[1]0 *,m 1 2@709@690 UIULC;D S'tates Patent Office Patented May 31, 1955 2 2,709,690 EPOXY RESINS ESTEIRWIED WITH DRYING OIL FATTY ACIDS AND PHOSPHORIC ACID Etic S. Narracott, Worcester Park, England, assignor to Shell Development Company, Emeryville, CaIif., a corporation of Delaware No Draiving. Application May 19, 1952, 10 Serial No. 288,760 contained in the average molecule of the polyether. In the case of glycidyl polyethers of a dihydric phenol, the 1,2epoxy equivalency is normally bet@veen 1.2 and 2.0. The simplest of the polyethers are diglycidyl dictliers of dihydric phenols which contain a single divaleut aromatic hydrocarbon radical from the dihydric phenol and have two glycidyl radicals linked thereto by ethereal oxygen atonis. More generally, the polyether is of resinous character and contains two or more arorriatic hydrocarbon radicals alternating with glyceryl groups whicli are 6 Claims. (Cl. 260-18) connected therewith through ether oxygen atoms. Ordinarily, the polyether is a complex mixture of compounds This inverition relat,-s to a process Lor producing a 15 rather than being a single particular coinpound The mixed estei- wliieh is adapted to coating metal surfaces principal product may be represented by l@he formula 0 0 C13r--CH-CHa-0- R-0-CH2-CHOH-Olf2-O@ R-0-CH2-CfZI-\CHj with protective filnis, particularly surfaces which consist @vh olly or priiii,,irily of aluminum, zinc and magnesiurn. Whe n protective coatings are applied to metals, it is 25 ofte n the practice to treat the metal surface with an initial primer which is known in the trade as an "etch primer," and then to apply conventional surface coatings such as und ercoats and paints, varnishes or enamels, the etch prim er sei'ving to protect the metal from corrosion and 30 also to bond the superimposed surface coatings to the ineta l. Etch primers in use at present consist of a fluid organic poly mer such as a mlxture of polyvi@yl alcohol and formalde hyde or butyraldehyde together with aqueous - phos- 35 phor ic acid. In such etch primers, the phosphoric acid i,-, adde d to the polymeric material immediately before use, and the resulting mixture has an undesirably short pot life befo re gelliiig occurs and renders the primer unusable. A method has now been discovered for producing a 40 spec ial n-iixed ester froiii aii aroinitic polyether compou nd which is esterified first with a drying oil fatty acid and then with pliosphoric acid. The mixed ester can be appli ed as a film to metal surfaces where it will air-dry 01- can be baked to a hard tough protective coating having un- 45 tisual adhesion. Furthermore, the pot life of the mixed ester is indefinite when stored in closed containers@ The esteriflable aromatic polyethers employed iii the proc ess are obtainable by reacting a polyhydric phenol with epichlorhydrin or dichlorhydrin and sufficient alkali 50 to combine with the released hydrogen chloride. The poly ethers of a dihydric phenol are particularly suited for use in the pi-ocess. These polyethers have a chemical struc ture wherein the glyceryl radicals ftom the epichlorhydr in or dichlorhydrin and the divalent aromatic hydro- 55 carb on radicals from the dihydric phenol are present as a chain with the two types of radicals alternating and being joined into the chain by ethereal oxygen atoms. The termi nal groups of the chain in the polyethers may contain 1,2-epoxy groups due to the presence of a glycidyl 60 radic al thereat altholigh some of the terminal grolips may be d;liycli-oxyl-clycerol ridicals from hydratioii of the glycidyl radical. The 1,2-epoxy equivalency of the glycidyl polyethers of a polyhydric pheiol employed in the process is a value 65 grea ter thaii 1.0, ttie 1,2-epoxy equivaleiicy being the num ber of epoxy groups 0 70 wherein n is an integer of the series 0, 1, 2, 3 and R represents the divalent hydrocarbon radical of the dihydric phenol. While for aliy single niolecule, i., will b,an integer, the fact that the polyether is a mixture of con-ipotiiids causes the determinect valiie for n, e. g., frori-i molecular weight measurement, to be an average which is not necessarily zero or a whole number. Although 'the polyether is a stibstance primarily of the above formula, it may contain some material with one or both of the terminal glycidyl radicals in hydrated fori-n. , The esteriflable groups contained in the polyethers ai-e attached io the glyceryl radicals 1 (-CH2-CH-0112-) therein. These esteriflable groups are epoxy groups and alcoholic hydroxyl groups, botti of which are attached to the glyceryl radicals. Upon reaction of the polyethers with the unsaturated fatty acids, both of these esterifiable groups form ester linkages to the glyceryl radicais by joinder thereto of acyloxy groups. While ii is ordinarily a value from 0 to about 12 in the polyethers, it is generally prefei-red to employ esters from polyethers wherein n is about 2 to 9. An ,y of the various dihydric phenols is used in prepar' ing the esteriflable polyethers including mononuclear phenols such as resorci-@iol, catechol, hydroqtiiiione, riiethyl resoreinol, etc.; or polynuclear phenols like 2,2-bis(4-hydroxyphenyl)oropane (bisphenol), 4,4'- difiydroxybotizopbe@none, bis(4- hydroxyphenyl)methane, 1,1-bis(4-hydroxyphenyl)ethane, 1, 1 - bis(4 - liydrox3,plieDyl)isobuta@-ic, 2,2bis(4- hydroxyphenyl)butane, 2,2-bis(A-hydroxy-'-)-nethylphenyl)propane, 2,2-bis(4-hydroxy-2- tertiarybuL@,lplienyl)propane, 2,2 - bis(2 - hydroxynaphthyl)penta!ie, 1,5 - clih),droxynaphthatene, etc. The esteriflable polyethers are prepared, in general, by heating at about 50' C. to 200' C. the dihydric phenol with epichlorhydrin in a basic @-eactioii i,@iedii@ini. Depending upon the type of product desired, there is used from more than 1 to 2 or more mols of epichlorhydrin per mot of dihydric phenol. Also preseiit is a base sucli ,is sodium hydroxide, generally in amount of about 5% to 30% stoichiometric excess of the epichlorhydrin, i. e., 1.05 to 1.3 equivalents of base per mol of epichlorhydrin. In effecting the reaction, the dihydric phenol is mixed with an aqueous solution of the base aid hea.ted. The epichlorhydrin is then added rapidly to the stirred reaction mass. The initial reaction is somewhat exo:Lhermic so that a temperature rise occurs to sonic exteiii:. After addi-
[2]2,709,690 3 tion of- the epi,-hlorhydriii, heating is applied for several hours while stirring in order to complete the reaction. Wl,.i!-, still i@,. moi'c,.i stite, the for.,i-ied i)olyether is washed with waller tintil free of base, and then heated to remove water. The natu.,:e of t'tie glyceryl polyethers from polyhydric phenols can be better understood by considering preparation of a particular product which is preforred for u!se in the iiivention. For convenience, this product will here@ inafter be designated as polyether B. Polyether B Tnto a reaction vessel fitted with a stirrer, 4 mols of2,2-bis(4-hydrOxyphenyl)propane (bis-phenol) and 6.43 mols of sodiiim hydroxide as a 10% aqueous sofution are introduced and heated to about 45' C. whereupon 5 mols of epichlorhydrin are added rapidly while agitating the mixttire. The temperature is then adjtisted so that the mixture is heated at about 100' C ' to 105' C. for abotit 80 minutes. The mixture separates into a two-phase system and the aqtieous layer is decanted. The product is then washed with hot water until neutral to litmus i@,hercup,op. -h,-, resulting polyetiier is drained and debydrated by heating at about 150' C. The polyetbei- lia,s a softenin,L, point of abolit 100' C. (Diirrans' merctiry method). The niolectilar weight is 1400 me-.stired ebulliosocopically in ethylene dichloride so average n=3.7. The e ' alent weight to c terificaquiv s tioii is 175 -,vhich value is the grams of polyether that will esterify and combine completely with one gram molecule of fatty acid. This vallic is obtained by eating a samp'@e of the polyether with about twice the theoretical amoui-it of hi,-,her fatty acid necessary to react with all of the hydroxyl and epoxy groups, the higher fattv acid being Armour's Neofat No. 3 consisting of about 50% linolcie acid, 40% olcie acid, and 10% stcaric acid. The heating is effected at about 230' C. until a constant acid value is obtained. This may reqtiire 10 hours heating. By back titrating the unreacted fatty acid with base, a m-eastire is obtained from i-,,hich the equivaleiit weight to esterification is calculated. The polyether als6 had an epoxy value of 0.103 eqiiivalent per 100 grams and a hydroxyl value of 0.328 equivalent per 100 grams. The 1,2-epoxy equivalency is, therefore, 1.44. In like maiiner, otlier polyetliers of bis-phenol or of other dihydric phenols may be prepared which iiill have different mo'eciilar wei,-,hts and values for 7i depending upo.i the molar ratio of epichlorhydrin to dihydric phenol used -in preparation thereof. This fact is illustrated with various glyceryl polyethers ofbis-phenol inade with variat;oi,i iii itiolar ratio as showji iii the following table. Alol Mol R@t@o Ratio Soften- T@',q E@ 1)1- . I - illol ulv' I 2-Epoxy Polyetbor elljor_ NAOEE ng n Wt- t( @quivato EpiPoint, Wt. Esterifllyd loney to b I'll, ciliol,- - C. cation is- liydi@in Phenol - - - - A -------- 1 71 900 2.0 130 1.8 B -------- 1: 2,5 'I loo 1 400 3.7 175 1.4 C -------- -------- -------- 130 2:9 9.0 190 1.4 Polyethers of still higher moleciilar weight are best ob, tainable by reacting a polyether of lower molecular weight with a small quantity of diliydric phenol. For example, a resinous polyether having a softening point of about 130' C., a molecular weiglit of 2900 and an eauivalent weight to esterificatioii of 190 is obtaiiied by re.teting polyether A with an added 5% of bis-phenol. This reaction is effected by heating the polyether to, 150' C., and then adding the bis-phenol. The heating is continued for about two hours while stirring the rea@tion 4 200' C. This product, designated as polyether C, is listed in the above table. The process of the inveiition comprises licatin- and esterifying glycidyl polyether of a polyhydric phenol having a 1,2-epoxy equivalency greater than 1.0 and containing alternating glyceryl radicals and aromatic 0carbon radicals united chain-wise by ethar oxygen atoms with glyceryl radicals at each end thereof, ivith a dryinff oil fatty acid in amount of about 25% to 65% of the 10 equivalent quantity needed to esterify coiiipletely tl-ic polyether, the heating bein g continued with removal from the reaction mixture of formed water of reaction unti the ester product has an acid nlimber of less thpn 10, and then further esterifying the ester prodtict as a soluIr) ti,n in aromatic hydrocarbon solvent with about an added I% to 3 % of orthophosphoric acid (H3PO4) based upon the weight of the ester product from the first step bf the process. The ester product obtained in t]-ic first step of the process contains alcoholic hydroxyl groups, but no cpoxy groups. Owing to the mucli greater reactivity of the epoxy groups than alcoholic hydroxyl groups with free fatty acids, the epoxy groups are converted first to ester groups by an addition reaction wherein a molecule of 2;-) fatty acid combines with an epoxy group to give a tei@minal glyceryl radical having an acyloxy radical and an alcoholic hydroxyl group linked thereto. Coiitinuation of the esterification in the first step causes the reniaiiiing free fatty acid to esterify part of these formed alcoholic 30 hydroxyl I groups as well as alcoholic hydroxyl grolips initially present in the polyether. The esterification is cont I inued until substantially all of the drying oil fatty acid in the reaction mixtiire is esterified as evidenced by reduction in the acid num-ber to less than 10, preferably '.5t 1 or less. The resu'ito less than 5, and often to about iiig ester product contains alcoholic hydroxyl groaps primarily because instifficient drying oil fatty acid is lieate and esterified with the polyether. Thus ther,- is i-ised about 25% to 65% of the equivalent amount needed to 40 esterify completely the polyether and thereby convert aJI the epoxy groups and hydroxyl grolps to ester groi-i,-s. Preferably about 45% to 55% of the equivalent quantity of dr 1. ying oil fatty acid is used. Any of the drying oil acids are suitable for use in the 4i5 process including the acids dei-ived from linseed, soyabean, perilla, t)jng, walnut, oiticica and dehydrated castor oil. The drying oil fatty acids are well known in the art. The esterification of the polyether witli the drying oil "O fatty acid is effected by heatiiig the mi)iture of reactants at about 125' C. to 275' C. Stirring is helpful and preferably the esterification is condticted in an inert atiiiosphere such as by sparging with nitrogen or carbon dioxide. The water of reaction is boiled from the reaction nlixture. Although not essential for this purpose, use of an inert azeotroping agent capable ot rei-iioving formed water by distillation in usual fashioli is desirable attiiiies. Xylene is an excellent material for such use, although other suitable agents include benzene, toluene and aromatic petroleum distillates. In preparing the ester, the lieating and esterification is continued until the acid number of the product (solids basis) is reduced to less than 10, a fact which may be ascertained by withdranving of the reaction mixture and subjecting them to ional analysis. The partially esterified polyether obtained in the first step of the process is reacted and further esterified with orthophosphoric acid. This further esterification is effected with the initial ester product contained as a solution in aromatic hydrocarbon solvent such as benzene, toluene, xylene or aromatic petroleum hydrocarbons. The ester is normally contained as about a 30% to 60% concentration by weight in the solvent. When an aromass and gradually increasing the temperature to@ about 7.r) m4tic hydrocarbon solvent is employed in the first step
[3]5 as an azeotrople agent to remove@ formed water, it is convenient to employ the resulting solution of ester product for the further reaction with phosphoric acid. The phosphoric acid is used in amount of about 1% to 3 % by wei.-ht of the drying oil acid partial ester of the 5 polyether. Upon addition of the phosphoric acid to the ester solution, the further esterification reaction occurs. For this purpose, low temperatures such as about 15' C. to 40' C. are satisfactory, although higher temperatures may be used if desired in order to shorten the titne of re- I action which will take about 2 days at 20' C. Formed water of esterification is decanted from the mixed ester product which may contain some free hydroxyl groups or may have aU of the hydroxyl groups esterified, the presence or absence of hydroxyl groups being primarily ,,) dependent upon the particular polyether employed in the process, and the proportions of drying oil fatty acid and phosphoric acid used therein. The mixed ester product is applied to metal surfaces 2 by brtishing or spraying where it hardens by air drying or 0 baking. The rate of hardening is increased by incorporating a drier with the mixed ester such as about 0.02% to 0.1% cobalt as the naphthenate salt. Use of baking temperatures between about 100' C. and 200' C. gives satisfactory hardening in about 30 minutes to an hour. @5 If desired, pigments such as zinc chromate may be incorporated with the mixed ester, and in such cases it is possible to obtain satisfactory results with one coat of the primer in place of the etch primer and undercoat previously used. 00 The primer of the present invention has been found to give particularly satisfactory results in cases where e surface coating is an alkyd resin varnish or paint. The mixed ester primer gives good results on surfaces which consist wholly or primarily of iron, cobalt, - nickel 35 or copper, as well as on surfaces consisting wholly or prima rily of aluminum, zinc or magnesium. The invention is illustrated by the following examples which are not to be construed as limiting the scope of the inventi on. The parts and percentages are by weight. 411) Exain ple I A mixture of 55 parts of polyether B and 45 parts of dehyd rated castor oil fatty acid was charged to a closed 45 kettle and heating started in an atmosphere of nitrogen. The proportion of reactants was such that the acid amou nted to about 5 1 % of the quantity needed to esterify compl etely the polyether. At about 120' C. a stirrer was started and heating continued until a temperature of 5( about 260' C. was reached. The water of reaction was expell ed through a condeiiser as formed by sparging the reacti on mixture with a slow stream of nitrogen. Samples were withdrawn periodically for determination of acid number. The heating was continued until an acid 55 numb er of 1.0 was reached. The heating was then stoppe d, and after the product had cooled to about 205' C., the partial ester was thinned with sufficient xylene that the resulting solution contained 50% of ester. 60 Orie part of orthophosphoric acid was added to 70 paris of the xylene solution and allowed to react at about 20' C. After 48 hours, an aqueous layer separated and was discarded to leave the desired mixed ester in solution. To the solution of mixed ester was added 0.05% cobalt 65 (solids basis) as the naphthenate salt. Application of the mixtur e as a coating to sheet metal panels gave hardened films by air drying in 12 hours, or by baking at about 150' C. in 30 ininutes. The clear films had excellent adhesi on to sheet steel and aluminum, and the films of 70 the coated panels withstood flexing over a one-eighth inch diame ter mandrel without fracture. Simflarly - prepared films which were pigmented with zinc chromate, and with red iron oxide in a pigment to binder ratio of 2: 1, and applie d to steel and aluminum panels withstood immersion 75 2,709,690 6 in water (panels partly immersed and partly in air) foir eight weeks, without any sign of breakdown, Example 2 The mixed ester in xylene solution mras prepared as described in Example 1. Cobalt naphthenate was incorporated with the solution to provide 0.04% of cobalt based upon the weight of mixed ester. The solution was then brushed on both sides of sheet zinc panels and allowed to dry in the air. The resulting films were found to be flexible and to adhere well to the zinc. An iron ball of one pound weight was dropped on a coated panel from a height of 12 inches without rupturing the film. Upon immersing a coated panel in an aqueous solution containing 3% of sodium hydroxide for 90 days at a temperature of 20' C., no dtillness was produced on the film surface nor any separation of the film from the zinc panel. When the strength of the caustic soda was increased to 5%, the saine degree of resistance to deterioration was maintained for 50 days. 1
