GB1566742A - Compositions of resin and pigment for use in auto deposition processes upon metals and methods of preparing such compositions - Google Patents

Description

(54) COMPOSITIONS OF RESIN AND PIGMENT FOR USE IN AUTODEPOSITION PROCESSES UPON METALS, AND METHODS OF PREPARING SUCH COMPOSITIONS (71) We, UNION CARBIDE AGRI CULTURAL PRODUCTS COMPANY INC., formerly Amchem Products, Inc., [formerly UCAR Corporation] a Corporation organized under the Laws of the Commonwealth of Pennsylvania, United States of America, of Brookside Avenue, Ambler, Pennsylvania, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the follow ing statement: This invention relates to compositions of resin and pigment for use in autodeposition processes upon metals, and methods of preparing such compositions.

A relatively recent development in the coating field is the provision of resinous coating compositions which are effective, without the aid of electricity, in forming on metallic surfaces immersed therein resinous coatings that increase in thickness or weight the longer the time the surfaces are immersed in the compositions. For convenience, such a coating is hereafter referred to as "a resinous coating which grows with time" or as an "autodeposited coating." Speaking generally, compositions which are effective in this way comprise acidic aqueous coating solutions having dispersed therein solid resin particles.AutoS deposited coatings are formed from such compositions as a result of their ability to attack and dissolve from the metallic surface metal ions in amounts which cause the resin particles to deposit on the surface in a manner such that there is continuous build up of resin on the surface. For convenience such a composition is hereafter referred to as an "autodepositing composition".

Autodeposited coatings formed upon metals by such autodepositing compositions are distinctly different from coatings formed by immersing the metallic surface in conventional latices, i.e. compositions consisting essentially of resin particles dispersed in water. The weight of thickness of a coating formed by immersing a metallic surface in a conventional latex is not influenced by the time the surface is immersed in the latex; if it varies it is influenced mainly by the amount of resin solids dispersed in the aqueous medium.

Autodeposited coatings are also distinctly different from coatings formed from earlier known acidic aqueous coating solutions containing dispersed solid resin particles and relatively high amounts of water-soluble corrosion inhibitors, such as sources of hexavalent chromium. The attack of such solutions on the metallic surface is deterred by the relatively high amounts of corrosion inhibitors therein to such an extent that resinous coatings which grow with time are not obtained.

There are certain definite advantages in autodeposition processes. Keeping other factors constant, they can be used to apply thicker resinous coatings to the metallic surface, in a shorter period of time and in a onestep operation. Moreover the coating thickness can if desired be controlled by varying the period during which the metallic surface is immersed in the autodepositing composition. Furthermore the autodeposited resinous coatings generally have excellent corrosion resistance, often better than can be attained otherwise, and a good aesthetic appearance.

Autodeposition processes however are not devoid of problems. When the autodeposited coatings are fused or cured the resins incorporated therein will often be found to be clear or transparent. For various purposes a coloured coating is however wanted and then pigment must be incorporated in the autodepositing compositions so as to impart a coloured appearance to the auto deposited coating. Although pigmented autodepositing compositions have given us little trouble in the laboratory, we have curiously found that industrially-prepared pigmented autodepositing compositions tend sometimes to form autodeposited coatings which are non-uniform in appearance.

This problem can be illustrated as follows.

Using a black-pigmented autodepositing composition on rectangular steel panels quite often the coating autodeposited thereon will be lightcoloured or even transparent at the face edges of the panel-yet the remaining, major portion of the coating increasing progressively as the light-coloured or transparent at the face edges of the panel can extend as much as a 1/4 inch (say 0.65 cm) or more from the edges, with the tinctorial strength (degree of pigmentation) of the coting increasing progressively as the distance from the edges increases, until it reaches full strength in places remote from the edges of the panel. Thus each of the faces of the panel has in effect a "border" of light coloured or transparent coating.This lack of tinctorial strength makes it appear as if insufficient coating has been deposited around the face edges of the pahel-but measurements have shown that the thickness of the autodeposited coating is substantially the same over the entire panel face. While there may be some applications where such non-uniformity in tinctorial strength does not matter-but in general, wherever the decorative effects and aesthetics of the coated surface are important, such variations in the pigmentation of the autodeposited coating are very undesirable.

The problem of non-uniformity in pigmentation of autodeposited coatings has been especially perplexing because it seems to occur only under certain conditions. While not encountered with a panel immersed in an autodepositing composition and either held stationary therein or moved only slowly toand-fro therein, it is very liable to be en countered with a panel moved rapidly to-andfro in an industrially-prepared autodepositing composition. It might seem easy to avoid such rapid measurement-but leaving aside the problem just discussed it is advantageous to maintain relative movement between the metal surface and the composition because the rate at which coating is autodeposited onto the metal surface is increased thereby.

Operating on an industrial scale, a bath of autodepositing composition may for example contain 25,000 to 50,000 United States gallons (approximately 95,000 to 190,000 litres, or roughly 21,000 to 42,000 Imperial gallons) of composition. Any such bath is normally made up by diluting an aqueous concentrate con taining the resin and pigment with additional water. The concentrate is prepared previously by combining an aqueous dispersion of the resin (for example, a latex) with an aqueous dispersion of the pigment-and it may be used not only to make-up the bath initially but also to replenish the bath as the resin and pigment are depleted during use.Although no problems of non-uniform pigmentation of the resultant coatings have been observed with autodepositing compositions made-up from aqueous/resin pigment concentrates prepared in laboratorysize quantities of for example one or several litres, we have encountered such problems with auto depositing coating compositions made-up from aqueous resin/pigment concentrates prepared in industrial-size quantities of for example several thousand gallons (or many thousand litres)aespite the fact that in each case the ingredients and proportions thereof were the same, and the same basic mixing techniques were used in preparing both the concentrates and in rnaking up the autodepositing compositions therefrom.

There is another observable difference between the aqueous resin/pigment concentrates prepared in industrial quantities and those prepared in laboratory quantities, besides their different performances. Although both have a homogeneous appearance after the mixing operation using conventional mixing techniques has been completed, we have on investigation found that upon standing, ingredients of the industrially-prepared concentrate separate into two layers, whereas this does not happen with the laboratory-prepared concentrate. The lower layer of these two layers consists of an aqueous dispersion of pigment and resin, but the upper layer consists of an aqueous dispersion of resin, with little or no pigment.Even though remixing of these two layers results in what appears to be a uniform or homogeneous mixture of the resin and pigment solids, autodepositing compositions formulated therefrom form autodeposited coatings which often do not display uniform tinctorial strength.

We have however now found that it is possible to provide an industrial auto depositing composition which forms auto deposited coating having uniform tinctorial strength (or pigmentation) via an aqueous concentrate containing particles of resin and pigment dispersed therein in such a way that there is no separation of pigmented and unpigmented layers, be ensuring that substantially all of the resin particles are associated with pigment particles.

As will also appear hereinafter we have also found a procedure whereby substantially all the resin particles can be associated with pigment particles by combining an aqueous dispersion of coating-forming resin solids with an aqueous dispersion of pigment solids in such a ratio and under such conditions that virtually all of the coating-forming solids have subs tank tially the same opportunity to associate with the pigment solids, the procedure including the step of subjecting the combined coating-forming and pigment particles to a vigorous inter mingling action before any significant degree of mere diffusion mixing thereof can occur.

According to one aspect of this invention there are provided aqueous pigmented resin compositions, for use in autodeposition processes, which comprise particles of an organic coating-forming resin dispersed in an aqueous medium by an anionic surfactant, said dispersed resin particles being associated substantially irreversibly with pigment particles dispersed in the aqueous medium by a non-ionic surfactant, and in which when the number of pigment particles is the same as or greater than the number of resin particles then substantially all of the resin particles are associated with pigment particles while when the number of resin particles is greater than the number of pigment particles then the pigment particles are associated substantially uniformly with the resin particles and virtually all of those resin particles which are associated with substantially the same number of pigment particles.

The particles of organic coating-forming resin and of pigment are referred to herein as being associated substantially-irreversibly with each other. It is not fully understood how the pigment particles are associated with the coating-forming resin particles-they may be absorbed onto the surfaces of the resin particles, or bonded to the resin particles through surfactant, or associated in some other way.

By whatever means the association is achieved, it seems to be substantially irreversible-the respective particles are strongly bonded or attached to one another, so that they do not readily disassociate even when subjected to vigorous mixing, and when the resin particles are deposited on the metallic surface by the autodeposition process they carry pigment par ticles with them which therefore are simul taneously deposited thereon. Thus the term 'associated" as used herein means that whatever the mechanism of the association the coating-forming particles carry pigment particles with them when they deposit upon the metal surface.

The dispersion of particles of the organic coating-forming resin normally and desirably will take the form of a latex; and the aqueous pigmented resin compositions of this invention are of course intended normally for use upon an industrial scale, and for that purpose will be prepared in bulk form as concentrates having a volume of 50 United States gallons or more.

The dispersed particles of the coatingforming resin are preferably associated with an anionic surfactant in an amount of from 1% o/o to 4% based on the resin.

The amounts of the solid ingredients in the aqueous pigmented resin compositions of the present invention can be varied as desired. They will however normally be prepared as concentrates, and then it is generally recommended that the aqueous concentrate should contain from about 350 g/l to about 650 g/l and preferably 350-550 g/l, of the organic coating-forming resin material and from about 5 g/l to about 35 g/l of pigment.

A preferred aqueous resin/pigment concentrate in accordance with the invention will desirably contain: (A) about 100 parts of resin particles, having an average particle size of about 2000 A, associated with an anionic surfactant; (B) from about 0.6 part to about 4.5 parts of pigment particles, having an average particle size within the range of from about 40 m,a to about 50 m,a, associated with a nonionic surfactant; and (C) from about 70 to about 150 parts of water.

In a concentrate according to the present invention wherein the number of resin and pigment particles is substantially the same, or in which the pigment particles outnumber the resin particles, it should be the case that there are pigment particles associated with substantially all of the resin particles, and indeed that roughly the same number of pigment particles are associated with each resin particle.

If on the other hand, the concentrate contains more resin than pigment particles it should still be the case that the pigment particles are substantially uniformly associated with the resin particles, and thus that substantially all of those resin particles associated with pigment particles are associated with substantially the same number of pigment particles, and that the pigmented and unpigmented particles are uniformly distributed throughout the composition.

As component (B) the concentrate will preferably contain from about 0.9 to about 3 parts of the pigment particles. The resin particles may be of various kinds, as will appear subsequently, but advantageously may consist of or include styrene/butadiene resin particles. The pigment may advantageously consist of or include carbon black particles.

According to another aspect of the invention there is also provided a process for the preparation upon an industrial scale of an aqueous composition, for use in autodeposi tion processes, comprising a dispersion of particles of an organic coating-forming resin and of particles of pigment, in which process an aqueous dispersion of the coating-forming resin particles associated with an anionic surfactant is brought together with an aqueous dispersion of the pigment particles associated with a non-ionic surfactant and these dispersions are vigorously intermingled before any significant diffusion can occur between the respective dispersions so that virtually all of the coating-forming resin particles have substantially the same opportunity to be associated with the pigment particles.

The respective dispersions are most con veniently brought together and vigorously intermingled by forming one stream of the aqueous dispersion of coating-forming resin material particles and another, separate stream of the aqueous dispersion of pigment particles, and then bringing these separate streams together into a single combined stream under conditions which create turbulent flow therein. Turbulent flow in each of the separate sueams may be established before they are brought together as well as afterwards in the combined stream.

In carrying out the preparative process by bringing together separate streams of an aqueous dispersion of coating-forming material resin particles and of an aqueous dispersion of pigment particles it is most convenient in order to obtain an aqueous resin/pigment composition having some predetermined desired resin/pigment ratio therein to employ respective streams each of predetermined solids content and to bring these together while controlling the flow rates of the respective streams so as to establish the predetermined desired resin/pigment ratio in the combined stream.

While it is possible to bring the streams together in such a manner that the turbulence thereby created is itself sufficient to effect the necessary vigorous intermingling of the particles it is best to ensure adequate intermingling by external mixing means, which conveniently may be a centrifugal pump, arranged desirably immediately down stream of the junction point of the two streams.

The invention of course extends to aqueous resin/pigment compositions, for use in autodeposition processes, whenever prepared by the preparative processes herein disclosed.

According to another aspect of this invention there are also provided pigmented autodeposition compositions, wherein the resin/ pigment dispersion is or includes an aqueous resin/pigment composition as herein disclosed.

The present invention is not primarily concerned with the formulation of these autodepositing compositions save as regards the resin/pigment components thereof. If however guidance on that score is required, further information especially as regards the formulation of the aqueous, acidic phase of the autodepositing compositions may be found in our United States Patents No.

3,585,084 and No. 3,592,699, in United States Patent No. 3,709,743, in our South African Patent No. 72/1146, in our Belgian Patent of Addition No. 811,841 or in our British Patent No. 1,241,991.

Briefly stated, United States Patent Nos.

3,585,084 and 3,592,699 disclose resinous coating compositions comprising an aqueous solution of acid and oxidizing agent, and solid resin particles dispersed therein; the preferred composition is prepared by admixing hydrofluoric acid and either hydrogen peroxide or dichromate with a latex. United States Patent No. 3,709,743 discloses a resinous coating composition comprising an acidic aqueous solution of nitric acid and dispersed resin solids.

South African Patent No. 72/1146 discloses an acidic aqueous coating solution prepared from an acid, a soluble iron compound and dispersed resin solids, and optionally an oxidizing agent; the preferred coating composition described in this patent is prepared from hydrofluoric acid, ferric fluoride, and a latex. Belgian Patent of Addition No. 811,841 discloses the use of other soluble metal compounds such as, for example, a compound of copper, cobalt, or silver in coating compositions which form resinous coatings which grow with time.

Much other useful information, especially as regards control of the surfactant concentration and also as regards the choice of the resin particles, will also be found in our copending Application for Letters Patent No. 12,190/76 (Serial No. 1,538,911).

It may however be convenient here to indicate that a preferred autodepositing composition, which we have found especially suitable for the formation of autodeposited coatings, is one including resin solids in an amount of from about 50 g/l to about 125 g/l, ferric fluoride in an amount equivalent to from about 0.05 g/l to about 2 g/l of ferric iron, and hydrofluoric acid in an amount of from about 0.7 g/l to about 3 g/l of HF, having a pH value within the range of from about 2 to about 3.2, and in which the ratio of pigment solids to resin solids is within the range of from about 0.005:1 to about 0.05:1.

Again for convenience it may here be noted that dispersions of insoluble resin particles in water, suitable for use in the resin/pigment compositions and indeed the autodepositing compositions of this invention, are readilyavailable commercially, and a few examples of such commercially-available materials are as follows: Darex 637-manufactured by W. R. Grace.

Darex 510manufactured by W. R. Grace.

Goodrite 1800 X 73-manufactured by B.

F. Goodrich Co.

(Note: "Darex" is a Registered Trade Mark.).

It is a fact that pigmented autodepositing compositions formulated in accordance with this invention form pigmented autodeposited coatings of improved, uniform tinctorial strength, even if made up via resin/pigment concentrates prepared in industrial-size quantities, such as for example 50 United States gallons or more. The reason for this however is not fully understood.

The resin/pigment concentrates prepared according to the present invention are homogeneously stable compared with those which separate into two layers within a short time after being prepared such as within about 1/2 to 1 hour. Without limiting ourselves by any theories we think that the matter probably can be partly explained as follows. In the conventional procedure typically several thousand gallons of the aqueous resin dispersion have been pumped into a tank equipped with a paddle mixer. Since the volume of resin dispersion is usually much greater, perhaps 25 times greater than that of the pigment dispersion the latter is added to the resin dispersion while stirring with the paddle mixer until the resin and pigment dispersions appear visually to be thoroughly intermixed and apparently homogeneous.In this type of non-vigorous mixing process, even when used to prepare batches of concentrate as small as 5 to 10 United States gallons, we believe that substantial amounts of pigment particles become associated with only relatively small amounts of resin particles, leaving substantial amounts of resin not associated with pigment-and once this has happened it appears to be irreversible, because continued mixing for several days had no effect.When however the resin and pigment dispersions are vigorously intermingled so that substantially all of the resin particles have the same opportunity to associate with the pig ment particles we believe that a higher uni form distribution of associated resin/pigment particles is achieved-and consequently the resin/pigment concentrates thus prepared even in large industrially-sized quantities of for for example several thousand or more United States gallons have the same desired charac teristics as those secured with laboratory amounts of concentrate.At all events when prepared in accordance with this invention the resin/pigment compositions display virtually no phase separation, and as previously indicated the autodepositing compositions prepared there from form autodeposited coatings of substan tially uniform tinctorial strength.

It is however perhaps more difficult to understand why an auto depositing composition containing a resin/pigment component in which substantially all of the resin is associated with pigment should be able to form autodeposited coatings having uniform tinctorial strength when conventionally-prepared compositions do not. We can offer no explanation of this at present which seems fully satisfac and accordingly will not attempt to do so.

The preparative process of this invention can conveniently be carried out in apparatus which comprises first and second liquid conduits respectively for carrying an aqueous dispersion of resin solids and for carrying an aqueous dispersion of pigment solids to a junction with a further liquid conduit in which the two aqueous dispersions are brought together, and a mixer positioned in the further liquid conduit at a location downstream of said junction such that the two dispersions after they have been brought together pass therethrough before any significant diffusion between the two dispersions can take place, the mixer being adapted vigorously to intermingle the two dispersions as they pass therethrough.

The mixer may most advantageously be a centrifugal pump.

In order that the invention may be well understood it will now be further described with reference to the accompanying drawings, in which: Figure 1 is a somewhat schematic elevational view of apparatus for use in a process according to the invention, shown as a flow-diagram therein, for preparing resin/pigment disper sions for use in autodepositing compositions; and Figure 2 is a similar schematic elevational view of another embodiment of apparatus for use in such a process.

Referring first to Figure 1, the apparatus there illustrated is a simple system that can be used in preparing an aqueous resin/pigment concentrate having a predetermined resin/pigment ratio, and which has been designed for manual control of the flow rate of an aqueous pigment dispersion so as to achieve that predetermined ratio.

The major components of the system are a resin/pigment concentrate storage tank A, an aqueous pigment dispersion storage tank B and an aqueous resin dispersion (latex) storage talk C. Latex having a predetermined resin solids concentration is pumped from the latex storage tank C through pipe 2 by the centrifugal pump 4 at some predetermined flow rate, while valve 6 and valve 8 are both in the closed position.

Whenever necessary latex can be drained off from the latex storage tank C through pipe 1 and valve 6. Similarly, the connecting pipes of the system can whenever necessary be flushed out with water drawn from a source (not shown) via pipe 3, the flow of such water being controlled by valve 8.

The aqueous pigment dispersion in storage tank B also has some predetermined pigment solids concentration; and it too is pumped, also by centrifugal pump 4, from its storage tank B through pipe 10 with valve 12 in the closed position and control valve 14 in the open position. As with the latex storage tank C described above, the pigment dispersion can be drained from its storage tank B, whenever necessary, via a pipe 11 and a valve 12.

Further check valves 9 and 13 are provided, valve 9 in pipe 2 and valve 13 in pipe 10, in order to prevent any reversal in the direction of flow of the respective dispersions flowing in pipes 2 and 10, since any flow reversal could result in contamination of the latex and pigment dispersion raw materials.

The stream of pigment dispersion in pipe 10 is brought together with the stream of latex in pipe 2 where the pipes 2 and 10 meet at junction J. The combined stream containing both the pigment dispersion and the latex then flows on through a pipe 16 into a centrifugal pump 4, where it is subjected to a vigorous intermingling action.

The resultant, intensively-mixed resin/pigment dispersion then flows on through pipes 18 and 20 into the resin/pigment concentrate storage tank A, while valve 22 is kept in the open position and valve 24 is kept in the closed position.

The resin pigment concentrate storage tank A is provided with pipe 23, valve 25 and pump 26 for removing concentrate from the tank. The concentrate can either be pumped into appropriately-sized drums or into road or rail tanker trucks for delivery to customers, or it can be pumped direct, as needed, to a bath of autodepositing composition.

It will be observed that the centrifugal pump 4 is positioned only a short distance down stream from the junction J, where the two streams are brought together, so that the combined stream of pigment dispersion and of latex is subjected to the vigorous intermingling action of the pump 4 promptly, before any significant diffusion can take place between the pigment dispersion and latex in the combined stream flowing in pipe 16.The intensive mixing action of the centrifugal pump 4 is effective in giving virtually all of the particles of resin solids substantially the same opportunity to associate with the particles of pigment solids; whereas if any signicant diffusion is allowed to take place prior to the aforementioned vigorous intermingling of the respective dispersions it seems that an undesirably small proportion of resin solids is apt to associate with a substantial amount of the pigment solids, leaving the undesirably large remaining proportion of resin solids not associated with pigment solids.

In the system illustrated in Figure 1 the rate at which the latex flows is kept fixed at some substantially constant, predetermined value. On starting up the system the following procedure can be used to determine and establish the rate of flow of the pigment dispersion so as to achieve the desired resin/pigment ratio. First of all it is necessary to observe the colour of a specimen of a concentrate used in formulating an autodepositing composition which is effective in forming coatings having the desired tinctorial strength. The colour of this specimen is then compared to the colour of the concentrate initially produced by the system; and in order to be able to do this samples of the initially-produced concentrate can be collected from pipe 19 as valve 22 is closed and valve 24 is opened.If the colour of such a sample does not correspond to the colour of the aforementioned specimen, control valve 14 is adjusted to alter the flow rate of the pigment dispersion through pipe 10.

This procedure is repeated until the colour of the pumped concentrate sample corresponds to that of the original specimen. Valve 24 is then closed as valve 22 is opened to allow the concentrate to flow into the storage tank.

This colour-comparison procedure can be used wherever experience has shown it to be a valid method for producing a concentrate which forms the desired coloured coatings when used in an autodepositing composition.

Alternatively it is possible to determine the resin and pigment solids concentrations of an autodepositing composition which forms desired coloured coatings, and then simply to adjust the flow rates of the latex and/or of the pigment dispersion so as to establish the desired resin/pigment ratio in the output.

Referring now to Figure 2, the apparatus there illustrated has been designed for use in an automated system for preparing concentrate according to the present invention. As in the embodiment of Figure 1 this apparatus includes a resin/pigment concentrate storage tank A and an aqueous pigment dispersion storage tank B, but unlike the previouslydescribed embodiment the apparatus here includes two latex storage tanks C/1 and C/2.

In operation pigment dispersion is pumped from its storage tank B by a gear pump 31 through a pipe 32 past an air-operated valve 39 which controls the rate of flow of the pigment dispersion through a flow meter 40 which senses the rate of flow of the pigment dispersion and past a 3-way air-operated plug valve 35 and an air-operated valve 34 to junction J' with a pipe 37 carrying latex.

Pigment dispersion can whenever necessary be drained from its storage tank B through a pipe 30 by opening a manually-operated valve 33. For reasons which will be explained below, pigment dispersion can also be recycled to its storage tank B through a pipe 32' by appropriate adjustment of the 3-way air-operated plug valve 35. The air-operated valve 34 functions to prevent any bacloflow of latex into the pipe 32 which carried the pigment dispersion.

As indicated above, and as can clearly be seen from Figure 2, the system includes two latex storage tanks, C/1 and C/2, and latex can be pumped from either or both of these tanks during the mixing operation. Latex is pumped from storage tank C/1 past a valve 50 through the pipe 37 and a transducer flowmeter 60, which senses the rate of flow of the latex in pipe 37, and after combination with the pigment dispersion at junction J finally through a pipe 41 to the centrifugal pump 42, where the combined streams of latex and pigment dispersion are promptly subjected to the intensive mixing action thereof. From the pump 42 the intermingled concentrate flows through a pipe 41' to a three-way air-operated control valve 45, which when suitably adjusted directs it into a pipe 43 which feeds into the concentrate storage tank A. Similarly, latex from storage tank C/2 is pumped through a pipe 36 past a valve 52 into pipe 37, through transducer flow meter 60 and after combination at junction J' with the pigment dispersion through the pipe 41 to the centrifugal pump 42.

For reasons which will be explained below, it is possible by appropriate adjustment of the valve 45 to recycle latex to the storage tanks C/i and C/2 through a pipe 43' and branch pipes 36' and 38' keeping valves 56 and 58 in the open position, while closing valve 34 and recycling pigment dispersion through pipe 32'.

The rate of flow of the concentrate to the storage tank A through pipe 43 can be adjusted by a hand-operated diaphragm valve 60. Further valves 62 and 62' are provided in pipe 43-A, as well as valves 64 and 64' in pipe 43-B, which can be operated to allow concentrate to flow through one or both of filters 66 and 68, which are intended to remove undesired solids that may be present in the concentrate. A batch meter 67 is provided to measure the amount of concentrate prepared; it can moreover be arranged so as automatically to turn off the system after the desired amount of concentrate has been pumped to the storage tank A. In order to shut down the system, an air-operated valve 70 closes as the final amounts of concentrate flow through a by-pass pipe 43C as air-operated valve 74 opens. This slows the flow rate of the concentrate and prevents hydraulic hammer.

Pipe 43 also incorporates a valve 76 which can be used to siphon off a sample of concentrate for quality-control testing. Should it be desired for any reason to keep concentrate from flowing into the storage tank A, by adjustment of a three-way valve 78 the concentrate can be made to flow through a pipe 80 into another container (not shown). The pipeline 43 also includes an air-operated valve 82, which is automatically opened as concentrate is pumped through pipe 43 and automatically closed when the pumping action is stopped.

Concentrate may be withdrawn from its storage tank A through a pipe 88, an airoperated valve 84 being automatically opened as a pump 86 is started. The concentrate flows through a batch meter 90, which automatically turns off pump 86 after the desired amount of concentrate has been withdrawn.

A three-way air-operated valve 92 is incorporated in the discharge pipe 88, which can be adjusted to allow concentrate to be recycled into the storage tank through pipe 89; this is useful, since by recycling the concentrate in this way the stored concentrate can be mixed up as needed.

When the desired amount of concentrate has been withdrawn from the storage tank A, and as the pumping operation is stopped, an airoperated valve 91 doses as the final amounts of concentrate flow through by-pass pipe 88-A as air-operated valve 93 opens. This slows down the flow rate of the concentrate and prevents hydraulic hammer.

A further three-way valve 100, incorporated in pipe 88 can be positioned so that concentrate can be pumped through a pipe 102 and past an open valve 104 into a shipment drum D, or it can be pumped through pipe 88 through an open valve 99 to a tank truck T for shipment.

A pipe 106 and a three-way valve 108 are provided through which steam can be fed as necessary to purge the connected pipes of concentrate.

The system is set in operation to mix the pigment dispersion and latex by adiusting batch meter 67 to deliver the desired amounts of concentrate; and as pumps 42 and 31 are started up, latex and pigment dispersion are recycled to their respective storage tanks, as described above. Recycling in this way allows the flow rates of the separate streams of latex and pigment dispersion to reach constant values.

As the system is described and shown above, the flow rate of the latex is substantially con stant, but in contrast the flow rate of the pig ment dispersion is adjustable and can be adjusted to various desired values. Thus, con centrates having different resin/pigment ratios can be produced as desired. When flow meter 60 senses that the desired flow rate of the latex stream has been established it adjusts the air-operated valve 39 through appropriate circuitry so that the flow rate of the stream of pigment dispersion is such that the desired ratio is obtained. When both streams are flow ing at the desired rates, valve 34 opens at the same time as valve 35 is adjusted to allow pigment dispersion to flow into the latex stream at junction J' and as valve 45 is adjusted to allow concentrate to flow into pipe 43.Al though turbulent flow is generally desirable, we have achieved good results in operation even with laminar flow of each of the latex and pig ment dispersion streams and with laminar flow of the stream containing both these constituents.

It should be appreciated that by utilizing the principles underlying the present developments, the coating-forming material/pigment compostion can be prepared in ways other than by use of the preferred embodiments described above. For example, instead of subjecting the stream of combined organic coating-forming material and pigment to a centrifugal pump or other type of mechanized mixer, it can be subjected to mixers of the type generally referred to as static or motionless mixers. Also, the aqueous dispersions or organic coating-forming material and pigment may be combined and mixed under conditions which result in turbulent conditions. For example, separate streams of turbulent-flowing coating-forming material and pigment may be combined with the turbulence thereof providing the desired mixing action.Till another example of a method for properly preparing the aqueous con centrate involves feeding pigment dispersion at a very slow rate into a vigorously agitated dispersion of the coating-forming material, with the agitation being maintained until all of the pigment dispersion has been added.

EXAMPLES In order to demonstrate the present invention, there are presented below a series of examples showing the use thereof. Comparative examples are set forth also.

EXAMPLE 1 This example illustrates the preparation of a laboratory amount of aqueous resin/pigment concentrate and the use thereof in an autodepositing composition which forms coatings having uniform tinctorial strength. Unless stated otherwise, the term "percent" means wt.

percent based on the total weight of the stated composition.

Five grams of an aqueous carbon black pig ment dispersion (sold under the trademark Aquablak 115) were added to a beaker. There after, 180 g of a latex containing about 54 per cent solids (the resin of the latex comprising about 62 percent styrene, about 30 percent butadiene, about 5 percent vinylidene chloride, and about 3 percent methacrylic acid) were poured into the beaker rapidly over a period of about 10 seconds with vigorous stirring. With such quantities of constituents, this mixing technique is effective in giving substantially all of the resin particles substantially the same opportunity to associate with the pigment par ticles.

The water soluble content of the latex em ployed was about 2 percent based on the weight of dried resin, with the water soluble content comprising about 10 percent sodium phosphate, about 13 percent sodium oleoyl iso propylamide sulfosuccinate, and about 75 per cent dodecylbenzene sulfonate. The sodium phosphate is a buffering agent used in prepar ing the latex and the other water soluble materials are surfactants. The pH of the latex is about 7.8 and the surface tension thereof about 45-50 dynes/cm. The average particle size of the resin in said latex is about 2000 A.

The black pigment dispersion employed has a total solids content of about 36 percent. The carbon black comprises about 30 percent of the dispersion. It has a pH of about 10 to about 11.5 and a specific gravity of about 1.17.

The dispersion contains a nonionic surfactant.

An autodepositing composition was prepared by combining the above resin/pigment com position, 3 g of ferric fluoride, 2.3 g of hydro fluoric add, and water to make 1 liter.

A 3" x 4" cold rolled steel panel was cleaned with a conventional alkali cleaner and rinsed with water. Thereafter the panel was immersed in the above coating composition with agitation (to and fro motion) for about 90 seconds. The panel was removed from the coating composition and dried in air for 1 minute, immersed in a water rinse for 30 seconds, and thereafter the coating was fused in an oven for 10 minutes at 1700C. The coating was visually observed to be uniformly black with no lack of tinctorial strength on any of its area, induding its face edges.

EXAMPLE 2 This example is similar to that of Example 1, except for the use of larger quantities of the resin/pigment constituents in preparing the concentrate.

The black pigment dispersion and the latex employed in Example 1 were used to prepare an aqueous resin/pigment composition according to the following method. Fifty grams of the black pigment dispersion were added to a large beaker and thereafter 1800 g of the latex were rapidly added to the pigment dispersion while stirring vigorously for about 10 seconds.

This mixing technique, with such quantities of constituents, is effective in giving substantially all of the resin particles substantially the same opportunity to associate with the pigment particles.

An autodepositing composition was prepared by combining 185 grams of the above resin/ pigment composition with 3 grams of ferric fluoride, 2.3 grams hydrofluoric acid, and water to make one liter.

A 3" X 4" unpolished cold rolled steel panel was cleaned with a conventional alkali cleaner and rinsed with water and thereafter immersed in the above coating composition with agitation (to and fro motion) for a period of 90 seconds. The coated panel was thereafter dried in air for 1 minute, immersed in a water rinse for 30 seconds, and thereafter the coating was fused in an oven for 10 minutes at 1700C. The coated panel was visually observed and the result, as shown in Table I below, was a uniformly black coating on all areas of the panel.

EXAMPLE 3 This example illustrates a mixing technique different from that used in Examples 1 and 2 to prepare a laboratory amount of aqueous resin/pigment concentrate and the use thereof in an autodepositing composition which forms coatings having uniform tinctorial strength. The latex and pigment dispersion used are those described in Example 1.

A resin/pigment composition was prepared by first adding 3600 g of latex to a 4 liter beaker and thereafter adding 100 g of black pigment dispersion to the beaker by means of a separatory funnel, such that all of the black pigment dispersion had been added over a period of 1 hour. During addition of the pigment dispersion, stirring was accomplished rapidly enough so that a vortex in the com deposition was maintained. This mixing tech nique was effective in glvmg substantially all of the resin particles substantially the same opportunity to associate with pigment particles.

A coating composition was prepared by combining 185 g of the above prepared resin/pigment composition with 3 g of ferric fluoride, 2.3 g of hydrofluoric acid, and water to make 1 liter.

A 3" x4" cold rolled steel panel was deaned with a conventional alkali cleaner and rinsed with water and thereafter immersed in the coating composition with agitation (to and fro motion) for a period of 90 seconds. The panel was thereafter removed from the coating composition and air dried for 1 minute, immersed in a water rinse for 30 seconds, and thereafter the coating was fused for 10 minutes in an oven at 1700C. The coated panel was thereafter visually observed and the result, as shown in Table 1 below, was a uniformly black coating on all areas of the panel.

The next two examples are set forth for comparative purposes. The latex and pigment dispersion used in the comparative examples are the same as those used in Examples 1-3 above.

EXAMPLE A A resin/pigment composition was prepared by adding 50 g of black pigment dispersion to a large beaker. The pigment dispersion was stirred such that a vortex was maintained therein. Eighteen hundred grams of latex were added gradually to the pigment dispersion over a period of 1 hour. Upon termination of the mixing action, the mixture appeared visually to be a homogeneous dispersion of the latex and pigment. Upon dose visual inspection of the top surface of the mixture, white swirls of material were observed. (It is noted that the latex used is milky white in appearance) In less than an hour, the mixture separated into two layers, with the bottom layer being black and the top layer being an overall grayish color and containing white swirls and patches.It is believed that the resin partides of that portion of the latex initially added to the pigment dispersion associated with substantially all of the pigment particles so that few, if any, pigment particles were left to associate with the resin particles later added.

A coating composition was prepared by combining 185 g of the above resin/pigment composition with 3 g of ferric fluoride 2.3 g of hydrofluoric acid, and water to make 1 liter. A 3" x 4" cold rolled steel panel, which had been cleaned with a conventional alkali cleaner and rinsed with water, was immersed in the coating composition with agitation (to and fro motion substantially the same as that of Examples 1-3 above) for a period of 90 seconds.

The coated panel was removed from the coating composition and air dried for a period of 1 minute, immersed in a water rinse for 30 seconds, and thereafter the coating was fused for 10 minutes in an oven at 1700C. The coated panel was visually observed and was found to have clear face edges, as noted in Table 1 below.

It is noted that prior to formulating the autodepositing from the concentrate, it was stirred until the concentrate appeared visually to be homogeneous.

It is noted also that autodepositing compositions formulated from aqueous resin/pigment compositions of the type described in Examples 1-3 and A are bluish-gray in color, being formulated from a latex having a white milky appearance and a pigment dispersion which is very black. The wet coatings formed from such compositions are also bluish-gray in color. The coating turns jet black after being heated and fused. Upon careful inspection of the wet coated panel immediately upon its being withdrawn from the autodepositing composition of this example, it can be seen that the face edges of the coating are bluish-white in contrast to the bluish-gray appearance of the other portions of the coating. In the fused coating, the face edges are clear, as mentioned above.

EXAMPLE B A resin/pigment composition was prepared by first addng 600 g of latex to a large beaker and thereafter adding 50 g of black pigment dispersion with stirring. This mixture was stirred for a period of 1 hour and thereafter 1200 g of additional latex were added slowly over a period of 45 minutes as mixing was continued. After termination of the mixing operation, the appearance of the composition was similar to the appearance of the composition of Example A, that is, it visually appeared to be homogeneous. However, within the hour, it separated into two layers of the type described in Example A.It is believed that the resin particles of the first batch of latex added to the pigment dispersion associated with substantially all, or at least a substantial portion of, the pigment particles so that few, if any, pigment particles were left to associate with the resin particles of the second batch of latex that was added.

An autodepositing composition was prepared by combining 185 g of the above resin/pigment composition (after it was restirred) with 3 g of ferric fluoride, 2.3 g hydrofluoric acid, and water to make 1 liter. A 3"x4" cold rolled steel panel which had been cleaned with a conventional alkali cleaner and rinsed with water, was immersed in the above coating composition with agitation (to and fro motion substantially the same as that of Examples 1-3 above) for a period of 90 seconds. Thereafter the coated panel was removed and air dried for 1 minute, immersed in a water rinse for 30 seconds, and the coating was fused for 10 minutes in an oven at 1700C. The coating was visually observed and was found to have clear face edges, as noted in Table 1 below.

TABLE 1 Coating Composition Appearance of Coating Example 2 uniform black coating on all areas of panel Example 3 uniform black coating on all areas of panel face edges of coating clear Example A and other portions uniformly black Example B face edges of coating clear and other portions uniformly black The results of the above examples show the criticality of preparing the aqueous resin/ pigment concentrate in a manner such that substantially all of the particles of coating-forming material have substantially the same opportunity to associate with the pigment particles.

Steel panels of the type described above are immersed in the autodepositing compositions of Examples 1 to 3 and A and B and are coated as described, except that the panels are positioned and moved in the compositions in a manner such that the faces of the panels are parallel to the direction of movement. The entirety of the coatings formed from the compositions of A and B have a brownish transparent appearance whereas those formed from the compositions of Examples 1 to 3 have a uniformly jet black appearance.

Steel panels of the type used in Examples A and B are coated with the autodepositing compositions of Examples A and B as described, except that the panels are moved in the compositions with a slower to and fro motion. (In Examples A and B, the panels were moved with a to and fro motion over a distance of about 2"/cycle, that is, about 1" forward and about 1" backward. The speed of movement was such that the panel was moved about 1 cycle/second. The slower to and fro motion involved moving the panel about 2 cycles every 10 seconds). The coatings, including the face edges, were uniformly black.

The next example illustrates the preparation of an industrial quantity of resin/pigment concentrate according to the present development.

EXAMPLE 4 The concentrate of this example was prepared from the latex and pigment dispersion described in Example 1. Preparation of the concentrate is described in connection with Figure 1.

The latex storage tank contained about 3000 gallons of latex and the pigment dispersion storage tank contained about 90 gallons of pigment dispersion. The pipe 2 carrying the latex stream had a diameter of about 1 inch and the pipe 10 carrying the pigment dispersion stream had a diameter of about 1/2 inch. The dia meters of the pipes 16 (carrying the stream of combined latex and pigment dispersion) and 18 (carrying the concentrate) were also about 1 inch. The centrifugal pump 4 was rated at 25 gpm, but due to head factors, frictional losses, etc., it delivered about 17 gpm of concentrate. The length of the pipe 16 between juncture J and pump 4 was about 13 inches.

Control valve 14 was adjusted to give a flow rate of the pigment dispersion such that about 1.95 parts of pigment solids were combined with every 100 parts of resin solids. Somewhat over 3000 gallons of concentrate were produced. The concentrate did not separate into layers and after a period of several days showed no tendency to do so.

An autodepositing composition was prepared from a 185 gram sample of the concentrate.

The sample was diluted with water and thereafter an aqueous concentrate of ferric fluoride and HF was added to the diluted concentrate, the amounts of water and other ingredients being such that 1 liter of the composition contained said 185 g sample, about 3 g of ferric fluoride and 2.3 g of HF. The composition was used to coat a steel panel using the procedure described in Example 1. The coating, including its face edges, was uniformly black.

The next example is a comparative example and illustrates that when the basic mixing technique used to prepare the laboratory quantity of the resin/pigment concentrate of Example 1 is used in preparing larger quantities of concentrate, different results are obtained.

EXAMPLE C The concentrate of this example was prepared from the latex and pigment dispersion described in Example 1. About 1.1 gallons of the pigment dispersion were added to a container and thereafter about 43.9 gallons of the latex were poured into the container rapidly with vigorous stirring which was effected with a Lightnin mixer having a propeller which rotated at about 1725 rpm. The mixture was stirred for about 1 hour. An auto depositing composition formulated from a sample of this concentrate in the manner described in Example 1 and used to coat a steel panel in the manner described in Example 1 formed a coating which was transparent at the face edges of the panel. The concentrate separates into two layers of the type described in Examples A and B within one hour after termination of mixing action.

The next series of examples illustrate the use of autodepositing compositions formulated from different amounts of pigment dispersion and the effect thereof on coating thickness.

EXAMPLE 5 The autodepositing compositions of this example were prepared from the latex and pigment dispersion described in Example 1. One liter batches of each of the compositions contained 180 g of latex, 3 g of ferric fluoride, 2.3 g of HF and the amount of pigment dispersion identified in Table 2 below. Each of the compositions which contained pigment was prepared from an aqueous concentrate of resin/ pigment prepared in the manner described in Example 1. The concentrates were diluted with water and the coating compositions were prepared by adding to the diluted concentrates appropriate amounts of aqueous concentrates of ferric fluoride and HF. The compositions were used to coat panels according to the procedure described in Example 1. Table 2 below shows the coating thickness obtained and the surface tension of the compositions.

TABLE 2 Amount of Pigment Coating Thickness, Surface Tension, Ex. Dlspersion, g/l mil dynes/cm 5-A none 1.1 54.4 5-B 5 1.1 50.4 Sc 10 1.0 50.0 25 25 0.85 47.0 5-E 50 0.1 47.0 5-F 100 < 0.05 50.0 From the results reported in Table 2, it can be seen that the use of relatively large amounts of pigment dispersion deterred or inhibited coating formation. It has been explained above that it is believed that surfactant-poor resin particles and surfactant of the pigment have an affinity for each other. The latex used in the examples set forth herein is an example of a latex which contains a relatively small amount of surfactant for maintaining the resin partides in their dispersed state.The concentration of the surfactant in the aqueous phase of the latex is below the critical micelle concentration and below the surfactant concentration which corresponds to the inflection point on a graph of surface tension (dynes/cm plotted as the ordinate) versus the logarithm of surfactant concentration (plotted as the abscissa). It is theorized that the decreases in coating weights shown in Table 2 above are experienced because of the increased proportion of the surfactant of the pigment that is obtained as a result of the additional amounts of pigment dispersion added.

It has been reported that the particle size of the carbon black used in the compositions of the above examples falls within the range of about 40 to about 50 mA. As noted above, the particle size of the resin is about 2000 .

Assuming a particle size of the carbon black of 40 mpb calculations show that a composition containing about 1.5 parts of carbon black for every 100 parts of resin is one in which there is about 1 resin particle for every carbon black particle. Assuming a particle size of the carbon black of about 50 nFL, calculations show that a composition containing about 1.5 parts of carbon black for every 100 parts of resin is one in which there are about 2 resin particles for every carbon black particle.

WHAT WE CLAIM IS: 1. Aqueous pigmented resin compositions, for use in autodeposition processes, which comprise particles of an organic coating- forming resin dispersed in an aqueous medium by an anionic surfactant, said dispersed resin particles being associated substantially irreversibly with pigment particles dispersed in the aqueous medium by a non-ionic surfactant, and in which when the number of pigment particles is the same as or greater than the number of resin particles then substantially all of the resin particles are associated with pigment particles while when the number of resin particles is greater than the number of pigment particles then the pigment particles are associated substantially uniformly with the resin particles and virtually all of those resin particles which are associated with pigment particles are associated with substantially the same number of pigment particles.

2. Compositions as claimed in claim 1, in which the dispersion of particles of the organic coating-forming resin takes the form of a latex.

3. Compositions as claimed in claim 1 or claim 2, for use upon an industrial scale, which have been prepared in bulk form as concentrates having a volume of 50 United States gallons or more.

4. Compositions as claimed in any of the preceding claims, in which the anionic surfactant with which the dispersed particles of the coating-forming resin are associated is present in an amount of from 1% to 4% based upon the resin.

5. A composition as claimed in any of the preceding claims, in the form of a concentrate, which contains from 350 g/l to 650 g/l of the organic coating-forming resin material and from 5 g/l to 35 g/l of pigment.

6. A composition as claimed in claim 5 which contains from 350 g/l to 550 g/l of the organic coating-forming resin material.

7. A composition as claimed in any of the preceding claims which contains: (A) for 100 parts of resin particles, having an average particle size of about 2000 A, associated with an anionic surfactant; (B) from 0.6 part to 4.5 parts of pigment particles, having an average particle size within the range of from 40 mp to 50 m,u, associated with a non-ionic surfactant; and

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (22)

**WARNING** start of CLMS field may overlap end of DESC **. 2.3 g of HF and the amount of pigment dispersion identified in Table 2 below. Each of the compositions which contained pigment was prepared from an aqueous concentrate of resin/ pigment prepared in the manner described in Example 1. The concentrates were diluted with water and the coating compositions were prepared by adding to the diluted concentrates appropriate amounts of aqueous concentrates of ferric fluoride and HF. The compositions were used to coat panels according to the procedure described in Example 1. Table 2 below shows the coating thickness obtained and the surface tension of the compositions. TABLE 2 Amount of Pigment Coating Thickness, Surface Tension, Ex. Dlspersion, g/l mil dynes/cm 5-A none 1.1 54.4 5-B 5 1.1 50.4 Sc 10 1.0 50.0 25 25 0.85 47.0 5-E 50 0.1 47.0 5-F 100 < 0.05 50.0 From the results reported in Table 2, it can be seen that the use of relatively large amounts of pigment dispersion deterred or inhibited coating formation. It has been explained above that it is believed that surfactant-poor resin particles and surfactant of the pigment have an affinity for each other. The latex used in the examples set forth herein is an example of a latex which contains a relatively small amount of surfactant for maintaining the resin partides in their dispersed state.The concentration of the surfactant in the aqueous phase of the latex is below the critical micelle concentration and below the surfactant concentration which corresponds to the inflection point on a graph of surface tension (dynes/cm plotted as the ordinate) versus the logarithm of surfactant concentration (plotted as the abscissa). It is theorized that the decreases in coating weights shown in Table 2 above are experienced because of the increased proportion of the surfactant of the pigment that is obtained as a result of the additional amounts of pigment dispersion added. It has been reported that the particle size of the carbon black used in the compositions of the above examples falls within the range of about 40 to about 50 mA. As noted above, the particle size of the resin is about 2000 . Assuming a particle size of the carbon black of 40 mpb calculations show that a composition containing about 1.5 parts of carbon black for every 100 parts of resin is one in which there is about 1 resin particle for every carbon black particle. Assuming a particle size of the carbon black of about 50 nFL, calculations show that a composition containing about 1.5 parts of carbon black for every 100 parts of resin is one in which there are about 2 resin particles for every carbon black particle. WHAT WE CLAIM IS:

1. Aqueous pigmented resin compositions, for use in autodeposition processes, which comprise particles of an organic coating- forming resin dispersed in an aqueous medium by an anionic surfactant, said dispersed resin particles being associated substantially irreversibly with pigment particles dispersed in the aqueous medium by a non-ionic surfactant, and in which when the number of pigment particles is the same as or greater than the number of resin particles then substantially all of the resin particles are associated with pigment particles while when the number of resin particles is greater than the number of pigment particles then the pigment particles are associated substantially uniformly with the resin particles and virtually all of those resin particles which are associated with pigment particles are associated with substantially the same number of pigment particles.

2. Compositions as claimed in claim 1, in which the dispersion of particles of the organic coating-forming resin takes the form of a latex.

3. Compositions as claimed in claim 1 or claim 2, for use upon an industrial scale, which have been prepared in bulk form as concentrates having a volume of 50 United States gallons or more.

4. Compositions as claimed in any of the preceding claims, in which the anionic surfactant with which the dispersed particles of the coating-forming resin are associated is present in an amount of from 1% to 4% based upon the resin.

5. A composition as claimed in any of the preceding claims, in the form of a concentrate, which contains from 350 g/l to 650 g/l of the organic coating-forming resin material and from 5 g/l to 35 g/l of pigment.

6. A composition as claimed in claim 5 which contains from 350 g/l to 550 g/l of the organic coating-forming resin material.

7. A composition as claimed in any of the preceding claims which contains: (A) for 100 parts of resin particles, having an average particle size of about 2000 A, associated with an anionic surfactant; (B) from 0.6 part to 4.5 parts of pigment particles, having an average particle size within the range of from 40 mp to 50 m,u, associated with a non-ionic surfactant; and

(C) from 70 parts to 150 parts of water.

8. A composition as claimed in claim 7 which for 100 parts of resin particles contains as component (B) from 0.9 part to 3 parts of pigment particles.

9. A composition as claimed in any of the preceding claims in which the resin particles consist of or include styrene/butadiene resin particles.

10. A composition as claimed in any of the preceding claims in which the pigment con sists of or includes carbon black particles.

11. Aqueous pigmented resin compositions as claimed in any of the preceding claims and substantially as herein described.

12. A process for the preparation upon an industrial scale of an aqueous composition, for use in autodeposition processes, comprising a dispersion of particles of an organic coatingforming resin and of particles of pigment, as claimed in any of the preceding claims, in which process an aqueous dispersion of coatingforming resin particles associated with an anionic surfactant is brought together with an aqueous dispersion of the pigment particles associated with a non-ionic surfactant under conditions whereby virtually all of the coatingforming resin particles have substantially the same opportunity to associate with the pigment particles, and these combined dispersions are vigorously intermingled before any significant diffusion can occur between the respective dispersions so that virtually all of the coating-forming resin particles have substantially the same opportunity to become associated with the pigment particles.

13. A process as claimed in claim 12, in which the respective dispersions are brought together and vigorously intermingled by forming one stream of the aqueous dispersion of coating-forming resin material particles and an other, separate stream of the aqueous disper sion of pigment particles, and then bringing these separate streams together into a single combined stream under conditions which create turbulent flow therein.

14. A process as claimed in claim 13, in which turbulent flow is created in each of the separate streams before they are brought to gether as well as afterwards in the com bined stream. ~~~~~~~~~~~~~~~~~

15. A process as claimed in any of claims 12 to 14, in which separate streams of an aqueous dispersion of coating-forming material resin particles and of an aqueous dispersion of pigment particles each having some predetermined desired solids content therein are brought together while controlling the flow rates of the respective streams so as to establish a prc- determined, desired resin/pigment ratio in the combined stream.

16. A process as claimed in any of claims 12 to 15, in which adequate intermingling is en sured by mixing means arranged downstream of the junction point of the two streams.

17. A process as claimed in claim 16, in which the mixing means is a centrifugal pump.

18. Processes for preparing aqueous resin/ pigment compositions for use in autodeposition processes, as claimed in any of claims 12 to 17 and substantially as herein described.

~

19 Aqueous resin/pigment composiuons, for use in auto depositing formulations whenever obtained by the preparative processes claimed in any of claims 12 to 18.

20. Pigmented autodepositing formulations, for use in autodeposition processes, wherein the resin/pigment dispersion is or includes an aqueous resin/pigment composition as claimed in any of claims 1 to 11 or 19.

21. Auto depositing formulations as claimed in claim 20, which include resin solids in an amount of from 50 g/l to 125 g/l, ferric fluoride in an amount equivalent to from 0.05 g/l to 2 g/l of ferric iron, and hydrofluoric acid in an amount of from 0.7 g/l to 3 g/l of HF, said formulations having a pH value within the range of from 2 to 3.2, and displaying a ratio of pigment solids to resin solids which is within the range of from 0.005:1 to 0.05:1.

22. Auto depositing formulations as claimed in claim 20 or claim 21 and substantially as herein described.