ENGINEERING RESEARCH INSTITUTE UNIVERSITY OF MICHIGAN ANN ARBOR DEVELOPMENT OF PAINT AND VARNISH REMOVERS July 1,.1954 to October 15,.1954 L<. L. CARRICK - F. L. KECK Project 2195 THE REARDON COMPANY ST. LOUIS, MISSOURI October, 1954

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ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN FOREWORD At the request of the Reardon Company the development of a paint and varnish remover suitable for trade sales was included in the project. Various formulas were developed and their effectiveness was compared with twenty-five commercial paint and varnish removers submitted by the Reardon Company. The comparative results may be found on the ensuing pages along with those formulations that show excellent promise for trade sales. ii

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN TABLE OF CONTENTS Page FOREWORD ii LIST OF TABLES iv PRELIMINARY COMPARATIVE RESULTS OF COMMERCIAL PAINT 1 AND VARNISH REMOVERS PAINT AND VARNISH REMOVER FORMULATIONS 2 PROCEDURE 3 DISCUSSION OF COMPARATIVE RESULTS OF COMMERCIAL PAINT 3 AND VARNISH REMOVERS AND LABORATORY FORMULATIONS CONCLUSIONS 5 iii

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN LIST OF TABLES Table Page I COMMERCIAL PAINT AND VARNISH REMOVERS 6 II COMPARATIVE RESULTS OF COMMERCIAL PAINT AND VARNISH 7 REMOVERS SUBMITTED BY THE REARDON COMPANY III BASIC PAINT AND VARNISH FORMULAS 9 IV COMPARATIVE RESULTS ON LABORATORY PAINT AND 11 VARNISH FORMULATIONS V COMPARISON OF COMMERCIAL AND LABORATORY COMPOUNDED 12 PAINT AND VARNISH REMOVERS _______________________________ IV _______________________________

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN DEVELOPMENT OF PAINT AND VARNISH REMOVERS On August 24, 1954, twenty-five commercial paint and varnish removers were received from the Reardon Company. These were evaluated on various coatings that were immediately available in our laboratory, For the most part all the paint and varnish removers were satisfactory on oleoresinous and other common finishes. However, differences in performance were noticed when they were applied to panels finished with clear alkyd urea furniture varnishes (low-temperature bake (140~F)). These finishes are gaining widespread acceptance throughout the furniture field and will probably replace many of the well-known furniture finishes. No rubber base finishes were included in this evaluation. PRELIMINARY COMPARATIVE RESULTS OF COMMERCIAL PAINT AND VARNISH REMOVERS The comparative results of eighteen commercial paint and varnish removers applied on panels 1, 2, and 3 finished with clear alkyd urea furniture varnishes and aged since July, 1953, may be found in Table II. Each panel had a different varnish system, since each varnish had a different acid combination as a catalyst. It is interesting to note that none of the removers applied on panel 2 produced blistering or even softening of the film after 30 minutes of contact. Two removers, J. B Day Company's Kut-Kote and National Chemical and Manufacturing Company's X-Cell-All gave satisfactory results on panel 1. All six of the removers applied to panel 3 gave satisfactory results. Since the system employed on panel 2 best withstood the action of the paint and varnish removers, a set of panels using this alkyd urea varnish system and acid catalyst combination was made. To promote the ultimate hardness that develops on aging, the panels were placed in the weatherometer for 75 hours without water spray. The effectiveness of all the paint and varnish removers was measured on these panels. Comparative results are listed under panels 4 and 5 in Table II. Eight of the removers, designated as formulas C, E, Q, S, T, U, V, and W (see Table I for listing of trade names and manufacturers), gave satisfactory results. These removers were chosen as standards with which our laboratory formulations would be compared. ~ I ~~~~~~~~~~~

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN PAINT AND VARNISH REMOVER FORMULATIONS Results obtained using the commercial paint and varnish removers on the clear alkyd urea varnish panels showed that removers based on chlorinated solvents were more effective than those removers using acetonemethanol-benzol as a base. Since low toxicity is a requirement in any paint and varnish remover, Dow's methylene chloride was chosen as the chlorinated solvent to be used in our development work. Methylene chloride not only is nonflammable, but is one of the least toxic of the commercially available solvents. According to the Dow Chemical Company it presents only minor hazards to health. Table III lists thirty-nine different laboratory paint and varnish remover formulations with their approximate raw material costs. All these are based on Dow's scrape-off type paint and varnish remover which uses methylene chloride, paraffin, methocel, and methanol. Various solvents were included in these formulations, since Dow's basic formulation did not give satisfactory results on an alkyd urea finish. Evaluation of the preliminary laboratory formulations (formulas 1 through 12) indicated that effectiveness varied with humidity conditionso As a result, formula 13 was compounded with a small percentage of water. Comparison between formulas 13 and 3 showed that the addition of water increased the rate and degree of blistering. Since water was beneficial, most of the subsequent formulations were formulated with a small quantity. In some cases the addition of water resulted in an incompatible system with little improvement in effectiveness. Removers containing solvents, e.go, benzene, that have negligible solubility of water in themselves behave this way. On the other hand, removers containing solvents like carbitol whose solubility of water in itself is infinite are greatly improved by the addition of water. The quantity of water that can be added to any given remover system will be discussed under "Comparative Results". In most cases the laboratory paint and varnish removers were formulated to a viscosity that would provide for satisfactory application to a vertical surface. The viscosities of laboratory formulas 1 through 39 are as follows: Formula No. Viscosity 1 - 16 Good 17 Low 18 - 22 Too low 23 Good 24 - 30 Too low 31 - 37 Excellent 38 Very low 39 Low - -_______ 2

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN PROCEDURE A satisfactory method for compounding the paint and varnish removers found in Table III is to add the components in the order listed below. 1o Prepare a stock solution of methylene chloride and paraffin by melting the paraffin over a water bath and adding it to the methylene chloride with adequate agitation. 2. To the stock solution add additional methylene chloride as required by the formulation (formulas 1 to 39). 3. Add the active solvento 4. Add the methocel 4000 HG with agitation. 5. Add the methanol with agitation. 6. Add the water-with agitation. The above procedure was found to be very satisfactory in all cases. It probably could be varied to some extent without serious results. However, the water should be added after all the other components have been added. Addition of water prior to the methanol addition resulted in a system that appeared to be slightly incompatible. DISCUSSION' OF COMPARATIVE RESULTS OF COMMERCIAL PAINT AND VARNISH REMOVERS AND LABORATORY FORMULATIONS Formulations 1 through 39 were evaluated on panels having the following varnish system: filler, clear alkyd urea sealer, clear alkyd urea topcoat. Most of these formulations were applied on panel A. The results are reported in Table IV. It is interesting to note that formulas 1 through 9 gave satisfactory results with formulas 1, 3, 5, 6, 7, and 9 being the best. In each formulation 3 percent by weight of active solvent was used in place of methylene chloride. Formulas 10, 11, and 12 represent combinations of the better solvents. Only formula 10 gave unsatisfactory results. 5

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN Formulas 13, 17, 18, 19, 20, 21, 22, and 23 were formulated to determine if there was a limiting quantity of water that could be added to the remover before losing effectiveness. It was found that formula 18 containing 5% water was an effective organic film remover, while formula 21 containing 60 water produced no visible effect on the finish. No difference in effectiveness was observed between those formulas containing 1 to 5 water. Formula 17 containing 3% water did produce some incompatibility; that is, a layer formed at the surface, but this was overcome by adding additional methocel (formula 35). Each remover system containing a given solvent will tolerate a certain amount of water before losing effectiveness and at the same time becoming incompatible. This quantity of water was determined only on the remover system containing carbitol in which case incompatibility occurred before loss of effectiveness. Formulas 24 through 30 are the same as some of the first formulas except for the addition of 2% water. These did not show up as well when applied to panel A because their viscosities had been decreased and as a result a much thinner coat had been applied. This thin coat evaporated too fast for the remover to be effective, The best of the commercial paint and varnish removers (C, E, Q, S, T, U, V, W) and our own formulations, Table III, were applied on panel D and their effectiveness observed (see Table V). All the removers were applied as a thick coat because this particular panel had two coats of lacquer sealer and alkyd urea sealer followed by one alkyd urea topcoat. Of the eight commercial paint and varnish removers that had appeared promising from their results on other panels, only three could be judged satisfactory. These are J. Bo Day Company's Kut-Kote Remover, Universal Technical Products' Universal Remover, and Dux Paint and Chemical Company's Atomic Remover (C, T, and U). All the other commercial removers showed blistering of the finish, but the degree of blistering was very limited. The surface of Pittsburgh Plate Glass Company's Extra Potent Remover remained satisfactory for over an hour; however, it blistered only slightly during this time. Formulas 23, 27, 28, 29, 35, 36, 37, and 39 of our own formulations were equivalent to or better than the best of the commercial paint and varnish removers tested. Formula 38, containing 10 percent by weight VM and P naphtha, was applied on panel D but with no results. A second heavy application 45 minutes after the first produced some blistering and lifting; however, the results after the two applications were similar to commercial removers classified as unsatisfactory, _____________________________________ _____________________4

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN CONCLUSIONS Generally speaking all the formulations listed in Table III gave satisfactory results when applied on clear alkyd urea varnishes. However, some of the solvents such as carbitol, cellosolve acetate, tetralin, cyclohexanol, and furfural gave superior results in combination with a small percentage of water. A general formulation found to be very satisfactory is as follows: Parts by weight Methylene chloride 177 to 172 Paraffin 2 Methocel 4000 HG 3 to 4 Methanol 12 Active solvent 6 Water 4 to 6 The average raw material cost for the above formulations regardless of the active solvent used, is approximately $1o50 per gallon. This could probably be lowered somewhat by adding a diluent such as VM and P naphtha. However, it should be remembered that the addition of any diluent will necessitate increasing the methocel 4000 HG content to insure adequate viscosity. If a solvent combination is used, a portion of this should be a glycol ether such as carbitolo It was found that carbitol in conjunction with water produced rapid blistering of the finish and at the same time excellent liftingo A 1* paraffin content retarded evaporation sufficiently for those removers having satisfactory viscosityo As shown in Table V, most of the best commercial paint and varnish removers produced blistering of the film within 5 to 6 minutes However, they failed to give a completely blistered and lifted film within 8 minutes; as was the case with formulas 35, 36, and 37. This may well have been the result of too much diluent which decreases the overall effectiveness of paint and varnish removers. _________________________________________ 5

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN TABLE I COMMERCIAL PAINT AND VARNISH REMOVERS Formula Reference Company Trade Name Letter A J. F. Kerns Company Liquisan Stripper B Wilson-Imperial Company Wonder Paste Special Remover C J. B. Day and Company Kut-Kote Remover D Savogran Company Strypeeze E National Chemical and Manufacturing X-Cell-All (nonflammable) Company F Turco Products Incorporated Striplac G W Mo Barr and Company Strip-X H Pittsburgh Plate Glass Company Paint and Varnish Remover (Liquid) I Wilson-Imperial Company No-Wash Remover J Technical Color and Chemical Works Red-Devil Liquid 99 K Prudential Chemicals Manufacturers Pronto L W. P. Fuller and Company Conqueror Paint and Varnish Remover M Boyle-Midway Incorporated Radiant Remover N W. M. Barr and Company Klean-Strip *O0 National Chemical and Manufacturing (a) Shure-Kutter Company (b) X-Cell-All (flammable) P Reliable Remover and Lacquer Corporation Reliable Remover Q Bishop and Conklin Company Paint and Varnish Remover R Samson Paint and Chemical Company Instant Paint and Varnish Remover S Pittsburgh Plate Glass Company Paint and Varnish Remover Extra Potent T Universal Technical Products Company Universal Remover U Landon Products Incorporated El-Pico V Dux Paints and Chemicals Incorporated Atomic Remover W Certified Solvents Company Certified Remover X Southern Lacquer and Paint Corporation Protekto Coatings *Shure-Kutter and X-Cell-All (flammable), both manufactured by the National Chemical and Manufacturing Company, have identical formulations.

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN TABLE II COMPARATIVE RESULTS OF COMMERCIAL PAINT AND VARNISH REMOVERS SUBMITTED BY THE REARDON COMPANY Formula Panel System Reference Observations No. Letter* 1 Filler, alkyd urea A Unsatisfactory; softens after 30 min sealer, alkyd urea topcoat. Air-dried B Unsatisfactory; softens after 30 min since July, 1953. C Softens enough for removal after 30 min D Unsatisfactory; no effect after 30 min E Best of these six; softens enough for removal after 30 min F Unsatisfactory; no effect after 30 min 2 Filler, alkyd urea G Unsatisfactory; no blistering or softensealer, alkyd urea ing of film after 30 min topcoat. Air-dried H Unsatisfactory; no blistering or softensince July, 19535 ing of film after 30 min I Unsatisfactory; no blistering or softening of film after 30 min J Unsatisfactory; no blistering or softening of film after 30 min K Unsatisfactory; no blistering or softening of film after 30 min L Unsatisfactory; no blistering or softening of film after 30 min 3 Filler, alkyd urea M Appears to be satisfactory; complete sealer, alkyd urea removal after 30 min topcoat. Air-dried N Appears to be good; complete removal since July, 1953. after 10 min 0 Appears to be satisfactory; complete removal after 30 min P Appears to be satisfactory; complete removal after 30 min Q. Appears to be good; complete removal after 10 min R Appears to be satisfactory; complete removal after 30 min *Refer to Table I. ~ 7 ___________________________________~~~~~~~~~~~~~~~~~~~~~~'..

ENGINEERING RESEARCH INSTITUTE - UNIVERSITY OF MICHIGAN TABLE II (Continued.) Formula Panel System Reference Observations No. Letter* Viscosity Blistering Removal 4 ' No filler, lacquer G Too thin None None Top sealer, alkyd urea (T) sealer, lacquer H Too thin None None sealer, alkyd urea sealer, alkyd urea I Too thin None None topcoat. J Too thin None None Removers applied for K Too thin None None 1/2 hour. Varnish removed from 1/2 of L Too thin None None the section; remaining left as is to C Too viscous 5 07 Some indicate the degree of blistering. E Excellent 90/ Complete 4 No filler, lacquer M Too thin Along edges Fair Bottom sealer, alkyd urea (B) sealer, lacquer N Little thin 24 Very slight sealer, alkyd urea sealer, alkyd top- 0 Too thin None None coat. Removers applied for 1/2 P Too thin None None hour. Varnish removed from 1/2 of Q. Good. 304 Some the section; remaining left as is to R Too thin None None indi.cate the degree of blistering. S Good. 0 Very slight T Good 100%o Complete 5 Filler, lacquer A Too thin Slight None Top sealer, alkyd urea (T) sealer, alkyd urea B Good Slight Slight topcoat. Aged 75 hours in- weatherometer D Good Slight Slight without water spray to thoroughly dry. F Good None None U Too thin 504o Fair V Too viscous 85o Fair W Good 95 Complete X Too thin Along edges Slight *Refer to Table I. i____________________________________ 8 ____________________________________I

TABLE IIII BASIC PAINT AND VARNISH FORMULAS m 1 2 3 4 j 6 7 8 9 Parts by weight et-hylene chloride 177 177 177 177 177 177 T 177 177 177 m Paraffin (50-520C np) _2 2 2 2 2 2 22 2 2 m Methocel 4000 HG 3 __3 3 133 3 3 3 3 3 Methanol 12 12 12 12 12 -12 12 12 12 12 Mesityl oxide 6_______ Isophorone 6_____________ n Carbitol 6 _______ _______I Tetralin _____6 - 3 ________ 4 Cellosolve acetate_ 6 ________ Dioxane ________ 6 ___ I Furfural______ 6 4 Benzene _________ 6 Water______________ i Cyclohexanol _______ ^o Tergitol NPX ________ Raw material cost/gal as of October 1. 1954 1.4 1.51 1.51 13 1, 2 19 *1. 1.48 1,45 1.51 __11 12 15 14 15 16 1 lb 19 20 Methylene chloride 177 177 175 177 175 177 171 167 i61 155 Paraffin (50-52C mp) 2 2 2 2 2 2 2 2 2 2 Methocel 4000 HG 3 3 3 3 3 3 3 3 m Methanol 12 12 12 12 12 12 12 12 12 12 Mesityl oxide________________ Isophorone Carbitol 4 4 6 6 6 6 6 6 Tetralin Cellosolve acetate_ __ _ __________ ____ ' ioxater______ 2______ Qyclohexanol T Tergitol NPX 0o. Raw material cost/gal October 1, 1954 $149 $1.47 $1.48 $1.52 $1.49 $1.51 $1.45 $l1 $.3 $.30Z

TABLE III (Continued) I 21 22 ~23 24 25 26 27 2 29 5 _____________________________2_ ___2______2 1(5__^____6____7___2 177 10 ____ Parts b)y -weight Methylene chloride____ 16 16 173 177 177 17 1 175 177 177 _ Paraffin (_0__2~C mp) 2 2 2 2 2 2 2 2 Methocel 40 HG_____ _3 3 3 3 3 3 3 3 _ Methanol___________________12 12 12 12 12 12 12 12 12 12 Mesityl oxide 6_______6________ Isophorone_______________ 6 Carbitol 6 6 6 4_______ _ _ Tetralin _______6 _ 4_________ Cellosolve acetate _ _____________________ Dioxane_____________________________ I Furfural______________6 4 4 ___ Benzene____________________ 4 Water ~~12 14 4 4 4 4 4 444 Wae_________________11 __ - khk Qyclohexanol H Tergitol NPX_ _________ 0 Raw material cost/gal as of October 1, 1954_ 1.39 lo7 $1.46 *1.44 A147 $LL..42 $1L9 _1.46 *14 S _______________________________^1 ^ ^i 5L 55 56 7 839_!Methylene chloride 173 173 17l 17 170 172 175 152 172 Paraffin (50-520C mp.) 2 2 2 2 2 2 2 2 2______Z Methocel 4000 HG 3 3 3 3 4 4 5 4 _4 Methanol 12 12 12 12 12 12 12 12 12 m Mesityl oxide + Isophorone Carbitol 3 3 Tetralin 3 ______________ Cellosolve acetate6_________6____ __ Dioxane 6____________________ Furfural______________________ Benzene 6 _____ I Water 4 4- 4 4_ 6 47 4 4 4- __ Cyclohexanol________ Naphtha _______20_____________1_ Raw material cost/gal_____________________________ ____ _________________ as of October 1, 1954 $1.48 146 $1.49 $1.41 $1.48 151 $1.49 $1.29 $1.49 ___

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN TABLE IV COMPARATIVE RESULTS ON LABORATORY PAINT AND VARNISH FORMULATIONS Panel A System: Filler, alkyd urea sealer, alkyd urea topcoat. In weatherometer 75 hours without water spray to thoroughly dry. Formula Percent Observations No.* Blistering 1 80 Satisfactory remover 2 60 Satisfactory remover 3 80 Satisfactory remover; very fast action 4 70 Satisfactory remover 5 100 Satisfactory remover; very fast action; complete blistering 6 90 Satisfactory remover 7 95 Satisfactory remover; very fast action 8 50 Satisfactory remover 9 85 Satisfactory remover; very fast action 10 10 Unsatisfactory remover 11 80 Satisfactory remover 12 65 Satisfactory remover 13 95 Satisfactory remover; very fast action; better puffing (lifting) than 3; water contributes to overall action 14 100 Satisfactory remover; very fast action; complete blistering 15 100 Satisfactory remover; very fast action; excellent lifting 16 85 Satisfactory remover 17 100 Satisfactory remover; very fast action 18 95 Satisfactory remover; very fast actions viscosity quite low; evaporates too fast; application on a "wet" day 19 None Unsatisfactory remover 20 None Unsatisfactory remover 21 None Unsatisfactory remover 22 None Unsatisfactory remover 18 95 Satisfactory remover; application on a "dry" day; action slightly slower with decreasing humidity 24 None Unsatisfactory remover 25 None Unsatisfactory remover 26 None Unsatisfactory remover 27 30 Fast action 28 40 Fast action 29 5 30 25 Fast action Note: All removers applied uniformly for comparison purposes except 24 -through 30. Formulas 24 through 30 were applied in a thinner coat. The addition of 2* water resulted in too low viscosity. *Refer to Table III. _______________________________________ 1 _______________...

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN TABLE V COMPARISON OF COMMERCIAL AND LABORATORY COMPOUNDED PAINT AND VARNISH REMOVERS Panel D System: No filler, lacquer sealer, alkyd urea sealer, lacquer sealer, alkyd urea sealer, alkyd urea topcoat. In the weatherometer 75 hours without water spray to thoroughly dry. Minutes Formula Before Percent Refer- Viscosity First Blister- Observations ence Blister ing C* Too viscous 5 65 Satisfactory remover E Good 5 25 Unsatisfactory remover Q Good 5 30 Unsatisfactory remover S Good 7+ 20 Unsatisfactory remover; film remains wet for more than 1 hour and is oily T Good 6 90 Good remover; good blistering U Too thin 10 10 Unsatisfactory remover V Too viscous 5 90 Good remover; fair blistering W Good 4 25 Unsatisfactory remover 39** Too thin e 4 95 Very satisfactory remover, but low viscosity 36 Little thin 5 100 Excellent remover; rapid acting; 1 minute for complete blistering 37 Very good 4 95 Excellent remover 3 Good 8 85 Good remover, but dries too rapidly 13 Good 6 85 Good remover, but dries too rapidly 23 Good 6 90 Good remover 17 Little thin 6 85 Good remover 35 Very good 5 100 Excellent remover 27 Little thin 6 100 Excellent remover 9 Good 9 10 Unsatisfactory remover 5 Good 5 30 Unsatisfactory remover 6 Good 8 5 Unsatisfactory remover 15 Good 5 35 Unsatisfactory remover 28 Too thin 4 90 Very satisfactory remover, but low viscosity 29 Too thin 4 90 Very satisfactory remover, but low viscosity 38 Very thin None One heavy application no effect 14 Too viscous 5 15 Unsatisfactory remover 38 Very thin 60 First heavy application no effect; second heavy application 45 minutes after first produced some blistering and lifting; result after two applications is similar to commercial removers classified as unsatisfactory *Refer to Table I. *Refer to Table III. Note: All removers applied liberally but uniformly for comparison purposes. 12

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