinium

Table 1 Approximate Composition of the Fatty Alkyl groups.

C18 C18’ C14 C16 Stearyl Oleyl Oleyl 5 20 75 Tallow 5 30 20 45 Hydrogenated tallow 5 30 65 Stearyl 5 95 Scheme 1 Synthesis of Imidazoline.

321 J. Oleo Sci., Vol. 55, No. 7, 319-329 (2006) D. Bajpai and V.K. Tyagi

dimethyl iminoethyl methacrylate and dodecyl bromide. The final quaternary compound can polymerize at the ethylenic function of the compound. The polymerisable compound had a critical micellar concentration of 6 Ã－ 10-5 m/litre. The electrical conductivity study revealed that there were three regions in the micro emulsion, viz., W/O region 20%, a bicontinuous region 20-65%; and an O/W region 65%. F. Wang has described the properties of alkyl imidazoline ester softener and of its quaternary ammonium salt. It appears that it is made by using a fatty acid, hydroxy ethyl amino ethylene diamine, a carboxylic acid (perhaps benzoic acid or phenyl acetic acid) and epichlorohydrin (or dimethyl sulphate). Two other derivatives were made by the above scientists, which were same as above but the quaternizing agents are interchanged (DMS and epichlorohydrin). This compound has softening antistatic and rewetting properties. The quaternary compound has good properties and is easy to formulate products of high concentrations and of low viscosity. Scheme 2 Synthesis of Quaternary Ammonium Salts Popa et al. (17) produced quaternary salts of 1, 2-di of Imidazoline. substituted imidazoline derivatives. They produced mono substituted Imidazoline derivatives by using lau- ric acid & stearic acid as fatty materials & ethylene di acid and diethylene triamine (DETA) were reacted amine, results into 2-lauryl-2-imidazoline and 2-stearyl- under reduced pressure to form 2-alkyl-l-amino ethyl 2-imidazoline. Which on reaction with propylic alcohol imidazoline, a ring compound. Then dimethyl sulphate give 1-acrylonitrile-2-lauryl-2-imidazoline & 1-acry- (DMS) was added drop wise and the quaternary com- lonitrile-2-stearyl-2-imidazoline and after quaterniza- pound, i.e., cationic imidazoline surfactant was tion with benzyl chloride these compounds give 1-ben- obtained. Reaction temperature, pressure and operation zyl-1-acrylonitrile-2-lauryil-2-imidazoline and 1-ben- time were studied. The yield under optimum conditions zyl-1-acrylonitrile-2-stearyl-2-imidazoline. These com- was 85% and the purity of the product was 93%. pounds are found to be good washing agents, dispers- A new cationic surfactant has been synthesized by K. ing, foaming agents, antistaticing agent, emulsifiers and Yne. This was made from benzoic acid, DETA, stearic disinfecting agents. acid and epichlorohydrin acid cyclisation to give an Uphues et al. (18) prepared surface alkyl (hydroxyl imidazoline derivative, reduction, ring opening, amida- alkyl) imidazoline derivatives as low viscosity solution, tion and quaternization. The reduction-ring opening in which a 2-alkyl-1-(2-hydroxy ethyl)-2-imidazoline conditions include molar ratio of the imidazoline inter- (alkyl contains 5-21 carbon) is quaternized or carboxy mediate to sodium borohydride (NaBH4, a strong reduc- methylated at pH 7.5-9 with a halogen containing car- ing agent) 1:2; reaction temperature, 20 ℃ for 1 hour at boxylic acid salts and simultaneously hydrolyzed with pH 7 in isopropanol (IPA), acting as a solvent. : aqueous base and the solution containing the reaction Another product is reported and is made by the same product is adjusted to pH 5-7 give a surfactant having a reaction, except that benzoic acid is replaced by phenyl low viscosity stability during storage. acetic acid. Walley et al. (19) also used stearic acid as fatty mate- In another case, P. Jiang, have synthesized new types rial in the synthesis of imidazolinium compound but of polymerisable dimethyl dodecyl methacryloyl ethyl instead of using ethylene di-amine they used hydroxy di ammonium bromide, which was prepared from ethylene di amine as base. In this exercise, a mixture of

322 J. Oleo Sci., Vol. 55, No. 7, 319-329 (2006) Fatty Imidazolines: Chemistry, Synthesis, Properties & Industrial Applications

2 mol of amine and 1.5 mol of stearic acid was heated water soluble and those that contain two or more radi- for 18 hrs at 165 ℃ and then for 4 hrs at 165 ℃ /0.2 cals with long chain are almost water insoluble, but sol- mm . The mixture was then cooled down to 120 ℃ and uble in non polar solving agents. More clearly, with treated with 1.5 mol of methyl stearate and again heated increasing molecular mass, the solubility in polar sol- for 24 hrs at 170 ℃ to give high yield of product, which vent diminishes and the solubility in non polar solvents was found to be very useful in liquid and solid compo- increases. The existence of polar groups, hydroxyl or sitions for softening laundered fabrics during rinsing or ethyl ether, in the compound structure, can increase the machine drying. solubility in polar solving agents. Hitz et al. (20) synthesized imidazoline derivatives Imidazoline are thermally stable organic nitrogenous by using C8-18 saturated and unsaturated fatty acids. bases. The unneutralized imidazolines being lipophillic They used 1 mol of corn oil as fatty material, 3.6 mol of are soluble in non polar solvents & mineral oils but hydroxyl di ethylene di amine and 6.6 mol of acrylic only dispersible in aqueous system. acid for this purpose. Imidazolinium compound made by using corn oil showed good mildness to skin and 5･3 Strongly Cationic eyes and were found to be very useful in detergents, Imidazolines are strongly cationic chemical com- shampoos and cosmetics. pound. The ability of imidazolines to form cations Cretu et al. (21) synthesized quaternary ammonium means they are strongly adsorbed on to negatively salts of disubstituted Imidazoline by quaternizing imi- charged surfaces of metals, fibres plastics, glass & min- dazoline derivatives with dihaloalkanes in the ratio of erals; thereby these hydrophilic surfaces are converted 1:1.5-6.5. They heated the reaction mixture at 1-5 atmos- to hydrophobic surfaces. pheric pressure and 80-140 ℃, optionally in alcoholic solvent. Thus 175 parts of 1.2 dichloroethane was 5･4 Acid Stable Detergent added in 30% isopropanolic solution of disubstituted Imidazoline salts are much more hydrophilic then imidazoline and the reaction mixture was heated at 70- their bases and functions as acid stable detergents with 80 ℃ for 2 hrs and then for additional 10 hrs to give good wetting agents. yellow quaternary ammonium salts of imidazoline, which showed better softening, antistatic effect on tex- 5･5 Good Water Propellant tiles and was also to be good corrosion inhibitors. Imidazolines are also found to be good water propellant. Imidazoline as a free base or aqueous dispersion of the acid will impart water resistance to surface such as 5 Properties of Imidazolines wood, concrete, plastics and metals. 5･1Physical Properties Most of the ammonium quaternary salts of imidazo- 5･6 Good Lubricity line are solid substances that have not defined smelting Imidazolines also show good lubricity to form com- point. Aliphatic quaternary salts with long chain (>C8) plexes with bentonites. Oleic acid salts of imidazolines are solid, crystalline of white color, sometime they are are used as a good lubricant. In addition imidazoline colorless, inodorous. When they contain an unsaturated may also be compatible with aqueous system. The film aliphatic radical with long chain or benzyl radical, they forming & corrosion inhibition properties tend them- are viscous liquids colored from light yellow to brown. selves to numerous and varied industrial applications. The quaternary salts of imidazoline that contain alkyl Metal surfaces are treated with stearic acid salts of imi- group of 10 atoms of carbon present supercritical active dazolines for such applications. Amido-ethyl imidazo- properties. lines are more resistant to corrosion during processing.

5･2 Solubility and Thermal Stability 6 Laundry Detergent Application of Solubility of the salts of imidazolines depends on the Imidazoline Derivatives substituent types. Those compounds that contain radicals with short chain (C8-14) are easily water soluble, Nowadays laundry detergent are becoming increas- those that contain radicals with long chain are less ingly popular for laundry work as they can be metered

323 J. Oleo Sci., Vol. 55, No. 7, 319-329 (2006) D. Bajpai and V.K. Tyagi automatically into the washing machine .Imidazolines positions by using imidazolinium compounds and stud- have many and varied applications as laundry detergent. ied their performance. For above purpose they treated Properties of imidazolines as laundry detergents are as isostearic acid with DETA to give 1 Methyl-2-heptade- follows: cyl-3-(2-isostearyl amino ethyl) imidazoline methosul-

phate. 6% of which was mixed with 94% of H2O to 6･1 Fabric Softness and Resiliency obtain the softening agent. A washed cotton knit, when Softeners are “an auxillary that when applied to tex- treated with this softening agent showed good softness. tiles materials improves its handle with more pleasing Hayase et al. (25) studied the performance of laundry to touch” Softening of textile fabrics is generally detergent compositions of organic salts or quaternized achieved by reducing the co-efficient of friction derivatives of imidazolines made up of C11-23 unsaturat- between the fibres, filaments or yarns. Chemically soft- ed hydrocarbyl fatty materials. A laundered cotton eners are surface active agents with long chain towel, when treated with aqueous dispersions of above hydrophobic part and a short chain hydrophilic polar compositions, dried and settled at 25 ℃ and 65% rela- water solubilizing group. Straight chain derivatives are tive humidity for 24 hrs, showed better softness and better then branched chains and unsaturation in the fatty resilience. alkyl groups reduces softening. Yamamura et al. (26) studied the performance of sur- The cationic fabric softeners are nitrogen containing factants made from Imidazoline, for imparting compounds which include imidazolines, amino improved resilience to fabrics. The title composition polysiloxanes and quaternaries. Conventional fabric contained (A) 3-30 % Imidazoline and their salts made softeners contain 1-9% of quat or imidazolinium com- up of C11-18 carbon chained alkyl or alkenyl fatty materi- 1 2 pounds in addition of preservatives, sometimes optional als and their salts. (B) 0.1-5% fatty acid esters R CO2R brighteners and other additives. (R1=H, Me, Et, alkali and alkaline earth metal; R2=

Imidazolines compounds are second to quaternary C11-18 alkyl or alkenyl imidazoline and their salts). (C) ammonium compounds in tonnage of cationic surfac- 0-2% ethylene oxide adducts of C8-22 higher alcohols. tants, produced for fabric softener. In practice imidazo- Thus a laundered cotton towel was rinsed using aque- line compounds are frequently blended with distearyl ous solution (pH=2) of above composition and additives dimethyl ammonium compounds to attain higher degree , dried and conditioned at 25 ℃ and 65% relative of softening performance. humidity for 24 hrs showed good softness and Many scientists have produced fabric softeners by resilience. using imidazoline derivatives and studied their performance in different laundry compositions. 6･2 Dispersibility Yamamura Masaki(22) studied the performance of a Dispersibility is a property of materials to inhibit composition comprises (A) 3-30% fatty imidazolines agglomeration or settling of solid particles in a fluid 2 C11-21 alkyl or alkenyl; X=OCOR ) or their salts (B) 0.1- medium. In particular, dispersants are useful in prevent- 4 3 3 5%>= of R CO2R (R =H, Me, Et, alkali metal, alkali, ing depositions, precipitation, agglomeration, caping earth metal;R4=R1).(C) 0-2% hydroxy imidazolines or etc. their salts and (D) 0.5-5% 3-50 mole ethylene oxide When imidazolines are mixed with positively adducts of C8-22 higher alcohols, monoamines or charged products a dispersing effect is observed. Solid diamines. A laundered towel when treated with aqueous fabric softeners comprise of mixtures of imidazoline solution of above composition, showed good softness derivatives showed improved dispersibility in water and resilience at 25 ℃ and 65 % relative humidity for (12). 24 hrs. Kolomeits et al. (27) gave the method for preparing Baker et al. (23) studied the performance of deter- foaming and/or dispersing agent for synthetic detergent plus softener made up of imidazoline derivatives gents. In the above method dispersing/foaming agents obtained by reacting C12-22 fatty acids, which provide were prepared by acylating imidazoline derivatives with good cleaning & fabric care benefits to textiles includ- 1-2.2 equivalent maleic anhydride in the presence of ing static control and softening properties. 0.1-6.0 equivalent water at 50-80 degree for 15-40 min

Tsumaderi et al. (24) produced fabric softener com- and sulfonating with Na2CO3 at 60-90 ℃ for 2-6 hrs,

324 J. Oleo Sci., Vol. 55, No. 7, 319-329 (2006) Fatty Imidazolines: Chemistry, Synthesis, Properties & Industrial Applications which showed good foaming and dispersing properties, 6･5 Rewettability when added to surfactants. Rewetting properties are important because they give Hasegawa et al. (28) studied the performance of fab- an indication of the absorbency of fabrics after treat- ric softeners compositions of imidazoline derivatives. ment with fabric softeners. The softener composition of 40-90.99% of 95*, 0.5-90 Yamamura Masaaki (33) prepared fabric softeners of wt ratio of mixture of imidazoline derivatives, made up imidazolinium compounds and studied their hygrosco- of C11-22 linear or branched fatty acids of alkyl, alkenyl picity. They treated laundered cotton towel with aqueous or optionally contained hydroxyl group; 0.1-6.0% urea, solution of composition containing 10% of quaternized urea derivatives, p-tolune sulfonic acid salts; water sol- imidazolinium compounds made up of stearic acid fatty uble inorganic salts and polyxylene compounds. This material, quaternized with MeCl and 0.2% di Me sili- composition showed improved dispersibility when cone, for 5 min at 25 ℃ and found to have improved added to surfactants. softness with good hygroscopicity.

6･3Antistaticness 6･6 Bleach Activators The measurement of the dissipation of the static Gosselink Eeugene P et al. (34) studied the com- charge from fabric is difficult to say the least. Many pounds containing 1 quaternary ammonium group. + factors influence this measurement including the e.g.1,4-[R(CH2)5N Me2CH2]2C6H4 2Cl, [R-p- C6H4 CH2 + – + – amount of buildup of static charge, the relative humidi- N Me2(CH2)3]82Cl or [R-p- C6H4 CH2 N Me2(CH2)]5R’Cl ty, and the time from maximum buildup and the time of (R=2-oxo-1-azacyclohept-1-yl carbonyl) are used with measurement. Imidazolines are known to have antistatic a source of H2O2 in bleaching compositions, laundry properties in both their salts and quaternized forms detergents, automatic dish water detergents etc. The (12). activators give advantageous ratios of rate of perhydrol- Lambert et al. (29) studied the performance of imida- ysis and rate of diacyl peroxide formation. zoline based surfactants and found to be good antistatic agents in laundry detergents. 2-(C8-24 alkyl or alkyl 6･7 Biodegradability aryl)-1-(2-hydroxyethyl)-1-H imidazolines were used in Detergent surfactants represent one of the best inves- detergent to impart softness and antistatic properties to tigated groups of chemicals in terms of their environ- laundered fabrics. mental fate and effects.Complete microbial degradation Rosario et al. (30) studied the fabric softening and of these chemicals exhibit common structural character- antistatic properties of compositions containing quater- istics. The hydrophilic moiety of anionic, non-ionic, nized disubstituted imidazoline esters and found that cationic and amphoteric surfactants is different, their the compositions contained imidazolines made up of hydrophobic part generally consists of a single linear or stearic acid fatty material, MeCl and HCl showed good 1-methyl-branched alkyl chain (C8-18). Consequently, storage stability, viscosity, softening and antistatic prop- the common principle of the microbial degradation of erties and more specially useful in rinse cycle during surfactants is either an enzymatic cleavage of the two laundering. surfactant molecule moieties (forming a fatty alcohol /acid and a hydrophilic organic or inorganic degradation 6･4Mildness to Eyes and Skin product) or is a terminal oxidation and subsequent step- Pomares et al. (31) prepared surfactants made up of wise degradation of the alkyl chain (leaving again a imidazolines and studied their effect to eyes and skin. hydrophilic degradation product). Both mechanisms Surfactant compositions made up of imidazolinium lead to products exhibiting a less complex structure and compounds showed low irritatibility to eyes and skin. more hydrophilic properties than the parent compound. Kubo et al. (32) synthesized amido/amino acid sur- Hence, the two structural moieties of every surfactant factants for shampoos and hair conditioners. For this are well known and can be assessed in terms of their purpose they used hydrolyzed product of 268 gm of 1- accessibility to biodegradation. hydroxyethyl-2-undeculimidazoline and found to have Comprehensive studies into the biodegradation path- good detergency with low irritatibility to eyes and skin. ways and metabolite formation have been published for many major surfactant groups used in detergents. Such

325 J. Oleo Sci., Vol. 55, No. 7, 319-329 (2006) D. Bajpai and V.K. Tyagi information is available for anionic surfactants (LAS, resistant to corrosion during processing. alcohol ether sulfates, alcohol sulfates, methyl estersul- fonates, secondary alkane sulfonates/ olefin sulfonates), 7･2 Emusifiers non-ionic surfactants (alcohol ethoxylates) and several Sanders et al. (37) studied the emulsifiers containing cationic surfactants. In cationic quaternary ammonium the imidazolinium salts that are useful in stabilizing surfactants, compounds with one linear alkyl chain microemulsion. Thus the title compound was mixed attached to the nitrogen degrade faster than those with with compound from oleic acid, safflower oil fatty acids two, and these degrade faster than those of three .The and the mixture was used in a microemulsion of paraf- replacement of methyl group attached to the nitrogen finic oil. by a benzyl group retards the rate of degradation slight- ly. Pyridinium compounds biodegrade significantly 7･3 Corrosion/ Rust Inhibitors more slowly than the corresponding tri methyl ammoni- There are many active inhibitor intermediates present um compounds while imidazolinium compounds biode- in the market. They are based on a few generic types of grade rapidly. chemistries , namely, imidazoline, amide, amidoamide Hayase et al. (35) studied the performance of storage and amine. stable liquid compositions containing biodegradable Imidazolines are widely used in the oil industry as softening agents for fabrics. The title compositions con- corrosion inhibitors, however their properties and tain an acid neutralized amine having 1-2 ester groups behaviour in such complex environment is far from as well as product of the reaction of an alkyl amine with being well known from a scientific point of view. For ethylene oxide and/or propylene oxide and/or a com- example, the mechanism by which these compounds pound having a long chain hydrocarbyl group, a N prevent corrosion is not entirely understood and their atom, and an ester group, amide group, and/or imidazo- obviously good performance has been only recently line ring in the molecule as softening agent which also supported by experimental evidence (38-44) and inves- impart antistatic properties and resilience to fabrics. tigated by molecular modeling techniques (6-11) this is because they are used in low concentrations and operate 6･8 Reusability in complex environment. For the very same reasons Kota and Kenjeiro (36) prepared the reusable nonwo- their quantification in produced water is particularly ven fabric softeners for washed garments in dryers. The difficult and only recently attempted (45- 48). title softeners are prepared by coating nonwoven3-9:7-1 The adsorption of imidazoline salts onto metal sur- rayon polyester blend fabrics with aqueous mixture of faces will displace any water and form a monomolecu- imidazolinium salts. This fabric softener was used to lar hydrophobic layer on the surface. The most effective soften undergarments in a dryer for 2 cycles and gave system for this type of application would be a solution good results. of imidazoline in oil, as the oil is also to the surface. The protective coating is resistant to aqueous and acid corrosion. 7 Other Industrial Applications Imidazoline may be incorporated into lubricants for 7･1 Lubricant Emulsions metal working, where it will function as an emulsifier Imidazolines have various applications in the prepa- and corrosion inhibitor. Best results would be obtained ration of lubricant emulsions where they are known to using a blend of hydroxyl ethyl imidazolines and amido act as emulsion, stabilizers, and corrosion inhibitors and ethyl imidazolines. improve the lubricity of oils. Imidazolines are recom- mended as oils and waxes emulsifiers for application in 7･4 Skin Preparations paper, textile and metal working industries. Imidazo- Skin preparations (49) for external use according to lines, or their chloride or acetate salts, are capable of the present invention are preferably used in combina- acting as both emulsifiers and corrosion inhibitors. The tion with amphoteric surfactants, among which imida- oleic acid salt of imidazoline is known to have applica- zoline-based amphoteric surfactants are especially pre- tions in tube and wire drawing. Metal surfaces which ferred. As used herein, the “imidazoline-based ampho- have been treated with imidazoline will be much more teric surfactants” refer to amphoteric surfactants con-

326 J. Oleo Sci., Vol. 55, No. 7, 319-329 (2006) Fatty Imidazolines: Chemistry, Synthesis, Properties & Industrial Applications taining an imidazoline ring in their molecules and 7･7 Acid Cleaners amphoteric surfactants having an opened imidazoline Imidazoline, phosphoric acid, and kerosene are the ring. Examples of imidazoline-based amphoteric sur- basis for good metal cleaning formulations. This type of factants include 2-alkyl-N-carboxymethyl-N-hydrox- product will clean the metal and deposit a corrosion yethyl imidazolinium betaine, sodium N-cocoyl-N’-car- resistant film to inhibit further attack. boxylethyl-N’-hydroxyethyl ethylenediamine, disodium N-cocoyl-N’-carboxymethoxyethyl-N’-carboxymethyl 7･8 Dewatering ethylenediamine and disodium N-cocoyl-N’-car- Imidazoline in low concentrations in hydrocarbon or boxymethoxyethyl-N’-carboxymethyl ethylenediamine chlorinated solvents, will remove traces of water from lauryl sulfate, among which 2-alkyl-N-carboxymethyl- steel or brass surfaces and deposit a protective coating N-hydroxyethyl imidazolinium betaine is especially which inhibits further corrosion. preferred. Imidazoline-based amphoteric surfactants are prefer- 7･9 Flocculants ably used in the amount of 0.01-50 parts by weight, The positive charge of imidazoline salts will neutral- more preferably 1-30 parts by weight, even more ize negative charge of certain silicates. An aqueous sus- preferably 3-5 parts by weight per part by weight of pension of colloidal silica can be precipitated by the propylene glycol hyaluronate esters of the present addition of imidazoline salts. Anionic detergents may invention. Compositions containing a propylene glycol also be eliminated from effluent streams using imidazo- hyaluronate ester of the present invention and an imida- lines. zoline-based amphoteric surfactant are characterized by less change in viscosity during storage because of their 7･10 Oil and Grease Thickeners high stability. Especially, propylene glycol hyaluronate Imidazolines are known to form complexes with ben- esters having an esterification degree of 40-60% pro- tonites and thus may be used as thickening/ gelling vide higher stability as compared with lower esters. agents for paraffin wax and paint system.

7･5 Car Washing 7･11 Biocidal Enhancement Automatic car washes often include a final rinse Imidazolines can be used to make salts of pen- which renders the car bodywork water repellent. Tradi- tachlorophenol which allows application to ropes etc to tional oil/solvent based rinse aid concentrates can be prevent mildew. prepared as follows: Imidazolines 28.2% 7･12 Agricultural Spray Acetic Acid 9.5% Insecticides and other products for application by Methylcyclohexonol 15.9% spray to their land may be emulsified into water by imi- Mineral seal oil 18.9% dazoline.

Alcohol Ethoxylate (C10+5EO) 7.6% ButylOxitol 19.9% 7･13 Paint Applications The incorporation of imidazolines into paint is The above product is a concentrates can be diluted in known to improve adhesion of paint even to wet sur- water (10-30%) to desired concentration and used faces. Water proofing properties are also improved. through brush wash system at 200-400 times dilution. 7･14 Pharmacology 7･6Water Repellents Zebrowska et al. (50) studied the pharmacological Imidazoline applied either as the free base in non value of imidazolines derivatives. These compounds polar solvent or aqueous dispersions of the acid salt will when tested in mice and rats, they were found to have impart water resistance to surfaces such as wood, con- central nervous system depressant activity; they crete, plaster and metal. decreased locomotor activity, prolonged hexabarbital sleeping time, and had anticonvulsant and antisero- toninergic activities. The toxicity of the compounds was

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