Abstract:
This invention relates to liquid compositions and methods of using them for removing coatings from coated metal surfaces, particularly metals, and especially those metals subject to attack by corrosive liquids. The compositions comprise from one-fourth to about 10% by weight of alkali metal hydroxide, from 40 to about 60% by weight of at least one liquid high boiling oxygenated solvent, and from 40 to about 60% by weight of at least one liquid high boiling amine. Optionally, the compositions may contain from one-half to about 20% by weight of a surface active or wetting agent. 
     The method of use comprises applying the anhydrous liquid composition to the coated object at a temperature from ambient up to the boiling point of the composition for a time sufficient to loosen or remove the coating.This application is a continuation-in-part application of Ser. No. 887,422, now abandoned, filed Dec. 22, 1969.

Description:
BACKGROUND OF THE INVENTION. 
     This invention broadly relates to coating stripping compositions and methods of removing coatings from surfaces, particularly metals which are subject to corrosion. More specially, the invention relates to removing enamels, acrylic lacquers, zinc chromate primers, epoxy coatings and polyurethane coatings from metals such as aluminum, magnesium, titanium and steel. 
     In the prior art the methods of removing such compositions from the listed metals have generally involved the use of corrosive materials such as nitric acid, sulfuric acid, chromic acid and hydrofluoric acid and aqueous alkaline solutions. It is apparent that these materials are not only difficult to handle but tend to corrode and deteriorate metals. Therefore, the removal of difficult to remove coatings from metals has formed a particularly difficlt problem for the art. Other paint and resin stripping compositions have relied on various combinations of organic solvents with or without the use of water and with or without alkali metal hydroxides. Patents relating to such stripping compositions and processes are Nos. 2,662,837, 2,710,843, 2,755,209, 2,898,246, 2,940,877, 2,992,995, 3,058,918, 3,216,945, 3,321,407, 3,324,039, 3,322,677, and 3,417,025. These compositions and processes have not been completely satisfactory. 
     This invention avoids these problems and provides a non-corrosive anhydrous stripping compositions adapted for use in removing coatings such as enamels, acrylics, epoxy, zinc chromate primers, epoxy-polyamide coatings and polylurethane coatings from metals. 
     SUMMARY OF THE INVENTION 
     The compositions and processes of our invention are especially useful in removing paint, resin and polymer coatings from coated surfaces, especially metals without corroding the surfaces. The compositions and processes are particularly suited for removing coatings from metals such as aluminum, magnesium and titanium which have been vulnerable to corrosion by many of the prior art compositions. The compositions and processes are also applicable to steel surfaces. 
     The compositions of our invention are in the form of liquid solutions or dispersions. The compositions are also anhydrous. By anhydrous is meant that there is less than 1% by weight of water present in the compositions. 
     The compositions of our invention comprise mixtures of at least one member from each of three chemical groups. In addition, each chemical group is present in the compositions within specified weight percentage ranges. The chemical groups and their weight percentage ranges are: 
     Alkali metal hydroxides -- one-fourth to about 10 %, liquid high boiling amine -- 40 to about 60%, and liquid high boiling oxygen containing organic solvent -- 40 to about 60%. 
     The alkali metal hydroxides are preferably the sodium, potassium, lithium, etc. hydroxides which may be used alone or in combination in weight quantities of one-fourth to about 10% by weight of the total mixture. These hydroxides can be added in flake or any dry form. 
     The liquid high boiling amines which are useful in this invention are those having a high boiling point, that is, a boiling point above about 65°C. and preferably above about 100°C. Amines having a boiling point under 100°C. and especially under 65°C. have too high a flash point or are too volatile for satisfactory and safe use in our compositions and processes. The use of the term liquid defines those amines which are liquid at ambient temperature. 
     Among the liquid high boiling amines which are useful in our compositions and processes are the following 
     1. Lower alkanol amines and alkanol polyamines such as 2-hydroxypropyl (ethylene diamine), 2-hydroxyethyl (ethylene diamine), tetraethanol propylene diamine, pentaethanol diethylene triamine, hexaethanol triethylene tetramine, triethanol amine, N,N,N 1  N 1  -tetrakis-(2-propano)-ethylene diamine, monoethanolamine, dimethylaminoethanol, ethylaminoethanol, diethylaminoethanol, diisopropylaminoethanol, and dibutylaminoethanol. One preferred amine is triethanolamine and especially preferred are the mono, di and tri lower alkylolamines with 2 to 12 carbon atoms. 
     2. Alkylamines -- the lower alkyl amines, such as methyl- and ethylamines are effective, but because of their low boiling point and high volatility they are less well adapted to this process than the higher alkylamines such as dibutylamine, diamylamine, octylamine, and the like, which are not driven off so easily under elevated temperature conditions. Other suitable alkylamines are triethylene tetramine, dipropylamine, tri-n-butylamine, triamylamine, n-hexylamine, di-n-hexylamine and tri-n-hexylamine. 
     3. Arylamines - benzylamine and benzyldiethanolamine have been found to be very effective for the purpose of this invention, particularly compounds such as aniline, p-toluidine, dimethyl aniline, diethyl aniline, benzyl diethylamine or the like. 
     4. Cycle tertiary amines -- amines of this nature have been found to be quite suitable for use in accordance with this invention. Examples are 2,4-lutidine, 2,5-lutidine, 3,5-lutidine, pyridine, hexyl pyridine, quinoline, N-vinyl-2-pyrolidine, N-methyl-2-pyrole, collidine, piperidine, 1-butyl piperidine, 1-propyl piperidine, pyrrolidine and pyrrole. 
     5. Hetero atom compounds containing nitrogen -- examples of this type of amine compound are hydroxyethyl piperazine, morpholine, 4 ethyl morpholine, N-aminopropyl morpholine, and pyrrolidone. 
     The liquid high boiling amines may be used singly or in admixture with other amines and of course in combination with the alkali metal hydroxide and liquid high boiling oxygenated solvent. 
     The liquid high boiling oxgenated solvents useful in our compositions and processes are selected from the group consisting of alcohols, carbonyls, esters, amides, lactones, tetramethyl urea, diphenyl ether and dimethyl sulfoxide. By liquid is meant those solvents which are liquids at ambient temperature. By high boiling is meant those solvents which have a boiling point in excess of about 100°C. This high boiling excludes those solvents boiling under 100°C. which are too volatile or which have too high a flash point for economical and safe stripping. A single oxygen containing solvent or a mixture of them can be used in our compositions. 
     1. The liquid high boiling alcohols which are used in our compositions and processes are the liquid high boiling aliphatic and aromatic alcohols and including glycols, polyglycols such as the poly (alkylene) glycols and polyols. Generally these alcohols will fall in the range of C 4  to about C 100  carbon atoms. Examples of suitable alcohols as defined above include triethylene glycol, polyethylene glycol, glycerin, triethylene glycol, polyethylene glycol, lisodecanol, trideconol, methoxy triglycol, ethoxy triglycol, thiodiglycol, ethylene glycol, polypropylene glycol, monoethoxy ethylene glycol, monobutoxy ethylene glycol, adonitol, tetrahydro furfuryl alcohol, cyclohexanol, furfuryl alcohol, 1,5-pentanediol, 1,2,6-hexanetriol, decyl alcohol, isoamyl alcohol, tolylol, cresol, butyl phenol, methyl phenyl carbinol, 1-butanol, 1-pentanol, 1-hexanol, 2-petanol, 2-methyl-1-butanol, 2-methyl pentanol, 4-methyl pentanol, 2-ethyl butanol, 2 -ethyl hexanol, iso-octanol, diisobutyl carbinol, 2,6,8-trimethyl-4-nonanol. 
     Preferred alcohols are the glycols and polyglycols. Triethylene glycol is a preferred species. Other preferred glycols are those diols of the aliphatic (preferably saturated) series with 2-12 carbon atoms. 
     2. The carbonyls useful in our compositions are the liquid high boiling aldehydes and ketones. As indicated previously, this class of oxygenated solvent as well as all other classes have boiling points in excess of about 100°C. Suitable carbonyls include isodealdehyde, 1-tetralone, tetrahydro benzaldehyde, isophorone, methyl hexyl ketone, 4-methoxy-4-methyl-2-pentone, methyl isoamyl ketone, valeraldehyde, 2-methyl pentaldehyde, 3-methyl butyraldehyde, 2-ethyl butyraldehyde, 2-ethyl hexaldehyde acetophenone, 4-chloro acetophenone, ethyl butyl ketone, hexahydro benzaldehyde, diisobutyl ketone, isobutyl heptyl ketone, mesityl oxide, 2,4-pentanedione diacetone alcohol, 1-tetralone, cyclohexanone. 
     The carboxylic acids are not suitable solvents in our compositions and processes because they react with the alkali metal hydroxides. However, the ester, amide, lactone and urea derivatives of carboxylic acids are useful in our compositions. 
     3. The esters which are useful in our compositions and processes are those high boiling esters which are liquid at ambient temperatures. Examples are carbitol acetate, glyceryl triacetate, diethyl maleate, n-butyl phthalate, methyl butyrate, methyl deconoate, n-butyl butyrate, ethyl decanoate, ethyl hydroxy iso-butyrate, propyl decanoate, methyl lactate, methyl octanoate, ethyl lactate, ethyl octanoate, butyl lactate, propyl octanoate, amyl formate, n-propyl acetate, butyl formate, n-butyl acetate, diethyl oxlate, sec-butyl acetate, n-butyl oxalate, isobutyl acetate, di-amyl oxalate, amyl acetate, n-butyl pentanoate, sec-amyl  acetate, sec butyl pentanoate, penta acetate, iso-butyl pentanoate, iso-propyl pentanoate, ethyl proprionate, methyl pentanoate, n-butyl proprionate, amyl proprionate, ethyl butyrate. 
     4. The amides are an unusual class of useful solvents in our compositions and processes since they can be used either as a member of the oxygen containing solvent class or as a member of the amine solvent class. However, two amides should not be used together as members of both classes of oxygenated solvents and amines. Suitable amides are dimethyl formamide, lauric diethanolamide, dimethyl acetamide, n-butyl acetamide, n,n-dipropyl acetamide, n-ethyl acetamide, n-methyl acetamide, n,n-dimethyl butyramide, n-ethyl formamide, n-methyl formamide, n,n-dimethyl pentanamide and tetramethyl urea. 
     5. The lactones which are useful in our compositions and processes are 4-butyl lactone, gamma valerolactone, delta-valerolactone and 2 ethyl, 4-butyryl lactone. 
     The compositions may, if desired, comprise a conventional wetting agent in an amoung of one half to about 20% by weight. These materials aid in washing the coating from the coated article and increase the overall solvent action of the compositions of this invention. Suitable wetting or surface active agents are the anionic, cationic and nonionic compositions which are well known in the art. 
     Examples of suitable nonionics are octyl phenoxy polyethoxy ethanol sold as Triton X-100 (Rohm &amp; Haas Co.), cetyl dimethyl amine oxide sold as Ammonyx CO (Onyx Chemical Co.), polyethylene glycol fatty esters sold as Airodyne 315 (Geigy Industrial Chemicals), fatty alkylol amine condensate sold as Alromine RA (Geigy Industrial Chemicals), alkyl aryl polyglycol ether sold as Basopon LN (BASF Corp.), blend of ethoxylated linear alcohols and amine condensate sold as Biofax 6200 (Charles S. Tanner), detergent combined with potassium dichloro-s-triazinetrione sold as Breakthrough HD (Proctor &amp; Gamble), myristic diethanolamide sold as Condensate M (Continental Chemical Co.), coconut fatty acid amide condensate sold as Drutergent D (Drew Chemical Co.), lauric isoproponolamide sold as Empilan LIS (Albright &amp; Wilson Ltd.), glyceryl monoricinoleate sold as Flexricin 13 (Baker Castor Oil Co.), complex phosphate ester sold as Fosterge NOH (Textilana Corp.), n,n-dimethyl caproamide sold as Hallcomid M-6 (C. P. Hall Co. of Illinois), ethylene oxide condensate sold as Invadline JFC (Ciba Chemical &amp; Dye Co.), ethoxylate castor oil sold as Lipal 9C (Drew Chemical Co.), fatty acid ester sold as Marcanon SX (Maper Color &amp; Chemical Co.), acylated polyamide sold as Nalco 70 (Nalco Chemical Co.), polyethylene glycol (400) monotallate sold as Pegosperce 400-MOT (Glyco Chemicals, Inc.), polyvinyl alcohol resin sold as Resin D-365 (Monsanto Corp.), sorbitan monooleate sold as Sorbitan Monooleate (Armour Ind. Chem. Co.). 
     Examples of suitable cationics are 1-hydroxyethyl,2-oleic imidazoline sold as Monozoline O (Monae Industries, Inc.), fatty amido alkyl quaternary chloride sold as Quatrene CA (Textilana Corp.), methyl polyethonol quaternary amine sold as Peregal OK (GAF Corp.), quaternary ammonium derivative sold as Gafstat S (GAF Corp.), n-alkyl trimethylene diamines RNH(CH 2 ) 3  NH 2  sold as Formonyte 801 (El Dorado Chem. Co.), primary fatty amine acetates RNH 2 .CH.sub. 3 COOH sold as Formonyte 601AC (El Dorado Chem. Co.), fatty imidazoline-1-hydroxyethyl 2-hepta-decadienyl imidazoline sold as Fatchemco-T (Universal Chemicals Corp.), flurochemical surfactant sold as FC-134 (3M Co. Minnesota Mining &amp; Manufacturing Co.), m(lauroyl colamine formyl metly) pyridinium chloride sold as Emcol E-607 (Witco Chem. Corp.), steryl dimethyl benzyl ammonium chloride sold as Triton X-400 (Rohm &amp; Haas Co.), ethoxylated quaternary sold as Variquat 638 (Varney Chemicals Div.), dimethyl disteryl ammonium lanolate sold as Chemactant Q (Chemactants Inc.), amido diamine from unsaturated C 18  acids sold as Cathol (Far-Best Corp.), complex higher alkylamine composition sold as Avitex ML (C. I. DuPont), tertiary fatty amines n-alkyl dimethylanines sold as Armeen DM12 (Armour Ind.). 
     Examples of suitable anionics are sodium n-methyl-n-oleoyltaurate sold as Igepon T-77 (GAF Corp.), free acid of a complex organic phosphate ester sold as Gafac RS-410 (GAF Corp.), fluoroalkyl phosphate sold as Zonyl S-13 (DuPOnt), a built salt of a complex phosphate ester sold as Whit-Steem (Whitfield Chemical Co.), (octyl) 5  Na 5  (P 3  O 10 ) 2  sold as Vicawet 35B (Stauffer Chemical Co.), sodium linear alkylate sulfonate sold as Ultrawet DS (Arco Chemical Co.), sulfonate mineral oil sold as Twitchell 8262 (Emery Industries, Inc.), sodium naphthalene sulfonate sold as Stablex B (Heveatex Co.), alkyl benzene sulfonate sold as Ormino (Miyoshi Oil &amp; Fat Co., Ltd), aromatic halogenide sold as Currier 51 (Nikka Chemical Inc., Co. Ltd.), alkyl aryl sulfonate sold as Naccanol 90F (Allied Chemical Co.), sulfonated sperm oil sold as Modicol P (Nopco Chemical Div.), styrene-maleic anhydride copolymer sold as Lytron 820 (Monsanto Co.), fatty ester sulfonate LAS derivitive sold as Hypochem, EM-1 (High Point Chem. Co.), ammonium oleate sold as Eumulgin 884 (Henkel International GMBH), dioctylsulfosuccinate sold as Cinwet KCX (Cindet Chemicals, Inc.), sodium lauryl sulfate sold as Avirol 101 (Standard Chem. Products, Inc.), sodium tetrahydronaphthalene sulfonate sold as Alkanol S Flakes (DuPont), bis(tridecyl) ester of sodium sulfosuccinic acid sold as Aerosol TR-100% (American Cyanamid), phosphated mixed alcohols(avg. mol. wt. of 131) mono and diesters in acid form, sold as, Actrofus 349 (Arthur C. Trask Co.). 
     In addition to the melting or surface active agents, other types of conventional additives may be used in our compositions as desired, such as thickeners, sequestrants, and corrosion inhibitors. 
     Examples of thickeners are fused silicas such as Santocel 54 (Monsanto), Syloid 266 (Grace Chemicals) and Aerosil 380 (Degussa), magnesium aluminum slicate sold as Attagel 40 (Minerals and Chemicals Philipp) and specialty clay products such as the Bentones (National Lead Corp.). 
     Examples of sequestrants are sodium gluconate, ethylene diamine tetraacetic acid sodium salts, sodium tartarate, sodium oxalate and sodium citrate. 
     Examples of corrosion inhibitors are potassium and sodium chromates, imidazoline of oleic acid sold as Mazoline OA(Mazer Chemical), organic phosphates such as Virco Pet 30 (Arco Refining), fatty amino propyl amines (Ashland Chemical), n-alkyl trimethylenediamine sold as Formonyte 801 (El Dorado Chemical) and Alox 575, 940, 1843 and 2000 sold by the Alox Corp. 
     The compositions of our invention may be put together in any convenient tank equipped with agitation. The liquid high boiling oxygenated solvent is usually placed in the vessel first and then followed by the alkali metal hydroxide and the liquid high boiling amine. The order of addition is not critical except that it is important to add the solid alkali metal hydroxide to one of the liquids. Application of heat may be desirable to aid in the dissolving or dispersing of the alkali metal hydroxide. Heating and stirring are continued until solution and/or dispersion of the alkali metal hydroxide takes place. It is desirable to have an exhaust vent over the mixing tank to confine the solvent fumes. 
     The preferred method of removing coatings comprises applying the anhydrous composition to the coated article at a temperature ranging from ambient to boil. The preferred method of application involves immersion of the coated part, however, where in view of the size of the part this is not feasible, the material can be sprayed onto the coated surface. When dealing with epoxy-polyamides and polyurethane coatings, it is necessary to operate generally at a temperature of from 200°F. to boil. Preferably, the compositions are used at temperatures approaching their boiling points in order to achieve the greatest attack on the coating and thus to shorten the time of treatment. Since spraying a solution causes a drop in temperature, immersion of the coated article is preferred to spraying. The efficiency of the treatment is increased by using a surface active agent. 
     The surfaces which can be treated include glass, woods, and ferrous or non-ferrous metals. The paints or coatings which are conventionally used and to which the invention is applicable include, in addition to the above polyesters (including alkyds), polyamides, polyesyter amides alone or in conventional combinations. Primers such as iron oxides or zinc chromates can be removed by this invention as well as top coat materials listed above. 
     The time of application varies but in an immersion type process conditions such as temperatures and particular materials and percentages used can generally be devised to completely remove or loosen (including powdering and blistering) enough to allow a total immersion time of one minute to one hour. After this time a high pressure water wash in a single or multi-stage treatment can be applied. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The invention will be more fully understood by reference to the following non-limiting specific examples which include the best mode known to the inventors of performing the invention. In these examples a test procedure for the corrosiveness of the coating stripper is referred to as the &#34;16 hour immersion corrosion test&#34;. This test procedure involves cleaning and wiping coated 1×2 panels in acetone and weighing them. The panels are then hung by string or plastic coated wire and suspended in a 4,000 ml beaker containing the stripping composition. The solution was agitated by magnetic stirring to keep a relatively uniform temperature throughout of 150° ± 5°C. (about 300°F.). The beaker was based on a 1/4 inch sheet of asbestos and jacketed by a Glas-Col heating mantel and finally covered by a 1/4 inch sheet of asbestos. A preheating time of 6 hours was used to ensure that the bath temperature could be properly maintained. The panels were immersed for 16 hours after which they were solvent cleaned, dried and again weighed. This procedure was used in order to test the corrosive influence of the composition and the composition tested as follows: 
     
         Triethanolamine     44.5%    by weightTriethylene glycol  44.5%    by weightTriton X-100        10%      by weightPotassium hydroxide, flake               1%       by weight 
    
     EXAMPLE 1 
     A panel of bare aluminum (No. 2024) was weighed before the corrosion test, the weight was 2.8317 grams. After following the above-noted procedure the sample was again weighed; the result being 2.8317 grams, indicating that no weight difference was effected. The total area of the panel was 3.5288 sq.in. and the average weight change in milligrams per square inch was 0. No visual change was observed in the final appearance of the panel. A duplicate run produced the same results. The composition tested was 
     
         Triethanolamine        441/2%Triethylene Glycol     441/2%Triton X-100           10%KOH                    1% 
    
     The following Table represents the results of testing according to Example 1 using the 16-hour immersion corrosion test described above. Each sample, except as noted, includes duplicate runs. 
     In the Examples the panels are designated by commerically used numbers as follows. With respect to the panels tested they comprise bare or clad panels which in the noted cases have coatings and/or primers thereon. Each metal is designated by alloy numbers conventionally used (e.g. Al. = 2024, 7075, 1100; Mg = AZ31B; Ti = 6% Al., 4% V; Steel = 1020). The coatings include chromate coats (Alodine No. 1000 and Dow No. 7) and anodized coatings. 
     
                                           TABLE I__________________________________________________________________________            Weight  Weight  Weight                                  Total Area                                         AverageEx. No. Metal      Before (grams)                    After (grams)                            Difference                                  of Panel                                         Wgt. Change                            (grams)                                  in Sq. In.                                         in mg/in.sup.2                                                 Final__________________________________________________________________________                                                 Appearance2    2024 Clad   1) 2.9095                    2.9099  0.0004Aluminum    2) 2.8929                    2.8929  0.0000                                  3.9255 0.051   No visual change3    2024 Clad Al,            1) 2.8789                    2.8783  0.0006Chromic Anod.            2) 2.8969                    2.8953  0.0016                                  3.9255 0.276   No visual change4    2024 Clad Al,            1) 2.7523                    2.7516  0.0007Alodine No. 1000            2) 2.7543                    2.7538  0.0005                                  3.5288 0.170   No visual change5    7075 Bare   1) 2.2499                    2.2517  0.0018Aluminum    2) 2.2736                    2.2736  0.0000                                  3.9225 0.225   No visual change6    7075 Clad   1) 2.8898                    2.8899  0.0001Aluminum    2) 2.8839                    2.8839  0.0000                                  3.9255 0.012   No visual change7    7075 Clad Al,            1) 3.5429                    3.5424  0.0005Chromic Anod.            2) 3.5492                    3.5494  0.0002                                  3.9255 0.037   No visual change8    7075 Clad Al,            1) 3.4395                    3.4394  0.0001Alodine No. 1000            2) 3.4607                    3.4597  0.0010                                  3.5288 0.159   No visual change9    Magnesium Az            1) 1.2093                    1.2085  0.000831B also (QQ-M44)            2) 1.2109                    1.2105  0.0004                                  3.5288 0.170   No visual change10   Magnesium Az            .8370    .8374  0.0004                                  3.9255 0.085   No visual change31B, Dow No. 7 coating11   Titanium-6 Al,            7.7082  7.7087  0.0005                                  3.5288  0.1415 No visual change4V Alloy alsoMIL-T-9046)12   1020 Steel  1) 7.8844                    7.8813  0.0031            2) 6.6303                    6.6272  0.0031                                  3.5288 0.876   No visual change13   Cd. Plated  1) 6.2464                    6.2413  0.00511020 Steel  2) 6.3842                    6.3767  0.0075                                  3.5288 1.788   No visual change14   1100 Alum.  1) 2.6816                    2.6808  0.0008            2) 2.6707                    2.6694  0.0013                                  3.5288  0.2975 No visual__________________________________________________________________________                                                 change 
    
     EXAMPLE 15 
     A steel test panel having a surface area of approximately 4 sq.in. and having been coated with a polyurethane composition known in the art as Finch Polyurethane (Finch Chemical Coatings Company) was immersed in a solution such as described in Example 1 for 15 minutes during which the temperature of the bath ranged from 266°-302°F. At the end of the specified time the panel was removed and given a cold water pressure rinse. The treatment resulted in 100% removal of the polyurethane coating. 
     Table II below illustrates the results of the testing procedure of Example 15. The listed panels are aluminum unless otherwise designated having a variety of various coating compositions applied thereto. 
     In the Examples the primers and coatings on parts are designated by their commercial designations. The panels are sometimes provided with an initial corrosion coat (e.g. Alodine 1000 or 1200) they are sometimes provided with primers. The resins used in coating the panels are designated by the manufacturer or supplier and its number, or by the Military Specification number covering a given paint or coating type (MIL). In the designations PRC is Products Research Company; BMS is Boeing (Aircraft) Materials Specifications; Kynar is a polyvinylidine fluorine made by the Pennwalt Company, King of Prussia, Pa. 
     
                                           TABLE II__________________________________________________________________________Ex. No. Paint System      Immersion                          Remarks                   Time__________________________________________________________________________16    a) Desoto 823-011 30 min.                           98% removal                                       pressure rings removed                                        (Desoto Paint                                       Co.)    additional 2%                                        MIL-C-27725C                                        did not remove alodine                                       coating                                       17 a) Epoxy Primer MIL P 30                                       min.  99% removal                                        remainder is readily                                       brushed                                        27316 with b) Poly-    or                                       peeled off                                        urethane top coat MIL                                        C27227                                       18 a) PRC 1560 15 min. 100%                                       removal                                        Mil Spec. MIL-C-                                        27725C Polyurethane                                       19 a) PRC 1560m MIL-C- 15                                       min. 100% removal                                        chromate conversion coating                                        27725C Polyurethane    remain                                       s                                       20 a) BMS-10-11 Type I                                       (epoxy) 15 min. 100% removal                                        on b) 1200 Alodine                                       21 a) MIL-C-22750 Epoxy- 35                                       min. 100% removal                                        lifted paint off rather                                       than                                        polyamide top coat,                                       on    dissolving or                                       decomposing it                                        b) MIL-P-23377 primer                                       epoxy-                                        polyamide                                       22 a) Boeing Epoxy- 15                                       min. 100% removal                                        after 15 min. paint was                                       severly                                        Phenolic Adhesive    blistere                                       d and was removed by                                        Primer    pressure cold                                       H.sub.2 O                                       23 a) Polyurethane top                                       coat 20 min. 99-44/100%                                       removal                                        powdery coating remained                                        over b) modified                                       MIL-C-    which was easily                                       wiped off                                        22750 Epoxy primer on                                        c) Anodized Alum.                                       24 a) MIL-P-27316 on 7-8 min.                                       0100% removal                                        Dow No. 7 chromate                                       conversion                                        Magnesium    coating                                       remains                                       25 a) Epoxy Primer 8-9 min.                                       99% removed  with pressure                                       rinse                                        b) over Clear Kynar                                        the remainder is easily                                       wiped                                            off                                       26 a) Unbaked Super                                       Koropon 8-9 min.  100%                                       removal                                        some conversion coating                                       remains.                                        (Desoto Paint Co.) Epoxy-                                        Polyamide top coat on b)                                        MIL-C-22750A,                                       Epoxy-polyamide                                        primer                                       27 a) Heat Room W-170 Al. 30                                       min. 100% removal                                        Silicone Coating (Speco                                       Inc.)                                        on b) Alodine 1200 on c)                                        3003 Al. Alloy                                       28 a) PRC-1560 mk Poly- 15                                       min. 100% removal                                        urethane coat MIL-C-                                        27725C                                       29 a) MIL-P-23377 Epoxy- 30                                       min. 100% removal                                        Polyamide Primer                                        1 yr. old                                        1 coat                                       30 MIL-P-23377 Epoxy- 30                                       min. 100% removal                                        Polyamide Primer                                        1 yr. old                                        2 coats                                       31 Zinc Chromate Primer 5                                       min. 100% removal                                        MIL-P-8585                                       32 Desoto No. 2012 Epoxy 25                                       min. 100% removal                                        conversion coating remains                                        Primer__________________________________________________________________________ 
    
     EXAMPLE 33 
     Using the composition of Example 1 the following modifications were run wherein instead of triethylene glycol, 44.5% of the following were used 
     a. Polyethylene glycol (avg. m.w. 300) - Carbowax 300, Union Carbide Company 
     b. Glycerin 
     c. Isodecanol 
     d. Tridecanol 
     e. Isodealdehyde 
     f. Tetrahydro benzaldehyde 
     g. Carbitol acetate 
     h. Glyceryl triacetate 
     i. Methoxy triglycol 
     j. Ethoxy triglycol 
     k. Thiodiglycol (Kromfax solution, Union Carbide Company) 
     l. Isophorone. 
     These compositions when applied to the panels of Examples 14-32 at the noted temperatures give the indicated results: 
     
         Sample Temperature   Results______________________________________a)     302-320       100% removalb)     &#34;             effects some removal but                solution separatesc)     221-239       100% removal generally but                only patly removes epoxy-                polyamide and did not remove                polyurethaned)     212-230       100% removal generally but                only partly removes epoxy-                polyamide and did not remove                polyurethanee)      180-200°F                effects some removal but                solution separatesf)     160-180       100% removal generally but                only partly removes epoxy-                polyamide and did not remove                polyurethaneg)     230-248       removes acrylic and zinc                chromate onlyh)     266-284       removes acrylic and zinc                chromate onlyi)     230-257       100% removalj)     248-266       100% removalk)     302- 320      100% removall)                   ketone reacts with alkali                hydroxide to some extent                but gives 100% removal______________________________________ 
    
     Example 34 
     Various formulations of liquid high boiling solvents and liquid high boiling amines in admixture with potassium hydroxide or sodium hydroxide were tested for removal of the following coatings: 
     POLYURETHANE 
     Polyurethane fuel tank coating, specification MIL-C-27725 on alclad aluminum substrate. 
     EPOXY-POLYAMIDE 
     First coat-MIL-P-23377 epoxy primer followed by two coats of MIL-C-83286 polyurethane on anodized aluminum. 
     DURACRON 200 
     Acrylic paint system on iron phosphated steel. 
     SUPER KOROPON 
     Epoxy-polyamide primer-MIL-C-22750A followed by DeSota epoxy-polyamide top coat on 2024 alclad aluminum. 
     ZINC CHROMATE 
     Zinc chromate primer-MIL-P8585 on alclad aluminum base. 
     One hundred grams of each formulation were prepared and placed in a glass beaker equipped with a magnetic stirrer. Heat was applied until the formulations were at or near their boiling points. The edges of the paint and resin systems were taped with lead and placed in the formulations. The time was observed for removal or blistering of the respective coatings at the temperature indicated. Where there was no effect on the coating the time indicates the length of immersion at the temperature indicated when the observation was made. The results appear in Table III. 
     
                                           TABLE III__________________________________________________________________________        Formulation - (Percent by Weight)                                Polyurethane Coating                                             Epoxy-Polyamide__________________________________________________________________________                                             Coating   Oxygen    Amine    Alkali         Time                                    Temp     Time                                                 TempNo.   Solvent   Solvent  Metal Surfactant                                (Min.)                                    °F                                        Remarks                                             (Min.)                                                 °F                                                     Remarks                 Hydroxide__________________________________________________________________________   Ethylene  Triethanolamine                 KOH   Triton X-100                                70  293 Complete   Glycol                                    Removal   44.5      44.5     1.0   10.02  Polypropylene        Triethanolamine                 KOH   Triton X-100                                 100                                    294 No   30  295 Topcoat   Glycol-Dow        44.5     1.0   10.0             Removal      Removal   P2000   44.53  Polyethylene        Triethanolamine                 KOH   Triton X-100                                70  295 No   30  293 Topcoat   Glycol (Car-        44.5     1.0   1.0              Removal      Removal   bowax 300)   44.54  Phenol 44.5        Triethanolamine                 KOH   Triton X-100                                60  294 No   15  294 Complete        44.5     1.0   10.0             Removal      Removal5  Resorcinol        Triethanolamine                 KOH   Triton X-100                                60  294 No   15  295 Complete   44.5      44.5     1.0   10.0             Removal      Removal6  Ethylene  Triethanolamine                 KOH   Triton X-100                                105 260 No    120                                                 260 Complete   Glycol    44.5     1.0   10.0             Removal      Removal   Monoethyl   Ether   44.57  Ethylene  Triethanolamine                 KOH   Triton X-100                                90  293 No   45  293 Topcoat   Glycol    44.5     1.0   10.0             Removal      Removal   Monobutyl   Ether   44.58  Tetrahydro-        Triethanolamine                 KOH   Triton X-100                                60  295 Complete   furfuryl  44.5     1.0   10.0             Removal   alcohol 44.59  Cyclohexanol        Triethanolamine                 KOH   Triton X-100                                60  295 No   30  293 Topcoat   44.5      44.5     1.0   10.0             Removal      Removal10 Furfuryl  Triethanolamine                 KOH   Triton X-100                                30  294 No   45  294 Topcoat   Alcohol   44.5     1.0   10.0             Removal      Removal   44.511 1,5-Penta-        Triethanolamine                 KOH   Triton X-100                                90  293 Complete                                             60  293 Topcoat   nediol 44.5        44.5     1.0   10.0             Removal      Removal12 1,2,6-Hexa-        Triethanolamine                 KOH   Triton X-100                                 120                                    295 No   60  295 Topcoat   netriol 44.5        44.5     1.0   10.0             Removal      Removal13 n-butylphtha-        Triethanolamine                 KOH   Triton X-100                                60  302 No   60  300 No   late 44.5 44.5     1.0   10.0             Removal      Removal14 Diethyl   Triethanolamine                 KOH   Triton X-100                                60  293 No   40  293 No   Maleate 44.5        44.5     1.0   10.0             Removal      Removal15 Methylhexyl        Triethanolamine                 KOH   Triton X-100                                60  294 No   30  294 Complete   ketone 44.5        44.5     1.0   10.0             Removal      Removal16 Diethyl   Triethanolamine                 KOH   Triton X-100                                60  298 No   90  293 Topcoat   Carbitol 44.5        44.5     1.0   10.0             Removal      Removal17 Dibenzyl Ether        Triethanolamine                 KOH   Triton X-100                                60  295 No   20  294 Topcoat   44.5      44.5     1.0   10.0             Removal      Removal18 Triethylene        Dibutyl Amine                 KOH   Triton X-100                                60  298 Topcoat                                             45  294 Topcoat   Glycol 44.5        44.5     1.0   10.0             Removal      Removal19 Triethylene        Amine 220                 KOH   Triton X-100                                80  293 No   60  293 Topcoat   Glycol 44.5        (C.sub.22 Amine)                 1.0   10.0             Removal      Removal        44.520 Triethylene        Dimethyl Aniline                 KOH   Triton X-100                                15  296 Complete   Glycol 44.5        44.5     1.0   10.0             Removal21 Triethylene        Quinoline                 KOH   Triton X-100                                30  294 Complete   Glycol 44.5        44.5     1.0   10.0             Removal22 Triethylene        4-Ethyl  KOH   Triton X-100                                60  293 90%  35  296 Topcoat                                        Coating   Glycol 44.5        Morpholine 44.5                 1.0   10.0             Removal      Removal23 Triethylene        Triethylene                 KOH   Tritn X-100                                20  298 Complete   Glycol 44.5        tetramine 44.5                 1.0   10.0             Removal24 Triethylene        N-aminopropyl                 KOH   Tritn X-100                                70  295 95%                                        Coating   Glycol 44.5        Morpholine 44.5                 1.0   10.0             Removal25 Triethylene        Hydroxyethyl                 KOH   Triton X-100                                30  293 Complete   Glycol 44.5        Piperazene                 1.0   10.0             Removal        44.526 Triethylene        Tetrakis-(2                 KOH   Triton X-100                                60  298 Complete                                             60  298 Topcoat   Glycol 44.5        propanol)                 1.0   10.0             Removal      Removal        Ethylene        Diamide        44.527 Triethylene        Benzyl Diethyl                 KOH   Triton X-100                                60  298 Complete                                             45  293 Topcoat   Glycol 44.5        Amine 44.5                 1.0   10.0             Removal      Removal28 Triethylene        Monoethanol-                 KOH   Triton X-100                                20  293 Complete   Glycol 44.5        amine 44.5                 1.0   10.0             Removal29 Triethylene        N-vinyl-2-                 KOH   Triton X-100                                20  294 Complete   Glycol 44.5        pyrrolidone                 1.0   10.0             Removal        44.530 Triethylene        m-pyrol  KOH   Triton X-100                                45  284 No   15  295 Complete   Glycol 44.5        44.5     1.0   10.0             Removal      Removal31 Triethylene        Dimethyl KOH   Triton X-100                                70  293 No   20  293 Complete   Glycol 44.5        Formamide                 1.0   10.0             Removal      Removal        44.532 Triethylene        Lauric   KOH   Triton X-100                                60  294 No   37  295 No   Glycol 44.5        Diethanol-                 1.0   10.0             Removal      Removal        amide 44.533 4-butyl lactone        Triethanolamine                 KOH   Triton X-100                                60  295 No   15  294 Complete   44.5      44.5     1.0   10.0             Removal      Removal34 Dimethyl  triethanolamine                 KOH   Triton X-100                                30  293 Complete                                             40  200 No   sulfoxide 44.5     1.0   10.0             Removal      Removal35 Tetramethyl        Triethanolamine                 KOH   Triton X-100                                90  293 Complete                                             40  294 Complete   urea 44.5 44.5     1.0   10.0             Removal      Removal36 Tetrahydro        Dipropylamine                 KOH   Triton X-100          30  246 Topcoat   furfuryl alcohol        44.5     1.0   10.0                          Removal   44.537 Triethylene        N,N-Dimethyl                 KOH   Triton X-100                                 120                                    295 Complete                                             20  295 Complete   Glycol 44.5        Acetamide                 1.0   10.0             Removal      Removal        44.538 n-butylphtha-   late      Triethanolamine                 KOH   Triton X-100   44.5      44.5     1.0   10.039 Diethyl Maleate        Triethanolamine                 KOH   Triton X-100   44.5      44.5     1.0   10.040 4-methoxy-4-        Triethanolamine                 KOH   Triton X-100                                45  255 No   30  255 Topcoat   methyl-2- 44.5     1.0   10.0             Removal      Removal   pentanone   44.541 Decyl Alcohol        Triethanolamine                 KOH   Triton X-100                                45  297 No   30  297 Complete   44.5      44.5     1.0   1.0              Removal      Removal42 Tetrahydro-        Triethanolamine                 KOH   Cetyl Dimethyl                                50  299 Complete   furfuryl Alcohol        49.0     1.0   amine oxide      Removal   49.0                     (Ammonox Co)                       1.043 Tetrahydro-        Triethanolamine                 KOH   Cetyl Dimethyl-                                23  294 No   15  294 Complete   furfuryl Alcohol        40.0      0.25 amine oxide      Removal   40.0                     (Ammonox Co)                       19.7544 Triethylene        Triethanolamine                 KOH   1-Hydroxy-                                45  299 90%  35  299 Topcoat   Glycol 49.0        49.0     1.0   ethyl, 2-oleic-  Removal                       imidazoline                       (Monozoline Co)                       1.045 Tetrahydro-        Triethanolamine                 KOH   1-Hydroxyethyl-                                45  299 75%  30  297 93%   furfuryl Alcohol        41.0     1.0   2-oleic-         Removal      Removal   40.0                     imidazoline 18.0                       (Ammonox CO)46 Triethylene        Monoethanol-                 KOH   Fatty amido                                 5  297 Complete   49.0      amine    1.0   alkyl quaternary Removal        49.0           chloride 1.0                       (Quantrene CA)47 Triethylene        Monoethanol-                 KOH   Fatty amido                                15  298 No    8  298 Complete   Glycol 41.0        40.0     1.0   alkyl quaternary Removal      Removal                       chloride 18.0                       (Quantrene CA)48 Triethylene        Triethanolamine                 KOH            60  301 No   30  301 Topcoat   Glycol 40.0        59.75     0.25                  Removal      Removal49 Tetrahydro-        Triethanolamine                 KOH            60  300 98%  20  300 Complete   furfuryl Alcohol        59.75     .25                   Removal      Removal   40.050 Triethylene        Triethanolamine                 KOH            30  300 No   30  300 Topcoat   Glycol 59.75        40.0      0.25                  Removal      Removal51 Tetrahydro-        Triethanolamine                 KOH            30  300 No    8  300 Complete   furfuryl  40.0      0.25                  Removal      Removal   Alcohol   59.7552 Triethylene        Triethanolamine                 KOH   Sodium N-methyl                                60  300 No   35  300 Topcoat   Glycol 40.0        58.75     0.25 oleoyl taurate   Removal      Removal                       (Igepon T77)                       1.053 Triethylene        Triethanolamine                 KOH   Sodium N-methyl                                50  297 No   45  297 Topcoat   Glycol    40.0      0.25 oleoyl taurate   Removal      Removal   58.75                    (Igepon T77)                       1.054 Tetrahydro-        Triethanolamine                 KOH   Organic phos-                                60  298 No   10  298 Complete   furfuryl  41.0     1.0   phate ester      Removal      Removal   Alcohol                  (Gafac RS 410)   40.0                     18.055 Triethylene        Triethanolamine                 KOH   Organic phos-                                60  295 No   40  298 Topcoat   Glycol 40.0        41.0     1.0   phate ester      Removal      Removal                       (Gafac RS 410)                       18.056 Isoamyl Alcohol        Triethanolamine                 KOH   Triton X-100                                 110                                    284 No   30  284 Topcoat   44.5      44.5     0.25  10.0             Removal      Removal57 N-butyl Alcohol        Triethanolamine                 KOH   Triton X-100          30  216 Topcoat   44.5      44.5     1.0   10.0                          Removal58 Di-phenyl mono-ethanol-                 KOH   Triton X-100                                 5  298 Complete   ether     amine 44.5                 1.0   10.0             Removal   44.559 Dimethyl  Triethanolamine                 KOH   Triton X-100                                45  295 No   10  296 Complete   formamide 44.5     1.0   10.0             Removal      Removal   44.560 N,N-Dimethyl        Monoethanol-                 KOH   Triton X-100                                15  298 Complete   Acetamide amine 44.5                 1.0   10.0             Removal   44.561 Triethylene        Triethanolamine                 KOH   Glycol 40.0        59.75     0.2562 Triethylene        Triethanolamine                 KOH   Organic phos-   Glycol 40.0        41.0     1     phate ester                       (Gafac 610)                       18.063 Triethylene        Triethanolamine                 KOH   Dodecyl ben-   Glycol 40.0        41.0      0.25 zene sulfonate                       (Nacconol 90F)                       18.064 Diphenyl  Triethanolamine                  NaOH Triton X-100                                50  297 Complete   Ether 22.25        44.5     1.0   10               Removal   Tetrahydro   furfuryl Alcohol   22.2565 Triethylene        Triethylene                  NaOH Triton X-100                                15  301 Complete   Glycol 44.5        tetramine 22.25                 1.0                    Removal        Hydroxyethyl        piperazine 22.25__________________________________________________________________________TABLE III (extended)__________________________________________________________________________Duracron 200 Coating               Super Koropon Coating                                  Zinc Chromate Coating__________________________________________________________________________Test   Time Temp        Time Temp.         Time Temp.No.   (Min.)   °F        Results               (Min.)                    °F                         Results  (Min.)                                       °F                                            Results__________________________________________________________________________2                   55   294  Complete                         Removal3  15   294  No Removal4567   5   293  Complete               5    213  Complete        Removal          Removal89  10   293  Complete        Removal10 10   295  Complete               5    294  Complete        Removal          Removal1112 15   294  Complete        Removal13 60   300  Topcoat        Removed14 45   293  No Removal               30   293  No Removal                                  12   300  Complete                                            Removal15  5   294  Complete               8    294  Complete        Removal          Removal16 25   294  No Removal               60   293  Topcoat                         Removal17 15   294  Complete               10   294  Complete        Removal          Removal18 15   293  Complete        Removal19 40   294  Complete        Removal20212223242526  1               15   298  Complete                         Removal27                  30   293  Complete                         Removal2829 10   294  Complete        Removal30 20   294  Complete        Removal31 60   293  No Removal               5    293  Complete                         Removal32 60   294  Complete               20   294  Complete        Removal          Removal33 45   294  No Removal3435  5   295  Complete        Removal36                  30   246  Complete                         Removal37                  15   295  Complete                         Removal38                                     2    300  Complete                                            Removal39                                      12  300  Complete                                            Removal40                  20   257  Complete                         Removal41424344                  20   298  Complete                         Removal45464748                  30   301  75% of Topcoat                         Removal4950                  45   300  Complete                         Removal5152                  20   300  Complete                         Removal53                  15   298  Complete                         Removal5455                  35   294  Topcoat                         Removal56                  5    284  Complete                         Removal57                  15   216  Complete                         Removal58596061                                     1    293  Complete                                            Removal62                  45   297  No Removal                                  2    297  Complete                                            Removal63                  20   284  Complete 2    295  Complete                         Removal            Removal6465__________________________________________________________________________