CA1099834A - Modified epoxy resins, processes for making and using same and substrates coated therewith - Google Patents

Abstract

Abstract Discloses a technique for modifying an epoxy resin by reacting with addition copolymerizable monomer in the presence of at least 3% of benzoyl peroxide at about 110°C to 120°C, or the free radical initiating equivalent thereof. The reaction mixture obtained contains:
(a) unreacted epoxy resin;
(b) graft polymer; and (c) associatively formed by ungrafted addition polymer.
The graft polymer is formed from the epoxy resin by the grafting of addition polymer onto aliphatic backbone carbons of the epoxy resin, such grafting being at carbons that have either one or two hydrogens bonded thereto in the ungrafted state. The process is useful for making polymer blends for coating compositions, and particularly, coatings for cans for foods and beverages, especially for beer. The coating compositions may be aqueous dispersions ready for spray application, or concentrate that can be made up readily into aqueous sprayable coating compositions. Solvent vehicles may also be used.

Description

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l' l Brief Statement About the In~ention This i.nvention relates to novel resinous composi~ions that are particularly useful in coating cornpositions. More specifically, the invention is concerned with water-based coating compositions, and especially such ¦, compositions that are suitable for can coatings, particularly beverage cans.
¦I The invention is also concerned with processes for making the novel com-¦~ positio~s, processes for using them, and wlth the coated objects that are ¦¦ produced.

¦ Background of the Invention A major use for the epoxy resins i~ a~ surface coating materials~
They combine toughness, flexibility, adhesion, and chemical resi~taIlce to a very desirable degree. However, they have inherent limitations that ha~re restricted their use.
Coatings that contain no ~ rents have been prepared from very low molecular weight epoxy resins. The resin itself, u~ su~h coatings, serves as the wetting agent and as the vehicle for any pigments Or ~iller~
desired. Because there i~ no ~olventO coatings of this type tend to be free rom pinholes, but they have disadvantageE3 ~uch as brittleness, poor thermal stability, relatively high Co~tJ and short pot life, Coating compositions based on higher molecular weight epoxy resins have been prepared as solutions, formulated with solvent vehicle, curing agents and modiIiers, arld o.ften, with pigrnents and~ci~ier~. The epoxy resin is often in the form OI an e~ter, obtained by reactin~ the epoxy resîn with a ~atty acid, drying oil, or the like. While suitable for marly purposes, epo~y ester-based coatings are vulnerable to caustic attack.
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Ii, ¦¦ The ester linkages are not considerecl to be as stable as would be desirable, ¦l for many applications.
In recent years there has been a trend toward water-based coating compositions containing epoxy resins, because of ease of handling and cleanup. Many attempts have been made to devel~p such coatings, and some of these have met with some success for particular applications. One I promising area for the possible application of such coatings is for so~t drink and beer cans. This application ha~ always presented a challenge because of taste sensitivity. Can coatings in the past ha~Te tencled to alter the produc:t taste of canned beverages, in a variety of ways, ~ometimes i~y leaching t>f coating compo~ents ~to the beverage, sometimes by ad~orption of flavor notes by the coating7 sometime~ by chemical reaction, and often by some combination of the~e. There is a commercially important, technically challenging, large potential applicatil)n in can coating~ for a water-based coating composition that is chemically stable, absolutely inert in taste response, easy to apply, and ec~nomically competitive, and that produces coatings that have all of the other de~anding characterietics that are associated with that application, a5 reflected in the many prior art attempts to develop satisfactory products.

Broad 5t~1eme~ of ~h. InveD~ n While thi~ invention provides practical beverage can ~oating com-positionæ ~at meet the long-felt needs of the beverage induætry, the inVentiOI;
is alæo concerned with coating compositions generally, and with modified epoxy re~in-based resinou~ n~aterials from which coating compositions can be made, _3_ ~' ~ .
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In its broad aspects, this invention relates to a process îor modi~ying Il an epo~ resin by reactmg it and addition polymerizable monomer in the presence of at least 3% by weight of the monomer of benzoyl peroxide or the free radical initiating equi~alent thereo~ at the reaction temperature, which is usually in the range from about llO~C to about 120~C. This reactior li leads to a reaction mixture containing a blend of resinous materials, in-cluding unreacted epoxy resin, a novel graft polymer, and associatively-formed but ungrafted addition polyrner, The graft polymer has an epc~xy resin component that has an addition polymer component grafted onto it at aliphatic backbone carbons of the epoxy resin~that have either one or two hydrogens bonded thereto in the ungrafted ~tate.
The grafting that occurs seems to have an important e~ect on the properties of coating compositions Inade from reaction rnixtures of this type. For water-dispersible coatings, the addition polymerizable monomer is, at least in large part, an acrylic acid, and both the graft polymer and the ungrafted addition polymer are acid-function~l as a result. In the presence of an ic~izing agent, stable aqueous dispersions are readily prepared.
Such water-dispersed coatings are particularly useful for the formu-lation of can coatings ~or preserving items for human consumption.
Coatings o this kind are often referred to as sanitary coatings, and these represent an important, preferred group of embodiments of the inventiorl.
A sanitary coating composition, in accordance with the present invention, is composed of a ~ea¢tion mixture that includes acid-functional graft 11 ' , 1.

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polymer and addition po1ymer, of particular compositions, respectively, dispersed in an aqueous vehicle with an ionizing agent. The isinizing agent is generally a basic-reacting material that is driven o~ under the conditions of cure, i. e., during baking, and such agents are therefore referred to as "fugitive".
When properly formulated, sanitar~ coatings prepared in accordance with this invention are highly suitable for use in beverage ca~ coat~ngs, ~1 and particularly in beer can coatings. Their outstanding ad~rantage5 include ¦l ease of application and essentially cornplete inertness relative to taste, which advantages are especially important in beer can coatings.

Detailed Desc ption of the Invention The present invention is based upon the somewhat surprising di~-covery that when an epoxy resin and addition polymerizable monomer are reacted together at an elevated temperature in the presence o~ at least 3%
or more oPbenzoyl peroxide by weig~ of the monomerr or in the presence of the free radical initiating equivalent thereof at that temperatureA, grafting and additioil polymerization go forward simultaneously~ The grafting takes place at aliphatic carbons in the aliphatic backb~ne carbon chai~s of the epoxy resin tbat have either one or two hydrogens bonded thereto in the urlgrafted state. The reaction mixture that is obtained, ~rom a reaction of thi~ type, includes graft pol~ner" associati~ely-formed but ungra~ted addition pol~ner, and, as well, unreacted epoxy recin.
The grafting that occur~ exerts a profound in1uence on the properties of the reaction mix~re. Thu,s, when the addi~on polymerizable monomer include~ a major amount of an aerylic acid, both the graft polymer and the I I
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ungrafted addition polymer, that are produced, are carboxylic acid-functional, and in the presence of an ionizing agent, the reaction product may be readily and stably dispersed in an aqueous vehicle. For satisfac-tory dispersion in an aqueous vehicle, the Acid Number of the reaction mixture should be sufficient for establishing and maintaining the polymer Ii in the dispersion. For optimum curing results, a cross-linking agent is added to the dispersion such as, for example, an aminoplast.
The effects o~ graft polymerization in accordance Yvith this invention can be obser~ed, in the case of water~reducible coatings, when there is sufficient acid-functic~nality so that stable dispersions are formed. There are different ways ~n which this can be measured. Tnus, the addition polymer, when formed from an acrylic acid-containing polymerizable monomer, will contain carbo~ylic acid units~ These unit~ shouL~ constitute at least 2% by weight of the graft polymerJ for ease of dlspersion. However, ~ivhen the initial reaction mixture is low in either epoxy resin or in an acrylic acid, this measurement alone may not suffice. Accordingly, it is best to couple this mea~urernent with an Acid Number ~aiue ~or the entire reaction mixblre, which value ~hould be above 30 and generally will not exceed 220. A preferred range is ~rom about 45 to about 150, and a more preferred range, for eanitary coating composition binders, is from about 80 to about 90.
Even when the initial epo}~sr re3in reactanlt constitutes a major part of the reactioll mix~re, surprisingly little grafting may take place, while neyertheless producing a reaction m~xture which is apparently profoundly influenced by the presence OI the novel graft polymer. Thus, the grafting - of the addition polymer onto the epoxy resin may be as low as to the extent ! of l-l/2 parts b.y weight of addition polymer for 100 parts by weight of the . 11 X! --6 '. . I

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epoxy resin. Generally, to secure the benefits of the invention, the amount of epoxy resin employed should b~ s~ficient so that the epoxy resin consti-tutes at least 5% and preïerably 10% of the initial weight of the reactants.
Superior binder blends are obtained when the amount of epoxy resin is 40%
or more by weight of the initial reactants, and 50q~ or more produces pre- j ferred binders, although for sanitary coating composition bin~lers, the arnount should be from 60% to 90%, One important feature of the process of the invention is the amount of free radical initiator that is used in the reachon. The amount of benzoyl ~ peroxide9 used at about 110C to 120C, must be at least 3% based on the weight of additio~i polymerizable monomer~ preferably at least 4%. A
preferred practical range is ô% to 7%, although up to 15% or more can be used. When other free radical initiators are used~ the amount can be adjusted to be equivalent in activil~y for this particular reaction, ta~cing the temperature of use into account.
When the amount of free radical initiator employed is less thar~ 3%
by weight of benzoyl peroxide or equivalent, e~ter-lype graft p~lymers apparently are formed. When the amount of peroxide~t3rpe free radical initiator is sufficient to be the equivalent of at least 3% or more by weight of benzoyl pero~ide, and of up to about 7% or more by weight of benzoyl peroxide, the predorn~ant type of grafting that occurs is ~t those aliphatic carbons in aliphatic backbone carbon chains G~ the epo~y resm component that have either one or two hydrogens bonded thereto in the ungrafted state.
When a greater amount of peroxide-type free radical initiator i5 employed, than the e~ivalent of about 7% of benzoyl peroxide at 110C to 120~C, generaUy gre ter expense is incurred without any accompanying ad~antage .

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, Il While tt~e preIerred reaction technique involves placing the epoxy component and a solvent for it in a reactor, and then slowly adding the monomer mixture, catalyst, and solvent, over a period of t~e that permits , facility of control over the exothermic heatJ other approaches to the process can be employed. For example, the epoxy resin and a solvent for it coulcl li be placed in a reactor, then all of the catalyst arld part of the monomer mix-ture could be added. After an initial reaction, taking place upon heat~g, the remainder of the monomer mixture could be added slowly over a period of time. As a variation on this process, some of the catalyst might be retained for addition to the reactor along with the monomer mixture. As a further alternative, the monomer mixture, epoxy resin component, and any desired solvents, could be placed in a reactor, and the catalyst added slowl~.
Once the final reaction product is obtained, it is generally useful to suspend it in an aqueous vehicle9 to facilitate itB application as a coating comEx~sition.
The process of converting the polymeric blend and solvent system to a stable water-borne system re~uires thè utili~ation of a base or mix ture~ of bases. The pre~erred neutralizing base is dimethyl ethanol a~ine and it is normally used at 4% to 12% by weight based on the total weight of polymerO The amount of base used determines the result~ng viscosity o~
the water-borne systern, which in turn affects application characteristics~
Higher levels o~ base give high er vis cosities and re quire larger arnounts o~ water d~ution for viscosi~y control.
Two diferent processing procedures can be used to convert the reaction product blend to a stable water-borne system. For ease o~ manu-l l I !
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facture, the preferred procedure involYes adcling the procluct blend with solvent to a mixture of water and climethyl ethanol amine, with mixing.
Usually a small amount of solvent (ethylene glycbl monobutyl ether) is included in the water to aid solubilization~
In the second procedure, water and amine are added to the product blend and solvent, with mixing. While the water-borne æystem prepared by this process is sat~sfactory as to quality, this procedure is not pre-ferred ~or best equipment utilization.
Water~borne systems prepared as described above norrnally have a pH in the range from about 7. 5 to 8. 0, a~d have been fa~nd to be stable for storage periods of over one year. Products so produced do not change unduly in viscosity, there is little or no settling or separation, and application characteristic~ remain ~atisfactory after storage.
To operate within the most preferred ranges for practicing the present invention, for the production of sanitary coating compositions ~or soft drink and beer cans, ffie amount of diepoxide resin should prefera~ly be about 80~o by weight, and the amount of monomer mixture employed, ~or reaction with the epoxy camponent, should ~e about 20% by weight. The amoun~
of benzoyl peroxide present during the reaction should be fram about ~0 to about 7% by weight, and preferably, about 6. 7% to 6. 8%. The amount o~
methacrylic acid in the monorner mixture is reElected in the Acid Number of the f~al reaction product mixture that is obtained. For presetlt purposes, this Acid Num~er should be in the range from 45 to 150, and preîerabl~, from a.bout 80 to 90, and most preferably, about 85.
¦ For a beverage can coating composition, for use in an 80 parts of ¦ diepoxide to 20 parts of monomer mixture reactiorl mixture, wi~ 6. 8 parts benzoyl peroxide, a preferred monomer mixture compo~ition is 70 I . I, . ' . I
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, parts methacrylic acid to 30 parts styrene with one mole percent ethyl ¦~ acr~late. The final reaction product mixture obtained should have all of the monomer mixture copolymerized to an addition copolymer, with about Il 2-1/2 weight parts grafted to the diepo~{ide re~sin, at aliphatic backbone iI carbons, and with the balance of the addition copolymer blended with the graft polymer in the reaction product mixture.
Both the graft polymer and the addition copolymer thus produced are carboxylic acid-functional. They ha~re enough ionization potential to be hydrophilic and are readily blendable.
With the 80/20 preferred reaction mixture of diepoxide to monomer mixhre, for beverage can coating, reacted at a level of 3% ~f benzoyl peroxide, generally about 1-1/2% to 2% of the addition copolymer is grafted (based on total addition copolymer îormecl from the monomer mixturel, and dispersibility in water is poGr. At 5% benzoyl peroxide, about 8% of the addition copolymer is grafted; at 7% benzoyl perox;de, about 12% of the addition copolymer i6 grafted; at 9% benzoyL peroxide, close to 20% is grafted; and at 15% benzoyl peroxide, oYer 40% of the addition copolymer is grafted. For clarity, it is emphasized ~at when 10% of the addition polymer is grafted, this mean~ that the final reaction product mixture consi~ts of about 82% graft polymer and about 18% o~ associatively-formed addition co-polymer.
For good coating compositions gener~lly, about 1-1/2 parts by weight of the addition copolymer ~hould be grafted for each 100 parts by weight of epo~y resin component in the graft polymer. The amount of adclition co-polymer grafted can be as high as 12 parts, iI enough benzoyl peroxide , is used, but a level of 5 -1/2 or so is a practicaï upper limit îor most pur-poses, and vl lues of 2-1/2 to 3 are generally preferred for can coatings.
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Generally the reaction product mixture obtained, from the 80/20 preferred reaction mixture of diepoxide resin to monomer mixture, will contain up to 18-112 parts of ungrafted addition copolymer. For many I coating applications, even more addition copolymer can be tolerated, and i! separately formed compatible addition copolymer, preferably of substan-tially the same composition as that present, can be addecl, up to a total of about 40 or so parts of ungrafted addition copolyrrler in the reaction product mixture. Similarly, additional ungrafted diepoxi.de resin can be tolerated, generally up to a total of about 10% by weight of the reaction product mixtur e.
~For ag.uçous dispersions at high epoxy contents, the carbo~yl content of the reaction mixture, measured as - COOH, should be at least 2% by weight of the reaction mixture. :F'or stability of dispersion, the amot3nt may be substantially higher. Tha practical range is at least abou~ 5%~ ~enerally, When $hé carboxyl content is below about 2~o, polymer blends are produced that are useful in solYen~ vehicles.
The several individual ~eatures of the invention will now be discussed in detail.

The ~po~ Resin The epoxy resin may be either aliphatic or aromatic. For preparing coating compositions ~or cans in which terms suitable for human csnsump-tion are preserYed, the aromatic epoxy resins are preferred.
The most prePerred epoxy resins are polyglycidyl ethers of bisphenol . A, especially those ha~ing 1, ~-epoxy equivalency of from about 1. 3 to about

2, and preferably about 2. The molecular weight should be :from about 350 to about 20, 000, and preferahly, for sanitary coating compositions, from ¦ about 49 000 to about 10, 0~0. Low molecular weight epoxy resins are , ' ' ' ': , .` ordinarily selected for use when the epo~fy resin content of the polymeric binder is to be low, that is, from about 10% to about 30% by weight. Low molecular weight epoxy resins are considered to be those having a rnolec:ular weight of less than 1, 000.
Ordinarily, when the polymeric blend is intended to contain from 50 to 90% by weight of epoxy resin based on total polymer solids, the epoxy resin selected will be one having a molecular weight in the range frc~ about 4, 000 to about 10, 000, particularly for the preparation of sanitary coating compositions, for which it is preferred that the epo~y resin contribute at least 60% af total solids.
While it is sometimes convenient to use a finished epoxy resin at the desired m~ecular weight, it is often more practical to start with bisphenol A
and ~e bisglycidyl ether of bisphenol A, which is a~ailable from carnmercial sources. The bisglycidyl ether of bisphen~l A9 kns3wn generally as liquid epoxy resin, is a~railable in precat~lyzed form not only ~rom Dow Chemlcal Co. under the trade name DER-333~ containing as the catal~st the cornplex of ethyl triphenyl phosphoniurn acetate with acetic acid9 but also from Shell Chemical Co~ under the trade name Epon 829, and these axe convenient initial starting materials. Uncatalyzed liquid epoxy resins are also avail-able and have been found to be suitable for use. when the proper catalyst is employed.
The precatalyzed liquid epoxy res~ fr~m Dow Chemieal Co., DER-333, has Ihe fo~lo ~ ing phy~ical properties:
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,' , Properties of DER-333 Epoxy Resin i Appearance Clear, vi~;cous liquid Color ~Gardner) 1-2 Specific gravity 1.15 Weight per gallon 9. 65 Nonvolatile by weight g6 ~1%
Volatile Xylene I Nonvolatile by volume 95% a~rg. .
I Yiscosity at 25C 2300-4600 cps.
¦ Epoxide equivalent weight* 199-202 *Epoxide equivalent weight i~ the grams of resin containin~
one gram equivalent weight of epoxide.

To increase the initial molecular weigh~ OI a liquid epoxy res}n ts) a level that is more satisfactory for many coating applicaffons~ the initial liquid epoxy resin ma~ be reacted not only with additional bisphenol A but also with other materials. Other polyfunctional aromatic alcc~hols can be used to make the glycidyl ether and to increase molecular weight, including such materials as bis ~4-hydroxyphenyl ) ~nethane; lbisphenol E';
2,2~1~is (4'-hydroxy-21, ~', 5', 5' - tetrachlorophenyl) propane;
tetrachlorobi~phenol A; 4,4-bis (hydroxyphenyl) pentanoic acid; diphenolic acid; novolac~ or low molecular weight phenol-~rrnaldehyde polymers;
1, 8 bis (hydroxyphenyl) pentadecane; resorcinol; 2, 2, 5, 5, -tetrakis (4'-hydroxyphenyl~ he~ane; and other~. However9 the preferred material, for simple practical control over the process, for increasing the weight of the initial liquid epoxy resin, ,is bisphenol A.

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The ratio of bisphenol A to DER-3~3 used to produce the most . desirable molecular weight is frorn 65% to 66.5% by weight DER-333 and 35% to 33. 5% by weight bisphenol A. The following table lists the characteristics of the finished epoxy resins:

Table II

Epoxy Resin Starting Materials for Grafting ¦ DER-333 level by wt. 65 66.5 Bisphenol A level by wto 35 33. 5 Approximate molecular wt. 90ûO 5000 % Epoxide oxygen . 4 . 6 -Gardner viscosity range Zl -7.3 X-Z
at 40 % wt . nv. in ethylene-glycol mono butyl ether . .~
The reaction conditions employed to increase the m~ecular ~veight of the li~uid epoxy resin, or other low molecular weight epo~;y re~s, include a reaction Semperature of about 175~C and atmospheric ER~e~ure.
While thiæ reacti~n can be conducted without a ~ol~7ent, it i~ preferred to use ethylene ~Iycol mono bulyl ether at about 15% by weight based total reaction charge,.
For many coating applications, the epo~y resin, ordinarily a diepo~ide, ma~ have a molecular weight in the r~ge from about 350 to about 20, 000. ~Iowever, ~or more demanding applicati~ns, particularly for applications urhere the end product is to be a sanitary coating, ep~y resin molecular weight values in the rangefrom about 4, 000 to ab~ut . I lOr 000 are preferred. These and other molecular weight determinations of the epo~y resin components are made by gel permeation chromato- I
graphy, preferably, but ~ny other standard technique may be employed. I
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Epoxy resin that are useful also can be modiîied with other con-densates such as phenolic resins, phenols, and polyols. Iypical modified epoxy resins are: epoxidized polybutadiene, glycidyl ethers formed by reacting phenol novolak resLns with epichlorohydrin; 4, 4'-isopropyl-idenediphenol- epi chlorohydrin or 4, 4- sec -butylidenediphenol-epichloro-hydrin reacted with one or more of the following drying 0~18 or ~t~y acids:
beechnut, candlenut, castor (including dehydrated), tung, coconut, corn, I cottonseed, fLsh (re~ined), hempseed, linseed, oiticica, perilla, poppyseed, ¦ pumpki~seed, safflower, sesame, soybean, sunflower, t:~ll oil, and ¦ walnut; 4, 4'-isopropylidenediphenol-epichlorohydrin chemically treated with one or more of the following: allyl ether of mono-, di-, or trimethylol phenol; 4, 4'-isopropylidenediphenol-fc~rmaldehyde, 4~ sec-butylidenedi- .
phenol-forrnaldehyde, melamine formaldehyde, and urea Eormaldehyde.
Commercial epc~y resins that ha~e useful molecular ~reight ~alues and that are !~uitable for use as is, ~rithout further increa~e in molecular weight, including DER 662, 664, 667, 668, and 669, all products af Dow Chernical Co. (with calculated average molecular weight~, rep~ectiv~ly, of 1,275~ 50; 3~ ~00; 5, 500; and 9, 00û); and EPON 836, 1007 and 1009, all products of Shell Chemical Co. (with calculated ~verage moleculaLr vveights, respectively, of 625; 4, 5û0; and 6, 500)~
While preferred diepoxide materials, for use in the practice OI the invention, are prcpared by reacting epichlorohydrin with bisptlenol A, o~er satis actory ~ t e&oxidee irclude su ch irttial r. aterials as the Eollowin9-, ! .
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provided the m~lecular weights are adjusted to the proper range:

Diepoxid,~ A
, ~ , . ,--CH--O~C--(CH ) - C~O~H C~
V 2 11 2 11 ~

Diepoxide 2 .
' ' 1\c ' ~\ ' '' ' H HCH O(C~I ) ûCH CH--CH
~ 2 ~ 2 2 Mepoxide 3 ~' .' ~->

CH--CE--CEI Cll --CÉ--CE

Diepo~id~ 4 ~CH--CH

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., Diepoxide 5 o~ ~CD

Il Diepoxide ô
i O . l ~~CH--CH--( H ~~~~>~ F ~ o_ ~C~2~ ~}~

O) ~ H .

N = O, 1 ~r more ! -17-' ~; ' .

~9 'i A further way of characterizing the epoxy resin component is in terms of its o~irane content. This value c~n be anything ~om zero to about 8%. A zero v~lue oxirane content would indicate that the epoxy groups have been completely reacted, as, for exampleD with excess bisphenol A~ The epoxy groups may not be needed ~or applications other than for good can coatings. The oxirane content is determined in the following way.

Determination of Oxirane Content - . . ....... , . . .,. _ A sarnple of Imown weight is placed into a 50 rnilhliter Erlenmeyer flask, and dissolved in 10 milliliters of chlorobenzene. To the solution i~ added 10 milliliters of tetraethylamm~nium bromide solution and 2 to 3 drops o~ 2% crystal violet indicator solutior~ in glacial acetic acid. Tlhe resulting solutiorl is then titrated to blue-green end poL~t with a standard-iæed 0.1 N perchloric ac;d (HClO4) using a 10 milliliter micr~buret.
% oxirane is calculated from the following equation:

. (ml. g N of HC1O4) X 1. 600 % C)xlrane - -- -Wt. of sample in gram~

The 0.1 N HC1O4 ~olu'don was prepared by mi~ng 8. 5 ml, o~ 72%
HC~l~ with 300 ml. of glacial acetic acid (99. 5%), 20 m7, of acetic anhydride was added, and the ~olution wa~ diluted to 1 liter with glacial acetic acid and allowed to s~nd overnight, It was then ~tandardized again~t potassium acid ph~alate.
The tetraethylammonium bromide ~olution required above was prepared b,y dissolving 100 g. of, tetraethylammonium bromide in 400 ml.

of glacial acetic acid (99-5%)- To neutralize basic impurities, a few drops of 2% c~y~tal violet indicator 801ution was added and the solution was i~!

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, titrated dropwise with the starldard 0,1 HC10,~ to the end poin~ eolor change.
This determination is applicable to both the initial epoxy resin and t~ the reaction mixture that includes the graft polymer.

Addition Polymerizable Monomer The second important group of materials, for u~ in practicing ~he present invention, consists of addition polymeri~able matexials.
To practice the present in~ention in its broadest aspect~, the a,ddition polymerizahle monomer, that is reacted in the presence ~ the epoxy resin and the free radical i~i~tiator to form the reaction mi~ture includi~g the graft .
polymer, may ~e a single monomer, or a mixture ~ copolymerizable mono-mers. The material selected will depend upon the o~jecti~es to be achieved in terms of properties and economics. Sty ene is a valuable mo~omer, ~or example, because it act~ as a~ e~rtender and i8 economical. Acrylamide is interesting because it enhances self-curing capabili13T, whether used alone or as a part of a monomer mi~ure. The acr~lic acid~ imp~rt aeid funetiorlally.
Currently approved epoxy-acrylic coatin~ for be~rerag~ c~n u~
include t~ree or more monomers in admixture,> i. e., styre~e9 methacrylic acid; and ethyl acrylate, a~d optionally, methyl methacrylat~. ~owe~r, ~rery u~eful water-reducible coatiDg~ can be produced from mixhre~ o~
methacr,Ylic acid and ~tyrene~ the acid normally being the major component9 to develop 6u~ficient acid functionality for forming ~table agueous dispersions Generally, fo~ ~alcing coating compositions In accordance vrith the present inv~tion~ the addition pol~rmeri~able monomer will be ~elected from among three general classe~ of such monomeric materials. The sel~ction may be a single monomer, or a 'mixture of ~uch monome3~s that is deeigned ¦ to aohiev~ s~me particular objective such as, for example, acid fI3nctionality.' The fir~t clas~ of monomer~ that may be used in the preparation of -19~

9~34L ` t ., coating composi~ons, are the acr;yLic acids. This category incl~de~ ~ue ', acrylic acid and lower allyl substi:tuted acrylic acids, that i5, those acids having ethylenic unsaturation in a positiorl tha t is alpha, beta to a single ,j carboxylic acid group. The preferred acrylic acid is methacrylic acid.
Il A second class o~ monomer that may be employed can be identified as ¦~ including those readily commercial available monomers that have vinyl un-¦ satur~tion a~d that do not impart functionality., This would include styrenic ¦ monorners such as styreneg vinyl toluene, and divinyl berlzene. O~er suitable monomer~ include isoprene, ccnjugated butadiene, arld the like.
A third class of monomers that are use~l, particularly to comply with current regulation~ that apply to sanitary coating~ ~r ~ddition to a methacrylic acid-styrene mixture, are ~e allyl ecter~ an acry~ic acid, genera~ly ~e lower alkyl esters, ~t is, those ester~ in which t~e esterifyi group contain~ ~rom 1 to 4 carbc>n atoms, and particularly, ethyl acrylate, I:)ther usefal monomer~ in this class. itlclude other Cl_l5 alkyl acrylate e8ters and methacrylate esters 6uch ac, for e~ample, propyl acrylate, i80propyl acrylate, butyl acIylate, isobutyl acrylate, terl;iary butyl aerylate, pexltyl acrylate, decyl acrylate, la~ryl acry~ate, i~obornyl acrylateJ
methyl methacrylate, bulyl me~acrylate, i~30butyl me~acrylate, hexyl methacx~rlate, 2--ethyl hexyl methacryl~te, oc~yl methacrylate, and nonyl methacrylate, Acrylamide and acryl~itrile are also u~e~ul, although not .
for ~oods.
Generally, ho~e addikion polymerizable monorner~ that are readily p~aymerizable under emu~sion polymerization conditions~ typically those ~ . ~ , .
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~1 . that cvntairl ethylenic unsaturation, are sllitable for use. This wo~ld includ~
acetylenically unsaturated materials such as, for example, acetylenic glycols. When a mixture of monomers is used in the production of a water- ¦
reducible coating, those monomers selected~, other than an acrylic acid .i monomer~ should copolymeri~e well with acryllc aeid mononaers~ and æh~uld form copolymers that by themselves are not cross linked.
i For most water-reducible coating compositions, generally the . ¦ monomer mixl:ure will contain a major proportion of a~ acryLic acid, and ¦ a minor proportion of a styrenic monomer, gen~rally ~tyrene. F4r tho~e coating compositions that may come in contact with food, in generaiJ and for the preparation of beer can coating compositions in particular, one preferred addition polymerizable monomer mi~ture i~ made ~rom 70 parts b~ weight of methacrylic ~eid to 30 parts by weight of ~tyrene, k~gçther with 1 weight pereen~ of ethyl acrylate. Another preferred monomer mixture .
includes methacrylic acid, ~tyrene, and eth~l acrylate, in the appro:acimate weigh~ ratio of 65:34:1, respectivel~, Free Radical Initiator The epoxy re~in and the ~ ture of polymerizable monomer are reacted together ln the presence vf a free radical initiatorl preferabl3r of the peroxide type.
Many free radical initiating materials may be used, but benzoyl peroxide is preferred. Those materials that may be used generally include . the material~ oiEten re~erred to as peroxid~-type catalyst.s. The cla~s o:~
~ree radical iniffators is generall~ well-known and is gener~lly useful to ~ome degree, including combination~; of free radical initiators and activators for the free radical initiators, including ultraviolet light and high energy electron bea~mBO under proper conditions. Typical, practical $ree radical .

~1 -21_ .~'', ' - , ', :
. .
, !

. initiators that are in common use include cumene h~rdroperoxide, benzoyl peroxide, t-butyl perbenzoate, t-butyl peroxide, lauroyl peroxide, methyl ethyl ketone peroxide, chlorobenzoyl peroxide, and the like. :l3enzoyl ¦
peroxide is preferred as the free radical initiator for use in the pra~tice ' ! l of the present invention to initiate and to conduct grafting and addition polymerization together.
The amount of free radical initiating acSivity is important. That amount is expressed herein in terms of percer~ge by weight of benzoyl ¦¦ peroxide based on the total weight of the poly~merizable monomer, or ' 10 1 equivalent, at the temperature of use, which is generally ~rom about llO~C .
to 120C. I'he amount ~hould be at least 3~0, and preIerably more thall 4%, by weight OI benzoyl peroxide or eguîvalent. Since ben~ yl peroxide i3 an expensive material, no more ~hould be u~ed than is nece8~ary ts~
produce the desired results.
When the amount of benzoyl peroxide or equival~nt used i~ about 3~o on monomer, minimum gra~ting occur~ A~ the amount of free rlldlcal initiator used i~ increased, gra~ing at the aliphatic backbon~ carbon~ i~
favored~ At a level of free radical iniffator equivalent to 6% - 7% of benzoyl peroxide based on polymerizable monoxner, with a reacffo~ ture of about 80% by weight epoxy resirl to 20% poly~nerizable mom~mer by weight, about 12% by ~eight of the initial monomer graft~ to the epo2~y orlto aliphatic backbone carbon8 that ha~e either one or two hydrogens bonded thereto in .
the u~grafted ætate. While the grafting appears to occur at those aliphatic backbone carbons that are in po~itions alpha to terminal epo~y groupæ, there iæ some grafting, apparently, at other locations. This type ~1 . , ' 1 .

1~)99~34 of grafting can be i~lustrated thus:
! - 1 ~3 0-- CH-- -- CH~ -- -, CH2 ~ H2 1 ]
:Y - Y .

where x i~ CH3 or H, and y i~ , ~C02H, r--C 2 Et, fbr _ompl~

The arithmetic of thus having 12% of the po~merizable monomer graft to the epo~y resin indicate~ that the addition pol~er, that i~ formcd fro~n the monc~ner, and that ~rafts, amo~lnt~ to about ~, 4 part~ of a~dition polymer out o~ about 82. 4 part~ c>f graft polymer, a~umiDg that all of the ~pClXy resingraf~:. Thi~ mean~ that the addition polymer component amount~ to ~bout 2.9% of the graft pD~yrner by welght. ~ctually a ~izable lpercentage of the epo~r re~in may not be ~aPted, but the ~ree epoxy i~ dif~icult to . detect; it may even be a~ much as 50% of the original that remai~s un-gra~ted.
. .
The Reactis:~n Proce~
The reacti~n geneI ally con~ist~ of reacting the ~pox~ resin com-ponent with po~ymeri:z;able monomer that constitutes frorn about 5% to about 20 . 95% of ~e reacti~n ;rnixture by weight, i~ the presenc~ of at least 3% of .
-':" . . . .

~ ~ -a3-8~

benzoyl peroxide by weight of the monomer, or the free radical initiating equivalent thereaf~ While the re~ction may be conducted in the absence of a solvent, ordinarily a solvent system is employed for coating production A prefcrred solvent system is one made up of two miscible solvents, one of which dissolves the epoxy resin and the other of which dissolves the i ' mono~n er.
A preferred technique for conductjng the reac~don i8 'CO place a solution of the epox~ resin in a reactor, heat, and then slowly add, over a period of t~,vo or three hours, with agitation~ the polymerizable mono~er, a solvent, and the ree radical initiator. Since the reaction is exothermic, this tech~ique enables the temperature to be maintained at a desired reac-kion level with sorne degree of control. ~At the end of the addition to the reactor" the contents of the reactor may be maintained at a preselected holding tempera~re for some additional period of time, to make sure that the reaction ha~ gone forward to the de6ired e~tent.
The particular solvents that ma~r be e~r ployed are well knowll in the art. Solvent~ such as xylene are satisf~ctory for the epoxy resin ccnnponer~t. Other ~uit~ble scl~en~s ~clude benzene, e~hyl benzene, toluene, an~ the alkoxy aLkanols. For the monorner, alcohols ~uch a~
methanol, ethanca, propa~ol, buta~ol, and th~ like, are suitable, ~ith butanol being preferred~ Ethylene glycol monobutyl ether, eth~lene glycol monobutyl ether acetate, and the like, hexane, mineral 3pirits, and tlhe like, are also suitable~ ~ the end product is to be used in an aque~us vehic~e, then the 501vent~ ~elected should be water--soluble materials, as are acetone~ butanol, ethanol, propanol, e~ylene glycol monoet~yl - e~er, and the like. ~
. . I
'.~, .' :j 9~

, Solvents may be introduced into the system initially during the initial reaction of a precatalyzed liquid epoxy resin~ to increase its molecula~
weight. For this purpose, a preferred solvent is ethylene glycol mono-butyl ether, at 15% by weight based on total reactants. It is also preferred to use a mixture of ethylene glycol monobutyl ether and normal bu~l 1' alcohol at about 40/60 by weight ratio, for efficiency in terms of perf~rmance ¦, for can coati~gs. Most of the solvent is present to moderate visco3ity and sorne soavent is added to the rnonomer to moderate reactivity.
The pressure during the grafting reaction ord~narily is atmospheric~
but it can be higher or lower. The reaction temperature preferably iB
mainta~ed in the range from about 80C to about 130C" althoug~ the temperature may be adjusted within a rela~ y wide range to accs~nmodlate the reactivity o~ the mixture. Thus, oper~;~ing temperatur~E~ in the rallge from about 30C to about 200C are fea~ible~ d~ending upon the end re~;ult~
and operating conditions selectedO
AR no~ed before, ~he grafting is done in ca~junctioP~ wi~ the ~rma-tion of ~e addition polymer. The react~nt8 are genera~y lprs~porti~ned to lea~re no moloe than abalt 3% o~irane in the reaction mi~Yt~Lre~ with 2~e~ ~o 1% oxirane content representing a typical level fc~r the ~roductic~ of bmde~s 2 0 for 8a~itary coal;ing compositions.
While the use of a solvent i~: optional" and ~e reacti~n may go forward in the absence of ~olvent, ordinari~y the amount of solvent may be ~n ~e range rom al~ut 5% to 30~o by weight of the sum s~f the other compon~nts.
To conc3~ade, conventi~nal solution copolymerization conditions are preferably employed for the grafting reaction. The monomers and free radical initiab~r can be b~tch c~rged to the epoxy resin but metered addi-tion is pre~erred for exotherm control. The reaction mixture is normally held for up to three hours at reaction temperature, after addition of ¦ monomer has been comple~ed3 to complete monomer conver~ion, I . Il ~;. I -25~ , _he Resulting Produc~
Under the reaction conditions described, and ~rith at least 3% and preferably 6% to 7% benzoyl peroxide by weight of the monomer mi~ture, Il two reaction products are formed at the same time~ in association with one il another. Thi~ is referred to herein as associative formation.
One product, that is present in the fir~l reaction mixtuxe, is a graft pciLymer Under the conditions describedJ grafting takes plac~ at ~e aliphatic bac~one carbons of the epoxy resin that have ei~er one or two hydrogens bonded thereto in the ungrafted state. When the arrlo~t of free radical initiator is at about 3% of benzoyl peroxide or equiYalRnt, or below that level, the grafting at the aliphatic bacl~o~ carbon atoms i~ les~
preferenti~l than when higher amounts are employed. Under all condi-tion~, if an acidic polymerizable monomer is pre~ent, 80me es~er-type . grafting apparently occurs9 but under the sperating conditi~ of the pre~ent in~rention" and particularly under the E~eferred operatirlg co~
tion~, the amount i~ very smalL
Ir~ addit;on to the gra~t polymer, the reaction mixture also cc~taln~
a~sociati~ely-~ormed ungrafted addition pol;ymer, ~o~med frt~n the m~omer mLsc~re. Unreacted epo~ resin iB difficult to detect in the reactis)n mixture, but up to about lO~o by weight of the resin so1fds present in the reaction mix-ture may be unreacted epo~y resin, arld in some case~D particularly where the epo~y resin consti~tes a ~ery high percentage by weight of ~e ltot~l materials reacted, a~ 2nuch as 5û% by weight may be unreacted epcQc~
resin. When the epoxy re~in is as little as 5% uf the initial reactiorl rn~x-tur-, a higber proportion of it rn~sr be graPted~

.' ., , ~ 9~33~ ' . ' , The epoxy resin may have very little grafting on it, bu~ what is there, is important in term~ of properties. It is generally preferred that there be sufficient epoxy re~in present initially, and su~ficient grafting, so that the epoxy resin cornponent of the graft polymer constitutes at lea~t about I
5~0 by weight of the final reaction mi}~ture. To demonstrate wh~t occurs in the production of a resin binder blend for a can coating composition, for i' example, when the reaction product mixture is formed from initial reactan~s made up of 80 parts by weight of a diepoxide resiIl to about 20 part~ by I weîght of a monorner mixture containing primarily rnetha crylic acid and 6tyrene, together with a mi~m~r amount of ethyl acrylate, in a weigh~ ~tio .
of 65:34:1; respectively, with the reaction taking place ~n tlle 501v~n~ ~ystem in the presence o~ ~rom about 6~o to abo~t 7% benzoyl peroxide by weight of the monomer mi~rture, then of the initîal 20 part~ by weight of tho monomer mi~ture, about 2-1/2 part~ appear in the graft polymer, and th~ r~2n~ning 17-1/2 parts from ungra~ted addition copolymer.
Because of the difficulty o~ ~eparating the gr~t pol~mer fr~n the other compone~t~ of the reaction mixture, molectllar w~ight measurerllent~
0n it have been d~~icult to make and ~t be~t are probably only approxima-tion~. The indication~ are that the molecular weight range o~ th~ graf~
polymer i~ in the range frc~m about 5, 000 to about 40, 000.
For coating comp~sitions, the grafflng between the add~tion pGl~xner component and the ep~y resin component ~hould take place to the extent .
of at least 1-1/2 weight parts o~ the additiorl polDmer component ~or each 100 w~ight parts of the epoxy re~in COmpQnent.
There are ~everal item~ o~ evidence indicating that the graft polymer that iB obtained doe~ have the ~tructure de~cribed, One important piece . OI evidence is that the Acid Number, that would be expected to be obtained from a ~imple mixture o~ the component~ clo5e to the Acid Number 11 .

1l -27-~.' 11 .

that is observed in the final reaction product mixture. This indicates that ,~ there is little ester fsxmation during gra~ing. In addition, evidence obtained through the use of Carbon 13 rluclear magnetic resonance spectro-scopy tends to confiIm the indication that there is little ester formation during grafting, as do chemical r~actionæ with ept)xy fragments (model structures ).
! For coating co~npositions, the Acid Number of the reaction product mixture ~hould be in the range from about 30 to about 200, preferably 45 to 150, and for sanitary co~ing composition~, the acid number should be in the range from abou~ 80 to about 90, and preferably, close to abou1: 85. .
When benzoyl peroxide i~ employed at a level greater than 3% by weight of polymeri~able monomer> grafting to arborls in the aliphatic backbone chain v~ the epoxide component i~` faY~sred, but at the 3% level of benzoyl pero~ide, little of such grafting occurs at the alipha~ic carbon~.
YVhen the amount of ~enzoyl peroxide or equivalellt is ~ncrea~ed to a pre-ferred operating level of abollt B% - 7%, optimum results in term~ of pro-duction o~ the de~ired kind of grafting and economy are u~ually attalned.
' C~
To collvert reaction mixture~ produced in accordance w~h the pre~ent invention to aqueous ~uspen~ion,s, the technigue,3 employ~d are e~0entiall~r conventlonal, The graM polymer i5 disper,~ed iIl deionized lwater, u~i2~ a fu~itîve ba~e (under curing condition~ for the coating~ ~uch aB primaryD
secondary, and tertia~ a1k,yl, a~anol, and aromatic amines and alkans~
aLkyl mixed amînes; e.g. mono ethanol amine, dimethyl ~thanol arnine, diethanol amine, triethyl amine,l dimeth~rl aniline, ammonlurn hydroxide7 ¦ or the lîke. ~Ordinarily thi~ i~ done by adding an amine with some water and ..
'` ~ jl ' : : , mixing vigorously while (optionally) warming, then diluting the dispersion with n~ore deionized water as is desired.
, The amount of water in the final dispersion depends on the viscosit~
desired~ which. in turn, is related to the method of application. For ~I spraying the dispersion, water amounting to about 60% by weight of the dispersion represents a typical level, within a preferred range of cornposi-li tion for the dispersion OI from 10% to 30% by weight of ~olids and îr~mabout 70% to 90% of volatiles, that is, base, water, and solvent~. Th~ base is usually about from 2% to 6%, water from about 30~0 to 90%" and the organic solvents fr~rn zero to 4~%; all percentages be~g by weight based on the sprayable diæpersion. The solids canprise ~e reaction mfxture solids, about 9% to 29%, and cross-linking agenti a:bout 1% to 10%, based on the 8prayable diæpersion.
A8 to a~plications other than spraying, the aqueou3 di9per~ion may CamE~riBe: ïO% to 40% ~olid8, which are proportioned a~ follow~: 001% to 16% ~y weight o~ a cros~-linking agent, and 6% to ~9, 9% by weight o the graft p~lymer-co2ltain~g rèaction mixture; and 60% to 90% vola~le component , generally divided into s~rganic solv~nt, 6% to 35%, and water, 25% to 80%.
It i~ preferred tl~t ~ome organic ~olvent be u~ed to facilitate applicatic)n, and i$ is gerlerally u~ed in the ratio of one part bSr weight of solvent to about three parts by weight of water~
l~e organic ~olvent can be made up of one or more of ffle known ~c~vcnt~ such a~ butanol (normal), 2-butoxy-ethanol~l, xylene, toluene, and o~er ~cilvents. It i~ preferred to u~e n butanol in combination with 2-buto~-ethanol-1, in equal amount~.
. .

. ., , '' ~ 9~33~ 1 ,iAn aminoplast resin is preferred ~or cross~linking with the graft polymer. It can be ad:led to the gr~ft polymer before neu~ali~atiorl and dlluting, or thereafter. Typical aminoplasts include melamirle3 benzo-quanamine~ acetoquanamine, and urea resins such as ureaformaldehyde.
Commercially available aminoplasts which are water soluble or water dispersible for the instant purpose include Cymel 301, Cymel 303, Cymel 370, and Cymel 373 (all being products of American Cyanamid, Stamford, Connecticut, said aminoplasts being melamine based, e. g., hexamethoxy-methyl melamine ~or (:ymel 301), and ~Beetle 80 (products of American Cyanamid which are methylated or butylated ureas, ) Other suitable aminoplast resins are of the type produced by the reaction of aldehyde and formo~anamine; ammeline; ~chloro-4,, ~-diami~e-1, 3, 5-triaziné; 2-phenyl-p-~y-4, 6-diamino-1, 3, 5-triazine; 2-phenyl-p-oxy-

4, 6~trihydrazine-l, 3, 5-triazine,, and 2, 4, 6-triethyl-triamino-1, 3, 5-triazine~
The mono-, di-, or triaryl rnelamine~, 8uch as 2, 4~ 6 triphenyl-triamino~
1, 3, 5-triazine, are pre~erred. Ot}ler aldehydes used to react with the amino ccJmpound to ~rm the resin~us material are crok~nic aldehyder acrolein" ~r compound~ whieh generate aldehyde~, such as hexamethylene-tetrELmine, paraldehyde, and the ~ike.
28 If there is lit~le or no oxirane ~nctionality in the graft polymer, then a croaa-linker is necessary; s~therwise, it ie de~irabler but the graft ps~lymer is self cro~s-linking with heat.
Anol;her l;vay to introduce cro~s~ cing capability into ~e reaction mi~ture and the graft polymer i5 by util~ing a~ all or part of the polymeri-zable monomer, in the i~tial reaction mixture. a material such a~ acryLamicl e or an alkyl derivativ~e thereo~ ~Ir a material Fuch as b~s maleimide.

( The coating composition oî the present invention can be pigmented and/or opacified with known pigments ancl opacifiers, For many uses, including food uses, the preferred pigment is titaniurn dioxide. Generally the pigment is used in a pigment-to-binder ratio of 0.1:1 to 1:1, hy weight.
Thus titanium dioxide pigment can be incorporated into the composition in amounts of from about 5% to 40yo by weight, based on solids in the composition.
The resulting aqueous coating composition can be applied satis~c-torily. by any conventional method known in the coating indu~try. Thus"
æpraying, rolling, dippingJ flow coating or electrodeposition applicatio~3 can be used for both clear and pigmented films. Often spraying i~ preferred.
After application onto the metal substrate, the coating iis cured th~rmall3r .
at temperatur~s in the .range from about 95~C to about 235C or higher"
for periods in the range ~rom 1 to 20 minute~, ~uch tim~ being 8uff~cient to e~fect complete curing a~ well as volatilizing o~ ~ny fugiti~e eornponent therein. Further9 films may be aix dried at ambient temperaturei3 for longer per;ods of t~me.
For metal isheet substPates intended as beverage contai~ers and particularly ~or carbon~ted beverag~s ~ueh a~ beer, the coatlng ~hould be applied at a ra~e in the range ~rom 0. 5 ~ 15 milligrams of polgmer coating psr 3quare inch o~ exposed metal ~urface. To attain the foregoing, ~he water-dispersible coating as applied oan be a~ thick a~ 1l10th to 1 mil.
For a better ullder~tandmg of the present in~vention, the following exa~ples are provided. In thi~ application, all parts are parts by weight, all percentages are weight pex centage~, and temperatures are degrees CeIltigrade urlless x3therwise expires91y noted.
:' I ' ~: I .
j~ -8~

: I . I

339~ 1 Example 1 Preparation of a Coating For a Beverage Cax A plant batch was prepared according to the following procedure:
1 231 pounds of epoxy resin ~DER 333) were heated in an agitated reactt)r to ¦ about 82; 117 pounds of bisphenol A were added with agitation. The reactor then was heated to about l91D over a period of about 2 hours and held there for an additional 2 hours. Periodic testing for viscosity and percent oxirane were made. Target oxirane value was about 0. 6~o and viscosity at 25C~ between Z and Zl (Gardner-Holt~. When these values were obtained, 135 pound~ of 2-butoxy ethanol-l were added, followed by 203 pound~ of N-butanol. The molecular weight of the epo~y resin at this point was about

5, 500 based on oxirane cont~nt.
In a separate ve~sel there was loaded and mixed the following:
64 pounds of methacrylic acid, 40 pounds of styrene, 44 pound~ ~f ethyl acrylate, and 10 pou~ds of benzoyl peroxide~ This monomer mixture was added gradually to the reactor containing the epoxy re~in over a period of 2 hour~ at uniform rate. The reaction temperature was maintained at 118.
Visco~ity was checked periodically on sample The batch was cooled t~
85; it~ .Acid Number on solids w~ 85.
~0 The resin bateh then was fed into an agitated- reducing vessel con-taining a mixture of 1, 095 pound3 of deionized water (resistivity at least 50, 000 ohm-crn. ) and ~7 pouxlds o~ dimethylethanolamine. The temperature ~f the resulting blead wa~ 50~ It wa~ held there for about an hour, then the bl~nd was coc~led to below 32 by adding 500 pounds of the cool deionized ¦ water. The ~ r ter-disper~ed re~in had the following propertie~:
'~' .',' ,. . . , .
I

( 33~
N. V. 20~o, dispersion stable pH 7. 8 Viscs~sity (Ford #4 cup) 22 ~ sec.
This water dispersion then was ~odified by the blending in of 25 pounds of an aminoplast resin (Cymel 370, American Cyanamid Company). The dis-persion remained stable.
Cans coated with the sanitary coating o~ the present example exhibited excellent properties and were suitable for the carbvnated beverage and beer ! indu stries . Coated cans were p~rticularly notable for their inertnes s. Theydid not impart any undesirable organoleptic property or h ze to the canned b everage .
~ . .
The Effect of Variations in Co~npo~ition In Example l" the amount of benzoyl peroxide emplc)yed d Lring the reaction wa~ about 6. B% by weight based upon the monomer mixture. To dem~n~trate ~e e~ect of change~ in compo~ition, with respect to proportions of the epo~y resin and the ~everal monomer~ ~n the monomer mixture9 ~everil addltional demonstration~ were made. ~ eacEl ca9e, the a~nc~nt of benzoyl pe~oxide employed was held at the level o~ about 8. 8% based upon the weight of the monomers in the monomer mixture, and the order of addition of the ~() reactants, reactioTl temperature and pressure, and other operating para-meters were similar to those in E~ample l~ Thua, the grafting and addi~on operati~ WaB carried on at 120C. I~e ~olvents utilized were n-butanol and 2 -buto~y-ethanol-1, in equal amQunts.
The amounts o~ the reac~a~ts employed in these additional demonstra-tion~, the characte~i~tics of thelepc)~y resin reactant, and the acicl number and a~irane content oî the fjnal reaction mixture are reported in Table 1 be~ow. The actual measurement~ of Acid Number~3 and ox~rane contents were made on 60% ~oluti~ o~ norrvol~tile matter ~N. V. - 60).

~, -33-. , 1, 3~ J
, . . .
O ~ 'd~ t t~

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,b~ ~ , ~ 3 as R c~ ~ ~ ~ ~ CD r to ~, v o I O . ¦ ~

ml ~ a . . ~ o o O ~ ~ c, o c~ o o o c, ~ . ~ ~ iD3 ) ~ . , ,.
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TABLE III (ContLtlued) . I
(1) Viscosity of epoxy resin at 40% nonvolatiles in 2-buto~y-ethanol-1.
(2) % O~irane of epox,y resin, on nonvolatiles.
(3) Molecular weight of epoxy resin, calculate(l from oxiran~ content, (4) Ep. = Epoxy Resin (5) MAA = Methacrylic Acid

(6) Sty. = Styrene

(7) EA - Ethyl Acrylate

(8) Ml\/IA = Methyl Methacr~late ~9) A.N. = Acid Number (on nonvolatile~:) (10) % Oxirane ~on nonvolatiles) Eaeh re6inous reaction product listed iz~ Table III ~or Exa~ple3 II
through XIII inclu~ive ~as diluted with deionized walter to 20~o ~olid~3 utilizing dimethyl etlhanolamine as the neu~raliz~ng or io~izi~g ager*.
Samples o~ the~e water di~per~ionR were kept on the sh~lit at room temper-ature over at 120F Ior periods of time exceeding 8 :E~o~t~o No gelatio~ 03r precipitati~n wa3 ob~erv~d ir~ any sa~ple. O~ly ~light chara~e~ both p~
and vi3co~ity were detected. The remaini~g exa~np~e~ e~:lbibi~ lar properties.
Each o~ th~e water-di~persed resin~ ~vas ~prayed s:~nto ffi~ plate metal ubstrates, and cured, and prop~rtis~ sucll as blî ter resistanceO
.co~erage, ~oaming resistance, electrical conduetion, adhesion, and ~m con-tix-~ were evaluated and in each case were ~o~nd to be satis~ctor~. A
brief de~cription,oI these test~ appears later ~ this specificationJ undex the head~, "General ~'omment~
Table IV report~ the respective initial visc~sitie~3 ~#4 Eord Cup/sec-onds at 25C) and pH of the re~inous reaetion products of Examples 2~13 o:f Table DtI. Both properties are reported as ~easured on aqueous dispersiorls~

æ ~1 -36-'' of the respective sa~nples, Table I~ reports ~lso the percentages of Il neutralization (ionization) with dimethyl etharlollmine for each example, I
,1 and the viscs)sity and pH of the dispersions, n~easured in the same manner I, as previously, but a~ter these products had been stored for eight months jl at about 49~ C.

g~
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- - . . .. . . . . .. . . . . . . .

39~
. I , Additional Examples . _ . .~ j ~ esirlous reaction products, prepared in accordance with the present invention are readily stored, transported, formulated, and applied in a liquid vehicle, either in a solvent vehicle, or in an aqueous dispersion. In either ca~e, the reaction product may easil~ be extended, u~ually for the sake of 1, economy, but also to achieve desired characteristics, by blendlng in either ¦, an added amount OI an epoxy resin, preferably that used as an initial re-i actant, or an added amount o~ additic>n polymer, pref~ra~ly similar to that produced duriIIg the reaction as ur~ra~ted addition pol~rmer, or both.
The followiD~ e~ample~ illustrate e~tension of the reaction mixture with added epoxy resins, at dif~ere~t molecular weight9.
~e~
Vse of a Solid Epoxy Resin Extender, MW 6, 500 1150 grams of Epon 829 epoxy resin were placed in a reactor, to which was added 606 gram~ of bisphenol A and 310 graTn~ of 2-butt)xy-ethanol-1. Epon 829 epoxy resin is a Liquld re~in that has a Gardner color of 3 max., a der~sity at 68F of 9O 6 Ib~¦gal., and arl epo~ide equivalen~ of I 33-203, as reported by It~ manufacturer, Shell Chemical Compan~ he ~
calculated average m olecular weight is about ~6. The material was heated .
to albout 82C beore the bisphenol A was added, then it heated further to 145~C. I~ was allowed to go up to 175C, at which temperature the ~iBCosity wa~ U-V. Then 170 grarn~ o~ 2-butoxy-ethanol-1 w~re added, and the temperature was rai~ed to 180C, and wa~ held there for about two hours.
Then 826 grams o~ N-4utyl alcohol wa~ added, In a separate vesse1, 283 grarns of methacrylic acid, l48 grams of ~tyrene, 4 grams of ethyl acrylate, and 30 gram~ of benzoyl peroxide (a~out ~.9% based on mont?m~rs~ were mixed~ In lll grams of 2-butoxy-.... _.. . .

.
.

3~

ethanol-1, this monomer mixture was added to the reactor containing the !
epox~ resin over a period o:f two hours at about 115C. After two hours, with the temperature at 117C, 62 grams of N-butyl alcohol was added, and the whole was mixed at 117C for two h~urs~ Then 339 grams of :E:pon 1009 was added and mixed in with the other ingredients until dissolve~.
Epon lO09 epoxy resin is a solid resin that has a Gardner-Holdt viscosity of Z2-z5~ a Gardner color OI 5 ma~., and an epo~ide equivalent OI 2500-li 4000, according to its manu~acturer, Shell Chemical Compa~y. The cal-¦1 culated average molecular weight is about 6, 500. The temperature of the 1 O reaction rnixture wa~ then ~ 16 .
The elltire resinous mixture was diluted with water to 25% llon-volatiles. Af~er ths addition o~ a neutralizing agent~ the ~mul~ion had ~he followi~g properties:
Nonv~olatiles 2B, 07%
Viscosity - ~4 Ford Cup 23 ~econd~
pH 6.~0 ~o Neutralized 50 A cid Number ~on nonvolatilesi) 74. 2 0 The abo~re-described water-reducible eomposition wa~ ~prayed on both tin plate and alum~num sub~itrate~ of the kind ui3ed ~or making two-piece cans for carbonated beverages, and the eoatings were cured by baking.
The re~ulting cured coating~ had excellerlt prop~rties in term~i o~ flavor inertne~, ab~ence of bli~tering, and adhe~iio~.
I . ' . ,1 ~

The 8ame procedure a8 in Example~ ~ was followed to make a i, reaction mixture containing a graft polymer. The reaction mixture W~6 i1 , f, -40 - , , ~ ..

~ ii9~3i~
"
then diluted with 339 grams of DER 664 epoxy resin înstead of the Epon !~ loog. According to the manufacturer, Dow Chemical Company, DER 664 epoxy resin is a. solid resin having an epoxide equivalent of 875-975, a softening point of 95C to 105C as measured by "Durrans' Mercury , Method" a Gardner-Holdt viscosity of P~-V as ~neasured in 40% by weight glycol ether solvent, and a weight of 9. 54 Ibs. per gallorl. The calculated average molecular we ight is 1, 8 50 .
. When thi~ epoxy-extended reaction mixture was neutralized and dispersed in water, the water-reducible composition had excellent appli~
cation properties and formed excellent cured coatingci.
The physical properties of the water emulsion were:
. Nonvc~latiles 26. 27%
Viscosity #4 Ford Cup 20 6eeonds -pH 6.90 .
% Neutraliz ed 5 o Acid Num~er . 74. ~o . , Exam~e XXI~l IJse o~ a E~elatively Low Molecular Vi*ight F~poxy Re~in Extender , . .
2D The reactiorl mixture of Ex. XXI, con~aining graft polymer, was diluted wi~h 339 grams of DER 661 epo~y resin. According to its manu-facturer, Dow Chemlcal Company, DER 6B1 epoxy resin i~ a solid resin having an epoxide equivalent oî 475 to 575, a softeniIlg point of 70C to ~0C
as measured by "Durrans' Mercury l\qethod", a Gardner~Holdt viscosity s:~f G-J a8 mea~ured in 40% by ~eight glycol ether solvent, and a weight of

9. 65 Ibs/gal. The calculated average molecular weight was 1,050.
. . . I
I

il l 39~3~

When the epoxy-extended reaction mixture was neutralized and dispersed in water, the water-reducible composition had excellent pro-perties for application and in the form of cured coatings. The physical properties of the emulsion were: !
Nonvolatiles 2 6. 14%
Viscosity - #4 Ford Cup 29 seconds p~ ~.90 % Neutralized 50 .

. Acid Number 75.20 ~
. ' ' . .
The emulsions of Examples XXI through XX~I were tested for dispersion siabllity over an e~ended period of time at 120F. Each exhibited excellent properties with substantially no detectable phase ~eparation and no changes in viscosity or pH.
. . .
xample X~IV
. Investi~ation of ~e ~;111~
A polymerlc blend i~ prepar~d by reaeting an epo~;y resin with an addition polymerizable monomer mixture in an 8û to 20 weight ratio, in the ~olls~wi~g manner.
~ irst, a DER 333 1iquid epoxy re~ is reacted with bisphenol A in 20 the proportion of a~out 65% of the resin to about 35% by weight of bisphenol A. In a ~eparate Ye3sel a mixture ls made of methacrylic acld, styrene) and ethyl acrylate, in ~he wei~h~ ratio of ~5 to 34 to 1, respectively. About 6. 8% of ben~oyl peroxide is added b~sr weight of the mixture~ and the mixture iB then gradually added to the epoxy resin at a reaction ternperature of about 120C during a two howr period. After an adclitional holrling period of ab~ut . two hour~ at the same elevated temperature, samples of the product are taken for ~tructural ~valuation.

~;~ ~2-~ = . . .. . . , ., : . .

~g~

Carb~n 13 nuclear rnagnetic resonance ~;p~ctro~3cop~ indicates that most OI the grafting between the addition copolyrner and the ~po~y resin is restricted te what had been, beîore the ~ra:e-ting, aliph~tic sec~ndary [and possibly aliphatic tertiary) backbone car7~on atc~ms ~f the epoxy resîn back-. bone.
In order to delineate Eur~her such graf~ing, several dif~ere~ model compounds, each ha~ g an aliphatic carbôn atom arrangement like some of jj those present in the epoxy resin, are reacted separately with the same mi-~-ture of monomers under conditions comparable to the grafting conditions described ab~ve. Carbon 13 nuclear magnetic resonancc ~pectroscopy on these resulting analog products indicates that gra~ting on aliphatic back-bone carbon atoms of the m~àel compoutlds occurs E~ra~ieally entir~ly on those carbons which had been aliphatic ~econdary carbons alpha to ox~rane groups prior to grafting. This suggests a ~air likelihood ~ the ~ame ~ituation prevailing in the instant resin~u~ blend reaction product. A
small decrease i8 noted in the Acid Number oP the reac~ion product, relative to the Acid N~ber calculated for the equivalen$ ma~ but based upon all of the methacrylic acid charged to the reactor" and this emall decrease in .9cid Number tends to cor~oborate the findi~g~ made through Carbon I3 20 spectro~copy.
Hence, it i~ concluded that while other graf~g to aliphatic carbon atoms o~ the epoxy re~i~ backbone rnay occur, the proportion i~3 rnlnor r~ative tD the gra~ting on tho~e aliphatic backbone carbon atoms in positions alpha to the oxirane group~ and on other aliphat1c backbone carborls that ha~e either one or two hydrogens in the ungra~ted ~tate.
. I
. . I

1l -43-, , E mple ~V

E~fect of Using Di:fferent.Arnou~lts of Benzoyl Peroxide A series of resinous blends are prepared in ~ssentially the same . manner as described in Example XXIV, but with each addition polyxnerization .
~, operatio~ using a dif~erent percentage of benzo~ peroxide free radical tiator based on the weight of the mixed monomers.
The approximate weight fraction OI total mixed monomers charged I that graft~ onto the epoxy resin is estimated b~r solvent extraction. The blends are observed for their ease of dispersibility in a~ueous amine ~olu-tion, and ~he resulting aqueous dispersions are ob~er~red for their re~ietance to precipitation (stability) for a week. The following observat~on for this work are typical.
.-Tsb1e V
Wt. % Ben~oyl Approximate wt. % total Peroxide based on mixed nnonomer~ gra~ted mi~ed mononners to epoxv r~in Rennarks 3 3.0 marginally dispe.r~ible;
t~ndi~g to ~eparatein .
abouta day ~1) 11.5 very 6table aqueous alkaline disper~ion nn~de readily 7 15.0 "
~ , .
~8.2 45. 0 " ~2) .

~1~ Would be considered borderline at best for sanitary coating u~e and mo~t likely would require considerable e~tra hydrophilic organic solvent fvr - 30 eaee of aqueou~ dilpersion. ' (2) The high proportion of ~ree radical initiator not only gives rise to con cern8 about h~gh co~ts, but also concerns about the possibility of ~ee radical iniffator fragment~ (e. g. ben~oie acid) giving rise to undesirahle organoleptic and other propertie0, e. g. tending to produce components extractable intobeverages, various low mc~l weight sub6tances~ etc.
. . .
. ' .

, !

General Comments i To sum up, this invention pro~rides associatively~formed reqinous . blend~ of epoxy resin, addition polymer, and grafts OI addition polymer Il onto the epox~ resin structure wherein such grafting is restricted mainly ¦, to what were, before such graMing, aliphatic secondary (and possibly li aliphatic tertiary) carbon atoms of the epoxy resin aliphatic carbon back-bone, i. e., the non-ogirane part of the molecule. Most likely such grafting i~ restricted mainly to former aliphatic ~econdar3~ (methylene) carbon atoms alpiha to terminal oxirane groups. At any rate9 this grafting pro-~rides an especially durable linkage for modif7i}lg enough epo~y resin pre~ent to exert a profound influence on the propertie~ of the reSinouB
blend product a~ w811 21S $o impart la~ting characteri~tic~ of the gra~ted-on addition polymer to the epoxy resin receptor. Thus, ~r example, such graft polymer ~hat is rich in oarbo~yl group~ ~nparts to the resinou~ blend prodtlct superior characteristic~ for making water-reduced ~anitar~r coatings used inside cans for beverage~ and the like, provided that there are a e~r part3 by weight of graf~ed carbox rlie acid-containing addition pol~mer supplyiTIg at least about one weight p~t of car~ yl group~ per 100 par~S of ~tartiDg epo~sr resin. Such a ~lend i~ highly resistant to . ~ undesirable reaction in and precipitation ~rom 2nildly alkaline aqueous dispersion. ~owever, to obtain even ~o mod~st a propnrtioll of thig durable gra~ting and attendant in~luence upon propertie6 of the as80ciatively-- ~ormed blend, it i6 es~ential to commence the addition polymerization with an urlusually large amount of free radical initiation with respe~-t lto the poly~nrrizing temperature and amount o~ pol~nerizable monomer being used~ e. g., from 4% to 7% or more by w0ight of benzoyl peroxide based on . '. ''., ~; . ~ 5~ - .
. . .

weight of such monomer when reactirl~ at a temperature about 115C, In its preferred embodi:rnent~ then, this invention is primarily con-cerned with the production of re~inou~ compositions that are intended :~r use in coating cans for items for hurnan c:>nsumption, and particularly, for soft dri~3ks and beer. There are several tests that are applied in order to deter- ¦
mine whether a particular coating composition is satis~actory for these sur-prisingly demanding end uses. Some of the more important tests are !i described brie1y below. Whenever a coating compo~ition has been indicated 11 in this application to be acceptable ~or use as a sanitary coating composition, 1 it carl pass many of these tests.
The Flavor Te~t. The ured coating in the can ~hould impart no discernable flavor to the contents of the can, nor ehould it alter the ~lavor of the can contents in any wa~. This lte~t i~Y particularl~ important with respec$ to beer can coatings.
Adhe~ion~ The adhesion te~t is con~ueted a1: room tempera~ture under ambient humidity condition~. The coated panel to be tested is cro~s-hatched by cutti~g $hree parallel lirles~ each approximately 1" lo~g, abo~
1/8~ apar$0 These lineB are in1:er~ected at ~0 with th~ee identical line~
~imilarly spaced. Usually a lsnife edge or razor blade i~ u~ed to cut the line3. A ~trip o Scotch cellophane tape i~ then ~irmly pressed diagonally acros the scribed ~quares. The tape i~ pulled of~ with a quick eontinuou~
pull, u8ing a peeling-back motion at an angle of pull of about 150, The cross-hatched area of the panel i~ then in~pected for removal of co7.ting.
. . I~ any coatir~ is removed, the percentage of removal is recorded a~ a ~umerical rati~g ln the range ofi zero to 10. A zero rating indicates a per-jl Iect score, with no removal, and a 10 rating indicate~ 100% remov~lO
!l ~. Water reducible coatings must demonstrate ac- I
1~ 1 ~6~ .

i~ !
.. ,ii .,,.",, . , I
.

il I
ceptable hydrolytic stability on extended storage. This is determined by making an initial measurement of all of the properties of the co~ting corn-pc>sition and then redetermining them after a period of storage, on samples stored not only at room temperature but also at 50~C. Some of the most significant parameters, with respect to stability, are ~reedom from gelation, freedom fro1m precipitation, and freedom from changes in pH.
To be acceptable as a sanitary coating composition, there should be little discernible change in viscosity aMer room temperature storage for 12 . . months or after ~torage ~ 50C for 8 months, indicating the absence of gelation.
Thermal Stability. In ~ome can manufacturing proce~se~ after the coating ha~ been applied, the coated metal i~ dipped in a solder bath at a temperature in the range ~rom about 340C to 370C for a period up to about 5 second~. The amourlt s7f di~coloration of the coating i~ an indicati~n of f the extent of decompo~ition. In other can fabricating operations, where ~æe is made of end~ that are die-~tamp~d~. the as~embled cans are ~ually in~ner~ed in a bath of acidic copper ~ulatç for 5 minutes,. to te~t ~or ansr cracking in the coa~g during the fabrication~ The presence of a craclc will be indicated ~y the deposition of a ~mall amount of copper on the rneSal of the ~0 c~
VVater Pa~teurization Te~t. This test is often performed on cure~l ..... ._ . .
coatings th~t have been ~prayed and ba~ed on the interiors o~ two-piece aluminum can~ ~or beverages. The te~t is al~o used to measure the re~
~i8tance of a coati~g material to water and to water vapor at pasteurization .- . temperature. For test purpose~, the coatlng weight i~ from 12 to 16 milli ¦ gram~ per 4 square inche~ of panel. After the coating has been applied and cured by baking for about 2 minuteE; at about 218C (390F), two test strips .
, . . ~' . ~ ' .

... . .

: . .

are cut from thQ coated panel, each appruximately l-l/21' X 9". The top 2" of each test strip is bent back upon itself, with the coated side expc~sed.
:Each test strip is then half-immersed in a water bath at about 94~C (170F) by hanging each strip over the edge of the water bath. After immer~ion for 1/2 hour, the strips are cooled lmder running tap w~ter at room tçm-. . perature, dried, and examined immediatel~y for blush and for adhesion.
Any blush (whit0ning) indicates the absorption of water dur~g p~s-teurization and is rated on a scale from zero to 10, zero being perfe~ and indicating no blush, and lO indicating complete whitening. Both the immersec area and the area e~posed nnly to water vapor are rated. A blu~h rating range of zero to 2 is acceptable.
The adhesion te~t, as described above, is appIied to both the .
immersed area and the water vapor exposed area, and ~ r~ted accord~ngly~
again on a ~ale of zero to lO. Coating removal ~rom a te~t strip ln th~
ra~ge from zqro to 1 is acceptable. .
E~ n.t.~ Thi~ is a test employed by canners, to evalu-ate metal exposur~ in coated cans. Under the conditiona of the te~t~ a low voltage iB applied between an electrode that i8 1mmer~ed in an electrolyte . filled canO and the can body. When the coating on the can ie imperfect, metal i~ exposed and current flows. The flow OI curre2~ is indicated on a meter,. arld the magnitude OI the cuxrent i8 related to the total area of metal that i~ expoeed to the electrolyte. Thus, the ~i~e of the curre~t ~low~ as ndicated by the reading Oll th~ milliammeter, provides a relative measure - of the total metal expo~ure. Generally each canner ha~ hi8 own ~pecifica-tion as to the permiasible current fIo~.
The conditîon~ of the te~t i~volve the u~e of a standar~ized electrolyte and a coating weig~t o~ 2. 5 mg~. per ~quare inch. For a 12-ounce beverage Il 1~ - .

9~

., can, this coating weight is approximately 110 to lZo mg~. per can. Under the usual test conditions, a current flow rate below 25 milliampers is accept-able for al~ninum beer cans, for many brewers.
i~ The requirements for soft drir~{ cans are more stringent and the normal requirement for aluminum soft drink cans in production i6 a current flow rate of less than 5 milliamperes. Accordingly, higher coating weights are normally appl;ed to coatings for soft drink cans, normally about 4. 5 mgs. /in.2, which amounts to about 160 to 200 mgs. for a 12-ounce ~oft drink can.
The following characteristics are also often ~valuated for 8prayable coating co~npositîon~ ~or two-piece can3.
~. The composition on the coated ~urgac~ must have the ability to ~orm a conti~uous wet ~ilm. Thi8 i~ a partic~llarly critical requir~-ment with respect to the lower wall area of two-pi~ce cans becau~e thiB i3 where the can is Iarthest from the ~pray gun.
Blister Resistance. Some applicatlons, ~uch a~ single coats for two-piece tin plated cans, require high coatirlg weights. l~ormally the highe3t wet film concentration wlll occur in the moa~ ar~a. 13ecau~e of the great thickne~ o~ the film in this areaO there is a tendency to bll3ter, which is a di~ruption of the film 8urface by volatilization of l;quid.
Foami~. When applied by an airless ~pray by 1, 000 p5i, the coatîl~g mu~t not foam on th~ can. When ~oaming OCCUI~3, it causes film discontinuity and a rough surIace.

! ~

3~

Water dispersion sanitary coating compositions made in accordance with embodiments of this inv~ntion can pass many of the tests mentioned above~ Such compositions perform exceptionally well whezl sprayed by both air and airless devices. :Excellent atomization can be obtained regardless of the type of nozzle or pressure, that is, excellent spraying applications can be obtained at pressures in the range frorn 2 psi up to 1~00 psi~
Coating materials made in accordance with the invention ha~e been .~ applied to tin plate, aluminum, to metal coated with primers, to pla~tics ,¦ made from ABS, polyolefins, polyesters, pol~7amides, and the li~e, in a range of application thicknesses producing cured weights per 12-~unoe can .

I in the range Irom 1 to 10 mgs/in, which is 50 to 30û mgs. per 12_our~ce can~
Film continuity ges~erally has been excellent throughout tlhis range.
:Moreover~ these composition~ ~ve excellen~ app3ication prc~perties and generally their use is free from problems with respect to bli6ter~, sagging~ solvent urashing, foaming, and excess flow. It is common with water-redudble coatings to encount~r odor problems in the æpraying equip-ment~ but no sueh problems ha~e been encounter ed wit~ compositîon~
prepared in accordance with this in~ention.
While the specific examples demonstrate, gen~rally~, preferred ~ J
bodiments of the in~reniion, other preferred erxlbodiments and practices also lead to excellent coating compositions. Thus, if the pr~cedure of Ex. XXI i~ ~ollow~d, and an added diluent i~ added ~in addition to the epo~r resin diluent), made by the addition copolymerization of the same monomer n~ixture as used in that example, quite ~atisfactory coatings can he obtained, generall~y atlower cost, up to addition levels of yieldin~ an ungrafted total , .

.

about 40% of addition polymer hased on ~e rnixture, and even more may be tolerated. Similar results are obtained when the orily diluent used i~

the addition polyrner, i. e., there is no additi~n to the reaction mixture ;
of urlgrafted epo~y resin.
; While the compositions described generally have been ~oæe using liquid ~ehicles, the binders may be prepared in the absence o~ solvents, cooled, and pulverized to form powdered products. These powders c~n ¦
be dissolved in solvent ~rehicles, and can be di;persed in aqueou~ v~hicles i~ some amine is added at the time of use.
The amount o~ free radical initiato~ " benzoyl peroxide, ha~ been e~pressed in term3 oî the p~olymerizable monorner. Based oal the entire reaction mixture, It is preferred ~at the amount be iD the r~nge fro~n not b2aow 0. 6% to no~ ~bove 5~o.

Con~u~ion VVhile the in~ntion has been di~closed by re~erence to the detaiL~
o~ preferred ~m~o~ments thereof, it i~ to be ll~derstood ~at ~uch di3-closure i~ intended in an illustr~ti~re" rather th n in a limiting ~ense, ancl it i~ conten~pla~ed that variou~ modi~atlon8 ~n he compQ3itifon8 and pro-ceB~iDg technique~ particular, wil~ readily occur to tho8e ~killed ~
:20 the ~rt, withm the ~pir~t of the invention and ~c~pe o~ the appended claims~ ¦
What i~ claimed i~
. I , . .

~ 51-. I

,

Claims (85)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An associatively formed resinous blend that is dispersible in a basic aqueous vehicle, and that has an oxirane content of no more than 3%, comprising:
a) carboxylic acid-functional graft polymer, b) ungrafted carboxylic acid-functional addition polymer, c) ungrafted aromatic 1,2-epoxy diepoxide resin;
said graft polymer being an aromatic 1,2-epoxy diepoxide resin component onto which is grafted an addition polymer component, said graft polymer and said ungrafted addition polymer containing carboxylic acid units derived/from the same monomer units and furnishing carboxyl groups that contribute at least 5% of the weight of said blend, the grafting between said addition polymer com-ponent and said epoxy resin component being at aliphatic backbone carbon atoms of said epoxy resin component, and being to the extent of at least 105 parts by weight of said addition polymer component per 100 parts by weight of epoxy resin component of the graft polymer, the epoxy resin component of said graft polymer having an oxirane content not substantially in excess of 8% in the un-grafted state and having an initial molecular weight above 350.
the epoxy resin component of said graft polymer constituting at least 5% of the blend by weight, the acid-functionality of the reaction product composition being sufficiently high to establish the blend as a dispersion in an aqueous medium containing a base that ionizes the acid functional polymers.

2. An associatively formed resinous blend according to claim 1, wherein said epoxy diepoxide resin has a mole-cular weight of at least 1,000.

3. An associatively formed resinous blend accord-ing to claim 1, wherein said epoxy diepoxide resin has a molecular weight in the range 4,000 to 10,000.

4. An associatively formed resinous blend according to any one of claims 1, 2 and 3, wherein said epoxy diepoxide resin is a bisphenol A/epichlorohydrin reaction product.

5. An associatively formed resinous blend accord-ing to any one of claims 1, 2 and 3 wherein said addition polymer and the addition polymer component of said graft polymer comprise copolymerized units of an acrylic acid and styrene.

6. An associatively formed resinous blend accord-ing to claim 1, wherein said addition polymer and the addition polymer component of said graft polymer comprise units of styrene and methacrylic acid.

7. An associatively formed resinous blend accord-ing to claim 6, wherein methacrylic acid and styrene units are present in a weight ratio of from 60:39 to 80:19.5.

8. An associatively formed resinous blend accord-ing to claim 7, wherein said ratio is about 70:30.

9. An associatively formed resinous blend according to any one of claims 6, 7 and 8, wherein there are also present units of a lower (C1-4) alkyl ester of acrylic acid.

10. An associatively formed resinous blend according to any one of claims 6, 7 and 8, wherein said epoxy diepoxide resin has a molecular weight in the range 4,000 to 10,000.

11. An associatively formed resinous blend according to any one of claims 6, 7 and 8, wherein said epoxy diepoxide resin has a molecular weight in the range 4,000 to 10,000 and wherein there are also present in said addition poly-mer and the addition polymer component of said graft polymer units of a lower (C1-4) alkyl ester of acrylic acid.

12. An associatively formed resinous blend according to any one of claims 6, 7 and 8, wherein the total of said epoxy diepoxide resin in the graft polymer and the ungrafted resin is present in an amount of 80 parts by weight per 20 parts by weight of the total of addition polymerizable monomer units present in said graft polymer and said addition polymer.

13. An associatively formed resinous blend according to any one of claims 6, 7 and 8, wherein said epoxy diepoxide resin has a molecular weight of at least 4,000 and is a bisphenol A/epichlorohydrin reaction product.

14. An associatively formed resinous blend according to any one of claims 6, 7 and 8, wherein said epoxy di-epoxide resin has a molecular weight of at least 4,000 and is a bisphenol A/epichlorohydrin reaction product and said addition polymer and the addition polymer component of said graft polymer comprise units of a lower (C1-4) alkyl ester of acrylic acid.

15. An associatively formed resinous blend accord-ing to any one of claims 6, 7 and 8, which has an Acid Number of from 45 to 150 and wherein said epoxy diepoxide resin has a molecular weight of at least 4,000 and is a bisphenol A/epichlorohydrin reaction product and said addition polymer and the addition polymer component of said graft polymer comprise units of a lower (C1-4) alkyl ester of acrylic acid.

16. An associatively formed resinous blend accord-ing to any one of claims 6, 7 and 8, which has an Acid Number of 80 to 90 and wherein said epoxy diepoxide resin has a molecular weight of at least 4,000 and is a bisphenol A/
epichlorohydrin reaction product and said addition polymer and the addition polymer component of said graft polymer comprise units of a lower (C1-4) alkyl ester of acrylic acid.

17. An associatively formed resinous blend accord-ing to any one of claims 6, 7 and 8, having an Acid Number in the range 45 to 150.

18. An associatively formed resinous blend accord-ing to any one of claims 1, 2 and 3, wherein said ungrafted epoxy resin together with the epoxy resin component of the graft polymer comprises 50-90% by weight of the blend.

19. An associatively formed resinous blend accord-ing to claim 1, wherein said epoxy diepoxide resin is a bisphenol A/epichlorohydrin reaction product and wherein said ungrafted epoxy resin together with the epoxy resin component of the graft polymer comprises 50-90% by weight of the blend.

20. An associatively formed resinous blend accord-ing to claim 19, wherein said ungrafted epoxy resin together with the epoxy resin component of the graft polymer comprises about 80% of the blend.

21. An associatively formed resinous blend accord-ing to either of claims 19 and 20, wherein said epoxy diepoxide resin has a molecular weight in the range 4,000 to 10,000.

22. An associatively formed resinous blend accord-ing to any one of claims 1, 2 and 3, wherein said blend has an Acid Number of from 45 to 150.

23. An associatively formed resinous blend accord-ing to claims 1, 2 and 3, wherein the blend has an Acid Number of from 80 to 90.

24. A process for modifying an epoxy resin with addition polymerizable monomer to produce a reaction mixture containing a blend of resinous material disper-sible in a basic aqueous vehicle including unreacted epoxy resin, a graft polymer being an epoxy resin having aliphatic backbone carbon atoms having either one or two hy-drogen atoms bonded thereto in the ungrafted state to which is grafted an addition polymer component derived from the polymerizable monomer, and associatively formed but ungrafted addition polymer, said blend having an oxirane content no higher than 3%, comprising reacting together:
a) an aromatic 1,2-epoxy diepoxide resin that has aliphatic backbone carbons, and that has a molecular weight of at least 1,000 and b) addition polymerizable monomer comprising an un-saturated carboxylic acid and optionally one or more further ethylenically unsaturated compounds;
the epoxy resin constituting at least 30% by weight of the solids of the reaction mixture and up to 90% by weight thereof;
in the presence of at least 3% benzoyl peroxide by weight based on the monomer or the free radical initiating equiv-alent thereof for this reaction, at an elevated temperature not substantially above 130°C, in an amount sufficient and at a sufficiently high temperature to effect simultaneous addition polymerization of the monomer through its ethylenic unsaturation and to promote graft formation and grafting at aliphatic backbone carbon atoms of the epoxy resin that have either one or two hydrogens in the ungrafted state, to form graft polymer with addition polymer grafted to such aliphatic backbone carbons of the epoxy resin and with ionizable carboxyl groups constituting at least 5%
by weight of the reaction product solids, the acid funct-ionality of the reaction product composition being sufficient-ly high to establish the product composition as a dispersion in an aqueous medium, containing a base that ionizes.

25. A process according to claim 24, wherein benzoyl peroxide is employed as the initiating compound in an amount of at least 3% based on the weight of monomer.

26. A process according to claim 25, wherein benzoyl peroxide is employed in an amount of at least 6% based on the amount of monomers.

27. A process according to any one of claims 24, 25 and 26, wherein said process is effected at a temper-ature of 110 to 130°C.

28. A process according to any one of claims 24, 25 and 26, wherein said aromatic 1,2 epoxy diepoxide resin has a molecular weight of at least 4,000.

29. A process according to any one of claims 24, 25 and 26, wherein said aromatic 1,2-epoxy diepoxide resin has a molecular weight of at least 4,000 and said reaction is effected at a temperature of 110 to 130°C.

30. A process according to any one of claims 24, 25 and 26, wherein said aromatic 1,2-epoxy diepoxide resin has a molecular weight of from 4,000 to 10,000.

31. A process according to any one of claims 24, 25 and 26, wherein said aromatic epoxy diepoxide resin is a bisphenol A/epichlorohydrin reaction product.

32. A process according to any one of claims 24, 25 and 26, wherein said aromatic 1,2-epoxy diepoxide resin is a bisphenol A/epichlorohydrin reaction product and said process is effected at a temperature of 110 to 130°C.

33. A process according to any one of claims 24, 25 and 26, wherein said aromatic epoxy diepoxide resin has an oxirane content of not substantially more than 8%.

34. A process according to any one of claims 24, 25 and 26, wherein said aromatic epoxy diepoxide resin constitutes from 50 to 90% of the initial reaction mixture.

35. A process according to any one of claims 24, 25 and 26, wherein said aromatic diepoxide resin is a bisphenol A/epichlorohydrin reaction product and con-stitutes from 50 to 90% of the initial reaction mixture.

36. A process according to any one of claims 24, 25 and 26, wherein said unsaturated carboxylic acid employ-ed is an acrylic acid.

37. A process according to any one of claims 24, 25 and 26, wherein said aromatic diepoxide resin is a bisphenol A/epichlorohydrin reaction product and said unsaturated carboxylic acid employed is an acrylic acid.

38. A process according to any one of claims 24, 25 and 26, wherein said aromatic diepoxide resin is a bisphenol A/epichlorohydrin reaction product and said unsaturated carboxylic acid employed comprises methacrylic acid.

39. A process according to any one of claims 24, 25 and 26, wherein said aromatic diepoxide resin is a bisphenol A/epichlorohydrin reaction product, said un-saturated carboxylic acid is an acrylic acid and said reaction mixture further comprises styrene as a monomer.

40. A process according to any one of claims 24, 25 and 26, wherein said aromatic diepoxide resin is a bisphenol A/epichlorohydrin reaction product, said un-saturated carboxylic acid is methacrylic acid and said reaction mixture further comprises styrene as a monomer.

41. A process according to any one of claims 24, 25 and 26, wherein said aromatic diepoxide resin is a bisphenol A/epichlorohydrin reaction product, said unsaturated carboxylic acid is methacrylic acid and said reaction mixture further comprises styrene as a monomer and wherein said methacrylic acid and styrene are present in the initial reaction mixture in a weight ratio of from 60:39 to 80.19.5.

42. A process according to any one of claims 24, 25 and 26, wherein said aromatic diepoxide resin is a bisphenol A/epichlorohydrin reaction product, said un-saturated carboxylic acid is methacrylic acid, styrene monomer is also present so as to result in a methacrylic acid:styrene weight ratio of 60:39 to 80:19.5 and said reaction mixture further comprises a lower (C1-4) alkyl ester of acrylic acid.

43. A process according to any one of claims 24, 25 and 26, wherein the acid employed is methacrylic acid.

44. A process according to any one of claims 24, 25 and 26, wherein styrene is present as a monomer.

45. A process according to any one of claims 24, 25 and 26, wherein methacrylic acid and styrene are present in the initial reaction mixture in a weight ratio of from 60:39 to 80:19.5.

46. A process according to any one of claims 24, 25 and 26, wherein said unsaturated carboxylic acid is methacrylic acid and a lower (C1-4) alkyl ester of acrylic acid is also present.

47. A process according to any one of claims 24, 25 and 26, which is effected in the presence of a water-miscible solvent.

48. A process according to any one of claims 24, 25 and 26, wherein said aromatic diepoxide resin is a bisphenol A/epichlorohydrin reaction product, said un-saturated carboxylic acid is methacrylic acid and said reaction mixture further comprises styrene as a monomer and wherein said methacrylic acid and styrene are present in the initial reaction mixture in a weight ratio of 60:39 to 80:19.5, which process is carried out in the presence of a water-miscible solvent.

49. A process according to any one of claims 24, 25 and 26, wherein said aromatic diepoxide resin is a bisphenol A/epichlorohydrin reaction product, said un-saturated carboxylic acid is methacrylic acid and said reaction mixture further comprises styrene as a monomer and wherein said methacrylic acid and styrene are present in the initial reaction mixture in a weight ratio of 60:39 to 80:19.5, which process is carried out at a temperature of 110 to 130°C.

50. A water-reducible coating composition comprising an associatively formed resinous blend according to claim 1 dispersed in an aqueous vehicle with a basic ionizing agent which ionizes said acid-functional graft polymer and said acid-functional addition polymer,the ionization of the acid-functional polymers being sufficient to establish a dispersion of the blend in the aqueous vehicle.

51. A water-reducible coating composition according to claim 50, which includes in the dispersed phase a supplemental quantity of addition polymer from an extraneous source dispersed in the aqueous vehicle.

52. A water-reducible coating composition according to either of claims 50 and 51, wherein the aqueous vehicle comprises a major amount of water and a minor amount of water-miscible organic solvent.

53. A water-reducible coating composition according to claim 50, wherein said composition comprises a base which is fugitive under curing conditions for the coating.

54. A water-reducible coating composition according to claim 53, which also contains up to 10% by weight based on said resinous blend of an aminoplast cross-linker.

55. A water-reducible coating composition according to either of claims 53 and 54, wherein the aqueous vehicle comprises a major amount of water and a minor amount of an organic solvent.

56. A water-reducible coating composition according to either of claims 53 and 54, wherein the aqueous vehicle comprises a major amount of water and a minor amount of an organic solvent and in said associatively formed resinous blend said aromatic 1,2-epoxy diepoxide resin has a molecular weight of at least 4,000 and is a bisphenol A/-epichlorohydrin reaction product, said carboxylic acid units comprise methacrylic acid units and wherein said addition polymer and the addition polymer component of said graft polymer comprise copolymerized units of metha-crylic acid and styrene.

57. A water-reducible coating composition accord-ing to any one of claims 50, 53 and 54, wherein in said associatively former resinous blend the epoxy diepoxide resin has a molecular weight of at least 4,000.

58. A water-reducible coating composition accord-ing to any one of claims 50, 53 and 54, wherein said associatively formed resinous blend the epoxy diepoxide resin has a molecular weight in the range 4,000 to 10,000.

59. A water-reducible coating composition according to any one of claims 50, 53 and 54, wherein said assoc-iatively formed resinous blend the aromatic diepoxide resin is a bisphenol A/epichlorohydrin reaction product.

60. A water-reducible coating composition according to any one of claims 50, 53 and 54, wherein in said associatively formed resinous blend the addition polymer and the addition polymer component of said graft polymer comprise copolymerized units of an acrylic acid and styrene.

61. A water-reducible coating composition accord-ing to any one of claims 50, 53 and 54, wherein in said associatively formed resinous blend said aromatic diepoxide has a molecular weight of at least 4,000 and is a bisphenol A/-epichlorohydrin reaction product and said addition polymer and the addition polymer component of said graft polymer comprise copolymerized units of an acrylic acid and styrene.

62. A water-reducible coating composition accord-ing to any one of claims 50, 53 and 54, wherein in said associatively formed resinous blend said aromatic diepoxide has a molecular weight of at least 4,000 and is a bisphenol A/epichlorohydrin reaction product and said addition polymer and the addition polymer component of said graft polymer comprise copolymerized units of methacrylic acid and styrene in a weight ratio of 60:39 to 80:19.5.

63. A water-reducible coating composition accord-ing to any one of claims 50, 53 and 54, wherein in said associatively formed resinous blend said aromatic diepoxide resin has a molecular weight of at least 4,000 and is a bisphenol A/epichlorohydrin reaction product and the addition polymer and the addition polymer component of said graft polymer comprise copolymerized units of methacrylic acid and styrene in a weight ratio of 60.39 to 80:19.5 and further comprise units of a lower (C1-4) alkyl ester of acrylic acid.

64. A water based coating composition comprising in percentages by weight of the composition:
a) from 60% to 90% of a liquid vehicle and b) from 10% to 40% by weight of solids comprising a polymer blend according to any one of claims 1, 2 and 3 in an amount of from 6 to 39.9% and a cross-linking resin in an amount of from 0.1 to 16%, said liquid vehicle consisting of from 6% to 35%
by weight of the composition of organic solvent r and from 25% to 80% of water, together with a sufficient quantity of a base that is fugitive at curing temperature for the compos-ition to ionize the acid-functional polymers, the ionization being sufficient to establish the blend in the aqueous vehicle as a dispersion.

65. A water based coating composition comprising in percentages by weight of the composition:
a) from 60% to 90% of a liquid vehicle and b) from 10% to 40% by weight of solids comprising a polymer blend according to any one of claims 6, 7 and 8 in an amount of from 6 to 39.9% and a cross-linking resin in an amount of from 0,1 to 16%, said liquid vehicle consisting of from 6% to 35% by weight of the composition of organic solvent, and from 25% to 80% of water, together with a sufficient quantity of a base that is fugitive at curing temperature for the composition to ionize the acid-functional polymers, the ionization being suf-ficient to establish the blend in the aqueous vehicle as a dispersion.

66. A water based coating composition comprising in percentages by weight of the composition:
a) from 60% to 90% of a liquid vehicle and b) from 10% to 40% by weight of solids comprising an amount of from 6% to 3909% thereof of a polymer blend according to any one of claims 1, 2 and 3, wherein said epoxy diepoxide resin is a bisphenol A-epichlorohydrin reaction pro-duct, and a cross-linking resin in an amount from 0.1% to 16 based on solids, said liquid vehicle consisting of from 6% to 35% by weight of the composition of organic solvent, and from 25 to 80% of water, together with a sufficient quantity of a base that is fugitive at curing temperature for the com-position to ionize the acid-functional polymers, the ioniza-tion being sufficient to establish the blend in the aqueous vehicle as a dispersion.

67. A water based coating composition comprising in percentages by weight of the composition:
a) from 60% to 90% of a liquid vehicle and b) from 10% to 40% by weight of solids comprising an amount of from 6% to 39.9% thereof of a polymer blend according to any one of claims 1, 2 and 3, wherein said epoxy diepoxide resin is a bisphenol A-epichlorohydrin reaction product, and a cross-linking resin in an amount from 0.1% to 16% based on solids, said liquid vehicle consisting of from 6% to 35% by weight of the composition of organic solvent, and from 25% to 80% of water, together with a sufficient quantity of a base that is fugitive at curing temperature for the composition to ionize the acid-functional polymers, the ionization being sufficient to establish the blend in the aqueous vehicle as a dispersion.

68. A water based coating composition comprising in percentages by weight of the composition:
a) from 60% to 90% of a liquid vehicle and b) from 10% to 40% by weight of solids comprising an amount of from 6% to 39.9% thereof of a polymer blend according to any one of claims 1, 2 and 3, wherein there are further present units of a (C1-4) alkyl ester of acrylic acid and wherein said epoxy diepoxide resin is a bisphenol A-epichlorohydrin reaction product, and a cross-linking resin in an amount from 0.1% to 16% based on solids, said liquid vehicle consisting of from 6% to 35% by weight of the composition of organic solvent, and from 25% to 80% of water, together with a sufficient quantity of a base that is fugitive at curing temperature for the composition to ionize the acid-functional polymers, the ionization being sufficient to establish the blend in the aqueous vehicle as a dispersion.

69. A water-based, sprayable coating composition for use for application as an internal sanitary liner for metal containers for beverages, comprising, in percentages by weight of the composition, a) up to 90% of a liquid vehicle, b) from about 9% to 29% of acidic resinous reaction product solids according to any one of claims 1, 2 and 3, dispersed in the vehicle, c) from about 1% to 10% of an added cross-linking agent, and d) from about 2% to about 6% of a fugitive base that ionizes the resinous product; said liquid vehicle consisting of water and up to 35% by weight of the coating composition of organic solvent.

70. A water based, sprayable coating composition for use for application as an internal sanitary liner for metal containers for beverages, comprising, in percentages by weight of the composition, a) up to 90% of a liquid vehicle, b) from about 9% to 29% of acidic resinous reaction product solids according to any one of claims 6, 7 and 8, dispersed in the vehicle, c) from about 1% to 10% of an added cross-linking agent, and d) from about 2% to about 6% of a fugitive base that ionizes the resinous product; said liquid vehicle consisting of water and up to 35% by weight of the coating composition of organic solvent.

71. A water based, sprayable coating composition for use for application as an internal sanitary liner for metal containers for beverages, comprising, in percentages by weight of the composition, a) up to 90% of a liquid vehicle, b) from about 9% to 29% of acidic resinous reaction product solids according to any one of claims 1, 2 and 3, wherein said diepoxide resin is a bisphenol A/-epichlorohydrin reaction product, said solids being dispers-ed in the vehicle, c) from about 1% to 10% of an added cross-linking agent, and d) from about 2% to about 6% of a fugitive base that ionizes the resinous product; said liquid vehicle consisting of water and up to 35% by weight of the coating composition of organic solvent.

72. A water based, sprayable coating composition for use for application as an internal sanitary liner for metal containers for beverages, comprising, in percentages by weight of the composition, a) up to 90% of a liquid vehicle, b) from about 9% to 29% of acidic resinous reaction product solids according to any one of claims 6, 7 and 8, wherein said epoxy diepoxide is a bisphenol A/epichlorohydrin reaction product, said solids being dispersed in the vehicle, c) from about 1% to about 10% of an added cross-linking agent, and d) from about 2% to about 6% of a fugitive base that ionizes the resinous product; said liquid vehicle consisting of water and up to 35% by weight of the coating composition of organic solvent.

73. A water based, sprayable coating composition for use for application as an internal sanitary liner for metal containers for beverages, comprising, in percentages by weight of the composition, a) up to 90% of a liquid vehicle, b) from about 9% to 29% of acidic resinous reaction product solids according to any one of claims 6, 7 and 8, wherein there are further present units of a lower (C1-4) alkyl ester of acrylic acid and wherein said epoxy is a bisphenol A/epichlorohydrin reaction product, said solids being dispersed in the vehicle, c) from about 1% to 10% of an added cross-linking agent, and d) from about 2% to about 6% of a fugitive base that ionizes the resinous product; said liquid vehicle consisting of water and up to 35% by weight of the coating composition of organic solvent.

74. A water based, sprayable coating composition for use for application as an internal sanitary liner for metal containers for beverages, comprising, in percentages by weight of the composition, a) up to 90% of a liquid vehicle, b) from about 9% to 29% of acidic resinous reaction product solids according to any one of claims 1, 2 and 3, dispersed in the vehicle, c) from about 1% to 10% of an added cross-linking agent, and d) from about 2% to about 6% of a fugitive base that ionizes the resinous product; said liquid vehicle consisting of water and up to 35% by weight of the coating composition of organic solvent wherein the cross-linker is an aminoplast resin and the liquid vehicle comprises water together with a mixture of 2-butoxy-ethanol-1 and n-butanol.

75. A process for applying a coating to the interior of a can for beverage use comprising spraying the can interior with a coating composition, then baking the can to cure the coating, the coating being applied to have a cured application distribution in the range from about 0.5 to 15 mg. per square inch, said coating composition being a water based coating composition comprising in percentages by weight of the composition:
a) from 60% to 90% of a liquid vehicle and b) from 10% to 40% by weight of solids comprising a polymer blend according to any one of claims 1, 2 and 3 in an amount of from 6 to 39.9% and a cross-linking resin in an amount of from 0.1 to 16%, said liquid vehicle consisting of from 6% to 35%
by weight of the composition of organic solvent, and from 25% to 80% of water, together with a sufficient quantity of a base that is fugitive at curing temperature for the composition to ionize the acid-functional polymers, the ionization being sufficient to establish the blend in the aqueous vehicle as a dispersion.

76. A process for applying a coating to the interior of a can for beverage use, comprising spraying the can interior with a coating composition, then baking the can to cure the coating, the coating being applied to have a cured application distribution in the range from about 0.5 to 15 mg. per square inch, said coating composition being a water based coating composition comprising in percentages by weight of the composition:
a) from 60% to 90% of a liquid vehicle and b) from 10% to 40% by weight of solids comprising a polymer blend according to any one of claims 6, 7 and 8 in an amount of from 6 to 39.9% and a cross-linking resin in an amount of from 0.1 to 16%, said liquid vehicle consisting of from 6% to 35%
by weight of the composition of organic solvent, and from 25% to 80% of water, together with a sufficient quantity of a base that is fugitive at curing temperature for the composition to ionize the acid-functional polymers, the ionization being sufficient to establish the blend in the aqueous vehicle as a dispersion.

77. A process for applying a coating to the interior of a can for beverage use, comprising spraying the can interior with a coating composition, then baking the can to cure the coating, the coating being applied to have a cured application distribution in the range from about 0.5 to 15 mg. per square inch, said coating composition being a water based coating composition comprising in percentages by weight of the composition:

a) from 60% to 90% of a liquid vehicle and b) from 10% to 40% by weight of solids comprising a polymer blend according to any one of claims 1, 2 and 3, wherein said epoxy diepoxide resin is a bisphenol A/-epichlorohydrin reaction product in an amount of from 5 to 39.9% and a cross-linking resin in an amount of from 0.1 to 16%, said liquid vehicle consisting of from 6% to 35%
by weight of the composition of organic solvent, and from 25% to 80% of water, together with a sufficient quantity of a base that is fugitive at curing temperature for the composition to ionize the acid-functional polymers, the ionization being sufficient to establish the blend in the aqueous vehicle as a dispersion.

78. A process for applying a coating to the interior of a can for beverage use, comprising spraying the can interior with a coating composition, then baking the can to cure the coating, the coating being applied to have a cured application distribution in the range from about 0.5 to 15 mg. per square inch, said coating composition being a water based coating composition comprising in percentates by weight of the composition:
a) from 60% to 90% of a liquid vehicle and b) from 10% to 40% by weight of solids comprising a polymer blend according to any one of claims 6, 7 and 8 wherein said epoxy diepoxide is a bisphenol A/-epichlorohydrin reaction product in an amount of from 6 to 39.9% and a cross-linking resin in an amount of from 0.1 to 16%, said liquid vehicle consisting of from 6% to 35%
by weight of the composition or organic solvent, and from 25% to 80% of water, together with a sufficient quantity of a base that is fugitive at curing temperature for the composition to ionize the acid-functional polymers, the ionization being sufficient to establish the blend in the aqueous vehicle as a dispersion.

79. A process for applying a coating to the interior of a can for beverage use, comprising spraying the can interior with a coating composition, then baking the can to cure the coating, the coating being applied to have a cured application distribution in the range from about 0.5 to 15 mg. per square inch, said coating composition being a water based coating composition comprising in percentages by weight of the composition:
a) from 60% to 90% of a liquid vehicle and b) from 10% to 40% by weight of solids comprising a polymer blend according to any one of claims 6, 7 and 8 wherein there are further present units of a lower (C1-4) alkyl ester of acrylic acid and wherein said epoxy is a bisphenol A/epichlorohydrin reaction product in an amount of from 6 to 39.9% and a cross-linking resin in an amount of from 0.1 to 16%, said liquid vehicle consisting of from 6% to 35%
by weight of the composition of organic solvent, and from 25% to 80% of water, together with a sufficient quantity of a base that is fugitive at curing temperature for the composition to ionize the acid-functional polymers, the ionization being sufficient to establish the blend in the aqueous vehicle as a dispersion.

80. A process for applying a coating to the interior of a can for beverage use, comprising spraying the can interior with a coating composition, then baking the can to cure the coating, the coating being applied to have a cured application distribution in the range from about 0.5 to 15 mg. per square inch, said coating composition being a water based, sprayable coating composition for use for application as an internal sanitary liner for metal containers for beverages, comprising, in percentages by weight of the composition, a) up to 90% of a liquid vehicle, b) from about 9% to 29% of acidic resinous reaction product solids according to any one of claims l, 2 and 3, dispersed in the vehicle, c) from about 1% to 10% of an added cross-linking agent, and d) from about 2% to about 6% of a fugitive base that ionizes the resinous product; said liquid vehicle consisting of water and up to 35% by weight of the coating composition of organic solvent.

81. A process for applying a coating to the interior of a can for beverage use, comprising spraying the can interior with a coating composition, then baking the can to cure the coating, the coating being applied to have a cured application distribution in the range from about 0.5 to 15 mg. per square inch, said coating composition being a water based, sprayable coating composition for use for application as an internal sanitary liner for metal containers for beverages, comprising, in percentages by weight of the composition, a) up to 90% of a liquid vehicle, b) from about 9% to 29% of acidic resinous reaction product solids according to any one of claims 6, 7 and 8, dispersed in the vehicle, e) from about 1% to 10% of an added cross-linking agent, and d) from about 2% to about 6% of a fugitive base that ionizes the resinous product; said liquid vehicle consisting of water and up to 35% by weight of the coating composition of organic solvent.

82. A process for applying a coating to the interior of a can for beverage use, comprising spraying the can interior with a coating composition, then baking the can to cure the coating, the coating being applied to have a cured application distribution in the range from about 0.5 to 15 mg. per square inch, said coating composition being a water based, sprayable coating composition for use for application as an internal sanitary liner for metal containers for beverages, com-prising, in percentages by weight of the composition, a) up to 90% of a liquid vehicle, b) from about 9% to 29% of acidic resinous reaction product solids according to any one of claims 1, 2 and 3, wherein said diepoxide resin is a bisphenol A/-epichlorohydrin reaction product, said solids being dispersed in the vehicle, c) from about 1% to 10% of an added cross-linking agent, and d) from about 2% to about 6% of a fugitive base that ionizes the resinous product; said liquid vehicle consisting of water and up to 35% by weight of the coating composition of organic solvent.

83. A process for applying a coating to the interior of a can for beverage use, comprising spraying the can interior with a coating composition, then baking the can to cure the coating, the coating being applied to have a cured application distribution in the range from about 0.5 to 15 mg. per square inch, said coating com-position being a water based, sprayable coating composition for use for application as an internal sanitary liner for metal containers for beverages, comprising, in percentages by weight of the composition, a) up to 90% of a liquid vehicle, b) from about 9% to 29% of acidic resinous reaction product solids according to any one of claims 6, 7 and 8, wherein said epoxy diepoxide resin is a bisphenol A/epichlorohydrin reaction product, said solids being dispersed in the vehicle, c) from about 1% to 10% of an added cross-linking agent, and d) from about 2% to about 6% of a fugitive base that ionizes the resinous product; said liquid vehicle consisting of water and up to 35% by weight of the coating composition of organic solvent.

84. A process for applying a coating to the interior of a can for beverage use, comprising spraying the can interior with a coating composition, then baking the can to cure the coating, the coating being applied to have a cured application distribution in the range from about 0.5 to 15 mg. per square inch, said coating com-position being a water based, sprayable coating com-position for use for application as an internal sanitary liner for metal containers for beverages, comprising, in percentates by weight of the composition, a) up to 90% of a liquid vehicle, b) from about 9% to 29% of acidic resinous reaction product solids according to any one of claims 6, 7 and 8, wherein there are further present units of a lower (C1-4) alkyl ester of acrylic acid and wherein said epoxy is a bisphenol A/epichlorohydrin reaction product, said solids being dispersed in the vehicle, c) from about 1% to 10% of an added cross-linking agent, and d) from about 2% to about 6% of a fugitive base that ionizes the resinous product; said liquid vehicle consisting of water and up to 35% by weight of the coating composition of organic solvent.

85. A process for applying a coating to the interior of a can for beverage use, comprising spraying the can interior with a coating composition, then baking the can to cure the coating, the coating being applied to have a cured application distribution in the range from about 0.5 to 15 mg. per square inch, said coating composition being a water based, sprayable coating composition for use for application as an internal sanitary liner for metal containers for beverages, comprising, in percentages by weight of the composition, a) up to 90% of a liquid vehicle, b) from about 9% to 29% of acidic resinous reaction product solids according to any one of claims 1, 2 and 3, dispersed in the vehicle, c) from about 1% to 10% of an added cross-linking agent, and d) from about 2% to about 6% of a fugitive base that ionizes the resinous product; said liquid vehicle consisting of water and up to 35% by weight of the coating composition of organic solvent wherein the cross-linker is an aminoplast resin and the liquid vehicle com-prises water together with a mixture of 2-butoxy-ethanol-1 and n-butanol.