Patented Mar. 11, 1947 2,417,344 UNITED STATES ‘OFFICE 420 Monsanto "Chemical ‘company, YSt. vlL‘ifllliS, ‘Mm, alcoriporation‘of Delaware ' ‘Noinawiiig. ii'ppiicajtionmayisfrei'z, serial No. 4423232 (Cl. 11064-186‘) :8 Claims. ‘1 improved coating compositions, and particularly This invention ~relatesfto ‘the preparationof ‘to the preparation of-la'cquer 'compositionscon ’ I It vhas been recognized forrnfany years Ethat ‘pigmented ooatin’ga'such asipaints and varnishes, are subject to what ‘is known as “h'ardisettli'ng,” i. e., that type of-‘settling-tvhiéh'resultslin'lthe formation er a hard cake ‘which ‘isyvery difficult ‘hinder in-thelacquer'isnot too-low. Lacquers, however, ‘commonly-1oompriselmixtures ¥ or more for ;less polar isdlvents, f-su'ch asl'es'ters, 'iketo'ne‘s. and to redisperse. IIn'generaL-"highIydispersed pig alcohols, ‘with hydrocarbons, which ;are essentially ‘non-pclan'and-as' the proportion of hydrocarbons I ine'nts settle slowly, ‘but are especially subject-to hardse'ttlin'g of'thetype described. riAe-?occulated pigment -'suspension, on ‘the other vhand, ‘settles rapidly, but ‘forms a voluminous, iloosely packed ‘‘ layer, enclosing considerable liquidin the pores and capable ofeasy redis‘persion. The extent of settling and the degree ofe?occulationlu'sually de— pend not only ‘upon what ‘is adsorbed at~the*s1ir ‘face of’ the ‘pigment but also upon the ‘nature :of the adsorbed layer and upon the nature or the ‘liquid in which the pigment and i-lits'a'dsorbed layer ‘are suspended. In the case of pure liquids, noni'polar-solvents tend to'yield ?occulated suspensions ‘while polar liquids tend to yielddispersed, hard settling types. In non-polar liquids,‘ such as benzene, the pres~ fence of or'addition of an amountcof-"water su?‘l ‘cient to coat the-suspended pigment with a mono molecular layer of water tends'toIpro-mote ?occu lation and the formation ‘of more voluminous sediments than is the c'as'e‘with pure liquids ‘not containing Water. ‘As thepolarity of the solvent increases, however, thatis, as its kinship @with water becomes closer, the'addition 'of‘waterrbe comes less effective and the pigment tends'more and more to settle hard. In the case of'ethyl acetate, for example, ‘which is more polar than benzene, a larger amount of Wateris'neces sary to give a certain degree of ‘?occulation as measured by the volume of the ‘settled, pigment layer. In the case of methanol, Which is more polar still, no amount'of'w'at'er produces ?occula tion. Numerous 'eifo'rts have beenmade to avoid ‘the e?ects ‘of- hard v-s'ettling,iin some instances, with considerable success. Small amounts of 'stearates, such‘ as sodium,‘ aluminum - and zinc stearate, "for example, ‘have been added to paints, varnishesand lacquersior ‘the purpose of ?occula'ting or pre venting the ‘hard settling of "suc'h‘subs'tances as diatomaceous earth. These'materiais, however, ‘tend to1vveaken'1the ?lm‘ formed upon-applying ‘jection‘all?lms. As indicated above, water is also in some 9in - stances -'e'ifective iii-‘preventing :hard settling, :and ‘this supp-lies vnot only‘to ' ordinary pigments, ‘but ' also '7 to Ia'ero‘gel containing »-l'ac'q'uers, particularly ‘if the co‘r1'centrationv of ‘the nitrocellulose ‘or other ‘Gaining pigments, aerogels or like substances tending toi‘rs‘ettle. 2 “er'ates which vresult ~"in rough or rotherwise ob~ is decreased ;~m'or'e and. ‘more water 1is- required? for i'?occu-lation, "While insome cases inc amount of "Water vwill produce ‘satisfactory suspensions. 'In “any case, the addition ‘of’ large amounts of ‘Water ‘is ‘inadvisableas it ‘increases the possibility 3.0f ~"c‘ontamination or‘ discoloration Lo'fcth'e ‘coating. in the presence of metals. lJItli's at primary‘ object-fofithe present :invention “to ipr’ovi'defa‘n 'improvedx'methodiof preventing ihardlsettling inicoating compositions. further i'objectiof the invention is to prepare soft ‘settling ‘coating :compo’sitions ‘which "do not lfo'rmi‘tveak orfpoorlyadhering ?lms lupon drying. 'furthersobj ect ‘ofi the invention is to prepare soft: settling rcoating .i'compositions of :the type de scribed; Iwhich previously;could ‘not-be. made‘ soft settling-'i-bec'ause-"of the low-concentration'iof the binder and/or the excessive polarity of the vehicle ‘used. L‘A"furth‘er object of theinvention ‘is'to'p'rovide an agent'for incorporation ‘in 'la'cquerspr' ‘other . coating 'compos'itionswvhich‘not "only'acts" to we ‘vent hard settling,'but ‘t‘endst'o‘prevent ‘deteriora tion 'or ‘discoloration vof ' the ‘ coating 'whe‘n‘in" the .ipres'en‘c'e‘ of ‘ metals. ‘ Still further objects and - advantages or the in "ventionwilrappear from the following description ~~andzappended ‘claims. :Beior'e explaining in de ‘itaiihtheipresent- invention, however, it is to-ibe ': understood-that the/invention’ is not limited in its "applicationit‘o the details-described herein,-since Lthe inventionis' capable'cof other embodiments and ~ofi1b'ein'gpra'cti‘ced orrcarried out in variousways. :--A1so1' it' 'isi-to bet-understood‘ that‘ithe ,phraseology for terminology employedxherein is- for-the-purpose of description andinot. oflimitationeand it-is'not ~lintended l-tosli'mit the invention claimed ‘herein? be 50 » yond: the requirements :of' the :prior art. The invention is‘ carriedi'out‘ inlzgeneralvby ad mixing withthetpigmentedcoating'solutionismall, ' and‘ inlmostinstances;minuteiamounts of; an. am 'the coating, and "to" reduce its adhesion-tometa'ls - monium,':aiky1amine; silkylblarhinaialicyciic amine "orother‘surfaces. They also tend'to‘form- agglom-' 55 or h'eterocy'cli'ci amineisailt of a suitable inorganic 2,417,344 the range of 1X10?‘3 to l.8><10'5. In order to be effective however, the amines should be used in the presence of, or in the form of salts of acids or organic acid. The salt employed should be sol uble in the coating vehicle in the small amount required and should be a salt of at least moder about as strong as or stronger than formic acid, ately ionizable constituents. Speci?c salts which which has a dissociation constant of 2.4><10-4. Moreover, the salts thus formed or used should may be used in accordance with the invention in clude: the mono, di and tributyl and amyl amine be suf?ciently soluble in the solution being treated to avoid any appreciable precipitation. Citric. acid, which has a primary dissociation constant salts of ortho and pyrophosphoric acids; dibutyl . amine sulfate; triamyl amine malate; the ammo nium salts of maleic andphthalic acids; and the of 8><l0-4, gives somewhat more satisfactory re diethyl amine, mono, di, and tributyl and amyl 10 sults than formic acid, while acetic acid, which has amine and the Cyclohexyl amine and morpholine a dissociation constant of 1.9><l0—5,,is, distinctly . salts of citric acid. ‘ less satisfactory than formic acid. Salicylic acid, Instead of adding salts, as such, to the coating which has a dissociation constant of 1>< 10-3, solution, it is also possible to add separately, a 'would be expected to be satisfactory, but was suitable amine or ammonia, and an acid capable 15 found to be entirely unsuitable, probably because of reacting with the amine to form a salt having of the formation of a complex ion, which pre- the desired anti-settling or flocculating action. cluded the formation of the R1 R2 R3 NH+ ion in ,In every instance it is essential that the resulting sufficient amounts. salt be thoroughly soluble in the solvents of the Tests were also made with pyridine, which has coating, that is, thoroughly soluble at least in the 20 a dissociation constant of 1.6X10f9, and. aniline, small amount required. Both substances should which has a dissociation constant of 4.6><l0—l°, also be at least moderately ionizable, as previously in both instances in combination with suitably indicated. ‘ I strong acids, Salts of these bases however do not In those instances Where the coating composi appreciably improve the hard settling character tion is already quite acid, thatis, already contains 25 istics of the lacquers treated, which indicates be appreciable quantities of acid, as for examplein yond doubt that the effectiveness of any soluble lacquer containing shellac, copals, alkyd resins, ammonium or amine compound employed depends et cetera, the'addition of acid is unnecessary, and suitable results may be obtained by merely adding an amine or ammonia to the coating composition. 30 Moreover, quaternary ammonium compounds, . When strong bases such as cyclohexyl trimethyl ammonium hydroxide are used, it is unneces sary to employ an acid, as such bases are suf such as cyclohexyl trimethyl ammonium hydrox ?ciently dissociated and have the desiredeffect on the lacquer, provided they are su?icientlysolu ide, dicyclohexyl dimethyl ammonium hydroxide, phenyl trimethyl ammonium hydroxide,‘ and phenyl ethyl dimethyl ammonium hydroxide, may largely upon the extent of its ionization. ‘ 35 ble, without the addition of acids. In the case of the weaker bases, such as ammonia and the be used in all instances without acid addition, as aliphatic amines, which in general have a dis these compounds are all very highly ionizable and sociation constant of not less than about 1x104, do not require the addition of an ionizable acid to it is necessary to employ in combination there obtain the desired results. with preferably an acid which is as strong or 40 In determining what substances are suitable stronger than citric acid, but in any case about and what degree of ionization is required for the as strong as formic acid. Thus, the acid should purposes of this invention, tests were made‘ by have a dissociation constant‘ of not less than adding varying but in all instances minute about lXl0'4. amounts of selected salts or hydroxides, or mix In general, exceedingly small amounts'of'the tures of amines and acids capable of forming salts or bases described herein as being suitable salts of the type described, to a lacquer solution may be used. For example, as little as .0001 prepared by mixing 9 parts by volume of commer mol of alkylamine and an equal amount of acid cial butyl acetate with one part by volume of a for each 100 cc. of lacquer solution is suflicient. base grind of the following composition: When the amounts of amine and acid are each Per cent by weight ' reduced to less than .0001 mol per 10000. of solution, protection against hard settling in the lacquer is lost. Cyclohexyl trimethyl ammonium hydroxide and like quaternary ammonium com Butyl acetate ___________________________ __ 25 Butyl alcohol ___________________________ __ 20 Toluene ___ __ 29 Denatured alcohol ______________________ __ 2.4 Blown castor oil ________________________ __ 5 1/2 sec. nitrocellulose ____________________ __ ‘ 5.5 Santocel (silica aerogel) ________________ __ 13.1 , pounds, however, may be used in amounts as lowas .00005 mols per 100 cc. of solution. Larger amounts of the anti-settling or flocculating agent ' may be required, when the amount of pigment in This permitted a relatively accurate comparison of the relative eiiectiveness of the various sub stances tested. As a result it was discovered that the amine or ammonium salts or hydroxides, or the mixtures of amines and acids, to be effective, must be soluble in the liquid being treated and must be capable of developing a high concentra tion of NR1 R2 R3 R4+ ions, in which R1, R2, R3, R4 represent either hydrogen or an organic radical. Where the amine or ammonium hydroxide, or the the coating is increased. ’, A further understanding of the invention will be obtained from the following examples: Erample I A commercial furniture lacquer was prepared by dissolving suitable amounts of 5 second nitro cellulose, a rosin-maleic aci-d-‘glyceride‘resin and a plasticizer in a conventional lacquer solvent mixture comprisingra mixture of esters,alc0ho1s and hydrocarbons. The resulting lacquer was acid in combination with it, has little tendency given a dull or ?at finish by incorporating there to dissociate, the effect is to produce in the solu 70 in a pebble mill grind of silica aerogel in, such an tion not the active NR1 R2 R3 R4+ ion, but the amount as to provide 15% by weight of’ silica free amine NR1 R2 R3, which is inactive. ' based on the weight of the solids in the lacquer. Of the amines tested, including'ammonia, those About 0.25% by weight of dibutyl amine _pyro which were e?ective for the purposes of this in ventionall had a dissociation constant within 75. phosphate based on the total weight of‘the lac agreem "5 '16 quee- wes then; added after ?rst dissolving; the nwiolihosphate: in about. an. equal; weight of de natured; alcohotto iacilitate mixing. The aerogel in; the lacquer’ settled, in a ?occulent. condition which permitted: easy redispersion. whereas the A. base. grind of silica aerogel in a. portion of the above, clear vehicle was then prepared by mixing the following materials in a pebble mill in the proportions given: same-lacquer was; subject to hard settling when the, pyrophosphate was omitted. Per cent by weight ' Clear base _______________ __‘ ______________ __ '74 Example II» To a solution- containing, '75 parts by; volume of,‘ ethyl; acetate. and. 25.‘ parts of ethyl alcohol Silica aerogel ____________________________ __ 15 Butyl acetate ____________________________ __ 1‘0 10 Citric, acid _______________________________ __ 1 The resulting grind was then, mixed with ad' there-was added about 6% by weight. of 5 sec ond nitrocellulose and about 0.2% of dewaxed shellac‘, The resulting‘ lacquer was flattened» by grindinginto it about 1% by. weight of. silica aero geibased on~,the_ solids in the lacquer. About ditional clear base and monoamyl amine in the following proportions to give a ?nal flat lacquer composition having very desirable soft settling 15 characteristics. , 0.201%, by. Weight of dibutylaminepyrophosphate Per cent by/weight leased; 0.11- the; total, weight of the lacquer was then added the: pyrophosphate being, first dis. solved inalcohol'to facilitate, mixing. The, addi Aerogel grind _________________________ __ 10 Clear base ______________________________ _. 89.96 Monoarnyl amine ______________________ I. 0.04 the?hardsettling, which occurred ._ when the pyroe ment of lacquers which have been ?atted with tion of_ the pyrophosphate e?ectually ‘ prevented 20 Although the examples refer solely to the treat silica aerogel, it should be understood that‘the phosphate was. Omitted... invention may be equally as well, if not more Example III advantageously applied to other types ofcoating Five percent by. weight of silica aerogel based on the lacquer solids was ground in a pebble mill into a celluloseacetate lacquer of the following composition‘: , materials, such as paints‘, varnishes and “syn thetics,” to which aerogels" or‘ other forms" of pigment have been added for any purpose. In general, however, there is- more need for the Per cent. by weight 30 ?occulating‘agents‘ described herein in lacquers, as ‘lacquer solutions frequently contain a large 9.2 proportion of polar solvents, which tend to‘in -g _____ __,__-___ ____ __._ _____ -- 11-5 Toluene,_____,,_g,_ ____ _________ ____________ __ Butyl acetate crease the possibilities of hard settling. The anti-settling ‘or ?occulating agents used‘ in accordance-with the invention may be added to 35 the coating solutions in anyv desired manner; It Methyl phthalyl ethyl glycollate ____ _,_____ 9.2 is preferableihowever to ?rst prepare a relatively Cellulose acetate _______________________ __ 4.1 concentrated solution of the ?occulating agent The silica’ aerogel in the above lacquer settled in in a solvent or solvent mixture which is readily a ~few>hours tosa compact mass, butwhen 0.05% miscible with the coating composition to be by weight Of dibutyl amine‘ pyrophosphate based 40 treated. Suitable solvents for this purpose in on the» total weight of the lacquer was added clude acetone, lower aliphatic alcohols, glycol thereto, only'a slight subsidence to a‘ soft volu mono ethers, and the like. minous layer‘ occurred. ' Aerogels may be added to the lacquer in vary Example IV ing amounts depending on the degree of flatting desired. Thus it is possible to employ the To a lacquer consisting of 37% by weight of aerogels in amounts varying from 0.02 to 30% ethyl cellulose and 93% of acetone was added, by. weight based on the weight of the lacquer‘ about 3% by weight of silica aerogel based on Acetonehgg-g-g ------------- _-,_ _______ -- 26.4 Ethyl acetate __________________________ __, 24.0 Methyl Cellosolve ___ ___________________ __ 15.6 solids. When relatively hlgh'COl'lCBIltl‘?tlOllS of the solids in the‘lacquer; The suspension of silica silica aerogels are~ employed, it is advantageous aerogel thus formed was effectively stabilized against hard settlingby adding‘ to, the lacquer 50 ?rst to incorporate in the lacquer a small por tion of acid, such‘ as phosphoric or citric acid, as about 0.3% by weight of "dibutyl amine pyro the presence ‘of the acid in the lacquer during the grinding tends either to lower the viscosity phosphatebased ‘on the total weight of the lac quer whereas when the pyrophosphate. was omitted theyaerogell settled. to ,acompact cake, of the grind for a given silica concentration or permit. a higher silica concentration for a, given not easily redispersed. viscosity. A composition free of hard settling can then‘ be obtained by treating the lacquer thus prepared with a suitable amine, which; if added during the grinding in of the aerogel, tends but- in which theethyll cellulose l was replaced by cellulose .acetobutyrate orchlorinated rubber. 60 to raise “the viscosity. The primary, secondary and tertiary butyl or Example V amyl amine salts of phosphoric or pyrophosphoric' Alsoft settling ?at lacquer was prepared by acid are preferred for the purposes of this in ?rst making a clear base of the following com vention, since they not only favorably aiiect the position: 65 suspension of the aerogel or other pigment'in the Per cent by weight coating solution, but have a marked anti-cor Equally good results were also obtained by = adding’ small amounts of- dibutyl amine pyro phosphate to compositions similar to the above, Ethyl Butyl Ethyl Butyl acetate acetate alcohol alcohol _________________________ __ __________________________ __ __________________________ __ __________________________ __ 10 17 10 l0 Aromatic petroleum naphtha ___________ __ 30 5 second nitrocellulose _________________ __ 5 Rosin-maleic ester resin ________________ __ 15 Dibutyl phthalate ______________________ __ 1.5 Blown castor oil _______________________ __ 1.5 rosive action when used in coatings which are to be packaged in metal containers. Where reference is made herein or in the ap 70 pended claims to “pigments,” it is to be under stood that this includes not only the inorganic oxides commonly added to coatings for coloring and other purposes, but also aerogels, which are usually added to obtain a ?at or dull ?nish in 75 the applied coating. The term. "hard settling” * 2911173344 solvent therefor, and silica aerogel, said aeroge'l is also intended to ‘referst'oithat form of settling cellulose esters’ and cellulose ethers, said deriv ative being thinned to a flowable consistency being present in an amount su?icient to provide from 0.02 to 30% of silica based on the weight of said nitrocellulose, said'composition having‘ added. thereto from 0.02 to 0.5% by weight of dibutyl amine pyrophosphate based on the total weight of the lacquer composition and su?lcient to substantially prevent the settling of said and inorganic aerogels, and a small amount of pigment suspended therein which tends to settle ' which results in a hard or compact cake, which is di?icult to redisperse by ordinary means. i What I claim is: 1. A lacquer composition comprising a cellulose derivative selected from the group consisting of aerogel in the form of a hard cake. with ‘a solvent therefor, an inorganic pigment 7. A coating composition comprising an organic ' suspended therein which tends to settle in the 10 ?lm-forming vehicle thinned to a ?owable' con form of a hard cake, said pigment being selected sistency with a solvent therefor,’ an ‘inorganic from the group consisting of inorganic oxides in the form of a hard cake, said pigment being ‘dibutyl amine pyrophosphate, said pyrophosphate selected from the group consisting of inorganic oxides and inorganic ,aerogels, and a small amount of an ammonium compound selected from the group consisting of ammonium‘ and amine salts of an acid other than salicylic acid, being present in the amount of not less than 0.0001 mols per 100 c.;c. of said composition and in anamount su?icient to subsantially prevent the settling of said pigment in the form of a hard cake. < 2. A lacquer composition comprising a cellulose en the basic constituent of said salts having a dis sociation constant of not less than 1><10-5 and derivative selected from the group consisting of the acid constituent of saidv salts having a dis cellulose esters and cellulose ethers, said deriv sociation constant of not less than 1><10-4, said ative being thinned to a ?owable consistency basic and acid constituents each being‘present with a solvent-therefor, an inorganic pigment suspended therein which tends to settle in the _. in the amount of not less than 0.0001 mols per 100 c. c. of said composition and in an amount form of a hard cake, said pigment being selected suf?cient to substantially prevent the settling of from the group consisting of inorganic oxides and said pigment in the form of a hard cake. 8. A coating composition comprising an organic ?lm-forming vehicle thinned to a ?owable con sistency with a solvent therefor, and an inorganic inorganic aerogels, and a small amount of mono amyl amine citrate, said citrate being present in the amount of not less than 0.0001 mols per 100 ' c. c. of said composition and in an amount suffi pigment suspended therein which tends to settle in the form of a hard cake, said pigment being selected from the group consisting of inorganic oxides and inorganicaerogels, said composition having added thereto small amounts of an am monic compound selected from the group con sisting of ammonia and amines and an acid other than salicylic acid, said ammonic compound hav cient to substantially prevent the settling of said pigment in the form of a hard cake. 3. A lacquer composition comprising a cellulose derivative selected from the group consisting of cellulose esters and cellulose others, said deriv ative being thinned to a flowable consistency with a solvent therefor, an inorganic pigment sus pended vtherein which tends to settle in the form of a hard cake, said pigment being selected from 40 ing a dissociation constant of not less than 1><10—5 and said acid having a dissociation con the group consisting of inorganic oxides'and in stant of not less than 1>< 10~4, said ammonic com organic aerogels, and a small amount of triamyl pound and said acid each being added in the amine malate, said malate being present in the amount of not less than 0.0001 mols per, 100 c. c. amount of not less than 0.0001 mols per 100 c. c. of said composition and in an amount sufficient of said composition and in an amount sufficient to substantially ‘prevent the settling of said pig to substantially prevent the settling of said pig ment in the form of a hard cake. 4. The lacquer composition substantially as de ment in the form of a hard cake. scribed in claim v1 but further characterized in that the inorganic pigment contained therein is an aerogel of an inorganic oxide. ' GERALD R. BARRETT. 50 ' 5. A lacquer composition comprising a cellulose " derivative selected from the group consisting of cellulose esters and cellulose ethers, said deriv ' REFERENCES CITED Thei'following referencep are of record in the ?le of this patent: a solvent therefor, and silica aerogel, said com position having added thereto a small amount of dibutyl amine pyrophosphate, said pyrophos phate being added in the amount of not less than 0.0001 mols per 100 c. c. of said composition and in an amount su?icient to substantially pre : “UNITED STATES PATENTS ative being thinned to a flowable consistency with . Number Name Date 2,245,104 Greubel __________ __ June 10, 1941 2,192,954 Sloan et a1. _.._>______ Mar. 12, 1940 2,192,956 Sloan et a1 ________ _.. Mar. 12, 1940 2,288,413 Morgan __________ __ June30, 1942. 2,192,955 2,126,925 Sloan et'jal ________ __ Mar. 12, 1940 vRyan et a1 ______ __ Aug. 16, 1938 7 2,371,866 6. A lacquer composition comprising nitrocel 65. lulose thinned to a ?owable consistency with a . Barrett -1 ________ __ Mar. 20, 1945' vent the settling of said aerogel in the form of a hard cake.