BE628488A - - Google Patents

Description

       

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   The present invention aims at an improvement concerning the method described in Belgian patent 621,473
 EMI1.1
 and relutive to the electrodeposition of a paint on an anode placed in an electrical circuit, from a bath of an aqueous medium in electrical contact with an anode and a cathode, this improvement consisting of:

   (a) to disperse in this bath a film-forming binder for: paint containing a resin of a polycarboxylic acid which this at least partially neutralism by an amino compound soluble in water, this acidic resin having an electrochemical equivalent of between approximately 1000 and 20,000, having an acid number of between about 30 and 300 and exhibiting in this bath the behavior of an anionic polyelectrolyte, as indicated by its deposition on this anode substantially in a manner directly proportional to the current.
 EMI1.2
 dlectriqu trtwaracstv4 10 buini (b) 1 send direct current to danis lodii. circuit, until a maximum voltage of about 50-500 volto is obtained, which causes the electrodeposition of a film containing said resin for this anode;

   
 EMI1.3
 (o) h remove the r6uulLüntu anode from 00 barrel (i) U 1 \ r i ri, t. futre f.) au J '1) ir pie ft 1 m, The present invention further violates a concentrated coating of film-forming binder for paint containing an organic resin, a composition which can be absorbed (: hard an aqueous electrodeposition bath, containing an additional quantity of compound aT..ir. $ soluble in water sufficient to impart, in this bath, the behavior of an anionic polyelectrolyte to the resin contained in the coor7poai tion ,: Wr as a binder, the latter being c:

  cr.cctéris3't by the

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 contains, on a basis free of filler and pigment, about 50-95% by weight of a resin of a polycarboxylic acid having an electrochemical equivalent of between about 1000 and 20,000 and having an acid number of between about 30 and 300, and approx: ron 1-10 of amino compound soluble in water, by rappo; by weight of said polycarboxylic acid resin, the additional component being water.



   The advantages of the present invention by rap. prior art methods include the operative flexibility of the paint bath and the paint binder compositions contained therein, even deposition of the paint film, simple operation control, satisfactory paint application in the cracks and at the angles, a deposit over a thickness automatically limiting, and the resistance of the deposited film to entrainment by the condensed vapors, before and during the final hardening, obtained for example by baking
In general, the present process is an improvement to the electroplating processes on an anode connected in an electrical circuit passing through a b of an aqueous medium in electrical contact with an anode a cathode.

   The improvement consists) in dispersing in this bath a film-forming binder for paint containing resin of a polycarboxylic acid at least partially neutralized with an amino compound soluble in water, this polycarboxylic acid resin having an average chemical equivalent of between approximately 1000 and 20,000, an acid number of between about 30 and 300, and exhibiting, in this bath, a behavior similar to that of anionic polyeleotrolyte, as indicated by its deposit in this anode substantially in a direct proportion

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 with the electric current passing through this bath;

   in passing direct current through this circuit until a maximum potential of about 50 to 500 volts is obtained, which causes the electrodeposition on this anode of a film containing this resin; removing from the bath the coated anode thus obtained; finally, to harden the aforementioned film.



   Another characteristic of this improvement lies in the maintenance of such coating operations providing for a period of prolonged tempo, during which the bath is depleted in polycarboxylic acid resin and the amino compound accumulates in the bath. An additional amount of polycarboxylic acid resin is gradually added to the bath, this amount (additional being or ±. Doing so to keep the pH of the bath below about.
8.4. The additional amount added at any time, that is of course small enough for said polycarboxylic acid resin to retain, in the bath, the behavior of an anionic polyelectrolyte.



   Another feature of the invention resides in a concentrated composition of a film-forming paint binder containing an organic resin, which composition can be dispersed in an aqueous electroplating bath containing an additional amount of the amino compound soluble in the solvent. sufficient water to confer, in the bath, a behavior analogous to that of an anionic polyelectrolyte, to the resin contained in the concentrated binder composition.

   The concentrated binder composition comprises about 50-95 by weight of a resin of a polycarboxylic acid having an electrochemical equivalent of between about
1000 and 20,000 and an acid number of between about 30 and 300; about 1-10 of a water soluble amino compound, based on the weight of the poly- acid resin

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 the arboxylic acid contained in the composition, the balance removing water. These percentages are given on a basis free of pigment and mineral filler.



   The single figure of the accompanying drawing shows in sectional elevation an apparatus for carrying out the coating and electrodialysis process (simultaneously deo accumulations of water-soluble amine compound in an anode zone.

   This apparatus and its) of operation are more fully described in the course of the example described below,
In this description, the term "pointed. By electrodeposition" is understood to mean the deposition of a finely ground pigment and / or filler contained in a binder, the deposition of a binder without pigment and / or without filler or not. containing very little, but which can be colored if desired, and the deposition of other water-reducing surface coating compositions containing the binder which can be considered to be roughly analogous to bases for enamel paints, for varnishes, or for lacquers, and the coating material used to form these deposits is called "paint". Thus, the binder,

   which is formed into a water resistant film by electrodeposition and which has finally formed into a durable film resistant to ordinary conditions of use by final curing, may form all or substantially all of the substance which is deposited to form the film, or it can be constituted by a vehicle for a filler consisting of a pigment and / or a mineral substance or even for other resins on which it exerts the desired action in view of. film deposit. In some cases it can be reduced with compatible organic solvents such as nonionic liquids which evaporate upon curing.

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 of the resulting filtn.

   When using pigmenta and / or fillers, it is advantageous that the content of water soluble salts, such as sodium or potassium salts, is very low or even zero, so that the electrical resistance of the bath and the deposited film does not undergo uncontrolled variations, and the control of the electrical conductivity in the operation is done mainly by means of the resinous binder and the neutralization of the amino compound dispersed in the bath.



   In some instances, as expressly indicated by Overnight, the partially neutralized monk resin of the present invention appears to dissolve to form a clear solution in the bath; in other cases, some of the resin appears to be dispersed in the bath or in the form of a veil of extremely fine particles, the maximum size of the resin particles present being estimated to be 500 millinicrons at most. In the latter cases, the applicant has often been able to obtain an apparent solution of these particles in the form of a clear aqueous solution by adding to the bath an additional amount of a water soluble amino compound.



   In any case, the dispersed and at least partially neutralized polycarboxylic acid resins which have contained in the bath exhibit the typical behavior of an anionic solute with regard to migration to the anode in the electric field used, because this Migration, for a particular resinous binder, varies directly with the intensity of the current passing through the bath.

   When one takes into account the electric current necessary to carry towards the cathode two variable concentrations of amino compound which are in excess of the minimum quantity necessary to give the behavior of a polyelectrolyte,

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 = ORIGINAL --- P; 6.TENlINCOMPLTIE OR BAD:
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 COUNTRv0iC- DOC NUMBER: 6eq a - KIND: .li5fa-C (- --- MISSING FRONTPAGE --- NO DRAWINGS
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 -itl- MISSING PAGE (S) --- BAD ORIGINAL --- DIVERSE

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 being an amino compound, is transferred and deposited for the anode, the electrochemical equivalent of the residue is approximately 1232, or 0.015 x 0.9 x 107.88 + 0.001118.



   The polycarboxylic acid resin can be modified
 EMI7.1
 . ot lengthened by dlvurùúu nstmibruu without its advantageous characteristics being altered. A modification can often really improve the paint, for example a hardener: the resulting baked film.

   Thus, a
 EMI7.2
 Applicant used den resins of palycarbox.ali.ques acids. thermoplastic and non-heat-reactive resin or phenols have been incorporated into them, the elongated resins being diaperaceae in water with the amino compound polyfunctional.
 EMI7.3
 together, preferably with stirring, the polycarboxylic resin and such phenolic resin, for at least about 1/2 hour, and more preferably for about
1 to 2 hours or more, at a temperature between 200 and 260 0 approximately, this heating seems to determine a chemical bond between these two constituents and one does not observe the presence of free phenolic renin in the mixture of
 EMI7.4
 r6a1noa.

   Thus, when the resulting resin is used in the electrodeposition process, the coating is completely homogeneous and, in an electrodeposition bath containing the resulting resinous product, no appreciable accumulation of free phenolic bodies occurs.
 EMI7.5
 diaooo1éo you start from the realm, this for a lapa of appreciable working time.



   Other suitable extender materials for polycarboxylic acid resins include resins derived from hydrocarbons such as polycarboxylic acid resins.
 EMI7.6
 coumarone-indene, which are generally inert and thernoplastic, and diolefin resins such as cellas which have a predominantly naphthenic structure and are thermo-

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 EMI8.1
 susceptible, for example the roots of eyclopentudiénes. The addition of telloa rScinoa can also impart increased chemical resistance to the resulting cured film.

   We can
 EMI8.2
 also use many other diluting materials and plasticizers of an olasic nature, provided however that their concentration is not al :: high to negate the characteristics of
 EMI8.3
 electrical migration - say to the behavior of the anionic polydtectrolyte of the ruminum of carboxylic acid in the olcotrodevooition bath and thus cause the deposition of a film which is mrulifotcement unequal and thicker on the edges and on both sides. anode constituted by a simple rectangular sheet that on the immorgdeu faces of this anode.



   In general, the polycarboxylic acid resins advantageous in the practice of the present invention are film-forming at the temperature of the electrode-position bath and can cure to form a non-film.
 EMI8.4
 sticky.

   These include: modified drying oils, for example drying and a1ccative oils such as sunflower oil, enrthar oil, .a, perilla oil, chnevis oil, walnut oil. , dehydrated castor oil, grape seed oil, tomato seed oil, menhadon oil, mata oil,
 EMI8.5
 Chinese wood oil, soybean oil, olticica oil, or CUHÙOt oils:

  , 1.1UI3, leu doublon liaiuonti oldfiniqura contained in the oil being conjugated or unconjugated, or a mixture of these oils, the modifying agent being a
 EMI8.6
 acrylic acid or anhydride oleir.ique, preferably maleic anhydride, but can also be crotonic acid, citraconic acid or anhydride, acid
 EMI8.7
 fumaric acid or an acyclic olefinic aldehyde or a cdter of '1 #. "#. ##' acyclic olefinic hyde, coiane acrolein, a- ¯1C" 1-

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 vinyl oetate, methyl maleate, etc ..., or even a polybasic acid such as phthalic or succinic acid,
 EMI9.1
 particularly modified glyceridic oils which have been further allowed to react with about 2-25 of a polymerizable vinyl monomer;

   unsaturated 6-graa acids treated with anhydride or maleic acid and rosin acids treated with anhydride or maleic acid; alkyd resins, for example products
 EMI9.2
 esterification of a polyol with a polybase acid, in particular the alkyd resins extended with a glyceridic drying oil; the polymers of aicoati es oils
 EMI9.3
 hydrocarbon acids such as those obtained by copolymers of butadiene and diisobutylene treated with anhydride or maleic acid;

     finally, acrylic and vinyl polymers and copolymers containing carboxylic acid groups, such as acrylato copolymers of methyl butyl methacrylate-methacrylic acid,
 EMI9.4
 oopolymoroo aootate of vinyl aorylic acid, the polymers ocontaining acrylic acid and an acrylic acid substituted by a lower alkyl group (Ci-0 4) $, that is to say those containing oarboxyl groups provided by alpha, beta-carboxylic acids or residues of these acids, etc. *
The acid number of the polycarboxylic acid resin used in the paint binder should be at least 30 in order to disperse effectively;

   the shape of
 EMI9.5
 plolyelectrolyte and it can reach about 300 in the practice of the present invention. When we use
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 of. u111: yde resins, the Applicant has found that an optimum eleotroddpoaition is obtained with those whose acid number is between approximately 60 and 200. The acne index.! ea. roainos without significant group content nn) Ydr1

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 can be determined using KOH by the standard method ASTM 555-54.

   If there is a noticeable amount of anhydride moiety, the acid number can be determined by refluxing a 1.5-2 gram sample of the part of the reoin, for 1 hour, with 50 cm3 of 0.5N aqueous KOH and 25 cm3 of pyridine, then by back titrution with 0.5N HCl until the change to phenolphthalein.



   The preferred polycarboxylic acid resin for incorporation into the concentrated paint binder composition is a modified glyceridic drying oil which has been reacted with about 2-25%. relative to the weight of the modified oil, of a polymerizable vinyl monomer such as vinyl toluene, styrene, alpha-methylstyrene, acrylonitrile, etc.

   The reaction with the vinyl monomer improves the film deposited by making it capable of dressing particularly rapidly from a dispersed and fluid state to that of an immobile, adherent, non-wettable (by water) and resistant film. water, deposited on the anode serving as a support, when the modified oil has reacted at least about 2% of the vinyl monomer; furthermore, the organic strength of Dain is desirably increased when using this resin. However, if more than about 25% of the vinyl monomer is introduced by this reaction into the modified oil, the film tends to trap oxygen bubbles and can occasionally give a blistered aspeot which is often undesirable.

   The economically and efficiently preferred vinyl monomer in the practice of the present invention is vinyl toluene, preferably in an amount limited to no more than 15% based on the weight of the modified oil. When this resin is extended with a non-thermosensitive phenolic resin by the high temperature process previously described, it constitutes a preferred renin to all for the learning of metals due to its safety.

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 final hardness.



     In general, the Applicant has found that the most strongly acidic polycarboxylic acid resins
 EMI11.1
 intended Quxcompooitlono of binders according to the invention, by Axamplo collou whose acid number outweighs Bn31blo- ment 100, form good diopersiono do polyelectrolyte in the process of the invention at a fold of aonez bat bath.



  So, for example, the louse could have used a one at pH 5 only; with a binder consisting of a polycarboxylic acid root having an acid number of 77.
 EMI11.2
 



  With resins and a mixture of those ruins which have a lower acidity value, for example about 100 or less, a higher minimum pH is usually required, such as 7-7 fold. , 3 by oxoraple, to obtain a porsintant polyelectrolyte behavior in the bath when treated with the water-soluble amino compound. Therefore, the lower bath pH advantageous in the process of the invention is function of enro and nonocn-
 EMI11.3
 tration of the particular paint binder to be dipped; it is usually between about 5-7.5, but it will be understood that operation at a somewhat higher pH or at a higher pH range gives a greater margin of safety in maintaining the behavior. persistent resistance of a polyelectrolyte.

   When adding an additional resin gyaut an acid number of less than 100, for example uno r4üine, base d '. modified glyceridic drying oil which has been reacted with a polymerizable vinyl monomer and extended with a phenolic renin, for example, the Applicant has found that it is advantageous to control this additional addition
 EMI11.4
 so maintain the pH of the bath between about 7 and 8.3.



  The compounds a: in3 solicited in water which con-

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 EMI12.1
 come particularly well in the implementation of
 EMI12.2
 the present invention are soluble in water h 20 * 0 at a rate of at least about 1 of the weight of the solution and they cotiproiiiient \, \ (loi-, hydroxyaiiiineb, polyamines and monoai'iinoa sheet metal as Nonoothanolaxdne, ditithanolaniineg lu tritst2tetnol; tmine3 la 1; -riititliyl othanolamine, N'-aminoothyl 6ttrnolnnrino, Pt-ni'tltyl didthanolamine;

   monoii3opropanul- aiaino, diis3oprop, n \ lzunine, triioopropanolamino, "thinned polyglycols" such as the compound of the formula HO (C2iI0) 2CfLIi;:, 1'hydzroxylnmina, butanolamine, hexanolandynci, m < (5 ethanolaminot octanolamine and the reaction products of alkylbene oxide with mono- and polyamino3, such as the reaction product of ethylene diviaine with ethylbene oxide or propylene oxide, laurylamine fyveo dleitliylbliel oxide etc ...; lthyltIne diamine, dichylone triatriine, triethylcne tEtrurnina, hexamthylne \ tdtrrtmine, tctraûthylenc 1> ont; ztnino, propylene diamine 1, 3-dian 'j.mino-bia-propyl amine, etc .; finally, leu mano-di- and tri-nlkyl inf. amiitos (alkyl groups such as leu mono, di- and triethyl-ttmiii (ec.



  The ri found that UI1 \ O1 held their best movies about 30-60; dei éy; dcvrxlent.m.crino present in the bath, both in combined form and in free form, come from a soluble polyamine (Iwia water, and this is why the Applicant prefers to proceed in this manner Preferably, she uses the aithylbn triina., For questions of roundness and economy.

   The 1) lywaine can be introduced into the bath as a binder composition, or if: purely * The hydroxy omines, in particular ofileo which \ are of the nature .hca, at the point of attachment dea groups; 'r <.' xy <conntb leu alkanol amines, are l: .rtl ::, u :: t tr: Lil-

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 tagging machines for the treatment of a resin of a polycarboxylic acid with a view to its dispersion, and it is found that they exert a certain solubilizing effect with respect to the resin in water, in addition to their effect neutralizing.

   In practice, the amount of water-soluble amino compound in the bath which exceeds the amount necessary to impart behavior similar to that of an anionic polyelectrolyte to the polycarboxy acid resin. ique contained in the binder, can be regarded as an excess and is desirable, provided that the pH of the bath does not reach a value high enough for the bath to absorb CO2 from the atmosphere, or for the concentration High amine lowers the electrical resistance of the bath to below about 500 ohm-cm.

   Generally speaking, the amount of amine used can be between about 2 and 7 times, more preferably between about 3.5 and 5.5 times; the minimum quantity necessary to confer, in the bath, a behavior similar to that of an anionic polyelectrolyte on the resin or on the mixture of resins constituting the particular binder; the specific resistance of the bath, when it has just been prepared, is advantageously between about 700 and 1000 ohm3-cm to deposit coatings of about 25 microns thick as a primer.



  Higher resistances of the bath give a thinner film and vice versa.



   Ammonia alone can be used, but it is less advantageous in the process of the invention, to partially neutralize the acidic resin or the mixture of resins, because it is so volatile at working temperatures than small amounts. additions of ammonia can cause relatively large changes in the pH of the bath, and that the baths in which it is used tend to readily absorb CO 2 from the air and are therefore susceptible to damage.

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 uncontrolled variations in their electrical characteristics.

   Therefore, the Applicant prefers to use ammonia only to facilitate the dispersion of the resin in the bath together with other water soluble amino compounds, and not to use it to the exclusion of other water soluble amino compounds.



   To replenish the bath with carboxylic acid resin as operations continue, Applicants may gradually add an additional amount of concentrated binder composition (optionally pigmented to provide replacement coloring solids) gradually, ie. that is to say continuously, or discontinuously.

   To facilitate dispersion and handling, applicants prefer to add this additional resin in the form of a concentrated aqueous dispersion containing, on a pigment and filler free basis, about 50-95% by weight of acid resin. polycarboxylic (elongated or not) - of which the electroohymic equivalent is between about 1000 and 20,000 and the acid number between about 30 and 300, and about 1-10% of amino compound soluble in water, relative to the weight of said polycarboxylic acid resin, the remainder being .. water.



   Although concentrations of the resin dispersion of less than 50% can be used in such a binder concentrate, this involves additional water handling, which is economically undesirable. For concentrations of the resin dispersion in excess of substantially 90%, the dispersion becomes even more difficult to handle, even when hot, and above about 95%, the dispersion is especially difficult to handle. The concentrated binder composition is mixed with a small amount

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 of water soluble amino compound to help disperse the resin in the bath.

   Advantageously, if desired, the additional resin can be mixed with an amount of water soluble amino compound sufficient to maintain a substantially constant pH of the bath, as well as with pigment and filler to replace those taken from the bath. the bath by the formation of deposits and the ports duos 4 handling, in order thus to obtain a volume of the immersion bath and an operation which are always substantially the same. The amino compound contained in the concentrated binder component also aids in the hydration of the anhydrides which are present together with water in this concentrated composition.



   It will be understood that the shape of the anode and its material of construction can be very diverse in the process of the invention; for example, this anode can be a metal wire, a plate, a perforated tubular profile, bevelled surfaces, perforated boots, continuous sheets, etc. The anode can be made of metal, of paper treated with saline solution or in other substances which conduct electricity under the conditions of use.



  .The final curing of the films can be activated (thermally hardened threads) by heating in an oven such as a conventional oven communicating with air at atmospheric pressure; the films can be air dried in most cases laying a longer time until satisfactory hardness and absence of tackiness are obtained, but forced hardening is preferred from the point of view of speed to obtain a finished film of superior quality.



   In practice, the intensity of the current used advantageously does not exceed approximately 45 amps / m2 of excess.

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 anode face immersed in the size bath, and the olle is preferably substantially smaller. Increasing the voltage for constant current is preferred during operation, the voltage across the bath being gradually increased to zero or substantially zero up to about 50-500 volts. - lization of appreciably higher voltages can cause an electrical breakdown of the deposited films and can give rise to an excessive release of nascent oxygen at the anode. It is also possible to maintain a substantially oonotating voltage and to allow the intensity of the current to vary ,

   
One of the characteristics of the preferred polycarboxylic acid resin as a component of the binder is that oxygen can escape therefrom without excessive permanent formation of bubbles or without being trapped in the film obtained by electrodeposition. In fact, in the drying of resins containing a drying oil, a small amount of absorbed oxygen seems to aid in obtaining a rapid and satisfactory curing of the deposited film when it is subsequently cured, and the metal siccatives may not be incorporated. conventional in the composition of the vehicle, if desired.

   In addition, various known oxygen sequestering agents, such as mercaptobenzotiazole, can be added to the vehicle in the bath and they further reduce the formation of oxygen bubbles in a deposited film. -
The bath can be kept in a tank or bao. conductor of electricity; this bin is connected in the circuit to. the manner of a cathode and the article to be coated constituting the anode is immersed in this tank. Direct current flows from the anode to the cathode from an external circuit. The tank can also be non-conductive and, in this case, one or more metal cathodes can be placed in the bath.

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 to allow the paaaage of the electric current therein.



   The "projection" of a coating can be measured by riveting three thin steel sheets together at their top so that their bases move apart from each other, and then using this set as an anode. A good "projection" involves the feeling of more than about
70% of the faces of the central sheet. The Applicant has been able to paint 90% of the faces of the central sheet in numerous experiments carried out by implementing this process.



   Contrary to what could have been predicted from close to theoretical considerations, the applicant has observed that - when the concentration of the binder based on polycarboxylic acid resin in the bath is appreciably less than
0.5-1%, film deposition is not as good as at higher concentrations. With even lower resin concentrations in the bath, the smoothness, surface smoothness, adhesion and thickness of the film become less satisfactory extremely quickly.



   When the concentration of the resin dispersion substantially exceeds about 35-40 by weight, the viscosity of the bath may become so high that size "streaks" form when the coated body is taken out of the bath, i.e. - ', say that the paint adheres and flows non-uniformly, giving an uneven deposit. It will be appreciated that the upper limit concentration in practice will depend to some extent on the particular resin contained in the bath at working temperature (eg about 15-50 ° 0 in general) in correlation with its ease of dispersion. or dissolution in water, its electrochemical equivalent and its specific rate of change in viscosity as a function of the concentration of the dispersion.

   The percentage of
35-40% is a practical maximum concentration.



   In addition, the viscosity of the bath is of great importance.

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 tanoe particularly in large-scale operations in which the electrical energy converted into heat has a relatively small area, per unit volume of the tank containing the bath, to dissipate. As a consequence, as the viscosity increases, the efficiency of heat transmission with coolers disposed inside or outside the bath and from the walls of the tank themselves decreases. significantly.

   Fluid handling in the bath and its drainage from the coated articles as they are taken out of the bath are also significantly less when the viscosity of the bath becomes significantly greater than that of water, i.e. - say exceeds more than 200 times that of water.



  Thermal control in the bath is important in a temperature range of approximately 15-50 ° C to prevent the formation of unwanted volatiles and even loss of stability or additional detrimental polymerization of paint dispersions in some cases. When the viscosity of the bath does not exceed 30 times that of water, thermal control can be very simple because the heat transfer efficiency is high.



   The proportion of amino compound, in particular hydroxyamines in the bath, can act on the viscosity of the bath, the higher proportions generally promoting an apparent solubilization of the resin and a certain reduction in the viscosity. The applicant can use and have in fact used other means to facilitate apparent atomization and viscosity control;

   for example, it advantageously used from about 0.1 to 10%, based on the weight of the carboxylic acid resin contained in the bath, of a nonionic organic liquid compatible with the resin contained in the dispersion,

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   as a lubricating aid or, more precisely, as a dispersion modifier. Typical examples of such liquids are petroleum-derived naphtha, especially aliphatic, naphthenic or aromatic hydrocarbons or mixtures thereof, having a boiling point of between about 30 and 240 ° 0 and preferably. , between approximately 150 and 200 0,

   so that they volatilize on curing or some other mode of curing the film, such as air curing, pine oil, glycerin, soluble alkoxy alkanols in euu tolu. as 2-butoxy-butanol-1 and other co-type compounds; have n, de monoalkyl ethers of glycols such as the mono .. butyl ether of diethylene glyool. These derivatives of alkylenoxide further reduce the surface tension of resins and promote the reduction of the viscosity of baths having a high density. high resin content. Using them in a concentration significantly exceeding 10% can make hardening more delicate and affect the electrical control of the bath.



  Usually 0.1-6% resin in the bath is adequate in all applications, but this concentration should be limited so that a distinct phase of such oil-lubricant does not appear in the bath. because this diatinct phaae would risk forming non-homogeneous films.



   In addition to the concentrated polycarboxylic acid resin binder composition, which is gradually added to the bath to prevent the amine from accumulating in a large amount (greater than about 8.4, level after which the quality of the film is impaired and CO 2 can be absorbed in air), the Applicant can add to the bath, as an entraining agent of the excess amine, polybasic acids, approaching a molecular weight of about 1000 (or an Average molecular weight of 1000 when using

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 a mixture of such acids) To obtain particularly good compatibility with the polycarboxylic acid reain, the applicant prefers to use low molecular weight polycarboxylic acids as an entraining agent,

   whose molecular weights are between about 500 and 800.



  Advantageously, these drive acids are polymers of a polyenoic acid having from 12 to 44 carbon atoms, more advantageously the acids called “dimbres” which are for the most part the dimer of C18 mono-unsaturated fatty acids, eto ..., mainly linoleic acid, and which contain a certain amount of trimer, These compounds easily form soaps with doo polyamines at internal temperatures of about 75 C ot after simultaneous deposition with the film and hardening, can to provide, in the resulting film, a polyamide which can enhance the corrosion resistance of the film;

   
Generally, the carrier acids which are advantageous include (linoleic, linolenic, oleic, sorbic, palmitolic, humoceric, eicosinic acid patches, and mixtures thereof. In addition, succinic, pyrotartaric, malic, tartaric acids can be used. , glutaric, adipic, pimelic, suberic, azalalk and sebacic, and unsaturated acids such as fumaric, maleic, phthalic and sorbiquo acids, as well as various other acids such as citric, pyromellitic, ubitic, and polymers and co-polymers containing acrylic acid and methacrylic acid which have several carboxylic functions,

   Acids greater than C12-C44 acids appear to provide optimum soap formation for simultaneous deposition with the polycarboxylic acid resins dispersed in the bath. Those with a dissociation constant of their first hydrogen ion in aqueous solution less than about 1.5 x 10-5 appear to have

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 sufficiently low reactivity with polyamines, on prolonged contact in dispersion at temperatures below 50 C, to prevent accelerated aaidation and the formation of high molecular weight substances which are liable to precipitate within a short period of time. time and prevent optimum operation of the bath.

   Polymers of drying polyenoic acids such as those referred to as "dimer" acids are of this nature and are preferred.



   In the coating process, the Applicant may direct the use of electrodialysis to remove the excess amine from the bath in the form of a dispersion entering the anode. Alternatively, bath oations can be used with ion exchange resin beds, such as the acid form of ion exchange carboxylic resins, to remove excess amino compound in the anode zone.



   Essentially, eleotrodialysis involves isolating the anode from the cathode to form anode zones. and oathodic separated by a dialysis membrane having deo e pores with a useful size between 20 and 200 A; to introduce a dispersion of paint, aqueous and dilute in the anode zone and of water in the cathode zone, such as running water. The membranes themselves are conventional and are made of regenerated cellulose (from the viscose), polymers of vinyl chloride, various permeable cellulosic materials and other sheets of synthetic resins which are commonly used in dialysis and which are water resistant at working temperatures, or sheets made of the material. ceramic.

   These elements can be reinforced internally or externally to give them the desired mechanical strength.



   Danu such an electrodialysis, only free amino compounds, the decomposition products of the resin

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 of low molecular weight and the products of the electrolyte, as well as dispersed mineral cations, migrate through the membrane in appreciable quantities while the paint settles on the anode as the electrical circuit passes the anode to the cathode in the compartment tank a.

   In any such operation, it is especially advantageous to maintain an amount of free amino compound in the anode zone which does not deposit substantially 2% of the weight of the coating dispersion contained in this zone, to obtain the optimum quality. den deposited films,
The following examples describe several embodiments by way of indication and without limitation of the scope of the invention. Parts and percentages are by weight, unless otherwise stated.



   In the paint baths exemplified in the following, the resin contained in the dispersions constituting the baths behave like an anionic polyelectrolyte because the deposition of the resin on the anode is essentially direct. proportional with the direct current flowing in the bath. The number of coulombs of electricity per gram of a particular resinous binder deposited is virtually independent of the voltage in the operating range (deviation less than about 5-10%) when allowance is made for the additional current used to drive drives. varying concentrations of amino compound to the cathode, even when the maximum voltage is doubled or tripled in the operating range of 50-500 volts.

   It is further observed that when the resinous binder acting as a polyelectrolyte tenaciously coats a pigment or other particle in the bath, this particle assumes migration properties to the anode similar to those of the polyoarboxylic acid resin
 EMI22.1
 el.o.-mtcm.

 <Desc / Clms Page number 23>

 



   In some cases, as expressly shown by the examples, the resin is in apparent aqueous solution in the bath and in other cases, part of the resin this court) forms a dispersion of extreme fineness in the bath, the maximum dimension of the rebino particles not helping about 500 millimicrono from the calcula,
In this checkered case, the dispersions can be made more fluid by adding additional amine compound to the bath, in order to obtain an apparent dissolution of the resin or in the form of a clear aqueous solution,
Loo polycarboxylic aoido resins contained;

  , in the bath seem to have the property of electric migration of anionic solutes, because -we can assume that the resin ions present correspond to the formula [R (COO) n], with ± negative charges (R representing the resin core and COO representing a carboxyl radical). By way of illustration, it can be assumed that the amino ions resulting from the neutralization of the resin in the bath (when the water-soluble amine used is for example a primary monoamine) corresponding to the formula [R ' NH3] + where R represents the nucleus of the suminate compound.



   The paint films of the examples are deposited on the anode very uniformly and in the form of a continuous film; the deposition ends up with a particular maximum tenure applied to the bath terminals when the desired thickness of the film has been obtained, generally about 12.7-75 microno, in about
1-3 minutes, and it effectively isolates the anode, which practically prevents the subsequent passage of current. This behavior is contrary to that of an emulsion, as in the deposition of rubber latex in ordinary electrophoresis operations.

 <Desc / Clms Page number 24>

 



   The electroohimic equivalent of the polyoarboxylic acid resins mentioned in the examples is between about 1000 and 2000, and the acid numbers of these resins are between about 30 and 300.



   EXAMPLE:
A size binder, based on an extended glyceride-modified drying oil, is formed by reacting, in a reaction vessel fitted with a stirrer, 8467 parts of alkali-refined linseed oil and 2025 parts. maleic anhydride (which was heated together at 232.2 ° 0 for about 3 hours until an acid level of 80-90 was obtained), after which this intermediate product is cooled to 1789 parts of vinyl toluene containing 48 parts of ditertiobutyl peroxide are added at 157.2 ° C. and reacted at 218.3 ° C. for about 1 hour.

   The resulting vinyl toluene-containing material is then cooled to 157.2 ° C. and 5294 parts of a thermoplastic, oil-soluble and heat-resistant phenolic resin are added, heated to 232. 2 C and the mixture is left to stand for 1 hour. The phenolic resin is a solid, lumpy resin having a softening point of 120-1409C, a specific gravity of 1.03-1.05 at 20C and which has been stripped to remove excess phenol and excess phenol. low molecular weight products. This resin is the condensation product of substantially equimolecular amounts of para-tert-butyl phenol and formaldehyde.

   The electro-ohimic equivalent of the resulting acidic resin, when stretched, is about 1640 and its acid number is 65.



   The product was then cooled to 93.3 ° C and 1140 parts removed to form a paint dispersion. To these 1140 parts, 100 parts of water are added, then

 <Desc / Clms Page number 25>

 
13.6 parts of triethylamine, the mixture is stirred for a few minutes, then a further 74 parts of water and 92.5 parts of amino diisopropanol are added. This mixture is further reduced with 1825 parts of water and 32.5 parts of diethylene triamine, while continuing to stir.



   To this paint dispersion is added 50 parts of a mixture of trout comprising mineral spirits, a light hydrocarbon in the liquid state, with a density of 0.8017-0.7818, having a flash point ( Clevelanl open cup) between 37.8 and 46 ° C, giving a negative result in the test for mercaptans and having no acidity, 12 parts of a wetting agent (oleic ester of sar- cosine, having a maximum of 2% free fatty acids, a density of 0.948, a color of 6 on the Gardner scale and a molecular weight of 340-350). This substance is compatible with the paint dispersion = a distinct hydrocarbon phase does not form at this time, even if a significant amount of hydrocarbon (mostly aliphatic) has been used,

   nor after the subsequent addition of the powdered pigment and addition of additional water to form the initial paint bath.



   A powdered pigment is obtained from 123 parts of linseed oil modified with maleic anhydride and treated with vinyl toluene, obtained in the same manner as the resin given above in the present example (at this except that the resulting polycarboxylic acid resin is not elongated with the phenolic resin), 8.4 parts of diisopropanolamine, 0.7 part of an anti-foaming agent (ditertio-aoetylenic glycol with groups of methyl and isopropyl substitution attached to tertiary carbon atoms), 233 parts of fine kaolin, 155 parts of titanium dioxide pigment, 7.8 parts of fine lead chromate,

 <Desc / Clms Page number 26>

 15.5 parts of fine red iron oxide, 16.9 parts of carbon black and 201 parts of water.

   The resulting powdered pigment is then mixed with the aforementioned paint dispersion and treatment mixture to obtain an oonent paint. The resulting paint is further reduced with water in the ratio of 1 part of the resulting paint to 5 parts of water, to obtain an initial paint bath for electrodeposition painting operations.

   The resulting bath has a resin solids (non-volatile) concentration of 7.24. The total of the amine equivalents used to make up the initial bath is about 4.5 times the minimum amount needed to maintain this polycarboxylic acid resin, once dispersed, under the condition of a. anionic polyeleotrolyte in the bath, and about 1.25 times the total neutralization of the acidic resin to its acidity rating (determined by the pyridine method described above).

   The amount of continuous current used for electrodeposition of 1 gram of this resin on an anode is practically constant and is 24 coulombs, the electrical energy used in addition to this amount being expended mainly to move the amino substance. in the bath. The specific resistance of the initial bath is approximately 900 ohm-cm.



   The solids in the paint are replaced by dispersing 1140 parts of the same expanded polyoarboxylic acid resin in 100 parts of water and 13.6 parts of triethylamine. The inorganic essenoe is added to this dispersion, the wetting agent and the aforementioned pigment powder, the compositions and the proportions of all these substances being the same as during the preparation of the initial paint dispersion formed to constitute the bath. .

 <Desc / Clms Page number 27>

 



   The painting operation is carried out in a metal tank provided with a stirrer, the tank is connected in the circuit in the manner of a cathode and a series of thin sheet metal panels to be coated are used as anode. aoier phosphated 22.85 om wide, submerged to a height of 26.64 om. The volume of the bath is 2500 car. Direct current is sent to the cathode formed by the tank and to the anode formed by a submerged panel from an external circuit.

   The intensity of the electric current is approximately 21.52 amps / m2 of the submerged surface of the pole,. and it reaches about 37.66 amps / m2 as the pH of the bath increases, that is, additional current is used to feed the amine compounds accumulated in the bath. The temperature of the paint bath during operation is between 35 and 37.8 C, and the coating time for a particular panel is 53 seconds when immersed, 74 seconds when fully immersed. submerged and 53 seconds when extracted.

   The voltage of the current sent to the bath for a particular panel is between 0 and 200 volts at most during a particular panel coating operation to deposit a film approximately 2594 @ microns thick before the electrical resistance of the film. practically stops deposition at the maximum voltage used.



   Before baking, the electrodeposited paint film is water resistant, slightly tacky and tenaciously adherent. After baking for 15-20 minutes at 176.7 ° C, the film cures to an excellent, non-pore and durable coating.



   The Initial pH of the bath is 8.1 and when four panels have been so coated it reaches 8.25. At a time, 25 parts of water and 30 replacement parts of solids are easily dispersed in the bath with stirring.

 <Desc / Clms Page number 28>

 The pH of the bath drops to about 7.9 and the resin solids concentration in the bath rises until it reaches approximately the initial value of 7.24. Electroplating operations are then carried out as preceded with consistently satisfactory results, for four panels.



  At this time, the pH is 8.1; Another similar addition of water and paint solids was made in replacement of the spent solids, and the pH of the bath reached 7.7. Four new panels were painted at a similar continuous rate and the pH of the pupil's bath up to 8. 27 parts of an aqueous amine solution are added, this solution comprising 86 parts of water, 25 parts of diethylene triamine and 86 parts of diisopropanol amine, and the pH of the bath rises to 8.25. 30 parts of paint solids are added to replace the spent solids, and the pH of the bath decreases to 7.95. The painting operations are then resumed as before, with similar consistently satisfactory results.



   EXAMPLE 2.-
We prepare an alkyd resin by heating 948 parts! graa acids from the liquid resin containing 97.6 fatty acids from the liquid resin, 1.2% acids from the rosin and 1.2% non-saponifiable products, having an acid number of 197, a saponification number of 198 and an initial viscosity of 128, and 155 parts of maleic anhydride, at 232.2 C for 1 hour, the mixture is cooled to 104.4 0, 503 parts of technical grade pantaerythrite are added, 394 parts of phthalic anhydride and 30 parts of xylol (solvent mixture entraining water), then the bath is subjected to reflux at 171.1 C, while separating the water from the reaction,

   until the resin

 <Desc / Clms Page number 29>

 resulting acid number of 102.6.



   125 parts of this resin, 10 parts of water and 1.3 parts of triethylamine are converted into a concentrated aqueous dispersion containing 91.7% resin solids by mixing these ingredients for 30 minutes. The concentrated dispersion (about 92% resin solids) is then mixed with 31.8 parts of amino diisopropanol, 5.5 parts of diethylene triamine and an amount of water sufficient to reduce the concentration of the materials. 5% resin solids (non-volatile matter). A clear aqueous varnish is thus obtained, in apparent solution and having a pH of 7.15. It is used in an electrodeposition operation.



   The paint is deposited in a manner similar to that described in example 1, but in a smaller installation capable of receiving panels of sheet steel 10.16 ounces wide which are submerged over 8. , 89 om in height and which constitute the Modes. The bath temperature is 26.7 C, the peak voltage is 100 volts and the amperage is 26.9 amps / m. The amount of current supplied is 108 coulombs / gram of coating applied. Before baking, the paint film formed by electrodeposition on a panel is slightly tacky, water resistant and adheres tenaciously. After baking for 15 to 20 minutes at 176.7 ° C, the film cures (without the addition of drier) giving an excellent, durable and pore-free coating.



   The painting operation with this bath can be continued in the same manner as in Example 1, with the addition in portions of the concentrated alkyd resin dispersion of this example in the bath when the pH of the latter tends to increase. towards a value of about 8.1. We can also

 <Desc / Clms Page number 30>

 maintaining the pH of the bath at a substantially constant value by continuously adding the concentrated resin dispersion and the amount of water necessary to maintain the volume of the bath, and further adding the water soluble amino compound to the bath while concurrently with the concentrated resin dispersion or periodically and alone In such an operation the minimum pH of the bath is desirably prevented from falling below about 6.

  5-7 for the resin in the bath to persistently behave as an anionic polyelectrolyte throughout the coating operation.



   EXAMPLE 3, -
An acrylic reagent is prepared by slowly adding a mixture of 60 parts of butyl aorylate, 25 parts of styrene, 15 parts of methacrylic acid, 1 part of tert-butyl perbenzoate, and 1 part. part of benzoyl peroxide in 34.7 parts of 2-butoxy-ethanol maintained at 157.2-160 C for a period of 2.5 hours, and kept at this temperature for a further 1 hour using a container reaction comprising a stirrer and provided with a reflux condenser. The resulting resin was cooled to 137.8 C and further reacted for 1/2 hour and 154.4 C, with 10 parts of tris-hydr.oxyl methylamino methane to increase its apparent solubility in water.

   The resulting resin dispersion has an acid number of 57.6 and a resin solids content of 75.6%, and has an apparent solubility in the paint bath described below.
A concentrated white paint is prepared by mixing 133 parts of the above resin dispersion, 10 parts of a mixture of water soluble amino compounds (oom-

 <Desc / Clms Page number 31>

 taking 86 parts of amino diisopropanol, 25 parts of diethylone triamine and 86 parts of water), 30 parts of a powdered ornament (comprising 16 parts of titanium dioxide, 8 parts of fine kaolin and 6 parts of the alkyd resin described in oxomple 2) and 47 parts of euu.



   The electrodepositon bath is prepared by shaking the concentrated blnoho size uvoo 10 additional parts of the mixture of many compounds (86 part of diisporotyl amine, 25 parts of diethylene triamine and 86 parts of water) and an additional 780 parts of water, to constitute a bath containing 12.8 parts of resin solids and having a pH of 7.5 which is subjected to stirring,
The anodes used are thin sheet steel panels 10.16 cm wide and submerged to a height of 8.89 m, where the painting operation is carried out in a manner similar to that described above. in the example The temperature of the bath used was 26.7-35 C,

   the teneion reaches 250 volts and the intensity is about 43.04 amps / m2 for a panel. Some panels are air dried at room temperature and a satisfactory, tack free film is obtained in about 2 hours. Oven drying of the other coated panels for 5 to 15 minutes at 176.7 ° C gives satisfactory gloss films.



   When the pH of the bath rises to a value of 8-8.3, the painting operation can be continued in a manner analogous to that described in Example 1, adding additional quantities of the mixture. acrylic paint concentrated to reduce the pH of the bath and maintain it between about 7 and 8.4, while also maintaining a desirable content of resin solids and pigment in the bath.

 <Desc / Clms Page number 32>

 



   EXAMPLE 4.-
A modified and elongated glyceridic aliooative oil is prepared in a manner analogous to that described in Example 1, unless otherwise specified in the example example.
Moderate steel panels Which are electrodeposited by immoruion in an aqueous electrodeposition bath, using dispersed partially neutralized fractions of the resin, at a concentration of 5% of the resin in the bath, the neutralization being performed in view of obtaining a pH of 8 with the particular water soluble amino compound indicated.



   The immersion tank is made of metal and this connected in the hole in the manner of a cathode. The anode this formed by the panel to be stuck. The experiments are carried out at room temperature (about 25 * 0). Direct current is passed between the electrodes using a constant intensity of about 21.5 amps / m from the submerged surface of the anode, and the voltage rises to a maximum of About 50400 volts in the coating process as a result of the decrease in electrical resistance in the part of the electrical circuit which is external to the bath.

   The voltage rises gradually with no significant sagging points which would indicate a breakdown or imperfections in the film applied to the anode.



   When each anode is coated, which takes about 1 to 3 minutes, it is removed from the bath, the excess adherent liquid is removed by blowing air, then the anode is baked for 10 to 15 minutes at about 193 ° C in an oven at atmospheric pressure Before baking, the film formed by electrodeposition is slightly tacky and adheres tenaciously. We can wash it by hand at this time, if we

 <Desc / Clms Page number 33>

 desired without damaging it, this washing can even improve the uniform appearance after cooking.

   After baking, the resulting cured film is tough, flexible and usually shiny, is about 25 microns thick and is not tacky, it adheres firmly to the metal panel even when bending the latter, as well as when bending the latter. we cut it or scratch it.



  The film is regular and smooth.
 EMI33.1
 
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  Amine <SEP> of <SEP> neutralization <SEP> Note
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<tb> Diisopropanol <SEP> amine <SEP> Satisfactory film <SEP>
<tb>
<tb> Diethanol <SEP> alder <SEP> "<SEP>"
<tb>
<tb> Ethylene <SEP> diamine <SEP> The <SEP> film <SEP> gives <SEP> the best <SEP>
<tb> resistance <SEP> during <SEP> of <SEP> 1 <SEP> test
<tb> of <SEP> projection <SEP> of salt <SEP> water
<tb> in <SEP> this <SEP> series
<tb>
<tb> Triethylamine <SEP> High gloss <SEP> film <SEP>
<tb>
<tb> Ammonia <SEP> The <SEP> electrical <SEP> resistance <SEP> of the
<tb> bath <SEP> is <SEP> more <SEP> difficult <SEP> to
<tb> check. <SEP> The <SEP> ban <SEP> shows
<tb> a <SEP> tendency <SEP> to <SEP> absorb <SEP> @ O2
<tb> in <SEP> atmosphere <SEP> when
<tb> the <SEP> pH <SEP> increases.
<tb>
<tb>



  Amino diisopropanol <SEP> <SEP> * <SEP> Film <SEP> acceptable, <SEP> but <SEP> not
<tb> also <SEP> satisfying <SEP> as <SEP> the
<tb> four <SEP> first <SEP> films.
<tb>
 



   * In this case, the polycarboxylic acid resin is prepared in a manner identical to that of Example 1, except that vinyl toluene is not used and the polycarboxylic acid resin is not used. not elongated with a phenolic resin,
In comparable operations, various film forming coating binders, in emulsion form, are applied to panels electrophoretically, from a bath, at a binder concentration of 5%. The power of projection is very poor; the coating is not uniform and tends to be deposited on the sharp edges of the panels to a much greater thickness than in the center of these panels.

   The emulsions are stabilized with isoootyl phenoxy polyethoxy ethanol and dodecyl benzene sulfonate soaps and comprising butadiene emulsions.

 <Desc / Clms Page number 34>

 styrene, vinyl acetate and general drying oils, In addition, the electrophoresis operation does not transform these emulsified film-forming agents into an insulating film; the film therefore cannot acquire electrical resistance, but becomes thicker and thicker and remains incapable of automatically ceasing to thicken because it is a conductor of electricity in the form of thin films.



     EXAMPLE 5
A resin (I) based on glyceridic drying oil modified and extended with a phenolic resin is prepared in a manner identical to that described in Example 1, except that the phenolic resin is incorporated into the resin. oil modified and treated with vinyl toluene at 176.7 C and for 1 hour instead of 232.2 C. Another resin (II) is prepared as described in Example 1. Each resin is transformed into paint and in a paint bath in a similar manner to the initial paint bath of Example 1, and each of the resulting baths is operated for a long period of time.



   At the end of each of its uses, in dialysis Each bath exhausted in the same way through an external dialyzer, using a regenerated cellulose membrane having pores of 43 A ... Analysis of the dyalysed material from the bath containing resin II does not show the presence of phenolic substance, which proves the satisfactory operational stability of the resulting resin (which may be considered to be chemically fixed for the present purpose), while the dialyzed material from the bath formed with resin I shows that about 40% of the phenolic resin does not deposit on the anodes with the polycarboxylic acid resin,

   but dissociate on the contrary and undoubtedly fragment in the bath in a way

 <Desc / Clms Page number 35>

 Any one to migrate through the dialysis membrane forms us as a low molecular weight phenolic material.



     EXAMPLE 6
An extended and modified glyceride drying oil base resin is prepared in the same manner as in Example 1. It is converted into several electroplating baths pigmented and neutralized with amine compounds, similar. in the initial paint bath of Example 1, with the exception that the quantity of water in each resulting bath is adjusted so as to obtain varying contents of resin solids in the baths, and as the viscosity of the baths varies, as indicated in the following table which gives the results of the electrodeposition, the maximum voltage used is 150 volts, the current intensity is about 21,

  52 amps / m2 and the electroplating operation is carried out at room temperature (about 25 * 0) on thin steel anodes, as described in Example 4. The viscosity is measured at using a Brooktield viscoeimeter using a # 1 spindle. The anodi panels will be baked. ques coated for 10 to 15 minutes at 193 C.

 <Desc / Clms Page number 36>

 
 EMI36.1
 
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  <SEP> solids <SEP> Viscosity, <SEP> Coulombs / gram
<tb> of <SEP> the <SEP> resin <SEP> in <SEP> Centipoises <SEP> of <SEP> paint <SEP> the anode,
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 the bath, eny.¯¯¯¯¯¯¯¯
 EMI36.3
 
<tb> 33 <SEP> 116 <SEP> 51 <SEP> Shiny, <SEP> uniform, <SEP> finish <SEP> excellent
<tb> 30 <SEP> 116 <SEP> 52.7
<tb> 20 <SEP> 20.8 <SEP> 52.3
<tb> 10 <SEP> 13.6 <SEP> 52.9
<tb>
 
 EMI36.4
 5 slightly higher 57.2
 EMI36.5
 
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 il 2.5 of 6202 Slight formation of "orange peel-
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  1 <SEP> d <SEP> 115.38 <SEP> Pilm <SEP> not <SEP> bright <SEP> and <SEP> tending <SEP> to <SEP> flake <SEP> slightly <SEP> to < SEP> cooking <SEP> course.
<tb> d <SEP> '<SEP> slightly <SEP> in <SEP> during <SEP> of <SEP> cooking.
<tb>
 

 <Desc / Clms Page number 37>

 



   When the resin concentration is further reduced, a scratched, stained, and thin finish is obtained which does not give absolute satisfaction (satisfaction, when the concentration of reain in the bath reaches less than 0.55; when the solids content of the resin is substantially greater than about 35%. the viscosity of the bath increases extremely rapidly. When the resin concentration in the bath exceeds 35-40%, the high viscosity of the bath causes the unwanted formation of paint streak. 'the anode is removed from the bath.



   EXAMPLE 7 In this operation, the paint bath uti. isé is similar to that which was initially constituted in Example 1, except that the concentration of the resin in the bath is 5% and that the concentration of the mineral spirits is modified. The electrodeposition and baking operation is carried out in the same manner as in Example 6.
 EMI37.1
 
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<tb> 0.6 <SEP> 25.4
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All coatings are excellent. Electrical efficiency generally improves as the amount of naphtha increases, but at no time can the presence of a distinct phase formed by the naphtha be detected.

   A general increase in film thickness is observed when additional nonionic liquid solubilizing aid (i.e., dispersion modifying agent) is added.

 <Desc / Clms Page number 38>

 



     EXAMPLE 8
A paint similar to that used in the initial paint bath of Example 1 is formed, except that 50 parts of a "dimer" acid (the polymerization product of aliphatic monobasic acids are added. unsaturated C18, mainly linoleic acid) containing about 83% of a C36 dibasic acid with a molecular weight of about 565 and about 1% or less of C18 fatty acids with a molecular weight of about 282, the "dimeric" acid having an acid number of 188-196, a saponification number of 192-193, a color of 8 on the Hardner scale and a neutralization equivalent of 287-289.

   The concentration of solids in the resulting paint is reduced to 5% and or applied to anodes formed as in Example 4 of metal panels, using maximum tones of between 150 and 350 volts, then carried out. bake coated panels for 15 to 20 minutes at 176.7 C until final hardening is achieved. These paint baths operate about twice as long as similar baths not containing amine stripping acid before the amine concentration reaches a level detrimental to the quality of the deposited film.

   The baked films deposited to a thickness of 25.4 microns on the panels have excellent corrosion resistance when sprayed on them for up to 250 hours with 3% sodium chloride solutions in a sealed enclosure. at 32.2 Cf films which have been scored so that the incisions thus formed extend to the support metal. This paint itself resists polymerization and side reactions when stirred at 35-36.7% for periods of time as long as 15 days.

   Polymerization- and reactions

 <Desc / Clms Page number 39>

 secondary tend to increase the electrical resistance of the dispersed resin and decrease the allowable thickness of the films deposited at a particular maximum voltage between 50 and 500 shutters.



     EXAMPLE 9
By examining the drawing, it can be seen that the anode zone comprises walls 11 of plastic material which connect to a bottom 12 which is perforated for connection with a distribution box 13 from which the paint circulates towards high to pass into the anode zone. The walls 11 are perforated in the manner shown, with a large number of small ports and large ports through which the liquid can reach dialysis membranes 17.



   The internal width, calculated between the walls 11, is 1.901 cm; this anode zone has a length of 22.85 cm and the paint contained therein over a height of 24.13 om, up to a level shown at 16; the dialysis membranes 17 consist of a pair of sheets of cellulose regenerated from viscose, 0.01092 cm thick. The anode 14 is formed by a rectangular piece, 21.58 x 30.5 cm, of a phosphated steel intended for the manufacture of shims, immersed so as to expose 929 cm2 of surface to the action of paint bath contained in the anode zone. On each vertical edge, the piece of shim steel is folded back 0.635 cm at a right angle, giving it the structural stability of an anode.



   The cathode areas are constructed in a similar manner with elements 18 of acrylic plastic, forming a chamber the internal dimensions of which are 21.58 cm in length, 20.33 cm in height and 0.953 cm in width; the elements 18 apply so

 <Desc / Clms Page number 40>

 seals the membranes of non-perforated parts against the walls 11 of the anode zone. The seal between the two cathode chambers and the walls of the anode zone is in fact ensured by a membrane 17; the tightness is also ensured against water by a consistent grease, and the assembly is held firmly assembled by metal bolts, not shown.



   In each cathode aone there is a cathode 19 made of bronze wire mesh which covers the wall of the cathode chamber at a distance from the membranes 17. Running water is introduced into each cathode chamber through copper tubes 21 d, at the end. The discharge point is near the bottom of each cathode zone, which also serves as conductors to absorb current to the bronze cathodes. The water containing the dialyzed amino compound leaves each cathode zone through two copper tubes 23. The flow control of the water entering the cathode zones and leaving the glues is ensured by a device which is not represented. - felt.

   In the drawing, 24 are designated rubber tubes arranged at random between the cathode 19 and the membrane 17, to compress the latter against the perforated hole 11.



   The paint is continuously pumped back by an external pump, not shown, into the distributor box 13 from which folds passes, circulating upwards, through the anode zone, and it overflows at level 16 (via a non-spillway). shown) to reach the suction side of the pump in view of its recirculation to the casing 13.



  During operation, the cathode areas are practically always full.



   An energy source, not shown, sends direct current which passes from the anode 14 to the cathodes 19 and which is gont @ ôfé by an external resistance, not

 <Desc / Clms Page number 41>

 shown, in order that a substantially constant current is maintained while a particular anode is being coated, the input is fed into the vessel through an anode connector 15 connected to the shim steel anode 14 and exits from the tank through cathode connectors 22, attached to the water inlet tubes 21. Unless stated otherwise in the present description, the body of the apparatus is made of clear and hard acrylic plastic.



   During the coating of a particular anode, the voltage reaches 150 volts across the combined electrodeposition-electrodialysis tank. The initial operations are carried out at room temperature with a current, for a particular anode, of 15.84-21.52 amps / m2 at the start of the coating operations and approaching 37.36 amps / m2 as the temperature increases, the conductivity of the cell increasing as the temperature approaches 43.3 from room temperature, during the series of operations-
A particular unpainted anode 14 is immersed in the anode zone, the voltage rises to 150 volts, this anode is removed from the anode zone, the excess adhering liquid is removed by blowing air over the coated anode ,

   and cook it for 10 to 15 minutes at
193.3 C. Before baking, the film deposited by electrophoresis is slightly tacky and adheres tenaciously. After curing, the cured film forms a tough, flexible and shiny film, about 25.4 microns thick, is non-sticky and adheres firmly to the metal even when subjected to flexion. The film on each anode, after deposition and curing carried out in this manner, is smooth, regular and free from visible defects.



   When an anode has been coated and taken out of the bath, another unpainted anode is introduced and coated with

 <Desc / Clms Page number 42>

 same way; when five anodes have been coated, a sample is taken from the bath to check the content of free amino substance (eg a diisopropanol amine) and hardly any increase is seen in any sample taken. , the excess amount being completely dialyzed at. through the membranes. 17 and passing through the cathode areas out of which it is entrained by the product leaving the cathode through the tubes 23.

   When about five panels have been painted, additional diluted paint (5% resin solids) is added to bring the resin solids content in the anode disperse bath to about 5, reducing the amount. of these solids being about% for each series of five coated panels.



   97 panels are successively painted during the series of operations.



   The size used is prepared in the same way as the initial paint bath of Example 1, except that in the bath the concentration of the dispersion used in resin solids is 5% instead of of 7.24.



   It is understood that various modifications can be made to the embodiments described above without departing for this from the scope of the present invention.

** ATTENTION ** end of DESC field can contain start of CLMS **.


    

Claims (1)

CLAIMS 1.- A method of electro-depoaition of a coating on an anode placed in an electrical circuit passing through a bath of an aqueous medium in contact with an anode and a cathode, characterized by the fact (a) that it is dispersed in this bath a film-forming binder for paint which contains a resin of a polycarboxylic acid which is at least partially neutralized with a water-soluble amino compound, said resin having <Desc / Clms Page number 43> an electrochemical equivalent comprised between approximately 1000 and 20,000, having an acid number of between about 30 and 300 and exhibiting, in this bath, the behavior of an anionic polyelectrolyte, as shown by its deposition on this anode substantially directly proportional to the electric current passing through this bath; (b) direct current is passed through said circuit until a maximum voltage of about 50 to 500 volta is obtained, which causes the electrodeposition of a film containing resin on the anode ; (c) removing the resulting coated anode from this bath; (d) finally, that we harden the film. 2. - Process according to claim 1, characterized in that as the coating operations continue, the bath is depleted in carboxylic acid resin, a reserve of amino compound accumulates in the bath, and an additional amount of this resin is added to the bath gradually, this additional amount being sufficient to maintain the pH of the bath below about 8.4-. 3.- A method according to claim 2, characterized in that the additional resin is in the form of a concentrated aqueous dispersion containing about 50 to 95% by weight of resin and about 1 to 10% of water soluble amino compound, based on the weight of the resin, and the pH of the bath is maintained between about 5 and 8.3. 4. A method according to claim 3, characterized in that the acid number of the resin is less than approximately 100 and that the pH of the bath is maintained between approximately 7 and 8.3. 5. - Process according to any one of claims 1 to 4, characterized in that at least a part <Desc / Clms Page number 44> of the water soluble amine pump is a polyamine. 6. A process according to any one of claims 1 to 4, characterized in that at least part of the water-soluble amino compound is a hydroxy amine. 7. - Process according to n'importo laquello of claims 1 to 4, characterized in that at the monk part of the amino compound soluble in water is a monoamine. 8. A process according to any one of claims 1 to 4, characterized in that at least part of the amino compound soluble in water is ammonia. 9. A process according to any one of the preceding claims, characterized in that this acidic resin oomprendre a polycurboxylic acid resin modified with a drying oil. 10. A process according to claim 9, characterized in that the polycarboxylic acid resin comprises a modified glyceridic drying oil which has been reacted with about 2 to 25 of a polymerizable monomer. 11. A method according to claim 9, characterized in that the polycarboxylic acid resin is extended by mixing it with a phenol-aldehyde resin which does not react under the effect of heat, at a temperature of between about 200 and 260 ° C and for at least about 30 minutes. 12. - Process according to claim 11, characterized in that the aforementioned mixture of resins contains approximately 5 to 50% of the phenolic elongation resin, the remainder being formed essentially pure polyoarboxylic acid renin. 13. - Process according to any one of claims 1 to 8, characterized in that the polycarboxylic acid resin contains an alkyd resin having an index <Desc / Clms Page number 45> acidity between 60 and 200. 14. - Process according to any one of claims 1 to 8, characterized in that said polycarboxylic acid resin contains carboxyl groups provided by an α, -unsaturated carboxylic acid. 15. - Process according to any one of the preceding claims, characterized in that a concentration of the polycarboxylic acid resin in the bath is established and maintained in the bath between approximately 1 and 35% of the weight of this. bath, the viscosity of the bath being limited simultaneously and in correlation to a value not substantially exceeding about 200 times that of water at the same temperature, and the temperature of the bath being maintained between about 15 and 50 C. 16. - Process according to any one of the preceding claims, characterized in that the bath contains approximately 0.1 to 10%, relative to the weight of the .'resin of oarboxylic acid which it oontient, d a liquid, organic and nonionic solubilization aid for the resin, the proportion of this nonionic liquid being insufficient to form a distinct phase in this bath. 17. - Process according to any one of the preceding claims, characterized in that the eleotrochemical equivalent of the polycarboxylic acid resin is between approximately 1000 and 2000. 18. - Process according to any one of the preceding claims, characterized in that an excess quantity of amino groups is in solution in the bath relative to the quantity necessary to maintain the polycarboxylic acid resin in the form. a dispersion of an anionic polyelectrolyte in the bath. 19.- Process according to any one of the preceding claims, characterized in that one adds - <Desc / Clms Page number 46> in the bath, a quantity of polybasic carboxylic acid with a molecular weight of less than approximately 1000 sufficient to neutralize: at least some of these amino groups in excess, 20. A method according to claim 19, characterized in that the polybasic carboxylic acid of a molecular weight less than about 1000 is a polymer of a polyenoic acid having 12 to 44 carbon atoms. 21. - Process according to either of the preceding claims, characterized in that the oathode is at least partially immersed in an electrically conductive aqueous liquid medium which is isolated from the bath by a dialysis membrane permeable to water and water soluble amino compound: -, which forms an anodic zone containing the paint binder and an oathodic zone, the water soluble amino compound is released in the anodic zone during the electrodeposition of the resin on an anode placed in the anodic zone and passes through this membrane by electro-dialysis to pass through the cathode zone, the concentration of the water-soluble amino compound in this anode zone being established and maintained at a value which is not substantially greater than 2% by weight of the dissolved resinous binder. persed into the anode zone, and the resulting aqueous solution containing the eleotrodialyated amino compound is passed out of this isolated cathode zone. 22. - An improved concentrated paint binder composition, resinous, organic and film forming, designed to be dispersed in an aqueous electroplating bath containing sufficient additional water-soluble amino compound to impart to the resin, contained in the concentrated binder composition, the behavior of an anionic polyelectrolyte in the bath, this concentrated binder composition being characterized by the fact that it comprises, on a basis free of pigment and mineral filler, about 50 to 95 % <Desc / Clms Page number 47> by weight of a polycarboxylic acid reain having an electroohimic equivalent of between about 1000 and 200,000 and an acid number of between about 30 and 300, and about 1 to 10% of an amino compound soluble in water, relative to the weight of the polycarboxylic acid resin, the remainder being water. 23. - Composition according to claim 22, characterized in that the electrochemical equivalent of the polycarboxylic acid resin is between approximately 1,000 and 2,000. 24. - Composition according to claim 22 u 23, characterized in that the polyoarboxylic acid resin comprises a modified glycédiique siccative oil. .25.- Composition according to claim 24, characterized in that the polycarboxylic acid resin contains a modified glyceridic drying oil which has been reacted with approximately 2 to 25% of a polymerizable vinyl monomer. 26. A composition according to claim 24, characterized in that said polycarboxylic acid resin has been extended with about 5 to 50% of a non-hot-reacting phenol aldehyde resin mixed at a temperature. re between about 200 and 260 C for at least about 30 minutes. 27. - Composition according to claims 22 or 23, characterized in that said polycarboxylic acid reain is an alkyd resin. 28.- Composition according to claims 22 or 23, characterized in that the carboxyl groups contained in the resin are provided by an unsaturated Ó, ss- carboxylic acid. 29.- Electroplating process for an eU coating! <Desc / Clms Page number 48> an anode in an electrical circuit substantially as described above. 30.- Unodiquo product provided with an electrodeposition coating and prepared by the process according to either of claims 1 to 21 and 29. <Desc / Clms Page number 49> We would like to point out to you that the following error re in the text filed in support of the aforementioned application: e 9, line 2, read: "1303" instead of "1232". Please kindly return the duplicate of this letter, which you will find in this envelope, duly. We would be grateful if you could place this in the patent file and issue a copy to those who request a copy of the patent. We are enclosing a fiscal stamp of .15, - in payment of the tax due for space adjustments. ; zinc coated. Please accept, Gentlemen, our ingue greetings.